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Thermal Conversion of Solid Wastes and Biomass
 9780841205659, 9780841207042, 0-8412-0565-5

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Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

Thermal Conversion of Solid Wastes and Biomass

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Thermal Conversion of Solid Wastes and Biomass Jerry L . Jones and Shirley B. Radding,

EDITORS

SRI International

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

ASSOCIATE EDITORS

Shigeyoshi Takaoka A. G . Buekens Masakatsu Hiraoka Ralph Overend

Based on a symposium sponsored by the Division of Environmental Chemistry at the 178th Meeting of the American Chemical Society, Washington, D.C., September 10-14, 1979.

130

ACS SYMPOSIUM SERIES

AMERICAN

CHEMICAL

SOCIETY

WASHINGTON, D. C. 1980

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

Library of Congress CIP Data Main entry under title: Thermal conversion of solid wastes and biomass. (ACS symposium series; 130 ISSN 0097-6156) Includes bibliographies and index. 1. Waste products as fuel—Congresses. 2. Biomass energy—Congresses. I. Jones, Jerry Latham, 1946. II. Radding, Shirley B., 1922. III. American Chemical Society. IV. American Chemical Society. Division of Environmental Chemical. V. Series: American Chemical Society. ACS symposium series; 130. TP360.T46 ISBN 0-8412-0565-5

662'.8 ASCMC8

130

80-14754 1-747 1980

Copyright © 1980 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each article in this volume indicates the copyright owner's consent that reprographic copies of the article may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc. for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating new collective works, for resale, or for information storage and retrieval systems. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

ACS Symposium Series M . Joan Comstock, Series Editor

Advisory Board David L. Allara

W . Jeffrey H o w e

K e n n e t h B . Bischoff

James D . Idol, Jr.

D o n a l d G . Crosby-

James P . Lodge

Donald D . Dollberg

Leon Petrakis

Robert E . Feeney

F. Sherwood R o w l a n d

Jack H a l p e r n

A l a n C . Sartorelli

B r i a n M . Harney

R a y m o n d B . Seymour

Robert A . Hofstader

Gunter Z w e i g

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.fw001

FOREWORD The A C S SYMPOSIUM SERIES was founded i n 1974 to provide

a medium for publishing symposia quickly i n book form. The format of the Series parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors i n camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously published papers are not accepted. Both reviews and reports of research are acceptable since symposia may embrace both types of presentation.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

PREFACE

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.pr001

T

he conversion to useful energy of solid wastes, agricultural residues, and forestry residues by thermal processes has long been practiced to varying extents in many industrialized and developing areas of the world. Within the last decade, however, environmental concerns and rising fossil fuel prices have led to increased efforts to develop and implement efficient and economical methods for recovering energy from solid wastes and biomass. During 1977, researchers within the Chemical Engineering Laboratory at S R I International reviewed the worldwide status of pyrolysis, gasification, and liquefaction methods to identify unique processes and topics for future research. A t that time very few books were available that presented comprehensive reviews of on-going research and development activities related to thermal conversion of solid wastes and biomass. Consequently, a symposium was planned under the auspices of the American Chemical Society (ACS) to discuss major research and development programs in the United States. Twenty-one papers from this symposium— held at the A C S National Meeting in Anaheim, California, during March 1978—were published as A C S Symposium Series N o . 76 during the summer of 1978. Because of the success of the first symposium and the interest expressed by participants in the status of research being done in other countries, planning began in August 1978 for a second symposium with an expanded scope. The symposium was to include speakers from North America, Western Europe, and Asia. Financial support for the symposium was obtained from: the Urban Waste and Municipal Systems Branch of the U . S . Department of Energy; the Municipal Environmental Research Laboratory and the Industrial Environmental Research Laboratory of the U.S. Environmental Protection Agency; and the Division of Environmental Chemistry of the American Chemical Society. The symposium, held at the September 1979 National Meeting of the American Chemical Society in Washington, D . C . , was jointly sponsored by the A C S Divisions of Environmental Chemistry, Fuel Chemistry, and Cellulose, Paper and Textiles. It was also planned in cooperation with other professional societies including: the American Institute of Chemical Engineers; the American Society of Agricultural Engineers; the American Society of Civil Engineers; and the Forest Products Research Society. J. L . Jones and S. B . Radding of S R I International were the chief editors of this book and were responsible for the overall planning of the symposium. The following individuals assisted in the planning and organixi In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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zation: A . G . Buekens, University of Brussels, Belgium; M . Hiraoka, Kyoto University, Japan; R . Overend, National Research Council, Canada; T. B . Reed, Solar Energy Research Institute, United States; and S. Takoka, S R I International, Japan. A . G . Buekens, M . Hiraoka, R . Overend, and S. Takaoka also served as associate editors and were responsible for editing many of the contributions from their respective regions or countries. The book contains 49 chapters, 47 of which were presented at the symposium. The remaining two chapters were contributed by authors who were interested in presenting a paper at the symposium but were unable to do so because of a lack of available time on the program. The first section describes the many research, development, and demonstration programs funded under the U.S. Department of Energy's Urban Waste and Municipal Systems Branch and the Biomass Energy Systems Branch. Conversion of wood to fuels, chemicals, and energy in the form of steam or electrical power is the subject of the second section. Chapter 3 deals with large wood conversion systems and presents a very comprehensive economic analysis of the different systems. Chapter 4 discusses the production of fuel gas from wood. A listing of process developers is provided, along with estimates of investment and operating costs. The third section deals with combustion processes, which currently represent the major thermal conversion route for biomass and solid waste fuels. Chapter 5 presents the findings of a survey of the current technological state of the art and system economics for combustion of municipal solid wastes (MSW) in Western Europe. Again, the units described are large field-erected boilers, some of which have the capacity to burn more than 1000 metric tons/day of solid wastes. The use of modular or shopfabricated combustion equipment by small municipalities or by commercial users is the topic of Chapter 6. Such small capacity systems are not yet widely used in the United States or elsewhere for energy production. A n economic analysis is given for hypothetical systems with capacities to fire up to approximately 100 metric tons/day of wastes. Chapters 7, 8, and 9 deal with fluidized-bed combustion systems. Chapter 7 describes a commercially available combustor now used at about 30 installations in the forest products industry for burning wood residues; Chapter 8 describes another commercially available fluidized-bed combustor for wood residues and also contains information concerning experiments with burning processed M S W . A multisolid fluidized-bed unit now under development in pilot-scale equipment for solid waste and sludge combustion is the topic of Chapter 9. Densification of solid wastes and biomass to produce solid fuels with more desirable physical properties is the subject of the fourth section. xii In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Densification produces solid fuels that are free flowing and easily handled as opposed to shredded wastes or agricultural residues. Chapter 10 considers the mechanical processing of M S W and describes individual unit processes that typically precede densification. The densification process (pelletizing) also is described, as are the physical properties of the product. Chapter 11 presents another approach to producing a densified fuel. After various mechanical processing steps, the cellulosic fraction is embrittled with acid and then ball-milled to produce a powdered solid fuel. This process currently is being demonstrated in a large commercial facility. Chapters 10 and 11 deal with processes to be used principally at large capacity facilities. Chapter 12 describes the development of densification equipment for solid wastes for use at naval bases. Such equipment also may have applications for commercial and industrial users as well as some small communities. Chapter 13 presents results of experiments conducted to determine the energy required for densification under laboratory conditions, and compares these results with the actual energy use of commercial scale equipment. The effects of temperature on energy consumption are shown to be very significant. Densification of agricultural residues and wood is the subject of Chapters 14 and 15. Chapter 14 reviews the types of equipment now available, product forms, and power requirements, and cites specific examples of commercial practice. Chapter 15 discusses a current business venture in the biomass densification field and characterizes emissions from burning the product fuel pellets. The fifth section is the first of four parts dealing with specific pyrolysis, gasification, and liquefaction projects in various regions. It includes chapters describing U . S . process development and commercialization activities, most of which were not described in the A C S Symposium Series N o . 76 published in 1978. Chapter 16 concerns pyrolysis work being conducted at the laboratory scale by U.S. Navy researchers, where pyrolysis of solid wastes or biomass is accomplished in an indirectly heated transport reactor. B y various separation steps, an olefin-rich gas is produced and then polymerized under high temperature and pressure conditions. The conditions under which formation of olefins is maximized rather than formation of char, tar, or water-soluble organics are discussed. Chapter 17 describes the use of a molten salt bath reactor for gasifying solid wastes such as refinery acid pit sludge, rubber tire scraps, wood, leather scraps, and waste photographic film. Experiments have been conducted in both bench-scale and pilot plant-scale equipment. Chapter 18 concerns pyrolysis research work conducted by a U . S . researcher in cooperation with French scientists at the Odeillo (France) solar furnace. The solar furnace was selected as a heat source so as to obtain an extremely high energy flux through the quartz window reactor. A t the extremely high flux rates, char yields were very low and condensible product yields were high. Chapter 19 xiii In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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describes experiments with a downdraft gasifier (previously described in the A C S Symposium Series N o . 76) that uses densified fuel pellets produced from processing M S W . Chapter 20 contains information on a mobile pyrolysis reactor now being tested in commercial applications. Such a unit can be moved to the biomass source to produce charcoal for later use as a fuel. Chapter 21 deals with the subject of retrofitting existing oil- or gas-fired industrial boilers with a crossflow biomass gasifier that would use densified fuel pellets. Prototype units currently are undergoing field testing. A description of a vertical shaft countercurrent-flow (or fixedbed) gasifier is given in Chapter 22. Two such units are being installed to gasify waste cigarette papers and filters, packaging paper, cardboard, and other wastes. The product fuel gas will be burned in a boiler. Chapter 23 discusses the energy requirements (in the form of steam) for activating carbon char produced from biomass or wastes. Efficient use of steam for activation can be very important to the overall system economics. Biomass utilization and conversion research in Canada are the topics addressed in the sixth section. Chapter 24 contains a review of the analysis procedure used to aid in the formulation of the government-supported biomass R & D program in Canada. The major goal is to produce a liquid fuel or a liquid fuel substitution product. A short-term goal is associated with synthesis gas production from biomass. The reader should note the Dulong diagrams used by the author for describing biomass conversion routes. Chapter 25 concerns pyrolysis of agricultural residues in a pilot plant-scale, continuous-flow, indirectly fired rotary retort. The principal products are char and a fuel gas of intermediate heating value. Conversion of M S W and wood to a low heating value fuel gas, using an air-blown fluidized-bed gasifier, is discussed in Chapter 26. The process has been demonstrated for wood gasification in a unit capable of processing approximately 25 metric tons/day of wood. A mechanical processing system and synthesis gas production are also discussed. Chapter 27 describes a direct wood liquefaction process being developed in a laboratory-scale batch feed system. The reported results indicate the ability to liquify wood at elevated temperatures i n the presence of a nickel catalyst and in the absence of hydrogen. Pyrolysis of wood in a bench-scale fluidized-bed reactor is discussed in Chapter 28. Experiments with and without alkali carbonate catalysts were conducted. Chapter 29 describes an air-blown, vertical shaft wood gasifier now being demonstrated. Preliminary performance data are given for the gasification system, which is coupled to a diesel engine power generation system. European technology for pyrolysis, gasification, and liquefaction is described in the seventh section. Chapter 30 includes an interesting discussion of why the development of such processes for M S W has not been as rapid in Europe as in the United States or Japan. During the xiv In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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period from 1960 to 1975, many large mass-burning incineration plants were constructed in Western Europe to recover energy from M S W . In general, these installations have proved to be an acceptable solution to the problem of disposal of M S W . A very comprehensive review of the process development activities is presented as well as an excellent review of the fundamentals of pyrolysis and gasification. A laboratory research program concerned with pyrolysis in a fluidized-bed reactor is also described. Chapter 31 describes the testing of a relatively large indirectly heated fluidizedbed pyrolysis reactor that is capable of accepting whole scrap tires on a semicontinuous feeding basis. Most other pyrolysis processes designed for scrap tires require that the tires be shredded prior to being fed to the reactor. Chapter 32 describes a pyrolysis process that uses an indirectly heated rotary retort and is now being demonstrated for commercial use. If the product fuel gas is to be used without tar or pyrolysis oil recovery, a second-stage autothermic cracking reactor is added. Use of a cocurrentflow vertical shaft reactor for wood gasification is the subject of Chapter 33. The process has been tested and modeled, so this chapter should prove to be quite useful to designers of cocurrent-flow biomass gasifiers. Chapter 34 describes another process that uses an indirectly heated rotary retort for pyrolysis of solid waste and presents the results of tests in a pilot plant-scale reactor. Chapter 35 describes the use of a countercurrentflow, oxygen-blown vertical shaft reactor being developed for gasification of M S W . A pilot plant system is described. The eighth section contains eight excellent chapters concerning the development and demonstration of pyrolysis and gasification technology in Japan. Chapter 36 presents an overview of the technologies being used and developed. The installation of large mass-burning incinerators based on European technology for disposal of M S W has been under way in Japan since the early 1960s. However, heat recovery is not as widely practiced in Japan as in Europe. Since 1973, more than a dozen major process development programs have been under way to develop new thermal processes that can recover energy more efficiently from the very wet M S W in Japan and thus minimize pollution problems. These processes are reviewed and an economic analysis is presented to illustrate why advanced processes are being developed. Chapter 37 describes a drying-pyrolysis process that incorporates a multiple hearth reactor and that was developed specifically for municipal sewage sludge. The new process is compared with two alternative thermal processes. Chapters 38 and 39 describe the use of dual fluidized-bed reactors (with sand circulating between the reactors) for pyrolysis of processed M S W . Pyrolysis of the M S W occurs i n a fluidized bed of hot sand. The char and sand from the first bed move to a second fluidized bed where the char is burned to heat the sand. The hot sand is then returned to the first bed. The basic concept in terms of xv In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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use of a dual reactor system is the same for the two processes, although differences exist in the mechanical details of how the sand circulates between the two beds. The fluidizing gases are also different. In the first process, steam is the fluidizing gas for the first reactor while in the second process, product gas is recirculated. Both processes have been under development for some time. A 450-metric-ton/day commercial plant is scheduled to begin operation in 1980 using the first process. A large 100-metric-ton/day prototype plant using the second process is to be fully operational before the end of 1979. Pyrolysis of scrap tires in an indirectly fired rotary retort is the subject of Chapter 40. The process now is being used on a commercial scale in a demonstration plant with a capacity to process 7000 tons/year of scrap tires. Shredded tires are pyrolyzed to produce an oil and a carbon black product. Chapter 41 describes the use of the Purox Process, originally developed in the United States, for thermal conversion of Japanese refuse. The slagging gasification reactor is a vertical shaft that is oxygen blown with the gases flowing countercurrent to the solids. A comparison of typical M S W samples from the United States and from Japan is presented to illustrate why special design features are necessary for the process. Product gas is burned immediately so as to avoid production of a large wastewater stream. A n economic comparison of the process is made with a conventional incineration process. Chapter 42 describes a process that uses a vertical shaft air-blown reactor and a second-stage ash melting furnace. The product gas is burned directly in a boiler for power generation. The process has been tested in a 20-metricton/day pilot plant. Chapter 43 describes yet another process that uses a vertical shaft furnace, blown with heated air or heated oxygen-enriched air, that operates as a slagging gasifier. The process has been developed with a pilot plant-scale reactor, and a facility with a 150-metric-ton/day capacity is now under construction. The final section deals with the use of thermal processes for biomass conversion in developing countries. Chapter 44 discusses the current extent of use of biomass for fuel among rural populations in several developing countries. Direct combustion is currently the most widely used means for energy production from biomass. The types of biomass available in various countries and the estimated current use are discussed, as well as difficulties in implementing large biomass conversion programs. Chapter 45 describes a commercially available biomass gasification unit coupled to a diesel engine electric power generation system. The gasifier and diesel engine are produced by a French company. The vertical shaft reactor is air-blown and operates in a cocurrent flow mode (or downdraft). The units can be used industrially as well as for rural electrification. U p to 9 0 % of the normal diesel fuel use may be substituted by using the low heating value fuel gas. Chapters 46 and 47 also are concerned with the xvi

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.pr001

gasification of biomass to produce a low heating value gas. Chapter 46 describes work being done in the Philippines on the operation of diesel engines using a fuel gas produced from air-blown gasifier s. The chapter presents a great deal of data and empirical correlations that will be useful to gasification system designers. Applications for gasifier/engine sets include electric power generation and irrigation pumping. Chapter 47 presents information on a gasifier that is being developed for use in rural areas. The unit is very simple to fabricate and requires a relatively low investment cost. The use of alcohol fuels produced from biomass and the use of vehicle-mounted biomass gasifiers are discussed in Chapter 48. These options offer the potential to reduce the amount of petroleum fuels currently being used for vehicles. While the use of alcohol fuels has been receiving a great deal of attention worldwide, the use of vehicle-mounted gasifiers apparently has not been considered in many cases where they would prove beneficial. Further study is required to determine if vehiclemounted gasifiers offer a reasonable solution to petroleum fuel shortages in developing countries. Chapter 49 has been prepared in part by the author of another chapter in the book concerned with the design of a cocurrent-flow biomass gasifier. In this chapter the authors present an analysis of how the introduction of biomass gasification into a developing country will benefit the owners of the gasification units as well as the national economy. The effects on employment, rural development, and balance of trade are examined. Tanzania is considered as a case study. This book represents the efforts of many individuals including those within the two U.S. agencies and ACS who arranged for financial support for the symposium, the representatives of cooperating technical societies who arranged for publicity, the session chairmen who invited many of the speakers, and the co-editors. Special recognition and appreciation is given to the many authors whose diligent efforts made the timely publication of this book possible. SRI International

JERRY L. JONES

333 Ravenswood Avenue Menlo Park, C A 94025

SHIRLEY B. RADDING

January 21, 1980

xvii

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

1 An Overview of the Department of Energy Program for the Recovery of Energy and Materials from Urban Solid Waste DONALD K. WALTER

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

Urban Waste and Municipal Systems Branch, U.S. Department of Energy, Mail Stop 2221-C, 20 Massachusetts Ave., Washington, DC 20545

The primary mission of the Department of Energy Urban Waste Program is to promote energy conservation through the widespread use of urban solid waste as a source of energy and materials. Specifically, the Urban Waste and Municipal Systems (UWMS) Branch seeks to replace conventional fuels with the energy recovered from urban solid wastes; replace virgin materials with materials recycled from urban solid waste; and reduce the amount of energy used in urban waste treatment and disposal. By recovering energy and materials from urban wastes, the word "waste" becomes a mis­ nomer. Garbage, refuse, certain sludges, and certain solids and liquids which are discarded by households, institutions, and businesses are more aptly defined as "urban byproducts" which are awaiting conversion to a useful form. Development of these previously neglected resources rein­ forces several national policies including energy, resource con­ servation, and the environment. For example, a typical 900 tonne (1,000 ton) per day energy and materials plant: ο Produces approximately two quadrillion joules (two tril­ lion Btu's) of low-sulfur fuel per year — the equivalent of roughly 300,000 barrels of oil; ο Produces in a year as much as 18,000 metric tons of ferrous, 1,100 metric tons of aluminum and other nonferrous metals, and 14,000 metric tons of glass for use by industry in various manufacturing processes; ο Reduces the amount of material for land disposal from over 270,000 metric tons of mixed wastes (including organic wastes and metals) per year to about 54,000 metric tons per year of relatively inert material. The use of energy and materials recovery technologies con­ serves fossil fuels directly by replacing them as sources of energy for combustion, and indirectly by replacing virgin materials with intermediate products which require less energy to reconvert into a final form. However, central plant pro­ cessing of urban solid waste to recover energy and materials is This chapter not subject to U.S. copyright. Published 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

4

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

s t i l l i n the e a r l y stages of development. In pursuing i t s mission to achieve maximum development of the resource p o t e n t i a l of urban s o l i d wastes, the UWMS Branch undertakes a c t i v i t i e s i n three areas: t e c h n i c a l processes, i n s t i t u t i o n a l impediments to waste use, and program (monetary) support. These areas, although l o g i c a l l y separable, are h i g h l y i n t e r r e l a t e d and u n d e r l i n e the Branch s t r a t e g y to demonstrate promising energy recovery technologies at a commercial s c a l e i n a v a r i e t y of i n s t i t u t i o n a l s e t t i n g s . This s t r a t e g y i s aimed at a s s i s t i n g p u b l i c and p r i v a t e e n t i t i e s to conserve energy by u t i l i z i n g the resources contained i n t h e i r urban s o l i d wastes; i t focuses on e x i s t i n g impediments to the implementation of energy recovery p r o j e c t s . The program a c t i v i t i e s — i n t e c h n i c a l processes, i n s t i t u t i o n a l impediments to waste use, and program support — address the problems that hinder progress i n demonstrating resource recovery t e c h n o l o g i e s . The f o l l o w i n g d i s c u s s i o n attempts to describe the breadth of Branch a c t i v i t i e s i n these areas. Technical

Processes

Figure 1 shows the range of t e c h n i c a l process options i n resource recovery. Three broad technologies are a v a i l a b l e to recover energy and energy i n t e n s i v e m a t e r i a l s from urban wastes: mechanical, thermal, and b i o l o g i c a l . Mechanical. Mechanical p r o c e s s i n g separates wastes i n t o v a r i o u s components i n c l u d i n g metals, g l a s s , and a r e f u s e d e r i v e d f u e l (RDF). G e n e r a l l y , a mechanical process i s a p r e l i m i n a r y step to the thermal and b i o l o g i c a l t e c h n o l o g i e s . The m e t a l l i c components, g l a s s , and paper f i b e r s are r e c y c l e d to d i s p l a c e v i r g i n materials. In general, mechanical processes are employed f o r s i z e r e duction and s e p a r a t i o n by s i z e , weight, shape, d e n s i t y and other p h y s i c a l p r o p e r t i e s . A t y p i c a l p r o c e s s i n g l i n e would u t i l i z e shredding f o r s i z e r e d u c t i o n of raw r e f u s e , followed by some form of a i r c l a s s i f i c a t i o n to separate the p a r t i c l e s i n t o l i g h t (organics) and a heavy ( i n o r g a n i c s ) m a t e r i a l stream. The l i g h t f r a c t i o n , without f u r t h e r p r o c e s s i n g , has come to be known as f l u f f RDF. A demonstration u n i t sponsored by the Environemtal P r o t e c t i o n Agency (EPA) to produce RDF at St. Louis proved the b a s i c f e a s i b i l i t y of mechanical s e p a r a t i o n processes, t r a n s p o r t and storage techniques, and combustion of f l u f f RDF to r e p l a c e 5 to 27 percent of the p u l v e r i z e d c o a l used i n s u s p e n s i o n - f i r e d u t i l i t y boilers. However, the refinement of equipment components and the t e c h n i c a l and economic o p t i m i z a t i o n of the b a s i c technology s t i l l r e q u i r e a great deal of work. There i s one operating f a c i l i t y at Ames, Iowa which recovers and uses f l u f f RDF on a d a i l y b a s i s . T h i s f a c i l i t y has encountered a s e r i e s of economic and t e c h n i c a l problems. A second f a c i l i t y at Milwaukee, Wisconsin i s e n t e r i n g i t s f i r s t year of

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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6

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

production e v a l u a t i o n p r i o r to f i n a l i z i n g f u e l s a l e s c o n t r a c t s . Several other f a c i l i t i e s are i n a shakedown phase or under cons t r u c t i o n at Chicago; Monroe County, New York; Bridgeport, Connecticut; etc. The p r e p a r a t i o n of d e n s i f i e d RDF (d/RDF) by p e l l e t i z i n g , b r i q u e t t i n g , or extruding i s being explored and evaluated. It i s p a r t i c u l a r l y adapted f o r stoker and spreader-stoker furnaces. However, i t has not been demonstrated commercially, and the c o s t s , handling c h a r a c t e r i s t i c s , and f i r i n g c h a r a c t e r i s t i c s are yet to be evaluated. The a n t i c i p a t e d advantages of d e n s i f i e d RDF are g r e a t l y improved storage and t r a n s p o r t a t i o n c h a r a c t e r i s t i c s . Production of powder RDF ( p a r t i c l e s smaller than 0.15 m i l l i meter) i s being developed i n a p r o p r i e t a r y p i l o t - p l a n t process by e m b r i t t l i n g waste with organic a c i d . A f t e r adding an e m b r i t t l i n g chemical, c o a r s e l y shredded waste i s p u l v e r i z e d . The r e s u l t i n g powder has a higher Btu content than f l u f f RDF, as w e l l as a greater d e n s i t y , homogeneity and decreased moisture content. In a d d i t i o n , powder RDF may be capable of d i r e c t c o - f i r i n g with f u e l oils. However, the d u s t - l i k e composition n e c e s s i t a t e s s p e c i a l handling to minimize the danger of e x p l o s i o n . A "wet" mechanical s e p a r a t i o n process u t i l i z e s hydropulping technology adapted from the pulp and paper i n d u s t r y to reduce raw waste to more uniform s i z e and consistency, followed by a s e r i e s of processes to separate the pulped mass i n t o l i g h t and heavy f r a c t i o n s and to remove some of the water. The o r i g i n a l EPA sponsored p i l o t p l a n t at F r a n k l i n , Ohio, i s s t i l l o p e r a t i n g , although i t no longer produces low grade f i b e r f o r a r o o f i n g p l a n t as o r i g i n a l l y intended. A f t e r s u c c e s s f u l t e s t burns of the 50 percent o r g a n i c s , 50 percent moisture pulp, a f u l l - s c a l e f a c i l i t y designed to burn the pulp to recover steam i s now i n s t a r t - u p at Hempstead, New York. Ferrous metal recovery systems are the most advanced m a t e r i a l recovery systems. Paper f i b e r recovery by both pulping and dry processes has been demonstrated s u c c e s s f u l l y , and aluminum and glass recovery has been demonstrated with l i m i t e d success. E f f o r t s are planned to improve system e f f i c i e n c i e s i n terms of energy use, q u a n t i t y , and q u a l i t y of m a t e r i a l recovered. Thermal. Combustion techniques burn waste f o r the recovery of heat energy. Waterwall combustors are the most t e c h n i c a l l y developed energy recovery systems and employ s p e c i a l grates to burn "as r e c e i v e d " urban waste and recover steam e i t h e r at s a t u rated or superheated c o n d i t i o n s . Over 250 p l a n t s are operating worldwide; seven of them i n the United States. Three of the seven were o r i g i n a l l y b u i l t as i n c i n e r a t o r s . Worldwide there have been a number of t e c h n i c a l problems, with the c o n t r o l of c o r r o s i o n and e r o s i o n being the most s e r i o u s . The most recent European designs have solved these problems but at an increased c a p i t a l c o s t . The more popular U.S. development seems to be the recovery of RDF f o r s a l e to c o a l - u s i n g f a c i l i t i e s although t h i s may be changing. With m o d i f i c a t i o n s , e x i s t i n g b o i l e r s can use RDF as a

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

1.

WALTER

Urban Solid Waste

7

supplemental f u e l . Most development has been aimed a t the l a r g e suspension c o a l f i r e d u t i l i t y b o i l e r . While t e s t burns have been encouraging, t e c h n i c a l problems have developed r e l a t e d to burning c h a r a c t e r i s t i c s , s l a g g i n g , and environmental c o n t r o l equipment performance. A l l can be solved. However, upgrading c o n t r o l devices such as e l e c t r o s t a t i c p r e c i p i t a t o r s may r e q u i r e s i g n i f i cant increases i n the c a p i t a l costs of the system. Another v a r i a t i o n being demonstrated i s the combustion of RDF i n a dedicated b o i l e r as a p r i n c i p a l f u e l . Normally the b o i l e r i s of spreader-stoker design with some c o n s i d e r a t i o n given to the use of f o s s i l f u e l s such as high s u l f u r c o a l as a load l e v e l e r and steam production s t a b i l i z e r . The only a v a i l a b l e s m a l l - s c a l e system i s a packaged two chamber i n c i n e r a t o r with waste heat recovery. This technique i s p r a c t i c a l at the 25 to 100 tons per day (TPD) s c a l e . In these u n i t s , p a r t i a l o x i d a t i o n occurs i n the f i r s t s e c t i o n of the u n i t and causes a p o r t i o n of the waste m a t e r i a l to degrade and give o f f combustible gases. These gases, as w e l l as products of combustion and p a r t i c u l a t e from the f i r s t chamber, flow to a second chamber where they are combusted with excess a i r and a n a t u r a l gas o r o i l p i l o t flame. The combustion products then flow through a p p r o p r i ate heat t r a n s f e r equipment to produce steam, hot water, or hot air. Today, four small c i t i e s and more than s i x t y i n d u s t r i a l p l a n t s use the technique with heat recovery equipment. Thermal g a s i f i c a t i o n and p y r o l y s i s systems are a l s o under development with s e v e r a l systems approaching the f u l l s c a l e demons t r a t i o n stage. S p e c i f i c d i s c u s s i o n i s not included on i n d i v i d u a l techniques s i n c e they are s t i l l i n the developmental stages. Fuels from these processes i n c l u d e gases, o i l s and chars. Biological. B i o l o g i c a l techniques use l i v i n g organisms t o convert organics i n t o u s e f u l energy forms. These processes are i n the developmental stages. The Department of Energy (DOE) i s sponsoring an anerobic d i g e s t i o n process that converts the organics i n urban waste to methane under c o n t r o l l e d c o n d i t i o n s . This process i s at the proof-of-concept stage and i s not expected to be commercialized u n t i l the l a t e 1980s. Another b i o c o n v e r s i o n process to recover methane from e x i s t ing l a n d f i l l s i s near commercialization. Because of the e x p l o s i v e nature o f the gas, i n c r e a s i n g a t t e n t i o n has been p a i d to c o n t r o l l i n g i t s m i g r a t i o n . Today there i s one operating s i t e , two s i t e s i n development, one s i t e under c o n s t r u c t i o n and t e n s i t e s i n an advanced planning stage to u t i l i z e the recovered gas. It i s estimated that 28 m i l l i o n cubic meters (one t r i l l i o n cubic f e e t ) of methane i s p o t e n t i a l l y recoverable from e x i s t i n g l a n d f i l l s , with 1.5 b i l l i o n cubic meters (55 b i l l i o n cubic f e e t ) of p i p e l i n e q u a l i t y methane a v a i l a b l e y e a r l y , j u s t from the 100 l a r g e s t l a n d fills. Generally, the mechanical, thermal and b i o l o g i c a l resource recovery technologies can be ranked i n order of t h e i r s t a t e s of development as shown i n Table 1. The DOE research, development

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

Table I.

Developmental Stage of Resource Recovery Technologies

L e v e l of Development

Technology

High • • • • • • • • •

Low

Ferrous Metal Recovery Anaerobic D i g e s t i o n of M u n i c i p a l S o l i d Wastes Waterwall and Modular Cont r o l l e d A i r Combustors Coarse, F l u f f , and Wet Pulped RDF Paper F i b e r Recovery L a n d f i l l Gas Recovery Glass, Aluminum and Other Nonferrous Metal Recovery Dust and D e n s i f i e d RDF P y r o l y s i s and G a s i f i c a t i o n Anaerobic D i g e s t i o n of S o l i d Waste Enzymatic and Fungal Synthesis

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

1.

WALTER

Urban Solid Waste

9

and demonstration (RD&D) program addresses a l l of these technologies and i s a c t i v e i n promoting t h e i r development. However, true development r e q u i r e s a good deal more than proving the s c i e n t i f i c or engineering v i a b i l i t y of a l t e r n a t i v e resource recovery options, H i s t o r y demonstrates that the major d i f f i c u l t i e s of p u t t i n g a new technology on a sound commercial f o o t i n g occur a f t e r the successf u l operation of the f i r s t prototype. The Branch's program i s fashioned to deal with these problems.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

Nontechnical

Issues

Figure 2 i l l u s t r a t e s the range of nontechnical i s s u e s i n resource recovery. The three broad c a t e g o r i e s — institutional, socioeconomic, and l e g a l — are i n t e r r e l a t e d and o f t e n r a i s e obstacles more d i f f i c u l t to overcome then t e c h n i c a l problems. Energy and m a t e r i a l recovery f a c i l i t i e s , f o r i n s t a n c e , are s i m i l a r to other c a p i t a l i n t e n s i v e manufacturing operations i n that they cannot operate economically unless they r e c e i v e regul a r l y s u f f i c i e n t feedstocks to u t i l i z e production c a p a c i t y . A guaranteed supply of waste i s the foundation upon which an economically f e a s i b l e energy recovery p r o j e c t i s b u i l t . However, m u n i c i p a l i t i e s f r e q u e n t l y c o n t r o l only a f r a c t i o n of the wastes collected within their j u r i s d i c t i o n s . Most urban waste i s c o l l e c t e d by p r i v a t e haulers who d e t e r mine the l e a s t cost p l a c e of d i s p o s a l . Attempts to mandate that p r i v a t e l y - c o l l e c t e d wastes be d e l i v e r e d to a recovery system have met with considerable o p p o s i t i o n from both p r i v a t e haulers and l a n d f i l l operators. One such attempt p r e c i p i t a t e d l i t i g a t i o n that i s now awaiting a d e c i s i o n i n the U.S. D i s t r i c t Court f o r the Northern D i s t r i c t of Ohio. The waste c o n t r o l problem i s f u r t h e r aggravated by the need to aggregate s u f f i c i e n t q u a n t i t i e s of waste f o r the recovery facility. Because many recovery technologies c u r r e n t l y are economically f e a s i b l e only at a l a r g e s c a l e , they f r e q u e n t l y r e q u i r e r e g i o n a l i z a t i o n of the waste management system. The p a r t i c i p a t i o n i n a recovery p r o j e c t of numerous communities — each with d i f f e r e n t perceptions, needs, and expectations — i s d i f f i c u l t to achieve because of the perceived r i s k s and costs a s s o c i a t e d with recovery systems. Thus, i n t e r m u n i c i p a l agreements to achieve r e g i o n a l i z a t i o n are d i f f i c u l t to develop and n e g o t i a t e . The comp l e x i t i e s of t h i s process are o f t e n a major cause of delay i n implementing promising p r o j e c t s . Another major impediment i s that resource recovery f a c i l i t i e s must compete with l a n d f i l l s i n most communities. Most of these l a n d f i l l s f a l l f a r short of s a t i s f y i n g even reasonable p r o t e c t i o n against p o l l u t i o n of ground waters and t h r e a t s to p u b l i c h e a l t h and s a f e t y . Further, few communities account f o r the f u l l cost of land d i s p o s a l . The value of land used as a l a n d f i l l d i s p o s a l f a c i l i t y w i l l diminish g r e a t l y as i t reaches capacity and must be c l o s e d . Few m u n i c i p a l i t i e s r e f l e c t t h i s decrease i n value i n c a l c u l a t i n g d i s p o s a l c o s t s . Sometimes

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Figure 2.

Legal

Socioeconomic

Institutional

Category

{ Contracts

Ownership

Waste Control ^

Guarantees

— -Model Codes/Guidelines

7

r~\

-Training/Education/Technology Transfer

P r i c e Supports

Evaluate A l t e r n a t i v e s

Incentives/Procedures

Regionalization/Coordination

Environmental/Price/1RS

Output

Nontechnical issues and their interrelationships

|"Ί

Manpower

Markets

Benefit/Cost

Lj \-A

Financing

r- !

-

P u b l i c / P r i v a t e Interface

Government I n t e r a c t i o n

Regulations

Issue

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

1.

WALTER

Urban Solid Waste

11

c a p i t a l equipment costs have not been considered i n the determination o f d i s p o s a l c o s t s . Consequently, the cost of l a n d f i l l i n g i s cheap i n areas that do not enforce reasonable environmental and p u b l i c h e a l t h standards. In a d d i t i o n , i t i s perceived as cheap i n areas which have good enforcement but f a i l to f u l l y account f o r the true c o s t s . T h i s s i t u a t i o n s e v e r e l y c o n s t r a i n s the a b i l i t y of energy and m a t e r i a l s recovery systems t o compete with land d i s p o s a l operations f o r the a c q u i s i t i o n of urban wastes. Economy i n transport a t i o n i s one p o t e n t i a l advantage that energy recovery f a c i l i t i e s enjoy r e l a t i v e to land d i s p o s a l . Because l a n d f i l l s i t e s a r e i n c r e a s i n g l y a v a i l a b l e only a t considerable d i s t a n c e from the urban centers which generate the waste, the costs of t r a n s p o r t i n g the waste i s g r e a t l y increased. Unfortunately, t h i s advantage i s l a r g e l y reduced because c e r t a i n types of energy recovery f a c i l i t i e s cannot be l o c a t e d i n urban areas that cannot meet EPA ambient standards f o r p a r t i c u l a t e s . These nonattainment areas may not add a new s t a t i o n a r y source o f p a r t i c u l a t e emissions without an equal or greater o f f set i n emissions from other sources. Current Federal e n v i r o n mental r e g u l a t i o n s do not recognize the other o f f s e t t i n g r e g i o n a l environmental b e n e f i t s of an energy and m a t e r i a l s recovery p l a n t . In order to increase the a b i l i t y of energy recovery systems to compete with land d i s p o s a l , DOE i s urging the Congress and the Environmental P r o t e c t i o n Agency to r e v i s e environmental regul a t i o n s so as to encourage demonstration of environmentally sound recovery systems. The Branch program addresses not only these p r e s s i n g i s s u e s but a l s o provides a s s i s t a n c e regarding f i n a n c i n g of resource systems, market development f o r recovered resources, advice on n e g o t i a t i n g equipment c o n t r a c t s and f o r developing procurement documents. Branch a c t i v i t i e s i n these n o n t e c h n i c a l areas as w e l l as i n t e c h n i c a l areas are coordinated through i t s program support efforts. Program

Support

DOE's Urban Waste Technology funds are p r i m a r i l y used to support RD&D. Most p r o j e c t s are funded by grants, c o n t r a c t s and cooperative agreements. The o b j e c t i v e s of our RD&D e f f o r t s are two-fold: to conduct research and development that w i l l provide planners with s u f f i c i e n t options f o r choosing a waste-to-energy system that f i t s s p e c i f i c l o c a l needs, and to provide the f i n a n c i a l support to demonstrate a wide range of these technolog i e s . Major e f f o r t s concentrate on developing technologies that can have wide a p p l i c a t i o n . DOE a l s o provides t r a i n i n g and t e c h n i c a l a s s i s t a n c e to maximize the e f f e c t i v e n e s s of i t s RD&D investment. Demonstration of e f f e c t i v e energy technologies w i l l reduce many of the b a r r i e r s that cause m u n i c i p a l i t i e s and the p r i v a t e sector t o h e s i t a t e i n undertaking energy recovery p r o j e c t s . In

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch001

12

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

the i t e r i m , DOE i s developing techniques to provide f i n a n c i a l and economic i n c e n t i v e s f o r moving d e s i r a b l e p r o j e c t s forward. These i n c e n t i v e s — loans, loan guarantees and p r i c e supports — w i l l be used to s h i f t much of the f i n a n c i a l r i s k from the l o c a l p a r t i c i pants to the Federal government. When i n p l a c e , a l i m i t e d program of p r i c e supports w i l l help develop markets f o r recovered f u e l , steam and e l e c t r i c i t y . Loan guarantees w i l l be used to guarantee 75 percent o f t o t a l p r o j e c t c o s t s , o r 90 percent of c o n s t r u c t i o n c o s t s . DOE w i l l , however, l i m i t i t s loan guarantee support to those p r o j e c t s f o r which there i s a reasonable assurance of repayment. As of w r i t i n g , loan guarantee and p r i c e support r e g u l a t i o n s are being developed. Appropriations are not yet a v a i l a b l e f o r these programs. An a c t i v e program of t r a i n i n g , t e c h n i c a l a s s i s t a n c e and information t r a n s f e r i s a l s o being i n i t i a t e d . This i n c l u d e s p r e p a r a t i o n of case s t u d i e s , conducting workshops and seminars and developing u n i v e r s i t y and apprenticeship programs. And l a s t l y , the program i s being coordinated among the Federal agencies so that the e x p e r t i s e of each i s used to the f u l l e s t . To summarize, the DOE Urban Waste Program aims at h e l p i n g the p u b l i c and p r i v a t e s e c t o r s conserve energy by u t i l i z i n g the energy resources contained i n urban wastes. The s t r a t e g y i s to reduce or e l i m i n a t e both the t e c h n i c a l and nontechnical b a r r i e r s to using resource recovery on a l a r g e s c a l e . The i n i t i a l goal i s to reduce the t e c h n i c a l b a r r i e r s by supporting R&D e f f o r t s that w i l l l e a d to commercial s c a l e demonstration o f promising technologies. S u c c e s s f u l demonstrations w i l l reduce many of the current r i s k s which i n h i b i t m u n i c i p a l i t i e s and the p r i v a t e s e c t o r from adopting resource recovery. In the i n t e r i m , the Federal government w i l l assume major f i n a n c i a l r e s p o n s i b i l i t y f o r p r o j e c t r i s k s . U l t i m a t e l y , i t i s hoped that a l l of these e f f o r t s w i l l make resource recovery a common and popular method of waste d i s p o s a l and energy production.

REFERENCES

1.

CSI Resource Systems Group, Inc., Federal Assistance by the Department of Energy in the Demonstration of Energy and Materials Recovery Systems. Contract No. 31-109-38-4493, Argonne National Laboratory (August 1978).

2.

Cohen, Alan S., An Overview of the Department of Energy's Research, Development and Demonstration Program for the Recovery of Energy and Materials from Urban Waste.

RECEIVED December 21,

1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

2 Thermochemical Conversion of Biomass to Fuels and Feedstocks: An Overview of R&D Activities Funded by the Department of Energy

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

G. F. SCHIEFELBEIN and L. J. SEALOCK, JR. Pacific Northwest Laboratory1, P.O. Box 999, Richland, WA 99352 S. ERGUN Lawrence Berkeley Laboratory2, Building 77F, Berkeley, CA 94720 This paper is intended to provide an overview of thermochemical conversion technology development activities within the Biomass Energy Systems Branch of the U.S. Department of Energy (DOE). The Biomass Energy Systems Branch (BESB) is a part of DOE's Division of Distributed Solar Technology. The biomass thermochemical conversion technology development activities sponsored by the Biomass Energy Systems Program can be catagorized into four main areas; direct combustion, direct liquefaction, gasification, and indirect liquefaction via synthesis gas. Pacific Northwest Laboratory (PNL) and Lawrence Berkeley Laboratory (LBL) have been selected to provide program management services to the Biomass Energy Systems Program. PNL is responsible for the technical management of development activities directed toward the thermochemical conversion of biomass feedstocks by direct combustion, gasification and indirect liquefaction via synthesis gas. LBL is responsible for the technical management of development activities on the direct liquefaction of biomass feedstocks. Biomass comprises all plant growth, both terrestrial and aquatic and includes renewable resources such as forests and forest residues, agricultural crop residues, animal manures, and crops grown on energy farms specifically for their energy content. Biomass production and conversion is considered a solar technology because living plants absorb solar energy and convert it to biomass through photosynthesis. Program Objective The objective of the thermochemical conversion technology development activities of the Biomass Energy Systems Program is to 'Operated for the U.S. Department of Energy by Battel le Memorial Institute Operated for the U.S. Department of Energy by The University of California

2

0-8412-0565-5/80/47-130-013$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

14

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

develop cost competative processes for the conversion of biomass feedstocks to fuels and other energy intensive products. This objective can be accomplished by the direct combustion of biomass materials and the substitution of biomass derived fuels and chemical feedstocks for those produced from conventional sources. Thermochemical conversion processes employ elevated temperatures to convert biomass materials to more useful energy forms. Examples include:

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

• Combustion to produce heat, steam, electricity, or combinations of these; • Pyrolysis to produce gases (low or intermediate BTU), pyrolytic liquids and char; •Gasification to produce low or intermediate BTU fuel gas; •Gasification to produce synthesis gas for the production of synthetic natural gas (SNG), ammonia, methanol, alcohol fuels, or Fischer-Tropsch liquids and gasoline via catalytic processes; and •Direct liquefaction to produce heavy oils, or with upgrading, lighter boiling liquid products such as distillates, light fuel oils and gasoline. Program Organization and Implementation Thermochemical conversion technology development activities sponsored by the Biomass Energy Systems Program can be divided into the following four categories: •Direct Liquefaction • Direct Combustion • Gasification •Indirect Liquefaction Via Synthesis Gas In the remainder of this paper we will briefly discuss individual projects in each of these catagories. Direct Combustion Systems. The direct combustion of biomass feedstocks is already widely practiced by several industries, especially the forest products industry. Many types of direct combustion equipment are commercially available for this purpose. New developments in direct combustion technology are expected to have a near term impact on energy supplies through the utilization

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

2.

SCHIEFELBEIN ET AL.

Overview of DOE-Funded R&D

15

forest residues and other readily available biomass feedstocks. Therefore, direct combustion technology development projects being funded by the Biomass Energy Systems Program are categorized as near term systems development activities. Two projects are currently being funded by the Biomass Energy Systems Program in the area of direct combustion technology. These projects are shown in the organization chart illustrated in Figure 1. The Aerospace Research Corporation project is developing a wood fueled combustor which can be directly retrofitted to existing oil or gas fired boilers. Direct retrofit requires that heat release rates equivalent to those obtained when firing oil or gas be obtained in the wood fired combustor. Heat release rates on this order have been achieved when firing wood by preheating the combustion air to 800-1000°F. The Wheelabrator Cleanfuel Corporation project is a demonstration of large scale co-generation based on wood feedstock. The scope of this project includes the design of the plant plus additional tasks such as preparation of an environmental impact statement, demonstration of large tree harvesting equipment and determination of feedstock availability for a large facility. The draft final report for this project has been completed and is currently being reviewed. Gasification-Indirect Liquefaction Systems. Development of biomass direct liquefaction, medium BTU gasification and indirect liquefaction technologies are catagorized as mid term development activities because these technologies are not expected to have a substantial impact on U. S. energy supplies for 10 to 20 years. Biomass gasification technologies can be divided into processes which produce a low BTU gas and those which produce a medium BTU gas. Low BTU gasification technology is commercially available for most types of biomass feedstocks and can be expected to have an impact on energy supplies by 1985. Many of these commercial processes are based on low BTU coal gasification technologies and the gas produced can best be used as fuel for supplying process heat, process steam or for electrical power generation. The versatility of low BTU gas is limited and its use is subject to the following limitations: •Substitution of low BTU gas for natural gas as a boiler fuel usually requires boiler derating and/or extensive retrofit modifications. •The low heating value of the gas usually requires that it be consumed on or near the production site in a close coupled process. •The high nitrogen content of low BTU gas precludes its use as a synthesis gas for most chemical commodities which can be produced from synthesis gas.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

DOE BIOMASS ENERGY SYSTEMS PROGRAM

PACIFIC N O R T H W E S T L A B S TECHNICAL OPERATIONS

G A S , OIL L A R G E BOILER RETROFIT P R O J E C T

AEROSPACE RESEARCH

Figure 1.

BCL TECHNICAL MANAGEMENT ASSISTANCE

ADVANCED CO-GENERATION SYSTEM D E S I G N E D FOR W O O D

WHEELABRATOR CLEANFUEL CORPORATION

Direct combustion development activities (near term)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

2.

SCHIEFELBEIN ET AL.

Overview of DOE-Funded R&D

17

Medium BTU gas (MBG) offers the following advantages over low BTU gas: •Boiler derating is usually less severe when substituting MBG for natural gas than when substituting low BTU gas for natural gas and may not even be required in some cases; •MBG can be transported moderate distances by pipeline at a reasonable cost;

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

•MBG is required for the synthesis of derived fuels and most chemical feedstocks and commodities which can be produced from synthesis gas. The versatility of MBG is illustrated in Figure 2. The major disadvantage of MBG is that its production by conventional means requires the use of an oxygen blown gasifier which is expensive to operate due to the cost of the oxygen. If the thermochemical conversion of biomass is to achieve its maximum potential for supplementing existing U. S. energy supplies in the mid term, the following two points will have to be addressed. •Barring serious coal production constraints, biomass conversion will have to be economically and environmentally competitive with synthetic fuels produced from coal. •Thermochemical biomass conversion must have an impact on the availability of liquid fuels and chemical feedstock supplies as well as supplementing gas for heating purposes. Biomass has two potential advantages over coal. First, biomass is a renewable resource and coal is not. Second, and more important from a thermochemical conversion standpoint, biomass is more reactive than coal. It has the potential for gasification at lower temperatures, without the addition of oxygen, to produce medium BTU gas. Several of the gasification process development activities sponsored by the Biomass Energy Systems Program are attempting to exploit this advantage. These development activities are also directed toward improving the competitiveness of biomass gasification through the use of catalysts and unique gasification reactors to produce, directly, specific synthesis gases for the production of SNG, methanol or methyl fuels, ammonia and hydrogen. Success in these efforts could eliminate the necessity for external water gas shift or methanation reactors when producing these commodities. The potential elimination of the oxygen requirement and the water gas shift step are indicated by the dashed lines in Figure 2.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch002

18

THERMAL

CONVERSION OF SOLID WASTES AND BIOMASS

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In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

s § ^ i l l

6.

BOMBERGER

AND JONES

Modular Incinerators for Energy Recovery

71

Technical Analysis

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

At the time of the study, most of the i n s t a l l a t i o n s i n the United States burning municipal refuse i n modular i n c i n e r a t o r s had been operating f o r only a few years or l e s s . Most i n s t a l l a t i o n s did not have heat recovery. I t i s d i f f i c u l t to analyze a t e c h n o l ogy with so l i t t l e operating experience. I t i s impossible to determine u n i t l i f e t i m e s and maintenance requirements because no u n i t has operated f o r much of i t s expected l i f e t i m e . However, based on s i t e v i s i t s , i t i s p o s s i b l e to make some observations : •

The technology i s s t i l l developing. The u n i t s s u p p l i e d by the major s u p p l i e r s are being improved with each i n s t a l l a t i o n and some f i e l d m o d i f i c a t i o n s are o f t e n r e quired.



Some u n i t s are experiencing problems with s l a g



Slag removal sometimes r e q u i r e s a j a c k hammer, which erodes the r e f r a c t o r y .



Heat recovery u n i t s (water tube b o i l e r s ) have experienced problems with c o r r o s i o n and buildup of soot on the heat transfer surfaces.



A high l e v e l of operator s k i l l i s d e s i r a b l e . Temperature and burning c o n t r o l i s achieved i n l a r g e measure by the loading s t r a t e g y . Units are not designed to provide the loading operator any d i r e c t i n f o r m a t i o n regarding the flame or stack c o n d i t i o n . This i n f o r m a t i o n i s provided to the operator by the s h i f t s u p e r v i s o r , who has to make p e r i o d i c i n s p e c t i o n s that i n v o l v e opening an access door to the combustion chamber.



Units with continuous ash removal are not producing a completely i n o r g a n i c , n o n - p u t r e s c i b l e ash.



Even on r e l a t i v e l y new u n i t s , r e f r a c t o r y damage and evidence of overheating are v i s i b l e .



Based on a l i m i t e d amount of t e s t data, i t appears that the u n i t s may not be able to meet s p e c i f i c l o c a l a i r p o l l u t i o n codes. P a r t i c u l a t e stack plumes are v i s i b l e , espec i a l l y when o p e r a t i o n r e q u i r e s an a c c e l e r a t e d l o a d i n g schedule to lower primary combustion temperatures.

formation.

As a r e s u l t o f these observations, s e v e r a l assumptions were made f o r use i n the economic a n a l y s i s : U n i t s operate a t 90% of t h e i r r a t e d c a p a c i t y .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

72

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS



A i r p o l l u t i o n c o n t r o l devices may be r e q u i r e d . Economics should be developed with and without a i r p o l l u t i o n c o n t r o l .



P o r t i o n s of the i n c i n e r a t o r f a c i l i t y w i l l have to be placed a f t e r 12-13 years of o p e r a t i o n .

re­

Economic A n a l y s i s The economics of modular i n c i n e r a t o r s was developed f o r a h y p o t h e t i c a l l o c a t i o n burning refuse t y p i c a l of Naval i n s t a l l a ­ tions. The modular u n i t s were assumed to be t y p i c a l two-stage combustion d e v i c e s . I t was assumed that some source s e p a r a t i o n would be p r a c t i c e d to remove most of the g l a s s and bulky items. The r e s u l t i n g refuse that was a c t u a l l y burned had a heating value of 1 1 . 7 2 χ 1 0 j o u l e / m e t r i c ton ( 1 0 . 1 m i l l i o n Btu/ton). This r e f ­ use i s somewhat d i f f e r e n t from a t y p i c a l municipal r e f u s e , but the economics are not s e n s i t i v e to the d i f f e r e n c e s . An important design assumption was that refuse would be c o l ­ l e c t e d 5 days a week f o r 5 2 weeks a year ( 2 6 0 days a year) but because of maintenance and downtime, refuse could be burned only 2 3 0 days a year. It was a l s o assumed that u n i t s could only burn refuse at 9 0 7 o of t h e i r rated design c a p a c i t y . Three b a s i c cases were considered: plants with rated c a p a c i t i e s of 1 8 . 2 , 4 5 . 5 , and 9 0 . 9 metric tons/day, r e s p e c t i v e l y . Table I I d e t a i l s the a c t u a l d a i l y and annual c a p a c i t i e s of the i n s t a l l a t i o n s . The small u n i t was evaluated f o r one- and t w o - s h i f t per day o p e r a t i o n with pe­ r i o d i c ash removal whereas the l a r g e r plants were assumed to operate three s h i f t s per day f o r f i v e days a week with continuous ash removal. In cases where heat recovery was p r a c t i c e d , the o v e r a l l thermal e f f i c i e n c y was assumed to be 5 0 7 . The major heat l o s s was the hot f l u e gases, but other l o s s e s i n c l u d e d s e n s i b l e heat plus the unburned f i x e d carbon i n the ash, and r a d i a t i o n l o s s e s from the i n c i n e r a t o r u n i t . Figure 1 shows a summary of the mass and energy balances f o r a metric ton refuse input to the i n c i n e ­ rator. Some a u x i l i a r y f u e l consumption was assumed (based on d i s ­ cussions with system designers and the a c t u a l operating experience of users) f o r s t a r t u p , temperature c o n t r o l , and p i l o t burners i n the secondary combustion chambers. Table I I I summarizes the b a s i c p l a n t operating requirements i n terms of u t i l i t i e s , manpower, and ash d i s p o s a l . E l e c t r i c power consumption f i g u r e s are provided f o r three d i f f e r e n t system designs: simple i n c i n e r a t i o n without heat recovery or an a i r p o l l u t i o n con­ t r o l device, i n c i n e r a t i o n with heat recovery but no a i r p o l l u t i o n c o n t r o l device, and i n c i n e r a t i o n with both heat recovery and a i r p o l l u t i o n c o n t r o l (stack gases f i l t e r e d through a baghouse). Table IV summarizes the economic bases. 1 8 . 2 - M e t r i c - T o n Incinerator For the small i n s t a l l a t i o n , four b a s i c cases were considered. These are d e t a i l e d i n Table V along with the c a p i t a l expenditures r e q u i r e d over the 2 5 - y e a r l i f e t i m e assumed f o r the p r o j e c t . A i r

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

9

o

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

6.

BOMBERGER AND JONES

Modular Incinerators for Energy Recovery

Table

73

II

INCINERATION PLANT CAPACITIES CONSIDERED FOR ECONOMIC ANALYSIS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

Plant Design M e t r i c Tons/Day

Capacity Tons/Day

18.2

(20)

16.4

45.5

(50)

40.9

9,408

(100)

81.8

18,816

90.9

Based

Q u a n t i t i e s o f R e f u s e Burned ^ M e t r i c Tons/Day M e t r i c Tons/Year

on b u r n i n g

Operating S h i f t s Per Day

3,763

230 days p e r y e a r .

Overall Heat Efficiency Is

1.85 Χ 1 0

9

joule

9

13.5 kg Fuel Oil 0.62 Χ 1 0 j o u l e "

Flue Gas 208.6 m / s e c " at 260° C 4.23 Χ 1 0 joule 3

9

15% Heat Loss

1000 kg Refuse 11.72 Χ 1 0 j o u l e "

50%

Two-State Incinerator

Steam " 6.17 Χ 1 0

9

joule

9

100% Excess A i r 8055 kg Dry A i r 35 kg Water

Figure 1.

111.7 kg Ash 0.09 Χ 1 0 joule 9

Mass and energy balance for an incinerator with heat recovery

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

74

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table I I I

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

SUMMARY OF PLANT OPERATING REQUIREMENTS

Amount

Required

9

Auxiliary fuel

0 . 5 8 χ 1 0 j o u l e / m e t r i c ton of r e f u s e burned ( 5 7 o of r e f u s e heating value)

E l e c t r i c power

1 1 kWh/metric ton ( 1 0 kWh/ton) 2 2 kWh/metric ton ( 2 0 kWh/ton) 3 3 kWh/metric ton ( 3 0 kWh/ton)

Operating labor

2 men/shift

Ash d i s p o s a l

0 . 1 1 1 7

Heat recovery b o i l e r

HRB HRB, PCD

dry m e t r i c ton/metric ton refuse burned

included i n i n s t a l l a t i o n .

Particulate collection

device included i n i n s t a l l a t i o n .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

6.

BOMBERGER AND JONES

Modular Incinerators for Energy Recovery

75

Table IV

ECONOMIC BASES

Cost

Mid-1978

Discount Rate

107o

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

Economic L i f e

Ash

Permanent b u i l d i n g s

25

I n c i n e r a t o r system

2 5 years (major maintenance and some replacement required halfway through l i f e . )

Heat recovery

boilers

25

years

Air pollution control devices

25

years

Disposal

$11.82/dry

Maintenance M a t e r i a l s Purchased

years

2 . 5 7 o

metric

ton ( i n l a n d f i l l )

of the t o t a l plant investment

Utilities

Water

$0.13/m

($0.60/1000 g a l )

E l e c t r i c power

3.0c/kWh

Fuel o i l

$2.37/10

9

j o u l e ($2.50/million Btu)

Labor Operating

labor

$6.0/hr

Supervision

207o

Maintenance labor

2 . 5 7 o

Administrative labor

207o of labor charges f o r operation, maintenance, and s u p e r v i s i o n

P a y r o l l burden

& support

307o

of operating

labor

of the t o t a l plant investment

of t o t a l d i r e c t labor costs

For the p a r t i c u l a t e c o l l e c t i o n system, 10% was assumed to cover bag replacement.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

76

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table V

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

ESTIMATED INVESTMENT COSTS FOR 18.2 METRIC TON (20 TONS/DAY) MODULAR INCINERATION SYSTEM

Case

Estimated Year 0

Investment Costs Year 13

1 shift/day-no heat recovery

$385,000

$190,000

2 shifts/day-no heat recovery

$230,000

$120,000

1 shift/day-heat recovery

$550,000

$190,000

2 shifts/day-heat recovery

$325,000

$120,000

"Replacement of a p o r t i o n of the i n c i n e r a t o r

facility.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

6.

BOMBERGER

A N D JONES

Modular Incinerators for Energy Recovery

11

p o l l u t i o n c o n t r o l (scrubber, f a b r i c f i l t e r , or p r e c i p i t a t o r ) i s not i n c l u d e d . Table VI summarizes the operating costs f o r the systems. For the heat recovery cases, i t was assumed that when the u n i t was s t a r t e d every day, an hour would be r e q u i r e d to remove ash and to heat the u n i t up to working temperature. Steam would be generated f o r 7 hours i n the o n e - s h i f t case and f o r 1 5 hours i n the two-shift case. Four hours of burndown on automatic c o n t r o l would complete the d a i l y c y c l e . I t was assumed that t h i s meant that 7 / 1 1 of the refuse heat content was a v a i l a b l e f o r conversion to steam i n the o n e - s h i f t case, and 1 5 / 1 9 was a v a i l a b l e i n the two-shift case. Note that labor charges represent from approximately one-half to two-thirds of the t o t a l operating costs ( i n c l u d i n g c a p i t a l charges) f o r the four cases considered. Without heat recovery included i n a 1 8 . 2 - m e t r i c - t o n / d a y plant, i t appears from the data presented i n Table VI that a o n e - s h i f t / day operation would be p r e f e r a b l e t o a two-shift/day operation. Figure 2 shows that f o r a plant with heat recovery, the d e c i s i o n between choosing a one- or two-shift o p e r a t i o n i s i n f l u e n c e d by the value of the steam produced. I f the steam has a value of more than $ 2 / 1 0 j o u l e , the two-shift operation i s more a t t r a c t i v e . Almost 2 5 7 o more steam can be produced from a two-shift operation than from a o n e - s h i f t operation. The a d d i t i o n of a p a r t i c u l a t e c o n t r o l system increases the c a p i t a l cost by approximately $ 8 0 , 0 0 0 and increases the operating cost by $ 7 / m e t r i c ton . 9

Large Modular

Installation

The 4 5 and 9 0 metric ton/day f a c i l i t i e s were designed to i n clude two and four i n d i v i d u a l modules, r e s p e c t i v e l y . The modules were operated three s h i f t s / d a y , f i v e days a week and included automatic ash removal. Heat recovery was included i n a l l of the cases considered. Table VII d e t a i l s the c a p i t a l costs f o r these u n i t s , both without a p a r t i c u l a t e c o n t r o l and with f a b r i c f i l t e r s f o r p a r t i c u l a t e c o n t r o l . Table V I I I summarizes the operating costs f o r the i n s t a l l a t i o n s . For both s i z e s of i n s t a l l a t i o n , part i c u l a t e c o n t r o l adds $ 4 / m e t r i c ton to the operating c o s t . Figure 3 i l l u s t r a t e s the e f f e c t of steam value on the operating c o s t s . The 9 0 - m e t r i c - t o n i n s t a l l a t i o n i s s i g n i f i c a n t l y cheaper to operate on a per ton b a s i s than the 4 5 - m e t r i e - t o n i n s t a l l a t i o n because the labor costs are almost equal f o r the two s i z e s . The economic a n a l y s i s i n d i c a t e s that operating costs are sens i t i v e to the value of the steam generated. For example, i f steam were worth $ 4 - 5 / 1 0 ^ j o u l e , the 9 0 - m e t r i c - t o n i n s t a l l a t i o n could operate at the break even p o i n t with only a small t i p p i n g f e e . At steam values near $ 2 / 1 0 ^ j o u l e , the 9 0 - m e t r i c - t o n i n s t a l l a t i o n would have to charge a t i p p i n g fee of almost $ 2 0 / m e t r i c ton to break even.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

C a p i t a l Cost

T o t a l annual cost ($/metric ton)

C a p i t a l charges

Utilities

Labor

Annual Operating Cost M a t e r i a l s and s u p p l i e s and ash d i s p o s a l

Initial

159,400 ($42.3)

170,200 ($45.2)

66,400 (39%)

29,200 (21%)

48,600 (35%)

139,300 ($37)

7,700 (4%)

6,400 (4%)

6,400 (5%)

77,400 (46%)

18,700 (11%)

$550,000

111,800 (68%)

12,000 (7%)

$230,000

69,700 (50%)

14,600 (10%)

$385,000

173,700 ($46.2)

39,200 (23%)

7,700 (4%)

113,700 (65%)

13,100 (8%)

$325,000

Heat Recovery No P a r t i c u l a t e C o l l e c t i o n 2 Shifts 1 Shift 5 days/week 5 days/week

i s 18.2 metric ton/day (20 ton/day)

No Heat Recovery No P a r t i c u l a t e C o l l e c t i o n 1 Shift 2 Shifts 5 days/week 5 days/week

Design capacity

COSTS OF SMALL MODULAR REFUSE INCINERATION SYSTEM

Table VI

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

>

Ο

Ο

>

Η W

00

$

Ο

Ο

> r ο ο < m *> δ

H X m

00

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

BOMBERGER

Figure 2.

AND

Modular Incinerators for Energy Recovery

JONES

Economics of operating an 18.2-metric ton/day (20 tons/day) refuse incinerator

Table VII

ESTIMATED INVESTMENT COSTS FOR LARGE MODULAR REFUSE INCINERATION SYSTEMS WITH HEAT RECOVERY

System C a p a c i t y (metric tons/day)

45 5 (no p a r t i c u l a t e 45 5 ( w i t h f a b r i c

90.9

(no

control)

filters)

particulate

90 9 ( w i t h f a b r i c

Y e a r

control)

filters)

965 000

1,064 000

4 000

18

13

6

0

*

4 ooo"

1,450 000

7 ,οοο"

1,650 000

7

*

280 ooo '

4 ooo"

280 ,000*

4 ooo"

1

420 ,000 1

f

420 ooo "

7

*

,000 7 ,000"

,000

Replacement o f r e f r a c t o r y "^Replacement o f p o r t i o n s

of the i n c i n e r a t o r

facility.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Capital

Cost

Cost

charges

($/metric ton)

Total

Capital

Utilities

Labor (3 s h i f t s / d a y )

Materials supplies and ash d i s p o s a l

Annual Operating

Initial

VIII

173,700 (36%)

126,400 (31%)

115,500 (32%)

($39)

$365,800

44,500 (8%) 38,300 (7%)

22,200 (6%)

19,100 (5%)

$560,800 ($30)

$486,600 ($26)

$402,400 ($43)

195,700 (35%)

239,500 (43%) 231,500 (44%)

207,300 (52%)

194,600 (53%)

81,100 (14%)

$1,650,000

61,100 (13%)

$1,450,000

46,500 (11%)

$1,064,000

90.9 M e t r i c Tons/Day (100 tons/day) I n s t a l l e d Capacity P a r t i c u l a t e Control

36,600 (10%)

$965,000

45.5 Metric Tons/Day (50 tons/day) I n s t a l l e d Capacity P a r t i c u l a t e Control

COST OF LARGE MODULAR REFUSE INCINERATOR SYSTEMS

Table

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

>

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Η W οο

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JONES

Modular Incinerators for Energy Recovery

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

BOMBERGER

Figure 3. Economics of operating large modular refuse incinerators with heat recovery and particulate control

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

82

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Summary

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

The economic analysis indicates that the modular incinerators are expensive to operate. Even with steam values of $5/10^ joule, the very small units are likely to need tipping charges of $20/ metric ton to break even. Larger installations can do much better and, at steam values of $5/10^ joule, require tipping fees of only $0-10/metric ton. The principal cause of the high cost found by this analysis is the labor component. Labor represents over 50% of the operating costs for the very small units and only f a l l s to 407o of the total operating cost at the 90-metric-ton/day size range. Total operating costs could be reduced by using less expensive labor and may actually be lower in some parts of the country where wage rates are low. Acknowledgments This paper is based principally on work done by SRI Interna­ tional and sponsored by the U.S. Navy, C i v i l Engineering Labora­ tory, Port Hueneme, California under Contract No. NOO123-78-C-0868. The paper has been adapted from an oral presentation made by Dr. Bomberger of SRI to the National Conference on Environmental Engineering, American Society of C i v i l Engineers, San Francisco, California, July 1979. LITERATURE CITED 1.

Jones, J. L . , and D. C. Bomberger, J r . , ''Mass Burning of Refuse in Shop Fabricated Incinerators," draft report appendix pre­ pared by SRI International for the Navy C i v i l Engineering Laboratory, Port Hueneme, CA (September 1978).

2.

Hathaway, S. Α . , "Recovery of Energy from Solid Waste at Army Installations," U.S. Army Construction Engineering Research Laboratory, Champaign, IL, Technical Manuscript E-118 (August 1977).

3.

Hathaway, S. Α . , and R. J. Dealy, "Technology Evaluation of Army-Scale Waste-to-Energy Systems," U.S. Army Construction Engineering Research Laboratory, Champaign, IL. Interim Report E-110 (July 1977), available through NTIS, AD/A-42 578.

4.

Mitchell, G. L . , et al., "Small Scale and Low Technology Resource Recovery Study," report prepared by SCS Engineers for the U.S. Environmental Protection Agency under Contract No. 68-01-2653 (January 1979).

5.

Anguil, G. Η., "Using Solid Waste as a F u e l , " Plant Engineer­ ing, (November 13, 1975).

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch006

6.

BOMBERGER AND JONES

Modular Incinerators for Energy Recovery 83

6.

M i l l e r , B. U . , "Using Solid Waste as a F u e l , " Plant Engineer­ ing (December 11, 1975).

7.

Erlandsson, Κ. I., "Using Solid Waste as a F u e l , " Plant Engineering (December 11, 1975).

8.

"Companies Mine Energy from Their Trash," Business Week (August 2, 1976).

9.

"Burning Waste for Heat in Horicon, Wisconsin," Solid Wastes Management (June 1976).

10.

"Paper M i l l Incinerator Solves Town Refuse Problem," Com­ bustion (February 1977).

11.

"Evaluation of Small Modular Incinerators in Municipal Plants," report prepared by Ross Hofmann Associates for the U.S. Envi­ ronmental Protection Agency, EPA Report SW-1130 (1976).

12.

Hofmann, R. E . , "Controlled-Air Incineration--Key to Prac­ t i c a l Production of Energy from Wastes," Public Works, 107(9): 72-79, 136, 138 (September 1976).

13.

"City Finds Disposal Solution, N. L i t t l e Rock Picks Modular Incinerator for Steam and Income," Solid Wastes Management (March 1978).

14.

Hart, C. Η . , "Modular Incineration Units: Hot New Disposal Equipment for Municipalities," Solid Wastes Management (July 1978).

15.

Statistical Abstract of the United States, 1973, U.S. Depart­ ment of Commerce (July 1973).

16.

Kleinhenz, Ν . , and H. G. Rigo, "Operational Testing of a Controlled Air Incinerator with Automatic Ash Handling," report prepared by Systems Technology Corp. for the Navy C i v i l Engineering Laboratory, Port Hueneme, CA (November 1976).

17.

Hathaway, S. Α . , J. S. L i n , and A. N. Collishaw, "Field Evaluation of the Modular Augered-Bed Heat-Recovery Solid Waste Incinerator," U.S. Army Construction Engineering Research Laboratory, Champaign, IL, Technical Report E-128 (May 1928).

RECEIVED December 3, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

7 Energy Recovery from Wood Residues by Fluidized-Bed Combustion

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

J. W. STALLINGS1 Energy Incorporated, P. O. Box 736, Idaho Falls, ID 83401 MIKE OSWALD Energy Products of Idaho, P. O. Box 153, Coeur d'Alene, ID 83814 Dramatic increases in costs of energy during the decade of the seventies have provided the economic incentive for the forest products industry to recover energy from their wood residues rather than purchasing fossil fuels. The Fluid Flame® System was designed by Energy Incorporated and its subsidiary, Energy Products of Idaho, to accomplish this task utilizing fluidized-bed technology. Thirty-one of these units are now in commercial operation burning various types of wood residues and recovering energy in the form of steam, hot gases, or a combination of the two. The total installed output is equivalent to 1.62 x 10 1 2 J/hr (1,540 MM Btu/hr) of thermal energy or 559,000 kg/hr (1,232,000 lb/hr) of steam. Applications have varied according to the energy needs of the individual customer. In steam production, fire-tube boilers are generally employed for systems providing less than 13,600 kg/hr (30,000 lb/hr) of steam, while water-tube boilers are used for larger installations. Either steam or hot gases from the Fluid Flame® systems have been used in plywood dryers, tube dryers, and both direct and indirect hot-gas dry kilns. In one installation, a steam turbine generates up to 2 megawatts of electricity on demand. This amount is equivalent to fifty percent of the total energy available from the facility. Fluidized-Bed Technology The term fluidized bed refers to a layer of sand-like particles suspended by the upward flow of a gas stream. A point of equilibrium is reached at which the upward drag force of the gas is equal to downward force of the weight of the particles. The fluidized gas-solid mixture exhibits a high degree of turbulence similar to boiling water. Additional fluidizing air increases the circulation of the particles and further expands the height of the bed. Fluidized-bed technology is ideally suited to energy recovery from wood wastes for a number of reasons. The high heat 'Current address: SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025 0-8412-0565-5/80/47-130-085$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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t r a n s f e r r a t e s and high s u r f a c e areas per u n i t volume ensure v i r t u a l l y complete combustion w i t h i n the burner. The l a r g e amount of energy stored i n the hot bed m a t e r i a l enables combust i o n of f u e l s with r e l a t i v e l y high moisture contents. The abras i v e a c t i o n of the turbulent bed m a t e r i a l continuously exposes unburned surface area of the f u e l to the intense heat and the oxygen supply. Thus, a wide s i z e d i s t r i b u t i o n of f u e l can be fed i n t o the burner without l o s s i n combustion e f f i c i e n c y .

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

Wood residues c u r r e n t l y burned i n commercial u n i t s i n c l u d e plywood t r i m and sander dust, wood shavings, whole l o g c h i p s , bark, and l o g yard wastes. Coal or a g r i c u l t u r a l residues can a l s o be burned i n the system e i t h e r separately or i n combination with other f u e l s . System D e s c r i p t i o n A schematic diagram of a t y p i c a l system f o r steam product i o n , i n c l u d i n g approximate mass and energy balances as w e l l as c a p i t a l and operating c o s t s , appears i n F i g u r e 1. A f t e r screening to remove p a r t i c l e s l a r g e r than a threei n c h nominal s i z e , the wood residues are t r a n s f e r r e d i n t o a live-bottom storage hopper by means of a pneumatic conveyance system. Hopper s i z e s vary with the amount of storage d e s i r e d . Those manufactured by Energy Products of Idaho employ h y d r a u l i c d r i v e s to provide adequate torque and power to a sweep auger. From the bottom of the storage b i n hopper, a screw conveyor t r a n s f e r s the wood residues to a metering b i n . The r a t e of discharge from the storage b i n hopper to the metering b i n i s c o n t r o l l e d by l e v e l i n d i c a t o r s on the s i d e s of the metering b i n . The rate of f u e l fed to the burners from the metering b i n i s c o n t r o l l e d by burner demand. The feed p i p e enters the combustion c e l l from the top and protrudes a t an angle from four to eight f e e t i n t o the vapor space to i n s u r e even d i s t r i b u t i o n of the feed on the bed. The combustion c e l l i s f a b r i c a t e d out of carbon s t e e l and i s l i n e d with high-temperature block i n s u l a t i o n covered by a l a y e r of c a s t a b l e r e f r a c t o r y . The o r i g i n a l combustion systems employed sand as a bed m a t e r i a l . However, excessive a t t r i t i o n n e c e s s i t a t e d the search f o r m a t e r i a l s which were more thermally s t a b l e and chemically i n e r t and thus would not e l u t r i a t e from the bed. C u r r e n t l y , two p r o p r i e t a r y bed m a t e r i a l s are employed. One i s a n a t u r a l l y o c c u r r i n g s t a b l e m i n e r a l , and the second i s a raw m a t e r i a l used i n the production of f i r e b r i c k s . With these improved bed m a t e r i a l s , a t t r i t i o n i s minimal. In f a c t , p a r t i c u l a t e from the wood residues

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

6

4

1 0 Kg/hr (11 SHORT T O N S / H R ) AS RECEIVED WOOD RESIDUES AT 5 0 % H_ 3 . 3 7 X 1 0 J/Kg ( 3 , 6 0 0 B t u / l b ) USEFUL ENERGY

Figure 1.

EFFICIENCY = 7 5 % CAPITAL COST * $ 1 . 5 MILLION INSTALLED ( 1 9 7 9 U.S. D O L L A R S ) OPERATING COST « $ 5 0 , 0 0 0 - 1 0 0 , 0 0 0 P E R Y E A R (INCLUDES BED MAKEUP, REFRACTORY REPAIR, POWER, CHEMICALS, AND EQUIPMENT MAINTENANCE) OPERATING T I M E « 8 , 0 0 0 H R S / Y R (91 % )

Flow diagram

6

MULTICLONE

EXHAUST

7

FLUIDIZING AND COMBUSTION AIR B L O W E R

1 0

COMBUSTION C E L L 8 . 4 4 Χ 1 0 J/hr ( 8 . 0 0 Χ 1 0 B t u / h r ) USEFUL ENERGY

4

2.72 X 1 0 Kg/hr ( 6 0 , 0 0 0 lb/hr) 1.03 X 1 0 Pa ( 1 5 0 p s i a ) SATURATED STEAM

T R A M P MATERIAL REMOVAL SYSTEM

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Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

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o f t e n b u i l d s up i n the bed and n e c e s s i t a t e s removal of p o r t i o n s of bed m a t e r i a l . G r i d p l a t e s were used i n the i n i t i a l u n i t s t o d i s t r i b u t e f l u i d i z i n g a i r to the system. However, the growing need f o r a tramp removal system and the excessive thermal s t r e s s on the p l a t e s l e d to the design of a manifold f o r a i r d i s t r i b u t i o n i n s t e a d of p l a t e s . An i n v e r t e d v i b r a t i n g cone below the m a n i f o l d was i n c l u d e d to g r a d u a l l y remove bed m a t e r i a l from the system i n order to screen o f f l a r g e pieces of i n o r g a n i c s , such as rocks and stones. The screened bed m a t e r i a l i s then r e i n j e c t e d back i n t o the burner. In a f u r t h e r improvement of t h i s design, a double s t a t i c cone assembly u t i l i z i n g g r a v i t y flow has been i n s t a l l e d to cut costs and maintenance. This removal system was designed to allow tramp m a t e r i a l up to 10.2 cm (4 i n . ) i n cross s e c t i o n to be removed from the combustion c e l l without shutdown. Larger pieces cannot f i t i n the spaces between the m a n i f o l d sections. The system described here uses hot combustion gases from a f l u i d i z e d - b e d combustion c e l l i n conjunction w i t h a package water-tube b o i l e r f o r steam production. The combustion gases are then r e l e a s e d to the atmosphere. More recent designs have employed v e n t u r i scrubbers f o r gas cleanup when necessary. However, the f i n a l d e c i s i o n on a gas cleanup method depends on the s p e c i f i c r e g u l a t i o n s f o r each l o c a t i o n . Some advantages of the r a d i a n t e f f e c t on heat t r a n s f e r can be gained by p l a c i n g the b o i l e r d i r e c t l y on top of the combustion cell. Burning takes place both i n the combustion c e l l and i n the boiler. This approach i s e f f e c t i v e with both f i r e - t u b e and water-tube b o i l e r s . The F l u i d F l a m e ® energy systems are designed to run thems e l v e s without the need f o r f u l l - t i m e operators. The system i s f u l l y automated and i s equipped w i t h annunciators to a l e r t operators when problems a r i s e . A number of e l e c t r i c a l process c o n t r o l l e r s a r e used to maintain constant temperatures i n the bed and i n the vapor space of the combustion c e l l i n order to prov i d e steam a t constant pressure. S i g n a l s from these c o n t r o l l e r s d i c t a t e the feed r a t e from the metering b i n and the amount of excess a i r f e d i n t o the system. The temperature i s c o n t r o l l e d i n order to maintain constant parameters throughout the system and to keep temperatures below the s l a g g i n g temperatures of the ash. Normal temperature v a r i a t i o n i s l e s s than +5C° (9F°), and the response time to process v a r i a t i o n s i s r a p i d . The maximum turn-down r a t i o f o r an operating system i s threeto-one. Operation i n an on-off mode can a l s o be employed to e f f e c t i v e l y increase t h i s r a t i o . Another approach i s the use of modular u n i t s . However, t h i s l a t t e r o p t i o n w i l l increase c a p i t a l costs considerably. The advantages of a f l u i d i z e d - b e d system over conventional systems are many. Wood residues with moisture contents as l a r g e as 63 percent can be burned without the need of a supplemental

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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A N D OSWALD

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Energy Recovery from Wood Residues

f u e l , other than during s t a r t u p . The absence o f grates removes a major maintenance problem, as does the use of an a i r d i s t r i b u t i o n system w i t h i n the f l u i d i z e d bed. The l a r g e heat s i n k i n the bed allows f o r automatic s t a r t u p a f t e r shutdowns of up to s i x t e e n hours. The o l d e s t F l u i d F l a m e ® system has been i n commercial opera­ t i o n f o r approximately s i x years. The o r i g i n a l r e f r a c t o r y i s s t i l l i n place but a new c o a t i n g was added a f t e r f i v e years. With improved techniques i n r e f r a c t o r y i n s t a l l a t i o n , systems which have not been i n o p e r a t i o n f o r f i v e years have a p r o j e c t e d r e f r a c t o r y l i f e t i m e of approximately ten years, assuming proper care and maintenance.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

System

Efficiency

The c a l c u l a t e d e f f i c i e n c y of the steam system as described here i s approximately 75 percent. This value i s derived by using the t o t a l u s e f u l energy of the f u e l as the energy i n p u t . The heat content of the wood i s approximately 1.9 χ 1 0 J/kg (8300 Btu/lb) on a dry b a s i s , which i s equivalent to 9.6 χ 1 0 J/kg (4100 Btu/lb) on a wet b a s i s . I f the assumption i s made that 1.2 χ 1 0 J (500 Btu) i s needed to b o i l o f f the water i n each pound of f u e l , the the energy l e f t i n the f u e l which can be used f o r steam production i s 8.4 χ 1 0 J/kg (3600 B t u / l b ) . V a r i a t i o n s i n e f f i c i e n c y a r e caused by d i f f e r e n c e s i n feedwater temperature and moisture content of the wood r e s i d u e s . The e f f i c i e n c y could be increased by employing the waste heat from the combustion gases to preheat e i t h e r the f l u i d i z i n g a i r o r the b o i l e r feedwater. Waste heat could a l s o be employed to p a r t i a l l y dry the f u e l . 9

6

6

6

System

Economics

Data f o r the payback p e r i o d i n years f o r the system described h e r e i n are presented i n F i g u r e 2. These r e s u l t s are f o r the 8.44 χ 1 0 J/hr (8.00 χ 1 0 Btu/hr) system and are based on r e ­ placement of n a t u r a l gas with wood r e s i d u e s . The cost of the n a t u r a l gas i s assumed to be $2.09/10 J ($2.20/10 Btu). These c a l c u l a t i o n s were made to show the payout p e r i o d i n terms of r e ­ placement of n a t u r a l gas. Labor and d e p r e c i a t i o n were not i n c l u d e d , and an operating cost of $100,000/year was assumed. F o r systems where the wood residues are owned by the operator, the payout p e r i o d has g e n e r a l l y been l e s s than two years f o r a twelve­ month operation. 1 0

7

9

Commercial

6

Facilities

Thirty-one f a c i l i t i e s are now i n commercial o p e r a t i o n . Figure 3 i n c l u d e s a map showing the l o c a t i o n s of these burners. The c a p a c i t i e s vary from 1.27 χ Ι Ο J / h r (1.2 χ 1 0 Btu/hr to 1 0

7

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

CONVERSION

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

PAY B A C K

OF

SOLID

WASTES

AND

BIOMASS

PERIOD

(YEARS) 9

Figure 2. Payback from biomass replacement of natural gas at $2.09/10 J {$2.20/10* Btu) for a system with a capacity of 8.44 χ 10 J/hr (8.00 χ 10 Btu/hr) 10

Figure 3.

Fluidflameenergy systems

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

7

7.

STALLiNGS A N D O S W A L D

Energy Recovery from Wood Residues

1 1

8

91

1.27 χ 1 0 J/hr (1.2 χ 1 0 Btu/hr). As the perceived market value of organic residues i n c r e a s e s , changes w i l l be made to the b a s i c system to increase e f f i c i e n c y . Further developments are a l s o planned to improve the o v e r a l l economics of the system. I f operated i n a s t a r v e d - a i r mode w i t h a f i r e box downstream from the combustion c e l l , c a p i t a l costs f o r the burner and b o i l e r per u n i t throughput can be decreased, and more advantage can be taken of the r a d i a n t e f f e c t s on heat t r a n s f e r . As the costs of energy continue to i n c r e a s e r e l a t i v e to the b a s i c p r i c e i n d i c e s , the economics of f l u i d i z e d - b e d combustion of biomass to recover energy w i l l continue to improve.

November 16, 1979.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch007

RECEIVED

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

8 Fluid-Bed Combustion of Solid Wastes ROBERT H. VANDER MOLEN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

Combustion Power Company, Inc., 1346 Willow Road, Menlo Park CA 94025

Solid waste disposal has traditionally been an economic cost to industry, institutions, and municipalities. Numerous disposal methods have been used with combustion, for purposes of volume reduction, i . e . , incineration, an acceptable method in limited applications. The current energy picture in the United States has resulted in many industries, institutions, and municipalities taking a new view of solid wastes; in many instances they are now seen as energy sources. One combustion approach which has received wide interest as a means of converting solid wastes to energy is the use of the fluidized bed combustor (FBC). The fluidized bed reactor is a relatively new approach to the design of high heat release combustors. The primary functions of the air-fluidized inert bed material are to promote dispersion of incoming solid fuel particles, heat them rapidly to ignition temperature, and to promote sufficient residence time for their complete combustion within the reactor. Secondary functions include the uniform heating of excess air, the generation of favorable conditions for residue removal, and the ability to reduce gaseous emissions by control of temperature or by use as a gas-solids reactor simultaneously with thermal conversion. The fluidized bed reactor greatly increases the burning rate of the refuse for three basic reasons: 1.

The rate of pyrolysis of the solid waste material is increased by direct contact with the hot inert bed material.

2.

The charred surface of the burning solid material is continuously abraded by the bed material, enhancing the rate of new char formation and the rate of char oxidation.

0-8412-0565-5/80/47-130-093$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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CONVERSION

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Gases in the bed are continuously mixed by the bed material, thus enhancing the flow of gases to and from the burning solid surface and enhancing the completeness and rate of gas phase combustion reaction.

A significant advantage of the fluidized bed reactor over conventional incinerators is its ability to reduce noxious gas emission and, finally, the fluidized bed is unique in its ability to efficiently consume low quality fuels. The relatively high inerts and moisture content of solid wastes pose no serious problem and require no associated additional devices for their removal. For over ten years Combustion Power Company has been conducting experimental programs and developing fluid bed systems for agencies of the Federal Government and for private industry and institutions. Many of these activities have involved systems for the combustion of solid waste materials. Discussed here will be three categories of programs, development of Municipal Solid Waste (MSW) fired fluid beds, development of wood waste fired fluid beds, and industrial installations. MSW development work began in 1967 with a program to convert waste directly into electrical energy by combustion in a pressurized fluid bed combustor (PFBC) and expansion of the hot gases through an industrial gas turbine. This work was funded entirely by the U.S. Environmental Protection Agency (EPA) until 1974 when the U.S. Department of Energy (DOE), then the Office of Coal Research, began funding tests on PFBC coal combustion. Currently, Combustion Power Company has a subcontract from Stanford University to conduct development tests on a CPC owned fluid bed boiler (FBB) using MSW as the sole fuel. Stanford has an EPA Research Grant to support this work and much of the Grant money came from the DOE's Office of Solar Energy and Conservation through an interagency transfer of funds. All of the wood waste fluid bed development work has been funded by the Weyerhaeuser Company or by CPC. This work began in 1973 when Weyerhaeuser paid for a feasibility study on the use of the PFBC to convert wood waste to electrical energy. In early 1974 a 100 hour wood burning test was conducted using the EPA's PFBC equipment. In 1975 CPC became a wholly owned subsidiary of Weyerhaeuser Co. and various research programs have been conducted to date using the FBC as a gas-solids reactor to suppress corrosion causing alkalai vapors and to develop proprietary fluid bed hardware. A current test program involves the use of wood wastes as fuel for the thermal degradation of sodium based pulp mill sludge. This research and development work on wood wastes has led to the design and construction of two large industrial fluid bed combustors. In one of these, a fluid bed is used for the generation of steam with a fuel that was previously suited only for landfill. Rocks and inerts are continuously removed from

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

8.

