Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement [1st ed.] 978-3-030-21208-7;978-3-030-21209-4

Table of contents :
Front Matter ....Pages i-xxxviii
Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 1-37
Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 39-110
Sintering: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 111-165
Blast Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 167-273
Basic Oxygen Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 275-301
Electric Arc Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 303-375
Smelting Reduction: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 377-417
Direct Reduced Iron: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 419-484
Carbon Capture and Storage: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 485-553
Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse Emissions Abatement (Pasquale Cavaliere)....Pages 555-576
Back Matter ....Pages 577-596

Citation preview

Pasquale Cavaliere

Clean Ironmaking and Steelmaking Processes Efficient Technologies for Greenhouse Emissions Abatement

Clean Ironmaking and Steelmaking Processes

Pasquale Cavaliere

Clean Ironmaking and Steelmaking Processes Efficient Technologies for Greenhouse Emissions Abatement

Pasquale Cavaliere Department of Innovation Engineering University of Salento Lecce, Italy

ISBN 978-3-030-21208-7 ISBN 978-3-030-21209-4 https://doi.org/10.1007/978-3-030-21209-4

(eBook)

© Springer Nature Switzerland AG 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

World steel demand and production is continuously growing. Being a high energyintensive and high-impact industry, the energy consumption and the greenhouse gases emissions are destined to double by 2050 if the actual processing routes are completely preserved. To avoid this, new paradigms must be developed and approached in order to transform the sector, making it sustainable in the future and compatible with the global warming reduction. By introducing and optimizing energy-efficient solutions to the actual route, only a maximum of 25% of global saving is expected; this target is insufficient for the goals, leading to global warming control and reduction. So, based on current climate change forecast, it is predicted that the steel industry will face greater challenges which cannot be solved with the past incremental technologies in the future. US and European reports underline that if the global warming should be avoided, the only way is to develop and apply breakthrough technologies very fast. The book describes the main available technologies employed in the traditional or innovative routes capable of reducing the energy consumption and the dangerous greenhouse emissions as well as the research efforts that see many scientists involved all around the world from industry, academia, and research centers. Obviously, the energy topic is largely described, taking into account the direct and indirect consumption per each analyzed technology and suggested solution. Regarding coke making, the last years’ technological innovations led to lowering air emissions and to the deep limiting of hazardous solid wastes. It is showed that the different technological choices are driven by regional and logistic issues. The treatment of wastewater as a very crucial issue in coke making is largely described. The development and the diffusion of technologies, such as coke dry quenching and coke stabilization quenching, are discussed. The use of coke oven gas in order to abate the dangerous emissions is largely taken into account. Those technologies leading to operational efficiency, coke quality, and productivity are underlined. Another fundamental process for raw materials preparation in the integrated ironmaking/steelmaking route is sintering. CO2, NOx, SOx, PCDD/Fs, and particulate matters are continuously produced during the whole sintering cycle; this is because of the fuel combustion, carbon in the fed material, v

vi

Preface

and other carbonaceous sources such as limestone and dolomite. All those solutions leading to these dangerous compounds’ abatement are described. The employment of biomass as inhibitor and the energy consumption reduction solutions are underlined. Heat recovery at the sinter plant is a means for improving the efficiency of sinter making. Exhaust gases are processed, adsorbed, decomposed, and/or collected as nontoxic by-products to increase the quantity and improve the quality of steam recovery, reaching high fuel savings; all the most efficient methods are reviewed. Computer control technologies for the sintering process were developed along with sinter technology, as sinter quality requirements for the blast furnace were upgraded. Many parameters are involved during sintering. The optimization of these parameters control can lead to the increase in productivity and in the quality of the sintered ores. All the emissions optimized sintering technologies are largely described. The technological evolution of the blast furnace plants led to high efficient reactors very close to their thermodynamic limits. The blast furnace-based production route covers the majority of the steel production all around the world with hundreds of plants. One of the main disadvantages of the integrated route is the necessity of a coke plant with high energy intensity and very high emissions levels. In the direction of reducing these impacts, the injection of carbon-bearing reductants at the tuyere level has given new impetus to blast furnace operational practice to reduce the coke consumption significantly. Another important innovation is represented by the top gar recovery technologies. In the new-generation blast furnaces, oxygen is employed as substitute of the air. Many online process monitoring and control are in use or under development with the overall goal of increasing the process efficiency and fuel consumption and environmental impact reduction. Conversion operations are necessary in the integrated steel plant. Large effort has been devoted to the energy efficiency improvement and to the greenhouse gases emissions reduction. The actual converting technologies are based on a combination of blowing oxygen from the top laces and inert gas or oxygen plus inert gases from the bottom of the reactors. Today’s highly efficient electric arc furnaces consume roughly 300 kWh/t-steel. The appropriate greenhouse gas reduction strategy is strongly influenced by the source of electricity generation (i.e., fossil fuel or nuclear). Reduction of indirect emissions requires reducing electrical energy consumption. The current trend toward increased addition of fuel and oxygen has resulted in chemical energy sources supplying a greater proportion of the furnace’s energy inputs. Oxyfuel burners in the furnace have become a necessity to increase the rate of scrap melting in cold spots and thereby make scrap melting more uniform and to reduce the electricity needing for the metal fusion. Waste gases recovery and utilization as well as foamy slag practices allow to reduce energy consumption. The bottom stirring practice is getting more and more important and even essential, especially for the furnaces having big temperature gradient in the bath, such as big shell furnace. Modern controls which use a multitude of sensors help to achieve power saving and precise process monitoring to a greater extent than older controls. Direct reduced iron production is destined to increase in the next and far future. This is due to the continuous innovations of the plants leading to less energy consumption and carbon dioxide emissions. In this direction, the technological solutions push

Preface

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toward the waste energy recovery and the use of CO and H2 as reductant agents. The gas-based processes are located in those regions where natural gas is available in abundance and at reasonable prices. Hydrogen production from water electrolysis to obtain the reducing agent is under development and appears exceptionally promising for the zero-emissions ironmaking. The current CO2 capture and usage solutions that are available or under development are reviewed. Only the capture of CO2 will be responsible for the achievement of the goals of the Blue scenario. Intergovernmental Panel on Climate Change (IPCC) scenarios associated with a more than even chance of achieving the 2
C target are characterized by average capture rates of 10 GtCO2 per year in 2050, 25 GtCO2 per year in 2100, and cumulative storage of 800–3000 GtCO2 by the end of the century. Carbon capture, storage, and utilization are recognized as crucial in climate change mitigations and in particular in a NET contest to limit warming well below the 2
C scenario. The capture technologies are grouped as chemical/physical absorption, solid adsorbents capture, membranes or molecular sieves physical separation, cryogenics separation, and carbonation. Obviously, this best available technology could be applied globally at current production levels, taking into account precise energy balances, economic feasibility, transition rates, and regulatory and social factors. The principal iron ore electrolysis routes under investigation and development are the molten oxide electrolysis and the electrowinning. Since electrolysis produces no CO2, it could theoretically be zerocarbon but only if the electricity needed to power the process is produced without generating CO2 emissions (renewable sources). They are very promising even if at a basic research and pre-industrialization stage. My special thanks to all the Springer editorial office people for their professionalism. Finally, I would like to dedicate the work to my “miracle” son Alessandro. Lecce, Italy

Pasquale Cavaliere

Contents

1

2

Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . 1.1 Introduction and Global Scenario . . . . . . . . . . . . . . . . . . . . . 1.2 Main Approaches to the Problem . . . . . . . . . . . . . . . . . . . . . 1.3 Technological Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Main Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .

1 1 6 13 22 32 33

Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 2.2 Wastewater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.3 Coke Dry Quenching (CDQ) . . . . . . . . . . . . . . . . . . . . . . . . . 50 2.4 Use of Coke Oven Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 2.5 Coke Making Control Systems . . . . . . . . . . . . . . . . . . . . . . . . 79 2.6 Coal Stamp Charging Battery (CSCB) . . . . . . . . . . . . . . . . . . 82 2.7 High-Pressure Ammonia Liquor Aspiration System (HPALA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 2.8 Coal Moisture Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 2.9 Non-Recovery Coke Ovens . . . . . . . . . . . . . . . . . . . . . . . . . . 88 2.10 Variable Speed Drive Coke Oven Gas Compressors . . . . . . . . 95 2.11 Coke Stabilization Quenching . . . . . . . . . . . . . . . . . . . . . . . . 95 2.12 Single-Chamber System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 2.13 SCOPE 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 2.14 Use of Biomass and Waste Materials . . . . . . . . . . . . . . . . . . . 99 2.15 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

ix

x

3

4

Contents

Sintering: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Waste Heat Recovery in Sinter Plant . . . . . . . . . . . . . . . . . . . 3.3 Exhaust Gas Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Improved Process Control and Quality Assurance . . . . . . . . . . 3.5 Improved Ignition Oven Efficiency with Multi-slit Burners . . . 3.6 Emissions Optimized Sintering (EOS) . . . . . . . . . . . . . . . . . . 3.7 EPOSINT Process, Selective Waste Gas Recycling . . . . . . . . . 3.8 Improved Charging of Materials . . . . . . . . . . . . . . . . . . . . . . . 3.9 Low Emissions and Energy Optimized Sintering Process . . . . . 3.10 Sectional Gas Recirculation . . . . . . . . . . . . . . . . . . . . . . . . . . 3.11 Curtain Flame Ignition System . . . . . . . . . . . . . . . . . . . . . . . . 3.12 Utilization of Waste Fuels in Sintering . . . . . . . . . . . . . . . . . . 3.13 Charcoal in Sintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.14 Biomass in Sintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.15 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

111 111 118 121 131 134 136 137 139 142 142 145 146 147 153 159 161

Blast Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 High-Quality Ore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Pulverized Coal Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Top-Pressure Recovery Turbines . . . . . . . . . . . . . . . . . . . . . 4.5 Increased Blast Furnace Top Pressure . . . . . . . . . . . . . . . . . . 4.6 Improved Hot Stove Process Control . . . . . . . . . . . . . . . . . . 4.7 Blast Furnace Process Control . . . . . . . . . . . . . . . . . . . . . . . 4.8 Heat Recuperation from Hot Blast Stoves . . . . . . . . . . . . . . . 4.9 Increased Hot Blast Temperature . . . . . . . . . . . . . . . . . . . . . 4.10 Injection of Coke Oven Gas . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Improved Recovery of Blast Furnace Gas . . . . . . . . . . . . . . . 4.12 Injection of Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 Natural Gas (NG) Injection . . . . . . . . . . . . . . . . . . . . . . . . . 4.14 Plastic Waste Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.15 Oxy-Oil Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.16 Injection of Residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.17 Biomass Combustion in the BF . . . . . . . . . . . . . . . . . . . . . . 4.18 Charging Carbon Composite Agglomerates (CCA) . . . . . . . . 4.19 COURSE50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.20 Top Gas Recycling Blast Furnace (TGRBF) . . . . . . . . . . . . . 4.21 Slag Heat Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.22 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

167 167 179 181 188 191 191 194 200 201 202 206 208 209 216 221 221 223 232 240 243 254 262 264

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Contents

5

6

7

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Basic Oxygen Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Use of Metallized Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 BOF Heat and Gas Recovery . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Energy Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 BOF Bottom Stirring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Improved Process Monitoring and Control . . . . . . . . . . . . . . . 5.7 Improved Ladle Preheating . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 In-Furnace Post-Combustion . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

275 275 280 281 287 291 293 295 296 297 298

Electric Arc Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Raw Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Oxyfuel Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Flue Gas Monitoring and Control . . . . . . . . . . . . . . . . . . . . . . 6.5 Post-Combustion Optimization in Steelmaking . . . . . . . . . . . . 6.6 Foamy Slag Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Scrap Preheating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 Shaft Furnace Scrap Preheating . . . . . . . . . . . . . . . . . . . . . . . 6.9 Tunnel Furnace Preheating . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10 Bottom Stirring/Stirring Gas Injection . . . . . . . . . . . . . . . . . . . 6.11 Direct Current (DC) Arc Furnace . . . . . . . . . . . . . . . . . . . . . . 6.12 Waste Heat Recovery for EAF . . . . . . . . . . . . . . . . . . . . . . . . 6.13 Contiarc Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.14 Twin-Shell DC Arc Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . 6.15 Post-Combustion of EAF Flue Gas . . . . . . . . . . . . . . . . . . . . . 6.16 Process Optimization and Control . . . . . . . . . . . . . . . . . . . . . 6.17 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

303 303 316 322 326 328 332 337 339 344 346 351 352 360 361 364 365 368 370

Smelting Reduction: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Corex Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 FINEX Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 HIsmelt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Tecnored . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Flash Ironmaking Technology . . . . . . . . . . . . . . . . . . . . . . . 7.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

377 377 381 402 406 408 412 413 413

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8

9

10

Contents

Direct Reduced Iron: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 MIDREX® Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Hyl-ENERGIRON Process . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 FASTMET© and FASTMELT© . . . . . . . . . . . . . . . . . . . . . . 8.5 ITmk3® Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 MXCOAL™: MIDREX© with Coal Gasification . . . . . . . . . . 8.7 SL/RN Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Waste Heat Recovery for Rotary Kiln Direct Reduction . . . . . . 8.9 FINMET Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Iron Carbide Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 CIRCORED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Redsmelt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13 Hydrogen Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

419 419 424 431 440 441 443 448 449 450 450 452 452 452 478 479

Carbon Capture and Storage: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . . . 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Energy Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Shift Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Chemical/Physical Adsorption . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Solid Adsorbents Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Membrane Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Cryogenics Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Carbonization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 CHG Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10 Post-combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.11 Chemical Looping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.12 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

485 485 495 502 503 511 516 518 521 527 534 538 547 549

Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse Emissions Abatement . . . . . . . . . . . . . . . . . . . . . 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Molten Oxide Electrolysis . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Electrowinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

555 555 557 566 574 575

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Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577

Abbreviations

A/O1/O2 A2/O AA AC ACARP AcC ADP AER AFT AISI AOD AOP AP ARA ASCM ASU BAT BET BF BFB BFD BFR BFS BFSG BFTG BHZ BIS BM BOD BOF BOFG

Anoxic/aerobic1/aerobic2 Anaerobic-anoxic-aerobic system Annual average Alternating current Australian Coal Industry’s Research Program Activated carbon Aquatic depletion potential Adsorption-enhanced reforming Adiabatic flame temperature American Iron and Steel Institute Argon oxygen decarburization Advanced oxidation process Acidification potential Auxiliary reducing agents Adsorption-selective carbon membrane Air separation unit Best available techniques Brunauer-Emmett-Teller Blast furnace Bubbling fluidized bed Blast furnace dust Blast furnace route Blast furnace slag Blast furnace shaft gas Blast furnace top gas Bottom heat exchange zone Blast furnace inner reaction simulator Biomass Biochemical oxygen demand Basic oxygen furnace Basic oxygen furnace gas xiii

xiv

BOFS BOP BOS BTP BTX CA CaL CAP CBP CC CCA CCD CCF CCPP CCS CCSC CO2 CCU CO2 CCUS CDA CDLC CDQ CDRI CE CFB CFP CHG CHP CLC CLH CMC CMCP CMSM CN CNT COD COG COS COSS COURSE50 CO2 CP CP/C CRACCK CO2 CRI

Abbreviations

Basic oxygen furnace slag Basic oxygen process Basic oxygen steelmaking Burn-through point Benzene toluene xylene Chronoamperometry/chronoamperogram Calcium looping Long-term CO2 capture scenario Composite burnout potential Continuous casting Carbon composite agglomerates Charge-coupled device Cyclone converter furnace Combined cycle power plant Carbon capture and storage Capture by slag carbonization Carbon capture and utilization Carbon capture use and storage Carbon direct avoidance Coal direct chemical looping Coke dry quenching Cold direct reduced iron Counter electrode Circulating fluidized bed Carbon footprint Compressed hydrogen gas Combined heat and power Chemical looping combustion Chemical looping hydrogen Coal moisture control Coal moisture control process Carbon molecular sieving membrane Cyanide Carbon nanotube Chemical oxygen demand Coke oven gas Carbonyl sulfide Continuous optimized shaft system Ultimate reduction in the steelmaking process by innovative technologies for cool earth 50 Coke plant Chronopotentiometry/chronopotentiogram Recycling and conversion to CO in Korea Index of reactivity to CO2

Abbreviations

CRR CRW CS CSCB CSN CSQ CSR CTM CTMCR CTMWOSC CTMWSC CV CV/V CW CW-EDI CWHS CWOHS CWQ CWW DAC DAPS DAV DC DDQ DEA DFB DHE DI DIPA DIPAM DMR DRI DRIP DSG DTCR DTF DU EAF EAFD EBF EBT EC ECOARC ECS

xv

Coke replacement rate Cold-rolling wastewater Cold steel Coal stamp charging battery Crucible swelling number Coke stabilization quenching Coke strength after reaction COG to methanol COG to methanol with CO2 recycle COG to methanol without supplementary carbon COG to methanol with supplementary carbon Calorific value Cyclic voltammetry/voltammogram Combined water Concentrated water from electrodeionization Coke oven gas with H2 separation Coke oven gas without H2 separation Coke wet quenching Coke wastewater Direct air capture Dry-cleaned and agglomerated pre-compaction system Direct alloying with vanadium Direct current Double dry quenching Diethylamine Dual fluidized bed Dynamic hydrogen electrode Deadman inlet Disopropanolamine Tetrahydrothiopene Dry methane reforming Direct reduced iron Direct reduction iron plant Dry slag granulation Dry-type top-gas cleaning and recovery Drop tube furnace Drying unit Electric arc furnace Electric arc furnace dust Experimental blast furnace Eccentric bottom tapping European Commission Ecologically friendly and economical arc Evaporative cooling system

xvi

ED EF EII EINO EMF EMS EMSy EoL EOR EOS EP EPA EPB EPOSINT EQ EQS EROI ESCS ESP ETC ETS EU EUA EUD EW EWC EWHR FA FAETP FAF FB FC ffs FGR FGR FGRS FIT FOG FSCM FST FT FWC GA GAC

Abbreviations

Electricity demand Anodic electro Energy-intensive industry Emission index of NO Electromotive force Electromagnetic stirring Environmental management system End of life Enhanced oil recovery Emissions optimized sintering Eutrophication potential Environmental protection agency Environment protection bureau Environmentally process optimized sintering Equilibrium Environmental quality standards Energy return on investment Electrostatic space cleaner super Electrostatic precipitator Energy transitions commission Emissions trading system European Union European emission allowances Energy utilization diagram Electrowinning European waste catalogue Exergy of waste heat recovery Fly ash Freshwater aquatic ecotoxicity potential Fuel arc furnace Fluidized bed Fixed carbon Flame front speed Flow gas recirculation Flue gas recirculation Flue gas recirculation sintering Flash ironmaking technology Fluidized bed reactor’s off-gas Fixed site carrier membranes Final sinter temperature Fischer-Tropsch Freshwater consumption Genetic algorithm Granular activated carbon

Abbreviations

GaCTO GBFS GCCSI GHG GOD GR GSC GWP HAP HB HBI HC HCI HCMB HDPE HDRI HECA HF HHF HHV HM HOD HPALA HpCDD HpCDF HR HRC HRT HS HTIR HTP HV HVM HW HxCDD HxCDF ICHB IEA IGAR IGCC inj IOSP IPCC IR

xvii

Coke-Oven Gas-Assisted Coal to Olefins Granulated blast furnace slag Global carbon capture and storage initiative Greenhouse gas Gas-oxidation degree Gas recycling Gas switching combustion Global warming potential Hazardous air pollutants Hot blast Hot briquetted iron Hydrocarbons Hot compacted iron High-carbon metallic briquettes High-density polyethylenes Hot direct reduced iron Hydrogen energy California Hearth furnace Hearth heating furnace Higher heating value Hot metal Heat of decomposition High-pressure ammonia liquor aspiration system Heptachlorodibenzo-P-dioxin Heptachlorodibenzo-P-furan High reactivity Hot rolled coil Hydraulic retention time Hot stoves High-temperature indirect reduction Human toxicity potential High volatile Heating value of mixture Hardwood Hexachlorodibenzo-p-dioxin Hexachlorodibenzo-p-furan Iron coke hot briquette International energy agency Injection de GAz Réformé Integrated gasifier combined cycle Injected Iron ore sintering plant Intergovernmental panel on climate change Indirect reduction

xviii

ISF ISM ISO I-TEF JISF JSM KET KPI LCA LD LDG LEEP LF LGMgO LHV LIBS LNG LPG LPM LPMC LPR LRI LS LSV LTIR LV M M40 MAC MAETP MBBR MBF MDEA MEA MEEP MES MFA MLSS MOE MP MPO MSFB MSR

Abbreviations

Intensified sifting feeder Integrated Steel Mill International Organization for Standardization International toxicity equivalent factors Japan Iron and Steel Federation Japanese Steel Mill Key enabling technology Key performance indicators Life cycle assessment Linz-Donawitz Linz-Donawitz gas Low emission and energy optimized sinter process Lower furnace Low-grade MgO Low heating value Laser-induced breakdown spectroscopy Liquefied natural gas Liquefied petroleum gas Lignin-rich press mud Lignin-rich press mud-derived carbons Liquid-phase reduction Low-reduced iron Liquid steel Linear scan voltammetry/voltammogram Low-temperature indirect reduction Low volatile Moisture Percentage of coke remaining on the +40 mm round hole after 100 revolutions Maximum allowable concentration Marine ecotoxicity potential Moving bed biofilm reactor Magnetic braking feeder Methyldiethanolamine Monoethanolamine Moving electrode electrostatic precipitator Multifunctional energy system Materials flow analysis Mixed liquor Molten oxide electrolysis Medium pressure Methane partial oxidation Magnetically stabilized fluidized bed Methane steam reforming

Abbreviations

MSWI MTL MTO MWCNT NEDO NET NF NG NGO NHE NI NMI O&M OBF OBM OCDD OCDF OCOG ODP OECD OEE OGS OP OPC OR OSD OS-RVFLNs OTI PAH PARAFAC PCB PCC PCDDs PCDFs PCI PCM PCOP PCR PE PeCDD PeCDF PEM PET

xix

Municipal solid waste incineration Metallization Methanol to olefins Multiwalled carbon nanotube New energy and industrial technology development organization Negative emissions technologies Nanofiltration Natural gas Nongovernmental organization Normal hydrogen electrode Normal Inlet Nonmetallic inclusions Operation and maintenance Oxygen blast furnace Oxygen bottom Maxhütte Octachlorodibenzodioxin Octachlorodibenzofuran Original coke oven gas Ozone depletion potential the Organisation for Economic Co-operation and Development Overall equipment effectiveness Operation guidance system Oxygen plant Ordinary portland cement Oxidation ratio One-step decarbonization Online sequential random vector functional-link networks Optical texture index Polycyclic aromatic hydrocarbons Parallel factor analysis Polychlorinated biphenyls Post-combustion capture Polychlorinated dibenzodioxins Polychlorinated dibenzofurans Pulverized coal injection Phase change materials Photochemical oxidation potential Pulverized coal ratio Polyethylene Pentachlorodibenzo-p-dioxin Pentachlorodibenzo-p-furan Proton exchange membrane Polyethylene terephthalate

xx

PG PI PID PIT PLA PM PM10 PM2.5 PMDR POP POR POSCO POX PP PS PSA PSu PtCR PU/TU PVC PwP Q-BOP R&D R&I R/H RAC RAFT RC RCA RCAt RCLA RCOG RD RDI RE RHF RMP RNG RPB RVI RWGS S/F S/S SBR

Abbreviations

Process gas Pipe inlet Proportional integral derivative Polymer injection technology Waste plastics Particulate matter Particulate pollution (10 μm) Particulate pollution (2.5 μm) Point of minimum direct reduction Persistent organic pollutants Partial oxidation reforming Pohang Iron and Steel Company Partial oxidation Polypropylene Polystyrene Pressure swing adsorption Priority substance Post-combustion ratio Pyrolysis/torrefaction unit Polyvinylchloride Power plant Bottom-blowing process Research and development Research and innovation Reforming gas/hematite Regenerated activated carbon Raceway adiabatic flame temperature Regression coefficient Reactive coke agglomerate Rotary cup atomizer Rotary cylinder atomizer Reformed coke oven gas Reduction degree Reduction disintegration Reference electrode Rotary hearth furnace Refractory material plant Reformed natural gas Rotating packed bed Reduction velocity index Reverse water gas reaction Sloping flue Solidification/stabilization Sequential batch reactor

Abbreviations

SCF SCL SCM SCNT SCPS SCR SCS SDQ SECOS SER SES SF SFu SI Sil SL/RN SMR SMS SNG SP SPARG SPH SR SRe SS SSAB SSB SSDO SSW ST STA SW SWV T TBF TCDD TCDF TCE TCLP TCT TEP TFN TG TGN

xxi

Standard cubic feet Syngas chemical looping Supplementary cementitious material Thiocyanate Selective crystallization and phase separation Selective catalytic reduction Single chamber system Single dry quenching Sintering energy control system Secondary energy resource Synthesis energy system Sinter feed Shaft furnace Shaft injection Silicate Stelco-Lurgi/Republic Steel-National Lead Steam methane reforming Steel melting shop Syngas Specific Pollutant Sulfur passivated reforming Scrap preheating Steam reforming Smelting reduction Suspended solids Svenskt stål AB Supersonic burner Solid-state diffusion of oxygen Segregation slit wire Hot stoves Simultaneous thermal analysis Softwood Square wave voltammetry/voltammogram Tapping Traditional blast furnace Tetrachlorodibenzodioxin Tetrachlorodibenzofuran Thermal and chemical energy of hearth gases Toxicity characteristic leaching procedure Theoretical combustion temperature Terrestrial ecotoxicity potential Technological fuel number Top gas Technological greenhouse number

xxii

TGRBF THM THZ TI TLS TmI TOC TP TRL TRM TRS TRT TRZ TSG TSP TSPM TTN TW TWC UBS UCS UF UHP ULCOS UNFCC UNIDO UV VAI VIU VLD VM VOC VODC VPSA VSA VSD WAC WACC WB WCP WE WFD WFGD WGSR

Abbreviations

Top gas recycling blast furnace Ton of hot metal Top heat exchange zone Tuyeres injection Ton of liquid steel Tumble index Total organic carbon Torrefied pellets Technology readiness level Tri-reforming of methane Thermal reactor system Top-pressure recovery turbine Thermal reserve zone Tata Steel Group Total suspended particulates Total suspended particulate matter Technological total number Terrified wood Total water consumption Unione di Banche Svizzere Unconfined compressive strength Upper furnace Ultrahigh power Ultralow CO2 steelmaking United Nations Framework Convention on Climate Change United Nations Industrial Development Organization Ultraviolet Voest-Alpine Industrieanlagenbau Value in use Vacuum ladle degasser Volatile matter Volatile organic compounds Vacuum oxygen decarburization converter Vacuum pressure swing adsorption Vacuum swing adsorption Variable speed drive Waste acceptance criteria Weighted average cost of capital Wind box Water cooled panels Working electrode Water framework directive Wet flue gas desulfurization Water gas shift reaction

Abbreviations

WHRS WISCO WL WP WPI WRZ WTCR YSZ ZR

xxiii

Waste heat recovery system Wuhan Iron and Steel Company Wind leg Wood pellets Waste plastic injection Wüstite reserve zone Wet-type top-gas cleaning and recovery Yttria stabilized zirconia Zero reformer

List of Figures

Fig. 1.1 Fig. 1.2 Fig. 1.3 Fig. 1.4 Fig. 1.5 Fig. 1.6 Fig. 1.7 Fig. 1.8 Fig. 1.9 Fig. 1.10 Fig. 1.11 Fig. 1.12 Fig. 1.13 Fig. 1.14 Fig. 1.15 Fig. 1.16 Fig. 1.17 Fig. 1.18 Fig. 2.1 Fig. 2.2 Fig. 2.3 Fig. 2.4 Fig. 2.5 Fig. 2.6

Global crude steel production (worldsteel.org) . . . . . . . . . . . . . . . . . . . Primary and secondary steelmaking production in the main producer countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . China crude steel production growing rate . . . . . . . . . . . . . . . . . . . . . . . . MFA of iron in the world for year 2000 presented as a standard MFA diagram . . .. . . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . . .. . .. . World total industry final energy consumption of the iron and steel sector in 2013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy employed and wasted in the BF-BOF-CC route . . . . . . . . . Wasted energy in the integrated route (all the numbers refer to GJ/ton steel) . . . . . . . .. . . . . . . . .. . . . . . . .. . . . . . . .. . . . . . . . .. . . . . . . .. . . . . CO2 emissions levels from the Chinese iron and steel industry . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ironmaking and steelmaking processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic of the different processing routes . . . . . . . . . . . . . . . . . . . . . . Major carbon flow in the integrated still mill . . . . . . . . . . . . . . . . . . . . . Emissions type in the integrated steel mill . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions in the integrated steel mill . .. . . . .. . . . .. . . . . .. . . . .. . Temperature anomaly May 2018 (NASA.gov) . . . . . . . . . . . . . . . . . . . CO2 emissions depending on the technological structure . . . . . . . . Direct emissions reduction potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pathways of technologies for GHG emissions abatement . . . . . . . . Energy-saving potential for the BAT applied to the integrated steel mill .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . World coke production in 2015 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coal in Europe 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials flow and emission sources in coke making . . . . . . . . . . . . Water consumption in an integrated steel plant, FWC (a); TWC (b) . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . COD removal efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coke wet quenching . . . . .. . . .. . . . .. . . . .. . . .. . . . .. . . . .. . . .. . . . .. . . . .. .

2 2 3 8 10 11 12 13 14 15 16 17 18 19 20 25 26 32 40 41 42 43 49 51 xxv

xxvi

Fig. 2.7 Fig. 2.8 Fig. 2.9 Fig. 2.10 Fig. 2.11 Fig. 2.12 Fig. 2.13 Fig. 2.14 Fig. 2.15 Fig. 2.16 Fig. 2.17 Fig. 2.18 Fig. 2.19 Fig. 2.20 Fig. 2.21 Fig. 2.22 Fig. 2.23 Fig. 2.24 Fig. 2.25 Fig. 2.26 Fig. 2.27 Fig. 2.28 Fig. 2.29 Fig. 2.30 Fig. 2.31 Fig. 2.32 Fig. 3.1 Fig. 3.2 Fig. 3.3 Fig. 3.4 Fig. 3.5 Fig. 3.6 Fig. 3.7 Fig. 3.8 Fig. 3.9 Fig. 3.10 Fig. 3.11 Fig. 3.12 Fig. 3.13

List of Figures

Coke dry quenching plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon flow analyses . . . .. . .. . .. . .. . . .. . .. . .. . . .. . .. . .. . .. . . .. . .. . .. . Energy recovery and use in the integrated steel plant . . . . . . . . . . . . Energy balance for a coke plant (European IPPC Bureau 2011, values in MJ/t coke) . .. . . . . .. . . . . .. . . . . .. . . . . . .. . . . . .. . . . . .. . . Coke oven gas utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Separation of coke oven gas by employing a PSA System . . . . . . Integrated COG-DRI plant .. . . . . . . .. . . . . . .. . . . . . .. . . . . . . .. . . . . . .. . . . Process flow diagram of syngas processing units of GaCTO . . . . Schematic diagram of GaCTO process . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic of the CWOHS and CWHS processes (units in kmol-C/h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy balance of the CWOHS and CWHS processes (units in MW) . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . Hydrogen Energy California (HECA) Facility Process . . . . . . . . . . Coke temperature monitoring . .. . .. .. . .. . .. . .. .. . .. . .. . .. .. . .. . .. . .. Coal stamp process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compressive strength as a function of the coal density . . . . . . . . . . Coal charge density in different coke making technologies . . . . . Coal moisture control plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-recovery coke plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-recovery and recovery coke ovens . . . . . . . . . . . . . . . . . . . . . . . . . . . Coke properties for non-recovery coke oven products . . . . . . . . . . . Annual emissions for non-recovery coke ovens compared to conventional ovens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CSQ . . . .. . . .. . . .. . .. . . .. . . .. . . .. . . .. . .. . . .. . . .. . . .. . .. . . .. . . .. . . .. . . .. . Schematic diagram of the single-chamber system . . . . . . . . . . . . . . . . SCOPE 21 plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy saving trend in Japan ironmaking . . . . . . . . . . . . . . . . . . . . . . . . . Energy intensity vs. country for ironmaking operations . . . . . . . . . Sintering operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Longitudinal section of the sinter bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reaction zones vs. temperature during the sintering process . . . . Energy-saving solutions in sintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heat recovery in the WHRS system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activated coke method . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . Gas treatment through selective catalytic reduction . . . . . . . . . . . . . . Dust after ESP vs. alkali input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activated carbon adsorption performance . . . . . . . . . . . . . . . . . . . . . . . . . Adsorption of PCDD/Fs on activated carbon . . . . . . . . . . . . . . . . . . . . . PCDD/Fs adsorption efficiency for activated carbon and MWCNTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regenerated activated carbon system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-temperature plasma treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53 56 58 59 61 65 66 67 67 75 76 78 81 83 85 86 88 89 90 91 92 96 97 98 99 99 112 113 114 118 120 122 122 124 126 126 127 128 129

List of Figures

Fig. 3.14 Fig. 3.15 Fig. 3.16 Fig. 3.17 Fig. 3.18 Fig. 3.19 Fig. 3.20 Fig. 3.21 Fig. 3.22 Fig. 3.23 Fig. 3.24 Fig. 3.25

Fig. 3.26

Fig. 3.27 Fig. 3.28 Fig. 3.29 Fig. 4.1 Fig. 4.2 Fig. 4.3 Fig. 4.4 Fig. 4.5 Fig. 4.6 Fig. 4.7 Fig. 4.8 Fig. 4.9 Fig. 4.10 Fig. 4.11 Fig. 4.12 Fig. 4.13 Fig. 4.14 Fig. 4.15 Fig. 4.16 Fig. 4.17

xxvii

Additive injection and bag filter dedusting . . . . . . . . . . . . . . . . . . . . . . . . SIMETAL schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ignition control system . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . Multi-slit burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Emissions optimized sintering plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EPOSIT process configuration plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Improving charging system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pre-reduced agglomerates .. . . . . . . .. . . . . . .. . . . . . . .. . . . . . . .. . . . . . .. . . . Energy optimized sintering process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sectional gas recirculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BFG employment in the sinter process . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concentrations of CO and CO2 during sintering with 0%, 20%, 50%, and 100% replacement of coke breeze energy with charcoal . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . . .. . .. . . .. . . .. . .. . . .. . .. . . .. . . .. . Concentrations of targeted PCDD/F congeners observed during sintering with coke breeze and with 20% and 50% replacement of the coke energy with charcoal . . . . . . . . . . . . . . . . . . . . Effects of biochar replacing coke breeze on yield and quality of sinter .. . . . . . . .. . . . . . . . .. . . . . . . .. . . . . . . .. . . . . . . . .. . . . . . . .. . . . . . . .. . . . Effects of biochar replacing coke on pollutant concentration of flue gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Technological solutions for environment impact mitigation . . . . . Blast furnace plant . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . Low reducing agent rate operation of blast furnace . . . . . . . . . . . . . . Approaches for lowering carbon in blast furnace . . . . . . . . . . . . . . . . . Coke rate range predicted in various processes . . . . . . . . . . . . . . . . . . . Dependence of the gas mixture and the solid-phase equilibrium composition on the temperature . . . . . . . . . . . . . . . . . . . . . . Gas-phase equilibrium of hematite reduction by CO and H2 . . . . Solid-phase equilibrium of hematite reduction by CO (a) and H2 (b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gas-phase equilibrium of reactions relating to hydrogen, carbon, and oxygen . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . .. . . . .. . . . .. . . BF main reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions in the traditional iron and steel production process . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . Fossil fuel and materials flows in the BF-BOF steelmaking system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pulverized coil injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BF tuyeres . .. . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . Heat balance in the BF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIU for BF injectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Top gas recovery system . . . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . . .. . . . . . .. . . Top-pressure control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

129 132 134 135 136 138 140 141 142 143 148

150

151 156 157 159 168 169 171 172 174 175 176 177 177 179 180 182 184 186 187 189 192

xxviii

Fig. 4.18 Fig. 4.19 Fig. 4.20 Fig. 4.21 Fig. 4.22 Fig. 4.23 Fig. 4.24 Fig. 4.25 Fig. 4.26 Fig. 4.27 Fig. 4.28 Fig. 4.29

Fig. 4.30

Fig. 4.31 Fig. 4.32 Fig. 4.33 Fig. 4.34 Fig. 4.35 Fig. 4.36 Fig. 4.37 Fig. 4.38 Fig. 4.39 Fig. 4.40 Fig. 4.41 Fig. 4.42 Fig. 4.43 Fig. 4.44 Fig. 4.45 Fig. 4.46 Fig. 4.47

List of Figures

Hot blast stove control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BF control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Process monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of process monitoring and control . . . .. . . . .. . . . . .. . . . . .. . Measurements at tuyeres level . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . . .. . . Torpedo infrared monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BF stack status monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stove hot gas recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hot blast use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coke oven gas injection in the BF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IGAR schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of the coke rate, CO2 intensity, and coke replacement rate (CRR) relative to the baseline case, for 180 kg/t-HM direct reduced iron in the furnace feed, 180 kg/t-HM cold CH4 injected through the tuyere, 180 kg/t-HM CH4 (preheated to 1200 K) partially combusted with O2 (1200 K) to yield hot CO + 2H2 and then injected in the furnace shaft, and 180 kg/t-HM CH4 (preheated to 1200 K) injected through the tuyeres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of the gas flow rate into the furnace and the heat transfer required to preheat the blast air and injectants for these cases, together with the net calorific value of the blast furnace top gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plastic waste injection plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flame temperature as a function of the injection rate . . . . . . . . . . . . Reduction potential of different plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . Residue injection scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of PCI and biomass injection . . . . . . . . . . . . . . . . . . . . . . . . Reducing agent rates in different injection cases . . . . . . . . . . . . . . . . . Thermochemical conversion products from woody biomass . . . . Emissions reduction potential through the employment of charcoal in primary ironmaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life cycle CO2 emissions of various biomass .. . . . . . . . .. . . . . . . .. . . Schematic of biomass pretreatment setup in the simulated steel plant .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . Combustion behavior of char, pulverized coal, and coke by rapid heating . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . Change of biomass composition and effect of CO2 reduction by carbonization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Model of the CCB reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results for the CCB model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gas generation rate from iron carbon ore composite . . . . . . . . . . . . . Gas generation rate from different iron carbon ore composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic of reduction of iron ore by biomass carbon . . . . . . . . . . .

