Oil Shale, Tar Sands, and Related Materials 9780841206403, 9780841208339, 0-8412-0640-6

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Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

Oil Shale, Tar Sands, and Related Materials

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Oil Shale, Tar Sands, and Related Materials H . C . S t a u f f e r , EDITOR

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

Gulf Research & Development Company

Based on a symposium sponsored by the Division of Fuel Chemistry at the Second Chemical Congress of the North American Continent, Las Vegas, Nevada August 25-29, 1980.

ACS

SYMPOSIUM AMERICAN

CHEMICAL

W A S H I N G T O N , D. C.

S E R I E S 163 SOCIETY 1981

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

Library of CongressCIPData Oil shale, tar sands, and related materials. (ACS symposium series, ISSN 0097-6156; 163) Includes bibliographies and index. 1. Oil shales—Congresses. 2. Oil sands—Congresses. I. Stauffer, H. C., 1922. II. American Chemical Society. Division of Fuel Chemistry. III. Chemical Congress of the North American Continent (2nd: 1980; Las Vegas, Nev.) IV. Series. TN858.A1038 665'.4 81-10948 ISBN 0-8412-0640-6 AACR2 ACSMC8 163 1-395 1981

Copyright © 1981 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 work, 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. PRINTED IN THE UNITED STATES OF AMERICA

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

ACS Symposium Series M . Joan Comstock, Series Editor

Advisory Board David L. Allara

James P. Lodge

Kenneth B. Bischoff

Marvin Margoshes

Donald D . Dollberg

Leon Petrakis

Robert E. Feeney

Theodore Provder

Jack Halpern

F. Sherwood Rowland

Brian M . Harney

Dennis Schuetzle

W . Jeffrey Howe

Davis L. Temple, Jr.

James D . Idol, Jr.

Gunter Zweig

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.fw001

FOREWORD The ACS SYMPOSIUM SERIES was founded in 1974 to provide

a medium for publishing symposia quickly in 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 in 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 Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

PREFACE omestic oil shale and tar sand deposits constitute a tremendous resource. The proven, recoverable oil shale reserves alone far exceed those remaining for petroleum. In light of this fact, it is not surprising that there are many people having trouble comprehending our vulnerable energy position. Attempts to develop a commercial oil shale industry historically have been on-again, off-again efforts. In almost yearly cyclical fashion, one has heard or read at least one paper enthusiastically suggesting the general theme, " A n Oil Shale Industry—Just Around The Corner." Until now, however, the corner has never been turned and the development pace of this sorely needed resource has been low key at best. All of our domestic heavy oil production and tar sands development endeavors have been in much the same category. The ability to turn the corner always has been stalled by unfavorable economics. Some combination of factors arises which continually delays the development of these alternative energy resources because of their noncompetitive position compared with the price of foreign oil. In reality, this has obscured the real issue—the fragile nature of our domestic energy structure which is so dependent on the ready availability of imported crude. Hope springs eternal, however, and recent developments have indicated that the corner may indeed have been turned at last. Although the D O E oil shale research, development, and demonstration program has been trying to foster a technically and environmentally sound industry capable of meeting the President's goal of 400,000 bbl/d by 1990, the recent sign ing of Senate Bill S.932 should provide a significant and needed impetus. This bill, The Energy Security Act, provides for a United States Synthetic Fuels Corporation which has the mission of encouraging the production of 500,000 bbl/d from alternative sources by 1987 and 2,000,000 bbl/d by 1992. Even more recently, several major developers have announced definitive plans for tract development. On-site activity has commenced to achieve a production goal of 50,000 bbl/d before 1990. These are most worthy goals, but past procrastination will make them difficult to attain. It should not be surprising that in situ retorting is still in its early development stage; that a single, commercial surface retort module has yet to be constructed and successfully demonstrated; or that a full slate of products refined from syncrude has still to be proven acceptably interchangeable with those derived from petroleum.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.pr001

D

ix

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.pr001

With respect to recent events the timing of this symposium was only coincidental. Its content, however, is not. The participants have recognized the diverse problems, and many of them are addressed in this volume. The novel concepts of oil shale fracturing and retorting as well as tar sands recovery processes need to be evaluated. Much needed input has been provided on rubbling and retorting kinetics and mechanisms, which still are poorly understood. Our tendency to look for simple solutions to complex problems is apparent in the discussion of "simple" hydrogenation of shale oil to products of questionable and perplexing stability characteristics. In view of our long-term domestic energy deficit, the stimulating discussion of the potential for a very large-scale oil shale operation merits serious consideration. Nature's petroleum supply is constrained now by what remains in the ground; development of our oil shale and tar sands resources appear only to be constrained by our own actions. The credit for the content of this symposium belongs to the participants and their sponsors. I sincerely appreciate their contributions and wish to acknowledge P. C . Scott and C. W. Matthews for their help in its organization. H . C. S T A U F F E R

Gulf Research & Development Company P.O. Drawer 2038 Pittsburgh, P A 15230 April 10, 1981

x In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

1 The Department of Energy's Oil Shale R, D, & D Program: An Overview ARTHUR M. HARTSTEIN and BRIAN M. HARNEY

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

Office of Oil Shale, Department of Energy, Washington, D.C. 20545

The largest untapped fossil fuel resource in the United States is the o i l bearing shales in the western part of the country and the black shales in the east. The o i l shale resource concentrated in three western states is estimated to be equivalent to more than two trillion barrels of crude o i l . An additional two trillion barrels of oil exists in the lean deposits of the Eastern U.S. Since the earliest commercial interest more than 100 years ago, the history of o i l shale has been one of ups-and-downs. In almost cyclical fashion, the shale industry has appeared to be on the verge of expanding rapidly, economics have appeared potentially viable, and the problems have seemed minimal. But then, a combination of factors, such as jumps in construction costs or the discovery of new conventional oil resources, have led to delays and in some cases, decisions to drop shale oil development. Recent events, however, have reversed this trend. The everrising price of imported petroleum, the continuing volatile situation in the middle east and the passage by the Congress of a variety of significant financial incentive programs for synthetic fuels has stimulated a new interest in moving previously dormant o i l shale projects ahead. The Department of Energy (DOE) has established a research, development, and demonstration (R,D&D) program for encouraging the development of the country's o i l shale resource to help in the mitigation of the present and future energy demands. The aim of the Oil Shale R,D&D Program is to stimulate the commercial production of shale o i l by eliminating technical and environmental barriers. This paper provides an overview of the DOE Oil Shale R,D&D Program, addressing its essential elements. It should be noted that budget constraints do not permit a l l portions of the program plan to be supported as yet. Moreover, in many cases, the program areas are addressed jointly with industry. Oil shale program funding for the plan is $31.3 million in Fiscal Year 1981. This chapter not subject to U.S. copyright. Published 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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MATERIALS

Program Goal and Objectives

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

The Department o f Energy's R,D&D o i l shale goal i s t o permit the e n t i r e o i l shale resource, both east and west, t o c o n t r i b u t e to domestic energy proportionate to the resource and with a r e c o g n i t i o n o f the unique environmental character o f the o i l shale areas. In concert with t h i s g o a l , the o b j e c t i v e s o f the R,D&D program are: o

To overcome t e c h n o l o g i c a l b a r r i e r s to o i l shale commercialization

o

To f o s t e r development o f innovative processes shales that reduce environmental impact

o

To obtain accurate environmental data and demonstrate or develop adequate environmental c o n t r o l systems

for a l l

The a n a l y s i s o f commercialization i n c e n t i v e s and m i t i g a t i o n of i n s t i t u t i o n a l b a r r i e r s i s the r e s p o n s i b i l i t y o f the A s s i s t a n t Secretary for Resource A p p l i c a t i o n s . R,D&D a c t i v i t i e s are the r e s p o n s i b i l i t y o f the A s s i s t a n t Secretary for F o s s i l Energy, although the lead f o r environmental planning r e s t s with the A s s i s t a n t Secretary for Environment. The R,D&D program, however, i n t e g r a t e s the a c t i v i t i e s under the A s s i s t a n t Secretary for F o s s i l Energy and the A s s i s t a n t Secretary for Environment. Program Strategy In essence, the DOE program goal i s t o develop the technology necessary for the production o f o i l shale on a commercial basis and i n an environmentally acceptable manner. The DOE strategy to accomplish t h i s end i s comprised o f two major a c t i v i t y elements: o

Research and Development

o

Development and Demonstration Support

Through the existence o f these p a r a l l e l a c t i v i t i e s , the DOE O i l Shale R,D&D Program focuses near term research and development (R&D) on supporting i n d u s t r i a l development while maint a i n i n g an adequate l e v e l o f more advanced R&D attuned to future needs. The technology developments that w i l l r e s u l t by achieving the program's o b j e c t i v e s w i l l be made a v a i l a b l e to the o i l shale i n d u s t r i a l community. I n d u s t r i a l p a r t i c i p a t i o n i n DOE sponsored demonstrations i s encouraged as means o f maintaining the techn o l o g i c a l alignment o f the R,D&D Program with the needs o f i n dustry. These demonstration a c t i v i t i e s involve the DOE Program

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

1.

HARTSTEIN A N D HARNEY

DOE's

Oil Shale

R, D, & D

Program

3

i n the i n d u s t r i a l d e c i s i o n process and f a c i l i t a t e o i l shale i n d u s t r y growth. Information and experience gained through the c o n s t r u c t i o n and o p e r a t i o n o f any f a c i l i t i e s r e s u l t i n g from these i n d u s t r y supportive a c t i v i t i e s w i l l be used d e f i n i n g future R&D requirements which may be s a t i s f i e d d i r e c t l y by the p r i v a t e sector through the program. The program i s designed i n concert with and i n support o f i n c r e a s i n g i n d u s t r y a c t i v i t y . The Program's R&D a c t i v i t y elements are s t r u c t u r e d to p a r a l l e l and complement a c t i v i t i e s that i n d u s t r i a l developers would need to perform when e s t a b l i s h i n g a commercial o i l shale o p e r a t i o n . The i n i t i a l a c t i v i t i e s o f a developer include tasks to c h a r a c t e r i z e the resource under c o n s i d e r a t i o n and s i t e planning f o r resource development. Following t h i s , the developer needs to consider the p o t e n t i a l p h y s i c a l environment and socioeconomic impacts before committing to a proposed p r o j e c t . O i l shale resource development and e x t r a c t i o n e n t a i l s i t e p r e p a r a t i o n , mining (except f o r true i n s i t u technologies) , and r u b b l i n g the i n s i t u r e t o r t i n preparation for i n place combustion or t r a n s p o r t i n g the mined o i l shale to a surface r e t o r t . R e t o r t i n g would then be undertaken, a f t e r which the shale o i l would be upgraded and r e f i n e d . At each point i n t h i s sequence, the o i l shale program w i l l develop enhanced technology to e s t a b l i s h a p o t e n t i a l developer's effectiveness . Key T e c h n i c a l and Environmental Needs i n R,D&D T e c h n i c a l . The O i l Shale R,D&D Program i s d i r e c t e d toward developing a greater understanding o f the o i l shale resource and p e r f e c t i n g an e f f e c t i v e means f o r the recovery o f shale o i l . Program a c t i v i t i e s are d i r e c t e d toward the s o l u t i o n o f key t e c h n i c a l and environmental needs r e p r e s e n t i n g s i g n i f i c a n t b a r r i e r s to commercial o i l shale development. Based on a review o f t e c h nology r e q u i r e d f o r o i l shale development, the f o l l o w i n g Key T e c h n i c a l Needs have been i d e n t i f i e d as those that should r e c e i v e the highest p r i o r i t y i n the R,D&D Program: o

E f f i c i e n t O i l Shale Rock Breakage and Retort Bed Prep a r a t i o n Techniques,

o

Development o f Retort Diagnostics and Instrumentation,

o

Development o f Retort Control Procedures,

o

Systems Engineering Methods f o r T o t a l O i l Shale Development,

o

E f f i c i e n t and E f f e c t i v e O i l Shale Mining

Process

Systems,

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

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o

Advanced Shaft Sinking Technology,

o

Chemical K i n e t i c s o f the T o t a l P y r o l y s i s Process,

o

Understanding Retorting Mechanisms and Developing a Prediction

o

Development o f A l t e r n a t i v e R e t o r t i n g Procedures.

Rock Breakage and Retort Bed P r e p a r a t i o n . Efficient recovery o f o i l from shale depends c r i t i c a l l y upon having a bed o f o i l shale rubble that i s r e l a t i v e l y uniform, both i n p a r t i c l e s i z e and v o i d f r a c t i o n . Mining and r u b b l i n g methods must be developed to assure optimal u n i f o r m i t y . Otherwise sweep e f f i c i e n c y w i l l be poor, and s i g n i f i c a n t amounts o f o i l shale rubble w i l l not be r e t o r t e d . It i s expected that the R,D&D e f f o r t w i l l r e s u l t i n the development o f technology f o r breaking o i l shale f o r mining and preparing rubble beds such that e f f i c i e n t and productive shale e x t r a c t i o n and modified i n s i t u r e t o r t i n g can be accomp l i s h e d . Retorts w i l l be designed and constructed which meet the processing requirements f o r p a r t i c l e s i z e d i s t r i b u t i o n , uniform p e r m e a b i l i t y , uniform void d i s t r i b u t i o n , and bounding of the f r a c t u r e d r e g i o n . Retort Diagnosis and Instrumentation. The development o f c o n t r o l instrumentation and methods f o r i n s i t u r e t o r t i n g i s important f o r determining r e t o r t performance and y i e l d e f f i c i e n c y . The e f f o r t o f the RD&D program w i l l r e s u l t i n the design o f thermal sensors, gas sampling devices, pressure probes, remote sensing d e v i c e s , s t r a i n and displacement gauges, and h e a l t h and s a f e t y monitoring equipment. This equipment w i l l be designed and then tested and modified through use i n s e v e r a l f i e l d t e s t s . Retort C o n t r o l Procedures. The development o f r e t o r t cont r o l and operating procedures i s c r u c i a l to the success o f both i n s i t u and modified i n s i t u r e t o r t i n g o f o i l s h a l e . The R,D&D e f f o r t w i l l e s t a b l i s h a set o f b a s e l i n e operating plans from data c o l l e c t e d from l a b o r a t o r y experiments, f i e l d t e s t s and the outputs o f p r e d i c t i v e models. From the data c o l l e c t e d , an e v a l u a t i o n w i l l be made on the e f f e c t s o f i n t e r m i t t e n t a i r flows, l i q u i d water a d d i t i o n s , and other c o n t r o l parameters. The r e s u l t o f t h i s e f f o r t w i l l be a r e t o r t operating plan that maximizes r e t o r t i n g rate and y i e l d while c o n t r o l l i n g temperature and burn front symmetry. Systems Engineering.

A systematic

procedure f o r resource

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

1.

HARTSTEIN A N D HARNEY

DOE's

OH Shale

R, D, & D

Program

5

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

i d e n t i f i c a t i o n and c h a r a c t e r i z a t i o n and for determination o f appropriate recovery processes i s needed to assure e f f i c i e n t and e f f e c t i v e use o f a l l domestic o i l shale r e s o u r c e s . The need r e l a t e d o b j e c t i v e s o f the R,D&D program are: (1) to develop and u t i l i z e methods f o r the planning o f o i l shale development by matching o i l shale resources with appropriate recovery processes; (2) to develop planning t o o l s (e.g., equipment s e l e c t i o n c r i t e r i a , production models, economic models) which w i l l a i d i n the design and a n a l y s i s o f e f f i c i e n t shale o i l production f a c i l i t i e s ; and (3) t o determine the o v e r a l l economics f o r the recovery o f energy products from o i l shale by the a l t e r n a t i v e processes . O i l Shale Mining Systems. Equipment and methods now used for c o a l and hard rock mining are w e l l developed but are not always a p p l i c a b l e to the demands o f o i l shale mining. Research and development i s needed t o meet the p a r t i c u l a r requirements of the o i l shale i n d u s t r y . The o b j e c t i v e o f the R,D&D program i s t o develop technology and equipment f o r high volume, cost e f f e c t i v e , underground and surface mining methods f o r e x t r a c t i n g o i l shale f o r subsequent surface and modified i n s i t u p r o c e s s i n g . Shaft Sinking Technology. The development o f shafe s i n k i n g systems i s c r u c i a l f o r the l a r g e s c a l e commercial u t i l i z a t i o n of o i l s h a l e . The R,D&D e f f o r t w i l l c a r e f u l l y examine the current state o f the a r t i n s h a f t / s l o p e development. A comprehensive research and development plan w i l l be e s t a b l i s h e d that attacks a l l the major d e f i c i e n c i e s i n the current s t a t e o f the art f o r accessing o i l shale r e s o u r c e s . Access development system concepts w i l l be defined a f t e r a s e r i e s o f tasks which examine c u t t i n g and d r i l l i n g methods, water/ground c o n t r o l , and l a r g e s c a l e d r i l l i n g . The expected r e s u l t o f t h i s e f f o r t w i l l be the development o f techniques f o r e f f i c i e n t , s a f e , and environmenta l l y acceptable shaft s i n k i n g . Chemical K i n e t i c s . Several models have been developed which simulate the p h y s i c a l p r o p e r t i e s o f o i l shale r e t o r t i n g (e.g., shale composition, r e t o r t i n g r a t e s , p a r t i c l e s i z e s , porosity d i s t r i b u t i o n , e t c . ) . For the models to a c c u r a t e l y simulate r e t o r t i n g , they should i n c l u d e the d e t a i l s o f the major chemical r e a c t i o n s i n the system. The R,D&D program w i l l develop the b a s i c data on chemical k i n e t i c s needed to model the complex r e a c t i o n s taking place i n r e t o r t i n g . Among these r e a c t i o n s are mineral decomposition, e s p e c i a l l y that o f carbonates, which are l a r g e consumers o f energy; r e a c t i o n s char with steam and carbonate to produce v a l u a b l e CO and hydrogen; degradation ( l o s s ) r e a c t i o n s o f o i l ; gas phase r e a c t i o n s producing hydrogen and CO2; gaseous s u l f u r e v o l u -

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

6

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MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

t i o n ; e t c . More work i s needed on gas phase r e a c t i o n s , e s p e c i a l l y on water gas and water gas s h i f t r e a c t i o n s , o i l cracking stoichiometry o f hydrocarbon combustion, and s u l fur r e a c t i o n s i n s h a l e . R e t o r t i n g Mechanisms. R e t o r t i n g i s only c r u d e l y understood i n lab and f i e l d r e t o r t s . Important o p e r a t i o n a l problems i n c l u d e c o n t r o l o f burn f r o n t , s t a r t u p and sweep e f f i c i e n c y , e f f e c t o f p a r t i c l e s i z e d i s t r i b u t i o n , i n l e t gas composition, e s p e c i a l l y steam and a i r mixtures, bed i r r e g u l a r i t i e s , flow r a t e , p e r m e a b i l i t y changes during r e t o r t i n g , and temperature c o n t r o l . Program research w i l l address key questions i n the area o f r e t o r t i n g mechanisms. A knowledge of the mechanisms t a k i n g place during r e t o r t i n g i s r e q u i r e d to i n t e r p r e t r e s u l t s o f experiments i n p i l o t and f i e l d r e t o r t s to develop p r e d i c t i v e models, and f i n a l l y t o suggest process m o d i f i c a t i o n s i n order to optimize r e t o r t performance, e s p e c i a l l y o i l y i e l d s , and production r a t e s . The development of r e t o r t i n g models w i l l a l s o be pursued as a means o f understanding and p r e d i c t i n g r e t o r t behavior. A l t e r n a t i v e R e t o r t i n g Procedures. O i l shale r e t o r t i n g i s approaching commercially v i a b l e l e v e l s o f development. However, the technology i s not s u f f i c i e n t l y advanced to assure that o p t i m a l l y e f f i c i e n t and cost e f f e c t i v e r e t o r t i n g methods are employed. The R,D&D program w i l l examine a l t e r n a t i v e r e t o r t ing processes with the o b j e c t i v e o f improving e x t r a c t i o n e f f i c i e n c y and economics. Studies w i l l i n c l u d e : (1) the use o f oxygen ( i n s t e a d o f a i r ) plus steam to o b t a i n high BTU o u t l e t gas and reduce e x i t gas handling and cleanup; (2) the s u b s t i t u t i o n of water mist f o r steam to improve heat balance; (3) determining r e t o r t i n g c o n d i t i o n s to produce v a r i o u s optimum product mixes, e.g., maximum naphtha, minimum r e s i d u a l s , e t c . ; and (4) d e t e r mining r e t o r t i n g c o n d i t i o n s to produce minimum environmental e f f e c t s (e.g., lowest s u l f u r i n o u t l e t gas, l e a s t s o l u b l e spent shale, e t c . ) ; (5) use o f f l u i d beds to increase throughput, improve y i e l d and lead to more favorable economics. Environmental R&D Needs. The environmental research i n the R,D&D Program represents a s i g n i f i c a n t p o r t i o n o f the DOE s Environmental Development Plan. The o v e r a l l o b j e c t i v e o f the Program's Environmental A c t i v i t y i s t o develop s o l u t i o n s t o environmental problems a s s o c i a t e d with the process technologies involved i n o i l shale production. To achieve t h i s o b j e c t i v e , a s e r i e s of Key Environmental Needs have a l s o been e s t a b l i s h e d : 1

o

Development o f Environmentally Acceptable Retort Abandonment Strategy,

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

1.

HARTSTEIN A N D HARNEY

DOE's

Oil

Shale

R,

D,

& D

Program

o

Guidelines to Ensure Health and and General P u b l i c ,

Safety o f Workers

o

Development of S o l i d Waste Management Systems,

o

Development of Water Treatment Systems,

o

Development of an Emission C o n t r o l Strategy,

o

M i t i g a t i o n of E c o l o g i c a l Impacts,

o

M i t i g a t i o n of S o c i a l and

o

Development of Compliance Plans, and

o

Development of Subsidence Control

Economic Impacts,

Procedures.

Development of Environmentally Acceptable Retort Abandonment Strategy. The spent shale remaining i n underground r e t o r t s a f t e r product recovery contains s a l t s and carbonaceous residues that can be leached by groundwater and thereby contaminate a q u i f e r s . In a d d i t i o n , some caving i n from the weight of the overburden may occur r e s u l t i n g i n subsidence at the surface . The research r e l a t e d to t h i s need w i l l determine (1) the p o t e n t i a l f o r groundwater i n t r u s i o n , what m a t e r i a l s are l i k e l y to be d i s s o l v e d i n groundwater, the p e r m e a b i l i t y of the geologic media to the s o l u b l e components, the t o x i c p r o p e r t i e s o f these components, and the p e r s i s t e n c e of any t o x i c l e a c h i n g and subsidence. The more general problem o f subsidence i n underground mines, the s a f e t y and e c o l o g i c a l aspects, are d e a l t with i n a separate area. Guidelines to Ensure Health and Safety of Workers and General P u b l i c . Operations o f an o i l shale i n d u s t r y w i l l i n t r o duce a new set o f i n d u s t r i a l working c o n d i t i o n s and p o s s i b l e p u b l i c h e a l t h r i s k s as a r e s u l t of plant operations or product distribution. The research d i r e c t e d toward t h i s need w i l l examine the p o t e n t i a l h e a l t h and s a f e t y r i s k s to workers and the general p u b l i c . A l l aspects o f the f u e l c y c l e w i l l be examined from the mine and r e t o r t to the r e f i n e r y and end use of the shale o i l products. P r o t e c t i v e measures, whether they be through c o n t r o l s , process m o d i f i c a t i o n s , or i s o l a t i o n o f high r i s k areas, w i l l be evaluated and e f f e c t i v e measures w i l l be applied. Development of S o l i d Waste Management Systems. Surface processes produce extremely high volumes o f s o l i d waste i n

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

7

8

OIL

SHALE, TAR

SANDS,

AND

RELATED

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

the form of spent s h a l e . This research w i l l evaluate methods of compacting and s t a b l i z i n g spent shale and other s o l i d wastes such as sludges and spent c a t a l y s t s . The research w i l l lead to the e v a l u a t i o n o f a l t e r n a t i v e s for s t a b l i z i n g and achieving s e l f - s u s t a i n i n g ecosystems on the s o l i d waste p i l e s with minimum p o t e n t i a l for water and wind e r o s i o n o f t o x i c m a t e r i a l s . Development of Water Treatment Systems. In s i t u processes produce approximately one b a r r e l o f r e t o r t water contaminated with carbonaceous residues f o r each b a r r e l o f shale o i l recovered. Surface processes also produce r e t o r t water but i n lower q u a n t i t i e s . Although current plans do not c a l l f o r discharge of wastewater, i t much be cleaned for reuse i n the process and other uses, such as dust c o n t r o l and s o l i d waste management. An o b j e c t i v e o f t h i s research i s to i d e n t i f y components i n the wastewater that present e i t h e r a h e a l t h or environmental hazard with respect to the intended use o f the water and to develop systems to remove these components. Another o b j e c t i v e i s to determine the consumptive water requirements o f d i f f e r e n t o i l shale processes. Development of an Emissions C o n t r o l Strategy. There are two major components to the emissions c o n t r o l need. One i s d i r e c t e d toward determination o f the emission c o n t r o l r e q u i r e ments based on the projected emission r a t e s and composition o f the emission streams. In the case o f c r i t e r i a or regulated p o l l u t a n t s , systems must be engineered to maintain ambient a i r q u a l i t y w i t h i n the r e g i o n . In a d d i t i o n , m o d i f i c a t i o n o f a v a i l able technology and development o f new systems may be r e q u i r e d i f r i s k a n a l y s i s i n d i c a t e s that unique substances i n the emission stream r e q u i r e d removal. The other component i s d i r e c t e d toward e s t i m a t i o n o f the c a p a c i t y o f the r e g i o n to accept i n d u s t r i a l development—the r e g i o n a l c a r r y i n g c a p a c i t y — b a s e d on the m e t e o r o l o g i c a l charact e r i s t i c s o f the r e g i o n . More s p e c i f i c needs are (1) more accurate atmospheric models to p r e d i c t the t r a n s p o r t and d i s p e r s i o n o f atmospheric p o l l u t a n t s , (2) determining r a t e s at which p o l l u t a n t s are removed from the atmosphere, and (3) q u a n t i t a t i v e information on the e f f e c t s o f a i r p o l l u t a n t s on c r i t i c a l atmospheric processes r e l a t e d to u n d e s i r a b l e e f f e c t s , e.g., p r e c i p i t a t i o n q u a l i t y , decreased v i s i b i l i t y , and l o c a l c l i m a t e m o d i f i cation . The research tasks that compose t h i s segment o f the plan lead to the development o f workable emission c o n t r o l s and estimates o f e f f e c t s o f i n d u s t r i a l i z a t i o n on r e g i o n a l a i r quality.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

1.

HARTSTEIN A N D HARNEY

DOEs

Oil Shale

R, D, & D

Program

9

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

M i t i g a t i o n o f E c o l o g i c a l Impacts. O i l shale operations w i l l cause much d i s r u p t i o n o f the surface environment through normal c o n s t r u c t i o n and operation a c t i v i t i e s — l a r g e amounts o f s o l i d waste s t o c k p i l e s on the s u r f a c e , water treatment operat i o n s , steam generation, mining, m a t e r i a l handling, e t c . The o b j e c t i v e s o f the e c o l o g i c a l research, i n a d d i t i o n to that which i s an i n t e g r a l part o f other a c t i v i t i e s such as the s o l i d waste management system, w i l l be t o (1) evaluate o v e r a l l e f f e c t s of the operation on the e c o l o g i c a l communities ( p l a n t s , w i l d l i f e , f i s h ) and (2) develop e c o l o g i c a l t e s t procedures that w i l l be used by other parts o f the program t o evaluate systems performance with respect t o e c o l o g i c a l c r i t e r i a . This work w i l l be geared to the environmental impact approach described above. M i t i g a t i o n o f S o c i a l and Community Economic Impacts. The s o c i a l and community economic aspects o f t e c h n o l o g i c a l developments are among the most d i f f i c u l t t o deal with. To a l a r g e extent, t h i s i s due to the f a c t that s o l u t i o n s i n v o l v e i n s t i t u t i o n a l arrangements and l e g i s l a t i v e i n i t i a t i v e s beyond the scope of most R&D operations. The problems do not lead themselves to c o n t r o l l e d experiments that can be c a r r i e d out i n the f i e l d or l a b o r a t o r y . I n s t a l l a t i o n o f m i t i g a t i n g measures such as front-end f i n a n c i a l support t o communities for planning and development w i l l be d e a l t with i n DOE s i n d u s t r i a l i z a t i o n p l a n t . This part o f the R,D&D plan w i l l focus on the s o c i a l and economic issues for which s o l u t i o n s are not known and which t h e r e f o r e require additional research. 1

Methods for C o n t r o l l i n g or Preventing Subsidence. Underground mines are always s u s c e p t i b l e to subsidence, which presents a concern for s a f e t y and environmental disturbance, i n c l u d i n g a q u i f e r d i s r u p t i o n and changes i n the surface land form. Some o f the r e t o r t abandonment c o n t r o l measures w i l l a l s o act to prevent subsidence. The R&D conducted to s a t i s f y t h i s need w i l l focus on general underground mining whether r e l a t e d to underground processes or surface r e t o r t i n g processes. It w i l l be c l o s e l y t i e d to the mining tasks and include analyses o f s a f e t y , h y d r o l o g i c a l d i s r u p t i o n , and changes i n surface f e a t u r e s . The research w i l l focus p r i m a r i l y on prev e n t i o n or planned, c o n t r o l l e d subsidence. Development o f Compliance Plans. The R,D&D tasks, f o r environmental as w e l l as the other three a c t i v i t i e s included i n the Management Plan are c a r r i e d out i n conjunction with, o r as part o f , major f i e l d p r o j e c t s . These p r o j e c t s , which involves engineering and c o n s t r u c t i o n a c t i v i t i e s , must comply with F e d e r a l , s t a t e , and l o c a l standards, and i n p a r t i c u l a r , with p r o v i s i o n s o f the National Environmental P o l i c y Act (NEPA).

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL

10

S H A L E , T A R SANDS,

AND RELATED

MATERIALS

DOE prepares Environmental Assessments, and Environmental Impact Statements when a p p r o p r i a t e , f o r those major f i e l d proj e c t s . A i r , water, and other environmental monitoring, as r e quired t o demonstrate compliance with NEPA and a p p l i c a b l e permits, i s conducted as part o f t h i s need; that data i s made a v a i l a b l e to other tasks f o r v a r i o u s analyses and d e c i s i o n s . Process S p e c i f i c R,D&D

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

In a d d i t i o n , t o s a t i s f y i n g key needs which p r e s e n t l y impede o i l shale commercialization the O i l Shale R,D&D Program w i l l simultaneously address the f o l l o w i n g processes. Surface Processing. The DOE i s pursuing a s u r f a c e module demonstration program as described i n P.L. 95-238. This program w i l l r e s u l t i n both design and business proposals f o r the c o n s t r u c t i o n o f a surface r e t o r t module. A d e c i s i o n to proceed with c o n s t r u c t i o n o f designed modules on a cost shared b a s i s i s being held i n abeyance pending i n d u s t r i a l a c t i o n s and the a v a i l a b i l i t y o f other f i n a n c i a l i n c e n t i v e programs such as those to be provided by the newly formed Synthetic Fuels Corporation. Other research and development supporting surface r e t o r t i n g i s mainly focused on mining and environmental e f f e c t s with long term R&D d i r e c t e d to improving surface r e t o r t i n g processes. In S i t u P r o c e s s i n g . The current near term emphasis o f the Program's research a c t i v i t i e s i s on developing and expanding i n s i t u r e t o r t i n g process technology, with p a r t i c u l a r emphasis on modified i n s i t u methods. This programmatic d i r e c t i o n i s based on the f a c t that i n s i t u o i l shale technology has not advanced to the point where i t has been proven t o be t e c h n i c a l l y or economically f e a s i b l e . Engineering analyses i n d i c a t e that i n s i t u processes have the p o t e n t i a l t o be more cost e f f e c t i v e and l e s s d i s r u p t i v e to the environment than surface r e t o r t i n g . Therefore, the program i s focused on developing the necessary t e c h n i c a l and environmental information from which an economic and environmentally acceptable i n s i t u technology can be engineered. In a d d i t i o n to t h i s technology base program, the DOE i s also sponsoring s e v e r a l major i n s i t u o i l shale f i e l d demons t r a t i o n t e s t s . The f i e l d demonstration t e s t program and the technology based R&D programs are i n t e g r a l l y r e l a t e d , i n that f i e l d demonstration s i t e s are o f t e n used as s i t e s f o r R,D&D program e f f o r t s and information gained from the f i e l d t e s t s i s used to guide the o v e r a l l R,D&D program. Each o f these p r o j e c t s has been evaluated to determine the program technology requirements that can be met by ongoing i n d u s t r y c o n t r a c t and the other t e c h -

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

1.

HARTSTEIN A N D HARNEY

DOEs

Oil Shale

R, D, & D

Program

11

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

nology requirements that can be achieved through m o d i f i c a t i o n of the ongoing e f f o r t . In a d d i t i o n t o p r o v i d i n g v a l u a b l e technology base i n f o r m a t i o n , i t i s a n t i c i p a t e d that one or more o f these p r o j e c t s could provide t e c h n i c a l evidence o f process f e a sibility. Use o f e x i s t i n g p r o j e c t s t o accomplish planned tasks w i l l be maximized to reduce t o t a l program c o s t s . Novel Processing Techniques. In a d d i t i o n to the development o f more advanced aboveground and i n s i t u methods, research i s being conducted i n t o new and novel technologies f o r e x t r a c t i o n and processing o f o i l shale products. Although not c u r r e n t l y competitive f o r near term commercial development, these e f f o r t s are i n d i c a t o r s o f l i k e l y second generation advances i n o i l shale technology. The novel technologies being developed are i n two general categories. o

Radio Frequency Heating

o

Hydrogen Retorting

Program Operating

Plans

The O i l Shale R,D&D Program i s defined i n a d r a f t document which include two main s e c t i o n s : a Management and S t r a t e g i c Plan which d e s c r i b e s the R,D&D program management s t r u c t u r e and the long term s t r a t e g i c aspects o f the Department o f Energy's program for achieving i t s technology o b j e c t i v e s , and an Implementation Plan which d e t a i l s o i l shale R,D&D a c t i v i t i e s over the next s e v e r a l years t o the s u b a c t i v i t y task l e v e l . In c o n t r a s t t o the Implementation Plan, the Management and S t r a t e g i c Plan d e s c r i b e s the Program's o b j e c t i v e s as they w i l l be a t t a i n e d by s a t i s f y i n g a s e r i e s o f t e c h n o l o g i c a l needs, each o f which may r e q u i r e the s u c c e s s f u l performance o f one or more sets o f tasks sometime i n the f u t u r e . Described are o i l shale R,D&D a c t i v i t i e s f o r a multiyear period i n terms o f needs, with emphasis placed upon s o l v i n g key t e c h n i c a l and environmental needs i n h i b i t i n g o i l shale commercialization and developing an a c t i v i t y b a s e l i n e f o r each o f s e v e r a l candidate technologies to e s t a b l i s h program d i r e c t i o n , resource requirements, and expected accomplishment. Both plans serve as a b a s i s f o r developing and j u s t i f y i n g future budget requests over t h e i r r e s p e c t i v e p e r i o d s . S t r a t e g i c Plan. The p o l i c y , management, o r g a n i z a t i o n , and long term aspects o f the O i l Shale R,D&D Program, as d i r e c t e d toward s a t i s f y i n g i t s goal and o b j e c t i v e s , are described i n the Management and S t r a t e g i c Plan. The d i s c u s s i o n i s i n three parts addressing planned program e f f o r t s concerned w i t h :

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch001

12

SHALE,

o

Key T e c h n i c a l Need R,D&D

o

Key Environmental

o

Process

T A R SANDS,

AND

RELATED

MATERIALS

Need R,D&D

S p e c i f i c R,D&D

These e f f o r t s are defined at the fundamental needs l e v e l , each R,D&D o b j e c t i v e (a key need being one such o b j e c t i v e ) r e q u i r i n g the f u l f i l l m e n t o f one o r more o f these fundamental needs before i t i s obtained. This i s i n c o n t r a s t to the manner in which the Implementation Plan i s d e f i n e d , wherein needs are s p e c i f i e d i n terms o f the d e t a i l e d tasks r e q u i r e d t o s a t i s f y them. S t r a t e g i c plans are o u t l i n e d i n a plane higher than that used i n the Implementation Plan. Another d i s t i n c t i o n between the two i s i n t h e i r planning time h o r i z o n . S t r a t e g i c plans are defined over a long term p e r i o d , g e n e r a l l y about ten years, whereas the Implementation Plan concentrates on the near term period not exceeding f i v e years. To show c o n t i n u i t y between the two plans, the time span addressed i n the Implementation Plan i s a l s o defined with the s t r a t e g i c plans and need i d e n t i f i e r s u n i quely assigned i n the Implementation Plan are referenced i n the S t r a t e g i c plans . Implementation Plan. Short term plans are defined i n the Implementation Plan i n terms o f the a c t i v i t i e s and tasks t o be performed. Outlined w i t h i n the Plan are the research tasks that w i l l be performed during the next f i v e year period t o enhance and encourage commercial o i l shale development. The R,D&D tasks are described with respect t o major a c t i v i t y areas (resource c h a r a c t e r i z a t i o n , environment, development and e x t r a c t i o n , and processing and i n s t r u m e n t a t i o n ) . Component s u b a c t i v i t i e s w i t h i n each o f these a c t i v i t i e s provides a framework f o r o r g a n i z i n g tasks around s p e c i f i e d technology areas. For each program task the performance periods are s p e c i f i e d i n c o n j u n c t i o n with task d e l i v e r a b l e s and p a r t i c i p a t i n g o r g a n i z a t i o n s . The Plan, conceived as a working document which i s annually updated, thus serves as a b a s i s f o r implementing the R,D&D Program by the various research and i n d u s t r y p a r t i c i p a n t s . RECEIVED

March 19,

1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2 Computer Simulation of Explosive Fracture of Oil Shale THOMAS F. ADAMS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

G-6, Mail Stop 665, Los Alamos National Scientific Laboratory, P.O. Box 1663, Los Alamos, NM 87545

A necessary first step in the recovery of o i l from o i l shale is the reduction of the rock to rubble. In mining operations, the o i l shale is blasted loose and hauled to the surface for further crushing or direct processing. In in situ methods, the o i l shale must be rubbled in place, with l i t t l e or no direct access to the resource bed. The efficiency and economic viability of shale o i l recovery, therefore, depend directly on blasting technology. The optimization of existing blasting methods and, especially for in situ applications, the development of new methods beyond the current state of the art will be needed to use our o i l shale resources effectively. Advances in blasting technology could perhaps be made by trial and error, but experiments on the required scale are costly. An alternative approach would be to develop analytical and computational methods to simulate blasting in rock, and to use the computer to aid in the design of new methods and the planning and analysis of critical experiments. The computer would not in itself specify blast patterns or delays, but would allow the basic phenomenology of blasting to be studied. Computer codes would become tools to study the effect of changing design parameters such as the depth of burial or explosive type on the results of blasting. New ideas could be explored at modest cost before going to the field for largescale tests. Computer Simulation Computer simulation of explosive fracture of rock can be carried out with finite difference stress wave propagation codes, such as the YAQUI code (J_). YAQUI integrates in time the coupled partial differential equations for the conservation of mass, momentum, and energy. For a compressible fluid, these equations are ^

+ V • (Pu) = 0

,

0097-615 6/ 81 /0163-0013$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

(1)

14

OIL

3u

+ + (u

V)u + _ V p

S H A L E , T A R SANDS,

AND RELATED

MATERIALS

(2)

= 0

3t and

2

2

\ v-

_ L (I + \ u ) + (u - v ) (I + ^ u ) + 9t 2 p

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

2

(pu) = 0

.