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MOLEN

Fluid-Bed Combustion

95

this combustor using a patented system. The second FBC is designed to use a variety of fuels as the source of energy to dry hog fuel for use in a high performance power boiler. Here the FBC burns green hog fuel, log yard debris, fly ash (char) from the boiler, and dried wood fines to produce a hot gas system for the wood dryer. The following sections discuss the above programs and applications in more detail.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

Municipal Solid Waste Programs CPU-400. In 1967 CPC began the development of an overall municipal solid waste management concept for the U.S. EPA known as the CPU-400 program. In 1970, construction began on an 82,000 kg/day pilot plant at CPC's development facilities in Menlo Park, California. The pilot plant consisted of four major subsystems; Figure 1 illustrates the interconnection of the solid waste processing and handling subsystem, the hot gas subsystem, and the turbo-electric subsystem, while the control system is both a part of each of the other three subsystems and it is also a separate subsystem in itself, causing the other subsystems to interact properly with one another and respond correctly to external commands. In preparation for the pilot plant design and testing, numerous tests were conducted in subscale fluid bed combustors to develop feed and gas cleanup hardware and to evaluate process conditions. The majority of these tests were accomplished using a 0.20 m FBC. Early testing of the pilot plant was conducted at atmospheric pressure conditons. Operation of the CPU-400 pilot plant on MSW at its design point of 4.5 atmospheres was short lived. After performing a series of initial checkout runs at high pressure and determining nominal performance on solid waste, an attempt was made to satisfy a two-hour test requirement before proceeding to longer tests. In this test, operating conditions were sufficiently stable that a slow, steady increase in compressor discharge pressure was apparent. A review of data logged in this and preceding tests indicated that the effective flow area in the compressor turbine had apparently been reduced. Pressure drops across other hot gas system components, including the power turbine just downstream of the compressor turbine, had not changed. Since surge margin had been reduced to levels which precluded further successful operation, the compressor turbine stator sections were removed for inspection and cleaning. The inspection revealed significant reduction of the nozzle area produced by hard deposits. The deposits were much thicker on the concave portions of first stage blades than on the second stage blades. The intervening first stage rotor 2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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96

Ci.

'S.

3

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blades were also inspected and showed somewhat lighter deposits uniformly distributed on concave surfaces. The lightest depo­ sition occurred on the second stage rotor blades. In order to identify the problem more precisely, testing was initiated to determine the characteristics of the deposits. Pilot plant tests were conducted on municipal solid waste fuel at inlet temperatures of 1010 K, 867 K, and 839 Κ and using aluminum-free fuel such as wood waste. Deposit analysis indi­ cates that the aluminum and glass are the primary elements involved in the deposit growth. While the MSW fired CPU-400 system has not evolved to a state of industrial application, much of the work accomplished in that program has been the foundation for other work both at CPC and elsewhere. During the CPU-400 program a laboratory was established to perform many of the required experiments on material samples drawn from the process operation. Laboratory samples and adjustments based on long term pilot plant mass balance measurements have yielded the following average weight distributions for the processed MSW during a 24hour and a 48-hour test period. Ash-free combustibles Moisture Inerts

0.489 0.351 0.160

During a 48-hour low pressure test, a series of 24 bomb calorimeter experiments in the laboratory on dried parallel samples produced an average higher heating value of 16,480 kJ/kg. Using an approximate ultimate analysis of C30H48O29 for the combustible fraction and converting to a lower heating value based on the combustibles only, a corresponding average value of 18,480 kJ/kg of combustibles is found. This result is in very good agreement with values determined by applying heat balance relations to observed pilot plant temperature and flow measurements. It also correlates well with expected values for cellulose-like material such as is approximated by the ^^ç^^ig formulation. The FBC in the CPU-400 was designed to operate under adiabatic conditions. That is, no energy was extracted from the FBC and thus the combustor ran at high excess air levels in order to maintain bed temperature control. Typical steady state operating characteristics of the FBC, using MSW having the described fuel properties, are shown on Table I. A set of instruments was installed for on-line concentration measurements of six specific constituents of the exhaust gas. Concentrations of the seventh constituent, HC1, were determined by laboratory titration of individual samples using the Volhard

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method. The gas sampling, conditioning, and distribution systems are integrated with the instruments and analog recorders in a mobile, rack-mounted complex.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

TABLE I PILOT PLANT OPERATING CHARACTERISTICS Qperating Characteristic

Low-Pressure 48-hr Test

Typical HighPressure Test

Solid waste feed rate Moisture Inerts

19 kg 38% 15%

45 kg 27% 18%

Combustor bed temperature

889 - 1000 Κ

967 - 989 Κ

Combustor freeboard temperature

1006 - 1089 Κ

1000 - 1028 Κ

Exhaust/turbine inlet temperature

1033 + 6 Κ

1006 +6 Κ

Superficial velocity

1.6 m/s

1.8 m/s

Combustion efficiency

99% +

99% +

Power generated

0

1000 + 100 kW

Measurements from the recent pilot plant test are presented in Table II. All instrument records were relatively steady and free from apparent anomalies considering the potential hetero­ geneous composition of the fuel form. The twenty-four discrete laboratory samples (two-hour intervals) and subsequent HCl analyses showed more variance from a low value of 84.5 ppm to a high of 256.9 ppm. TABLE II PILOT PLANT EMISSION DATA Constituent

Low Pressure

High Pressure

13.4%

16.1%

C0

5.8%

5.2%

CO

30 ppm

30 ppm

CH

0 ppm

2 ppm

N0

139 ppm

100 ppm

HCl

161 ppm

63 ppm

0

2

2

X

X

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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99

A 230 sq m solid waste receiving building was constructed on a 510 sq m pad to provide for the 82,000 kg/day throughput required during continuous operation of the pilot plant. The processing facility utilizes two vertical axis shredders of 56 kW and 75 kW in size. Facility tests have been conducted to insure the required throughput and a nominal rate of 4500 kg/hr has resulted. The air classifier typically drops out about 16 percent of the processed material while another 6 percent reduction results due to the moisture loss during the shredding operating. A total of 934,000 kg of municipal waste has been shredded, 481,000 kg in this processing facility. The shredded and air classified solid waste fuel form is a mixture whose visual appearance is homogeneous and dominated by identifiable oaper products. A typical kilogram of the material consists of 320 g of water, 440 g of ash-free combustibles, and 240 g of inerts (including ash). The latter two fractions are typically subdivided as seen in Figure 2. As would be expected, all of these values are subject to considerable variation. As an example, moisture content in the final fuel form ranges from 10 to 40 percent by weight depending upon the origin of raw material (e.g., residential or commercial sources), time of year, weather conditions, and municipal collection policies. SSWEP. In October of 1978 a program designated as the Stanford Solid Waste Energy Program (SSWEP) was initiated. CPC, under subcontract to Leland Stanford University, will conduct combustion tests, at low excess air to simulate boiler conditons. The main objective of the test program is to burn processed MSW in a fluidized-bed boiler environment to investigate combustion characteristics, heat transfer, corrosion and erosion, and control parameters. The tests, are being conducted in a CPCowned 0.7 sq m fluidized-bed combustor which has been reworked to incorporate water tubes for heat extraction in both the bed region and exhaust. Additional tubes will be air cooled to simulate boiler temperatures and to observe erosion and corrosion phenomena. Hetallographic examination will be made of these materials. The program plan is to accomplish 400 hours of testing consisting of two (2) 50-hour tests and one (1) 300-hour test. Material elutriated from the fluid bed will be recycled back to the bed in two (2) tests to investigate its effect on fouling. Offgases will be sampled for total particulate, particle distribution Op, C0 CO, HCl, CH , N0 , and S0 , for characterization of potential environmental impact. The two 50-hour tests were completed and a test report submitted to Stanford in early August 1978. These tests were conducted at various operating conditions to probe the expected boundaries of the operating envelope. Stable conditions were 2

X

X

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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AS-RECEIVED SOLID WASTE ) Combustibles -44.3% ) Moisture -31.5% J Inert/Ash -24.2%

LIGHT FRACTION ο Organic* (paper, plastic, fabric, wood, foodstuffs.

-66%

ο Inerts (glass, ston metal lids, ash)

-12%

WASTES

AND

BIOMASS

MOISTURE LOSS

HEAVY FRACTION •52 .% is Metals •52 .% 3 Glass 0.9% 3 Stone, Ceramic •07 .% •03 .% ) Otlier Metals •38 .%

AIR CLASSIFIER f

78% SURGEVESSEL

MRS (OPTIONAL)

80.8% COMBUSTOR ο Combustible 44.4% ο Moisture 24.4% ο Inert/Ash 12.0%

FERROUS METAL

AGGREGATES (glass, stone)

OTHER METALS

UNSORTED WASTE

—fr-j WASTE j

Figure 2. MSW processing facility materialsflowdiagram

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP SSWEP

TEST POINT

1/1 1/2 1/3 1/4 1/5 1/6 2/1 2/2 2/3 2/4 2/5

1124 1123 1147 1136 1150 1062 1026 1097 1143 1149 1089

Not recorded Calculated (Gas analysis sense line leaking) Orsat analysis

(1) (2) (3)

992 948 980 976 965 918 982 1029 1026 1016 1039

TEMPERATURES BED FREEBOARD Κ Κ

Notes:

2.5 3.0 2.7 12.9 23.6 22.9 3.5 2.5 2.0 1.2 1.5

FREEBOARD PRESSURE kPa

26.6 11.0 34.1 53.3 53.1 (1) 40.5 74 (2) 51 (2) 29 (2) 65.9 (3)

%

EXCESS AIR

2.2 1.8 1.9 1.6 1.6 1.6 2.1 2.0 1.5 1.2 1.3

SUPERFICIAL VELOCITY m/s

TABLE III SSWEP PARAMETRIC TEST RESULTS DATA SUMMARY

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96.3 95.6 90.6 96.2 97.4 97.0 96.9 97.5 97.9 87.0 97.5

COMBUSTION EFFICIENCY

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attained above an excess air level of approximately 40% and with a settled bed depth of over 1 m. Table III contains a summary of the eleven operating points attained during these two tests. The MSW processing facility built for the CPU-400 program was used to prepare the fuel for this test program also. Since the single feed line to the 0.7 sq m combustor is only 7.6 cm in diameter, the shredder choke bars were set to produce a finer material size. Also, during SSWEP #1, numerous feed line plugs resulted due to plastic lids of 7.6 cm diameter and larger. Subsequent modification of the air classifier air damper settings allowed the virtual elimination of these lids from the lightfraction carry over. Properties of the derived fuel are shown on Table IV. TABLE IV SSWEP PARAMETRIC TEST RESULTS MSW PROPERTIES (AS FIRED) AVERAGE Moisture Fraction (%) Ash Fraction(%) Volatile Fraction (%) Fixed Carbon Fraction (%) Higher Heating Value (kJ/kg) Sulfur (%). Chlorine (%)

2S.2 11.9 52.2 7.6 11,900 0.15 0.16

RANGE 15.9 8.2 44.1 4.7 11,900 0.120.12-

40.0 16.0 59.8 10.0 14,200 0.19 0.25

Wood Waste Programs CPU-400 Test. In August 1973 a short checkout test was conducted operating the CPU-400 pilot plant on waste wood. The results v/ere very encouraging and no turbine blade deposits or erosion was detected. In January and February 1974, a 100-hour demonstration test was run but in contrast to the previous test, turbine blade deposition occurred. For purposes of completion of the planned test, the problem was solved by incorporation of a turbine cleaning system based on periodic injection of milled walnut shells. Post test inspection revealed, however, that erosion was significant and other measures would be required for depend-able long duration operation. Studies indicated that the problem depends strongly on the alkalai/silica ratio of the wood content. Investigation showed that this ratio is species dependent and that a favorable ratio exist in Ponderosa pine bark (used in August 1973) but not in white f i r bark such as predominated in the 100-hour test. Table V shows pertinent data from this test. Work has continued, over the years, to obtain more information on the problem of alkalai vapor formation and on a means to suppress this formation. A new 0.5 sq m fluid bed was constructed and has been used to

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conduct well over 1000 hours of tests using various addi­ tives to encourage the suppression of condensible alkali vapors. The results have been encouraging but the details are proprietary

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

TABLE V CPU-400 WOOD TEST DATA Total wood burn time Average load Total wood consumes Average feed rate Average moisture Average heating value Average bed temperature Average freeboard temperature Average turbine inlet temperature S0 Λ N0 Test averages CO CH J 2

X

X

101 hours 905 kW (91,000 kWh) 254,000 kg 42.2 kg/mi η 42.6% (40.3 to 45.9) 19,360 kJ/kg (18,840 to 19,900) 1004 Κ 1074 Κ 991 Κ 0.0 0.113 g/MJ 45 ppm 5 ppm

In a test program currently underway, dried wood fines will be used as fuel for the thermal degradation of a sodium based pulp mill secondary sludge. Key questions to be answered are: What is the minimum temperature required to destroy odors? What is the maximum bed temperature allowable to avoid bed agglomeration and fusion? and, What are equili­ brium levels of sodium and calcium in the bed and their effects on process operation? These tests will be conducted using the 0.20 sq m FBC. Industrial Applications Boiler Application. At the Weyerhaeuser facility in Longview, Washington, a survey of potential fuels indicated that a major quantity of energy was available in the form of waste wood from their log sort and storage operation. This material consists of the bark, limbs, and log butts that are broken off during log yard operation. At the time of this survey, this material was being cleaned off the log decks and hauled off to landfill areas near Longview. Therefore, by using this materials as fuel, landfill costs could be reduced along with the reduction in power plant fuel costs. Weyerhaeuser developed the specification shown on Table VI for a combustor to utilize this energy resource.

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TABLE VI LONGVIEW FUEL SPECIFICATION SUMMARY Debris Flow Moisture (% wood) Combustible (kg/hr) Moisture (kg/hr) Inerts (kg/hr)

55 5,390 11,000 3,600

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

Fly Carbon (Char) 540 540

Combustible (kg/hr) Inerts (kg/hr) Total Fuel Flow (kg/hr)

21,000

Further, the specification required the handling of limbs and log butts up to 7.6 cm in diameter and to 0.91 m long. Also, the inerts could come in the form of rocks up to 20 cm maximum cross-section. CPC designed, built, and installed an FBC with special features to meet these specifications. The installation and schematic are pictured on Figure 3. The FBC specifications are shown on Table VII. TABLE VII LONGVIEW FBC SPECIFICATIONS Internal Gas Flow Area External Diameter Overall Height Bed Height Operating Exit Temperature Excess Air

35.4 m 907 cm 768 cm 61 cm 1260 Κ 65%

2

Debris fuel is fed to the combustor through a single above bed feed point by use of a conveyor. Fly carbon is pneu­ matically injected. To avoid defluidization caused by an accumulation of the large inerts, a patented rock removal system continuously clears the bed of high density, over­ sized solids. The Longview FBC encountered numerous difficulties during startup. During its first year of operation major changes were made to improve system relia­ bility. This combustor is now fully operational. Drying Application. A second industrial FBC system (Figure 4) has been designed and installed at Cosmopolis, Washington to provide hot gas to a rotary dryer; the dryer in turn provides dried wood fuel to a boiler that supplies steam for inplant power generation. Drying the fuel

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch008

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+4 FT. A M ) S( R A P M E T A L

Figure 3. View and schematic of FBC boiler installation

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106

Figure 4.

View and schematic of FBC hog fuel drying installation

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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allows operation of the existing boiler at rated conditions without auxiliary fuel such as o i l . This fluid bed combus­ tor can be operated on mill wastes, on a portion of the fuel being supplied to the dryer, or on secondary sludge, ι his unit is rated at 70 GJ/hr. Fluid bed burners are typically limited to a turndown ratio of three to one; this dryer system, however, has been designed for a turndown ratio of four to one, accomplished by zone control of the fluidizing combustion air. In this application, it is necessary to blend the FBC exhaust gas with recycled gas in order to reduce the gas temperature to the dryer. This blending is accomplished in the upper zone of the fluid bed unit in order to eliminate a separate blend chamber and to reduce the refractory requirements in the combustor. Figure 4 shows a view of this installation and its schematic. These industrial systems are demonstrating the versa­ tility of the fluid bed in using waste materials for fuel. Through such systems, it is possible to provide alternate sources of energy for mill operations. RECEIVED

November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

9 Energy Recovery from Municipal Solid Waste and Sewage Sludge Using Multisolid Fluidized-Bed Combustion Technology WAYNE E. BALLANTYNE, WILLIAM J. HUFFMAN, LINDA M. CURRAN, and DANIEL H. STEWART

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch009

Battelle's Columbus Laboratories, 505 King Avenue, Columbus OH 43205 This study was initiated to investigate the potential for energy recovery from municipal solid waste and sewage sludge using Battelle's multi-solid fluidized bed combustion (MS-FBC) technology. The MS-FBC technology was chosen because it represents an advanced fluidized-bed combustion technology that is designed to operate with heterogeneous solids while achieving higher throughputs and larger turn-down ratios than conventional fluidization. The technology, originally developed for coal, was thought to be highly adaptable to the diverse solids that are inherently difficult to process when using municipal solid waste (MSW) and domestic sewage sludge (DSS). Steam generation from MSW and DSS has been studied by many investigators, but fouling of heat transfer surfaces can be a major problem. Thus, this research study also sought to investigate direct steam generation using hot sand to vaporize the water in DSS (4 percent solids) in a conventional fluidized bed that is an integral part of the MS-FBC technology. The research program incorporated several items and the two tasks discussed in this paper were: Task 1. Obtain experimental data using a MS-FBC pilot plant to validate calculated energy recovery. Task 2. Demonstrate the technical feasibility of direct steam generation using DSS as 4 percent solids. Background on MS-FBC Technology Multi-solid fluidized bed combustion (MS-FBC) was initially developed by Battelle(1) as an advanced fluidization technology for achieving high rates of combustion of high sulfur coal while eliminating the need for flue gas desulfurization or extensive coal cleaning. This coal technology was shown to be feasible during numerous runs in the 15 cm pilot plant system described in this paper and it was then further developed over a 1500 0-8412-0565-5/80/47-130-109$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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cumulative hour operating p e r i o d using a 4.4 metric ton/day p i l o t facility. Other feedstocks (e.g., wood) have a l s o been shown to be compatible with MS-FBC and the b a s i c processing c a p a b i l i t y has r e c e n t l y been adapted to the g a s i f i c a t i o n o f wood.(2). The b a s i c MS-FBC concept incorporates an entrained f l u i d i z e d bed superimposed on an i n e r t , dense-phase f l u i d i z e d bed as shown i n Figures 1 and 2 f o r the MSW/DSS a p p l i c a t i o n . As c u r r e n t l y operated i n the MSW/DSS experiments, the dense phase i s A f r i c a n i r o n ore. This dense bed remains i n the comb i t o r and i t s height e s s e n t i a l l y d e f i n e s the combustion zone (760-870 C); i t s high density permits dense-phase turbulent f l u i d i z a t i o n to be achieved at gas v e l o c i t i e s exceeding 9.0 m/sec. The entrained phase i s commonly s i l i c a sand and i t s a d d i t i o n to the dense-phase bed i s g e n e r a l l y c r e d i t e d with improving the q u a l i t y of the dense-phase f l u i d i z a t i o n . The entrained phase a l s o moderates the combustion by absorbing the heat o f r e a c t i o n . A f t e r passing through the dense-phase region, the entrained phase along with f l u e gas and ash pass through a free-board region and are separated. The heated sand i s then t r a n s f e r r e d a conventional f l u i d i z e d bed shown i n Figures 1 and 2. This bed i s operated at gas v e l o c i t i e s l e s s than 0.39 m/sec. Steam tubes can be i n c o r p o r ated i n t o t h i s f l u i d i z e d bed f o r the production o f high pressure steam (Figure 2). In one MSW/DSS a p p l i c a t i o n , no tubes are employed and d i r e c t - c o n t a c t heat t r a n s f e r between hot sand and a 3-4 percent DSS mixture i s accomplished (Figure 1). The cooled, ent r a i n e d m a t e r i a l i s then returned to the combustor where the c y c l e s t a r t s over again. The v a l v e shown i n the sand r e t u r n - l i n e i s used to c o n t r o l the r a t e of the entrained-phase r e c i r c u l a t i o n which, i n t u r n , c o n t r o l s the amount o f combustion that can be permitted i n the combustor. Some of the more s i g n i f i c a n t features of the MS-FBC process that have been experimentally proven a t the 4.4 metric ton/day s c a l e using c o a l as a feedstock i n c l u d e the f o l l o w i n g items: (a) High s p e c i f i c r a t e s o f combustion (grams feed/hr-cm^ grate area) due to the high amount o f heat removal achieved a t v e l o c i t i e s greater than 9 m/sec. (b) "Turn-down" of 3:1 can be achieved a t 20 percent excess a i r by a d j u s t i n g the r a t e o f r e c i r c u l a t i o n of the e n t r a i n e d phase; t h i s r e c i r c u l a t i o n c o n t r o l e l i m i n a t e s the need f o r bed-slumping that i s common to r e g u l a r f l u i d i z e d bed combustors. (c) D i f f e r e n t types and s i z e s of c o a l feed can be handled with minimum feed p r e p a r a t i o n ; lump-coal approximately 2.5 cm i n diameter i s p r e f e r r e d . D e s c r i p t i o n o f Equipment

and

A process flow schematic of the combustor, sand disengager, the EHE used i n t h i s i n v e s t i g a t i o n i s given i n Figure 3.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

ET AL.

Energy Recovery Using MS-FBC

Technology

11

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BALLANTYNE

Figure 1.

Battelle's MS-FBC process with contact evaporation of domestic sewage sludge

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THERMAL

Figure 2.

Β attelle's MS-FBC

process with steam generation in external heat exchanger

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

ET AL.

Energy Recovery Using MS-FBC

Technology

1

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BALLANTYNE

Figure 3.

Thermocouple and pressure tap locations on MS-FBC combustor and EHE

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MSW Feed System. The MSW feed system c o n s i s t e d of a sealed weigh hopper supported by load c e l l s , a 10.2 cm diameter by 102 cm long screw feeder powered by a v a r i a b l e speed DC motor, and a 7.6 cm diameter feed chute f i t t e d with an expansion bellows and a k n i f e gate v a l v e . An a i r c o o l e r was i n s t a l l e d to keep the feed chute near the combustor from overheating. DSS Feed System. The DSS feed system c o n s i s t e d of an a g i tated, 55-gallon polyethylene supply tank f o r the sewage sludge and standard p i p i n g and pumps. The feed system s u p p l i e d two a i r sparged tubes l o c a t e d 25 cm and 46 cm above the d i s t r i b u t o r p l a t e i n the EHE. Each tube contained s i x , 2.36 mm diameter holes d r i l l e d h o r i z o n t a l l y (3 on each side) through which DSS and a i r were f e d . Because the c l a y and lime a d d i t i v e s used i n the study had a tendency to s e t t l e out i n the supply tank, a r e c i r c u l a t i o n l i n e was a l s o i n s t a l l e d . Combustor. The combustor assembly of the MS-FBC system cons i s t e d o f the combustion chamber and the g a s - f i r e d burner. The combustion chamber c o n s i s t e d of a v e r t i c a l , 15 cm I.D. by 6.7 m high pipe constructed o f Type 304 s t a i n l e s s s t e e l . The d i s t r i b u t o r p l a t e was a 0.63 cm t h i c k d i s c l o c a t e d on the bottom flange p e r f o r a t e d with 96 uniformly-spaced holes of 0.238 cm diameter. The r e c y c l e d s i l i c a sand entered the combustor through a 7.62 cm diameter pipe l o c a t e d approximately 10 cm above the d i s tributor plate. This pipe was i n s t a l l e d at an angle of approximately 20 degrees to the combustor and was equipped with a s l i d e gate valve to regulate the sand flow from the EHE i n t o the combustor. A l l m a t e r i a l s i n the combustor and gas burner were of Type 304 s t a i n l e s s s t e e l . Entry ports i n t o the combustor were a l s o constructed from s t a i n l e s s s t e e l . The combustor, sand disengager, EHE, and sand r e c y c l e l e g were wrapped with two l a y e r s of F i b e r f r a x ( r e g i s t e r e d trade name of Carborundum Corporation) i n s u l a t i o n to reduce heat l o s s e s . Sand Disengager. The sand disengager was a modified 61 cm cyclone equipped w i t h a s p o i l e r i n t o which a i r could be i n t r o duced to c l a s s i f y the f l y ash from the heavier entrained sand. Type 304 s t a i n l e s s s t e e l was used i n the c o n s t r u c t i o n of the disengager. EHE. The EHE c o n s i s t e d of a 35.6 cm diameter by 2.13 m high f l u i d i z e d bed. A sketch o f the EHE i s included i n Figure 1. The d i s t r i b u t o r p l a t e was 0.63 cm t h i c k and had 128 h o l e s , each 0.238 cm i n diameter uniformly spaced across the p l a t e . An a d j u s t a b l e overflow tube was l o c a t e d i n s i d e the EHE to regulate the height of the bed. The EHE was constructed from Schedule 10 carbon s t e e l pipe.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

9.

BALLANTYNE

ET AL.

Energy Recovery Using MS-FBC

Technology

115

C o n t r o l System. The operating c o n t r o l system contained s t a n ­ dard rotameters, manometers, gauges, thermocouples, r e c o r d e r s , etc., f o r c o n t r o l l i n g / m o n i t o r i n g the MSW feed a i r , EHE nozzle sparge a i r , disengager s p o i l e r a i r , pressure tap purge a i r , n a t u r a l gas flow, combustor a i r flow, EHE f l u i d i z i n g a i r , bed pressures, DSS feed, and temperatures. The f l u e gas monitoring system c o n s i s t e d o f analyzers and recorders f o r continuous monitoring o f SO2, CO2, CO, NO, and 02 from e i t h e r the combustor o r EHE. A d i g i t a l readout i n d i c a t o r provided the weight o f MSW i n the hopper. SCR c o n t r o l s were pro­ vided f o r the MSW screw feeder and the DSS feed pump.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch009

Materials The feedstock s e l e c t e d as the most a p p l i c a b l e f o r the p i l o t f a c i l i t y was p e l l e t i z e d MSW. The p e l l e t s , obtained from the Teledyne N a t i o n a l Company, had been preprocessed to remove metal and most o f the moisture before p e l l e t i z i n g . A representative a n a l y s i s based on an average o f s e v e r a l analyses i s presented i n Tables I and I I . The p e l l e t s were p r e f e r r e d over shredded MSW due to the r e l a t i v e ease o f handling i n the 10 cm diameter screw feeder used i n the p i l o t f a c i l i t y . A l a r g e r combustor system would not be l i m i t e d to the use of a p e l l e t i z e d feed.

TABLE I.

TYPICAL MSW ANALYSIS

Item C 0 (by d i f f . ) H 0 Ash H Ν S 2

Heating value (as received) Bulk density

Weight % 39.90 33.98 13.50 6.80 5.40 0.30 0.12 100.00 4252 c a l / g 0.48 g/cm3

The DSS i n j e c t e d i n t o the EHE was obtained from the concen­ t r a t o r underflow a t Columbus' Jackson Pike wastewater treatment p l a n t . Within a few hours p r i o r to each run, the sludge was loaded i n t o 55-gallon drums which were trucked to B a t t e l l e and emptied i n t o the DSS feed tank. The sludge was nominally 3 to 4 percent s o l i d s . A t y p i c a l a n a l y s i s of the metal content i s pro­ vided i n Table I I . The h e a t i n g value of the d r i e d DSS s o l i d was

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

116

THERMAL

TABLE I I .

Compound or Element

Dried MSW Weight Percent

4

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O F SOLID

WASTES

A N D BIOMASS

TYPICAL CONCENTRATION OF METALS AND OTHER CONSTITUENTS IN MSW, SEWAGE SLUDGE, AND SCALE

S0 0.16 CI 0.08 Al 0.8 Fe 0.2 Si 2.0 Na 0.5 Ca 0.8 Κ 0.5 Mg 0.1 Mn, Pb 0.02-0.03 Cr Na20.3Ca0.6S1O2

.

The r e s u l t s o f adding limestone were encouraging as the system was operated with no o s t e n s i b l e plugging f o r 7 hours. The system was then dismantled f o r a thorough v i s u a l i n s p e c t i o n of the disengager and connecting l i n e s . Only s l i g h t t r a c e s of s c a l e formation were found. I t i s p a r t i c u l a r l y important to note that 2/3 of the sand' used i n t h i s run was from Run 215. The use o f t h i s " o l d " sand was thought to be a r a t h e r severe t e s t of the assumed chemistry and use of limestone. Thus, the absence o f s c a l e i n the disengager a f t e r Run 216 was thought to be q u i t e s i g n i f i c a n t . In both of these runs, a s t o i c h i o m e t r i c amount (no excess) o f limestone was added as i n d i c a t e d i n the above r e a c t i o n . The amount of sodium i n both the MSW and DSS (Table II) was used f o r c a l c u l a t i n g the s t o i c h i o m e t r y . The r a t i o o f limestone to a s - r e c e i v e d MSW and dry DSS was 0.047 g/g and 0.5 g/g, r e s p e c t i v e l y . Run 217 was intended to be an extension of Run 216 to demons t r a t e prolonged o p e r a t i o n of the system. The system was operated using sand from Run 216 f o r about 13 hours. Then, combustor pressures b u i l t - u p , the MSW became d i f f i c u l t to feed, and the system had to be shutdown. On d i s m a n t l i n g the system, a p l u g was found about half-way up the combustor. The plug contained high amounts of s i l i c a and s a l t and may have e x i s t e d p r i o r to the a d d i t i o n o f

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

120

THERMAL

CONVERSION

OF

SOLID

WASTES

AND

BIOMASS

limestone, g r a d u a l l y growing i n s i z e with each run. The b e l i e f that the plug e x i s t e d p r i o r to Runs 216 and 217 was supported by the f a c t that there was minimal s c a l e formation elsewhere i n the combustor and disengager. A f t e r c l e a n i n g the combustor, Run 218 was made. The major goal of t h i s experimental run was to show that agglomeration/ s c a l i n g could be minimized over an extended p e r i o d by adding comm e r c i a l c l a y to the DSS feed s i n c e c l a y would be a more economical inhibitor. The c l a y i s b e l i e v e d to r e a c t with the a l k a l i s a l t s present i n the DSS to form a l b i t e or nephaline(5), double a l k a l i s a l t s (Mp-1108 and 1280 C, r e s p e c t i v e l y ) which melt above the comb u s t i o n temperature. The r e a c t i o n s f o r the c l a y were assumed to be as f o l l o w s : Na 0-3Si0 Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch009

2

Na 0-3Si0 2

2

+ A1 0

2

+ A l ^ -> N a ^ - A ^ O y 2 S i 0

2

3

+ 3Si0

2

+ Na 0. A l ^ . 6 S i 0 2

2

+ SK>

2

2

Clay was added at the s t o i c h i o m e t r i c q u a n t i t y needed f o r the sodium r e a c t i o n s and the r a t i o s to MSW and DSS were 0.0235 g/g asr e c e i v e d MSW and 0.25 g/g dry DSS. During the run, considerable d i f f i c u l t y with the MSW feed system was encountered. Upon shutdown and i n s p e c t i o n of the MSW, i t was found that l a r g e m e t a l l i c objects were present i n the hopper and screw and were probably h i n d e r i n g the MSW feed to the combustor. During uninterrupted feed p e r i o d s , the MS-FBC system operated smoothly as evidenced by the temperature p r o f i l e i n Figure 4. Furthermore, as can be seen by the s t a b l e EHE bed temperature p r o f i l e , the s t a b i l i t y of MS-FBC permitted quick recovery a f t e r the i n t e r ruptions. T o t a l operating time with feed was 31 hours and the DSS feedrate was 38 1/hr or 0.4 1 / h r - l of bed volume. The o b j e c t i v e of minimizing s c a l e formation was met because no s i g n i f i c a n t build-up of sand or other m a t e r i a l s could be det e c t e d i n the combustor, e x t e r n a l b o i l e r , p i p i n g , and cyclones a f t e r shutdown and i n s p e c t i o n . The problem of agglomeration and build-up was apparently minimized by the a d d i t i o n of c l a y . Other Results R e l a t i v e l y high CO l e v e l s p r e v a i l e d throughout most of the runs. This was not regarded as a s e r i o u s problem and d i d not r e c e i v e much a t t e n t i o n . That i s , high CO l e v e l s are common to the 15 cm diameter p i l o t p l a n t because i t does not have s u f f i c i e n t combustor freeboard height to ensure combustion of CO. This high CO emission was a l s o a d e f i c i e n c y i n burning c o a l , but, i n runs made with c o a l i n a l a r g e r MS-FBC p i l o t p l a n t (4.4 metric ton/day) with a d d i t i o n a l freeboard, acceptable emissions of CO were achieved and the same r e s u l t i s f u l l y expected to be true when burning MSW. Emissions of N0 and S02 were w i t h i n F e d e r a l l i m i t s . The combustor e f f i c i e n c y of the MSW and DSS i n the e x p e r i mental system was high and approached 99+ percent i n some runs. X

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Figure 4.

(a)

Six-inch MS-FBC operating conditions for run 218

Data i n t e r r u p t e d due to d i f f i c u l t i e s w i t h MSW caused by f o r e i g n o b j e c t s i n the MSW.

Time (hours)

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch009

feed

^ g*

CO

^

?3

122

THERMAL

CONVERSION

O F SOLID

WASTES

A N D BIOMASS

This high e f f i c i e n c y i s i n d i c a t e d by the low amount o f unburned carbon that was determined to e x i s t i n various streams during Run 212 (Table I I I ) . TABLE I I I .

ANALYSIS FOR ASH AND TOTAL CARBON IN SOLID STREAM FROM RUN 212

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch009

Stream Recycled sand Sand i n EHE Sand i n EHE cyclone Sand i n combustor cyclone Combustor Fresh sand Sand taken from disengager

Present Ash

Total Carbon

99.7 99.7 99.1 98.6 100.0 99.9 99.9

0.2 0.2 1.9 1.3

0 H H m rd x 3 >

Φ c

0 u >,

U 4-1 •H 5H 4-> 0 rd ci,

u

φ

ΓΜ

G

rd Cn

rH

φ 0

0



Οι

rd

rd •Η

G





0

Η Φ

Χ

ε

4-1 Ο Η

Φ rH

Ω

c3

Φ C

O rH υ

4-1

u

en LD 4-1 •HOOT ( H X ex ΓΜ

Η

•Η S

H

0 u 4-1 en 3 Xi rd 2

1 rH 5-1 Cn >i φ 54 ΧΙ ΓΜ rd



54 >l Φ 5-1 Ό (d Ό ε 0) •rH 54 54 x: Cn ω

1

2 >,
ι 54 5Η rd Φ

0



rd



Φ

4->

54 Φ

ε en Φ 3 C 4-1 0GΦ Φ m en U 5Η GE-* UW >i Φ χ : d,

Φ Φ > •Η φ -} Cn

Ω

LD

Γ­

œ

η

en c φ

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch010

10.

ALTER

AND CAMPBELL

129

Densified Refuse-Derived Fuel

Screening. A v i b r a t o r y screen was used as a feeder f o r the shredded MSW t o the a i r c l a s s i f i e r . I t was a l s o intended t o r e ­ move m a t e r i a l c I

I

C

H

H

^ C v . HC

/ C ,

c

'CH

II

700-«50 C O

ΔΘ ~ M I N U T E S

CH

HC



C

I

H C

H

^ C ^ C '

I

II

C

H REACTIVE

II Il

H C

^ /C^ /C^ C

/ C

HC

H SECONDARY

*

C
C .

*

^CH

II CH

/ C

HC.

H

H

H

CH

HC'

C

CH

I .

^ C H

H

I

>CH H

PRODUCTS

Figure 9.

CARBON

BLACK

(CHAR)

Formation of char

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

16.

DiEBOLD

221

Gasoline from Solid Wastes

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch016

6

only 185°C. At 750°C the half-life of acetone is calculated to be 0.290 second, whereas the half-life of acetaldehyde is only 0.006 second.^ Interestingly enough, the reported acetone decomposition products for short pyrolysis times had nearly the same ratio of ethylene to carbon monoxide as noted herein for ECO II feedstock, although the acetaldehyde decomposed to give only methane and carbon monoxide. It is doubtful that the oxygenated organic formation could be explained by a mechanism involving incomplete pyrolysis because the gasification reaction to olefins did not appear very dependent on cracking severity; e.g., residence time and temperature. If the oxygenated water soluble compounds were products of unimolecular degradation, the relative dilution should have had no effect on yields and the more severe pyrolysis reactions would have been expected to increase the overall gasification, but these trends were not observed. It should be noted that the hypothesis for pyrolysis in the entrained bed reactor is based only on experiments using ECO II as feedstock. Pure cellulosic feedstock or biomass feedstocks may behave differently when pyrolyzed in this manner. For a discrete particle of organic feedstock to undergo the selective gasification, a very rapid heating rate appears to be necessary. Referring to Table I, many of the residence times were in the neighborhood of 0.050 second. The temperature rise was from 25°C to about 750°C during pyrolysis. This results in a heating rate greater than 15,000°C/sec. If the particle were to attain the pyrolysis temperature part way through the pyrolysis reactor, the heating rate would be much higher. High heating rates minimize the time during which the particle is acted upon by competing reactions favored at lower temperatures which do not form the desired olefin-containing products. In order to achieve this high heating rate, the following are necessary: (1) the surface-to-volume ratio of the feed must be high; (2) the thickness of the particle must be relatively low to reduce the thermal gradient in the particle, and (3) the rate of heat transfer into the particle surface must be very high. The first two requirements can be met with a very small particle size, and/or a "two-dimensional" particle (paper), and/or a ''one-dimensional'' particle (fiber). The heat transfer requirement needed for good gasification is a function of the reactor design and apparently can be met with pure radiation** or with fluidized beds^ and entrained flow reactors which combine radiation, conduction, and convection. The molecular fragments or free radicals formed by the shattering of the cellulosic molecules are small enough to lose their cellulosic identities in the process. This implies that the free radicals will react to form a similar product distribution; the ancestral origins or feedstock would be of secondary importance since the water and carbon oxides are relatively inert. Thus, it would be expected that the relative hydrocarbon product distribution would have similar trends whether the free radicals were made from cellulosic, hydrocarbon, or kerogen (shale oil) feedstocks. The weight percent conversions will, of course, have a direct correlation to feedstock characteristics. As shown in Figure 10, the pyrolysis product distribution obtained from naphtha, oil shale, and from MSW (ECO II) are indeed remarkably similar considering the very different nature of the feedstocks. 2 In summary, when the cellulosic molecule is rapidly heated to the 700°C temperature regime, very reactive free radicals are formed. These free radicals are 10

11

10

1

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch016

222

MSW (ECO ID OIL SHALE NAPHTHA

J Ρ

10 h

) M

J

1

(WEIGHT PERCENTAGES CALCULATED AFTER CO AND C0 DELETED) 2

American Society of Mechanical Engineers

Figure 10.

Pyrolysis products comparison using various feedstocks (12)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

16.

DiEBOLD

Gasoline from Solid Wastes

223

very short lived and form the more stable primary pyrolysis products. If the system is relatively dilute (low free-radical partial pressure), the formation of olefins rather than aromatic tars and oxygenated organics is favored. If the pyrolysis reaction is not stopped or quenched, the primary reaction products themselves react to form aromatic tars. With more time, the molecular weight of the tars increases so that they are solid in nature to become carbon black. At this point thermodynamic equilibrium is being approached and the products are those of the coking ovens: hydrogen, carbon monoxide, char, water, carbon dioxide, and methane. To maximize gaseous hydrocarbon production (e.g., ethylene) it appears necessary to have rapid heating rates, low partial pressures, and short residence times.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch016

High Pressure Gas Purification The goal of the gas purification portion of the program was to reject the hydrogen sulfide, carbon dioxide, carbon monoxide, hydrogen, and methane from the pyrolysis gases. This would provide a product gas stream consisting primarily of low molecular weight olefins (ethylene, propylene, butylène, etc.). Since petrochemical reactors are operated at elevated pressures, it was assumed that the pyrolysis gases would be compressed to some intermediate pressure for purification. The effect of hydrogen sulfide in the purified gas stream fed to a reactor would be to react with the olefins to form odiferous mercaptans or to poison most catalytic processes. The presence of methane or hydrogen in the purified gases would reduce the effective olefinic pressure and slow bimolecular reaction rates. Gas purification can be accomplished at cryogenic temperatures by distillation techniques. However, it was reported to be more energy efficient to use solubility differences of the gases at ambient or elevated temperatures and pressures. The absorption of low molecular weight olefins into a light oil from gases formed by the pyrolysis of propane has been commercialized and ethylene recoveries of 99% reported. 13 These propane pyrolysis gases were very similar in general composition to those made from cellulosic pyrolysis except for the oxides of carbon found with the latter. Carbon dioxide has a solubility in light aromatic oils approaching that of ethylene, so it must be removed first. Figure 11 shows the high pressure gas purification system used to concentrate the olefins. The carbon dioxide was removed very selectively with a hot carbonate solution at a system pressure of about 3100 kPa. This resulted in a relatively pure stream of carbon dioxide being rejected. The semipurified pyrolysis gases then passed to the hydrocarbon absorber where the hydrocarbons other than methane were absorbed. The low molecular weight olefins were then boiled off the absorbing oil to result in a concentrated product stream. At this point in the process, several different uses for the olefins can be imagined: (a) the olefins could be further purified and marketed as pure compounds; (b) the olefin mixture could be passed through a series of catalytic reactors to form alcohols or hydrocarbon liquids; or (c) the olefin mixture could be passed through a noncatalytic, polymerizing reactor to form polymer gasoline. This latter option is the one which was pursued due to its apparent simplicity and the extensiveness of the gasoline market.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch016

224

CONVERSION OF SOLID WASTES AND BIOMASS

BY-PRODUCT GASES (CO, CH* H ) 2

7B»F

l_70 F e

TO RECYCLE OLEFINS

2S0°F I 44· PSiL H0 2

KHCO3 KHS

sa 430 PSI

430 PSI

POLYMER GASOLINE STORAGE 1 ATM

PRESSURE BOOSTER 750 PSI

850°ί BOILING SULFUR THERMOSYPHON

s

POLYMERIZATION COIL

American Society of Mechanical Engineers Figure 11.

Pyrolysis gas purification and polymerization to gasoline (12)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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DiEBOLD

Gasoline from Solid Wastes

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Polymerization to Gasoline The polymerization of olefins to form a liquid product primarily composed of gasoline was researched in the early 1930s when the cracking of crude oil to make gasoline resulted in a large amount of gaseous by-product olefins. Although phosphoric acid was found to polymerize propylene and butylène fairly readily, ethylene was fairly resistant to its catalytic effect. In contrast, at the relatively more severe conditions required to polymerize olefins without catalysis, ethylene was found to polymerize more readily than propylene or b u t y l è n e . ^ Since the primary olefin formed by pyrolysis of organic wastes was ethylene, thermal polymerization to make gasoline was selected. Early experiments in the program were made with pure ethylene which produced a synthetic crude oil containing 90% gasoline which was shown to have an unleaded ASTM motor octane of 90. A polymer gasoline sample held at ambient temperature for 3-1/2 years visually appeared not to change color, although some commercially produced gasoline turned to a dark orange during this time. The distillation curve for the liquid product appeared to be fairly continuous and reflected the relatively extensive rearrangement of the molecules at the 450 to 500°C reactor temperature until a stable molecular structure was attained, such as highly branched or cyclic. (Fortunately, these complex molecular structures result in high octane ratings.) Synthetic crude made from relatively impure pyrolysis gases had a very similar physical appearance and distillation curve. With efficient processing of the pyrolysis gases, a polymer gasoline yield is projected of about 0.18 liter/kg of feed (MSW containing 60% by weight organic material), which is about one petroleum barrel per ton of MSW. Summary The ability to convert organic wastes to pyrolysis gases containing relatively large amounts of olefins has been demonstrated by using a very selective pyrolysis process. Pyrolysis appears to involve a large number of competing reactions, most of which do not favor the formation of olefins. Rapid heating rates, short residence times, small feed particle size, and dilute pyrolysis conditions appear to favor the formation of olefins rather than char, tar, or water soluble organics. Although the olefins produced could be used for petrochemical feedstock, their potential for a straightforward conversion to high octane gasoline was demonstrated using 1930s technology. The economics^ and the commercialization potential of the process^ look very favorable and have been reported previously in detail. Acknowledgements The financial support of the Environmental Protection Agency (IERL) made the bench scale demonstration of the process possible, and much of this paper will be appearing in the forthcoming final report. Dr. Charles B. Benham (presently at SERI) was instrumental in the polymerization demonstration with pure ethylene and with the early phases of the program from which this process evolved.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

226

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

References

1. Diebold, J.P., C.B. Benham, and G.D. Smith. "R&D in the Conversion of Solid Organic Wastes to High Octane Gasoline," AIAA Monograph on Alternate Fuel Resources, Volume 20, 1976. (Western Periodicals Co., No. Hollywood, CA.) 2. Shafizadeh, F. "Pyrolysis and Combustion of Cellulosic Materials", Adv. in Carbohydrate Chem., 23, 419-475. (1968)

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch016

3. Brink, D.L., M.S. Massoudi, and R.F. Sawyer. "A Flow Reactor Technique for the Study of Wood Pyrolysis," presented at the 1973 Fall Meeting of the Western States Section of the Com­ bustion Institute in El Segundo, CA (October 1973). 4. Cadman, W.H. "II. Semi-Industrial Production of Aromatic Hydrocarbons from Natural Gas in Persia,"Ind Eng Chem, 26, No. 3, 315-320. (1934) 5. Hilado, C.J. and S.W. Clark, "Autoignition Temperatures of Organic Chemicals," Chem Eng, 4 Sept 1972. pp. 75-80. 6. Hinshelwood, C.N. and W.K. Hutchinson. "A Homogeneous Unimolecular Reaction - the Thermal Decomposition of Acetone in the Gaseous State," Proc. Roy. Soc., 111A, 245-257. (1926) 7. Hinshelwood, C.N. and W.K. Hutchinson. "A Comparison between Unimolecular and Bi­ molecular Gaseous Reactions. The Thermal Decomposition of Gaseous Acetaldehyde," Proc. Roy. Soc.,111A,380-385. (1926) 8. Lincoln, Κ Α., "Flash-Pyrolysis of Solid-Fuel Materials by Thermal Radiation," Pyrodynamics, 2, 133-143, Gordon and Breach, No. Ireland. (1965) 9. Finney, C.S. and D.E. Garrett. "The Flash Pyrolysis of Solid Waste," 66th Annual AIChE meeting, November 1973, paper 13-E. 10. Sohns, H.W., et. al. "Development and Operation of an Experimental, Entrained Solids Oil-Shale Retort," BUMINES, RI 5522 (1959) 11. Prescott, J.H. "Pyrolysis Furnace Boosts Ethylene Yield by 10-20%," ChemEng,July 1975, 52-53. 12. Diebold, J.P. and G.D. Smith. "Noncatalytic Conversion of Biomass to Gasoline," presented to the ASME sponsored Solar Energy Conference in San Diego, March 1979. 79-Sol-29. 13. Kniel, L. and W.H. Slager. "Ethylene Purification by Absorption Process," Chem. Eng. Prog., 43, No. 7, 335-342. (1947) 14. Sullivan, F.W. Jr., R.F. Ruthruff and W.E. Kuentzel. "Pyrolysis and Polymerization of Gaseous Paraffins and Olefins," Ind Eng Chem, 27, No. 9, 1072-1077. (1935) 15. Diebold, J.P. and G.D. Smith. "Commercialization Potential of the China Lake Trash-to­ -Gasoline Process," presented at the Engineering Foundation Sponsored Conference "Municipal Solid Waste, the Problems and the Promise," held in Henniker, NH, July 1979. RECEIVED November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

17 Fuel Production from Wastes Using Molten Salts R. L. GAY, Κ. M. BARCLAY, L. F. GRANTHAM, and S. J. YOSIM

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch017

Rockwell International Corporation, Energy Systems Group, 8900 De Soto Avenue, Canoga Park, CA 91304

The disposal of municipal and industrial wastes has become an important problem because the traditional means of disposal, landfill, has become environmentally much less acceptable than previously. In addition, special incinerator systems are required to meet environmental standards for disposal by incineration. Disposal of wastes by landfill or incineration also includes a potential loss of energy sources and, in some cases, valuable mineral resources. New, much stricter regulation of these dis­ posal methods will make the economics of waste processing for resource recovery much more favorable. One method of processing waste streams is to convert the energy value of the combustible waste into a fuel. One type of fuel attainable from wastes is a low heating value gas, usually 3.7-5.6 MJ m - 3 (100-150 Btu/scf), which can be used to generate process steam or to generate electricity. Described here are some results which show the feasibility of processing wastes in molten salts into usable fuels. The molten salt acts as a reaction medium for the conversion of the waste into a low heating value gas (by reaction with air) and the simultaneous retention of potential acidic pollutants in the molten salt. The waste is converted to a fuel gas by reacting it with deficient air, that is, insufficient air for complete con­ version to CO2 and H2O. Results are presented for a high-sulfur o i l refinery waste, rubber, wood, leather scraps, and waste X-ray film. These waste streams represent a small segment of the large variety of wastes which may be processed using molten salts. Process Description A flow diagram of the Rockwell International process for fuel production from wastes is shown in Figure 1. In this pro­ cess, combustible waste and air are continuously introduced beneath the surface of a sodium carbonate-containing melt at a 0-8412-0565-5/80/47-130-227$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

228

Off-Gas Stack

Baghouse o r V e n t u r i Scrubber

Fuel-Gas

Waste Molten Salt Gasif1er

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Air

Figure 1.

Melt Processing for Carbonate Recovery

Molten salt process for fuel production from wastes

Figure 2.

Bench-scale molten salt gasifier

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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229

temperature of 900-1000°C. The waste r e a c t s c h e m i c a l l y w i t h the molten s a l t and a i r t o produce a p o l l u t a n t - f r e e combustible gas c o n t a i n i n g mainly CO, H 2 , N 2 , and a small amount of CH4 and C 2 H 6 . The product gas i s cleaned of p a r t i c u l a t e s u s i n g a baghouse or v e n t u r i scrubber. I t i s then burned i n a b o i l e r to produce steam or as an a l t e r n a t i v e , the product gas may be burned i n a gas t u r b i n e as p a r t of a combined-cycle process. Sodium carbonate i s a s t a b l e , n o n v o l a t i l e , inexpensive, and nontoxic m a t e r i a l . I t i s the i n t i m a t e contact of the waste m a t e r i a l w i t h the molten s a l t and a i r that provides f o r complete and r a p i d r e a c t i o n o f the waste. Any gas that i s formed during g a s i f i c a t i o n i s forced t o pass through the b a s i c carbonate melt. Halogens i n the waste ( f o r example, c h l o r i n e from c h l o r i n a t e d o r g a n i c compounds) form the corresponding sodium h a l i d e s a l t s . Any s u l f u r i n the waste i s r e t a i n e d as sodium s u l f i d e , and any ash i n the waste w i l l a l s o be r e t a i n e d i n the melt. The temperatures o f o p e r a t i o n are too low to permit a s i g n i f i c a n t amount of n i t r o g e n oxides to be formed by f i x a t i o n of the n i t r o g e n i n the a i r . A l s o , a t these operating temperatures, odors and i n f e c t i o u s m a t e r i a l are completely destroyed. A p o r t i o n o f the sodium carbonate melt i s withdrawn from the molten s a l t r e a c t o r , quenched, and processed i n an aqueous recovery system. The recovery system removes the ash and i n o r g a n i c combustion products (mainly sodium s a l t s such as NaCl and N a 2 S ) r e t a i n e d i n the melt. Unreacted sodium carbonate i s returned t o the molten s a l t furnace. The ash must be removed when the ash c o n c e n t r a t i o n i n the melt approaches 20 to 25 wt % i n order to preserve the melt f l u i d i t y . The i n o r g a n i c combustion products must be removed b e f o r e a l l o f the sodium carbonate i s completely converted to noncarbonate s a l t s . For the case o f a waste c o n t a i n ing a v a l u a b l e m i n e r a l resource, the v a l u a b l e m i n e r a l resource i s r e t a i n e d i n the melt during the g a s i f i c a t i o n process and may be recovered as a by-product of the r e g e n e r a t i o n process. T h i s molten s a l t g a s i f i c a t i o n process i s the b a s i s f o r the Rockwell I n t e r n a t i o n a l molten s a l t c o a l g a s i f i c a t i o n process. A 900-kg-h~l ( i ton/h) process development u n i t p i l o t p l a n t has been b u i l t and i s being t e s t e d under contract from the Department of Energy. T h i s p l a n t i n c l u d e s the g a s i f i e r and a complete sodium carbonate recovery and r e g e n e r a t i o n system. Experimental Bench-Scale Test Apparatus. A schematic diagram of the bench-scale t e s t apparatus i s shown i n F i g u r e 2. T h i s apparatus i s used t o t e s t the f e a s i b i l i t y o f g a s i f y i n g wastes b e f o r e p i l o t s c a l e t e s t s are performed. The waste throughput of the benchs c a l e apparatus i s 1 t o 3 kg h-1 (2 t o 6 l b / h ) . Approximately 5.5 kg (12 l b ) of molten s a l t are contained i n a 15-cm ID by 76-cm h i g h alumina tube placed i n s i d e a type 321 s t a i n l e s s s t e e l

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL

CONVERSION

OF SOLID WASTES AND

BIOMASS

r e t a i n e r v e s s e l . T h i s s t a i n l e s s s t e e l v e s s e l , i n t u r n , i s cont a i n e d i n a 20-cm ID, four heating zone Ohio Thermal furnace. Each h e a t i n g zone i s 20 cm i n height, and the power to each zone i s c o n t r o l l e d by a s i l i c o n - c o n t r o l l e d r e c t i f i e r c i r c u i t . An a d d i t i o n a l f l a t p l a t e heater i s l o c a t e d a t the bottom of the v e s s e l . Furnace and r e a c t o r temperatures are recorded on a 12-point Barber-Colman chart r e c o r d e r . S o l i d s are p u l v e r i z e d i n a Wiley l a b o r a t o r y k n i f e - b l a d e m i l l to l e s s than 1 mm i n s i z e . These s o l i d s are then metered i n t o a 1.3-cm OD s t a i n l e s s s t e e l i n j e c t i o n tube by a screw feeder. The speed of the screw feeder i s v a r i a b l e between 0-400 rpm. The s o l i d s are mixed w i t h process a i r i n the i n j e c t i o n tube. The s o l i d s - a i r mixture comes out of the end of the 1.3-cm OD tube and i n t o the annulus of a 3.7-cm ID alumina tube. T h i s alumina tube extends to w i t h i n 1.3 cm of the bottom of the 15-cm ID alumina containment v e s s e l . During normal operation of the r e a c t o r , the depth of the molten s a l t expands from a quiescent l e v e l of 15 cm to an expanded depth of about 30 cm. In the case of l i q u i d s , a l a b o r a t o r y p e r i s t a l t i c pump i s used to pump the l i q u i d i n t o the 1.3-cm OD s t a i n l e s s tube. The feed r a t e of the l i q u i d i s c o n t r o l l e d by the pump speed. Heat balance of the bench-scale r e a c t o r i s maintained i n one of two ways. I f the feed m a t e r i a l i s of r e l a t i v e l y h i g h heating v a l u e (greater than 14.0 MJ kg-1, 6000 B t u / l b ) , a small a i r c o o l e r at the bottom of the furnace i s used to maintain the v e s s e l a t the operating temperature. I f the waste m a t e r i a l i s low i n h e a t i n g v a l u e , the melt temperature i s maintained by an e l e c t r i c a l l y heated furnace, or by adding a u x i l i a r y f u e l to the waste. Off-Gas A n a l y s i s . Gas samples are i n i t i a l l y cleaned of p a r t i c u l a t e s and d r i e d to 2% moisture b e f o r e a n a l y s i s . Carbon monoxide and carbon d i o x i d e are measured continuously using a Horiba Mexa-300 CO analyzer and a Horiba Mexa-200 CO2 a n a l y z e r . Syringe samples are taken downstream of the CO2 analyzer f o r gas chromatographic a n a l y s i s . A room temperature molecular s i e v e 13X column i s used to analyze f o r carbon monoxide, oxygen, and n i t r o gen. A Poropak Q column at 130°C i s used to analyze f o r carbon d i o x i d e , methane, ethane, ethylene, s u l f u r d i o x i d e , and hydrogen sulfide. 1

Molten S a l t Test F a c i l i t y . A 90-kg-IT (200 lb/h) p i l o t p l a n t at the Rockwell f i e l d l a b o r a t o r y at Santa Susana i s used f o r l a r g e r s c a l e t e s t i n g . The molten s a l t g a s i f i c a t i o n v e s s e l i s made of Type 304 s t a i n l e s s s t e e l and i s 4.6 m h i g h w i t h a 0.9 m i n s i d e diameter. The i n s i d e of the v e s s e l i s l i n e d w i t h 15-cmt h i c k r e f r a c t o r y b l o c k s . The g a s i f i e r contains 900 kg of sodium carbonate, which has an unexpanded bed height of 0.9 m. During o p e r a t i o n , the bed height approximately doubles. A n a t u r a l gas preheater i s used to heat the v e s s e l on s t a r t - u p .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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A flow schematic f o r the Santa Susana molten s a l t t e s t f a c i l i t y i s shown i n F i g u r e 3. S a l t i s loaded i n t o the v e s s e l from a carbonate hopper and a weigh b e l t feeder. Waste m a t e r i a l s a r e shredded and crushed u s i n g a r o t a r y k n i f e shredder and a hammerm i l l and a r e then metered i n t o a pneumatic feed l i n e w i t h a v a r i a b l e - s p e e d auger. Product gases produced i n the molten s a l t v e s s e l u n i t flow through r e f r a c t o r y - l i n e d d u c t i n g to a spray c o o l e r and i n t o a secondary combustor. The gases are burned i n the secondary combustor and the o f f - g a s i s cleaned of any p a r t i c u l a t e matter w i t h a baghouse o r a v e n t u r i scrubber. The o f f - g a s i s then r e l e a s e d t o the atmosphere. A photograph o f the molten s a l t t e s t f a c i l i t y i s shown i n F i g u r e 4. Results G a s i f i c a t i o n o f A c i d P i t Sludge. Crude or p a r t i a l l y r e f i n e d crude i s t r e a t e d w i t h s u l f u r i c a c i d during r e f i n i n g . T h i s produces a waste product which contains s u b s t a n t i a l amounts of water (12-40 wt % ) , s u l f u r (2-14 wt % ) , ash (1-55 wt %) , and s i g n i f i c a n t combustible m a t e r i a l (11.6 to 20.9 MJ k g ~ l ) (5000-9000 B t u / l b ) . Normal i n c i n e r a t i o n of t h i s waste i s not economic due t o the high water, ash, and s u l f u r content. Therefore, the waste i s g e n e r a l l y ponded and not processed. The n i c k e l and vanadium content and energy v a l u e of t h i s waste product, as w e l l as the v a l u e of the l a r g e area o f land dedicated t o current d i s p o s a l techniques, o f f e r s i g n i f i c a n t economic p o t e n t i a l f o r improved d i s p o s a l processes. Data on the g a s i f i c a t i o n o f a c i d p i t sludge a r e given i n Table I . I n t h i s t e s t , the water-sludge mixture was heated to the c o n s i s t e n c y o f l i g h t o i l (about 90 to 95°C) and f e d to the r e a c t o r without removing any water from the a s - r e c e i v e d m a t e r i a l . A gas c o n t a i n i n g a higher heating value of 8.57 MJ m~3 (230 Btu/ s c f ) was produced. During t h i s t e s t , some a u x i l i a r y heat was f u r n i s h e d by the outer furnace to maintain the operating temperat u r e . I t i s estimated that a steady-state t e s t without a u x i l i a r y heat would produce a gas w i t h a higher heating v a l u e o f 6.33 MJ m~3 (170 B t u / s c f ) . Emissions of H 2 S were below the l i m i t of d e t e c t a b i l i t y (40 ppm). G a s i f i c a t i o n o f Rubber T i r e s . Conventional i n c i n e r a t i o n of rubber t i r e s produces a l a r g e amount of p a r t i c u l a t e s which c o n t a i n unburned hydrocarbons. As an a l t e r n a t i v e to i n c i n e r a t i o n , molten s a l t g a s i f i c a t i o n was t e s t e d . Two g a s i f i c a t i o n t e s t s were made u s i n g b u f f i n g s from a rubber t i r e . The r e s u l t s of these t e s t s were averaged and a r e presented i n Table I . Since the rubber contained organic s u l f u r that would form N a 2 S i n the melt, the N a 2 C 0 melt o r i g i n a l l y contained 6 wt % Na S to approximate steadys t a t e c o n d i t i o n s . Using a s t o i c h i o m e t r y of 33% t h e o r e t i c a l a i r 3

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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232

I 1 δ

.ο

v. S

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GAY ET AL.

Fuel from Wastes Using Molten Salts

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch017

17.

Figure 4. Santa Susana molten salt test facility

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

233

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

2>

^Auxiliary heat provided by the e l e c t r i c furnace during testing. produced without auxiliary heat.

Not determined.

Remainder i s N

Estimated 6.33 MJ m

Gas volumes are defined at conditions of 101.3 kPa (1 atm) pressure and 15 .6°C (60'°F).

3.99 6.67

4.03

6.74

5.77

8.57

d

Higher Heating Value (MJ m-3)

a

gas would be

0.2 1.2 2.6 5 .2 11.7 14.1

1015 958

12.0 18.3

16.5 16.0

7.2 4.0

2.4 3.0

935

Leather Offal

2.2

12.9

C

0.9 ND

3.0

21.1

13.7

16.5

3.6

20.3

14.5

3.3

1.0 2.0

951

Wood

1.1

2.4

16.0

18.4

4.0

2.6

0.8

C

2

2.5

920

a

4

8.4

Rubber Tires

Film

2

b

15.8

7.0

16.0

4.0

3.4

935

2

Composition of Off-Gas (Vol % ) H CH C C0 CO

Acid P i t Sludge

3

Temperature (°C) 1

Air Feed Rate (m3 h " )

Waste Material

Waste Feed Rate (kg h-1)

GASIFICATION OF WASTES

TABLE I

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Fuel from Wastes Using Molten Salts

(100% t h e o r e t i c a l a i r i s r e q u i r e d to o x i d i z e the m a t e r i a l comp l e t e l y to CO? and H 0 ) , a product gas w i t h a higher heating v a l u e of 5.77 MJ m"3 (155 Btu/scf) was made. No H S o r s u l f u r - c o n t a i n ing gases ( l e s s than 30 ppm) were detected i n the o f f - g a s . 2

2

G a s i f i c a t i o n of Wood. Pine wood was chosen as r e p r e s e n t a t i v e of t y p i c a l biomass. A t y p i c a l composition of pine wood on a dry b a s i s i s 51.8 wt % carbon, 6.3 wt % hydrogen, 0.5 wt % ash, and 41.3 wt % oxygen. The pine wood t e s t e d here was sawdust with a moisture content o f 2.8 wt %. The heating v a l u e i s t y p i c a l l y 21.2 MJ kg-1 (9100 B t u / l b ) . A pure sodium carbonate melt was used w i t h 30% t h e o r e t i c a l a i r . G a s i f i c a t i o n of wood was r a p i d and complete w i t h p r o d u c t i o n of a gas w i t h a higher heating value of 6.74 MJ m~ (181 B t u / s c f ) , as given i n Table I . Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch017

3

G a s i f i c a t i o n of Leather O f f a l . Chrome-leather tanning scraps o r o f f a l a r e a waste product of the tanning and l e a t h e r i n d u s t r i e s . These wastes a r e u s u a l l y the r e s u l t of trimming o p e r a t i o n s and c o n t a i n 3.5 wt % chromium and about 50 wt % water. The wastes cannot be i n c i n e r a t e d because malodorous substances and c a r c i n o g e n i c chromium-containing p a r t i c u l a t e s a r e formed. L a n d f i l l d i s p o s a l i s p r e s e n t l y used. The tanning scraps used f o r these t e s t s were a i r - d r i e d and contained 37.2 wt % carbon, 5.7 wt % hydrogen, 12.8 wt % n i t r o gen, 2.5 wt % chromium, and approximately 5 wt % nonchrome ash. The heating v a l u e of the chrome-waste was approximately 18.8 MJ kg" (7800 B t u / l b ) . The a n a l y s i s of the o f f - g a s from l e a t h e r g a s i f i c a t i o n i s given i n Table I . Approximately 50% of t h e o r e t i c a l a i r was used. The product gas had a heating v a l u e of 4.03 MJ m"" (108 B t u / s c f ) . The N 0 emissions were only 40 ppm even through the l e a t h e r contained 12.8 wt % organic n i t r o g e n . The chromium emission i n the form of p a r t i c u l a t e s was 0.3 mg m~ (0.00013 g r a i n / f t ) , which corresponds to a chromium r e t e n t i o n of 99.998%. T h i s chromium could be recovered and r e c y c l e d to the tanning process by processing the s a l t bed. 1

3

X

3

3

G a s i f i c a t i o n of Waste F i l m . Two s e r i e s of t e s t s were conducted w i t h waste X-ray f i l m . The f i r s t s e r i e s was performed i n the bench-scale g a s i f i e r ; the second s e r i e s was run i n the molten salt test f a c i l i t y . Bench-scale g a s i f i c a t i o n of f i l m a t 51% and 22% t h e o r e t i c a l a i r produced product gases of 3.99 MJ m" (107 Btu/scf) and 6.67 MJ m" (179 B t u / s c f ) , r e s p e c t i v e l y . Small p e l l e t s of pure elemental s i l v e r (greater than 99.9% pure Ag) were recovered from these t e s t s . In the p i l o t t e s t , 6,800 kg (15,000 l b ) of waste X-ray f i l m were burned a t the r a t e of 90-105 kg t r (200-230 l b / h ) . The average a i r feed r a t e was 290 m h"* (180 scfm). The a i r / f i l m r a t i o corresponded to 50% t h e o r e t i c a l a i r . Since the main purpose o f t h i s t e s t was to recover s i l v e r , no attempt was made to 3

3

1

3

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

analyze the o f f - g a s . A f t e r the f i l m had been g a s i f i e d , the s i l v e r and s a l t were drained from the v e s s e l and 160.5 kg (354 l b ) of 99.97% pure m e t a l l i c s i l v e r were recovered.

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Conclusion The Rockwell I n t e r n a t i o n a l molten s a l t process f o r g a s i f i c a t i o n of wastes w i t h resource recovery has been shown here to be w e l l - s u i t e d f o r the p r o c e s s i n g of a v a r i e t y of wastes. A v a r i e t y of waste forms may be processed, t h a t i s , s o l i d s , l i q u i d s , and s o l i d - l i q u i d mixtures. The process i s s u i t a b l e f o r a p p l i c t i o n s which i n v o l v e e i t h e r s m a l l or l a r g e throughputs. The g a s i f i c a t i o n medium, sodium carbonate, i s s t a b l e , n o n - v o l a t i l e , inexpensive, and nontoxic. S u l f u r - c o n t a i n i n g p o l l u t a n t s are r e t a i n e d i n the melt when s u l f u r - c o n t a i n i n g wastes are g a s i f i e d . In the same manner, halogen-containing p o l l u t a n t s are r e t a i n e d during g a s i f i c a t i o n of halogen-containing wastes. The g a s i f i c a t i o n of a h i g h n i t r o g e n - c o n t e n t waste ( l e a t h e r scraps) produces very l i t t l e N0 i n the o f f - g a s . V a l u a b l e minerals may be recovered by p r o c e s s i n g of the s a l t a f t e r g a s i f i c a t i o n of m i n e r a l - l a d e n wastes. In g e n e r a l , the molten s a l t process i s best a p p l i e d to waste materi a l s i n v o l v i n g p o t e n t i a l p o l l u t a n t s (such as s u l f u r or chromium) or to wastes where g a s i f i c a t i o n and resource recovery are important (such as the recovery of s i l v e r w i t h simultaneous g a s i f i c a t i o n of X-ray f i l m ) . X

RECEIVED November 16,

1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

18 Biomass Gasification at the Focus of the Odeillo (France) 1-Mw (Thermal) Solar Furnace M. J. ANTAL, JR. Princeton University, Princeton, NJ 08544

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C. ROYERE and A. VIALARON C.N.R.S., Odeillo, France

Recently completed research at Princeton University (1-3) has shown biomass gasification to be a three step process: 1. Pyrolysis. At modest temperatures (300°C or more, depending upon heating rate) biomass materials lose between 70% and 90% of their weight by pyrolysis, forming gaseous volatile matter and solid char. As discussed in this paper, very high heating rates enhance volatile matter production at the expense of char formation. Recent Princeton publications review mechanistic and kinetic research on cellulose (4), lignin (5), and wood (6) pyrolysis in more detail. 2. Cracking/Reforming of the Volatile Matter. At somewhat higher temperatures (600°C or more) the volatile matter evolved by the pyrolysis reactions (step 1) reacts in the absence of oxygen to form a hydrocarbon rich synthesis gas. These gas phase reactions happen very rapidly (seconds or less) and can be manipulated to favor the formation of various hydrocarbons (such as ethylene). Rates and products of the cracking reactions for volatile matter derived from cellulose, lignin, and wood are now available in the literature (1, 3, 5, 6). 3. Char Gasification. At even higher temperatures char gasification occurs by the water gas and Boudouard reactions, and simple oxidation: (water gas) C + H20 -> CO + H 2 (Boudouard) C + C02 + 2C0 C + ^o 2 -> CO ) C + o 2 + co 2 )

(oxidation)

Because pyrolysis (step 1) produces less than 30% by weight char for most biomass materials, the char gasification reactions (step 3) play a less important role in biomass gasification than steps 1 and 2. 0-8412-0565-5/80/47-130-237$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

238

Figure 1 i l l u s t r a t e s the c r i t i c a l r o l e played by step 2 i n cellulose gasification. By i n c r e a s i n g the temperature achieved by the gas phase v o l a t i l e matter from 500°C to 750°C, the carbon con­ v e r s i o n e f f i c i e n c y η i s increased from η = 0.1 to n = 0.76. Here the carbon e f f i c i e n c y n i s defined by η = carbon i n perma­ nent gases ν carbon i n s o l i d feed. 0

0

c

c

0

The carbon conversion e f f i c i e n c y i s emphasized here because ( f o r non-oxidative conversion processes) η provides an e x c e l l e n t measure o f how w e l l the energy and chemical content of the s o l i d f u e l feedstock i s converted to gaseous f u e l s and chemicals. Because about 20% o f the carbon i n i t i a l l y i n the c e l l u l o s e i s c a r r i e d by the char product o f step 1, the data presented i n Figure 1 i n d i c a t e s that f o r gas phase temperatures above 750°C and residence times o f 2 sec o r more, permanent gases and char are e s s e n t i a l l y the only products o f c e l l u l o s e g a s i f i c a t i o n . Less than 4% o f the feedstock carbon i s c a r r i e d by the condensible f r a c t i o n of the r e a c t o r e f f l u e n t .

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0

Because char commands a low market value, there i s some i n c e n t i v e to increase gas production at the expense o f char form­ a t i o n . The t r a d i t i o n a l approach i s to use the water gas, Boudouard, and combustion r e a c t i o n s (step 3) to g a s i f y the char produced by step 1. An a l t e r n a t i v e approach i s to r a p i d l y heat s o l i d biomass feed, modifying the p y r o l y s i s mechanism (step 1) and reducing the i n i t i a l formation o f char by the p y r o l y s i s r e a c t i o n s . The l a t t e r approach has been emphasized i n the research reported here. The work o f Broido (7), Shafizadeh (8), Lewellen (9) and others (10) has shown c e l l u l o s e p y r o l y s i s to be d e s c r i b a b l e i n terms o f a competitive mechanism: v o l a t i l e tars

(levoglucosan)

c e l l u l o s e -==CCII^I3L ~2

char + low molecular weight volatiles

Two p y r o l y s i s r e a c t i o n s compete to consume the c e l l u l o s e ; however only one r e a c t i o n produces char. The f i r s t r e a c t i o n i s favored by high temperatures and r a p i d heating, producing combustible v o l a t i l e matter at the expense of char formation. The second r e a c t i o n i s favored by low temperatures and slow heating o f the c e l l u l o s e . Thus chemical r e a c t o r s designed to provide very r a p i d heating ("flash p y r o l y s i s " ) o f s o l i d c e l l u l o s i c feedstocks can minimize char form­ a t i o n with the p o t e n t i a l o f s i g n i f i c a n t l y i n c r e a s i n g gas y i e l d s . With but one exception, past s t u d i e s o f the f l a s h p y r o l y s i s o f c e l l u l o s e using l a b o r a t o r y equipment have r e l i e d on r a d i a t i o n to achieve the high heating r a t e s r e q u i r e d . L i n c o l n (11) used pulsed carbon arcs and xenon f l a s h tubes to achieve the complete v o l a t i l ­ i z a t i o n of c e l l u l o s e by p y r o l y s i s r e a c t i o n s . Berkowitz-Mattuck

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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ANTAL ET AL.

239

Biomass Gasification

1 .0 CARBON EFFICIENCY

0.8

Χ

-

O W

υ Π3^ Μ

0.2

Ο Δ





• 4

5

6

7

R e s i d e n c e Time ( s e c )

Figure 1.

Cellulose carbon conversion efficiency as a function of gas-phase residence time for various gas-phase temperatures Vc

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

240

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

and Noguchi (12) used carbon arc and s o l a r furnace r a d i a t i o n sources to achieve f l a s h p y r o l y s i s o f cotton c e l l u l o s e . They p r o j e c t no char formation f o r r a d i a n t f l u x e s i n excess of 120 w/cm . Martin (13) used a high current carbon arc r a d i a t i o n source f o r h i s experiments, and noted that char formation was reduced to 4% o f the o r i g i n a l c e l l u l o s e weight with a r a d i a n t f l u x l e v e l o f 49 w/cm . Martin speculates that no char formation should occur f o r r a d i a t i o n f l u x e s exceeding 400 to 4000 w/cm . E x p l o r a t o r y research a t P r i n c e t o n has r e c e n t l y achieved 99% v o l a t i l i z a t i o n o f c e l l u l o s e with a f l u x l e v e l o f 30 w/cm . Other researchers (14-15) have also employed r a d i a t i o n sources to achieve very r a p i d heating o f c e l l u l o s i c m a t e r i a l s ; however t h e i r r e s u l t s are not p e r t i n e n t to t h i s research. 2

2

2

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2

Lewellen e t a l . (9) at M.I.T. studied f l a s h p y r o l y s i s of c e l l u l o s e using a bench s c a l e , e l e c t r i c a l l y heated screen. They found that f o r heating r a t e s ranging between 400 and 10,000°C/sec i n an i n e r t helium atmosphere the c e l l u l o s e completely vaporized by p y r o l y s i s reactions, leaving no char r e s i d u e . Only by extended heating o f the c e l l u l o s e at 250°C was the M.I.T. group able to produce some char (2% by weight o f the i n i t i a l c e l l u l o s e ) . Only l i m i t e d data i s a v a i l a b l e on the f l a s h p y r o l y s i s of l i g n o c e l l u l o s i c m a t e r i a l s . R e n s f e l t et a l . have reported a s i g n i f i c a n t r e d u c t i o n i n char y i e l d s f o l l o w i n g the f l a s h p y r o l y s i s o f various biomass m a t e r i a l s (17) . D i e b o l t has obtained high gas y i e l d s from Eco Fuel II by f l a s h p y r o l y s i s (18) . These r e s u l t s suggest that f l a s h p y r o l y s i s may be the p r e f e r r e d thermochemical method f o r o b t a i n i n g gaseous f u e l s and chemicals from a l l biomass m a t e r i a l s . The f a c t that most f l a s h p y r o l y s i s studies have used r a d i a n t heating suggests s o l a r heat as a n a t u r a l means f o r e f f e c t ing f l a s h p y r o l y s i s o f biomass f e e d s t o c k s . Since s o l a r r a d i a t i o n has a c h a r a c t e r i s t i c temperature o f almost 6000°K, i t can be used to achieve very r a p i d heating of opaque, s o l i d p a r t i c l e s . E a r l i e r s t u d i e s (2) have shown that the q u a n t i t y o f heat required f o r biomass g a s i f i c a t i o n i s small: l e s s than 1 Gj per Mg o f dry s o l i d feed. Consequently, small amounts o f s o l a r heat can be used to process large q u a n t i t i e s o f biomass. F i n a l l y , a recent study f o r the P r e s i d e n t s C o u n c i l on Environmental Q u a l i t y (19) concluded that the use o f s o l a r heat f o r f l a s h p y r o l y s i s o f biomass appears to be more economical than conventional g a s i f i c a t i o n processes. References 19-24 d i s c u s s i n greater d e t a i l these and other reasons f o r using s o l a r heat to g a s i f y biomass. Experiments described i n t h i s paper were undertaken to explore the use o f concentrated s o l a r r a d i a t i o n f o r the f l a s h p y r o l y s i s o f biomass. APPARATUS AND PROCEDURE The O d e i l l o 1000 kw ^ s o l a r furnace has been described i n d e t a i l by Royere (25); consequently only a summary w i l l be given t

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

18.

ANTAL

ET A L .

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here. The furnace c o n s i s t s o f s i x t y - t h r e e 6 χ 7.5 m h e l i o s t a t s which track the sun and r e d i r e c t the s o l a r r a d i a t i o n onto a 2000 m p a r a b o l i c concentrator which focuses the r a d i a t i o n w i t h i n a c i r c l e of about 20 cm r a d i u s . The h e l i o s t a t s are composed o f eleven thousand three hundred f o r t y 50 χ 50 cm f l a t , back surfaced mirrors and the parabola c o n s i s t s o f over 9000 mechanically warped m i r r o r s . Radiant f l u x l e v e l s o f 1600 w/cm are a v a i l a b l e a t the f o c a l point, and temperatures i n excess o f 3800°C can be obtained. 2

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2

The biomass f l a s h p y r o l y s i s r e a c t o r s , designed and f a b r i c a t e d at Princeton, followed i n part a c o a l g a s i f i c a t i o n r e a c t o r design described by Badzioch and Hawksley (26), and Howard (27). A v i b r a t i n g feeder with a c a p a c i t y o f about 1 g f e d about 0.01 g/s of powdered biomass m a t e r i a l i n t o a flow s t r a i g h t e n e r (see Figure 2). A small flow (40-100 ml/min) o f He was used as à c a r r i e r gas, and p a r t i a l l y f l u i d i z e d the bed o f biomass m a t e r i a l i n the feeder. E x i t i n g the flow s t r a i g h t e n e r , the biomass m a t e r i a l was entrained by flowing superheated steam (about 3 g/min) and c a r r i e d i n t o the s o l a r f l u x passing through the wall o f the r e a c t o r . Char residue was c o l l e c t e d i n a bucket and weighed. E x i t i n g the quartz r e a c t o r , the steam was condensed i n a t a r trap/condenser and permanent gases were c o l l e c t e d i n 1.2 1 t e f l o n bags f o r a n a l y s i s by gas chromatography. Following an experiment, the volume o f the i n f l a t e d bags was measured by water displacement and the volume o f gas produced during the experiment was c a l c u l a t e d . Two o f the f l a s h p y r o l y s i s r e a c t o r s used f o r the experiments were f a b r i c a t e d from Amersil T08 commercial grade 50 mm OD quartz tube, and one from 25 mm OD vycor tube (Corning Glass Co.). The flow straightener/female j o i n t was made o f quartz f o r one o f the 50 mm OD r e a c t o r s , and pyrex f o r the other two r e a c t o r s . The feeder was made p r i m a r i l y from p l e x i g l a s . T e f l o n tube (6 mm ID) was used to connect the r e a c t o r to the pyrex t a r t r a p . Biomass samples taken to France f o r use with the r e a c t o r included A v i c e l ® PH 101 and 102 powdered m i c r o c r y s t a l l i n e c e l l u l o s e , ground corn cob m a t e r i a l , hardwood and softwood sawdust, K r a f t l i g n i n , and Eco Fuel I I . The corn cob and softwood m a t e r i a l was sieved and samples with p a r t i c l e s i z e s 0.27

The very low char y i e l d s f o r the low f l u x experiments (Tables I - I I I ) , and the high y i e l d f o r the high f l u x experiment (Table IV) are a s u b j e c t o f i n t e r e s t . The r e a c t o r used i n the low f l u x experiments bent s l i g h t l y under exposure to the intense s o l a r f l u x ; consequently some o f the char may not have f a l l e n i n t o the bucket. However, very l i t t l e char was observed w i t h i n the r e a c t o r o u t s i d e o f the bucket f o l l o w i n g the experiments. On the other hand, copious amounts o f soot were p r e s e n t . More char was obtained i n the high f l u x experiment (using a l a r g e r bucket p r o p e r l y o r i e n t e d below the flow s t r a i g h t e n e r ) , and very l i t t l e soot was formed. The i n c r e a s e d formation o f char may have been the r e s u l t o f premature i n i t i a t i o n o f the p y r o l y s i s r e a c t i o n s by (lower i n t e n s i t y ) s c a t t e r e d r a d i a t i o n contained between the s h i e l d and the backplate surrounding the r e a c t o r . The c a v i t y c o n t a i n i n g the r e a c t o r acted as a conduit f o r the r a d i a t i o n , c a r r y i n g i t up and down the length of the r e a c t o r . T h i s unfortunate a r t i f a c t o f the experimental design could not be avoided because o f necessary s a f e t y precautions i n using the l a r g e s o l a r furnace.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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AND

BIOMASS

CONCLUSIONS

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Biomass m a t e r i a l s (powdered, m i c r o c r y s t a l l i n e c e l l u l o s e and ground corn cob m a t e r i a l ) have been s u c c e s s f u l l y g a s i f i e d i n a windowed chemical r e a c t o r operating at the focus o f the O d e i l l o 1 Mw-th s o l a r furnace. The quartz window survived r a d i a n t f l u x l e v e l s i n excess of 1000 w/cm2; however i m p u r i t i e s c a r r i e d by the steam flow i n t o the r e a c t o r u l t i m a t e l y clouded the window. Some d e v i t r i f i c a t i o n may a l s o have occured. Future experiments should be designed to i n s u r e that no mineral matter i s deposited on the chemical r e a c t o r ' s windowed area. P y r o l y t i c char y i e l d s o f the O d e i l l o experiments were q u i t e low: ranging between one and f o u r percent. Gas y i e l d s were a l s o r e l a t i v e l y low, but condensible y i e l d s were h i g h . These r e s u l t s r e f l e c t the important r o l e played by the gas phase chemistry ( l a r g e l y u n a f f e c t e d by the high s o l a r f l u x ) i n the production of permanent gases from biomass. The O d e i l l o r e s u l t s are i n good agreement with e a r l i e r f l a s h tube and arc image furnace work a s s o c i a t e d with the s i m u l a t i o n of thermonuclear weapons e f f e c t s . They are also i n concord with e a r l i e r P r i n c e t o n work on biomass g a s i f i c a t i o n . A c o n s i d e r a t i o n of the c h a r a c t e r i s t i c times f o r chemical k i n e t i c and heat t r a n s f e r phenomenon w i t h i n a r a p i d l y p y r o l y z i n g p a r t i c l e i n d i c a t e that heat t r a n s f e r (not chemical k i n e t i c s ) i s the r a t e l i m i t i n g s t e p . However, the thermochemical and o p t i c a l p r o p e r t i e s o f biomass m a t e r i a l s are p o o r l y understood and much more experimental work must be completed before d e f i n i t i v e conclusions i n t h i s important area can be made. Because the use of concentrated s o l a r r a d i a t i o n f o r d i r e c t g a s i f i c a t i o n of biomass m a t e r i a l s r e s u l t s i n the formation o f l i t t l e or no char without r e l i a n c e on the water gas or Boudouard r e a c t i o n s , s o l a r f l a s h p y r o l y s i s of biomass holds unusual promise f o r the economical production of l i q u i d and gaseous f u e l s from renewable resources. ACKNOWLEDGMENTS At P r i n c e t o n , much of the p r e l i m i n a r y experimental work was done by Mr. W. Edwards and Mr. F. Conner. The p l e x i g l a s feeder was f a b r i c a t e d by Mr. B. Reavis and the quartz r e a c t o r s by Mr. H. Olson. P r o f e s s o r W. Russel o f f e r e d h e l p f u l i n s i g h t s i n t o the r o l e of c h a r a c t e r i s t i c times discussed i n t h i s paper. In France, the gas a n a l y s i s was a b l y performed by Dr. Rivot. Dr. Tuhault, Mr. R i b e i l l and Mr. Peroy were of great a s s i s t a n c e i n operating the experiment. H e l p f u l information on the o p t i c a l p r o p e r t i e s o f quartz

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

was

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obtained from Mr. H. Hoover (Corning Glass), andAmersil Corporation. The Avicel microcrystalline cellulose was obtained from Dr. L.Jones with the FMC Corporation, and the ground corn cob material from Mr. S. Bosdick with DeKalb AgResearch. Support for this work was obtained jointly from the Solar Thermal Test Facilities Users Association and Centre National De La Recherche Scientifique. The authors also wish to thank F.Smith and M. Gutstein for their interest in this work.

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2.

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3.

Antal, M. J.; Friedman, H. L.; Rogers, F. E.; "A Study of the Steam Gasification of Organic Wastes", (Final Progress Report, U.S.Ε.P.A.)", Princeton University, Princeton, N. J., 1979.

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Antal, M. J.; Friedman, H. L.; Rogers, F. E. "Kinetic Rates of Cellulose Pyrolysis in Nitrogen and Steam", to appear in Combustion Science and Technology, 1979.

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8.

Shafizadeh, F.; Groot, W. F. "Combustion Characteristics of Cellulosic Fuels" in "Thermal Uses and Properties of Carbo­ hydrates and Lignins", Shafizadeh, F. et a l . (ed.), Academic Press, New York, 1976.

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Martin, S. "Diffusion Controlled Ignition of Cellulosic Materials by Intense Radiation", 10th International Symposium on Combustion, Cambridge, Mass. 1964.

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Shivadev, U.; Emmons, Η. W. Combustion and Flame, 1974, 22, 223.

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Rensfelt, Ε . ; Blomkvist, G; Ekstrom, C.; Engstrom, S.: Espenas, B-G.; Liinanki, L. "Basic Gasification Studies for Develop­ ment of Biomass Medium Btu Gasification Process", IGT Conference on Energy from Biomass and Wastes, Washington, D.C., 1978.

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Diebolt, J.; Smith, G. "Conversion of Trash to Gasoline", NWC Tech. Pub. 6022, Naval Weapons Center, 1978.

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Antal, M. J. "Biomass Energy Enhancement, A Report to the Presidents Council on Environmental Quality", Princeton University, Princeton, N. J. 1978.

20.

Antal, M. J.; Rodot, M.; Royere, C.; Vialaron, A. "Solar Flash Pyrolysis of Biomass" in Proceedings of the ISES Silver Jubilee International Congress, Atlanta, Ga., 1979.

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Antal, M. J. "Tower Power: Producing Fuels from Solar Energy" in Towards a Solar Civilization, Williams, R. (ed.), M.I.T. Press, Cambridge, Mass. 1978.

22.

Antal, M. J. "The Conversion of Urban Wastes" in Energy Sources and Development, Barcelona, Spain, 1978.

23.

Antal, M. J.; Feber, R. C.; Tinkle, M. C. "Synthetic Fuels From Solid Wastes and Solar Energy" in Proceedings of the World Hydrogen Energy Conference, Miami, Fla., 1976.

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Feber, R. C.; Antal, M. J. "Synthetic Fuel Production from Solid Wastes", EPA-600/2-77-147, Cincinnati, 1977.