192 195 195 196 197 198 199 200 202 203 208

210

212 216 217 218 222 224 225 226 227 228 229 231 232 234 235 236 237 238

List of Figures

Fig. 4.48 Fig. 4.49 Fig. 4.50 Fig. 4.51 Fig. 4.52 Fig. 4.53 Fig. 4.54 Fig. 4.55 Fig. 4.56 Fig. 4.57 Fig. 4.58 Fig. 4.59 Fig. 4.60 Fig. 4.61 Fig. 4.62 Fig. 5.1 Fig. 5.2 Fig. 5.3 Fig. 5.4 Fig. 5.5 Fig. 5.6

Fig. 5.7 Fig. 5.8 Fig. 5.9 Fig. 5.10 Fig. 5.11 Fig. 5.12 Fig. 5.13 Fig. 6.1 Fig. 6.2 Fig. 6.3 Fig. 6.4 Fig. 6.5 Fig. 6.6

xxix

Reacted fraction of a volatile carbon and b nonvolatile carbon at different temperatures during reduction . . . . . .. . . . . . . . . . . . . .. . . . . COURSE50 technologies scheme . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . Iron reduction with H2 use . .. . . . . .. . . . . .. . . . . . .. . . . . .. . . . . .. . . . . .. . . Schematic gas flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions in BF with different solutions . . . . .. . . . .. . . .. . . . .. . Scheme of the TGR-OBF plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BF configuration . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . Hydrogen reduction to the entire indirect reduction of iron-bearing burdens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon consumption for direct reduction in TBF . . . . . .. . . . . . . .. . . Pilot plant for the top gas recycling OBF . . . . . . . . . . . . . . . . . . . . . . . . . Carbon consumption for direct reduction in OBF . . . . . . . . . . . . . . . . Carbon consumption vs. degree of direct reduction in OBF . . . . . Conventional BF vs. advanced oxygen BF .. . . .. . . .. . . . .. . . .. . . .. . Slag heat recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slag granulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

239 241 242 242 244 245 246 246 249 250 250 252 253 256 260

BOF process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BOF reactions . .. . . . .. . . . .. . . .. . . . .. . . . .. . . .. . . . .. . . . .. . . .. . . . .. . . . .. . Melt composition variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slag composition variation .. .. . .. .. . .. .. . .. .. . .. .. . .. .. . .. .. . .. .. . .. Materials flow and emission sources during the BOF process . . . Sensible heat in iron and steelworks, (1) cooler exhaust gas; (2) main exhaust gas; (3) main exhaust gas after heat recovery; (4) coke oven flue gas after heat recovery; (5) COG sensible heat; (6) COG ammonia water; (7) BF slag sensible heat; (8) hot stove gas; (9) slag granulation tank water; (10) BOF slag sensible heat; (11) BOF gas sensible heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BOF gas recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RecoDust schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy saving potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inert gas injection . . .. . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . Censoring for process parameters monitoring . . . . . . . . . . . . . . .. . . . . . Ladle preheating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High-volume ladles preheating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

276 277 278 278 280

Electric arc furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Percentage of electric steel production in the different regions (2017) . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . .. . . .. . Energy sources for ironmaking and steelmaking in the different regions . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . . Scrap charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Major technology developments in the EAF . . . . . . . . . . . . . . . . . . . . . . EAF electricity consumption as a function of the charged DRI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

304

281 283 289 290 292 294 295 296

305 306 308 310 318

xxx

Fig. 6.7 Fig. 6.8 Fig. 6.9 Fig. 6.10 Fig. 6.11 Fig. 6.12 Fig. 6.13 Fig. 6.14 Fig. 6.15 Fig. 6.16

Fig. 6.17 Fig. 6.18 Fig. 6.19 Fig. 6.20 Fig. 6.21 Fig. 6.22 Fig. 6.23 Fig. 6.24 Fig. 6.25 Fig. 6.26 Fig. 7.1 Fig. 7.2 Fig. 7.3 Fig. 7.4 Fig. 7.5 Fig. 7.6 Fig. 7.7 Fig. 7.8 Fig. 7.9 Fig. 7.10 Fig. 7.11 Fig. 7.12

Fig. 7.13 Fig. 7.14 Fig. 7.15 Fig. 7.16

List of Figures

Energy consumption for the DRI addition in the EAF . . . . . . . . . . . Energy consumption for the DRI by varying the temperature . . . EAF outputs as a function of DRI charge . . . . . . . . . . . . . . . . . . . . . . . . . Burners for the EAF . .. . . . . . . . . .. . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . .. . . . . EAF electrodes at high temperature . . . . . .. . . . . . . . . . .. . . . . . . . . .. . . . . Energy saving as a function of the adopted solution . . . . . . . . . . . . . Consteel furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preheating schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scrap heating through waste gas (direct from Tenova) . . . .. . . . .. . Direct and indirect GHG sources for two cases. Top, convention EAF using Canadian electricity generation source distribution; bottom, scrap preheating EAF . . . . . . . . . . . . . . . Bottom stirring effect in EAF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bottom gas stirring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electromagnetic stirring (direct from Tenova) . . . . . . . . . . . . . . . . . . . . EAF performances with EMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single electrode furnace .. . .. . . .. . .. . .. . .. . .. . . .. . .. . .. . .. . . .. . .. . .. . EAF energy balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Waste heat recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Waste heat recovery strategies in a Consteel furnace . . . . . . . . . . . . Contiarc furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iEAF system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

318 320 321 323 325 327 330 337 338

Smelting schematic and smelting reactor . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of smelting reduction processes . . . . . . . . . . . . . . . . . . . . Fluidized bed schematic . . .. .. . .. .. . .. . .. .. . .. .. . .. .. . .. .. . .. . .. .. . .. RHF-Smelter schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corex process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Melter-gasifier schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bauer-Glaessner diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calculations of Bauer-Glaessner and Bogdandye-Engel diagrams . .. . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . Melter-gasifier reaction zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermodynamic model of the melter-gasifier in Corex . . . . . . . . . . Thermodynamic model of the reduction shaft in Corex . . . . . . . . . . Reducing gas requirement in reduction shaft and gas generation in smelter gasifier with different degrees of metallization for different types of coal . . . . . . . . . . . . . . . . . . . . . . . . Upstream and downstream CO2 emission at different carbon rates . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . Metallization degree as a function of gas composition and temperature . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . Desulfurizer preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Large-scale plant . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . . .. .

378 380 381 382 383 384 384

340 346 346 347 348 352 353 354 359 360 368

385 387 389 390

391 392 394 395 396

List of Figures

Fig. 7.17

Fig. 7.18 Fig. 7.19 Fig. 7.20 Fig. 7.21 Fig. 7.22 Fig. 7.23 Fig. 7.24 Fig. 7.25 Fig. 8.1 Fig. 8.2 Fig. 8.3

Fig. 8.4 Fig. 8.5 Fig. 8.6 Fig. 8.7 Fig. 8.8 Fig. 8.9 Fig. 8.10 Fig. 8.11 Fig. 8.12 Fig. 8.13 Fig. 8.14 Fig. 8.15 Fig. 8.16 Fig. 8.17 Fig. 8.18 Fig. 8.19 Fig. 8.20 Fig. 8.21 Fig. 8.22 Fig. 8.23 Fig. 8.24 Fig. 8.25 Fig. 8.26 Fig. 8.27 Fig. 8.28

xxxi

CO2 emission of BF ironmaking system and COREX as function of power generation efficiency and electricity CO2 emission factor . .. . .. . . .. . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . . .. . .. . . .. . . .. . .. . . .. . .. . . FINEX process .. . .. . .. . . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . . .. . .. BF and FINEX integration . . .. . . .. . . . .. . . . .. . . .. . . . .. . . .. . . . .. . . . .. . CO2 saving due to the use of LRI and PSA gas in the BF . . . . . . . HIsmelt plant . . . .. . . . .. . . .. . . .. . . .. . . . .. . . .. . . .. . . .. . . . .. . . .. . . .. . . .. . Coal consumption as a function of production rate . . . . . . . . . . . . . . . Tecnored plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tecnored furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Charification of solid fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main reduction volume capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Different types of DRI (direct from Midrex) . . . . . . . . . . . . . . . . . . . . . . Relationship between iron resources and reductants in various ironmaking processes (the production scale is million ton/year) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of direct reduction processes . . . . . . . . . . . . . . . . . . . . . . . Midrex process .. . .. . .. . . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . . .. . .. Midrex plant with gasification and CO2 removal equipment . . . . Used and wasted energies in the cola-based and the gas-based DRI plants . .. . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . Hyl-ENERGIRON process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRI use in BF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Furnace model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy balance .. . .. . .. . . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . . .. . .. FASTMELT process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ITmk3 process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions for Fastmelt and ITmk3 vs. BF . . . . . . . . . . . . . . . . . . . MXCOAL™ process . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . Reduction rate of oxidized pellets . . . . . .. . . . . . . .. . . . . . . . .. . . . . . . .. . . Global natural gas producers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRI production in 2015 by region (direct from Midrex) . . . . .. . . . SL/RN process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rotary kiln DRI process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FINMET process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iron carbide reduction process .. . . .. . . . .. . . .. . . .. . . . .. . . .. . . . .. . . .. . CIRCORED process . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . Redsmelt process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRI reduction through H2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Midrex process with H2 addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Midrex H2 process . . . . .. . . .. . . .. . . . .. . . .. . . . .. . . .. . . .. . . . .. . . .. . . .. . . Production costs due to H2 transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

401 402 404 406 407 407 409 410 411 420 421

421 424 425 425 427 432 436 437 438 441 442 442 443 444 445 447 448 449 450 451 453 454 459 459 460 466

xxxii

Fig. 8.29

Fig. 8.30 Fig. 8.31 Fig. 8.32 Fig. 8.33 Fig. 9.1 Fig. 9.2 Fig. 9.3 Fig. 9.4 Fig. 9.5 Fig. 9.6 Fig. 9.7

Fig. 9.8 Fig. 9.9 Fig. 9.10 Fig. 9.11 Fig. 9.12 Fig. 9.13 Fig. 9.14 Fig. 9.15 Fig. 9.16 Fig. 9.17 Fig. 9.18 Fig. 9.19 Fig. 9.20 Fig. 9.21 Fig. 9.22 Fig. 9.23 Fig. 10.1 Fig. 10.2

List of Figures

Baur-Glaessner type diagram for mixed gases depending on fraction, C, of carbonaceous gas molecules. R denotes unoxidized gas species (CO + H2), and RO denotes the oxidized gas species (CO2 + H2O) . . .. . . .. . . .. . . .. . . .. . . .. . . .. . Water-gas shift reaction (WGSR) equilibrium diagram in general and definition of gas variables .. . . . .. . . . . .. . . . . .. . . . . .. . Water electrolysis plant (www.thyssenkrupp-industrialsolutions.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flowsheet for hydrogen-based DRI production . . . . . . . . . . . . . . . . . . . Hydrogen value chains by thyssenkrupp (www.thyssenkruppindustrial-solutions.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global emissions from the seven most CO2-intensive industrial sectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions per ton of crude steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions for selected countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon capture and utilization pathways . . . . . . . . . . . . . . . . . . . . . . . . . . Aqueous ammonia plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 capture and storage system process flow . . . . . . . . . . . . . . . . . . . . Principle of the PSA CO2-scrubbing techniques and various domains of application and performances of the variant techniques, PSA, VPSA, and VSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steelanol schematic . .. . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . .. . . .. . .. . . .. . .. . Block diagrams that outline the modeling blocks and the COG, BFG, OBFG, and PG connections: base case . . . . . . . . . . . . . . . . . . . . . Block diagrams that outline the modeling blocks and the COG, BFG, OBFG, and PG connections: CO2 capture case . . . . . . . . . . . . Phase diagram of pure CO2 . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . .. . . . Costs and CO2 emissions for different capture technologies applied to various processing routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fans capture scheme of the proposed technology . . . . . . . . . . . . . . . . Proposed process chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Industrial scheme of the plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prototype module capable of capturing 100 kt CO2/year . . . . . . . . Prototype module capable of capturing 100 kt CO2/y . . . . . . . . . . . . Oxyfuel combustion scheme . .. . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . .. . Principle of CaL process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simulated CaL process . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . Energy integration of the CaL treating BFG . . . . . . . . . . . . . . . . . . . . . . Simplified scheme of the Ca-Cu looping process . . . . . . . . . . . . . . . . . Cost comparison of different steel production decarbonization technologies depending on price of zero-carbon electricity . . . . . .

469 470 475 476 476 486 488 489 492 506 509

512 513 514 515 519 523 524 524 525 526 534 537 539 541 542 546 548

Scoring criteria (with equally distributed weighting) . . . . . . . . . . . . . 557 Electrical energy required per ton of liquid iron as a function of the electrical conductivity of the molten oxide electrolyte . . . . 558

List of Figures

Fig. 10.3 Fig. 10.4 Fig. 10.5 Fig. 10.6

Fig. 10.7

Fig. 10.8 Fig. 10.9 Fig. 10.10

Fig. 10.11 Fig. 10.12 Fig. 10.13 Fig. 10.14 Fig. 10.15 Fig. 10.16 Fig. 10.17

xxxiii

CO2 mitigation factor for the MOE technology . . .. . . .. . .. . . .. . .. . Iron-oxygen phase diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T-logpO2 diagram for iron and its oxides . . . . . . . . . . . . . . . . . . . . . . . . . E-logpO2 diagram for iron and its oxides for the 1473 and 1873 K isotherms. The solid lines indicate phase boundaries, while the dashed lines indicate iso-activity lines for some solid solutions of oxygen in the oxides . . . . . . . . . . . . . . . . . Valence distribution diagram of iron in liquid oxide at the 1873 K isotherm. The solid lines indicate phase boundaries, while the dashed lines indicate iso-pressure contours of oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrolysis of molten oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Industrial MOE cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fe fraction vs. Fe3O4 density (a), current-time transients for magnetite samples recorded at E ¼ 1.15 V in 10 M NaOH and 90
C (b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Principle of iron electrowinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pourbaix diagram for Fe-H2O at 110
C . . . . . . . . . . . . . . . . . . . . . . . . . . Efficiency of the iron reduction according to the production rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iron electrodeposited through electrowinning . . . . . . . . . . . . . . . . . . . . . Anode materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrowinning route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current density along electrolysis time for hematite, goethite, magnetite, and NaOH-H2O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

559 560 560

561

562 563 564

567 568 569 570 571 571 572 573

List of Tables

Table 1.1 Table 1.2 Table 1.3

Table 1.4 Table 1.5 Table 1.6 Table 1.7 Table 1.8 Table 2.1

Table 2.2 Table 2.3 Table 2.4 Table 2.5 Table 2.6 Table 2.7 Table 2.8 Table 2.9 Table 2.10 Table 2.11 Table 2.12 Table 2.13

World first 20 steelmaking companies (Worldsteel.org) . . . . . . . . . Net export-import per country (2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Volumetric flow rates, lower heating values, and composition of the steelwork off-gases after cleaning of a modern steel plant producing 6 Mt. steel/year . . .. . .. . .. . .. . .. .. . .. . .. . .. . .. . .. . .. .. . .. . Energy consumption for the different ironmaking routes . . . . . . . . Illustrative technology innovation and diffusion policy approaches matched to realistic timescales of outcomes . . . . . . .. . Emissions trend in the BLUE scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRI production in 2016 (Worldsteel.org) . . . . . . . . . . . . . . . . . . . . . . . . . Breakthrough programs . . .. . . .. . .. . . .. . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . Environmental quality standards for the PHS and priority substance identified in the WFD and list of specific pollutants that are relevant to the iron and steelmaking industry . . . . . . . . . . . Effluent discharge limits and typical emissions expressed in mg/L of pollutants for coke making operations . . . . . . . . . . . . . . . Documented values from EPB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average concentration of substances before and after treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Quality indexes of coke produced trough wet or dry quenching . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . Raw COG yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Raw COG composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coke oven gas utilization routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Production ratios of coke vs. coal, COG vs. coke, H2 vs. COG . . . Potential annual H2 production from COG in the US . . . . . . . . . . . Consumption, product output, and energy efficiency of CTO and GaCTO . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . Advantages and disadvantages of the different technologies for COG use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performances of the different CTM processes . . . . . . . . . . . . . . . . . . . .

4 5

18 21 24 25 28 29

44 44 47 47 56 59 59 62 65 65 69 70 77 xxxv

xxxvi

Table 2.14 Table 2.15 Table 3.1 Table 3.2 Table 3.3 Table 3.4 Table 3.5 Table 3.6 Table 4.1 Table 4.2 Table 4.3

List of Tables

CO2 emission reduction in the MES system (COG discharged after combustion) . . .. . .. . . .. . .. . .. . . .. . .. . . .. . .. . .. . . .. . .. . .. . . .. . .. . Coal properties vs. emissions parameters . . . . . . . . . . . . . . . . . . . . . . . . . Limits for toxic emissions in different countries . . . . . . . . . . . . . . . . . Data for various ESP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Emissions levels after RCA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Emissions after wet fine scrubbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of conventional and curtain flame ignition systems .. . . . .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . Solid fuels properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

80 93 116 125 128 130 147 153

Table 4.4 Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9 Table 4.10

Emerging technologies for CO2 abatement in the BF . . .. . . . . .. . . TRT costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . Simulation scheme of top gas recycling optimization operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BF performances for the studied cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . Furnace conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical composition of wood-based biomass . . . . . . . . . . . . . . . . . . COG composition (vol. %) . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . Coke composition (wt. %) . .. . .. . .. .. . .. .. . .. .. . .. .. . .. .. . .. .. . .. .. . BF conditions . . .. . . .. . .. . .. . .. . .. . .. . . .. . .. . .. . .. . .. . .. . . .. . .. . .. . .. . Summary of the proposed chemical methods . . . . . . . . . . . . . . . . . . . . .

Table 5.1 Table 5.2

BOF off-gas composition . . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. .. . .. . 279 Typical gas composition and characteristics . . . . . . . . . . . . . . . . . . . . . . 282

Table 6.1

Comparison of theoretical minimum energy and actual energy requirements for selected processes . . . . . . . . . . . . . . . . . . . . . . . Comparison of theoretical minimum and actual CO2 emissions . . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . Input vs. output as a function of DRI percentage . . . . . . . . . . . . . . . . Twin-shell EAF details (ABB industries) . . . . . . . . . . . . . . . . . . . . . . . . . Energy efficiency technology applied in EAFs . . . . . . . . . . . . . . . . . . . Direct and indirect GHG emission factors in EAF . . . . . . . . . . . . . . .

Table 6.2 Table 6.3 Table 6.4 Table 6.5 Table 6.6 Table 7.1 Table 7.2 Table 7.3 Table 7.4 Table 7.5 Table 7.6 Table 7.7 Table 7.8

Smelting reduction processes comparison . . . . . . . . . . . . . . . . . . . . . . . . Reactions in the different zones of the melter-gasifier . . . . . . . . . . . Top gas composition . . . . .. . . . . .. . . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . . .. . . Generator gas composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metal and slag composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Composition and calorific values of the employed coals . . . . . . . . Lowest carbon rate for optimal metallization and emissions for different types of coals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics of commonly used desulfurizers for dry desulfurization . . . . .. . . . . . . .. . . . . . .. . . . . . . .. . . . . . . .. . . . . . .. . . . . . . .. . . .

170 190 204 213 213 224 245 245 245 259

310 310 319 361 366 367 379 386 390 390 390 391 392 399

List of Tables

Table 7.9 Table 7.10 Table 7.11 Table 7.12 Table 7.13 Table 7.14 Table 7.15 Table 8.1 Table 8.2 Table 8.3 Table 8.4 Table 8.5 Table 8.6 Table 8.7 Table 8.8 Table 8.9 Table 8.10 Table 8.11 Table 8.12 Table 8.13 Table 8.14 Table 8.15 Table 8.16 Table 8.17 Table 8.18 Table 8.19 Table 8.20 Table 8.21

Table 8.22 Table 8.23 Table 9.1 Table 9.2 Table 9.3

xxxvii

Composition and calorific value of coke oven, BF, and COREX gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Material consumption and CO2 emission of BF ironmaking system . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . Material consumption and CO2 emission of COREX . . . . . . . . . . . Balance data for BF and FINEX . . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . CO2 emission rate . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . Fixed process parameters for all the cases . . . . . . . . . . . . . . . . . . . . . . . . Fuel consumption and savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of direct reduction processes . . . . . . . . . . . . . . . . . . . . . . . . Energy use and productivity of Midrex . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions analysis . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . Energy consumption analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRIs considered in the calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operating conditions assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emissions by DRI production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PMDR for different type of DRI .. . . .. . .. . .. . .. . .. . . .. . .. . .. . .. . .. . PMDR for different types of DRI and different PC rates . . . . . . . . Minimum CO2 measured in the present model . . . . . . . . . . . . . . . . . . . CO2 emissions in different processes . . . .. . . .. . . .. . . .. . . .. . . .. . . .. . CO2 emissions in different process configurations . . . . . . . . . . . . . . . Input-output description of the proposed approach compared to traditional routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy balance of the proposed approach compared to traditional routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Techno-economic parameters of the available hydrogen production technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steel industry global energy demand and emissions . . . . . . . . . . . . . Energy and emissions comparison for the proposed solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data to calculate TFN and TGN a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data to calculate TFN and TGN b) . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Data to calculate TFN and TGN c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Values of CO2 emissions and end-to-end TGNs and TFNs for different combinations of metallurgical conversions in the production of steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ranking of the conversions based on the TFN, TGN, and TFN + TGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrolysis module parameters (www.thyssenkrupp-uhdechlorine-engineers.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

400 400 401 405 405 405 406 423 428 429 430 436 438 439 439 440 440 455 455 456 457 464 467 467 472 473 474

475 475 477

CO2 sources in integrated and mini steel mills . . . . . . . . . . . . . . . . . . . 491 Technical energy efficiency and CO2 reduction potentials . . . . . . 501 Commercial CO2 solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503

xxxviii

Table 9.4 Table 9.5 Table 9.6 Table 9.7 Table 9.8 Table 9.9

Table 9.10 Table 9.11

List of Tables

Comparisons of amine-based and ammonia CO2 capture systems .. . . . .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . CCS costs using Selexol . .. . . .. . .. . . .. . .. . . .. . . .. . .. . . .. . . .. . .. . . .. . Direct emissions for a 5 Mt/year integrated steel mill . . . . . . . . . . . Direct emissions for a 5 Mt/year ISM, TGRBF, HIsmelt, and Corex . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . CO2 captured for the studied plants, costs, and energy consumption for the different adopted solutions . . . . . . . . . . . . . . . . . Performances of the described cases; Case 1, includes compression to 11 MPa for pipeline transport; Case 1, taken as the compressor duties from where feed enters battery limits up to and including compression of CO2 product to 0.15 MPa; Case 2, adiabatic efficiency of 75% used; Case 2, energy recovered in expander taken into account . . . . Mature CO2 capture technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mature COG usage technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

507 509 510 511 511

518 522 528

Chapter 1

Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement

1.1

Introduction and Global Scenario

Steel is the base material for the global industry. In 2018, over 1.7 billion tons of steel was produced; it is expected that its demand and production will grow in the next future (Fig. 1.1). The production increase of steel is destined to continue in the future, and the only open doubt is the exact years when production level will pass the two billion ton threshold and then the three billion one (Bellevrat and Menanteau 2009). Iron and steel production has passed through many transformations and evolutions in processing during their long historical presence and their properties, as well as the technologies used for making them have transformed congruently by several orders of magnitude (Freytag 2007). If steel is an invariant of the technological growth of society, it is because of its plasticity to adapt to changing times and changing needs. This is what is called today in European Commission (EC) speech a key enabling technology (KET) – advanced materials are the relevant KET, which introduces the idea that new materials are being invented continuously but also that existing ones are being refined, reformulated, and changed just as continuously. A former expression used by the EC was that of cumulative technologies, thus emphasizing that materials like steel demonstrate a pawl and ratchet effect, where features accumulate and do not vanish, as they would in a marketing product of limited life (Birat 2016). The energy-intensive industry (EII) is responsible for two thirds of industrial carbon dioxide emissions in the EU and sometimes more in other regions. It has been recognized by both public and private stakeholders that a far-reaching transformation of these industries is required to comply with the overall emissions reduction goals stated by the European Union for 2050. Unfortunately, there is little consensus on how deep decarbonization of the EII will be achieved (Gerres et al. 2019). From Fig. 1.2 it is clear how the highest production quantities belongs to primary metallurgy processes with a growing percentage of secondary steelmaking processes in North America and India. © Springer Nature Switzerland AG 2019 P. Cavaliere, Clean Ironmaking and Steelmaking Processes, https://doi.org/10.1007/978-3-030-21209-4_1

1

2

1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.1 Global crude steel production (worldsteel.org)

Fig. 1.2 Primary and secondary steelmaking production in the main producer countries

It should be underlined that the production in the most growing countries (China and India) increased four times in the last 10 years (Khanna et al. 2019). As a matter of fact, the China steel production is growing so fast (Duan et al. 2018) that a

1.1 Introduction and Global Scenario

3

Fig. 1.3 China crude steel production growing rate

prevision for the future 15–20 years (Zhou et al. 2017) becomes very difficult to be defined (Fig. 1.3). The first 20 steelmaking companies with the relative produced tonnage are listed in Table 1.1 (the nation is relative to the company main quarter). At the present time, the European steel sector turnover is estimated around €150 billion. The sector employs 410,000 people, representing 1.25% of the total employment in EU manufacturing. Currently, 36 integrated steel plants are active (with 85 blast furnaces and 102 basic oxygen furnaces) and 222 electrical arc furnaces operating in the EU-27 (Steel Institute VDEh 2009). A large proportion of the capital stock involved in primary steelmaking in the EU was commissioned during the postwar expansion of the steel industry. More than 80% of the blast furnaces (corresponding to approximately 80% of the production capacity) were commissioned and built before 1980. Steel is heavily traded with about 40% of production traded globally. Although such trade mainly takes place within regions, there is also some trade between different regions (Zhong et al. 2018). The EU passed form to be an exporter to become a net importer in the very recent years. Today the EU is the world’s third biggest exporter and primary importer. China is the biggest supplier followed by Russia and Ukraine. The EU imports more than 90% of its needs of primary raw materials, iron ore, and coking coal. The exports and imports per country are listed in Table 1.2. While steel moves further into becoming a material embedded in artifacts, which are used for short or long lives and then eventually get discarded, the by-products are either used in other sectors in an industrial ecology synergy or landfilled. All may be

4

1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Table 1.1 World first 20 steelmaking companies (Worldsteel.org) Company ArcelorMittal China Baowu Group HBIS Group Nippon Steel and Sumitomo Metal Corporation (NSSMC) POSCO Baosteel Group Shagang Group Ansteel Group JFE Steel Corporation Shougang Group Tata Steel Group Wuhan Steel Group Shandong Steel Group Nucor Corporation Hyundai Steel Company Maanshan Steel Thyssenkrupp Novolipetsk Steel (NLMK) Jianlong Group Gerdau S.A.

Nation Luxemburg China China Japan South Korea China China China Japan China India China China USA South Korea China Germany Russia China Brazil

Production (Mt.) Over 95 Over 65 Over 50 Over 50 Over 40 Over 35 Over 30 Over 30 Over 30 Over 25 Over 25 Over 25 Over 20 Over 20 Over 20 Over 18 Over 17 Over 16 Over 15 Over 15

dissipated to the environment to a small extent. Steel itself can be reused or recycled, and, indeed, steel is the most recycled material (Birat 2015). In the changing global market scenario for raw materials for the steel industry, a number of novel iron and steelmaking process technologies are being developed to provide the steel companies with economically sustainable alternatives for iron- and steelmaking (Ghanbari 2019). In addition, the steel industry is also focusing on reduction of energy consumption as well as greenhouse gas (GHG) emissions to address the crucial subject of climate change (Pardo and Moya 2013). Climate change is presenting new risks to the high-energy and carbon-intensive iron and steel industry. The industry needs to focus on reduction of energy consumption as GHG emissions to address climate change (Bataille et al. 2018). Development of alternate iron and steelmaking process technologies can provide steel companies with economically sustainable alternatives for steel production (Gordon et al. 2015). A very recent study from Voestalpine analyzes the scenario of potential decarbonization in Europe through the energy issues (Voestalpine 2018). The study underlines how the EU steel industry committed to substantial reduction of CO2 emissions. Being the limits of existing production techniques (mainly coalbased) reached, the development and implementation of new breakthrough technologies together with supportive energy infrastructure and services are required. The EU steel companies have intensely explored a number of possible emissions reduction approaches leading to the global conclusion that coordinated and

1.1 Introduction and Global Scenario Table 1.2 Net export-import per country (2017)

Country China Japan Russia Ukraine Brazil South Korea Taiwan Belgium Austria Slovakia Country USA Vietnam Thailand Indonesia EU(28) Egypt Mexico Saudi Arabia Algeria Pakistan

5 Net export (Mt.) 94.5 34.5 26.9 17.1 11.5 7.3 4.4 3.7 3 2.1 Net import (Mt.) 21.7 17 16.1 11 10.5 8.3 8.1 6.2 5.4 4.3

comprehensive energy and funding strategy on EU level is the key. In addition, there is no short-term solution. The general indications are related to CDA (carbon direct avoidance) and CCU (carbon capture and usage), directly avoiding CO2 emissions through an increased use of renewable electrical power in basic steelmaking (e.g., hydrogen replacing carbon in metallurgical processes) and chemical conversion of CO2 captured from industrial processes and using the CO2 as a raw material, respectively. Voestalpine indicates that breakthrough technologies for decarbonization (e.g., on hydrogen basis) will not be available before ~2035. In addition, transformation has to be technically and economically feasible. This is because the fully renewable transformation nearly results in a doubling of the production costs basing on the current situation. The ETC is confident that a complete decarbonization of the steelmaking industry is achievable by mid-century, with a modest impact on end-consumer prices and cost to the overall economy, although an uneven transition on a global scale may create competitiveness issues (ETC 2018). The last report suggests that given that the two main routes for primary steel production decarbonization will almost certainly be CCS and hydrogen-based reduction, public and private R&D spending, as well as investment in pilot plants, should focus on driving down the cost and increasing the efficiency of electrolysis equipment, piloting and driving down the cost of hydrogen-based reduction, ensuring the feasibility and driving down the cost of innovative BF-BOF designs which

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

would reduce CCS costs, and helping to increase the feasibility and reduce the cost of CCS – in those locations where storage capacity is available and where higher electricity prices are likely to make the hydrogen route a more expensive option. The report also gives useful indications on the actual and future R&D priorities, driving down the cost of energy efficiency and carbon efficiency technologies that can drive down carbon emissions from existing plants, developing iron electrolysis as a potentially lower-cost solution in the very long term, and developing innovations that enable higher-quality and higher-value recycling of steel, also indicating the governmental priorities to this end, supporting specific pilot projects designed to achieve early decarbonization of a country’s steel industry, supporting early-stage R&D in technologies which are currently further away from commercial readiness – such as electrochemical approaches to iron ore reduction – and supporting the development of shared CO2 transportation networks which may be required to make CCS a feasible solution in those locations where it is likely to be significantly cost advantaged.