(3)

Here, it i s the v e l o c i t y , p i s the mass d e n s i t y , p i s the pressure, and I i s the s p e c i f i c i n t e r n a l energy. Viscous terms, not shown here, a l s o enter the equations. Rock i s a m a t e r i a l with strength. Therefore, i n the s o l i d dynamics v e r s i o n o f YAQUI, the pressure terms i n the momentum and energy equations are replaced with analogous terms i n v o l v i n g the s t r e s s tensor. YAQUI i s a two-dimensional code, so i t can t r e a t problems i n plane s t r a i n or c y l i n d r i c a l symmetry. T h i s i s s u f f i c i e n t f o r many b l a s t i n g a p p l i c a t i o n s , such as a c y l i n d r i c a l charge i n a borehole d r i l l e d i n p e r p e n d i c u l a r to the rock face. YAQUI i s an "ALE" ( A r b i t r a r y Lagrangian-Eulerian) code ( 2 ) , although f o r these applications the Lagrangian option i s g e n e r a l l y used. Numerical methods to s o l v e f l u i d flow and s t r e s s wave propagation problems have been developed over the years a t Los Alamos. Given these methods and l a r g e modern computers, the d i f f i c u l t y i n s o l v i n g these equations l i e s i n s p e c i f y i n g the initial and boundary c o n d i t i o n s and i n the model used t o describe the m a t e r i a l response. In p r a c t i c e , this means s i m u l a t i n g n u m e r i c a l l y the detonation o f the high e x p l o s i v e and the subsequent behavior o f the r e a c t i o n products, and developing a constitutive relation. In f l u i d problems, the analog o f the c o n s t i t u t i v e r e l a t i o n i s the equation o f s t a t e , which gives the pressure as a f u n c t i o n o f the d e n s i t y and i n t e r n a l energy. The s p e c i f i c a t i o n o f the equation o f s t a t e c l o s e s the s e t o f equations (1-3) and makes a numerical s o l u t i o n p o s s i b l e . The c o n s t i t u t i v e r e l a t i o n f o r rock serves the same r o l e , except that i t i n v o l v e s the s t r e s s and s t r a i n tensors. I t must be w r i t t e n i n incremental form, s i n c e the current s t a t e o f a s o l i d depends on i t s l o a d i n g h i s t o r y . The d e s c r i p t i o n o f rock f r a c t u r e and fragmentation i s an i n t e g r a l p a r t o f the c o n s t i t u t i v e r e l a t i o n . E x p l o s i v e Behavior. The behavior o f the e x p l o s i v e must be a c c u r a t e l y described, s i n c e the e x p l o s i v e i s the source o f energy i n b l a s t i n g . Numerical methods f o r modeling e x p l o s i v e s and the p r o p e r t i e s o f many common e x p l o s i v e s have been d i s c u s s e d i n a book by Mader (3.). An i d e a l detonation i s one i n which the chemical energy o f the e x p l o s i v e i s r e l e a s e d n e a r l y i n s t a n t a neously a t the detonation f r o n t . Many m i l i t a r y e x p l o s i v e s are i d e a l i n t h i s sense, while commercial e x p l o s i v e s , such as ANFO, are n o n - i d e a l . In non-ideal e x p l o s i v e s , the chemical energy i s released over some d i s t a n c e behind the detonation f r o n t . The behavior o f such e x p l o s i v e s , i n c l u d i n g the detonation v e l o c i t y ,

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

2.

ADAMS

Computer

Simulation

of Explosive

Fracture

15

Chapman-Jouguet (C-J) pressure, and the d e t o n a b i l i t y , can depend s t r o n g l y on the charge diameter, confinement, and method o f initiation. I t i s , therefore, important that commercial e x p l o s i v e s be t e s t e d under circumstances as c l o s e as p o s s i b l e to those where they w i l l be used i n the f i e l d . The behavior o f ANFO i n 0.1- and 0.2-m-diameter c y l i n d e r s has been studied i n f i e l d t e s t s 5). Most o f the data were obtained i n high-speed photography o f detonations o f e x p l o s i v e f i l l e d p l a s t i c or c l a y pipes immersed i n water. The detonation v e l o c i t y can be determined q u i t e a c c u r a t e l y and i n the water tank t e s t s , the propagation o f the shock i n the water and the motion o f the i n t e r f a c e between the water and the pipe can be followed. An equation o f s t a t e f o r the e x p l o s i v e r e a c t i o n products i s then c a l c u l a t e d with a chemistry code. The equation o f s t a t e i s used i n a two-dimensional s t r e s s wave code to simulate the water tank t e s t . The equation o f s t a t e i s modified i n f u r t h e r chemistry c a l c u l a t i o n s by v a r y i n g the degree o f combustion a t the detonation f r o n t u n t i l the s i m u l a t i o n c l o s e l y reproduces the a c t u a l t e s t . The data obtained f o r ANFO a r e summarized i n Table I . S e v e r a l commercial e x p l o s i v e s besides ANFO have a l s o been c h a r a c t e r i z e d i n t h i s way.

Table I Behavior o f ANFO i n Various Diameters (4) Diameter 0.1 m 0.2 i n f i n i t e (ideal)

Detonation V e l o c i t y 3500 m/s 4100 5400

C-J Pressure 2.4 GPa 3.6 7.3

Constitutive Relations Geologic m a t e r i a l s l i k e o i l shale are commonly t r e a t e d as elastic/plastic solids. F r a c t u r e under i n t e n s e l o a d i n g i s then modeled as an extension o f p l a s t i c i t y or i s t r e a t e d with a separate f r a c t u r e model. In a p p l i c a t i o n s l i k e rock b l a s t i n g , the l a t t e r approach i s p r e f e r a b l e , s i n c e f r a c t u r e o f rock i s q u a l i t a t i v e l y d i f f e r e n t from p l a s t i c flow. Even so, continuum damage models have been used to model b l a s t i n g f o r engineering applications. Some c a l c u l a t i o n s with such a model w i l l be presented below. Fracture Model. A powerful fracture model based on S t a t i s t i c a l Crack Mechanics (SCM) i s being developed a t Los Alamos (6^. I n t h i s model, the rock i s t r e a t e d as an e l a s t i c m a t e r i a l c o n t a i n i n g a d i s t r i b u t i o n o f penny-shaped flaws and cracks o f v a r i o u s s i z e s and o r i e n t a t i o n s . P l a s t i c i t y near crack t i p s i s taken i n t o account through i t s e f f e c t on the f r a c t u r e toughness.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

16

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SHALE,

T A R SANDS,

AND RELATED

MATERIALS

The SCM model makes use o f two r e s u l t s from fracture mechanics: the c o n d i t i o n f o r s t a b i l i t y against crack growth f o r an a r b i t r a r y s t a t e o f s t r e s s , and the r e d u c t i o n i n the e f f e c t i v e e l a s t i c moduli o f a body c o n t a i n i n g a penny-shaped crack. The f i r s t r e s u l t i s a g e n e r a l i z e d G r i f f i t h c r i t e r i o n , which can be used to say which cracks i n the s t a t i s t i c a l d i s t r i b u t i o n w i l l grow given the a p p l i e d s t r e s s e s . The second r e s u l t allows the weakening o f the rock as i t i s f r a c t u r e d to be modeled. The use o f the g e n e r a l i z e d G r i f f i t h c r i t e r i o n not only allows cracks to extend under t e n s i l e l o a d i n g , but a l s o allows cracks to extend i n shear, even under moderate normal compression. T h i s means that closed shear cracks can extend under i n t e n s e l o a d i n g (as near an e x p l o s i v e charge), causing the m a t e r i a l to be much weaker under subsequent t e n s i l e l o a d i n g . The r e d u c t i o n i n the e l a s t i c moduli i s a l s o important i n that i t leads to the c o r r e c t d i r e c t i o n a l response as the rock i s fractured. Thus, phenomena such as s p a l l are modeled i n a r e a l i s t i c fashion. The SCM theory i s being implemented and t e s t e d i n s t r e s s wave codes a t t h i s time. E a r l y r e s u l t s are encouraging, and t h i s approach holds great promise f o r the f u t u r e . Damage Model. I t i s possible to extend the usual elastic/plastic theory for solids to include fracture phenomenologically i n terms o f a "damage parameter. T h i s has been done by v a r i o u s i n v e s t i g a t o r s (7, .8), i n c l u d i n g Johnson (5) with h i s Continuum Damage Model (CDM). In the CDM, the damage parameter v a r i e s from zero to one as the rock goes from f u l l y i n t a c t to h e a v i l y broken. The c o n s t i t u t i v e r e l a t i o n i n the CDM i s a standard e l a s t i c / p l a s t i c model, except that the f a i l u r e s u r f a c e i s a f u n c t i o n o f the damage parameter. The damage parameter can be i n t e r p r e t e d as a measure o f the l o s s o f shear strength a t zero c o n f i n i n g pressure. The l e v e l o f damage i n a computational c e l l i n c r e a s e s during p l a s t i c flow. The CDM has two a d d i t i o n a l f e a t u r e s that allow i t to represent f r a c t u r e i n rocks. F i r s t , there i s a b r i t t l e / d u c t i l e t r a n s i t i o n pressure. Above t h i s pressure, the rock behaves as an elastic/plastic ductile solid, the f a i l u r e surface i s independent o f the l e v e l o f damage, and the damage i s not allowed to i n c r e a s e , even i f the f a i l u r e surface i s exceeded. Second, the CDM allows f o r non-vanishing p l a s t i c volume s t r a i n to approximate the d i l a t a n c y observed i n certain laboratory experiments on o i l s h a l e . The CDM has the disadvantage o f being built around p l a s t i c i t y , which i s i n h e r e n t l y d i f f e r e n t from f r a c t u r e . In a d d i t i o n , as a s c a l a r model ( f r a c t u r e described by a s i n g l e damage parameter), i t cannot represent the tensor response o f rock as a c c u r a t e l y as the SCM model. Nevertheless, i t does have appropriate phenomenological features and, p r o p e r l y c a l i b r a t e d , should allow u s e f u l engineering c a l c u l a t i o n s . 11

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

2.

ADAMS

Computer

Simulation

of

Explosive

Fracture

17

Material Constants. Elastic wave v e l o c i t i e s have been obtained f o r o i l shale by u l t r a s o n i c methods f o r v a r i o u s modes o f propagation. E l a s t i c constants can be i n f e r r e d from these data i f the o i l shale i s assumed to be a t r a n s v e r s e l y i s o t r o p i c s o l i d ( 9 . ) . T h i s i s a reasonable approximation c o n s i d e r i n g the bedded nature o f the rock. Many of the p r o p e r t i e s of o i l shale depend on the grade (kerogen content), which i n turn i s c o r r e l a t e d with the d e n s i t y ( 1 0 ) . The high pressure behavior o f o i l shale under shock l o a d i n g has been s t u d i e d i n gas-gun impact experiments ( 1 1 ) . Data on the strength o f o i l shale are more d i f f i c u l t to obtain, especially data f o r the intermediate strain rates (10-103/s) relevant to blasting. Extensive quasi-static t r i a x i a l t e s t i n g data are a v a i l a b l e f o r o i l shale of two grades at a range o f c o n f i n i n g pressures (Jj?). These data were averaged over sample o r i e n t a t i o n to g i v e mean y i e l d strengths. I t has been shown that y i e l d strength varies significantly depending on the o r i e n t a t i o n with respect to the bedding planes ( 1 3 ) , at least i n q u a s i - s t a t i c tests. The triaxial testing data and other data (e.g., from three-point bending t e s t s ) can a l s o be i n t e r p r e t e d i n terms of the f r a c t u r e toughness o f o i l s h a l e . Rather than r e f e r r i n g to a p l a s t i c y i e l d s t r e n g t h , the f r a c t u r e toughness serves as an input constant f o r the SCM f r a c t u r e model. Other input data needed f o r the SCM model include the mean crack (or flaw) s i z e and d e n s i t y as a f u n c t i o n o f o r i e n t a t i o n throughout the sample. These data could be obtained d i r e c t l y by examination of samples or i n d i r e c t l y i n simple l a b o r a t o r y t e s t s . Regardless of the m a t e r i a l model being used, data at i n t e r mediate s t r a i n r a t e s under c o n t r o l l e d l a b o r a t o r y c o n d i t i o n s are needed. Such data should be obtainable soon with the new l a r g e diameter gas gun and Split-Hopkinson Bar facilities being e s t a b l i s h e d at Los Alamos. Comparison between C a l c u l a t i o n s and F i e l d

Experiments

Any complex code, such as YAQUI, must be c a l i b r a t e d and v e r i f i e d by comparing c a l c u l a t i o n s with the r e s u l t s of r e a l i s t i c f i e l d experiments. A s e r i e s of e x p l o s i v e f i e l d t e s t s u s i n g ANFO i n o i l shale has been conducted i n the Colony Mine near R i f l e , Colorado. These experiments were performed under DOE auspices with the cooperation o f A t l a n t i c R i c h f i e l d , TOSCO, and the Colony Development Corporation. They were conducted for comparison with code calculations and to o b t a i n e m p i r i c a l i n f o r m a t i o n about b l a s t i n g i n o i l s h a l e . Field Experiments. Fifteen i n t e r m e d i a t e - s i z e experiments were conducted with amounts of ANFO ranging from 5 kg to over 1 0 0 kg. Three of the ,experiments were h e a v i l y equipped with s t r e s s and v e l o c i t y gauges i n separate instrumentation boreholes and d i a g n o s t i c cables i n s i d e the e x p l o s i v e boreholes (to g i v e

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

18

OIL

SHALE,

T A R SANDS, A N D R E L A T E D

MATERIALS

r e a l - t i m e data on the detonation). The other experiments had v a r y i n g l e v e l s o f i n s t r u m e n t a t i o n . E x t e n s i v e p r e - and post-shot g e o l o g i c mapping were conducted a t each experiment s i t e . Preand post-shot core samples were taken i n the v i c i n i t y o f some o f the experiments. Where r u b b l i n g extended to the s u r f a c e , c r a t e r p r o f i l e s were measured and data concerning the rubble were taken. A complete a n a l y s i s and c o r r e l a t i o n o f the data i s i n progress and w i l l be published elsewhere. The a n a l y s i s i s being done p a r t l y i n the framework o f s c a l i n g r e l a t i o n s , where v a r i o u s experiments are compared a f t e r removing f i r s t order e f f e c t s due to d i f f e r e n t charge s i z e or depth o f b u r i a l . This aids i n q u a n t i f y i n g e f f e c t s , such as the i n f l u e n c e o f s i t e - s p e c i f i c geology (e.g., j o i n t and f a u l t s t r u c t u r e s ) , on c r a t e r s i z e and shape. In the remainder o f t h i s r e p o r t , we compare three YAQUI calculations with the r e s u l t s o f the corresponding field experiments. The c a l c u l a t i o n s and experiments to be discussed a l l i n v o l v e d s i n g l e c y l i n d r i c a l charges o f 0.15-m-diameter ANFO emplaced i n boreholes d r i l l e d s t r a i g h t i n t o the mine f l o o r . The charge lengths and depths o f b u r i a l are given i n Table I I . The detonator was placed a t the bottom o f the charge i n each case.

Table I I Data f o r Three O i l Shale B l a s t i n g Experiments

Designation 79-7

Charge Length 0.99 m

Depth o f B u r i a l Charge Bottom Charge Top 4.57 m 3.58 m

79-8

0.99

3.30

2.31

79-10

1.73

3.30

1.57

These three experiments form an i n t e r e s t i n g subset o f the larger series. Experiment 79-7 was buried deeply enough that i t was f u l l y contained, with no c r a t e r formation or even s u r f a c e flaw a c t i v a t i o n . Post-shot d r i l l i n g d i d r e v e a l a rubbled region around the charge. In experiment 79-8, the same s i z e charge was used, buried 1.3 m c l o s e r to the s u r f a c e . An extensive shallow c r a t e r was formed, s t a r t i n g about midway from the top o f the charge to the mine f l o o r and extending outward. The c r a t e r was asymmetric as a r e s u l t o f the i n f l u e n c e o f the l o c a l joint structure. F i n a l l y , experiment 79-10 had the same charge bottom depth as 79-8, but had more e x p l o s i v e . T h i s experiment produced a roughly c o n i c a l crater s t a r t i n g near the center o f the charge. T h i s c r a t e r was a f f e c t e d very l i t t l e by the j o i n t structure. YAQUI C a l c u l a t i o n s . The YAQUI code described above was used to simulate experiments 79-7, 79-8, and 79-10. A continuum damage model s i m i l a r to the one developed by Johnson (5.), using Johnson's damage constants, was used with a rate-independent

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

2.

ADAMS

Computer

Simulation

of

Explosive

Fracture

19

elastic/plastic routine. I t i s instructive to f o l l o w the sequence o f events that occurred i n experiment 79-8. Figures 1-4 show the l o c a t i o n o f the shock wave and the extent o f the "damage" 0.2, 0.6, 1.0, and 2.0 ms, r e s p e c t i v e l y , a f t e r the f i r i n g o f the detonator. At 0.2 ms (Figure 1), the detonation f r o n t has moved more than halfway up the charge. The upwardmoving shock can be seen along with the region of intense damage around the bottom o f the charge. By 0.6 ms (Figure 2 ) , the detonation i s over and the shock wave i s propagating through the o i l shale toward the f r e e s u r f a c e . Extensive r u b b l i n g has occurred i n the v i c i n i t y o f the charge. The shock wave i s approaching the f r e e surface a t 1.0 ms (Figure 3 ) . Some a d d i t i o n a l damage has now occurred i n a region bounded roughly by an i n v e r t e d 45° cone extending upward from near the top o f the charge. T h i s i s the region where the maximum shear l o a d i n g occurred during the f i r s t passage o f the shock wave. The 45° angle i s r e l a t e d to the r a t i o o f the sound speed i n o i l shale to the detonation v e l o c i t y i n ANFO. Had the SCM model been used i n s t e a d o f the damage model, c l o s e d shear cracks would have grown i n t h i s region as the shear wave passed. A t e n s i l e r e l i e f wave propagates downward a f t e r the shock reaches the f r e e s u r f a c e . T h i s causes a l a y e r of s p a l l damage to occur near the surface above the charge. By 2.0 ms (Figure 4 ) , the s p a l l l a y e r has formed and the f u l l extent o f the computed damage can be seen. The c a l c u l a t i o n was c a r r i e d out long enough to f o l l o w a l l the dynamic phases o f the b l a s t , but not long enough to f o l l o w the throwout of d e b r i s or the formation o f the a c t u a l c r a t e r . The combination o f heavy damage near the charge, the shear-damaged region, and the s p a l l l a y e r presumably represent the c r a t e r that w i l l be formed. The c a l c u l a t i o n does not, i n f a c t , show complete r u b b l i n g i n the region above the charge. T h i s i s c o n s i s t e n t with the f a c t that i n the f i e l d only a shallow c r a t e r , h e a v i l y i n f l u e n c e d by the l o c a l geology, was formed. F i g u r e 5 shows the extent o f damage c a l c u l a t e d a t 2.0 ms f o r experiment 79-7. The regions o f damage around the charge and shear damage above the charge are v i s i b l e , as i n the c a l c u l a t i o n f o r experiment 79-8. However, n e i t h e r damaged region reaches the s u r f a c e , and the t e n s i l e r e l i e f wave was too weak to produce a s p a l l l a y e r . Thus, the c a l c u l a t i o n i s i n good agreement with the observation i n the f i e l d that there was no surface damage, although there was an extensive rubbled region around the charge. F i g u r e 6 shows the c a l c u l a t e d damage d i s t r i b u t i o n a t 2.0 ms f o r experiment 79-10. The r e l a t i v e l y shallow depth o f b u r i a l f o r t h i s charge r e s u l t s i n intense damage. The three regions o f damage seen i n e a r l i e r c a l c u l a t i o n s now merge to form a c r a t e r much l i k e the one that was observed. The i n t e n s i t y o f rock breakage shown i n the c a l c u l a t i o n makes i t easy to understand why the j o i n t s t r u c t u r e had l i t t l e i n f l u e n c e on the c r a t e r i n the f i e l d .

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

20

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Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

11

Figure 1. Damage distribution and mean stress contour plot at 0.2 ms in computer simulation of Experiment 79-8. The mean stress contour level is lOMPa compressive. The distribution and density of the dots show the extent of the damage. The blank region inside the damaged area is the explosive, which lies on an axis of cylindrical symmetry. The dimensions of the plot frame are 14 m X 9 m. The top boundary is the mine floor. At this time, the detonation front is traveling upward through the explosive. A shock wave is propagating upward and away from the charge, and damage is occurring near the portion of the charge that has been detonated.

Figure 2. Damage distribution and mean stress contour plot at 0.6 ms in computer simulation of Experiment 79-8. The contour level and plot dimensions are the same as in Figure 1. At this time, the detonation is complete. A shock wave is propagating upward toward the free surface. Extensive damage has occurred around the charge.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

ADAMS

Computer

Simulation

of

Explosive

Fracture

Figure 3. Damage distribution and mean stress contour plot at 1.0 ms in computer simulation of Experiment 79-8. The contour level and plot dimensions are the same as in Figure 1. At this time, the shock wave is approaching the free surface. Damage has occurred above the charge in addition to the damage around the charge.

Figure 4. Damage distribution and mean stress contour plot at 2.0 ms in computer simulation of Experiment 79-8. The contour level and plot dimensions are the same as in Figure 1. At this time, a layer of spall damage can be seen near the free surface. It developed as the tensile relief wave propagated downward following the interaction of the explosively generated shock with the free surface. This figure shows the final computed damage distribution.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

OIL

SHALE,

T A R SANDS,

ANDRELATED

MATERIALS

Figure 5. Damage distribution and mean stress contour plot at 2.0 ms in computer simulation of Experiment 79-7. The contour level and plot dimensions are the same as in Figure 1. Note that the charge is buried more deeply here. This figure shows the final computed damage distribution. No spall damage has occurred near the surface because of the increased depth of burial.

Figure 6. Damage distribution and mean stress contour plot at 2.0 ms in computer simulation of Experiment 79-10. The contour level and plot dimensions are the same as in Figure 1. Note that the bottom of the charge is at the same depth as in Experiment 79-8 (Figures 1-4), but the charge is larger and extends closer to the free surface. The shallower effective depth of burial has resulted in the formation of a crater-shaped damage region, much as was observed in the corresponding field experiment.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2.

ADAMS

Computer

Simulation

of

Explosive

Fracture

23

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

Conclusion The steps in assembling the computational tools needed to simulate the explosive fracture of o i l shale have been described. The resulting code, with its input data, was then used to simulate three explosive field experiments. The results of the calculations are in good agreement with what actually occurred in the field. Further detailed comparisons are in progress for these experiments and the others that have been conducted. As this is done, improvements will be made in the input data and in the code physics. The development of computer codes as tools to predict rock breakage makes a variety of interesting studies possible. The properties of the explosive can be changed to see how the extent of rubbling is affected. Studies of spacing and delays for decked charges are also possible. Finally, the codes can be applied in situations, such as confined-volume blasting, at the frontiers of blasting technology. These areas are vital to the effective utilization of our o i l shale resources, especially with in situ techniques. Computer simulation will play a central role in the development of new technology for energy and mineral resource recovery. Acknowledgment This work was performed Department of Energy.

under the auspices of the U. S.

Literature Cited 1. Amsden, A. A.; Hirt, C. W. "YAQUI: An Arbitrary Lagrangian-Eulerian Computer Program for Fluid Flow at All Speeds," Los Alamos Scientific Laboratory report LA-5100, March 1973. 2. Hirt, C. W.; Amsden, A. A.,; Cook, J. L. "An Arbitrary Lagrangian-Eulerian Computing Method for A l l Flow Speeds," J. Comput. Phys. 1974, 14, 227. 3. Mader, C. L. "Numerical Modeling of Detonations"; University of California Press: Berkeley, 1979. 4. Craig, B. G.; Johnson, J. N.; Mader, C. L.; Lederman, G. F. "Characterization of Two Commercial Explosives," Los Alamos Scientific Laboratory report LA-7140, May 1978. 5. Johnson, J. N. "Calculation of Explosive Rock Breakage: Oil Shale," in "Proceedings of the 20th U. S. Symposium on Rock Mechanics," U. S. National Committee for Rock Mechanics, June 1979, pp. 109-118. 6. Dienes, J. K.; Margolin, L. G. "A Computational Approach to Rock Fragmentation," presented at the 21st U. S. Symposium on Rock Mechanics, Rolla, Missouri, May 1980.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

24

7.

8.

9.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch002

10. 11.

12.

13.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

Butkovich, T. R. "Correlations between Measurements and Calculations of High-Explosive-Induced Fracture in a Coal Outcrop," Int. J. Rock Mech. Min. Sci. and Geomech. Abstr. 1976, 13, 45. Kipp, M. E.; Grady, D. E. "Numerical Studies of Rock Fragmentation," Sandia Laboratories report SAND-79-1582, presented at the 2nd International Conference on Numerical Methods in Fracture Mechanics, Swansea, July 1980. Olinger, B. "Oil Shales under Dynamic Stress," in "Explosively Produced Fracture of Oil Shale, April 1977March 1978," Los Alamos Scientific Laboratory report LA-7357-PR, November 1978, pp. 2-10. Smith, J. W. "Specific Gravity-Oil Yield Relationships of Two Colorado Oil Shale Cores," Ind. Eng. Chem. 1956, 48, 441. Carter, W. J. "Hugoniot of Green River Oil Shale," in "Explosively Produced Fracture of Oil Shale, March 1976-March 1977," Los Alamos Scientific Laboratory report LA-6817-PR, September 1977, pp. 2-6. Johnson, J. N.; Simonson, E. R. "Analytical Failure Surfaces for Oil Shale of Varying Kerogen Content," in Timmerhaus, K. D.; Barber, M. S., Eds., "High Pressure Science and Technology, Sixth AIRAPT Conference," Vol. 2; Plenum: New York, 1979, pp. 444-454. McLamore, R.; Gray, J. "The Mechanical Behavior of Anistropic Sedimentary Rocks," J. Eng. Ind. 1967, 89, 62.

RECEIVED January 19,

1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

3 Fracturing of Oil Shale by Treatment with Liquid Sulfur Dioxide D. F. BUROW and R. K. SHARMA

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

Department of Chemistry, University of Toledo, Toledo, OH 43606

Development of o i l shale deposits as sources of fuels, lubricants, and chemical feedstocks is being considered as an alternative to present reliance on conventional petroleum reserves. Procedures, advantages, and disadvantages for mining/ surface processing and for in situ retorting have been widely discussed (1, 2, 3). In the former approach, crushing of the shale is essential for efficient o i l recovery. As a result of tests with a variety of mechanical crushers (4), i t is apparent that the effectiveness of mechanical crushing is limited by the characteristics of the shale. A slab-forming tendency allows large pieces to pass through many conventional crushers. The resilience and slippery nature of the shale limits the effectiveness of mechanical impact. Furthermore, shale abrasiveness and a tendency for the shale to adhere to crusher surfaces causes maintenance problems with crushers. In situ retorting is enhanced by fracturing with explosive charges or expansion of existing fractures with fluids such as water. Fracturing by explosive charges is frequently limited to the vicinity of the charge since the explosive shock is dissipated by shale resilience. Efficient fracturing by aqueous fluids is limited by a tendency for capillary adhesion of water in the fissures and by available water supplies in arid regions where o i l shale deposits often occur. Employment of chemical comminution techniques for surface processing of o i l shales could circumvent many of the limitations to mechanical crushing as well as reduce or eliminate capital and maintenance costs of crushers. For in situ processing, such techniques could provide an alternative to explosive or hydrostatic fracturing. Our recent success in comminuting and desulfurizing coal by treatment with liquid sulfur dioxide 05, 6), suggested that similar treatments might be successfully applied to o i l shale processing. Liquid SO2 is a remarkably subtle and selective solvent with moderate Lewis acid properties, a substantial resistance to oxidation and reduction when pure, and a propensity to support a 0097-615 6/81/0163-0025 $05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

26

OIL

SHALE,

T A R SANDS,

AND RELATED

MATERIALS

v a r i e t y o f i o n i c , f r e e r a d i c a l , and molecular r e a c t i o n s (7) . P h y s i c a l p r o p e r t i e s of l i q u i d SO2 which can be e x p l o i t e d advantageously i n c l u d e : a -10° bp, moderate vapor pressure a t room temperature, high d e n s i t y , low v i s c o s i t y , and low surface t e n s i o n . Since SO2 has a b o i l i n g p o i n t of -10°C, i t i s e a s i l y l i q u i f i e d and/or removed a f t e r r e a c t i o n ; i t can be e a s i l y manipulated without the need f o r e x o t i c c o n s t r u c t i o n m a t e r i a l s . Furthermore, i t i s an inexpensive m a t e r i a l which i s r e a d i l y a v a i l a b l e i n l a r g e q u a n t i t i e s from smelting and f o s s i l f u e l combustion; i f not u t i l i z e d , i t must be disposed o f i n some s t a b i l i z e d form a t cons i d e r a b l e expense. Thus, the d i r e c t use of s u l f u r d i o x i d e could provide an a l t e r n a t i v e means o f cost recovery f o r p o l l u t i o n abatement technology. Here we wish t o r e p o r t the r e s u l t s o f p r e l i m i n a r y e x p e r i ments i n which o i l shales are t r e a t e d with l i q u i d s u l f u r d i o x i d e to e f f e c t f r a c t u r i n g ; observations made during these experiments suggest that l i q u i d SO2 may a l s o be of u t i l i t y i n other phases of o i l shale p r o c e s s i n g . We a r e , p r e s e n t l y , unaware of any previous r e p o r t s o f such experiments. Experimental S u l f u r d i o x i d e was d r i e d and manipulated as described e l s e where ( 7 ) . A 1 - l i t e r s t a i n l e s s s t e e l autoclave (Parr Model 4641) was u t i l i z e d f o r p r o c e s s i n g a t pressures i n excess o f c a . 3 atm. In experiments u t i l i z i n g l a r g e r shale pieces (6-8 cm), clamped shale samples, or s u p e r c r i t i c a l c o n d i t i o n s , samples were placed d i r e c t l y i n the autoclave. For s u b - c r i t i c a l experiments using small shale p i e c e s , samples were sealed i n f r i t t e d g l a s s tubes with l i q u i d SO2 ( c a . 2:1 or l e s s S02/shale by weight) to f a c i l i t a t e recovery of e x t r a c t s . S u l f u r d i o x i d e was d i s t i l l e d on to the shale a t -78°C; the system was then sealed and brought up to p r o c e s s i n g temperature. Temperatures of 25, 70, and 170°C were used; s u p e r c r i t i c a l c o n d i t i o n s f o r SO2 were achieved a t the l a t t e r temperature. Processing time was c a . 2 hours f o r elevated temperature experiments; f o r room temperature experiments, the time ranged from 2 t o 24 hours. No mechanical a g i t a t i o n was employed. Upon c o o l i n g , the SO2, s h a l e , and e x t r a c t were recovered. The shales were inspected immediately upon recovery and a t s e v e r a l i n t e r v a l s thereafter. S u l f u r analyses and i n f r a r e d s p e c t r a o f the shales were performed on o r i g i n a l , processed, and processed/heated samples to determine r e s i d u a l SO2 content. I n f r a r e d s p e c t r a of the e x t r a c t s were a l s o obtained. A l l i n f r a r e d s p e c t r a were recorded on a P e r k i n Elmer Model 621 spectrophotometer; s o l i d samples were examined as KBr p e l l e t s and shale e x t r a c t s were examined as t h i n f i l m s (neat) between NaCl p l a t e s . Shale samples were a l s o t r e a t e d with gaseous SO2, l i q u i d CO2, l i q u i d NH3, water, and s e v e r a l organic l i q u i d s at 25°C f o r 2 days. Procedures e q u i v a l e n t t o those used with l i q u i d SO2 were

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

3.

BUROW A N D SHARMA

Fracturing

of

Oil

Shale

27

employed f o r treatment with gaseous SO2, l i q u i d CO2, and l i q u i d NH3. Treatment with other l i q u i d s c o n s i s t e d of immersion of shale samples i n the l i q u i d contained i n covered beakers. Samples of Antrim, Green R i v e r , and Moroccan o i l shales were obtained from the Laramie Energy Technology Center. The composit i o n of t y p i c a l samples of these three shales i s i l l u s t r a t e d i n Table I.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

Results and D i s c u s s i o n Upon exposure of the shales to l i q u i d SO2, h i g h l y c o l o r e d s o l u t i o n s develop due to formation of donor-acceptor complexes between e x t r a c t e d o i l c o n s t i t u e n t s and the SO2. Green R i v e r shale produces red-brown s o l u t i o n s , Moroccan shale forms orange s o l u t i o n s , and Antrim shale forms yellow s o l u t i o n s ; i n each case, these c o l o r s are more intense when higher p r o c e s s i n g temperatures are used. F r a c t u r i n g of Shales. L i q u i d SO2 causes extensive f r a c t u r i n g i n each of the three shales examined i n t h i s p r e l i m i n ary study; Figure 1 i l l u s t r a t e s r e p r e s e n t a t i v e examples of t h i s f r a c t u r i n g . T h i s f r a c t u r i n g occurs both along and across l a m i n a t i o n s . With the l a r g e r lumps, laminations are f r e q u e n t l y expanded to 1-2 cm; f r a c t u r e s across laminations are l e s s pronounced but d i s t i n c t l y v i s i b l e . Green River shale e x h i b i t s numerous small cracks whereas the other two shales e x h i b i t a fewer number of l a r g e r cracks. With p r o c e s s i n g temperatures below 25°C, the degree of f r a c t u r i n g i s g r e a t e s t i n Moroccan and l e a s t i n Antrim shale; with higher p r o c e s s i n g temperatures, d i f f e r e n c e s i n degree of f r a c t u r i n g are not so apparent. Samples of each of the s h a l e s , r i g i d l y clamped both across and along laminations a l s o e x h i b i t e d extensive f r a c t u r i n g . Immedia t e l y upon recovery from the r e a c t o r , the samples are so b r i t t l e as to be e a s i l y broken with the f i n g e r s ; a f t e r standing f o r a time, the samples become s l i g h t l y l e s s b r i t t l e but a l l f r a c t u r i n g i s maintained. Although no q u a n t i t a t i v e t e s t s of mechanical p r o p e r t i e s have been made, i t appears t h a t l i t t l e of the r e s i l i e n c e and s l i p p e r y n e s s of the o r i g i n a l shales i s r e t a i n e d . Surfaces of the processed samples have a s o f t l u s t e r o u s appearance. Shale samples were subjected to treatment with other f l u i d s at 25°C to provide comparative data on t h e i r a b i l i t y to f r a c t u r e these s h a l e s . From among these f l u i d s o n l y gaseous SO2, l i q u i d NH3, and methylene c h l o r i d e were e f f e c t i v e f r a c t u r i n g agents under these c o n d i t i o n s . The r e s u l t s are summarized i n Table I I . Under the same c o n d i t i o n s of temperature and pressure, gaseous SO2 i s l e s s e f f e c t i v e than the l i q u i d i n producing f r a c t u r e s . Both l i q u i d NH3 and methylene c h l o r i d e produce roughly the same degree of f r a c t u r i n g as l i q u i d SO2. L i q u i d NH3, however, appears to produce the greatest f r a c t u r i n g with Antrim shale and the

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

a. b. c. d. e.

Organic Matter: Oil Yield:

9

d e

C nmr

d e 11% (3:1 a l i p h a t i c / a r o m a t i c ) * vL8 gal/ton

9% (1:1 a l i p h a t i c / a r o m a t i c ) VL0 gal/ton 45% 30% 5% 5%

Samples provided by F. M i k n i s , LETC Ref. 8. Ref. 9. Ref. 10. A l i p h a t i c / a r o m a t i c r a t i o e s t a b l i s h e d from s o l i d s t a t e s p e c t r a , Ref. 10.

Moroccan

Organic Matter: Oil Yield: Illite: Quartz: Pyrite: Carbonates:

Organic Matter: Oil Yield: Dolomite and C a l c i t e : Feldspar and P l a g i o c l a s e : I l l i t e , M o n t m o r i l l i n i t e , Muscovite: Quartz: c Antrim (Michigan)

Examined

d e 14% (mostly a l i p h a t i c ) ' ^25 gal/ton 43% 16% 13% 9%

T y p i c a l Composition of O i l Shales

Green River (Colorado)

Table I.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

Fracturing

of

Oil

Shale

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

BUROW AND SHARMA

Figure 1. Representative examples of the fracturing of oil shales by liquid S0 ; (left) treated samples; (right,) untreated samples; (a) Antrim shale treated at 170°C for 2 h; (b) Green River shale treated at 70°C for 2 h; (c) Moroccan shale treated at 70°Cfor2 h. 2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981. 2

N N N HF,E

-

-

DMF

HMPA

2

H

b.

a.

-

-

-

-

-

-

HF,E

N

HF,E HF,E HF,E HF,E

-

Moroccan

3

Except f o r l i q u i d S 0 , t e s t s were run a t 25°C f o r 2 days. N: no apparent f r a c t u r i n g , MF: moderate f r a c t u r i n g , HF: extensive f r a c t u r i n g , E: e x t r a c t observed.

6 6 H CC1

2

N

-

C

N

DMSO

3

N

2

-

HF,E

HF,E

N

-

( L i q u i d , VL0 atm)

N

CH CN

3

NH

( L i q u i d , ^60 atm)

H 0

2

C0

MF,E MF,E HF,E HF,E HF,E

-

Gas (^3 atm) L i q u i d (-78°C) L i q u i d (25°C) L i q u i d (70°C) S u p e r c r i t i c a l (170°C) N MF,E HF,E HF,E

Green R i v e r

3

Antrim

Shales*

F r a c t u r i n g o f O i l Shales by Various F l u i d s

Fluid

Table I I .

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

3.

BUROW A N D SHARMA

Fracturing

of

Oil

Shale

31

l e a s t with Moroccan shale; t h i s trend i s j u s t the opposite o f that observed with l i q u i d SO2. Our r e s u l t s with l i q u i d CO2 are i n apparent c o n f l i c t w i t h r e s u l t s reported by M i l l e r , et a l . (11) for treatment o f Devonian shales with CO2 f l u i d s . From among the f l u i d s t e s t e d , l i q u i d SO2 has s e v e r a l advantages as a f r a c t u r i n g agent f o r o i l s h a l e s : i t i s low i n c o s t , i t i s a v a i l a b l e i n q u a n t i t y , i t i s not d e r i v e d from e i t h e r petroleum or n a t u r a l gas, and i t i s r e a d i l y manipulated due t o i t s moderate vapor pressure. The s u l f u r content of the shales i s increased somewhat by p r o c e s s i n g i n l i q u i d SO2; r e s i d u a l s u l f u r i n c r e a s e s s i g n i f i c a n t l y with the temperature of the treatment, however. For example, at room temperature, r e s i d u a l s u l f u r i n c r e a s e s by 1-2% but a t 170°C, i t i n c r e a s e s by 5-10%. Comparison of i n f r a r e d s p e c t r a of untreated and t r e a t e d shale samples (Figures 2-4, A and B) i n d i c a t e s that t h i s increased s u l f u r content i s due to formation of sulfur-oxygen c o n t a i n i n g r e s i d u e s , probably s u l f i t e s and/or s u l f a t e s , i n the s h a l e s . I t might appear that the increase i n s u l f u r content o f any shale f r a c t u r e d by l i q u i d SO2 would be d e l e t o r i o u s to o i l produced i n a subsequent r e t o r t i n g step. However, s i n c e t h i s r e t a i n e d SO2 appears t o be i n the i n o r g a n i c part o f the shale as adsorbed SO2, s u l f i t e s , or s u l f a t e s , l i t t l e contamination o f the r e t o r t e d o i l should occur: adsorbed SO2 can be removed i n a m i l d preheating step and the s u l f i t e / s u l f a t e species are s u f f i c i e n t l y s t a b l e to remain i n t a c t during any r e t o r t i n g step. S u l f u r elemental and i n f r a r e d analyses o f t r e a t e d shale samples, performed before and a f t e r m i l d h e a t i n g , demonstrated that adsorbed SO2 can be removed e a s i l y . P r e l i m i n a r y SEM/EDXA r e s u l t s f o r Green River Shale i n d i c a t e that these sulfur-oxygen r e s i d u e s are apparently a s s o c i a t e d with s e l e c t e d i n o r g a n i c c o n s t i t u e n t s of the s h a l e . EDXA o f untreated Green River shale samples i n d i c a t e d a Si/Ca r a t i o o f c a . 1.5; t h i s r a t i o corresponds c l o s e l y to that expected from the b u l k composition o f the shale (Table I ) . The s u l f u r which i s present i n untreated samples was observed to be c o r r e l a t e d with Ca r a t h e r than Fe l o c a t i o n s , suggesting that l i t t l e p y r i t i c s u l f u r was present i n these p a r t i c u l a r samples. Treated samples of Green River shale e x h i b i t e r o s i o n and p i t t i n g o f the s u r f a c e i n Ca r i c h areas but no apparent changes i n S i r i c h areas. The p i t s have diameters i n the 2-10 ym range. In t r e a t e d samples, the Si/Ca r a t i o was o f t e n found to be s i g n i f i c a n t l y higher than i n untreated samples; t h i s observation suggests that l i q u i d SO2 causes a surface d e p l e t i o n o f Ca i o n s . The increased s u l f u r content of t r e a t e d samples i s r e a d i l y apparent i n the EDXA r e s u l t s ; t h i s increased S content i s a s s o c i a t e d with Ca r i c h but not S i or Fe r i c h regions i n the s h a l e . These SEM/EDXA data suggest that l i q u i d SO2 a t t a c k s the c a l c i t e and/or dolomite c o n s t i t u e n t s o f Green River shale and, perhaps, thereby causing the observed f r a c t u r i n g . S i m i l a r data on the other shales were not obtained during t h i s e x p l o r a t o r y work.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2

2

Figure 2. IR spectra of Green River oil shale: (a) untreated sample; (b) sample treated with liquid S0 at 70°C for 2 h; (c) sample treated with S0 fluid at 170°C for 2 h; (d) extract isolated from treatment in b.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

on

r

Η W

α >

Η W

>

w

σ

>

> υ

w Η

on

ssr

F

Ο

to

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Figure

3. 2

IR spectra of Morrocan oil shale: (a) untreated sample; (b) sample treated with SO at70°C for 2 h; (c) extract isolated from treatment in b.

W A V E N U M B E R (CM)

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

liquid

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Figure 4. 2

IR spectra of Antrim oil shale: (a) untreated sample; (b) sample treated with liquid SO at70°C for 2 h; (c) extract isolated from treatment in b.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

00

Η W

>

σ

Η W

>

Ζ

>

GO

>

Η

w

Ρ a r

Ο

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

3.