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In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Badzioch, S.; Hawksley, P. G. W. Ind. Eng. Chem. Process. Des. Develop., 1970, 9, 521.

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Kobayashi, H.; Howard, J. B.; Sarofim, A. F. "Coal Devolatilization at High Temperatures", 16th International Symposium on Combustion, Cambridge, Mass., 1976.

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In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

19 Operation of a Downdraft Gasifier Fueled with Source-Separated Solid Waste S. A. VIGIL, D. A. BARTLEY, R. HEALY1, and G. TCHOBANOGLOUS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch019

Department of Civil Engineering, University of California, Davis, CA 95616

THE SOLID WASTE PROBLEM The disposal of solid waste is a critical problem faced by most communities. It is also costly in terms of capital and energy resources. In 1971, 109 million metric tons of solid waste were collected in the United States at a total cost of $2.64 billion for collection and disposal. By 1985, this quantity is expected to increase to between 150 and 200 metric tons per year with an annual cost between $4.02 to $5.06 billion.(1). Although the composition of municipal solid waste varies greatly both geographically and by season, an analysis of data from many cities in the United States shows a remarkable similarity. Typically, municipal solid waste in the United States contains about 40 percent combustible material by weight. Although resource recovery and recycling are receiving considerable attention today, most solid waste is still disposed of in a sanitary landfill. Even though it is widely recognized that placing solid wastes in a landfill is a misuse of potentially valuable resources, this practice will continue until economic and environmentally acceptable alternatives are found. One such alternative, the gasification of the paper fraction of solid waste is considered in this report. Recently, interest has developed in pyrolysis, thermal gasification, and liquefaction (PTGL) processes for the recovery of energy. The PTGL processes offer the advantage of producing a usable fuel (gas or liquid) from the combustible portion of solid waste. Jones, (2), provides an overview of the many processes currently under consideration. Unfortunately, most of these processes have one characteristic in common. They are more complex than conventional incineration systems. They are also very capital intensive. For example, one such system, the PUROX Process, developed by Union Carbide Corporation, is economic only in capacities ranging from 363 to 1814 metric tons per day of solid waste (3). The corresponding size of cities vary from about 200,000 to 1,000,000 in population. Because of the cost and complexity of such systems, they are not cost-effective for smaller cities. 'Current Address: Los Angeles County Sanitation District, Los Angeles, California.

0-8412-0565-5/80/47-130-257$05.00/0 © 1980 American Chemical Society

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A PTGL SYSTEM FOR SMALL COMMUNITIES Since small communities (< 100,000 population) cannot afford either conventional mass fired incinerators or the new generation of P T G L processes, they currently have few options for solid waste disposal other than landfills. Unfortunately, landfill sites near communities are getting scarce, and the cost of operating them is rapidly increasing. One possible system which could be used by smaller communities is to combine source separation of solid waste with a simple P T G L process for energy conversion of the paper fraction of the waste. Since typical solid waste contains over 40, percent paper, energy recovery from the paper fraction could reduce landfill requirements by the same amount. A low cost system for smaller communities is shown in Figure 1. It consists of a shredder to reduce the size of waste paper, a densification system to convert the shredded waste paper to a dense fuel "cube," the gasification reactor, a gas cleanup system, and an engine-generator to convert the gas to electrical power.

SOURCE SEPARATION OF SOLID WASTE It has been assumed for the past few years that the recycling of waste paper into newsprint or low quality paper is both economically and ecologically sound. However, current energy prices, coupled with the fluctuating nature of newsprint prices, are making energy recovery a viable option. Also, since only prime, hand selected, clean newsprint is suitable for recycling purposes, far more waste paper is available for energy recovery since cleanliness is unimportant. In a source separation system, residents are requested to place bundles of newspaper out with their weekly trash collection. The newspapers are picked up by the regular collectors and carried in special containers or racks on the trash trucks. Other cities use a smaller separate vehicle to collect paper and other recycable materials. Usually cities require that newspapers be tied into bundles. Magazines, paper bags, and food packaging are not accepted. Such a system is currently operated by the city of Davis, California as shown schematically in Figure 2. A source separation system designed to recover waste paper as a fuel could be less restrictive and as a result, a higher proportion of a given community's waste paper could be recovered. Such a system is shown in Figure 3. In this system, only a combustible fuel fraction and aluminum cans are recovered. No attempt is made to recover steel cans and glass because marketing of these components is difficult and seldom economic for smaller communities. Shredding the aluminum cans reduces on site storage requirements and increases the market value of the aluminum from $0.51/kg to $0.73/kg .

DENSIFICATION OF SOLID WASTE Although source separated solid waste could be directly fired in some types of furnaces or P T G L reactors, there are many advantages to densifying the waste before combustion. These advantages include: 1. Increased storability

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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259

Operation of a Downdraft Gasifier

DENSIFICATION

GAS CLEANUP

WASTE - ELECTRIC

PAPER

Figure 1.

POWER

Solid waste gasification system for small communities

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260

COMPACTOR TRUCK

Figure 2.

Conventional source-separation system—Davis, California

J ALUMINUM I ]SHREDDERΓ

COMBUSTIBLES

SHREDDED • ALUMINUM TO M A R K E T

ALUMINUM CANS A DENSIFICATIONkCOMBUSTIBLES TRUCK

FUEL " CUBES

NON-COMBUSTIBLES a FOOD W A S T E S

SANITARY LANDFILL COMPACTOR TRUCK

Figure 3.

Proposed combustible fuel source-separation system

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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2. 3.

Increased transportability Densified waste can be burned in stoker-type boilers designed for coal or the simplest types of P T G L systems (i,e., packed bed) The simplest type of densification system consists of a shredder followed by an agricultural type "cubing" machine. These machines were originally built to produce densified animal feeds, but can be modified easily to produce solid waste fuel cubes. One of the first systems of this type was operated during the early 1970's in Fort Wayne, Indiana, to produce a solid waste fuel for the city power plant (4). A more recent application of densification was demonstrated by the Papakube Corporation of San Diego, California, which manufactures solid waste cubes as a boiler fuel (5). Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch019

GASIFICATION Gasification is an energy efficient technique for reducing the volume of solid waste and the recovery of energy. Essentially, the process involves partial combustion of a carbonaceous fuel to generate a combustible fuel gas rich in carbon monoxide and hydrogen. The reader is referred to reference (6) for an excellent review of gasification reactions. The inventor of the process is unknown, but stationary gasifiers were used in England in the early 1800's (7). By the early 1900 s, gasifier technology had advanced to the point where virtually any type of cellulosic residue such as rice hulls, olive pits, straw, and walnut shells could be gasified. These early gasifiers were used primarily to provide the fuel for stationary gasoline engines. Portable gasifiers emerged in the early 1900's. They were used for ships, automobiles, trucks, and tractors. The real impetus for the development of portable gasifier technology was World War II. During the war years, France had over 60,000 charcoal burning, gasifier equipped cars while Sweden had about 75,000 wood burning cars. With the return of relatively cheap and plentiful gasoline and diesel o i l , after the end of World War II, gasifier technology was all but forgotten. However, in Sweden, research has continued into the use of wood fueled gasifiers for agriculture (8) and currently, downdraft gasification of peat is being pursued actively i n Finland (9). In the United States, gasification technology was, until recently, virtually ignored. In the early 1970's, work was started in the United States on "pyrolysis" systems for energy recovery from solid wastes. Many of these "pyrolysis" systems are actually complex adaptations of the simple gasification process. For example, the BSP/Envirotech multiple hearth pyrolysis system (10) and the P U R O X process (3) are in reality gasification systems. The reader is referred to (2) and ( H ) for an in-depth review of current research into pyrolysis and gasification systems. f

Reactor Types Four basic reactor types are used in gasification. 1. vertical packed bed 2. multiple hearth

They are:

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WASTES

A N D BIOMASS

3. rotary kiln 4. fluidized bed Most of the early gasification work in Europe was with the packed bed type reactors. The other types are favored in current United States practice, with the exception of the P U R O X oxygen blown gasifier. The simple vertical packed bed type reactor has a number of advantages over the other types including simplicity and relatively low capital cost. However, it is more sensitive to the mechanical characteristics of the fuel. Eggen and Kraatz, (12), discussed the merits and limitations of vertical bed gasifiers in detail. For this work, a co-current flow, packed bed vertical reactor (also called downdraft gasifier) was chosen. As shown in Figure 4, fuel flow is by gravity with air and fuel moving co-currently through the reactor. A t steady state, four zones form in the reactor. In the hearth zone, where air is injected radially into the reactor, exothermic combustion and partial combustion reactions predominate. Heat transfers from this zone upward into the fuel mass, causing pyrolysis reactions in the distillation zone and partial drying of the fuel in the drying zone. Actual production of the fuel gas occurs in the reduction zone, where endothermic reactions predominate, forming C O and H ^ The end products of the process are a carbon rich char and the low-feTU gas.

Gasification of Solid Waste As mentioned earlier, downdraft gasifiers are simpler to construct and operate than the other reactor types, but they have more exacting fuel requirements which include: 1. moisture content < 30 percent 2. ash content < 5 percent 3. uniform grain size Since wastes can be dried prior to gasification, excessive moisture can be overcome. However, ash content and grain size are more difficult to handle. When the ash content is higher than 5 percent solidified particles known as clinkers tend to form which can cause severe maintenance problems. Excessive fine material in the fuel can cause mechanical bridging in the fuel hopper. One method of overcoming these problems is to use more complex reactors sulch as the Envirotech Multiple Hearth System or a high temperature slagging gasifier, such as the P U R O X process, in which the ash is melted. Although these approaches work, they are costly and complex. A lower cost approach is to utilize the simplest reactor type, the downdraft gasifier, and tailor the fuel accordingly. A suitable fuel can be made by densifying the paper fraction of source separated solid waste to produce a densified refuse derived fuel (d-RDF), that has low moisture content, low ash content, and uniform grain size.

SMALL SCALE ENERGY CONVERSION The low-BTU gas from a downdraft gasifier can be utilized in several ways. The simplest technique is to burn the gas with stoichiometric amounts of air in a standard boiler designed for natural gas. This

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Operation of a Downdraft Gasifier

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19.

Figure 4.

Downdraft gasification

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264

requires minor modifications to the burner head to allow for more combustion air and enlargement of the gas feed pipes to account for the lower energy content of the gas (- 5.6 M J / m ) as compared to natural gas 37.3 M J / m ) Another approach is to cool and filter the gas and utilize it as an alternative fuel for internal combustion engines. Skov and Pap worth, (2), described the operation of trucks, buses, and agricultural equipment in Europe with gas produced using portable wood fueled gasifiers. Gasifiers can also be used to operate diesel engines as described in (6) and (9). In a solid waste gasification system for a small community, the low-BTU gas could be burned in a dual-fueled engine-generator. Two modes of operation are possible: 1. Operation of the gasifier-engine-generator set at the fuel cubing site. Electricity produced in excess of local requirements would be fed into the local power grid. 2. Production of fuel cubes at a central location and transport of the cubes to satellite gasifier systems in other locations.

THE EXPERIMENTAL SYSTEM To demonstrate the feasibility of operating a downdraft gasifier with densified solid waste, an experimental gasifier was designed and constructed. The complete system consists of three subsystems: 1. Batch fed downdraft gasifier 2. Data aquisition system 3. Solid waste shredding and densification system

Downdraft Gasifier The gasifier is a batch fed unit with a 46 cm diameter firebox. A cross section of the gasifier is shown in Figure 5. The unit is based on agricultural waste gasifiers designed and built by the Agricultural Engineering Department at the University of California, Davis Campus (13 and jl4). The gasifier was designed to operate at a rate of 23 kg/hr The gasifier is shown in operation in Figure 6.

Data Aquisition System Five type Κ (chromel-alumel) thermocouples are installed in the gasifier as shown in Figure 5. Additional thermocouples are installed on the air inlet and gas outlet lines. Temperature readings are recorded on paper tape with a Digitec Model 1000 Datalogger.

Shredding and Densification Equipment A 5 HP hammermill rated at 9 kg/hr was used to shred recycled newsprint. The shredded newspaper was densified with a John Deere Model 390 stationary Cuber rated at 4.5 metric tons per hour. Since the gasifier and shredder used in the experiments only have a capacity of 23kg/hr and 9kg/hr., respectively, an obvious mismatch exists in the

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Operation of a Downdraft Gasifier

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19.

Figure 5. Cross section—laboratory-scale solid waste gasifier

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266

Figure 6.

Solid waste gasifier in operation

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equipment. However, in full scale systems, the components would be matched in capacity.

LABORATORY TESTS Proximate analyses of the fuel and char were run using a standard laboratory drying oven, muffle furnace, and analytical balance according to A S T M Standard Methods. Ultimate Analysis for percent C , H , N , S, and Ο in the fuel char, and condensate was conducted by the Chemistry Department, University of California, Berkeley. The energy content of the fuel and char was determined with a Parr Oxygen Bomb Calorimeter. Gas samples were collected in Tedlar gas sample bags and analyzed for their content of C O , C 0 , Η - , Ο-, and total hydrocarbons using the process analyzer described in (U). Moisture content of the gas was determined by the condensation method (15).

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2

EXPERIMENTAL RESULTS To date, eight experimental runs have been conducted. Significant data from two of the runs, R U N 02-wood chips, and R U N 08-solid waste cubes, are shown in Tables I and II. The gas sampling equipment was not in operation for R U N 02, so a gas analysis is not available for that run; however, a good quality low-BTU gas was generated as evidenced by the clean burning gas flare. R U N 08, using solid waste cubes, is more completely documented.

COMPARISON OF SOLID WASTE CUBES WITH WOOD CHIPS Since the experimental gasifier is a batch fed device, i t must be periodically refueled. Due to the greater bulk density^of solid waste cubes (495 kg/m ) as compared to wood chips (231 kg/m ), a longer run time between refuelings is possible. In a commercial sized gasifier, the greater density of cubed fuels would reduce the size of fuel storage and transport equipment. A comparison can also be made of the operating temperatures of the reduction zone as measured by Thermocouple T2 (See Figures 5 and 7). Note that the gasifier reached steady state conditions faster with the cubed solid waste than with the wood chips. (Note: Flucuations in the reduction zone temperature for R U N 02 were caused by shutting down the gasifier for refueling. The large drop in reduction zone temperature for R U N 08 starting at T=140 minutes was caused by shutting down the gasifier to connect gas sampling equipment.)

TENTATIVE ECONOMICS OF A GASIFICATION SYSTEM Gasification is an emerging technology, therefore, any cost estimates of full scale systems must be used with caution. However, since full scale gasifier systems are now commercially available in the United States 0 6 and _17), tentative cost estimates can be made. Estimates were made of solid waste gasification systems for cities of 10,000 and 20,000 population. The estimates include capital and labor

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Table I

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FUEL AND OPERATIONAL DATA FOR TWO EXPERIMENTAL GASIFICATION RUNS Run 02 Wood Chips

Run 08 Solid Waste Cubes

Ultimate Analysis C,% H,% N,% S,% 0,% Residue

59.0 7.2 N/A N/A 32.7 1.1

44.4 5.6 0.3 0.1 45.8 3.8

Proximate Analysis VCM,% FC,% Ash,% Moisture,%

N/A N/A N/A 9

83.5 7.9 3.1 5.5

20.9

19.8

140 25.4 2.7 0.2 33 900 210 89

266 20.6 2.5 0.7 28 940 220 84

Item Fuel Summary

Energy Content, M3/kg (Dry Basis HHV) Operational Summary Net Run Time, min. Gasification Rate, kg/hr Char Production, kg/hr Condensate Production, kg/hr Air Input Temperature, °C Reduction Zone Temperature, °C Gas Outlet Temperature, °C Fuel Weight Reduction,%

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Table II

GAS ANALYSIS - RUN 08 Item

Value

Dry Gas Analysis, % by volume CO C0

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H

16.5 2

2

°2 N 2

Gas Moisture Content,% by volume

8.5 12.5 2

Λ

60.1

13.6

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Table III OPERATING AND CAPITAL COSTS FOR SOURCE SEPARATION OF SOLID WASTE Population, persons

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Item

10,000

Combustibles Collected Metric tons/year Metric tons/day Capital Costs Total C o s t Annual C o s t

20,000

3

1161 4.4

2322 8.8

$40,000 $ 7,830

$40,000 $ 7,830

Operating Costs Maintenance, tires, o i l , insurance Gasoline ($0.26/liter) Gasoline ($0.53/liter)

$ 7,440 $ 2,840 $ 5,680

$ 8,470 $ 5,220 $10,440

Labor Opet Operator ($ll/hr) Supervision & Overhead

$12,430 $ 3,110

$22,880 $ 5,720

Total Yearly Cost (Gasoline @ $0.26/liter) (Gasoline @ $0.53/liter)

$33,600 $36,500

$50,100 $55,300

Total Unit Cost ($/metric ton) (Gasoline @$0.26/iiter) (Gasoline @$0.53/liter)

$ 28.94 $ 31.44

0

0

d

u

$ 21.57 $ 23.83

a. Assumes 50% participation, solid waste @ 40% combustible, and solid waste generation = 1.6 kg/cap-day. b. Based on one 12.2 m , gasoline powered, side loading compactor truck, June 1979. c. Six year l i f e , 15% salvage value, 8% interest. d. 25% of direct labor.

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costs for a solid waste source separation system and capital costs only for a gasification system.

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Costs for the Source Separation of Solid Waste Costs were estimated for a source separation system as shown in Figure 3. It was assumed that 50 percent of the theoretically available combustible solid waste could be recovered. The total costs ranged from $28.94/metric ton for a city of 10,000 population (gasoline at $0.26/liter) to $23.83/metric ton for a city of 20,000 population (gasoline at $0.53/liter). The computations and all assumptions made are summarized in Table III. The computations do not include a credit for savings on tipping fees and the extension of landfill life as these costs are site specific. Gasification of 50 percent of the available combustible solid waste in a community could reduce landfill requirements by 20 percent.

Capital Costs of a Gasification System for Small Communities A cost estimate was obtained for a 122 cm diameter downdraft gasifier with gas cleanup and a dual fuel diesel engine-generator of 400KW capacity. One such system, operating two shifts per day, could handle the source separated solid waste from a community of 10,000 population. Two such systems, operating two shifts per day, would be required for a city of 20,000 population. Shredding and densification equipment would also be required for each system. Capital costs of each system (as of June 1979) are summarized i n Table IV. Construction, installation, and operating costs are not included.

CONCLUSIONS Based on experimental work with a downdraft gasifier the following conclusions can be made: 1. Densified, source separated solid waste is an acceptable fuel for downdraft gasifier. 2. A source separation system can be operated by small communities to produce a combustible fuel in the range of $23.83 per metric ton to $28.94 per metric ton. 3. Capital costs for a gasification system for a communities of 10,000 and 20,000 population would be on the order of $305,000 and $555,000 respectively.

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Table IV CAPITAL COSTS - GASIFICATION SYSTEM Population, persons 20,000

10,000 Quantity

Cost

Quantity

Cost

Gasifier-Engine-Generator

1

$250,000

2

$500,000

Shredder-Conveyor System**

1

15,000

1

15,000

1

40,000

1

40,000

Item a

0

Densification System Total Capital Cost

$305,000

$555,000

a.

MK VII Gasifier system (1.22 Meter Diameter Firebox) w/dual fuel diesel engine and 400 KW generator, Biomass Corporation. FOB Yuba City, California (June 1979).

b.

Shredder-Conveyor System, Miller Manufacturing Co., 0.91 metric tons per hour capacity, FOB Turlock, California Dune 1979).

c.

John Deere Model 390 Stationary Cuber w/electric motor and switchgear, 2.2 metric tons per hour capacity, FOB Moline, Illinois (June 1979).

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ACKNOWLEDGEMENTS The assistance of J. Goss, B. Jenkins, J. Mehlschau, and N. Raubach of the Department of Agricultural Engineering, University of California, Davis, is gratefully acknowledged. The research discussed in this paper was supported by grants from the University of California Appropriate Technology Program and the U.S. Environmental Protection Agency (Grant No. R-805-70-3010). The contents do not necessarily reflect the views of the University of California or the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

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LITERATURE CITED 1.

Tchobanoglous, G., Theissen, H., and Eliassen, R., "Solid Wastes Engineering Principles and Management Issues", McGraw-Hill Book Company, Inc., New York, 1977.

2.

Jones, J., "Converting Solid Wastes and Residues to Fuel", Chemical Engineering, Jan. 2, 1978, McGraw-Hill Inc. New York, 1978.

3.

Fisher, T.F., Kasbohm, M.L., and Rivero, J.R., "The PUROX System," in Proceedings 1976 National Waste Processing Conference, Boston, May 23-26, 1976, American Society of Mechanical Engineers, 1976.

4.

Hollander, H.I. and Cunningham, N.F., "Beneficiated Solid Waste Cubettes as Salvage Fuel for Steam Generation," in Proceedings 1972 National Incinerator Conference, New York City, June 4-7, 1972, American Society of Mechanical Engineers, 1972.

5.

Anonymous, "Strategy for Selling Dense RDF: 'Energy Factories'," Waste Age, July 1977.

6.

Williams, R.O., Goss, J.R., Mehlschau, J.J., Jenkins, B., and Ramming, J., "Development of Pilot Plant Gasification Systems for the Conversion of Crop and Wood Residues to Thermal and Electrical Energy," in "Solid Wastes and Residues Conversion by Advanced Thermal Processes," Jones, J.L., and Radding, S.B., Editors, American Chemical Society, Washington, D.C., 1978.

7.

Skov, N.A. and Papworth, M.L., "The PEGASUS Unit -Petroleum/Gasoline Substitute Systems," Pegasus Publishers, Inc., Olympia, Washington, 1974.

8.

Nordstrom, O., "Redogorelse for Riksnamndens for ekonomish forsvar sberedskap forskningsock fursosverksamhet pa gengasomradet rid statens maskinpravnigar 1957-1963", Chapters 1-5, Obtainable from National Swedish Testing Institute for Agricultural Machinery, Box 7035, 75007 Uppsala, Sweden.

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9.

Jantunen, M., and Asplund, D., "Peat Gasification Experiments and the Use of Gas in a Diesel Engine," Technical Research Center of Finland, Fuel and Lubricant Research Laboratory, Espoo, Finland, 1979.

10. Brown and Caldwell, Consulting Engineers, "Central Contra Costa County Sanitary District Solid Waste Recovery Full Scale Test Report, Volume One", Walnut Creek, California, March 1977.

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11. Jones, J.L., Phillips, R.C., Takaoka, S., and Lewis, F.M., "Pyrolysis, Thermal Gasification, and Liquefaction of Solid Wastes and Residues - Worldwide Status of Processes," Presented at the ASME 8th Biennial National Waste Processing Conference, Chicago, May 1978. 12.

Eggen, A.C.W. and Kraatz, R., "Gasification of Solid Waste in Fixed Beds," Presented at the Winter Annual Meeting, ASME, November 17-22, 1974, New York City.

13.

Williams, R.O. and Horsfield, B., "Generation of Low-BTU Fuel Gas from Agricultural Residues - Experiments with a Laboratory Scale Gas Producer", in Food, Fertilizer, and Agricultural Residues Proceedings of the 1977 Cornell Agricultural Waste Management Conference, Ann Arbor Science Publishers, Inc., Ann Arbor, 1977.

14.

Williams, R.O., and Goss, J.R., "An Assessment of the Gasification Characteristics of Some Agricultural and Forest Industry Residues Using a Laboratory Gasifier", Resource Recovery and Conservation, 3 (1979), pp 317-329.

15. Cooper, H.B.H. Jr. and Rosano, A.T. Jr., Source Testing for Air Pollution Control, McGraw-Hill Book Co., Inc., New York, 1974. 16.

Biomass Corporation, "The Fuel Conversion Project", Sales Brochure, Yuba City, California, 1979.

17. Industrial Development and Procurement, Inc., "Moteurs Diesel Duvant - Gasifier-Diesel Engine Electric Generating Plants", Sales Brochure, Pittsburgh, Pennsylvania, 1978. 18.

Williams, R.O., Personal Communication, Biomass Corporation, Yuba City, California, July 6, 1979.

RECEIVED November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

20 The Enerco Pyrolysis System E. W. WHITE and M. J. THOMSON

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

Enerco, Inc.,126Old Oxford Valley Road, Langhorne, PA 19047

P y r o l y s i s i s the one process by which wood wastes and residues can be converted economically to transportable high grade fuels and l i q u i d chemical feedstocks on a small scale consistant with the very dispersed nature of the forest resource. E f f i c i e n t p y r o l y s i s can be achieved at atmospheric pressure with temperatures of only 3 5 0 ° to 500°C. These conditions lend themselves to simple and inexpensive system design. P y r o l y s i s can be an energy e f f i c i e n t process y i e l d i n g a favorable energy balance because the process uses only a f r a c t i o n of the energy contained i n the wood. Enerco's goal i n the development of a mobile pyrol y s i s system has been to maximize the q u a l i t y and y i e l d of charcoal while making provision to o p t i o n a l l y c o l lect liquid distillates and to utilize the gases as an on-site f u e l . Some markets for charcoal are well established but the uses of the char oil as f u e l and e s p e c i a l l y as chemical feedstocks are not w e l l defined at t h i s time. With that i n mind, provision i s made to clean burn the uncondensed gases when the l i q u i d f r a c tions are not wanted. This development was i n i t i a t e d i n an e f f o r t to help stimulate improved forest management by making i t possible to produce valuable products from the kinds of unused residues that r e s u l t from intensive forest management programs. This argument has been discussed i n considerable d e t a i l i n two e a r l i e r publications (1,2). The first patent r e s u l t i n g from t h i s development has r e c e n t l y issued (3). Throughout t h i s development, major emphasis has been placed on c o n t r o l l i n g the environmental problems of smoke and p a r t i c u l a t e emission that t r a d i t i o n a l l y have been associated with charcoal production. Construction of a 10 ton per day prototype unit 0-8412-0565-5/80/47-130-275$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

was begun i n the s p r i n g of 1 9 7 6 . T e s t s were conducted i n f a l l 1 9 7 6 and s p r i n g 1 9 7 7 . A v a r i e t y of wood f e e d s were r u n i n c l u d i n g wet (50% HoO) and d r y (6% HoO) r u n o f - m i l l sawdust, wet (50% H 0 ) and a i r d r y (21% H2O) c h i p s and d r y (10% Η £ θ ) hogged wood. The p r o t o t y p e u n i t was m o d i f i e d t h r e e t i m e s to e v a l u a t e d i f f e r e n t r e a c t o r , combustion and condenser c o n f i g u r a t i o n s . D e s i g n o f the 2k t / d u n i t was i n i t i a t e d summer 19771 and s e r i o u s d i s c u s s i o n s were u n d e r t a k e n v/ith p o t e n t i a l customers. Two customers f i n a l l y p l a c e d f i r m orders with Enerco. These were F o r e s t Energy C o r p . , K i n g of P r u s s i a , P A . and the Tennessee V a l l e y A u t h o r i t y . Mr. C . Robert Enoch o f F o r e s t E n e r g y was i n t e r e s t e d i n the system p r i m a r i l y f o r the c h a r c o a l p r o d u c t i o n c a p a ­ bilities. H i s p l a n s were t o use the 24D u n i t a t a c o n v e n t i o n a l s a w m i l l s i t e and to supplement the m i l l ' s r e s i d u e s u p p l y w i t h r e s i d u e s from nearby s o u r c e s . D r . E . Lawrence K l e i n , who headed the TVA i n q u i r y , became i n t e r e s t e d i n the 24D u n i t , not o n l y f o r i t s c h a r c o a l and c h a r o i l p r o d u c t i o n but a l s o f o r i t s p o t e n ­ t i a l t o s u p p l y excess wood gas t h a t c o u l d be used as a s u b s t i t u t e f o r f u e l o i l or n a t u r a l gas w h i l e the c h a r ­ c o a l was b e i n g p r o d u c e d . TVA was i n t e r e s t e d i n b e i n g a b l e t o c o l l e c t the o i l s from a v a r i e t y of wood f e e d s f o r e v a l u a t i o n and use as a low s u l f u r f u e l . TVA s t u d i e s l e a d t o f o r m u l a ­ t i o n of the M a r y v i l l e p r o j e c t . \ ± ) At M a r y v i l l e College, the 24D u n i t w i l l be used to produce c h a r c o a l from p u r c h a s e d wood f e e d . D u r i n g o p e r a t i o n excess wood gas w i l l be burned i n one o f the c o l l e g e ' s two b o i l e r s t o s u p p l y steam. O i l s w i l l be c o l l e c t e d and s t o r e d f o r s a l e or use d u r i n g p y r o l y z e r downtime or d u r i n g peak fuel loads. The c h a r c o a l w i l l be s o l d to g e n e r a t e i n ­ come t o the c o l l e g e . The TVA u n i t was d e l i v e r e d e a r l y J a n u a r y 1 9 7 9 · The F o r e s t E n e r g y u n i t was d e l i v e r e d e a r l y May 1 9 7 9 . Both u n i t s have been u n d e r g o i n g shakedown t e s t s and evaluation. A t p r e s e n t , the TVA u n i t i s b e i n g f i t t e d w i t h automated f e e d l o a d i n g and c h a r c o a l h a n d l i n g equipment. A d d i t i o n a l l y , TVA has r e c o n f i g u r e d some o f the components t o s h o r t e n wood gas r u n s and has added a d d i t i o n a l c o n t r o l s to make the r o u t i n e o p e r a t i o n o f the system more s t r a i g h t f o r w a r d . A l l components, i n c l u d i n g b u r n e r and d u c t i n s u l a ­ t i o n , a r e r u g g e d l y c o n s t r u c t e d and weather p r o o f e d t o w i t h s t a n d r e p e a t e d s i t e t o s i t e moves. F i g u r e 1 shows the TVA u n i t the day i t a r r i v e d a t A l c o a , T N . i n a snow s t o r m . The t r i p o r i g i n a t e d the p r e v i o u s a f t e r n o o n a t D u B o i s , P A . Temperatures d u r i n g the f i r s t e v e n i n g ' s t r a v e l were below - 1 6 ° C . The 24D u n i t w i t h g r o s s

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

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WHITE AND THOMSON

The Enerco Pyrolysis System

277

Figure 1. Photograph of Enerco 24D pyrolyzer delivered to TVA, Alcoa, TN, January 1979

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

278

weight o f a p p r o x i m a t e l y 1 2 t o n rode smoothly a t speeds of up t o 9 0 km/hr and a r r i v e d i n l e s s t h a n 2k hours a t the end o f the 1 1 0 0 km t r i p w i t h no apparent r o a d damage.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

Design

Concept

A schematic o f the 2kD system i s shown i n F i g u r e 2. The t i t l e 2kO i s d e r i v e d from the d e s i g n c a p a c i t y of 2k t o n p e r day c h a r c o a l o u t p u t . The b a s i c t r a i l e r mounted system i s comprised o f t h r e e subsystems! 1 ) a r e a c t o r , 2 ) a r e c i r c u l a t i n g gas l o o p t o b r i n g heat i n t o the r e a c t o r by i n d i r e c t c o n t a c t o f t h e r e c i r c u l a t i n g gas w i t h h o t p r o d u c t s o f combustion i n a heat exchanger and 3 ) the combustion system. A n c i l l a r y subsystems such as a condenser t o o b t a i n l i q u i d d i s t i l l a t e s (shown i n s k e t c h ) and secondary heat exchangers ( n o t shown) are n o t c r i t i c a l t o the o p e r a t i o n o f the 2kO system. The r e a c t o r a c c e p t s comminuted wood i n t h e form o f r u n - o f - m i l l sawdust, hogged wood, c h i p s or s h a v i n g s . The f e e d e n t e r s the t o p o f the s t a t i c v e r t i c a l bed reactor. L e v e l s e n s o r s a u t o m a t i c a l l y i n t e r r u p t the l o a d i n g when t h e r e a c t o r i s f i l l e d t o the p r o p e r l e v e l . Whenever the wood f e e d l e v e l drops below a second s e l e c t e d l e v e l , the l o a d auger a u t o m a t i c a l l y r u n s u n t i l the f u l l l o a d l e v e l i s r e a c h e d . Throughput r a t e o f the r e a c t o r i s governed by t h e char o f f - l o a d i n g r a t e . T h i s i s c o n t r o l l e d by the o p e r a t i n g s c h e d u l e o f t h e o f f - l o a d auger which can e i t h e r be r u n c o n t i n u o u s l y or i n t e r m i t t e n t l y . At a g i v e n throughput r a t e t h e q u a l i t y o f t h e char i s dependent on 1 ) t h e d i m e n s i o n o f the l a r g e r p i e c e s o f wood i n t h e f e e d 2 ) temperature and volume o f the r e c i r c u l a t i n g gas stream and 3 ) m o i s t u r e c o n t e n t o f t h e f e e d . The r e a c t o r i s b u i l t t o a c c o m p l i s h a h o r i z o n t a l f l o w o f gases through t h e beds i n such a way t h a t t h e t o p and bottom o f the r e a c t o r a r e stagnant zones and the gases e x i t i n g from the beds do so a t a s u f f i c i e n t l y low v e l o c i t y t o p r e v e n t l o f t i n g and entrainment o f f i n e s . A hot f a n ( F j ) i n F i g u r e 2 a c t s i n a p u s h - p u l l mode t o suck gases from t h e r e a c t o r and p r e s s u r i z e them to move through the c i r c u i t s . The volume o f r e c i r c u l a t e d gas t h r o u g h the h e a t e x c h a n g e r - r e a c t o r l o o p i s set by v a l v e V £ . The o f f - g a s v a l v e V± o p e r a t e s a u t o m a t i c a l l y i n r e s p o n s e t o a p r e s s u r e impulse l i n e i n t h e top o f the r e a c t o r above the wood f e e d . T h i s l i n e p r o v i d e s a p r e s s u r e s i g n a l r e f e r e n c e d t o ambient b a r o metric pressure f o r adjusting t o a c c o m p l i s h the desired pressure d i f f e r e n t i a l . T y p i c a l l y t h i s i s set at z e r o or minus 3 · 0 Pa t o p r e v e n t wood gas escape

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

20.

WHITE AND THOMSON

The

279

Enerco Pyrolysis System

FEED C O M B . AIR

j

.OIL S T A R T

|\SI h

iVl LN

BURNER

R Ε A C . T,

, \CHAR t.

el ®i COND.

W O O D GAS

01 F

2

Figure 2.

Schematic of Enerco pyrolysis unit

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch020

280

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

w h i l e m i n i m i z i n g i n t a k e o f ambient a i r through the f e e d auger. T h u s , a c t i o n o f the o f f - g a s v a l v e V i i s the dominant c o n t r o l over f u g i t i v e smoke e m i s s i o n from the system. By u s i n g the p y r o l y s i s gas as the h e a t c a r r i e r to the r e a c t o r , n i t r o g e n i s e s s e n t i a l l y e x c l u d e d from the r e a c t i o n . T h i s i s important i n p r e v e n t i n g format i o n of nitrogenous p y r o l y s i s products i n c l u d i n g , of c o u r s e , the n i t r i c a c i d t h a t forms i n a i r - u s i n g p y r o l y s i s processes. The heat exchanger i s o p e r a t e d i n c o u n t e r flow w i t h the wood gas e n t e r i n g a t the top w h i l e the hot p r o d u c t s of combustion (POC) from the combustion chamber e n t e r s a t the b o t t o m . Temperature of the r e t u r n i n g wood gas i s c o n t r o l l e d by a u t o m a t i c a l l y a d j u s t i n g the volume ( V 3 ) of POC a l l o w e d to pass through the heat exchanger. The temperature can be set anywhere i n the range o f 3 0 0 ° t o 5 0 0 ° C w i t h a c o n t r o l p r e c i s i o n o f +I50C. The combustion system uses an o i l - f i r e d s t a r t u p b u r n e r to i n i t i a t e the p y r o l y s i s r e a c t i o n and t o i n c i n e r a t e the e a r l y wood gas stream t h a t i s too d e f i c i e n t i n f u e l v a l u e t o s u s t a i n i t s own f l a m e . Once the r e a c t i o n produces b u r n a b l e wood g a s , the o i l b u r n e r can e i t h e r be shut down o r put on low f i r e . Because the wood gas v a r i e s b o t h i n volume and f u e l v a l u e , and b e cause no gases are p e r m i t t e d to escape t o the atmos p h e r e , the gas b u r n e r must be q u i t e f l e x i b l e . A prepackaged r a t i o c o n t r o l l e r (not shown on s k e t c h ) senses the wood gas flow u s i n g the p r e s s u r e drop a c r o s s an orifice plate. Combustion a i r i s a u t o m a t i c a l l y metered i n a f i x e d r a t i o t o the b u r n e r . Compensation f o r g r o s s changes i n wood gas f u e l v a l u e a r e made m a n u a l l y by c h a n g i n g the wood g a s / c o m b u s t i o n a i r volume r a t i o . Temperature o f the POC a t the r e a r o f the combustion chamber ( b u r n e r ) i s r e a d out c o n t i n u o u s l y . The POC s t a c k i s equipped w i t h an a u t o m a t i c back p r e s s u r e d e v i c e to g i v e the h e a t exchanger f i r s t p r i o r i t y c a l l on POC. The base o f the s t a c k has a f l a n g e d p o r t from which POC can be d u c t e d t o d r i e r s or o t h e r equipment. S i m i l a r i l y , a b l a n k e d o f f p a r t on the wood gas r u n can be used t o d i r e c t some o f the wood gas t o an a d j a c e n t burner i f d e s i r e d . R e s u l t s and D i s c u s s i o n T a b l e I g i v e s r e s u l t s o f the proximate a n a l y s i s o f c h a r c o a l and c h a r o i l o b t a i n e d from the 1 0 t / d p r o t o t y p e . The c h a r c o a l i s o f e x c e l l e n t q u a l i t y f o r most uses. However, the v a l u e of 0 . 3 ^ % s u l f u r i n t h i s sample was q u i t e s u r p r i s i n g . A n a l y s e s o f t h r e e o t h e r

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

20.

WHITE AND THOMSON

TABLE I .

A n a l y s i s o f E n e r c o P r o d u c t s From P r o t o t y p e

Heat o f Combustion MJ/kg (BTU/lb) % ASH

CHARCOAL

CHAROIL

29.85 (12,834)

22.27 (9,573)

4.7^

1.14

.35

.11

% VOLATILE MATERIAL

23.03

N/A

% FIXED CARBON

68.44

N/A

%s

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The Enerco Pyrolysis System

samples o f t h e same r u n were made t o check t h i s r e s u l t . A l l t h r e e y i e l d e d v a l u e s i n the range o f 0 . 0 7 "to 0.10 vrffo s u l f u r . T a b l e I I summarizes r e s u l t s o b t a i n e d from TVA f o r t h e i r 24D system. A g a i n , the c h a r c o a l i s o f h i g h q u a l i t y w i t h s u l f u r r e s u l t s i n the range one would e x p e c t . TABLE I I .

P r e l i m i n a r y T e s t i n g o f TVA P y r o l y s i s Specimens G r o s s Heat o f Combustion MJ/kg (BTU/lb)

White Oak ( U n c a r b o n i z e d )

18.81

(8089)

White Oak ( P a r t l y C a r b o n i z e d )

20.52

(8822)

C a r b o n i z e d White Oak (No H 0 ) Average o f 2 Specimens

31.11

(13377)

C a r b o n i z e d Wood ( P o s s i b l y w i t h H 0 C o o l Down)

30 .84

(13261)

Condensate

28.39

(12207)

Condensate and C a r b o n i z e d Wood ( S o l i d )

32.04

(13774)

Condensate

25.83

(11106)

2

2

(Solid)

(Viscous)

At t h i s p o i n t i n the development o f t h e E n e r c o 2^D p y r o l y s i s system the d e s i g n c o n c e p t and i t s advantages have been demonstrated. I n p a r t i c u l a r , t h e r e a c t o r d e s i g n s u c c e s s f u l l y e x c l u d e s n i t r o g e n from the r e a c t i o n and does n o t r e q u i r e c y c l o n e s o r o t h e r p a r t i c u l a t e c l e a n u p downstream. The combustion system c l e a n l y

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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282

i n c i n e r a t e s t h e low f u e l v a l u e s t a r t u p gases and t a k e s over t o c l e a n l y burn t h e v a r i a b l e ( q u a n t i t y and q u a l i t y ) pyro g a s e s . As o f t h i s w r i t i n g , n e i t h e r u n i t has c o n f i r m e d a l l t h e economic assumptions t h a t have t o be f i n a l l y met b e f o r e t h e n e x t u n i t s a r e t o be b u i l t . I n p a r t i c u l a r i t i s n o t y e t c e r t a i n j u s t what t h e exact s i z e o f t h e r e a c t o r and h e a t exchanger needs t o be t o meet t h e 2k t / d p r o d u c t i o n c a p a c i t y f o r a l l t h e k i n d s o f wood f e e d one would l i k e t o p y r o l y z e . I t i s , however, becoming i n c r e a s i n g l y apparent t h a t d e f i n i t e advantages a c c r u e from u s i n g bone d r y wood f e e d . The h i g h e r t h e m o i s t u r e c o n t e n t , t h e slower t h e p y r o l y s i s p r o c e e d s and t h e o i l s appear t o be o f lower q u a l i t y . The o r i g i n a l premise t h a t c h a r c o a l would f i n d mark e t s a s an a l t e r n a t i v e f u e l f o r power g e n e r a t i o n and f o r home h e a t i n g i s now w i d e l y d i s c u s s e d . TVA has c o n c l u d e d t h a t c h a r c o a l c o u l d be used i n c o a l f i r e d g e n e r a t i n g p l a n t s e i t h e r a l o n e o r as an e x t e n d e r t o be mixed w i t h h i g h s u l f u r c o a l s . Two l a r g e e l e c t r i c u t i l i t i e s have i n d i c a t e d t o t h e a u t h o r s t h a t they would purchase c h a r c o a l i f i t were t o become a v a i l a b l e i n q u a n t i t i e s on t h e o r d e r o f 1 0 , 0 0 0 t / y o r more and assuming t h a t no u n u s u a l d u s t i n g problems r e s u l t e d . R e c e n t l y Brooks and F i e l d have r e p o r t e d on t h e i r a n a l y s i s o f t h e r o l e c h a r c o a l c o u l d p l a y as a domestic h e a t i n g f u e l i n Maine. (£) Acknowledgements Mr. F r e d K n o f f s i n g e r and F r a n c i s Gross c o l l a b o r a t e d i n t h e development and e a r l y t e s t i n g o f t h e o r i g i n a l p r o t o t y p e u n i t . Lee-Simpson A s s o c i a t e s a i d e d i n e n g i n e e r i n g t h e f i r s t p r o d u c t i o n s c a l e u n i t . Mr. C. Robert Enoch o f F o r e s t E n e r g y has been h i g h l y i n s t r u mental i n s u p p o r t i n g the commercial development o f t h e 2kD u n i t and has been v e r y h e l p f u l i n d e s i g n and t e s t i n g o f h i s u n i t . D r . E . Lawrence K l e i n o f TVA has been p a r t i c u l a r i l y i n s t r u m e n t a l i n promoting t h e p y r o l y s i s c o n c e p t . H i s i n s i g h t s i n t o p r a c t i c a l f o r e s t r y and the r o l e t h a t wood energy should have i n o v e r a l l timber and w i l d l i f e management have been most i n s t r u c t i v e and stimulating. Mr. Robert M a r s h a l l o f N o r t h American Mfg. has been i n v a l u a b l e by working out t h e combustion burner and c o n t r o l system as w e l l as d e v o t i n g a g r e a t d e a l o f time t o t h e e n t i r e 2kD system. T h i s d e v e l o p ment program has been supported by p r i v a t e i n d i v i d u a l s and by t h e s a l e o f t h e two u n i t s .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

20. WHITE AND THOMSON

The Enerco Pyrolysis System

283

Literature Cited 1.

2. 3.

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4. 5.

White, E. W., "Wood Charcoal as an Extender or Alternative for Coal: An Immediately Available Energy Source", Earth and Mineral Sciences Vol. 46 No. 4 (Publication of the College of Earth and Mineral Sciences, Penn State University) 1977. White, E. W., "Charcoal: Fuel for Thought", American Forests, p. 21, Oct. 1978. White, E. W., F. M. Gross and F. E. Knoffsinger, "Continuous Drying and/or Heating Apparatus" U.S. Patent No. 4,165,216, 1979. Klein, E. L . , "Maryville College Pyrolysis Project", Southern Lumberman. Dec. 1978. Brooks, D. J. and D. B. Field, "Potentials of Charcoal Production for Forest Stand Improvement and Domestic Space Heating in Maine" Cooperative Forestry Research Unit, University of Maine, Orono, Research Bulletin 1, March 1979, 52 pp.

RECEIVED

November 20, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

21 Development of Modular Biomass Gasification and Combustion Systems JAMES FLETCHER and RICHARD WRIGHT

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch021

Industrial Combustion Inc., 4465 N. Oakland, Milwaukee, WI 53211

The need for retrofit devices to convert biomass materials to combustible fuel gas is well established. Several developers have built and operated successful biomass gasifiers, for example the systems reported by the University of California-Davis and Georgia Tech Engineering Experiment Station. The objective of the development reported here is to reduce tradional gas producer technology to commercial practice so that unattended biomass utilization systems under completely automatic control can be available to boiler operators now burning fluid fuels in packaged steam and heat generators. The system is to be designed for maximum gas production with minimum carbon remaining in the ash and zero liquid wastes production. The system must be highly reliable and simple enough to operate at optimum efficiency with a minimum of unskilled attention. Defined specifications are: 1. Feed stock to be densified pellets. 2. Generator to be of crossflow type. 3. Gas combustor to be close coupled to generator. 4. Structure to be an integrated packaged unit. 5. Able to resist abnormal conditions. 6. Minimum power required to operate. 7. Combustion and system operating controls to include programming, combustion monitoring and operating rate regulation. 8. Gas combustor to have integral automatic ignitor and electronic flame sensor. 9. Capacity ranges to be from 2 x 106 to 30 x 106 B.t.u. per hour. (2.1 to 31.7 GJ/hr.). Biomass gas producers can generate liquid, gaseous and solid end products. The desired end product of this unit is gas. Gas temperature is maintained high enough to inhibit condensation of low boiling point distillates. Design and development tasks were separated into individual projects : 1. Feed stock supply. 0-8412-0565-5/80/47-130-285$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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2. Feed s t o c k s u r g e r e s e r v o i r . 3. Pyrolysis reactor. 4. O x i d a t i o n - R e d u c t i o n r e a c t o r . 5. Refuse removal. 6. Forced d r a f t a i r supply. 7. Gas c o m b u s t o r . 8. Generator c o n t r o l s . 9. System and c o m b u s t o r c o n t r o l s . To v e r i f y d e s i g n p a r a m e t e r s , a s e r i e s o f s t r u c t u r e s d e s i g n e d f o r a p p r o x i m a t e l y 4 χ 10^ B . t . u . (4.22 GJ) w e r e c o n s t r u c t e d and m o d i f i e d a s improvements w e r e i n d i c a t e d and b e t t e r components became a v a i l a b l e . The f i r s t c r u d e p r o t o t y p e m i g h t have been c o n s i d e r e d a s c o m m e r c i a l l y v i a b l e by some based upon an o f f e r t o p u r c h a s e " a s i s " by a s e r i o u s p r o s p e c t i v e c u s t o m e r . R e g u l a t i o n o f p r o c e s s r a t e i n r e s p o n s e t o l o a d demand has been a c c o m p l i s h e d . A modulating type a c t u a t o r simultaneously p o s i t i o n s v a l v e s s e p a r a t e l y r e g u l a t i n g g e n e r a t o r a i r and gas combustor a i r f l o w r a t e s . The r a t e o f a s h removal i s r e g u l a t e d 1n p r o p o r t i o n t o f u e l and a i r s u p p l y . The heat o u t p u t demand i s t h e r e f o r e matched by t h e a i r d e l i v e r y r a t e t o t h e m a c h i n e . C o n t r o l s f o r r e a c t o r t e m p e r a t u r e and g a s t e m p e r a t u r e have been d e v e l o p e d f o r b o t h r e g u l a t i o n and emergency h i g h l i m i t protection. Temperature i n t h e r e a c t o r o x i d i z i n g zone i s a t t e n u a t e d by w a t e r v a p o r i n t r o d u c e d i n t o t h e a i r f l o w . The optimum r e a c t o r t e m p e r a t u r e depends l a r g e l y upon a s h f u s i o n temperature. Maximum r e a c t i o n r a t e o c c u r s a t 2500°F (1370°C) o r h i g h e r . W i t h most f u e l s i t i s n o t p r a c t i c a l t o o p e r a t e s u b s t a n t i a l l y above 2200°F (1200°C) b e c a u s e o f a s h and d i r t contaminant f u s i o n . A i r f o r g a s i f i c a t i o n and f o r c o m b u s t i o n o f p r o d u c t g a s i s d e l i v e r e d by a common b l o w e r w i t h i n d i v i d u a l r e g u l a t i o n o f s e p a r a t e steams t o t h e r e a c t o r and t o t h e c o m b u s t o r . Hot gas i s d e l i v e r e d t o t h e c o m b u s t o r a b o v e a t m o s p h e r i c p r e s s u r e . The gas c o m b u s t o r i s d e s i g n e d t o f i r e a g a i n s t n e g a t i v e , balanced o r p o s i t i v e b o i l e r f i r e b o x p r e s s u r e t o conform w i t h t h e b o i l e r r e q u i r e m e n t s . The c o m b u s t o r i s c o m p a r a b l e i n s i z e and s i m i l a r i n c o n f i g u r a t i o n t o o t h e r I n d u s t r i a l C o m b u s t i o n f i r i n g heads. R e l i a b i l i t y i s enhanced by c o m p l e t e a b s e n c e o f g a s v a l v e s . Maximum s a f e t y i s a c h i e v e d w i t h o u t d e p e n d i n g upon p r e s s u r e r e l i e f valves or explosion discs. Wide open b u r n e r d e s i g n w o u l d r e l i e v e any a b n o r m a l l y e l e v a t e d p r e s s u r e d i r e c t l y i n t o t h e b o i l e r w h i c h i n t u r n i s d i r e c t l y vented t o atmosphere. The need f o r c o n v e r s i o n o f p y r o l y s i s p r o d u c t s t o gas and v a p o r s h a v i n g b o i l i n g p o i n t s l o w e r t h a n t h e gas t e m p e r a t u r e narrowed t h e d e s i g n arrangement d e c i s i o n t o e i t h e r a downflow o r crossflow reactor. Many o t h e r f a c t o r s were c o n s i d e r e d i n t h e s e l e c t i o n o f a c r o s s f l o w r e a c t o r as most s u i t e d f o r t h e d e s i g n o b j e c t i v e s i n c l u d i n g f e e d s t o c k and r e f u s e h a n d l i n g , a i r p r e s s u r e r e q u i r e m e n t s , compact a r r a n g e m e n t and p r o c e s s c o n t r o l c h a r a c t e r i s ­ tics.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch021

21.

FLETCHER AND WRIGHT

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287

Complete achievement o f performance g o a l s r e q u i r e c o n t r o l o f feed stock p r o p e r t i e s . A t t h e s t a r t i t was assumed t h a t c o m m e r c i a l l y a v a i l a b l e d e n s i f i e d wood p e l l e t s w e r e s u b s t a n t i a l l y consistent in properties. F o r e x a m p l e , 7500 t o 8500 B . t . u . / l b . (17.5 t o 19.7 MJ/kg) \-k% a s h and 7~12£ m o i s t u r e . Experience has shown t h a t w h i l e t h e s e r a n g e s a r e t y p i c a l , a v a i l a b l e p r o d u c t s may s o m e t i m e s v a r y a p p r e c i a b l y . T h i s d e m o n s t r a t e s t h e need f o r commercial f u e l p e l l e t s t a n d a r d s . T h i s need i s r e c o g n i z e d by b o t h s u p p l i e r s and u s e r s . Several agencies i n c l u d i n g the Forest R e s o u r c e s Department o f N o r t h C a r o l i n a S t a t e U n i v e r s i t y have expressed i n t e r e s t in preparing standard s p e c i f i c a t i o n language. An ASTM s u b c o m m i t t e e i s l o o k i n g a t s p e c i f i c a t i o n s f o r c e l l u l o s e fuel p e l l e t s . The c h e m i c a l r e a c t i o n s and s t o i c h i o m e t r y o f t h e s y s t e m d e s c r i b e d a r e b a s i c a l l y t h e same a s a l l o t h e r t y p e s o f p y r o l y s i s b a s e d gas g e n e r a t o r s , s o a r e n o t d i s c u s s e d h e r e . The s c h e m a t i c a r r a n g e m e n t o f t h e m a c h i n e and l o c a t i o n o f t h e v a r i o u s r e a c t i o n z o n e s i s shown i n F i g u r e 1. F i g u r e 2 shows t h e g e n e r a l a r r a n g e m e n t o f a g a s i f i e r / r e a c t o r / c o m b u s t o r a p p l i e d t o a t y p i c a l h e a t i n g o r power b o i l e r . Many d i f f i c u l t p r o b l e m s w e r e s o l v e d . Most were o f an e l e m e n t a r y n a t u r e n o t r e q u i r i n g new t e c h n o l o g y , but a g r e a t d e a l o f g e n i u s was r e q u i r e d t o d e v e l o p s o l u t i o n s . The p r o b l e m s m i g h t be c l a s s i f i e d a s m a t e r i a l h a n d l i n g t e c h n i q u e s , s e l e c t i o n o f c o m m e r c i a l l y a v a i l a b l e components and a p p l i c a t i o n o f s u i t a b l e c o n t r o l s and r e g u l a t i n g s y s t e m s . A r r a n g i n g r e l i a b l e components i n t o a c c e p t a b l e c o m p a c t , b u t d e p e n d a b l e p a c k a g e s many t i m e s s m a l l e r t h a n t h o s e p r e v i o u s l y used by o t h e r g a s i f i e r d e v e l o p e r s was a d i f f i c u l t assignment. P r o b a b l y t h e most t r y i n g t a s k was a r r a n g i n g t h e f l o w p a t h o f v o l a t i l e p y r o l y s i s p r o d u c t s t h r o u g h t h e c h a r o x i d a t i o n and r e d u c t i o n z o n e s i n s u c h a manner t h a t c o n d e n s e d t a r w o u l d n o t render the r e d u c t i o n process i n e f f e c t i v e . P e r f o r m a n c e t e s t i n g was c o n d u c t e d w i t h o u t soph i s i t i c a t e d g a s a n a l y s i s i n s t r u m e n t a t i o n . T h i s m i g h t be b e s t d e s c r i b e d a s an e n g i n e e r i n g r a t h e r than s c i e n t i f i c approach. Measured o u t p u t d i v i d e d by measured i n p u t i s a p r a c t i c a l means f o r d e t e r m i n i n g system e f f i c i e n c y . This i s e n t i r e l y compatible w i t h the o b j e c t i v e o f r a p i d l y d e v e l o p i n g a p r a c t i c a l m a c h i n e f o r commercial utilization. H i s t o r i c a l p r a c t i c e s o n c e used w i t h c o k e a n d a n t h r a c i t e c o a l gas p r o d u c e r s do n o t a p p l y t o s y s t e m s f o r g a s i f y i n g h i g h v o l a t i l e b i o m a s s . The o n l y s i m i l i a r i t y between a b i o m a s s g a s i f i e r and a low v o l a t i l e c o a l g a s p r o d u c e r i s t h a t b o t h c o n v e r t s o l i d f u e l t o a low h e a t i n g v a l u e g a s . T h e s y s t e m s by n a t u r e a r e a l m o s t entirely different. P u b l i s h e d d a t a f o r wood c h a r shows r e a c t i o n r a t e s s i x t o t e n t i m e s a s r a p i d as r e a c t i o n r a t e s f o r c o k e o r a n t h r a c i t e c o a l . T h i s m i g h t l e a d t o c o n c l u s i o n t h a t wood c h a r g a s i f i c a t i o n s h o u l d be many t i m e s more r a p i d t h a n t h a t o f c o a l based m a t e r i a l s .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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288

Figure 1.

Schematic arrangement of pyrolysis-based gas generator and location of reaction zones

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

FLETCHER AND WRIGHT

Modular Biomass Gasification

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch021

21.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

289

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290

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W h i l e t h e w e l l documented wood c h a r r e a c t i o n d a t a i s p r o b a b l y a c c u r a t e , i t does not s p e c i f i c a l l y a p p l y t o t h i s system. P r e c i s e l a b o r a t o r y d e t e r m i n e d r e a c t i o n d a t a does n o t n e c e s s a r i l y a p p l y t o t h e wood g a s i f i e r b e c a u s e o f p o s s i b l e i n c o m p l e t e p y r o l y s i s t o pure char o r p o l l u t i o n o f char w i t h i n the r e d u c t i o n r e a c t o r w i t h condensed t a r . In o r d e r t o a c c u r a t e l y t e s t t h e s y s t e m w i t h a minimum o f i n s t r u m e n t a t i o n , a c c u r a t e a n a l y s i s o f t h e f e e d s t o c k was necessary. T h i s i n c l u d e s both proximate a n a l y s i s t o e s t a b l i s h v o l a t i l e f i r e d c a r b o n , m o i s t u r e , a s h and u l t i m a t e a n a l y s i s f o r c a r b o n , h y d r o g e n and o x y g e n . C a l o r i m e t e r d e t e r m i n e d h e a t i n g v a l u e i s needed. Efforts to c a l c u l a t e h e a t i n g v a l u e from u l t i m a t e a n a l y s i s d i s c l o s e d t h a t t h e D u l o n g and s i m i l a r e q u a s i o n s g e n e r a l l y s u i t a b l e f o r c o a l g i v e e x c e s s i v e d e v i a t i o n f r o m measured h e a t i n g v a l u e . Oxygen c o n t e n t i s an i m p o r t a n t f u e l p r o p e r t y . This i s a measure f o r t h e amount o f c h e m i c a l l y bound w a t e r i n t h e d r y f u e l . T h i s has an i m p o r t a n t b e a r i n g upon b o t h t h e p r o c e s s o p e r a t i o n and f i n a l gas c o m p o s i t i o n . The p r e s e n t s t a t e o f d e v e l o p m e n t i s t h e c o m p l e t i o n o f several t h i r d generation production units f o r outside evaluation by q u a l i f i e d i n t e r e s t e d i n s t i t u t i o n s and u s e r s . In house t e s t i n g and d e v e l o p m e n t o f l a r g e r c a p a c i t y u n i t s i s c o n t i n u i n g a t an increasing rate. RECEIVED November 16,

1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

22 Solid Waste Gasification and Energy Utilization FRANKLIN G. RINKER

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch022

Midland-Ross Corporation, Thermal Systems Technical Center, P.O. Box 985, Toledo, OH 43696

Until recently, solid waste has been considered only in the context of a disposal problem. With the threat of possible fuel curtailments and subsequent price increases, the energy content of solid waste is being recognized as a viable energy resource. The U. S. Bureau of Mines has forecast that the gross energy consumption will double by the year 2000 to approximately 193.4 quadrillion BTU's. Of this, approximately 41.2% will be consumed by industrial users. In many cases, these same industrial users are generating waste materials containing a significant amount of recoverable energy. Gasification of hydrocarbon bearing materials is not new. Gasification of coal and wood was practiced from the mid-19th century until the advent of large natural gas distribution systems. The gasification of solid wastes can be thought of as an extension of this existing technology, using updated materials, process control, and end use combustion techniques. In my discussion, I will attempt to answer the following questions concerning solid waste gasification: 1. What is gasification? 2. Why gasify solid waste? 3. How is gasification accomplished? 4. What is the present industrial application? 5. What is the future of solid waste gasification? What is Gasification? Technically speaking, gasification is the controlled thermal decomposition of organic material, producing a gaseous fuel and an inert solid ash residue. This controlled thermal processing can be accomplished through two types of reactions: 1. Pyrolysis of the solid waste is generally a low temperature endothermic reaction yielding a fuel rich offgas and solid residue containing the inert gas and fixed carbon fractions of the original material. 2. Complete gasification consists of the pyrolyzer reaction and an additional exothermic reaction of the fixed car0-8412-0565-5/80/47-130-291$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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BIOMASS

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bon with oxygen. The r e s u l t a n t products of t h i s process a r e a f u e l r i c h gas and a s o l i d i n e r t ash r e s i d u e . P y r o l y s i s has the advantage of not r e q u i r i n g an o x i d i z i n g agent such as a i r ; thus the offgas has a high heating value and, i n some cases, l i q u i d hydrocarbon f r a c t i o n s can be separated and stored. The process i s normally c a r r i e d out under r e l a t i v e l y low temperatures (800-1200°F), s i m p l i f y i n g equipment design and mat e r i a l handling requirements. The main disadvantage of p y r o l y s i s i s that a s i g n i f i c a n t p o r t i o n of the chemical energy contained i n the o r i g i n a l m a t e r i a l e x i t s the p y r o l y s i s process as s o l i d char. The u t i l i z a t i o n of t h i s char f o r end use heating a p p l i c a t i o n s i n v o l v e s s p e c i a l combustion and handling equipment. I t i s , theref o r e , u s u a l l y l a n d f i l l e d as char with a r e s u l t i n g l o s s i n i t s h e a t i n g value. Why

G a s i f y S o l i d Waste?

S o l i d waste g a s i f i c a t i o n o f f e r s the f o l l o w i n g b e n e f i t s over conventional d i s p o s a l means: 1. G a s i f i c a t i o n provides a c a p t i v e energy source i n a time of questionable energy a v a i l a b i l i t y and c o s t . 2. G a s i f i c a t i o n reduces the quantity of waste m a t e r i a l to be l a n d f i l l e d and the a s s o c i a t e d c o s t s . 3. The i n e r t ash m a t e r i a l discharged from the process i s o f t e n more compatible with l a n d i l l r e s t r i c t i o n s than the o r i g i n a l waste. 4. The f u e l gas can be used i n conventional end use systems, such as steam b o i l e r s , process and l i q u i d a i r h e a t e r s , and l a r g e i n d u s t r i a l furnaces. 5. The low process v e l o c i t i e s inherent i n g a s i f i c a t i o n m i n i ~ mize the need f o r offgas p a r t i c u l a t e c l e a n i n g devices r e q u i r e d f o r a i r q u a l i t y assurance. From a f u e l gas generation standpoint, the complete g a s i f i c a t i o n of s o l i d waste i s d e s i r a b l e . P r e v i o u s l y , the high temperatures r e s u l t i n g from the o x i d a t i o n r e a c t i o n of the f i x e d carbon contained i n the o r i g i n a l m a t e r i a l l i m i t e d the a p p l i c a t i o n of gasi f i c a t i o n to w e l l d e f i n e d feedstocks, such as c o a l , where the operating parameters were somewhat w e l l d e f i n e d . We have found that by using steam as an o x i d i z i n g agent i n the g a s i f i c a t i o n process, these r e a c t i o n temperatures can be c o n t r o l l e d , thus widening the a p p l i c a t i o n of g a s i f i c a t i o n to the s o l i d waste area. How

i s G a s i f i c a t i o n Accomplished?

G a s i f i c a t i o n of s o l i d waste can be accomplished i n a v a r i e t y of furnace designs. At Midland-Ross, we have s e l e c t e d the v e r t i c a l s h a f t furnace p r i m a r i l y because of i t s uncomplicated m a t e r i a l transport m e t h o d — g r a v i t y — a n d i t s e f f i c i e n t counterflow of mat e r i a l and process gas. This furnace i s shown on Figure #1.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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22.

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Solid Waste Gasification and Energy Use

FUEL GAS TO PROCESS

Figure 1.

Solid waste gasifier

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M a t e r i a l enters the top of the furnace through a charging hopper and metering mechanism and f a l l s through to the top of the m a t e r i a l bed. I t then moves down slowly through the four zones of r e a c t i o n and i s discharged f o r d i s p o s a l at the bottom as ash. At the same time, a i r and steam are admitted at the bottom of the shaft i n a manner designed to promote uniform d i s t r i ^ b u t i o n of these gases throughout the c r o s s - s e c t i o n of the s h a f t furnace. These gases then t r a v e l upward through the ash c o o l i n g zone, c o o l i n g the ash and p i c k i n g up super heat as they t r a v e l . As the a i r and steam enter the char r e a c t i o n zone, two d i s t i n c t and d i f f e r e n t chemical r e a c t i o n s occur. The oxygen contained i n the a i r r e a c t s with the carbon l i b e r a t i n g heat and forming carbon monoxide and carbon d i o x i d e . Concurrently, the steam r e a c t s with the carbon, g i v i n g o f f carbon monoxide and hydrogen. This water gas s h i f t r e a c t i o n i s endothermic and absorbs heat. By c a r e f u l l y c o n t r o l l i n g the balance of these two r e a c t i o n s , the temperature of the char r e a c t i o n zone can be c o n t r o l l e d producing optimum r e a c t i o n . The determination of t h i s balance i s best accomplished by p i l o t s c a l e t e s t i n g on the a c t u a l s o l i d waste to be g a s i f i e d . A f t e r passing through the char r e a c t i o n zone, the steam and a i r have been converted to a high temperature gas stream c o n s i s t i n g of mainly n i t r o g e n , hydrogen, carbon d i o x i d e , and carbon monoxide. This h i g h temperature gas stream then passes through the v o l a t i l i z a t i o n zone where i t t r a n s f e r s t h i s heat to the waste m a t e r i a l and causes a p y r o l y t i c r e a c t i o n , r e l e a s i n g the v o l a t i l e hydrocarbons contained i n the waste m a t e r i a l . These hydrocarbons c o n s i s t mainly of methane and ethane with h e a v i e r f r a c t i o n s o c c u r r i n g at lower r e a c t i o n temperatures. The f i n a l r e a c t i o n i s the forced d r y i n g of the incoming waste m a t e r i a l through the t r a n s f e r of heat from the hot v o l a t i l e gases to the waste by convection. The now f u e l r i c h gas then e x i t s the bed and passes out of the g a s i f i e r f o r end use a p p l i c a tion. What i s the Present I n d u s t r i a l A p p l i c a t i o n of G a s i f i c a t i o n ? The g a s i f i c a t i o n of i n d u s t r i a l s o l i d wastes i s not u n i v e r s a l in application. The f o l l o w i n g p o i n t s must be considered p r i o r to a p p l i c a t i o n : M a t e r i a l C o n s i d e r a t i o n s . The m a t e r i a l should conform to c e r t a i n c r i t e r i a f o r the s u c c e s s f u l a p p l i c a t i o n of g a s i f i c a t i o n . F i r s t , i t should have a r e l a t i v e l y low moisture content i n the range of 0-50%. The a d d i t i o n of water to the incoming m a t e r i a l causes a decrease i n o v e r a l l process e f f i c i e n c y as the excess moisture must be c a r r i e d through the process and discharged from the process at elevated temperatures. Second, the m a t e r i a l should not melt or s o f t e n when exposed to g a s i f i c a t i o n temperatures. Since these temperatures range

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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from 1200-2200°F most p l a s t i c wastes would be e l i m i n a t e d f o r consideration. However, even these m a t e r i a l s can be g a s i f i e d using a p y r o l y t i c process and a d i f f e r e n t furnace design. T h i r d , the m a t e r i a l should have a r e l a t i v e l y high h e a t i n g value somewhere i n the order of 5000-20,000 BTU/lb as r e c e i v e d . Fourth, the m a t e r i a l should be able to be s i z e d f o r proper flow through the s h a f t furnace. S i z i n g s i m p l i f i e s continuous charging of the m a t e r i a l while s t i l l maintaining an atmosphere seal. I d e a l p a r t i c l e s i z e s range from 1/2" to 6" mean dimension. End Use Considerations. The main requirement f o r s u c c e s s f u l end use of energy generated by g a s i f i c a t i o n i s a s u f f i c i e n t and continuous c a p a c i t y to u t i l i z e a l l of the energy produced. The most common end use i s the production o f process steam where the g a s i f i e r f u e l gas i s burned i n the conventional water tube b o i l e r and the steam produced i s f e d to the main plant steamline, r e l i e v i n g the load on f o s s i l f u e l f i r e d b o i l e r s . Other end uses are process a i r heaters f o r l a r g e product d r y e r s , i n d u s t r i a l furnace f i r i n g , and e l e c t r i c a l generation b o i l e r s . Economic Considerations. Economics, of course, w i l l j u s t i f y the technique o f s o l i d waste d i s p o s a l and f u e l gas generation. Some important v a r i a b l e s to be considered i n the economic balance are as f o l l o w s : 1. The q u a n t i t y of s o l i d waste generation should provide a s u f f i c i e n t load f o r maximum u t i l i z a t i o n o f the s i z e g a s i f i e r selected. 2. S o l i d waste generation should be c o n s i s t e n t or s u f f i c i e n t storage c a p a c i t y should be i n s t a l l e d to provide cons i s t e n t l o a d i n g of the g a s i f i c a t i o n system. 3. The present and f u t u r e f u e l cost and a v a i l a b i l i t y must be balanced against the c a p i t a l and operating c o s t . 4. The present and f u t u r e s o l i d waste l a n d f i l l cost and r e s t r i c t i o n s must be considered. Taking the above c o n s i d e r a t i o n s i n t o account along with- the cost of c a p i t a l and r e t u r n on investment goals, the economic j u s t i f i c a t i o n of s o l i d waste g a s i f i c a t i o n can be evaluated. An example of the proper a p p l i c a t i o n of s o l i d waste g a s i f i c a t i o n i s a p r o j e c t Midland-Ross i s p r e s e n t l y c o n s t r u c t i n g f o r a major t o bacco manufacturer. The s o l i d waste c o n s i s t s of c i g a r e t t e papers and f i l t e r s , packaging paper, cardboard, used tobacco c o n t a i n e r s , and transport p a l l e t s . The average heating value of t h i s m a t e r i a l i s 7500 BTU/lb as r e c e i v e d , with an average moisture content of 10%. The waste i s p r e s e n t l y baled and t r a n s p o r t ed to a l a n d f i l l . A c o n s i s t e n t end use heat requirement e x i s t e d i n the form of process steam generation f o r the manufacturing operation. The g a s i f i c a t i o n system s e l e c t e d f o r t h i s a p p l i c a t i o n cons i s t e d of two (2) v e r t i c a l s h a f t g a s i f i e r s , each capable of g a s i -

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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296

f y i n g 5000 l b s / h r of s o l i d waste, one conventional water tube b o i l e r r a t e d a t 50,000 l b s of steam per hour a t 175 p s i g and equipped with a Surface r i c h fume burner u n i t designed to combust the hot f u e l r i c h gases produced by g a s i f i c a t i o n ; and f i n a l l y , a Surface Rich Fume I n c i n e r a t o r , used as a standby fume d i s p o s a l means i n the event of a b o i l e r shutdown. R e f e r r i n g to Figure #2, the g a s i f i c a t i o n system w i l l be charged with 10,000 l b s / h r of s o l i d waste with the waste flow being e q u a l l y d i s t r i b u t e d to each g a s i f i e r . The steam and a i r mixture w i l l be proportioned to the waste flow to each g a s i f i e r . The r a t i o of t h i s a i r to steam w i l l a l s o be adjusted to provide proper g a s i f i c a t i o n temperatures. The ash discharge r a t e i s adj u s t e d to maintain a constant bed l e v e l at a l l times. The gas generated from the g a s i f i e r w i l l amount to approximately 25,000 l b s / h r with a gross heat content of 68 MM BTU/hr. This gas i s then mixed with an appropriate amount of a i r i n the r i c h fume burner to f u l l y combust the fumes a t an excess a i r l e v e l of 10%. The p r o p o r t i o n of a i r and f u e l i s c o n t r o l l e d to maint a i n t h i s 10% excess a i r r a t e under v a r i o u s waste loadings thus a c h i e v i n g a high b o i l e r e f f i c i e n c y . A l l process v a r i a b l e s are monitored at a c e n t r a l system c o n t r o l panel operated by one man. On weekends, or o f f s h i f t s , when the waste generation i s h a l t e d , the system i s put i n a banked c o n d i t i o n and operating temperatures are maintained u n t i l resumption of waste flow, thus m i n i mizing r e s t a r t time and maintaining system p r o d u c t i v i t y . The operating economics of g a s i f i c a t i o n as compared to a l a n d f i l l o p e r a t i o n break down as f o l l o w s : Gasification Operating annual c o s t s (4000 h r s / y r ) : Manpower $110,000 Fuel 13,800 Power 10,000 Maintenance 60,000 Ash l a n d f i l l 25,000 T o t a l Operating Costs $218,800 Income Steam production @ $4/1000 l b s steam Net Income

$800,000 $581,200

Landfill T o t a l annual cost

$300,000

Net savings through g a s i f i c a t i o n

$881,200

This i s shown g r a p h i c a l l y as a f u n c t i o n of operating hours

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

STEAM

REACTION A.R

COMBUSTION

loci

m

RICH FUME INCINERATION (STAND BY ONLY)

OXYGEN CONTROL

AIR FLOW CONTROL

Figure 2. Solid waste gasification system

10,000 #/HR

WASTE FLOW

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298

1600

Figure 3.

Income generation curve

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per year on F i g u r e 3. As seen i n t h i s f i g u r e , the energy u t i l i z a t i o n provides the bulk of operating savings, although the l a n d f i l l volume r e d u c t i o n of 30:1 and weight r e d u c t i o n of 15:1 prov i d e a p p r e c i a b l e savings.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch022

What i s the Future of S o l i d Waste G a s i f i c a t i o n ? During the next decade, a t Midland-Ross we expect s o l i d waste g a s i f i c a t i o n to grow t e c h n i c a l l y i n two areas: waste product a p p l i c a t i o n and f u e l product end use. In our p i l o t s c a l e g a s i f i e r we have demonstrated the s u c c e s s f u l g a s i f i c a t i o n of many indust r i a l waste m a t e r i a l s , from rubber t i r e s to f o r e s t r y waste to waste paper to pharmaceutical sewage sludge. Each a p p l i c a t i o n has i t s unique o p e r a t i n g parameters to d e f i n e . As more a p p l i c a t i o n s a r e i n v e s t i g a t e d , t h i s parameter development w i l l become less tedious. F u e l product end use i s p r e s e n t l y r e s t r i c t e d to "same time" energy users such as steam b o i l e r s , process a i r and l i q u i d heate r s , and l a r g e furnaces. Midland-Ross, through i t s Thermal Systems T e c h n i c a l Center, i s p r e s e n t l y i n v e s t i g a t i n g and developing processes to s t o r e t h i s energy i n a r e a d i l y t r a n s p o r t a b l e and usable form. This would be e i t h e r as a concentrated h i g h BTU gas or an o i l - l i k e product. This development, when i t comes, w i l l enable i n d u s t r y to generate i t s own f u e l and s t o r e i t f o r end use as economic or a v a i l a b i l i t y f a c t o r s d i c t a t e . In summary, s o l i d waste g a s i f i c a t i o n i s a here and now technology f o r i n d u s t r y ' s p r o f i t a b l e use. Using a process developed over a century ago and a p p l y i n g today's method and m a t e r i a l s , we are able to r e l i e v e the burden placed on our l a n d f i l l s and produce a d d i t i o n a l income through an environmentally acceptable process. RECEIVED November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

23 Thermodynamics of Pyrolysis and Activation in the Production of Waste-or Biomass-Derived Activated Carbon F. MICHAEL LEWIS 142 Waverly Place, Mountain View, CA 94040

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch023

C. M. ABLOW SRA International, Menlo Park, CA 94025

The use of activated carbon, or activated charcoal as i t is sometimes called, dates back as far as 2000 B.C. when i t was first used by the ancient Egyptians. The term "activated" refers to the chemical or thermal treatment given to the carbon to increase its adsorptive capacity. Estimates for activated carbon demand in the U.S. vary but a nominal value for current U.S. usage would be 108 kg/yr. Government regulations, such as the recent proposal to reduce trace organic compounds in drinking water with the use of activated carbon, if enacted, could substantially increase demand. However, the market growth anticipated when the Federal Water Pollution Control Act Amendments of 1972 were passed never came to fruition. With this degree of uncertainty, the best estimates for demand growth appear to be in the range of 5% - 11% per year. Raw materials for the production of activated carbon have historically included coal, sulfite mill liquor, lignite, peat, coconut shell, and wood. Changing economics and a realization that some materials previously discarded represent a potential resource have stimulated investigations into using municipal solid waste and agricultural and forestry residues as feedstocks. In a study conducted by Stanford University, municipal solid waste was thermally processed into activated carbon and after removal of inert material, compared favorably with commercial grades of activated carbon for use in wastewater treatment. A commercial firm in Northern California is processing redwood sawdust to make activated carbon that can be used for cleaning and decolorizing food oils, water, fabrics, industrial gases and fluid wastes. Practical processes for activating carbon include high temperature thermal processes, where the carbon is reacted with steam and carbon dioxide, and chemical processes where activation takes place in the presence of metallic chlorides. These processes were developed at the turn of the century and today variations of this basic technology are still used to manufacture nearly a l l activated carbons. In this paper conditions are presented for maximizing the thermal efficiency of the high temperature processes. 0-8412-0565-5/80/47-130-301$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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The combustible f r a c t i o n of municipal s o l i d waste and biomass c o n s i s t s p r i m a r i l y of carbon, hydrogen, and oxygen. The q u a n t i ­ t i e s of these elements vary s l i g h t l y but f o r i l l u s t r a t i v e purposes we can t r e a t both combustible f r a c t i o n s as pure c e l l u l o s e ( C H 0 ) w i t h the f o l l o w i n g weight percents: 6

1 0

5

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Carbon Hydrogen Oxygen

44.4% 6.2% 49.4%

The heating value of a t y p i c a l biomass i s s u f f i c i e n t to pro­ duce steam i n excess of that r e q u i r e d by the a c t i v a t e d process i f the system has been designed f o r maximum thermal e f f i c i e n c y . This can be e s p e c i a l l y important to developing c o u n t r i e s who have l a r g e s u p p l i e s of biomass such as r i c e h u l l s or coconut s h e l l s and who are c u r r e n t l y contemplating the manufacture of a c t i v a t e d carbon f o r export or l o c a l water treatment. Designing a process to maximize energy recovery r e q u i r e s a fundamental understanding of the system thermodynamics. Unfortu­ n a t e l y most commercial firms consider t h e i r processes h i g h l y p r o p r i e t a r y and tend to t r e a t the thermodyanmics as a kind of "black magic." As a r e s u l t there i s l i t t l e or no t e c h n i c a l data available. A process that i s s i m i l a r to carbon a c t i v a t i o n i s c o a l g a s i ­ f i c a t i o n . Here c o a l , c o n s i s t i n g p r i m a r i l y of carbon, i s reacted at high temperatures with v a r i o u s mixtures of a i r , oxygen, and steam to produce a f u e l gas. We have a p p l i e d some of the t e c h n i ­ ques used to analyze the thermodynamics of c o a l g a s i f i c a t i o n systems to develop a t e c h n i c a l data base. Thermodynamic Fundamentals The thermodynamic c o m b u s t i o n / g a s i f i c a t i o n processes i n v o l v e d can be analyzed on the b a s i s of the F i r s t Law of Thermodynamics (Heat i n = Heat out: M a t e r i a l i n = M a t e r i a l out) and chemical e q u i l i b r i u m . The s e t of nine r e a c t i o n s l i s t e d i n Table I d e s c r i b e the most important r e a c t i o n s f o r c o m b u s t i o n / g a s i f i c a t i o n proces­ ses. Thermodynamic data p e r t a i n i n g to these r e a c t i o n s can be found i n engineering texts but Kg, the e q u i l i b r i u m constant f o r Reaction (9), i s g e n e r a l l y given f o r beta-graphite. Experimental data obtained from g a s i f i e r s operating on peat i n d i c a t e that methane i s found i n the output gases a t concentrations higher than that p r e d i c t e d by the beta-graphite e q u i l i b r i u m constant. In our a n a l y s i s we have compared the output p r e d i c t i o n s f o r the betagraphite e q u i l i b r i u m , the "textbook" value, and f o r the l a r g e s t reported carbon e q u i l i b r i u m constant, the "experimental" value. From data reported by Feldmann (1975) we use In K9 = A/T-B where Τ i s i n degrees K e l v i n and (A,B) = (10885, 13.208) f o r the t e x t ­ book value and (18397, 17.445) f o r the experimental value.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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LEWIS AND ABLOW

303

The f i v e product gases of the forward r e a c t i o n s i n Table I are H 0, C 0 , CO, H , and CH . Higher order hydrocarbons, some­ times c a l l e d i l l u m i n a n t s , occur i n small q u a n t i t i e s that can be neglected i n a heat and mass balance a n a l y s i s as can the small changes i n n i t r o g e n concentration. Carbon, hydrogen, and oxygen balances provide three equations f o r determining the e q u i l i b r i u m concentrations. Reaction (8), which i s sometimes c a l l e d the water gas s h i f t , i s a gas phase r e a c t i o n that has been experimentally shown to approach e q u i l i b r i u m . The known value of the e q u i l i b r i u m constant gives us a f o u r t h r e l a t i o n . Reaction (9) i s a gas s o l i d r e a c t i o n that i s probably not i n e q u i l i b r i u m i n a t y p i c a l furnace. However, c a l c u l a t i o n s based on e q u i l i b r i u m f o r r e a c t i o n (9) give methane concentrations not f a r from experimentally determined values. The quantity of CH* that i s produced under t y p i c a l a c t i v a t i o n c o n d i t i o n s i s small enough that no s i g n i f i c a n t e r r o r i n the heat and mass balance i s introduced. 2

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch023

Thermodynamics of Pyrolysis and Activation

2

2

4

Table I P y r o l y s i s and A c t i v a t i o n Reactions 1. 2.

3. 4. 5. 6. 7. 8. 9.

C + 0 C + 1/2 0 C + C0 CO + 1/2 0 H + 1/2 0 C + H 0 C + 2 H 0 C0 + H C + 2H 2

2

2

^=^C0 ^=rC0 τ -2C0 "5=^C0 2

2

2

2

2

2

2

2

2

» CO + H C 0 +2 H =• CO + H 0 2

^ -«

2

2

2

2

Reaction (6) plays a major r o l e i n the a c t i v a t i o n process but t h i s g a s - s o l i d r e a c t i o n does not approach e q u i l i b r i u m . Steam i s the gaseous reactant i n the forward r e a c t i o n . A f r a c t i o n of com­ p l e t i o n o r Percent Steam U t i l i z a t i o n (PSU) f o r t h i s r e a c t i o n i s needed i n order to c a l c u l a t e the mole percent of the d i f f e r e n t output gases. We have d i s p l a y e d the r e s u l t s of a l l c a l c u l a t i o n s g r a p h i c a l l y with PSU as one of the v a r i a b l e s . P y r o l y s i s and A c t i v a t i o n The f i r s t u n i t o p e r a t i o n i n the production of waste o r b i o ­ mass derived a c t i v a t e d carbon i s p y r o l y s i s , a l s o known as baking or c h a r r i n g . In t h i s process the m a t e r i a l i s heated i n an essen­ t i a l l y oxygen-free atmosphere to d r i v e o f f the f r e e moisture and volatiles. The m a t e r i a l that remains i s c a l l e d char or f i x e d carbon. The char y i e l d i s dependent upon heating r a t e and i n a study performed by Roberts e t a l . (1978) on the production of muni­ c i p a l s o l i d waste derived a c t i v a t e d carbon, the f o l l o w i n g

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

304

equation was

experimentally Y

-2.4

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch023

Y τ C

determined: Ιητ + C

Percent char y i e l d (dry b a s i s ) Heating r a t e , °C/min Experimentally determined constant r e l a t e d to feedstock m a t e r i a l and f i n a l temperature.

Figure 1 i l l u s t r a t e s t h i s equation f o r C = 26.5%, a value c o n s i s ­ tent with values reported f o r pure c e l l u l o s e and municipal s o l i d waste, and with data obtained i n d i s c u s s i o n s with commercial f i r m s . The importance of a slow heating r a t e to maximize the char y i e l d i s q u i t e apparent i n the f i g u r e . I t follows that f l u i d beds and downdraft or updraft g a s i f i e r s , though e x c e l l e n t f o r maxi­ mizing gas y i e l d , are not d e s i r a b l e f o r char production. P y r o l y s i s i s an endothermic process that r e q u i r e s heat. This heat can be generated by admitting a small q u a n t i t y of a i r i n t o the furnace where i t h o p e f u l l y consumes some of the v o l a t i l e gases without burning any of the char. I n d i r e c t h e a t i n g i s a t t r a c t i v e because i t avoids any opportunity to l o s e the char. To a c t i v a t e the char produced i n the p y r o l y s i s step, a por­ t i o n of the carbon i s reacted with steam as i n Reaction (6) to develop the i n t e r n a l pore s t r u c t u r e which gives the carbon i t s high adsorptive p r o p e r t i e s . The percent of carbon that i s reacted w i l l depend upon the f i n a l p r o p e r t i e s d e s i r e d but 25% to 50% i s a t y p i c a l range. T h i s r e a c t i o n between steam and carbon i s h i g h l y endothermic so that heat must be s u p p l i e d to s u s t a i n the process. The f o l l o w i n g l i s t represents a l t e r n a t i v e s f o r generating or supplying t h i s heat. 1. Admission of a small q u a n t i t y of a i r i n t o the furnace: Carbon-Steam-Air system 2. Admission of a small quantity of oxygen i n t o the furnace: Carbon-Stearn-Oxygen system 3. F i r i n g the furnace with a n a t u r a l gas (CH

eu

ΙΟ

eu PH

XI

ο ο

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

rJ

PH

Ρ Ο •Η

cd CU

4-> 4J CO

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

326

THERMAL

CONVERSION

OF

SOLID

WASTES

AND

BIOMASS

5

Β / A

Figure 3.

Equation C / A = E/(l + 0.15Ό) - Β / Α · l/ (Ό/1 + 0.15Ό) where η = 20 years, i = 10%, and f 3% v

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

24.

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Canada's Biomass Conversion Technology

Reference p r i c e s f o r the opportunity Oil

Gasoline

327

cost "A" are:

20$/Bbl (U.S.) or 23.50$/Bbl (Cdn) =

3.84$/GJ f o r both O i l and Gas

=

5.49$/GJ

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

E l e c t r i c i t y 2.5c/kWh = 6.94$/GJ eg nuclear

N.N.

5.0c/kWh

13.89$/GJ

eg f o s s i l f u e l e d

15.0c/kWh

41.67$/GJ

eg remote northern communities.

1 Btu = 1.055 kJ 1 kWh = 3.6 MJ

Technology Assessment

Conclusions

The t a b l e I can be summarised i n t o generic c l a s s e s and using a conversion of 18.6 GJ/tonne f o r wood biomass the data i n t a b l e II can be generated i n which biomass costs t e c h n i c a l r i s k and l i k e l y market share are enumerated. Quick i n s p e c t i o n of t h i s table shows that the "easy" low cost m i l l residues w i l l l i k e l y be consumed w i t h i n the f o r e s t i n d u s t r i e s using w e l l developed combust i o n technology. Conversely l i q u i d f u e l s while having an extremely l a r g e p o t e n t i a l market are constrained to a very low cost requirement f o r t h e i r feedstock which cannot be met by current harvesting technology. The supply curve of f i g u r e 2 i n d i c a t e s that the l i k e l y average cost of the 500 PJ/annum increment beyond the a n t i c i p a t e d f o r e s t i n d u s t r i e s expansion w i l l be around 30$/0dt f o r the supply. These f i g u r e s may appear to be daunting economic goals f o r biomass not to be r e s t r i c t e d to e s s e n t i a l l y c a p t i v e use w i t h i n the present biomass i n d u s t r i e s . An opportunity cost of 3.84 $/GJ coupled to a 40% e f f i c i e n t process c o n s t r a i n s the c a p i t a l cost to 1.5 k$/TJ/annum output c a p a c i t y . Only the d e n s i f i e d biomass option coupled with g a s i f i e r s a t the point of use can meet t h i s cost c r i t e r i o n allowing that there w i l l be prepared f u e l t r a n s p o r t a t i o n c o s t s . I f the l i q u i d f u e l opportunity cost of $5.49 i s used then the c a p i t a l cost f o r the conversion has to be l e s s than 7.9 k$/TJ/annum output c a p a c i t y . Allowing that the usual s c a l i n g law of an exponent to the 0.7 power i s l i k e l y to apply to methanol p l a n t s f o r example then a 4000 tpd p l a n t would be f e a s i b l e . MacKay (_3) has shown that s c a l e increases e f f e c t i v e l y outweigh

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

U t i l i t y p l a n t s of greater than 50 MW. Very dependent on r e g i o n . Market share l i k e l y to be low. Depends on r e g i o n . Unit s i z e i s l e s s than 250 kW i n Canada. 50 MW market i n northern r e g i o n s . P o t e n t i a l market 1 EJ. End use compatibi­ l i t y problems f o r MeOH upgrading d i f f i c u l ­ t i e s f o r hydrogenated wood products.