1.2

Main Approaches to the Problem

A popular and contemporary concept describing how materials life and resources can be optimized in the future is named “circular economy.” “Circular economy” is obviously based on the materials recycling and on energy saving. Materials are recovered from the collection of end-of-life (EoL) investment or consumer goods. The key word is therefore recycling of EoL goods, materials, metals, minerals, residues, and by-products and also dangerous emissions, like CO or CO2 (carbon capture use and storage, CCUS). Resource efficiency is an instrumental mitigation option in the steel industry, but existing studies have failed to provide a global analysis of the sector’s energy and material use. Despite the interactions between energy and materials in steelmaking, recent studies investigate each of these resources in isolation, providing only partial insight into resource efficiency. Gonzalez Hernandez et al. (2018) analyze the latest, most comprehensive resource data on the global steel industry and quantify the savings associated with reducing this through energy- and material-saving measures. The sector’s resource efficiency – accounting for energy and materials – is expressed in exergy and measured at two levels, that of production routes and plants. The results show that the sector is 32.9% resource-efficient and that secondary steelmaking is twice as efficient (65.7%) as ore-based production (29.1%). Energy-saving options, such as the recovery of off-gases, can save about 4 EJ/year (exergy). Material saving options, such as yield improvements, can deliver just under 1 EJ/year extra (Chowdhury et al. 2018). A global shift from average ore-based production to best available operation can save up to 6.4 EJ/year, a 26% reduction in global exergy input to steelmaking (An et al. 2018). Shifting to secondary steelmaking can save 8 EJ/year, limited only by the need to still produce half of steel from ore in 2050.

1.2 Main Approaches to the Problem

7

Recycling procedures bring materials savings consequently reducing the need for virgin resources (primary raw materials). When materials are recycled to the same material, additional environmental benefits and credits can contemporarily be collected, like energy savings, greenhouse gas emissions reduction, and a smaller environmental footprint in general. The optimal route will consequently be the one capable of favoring all this aspects at the same time in order to reach the highest efficiency. This is the basis of the holistic ironmaking optimization (Bettinger et al. 2017). While process optimization systems have been widely introduced in many facilities of ironmaking plants, in a lot of cases, there is no overall automation system, supporting coordination and through-process optimization of all ironmaking facilities in place. This approach allows for automated production control systems to achieve standardized operation throughout all ironmaking facilities by coordinating the individual aggregates, such as raw material management, coke oven plants, sintering, pelletizing, direct reduction, pulverized coal injection plant, and blast furnace operation. Holistic ironmaking optimization enhances the performance of ironmaking plants by the consistent, methodical, and comprehensive consideration of the global optimum rather than aiming at local optima for each plant. The resulting traceable production decisions and the increase in transparency allow for thorough process optimization, which leads to reduced conversion costs and more consistent quality, higher efficiency, and increased production. As an example, ore-based ironmaking generates a variety of residues, including slags and fines such as dust and sludges. Recycling of these residues within the integrated steel plant or in other applications is essential from a raw material efficiency perspective. The main recycling route of off-gas dust is to the blast furnace (BF) via sinter, cold-bonded briquettes, and tuyere injection. However, solely relying on the BF for recycling implicates that certain residues cannot be recycled in order to avoid buildup of unwanted elements, such as zinc. By introducing a holistic view on recycling where recycling via other process routes, such as the desulfurization (deS) station and the basic oxygen furnace (BOF), landfilling can be avoided (Andersson et al. 2018). The holistic approach considered a compromise between energy efficiency and raw material efficiency for the process system including the BF, BOF, and deS station. Furthermore, the approach accounted for tramp elements, mainly zinc, while maintaining the production of high-quality steel. The study suggested that the offgas dust could be recycled, minimizing the amount of non-recycled residues. The circular economy should be described material by material, in order to analyze in detail what is already being done and what can still be improved: the various materials achieve very different levels of recycling, and thus policies for going beyond present achievements will differ according to each material. The circular economy has an important time dimension, as many materials are stocked in the economy for long times, sometimes half a century or more. The life span of the material stocks means that high recycling rates today will be translated into highrecycled contents only in the future, sometimes in the long time. The circular economy is a long-time endeavor! A first step towards capturing the broader impacts – environmental, social, or otherwise – in complex systems is to trace the impacts of consumption up the supply chain. Well-established methods such as life cycle

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

analysis (LCA) and MFA (materials flow analysis) address precisely this issue, their core aim being to estimate environmental impacts throughout supply chains – extraction, manufacture, transport, etc. – and reallocate these to final materials or products (Millward-Hopkins et al. 2018). LCA is an important tool in implementing the environmental management system (EMSy). LCA is a technique for assessing the environmental aspects and potential impacts associated with the product or technology. LCA is an environmental assessment tool for evaluation of impacts that a technology or product has on the environment over the entire period of its life – from the extraction of the raw material through the manufacturing, packaging, and marketing processes and the use, reuse, and maintenance of the product to its eventual recycling or disposal as waste at the end of its useful life. It is important to integrate environmental assessment and results of LCA with other economic methods into product design at an early stage to improve the environmental and economic performance of the product or technology and to eco-efficiency analysis. Environmental life cycle assessment study in iron and steel industry is widely developing in the world. This method can be used for selecting new optimal technologies or products. LCA is an important method used for environmental impact assessment of current, alternative, and future technologies in ironmaking (Burchart-Korol 2011). LCA and MFA incorporate the cycle time of recycling but need to be expanded into dynamic LCA and MFA in order to become fully time-dependent. The complexity of MFA of iron can be viewed in Fig. 1.4 (Allwood et al. 2012).

Fig. 1.4 MFA of iron in the world for year 2000 presented as a standard MFA diagram (Allwood et al. 2012)

1.2 Main Approaches to the Problem

9

Policies founded on LCA at a microeconomic scale and MFA at a macroeconomic scale are the most apt to mirror how the socioeconomic system works and thus to avoid negative rebound effects. Fostering the use of these tools is an important element in encouraging the circular economy. But it is also important to understand that the rationale for moving in this direction is environmental and political, not necessarily economical (Hellweg et al. 2014). Thus it will not be enough to foster technological R&D (research and development) and to achieve R&I (research and innovation): tools to internalize these externalities in the market economy will need to be introduced more widely. The complexity of this scheme is obvious but is compounded by the fact that steel is not simply iron but contains other elements, either originating from the initial raw materials or added as alloying and similar elements. These have a different fate in the recycling loop from irons: some are also recycled, often co-recycled with iron, while others are simply lost. Steel is thus not simply identical to element iron, even if carbon steel is one of the simplest alloys in metallurgy (Dente et al. 2019). Steel is a complex mixture of elements, a complex alloy, and a complex set of phases, NMI, depending on temperature and kinetics histories. Steel is mainly a binary alloy of iron and carbon, but many more elements are part of its composition. Some remain as a memory of the raw materials and reactants used in the iron and steelmaking processes, while some more have been added voluntarily, since it was understood in the Neolithic that properties could be changed greatly by adding some small amounts of alloying elements. Another conceptual dimension is related to how useful or perturbing the minor components are: the minor elements/components that bring positive value or usefulness to steel have been given specially positive names, like alloying elements, additions, precipitates, or, more recently, nano-features. Those that bring negative value are given negative names, like tramp elements, inclusions and non-metallic inclusions, impurities, third phases, slag particles, etc. Raw materials for steel production – iron ore and coal mostly – are neither rare nor scarce, except for a very few alloying and reactant elements, for the fundamental reason that iron is the most abundant element in the Earth and a fairly common one as well in the Earth crust. This does not mean, however, that they will be used indiscriminately in the future, because steel is presently already recycled to a high level (83% and 36 years of average life), and, when peak steel production is reached, probably towards the end of this century, a full circular economy will take over, except, possibly at the margin for a small number of niche applications (Babich and Senk 2019). Among several greenhouse gases with different impact on the air quality, CO2 is the main contributor accounting for about 60% of the greenhouse effect because of its huge and broad emission levels. Among all the industrial sectors, ironmaking and steelmaking one is calculated and measured to be the largest emitter of carbon dioxide (over 160 Mt. CO2/year in 2017) and one of the users with largest energy demand (over 25 EJ/year in 2017). It accounts for an estimated 5.2% of total global greenhouse gas emissions and 21% of total EU industrial emissions. Taking into account the emissions of the only ironmaking and steelmaking sector, about 80–90% of the emissions are related to the blast furnace-converter process. The World Steel

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.5 World total industry final energy consumption of the iron and steel sector in 2013 (IEA 2016)

Association estimates an average energy intensity of 18.68 GJ/tCS for the integrated steel route with an average CO2 intensity of 1.77 tCO2/tCS (Janjua 2017). The ongoing increase in world steel demand means that this industry’s energy use and CO2 emissions will continue to grow, so there is significant industrial and governmental incentive to develop, commercialize, and adopt emerging energy efficiency and CO2 emissions reduction technologies for steel production (Otto et al. 2017). New developments will obviously include different processes and materials as well as technologies that can economically capture and store the industry’s CO2 emissions. Deployment of these new technologies in the market will be critical to the industry’s climate change mitigation strategies for the mid and long term. As a matter of fact, it should be noted that the technology adoption in regions around the world is driven by economic viability, raw materials availability, energy type used and energy cost, as well as regulatory regime (Perkins 2017). Anyway, steel is not particularly energy-intensive as compared to other materials; indeed materials are in essence all energy intensive, which is the price to pay for the functions they provide to society. Moreover, the energy involved is mainly exergy, not simply heat dissipated as is the case for combustion processes (Birat et al. 2013). In 2013, the world total industry final energy consumption was 113,131 PJ, of which the consumption of the iron and steel sector accounted for 18%. Figure 1.5 shows the shares of different fuels used in the world iron and steel industry. As shown in the figure, coal is the major resource for power generation, accounting for over 60% of the final energy use; 21% of the final energy use is from electricity, 11% is from natural gas, and approximately 8% is from other energy sources (such as oil, biofuels, waste, and heat). Now, as shown in Fig. 1.6, 52% of the energy input is employed, and 48% represents wasted energy.

1.2 Main Approaches to the Problem

11

Fig. 1.6 Energy employed and wasted in the BF-BOF-CC route

This shows the broad potential for energy recovery and reuse in an integrated steel plant. The situation is clarified also for all the sections of the integrated steel plant (Fig. 1.7). A big effort has been conducted by all the producing companies in order to improve energy efficiency to sustain reduction in specific energy consumption; among these they have to be generally mentioned: utilization of by-product gases for steam and power generation, phasing out old and energy-inefficient units, enhancing by-product gas recovery and optimization of operating practices, regular energy audit and implementation of its recommendations, coal injection at blast furnaces, waste heat recovery from waste gas of blast furnace stoves, installation of top recovery turbine, the use of regenerative burners at hot strip mill for maximizing fuel efficiency, coke dry quenching, application of V/F drives, upgraded centralized energy management center, large size BFs with higher energy efficiency, use of pellets and shift to alternate fuel for utilizing lean by-product gases, promoting use of renewable energy in operations, and coal injection (Chittrey 2016). Thanks to the continuous development and implementation of incremental technologies, the steel industry has largely improved its energy efficiency and deeply reduced its specific energy consumption by about 60% over the past 50–60 years. Actually, the unit energy consumption for iron and steel production differs greatly depending on the country because of energy supply and cost issues. In those countries where energy prices are high, relevant levels of energy saving by various advanced technologies

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.7 Wasted energy in the integrated route (all the numbers refer to GJ/ton steel)

have been already developed and applied (Kan et al. 2016). The close linkage between energy consumption and CO2 emission has resulted in a similar reduction in specific CO2 emission, where currently about 2.2 tCO2 is produced per ton of crude steel manufactured through efficient integrated blast furnace and BOF plants. The very fast production growth in the global steel industry encounters new and increased problems related to raw material quality and availability, industry structure, and pricing and environmental issues impacting the preferred ironmaking route in different regions of the world (Cavaliere 2016). Better targets could be achieved if radical changes in the steel production processes are introduced (thus reaching 15–25% of energy efficiency increase). However the business model for introducing these changes is still elusive, which means that the cost of introducing more energy savings is far higher than the value of the energy saved (Birat 2010). The energy transition, which is taking place now and especially in Europe with different flavors in each country, is also a challenge for the steel sector (Rootzén and Johnsson 2013; Madureira 2012).

1.3 Technological Issues

1.3

13

Technological Issues

The integrated steelworks is a complex system in which huge quantities of coal and other fossil materials are consumed as reducing agents and energy resources in the upstream process, that is, the ironmaking process centering on the blast furnace, and the gases generated by the ironmaking process are supplied to downstream processes as energy. These systems have been highly optimized to produce steel products from the viewpoint of energy utilization. However, in order to address the issues of global warming and energy security, the steel industry must now deeply review its utilization of carbon and energy (Shatoka 2016a). Since the steel industry depends on coal as the main reductant in the production of steel products, efforts to decrease carbon consumption are being pursued from the mid- and long-term viewpoints on global warming (Sato et al. 2015). Obviously, CO2 emissions are related to the growing of steel needing; this aspect becomes particularly crucial in those countries where population and economic growing is relevant (Fig. 1.8). Based on current climate change forecast, it is predicted that the steel industry will face greater challenges which cannot be solved with the past incremental technologies in the future. Thus, a more comprehensive social system to support clean steel production will be required. Climate change is a global issue which requires a global response and responsibility. There still exist many subjects to be considered. The optimal solutions cannot be seen, and the discussions to find a better pathway to attain the long-term goal have just started (Ariyama et al. 2019). Industries and scientists are all aimed to reduce emissions and energy consumptions by 30% (400 Mt. and 5 EJ/year, respectively) in the next 30 years. Ironmaking and

Fig. 1.8 CO2 emissions levels from the Chinese iron and steel industry

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.9 Ironmaking and steelmaking processes

steelmaking involves various processes and technologies that can be operated and organized in different combinations depending on the charging materials properties and the final required products. Different raw materials, energy requirements, and investments can vary as a function of the different plant configurations and the chosen advanced technologies employed for the emissions reductions (He and Wang 2017). The main processing routes can be summarized as (schematically described in Fig. 1.9): – Blast furnace (BF)/basic oxygen furnace (BOF) route. Here pig iron is obtained by employing primarily iron ore and hydrocarbons (mainly carbon coke) by iron oxide reduction at high temperatures in the blast furnace. In the blast furnace, coke, ores, and limestone are continuously charged from the top of the furnace; the hot blast is injected through the tuyeres in order to allow the reducing reactions to take place as the charging materials move down. The molten metal and the slag are concentrated at the bottom of the furnace, while the flue gases are eliminated from the top. The material is then converted into steel in the basic oxygen furnace. Due to sintering operations and coke making, this route is highly energy expensive and subjected to the problem of high-impact greenhouse emissions (dioxins, furans, CO2, SOx, and NOx). – Scrap/electric arc furnace (EAF) route. Here, selected steel scraps are used as input for the EAF processing to obtain a product of the required composition. The energy requirements are lower if compared to the blast furnace (BF)/basic oxygen furnace (BOF) route thanks to the absence of coke making and sintering operations.

1.3 Technological Issues

15

Fig. 1.10 Schematic of the different processing routes

– Smelting reduction route. Smelting basically employs reducing agents at high temperatures to decompose the iron ores. Gases and slags are eliminated, and the molten metal is lived at the end of the smelter. The reducing agent is mainly the charcoal so eliminating the necessity to use coke. The carbon reduces the oxygen from the ore, and then it is oxidized to CO and CO2. Other impurities are separated from the iron through the injection of reducing substances that, once reacted, are collected in the slag. – Direct reduced iron (DRI)/EAF route. Iron ores are reduced through the employment of natural gas. The energy intensity of these processes is similar or slightly lower with respect to the blast furnace (BF)/basic oxygen furnace (BOF) route. The employed raw materials and the different processes belonging to the various routes are schematically described in Fig. 1.10. In the integrated steel plant, carbon enters mainly as coal and in a minor percentage as limestone, and then it is emitted (under the form of different compounds) by various routes described schematically in Fig. 1.11. Given the different sectors of an integrated steel plant indicating the raw materials, the different types of the produced dangerous compounds are shown in Fig. 1.12. The sinter plants are responsible for the 50% of dust emissions in the integrated steel plant. Other relevant emissions are heavy metals, SO2, HCl, HF, PAHs, and

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.11 Major carbon flow in the integrated still mill

persistent organic compounds such as PCB and PCDD/PCDFs (Cavaliere et al. 2011; Cavaliere and Perrone 2013). Many of the emissions to be taken into account from the coke oven operations are the coal storing, handling, crushing, and blending. VOC emissions to air come from the oven batteries along with toluene, benzene, ammonia, and xylene. CO2 and SO2 are the more impacting greenhouse emissions of these plants. The many environmental problems related to the BF operations are related to dust, wastewater, SO2, and H2S as well as CO2 (Kuramochi 2016). A recent estimation of the main off-gases generated in a 6 Mt. steel/year is shown in Table 1.3. These off-gases have a reasonable LHV, implying that the current main utilization of these off-gases is the thermal use. But, these off-gases contain also valuable compounds that may be used as reducing agents, such as CH4, H2, and CO in order to synthetize a high-added value product. For this reason, the thermochemical processing of these gases is an option to use them. Many products may be synthesized from the steelwork off-gases. To do this, several processes have been proposed. In particular, H2 recovery schemes may be mentioned. The water-gas shift reaction applied to the CO-rich streams (BFG and BOFG) and methane reforming applied to the COG may increase the amount of available H2. In this case, the recovery of H2 contained in the COG using gas permeation or a PSA system is needed as well as CO from the BFG and the BOFG using a chemical absorption process or a PSA system (Nestler et al. 2018). By focusing on CO2 emissions, the quantification for a typical steel mill is shown in Fig. 1.13. The emissions of EAFs to air are inorganic compounds and persistent organic compounds. Regarding GHG emissions, the ambition of the UNFCC is to cut emissions by 80% by 2050 in order to avoid a surface temperature increase of more than 2  C. This cannot be achieved in the steel sector by implementing energy efficiency solutions, which fall short of the target by a factor 6. New breakthrough processes are needed (Holappa 2017). Engaging in these major changes for making steel with greatly

1.3 Technological Issues

17

Fig. 1.12 Emissions type in the integrated steel mill

reduced CO2 emissions is similar to engaging in the energy transition. The change will only happen when R&D is finished and confirmed and when a “business model” is developed in connection with the world governance of climate change policies –

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Table 1.3 Volumetric flow rates, lower heating values, and composition of the steelwork off-gases after cleaning of a modern steel plant producing 6 Mt. steel/year (Uribe Soto et al. 2017) Volumetric flow rate (Nm3/h) Lower heating value (kJ/Nm3) Thermal power (MW) Compound CO2 CO H2 CH4 CxHy N2 H2O Ar + O2

COG BFG 40,000 730,000 15,660 3365 174 682 Basic molar fraction (%) 1.2 21.6 4.1 23.5 60.7 3.7 22 0 2 0 5.8 46.6 4 4 0.2 0.6

BOFG 35,000 7163 70

Mix 805,000 4141 926

20 54 3.2 0 0 18.1 4 0.7

20.5 23.9 6.5 0.1 0.1 43.3 4 0.6

Fig. 1.13 CO2 emissions in the integrated steel mill

as any climate-related transformation is today still an externality in the market economy. A very recent report from the European Commission affirms that the current changes in our planet’s climate are redrawing the world and magnifying the risks for instability in all forms. The last two decades included 18 of the warmest years on record (Fig. 1.14).

1.3 Technological Issues

19

Fig. 1.14 Temperature anomaly May 2018 (NASA.gov)

The trend is clear. Immediate and decisive climate action is essential (European Commission 2018). The Intergovernmental Panel on Climate Change (IPCC) issued in October 2018 its Special Report on the impacts of global warming of 1.5  C above pre-industrial levels and related global greenhouse gas emission pathways (Bataille et al. 2018). Based on scientific evidence, this demonstrates that human-induced global warming has already reached 1  C above pre-industrial levels and is increasing at approximately 0.2  C per decade. Without stepping up international climate action, global average temperature increase could reach 2  C soon after 2060 and continue rising afterwards. Irreversible loss of the Greenland ice sheet could be triggered at around 1.5–2  C of global warming. This would eventually lead to up to 7 m of sea level rise affecting directly coastal areas around the world including low-lying lands and islands in Europe. The Paris Agreement, ratified by 181 parties, requires strong and swift global action to reduce greenhouse gas emissions, with the objective to hold global temperature increase to well below 2  C and to pursue efforts to limit it to 1.5  C. It also has the goal to achieve a balance between emissions by sources and removals by sinks of greenhouse gases on a global scale in the second half of this century. All parties are to present long-term low greenhouse gas emission development strategies by 2020 that deliver on its objectives. CCS plays a major role in decarbonizing the industry sector in the context of 1.5  C and 2  C pathways, especially in industries with higher process emissions, such as cement, iron, and steel industries. In 1.5  C-overshoot pathways, CCS in industry reaches 3 GtCO2/year by 2050, albeit with strong variations across pathways. Given the projected long-lead times and need for technological innovation, early scale-up

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

of industry-sector CCS is essential to achieving the stringent temperature target (Rogelj et al. 2018). The estimated sinter energy intensity is in the range 0.70 MMBtu/ton (0.82 GJ/ ton)–1.32 MMBtu/ton sinter (1.54 GJ/ton). US coke making energy values, estimated to be 3.83 MMBtu/ton coke (4.45 GJ/ton), are specific to coke making facilities at integrated steel plants (US Department of Energy 2015). Blast furnace ironmaking energy intensity is estimated at 11.72 MMBtu/ton of hot metal (13.63 GJ/ton). Steelmaking in the basic oxygen furnace (BOF) with subsequent refining operations (ladle metallurgy, vacuum treatment, slag management, etc.) can have a fairly wide range of energy use. Energy intensity for BOF steelmaking is estimated at 0.58 MMBtu/ton of liquid steel (0.67 GJ/ton). Final energy intensity for EAF steelmaking is estimated at 1.86 MMBtu/ton liquid steel (2.16 GJ/ton). A range of technologies and measures exist for lowering CO2 emissions including minimizing energy consumption and improving energy efficiency, changing to a fuel and/or reducing agent with a lower CO2 emission factor (such as wood charcoal), and capturing the CO2 and storing it underground. Significant CO2 reductions can be achieved by combining a number of the available technologies. If carbon capture and storage is fitted, then steel plants could become near-zero emitters of CO2 (Jahanshahi et al. 2016). In terms of CO2 emissions levels, the provisional scenario is given in Fig. 1.15. With the present technological routes, the CO2 emissions are destined to increase of 50% by 2050. The 2  C scenario will be possible only if the emissions will be reduced by 50% (Delasalle 2019). The book will describe the main available technologies employed in the traditional or innovative routes capable of reducing the energy consumption and the

Fig. 1.15 CO2 emissions depending on the technological structure

1.3 Technological Issues Table 1.4 Energy consumption for the different ironmaking routes

21 Process BF Smelting DRI BOF EAF

Energy consumption (GJ/ton) 12.7–18.6 13–18 10.9–16.9 0.7–1 4–6.5

dangerous greenhouse emissions. Obviously the energy topic will be described taking into account the direct and indirect energy consumption per each analyzed technology. The methods to improve the energy efficiency are the energy consumption optimization, the online monitoring, and the energy audits. To give a preliminary idea, Table 1.4 describes the energy consumption ranges for the indicated main routes. As a summary, at the end of each chapter, we’ll indicate the potential of the main greenhouse emissions abatement per each described technology. The data will be related to the energy consumption/saving and, once available, an estimation of the costs related to the introduction of the innovation. As a matter of fact, many of the industrial choices are related to a scenario finalized to reduce the global CO2 emissions in order to avoid global warming. The key emissions abatement options in the steel industry include: – Improved energy efficiency; the steel industry has managed to improve considerably the energy efficiency of the production process over the last decades. However, a multitude of measures, both in primary and secondary steelmaking, could be implemented that would reduce significantly energy use and associated CO2 emissions (Mohsenzadeh et al. 2019). – Fuel shift; the blast furnace is the single most energy-consuming process in the production of steel. Coke, which is derived from coal, often functions as both a fuel and reducing agent. Replacing coke with natural gas or biofuel could potentially reduce CO2 emissions from the blast furnace process (Ng et al. 2018). – Carbon capture and storage; opportunities for CO2 capture in the steel production vary depending on the process and the feedstock used. The largest flow of CO2 in a conventional integrated steel mill is generated in the blast furnace. Recovery of CO2 from blast furnace gas is a feasible capture option for the steel industry (Mandova et al. 2019). Applying current end pipe technologies to existing blast furnaces, ~30% of the overall CO2 emissions from a conventional integrated steel plant could be captured. Capture could be applied to other gas flows in the production process, although the costs are likely to be higher, since the volumes and concentrations CO2 are lower. One of the most promising opportunities for CO2 capture in the steel industry is to replace or retrofit conventional blast furnaces with top gas recycling blast furnaces (TGR-BF). In a TGR-BF, the CO2 is separated from the BF gas, and the remaining CO-rich gas stream is recirculated back into the furnace (Liu et al. 2018). Simultaneously replacing the preheated air with pure oxygen would ensure that the blast furnace gas stream was

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free of N2, thereby simplifying CO2 capture. It has been estimated that 70% of the CO2 emitted from an integrated steel plant could be recovered if TGR-BF with CO2 capture was introduced (Rootzén et al. 2011). – Structural change; secondary steelmaking in electrical arc furnaces is expected to continue to gain market share at the expense of primary steelmaking in integrated steel plants, thereby lowering the carbon intensity of steel production. – New steelmaking processes; the steel companies and associations identified a number of process technologies that could reduce CO2 emissions by at least 50% compared to the current best routes (often in combination with CCS).

1.4

Main Solutions

Meeting the targets will require rapid and comprehensive implementation of mitigation technologies and measures that are commercially available today and emerging technologies that are still in the early phases of development. Preliminary results and evaluations through simulations indicate that some 60–75% of the emissions could be avoided annually if the full potential of emerging CCS technologies was to be realized. Furthermore, several regions were identified as being particularly suitable to facilitate integrated networks for the transportation and storage of the captured CO2. The most promising prospects for early deployment of CCS are found in the regions bordering the North Sea. Other evaluations illustrate how the access to infrastructures, such as district heating networks, natural gas grids, chemical industries, and possible CCS storage sites, which could facilitate CO2 abatement in the petroleum refining industry, is optimal. Furthermore, it is shown that the potential for currently available mitigation measures in the refining industry is relatively limited and that the potential for CO2 capture varies widely depending on which sub-process is targeted. Near-term targets for emissions reductions can probably be met through measures that are already available, such as increased energy efficiency, optimization of production processes, and shifts in the usage of fuel and feedstock mixes. To realize the goals of future, stricter, emission targets, more radical alterations to production processes are required. In the iron and steel manufacturing sector, in which breakthrough technologies are still in their infancy, to enable significant reductions in emissions up to year 2050, the ongoing efforts to develop new steelmaking processes must be accelerated considerably (Quader et al. 2016a). As emphasized above, the technological transition required to reduce radically the CO2 emissions in less than four decades involves both the phasing out of current carbonintensive technologies and the phasing in of new zero- or low-carbon technologies (Ökvist et al. 2017). A CO2 price set at a level significantly higher than it is today is a prerequisite for incentivizing near-term mitigation measures, as well as for stimulating investments aimed at further developing emerging technologies and processes. However, developing and phasing in new zero- or low-carbon technologies, at scale, will require complementary policy interventions, including R&D funding, support for niche

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markets, and adaptation of infrastructure policies (Wilson and Grubler 2011). While policy support plays an important role in the development and deployment of many low-carbon technologies, it is especially crucial for CCS. This is because, in contrast to, e.g., renewable energy or applications of energy efficiency, CCS generates no income nor other market incentives, so long as the cost of emitting CO2 remains low. Shifting away from conventional processes and products will require a number of developments including education of producers and consumers, new standards, aggressive research and development to address the issues and barriers confronting emerging technologies, government support and funding for development and deployment of emerging technologies, rules to address the intellectual property issues related to dissemination of new technologies, and financial incentives (e.g., through carbon trading mechanisms) to make emerging low-carbon technologies, which might have a higher initial costs, competitive with the conventional processes and products. The authors suggest how different policy mechanisms may generate outcomes over different timescales (Table 1.5). In future scenarios, a lack of credibility in international climate policy imposes significant costs on climate stabilization as investment decisions in energy plant and infrastructure become increasingly myopic. Alongside stability and credibility, innovation policy needs to be aligned. Policies to support innovations through early research and development can be undermined by an absence of support for their demonstration to potential investors and their subsequent deployment in potential markets (e.g., promoting energy-efficient building designs without strengthened building codes or CCS development without a price on carbon). Alignment means an integrated approach, stimulating both the development and the adoption of energy technologies. R&D initiatives without simultaneously incentivizing users to adopt the outcomes of innovation efforts risk not only being ineffective but also precluding the market feedbacks and learning that are critical for continued improvements in the technologies. Incentives can also be perverse. Support for low-carbon innovations is undermined by diffusion subsidies for carbon-intensive technologies. Policies promoting the demand for mobility mean efficiency improvements are swamped by rising activity levels. Static innovation incentives can undermine continual improvement. By comparison, dynamic technology standards can spur a continuous innovation “recharge.” Aligned policies are also systemic policies. The innovation system comprises not just technologies and infrastructures but also actors, networks, and institutions. Technology policies supporting market deployment can support a build-out of numbers of units or an upscaling of unit capacity or both. Policies to support growth in numbers of units might diversify market niches, promote modularity, or advance flexibility and adaptability to different contexts. Policies to support upscaling might co-fund demonstration projects and field trials, streamline the licensing process for retrofits (or support leasing business models for process technologies), or provide testing infrastructure. Timing, however, is important. The importance historically of a formative phase of building out large numbers of units over an often extended period strikes a cautionary note for policies acting too early in a technology’s commercial life cycle to support upscaling. More broadly, managing expectations among the many innovation system actors is important.