Fracturing

BUROW A N D SHARMA

of

Oil

Shale

35

F r a c t u r i n g of Model M i n e r a l s . Further i n s i g h t i n t o the p r o cesses r e s p o n s i b l e f o r l i q u i d SO2 f r a c t u r i n g of these shales i s provided by the behavior of s e v e r a l m i n e r a l s when subjected to l i q u i d SO2. Authenic samples of c a l c i t e ( c r y s t a l s ) , dolomite (hard lumps), gypsum (hard lumps), and i l l i t e (hard lumps) were t r e a t e d with l i q u i d SO2 at 25°C f o r 2-5 hours; a f t e r removal of the SO2, the t r e a t e d minerals were heated f o r 2 hours at 100°C; i n f r a r e d s p e c t r a and s u l f u r analyses were then obtained. Calcite c r y s t a l s developed numerous f i n e cracks and a f i n e powder f l a k e d off. Although the powder contained no s u l f u r (elemental a n a l y s i s ) or S-0 m o i e t i e s (IR s p e c t r a ) , the cracked c r y s t a l s were shown to c o n t a i n 0.18% s u l f u r i n the form of sulfur-oxygen s t r u c t u r e s . Although these data are c o n s i s t e d w i t h a 0.7% conversion v i a O p Z5

CaC0 (s) + S 0 U ) 3

±

-

2

> CaS0 (s) + C 0 ( s ) 3

2

other processes cannot he excluded at t h i s stage. Dolomite, on the other hand, d i d not appear to be e f f e c t e d by l i q u i d SO2 under the c o n d i t i o n s employed: t r e a t e d dolomite e x h i b i t e d no f r a c t u r ing, no s u l f u r content, and no mass change. Gypsum chunks were f r a c t u r e d by l i q u i d SO2. I n f r a r e d and s u l f u r analyses i n d i c a t e that l i q u i d S0 i n t e r a c t s with gypsum i n two ways: f i r s t , simple e x t r a c t i o n o f water of c r y s t a l l a t i o n and, second, r e a c t i o n with a p o r t i o n of the remaining water of c r y s t a l l a t i o n to form H and HSO3. Large cracks develop and a powder f l a k e s o f f when i l l i t e lumps are t r e a t e d with l i q u i d SO2; s u l f u r analyses i n d i cate approximate compositions to be iKAl^SiAK^o(OH)4]•(SO2)0.3 (lumps) and [KAli SiA10 o(OH)i ] • (S0 ) o.> (powder). I n f r a r e d s p e c t r a l changes suggest p a r t i a l r e a c t i o n of the OH groups to form SO3H groups. 2

+

t

2

+

2

F r a c t u r i n g Mechanisms. These observations with model minerals suggest that s e v e r a l mechanisms be considered f o r the observed f r a c t u r i n g of o i l shales by l i q u i d SO2. P a r t i a l conv e r s i o n of carbonates to s u l f i t e s could d i s r u p t m i c r o c r y s t a l l i n e l a t t i c e s i n carbonate r i c h s h a l e s . P a r t i a l r e a c t i o n of the OH groups i n a l l u m i n o s i l i c a t e s could cause s i m i l a r changes i n s i l i c e o u s s h a l e s . E x t r a c t i o n of or r e a c t i o n with water of c r y s t a l l i z a t i o n i n shale components could be o p e r a t i n g i n both types of s h a l e . P u r e l y p h y s i c a l processes, perhaps i n v o l v i n g p e n e t r a t i o n o f pores and m i c r o s c o p i c vacancies w i t h subsequent a d s o r p t i o n to modify surfaces or d i s p l a c e s u r f a c e water, need to be considered as w e l l . F i n a l l y , our observations that the v i t r i n i t e s are e x t e n s i v e l y f r a c t u r e d when c o a l s are t r e a t e d with l i q u i d SO2 (.5, 6) suggests that s w e l l i n g and/or e x t r a c t i o n of organic c o n s t i t u e n t s of the shale may a l s o p l a y a r o l e . At t h i s stage, i t i s b e l i e v e d that the f r a c t u r i n g of a p a r t i c u l a r type of o i l shale by l i q u i d S0 i s probably due to a combination of s e v e r a l of these modes. I n i t i a l comparison of the f r a c t u r i n g r e s u l t s obtained v i a 2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

36

OIL

SHALE,

TAR

SANDS,

AND

RELATED

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

l i q u i d SO2 treatment with those obtained v i a l i q u i d NH3 t r e a t ment might suggest that the d i f f e r e n c e s could be a t t r i b u t e d simply to d i f f e r e n c e s i n the acid/base c h a r a c t e r i s t i c s of the l i q u i d s and the s h a l e s . Further c o n s i d e r a t i o n of the p o s s i b l e mechanisms i n v o l v e d i n l i q u i d SO2 f r a c t u r i n g , however, would suggest such an explanation to be o v e r l y s i m p l i s t i c . E s t a b l i s h ment of f r a c t u r i n g mechanisms f o r these f l u i d s must await the r e s u l t s of f u t u r e experiments. Extracted M a t e r i a l . E x t r a c t s , comprising 2-4% of the o r i g i n a l shale mass, were i s o l a t e d by f i l t e r a t i o n and subsequent evaporation of the l i q u i d SO2 s o l u t i o n s which were i n contact with these s h a l e s . Although no attempt was made to e x t r a c t these shales e x h a u s t i v e l y , i t i s apparent that a p p r e c i a b l y more m a t e r i a l can be e x t r a c t e d by l i q u i d SO2 under r a t h e r mild c o n d i t i o n s . The bulk (90% or more) of the e x t r a c t i s organic although some water i s removed and small amounts of c o l o r l e s s or l i g h t brown c r y s t a l l i n e m a t e r i a l are found i n the cracks and f i s s u r e s of t r e a t e d s h a l e s . I n f r a r e d s p e c t r a (Figures 2-4) of the e x t r a c t r e v e a l s a l i p h a t i c CH and carbonyl groups i n the Green River shale e x t r a c t ; the Moroccan shale e x t r a c t has a s i m i l a r content. These e x t r a c t s represent bitumen p o r t i o n s of the shale. Kerogen f r a c t i o n s , presumably, remain i n the shale; i n f r a r e d s p e c t r a (Figures 2 and 3, Traces B) i n d i c a t e considerable organic content remaining i n the t r e a t e d s h a l e s . The e x t r a c t from the Antrim shale i s somewhat d i f f e r e n t from that of the other two shales i n that both a l i p h a t i c and aromatic C-H but l i t t l e carbonyl i s present (Figure 4C). The aromatic content of t h i s e x t r a c t i s not unexpected s i n c e the organic c o n s t i t u e n t s of Antrim shale are h i g h l y aromatic (Table I ) . Although more d e f i n i t i v e data i s necessary to s u b s t a n t i a t e the p r o p o s i t i o n , i t would appear (Figure 4, A and B) that a s i g n i f i c a n t p o r t i o n of the organic matter i s removed from Antrim shale by treatment w i t h l i q u i d SO2. E x t r a c t s of organic m a t e r i a l were a l s o obtained with other f l u i d s as i n d i c a t e d i n Table I I . Although no d e t a i l e d analyses of these e x t r a c t s were obtained, i t would appear that these e x t r a c t s are of the bitumen f r a c t i o n as expected. Summary P r e l i m i n a r y experiments have demonstrated that l i q u i d SO2 i s e f f e c t i v e i n f r a c t u r i n g and e m b r i t t l i n g both carbonaeceous and s i l i c e o u s o i l s h a l e s . L i q u i d SO2 has advantages over other f l u i d f r a c t u r i n g agents, v i z . , low c o s t , a v a i l a b i l i t y i n q u a n t i t y , and non-petroluem or n a t u r a l gas o r i g i n . Several p o s s i b l e mechanisms f o r shale f r a c t u r i n g have been suggested f o r f u t u r e e x p l o r a t i o n . Organic components can be removed from the shale under mild c o n d i t i o n s . On the b a s i s of these r e s u l t s , f u r t h e r e f f o r t s i n the use of l i q u i d SO2 f o r o i l shale p r o c e s s i n g are j u s t i f i e d . The general a p p l i c a b i l i t y or l i m i t a t i o n s of these procedures

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

3.

BUROW A N D SHARMA

Fracturing

of

Oil

Shale

37

need to be established; a knowledge of the mechanisms of shale fracturing would aid in this development. Enhancement of organic constituent recovery needs to be explored. Adaptation of these procedures to practical and economical processes in both surface processing and in situ recovery could result. Several of these areas will be discussed in future reports.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch003

Acknowledgement s The support of this research by the U. S. Department of Energy under Contract No. ET-78-G-01-3316 is gratefully acknowledged. Provision of o i l shale samples and documentation by Dr. F. P. Miknis (LETC), mineral samples by Dr. W. A. Kneller, preliminary SEM/EDXA results by Dr. S. N. K. Chaudhari, and aid in obtaining the mineral/S02 results by Mr. R. Carter are also gratefully acknowledged.

Literature Cited 1. Perrini, E. M. "Oil from Shale and Tar Sands," Chemical Tech. Rev. No. 51, Noyes Data Corp.: Park Ridge, N. J . , 1975. 2. Yen, T. F. "Shale Oil, Tar Sands, and Related Fuel Sources," Adv. Chem. Series, No. 151, American Chemical Society: Washington, D. C., 1976. 3. Yen, T. F.; Chilingarian, G. V., Dev. Pet. Sci., Vol. 5, Elsevier: Amsterdam, 1976. 4. Matzick, A.; Dannenberg, R. O.; Guthrie, B. "Experiments in Crushing Green River Oil Shale," Bureau of Mines Report No. 5563, 1958. 5. Burow, D. F.; Glavincevski, B. M. "Preprints", Div. of Fuel Chemistry, American Chemical Society, Vol. 25, No. 2, 1980, p. 153. 6. Burow, D. F.; Sharma, R. K. "Liquid Sulfur Dioxide Treatment of Coal," Conf. Chem. Phys. of Coal Utilization, Morgantown, W. Virginia, 1980, Paper T-4. 7. Burow, D. F., In "Chemistry of Non-Aqueous Solvents"; Lagowski, J. J . , Ed.; Academic: New York, 1970, Vol. III, Chapter 2. 8. Yen, T. F.; Chilingarian, G. V. Ref. 3, Chapter 1. 9. Musser, W. N., Dow Chemical Co. Report FE-310, 1976. 10. Miknis, F. P., private communication. 11. Miller, J. F.; Boyer, J. P.; Kent, S. J.; Snyder, M. J. Morgantown Energy Technol. Center, Spec. Publ. (METC/SP-79/6) 1976, 473; Chem. Abstr. 1980, 93, 49920j. RECEIVED

January 19, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

4 Chemistry of Shale Oil Cracking A. K. BURNHAM

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550

Oil shale contains organic material consisting mostly kerogen (a solid polymer) and a small amount of bitumen (a soluble, high-molecular-weight material) (1). Most currently proposed methods for recovering the energy from oil shale involve the pyrolysis of kerogen (and bitumen) to shale o i l at temperatures of about 400 to 550°C. Depending on the processing conditions, part of this oil may be degraded into less desirable products: coke and gas (2-11). Previous work here at Lawrence Livermore National Laboratory (LLNL) developed a quantitative kinetic scheme for the degradation of liquid o i l to mostly solid products (coking) at temperatures below 450°C (9,12). We now describe a kinetic scheme for the degradation of vapor-phase o i l into mostly gaseous products (cracking) at temperatures above 500°C. Shale o i l cracking can be significant in an indirect-heat retort in which the o i l shale is pyrolyzed by contact with hot solids or hot oxygen-free gas. To minimize the shale residence time in surface processes, the retorting temperature is frequently maintained above 500°C. The residence time of the shale o i l vapor in the reactor may be long enough that a significant amount of thermal cracking may occur, especially in a hot-solids retort to which no sweep gas is added. Significant shale o i l cracking can also take place in an in-situ retort in which thermal cracking may occur both inside large shale blocks and in the gas stream. If the thermal gradient within a block is large, o i l produced near the center of the block can crack (mostly to form gas) as it travels to the hotter block surface. More important, the o i l emerging from the block enters a gas stream that may be 200°C hotter than the block surface (13) . Because this gas stream may also contain oxygen, high-temperature oil-yield loss in the gas stream may take place by both combustion and associated cracking. In this work, we report kinetics for the thermal cracking of shale o i l over shale. The data are most appropriate for thermal cracking inside large blocks during in-situ processing and in the TOSCO-II and Lurgi processes, where relatively low temperatures 0097-6156/81/0163-0039$05.50/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

40

OIL

SHALE,

T A R SANDS,

A N DRELATED

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

(500 to 600°C), r e l a t i v e l y long residence times ( s e v e r a l seconds), and n e a r l y autogenous c o n d i t i o n s p r e v a i l . We p r e v i o u s l y gave a more d e t a i l e d report of our k i n e t i c measurements (JA) . We a l s o demonstrate the e f f e c t o f thermal c r a c k i n g on shale o i l composition and present r e s u l t s of C, H, and N a n a l y s i s , c a p i l l a r y - c o l u m n gas chromatography (GC), and GC/MS. We compare the compositions of shale o i l samples produced under l a b o r a t o r y c o n d i t i o n s with those of samples produced i n l a r g e - s c a l e experiments. A more d e t a i l e d i n v e s t i g a t i o n of o i l p r o p e r t i e s i n c l u d i n g IR and 13c NMR spectra (_15) and a r e s u l t i n g d i a g n o s t i c method based on o i l composition (16) have been reported e a r l i e r . Experimental Figure 1 shows the apparatus used i n the c r a c k i n g experiments. T h i s assay apparatus i s a m o d i f i c a t i o n of the LLNL modified F i s c h e r assay apparatus described p r e v i o u s l y (17). I t i s used f o r a complete mass- and carbon-balanced assay under various heating schedules. For the c r a c k i n g experiments, a second furnace and reactor were added. Both r e a c t o r s were made of Type 304 s t a i n l e s s s t e e l . A 165-ym s t a i n l e s s s t e e l f r i t (6.3 mm high by 32 mm i n diam) allowed gases but not shale to pass through the bottom of the r e a c t o r s . Raw shale samples were taken from a 92-litre/Mg (22-gal/ton) master batch (17) o f Mahogany Zone o i l shale mined from the Department o f Energy f a c i l i t y at A n v i l P o i n t s , Colorado. The raw shale had been ground to pass a 20-mesh screen (< 841 pm) and then s p i n - r i f f l e d to obtain 95-g a l i q u o t s . The shale contained 9.9% organic carbon (12.2% kerogen), 22.2% acid-evolved C 0 (48.3% c a l c i t e and dolomite), and the remainder mostly quartz and s i l i c a t e s . A l l percentages are c a l c u l a t e d on a weight b a s i s . Organic carbon i s determined by the d i f f e r e n c e between t o t a l carbon and carbon from acid-evolved CO2. Raw shale contained i n the top furnace and r e a c t o r was r e t o r t e d at a l i n e a r heating r a t e . Gases and vapors evolved during r e t o r t i n g passed through the second reactor at 504 to 610°C where the o i l was thermally cracked. Temperatures were measured at the center of the bottom r e a c t o r by a s t a i n l e s s - s t e e l - s h e a t h e d thermocouple (Type K). Temperature v a r i a t i o n across the r e a c t o r was less than 3°C. To simulate c o n d i t i o n s i n s i d e a shale block, the bottom reactor contained pieces o f shale. We used burnt shale (mostly s i l i c a t e s and MgO) i n most o f the experiments because i t i s thermally s t a b l e above 500°C. In two experiments, we used r e t o r t e d shale (2.7% organic carbon, 24.4% acid-evolved CO2) and no shale, r e s p e c t i v e l y . The r a t e o f gas e v o l u t i o n was monitored by a pressure transducer i n the c o l l e c t i o n b o t t l e . The r a t e of gas e v o l u t i o n peaked sharply during the kerogen p y r o l y s i s at about 460°C. To minimize d i f f e r e n c e s i n residence times caused by the 2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

BURNHAM

Chemistry

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

4.

of

Shale

Oil

41

Cracking

3

A r g o n , 3 t o 10 c m / m i n

Heated t o 5 0 0 ° C

(

at 6 and 1 2 ° C / m i n

j

Isothermal, 504to610°C

) (

0

O i l generated

II u

cracked ,

,

c

r

a

c

k

e

d

Gas collection system

Ice baths

Figure 1.

Experimental

apparatus

used in the gas-phase cracking shale

of shale oil over

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

42

OIL

SHALE,

TAR

SANDS, A N D R E L A T E D

MATERIALS

time-dependent gas e v o l u t i o n r a t e , we purged the r e a c t o r with a slow sweep of argon (3 to 10 cm^/min). (The argon c o n s t i t u t e d 10 to 20% of the c o l l e c t e d gases.) The average residence time was v a r i e d by changing both the h e a t i n g rate and the volume of the second r e a c t o r . Products were c o l l e c t e d and weighed to determine a mass balance. Except f o r two experiments, i n which the volume of gases exceeded the capacity of the gas c o l l e c t i o n system and the l a s t p o r t i o n was vented, the mass balance ranged from 95 to 98% (_14). We measured C, H, N, and acid-evolved C0 content for a l l r e t o r t e d shales and f o r some burnt shales from the c r a c k i n g experiments. O i l s were analyzed f o r C, H, and N. Gases were analyzed by gas chromatography (thermal c o n d u c t i v i t y detector f o r H2, CO, CO2, N , and CH4; flame i o n i z a t i o n detector f o r hydrocarbons) and by mass spectrometry. The analyses permitted an organic carbon balance to be c a l c u l a t e d for the four experiments i n which the shale i n the bottom reactor was analyzed; values from 100 to 105% were obtained (14). Further measurements were made on the o i l samples. In a d d i t i o n to the samples prepared on the above apparatus, other 011 samples were obtained from the LLNL 6-ton r e t o r t , the Laramie Energy Technology Center (LETC) 150-ton r e t o r t , the 1972 TOSCO-II semi-works operation, O c c i d e n t a l O i l Shale's modified i n - s i t u experiment No. 6, and LETC s Rock Springs No. 9 true i n - s i t u experiment. Spectroscopic techniques used were c a p i l l a r y - c o l u m n GC/MS, IR, and 13c NMR spectroscopy. These studies have been reported i n d e t a i l p r e v i o u s l y (15). Only c a p i l l a r y - c o l u m n gas chromatography r e s u l t s are reported i n d e t a i l here. A Hewlett-Packard Model 5880 chromatograph with a f l a m e - i o n i z a t i o n detector (FID) was used f o l l o w i n g a p r e v i o u s l y described procedure (16) . Samples were made by d i s s o l v i n g about 0.5 ml of neat shale o i l in 2 ml of CS . A Quadrex f u s e d - s i l i c a column (0.23 mm i . d . by 50 m) coated with SP2100 (methyl s i l i c o n e o i l ) was used. The temperature was programmed from 60°C to 275°C at the rate of 4°C/min and held at 275°C f o r 30 min.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

2

2

1

2

Result s K i n e t i c Measurements. The r e s u l t s of the shale o i l cracking experiments are summarized i n Table I . O i l y i e l d s are reported as a percentage of the LLNL assay r e s u l t on both a condensed-oil b a s i s and a C5+ b a s i s . To conduct the k i n e t i c a n a l y s i s , an e f f e c t i v e residence time had to be determined. I t was assumed for s i m p l i c i t y that the gas-and-oil e v o l u t i o n p r o f i l e could be approximated by a square pulse. The average residence time was c a l c u l a t e d by m u l t i p l y i n g the void volume of the bottom r e a c t o r by the time i n t e r v a l over which three-fourths of the products were evolved and then d i v i d i n g by the t o t a l volume of gases and vapors at the c r a c k i n g temperatures (14). The void volume was

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

4.

BURNHAM

Table I:

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

Experiment number

111 113 115 119 121 123 125 127

Chemistry

of

Shale

Oil

Cracking

43

Conditions for p r e p a r a t i o n of l a b o r a t o r y o i l samples.

Temperature of bottom reactor (°C)

508 610 505 558 504 585 585 610

Residence t ime (s)

7.0 3.8 10.4 4.9 9.3 2.5 2.7 2.0

Shale i n bottom reactor

Burnt Burnt Spent Burnt Burnt Burnt Empty Burnt

Oil yield (wt% of assay) Condensed C5+

95 55 90 81 91 77 87 68

96 59 91 83 92 82 89 74

determined by s u b t r a c t i n g the volume of the burnt or r e t o r t e d shale from the volume of the empty r e a c t o r . (The former value was c a l c u l a t e d by d i v i d i n g the weight of shale by i t s d e n s i t y , which was determined by mercury porosimetry). T h i s method of determining the residence time was checked f o r Experiment 115 by using a more complicated method. A time-dependent gas and o i l - v a p o r e v o l u t i o n r a t e was estimated from oil-and-gas e v o l u t i o n r a t e measurements (12,18). Residence times c a l c u l a t e d from t h i s r a t e ranged from 80 s at 350°C to about 6 s at 450°C. A weighted average of t h i s residence-time d i s t r i b u t i o n gave an average residence time of 11 s, which was i n s u r p r i s i n g l y good agreement with the value of 10.4 s determined by the simple method. However, the more complicated method i s a l s o approximate because the c a l c u l a t i o n of the residence time does not allow the extent of c r a c k i n g during the experiment (and hence instantaneous product volume) to depend on the instantaneous residence time. For t h i s reason, we have used the simpler method to estimate residence time. T h i s introduces a systematic u n c e r t a i n t y into the k i n e t i c parameters. In our previous report (_14), we determined a global r a t e constant at each temperature on the b a s i s of the y i e l d of condensed o i l . The r e s u l t i n g four r a t e constants were then f i t t e d to an Arrhenius expression. In the present r e p o r t , we use a s l i g h t l y d i f f e r e n t technique. The t y p i c a l f i r s t - o r d e r r a t e expression,

dt

yAe

-B/T

can be rearranged to give

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

(1)

44

OIL

In

= In k

=

SHALE,

T A R SANDS,

AND RELATED

In A - B/T ,

MATERIALS

(2)

where y i s the y i e l d of shale o i l and A and B are Arrhenius parameters. In e f f e c t , a f i r s t - o r d e r r a t e constant i s determined from each experiment, and a r a t e expression can be determined from a t y p i c a l Arrhenius p l o t . The r e s u l t i n g p l o t i s shown i n F i g u r e 2 f o r the y i e l d of C5+ o i l . T h i s gives a r a t e expression o f

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

k

1

f

( s " ) = 4.8 x 10

8

exp (-19340/T)

(3)

T h i s r a t e constant has a s l i g h t l y higher a c t i v a t i o n energy and i s 1.2 times less at 550°C than the r a t e constant reported p r e v i o u s l y (14) f o r the y i e l d of condensed o i l . Given the systematic u n c e r t a i n t y i n the residence time, the d i f f e r e n c e s are not s i g n i f i c a n t . Two a d d i t i o n a l cautions should be mentioned concerning the use of Equation ( 3 ) . Experiment 125 (no shale i n the bottom r e a c t o r ) was used i n n e i t h e r k i n e t i c a n a l y s i s because the conversion was s u b s t a n t i a l l y lower than expected on the b a s i s o f the other experiments. T h i s discrepancy may have r e s u l t e d from e i t h e r a c a t a l y t i c e f f e c t of the shale or a h e a t - t r a n s f e r l i m i t a t i o n . In a d d i t i o n , Dickson and Yesavage (_19) found that there i s a 60 to 70% conversion l i m i t f o r shale o i l c r a c k i n g . T h i s r e s u l t s from the presence and a d d i t i o n a l formation of aromatics, which are r e s i s t a n t to c r a c k i n g . T h i s implies that our expression w i l l f a i l at high conversions. Table I I gives the product d i s t r i b u t i o n f o r thermal c r a c k i n g o f shale o i l . We defined o i l as the sum of condensed o i l and C5-C9 hydrocarbons i n the gas. The amount of each gaseous product was determined from the slope of the curve p l o t t i n g gas production versus cracking l o s s (conversion) (14). The amount of coke produced was determined by d i f f e r e n c e , but i t agreed w e l l with the measured value f o r the few experiments i n which carbon was analyzed i n the shale from the bottom r e a c t o r . The alkene/alkane r a t i o s i n the gas depended more s t r o n g l y on the c r a c k i n g temperature than on the extent of conversion. This t o p i c i s discussed i n greater d e t a i l i n another paper published in these proceedings (20). O i l P r o p e r t i e s of Laboratory Samples. The p r o p e r t i e s of the l i q u i d a l s o change during the conversion o f a hydrocarbon l i q u i d to gas and s o l i d . S p e c i f i c a l l y , the H/C r a t i o decreases and the concentration of aromatic molecules increases g r e a t l y . Elemental and spectroscopic analyses confirmed these trends f o r the shale o i l s produced i n our experiments. The H/C r a t i o and percentage n i t r o g e n are p l o t t e d i n Figure 3 as a f u n c t i o n of conversion to gas and coke. I t i s

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

4.

BURNHAM

Chemistry

of

Shale

Oil

45

Cracking

Temperature, ° C

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

600

I 1.1

550

l

I

Arrhenius

I

1.2 1000/T,

Figure 2.

500

I 1.3

k"

1

plot of shale oil cracking data from which the rate in Equation 3 was determined

O i l c r a c k i n g loss, %

expression

O i l cracking loss, %

Figure 3. The effect of oil cracking on the H/C atomic ratio and nitrogen content of the shale oil. The data points indicate cracking over burnt shale (O), retorted shale (%), and in an empty reactor ([J). The H/C ratio is probably a function of both cracking temperature and loss. Aromatic nitrogen compounds are concentrated selectively by cracking.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE,

46 Table

Compound

H CO CH c

Products

II.

a

184 22 151 155 85 68

4

2

4 Coke

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

C

a

C+ 5

from s h a l e

Volume (cm3/g t

2

TAR SANDS, AND RELATED

STP)

oil

cracking.

Weight

MATERIALS

3

(g/g)

0.02 0.03 0.11 0.20 0.16 0.17 0.31

= oil.

evident that the H/C r a t i o decreases as c r a c k i n g i n c r e a s e s . Of f u r t h e r i n t e r e s t i s the increase i n n i t r o g e n content as c r a c k i n g i n c r e a s e s . T h i s increase occurs because the n i t r o g e n in shale o i l i s contained i n aromatic molecules O ) , which are r e s i s t a n t to c r a c k i n g ( i . e . , thermodynamically more s t a b l e ) . As the alkanes and alkenes are p a r t i a l l y converted to gases, the n i t r o g e n compounds become s e l e c t i v e l y concentrated. Therefore, a 50% c r a c k i n g conversion r e s u l t s i n a doubling of the n i t r o g e n content. The trends reported here for c r a c k i n g are the d i r e c t opposite of those observed by Stout et a l . (8) for o i l coking (Figure 4). O i l coking i s caused by liquid-phase polymerization and condensation r e a c t i o n s . I t i s most important at low temperatures and slow h e a t i n g r a t e s — c o n d i t i o n s under which residence times i n the l i q u i d phase are g r e a t e s t . Nitrogen content i n the o i l i s reduced and the H/C r a t i o i s increased by o i l coking because the aromatic n i t r o g e n compounds are apparently the most s u s c e p t i b l e to coking r e a c t i o n s . Lower temperatures a l s o favor alkane rather than alkene formation i n the o i l , as demonstrated elsewhere for ethane and ethene (200 • In Figures 5a and 5b, we compare the FID chromatogram of o i l produced under F i s c h e r assay c o n d i t i o n s with o i l that has undergone extensive thermal c r a c k i n g at 610°C. S p e c i f i c aromatic compounds formed i n shale o i l by thermal c r a c k i n g were i d e n t i f i e d by IR and c a p i l l a r y column GC/MS (15) ; a l k y 1 - s u b s t i t u t e d aromatics are e s p e c i a l l y p r e v a l e n t . Because of t h e i r usefulness as i n d i c a t o r s i n combustion r e t o r t s (16) , we show three 1-alkene/n-alkane r a t i o s and the naphthalene/(C;Q + C i ) r a t i o , r e s p e c t i v e l y , as a f u n c t i o n of o i l - y i e l d loss by c r a c k i n g ( F i g u r e s 6 and 7). (In t h i s case, C]_]_ i s the sum of n-undecane and 1-undecene and C^ i s the sum of n-dodecane and 1-dodecene.) Alkene/alkane r a t i o s are shown for Cg, C i , and Ci8 because these regions of the chromatograms appeared to be 2

2

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

BURNHAM

Chemistry

of

Shale

Oil

Cracking

Figure 4. The effect of oil coking on the H/C atomic ratio and nitrogen content of the shale oil. Coking reduces the alkene and aromatic nitrogen content of the oil.

American Chemical Society Library 1155 16th St. N. w. In Oil Shale, Tar Sands, 0. and C. Related Materials; Stauffer, H.; Washington, 20030 ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

S1VIH3JLVJM Q31V13H QNV 'SCINVS tfVl '31VHS 1IO

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981. 41% o i l cracking loss

Figure 5. A comparison of the FID chromatograms of (a) shale oil produced under Fischer assay conditions and (b) shale oil that has undergone extensive thermal cracking (41% conversion to gas and coke). The proportion of aromatic hydrocarbons in the cracked oil has increased dramatically.

b)

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

OIL SHALE, TAR SANDS, AND RELATED

50

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

i

1

1

MATERIALS

r

O i l cracking loss, %

Figure 6. Effect of the extent of cracking (condensed-oil basis) on three 1-alkene/ n-alkane ratios. The ratios were determined by capillary column chromatography with an FID detector. C (%); C (O); C O8

0

10

20

12

30

18

40

Oil crackingtoss,% Figure 7. Effect of the extent of cracking (condensed-oil basis) on a naphthalene/ (Cii + C ), where C and C are the sums of the respective n-alkanes and 1alkenes. Comparing these results with those in Figure 6 shows that cracking to 30% conversion produces primarily alkenes and that further cracking produces primarily aromatic compounds. 12

u

12

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

4.

BURNHAM

Chemistry

of Shale

Oil

Cracking

51

p a r t i c u l a r l y free o f i n t e r f e r i n g compounds. For Cg, the 1-alkene/n-alkane r a t i o increases with conversion. For longer chains, the r a t i o becomes constant or even decreases at the highest conversion. For comparison, the ethene/ethane r a t i o seemed to c o r r e l a t e b e t t e r with c r a c k i n g temperature than with the extent of conversion ( c r a c k i n g l o s s ) . We a l s o made two q u a l i t a t i v e observations on o i l q u a l i t y . F i r s t , the v i s c o s i t y of the o i l appeared to decrease with c r a c k i n g . A small amount of c r a c k i n g to reduce v i s c o s i t y ( v i s - b r e a k i n g ) i s a common i n d u s t r i a l process (21). Second, the o i l s with 19% or more cracking loss d i d not s o l i d i f y on c o o l i n g to -15°C. T h i s might be expected since the pour point i s dominated by long-chain alkane components (wax), which are the most s u s c e p t i b l e to c r a c k i n g r e a c t i o n s (21). P i l o t and F i e l d Retort O i l Samples. The data we have presented to t h i s point are for o i l c r a c k i n g at r e l a t i v e l y low temperatures (500 to 610°C) and long residence times (2 to 11 seconds) under an e s s e n t i a l l y autogenous atmosphere. These c o n d i t i o n s e x i s t i n at l e a s t two aspects of o i l shale r e t o r t i n g : 1) a h o t - s o l i d s r e t o r t such as TOSCO-II or L u r g i , and 2) the i n t e r i o r of large blocks i n an i n - s i t u r e t o r t . In the TOSCO-II process, ceramic b a l l s heated to 600°C are mixed with raw shale to heat i t to about 500°C (22). L o c a l hot spots or long residence times can cause shale o i l c r a c k i n g . For large b l o c k s i n an i n - s i t u r e t o r t , the temperature of the i n t e r i o r t y p i c a l l y lags that o f the surface by 200°C. O i l generated i n the i n t e r i o r can be cracked as i t migrates to the hot block surface. However, we demonstrate below that high-temperature c r a c k i n g i n the gas stream i s more important i n combustion r e t o r t s . We f i r s t consider the o i l from the 1972 operation o f the TOSCO-II semi-works. F i g u r e 8 shows the FID chromatogram o f t h i s oil. In comparison to F i s c h e r assay o i l , s i g n i f i c a n t l y higher concentrations o f aromatics are evident. We determined 1-alkene/n-alkane and n a p h t h a l e n e / ( C ^ + C12) r a t i o s from the FID chromatogram. We obtained C g C\2, and C18 r a t i o s o f 1.36, 1.22, 1.05, and a naphthalene/(C^^ + C12) r a t i o of 0.047. These r a t i o s a l s o i n d i c a t e a y i e l d o f from 75 to 85% on a condensed-oil b a s i s and 80 to 85% on a C5+ b a s i s . In c o n t r a s t , TOSCO r e p o r t s a 93% y i e l d f o r i t s 1972 run (22). A probable source o f t h i s discrepancy i s the d i f f e r e n c e i n p y r o l y s i s temperature. There i s nothing i n the mechanism described i n our i n t r o d u c t i o n that r e q u i r e s absence of o i l coking in a F i s c h e r assay (12°C/min). In f a c t , i t has been demonstrated that y i e l d s greater than 100% of F i s c h e r assay ( i . e . , l e s s coking than i n F i s c h e r assay) might be obtained under very f a s t h e a t i n g r a t e s and higher p y r o l y s i s temperatures (10, 23). However, our experiments were conducted so that the maximum p o s s i b l e y i e l d (no cracking) would be 100% o f F i s c h e r assay. T h i s i s not n e c e s s a r i l y true i n the TOSCO-II process. Therefore, f u r t h e r 5

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981. "16

^M/W

Figure 8. FID chromatogram of TOSCO-II oil from the 1972 semiworks operation. Thel-alkene/ n-alkane ratios and aromatic hydrocarbon content are high compared with those of the Fischer assay oil fsee Figure 5a).

Retention time-

-15

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

"19

1

> r

2

W

> H

a

m r > H w

> a

> o

C/J

> w H >

a

g P

to

4.

BURNHAM

Chemistry

of Shale

Oil

Cracking

53

experiments are required to develop a q u a n t i t a t i v e method to determine o i l y i e l d from o i l composition f o r h o t - s o l i d s r e t o r t s . We next compare the compositions o f our cracked shale o i l s with those from combustion r e t o r t s . We show i n F i g u r e 9 the FID chromatogram of shale o i l from Rock Springs No. 9, one of LETC s true i n - s i t u experiments. Several d i f f e r e n c e s are evident between the chromatogram of t h i s sample and those shown i n Figure 5. O i l s produced by combustion r e t o r t i n g u s u a l l y have much lower C^-Cg content than those produced i n r e t o r t i n g experiments with no sweep gas. A corresponding increase i s observed i n the C5-C9 content of the offgas from combustion r e t o r t s compared to the gas c o l l e c t e d from the laboratory experiments. I t should be noted that some of the l i g h t ends of the laboratory-produced samples evaporated during h a n d l i n g . The low 1-alkene/n-alkane r a t i o s i n d i c a t e that more than 20% of the o i l generated was converted to coke because o f the low r e t o r t i n g temperature. The high concentration of naphthalenes i n d i c a t e s that high-temperature thermal cracking occurred to part of the generated o i l . However, t h i s thermal c r a c k i n g occurred i n such a way that e s s e n t i a l l y no 1-alkenes were formed. As discussed below, t h i s i s c h a r a c t e r i s t i c of o i l burning i n a combustion r e t o r t . The c a p i l l a r y GC/MS was quite h e l p f u l i n e s t a b l i s h i n g the d i f f e r e n c e between o i l c r a c k i n g i n our laboratory experiments and that associated with o i l burning i n a combustion r e t o r t (15). Naphthalene/2-methylnaphthalene r a t i o s were determined from the r e l a t i v e 128- and 142-m/e peak heights i n s p e c i f i c - i o n - c u r r e n t chromatograms from the GC/MS when the concentrations were too low to be measured a c c u r a t e l y from the FID chromatogram. To convert the ion r a t i o s to weight r a t i o s , we compared the ion r a t i o s to area r a t i o s from the FID chromatogram o f Samples 113, Oxy No. 6, and Rock Springs No. 9. In Table I I I we l i s t the naphthalene/2-methylnaphthalene weight r a t i o s determined f o r these and other samples. We a l s o l i s t some previous r e s u l t s obtained by Dinneen (24). One trend that stands out from Dinneen's data and from Experiments 113 and 127 i s that the naphthalene/2-methy1naphthalene r a t i o depends strongly on the temperature at which o i l c r a c k i n g occurs and only weakly on the amount of c r a c k i n g . T h i s apparently occurs because the a c t i v a t i o n energy for d e a l k y l a t i o n of aromatics i s higher than for aromatic formation. Even at very high conversions, t h i s r a t i o i n o i l s cracked near or below 600°C i s not d r a m a t i c a l l y d i f f e r e n t than that i n assay o i l — e v e n though the amount o f naphthalene has increased t e n f o l d . The naphthalene/2-methylnaphthalene r a t i o i n o i l s from combustion r e t o r t s i n which a s i g n i f i c a n t amount o f o i l burning has occurred i s s u b s t a n t i a l l y higher than the r a t i o i n assay oil. T h i s i n d i c a t e s that most cracking i n i n - s i t u r e t o r t s occurs at high temperatures associated with combustion. Preferential o x i d a t i o n of a l k y l aromatics may a l s o c o n t r i b u t e . A t these high

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch004

1

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Xki

Q. C 1—

21 I

Retention time-

F/gwre 9. Chromatogram of shale oil from Rock Springs No. 9, a true in situ experiment. The alkene/alkane ratios are very low (coking) and the naphthalene content are very high (combustion and associated cracking). The naphthalene/methylnaphthalene ratios are high compared with the cracked shale oil in Figure 5b.

JLLJJIJJ.«J1WI»1

-C

+J

>> +->

i—

c k 2

+

c

c

2

k

k

930° F

950°F

0.887 16.8 0.875 0.776 0.111

1.04 16.8 0.875 0.908 0.130

0.442 15.6 0.813 0.359 0.083

0.545 15.6 0.813 0.443 0.102

0.292 14.5 0.755 0.220 0.072

0.367 14.5 0.755 0.277 0.090

0.197 11.2 0.583 0.115 0.082

0.296 11.2 0.583 0.173 0.123

980°F

1000°F

0.378 14.5 0.755 0.285 0.093

0.587 14.5 0.755 0.443 0.144

2

k

+

k

2 c Coke Y i e l d k /(k c

2

+ c> k

k

c k

2

k

+ k

2

Coke Y i e l d k /(k + c> c k c

2

k

k

0.186 14.5 0.755 0.140 0.046

2

0.4

k

+

k

2 c Coke Y i e l d k /(k + k > c

2

c

k

c k

2

RECEIVED

January 19, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

8 Kinetics of Oil Shale Char Gasification 1

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

W. J.THOMSON ,M. A. GERBER, M. A. HATTER, and D. G. OAKES Department of Chemical Engineering, University of Idaho, Moscow, Idaho 83843

During o i l s h a l e r e t o r t i n g , whether i t be by i n - s i t u o r s u r face techniques, a c e r t a i n f r a c t i o n o f the o r g a n i c carbon i s l e f t behind on the r e t o r t e d s h a l e . T h i s "char" c o n t a i n s a s i g n i f i c a n t f r a c t i o n o f t h e a v a i l a b l e e n e r g y i n t h e raw s h a l e and can a c t u a l l y supply a l l the energy f o r the r e t o r t i n g process f o r s h a l e s assayed a t 20 g a l l o n s / t o n o r g r e a t e r ( l _ ) . T o r e c o v e r t h i s e n e r g y , t h e c h a r can b e b u r n e d i n a i r o r g a s i f i e d i n o x y g e n - s t e a m e n v i r o n m e n t s ; t h e l a t t e r i n o r d e r t o p r o d u c e a low t o medium BTU gas w h i c h can be b u r n e d e l s e w h e r e i n t h e p l a n t . C o n s e q u e n t l y we have been c o n d u c t i n g k i n e t i c s t u d i e s o f t h e r e a c t i o n s o f o i l s h a l e c h a r i n a n ong o i n g r e s e a r c h p r o g r a m . E a r l i e r we r e p o r t e d o n t h e r e s u l t s o f o u r o x i d a t i o n experiments[2) and h e r e we w i l l d i s c u s s o u r work w i t h CO2 and s t e a m g a s i f i c a t i o n o f t h e c h a r . I t s h o u l d be n o t e d t h a t t h e r e has been some p r e v i o u s l y publ i s h e d work d e a l i n g w i t h t h e s e r e a c t i o n s . S t u d i e s a t U n i o n O i l R e s e a r c h i n t h e e a r l y 1970*5 a p p e a r t o be among t h e f i r s t t o a t tempt t h e e x p l o i t a t i o n o f t h e s t e a m - c h a r r e a c t i o n and l e d t o t h e d e v e l o p m e n t o f t h e SGR r e t o r t i n g p r o c e s s ( 3 j . L a t e r , Burnham a t L a w r e n c e L i v e r m o r e L a b o r a t o r i e s ( 4 , 5 _ 6 ) c o n d u c t e d b o t h noni s o t h e r m a l and i s o t h e r m a l e x p e r i m e n t s and o b t a i n e d r e a c t i o n r a t e e x p r e s s i o n s f o r t h e r a t e o f c h a r c o n s u m p t i o n due t o b o t h r e a c tions 9

COo + C + 2C0 + C + CO + H 2

H0

They observed, a s d i d the e a r l i e r r e s e a r c h e r s a t Union O i l t h a t t h e w a t e r gas s h i f t r e a c t i o n CO + H 0 t CO2 + H 2

(3)

Current address: Department of Chemical Engineering, Washington State University, Pullman, WA 99164. 1

0097-6156/81/0163-0115 $05.00/0 ©

1981

American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

116

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

a l s o o c c u r r e d a t a r a p i d r a t e so t h a t t h e primary gaseous products were e s s e n t i a l l y H a n d C 0 . S i n c e we w i l l be c o m p a r i n g o u r c u r r e n t r e s u l t s w i t h t h o s e m e a s u r e d by Burnham a t L a w r e n c e L i v e r m o r e L a b o r a t o r i e s ( L L L ) , i t i s a p p r o p r i a t e t o r e p e a t them h e r e . Burnham was b e s t a b l e t o f i t h i s d a t a by a s s u m i n g t h e p r e s e n c e o f two s e p a r a t e c a r b o n s p e c i e s w h i c h r e a c t e d i n p a r a l l e l and s u g g e s t e d t h e f o l l o w i n g r a t e e x pression 2

r

C0

=

k

C

( l C!