ν - low

moderate

moderate to high

12

160

0-10

Electricity

Remote Community and LDC a p p l i c a t i o n s of G a s i f i e r / D i e s e l

Liquid

Fuels

Gasification

High temperature processes and n a t u r a l gas s u b s t i t u t i o n . Retrofit potential for o i l and gas b o i l e r s .

51

Densified Biomass

moderate

Large steam users i n f o r e s t Ind. about 600 MW f e a s i b l e . (20 PJ)

ν - low

55

Forest I n d u s t r i e s S e l f - S u f f i c i e n c y present 300 P J . 1985 600 PJ

POSSIBLE END USE MARKET & SHARE

ν - low

TECHNICAL RISK

E x t e r n a l to F o r e s t I n d u s t r i e s . Mining, I n d u s t r i a l process steam heating plants e t c . Mainly to d i s p l a c e d i s t i l l a t e fuels.

44-70

70

BIOMASS COST $/ODt

low

Co-Generation i n Forest Ind.

Direct Combustion

TECHNOLOGY

TECHNOLOGY ASSESSMENT SUMMARY

TABLE I I

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

Κ) oo

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Canada's Biomass Conversion Technology

329

the incremental h a r v e s t i n g costs of i n c r e a s i n g the supply base so that t h i s option i s not e n t i r e l y out of reach. I t i s worth exam­ i n i n g not only the economic c o n s t r a i n t s but a l s o some of the chemical and end use c o n s t r a i n t s f o r biomass derived f u e l s . T

Dulong s Formula and the Choice of Biomass Derived F u e l Form Uulong's formula i s used to p r e d i c t the higher heating value of f u e l s c o n t a i n i n g v a r i o u s percentages by weight of carbon, hydrogen and oxygen. Q, = 338.3 C + 1442 (H-0/8) η

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

where

= higher heating value of f u e l i n J/g C

= per cent of carbon

Η

= per cent of hydrogen

0

= per cent of oxygen.

The percentages of C,H,0 are by mass on a dry and ash f r e e b a s i s . I f the t a b l e of higher heating values f o r simple organic compounds i n Perry (4) i s used as the true values then the c a l c u l a t e d values from the above formula f i t a s t r a i g h t l i n e of slope 1.04 with an i n t e r c e p t of - 1502 J/g and a c o r r e l a t i o n c o e f f i c i e n t of 0.99. The r e l a t i o n s h i p i s e v i d e n t l y a good f i t with at most 5 per cent e r r o r i n p r e d i c t i n g the higher heating value of a compound of s p e c i f i e d C,H and 0 composition. The greatest e r r o r i s obtained for carbon monoxide where 4208 J/g i s c a l c u l a t e d when the true value i s 10110 J/g. Since biomass i s e s s e n t i a l l y f r e e of n i t r o g e n and sulphur the three components c o n t r o l the heating value and s a t i s f y the r e l a t i o n s h i p 100 = C + Η + 0. Thus a l l biomass derived compounds can be assigned a unique coordinate on a t r i a n g u l a r g r i d as i s i n d i c a t e d i n f i g u r e 4, on which the Dulong heats of combustion are a l s o i n d i c a t e d . The t r i a n g u l a r coordinates i n c l u d e a l l com­ p o s i t i o n s unconstrained by chemistry so that heating values f o r compositions c o n t a i n i n g more than 24 per cent hydrogen are not feasible. Inspection however shows that the i d e a l conversion technology f o r biomass w i l l be one that l o s e s oxygen while maxi­ mising the hydrogen to carbon r a t i o . Figure 5, i s the same f i g u r e as the previous one with the v e c t o r s shown f o r d i f f e r e n t techniques of oxygen removal namely as water, carbon d i o x i d e and carbon monoxide. Ignoring f o r the present the p r e c i s e chemistry by which t h i s i s achieved some general p o i n t s can be made i ) Methanol i s a compound that i s l e s s optimum i n composi­ t i o n than wood with the s o l e v i r t u e of being a l i q u i d that i s j u s t and so compatible with the g a s o l i n e system, i i ) Water removal w i l l produce a carbonaceous f u e l , i i i ) The most l o g i c a l moiety to remove i s carbon monoxide as the product v e c t o r i s most c l o s e to a saturated hydro­ carbon f u e l .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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330

Figure 4.

Dulong diagram heat of combustion and CHO composition

Figure 5.

Biomass conversion routes

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

24.

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Canada's Biomass Conversion Technology

The removal of a l l oxygen as carbon monoxide can be summarised as follows on a mole b a s i s .

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

(CH

)

1.45°0.64 n

n

°'

3 6C H

4

+

n

°-

6 4 C

0

The thermochemistry of the three vectors ranges from thermoneutral for water removal to 2.2 GJ/t endothermic f o r carbon d i o x i d e removal and 4.5 GJ/t endothermic f o r carbon monoxide removal. The heat of combustion of the carbon monoxide i s however 7.66 GJ so that i t could be used e i t h e r as a chemical reagent or as a heat source i n an e n t i r e l y biomass f u e l e d process to produce f u e l s that most c l o s e l y approximate todays p r e f e r r e d hydrocarbon f u e l s . Canadian PTGL R&D Goals P y r o l y s i s , G a s i f i c a t i o n and L i q u e f a c t i o n have high p r i o r i t i e s w i t h i n the Canadian R&D program with minor emphasis on d i r e c t combustion technology. D i r e c t combustion i s an o l d but w e l l e s t a b l i s h e d technology with nevertheless some c h a r a c t e r i s t i c s that s t i l l r e q u i r e development e f f o r t s . The present day systems used to burn bark and hog f u e l use supplementary f u e l s such as f u e l o i l and n a t u r a l gas to minimise emissions and the compensate f o r feedstock moisture v a r i a t i o n s . The net e f f i c i e n c y of burning wet wood with considerable excess a i r r a t i o s i s poor and leaves a l o t to be d e s i r e d . During the eco-excesses of the s i x t i e s t h i s was acceptable because the l a r g e hog b o i l e r s were used as d i s p o s a l u n i t s f o r excess r e s i d u e s . Since that time more r e s i d u e has entered the process as f i b r e and of course the over f i r e f u e l s have become very expensive. Because of the f o r e s t i n d u s t r i e s economic importance and the s i g n i f i c a n t savings of f o s s i l f u e l s that might accrue i t i s l i k e l y that d i r e c t combustion w i l l become a higher p r i o r i t y . Already i n the case of experimental work on f l u i d bed combustors f o r high sulphur coals p r o v i s i o n i s being made to study low grade f u e l s such as wet wood and d r i e d peats. In the Canadian context there need not be a r e s t r i c t i o n on biomass conversion processes to be s e l f - s u f f i c i e n t and therefore be r e q u i r e d to s a c r i f i c e carbon to d r i v e the processes, N a t u r a l gas and hydro/nuclear e l e c t r i c i t y are l i k e l y to be a v a i l a b l e on a large s c a l e through to the e a r l y decades of the next century. One or a l l of the f o l l o w i n g options have been discussed i n the context of biomass conversion and i n the s p e c i f i c case of methane a d d i tions to a l t e r hydrogen to carbon monoxide r a t i o s i n syn gas work i s p r e s e n t l y under way to combine oxygen blown wood g a s i f i c a t i o n with the reforming of n a t u r a l gas, (5). 1

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

332

CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

Table of Supplementary Sources f o r Biomass Conversion Supplementary Source

Chemical Effect

E x t e r n a l Heat

E l i m i n a t e s need to s a c r i f i c e carbon

Thermal Power S t a t i o n s eg f l u i d bed c o a l combustion or nuclear e l e c t r i c "Co-generated" thermal energy

Hydrogen

Chemical reagent f o r "CO" removal and hydrogénation

Steam reformed n a t u r a l gas, e l e c t r o l y t i c hydrogen generation from WECS, Hydro or nuclear

Electricity

Very high temperature plasma chemistry and or d i r e c t electrochemical r e d u c t i o n of biomass

WECS, Hydro or nuclear sources

Origin

Such complimentary synthesis routes or "HYBRIDS" can achieve remarkable reductions i n c a p i t a l cost and expensive biomass carbon u t i l i s a t i o n . The methane and wood hybrid to produce methanol from the r e s u l t i n g syn-gas would use 7 2 2 m of n a t u r a l gas and 0 . 4 tonne of biomass to produce 1 tonne of methanol a t a c a p i t a l cost of around 1 0 k$/TJ/annum c a p a c i t y on the 1 0 0 0 tpd product s c a l e . Though part of the feedstock i s then p r i c e d a t the i n t e r n a t i o n a l o i l p r i c e (energy equivalent) a p l a n t s c a l e of 3 0 0 0 tpd operating a t 6 0 per cent e f f i c i e n c y w i l l meet the economic c r i t e r i a of the simple model used i n t h i s paper. Hybrids can be viewed as "bridge" technologies which w i l l smooth the t r a n s i t i o n from d e p l e t a b l e resources to an era i n which renewables and i n e x h a u s t i b l e s such as c o a l and p o s s i b l y nuclear f i s s i o n (breeder) are the dominant resources, ( 6 ) . The Canadian Programme The Canadian R&D program i s described a t the i n d i v i d u a l p r o j e c t l e v e l i n Bioenergy Research and Development Program Review 1 9 7 8 , Ç 7 ) . From the preceeding d i s c u s s i o n i t can be seen that the major goal i s to produce a l i q u i d f u e l or l i q u i d f u e l s u b s t i t u t i o n product. A 1 EJ displacement of f o s s i l f u e l s would be equivalent to a doubling of todays roundwood harvest, ( 8 ) . Feedstock cost r e d u c t i o n i s r e q u i r e d and t h i s i s l i k e l y to be obtained by developing technology appropriate to biomass harvesting rather than the present roundwood systems.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

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333

A short term goal of the feedstock conversion programme i s to prove the gasification process step of synthesis gas produc­ tion from biomass. This i s being developed for both the methane HYBRID and the biomass only case for both oxygen and a i r blown gasifiers. The short term goal to produce synthesis gas as a precursor for methanol acknowledges the possible wide-spread adoption of methanol i n the early nineties as a result of catas­ trophic shortfalls i n the world petroleum supply. Preparation of non-oxygenated or essentially hydrocarbon fuels i s i n an early stage of development; however, provided that early adoption of methanol does not occur, this route offers f l e x i b i l i t y of choice for what i s after a l l an unknown vehicle power plant configura­ tion of the 21. The current program i s funded out to 1984 at which time i t i s anticipated that there w i l l be sufficient data available to make a decision on whether or not to have a large bioenergy contribution to the energy diet of the nineties.

REFERENCES 1.

InterGroup Consulting Economists. Resources: F e a s i b i l i t y Study";

"Liquid Fuels from Renewable

Volume C: Forest Studies; Volume D: Agricultural Studies; Volume E: Municipal Waste Studies. Fisheries and Environment Canada:

Ottawa 1978.

2. Montreal Engineering Co L t d , "The Mining of Peat - A Canadian Energy Resource"; Energy Mines and Resources Canada: Ottawa 1978. 3. Chemical Engineering Research Consultants L t d , "The Production of Synthetic Liquid Fuels for Ontario"; Ministry of Energy Ontario: Toronto 1977; Volume 5. 4. Perry, R. H . ; Chilton, C. Η., Eds. "Chemical Engineers Handbook"; McGraw Hill: New York 1963; 5th Edition. 5. InterGroup Consulting Economists, "Liquid Fuels from Renewable Resources: F e a s i b i l i t y Study"; Volume B: Conversion Studies; Fisheries and Environment Canada: Ottawa 1978. 6.

Gander, J.E.; Belaire, F. W. "Energy Futures for Canadians," Report EP 78-1; Energy Mines and Resources: Ottawa 1978.

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Summers, Β.A. "Bioenergy Research and Development - Program Review," NRCC 17671; National Research Council of Canada: Ottawa 1979.

8. Love, P . ; Overend, R. "Tree Power: An Assessment of the Energy Potential of Forest Biomass i n Canada," Report ER 78-1; Energy Mines and Resources: Ottawa 1978.

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9. Levelton, B . H . ; and Associates. "An Evaluation of Wood Waste Energy Conversion Systems," Report to the B r i t i s h Columbia Wood Waste Energy Co-Ordinating Committee: Fisheries and Environment Canada: Ottawa 1978. 10.

Acres Shawinigan Ltd. "Hearst Wood Waste Energy Study: Report," Ministry of Energy Ontario: Toronto 1979.

Summary

11. H.A. Simons (International) Ltd. "Hog-Fuel Co-Generation Study. Quesnel, B r i t i s h Columbia," Report to the B r i t i s h Columbia Wood Waste Energy Co-ordinating Committee: Fisheries and Environment Canada: Ottawa 1978. 12. S.N.C. Tottrup Services Ltd. "Energy and Chemicals from Wood," ENR Report No. 90; Department of Energy and Natural Resources Alberta: Edmonton 1979. 13.

Kohan, S.M.; Barkhordar, P.M. "Mission Analysis for the Federal Fuels from Biomass Program, Volume IV: Thermochemical Conversion of Biomass to Fuels and Chemicals, "Report prepared by SRI International for the US DOE: Washington D.C. 1979.

14. Archibald, W.B.; Gabriel, J . A . "Economics of Co-generation i n "Hardware for Energy Generation i n the Forest Products Industry": Proceedings of the FPRS meeting January 1979 i n Seattle: FPRS Madison, Wisconsin 1979.

15.

T. B. Reed - Personal Communication.

16. Overend, R. "Gasification an Overview" i n "Retrofit 1979" Edited by T. B. Reed and D. E. Jantzen SERI/TP-49-183: Golden Colorado 1979. 17. Biomass Energy Institute Inc. "Biogas Production from Animal Manure," Biomass Energy Institute: Winnipeg, 1978.

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24.

18.

19.

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335

Burford, J.; Varani, F.T. Design and Economics of Lamar, Colorado Bioconversion Plant," CSM Mineral Indusries Bull., V21 (no 4): Golden Colorado 1978. Moon, G.D.; Messick, J . R . ; Easley, C . E . ; Katzen, R. "Technical and Economic Assessment of Motor Fuel Alcohol from Grain and other Biomass," Report to U.S. DOE - Contract EJ-78-C-01-6639; Washington, D.C. 1978. December 18, 1979.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch024

RECEIVED

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

25 Pyrolysis of Agricultural Residues in a Rotary Kiln R. H. ARSENAULT, M. A. GRANDBOIS, E. CHORNET, and G. E. TIMBERS1

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

Sandwell Beak Research Group, 6870 Goreway Drive, Mississauga, Ontario, Canada L4V 1L9

The conversion of agricultural residues to more amenable forms of energy such as gas, oil or char shows good potential both on the large and small scale. This paper is concerned with the pyrolysis of agricultural residues using a rotary kiln to potentially supply the energy needs of one or a few farm operations. The rotary kiln pyrolysis unit used in these experiments was originally used for studies in peat conversion directed by E. Chornet at the University of Sherbrooke, Québec (Campion, 1978). The scope of work in a first phase of the project included the adaptation of this peat pyrolysis system for conversion of agricultural residues, preliminary testing to identify operating problems, characterization of two feedstocks (oat straw and corn stover) and finally, experiments to determine product yield and composition at various operating conditions. The work was performed by the Sandwell Beak Research Group and supported by Agriculture Canada under contract number AERD 8-1802. This first phase lasted one year and results are presented in this paper. The second phase of the work is now underway detailing the pyrolysis study and some gasification and based on these two phases, design criteria for small scale pyrolytic conversion of agricultural biomass will be recommended. Description of Process A schematic diagram of the process is shown in Figure 1. The feed was chopped to 5-10 cm in a forage harvester and air dried to less than 10% moisture content before use. The feeder system consisted of a funnel-shaped 0.2 m3 capacity hopper with chain-driven mixer arms, emptying onto a 5 cm diameter screw 'Current Address: Engineering and Statistical Research Institute, Agriculture Canada, Ottawa, Ontario, Canada 0-8412-0565-5/80/47-130-337$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

338

THERMAL

C O N V E R S I O N O F SOLID W A S T E S A N D BIOMASS

CZO/

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

3

p/zETzeATMeuT

EXTERNAL

CXHAUST

GAS£$

(FOR PROCSSS HEATING)

ZEACTOZ

TU&e(3.Hm

*0J€>

m

PZOPAK/E

&UJZMEZ3

I.Ο.) gas TA/ZS GASCS

V/ATÇ8. WASH WATEJZS

5C&ue>&E€ CLSAU GAS

FILTE ft

SOU Ο

FUEL

Figure 1.

N2> CH*+ y > CO^and C^Hy and the remainder of the gas was f l a r e d . Char samples were analysed f o r C, H, 0, S, Ν and mois­ ture content (moisture content by oven drying at 378 K); the remainder was stored i n l a r g e p l a s t i c bags. The tars were not analysed since v e r y small amounts were produced. The feed and char were weighed and gas production was con­ t i n u o u s l y monitored with a test meter to permit mass and energy balances. The water product was not determined, however, be­ cause of condensation problems i n the scrubber. 2

co

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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340

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

25.

ARSENAULT ET A L .

Pyrolysis of Agricultural Residues

Heat inputs (propane) and outputs were monitored.

(combustion

exhaust

341 gases)

Results

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

Feedstock C h a r a c t e r i s t i c s . Feedstock c h a r a c t e r i s t i c s are presented i n Table I . Results o f the metal analysis w i l l be considered i n Phase I I o f the p r o j e c t . Calorific v a l u e s were approximated using Dulong's formula and not a c t u a l l y measured. The oat straw had a lower ash content than the stover and a correspondingly higher c a l o r i f i c v a l u e . C a l o r i f i c v a l u e s , cal­ culated on a d r y b a s i s and i n c l u d i n g the l a t e n t heat of water vapour i n the products o f combustion (high heat v a l u e ) , were 17.9 MJ/kg f o r the straw and 16.0 MJ/kg f o r the s t o v e r . Table I : Feedstock C h a r a c t e r i s t i c s Type of Feed :

Straw Mean S.D.

5

1

Stover Mean S.D.

b

z

Ultimate A n a l y s i s - % wt 0.4 43.2 Carbon 0.7 48.1 5.2 0.1 Hydrogen 0.1 6.1 0.2 34.0 Oxygen 1.0 41.6 0.01 0.25 Sulphur 0.01 0.05 2.8 0.1 Nitrogen 0.4 0.1 16.0 0.3 0.4 C a l o r i f i c v a l u e (MJ/kg) 17.9 Proximate Analysis--% wt 1.4 7.8 Moisture 0.7 5.4 0.6 Ash 0.4 14.6 3.8 0.4 0.4 Fixed c a r b o n 0.7 0.1 77.2 0.9 V o l a t i l e matter 0.6 90.1 1 From the a n a l y s i s o f 5 d i f f e r e n t samples f o r each feedstock 2 Moisture f r e e 3 High heat value approximated using Dulong's formula h- Calculated by d i f f e r e n c e ( 1 0 0 % - % a s h - % m o i s t u r e - % v o l a t i l e matter) 5 S.D. = Standard d e v i a t i o n 3

4

Product Y i e l d and Composition. Product y i e l d and composi­ t i o n d i d not v a r y s i g n i f i c a n t l y within the range of residence times s t u d i e s . Feed rate d i d not have a n o t i c e a b l e effect e i t h e r , although f u r t h e r experiments a t 10 kg/h are r e q u i r e d . The system output was l i m i t e d by the feeding system used. I t i s l i k e l y that the k i l n could convert more m a t e r i a l since conver­ sion was completed w i t h i n 10 minutes. This was i n d i c a t e d by the f a c t that gas production f e l l to zero w i t h i n 5 to 10 minutes a f t e r feeding was stopped. As w e l l , during previous experiments with peat (Campion, 1978), feed r a t e s up to 18 kg/h were used. Product mass y i e l d s are shown i n Figure 3. Char y i e l d s de­ creased almost by a f a c t o r of 2 from 870 Κ to 1170 K; converse-

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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342

Figure 3.

Mass product/feed ratios ((

) char; (

) gas)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

25.

ARSENAULT

ET AL.

Pyrolysis of Agricultural Residues

343

l y , gas y i e l d s doubled. Char y i e l d s were greater f o r stover than f o r straw by about 20%; gas y i e l d s were lower by the same amount. Gas production at 1020 Κ averaged 0.55 m /kg f o r straw and 0.44 m /kg f o r s t o v e r . I t was s u r p r i s i n g to f i n d that t a r y i e l d s were only around 1% or l e s s . Apparently the l a r g e mole­ cules c o n s t i t u t i n g the tar are e a s i l y broken down i n secondary p y r o l y s i s and g a s i f i c a t i o n s t a g e s . The primary p y r o l y s i s stage where t a r s are produced w i l l be studied i n a bench s c a l e r e t o r t i n Phase I I to v e r i f y the secondary p y r o l y s i s and g a s i f i c a t i o n assumptions· Results o f gas composition a n a l y s i s are presented i n Figure 4 f o r the straw experiments and Figure 5 f o r the stover experiments. As expected, C 0 content fell c o n s i d e r a b l y (by about 1/2) when temperature was increased from 870 Κ to 1170 K. CO and H 2 increased with temperature and CH^ content was a max­ imum at 1020 K. Although the C f r a c t i o n was not analysed f o r the i n d i v i d u a l components, approximate molecular weights and c a l o r i f i c values were used to c a l c u l a t e the s p e c i f i c gravity and c a l o r i f i c values o f the gases. These were quite s i m i l a r f o r both product gases (straw and s t o v e r ) . C a l o r i f i c v a l u e s averag­ ed 12 MJ/m . Higher c a l o r i f i c values around 14 MJ/m were ob­ tained a t 1020 Κ where CHi+ production was g r e a t e s t . Specific g r a v i t y v a r i e d from 1.1 a t 870 Κ to 0.8 at 1170 K. Results o f the char analyses are given i n Table I I . They are only presented f o r two s p e c i f i c experiments since the char­ a c t e r i s t i c s d i d not v a r y c o n s i d e r a b l y with r e a c t o r temperature or residence times. The c a l o r i f i c value of the straw char was higher than that of the stover char by about 20%. The c a l o r i f i c value of the straw char on a u n i t weight b a s i s was about 1.6 times g r e a t e r than the straw feed and the c a l o r i f i c value of the stover char was about 1.4 times g r e a t e r than the stover feed. Further c h a r a c t e r i z a t i o n of the char w i l l be c a r r i e d out i n Phase I I . Of p a r t i c u l a r i n t e r e s t are the burning c h a r a c t e r ­ i s t i c s , h y g r o s c o p i c i t y , ash and a c i d i n s o l u b l e ash content and measured c a l o r i f i c v a l u e . 3

3

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

2

2

3

Table I I :

Feed Straw

3

Results o f char a n a l y s i s f o r p y r o l y s i s o f straw and stover at 1020 Κ and 0.5 hour residence time

C 74.9

Elemental A n a l y s i s o f Char ( a i r d r i e d ) (% by weight) Η Ashl 0 S Ν 2.4

7.0

0.20

1.8

13.7

Calculated Calorific V a l u e 2 MJ/kg 27.6

Stover 60.0 1.7 21.1 9.2 25.7 0.28 3.1 1 Calculated by d i f f e r e n c e (100% - %C, H, 0, S, N) 2 Dulong's formula Average f o r a l l experiments: straw char - 27 MJ/kg stover char - 23 MJ/kg

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

344

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

50-»

ZEACTOe. TEMPE£ATU£.e Figure 4.

(K)

Gas composition from straw pyrolysis—Series Π (Note: heavy com­ ponents not considered)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

25.

ARSENAULT

ET

AL.

345

Pyrolysis of Agricultural Residues

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

5θ—ι

370

I020 SEACTOZ

TEMPERATURE

U70 (Κ)

Figure 5. Gas composition from corn stover pyrolysis—Series III (Note: heavy components not considered)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

346

Energy Data, Figure 6 gives the energy product/feed r a t i o s , that i s , the energy content found i n the gas or char for a u n i t q u a n t i t y of feed. At 870 Κ there i s almost 3 times more energy i n the char than i n the gas. However, a t 1170 Κ the energy i n the char and gas are about equal using stover feed­ stock and approximately twice as much i n the gas as i n the char using straw feedstock. Therefore, i f char i s the d e s i r e d prod­ uct, r e a c t o r temperatures should be low (870 Κ ) , but i f gas i s the d e s i r e d product, r e a c t o r temperatures should be higher (1020 Κ or 1170 K ) . Mass balances averaged 85%. Losses i n the operation were mainly due to the i n a b i l i t y to adequately condense and trap p y r o l y s i s waters. Experiments of longer d u r a t i o n would improve the mass b a l a n c e s . Energy i n the char and gas averaged 77% of the gross cal­ o r i f i c value of the feedstock. In these experiments, energy to pyrolyse the feedstock was supplied by propane. About 100 MJ were required to heat the k i l n to 870 K. Another 121 MJ/h were required to maintain t h i s temperature and 189 MJ/h were r e q u i r ­ ed to maintain a temperature of 1170 K. About 90% of t h i s heat was l o s t i n the exhaust and i n an a c t u a l system most could be recovered f o r process h e a t i n g . C a l c u l a t i o n s were made to pre­ d i c t thermal e f f i c i e n c i e s of a s e l f - s u s t a i n i n g system where a p o r t i o n of the product i s r e c y c l e d and combusted to provide process heat; thermal e f f i c i e n c i e s of about 65% were p r e d i c t e d . Product Uses The most convenient a p p l i c a t i o n f o r the f u e l s obtained would be to provide s u b s t i t u t e heat f o r d i r e c t use on the pro­ ducing farm or w i t h i n short d i s t a n c e s r e q u i r i n g a minimum of t r a n s p o r t a t i o n . The char has a s i m i l a r heat output to bitumin­ ous c o a l on a mass b a s i s , while the gas has about one-third the value of n a t u r a l gas. R e l a t i v e l y l i t t l e c a p i t a l would be r e ­ quired to modify e x i s t i n g equipment f o r burning p y r o l y s i s prod­ u c t s . The p o s s i b i l i t y of mixing ground char and f u e l o i l will be considered i n Phase I I . To provide some i n d i c a t i o n of the use p o t e n t i a l i n Eastern Canada, the f o l l o w i n g example was developed f o r an Eastern Canadian farm producing 50 ha of g r a i n corn per year. Assume the mean production given by Southwell and Rothwell (1977) of 5604 kg g r a i n corn/ha at 28% moisture and 4700 kg stover/ha. Assume as w e l l that one-half the stover can s a f e l y be harvested without damaging the s o i l or i n c r e a s i n g winter r u n o f f . Con­ v e r t i n g a l l of the harvested stover to p y r o l y s i s products and using a 10 kg/h, s e l f - s u s t a i n i n g process would y i e l d 1.5 χ 10 MJ/yr. About 20% to 30% of the energy produced may be required to dry the feedstock, depending on the year and h a r v e s t i n g con­ d i t i o n s . About 20% of the output would supply adequate f u e l f o r an average farm r e s i d e n c e , l e a v i n g about 50% of the output f o r

6

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

ARSENAULT ET AL.

Pyrolysis of Agricultural Residues

370

Figure 6.

I02Q

Energy product/feed ratios ((

—I η'70 ) char; (

)

American Chemical Society Library 1155 16th St. N. W. In Thermal Conversion of Solid Wastes Biomass; Jones, J., el al.; Washington, D. C.and20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

348

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

other p o t e n t i a l on-farm a p p l i c a t i o n s such as g r a i n drying and farm h e a t i n g . Other uses may i n c l u d e replacement of hydrocarbon fuels with char i n engines equipped with g a s i f i e r s . The gas may also have an a p p l i c a t i o n as an engine f u e l although storage may be expensive· I n t e g r a t i o n of crop-residue p y r o l y s i s into the work routine on the farm would d i f f e r depending on the crop residue a v a i l a b l e , the end-use o b j e c t i v e , the kind of farm, and the weather zone i n which the farm i s l o c a t e d . A 10 kg/h unit would r e q u i r e w e l l over a year to process the crop residue from the 50 ha farm discussed e a r l i e r . A 50 kg/h k i l n operating continuously would process the same amount i n 100 days. The r e s u l t i n g char could be stored more e a s i l y than the feedstock. Economic A n a l y s i s An elementary economic a n a l y s i s of the s i t u a t i o n follows. We have seen that a t y p i c a l 50 ha farm could y i e l d about 10 MJ of energy i n the form of high energy char or low energy gas. Compared to f u e l o i l at (U.S.) $ 0 . 1 1 / l i t r e (U.S. values $0.45/ g a l l o n ) t h i s would have a value of about (U.S.) $3,400. Design c r i t e r i a f o r the small scale pyrolytic conversion of a g r i c u l t u r a l biomass w i l l be proposed i n Phase I I , keeping t h i s f i g u r e i n mind. Increased expenditures f o r h a r v e s t i n g , t r a n s p o r t , storage of residue f u e l , and equipment m o d i f i c a t i o n s required to use the product w i l l have to be c o n s i d e r e d . There may a l s o be economies of scale i n v o l v e d . A co-operative of a few farms w i t h i n a small radius of each other may be more prac­ t i c a l . Larger western farms ( t y p i c a l l y 500 ha) should also be considered - the s c a l e up may prove advantageous· 6

Comparison with Peat P y r o l y s i s It i s i n t e r e s t i n g to compare these experiments with p r e v i ­ ous experiments on peat p y r o l y s i s using the same u n i t . Ground sod peat with a degree of decomposition of 27% (Baturin formula - B a t u r i n , 1975; H4 on the Von Post s c a l e ) was a i r d r i e d to 12% moisture content and fed i n at r a t e s up to 18 kg/h (Campion, 1978). Y i e l d s and c a l o r i f i c values at r e a c t i o n temperatures of 1120 Κ are compared with stover and straw p y r o l y s i s at 1170 Κ i n Table I I I . Mass y i e l d s are s i m i l a r f o r the d i f f e r e n t feedstocks but c a l o r i f i c values f o r both feed and products are somewhat higher f o r peat. C l e a r l y , a l l three feedstocks show good potential. Depending on l o c a t i o n , a farm could conceivably use peat as feedstock when a g r i c u l t u r a l residue was not a v a i l a b l e .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

25.

ARSENAULT ET AL.

Table III:

Pyrolysis of Agricultural Residues

Comparison of straw, stover and peat pyrolysis Type of Feed:

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch025

349

Oat Straw1

Corn Stover1

Sod Peat2

Feedstock Calorific value (MJ/kg)

17.9

16.2

20.1

Char Yield (%) Calorific Value (MJ/kg)

22 26.0

30 24.0

30 26.9

ο w

to as

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

354

Results. The experimental program for the RDF module was designed to examine both separation e f f i c i e n c i e s and t o t a l power requirements. Evaluation of t h i s module i s now complete and the data are summarized i n Table I . TABLE I Summary of RDF Production Tests CIL (Kingston)

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch026

Plant Location

Ames, : 30 45 1790 26 84 16

Average load Mg/h 20 Peak load Mg/h 40 Installed power kW 140 Power consumption kW.h/Mg 2.7 RDF production % by wt of input MSW 77 Residue production % by wt of imput MSW 23 (glass, metals, etc)

Also included i n the Table are data from a more convent i o n a l garbage processing f a c i l i t y a t Ames, Iowa (1). The power consumption results f o r Ames only include priinary and secondary shredding and a i r c l a s s i f i c a t i o n . The Table shows that the Kingston Plant operates with s i g n i f i c a n t l y less power than conventionally designed RDF plants, i . e . systems i n which size reduction precedes material separation. Actual maintenance costs are d i f f i c u l t to predict because of the intermittent nature of the P i l o t Plant Program. To t h i s point, 3 years after i n s t a l l a t i o n , the only component which has been repaired i s the shredder. The teeth were resharpened after the second year of operation. The second phase of the refuse program, f l u i d i z e d bed g a s i f i c a t i o n , incorporates heat and energy balances, gas analyses and environmental monitoring. Because of i n i t i a l d i f f i c u l t i e s with feeding systems, the evaluation i s not yet complete. Typical gas analysis are shown i n Table I I . TABLE I I Analysis of Fuel Gas (Dry Basis) Fuel

Gas Analysis H

Refuse Rubber Wood

2

12.5 14.0 17.9

CO 11.6 14.4 16.0

CH

co N 15.4 45.1 2.5 3.2 7.9 52.0 5.5 2.9 0.3 5.8 0.1 1.4 0.3 16.7 40.8 4

C H C H C H 2

2

2

4

2

6

2

2

°2 0.8 0.6 0.8

Commercial A c t i v i t i e s . Proposals f o r two plants have been submitted. The f i r s t , a plant t o provide 150 TPD of RDF for use as a f u e l i n a cement plant was guaranteed a t an i n s t a l l e d cost of $1 m i l l i o n including building and s i t e preparat i o n . A submission for conversion of refuse to steam has also been made. This plant i s designed f o r 200 TPD of mixed municipal refuse a t a steam capacity of 20 Mg steam/h.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

26.

BLACK ET

AL.

Fluidized-Bed Gasification (CIL

Program)

355

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch026

Wood Gasification Program Because of strong government interest and a more immediate market potential, CIL redirected the g a s i f i c a t i o n program to incorporate forest biomass. I t became apparent that there were three areas of interest. In order of increasing complexity these are, 1) An a i r f i r e d , atmospheric pressure system suitable f o r small and medium scale energy producers such as i n d u s t r i a l steam plants or hot gas generators, 2) An a i r f i r e d , high pressure g a s i f i e r more appropriate to large power plants f o r high e f f i c i e n c y , combined cycle e l e c t r i c a l generation, 3) An oxygen f i r e d , high pressure g a s i f i e r necessary f o r chemicals and l i q u i d f u e l production. A program was established to incorporate these three phases of development. We have completed Phase I and are planning f o r Phases 2 and 3. Part of the work has been supported by the Ontario Ministry of Energy and by the ENFOR program of

the Environment Department of the F e d e r a l Government.

Program f o r the Production of a Fuel Gas From Wood. The refuse g a s i f i c a t i o n unit was modified to f a c i l i t a t e wood handl i n g and to incorporate a t e s t u n i t f o r hot gas cleanup, reforming and condensation. The essential system components are shown i n Figure 2. Various forms of forest biomass including wood chips, bark, sawdust and shavings have been evaluated i n the g a s i f i e r . The testing program was i n i t i a l l y designed to evaluate the e f f e c t of parameters such as moisture content, bed temperature and the physical nature of the feed. Subsequently, experiments were conducted to examine long term effects, by simulating commercial operation under a variable load/demand situation for extended periods of time (2 periods of 670 hours continuous operation). Also included i n the program were stack sampling tests, and t a r production measurements. Typical operating characteristics are presented i n Table III. TABLE I I I Operating Characteristics During Wood Gasification Tests Moisture i n Wood Residue Production Combustible Fraction of Residue Turndown Ratio Dust Loading i n Stack (after cyclone) Tar Loading i n Gas Organic Loading of Condensate

12-55% 0.017 kg/kg wood 0.4 kg/kg residue 5:1 1.2g/Nm^ Char + CO + C0 + H 0 2

2

+ CH + C H k

2

[+

+ Pyroligneous acids + tar The oxidation or partial oxidation of char occurs next (300°C upwards). Char + 0 + H 0 (Steam) -> CO + C0 + H + heat 2

2

2

2

The first two processes are driven by the heat given out by the third process. The detailed thermo-chemistry can be summarized as follows: C +0

2

C + C0

2

Ζ

C0 , Exothermic

(1)

Ζ

2C0, Endothermic, Boudouard Reaction

(2)

H 0 + CO Ζ 2

2

C0 + H , Endothermic, Water gas Shift 2

2

Reaction H0 + C Ζ 2

CO + H , Endothermic 2

(3) (4)

C + 2H Ζ CHi+j Exothermic (5) The first reaction is the only one which provides the thermal energy for carrying out the other endothermic reactions. Reaction 5 is favoured only at lower temperatures and high pressures. Because of this, most of the methane formed in the product gas in gasifiers operating under atmospheric pressures, is a result of the pyrolysis step. 2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

29.

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AND

WEiSGERBER

Wood Gasification for Gas Generation

381

Hudson Bay Plant Details Following are some of the details of the plant. details may be seen elsewhere (6).

Complete

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

Gasifier Design Criteria. The gasification plant (Figure 1) has incorporated considerable design improvements and modifications over the smaller unit although the gasifier output target of 4.22 GJ/h and the grate heat release rates determined from B.C. Research unit served as the basis for determining the gasifier internal diameter. An expanded freeboard model was decided upon to reduce gas velocities in order to lower particulate entrainment in the gas exit stream. Design parameters are listed below: Net reactor output Conversion efficiency Gas H.H. V. Waste Wood Moisture Content Fuel Consumption

4.22 72% 5.59 50% 568

GJ/h ~ MJ/m (wet basis) kg/h (as fired) J

Gasifier. The gasifier is approximately 4 m in height having an internal diameter of 1.2 m in the lower section and 1.8 m in the expanded freeboard section. The gasifier outer shell is composed of carbon steel. A layer of refractory forms the inner surface of the gasifier. The windbox region of the gasifier is bolted to the bottom section of the gasifier to facilitate repairs to the ash removal system. Distribution of the incoming air is accomplished with a pinhole grate supported above the windbox. The sectional grate has refractory lining to protect the steel from the 1000°C temperatures expected in the combustion zone immediately abovç. Access to the gasifier is through a manhole. The windbox zone is also supplied with a clean out door. The gasifier is equipped with 8 ports for thermocouple installation and 4 ports for pressure sensing. Two sets of ports at 180 degrees to each and capped with tempered glass are provided for the fuel height optical sensors. Wood Feeding System. The feed system consists of a shift drag conveyor, metering bin, air lock and screw conveyor. The live bottom shift bin has a capacity of 6 m . A grid covers the bin to prevent large sized particles from damaging the system. An inclined drag conveyor transports fuel from the shift bin to the metering bin. The metering bin has a capacity of 1.6 tp? and has a live bottom discharge. A hydraulic motor drives the drag chain conveyor. A hydraulic power unit equipped with an electrically driven pump, flow regulator valve, pressure relief valve, and solenoid valve control the flow and pressure of hydraulic fluid bin,

3

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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to the hydraulic motor. When the solenoid valve which allows fluid to reach the hydraulic motor is closed the fluid circulates within the reservoir. The 12 position flow regulator valve directs the required flow of fluid to the hydraulic motor and bypasses the excess back into the reservoir. A gear motor drives the rotary air lock and screw conveyor. The air lock provides a seal between the screw conveyor below and the small fuel hopper above. The 15 cm diameter screw conveyor has heavy duty 0.62 cm thick flighting. It extends to the inner refractory wall of the gasifier. Air Feed System. A turbo pressure blower heat exchanger and burner compose the air feed system. The blower is designed to deliver 12 m^/min of air at 12 kPa guage pressure at 70°C. At 315°C this decreases to 6 kPa guage pressure. On the outlet of the blower is a manually controlled damper to regulate flow of air. Air is transported to the windbox area via a pipe equipped with an orifice plate. The air preheater is a double shell direct-fired heat exchanger designed to deliver air at a maximum of 315°C. It is 1.2 m in diameter and is 2.3 m in length. A 0.45 GJ/h oil burner supplies the heat. Ash Removal System. A rake, screw conveyor and ash box comprise the ash removal system. A rake mounted above the pinhole grate ploughs ash towards the centrally mounted ash discharge screw. A screw conveyor transports the ash via a gate equipped chute into the ash bin below. Flare System. Following the gasifier is the flare system which is composed of a cyclone, cyclone hopper, butterfly valve, flare and stack. The cyclone is 2 m tall with the diameter decreasing from 1.2 m at the raw gas entrance to 0.3 m at the particulate discharge point at the bottom. The 0.95 m^ cyclone hopper is castor mounted and equipped with a cleanout door. On top of the cyclone is located a cross-tee which is equipped with two manually operated, and one motorized butterfly valve. The manual valves are employed to direct the gas to a particular end use. The motorized valve controls the gas entering the flare. The flare chamber is refractory lined and has an adjustable louvre at the bottom to regulate combustion air. Ignition is provided with a 0.20 MJ/h oil burner. A totally enclosed hood captures the combustion products and directs them to the 0.30 m diameter stack which extends above the hood. Gas Sampling System. The gas sampling system consists of a knockout pot, filters, gas partitioner, integrator and pressure-vacuum pump.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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The pump draws gas from the gasifier outlet through a knockout pot where moisture, tars and dust are removed. Between the knockout pot and the gas partitioner are a couple of filters which ensure the gas is clean and will not damage the analyzer. The gas is drawn through a Fisher gas partitioner and is exhausted outside. The integrator then provides the gas composition on a volume per cent basis. Wood Gas Cleaning System. The wood gas cleaning system consists of a cyclone, centrifugal tar extractor, drier and blower. In the cyclone hot raw gas enters tangentially with ash and carbon particles dropping to the bottom into a hopper and the gas exiting from the top. The hot gas is directed from the cross-tee to the mechanically driven tar extractor in which water is injected to cool the gas and condense the tars which are then separated from the gas by the centrifugal force. The blower draws the cool gas through the column filled with dry wood blocks which remove moisture. The water and tar mixture is taken to a separation tank where the water and tar are separated by gravity. The water is recirculated back to the tar extractor. Diesel Generator System. The cool clean gas can be combusted in a naturally aspirated 250 HP Deutz diesel engine (Model F12L413F) which has been modified for burning wood gas. This has been purchased from Imbert Co. in Germany. The diesel oil injection system has been modified to allow approximately 10 per cent of the normal flow to be injected. This amount of 011 is ignited in compression which in turn ignites the wood gas and air mixture. The wood gas is fed into the engine intake system, mixed with air and sucked into the engine. A Brown Boveri generator rated at 150 kW is frame mounted with the diesel engine. Three banks of 75 kW electric furnaces act as the loading units. Burner System. A modified 5.28 GJ/h burner is also on site to combust the low heating value gas. The burner consists of a 15 cm special wide range burner, pressure pilot, flame rod, combustion air blower with motor, micro ratio valve assembly and an emergency shut off valve. The burner size has been increased compared to a normal burner operating with natural gas. The pilot is operated on propane to ensure adequate ignition. Because of the low heating value of the gas, the air enters the normal gas inlet and the wood gas enters through the normal air inlet. Process Control. The control panel contains the start-stop locations and indicating lights. Temperature, pressure and flow parameters are also displayed. A bindicator on the metering bin and a timer control the wood feed addition to the metering bin. The bindicator shuts

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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off the conveyor from the shift bin when the metering bin is full. A timer which can be varied from 0 to 30 minutes auto­ matically starts the shift bin conveyor after the selected time interval. The rate of addition of solid fuel is controlled from the metering bin. A hydraulic system drives the metering bin conveyor. When the metering bin conveyor is stationary the electrically driven pump on the hydraulic power unit recirculates the hydraulic fluid to the reservoir. To start the metering bin conveyor a solenoid valve is opened allowing hydraulic fluid to turn the hydraulic motor. The flow and pressure of fluid to the hydraulic motor and ultimately the conveyor speed is controlled by a 12 position regulator valve on the hydraulic power unit. A single motor drives both the screw conveyor and airlock. The motor is equipped with reversible switch gear. Both the solenoid valve on the hydraulic power unit and the screw conveyor motor are actuated by one start location on the control panel. Flow of combustion air to the gasifier is controlled by a manually adjustable damper at the outlet of the turbo blower. An orifice plate in the air line to the gasifier indicates the rate of air addition on the control panel. Hot combustion air for start-up of the gasifier is obtained by operating the oil burner on the air preheater. Ash removal is on an intermittent basis with time between removal and amount removed at a single time determined by operating experience. The gasifier is equipped with chromel-alumel Type Κ thermocouples which are tied into a multipoint temperature chart recorder housed in the control panel. Temperatures of the combustion air, fuel bed at various heights, exit gas and combustion products in the stack are monitored. Ports in the gasifier are connected to manometers to provide pressure data. Two sets of optical sensors provide fuel bed height determination by operating indicating lights on the control panel. Fuel bed height is maintained between the two sets of sensors. The operating pressure of the gasifier is controlled between 5 and 16.5 cm water column. The pilot oil burner on the flare can be operated manually or automatically with it starting and stopping as the flare valve opens and closes. Several safety features have been included in the control system. The exit gas thermocouple is connected to a variable temperature controller to maintain gasifier temperatures below safe operating limits. A pressure switch is connected to the outlet point of the gasifier which will shut the combustion fan down if the pressure exceeds 120 cm water column. Various pieces of equipment are also interlocked to protect the system.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

386

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Results and Analysis The Gasifier. Table 1 shows a typical analysis of wet spruce chips of nearly 58% moisture content. Data for the gasification of these is shown in Table 2. The gas compositions are only preliminary and do not represent gas quality when the gasifier is operated under optimized conditions. Even in these preliminary runs the gas heating value has been determined to be in the range 4.4 - 5.07 MJ/m3. The gasifier output was 4.27 GJ/h. Optimization of the gasifier operation is proceeding. Figure 2 shows the temperatures of the various points in the gasifier over a two hour period while gasifying wet spruce chips. The temperature in the combustion zone varied between 600 - 700°C with less than 1% oxygen showing in the exit gases. Other temperatures were considerably lower. Large differences between thermocouple points 1 and 5 indicate that the bed is not in a fluidized state. This was confirmed by further experimental tests carried out on a three dimensional cold model. It was observed that the chips tend to lock with one another and cannot be fluidized under the design flow conditions in the reactor. It was also observed that some channeling also occurs in the bed. Further work is presently under way to determine the fluidizing conditions for other types of waste wood fuels. The Burner. The burner to date has been run effectively with clean wood gas without any problems and it has been demonstrated without a doubt that the clean gas can be easily utilized in a modified burner or a burner designed to burn wood gas. The hot raw gas also burns effectively in the burner. The Engine. The diesel engine, by the time of writing, had run for eight hours total under part load, using the wood gas from this gasification plant. However, the same engine was run on wood gas from a down draft gasifier having similar quality gas. Data from this run is shown in Table 3. As may be seen, with 11% diesel and balance wood gas, the output of the engine drops by 20%. The rest of the engine performance is similar to that when operating with diesel fuel alone. Environment, Resource and Social Impact of Gasification. Here, the forest resources and the social - environmental consequences of power generation via wood gasification were evaluated on 15 northern communities in Saskatchewan which are serviced by diesel electric generators. A general assessment was undertaken for 14 communities and a detailed one for 'Pinehouse'. These communities are listed in Table 4. The table shows the size and the electrical load at these communities. The general assumptions of this study were that forest

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

29.

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Wood Gasification for Gas Generation

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

Table I Typical Analysis of Spruce Wood Chips 1.

Moisture (as received), %

2.

Proximate Analysis (dry basis) Ash, % Volatile Matter, % Fixed Carbon, % Heating Value

3.

Ultimate Analysis Carbon, % Hydrogen, % Nitrogen, %

44.11 5.59 0.08

4.

Ash Analysis, % A1 0 Si0 CaO MgO Na 0 K0 P,0 Fe 0

0.21 1-34 39.72 5.56 17.27 11-59 5.78 0.01

2

3

2

2

2

5

2

3

57.74 0.79 79.40 19.82 20,099 J/g

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

387

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4.54 4.36 4.60 4.98

4.62 4.43 4.68 5.07

17.39 16.49 19.03 22.7

1.712 1.661 1.91 2.05

55.69 56.79 55.74 54.3

0.99 1.37

0.61

9,.93 9..84

11.42

9.62

At 14.73 psia & 60°F.

.991

0.56

11..74

11.77

0.507

1.065

0.604

11..97

11.55

4.77 4.86

18.5

1.86

53.54

0.908

0.605

12..37

12.21

4.46

4.53

55.35

0.898

1.63

17.3

CO 17.91

0.525

12..05

4

CH 1.95

54.79

12.24

2

N

4.62

2

H.H.U, MJ/m3 Sat. Dry 4.69

0 0.880

0.501

11..89

6

12.08

2

CH

ι

2

co

Composition of gas produced from 57.74% Moisture Spruce Chips

Table II

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

AND

WEisGERBER

Wood Gasification for Gas Generation

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

VERMA

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

390

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table

III

Performance Data of Deutz Engine (F12L 413F) Unmodified engine performance with 100% diesel fuel

Ambient Air Temp. °C rpm Total kW Horse Power

15 1,800 196.5 267

Modified engine performance with 11% diesel, balance wood gas

15 1,800 156 212.4

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Camsell Portage Fond du Lac Stony Rapids Black Lake Wollaston Kinoosao Southend Deschambault Sturgeon Landing Stanley Mission Pinehouse Patuanak Di11 on Michel Brabant

Community

100 500 500 500 600 100 350 425 125 500 600 500 550 100 125

Total Capacity (kW) 30 100 110 90 120 20 80 50 25 100 100 100 no 15 25

Average Load (kW)

TOTAL

45 150 180 130 200 35 130 95 45 175 175 175 185 25 45

Peak Load (kW)

2,731,764

75,009 272,760 270,487 264,577 268,214 75,009 183,972 184,113 102,740 233,033 206,566 225,695 220,936 73,645 75,009

Diesel Fuel Consumption (litres) 1977 24 92 95 94 92 20 87 77 40 121 82 111 80 14 17

No. of Electrical Connections 1978

Table IV Communities in Northern Saskatchewan Using Diesel for Power Generation

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

5 6 2 6 5 4 7 6 5 9 7 6 5 8 3

No. of Persons per Connection

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

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392

resources would have to be harvested on a sustained yield basis and use of waste wood could be made in the gasification plant. Wood reserve data was found adequate for 9 of the 15 communities. The remaining 6 communities which are located north of 57 degrees latitude did not have sufficiently detailed forest volume information to allow an accurate assessment of its wood reserves. Nevertheless, the findings indicate that forest resources are adequate to supply a small wood gasification plant for at least 50 years in each community. Such a time frame work for logging ensures a renewable timber resource even without an active reforestation program although it is desirable. One of the major findings was that waste wood could provide an adequate supply of fuel for a few communities. Examples of wood waste could be found at local sawmills, right of way clearing for roads, and wood damaged by forest fires. The social consequences of wood gasification on a community are positive. Though the scale of the gasification project is small, it may require local people to operate the gasifier and to harvest an adequate supply of wood. With the use of local labour, the construction of the project in the community would also have mainly positive implications for the community. The environmental consequences based on emission data could not be completed as the data is being collected but the effect of gasification on vegetation, wildlife and aquatic l i f e , etc. was estimated to be minimal. Overall, the project would offer permanent local employment and ensure a greater electrical power capacity. Earned income would be increased and spin-off benefits could result in the establishment of small businesses. The utilization of waste wood is another positive element associated with this proposed project. As a result, the gasification project is likely to be viewed positively in northern communities. v

Conclusions i)

ii) iii) iv)

The scale up version of the B.C. Research gasification unit did not perform as a fluidized bed gasifier when operating on wet spruce chips. It essentially operated in a fixed updraft flow mode, The fuel gas produced from wood can be easily combusted in a modified burner or a burner built to combust this type of gas. The naturally aspirated modified diesel engines can be run successfully with wood gas while using 10% diesel fuel for ignition purposes. The drop in output is 20%. Power generation via wood gasification in Northern Communities has a minimal impact on the environment and resources while it has a net positive social impact.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

Abstract A 4.22 GJ/h waste wood gasification plant is being evaluated at Hudson Bay, Saskatchewan, Canada. The demonstration scale gasifier is a scale up of a smaller unit at the B.C. Research Council, Vancouver. The gasifier is designed to convert minus 1 inch wood waste with less than 50% moisture into a low heating value gas of approximately 4.5 - 5.6 MJ/m3. In operation wood waste is metered out from a live bottom storage hopper into the gasifier via a feed screw. Air is fed into the windbox under the pinhole grate. Hot raw gas exits from the expanded freeboard gasifier at the top. The gas is cleaned in a 'Crossley' type cleaning train consisting of a cyclone, centrifugal extractor and a drier. The clean gas is fed to a modified diesel engine or a burner. The aim of the work is to evaluate the gasification plant for production of fuel gas suitable for use in a burner and a modified engine for electrical power production. Plant details and preliminary performance data are discussed in the paper, along with environment, social and resource impact of wood gasification on northern communities in the province. References 1.

Verma, Α., Stobbs, R.A., "Wood for Power generation in isolated Northern Communities." Saskatchewan Power Corporation report, 1977.

2.

Verma, Α., Weisgerber, Gordon, "Thermochemical Conversion and other biomass related work at Saskatchewan Power Corporation", Proceedings of "Energy from Biomass seminar", Ottawa, March 1979.

3.

"Engineering Feasibility Study of the British Columbia Research Hog Fuel Gasification system", H.A. Simons (International) Ltd., May 1978.

4.

Liu, M.S., Serenius, R., "Fluidized Bed Solids Waste Gasifier", Forest Products Journal 26a, 56-59, 1976.

5.

"The Social, Environmental and Resource Impact of Wood gasification on Isolated Northern Communities, Part I"; March 1979, Report by Saskatchewan Power Corporation for the Federal Government of Canada under contract. DSS File No. 07SB.KL016-8-0060.

6.

"Evaluation of the Saskatchewan Power Corporation Wood gasifier at Hudson Bay, Saskatchewan, 1978-79". May 1979, Report by Saskatchewan Corporation for the Federal Government of Canada under contract. DSS File No. 07SB.KL016-8-0061.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

394

THERMAL

CONVERSION

O F SOLID

WASTES

A N D BIOMASS

Acknowledgement: This project is a joint project of Saskatchewan Power Corporation, Saskatchewan Forest Products Corporation and the Federal Government of Canada. November 16, 1979.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch029

RECEIVED

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

30 Basic Principles of Waste Pyrolysis and Review of European Processes A. G. BUEKENS and J. G. SCHOETERS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

Department of Chemical Engineering and Industrial Chemistry, Vrije Universiteit Brussels, Pleinlaan 2, B-1050 Brussels, Belgium

1. Introduction In the early fifties more and more Municipalities in W. Europe were confronted with a declining availability of suitable landfill sites. This resulted in the large scale introduction of incinerator plant during the period 1960-75. Initially quite a few of these units showed mechanical deficiencies in the handling of refuse and clinker as well as corrosion problems in the boiler and gas cleaning plant ; some even suffered from gross design errors. As years went by more experience was gained and through the combined skills of designers, manufacturers and operators refuse incineration attained its present status of a well proven though expensive method of waste disposal. Gradually the densely populated regions of W. Europe were amply equipped with incinerator plants. The latter complied with the air pollution regulations of that time by using highly efficient electrostatic precipitators. Thus they could be situated in the very centre of the refuse generating territory reducing the cost of collection and transportation. In large plants the heat of combustion was recovered under the form of medium to low pressure steam, used for power generation and district heating. The low volume, sterile residue was a suitable substitute for gravel, provided the material is graded and the unburnt and magnetic substance is removed.[1,2,3 ] This explains why the progress of PTGL-technology was slower in W. Europe than in the U.S.A. or Japan. Even now, the only process that attained commercial operation in Europe is of American origin. A l l other processes only exist at pilot scale, although a few have been conceived at a larger scale and participate in public tenders. Unfortunately innovation is both difficult and dangerous. Municipalities are very well aware of this fact and will not embark on a yet unproven demonstration project unless very important incentives are provided by the Government. The spectacular failure of a couple of large scale American PTGL-units could only corroborate this tendency. 0-8412-0565-5/80/47-130-397$06.25/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

2 τ) •μ !Η û

•Η

CM •Η

W CO ci ·

M M C

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

•H

Ο

Q

ft

M O

fi M

Λ EH

cd Ο

τ3

M



-μ -ρ -ρ . ρ Ο Ο Ο Ο Ο t— Ο Ο 0J OJ CVJ

Ρ

Η

ω G -Ρ

M M CO > Κ Ο

sa :g

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980. X X

X

X

X

-

1975 1976

1977 1976 1978

800°C 800°C 500°C T00°C 8oo°c 850°C U50°C

6t/d 1t/d

2.5t/d 5t/d

.5t/d .2t/d 1t/d

Stevenage

Hartlepool

Meckesheim

Bochum

Hamburg

Brussels

BATCHELORROBINSON

FOSTERWHEELER

HERBOLD

G MU

UNIVERSITY HAMBURG

UNIVERSITY BRUSSELS

-

-

U30°C

500°C

0"berhausen

Hanover

Essen

BRD

RUHRCHEMIE

PPT

RAMMS

GUILINI

X

X

500°C

CHAR

6t/d

DATE*

Goldshofe

MAX

HERKO/KIENER

Τ

LOCATION

NAME

SIZE

Uses no a f t e r b u r n e r .

See PPT. V e r t i c a l shaft g a s i f i e r . For t i r e s .

-

-

I n d i r e c t l y heated f i x e d bed. For r e c o v e r y o f metals and heat from c a b l e , p a i n t e d m e t a l s . . .

S t i r r e d , i n d i r e c t l y heated r e t o r t . For p o l y e t h y l e n e waste.

I n d i r e c t l y h e a t e d f l u i d i z e d bed. For p l a s t i c s , t i r e s , wood waste.

I n d i r e c t l y h e a t e d f l u i d i z e d bed. For t i r e s .

I n d i r e c t l y h e a t e d r o t a t i n g conveyor. For t i r e s , c a b l e , p l a s t i c s .

I n d i r e c t l y heated screw conveyor. For t i r e s .

Same as Warren S p r i n g .

Warren S p r i n g p r o c e s s f o r t i r e s .

Same as K i e n e r . For t i r e s .

REMARKS

-

-

-

-

-

X

-

-

X

STEAM

-

-

X

X

-

X

X

X

X

GAS

-

-

X

X

X

X

X

X

X

X

OIL

TABLE 1 b : PTGL - P r o c e s s e s f o ri n d u s t r i a l wastes and t i r e s .

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

ο

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

THERMAL

U Ο

CONVERSION OF

SOLID W A S T E S

AND

- H aromatics -*·

p o l y e y e l i e aromatics ( t a r ) -> carbon + hydrogen. At lower temperature the o l e f i n s and d i o l e f i n s tend t o polymerize t o t a r w i t h a h i g h l y complicated, a l i p h a t i c s t r u c t u r e . The thermal decomposition of oxygenated compounds y i e l d s simpler and s t a b l e r compounds, such as formaldehyde, acetone, a c e t i c a c i d , e t c . F i n a l products are o f t e n CO, CO^, H^O, CH =C0.. 2

Van Krevelen and H o f t y z e r [hQ] c h a r a c t e r i z e d the r e l a t i v e s t a b i l i t y o f v a r i o u s polymers and p o l y m e r i z a t i o n i n i t i a t o r s by means o f the temperature T^ at which the s u b s t r a t e i s h a l f decomposed a f t e r a r e a c t i o n p e r i o d of 30 minutes. These authors found a l i n e a r c o r r e l a t i o n between t h i s parameter T. and the energy o f the weakest bond o f the decomposing molecule. Thermodynamic c o n s i d e r a t i o n s thus a l l o w one to p r e d i c t the r e l a t i v e s t a b i l i t y o f d i f f e r e n t r e a c t i n g compounds or t o e x p l a i n the e v o l u t i o n i n a r e a c t i n g system. In the Hamburg p y r o l y s i s process (29) f o r example, a h i g h y i e l d o f aromatic compounds i s obt a i n e d by combining a h i g h p y r o l y s i s temperature w i t h the r e c i r c u l a t i o n of l e s s d e s i r a b l e and l e s s s t a b l e gaseous r e a c t i o n products . Another very important f a c t o r i n p y r o l y s i s i s the heat o f

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

408

Cracking

severity The Petroleum Publishing Company

Figure 1. Evolution of the product distribution with cracking severity (Naphta cracking): (1) C ; (2) C H, + C H ; (3) C H,; (4) C ; (5) C ; (6) H + CH 5+

h

4

19

h

3

2

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2

h

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r e a c t i o n . The l a t t e r can e a s i l y he c a l c u l a t e d from the heat o f formation o f the r e a c t i n g m a t e r i a l and t h e r e a c t i o n products. Unf o r t u n a t e l y these data are not always known w i t h p r e c i s i o n f o r polymeric or b i o l o g i c a l m a t e r i a l and the product a n a l y s i s i s o f t e n incomplete. I n the f i r s t case t h e heat o f r e a c t i o n can be d e t e r mined e x p e r i m e n t a l l y by means o f bomb c a l o r i m e t r y . The heat o f p y r o l y s i s can a l s o be obtained by d i f f e r e n t i a l thermal a n a l y s i s (D.T.A.). I n t h i s technique the temperature o f t h e product sample i s compared t o t h a t o f a reference sample ; i n t e g r a t i o n o f t h e temperature d i f f e r e n t i a l vs. the o p e r a t i n g time y i e l d s a q u a n t i t y r e l a t e d t o t h e heat o f r e a c t i o n .

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2. Gasification Both the thermodynamic e q u i l i b r i u m and the heat o f r e a c t i o n are reasonably w e l l known f o r t h e heterogeneous g a s i f i c a t i o n o f carbon i z e d r e s i d u e w i t h oxygen, steam, carbon d i o x i d e and hydrogen. The o u t l e t gas composition i s normally computed by a t r i a l and e r ror procedure ; f o r each o p e r a t i n g temperature t h e r e s u l t i n g comp o s i t i o n i s c a l c u l a t e d , then t h e a t t a i n e d temperature i s determined from an enthalphy balance and t h e temperature correspondence i s checked. The most important f a c t o r a f f e c t i n g e q u i l i b r i u m gas compos i t i o n i s temperature. D e v i a t i o n s from e q u i l i b r i u m can be explained by t h e presence o f p y r o l y s i s gas, a r i s i n g d u r i n g thermal decomposition, by uneven gas and s o l i d d i s t r i b u t i o n , due t o channeling, b a k i n g , c l i n k e r i n g o r formation o f blowholes, o r by inadequate r a t e s o f r e a c t i o n . I n c r e a s i n g t h e o p e r a t i n g pressure has an unfavorable i n f l u e n c e on the g a s i f i c a t i o n e q u i l i b r i a o f steam and carbon dioxide, but f a v o r s t h e formation o f methane. I n p r a c t i c e a l l processes operate at s u b s t a n t i a l l y atmospheric pressure.

4.3. Kinetics and Mechanism 1. Pyrolysis The d i s t r i b u t i o n o f primary r e a c t i o n products i s mainly d e t e r mined by the s t r u c t u r e o f t h e raw m a t e r i a l and by t h e r e a c t i o n c o n d i t i o n s . A t low temperatures r e a c t i v e primary products may immediately polymerize t o a t a r , obscuring t h e primary r e a c t i o n steps. At h i g h temperatures t h e primary fragments are s u f f i c i e n t l y s t a b l e or rearrange t o s t a b l e p r o d u c t s , so t h a t t h e f i r s t react i o n steps are o f t e n e a s i l y r e c o g n i z a b l e . The r e a c t i o n p a t t e r n s i n the thermal decomposition o f polymers are f a i r l y w e l l known. G e n e r a l l y one o f t h e f o l l o w i n g mechanisms dominates - thermal depolymerization o f a polymer i n t o a monomer

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- s t o c h a s t i c fragmentation o f a polymer chain i n t o smaller molecules of v a r i o u s l e n g t h - e l i m i n a t i o n o f side chains or adjacent s u b s t i t u e n t s y i e l d i n g products such as H 0, C0 , NH~, HC1, H S, CH^ and higher p a r a f fins . 2

2

2

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It i s p o s s i b l e to p r e d i c t the r e l a t i v e importance o f the s e v e r a l modes o f decomposition from an a n a l y s i s of the polymer s t r u c t u r e l l|J_] . Van Krevelen[hO ] even showed that the tendency f o r coke formation i s an a d d i t i v e property, which can be computed from the monomer s t r u c t u r e . The p y r o l y s i s o f c e l l u l o s e i s o f outstanding importance i n the study o f PTGL-processes i n v o l v i n g r e f u s e , wood waste or a g r i c u l t u r a l waste. Unfortunately the products and mechanism o f t h e r mal decomposition are extremely s e n s i t i v e t o a number of p h y s i c a l and chemical f a c t o r s . Even the decomposition o f the purest exc e l l u l o s e has l e d to c o n f l i c t i n g opinions regarding k i n e t i c s and mechanism[h3]. I t i s g e n e r a l l y accepted now that there are 2 competitive methods o f breakdown : - c a r b o n i z a t i o n , proceeding by a r i n g opening o f i n d i v i d u a l monomer u n i t s with a l o s s o f CO, CO^, or H^O, but with conservation of a polymeric carbon-chain -depolymerization t o levoglucosan t a r a f t e r complete "unzipping" of c e l l u l o s e c r y s t a l l i t e s . The r e l a t i v e importance o f the two modes o f decomposition depends on temperature, s t r u c t u r e , moisture and ash content and presence o f a d d i t i v e s . Low temperatures and the presence o f flame retardants favor c a r b o n i z a t i o n . Paper, board, a g r i c u l t u r a l , garden and wood waste l a r g e l y c o n s i s t o f c e l l u l o s i c m a t e r i a l . H e m i c e l l u l o s e , a low molecular weight p o l y s a c c h a r i d e present i n vegetable m a t e r i a l and i n paper, gives a higher y i e l d o f methanol and a c e t i c a c i d than c e l l u l o s e . L i g n i n i s a f a i r l y s t a b l e , c a r b o n - r i c h aromatic compound present i n wood. I t y i e l d s mainly t a r and carbon. The k i n e t i c s and mechanism o f thermal decomposition have o f t e n been s t u d i e d by methods such as thermogravimetric a n a l y s i s (TGA), d i f f e r e n t i a l thermal a n a l y s i s (DTA), p y r o l y s i s gas chromatography, or - by means o f small e x t e r n a l l y heated r e t o r t s , a g i t a t e d v e s s e l or f l u i d i z e d bed r e a c t o r s . The u s e f u l l n e s s o f the r e s u l t s o f these s t u d i e s i s o f t e n l i m i t e d because : - k i n e t i c s and mechanism can be v a s t l y d i f f e r e n t from one temper a t u r e domain t o another or be profoundly i n f l u e n c e d by the presence o f f o r e i g n matter (ash, moisture, c a t a l y s t s ) - even i n one and the same temperature domain the r a t e c o n t r o l l i n g step may d i f f e r depending on the s i z e o f the p a r t i c l e or on the flow c o n d i t i o n s . - g e n e r a l l y the k i n e t i c data show so much spread that data s e l e c -

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t i o n and i n t e r p r e t a t i o n becomes a problem. In the case of c e l l u l o s e p y r o l y s i s a c t i v a t i o n energies ranging from TO t o 230 kj/mole have been r e p o r t e d .

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

Such d i f f e r e n c e s can be a t t r i b u t e d t o d i f f e r e n c e s i n s t a r t ing m a t e r i a l and experimental c o n d i t i o n s and techniques. F u r t h e r i t should be born i n mind t h a t thermal decomposition processes occur along complex mechanisms t h a t cannot adequately be d e s c r i b e d by a simple r a t e law. This e x p l a i n s why apparent energies o f act i v a t i o n or r e a c t i o n orders can vary almost c o n t i n u o u s l y w i t h experimental conditions. A number o f models t h a t take account o f some of the p h y s i c a l phenomena o c c u r i n g during p y r o l y s i s have been developed f o r a s i n g l e wood p a r t i c l e [ . The r e l e v a n t phenomena are : - heat t r a n s f e r by convection and r a d i a t i o n from the surroundings t o the wood p a r t i c l e - i n t e r n a l conductive and convective heat t r a n s f e r . - d r y i n g and thermal decomposition o f the m a t e r i a l . - i n n e r d i f f u s i o n and outer convection o f the p y r o l y s i s products.

1^,1+^.]

A p r a c t i c a l d i f f i c u l t y i n the a p p l i c a t i o n o f such models t o r e a l r e a c t o r s i s the poor knowledge o f the numerical values of the parameters i n v o l v e d ( p o r o s i t y , heat o f r e a c t i o n , thermal cond u c t i v i t y , heat c a p a c i t y , k i n e t i c parameters). Yet from these s t u d i e s i t f o l l o w s t h a t heat and mass t r a n s f e r phenomena by no means can be ignored. Kung [ h6] showed t h a t among wood p a r t i c l e s o f 2, 0.2, 0.02 cm only the s m a l l e s t ones showed a uniform temperature d i s t r i b u t i o n . Hence i n a c t u a l p y r o l y s i s r e a c t o r s the r a t e of conversion w i l l u s u a l l y be c o n t r o l l e d by heat t r a n s f e r . When the l a t t e r i s very slow, as i n the Destrugas process, p l a n t o p e r a t i n g c a p a c i t y may be s t r o n g l y a f f e c t e d by the moisture content of the r e f u s e . 2. G a s i f i c a t i o n G a s i f i c a t i o n i s a heterogeneous g a s - s o l i d r e a c t i o n , composed of three elementary steps : - a d s o r p t i o n o f the gaseous r e a c t a n t s onto the carbon s u r f a c e . - chemical r e a c t i o n between adsorbed gas and s o l i d . - desorption of the gaseous product. The chemical r a t e of r e a c t i o n i s determined by the slowest o f these 3 s t e p s . A s i m p l i f i e d r a t e low i s given by r

= k.A.m c

,p^ c *G

where r k A m c P G

= = = = =

r a t e o f carbon consumption r a t e parameter, f o l l o w i n g an Arrhenius law s p e c i f i c s u r f a c e of the carbonized r e s i d u e amount of C c o n c e n t r a t i o n o f the g a s i f y i n g agent

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The r e a c t i o n with oxygen i s extremely f a s t . The r e l a t i v e rates o f the k heterogeneous g a s i f i c a t i o n reactions at 800°C and Pa (0.1 atm) are : carbon-oxygen : 105 carbon-steam : 3 carbon-carbon dioxide : 1 carbon-hydrogen : 3.10"3

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

Chemical r e a c t i o n i s only r a t e determining i n a f i r s t low temperature domain, s i t u a t e d roughly below 1000°C. In a second, medium temperature domain the gaseous reactant i s gradually deplet­ ed i n s i d e the porous p a r t i c l e , so that the r e a c t i o n proceeds at the r a t e at which i n t e r n a l d i f f u s i o n supplies new r e a c t a n t s . In t h i s i n t e r n a l d i f f u s i o n c o n t r o l l e d region the apparent energy o f a c t i v a t i o n f a l l s o f f t o h a l f i t s i n i t i a l value. At very high temperatures, i . e . above 1200°C, chemical r e a c t i o n i s so f a s t that the gaseous reactant i s immediately con­ sumed upon contact with carbon. At that moment the r a t e i s con­ t r o l l e d by e x t e r n a l d i f f u s i o n . The a c t i v a t i o n energy becomes a l ­ most zero. In each o f the 3 domains the r a t e o f g a s i f i c a t i o n i s pro­ p o r t i o n a l t o the quantity o f f u e l and t o the p a r t i a l pressure p ^ ( a l l other f a c t o r s remaining equal). I t i s also proportional to the s p e c i f i c surface A, except at high temperature when exter­ n a l d i f f u s i o n i s the c o n t r o l l i n g step. Smaller p a r t i c l e s have a r e l a t i v e l y l a r g e r outer surface and a shorter pore length ; they react f a s t e r i n the domains o f e x t e r n a l and i n t e r n a l d i f f u s i o n c o n t r o l , but not i n the l o w temperature domain. A high gas v e l o ­ c i t y (u) stimulates e x t e r n a l t r a n s f e r ; i t thus enhances t h e over­ a l l r a t e o f r e a c t i o n at the highest temperatures (Figure 2). In p r a c t i c e the gas composition can o f t e n be approximated by the a c t u a l e q u i l i b r i u m composition. The d e v i a t i o n can be cor­ r e c t e d f o r by assuming a somewhat lower g a s i f i e r temperature than the r e a l one. Another c o r r e c t i o n method defines an apparent equi­ l i b r i u m parameter determined experimentally : Κ = x.K app theory In the updraft g a s i f i e r χ e s s e n t i a l l y equals 1 f o r g a s i f i ­ c a t i o n by steam and carbon d i o x i d e , but a t t a i n s only 0.1 -0.6 f o r the methanation r e a c t i o n , the exact f i g u r e depending on the reac­ t i v i t y o f the coke [ U81. F l u i d i z e d bed and suspended p a r t i c l e g a s i f i c a t i o n are cha­ r a c t e r i z e d by much shorter r e a c t i o n times. The e q u i l i b r i u m ap­ proach i s incomplete even f o r g a s i f i c a t i o n with steam o r carbon dioxide so that more elaborate computation methods are required!U8] . G a s i f i c a t i o n o f a s i n g l e p a r t i c l e has a l s o been the sub­ j e c t o f a number o f mathematical models, that take i n t o account part o f the heat and mass t r a n s f e r aspects o f the problem [ ^9 50 ] Here a l s o the l a c k o f hard data and the mathematical complexity a

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

BUEKENS AND SCHOETERS

Principles of Waste Pyrolysis

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414

hinder the p r a c t i c a l a p p l i c a t i o n o f such models. In case chemical r e a c t i o n i s f a s t compared t o i n t e r n a l d i f f u s i o n o r when the p o r o s i t y o f the s o l i d i s very low, conversion s t a r t s at the outer surface o f the p a r t i c l e . As r e a c t i o n proceeds f u r t h e r , a r e a c t i n g boundary l a y e r p r o g r e s s i v e l y moves inwards. The p a r t i c l e thus c o n s i s t s o f an unreacted inner core surrounded by an outer ash l a y e r (provided the p a r t i c l e contains ash). This concept i s the b a s i s o f the w e l l known s h r i n k i n g core model ; i t y i e l d s some p r a c t i c a l conversion (X)-time ( t ) r e l a t i o n s . [ 51 ] » Assuming a steady-state and isothermal conditions the s h r i n k i n g core model gives f o r s p h e r i c a l p a r t i c l e s [ 5 2 ] :

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C o n t r o l l i n g step

Conversion/time r e l a t i o n

e x t e r n a l gas f i l m d i f f u s i o n

^ = X

ash l a y e r d i f f u s i o n

| = 1 -

chemical r e a c t i o n

±- = 1 - 0 - x )

3d-x)

2 / 3

+2(i-x)

1 / 3

(τ = time r e q u i r e d f o r complete conversion ; f u n c t i o n o f density of the p a r t i c l e , bulk gas concentration and mass t r a n s f e r or che­ m i c a l r e a c t i o n parameters).

When the behavior o f a s i n g l e p a r t i c l e i n a p y r o l y s i s or g a s i f i c a t i o n r e a c t o r i s s t u d i e d , the p a r t i c l e i s g e n e r a l l y assumed t o be at a given temperature and surrounded by a gas o f w e l l known composition. In the design o f an a c t u a l r e a c t o r a more comprehensive model i s needed t o account f o r the s p a t i a l d i s t r i b u t i o n o f temper­ ature, concentration or extent o f conversion. The r e a c t o r model describes how gas and s o l i d reactants flow and are contacted and how heat and mass are t r a n s f e r r e d . The simplest types o f flow p a t t e r n conceivable are : p e r f e c t mixing and plug flow. TABLE__III Type o f r e a c t o r

Flow_

type

gas

solid

v e r t i c a l shaft

plug

plug

rotating k i l n

plug

f l u i d i z e d bed

plug

deviations

c h a n n e l l i n g , r a d i a l flow due to uneven p o r o s i t y plug r a d i a l concentration patterns i n gas, a x i a l d i s p e r s i o n w e l l mixed two phase gas flow,backmixing of gas, s l u g g i n g , c h a n n e l l i n g plug uneven mixing o f g a s - s o l i d s , axial dispersion 9

entrained r e a c t o r p l u g

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S e v e r a l examples o f r e a c t o r modelling have been d e s c r i b e d elsewhere [53., j>U, 55.] . The g a s i f i c a t i o n o f c o a l has been modelled s e v e r a l times [ 55 56 ] f o r a v e r t i c a l s h a f t r e a c t o r . The models assume plug flow f o r both the gaseous and s o l i d r e a c t a n t s , and homogeneous' or s h r i n k i n g core behavior f o r the i n d i v i d u a l p a r t i c l e s . The value of the various models i s d i f f i c u l t t o evaluate, because the d e t a i l ed computational r e s u l t s can only be compared with experimental data at the o u t l e t o f the r e a c t o r . The models o f c o a l g a s i f i c a t i o n do not consider the e f f e c t o f d e v i a t i o n s from i d e a l i z e d flow. The phenomena t a k i n g p l a c e during r e f u s e g a s i f i c a t i o n and the e f f e c t o f the d e v i a t i o n s from an i d e a l packing have been d i s c u s s e d elsewhere [k^ 5j) · 9

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9

The modelling o f a f l u i d i z e d bed r e a c t o r i s r a t h e r d i f f i c u l t because o f the complicated flow o f gas and s o l i d s i n the r e actor. In a w e l l - f l u i d i z e d r e a c t o r i t i s o f t e n p o s s i b l e t o assume p e r f e c t mixing of the s o l i d s , since only l a r g e d i f f e r e n c e s i n d e n s i t y and s i z e o f the p a r t i c l e s l e a d t o segregation. But the gas flows through the r e a c t o r according t o two d i f f e r e n t mechanisms. A f i r s t part creeps slowly upward through the dense phase and has a good contact with the bed m a t e r i a l . The remainder flows through the bed under the form o f f a s t l y r i s i n g bubbles and has but a poor contact with the bed m a t e r i a l . It f o l l o w s t h a t the c o n c e n t r a t i o n o f the gaseous reactant i s d i f f e r e n t i n the "dense" and i n the "bubble" phase and a l s o v a r i e s with h e i g h t . Hence there i s no simple or d i r e c t r e l a t i o n between the observable gas o u t l e t c o n c e n t r a t i o n and the k i n e t i c parameters o f the g a s / s o l i d r e a c t i o n . The conversion a l s o depends on the r a t e of mass t r a n s f e r between the two phases, which v a r i e s i n a complicated manner with bubble s i z e and r i s e v e l o c i t y , p a r t i c l e s i z e d i s t r i b u t i o n , d i f f u s i v i t y , bed geometry, t h e presence o f bed i n s e r t s , e t c . A number o f e m p i r i c a l c o r r e l a t i o n s are a v a i l a b l e t o estimate these parameters. In most modelling s t u d i e s however, a d j u s t a b l e parameters such as the bubble s i z e are used t o f i t the experimental data. The s a f e s t method o f designing a f u l l s c a l e r e a c t o r i s l a r g e l y based on experiments at s u c c e s s i v e l y l a r g e r s c a l e s o f c a p a c i t y . The use o f a comprehensive mathematical model as a guide i n the design i s s t i l l out o f question because o f the mathematic a l complexity o f such a model, the l a c k o f accurate p h y s i c a l and chemical data, and the n e c e s s i t y o f mastering a number o f t e c h n i c a l and o p e r a t i n g problems. On the other hand i t i s u s e f u l t o t r y and understand the o p e r a t i n g p r i n c i p l e s and the behavior o f such a r e a c t o r and the main features o f the c o n t r o l l i n g mechanism. Spectacular e r r o r s i n the s c a l i n g - u p o f PTGL-reactors may thus be avoided.

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The PTGL-Pro.ject o f the U n i v e r s i t y o f Brussels

BIOMASS

(V.U.B.)

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Since i t s foundation the Department o f Chemical Engineering and I n d u s t r i a l Chemistry of the V.U.B. acquired considerable experience in the f i e l d o f high temperature processes, with studies on steam-reforming of n a t u r a l gas, p y r o l y s i s o f hydrocarbons and catalytic combustion of hydrocarbons. The Department conducted fundamental studies as w e l l as contract work f o r i n d u s t r y , e.g. i n the domain o f f l u i d i z e d bed techniques, i n c i n e r a t o r grate mechanisms and small waste-fed b o i l e r s . An assessment on current t h e r mal d i s p o s a l techniques was prepared on b e h a l f of E.E.C.[ 5,57»58] · In autumn 1976 a contract was signed with the M i n i s t r y of Science P o l i c y f o r a study on the p y r o l y s i s of waste. At that moment i t seemed impossible to catch up with the work of e x c e l l e n t companies such as Union Carbide, Monsanto or O c c i d e n t a l Petroleum and develop a p r o p r i e t a r y process. Furthermore the amount of f i n a n c i a l funds provided and the extent of f a c i l i t i e s a v a i l a b l e at the U n i v e r s i t y precluded such an approach. So i t was decided to concentrate on more fundamental aspects of p y r o l y s i s and g a s i f i c a t i o n and t o l i m i t l a r g e s c a l e work t o c o l l a b o r a t i o n p r o j e c t s with i n d u s t r y , such as the development of small b o i l e r s f o r f i r i n g miscellaneous wastes, moving bed carbon i z a t i o n of wood s l a b s , f l u i d i z e d bed g a s i f i c a t i o n and p y r o l y s i s and moving bed g a s i f i e r s f o r various a p p l i c a t i o n s o f the product gas [ 59 ]. The fundamental research work was subvided i n t o 3 parts [ 6o ]: - thermogravimetric a n a l y s i s (TGA) and d i f f e r e n t i a l thermal a n a l y s i s (PTA) o f minute samples (5~50 mg) of the m a t e r i a l t o be studied. Both techniques y i e l d information on the r a t e o f thermal decomposition, the heat of r e a c t i o n , the k i n e t i c parameters o f t h i s process (pseudo-order and a c t i v a t i o n energy) and the amount of residue. The a n a l y s i s of the evolving product has been monitored by means of gas chromatography. High temperature o x i d a t i o n of the residue allows to compare the r e a c t i v i t y of the carbonized r e sidue . - p y r o l y s i s gas chromatography (Py.G.C.) o f microsamples (10 -200 yg) r a p i d l y y i e l d s information on the r a t e and products o f decomposition i n an extremely broad range of r e a c t i o n temperatures. P r e c i s e measurement o f the t r a n s i e n t temperature p r o f i l e s o f the sample holder and of the e v o l u t i o n v o l a t i l e products as a f u n c t i o n o f time allowed to obtain a much b e t t e r i n s i g h t of the p h y s i c a l and chemical phenomena occuring during Py.G.C. This i n s i g h t i s obviously r e q u i r e d f o r the comparison with or the e x t r a p o l a t i o n to r e a l s c a l e experiments. - p y r o l y s i s i n a f l u i d i z e d bed bench s c a l e r e a c t o r . The t e s t u n i t i s composed of a 15 cm I.D. f l u i d i z e d bed r e a c t o r , a hopper and a screw feeder mounted on top o f the expansion s e c t i o n of the bed, a t u b u l a r furnace preheater f o r the f l u i d i z i n g agent,a quench c o o l e r , cyclone, t u b u l a r condensor and o i l mist scrubber ( F i g . 3 ) .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

BUEKENS AND SCHOETERS

Principles of Waste Pyrolysis

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30.