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Table 1.5 Illustrative technology innovation and diffusion policy approaches matched to realistic timescales of outcomes Timescale of policy outcome Short-term (e.g., to 2020) Capital stock additions (some)

Medium-term (e.g., to 2050) Capital stock additions (all), capital stock turnover (some)

Long-term (e.g., to 2100) Capital stock additions (all), capital stock turnover (all)

Throughout (present–2100)

Examples of policy approaches Create, stimulate, and protect market niches around performance advantages of new technologies Deploy market-ready clean technologies through credible and stable incentive mechanisms Develop long-term technology innovation and market deployment strategies in a consultative process, creating “joint expectations” Reduce/eliminate direct or indirect subsidies for technologies not aligned to long-term technology strategy and portfolios Use “sunset” clauses for planned retirement of depreciated inefficient or polluting capital vintages Expand public and private R&D investments stably in diversified portfolios designed to manage risks and corresponding with end-use needs Underwrite many, granular, and multifarious technology demonstration and learning cycles Support disclosure, interaction, and feedback between innovation system actors Engage in multiple international collaborative projects to further knowledge dissemination and technology spillovers Align innovation and market deployment incentives (e.g., recycling externality pricing revenues back to R&D and market deployment incentives) Set long-term targets with appropriate monitoring and enforcement mechanisms to sustain shared technology expectations Maintain portfolio diversity to prevent premature lock-in or standardization Set technology standards for the gradual phase out of “bridging” technologies Create and nurture formal and informal institutional settings for technology assessment, evaluation, portfolio design, and knowledge sharing

Ill-timed policies or stop-start policies, if short-term objectives are not being met, can undermine long-term innovation investments. The IEA developed a BLUE scenario examining the implications of a policy objective to reduce CO2 by 2050; these subjects are specified in Table 1.6. This scenario provide also the potential of direct emissions reduction, indicating that more than 50% of reduction will be ensured by the development of CCS technologies (Fig. 1.16). It is globally believed that the short- to medium-term approach is mainly focused on the energy efficiency and on the energy-saving/recovering technologies as well as the quick development of technologies such as CDQ and TRT. The long-term approaches are mainly devoted to deeply include the use of renewables and CCS

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Table 1.6 Emissions trend in the BLUE scenario Today scenario Energy-related CO2 emissions roughly double Primary energy consumption rises by 84%; carbon intensity energy use rises by 7% Liquid fuels consumption rises by 57%; primary coal demand rises by 138%; gas consumption rises by 85%

CO2 emissions from power generation double; CO2 intensity of power generation declines to 459 g/kWh Fossil fuels supply more than two thirds of power generation; renewable sources supply increases by 22% CCS is not commercial

CO2 emissions increase by almost half as industrial production increases

Fig. 1.16 Direct emissions reduction potential

BLUE map scenario Energy-related CO2 emissions reduced by 50% Primary energy consumption rises by 32%; carbon intensity energy use falls by 64% Liquid fuels consumption falls by 4% with biofuels meeting 20% of the total consumption; primary coal demand drops by 36%; gas consumption falls by 12% with renewable sources providing 40% of the total energy requirement CO2 emissions from power generation are cut by 76%; CO2 intensity of power generation falls to 67 g/kWh Renewables account for 48% of power generation; nuclear provides 24%; plants equipped with CCS provide 17% CCS is capable of capturing 9.4 Gt of CO2 from power generation (55%), industry (21%), and fuel transformation (24%) CO2 emissions falls by a quarter due to energy efficiency, fuel switching, recycling, energy recovery, and CCS

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1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Fig. 1.17 Pathways of technologies for GHG emissions abatement

technologies and their combination with pure oxygen top gas recycled blast furnace (Xu and Cang 2010). The exiting steel technologies are based on fossil fuels, i.e., mostly on carbon, natural gas, mix of carbon and hydrogen, and electric arc furnaces. For CO2-lean process routes, three major ways of solutions have been identified: decarbonizing whereby coal would be replaced by hydrogen or electricity in hydrogen reduction or electrolysis of iron ore processes, CCS technology introduction, and the use of sustainable biomass (Fig. 1.17). This triangle matrix explains how reducing agents and fuels can be selected from three possibilities such as carbon, hydrogen, and electrons. The mock ternary diagram represents all existing energy sources where coal is near to carbon on the carbon-hydrogen line, natural gas is near to hydrogen, hydrogen from electrolysis of water is on the hydrogen-electricity line, etc. Minimizing energy consumption and improving energy efficiency offer the greatest scope for cutting CO2 emissions in the short term, as well as lowering costs. The principal measures for improving energy efficiency include enhancing continuous processes to reduce heat loss, increasing the recovery of waste energy and process gases, and efficient design. Recycling wastes generated within and outside the steelworks can help reduce overall CO2 emissions per ton of steel produced (Gonzalez Hernandez et al. 2018). Thus increasing the recycling rate of

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steel scrap will lower CO2 emissions. There is still room to increase scrap recycling rates as only around 40% of the steel produced globally is recycled steel. Over the years the iron and steel industry has made significant efforts to reduce energy consumption and lower CO2 emissions by improving energy efficiency, reducing coke and coal consumption, utilization of by-product fuels, increasing the use of biomass and renewable energy, and other techniques (Suopajärvi et al. 2018). But the scope for further reduction by these means is limited in state-of-the-art facilities. Further significant reductions will depend on the development of carbon capture and storage (CCS) technologies. One of the largest sources of CO2 emissions is from the use of carbon-based agents to reduce the iron ore to iron. The production of steel is a complex process incorporating a variety of process technologies with different plant layouts. These processes interact with one another, and a change in one process can affect other upstream or downstream processes. A systematic study of the steelworks as a whole should first be carried out to assess the energy balance and CO2 emissions before any abatement measures are introduced. This includes an energy audit to identify points of energy loss and how to minimize them. Not all of the BATs are necessarily suitable for all installations or can be retrofitted, and the cost-effectiveness of the technologies will vary from plant to plant (Shatoka 2016b). Blast furnace is the most energy-consuming process in integrated steel plants. So it is essential to reduce fossil CO2 emissions from this process. Top gas recycling blast furnace is a blast furnace gas separation technology for clean steel production. Top gas used to absorb CO2 inside blast furnace acts as a reducing agent. It effectively reduces carbon emission around 50%. The integrated use of TGR-BF and CO2 capture and storage (CCS) technologies is helpful to remove nitrogen from the TGR-BF, and oxygen injection into BF can also effectively recover CO2 (Kumar Sahu et al. 2016). After extraction of CO2 from recycled gas by using VPSA CCS technology, the cryogenic technique is applied to store. Smelting technologies are employed for coal preheating and partial pyrolysis in a reactor, melting cyclone for ore melting, and melter vessel for final ore reduction and iron production. By removing sintering and coking processes, it reduces CO2 emission. Moreover, by using biomass or natural gas instead of coal, processing combustion gases, storing CO2, and recycling heat energy, the technology reduces almost 70% CO2 emission (Kitamura et al. 2019). To produce direct-reduced iron (DRI) for sending to electric arc furnace, the reducing agent such as natural gas or biomass gas is used in a reactive level for the iron ore sintering process. In gas purification process, traditional reducing agent is replaced by natural gas. Top gas recycling and preheating processes reduce natural gas consumption (Perato et al. 2018). Obviously, the DRI production is related to the fuel supply and price as shown in Table 1.7. The principle of the direct electrolysis of iron ore has been applied to produce iron and oxygen with zero-carbon emission (Wiencke et al. 2018). By hydrogen-based steelmaking route, CO2 emissions would be reduced by more than 80%. Hydrogen steelmaking will depend profoundly on the availability of green hydrogen. It can be generated from natural gas by steam reforming or from water by electrolysis. Today hydrogen-based steelmaking is a potential low carbon

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Table 1.7 DRI production in 2016 (Worldsteel.org)

Region Middle East Asia NAFTA Russia Africa Central and South America Europe (28)

DRI production (Mt.) 28.9 15.3 7.7 5.7 4 1.8 0.7

and economically attractive route in a few countries where natural gas is cheap (Xing et al. 2019). Carbon capture and storage presents one of the most promising options for largescale CO2 emissions reduction for the future. Iron and steel plants are suitable for CCS because emissions are generated from single fixed and easily accessible points. In order to capture CO2 from emissions, carbon dioxide must be separated from flue gases and then compressed and/or cooled and transported by pipeline network for underground storage. TGR-BF experiments show that chemisorption technologies such as amine scrubbing, physisorption, the VPSA or PSA, and cryogenics have different fields of optimality. The level of CO2 concentration of the gas stream to be treated in the TGR-BF for physisorption systems is the best in terms of technical performance and economical operation (Quader et al. 2016b). An increasing number of countries around the world are taking economic measures to reduce their CO2 emissions through emission trading schemes (e.g., the EU and South Korea), carbon taxes, or energy efficiency initiatives. Steelmakers are involved in many programs to transfer technologies and best practices, thereby improving or replacing existing processes or reducing process steps. Steel producers are researching and investing in low-carbon technologies that would radically reduce their environmental impact (worldsteel.org). The targets set out by governments and international bodies require breakthrough technologies via innovation and exploration of new production processes (Table 1.8). The programs identify steelmaking technologies most likely to succeed in reducing CO2 emissions. Feasibility studies are carried out on various scales – from lab work to small pilot plant and eventually commercial-sized implementation or testing the improvement at an existing plant. There are no restrictions placed on the scope of the projects, and the output is intended to be aspirational and develop breakthrough technologies that can reduce the GHG emission to atmosphere by at least 50%, potentially revolutionizing the way steel is made. Each regional initiative explores the solutions that seem best suited to local constraints, energy generation sources, and raw materials. Four possible directions are under examination: – Carbon will continue being used as a reducing agent, but the CO2 produced will need to be captured and stored. The approach is similar to the power industry’s effort to cut emissions from fossil fuel-based power plants, but the steel production solutions include maximum use of scrap, best practice operations, and CO2

Involving Baosteel (China)

Taiwan CCS Alliance coordination (Taiwan)

Japan Iron and Steel Federation (JISF), Japanese Ministry of Economy, Trade and Industry

POSCO, RIST, POSLAB, POSTECH

Program Baosteel program

China Steel Corporation (CSC)

COURSE50

POSCO CO2 breakthrough framework

Table 1.8 Breakthrough programs

Objective is to find new solutions for CO2 emissions reduction in the steel industry, and climate change adaptation using steelmaking by-products. The framework consists of six projects: (1) Prereduction and heat recovery of hot sinter, (2) CO2 absorption using ammonia solution, (3) bio-slag utilization for the restoration of marine environments, (4) hydrogen production using coke oven gas and wastes, (5) iron ore reduction using hydrogen-enriched syngas, and (6) carbonlean FINEX process

Purpose Objective is to reduce emissions from flares The Alliance is focusing their research activities on two main technologies: the oxy-fuel burner technology which aims at purifying CO2 by burning without nitrogen content and the chemical absorption pilot plant which seeks to further decrease energy consumption per unit of CO2 captured. Additionally, academic cooperation projects in CSC include BOF slag carbonation and microalgae carbon fixation Objective is to develop innovative technologies to help solve global environmental problems. Includes R&D projects and public relations activities and promotes industry/institute cooperation

(continued)

(1) Scenario-making for global warming mitigation; (2) CO2 separation, capture, and storage; (3) CO2 fixation by plants and its effective use; (4) hydrogen reduction has been tested with interesting results; limits have also been identified (1) CO2 absorption using ammonia solution; (2) carbon-lean FINEX process

Best results (1) Photovoltaic cells, (2) ethanol production from BOF gas (LanzaTech) (1) CO2 purification; (2) energy use reduction; (3) BOF slag carbonation and microalgae carbon fixation

1.4 Main Solutions 29

Involving ArcelorMittal, Tata Steel, Thyssenkrupp, and voestalpine

All major EU steel companies, energy and engineering partners, research institutes and universities. Also supported by the European Commission

Public-private partnership between AISI and the US Department of Energy (DOE), Office of Industrial Technology

BlueScope Steel and OneSteel, CSIRO coordination (Australia)

Program HIsarna ironmaking process

ULCOS ultra-low carbon dioxide steelmaking (EU)

AISI Technology Roadmap Program

Australian program

Table 1.8 (continued) Purpose E-designed smelting reduction process. The HIsarna ironmaking process has reached a sizeable pilot stage Cooperative R&D initiative to research radical reductions in carbon dioxide (CO2) emissions from steel production. Includes process science, engineering, economics, and foresight studies in climate change (more details on this project are available in the Carbon section below) Joint DOE/AISI collaborative program designed to (1) increase energy efficiency, (2) increase competitiveness of the North American steel industry, (3) and improve the environment. Different to other program because the steel program is required to pay back the federal cost sharing CSIRO working with BlueScope and OneSteel on two projects aimed at cutting CO2 emissions: biomass, which uses renewable carbon derived from biomass in steel manufacturing, and heat recovery from molten slags through dry granulation, which captures the waste heat released from slag cooling, thus reducing CO2 emissions. These programs received large support from the Australian government (1) CO2 emissions decrease through the use of biomass and by-products

(1) Suspension hydrogen reduction of iron oxide concentrate; (2) molten oxide electrolysis

Top gas recycling blast furnace with CO2 capture and storage (CCS); (2) HIsarna with CCS; (3) advanced direct reduction with CCS; (4) electrolysis

Best results Potential reduction of approximately 20% of CO2 per ton of steel produced

30 1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

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capture for storage. This is in contrast to oxy-fuel combustion and pre- or postcombustion capture. In this context, the ironmaking solutions include the blast furnace with integrated CCS as in the HIsarna program, which is a redesigned smelting reduction process enabling a potential reduction of approximately 20% of CO2 per ton of steel produced (Chen et al. 2018). – Hydrogen is used as a reducing agent replacing carbon, as the reaction produces only water vapor. Hydrogen, either pure or as a synthesis gas (syngas) through reforming methane or natural gas, can be used in conventional direct-reduction reactors or in more futuristic flash reactors. The hydrogen will need to be produced using carbon-free energy hydro, nuclear, or renewable for the new processes such as water electrolysis or natural gas reforming – which require high-pressure steam or carbon-free electricity – otherwise, it would defeat the purpose as the energy requirement is higher than using it directly in the steelmaking process. The energy used in a hydrogen reduction process is significantly higher than with carbon due to its cooling effect and may require 4–5 times the energy needed currently. This energy also needs to be generated from carbon-free sources to avoid shifting the emissions elsewhere. – Biomass can be used to generate the reducing agent (carbon), either from charcoal, for example, or syngas. Biomass in such a scheme would need to be grown effectively near the place of use and in sufficient quantities to make it economically viable and sustainable (Mandova et al. 2018). Interest in biomass is strong in Brazil, Australia, Canada, and Europe. Biomass can be added as charcoal in blast furnaces, to the coke oven charge, burned as fuel in steelmaking reactors or used in direct reduction as syngas etc. A balance needs to be considered in the amount of land area used to grow the biomass and the volume of steel required in the region. – CCS – carbon capture and storage technology (CCS) is a necessary process to achieve the large shift in emissions to the atmosphere; it requires storing the CO2 or using it for other purposes. Storage can be in deep saline aquifers, depleted oil, or gas fields, compensated for existing gas field extraction or enhanced oil/gas recovery and used in coal mines as geological storage, or turned back into carbonates (mineralogical storage). Process gas from steel production differs from that of other industries by its CO2 and dust content, the composition of minor gases, temperature, and pressure. Specific projects have been completed over the past decades in the EU, Japan, China, and the USA. Many uses for the CO2 have also been developed such as gaseous cement used as reef replacement or building water barriers. Emirates Steel in the United Arab Emirates is involved in a project, whose aim is to capture and use the CO2 for enhanced oil recovery (EOR) and store 800,000 tons of CO2 from its steel plant annually. The project was completed in 2016. The breakthrough programs have identified over 40 technologies of which seven show promise. The most promising projects in terms of CO2 reduction are now going through various stages with few technologies progressing from laboratory stage to pilot plant, and their potential, constraints, and technical limits are being evaluated.

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Fig. 1.18 Energy-saving potential for the BAT applied to the integrated steel mill

Obviously the energy issue is fundamental; the potential energy saving for the main techniques applicable to the integrated route have been evaluated and summarized in Fig. 1.18. The most likely to succeed are still carbon-based ironmaking technologies coupled with CCS. Biomass solutions may be an intermediate future. Hydrogenbased steelmaking is upcoming, but the energy sources are an issue if they are not carbon-free. Funding of the projects has been difficult in the short-term as economic realities have hit most regions over the past 10 years; from the seven projects, only four are being actively continued, research being postponed, or test facilities being deferred over years rather than months. New avenues of research are being considered such as integration of steelmaking with renewable energy storage technologies and next-generation nuclear power plants, etc. Funding is needed to drive the innovation as quickly as it is needed to meet the two-degree scenario.

1.5

Conclusions

The base alloys for industrial operations are steel ones. Its production volume of 1.7 billion tons in 2017 is destined to grow in the next future with a very sharp acceleration in the growing countries. Ironmaking and steelmaking sector is a high energy-intensive and is responsible for one third of the global dangerous emissions to atmosphere of all the human industrial activities. Due to this and to the increase

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growing, new paradigms must be developed and approached in order to transform the sector in order to make it sustainable in the future and compatible with global warming reduction. A big effort has been conducted by all the producing companies in order to improve energy efficiency to sustain reduction in specific energy consumption. Better targets could be achieved if radical changes in the steel production processes are introduced (thus reaching 15–25% of energy efficiency increase). However the business model for introducing these changes is still elusive, which means that the cost of introducing more energy savings is far higher than the value of the energy saved. As a matter of fact, based on current climate change forecast, it is predicted that the steel industry will face greater challenges which cannot be solved with the past incremental technologies in the future. US and European reports underline that if the global warming should be avoided, the only way is to develop and apply breakthrough technologies very fast. In fact, with the present technological routes, the CO2 emissions are destined to increase of 50% by 2050. The 2  C scenario will be possible only if the emissions will be reduced by 50%. For the 1.5  C scenario, the situation will become much more complex and hard. The following chapters will describe the main available technologies employed in the traditional or innovative routes capable of reducing the energy consumption and the dangerous greenhouse emissions as well as the research efforts that see many scientists involved all around the world from industry, academia, and research centers. Obviously the energy topic will be described taking into account the direct and indirect energy consumption per each analyzed technology and suggested solution.

References Allwood JM, Cullen JM, Carruth MA, Cooper DR, McBrien M, Milford RL, Moynihan M, Patel ACH (2012) Sustainable materials: with both eyes open. UIT, Cambridge An R, Yu B, Wei YM (2018) Potential of energy savings and CO2 emission reduction in China’s iron and steel industry. Appl Energy 226:862–880. https://doi.org/10.1016/j.apenergy.2018. 06.044 Andersson A, Gullberg A, Kullerstedt A, Sandberg E, Andersson M, Ahmed H, SundqvistÖkvist L, Björkman B (2018) A holistic and experimentally-based view on recycling of off-gas dust within the integrated steel plant. Metals 8:760. https://doi.org/10.3390/met8100760 Ariyama T, Takahashi K, Kawashiri Y, Nouchi T (2019) Diversification of the ironmaking process toward the long-term global goal for carbon dioxide mitigation. J Sustain Metall. https://doi.org/ 10.1007/s40831-019-00219-9 Babich A, Senk D (2019) New raw materials for the iron and steel industry. Chernye Metally 1:6–15 Bataille C, Åhman M, Neuhoff K, Nilsson LJ, Fischedick M, Lechtenböhmer S, Solano-Rodriquez B, Denis-Ryan A, Stiebert S, Waisman H, Sartor O, Rahbar S (2018) A review of technology and policy deep decarbonization pathway options for making energy-intensive industry production consistent with the Paris Agreement. J Clean Prod 187:960–973. https://doi.org/10. 1016/j.jclepro.2018.03.107

34

1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

Bellevrat E, Menanteau P (2009) Introducing carbon constraints in the Steel sector: ULCOS scenario and economic modeling. La Revue de Métallurgie-CIT 106(09):318–324. https://doi. org/10.1051/metal/2009059 Bettinger D, Gobi D, Fritschek H, Schaler M (2017) Recent developments in ironmaking process control—Holistic optimization models. AISTech - Iron Steel Technol Conf Proc 1:431–437 Birat JP (2010) Steel sectoral report, Contribution to the UNIDO roadmap on CCS, Global Technology Roadmap for CCS in Industry sectoral workshop, Abu Dhabi, 30 June–1 July Birat JP (2015) Life-cycle assessment, resource efficiency and recycling. Metall Res Technol 112:206. https://doi.org/10.1051/metal/2015009 Birat JP (2016) Steel cleanliness and environmental metallurgy. Metall Res Technol 113:201. https://doi.org/10.1051/metal/2015009 Birat JP, Chiappini M, Ryman C, Riesbeck J (2013) Cooperation and competition among structural materials. Rev Metal 110:97–131. https://doi.org/10.1051/metal/2013057 Burchart-Korol D (2011) Evaluation of environmental impacts in iron-making based on life cycle assessment. Metal Brno, Czech Republic, May 18–20 Cavaliere P (2016) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. Springer, Cham. https://doi.org/10.1007/978-3-319-39529-6 Cavaliere P, Perrone A (2013) Analysis of dangerous emissions and plant productivity during sintering ore operations. Ironmak Steelmak 40(1):9–24. https://doi.org/10.1179/1743281212Y. 0000000019 Cavaliere P, Perrone A, Tafuro P, Primavera V (2011) Reducing emissions of PCDD/F in sintering plant: numerical and experimental analysis. Ironmak Steelmak 38(6):422–431. https://doi.org/ 10.1179/1743281211Y.0000000034 Chen Z, Qu Y, Zeilstra C, van der Stel J, Sietsma J, Yang Y (2018) Thermodynamic evaluation for reduction of iron oxide ore particles in a high temperature drop tube furnace. Ironmak Steelmak. https://doi.org/10.1080/03019233.2018.1498762 Chittrey RK (2016) Energy efficiency Tata Steel Ltd. In: First workshop on best practices in energy efficiency in sponge iron & steel sector. Raipur, India 4th March 2016 Chowdhury JI, Hu Y, Haltas I, Balta-Ozkan N, Matthew G Jr, Varga L (2018) Reducing industrial energy demand in the UK: a review of energy efficiency technologies and energy saving potential in selected sectors. Renew Sustain Energy Rev 94:1153–1178. https://doi.org/10. 1016/j.rser.2018.06.040 Delasalle F (2019) Steel in the global value chain and in the circular economy. In Steel and coal: a new perspective, Bruxelles, 28 March 2019 Dente SMR, Aoki-Suzuki C, Tanaka D, Kayo C, Murakami S, Hashimoto S (2019) Effects of a new supply chain decomposition framework on the material life cycle greenhouse gas emissions— the Japanese case. Resour Conserv Recycl 4:273–281. https://doi.org/10.1016/j.resconrec.2018. 09.027 Duan W-J, Lang J-L, Cheng S-Y, Jia J, Wang X-Q (2018) Air pollutant emission inventory from Iron and steel industry in the Beijing-Tianjin-Hebei region and its impact on PM2.5. Huan Jing Ke Xue 39(4):1445–1454. https://doi.org/10.13227/j.hjkx.201709053 Energy Transitions Commission (2018) Reaching zero carbon emissions from steel. http://www. energy-transitions.org European Commission (2018) A Clean Planet for all A European strategic long-term vision for a 849 prosperous, modern, competitive and climate neutral economy. Communication from the commission, Brussels 28 November 2018 Freytag D (2007) The history, making and modeling of steel. National Model Railroad Association. ISBN: 978-0964705098 Gerres T, Chaves Ávila JP, Llamas PL, San Román TG (2019) A review of cross-sector decarbonisation potentials in the European energy intensive industry. J Clean Prod 210:585–601. https://doi.org/10.1016/j.jclepro.2018.11.036

References

35

Ghanbari H (2019) Polygeneration systems in Iron and steelmaking. In Polygeneration with polystorage for chemical and energy hubs: for energy and chemicals, pp 287–239. https://doi. org/10.1016/B978-0-12-813306-4.00010-0 Gonzalez Hernandez A, Paoli L, Cullen JM (2018) How resource-efficient is the global steel industry? Resour Conserv Recycl 133:132–145. https://doi.org/10.1016/j.resconrec.2018. 02.008 Gordon Y, Kumar S, Freislich M, Yaroshenko Y (2015) The modern technology of iron and steel production and possible ways of their development. Steel Translat 45(9):627–624. https://doi. org/10.3103/S0967091215090077 He K, Wang L (2017) A review of energy use and energy-efficient technologies for the iron and steel industry. Renew Sustain Energy Rev 70:1022–1039. https://doi.org/10.1016/j.rser.2016. 12.007 Hellweg S, Mila I, Canals L (2014) Emerging approaches, challenges and opportunities in life cycle assessment. Science 344(6188):1109–1113. https://doi.org/10.1126/science.1248361 Holappa L (2017) Recent achievements in iron and steel technology. J Chem Technol Metall 52 (2):159–167 IEA-International Energy Agency (2016) Energy balance flows. http://www.iea.org/Sankey/index. html Jahanshahi S, Mathieson JG, Reimink H (2016) Low emission steelmaking. J Sustain Metall 2 (3):185–190. https://doi.org/10.1007/s40831-016-0065-5 Janjua R (2017) Energy use in the steel industry. https://www.worldsteel.org Kan T, Xu W, Shao M (2016) CO2 emission in China’s iron and steel industry. In Cavaliere P (ed) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. https://doi.org/10.1007/978-3-319-39529-6_20 Khanna N, Fridley D, Zhou N, Karali N, Zhang J, Feng W (2019) Energy and CO2 implications of decarbonization strategies for China beyond efficiency: modeling 2050 maximum renewable resources and accelerated electrification impacts. Appl Energy 242:12–26. https://doi.org/10. 1016/j.apenergy.2019.03.116 Kitamura S-Y, Naito K-I, Okuyama G (2019) History and latest trends in converter practice for steelmaking in Japan. Trans Inst Min Metall Sect C Miner Process Extr Metall 128(1–2):34–45. https://doi.org/10.1080/25726641.2018.1504661 Kumar Sahu R, Halder C, Sen PK (2016) Optimization of top gas recycle blast furnace emissions with implications of downstream energy. Steel Res Int 87(9):1190–1202. https://doi.org/10. 1002/srin.201500312 Kuramochi T (2016) Assessment of midterm CO2 emissions reduction potential in the iron and steel industry: a case of Japan. J Clean Prod 132:81–97. https://doi.org/10.1016/j.jclepro.2015. 02.055 Liu L, Jiang Z, Zhang X, Lu Y, He J, Wang J, Zhang X (2018) Effects of top gas recycling on in-furnace status, productivity, and energy consumption of oxygen blast furnace. Energy 163:144–150. https://doi.org/10.1016/j.energy.2018.08.114 Madureira NL (2012) The iron industry energy transition. Energy Policy 50:24–34. https://doi.org/ 10.1016/j.enpol.2012.03.003 Mandova H, Gale WF, Williams A, Heyes AL, Hodgson P, Miah KH (2018) Global assessment of biomass suitability for ironmaking – opportunities for co-location of sustainable biomass, iron and steel production and supportive policies. Sustain Energy Technol Assess 27:23–39. https:// doi.org/10.1016/j.seta.2018.03.001 Mandova H, Patrizio P, Leduc S, Kjarstad J, Wang C, Wetterlund E, Kraxner F, Gale W (2019) Achieving carbon-neutral iron and steelmaking in Europe through the deployment of bioenergy with carbon capture and storage. J Clean Prod 218:118–129. https://doi.org/10.1016/j.jclepro. 2019.01.247 Millward-Hopkins J, Zwirner O, Purnell P, Velis CA, Iacovidou E, Brown A (2018) Resource recovery and low carbon transitions: the hidden impacts of substituting cement with imported

36

1 Clean Ironmaking and Steelmaking Processes: Efficient Technologies. . .

‘waste’ materials from coal and steel production. Glob Environ Change 53:146–156. https://doi. org/10.1016/j.gloenvcha.2018.09.003 Mohsenzadeh FM, Payab H, Abedi Z, Abdoli MA (2019) Reduction of CO2 emissions and energy consumption by improving equipment in direct reduction ironmaking plant. Clean Techn Environ Policy. https://doi.org/10.1007/s10098-019-01672-6 Nestler F, Krüger M, Full J, Hadrich MJ, White RJ, Schaad A (2018) Methanol synthesis – industrial challenges within a changing raw material landscape. Chemie- Ingenieur- Technik 90(10):1409–1418. https://doi.org/10.1002/cite.201800026 Ng KW, Giroux L, Todoschuk T (2018) Value-in-use of biocarbon fuel for direct injection in blast furnace ironmaking. Ironmak Steelmak 45(5):406–411. https://doi.org/10.1080/03019233. 2018.1457837 Ökvist LS, Lagerwall P, Sundelin B, Orre J, Brämming M, Lundgren M (2017) Low CO2 ironmaking in the blast furnace. Stahl und Eisen 137(9):29–37 Otto A, Robinius M, Grube T, Schiebahn S, Praktiknjo A, Stolten D (2017) Power-to-steel: reducing CO2 through the integration of renewable energy and hydrogen into the German steel industry. Energies 10(4):451. https://doi.org/10.3390/en10040451 Pardo N, Moya JA (2013) Prospective scenarios on energy efficiency and CO2 emissions in the European Iron & Steel industry. Energy 54:113–128. https://doi.org/10.1016/j.energy.2013. 03.015 Perato M, Magnani S, Astoria T (2018) Integration of MIDREX technologies in North American steel plants: evaluation of economical and CO2 impacts. Iron Steel Technol 15(5):48–55 Perkins JH (2017) Changing energy: the transition to a sustainable future. University of California Press, Berkeley, pp 1–343 Quader MA, Ahmed S, Ghazillaa RAR (2016a) Recent progress and future trends of CO2 breakthrough iron and steelmaking technologies for CO2 mitigation. In Cavaliere P (ed) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. https://doi.org/10. 1007/978-3-319-39529-6_22 Quader MA, Shamsuddin A, Dawal SZ, Nukman Y (2016b) Present needs, recent progress and future trends of energy-efficient Ultra-Low Carbon Dioxide (CO2) Steelmaking (ULCOS) program. Renew Sustain Energy Rev 55:537–549. https://doi.org/10.1016/j.rser.2015.10.101 Rogelj J, Shindell D, Jiang K, Fifita S, Forster P, Ginzburg V, Handa C, Kheshgi H, Kobayashi S, Kriegler E, Mundaca L, Séférian R, Vilariño MV (2018) Mitigation pathways compatible with 1.5 C in the context of sustainable development. In Masson-Delmotte V, Zhai P, Pörtner H-O, Roberts D, Skea J, Shukla PR, Pirani A, Moufouma-Okia W, Péan C, Pidcock R, Connors S, Matthews JBR, Chen Y, Zhou X, Gomis MI, Lonnoy E, Maycock T, Tignor M, Waterfield T (eds) Global Warming of 1.5 C. An IPCC Special Report on the impacts of global warming of 1.5 C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. http://pure.iiasa.ac.at/15515 Rootzén J, Johnsson F (2013) Exploring the limits for CO2 emission abatement in the EU power and industry sectors—awaiting a breakthrough. Energy Policy 59:443–458. https://doi.org/10.1016/ j.enpol.2013.03.057 Rootzén J, Kjärstad J, Johnsson F (2011) Prospects for CO2 capture in European industry. Manag Environ Qual 22(1):18–32. https://doi.org/10.1108/14777831111098453 Sato M, Takahashi K, Nouchi T, Ariyama T (2015) Prediction of next-generation ironmaking process based on oxygen blast furnace suitable for CO2 mitigation and energy flexibility. ISIJ Int 55(10):2105–2114. https://doi.org/10.2355/isijinternational.ISIJINT-2015-264 Shatoka (2016a) Environmental sustainability of the iron and steel industry: towards reaching the climate goals. Europ J Sustain Dev 5(4):289–300. https://doi.org/10.14207/ejsd.2016.v5n4p289 Shatoka V (2016b) Potential of best available and radically new technologies for cutting carbon dioxide emissions in ironmaking. In Cavaliere P (ed) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. https://doi.org/10.1007/978-3-319-39529-6_24

References

37

Steel Institute VDEh (2009) Description of the Plantfacts database, Steel Institute VDEh, Technical information department and Library Suopajärvi H, Umeki K, Mousa E, Hedayati A, Romar H, Kemppainen A, Wang C, Phounglamcheik A, Tuomikoski S, Norberg N, Andefors A, Öhman M, Lassi U, Fabritius T (2018) Use of biomass in integrated steelmaking – status quo, future needs and comparison to other low-CO2 steel production technologies. Appl Energy 213:384–407. https://doi.org/10. 1016/j.apenergy.2018.01.060 U.S. Department of Energy (2015) Bandwidth study on energy use and potential energy saving opportunities in U.S. iron and steel manufacturing. Report from The U.S. Department of energy (DOE)’s advanced manufacturing office. June 2015 Uribe Soto W, Portha JF, Commenge JM, Falk L (2017) A review of thermochemical processes and technologies to use steelworks off-gases. Renew Sustain Energy Rev 74:809–823. https://doi. org/10.1016/j.rser.2017.03.008 Voestalpine (2018) Energy in future steelmaking. EU Seminar “European Steel: The Wind of Change”, Brussels, January 31, 2018 Wiencke J, Lavelaine H, Panteix P-J, Petitjean C, Rapin C (2018) Electrolysis of iron in a molten oxide electrolyte. J Appl Electrochem 48(1):115–126. https://doi.org/10.1007/s10800-0171143-5 Wilson C, Grubler A (2011) Lessons from the history of technological change for clean energy scenarios and policies. Nat Res Forum 35:165–184. https://doi.org/10.1111/j.1477-8947.2011. 01386.x Xing L-Y, Zou Z-S, Qu Y-X, Shao L, Zou J-Q (2019) Gas–solid reduction behavior of in-flight fine hematite ore particles by hydrogen. Steel Res Int 90(1):1800311. https://doi.org/10.1002/srin. 201800311 Xu C, Cang DQ (2010) A brief overview of low CO2 emission technologies for iron and steel making. J Iron Steel Res Int 17(3):1–7. https://doi.org/10.1016/S1006-706X(10)60064-7 Zhong W, Dai T, Wang G, Li Q, Li D, Liang L, Sun X, Hao X, Jiang M (2018) Structure of international iron flow: based on substance flow analysis and complex network. Resour Conserv Recycl 136:345–354. https://doi.org/10.1016/j.resconrec.2018.05.006 Zhou D, Cheng S, Wang Y, Jiang X (2017) The production of large blast furnaces during 2016 and future development of ironmaking in China. Ironmak Steelmak 44(10):714–720. https://doi.org/ 10.1080/03019233.2017.1339398

Chapter 2

Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

2.1

Introduction

The integrated ironmaking route is based on coke. It is a high carbon porous material with very high resistance to fracture and is characterized by a low reactivity with gases at high temperatures. Coke making is the fundamental process related to the traditional blast furnace route. Coke provides the reducing actions, increases temperature through its thermal energy, and physically supports the material during the reactions. No other materials can provide the thermal and physical role of coke in the BF; for this reason, it is impossible to replace all the coke in the huge plants. In the modern ironmaking, each ton of molten metal requires 500 kg of coke to be produced. If additional fuels are adopted (this aspect will be larger discussed in the following), this quantity can be reduced up to 300 kg/t-hot metal. Coke is produced in the coke ovens by air, overheating coal up to temperatures of 1200
C. The heating time is in the order of several hours in order to eliminate the volatile compounds and to reduce the coal moisture. 1.6 ton of coal are needed to produce 1 ton of coke; the required energy is in the order of 5 GJ/t. Coke making consumes over 10% of the total energy demand of the whole integrated steel plant. It is a production unit where the emissions to air are the most significant. In Fig. 2.1, it is shown the world production of coke divided by region. The coal market of Europe is described by Fig. 2.2. In the recent past, coke making faced important issues related to the increasing environmental pressure, the reduction of the availability of good coking coals, and the need to renew old coke making facilities. These aspects resulted in the needing for new technologies capable of processing greater amounts of low-grade coking coals or even non-coking coals and yet maintain/increase coke quality (North et al. 2018). Obviously, all the GHG and in particular CO2 emissions strongly depend on the types and quality of the reducing agents (Babich and Senk 2019). In addition, many other emissions are diffusive and related to the storage, transport, charging, and grading phases (Cavaliere 2016). Dust and SO2 emissions are also relevant. © Springer Nature Switzerland AG 2019 P. Cavaliere, Clean Ironmaking and Steelmaking Processes, https://doi.org/10.1007/978-3-030-21209-4_2

39

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Fig. 2.1 World coke production in 2015

In addition, wastewater is a crucial issue for coke plants. The materials flow and the emission sources of the coke making operations are shown in Fig. 2.3. Many and different technologies have been developed for integrating or substituting the existing ones in order to reduce the coke needing in the traditional integrated steelmaking plant. All these solutions will be described in the present chapter.