2

+

k

C

2 c )

( p

2

C0

0.2 '

) 2

(4)

where C and C i n i t i a l l y r e p r e s e n t e d 7 5 % a n d 25%, r e s p e c t i v e l y , o f t h e t o t a l o r g a n i c c a r b o n . T h e C] s p e c i e s had a h i g h e r a c t i v a t i o n e n e r g y (205 k i l o j o u l e s / m o l e v s 134) and was t h u s more s e n s i t i v e t o increases i n temperature. T h e i r steam g a s i f i c a t i o n d a t a were a l s o f i t t o a p a r a l l e l r e a c t i o n r a t e e x p r e s s i o n c l

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

2

C 2

r

H 0 2

k

C

" 3 cJ

( P

H oi" 2

5 +

k C 4

(5)

C 2

b u t i n t h i s c a s e C -j a c c o u n t e d f o r 57% o f t h e i n i t i a l o r g a n i c c a r b o n and a g a i n had a h i g h e r a c t i v a t i o n e n e r g y (184 k i l o j o u l e s / mole v s 1 3 4 ) . The e m p i r i c a l n a t u r e o f t h e s e e x p r e s s i o n s i s a p p a r e n t and t h u s a m a j o r g o a l o f o u r work was t o a t t e m p t t o d e r i v e r a t e e x p r e s s i o n s more t y p i c a l o f what w o u l d be e x p e c t e d f o r c h a r g a s i f i c a t i o n r e a c t i o n s based on t h e c o a l l i t e r a t u r e ^ ) . Another goal was t o be a b l e t o p r e d i c t make-gas c o m p o s i t i o n s and t h u s a s e p a r a t e d e t e r m i n a t i o n o f t h e w a t e r - g a s s h i f t r e a c t i o n r a t e was a l s o undertaken. F i n a l l y , because o f evidence t h a t the i r o n p r e s e n t i n t h e s h a l e a c t e d t o c a t a l y z e t h e s h i f t r e a c t i o n , a number o f o x i d a t i o n / r e d u c t i o n e x p e r i m e n t s were r u n i n o r d e r t o a s s e s s t h e a b i l i t y o f t h e r e a c t i n g gases t o a f f e c t the o x i d a t i o n s t a t e o f the i r o n . S i n c e some o f t h e m i n e r a l s i n d i g e n o u s t o t h e s h a l e c a n a c t a s c a t a l y s t s , i t i s relevant t o l i s t the pertinent mineral reactions which can take p l a c e : c

CaMg(C0 ) CaC0 CaC0 + S i 0 CaFe(C0 ) 3

3

3

2

2

3

2

+ t + +

CaC0 + MgO + C 0 CaO + C 0 Silicates + C0 FeO + C a C 0 + C 0 3

2

2

3

2

2

(6) (7) (8) (9)

E q u a t i o n ( 6 ) , " d o l o m i t e d e c o m p o s i t i o n , " i s i r r e v e r s i b l e and takes p l a c e a t T >875K. E q u a t i o n ( 7 ) , " c a l c i t e d e c o m p o s i t i o n , " i s r e v e r s i b l e and c a n be p r e v e n t e d i f t h e r e i s a s u f f i c i e n t C 0 o v e r p r e s s u r e . E q u a t i o n ( 8 ) , " s i l i c a t i o n , " i s i r r e v e r s i b l e and t a k e s p l a c e a t h i g h e r t e m p e r a t u r e s (>1050K) p r o v i d e d t h a t c a l c i t e d e c o m p o s i t i o n i s p r e v e n t e d . E q u a t i o n (9) o c c u r s a t l o w e r temperat u r e s and i s s i g n i f i c a n t because the i r o n oxides t h a t r e s u l t can 2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

8.

THOMSON E T AL.

Oil Shale

Char

Gasification

111

a c t a s c a t a l y s t s d e p e n d i n g on t h e v a l e n c e s t a t e o f i r o n , a n d t h i s can b e i n f l u e n c e d by t h e t e m p e r a t u r e a n d c o n c e n t r a t i o n o f t h e s u r rounding gases.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

E x p e r i m e n t a l Equipment

and Procedures

Equipment. A l l o f t h e g a s i f i c a t i o n e x p e r i m e n t s were c o n d u c t e d w i t h t h e same a p p a r a t u s employed i n t h e e a r l i e r o x i d a t i o n work and h a s been d e s c r i b e d i n d e t a i l e l s e w h e r e ( 2 j . T h e t e c h n i q u e i n v o l v e d s i m u l t a n e o u s measurements o f mass l o s s (TGA) a n d e x i t g a s c o m p o s i t i o n s (gas c h r o m a t o g r a p h ) i n a v e s s e l w h i c h behaved a s a n i d e a l b a c k - m i x r e a c t o r . A l l e x p e r i m e n t s were r u n u n d e r i s o t h e r m a l c o n d i t i o n s . A s b e f o r e , powdered s h a l e samples (200 mesh) o f p r e v i o u s l y r e t o r t e d o i l s h a l e f r o m t h e P a r a c h u t e C r e e k member i n C o l o r a d o were s u s p e n d e d f r o m an e l e c t r o b a l a n c e a n d p l a c e d i n a f u r n a c e . I n t h i s way c o n t i n u o u s g r a v i m e t r i c r e a d i n g s were a v a i l a b l e t o m o n i t o r t h e c o n s u m p t i o n o f t h e c h a r . T h e o f f - g a s e s were a n a l y z e d on a C a r l e g a s c h r o m a t o g r a p h e q u i p p e d w i t h a C a r b o s i e v e B column. P r o c e d u r e s . S i n c e t h e c h a r r e a c t i o n s c a n be a c c o m p a n i e d b y m i n e r a l d e c o m p o s i t i o n r e a c t i o n s , some o f w h i c h a r e c a t a l y t i c , e v e r y a t t e m p t was made t o i s o l a t e t h e p e r t i n e n t r e a c t i o n s . O f course t h e r e i s always t h e p o s s i b i l i t y t h a t s i g n i f i c a n t i n t e r a c t i o n s w i l l be m i s s e d b y t h i s p r o c e d u r e a n d t h u s i t i s i m p o r t a n t t o s t a t e t h e p r o c e d u r e s w h i c h were employed. C0 - Gasification. The p r e v i o u s l y r e t o r t e d s h a l e (see (8) f o r d e t a i l s ) was f i r s t r a i s e d t o 900K i n a h e l i u m a t m o s p h e r e t o allow i r r e v e r s i b l e dolomite decomposition t o take place. F o r t h o s e e x p e r i m e n t s i n w h i c h CO2 was t h e o n l y s p e c i e s i n t h e f e e d g a s , t h e r a t e o f CO2 g a s i f i c a t i o n was f o l l o w e d by m o n i t o r i n g t h e r a t e o f p r o d u c t i o n o f CO; i . e . , f r o m G.C. m e a s u r e m e n t s . However t h i s was n o t a c c u r a t e i n t h o s e e x p e r i m e n t s w h i c h h a d CO i n t h e i n l e t g a s , a n d i n t h e s e c a s e s t h e r a t e was d e t e r m i n e d s o l e l y by g r a v i m e t r i c measurements. A f u r t h e r c o m p l i c a t i o n d u r i n g these e x p e r i m e n t s was t h e f a c t t h a t t h e p r e s e n c e o f even s m a l l q u a n t i t i e s o f CO r e t a r d e d t h e C 0 g a s i f i c a t i o n r a t e t o t h e p o i n t where s i l i c a t i o n r a t e s were on t h e same o r d e r o f m a g n i t u d e . Consequentl y t h e sample was p u r p o s e l y p r e t r e a t e d by a l l o w i n g c o m p l e t e s i l i c a t i o n t o t a k e p l a c e . T h i s was a c h i e v e d by e x p o s i n g t h e sample t o a 4 0 % C 0 - 3 0 % CO m i x a t H O O K f o r 8-12 h o u r s . T h e C 0 p r e v e n t e d c a l c i t e d e c o m p o s i t i o n ( e q u a t i o n ( 7 ) ) a n d t h e h i g h CO c o n c e n t r a t i o n r e t a r d e d C 0 g a s i f i c a t i o n s o t h a t o n l y 5-10% o f t h e c a r b o n was consumed d u r i n g t h e p r e t r e a t m e n t . 2

2

2

2

2

Steam Gasification.

Because o f t h e temperatures

required

f o r steam g a s i f i c a t i o n (>950K), s i g n i f i c a n t C 0 p r e s s u r e s w o u l d b e r e q u i r e d t o p r e v e n t c a l c i t e d e c o m p o s i t i o n . S i n c e we were a t t e m p t ing t o study t h e H 0 + C r e a c t i o n i n t h e absence o f C 0 g a s i f i c a t i o n , we d e c i d e d t o a l l o w t h e c a l c i t e t o decompose c o m p l e t e l y t o t h e o x i d e s . T h i s was done i n a h e l i u m purge s t r e a m a t 975K. T h e d e c o m p o s i t i o n t i m e and p u r g e r a t e were s u c h t h a t a t t h i s tempera2

2

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

118

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

t u r e o n l y a b o u t 1 0 % o f t h e c a r b o n was consumed d u e t o CO2 g a s i f i c a t i o n . A l t h o u g h t h e k i n e t i c d a t a were t a k e n i n t h e p r e s e n c e o f o x i d e s , a f e w r u n s were a l s o c o n d u c t e d w i t h s h a l e samples subjected toacid leaching(9). Water Gas Shift Reaction (WGSR). T h e WGSR was s t u d i e d o v e r s h a l e samples w h i c h had been p r e v i o u s l y d e c h a r r e d a n d s i l i c a t e d . A f t e r d e - c h a r r i n g a t 700K i n a 1 0 % 0 s t r e a m , t h e sample was e x posed t o 4 0 % C 0 a t H O O K f o r 12 h o u r s . Upon c o m p l e t i o n o f s i l i c a t i o n t h e t e m p e r a t u r e was a d j u s t e d t o t h e d e s i r e d v a l u e a n d t h e s h a l e was e i t h e r o x i d i z e d ( i n a i r o r C 0 ) o r r e d u c e d ( i n H o r CO). T h i s was f o l l o w e d by WGSR e x p e r i m e n t s i n w h i c h v a r i o u s c o n c e n t r a t i o n s o f CO, H 0 , C 0 a n d H were f e d t o t h e r e a c t o r . V a r i a b l e s . C 0 g a s i f i c a t i o n d a t a were o b t a i n e d up t o P c o 100 kPa a n d a t t e m p e r a t u r e s between 975K a n d H O O K . Steam g a s i f i c a t i o n was s t u d i e d a t H 0 p r e s s u r e s between 15 a n d 75 kPa a n d a t t e m p e r a t u r e s between 975K a n d 1150K. T h e k i n e t i c s o f t h e WGSR were a l s o s t u d i e d o v e r t h i s same t e m p e r a t u r e r a n g e a n d w i t h v a r i ous f e e d g a s c o m p o s i t i o n s c o n s i s t i n g o f H 0 , CO, C 0 a n d H . I n o r d e r t o r e m a i n o n t h e l e f t hand s i d e o f t h e WGSR e q u i l i b r i u m , t h e maximum p r e s s u r e s o f C 0 a n d H were 30 kPa. T h e o i l s h a l e was f r o m t h e P a r a c h u t e C r e e k Member i n C o l o r a d o a n d a s s a y e d a t 50 g a l l o n s / t o n . O u r e a r l i e r w o r k ( 2 j h a d i n d i c a t e d t h a t t h e r e was no e f f e c t o f a s s a y o n t h e c h a r o x i d a t i o n k i n e t i c s . 2

2

2

2

2

2

2

=

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

2

2

2

2

2

2

2

2

Results C 0 G a s i f i c a t i o n . The r a t e e x p r e s s i o n which r e s u l t s from an analysis o r t h e u u g a s i f i c a t i o n data i s given i n equation (10). 2

2

r

C0

C

k 2

1 +

c

P

5 C0 K l

2

P

C 0 2

+ K P 2

( 1 0 ) C Q

where k, K? K 2

4

= 7.83 x 1 0 e x p (-184/RT) ( k P a - s e c ) " = 0.0495 ( k P a ) = 5.0 ( k P a ) "

1

1

1

T h i s f o r m o f t h e r a t e e x p r e s s i o n i s t y p i c a l o f t h a t used t o c o r r e l a t e much o f t h e e a r l y g a s i f i c a t i o n d a t a on c o a l . T h e p a r a m e t e r s t h e m s e l v e s were o b t a i n e d f r o m a. m u l t i p l e r e g r e s s i o n a n a l y s i s o f t h e r e c i p r o c a l o f e q u a t i o n ( 5 ) . An i n i t i a l v a l u e o f t h e a c t i v a t i o n e n e r g y was o b t a i n e d f r o m a power l a w f i t a n d was t h e n a d j u s t e d by t i r a l a n d e r r o r u n t i l i t was c o m p a t i b l e w i t h t h e b e s t f i t f r o m t h e r e g r e s s i o n . F i g u r e 1 g i v e s some i d e a o f t h e a b i l i t y o f t h e equation t o f i t t h e data over a wide C 0 pressure range. Of p a r t i c u l a r s i g n i f i c a n c e i s t h e f i t t o t h e data c o r r e s p o n d i n g t o t h e d a s h e d l i n e w h i c h were o b t a i n e d d u r i n g m i n e r a l d e c o m p o s i t i o n . T h a t i s , t h e o n l y s o u r c e o f C 0 was t h a t r e l e a s e d 2

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Oil

Shale

Char

1

Gasification

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

THOMSON ET A L .

Figure

1.

Arrhenius plot for C0 gasification: 1.0 atm CO (^J; 0.5 atm (%); 0.1 atm C0 (A); 0.016 atm CO (0). 2

z

2

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

C0

2

120

OIL SHALE, TAR SANDS, AND RELATED

d u r i n g m i n e r a l d e c o m p o s i t i o n and, s i n c e t h e h e l i u m sweep gas r a t e was h i g h , t h i s r e s u l t e d i n v e r y low CO2 p r e s s u r e s . The s i m i l a r i t y between t h i s e x p r e s s i o n and r a t e e q u a t i o n s w h i c h have been d e r i v e d f r o m c o a l c h a r g a s i f i c a t i o n d a t a ( 7 j i n t h e a b s e n c e o f CO i s s t r i k i n g . A l t h o u g h t h e v a l u e o f Ki i s a l m o s t i d e n t i c a l t o t h e v a l u e r e p o r t e d by Smoot and P r a t h u ) f o r t h e CO2 g a s i f i c a t i o n o f c h a r , t h e v a l u e o f K2 f o r o i l s h a l e c h a r i s t e n t i m e s g r e a t e r . C o n s e q u e n t l y , even low p r e s s u r e s o f CO w i l l have a s t r o n g i n h i b i t i n g e f f e c t o n CO2 g a s i f i c a t i o n . D u r i n g t h e d e r i v a t i o n o f e q u a t i o n (10) we a l s o a t t e m p t e d t o f i t o u r d a t a t o t h e e x p r e s s i o n s u g g e s t e d by E r g u n and Menster(]_0) w h i c h i s s i m i l a r t o e q u a t i o n (10) e x c e p t t h a t K] Pc02 * ^2 C 0 t a k e n t o be much g r e a t e r t h a n 1.0. When t h i s was done, a v e r y p o o r f i t was o b t a i n e d and i t was c o n c l u d e d t h a t t h e i r e x p r e s s i o n i s n o t a p p r o p r i a t e f o r o i l s h a l e c h a r . I t i s a l s o i n t e r e s t i n g t o compare e q u a t i o n (10) t o t h e e x p r e s s i o n p r o p o s e d b y Burnham, e q u a t i o n (4). B e c a u s e o f t h e h i g h v a l u e o f K-|, t h e r e a c t i o n r a t e i s c e r t a i n l y f r a c t i o n a l o r d e r w i t h r e s p e c t t o CO2 and t h i s e x p l a i n s h i s r e a c t i o n o r d e r o f 0.2. T a b l e I shows a c o m p a r i s o n o f o u r i n i t i a l r a t e s w i t h h i s and, a s can be s e e n , e q u a t i o n (4) c o n s i s t e n t l y p r e d i c t s a r a t e which i s about f o u r times h i g h e r than ours. anc

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

MATERIALS

P

a r e

TABLE I RATES OF C0 GASIFICATION 2

Rate x 10 T (K)

975 975 975 1100

PC0 (kPa) 2

10 10 40 10

4

1

(sec" )

p

CO (kPa) 0 1.0 0 0

T h i s Work R e f e r e n c e 5 E q . (10) Eq. (4) 0.75 0.17 1.0 9.8

3.1

-

4.1 53

Charcoal Ref. ( 7 ) 0.0076 0.0027 0.0268 0.19

Note a l s o t h a t even w i t h a low CO p r e s s u r e o f 1 kPa, t h e CO2 g a s i f i c a t i o n r a t e drops by a f a c t o r o f almost f i v e . R e c a l l t h a t Burnham p r o p o s e d two p a r a l l e l r e a c t i o n s , p r e s u m a b l y due t o two separate carbon species o f d i f f e r e n t a c t i v i t y . Since carbon s p e c i e s ' l ' i s more a c t i v e , one e x p l a n a t i o n c o u l d be t h e f a c t t h a t we l o s t 5-10% o f t h e c a r b o n d u r i n g p r e t r e a t m e n t and t h e m o s t a c t i v e c a r b o n w o u l d be e x p e c t e d t o g a s i f y u n d e r t h o s e m i l d c o n d i t i o n s . However t h i s i s s u b s t a n t i a l l y l e s s t h a n t h e 7 5 % a s s i g n e d t o s p e c i e s '1' b y Burnham and i n o u r o p i n i o n t h e d i f f e r e n c e s a r e more l i k e l y due t o t h e s t a t i s c a l a n a l y s e s o f r a t e data which are d i f f i c u l t t o measure. A t higher carbon c o n v e r s i o n s t h e two r a t e e x p r e s s i o n s a r e c l o s e r due t o t h e l o w e r a c t i v i t y o f c a r b o n s p e c i e s '2' i n e q u a t i o n (4).

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

THOMSON E T AL.

8.

Oil

Shale

Char

121

Gasification

Steam G a s i f i c a t i o n . The r a t e e x p r e s s i o n f o r steam g a s i f i c a t i o n i s given i n equation (11). r

k

H20 . C

+

1

C

P

6 H20

K P 0 3

(

h

+

H 2

n

)

\

where k K3 K 6

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

4

= 6.62 exp (-100.7/RT) ( k P a - s e c ) " = 0.20 exp (-17/RT) ( k P a ) ' = 0.15 ( k P a ) "

1

1

1

A g a i n t h e r e a c t i o n r a t e i s f i r s t o r d e r w i t h r e s p e c t t o c h a r and t h e r e m a i n i n g p a r a m e t e r s were d e t e r m i n e d as d e s c r i b e d a b o v e f o r C 0 g a s i f i c a t i o n . I t i s i n t e r e s t i n g t h a t t h e v a l u e o f Ko i s such t h a t i t i s e f f e c t i v e l y o n e - h a l f o r d e r w i t h r e s p e c t to H 0, c o n s i s t e n t w i t h t h e f i r s t o f t h e two r e a c t i o n r a t e e x p r e s s i o n s g i v e n by Burnham(j5). T a b l e I I shows a c o m p a r i s o n o f t h e r a t e s p r e d i c t e d by e q u a t i o n (11) w i t h t h o s e p r e d i c t e d by e q u a t i o n (5) and w i t h c h a r c o a l as r e p o r t e d by Smoot and P r a t h ( 7 ) . A g a i n Burnham*s r a t e expression p r e d i c t s higher rates but, i n t h i s case, the d i s c r e pancy i s a l m o s t a f a c t o r o f 20 a t t h e h i g h e r t e m p e r a t u r e . T h e l a t t e r i s due t o t h e v e r y h i g h a c t i v a t i o n e n e r g i e s r e p o r t e d b y Burnham w h i c h a r e 30-80% h i g h e r t h a n o u r v a l u e s . One p o s s i b l e e x p l a n a t i o n i s t h a t Burnham b a s e d h i s r a t e e x p r e s s i o n on t h e r a t e 2

2

TABLE I I RATES OF STEAM GASIFICATION Rate x 1 0 ( s e c ) 4

T (K)

975 975 975 1150

P^Q (kPa)

PH (k?a)

T h i s work Eq. (11)

30 30 70 30

0 10 0 0

4.64 2.50 5.6 26.5

- 1

Reference 6 Eq. (5) 15.8

-

19.5 474

Char Ref. (7) 0.75 0.21 1.33 53.3

o f H p r o d u c t i o n i n t h e make-gas. As m e n t i o n e d e a r l i e r , . t h e w a t e r gas s h i f t r e a c t i o n i s v e r y f a s t o v e r r e t o r t e d o i l s h a l e and t h i s w o u l d r e s u l t i n a d d i t i o n a l H t h a n t h a t p r o d u c e d by t h e s t e a m - c h a r r e a c t i o n . What i s more, t h e C 0 - c h a r r e a c t i o n w o u l d a l s o t a k e p l a c e u n d e r t h e s e c o n d i t i o n s and, i n t h e n o n - i s o t h e r m a l e x p e r i m e n t s employed by Burnham, i t i s d i f f i c u l t t o d i s t i n g u i s h between them. E q u a t i o n (11) o n t h e o t h e r hand, i s b a s e d s o l e l y on i n i t i a l r a t e d a t a so t h a t i t a p p l i e s s t r i c t l y t o t h e s t e a m - c h a r r e a c t i o n . In c o m p a r i n g o u r r e s u l t s t o t h o s e f o r t h e steam g a s i f i c a t i o n o f c h a r c o a l , i t i s seen t h a t t h e steam g a s i f i c a t i o n 2

2

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

122

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

r a t e s f o r o i l s h a l e a r e 5-10 t i m e s h i g h e r a t t h e l o w e r t e m p e r a t u r e b u t l o w e r b y a f a c t o r o f two a t t h e h i g h e r t e m p e r a t u r e . It is i n t e r e s t i n g t h a t t h i s i s q u i t e d i f f e r e n t f r o m CO2 g a s i f i c a t i o n where t h e r a t e s f o r o i l s h a l e c h a r were a l m o s t two o r d e r o f magnitudes h i g h e r . R e c a l l t h a t e q u a t i o n (11) i s b a s e d o n d a t a c o l l e c t e d f o r steam g a s i f i c a t i o n i n t h e p r e s e n c e o f CaO; i . e . , a t h e r m a l l y d e c a r b o n a t e d s h a l e sample. F i g u r e 2 i s a f i r s t o r d e r p l o t which compares t h e r a t e o f c h a r c o n s u m p t i o n f o r samples w h i c h were l e a c h e d i n a c i d w i t h a t h e r m a l l y decarbonated sample under t h e same c o n d i t i o n s . T h e f a c t t h a t t h e l e a c h e d samples have s i g n i f i c a n t l y l o w e r r a t e s i s a p p a r e n t l y d u e t o changes i n d u c e d i n t h e mineral matrix as a r e s u l t o f t h e acid leaching. This i s b e t t e r u n d e r s t o o d when t h e r e s u l t s f o r g a s i f i c a t i o n i n t h e p r e s e n c e o f CO2-H0O m i x t u r e s a r e a n a l y z e d . F i g u r e s 3 a n d 4 show t h e p r e d i c t e d a n d e x p e r i m e n t a l r e s u l t s f o r two e x p e r i m e n t s c o n d u c t e d u n d e r s i m i l a r g a s c o m p o s i t i o n s b u t a t two d i f f e r e n t t e m p e r a t u r e s . The r e s u l t s shown i n F i g u r e 3 a r e a t a t e m p e r a t u r e o f 980K a n d , a t t h i s t e m p e r a t u r e , a CO2 p r e s s u r e o f 10 k P a i s s u f f i c i e n t t o prevent c a l c i t e decomposition. The p r e d i c t e d r a t e o f char cons u m p t i o n i s b a s e d o n a d y n a m i c m a t h e m a t i c a l model w h i c h i n c o r p o r a t e s e q u a t i o n s (10) a n d ( 1 1 ) . N o t e t h a t t h e a c t u a l r a t e i s much s l o w e r t h a n t h a t p r e d i c t e d by e q u a t i o n s (10) a n d ( 1 1 ) . T h e d a t a shown i n F i g u r e 4 were a l s o o b t a i n e d a t PCO2 = 10 kPa b u t a t a h i g h e r t e m p e r a t u r e o f 1040K. I n t h i s c a s e a p p r o x i m a t e l y o n e h a l f o f t h e a v a i l a b l e CaC03 decomposed t o CaO and, a s c a n b e seen, t h e p r e d i c t e d char consumption r a t e s a r e c l o s e t o those measured. Given these r e s u l t s and t h e lower r a t e s measured w i t h a c i d l e a c h e d s h a l e (where a l l t h e c a l c i u m i s r e m o v e d ) , i t i s a p p a r e n t t h a t CaO c a t a l y z e s t h e s t e a m - c h a r r e a c t i o n . T h i s o f c o u r s e i s no s u r p r i s e t o t h o s e f a m i l i a r w i t h t h e l i t e r a t u r e o n c o a l g a s i f i c a t i o n where a l k a l i n e e a r t h o x i d e s have been known t o c a t a l y z e t h e s e v e r y same r e a c t i o n s ( 1 1 ] 2 ) . W a t e r Gas S h i f t R e a c t i o n (WGSRjT AS d e s c r i b e d e a r l i e r , t h e WGSR was s t u d i e d o v e r d e c h a r r e d a n d t o t a l l y s i l i c a t e d s h a l e samp l e s . E a r l y i n t h e c o u r s e o f t h i s phase o f t h e s t u d y we d i s covered t h a t t h e i r o n p r e s e n t i n t h e s h a l e c o u l d be r e v e r s i b l y o x i d i z e d o r reduced, depending on t h e gas c o m p o s i t i o n and temperat u r e . A l t h o u g h t h e WGSR r a t e s were d e t e r m i n e d o n l y f o r samples w h i c h h a d been s u b j e c t e d t o r e d u c t i o n i n H2, a l i m i t e d number o f o x i d a t i o n / r e d u c t i o n e x p e r i m e n t s were a l s o c o n d u c t e d . A g a i n , t h e s e were a c c o m p l i s h e d i n t h e TGA a p p a r a t u s m e n t i o n e d above. T h e p r o c e d u r e was t o i n i t i a l l y r e d u c e t h e s a m p l e i n f l o w i n g H2 (100 kPa) p r i o r t o e x p o s i n g i t t o a n o x i d i z i n g a t m o s p h e r e (CO2 o r a i r ) and t o r e c o r d the weight gain as a f u n c t i o n o f time. Prior to r e d u c t i o n e x p e r i m e n t s t h e s a m p l e was c o m p l e t e l y o x i d i z e d i n 100 k P a a i r a n d t h e n e x p o s e d t o a r e d u c i n g a t m o s p h e r e (H2 o r C O ) . The o x i d a t i o n / r e d u c t i o n r a t e s were f o u n d t o be f i r s t o r d e r w i t h respect t o t h e gas c o n c e n t r a t i o n as well as t o t h e q u a n t i t y o f unconverted iron present i n t h e shale. Table III gives t h e values h a d

9

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Oil

Shale

Char

Gasification

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

THOMSON E T AL.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

124

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

OIL SHALE, TAR SANDS, AND RELATED

01

0

1

I

10

20

30

Time - Min Figure 4.

Mixed gasification-CaO present (?h o = 37 kPa, P o = 10 kPa, T = 1040 K) predicted ( ); experimental data (%). 2

C

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

8.

THOMSON E T AL.

Oil Shale

Char

125

Gasification

TABLE I I I FIRST ORDER RATE CONSTANTS FOR THE OXIDATION/REDUCTION OF IRON 1

Rate C o n s t a n t C0 Oxidation (T = 980K)

H

CO

2

0.07 3.18

Reduction (T = 1040K) Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

AIR

2

(sec" )

-

-

0.22

0.20

o f t h e f i r s t o r d e r r a t e c o n s t a n t s o b t a i n e d a t two d i f f e r e n t temp e r a t u r e s f o r o x i d a t i o n i n t h e p r e s e n c e o f 10 kPa o f a i r a n d CO2 and f o r r e d u c t i o n a t 10 kPa o f CO a n d H . As w o u l d be e x p e c t e d , t h e r a t e o f o x i d a t i o n i n a i r i s more t h a n an o r d e r o f m a g n i t u d e h i g h e r t h a n o x i d a t i o n i n CO2 whereas t h e CO a n d H r e d u c t i o n r a t e s are comparable. E q u a t i o n ( 1 2 ) i s a n e x p r e s s i o n f o r t h e WGSR r a t e . T h e d a t a were p u r p o s e l y f i t t o t h e e l e m e n t a r y r e a c t i o n r a t e e x p r e s s i o n g i v e n i n b r a c k e t s s o t h a t t h e r a t e w o u l d go t o z e r o a s e q u i l i b r i um was a p p r o a c h e d . 2

2

k

7 t C0 H 0 " V K E C 0 R

P

" k

1 h

W G S R

+

P

3

y

K

5

C0

= 4.16 X 1 0 ' e x p [ - 8 2 . 1 / R T ] =

.0278 ( k P a ) "

V

P

2

h

+ 2

R

2

H 0 2

2

moles/g-kPa -sec

1

K = .0492 ( k P a ) I t s h o u l d be n o t e d t h a t e q u a t i o n (12) p r e d i c t s a n i n h i b i t o r y e f f e c t o f C 0 on t h e r e a c t i o n r a t e . However j u s t t h e o p p o s i t e was o b s e r v e d f o r C 0 p r e s s u r e s l e s s t h a n 10 kPa a n d c o n s e q u e n t l y e q u a t i o n (12) i s o n l y v a l i d f o r Pco? 10 kPa C a t a l y t i c E f f e c t s . A l t h o u g h f t i s y e t t o b e p r o v e n , we b e l i e v e t h a t t h e anomalous b e h a v i o r o f C 0 on t h e WGSR r a t e i s d u e to i t s i n f l u e n c e on t h e o x i d a t i o n s t a t e o f i r o n . In f a c t d u r i n g t h e WGSR r a t e e x p e r i m e n t s we o b s e r v e d c h a n g e s i n t h e mass o f t h e s h a l e sample a s t h e g a s c o m p o s i t i o n was v a r i e d . C o n s e q u e n t l y a c o m p l e t e u n d e r s t a n d i n g o f t h e WGSR i s d e p e n d e n t o n a q u a n t i t a t i v e knowledge o f how t h e c a t a l y t i c a c t i v i t y o f i r o n v a r i e s w i t h i t s o x i d a t i o n s t a t e . Once t h i s i s known, r e a c t i o n r a t e e x p r e s s i o n s f o r t h e o x i d a t i o n / r e d u c t i o n o f i r o n c o u l d be c o m b i n e d w i t h WGSR r a t e e x p r e s s i o n s t o p r o v i d e a more a c c u r a t e p r e d i c t i o n o f t h e make-gas c o m p o s i t i o n s . 1

6

2

2

>

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

126

MATERIALS

The r o l e o f CaO a s a c a t a l y s t f o r t h e s t e a m - c h a r r e a c t i o n c a n be i n f e r r e d f r o m t h e r e s u l t s o b t a i n e d d u r i n g m i x e d CO2-H2O g a s i f i c a t i o n ( f i g u r e s 3 a n d 4 ) . I n many r e s p e c t s i t i s d e s i r a b l e t o p r e v e n t t h e d e c o m p o s i t i o n o f CaC03 t o CaO b e c a u s e o f t h e h i g h endothermic heats o f r e a c t i o n a s s o c i a t e d with t h i s r e a c t i o n . However, a s we have shown, t h e steam g a s i f i c a t i o n o f o i l s h a l e c h a r i s a b o u t t e n t i m e s s l o w e r when CaO i s n o t p r e s e n t . A b e t t e r e v a l u a t i o n o f t h e i m p o r t a n c e o f CaO r e q u i r e s a knowledge o f t h e d e p e n d e n c e o f t h e r e a c t i o n r a t e on t h e q u a n t i t y o f CaO p r e s e n t . Nomenclature C - char c o n c e n t r a t i o n , moles/g s h a l e k - rate constants K - a d s o r p t i o n c o n s t a n t s , kPa"' K[: - e q u i l i b r i u m c o n s t a n t Pi - p a r t i a l p r e s s u r e o f i , kPa r - r e a c t i o n r a t e s , moles char r e a c t e d / s - g s h a l e R - g a s c o n s t a n t , 0.008324 k j o u l e s / m o l e - ° K T - t e m p e r a t u r e , °K

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

c

Abstract The kinetics of oil shale char gasification have been studied for Colorado oil shale from the Parachute Creek member. Reaction rate expressions similar to those previously reported for coal char were obtained f o r the H O-char, CO char and water gas s h i f t reactions. Evidence is presented to suggest that CaO, a product of mineral decomposition, catalyzes the H O-char reaction and that indigeneous iron catalyzes the water gas s h i f t reaction. The l a t t e r reaction proceeds rapidly so that the make-gas cons i s t s primarily of H and CO . 2

2-

2

2

2

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9.

Dockter, L., paper presented at 68th Annual Meeting of AIChE, Los Angeles, Ca., November 20, 1975. Soni, Y.; Thomson, W. J., I&EC PROC. DES. & DEV., 1979, 18, 661. OIL & GAS JOURNAL, June 17, 1974, p.26. Burnham, A. K., FUEL, 1979, 58, 285. Burnham, A. K., FUEL, 1979, 58, 713. Burnham, A. K., FUEL, 1979, 58, 719. Smoot, L . K.; Prath, D. T., ''Pulverized Coal Combustion and Gasification," PLENUM PRESS, N . Y . , 1979. Soni, Y.; Thomson, W. J., "PROC 11TH OIL SHALE SYMP," Colorado State Univ. Press, Golden, C O . , 1978. Thomson, W. J., paper presented at National Meeting of AIChE, Houston, T X . , March 30, 1979.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

8.

THOMSON

ET

AL.

Oil

Shale

Char

Gasification

127

10. Ergun, S.; Menster, M., in "Chemistry and Physics of Carbon," Vol. 1, (ed. P. L. Walker, Jr.), Marcel Dekker, N.Y., 1965, p.203. 11. Lewis, W. K.; Gilliland, E. R.; Hipkin, H . , IND & ENG CHEM, 1953, 45, 1697. 12. Eakman, J . M.; Wesselhoft, J . J.; Dunkleman, J. J.; Vadovic, C. J., paper No. 63d, presented at 72nd Annual Meeting of AIChE, San Francisco, November 1979. January 19, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch008

RECEIVED

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

9 A Comparison of Asphaltenes from Naturally Occurring Shale Bitumen and Retorted Shale Oils: The Influence of Temperature on Asphaltene Structure

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

FENG FANG SHUE and TEH FU YEN School of Engineering, University of Southern California, Los Angeles, CA 90007 The majority of the organic material in oil shale is known as kerogen (organic solvent-insoluble fraction). Bitumen (organic solvent-soluble fraction) generally comprises only a small part of the total organic matter in oil shale. During retorting of the oil shale, kerogen and bitumen undergo thermal decomposition to oil, gas and carbon residue. According to a number of investigators (1,2,3), the mechanism for thermal cracking of oil shale is by decomposition of kerogen to bitumen and subsequently decomposition of bitumen to oil, gas and coke. Since bitumen is the intermediate formed from kerogen during thermal cracking, it may be accepted as representative of the natural-occuring organic matter in oil shale. According to the solvent fractionation scheme for the fossil fuel products, asphaltene is defined as the pentane-insoluble and benzene-soluble fraction. The role of asphaltene is significant (4). Asphaltene is suggested to be the "transitional stage" in the conversion of fossil to oil (5). Therefore the structures of asphaltene fractions produced at various temperatures may be useful indicators of the severity of temperature effects during processing. In this research, the asphaltene fractions produced from natural-occuring shale bitumen and shale oils retorted at 425 and 500°C were compared to investigate structural changes during thermal cracking. Due to the complexity of the asphaltene structure, an approach using the so called "average structural parameters" (6,7) was used to characterize the gross structural features. The average structural parameters were calculated principally from proton and carbon-13 NMR data (8-14). Comparisons of the relative values of these structural parameters clearly indicate the effects of thermal treatment on asphaltene structures. Experimental Solvent E x t r a c t i o n . A sample o f the Green R i v e r o i l shale from A n v i l P o i n t s , Colorado was crushed to 8-20 mesh s i z e p r i o r 0097-6156/81/0163-0129$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

130

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

to s o l v e n t e x t r a c t i o n or r e t o r t i n g . Bitumen was e x t r a c t e d from the shale by exhaustive Soxhlet e x t r a c t i o n with 10% methanol i n benzene f o r 72 h r s . T o t a l bitumen y i e l d was 2.1% by weight. Shale R e t o r t i n g . The r e t o r t chamber was a c y l i n d r i c a l quartz column, 47 mm i n diameter and 300 mm i n length with a screen o f 20 mesh s i z e welded to the bottom. Heat was t r a n s f e r e d to the shale through the quartz w a l l wrapped with two h e a t i n g wires connected t o a transformer. A s t a i n l e s s s t e e l sheathed chromel-alumel (type k) thermocouple was i n s e r t e d i n the center o f the r e t o r t chamber. The temperature was r a i s e d r a p i d l y to 425°C i n one experiment and to 500°C i n another, and maintained there f o r three hours. A i r entered through the top o f the chamber at a flow r a t e o f 1 cc/sec and moved downward together with the product o i l through the c o o l i n g column. The product o i l was c o l l e c t e d i n t o the r e c e i v e r and then seaprated from the water phase. The y i e l d s o f shale o i l s were 10.0% at 425°C and 12.5% at 500°C. Gas and coke were not analyzed. I s o l a t i o n o f Asphaltene. Asphaltenes were i s o l a t e d by prec i p t a t i n g with a 2 0 - f o l d volume o f n-pentane. The o i l / r e s i n f r a c t i o n was separated from the p r e c i p t a t e by f i l t r a t i o n through the thimble f o l l o w e d by Soxhlet e x t r a c t i o n with n-pentane. The asphaltene f r a c t i o n was obtained by Soxhlet e x t r a c t i o n o f the residue with benzene. In the f o l l o w i n g t e x t , the three asphaltenes w i l l be abbreviated as B i t u , R and R ^ Q Q r e p r e s e n t i n g bitumen asphaltene and asphaltenes d e r i v e d from shale o i l s r e t o r t e d at 425 and 500°C r e s p e c t i v e l y . 4 2 5

P h y s i c a l and Chemical A n a l y s i s . Elemental analyses were done by Elek M i c r o a n a l y t i c a l L a b o r a t o r i e s , Torrance, C a l i f o r n i a . Mol e c u l a r weights were determined on a Mechrolab Model 301A Vapor Pressure Osmometer using THF as the s o l v e n t at 40°C. IR s p e c t r a were recorded at a c o n c e n t r a t i o n o f 25 mg/ml i n CH C1 u s i n g 0.5 mm NaCl c e l l s on a Beckman Acculab 6 instrument. Proton and carbon-13 NMR s p e c t r a were obtained on a V a r i a n XL-100 spectrometer o p e r a t i n g at 100.1 MHz f o r proton o r 25.2 MHz f o r carbon. Proton NMR was measured i n C D C 1 ( c e n t r a l residue peak at 5.3 ppm). Carbon-13 NMR was measured i n CDCl^ ( c e n t r a l peak at 77.1 ppm). A sample o f asphaltene (0.5 g) was d i s s o l v e d i n 2.5 ml o f CDC1_ with 35 mg o f C r ( a c a c ) added to i t . To o b t a i n r e l i a b l e q u a n t i t a t i v e r e s u l t s , a delay time o f 4 sec a f t e r each 35° p u l s e and 0.68 sec a c q u i s i t i o n time was used i n the gated decoupling sequence. A l l chemical s h i f t s were reported i n ppm downfield from TMS. 2

2

2

3

Results and D i s c u s s i o n F r a c t i o n a t i o n o f the three samples a f f o r d e d the asphaltene f r a c t i o n s c o n s t i t u t i n g 7.3%, 0.39% and 0.74% by weight f o r the shale bitumen, shale o i l s r e t o r t e d at 425 and 500°C r e s p e c t i v e l y .

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

9.