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419

Pyrolysis tests have been made on polyethylene and polystyrene with steam as the fluidizing agent. Polyethylene yielded a gas and a wax. Their relative amounts could he adjusted by varying the operating temperature[ 6l] . Polystyrene pyrolysis yielded an o i l with a high content of styrene monomer (Fig.4). The reaction conditions were optimized to maximize the yield of styrene. A maximum of 76% (by weight) was obtained. The oil is suitable for reuse in the styrene manufacturing process. Presently, tests are performed on various agricultural and wood wastes such as bark, soy hulls and wood shavings.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch030

ACKNOWLEDGEMENTS The research work described here was carried out as part of the R & D Programme "Economy of Wastes and Secondary Raw Materials", sponsored by the Prime Minister1s Services -Science Policy. LITERATURE CITED 1. Buekens,A; Schoeters,J 2 n d World Recycling Conference, Manilla, Exhibitions for Industry Ltd, Oxted,Engl., 1979. 2. Martin,W; Weiand,H 1978 National Incinerator Conference, Chicago, Ill.,ASME, 1978, p.83. 3. Mutke,R."Conversion of Refuse to Energy",Montreux, 1975,p.105. 4. Buekens,A. Müll und Abfall, 1978, 10(12), 353. 5. Buekens, A. and Schoeters,J. "Assessment of Current Technology of thermal processes for Waste Disposal",E.E.C. Contract 282 76-9,ECIB, Nov. 1977. 6. Mélan, C. Müll und Abfall, 1978,10( 12),363. 7. Roslund,J. in ref. 63,136. 8. Besch,G.M. in ref. 64,196. 9. Besch,G.M. Müll und Abfall,1978,10(12),384 10.Müller,H. in ref. 64,154. 11.Rymsa,K.H. in ref. 63,87. 12.Rymsa,K.H. Müll und Abfall, 1978,10(12), 377. 13.Heil, J. in ref. 64,112. l4.Segebrecht, J. in ref. 64,92. 15.Link, K. in ref. 64, 100. 16.Tabasaran,O. To be presented at this meeting. 17.Tabasaran,O; Besemer,G; Thomanetz,E. Müll und Abfall, 1977, 9 (10), 293. 18.Nowak,F. 1978, Natl. Waste Conf., Chicago,ASME, 1978, 29. 19.Lenz,S. Müll und Abfall, 1978, 10(2), 371. 20.Willerup,O.C.R.E.Conference, Montreux, 1975, 235. 21.Schmidt,R.Müll und Abfall, 1978, 10(12), 375. 22.Bracker,G.P. Metall, 1977, 31(5), 534. 23.Collin,G;Grigoleit,G; Bracker,G.P. Chem. Ing. Techn.; 1978, 50,(11) ,836. 24.Collin, G; Grigoleit,G; Michel,E. Chem. Ing. Techn., 1979, 51 (3), 220.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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a420

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25. Bracker, G.P. Müll und Abfall, 1979, 11(4), 96. 26. Douglas,E; Webb,M; Daborn,G.R. Presented on "Treatment and Recycling of Solid Wastes", Manchester, Jan. 1974. 27. Wilson, H.T., Fletcher, R. Presented on "2nd World Recycling Conference", Manilla, Exhibitions for Industry Ltd, Oxted, England, 1979. 28. Anon. "Pyrolysis Review", Foster Wheeler Power products Ltd. 29. Kaminsky,W, to be presented at this meeting. 30. Sinn, H. Chem. Ing. Techn. , 1974, 46, 579. 31. Kaminsky, W, Menzel,J, Sinn,H. Conserv. and Recycling, 1977, 1 , 91. 32. Sinn, H. Kautschuk. + Gummi Kunststoffe,1979, 32 (1), 23. 33. Kox, W. Thesis, T.H. Eindhoven, 1975. 34. Speth, S. Chem. Ing. Techn, 1973, 45 (6), 256. 35. Besemer, G. "Disposal of Industrial Wastewater and Wastes", Symposium, Wroclaw, 1977, 282. 36. Anon.Metalloberfläche,1978, 32(8), 357. 37. Anon.Wasser, Luft und Betrieb, 1978, 22(8). 38. Groeneveld, M. to be presented at this meeting. 39. Zdonik,S.B., Green, E.J., Hallee, L.P. "Manufacturing Ethylene" Petr.Pub. Co. 1970. 40. Van Krevelen, D.W., Hoftijzer, P.J. "Properties of Polymers", Elsevier Scient. Pub.Co, Amsterdam, 1976. 41. Cameron, G.G. "The mechanisms of Pyrolysis, Oxidation and Burning of Organic Material", N.B.S. special pub. 357, June 1972, 62. 42. Madorsky,S.L. "Thermal Degradation of Organic Polymers", Interscience Publishers, 1964. 43. Alger,R. "The Mechanisms of Pyrolysis, Oxidation and Burning of Organic Material",N.B.S. Special pub. 357, June 1972,171. 44. Maa, P.S., Bailie, R.C. "Combustion Science and Technology", 1973, 7, 257. 45. Miyanami, K. Fan, L.S., Fan,L.T., Walawender, W.P. Can. Ind. Chem. Engineering, 1973, 55, 317 46. Kung, H.C. Combustion and Flame, 1972, 18, 185. 47. Walker, P.L., Rusinko, F. Austin, L.G. Advances in Catalysis, 1959, 11, 133. 48. Rammler, E."Technologie und Chemie der Braunkohleverwertung", 1962, 296. 49. Szekely,J. Evans, J, Sohn, H.Y. "Gas-Solid Reactions", Academic Press, N.Y., 1976. 50. Petersen, Ε. A.I. Ch. Ε. J., 1957, 3, 443. 51. Smith, J.M. "Chemical Engineering Kinetics", McGraw Hill, N.Y. 1970. 52. Levenspiel, O. "Chemical Reaction Engineering", J.Wiley & Sons, N.Y., 1972. 53. Yoshida, K. Kunii, D.,J. Chem. Eng. Japan,1974, 7,(1) 34. 54. Ubhayakar, S.K., Stickler, D.B., Gannon, R.E. Fuel, 1977, 56, 281. 55. Amundson, N.R., Arri, L.E. A.I. Ch. Ε. Journal,1978,24(1),87.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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BUEKENS AND SCHOETERS

Principles of Waste Pyrolysis

421

56. Klose, E, Toufar, W. Energietechnik, 1976, 26(12), 546. 57. Eggen,A.C., Kraatz, R. Winter Annual meeting, Power Division of ASME, N.Y., Nov. 1974, 17. 58. Buekens, Α., Schoeters, J. "W. European Experience on Small Waste fed Incinerators with Heat Recovery", Preliminary Report prepared for S R I, 1978. 59. Buekens,A.G. Conservation and Recycling, 1977, 1, 247. 60. Buekens,A.G.; Masson, H. 2nd World Recycling Conf.Manilla 1979. 61. Buekens,A.;Mertens,J.;Schoeters,J.Steen,P. 1st World Recycling Conference, Basel, 1978. 62. Schoeters,J.;Buekens,A. MER/CRE Conference, Berlin, Oct.1979. 63. "New Technologies in Waste Disposal" (in German ), Symposium at T.U. Berlin, Erich Schmidt Verlag, 1977. 64. "Thermal Treatment of Household Refuse" (in German ), Sympo­ sium at T.U. Berlin, Jurgen Kleindienst, 1978. RECEIVED November 30, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

31 Pyrolysis of Plastic Waste and Scrap Tires Using a Fluidized-Bed Process WALTER KAMINSKY and HANSJÖRG SINN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch031

Universität Hamburg, Institut für Anorganische und Angewandte Chemie, Martin-Luther-King-Platz 6, 2 Hamburg 13, West Germany

Increasing numbers of old tyres and waste plastics are creating problems regarding their disposal. Alternatively, there is a continuing search for new sources of hydrocarbons as a result of increasing energy and raw material needs. Old tyres and waste plastic can be converted by pyrolysis into almost residue free organic raw materials, to meet this need (1, 2, 3, 4, 5). About 340.000 t.a. of scrap tyres arise out of Western Germany's total production of 6.4 million tons p.a. of plastic and rubber which are dealt with in the following ways (6). Table I Removal or Reuse of O l d Tyres. Scrap Tyres t/a.

Methods o f Removal or Reuse Regeneration o f Rubber Recycling Pyrolysis Burning Remoulding C o n t r o l l e d Dumping Uncontrolled Dumping (whereabouts unknown) Others (e.g. boat-fenders) Total

7.000 90.000 85.000

-

100.000 6.000

30 1

338.OOO

lOO

20.000 30.000

circa

% 6 9 0 2 27 25

About 180.000 t/a. of scrap tyres remain to be processed, for instance by pyrolysis. In comparison the amount of plastic waste is about 1.4.106 t/a which is significantly higher. The main part (about 1.1.106 t/a) is mixed up with household waste (7), and therefore only a few hundred thousand tons are easily available from the producing and processing industries. Two different procedures exist for dealing with the latter 0-8412-0565-5/80/47-130-423$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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424

waste. Through Re-use the macro-molecular s t r u c t u r e stays i n t a c t i n c o n t r a s t to other methods ( P y r o l y s i s , H y d r o l y s i s , Burning) which change the chemical s t r u c t u r e to produce raw m a t e r i a l s or energy. F i f t y percent of the t o t a l energy needed t o produce p l a s t i c m a t e r i a l s i s used i n the p o l y m e r i z a t i o n process. Thus at f i r s t s i g h t , i t seems s e n s i b l e to re-use p l a s t i c and rubber waste mat e r i a l s (J3) . But Re-use processes have a negative i n f l u e n c e on the macro-molecular s t r u c t u r e which i s mainly a chain depolymerisation e f f e c t (9_) . Therefore Re-use by i t s e l f i s not a s a t i s f a c t o r y process. In a d d i t i o n , a l a r g e p r o p o r t i o n o f the p l a s t i c waste i s p o l l u t e d and mixed with other types o f waste so t h a t Re-use i s impossible . Therefore, the way i s open f o r p y r o l y s i s processes. These take place e i t h e r i n the t o t a l absence o f oxygen or with a lack of a s t o c h i o m e t r i c a l l y needed amount of oxygen. These processes aim to maintain the valuable C-H-bonding of the macro-molecules t o obt a i n smaller molecules, which can be used as energy recources or chemical raw m a t e r i a l s . These processes take place i n r o t a r y k i l n s , screw-kilns, melting v e s s e l s , or f l u i d i z e d bed r e a c t o r s . The problem l i e s i n t r a n s f e r r i n g the heat to s o l i d m a t e r i a l s i n such a way that the c o n d i t i o n s of p y r o l y s i s are evenly d i s t r i b u t e d t o produce the d e s i r e d product spectrum. Using r o t a r y or other i n d i r e c t l y heated k i l n s with t h e i r v a r y i n g temperature zone r e s u l t s i n an uneven decomposition of the m a t e r i a l . However by using a quartz sand or carbon black f l u i d i z e d bed with i t s even heat t r a n s f e r propert i e s , uniform c o n d i t i o n s f o r decomposition can be reached (_10, 11 ) . At the U n i v e r s i t y of Hamburg we have been developing a f l u i d i z e d bed process f o r the p y r o l y s i s of p l a s t i c waste and scrap t y r e s since 1970. We used three stages of u p - s c a l i n g - 0.1 kg/h; 10 kg/h; 100 kg/h. Laboratory s c a l e

experiments

Figure 1 shows a flow diagram of the p l a n t f o r l a b o r a t o r y e x p e r i ments with a continuous throughput o f O.l kg/h (12): A screw conveyor feeds through a cooled downpipe the e l e c t r i c a l l y heated q u a r t z - r e a c t o r which has a diameter of 5 cm and a f l u i d i z i n g zone o f up to 8 cm. The f l u i d i z i n g gas i s about 500 1/h of e i t h e r n i t r o g e n or c i r c u l a t e d cracker gas. A cyclone separates s o l i d s from the hot p y r o l y s i s gas stream; an e l e c t r o s t a t i c p r e c i p i t a t o r and a system o f i n t e n s i v e c o o l e r s and hydrocyclones condense the l i q u i d p o r t i o n s o f the cracked products, The non-condensable p y r o l y s i s - g a s e s are measured. The f i r s t column i n Table II shows the composition of the pyr o l y s i s products from an input o f p o l y e t h y l e n e . Beside the gaseous products, i . e . mainly methane, ethane, ethylene and propene, the l i q u i d products c o n s i s t o f up to 95 % benzene, toluene, styrene and naphthalene. Only a small amount (1.0 wt-%) of carbon black i s produced. The product spectrum can be i n f l u e n c e d to a c e r t a i n degree by changes i n temperature, Figure 2 shows the p y r o l y s i s of granulated

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch031

KAMiNSKY AND SINN

Figure 1.

Pyrolysis of Plastic Waste and Scrap Tires

425

Flow diagram of the laboratory test plant offluidized-bedpyrolysis.

(1) plastic feed hopper; (2) screw conveyor; (3) downpipe with cooling jacket; (4) fluidized-bed reactor; (5) heater; (6) cyclone; (7) cooler; (8) electrostatic precipitator; (9) intensive cooler; (10) cyclone; (11) gas sampler; (12) gas meter; (13) throttle; (14) compressor; (15) rotameter.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

426

Table I I . Products o f f l u i d i z e d bed p y r o l y s i s o f p l a s t i c waste and scrap t y r e s (wt-%) TWS-1

TWS-1

TWS-1

TWS-2

PE

PE

used Syringes

tyre pieces

whole tyres

740

780

720

7 50

700

Hydrogen Methane Ethane Ethylene Propane Propene Butene Butadiene Isoprene Cyclopentadiene Other a l i p h a t i c compounds Benzene Toluene Xylene Styrene Indan, Indene Naphthalene Methylnaphthalene Diphenyl Fluorene Phenanthrene Pyrene Other aromatic compounds Carbon monoxide Carbon dioxide Water Hydrogen S u l f i d e Thiophene Carbon soot, f i l l e r s S t e e l cord

0,5 16,1 5,3 25,4 + 9,3 0,5 2,8 + 1,0

1,17 20,27 4,33 16,89 0,80 5,35 0,08 1,28 0,09 2,63

0,49 19,09 6,64 15,44 0,12 9,93 3,03 1,38 0,31 2,08

1,30 15,13 2,95 3,99 0,29 2,50 1,31 0,92 0,34 0,39

0,42 6,06 2,34 1,65 0,43 1,53 1,41 0,25 0,35 0,25

13,3 12,2 3,6 1,1 If 1 0,3 0,7 0,15 0,02 0,01 0,02 +

0,69 24,75 5,94 + 1,46 1,27 3,73 0,84 0,34 0,29 0,59 0,22

3,13 13,62 4,20 + 0,45 0,46 2,48 0,92 0,33 0,15 0,47 +

0,36 4,75 3,62 + 0,17 0,31 0,85 0,83 0,49 0,16 0,29 0,21

1,07 2,42 2,65 + 0,35 0,48 0,42 0,67 0,39 + 0,19 0,06

5,1

5,40

8,24

0,9

1,50

5,80

8,50 3,80 1,95 0,10 0,23 0,15 40,59 1,62

13,67 1,48 1,74 5,11 0,02 0,25 40 11,30

Balance

99,4

99,91

98,76

98,10

96,96

Reactor

LWS

Feed m a t e r i a l

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Temperatur

ο C

LWS: l a b o r a t o r y s c a l e d r e a c t o r , TWS-1: p i l o t p l a n t , TWS-2: p i l o t p l a n t f o r whole t y r e s , PE: polyethylene, + : t r a c e d e t e c t i o n

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

KAMiNSKY AND SINN

Pyrolysis of Plastic Waste and

Scrap Tires

All

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch031

31.

Figure 2.

Product composition from fluidized-bed pyrolysis of granulated rubber tires, plotted as weight percent vs. temperature

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch031

428

THERMAL

CONVERSION

OF SOLID WASTES AND

BIOMASS

scrap t y r e s . By i n c r e a s i n g the temperature, the y i e l d of carbon b l a c k , hydrogen, methane and benzene r i s e s , and the y i e l d o f o i l f a l l s . Because a high percentage (about 35 wt-%) o f the o r i g i n a l feed m a t e r i a l i s carbon black, i t i s evident that, i t w i l l form a l a r g e p a r t o f the p y r o l y s i s products (over 38 wt-%). The l i q u i d f r a c t i o n has a l s o a high aromatic content. The bound c h l o r i d e i n p l a s t i c s c o n t a i n i n g PVC i s recovered as hydrogen c h l o r i d e gas from p y r o l y s i s . Considerable amounts o f carbon soot are produced i n t h i s r e a c t i o n . By adding superheated steam and hydrogen, the amount of carbon black produced can be r e duced from 8.8 to 2.1 wt-% (13). For the p y r o l y s i s of p l a s t i c waste with a high PVC content, i t i s probably b e t t e r to f i r s t dehydrohalogenize i t i n a r e a c t o r with added sand. Tests have shown that hydrogen c h l o r i d e gas can be produced from PVC at temperatures o f between 350 and 400°C, which i s up to 99 % pure and, a f t e r adsorption of the r e s i d u a l hydrocarbons, may be used to make very pure h y d r o c h l o r i c a c i d . A f t e r t r e a t i n g PVC f o r 20 minutes at a temperature of 350°C, more than 90 % of the bound c h l o r i d e has s p l i t o f f . This time i s reduced to l e s s than 10 minutes i f the temperature i s i n c r e a s e d to 400°C

(12) . I f the PVC content of the p l a s t i c waste i s low, the hydrogen c h l o r i d e produced can be absorbed e i t h e r d i r e c t l y i n the f l u i d i z e d bed to which calcium oxide or magnesium oxide i s added, or i n a separately connected f l u i d i z e d bed. This method has proved s a t i s f a c t o r y , at l e a s t f o r the absorption of hydrogen f l u o r i d e i n the p y r o l y s i s o f PTFE-containing p l a s t i c wastes and f o r hydrogen s u l fide i n the p y r o l y s i s of rubber. P i l o t p l a n t experiments These r e s u l t s l e d to the design o f a p i l o t p l a n t with a throughput o f 10 kg/h whose o v e r a l l layout i s shown i n Figure 3. The p r o j e c t was financed by the A s s o c i a t i o n of the P l a s t i c Produc i n g Industry (Verband Kunststofferzeugende I n d u s t r i e , VKE) and the F e d e r a l M i n i s t r y o f Research and Technology (BMFT). P l a s t i c m a t e r i a l i s p y r o l y z e d i n a f l u i d i z e d bed r e a c t o r u t i l i z i n g quartz sand heated to about 800°C. The f l u i d i z i n g medium i s preheated p y r o l y s i s gas. To observe the p r i n c i p l e o f i n d i r e c t heating and to avoid any p o l l u t i o n of the products, we used f i r e tubes i n s i d e the sand bed, i n which e i t h e r propane (for the s t a r t i n g period) or p y r o l y s i s gas can be burned. The feed enters the sand bed e i t h e r at the top of the r e a c t o r through an a i r lock (ZR 1) or through a water-cooled screw feeder ( ZR 2 with S 1) a t the s i d e . A water-cooled screw conveyer (S 2) i s i n s t a l l e d as an o u t l e t f o r the quartz sand. At the top of the r e a c t o r i s a safety b u r s t i n g d i s c . The lower h a l f of the r e a c t o r i s b r i c k e d with f i r e - p r o o f mortar. The r e a c t o r i s b u i l t up with three p a r t s , each o f a diameter of 0.5 m and d i f f e r e n t lengths of

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Flow diagram of the pilot plant for the pyrolysis of plastic waste and scrap tires.

(PI) Pressure indication device; (PIC) automatic pressure control; (TI) temperature indicating device; (TIC) automatic temperature control; (FI) flow-meter; (LC) level indicator; (R) reactor; (M) motor; (WT) heat exchanger; (ZR) bucket wheel lock; (KM) membrane compressor; (KR) cryostat; (Κ) cooler; (S) screw feeder; (G) container; (F) flare; (TG) dip pipe; (Z) cyclone; (P) pump; (EF) electric separator; (DK) packed distillation column

Figure 3.

Pla sties

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THERMAL CONVERSION OF SOLID WASTES AND

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1.0 m, 0.5 m and 0.3 m. The upper p a r t c a r r i e s the feeding tunnel f o r coarse m a t e r i a l (e.g. rubber pieces) and sand, the s a f e t y d i s c and the connection flange f o r the gas o u t l e t . The feed screw con­ veyor and the four P-shaped burners - two of each are r e s p e c t i v e l y above and below the conveyor l e v e l - are i n s t a l l e d i n the middle p a r t . The power output of the four burners i s r e g u l a t e d by varying the pressure of the burning gas. The bottom of the f l u i d i z e d bed has an i n c l i n e of about 15° and c a r r i e s the bent gas i n l e t tubes. These tubes are movable ver­ t i c a l l y so that t h e i r distance from the bottom of the f l u i d i z e d bed can be v a r i e d . With t h i s arrangement there i s a v a r i a b l e s e t t ­ l i n g zone f o r small metal p i e c e s such as w i l l be deposited on pyr o l y t i c s t r i p p i n g of copper-cored w i r i n g . A flanged i n s p e c t i o n cover i s f i t t e d to the bottom of the gas d i s t r i b u t i o n zone. A p i c t u r e of t h i s p y r o l y s i s r e a c t o r i s shown i n Figure 4. The p y r o l y s i s gas produced i s cleaned together with the f l u i d i z i n g gas i n a cyclone (Z 1); i f the feed contains scrap t y r e m a t e r i a l , char and z i n c oxide w i l l be p r e c i p i t a t e d . The cleaned gas i s l e d to the condenser (Κ 1) which i s a c t u a l l y a v e r t i c a l t u b u l a r heat exchan­ ger. In the case o f condenser f a i l u r e , a three way cock allows the gas to be fed d i r e c t l y to the f l a r e . The gas leaves the condenser (Κ 1) a t 20 to 50°C, or at 100°C i f the c o o l i n g c a p a c i t y i s r e ­ duced to avoid clogging by p a r a f f i n waxes* Condensed products are c o l l e c t e d i n a r e c e i v e r (G l ) . I n a counter-current packed washer (K 2) the gas i s then cooled to -20 C. The condensed products are d i s s o l v e d i n a scrubber o i l pump. For c o o l i n g the scrubber o i l to -20°C a counter-current t u b u l a r heat exchanger (WT 1) i s used. The l i q u i d products c o l l e c t e d are processed together with the scrubber o i l f i r s t i n a 0.1 m diam packed g l a s s r e c t i f i c a t i o n column, i n which high b o i l i n g (b»p. above 150°C) and low b o i l i n g products are separated. Gaseous products are r e c i r c u l a t e d to become the p y r o l y ­ s i s gas. The low b o i l i n g f r a c t i o n i s r e f i n e d again i n a second 8 cm diameter packed column to give four f r a c t i o n s : a low b o i l i n g , a high b o i l i n g , a benzene, and a toluene f r a c t i o n . The high b o i ­ l i n g f r a c t i o n ( i . e . xylene) i s pumped back continuously i n t o the washing tower, any excess being taken o f f . A l l products are drawn o f f and s e p a r a t e l y analyzed. The non-condensable components of the p y r o l y s i s gas are com­ pressed to 2 to 3 bar and s t o r e d i n a gasometer. F l u i d i z i n g gas as w e l l as f u e l gas f o r the r a d i a t i n g f i r e tubes i s drawn o f f as r e ­ q u i r e d . The f l u i d i z i n g gas i s preheated to 400°C i n a countercurr e n t heat exchanger (WT 2) by the exhaust gas of the four f i r e tubes. Because o f s a f e t y reasons i t i s necessary to avoid any a i r or oxygen w i t h i n the whole product cycle- Therefore i n case of a drop below atmospheric pressure,a by-pass f o r the compressor allows product gas to flow back from the gasometer i n t o the system. The p l a n t i s equipped with numerous d a t a - c o l l e c t i n g i n s t r u ­ ments. Because we have d e l i b e r a t e l y separated the hot and c o l d p a r t s o f the p l a n t , the l a t t e r , together with the p r o c e s s i n g of

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

KAMiNSKY AND SINN

Pyrolysis of Plastic Waste and

Scrap Tires

431

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31.

Figure 4.

Pyrolysis reactor with a feed screw for plastic, a withdrawal screw for solid materials, and a cyclone

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

432

THERMAL

CONVERSION OF SOLID WASTES AND BIOMASS

the p y r o l y s i s o i l , are s i t u a t e d i n an explosion proof room. Sur­ v e i l l a n c e i s c a r r i e d out by continuous a n a l y s i s of the room a i r as w e l l as by e x p l o s i o n l i m i t c o n t r o l s . The p y r o l y s i s gas i s analyzed a u t o m a t i c a l l y by a gas chromatograph. A l l data c o l l e c t e d are graphed to achieve energy- and massbalances . Some b a s i c components are continuously monitored by i n f r a r e d spectroscopy, i . e . ethylene i n the p y r o l y s i s gas, sulphur d i o x i d e and oxygen i n the exhaust gas. The d e s c r i b e d p i l o t p l a n t has been operating f o r more than 700 running hours. Within these runs, i t has been proved t h a t the process i s s e l f - s u f f i c i e n t i n i t s energy needs (Table I I I ) .

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Table I I I Energy balance f o r the p y r o l y s i s o f 19,1 kg/h Polyethylene/Polypropylene ( r a t i o 1:1) a t 71^°C . P y r o l y s i s gas (produced): 8,0 m /h 3

Heat s u p p l i e d (burning of 4,6 m /n D i s s i p a t e d heat Burner gases P y r o l y s i s gases Crack energy Cooler (Κ 1) Water c o o l i n g I n s u l a t i o n l o s s e s (remainder)

Gas)

6

209,8·10 J 6. 77,0·10^J 2,1· 47,3*10 J 46 9-10 J 14,7-10 J 21,8*10 J f

Almost h a l f the amount o f p y r o l y s i s gas produced was burnt i n the exhaust gas f l a r e ; the other p a r t was s u f f i c i e n t to support the energy demands o f the process, being burnt i n the r a d i a t i o n f i r e tubes. Waste heat from the r e a c t o r heating (cooler) was s u f f i c i e n t to heat the d i s t i l l a t i o n column. A n a l y s i s o f the product spectrum shows t h a t between 40 and 60 wt-% o f the feed i s gained as worthwhile l i q u i d products (Table ID · Table IV shows the p a r t i c u l a r f r a c t i o n s which are obtained from the process, In the p y r o l y s i s of polyethylene at 810°C, the low b o i l i n g f r a c t i o n contains, apart from benzene, more than 10 wt-% of c y c l o pentadiene. I f benzene-rich f i r s t runnings and l a s t runnings (to­ luene-rich) are removed, one can o b t a i n a f r a c t i o n c o n t a i n i n g about 98 wt-% o f benzene. The main c o n s t i t u e n t s o f the high b o i ­ l i n g f r a c t i o n s are naphthalene, methylnaphthalene and indene, as w e l l as h i g h l y condensed aromatics. As a general example f o r contaminated p l a s t i c scrap we pyrol y z e d shreddered syringe m a t e r i a l s - c o n t a i n i n g p o l y e t h y l e n e , p o l y ­ propylene and rubber (Table I I ) . The p y r o l y s i s of these syringes i s without doubt h y g i e n i c and gives n e a r l y the same products as

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

31.

KAMiNSKY AND SINN

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433

Table IV Composition o f v a r i o u s product f r a c t i o n s obtained through the p y r o l y s i s o f p o l y ethylene a t 810°C

vol %

low boiling wt-%

benzenerich wt-%

20,7 40,8 7,1 22,2 5,9 0,2 1,0 0,2

10,6 76,9 2,0

0,1 97,9 0,9

1,9

10,5

1,1

gas

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Substance

Hydrogen Methane Ethane Ethylene Propene Cyclopentadiene Benzene Toluene Styrene Naphthalene Others 1

50-70

B o i l i n g r a n g e ( °C)

high boiling wt-%

toluenerich wt-%

47,6 51,9 0,2

0,1 2,3 24,5 73,1

0,3 80-100

70- 80

above 150

f r o m a n i n p u t o f p o l y e t h y l e n e . The p r o d u c t s show o n l y t r a c e s o f w a t e r , c a r b o n d i o x i d e and m o n o x i d e , and a c e t o n i t r i l e ; t h e p e r c e n t a g e o f c a r b o n s o o t can b e up t o 5.8 wt-% b e c a u s e o f t h e r u b b e r content. These r e s u l t s p r o v e t h a t p y r o l y s i s i s an a d e q u a t e p r o c e s s t o reprocess pure p l a s t i c m a t e r i a l s as w e l l as contaminated p l a s t i c f r a c t i o n s o f household waste. P r e v a i l i n g c o n d i t i o n s i n West Germany mean t h a t a r o m a t i c s a r e t o be f a v o u r e d as p r o d u c t s . We have now o p t i m i z e d t h e p r o c e s s t o a c h i e v e t h e maximum y i e l d o f benzene p o s s i b l e , b y v a r y i n g t h e temperature o f the f l u i d b e d , t h e f e e d and t h e f l o w o f t h e f l u i d i z i n g g a s . S t a t i s t i c a l p l a n n i n g o f t e s t r u n s l e d t o t h e f o l l o w i n g e f f e c t s and r e g r e s s i o n e q u a t i o n s . The y i e l d s o f b e n z e n e and e t h y l e n e can be c a l c u l a t e d from the f o l l o w i n g e q u a t i o n , u s i n g percentage w e i g h t i n r e l a t i o n to the feed. wt-% b e n z e n e

= 21.095 + 2.323 t - 1.381 d + 0.731 w - 0.680 t d + 0.581 dw + 0.104 t w - 0.377 t - 0.910 d 0.457 w 2

2

2

wt-% e t h y l e n e = 18.733 - 1.195 t - 0.132 d - 1.785 w - 2.436 t d + 2.643 dw - 0.341 tw - 1.618 t + 3.240 d + 1.263 w 2

2

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

434 in

CONVERSION

OF SOLID WASTES AND

BIOMASS

which t

temperature - 750°C 30°C

d

throughput - 14,18 5,03 kg/h

kg/h 3

w

f l u i d i z i n g gas/h - 32,85 m /h

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365

3

m /h

Figure 5 shows the graphing of the flow of f l u i d i z i n g gas against the feed; i t w i l l be n o t i c e d that a maximum i n the y i e l d of benzene almost corresponds to a minimum i n the y i e l d o f e t h y l e ne. From these r e s u l t s and from experiments with s i n g l e p a r t i c l e s , i t can be concluded that aromatics are produced from o l e f i n s such as ethylene, propene and butadiene. The s l i g h t d i f f e r e n c e between the above maximum and minimum y i e l d s , and the d i f f e r e n t gradients of the y i e l d curves i n d i c a t e the existence of successive and parallel r e a c t i o n s : the p y r o l y s i s r e a c t i o n has a two-stage mechanism. In the f i r s t stage, macromolecules are decomposed i n t o small, mostly o l e f i n i c compounds. During the second stage, aromatics are produced from the i n t e r - r e a c t i o n of these compounds, and hydrogen and methane are given o f f . By r a i s i n g the temperature, the flow of f l u i d i z i n g gas and the residence time, the y i e l d of aromatics i n creases. Larger amounts of benzene were produced by the p i l o t p l a n t than by the l a b o r a t o r y s c a l e p l a n t , as a r e s u l t of a longer residence time i n the r e a c t o r . Prototype f o r Whole-Tyre

Pyrolysis

F l u i d i z e d sand beds are s u r p r i s i n g l y i n s e n s i t i v e to the u n i t s i z e of the feed m a t e r i a l . P i e c e s of scrap t i r e s up to a weight of 2.7 kg/each were fed and q u a n t i t a t i v e l y pyrolyzed. These r e s u l t s proved the f e a s i b i l i t y o f p y r o l y t i c processing of scrap tyres without p r i o r s i z e r e d u c t i o n . Most p y r o l y s i s processes use crushed feed down to between 200 and 20 mm i n s i z e which causes considerable expense (_10, 14, 15) . The f o l l o w i n g companies have c a r r i e d out p y r o l y s i s e x p e r i ments i n i n d i r e c t l y heated r o t a r y k i l n s using such feed m a t e r i a l : Kobe S t e e l (_16) i n Japan Goodyear and TOSCO (_17) i n the U.S.A. GMU (_18) n d Herko-Kiener (19) i n West Germany. a

In cooperation with the Hamburg company C.R.Eckelmann and promoted by the F e d e r a l M i n i s t r y of Research and Technology a p i l o t p l a n t f l u i d bed r e a c t o r f o r a 1.5 to 2.5 t / d throughput of scrap tyres

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Pyrolysis of Plastic Waste and Scrap Tires

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KAMiNSKY AND SINN

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

was b u i l t at the Hamburg i n s t i t u t e (20_, 21) . The f l u i d bed has i n ­ t e r n a l dimensions of 900 χ 900 M.M. so that i n d i v i d u a l unshredded t y r e s of up to 20 kg i n weight can be processed. The high cost of shredding can t h e r e f o r e be dispensed with ( F i g . 6). The p y r o l y s i s zone, a f l u i d i z e d sand bed or carbon black bed i s i n d i r e c t l y heated up t o between 650 t o 850°C by seven r a d i a t i n g f i r e - t u b e s , arranged i n 2 l a y e r s . One p a r t of the product gas i s used t o f l u i d i z e the bed, the other being burnt to heat the pro­ cess . The whole t y r e s r o l l through a g a s t i g h t lock i n t o the r e a c t o r (Fig. 7). Observable events can be d e s c r i b e d as f o l l o w s . The t y r e / landing on the f l u i d bed g r a d u a l l y s i n k s i n t o the sand. The mate­ r i a l heats up and s o f t e n s , i t s surface becoming covered with hot sand g r a i n s . Through the shearing f o r c e s of the f l u i d bed - increased be­ cause of the r e d u c t i o n of the f r e e cross s e c t i o n of the bed - an "exchange" o f sand g r a i n s takes p l a c e at the surface of the softened m a t e r i a l ; the abrasion o f small p a r t i c l e s and t h e i r de­ composition begins. A methane and ethylene r i c h gas as w e l l as a condensable l i q u i d p a r t with a high percentage o f aromatics are produced (see Table I I ) , The main p a r t o f the f i l l e r m a t e r i a l s - carbon soot and z i n c o x i d e - i s blown out of the f l u i d bed and can be separated i n a cyclone. The carbon soot i s dry and t r i c k l e s out of the cyclone. A f t e r 2 or 3 minutes, the t y r e i s completely p y r o l y z e d . What remains i n the sand bed i s a mass o f t w i s t e d s t e e l wires, which are removed by a t i l t a b l e grate extended i n t o the f l u i d bed. The p y r o l y s i s products together with the f l u i d i z i n g gas ( i . e . the non-condensable p y r o l y s i s gases) leave the r e a c t o r v i a a cyclone, where dry carbon soot and f i l l e r m a t e r i a l s are p r e c i p i t a ­ ted. The hot gases are cooled t o room temperature by an o i l scrub­ ber and then r e f i n e d i n the washer and r e c t i f i c a t i o n u n i t used i n the smaller p i l o t p l a n t d e s c r i b e d above. The p i l o t p l a n t has been running since l a t e 1978. I t was proved i n a t e s t run with a feed o f more than 150 car t y r e s , that the process i s s e l f - s u f f i c i e n t i n i t s energy needs, producing a t a temperature o f 720°C, even excess p y r o l y s i s gas t o supply other heat necessary. Waste heat from the r e a c t o r heating i s s u f f i c i e n t to heat the d i s t i l l a t i o n column. The balance o f the products i s as f o l l o w s (compare with Table I I ) : 22 27 39 12

wt-% wt-% wt-% wt-%

gas liquids carbon soot s t e e l cord

The sulphur content of the aromatic f r a c t i o n i s l e s s than 0.4 wt-% and that of the gas l e s s than 0.1 wt-%. Carbon b l a c k con­ t a i n i n g z i n c oxide and sulphides can be separated i n t o re-usable

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Pyrolysis of Plastic Waste and Scrap Tires

437

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Figure 6. Flow diagram of the prototype reactor for whole-tire pyrolysis. (1) steel wall with fireproof bricking; (2) fluidized bed; (3) tillable grate; (4) radiation fire tubes; (5) nozzles to remove sand and metal; (6, 8, and 9) flange for observation and repairs; (7) gastide lock; (10) shaft for steel cord.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Figure 7. Placement of whole tires into the lock of the prototype reactor

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch031

31.

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Pyrolysis of Plastic Waste and Scrap Tires 439

Η.A.T.-quality and waste carbon black by an air classifier. The waste carbon black is an interesting source of zinc (4-5 wt-%). If the price we can obtain for pyrolysis o i l stays above 580 DM/t (this corresponds to a benzene price level of llOO DM/t) and that of carbon black over 300 DM/t, then operating costs and capital costs of a plant with a capacity of 7500 t/a will show a profit of 7 % p.a. At present, the price of benzene amounts to 900 - 1000 DM/t, and prices of up to 600 DM/t for carbon black are possible. As a result of our work, the firm C.R. Eckelmann are planning to build a commercial plant with a capacity of 6.OOO to lO.OOO t/a of unshredded scrap tyres and hydrocarbon-containing waste. In addition, we have succeeded recently in treating aliphatic waste o i l and the liquid extracts of oil-sands to produce aromatic compounds. In conclusion,it may be possible to gain aromatic liquids from oil-sands in a one-stage process, using the sand in the feed as the medium for the fluid bed. Literature Cited 1. Sanner, W.S. Bureau of Mines TN 23. U7 No. 742862206173 2. Kaminsky, W.; Menzel, J.; Sinn, H. Int. J. Conservation & Re­ cycling 1976, 1, 91 3. Tsutsumi, S. CRE Conference Paper, Montreux 1976, 567 4. Beckmann, J.A.; Crane, G.; Kay, E.L.; Laman, J.R. Rubber Chem. Technol., 1974, 47, 597 5. Spendlove, M.J. Umschau, 1973, 73, 364 6. Umweltbundesamt der BRD, Materialien zum Abfallwirtschaftspro­ gramm '75, Materialien 2/76, Berlin 1976 7. Glenz, W. Kunststoffe, 1977, 67, 165 8. Data received from Stanford Research Institute, April 1973 9. Ranby, B. Kunststoffe German Plastics, 1978, 68, 10 10. Sinn, H.; Kaminsky, W.; Janning, J. Angew. Chem. Ed. Engl., 1976, 15, 660 11. Kaminsky, W.; Menzel, J.; Sinn, H.; Plastic and Rubber, Pro­ cessing June 1976, 69 12. Menzel, J. Chem.-Ing.-Techn., 1974, 46, 607 13. Kaminsky, W.; Sinn, H. Kunststoffe German Plastics, 1978, 68, 14 14. Schnecko, H.W. Chem.-Ing.-Tech. 1976, 48, 443 15. Luers, W. Gummi-Asbest-Kunstst., 1975, 28, 770 16. Takamura, Α.; Inone, K.; Sakai, T. CRE Conference Paper, Montreux 1976, 532 17. Ricci, L.J. Chem. Eng. (Aug. 1976) 52 18. Collin, G.; Grigoleit, G.; Bracker, G.-P. Chem.-Ing.-Tech., 1978, 50, 836 19. Tabasaran, O.; Besemer, G.; Thomanetz, E. Müll Abfall, 1977, 9, 293 20. Kaminsky, W.; Sinn, H.; Janning, J. European Rubber J., 1979 161, 15 21. Kaminsky, W.; Sinn, H.; Janning, J. Chem.-Ing.-Tech., 1979, 51, 419 RECEIVED November 16, 1979. In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

32 Two-Stage Solid Waste Pyrolysis with Drum Reactor and Gas Converter O. TABASARAN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

University of Stuttgart, Bandtaele 1, 7000 Stuttgart - 80, West Germany

1. Introduction Results of experiments conducted so far indicate that p y r o l y s i s offers a number of basic advantages when compared with thermooxidative waste treatment. Examples of said advantages are: R e l a t i v e l y good a d a p t a b i l i t y towards fluctuations i n quantity and q u a l i t y of input m a t e r i a l . P o s s i b i l i t y of t r e a t i n g d i f f e r e n t wastes that normally c l a s s i f i e d as being problematic. Simpler and more e f f i c i e n t gas p u r i f i c a t i o n . Low fresh water requirements. Small amounts of waste water. High energy y i e l d . P r i n c i p l e p o s s i b i l i t y of storing energy. -

R e l a t i v e l y quick starting-up and shutting-down operations. Simple separation of g l a s s , i n e r t material and metals from residues. Direct product

utilization

i n gas

engines.

Economical operation, also i n connection with decentralized systems.

0-8412-0565-5/80/47-130-441$05.50/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

are

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442

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

The a u t h o r knows o f s e v e r a l p i l o t p l a n t s i n Europe w i t h t e c h n i c a l d i m e n s i o n s , e. g. t h e waste d e g a s i n g p l a n t D e s t r u g a s i n K a l u n d b o r g , Denmark, w i t h a t h r o u g h p u t o f 5 t/24 h; t h e K i e n e r System p y r o l y s i s p l a n t i n Goldshôfe/Aalen, West Germany, w i t h a c a p a c i t y o f a p p r o x i m a t e l y 6 t/24 h; a gas g e n e r a t o r f o r 50 t/24 h f o r used t y r e t r e a t m e n t i n G i s l a v e d , Sweden. F u r t h e r systems a r e b e i n g d e v e l o p e d i n West Germany by K r a u s - M a f f e i , GMU and Saarberg-Fernwarme. The f i r s t high-temperature p y r o l y s i s p l a n t w i t h l i q u i d slag r e m o v a l , Andco-Torrax-System ( c a p a c i t y : 120 t/24 h ) , has a l r e a d y been p u t t o work i n Luxembourg. I t has been f o l l o w e d by a s i m i l a r p l a n t w o r k i n g under the same p r i n c i p l e i n F r a n k f u r t , West Germany. The D e s t r u g a s System p i l o t p l a n t has been t h o r o u g h l y examined by t h e a u t h o r on o r d e r o f t h e M i n i s t e r o f t h e I n t e r i o r o f t h e F e d e r a l R e p u b l i c o f Germany, whereas t h e K i e n e r System e x p e r i m e n t a l p l a n t was s u b j e c t t o e x a m i n a t i o n by o r d e r o f the M i n i s t e r f u r W i r t s c h a f t , M i t t e l s t a n d und V e r k e h r and t h e M i n i s t e r f i i r E r n a h r u n g , L a n d w i r t s c h a f t und Umwelt, b o t h i n t h e S t a t e o f BadenWiirttemberg, f u r t h e r m o r e by o r d e r o f t h e Umweltbundesamt (German E n v i r o n m e n t a l P r o t e c t i o n A g e n c y ) . I n p a r t i c u l a r t h i s i n v e s t i g a t i o n was t o t a k e p l a c e w i t h a view to data t h a t a l l y to environmental c o n s i d e r a t i o n s . The f o l l o w i n g i s a p r e s e n t a t i o n o f t h e p r o b l e m o f harmf u l s u b s t a n c e s i n p y r o l y s i s gases and some o f t h e r e s u l t s o f t h e work done a t t h e p l a n t mentioned l a s t . 2. H a r m f u l S u b s t a n c e s i n P y r o l y s i s Gases The t y p e s o f waste p r i m a r i l y c o n s i d e r e d f o r p y r o l y s i s t r e a t m e n t , such as m u n i c i p a l r e f u s e , p l a s t i c s o r used t y r e s c o n t a i n a number o f c h e m i c a l s u b s t a n c e s w h i c h r e a c t t o new p r o d u c t s d u r i n g d e g a s i n g as w e l l as d u r i n g c o m b u s t i o n , e. g. s u l p h u r , c h l o r i n e and n i t r o g e n compounds. Such compounds may p o l l u t e t h e atmosphere and must t h e r e f o r e be removed i n t h e i r gaseous p h a s e s . S u l p h u r c o m p o u n d s are present primar i l y i n t h e form o f hydrogen s u l p h i d e s which a r e s p l i t o f f a t r e l a t i v e l y low t e m p e r a t u r e s o f about 250° C. By t h e r m a l d i s s o c i a t i o n o f the hydrogen s u l p h i d e on h o t o r ovenheated s u r f a c e s e l e m e n t a l s u l p h u r i s p r o d u c e d . I t may r e a c t w i t h c a r b o n t o form c a r b o n d i s u l p h i d e and w i t h c a r b o n monoxide t o form c a r b o n o x y s u l p h i d e ( c a r b o n y l s u l p h i d e ) . O r g a n i c s u l p h u r compounds such as c a r b o n d i s u l p h i d e , c a r b o n o x y s u l p h i d e , hydrogen t h i o c y a n a t e , t h i o p h e n e s and e t h y l h y d r o s u l p h i d e a r e u s u a l l y formed i n s m a l l q u a n t i t i e s o n l y . The sometimes u n p l e a s a n t odour of t h e o i l d e r i v e d from c a r b o n i z a t i o n must be a t t r i b u -

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

32.

TABASARAN

443

Two-Stage Solid Waste Pyrolysis

ted p r i m a r i l y t o t h e p r e s e n c e o f s u l p h u r compounds, t r a c e s o f which are noxious. N i t r o g e n c o m p o u n d s are present p a r t l y i n t h e form o f ammonia and hydrogen c y a n i d e . The i n t e n s i t y o f ammonia f o r m a t i o n i s h i g h i f t h e p y r o l y ­ s i s ( c a r b o n i z a t i o n ) t e m p e r a t u r e i s low and i f t h e r e s i ­ dence t i m e o f t h e c a r b o n i z a t i o n gas a t h i g h t e m p e r a t u r e l e v e l s i s s h o r t . Here, t h e e q u i l i b r i u m

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

2 NH

~

3

N

2

+ 3H

2

must be c o n s i d e r e d . I t w i l l be s h i f t e d t o t h e r i g h t a t high temperatures. The h i g h e r t h e t e m p e r a t u r e t h e more hydrogen c y a n i ­ de w i l l be p r e s e n t i n t h e g a s , and t h e ammonia w i l l r e a c t w i t h t h e carbon i n accordance w i t h t h e e q u a t i o n : C + NH

*"

3

HCN + H

2

As a r u l e approx. 4 % o f t h e t o t a l ammonia w i l l be c o n v e r t e d i n t o f e r r o c y a n i d e a t a t e m p e r a t u r e o f about 800°C. A t a t e m p e r a t u r e o f 1000°C t h e p o r t i o n may amount t o 24 %. The f o r m a t i o n o f n i t r o g e n o u s g a s e s i s n o t t o be e x p e c t e d t o an e x t e n t w o r t h m e n t i o n i n g d u r i n g p y r o l y s i s alone. During h y b r i d processes o r as a r e s u l t o f p a r t i a l o r complete c o m b u s t i o n t h e s e gases are formed c o m p u l s o r i l y : N

+0

2

4 NH

3

(2 NO

2

T"""^ 2 NO ( T > 1000°C)

+ 50 ~

4 NO + 6 H 0

+0

2 N0 )

2

2

1

2

2

The p y r o l y s i s o f m a t e r i a l c o n t a i n i n g c h 1 ο r i n e such as PVC produces p r i m a r i l y h y d r o c h l o r i c a c i d w h i c h i n t h e p r e s e n c e o f ammonia i s t r a n s f o r m e d i n t o ammonium c h l o r i d e as t h e gases c o o l down. In c o n t r a s t t o o x i d a t i v e t h e r m a l t r e a t m e n t lowt e m p e r a t u r e p y r o l y s i s shows t h a t sodium c h l o r i d e does n o t r e a c t t o y i e l d h y d r o c h l o r i c a c i d , and t h e r e f o r e t h e f o r m a t i o n o f v o l a t i l e heavy m e t a l c h l o r i d e s i s n e g l i ­ g i b l y s m a l l . C h l o r i n e s a l t s ( c h l o r i d e s ) as w e l l as heavy m e t a l s l e a v e t h e system m a i n l y w i t h t h e s o l i d residues. H y d r o f l u o r i c a c i d i s found i n s m a l l q u a n t i t i e s i n p y r o l y s i s gases. I t i s l i k e l y t h a t t h e c o n t e n t s a r e s i m i l a r t o t h o s e o b t a i n e d from burning.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

444

THERMAL

CONVERSION

OF SOLID WASTES AND

BIOMASS

H e a v y m e t a l vapours o r heavy m e t a l d u s t s are produced by t h e h i g h - t e m p e r a t u r e p y r o l y s i s p r o c e s s , whereas t h e y remain i n t h e s o l i d r e s i d u e s -save f o r mercury- i n c o n n e c t i o n w i t h t h e lowtemperature p r o c e s s . C a r b o n i z a t i o n gas u s u a l l y c o n t a i n s c o n s i d e r a b l e q u a n t i t i e s o f l o n g - c h a i n hydrocarbons o r h i g h e r - c o n densed a r o m a t i c and p h e n o l i c h y d r o c a r b o n s which condense d u r i n g c o o l i n g t o o i l y , t a r - r e s e m b l i n g s u b s t a n c e s o r which contaminate t h e gas s c r u b b i n g water c o n s i d e r a b l y . T h e r e f o r e a number o f low-temperature p y r o l y s i s p r o c e s s e s have an i n t e g r a t e d high-temperat u r e s t a g e t h r o u g h which t h e c a r b o n i z a t i o n gas c i r c u l a t e s t o a c c o m p l i s h t h e c r a c k i n g o f such s u b s t a n c e s t o l o w e r - m o l e c u l a r compounds. The f u n c t i o n and d e s i g n o f t h e c r a c k i n g zones determine t o what e x t e n t remains o f t h e t a r r y s u b s t a n c e s r e a c h t h e s c r u b b i n g water o f the o n - l i n e gas p u r i f i c a t i o n u n i t and t h e r e b y charge i t w i t h s u b s t a n c e s t h a t are a t times d i f f i c u l t t o decompose b i o l o g i c a l l y i n sewage t r e a t m e n t p l a n t s . Dusts c o n t a i n e d i n p y r o l y s i s gas may cause d i f f i c u l t i e s i n p i p e s and equipment because o f t h e i r tendency t o s e t t l e t h e r e . I t i s , however, no problem t o remove them from t h e exhaust gas. 3· K i e n e r Waste P y r o l y s i s System As f a r as the K i e n e r p y r o l y s i s system i s c o n c e r n e d t h e r e i s e x p e r i e n c e a v a i l a b l e from p i l o t p l a n t s . In F e b r u a r y 1979 t h e f o r m a l o f f i c i a l p l a n n i n g p r o c e dure was c o n c l u d e d w i t h t h e o b j e c t i v e o f s e t t i n g up a r e f u s e t r e a t m e n t p l a n t w i t h a c a p a c i t y o f approx. 140 t / d i n the c i t y o f A a l e n , West Germany. F i g u r e 1 i s a f l o w diagram o f t h e p l a n t . The system o f f e r s i n p r i n c i p l e two modes o f o p e r a t i o n . One mode emphasizes t h e r e c o v e r y o f raw m a t e r i a l s whereas t h e o t h e r emphasizes t h e p r o d u c t i o n o f energy. The type o f o p e r a t i o n chosen depends on t h e i n p u t m a t e r i a l and on t h e economic e x p e c t a t i o n s i n v o l v e d 3.1 O p e r a t i o n w i t h Emphasis on M a t e r i a l Recovery F i g u r e 2 shows t h i s t y p e o f o p e r a t i o n . The i n p u t m a t e r i a l c o n s i s t s p r i m a r i l y o f substances with r e l a t i v e l y h i g h energy c o n t e n t s , such as used t y r e s , p l a s t i c s , r u g s , wood and s p e c i a l o r g a n i c i n d u s t r i a l wastes. The c o n t i n u o u s l y f e d p y r o l y s i s r e a c t o r c o n s i s t s o f a r o t a t i n g s t e e l drum which i s h e a t e d i n d i r e c t l y w i t h the exhaust gases o f a gas e n g i n e o r t h e f i r i n g gases o f a gas o r o i l b u r n e r by p a s s i n g t h e s e hot gases t h r o u g h a system o f s p e c i a l l y d e s i g n e d , i n t e r n a l l y mounted heat exchanger t u b e s . G a s t i g h t a i r - l o c k s

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Carbonization Gas T o r c h

Carbonization drum

Discharge Unit

Warm A i r Cooling Unit

Coal

Gas C o n v e r t e r

Tanks f o r Wastewater

Fresh

Air

Gas S t o r a g e Unit

Treatment f o r Wastewater

Waste w a t e r t o sewage plant

liferent

Gas

Blower Unit

Gas p u r i f i c a t i o n

Gas Cooling Unit

electric power

Gas e n g i n e w i t h generator f o r electricity

General outline of the Kiener System two-stage refuse plant with drum reactor and gas converter

Exhaust gas condensation

Ashes Residues Exhaust Residues

Figure 1.

Conveyer

Refuse

Feeding

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Figure 2.

material

Feed

Ai

Exhaust heat

Gas f o r h e a t i n g

O i l condensates, Heat

eventually sulphur

PURIFICATION

GAS

the reactor

E x c e s s gas

Variant 1—degasing and condensing with emphasis on the recovery of raw materials

Τ = 30°C

CONDENSATION

AT.

Solid residues, e.g. s o o t , m e t a l s

REACTOR

PYROLYSIE

Τ = 500°C

gases,

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

>

Ο ω ο

>

GO

w

Η

Ο

ο

δ

GO

< m

ο

ο

> r

X m

Η

-4ΡS^* O

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

32.

TABASARAN

Two-Stage Solid Waste Pyrolysis

441

p r o v i d e d a t b o t h ends o f t h e drum make c o n t i n u o u s f e e d i n g as w e l l as c o n t i n u o u s s l a g and s o o t removal p o s s i b l e . The t u b i n g n o t o n l y o f f e r s o p t i m a l h e a t t r a n s f e r b u t a l s o r o l l s t h e m a t e r i a l around and advances i t s u b j e c t t o u n i f o r m drum r o t a t i o n . O p e r a t i o n a c c o r d i n g t o v a r i a n t " 1 ) " comprises a condenser succeedi n g t h e drum. I t i s c o o l e d w i t h a i r and i s t h u s i n d e pendent o f w a t e r . Typ^/ q u a n t i t y and q u a l i t y o f t h e r e a c t i o n p r o d u c t s n a t u r a l l y depend upon t h e p r o p e r t i e s o f t h e i n put m a t e r i a l . The f o l l o w i n g are examples o f p r o d u c t s o b t a i n e d b y t h e p y r o l y s i s o f used t y r e s ( F i g u r e s 3 and 4 ) . Gas : The gas w h i c h i s c l e a n e d b y s c r u b b i n g c a n be used advantageously f o r the a s p i r e d , s e l f - s u f f i c i e n t o p e r a t i o n o f the p l a n t i n r e s p e c t t o energy. Excess q u a n t i t i e s o f t h e gas may be f l a r e d o f f . The c o m p o s i t i o n o f t h e h i g h - c a l o r i f i c gas o b t a i n e d from t h e p y r o l y s i s o f o l d t y r e s i s shown i n t a b l e 1. As can be seen t h e p y r o l y s i s gas c o n t a i n s m a i n l y hydrogen, methane and o t h e r h y d r o c a r b o n s . I n o u r case t h e y i e l d was 167 k g f o r e a c h t o n o f used t y r e s . The average c a l o r i f i c v a l u e was d e t e r m i n e d t o be approx. 3 4 . 5 0 0 k J / m . The odour was s p e c i f i c and i n t e n s e . Oils; The complex-compounded o i l y p r o d u c t s o b t a i n e d t h r o u g h c o n d e n s i n g c a n be used p r i n c i p a l l y as e n g i n e f u e l o r as f u e l f o r o i l b u r n e r s . T h e y may a l s o be used a s a d d i t i v e s o r b a s i c m a t e r i a l s f o r rubber production or i n the chemical i n d u s t r y . On t h e average 1 t o n o f used t y r e s y i e l d s 468 k g o f condensate h a v i n g a t y p i c a l and i n t e n s e odour and a c a l o r i f i c v a l u e o f 40- 000 k J / k g . The f l a s h p o i n t i s n e a r 8°C. F o r f u r t h e r d e t a i l s p l e a s e r e f e r t o table 2. S o l i d Residues; These c o n s i s t p r i m a r i l y o f m a t e r i a l h i g h i n c a r b o n c o n t e n t , w h i c h i s p r a c t i c a l l y o d o u r l e s s . Because o f t h e i r h i g h c a l o r i f i c v a l u e s o f more t h a n 3 0 . 0 0 0 k J / k g i t i s p o s s i b l e t o use them as f u e l o r as raw m a t e r i a l f o r gas g e n e r a t o r s . I f p r o p e r l y t r e a t e d , t h e y c a n a l s o be used as f i l l e r m a t e r i a l s b y t h e r u b b e r i n d u s t r y o r as f i l l e r s o r dyes b y t h e c h e m i c a l i n d u s t r y (see t a b l e 3 ) . I n o u r c a s e t h e p y r o l y s i s o f 1 t o n o f used t y r e s p r o d u c e d 365 k g o f s o l i d r e s i d u e s , most o f w h i c h , namely 4 9 . 7 % had a g r a i n s i z e between 0 . 1 and 0. 5 mm. 3

American Chemical Society Library 1155

16th St. N. W.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; Washington, D. C.Society: 20036 ACS Symposium Series; American Chemical Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

448

9

0

1D

20

30

a

Temperature °C Figure 4.

Viscosity of the condensate from the pyrolysis of old tires (determined by DIN procedure 51562)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

TABASARAN

32.

Table I.

449

Two-Stage Solid Waste Pyrolysis

Mean Values of the Parameters Characterizing the Process Gas Obtained Through the Pyrolysis of Old Tires

Parameter

Method o f Determination gravimetric Nose

Y i e l d (based on tyres) Odour Net c a l o r i f i c value Gross c a l o r i f i c value

Unit of Measurement % by weight

3

H u

from GC

kJ/m η

H

from GC

kJ/m η

3

ο Relative density

d

Value 16.7 intensive, specific 34 580 46 180 0,959

from GC

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

V

from GC GC

% by volume

11 260 4,6

GC

% by volume

0,31

GC

% by volume

16,36

GC

% by volume

15,66

GC GC

% by volume % by volume

4,66 21,86

GC

% by volume

13,9

C2-hydrocarbons

GC

% by volume

9,53

C^-hydrocarbons

GC

% by volume

6,7

C^-and C^-hydrocarbons

GC

% by volume

5,32

HS

GC Draeger

% by volume ppm

1,1 6 000

H

Draeger

ppm

n. d.

HCN Draeger

ppm

6

HCN Draeger

ppm

4

Draeger 3 HC1 Draeger NO Draeger

ppm

n. d.

ppm ppm

n. d. n. d.

Wobbe number Carbon d i o x i d e

C 0

Oxygen

2

°2

Hydrogen

H

2 N

Nitrogen

2

Carbon monoxide Methane

CO C H

Ethane and Ethene

6 C

2 4

Other hydrocarbons Hydrogen sulphide before p u r i f i c a t i o n Hydrogen sulphide after purification Hydrogen cyanide before p u r i f i c a t i o n Hydrogen cyanide after purification Ammonia Hydrogen c h l o r i d e Nitrogen oxides

4

H

2

2

S

N H

X

VDI 2066

Dust

GC n. d.

: :

3

mg/m

n. d.

Gas chromatography not d e t e c t a b l e

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

450

THERMAL

Table II.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

SOLID W A S T E S

AND

BIOMASS

Mean Values of the Parameters Characterizing the Condensate Obtained Through the Pyrolysis of Old Tires

Parameter

Yield

CONVERSION OF

Method of Unit o f Determination Measurement

(based on tyres)

gravimetric

Colour

Eye

Odour

Nose

Value

% by weight

46.8 black intensive, specific

Net c a l o r i f i c value

H u

calorimeter

kJ/kg

40 161

Gross c a l o r i f i c value

H

calorimeter

kJ/kg

42 406

DIN 51 582

% by weight

depending on moisture i n the t y res up t o 7

DIN 51 757

g/ml

Water

content

Density a t

15° C

Viscosity at

15° C

8.42

Viscosity at

20° C

7.09

Viscosity at

25° C

Viscosity at

30° C

5.21

Viscosity at

35° C

4.55

Viscosity at

40° C

4.13

DIN 51 562

m Pas

0.937

6.03

Coke residue acc. t o Conradsen

DIN 51 511

% by weight

2.7

Closed-cup f l a s h p o i n t

DIN 51 758

° C

+

Combustion p o i n t

DIN 51 356

° C

+ 35

S e t t i n g p o i n t , lower

DIN 51 583

° C

- 23

S e t t i n g p o i n t , upper

DIN 51 583

° C

- 30

Ash

DIN 51 575

% by weight

0.016

content

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

8

32.

TABASARAN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Table II.

451

Two-Stage Solid Waste Pyrolysis

Continued

Neutralization number

NZ

DIN 51 558/1

mg/KOH/g

2.4

Saponif i c a t i o n

VZ

DIN 51 559

mg KOH/g

5.8

Bromine-number

BZ

DIN 51 774

% by weight

54

Carbon

C

EA

% by weight

86

Hydrogen

H

EA

% by weight

10.3

Oxygen

0

EA

% by weight

0.4

Nitrogen

Ν

EA

% by weight

0.7

Sulphur

S

EA

% by weight

1.3

Chlorine

Cl

EA

% by weight

1.3

Zinc

Zn

AAS

ppm

Lead

Pb

AAS

ppm

0.1

Cadmium

Cd

AAS

ppm

0.1

Mercury

Hg

AAS

ppm

0.1

Tin

Sn

AAS

ppm

2

Manganese

Mn

AAS

ppm

0.31

Iron

Fe

AAS

ppm

3.5

Chromium

Cr

AAS

ppm

0.14

Nickel

Ni

AAS

ppm

0.39

Copper

Cu

AAS

ppm

0.7

Aluminium

Al

AAS

ppm

2

S p e c i f i c heat a t 20° C

Cp

calorimeter

kJ/kg · Κ

1.96

EA AAS DIN

26

Elementary A n a l y s i s Atomic Absorption Spectralphotometry German I n d u s t r i a l Norm

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

452

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table III.

Mean Values of Parameters Characterizing the Solid Residues Obtained Through the Pyrolysis of Old Tires

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Parameter

Method of U n i t of Determination Measurement

Value

Total y i e l d (based on tyres)

gravimetric

% by weight

36.5

Soot f r a c t i o n (based on tyres)

gravimetric

% by weight

30.5

Steel fraction (based on tyres)

gravimetric

% by weight

6

Soot f r a c t i o n gravimetric (based on s o l i d residues)

% by weight

83.5

Steel fraction gravimetric (based on s o l i d residues)

% by weight

16.5

A l l f u r t h e r data given below are v a l i d only f o r the soot of the s o l i d r e s i d u e s .

fraction

Bulk d e n s i t y

gravimetric

Colour

Eye

black

Odour

Nose

odour­ less

Net c a l o r i f i c

value

Gross c a l o r i f i c value Annealing

H u

calorimeter

kJ/kg

30 355

H ο

calorimeter

kJ/kg

30 600

DEV

% by weight

loss

Extractable substance

0.42

3

t/m

organic

88.3

Tetra/Chloroform

0.8

E x t r a c t a b l e waters o l u b l e substance

Eurocop.Cost.

% by weight

0.6

Bulk d e n s i t y

gravimetric

g/ml

0.42

Carbon

C

EA

% by weight

85.8

Hydrogen

H

EA

% by weight

1.1

Nitrogen

Ν

EA

% by weight

0.4

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

32.

TABASARAN

453

Two-Stage Solid Waste Pyrolysis

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Table III. Continued Sulphur

S

EA

% by weight

2.6

Chlorine

Cl

EA

% by weight

0.7

Zinc

Zn

AAS

ppm

Zinc oxide

ZnO

Calculated from Zn

% by weight

7.7

Lead

Pb

AAS

ppm

229

Cadmium

Cd

AAS

ppm

22

Mercury

Hg

AAS

ppm

Tin

Sn

AAS

ppm

400

Manganese

Mn

AAS

ppm

40

Iron

Fe

AAS

ppm

3 800

Chromium

Cr

AAS

ppm

28

Nickel

Ni

AAS

ppm

31

Copper

Cu

AAS

ppm

157

Aluminium

Al

AAS

ppm

3 400

Tellurium

Te

AAS

ppm

DEV EA AAS

: : :

61 680

German Standards Methods f o r the Examination o f Water Elementary A n a l y s i s Atomic Absorption Spectralphotometry

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

454

THERMAL

CONVERSION

OF

SOLID

WASTES

AND

BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Metals : The s o l i d r e s i d u e s c o n t a i n m e t a l l i c substances w h i c h can be removed w i t h ease from the s o o t a f t e r p y r o l y s i s because they a r e the shredded s t e e l components o f tyres. Harmful Gaseous Substances: The s u l p h u r compounds c o n t a i n e d i n t y r e m a t e r i a l e n t e r the gas phase i n the form o f hydrogen s u l f i d e , which can be brought t o r e a c t w i t h p e l l e t e d f e r r i c o x i d e i n a d r y c l e a n i n g s t a g e . The p u r i f y i n g agent w i l l become s a t u r a t e d a f t e r a c e r t a i n p e r i o d o f time and can be r e g e n e r a t e d by e x p o s i n g i t t o a i r . 3.2 O p e r a t i o n w i t h Emphasis on Energy Y i e l d A l l s u b s t a n c e s w i t h l a r g e r p r o p o r t i o n s o f i n e r t components o r lower energy c o n t e n t s are s u i t a b l e as i n p u t m a t e r i a l s f o r t h i s second p r o c e s s v a r i a n t . Such subs t a n c e s a r e , f o r example, m u n i c i p a l r e f u s e and sewage s l u d g e . In p r i n c i p l e the same drum r e a c t o r i s used as e x p l a i n e d f o r the f i r s t p r o c e s s v a r i a n t . However the c a r b o n i z a t i o n gases are not condensed b u t t h e r m a l l y c r a c k e d i n a gas c o n v e r t e r . The gas c o n v e r t e r i s a s o l i d - b e d g e n e r a t o r f i l l e d w i t h c h a r c o a l o r coke h a v i n g a low ash c o n t e n t and a c e r t a i n s i z e . In c o n t r a s t t o c o n v e n t i o n a l s o l i d - b e d g e n e r a t o r s i t s purpose i s not to g a s i f y s o l i d f u e l but much r a t h e r t o c o n v e r t the c a r b o n i z a t i o n gas and t o i n i t i a t e the hydrogen gas and methane-forming r e a c t i o n s . A hot c o a l bed a c t s p a r t i a l l y as a c a t a l y s t . The hot c a r b o n i z a t i o n gas l e a v e s the r e a c t o r a t a temperature between 340 and 450°C and i s mixed w i t h a c e r t a i n s t o i c h i o m e t r i c a l l y i n s u f f i c i e n t q u a n t i t y of a i r to achieve p a r t i a l o x i d a t i o n , thus c a u s i n g the temperature o f the gas t o r i s e t o approx. 1100°C. T h i s a l s o heats up the c o a l bed where the subsequent r e a c t i o n s are i n i t i a t e d . The gas mixt u r e t h u s produced l e a v e s the g e n e r a t o r a t a temperat u r e o f about 4 50°C because o f thermochemical and m a i n l y endothermic p r o c e s s e s and i s passed t h r o u g h a c y c l o n e t o s e p a r a t e f i n e - g r a i n s o l i d s , t h r o u g h a gas c o o l e r t o reduce the temperature, t h r o u g h a gas s c r u b b e r f o r c l e a n i n g and e v e n t u a l l y t o the gas engine a f t e r i t has been mixed w i t h a i r ( F i g u r e 5 ) . The gas engine i s coupled d i r e c t l y t o an e l e c t r i c g e n e r a t o r . Having reached a u n i f o r m speed, the o p e r a t i n g temperature t h a t has been s e t i n s i d e the drum r e a c t o r can be kept c o n s t a n t w i t h t h e a i d o f the hot exhaust gases from the gas e n g i n e . The gas c o n v e r t e r i s shown i n F i g u r e 6. T a b l e s 4 and 5 show the mean v a l u e s o f the r e s u l t s o f e x p e r i -

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

material

Feed

ι

Figure 5.

Variant 2—degasing and

GENERATOR FOR ELECTRICITY

*7

GAS PURIFICATION UNIT

30°C

GAS ENGINE



Heat

GAS PURIFICATION

cracking with emphasis on the production of heat and elec­ trical energy

S o l i d Residues; p r i n c i p a l l y i n e r t matter, m e t a l s and c a r b o n

GAS CONVERTER

Τ = 1200°C

Hot e x h a u s t gases used f o r h e a t i n g t h e r e a c t o r Τ = 650°C

PYROLYSIS REACTOR

Τ = 500°C

Exhaust

g a s e s , Heat

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Η

2

> >

CO

> >

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

456

Table IV. Mean Values of Parameters Characterizing the Raw Material and the Reaction Products in Experiments with Municipal Refuse

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Raw

Refuse

Water c o n t e n t a f t e r p r e - d r y i n g

18

% by w e i g h t

Annealing loss

44

% by w e i g h t

Organic carbon content

40

% by w e i g h t

Net c a l o r i f i c v a l u e

8 370

kJ/kg

Net c a l o r i f i c Density

5 700

kJ/m

3

kg/m

3

H

2 CO CH

4

CnH

m

°2

co

2

value

1 .1 20

% by volume

14

% by volume

3

% by volume

1

% by volume

3

% by volume

8

% by volume

2 HS

51

% by volume

10

ppm

so

20

ppm

30

ppm

N

2

2

HCN NO

n.d.*

X

HC1

n.d.* n.d.*

Hg NH

120

3

Dust c o n t e n t

n.d. * n. a. *

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

TABASARAN

32.

Two-Stage Solid Waste Pyrolysis

457

S o l i d Residues Annealing loss

15

Organic carbon content

12

% by w e i g h t

Bulk d e n s i t y

1 .00

kg/dm

3

Apparent

1.15

kg/dm

3

density

Net c a l o r i f i c

density

Heavy m e t a l s :

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

% by w e i g h t

kJ/kg

2500 Cr

2.9

ppm

Mn

8.0

ppm

Ni

1 .6

ppm

Co Zn Cd

2.2 41 .0

ppm ppm

0.2

ppm

Cu

5.4

ppm

Pb

20.0

ppm

Hg

1.0

ppm

Gas S c r u b b e r Water 8

Total solids

35

Annealing loss COD BOD

1 700

mg/1

5

N

(Total) Ν (NH ) 3

ΝΟ

160

mg/1

700

mg/1

650

mg/1

3.2

χ

290

Chlorides C l "

7.4

C y a n i d e s CN~* Sulfates S 0

g/i % by w e i g h t

4

S u l f i d e s S--

mg/1 mg/1 mg/1

400

mg/1

14

mg/1

4

mg/1

22.5

mg/1

Tars

5.2

mg/1

pH-value

7.7

mg/1

P

(Total) T o t a l phenols

n.a. =

not assayed

n.d. =

not detectable

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

458

Figure 6.

Schematic of the gas converter

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

32.

TABASARAN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

Table V.

459

Two-Stage Solid Waste Pyrolysis

Composition of the Eluates of Pyrolysis Slag from Experiments with Municipal Refuse

Kind o f substance

Eluate of the p y r o l y s i s slag mg/1

3

mg/1

10

COD

mg/1

450

CN~

mg/1

N

(Total)

BOD

5

0 ,06 900

Cl"

650

so "

mg/1

P O

mg/1

0,50

Tars

mg/1

1

Phenoles

mg/1

Traces

4

4

~ "

pH-value

7.1

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

460

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

ments d u r i n g a m e a s u r i n g p e r i o d f o r " M u n i c i p a l R e f u s e " . F i g u r e s 7 and 8 i l l u s t r a t e m a t e r i a l and e n e r g y b a l a n c e s . M a t e r i a l balance: I n s h o r t i t can be s t a t e d t h a t t h e p y r o l y s i s o f 100 kg of municipal refuse/ predried to a water content of 18 % by w e i g h t and h a v i n g a c a l o r i f i c v a l u e o f 8370 k J / k g and t o w h i c h 77.6 kg o f a i r have been added, p r o d u c e s i n t h e t w o - s t a g e p l a n t an average o f 10 6.9 k g o f pure gas and 56.8 kg o f s o l i d r e s i d u e s . The b a l a n c e o f 13.9 kg can be e x p l a i n e d by gas and w a t e r l o s s e s t h a t cannot be a c c o u n t e d f o r . S u b s t a n c e s s u c h as g l a s s and m e t a l s can be s e p a ­ r a t e d w i t h r e l a t i v e ease. P r o v i d e d t h e r e s i d u e s a r e deposited i n a l a n d f i l l t h i s process r e s u l t s i n a s p a c e - s a v i n g o f approx. 60 % when compared w i t h t h e s a n i t a r y l a n d f i l l i n g o f raw w a s t e s . Solid residues: I n o u r c a s e t h e s o l i d r e s i d u e s c o n t a i n e d approx. 12 % o r g a n i c c a r b o n . The heavy m e t a l c o n c e n t r a t i o n s were low, p r o b a b l y and p r i m a r i l y due t o t h e low q u a n t i t i e s o f such s u b s t a n c e s i n t h e i n p u t m a t e r i a l . L e a c h i n g e x p e r i m e n t s showed t h a t t h e drum r e a c t o r r e s i d u e s y i e l d e d mainly chloride-and sulphate-containing e x t r a c t s . The c h e m i c a l oxygen demand o f t h e s e s o l u t i o n s was r e l a t i v e l y h i g h when compared w i t h t h e BOD. S c r u b b e r Water: I n t h e e x p e r i m e n t s i n v o l v e d t h e amount o f w a t e r from the gas s c r u b b e r r e l a t e d t o the amount o f raw i n p u t m a t e r i a l was about 0.18 m /t. The pH-value o f t h e w a t e r was m i l d l y a l k a l i n e , t h e c h l o r i d e c o n c e n t r a t i o n was about 2 90 mg C l " / 1 and t h e t o t a l amount o f p h e n o l s about 23 mg/1. A n n e a l i n g l o s s o f t h e s c r u b b e r w a t e r sediment was 2800 mg/1, and the a n n e a l i n g r e s i d u e amoun­ t e d t o 8000 mg/1. S u l p h u r was found m a i n l y i n an o x i d i ­ zed form. R e s u l t s o f i n i t i a l e x p e r i m e n t s u s i n g an a p p a r a ­ t u s f o r t h e d e t e r m i n a t i o n o f t h e b i o c h e m i c a l oxygen de­ mand a l l o w e d the c o n c l u s i o n t h a t an u n d i s t u r b e d decompo­ s i t i o n o f t h e o r g a n i c components can t a k e p l a c e . Gas : The pure gas w i t h a s p e c i f i c g r a v i t y o f 1.1 kg/m had a n e t c a l o r i f i c v a l u e o f 5700 kJ/m o r 5180 k J / k g . I f an e x c e s s f a c t o r o f η = 1.5 i s a t t r i b u t e d t o t h e c o m b u s t i o n o f t h e pure gas a t a t h e o r e t i c a l a i r demand o f 1.5 m a i r / m gas t h e s p e c i f i c e x h a u s t gas p r o d u c t i o n w i l l be 2700 m /t o f w a s t e . The low harm­ f u l s u b s t a n c e c o n c e n t r a t i o n s i n t h e pure gas a l l o w t h e e x p e c t a t i o n t h a t t h e e m i s s i o n v a l u e s w i l l be low w h i c h means t h a t t h e c l e a n a i r r e q u i r e m e n t s o f e n v i r o n 3

3

3

3

3

3

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

TAB AS ARAN

Figure 7.

Two-Stage Solid Waste Pyrolysis

461

Outline of the material balance for the pyrolysis of municipal refuse in the two-stage Kiener System

of municipal refuse in the Figure 8. Simplified energy balance forpyrolysis the System two-stage Kiener

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

462

THERMAL CONVERSION OF SOLID WASTES AND

BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch032

m e n t a l p r o t e c t i o n a g e n c i e s can be c o m p l i e d w i t h w i t hout problems. Energy b a l a n c e : I t i s not p o s s i b l e t o s e t up an e x a c t energy b a l a n c e because such f u n c t i o n s as m a t e r i a l f e e d i n g , r e m o v a l , t r a n s p o r t and t h e l i k e were performed m a n u a l l y i n t h e e x p e r i m e n t a l p l a n t . An e s t i m a t e shows, however, t h a t t h e p y r o l y t i c t r e a t m e n t o f the a v a i l a b l e energy i n t h e waste t r a n s f o r m e d 68 % i n t o t h e gas and 17 % i n t o t h e s o l i d r e s i d u e s . I f a gas e n g i n e i s o p e r a t e d , t h e energy c o n t e n t o f t h e exhaust i s s u f f i c i e n t t o b r i n g the drum t o t h e r e q u i r e d r e a c t i o n temperature. 4. Summary P y r o l y s i s as a waste t r e a t m e n t method has made cons i d e r a b l e progress d u r i n g recent years. A f t e r laborat o r y and s e m i - t e c h n i c a l s c a l e t e s t i n g , s e v e r a l demons t r a t i o n p l a n t s have been s e t up. O t h e r s a r e i n t h e planning or c o n s t r u c t i o n stage. As r e g a r d s t h e economy o f t h e d i f f e r e n t systems t h e r e e x i s t o n l y t h e o r e t i c a l e l a b o r a t i o n s which s t i l l must be v e r i f i e d by p r a c t i c a l e x p e r i e n c e . There a r e s t i l l a number o f q u e s t i o n s t o be answered t h a t r e f e r t o t h e t e c h n o l o g y , t h e o p e r a t i n g t e c h n i q u e and t h e o p e r a t i o n a l s a f e t y . These gaps i n o u r knowledge must be c l o s e d d u r i n g t h e y e a r s t o come. In l i g h t o f t h e e n c o u r a g i n g e x p e r i m e n t a l r e s u l t s a c h i e v e d so f a r and i n t h e i n t e r e s t o f a f u r t h e r p o s i t i v e development o f waste management p u b l i c a g e n c i e s s h o u l d be w e l l - a d v i s e d i n s p o n s o r i n g e f f o r t s a i m i n g at t h e r e a l i s a t i o n o f more r e s e a r c h and d e m o n s t r a t i o n plants. RECEIVED

November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

33 The Design of Co-Current MovingBed Gasifiers Fueled by Biomass MICHIEL J. GROENEVELD and W. P. M. VAN SWAAIJ

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

Department Chemical Engineering, Twente University of Technology, P.O. Box 217, 7500 AE Enschede, Netherlands

Co-current moving bed gasifiers have been selected for the gasification of biomass during one century and even now this reactor-type seems to be attractive for this purpose in comparison to other possible types like counter-current, fluid bed and entrained bed [l], The main advantages are that a) the reactor is simple to construct, b) a tar free gas is produced and c) if required, chlorine and sulphur components can be removed during gasification by means of e.g. dolomite addition. A disadvantage is the high outlet temperature (900 K). For the classical design the use of feedstocks with a small particle size or a high ash content and scaling up of the reactor to capacities larger than 250 kg/h seem to be difficult if a tar free product gas is required. The reactor know-how is largely empirical and dates mainly from 1925 - 1945 when the gasification of dried woodblocks (0.04 m) for traction of cars and lorries was practiced in Europe. An extensive survey of the various co-current moving bed gasifier designs and their design rules has already been presented by Schläpfer and Tobler [2]. The present revival of interest in biomass gasification envisages the utilization of difficult feedstocks varying in particle size, moisture and ash content etc. To use these feedstocks properly, an analysis of the physical and chemical phenomena taking place during gasification is necessary. To this aim we studied the gasification of wood varying in particle size and moisture content, utilizing models for different parts of the gasifier. From this analysis existing empirical design rules and process limitations can be understood and an improved design suitable for many types of biomass and wastes has been derived. Description of the co-current moving bed gasifier. Gasification is a complex process during which the solid fuel successively dries, pyrolyses (organic gases and liquids are distilled off, consequently the solid residue achieves a higher carbon content) and reacts with O2, CO2, H 2 ° ^ n a c o m p l e x manner given 0-8412-0565-5/80/47-130-463$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

464

below i n a s i m p l i f i e d form: C + O2 = CO2 C + C02 = 2 CO C + H0 = CO + H CO + H 0 = C02 + H2 In the g a s i f i e r (see F i g . 1) these processes can be found i n d i f f e r e n t zones which show some overlap, however. The s o l i d feedstock i s introduced at the top of the g a s i f i e r and has to flow downwards. Drying and p y r o l y s i s take place due to h e a t t r a n s f e r from the oxydation zone c l o s e to the a i r i n l e t . In the oxydation zone the r e a c t i o n s with oxygen r e s u l t i n a sharp r i s e i n temperature upto ± 1600 K. An important f u n c t i o n apart from t h i s heat generation of t h i s zone i s to convert a l l condensable organic products ( t a r ) from the p y r o l y s i s zone. In a prop e r l y designed g a s i f i e r the products of the oxydation zone are charcoal and a hot gas r i c h i n CO2 and H2O but not c o n t a i n i n g t a r . In the r e d u c t i o n zone the s e n s i b l e heat of the hot char and gases are absorbed i n the endothermic r e a c t i o n s of CO2 and H2O with the carbon. Consequently a gas c o n t a i n i n g N2, H2, CO, CO2, H2O and some CH4 i s produced. This gas can be used f o r energy production i n furnaces, turbines or i n t e r n a l combustion engines, as w e l l as f o r f u r t h e r s y n t h e s i s . Deal wood being taken as a model feedstock, the d i f f e r e n t zones w i l l be analysed. 2

2

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

2

A n a l y s i s of a co-current moving bed wood g a s i f i e r . The i n f l u e n c e of geometrical f a c t o r s , the s p e c i f i c r e a c t o r l o a d and the feedstock p r o p e r t i e s on the f u e l gas production i n c l u d i n g the amount of t a r r y components w i l l be analysed. No a t t t e n t i o n w i l l be p a i d to the p o s s i b i l i t y of i n s i t u sulphur or c h l o r i n e removal. E a r l i e r attempts to p r e d i c t the product gas composition were based on thermodynamic models i . e . a combination of mass and energy balances assuming f o r one or more r e a c t i o n s chemical e q u i l i b r i u m at an e m p i r i c a l l y determined temperature e.g. o u t l e t temperature. Thermodynamic models. To c a l c u l a t e the product gas compos i t i o n from the f u e l c h a r a c t e r i s t i c s the models assume e i t h e r the heterogeneous char H2O, CO2 and H2 r e a c t i o n s at e q u i l i b r i u m (Gumz model) [3] or the homogeneous w a t e r s h i f t r e a c t i o n at e q u i l i b r i u m and a f i x e d amount of methane produced as a pyrol y s i s product (Schlapfer model) [ 2 ] , In F i g . 2 -a ternary CHO diagram- f r e e oxygen and s o l i d carbon boundaries, and the dry wood composition are shown. By g a s i f i c a t i o n a c e r t a i n amount of oxygen i s added so that about a l l the s o l i d carbon i s converted. The Gumz model i s a p p l i c a b l e i n the r e g i o n between corner C and the s o l i d carbon boundary, the Schlapfer model between the s o l i d carbon and the f r e e oxygen boundaries. Both models can e a s i l y be solved using the element balances, the energy balance and the e q u i l i b r i u m constants. In the energy balance a f i x e d e m p e r i c a l l y f i t t e d amount of heat losses has to

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

33. GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers

465

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

air

Figure 1.

Co-current moving-bed gasifier

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

4 6 6

THERMAL

CONVERSION OF SOLID WASTES AND BIOMASS

be introduced. In Table 1 an example of experimental and model r e s u l t s i s presented. Table 1 Example of our experiments and thermodynamic model c a l c u ­ l a t i o n s (wood composition dry wt% C = 49.1; H = 6.1; 0 = 44.6; ash = 0.6; H2O = 12.7) [ 5 ] . gas composition ( v o l % ) m3 gas/ AH hem/ CO H2 CO2 H2 CH4 H2O kg wood ΔΗίη experiment 2.98 17 16 11 47 1 8 79% Gumz model 17 16 12 48 1 6 2.66 69% Schlapfer model 16 15 12 45 2 10 73% 2.71

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

c

equil. temp. Κ 910 1073

I t can be concluded that the gas composition and production f o r the g a s i f i c a t i o n of a feedstock can be estimated from simple thermodynamic c a l c u l a t i o n s . However, i t i s not sure whether e q u i ­ l i b r i u m i s reached and no information i s obtained about the dimen­ sions r e q u i r e d f o r the r e a c t o r . To o b t a i n these data, a more com­ plex r e a c t o r model w i l l be necessary, the v a r i o u s chemical and p h y s i c a l steps being taken i n t o account. Reaction engineering model of the r e d u c t i o n zone. By t h i s model the conversion i s c a l c u l a t e d of the s o l i d f u e l and the gas composition as a f u n c t i o n of the d i s t a n c e from the a i r i n l e t , where the reductionzone i s supposed to s t a r t . I t i s assumed that the p y r o l y s i s and oxydation zone produce only char, CO2, H2O and some CH4. The i n l e t c o n d i t i o n s of the r e d u c t i o n zone are obtained from mass and energy balances over the previous zones only. The s e n s i b l e heat of the i n l e t flows, char and gases, i s absorbed i n endothermic r e a c t i o n s of C + CO2 and C + H2O producing H2 and CO while CH4 and N2 remain unchanged. The r a t e of these processes can be l i m i t e d by 1) mass and heat t r a n s f e r from the gas phase to the p a r t i c l e s ; 2) d i f f u s i o n of the gaseous reactants i n t o the porous p a r t i c l e ; 3) chemical r e a c t i o n at the a c t i v e surface of the p a r t i c l e ; 4) d i f f u s i o n and convection of the gaseous products out of the p a r t i c l e to the gasphase. The l a s t three steps have been analysed i n a p a r t i c l e model which was t e s t e d on s i n g l e char p a r t i c l e s [ 4 ] . With a l o c a l volumetric rate model i t was p o s s i b l e to p r e d i c t the measured carbon conver­ s i o n p r o f i l e s w i t h i n the p a r t i c l e based on s e p a r a t e l y measured chemical r e a c t i o n k i n e t i c s and d i f f u s i v i t i e s . This p a r t i c l e model i s combined with the mass and heat t r a n s f e r equations, mass and heat balances and flow equations f o r the gas and s o l i d phase [ 5 ] , the l a t t e r flow being governed by the s h r i n k i n g of the p a r t i c l e s and the ash removal. In t h i s r e a c t i o n engineering model the r e a c t o r geometry i s s i m p l i f i e d to a c y l i n d e r with the throat diameter. I t was found that under p r a c t i c a l con­ d i t i o n s about 2% of the carbon was removed together with the ash. Heat leakage occurred and was taken to be p r o p o r t i o n a l to the r e a c t o r length and temperature d i f f e r e n c e . In Table 2 c a l c u l a t e d and t y p i c a l experimental data are presented, more experiments at d i f f e r e n t conditions can be found elsewhere [ 5 ] . In F i g . 3 conversion and temperature p r o f i l e s are given showing

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers

467

Table 2. T y p i c a l experimental data and r e s u l t s from the r e a c t i o n engineering model f o r the reduction zone moisture^ Τ wood exp c a l c ζ Ψ airt +

V

In: wood

kg/s/m

2

.225 .225 .225 .225 .225 2.25

.225 .225

moisture

kg/s/m

2

.036 .036 .036 .036 .036 0.36

.036 .248

air

kg/s/m

2

.596 .596 .536 .596 .596 5.96

.504 .724

24.8

24.8 24.8

dp

10

3

m

24.8 24.8 24.8 10

Ζ

m

0.45 0.53 4.38 0.44 0.44 3.74

Τ air

Κ

300

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

Out: gas

kg/s/m

2

300

300

300

50

300

300

1.6

1.0

750

300

.846 .852 .794 .852 .852 8.52

.757 1.17

N2

vol%

49.Û 47.5 44.9 47.5 47.5 47.5

43.6 39.7

CO

vol%

15.0 15.3 15.9 15.4 15.4 15.4

18.2

co

vol%

11.3 12.1 12.7 12.0 12.0 12.0

11.1 15.1

H

vol%

13.4 12.4 15.7 12.3 12.3 12.3

16.6

8.4

0.8

1.0

2

2

CH

4

vol%

H0

vol%

Δ Η

kW/m

2

0.8

A H

A H

chem/ in

AH ns/AH se

Figure 3.

in

% %

0.8

0.8

0.8

0.8

10.5 11.9 10.0 12.0 12.0 12.0 2

ίη

0.8

2.3

9.6 33.5

4068 4068 4068 4068 4068 40680 4068 3739 67

66

70

66

66

66

75

50

27

21

27

27

27

16

42

Experimental and calculated conversion temperature and char particle diameter for Experiment 1

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

468

THERMAL CONVERSION OF SOLID WASTES AND

that the model d e s c r i b e s the experiments w e l l . From the t a b l e the i n f l u e n c e of the r e d u c t i o n zone length, p a r t i c l e s i z e , moisture content and heat recovery of the f u e l gas can be seen. In a longer r e d u c t i o n zone some more s e n s i b l e heat of the gas i s consumed f o r CO and H2 production, lowering the o u t l e t temperature to ± 950 K. In t h i s f i n a l stage of the process no mass and heat t r a n s f e r l i m i t a t i o n s occur, so that the length as w e l l as the diameter could be increased to o b t a i n the r e q u i r e d volume. From the model c a l c u l a t i o n s and the experiments the p a r t i c l e s i z e appears to have hardly any i n f l u e n c e on the performance of the reduction zone. A l a r g e r c a p a c i t y needs a longer r e a c t o r or more p r e c i s e l y a l a r g e r r e d u c t i o n zone volume. Experimentally s p e c i f i c r e a c t o r loads between 0.05 and 0.7 kg/s/m (throat area) have been used s u c c e s f u l l y . A higher moisture content of the feedstock makes the amount of water i n the product gas increase and thus i t s s e n s i b l e heat at the cost of the chemically bounded energy. It was found, however, that with a feedstock with 50% moisture the r e d u c t i o n zone model i s not v a l i d any more. As under these c o n d i t i o n s tars have been found i n the gas, the assumption that a l l the p y r o l y s i s products are converted i n the oxydation zone i s i n c o r r e c t . More chemically bounded energy i n the f u e l gas can be obtained i f some s e n s i b l e heat of the gas i s used f o r preheating of the a i r or p r e f e r a b l y f o r drying of the f u e l . Due to t h i s e x t r a input of energy i n the g a s i f i e r l e s s a i r i s r e q u i r e d and the Joule value of the gas i s increased. The r e d u c t i o n zone model can thus be used to c a l c u l a t e the r e q u i r e d dimensions together with the product gas temperature and composition, i n case no p y r o l y s i s products are present there. A n a l y s i s of the oxydation and p y r o l y s i s zone. The most c r i t i c a l f u n c t i o n of these zones are the complete d e v o l a t i l i z a t i o n and subsequent conversion of the t a r s . Tar i s produced during the p y r o l y s i s of the wood p a r t i c l e s and c o n s i s t s of many organic components. Quantity and composition of the p y r o l y s i s products h i g h l y depend on the p y r o l y s i s c o n d i t i o n s such as heating r a t e , temperature and p a r t i c l e s i z e [6]. Although p y r o l y s i s i s a very complex process f o r l a r g e dry p a r t i c l e s at high heating r a t e s , the r a t e of p y r o l y s i s i s mainly determined by the heat conduction i n t o the s o l i d p a r t i c l e [5,7]. Therefore, the residence time f o r comp l e t e d e v o l a t i l i z a t i o n can be estimated from heat p e n e t r a t i o n times. The time needed f o r a p a r t i c l e to reach a centre temperature of 750 K, which i s u s u a l l y s u f f i c i e n t [ 8 ] , i s given i n Table 3. If incompletely d e v o l a t i l i z e d char enters the r e d u c t i o n zone, t a r may evolve there and w i l l remain l a r g e l y unconverted i n the gas. The second reason f o r undesired t a r i n the product gas may be incomplete conversion of t a r i n the oxydation zone. To study t h i s problem, three types of experiments have been c a r r i e d out: a) methane t r a c e r i n j e c t i o n i n the g a s i f i e r ; b) c o l d flow model t e s t s ; c) t a r production measurement at d i f f e r e n t geometries. îÎËïî}§îlê_iîîiË££Î2 · Methane was chosen as a t r a c e r , because 2

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

BIOMASS

n

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

33.

GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers

469

i t i s the only p y r o l y s i s product which i s never completely conv e r t e d . In F i g . 4 the i n j e c t i o n places and the conversion of the a d d i t i o n a l l y i n j e c t e d methane are presented. I t i s c l e a r l y shown that the place of i n j e c t i o n i n the t h r o a t s e c t i o n makes h a r d l y any d i f f e r e n c e . Moreover, the methane c o n c e n t r a t i o n i n the bunker was found to i n c r e a s e f o r a l l cases. Apparently there i s a cons i d e r a b l e mixing i n the throat s e c t i o n and methane flows upwards i n t o the bunker. Cold__flow_models. In a two dimensional c o l d model the flow patterns could be made v i s u a l by u s i n g a gas flow with char powder or water and i n k [ 5 ] . The patterns observed are sketched i n F i g . 5. The double c i r c u l a r flow patterns prevent the p y r o l y s i s products flow along the c o l d w a l l d i r e c t l y i n t o the product gas. The c i r c u l a r y flow patterns induced by the h o r i z o n t a l a i r j e t should reach the w a l l , however. This i s an important design critérium f o r the throat geometry. S i m i l a r patterns can be expected i f the a i r i s introduced through the s i d e w a l l s . P e n e t r a t i o n of an a i r j e t i n a packed bed was studied by measuring the r a d i a l v e l o c i t y d i s t r i b u t i o n (see F i g . 6). As an example a t y p i c a l v e l o c i t y d i s t r i b u t i o n i s given i n F i g . 7, together with the v e l o c i t y i n the centre of the j e t as a f u n c t i o n of the length (z) f o r d i f f e r e n t i n l e t flows and packing s i z e s (see F i g . 8 ) . I t i s found that f o r the 0.02 m packing and d i f f e r e n t i n l e t tubes i n c r e a s i n g of the i n l e t v e l o c i t y at the same mass flows d i d not i n f l u e n c e the velocity distribution. From F i g . 9 i t can be seen that the penet r a t i o n length of the j e t defined as the d i s t a n c e at which the centre v e l o c i t y i s 20% of the centre v e l o c i t y a t ζ = 0.02 m ( f i r s t measurement p o i n t ) , i s independent of the mass flow. For the 0.0037 m packing the j e t reached 0.045 m and 0.095 m f o r the 0.02 m packing. Although the p e n e t r a t i o n of the j e t under r e a c t i o n c o n d i t i o n s might be d i f f e r e n t , i t i s c l e a r that the p e n e t r a t i o n of the j e t and thus the dimension of the c i r c u l a r y flow patterns are mainly determined by the p a r t i c l e s i z e . This explains the e m p i r i c a l l y found f a c t that f o r most co-current g a s i f i e r s a minimum p a r t i c l e s i z e i s r e q u i r e d f o r t a r - f r e e o p e r a t i o n . Tar_£roduction a t _ d i f f e r e n t _ g e o m e t r i e s . Experiments during g a s i f i c a t i o n confirmed the importance of c o r r e c t p o s i t i o n i n g of the a i r i n l e t , with i t s r e l a t e d double c i r c u l a r y flow p a t t e r n s , i n the t h r o a t . While i n normal p o s i t i o n no t a r , e.g. ± 250 mg/m^, was produced, a sharp increase i n t a r production was observed i f the a i r i n l e t was moved upwards thus i n c r e a s i n g the d i s t a n c e between the i n l e t and the throat w a l l . I t was a l s o found to be p r e f e r a b l e to have the a i r h o r i z o n t a l l y flow i n t o the r e a c t o r . No i n f l u e n c e on the r e a c t o r performance could be observed f o r d i f f e r e n t i n l e t tube s i z e s , which i s i n accordance with the c o l d j e t experiments. The a i r i n l e t being placed up to a p o s i t i o n of 0.12 m above the t h r o a t , t a r - f r e e g a s i f i c a t i o n was p o s s i b l e , with 0.01 m woodchips and a throat diameter of 0.25 m.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Figure 4. Methane tracer injection; conversion of additionally injected methane in Point (1) 0.36; (2) 0.24; (3) 0.35; (4) 0.38

Figure 5. Double circularflowpatterns occurring in the gasifier

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

33. GROENEVELD AND VAN SWAAU

CQnççntriç

Co-Current Moving-Bed Gasifiers

All

rings

Figure 6. Experimental set-up for behavior of a jet in a packed bed

the

R[10"m]

€ 2 A •0 2 0 2 •4 0 2 0 2

Figure 7. Radial velocity distribution: (φ!) 4.210- m /sec; ( ) 5.610~ m 1 sec; (dp) 0.02m 3

3

3

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

3

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

472

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

33.

GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers

473

The d i s t a n c e a i r i n l e t - throat w a l l was then 0.17 m. A d d i t i o n of large amounts of sawdust (up to 75%) d i d not i n f l u e n c e t h i s be­ haviour. Discussion. To prevent t a r occurrence i n the product gas i t i s necessary to have the p a r t i c l e s completely d e v o l a t i l i z e d on passing the t h r o a t . Tar produced above the throat should not s l i p along the w a l l s but should be mixed up i n the c i r c u l a r y flow system c l o s e to the a i r i n l e t . In s p i t e of the gas mixing the temperature c l o s e to the a i r i n l e t was found to be much higher (T = 1600 - 1800 K, f o r deal woodblocks 15% moisture) than the temperatures c l o s e to the throat w a l l ( Τ = 800 - 1500 Κ, depen­ ding on the c a p a c i t y ) . At a low c a p a c i t y of 0.1 kg/s/m^ throat area t a r - f r e e operation was p o s s i b l e at w a l l temperatures of 800 K. At t h i s low temperature none or l i t t l e t a r conversion can be expected C9l, t h i s showing c l e a r l y that t a r s have been t r a n s ­ ported to the a i r i n l e t where temperatures are high and f r e e oxygen e x i s t s . The zone of f r e e oxygen i s l i m i t e d , however. On experimental combustion of char c o a l with a i r i t was found that a f t e r two p a r t i c l e diameters (dp = 0.02 m) a l l the oxygen was con­ sumed [ 5 l . In the g a s i f i e r oxygen r e a c t s s t i l l f a s t e r with the gaseous components i n the order of : hydrocarbons, H2 > CH^ > CO > s o l i d C. [10], Because even pre-mixed methane i n the a i r i n l e t i s not completely converted (see F i g 4 . ) , H2 and t a r s must be r e s ­ ponsible f o r most of the oxygen consumption. In some g a s i f i e r designs p y r o l y s i s products are sucked out of the r e a c t o r , mixed with the a i r and combusted p r i o r to i t s i n t r o d u c t i o n i n the g a s i ­ f i e r . In a well-designed oxydation zone t h i s process takes place w i t h i n the r e a c t o r i t s e l f . Design

considerations

From the previous a n a l y s i s three main design f a c t o r s f o r co-cur­ rent moving bed wood g a s i f i e r s are d i s t i n g u i s h e d : a). Heat_2ËBË£i§£Î2B ^ complete d e v o l a t i l i z a t i o n the residence time i n the p y r o l y s i s zone should be equal to or longer than the F o u r i e r time f o r heating up. This leads to a maximum r e a c t o r load which can be estimated i n the f o l l o w i n g way. Due to r a d i a t i v e and convective heat t r a n s f e r the p y r o l y s i s zone i s assumed to s t a r t roughly three p a r t i c l e diameters above the a i r i n l e t , and to end at the smallest c r o s s - s e c t i o n of the throat. In Table 3, the heat p e n e t r a t i o n times and t h e i r r e l a t e d maximum r e a c t o r loads are presented. o r

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

474

Table 3. Heat p e n e t r a t i o n times and maximum ( s p e c i f i c ) r e a c t o r loads. Assumptions: Fo = 0.1; a = 2 10"? m^/s; i n l e t height = throat diameter, throat angle 45° d m

maximum r e a c t o r load kg/s

p

s

d

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

0.1 0.05 0.02 0.01 0.005 * **

5000 1250 200 50 12.5

throat

:

°-

1 m

(3 10-3) * (4 10-3) * 0.01 0.03 0.1

°-

3

0.02 0.04 0.2 0.7 (2.4)**

maximum s p e c i f i c r e a c t o r load kg/s/m^ 0.1 m 0.3 m (0.4)* (0.5)* 1.3 3.8 12.7

0.3 0.6 2.8 9.9 (34)**

p a r t i c l e s too l a r g e f o r the throat area a i r j e t w i l l not reach the w a l l see b ) .

For an IMBERT g a s i f i e r (throat diameter 0.15 m, dp = 0.05 m) a maximum load of 0.016 kg/s i s so c a l c u l a t e d , which i s i n agreement with the experimentally determined maximum load of 0.014 kg/s [2]. b) . 2ËBËÏI§£i2B_iËDSÎÎ}_2Î_£^Ë_êil_iË£· This critérium l i m i t s the area which can be covered by one a i r i n l e t p o i n t . The p a r t i c l e s i z e i s the most important f a c t o r here, but no q u a n t i t a t i v e r e l a t i o n s can be given y e t . I f a l a r g e c a p a c i t y per u n i t i s r e q u i r e d , a l a r g e c r o s s - s e c t i o n a l area with many i n l e t p o i n t s i s necessary. However these a i r i n l e t s should not hinder the s o l i d s flow i n the reactor. c) . ^2Βδ£Ϊ}_2ί_£Ϊΐ2.ΐΕ^Η££Ϊ2Β zone. The length depends on the f u e l c h a r a c t e r i s t i c s , s p e c i f i c c a p a c i t y , heat l o s s e s and gas q u a l i t y r e q u i r e d . I t can be c a l c u l a t e d by u t i l i z i n g the r e a c t i o n engineering model f o r the r e d u c t i o n zone. Many a d d i t i o n a l f a c t o r s may i n f l u e n c e the f i n a l design: pressure drop ( e s p e c i a l l y with small p a r t i c l e diameters); s o l i d s flow ( f o r some feedstocks and at high s p e c i f i c c a p a c i t i e s ) ; cinder or s l a g formation; entrainment of f i n e char p a r t i c l e s ; heat recovery of the f u e l gas, e t c . Design of a 100 t/d g a s i f i e r . From the previous a n a l y s i s i t i s concluded that the c l a s s i c a l throat design i s not s u i t e d w e l l f o r s c a l i n g up because of the l i m i t e d p e n e t r a t i o n of the a i r j e t . Introducing more i n l e t p o i n t s over the throat area would e a s i l y hinder the downward s o l i d s flow. A s o l u t i o n may be the use of an annular throat with a ring-shaped a i r d i s t r i b u t o r i n the centre and/or a i r i n l e t p o i n t s along the side w a l l s [11], An example w i l l be given here f o r a 100 t/d r e a c t o r g a s i f y i n g biomass (dp = 0.002 - 0.03 m, moisture content 14%, bulk d e n s i t y 400 kg/m ). A sketch of the design i s given i n F i g . 10. The volume of the p y r o l y s i s zone i s chosen such so as to be s u f f i c i e n t f o r complete d e v o l a t i l i z a t i o n of the 0.03 m p a r t i c l e s ( residence time > heat p e n e t r a t i o n time = 450 sec.) 3

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

33. GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers

475

rotating cone

Figure 10.

Sketch of a 100 t / d co-current moving-bed gasifier fueled by wood (type Τwente)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

476

2

The s p e c i f i c r e a c t o r load i s 0.77 kg/s/m (throat area). A i r i s introduced through both side w a l l s , so that the penetra­ t i o n depth of 0.17 m expected f o r the a i r j e t w i l l be s u f f i c i e n t f o r t a r - f r e e operation. On the b a s i s of the model the required r e d u c t i o n zone and the mass and energy balances are c a l c u l a t e d . Two cases are presented, the f i r s t without any heat recovery from the f u e l gas, the second with a i r preheated to 700 K. (See Table 4.)

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

Table 4. Mass and energy balances f o r a 100 t/d g a s i f i e r , f u e l e d by wood. In: wood moisture air Τ air

1.16 0.19 2.49 300

1.16 0.19 2.00 913

kg/s kg/s kg/s Κ

Out: gas composition N CO C02 H

3.83

3.34

kg/s

2

2

CH4

H0 2

43.2 17.5 1 1.0 16.6 0.9 10.8

21 In:Energy Out: Chemical energy 73 Sensible Heat 22 Heat losses 2 Unconverted char• 3

37.9 21.1 10.2 21.5 1 .0 8.3

vol% vol% vol% vol% vol% vol%

21

MW

82 12 3 3

% % % %

The r e q u i r e d r e d u c t i o n zone length i s ± 3 m based on a c r o s s - s e c ­ t i o n equal to the annular area. As i n c r e a s i n g of the c r o s s - s e c t i o n below the throat i s p o s s i b l e , too, the reduction zone length can be reduced. The height of the bunker can be chosen based on r e f i l ­ l i n g and f u e l spreading arguments. The inner s i d e w a l l of the annulus can be shaped as a slowly r o t a t i n g cone to overcome s o l i d s flow problems. The top of the cone i s then used f o r f u e l spread and enhancing the bunker flow p r o p e r t i e s , the lower parts of the r o t a t i n g cone f o r crushing cinders or slags formed from the ash. Summary and conclusions The p h y s i c a l and chemical phenomena o c c u r r i n g i n a co-current mo­ v i n g bed g a s i f i e r have been analysed from experimental r e s u l t s and model c a l c u l a t i o n s f o r d i f f e r e n t zones of the g a s i f i e r . A number of p r e v i o u s l y known e m p i r i c a l design r u l e s can be understood and p o s s i b l e process l i m i t a t i o n s are p r e d i c t e d . With the r e a c t i o n engineering model f o r the r e d u c t i o n zone the gas composition can be r e l a t e d to the f u e l c h a r a c t e r i s t i c s , r e d u c t i o n zone dimensions, heat losses and recovery. From the a n a l y s i s of the p y r o l y s i s /

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch033

33. GROENEVELD AND VAN SWAAU

Co-Current Moving-Bed Gasifiers All

oxydation zone it can be concluded that its dimensions are limi­ ted by the time to complete the devolatilization and the penetra­ tion length of the air jet. For larger capacities an annular throat is thus preferred over the classical throat design. An example is given for a 100 t/d gasifier. List of symbols a thermal diffusivity m2/s dp particle diameter m ^throat throat diameter m Fo Fourier number R radius m t heat penetration time s Τ temperature Κ ν velocity m/s X conversion ζ distance from the air inlet m ΔΗ specific enthalpy flow kW/m2 ΔΗίη ΔΗ of the fuel kW/m2 M*chem chemically bounded ΔΗ of the gas kW/m2 A H s e n s sensible heat of the gas kW/m2 φ flow m3/s Literature Cited 1. Groeneveld, M.J.; Van Swaaij, W.P.M., Applied Energy 1979, 5, 165-179 2. Schläper, P.; Tobler, J., "Theoretische und praktische Untersuchungen über den Betrieb von Motorfahrzeuge mit Holzgas", Bern 1937. 3. Gumz, W., "Vergasung fester Brennstoff", Springer-Verlag, Berlin 1952. 4. Groeneveld, M.J.; Van Swaaij, W.P.M., Sixth International Symposium on chemical reaction engineering, Nice, 1980. 5. Groeneveld, M.J., Ph-D-thesis, Twente University of Technology, Enschede, Netherlands. 6. Murty Kanury, Α., Combust. Flame, 1972, 18, 75-83. 7. Hsiang-Cheng Kung, Combust. Flame, 1972, 18, 185-195. 8. Rensfelt, E . , Symposium papers "Energy from biomass and wastes", I.G.T., Washington D.C. 1978. 9. Antal, M.J., Symposium papers "Energy from biomass and wastes" I.G.T., Washinton D.C., 1978 10. Field, M.A.; G i l l , D.W.; Morgan, B.B.; Hawksley, P.G.W.; "Combustion of pulversised coal" B.C.U.R.A. Leatherhead, England, 1967. 11. Dutch Patent application, 79 03893. RECEIVED November 20, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

34 Pyrolytic Recovery of Raw Materials from Special Wastes GERD COLLIN

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

Rütgerswerke AG, D-4100 Duisburg-Meiderich, West Germany

Summary P y r o l y s i s can be used f o r the thermal decomposition of waste materials that are predominantly organic i n nature, e.g. scrap t y r e s , scrap cables, waste p l a s t i c s , shredder wastes, and a c i d sludge. Rotary k i l n s are p a r t i c u l a r l y s u i t a b l e as u n i v e r s a l l y a p p l i c a b l e p y r o l y s i s u n i t s for continuous operation. Highly aromatic p y r o l y s i s o i l s for use as chemical raw materials are obtained at reactor temperatures of about 700 ° G . Such p y r o l y s i s o i l s could form the basis for the production of aromatics such as benzene, naphthalene, and t h e i r homologues, thermoplastic hydrocarbon r e s i n s and precursors of i n d u s t r i a l carbon, when the proven processes for the r e f i n i n g of coal t a r and crude benzene are a p p l i e d .

Numerous p r o j e c t s i n i n d u s t r i a l countries with waste and raw materials problems, i n c l u d i n g the Federal Republic of Germany, have been concerned f o r some years with the t e c h n i c a l possibilities and the economic viability of recovering materials from waste (1, 2). Suitable conversion technologies, s p e c i f i cally for s o l i d wastes of mainly organic nature include p y r o l y s i s processes, i.e. the thermal decomposition i n the absence of oxygen, l e a d i n g to the decomposition of organic substances i n t o char and low molecular gaseous and liquid chemicals (3). Can p y r o l y s i s be considered as a u n i v e r s a l conversion technology for the recovery of raw materials from such wastes and what possibilities are there for the utilization of the p y r o l y s i s products? To c l a r i f y t h i s question, a R and D project 0-8412-0565-5/80/47-130-479$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

480

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

f o r the p y r o l y s i s o f d i f f e r e n t s p e c i a l wastes, c a r r i e d out j o i n t l y by the companies E i s e n und M e t a l l AG, Rutgerswerke AG, and Veba Oel Umwelttechnik GmbH i s b e i n g d e a l t w i t h among o t h e r s . T h i s p r o j e c t i s s p o n s o r e d by the F e d e r a l M i n i s t r y of R e s e a r c h and T e c h n o l o g y and the M i n i s t r y o f Food, A g r i c u l t u r e and F o r e s t r y o f t h e L a n d N o r t h r h i n e W e s t p h a l i a . The l a b o r a t o r y s c a l e t e s t s began i n 1976, and the semit e c h n i c a l t r i a l s w i l l be c o n c l u d e d by the end of 1979. The development c o s t s have so f a r amounted t o some 10 m i l l i o n DM. W i t h i n the scope o f t h i s p r o j e c t the p y r o l y s i s o f d i f f e r i n g s p e c i a l wastes was i n v e s t i g a t e d f o r the f i r s t time under i d e n t i c a l c o n d i t i o n s . The r e s u l t s r e v e a l p o s s i b i l i t i e s o f how t o p r o d u c e h i g h l y a r o m a t i c p y r o l y s i s o i l s by p y r o l y z i n g h y d r o c a r b o n s c o n t a i n i n g s p e c i a l wastes, such as s c r a p t y r e s , s c r a p c a b l e s , waste p l a s t i c s , s h r e d d e r waste from u s e d c a r s , and a c i d s l u d g e i n an i n d i r e c t l y h e a t e d r o t a r y drum r e a c t o r at a r e a c t i o n t e m p e r a t u r e o f some 700 °G i n y i e l d s up t o above 50 % i n r e l a t i o n t o the o r g a n i c s u b s t a n c e . From t h e s e the c h e m i c a l raw m a t e r i a l s benzene, t o l u e n e , x y l e n e , n a p h t h a l e n e and i t s homologues can be m a n u f a c t u r e d . I n a d d i t i o n , t h e r m o p l a s t i c r e s i n s can be p r o d u c e d by p o l y m e r i ­ z a t i o n of f r a c t i o n s c o n t a i n i n g s t y r e n e , i n d e n e and t h e i r homologues (V) . I n F i g . 1 the concept o f the p y r o l y s i s p l a n t i s d e p i c t e d ; F i g . 2 shows the scheme of the p i l o t p l a n t . The s e m i - t e c h n i c a l c o n t i n u o u s r e a c t o r c o n s i s t s o f a r o t a r y k i l n f u r n a c e D 1 w i t h a t o t a l l e n g t h of 7.7 m, a d i a m e t e r of 0.8 m, and a h e a t i n g zone o f 4.75 m. The t h r o u g h p u t amounts to r o u g h l y 200 kg/h when the r e a c t o r i s i n o p e r a t i o n a t a w a l l tempera­ t u r e of 700 °G. S o l i d s are d i s c h a r g e d v i a a s o l i d s s e t t l e r u n i t . Condensable p a r t s of the raw p y r o l y s i s gas are s e p a r a t e d by q u e n c h i n g w i t h p y r o l y s i s o i l i n Q 1 , i n d i r e c t c o o l i n g i n W 4-/5 and c o u n t e r c u r r e n t s c r u b b i n g w i t h m e t h y l n a p h t h a l e n e i n Κ 3. The a c i d n o x i o u s gases HC1, SO2 and H2S are removed i n Κ 1 and Κ 2 by c o u n t e r c u r r e n t s c r u b b i n g w i t h water and c a u s t i c soda l y e . The p u r i f i e d p y r o l y s i s gas i s u s e d f o r a u t o t h e r m a l i n d i r e c t h e a t i n g o f the r e a c t o r . The p y r o l y s i s o i l s are s e p a r a t e d from the quench and s c r u b b e r o i l s i n the d i s t i l a t i o n u n i t s Κ 4- and Κ 7/8; t h e y can be f u r t h e r r e f i n e d into c h e m i c a l raw m a t e r i a l s by the a p p l i c a t i o n of p r o ­ c e s s e s u s e d i n u p g r a d i n g c o a l t a r and coke oven benzene. F i g . 3 shows the y i e l d s which can be o b t a i n e d

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

34.

COLLIN

Pyrolytic Recovery of Raw Materials

IWASTESI Pyrolysis · '

Down-stream Drocessina

[NEW RAW MATERIALS!

Scrap tyres

Condensation! and H Scrubber Section!

Heating gas for captive use Sulphur Hydrochloric acid

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

1

7

Scrap cables ^ Shredder waste from scrapped"" 7oo°C cars Plastic wastes

HI:

Pyrolysis oil

Solids removal

Figure 2.

• BTX - Aromatics - Hydrocarbon resins » Industrial oils • Pyrolysis pitch - Char

Acid sludge _

Figure 1.

481

- Steel Zinc sulphide •Copper, Aluminium

Recovery of raw materials by pyrolysis

Schematic of the semitechnical rotary drum pyrolysis plant

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

482

TYPES

WASTE

OF

YIELDS

Pyrolysis gas

Pyrolysis oil

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

[WEIGHT */.]

Pyrolytic char

Metals

12

Scrap

tyres

23

1 7

Waste

plastics

53

30

1 5

13

1 2

33

AO

cables

9

1 4

31

A3

sludge

13

37

3 1

-

Shredder Scrap Acid

Figure 3.

wastes

-

Main product yields of pyrolysis of special wastes

COMPONENTS

1%)

0 F Τ Υ Ρ Ε S Shredder Scrap Waste plastics wastes tyres

W A S Scrap cables

Τ

Ε Acid tar trace

1

2

Benzene

22

22

2U

40

5

Toluene

1 θ

23

1 9

20

1 8

Aliphatic

Hydrocarbons

0.5

trace

^ 8 / 9" benzene Homologues Indane + Homologues

8

5

8

5.5

1 0

Styrene, Indene and Homologues

6

1 0.5

6

4.5

1 0

9

A

1 4

1 0

Naphthalene Naphthalene Homologues Higher bicyclic to tetracyclic Aromatics Pyrolysis Resins (bp > A 5 0 ° C )

Figure 4.

1 0

6

6.5

3.5

5

3

6

8

7

5

2 1

20

20

1 3

4 1

Pyrolysis oils from special wastes (700°C)

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

34.

COLLIN

P y r o l y s i s oi I . crude

DISTI

IPOLYMERIZATION I

^

Pyrolysis residue resins

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

483

Pyrolytic Recovery of Raw Materials

Hydrocarbon resins

LLATIO

IEXTRACTÏONI

| * - Refined fractions

C RYSTALLIZATI



Naphthalene Carbon black Methyl naphthalenes Wash ° oils Acenaphthene Fluxing oils Phenanthrene Anthracene j

I

*

Plastics Synthetic fibres Motor fuels

Figure 5.

Dyestuffs Plant protecting Plastici zers agents

B ASIC SUBSTANCES

Hydrofining Arom. Extraction [therm, • c a t a l y t i c Polymerization

Cry stal li z a t i o n Granulation

Figure 6.

,

s

Pigment black Carbon black fillers Solvents

Pyrolysis oil processing

JRAW M A T E R l A L | ~ H R E F I N I N G h

Pyrolysis oil crude iDist. 500.000 t

I

ON

.1

ι Benzene Toluene

Cg/g-Benzene homologues

Plastics Adhesi ves Binding agents

I

Ν

CHEMICALS VALUE QUANTITIES [Mill DM) it)

Benzene

100,000"!

Toluene

100,000 J

uo

50.000

75

50,000

25

Hydrocarbon resins

Naphthalene

A 0.000*1

M-naphthalenes

10.000 J

tricyclic Aromatics Carbon black oils Pyrolysis resins (and Losses)

50.000

45

15

100.000

30

500.000

3 30

Pyrolysis oil refinery

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch034

484

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

as main products; a breakdown of the chemical comp o s i t i o n of the p y r o l y s i s o i l s i s given i n F i g . 4. The r e f i n i n g of the p y r o l y s i s o i l and the downstream processing i n t o chemical products i s schematically presented i n F i g . 5 ; a balance of products from a l a r g e i n d u s t r i a l r e f i n e r y i s shown i n F i g . 6 f 5 ) » The r e f i n i n g of h i g h l y aromatic p y r o l y s i s o i l s from waste y i e l d s the following range of products: - Benzene f o r further processing i n t o styrene, phenol, cyclohexane and a n i l i n e as intermediate products for thermoplastics and uhermosets, synthetic rubber, synthetic f i b r e s ana dyestuffs, - Toluene for further processing into n i t r o - , c h l o r o and i s o p r o p y l toluenes for polyurethane p l a s t i c s , explosives, dyestuffs, antioxidants and p l a n t p r o t e c t i n g agents, and i f r e q u i r e d , f o r dealkyl a t i o n to benzene, - Cs/9-benzene homologues as high-octane blending components f o r low-lead and non-leaded supergrade gasolines, - Condensed aromatic hydrocarbons such as naphthalene, methylnaphthalenes, acenaphthene, phenanthrene and anthracene for the synthesis of t e x t i l e and pigment dyestuffs, and of aromatic carboxylic acids for P V C - p l a s t i c i z e r esters and polyester resins, - Thermoplastic hydrocarbon r e s i n s and residue r e s i n s f o r the formulation of p l a s t i c s , adhesives and binding agents, - Highly aromatic o i l s as primary products for the production of carbon black f i l l e r s and pigment black for automobile t y r e s , other rubber a r t i c l e s , p r i n t i n g inks and p a i n t s . References 1 . B u n d e s m i n i s t e r des Innern: A b f a l l w i r t s c h a f t s -programm ' 7 5 der Bundesregierung. Bonn, 2 2 . 1 0 . 7 5 2. Umweltbundesamt: M a t e r i a l i e n zum A b f a l l w i r t schaftsprogramm ' 7 5 . M a t e r i a l i e n 6 / 7 6 , B e r l i n 1976 3. C o l l i n , G . ; G r i g o l e i t , G . ; Bracker, G . - P . : Chem.-Ing.-Techn. 50 (1978) No. 10, pp. 836/841 4. C o l l i n , G . ; G r i g o l e i t , G . ; M i c h e l , E.: Chem.-Ing.-Techn. 51 (1979) No. 3, pp. 220/224 5 . C o l l i n , G . : Paper presented on the CRE/MER Conference, B e r l i n , October 1 to 3, 1979 RECEIVED November 20, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

35 Gasification of Solid Waste in Accordance with the SFW-FUNK Process HARALD FUNK and HORST HUMMELSIEP

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch035

Saarberg-Fernwärme, GmbH, Sulzbachstrasse 26, 66 Saarbruecken 3, West Germany

The Saarberg-Fernwärme i n Saarbrücken, West Germany, decided to b u i l d a p i l o t plant to demonstrate the feasibility of s o l i d waste g a s i f i c a t i o n after having gained long range experience i n operating i n c i n e r a t o r s . The Federal M i n i s t r y of Research and Technology of West Germany agreed to support t h i s project because the two committees, one for energy conservation and the other for environmental p r o t e c t i o n , recommended it for implementation. Incentives for

gasification

The reason for developing such a g a s i f i c a t i o n process was a c e r t a i n shortcoming of the i n c i n e r a t o r . The incinerator with i t s moving grates cannot burn i n d u s t r i a l waste or t o x i c waste or used l u b r i c a t ing oil since the generation of excessive heat w i l l cause some damage. Furthermore the i n c i n e r a t o r , a l though equipped with waterwalls, secondary combustion chamber, e l e c t r i c p r e c i p i t a t o r , large scrubbing facility and a tall stack, still i s an open system. In spite of all the extra equipment, a tall stack i s r e quired to d i s t r i b u t e impurities widely. Furthermore, some components of the flue gas are corrosive and the r e s u l t s are c o s t l y r e p a i r s . Another disadvantage i s the large amount of water required for scrubbing which i n average amounts to at least 120 gallons per ton of solid waste burnt. After all, the volume of flue gas i s about 10 times that of the gas generated i n a gas producer. The steam y i e l d e d from an incinerator has to be used r i g h t there since the distance of steam transport is rather l i m i t e d i n contrast to p i p i n g of gas. These shortcomings of the incinerator gave an incentive to compensate i n a g a s i f i c a t i o n u n i t .

0-8412-0565-5/80/47-130-485$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

486

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch035

Process

description

The g a s i f i c a t i o n u n i t i s b a s i c a l l y a s i m p l e d e s i g n i n the form o f a s h a f t f u r n a c e w i t h r e v o l v i n g g r a t e s . The s o l i d waste i s f e d through locks from t h e t o p and then the ash i s d i s c a r d e d i n charges from t h e bottom, avoid­ ing t h e e s c a p e o f gas o r h a r m f u l components. The gas d i s c h a r g e d o v e r h e a d f r o m t h e r e a c t o r i s c o o l e d down t o ambient temperature, thus condensing t a r s , l i g h t oils and steam. The t a r s a n d o i l s a f t e r t h e i r s e p a r a t i o n f r o m water a r e r e c y c l e d t o t h e r e a c t o r t o e n r i c h t h e gas s t r e a m b y means o f a c a r b u r e t t i n g e f f e c t . A p o r t i o n o f the water recovered i n t h e condensation phase i s used for c o o l i n g the gas and t h e excess i s d i s c a r d e d a f t e r t r e a t m e n t . The a s h d i s c h a r g e d i s i n e r t a n d c a n be d i s ­ c a r d e d f o r l a n d f i l l o p e r a t i o n s . The p r i m a r y o b j e c t o f t h i s system i s t o y i e l d gas a t a h i g h thermal e f f i ­ c i e n c y (Figure 1). The p r o c e s s i s c a r r i e d o u t i n p h a s e s : a) Raw m a t e r i a l p r e p a r a t i o n b) Gasification c) C o n d e n s a t i o n d) Gas p u r i f i c a t i o n House-hold and i n d u s t r i a l waste i s shredded i n a hammer m i l l w h e r e p i e c e s o f 4 i n c h maximum l u m p s i z e are c a r r i e d by a conveyor t o screens through which glass, ceramics, slag, ash and other inerts smaller than 3/8 a r e d i s c a r d e d . P i e c e s l a r g e r t h a n 4" a r e s e p ­ arated by gravity. Then t h e s o l i d waste i s charged t o t h e r e a c t o r t h r o u g h l o c k s . W h i l e t h e m a t e r i a l s l i d e s down t h r o u g h the v a r i o u s zones a s : Drying, Devolatilizing or carbonizing, Reducing, Reaction or p a r t i a l oxidation. The g a s d i s c h a r g e d f r o m t h e t o p o f t h e r e a c t o r h a s a temperature o f 500 t o 600 Κ and a f t e r c o n d e n s i b l e s are s e t t l e d o u t , i t i s compressed and charged t o t h e p u r i f i c a t i o n s e c t i o n . This gas p u r i f i c a t i o n system works on a p h y s i c a l p r i n c i p l e , s i n c e t h e h e a v i e r and h a r m f u l components a r e f r o z e n o u t - e i t h e r condensed o r s u b l i m e d - i n t h e r e g e n e r a t o r b y c o o l i n g down t h e s t e a m t o 1 7 0 o r 1 3 0 K. T h e n t h e i m p u r i t i e s r e t a i n e d i n t h e r e g e n e r a t o r a r e r e c o v e r e d b y s w i t c h i n g t o a vacuum c y c l e , w h i l e t h e p u r e g a s c o n t a i n i n g m a i n l y H^* C O , C H ^ a n d some C 0 ~ i s y i e l d e d a t a m b i e n t t e m p e r a t u r e . T h e s e 3 c y c l e s , tlie l o a d i n g phase ( r e t a i n i n g h e a v i e r components) M

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

FUNK AND HUMMELSIEP

SFW-FUNK

Gasification of Solid Waste 487

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch035

35.

2 κ •S

1 ÛO

1 s

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

488

are

r e c o v e r y phase (vacuum c y c l e ) c o o l i n g down p h a s e ( y i e l d i n g p u r e switched every 6 or 8 minutes.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch035

Product

gas)

gas

The r a w g a s a f t e r c o n d e n s a t i o n o f l i q u i d s a t a m b i e n t temperature i s r e c o v e r e d a t a volume o f 500 t o 1000 normal cubic meters p e r t o n o f s o l i d waste (about 19 0 0 0 t o 37 0 0 0 S C F / t ) c o n t a i n i n g u p t o 8 0 % o f t h e heating value charged w i t h s o l i d waste. I t c a n be used f o r h e a t i n g , power g e n e r a t i o n o r as reducing gas f o r m e t a l l u r g i c a l processes o r as a synt h e s i s gas f o r t h e p r o d u c t i o n o f methanol. Methanol i n turn i s a clean f u e l and can be charged t o a gas t u r b i n e f o r power g e n e r a t i o n o r as a d d i t i v e o r b l e n d i n g component t o g a s o l i n e . I t c a n be s t o r e d more c h e a p l y t h a n LNG ( l i q u i d n a t u r a l g a s ) a t l e s s o f a r i s k , t o make i t more s u i t a b l e f o r p e a k s h a v i n g , s i n c e i t c a n b e c o n v e r t e d t o pure methane i n a matter o f hours. M e t h y l a l c o h o l i s used as a base product f o r formaldehyde (for p l a s t i c s ) or a c e t i c acid (pharmaceutical industry) or f o r t h e p r o d u c t i o n o f p r o t e i n s and even f o r h i g h octane gasoline (via Mobil process). Earlier

test

runs

Prior to the erection of the pilot plant at Velsen, a s m a l l t e s t r e a c t o r consuming up t o 60 k g / h o f s o l i d w a s t e was i n s t a l l e d a t N e u n k i r c h e n n e x t t o a n i n c i n e r a t o r , w h i c h was t o p r o v e f e a s i b i l i t y o f s o l i d waste g a s i f i c a t i o n . D u r i n g 2 1/2 y e a r s o f t e s t r u n s amounting t o about 10 000 hours, a l l k i n d s o f m a t e r i a l s were charged t o t h i s reactor. For instance: rubber, plast i c s , wood, used l u b r i c a t i n g o i lmixed w i t h h o u s e h o l d waste. A reasonable gas composition could be maintained for any length of time: H : 30 V o l . - % 2

CO C0

2

:

20

:

36

plus

CH^ a n d some h i g h e r h y d r o c a r b o n s w i t h n i t r o g e n . As a r u l e about 10 % o f oxygen was added t o t h e c h a r g e a n d 0.25 t o 0.40 k g o f s t e a m p e r k g o f s o l i d waste t o keep t h e r e a c t i o n temperature a t a l e v e l bet w e e n 1 1 0 0 a n d 1 2 0 0 K. T h e r e s u l t s w e r e e n c o u r a g i n g and t h e r e f o r e i t was d e c i d e d t o p r o c e e d w i t h t h e l a t t e r approach t o s o l i d waste gasification.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

35.

FUNK AND HUMMELSIEP

Sampling

SFW-FUNK

Gasification of Solid Waste 489

o f rawmaterial and product

The s o l i d w a s t e f r o m h o u s e h o l d w a s s a m p l e d l y s e d f r e q u e n t l y a n d v a r i e s i nc o m p o s i t i o n 22 20 20 3.0 20 0.34 0.30 0.36 0.014

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch035

Moisture Inerts Carbon Hydrogen Oxygen Nitrogen Sulfur Chlorine Fluorine

-

and anaas follows:

3 6 WT.~% 47 43 6.0 42 (by d i f f e r e n c e ) 0.75 0.45 0.53 0.02

Upper

heating

value:

as delivered 9500-12000 dry 13500-15500

k J A g k J A g

Lower

heating

value:

as delivered 8500-10500 dry 12000-14500

kJ/kg k J A g

Shredded Lower

and screened:

heating

value:

moist dry

9500-12500 12500-17000

k J A g k J A g

The lower h e a t i n g value o f the product gas p r i o r t o g a s p u r i f i c a t i o n was measured a t 7500 t o 9500 k J / normal-cubic meter w h i l e a volume o f g a s o f 700 t o 1100 n r p e rt o n o f g a s was p r o d u c e d a t n o r m a l o p e r a t i n g conditions keeping the r e a c t i o n temperature a t about 1300 K. The c o m p o s i t i o n o f t h e g a s v a r i e s a s f o l l o w i n g : H : 25 - 35 V o l . - % 2

CO

:

C0 : 2

CH : illuminants. 4

plus

some

13 - 40 18 - 4 0 5 - 1 0

Conclusion The Saarberg-Fernwârme C o . , i s t h e o n l y c o m p a n y i n E u r o p e w h i c h i s e n g a g e d i na l l k i n d s o f s o l i d w a s t e utilization, i.e. incineration, recycling operations and g a s i f i c a t i o n , t o conserve r a wm a t e r i a l s a n d energy. The g a s i f i c a t i o n o f s o l i d w a s t e a s a s u p p l e m e n t t o o p e r a t i o n o f i n c i n e r a t o r s i si n t e r e s t i n g enough t o continue t h e development o f such an approach. The intermediate step f o r commercialization i s the design o f a gasproducer a t a capacity o f 3 t o 5 tons p e r h o u r o f s o l i d w a s t e w h i c h i s now i nt h e p l a n n i n g stage. RECEIVED

December 3, 1979

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

36 Overview of Pyrolysis, Thermal Gasification, and Liquefaction Processes in Japan M. HIRAOKA

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

Department of Sanitary Engineering, Kyoto University, Kyoto, Japan

The system of treatment and disposal of municipal refuse in Japan since 1963, is made up of collection and transportation followed by the incineration and disposal of the residues or direct landfilling. A large number of incineration facilities have been constructed in many cities, with grant-in-aid from the government. Indeed, the incineration process is excellent in the respect that perishable organic refuse can be converted to stable inert mater i a l , reduced in volume and disposed under good sanitary conditions, and for recovering energy from refuse. But it is inevitably apt to cause some pollution problems such as air and water pollution and leaching of heavy metals from ash. The facilities for air pollution control, water treatment, stabilization of ash in the incineration process and residues disposal, have become more costly as new standards are promulgated. On the basis of these circumstances, the need for a better solid waste disposal system has stimulated a great deal of interest in the application of pyrolysis to solid wastes instead of the traditional incineration system in our country. Since the Agency of Industrial Science & Technology, MITI had launched the national project on development of technology and system of resource recovery from refuse in 1973, more than a dozen processes of PTGL* are being developed at the national level, municipal level, and the level of private companies as shown in Table I. On the other hand, the spread of the activated sludge method to treat sewage has created problems of sludge disposal. The incineration process has been increasingly adopted as the method for reducing the volume and residues. But it has been recently pointed out that incineration of sewage sludge causes air and water pollution and leaching of heavy metals (especially Cr+6 compounds) from ash, the same as in incineration of domestic refuse. To cope with this situation, the drying-pyrolysis process has been developed as *PTGL = pyrolysis, thermal gasification and liquefaction 0-8412-0565-5/80/47-130-493$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

494

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

Table I. Pyrolysis Process Developing in Japan Process Name

Company or Organization

Type of Reactor

Phase of R&D

1

Dual chamber fluidized bed system

AIST (MITI) & Ebara MFG. Co. Ltd.

Dual chamber fluidized bed

5 t/d p i l o t plant test, 100 t/d DP i s under construction

Pyrolysis/ Gas

2

A fluidized bed system

AIST & Hitachi Ltd.

Single fluidized bed

5 t/d p i l o t plant test

Pyrolysis/ Gas

3

Pyroxsys tem

Tsukishima Kikai Co. Ltd.

Dual chamber fluidized bed

150 t/d p r a c t i c a l plant i s being planned

Pyrolysis/ Gas, O i l

4

Incineration system

IHI Co. Ltd.

Single fluidized bed

5

Waste melting system

Nippon Steel Co. Ltd.

Moving bed shaft k i l n

6

Magma bed process

Shinmeiwa Industry Co.

Bench-scale Fixed bed el e c t r i c furnace test

7

Shaft Kiln pyrolysis system

Hitachi Ship-building Co. Ltd.

Moving bed shaft k i l n

20 t/d p i l o t plant test

Pyrolysis/ Gas

8

Destragas process

Hitachi Plant Const. Ltd.

Moving bed shaft k i l n

Pilot plant test

Pyrolysis/ Gas

9

Purox system

Showa Denko Co. Ltd.

Moving bed shaft k i l n

75 t/d p r a c t i c a l plant i s being planned

Pyrolysis/ Gas

10

Torrax system

Takuma Co. Ltd.

Moving bed shaft k i l n

11

Landgard process

Kawasaki Heavy Industries Ltd.

Rotary k i l n

30 t/d p i l o t plant

Pyrolysis/ Gas/Steam

12

M. Gallet system

Mitsubishi Heavy Industries Ltd.

Flash type reactor

Bench-scale test

Pyrolysis/

13

Pyrolysis of scrap tires

Kobe Steel Ltd.

External heated 23 t/d p r a c t i c a l plant i s under rotary k i l n construction

Pyrolysis/ Gas/Oil

14

Pyrolysis of sewage sludge

NGK. Insulators Ltd.

Multiple hearth 40 t/d p r a c t i c a l plant i s furnace installed

Pyrolysis

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

No.

Process

Incineration/Steam

Pilot plant 30 t/d 150 t/d p r a c t i c a l plant i s under construction

Pyrolysis/ Gas

Pyrolysis/ Gas

Pyrolysis/ Gas

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Oil

and Combustion

36.

HiRAOKA

PTGL

495

Processes in Japan

the most f e a s i b l e method of sludge treatment and d i s p o s a l which minimizes the secondary p o l l u t i o n problems as discussed by Hiraoka et a l . (1). The aim of t h i s paper i s to describe the present status of development and a p p l i c a t i o n , and e v a l u a t i o n of PTGL processes i n our country. C h a r a c t e r i s t i c s of M u n i c i p a l Refuse (MR) i n Japan

and Sewage Sludge

(SSL)

The general c h a r a c t e r i s t i c s of MR and SSL i n Japan are shown i n Table I I and Table I I I . The Japanese MR has, on the average, a heating value of 1,300 Kcal/Kg, g e n e r a l l y ranging from 800 to 1,800 Kcal/Kg, and has a water content ranging 40-607 . Although, the c a l o r i f i c value of MR tends to i n c r e a s e , t h i s r e l a t i v e l y lower heating value and high moisture content compared with that of the United States must be considered i n the design of resource recovery systems from MR i n Japan.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

o

Heat Recovery System from MR. Since the Japanese government adopted i n c i n e r a t i o n and l a n d f i l l systems f o r treatment of MR i n 1963, the technology of European i n c i n e r a t i o n has been used mainly f o r c o n s t r u c t i n g the l a r g e s c a l e i n c i n e r a t o r ; except f o r a few i n c i n e r a t o r s , the Japanese i n c i n e r a t i o n system does not have the heat recovery subsystem as i n Europe. Since the Arab O i l Embargo i n 1973, the need f o r heat recovery from i n c i n e r a t o r s i n l a r g e c i t i e s i s i n c r e a s i n g l y emphasized. As the main c i t i e s i n Japan are l o c a t e d i n the temperate climate r e g i o n , d i s t r i c t heating i s not p r a c t i c a l except i n Hokkaido. E l e c t r i c a l power generation i s , i n p r i n c i p l e , q u i t e reasonable f o r recovering the energy from MR i n Japan. The Nishiyodo i n c i n e r a t i o n p l a n t of Osaka C i t y has a processing c a p a c i t y of 400 tons of MR per day, and i s equipped with two 2,700 KW generators, with output voltage of 6,600 V. In Tokyo, Katsushika i n c i n e r a t i o n plant which i s i n operation generates e l e c t r i c i t y of 12,000 KW, with a refuse feed of 1,200 tons per day. A p p l i c a t i o n of PTGL Processes as an A l t e r n a t i v e to Incinerat i o n f o r Treatment of MR. As stated above, as a f i r s t stage, various PTGL process systems o f f e r the p o s s i b i l i t y of decreasing several p o l l u t i o n problems caused i n the i n c i n e r a t i o n process. The p y r o l y s i s and melting process developed by Nippon Steel Co., L t d . was adopted at Ibaraki C i t y to t r e a t 450 tons/day (150 tons/ day X 3) of MR, and i s under c o n s t r u c t i o n . Funabashi C i t y has decided to use the dual f l u i d i z e d bed r e a c t o r system (Pyrox process) to t r e a t 450 tons/day (150 tons/day X 3) of MR, and Chichibu C i t y has decided to use the Purox process developed by Showa Denko Co., L t d . and Union Carbide Co., L t d . . The design and construct i o n of these p l a n t s were s t a r t e d t h i s A p r i l .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

496

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table TI (a). General C h a r a c t e r i s t i c s of MR

1. P h y s i c a l

Properties

Garbage Combus t i b l e s Uncombustibles Moisture

15-30% 20-50% 10-20% 40-60%

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

2. Chemical P r o p e r t i e s C H 0 Ν Cl S

(WB)

10-25% 1.5-3.0% 10-20% 0.5-1.0% 0.2-1.0% 0.2-0.3%

3. C a l o r i f i c Value

800-1,800 Kcal/Kg

Table IL ( b ) . General C h a r a c t e r i s t i c s of Sewage Sludge

1. P h y s i c a l

Properties

Comb us t i b l e s Uncombustibles Moisture

15-50% 10-20% 60-85%

2. Chemical P r o p e r t i e s

(DB)

C

15-25%

H 0 Ν S

1- 5% 15-20% 2- 7% 0.2-1%

3. C a l o r i f i c Value

0-300 Kcal-Kg

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980. 3.0 4.8 100.0 95.5 30.0

17.3

47.0 55.2 0.0 0.0 19.7

38.6

50.0 40.0 0.0 4.5 50.3

44.0

5.0 2.5 2.3 5.5 8.0

4. Wood

5. Cloth

6. Ferrous metals

7. Glass, b r i c k & pebbles 8. Miseelleneous & uncategorized

Total

11.1

63.3

25.6

10.8

3. P l a s t i c s

8.6

53.4

38.0

40.6

2. Paper

9.6

19.1

71.3

25.3

Un comb us t ib l e (%)

Comb us t i b l e (%)

Moisture (%)

1. Garbage

Wet b a s i s content (%)

Table ΊΠ. An Example of Composition o f MR

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

498

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Resource Recovery Process System Developed by National Project. Phase I of the n a t i o n a l p r o j e c t was c a r r i e d out from 1973 to 1976 f o r developing the f e a s i b l e technology and systems of resource recovery from s o l i d wastes, and the demonstration plant (100 tons/day) f o r the m a t e r i a l - reclamation system i n phase II i s under c o n s t r u c t i o n . The p y r o l y s i s processes which have been developed i n phase I of the n a t i o n a l p r o j e c t are as f o l l o w s : a) Dual F l u i d i z e d Bed Reactor System f o r Fuel Gas Recovery (Ebara Corporation) b) F l u i d i z e d - B e d P y r o l y s i s f o r O i l Recovery ( H i t a c h i Ltd.) These reclamation systems may be s u i t a b l e f o r the c h a r a c t e r i s t i c Japanese MR. As the MR i n Japan has a r e l a t i v e l y high moisture content, d i r e c t a i r c l a s s i f i c a t i o n of the crushed refuse as seen i n the United States i s hard to apply. A d r y i n g process may be necessary p r i o r to the a i r c l a s s i f i c a t i o n . In t h i s respect, a s e l e c t i v e p u l v e r i z i n g c l a s s i f i e r has been developed i n the nationa l p r o j e c t which i s q u i t e s u i t a b l e to separate garbage of high moisture content and paper i n Japanese MR. This demonstration plant with a c a p a c i t y of 100 tons/day w i l l be i n f u l l operation on November of 1979. A p p l i c a t i o n of PTGL Processes to I n d u s t r i a l Wastes. Indust r i a l wastes which have a high c a l o r i f i c value such as scrap t i r e s and p l a s t i c s are s u i t a b l e f o r PTGL processes. Though the many processes as shown i n Table I can be a p p l i e d to t r e a t i n d u s t r i a l wastes, a PTGL process using a external-heated r o t a r y k i l n has been developed by Kobe S t e e l Co., L t d . to decompose the scrap t i r e s and to get a l i q u e f i e d f u e l . The Clean Japan Center which was e s t a b l i s h e d to promote the resource recovery e f f o r t sponsored by MITI and the r e l a t e d p r i v a t e companies, are planning to cons t r u c t the commercial p l a n t which w i l l t r e a t the scrap t i r e s by use of t h i s technology and use the l i q u e f i e d o i l as the f u e l f o r a cement k i l n . E v a l u a t i o n of PTGL Processes Various PTGL processes have been developed and are i n demons t r a t i o n and commercial stages. From a comparison of municipal refuse handling options, we w i l l determine i f p y r o l y s i s can be competitive with conventional handling options and how recovered m a t e r i a l and energy values a f f e c t the operation c o s t s . Three municipal refuse handling options were c o n c e p t i o n a l l y designed and compared i n t h i s study. These are: Option 1, I n c i n e r a t i o n System, Option 2, P y r o l y s i s - M e l t i n g System, and Option 3, M a t e r i a l Recovery and P y r o l y s i s System. Option 1 i s a conventional stoker i n c i n e r a t i o n system with heat recovery. E l e c t r i c power w i l l be generated with the steam from the waste heat b o i l e r . To meet the a i r p o l l u t i o n standards, exhaust gas has to be cleaned by an e l e c t r o s t a t i c p r e c i p i t a t o r and

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

36.

HiRAOKA

PTGL

Processes in Japan

499

a scrubber. Caustic soda s o l u t i o n w i l l be a p p l i e d i n the scrubber to absorb hydrogen c h l o r i d e and s u l f u r oxides. Residual ash w i l l be disposed of by l a n d f i l l i n g . In option 2, municipal refuse w i l l be size-reduced by a crusher and fed i n t o the converter. Oxygen w i l l be supplied to the converter and municipal refuse w i l l be d r i e d , pyrolyzed and melted at high temperature. P y r o l y s i s gas w i l l be d i r e c t l y combusted i n the combustor, where waste water w i l l be evaporated and o x i d i z e d . Energy w i l l be recovered i n the form of steam by a waste heat b o i l e r and e l e c t r i c power w i l l be generated. Lime w i l l be applied to absorb hydrogen c h l o r i d e and s u l f u r oxides i n the f l u e gas. Slag may be used f o r the c o n s t r u c t i o n of roads, e t c . . Option 3 includes both m a t e r i a l and heat recovery. A semiwet p u l v e r i z i n g c l a s s i f i e r developed by the Agency of I n d u s t r i a l Science and Technology, MITI i s a p p l i e d to recover garbage which has low c a l o r i f i c value and high moisture content. The h i g h l y c a l o r i f i c part of municipal refuse which mainly contains paper and p l a s t i c s w i l l be supplied to p y r o l y s i s r e a c t o r . The p y r o l y s i s reactor c o n s i s t s of two f l u i d i z e d beds; cracking r e a c t o r and regener a t o r . P y r o l y s i s gas w i l l be cleaned through the scrubber and stored i n the storage tank. The cleaned gas w i l l be combusted to produce high pressure steam with which e l e c t r i c power w i l l be generated e f f i c i e n t l y . Compost w i l l be obtained from garbage through a process c o n t a i n i n g fermentator, dryer and separators. E l e c t r i c i t y , f e r r o u s metal, and compost w i l l be recovered i n t h i s system. Basis f o r Plant Design. The composition of municipal refuse i s assumed as shown i n Table I I I . The municipal refuse has the lower c a l o r i f i c value of ca. 1,500 Kcal/Kg. Plant s i z e of 600 T/D i s assumed. The c a p i t a l investment c o s t s , u t i l i t i e s , e t c . were c a l c u l a t e d using contacts with equipment vendors. Cost f o r rep a i r s are assumed to be two percent of the plant c o n s t r u c t i o n cost per year. Unit costs of u t i l i t i e s and u n i t p r i c e s of recovered energy and m a t e r i a l are assumed, based on the a c t u a l p r i c e s i n 1979. Ash and other residues d i s p o s a l cost i s assumed to be 2,450 Yen/T, taking note of the r e p r e s e n t a t i v e cost data of l a r g e c i t i e s i n Japan. The grant a v a i l a b l e to a m u n i c i p a l i t y i s assumed to pay up to f i f t y percent of the c a p i t a l investment. The remaining i n vestment cost must be amortized i n f i f t e e n years with the i n t e r e s t rate of s i x percent. I n c i n e r a t i o n System (Option 1). The system flow diagram i s shown i n Figure 1. About 70.5 percent of the heat of the municipal refuse i s recovered i n the form of steam (265°C). A p o r t i o n of the steam i s used i n the a u x i l i a r y equipment i n the i n c i n e r a t i o n system such as the a i r heater. The e f f i c i e n c y of the low pressure turbine generator i s about 0.21. U t i l i t i e s f o r the o p e r a t i o n of the system and operating costs are l i s t e d i n Table IV. The caustic soda s o l u t i o n costs to meet the a i r p o l l u t i o n standards are high.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

500

THERMAL CONVERSION OF SOLID WASTES AND

Turbine

BIOMASS

Generator

£5

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

600

T/D

^170 Waste Water Treatment

T/D^

Effluent

EP: E l e c t r o s t a t i c Precipitator Electricity

C i t y Water

Figure 1.

Industrial Water

Flow diagram of incineration option

Table Έ . U t i l i t i e s and O p e r a t i n g Cost ( I n c i n e r a t i o n )

City Water Industrial Water NaOH (48 wt%)

6

T/D

X10 Yen/year

91

5.9

337

6.1

7.3

65.8

other Consumption Material

151.7

Repairs

183.3

Ash Disposal

149

Total

Revenue(Electric Power)

131.4

544.2

72 MWH/D

129.6

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

36.

HiRAOKA

PTGL

Processes in Japan

501

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

As t h i s o p t i o n i n c l u d e s no m a t e r i a l recovery process, the r e s i d u a l ash which amounts to about 25 percent of the raw municipal refuse i n weight has to be disposed of. The generated e l e c t r i c i t y amounts to 117 MWH/D, and the plant operation needs 45 MWH/D of e l e c t r i c i t y . The outcome of t h i s i s that 72 MWH/D of e l e c t r i c i t y can be d e l i vered. P y r o l y s i s - M e l t i n g System (Option 2). The system flow diagram i s shown i n Figure 2. The heat recovery e f f i c i e n c i e s of the conv e r t e r and combustor are 0.81 and 0.71, r e s p e c t i v e l y . About 60 percent of fed heat i s recovered i n the form of steam. The e f f i ciency of the low pressure turbine generator i s about 0.21 as i n option 1. The 104 tons per day of s l a g are assumed to be taken by the c o n s t r u c t i o n f i r m s . U t i l i t i e s f o r the operation of the system and operating costs are l i s t e d i n Table V. A u x i l i a r y f u e l cost takes the greater part of the t o t a l operating c o s t . As the oxygen generator needs much e l e c t r i c i t y (about 41 percent of the t o t a l usage of e l e c t r i c i t y ) , d e l i v e r a b l e e l e c t r i c i t y i s only 17 MWH per day. The recovered energy i s used f o r the improvement of the char a c t e r i s t i c s of the residues i n t h i s system. Thus, ash d i s p o s a l cost i s small; on the other hand, revenue from the s a l e of e l e c t r i c i t y i s small. M a t e r i a l Recovery and P y r o l y s i s System (Option 3). The system flow diagram i s shown i n Figure 3. A semi-wet p u l v e r i z i n g c l a s s i f i e r and a magnetic separator recover garbage and f e r r o u s metal. M a t e r i a l fed to the p y r o l y s i s r e a c t o r w i l l have a c a l o r i f i c value of about 2,200 Kcal/Kg. About 54 percent of the heat of the feed m a t e r i a l i s recovered i n the form of gaseous f u e l . The conv e r s i o n of the f u e l gas to steam (390°C) i s about 65.6 percent. About 29 percent of steam i s used f o r d r y i n g the fermentated garbage. The e f f i c i e n c y of the intermediate high pressure turbine generator i s about 0.46. The cleaned gas f u e l through the scrubber make i t p o s s i b l e to r a i s e the steam temperature to 390°C. The strength of the waste water q u a l i t y i s o f f e r e d up i n the i n t e r e s t of the high e f f i c i e n c y of the turbine generator i n t h i s system. The u t i l i t i e s f o r the operation of the system and the operating costs are l i s t e d i n Table VI. The consumptive m a t e r i a l s take the greater part i n the t o t a l operating c o s t , r e f l e c t i n g much r e q u i r e ment f o r the maintenance of the complex system. The recovery i n t h i s system includes e l e c t r i c i t y , f e r r o u s metal and compost. The t o t a l revenue i s the maximum of the three systems. Comparison. The t o t a l operating costs are compared i n Figure 4 f o r the aforementioned three options. Revenues from recovered m a t e r i a l s and energy are a l s o shown i n the f i g u r e . Gross operating cost i s lowest f o r P y r o l y s i s - M e l t i n g Process (Option 2). Gross operating cost minus revenue, or net d i s p o s a l cost i s lowest f o r I n c i n e r a t i o n Process (Option 1). However, d i f f e r e n c e s i n the net d i s p o s a l costs are small f o r these three

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

502

THERMAL CONVERSION OE SOLID WASTES AND BIOMASS

EP: E l e c t r o s t a t i c P r e c i p i t a t o r

Electricity

Figure 2.

C i t y Water

Industrial Water

Flow diagram of pyrolysis-melting option

Table V. U t i l i t i e s and Operating Cost

T/D

(Pyrolysis-Melting)

X10° Yen/Year

C i t y Water

120

7.8

I n d u s t r i a l Water

972

17.5

Oil Lime

19.7

212.8

3.3

16.6

Other Consumptive M a t e r i a l

17.3

Repairs

176.2

Ash D i s p o s a l

11

Total

Revenue(Electric

9.7 457.9

Power)

17MW

30.6

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

£S

0T/D|

MWHAD}

( ^ * 9 1

City

T/D

Water

Figure 3.

>

o

separator

Industrial Water

Landfill

)

23.9 T / D j

55.9 T/D

Electrostatic Separator

to

Grade

Compost

Lower Grade Compost

Higher

Flow diagram of material recovery and pyrolysis option

SPC: Semi-wet P u l v e r i z i n g C l a s s i f i e r MS : M a g n e t i c S e p a r a t o r EP : E l e c t r o s t a t i c P r e c i p i t a t o r

**69

Electricity

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

^^T^^/D^

504

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

Table M . U t i l i t i e s and Operating Cost ( M a t e r i a l Recovery + Pyrolysis)

T/D C i t y Water

171

11.1

I n d u s t r i a l Water

268

4.8

Other Consumptive M a t e r i a l

301.0

Repairs

216.4

Residue

Disposal

107

Total

94.3 627.6

Revenue E l e c t r i c Power

68 MWH/D

122.4

Ferrous Metals

13.8 T/D

23.0

Higher Grade Compost

55.9

30.2

Lower Grade Compost

23.9

4.3

Total

179.9

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

36.

PTGL

HiRAOKA

505

Processes in Japan

6735 Yen/T

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

Yen/T

Residues Disposal

(%)

4903 Yen/T

Labor 542 (10.3) Repairs 849 (16.2)

(6.5)

Labor 1250 (18.6)

5246 Yen/T Ash D i s p o s a l 608 (11.6)

%37

Ash D i s p o s a l 45 (0.9)

Labor 750 (15.3)

Repairs 1002 (14.9)

Repairs 816 (16.6) Utility 1467 (21.8)

Utility 1063 (20.3)

Amortization 2184 (41.6)

Electricity 600

Incineration

Figure 4.

Utility 1259 (25.7)

Amortization 2579 (38.3) Amortization 2078 (424)

'Electricity 142

Pyrolysis-Melting

Electricity 567

F e r r o u s M e t a l 106 ^Compost 160

MR + P y r o l y s i s

Total operating costs for MR handling options

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Nm /D)

72 — —

170 149

3.39 364 155 88

a) Almost a l l water i s used f o r cooling

E l e c t r i c i t y (MWH/D) Ferrous Metals (T/D) Compost (T/D)

Recovery

Waste Wat e r (T/D) Residue (T/D)

X

Flue Gas Volume (X10 NO as NO (Kg/D) S 0 as SO (Kg/D) HCÏ (Kg/Dj

Effluence

Incineration

17 — —

N

3.30 308 131 75 _ a) nearly zero ' 11

Pyrolysis-Me1ting

Table VLT. Comparison of E f f l u e n c e and Recovery

68 14 56 (Higher grade) 24 (Lower grade)

154 107

0.91 103 20 11

M a t e r i a l Recovery + P y r o l y s i s

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

36.

HiRAOKA

PTGL Processes in Japan

507

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch036

options. For Pyrolysis-Melting System and Material Recovery and Pyrolysis (Options 2 and 3), the shares of the labor cost and utility cost are higher than Incineration System (Option 1). The high percentages of labor cost in option 2 and 3 are due to the increase of the number of unit operations. Those of utility costs for option 2 and 3 are due to the expenditure for auxiliary fuel and deodorizing chemicals, respectively. The inflation of the selling prices of electricity and other recovered materials makes option 3 to be competitive to other options. The shortage of landfilling site makes option 2 relative to others. A comparison of effluents and recovery from the systems is shown in Table VII. The table shows Pyrolysis-Melting System, and Material Recovery and Pyrolysis System (Option 2 and 3) are favorable in the respect of the air and water pollution protection. Acknowledgment The authors wish to acknowledge Dr. N. Takeda for his assistance of a portion of the work presented in this article. References 1. Majima, T.; Kasakura, T.; Naruse, M.; Hiraoka, M. Prog. Wat. Tech., 1977, 9, 381. 2. Hiraoka, M.; Kawamura, M. The Third Japan - U.S. Conference on Solid Waste Management - Special Subject 2, 1976, May, 12, at Tokyo, Japan. 3. Hiraoka, M.; Takeda, N.; Fujita, K. 2nd Recycling World Congress , 1979, March 19-22, at Manila, Philippines. 4. Hiraoka, M. The International Congress of Scientist on The Human Environment, 1975, November 17-26, at Kyoto, Japan. RECEIVED November 16, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

37 Pilot Plant Study on Sewage Sludge Pyrolysis T. KASAKURA NGK Insulators, Ltd., Nagoya, Japan

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch037

M. HIRAOKA Kyoto University, Kyoto, Japan

Sludge incineration process has been increasingly adopted by many municipalities as one of the effective methods for reducing the volume and stabilizing the organic materials of sewage sludge. But recently the incineration process has been pointed out to have several serious problems, namely higher energy consumption, and secondary pollution such as Cr+6 formation in ash and NOx formation in exhaust gas. Some investigators had proposed that "pyrolysis" would have a possibility to solve these problems, and have studied pyrolysis of sewage sludge. The authors had already conducted the laboratory scale study and the preliminary pilot plant study, and proposed that "drying-pyrolysis process" (pyrolysis followed by indirect steam drying of dewatered sludge cake) (Fig.-1) could be one of the most economical and feasible alternatives for conventional incineration process. The authors have further conducted the feasibility study on a continuous system of "drying-pyrolysis process" to evaluate the performance of the process in pilot scale, and to demonstrate its effectiveness as a thermal processing of sewage sludge. This paper presents the results of this pilot plant study. The purpose of this study can be summarized as; (i) To evaluate the performance of drying-pyrolysis process in pilot scale (ii) To demonstrate the effectiveness of drying-pyrolysis process as a thermal processing of sewage sludge (iii) To compare drying-pyrolysis process with other thermal processes of sewage sludge (iv) To show the feasibility of the practical plant of drying-pyrolysis process PILOT PLANT and EXPERIMENTAL PROCEDURE The pilot plant for this study consists of a four shaft indirect steam dryer of paddle type, a four hearth furnace for 0-8412-0565-5/80/47-130-509$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

=3c

paddle dryer




P y rràytic olytic furnace

H—I Scrubber f o r dryer exhaust gas

Q (^Quenching t a n k Q * Gas' Sampling p o i n t G£, G j , G^,

Residue

Fuel O i l

Θ-

LPG

Γ

Cake feeder DQOQI

Cake

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch037

Waste Gas

Θ

Treated Sewage Water

Waste Gas

—Θ

Tap Water

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch037

37.

KASAKURA AND HiRAOKA

Sewage Sludge Pyrolysis

511

p y r o l y s i s , a c o m b u s t i o n chamber f o r p y r o l y t i c gas ( a f t e r b u r n e r ) , and a h e a t r e c o v e r y b o i l e r f o r c o m b u s t i o n chamber e x h a u s t g a s . The o v e r a l l l o a d i n g c a p a c i t y o f t h i s p l a n t i s a b o u t k t o 5 t o n s per day a s d e w a t e r e d cake w i t h w a t e r c o n t e n t 75 %· ( F i g - l ) F i v e d i f f e r e n t k i n d s o f d e w a t e r e d c a k e s were s e l e c t e d f o r t h e p i l o t t e s t , w a t e r c o n t e n t and h i g h e r h e a t i n g v a l u e o f sample c a k e s were v a r i e d from kG t o 76 %, from 1 , 5 0 0 t o 2 , 9 6 0 k c a l / k g D. S. r e s p e c t i v e l y . ( T a b l e - I ) Cake A; S l u d g e from a combined sewerage s y s t e m sewage t r e a t m e n t p l a n t of a r e p r e s e n t a t i v e c i t y i n Japan. The c a k e was d e w a t e r e d by vacuum f i l t e r a f t e r l i m e and f e r r i c c h l o r i d e w e r e added t o m i x e d p r i m a r y and e x c e s s s l u d g e . Cake B; S l u d g e from a r e g i o n a l sewerage s y s t e m sewage t r e a t m e n t p l a n t c o n t a i n i n g i n d u s t r i a l w a s t e w a t e r . The c a k e was d e w a t e r e d b y f i l t e r p r e s s a f t e r a n o r g a n i c p o l y m e r was added t o m i x e d p r i m a r y and e x c e s s s l u d g e . Cake C; The same s l u d g e a s c a k e B, b u t t h e c a k e was d e w a t e r e d b y f i l t e r p r e s s a f t e r l o w t e m p e r a t u r e ( I 5 0 - l 6 0 °C) t h e r m a l conditioning. Cake D; S l u d g e from s e p a r a t e d sewerage s y s t e m sewage t r e a t m e n t p l a n t f o r domestic waste. The c a k e was d e w a t e r e d b y f i l t e r p r e s s a f t e r c o n v e n t i o n a l ( l 8 0 - 200 °C) t h e r m a l c o n d i t i o n i n g o f the mixed s l u d g e . Cake E; S l u d g e o f chromium t a n n e r i e s ' w a s t e . The cake was d e w a t e r e d b y vacuum f i l t e r a f t e r a n o r g a n i c p o l y m e r was added t o raw s l u d g e . The d e w a t e r e d c a k e was d r i e d t o t h e w a t e r c o n t e n t o f 30 t o *f0 % i n t h e i n d i r e c t steam d r y e r , and f e d i n t o t h e p y r o l y t i c f u r n a c e t h r o u g h the screw conveyor. Combustion a i r l e s s than the t h e o r e t i c a l amounts f o r s l u d g e i s s u p p l i e d i n t o t h e f u r n a c e f o r p a r t i a l combustion o f c o m b u s t i b l e p y r o l i t i c gas. That i s , p y r o l y s i s was c a r r i e d out by " D i r e c t H e a t i n g " method. O f f g a s from f u r n a c e i s i n t r o d u c e d i n t o t h e c o m b u s t i o n chamber t o b u r n i t s r e m a i n i n g c o m b u s t i b l e s , and t o decompose i t s p o l l u t a n t and o t h e r odor c o m p o n e n t s . E x c e s s a i r i s a u t o m a t i c a l l y c o n t r o l l e d by t h e oxgen c o n c e n t r a t i o n a t t h e e x i t o f t h e comb u s t i o n chamber. Heat o f o f f gas from t h e c o m b u s t i o n chamber i s r e c o v e r e d by the waste heat b o i l e r . Steam g e n e r a t e d i n t h e b o i l e r i s s u p p l i e d t o t h e i n d i r e c t steam d r y e r . When t h e amounts o f steam g e n e r a t e d i s n o t s u f f i c i e n t f o r d r y i n g d e w a t e r e d c a k e , a u x i l i a r y f u e l i s used t o g e n e r a t e t h e a d d i t i o n a l s t e a m . I n t h i s s t u d y , t o make a c o m p a r i s o n w i t h d r y i n g - p y r o l y s i s p r o c e s s , t h e e x p e r i m e n t s on d i r e c t f e e d p r o c e s s e s , i . e . , d i r e c t p y r o l y s i s p r o c e s s and i n c i n e r a t i o n p r o c e s s , were c o n d u c t e d . I n t h e s e p r o c e s s e s , t h e d e w a t e r e d cake was d i r e c t l y f e d i n t o t h e furnace. The p l a n t was o p e r a t e d a t s t e a d y s t a t e f o r a t l e a s t 5 or 6 h o u r s i n a l l r u n s .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

512

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch037

Table I .

A n a l y t i c a l r e s u l t of f e d cake.

Cake Run No. M o i s t u r e content (wt%) Ignition loss (wt% on dry b a s i s ) Higher h e a t i n g value ( k c a l / k g on d r y b a s i s )

A 803 75.8

Β 816 74.0

59-5

56.7

2,960

3,290

C 922 45-7

D 819 55.3

Ε 823 76.4

32.0

83.6

64.3

1,500

4,310

4,000

100

90

ο Cake A •

Β

Δ

C

A

D

*

Ε

Decomposition

r a t i o of combustibles

(%)

I g n i t i o n l o s s of residue

20

10

50

10 Loading r a t e of d r i e d Figure 2.

cake (kg'DS/m *hr)

Variation of ignition loss of residue and decomposition ratio of com­ bustibles with loading rate of dried cake

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

37.

KASAKURA AND HIRAOKA

513

Sewage Sludge Pyrolysis

EXPERIMENTAL RESULTS AND DISCUSSION Performance of Drying-Pyr-olysis Process I n d i r e c t steam drying operation was a v a i l a b l e to a l l kinds of dewatered cakes tested and i t s e f f i c i e n c y ( o v e r a l l heat t r a n s f e r c o e f f i c i e n t U) v a r i e d with the kinds of cakes. Cake A U(Kcal/m

hr °C)

l

k

Q

_

1

5

0

Cake B _

l 6 o

1 7 0

Cake C

Cake D

275

300-360

Cake Ε

220-280

The o v e r a l l heat t r a n s f e r c o e f f i c i e n t (U) based on the input heat was c a l c u l a t e d from the amount of condensed drain which r e l e a s e d from the dryer by the f o l l o w i n g equation. Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch037

q = U-A ( at) where q i s supplied heat and A i s t o t a l heat t r a n s f e r area. The temperature d i f f e r e n c e ( Δ t) was obtained from the d i f f e r e n c e between cake temperature (95°0 constant) and steam temperature. The operating conditions i n t h i s study were s e l e c t e d on the previous work (Majima et a l . , 1977) and the p r e l i m i n a r y study by the p i l o t p l a n t . P y r o l y t i c furnace was mostly operated under the f o l l o w i n g c o n d i t i o n ; a i r r a t i o f o r combustibles i n sludge 0 . 6 , p y r o l y t i c temperature 900°C, and r e t e n t i o n time 60 minutes. In t h i s study, to evaluate the weight r e d u c t i o n e f f e c t of thermal processing, "Decomposition R a t i o " d i f i n e d as follows was introduced. Decomposition Ratio of Combustibles (%)

K l

lc

100 - l r

;

1

U

U

'

l c ; i g n i t i o n l o s s of fed cake (%) l r ; i g n i t i o n l o s s of residue {%) When the loading rate to furnace was taken under 25 kg D.S./m^«hr more than 95 % of combustibles i n sludge cake was de­ composed by p y r o l y s i s r e g a r d l e s s of the kinds of cakes. Thus, p y r o l y s i s i s estimated to be as e f f e c t i v e as i n c i n e r a t i o n i n weight r e d u c t i o n of sewage sludge. The r e l a t i o n s h i p between l o a d i n g rate and decomposition r a t i o or i g n i t i o n l o s s i n s o l i d residue i s shown i n Figure 2 . r

Heavy Metals Table 2 shows the behaviour of chromium VI (Cr+6) i n p y r o l y t i c operation. The behaviour of C r ° i n i n ­ c i n e r a t i n g operation on cake Ε i s a l s o shown i n the t a b l e . The r a t i o of C r ° to t o t a l chromium (Cr ^/T-Cr) i s an i n d i c a t o r of the behaviour of chromium compounds i n thermal processings. As i n d i c a t e d i n the table, a part of chromium HE (Cr 3) i n fed cake i s oxidized into Cr 6 d u r i n g i n c i n e r a t i n g operation, whereas a considerable p o r t i o n of Cr 6 i n fed cake i s reduced during p y r o l y ­ t i c operation. +

+

+

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

514

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Table I I .

+

Behaviour of C r ^ i n p y r o l y t i c + 6

cake

( r u n No.)

+ 6

operation

T

/ - C r Dissolved Cr {%) (mg/ )

Ε Ε

Table m .

Drying-pyrolysis Direct pyrolysis Incineration

Table IV. Process

Dispersion

ratio

Run No. 803 903 904

X

2

-

N.D.

-

l40

gas

Direct pyrolysis A (903) 04 3 290-345 45.6 6.5 111 75 0.04 Ο.76

r ο ο < w

m

AND

FISHER

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

MASUDA

Figure 3.

PUROX

577

System Demonstration Test

Overall view of the pilot plant

Japanese

refuse

Simulated Japanese

refuse

A - High Moisture Β - Intermediate moisture C - Standard moisture D - Low Moisture

10

20

Ash content (wt.%) Figure 4.

Quality of Japanese refuse and simulated Japanese refuse

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

578

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

TABLE I I .

TYPICAL REFUSE MIXING RATIO H.M.R.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

Raw shredded r e f u s e (wt.%) Silage Shredded potato Polyvinylchloride Polyethylene Glass Water

17.6 0.0 58.0 0.9 1.8 1.6 20.1

S.M.R. 37.0 10.4 10.4 1.8 3.8 5.1 30.2

- 38 .2 - 10 .6 - 11 .1 - 1 .9 - 5 .2 - 30 .6

L.M.R. 46.8 3.0 9.1 2.9 5.9 9.8 21.9

- 47.6 - 3.1 -

3.0

- 10.0 - 22.0

Although the p i l o t p l a n t had a refuse treatment c a p a c i t y of 20 Mg/d, i t was u s u a l l y operated a t reduced load due t o l i m i t a t i o n s coming from the r e f u s e p r e p a r a t i o n s i t e . Also schedule c o n s t r a i n t s prevented replacement o f the desuperheater and scrubber employed to c l e a n f u e l gas i n the p i l o t p l a n t , by a waste heat b o i l e r and e l e c t r o s t a t i c p r e c i p i t a t o r , such as a r e employed i n the Dry Process PUROX System design. Consequently, dust was not r e c y c l e d . Refuse prepared a t a s e t mixing r a t i o was supplied by apron conveyor to the feeder. The feeder p e l l e t i z e d the r e f u s e and charged the p e l l e t s i n t o the converter, where i t was d r i e d , pyrol y z e d , combusted and melted to form p y r o l y s i s gas and molten s l a g . The s l a g , o r i n o r g a n i c r e s i d u e , was c o n t i n u o u s l y tapped from the converter, quenched i n the water tank and c o l l e c t e d i n the s l a g bunker. The p y r o l y s i s gas was combusted i n the combustor and discharged a f t e r scrubbing. The process flow of the p i l o t plant i s shown i n F i g u r e 5, together with a m a t e r i a l balance f o r the case of high moisture r e f u s e . A t y p i c a l energy balance i s shown i n F i g u r e 6. TABLE I I I . ANALYSIS OF PYROLYSIS GAS Japanese Refuse" L.M.R. H.M.R. S.M.R. CO dry gas v o l . % C02 H CH4 CmHn " Others H2O Nm3/Nm3 dry gas Lower H.V. kJ/Nm3 dry gas (kcal/Nm^ dry gas) 2

11

11

16.00 58.91 18.41 2.96 2.30 1.42 1.3

30.09 38.93 24.16 2.52 2.33 1.97 1.2

6,900 (1,650)

9,420 (2,250)

U.S. Refus

28.64 36.40 25.69 3.77 3.85 1.65 0.8

38 27 23 5.0 5.1 1.9 0.7

11,510 (2,750)

14,570 (3,270)

See a b b r e v i a t i o n s

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

MASUDA

A N D FISHER

PUROX

System Demonstration Test

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

41.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

579

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Basis:

0.36 EU

Air 0.0

Combustor

Heat loss 0.09 EU

Propane 0.67

0.05 EU

Cooling

Water

1.53 EU

Off-gas

Δ

Δ

Off-gas 0.12 EU

Wastewater 1.41 EU

Scrubber

Δ

Energy balance of the pilot plant (high moisture refuse)

Residue 0.08 EU

Converter

Heat loss 0.08 EU

Figure 6.

1 EU of feed (EU = energy unit)

Cooling 0.20 EU

Limestone

Wastewater

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

δ >

U W

>

00

W

ΟΟ Η

3 >

Ο r

Ίϊ ΟΟ

Ο

Ο

οο


r ο ο ζ

H

Χ w

ο

00

41.

MASUDA

A N D FISHER

PUROX

System Demonstration Test

581

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

A comparison o f the p y r o l y s i s gas obtained with Japanese standard r e f u s e and with U.S. r e f u s e (dry gas base) i s given i n Table I I I . I t i s apparent that higher percentage o f water and CO2 i n the gas are obtained i n the case o f Japanese r e f u s e and that the heating value per u n i t volume of the dry gas obtained i s lower. A comparison o f the s l a g composition i s given i n Table IV. The i g n i t i o n weight l o s s f i g u r e s , which show the percentages o f uncombusted m a t e r i a l s , f o r both the Japanese and the U.S. r e f u s e are s u b s t a n t i a l l y lower than the standard Japanese values obtained with the conventional stoker type i n c i n e r a t o r , which are below 10 wt.% f o r a furnace of l e s s than 200 Mg/d and below 7% f o r a furnace of more than 200 Mg/d. TABLE IV.

SLAG COMPOSITION

Japanese Refuse H.M.R. L.M.R. S.M.R. Si0 (wt.%) A1 0 CaO Na 0 FeO Ignition loss 2

2

2

3

51.6 6.7 21.9 5.3 7.4 0.2

59.3 7.1 10.2 7.3 8.1 0.05

56.4 4.8 18.0** 5.9 10.9 0.1

U.S.

Refuse

59.7 10.5 10.3 8.0 6.2 0.4

** Limestone added as n e u t r a l i z a t i o n agent. The s l a g l e a c h i n g t e s t r e s u l t s are given i n Table V. The analyses were conducted i n accordance with N o t i f i c a t i o n No. 13 o f the Environment Agency of Japan. For purposes of comparison, the leachate standards e s t a b l i s h e d by the Prime M i n i s t e r ' s O f f i c e of Japan are a l s o given. These r e s u l t s c l e a r l y show that the amounts of hazardous substances leached from PUROX System s l a g are much l e s s than those of the standards. The i n e r t nature o f the s l a g i s considered a t t r i b u t a b l e s to the p y r o l y s i s o f hazardous m a t e r i a l s such as organic phosphorus, cyanide, and PCB to form more s t a b l e and l e s s environmentally o b j e c t i o n a b l e substances, the temperature being as high as 1,650°C a t the bottom o f the converter, and t r a p p i n g of t r a c e metals i n the g l a s s y matrix. Refuse to which PCB and dry c e l l s and Ni-Cd c e l l s had been added was t e s t e d . I t was not p o s s i b l e , however, to observe the behavior o f PCB and heavy metals s i n c e t h e i r concentrations i n the s l a g d i d not show any marked d i f f e r e n c e . T h i s may have been due to a d d i t i o n of c e l l s that had each been cut i n t o three p i e c e s , thereby causing spotty d i s t r i b u t i o n of the heavy metals. Table VI gives the composition of s l a g when PCB was and when i t was not added. As shown i n the Table, the PCB content was below the d e t e c t i o n l i m i t i n both cases. I t i s considered that

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

582

THERMAL CONVERSION

OF SOLID WASTES AND

BIOMASS

PCB e i t h e r decomposes or e x i s t s i n the s l a g i n such a form as not to l e a c h out and, t h e r e f o r e , does not cause environmental problems. TABLE V.

SLAG LEACHING TEST RESULTS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch041

Inland L a n d f i l l i n g Detection Analysis Limit Standard (mg/1) Alkyl mercury Total mercury Cadmium Lead Organic phosphorus Hexavalent chromium Arsenic Cyanide PCB

ND

0.0005

ND

ND

0.0005

ND

ND ND 0.023

0.0002 0.0025 0.005

0.005 0.3 3

ND ND 0.015

0.0002 0.0025 0.005

0.005 0.1 1

ND

0.0006

1

ND

0.01

1

ND 0.0025 ND ND

0.01 0.0007 0.002 0.0005

1.5 1.5 1 0.003

ND 0.0042 ND ND

0.01 0.0007 0.002 0.0005

0.5 0.5 1 0.003

TABLE V I .

EFFECT OF PCB ADDITION ON SLAG COMPOSITION (Standard Moisture Refuse)

composition (wt.%) Si0 A1 0 CaO Na 0 FeO leaching test (ppm) PCB - pH 6 - pH 8 2

2

2

3

L a n d f i l l i n g on the Sea Detection Analysis Limit Standard

PCB added

PCB not added

59.3 7.1 10.2 7.3 8.1

48.8 6.2 17.6 5.5 17.9

g

M

H

^ >

to

43.

ONOZAWA

Solid Waste Disposal with Pyrolysis and Melting

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch043

Table VII·.

613

Comparison of Gas Processing Methods D i r e c t Combustion Method

Description

Inflammable Gas Recovery Method

Gas Processing

Though dust c o l l e c t o r i s simple, water and t a r processing systems are complex and r e q u i r e l a r g e amounts of space.

Gases e n t e r i n g b o i l e r and heat exchanger are h e a v i l y laden with dust. Measures to prevent dust t r o u b l e are needed. Dust c o l l e c t o r takes up much space.

A i r Preheating

High temperature i s attainable.

High temperature i s d i f f i c u l t to a t t a i n .

Operation

Complicated by process-j ing of dustladen water.

Environmental Pollution

Much lower i n SOx and HC1 than the i n c i n e r ators

Simple.

Lower i n HC1 and NOx than the i n c i n e r a t o r s , j but a l i t t l e higher i n SOx and HC1 than the gas recovery method. !

For l a c k of s u f f i c i e n t l y long o p e r a t i o n a l experience, Nippon S t e e l cannot yet say which of the two methods i s more advantageous. The d i r e c t combustion system i s adopted f o r the I b a r a g i and Kamaishi p l a n t s . Generally, the choice between the two c a l l s f o r very c a r e f u l c o n s i d e r a t i o n of v a r i o u s f a c t o r s p e c u l i a r to each p l a n t . ).2.

Process Economics

In respect to economics, the p y r o l y s i s and m e l t i n g waste d i s p o s a l system under d i s c u s s i o n has the f o l l o w i n g advantages over the stoker i n c i n e r a t o r s that are most widely used i n Japan: (1) The NSC system i s capable of processing r e f u s e that are unsuited f o r burning or incombustible, and cannot be processed by the stoker i n c i n e r a t o r s . (2) There are few a i r p o l l u t a n t s emitted i n the NSC system, e s p e c i a l l y low are HC1 emissions. (3)

Whereas the ash from the stoker i n c i n e r a t o r s i n v o l v e

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

614

THERMAL

CONVERSION

O F SOLID W A S T E S

A N D BIOMASS

the r i s k of e l u t i n g organic matter and heavy metals, the s l a g from the NSC system i s p e r f e c t l y s t a b l e . When b u r i e d i n the reclaimed land, the volume of s l a g decreases t o h a l f of the stoker i n c i n e r a t o r ash, thus making the land s e r v i c e a b l e f o r a longer p e r i o d . I t cannot be denied that the processing cost of the NSC system i s a l i t t l e higher, because of i t s need f o r coke and limestone. Despite t h a t , the p y r o l y s i s and melting system i s economical when advantages (2) and (3) are d e s i r e d o r when u n d e r i r a b l e combustible refuse have t o be processed.