2.2

Wastewater Treatment

Iron and steel production is one of the most water-intensive industry processes, and it not only consumes large quantities of water but also discharges higher quantities of wastewater. The World Steel Association identified water as the most important issue for a sustainable steel industry, following climate change and air quality (Suvio et al. 2012). Thus, water resources have become one of the most serious constraint factors for the sustainable development of the steel industry. The Chinese iron and steel industry remains one of the largest freshwater consumers in the industrial field, ranking 5th. In 2015, the total quantity of fresh water used in China’s steel industry was 15.5  108 m3, which accounted for 1.12% of the annual industrial fresh water consumption (FWC), and the industrial FWC occupied 22.3% of the nation. The specific FWC was 3.25 m3 per ton of crude steel in China, whereas the number was merely 1–2.6 m3/t-s in other developed countries. An evaluation of water FWC and TWC as a function of the plant sector is shown in Fig. 2.4 (Tong et al. 2018).

2.2 Wastewater Treatment

41

Fig. 2.2 Coal in Europe 2017

When coal is heated in the absence of air, it becomes buoyant, and all the volatile matter breaks down to yield gases, liquid and solid organic compounds of lower molecular weight, and the nonvolatile carbonaceous residue known as coke (1,4,6). Then, the coke is cooled by water. The resulting water is a complex industrial waste to be managed in steel production facilities that originates from the process of making coke. The resulting wastewater contains sizable amount of ammonia salts and toxic compounds such as phenols, PAHs, SCN, and CN. Much of the chemical oxygen demand (COD) occurs from phenols, which is a carbon source for acclimatized microorganisms but also a toxic inhibitory substrate for microorganisms (Zhang et al. 2019). In the Water Framework Directive (WFD), a list of priority substances that are deemed to be persistent, toxic, and liable to bioaccumulate has been identified. Within this list, a range of polycyclic aromatic hydrocarbons (PAHs) and certain trace metals are relevant to the steel industry. This study summarizes work carried out by Tata Steel Europe (Rotherham, U.K.) to characterize the emissions of PAHs and trace metals from wastewater streams at one of its main integrated steelworks in the United Kingdom over a 3-year period (2010–2012). The emission inventory revealed that PAH emissions to water were

Pond water

Coke fines (recovered)

Coke Combustion BF/BOF quench gas air tower COG

Regenerative coke ovens

Fig. 2.3 Materials flow and emission sources in coke making

Make-up water

Release to atmosphere

Run-off water

Coal blending area

Release to atmosphere dust lift-off

Reclaimer

Emergency

Surface water collection

Reclaimer

Release to atmosphere airborne dust

Run-off water

Coal stocking area

Release to atmosphere dust lift-off

Run-off water

Blended coal bedding area

Release to atmosphere dust lift-off

Coke wharf

Wharfside spray quench

Coke screening plant

Release to vent/flare Battery Coke oven gas atmosphere Release to top to dust waste gas storage atmosphere treatment and flue bunker charging by-products emissions recovery planr Door Top leakage Release to leakage Dust release to atmosphere atmosphere pushing emissions

Coal storage bunker

Quaside coal unloading

Dust release to atmosphere during grabbing

Reclaimer

Hammer mill

To export

To sinter plant

To blast furnace

Coal storage bunker

Release to Release to atmosphere atmosphere airborne dust airborne dust

42 2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

2.2 Wastewater Treatment

43

Fig. 2.4 Water consumption in an integrated steel plant, FWC (a); TWC (b)

almost entirely attributable to the coke making process, with emission factors ranging from 20 to 55 mg/ton of coke (Chen et al. 2015). Furthermore, the analysis of the PAH distribution in coke oven effluents revealed that medium- and highmolecular-weight PAHs were associated with the suspended solids (particle-bound). As shown in Table 2.1, the substances classified as PHS include two trace metals (Hg and Cd) and six PAHs (anthracene, benzo [a] pyrene, benzo[b] fluoranthene, benzo[k] fluoranthene, benzo [g,h,i] perylene, and indeno [l,2,3-cd] pyrene). Four substances are classified as priority substances including two trace metals (Pb and Ni) and two PAHs (naphthalene and fluoranthene). The most significant process emissions are the coke making effluents. For these discharge points, pH, emission limit values, and typical observed emissions for a series of key pollutants including COD, biochemical oxygen demand (BOD), suspended solids, ammoniacal nitrogen as N (N), thiocyanate (SCNT), and cyanide (CN) are summarized in Table 2.2.

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Table 2.1 Environmental quality standards for the PHS and priority substance identified in the WFD and list of specific pollutants that are relevant to the iron and steelmaking industry

Substances classified in WFD PHS Anthracene Benzene Cd and its compounds

Hg and its compounds

AA-EQS inland surface water (μg/l) 0.1 10 0.08–0.25 (dissolved, depending on water hardness) 0.05 (dissolved)

AA-EQS other surface water (μg/l) 0.1 8 0.25 (dissolved)

MAC-EQS inland surface water (μg/l)

MAC-EQS other surface water (μg/l)

0.4 50 0.45–1.5 (dissolved, depending on water hardness) 0.07

0.4 50 0.45–1.5 (dissolved, depending on water hardness) 0.07

0.1 –

0.1 –

Benzo (a) pirene Benzo (b) fluoranthene + Benzo (k) fluoranthene Benzo (g,h,i) perylene + Indeno (1,2,3cd) pyrene PSu Fluoranthene Pb and its compounds

0.05 0.03

0.05 (dissolved) 0.05 0.03

0.002

0.002

–

–

0.1 7.2 (dissolved)

1 –

1 –

Naphthalene Ni and its compounds

2.4 20 (dissolved)

0.1 7.2 (dissolved) 1.2 20 (dissolved)

– –

– –

SP Fe, As, Cr, Fe, free cyanide, Zn Table 2.2 Effluent discharge limits and typical emissions expressed in mg/L of pollutants for coke making operations

Effluent discharge limit Typical emission levels

COD 500

BOD 100

Suspended solids 150

N 200

SCN 10

CN 0.3

pH –

125–180

3–15

20–100

75–150

0.5–1.5

0.05–0.08

6.5–7.2

In a typical treatment plant, the wastewater is directed through a series of treatment steps with specific waste load reduction tasks (Kwiecińska et al. 2016), such as pre-treatment (physical and/or chemical), primary treatment (physical), secondary treatment (biological), and advanced treatment (physical and/or chemical and/or biological).

2.2 Wastewater Treatment

45

Physical pre-treatment methods include flow balancing, screenings, and grit removal. Besides the physical pre-treatment, industrial wastewater often need to combine the pre-treatment with chemical methods, such as air flotation (oil removal) and air stripping (ammonia removal). The primary treatment (clarification, sedimentation, or settling) allows the wastewater to settle for a period of ~2 h in a settling tank. Consequently, it produces a more clarified liquid effluent in one stream and a liquid-solid sludge in a second stream. Biodegradation is the dominant mechanism of organics removal for wastewater. The microorganisms convert biodegradable organic substances and some inorganic fractions into new biomass and by-products such as water and carbon dioxide. If the composition of the wastewater is not satisfactory, an advanced treatment is often used, for example, ion exchanger, sand filter, and more (Perez 2010). The most widely used form of wastewater treatment for industrial wastewater is the biological treatment method, activated sludge process. However, research has indicated that the technique sequential batch reactor (SBR) is more efficient reducing ammonia, phenol, COD, SS, and BOD concentration than an active sludge process. A SBR is a complete mix activated sludge system, with suspended growth and without a secondary clarifier. Aeration and clarification are carried out in one tank and within the single aeration basin (Marañón et al. 2008). A conventional activated sludge system is a suspended-growth process and includes an aeration tank and a sedimentation tank. In the aeration tank, the aerobic oxidation of organic matter occurs to CO2, H2O, NH4, and new cell biomass, while the sedimentation tank is used for sedimentation of microbial flocks (sludge) produced while oxidation phase in the aeration tank. The recycling of a large portion of the biomass is an important characteristic of this process. The primary effluent is introduced and mixed together with return activated sludge to form the mixed liquor (MLSS). Then, the MLSS is transferred to the settling tank where the sludge separates from the treated effluent. A fraction of the sludge is recycled back to the aeration tank, while the rest is further treated in an aerobic or anaerobic digestion. The popularity of using this method depends mainly of both an efficient reduction of organic substances and the non-to-hard maintenance. Moving bed biofilm reactor (MBBR) is based on the process of fixed films (Taylor 2015). The advantages of MBBR are a continuous process without any risks for clogs and needs for backflash, with low pressure and highly accessible specific surface. This is achieved by letting biofilm grow on a numerous small plastic carrier that moves along with the water in the reactor. The microorganisms are well protected which make the process strong towards variations, disturbance, and extreme strains. The process is easy manageable, and the amount of active biomass is self-regulated and depends on the income strains. The carrier is continuous in movement due to oxygen from a bottom air system, which makes the process insensitive towards suspended material in the influent water. The effluent leaves the reactor through grating or strainers, which keeps the carrier behind in the process. The surplus sludge, which continuously repeals from the carrier in a natural process, transports with the effluent through the grating next to a posttreatment step.

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Nanofiltration can be used as an advanced treatment. NF is a membrane technology and is used for removal of dissolved particles (>0.001 μm) from wastewater and can be used as a disinfected method before storage for reclaimed water. NF removes everything over the pore limits, including both organic and inorganic substances, bacteria, and viruses. However, this method is not going to be discussed any further (Kumar et al. 2011). Ozone can increase the biodegradability of wastewater, to be precise, increase the ratio BOD/COD before the activated sludge process with a factor of 10, if used as a pre-treatment step. The AOPs are called the water treatment processes of the twenty-first century. When applied in the right place, it can reduce the contaminant concentration from several 100 ppm to less than 5 ppm (Krzywicka and Kwarciak-Kozłowska 2014). AOPs are defined as near-ambient temperature and pressure water treatment processes which initiate complete oxidative destruction of organics based on the generation of hydroxyl radical OH. AOPs used for wastewater treatment include, among others: – Ozone at elevated temperature pH (8.5) 3O3 þ OH þ Hþ ! 2OH þ 4O2 – Ozone + hydrogen peroxide

– Fenton system

2O3 þ H2 O2 ! 2OH þ 3O2 Fe2þ þ H2 O2 ! Fe3þ þ OH þ OH

– Ozone + hydrogen peroxide + UV radiation
O3 þ hv ! O2 þ O 1 D
O 1 D þ H2 O ! H2 O2 þ 2OH For phenol and PAHs treatment, the best alternative is to generate hydroxyl radicals by the use of ozone and hydrogen peroxide. AOPs are often used as either a primary treatment step or as posttreatment step (Ghosh 2019). Many persistent organic compounds, such as PAHs have been found to degrade more rapidly under anaerobic conditions than under aerobic conditions. The critical steps in anaerobic degradation of these compounds include partial scission of polycyclic or heterocyclic rings and degradation of organics through anaerobic fermentation. The system includes an anaerobic tank followed by anoxic and aerobic tank. The anaerobic unit mainly uses three biochemical reactions as a pre-treatment step:

2.2 Wastewater Treatment

47

Table 2.3 Documented values from EPB

Measure NH3-N COD Phenols

Table 2.4 Average concentration of substances before and after treatment

Substance N-NH3 Phenol COD Cyanide free SS PAHs

Before treatment (mg/l) 2900 4500 5000

Influent (mg/l) 50 700–1000 4500 100–200 10,000–15,000 –

After treatment (mg/l) 74 196 158

Effluent (mg/l) 16 0.05 240 8.9 0.05

1. Hydrolysis – enzyme-mediated transformation of complex organic compounds into more simple ones 2. Acidogenesis – bacterial conversion of simple compounds into substrates for methanogenesis (acetate, formate, hydrogen, carbon dioxide) 3. Methanogenesis – bacterial conversion of methanogenic substrates into methane and carbon dioxide In the anoxic unit, organic compounds are oxidized by nitrate and phenol, while nitrate is also reduced to nitrogen gas and excess from the system. The efficiency of A2/O system is significantly influenced by the chemical nature of wastewater, pH, temperature, hydraulic retention time (HRT), and so on. The high ammonia content in the wastewater generated from coke industry renders the efficient of the activated sludge process in dire straits. A normal treatment method for these wastewaters is steam stripping as a pre-treatment method. Steam stripping or hot gas, such as air, can remove most of the ammonia, hydrogen sulfide, carbon dioxide, and substances such as phenol, cyanides, and light organics. The whole process applied to a Chinese plant gives the results listed in Table 2.3. Based on the amount of produced coke per year, the most probable flow is 30 m3/h. A plant active at SSAB (process water flow at 25 m3/h, HRT of 48 h and MLSS of 10 kg/h) provides a good reduction of phenols and cyanides and PAHs (Table 2.4). SSAB Tunnplåt AB has chosen a NH3 stripper as a pre-treatment step followed by a settling secondary one. The NH3 stripper reduces the ammonia by heating up NH3 with the steam. A NH3 stripper is necessary to have low ammonia concentrations in the influent. After the ASP, the water pass a flotation step and a sand filter to be able to reduce the suspended sludge. The suspended sludge produced in the ASP is after advanced treatment such as flotation, biosludge thickener, and centrifuge burned together with the coal. With further plant modifications, treatment of pretreated coking wastewater by flocculation, coagulation, alkali out, air stripping, and 3-D electrocatalytic oxidation was effective and practicable. All processes developed into an organic system, and

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

each process had made its own contribution to the decrease of residual COD and NH3-N. The pH adjusted from 3.7 to 6.1 was necessary for coagulants to exert effectively their functions on the effluent. The process of alkali out had played an important role in improving the quality of effluent because it brought up some precipitation containing higher fatty acids plus other organic contaminants so as to decrease the residual COD to some extent; furthermore, it had forced the drastic reduction of residual NH3-N by incorporating with the process of air stripping. For the process of 3-D electrocatalytic oxidation with a commercial bleaching liquid assisting, the initial pH of about 8.5 of the effluent was suitable for the stability, performance, and lifetime of Cu-Mn/GAC. It was considered that in the course of 3-D electrocatalytic oxidation, the Cu component over Cu-Mn/GAC was dedicated to the decrease of COD as well as NH3-N, while its Mn component played an excellent role in the decay of NH3-N. This work was characteristic of feasibility, short time-consuming, and low cost as well as high effectivity, and it also displayed a way how to reuse the used electrodes, indicating that the life spans of the spent electrodes might be prolonged to a certain degree (Wen-wu et al. 2014). In recent studies (Peng et al. 2017), the posttreatment of coking wastewater was investigated by the Fenton and EF-Feox methods. It was found that the EF-Feox process demonstrated a more remarkable treatment performance than Fenton. Compared with the direct Fenton and EF-Feox processes, the results have indicated that more than 90% of COD removal and 8% of TOC removal were obtained in the EF-Feox method; however, only 61.96% of COD and 48.12% of TOC were removed by Fenton’s method. In the optimization experimentation, the current density and H2O2 concentration have a considerable effect on the efficiency of EF-Feox process. Moreover, the H2O2 feeding type and pH also have strongly influenced the performance of EF-Feox process. The gradual addition of H2O2 was found to be an effective way to increase COD and TOC removal efficiency (Fig. 2.5). The optimum operation conditions for EF-Feox were determined as 50 mA/cm2 current density, 5000 mg/l H2O2 concentration, and initial pH of 3 for electrolysis process at 120 min. Under these conditions, the COD and TOC removal efficiencies were obtained as 95.3% and 84.4%, respectively. The amount of sludge production of EF-Feox was found to be 1.28 kg/m3. Research indicates that the more efficient method for coke plant wastewater treatment was the photo-Fenton process. At the optimal reagent ratio – 20:1 H2O2/ Fe2+  the ferrous sulfate addition was minimized, which resulted in slight production of sludge. TOC and COD removal efficiencies were 76% and 84%, respectively; however, the permissible standards were exceeded. It indicates that these AOPs should be modified or supported with other methods (Krzywicka and Kwarciak-Kozłowska 2014). With the addition of a pre-microfiltration step, nanofiltration was carried out using real coke wastewater under different operating conditions. Under the optimum

2.2 Wastewater Treatment

49

Fig. 2.5 COD removal efficiency

operating pressure of 13 bars and a pH of 10.0, a rate of more than 95% separation of cyanide was achieved (Pal et al. 2015). Coke dusts, which are a by-product of the process of dry quenching of coke, have specific properties beneficial in terms of using these materials in adsorptive treatment of wastewater which contains relatively large molecules of organic pollutants (Burmistrz et al. 2014). Adsorptive treatment of coke plant wastewater after biological reactor using 15 g/l of coke dust obtained from the dry quenching of coke removes 96% of PAHs from the wastewater, including 98% of benzo[a]pyrene, more than 90% of phenols, and 87% TOC. Enhancing biological treatment with coke dust addition allowed synergic effect in removal of pollutants (163 gCOD/kg, including 66 gTOC/kg). The enhanced biological treatment proved the most effective from all tested scenarios. Coke dust addition before biological treatment of wastewater lowered concentration of biodegradation inhibitors (PAHs and oil substances). Removal of those established better conditions for microorganisms in the activated sludge and intensified biodegradation, nitrification, and denitrification processes (Raper et al. 2018). Fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) was applied to investigate the contaminant removal efficiency and fluorescent characteristic variations in a full-scale coke wastewater (CWW) treatment plant with a novel anoxic/aerobic1/aerobic2 (A/O1/O2) process, which combined with internal-loop fluidized-bed reactor (Liu et al. 2016). Routine monitoring results indicated that primary contaminants in CWW, such as phenols and free cyanide,

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

were removed efficiently in A/O1/O2 process (removal efficiency reached 99% and 95%, respectively). Three-dimensional excitation-emission matrix fluorescence spectroscopy and PARAFAC identified three fluorescent components, including two humic-like fluorescence components (C1 and C3) and one protein-like component (C2). Principal component analysis revealed that C1 and C2 correlated with COD (correlation coefficient (r) ¼ 0.782, p < 0.01 and r ¼ 0.921, p < 0.01), respectively) and phenols (r ¼ 0.796, p < 0.01 and r ¼ 0.914, p < 0.01, respectively), suggesting that C1 and C2 might be associated with the predominating aromatic contaminants in CWW. C3 correlated with mixed liquor suspended solids (r ¼ 0.863, p < 0.01) in fluidized bed reactors, suggesting that it might represent the biological dissolved organic matter. In A/O1/O2 process, the fluorescence intensities of C1 and C2 consecutively decreased, indicating the degradation of aromatic contaminants. Correspondingly, the fluorescence intensity of C3 increased in aerobic1 stage, suggesting an increase of biological dissolved organic matter (Ou et al. 2014).

2.3

Coke Dry Quenching (CDQ)

CDQ is a system to cool the hot coke brought out of coke oven at a temperature of approximately 1000
C through the employment of an inert gas, and it generates the electric power by the steam produced from the waste heat recovery boiler. CDQ (coke dry quenching) is a gradual coke quenching system, capable of improving coke strength and coke size distribution. Consequently, while the blending ratio of inexpensive non- or slightly caking coal for coke oven material is only approx. 15% in case of CWQ (coke wet quenching) system (Fig. 2.6), it can be increased up to approx. 30% by CDQ; this results in a cost reduction related to the raw materials for coke oven. The coke oven energy recoveries are not totally justified on the grounds of the actual energy prices, especially in existing plants. However, taking into account the increasing demands made on the measures for environmental protection, the indirect advantages as coke quality and productivity, as well as a likely increase of energy prices in the medium-long term, an integrated fulfillment of all the possible recoveries in coke oven plants is completely justified and normally greatly suggested. Coke dry quenching appears as the most valid system to reduce air pollution allowing at the same time a remarkable energy recovery or saving, especially when it is associated with coal preheating. In addition, dry quenched coke is harder and stronger, and obviously its moisture content is much lower than that of wet quenched coke. To obtain these purposes, some different solutions have been realized or proposed. Also, even if energy analysis is useful, exergy analysis is considered the most valid tool to examine the various alternatives (Bisio and Rubatto 2000). In a system-environment combination, exergy is usually defined as the amount of work attainable when the system is brought to a state of unrestricted equilibrium (thermal,

2.3 Coke Dry Quenching (CDQ)

51

Fig. 2.6 Coke wet quenching

mechanical, and chemical) by means of reversible processes, involving only the environment at a uniformly constant temperature and pressure and comprising substances that are in thermodynamic equilibrium. Notwithstanding the quite different meaning, chemical exergies differ from lower heating values slightly. The chemical exergy generally falls between the higher and lower heating values but is closer to the higher. The parameter “usable exergy,” as has been defined and applied in, is suitable in the examination of plants, which utilize fuel mixing, when the aim is to reduce both the total fuel consumption and, chiefly, the more valuable component one. The chemical energy of a fuel gas, which is used for a coke oven, amounts to 2500–3200 MJ/t dry coal. This energy, degraded to thermal energy of various operative values, is discharged from the plant in the following forms: thermal energy of incandescent coke (43–48%), thermal enthalpy of coke oven gas (24–30%), thermal energy of waste gas (10–18%), and permeability, convection, and radiation heat from the external surface of coke oven and various losses (10–17%). Errera and Milanez (2000) underlined the importance of complete thermodynamic analysis of CDQ, the conclusions one can draw by accounting for the lost exergy or irreversibility generated in a system, the reasons why concepts such as the CWQ are still in use, and the trends for the future of CDQ plants. The implications of the difference between the amount of lost (destroyed) exergy in the two processes are of great importance. There is a broadly accepted trend that the exergy is one, or perhaps the one, measure of the ecological impact associated with

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

a given process. To some extent, exergy accounts for the expenditure of natural resources, for the degree that emissions pollute the environment, for how processes are adequate for their purposes, and for how well those processes are being operated. The thermodynamic superiority of the CDQ process over the CWQ process is verified by the lower impact (almost half of the destroyed exergy of the CWQ system) of the CDQ systems on the environment. It is worth noting that this complies with the insight of plant engineers that the heat released from the hot coke should be recovered. Furthermore, this analysis can be used as a communication tool among engineers. There are the ones who advocate the CWQ process is economically superior to the CDQ process, and others claim the quality of the yield coke in the CWQ process is better. That and the ending useful life of many plants are the main reasons why there are so many CWQ units still in operation. The CDQ concept has been used for decades in the steelmaking industry. It has been gradually improved and has led to newer concepts as, for instance, a hybrid two-stage system that starts by partially cooling the coke by means of contact with an inert gas in a hermetic chamber and then fully cooling it by pure water spray. The CDQ coke has lower moisture content (0.1% to 0.3%) than CWQ coke (2% to 5%), and the coke ratio of blast furnace can be reduced. Combustible component and coke dust in circulating gas are burned by blowing air into the gas, and so the temperature of the circulating gas can be raised. Thus, this leads to the increase of the steam generated by the waste heat boiler. The injection of coke dry quenching dust in the blast furnace can reduce the smelting costs; in addition, it could also lead to a reduction in the use of the anthracite and benefits to the environment protection (Jiang et al. 2017). Since the sensible heat recovered by means of the heat exchange in the cooling chamber is utilized as the heat resource to produce the steam, then the electric power generated from CDQ without the additional fuel consumption is described as the clean energy. In addition, comparing with conventional wet quenching system, CDQ provides many advantages such as to reduce the fuel ratio at BF and reduce the dust emission during the quenching of the hot coke. Coke dry quenching is a technology developed to substitute the traditional wet coke making. It has been developed in order to reduce dust emissions, to improve the working climate, and to recover the sensible heat of the coke. Hot coke from the coke oven is cooled in specially designed refractory lined steel cooling chambers by countercurrently circulating an inert gas media in a closed circuit consisting of a cooling chamber, a dust collecting bunker, a waste heat boiler, dust cyclones, a mill fan, a blowing device (to introduce the cold air form the bottom), and circulating ducts. The circulating gas (consisting of inert gases mainly nitrogen) acts as coke cooler (Fig. 2.7). The mixture forms for oxygen burning during the beginning of the cycle (Sultanguzin et al. 2016). The circulating gas has a temperature of 780
C at the chamber exit. The dry quenching chamber has a temperature of 1050
C. The process has duration of 5 h. A typical CDQ plant has a capacity of 100 t/h per chamber, and 25 t/h of high-pressure steam can be produced. In this way, CO2 is reduced thanks to the elimination of cooling water; in addition, the heating from the cooling gas can be recovered. The thermodynamic superiority of the CDQ process over the CWQ process is largely demonstrated by the lower impact (almost

2.3 Coke Dry Quenching (CDQ)

53

Fig. 2.7 Coke dry quenching plant

half of the destroyed exergy of the CWQ system) of the CDQ systems on the environment (Bejan and Mamut 1999). The strength and size distribution of the coked material are increased. The thermal energy belonging to the cooling is employed for the production of steam or electric energy or in the same plant to preheat the coke. It is demonstrated that CDQ leads to an improvement of the coke quality by reducing its consumption in the blast furnace (Danilin 2017). The dry quenching of coke is an efficient, energy-saving technology. However, various deficiencies in the design and operation of dry-quenching units reduce the overall efficiency. In particular, coke losses reduce the gross coke yield. The coke losses on quenching depend on the physical processes and thermochemical reactions in the quenching chamber. The coke losses are due to the transfer of carbon from the coke to the gas phase on account of reaction with components of the circulating gases. This process may also impair coke quality: in particular, the ash content may be increased. The atmospheric emission of the excess circulating gases also entails loss of heat. In addition, the coke losses are associated with environmental pollution. The pollutants present in the emitted excess circulating gases include carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, and phenol. In particular, the primary components of atmospheric pollution are carbon monoxide (CO) and coke dust. The dry-quenching units are the major sources of CO emissions in coke production. Thus, the coke losses help determine the performance and environmental impact of the dry-quenching unit, which will depend on its design, its condition, and the operating conditions. The main sources of pollutant emissions with the excess circulating gases from the dry-quenching unit are the flare of the blast fan, the system for portion-by-portion

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

coke discharge, and the prechamber flare. In addition, the system for charging coke in the prechamber is also a source of pollutant emissions. The following factors tend to increase gas emissions from the dry-quenching unit and hence increase the coke losses: gas leakage from the coke-discharge system on account of design deficiencies, leakage of air into the gas-circulation loop at the low-pressure channel, organized supply of air to the annular gas line beyond the quenching chamber for partial combustion of the carbon monoxide, and incomplete coke preparation. The readiness of the coke is greatly increased by holding in the prechamber. The following measures decrease the gas emissions from the dry-quenching unit: continuous coke discharge from an aerodynamic gate and automatic maintenance of optimal pressure in the upper part of the prechamber with an enclosed flare. When working with an open flare, increase in pressure in the prechamber leads to gas emissions to the atmosphere; decrease in pressure in the prechamber draws in air (including an air draught through the prechamber flare, increases the coke losses, and impairs coke quality. Development of designs and operating conditions such as gas emissions from the prechamber reduction or intake of air that accompanies coke loading in the prechamber reduction; maintenance of the CO concentration in the circulating gases beyond the quenching chamber at the maximum permissible level (12%) by sealing the gas channel in the dry-quenching unit. With increase in CO content in the circulating gases, coke losses decline and vice versa; increase in CO content in the circulating gases beyond the quenching chamber above the maximum level currently permitted (12%) by the development of special designs and operating conditions; Minimization of the circulating-gas consumption for the specific quenching-chamber design. Since the coke losses depend on the gas consumption, automatic monitoring of the gas flow rate is a very effective means of minimizing the coke losses. The temperature of the superheated steam in the waste heat boiler is directly associated with the gas consumption; increase in gas consumption reduces the temperature of the superheated steam and vice versa. It is important to assess the effectiveness of the dry quenching conditions in terms of gas consumption with a view to minimizing coke losses. The operational efficiency of the dry-quenching unit may be considerably improved by continuous monitoring of the coke losses, with selection and maintenance of the optimal operating conditions. Undoubtedly, continuous monitoring of the coke losses will focus the operating staff and improve the utilization of the dry-quenching unit. Several methods have been proposed to continuously monitor the coke losses. Approaches employed in determining the coke losses include determination on the basis of the steam generated; determination on the basis of the carbon content in the excess gases emitted from the dry-quenching unit; determination on the basis of the mass loss of the coke in a container; determination on the basis of the thermal balance of the dry-quenching unit; determination on the basis of the composition of the circulating gases (the difference in CO2 content ahead of and beyond the quenching chamber), taking account of the dependence of the coke losses on the reactivity of the coke; and determination on the basis of the material balance of the ash: the ash content of the quenched coke and

2.3 Coke Dry Quenching (CDQ)

55

the batch, the ash content of the quenched coke, and the ash content and quantity of coke dust formed or the ashing of the coke fractions on quenching. The high quality allows for the increase of non-coking coal in the blast furnace, so reducing the costs. CDQ are largely employed in Korea and Japan (Habashi 2016). The application of CDQ allows to reduce the energy demand on the plant up to 40%. The total energy balance confirms that per each ton of produced coke, 1.5 GJ heat of steam and 0.55 GJ electricity can be recovered (Gilyazetdinov et al. 2015). Gross toxic emissions are reduced by 19.5% with 25% reduction in CO emissions. In addition, the efficiency of dry quenching of coke is increased. In Japan, for a blast furnace of a 1 ton capacity, requiring 400–500 kg of coke, 450 GWh/year of steam and 450 GWh/year are produced. In China, more than ten CDQ facilities are installed. Their use allowed the reduction from 5.6 GJ/t-coke to 4.2 GJ/t-coke in 10 years. The blending with low-quality coal is 15% maximum in the wet system, and it arrives to 30% in the dry configuration. By converting coke ovens (50 t/h capacity) from wet to dry, a reduction of over 130,000 t/year of CO2 can be reached; this corresponds to 8% of net reduction of CO2 emissions in the atmosphere. It is estimated that from a conversion of the 300 Mt. of coke from wet to dry, coupled with an energy saving leading to a reduction of emissions of 600 gCO2/kWh, a global reduction potential of 25 Mt. is expected. The oven can be built with different chambers (normally maximum 3), and it has a cost around 70 million euro with a payback time of 3 years. Because one single-chamber CDQ results more efficient than small multiple chambers CDQ, almost all users choose a plant configuration with single-chamber CDQ. The Nippon Steel and Sumitomo Metal Corporation have developed the world’s largest single-chamber CDQ with 280 t/h of capacity. In the USA, a power generation plant connected with the oven (with 25 t/h capacity) allows to produce 15 MW of electricity with a total annual saving of nine million dollars of electricity and one million dollars of saved quenching water. Two or more quenching chambers are combined with waste heat boilers and charging cranes. Nitrogen and other inert gases are employed as circulation gases (at a temperature of 780
C) to cool the coke. The coke is charged at a temperature of 1050
C and exits at 150
C. The comparison with the traditional wet quenching route is described by the quality indexes listed in Table 2.5. In general, many advantages are presented in comparison with the traditional wet quenching system. The SO2 emissions are in the order of 20 mg/Nm3. A 200 t/h of capacity CDQ allows the generation of 36 MW of electric power saving 36 t/h of CO2. For a plant with an annual production of ten million tons of crude steel, 0.5 million t/h of CO2 can be reduced by power generation. In addition, dust emissions can be prevented during CDQ. Normally, 300–400 g/t-coke of dust are emitted from the wet quenching tower. The dust emission of CDQ is 100 times lower; this is also more efficient with respect to the Coke Stabilization Quenching (CSQ). CDQ improves the BF productivity thanks to the improved strength of coke and to the lower moisture. This leads to lower fuel consumption and CO2 emissions and to the increase of potential percentage of pulverized coal injection.

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Table 2.5 Quality indexes of coke produced trough wet or dry quenching Wet quenching 2–5 11 0.5 65 50

Water content (%) Ash content (%) Volatile content (%) Average particle size (mm) Porosity (%) Carbon in coal Carbon in chemical adsorption Carbon in COG Carbon in BFG 1.23kg 0.66kg Carbon in LDG Carbon in CO2

7.76kg 3.35kg

0.83kg

32.28kg

COG

78.84kg 0.43kg

36.35kg

BFG 174.94kg

88.98kg

0.73kg

Carbonates 14.43 kg

8.17kg

LDG

43.13kg

6.9kg

8.56kg

10.02kg

15.68kg

8.5kg

sinter

cast

0.43kg

355.91kg

coke 14.46kg

50.41kg

-54.07kg

9.83kg

167.74kg

24.5kg

roll

27.58kg

26.39kg

carbonating

25.43kg

pellet

CCPP

BOF

62.64kg

Carbon arising by electricity 31.54 kg

7.34kg

86.43kg

17.16kg

7.29kg

15.39kg

BF 107.42kg

40.34kg

Coal 420.91 kg Blind coal 121.88 kg

18.12kg

422.84kg

3.3kg

CDQ

Dry quenching 0.1–0.3 11 0.4 55 45

Byproduct -54.07kg

Carbon in chemical products 19.72kg

Slag 7.63kg

CO2 474.87kg

Carbon in steel 5.58kg

As araginite calcium carbonate 53.41kg

Fig. 2.8 Carbon flow analyses (Zhang et al. 2013)

Coke dry quenching (CDQ), combined cycle power plant (CCPP), and CO2 capture by slag carbonization (CCSC) and CCSC allow to reduce the net carbon emissions by 56.18, 134.43, and 222.89 kgCO2 per ton crude steel inside the industrial parks, respectively, including both direct and indirect emissions (Fig. 2.8). A CDQ system with a capacity of two million tons of coke costs 100 million euro, depending on the energy prices the payback time is estimated in 3 years. Steam generation is directly depending on hot coke charged into CDQ chamber, and cold coke discharged from the CDQ. The operation of CDQ should be done by complete combustion operation; circulation gas composition for complete combustion operation is H2, 0.1% (Vol. %); CO, 0~0.3% (Vol. %); and O2, almost 0% (Vol. %). Cooled coke temperature should be operated below 200
C. There are two methods to adjust cooled coke temperature: keep the coke process volume constant,

2.4 Use of Coke Oven Gas

57

and adjust with cooling gas volume; keep the cooling gas volume constant, and adjust with coke process volume (Rudramuni and Nataraj 2016). When circulation gas volume is changed, the changed volume shall be within 3000 Nm3/h with one action excessive change in circulating gas volume brings about a large temperature fluctuation at S/F and gives damage to brick, as well as increasing the amount of flying dust to cause the wear of boiler. Coke oven can increase the amount of steam generation of 59.3 t/h to 70.2 t/h by the injection of 13,000 Nm3/h BFG at a coke discharge rate of 94 t/h, and power generation rate increased from 65 to 70 MW. Uniform quenching of coke takes place, and the recovered more heat efficiency takes place which can send to waste heat boiler once double flue gas quenching is employed (Aravinda and Kumarappa 2014). Due to the fact that the pressure of quenching gas in the lower cavity of the collector is equalized, the proposed apparatus ensures that the quenching gas flow rate through all the peripheral gas withdrawal conduits is practically equal, which provides for a uniform cooling of the whole mass of the coke being treated. This permits the consumption of quenching gas to be reduced and the efficiency of the process to be raised. The velocity near sloping flue in single dry quenching (SDQ) is 2.83 m/s, whereas in double dry quenching (DDQ), the velocity is around 4.75 m/s. The exit velocity at the common withdrawal conduit is not uniform, whereas in DDQ, the uniform velocity is confirmed. The more recirculation takes place in DDQ as a result, there will still more uniform quenching of coke. The highest velocity in SDQ is 5.67 m/s, whereas in DDQ, the highest velocity is around 10.62 m/s. In general (as discussed in the following and also in Chaps. 3 and 4), an integrated ironmaking plant main installations are blast furnace, coking plant, sintering, and/or pelletizing plant. Both coking plant and blast furnace generate significant amount of extra heat in the form of COG and blast furnace top gas. Both gases are secondary fuels and are utilized in most cases internally (within ironmaking and steelmaking plants) for providing energy sources in other unit operations. Energy recovery of the whole ironmaking plant is illustrated in Fig. 2.9. The COG from coking plant is used as gaseous fuel in the sintering plants, in the rolling mill furnaces, and sometimes in the power station. All these issues will be largely discussed in the following paragraphs.