SHUE A N D Y E N

A Comparison

of

131

Asphaltenes

Elemental Composition. Elemental a n a l y s i s data f o r the three asphaltene samples are presented i n Table I.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

Table I .

Elemental Compositions

of Green R i v e r Asphaltenes

Bitu

R

Wt. % C

74.53

76.50

78.22

wt. % H

8.86

7.97

7.02

wt. % N

2.71

4.49

5.03

wt.

% S

1.80

1.37

1.08

wt.

% o

8.01

7.71

wt.

% Ash

1.78

1.59

0.94

H/C

1.42

1.25

1.08

N/C

0.031

0.050

0.055

s/c

0.009

0.0067

0.0052

0/C

0.104

0.079

0.074

1100

660

620

a

Molecular

10.32

425

R

500

3

a

by d i f f e r e n c e

b

by VPO i n THF

The r e s u l t s o f the elemental a n a l y s i s show that asphaltenes d e r i v e d from r e t o r t e d shale o i l s have s m a l l e r values o f H/C r a t i o and s m a l l e r oxygen and s u l f u r contents, but g r e a t e r n i t r o g e n content than that d e r i v e d from shale bitumen. I n f r a r e d Data. I n f r a r e d s p e c t r a o f the three asphaltene samp l e s are presented i n F i g u r e 1. A number o f w e l l d e f i n e d ban^s were used f o r comparison: 0-H s t r e c h i n g o f phenols (3600 cm" ) , N-H s t r e c h i n g o f p y r r o l e s (3460 cm" ) , C-H s t r e c h i n g o f a l i p h a t i c a l k y l groups (2925 and 2860 cm" ) , C=0 s t r e c h i n g o f carbonyl com^ pounds (1800 - 1650 cm" ) , C-C s t r e c h i n g o f aromatics («1600 cm" ) and C-0 s t r e c h i n g o f aromatic ethers and phenols (1320 - 1200 1

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

132

OIL SHALE, TAR SANDS, AND RELATED

4000

4000

5000

3000

2000 1800 Wavenumber, c m

2000

MATERIALS

1600

1400

1200

1000

1600

1400

1200

1000

- 1

1800

Wavenumber, cm"**

4000

2000

1800

1600

1400

1200

1000

Wavenumber, cnr*

Figure 1.

IR spectra of shale oil

asphaltene

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

9.

A Comparison

SHUE A N D Y E N

R

a n c

R

a

v

of

133

Asphaltenes

es t r

cm" ) . A2S * 500 ^ ° n g e r absorption i n t e n s i t i e s f o r p h e n o l i c 0-H and p y r r o l i c N-H groups and C-0 s t r e c h i n g o f aromatic ethers and phenols. As the p r o c e s s i n g temperature i n c r e a s e s , the a l i p h a t i c C-H absorptions decrease and the aromatic C-C a b s o r p t i o n i n c r e a s e s . Band shapes f o r the carbonyl s t r e c h i n g r e g i o n o f the three samples a l s o show remarkable d i f f e r e n c e s . B i t u has very strong carbanyl absorption at 1700 cm" . F o r d 5QQ> " bonyl absorptions were s h i f t e d toward lower f r e q u e n c i e s . Since i t i s w e l l known that e i t h e r hydrogen bonding o r conjugation with an o l e f i n i c o r phenyl group causes a s h i f t o f the carbonyl abs o r p t i o n a t lower f r e q u e n c i e s , the r e s u l t seems t o i n d i c a t e a r e l a t i v e l y g r e a t e r p r o p o r t i o n o f hydorgen-bonded and/or conjugated carbonyl groups f o r R and R Q Q than f o r B i t u . a

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

4 2 5

n

R

C

A

a

r

R

5

e

*H NMR Data. Proton NMR s p e c t r a o f B i t u , R425 and R500 shown i n Figures 2-4. I f c o n t r i b u t i o n s from a c i d i c protons ( i . e . 0-H and N-H, such protons show very broad chemical s h i f t ranges (15)) are neglected, the s p e c t r a can be d i v i d e d i n t o d i f f e r e n t proton groups based upon chemical s h i f t ranges. Proton type d i s t r i b u t i o n s are d e f i n e d as f o l l o w s : H^(9.0-6.0 ppm), protons on aromatic r i n g s ; H (4.5-1.9 ppm), alpha a l k y l protons; Hg(1.9-1.0 ppm), beta a l k y l protons p l u s methine and methylene protons i n the gamma p o s i t i o n s o r f u r t h e r from aromatic r i n g s ; Hy(1.0-0.4 ppm), methyl protons i n the gamma p o s i t i o n s o r f u r t h e r from aromatic r i n g s . The i n t e g r a t e d proton i n t e n s i t i e s f o r each s p e c i f i c group were obtained d i r e c t l y from i n t e g r a t i o n curves. Normalized proton type d i s t r i b u t i o n s are given i n Table I I . A s p e c i f i c group o f protons with chemical s h i f t s i n the range o f 4.5-3.3 ppm, assigned as protons on carbons alpha t o two aromatic r i n g s , were observed i n the NMR s p e c t r a o f B i t u and R425- The r e s u l t seems t o i n d i c a t e that diphenyl methane type o f s t r u c t u r e remains s t a b l e at 425°C but i s cleaved a t 500°C. a

Carbon-13 NMR Data. Carbon-13 NMR data were f r a c t i o n a t e d i n t o groups based upon chemical s h i f t ranges: carbonyl carbons (220168 ppm); aromatic carbons j o i n e d t o oxygens, i . e . , aromatic ethers and phenols (168-148 ppm); aromatic carbons not j o i n e d t o oxygens (148-100 ppm) and a l i p h a t i c carbons (60-9 ppm). Aromatic i t y was c a l c u l a t e d as f r a c t i o n o f aromatic carbons (168-100 ppm) over t o t a l carbons. For s i m p l i c i t y , carbons a s s o c i a t e d with nitrogens were discounted i n the above scheme due t o the r e l a t i v e l y small percentage o f n i t r o g e n present i n the samples. Carbon group d i s t r i b u t i o n s and a r o m a t i c i t i e s o f three asphaltene samples are compared i n Table I I I . We have observed very poor agreement between the oxygen contents determined by u l t i m a t e a n a l y s i s (see Table I) and by C NMR (see Table III) f o r a l l three samples. For B i t u , 0/C = 0.104 by elemental a n a l y s i s but 0/C =0.024-0.037 by 13Q NMR. We think q u a n t i t a t i v e a n a l y s i s o f carbonyl carbons by !3c ^MR ^ d i f f i c u l t f o r two reasons: 1) carbonyl carbons gener a l l y have very long r e l a x a t i o n times (16) and are q u a n t i t a t i v e l y underestimated even under current c o n d i t i o n s ; 2) the disappearance of a large number o f carbonyl absorptions i n the n o i s e i s accen1 3

s

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

134

OIL SHALE, TAR SANDS, AND RELATED

9.0

8.0

7.0

Figure 2.

9.0

8.0

Figure 3.

9.0

8.0

Figure 4.

6.0

5.0 4.0 3.0 2.0 Chemical Shift,ppm

1.0

H-l NMR spectrum of asphaltene from shale

7.0

6.0

5.0 4.0 3.0 2.0 Chemical Shift,ppm

1.0

MATERIALS

0.0

bitumen

0.0

H-l NMR spectrum of asphaltene from shale oil retorted at

6.0

5.0 4.0 3.0 2.0 Chemical Shift,pp:s

425°C

0.0

H-l NMR spectrum of asphaltene from shale oil retorted at

500°C

( % and 13c NMR are being used only to c h a r a c t e r i z e the hydrocarbon p o r t i o n and, thus, the c o n t r i b u t i o n from heteroatom p o r t i o n s of the molecule have been minimized.)

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

SHUE AND Y E N

A Comparison

of

Asphaltenes

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

Table I I . F r a c t i o n a l Proton D i s t r i b u t i o n s o f Green R i v e r Asphaltenes by *H NMR

Proton Type

Bitu

R

H

A

(9.0-6.0 ppm)

0.046

0.145

0.179

H

a

(4.5-1.9 ppm)

0.204

0.337

0.402

Hg (1.9-1.0 ppm)

0.525

0.389

0.330

Hy (1.0-0.4 ppm)

0.225

0.129

0.089

Table I I I .

R

425

500

Percentage Carbon Group D i s t r i b u t i o n s o f Green R i v e r Asphaltenes by l^C NMR

Carbon Type

Bitu

R

4 2 5

R

5 Q 0

carbonyl carbons(220-168 ppm) 1.3 aromatic carbons j o i n e d t o oxygens(168-148 ppm)

1.1

2.4

2.8

to oxygens(148-100 ppm)

23.0

48.7

56.8

a l i p h a t i c carbons(60-9 ppm)

74.6

49.9

40.4

aromatic carbons not j o i n e d

Aromaticity

0.24

0.51

0.60

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

136

tuated due to the i n e f f i c i e n t number o f scans and the broader range o f carbonyl resonance f o r a sample c o n t a i n i n g many components. A conversion o f C=0 f u n c t i o n s i n t o CHOH o r CH groups by r e d u c t i o n would b e n e f i t t h e i r d e t e c t i o n by l^C NMR. Indeed we have observed new absorption i n the a l i p h a t i c e t h e r and a l c o h o l region (75-60 ppm) and i n c r e a s e d a b s o r p t i o n i n the a l i p h a t i c amine region (60-50 ppm) i n the C NMR spectrum o f Green R i v e r Bitumen asphaltene reduced by LiAlH4(17). Reductions o f carbox y l i c acids and ketones to a l c o h o l s , e s t e r s to ethers and amides to amines by L i A l H are w e l l known r e a c t i o n s (18). Further e v i dence f o r the presence o f carbonyl f u n c t i o n s i"n~"these samples was discussed e a r l i e r from i n f r a r e d data. 2

1 3

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

4

S t r u c t u r a l Parameters. Average s t r u c t u r a l parameters i n c l u d e : a r o m a t i c i t y ( f ) , degree o f s u b s t i t u t i o n o f the aromatic s h e e t ( a ) , number o f carbon atoms per a l k y l s u b s t i t u e n t (n), r a t i o o f p e r i pheral carbons p e r aromatic sheet to t o t a l aromatic carbons (Haru/Car) and a l i p h a t i c H/C r a t i o can be c a l c u l a t e d according to Eq. ( D - ( 5 ) a

C/H-QWX + Ho/Y

a

= —

n-

+

H /3) y

Hyx a

( 2 )

H. + H /X A ct Hq/X + H /Y 6

+ Hy/3

m

H /X a

H

+H /X A a C/H - (H /X + H /Y H H aliphatic — g — ratio = -g- x A

Haru C

a

^

r

a

3

+

H /3) A y

1 _ H

^

(5)

F

a where X and Y are the assumed atomic H/C r a t i o s f o r H and Hg f r a c t i o n s . Assuming X=Y, these values were chosen to give f (aromaticity) values c o n s i s t e n t with those measured d i r e c t l y by C NMR. The c a l c u l a t e d values o f X o r Y were 1 . 6 0 f o r B i t u , 2.08 f o r R 4 2 5 and 2 . 1 5 f o r R Q Q r e s p e c t i v e l y . C a l c u l a t e d average s t r u c t u r a l parameters are presented i n Table IV. These s t r u c t u r a l parameters h i g h l i g h t the d i f f e r e n c e s among the three asphaltene samples. As the temperature o f treatment i n c r e a s e s , the aromatic i t y a l s o increases but average a l k y l chain length, degree o f subs t i t u t i o n and degree o f condensation o f the aromatic system decrease. The o v e r a l l a l i p h a t i c H/C r a t i o f o r B i t u was 1 . 8 , implyi n g a s i g n i f i c a n t amount of condensed naphthenic r i n g s t r u c t u r e . The a l i p h a t i c H/C r a t i o f o r R 4 2 5 o r R Q Q was above 2 , implying the growing number o f methyl groups upon h e a t i n g . Although assumptions were made i n c a l c u l a t i o n s o f these s t r u c t u r a l paramet e r s , the trend o f changes i n s t r u c t u r e with temperature was clearly indicated. a

a

l 3

5

5

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

9.

SHUE A N D Y E N

Table IV.

A Comparison

137

Asphaltenes

Average S t r u c t u r a l Parameters o f Green R i v e r Asphaltenes

S t r u t u r a l Parameter

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

of

Bitu

R

425

R

500

f

0,.24

0,.51

0.60

a o

0..73

0,.53

0.51

n

4..16

2,.42

1.98

0,.99

0 .75

0.66

1,.80

2 .18

2.22

Haru/Car a l i p h a t i c H/C r a t i o

Summary A s t r u c t u r a l comparison o f asphaltenes d e r i v e d from shale bitumen and r e t o r t e d shale o i l has been undertaken i n order t o i n v e s t i g a t e s t r u c t u r a l changes during thermal c r a c k i n g . The r e s u l t s o f elemental a n a l y s i s i n d i c a t e that asphaltene d e r i v e d from r e t o r t e d s h a l e o i l has lower H/C r a t i o and l e s s oxygen and s u l f u r contents, but more n i t r o g e n content than that d e r i v e d from shale bitumen. Heteroatom f u n c t i o n a l groups have a l s o been i n v e s t i g a t e d f o r these asphaltenes. The r e t o r t e d shale o i l asphaltene has more 0-H and N-H f u n c t i o n a l groups as i n d i c a t e d i n the IR s p e c t r a . R e t o r t i n g processes a l s o i n c r e a s e the aromatic i t y , decrease the degrees o f s u b s t i t u t i o n and condensation o f the aromatic sheet and shorten the chain length o f the a l k y l substituent. Acknowledgement This work has supported by U.S. Department o f Energy, O f f i c e o f Environment under Contract No. 79EV10017,000.

Literature Cited 1. Allred, V.D., Quart. Colorado School of Mines, 1967, 62 (3), 91. 2. Hubbard, A.B. and Robinson, W.E., "A Thermal Decomposition Study of Colorado Oil Shale," U.S. Bureau of Mines, 1950, R.I. 4744. 3. Wen, C.S. and Yen, T.F., Chem. Eng. Sci., 1977, 32, 346.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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OIL SHALE, TAR SANDS, AND RELATED MATERIALS

4. Yen, T.F., "The Role of Asphaltene in Heavy Crudes and Tar Sands," Proceeding of the First International Conference on the Future of Heavy Crude and Tar Sands, paper 54, UNITAR, 1979. 5. Weller, S., Pelipetz, M.G. and Friedman, S., Ind. Eng. Chem. 1951, 43, 1572. 6. Williams, R.B., Sym. on Composition of Petroleum Oils, Determination and evaluation, ASTM Spec. Tech. Publ., 1958, 224, 168. Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch009

7. Brown, J.K. and Ladner, W.R., Fuel, 1960, 39, 87. 8. Bartle, K. D., Martin, T.G. and Williams, D. F., Fuel 1975, 54, 226. 9. Cantor, D. M., Anal. Chem., 1978, 50, 1185. 10. Wooton, D. L., Coleman, W. M., Taylor, L. T. and Dom, H. C., Fuel, 1978, 57, 17. 11. Dereppe, J. M., Moreaux, C. and Castex, H. Fuel, 1978, 57, 435. 12. Bartle, K. D., Ladner, W. R., Martin, T. G., Snape, C. E. and Williams, D. F., Fuel, 1979, 58, 413. 13. Ladner, W. R., Martin, T. F. and Snape, C. E., ACS Div. Fuel Chem. Preprints, 1980, 25(4), 67. 14. Dickinson, E. M., Fuel, 1980, 59, 290. 15. Jackman, L. M. and Sternhell, S., "Applications of Nuclear Magnetic Resonance Spectroscopy in Organic Chemistry," Pergamon Press, 1969, p.215. 16. Levy, G. C. and Nelson, G. L., "Carbon-13 Nuclear Magnetic Resonance for Organic Chemists", Wiley-Interscience, 1972. 17. Shue, F. F. and Yen, T. F., unpublished work. 18. House, H. O., "Mordern Synthetic Reactions", W. A. Benjamin, Inc., 1972. RECEIVED March 19, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

10 Beneficiation of Green River O i l Shale by Density Methods OLAF A. LARSON Gulf Research & Development Company, Pittsburgh, PA 15230

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

C. W. SCHULTZ and ELLERY L. MICHAELS Institute of Mineral Research, Michigan Technological University, Houghton, MI 49931

Green River oil shale, found in Colorado, Utah, and Wyoming is an extremely complex and challenging resource. The C-a tract in Colorado has been Gulf's main interest in oil shale since about 1974. Initial plans called for the use of an open pit mine with conventional surface retorting. From a process point of view, the most important property of much of the oil shale throughout the Green River formation is its low organic content. For example, the integral average of shale on the C-a tract, measured from the top of the Mahogany Zone through the Blue Marker (over a 1,000-foot interval) is about 23 GPT. This corresponds to an organic concentration of 14.7% by weight. Retorting of shale is the most commonly considered method for oil recovery from the rock. Despite the apparent simplicity of retorting, it is a complex process. This complexity is due to the lean nature of the ore, the requirement to add heat at high temperature, and the chemical and physical changes which take place in retorting. There are two principal reasons for the beneficiation of oil shale. First, a reduction in solids handling intensity of lean shale movement and retorting may be possible. Secondly, beneficiation to higher concentration levels might allow the substitution of alternate technology for retorting. Overall, the incentive is to reduce costs and improve thermal efficiency of the conventional mining and process routes. A survey of the l i t e r a t u r e indicated that little information had been published on o i l shale b e n e f i c i a t i o n . Dismant (1) reviewed the p o t e n t i a l f o r various b e n e f i c i a t i o n methods. A density method has been used i n the i n d u s t r y , mainly as an a n a l y t i c a l t o o l , to prepare o r g a n i c - r i c h concentrates (2). Most r e c e n t l y , Fahlstrom (3) has described f i n e - g r i n d i n g and f r o t h f l o t a t i o n on Green River and Kvarntorp (Sweden) o i l shales. A f t e r reviewing the problem, we decided to focus on 0097-6156/81/0163-0139$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

140

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

what kinds of separation are possible using coarse size fractions. Avoidance of f i n e g r i n d i n g and h y d r o - m e t a l l u r g i c a l c i r c u i t s seemed most d e s i r a b l e to reduce complexity and c o s t . Access to shale at the C-a t r a c t was not p o s s i b l e when t h i s study was s t a r t e d . The Mahogany Zone shale from the A n v i l Points Mine was used i n t h i s study.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

Experimental Shale Sampling. O i l shale used i n t h i s work was from the Mahogany Zone of the Green R i v e r formation. The Bureau of Mines room-and-pillar mine at A n v i l Points has access to the Mahogany Zone shale i n the U.S. Naval O i l Shale Reserve. Figure 1 shows a (72-foot) i n t e r v a l of shale which i s mined at A n v i l P o i n t s . The histogram p l o t of a t y p i c a l core i s adapted from the Bureau of Mines report ( 4 ) . The average F i s c h e r Assays of the various beds of shale have been noted i n Figure 1. A d d i t i o n a l reference can be made to the Bureau of Mines' reports f o r c h a r a c t e r i s t i c s of the mine ( 5 ) . The mineable beds l a b e l l e d A through J correspond to the o r i g i n a l designations of the Bureau of Mines. During our sampling p e r i o d , shale was being mined mainly from beds A through F as a part of the Paraho demonstration program. The normal f l o o r l e v e l i n the mine i s at -20 f e e t below the Mahogany marker. The r e l a t i v e l y lean shale i n Beds A, C, and D r e s u l t s i n a low grade of shale as run-of-mine material. The Mahogany marker itself is a thin bed approximately 4 to 6 inches i n thickness, which contains l i t t l e organic matter. The i n t e g r a t i o n of a l l of the zones from A through F give a shale averaging about 26 GPT. As w i l l be shown l a t e r , our assay r e s u l t s were c o n s i s t e n t with t h i s value, which v e r i f i e d that the mine b l a s t i n g and blending procedure was i n good c o n t r o l . A second o b j e c t i v e of sampling at the A n v i l Points mine was to o b t a i n a r e p r e s e n t a t i v e sample of a f u l l 60-foot i n t e r v a l . The zone s e l e c t e d was from 20 feet above the Mahogany marker to 40 feet below. This procedure gave us samples of shale from beds G and H, which show a h i g h l y c y I l e a l grade change with depth i n the core a n a l y s i s histograms. Every e f f o r t was taken to assure uniform and accurate sampling i n the mine. C a r e f u l measuring was done by d r i v i n g a s t e e l p i n i n t o the face at the upper edge of the Mahogany marker. V e r t i c a l i n t e r v a l s were measured from the reference p o i n t s and marked with spray p a i n t . Samples were broken from the face using a hammer and rock c h i s e l . Ten to twelve pounds of sample were taken from each one-foot i n t e r v a l . Samples f o r the i n t e r v a l from 2 feet below the Mahogany marker to 20 feet above the marker were taken from the face of G (George) d r i f t , approximately 20 feet south of number 11 c r o s s cut. The s t r a t a from 2 feet to 20 feet below the Mahogany marker were taken at the i n t e r s e c t i o n of A (Able) d r i f t and

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Green

River

Oil

Shale

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

LARSON E TAL.

Figure 1.

Core intervals and mineable beds at Anvil Points mine, Rifle, CO

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

141

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

142

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

number 11 c r o s s c u t . The only l o c a t i o n i n the mine where the s t r a t a from 20 feet to 40 feet below the marker i s exposed i s at the north end of the A d r i f t . At number 11 c r o s s c u t , A d r i f t d e c l i n e s to -40 feet at the number 13 c r o s s c u t . The samples f o r the lower zone were taken from t h i s l o c a t i o n . Sample P r e p a r a t i o n . The mine-run sample was received i n a nominal crushed form of 3 inch by 1/4 i n c h . An a l i q u o t p o r t i o n of a 470 pound l o t was screened again over a 1/4-inch screen. Only about 0.5% was recovered as f i n e s , which i n d i c a t e d good screening at the mine s i t e . The +1/4 inch m a t e r i a l was d i v i d e d i n t o two p o r t i o n s . The f i r s t p o r t i o n was reserved f o r heavy media t e s t s . The other h a l f of the 3 inch by 1/4 inch m a t e r i a l was crushed to pass a 3/4-inch screen. This sample was then screened through a 1/4-inch screen and 19% of the sample was recovered as f i n e s . The remaining 3/4 inch by 1/4 inch m a t e r i a l was reserved f o r heavy media t e s t s . Each i n d i v i d u a l hand-picked sample was stage crushed to pass a 2-inch screen and was screened at 1/4 inch to remove fines. Three composites were made from the 60 interval samples. The f i r s t composite was from 0 to +20 feet above the Mahogany marker. The other two samples were from 0 to -20 feet below the marker and from -20 to -40 feet below the marker. Each composite c o n s i s t e d of an equal weight of each one-foot interval. Heavy Media Tests. The general t e s t procedure i s i l l u s t r a t e d s c h e m a t i c a l l y i n Figure 2. Heavy media suspensions were made by adding magnetite (-65 mesh) to water i n a s t i r r e d separating v e s s e l . The f i r s t separating g r a v i t y was 1.8. The pre-wetted shale sample was introduced i n t o the v e s s e l with constant s t i r r i n g . A f t e r removal of the f l o a t product, the sink m a t e r i a l was removed and r i n s e d of a l l adhering media. The process was repeated at s p e c i f i c g r a v i t i e s of 1.95, 2.10, 2.25, and 2.40. A mixture of 75% by weight magnetite and 25% by weight f e r r o s i l i c o n was used to prepare the 2.40 specific g r a v i t y suspension. A l l products from the l a b o r a t o r y heavy media separation were thoroughly r i n s e d to remove adhering medium and were a i r d r i e d at 90°C. Representative samples were crushed to -10 mesh. S p e c i f i c g r a v i t i e s were obtained with an a i r pycnometer and standard F i s c h e r Assays were run. Results The heavy media separation procedure r e s u l t e d in six separate f r a c t i o n s f o r each composite. Table I shows the y i e l d r e s u l t s , s p e c i f i c g r a v i t y , and F i s c h e r Assay r e s u l t s f o r the mined composite of 3 Inch to 1/4 inch m a t e r i a l . Similarly, Table I I gives the r e s u l t s f o r the 3/4 inch by 1/4 inch crushed material.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

10.

LARSON E T A L .

Green

River

Oil

Shale

Table I R i f l e Mine (Mined Composite, -3 inch + 1/4

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

Product F l o a t (1.80) Sink (1.80), F l o a t Sink (1.95), F l o a t Sink (2.10), F l o a t Sink (2.25), F l o a t Sink (2.49) Total

(1.95) (2.10) (2.25) (2.40)

Specific Gravity 1.76 1.98 2.14 2.28 2.44 2.62 2.265

Weight % Yield 3.07 7.67 22.53 34.45 30.06 2.22 100.00

Table I I R i f l e Mine (Mined Composite, -3/4 inch to +1/4

Product F l o a t (1.80) Sink (1.80), F l o a t Sink (1.95), F l o a t Sink (2.10), F l o a t Sink (2.25), F l o a t Sink (2.40) Total

(1 .95) (2 .10) (2 •25) (2 .40)

Specific Gravity 1.74 2.04 2.18 2.38 2.50 2.72 2.261

Weight % Yield 2.74 13.96 31.33 45.33 6.25 0.39 100.00

143

inch) F i s c h e r Assay, GPT 70.1 49.4 35.2 22.7 13.6 (-5.0) e s t . 25.8

inch) F i s c h e r Assay, GPT 70.4 36.0 29.0 17.4 10.7 (0.0) e s t . 24.6

Some s h i f t i n the y i e l d s of each d e n s i t y f r a c t i o n can be noted i n comparing r e s u l t s i n Tables I and I I . For example, n e a r l y 65% of the m a t e r i a l i s c o l l e c t e d i n the two f r a c t i o n s averaging about 18 GPT f o r the coarse sample. A f t e r crushing to 3/4 i n c h , only about 50% of the t o t a l i s found i n these f r a c t i o n s , and the average grade was decreased s l i g h t l y from 18 GPT. However, very l i t t l e r i c h m a t e r i a l has been l i b e r a t e d through the crushing to f i n e r s i z e . The e f f e c t of crushing can be seen i n F i g u r e 3. The cumul a t i v e weight f r a c t i o n of shale, when p l o t t e d versus d e n s i t y , shows a s h i f t to lower s p e c i f i c g r a v i t y upon c r u s h i n g . However, the steep slope of the curve between s p e c i f i c g r a v i t y of 1.95 and 2.10 shows that most of the m a t e r i a l i s found between these two extremes. When i t i s noted that 19% of the coarse shale was removed as -1/4 i n c h f i n e s , i t i s apparent that crushing the shale to the f i n e r s i z e had very l i t t l e e f f e c t i n l i b e r a t i o n of rich material. Crushing appears to have s h i f t e d the curve without changing i t s shape significantly in the richer fractions. The r e s u l t s f o r each of the hand-picked composites are given i n Tables I I I , IV, and V. The i n t e r v a l f o r 20 feet above the Mahogany marker, shown i n Table I I I , has a behavior s i m i l a r

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

144

OIL

SHALE,

TAR SANDS, AND RELATED

MATERIALS

Sample

T

Heavy Madia Separation (1.80) Sink Float Haavy Madia Separation

^Slnk

Float

Haavy Madia Separation

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

(2.10)

"1

J

Sink

Float

(2.25)

Haavy

"1

Float

Sink

Haavy Madia Separation

(2.40)

"1

r Float Figure

(1.95)

1

I

Sink

2.

Heavy-media

test flowsheet

100 90

f-

80 70 -3/4

60 50

x 1 / 4 inch / /

0) #

-

JZ 9 e

40 30

-

20

-

E o

10 J 1.80

i

I

l

I

Specific Gravity Figure

3.

i.

I

I

1.90 2 . 0 0 2 . 1 0 2 . 2 0

Weight recovery

I

1

2 . 3 0

L.

100

2 . 4 0

of Madia

vs. specific gravity for mine-run

composites

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

10.

LARSON E T A L .

Green

River

Oil

Shale

145

to the run-of-mine m a t e r i a l . For example, about 61% of the material falls i n two fractions, averaging about 18 GPT. Moreover, only a l i t t l e m a t e r i a l i s found i n the r i c h f r a c t i o n s above 40 GPT.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

Table I I I R i f l e Mine Hand Picked Composite, 0 to +20 Feet

Product F l o a t (1.80) Sink (1.80), F l o a t Sink (1.96), F l o a t Sink (2.12), F l o a t Sink (2.26), F l o a t Sink (2.41) Total

(1.96) (2.12) (2.26) (2.41)

Specific Gravity 1.85 2.02 2.22 2.32 2.43 2.58 2.31

Weight % Yield 2.9 7.8 21.3 33.2 28.0 6.8 100.00

F i s c h e r Assay, GPT 53.1 38.5 27.0 21.6 14.4 8.6 22.1

Table IV Hand Picked Composite, 0 to -20 Feet

Float Sink Sink Sink Sink

Product (1.79) (1.79), F l o a t (1.95), F l o a t (2.11), F l o a t (2.25), F l o a t Sink (2.40)

(1.95) (2.11) (2.25) (2.40)

Total

Specific Gravity 1.76 1.93 2.12 2.31 2.48 2.54 2.132

Weight % Yield 21.3 16.2 19.2 22.3 18.8 2.2 100.00

Fia scher Assay, GPT 65.6 43.6 33.1 22.9 12.0 5.8 34.9

Table V Hand Picked Composite, -20 to -40 Feet

Float Sink Sink Sink Sink Total

Product (1.78) (1.78), F l o a t (1.95), F l o a t (2.11), F l o a t (2.25), F l o a t Sink (2.39)

(1.95) (2.11) (2.25) (2.39)

Specific Gravity 1.81 1.93 2.13 2.29 2.43 2.53 2.192

Weight % Yield 13.8 12.5 15.6 31.6 25.4 1.1 100.00

F i s c h e r Assay, GPT 58.9 46.7 32.3 23.4 16.2 9.2 30.6

The richest material sampled i s that i n the 20-foot interval below the Mahogany marker. These r e s u l t s are summarized i n Table IV. About 38% of the m a t e r i a l averages about 55 GPT. A l s o , only about 20% of the t o t a l m a t e r i a l i s i n the leanest f r a c t i o n s .

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

146

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

The lowest i n t e r v a l sampled, from 20 feet to 40 feet below the Mahogany marker, i s summarized i n Table V. In one respect, this interval i s similar to the i n t e r v a l above i t . For instance, a s i g n i f i c a n t f r a c t i o n of the samples i s contained i n the r i c h e r f r a c t i o n s . However, the degree of enrichment i s not q u i t e as good as i n the upper zone. This can be noted i n that the r i c h e s t f r a c t i o n was 58.9 GPT. In c o n t r a s t , a l a r g e r f r a c t i o n of r i c h e r m a t e r i a l (65.6 GPT) was obtained i n the upper interval.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

Discussion L i b e r a t i o n by Fine G r i n d i n g . Two samples shown i n Table I (49.4 GPT, s p e c i f i c g r a v i t y of 1.98) and (13.6 GPT, specific g r a v i t y of 2.44) were examined f u r t h e r f o r l i b e r a t i o n of organic matter by f i n e g r i n d i n g to a p a r t i c l e s i z e of l e s s than 45 microns. The samples were sent to H. T i n s l e y and Company i n London f o r a Micro V i b r a t o r y S l u i c e s e p a r a t i o n . A f t e r separation at l e s s than 45 microns, the r i c h sample (49.4 GPT) contained most of the f i n e p a r t i c l e s below 2.00 gravity. Moreover, l e s s than 10% of the m a t e r i a l was contained between 2.0 and 2.20 and less than 5% over 2.2 specific gravity. The lean sample (13.6 GPT) had a main band at 2.33 g r a v i t y and other bands at 2.40 and 2.46 g r a v i t y . In the lean sample, about 90% of the m a t e r i a l was between 2.20 and 2.47, with about 40% below 2.30 s p e c i f i c g r a v i t y . These finely ground samples represent narrow specific gravity distributions. I t i s apparent that l i t t l e a d d i t i o n a l organic and mineral separation i s p o s s i b l e by f i n e g r i n d i n g down to about 45 microns. Geochemlcal B a s i s . The existence i n Green River shale of the minute seasonal p a i r s of lamina c a l l e d varves i s important to the understanding of b e n e f i c i a t i o n p o t e n t i a l . The most c l a s s i c work i n the areas of geology and geochemistry i s by Bradley (6^ 7). Bradley estimated that r i c h shale of about 35 GPT required 8,200 years per foot of accumulation. Lean shale of 10-14 GPT required about 2,000 years per foot with other shale intermediate to these extremes. Accordingly, the annual thickness of the l a y e r p a i r s range from about 150 microns f o r lean shale to about 25-35 microns f o r r i c h s h a l e . Moreover, Bradley found that the thickness of the r i c h shale (designated o i l shale) and the thickness of the lean shale (designated raarlstone) followed q u i t e p r e c i s e rhythmical changes. The length of the c y c l e over the e n t i r e depth averaged about 22,000 years. Bradley pointed out that the average of the precession c y c l e and e c c e n t r i c i t y c y c l e i n the earth's o r b i t would give a resultant c y c l e of about 21,000 years. Most of the lean marlstone beds are about 6 feet t h i c k , though the range was from 3.8 to 8.8 f e e t . The r i c h e r o i l shale beds range from 0.6 to

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

10.

Green

LARSON E T A L .

River

Oil

Shale

147

3 . 0 feet. These rhythmic c y c l e s can e a s i l y be v i s u a l i z e d by examining Figure 1 . Bradley's observations of more than 5 0 years ago are remarkable. Recent modeling of c l i m a t i c responses to o r b i t a l v a r i a t i o n s seems to suggest a general r e l a t i o n s h i p i n a l l organic sediments ( 8 ) . A c c o r d i n g l y , the c y c l i c a l ups and downs of shale grade i n the Green R i v e r are due to changes i n weather c y c l e s which, i n t u r n , were due to changes i n the earth's o r b i t . C o r r e l a t i o n of Grade with S p e c i f i c G r a v i t y . Correlation between d e n s i t y of o i l - s h a l e rock and the rock's organic content have been known f o r some time. For example, F r o s t and S t a n f i e l d ( 2 ) , and Smith and co-workers ( 9 , 10, 1 1 ) have published data s p e c i f i c a l l y f o r Green River s h a l e . An e m p i r i c a l expression has been developed between o i l - s h a l e d e n s i t y and o i l yield: (1)

O i l Yield

(GPT)

=

31.563

D

R

2

-

205.998

1^

+

326.624

where D i s the rock d e n s i t y i n gm/cm . This i s a p a r a b o l i c f u n c t i o n , which i s s t r o n g l y curved, p a r t i c u l a r l y i n r i c h shale above 3 5 GPT. I t has been g e n e r a l l y recognized that the F i s c h e r Assay i s a r e l a t i v e l y poor measure of the grade or q u a l i t y of shale. The q u a l i t y and q u a n t i t y of l i q u i d can vary, h i g h l y dependent on the elemental and minerals a n a l y s i s and how the r e t o r t i n g Is c a r r i e d out. The F i s c h e r Assay r e s u l t s and s p e c i f i c g r a v i t y obtained i n t h i s study have been p l o t t e d i n Figure 4 . The c o r r e l a t i o n shown above has been p l o t t e d i n Figure 4 to see how i t compares. Between a s p e c i f i c g r a v i t y of 1 . 9 5 and 2 . 0 5 , the agreement i s q u i t e good. However, the heavy media samples of lean shale between s p e c i f i c g r a v i t i e s of 2 . 2 0 and 2 . 5 0 seem to c o n t a i n more organic matter than the Smith c o r r e l a t i o n would i n d i c a t e . This difference i s not s u r p r i s i n g . The Smith c o r r e l a t i o n was developed by averaging core data of long i n t e r v a l s f o r the e n t i r e Green R i v e r formation, while the data i n Figure 4 a r e s p e c i f i c , small p a r t i c l e r e s u l t s f o r extremely narrow s p e c i f i c gravity fractions. Volume percent of organic matter i s a l i n e a r f u n c t i o n of rock d e n s i t y . Smith ( 6 ) has a l s o shown that 3

R

(2)

V

- 100 ( 1 ^ - \)/(\

Q

~ D ) Q

where V i s volume percent of o r g a n i c . Using an average d e n s i t y of mineral matter, of 2 . 7 2 and 1 . 0 7 f o r organic d e n s i t y , D Q , the equation reduces t o : Q

(3)

V

»

Q

where D

R

164.85

-

60.61

i s the d e n s i t y of the s h a l e .

American Chemical Society Library 1155

16th St. N. W.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; Washington, 0 . C. 20038 ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Figure

0

4.

Fischer

1.80

2.10

Specific Gravity,

2.00

2.40

gravity

2.50

based on specific

2.30

correlation

gm/cm*

2.20

assay results for separated fractions: (-•-)(10).

1.90

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

10.

LARSON E T A L .

Green

River

Oil

Shale

149

Equation (3) i s the standard form recommended f o r Mahogany Zone s h a l e . However, s e v e r a l l i n e a r p l o t s are shown i n Figure 5. The s p e c i f i c g r a v i t y f o r the mineral matter has been v a r i e d from 2.66 to 2.78. A l s o , the organic g r a v i t y has been v a r i e d from 1.02 to 1.12 gm/cm . I t i s c l e a r that the lean shale p a r t i c l e s show an extreme s e n s i t i v i t y to v a r i a t i o n s i n the mineral density and organic d e n s i t y . For example, a p a r t i c l e of 2.60 s p e c i f i c g r a v i t y shows a range from 4.0 volume % organic to 10.0% f o r the d i f f e r e n t d e n s i t i e s chosen. Moreover, the c a l c u l a t e d organic content of r i c h shale p a r t i c l e s show much lower s e n s i t i v i t y to the d e n s i t i e s of the mineral and organic components. A c c o r d i n g l y , the d e n s i t y c o r r e l a t i o n developed by Smith must be used with c a u t i o n f o r lean shale p a r t i c l e s . For lean shale p a r t i c l e s , the d e n s i t y of the organic phase i s lower than average while the mineral phase i s higher than average. In comparison, i n the r i c h shale p a r t i c l e s , the organic phase i s higher than average while the mineral phase i s lower than average. These e f f e c t s are masked by the average values of Smith (10, 11). Bi-Modal Nature of Shale

Deposits

Our r e s u l t s i n d i c a t e that the organic concentration and s t r a t i g r a p h y of shales f a l l i n t o two d i s t i n c t c l a s s e s . These c l a s s e s are shown by the data i n Tables I I I , IV, and V. The shale i n t e r v a l above the Mahogany marker contains very l i t t l e r i c h shale which can be freed by crushing to about 1 inch i n size. In c o n t r a s t , the two i n t e r v a l s below the marker c o n t a i n much r i c h m a t e r i a l which i s separable at coarse s i z e f r a c t i o n s . The bi-modal nature of the shale over the f u l l 60-foot zone is shown more c l e a r l y i n Figures 6, 7, and 8. The weight percent of organic m a t e r i a l present i n each f r a c t i o n has been calculated from Fischer Assay using the Smith (11) correlations. The d i s t r i b u t i o n of organic m a t e r i a l i n each f r a c t i o n i s p l o t t e d as histograms f o r each of the three subzones. The upper and lower zones of shale shows a r e l a t i v e l y sharp maximum at about 25 GPT. The middle zone, immediately below the marker, does not show t h i s maximum (Figure 7 ) . The two zones below the marker show a trend toward a second maximum i n the range of 60-70 GPT. Our lowest separation g r a v i t y was at 1.80, so there i s no way of d e f i n i n g the second maximum precisely. Since the i n t e r v a l s of organic l e v e l i n the r i c h e r zones above 30 GPT are somewhat broader, t h i s adds to the i m p r e c i s i o n i n d e f i n i n g the second maximum. This bi-modal nature of Mahogany Zone shale i s c o n s i s t e n t with the observations of Bradley (6). In t h i s c l a s s i c work Bradley noted the d i s t i n c t c y c l i c behavior of accumulations of a lean marls tone and a r i c h o i l s h a l e . As p r e v i o u s l y noted, the c y c l i c accumulations were c o r r e l a t e d with the earth's o r b i t and subsequent weather c y c l e s . Since the c y c l e s were detected at

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

F/gwre 5.

Dependence of calculated organic volume on organic and mineral specific gravity

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

oo

r

2>

H W

α >

H W

>

> α w r

CO

α

>

oo

>

H

w

ssr

GO

ο r

Ο

Green

LARSON E T A L .

UPPER

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

+20

River

Oil

ZONE

t o 0 ft.

10

20

30 Fischer

Figure

6.

15

Shale

40

JZL

50

—I— 60

—i 70

A»iay,GPT

Distribution of organic matter in Mahogany mine, upper zone, -j- 20 ft to Mahogany

zine shale, Anvil marker

Points

40 r MIDDLE ZONE 0 to-20 ft.

10

20

30

40

—i— 50

60

70

Fischer Assay, GPT

Figure

7.

Distribution of organic matter in Mahogany zone shale, Anvil mine, middle zone, Mahogany marker to — 20 ft

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Points

152

OIL

LOWER

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

-

SHALE,

T A R SANDS,

AND RELATED

MATERIALS

ZONE

- 2 0 to - 4 0 ft.

10

20

3 0

4 0

60

50

70

Fischer Assay, G P T

Figure

8.