November 16, 1979.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch043

RECEIVED

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

44 The Potential of Biomass Conversion in Meeting the Energy Needs of the Rural Populations of Developing Countries — An Overview V. MUBAYI and J. LEE

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Brookhaven National Laboratory, Upton, NY 11973 R. CHATTERJEE Institute for Energy Research, State University of New York, Stony Brook, NY 11794

Biomass, in the form of firewood, dried crop residues and animal dung, is the fuel most extensively utilized in the rural areas of most developing countries. What was true of the United States over a hundred years ago, when wood accounted for over 90% of energy consumption, s t i l l holds good for many developing nations, particularly in their rural settlements. Current utilization of these resources generally takes place outside of a market economy (hence the term "noncommercial" usually applied to these resources) and in varying amounts for both energy and nonenergy uses. Crop residues, for example, are used as fuel, building material and as animal feed. Dung is used both as fuel and fertilizer. Practically all of the biomass use that takes place at present is in the form of direct combustion at very low efficiencies to supply heat for essential human needs such as food preparation. The mechanical power needs of agricultural production are largely met through the metabolic energy input of draft animals and human labor. Constraints on land and the population it can support make the raising of agricultural productivity essential if food production is to expand in step with population growth. Furthermore, the provision of basic human needs and amenities to improve the "physical quality of life" is an important social goal of almost all of the developing countries. Energy is universally recognized as essential for development. Greater amounts of energy capable of being utilized more efficiently and productively are particularly needed in rural areas of LDCs in order to raise agricultural productivity, provide off-farm employment, essential amenities such as lighting and to improve the physical quality of life. Hence, in addition to low temperature heat necessary for subsistence, mechanical energy is required for agricultural tasks (e.g., pumping water for irrigation), transportation, and small industry, chemical feedstocks whose manufacture requires energy are needed as fertilizer and electricity is needed for lighting. 0-8412-O565-5/80/47-130-617$05.O0/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

618

THERMAL

CONVERSION OF SOLID WASTES AND Β TOM ASS

H i s t o r i c a l l y , i n those r u r a l areas where modernization has occurred, petroleum products have provided the necessary energy inputs required f o r a v a r i e t y of a c t i v i t i e s . Kerosene i s a widely used i l l u m i n a n t , d i e s e l o i l f o r powering i r r i g a t i o n pumps and other farm equipment, g a s o l i n e f o r t r a n s p o r t a t i o n and f e r t i l i z e r s are o f t e n manufactured from naphtha. However, the world o i l s i t u ­ a t i o n now makes the "petroleum route" to development an i n c r e a s ­ i n g l y d i f f i c u l t one f o r many developing countries to undertake. Biomass conversion technologies, which can convert already a v a i l a b l e biomass into a v a r i e t y of s o l i d , l i q u i d , and gaseous f u e l s , capable of being u t i l i z e d more e f f i c i e n t l y and productive­ l y , w i l l be e s s e n t i a l i f the future subsistence and developmental energy needs of r u r a l areas i n developing countries are to be met. This paper represents a very p r e l i m i n a r y attempt at assess­ ing the c o n t r i b u t i o n biomass conversion could make i n the context of the r u r a l areas of s i x developing c o u n t r i e s : India, Indonesia, Peru, Sudan, Tanzania, and T h a i l a n d . The choice of countries was d i c t a t e d p a r t l y by the a v a i l a b l i t y of data on resources and con­ sumption and p a r t l y by the f a c t that these countries t y p i f y the r u r a l energy s i t u a t i o n i n a l a r g e number of developing countries l o c a t e d i n South and South-East A s i a , A f r i c a , and South America. This overview assesses the p o t e n t i a l resources of biomass a v a i l a b l e i n the s i x countries s e l e c t e d . With a few exceptions (such as Peru's f o r e s t resources) these resources are already being c o l l e c t e d and used, a l b e i t i n e f f i c i e n t l y . We focus on r u r a l energy end-uses i n each of the c o u n t r i e s , i n c l u d i n g a d i s c u s s i o n of the current energy consumption patterns and t h e i r magnitudes. Current consumption i s projected i n t o the f u t u r e , to the year 2000, with emphasis placed on c o n c e p t u a l i z i n g both subsistence needs (e.g., cooking) and developmental needs ( i n c r e a s i n g produc­ t i v i t y and l i v i n g standards). The method adopted i n our approach i s that i n the context of r u r a l development an assessment of new technologies has to be anchored w i t h i n the perspective of future energy requirements to s a t i s f y both the b a s i c subsistence needs of growing populations as w e l l as t h e i r developmental needs. The technologies s e l e c t e d f o r a n a l y s i s are: anaerobic d i g e s ­ t i o n of wet biomass to produce methane and p y r o l y s i s of dry b i o ­ mass to produce c h a r c o a l , l i q u i d f u e l s , and low-Btu gases. Pre­ l i m i n a r y estimates are made of the amounts of f u e l s that could be produced i n each of the s e l e c t e d countries by a combination of these technologies. We f i n d that i n f i v e of the s i x c o u n t r i e s , with the exception of India, implementation of these technologies could p o t e n t i a l l y meet the future energy needs of t h e i r r u r a l populations f o r both subsistence and development. Current Sources of Biomass Supply The p r i n c i p a l sources of biomass used f o r energy purposes are wood, gathered from f o r e s t s , orchards and farms, a g r i c u l t u r a l crop residues and animal wastes. Human wastes can a l s o be p o t e n t i a l l y

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

44.

MUBAYI

ET AL.

Biomass Conversion to Meet Energy Needs

619

considered as an energy resource f o r biomass conversion technolo­ gies such as anaerobic d i g e s t i o n i f appropriate c o l l e c t i o n prac­ t i c e s are employed (as, f o r example, i n many Chinese v i l l a g e s ) . We exclude from our purview organic matter which could be poten­ t i a l l y grown i n "energy p l a n t a t i o n s " i n a g r i c u l t u r e , s i l v i c u l t u r e , or aquaculture. This i s not to suggest that such p l a n t a t i o n s are not p o t e n t i a l l y important sources of biomass energy i n developing c o u n t r i e s . However, an e v a l u a t i o n of t h e i r c o n t r i b u t i o n would r e ­ quire an a n a l y s i s of a l t e r n a t i v e land-use patterns which are spe­ c i f i c to each country and f a l l s outside the scope of our a s s e s s ­ ment. Table I provides estimates of the biomass produced annually i n each of the s i x c o u n t r i e s . However, t h i s biomass i s not a l l a v a i l a b l e f o r energy conversion. There are numerous u n c e r t a i n t i e s i n v o l v e d i n attempting to estimate the amounts of biomass that could be used as an energy source such as the f r a c t i o n of wood, crop r e s i d u e s , and animal wastes that can be c o l l e c t e d and the a l ­ t e r n a t i v e non-energy uses that e x i s t f o r the amounts that are cur­ rently collected. Crop r e s i d u e s , f o r example, are commonly u t i l ­ i z e d f o r animal feed and sometimes as b u i l d i n g m a t e r i a l s , animal dung i s u t i l i z e d as a f e r t i l i z e r , and so f o r t h . We have neverthe­ l e s s attempted p r e l i m i n a r y estimates of the biomass a v a i l a b l e f o r energy conversion i n the s i x countries based i n part on data pro­ vided i n other studies and i n part on reasonable assumptions made i n these s t u d i e s . However crude, f o r the purposes of an o v e r a l l assessment of the impact of biomass conversion technology on r u r a l energy needs, these estimates are b e l i e v e d to be r e a l i s t i c approxi­ mations of the amounts of biomass that could be made a v a i l a b l e f o r energy conversion. Assuming an average energy content of 14 b i l ­ l i o n j o u l e s / d r y ton f o r crop r e s i d u e s , 15 b i l l i o n j o u l e s / d r y ton for animal wastes and 16 b i l l i o n j o u l e s / d r y ton f o r fuelwood, the t o t a l p o t e n t i a l f o r energy from biomass can then be c a l c u l a t e d based on these estimates (Table I I ) . In order to assess the s i g n i f i c a n c e of these estimated energy p o t e n t i a l s , we have compiled the best a v a i l a b l e data on the cur­ rent r u r a l biomass consumption f o r energy i n the s i x c o u n t r i e s (Table I I I ) . I t appears that f o r Sudan the biomass energy poten­ t i a l , estimated a t 650 χ 1 0 ^ j o u l e s , i s about ten times i t s cur­ rent biomass consumption. For Peru, the p o t e n t i a l i s estimated at 1341 χ 1 0 ^ j o u l e s , which i s enough to supply a l l i t s r u r a l b i o ­ mass energy needs 7.5 times. The p o t e n t i a l f o r other countries i s about twice the r u r a l consumption f o r Indonesia, Thailand, and Tanzania, and 1.5 times f o r I n d i a . To f u l l y u t i l i z e t h i s poten­ t i a l , however, r e q u i r e s an understanding of a disaggregated pat­ t e r n of r u r a l energy needs and the biomass conversion technologies that can transform t h i s p o t e n t i a l into usable f u e l s .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

620

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Estimated

10

6

10

Ton Human Waste

3

Animal^ Manure Crop Residues

15

S o u r c e s o f Biomass i n R u r a l (per annum)

Ton

Joulgg

Tanzania

Indonesia 1Ô Ι Ο Ton Joulei 5

Joulci

1

Areas

10*To

5

Ton

Ton ... Joulag

Joulis

Ton

1 5

Joules

0.2

3.0

1.0

15.0

3.2

48.0

14.3

214.5

0.5

7.3

0.4

6.0

6.9

103.5

12.8

192.0

10.0

150.0

L98.0

2970.0

24.0

360.0

20.6

209.0

6.0

84.0

37.0

520.0

52.0

728.0

160.0

2240.0

9.3

130.0

2.1

29.4

Fuelwood^

510.0

8160.0

198.0

3168.0

720.0

11520.0

300.0

4800.0

132.0

2112.0

152.0

2432.0

Total

523.1

8350.5

248.8

3895.0

785.2

12446.0

632.3

10224.5

165.2

2609.3

175.1

2776.4

b

c

d

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Potential

Based Based Based Based

on on on on

UN s t a t i s t i c s (1,2) and 33 Kg ( d r y w e i g h t ) o f waste p r o d u c t i o n p e r p e r s o n p e r y e a r . l i v e s t o c k p o p u l a t i o n (1) and manure p r o d u c t i o n r a t e o f m a j o r l i v e s t o c k s 13,4.). p r o d u c t i o n o f m a j o r c r o p s p r o d u c t i o n (I) and t h e i r r e s p e c t i v e r e s i d u e c o e f f i c i e n t s (5,6). a c t u a l f o r e s t r y a r e a (6-11) and p e r u n i t a r e a i n c r e m e n t o f wood by t y p e o f f o r e s t (12).

Estimated A v a i l a b i l i t y

Peru 5

10* Ton

1 5

10 Joules

Thailand 1Ô ÏÔ Ton Joules 5

1 5

o f Biomass f o r E n e r g y C o n v e r s i o n ( p e r annum) Indonesia lô

Human Waste

0.1

1.5

0.5

7.5

Animal^ Manure

5.2

77.6

9.6

144.0

2.7

38.0

76.5

1224.0

29.7

475.0

84.5

1341.1

56.5

860.5

c

16.7

10" Ton

io -

Sudan

10 Ton

A

Joules

Areas

To«15 Joules

1

7.2

107.3

0.3

4.4

0.2

3.0

148.5

2227.5

18.0

270.0

15.5

231.8

24.0

560.0

4.2

58.5

1.0

13.2

119.0

1900.0

19.8

316.8

22.8

365.0

298.7

4794.8

42.3

649.7

39.5

613.0

24.0

7.5

112.5

23.4

328.0

234.0

108.0

1728.0

140.5

2192.5

^Assuming 50% c o l l e c t i b i l i t y . Assuming 75% o v e r a l l c o l l e c t i b i l i t y . Assuming 50% o v e r a l l c o l l e c t i b i l i t y . I t i s f u r t h e r assumed t h a t 50% o f t h e c o l l e c t e d c r o p r e s i d u e s i s used f o r a n i m a l f e e d i n I n d i a , 10% i n T a n z a n i a (5) and t h e r e m a i n i n g c o u n t r i e s . Assuming 15% u s e o f t h e e s t i m a t e d t o t a l a n n u a l i n c r e m e n t o f wood ( t h e p e r c e n t a g e may be an o v e r e s t i m a t e f o r P e r u and I n d o n e s i a due t o t h e l o c a t i o n o f f o r e s t r e s o u r c e s ) . F o r I n d i a , t h e a v a i l a b i l i t y has been assumed t o e q u a l c u r r e n t consumption. d

Estimated

Consumption o f Biomass a s an Energy Source (10 Joules)

i n Rural

Areas

15

Peru

Thailand

Indonesia

0

India

d

Sudan

6

Tanzania

f

Human Waste Animal Manure Crop Residue

5

1 0 * 1 0 Ton Joules

Joules

1.6

Crop Residues

f

5

Ton

i n Rural

8.7

54.4

200.0

472.0

2.4

138.0

440.0

800.0

1900.0

60.0

320.0

Sources: U.S. Dept. o f E n e r g y (6). U.S. Agency f o r I n t e r n a t i o n a l Development (13), assuming a l l c r o p r e s i d u e s a r e consumed i n r u r a l a r e a . °Mubayi e t . a l . ( 1 4 ) . Mubayi e t . a l . (15) . A b a y a z i d OU) . Per c a p i t a c o n s u m p t i o n o f fuelwood i n r u r a l a r e a from R e v e l l e (16). E s t i m a t e d 1975 r u r a l p o p u l a t i o n from UN (2). 3

e

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

44.

MUBAYI

ET AL.

Biomass Conversion to Meet Energy Needs

621

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Rural Energy Supply-Demand P a t t e r n Table IV shows the estimated energy use by type and end use f o r the s i x countries studiedIt appears that the energy share of cooking and heating, which i s p r i m a r i l y by wood, ranges from a high of 98.5% (Tanzania) to a low of 86.4% ( I n d i a ) . Lighting (mainly supplied by kerosene) accounts f o r about 3% or less of the t o t a l r u r a l energy consumption. Although the d i r e c t f u e l use i n a g r i c u l t u r e ( i r r i g a t i o n , s o i l p r e p a r a t i o n and harvesting) i s pro­ p o r t i o n a t e l y small (from 0.3% i n Tanzania to 9.7% i n Sudan), the t o t a l energy requirements of t h i s sector are i n general much greater i f draft animal power were to be included. This i s per­ haps more true i n the case of r u r a l t r a n s p o r t a t i o n which p r i m a r i l y depends on animal draft power. In order to assess the p o t e n t i a l increase of f u e l demand due to mechanization of a g r i c u l t u r e and t r a n s p o r t a t i o n , we have estimated the amount of u s e f u l work con­ t r i b u t e d by d r a f t animals i n the s i x LDCs based on the number and i n t e n s i t y of u t i l i z a t i o n of these animals i n each of these coun­ t r i e s (5,11,16). The estimates show that t o t a l animal energy demand v a r i e s widely, from a n e g l i g i b l e amount i n Tanzania to about 94 χ 1 0 joules i n India. Cottage i n d u s t r i e s which include a c t i v i t i e s such as brick-making, p o t t e r y and metal works mainly use energy to provide process heat and t h e i r energy share appears g e n e r a l l y small except i n India (9.3%). 1 5

Technology

Overview

Biomass conversion technologies can be c l a s s i f i e d into three main types: Anaerobic d i g e s t i o n , p y r o l y s i s and a l c o h o l fermenta­ tion. In anaerobic d i g e s t i o n , organic m a t e r i a l s are broken down by microorganisms i n the absence of oxygen to produce methane. Although t h i s process has been used i n urban waste d i s p o s a l f o r many decades, i t s u t i l i z a t i o n f o r producing energy at the v i l l a g e or i n d i v i d u a l household l e v e l i s s t i l l r e l a t i v e l y new. China and India are two countries where the technology has, perhaps, been most e x t e n s i v e l y implemented i n r u r a l areas (4,21,22). Animal wastes are the most widely used input m a t e r i a l s i n the d i g e s t o r s c u r r e n t l y operating although crop residues or a mixture of crop residues and animal wastes can also be u t i l i z e d . One great advan­ tage of anaerobic d i g e s t i o n i s that the l e f t - o v e r s l u r r y a f t e r the d i g e s t i o n process g e n e r a l l y preserves the n u t r i e n t values of the input feed and can be used as a good organic f e r t i l i z e r . P y r o l y s i s i s an i r r e v e r s i b l e chemical change through heating i n an oxygen-free or low-oxygen atmosphere. Depending on the sys­ tem c o n d i t i o n s and input m a t e r i a l , the p y r o l y s i s of biomass y i e l d s a mixture of s o l i d , l i q u i d and gaseous f u e l s . Although p y r o l y t i c conversion of wood into charcoal by means of simple earth-covered k i l n s has been widely used f o r many centuries i n the r u r a l areas of many LDCs the process i s very i n e f f i c i e n t and does not permit the recovery of the l i q u i d and gaseous energy by-products. How-

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

622

CONVERSION OF SOLID WASTES AND BIOMASS

TABLE IV

Peru (1977) FUELWOOD

CROP RESIDUES

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

X OF TOTAL

RESIDENTIAL Cooking/Heating

138.0

24.0

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Lighting AGRICULTURE

6.3

168.3

90.8

5.6

5.6

3.0

9.5

9.5

5.7

1.0

1.0

0.5

1.0

1.0

0.5

23.4

185.4

Irrigation Soil Preparation,etc. COTTAGE INDUSTRY TRANSPORTATION TOTAL

138.0

Estimated Animal work in agriculture and transportation: Source: (6).

7 χ 10 15 Joules

Thailand (1978) FUELWOOD

CROP RESIDUES

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

% OF TOTAL

RESIDENTIAL Cooking/Heating

440.0

446.7

86.5

13.4

13.4

2.6

46.5

46.5

9.0

1.7

8.0

1.5

1.7

1.7

0.4

63.3

516.3

100.0

6.7

Lighting AGRICULTURE Irrigation Soil Preparation,etc. 6.3

COTTAGE INDUSTRY TRANSPORTATION TOTAL

440.0

13.0

Estimated Animal work in agriculture and transportation: Sources: (1) and (19).

15 8 χ 10 Joules

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

44.

MUBAYI

623

Biomass Conversion to Meet Energy Needs

ET AL.

TABLE IV (cont.) Tanzania (1977) FUELWOOD

CROP RESIDUES

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

X OF TOTAL

RESIDENTIAL* Cooking/Heating

320.0

320.0

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Lighting

4.0

AGRICULTURE

4.0

1.2 0.3

1.0

Irrigation Soil Preparation,etc. COTTAGE INDUSTRY TRANSPORTATION TOTAL

320.0





5.0

Estimated Animal work in agriculture and transportation: Sources: (15) and (20) .

325.0

100.0

Negligible

India (1972) FUELWOOD

CROP RESIDUES

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

X OF TOTAL

RESIDENTIAL Cooking/Heating Lighting

1700.0

460.0

760.0

50.0

292.0

86.4







74.0

74.0

2.2

--



--

55.0

55.0

1.6





--

13.0

13.0

0.4

200.0

12.0

100.0

4.0

316.0

9.3

AGRICULTURE Irrigation Soil Preparation,etc. COTTAGE INDUSTRY TRANSPORTATION TOTAL

— 1900.0

~



472.0

860.0

Estimated Animal work in agriculture and transportation: Source: (15).

2.0

2.0

0.1

198.0

3380.0

100.0

94 χ 10

Joules

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

624

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

TABLE IV (cent,) Indonesia (1972) FUELWOOD

CROP RESIDUES

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

X OF TOTAL

RESIDENTIAL

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Cooking/Heating

800.0

1000.0

Lighting AGRICULTURE

96.4

30.0

30.0

2.8

4.0

4.0

0.4

1.6

1.6

0.2

1.7

1.7

0.2

37.3

1035.7

100.0

Irrigation Soil Preparation,etc. COTTAGE INDUSTRY TRANSPORTATION TOTAL

800.0

200.0

Estimated Animal work in agriculture and transportation: Source: (14).

67 χ 1015 Joules Λ

Sudan (1974) FUELWOOD

CROP RESIDUES

250.0

2.4

ANIMAL WASTES

COMMERCIAL FUEL

SUBTOTAL

X OF TOTAL

RESIDENTIAL Cooking/Heating Lighting

252.4

96.0

3.0

3.0

1.1

3.0

3.0

1.1

4.0

4.0

1.5

0.2

0.2

0.1

0.4

0.4

0.2

9.6

263.0

100.0

AGRICULTURE Irrigation Soil Preparation,etc. COTTAGE INDUSTRY TRANSPORTATION TOTAL

250.0

2.4

Estimated Animal work in agriculture and transportation: Sources: (10) and (18).

1.0 χ 10

15

Joules

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

44.

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ET AL.

Biomass Conversion to Meet Energy Needs

625

ever, a number of promising pyrolytic processes have been developed to produce charcoal and other high grade f u e l s : (a) continuous low-temperature p y r o l y s i s of wood and crop residues with various r e t o r t designs (22), (b) small scale g a s i f i c a t i o n of wood and crop residues (24,25), ( c ) medium to l a r g e scale d i s t i l l a t i o n of wood to produce methanol (25,26)* A l c o h o l fermentation i s a m i c r o b i o l o g i c a l process to produce ethanol from a v a r i e t y of sugar containing m a t e r i a l s . Various c e l l u l o s i c forms of biomass which can be converted to glucose sugar through enzymatic or a c i d h y d r o l y s i s are also being tested as substrates i n t h i s process i n many on-going research p r o j e c t s (27). Because of geographical, economical and other c o n s t r a i n t s on producing the fermentable sugar needed i n t h i s process on a l a r g e s c a l e , B r a z i l i s the only country, at present, which has developed a s u b s t a n t i a l program to produce ethanol f o r energy use. Table V l i s t s eight processes that appear as the most l i k e l y candidates f o r processing organic m a t e r i a l s into f u e l s . I t should be noted that the table i s intended f o r d e s c r i p t i v e purposes only and not f o r comparison of these processes. In a d d i t i o n , the determination of the maintenance requirements were h i g h l y q u a l i t a t i v e and the energy costs of each process were not n e c e s s a r i l y derived on the same basis or d e f i n i t i o n s . In the assessment that f o l l o w s , we have excluded a l c o h o l fermentation because i n i t s present status of development, i t requires grown organic m a t e r i a l s such as sugarcane as s u b s t r a t e s . In planning a future biomass conversion development s t r a t e g y , however, the s e l e c t i o n of technologies f o r a country are much more complicated and the f o l l o w i n g c r i t e r i a should be taken i n t o c o n s i d e r a t i o n : (a) sustainability of substrate (b) maintenance and technology requirements (c) c a p i t a l costs (d) a d a p t a b i l i t y to a v a r i e t y of d i f f e r e n t environments (e) a b i l i t y to supply the e x i s t i n g and p r o j e c t e d p a t t e r n of end use needs ( f ) a c c e p t a b i l i t y i n the c u l t u r a l and s o c i a l s t r u c t u r e . Supply-Demand I n t e g r a t i o n Based on the current end-use patterns discussed e a r l i e r , we have generated a scenario f o r the year 2000 to examine the f u t u r e r u r a l energy demands and the p o t e n t i a l of biomass conversion to meet these demands. It was assumed that energy f o r subsistence would grow at the same average growth rate of 2.5% as projected f o r the r u r a l population i n the s i x L D C s . Direct f u e l use f o r development has been projected to grow at 5% annually. In a d d i t i o n , i t was also assumed that 20% of the animal d r a f t energy used i n a g r i c u l t u r e and t r a n s p o r t a t i o n would be replaced by mechanization. The aggregate r u r a l energy growth implied by these assumptions are r e l a t i v e l y on the high side when compared with other LDC energy p r o j e c t i o n s (32). On the supply end, we have held the biomass a v a i l a b i l i t y at the current l e v e l to provide a "lower bound" of the future biomass energy p o t e n t i a l . The f u t u r e

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Wood Crop r e s i d u e s

Wood

Sugarcane

Crop r e s i d u e s

Wood

Charcoal, pyrolytic o i l

Methanol

Ethanol

Ethanol

SNG

Research stage Development stage

Gasification

Available

Batch fermentation

Batch fermentation

High

Med ium

High

High

Available

Pyrolysis/ distillation

Low

Low

High

developed

developed

Available

Well

Well

Pyrolysis

Carbonization by k i l n s

Anaerobic digestion

Country dependent

High

Country dependent

Country dependent

High

Country dependent

High

Sustainability of S u b s t r a t e

C

b

d

e

6-8

6

30-5$

18-20

8-10

1-3

2-6

2-4~

Estimated Energy Cost ($/lCrJ)

6

^Based on a 75 m^/day community s i z e p l a n t . Does not i n c l u d e c o l l e c t i o n c o s t of wastes (28)• Lower l i m i t based on r e t a i l p r i c e of c h a r c o a l (1977) i n T h a i l a n d (29) and upper l i m i t based on r e t a i l p r i c e of c h a r c o a l (1977) i n Ghana (23). Lower l i m i t based on p r o d u c t i o n cost of a p y r o l y t i c c o n v e r t e r w i t h one ton/day c a p a c i t y (7_) . ^Upper l i m i t based on p r o d u c t i o n cost of a designed c o n v e r t e r w i t h s i x ton/day c a p a c i t y i n Ghana ( 2 3 ) . Based on the economic f e a s i b i l i t y of a p l a n t of 100,000 gallon/day c a p a c i t y a t a f e e d s t o c k c o s t of $19/ton dry wood (13). ^ C a l c u l a t e d s e l l i n g p r i c e based on a f e e d s t o c k c o s t of $13.6/ton i n B r a z i l (30). Based on the economic f e a s i b i l i t y of a p l a n t of 75,800 gallon/day c a p a c i t y a t a f e e d s t o c k c o s t of $15/ton dry wood (13). ^Based on the economic f e a s i b i l i t y of a p l a n t of 6.4 χ 10 SCF/day c a p a c i t y a t a f e e d s t o c k c o s t of $19/ton dry wood (13).

Wood

Charcoal

Substrate

Crop r e s i d u e s Animal wastes

Energy Product

Methane

Maintenance Requirement

Technologies

Status of Technology

Biomass C o n v e r s i o n

TABLE V

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

44.

MUBAYI

E T AL.

Biomass Conversion to Meet Energy Needs

627

supply of biomass i n these countries could be higher because of f a c t o r s such as increased a g r i c u l t u r a l production. This scenario can therefore be judged as a conservative one i n assessing the p o t e n t i a l of biomass conversion. In matching the projected energy demands by end use and the various f u e l s that can be produced through the few biomass convers i o n technologies s e l e c t e d f o r t h i s study, we have converted the projected biomass energy needed f o r d i r e c t combustion (predominantly cooking at 10%-20% e f f i c i e n c y ) i n t o the energy equivalent of converted f u e l forms which can be u t i l i z e d at a much higher end-use e f f i c i e n c y (30% to 50%). In t h i s study we have used a conversion f a c t o r of 0.4 to estimate f u e l requirements i n 2000. This conversion i s important because greater end use e f f i c i e n c y requires l e s s energy input to generate a f i x e d amount of u s e f u l energy. Figure 1 i s a general network diagram which i n d i c a t e s energy flows from resources a v a i l a b l e i n r u r a l areas of LDCs through current and projected conversion technologies to the d i s aggregated end uses. This network, which i s a subsystem of the Less Developed Countries Energy System Network Simulator (LDC-ESNS) developed at Brookhaven N a t i o n a l Laboratory (33), can be u t i l i z e d to make q u a n t i t a t i v e assessments of the impacts of new technologies. Table VI shows the amounts of energy that can be produced by the technologies we have s e l e c t e d matched against the end-use demand f o r energy i n the s i x countries f o r the year 2000. Energy f o r subsistence denotes almost e n t i r e l y the domestic household demand f o r cooking and l i g h t i n g . Energy f o r development focusses on the energy needs of a g r i c u l t u r a l production, r u r a l i n d u s t r i e s , t r a n s p o r t a t i o n and improving l i v i n g standards of the r u r a l populat i o n ( 17,32). A very rough attempt has been made to d i v i d e the developmental energy needs into the need f o r heat energy and the need f o r motive power, which we assume w i l l have to be met almost completely by l i q u i d f u e l s , and s t a t i o n a r y mechanical power, which can be met by gaseous f u e l s as w e l l (e.g., biogas) or by conversion to e l e c t r i c i t y . This d i v i s i o n , however, i s subject to a large number of u n c e r t a i n t i e s . It i s provided here as a purely normative estimate to serve as a q u a n t i t a t i v e benchmark against which the impacts of biomass conversion technologies can be evaluated. From t h i s p r e l i m i n a r y a n a l y s i s we see that biomass conversion technologies have the p o t e n t i a l to meet the projected r u r a l energy demands i n both the subsistence and developmental categories i n f i v e out of the s i x c o u n t r i e s . Only i n the case of India does there appear to be a r e l a t i v e s h o r t f a l l and much of that i s i n the category of l i q u i d f u e l s . This shortage r e f l e c t s the fact that the technology we have chosen, methanol from wood, requires an input which i s i n r e l a t i v e l y short supply i n I n d i a .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL

C O N V E R S I O N O F SOLID W A S T E S

AND

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

628

BIOMASS

1 to

5C ^>

Si v.

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

230

Tanzania

230

200

2530

960

330

130

a

1

1

505

7

15

3

1

1

400

7

15

3

Developmental, Energy (Heat) Demand Supply

4

27

370

90

150

40

4

>100

>100

86

— 27

>100

99

>100

Supply/Demand (%)

90

145

40

Developmental (Mech. Energy Power) Demand Supply

Joules)

215

240

-1070

500

- 10

1040

In

form of Methanol.

Assuming 50% e f f i c i e n c y f o r p y r o l y s i s / d i s t i l l a t i o n of wood.

^In terms of energy content of biomass wastes.

C

^In forms of charcoal, p y r o l y t i c o i l , and pyrogas. Assuming 75% e f f i c i e n c y f o r g a s i f i c a t i o n u n i t s of feedstock produce 5.8 u n i t s of gas and 1.7 u n i t s of charcoal).

(

Biomass 'd Surplus

(10 energy

I n forms of charcoal, biogas, and p y r o l y t i c o i l . Assuming 55% conversion e f f i c i e n c y f o r anaerobic d i g e s t i o n and 66% f o r p y r o l y s i s of crop residues and fuelwood (15 energy u n i t s of feedstock produce 6 units of charcoal and 4 u n i t s of p y r o l y t i c o i l ) .

a

200

Sudan

960

Indonesia

2530

330

Thailand

India

130

Peru

Country

Subsistent Energy Demand Supply

(10

Projected Rural Energy Demand (2000) and Supply of Bioconverted Fuels

TABLE VI

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630

THERMAL CONVERSION

OF SOLID WASTES AND

BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

Conclusion We have shown, that from an o v e r a l l t e c h n o l o g i c a l and r e source standpoint, biomass technologies do appear to o f f e r a s i g n i f i c a n t p o s s i b l i t y f o r meeting the future energy needs of the r u r a l areas of a number of developing c o u n t r i e s . In p a r t i c u l a r , biomass conversion technologies can p o t e n t i a l l y provide the kind of high-grade energy, e s p e c i a l l y l i q u i d f u e l s , necessary f o r f u r ther development and which can serve as an a l t e r n a t i v e f o r scarce petroleum f u e l s . Biomass resources are, i n many cases, l o c a l l y a v a i l a b l e and renewable, i f proper resource management, e s p e c i a l l y of f o r e s t s , i s p r a c t i c e d . (An exception to t h i s f o r the countries studied i n t h i s paper are the f o r e s t resources of Indonesia and Peru which are remote from the main areas of r u r a l settlement.) From a system point of view, since r u r a l energy demand a r i s e s from a large number of dispersed and poorly connected uses, the a v a i l a b i l i t y of l o c a l resources which can be transformed into u s e f u l energy products on a d e c e n t r a l i z e d l e v e l i s a d e f i n i t e b e n e f i t . It avoids the n e c e s s i t y of i n v e s t i n g i n an elaborate c e n t r a l i z e d energy d i s t r i b u t i o n system which i s s u s c e p t i b l e to a number of problems, as i s i l l u s t r a t e d , f o r example, by the experience of r u r a l e l e c t r i f i c a t i o n programs i n many developing countries. However, the d i f f i c u l t i e s of implementation of biomass t e c h n o l o g i e s i n the r u r a l context should not be underestimated. Current biomass use p r a c t i c e s have evolved through many m i l l e n i a of s o c i a l and c u l t u r a l adaptation and new ways of dealing with the same resource w i l have to overcome a number of i n s t i t u t i o n a l , c u l t u r a l , and s o c i a l b a r r i e r s . For example, a community s i z e anaerob i c d i g e s t e r operating on the animal waste inputs from p r i v a t e l y owned c a t t l e or other animals presupposes a c e r t a i n degree of cooperative arrangements among the owners f o r e f f e c t i v e management of a c o l l e c t i o n scheme. Wood that was formerly gathered p r i v a t e l y and used i n i n d i v i d u a l households but now has to be turned over to a processing plant f o r manufacture of higher-grade f u e l s requires new i n s t i t u t i o n a l set-ups to ensure that b e n e f i t s are properly distributed. Furthermore, even f o r technologies that are r e l a t i v e l y simple, a c e r t a i n number of t e c h n i c a l s k i l l s are necessary f o r adequate maintenance and o p e r a t i o n . Such s k i l l s are not usua l l y a v a i l a b l e i n most r u r a l areas and t r a i n i n g and education programs w i l l be needed. Also important i s the fact that r u r a l areas are not a closed system by themselves. Given previous development patterns i t i s l i k e l y that high-grade f u e l s would be siphoned to b e t t e r - o f f urban areas l e a v i n g the r u r a l areas short of energy as before. The B r a z i l i a n ethanol program whose output l a r g e l y goes to f u e l urban automobiles i s an i l l u s t r a t i o n of t h i s problem. Most importantly, implementing a biomass conversion program w i l l require s u b s t a n t i a l inputs of c a p i t a l i n r u r a l areas. The low energy consumption and correspondingly low standard of l i v i n g of most r u r a l inhabitants r e f l e c t s t h e i r low l e v e l s of income and the economics of biomass conversion has to take t h i s fact into

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch044

44.

MUBAYI ET AL.

Biomass Conversion to Meet Energy Needs 631

account. Unlike the situation in developed countries, the collec­ tion costs of the basic raw material will be low, but the capital constraints will be high. In this overview, we have not tried to analyze the potential implementation of biomass conversion tech­ nologies in terms of a market penetration model. We feel that such an approach would make little sense in analyzing resources and consumption patterns that, broadly speaking, currently occur outside of a market economy. A normative approach that analyzes the energy needs of development and the resources available to supply those needs, appears to us more feasible at present in assessing the impact of conversion technologies. However, a great deal of further analysis aimed at reducing the uncertainties in making quantitative judgements of technology impacts is necessary to better define the potential of biomass conversion in developing countries.

Literature Cited 1. 2. 3.

4. 5. 6. 7.

8. 9. 10.

Dept. of Economic and Social Affairs, "1976 Statistical Year­ book," United Nations, New York, 1977. Dept. of Economic and Social Affairs, "Trends and Prospects in Urban and Rural Population, 1950-2000," United Nations, New York, 1975. Mubayi V.; Kahn, P.; Keane, J, "Some Considerations on the Use of Village-Scale Biogas Plants in Developing Countries," (Internal Report), Brookhaven National Laboratory, Upton, New York, 1976. Barnett, Α.; Pyle, L.; Subramanian, S. "Biogas Technology in the Third World: A Multidisciplinary Review," International Development Research Center, Ottawa, Canada, 1978. Makhijani, Α.; Poole, Α., "Energy and Agriculture in the Third World," Ballinger Publishing Company, Cambridge, Mass., 1975. "Joint Peru/United States Report on Peru/United States Coop­ erative Energy Assessment, Volumes I and V," U.S. Dept. of Energy, Washington, D.C., 1979. Henderson, J.; Barth, H.; Heimann, J.; Moeller, P.; Shinn, R., Soriano, F.; Weaver, J.; White, Ε., "Area Handbook for Thailand," U.S. Government Printing Office, Washington, D.C., 1970. Vreeland, N.; Just, P.; Martindale, K.; Moeller, P.; Shinn, R.; "Area Handbook for Indonesia," U.S. Government Printing Office, Washington, D.C., 1974. Fuel Policy Committee, "Report of the Fuel Policy Committee,: Government of India, New Delhi, India, 1974. Abayazid, O., "Prospects of Fuel and Energy in the Sudan," University of Khartoum, Sudan, 1975.

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632 11. 12. 13. 14. 15.

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16. 17. 18. 19. 20. 21. 22. 23.

24. 25. 26.

27. 28.

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS Herrick, Α.; Harrison, S.; John, H.; MacKnight, S.; Skapa Β., "Area Handbook for Tanzania," U.S. Government Printing Office, Washington, D.C., 1968. Earl, D., "Forest Energy and Forest Development," Clarendon Press, Oxford, 1975. Agency for International Development, "Thailand-Renewable Non-Commercial Energy" (Draft), USAID/Thailand, 1979. Mubayi, V.; Lee, J., "A Preliminary Analysis of Energy Supply and Consumption in Indonesia," Brookhaven National Labora­ tory, Upton, N.Y., 1977. Mubayi, V., "Background Information for the Assessment of Energy Technologies for Developing Countries," Brookhaven National Laboratory, Upton, N.Y., 1976. Revelle, R., "Requirements for Energy in Rural Areas," AAAS Selected Symposium 6, Westview Press, Boulder, Colorado, 1978. Reddy, Α.; Prasad, Κ., "Technological Alternatives and the Indian Energy Crisis," Economic and Political Weekly, 1977. Food and Agriculture Organization, "1977 Yearbook of Forest Products," United Nations, Rome, 1979. Lee, J.; Mitchell, G.; Mubayi, V., "A Preliminary Analysis of Energy Supply and Consumption in Thailand," Brookhaven National Laboratory, Upton, N.Y., 1978. "Workshop on Solar Energy for the Villages of Tanzania," Tan­ zania National Scientific Council and USNAS, Dar Es Salaam, 1977. Food and Agriculture Organization, "China: Recycling of Organic Wastes in Agriculture," United Nations, Rome, 1977. Parikh, J.; Parikh, Κ., "Mobilization and Impacts of Biogas Technologies," Energy, 1977, Volume 2. Chiang, T.; Tatom, J.; Graft-Johnson, J.; Powell, J., Pyro­ lytic Conversion of Agricultural and Forestry Wastes in Ghana,: Georgia Institute of Technology, Atlanta, Georgia, 1976. "Symposium Papers: Clean Fuels from Biomass, Sewage, Urban Refuse, Agricultural Wastes," Institute of Gas Technology, Chicago, Illinois, 1976. "A Conference in Capturing the Sun Through Bioconversion: Proceedings," Washington Center for Metropolitan Studies, Washington, D.C., 1976. Jones, J.; Barkhorder P.; Bomberger, D.; Clark, C.; Dicken­ son, R.; Fong, W.; Johnk, C.; Kohan, S.; Phillips, R.; Sem­ ran, K.; Terter, Ν., "A Comparative Economic Analysis of Alcohol Fuels Production Options," SRI International, Menlo Park, California, 1979. "3rd Annual Biomass Energy Systems Conference Abstracts," Biomass Energy Systems Conference, 1979. Ghate, P., "Biogas: A Pilot Project to Investigate a Decen­ tralised Energy System," State Planning Institute, U.P., Lucknow.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

44. 29. 30. 31.

32.

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33.

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633 Biomass Conversion to Meet Energy Needs

"Energy Situation in Thailand-1977" National Energy Adminis­ tration, Bangkok, Thailand, 1978. Yang, V.; Trindade, S., "The Brasilian Fuel Alcohol Program," Centro de Tecnologia, Promon, Brazil, 1979. Schooley, F.; Dickenson, R.; Kohn, S.; Jones, J.; Meagher, P.; Ernest, K.; Crooks, G.; Miller, K.; Fong, W., "Mission Analysis - Market Penetration Modeling," SRI International, Menlo Park, Calif., 1979. Palmedo, P.; Nathans, R.; Beardsworth, E.; Hale, S. Jr., "Energy Needs, Uses and Resources in Developing Countries," Brookhaven National Laboratory, Upton, N.Y., 1978. Reisman, Α.; Malone, R., "Less Developed Countries Energy Network Simulation LDC-ESNS: A Brief Description," Brook­ haven National Laboratory, Upton, Ν.Y., 1978.

RECEIVED November 16,

1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

45 Power Generation from Biomass Residues Using the Gasifier/Dual-Fuel Engine Technique ANDRE A. DENNETIERE — DUVANT Motors, Valenciennes, France FRANCOIS LEORAT — RENAULT New Technologies, 92508 Rueil-Malmaison, France

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

GEORGE F. BONNICI — IDP/RENAULT, One Old Country Road, Carle Place, NY 11514

The increase of the cost of all forms of energy has forced industry to look for the cheapest and most dependable ways of producing and purchasing energy. Potential biomass energy, either under the form of natural resources or by recycling wastes, is rather important throughout the world. For a long time, surface natural combustibles, such as wood and agricultural wastes of some specific products, have been part of energy utilization in plants. They have often been outclassed, in quality as well as in flexibility, by fossile combustibles and so have been abandonned. While waiting for new energy utilization, these surface natural products can be used again. The energy conversion of some wastes may also be considered when they have no other use by reprocessing. The first technical idea is generally to burn these products and use the direct thermal effect (heat and thermal fluids) or indirect mechanical effect (steam engines). However, this kind of technique is generally costly, inefficient or simply not usable with some processes. As a result, a great deal of biomass waste is poorly converted, lost, or burnt without energy production. Conversely, by gasification of vegetable cellulose, and with the help of well adapted equipment, excellent results may be obtained in converting these products to useful energy, without sacrificing the available energy and flexibility. Gasification Cycle and Mechanical Power Generation Overall Performances The cycle consists in converting potential thermal energy of organic wastes into a combustible gas for heavy duty thermal engines. The efficiency of the gasification process is generally about 70 to 80 % (Figure 1) . The thermodynamic efficiency of thermal engines is about 37 %. As we shall see, the best suited engines are of the dualfuel type, whose output power results from the simultaneous work of two combustibles. A small quantity of liquid combustible 0-8412-0565-5/80/47-130-635$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

636

THERMAL

CONVERSION

O F SOLID W A S T E S A N D

si •S

1g

I «S

ο ο

I •S

I

Ci-

Ο *-< 3

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

45.

DENNETiERE E T A L .

Power Generation from Biomass Residues

637

( s t r a i g h t D i e s e l o i l ) i s i n j e c t e d according to D i e s e l p r i n c i p l e s and ensures i g n i t i o n of the gaseous load e n t e r i n g the c y l i n d e r d u r i n g the admission s t r o k e . In f a c t , gas has the most impor­ tant r o l e during the i n t e r n a l c y c l e working p r o c e s s . As a r e ­ s u l t , the gas flow r a t e i s c o n t r o l l e d depending on the d e s i r e d power output, while D i e s e l f u e l i n j e c t i o n remains constant r e ­ gardless of engine l o a d . I t amounts t o a constant reduced D i e s e l o i l consumption per hour. For u t i l i z a t i o n with the low BTO gas obtained through g a s i ­ f i c a t i o n of organic waste, the energy brought t o the engine by D i e s e l o i l i s l i m i t e d at l e s s than 10 % of the o v e r a l l f u e l c o n ­ sumption at f u l l l o a d . I t means that D i e s e l f u e l savings under u s u a l o p e r a t i n g c o n d i t i o n s i s no l e s s than 80 % of the consump­ t i o n of conventional D i e s e l engines of i d e n t i c a l power. Most of the t i m e , the engine i s coupled to an a l t e r n a t o r allowing e l e c ­ t r i c i t y generation with an e f f i c i e n c y of 93 %. Each kWh (3.6 χ 10 J) i s obtained from: - 0.055 l b (25g) of D i e s e l f u e l - 2200 k c a l (92.11 χ 10 J) under gaseous form. The low BTU gas a v a i l a b l e from the g a s i f y i n g equipment i s a mixture of: - combustible elements: CO (14-15 %), H (15-20 %), methane CH4 ( l e s s than 2 %), and some hydrocarbons of a higher order than methane. - i n e r t elements: C 0 and Ν · I t s NCV i s about 1100 k c a l / n o r m a l m (46.05 χ 1 0 J / m ) . T h e r e f o r e , the production of 1 kWh r e q u i r e s about 2.2 m of t h i s gas. C e l l u l o s e wastes can be regarded as i n c l u d i n g about 50 % carbon and 50 % water. Carbon o x y d i z i n g conversion means, as a general r u l e that w i t h a mean g a s i f i c a t i o n e f f i c i e n c y of 75 %, 1 kWh i s obtained from 800 t o 900 g of anhydrous p r o d u c t . Good g a s i f i c a t i o n c o n d i t i o n s are obtained when the moisture content of the product i s low, 10 t o 20 % of water, r e f e r r i n g to gross weight. So, i t i s p o s s i b l e t o c o n s i d e r , without great e r r o r , the f o l l o w i n g r a t i o : with 1 kg of so c a l l e d dry waste, we get 1 kWh at the a l t e r n a t o r output. This r e s u l t i s quite s a t i s ­ factory. 6

5

2

2

2

3

5

3

Some C h a r a c t e r i s t i c s of Low BTU Gas Engines These engines are d i r e c t l y d e r i v e d from standard 4 stroke D i e s e l engines. They are p a r t i c u l a r l y s u i t e d f o r continuous operation. Patented design features allow a p e r f e c t l y r e l i a b l e and h i g h output gas, even with low BTO gas as the main f u e l . The D i e s e l c y c l e ' s high compression r a t i o i s c o n t i n u o u s l y main­ t a i n e d , p r o v i d i n g h i g h e f f i c i e n c y performance. I g n i t i o n power, obtained by combustion of a s m a l l amount of i n j e c t e d D i e s e l f u e l , i s much g r e a t e r than c o n v e n t i o n a l spark i g n i t e d engines. T h i s ensures an e x c e l l e n t combustion s t a b i l i t y

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

638

THERMAL

CONVERSION OF SOLID WASTES AND BIOMASS

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

of the combustible gas mixture, even with excess a i r . T h i s i s q u i t e i n t e r e s t i n g when gas composition may vary, which i s p r e c i s e l y the case with g a s i f i c a t i o n or p y r o l y s i s gas. For p a r t i a l load o p e r a t i o n , the a b i l i t y t o operate outside the s t o c c h i o metric l i m i t s allows i t t o maintain a high e f f i c i e n c y , as i n a pure D i e s e l c y c l e (see t e s t r e s u l t s i n Table I) . Independent f u e l l i n e s provide f o r the s e p a r a t i o n of a i r and gas intake manifolds up t o the c y l i n d e r s , ensuring a good mixture i n s i d e them. T h i s f e a t u r e prevents any r i s k of e x p l o s i o n outside the engine. Moreover, a i r and gas intake being s e p a r a t e l y c o n t r o l l e d , burnt gases are e f f i c i e n t l y scavenged r e s u l t i n g i n reduced i n t e r n a l thermal load and supercharging i s p o s s i b l e without any f u e l l o s s e s . Supercharging Supercharging i s performed by means of a turbo-compressor, as i n a pure D i e s e l c y c l e . In the general case, gas i s a v a i l able without any r e l a t i v e p r e s s u r e . T h e r e f o r e , our engines are equipped with two turbo-compressors: one f o r gas, the other f o r combustive a i r . Engine power r e g u l a t i o n , i . e . the a b i l i t y t o keep a d r i v e n machine's speed constant whatever the l o a d , i s automatic. The engine i s s t a r t e d i n D i e s e l c y c l e , and brought t o the d e s i r e d power l e v e l . Then, gas i s s u p p l i e d , and the maximum p o s s i b l e gas q u a n t i t y r e p l a c e s D i e s e l f u e l a u t o m a t i c a l l y . T h i s i s accomplished without d i m i n i s h i n g the engine's performance. In the case of gas production f a i l u r e ( q u a l i t y and quantity) the l a c k of energy i s a u t o m a t i c a l l y compensated f o r by complementary D i e s e l f u e l (with, of course, a r e d u c t i o n o f the savings during t h i s t i m e ) . I f the l a c k of gas p e r s i s t s , the engine w i l l operate on pure D i e s e l c y c l e and w i l l continue d e l i v e r i n g the d e s i r e d power. The r e g u l a t i n g f u n c t i o n s ( t r a n s i e n t or working changes) occur i n s i d e a narrow s t a t i s t i c a l range ( l e s s than 5%). These generating s e t s can accomplish the f o l l o w i n g programs: - autonomous generating sets supplying e l e c t r i c i t y t o l o c a l consumers under v a r i a b l e l o a d . - coupled generating s e t s . - f i x e d power generating s e t s f o r i n t e r n a l or l o c a l e l e c t r i c i t y , or l i n k e d t o u t i l i t i e s f o r cogeneration. - d i r e c t d r i v e of v a r i o u s machines. - b a s i c elements f o r " t o t a l energy" systems. A b a s i c q u a l i t y of these sets i s a very h i g h operation f l e x i b i l i t y . T h i s e s s e n t i a l l y r e s u l t s from the d u a l - f u e l concept. Because the engines are able t o operate i n pure D i e s e l c y c l e , a power s t a t i o n can be q u i t e autonomous, provided that a small D i e s e l f u e l storage reserve can be kept.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

*5

4



700

7.4

24,717

"NOTE:

CORRESPONDS

3 4 5* -

5.7 410

700

0.3

550

7.7

6.7 475

290

4.1

AIR

TO O P E R A T I O N

530

12.3 330

8.5 610

535

35,663 1,010

970

34,250

910

GAS C A L O R I F I C V A L U E _ A C C O R D I N G TO A N A L Y S I S

540

715

600

3

3.2

32,132

545

2

5.8 413

£

22,775 645

375

Nm3/h

lb/in^ g/cm -

ft-Vh

HP

GAS

GAS ADMITTED

SUPERCHARGE PRESSURE

55

131

36 30

WATER

103.5 106 . 0

SUPPLY

23.2 10.55

10.55

23.2

11.8

26 . 0

25.7 11.7

39.5

37.1

36.6

3 ^ .2

31.Ί

of l'0

TOTAL EFF.

COOLANTS

4,438.2

4.605.7

3.998.6

4 ,061.4

TO A I R A N D OAS

123 118

815 4 35

122 50

833 445

763 406

72 22

77 25

63

77 25

727 336

65 18

20

24 . 4

11.1

622 328

lb/h kg/h

FUEL OIL QUANTITY

F C

CYLINDER EXHAUST TEMP

57 14

16

WITHOUT

970 955 1100 1060

F C

F C 61

AIR

GAS

TEMPERATURE AFTER COOLING

R E S U L T S OP ONE 5 0 0 kW GENERATING S E T WITH DUAL F U E L g CYLINDERS SUPERCHARGED ENGINE (WOOD GAS RUNNING)

POWER

1

TEST

Table I Table

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

640

THERMAL CONVERSION OF

S p e c i f i c a t i o n s of the G a s i f i c a t i o n

BIOMASS

Facility

A) G a s i f i c a t i o n Apparatus. The above defined generating s e t s are g e n e r a l l y fed with low BTU gas by a down d r a f t g a s i f i e r with a f i x e d c a r b o n i z a t i o n bed. G a s i f i c a t i o n i s the decomposition of hydrocarbon combustib l e s , such as c e l l u l o s e , at high temperature by p a r t i a l combustion, that i s t o say with a l a c k of a i r . A f a s t , but p a r t i a l , combustion generates carbon d i o x i d e C0 with h i g h e x o t h e r m i c i t y . C 0 can then be reduced i n the presence of the remaining incandescent carbon, y i e l d i n g CO, a combustible gas. Water from the chemical s t r u c t u r e or moisture content a l s o p l a y s a p a r t , generating hydrogen and CO. CO2 and water reduction are endothermic. Thus, a thermal e q u i l i b r i u m takes p l a c e between combustion r e a c t i o n and g a s i f i c a t i o n r e a c tions: the energy of the f i r s t one being used i n the best way to ensure the second ones. With l i g n o - c e l l u l o s i c products, we are not d e a l i n g with pure carbon. As a r e s u l t , the needed p h y s i c a l carbon bed must be generated. Therefore, the f i r s t r e a c t i o n i s a d i s t i l l a t i o n or p y r o l y s i s of the combustible that has t o pass a f i r s t h e a t i n g phase, where v o l a t i l e matters are exhausted. These v o l a t i l e matters would give an important c a l o r i f i c v a l u e , but cannot be used d i r e c t l y in engines r e q u i r i n g low intake temperature, because of thermodynamic c y c l e c o n s i d e r a t i o n s . The c o o l i n g of such gas would generate p y r o l i g n o u s acids and t a r condensations that would cause an important l o s s i n the c a l o r i f i c value and increase the r i s k s of c l o g g i n g . Combustible gases are sucked from the lower p a r t of the gas generator. Thus there e x i s t s a p a r a l l e l downward path f o r comb u s t i b l e a i r and produced gases, pyrolignous j u i c e s , a c i d s and t a r s . These are cracked on an incandescent c o a l bed. The apparatus c o n s i s t s i n a v e r t i c a l tower f i t t e d with r e f r a c t o r y m a t e r i a l s and i n c l u d i n g : - i n the upper p a r t , a combustible reserve fed by a continuous or s e q u e n t i a l l o a d i n g mechanism adapted to the working c o n d i t i o n s ; - i n the c e n t r a l p a r t a combustion and d i s t i l l a t i o n area fed w i t h a i r by nozzles; - i n the lower p a r t , a reduction area followed by a g r i l l e designed f o r ash removal, g e n e r a l l y performed in a hydraulic lock. In order t o improve e f f i c i e n c y , f e d - i n a i r i s preheated by the combustible gases' s e n s i b l e heat, by means of i n t e g r a t e d heat exchangers. The complementary c o o l i n g and c l e a n i n g of these gases i s performed i n a f i n a l scrubbing u n i t . This scrubber i s a v e r t i c a l tower where the upward flow i s mixed with atomized water. The gases, now cleaned and cooled i n the scrubber, are d r i v e n by a 2

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

SOLID WASTES AND

2

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

45.

DENNETiERE E T A L .

Power Generation from Biomass Residues

641

compressor that c r e a t e s the necessary pressure f o r p i p i n g them to the engine through an intermediate f i l t e r . T h i s chain of equipment allows the g a s i f i c a t i o n o f a l l kinds of s o l i d organic wastes o f adequate s i z e . For example, wood wastes i n c l u d i n g wood bark, coconut s h e l l s , corn cobs, e t c . can be used without p r e l i m i n a r y p r e p a r a t i o n . More d i v i d e d combustib l e s may be added t o these, i n p r o p o r t i o n s up t o 20 % i n weight. In order t o use h i g h l y d i v i d e d wastes such as small seed s h e l l s , c o f f e e s h e l l s , e t c . a combustible has t o be prepared by d e n s i f i c a t i o n . The humidity o f these products has t o be low. A moisture content l e s s than 20 % i s r e q u i r e d t o get a good steady operation. For more humid products, which i s f r e q u e n t l y the case, a d r y i n g stage i s needed and g e n e r a l l y takes p l a c e j u s t before l o a d i n g . Thermal energy necessary f o r d r y i n g i s provided by engine thermal l o s s e s : c o o l i n g c i r c u i t water and exhaust gas. B) P y r o l y s i s Equipment. The p y r o l y s i s process i s a l s o relèvent. In that case, the operation aims a t u t i l i z i n g waste by producing a r e s i d u a l char . A s p e c i f i c combustible i s obt a i n e d ( a c t i v e char or c h a r c o a l , r e f r a c t o r y ashes...) a t the r a t e of approximately 25 % of the i n i t i a l weight. Of course, these combustibles may i n t u r n be g a s i f i e d i n simpler equipment than the ones d e s c r i b e d i n Paragraph A. The gases exhausted d u r i n g the m a t e r i a l h e a t i n g can be u t i l i z e d . These gases are o f t e n of higher c a l o r i f i c value than the low BTU gas obtained with gas generators, but i n c l u d e higher hydrocarbons. These products must be separated by condensation, i n order that the engine burn only the incondensable p a r t . The condensates may f i n d i n t e r e s t i n g commercial value or be used as a thermal supply t o the p y r o l y s i s process i t s e l f . The hydrocarbons can a l s o be d i s s o c i a t e d i n c r a c k i n g equipment fed with c h a r c o a l burning with a i r d e f i c i e n c y . T h i s equipment works i n n e a r l y the same way as the lower p a r t o f the above described down d r a f t g a s i f i e r . F i e l d s of A p p l i c a t i o n The f i e l d of a p p l i c a t i o n f o r the generating s e t g a s i f i e r system t h a t seems t o o f f e r the most i n t e r e s t i n g o p p o r t u n i t i e s i s i n the power range from 100 kW t o a few thousand kW. S i n g l e commercially a v a i l a b l e generating s e t s cover the 150 t o 1000 kVA (approx. 120 t o 800 kW) range (Figure 2 ) . A v a i l a b l e g a s i f i c a t i o n equipment i s w e l l adapted t o t h i s range. S e v e r a l generating s e t s can be coupled t o one source of gas. Conversely, s e v e r a l g a s i f i e r s can be coupled t o feed a single set. Power s t a t i o n s of l e s s than 100 kW are p e r f e c t l y f e a s i b l e too. I t a l l depends on l o c a l economic c o n d i t i o n s , which w i l l d e f i n e the p r o f i t a b i l i t y of the system.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

642

THERMAL

C O N V E R S I O N O F SOLID W A S T E S

AND

I fa

& Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch045

V.

I v. Ο Ο

S

t3 J*.

$ l V g a l ( o r > $ 0 . 2 6 / l i t e r ) 0-1). Methanol Production from Biomass Feedstock Options. Numerous l i g n o c e l l u l o s i c m a t e r i a l s could be used f o r the production of methanol. The conversion technology e n t a i l s thermal g a s i f i c a t i o n to produce a synthesis gas stream (CO and H2) followed by synthesis to methanol. A g r i c u l t u r a l residues could be used a f t e r chopping and perhaps d e n s i f i c a t i o n into p e l l e t s . The amount of processing r e q u i r e d before g a s i f i c a t i o n w i l l depend on the type of g a s i f i e r chosen. The most s u i t a b l e feedstock i s probably wood, because i t w i l l g e n e r a l l y be the mater i a l a v a i l a b l e at the lowest cost i n the q u a n t i t i e s r e q u i r e d . To produce an amount of methanol equivalent on a volumetric b a s i s to 1000 b a r r e l s / d a y (365,000 b a r r e l s / y e a r ) of petroleum f u e l would r e q u i r e the processing of ~ 500 metric tons/day of wet wood (at 50 weight percent moisture) f o r 330 days/year. This estimate i s based on data presented by Kohan f o r a wood-to-methanol plant (12).

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

698

THERMAL CONVERSION

OF SOLID WASTES AND

BIOMASS

Wood A v a i l a b i l i t y . Table V summarizes data f o r worldwide wood production i n 1974, plus projected production l e v e l s f o r 1985 and 2000. Note that i n 1974, 47% of the estimated world wood product i o n was f o r f u e l ; 75% of that use was i n developing nations. In 1974, 82% of the roundwood production i n developing nations went for f u e l use. I t has been estimated that the use of wood f o r f u e l w i l l increase by 10% worldwide by 2000, while the t o t a l production of wood w i l l increase by 50% (13). The use of wood f o r f u e l by developing nations has been estimated to increase by 43%, or by 374 m i l l i o n cubic meters/year. In terms of the a c t u a l percent increase i n production, however, pulpwood production f o r LDCs has been estimated to increase the most, 15-fold. These data on pulpwood production i l l u s t r a t e an important point concerning wood use. As c o u n t r i e s develop, wood i s v i t a l l y needed f o r the cons t r u c t i o n of commercial b u i l d i n g s and residences, and f o r paper production. Therefore, even i f the f u e l demand met by wood remains at a constant l e v e l , e i t h e r the t o t a l harvest must increase to s a t i s f y other demands f o r wood or the e f f i c i e n c y of wood u t i l i z a t i o n f o r f u e l must increase so as to r e q u i r e l e s s wood f o r f u e l purposes. In c e r t a i n developing areas of the world, i n c r e a s i n g wood production or even maintaining current production l e v e l s may be d i f f i c u l t . Wood f o r f u e l i s now reported to be scarce i n l a r g e regions of Southern A s i a , A f r i c a n countries bordering the Sahara from Senegal to E t h i o p i a , the Andean c o u n t r i e s , C e n t r a l America, and the Caribbean. D e f o r e s t a t i o n i s already viewed as a s e r i o u s problem i n numerous areas, and r e f o r e s t a t i o n must be s t a r t e d before l a r g e increases i n wood production can be achieved ( I d ) . TABLE V

WORLDWIDE PRODUCTION OF WOOD PRODUCTS

1974 Fuelwood and charcoal I n d u s t r i a l roundwood Sawlogs and veneer logs Pulpwood Other products T o t a l Roundwood

Figures i n parentheses Source:

M i l l i o n Cubic Meters 1985 2000

1170 (860)*

1200 (1014)

799 (136) 340 (15) 202 (40)

983 (200) 669 (96) 208 (51)

1191 (272) 1111 (222) 206 (62)

2511 (1051)

3060 (1361)

3800 (1792)

( ) are f o r developing

1292 (1236)

nations.

Adapted from data i n reference 13.

In view of current f o r e s t resources, i t appears South America o f f e r s the g r e a t e s t opportunity f o r wood use as f u e l . Brazil, for example, i s c u r r e n t l y planning a l a r g e methanol production program based on wood as a feedstock to complement present ethanol

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

48.

JONES AND CHATTERJEE

Biomass Fuels for Vehicle Engines

699

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

production operations that use sugar cane j u i c e or molasses as the main carbohydrate source (14) . In some, other developing c o u n t r i e s , however, i n A f r i c a and Southeast A s i a , the p o t e n t i a l does e x i s t f o r increased long-term use of f o r e s t resources f o r f u e l . But, because of the many v a r i e t i e s of wood produced and the d i f f e r e n c e s i n v a l u e as a f u n c t i o n of wood grade and end use, a d i s c u s s i o n of wood v a l u e i s beyond the scope of t h i s e f f o r t . Investment Requirements f o r Methanol Production from Wood. According to investment cost estimates prepared by Kohan, a p l a n t that would operate 330 days/year and produce 48,000 gallons/day of methanol (182,000 l i t e r s / d a y ) would cost roughly $50 m i l l i o n (12). This investment i s e q u i v a l e n t to $2.50/gallon of annual c a p a c i t y (or $ 0 . 6 6 / l i t e r of annual c a p a c i t y ) . Because s i g n i f i c a n t economies of s c a l e are a c h i e v a b l e i n methanol production, a l a r g e p l a n t i s p r e f e r a b l e to minimize the investment requirements per u n i t of c a p a c i t y . S i n g l e methanol plant c a p a c i t i e s f o r B r a z i l have been proposed with s i g n i f i c a n t l y more than 10 times t h i s c a p a c i t y , and investment costs per u n i t of annual c a p a c i t y have been estimated to be l e s s than $1.25/gallon (14). Vehicle-Mounted

Gasifiers

Feedstock Options In t h i s a n a l y s i s , only a i r - d r i e d wood chips or b i l l e t s , and p e l l e t i z e d a g r i c u l t u r a l r e s i d u e s w i l l be considered. The moisture content of these f u e l s i s assumed to be ^ 20 weight percent. Charc o a l b r i q u e t s a r e a l s o a h i g h l y d e s i r a b l e f u e l , but t h e i r prod u c t i o n r e q u i r e s s i g n i f i c a n t c a p i t a l investment. The use of c h a r c o a l , however, warrants c o n s i d e r a t i o n i n f u t u r e s t u d i e s . (See r e f e r e n c e s _3 and 15 f o r d e t a i l e d d i s c u s s i o n s of biomass f u e l use i n v e h i c l e engines.) Investment

Requirements

The investment requirements f o r r e p l a c i n g 1000 b a r r e l s / d a y of petroleum f u e l by burning a low-heating-value gas produced using v e h i c l e mounted g a s i f i e r s have been estimated based on the c a l c u l a t i o n s and assumptions described i n Table VI. Retrofitting of l a r g e s h o r t - h a u l trucks or buses i n r u r a l areas i s the b a s i s f o r the estimate of an investment cost of from $2 to 4 m i l l i o n . R e t r o f i t t i n g 2000 smaller v e h i c l e s (also operating i n r u r a l areas) at a cost of ^ $2000 each might be a more p r a c t i c a l i n i t i a l g o a l and might be achieved f o r e s s e n t i a l l y the same cost. If f i v e p l a n t s were r e q u i r e d f o r the p r o d u c t i o n of d e n s i f i e d f u e l p e l l e t s from a g r i c u l t u r a l r e s i d u e s , the investment costs f o r a t o t a l c a p a c i t y of 580 m e t r i c tons/day would probably exceed $10 m i l l i o n . Therefore, the investment costs a s s o c i a t e d with the option of using vehicle-mounted g a s i f i e r s may be about $15 m i l l i o n .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

1 2

Γ Λ Λ Λ Λ

-ιΤ_

3.65

kg s o l i d f u e l

, Ο Λ

-,

ι.j

£

ι / b

11

\

are used.

The average cost to r e t r o f i t l a r g e v e h i c l e i s estimated to range from $5,000 to $10,000; Therefore, r e t r o f i t t i n g 400 v e h i c l e s would cost from $2 to $4 m i l l i o n .

To r e p l a c e 1000 b a r r e l s of petroleum f u e l w i l l r e q u i r e r e t r o f i t t i n g 400 l a r g e v e h i c l e s (580,000 kg s o l i d fuel/day)/(1425 kg/vehicle/day) = 400 v e h i c l e s .

For 1 hour of o p e r a t i o n with wood, the g a s i f i e r volume must be ~ (285 kg/hr)(/300 kg/m^) =1

The volume could be 50% t h i s amount i f d e n s i f i e d f u e l p e l l e t s

m^

cubic meter (168 cubic meter)

kg/vehicle/day

(300 kg/cubic meter)] = 4.75

f o r 5 hours of operation/day i s 1425

The volume of t h i s f u e l i s at most [1425 kg/

The s o l i d f u e l requirement

kg/hr.

the s o l i d f u e l requirement i s

(300 HP χ 5 hrs) (0.95 kg s o l i d fuel/HP-hr) = 285

For a 300-HP engine operated 5 hours/day,

ι

τ~Γ> ΓΓ~Η—Τ TTT % -i . r j - 7 — τ (or ~ 30 l b s s o l i d f u e l / g a l l o n ) . 159,000 l i t e r s of l i q u i d f u e l l i t e r of l i q u i d f u e l C a l c u l a t i o n of s p e c i f i c f u e l consumption i s based on an engine e f f i c i e n c y of 27% and i s equal to 0.95 kg of s o l i d fuel/HP-hr. =

j o u l e s / d a y / (14.7 χ 1θ6 joules/kg) (0.7)] =580,000 kg/day

580,000 kg s o l i d f u e l

[6 χ 1 0

A thermal e f f i c i e n c y of 70% i n conversion of s o l i d f u e l to a low heating v a l u e gas i s assumed to c a l c u l a t e the s o l i d f u e l requirement.

Wood b i l l e t s or p e l l e t i z e d f u e l s with ^ 20 weight percent moisture are to be used i n downdraft g a s i f i e r s ; the average heating v a l u e of the f u e l i s 6337 Btu/lb (or 14.7 χ 10^ j o u l e s / k g ) .

engines are considered f o r r e t r o f i t t i n g .

BASES AND ASSUMPTIONS FOR THE ANALYSIS OF THE VEHICLE MOUNTED GASIFIER OPTIONS (Replacement of 1000 Barrels/Day of Petroleum Fuels or ~ 6 χ Ι Ο ^ Joules/Day)

Large short h a u l trucks and bases with d i e s e l

TABLE VI

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

48.

JONES AND CHATTERJEE

Biomass Fuels for Vehicle Engines

701

Summary and D i s c u s s i o n of F i n d i n g s Investment costs to allow replacement of biomass f u e l s f o r petroleum f u e l s used i n t r a n s p o r t a t i o n appear to be s i g n i f i c a n t for a l l o p t i o n s . To r e p l a c e 1000 b a r r e l s / d a y of petroleum f u e l s w i l l r e q u i r e c a p i t a l investments f o r conversion f a c i l i t i e s as follows :

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

Option Ethanol p r o d u c t i o n From sugar cane j u i c e From molasses alone Methanol production Vehicle-mounted G a s i f i e r s R e t r o f i t t i n g alone Retrofitting + densified f u e l s production

Estimated Investment ( M i l l i o n s of 1979 U.S. D o l l a r s )

14-20 20 40

£ 4 - 15

For both the cases of methanol production and the use of v e h i c l e mounted g a s i f i e r s , a d d i t i o n a l investments w i l l be a s s o c i a t e d with f a c i l i t i e s and equipment f o r h a r v e s t i n g and t r a n s p o r t of the b i o mass to the conversion s i t e s . In the case of ethanol p r o d u c t i o n from c u r r e n t l y produced sugar cane j u i c e or molasses, the convers i o n f a c i l i t i e s would be constructed adjacent to sugar m i l l s that already are r e c e i v i n g the biomass raw m a t e r i a l . Thus, a d d i t i o n a l investments f o r h a r v e s t i n g and transport equipment would not be required. The use of vehicle-mounted g a s i f i e r s would probably present more l o g i s t i c a l problems (e.g., the need f o r frequent r e f u e l i n g ) than would the use of a l c o h o l f u e l blends. The environmental consequences of u s i n g vehicle-mounted g a s i f i e r s could a l s o be a problem, as could operating r e l i a b i l i t y and engine performance (engine d e r a t i n g and response to l o a d ) . The use of v e h i c l e mounted g a s i f i e r s , however, may represent a simple t e c h n o l o g i c a l o p t i o n that o f f e r s employment i n r u r a l areas and s i g n i f i c a n t savings i n imported f u e l s f o r t r a n s p o r t a t i o n . The use of sugar cane j u i c e or molasses to produce an a l c o h o l f u e l may be d i f f i c u l t to j u s t i f y economically i n c o u n t r i e s where a l l of the excess raw sucrose production (and molasses) can be exported at competitive world p r i c e s . Although much enthusiasm c u r r e n t l y e x i s t s f o r producing ethanol f u e l s from l o c a l sugar crops i n developing n a t i o n s , the r e s u l t s of t h i s very cursory a n a l y s i s i n d i c a t e to us that a t l e a s t one other o p t i o n could supplement petroleum f u e l s used i n t r a n s p o r t a t i o n with biomass f u e l s a t comparable or lower c a p i t a l investments. This o p t i o n i s the use of vehicle-mounted g a s i f i e r s .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

702

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Conclusions and Recommendations

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

On the basis of this cursory analysis, vehicle-mounted biomass gasifiers as well as alcohol fuels appear to us to represent possible means to reduce petroleum fuel use in developing nations. Biomass availability for use as a fuel, however, could restrict the use of the option to only a few LDCs. We recommend that, in the future, transportation development plans and energy studies for LDCs include consideration of vehiclemounted gasifiers (especially in rural areas), along with the other options being evaluated. The potential problems with the use of such gasifiers that we have identified in this paper should also be carefully analyzed. LITERATURE CITED 1.

Palmedo, P. F., et a l . , "Energy, Needs, Uses and Resources in Developing Countries," National Center for Analysis of Energy Systems, Brookhaven National Laboratory, (a) p. XV, (b) p. 95 (c) p. XIX (d) pp 52 to 55, March 1978.

2.

Egloft, G., et a l . , "Motor Vehicles Propelled by Producer Gas" The Petroleum Engineer, 115, December 1943 (pp. 65-73).

3.

"Generator Gas—The Swedish Experience from 1935-1945", report translated from Swedish to English by the Solar Energy Research Institute, Golden, Colorado, SERI Publication No. SP-33-140, January 1979, published in Swedish, Stockholm, 1950.

4.

O'Sullivan, D. Α., "UN Workshop Urges Wider Use of Ethanol," Chemical and Engineering News, April 23, 1979.

5.

Molasses and Industrial Alcohol," Proceedings of the Meeting of Experts Organized by the Development Center of the Organisation for Economic Co-operation and Development, Paris, 1976, published by the OECD, Paris, France, 1978.

6.

International Sugar Organization, "Sugar Year Book 1977"; The Whitefriars Press Ltd: London, England, July 1978.

7.

"Report on World Sugar Supply and Demand, 1980 and 1985"; Foreign Agricultural Service, United States Department of Agriculture, Washington, D.C., November 1977.

8.

"An Update on World Sugar Supply and Demand, 1980 and 1985"; Foreign Agricultural Service, United States Department of Agriculture, Washington, D.C., May 1978.

9.

Jones, J. L., Fong, W. S., "Mission Analysis for the Federal Fuels from Biomass Program, Volume V: Biochemical Conversion of Biomass to Fuels and Chemicals"; report prepared by SRI International, Menlo Park, California, for the U.S. Department of Energy, December 1978.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

48.

10.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

11.

JONES AND CHATTERJEE

Biomoss Fuels for Vehicle Engines703

Lipinsky, E. S., et a l . , "Second Quarterly Report on Fuels from Sugar Crops"; report prepared by Battelle Memorial Institute, Columbus, Ohio for the U.S. Department of Energy, October 1977. Yang, V., and Trindade, S. C., "Brazil's Gasohol Program"; Chemical Engineering Progress, 75, 4, April 1979 (p. 14).

12.

Kohan, S. Μ., Barkhordar, P. Μ., "Mission Analysis for the Federal Fuels from Biomass Program, Volume IV: Thermochemical Conversion of Biomass to Fuels and Chemicals"; report prepared by SRI International, Menlo Park, CA, for the U.S. Department of Energy, January 1979.

13.

Stone, R. N, Saeman, J. F., "World Demand and Supply of Timber Products to the Year 2000"; Forest Products Journal, 1977, 27(10). "Brazil out to Show Methanol Grows on Trees"; Chemical Week, 1979, 124 (11).

14. 15.

Skov, Ν. Α., Papworth, M. L., "The Pegasus Unit". Publishers, Inc., Olympia, Washington, 1974.

RECEIVED November 20,

Pegasus

1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

49 Social and Economic Aspects of the Introduction of Gasification Technology in Rural Areas of Developing Countries (Tanzania) MICHIEL J. GROENEVELD and K. R. WESTERTERP

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

Department of Chemical Engineering, Twente University of Technology, P.O. Box 217, 7500 AE Enschede, Netherlands

The development of rural areas in the Third World depends a.o. on the availability of energy [1,2], Makhijani showed that for the improval of the agricultural production an increase in energy consumption is required. This energy in whatever form has to be available in the rural areas in relatively small quantities per user. Consequently energy production by small-scale units scattered throughout the country is required. Nowadays mostly internal combustion engines are used to drive tractors, water pumps, machinery for processing agricultural products or electric generators. It seems attractive to replace the fossil liquid fuels needed for these engines by locally produced fuels. One of the possibilities is the thermal gasification of agricultural waste, which produces a low-caloric combustible gas that can be used directly to drive these engines. In the thermal gasification process the heat of combustion of the waste is transferred to the combustible gas by means of partial oxidation. The same process had been used in World War II with wood blocks as feedstock to drive cars and lorries in countries where petrol was scarce. In our laboratory [3] relatively simple, small scale gasifiers have been built and tested for agricultural and forestry wastes. The fuel gas was used to drive stationary engines. To identify the social and economic advantages of our process a study has been made of its applicability in rural areas of Tanzania. The evaluation included the selection of a suitable feedstock, the macro- and micro-economical effects and the fitting into the existing social-cultural system. D e s c r i p t i o n of the process A g a s i f i c a t i o n process to generate power consists of a g a s i f i e r , a gas c o o l e r , a g a s - a i r mixer and a combustion engine and will be described :

0-8412-0565-5/80/47-130-705$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

706

THERMAL

CONVERSION OF SOLID WASTES AND BIOMASS

G a s i f i e r From the various p o s s i b l e types the co-current moving bed g a s i f i e r was s e l e c t e d because of i t s t a r f r e e gas production and i t s simple c o n s t r u c t i o n As feedstock a g r i c u l t u r a l (forestry waste with a low ash and water content i s p r e f e r red because of the high c a l o r i c value per kg. waste. The g a s i f i er can be d i v i d e d i n four zones (see f i g . 1) from top to bottom: a) bunker. The bunker volume allows f o r discontinuous f i l l i n g of waste i n t o the g a s i f i e r by hand. In the lower p a r t of the bunker volume drying occurs. b) p y r o l y s i s zone. Due to the heat t r a n s f e r from the h o t t e r zones the feedstock pyrolyzes here and thus produces char and (condensable and non-condensable) gases i n c l u d i n g t a r . c) o x i d a t i o n zone. In t h i s part a i r i s introduced and a p a r t i a l combustion takes place, r e s u l t i n g i n temperatures of 1200 1600 °C. Due to these high temperatures the t a r s produced i n the p y r o l y s i s zone are cracked. d) r e d u c t i o n zone* Here the CO2 and H2O from the o x i d a t i o n zone r e a c t with the charcoal forming hydrogen and carbon monoxide. The hot product gas i s sucked out of the g a s i f i e r v i a the gas c o o l e r by an engine. The ash, which c o l l e c t s i n the bottom of the g a s i f i e r , should be removed o c c a s i o n a l l y . A more d e t a i l e d d e s c r i p t i o n of the g a s i f i c a t i o n of s o l i d waste i s presented elsewhere [ 4 ] . I t i s p o s s i b l e to construct the g a s i f i e r simply from brickwork and s t e e l , see f i g u r e 2, and i t has no moving p a r t s . Gas c o o l e r To increase the output of the engine the gas should be cooled down to approximately the temperature of the surroundings. This can be done simply with a water or a i r c o o l e r and with a pebble bed: here the l a t e n t heat of the gas i s accumulated, so that the bed should be cooled down o c c a s i o n a l l y . The pebble bed should c l e a n the gas of t a r , dust or soot, i f by bad operation the gas i s d i r t y . Gas-air mixer The gas volume has to be mixed with an about 1.1 times l a r g e r , a d j u s t a b l e a i r flow, which i s almost stoichiomet r i c . The t o t a l g a s - a i r flow passes through the normal engine f i l t e r f o r f i n a l dust removal. Engine I t i s p o s s i b l e to use any i n t e r n a l combustion engine. In a spark i g n i t i o n 4 stroke engine a l l the p e t r o l can be r e placed by gas without any adjustment. I n case a two-stroke spark engine i s used l u b r i c a t i n g o i l has to be i n j e c t e d separately, i n a d i e s e l engine only about 90% of the d i e s e l o i l can be replaced by gas: the a d d i t i o n of the same d i e s e l o i l i s necessary f o r the i g n i t i o n . The thermal e f f i c i e n c y of the engine i s not a f f e c t e d by the use of gas, but due to the lower c a l o r i c value of a gasa i r mixture the mechanical output i s decreased by +_ 30% i n comparison to p e t r o l or d i e s e l o i l d r i v e n engines. Our p i l o t p l a n t consumed 2,5 kg fuel/kWh (mechanical), but r e s u l t s can be much

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

49.

GROENEVELD AND WESTERTERP

Gasification Technology

707

air

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

1

fuel

Figure 1.

Figure 2.

Co-current moving-bed gasifier

Gasifier appropriate for developing countries

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

708

THERMAL

improved with b e t t e r engines

CONVERSION OF SOLID WASTES AND BIOMASS

[5,6].

Evaluation c r i t e r i a Energy production from a g r i c u l t u r a l waste by g a s i f i c a t i o n competes with s e v e r a l other p o s s i b l e uses. The a v a i l a b i l i t y of a g r i c u l t u r a l waste The production of p l a n t m a t e r i a l depends on the s o l a r r a d i a t i o n , the type of v e g e t a t i o n , the c l i m a t e , the s o i l and the a g r i c u l t u r a l system. I f and how much of the p l a n t m a t e r i a l can be removed from the s i t e f o r e i t h e r food or energy production, i s determined by the e f f e c t on the s o i l , e s p e c i a l l y on the humus content. In case of an energy p l a n t a t i o n i n t r o p i c a l areas, the s o l a r r a d i a t i o n (yearly average 250 W/m ) i s f o r 3.8% converted i n t o p l a n t m a t e r i a l [ 7 ] ; assuming an o v e r a l l e f f i c i e n c y f o r g a s i f i c a t i o n of maximal about 45%, t h i s r e s u l t s i n 4 W/m^ ( e l e c t r i c a l ) . This output can only be obtained i n s p e c i a l areas with i n t e n s i v e use of f e r t i l i z e r i n parts of a country s p e c i a l l y used f o r energy production. In the r u r a l areas of developing c o u n t r i e s , however, most of the f e r t i l e land has to be used f o r food production. Consequently only those waste products are a v a i l a b l e , that can not remain or be returned on the land as a mulch f e r t i l i z e r . These waste products represent only part of the t o t a l crop production, so that energy production depends h i g h l y on the o r g a n i z a t i o n of the a c t u a l a g r i c u l t u r a l system: only those waste products can be used f o r energy production, that are already being c o l l e c t e d or produced during the processing of the crop. G a s i f i c a t i o n should help the development of the country and e s p e c i a l l y the poorest s t r a t a of the s o c i e t y according to the requirements of the IMF and World Bank. Many poor people l i v e i n r u r a l areas, where except i n the harvest season a high unemployment e x i s t s . The i n t r o d u c t i o n of new sources of energy should create jobs and/or r e p l a c e unworthy work. New technology used i n the r u r a l areas i m p l i c a t e s however, that i t should be based on u n s k i l l e d or h a r d l y s k i l l e d labour. L o c a l c o n s t r u c t i o n or at l e a s t l o c a l maintenance and r e p a i r r e q u i r e s the equipment to be made of w e l l know m a t e r i a l s and with simple techniques; so that l o c a l t e c h n o l o g i c a l development i s stimulated i n an appropriate way.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

2

F i n a l l y i t i s necessary that the i n t r o d u c t i o n of g a s i f i c a t i o n u n i t s b e n e f i t s not only the owner but a l s o the n a t i o n a l economy and that i t f i t s i n with government p o l i c i e s f o r unemployment, r u r a l development, trade balance, e t c . C o n c l u s i v e l y the g a s i f i c a t i o n of a g r i c u l t u r a l waste as an a l t e r n a t i v e method f o r energy production must be evaluated according to the f o l l o w i n g c r i t e r i a : 1. The waste has to be a v a i l a b l e and usable without damaging the a g r i c u l t u r a l system o r the environment. 2. The technology should f i t i n the e x i s t i n g s o c i o c u l t u r a l system. 3. The use has to b e n e f i t the development of the poorest s t r a t a of the s o c i e t y .

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

49.

GROENEVELD AND WESTERTERP

Gasification Technology

709

4. The use should be p r o f i t a b l e f o r the owner and the users. 5. The i n t r o d u c t i o n should be of n a t i o n a l i n t e r e s t .

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

A p p l i c a b i l i t y i n the r u r a l areas of Tanzania S e l e c t i o n of a feedstock f o r the g a s i f i c a t i o n process In Tanzania dominate the moist savanne, the dry savanne and the steppe c l i mates. The moist savanne areas show the h i g h e s t crop production, and a good i n f r a s t r u c t u r e (roads) e x i s t s . The a g r i c u l t u r a l system i n Tanzania c o n s i s t s o f : 1) p r i v a t e farmers 2) l a r g e s t a t e farms (or p l a n t a t i o n s ) 3) TJjamaa-villages. The s t a t e promotes the s t a t e farms and e s p e c i a l l y the Ujamaa-villages [ 8 ] . In such an Ujamaa-village the t r a d i t i o n a l A f r i c a n c u l t u r e i s combined with a modern l o c a l l y adapted s o c i a l i s m . These v i l l a g e s are regarded as the b a s i s and centre f o r the r u r a l development and as a communal and cooperative production and marketing u n i t . In these v i l l a g e s the land i s d i v i d e d i n t o small i n d i v i d u a l p l o t s f o r each f a m i l y and a l a r g e r communal p l o t f o r the p r o d u c t i o n of cash crops, which enables the Ujamaa to buy t r a c t o r s , f e r t i l i z e r s and high q u a l i t y seeds and to m a i n t a i n a s c h o o l , a dispensary, a shop and water supply. The l o c a l a v a i l a b i l i t y of a f u e l would be very b e n i f i c i a l . The Arusha area has been s e l e c t e d f o r our f i e l d study. In t h i s area a l l crops and the a s s o c i a t e d products have been studied with s p e c i a l emphasis on: 1. The type and q u a n t i t y of waste. 2. The need f o r use as a mulch f e r t i l i z e r , thus s t a y i n g on or r e turned to the s o i l . 3. The present or planned use. 4. The p o s s i b i l i t y to gather the waste a t the g a s i f i c a t i o n s i t e . 5. The expected t e c h n o l o g i c a l problems f o r g a s i f i c a t i o n although thesemight be overcome by f u r t h e r r e s e a r c h . 6. The expected power output per u n i t of area. 7. The most l i k e l y use of the power produced, p r e f e r a b l y f o r the crop p r o c e s s i n g . I f the waste can be used by the producers or processors, c o s t l y t r a n s p o r t i s avoided and no marketing i s required. The r e s u l t s of our f i e l d study are summarized i n t a b l e 1 with an e v a l u a t i o n of d i f f e r e n t crops. Three crops got a p o s i t i v e judgement and f i v e have to be s t u d i e d more i n d e t a i l . Corn cobs look a very a t t r a c t i v e feedstock f o r g a s i f i c a t i o n , because they are reasonably abundant w i t h i n the v i l l a g e s . Corn i s the major food crop i n t h i s r e g i o n ; i t s production i s stimulated by the N a t i o n a l Corn Program of Tanzania, which aims at the food production f o r urbanized areas. In t h i s program Ujamaa v i l l a g e s play an important r o l e . The corn i s produced as f o l l o w s : the s o i l i s c u l t i v a t e d by a t r a c t o r and/or by handwork. A l l the other a c t i v i t i e s are done manually. At h a r v e s t i n g the corn i s picked by hand and transported to the v i l l a g e . There the leaves and the cobs are removed and the g r a i n e i t h e r s t o r e d or s o l d to the N a t i o n a l Corn Program. Thus the corn cobs are removed from the land, but f i n d no use at a l l f o r the moment, except sometimes as

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

710

Table

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

Crop

THERMAL

1. E v a l u a t i o n o f t h e u s e o f a g r i c u l t u r a l waste from Arusha f o r small s c a l e energy p r o d u c t i o n by g a s i f i c a t i o n . Yield

Coffee

500-1000

Beans

200-1000

Corn hybr ide

CONVERSION OF SOLID WASTES AND BIOMASS

Waste

branches pulp

Dry waste yield kg/ha,j

Recycling to the soil

Possi c o l l e c t gasify

400-800 100-200

Recommendat ion

Energy use for crop processing

ι

270-530 67-130

industrial

-

1590-2010

milling

cattlefeed

2500-3000

2500-3000

cattlemulch

375-450 Sorghum hybride

Output mechanical energy kWh/ha,j

1 700

+/++

shel1ing drying

250-300

1 700

1 1 300

milling

"j

feed 750

shelling drying

500

> J

gation

Traditio­ nal

900-1800

300-600

chaff

300-600

chaff

+ 10

300-750

chaff

150-375

28.000

bagasse

Millet

300-750

600-1200 cattle•

200-500

milling

mulch +/++

7

shelling

I

millet

gation drying

100-250

J

millet Sugercane Bananas

?

Sisal

750-1600

Sunflower

500-1500

3500

?

fuel

stem

?

+

mulch

pulp

3000-6000

-

waste

+

100-400 acle Cotton

mulch

P

220-450

residue

Wheat

?

-

-

2000-4000

industrial



chaff

160-240

waste

chaff

280

waste

1400

-



67-270 2000 400-800

industrial gation

1070 1 100-160 J

+

800-1200

-

2300



destroyed oil cattlefeed

600-1200

Traditio­ nal Rice

*

-

* 190

}

polishing drying milling drying

further gation

Ground-

Wood

450-700

1000-1500

shells

100-175

branches sawmi11

200-800 100-150

67-120

fuel fuel

135-200 67-100

further

saw m i l l

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

*

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

49.