2.4

Use of Coke Oven Gas

Coke oven gas (COG) is a point of high interest to enhance energy efficiency and reduce GHG emissions in the steel industry (Uribe-Soto et al. 2017). COG is a by-product of coal carbonization to coke which is cogenerated in the coking process. The COG composition is very complex. After leaving the coke oven, firstly, the gas is cooled down to separate tars to subsequently undergo different scrubbing processes to eliminate NH3, H2S, and BTX (Diemer et al. 2004). After these conditioning stages, cold COG comprises H2 (~55–60%), CH4 (~23–27%), CO

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Fig. 2.9 Energy recovery and use in the integrated steel plant

(~5–8%), N2 (~3–6%), and CO2 (less than 2%) along with other hydrocarbons in small proportions. The main goal of the energy saving in steelmaking is the optimal distribution and utilization of process gases such as coke oven gas (COG). As previously shown, COG is a valuable gas due to its high hydrogen and methane contents. As previously mentioned, more than 30% of the coil used to produce the coke is eliminated as gas. The concept is shown through Fig. 2.10. This shows how COG (for 1.4 Mt. of production per year) plays a fundamental role in the energy balance of an integrated steel plant. Its properties are listed in Table 2.6. The COG composition after leaving the coke oven (Table 2.7). Raw COG has a relatively high calorific value (CV) due to the presence of hydrogen, methane, carbon monoxide, and hydrocarbons; in addition, it contains economically valuable by-products, such as tar and light oils. After cleaning through the separation from oil, sulfurs, and tail, it is collected as coke oven gas (Meng et al. 2018). Various technologies have been developed to treat air pollutants. Wet flue gas desulfurization (WFGD) is the dominant technology for SO2 reduction. Meanwhile, selective catalytic reduction (SCR) is a mature and efficient method for denitrification from coal-fired power plants with a flue gas temperature of over 300
C.

2.4 Use of Coke Oven Gas

59

Fig. 2.10 Energy balance for a coke plant (European IPPC Bureau 2011, values in MJ/t coke) Table 2.6 Raw COG yield COG Yield (m3/t coal) Density (kg/m3) CV (MJ/m3)

Properties 280–450 0.42–0.65 17.4–20

Table 2.7 Raw COG composition Compound H2 CH4 CxHy CO CO2

Composition (vol.%) 39–65 20–42 2–8.5 4–7 1–3

However, drawbacks, such as a narrow temperature range and ammonia escape, remain. For example, coke oven flue gas exhibits a low temperature ( 1) as it prevents catalyst deactivation caused by carbon deposits on the catalyst. Excess steam is used to prevent the formation of coke, while additional heat is needed, so a lower H2O/CH4 ratio is desired to improve the energy efficiency of the process. In the case of the steam reforming of COG, this ratio may differ from that used in the steam reforming of methane, as the presence of H2, CO2, and CO in COG influences the equilibriums of the different reactions involved in the process. The thermodynamically permissible H2O/CH4 value should be in 1.1–1.3 range, at temperatures between 950 and 1000
C. The use of hot COG (no conditioning processes prior to leaving the coke oven) in the steam reforming process has been widely proposed to reform methane as well as the tarry components, taking advantage of the high temperatures of the gas to promote the desired reactions. Giving that hot COG contains ca. 10–15% steam,

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

the energy efficiency and cost of the process can be improved as lower quantities of steam need to be injected in the system. Tars usually account for 30 wt.% of hot COG, the main components being naphthalene, benzene, pyrene, and toluene. These species compete with each other, and with methane in steam reforming processes, especially naphthalene (the only component which reacts at temperatures below 750
C, while at higher temperatures, the other compounds react once naphthalene has been completely converted). Steam reforming of hot COG can be carried out in the presence or absence of catalysts, but the presence of a catalyst significantly improves the obtained results. The main disadvantage of using hot COG is related to the lower ratio H/C obtained as compared to conditioned COG which in turn leads to a very important production of carbonaceous deposits of different nature in the system (i.e., well-ordered graphite, non-oriented carbon forms, carbon filaments, and metal carbides) depending on the working temperatures. The deactivation rate of the catalyst is increased by the generation of carbonaceous deposits. The reduction of such deactivation rate can be accelerated by the presence of hydrogen, an adequate load of active metal, as well as an appropriate steam/carbon ratio. The presence of H2S is also highly undesirable due to its poisoning effects on catalysts (e.g., Ni), but generally, this deactivation effect is low, and the catalyst can easily be regenerated. Remarkably, this technology can potentially generate 3–5 times more H2 to that of the COG before undergoing the reforming process, making the steam reforming of hot COG one of the most promising alternatives for H2 production from COG. Many available reports indicate that the hydrogen can be produced by combining steam reforming and partial oxidation of hot COG, reducing by 30% production costs as compared to PSA-mediated direct hydrogen separation from the COG. When the reforming gas is used for indirect reduction (IR) of iron oxides in blast furnaces (BFs), carbon dioxide emissions can be lessened. COG possesses the potential as a reducing agent in BFs. The reactions of IR from the two reforming gases are almost identical, implying that the operation of SR from COG for producing hydrogen or syngas and reducing iron oxides in BFs is flexible (Chen et al. 2012). With 55% hydrogen content by volume, this amount of COG could provide a significant hydrogen source. The large amount of hydrogen in COG can be efficiently separated using the PSA technology. Installing a PSA unit to recover hydrogen from COG for onsite use or separate sale is highly recommended in the steel industry (Fig. 2.12). The high hydrogen content of COG also makes COG an ideal feedstock for syngas and methanol production. The installation of such COG utilization units within a coking facility can promote the self-sufficiency and environmental friendliness of the steel industry. The data belonging to US plant studies show the potential of hydrogen production from COG by employing PSA facilities (Joseck et al. 2008) are listed in Tables 2.9 and 2.10.

2.4 Use of Coke Oven Gas

65

Fig. 2.12 Separation of coke oven gas by employing a PSA System (Joseck et al. 2008) Table 2.9 Production ratios of coke vs. coal, COG vs. coke, H2 vs. COG Production Coke/coal (t/t) COG/coke (scf/t) H2/COG (g/scf)

Ratio 0.72 17.88 1.23

Table 2.10 Potential annual H2 production from COG in the US Year 2004 2005

Coke production (Mt) 16.9 16.7

COG (billion scf) 302.2 298.6

H2 from COG 370.482 366.097

The coal char catalyst is a highly promising catalyst for the CO2 reforming of methane to syngas. The CO/H2 ratio in the CO2 reforming of methane can be adjusted by means of adjusting by feed ratio of CO2/CH4, which range from 0.2 to 1.1. The modified coal char catalyst has more active than coal char catalyst I and II in CO2 reforming of CH4. For the modified coal char catalyst, the conversion of methane can be divided into two stages. In the first stage, with the reaction time extend, the conversion of CH4 gradually decreases. In the second stage, the conversion of methane maintains nearly constant. The conversion of CO2 decreases slightly during the overall CH4- CO2 reforming reactions (Zhang et al. 2010). Studies from Li et al. (2018) evaluated the environmental and economic performance of COG-based methanol production and compared these with coal and natural gas routes. In COG route, methanol production stage presents the highest contribution, while coke production stage is responsible for less than 10% due to mass allocation among the six products in coking plant. Compared to coal route,

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

COG route shows better environment performance in all the selected categories. The methanol production cost of COG route is 160.89–247.75 $/t methanol, which is competitive with coal and natural gas routes thanks to the cheaper feedstock. Sensitivity analysis indicates that electricity and medium pressure steam consumption are the key contributors to the majority of environmental categories in COG route. Supplying MP steam from CDQ system is proposed to reduce the environmental impacts of COG route. The work has demonstrated the favorable environmental and economic benefits of COG-based methanol production for coke enterprises. COG from an existing coking facility can be used as an alternative reducing agent to natural gas in the DRI process for steel production (Fig. 2.13). Alternatively, purified COG can be converted into a reformed gas under steam reforming, and the resulting gas can produce DRI. A mixture of recycled gas from the direct reduction plant and COG is heated in a reducing gas heater and introduced as the reducing gas to the reduction zone of the DRI reactor. The process is conducted at a counter flow, with an introduction of oxygen and hot tar gas inducing partial oxidation to produce DRI. CH4 from COG is converted to hydrogen and carbon monoxide at the bottom of the reduction zone. Gas leaving the DRI reactor is cleaned via CO2 removal to produce tail gas. The resulting DRI may be used in the BF, in the converter, or in the EAF (Ahrendt and Beggs 1981). The coke oven gas (COG)-to-natural gas (CGtNG) is a promising process of chemical industry. However, the CGtNG suffers from low hydrogen utilization efficiency and natural gas capacity due to the high ratio of hydrogen to carbon of the COG. The CO2 derived from chemical-looping hydrogen process can be an effective carbon source to optimize syngas composition for high efficient natural gas production. Therefore, a novel process of COG chemical-looping hydrogenassisted COG-to-natural gas (CGCLH-CGtNG) was developed (Xiang et al. 2018). Results show that the novel process could solve the issues of CO2 utilization in the chemical-looping hydrogen process and low natural gas production in the CGtNG. At the cost of additional 4.36 t/h COG consumption, the novel process produce about 19% more natural gas and additional 1.39 t/h hydrogen compared with the conventional CGtNG process. The corresponding hydrogen utilization and exergy efficiencies of the novel process are increased from 61.1% to 78.5% in the CGtNG to 82.4% and 87.6% through intensive mass and energy integration, respectively. Fig. 2.13 Integrated COG-DRI plant (Johansson and Soderstrom 2011)

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67

An interesting frontier solution proposes a novel co-feed process of coke oven gas-assisted coal to olefins (GaCTO). In the GaCTO, CH4 from COG is sent to a dry methane reforming (DMR) unit and a steam methane reforming (SMR) unit, for the purpose of CO2 mitigation and H/C ratio increase (Fig. 2.14). The schematic diagram of the proposed solution is shown in Fig. 2.15.

Fig. 2.14 Process flow diagram of syngas processing units of GaCTO (Man et al. 2014)

Fig. 2.15 Schematic diagram of GaCTO process

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CH4/CO2 reforming (dry methane reforming, DMR). Desulfurized COG is separated into H2 and CH4. Part of CH4 is sent to the DMR unit to react with the CO2 from coal gasification. The main coal gasification reactions are: – Reaction with oxygen:

C þ O2 ¼ CO2 þ 393kJ=mol 2C þ O2 ¼ 2CO þ 111kJ=mol C þ CO2 ¼ 2CO  171kJ=mol

– Reaction with steam: C þ H2 O ¼ CO2 þ H2  131kJ=mol C þ 2H2 O ¼ CO2 þ 2H2  76kJ=mol CO þ H2 O ¼ CO2 þ H2 þ 41kJ=mol – Reaction with hydrogen: C þ 2H2 ¼ CH4 þ 75kJ=mol CO þ 3H2 ¼ CH4 þ H2 O þ 206kJ=mol DMR unit produces clean syngas and reduces CO2 emission. The rest of CH4 from COG is sent to SMR unit to react with steam and generate syngas with H/C ratio of 3.5–4. As a result, the syngas with suitable H/C ratio for methanol synthesis could be obtained by adjusting the proportion of DMR syngas, SMR syngas, coal gasification syngas, and hydrogen from COG. DMR is an effective way to recycle CO2 from coal gasification process. The major advantages of the proposed GaCTO process are indicated as the GaCTO process ensures the effective utilization of coal resources and reduction of energy waste thanks to co-feed of coal and COG. Moreover, at the same time, CO2 emission is considerably reduced (Table 2.11). The GaCTO uses the latent heat released from coal gasification to supply energy for CH4 reforming. It allows recycling the physical energy of coal to achieve the higher value of chemical energy of syngas. The main employed or explored COG-related technologies are summarized in Table 2.12. These alternatives can be divided in three main blocks: hydrogen separation, synthesis gas production, and other technologies. Hydrogen separation has a huge potential since COG is a H2-rich gas, which would allow a “green” production of H2, since, instead of the pollution and GHG emission characteristic of conventional H2 production technologies, using COG as H2 source would eliminate the pollution

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Table 2.11 Consumption, product output, and energy efficiency of CTO and GaCTO Item Consumption Coal (t/t olefins) COG (m3/t olefins) Water (t/t olefins) Electricity (kWh/t olefins) Steam (MJ/t olefins) Total energy input (MJ) Product output Ethylene (t/t olefins) Propylene (t/t olefins) C4 (t/t olefins) CO2 emissions (t/t olefins) Olefins energy (MJ) Energy efficiency (%)

CTO

GaCTO

Lower heating value

GaCTO/OTO

4.1 N/A 30 1670 8750 130,050

0.97 3280 48 2060 11,410 103,200

28.1 MJ/t 17.4 MJ/m3 – 3.6 MJ/kWh – –

– – 1.6 1.23 1.3 0.79

0.45 0.45 0.1 5.79 47,000 36.1

0.45 0.45 0.1 0.3 47,000 46.5

47,000 MJ/t 47,000 MJ/t – – – –

– – 0.05 – – 1.28

resulting from its combustion. Hydrogen separation has been one of the most studied alternatives for using the COG surplus. Moreover, some of these technologies, such as PSA and membrane separation, are already in use in other industrial processes, so their implantation in coking plants would not present any special difficulty. However, the H2 recovery from COG surplus has an important drawback that needs to be overcome. With these technologies, no advantage is taken of the other gases, especially those containing carbon, i.e., CH4, CO, CO2, and light hydrocarbons. For this reason, H2 separation needs to be combined with other technologies in order to exploit all of the components of the COG surplus. For syngas production, COG is upgraded by means of the different technologies currently available (steam reforming, dry reforming, and partial oxidation), making these processes interesting alternatives for H2 amplification of the original COG or for the production of chemicals, thereby supplanting conventional production from natural gas or petroleum. Synthesis gas production from COG surplus seems to be the most interesting alternative for the use of this interesting source. The large number of processes available (steam reforming, dry reforming, partial oxidation) allows obtaining a wide variety of H2/CO ratios (from 2 in dry reforming to nearly 5 in steam reforming), making the COG alternative highly versatile for obtaining different final chemical products. Moreover, even for the production of H2, COG is a more interesting alternative than H2 separation, since the hydrocarbons (CH4 and CnHm) are also used. However, reforming processes are energy-intense technologies, so their industrial implantation needs to study in depth the energetic requirements and benefits. Besides, the construction of reforming plants requires a high level of capital investments. Special attention has been paid to methanol production, due to the interest of this product as a gasoline substitute or H2 carrier. In this case, dry reforming of COG seems to be the preferable technology, since it will

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Table 2.12 Advantages and disadvantages of the different technologies for COG use (Bermúdez et al. 2013) Process Hydrogen separation

Technology PSA

 Membranes

 Hydrates

Syngas production

 Cryogenic Steam reforming

Dry reforming

Partial oxidation

Other technologies

Chemicallooping combination

Advantages  Developed  Industrial implemented  Low costs  High H2 purity  Developed  Industrialized  Easy operation  Low costs  Low energy consumption  Mild operating conditions  No needing of light hydrocarbons removal  High purity H2  Low CO2 emissions  Sulfur elimination  Well developed  High H2/CO ratio  Possible use of hot COG  Low energy needing  CO2 reduction  H2S elimination  High energy efficiency  High reaction rates  Use of hot COG  CO2 capture  Optimal use of COG

Disadvantages  Needing of additional technologies for COG surplus  Previous separation of tar, BTX, H2S, NH3  H2 purity by 95%

 Under development  Low H2 concentration  Additives needing  Under development  High energy consumption  High costs  High H2O/CH4 ratio leading to energy inefficiency  Mild pressures  Complete elimination of BTX and NH3 needing  High temperatures  High costs  Low operation margin in the O2/CH4 ratio  Under development

require fewer process units than the other thermal upgrading technologies. In the particular case of methanol, it is already industrially implanted and employed. CO2 reforming or dry reforming of methane has been widely proposed as an alternative process to steam reforming of methane. The increasing interest in this process is based on the lower energy requirements compared to steam reforming together with the consumption of two commonly extended greenhouse gases such as CH4 and CO2, with an eventual generation of highly valuable products. CO2 reforming also allows the production of a low H2/CO ratio syngas (theoretically 1/1, although the presence of side reactions, such as reverse WGS slightly reduces it), which is suitable for the production of higher hydrocarbons and oxygenated derivatives. As in the case of steam reforming, dry reforming must be carried out in the presence of a catalyst. Once again, Ni has been the most commonly metal utilized as catalyst in dry reforming chemistries, but the drawback to this process

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is the intense formation of carbonaceous deposits which leads to a rapid catalyst deactivation. The SPARG process could be especially interesting in the application of dry reforming methodologies to COG. This technology is based on the addition of H2S to the process stream which leads to a partial poisoning of the catalyst but prevents at the same time the formation of carbonaceous deposits in the active centers of the catalyst, keeping high conversions of CH4 and CO2 in the systems. In this way, the previous scrubbing step required to remove H2S from COG can be eliminated in the conditioning stages, improving the economics of COG valorization. Until now, the application of dry reforming to COG has received less attention than steam reforming or partial oxidation. Results reported are encouraging, pointing to a potentially optimum way to transform COG into syngas with a close to optimum H2/CO ¼ 2 ratio to be employed in Fischer–Tropsch (FT) synthesis of chemicals as well as in methanol production. Comparatively, steam reforming of COG gives rise to H2/CO ratios that are considerably higher than 3 (ratio obtained with methane). In the case of partial oxidation, the H2/CO ratio obtained with methane is ca. 2, so that an expected H2/CO ratio of 2.5–3 will be likely to be the case in COG partial oxidation due to its hydrogen content. Side reactions may also influence the theoretical results in COG dry reforming as observed in other processes. In this case, the reverse WGS is the most critical. It is a reaction leading to two different alternatives: or a direct dry reforming where methane is decomposed into hydrogen and carbon and then carbon is gasified to CO through the Boudouard equilibrium; or a reverse WGS followed by steam reforming (SR). The large amount of hydrogen contained in COG promotes the RWGS reaction, producing water which subsequently reacts with methane (steam reforming) to generate CO and H2. The direct dry reforming generates carbon as by-product as CO2 is not generally able to convert all carbon produced to CO, resulting in the deactivation of the catalyst. Comparatively, the RWGS+SR pathway generates water as by-product which influences H2 selectivity (reduced), and consequently, H2/CO ratios differ from 2. Three different types of catalysts have been studied for dry reforming processes. These include carbonaceous materials, Ni-supported catalysts, and mixtures of both catalysts. The most interesting results have been obtained with mixtures of activated carbon and Ni/Al2O3 catalysts, since these have been reported to have a synergetic effect, which was previously observed in the dry reforming of methane. Interestingly, this synergism that leads to higher activities and selectivities was more noticeable in COG dry reforming, with catalysts also being more stable (in terms of BET surface area reduction) and generating less water, CO was found to have a negative influence on such synergetic effect, pointing out that these catalysts will be more efficient in processing COG of low CO content. The partial oxidation of methane is a mildly exothermic reaction which yields a syngas with an intermediate H2/CO ratio between those obtained with steam and dry reforming. In this case, side reactions may also affect the process, changing the H2/CO ratio and reducing its selectivity and efficiency.

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The partial oxidation of methane can be carried out in two different ways: non-catalytic and catalytic. The non-catalytic method is an established industrial process which operates at high temperatures (>1100
C) and mild pressures (50–70 atm, mainly due to the high-pressure downstream process, as in the case of steam reforming) and which requires very complex equipment. This normally makes the process even less energy efficient to that of methane steam reforming. The catalytic method has a long history (like steam reforming) but has attracted significantly less attention until the past decade. However, its importance will most probably increase during the next few years due to several advantages: – It is a mildly exothermic process. This will increase the energetic efficiency of the process in addition to the lower operating temperatures needed due to the use of catalyst (750–1000
C). This is probably the most important advantage of the partial oxidation of methane. – The final H2/CO ratio is generally 2, which is required for methanol production and FT processes. However, this advantage disappears in COG valorization practices if hydrogen contained in COG is not previously removed (otherwise, the final H2/CO ratio will exceed 2, making it less suitable than in the case of the dry reforming for the synthesis of chemicals such us methanol or dimethyl ether. – Product gases have a very low CO2 concentration, which often needs to be removed prior to the use of syngas in downstream processes. – Reaction rates are higher compared to those of steam or dry reforming under otherwise identical operating conditions, giving rise to a faster process. Most research efforts in the field of partial oxidation have been focused on the development of appropriate catalysts for the process, which overcome drawbacks including carbon deposition or loss of active compound during the reaction. Three main types of catalysts have been proposed based on transition metals (nickel, cobalt, and iron) and noble metal-supported catalysts as well as transition metal carbide catalysts. Due to their lower price and wider availability, Ni, Co, and Fe have been the focus of most studies in spite of the improved resistance to deactivation of noble metal-supported catalysts. Nickel has been reported to be highly active and selective for syngas production, but it also efficiently catalyzes carbon formation (Khzouz et al. 2018). The use of this particular type of catalyst requires O2 excess working conditions to work with an excess of O2 to reduce carbon formation. Modification of the support has been reported to improve the stability of the catalyst, but its deactivation is unavoidable with time due to a reduction in the surface area of nickel and carbon deposition (Seo 2018). The addition of Co and Fe has been reported to enhance the resistance of the catalyst to deactivation (Argyle and Bartholomew 2015). Iron addition stabilizes nickel, as compared to a reduction in carbon formation strongly promoted by cobalt addition (which makes possible to work at lower temperatures in Co-promoted catalysts). Reports focusing on the application of partial oxidation to COG have been mostly catalytic, with only a few reports on non-catalyzed partial oxidation. A deep analysis of the influence of different reaction conditions on the final syngas produced using

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Ni/SiO2 catalysts indicated that oxygen was completely consumed at temperatures from 600 to 900
C, and H2 and CO selectivities increased (H2/CO ratio decreased) at increased temperatures. This behavior was claimed to be influenced by methane combustion at low temperatures, whereas partial oxidation processes prevailed at high temperatures. The influence of O2/CH4 ratio was also studied and shown to be of critical importance in the process. Conversion increased dramatically when O2/CH4 ratio was increased from 0.125 to 1.0 at a temperature of 750
C. Selectivities to H2 and CO decreased at O2/CH4 ratios higher than 0.5. It was suggested that these results were a consequence of the consumption of the surplus of oxygen in the complete oxidation of methane and/or the complete oxidation of the produced H2 and CO. An increase in space velocity favored the combustion of methane in detriment to partial oxidation. Therefore, the value of the space velocity was suggested to play an important role in order to be able to treat as much gas as possible while avoiding high rates of methane combustion, which will lead to a lower selectivity. One of the most important issues in the industrial implementation of partial oxidation technologies relates to its elevated cost (in both economic and energetic terms) to supply pure oxygen to carry out the reaction (Lulianelli et al. 2014). In fact, as much as 40% of the expenses of a partial oxidation plant come from oxygen production processes. To overcome this problem, the use of membrane reactors has become an attractive alternative to conventional technologies. In the particular case of COG partial oxidation, membrane reactors have been pretty much the only technology to be investigated in recent years. These reactors offer the possibility to feed air directly instead of the need for previous separation processes to feed pure oxygen. Inside the reactor, an oxygen permeable membrane exclusively allows oxygen to reach the catalyst, but not the other components present in the air. This technology has shown promising results to date, with yields, conversions, and selectivities being as high as those reported using the conventional technology. It can therefore be considered as a potential future alternative for syngas production from COG valorization (Cheng et al. 2011). The presence of other species different from methane influences the performance of the membrane in terms of stability and oxygen flux. Hydrogen is a particularly interesting compound which behaves as a “pseudo-catalyst” and favors the oxygen permeation through the membrane when BCFNO membranes (composed of Ba, Co, Fe, Nb, and O) are employed. These membranes also show excellent long-term stability. In the light of these premises, research into this type of membrane technologies and reactors for the partial oxidation of COG are likely to take over during the next few years. In fact, such technology has also been applied to hot COG, and results were even more interesting to those of cold preconditioned COG. Quantitative conversions could be achieved for heavy components (e.g., toluene) at methane conversions higher than 90%. Besides, by using dry reforming as the method for the production of synthesis gas, it will be possible to partially recycle the CO2 produced when methanol has been consumed. Moreover, the economic studies carried out on this matter suggest that it would be economically competitive with classical methanol

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synthesis processes. Even so, the complete process of methanol production will require a higher level of investment and more complex facilities. Another example is deeply described by Gong et al. (2017). First of all, iron-molybdenum hydrodesulphurization technology is employed for COG fine desulfurization. Sulfides are converted to H2S by hydrogenation over the iron-molybdenum catalyst under a high temperature (350–430
C). Then, H2S is removed by desulfurizer (Wang et al. 2013; Salkuyeh and Adams 2013). The purified COG is then treated into two different process: the CWOHS and the CWHS. In the CWOHS process, the purified is split into two parts, one is used for reforming and another for combustion. During CWHS, about 99.9% of hydrogen in COG is separated initially (the COG without H2 is named H2-free COG) and then is mixed with the reformed gas, and after that, the mixed gas is sent for methanol synthesis. The reformed syngas is compressed to 60 bars and then sent to the Lurgi shell and tube methanol synthesis reactor which is a well-developed technology and under operation in many plants (Xiang et al. 2015). Methanol steam is condensed and partly refluxed to the pressurized rectifying column, while the other part is cooled and then introduced to the methanol tank. The heavy components (some salts, methanol, and water) in the bottom of the pressurized rectifying column are introduced to the atmospheric rectifying column, and then the fine methanol can be obtained from the top of the column. A part of the CO2 is recycled to reforming reactor, and another part is sent to the coke oven combustor. The scheme of the two processes with the indication of the equivalent carbon balance is shown in Fig. 2.16; the energy balance is shown in Fig. 2.17. The process performances are analyzed and compared with those belonging to traditional conventional COG to methanol process without supplementary carbon (CTMWOSC), the conventional COG to methanol process with supplementary carbon (CTMWSC) where the gas making subsystem is adopted to produce carbon-rich gas, and the COG to methanol process with CO2 recycle using POR technology for COG and CO2 conversion (CTMCR); these results (coupled with the investment costs) are listed in Table 2.13. Coke oven gas could be made of better use when it is reformed to produce highervalued CO and H2 (Duan et al. 2016). There are three common approaches to convert methane from COG to syngas: steam methane reforming (SMR), dry methane reforming (DMR), and methane partial oxidation (MPO). Three fundamental reactions are shown: SMR : CH4 þ H2 ¼ CO þ 3H2 ΔH ¼ 247:3kj=mol DMR : CH4 þ CO2 ¼ 2CO þ 2H2 ΔH ¼ 206:3kj=mol MPO : CH4 þ 0:5O2 ¼ CO þ 2H2 ΔH ¼ 35:6kj=mol SMR and DMR are endothermic reactions with high energy consumption, while MPO is an exothermic reaction. If the three reactions could be coupled, self-heating would be good for energy saving. Quian et al. (2015) proposed an integrated coke oven gas tri-reforming and coal gasification to methanol process, in which

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Fig. 2.16 Schematic of the CWOHS and CWHS processes (units in kmol-C/h)

the tri-reforming unit makes the CH4 of COG react with CO2 of coal gasification for the purpose of CO2 mitigation and efficiency improvement. A tri-reforming of methane (TRM) to couple SMR, DMR, and MPO reaction together in a single reactor is proposed and utilized to produce chemical in the industrial scale. The novel process takes advantages of hydrogen-rich COG to adjust H/C ratio of

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Fig. 2.17 Energy balance of the CWOHS and CWHS processes (units in MW)

the syngas to a suitable range, with appropriate energy consumption, for better carbon utilization and less CO2 emissions. The integrated process takes advantage of the wasted COG in China’s coke industry, what allows to optimize the allocation of resources and enhances the economic value of COG and CTM processes. Two schemes of the integrated process are analyzed. (1) For integration of existing industrial scale of coking plant and coal gasification plant, the scale ratio of coal

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Table 2.13 Performances of the different CTM processes Investment Total investment (M$) O&M cost (M$/year) Labor number COG cost (M$/year) Electricity cost (M$/year) Consumption Steam (t/t methanol) Electricity (kWh/t methanol) Oxygen (m3/t methanol) COG (m3/t methanol) Performance Methanol production (104t/year) CO2 emissions (t/t methanol) Energy efficiency (%) Exergy efficiency (%) Methanol cost ($/t) Internal rate of return (%)

CTMWOSC

CTMWSC

CTMCR

CWOHS

CWHS

80 3.2 300 25.4 12.9

120.6 4.8 340 25.4 13.6

103.2 4.1 320 27.9 16.9

116.3 4.65 320 27.9 27.3

99.6 3.98 330 27.9 18.5

Bal. 620 385 2200

Bal. 651 470 1700

Bal. 812 1513 1600

Bal. 937.7 1493 1449

Bal. 629.8 1483 1444

18

24

24

26.5

26.6

1.96 50.1 57.8 323 20.5

2.2 54.4 61.6 292.6 25.2

0.9–1.64 59–5 68.9 272 29.1

0.7–1.56 64.9 71 286.1 29.3

0.69–1.32 67.7 73.9 240.5 35.1

coking to coal gasification is designed as 3. The carbon utilization efficiency and the energy efficiency of the integrated process are 45% and 62.4%, which increase by 4.3% and 11.4% when compared to conventional CTM process. (2) For a new planning of industrial park or an integrated project, the scale ratio of coal coking to coal gasification can be designed as 7, and the WGS unit could be canceled in the integrated process. The carbon utilization efficiency and the energy efficiency of the integrated process are 55.2% and 67.8%, which increase by 14.5% and 16.8% when compared to conventional CTM process. In the Hydrogen Energy California (HECA) Facility Process (Fig. 2.18), a simplified gas cleaning is obtained with production of syngas and Fischer-Tropschfuels or methanol (Delasalle 2019). The detailed GHG generation in methanol production process is discussed in Qin et al. (2016). Hierarchical attribution management provides a classified method to identify the related direct and indirect emissions. The results show that the raw coal demanded for the methanol plant with an annual production of 0.6 million tons level is 2.074 t coal/t methanol and the life cycle carbon footprint is 2.971 tCO2e/t methanol. The hierarchical attribution management shows that methanol production is the largest contributor in life cycle emission with a share of 92.86%, followed by coal mining process with 4.34%. In methanol production process, water-gas shift unit and gasification unit generate the most of greenhouse gas, while methanol synthesis unit possesses the potential for CO2 utilization. Furthermore, a global sensitivity analysis has been performed to discuss the influence of four key

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Fig. 2.18 Hydrogen Energy California (HECA) Facility Process

parameters on life cycle carbon emission, including coal mining emission factor, coal transport mode, the ratio of syngas into WGS, and electricity emission factor. Results show that electricity emission factor with a sensitivity factor of 189.11 is the most extensive influence factor due to its widest application. Thus, it is suggested that all companies should take measures to enhance the operating efficiency of electrical equipment and reduce the indirect emission caused by electricity consumption. In the technological routing of methanol production, the results show that the ratio of syngas into WGS has little effect on life cycle emission. But it obviously reduces the carbon footprint due to the enhanced yield of methanol product. Interestingly, there are other emerging technologies that could become important alternatives in the near future. For example, the chemical-looping combustion (CLC) of COG, with the objective to improve combustion efficiency and facilitating the capture of the CO2 produced in the system, has been proposed. This technology is an elegant and energy-efficient method to capture CO2 from fuel combustion. It consists of two reactors and a circulating metal oxide that works as oxygen carrier (Wang et al. 2010). The metal oxide is reduced in the fuel reactor and then circulates to the air reactor where it is oxidized to its initial state. In this process, H2O and CO2 are the only combustion products, and CO2 is easier to capture as these products are not diluted with N2 from air. Different oxygen carriers were studied, the best results being obtained with that comprising 45% of Fe2O3, 15% of CuO, and 40% of MgAl2O4. This carrier showed a high and stable activity over 15 reductionoxidation cycles and achieved a maximum fuel conversion of 92%.