Distribution

of organic matter in Mahogany zone shale, Anvil mine, lower zone, —20 to —40 ft

Points

25 r 20

C-A

•u 5

10

15

20

25

30

35

Tract

Ua 40

45

50 55

NOSR Tract

5

-

•

0 10

15

20 25

30

35

40

45

50

55

60 65

Fischer Assay, GPT

Figure 9. Relative distribution of shale grade on C-a tract and Mahogany zone, Anvil Points:/upper figure,) based on CE-205 core, 2-ft increments, 1050-ft interval; flowerfigure)based on A-core, 1-ft increments, 73-ft interval.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch010

10.

LARSON E T A L .

Green

River

Oil

Shale

153

i n t e r v a l s of about 1-9 f e e t , c o n s i s t e n t with the frequency of 21,000 years, there i s every reason to b e l i e v e t h i s c y c l e would be detected at our dimensions of 1/4 to 3 inches. As noted by Bradley, the c l a s t i c s - r i c h (lean marlstone) p o r t i o n s have varve thicknesses of about 150 microns. A c c o r d i n g l y , a lean p a r t i c l e averaging 1.18 inches (3 cm) i n dimension perpendicular to the varves would represent a 20-year i n t e r v a l . In c o n t r a s t , an extremely r i c h p a r t i c l e of about 65 GPT with s i m i l a r dimensions would represent an i n t e r v a l of at l e a s t 100 years. Finally, i t can be noted that the f i n e crushing of shale down to about 45 microns f a i l e d to change the d e n s i t y d i s t r i b u t i o n of the particles significantly. A c c o r d i n g l y , i t can be concluded that the histograms shown i n Figure 6 would not change s i g n i f i c a n t l y i f the m a t e r i a l were separated at these smaller s i z e s . A p p l i c a t i o n to Other Shale Zones The r e s u l t s described i n t h i s study were on shale from the Mahogany Zone i n the southern Perimeter of the Piceance B a s i n . Given the r e l a t i v e l y constant s t r a t i g r a p h y , i t may be assumed that the r e s u l t s are at l e a s t q u a l i t a t i v e l y a p p l i c a b l e to the Mahogany Zone. For example, Curry (12) demonstrated the p r e c i s e match of i n d i v i d u a l t i n y annual varves i n two core s e c t i o n s taken 8-1/2 miles apart. Smith and Robb (13) have a l s o remarked on the s i m i l a r i t y i n mineral character and organic character throughout the shale measures i n the Green River formation. Yet, c a u t i o n should be e x e r c i s e d i n e x t r a p o l a t i n g these r e s u l t s to the deeper shale. For example, n a h c o l i t e and dawsonite are found i n the S a l i n e Zone, while dawsonite i s much more common i n the Leached Zone. A l s o , the s p e c i f i c g r a v i t y of the organic matter i s known to change with depth. We were g e n e r a l l y i n t e r e s t e d i n comparing the d i s t r i b u t i o n of r i c h and lean zones of shale throughout the C-a tract relative to the Mahogany Zone on the southern perimeter. A c c o r d i n g l y , the F i s c h e r Assay r e s u l t s f o r one core i n the c e n t r a l p o r t i o n of t r a c t C-a have been compared with the r e s u l t s from a core i n the southern Mahogany Zone. This comparison i s shown i n Figure 9. The data are based on a 2-foot i n t e r v a l sampling on C-a t r a c t versus a 1-foot i n t e r v a l i n the southern perimeter shale. Several i n t e r e s t i n g comparisons are noted. The C-a t r a c t shale shows a peak at 15 GPT i n s t e a d of 20 GPT. A l s o , the C-a shale i n t e r v a l shows more of the m a t e r i a l i n the medium-grade i n t e r v a l of 25-35 GPT. I t i s a l s o apparent that i n t e r v a l s of 40 GPT and r i c h e r shale blocks are a much lower percentage on the C-a t r a c t . Nevertheless, i t seems apparent that the paleo-limnology and paleo-climatology of the Green R i v e r Lakes, which was so beautifully analyzed by Bradley, has a dominant e f f e c t i n predicting results.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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Acknowledgements The authors are indebted to J- F. Patzer and P. S. Sundar for t h e i r a s s i s t a n c e , d i s c u s s i o n s , and t h e i r reviews.

Literature Cited 1. Dismant, John H. The Mines Magazine March, 1961, pages 1522.

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2. Frost, I.C. and Stanfield, K. E. Anal. Chem. March, 1950, 22, pages 491-492. 3. Fahlstrom, P. H., Proceedings of 12th Oil Shale Symposium, Colorado School of Mines, 1979. 4. Stanfield, K. E.; Frost I. C.; McAuley, W. S.; Smith, H. N., Bureau of Mines, RI 4825, November, 1951. 5. East, J. H., Jr. and Gardner, E. D., Bureau of Mines, Bull 611, 1964. 6. Bradley, Wilraot H., U.S. Geological Survey, Professional Paper 158-E, 1929. 7. Bradley, W. H. Geological Society of America Bulletin 1948, 59, pages 635-648. 8. Imbrie, John, and Imbrie, John Z. Science February 29, 1980, 207, pages 943-953. 9. Smith, John Ward Chem. Eng. Data Series 1958, 3, No. 2, pages 306-310. 10. Smith, John Ward, Bureau of Mines RI-7248, 1969, 14 pages. 11. Smith, John Ward, LERC/RI-76/6, September, 1976. 12. Curry, H. D., Intermountain Assoc. Petrol. Geol., 13th Ann. Field Conf. Guidebook, 1964, pages 169-171. 13. Smith, John Ward and Robb, William A., Bureau of Mines RI-7727, 1973. RECEIVED February 18,

1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

11 Beneficiation of Green River Oil Shale by Pelletization J. REISBERG

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch011

Shell Development Company, P.O. Box 481, Houston, TX 77001

Green River shale i s a sedimentary, h i g h l y laminated, f i n e textured rock composed mainly of the minerals dolomite, c a l c i t e , quartz, f e l d s p a r , c l a y and f r e q u e n t l y , p y r i t e . A minor p o r t i o n , l e s s than 50 percent by weight and averaging about 10 percent, c o n s i s t s of kerogen, a s o l i d organic, h i g h l y c r o s s - l i n k e d polymeric substance, p o l y c y c l i c i n nature, with an appreciable hetero-atom content. O i l shale, u n l i k e t a r sands and g i l s o n i t e , i s l a r g e l y i n s o l u b l e i n organic s o l v e n t s . However, i t e x h i b i t s a s t r i k i n g tendency to imbibe and swell i n the presence of organic liquids. Kerogen can be converted by p y r o l y s i s to l i q u i d and gaseous f u e l s and to a carbonaceous r e s i d u e . The high mineral content of o i l shale imposes a huge heat demand upon a thermal upgrading process and c a l l s for very l a r g e processing f a c i l i t i e s . A r e d u c t i o n i n the mineral content of the feed by an ore b e n e f i c i a t i o n step can s t r o n g l y i n f l u e n c e the process economics and may a l s o a f f o r d the a n c i l l a r y advantage of a decreased volume of contaminated, p o s s i b l y b i o l o g i c a l l y harmful retort tailings. A process for the b e n e f i c i a t i o n of Green River shale was i n v e s t i g a t e d which y i e l d s kerogen-enriched o l e o p h i l i c p e l l e t s and a d i s p e r s i o n i n water of most of the mineral matter. BACKGROUND There e x i s t a number of f a m i l i a r procedures for e f f e c t i n g mineral separations, i n c l u d i n g s i n k - f l o a t methods based on d e n s i t y d i f f e r e n c e s and f r o t h f l o t a t i o n based on w e t t a b i l i t y . Because of the tendency of kerogen to swell and s o f t e n i n the presence of organic l i q u i d s and thus p o s s i b l y to m o b i l i z e trapped mineral p a r t i c l e s , and because most minerals are water-wetted and thus e x t r a c t a b l e with water, we i n v e s t i g a t e d a l i q u i d - l i q u i d ( o i l water) p e l l e t i z a t i o n method. Several r e l a t e d procedures for upgrading shales have been described i n the l i t e r a t u r e . G e n e r a l l y these were developed as an adjunct to the chemical a n a l y s i s of kerogen, the purpose being to reduce i n t e r f e r e n c e by minerals and to avoid the r i s k of o x i d a t i o n of the organic matter by severe chemical deashing. 0097-6156/81/0163-0155$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE,

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TAR SANDS, AND RELATED

MATERIALS

A South A f r i c a n shale, Torbanite,(_L^ was ground with water in a porcelain b a l l m i l l . O i l ( u n s p e c i f i e d ) was added i n s u f f i c i e n t quantity to form a paste with the o r g a n i c - r i c h f r a c t i o n and g r i n d i n g was continued. Mineral matter became suspended i n the aqueous phase and t h i s was discarded. The o i l y paste was solvent washed, d r i e d and analyzed. The ash content was reduced from an o r i g i n a l value of l e s s than 40 percent to a value of about 10 percent. A new Brunswick o i l shale c o n t a i n i n g 58 percent mineral m a t t e r ^ ) was processed i n a s i m i l a r way except that i t was preground i n a heavy g a s - o i l p r i o r to the i n t r o d u c t i o n of water. Following a 16-hour g r i n d i n g p e r i o d , the d r i e d , enriched m a t e r i a l had a mineral content of 34 percent. Green River o i l shale^.?/ was treated with 5 percent a c e t i c acid to remove carbonate minerals p r i o r to g r i n d i n g i n a water, n-octane system. The aqueous mineral suspension was removed and replaced repeatedly with fresh water u n t i l no mineral matter was observable i n the water. A n a l y s i s of the residue i n d i c a t e d that the mineral content was reduced from an i n i t i a l 75 percent to 16 percent. These procedures resemble the process for c o a l p u r i f i c a t i o n described i n 1922 by W. E. T r e n t . I t comprised g r i n d i n g of coal to a 100/200 mesh s i z e , s u f f i c i e n t to detach the mineral p a r t i c l e s from the c o a l , then a g i t a t i n g with an organic, water i n s o l u b l e l i q u i d possessing a " s e l e c t i v e a f f i n i t y " f o r the c o a l . The process produced an "amalgam" of c o a l and organic l i q u i d and r e j e c t e d the i n o r g a n i c gangue as aqueous s l u r r y . Recently, s i m i l a r methods have been a p p l i e d to the separat i o n of t a r from A l b e r t a t a r sands. EXPERIMENTAL Procedure. The l a b o r a t o r y work described here was performed with two shale samples; one c o n s i s t e d of m a t e r i a l from cores taken at a depth of 1830-1860 feet from the Marathon lease and the second i n the form of rock fragments from the Colony mine (Dow p r o p e r t y ) . For the b e n e f i c i a t i o n we used a 5.5 g a l l o n p o r c e l a i n b a l l m i l l , and 1.5-inch g r i n d i n g medium (Burundum, of c y l i n d r i c a l form). The m i l l was charged with 10 pounds of g r i n d i n g medium, 400-800 ml of water, 100-200 grams of shale ( p u l v e r i z e d e a r l i e r to pass through a 100 mesh screen) and 50-100 ml of organic l i q u i d binding agent (heptane). The m i l l was r o t a t e d f o r an hour. T y p i c a l l y , a f t e r about 10 minutes of operation, a kerogenenriched f r a c t i o n i n the form of d i s c r e t e flakes or p e l l e t s began to separate. A f t e r a one-hour m i l l i n g c y c l e , the aqueous gangue d i s p e r s i o n was removed and replaced with fresh water. A small sample, 0.2-0.3 grams, of the enriched p e l l e t s was recovered f o r a n a l y s i s and the m i l l i n g o p e r a t i o n repeated f o r as many

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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c y c l e s as deemed necessary. Both gangue and kerogen-enriched p e l l e t s were d r i e d under vacuum at 70°C-80°C (see P l a t e I ) . The kerogen content was determined as weight l o s s by plasma ashing. (We used two plasma ashing d e v i c e s : I n t e r n a t i o n a l Plasma Corporat i o n , Model 1003B-248AN and LFE Corporation, Low Temperatures Asher, No. LTA-600.) Since the plasma combustion temperature does not exceed 50°C we avoid the p o s s i b i l i t y of mineral decomp o s i t i o n ( e s p e c i a l l y of carbonates) encountered during high temperature combustion. Results. The s i z e of the enriched p e l l e t s i s a f u n c t i o n of the q u a n t i t y of added organic binding agent. An i n s u f f i c i e n t quantity of b i n d i n g agent y i e l d s p e l l e t s too small f o r easy separation from the gangue suspension by means of coarse s i e v e s . An excess of binder r e s u l t s i n the formation of a voluminous, s o f t kerogen paste which e n t r a i n s gangue. The optimum c o n d i t i o n described above y i e l d s p e l l e t s about 1 cm i n diameter. The r e s u l t of a t y p i c a l b e n e f i c i a t i o n experiment with Marathon lease m a t e r i a l i s shown i n Figure 1. This e n t a i l e d four one-hour m i l l i n g c y c l e s , the aqueous mineral d i s p e r s i o n being removed and replaced with fresh water a f t e r each c y c l e . Kerogen contents for both the o r g a n i c - r i c h p e l l e t s ( o l e o p h i l i c ) and the water d i s p e r s i b l e mineral gangue ( h y d r o p h i l i c ) are shown. The f i g u r e a l s o shows the r e s u l t s of two s i n g l e c y c l e experiments. The Marathon sample was obtained from a depth of more than 1800 f e e t . Since an ore b e n e f i c i a t i o n step would be more approp r i a t e f o r a minable, shallow formation, we a l s o tested samples from the Dow-Colony (Parachute Creek) mine. S t a r t i n g with p a r t i c l e s i n the 8 to 10 sieve s i z e range, t h i s m a t e r i a l was m i l l e d i n water u n t i l 90 percent passed through a 100 mesh screen. Organic binder was added to the aqueous s l u r r y and the process was continued as described above. Results of d u p l i c a t e e x p e r i ments are shown i n Figure 2. The b e n e f i c i a t i o n obtained with t h i s Dow-Colony shale i s l e s s favorable than that with Marathon lease m a t e r i a l . A n a l y s i s of o i l shale surfaces by the scanning e l e c t r o n microscope p r i o r to and f o l l o w i n g low temperature ashing r e v e a l s that the mineral matter occurs i n the form of f i n e , d i s c r e t e p a r t i c l e s w i t h i n a continuous kerogen matrix. Figure 3 shows the s i z e d i s t r i b u t i o n s of inorganic mineral p a r t i c l e s obtained by low temperature ashing of unprocessed o i l shales. These minerals have mean p a r t i c l e diameters (50 percent frequency l e v e l ) of 5-6 microns. X-ray d i f f r a c t i o n a n a l y s i s of the products of the b e n e f i c i a t i o n of Dow-Colony shale i s shown i n Table I. I t i s c l e a r that the o l e o p h i l i c e x t r a c t ( p e l l e t s ) r e t a i n s or concentrates the calcium and magnesium carbonates (dolomite, c a l c i t e , a r a g o n i t e ) , p a r t i c u l a r l y the dolomite. The h y d r o p h i l i c gangue c o n s i s t s mainly of f e l d s p a r and quartz. Since s i l i c a , s i l i c a t e s and Ca/Ca-Mg carbonates, i n a c l e a n c o n d i t i o n , are water wettable

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

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158

Plate I.

Beneficiation

products of Green River oil shale

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

MATERIALS

11.

REISBERG

Pelletization

159

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90

NUMBER

OF

PROCESS

CYCLES

Figure 1. Recovery of Marathon Lease kerogen as a function of the number of beneficiation cycles. (Kerogen determined by weight loss on low-temperature ashing.)

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

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160

Figure 2.

Beneficiation

of Dow-Colony

shale

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

MATERIALS

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161

Pelletization

REISBERG

1.0

10

100

PARTICLE SIZE ( M I C R O N S )

Figure

3. Cumulative particle-size distribution of the mineral constituents shales (by low-temperature ashing). Particle size by Coulter counter.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

of

oil

OIL

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162

SHALE, TAR SANDS, AND RELATED MATERIALS

the above r e s u l t s would i n d i c a t e that the b e n e f i c i a t i o n procedure renders at l e a s t a p o r t i o n of the carbonates o i l - w e t t a b l e . The mechanism for the w e t t a b i l i t y r e v e r s a l of the carbonates may r e s i d e i n the adsorption of c e r t a i n c a r b o x y l i c c o n s t i t u e n t s of the shale, v i z . , the bitumens. Bitumens, the s o l v e n t - e x t r a c t a b l e organic components of o i l shale are r i c h i n c a r b o x y l i c f u n c t i o n a l groups; they contain about 35 percent f a t t y a c i d s , resinous a c i d s , polymer acids and benzenoid a c i d s ^ ^ / (see below). Their d i s s o l u t i o n i n the added organic binder would make them a c c e s s i b l e to adsorption by the carbonates. Carboxylic acids are a commonly u t i l i z e d " c o l l e c t o r " for carbonate minerals i n f r o t h f l o t a t i o n processes.^Z^ They adsorb s t r o n g l y and decrease the water wettab i l i t y of calcium carbonate thus f a c i l i t a t i n g i t s separation from a h y d r o p h i l i c gangue with the gas phase. S i m i l a r l y , i n t h i s p e l l e t i z a t i o n process, the a c t i o n of the adsorbed bitumen c o n s t i t u e n t s on the Ca/Ca-Mg carbonate mineral p a r t i c l e s renders them l a r g e l y inseparable from the o l e o p h i l i c , o i l swollen kerogen. Where p y r i t e i s present, one would expect that, due to i t s inherent o i l w e t t a b i l i t y , i t too would accumulate i n the o l e o philic pellets. TABLE I.

Calcite Dolomite Aragonite Quartz Feldspar Dawsonite

MINERAL DISTRIBUTION FOLLOWING BENEFICIATION STEPS DOW-COLONY SAMPLE (Estimated Weight Percent i n C r y s t a l l i n e P o r t i o n by X-ray D i f f r a c t i o n )

Untreated

Kerogen E x t r a c t (Oleophilic Pellets)

Gangue (Hydrophilic)

10 65 5 10 10

10 83 5 1 1

5 20

—

—

20 52 3

Samples of p u l v e r i z e d Dow-Colony o i l shale were extracted both at room temperature and by Soxhlet re f l u x i n g with n-heptane and with toluene. Solvent was s t r i p p e d from the e x t r a c t under vacuum and the a c i d numbers of the t a r - l i k e r e s i d u a l bitumens were determined. Results for d u p l i c a t e samples are shown i n Table I I . We note that s i g n i f i c a n t q u a n t i t i e s of c a r b o x y l i c acids are indeed extracted. In view of the above, one would a n t i c i p a t e d i f f i c u l t y i n upgrading by t h i s method, shales containing large q u a n t i t i e s of carbonate mineral (dolomite, c a l c i t e , aragonite) and/or p y r i t e (FeS2). In Table I I I we show the mineral d i s t r i b u t i o n s , d e t e r mined by X-ray d i f f r a c t i o n , of samples from the Marathon and

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

11.

REISBERG

TABLE I I .

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Toluene, Heptane, Toluene, Heptane,

Pelletization

163

EXTRACTION OF BITUMEN FROM DOW-COLONY SHALE Bitumen Recovered % of Shale

Acid Number, MgKOH/gram

0..7 0.,9 1..5 1..6

9. 2, 9,.5 2..6 3. 6, 12..7, 18..8 19. 2, 13..1

Room Temp. Room Temp. Soxhlet Soxhlet

Dow-Colony l e a s e s . The sums of the weight percent of the Ca/CaMg carbonates and p y r i t e s i n the Marathon samples l i e between 30 and 35 percent whereas i n the Dow-Colony samples, they l i e between 47 and 80 percent. This o b s e r v a t i o n supports the f i n d i n g that the superior upgrading of the Marathon lease shale i s due to i t s lower carbonate/pyrite content. TABLE I I I . MINERAL CONSTITUENTS OF MARATHON LEASE AND DOW-COLONY MINE SHALE SAMPLES (Estimated Weight Percent i n C r y s t a l l i n e P o r t i o n ) Marathon Lease Calcite Dolomite Aragonite Pyrite Quartz Feldspar Analcite Dawsonite Nahcolite Clay Unidentified

35

30

-

-

15 15

20 20

-

-

20 10

15 10

-

-

5

5

Dow-Colony 10 27

10 40

-

-

10 12 25 3 5

10 10 15 10

5 3

5

10 65 5

10 10

-

In an e f f o r t to improve the ore upgrading process by i n c r e a s ing the l e v e l of carbonate minerals r e j e c t i o n , we studied the e f f e c t of the chemical a d d i t i v e s shown below. 1. F l o t a t i o n depressants: It was i n d i c a t e d e a r l i e r that the r e l e a s e of o i l s o l u b l e carboxyl i c acids may be r e s p o n s i b l e for the r e t e n t i o ni of Ca/Ca--Mg carbonates by the kerogen-organic binder p e l l e t s . Chemical f l o t a t i o n depressants are sometimes a p p l i e d to overcome the c o l l e c t i n g tendency of f a t t y acids and thus to increase the water w e t t a b i l i t y of the carbonate p a r t i c l e s i n the presence of c a r b o x y l i n acids.(j) The i n t r o d u c t i o n of such f l o t a t i o n depressants, i n c l u d i n g sodium o x a l a t e , chromium n i t r a t e , copper n i t r a t e , f e r r i c s u l f a t e and aluminum n i t r a t e f a i l e d to improve the b e n e f i c i a t i o n process d e s c r i b e d here.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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164

2. Sodium bicarbonate: Marathon lease samples which e x h i b i t high l e v e l s of b e n e f i c i a t i o n a l s o c o n t a i n n a h c o l i t e (NaHC03). The b e n e f i c i a t i o n process thus operates at an elevated pH. To i n v e s t i g a t e the e f f e c t of high pH on Dow-Colony shale, e x p e r i ments were performed with added sodium bicarbonate and sodium hydroxide. No improvement i n kerogen enrichment was obtained. 3. S u r f a c t a n t s : A s e l e c t i o n o f t y p i c a l commercial surface a c t i v e agents, both a n i o n i c and nonionic, were tested to determine whether b e n e f i c i a l i n t e r f a c i a l or wetting c o n d i t i o n s could be obtained. These agents i n c l u d e d : T r i t o n X-100 (nonionic, ethoxylated o c t y l phenol) P l u r o n i c F68 (nonionic, ethylene oxide - propylene oxide condensation product) NEODOL® 25-7, 25-9, 25-30, 25-45 (nonionic, l i n e a r primary a l c o h o l ethoxylates) NEODOL 25-3S ( a n i o n i c , s u l f a t e d form o f NEODOL 25-3). The e f f e c t s o f several d i s p e r s a n t s were a l s o examined; they included: Marasperse N22 and CB ( l i g n o s u l f o n a t e s ) Guartec ( i n d u s t r i a l grade guar gum) These approaches were a l s o unrewarding. Product Assay. F i s c h e r Assays were performed with samples of Marathon lease m a t e r i a l , with both raw shale and with the beneficiated pellets. Spent shale (char) from the assay was subjected to heat value (Btu content) a n a l y s i s . Results are shown i n Table IV. TABLE IV.

O i l , gal/ton O i l , % by weight Water, g a l / t o n Water, % by weight Spent Shale ( c h a r ) , % by weight Gas + Loss, % by weight Btu/lb o f char

FISCHER ASSAYS, MARATHON LEASE SHALE

Raw Shale

Beneficiated Product

44.3 16.6 6.4 2.7 74.4

154.2 57.4 2.5 1.0 33.0 8.6

6.3 693.0

5,352.0

DISCUSSION Kerogen, as noted e a r l i e r , i s a polymeric substance that can imbibe large q u a n t i t i e s o f organic l i q u i d s . This i s accompanied

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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11.

REISBERG

Pelletization

165

by s w e l l i n g and a s l i g h t s o f t e n i n g o f the matrix. Such gross s w e l l i n g , as w e l l as e x f o l i a t i o n , under the i n f l u e n c e o f v a r i o u s organic l i q u i d s can be observed v i s u a l l y with raw o i l shale. We suggest that t h i s s w e l l i n g and s o f t e n i n g o f the kerogen i s a key element i n the b e n e f i c i a t i o n scheme described here. During the m i l l i n g process the inorganic mineral p a r t i c l e s are not e j e c t e d v i a comminution of a b r i t t l e matrix (chopped out o f the kerogen, so to speak) but are instead worked out o f the softened kerogen mass by a deforming and kneading process. The kerogen p a r t i c l e s become fused r a t h e r than bridged by pendular r i n g s o f binding agent as i n coal p e l l e t i z a t i o n . A f t e r d r y i n g , the gangue d i s i n t e g r a t e s i n t o i t s component small p a r t i c l e s but the kerogen p e l l e t s dry to a hard b r i t t l e mass e x h i b i t i n g no evidence of the presence o f d i s c r e t e small p a r t i c l e s . Two shale samples were studied; one from the Marathon lease (cores) and the other from the Dow-Colony mine. C l e a r l y , the l a t t e r i s the more r e l e v a n t to an ore b e n e f i c i a t i o n process. The r e s u l t s obtained with t h i s m a t e r i a l are l e s s favorable than those achieved with the Marathon cores. S t i l l the increase i n kerogen content from a value o f 21 percent f o r the raw m a t e r i a l to 62 percent for the upgraded p e l l e t s represents a r e j e c t i o n of 83 percent o f the mineral matter ( n e g l e c t i n g a small loss of kerogen to the gangue). This upgrading can represent a s i z a b l e decrease i n the heat demand of a r e t o r t i n g process. There may also be an a n c i l l a r y environmental b e n e f i t . The r e j e c t e d inorgani c gangue contains only a small residue o f kerogen, i n unmodified form. This i s no more damaging than the kerogen i n the o r i g i n a l o i l shale. The r e s i d u a l char from the r e t o r t i n g o f the enriched p e l l e t s has a s u f f i c i e n t l y high Btu content (Table IV) and low minerals content to be i t s e l f u s e f u l as a process f u e l . I t s ash would be free o f organic matter and low i n s i l i c a dust. Thus the m a t e r i a l returned to the environment from a process i n v o l v i n g ore b e n e f i c i a t i o n , r e t o r t i n g of the kerogen-enriched p e l l e t s and char burning would be free o f organic p y r o l y s i s products. The l a b o r a t o r y experiments were performed batchwise i n small ball mills. A l a r g e r scale operation would c a l l f o r continuous processing, probably i n a rod m i l l . At present the procedure does not appear to be economically f e a s i b l e . A major cost i s that o f the i n i t i a l comminution of the shale. Because the m a t e r i a l possesses a very unfavorable g r i n d a b i i l t y work index, t h i s step r e q u i r e s an excessive power o u t l a y . Furthermore, the process c a l l s for a large quantity o f organic binding agent, the recovery of which i s a l s o very c o s t l y . Whether or not means can be devised for improving the economics must await f u r t h e r i n v e s t i gation .

ABSTRACT A procedure is described for the beneficiation of Green River oil shale, based on the wettability contrast between the

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

166

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

organic kerogen and its inorganic minerals. It entails the milling of the shale in a mixture of water and a liquid hydrocarbon binding agent followed by the separation of kerogen-enriched pellets and the rejection of an aqueous dispersion of hydrophilic mineral particles. A portion of the calcite and dolomite is rendered oleophilic and inseparable from the hydrocarbon-swollen kerogen pellets. This is brought about by the adsorption of oil soluble carboxylic constituents contained in the bitumens. Certain shale samples were upgraded from an initial kerogen content of 15 percent to a kerogen content in excess of 80 percent. Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch011

LITERATURE CITED 1. Quass, F. W., The Analysis of the Kerogen of Oil Shales, Inst. Pet. J., 1939, 25, 813. 2. Himus, G. W. and Basak, G. C., Analysis of Coals and Carbonaceous Materials Containing High Percentages of Inherent Mineral Matter, Fuel, 1949, 28, 57. 3. Smith, J. W. and Higby, L. W., Preparation of Organic Concentrate from Green River Oil Shale, Anal. Chem., 1960, 32, 1718. 4. Trent, W. E., Process of Purifying Materials, U. S. Patent No. 1,420,164, 1922. 5. Puddington, I. E. and Farnard, J. R., Oil Phase Separation, U. S. Patent No. 3,999,765, 1968. 6. Investigation of Colorado Oil Shale, First Annual Report, Denver Research Institute, 1966, pp. 19-20. 7. Sutherland, K. L. and Wark, I. W., Principles of Flotation, Australasian Institute of Mining and Metallurgy, 1955, pp. 317-321. RECEIVED January 19, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

12 Shell Pellet Heat Exchange Retorting: The S P H E R Energy-Efficient Process for Retorting O i l Shale

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

J. E. GWYN, S. C. ROBERTS, D. E. HARDESTY, G. L. JOHNSON, and G. P. HINDS, JR. Shell Development Company, P.O. Box 1380, Houston, TX 77001 Oil shales o f primary interest f o r surface processing occur mainly i n the Piceance Basin o f western Colorado. These shales c o n t a i n , t y p i c a l l y , 10 t o 20 p e r c e n t w e i g h t o f h y d r o c a r b o n s r e coverable by simple p y r o l y s i s . Process r e s e a r c h and development i n s h a l e o i l p r o d u c t i o n has gone o n f o r d e c a d e s , b u t t h e once p l e n t i f u l s u p p l y o f low c o s t p e t r o l e u m c r u d e s made t h e e c o n o m i c s o f s u c h p r o c e s s e s v e r y u n f a v o r a b l e . T h e r e c e n t s h o r t a g e s and c o s t e s c a l a t i o n o f p e t r o l e u m c r u d e s have renewed i n t e r e s t s i n " u n c o n v e n t i o n a l " raw m a t e r i a l s o u r c e s s u c h a s c o a l and o i l s h a l e . S e v e r a l p r o c e s s e s f o r above ground r e t o r t i n g o f o i l s h a l e , w h i c h have been under d e v e l o p m e n t f o r some t i m e , i n c l u d e t h e T 0 S C 0 - I I , PARAH0, and U n i o n t e c h n o l o g i e s . ' S h e l l had p a r t i c u l a r i n t e r e s t s i n t h e f i r s t two. The TOSCO (The O i l S h a l e Company) p r o c e s s u s e s h o t b a l l s t o h e a t p r e h e a t e d s h a l e i n a r o t a r y k i l n t o r e t o r t i n g temperat u r e s . The s h a l e i s preheated d u r i n g staged, pneumatic t r a n s p o r t u s i n g f l u e gas f r o m t h e r e t o r t b a l l h e a t e r . The PARAH0 r e t o r t i s a v e r t i c a l k i l n e m p l o y i n g a downward moving r o c k bed w i t h u p f l o w i n g r e c y c l e gas and c o m b u s t i o n p r o d u c t s w h i c h sweep r e t o r t e d h y d r o c a r b o n s f r o m t h e v e s s e l . The U n i o n p r o c e s s i s s i m i l a r b u t u t i l i z e s an upward f l o w o f c r u s h e d s h a l e . S h a l e i s i n t r o d u c e d a t t h e bottom o f t h e r e t o r t and pushed upward b y a m e c h a n i c a l " r o c k pump". F l u i d i z e d bed r e t o r t i n g o f o i l s h a l e was p r o p o s e d i n t h e e a r l y f i f t i e s but was n e v e r developed t o a commercial s t a t e . The T 0 S C 0 - I I p r o c e s s i s c a p i t a l i n t e n s i v e b e c a u s e i t r e q u i r e s a l a r g e volume o f h e a t i n g g a s e s and m e c h a n i c a l l y complex e q u i p m e n t ; t h e PARAH0 and Union p r o c e s s e s a r e a l s o c a p i t a l i n t e n s i v e b e c a u s e t h e y have l o n g r e s i d e n c e t i m e r e q u i r e m e n t s t h a t e n t a i l m a s s i v e h a r d w a r e . The PARAH0 and Union p r o c e s s e s a r e , however, h e a t e f f i c i e n t a s a r e s u l t o f c o u n t e r c u r r e n t s h a l e and gas f l o w . But t h e TOSCO p r o c e s s , a l t h o u g h h a v i n g some d e g r e e o f h e a t r e c o v e r y , uses h e a t r e l a t i v e l y inefficiently. The p u r p o s e o f t h i s work was t o d e v e l o p a new r e t o r t i n g p r o c e s s o f r e l a t i v e l y low c a p i t a l c o s t t h a t i s m e c h a n i c a l l y s i m p l e , h i g h l y r e l i a b l e , and u s e s h e a t e f f i c i e n t l y . The p r o c e s s , ' t e r m SPHER f o r 1

2

0097-6156/81/0163-0167$05.00/0 ©

1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

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MATERIALS

S h e l l P e l l e t Heat Exchange R e t o r t i n g , i s a f l u i d i z a t i o n bed p r o c e s s conceived f o r the r e t o r t i n g o f o i l shale. T h e f l u i d i z a t i o n mode r e f e r r e d t o i n t h i s d i s c u s s i o n a p p l i e s t o a range o f s u p e r f i c i a l gas v e l o c i t i e s between t h o s e used f o r r i s e r t r a n s p o r t and d e n s e b e d o p e r a t i o n i n p r o c e s s e s such a s c a t a l y t i c c r a c k i n g . By t h i s mode, s h a l e can be made t o f l o w upward, c o u n t e r c u r r e n t l y t o l a r g e r h e a t c a r r i e r p e l l e t s that f a l l through t h e f l u i d i z e d mixture. This c o u n t e r f l o w o f h e a t - c a r r i e r p e l l e t s and r e l a t i v e l y c o a r s e s h a l e p a r t i c l e s i s the b a s i c idea around which n o v e l , small s i z e d , t h e r m a l l y e f f i c i e n t and e c o n o m i c a l l y v i a b l e p r o c e s s e s have been c o n c e i v e d . O t h e r f e e d s t o c k s t o w h i c h SPHER may have p o t e n t i a l a p p l i c a b i l i t y i n c l u d e numerous c o a l s , l i g n i t e , wood and bark w a s t e , a g r i c u l t u r a l r e s i d u e s , b i o t r e a t e r s l u d g e s , and i n d u s t r i a l and m u n i c i p a l s o l i d w a s t e s . Some s p e c i f i c p r o c e s s d e s c r i p t i o n s , w i t h some v a r i a t i o n s , are d i s c u s s e d below. B r i e f D e s c r i p t i o n o f Process Applied t o O i l Shale The SPHER p r o c e s s as o r i g i n a l l y c o n c e i v e d i s shown s c h e m a t i c a l l y i n F i g u r e 1. T h i s c o n c e p t u a l d e s i g n p r o d u c e s 55,000 b b l / d a y (7575 t / d ) * o f raw s h a l e o i l f r o m 66,000 t o n / d a y (60,000 t / d ) o f 35 g a l / t o n (13.6%w) o i l s h a l e . I t c a n be seen t h a t t h e r e a r e two l o o p s f o r c i r c u l a t i o n o f h e a t c a r r y i n g b a l l s . The c o o l b a l l l o o p c a r r i e s heat f r o m t h e heat r e c o v e r y column t o t h e p r e h e a t e r . T h e hot b a l l l o o p c a r r i e s heat from the b a l l heater t o the r e t o r t . Shale i s crushed o r ground t o a f l u i d i z a b l e s i z e ; p r e f e r a b l y as l a r g e as i s compatible with heat t r a n s f e r requirements and ready s e p a r a t i o n from h e a t - c a r r y i n g b a l l s . I n i t i a l work i n d i c a t e s t h a t 1 / 1 6 - i n c h (1.6 mm) minus s h a l e and 1/4 (6 mm) o r 5/16 (8 mm) i n c h b a l l s are d e s i r a b l e . The s h a l e i s p r e h e a t e d i n a f a s t - f l u i d i z e d ( e n t r a i n i n g ) b e d b y outer loop, h e a t - c a r r y i n g b a l l s t h a t r a i n through the bed i n count e r c u r r e n t f a s h i o n ( F i g u r e 2 ) . W i t h a i r a s t h e f l u i d i z i n g medium, p r e h e a t i n g i s l i m i t e d t o a b o u t 600°F ( 3 1 5 ° C ) b e c a u s e t h e r e i s d a n g e r from a u t o - i g n i t i o n , w h i c h i s t i m e , t e m p e r a t u r e , and o x y g e n d e p e n d e n t . ) With other n o n o x i d i z i n g gases, p r e h e a t i n g i s l i m i t e d t o about 650°F (343°C) b y t h e o n s e t o f k e r o g e n p y r o l y s i s . In a d e n s e - b e d f l u i d i z e d b e d t h e p r e h e a t e d s h a l e i s f u r t h e r h e a t e d t o and h e l d a t t h e r e t o r t i n g t e m p e r a t u r e f o r s u f f i c i e n t t i m e t o c o m p l e t e t h e p y r o l y s i s r e a c t i o n s ( F i g u r e 3 ) . The t o t a l i n v e n t o r y o f shale i n the r e t o r t i n g v e s s e l i s determined by the r e q u i r e d r e s i d e n c e t i m e f o r c o m p l e t e k e r o g e n c o n v e r s i o n and t h e s h a l e t h r o u g h p u t . T h e r e t o r t h e a t r e q u i r e m e n t s a r e s u p p l i e d by c e r a m i c b a l l s w h i c h c i r c u l a t e i n t h e i n n e r l o o p . T h e y are r e h e a t e d i n a s e p a r a t e v e s s e l w h i c h may o p e r a t e a s a moving bed, r a i n i n g p e l l e t bed, o r e n t r a i n e d flow heater. The s p e n t s h a l e i s c o o l e d i n a f a s t - f l u i d i z e d b e d b y t h e r e c i r c u l a t e d cool p e l l e t s from the p r e h e a t e r . In t h i s manner, c o u n t e r c u r r e n t f l o w o f heat c a r r i e r s and t h e s h a l e a s s u r e s efficient * t o n = 2000 pounds, t = m e t r i c t o n = 1000 k g . 3

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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Figure 1. SPHER oil shale process

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

170

65°C Figure 2.

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preheater

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

GWYN ET A L .

Shell

Pellet

Heat

Exchange

Retorting

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

12.

Figure 3.

SPHER

retort

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

171

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

172

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

energy u t i l i z a t i o n . T h i s c h a r a c t e r i s t i c i s a prime advantage o f the process. Most c o n d i t i o n s a n d f e a t u r e s o f t h e c o n c e p t u a l p r o c e s s a r e c h o s e n t o a s s u r e h i g h t h r o u g h p u t s ( s m a l l e q u i p m e n t ) and hence r e l a t i v e l y low c a p i t a l and f i x e d c o s t s . T h e s e i n c l u d e t h e c h o i c e o f f l o w r e g i m e s , h e a t c a r r i e r s ( d e n s i t y and h e a t c a p a c i t y ) and t h e s o l i d s - t o gas w e i g h t r a t i o s . A t t e n d a n t f e a t u r e s o f t h e p r o c e s s , such a s b a f f l e d e s i g n and gas r o u t i n g , a r e c h o s e n t o a c h i e v e o p e r a b i l i t y and optimum operation. S e g r e g a t i o n o f t h e two b a l l l o o p s p e r m i t s t h e t a i l o r i n g o f t h e b a l l m a t e r i a l , shape and s i z e t o e a c h s p e c i f i c t a s k . C i r c u l a t i o n o f b a l l s i n t h e o u t e r l o o p i s a r e l a t i v e l y low t e m p e r a t u r e o p e r a t i o n and i s d e d i c a t e d t o heat t r a n s f e r . T h e r e f o r e , d e s i r e d b a l l p r o p e r t i e s i n c l u d e high heat c a p a c i t y , small s i z e o r l a r g e heat t r a n s f e r s u r f a c e , e r o s i o n r e s i s t a n c e , and low c o s t . Hence, a pea g r a v e l may be s u i t a b l e . C o r r o s i o n r e s i s t a n c e may n o t be needed u n l e s s c o n d e n s a t i o n o c c u r s i n t h e h e a t r e c o v e r y s e c t i o n . T h e use o f t h e s m a l l e s t b a l l s s e p a r a b l e f r o m t h e s h a l e i n c r e a s e s h e a t t r a n s f e r and r e d u c e s t h e s i z e o f the exchange v e s s e l r e q u i r e d . In c o n t r a s t , c i r c u l a t i o n o f b a l l s i n t h e i n n e r l o o p i n v o l v e s t h e b a l l h e a t e r and r e t o r t where h i g h t e m p e r a t u r e s a n d l o n g e r r e s i d e n c e times a r e r e q u i r e d . Reaction r a t e r a t h e r than heat t r a n s f e r i s e x p e c t e d t o be t h e c o n t r o l l i n g f a c t o r i n t h e r e t o r t d e s i g n . I n o r d e r t o a c h i e v e t h e r e s i d e n c e t i m e needed f o r h i g h c o n v e r s i o n a p s e u d o p l u g - f l o w d e v i c e such a s a r o t a r y k i l n o r a s t a g e d , d e n s e - p h a s e f l u i d i z e d b e d may be d e s i r a b l e . Since heat t r a n s f e r i s n o t c o n t r o l l i n g , t h e b a l l s can be l a r g e r f o r e a s i e r s e p a r a t i o n f r o m s h a l e but t h e y must s t i l l be s m a l l enough t o p e r m i t p n e u m a t i c t r a n s p o r t . T h e s e i n n e r l o o p b a l l s must a l s o be r e s i s t a n t t o t h e r m a l s h o c k , c h e m i c a l a t t a c k b y t h e hot g a s e s and s p e n t s h a l e and e x p o s u r e t o h i g h temperatures. Thus, the c h o i c e of the inner loop b a l l s i s l i m i t e d t o m a t e r i a l s such a s c e r a m i c s . Detailed Process D e s c r i p t i o n A more p r o c e s s o r i e n t e d s c h e m a t i c F i g u r e 4.

o f the process

i s shown i n

S h a l e Feed P r e p a r a t i o n . S h a l e p r e p a r a t i o n f o r SPHER r e q u i r e s more e n e r g y t h a n i t d o e s f o r p r o c e s s e s such a s T 0 S C 0 - I I i n t h a t t h e l a r g e r c r u s h e d s h a l e used i n T 0 S C 0 - I I , e.g., 1 / 2 - i n c h (13 mm) m i n u s , must be r e d u c e d t o a r e a d i l y f l u i d i z a b l e s i z e , e.g., 1 / 1 6 - i n c h (1.6 mm) m i n u s , f o r use i n SPHER. G r i n d i n g b y s e p a r a t i n g and r e c y c l i n g coarse shale i s expected t o produce a b e t t e r s i z e range with l e s s f i n e s t h a n o n c e - t h r o u g h g r i n d i n g i s f o r t h e same maximum p a r t i c l e size. S e p a r a t i o n o f s h a l e with t h e d e s i r e d s i z e from o v e r s i z e d m a t e r i a l may be a c c o m p l i s h e d b y e l u t r i a t i o n w i t h gas o r b y s c r e e n i n g . The r e c o v e r e d c o a r s e s h a l e i s c o n v e y e d back t o t h e g r i n d e r . Shale w i t h t h e d e s i r e d t o p s i z e may t h e n be p n e u m a t i c a l l y t r a n s p o r t e d t o a feed hopper o r standpipe.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Raw Shale

0

Air + Fuel Gas

Ball Mill

50F 10C

1000F 538C

100F 38C

Air

Preheat

550F 288C

-8

625F 329C

Figure 4.