G R O E N E V E L D A N D WESTERTERP

Gasification Technology

111

c a t t l e f e e d i n very dry p e r i o d s . Some l a r g e s c a l e producers use them as mulch, but the compos t a t ion of the corn cobs takes several years and returns only a small amount o f organic m a t e r i a l to the s o i l and i s 10% of the t o t a l plant production, poor i n inorganics l i k e Nitrogen and Phosphate. The corn cobs therefore are already a v a i l a b l e i n the v i l l a g e without having an a l t e r n a t i v e use; the a g r i c u l t u r a l system i s not endangered by burning them. The power produced by the g a s i f i c a t i o n of corn cobs can be used f o r water supply, l o c a l e l e c t r i c i t y or d r i v i n g a corn m i l l . Such corn m i l l s are already operating i n many v i l l a g e s . In Arusha corn m i l l s , d r i v e n by an imported d i e s e l engine, are l o c a l l y constructed and s o l d i n the r u r a l areas. I t i s p o s s i b l e to include i n t h i s system a corn s h e l l e r and a g a s i f i c a t i o n u n i t . The s h e l l e r replaces the hand p i c k i n g of grains from the cob and so diminishes the amount of work i n the busy h a r v e s t i n g p e r i o d . In t h i s way the cobs are produced at the g a s i f i c a t i o n s i t e . The s h e l l e r can be d r i v e n by the same engine as i s used f o r the corn m i l l because i t consumes only a small amount of energy (2 kW) . The i n t r o d u c t i o n of g a s i f i c a t i o n of corn cobs i n an Ujamaa thus agrees with the f i r s t two e v a l u a t i o n c r i t e r i a , the other three c r i t e r i a w i l l be studied i n a s o c i a l - c o s t - b e n e f i t a n a l y s i s . Social cost-benefit analysis A s o c i a l c o s t - b e n e f i t a n a l y s i s gives information on the p r o f i t of a p r o j e c t and f u r t h e r on the i n f l u e n c e of the p r o j e c t on employment, production, consumption, savings, trade balance, r e d i s t r i b u t i o n of income e t c . Here the 'Guidelines f o r p r o j e c t evaluat i o n * of the Unido [9] are used. Both the investment and operat i n g costs of a p r o j e c t have to be d i v i d e d i n t o a) m a t e r i a l s , imported or d o m e s t i c a l l y produced b) labour, s k i l l e d or u n s k i l l e d c) i n t e r e s t depending on the way of f i n a n c i n g d) taxes p a i d . For the various s o c i a l groups (the government, labourers, tax payers, etc.) i t has to be determined to what extent they consume the a d d i t i o n a l income out of a p r o j e c t and how much w i l l be saved f o r reinvestment. F u r t h e r a premium has to be a l l o c a t e d f o r the import savings, the increase i n the use of u n s k i l l e d labour and a penalty f o r the use of scarce s k i l l e d labour. Based on t h i s information i t can be c a l c u l a t e d , whether the p r o j e c t i s p r o f i t a b l e f o r the v a r i o u s s o c i a l groups and the country as a whole. B e n e f i t s of corn m i l l i n g i n Tanzania f o r the owner. In many Tanzanian v i l l a g e s the corn f o r the l o c a l consumption i s brought once a week to the m i l l , where people pay 0.15 Tsh/kg (1 Tsh = 0.15 $ 1977) f o r the g r i n d i n g . The corn m i l l has a nominal c a p a c i t y of 600 kg/h and i s d r i v e n by a 20 kW engine. Such a u n i t of m i l l and engine costs around 33000 Tsh, however i t i s apparently too l a r g e f o r most of the v i l l a g e s . In these v i l l a g e s l i v e around 400 f a m i l i e s (average two a d u l t s , four c h i l d r e n ) each consuming about 800 kg corn/year. This f i g u r e has been obtained

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

from statements i n the v i l l a g e s and i s equivalent to 8 kJ/day f o r adults and 4 kJ/day f o r c h i l d r e n . The corn m i l l operates twice a day at sun r i s e and at sunset f o r a p e r i o d of around 2.5 hours/day; i t consumes d a i l y around 30 l t r of d i e s e l o i l , which costs 2.14 T s h / l t r . The s a i d d i e s e l o i l consumption r e l a t e s to a motor e f f i c i e n c y of about 15%, which i s r e l a t i v e l y low. Based on a d e p r e c i a t i o n of 5 years and 10% i n t e r e s t rate a cost b e n e f i t a n a l y s i s i s included i n table 2. In the same table a cost - b e n e f i t a n a l y s i s i s given i n case the corn m i l l e r would be able to replace the l i q u i d f u e l r e q u i r e d , by gas from corn cobs. Then the corn m i l l i s enlarged with a s u i t a b l e g a s i f i e r f o r 2000 Tsh. The economic advantages of the g a s i f i e r f o r the corn m i l l e r are evident i n view of the p r o f i t i n c r e a s e . Table 2 cost - b e n e f i t a n a l y s i s of a corn m i l l without (A) with g a s i f i c a t i o n (B) i n Tsh/day.* Daily benefits: 800 kg/day à 15 Tsh/100 kg Costs : 30 l t r fuel/day ; 3 l t r . labour (1 man) r e p a i r and maintenance d e p r e c i a t i o n (5 yr) i n t e r e s t (10%) total D a i l y p r o f i t f o r the Ujamaa community * 1 Tsh = 0.15

A

Β

120

120

64 16 14 18 5. 117' 3

and

6 16 16 19 6, 63' 57

$ (1977) .

S o c i a l c o s t - b e n e f i t a n a l y s i s of a g a s i f i e r From the preceding c a l c u l a t i o n i t can be seen that i n t r o d u c t i o n of g a s i f i c a t i o n i s very b e n e f i c i a l f o r the m i l l owner, i n this case the v i l l a g e community. We now w i l l evaluate the s o c i a l costs and ben e f i t s according to the Unido g u i d e l i n e s with t h e i r d i f f e r e n t methods of i n c r e a s i n g complexity: 1. at market value; 2. at a n a t i o n a l l e v e l ; 3. per s o c i a l group. ^^iZ£Î£_§£_5î§E}SÊ£_YËly k e a s o c i a l cost b e n e f i t a n a l y s i s of the a d d i t i o n of g a s i f i c a t i o n to a corn m i l l the i n vestment costs have to be on annual b a s i s . We assume that the i n vestments are financed by the government and are repaid by the Ujamaa community i n f i v e years i n c l u d i n g an i n t e r e s t of 10%, i n equal i n s t a l l m e n t s (annuity of 0.26). Investment costs f o r the g a s i f i e r (Tsh) annual gasifier costs - m a t e r i a l s imported 800 208 - l o c a l u n s k i l l e d labour 200 52 - m a t e r i a l s , domestic 1000 260 total 2UÔÏÏ ~520 e

T o

m a

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

49.

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Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

Further i t i s assumed that 25 Tsh of the f u e l cost i s the net import saving of o i l per day, thus 9125 Tsh/yr. The e x t r a operating costs f o r the use o f g a s i f i c a t i o n can be seen from t a b l e 2: 2 Tsh/ day f o r r e p a i r , thus 730 Tsh/yr i n the category of domestic mater i a l s . In t a b l e 3 an input-output a n a l y s i s f o r the g a s i f i c a t i o n p r o j e c t i s given from the n a t i o n a l p o i n t of view f o r a p e r i o d of 5 years of operation. Table 3 Input-output a n a l y s i s of the a d d i t i o n of a g a s i f i e r to a corn m i l l (Tsh/yr) . Annual input : c o n s t r u c t i o n costs (imported), annuity + 208 c o n s t r u c t i o n costs (domestic), annuity + 312 operating costs (domestic) + 730 Annual output: f o r e i g n exchange savings FE - 9125 [Annual n a t i o n a l aggregated consumption at market value, MC 7875 The remainder of the savings to the Ujamaa v i l l a g e s of 64-25 Tsh/ day r e f e r to the costs i n c u r r e d i n Tanzania f o r converting the imported crude o i l i n t o d i e s e l o i l i n the s t a t e owned o i l r e f i n e ry, transport of the d i e s e l o i l to the Ujamaa v i l l a g e and l o c a l taxes. These savings to the v i l l a g e , however, do not represent a saving to the n a t i o n as a whole. On the contrary s k i l l e d labour (o.a. l o r r y d r i v e r s ) w i l l loose some work and thus wages (+_ 2 Tsh/ day), the r e s t i s l o s t by the government. On an annual b a s i s the d i e s e l o i l savings per g a s i f i e r represent around 78 b a r r e l s of crude o i l . In Tanzania e a s i l y 4000 g a s i f i c a t i o n u n i t s can be i n s t a l l e d l e a d i n g to a p o t e n t i a l savings of around 300000 b a r r e l s of imported crude o i l per year. ^ £ § I X Ë Î Ë _ 2 I L § - D § £ i 2 D I _ l Ê Y Ë l The market value of the net aggregate-consumption b e n e f i t s i n a given year of the p r o j e c t as given i n t a b l e 3 does not r e f l e c t the s o c i a l opportunity costs on a n a t i o n a l s c a l e . As f o r the f o r e i g n exchange p o s i t i o n the heavy pressure on the balance of payment has r e s u l t e d i n s t r i c t q u a n t i t a t i v e import c o n t r o l and export s u b s i d i e s to maintain the d o l l a r value of the Tsh. A d o l l a r of f o r e i g n exchange i s worth substant i a l l y more than the o f f i c i a l exchange r a t e : the opportunity cost of f o r e i g n exchange r e l a t i v e to i t s o f f i c i a l market p r i c e i s 1 + φ, φ r e p r e s e n t i n g an premium. U n s k i l l e d labour i s found i n surplus and the market wage exceeds the opportunity costs of employing a d d i t i o n a l workers; the opportunity costs w i l l be denoted 1 + λ, i n which λ represents the u n s k i l l e d labour premium; λ w i l l be zero or negative. The s o c i a l value of s k i l l e d labour i s measured by the c o n t r i b u t i o n i t s s e r v i c e s make to aggregate consumption b e n e f i t s for the country: u s u a l l y s k i l l e d labour i s underpaid. In p a r a l l e l with φ and λ, χ i s defined as the s o c i a l premium on the market value of a s k i l l e d worker. With respect t o the absolute value of the parameters φ, λ and χ the f o l l o w i n g can be s a i d . If f o r example φ = 1, t h i s means that imported goods are put at the d i s p o s a l o f t h e i r consumers a t only 50% o f t h e i r r e a l p r i c e . A l s o i f λ = -1 (extreme v a l u e ) , u n s k i l l e d labour has no s o c i a l value because otherwise s t i l l the primary n e c e s s i t i e s a

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

714

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

of l i v e f o r unemployed u n s k i l l e d labourers has to be provided f o r . And a l s o i f χ = 1, a s k i l l e d worker earns only 50% as wage of h i s r e a l c o n t r i b u t i o n to the n a t i o n a l economy. The net aggregate consumption b e n e f i t s a f t e r i n c o r p o r a t i n g the opportunity cost premiums, SC, now becomes: SC = MC + φ FE + XL + xW i n which FE are the f o r e i g n exchange savings, L the u n s k i l l e d l a ­ bour costs and W the s k i l l e d labour c o s t s . With the values of φ = 0.5, λ = -1.0 and χ = 1.0 we f i n d SC = 7875 + 0.5(9125-208) - 1 * 52 + 1 * 700 = 12982 Tsh/year. We see that the b e n e f i t s f o r the n a t i o n a l economy are much l a r g e r f o r the i n t r o d u c t i o n of the g - a s i f i c a t i o n technology a f t e r c o r r e c ­ t i n g f o r the s o c i a l opportunity c o s t s . èîîêIlËÎË_22_§_iîê£i:2Bêî-.I^YêI_êBË--2ËI-Ë2£ÎËl_SÎ2HE Another and more p r e c i s e approximation to the net aggregate consumption b e n e f i t s of the p r o j e c t takes i n t o account the adjustments necessary when the s o c i a l value of funds devoted to investments exceed the s o c i a l value of the same funds devoted to consumption. This i s the case when the government has not been i n a p o s i t i o n to r a i s e savings - and investment - to the point where the marginal r a t e of r e t u r n on investment, q, i s equal to the s o c i a l r a t e of discount, i . I f 100 u n i t s consumed now i s considered equivalent to 110 u n i t s consumed the next year, the s o c i a l r a t e of discount i i s 10%. A u n i t of money withdrawn from consumption to an i n v e s t ment now should have a r a t e of r e t u r n of at l e a s t i i n order to increase the consumption i n f u t u r e years to the d e s i r e d l e v e l . The opportunity cost of investment, p , i s defined as the r a t i o of the s o c i a l value of investment to the s o c i a l value of consumpt i o n , where " s o c i a l value" i s understood to mean the value of the r e l e v a n t time stream of aggregate - consumption b e n e f i t s discounted back to the present at the s o c i a l r a t e of discount. The value of p can be determined according to the f o l l o w i n g formula [ 9 ] : inv Q-s)q i-sq i n which s i s the economy-wide marginal r a t e of reinvestments of p r o f i t s , expressed as a f r a c t i o n of t o t a l p r o f i t s ; a l l the parameters are assumed to remain constant over time. This means that the value of one Tsh f o r f u t u r e consumption, i f invested now, equals p Tsh's consumed now. Once i t i s recognized that p does not equal 1, i t becomes e s s e n t i a l to evaluate the net e f f e c t of a p r o j e c t on the mix of consumption and investment i n the economy. To evaluate the net e f f e c t of the g a s i f i c a t i o n p r o j e c t on the r a t e of investment, i t i s necessary to d i s t i n g u i s h a l l the b e n e f i t and cost flows that make up SC as w e l l as the accompanying cash t r a n s f e r s according to the group that gains or loses and to estimate the r e s p e c t i v e marginal consumption and saving propensit i e s of each group. Three broad groups of gainers and l o s e r s have to be d i s t i n g u i s h e d i n the g a s i f i c a t i o n p r o j e c t : the Ujamaa farmers F, s k i l l e d labourers W and the Government G. I f the construct i o n costs of the p r o j e c t are paid out of government revenues. l n v

i n v

=

i n v

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

i n v

G R O E N E V E L D A N D WESTERTERP

49.

715

Gasification Technology

1

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

without any corresponding r e c e i p t s - so that the governments budget i s not r a i s e d by general t a x a t i o n - the government i s the l o s e r and the taxed p u b l i c i s not a f f e c t e d . Moreover we assume that the u n s k i l l e d labour i s provided by the Ujamaa v i l l a g e s f o r the l o c a l e r e c t i o n of the g a s i f i e r . The s i m p l i f i e d approach used before f o r MC and SC now no more can be a p p l i e d and cash flows have to be used f o r every year of the p r o j e c t . This i s done i n t a b l e 4. Table 4 Cashflows i n 1000 Tsh/year f o r one g a s i f i e r . 0 Years Benefits 1. F u e l savings 1 D Domestic currency 1 F Foreign exchange 1 W S k i l l e d labour Costs 2. Construction costs 0.2 2 L U n s k i l l e d labour 1.0 2 D Domestic m a t e r i a l s 2 F Foreign exchange 0.8 3. Operating costs 3 D Domestic m a t e r i a l s Transfers 4. Rental and i n t e r e s t paid -

4

5

2

3

13.50 9.13 0.73

13.50 9.13 0.73

13.50 9.13 0.73

13.50 9.13 0.73

13.50 9.13 0.73

-

-

-

-

-

.73

.73

.73

.73

.73

.52

.52

.52

.52

.52

1

The government G loses the f u e l savings and c o n s t r u c t i o n c o s t s . S k i l l e d labour W loses some work. The Ujamaa farmers F gain the f u e l savings and lose the operating c o s t s . The a d d i t i o n a l oppor­ t u n i t y costs due to the f o r e i g n exchange exponents are sustained by the government, since the government i s i n e f f e c t s u b s i d i z i n g the use o f imported inputs i n a g r i c u l t u r e by making them a v a i l a b l e to the farmer a t the o f f i c i a l exchange r a t e . The same reasoning can be set up f o r the other s o c i a l groups. Although the cash t r a n s f e r item 4. i s not r e l e v a n t to the e v a l u t a t i o n of aggregate b e n e f i t s and c o s t s , they are c e r t a i n l y r e l e v a n t to the d i s t r i ­ b u t i o n of these b e n e f i t s and c o s t s . Hence, they too must be con­ sidered here i n assessing the a l l o c a t i o n of net b e n e f i t s among the three groups G, W and F. Item 4. represents a gain to G and a l o s s to F. The d i s t r i b u t i o n of net consumption b e n e f i t SC by group can be summarized as f o l l o w s : SC = SC + SC + SC SC = 1 D + 1 F + 1 W - 3 D - 4 - X2L SC = - (1 + χ) 1 W SC = - l D - 2 + 4 + 0. Θ means that the go­ vernment i s w i l l i n g to lose 1 + Θ Tsh i n other more developped areas i n the country i n order that the consumption i n the Ujamaa v i l l a g e r a i s e s with 1 Tsh. The s o c i a l r a t e of discount i i s s t i l l unknown and we w i l l c a l c u l a t e V f o r s e v e r a l values of i and Θ. The values of the general parameters we have assumed are given i n t a b l e 5. The present v a l u e s of the cash flows i n the year 0 f o r the v a r i o u s r a t e s of s o c i a l discount and the general parameter values are given i n t a b l e 6. With these data the v a r i o u s c a l c u l a t i o n s are executed, r e s u l t s are given i n t a b l e 7 and Figure 3. C

S

S

S

W

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

F

Table 5 Value of general parameters F o r e i g n exchange premium u n s k i l l e d labour premium s k i l l e d labour premium marginal r a t e of r e t u r n on investment m a r g i n i a l r a t e of reinvestment of p r o f i t s s o c i a l r a t e of discount a s s o c i a t e d s o c i a l p r i c e of investment marginal propensity to save: farmers s k i l l e d workers government

Table 6

Φ λ

= + 0.5 - 1 .0 + 1 .0 Χ 0. 20 q 0. 30 s i = 0. 075; 0.10; 0.20 pinv = 9. 33; 3.50; 1 .0 SF s

w

SG

= 0. 20 s

0. 30

= 0. 90

Present values of cash flows i n year 0 (1000 Tsh) S o c i a l r a t e of discount

Fuel savings 1 D Domestic currency 1 F F o r e i g n exchange 1 W S k i l l e d labour C o n s t r u c t i o n costs 2 L U n s k i l l e d labour 2 D Domestic m a t e r i a l s 2 F F o r e i g n exchange 3 D Operating costs 4 Rental and i n t e r e s t paid

7.5%

10%

20%

50.69 34.28 2.74

46.52 31.50 2.52

33.19 22.73 1 .82

0.2 1.0 0.8 2.74 1 .95

0.2 1 .0 0.8 2.52 1 .79

0.2 1 .0 0.8 1 .82 1 .28

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

49.

GROENEVELD AND WESTERTERP

Gasification Technology

111

ν

Figure 3.

Socioeconomic present value of the project: (A) one gasifier; (B) gasifier and shelter

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

one

718

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

Table 7 Present value of net b e n e f i t s of one g a s i f i e r i n year 0 (1000 Tsh) Item S o c i a l r a t e of discount 7.5% 10% 20% MC , n a t i o n a l aggregate consumption 29.5 26.1 16.1 f o r e i g n exchange savings F 21.9 33.5 30.7 SC , net consumption b e n e f i t , farmers 83.2 76.4 54.8 SC , net consumption b e n e f i t , government - 34.0 - 31.4 - 23.0 sc w ; net consumption b e n e f i t , s k i l l e d labour - 5.5 - 5.0 - 3.6 SC , net consumption b e n e f i t , t o t a l 28.2 43.7 40.0 s o c i a l value of SC 222 115 54.8 l ' C s o c i a l value of SC -102 -289 - 23.0 - 19 3.6 - 9 c w s o c i a l value of S s o c i a l value of SC - 86 4 28 c V B e n e f i c i a l e f f e c t s of the p r o j e c t , 0=0 - 86 4 28 9 0= 0.5 weight on r e d i s t r i b u t i o n to Ujamaa 25 61 55 1 .0 136 119 83

V F

G

F

c

G

G

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

w

At small values of i and Q the net present value i s negative because the government has a much l a r g e r propensity to r e i n v e s t then the Ujamaa v i l l a g e r s . But i f the government i s serious i n t r y i n g to increase the net aggregate consumption b e n e f i t s i n the Ujamaa v i l l a g e s (0 > 0.4) the p r o j e c t has to be evaluated p o s i t i v e (V > 0). The government i s the l o s e r i n t h i s p r o j e c t because the s t a t e owned r e f i n e r y produces l e s s d i e s e l o i l and the tax income on the s a l e s of d i e s e l o i l i s l o s t . The Ujamaa v i l l a g e r s l o s e the operating costs but gain the much higher value of the f u e l savings. The s k i l l e d labour loses some employment, but i t seems l i k e l y that they can f i n d work somewhere e l s e . The i n t r o d u c t i o n of g a s i f i c a t i o n i s thus b e n e f i c i a l f o r the U j a m a a - v i l l a gers and i s under almost a l l circumstances of n a t i o n a l i n t e r e s t . I f not only a g a s i f i e r i s i n s t a l l e d but a l s o a s h e l l e r at the corn m i l l , so that hand p i c k i n g of the cobs i s replaced by a machine, investment i s increased. At the same time unworthy work i n the already very busy h a r v e s t i n g season i s avoided. The investment i n a s h e l l e r i s around 6000 Tsh. The preceding c a l c u l a t i o n s have been repeated f o r a p r o j e c t , where a g a s i f i e r plus a s h e l l e r are i n s t a l l e d i n a v i l l a g e . Results are given i n graph IB. From t h i s graph can be read that at 0 > 0.5 t h i s extended p r o j e c t has a pos i t i v e value with as b e n e f i t s mainly the replacement of unworthy work, f o r which the government has to pay i n f o r e i g n currency f o r the imported p a r t s of a l o c a l l y constructed s h e l l e r . As 0 f o r the g a s i f i e r and s h e l l e r i s higher than f o r the g a s i f i e r alone, the government has to s a c r i f i c e more i n the c i t i e s to b e n e f i t the r u r a l areas. Conclusions - According to the presented e v a l u a t i o n c r i t e r i a the g a s i f i c a t i o n of corn cobs i s acceptable from the economical and a g r i c u l t u r a l p o i n t of view i n the r u r a l areas around Arusha (Tanzania).

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch049

49.

GROENEVELD AND WESTERTERP

Gasification Technology

719

- The gasification system is relatively simple of construction and local maintenace is possible. If the sytem is connected to the already existing corn mills in the villages it is appropriate to the existing socio cultural system. - The economic calculations made clear that the use of gasification is attractive for both the owners of the corn mill and the government. The advantages for the government are the savings on imported oil and the extra income created for the users of the corn mill (inhabitants of the rural villages). The government loses income from taxes and from the production and transport of diesel o i l . - The presented evaluation methods can and should be used for gasification projects in other areas as they are undertaken at the moment in Nigeria and Indonesia, taking into account the differing government policies in their countries. Aknowledgement We are grateful to professor Feil, for his continuing stimulating interest and professor Van Swaaij, who is the research director of our gasification studies at the Twente University of Technology. We are also grateful to our colleagues Schaffers, Skolnik and Hartoungh, who contributed considerably in some part of these studies and to the Dutch Ministery of Development Cooperation and the Tanzania Small-Industry Development Organisation, who made the activities in Tanzania possible. Literature cited 1. Energy and Power, Scientific American Book, 1971. 2. A. Makhijani, Energy and Agriculture in the Third World, Ford Foundation, Energy Policy Project Report, 1974. 3. M.J. Groeneveld, W.P.M. van Swaaij, The design of co-current moving bed gasifiers fuelled by biomass, this symposium. 4. M.J. Groeneveld, W.P.M. van Swaaij, Gasification of char particles with CO2 and H2O, Sixth International Symposium on chemical reaction engineering, Nice, 1980. 5. I.E. Cruz, Producer gas as a fuel for the diesel engine, University of the Philippines, 1977. 6. P. Schläpfer, J. Tobler, Theoretische und praktische Untersuchungen über den Betrieb von Motorfahrzeuge mit Holzgas, Bern, 1937. 7. C.K. Dietz, Ammonia production from Brava Cane, IGT symposium Energy from biomass and wastes, Washington, D.C., 1978. 8. J. Nyerere, Freedom and development, Oxford University Press, 1973. 9. P. Dasgupta, Guidelines for project evaluation United Nations, New York, 1972. RECEIVED

December 7, 1979.

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

INDEX

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

A Acetaldehyde 218 Acetone 218 decomposition products 221 Acid, acetic 218 Acid, formic 218 Activation 303-306 reaction, pyrolysis 303/ thermodynamics of 307 African iron ore 110 Afterburning 60, 405 by the multiple combustion method, N O prevention at 516/ Agricultural and forestry wastes, third world applications of pyrolysis of 671-688 residues 86,317,337,691,697 crop 618 densification systems for 179-193 pelleted 187 in a rotary kiln, pyrolysis of 337-350 as supplementary fuel for diesel engines, producer gas from 649-669 waste, availability of 708 Air 292,307 classification 4, 129, 352 classifier light fraction yield, research 131/ classifier test configuration, vertical 130/ equilibria, carbon-steam- 308/, 309/, 310/ -CH /stoichiometric 311/ feed system 383 for gasification 286 heaters, process 295 introduction technique, pebble bed process 678 pollution control 65-66 devices 67 pressure requirements 286 secondary (overfire) 64 soot blowing, compressed 64 Alcohol(s) biological conversion to 209 fermentation 621, 647 fuels production 691-699 Alkali carbonates 370 concentrations 119 silica ratio 102 x

4

Alternator system, Duvant gasifier/ dual-fuel diesel motor 642/ Aluminum 63, 97 eliminator 552/ mixed in municipal refuse, elimination of 550 Ammonia 43, 358, 443 capacity, requirement for additional 351 case investment 38 from wood 38 Anaerobic digestion 619,621 process 7 of wet biomass 618 Animal(s) 153 dung 617 wastes 618, 621 Anthracene start up oil 25 Apparatus, bench-scale test 229 Aromatic(s) by-products 209 highly condensed 432 hydrocarbons, condensed 484 oils, highly 484 products 218 polynuclear 357 Ash 134, 198, 200, 229, 534, 589 chute quenching system 66 content 135,262,454 char, high 351 -free combustibles fuel 144 fusion temperatures 139 average 139/ leaching of heavy metals from 493 heavy metal in 535/ pyrolysis 550 -melting furnace 589 -melting and waste heat power generation, integrated system for solid waste gasification and 588/ removal 46, 385, 466 continuous 71 section of gasifier 645/ system 383 residue, inert solid 291 and slag, properties of pyrolytic .... 593 and total carbon, analysis for 122/ zone 46 Assessment conclusions, technology 327,328/ Athabasca oil sands 317

723 In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

724

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Β Bacteria 153 Baking 303 Bale, rectangular 186 Barbados 694 Bark 86,355 Ponderosa pine 102 white fir 102 Bed unit, auger 67 Benzene 424, 428, 433, 480, 484 homologs, C / 9 484 production 435/ yield of ethylene and 435/ Biological activity 160 process 7 stability 155, 160 Biomass anaerobic digestion of wet 618 conversion 22 in meeting the energy needs of the rural populations of devel­ oping countries, potential of 617-633 routes 330/ table of supplementary sources for 332 technology of R&D program, Canada's 317-333 -derived activated carbon, thermo­ dynamics of pyrolysis and acti­ vation in the production of waste- or 301-314 design of co-current moving-bed gasifiers fueled by 463-477 Energy Systems Branch 13 ethanol production from 691-697 to fuels and feedstocks, thermochemical conversion of 13-26 methanol production from 697-699 replacement of natural gas, payback from 90/ residues using the gasifier/dual fuel engine techniques, power gen­ eration from 635-647 resources at various cost levels, availability of 320/ supply, current sources of 618-620 technology and resource assessment chart 319/ Birds 153 Boiler(s) 6, 7, 38, 64, 148, 196 application 103-104 cleaning methods 64 dacha 64 electrical generation 295 emissions grate burning pelleted fuels, stoker-fired 202/

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8

Boiler(s) (continued) energy recovery in 65 fuel 15,38 heat recovery 511 installation, FBC 105/ oil/gas fired 51 rertofit system, capital and operating costs for a wood gasification/ .. 52t shutdown 296 stoker 135 tube corrosion 60 water-tube wall furnace/ 65 Boiling behavior of the condensate from the pyrolysis of old tires ... 448/ Bolivia 694 Brazil 625 Brick-making 621 Briquetting 205 Bulk densities 134 Bunker 706 Bureau of Mines 291 Burner 386 emission rate, demonstration unit Roemmc 202/ system 384 Burning 424 of municipal solid waste, mass 50-66 rate per person 60 rate of the refuse 93 Butadiene 434 Butane 365 Butter 63 Butylène 209

Cs/9-benzene homologs 484 CH /stoichiometric air equilibria, carbon-steam311/ Cables 480 Calcium oxide 374, 428 Calorific value(s) 341, 348 gas, low 351 product gas, typical yield and 401/ Canada's biomass conversion technology R&D program 317-333 Canadian hybrid poplar 370 Carbon 302, 307 activated 301 analysis for ash and total 122/ black 428, 557, 564 dispersion of 568/ and rubber vulcanization, properties of 565/ content and volumetric reduction ratio, comparison of ignition loss, caustic-soluble 595/ conversion efficiency 238 dioxide 11,294,301,329,365,640 4

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

725

INDEX

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

Carbon (continued) disulphide fixed monoxide

442 303 120,211,261,294, 329, 364,·365 and hydrogen synthesis gas Fischer-Tropsch liquids via 209 oxides 209, 352 oxysulphide 442 -steam-air equilibria 308/, 309/, 310/ -steam-methane/stoichiometric air equilibria 311/ -steam equilibria 311/, 312/ -steam-oxygen equilibria 312/ thermodynamic of pyrolysis and activation in the production of waste- or biomass-derived activated 301-314 weight of 329 Carbonates 119 alkali 370 Carbonization bed, fixed 640 Carbonization gas 444 Carcinogens 36 Cardboard 295 Cashflowsin year 0, present values of 716/ Cashflowsin 1000 Tsh/year for one gasifier 715/ Catalysis in wood gasification, role of 369-378 Catalysts, direct liquefaction of wood using nickel 363-368 Catalysts, inorganic salts as gasification 370 Catalytic gasification 46 Caustic soda 499 Cellulose 363 carbon conversion efficiency 239/ cotton 240 prior research on 251/ fuel pellets 287 gasification 238 physical properties for 248 pure 304 pyrolysis 240, 244, 247, 410 equilibria 306/ volatilization of 238 Cellulosic materials, pyrolysis of 216 Ceramics 603 Cigarette papers and filters 295 Cleaning methods, boiler 64 shot 64 system, wood gas 384 Chain cleavage 216 Channeling 403 Char 36, 38, 210, 216, 238, 240, 251,267, 303,369, 526, 541,564, 598, 678, 682

Char (continued) analysis for pyrolysis of straw and stover 343/ compression strength of 568/ formation 93, 220/, 364 gasification 237 high ash content 351 oil 275 mixture composite, percent available energy in 673/ yields as a function of air/feed .... 684/ oxidation 93 and reduction zones 287 particle diameter 467/ by pyrolysis of wood, production of oil and 35/ reaction zone 294 refining of 557, 563 residue 240 selling price of 40/ yield(s) 343 from biomass by pyrolysis, typical 305/ Charcoal 275,618,643,650, 655, 681,690 briquettes 190 consumption 660 Charring 303 Chemicals, low molecular gaseous and liquid 479 Chemical production 38-41 from wood—estimated investment.. 39/ from wood—product revenue requirements 41/ Chicago 59 China 621 Chloride(s) 119 corrosion 59 metallic 301 Chlorine 64 Chopping 185 Coal 17,86,301,371,654 anthracite 287 cleaning 109 conversion 22 gas producer, low volatile 287 gasification technology 369 particle density of 135 supplementary firing and co-firing of 65 Coconut shell 301 Cogenerated products 30-32 costs 32 Cogeneration (production of electricity and steam) 360/ based on wood feedstock 15 facilities 32 by wood combustion 34/ Coke 287,604

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

THERMAL CONVERSION OF SOLID WASTES AND

726

Combustibles, better thermal conversion of very poor 644 Combustion 14, 109 chamber 511 complete 64 development activities, direct 16 energy recovery from wood residues by fluidized-bed 85 equipment, stationary 689 facilities—estimated investment, wood 31 /gasification processes 302 heat of 330/ of liquid wastes 143 method, NO prevention at afterburning by the multiple 516/ of pine sawdust and pellets, heats of 171/ reaction, gas phase 94 residues 181-183 of solid wastes, fluid bed 93-108 system(s) development of modular biomass gasification and ...285-290 systems, direct 14-15 for ordinary refuse 605/ tests 99 wood 30 facilities—product revenue requirements 33/ production of electricity by 35/ and steam (cogeneration) by .. 34/ zone 46 Combustor(s) 110, 114 gas 285 gasifier/reactor/ 287 general arrangement of a gasifier/reactor 289/ high heat release 93 industrial fluid bed 94 MS-FBC 113/ off-gas analysis 583/ pressurized fluid bed 94 two-stage 67 waterwall 6 wood-fiueled 15 Commercial activities 354, 358 application 48 facilities 89-91 Comparison of ignition loss, causticsoluble carbon content, and volumetric reduction ratio 595/ Composition 167 Compost plant 60 Composting 61 Compression direct 169 experiments 171/ strength of char 568/ Compressors, stacks, and bales 186

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x

BIOMASS

Condensate from the pyrolysis of old tires 450/-451/ boiling behavior of 448/ viscosity of 448/ Condensation 486 Condenser mounted on top, gas scrubber with 646/ Condensing 563 Conservation and Recover Act, Resource (RCRA) 66 Controlled-air incinerators 67 Conversion to alcohols, biological 209 efficiency, carbon 238 cellulose 239/ to methanol, catalytic chemical 209 other methods of effective waste .... 644 process evaluations 317 processes, economic assessment for bioenergy 324/-325Z thermochemical projectedfiscalyear 1979 budget— 24/ projects, biomass 25 projects, geographical distribution of 24/ systems using wood feedstocks, economic overview of largescale thermal 29-42 technology in biomass, the role of .. 317 technology R&D program, Canada's biomass 317-333 temperature 467/ Convertor appropriate technology pyrolysis .... 675 design, Ghana 678 system, Indonesian technology development pyrolytic 680/ Conveyor belts 569 Conveyor, screw 405 Corn cob(s) 711 pyrolysis powdered 245/ mill, cost-benefit analysis of 712/ mill, input-output analysis of the addition of a gasifier to 713/ milling in Tanzania for the owner, benefits of 711 stover pyrolysis, gas composition from 345/ Corrosion 6,62,71,99 boiler tube 60 causes 64 chloride 59 tube erosion64 Cost(s) -benefit analysis of a corn mill 712/ -benefit analysis, social 711 of a gasifier 712

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

727

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INDEX

Cost(s) (continued) capital estimate 323 of a gasification system for small communities 271 of wood gasification systems 48 cogenerated products 32 considerations, production 203 for conventional and densified waste collection 163/ disposal 11 of dry process PUROX system, running 585/ electricity 32 energy 204 feedstock 48 of large modular refuse " incinerator systems 80/ with heat recovery, investment.... 79/ LBG gas 50/ MBG gas 50/ net disposal 62 operating 160, 501 comparison of plant space, capitol cost and 600/ effect of steam value on 77 for the installations 77 for the pyrolysis case 38 for scrap tires, disposal 571/ of small modular refuse incineration system 78/ solid waste collection 161 of solid waste management unit operations 152/ for the source separation of solid waste 271 steam 32 for the wood biomass feedstock 53 wood gas production 48 for a wood gasification/boiler retrofit system, capital and operating 51/ utilities and operating 504/ Cotton cellulose 240 Countercurrent operation 406 Countries gasifier appropriate for 707 potential of biomass conversion in meeting the energy needs of the rural populations of developing 617-633 social and economical aspects of the introduction of gasification technology in the rural areas in developing 705-719 with sucrose production levels, lesser-developed 693/ Cracking, naphtha 408/ Cracking/reforming of volatile matter 237

Crop(s) irrigation residues Cubes

317 649 619 188

D Data acquisition system 264 Decomposition 140,410 of polymers, thermal 409 ratio of combustibles 512/ Defense, Department of 69 Deflection 172 Dehydration 216 Demand integration, supply 625 facility, actual 526-529 plant, flow sheet of 528/ plant test, operation data of 529 Densification 197 apparatus, energy requirements for commercial 175/ balance sheet 192 device, experimental ram 165/ energy requirements, biomass ...169-177 plant processes 197 power requirements for 191 process(es) 158, 164, 175 sequence, typical 183 of solid waste 258-261 system(s) 258 for agricultural residues 179-193 available today 183-184 solid waste shredding and 264 test configuration 170/ work vs. density 170/ Densified biomass fuels, benefits of the use of 196 Densifier 132-134 Density(ies) bulk 179 HC1 597/ NO 97/ for various products, values and .... 182/ Department of Defense 69 Department of Energy (DOE) 13-26, 29, 94 Design(s) of co-current moving-bed gasifiers fueled by biomass 463-477 concept, basic 672-676 criteria, gasifier 381 of a 100 t/d gasifier 474 modular unit 68 plant 29-30 Destrugas process 405 Desulfurization, flue gas 109 Devolatization of wood 46 Diesel engine, producer gas from solid waste fuels in 651/ x

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

728

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Diesel (continued) generator system 384 for power generation, Northern Saskatchewan using 391/ Differential thermal analysis 410, 416 Digestion process, anaerobic 7 Disposal costs 11 Disposal of municipal refuse by the two-bed pyrolysis system 541-555 Distillation 640 techniques 223 Dockfenders 569 DOE (Department of Energy) 13-26, 29, 94 Drainage 610 Drop-shatter test(s) 136 results 138/ Dryer, steam 509 Drying 197 application 104 -devolatization zone 46 installation, FBC hog fuel 106/ -pyrolysis process 509 behavior of nitrogen oxide in exhaust gas of 516/ direct pyrolysis process and incineration process, comparison of 517 performance of 513 pilot plant 510/ zone 44 DSS 115 feed system 114 feedstocks, experiments with MSW and 118-120 Dual fuel engine set-up, multicylinder 657/ Dulong diagram 330/ Dulong's formula 329, 341 Dust 611 from the direct combustion system, chemical composition of 611/ Eco-fuel II process 143-149 description of the Bridgeport .146-149 Eco-fuel II properties of 145/ Economic(s) 161-164,569 analysis 72-81,348,685-687 incineration plant capacities considered for economic analysis 73/ assessment for bioenergy conversion processes 324/-325/ bases 75/ comparison model 321-328 considerations 295-299 of the dry process PUROX system . 584 evaluation 48-55 feasibility of the system, a preliminary 553

Economic(s) (continued) of gasification system, tentative .267-271 of operating large modular refuse incinerators with heat recovery and particulate control 81/ of operating an 18.2 metric tons/day refuse incinerator .... 79/ overview of large-scale thermal conversion systems using wood feedstocks 29-42 process 358, 538, 613 system 89 Economical aspects of the introduction of gasification technology in the rural areas in developing countries, social and 705-719 Efficiency of the steam system 89 Effluence and recovery comparison of 506/ EHE 110, 113/, 114, 115 El Salvador 694 Electric power plant 32 Electrical energy, production of heat and 455/ Electricity 30-32,360 costs 32 hydro/nuclear 331 selling price of 34/ and steam (cogeneration) by wood combustion 34/ steam production and cogeneration of 360 by wood combustion, production of 35/ Electrification by biomass conversion of local wastes, potential for rural 643 Electrostatic precipitator 65 Eluates of pyrolysis slag from experiments with municipal refuse 459/ Emission data pilot plant 98/ Energy 662/ balance 462,580/ mass and 476/ of municipal refuse pyrolysis unit 532/ for the pyrolysis of municipal refuse in Kiener System 461/ in char-oil mixture composite, percent available 673/ conversion, small scale 262-264 costs 204 data 346 Department of (DOE) 3-12, 94 and materials, recovery of 3-12 for the MMC, replenishable organic 195-205 needs of the rural populations of developing countries, potential of biomass conversion in meeting 617-633 plants, refuse-fired 61

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

729

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Energy (continued) from producer gas, percentage 668 product/feed ratios 346, 347/ production of heat and electrical .... 455/ recovery in boilers 65 from MSW and sewage sludge using MS-FBC technology 109-123 rate vs. temperature 549 of resource and 593 from solid wastes, modular incinerators for 67-82 and volumetric reduction by new pyrolysis furnace, integrated system for solid waste disposal with 587-601 from wood residues by fluidizedbed combustion 85 requirements, biomass densification 169-177 requirements for commercial densification apparatus 175/ revenue 322 supply-demand pattern, rural 621 systems, fluid flame 90/ system, rural reference 628/ utilization, solid waste gasification and 291-299 yield, operation with emphasis on 454 Engine(s) 386, 706 characteristics of low Btu gas ... 637-638 diesel 379 dual-fuel engine operation of single cylinder 665/ dual-fuel engine operation of a six-cylinder 664/ experimental work with a single-cylinder 650-655 experimental work with a six-cylinder 655-663 and gas producer performance, equations for evaluating 667 -gas producer systems, multicylinder and single cylinder ... 666/ 1000kVA gen set with dual- diesel 646/ generating set with dual-fuel six cylinders supercharged 639/ -generator 258 set-up, multicylinder dual-fuel 657/ performance data of Deutz 390/ potential for developing nations to use biomass fuels in vehicle 689-703 producer gas from agricultural residues as supplementary fuel for diesel 649-669 producer gas from solid waste fuels in a diesel 651/

Engine(s) (continued) technique, power generation from biomass residues using the gasifier/dual fuel 635-647 Engineering model of the reduction zone, reaction 466 Entrainedflow,reactors characterized by 44 Environmental pollution data 610 Environmental Protection Agency (EPA) 4,36,64,94,210 Erosion 6, 99 -corrosion, tube 64 Ethane 294, 365 Ethanol 625,691 fermentation, investment requirements for 696 production from biomass 691-697 Ether, triethylene glycol dimethyl 218 Ethyl formate 218 Ethyl hydrosulphide 442 Ethylene 209,211,434 and benzene, yield of 435/ Europe 60 European processes, review of 397-421 PTGL-plants, status of 403 PTGL-technology, survey of 401 Eutectics, low melting 119 Evaporation of domestic sewage sludge, multisolid fluidized-bed combustion process with contact 111/ Exhaust gas(es) 515 air pollutants in 610/ combustion 341 of drying-pyrolysis process, behavior of nitrogen oxide in .... 516/ N O and HC1 contents of 596 results of analyses of py rolytic gas and 5 89 Experimental procedure 339-341, 509-523 results and discussion 513 results, typical 609/ Experiments, high-flux 246 Experiments, low-flux 243 Explosives 38 Exports as a function of the prices of raw sucrose, molasses, and petroleum fuels, imports and 695/ Extruded logs 188 Extruded solid waste, samples of ram and screw 157/ Extrusion modified mil-pac system, ram 154/ process 169 schematic of 154/ screw 154/ processing, distortion of die wall during 166/ x

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

730

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Extrusion (continued) ram rate vs. pressure of RDF, work of screw temperature vs. pressure

153 174/ 172/ 153 174/

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

F Farm heating 348 FBC boiler installation 105/ hog fuel drying installation 106/ specifications, longview 104/ Feed material 371 physical nature of 355 system, air 383 system, wood 367, 381 Feeder 545 Feedstock(s) 285 characteristics 341 cost(s) 48 for the wood biomass 53 experiments with MSW and DSS 118-120 experiments with MSW and water 117-118 for the gasification process, selection of 709 methanol from biomass 22 options 691-694, 697, 699 oxygenated 209 pyrolysis products comparison using various 222/ refuse as a substitute 351-354 stover 339 straw 339 thermochemical conversion of biomass to fuels and 13-26 wood 22 economic overview of large-scale thermal conversion systems using 29-42 Fermentation, alcohol 621,647, 689 Fertilizers 618 synthetic nitrogen 38 Fibers 186 synthetic 38 wet 186 Fiji 694 Film, gasification of waste 235 Fines, content of 134 Fire hazard 151 Firing and co-firing, supplementary of coal 65 of fuel-oil 65 of solvents 65 of waste oil 65 Firewood 617

Fischer-Tropsch liquids via a carbon monoxide and hydrogen synthesis gas 209 Fixed-bed pyrolysis 38 reactors characterized by 44 wood gasifier 47/ single stage 45/ Flare system 383 Flies 151 Florida 69 Flow models, cold 469 patterns, double circular 470/ process 557 sheet 612/ rates, recycle 117 Fluid bed(s) combustion of solid wastes 93-107 combustors, industrial 94 combustors, pressurized 94 Municipal Solid Waste fired 94 wood waste fired 94 Fluidized-bed 262, 557 combustion energy recovery from wood residues by 85 process with contact evaporation of domestic sewage sludge, multisolid 111/ process with steam generation in external heat exchanger, multisolid 112/ dense-phase 110 entrained 110 external 117 gasification 46, 354 process, pyrolysis of plastic waste and scrap tires using 423-439 pyrolysis 425/, 427/ of plastic waste and scrap tires, products of 426/ reactors 424,527/ gasification of solid waste in dual 525-540 single 543 system for wood gasification 356/ technology 85 Footwear 569 Forest biomass 355 Forestry 317 wastes, third world applications of pyrolysis of agricultural and 671-688 Forintekfluid-bedgasifier 373/ Forintek, laboratory studies at 371 Fossil fuel 146 France 689 Fruits 575

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

731

INDEX

Fuel(s) 267 aluminum-free 97 analysis distribution by size, peanut hills 198/ ash 144 automotive 38 benefits of the use of densified biomass 196 biomass 317 gasification at the focus of the Odeillo (France) 1 Mw solar 237-255 boiler 38 carbonaceous 261 cells 38 for co-combustion with oil, producing a storable transportable 143-149 consumption, auxiliary 519/ consumption, diesel 660 debris 104 for diesel engines, producer gas from agricultural residues as supplementary 649-669 densified biomass 198 engine operation of single-cylinder engine, dual665/ engine operation of six-cylinder engine, dual664/ and feedstocks, thermochemical conversion of biomass to 13-26 form, choice of biomass derived 329-331 fossil 146 gas(es) 46, 302 analysis of 354/ by-product 210 effect of oxygen enrichment on heating value of 359/ effect of wood moisture on heating value of 356/ from wood, program for the production of 355 gaseous 291 high moisture 144 imports and exports as a function of the prices of raw sucrose, molasses, and petroleum 695/ mode, diesel 659/ single 656/ mode, dual656/, 659/ oil 36 supplementaryfiringand co-firing of 65 pellet(s) analyses 199/ cellulose 287 sale of roemmc 204/ product end use 299 production alcohol 691-699

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

th

Fuel(s) {continued) production (continued) liquid 36-38 for wastes process for 227-236 molten salt 228/ from wood—estimated investment, liquid 37/ from wood—product revenue requirements, liquid 39/ properties 138-139 refuse-derived (RDF) 4,63 saving, diesel 662/ shredded and air classified solid waste 99 solid, liquid, and gaseous 621 source separation system, proposed combustible 260/ specification summary, longview ... 104/ stokerfiredboiler emissions grate burning pelleted 202/ substitutes, fossil 143 user experience with densified biomass 201 in vehicle engines, potential for developing nations to use biomass 689-703 Furnace(s) 6, 509 application of theoretical data to real world 313 ash-melting 589 /boiler, water-tube wall 65 electric 560 firing, industrial 295 high efficiency wood 379 integrated system for solid waste disposal with energy recovery and volumetric reduction by new pyrolysis 587-601 melting 604 profile of 606/ rotary kiln 480 pyrolysis 589 schematic of 591/ shaft 486,557,604 vertical 292 stoker-fired 201 wall 63 temperature in pyrolysis 599/ Funds, Urban Waste Technology 11

Garbage 351 Gas(es) 351,419,447,460,569 -air mixer 706 air pollutants in exhaust 610/ analysis 372 combustor off583/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

732

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Gas(es) (continued) analysis (continued) off230 produced pyrolytic 594/, 595/ carbonization 444 cleanup system 258 combustible 533 produced from the mixed waste .. 538/ from pulp sludge 535/ combustor 285 components vs. temperature 549/ composition, product 592/ converter, drawing of 458/ converter, two-stage solid waste pyrolysis with drum reactor and 441-462 cooler 706 cost, LBG and MBG 50/ emission, noxious 94 exhaust 515 gas, results of analyses of pyrolytic 589 N O and HC1 contents of 596 -fired boiler, oil/ 51 flue 533 analysis of incineration 537/ incineration from pulp sludge 534/, 535/ fuel 46,302 effect of oxygen enrichment on heating valve of 359/ effect of wood moisture on heating valve of 356/ generation 358-360/ generator and location of reaction zones, schematic arrangement of a pyrolysis-based 288/ hazardous 160 hydrogen chloride 428 intermediate-Btu 32 lean 401 low-Btu 15,262,618,637 engines, some characteristics of 637-638 installation, operation diagram of 636/ low calorific value 351 low heating value 227 medium-BTU 17 natural 17, 53, 331 noxious 610 obtained through the pyrolysis of old tires, process 449/ -phase combustion reaction 94 power generation, wood gasification for 379-394 processing methods, comparison of 613/ producer cross-section of down-draft suction-type 658/ x

Gas(es) (continued) producer (continued) percentage energy from 668 performance 663 equations for evaluating engine and 667 system, multicylinder and single cylinder engine666/ product 488, 610 purification 486 high pressure 223 pyrolysis 280 analysis of 578/ components, produced 547/ composition, from corn stover .... 345/ composition, from straw 344/ harmful substances in 442-444 recovery system for classified refuse 605/ sampling system 383-384 scrubber with condenser mounted on top 646/ from solid waste fuels in a diesel engine, producer 651/ stream, high temperature 294 supply, threatened curtailment of natural 351 synthesis 15, 32 turbines 38, 360 typical yield and calorific value of product 401/ utilization of recovered 573 utilization, surplus 644 velocity and reaction rate 413/ wood 53, 276 cleaning system 384 production costs 48 reforming of 375/ yields 343 vs. temperature 548/ Gaseous substances, harmful 454 Gasifier(s) 46, 230, 386, 706 appropriate for developing countries 707/ ash removal section of 645/ batch fed downdraft 264 bench-scale molten salt 228/ biomass 287 cashflows in 100 Tsh/year for one 715/ coal 22 co-current moving-bed .. .465/, 475/, 707/ description of 463-464 fueled by biomass, design of .463-477 construction of 589 to a corn mill, input-out analysis of the addition of 713/ design criteria 381 design of a 100 t/d 474 downdraft 262 or updraft 304

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

733

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Gasifier(s) (continued) /dual-fuel diesel motor alternator system, Duvant 642/ /dual-fuel engine technique, power generation from biomass residues using 635-647 fluidized-bed 406 Forintek fluid-bed 373/ fueled with source separated solid waste, operation of a downdraft 257-274 for a 1000 kVA system 645/ laboratory-scale solid waste 265/ in operation, solid waste 266/ options, analysis of the vehicle mounted 700/ oxygen blown 17 /reactor/combustor 287 general arrangement of 289/ social cost-benefit analysis of 712 solid waste 293/ temperature profile 389/ 20 TPD test 590/ vehicle-mounted 699-700 vertical shaft 295, 403 wood analysis of co-current moving-bed 464 fixed-bed 47/ single-stage fixed-bed 45/ in year 0, present value of net benefits of one 718/ Gasification 14, 261-262, 291, 296, 364, 409,411-414, 486 accomplishment of 292-294 air for 286 apparatus 640 of acid pit sludge 231 of biomass 22 and combustion systems, development of modular 285-290 at the focus of the Odeillo (France) 1 Mw solar furnace 237-255 -indirect liquefaction process development units 21/ catalytic 370 catalysts, inorganic salts as 370 catalytic 46 cellulose 238 char 237 cycle and mechanical power generation overall performances . 635 downdraft 263/ environment, resource and social impact of 386 facility, specification of 640-641 fluidized-bed 46,412 fundamentals of pyrolysis and 402 future of solid waste 299 th

Gasification (continued) graphite 370 hybrid popular 374 -indirect liquefaction systems 15-22 of leather offal 235 of organic waste 637 plant, V.U.B. pyrolysis and 417/ present industrial application of 294-299 process 705 combustion/ 302 description 43-46 selection of a feedstock for 709 solid waste 487/ thermal 257 reactions 216, 380 results of hybrid poplar 375/, 376/ of rubber tires 231-235 of solid waste 262 in accordance with the SFWFUNK-PROCESS 485-489 ash-melting and waste heat power generation integrated system for 588/ in dualfluidized-bedreactors 525-540 and energy utilization 291-299 future of 299 system 297/ for small communities 259/ suspended particle 412 systems 7 for small communities, capital costs of 271 tentative economics of 267-271 technology low-BTU 15 in the rural areas in developing countries, social and economical aspects of the introduction of 705-719 of waste film 235 wood 32-36, 43-55, 235, 379 /boiler retrofit system, capital and operating costs for 51/ facilities—estimated investment . 33/ facilities—product revenue requirements 37/ fluidized-bed system for 356/ for gas and power generation 379-394 oxygen blown 331 plant, schematic of 382/ 355 program role of catalysis in 369-378 status 46-48 systems, capital costs of 48 technology · 369 tests, operating characteristics during 355/ zone 46 and oxidation 44

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

734

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Gasoline 327,618 polymerization to 225 pyrolysis gas purification and polymerization to 224/ from solid wastes by noncatalytic, thermal process 209-226 Generation curve income 298/ Generator 285 refuse-fired steam 60 system, diesel 384 Geographic distribution of thermochemical conversion projects 24/ Geometries, tar production at different 469 Germany 61,689,690 Ghana convertor design 678 Glass 97,352,575,693 Goals, Canadian PRGL R&D 331-332 Grain drying 348 Grain size 262 Graphite gasification 370 Grate system, mass burning 63 Grate units, basket 67 Grinding 185 Guatamala 694 Gumz model 464 Guyana 694

H HC1 removal, scrubbers for 66 Halogens 229 Hamburg 59 Harmful gaseous substances 454 Harmful substances in pyrolysis gases 442-444 Hazard, explosion 401 Hazardous substances 581 Health 587 Hearth, multiple 261 Heat balance 531 of mixed waste pyrolysis 537/ and electrical energy, production of 455/ exchanger, multisolid fluidized-bed combustion process with steam generation in external 112/ penetration 473, 474/ power generation, integrated system for solid waste gasification, ash-melting and waste 588/ of reaction 407-409 recovery boiler 511 estimated investment costs for large modular refuse incineration systems with 79/ mass and energy balance for an incinerator with 73/

Heat (continued) recovery (continued) and particulate control, economics of operating large modular refuse incinerators with 81/ system from MR 495 source considerations 307-313 transfer 99,403,473 equations 466 Heating direct 406 indirect 406 internal 403 value of fuel gas, effect of oxygen enrichment on 359/ value of fuel gas, effect of wood moisture on 356/ Hemacellulose 363, 410 hydrolysis of 368 Hides 603 Homologs, naphthalene and its 480 Horsepower, brake 655 Horsepower distribution 204/ Hudson Bay plant details 381-385 Human scavengers 153 Human wastes 618 Hydrocarbon(s) 358 condensed aromatic 484 destroying pathogens and other 65 low molecular weight 352 resins, thermoplastic 484 Hydrochloric acid 443 Hydrofluoric acid 443 Hydrogen 261,302,352,364,428 chloride 352, 499 gas 428 cyanide 443 sulphide 352 synthesis gas, Fisher-Tropsch liquids via a carbon monoxide and 209 thiocyanate 442 weight of 329 Hydrolysis 424 Hydropulping technology 6 Ignition loss, caustic-soluble carbon content and volumetric reduction ratio, comparison of Ignition loss of residue Illuminants Imports and exports as a function of the prices of raw sucrose, molasses, and petroleum fuels Incineration flue gas analysis of from pulp sludge

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

595/ 512/ 303 695/ 493 534/ 537/ 535/

735

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Incineration (continued) option, flow diagram of 500/ plant capacities for economic analysis 73/ process, comparison of dryingpyrolysis process, direct pyrolysis process and 517 system(s) 498,499 costs of small modular refuse .... 77/ estimated investment for 18.2metric ton modular 76/ with heat recovery, estimated in­ vestment costs for large modular refuse 79/ for treatment of MR, application of PTGL processes as an alternative to 495 Incinerator(s) 6, 60, 65, 485 controlled-air 67 economics of operating an 18.2 metric tons/day refuse 79/ for energy recovery from solid wastes, modular 67-82 extent of use of modular 68 with heat recovery, mass and energy balance for 73/ with heat recovery and particulate control, economics of operat­ ing large modular refuse 81/ 18.2-metric-ton 72 plants 397 surface-rich fume 296 starved-air 67 systems 227 cost of large modular refuse 80/ India 618,619,621,627,694 Indonesia(n) 618,619 preliminary test data from 685/ technology development pyrolytic convertor system 680/ Inerts 97 Infectious material 229 Installation, large modular 77 Investment ammonia case 38 capital 61-62 costs for large modular refuse incineration systems with heat recovery 79/ estimated chemicals production from wood 39/ costs for 18.2-metric ton modu­ lar incineration system 76/ liquid fuels production from wood 37/ wood combustion facilities 31/ wood gasification facilities 33/ methanol case 38 plant facilities 30

Investment (continued) requirements for ethanol fermentation for methanol production from wood Iron Italy

699 696 699 610 689

J Jamaica 694 Jamming phenomena 164 Japan 59, 65, 525 characteristics of municipal refuse and sewage sludge (SSL) in 495-498 overview of PTGL processes in 493-507 pyrolysis developing in 494/ Japanese refuse 577/ PUROX system demonstration test on simulated 573-586 Japanese and U.S. refuse, compari­ son of 573/ Jet, penetration depth of 472/ John Deere/Papakube Cuber, schematic of 157/ Κ Kiener System energy balance for the pyrolysis of municipal refuse in 461/ material balance for the pyrolysis of municipal refuse in 461/ two-stage refuse plant 445/ Kiener waste pyrolysis system 444-462 Kerosene 618, 621 Kiln pyrolysis 563 rotary 67,262,424,557 furnace 480 indirectly heated 434 pyrolysis of agricultural residues in 337-350 pyrolysis process 338/ screw424 Kinetics and mechanism 409-415 Kunii-Kunugi process 525

Labor charges 77 Laboratory-scale experiments 424-428 Laboratory studies at Forintek 371 Laguna 655 Landfill(s) 9, 60, 227, 295, 296 life 161 sanitary 257 concept 61 Landfilling, direct 493 Leachate 160

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

736

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Leaching of heavy metals from ash .... 493 Leather 603 offal, gasification of 235 scraps 227 Leaves 185 Levoglucosan 218 tars 216 Lignin 363 Lignite 301 Lignocellulosic materials 240, 692, 697 Lime 499 Limestone 119, 583, 604 Liquefaction catalytic 36 direct 14 systems 22-25 of wood using nickel catalysts 363-368 processes 257 development units, biomass gasification-indirect 21/ studies, thermal 364 systems (midterm), gasificationindirect 15-22, 20/ technology, medium BTU gasification (MBG) 18/ Liquid fuels 618 production 36-38 from wood—estimated investment 37/ from wood—product revenue requirements 39/ Log chips, whole 86 Log yard wastes 86 Lubrication, die 135

M Magnesium 119 chips 63 oxide 371,428 Magnet 148 Manure 180, 371 Market value, analysis at 712 Mass and energy balances 476/ Mass transfer equations 466 Material balance 460,531 for the pyrolysis of municipal refuse in Kiener System 461/ composition of input 546/ considerations 294-295 recovery operation with emphasis on 444 and pyrolysis option, flow diagram of 503/ and pyrolysis system 498, 501 Mechanical rapping 64 Melting development of solid waste disposal system with pyrolysis and .603-614

Melting (continued) furnace 604 profile of 606/ system, pyrolysis498, 501 vessels 424 Metal(s) 352, 454, 603, 621 concentration and solubility test result 594/ disposition in slag, trace 584/ heavy 513 in ash 535/ pyrolysis 550 molten 403 and other constituents in MSW, typical concentrations of 116/ in scale, typical concentrations of 116/ in sewage sludge, typical concentrations of 116/ Methanation reactors 17 Methane 7,211,294,307,364, 365, 380, 428,618,621 additions 331 injection 468-469 tracer 470/ and wood hybrid 332 Methanol 36, 38, 43, 332, 691, 697 from biomass feedstocks 22 case investment 38 catalytic chemical conversion to ... 209 production 361,361/ from biomass 697-699 from wood investment requirements for 699 synthesis 647 358 gas to Methyl acetate 218 Methyl ethyl ketone 218 Methylnaphthalene 432 Military bases, potential use of modular incinerators 69 Mill, hammer-type 529 Mines, Bureau of 291 Model calculations, thermodynamic 466/ Gumz 464 of the reduction zone, reaction engineering 166 Schlâpfer 464 Modular incinerators on military bases, potential use of 69 Moisture 97, 134, 198 content 167,355 of the refuse 155 Molasses and petroleum fuels, relative value of raw sucrose and 694-696 Motor/alternator system, Duvant gasifier/dual-fuel diesel 642/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

737

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Moving bed gasifier, co-current 465/, 475/, 707/ analysis of 464 description of 463-464 Mozambique 694 Municipal refuse (MR) 442, 529 analysis 530/ composition of 497/, 589, 592/ elimination of aluminum mixed in .. 550 eluates of pyrolysis slag from ex­ periments with 459/ general characteristics of 496/ handling options, operating costs for 505/ in Kiener System, energy and mate­ rial balance for the pyrolysis of 461/ pulverized 530/ pyrolysis 531/ unit, energy balance of 532/ raw material and the reaction prod­ ucts in experiments with 456/-457/and sewage sludge (SSL) in Japan, characteristics of 495-498 by the two-bed pyrolysis system, disposal of 541-555 Municipal solid waste (see MSW) Municipal waste, comparison of alter­ native facilities for disposal of .... 598 Muskeg 317 MS-FBC combustor 113/ operating conditions 121/ technology, background on 109-110 technology, energy recovery from MSW and sewage sludge using 109-128 MSW (municipal solid waste) 127, 145,221,317 analysis, typical 115/ and DDS feedstocks, experiments with 118-120 feed system 114 pelletized 115 processing facility materials flow diagram 100/ properties of 145/ and sewage sludge using MS-FBC technology, energy recovery from 109-123 typical concentration of metals and other constituents in 116/ and water feedstocks, experi­ ments with 117-118

Ν Naphtha cracking

221 408/

Naphthalene 424,432 and its homologs 480 Nations to use biomass fuels in vehicle engines, potential for developing 689-703 Nature, fibrous or nonfibrous 179 New York 59 markets, average sucrose prices on London and 696/ Nicaragua 694 Nickel carbonate 367 catalysts, direct liquefaction of wood using 363-368 Raney 364,367 Nitrogen 280,294,329 compounds 443 content 15 fertilizers, synthetic 38 oxide(s) 229 in exhaust gas of drying-pyrolysis process, behavior of 516/ NO prevention at afterburning by the multiple combustion method 516/ Nuclear fission (breeder) 332 x

Oat straw 341 Odors 160 Oil 327, 369, 401, 447, 486, 557, 678 anthracene start up 25 char mixture composite, percent available energy in 673/ and char by pyrolysis of wood, production of 35/ diesel 618, 637 distillate 53 drums 678 fuel 36 /gas fired boiler 51 heavy 317 highly aromatic 484 properties of 564/ producing a storable, transportable fuel for co-combustion with 143-149 pyrolysis 432,480 condenser 677/ processing 483/ refinery 483/ from special wastes 482/ residual 53 sands 317, 363 Athabasca 317 selling price of pyrolytic 40/ shale 221 yields as function of air/feed, char and 684/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

738

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Olefin(s) 223 mixture, polymerization of 210 selective pyrolysis to 210-223 Organic(s) compounds, trace 301 industrial wastes, special 444 liquid 351 disposal of 46 oxygenated 223 Oxidation zone 706 gasification and 44 and pyrolysis zone, analysis of 468 Oxidizing agent 292 steam as an 292 Oxygen 302, 307, 363, 364 blowing 313 -blown wood gasification 331 content 290 enrichment experiments 358 enrichment on heating value of fuel gas, effect of 359/ equilibria, carbon-steam312/ weight of 329

Pallets, transport 295 Panama 694 Paper 371 packaging 295 Paraffin waxes 430 Paris 59 Particulate(s) analysis of 583/ control, economics of operating large modular refuse incinerators with heat recovery and 81/ fine 360 Pathogens and other hydrocarbons, destroying 65 PCB addition on slag composition, effect of 582/ Peanut hulls, fuel analysis distribution by size 198/ Peat 301, 317 conversion 337 pyrolysis, comparison 348 of straw, stover, and 349/ pyrolysis system 337 Pebble-bed process air introduction technique 678 Pellet(s) 188 cohesion 135 densified 153 densities 134, 135 length 134 distribution 137/ quality 201 Pelleted byproduct 187

Pelletizer, animal feed 132 Peru 168, 619 Petroleum fuels, relative value of raw sucrose, molasses, and 694-696 Phenol(s) 218,357 formation 366 Philippines 649 Pilot plant 509-512,544/ experiments 428-439 Pipe, galvanized 678 Plant actual 560 description 541 design, basis for 499 facilities investment 30 life 321 operating requirements 72, 74/, 598 Plastic(s) 38, 442, 444, 480, 575, 603 film 63 pyrolysis reactor with a feed screw for 431/ waste and scrap tires, pyrolysis of .. 429/ products of fluidized-bed 426/ Plumes, particulate stack 71 Plywood trim 86 Pollutants, atmospheric 196 Pollutants in exhaust gas, air 610/ Pollution air and water 493 control 161 air 65-66 devices 67 data, environmental 610 regulations, air 397 Polyethylene 402,419,432 pyrolysis of 432, 433/ Polymers, thermal decomposition of .. 409 Polypropylene 432 Polystyrene 419 pyrolysis 418/, 419 Poplar hemicellulose 366 Poplars, hybrid 363 Canadian 370 gasification 374 results of 375/, 376/ Potassium carbonate 370, 374 Pottery 621 Powder, high density 145 Power comparison of generating and required 596/ consumption 134 generation from biomass residues using the gasifier/dual fuel engine technique 635-647 integrated system for solid waste gasification, ash-melting and waste heat 588/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

739

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Power (continued) Northern Saskatchewan using diesel for 39It overall performances, gasification cycle and mechanical 635 wood gasification for gas and 379-394 requirements for densification 191 Precipitator, electrostatic 65, 583 Pressure 189-191 application 175 to bale straw or fiber 190/ tap locations, thermocouple and 113/ Price of char, selling 40/ of electricity, selling 34/ of pyrolytic oil, selling 40/ of steam, selling 34/ Process analysis 517-520 development units, biomass gasification-indirect liquefaction 21/ equipment capacities 200 material streams, three-way split . 198/ options in resource recovery, technical 4 Processes, pyrolysis 406 Product(s) cogenerated 30-32 feed ratios, mass 342/ ligno-cellulosic 640 sampling of raw material and 489 uses 346-348 yield and composition 341-345 Programming, linear 19 Propane 341, 365 Propene 434 Propylene 209 Prototype unit, description of 352 PTGL processes as an alternative to incineration for treatment of MR, application of 495 evaluation of 498-507 to industrial wastes, application of 498 in Japan, overview 493-507 PTGL-project of the University of Brussels 416 Public Health Service 61 Pulp sludge, combustible gas from .... 535/ Pump, peristaltic 230 PUROX system demonstration test on simulated Japanese refuse 573-586 economics of the dry process 584 running costs of dry process 585/ schematic flow of a typical 574/ schematicflowsheetof the dry process 576/ Pyrolysis 14, 237, 275-283, 292, 303-306, 407, 409-411, 621, 640

Pyrolysis (continued) and activation in the production of waste- or biomass-derived activated carbon, thermodynamics of 301-314 and activation reactions 303/ of agricultural and forestry wastes, third world applications of 671-688 of agricultural residues in a rotary kiln 337-350 ash, heavy metals in 550 -based gas generator, and location of reaction zones, schematic arrangement of 288/ basic principles of waste 397-421 of cellulose 216,244,247,410 flash 240 prior research on 251/ characteristic times for solar flash .. 248/ comparison with peat 348 comparison of straw, stover, and peat 349/ convertor, appropriate technology .. 675/ convertor system, Indonesian technology development 680/ data, experimental 213/ of differing special wastes 480 with drum reactor and gas converter, two-stage solid waste 441-462 of dry biomass 618 energy balance of municipal refuse 532/ equilibria, cellulose 306/ equipment 641 fixed-bed 38 fluidized-bed 425/ furnace 589 integrated system for solid waste disposal with energy recovery and volumetric reduction by new 587-601 schematic of 591/ wall temperature in 599/ gas(es) 280 analysis of 578/ chromatography 410, 416 components 547/ composition from corn stover .... 345/ composition from straw 344/ harmful substances in 442-444 purification and polymerization to gasoline 224/ and gasification, fundamentals of .. 402 and gasification plant, V.U.B 417/ heat balance of mixed waste 537/ kiln 563 of agricultural residues in a rotary 337-350

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

740

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Pyrolysis (continued) mechanism 238 and melting, development of solid waste disposal system with 603-614 -melting option, flow diagram of .... 502/ -melting system 498, 501 of mixture of sludge and plastic waste 536 municipal refuse 531/ in Kiener System, energy and material balance for 461/ oil(s) 36,480 condenser 677/ processing 483/ refinery 483/ from special wastes 482/ of old tires boiling behavior of the condensate from 448/ condensate obtained through 450/-451/ process gas obtained through 449/ solid residues obtained through 452/-453Z viscosity of the condensate from 448/ to olefins, selective 210-223 option,flowdiagram of material recovery and 503/ physical phenomena occurring during 411 pilot plant study on sewage sludge 509-523 plant flow sheet of 558/ layout of 562/ rotary drum 481/ plastic waste and scrap tires 429/ products of fluidized-bed 426/ using afluidized-bedprocess 423-439 of polyethylene 432, 433/ polystyrene 418/, 419 process(es) 257, 404, 406 behavior of nitrogen oxide in exhaust gas of drying516/ developing in Japan 494/ drying509 direct and incineration process, comparison of 517 performance of 513 pilot plant 510/ partial oxidation 671 rotary kiln 338/ for scrap tires 557-572 test plants for 560/ products comparison using various feedstocks 222/ formation of primary 219/

Pyrolysis (continued) products (continued) formation of secondary 220/ nitrogenous 280 prototype for whole-tire 434-439 of pulp and paper sludge 535 rate of 93 reaction overview, high temperature 217/, 219/ reactor(s) 430 the biomass flash 241 with a feed screw for plastic 431/ recovery of raw materials by 481/ schematic 212/ slag from experiments with municipal refuse, eluates of 459/ of the solid waste 291 of special wastes 482/ of straw and stover, char analysis for 343/ system(s) 7 detailed schematic of 340/ Kiener waste 444-462 material recovery and 498, 501 peat 337 two-bed disposal of municipal refuse by 541-555 flow diagram of 542/ pilot plant of 545 temperature 558/, 566/-567/, 568/ thermochemical formation of gases of oxygenated liquids by 209 typical char yield from biomass by 305/ unit 279/ basic principles of 399-421 of differing special 480 with drum reactor and gas converter, two-stage solid .. .441-462 heat balance of mixed 537/ water, treatment of 550 of wood, production of oil and char by 35/ zone 44, 706 analysis of the oxidation and 468 Pyrolytic gas and exhaust gas, results of analyses of 589 oil, selling price of 40/ recovery of raw materials from special wastes 479-484 Pyrolyzer 277/

Quenching system, ash chute

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

563 66

741

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Recovery R comparison of effluence and 506/ Radiation, solar 240 of energy and materials 3-12 Raney nickel 364 operation with emphasis on Raw material(s) 203/ material 444 heterogeneous biomass 19.8 resource preparation 486 nontechnical issues in 9 and product, sampling of 489 process system developed by by pyrolysis, recovery of 481/ national project 498 and the reaction products in extechnologies, developmental periments with municipal studies of 8/ refuse 45^-457/ technical process options in 4 recovery of 466/ Recycling 257 from special wastes, pyrolytic 706 recovery of 479-484 Reduction zone reaction engineering model of 466 d-RDF 483/ process flow 127-134 Refinery, pyrolysis oil 563 storage 140-141 Refining, char 71 effects 140/ Refractory damage physical properties of 134-138 Refuse Reaction burning rate of 93 exothermic 291 co-disposal of scrap tire and 593 gasification 380 comparison of Japanese and U.S 573/ of heat 407-409 composition of 60, 573 low temperature endothermic 291 direct combustion system for products in experiments with ordinary 605/ municipal refuse raw matederived fuel (RDF) 4, 63, 144, 181 rial and 456/-457Z low-grade 146 pyrolyzer 291 preparation and proprieties of watershift 464 densified 127-142 zones 44 processing plants 148 Reactor(s) production tests, summary of 354/ assembly 372 properties of 139/ biomass flash pyrolysis 241 work of extrusion of 172/ characterized during storage tests, daily temby entrained flow 44 peratures for cubed and by fixed-bed 44 shredded 159/ by fluidized-bed 44 -fired energy plants 61 by stirred moving-bed 44 -fired steam generator 60 combustor, gasifier 287 gas recovery system for classified .. 605/ general arrangement of 289/ generation per person 60 continuous 480 handling 62-63, 286 cracking 526 high moisture 579/ engineering aspects, chemical 414-415 incineration system, costs of small fluidized-bed 374, 403,415, 527/, 543 modular 77/ bench-scale 416 incineration systems with heat and gas converter, two-stage solid recovery, estimated investwaste pyrolysis with drum 441-462 ment costs for large modular .. 79/ gasification 258 incinerator(s) of solid waste in dual fluidizedeconomics of operating an 18.2 bed 525-540 metric tons/day 79/ prototype 438/ with heat recovery and particufor whole-tire pyrolysis 437/ late control, economics of pyrolysis 430 operating large modular .... 81/ with a feed screw for plastic 431/ systems, cost of large modular .... 80/ quartz 242/ Japanese 577/ spout-fluid bed 402 PUROX system demonstration stirred-tank 402 test on simulated 573-586 types 261-262 from Kitakyushu City, properties vertical shaft 415 of urban 607/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

742

THERMAL

CONVERSION OF SOLID WASTES AND

Refuse (continued) mixing ratio, typical 578/ moisture content of 155 municipal 68, 371 solid fuel (RDF) from mixed 351 plant, Kiener System two-stage 445/ properties 607, 608 as a substitute feedstock 351-354 treated at the Tokyo plant, properties of classified 608/ Regulated utility 30 Residue(s) agricultural 691,697 conversion 46 crop 618 as supplementary fuel for diesel engines, producer gas from 649-669 characteristics of 180-181 combustion 181-183 composition of 189 conversion, wood 46 crop 180 dried 617 forest 180 ignition loss of 512/ logging 181 pelleted agricultural 187 sawmill 181, 192 solid 447, 460 obtained through the pyrolysis of old tires 542/-453Z Resource assessment chart, biomass technology and 319/ Conservation and Recovery Act (RCRA) 66 and energy, recovery of 593 recovery 257 pilot plant 353/ Revenue requirements, product chemicals production from wood— 41/ liquid fuels production from wood— 39/ wood combustion facilities 33/ wood gasification facilities 37 Rice hulls 654 Rice husks 678, 679, 681 Rodents 151 Rubber 227,432,603 compounds 566/, 567/ sheets 569 tires, gasification of 231-235 Rugs .. 444 Rural energy supply-demand pattern 621 Rural populations of developing countries, potential of biomass conversion in meeting the energy needs of 617-633

BIOMASS

S Safety 587 shoes, actual use tests of 570f Salt(s) 403 as gasification catalysts, inorganic .. 370 molten 402 fuel production from wastes using 227-236 gasifier, bench-scale 228/ process for fuel production for wastes 228/ test facility 230-231 Santa Susana 233/ sodium halide 229 test facility, schematic diagram of .. 232/ Sampling system, gas 383-384 Sand(s) oil 317,363 disengager 110, 114 recycle rate 117 Sander dust 86 Sanitary landfill concept 61 Sawdust 185,278,355 analysis of pine 171/ and pellets, heats of combustion of pine 171/ Scale, typical concentration of metals and other constituents in 116/ Scandinavia 59 Schlapfer model 464 Screening 129 Scrubber(s) 65,339 with condenser mounted on top, gas 646/ for HC1 removal 66 venturi 88 water 460 Scrubbing 485 SFW-FUNK-PROCESS, gasification of solid waste in accordance with 485-489 Silage 575 Silica sand 110 Slag(s) 403,610,611 composition 581/ effect of PCB addition on 582/ formation 71 leaching test results 582/ properties of pyrolytic ash and 593 removal 71 and soot 447 trace metal disposition in 584/ Sludge 371 acid 480 and plastic waste, pyrolysis of mixture of 536 pulp 537/ incinerationfluegas from 535/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

743

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Sludge (continued) pyrolysis of pulp and paper 535 sodium-based pulp mill secondary .. 103 Slugs 153 Separation of the product, cryogenic 404 system, conventional source 260/ system, proposed combustible fuel source 260/ sludge (SSL) 59 general characteristics of 496/ in Japan, characteristics of municipal refuse and 495-498 multisolid fluidized-bed combustion process with contact evaporation of domestic ... 111/ pyrolysis, pilot plant study on 509-523 typical concentration of metals and other constituents in .... 116/ using MS-FBC technology, energy recovery from MSW and 109-123 Shavings 278, 355 Shells, coconut 654 Shoes, actual use tests of safety 570/ Shredded refuse 153 Shredded solids 143 Shredder 258,354 scrap tire 562/ waste 480 Shredding 4, 352, 560 and densification system, solid waste 264 process 144 secondary 129-132 SNG 32 Social and economical aspects of the introduction of gasification technology in the rural areas in developing countries 705-719 Social group, analysis on a national level and per 714 Socio-economic present value of the project 717/ Sodium 119 -based pulp mill secondary sludge .. 103 carbonate 370 melt 229 Solar flash pyrolysis, characteristic times for 248/ Solar radiation 240 Solid fuel (RDF) from mixed municipal refuse 351 Solid waste 292 commercial 68 costs for the source separation of .... 271 cubes with wood chips, comparison of 267

Solid waste (continued) densification of 258-261 disposal with energy recovery and volumetric reduction by new pyrolysis furnace, integrated system for 587-601 disposal system with pyrolysis and melting, development of ...603-614 fluid-bed combustion of 93-108 fuel, shredded and air classified 99 fuels in a diesel engine, producer gas from 651/ gasifier 293/ laboratory-scale 265/ in operation 266/ gasification 262 in accordance with the SFWFUNK-PROCESS 485-489 ash-melting and waste heat power generation, integrated system for 588/ in dualfluidized-bedreactors 525-540 and energy utilization 291-299 process 487/ gasification system 297/ for small communities 259/ modular incinerators for energy recovery from 67-82 municipal 67, 69, 181, 209, 304 experimental results from pyrolyzing material derived from 211 firedfluidbeds 94 programs 95-102 by a noncatalytic, thermal process, gasoline from 209-226 operation of a downdraft gasifier fueled with source separated 257-274 problem 257 pyrolysis with drum reactor and gas converter, two-stage 441—462 shredding and densification system 264 source separation of 258 urban 3-12 Solubility test result, metal concentration and 594/ Solvents, supplementary firing and co-firing of 65 Soot blowers, high-pressure steam 64 blowing, compressed air 64 corrosion and buildup of 71 formation 246 removal, slag and 447 SSWEP 99 parametric test results 101/, 102/ Starch content 179 Steam 30-32,360,499

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

744

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Steam (continued) carbon-CH /stoichiometric air equilibria 311/ -air equilibria 308/, 309/, 310/ equilibria 312/ -oxygen equilibria 312/ costs 32 dryer 509 generation 109 in external heat exchanger, multisolidfluidized-bedcombus­ tion process with 112/ generator(s) 196 pulverized coal-fired 203 refuse fired 60 as an oxidizing agent 292 -producing facilities 32 production and cogeneration of electricity . . 360 typical system for 86 of process 295 selling price of 34/ soot blowers, high-pressure 64 system, efficiency of 89 value on the operating costs, effect of 77 (cogeneration) by wood combustion, production of electricity and .. 34/ Steel 569 Stirred moving-bed, reactors characterized by 44 Stover, char analysis for pyrolysis of straw and 3431 Stover and peat pyrolysis, comparison of straw and 349/ Straw(s) 185,343 pyrolysis, gas composition from .... 344/ and stover, char analysis for pyrolysis of 343/ stover and peat pyrolysis, com­ parison of 349/ Strawdust 185 Styrene 424 Sucrose molasses, and petroleum fuels, imports and exports as a func­ tion of the prices of raw 695/ molasses, and petroleum fuels, relative value of raw 694-696 prices in London and New York markets, average 696/ production levels, lesser-developed countries with 693/ selected major exporters of 693/ 1977 world production and con­ sumption of 693/ Sudan 618,619,621 Sulfates 119

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

4

Sulfite mill liquor Sulfur compounds, organic dioxide emission oxides Supercharging Supply-demand integration Suspension burner, cyclonic Suspension fired systems Swaziland Sweden Switzerland Syncrudes Synthesis gas to methanol production Synthetic fibers

301 64, 229, 329 442 196 499 638 625 201 63 694 689,690 63 317 32 358 333, 357 38

Τ Tanzania 618, 619, 621 applicability in the rural areas of .... 709 for the owner, benefits of corn milling in 711 Tar(s) 46,468,486,604 aromatic 223 condensed 287 production at different geometries . 469 yields 343 Technical processes 5/ Technologies, bridge 332 Technology overview 621 Temperature(s) ash fusion 139 average 139/ bed 355 constraints 117 conversion 467/ for cubed and shredded refuse during storage tests, daily 159/ energy recovery rate vs 549/ gas components vs 549/ gas yields vs 548/ profile, gasifier 389/ profile, typical 118 pyrolysis 558/, 566/, 567/, 568/ in pyrolysis furnace, wall 599/ vs. elapse time, reduction zone 269/ Thailand 618,619 Thermal conversion systems using wood feedstocks, economic overview of large-scale 29-42 decomposition 479 efficiency cold gas 668 brake 660, 667 maximum 302

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

745

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

INDEX

Thermal (continued) gasification and synthesis (methanol) 689 gasoline from solid wastes by a noncatalytic 209-226 Thermochemical conversion of biomass to fuels and feedstocks .13-26 catalysis in 22 process 14 projected fiscal year 1979 budget— 24/ projects, biomass 25 projects, geographic distribution of 24/ Thermochemical formation of gases or oxygenated liquids by pyrolysis 209 Thermocouple and pressure tap locations 113/ Thermodynamic fundamentals 302-303 model(s) 464 calculations 466/ of pyrolysis and activation in the production of waste- or biomass-derived activated carbon 301-314 Thermogravimetric analysis 410,416 Thermoplastic hydrocarbon resins .... 484 Third world applications of pyrolysis of agricultural and forestry wastes 671-688 Tires 444,480,569 gasification of rubber 231-235 granulated rubber 427/ pyrolysis of old boiling behavior of the condensate from 448/ condensate obtained through 450/-451/ process gas obtained through 449/ solid residues obtained through 452/-453Z viscosity of the condensate from 448/ pyrolysis, prototype reactor for whole 437/ removal or reuse of old 423/ scrap disposal cost for 571/ and refuse, co-disposal of 593 products of fluidized-bed pyrolysis of plastic waste and 426/ pyrolysis of plastic waste and .... 429/ pyrolysis process for 557-572 shredder 562/ shredded 402 using afluidized-bedprocess, pyrolysis of plastic waste and 423-439 Tobacco containers, used 295 Tobago 694 Tobata pilot plant 607

Tokyo test plant Toluene Trash, industrial plant Trinidad Turbines, gas

608 424, 480, 484 68 694 38, 360

U University of Brussels, PTGL-project of the Urban Waste and Municipal Systems Branch U.S. refuse, comparison of Japanese and

416 3 573/

V Vegetable(s) 575 fiber "ijuk" 676 Viruses 153 Viscosity of the condensate from the pyrolysis of old tires 448/ Volatiles, combustible 216 Volatilization of cellulose 238 Vulcanizates, rubber 566/-567/ Vulcanization, properties of carbon black and rubber 565/

W Waste availability of agricultural 708 or biomass-derived activated carbon, thermodynamics of pyrolysis and activation in the production of 301-314 cellulose 637 collection 162 comparison of costs for conventional and densified 163/ combustible gas produced from the mixed 538/ combustion of liquid 143 control problem 9 conversion, other method of effective 644 disposal company, acquisition of 351 Facility, Municipal 143 municipal solid 46 -to-energy systems, worldwide inventory of 59 film, gasification of 235 gas shift reaction 294 gasification of organic 637 high-sulfur oil refinery 227 hints for recycling 643 molten salt process for fuel production for 228/

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

746

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

Waste (continued) oil, supplementaryfiringand co-firing of 65 plastic 537/ and scrap tires, pyrolysis of 429/ products of fluidized-bed 426/ using a fluidized-bed process 423-439 potential for rural electrification by biomass conversion of local 643 process for fuel production from .... 227 product application 299 programs, wood 102-103 pyrolysis basic principles of 397 heat balance of mixed 537/ of mixture of sludge and plastic .. 536 of special 482/ differing 480 oils from 482/ system, Kiener 444-462 pyrolytic recovery of raw materials from special 479-484 shredder 480 slugs 155 solid collection costs 161 management unit operations, cost of 152/ mass burning of municipal 59-66 municipal 172 pyrolysis of 291 small scale source densification of Navy 151-168 third world applications of pyrolysis of agricultural and forestry .671-688 urban 644 technology funds 11 using molten salts, fuel production from 227-236 water 499, 529 raw and treated water quality of pyrolysis 551/ treatment of pyrolysis 550 wood 641 Water 575 absorption 160 drinking 301 feedstocks, experiments with MSW and 117-118 gas shift 17, 303 shift reaction 370 purification 38 raw and treated water quality of pyrolysis waste 551/ scrubber 460 treatment 493, 575 of pyrolysis waste 550 vapor 216

Watershift reaction 464 Wax(es) 185,419 paraffin 430 West Germany 59, 65 Wood 227,301,371,444,697 ammonia from 38 availability 698-699 biomass feedstock, costs for 53 char 187 chips 46,355,691 comparison of solid waste cubes with 267 typical analysis of spruce 387/ combustion 30 facilities—estimated investment 31/ facilities—product revenue requirements 33/ production of electricity by 35/ content 102 devolatilization of 46 —estimated investment, chemicals production from 39/ —estimated investment, liquid fuels production from 37/ feed system 367, 381 feedstock(s) 22 cogeneration based on 15 economic overview of large-scale thermal conversion systems using 29-42 fines, dried 103 furnaces, high efficiency 379 gas production costs 48, 53, 276 cleaning system 384 reforming of 357/ gasification 32-36, 43-55, 235 boiler retrofit system, capital and operating costs for 51/ facilities—estimated investment.. 33/ facilities—product revenue requirements 37/ fluidized-bed system for 356/ for gas and power generation 379-394 plant, schematic of 382/ program 355 role of catalysis in 369-378 systems, capital costs of 48 tests, operating characteristics during 355/ gasifier analysis of co-current moving-bed 464 fixed-bed 47/ single stage 45/ hogged 278 hybrid, methane and 332 investment requirements for methanol production from 699

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

747

INDEX

356/ 287 41Ζ

Wood (continued) tropical hard681 using nickel catalysts, direct liquifaction of 363-368 waste 97, 641, 654 fired fluid beds 94 programs 102-103

39/ 698/ 35/

X

X-ray film, waste Xylene

355 85 86

227 480

Ζ Zinc oxide Zurich

Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ix001

Wood (continued) moisture on heating value of fuel gas, effect of pellets —product revenue requirements, chemicals production from ... —product revenue requirements, liquid fuels production from .. products, worldwide production of production of oil and char by pyrolysis of program for the production of fuel gas from residues byfluidized-bedcombus­ tion, energy recovery from shavings

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

430 59