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Other systems proposed during recent years are based on the combination of more than one technology. Single technologies will not be able to achieve an optimal utilization of COG. However, combinations of such systems could possibly produce the needed synergy to improve single technologies. A system in which PSA-mediated separation of hydrogen was combined with subsequent thermal upgrading of COG to produce syngas (and more H2) was recently proposed by Wang and Wang (2012). This study also included the necessary CO2 adsorption technology to improve hydrogen production. Such combination led to an H2 production increase of about 9%. Comparatively, Jin et al. (2009) proposed a new kind of multifunctional energy system, which can utilize COG and coal more effectively through the synthetic utilization of COG and coal by the coal-fired coke oven. With the same inputs of COG and coal, the new system provided about 65% hydrogen more than that of the reference systems, when almost the same quantity of coking heat and power was generated. Based on the integration of chemical processes and the power generation system, the fuel and thermal energy were utilized efficiently from the viewpoint of the whole system. The graphical exergy analyses EUD methodology revealed that the COG and coal were utilized synthetically through the coal-fired coke oven. The new method allows for the elimination of gasification processes. Compared with the conventional methods, the exergy destruction of gasification, which accounts for 6.1% corresponding to the input exergy of the system, is avoided. The exergy destructions for heat exchangers were decreased by 30%, which accounts for 1.8% corresponding to the input exergy of the system. The proposed MES system provides a new method to utilize coal and COG synthetically, which does not only simplify the system and decrease the investment but also improves the thermal efficiency and reduces CO2 emission. Furthermore, it will provide a promising option for sustainable energy systems. In order to gain the same quantity of coke, hydrogen, and power as the proposed system, the conventional methods discharge about 4.39  106 tons of CO2 equivalents. However, the proposed MES system only discharges about 1.16  106 tons of CO2. Therefore, the CO2 emission in the proposed system will be reduced by 3.23  106 tons per year as compared with that in the conventional methods with the same outputs, which is shown in Table 2.14.

2.5

Coke Making Control Systems

Worldwide steel makers focused on the reduction of fugitive emission during charging of coal into the oven and pushing the hot coke. The gas evolved during charging contains the higher level of toxicity which is an adverse impact on human health. Efforts have been made over the years to reduce this emission level through installing pollution control measures and technological change, particularly in coke making operation (Tiwari et al. 2017). The goals of coking process control are realizing steady heating of coke oven, enhancing production of coke oven and

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Table 2.14 CO2 emissions reduction in the MES system (COG discharged after combustion)

MES system Conventional system Coke oven COG discharge Power generation Hydrogen product CO2 emissions reduction

CO2 emission (104 tons) 116 439(272) 29 231(35) 136 72 323(156)

quality of coke, reducing energy consumption and prolonging coke oven service life, and decreasing environment pollution in the course of coking production. Automation and control systems allow to precisely govern the coke battery heating. The intelligent control of flue temperature is important to stabilize furnace temperature, improve coke quality, reduce gas consumption, reduce the workers labor intensity, and extend the service life of coke oven (Poraj et al. 2016). All the process data are collected from earlier monitoring system in order to optimize the overall model calculations (Fig. 2.19). So, instead of conventional constant heating, the optimized programmed heating of the charge allows to reduce the fuel gas consumption. The optimization of the heating parameters through the fuel injection control results also in the improvement of the coke quality. The system allows a reduction of fuel consumption of 10% (around 0.17 GJ/t coke) with an indirect reduction of the CO2 emissions of 3.8 Kg/t coke. The modern advanced coke oven heating control systems all use the control method of combining feedback with feed-forward and control merged with management; use artificial intelligence, such as fuzzy control, expert system and neural networks, and so on; and adopt multilevel control system to reach a new level of coke oven computer control. It will be a main direction of coke oven automation control in the future. In recent years, in order to introduce, digest, and absorb the advanced technology of coking process management system, and realize the innovation of technology and management, it develops towards the direction of putting forward the concept and thoughts of integration control and management system of coke oven to realize the global optimization (Li et al. 2013). Integrated management and control system of coke oven is the integration of management system and control system of coke oven, and this system should have high level of automatic test, control, and management. A total frame of integrated management and control system of coke oven and logic relationship of every model are established. Intelligent control model of coke oven heating and actual application research are combined by using mathematic analysis, fuzzy control, linear programming, neural networks, and genetic algorithm. Some models suitable for integrated control and management system of coke oven are set up. The factor relationship fitting for automatic control and management of coke oven is determined through correlative parameters of temperature and flux of coke oven.

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Fig. 2.19 Coke temperature monitoring

The coke making process of the steel industry was modeled, and a computerbased control system was developed to help improve the process operation. Due to the complexity of the nature of the coal, which is the raw material used to make coke, the operations of the coke making process are presently based on the judgment of experienced operators and the use of the results of regression analyses. Consequently, there is high variation in the required production time of the coke, including an overlong cooking time, to guarantee a well-coked product. The latter results in excessive energy costs. In a study from Tang, a coking thermal model and a flue combustion model were integrated into an overall, multi-oven, computer simulation package. The coking times, energy costs, and flue temperature patterns generated from the package have been validated by comparison with data available from industrial measurements. A new heating pattern strategy that would reduce the required energy costs of the operation is proposed and demonstrated. This simulation package was also used as the real-plant example in a computer simulation used to design the adaptive, self-tuning controller proposed here. The pole placement, selftuning, adaptive control method was utilized to develop the controller which would be implemented by a computer in the plant. The simulation results obtained have demonstrated the effectiveness of this controller method in compensating for any uncertainties in the characteristics of the coal which was charged into the oven. Further applications of the simulation package to the industrial computer control of the coke plant were also investigated. An intelligent integrated hybrid optimization and control system for the temperature of a coke oven have been developed by Lei et al. (2008) based on the features of the combustion process. The framework of the control system consists of a decision layer, an optimization and control layer, and a process control layer.

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For the decision layer, the operating states of the combustion process were classified into several types to enable the control problem to be solved simply; and a two-stage decision method was devised to determine the operating state in real time. In the optimization and control layer, an on-line switching control strategy was employed to select a suitable controller for the current operating state. The temperature control system contains one control loop for temperature and one for gas flow rate and air suction power. In the temperature control loop, a multiple objective optimization method employs an adaptive genetic algorithm to optimize the controller parameters. In the other control loop, controllers for valve openings stabilize the gas and air fluxes. The results of actual runs show that the system stabilizes the oven temperature, improves the quality of coke, and reduces energy consumption. Nippon Steel has developed and put to practical use a heat-resistant diagnostic system that permits obtaining not only thermal images of the coking chamber walls by inserting a water-cooled probe into the chamber but also three-dimensional profiles of the chamber walls using laser metrology (Sugiura et al. 2010). Two-dimensional images of the chamber walls are obtained by moving the line CCD camera longitudinally. The irregularities of any damaged part are measured by projecting laser beams into the linear field of the camera obliquely from below. The laser beams on the images are observed as horizontal lines. If the chamber wall has irregularities, the laser beam fluctuates according to the principle of the light-section method. The diagnostic system has dramatically improved the level of diagnosis of damage to oven walls that was formerly dependent on visual inspection from the oven opening. The coke oven maintenance management employing the diagnostic system and a repair system developed at the same time has prolonged the service life of coke ovens.

2.6

Coal Stamp Charging Battery (CSCB)

The technique of charge preparation consists in preparing a cake with the coal blend in a metallic box and then charging it in the coke oven (Fig. 2.20). The higher charge density implies better coke quality when compared with conventional charging. So, depending on the situation, either better coke quality may be obtained or poorer coking coals may be included in the blend. The stamping process consists in general in introducing the coal blend previously ground at a specific size, within a steel box, as successive layers that are rammed mechanically. Additionally, vibration may be applied to facilitate the accommodation of the particles. Two aspects have to be taken into account: densification and mechanical properties. Densification is required by the coking process. The denser is the cake, the better is the coke quality, taking into account both cold mechanical strength and behavior at high temperature (Lesch 2016). Mechanical properties should be enough to support transport of the cake and charge into the oven. When the densification starts, coal particles yield under the stress applied by the stamping machine, filling the interstitial voids with smaller particles. The rearrangement of the particles is supported by the surface

2.6 Coal Stamp Charging Battery (CSCB)

83

Fig. 2.20 Coal stamp process

moisture, reducing the internal friction. With further strain, an elastic-plastic deformation of the particles takes place partly resulting in particle breakage and filling of small pores with the fragments. While the pore volume decreases, the pore saturation with water rises causing a damping effect. The aim of pre-carbonization technologies is to improve the bulk density of charged coal. The resultant proximity of adjacent coal particles during softening leads to stronger bonds between the coke cells, which improve the coke strength. The pre-carbonization technologies which are being practiced in different steel plants all over the world are selective crushing, preheating, briquette blending, and stamp charging. In briquette blending, tar/pitch is the binder for briquette forming, whereas in stamp charging, moisture acts as a binder (Nomura 2016). It is possible to compact the coal into stable briquettes with all the same dimensions through the stamp charging process. Coal is compacted by stamping, if the so-called stamp charging process applied. Stamp charging means coke production in conventional chamber ovens, where the coal blend is previously compacted to a so-called coal cake with slightly smaller dimensions than those of the oven and charged vertically standing into the oven on a coal cake charging plate from the battery ram side through the oven door. Compacting of the coal by pressing is practiced in case of the coke making with so-called heat recovery ovens (Buczynski et al. 2018). In this case, the oven charge is compacted to a coal cake with significantly lower height than of the oven and charged horizontally lying into the oven on a charging plate through the oven door. The stamped coal cake with dimensions of 0.5 m in width, 4–6 m in height, and 13–16 m in length and the pressed coal cake with typical dimensions of 3–4 m in width, 1 m in height, and 13–16 m in length are used in industrial coke making operations. Stamped and pressed coal cakes require over the cake volume uniform high density and mechanical stability. Besides the aspects of the coal selection, the efficiency of the process is mainly determined by the operating parameters compacting time and compacting energy for coal cake making. At the beginning of the densification process, the particulate material yields under the stress applied by the compacting equipment, thereby filling the interstitial voids of the particle

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system with smaller particles. The rearrangement of the particles is supported by the surface moisture which reduces the internal friction. With further strain, an elasticplastic deformation of the particles takes place partly resulting in particle breakage and filling of small pores with the fragments. While the pore volume decreases, the pore saturation with water rises causing a damping effect. Besides the influence of the capillary water on the densification process itself also the mechanical properties of the compact are determined by the surface water as it serves as a binding agent in the formation of adhesive forces. Within the systematic of process engineering, the stamp cake can be classed as so-called wet agglomerate which is characterized by the adhesive forces resulting from liquid bridges within the capillary pore system. The following objectives are relevant to the technical compacting process: the realization of a certain cake density, homogeneous within the cake volume, in combination with a maximum mass throughput taking account of the carbonization properties of the coal blend, the guarantee of a sufficient cake strength in terms of operating safety while charging the coal cake to the oven, and the achievement of short compacting time for increasing productivity. It is well known that the charged coal density has a fundamental effect on the coke quality (Rejdak and Vasiliewski 2015). Stamp charge coke making technology could be accumulated a good amount of high ash medium coking coal in coal blend as compared to other pre-carbonization technology which also helps for designing of cheaper coal blend to produce the quality of coke. The increase in coke strength due to compaction is allowed through grain size distribution control, moisture reduction, oil addition, and mechanical treatment such as briquetting and stamping (Indimath et al. 2018). In addition, the coal density strongly influences the coke plant productivity (Karcz and Strugala 2008; Czaplicki and Janusz 2012). This process allows to increase the material density up to 35% so increasing the oven productivity up to 15%. There are a few possibilities to increase the coal charge bulk density: adjusting the grain size distribution or moisture content (drying), oil addition, and mechanical treatment (e.g., partial briquetting or stamping). This technology also permits to use lower-quality coal to obtain the same productivity (Rejdak and Vasiliewski 2015). Coking of coal blends using high volatile coals with poor coking abilities to produce a high-quality coke for blast furnace application can be achieved by compacting the coal blend prior to the carbonization process. Here, densification up to a relative material density of 80%, i.e., a compact density around 1100 kg/m3, has proven to be advantageous. Coal is compacted by stamping, if the so-called stamp charging process applied. Compacting of the coal by pressing is used in case of the coke making with heat recovery ovens. Stamped and pressed coal cakes require over the cake volume uniform high density and mechanical stability. Besides the aspects of the coal selection, the efficiency of the process is mainly determined by the operating parameters compacting time and compacting energy for coal cake making and by the sufficient cake mechanical stability to ensure trouble-free charging the ovens. A stamp charging system allows for the increase in mechanical

2.6 Coal Stamp Charging Battery (CSCB)

85

strength of the coke with a particular beneficial effect on the abrasion index. In addition, weaker coals can be employed in the coking beds thanks to the adoption of this technological solution (Kuyumcu and Sander 2014). This solution leads to obtain a bulk density around 1100 kg/m3 (Fig. 2.21) that is over 30% higher with respect to the one obtained from the traditional top charged coke ovens (~1100 kg/m3). To maintain the operational efficiency, coke quality and productivity is a big challenge for coke makers in stamp-charged coke making technology unless all sets of machines are state-of-the-art automated function with high degree of maintainability. Stamp-charged technology provides scope for using inferior coals effectively without impairing the coke quality (Veit and D’Lima 2002). The coal blend quality and process control of coke making technologies are an important lever to produce quality coke with optimal cost. Apart from impacting cost, this improves the CO2 footprint. Heat recovery stamp-charged coke making technology was introduced in Tata Steel in 2008. This is the Asia’s single largest heat recovery coke plant with 1.6 million tons per annum (mtpa) of metallurgical coke production with 120 megawatt (MW) of electrical power by utilizing its sensible heat (Tiwari et al. 2010). The temperature of the crude COG entering the ascension pipes above the coke oven is ~650–1000
C, which is sufficiently high to allow recovery of its sensible heat. The recovered heat could be used on-site for preheating the coal or fuel gas or off-site as district heating. Heat recovery is rarely carried out since it poses both installation and operational problems relating to the high levels of tars and other by-product components condensing at the lower temperatures, leading to corrosion and clogging of the ductwork and their buildup on heat exchanger surfaces.

Fig. 2.21 Compressive strength as a function of the coal density

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Figure 2.22 clearly shows that stamp charging technology has higher bulk density (wet basis) with respect to other traditional technologies. By adopting CDQ facility, it is possible to reduce the coke oven battery emission further. The adopted facility also helps for improving the coke quality, i.e., coke CSR and M40. In this process, coke is free from surface pore due to aquatic gasification reaction and internal crack that may occur in wet quenching. Further improvement in productivity of blast furnace by reducing coke moisture and hence conservation of water apart from reduction in dust emission arising during wet quenching (Biswas et al. 2015). The influence of selected parameters (i.e., stamping energy, coal type, moisture content, and crushing fineness) on coal cake density and mechanical strength has been described by Rejdak and Vasiliewski (2015). Increase of stamping energy causes increase of density of coal cake. Increase in moisture content positively influences both wet and dry bulk density of coal cake. Changes of wet bulk density were from 6.9% to 9.5% (depending on the coal type). In the case of dry bulk density, the differences were lower (from 1.7% to 2.4%). Coal type has an impact on density of stamped cake. For constant stamping energy, the density of stamped cake is greater for higher-rank coals. The density of coal cake influences mechanical strength of stamped coal cake. The higher the density, the higher the strength of coal cake. There is an optimum level of moisture content in coal charge which provides maximum strength of cake. For the investigated samples, this level was 8.5–10%. Increase in crushing fineness reduces the coal cake density while mechanical strength is improved.

Fig. 2.22 Coal charge density in different coke making technologies (Tiwari et al. 2017)

2.8 Coal Moisture Control

2.7

87

High-Pressure Ammonia Liquor Aspiration System (HPALA)

The high-pressure ammonia liquor aspiration system (HPALA) is effective for controlling charging emissions in coke oven batteries. In this system, the ammoniacal liquor, which is a by-product, is pressurized to about 35–40 Kg/Sq cm and injected through special nozzles provided in the goose neck at the time of charging. This creates sufficient suction inside the oven thereby retaining the pollutants from being released to the atmosphere. The system consists of high-pressure multistage booster pumps, sturdy pipe work, specially designed spray nozzles, suitable valves, and control instruments. This system emission control results in saving in quantity of process steam and increase in the yield of raw gas. The system is characterized by high reliability and simplicity of operation, low operational, and maintenance costs. Other advantages are appreciable saving in quantity of process steam required and increased raw gas yield/by-products generation, due to elimination of gases vented into the atmosphere. By the use of HPALA system, it is possible to achieve 60% reduction in charging emissions.

2.8

Coal Moisture Control

A by-product coke making plant is required to supply sufficient coke of good quality and adequate gas of high calorific value for the integrated steel plant to be a going concern. The one element that influences the handling of coal and impacts the operation and efficiency of the plant is moisture. Compared to other important properties of the coal blend, moisture can be easily manipulated (Wu et al. 2017). Moisture content is one among the many variables affecting the bulk density of coal blend and those controlling the coke qualities and yield. Increase in moisture reduces coal grindability, coking pressure, and internal gas pressure, helps in dust suppression during charging, and hence reduces jamming of ascension pipes and hydraulic main (Yang et al. 2019). Batteries charging coals with high moisture content are not troubled with roof carbon deposits. An optimum level of moisture content of charge coal needs to be maintained for improving coke oven productivity, coke quality, and operational smoothness. The coal moisture control process (CMCP) is employed to monitor and adjust the moisture content of charge coals in the coal pre-treatment procedure, for increasing the production of coke and enhancing the coke quality (Makgato et al. 2019). This technique employs the waste heat from the coke oven gas in order to dry the coal used to produce coke. The coal moisture control allows to reduce the heat demand, increases productivity, and improves the material quality (Fig. 2.23). Normally, coal drying during coke making is an high energy-consuming operation. High and variable moisture contents affect both the coke rate and the balances within the blast furnace. The coil moisture control system dries the coal from around 12% up to 5% reducing the energy

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Fig. 2.23 Coal moisture control plant

consumption in the coke oven by 150 MJ/t. The coke can pre-be heated to reduce the moisture through the use of COG or other waste heating sources. In this case, up to 100 MJ/t will be necessary with a reduction of the potential energy saving but with the improvement of productivity by 7%. For the plant solutions, the equipment could be realized in the coal stoking areas also in the existing coke plants (Couch 2001). The potential reduction of CO2 emissions is 6.7 kg/t with a net fuel saving of 0.3 GJ/t (Worrell et al. 2010). The fluidized-bed moisture control technology has very wide application in many fields because of better heat transfer efficiency, simple process, and equipment with low cost. And the flue gas can be used directly as heating medium. Moreover, fluidized bed can be used to classify coal. A Japanese plant costs resulted in $21.9/t. This is characterized by low investment and running costs with productivity increases of over 10% with the same percentage of energy saving.

2.9

Non-Recovery Coke Ovens

In non-recovery coke plants, originally referred to as beehive ovens, the coal is carbonized in large oven chambers (Fig. 2.24). The carbonization process takes place from the top by radiant heat transfer and from the bottom by conduction of heat through the sole floor. The primary air for combustion is introduced into the oven chambers through several ports located above the charge level in pusher and coke side doors of the oven. Partially combusted gases exit the top chamber through “down-comer” passages in the oven wall and enter the sole flue thereby heating the sole floor of the oven. The combusted gases are collected in a common tunnel and exit via a stack, which creates a natural draft in the oven. Since the by-products are not recovered, the process is called “nonrecovery coke making” (Valia 2019).

2.9 Non-Recovery Coke Ovens

89 Generator Turbine

Condenser

Cooling tower

Feed water heaters, pumps, deareators

Emergency vent stack

Cooled flue gas Heat recovery steam generator

Desulphurization system

Coal Wet quench Coke ovens

Screening and crushing

Coke loadout

Fig. 2.24 Non-recovery coke plant

The schematic of a non-recovery coke oven compared with a recovery oven is shown in Fig. 2.25. In many applications, some secondary products belonging to the coking process, such as the gas and the slag, can be used for the coke combustion in the oven for further operations. This process allows for the heat necessary for the coking. The prior combustion air is introduced into the oven in order to partially contribute to the combustion of volatiles in the oven. A secondary flux of air is forced into the oven to complete the combustion. The gas can still be recovered for the steam or for the electric power production. This configuration is known as heat recovery coke making. In conventional process, the coal charged receives the heat indirectly through the furnace walls, by combustion of external gas; inside the oven, positive pressure develops. Gas generated in the coking process is sent to the by-product plant. In non-recovery ovens, coking proceeds from the top through direct heating by the partial combustion of the volatile matter over the coal bed and from the bottom by heat coming from full combustion of gases escaping from the oven. In these plants, the offgas is treated and sent to the stack, in many cases after recovering sensible heat to produce vapor and electric power (Madias and de Cordova 2011). This technology reduces the fuel consumption allowing also to use raw material of lower quality. They may be useful to obtain high-quality coke for blast furnace operation with high PCI, where better properties are needed, or to obtain standard quality based on blends with a proportion of non-coking coals up to 25% (Kumar et al. 2008). Vibro-compaction is a recent development in the class of

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Fig. 2.25 Non-recovery and recovery coke ovens

pre-carbonization techniques. Conceptually, this technique is similar to the stamp charging but does not require very fine crushing of coal. A coal cake bulk density of 1.1 t/m3 could be achieved by optimizing coal blend moisture, coal size, and vibrocompacting technique. Inferior coals comprising up to 35% of the blend have been successfully used to produce coke with a CSR in the range of 64–66%, a CRI between 23% and 25%, and an M10 in the range of 4–6% (Fig. 2.26). The correlation between CRI and CSR has been recently evaluated; the procedure and results are described by Lech et al. (2019). The plant costs are high, and they are justified where the emission regulations are strict. The costs are huge if a power station is connected to the oven. In the US, the whole plant (including the coke oven) for a production of 1.2 million tons per year

2.9 Non-Recovery Coke Ovens

91

Fig. 2.26 Coke properties for non-recovery coke oven products

costs 365 million dollars. The power station with a capacity of 700 kWh/t costs 140 million dollars. From an environmental point of view, the results for plants charging 1 Mt./year are depicted in Fig. 2.27. SO2, NOx, CO, and volatile organic compounds (VOCs) are considerably lower for the non-recovery system. Total suspended particulates (TSP) and PM10 levels are higher. The reason for the emissions reduction is mainly due to the residence time of gas in the oven and the high temperature, turbulence, and oxygen, enough to destroy hazardous air pollutants (HAP). In addition, no liquids are generated from non-recovery coke ovens. In the traditional ovens, the employed liquid is in the order of 0.5 m3/t of coke. Obviously, the emission levels are directly related to the coke properties and quality (Table 2.15). The emissions of particulates (PM10, PM2.5, and TSPM) show a positive correlation with the feed coal properties like VM, FC, C, and H. Flue gases like CO2 and CO are positively correlated with VM and FC of the feed coal. The H2S concentration shows strong negative correlation with coal parameters like VM, FC, H, and S. The statistical analysis also indicates that emission of SO2 during coke making completely depends upon the sulfur content of the feed coal. It is suggested that alkaline solution (0.1 N NaOH) could be used to absorb the emitted gases during carbonization period, which shows about 99% absorption of SO2 during the coke making process (Saikia et al. 2015; Vega et al. 2019).

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Fig. 2.27 Annual emissions for non-recovery coke ovens compared to conventional ovens

A detailed understanding of fundamental structural and operational differences that lead to differences in coke strength after reaction (CSR) between cokes that are produced from the same coal blend, using byproduct and heat recovery coke making technology, is described by Nyathi et al. (2017). Because of differences in design between heat recovery ovens and slot ovens, operational conditions in these two technologies are significantly different. Industry observers report a retrospective coke quality, as expressed by coke strength after reaction (CSR), variation that overrides coal properties of blend used between these two technologies. In by-product coke making technology, the oven is relatively narrow and has a vertical orientation; thus, the coal bed is heated from the sides by conduction in an oxygendeficient environment. The off-gas is collected and sent to a chemical plant, where by-products such as light oil, tar, and benzol are recovered. On the other hand, heat recovery coke making does not form by-products, because the off-gas from the coal charge is partially combusted in the free space above a relatively thick horizontally oriented coal bed prior to being fully combusted in the sole flues below the oven floor. Hence, the carbonization process proceeds from the top of the oven by radiant heat transfer and from the bottom of the oven by heat conduction through the sole flues. The coal charge is constrained by flue walls in by-product ovens, whereas in a heat recovery oven, the coal bed is not constrained and, thus, can swell upwards into free space above the charge. These differences in oven design mean that the heat recovery oven coke is produced from a thicker coal bed under unconstrained conditions, using longer coking cycles and achieving higher final temperatures, in comparison to by-product oven coke. The ultimate consequence of these design differences is the discrepancy in CSR of coke produced using these two oven types. Differences in coke quality between these two technologies have implications on,

SO2 NO2 NH3 M Ash VM FC C H S CO2 CO H2S PM10 TSPM PM2.5

SO2 1 0.872 0.638 0.990 0.538 0.999 0.999 0.203 0.926 0.934 0.271 0.116 0.676 0.418 0.904 0.951

NO2 0.872 1 0.934 0.933 0.056 0.896 0.895 0.656 0.992 0.989 0.708 0.588 0.228 0.080 0.998 0.981

NH3 0.638 934 1 0.742 0.306 0.678 0.675 0.883 0.882 0.871 0.914 0.839 0.136 0.432 0.906 0.845

M 0.990 0.933 0.742 1 0.411 0.996 0.995 0.341 0.971 0.976 0.406 0.258 0.563 0.284 0.956 0.985

Ash 0.538 0.056 0.306 0.411 1 0.493 0.496 0.717 0.180 0.201 0.666 0.775 0.985 0.991 0.126 0.250

Table 2.15 Coal properties vs. emissions parameters VM 0.999 0.896 0.678 0.996 0.493 1 1 0.254 0.945 0.951 0.321 0.168 0.637 0.370 0.925 0.966

FC 0.999 0.895 0.675 0.995 0.496 1 1 0.250 0.943 0.950 0.318 0.165 0.639 0.373 0.924 0.965

C 0.203 656 0.883 0.341 0.717 0.254 0.250 1 0.557 0.539 0.998 0.996 0.585 0.805 0.601 0.496

H 0.926 0.992 0.882 0.971 0.180 0.945 0.943 0.557 1 1 0.614 0.482 0.348 0.045 0.999 0.997

S 0.934 0.989 0.871 0.976 0.201 0.951 0.950 0.539 1 1 0.597 0.464 0.368 0.066 0.997 0.999

CO2 0.271 0.708 0.914 0.406 0.666 0.321 0.318 0.998 0.614 0.597 1 0.988 0.526 0.761 0.656 0.555

CO 0.116 0.588 0.839 0.258 0.775 0.168 0.165 0.996 0.482 0.464 0.988 1 0.653 0.854 0.529 0.418

H2S 0.676 0.228 0.136 0.536 0.985 0.637 0.639 0.585 0.348 0.368 0.526 0.653 1 0.952 0.297 0.415

PM10 0.418 0.080 0.432 0.284 0.991 0.370 0.373 0.805 0.045 0.066 0.761 0.854 0.952 1 0.010 0.116

TSPM 0.904 0.998 0.906 0.956 0.126 0.925 0.924 0.601 0.999 0.997 0.656 0.529 0.297 0.010 1 0.992

PM2.5 0.951 0.981 0.845 0.985 0.250 0.966 0.965 0.496 0.997 0.999 0.555 0.418 0.415 0.116 0.992 1

2.9 Non-Recovery Coke Ovens 93

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

among other things, measure to effectively design coal blends and predict CSR for heat recovery oven coke (Xing et al. 2019). Understanding the nature and cause of the differences in coke quality between cokes produced in these technologies will enable a flexible and economical designing of coal blends for heat recovery ovens. Improved knowledge in this regard will enable coke makers to incorporate the advantages afforded by the fact that, in heat recovery ovens, the unconstrained nature of the bed eliminates the oven coking pressure concerns typically encountered in slot ovens. Understanding these differences is also important for developing a path towards re-evaluating existing CSR prediction models followed by, if necessary, either modifying or replacing these models. As expected, the moveable wall slotoven coke displayed a lower overall CSR than the heat recovery coke. However, because of the narrower width of the slot oven and its bilateral heating system, the slot-oven coke had a more homogeneous CSR along the length of the coke fingers than did the heat recovery oven coke. The heat recovery oven top-center coke displayed distinct characteristics, because of the absence of physical pressure and the use of radiant heat in producing this coke. On the other hand, porous structural similarities observed in both the slot-oven coke and the heat recovery bottom center coke are attributable to the presence of physical pressure and the use of a conduction heating mechanism to produce these cokes. The slot-oven wall lateral pressure and the off-gases escape pathway resulted in low surface area and low total porosity in the slot-oven coke. Similarly, limited swelling that was attributed to the coal charge weight overlying the heat recovery oven bottom coke and off-gas route in the bottom section of the oven resulted in low surface area and total porosity in heat recovery bottom center coke. However, slot-oven coke developed an unfavorable pore structure, because of off-gases passing the semi-coke, thus promoting pore coalescence and, possibly, pore distortion. Moreover, a shorter coking time in slot-oven coke resulted in noticeably weaker development of slot-oven carbon structure compared to heat recovery oven coke. The heat recovery oven top-center coke shows that when a large amount of surface area is available for solution loss, the significance of carbon forms, with regard to impacting coke reactivity, diminishes. Properties that potentially influence coke reactivity are ash content, catalytic index, surface area, and crystallite size. Coke reactivity is positively affected by catalytic index but inversely affected by ash content (Koval and Sakurovs 2019). Although crystallite size inversely affects reactivity, the reaction rate at the initial stage is more predominantly influenced by the mineral matter. Therefore, the influence of surface area and crystallite size is overshadowed by the impact of ash content and catalytic index at the initial stage of reaction (Zhang 2019). A mathematical model has been developed to predict the temperature profile of then on recovery coke oven with intervals of 50 mm in distance and 2.5 h in time by using a set of experimental data and a Lagrange extrapolation technique (Tiwari et al. 2014). The developed model could be used to investigate the performance of carbonization throughout the coking cycle, especially where the crown and sole flue temperature deviate. It was also found that there is a decreasing trend of heating rate towards the center of the charged coal cake that agrees with the plant data. It was concluded that, with an increase in the carbonization time from 64 to 71.25 h,, the

2.11

Coke Stabilization Quenching

95

coke strength after reactivity value decreased from 67.19 to 64.68 and the M40 value decreased from 91.75 to 88.28, whereas arithmetic mean size value and productivity decreased from 58.80 to 55.80 and 1.0 to 0.898, respectively. It may be concluded that there is an indication of an increase in the coke quality in terms of coke strength after reactivity, M40, and arithmetic mean size and productivity at a higher heating rate of a non-recovery oven.

2.10

Variable Speed Drive Coke Oven Gas Compressors

COG has low pressure, and then it needs to be pressurized in order to be transported in the grid interior. The gas pressure can vary during the process due to coking reactions; here, it is possible to employ variable speed drives on the compressors in order to reduce the compressive energy. The use of variable speed drive (VSD) COG compressors can reduce the energy required for compression of the low-pressure gas for transport. The VSDs help to compensate for variability in the gas flow due to coking reactions. For a plant applied in the Netherlands, 8 MJ/ton-coke are saved with a reduction in CO2 emissions of 0.12 kg/ton-coke. The facility costs are 0.47 dollars/t.

2.11

Coke Stabilization Quenching

CSQ (Coke Stabilization Quenching) is an advanced wet quenching system with low environmental impact (Toll et al. 2000). It was developed as an environmental friendly alternative to CDQ (Coke Dry Quenching). Coke Stabilization Quenching allows to quench the coke by pressurizing water for the top and the bottom of the oven (Fig. 2.28). The process itself is a combination of bottom and top quenching methods, providing extremely short cooling time. The coke is popped-up approximately 30 m during quenching. An additional hood inside the quench tower prevents the down falling coke from being deposed outside the quench car. The coke is fairly stabilized by the described handling and needs no further treatment except screening as usual. This leads to gaining higher quenching rates and productivity (Yang et al. 2014). The process improves the coke quality with consequent improved productivity in the blast furnace. The high quenching rate enables a rapid reduction of the coke temperature and shorter reaction time to obtain a better quality of coke. The technical equipment employing a single-point quenching car contributes to the reduction of emissions. It also provides a reduced air contact area of coke and a new quenching tower design which checks the entry of large volumes of ambient air. By this process, the moisture content of the coke can also be controlled. The CSQ process is suitable for coke ovens with large chambers in addition to providing economic, production-technological, as well as product-related advantages.

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Fig. 2.28 CSQ

2.12

Single-Chamber System

Single-chamber system (SCS) coking reactors are large-volume coke ovens that are 45 to 8 cm wide (Alvarez et al. 2005). Single-chamber reactors are separate, processcontrolled units with rigid wall that can absorb high coking pressure (Fig. 2.29). The single-chamber design allows much thinner heating walls than in other systems. This enhances heat transfer and combustion and allows for greater design flexibility in the plant. The load-bearing capacity of the single-chamber reactor walls means that a greater range of coal blends can be charged than in conventional coke ovens. The large-dimension oven in the SCS design reduces environmental emissions compared to those from multichamber reactors. SCS coke ovens are expected to take the place of current multichamber coke ovens whose walls have more limited flexibility. SCSs are 38–70% more thermally efficient than other coke ovens. The SCS technology is currently under development.

2.13

SCOPE 21

97

Fig. 2.29 Schematic diagram of the single-chamber system

2.13

SCOPE 21

Recently, the Japanese coke making industry has faced a lot of problems such as price increase and quality deterioration of metallurgical coal, coke oven aging, and social demand for environmental contribution. To meet these challenges, Japan has developed various technologies, such as coal pre-treatment technology for utilizing low-grade semisoft coking coal (e.g., CMC, DAPS, and SCOPE21), diagnosis and repair apparatus for coke oven chamber wall (DOC), and a method to turn waste plastics into chemical raw materials using coke ovens (Nomura 2017). The SCOPE21 (Super Coke Oven for Productivity and Environment enhancement towards the twenty-first century) is an innovative coke making technology developed in Japan in order to reduce emissions and energy consumption (Kato and Matsueda 2017). The process scheme is shown in Fig. 2.30; it implies a coil preheating at 350
C followed by a rapid carbonization at low temperature. The final heating is operated at medium temperatures (850
C). The resultant coke is reheated to 1000
C in a CDQ unit to complete the processing (Kojima 2009). This process reduces the CO2 emissions with an increase in productivity up to 250% thanks to the reduction in the time needed for the coke production. It allows employing poor

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Fig. 2.30 SCOPE 21 plant

coking coal from 20% to 50%. NOx are reduced by 30%. A plant with a capacity of one million t/year is capable of reducing the emissions of 400,000 t-CO2/year at a reduced plant cost (~18%) with respect to the traditional ovens. The energy consumption is reduced by 20%. A similar approach is represented by Carbonyx Inc., a coke substitute synthesis process to produce Cokonyx carbon alloy material from non-coking coals. Other pre-specified carbonaceous materials can also be included. Coal is combined with a binder and shaped into briquettes. These are heated to drive off the volatiles and to harden the resultant product in a continuous process. The by-product gases can be recovered and recycled back into the process as fuel and/or used to generate electricity. Japanese steel industry reduced gross consumption by process improvements. Energy recovery is contributing to reduce net consumption in recent years (Fig. 2.31). The Japan Iron and Steel Federation ensures that Japanese steel industry achieves the lowest energy intensity (unit energy consumption per ton of crude steel) among the world’s major steel producing countries (Fig. 2.32).