Aii from Heat Recovery

-67

Superheater Flue Gas

Raining

Steam

900F 482C

• 0 -

—g

scheme

Xir

560F 293C

Air to fteheat

11 OOF 593C

ball oil shale pyrolysis

900F 482C

900 F 482C

Retort

Steam

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch012

Moisturizer

.— _ 50F 10C

500 F 260C

175F

79C

=^> Spent Shale

• Flue Gas

Water

Product Vapor

% too

50 -

-i 20

1

1

40

60

L

INDIRECT HEAT STANDARQ COMPACTION DENSITY = 92.5 pcf

1

1

80

100

-(10) r 120

OAYS CURING AT 125° F U.S. Bureau of Mines

Figure

5.

Compression

test results. Paraho retorted shale, .75-in. maximum size jraction.

semiworks

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

plant;

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch013

190

OIL SHALE,

TAR SANDS, AND RELATED

MATERIALS

p e r m e a b i l i t y of t h i s m a t e r i a l i s q u i t e high, e f f l u e n t s c o u l d be contained i n a d i s p o s a l area u s i n g p r o p e r l y - p l a c e d , w e l l c o n s t r u c t e d m a t e r i a l such as used i n Pond I . Even though the l o o s e l y compacted Pond I e x h i b i t e d a high p e r m e a b i l i t y r a t e , an a d d i t i o n a l f i e l d experiment i n d i c a t e d t h a t p e r m e a b i l i t y may not pose a s e r i o u s problem. A f t e r Pond I I ( l i g h t compaction) had d r i e d thoroughly f o r s e v e r a l months f o l l o w i n g the f i e l d i n f i l t r a t i o n t e s t , a s p e c i a l t e s t was conducted. The surface was sprayed with 17,400 & of water to represent a r a i n f a l l of 5 cm i n 30 minutes. No e f f l u e n t occurred f o r n e a r l y one f u l l day. A small seepage began the second day and continued f o r two days. Only 7 £ were c o l l e c t e d from the d r a i n p i p e . E s s e n t i a l l y a l l of the simulated r a i n f a l l was l o s t to a b s o r p t i o n and subsequent evaporation. T h i s i n d i c a t e s t h a t l e a c h i n g and p e r m e a b i l i t y may not be a problem f o r Paraho r e t o r t e d shale, even when l i g h t l y compacted, because even heavy r a i n f a l l w i l l not penetrate the p i l e to s i g n i f i c a n t depths. Chemical and P h y s i c a l P r o p e r t i e s . Paraho r e t o r t e d shale i s d e s c r i b e d according to standard s o i l s c l a s s i f i c a t i o n as a silty-gravelly material{4). A s i z e d i s t r i b u t i o n diagram i s presented i n F i g u r e 6. Some of the f a v o r a b l e p r o p e r t i e s of the r e t o r t e d shale i s a t t r i b u t e d to t h i s s i z e d i s t r i b u t i o n - l i k e a good aggregate mix, t h i s m a t e r i a l has the proper r a t i o of f i n e s to l a r g e r s i z e d p i e c e s so t h a t v o i d s between the l a r g e r p i e c e s are f i l l e d with f i n e s . This r e l a t i o n s h i p increases d e n s i t y , promotes s t r e n g t h , and reduces d u s t i n g and e r o s i o n . The chemical composition of r e t o r t e d shale depends on the composition of the raw shale and the r e t o r t i n g p r o c e s s . The m i n e r a l composition of the Green R i v e r shale used i n the Paraho operations c o n s i s t s of a complex mixture o f m i n e r a l s . These i n c l u d e : carbonates (50%), c l a y s (40%), quartz (8%), and s u l f i d e s and others (2%). The p r i n c i p a l carbonate m i n e r a l undergoing thermal r e a c t i o n s during the normal r e t o r t c o n d i t i o n s i s dolomite (CaC03*MgC03), or more p r o p e r l y f e r r o a n (CaC03«Fe , 9 l - x 3 ) where a p o r t i o n of the magnesium i s r e p l a c e d by i r o n . I t i s b e l i e v e d t h a t f e r r o a n undergoes the f o l l o w i n g chemical r e a c t i o n during normal r e t o r t i n g c o n d i t i o n s : x

M

c o

(1) Ferroan + Heat — • + FeO + CO2

Calcite

(CaC03) + Magnesia

(MgO)

Many s t u d i e s have been made concerning the mean chemical a n a l y s i s o f Paraho r e t o r t e d s h a l e ( 7 ) . Although i t i s important to know t h i s chemical composition, i t i s not h e l p f u l i n a s s e s s ing the components r e s p o n s i b l e f o r the cement-like p r o p e r t i e s . Much emphasis has been p l a c e d upon the formation o f r e a c t i v e oxides, such as f r e e lime and magnesia, from carbonate decompos i t i o n . Although f r e e lime can be formed under l a b o r a t o r y c o n d i t i o n s ( 8 ) , i t has not been detected i n the r e t o r t e d shale used i n the f i e l d s t u d i e s . Although f r e e lime was not detected,

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

13.

Retorted

HEISTAND

Oil Shale

Disposal

191

Research

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch013

SILT-CLAY SIZE ^

SAND SIZE (STANDARD SIEVE SERIES)

#200

#100

#50

#30

#16

•

#8

a

#4

GRAVEL SIZE (INCHES) |

|

I

l£

I 100 U.S. Bureau of Mines

Figure

6.

Gradation

data. Paraho retorted shale, semiworks 1.5-in. maximum size fraction.

plant—direct

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

heat;

192

OIL

SHALE,

TAR

SANDS,

AND

R E L A T E D

MATERIALS

magnesia has been found i n Paraho r e t o r t e d s h a l e . S u l f u r minerals, known to e x h i b i t cement-like p r o p e r t i e s , have been found i n Paraho r e t o r t e d shale ( and C H . . n

2n

n

2 n

series are

J 8

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

CJi

i n

. , u

246

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

Table I I I . Hydrocarbon Classes i n JP-5 Samples by FIMS*

Hydrocarbon Series

C

50.8

30.4

40.6

12.2

16.9

20.8

4.1

7.1

11.2

H

1.9

0.8

3.2

H

16.6

19.6

14.4

H

12.2

23.8

7.3

H

1.7

1.0

2.2

H

n 2n+2

C H n 2n 0

C H n 2n-2 0

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch016

AF-Exxon Shale-II (Fractionation & (Hydrocracking) Hydrogenation)

Shale-I (Coking)

0

C

n 2n-4

C

n 2n-6

C

n 2n-8

C

n 2n-10

* Ion i n t e n s i t i e s

(total

100)

R e p e a t a b i l i t y + 5%

Table IV.

Y i e l d s From LC Separation

Percent Y i e l d Fraction 1 2 3

4 5 6 7 8 9

% recovered

DFM

JP-5

68.9 0.8 19.6 7.1 1.2 0.6 0.7 0.5 0.7

73.6 2.9 21.7 1.6 0.3

96

93

R e p e a t a b i l i t y + 4%

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

SOLASH ET A L .

Fuel

Properties

and

Chemical

I I

+

M

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch016

+

g o

M M

1 CD tH

+

ao

•H 4-> a

+

cO u

+

CO &

247

Composition

r i i i

+

II i

*

+

I

+

CO

C •H

M i l *

CO CD •H CD

I I

C o

u co o o

> tH

* t H I I I *

' * 1

o •H

"

O CO

O

u

co H

M-l

CD W CD •H CD W

>-t O

CO CN

+ CN

c

CM

VO

00

O tH

CN tH

I

I

I

a

a

I

I

I

I

c

C

a

a

CN

CN

CN

CN

CN

CN

tH CN

VD tH

I CN

00 rH

I

c

CN

American Chemical Society Library 1155 16th St. N. W. In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; D. C. 20036 ACS Symposium Series;Washington, American Chemical Society: Washington, DC, 1981.

s

w CO

o •H

£ a ^ > H w 2 > r

W

o

> 2:

s

|

>

r

X >

00

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch016

16.

SOLASH

E T

A L .

Fuel

Table V I I .

Properties

and

Chemical

Composition

249

Average Molecule i n F r a c t i o n Three

Parameter

JP-5

DFM

Aromaticity

0.49

0.39

Aromatic Rings/Molecule

1.0

1.0

Average Mol. Wt.

164

206

Average Mol.

Formula

C

H

12.2 16.8

C

H

15.2 23.3

A l k y l Substituents/Molecule

3.2

3.1

Carbons/Alkyl Substituent

2.0

3.0

Naphthene Rings/Molecule

0.5

0.7

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

250

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

and a f a i r amount of t r i c y c l i c alkanes were a l s o found. T e t r a l i n s / i n d a n e s were a l s o found i n abundance. Some p a r t i a l l y hydrogenated t r i c y c l i c aromatics — n

70

>

X > r

O r

to

22.

SCHUCKER

AND KEWESHAN

Cold

Lake

Asphaltenes

333

above the thermal base case would e x p l a i n the s t a b i l i z a t i o n of r e s i n fragments shown i n F i g u r e 2 and the lower o l e f i n / p a r a f f i n r a t i o i n the gas i l l u s t r a t e d i n Table II f o r the C gases. The temperature dependence of the r e a c t i o n rate constants obtained f o r the thermal and c a t a l y t i c runs was assumed to f o l l o w the Arrhenius r e l a t i o n s h i p and the r e s u l t i n g p l o t of these data i s shown as Figure 3. As we can see, the c a t a l y s t had no r e a l e f f e c t on the a c t i v a t i o n energy. I t d i d , however, increase the rate of r e a c t i o n at a l l temperatures. I n t e r p r e t a t i o n of these data, though, i s at best somewhat s u b j e c t i v e . In complex react i o n systems l i k e these, the measured rate i s g e n e r a l l y considered to be that of the slowest or r a t e - l i m i t i n g step i n the r e a c t i o n sequence. The low values of the a c t i v a t i o n energies obtained s t r o n g l y suggest that primary bond breaking i s not the r a t e - l i m i t i n g step and that some other step such as hydrogen t r a n s f e r might be. This i s supported by the f a c t that the observed rate increased under improved hydrogen t r a n s f e r conditions . While the y i e l d of asphaltenes and other products during the e a r l y stages of r e a c t i o n are s i m i l a r (as shown i n Figures 1 and 2), the thermal asphaltenes e x h i b i t e d lower H/C r a t i o s and higher number average molecular weight (M ) and r e s u l t e d i n s u b s t a n t i a l coke formation. The unique behavior of the asphaltenes i n the presence of molybdenum on the other hand provided us with an e x c e l l e n t opportunity to look c l o s e r at the s t r u c t u r e of the reacted asphaltenes. Since these r e a c t i o n s were c a r r i e d out neat, maltenes could be separated and analyzed d i r e c t l y . There were no maltenes i n i t i a l l y so these molecules must at one time have been attached to the reactant asphaltene molecules. Furthermore, the reacted asphaltenes could a l s o be analyzed to determine what chemical changes were t a k i n g place during reaction. Elemental a n a l y s i s showed some i n t e r e s t i n g r e s u l t s with regard to H/C, s u l f u r and n i t r o g e n l e v e l s . Figure 4 shows a p l o t of the (H/C) values i n the reacted asphaltenes and the product maltenes. As can be seen, the (H/C) r a t i o i n the reacted asphaltenes drops continuously while that of the product maltenes r i s e s continuously. The weighted average of the measured asphaltene and maltene f r a c t i o n s r i s e s s l i g h t l y i n d i c a t i n g the a d d i t i o n of some hydrogen to the system. This i s the kind of behavior that might be expected of an asphaltene s t r u c t u r e c o n t a i n i n g a l a r g e , hydrogen d e f i c i e n t core to which are attached smaller, hydrogen-rich molecules. I t i s not c o n s i s t e n t with the smaller asphaltene s t r u c t u r e proposed by Ignasiak et a l (2) f o r Athabasca asphaltenes. Next the question of s u l f u r d i s t r i b u t i o n was addressed. S u l f u r i n the asphaltene and maltene f r a c t i o n s was measured d i r e c t l y and that i n the gas was obtained by d i f f e r e n c e . The r e s u l t f o r t h i s same s e r i e s of runs i s shown i n Figure 5. What we found was that approximately 50% of the s u l f u r remained i n

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

3

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

334

SHALE,

TAR

T A B L E

SANDS, AND

RELATED MATERIALS

II

EFFECT OF HYDROGEN TRANSFER ON OLE

FIN/PARAFFIN

R A T I O IN G A S P R O D U C T S

C

3 ^

C

3

REACTION TEMP. (°C)

T I M E (MIN.)

THERMAL

365

42

0.18

0.08

335

200 p p m

MOLYBDENUM

87

0.13

0.05

177

0.07

0.03

357

0.04

0.02

87

0.26

0.14

177

0.15

0.06

357

0.08

0.03

747

0.04

0.02

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

SCHUCKER

AND KEWESHAN

Cold

Lake

Asphaltenes

335

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

22.

Figure 3.

Arrhenius

plot for hydroconversion of Cold Lake asphaltenes: molybdenum (A A' thermal (

200

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

ppm

336

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

OIL SHALE, TAR SANDS, AND RELATED

Figure

4.

Hydrogen-to-carbon ratios in reaction products: maltenes product (calculated) ( ); asphaltenes (AA

(%);

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

total

Cold

Lake

Asphaltenes

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

SCHUCKER AND KEWESHAN

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

337

338

OIL SHALE, TAR SANDS, AND RELATED

the reacted asphaltene, 28% was found i n the maltenes while 22% wound up i n the gas (presumably as H S ) . Studies with model s u l f u r compounds ( i n c l u d i n g dibenzothiophene, diphenyl s u l f i d e , benzyl phenyl s u l f i d e and d i b e n z y l d i s u l f i d e ) under the same r e a c t i o n c o n d i t i o n s l e d us to conclude that the m a j o r i t y of the s u l f u r i n both the asphaltene and maltene products was e i t h e r h e t e r o c y c l i c or an intermediate r e a c t i o n product from the c l e a v age of d i a r y l or a l k y l - a r y l s u l f i d e l i n k a g e s . More e a s i l y cleaved bonds such as those i n d i a l k y l s u l f i d e s or d i s u l f i d e s were found to be converted very q u i c k l y . Nitrogen was a l s o measured i n the asphaltenes and maltenes and the r e s u l t s are shown i n Table I I I . What we found was t h a t , u n l i k e s u l f u r which i s d i s t r i b u t e d p r e t t y evenly between the asphaltene core and the p e r i p h e r a l groups, n i t r o g e n i s p r i m a r i l y i n the core s t r u c t u r e . In a d d i t i o n , during r e a c t i o n very l i t t l e i f any of the n i t r o g e n i s removed from the system. This suggests that n i t r o g e n i s i n predominantly condensed h e t e r o c y c l i c s t r u c tures i n the core with only about 12-14% e x i s t i n g as smaller condensed n i t r o g e n s t r u c t u r e s on the periphery. Oxygen was measured only i n the asphaltenes due to sample size limitations. Combined r e s u l t s i n d i c a t e d that over 50% of the oxygen was l i b e r a t e d during these r e a c t i o n s as gaseous species and t h i s i s i n good agreement with r e c e n t l y p u b l i s h e d work of Moschopedis et a l (5) suggesting the presence of carb o x y l i c a c i d and aldehyde f u n c t i o n a l i t y . In a d d i t i o n to elemental analyses, number average molecular weights (M ) were obtained on both asphaltene and maltene f r a c t i o n s from s e r i e s . The r e s u l t i n g curves are shown i n F i g u r e 6. The s t a r t i n g asphaltenes are observed to have a number average molecular weight of 6640 ± 120. This decreases monotonically to an apparent asymptote of 3400. At the same time, maltenes which are produced e x h i b i t much lower molecular weights s t a r t i n g at 645 and decreasing to 415. I t i s not unreasonable at t h i s p o i n t to p o s t u l a t e that the maltenes, once formed, continue to break down. Here again, the observed v a r i a t i o n i n average molecular weight i s c o n s i s t e n t with the concept that asphaltenes have a l a r g e r core s t r u c t u r e to which are attached smaller (M/10 the s i z e of the core) groups. We are not saying t h a t 3400 represents the molecular weight of the core s t r u c t u r e . Experimental nmr and other VPO evidence p o i n t s to the contrary. We are saying that at 400°C we have broken a l l bonds that can be thermally broken at a reasonable rate and are l e f t with the core plus p e r i p h e r a l groups attached by much stronger bonds ( i . e . b i p h e n y l l i n k a g e s , e t c . ) and some a l k y l s i d e chains. One of the most powerful t o o l s a v a i l a b l e to us f o r charact e r i z a t i o n of these f r a c t i o n s i s nuclear magnetic resonance spectroscopy. Proton and C F o u r i e r transform nmr spectra were run i n deuterochloroform on these same asphaltene and maltene samples and some of the spectra are shown i n F i g u r e s 7 and 8. One of the f i r s t i n t e r e s t i n g p o i n t s we f i n d i s t h a t the asphal2

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

MATERIALS

1 3

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

22.

SCHUCKER

Cold

AND KEWESHAN

T A B L E

NITROGEN CONTENT

REACTION

% ASPHALTENE

T I M E (MIN)

CONVERSION

0

0

Lake

339

Asphaltenes

III

O F REACTION

PRODUCTS

N / N ASPHALTENES

n

MALTENES

1.0

0

27

26.0

0.83

0.12

57

38.3

0.83

0.12

117

42.7

0.76

0.14

4 0 0 ° C , 200 ppm Mo

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

340

80001

,

,

1

I 20

I 40

I

I

60

80

MATERIALS

r

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

7000r-

3001 0

TIME a) 400°C

Figure 6.

Molecular

I 1

I 00

(MIN)

weights of reaction

products

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

1

20

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

SCHUCKER

A N D KEWESHAN

Cold

Lake

Asphaltenes

, i • i . i i i •i . i . i • i • i • i • i • i • i 10 9 8 7 6 5 4 3

i | i | i | i | i | ' i ' i i i i i ' I • I ' I • I

i • i . i • i , i , i , i • i • I . I 10 9 8 7 6 5

4

3

1

2

I

1

. i . i . l 0

1

i

1

I

1

I

1

I

1

I

1

I

I i i . i • i . i i I . I i I 2 1 0

6 (PPM FROM TMS)

Figure

7. H-l NMR spectra of (top) crude and (bottom; reacted (400°C, asphaltenes

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2 h)

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I

I

I ' I I I | I I I I

11

| ' M II

I I | I I I I | I I I I | I I I I | I II I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | M M |

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1

MATERIALS

6 (PPM FROM TMS)

Figure

8.

C-13 NMR spectra of (top) crude and (bottom; reacted (400°C, asphaltenes

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2 h)

SCHUCKER

AND KEWESHAN

Cold

Lake

Asphaltenes

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22.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

MATERIALS

22.

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A N D KEWESHAN

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Lake

Asphaltenes

345

1 3

tenes with M = 3400 s t i l l have 40% a l i p h a t i c carbon. Both C and H specfra confirm these as predominantly p a r a f f i n i c s i d e chains although some naphthenic character s t i l l remains. These side chains need not be connected to the asphaltene core s i n c e the smaller p e r i p h e r a l groups are a l s o known to be h i g h l y a l k y l substituted. In general we can say that the increase i n the f r a c t i o n o f aromatic carbon and hydrogen during r e a c t i o n i s c o n s i s t e n t with (1) the loss of a l k y l side chains, (2) l o s s o f h i g h l y s u b s t i t u t e d aromatic and naphthenic groups, and (3) l o s s of naphthenic hydrogen. We b e l i e v e that to a c e r t a i n degree a l l of these are o c c u r r i n g but that (2) i s the dominant r e a c t i o n . We can a l s o say based on subsequent experimental work using n-decyl benzene as a model a l k y l aromatic that under these condit i o n s (400°C, 120 min, 7 MPa H ) p - s c i s s i o n of a l k y l side chains i s p r e f e r r e d 20:1 over Of. One maltene sample generated under somehwat milder condit i o n s (3 h r s . , 365°C, CoMo/y-Al 0 ) to minimize secondary cracking r e a c t i o n s was analyzed by gas chromatography and the r e s u l t i n g chromatogram i s shown i n F i g u r e 9. I t i s c l e a r that while the vast m a j o r i t y o f the area i s contained i n the lower envelope, a d e f i n i t e p a t t e r n o f r e g u l a r l y - s p a c e d peaks i s observa b l e above the base. These were i d e n t i f i e d by gas chromatography/mass spectrometry as n - p a r a f f i n s ranging i n length from C11 to C 3 9 . The smaller peaks i n between were i d e n t i f i e d as p r i m a r i l y i s o - p a r a f f i n s which may have been formed by i s o m e r i z a t i o n during hydroconversion over the somewhat a c i d i c CoMo/v-Al 0 or which may represent the n a t u r a l d i s t r i b u t i o n of i s o p a r a f f i n s i n the a l k y l side chains. In summary, we have presented experimental evidence which supports the concept that Cold Lake asphaltenes have somewhat l a r g e , hydrogen-deficient core s t r u c t u r e s to which are attached a l k y l side chains and h i g h l y s u b s t i t u t e d aromatic groups. We have shown that s u l f u r tends to be r e l a t i v e l y evenly d i s t r i b u t e d between the core s t r u c t u r e s and the p e r i p h e r a l groups and that n i t r o g e n i s concentrated predominantly i n the cores. The o v e r a l l p i c t u r e of asphaltene r e a c t i v i t y that has emerged from t h i s i s shown s c h e m a t i c a l l y i n F i g u r e 10. During m i l d hydroconversion, weaker linkages are thermally broken r e s u l t i n g i n the formation of maltenes having a higher (H/C) and reacted asphaltenes having a lower (H/C). Some a l k y l s i d e chains are a l s o l o s t predomi n a n t l y by p - s c i s s i o n . In the absence o f e f f e c t i v e hydrogen t r a n s f e r , some o f these r e a c t i o n fragments can recombine to form coke. With improved hydrogen t r a n s f e r the coking r e a c t i o n s can be s i g n i f i c a n t l y delayed. T o t a l conversion o f these asphaltenes to maltenes would a t t h i s p o i n t seem to be an improbable g o a l ; however, more research i s needed i n order to see how f a r the s t r u c t u r a l concepts developed here f o r Cold Lake asphaltenes can be g e n e r a l i z e d to others.

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X

2

2

3

2

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

3

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Literature Cited 1. Speight, J. G., "A Structural Investigation of the Constituents of Athasbaca Bitumen by Proton Magnetic Resonance Spectroscopy," Fuel, 1970, 49, 76-90.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch022

2. Ignasiak, T., Kemp-Jones, A. V. and Strausz, O. P., "The Molecular Structure of Athabasca Asphaltenes. Cleavage of the Carbon-Sulfur Bonds by Radical Ion Electron Transfer Reactions," J. Org. Chem., 1977, 42(2), 312-320. 3. Bearden, R., Jr. and Aldridge, C. L., U.S. Patent 4,134,825 (1979). 4. Bearden, R., Jr., private communication. 5. Moschopedis, S. E., Parkash, S. and Speight, J. G., "Thermal Decomposition of Asphaltenes," Fuel, 1978, 57, 431-434. RECEIVED January 29, 1981.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

23 Influence of Thermal Processing on the Properties of Cold Lake Asphaltenes: The Effect of Distillation

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

KENNETH A. GOULD and MARTIN L. GORBATY Corporate Research Science Laboratories, Exxon Research and Engineering Company, P.O. Box 45, Linden, NJ 07036 A better understanding of the composition and properties of heavy feeds such as Cold Lake and Arabian Heavy oils is central to the development of improved upgrading technology. An important question which must be answered is to what extent these materials are thermally altered during refinery distillation. These heavy oils already contain large percentages of refractory materials such as asphaltenes, and it would be highly undesirable to increase the amount or degrade the quality of these components. We have, therefore, investigated the effect of heat treatment during distillation on the quantity and physical and chemical properties of asphaltenes. Cold Lake crude was chosen for this study since it is known to be a thermally sensitive material. Any changes caused by thermal treatment should, therefore, be more obvious than with a more stable feed. We report here the results of a variety of measurements made on the asphaltenes isolated from Cold Lake crude oil and from its vacuum distillation residue. It should be borne in mind that Cold Lake crude is subjected to the high temperatures of pressurized steam used in the production process and may conceivably have already undergone some thermal alteration. The present study, however, is designed primarily to learn if any further changes might occur during refining. Background The q u e s t i o n o f whether and t o what extent asphaltenes are formed or a l t e r e d during crude o i l h a n d l i n g and p r o c e s s i n g has remained unresolved. In one i n v e s t i g a t i o n , samples of a T a r t a r m i n e r a l o i l d i s t i l l a t i o n r e s i d u e were heated f o r f i v e hours to 163°C and then f o r another f i v e hours to 400°C t o simulate cond i t i o n s during d i s t i l l a t i o n . ( 1 ) Both an i n c r e a s e i n asphaltene content and a decrease i n asphaltene H/C r a t i o were observed. In a d d i t i o n , d i s t i l l a t i o n r e s i d u e s from v a r i o u s other crudes were heated to v a r i o u s temperatures f o r three hours and then pentane deasphaltened. I t was observed that asphaltene H/C r a t i o s decreased r a p i d l y above 6.

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Washington, D. C.

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In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

348

OIL SHALE, TAR SANDS, AND RELATED

MATERIALS

These i n v e s t i g a t o r s a l s o heated maltenes i n sealed v i a l s to v a r i o u s temperatures. The asphaltene y i e l d s obtained a t 350°C, 400°C, and 450°C were 18, 32, and 36%, r e s p e c t i v e l y . Although the conversions were approximately f i r s t order a t the lower temperatures, they changed s i g n i f i c a n t l y a t 450°C, the r e g i o n of t e c h n i c a l i n t e r e s t f o r many r e f i n i n g o p e r a t i o n s . Significant formation o f new asphaltenes was seen t o occur. Deasphaltened maltenes were a l s o separated by alumina chromatography i n t o a non-aromatic " g a s o l i n e " e l u a t e , a s t r o n g l y aromatic benzene e l u a t e , and a resinous benzene-methanol e l u a t e . Pentane i n s o l ubles were obtained from a l l three f r a c t i o n s upon h e a t i n g a t r e l a t i v e l y low temperatures, although the r a t e s were q u i t e d i f f e r e n t . Resins gave the h i g h e s t y i e l d s a t the f a s t e s t r a t e s while the aromatic o i l s showed about the same y i e l d , but a t a much slower r a t e . The y i e l d and r a t e were lowest f o r the nonaromatic o i l s , and t h e i r pentane i n s o l u b l e s were mostly toluene i n s o l u b l e s and p y r i d i n e i n s o l u b l e s r a t h e r than asphaltenes. The r e p o r t a l s o claimed that asphaltenes were formed even a t 20°C i n the absence of a i r a t r e l a t i v e l y slow r a t e s . A study of the e f f e c t o f heat on asphaltene decomposition a t 350-380°C i n a helium flow system (2) r e s u l t e d i n the f o l l o w i n g observations: 1. decomposition was found t o be f i r s t order i n asphaltenes 2. the percent coke make expressed as a percent of asphaltenes decomposed d i d not vary w i t h the extent of c r a c k i n g , implying that the mechanism i s independent of the percent c r a c k i n g . 3. a "20,000-fold i n c r e a s e i n s u r f a c e area of the asphaltenes v i a i n t r o d u c t i o n of carbon b l a c k (manner not s p e c i f i e d ) d i d not change the r e a c t i o n r a t e 4. toluene i n s o l u b l e s were formed i n amounts that decreased with i n c r e a s i n g r e a c t i o n time, implying t h a t these products are intermediates i n p y r i d i n e i n s o l u b l e formation. These observations l e d to the p r o p o s a l o f a f r e e r a d i c a l , c h a i n r e a c t i o n mechanism. Aspects of the mechanism i n c l u d e : (1) formation o f s m a l l r a d i c a l fragments which could a b s t r a c t hydrogen and leave as l i g h t products, (2) r e a c t i o n of s t a b i l i z e d f r e e r a d i c a l s (formed by hydrogen a b s t r a c t i o n ) which could i n t e r a c t w i t h asphaltenes to form l a r g e r and l a r g e r condensation products, and (3) formation of toluene i n s o l u b l e s , i . e . l i n e a r condensation products, and p y r i d i n e i n s o l u b l e s , i . e . c r o s s - l i n k e d products. These c h a i n r e a c t i o n s could be terminated by formation of very s t a b l e r a d i c a l s that could not r e a c t f u r t h e r . ( 2 ) T h i s mechanism i s i n accord with the c o n c l u s i o n s of Speight, who has s t a t e d that formation of p a r a f f i n s d u r i n g p y r o l y s i s of Athabasca asphaltenes probably occurs v i a i n t e r a c t i o n of a l k y l r a d i c a l s with hydrogen produced during a r o m a t i z a t i o n and condensation o f p o l y c y c l i c s t r u c t u r e s . ( 3 ) Carbon-carbon bond breaking i n these asphaltenes was found to occur p r i m a r i l y $ to aromatic r i n g s . 11

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

23.

GOULD A N D GORBATY

Thermal

Processing

349

In other work (4), x-ray a n a l y s i s l e d to the c o n c l u s i o n that not only d i d asphaltene m e l t i n g p o i n t i n c r e a s e w i t h i n c r e a s i n g f r a c t i o n a l a r o m a t i c i t y , f , but thermal s e n s i t i v i t y i n c r e a s e d i n the same d i r e c t i o n . Thus, asphaltenes with f 0.32 were more s e n s i t i v e and were transformed to a l a r g e extent to toluene i n s o l u b l e s a f t e r one hour at 375°C. When f was 0.17 and 0.24, only 18-32% conversion to toluene i n s o l u b l e s was observed. a

a

a

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

Experimental P r e p a r a t i o n of Asphaltenes. Asphaltenes were obtained by n-heptane p r e c i p i t a t i o n from e i t h e r Cold Lake crude or vacuum residuum using t y p i c a l deasphaltening procedures. ( i . e . One p a r t of residuum was r e f l u x e d f o r one hour with 10 p a r t s of heptane. The mixture was then f i l t e r e d and the i n s o l u b l e asphaltenes washed s e v e r a l times with heptane and pentane and d r i e d i n vacuo at 80°C.) P y r o l y s i s of Asphaltenes. Pyrolyses were performed u s i n g the apparatus shown i n Figure 1.(5) The a p p r o p r i a t e m a t e r i a l was placed i n a quartz tube w i t h 24/40 ground j o i n t s and a dry i c e condenser was attached. A f t e r a l t e r n a t e l y evacuating and f l u s h i n g with n i t r o g e n s e v e r a l times, the m a t e r i a l was pyrolyzed at the a p p r o p r i a t e temperature f o r 10 min. Char and l i q u i d y i e l d s were c a l c u l a t e d from the weights of the p y r o l y s i s tubes and condensers before and a f t e r r e a c t i o n . A n a l y t i c a l Data. Instrumental analyses and s p e c t r a were made on the f o l l o w i n g equipment: i n f r a r e d spectroscopy, D i g i l a b FTS14 F o u r i e r transform spectrophotometer; vapor pressure osmometry, H i t a c h i - P e r k i n Elmer 115; g e l permeation chromatography, Waters Assoc. 200; nuclear magnetic resonance spectrometry, V a r i a n Assoc. A60 and XL100; thermogravimetric a n a l y s i s , modified Stanton thermobalance; d i f f e r e n t i a l scanning c a l o r i m e t r y , P e r k i n Elmer DSC 2; and e l e c t r o n s p i n resonance spectrometry, V a r i a n Assoc. Century spectrometer with E102 X band microwave b r i d g e o p e r a t i n g at 9.5 GHz. Results and D i s c u s s i o n The f i n d i n g s discussed above (1-4) i n d i c a t e that changes i n asphaltene q u a l i t y and q u a n t i t y during thermal treatment depend s t r o n g l y on both the o r i g i n of the o i l and the s e v e r i t y of the treatment. This means that s p e c i f i c questions concerning s t a b i l i t y can only be answered v i a s t u d i e s on the p a r t i c u l a r o i l at the p a r t i c u l a r c o n d i t i o n s of i n t e r e s t .

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

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350

Figure 1.

Rapid heat-up pyrolysis

unit

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

23.

GOULD A N D GORBATY

Thermal

351

Processing

To provide raw m a t e r i a l f o r t h i s comparative study of untreated and h e a t - t r e a t e d o i l s , asphaltenes from Cold Lake crude (crude asphaltenes) and from Cold Lake vacuum residuum (residuum asphaltenes) were prepared by n-heptane p r e c i p i t a t i o n as d e s c r i b e d i n the Experimental s e c t i o n . The Cold Lake residuum f r a c t i o n was prepared by Imperial O i l E n t e r p r i s e s , L t d . a t S a r n i a , Ontario, Canada. The d i s t i l l a t i o n h i s t o r y of t h i s bottoms f r a c t i o n i n d i c a t e s that the pot m a t e r i a l was subjected to temperatures as h i g h as 314-318°C d u r i n g atmospheric and vacuum distillation. The length of time at 300°C or higher was about two hours. T h i s i s w e l l i n excess of what would be experienced i n a p i p e s t i l l and should have provided ample time f o r any decomposition. I t should be noted, however, that s i n c e i t was poss i b l e to maintain the system vacuum a t 0.35 mm, the maximum temperature experienced by the residuum was not q u i t e as h i g h as i t might be during r e f i n e r y d i s t i l l a t i o n (e.g. ca 350°C). Table I shows the y i e l d s of asphaltenes obtained from s e v e r a l deasphaltening operations on crude o i l and bottoms. The y i e l d s on bottoms were normalized to y i e l d s on crude by c o r r e c t i n g f o r the q u a n t i t y of d i s t i l l a t e s i n the crude. Table I Asphaltene Y i e l d s from Cold Lake Crude and Residuum Source Residuum Residuum Crude Crude Crude

% Asphaltenes

(On Crude)

10.6 10.9 9.9 9.8 10.8

The average percentage of asphaltenes i n the bottoms i s 10.8% (based on crude) and i s thus s l i g h t l y higher than the average value of 10.2% f o r the crude o i l . The 0.6% d i f f e r e n c e i s , however, w i t h i n the observed experimental v a r i a t i o n of 1.0% and i s t h e r e f o r e not considered s i g n i f i c a n t . The average elemental compositions f o r s e v e r a l p r e p a r a t i o n s of crude and residuum asphaltenes are shown i n Table I I . As can be seen, the two asphaltenes are q u i t e s i m i l a r with the d i f ferences between them being l e s s than the t y p i c a l e r r o r s from a n a l y s i s to a n a l y s i s . The H/C r a t i o s are almost i d e n t i c a l .

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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MATERIALS

Table I I

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

Average Elemental Analyses f o r Crude and Residuum Asphaltenes Asphaltene Source

% C

Residuum Crude

81.81 82.14

% H 7.75 7.65

% N 1.42 1.28

% S 8.01 7.78

Ni (ppm)

V (ppm)

H/C

329 345

893 935

1.14 1.12

Both the number average molecular weights as determined by vapor pressure osmometry and e x t r a p o l a t e d to zero c o n c e n t r a t i o n and the g e l permeation chromatographic molecular weight d i s t r i b u t i o n s i n d i c a t e that the crude and residuum asphaltenes do d i f f e r i n molecular weight. The VPO r e s u l t s are summarized i n Table I I I and comparative GPC t r a c e s are shown i n F i g u r e 2. As can be seen from these data, both techniques i n d i c a t e that the crude asphaltenes have a s i g n i f i c a n t l y higher molecular weight than the residuum asphaltenes. T h i s r e s u l t i s somewhat s u r p r i s i n g s i n c e one would not a. p r i o r i expect thermal c r a c k i n g a t such low temperatures, ^320°C, even w i t h a thermally s e n s i t i v e crude such as Cold Lake. T h i s e x p l a n a t i o n , however, cannot be r u l e d out. Another p o s s i b i l i t y which could account f o r lower molecular weights i n the residuum asphaltenes, s i d e c h a i n d e a l k y l a t i o n , can be e l i m i n a t e d on the b a s i s of n u c l e a r magnetic resonance r e s u l t s (vide i n f r a ) . Another p o s s i b l e cause of the molecular weight r e d u c t i o n i s thermally induced d i s s o c i a t i o n of II- II complexes which may help to hold the asphaltene macros t r u c t u r e together. Deasphaltening done at higher s o l v e n t - t o o i l r a t i o s , i . e . from 20:1 to 40:1, showed s i m i l a r molecular weight d i f f e r e n c e s between crude and residuum asphaltenes, implying that the r a t i o used here, 10:1, d i d not cause the observed d i f f e r e n c e s . ( 6 ) Table I I I Number Average Molecular Weights (M^) f o r Crude and Residuum Asphaltenes Asphaltene Source Residuum

Crude

Average 5120 4400 5850 5850 8250 6120 6850 6600

5305

6955

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

23.

GOULD A N D GORBATY

Thermal

353

Processing

The two asphaltenes were a l s o examined by i n f r a r e d , n u c l e a r magnetic resonance, and e l e c t r o n s p i n resonance techniques. Figures 3, 4, and 5 show the r e s u l t s of the IR analysis. I t i s immediately apparent that the two asphaltene s p e c t r a (Figures 3 and 4) are q u i t e s i m i l a r , showing no obvious q u a l i t a t i v e d i f f e r e n c e s . To l e a r n i f more s u b t l e d i f f e r e n c e s e x i s t e d , a d i f f e r e n c e spectrum (Figure 5) was generated by computer u s i n g the data accumulated f o r Figures 3 and 4. T h i s demonstrates that v i r t u a l l y complete c a n c e l l a t i o n can be obtained. The only r e s i d u a l a b s o r p t i o n of any s i g n i f i c a n c e i n t h i s h i g h l y magnified spectrum i s the s m a l l peak at 2950 cm~l. T h i s may r e s u l t from t r a c e s of r e s i d u a l s o l v e n t or i t may represent a very minor d i f f e r e n c e between the two asphaltenes. In the case of the magnetic resonance c h a r a c t e r i z a t i o n , both ! 3 c NMR and proton NMR were employed to o b t a i n the percentages of aromatic carbon and hydrogen. The r e s u l t s are shown i n Table IV. Although the measured l e v e l s o f aromatic hydrogen are w i t h i n experimental u n c e r t a i n t y of each other, the d i f f e r e n c e i n aromatic carbon i s probably s i g n i f i c a n t . Nevertheless, t h i s d i f f e r e n c e i s s m a l l and i n d i c a t e s that the aromatic carbon contents are q u i t e s i m i l a r . In a d d i t i o n , attempts to d i s c e r n q u a l i t a t i v e d i f f e r e n c e s i n the 13C NMR were i n v a i n . These r e s u l t s imply that very l i t t l e , i f any, d e a l k y l a t i o n or aromatizat i o n has occurred d u r i n g the crude d i s t i l l a t i o n procedure. Table IV Aromatic Carbon and Hydrogen Contents of Cold Lake Asphaltenes Asphaltene Source Crude Residuum

%__C^ 52.0 + 1 50.4 + 1

% H^ 13.7 14.2

+ +

0.5 0.5

Petroleum asphaltenes e x h i b i t two general types of s i g n a l s when examined by e l e c t r o n s p i n resonance techniques. One i s the 1 6 - l i n e , a n i s o t r o p i c , vanadyl (V=CH"2) resonance of the s o l i d s t a t e while the other a r i s e s from unpaired e l e c t r o n s which are present i n the form of r e l a t i v e l y s t a b l e f r e e r a d i c a l s . The crude and residuum asphaltenes were examined by ESR, and the r e l e v a n t data are summarized i n Table V.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

354

OIL SHALE, TAR SANDS, AND RELATED

700

1

? 600 •o

c

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|

500

l

Resid Asphaltenes

-

MATERIALS

Crude Asphaltenes

y 100

1000

10000

100000

Molecular weight (Polystyrene) Figure

2.

Molecular-weight

distributions of Cold asphaltenes

Lake

crude

and

residuum

W A V E L E N G T H (jim)

r

i

i

i

4000

3500

3000

2500

u

i

1

2000 1800

WAVENUMBER

Figure 3.

i

i

1

i

1400 1200 1000 800 600 (CM ) - 1

IR spectrum of Cold Lake crude

asphaltenes

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

23.

GOULD

Thermal

A N D GORBATY

355

Processing

W A V E L E N G T H (jim)

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

2.5

4000

3

3500

3.5

3000

4 4.5 5

2500

5.5

2000 1800

WAVENUMBER

Figure 4.

7

8

9 10

1400 1200 1000

12

15

800 600

(CM" ) 1

1R spectrum of Cold Lake residuum

asphaltenes

W A V E L E N G T H (\im)

4000

3500

3000

2500

2000 1800

WAVENUMBER

Figure 5.

Differential

1400 1200 1000 800

600

(CM ) - 1

IR spectrum of crude and residuum

asphaltenes

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

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MATERIALS

Table V ESR Parameters f o r Cold Lake Asphaltenes Parameter

Crude Asphaltenes

Residuum Asphaltenes

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

Vanadyl: Ml

(G)

174.0

174.4

A,

(G)

56.3

56.7

g|

1.9632

1.9629

1.9837

1.9813

2.00308

2.00307

6.4

6.6

Free R a d i c a l : g linewidth

(G)

I t i s apparent from the chemical s h i f t s ( g - v a l u e s ) , the h y p e r f i n e c o u p l i n g constants (A-values), and the l i n e w i d t h s t h a t the f r e e r a d i c a l s and vanadyl species are i n very s i m i l a r e n v i r o n ments i n both samples. I t was not p o s s i b l e to o b t a i n meaningful values f o r the absolute numbers of spins per gram f o r e i t h e r s p e c i e s , but estimates of the r e l a t i v e concentrations obtained by measuring peak h e i g h t s i n d i c a t e that the vanadyl and f r e e - r a d i c a l concentrations do not d i f f e r s i g n i f i c a n t l y between the two asphaltenes. I t thus appears that heat treatment of Cold Lake asphaltenes to 320°C does not a l t e r the nature or abundance of paramagnetic c e n t e r s . Since most of the p h y s i c a l p r o p e r t i e s of the asphaltenes d i d not show any major d i f f e r e n c e s , thermal r e a c t i v i t y was i n v e s t i gated to d i s c e r n any d i f f e r e n c e s which might e x i s t i n chemical r e a c t i v i t y . D i f f e r e n t i a l scanning c a l o r i m e t r y and thermogravimetric a n a l y s i s as w e l l as r a p i d p y r o l y s i s were employed. The only n o t a b l e f e a t u r e s of the DSC analyses were what appeared to be g l a s s t r a n s i t i o n s o c c u r r i n g at 175°C and 172°C f o r the crude and residuum asphaltenes, r e s p e c t i v e l y . The TGA curves f o r the two m a t e r i a l s were a l s o v i r t u a l l y i d e n t i c a l , d i f f e r i n g by l e s s than one percent v o l a t i l e matter at any temperature. Both of these techniques thus i n d i c a t e e s s e n t i a l l y no d i s c e r n a b l e d i f f e r ences i n the two asphaltenes. S i m i l a r l y , when the p y r o l y s i s behavior was s t u d i e d i n a r a p i d h e a t i n g u n i t w i t h a heatup time of one to two minutes, v i r t u a l l y i d e n t i c a l r e s i d u e y i e l d s were obtained. Summary and

Conclusions

The c h a r a c t e r i s t i c s of Cold Lake crude and residuum a s p h a l t enes have been compared by a number of i n s t r u m e n t a l and p h y s i c a l techniques. The asphaltenes were e s s e n t i a l l y i d e n t i c a l i n q u a l i t y

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch023

23.

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Thermal

Processing

357

and q u a n t i t y except that the crude asphaltenes e x h i b i t e d higher average molecular weights as w e l l as molecular weight d i s t r i b u t i o n s peaking a t higher molecular weights than d i d the residuum asphaltenes. The thermal h i s t o r y of these p a r t i c u l a r residuum asphaltenes i s much more severe i n terms of h e a t i n g time than would o r d i n a r i l y be the case f o r a r e f i n e r y product from a p i p e s t i l l s i n c e , i n the present i n s t a n c e , a pot d i s t i l l a t i o n was used. I t t h e r e f o r e seems l i k e l y that r e f i n e r y asphaltenes should be even l e s s d i f f e r e n t from t h e i r r e s p e c t i v e crude asphaltenes than i n t h i s i n v e s t i g a t i o n , assuming that p i p e s t i l l temperatures would be kept below the decomposition temperatures f o r the asphaltenes, i . e . l e s s than about 350°C. Furthermore, any d i f f e r e n c e s should be f u r t h e r diminished i n the event that a crude which i s l e s s thermally s e n s i t i v e than Cold Lake i s i n v o l v e d . Since the Cold Lake crude used i n t h i s i n v e s t i g a t i o n has been exposed to the temperature of the p r e s s u i z e d steam used i n the o i l p r o d u c t i o n , one cannot be c e r t a i n that some thermal changes had not a l r e a d y occurred i n the crude o i l . To study t h i s p o s s i b i l i t y the p r o p e r t i e s of c o l d b a i l e d ( i . e . recovered without steam i n j e c t i o n ) Cold Lake crude asphaltenes are being i n v e s t i g a t e d by many of these same techniques and w i l l be described i n a f u t u r e r e p o r t . Acknowled gments We would l i k e to thank R. B. Long f o r h i s a s s i s t a n c e i n the p r e p a r a t i o n of t h i s manuscript, R. R i f f o r help with the experimental work, and the f o l l o w i n g i n d i v i d u a l s f o r t h e i r a s s i s t ance i n the v a r i o u s a n a l y t i c a l measurements: L. Ebert, J . E l l i o t t , B. Hager, B. Hudson, M. M e l c h i o r , E. P r e s t r i d g e , W. Schulz, and B. S i l b e r n a g e l .

Literature Cited 1. Hrapia, H. Meyer, D., and Prause, M., Chem. Tech., 1964, 16, (12), 733. 2. Magaril, R. Z., and Aksenova, E. J., Khim. Technol. Top. Masel, 1970, 15, (7), 22. 3. Speight, J. G., Am. Chem. Soc., Div. Fuel Chem. Prepr., 1971, 15, (1), 57. 4. Bestougeff, M. A., and Genderel, P., Am. Chem. Soc., Div. Petrol. Chem. Prepr., 1964, 9, (2), B51. 5. Design supplied by R. J. Lang, Exxon Res. and Eng. Co., Baytown, Texas. 6. R. C. Schucker, private communication from these laboratories. RECEIVED February 18, 1981. In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

24 Thermal Recovery of Oil from Tar Sands by an Energy-Efficient Process 2

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

K. M.JAYAKAR1,J. D. SEADER, A. G. OBLAD, and K. C. HANKS Departments of Chemical and Fuels Engineering, University of Utah, Salt Lake City, UT 84112

Oil-impregnated rock d e p o s i t s , more commonly r e f e r r e d to as tar sands, are found on every continent except A u s t r a l i a and A n t a r c t i c a (1). The l a r g e s t known d e p o s i t s occur in northern A l b e r t a , Canada, where two full-scale commercial p l a n t s f o r producing s y n t h e t i c crude oil a r e in o p e r a t i o n and two more p l a n t s have been approved f o r c o n s t r u c t i o n . Of the 24 s t a t e s that cont a i n t a r sands in the United S t a t e s , Ritzma (2) estimates that about 90-95 percent o f these t a r sands lie in Utah. Although the Utah deposits c o n t a i n only about 25 billion b a r r e l s of i n - p l a c e bitumen, compared t o 900 billion b a r r e l s in Canada, as d i s c u s s e d by Oblad et al. (3), the Utah d e p o s i t s represent an important p o t e n t i a l domestic source o f s y n t h e t i c petroleum. Operating p l a n t s in Canada employ a hot-water process f o r r e c o v e r i n g bitumen from t a r sands. Although Utah t a r sands can be c o n s i d e r a b l y d i f f e r e n t from Canadian t a r sands w i t h respect t o p h y s i c a l and chemical p r o p e r t i e s (4), Sepulveda and Miller (5) have s u c c e s s f u l y processed t a r sands from high-grade Utah d e p o s i t s with a m o d i f i e d hot-water process that uses high-shear c o n d i t i o n s to overcome the higher v i s c o s i t y of Utah tar-sand bitumens. More recent work by M i s r a and Miller (6) has been s u c c e s s f u l in processing medium-grade Utah d e p o s i t s . Other methods f o r p r o c e s s i n g tar sands that have been s t u d i e d e x t e n s i v e l y (1) i n c l u d e v a r i o u s in-situ techniques and mining followed by d i r e c t coking, s o l v e n t e x t r a c t i o n , or cold-water s e p a r a t i o n . Of the other methods that use mined m a t e r i a l as the feed stock, d i r e c t coking processes, g e n e r a l l y r e f e r r e d to as thermal recovery methods, appear t o exhib i t the most promise as a l t e r n a t i v e s to hot-water processing because thermal recovery methods avoid handling of v i s c o u s bitumen, recovery of sediment from s o l u t i o n s , and recovery and r e c y c l e of water and/or s o l v e n t s . In the work presented here, a new energye f f i c i e n t thermal process was developed and a p p l i e d to t a r sands from three Utah d e p o s i t s . 1

Current address: Eastman Kodak Company, Rochester, NY, 14605.

2

Current address: Celanese Chemical Company, Pampa, TX, 78408. 0097-6156/81/0163-0359$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED

360

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

Thermal Recovery

MATERIALS

Process

The concept of r e c o v e r i n g l i q u i d and/or gaseous hydrocarbons from s o l i d hydrocarbon-bearing m a t e r i a l s by thermal treatment has been known f o r s e v e r a l c e n t u r i e s (7). Thermal treatment essent i a l l y e n t a i l s p r o c e s s i n g at high temperature. In most thermal processes, the feed m a t e r i a l i s heated i n an i n e r t or nono x i d i z i n g atmosphere. The mode of h e a t i n g and the operating temperature l a r g e l y determine the type of changes o c c u r r i n g to the feed, which can i n c l u d e : 1) v o l a t i l i z a t i o n of any low-molecularweight components i n the feed, 2) generation of vapors by c r a c k i n g r e a c t i o n s , and 3) conversion of part of the m a t e r i a l i n t o coke, by r e a c t i o n s such as p o l y m e r i z a t i o n . In the case of feed m a t e r i a l s such as t a r sand, which c o n t a i n a s i g n i f i c a n t amount of s i l i c a sand or other i n o r g a n i c i n e r t matter that remains s u b s t a n t i a l l y unchanged through the thermal treatment, coke i s obtained as a deposit on the i n o r g a n i c matter. Thermal p r o c e s s i n g can r e q u i r e a s u b s t a n t i a l input of energy to provide the necessary s e n s i b l e , l a t e n t , and r e a c t i o n h e a t s . However, as d i s c u s s e d by Oblad et a l . (3), coke, when produced as above and subsequently combusted, can g e n e r a l l y provide much or a l l of t h i s energy requirement. Combustion, r e f e r r e d to some authors as decoking or burning, i s t h e r e f o r e an important aspect of thermal-recovery methods. Moore et a l . (8) c l a s s i f y thermal processes i n t o two general groups, d i r e c t heated and i n d i r e c t heated, depending on whether p y r o l y s i s and combustion steps are c a r r i e d out i n one or two r e a c t i o n v e s s e l s . The processes f u r t h e r d i f f e r from each other with r e s p e c t to f l u i d i z e d - b e d or moving-bed s t a t e of s o l i d s i n each of the two s t e p s . Table I shows a general process c l a s s i f i c a t i o n scheme that f i t s most known thermal processes. References are i n c l u d e d i n that t a b l e . Regardless of the thermal process used, as d i s c u s s e d i n d e t a i l by Bunger (4), the s y n t h e t i c crude o i l product obtained cannot, i n general, be used as a subs t i t u t e f o r crude petroleum but must be upgraded to reduce s u l f u r and n i t r o g e n contents, average molecular weight, and C/H r a t i o . In a l l thermal recovery processes, t a r sand i s subjected to high p r o c e s s i n g temperatures, about 450-550°C f o r p y r o l y s i s , and the r e s i d u a l coked sand i s f u r t h e r heated to about 550-650°C during the combustion s t e p . At these c o n d i t i o n s , an acceptable thermal e f f i c i e n c y can only be obtained i f a s i g n i f i c a n t p o r t i o n of the s e n s i b l e heat i n the spent sand i s recovered and introduced back i n t o the process. Almost a l l the processes i n Table I provide f o r heat recovery from spent sand before i t i s d i s c a r d e d . Perhaps the best-known f l u i d i z e d - b e d process i s the one developed by G i s h l e r and Peterson (17, 24-, 25) i n Canada. The process scheme resembles that of c a t a l y t i c c r a c k i n g as used i n the petroleum i n d u s t r y . Tar sand i s fed to the p y r o l y s i s or coker bed, where the o i l vapor produced i s c a r r i e d by the f l u i d i z i n g gas to the product c o l l e c t i o n system. Coked sand i s withdrawn from the coker and blown by preheated a i r i n t o the burner where the coke

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

24.

JAYAKAR

ET AL.

Thermal

Recovery

of

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361

i s burned. A p o r t i o n of the hot sand i s r e c y c l e d to the coker to supply heat f o r the p y r o l y s i s step, with the remainder d i s c a r d e d through an overflow pipe i n the burner bed. Two s e r i o u s drawbacks of t h i s process, as noted by Camp (1), are the l a r g e r e c y c l e of hot sand r e q u i r e d and the high energy content of the net spent sand. Rammler (23) has d e s c r i b e d the a p p l i c a t i o n of the L u r g i Ruhrgas process to t a r sands. L i k e the G i s h l e r and Peterson process, i t uses sand as the heat c a r r i e r .

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

Development of an E n e r g y - E f f i c i e n t Thermal

Process

The p a r t i c u l a t e nature of the m i n e r a l matter i n most t a r sands permits f l u i d i z e d p r o c e s s i n g with s e v e r a l advantages: 1) d i s i n t e g r a t i o n of lumps of t a r sand to i n d i v i d u a l p a r t i c l e s upon the p y r o l y s i s of the bitumen; hence such feeds do not have to be reduced to a s m a l l s i z e p r i o r to entry i n t o the p y r o l y s i s reactor; 2) r e l a t i v e ease of handling s o l i d s because f l u i d i z e d s o l i d s flow through pipes l i k e l i q u i d ; 3) h i g h h e a t - t r a n s f e r r a t e s between f l u i d i z i n g medium and s o l i d p a r t i c l e s ; 4) n e a r l y i s o t h e r m a l operat i o n , which permits c l o s e c o n t r o l of the temperature of p y r o l y s i s , a v a r i a b l e a f f e c t i n g product y i e l d s , q u a l i t y and energy r e q u i r e ments; 5) high r a t e s f o r mass t r a n s f e r between p a r t i c l e s u r f a c e and f l u i d i z i n g medium, which i s important f o r a h i g h r a t e of feed per u n i t area without forming agglomerates; 6) accommodation of v a r i a t i o n s i n bitumen content of feed by r e g u l a t i n g the flow of f l u i d i z i n g gas; and 7) ease of immersion of heat t r a n s f e r tubes or heat exchangers i n the f l u i d i z e d beds w i t h accompanying h i g h h e a t - t r a n s f e r c o e f f i c i e n t s . The l a s t f a c t o r i s p a r t i c u l a r l y important f o r the type of process developed i n t h i s study and c o n s t i t u t e s the primary reason f o r the choice here of f l u i d i z e d p y r o l y s i s . A f l u i d i z e d bed recommends i t s e l f f o r burning coke f o r e s s e n t i a l l y the same reasons as f o r p y r o l y s i s and was used, t h e r e f o r e , f o r the process developed here. P r e v i o u s l y developed processes employ v a r i o u s f e a t u r e s to accomplish heat t r a n s f e r f o r preheat and p y r o l y s i s . These i n clude 1) preheating the tar-sand feed, s e p a r a t e l y from the p y r o l y s i s step, g e n e r a l l y to recover heat from outgoing hot gaseous streams; 2) preheating the incoming process gas streams, genera l l y to recover heat from spent sand or s o l i d s r e s i d u e l e a v i n g the process; 3) t r a n s f e r of heat from the burner to the p y r o l y s i s r e a c t o r i n the form of s e n s i b l e heat of gases l e a v i n g the burner, g e n e r a l l y by d i r e c t heat exchange with the contents of the p y r o l y s i s zone; and 4) i n t e r n a l combustion of coke i n the p y r o l y s i s r e a c t o r i t s e l f with a c o n t r o l l e d amount of o x i d i z i n g gas so that only a p o r t i o n of the hydrocarbons i n the p y r o l y s i s zone, p r e f e r ably coke, i s combusted; 5) t r a n s f e r from the burner to the p y r o l y s i s step by r e c y c l e of hot, spent sand as a heat c a r r i e r . Feature 1 has not been shown to be p r a c t i c a l because, when preheated, t a r sand becomes s o f t and s t i c k y , making i t impossible

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

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to feed by common feeding devices such as a screw conveyor. Feature 2 can be and g e n e r a l l y i s incorporated i n t o most thermal processes. However, a maximum of only about 25 percent of the energy i n the hot, spent sand can be recovered by preheating the o x i d i z i n g g^s f o r coke combustion. In Feature 3, the amount of energy that can be c a r r i e d by gases from the combustion zone to the p y r o l y s i s zone i s r e l a t i v e l y s m a l l . Feature 4 r e q u i r e s a means f o r d i r e c t heat t r a n s f e r between the two zones by conduct i o n , convection, and/or r a d i a t i o n . Unless t h i s can be accomp l i s h e d on a l a r g e s c a l e w i t h l i t t l e or no combustion of bitumen, Feature 4 i s not p r a c t i c a l . Feature 5 i s p r a c t i c a l , but excessive r e c y c l e of hot, spent sand i s r e q u i r e d , thus g r e a t l y i n c r e a s i n g the r e q u i r e d s i z e s of p y r o l y s i s and combustion r e a c t o r s and n e c e s s i t a t i n g l a r g e devices to convey the sand. Another p o s s i b l e means of t r a n s f e r r i n g heat from the cokecombustion stage to the p y r o l y s i s stage i s by the use of i n d i r e c t heat exchange not i n v o l v i n g sand or gas. In the process developed i n t h i s work, t h i s means was implemented by i n c o r p o r a t i n g heat pipes to t r a n s f e r the bulk of the energy r e q u i r e d f o r s o l i d preheat and p y r o l y s i s from the coke-combustion stage. A heat pipe, f o r the purpose here, may be d e f i n e d simply as a completely enclosed tubular device w i t h very high e f f e c t i v e thermal conductance, which t r a n s f e r s heat by two-phase c i r c u l a t i o n of a working f l u i d (28). In o p e r a t i o n , heat i s t r a n s f e r r e d to one end of the heat pipe, causing the working f l u i d to v a p o r i z e . The vapor flows to the other, c o o l e r end due to the pressure g r a d i e n t s e t up i n s i d e the c e n t r a l vapor core of the heat p i p e . There, the vapor condenses on the tube w a l l and i n s i d e a wick, t r a n s f e r r i n g heat to the surroundings. The condensate then returns to the warmer end, thus completing the c y c l i c flow of the f l u i d . Because a l a r g e amount of heat can be t r a n s f e r r e d by a heat pipe, i t s s o - c a l l e d e f f e c t i v e thermal c o n d u c t i v i t y can be extremely h i g h . For a p p l i c a t i o n to thermal processing of t a r sands, potassium was s e l e c t e d as the working f l u i d . The e s s e n t i a l f e a t u r e s of the r e a c t o r system f o r the new thermal process developed i n the work reported here are i l l u s t r a t e d i n the s i m p l i f i e d process scheme of F i g u r e 1. F r e s h l y mined and s i z e d t a r sand i s dropped i n t o the upper bed of a m u l t i staged f l u i d i z e d - b e d column. The upper bed i s a p y r o l y s i s r e a c t o r , which i s maintained a t a temperature of g e n e r a l l y between 400° and 550°C. Here, bitumen i n the feed i s cracked and/or v o l a t i l i z e d , l e a v i n g a coke deposit on the sand p a r t i c l e s . The o i l vapors and l i g h t hydrocarbon gases produced are c a r r i e d o f f by the i n e r t f l u i d i z i n g gas to f i n e s - s e p a r a t i o n and productrecovery s e c t i o n s , w h i l e coked sand flows down by g r a v i t y through a c o n t r o l v a l v e to the burner s e c t i o n of the column where the coke i s burned to generate heat. The burner i s maintained at a temperature of g e n e r a l l y between 550° and 650°C. Preheated a i r i s used to f l u i d i z e the s o l i d s i n the combustion bed and to pro-

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

24.

JAYAKAR

E TAL.

Thermal

Recovery

of

Oil

Products to Recovery

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T a r Sand

Pyrolysis

Heat P i p e -

tit

Combustion

Heat Recovery

Air .

*Sc 'Spent Figure 1.

Sand

University of Utah process

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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364

MATERIALS

v i d e oxygen f o r combustion. Gaseous products of combustion, mostly n i t r o g e n and carbon d i o x i d e , then flow upwards to f l u i d i z e s o l i d s i n the upper bed as noted above. A number of heat pipes, as r e q u i r e d by the h e a t - t r a n s f e r load, are placed v e r t i c a l l y i n the f l u i d i z e d - b e d column such that they extend i n t o the p y r o l y s i s and combustion beds as d e p i c t e d i n F i g u r e 1. The heat pipes t r a n s f e r excess heat generated i n the burner to the p y r o l y s i s r e a c t o r , thus m a i n t a i n i n g the r e a c t o r and burner at proper temperatures. Hot, spent sand l e a v i n g the burner flows down through a cont r o l v a l v e to a heat-recovery s e c t i o n , where process a i r recovers heat from the spent sand. A d d i t i o n a l energy can be recovered from the sand by heat exchange to produce steam. A more d e t a i l e d d e s c r i p t i o n of the process i s given by Seader and Jayakar (26). The new process r e t a i n s most of the s i m p l i c i t y of d i r e c t heated processes. S o l i d s move only downwards by g r a v i t y , the equipment i s e s s e n t i a l l y a s i n g l e v e s s e l , and there i s no r e c y c l e of s o l i d s . Most importantly, the h e a t - t r a n s f e r f e a t u r e s u s e d — heat p i p e s , heat recovery from spent sand to preheat process a i r , t r a n s f e r of some heat by combustion gases, and some r a d i a t i v e heat t r a n s f e r from coke-combustion stage to the p y r o l y s i s r e a c t o r — permit e f f i c i e n t management of the energy that i s w i t h i n t a r sand i t s e l f to h e l p achieve high energy e f f i c i e n c y . The heat pipes e f f e c t i v e l y l i n k the p y r o l y s i s r e a c t o r and the coke-combustion stage thermally without n e c e s s a r i l y imposing any other c o n s t r a i n t s on the process such as flow p a t t e r n s , r e a c t o r c o n f i g u r a t i o n , or dimensions of the column (except f o r the volume of heat pipes, which i s a s m a l l f r a c t i o n of bed volumes). The b a s i c process as o u t l i n e d above i s very f l e x i b l e , and m o d i f i c a t i o n s and v a r i a t i o n s can be e a s i l y i n c o r p o r a t e d i n t o i t to f u r t h e r improve the o v e r a l l e f f i c i e n c y and/or to make i t more s u i t a b l e f o r s p e c i f i c types of feeds. Thus, e x t e r n a l f u e l , r e c y c l e gas, or l i q u i d f u e l s can be e a s i l y introduced i n t o the burner i n the case of l e a n t a r sands. By p r o v i d i n g f o r a purge gas stream o f f the top of the combustion bed, one can adjust the flow r a t e of f l u i d i z i n g gas to the p y r o l y s i s bed. I f desired, after recovery, gas produced i n the p y r o l y s i s bed can be r e c y c l e d back to that bed and used i n s t e a d of combustion gases to f l u i d i z e i t . This i s very important f o r l e a n t a r sands which would otherwise have very low product c o n c e n t r a t i o n i n the combined e x i t gas stream, making product recovery d i f f i c u l t . Laboratory T e s t i n g of New

Process

A l a b o r a t o r y apparatus was used to demonstrate the new t h e r mal process. I t c o n s i s t e d of a 10-foot-high by nominal 2-inch diameter, two-staged, f l u i d i z e d - b e d column, a screw feeder f o r feeding t a r sand, a hot cyclone and f i l t e r system f o r s e p a r a t i o n of f i n e s from the products, and a product-recovery s e c t i o n c o n s i s t ing of condensers, phase s e p a r a t o r s , cyclones, and an e l e c t r o -

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

s t a t i c p r e c i p i t a t o r . A s i n g l e 0.75-inch-diameter by 7-foot-long heat pipe extended i n t o the p y r o l y s i s and coke-combustion beds. The apparatus was completely i n s u l a t e d and instrumented with thermocouples, pressure taps, flow meters, and sampling taps. E l e c t r i c a l heaters and a propane burner were used to provide heat during s t a r t u p c o n d i t i o n s . The equipment was designed to handle a nominal feed r a t e of 5 l b / h r of t a r sands c o n t a i n i n g up to 14 weight percent bitumen. F u r t h e r d e t a i l s of the apparatus are given by Jayakar (27). Several problems i n s o l i d s handling were encountered i n operating the l a b o r a t o r y apparatus. O r i g i n a l l y s o l i d s were transf e r r e d from the p y r o l y s i s bed to the combustion bed by means of a weir and d i p l e g . Because gas tended to flow up through the d i p l e g , t h i s system was abandoned i n favor of a simple s o l i d s downcomer with a s p e c i a l l y designed s o l i d s f l o w - c o n t r o l v a l v e . Although t h i s v a l v e permitted proper o p e r a t i o n of the bed, i t was a r e c u r r e n t source of o p e r a t i n g d i f f i c u l t y as i t tended to s t i c k a f t e r a few runs and had to be dismantled and cleaned every two to f o u r runs. Flow of s o l i d s from the combustion bed was cont r o l l e d by a s i m i l a r v a l v e , which presented no o p e r a t i n g problems. Tar-sand feed m a t e r i a l s were ground to p a r t i c l e s or p i e c e s no l a r g e r than about 1/4-inch i n s i z e . M a t e r i a l s tending to be s t i c k y were dusted with f i n e s o r c o a l dust p r i o r to f e e d i n g . The screw feeder d i d not plug as long as i t was kept a t a nearambient temperature. Run d u r a t i o n s were t y p i c a l l y one hour a f t e r spending s e v e r a l hours to reach e s s e n t i a l l y s t e a d y - s t a t e conditions. The experimental work was d i v i d e d i n t o three p a r t s : f l u i d i z a t i o n s t u d i e s a t elevated temperatures, p r o c e s s i n g of t a r sands i n the p y r o l y s i s s e c t i o n without use of the heat pipe, and o p e r a t i o n of the complete heat-piped apparatus. Only t y p i c a l r e s u l t s o f some of the l a t t e r t e s t s are reported here. A t o t a l of 75 runs was made under thermal p r o c e s s i n g c o n d i t i o n s a t near-ambient pressure with t a r sands from three d i f f e r ent d e p o s i t s : Tar Sand T r i a n g l e , Sunnyside, and Asphalt Ridge. Data from r e p r e s e n t a t i v e runs f o r feed m a t e r i a l s from each o f the three d e p o s i t s a r e given i n Table I I . A complete accounting of a l l the bitumen i n the feed m a t e r i a l was g e n e r a l l y not achieved mainly because of d i f f i c u l t i e s i n removing o i l product from the product recovery equipment. Thus, values reported f o r o i l y i e l d are b e l i e v e d to be low. Based on the best runs, i t i s estimated that f o r Sunnyside and Asphalt Ridge m a t e r i a l s , a t y p i c a l y i e l d s t r u c t u r e f o r near-optimal operating conditions would be: 70 wt% o i l , 10 wt% gas, and 20 wt% coke. Conclusions 1. The b a s i c concept of a thermal process using p y r o l y s i s and combustion stages coupled by heat pipes i s workable and e l i m i n a t e s the need to r e c y c l e l a r g e amounts o f sand.

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

366 Table I .

C l a s s i f i c a t i o n o f and References f o r Thermal Recovery Processes

I n d i r e c t Heated

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch024

D i r e c t Heated Moving-bed p y r o l y s i s and combustion

Cheney et a l . (9) Dannanberg and Matzick (10) Saunders (11)

Bennett (12) Berg (13) F i t c h (14)

Fluidized-bed pyrolysis and combustion

G i f f o r d (15) Peck et a l . (16)

G i s h l e r and Peterson (17) Nathan e t a l . (18) R o e t h e l i (19) Murphree (20) Alleman (21)

Fluidized-bed pyrolysis and moving-bed combustion

Donnelly

No examples known

Moving-bed p y r o l y s i s f l u i d i z e d - b e d combustion

No examples known

Table I I .

et a l . (22)

Rambler (23)

Laboratory R e s u l t s f o r Processing of Utah Tar Sands Deposit Tar

Run No. Bitumen Content of Feed, wt% Tar-Sand Feed Rate, lb/hr P y r o l y s i s Bed Temperature, °C Combustion Bed Temperature, °C O i l Y i e l d , wt% Gas Y i e l d , wt% Coke Y i e l d , wt% T o t a l Y i e l d , wt% API G r a v i t y of O i l , 20 °C V i s c o s i t y of O i l , cps, 25°C

Sand T r i a n g l e 58 4.70

Asphalt Ridge

Sunnyside

67

74

11.67

10.56

3.90

4.41

3.85 475 482

449

649

604

603

20.6 22.0 92.1

52.7 15.7 7.8 76.2

45.4 6.2 17.2 68.8

13.1

15.2

18.2

49.5

142

102

291

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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2. Tar sands c o n t a i n i n g as low as 8 percent bitumen can be thermally processed without e x t e r n a l energy input to get s a t i s f a c t o r y y i e l d s of o i l . Tar sand with even lower bitumen content can be processed with good o i l y i e l d i f a p o r t i o n o f the gas or o i l products or some cheaper e x t e r n a l f u e l , such as c o a l , can be added to the combustion stage to provide energy. 3. M o d i f i c a t i o n s of the process, such as i n t r o d u c i n g recycle of gas and o i l , a l l o w i n g f o r purge o f some combustion gas, e t c . , can improve the energy e f f i c i e n c y o f the process and the y i e l d s of o i l and gas. 4. The process developed during the course of t h i s work i s simple, d i r e c t , and e f f i c i e n t . I t i s capable of wide a p p l i c a t i o n to processing o f t a r sands i n Utah, Canada, and perhaps other d e p o s i t s . Moreover, the concept of using heat pipes i s o f even broader a p p l i c a b i l i t y i n the process i n d u s t r i e s i n general and i n e n e r g y - r e l a t e d i n d u s t r i e s i n p a r t i c u l a r . For example, the b a s i c processing concepts i n v e s t i g a t e d here may have p o t e n t i a l f o r a p p l i c a t i o n i n the processing of o i l shale and c o a l .

ABSTRACT Tar sands from the Asphalt Ridge, Sunnyside, and Tar Sand Triangle deposits in Utah were processed in a small-scale, two-stagefluidized reactor system operating under continuous, steady-flow conditions. The oil products obtained were analyzed for viscosity, refractive index, density, sulfur content, distillation yield, and proton nmr spectra. In the first stage of the reactor, mined and suitably sized tar sand is pyrolyzed at temperatures of 450 to 500°C in an inert atmosphere to crack and volatilize most of the contained bitumen, which is then condensed and collected to give a synthetic crude oil. In the second stage, coke formed as a by-product in the first stage is combined with air at temperatures of 550 to 650°C. The energy released during combustion in the second stage is transferred by a heat pipe to the first stage where the heat is utilized to provide for preheat and heat of pyrolysis of tar-sand feeds. Gaseous combustion products from the second stage, containing very little oxygen, are used to fluidize the pyrolysis bed. The process permits recovery of oil from tar sands with high energy efficiency in a once-through operation with respect to sand. References

1. Camp, F. W., "Tar Sands" in Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Edition, Vol. 19, John Wiley and Sons, New York, pp. 682-732 (1969). 2. Ritzma, H. R., AIChE Symposium Series No. 155, 72, 47 (197 3. Oblad, A. G., J. D. Seader, J. D. Miller, and J. W. Bunger, AIChE Symposium Series No. 155, 72, 69 (1976).

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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4. Bunger, J. W., K. P. Thomas, S. M. Dorrance, Fuel 58, 183 (1979). 5. Spulveda, J. E., and J. D. Miller, Mining Engineering, 30, 1311 (1978). 6. Misra, M., and J. D. Miller, Mining Engineering, 32, 302 (1980). 7. Gustafson, R. E., "Shale Oil" in Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Edition, Vol. 18, John Wiley and Sons, New York, pp 1-20 (1969). 8. Moore, R. G., D. W. Bennion, J. K. Donnelly, "Anhydrous Extraction of Hydrocarbons from Tar Sands," Paper presented at local ISA Meeting, Calgary Section, April 1975. 9. Cheney, P. E., R. W. Ince, and C. M. Mason, U. S. Patent 3,487,002, December 30, 1969. 10. Dannanberg, R. O., and A. Matzick, "Bureau of Mines Gas-Combustion Retort for Oil Shale," U. S. Bureau of Mines Report of Investigation 5545 (1960). 11. Saunders, F. J., U. S. Patent 3,130,132, April 21, 1964. 12. Bennett, J. D., U. S. Patent 3,623,972, November 1971. 13. Berg, C. H. O., U. S. Patent 3,905,595, September 22, 1959. 14. Fitch, C. M., U. S. Patent 3,267,019, August 16, 1966. 15. Gifford, P. H., II. U. S. Patent 4,094,767, June 1978. 16. Peck, E. B., E. Tomkins, and D. G. Tomkins, U. S. Patent 2,471,119, May 1949. 17. Gishler, P. E., and W. S. Peterson, Treatment of Bituminous Sand. Canadian Patent 530,920, September 25, 1956. 18. Nathan, M. F., G. T. Skaperdas and G. C. Grubb, U. S. Patent 3,320,152, May 16, 1967. 19. Roetheli, B. E., U. S. Patent 2,579,398, December 18, 1951. 20. Murphree, E. V., U. S. Patent 2,980,617, October 13, 1959. 21. Alleman, C. E., U.S. Patent 2,647,077, July 28, 1953. 22. Donnelly, J. K., R. G. Moore, D. W. Bennion, and A. E. Trenkwalkder, "A Fluidized Bed Retort for Oil Sands," Paper presented at the AIChE Meeting, Florida, 1978. 23. Rammler, A. W., "The Production of Synthetic Crude Oil from Oil Sand by Application of the Lurgi-Ruhrgas Process," Canadian Journal of Chemical Engineering, 48 (October 1970): 552-560. 24. Peterson, W. S., and P. E. Gishler, "A Small Fluidized Solids Pilot Plant for the Direct Distillation of Oil from Alberta Bituminous Sands," Canadian Journal of Research, 28 (January 1950): 62-70. 25. Peterson, W. S., and P. E. Gishler, "Oil from Alberta Bituminous Sand," Petroleum Engineer, 23 (April 1951): 553561. 26. Seader, J. D., and K. M. Jayakar, Process and Apparatus to Produce Synthetic Crude Oil from Tar Sands, U. S. Patent 4,160,720, July 10, 1979. 27. Jayakar, K. M., "Thermal Recovery of Oil from Tar Sands," Ph.D. Thesis in Chemical Engineering, University of Utah (1979). 28. Dunn, P., and D. Reay,HeatPipes,2nd., Pergamon Press, 1978. RECEIVED January 23, 1981. In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

25 Hydropyrolysis: The Potential for Primary Upgrading of Tar Sand Bitumen

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch025

J. W. BUNGER, D. E. COGSWELL, R. E. WOOD, and A. G. OBLAD Department of Mining and Fuels Engineering, 320 WBB, University of Utah, Salt Lake City, UT 84112 Upgrading of high molecular weight, residual materials is becoming increasingly important as a result of decreasing availability of lighter feedstocks. Conversion processes for residual materials must contend with high heteroatom content, high molecular weight (low volatility), high aromaticity and high metals content not encountered to the same degree in lighter feedstocks. These characteristics result in higher process costs and typically lower conversion and yield of desired products. But as production recovery and processing costs rise, yield and conversion efficiency become increasingly important. As a result, conventional techniques for primary conversion of residual materials such as tar sand bitumen, e.g. coking, may prove economically unacceptable. A possible alternative for the primary conversion of residual material is hydropyrolysis. Hydropyrolysis (HP) is a process for thermal cracking in the presence of hydrogen. This process has been shown to dramatically improve the yields of liquid and gaseous products compared to coking (1,2,3,4,5). Hydropyrolysis does not require the introduction of heterogeneous catalysts but requires elevated pressures. Through model compound work (5) and characterization (6) and processing (7) of high molecular weight tar sand bitumen, an understanding of the chemistry of this reaction is beginning to emerge. This paper reports our latest results and discusses the chemical changes effected by hydropyrolysis. The implication of the possible reactions to the suitability of various feedstocks for processing by hydropyrolysis is also discussed. Experimental Feedstock Source. Three feedstocks were used i n t h i s study. A l l were derived from U i n t a Basin, Utah Tar Sand d e p o s i t s . A Sunnyside bitumen was solvent extracted by procedures p r e v i o u s l y reported (6) from a f r e s h l y mined sample obtained from the o l d Asphalt Quarry northeast of Sunnyside, Utah. An Asphalt Ridge bitumen was extracted s i m i l a r l y from a sample f r e s h l y mined from

0097-6156/8l/0163-0369$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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SHALE, TAR SANDS, AND RELATED MATERIALS

Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch025

the U i n t a County Quarry southwest of V e r n a l , Utah. The TS-IIC o i l was used as r e c e i v e d from the U.S. Department of Energy, Laramie Energy Technology Center (LETC). The TS-IIC o i l i s r e p r e s e n t a t i v e of the o i l produced during an echoing i n - s i t u combustion o i l recovery p r o j e c t conducted at Northwest Asphalt Ridge by the LETC l a b o r a t o r i e s (8). Elemental A n a l y s i s and P h y s i c a l P r o p e r t i e s . Elemental a n a l y s i s was accomplished by conventional m i c r o a n a l y t i c a l techniques i n a commercial t e s t i n g l a b o r a t o r y . D e n s i t i e s were measured on a Mettler/Paar d i g i t a l d e n s i t y meter, model D.M. 40. Number average molecular weights were determined by VPO i n benzene. Simulated d i s t i l l a t i o n was accomplished using a 1/4" by 18" column of 3% d e x s i l 300 on chromosorb W, programmed from -30° to 350°C at 10°/minute with a 4 minute hold at 350°C. The detector was a flame i o n i z a t i o n detector maintained at 400°C. The percent n o n d i s t i l l a b l e m a t e r i a l was determined by using as an i n t e r n a l standard, an equal volume^mixture of C^ to C ^ n - a l k y l benzenes (See a l s o reference 9). C-NMR spectra data were obtained as reported i n reference (_3) . Hydropyrolysis Process. Two h y d r o p y r o l y s i s r e a c t o r s were used i n t h i s study. The Sunnyside and Asphalt Ridge bitumen were processed i n a r e a c t o r c o n s i s t i n g of a c o i l e d s t a i n l e s s s t e e l tube 3/16" i . d . x 236" long. T h i s r e a c t o r has been p r e v i o u s l y described by Ramakrishnan (1). The TS-IIC o i l was processed i n a r e a c t o r o r i g i n a l l y developed f o r short residence time c o a l l i q u e faction. T h i s r e a c t o r a l s o c o n s i s t s of c o i l e d s t a i n l e s s s t e e l tubes 3/16" i . d . The length of t h i s tube system can be v a r i e d from 20 to 120 f e e t , and has been p r e v i o u s l y described by Wood, et a l . (10). The length of the r e a c t o r f o r runs reported i n t h i s paper was 100 f e e t . Average residence times were c a l c u l a t e d from the volumetric flow r a t e s and the r e a c t o r volume at process c o n d i t i o n s . The r e a c t i o n mixture, which i s predominantly H^, was assumed f o r purposes of t h i s c a l c u l a t i o n to behave as an i d e a l gas. The r e a c t o r s were p r e - s u l f i d e d with H^S to i n h i b i t c a t a l y t i c r e a c t i o n s from w a l l s u r f a c e s . Results The elemental a n a l y s i s and p h y s i c a l p r o p e r t i e s f o r the U i n t a Basin d e r i v e d feedstocks are given i n Table I. The elemental analyses r e v e a l compositions t y p i c a l of U i n t a Basin bitumens (11) i n that H/C r a t i o s f a l l between 1.53 and 1.66, n i t r o g e n contents are a p p r e c i a b l e (~1%) and s u l f u r content i s low (