2.14

Use of Biomass and Waste Materials

99

Fig. 2.31 Energy saving trend in Japan ironmaking

Fig. 2.32 Energy intensity vs. country for ironmaking operations

2.14

Use of Biomass and Waste Materials

Biomass feedstock is considered to be “CO2 neutral” since its CO2 emissions from combustion are offset by the absorption of atmospheric CO2 during plant photosynthesis. Adding biomass to coking coal blends could therefore mitigate CO2 emissions from coke ovens and BFs, if renewable and sustainable biomass is used. However, there is a limit to the amount than can be added due to the adverse effect on coke quality. Charcoal addition has the benefit of enhancing coke reactivity, thus lowering the thermal reserve zone temperature in the BF. This decreases

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

the amount of carbon required in the BF and therefore CO2 generation. Raw wood wastes and charcoal are limited to around 1–3% (Hanrot et al. 2009). Reducing the mineral matter content in charcoal produced from trees is one way for more of the material to be used. If 10% of charcoal could be added to the coking coal blend without detrimental effects on the resultant coke quality, then CO2 emissions from BFs can be reduced by 56 m3/t-HM, which corresponds to a 31% reduction (Ng et al. 2008). In Canada, the steel industry annually uses 3.7 Mt. coke in BFs, equivalent to 13 MtCO2. The requisite amount of charcoal would be available from Canadian sources although this is not the case for many countries in the developed world. An Australian project, funded by ACARP (Sustainable Technology Australia) investigated the production of charcoal from eucalyptus wood and the costs associated with charcoal production. The project also investigated the production of metallurgical coke from a commercial coal blend with 5% and 10% added charcoal. Replacing 10% of coke by charcoal would reduce CO2 emissions by 1.3 Mt./year (MacPhee et al. 2009). The formation of metallurgical coke from coal is related to the development of thermoplasticity during coking with a variety of factors coming into play. The introduction of anything other than coking coal into a coking coal blend must therefore be given careful consideration. Introduction of finely divided charcoal into a coking coal blend produces low-quality coke. This may be the result of the high calcium concentration as well as other ash constituents in the charcoal which produces a coke that is more reactive to CO2. Within a narrow range, variation blend composition does not affect coke quality. Larger particle size charcoal (3/8 + 1/4 in.) produces significantly better coke. Biomass sustainability, availability, and productivity, as well as its conversion into charcoal, have been investigated (Fallot et al. 2008). This has progressively focused on charcoal supply from tropical eucalyptus plantations; while the global potential for biomass production is large, there is only a finite area of land available without compromising food production. In addition, the price of biomass is likely to rise as the power and other industries utilize it for CO2 abatement. The addition of waste plastics to the coking coal blend not only reduces energy consumption and hence CO2 emissions from BFs but also allows recycling of a waste that may otherwise be landfilled or incinerated. Adding 2 wt.% waste plastics to coke mitigates BF CO2 emissions by 2%. The main downside is the cost of the collection and treatment of the material. The recycling of waste plastics in coke ovens uses existing equipment. However, waste processing equipment will be needed unless suitably treated waste plastics can be bought. Again, like wood wastes, the amount of waste plastics that can be added to the coking coal blend is currently limited to less than 2 wt.% due to detrimental effects on coke quality. Just 1 wt.% waste plastic is added to the coke ovens at the Japanese steelworks. In addition, the relative proportions of the different plastic types (polyolefins to polystyrene (PS) and polyethylene terephthalate (PET)) in municipal waste plastics are a critical factor (Diez et al. 2007). It has been found that chlorine does not cause problems as most of the chlorine from the waste plastics is removed by the ammoniacal liquor used for flushing the COG when it exits the coke oven (Kato et al. 2006). It was found that the carbonization yield of coke, tar and light oil, and

2.14

Use of Biomass and Waste Materials

101

gas produced from waste plastics was about 20%, 40%, and 40% respectively. It was found that coke strength in the case of 1% waste plastics addition to coal is almost equal to that in the case of no waste plastic addition. It was clarified that the waste plastics recycling process using coke ovens are feasible, from the fact that the coke, tar and light oil, and gas were collected without affecting coke strength. Sekine et al. (2009) calculated the reduction potential of CO2 emissions when polyethylene (PE), polypropylene (PP), PS, and PET are added to the coking coal blend. The system boundary in the life cycle inventory included the pre-treatment of the waste plastics, the processes within the steelworks that are affected by waste plastics usage (such as the coke oven and BF), and the associated power plant (where the surplus gas is utilized). PS had the highest CO2 reduction potential, followed by PP and PE, while PET increases CO2 emissions. The differences were attributed to differences in the calorific values and coke product yields of each plastic type. The inclusion of sawdust in coal blends for coke making has clear advantages such as its low sulfur and ash content and its zero contribution to CO2 emissions, but it also has a number of disadvantages including its low char yield, deleterious effect on coal fluidity, and low bulk density (Montiano et al. 2016). A possible way to increase the bulk density of the biomass is to prepare briquettes. Various binders can be used for the preparation of briquettes. However, both sawdust and non-coking coal have a deleterious effect on the development of coal fluidity making pitch and coal tar preferable binders considering that both of these produce an increase in coal fluidity. Coal-tar pitch has already been successfully used as a binder. The role of pitch in briquettes comprising high rank and coking coals is to interact with them and modify their carbonization behavior so that the system is sufficiently fluid to wet the surface of non-fusing coals. In addition, it needs to be able to form a binder coke with a mosaic optical texture that connects coal-derived coke with inerts. The drawback with coal-tar pitch is its high carcinogenic compound content. An alternative option is to use coal tar which does not cause as great an increase in fluidity as coal-tar pitch but is nevertheless liquid and has fewer carcinogenic polyaromatics. The addition of briquettes caused a decrease in the fluidity of the industrial coal blends irrespective of the amount added. However, coke was produced by every mixture. The incorporation of briquettes containing sawdust, regardless of their origin, impaired the cold mechanical strength, coke reactivity, and post-reaction strength. Nevertheless, slight differences between the two sawdusts were apparent at 15 wt.% addition. The JIS index values improved due to the lower density of the briquettes, while CRI and consequently CSR improved with the addition of briquettes containing pine sawdust due to the amount and composition of the ashes. Coal tar sludge was only better than tar as binder when briquettes with sawdust were added and as regards cold mechanical strength (JIS index). Additions of up to 10 wt.% of briquettes containing biomass prepared with tar as binder yielded good results because the variation in the CSR was lower than 2 points. The inclusion of briquette fines produced cokes with lower CSR than when full-size briquettes were used. When evaluating the effect of biomass containing briquettes, the environmental benefits should be also considered.

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Plastic blends used, simulating plastic composition in MSW in Brazil, proved to be technically viable, considering coke quality results (Lange and Ferreira 2016). No improvement was found in CRI and CSR resulting from the addition of oil to the blends. Variations in CSR and CRI tests are due to differences in temperature, bulk density, heating regime, and fuels used. Chemical analyses of coke ash, sulfur, and volatile matter showed small oscillations in sulfur content for box tests and greater variations in volatile matter resulting from the hearth heating furnace tests. These variations are due to the persistence of organic matter, as the HHF does not reach over-coking temperatures. Among the different percentages of plastics used, 3% plastic blends provided the most stable CSR results. Identification of the optimum percentage was not possible, due to oscillations in the values obtained. Therefore, performing a greater number of experiments with the same blend, using a mass of 250 kg in the pilot oven, would allow better understanding of the behavior of the variation found for these percentages of the plastics. Adding plastics to coal blends provides better or equal CSR and CRI values, when compared to coke quality results for blends without plastics. From an environmental standpoint, the use of plastics in coking plants is a relevant option for energy recovery from plastics, especially considering the energy wasted in Brazil due to the approximately 5.2 million tons of plastic that are not recycled every year, and the impact these wastes have on the environment. Metallurgical coke manufacture is a valuable alternative to the feedstock recycling of mixed plastic wastes (Melendi et al. 2011). The key compositional parameters of these feedstocks are directly linked to the relative proportions of the polyolefins and the aromatic polymers APS plus PETA. As the total amount of polyolefins increases, the pressure exerted on the wall also increases. To avoid the risk of wall damage and the deterioration of coke quality, the composition of the waste added to the coal blend needs to be carefully controlled. A mechanism for the generation of high coking pressures caused by the addition of polyolefins is proposed taking into account the interrelated phenomena that occur during the co-carbonization of coal and plastics: (1) the carbonization stage when coal is transformed into semicoke-coke and thermal decomposition of the plastics takes place, (2) the yield and composition of degradation products from the plastics, and (3) the heavy hydrocarbon fragments formed during the pyrolysis of polyolefins incorporated inside the coal and semicoke inner surface, which are released at much higher temperatures, after the fluid coal has resolidified and condense as oil and wax in the tar. All the above phenomena are controlled by the chemical composition of the waste, which determines whether coal and plastics are compatible for carbonization so that pressure remains within a safe range. The best quality coke was obtained by the addition of single HDPE, and the coke reactivity seems to be affected by the addition of the other mixed plastic wastes. In addition, polyolefinenriched wastes which contain a small amount of organic materials that are different to polymers have a negative effect on coke quality. In general, the cokes produced by the plastic addition are less dense and more macroporous, and the pores become smaller. In summary, the ratio of polyolefins to polyaromatic polymers (PS and PET) present in the waste is critical for coke making, since this ratio determines not only

2.15

Conclusions

103

the fluidity of the coal blend but also the wall pressure generated during the process and the quality of the coke produced in terms of reactivity towards CO2 and mechanical strength after reaction. An amount of polyolefins lower than 65 wt.% in the waste was established to avoid negative effects on the coking pressure generation.

2.15

Conclusions

The technological advancements for coke making in the recent years led to lowering air emissions and to the deep limiting of hazardous solid wastes. Obviously, the different technological choices are driven by regional and logistic issues. As a matter of fact, heat recovery ovens are able to produce coke of superior hot and cold strength properties by employing a wide range of coal ranks. Coke making faces many environmental issues. First of all, hazardous effluent management optimization through primary treatment (physical), secondary treatment (biological), and advanced treatment (physical and/or chemical and/or biological) is needed. Coke dry quenching appears as the most valid system to reduce air pollution allowing at the same time a remarkable energy recovery or saving, especially when it is associated with coal preheating. In addition, dry quenched coke is harder and stronger, and obviously its moisture content is much lower than that of wet quenched coke. CSQ (Coke Stabilization Quenching) is an advanced wet quenching system with low environmental impact developed as an alternative to CDQ. The main goal of the energy saving in steelmaking is the optimal distribution and utilization of process gases such as coke oven gas. COG is a valuable gas due to its high hydrogen and methane contents. COG has the highest calorific power among all the integrated steel plant off gases. So, it can be employed also to increase the calorific power of other process gases. Efforts have been made over the years to reduce this emission level through installing pollution control measures and technological change, particularly in coke making operation. The goals of coking process control are realizing steady heating of coke oven, enhancing production of coke oven and quality of coke, reducing energy consumption and prolonging coke oven service life, and decreasing environment pollution in the course of coking production. Operational efficiency, coke quality, and productivity are the main challenges obtained through stampcharged coke making technology. The coal moisture control process (CMCP) is employed to monitor and adjust the moisture content of charge coals in the coal pre-treatment procedure, for increasing the production of coke and enhancing the coke quality. The large-dimension oven in the SCS design reduces environmental emissions compared to those from multichamber reactors. SCS coke ovens are expected to take the place of current multichamber coke ovens whose walls have more limited flexibility. Japan SCOPE 21 activities have developed various technologies, such as coal pre-treatment technology for utilizing low-grade semisoft coking coal, diagnosis and repair apparatus for coke oven chamber wall (DOC), and a method to turn waste plastics into chemical raw materials using coke ovens in order

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2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

to reduce emissions and energy consumption. Adding biomass to coking coal blends helps mitigate CO2 emissions from coke ovens, if renewable and sustainable biomass is used. Emissions reduction and energy efficiency potential for coking innovations

Technology Coke dry quenching Coke making control systems Coal moisture control Variable speed drive COG compressor COG recovery Non-recovery coke oven SCOPE21 CSQ MES

Emissions reduction (kgCO2/t product) 27.5

Fuel saving (GJ/t product) 1.2

3.8

0.17

Electricity saving (GJ/t product) 300 (kWh/t) –

6.7

0.3

0.12

–

Capital costs ($/t product) 109.5

Operating costs ($/t product) 0.78

Payback time (year) 35.7

0.37

–

0.7

–

76.6

–

50

–

0.47

–

21.2

6–8

1 630–700 (kWh/t)

400 323

21(%) 2(%) 12.5(%)

365 (plant of 1.2 t/year)

220 (plant)

References Ahrendt WA, Beggs D (1981) Apparatus for direct reduction of iron using high sulfur gas. US patent 4270739 Alvarez R, Diez MA, Barriocanal C, Cimadevilla JLG (2005) Cimadevilla JLG La tecnología de producción de coque de horno alto ante el nuevo milenio. Rev Metal Madrid Vol Extr 29–34 Aravinda PA, Kumarappa S (2014) Computational fluid dynamics analysis of double flue technology in Coke Dry Quenching. Int J Lat Technol Eng Manag Appl Sci 3(10):117–121 Argyle MD, Bartholomew CH (2015) Heterogeneous catalyst deactivation and regeneration: a review. Catalysts 5:145–269. https://doi.org/10.3390/catal5010145 Babich A, Senk D (2019) Coke in the iron and steel industry. In: New trends in coal conversioncombustion, gasification, emissions, and coking, pp 367–404. https://doi.org/10.1016/B978-008-102201-6.00013-3 Bejan A, Mamut E (eds) (1999) Thermodynamic optimization of complex energy systems (NATO Advanced Study Institute, Romania). Kluwer, Dordrecht. https://doi.org/10.1007/978-94-0114685-2

References

105

Bermúdez JM, Arenillas A, Luque R, Menendez JA (2013) An overview of novel technologies to valorise coke oven gas surplus. Fuel Proc Technol 110:150–159. https://doi.org/10.1016/j. fuproc.2012.12.007 Bisio G, Rubatto G (2000) Energy saving and some environment improvements in coke-oven plants. Energy 25:247–265. https://doi.org/10.1016/S0360-5442(99)00066-3 Biswas B, Kumar A, Sahu R, Mishra P, Haldar SK (2015) Experience of Tata Steel’s first CDQ stabilization, METEC & ESTAD, Dusseldorf Buczynski R, Weber R, Kim R, Schwöppe P (2018) Investigation of the heat-recovery/nonrecovery coke oven operation using a one-dimensional model. Appl Therm Energy 144:170–180. https://doi.org/10.1016/j.applthermaleng.2018.08.055 Burmistrz P, Rozwadowski A, Burmistrz M, Karcz A (2014) Coke dust enhances coke plant wastewater treatment. Chemosphere 117(1):278–284. https://doi.org/10.1016/j.chemosphere. 2014.07.025 Cavaliere P (2016) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. https://doi.org/10.1007/978-3-319-39529-6 Chen WH, Lin MR, Yu AB, Dud SW, Leu TS (2012) Hydrogen production from steam reforming of coke oven gas and its utility for indirect reduction of iron oxides in blast furnace. Int J Hydrogen Energy 37:11748–11758. https://doi.org/10.1016/j.ijhydene.2012.05.021 Chen J, Aries E, Collins P, Anderson DR, Hodges JS (2015) Characterization of priority substances in effluents from an integrated steelworks in the United Kingdom. Water Environ Res 87(3):132–144. https://doi.org/10.2175/106143014X14062131179311 Cheng H, Lu X, Hu D, Zhang Y, Ding W, Zhao H (2011) Hydrogen production by catalytic partial oxidation of coke oven gas in BaCo0.7Fe0.2Nb0.1O3δ membranes with surface modification. Int J Hydrogen Energy 36(1):528–538. https://doi.org/10.1016/j.ijhydene.2010.10.002 Couch GR (2001) Metallurgical coke production. CCC/57, London, UK, IEA Coal Research Czaplicki A, Janusz M (2012) Preparation of coal batch for top loading: experimental research. Coke Chem 55:366–371. https://doi.org/10.3103/S1068364X12100031 Danilin EA (2017) Improving the performance of dry-quenching units by minimizing coke losses. Coke Chem 60(2):59–70. https://doi.org/10.3103/S1068364X17020028 Delasalle F (2019) Steel in the global value chain and in the circular economy. Steel and coal: a new perspective, Bruxelles, 28 March 2019 Diemer P, Killich HJ, Knop K, Lüngen HB, Reinko M, Schmöle P (2004) Potentials for utilization of coke oven gas in integrated iron and steel works. In: 2nd international meeting on ironmaking and 1st international symposium on Iron Ore and parallel event- 5th Japan-Brazil Symposium on Dust Processing-Energy-Environment on Metallurgical Industries, pp. 433–446 Diez M A, Alvarez R, Melendi S, Barriocanal C (2007) Feedstock recycling of plastic wastes in cokemaking. In: 2007 international conference on coal science and technology. Programme and full papers, Nottingham, UK, 28–31 August 2007. IEA Clean Coal Centre, CD-ROM, London, Paper 2P43 Duan W, Yu Q, Liu J, Qin Q (2016) Thermodynamic analysis of hydrogen production from COG-steam reforming process using blast furnace slag as heat carrier. Energy Technol 23–29. https://doi.org/10.1007/978-3-319-48182-1_3 Errera MR, Milanez LF (2000) Thermodynamic analysis of a coke dry quenching unit. Energy Convers Manag 41:109–127. https://doi.org/10.1016/S0196-8904(99)00090-4 European IPPC Bureau (2011) Best available techniques (BAT) reference document for iron and steel production. Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control) Fallot A, Saint-André L, Laclau J-P, Nouvellon Y, Marsden C, Le Maire G, Silva T, Piketty M-G, Hamel O, Bouillet J-P (2008) Biomass sustainability, availability and productivity. Paper presented at: 4th ULCOS seminar, Essen, Germany, 1–2 Oct 2008. https://doi.org/10.1051/ metal/2009072 Garcia SG, Montequin VR, Fernandez RL, Fernandez FO (2019) Evaluation of the synergies in cogeneration with steel waste gases based on Life Cycle Assessment: a combined coke oven and steelmaking gas case study. J Clean Prod 217:576–583. https://doi.org/10.1016/j.jclepro. 2019.01.262

106

2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Ghosh SK (2019) Waste water recycling and management. https://doi.org/10.1007/978-981-132619-6 Gilyazetdinov RR, Sukhov IY, Nechaev VV, Yakimov VS (2015) Energy-efficient dry quenching of coke. Coke Chem 58(6):229–231. https://doi.org/10.3103/S1068364X1506006X Gong MH, Yi Q, Huang Y, Wu GS, Hao YH, Feng J, Li WY (2017) Coke oven gas to methanol process integrated with CO2 recycle for high energy efficiency, economic benefits and low emissions. Energy Convers Manag 133:318–331. https://doi.org/10.1016/j.enconman. 2016.12.010 Habashi F (2016) Dry quenching: clean technology in coke production. Coal Age 121(5):40–41 Hanrot F, Sert D, Delinchant J, Pietruck R, Bürgler T, Babich A, Fernández M, Alvarez R, Diez M A (2009) CO2 mitigation for steelmaking using charcoal and plastic wastes as reducing agents and secondary raw materials. Paper presented at: 1st Spanish national conference on advances in materials recycling and eco-energy, Madrid, Spain, 12–13 November Indimath S, Shunmugasundaram R, Balamurugan S, Das B, Singh R, Dutta M (2018) Ultrasonic technique for online measurement of bulk density of stamp charge coal cakes in coke plants. Fuel Precess Technol 172:155–161. https://doi.org/10.1016/j.fuproc.2017.12.017 Jiang X, Bai X-Q, Zhou D-D (2017) Injection of coke dry quenching dust in blast furnace. Kang T’ieh/Iron Steel 52(11):64–68. https://doi.org/10.13228/j.boyuan.issn0449-749x.20170174 Jin H, Sun S, Han W, Gao L (2009) Proposal of a novel multifunctional energy system for cogeneration of coke, hydrogen, and power. J Eng Gas Turbine Power. https://doi.org/10. 1115/1.3078791 Johansson MT, Soderstrom M (2011) Options for the Swedish steel industry – energy efficiency measures and fuel conversion. Energy 36:191–198. https://doi.org/10.1016/j. energy.2010.10.053 Joseck F, Wang M, Wu Y (2008) Potential energy and greenhouse gas emission effects of hydrogen production from coke oven gas in U.S. steel mills. Int J Hydrogen Energy 33:1445–1454. https://doi.org/10.1016/j.ijhydene.2007.10.022 Karcz A, Strugala A (2008) Increasing chances of utilizing the domestic coking coal resources through technological operations in coal blend preparation. Miner Resour Manag 24:5–18 Kato K, Matsueda K (2017) Leading edge of coal utilization technologies for gasification and cokemaking. Kona 2018(35):112–121. https://doi.org/10.14356/kona.2018018 Kato K, Nomura S, Fukuda K, Uematsu H, Kondoh H (2006) Development of waste plastics recycling process using coke oven. Nippon Steel Tech Rep (94):75–79. https://doi.org/10.2355/ isijinternational.42.Suppl_S10 Khzouz M, Gkanas EI, Du S, Wood J (2018) Catalytic performance of Ni-Cu/Al2O3 for effective syngas production by methanol steam reforming. Fuel 232:672–683. https://doi.org/10.1016/j. fuel.2018.06.025 Kojima A (2009) Steel industry’s global warming measures and sectoral approaches. Q Rev (33):55–68 Koval L, Sakurovs R (2019) Variability of metallurgical coke reactivity under the NSC test conditions. Fuel 241:519–521. https://doi.org/10.1016/j.fuel.2018.12.053 Krzywicka A, Kwarciak-Kozłowska A (2014) Advanced oxidation processes with coke plant wastewater treatment. Water Sci Technol 69(9):1875–1878. https://doi.org/10.2166/wst.2014. 098 Kumar PP, Barman S, Ranjan M, Gosh S, Raju VVS (2008) Maximization of non-coking coals in coke production from non-recovery coke ovens. Ironmak Steelmak 25(1):33–37. https://doi. org/10.1179/174328107X174762 Kumar R, Bhakta P, Chakrabortty S, Pal P (2011) Separating cyanide from coke wastewater by cross flow nanofiltration. Sep Sci Technol 46(13):2119–2127. https://doi.org/10.1080/ 01496395.2011.594479 Kuyumcu HZ, Sander S (2014) Stamped and pressed coal cakes for carbonization in by-product and heat-recovery coke ovens. Fuel 121:48–56. https://doi.org/10.1016/j.fuel.2013.12.028 Kwiecińska A, Figa J, Stelmach S (2016) The use of phenolic wastewater in coke production. Pol J Environ Stud 25(2):465–470. https://doi.org/10.15244/pjoes/60725

References

107

Lange LC, Ferreira AFM (2016) The effect of recycled plastics and cooking oil on coke quality. Waste Manag. https://doi.org/10.1016/j.wasman.2016.08.039 Lech K, Jursova S, Kobel P, Pustejovska P, Bilik J, Figiel A, Romański L (2019) The relation between CRI, CSR indexes, chemical composition and physical parameters of commercial metallurgical cokes. Ironmak Steelmak 46(2):124–132. https://doi.org/10.1080/03019233. 2017.1353764 Lei Q, Wu M, Cao W-H, She J-H (2008) Operating-state-based intelligent control of combustion process of coke oven. In Proceedings of the 17th world congress the international federation of automatic control, Seoul, Korea, July 6–11 Lesch R (2016) Situation with coking coals on a global scale. Stamp charging technologies as a way to improve the situation. Technical contribution to the 46
Seminário de Redução de Minério de Ferro e Matérias-primas, to 17
Simpósio Brasileiro de Minério de Ferro and to 4
Simpósio Brasileiro de Aglomeração de Minério de Ferro, part of the ABM week, September 26th–30th, 2016, Rio de Janeiro, RJ, Brazil Li G, Qu P, Kong J, Jiang G, Xie L, Gao P, Wu Z, He Y (2013) Coke oven intelligent integrated control system. Appl Math Inform Sci 7(3):1043–1050. https://doi.org/10.12785/amis/070323 Li J, Ma X, Liu H, Zhang X (2018) Life cycle assessment and economic analysis of methanol production from coke oven gas compared with coal and natural gas routes. J Clean Prod 185:299–308. https://doi.org/10.1016/j.jclepro.2018.02.100 Liu J, Ou HS, Wei CH, Wu HZ, He JZ, Lu DH (2016) Novel multistep physical/chemical and biological integrated system for coking wastewater treatment: technical and economic feasibility. J Water Process Eng 10:98–103. https://doi.org/10.1016/j.jwpe.2016.02.007 Lulianelli A, Ribeirinha P, Mendes A, Basile A (2014) Methanol steam reforming for hydrogen generation via conventional and membrane reactors: a review. Renew Sustain Energy Rev 29:355–368. https://doi.org/10.1016/j.rser.2013.08.032 MacPhee JA, Grandsen JF, Giroux L, Price JT (2009) Possible CO2 mitigation via addition of charcoal to coking coal blends. Fuel Process Technol 90(1):16–20. https://doi.org/10.1016/j. fuproc.2008.07.007 Madias J, de Cordova M (2011) Nonrecovery/heat recovery cokemaking: a review of recent developments. In: AISTech 2011 proceedings-volume I, pp 235–251 Makgato SS, Falcon RMS, Chirwa EMN (2019) Reduction in coal fines and extended coke production through the addition of carbonisation tar: environmentally clean process technology. J Clean Prod 221:684–694. https://doi.org/10.1016/j.jclepro.2019.02.242 Man Y, Yang S, Zhang J, Quian Y (2014) Conceptual design of coke-oven gas assisted coal to olefins process for high energy efficiency and low CO2 emission. Appl Energy 133:197–205. https://doi.org/10.1016/j.apenergy.2014.07.105 Marañón E, Vázquez I, Rodríguez J, Castrillón L, Fernández Y, López H (2008) Treatment of coke wastewater in a sequential batch reactor (SBR) at pilot plant scale. Bioresour Technol 99(10):4192–4198. https://doi.org/10.1016/j.biortech.2007.08.081 Melendi S, Diez MA, Alvarez R, Barriocanal C (2011) Relevance of the composition of municipal plastic wastes for metallurgical coke production. Fuel 90:1431–1438. https://doi.org/10.1016/j. fuel.2011.01.011 Meng Z, Wang C, Wang X, Chen Y, Li H (2018) Simultaneous removal of SO2 and NOx from coal-fired flue gas using steel slag slurry. Energy Fuel 32(2):2028–2036. https://doi.org/10. 1021/acs.energyfuels.7b03385 Montiano MG, Diaz-Faes E, Barriocanal C (2016) Effect of briquette composition and size on the quality of the resulting coke. Fuel Process Technol 148:155–162. https://doi.org/10.1016/j. fuproc.2016.02.039 Ng KW, Hutny W, MacPhee T, Gransden J, Price J (2008) Bio-fuels use in blast furnace ironmaking to mitigate GHG emissions. In: Proceedings, 16th European biomass conference and exhibition, Valencia, Spain, 2–6 Jun 2008. Florence, Italy, ETA-Florence renewable energies, DVD, paper OE5.1, pp 1922–1928

108

2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Nomura S (2016) Coal briquette carbonization in a slot-type coke oven. Fuel 185:649–655. https://doi.org/10.1016/j.fuel.2016.07.082 Nomura S (2017) Recent developments in cokemaking technologies in Japan. Fuel Process Technol 159:1–8. https://doi.org/10.1016/j.fuproc.2017.01.016 North L, Blackmore K, Nesbitt K, Mahoney MR (2018) Methods of coke quality prediction: a review. Fuel 219:426–445. https://doi.org/10.1016/j.fuel.2018.01.090 Nyathi MS, Kruse R, Mastalerz M, Bish DL (2017) Investigation of coke quality variation between heat-recovery and byproduct Cokemaking technology. Energy Fuel 31(2):2087–2094. https:// doi.org/10.1021/acs.energyfuels.6b02817 Ou H-S, Wei C-H, Mo C-H, Wu H-Z, Ren Y, Feng C-H (2014) Novel insights into anoxic/aerobic1/ aerobic2 biological fluidized-bed system for coke wastewater treatment by fluorescence excitation-emission matrix spectra coupled with parallel factor analysis. Chemosphere 113:158–164. https://doi.org/10.1016/j.chemosphere.2014.04.102 Pal P, Bhakta P, Kumar R (2015) Cyanide removal from industrial wastewater by crossflow nanofiltration: transport modeling and economic evaluation. Waste Environ Res 86(8):698–706. https://doi.org/10.2175/106143014X13975035525744 Peng R, Yu P, Luo Y (2017) Coke plant wastewater posttreatment by Fenton and electro-Fenton processes. Environ Sci Technol 34(2):89–95. https://doi.org/10.1089/ees.2015.0520 Perez AR (2010) Characterization of cokery wastewater biodegradation by SBR. Tecnologia del Agua 30(325):44–51 Poraj J, Gamrat S, Bodys J, Smolka J, Adamczyk W (2016) Numerical study of air staging in a coke oven heating system. Clean Technol Environ Policy 18(6):1815–1825. https://doi.org/10. 1007/s10098-016-1234-8 Qin Z, Zhai G, Wu X, Yu Y, Zhang Z (2016) Carbon footprint evaluation of coal to- methanol chain with the hierarchical attribution management and life cycle assessment. Energy Convers Manag 124:168–179. https://doi.org/10.1016/j.enconman.2016.07.005 Quian Y, Man Y, Peng L, Zhou H (2015) An integrated process of coke-oven gas tri-reforming and coal gasification to methanol with high carbon utilization and energy efficiency. Ind Eng Chem Res. https://doi.org/10.1021/ie503670d Raper E, Stephenson T, Simoes F, Fisher R, Anderson DR, Soares A (2018) Enhancing the removal of pollutants from coke wastewater by bioaugmentation: a scoping study. Chem Technol Biotechnol 93(9):2535–2543. https://doi.org/10.1002/jctb.5607 Razzaq R, Li C, Zhang S (2013) Coke oven gas: availability, properties, purification, and utilization in China. Fuel 113:287–299. https://doi.org/10.1016/j.fuel.2013.05.070 Rejdak M, Vasiliewski R (2015) Mechanical compaction of coking coal for carbonization in stampcharging coke oven batteries. Physicochem Probl Miner Process 51(1):151–161. https://doi.org/ 10.5277/ppmp150114 Rudramuni G, Nataraj CN (2016) Enhancement of steam generation in CDQ power plant. Int Res J Eng Technol 3(5):1441–1445 Saikia J, Saikia P, Boruah R, Saikia BK (2015) Ambient air quality and emission characteristics in and around a non-recovery type coke oven using high Sulphur coal. Sci Total Environ 530–531:304–313. https://doi.org/10.1016/j.scitotenv.2015.05.109 Salkuyeh YK, Adams ITA (2013) Combining coal gasification, natural gas reforming, and external carbonless heat for efficient production of gasoline and diesel with CO2 capture and sequestration. Energy Convers Manag 74:492–504. https://doi.org/10.1016/j.enconman.2013.07.023 Sekine Y, Fukunda K, Kato K, Adachi Y, Matsuno Y (2009) CO2 reduction potentials by utilizing waste plastics in steel works. Int J Life Cycle Assess 14(2):122–136. https://doi.org/10.1007/ s11367-008-0055-3 Seo HO (2018) Recent scientific Progress on developing supported Ni catalysts for dry (CO2) reforming of methane. Catalysts 110(8):1–18. https://doi.org/10.3390/catal8030110 Sugiura M, Irie K, Sakaida M, Fujikane Y (2010) The society of instrument and control engineers. In: Proceedings of 27th sensing forum, p 343

References

109

Sultanguzin IA, Bologova VV, Gyulmaliev AM, Glazov VS, Belov RB (2016) Improving cokeplant efficiency by dry quenching with natural gas. Coke Chem 59(2):61–67. https://doi.org/10. 3103/S1068364X16020046 Suvio P, van Hoorn A, Szabo M (2012) Water management for sustainable steel industry. Ironmak Steelmak 39(4):263–269. https://doi.org/10.1179/03019231113135947813898 Taylor D (2015) Case study: integrated steel coke by-products wastewater treatment plant. In: Proc Water Environ Fed, WEFTEC 2015: Session 500 through Session 509, pp. 5802–5808. https://doi.org/10.2175/193864715819542106 Tiwari HP, Suri S, Banerjee PK, Sharma R, Agarwal R (2010) Optimization of coal blend for nonrecovery coke oven. Tata Search 1:135–139 Tiwari HP, Banerjee PK, Saxena VK, Sharma R, Haldar SK, Paul S (2014) Effect of heating rate on coke quality and productivity in nonrecovery coke making. Int J Coal Prep Util 34:306–320. https://doi.org/10.1080/19392699.2014.896349 Tiwari HP, Haldar SK, Mishra P, Kumar A, Dutta S, Kumar A (2017) Prospect of stamp charge coke making at Tata Steel: an experience. Metall Res Technol 114:501. https://doi.org/10.1051/ metal/2017046 Tiwari HP, Kumar R, Bhattacharjee A, Lingam RK, Roy A, Tiwary S (2018) Prediction of operating parameters range for ammonia removal unit in coke making by-products. Metall Res Technol 115(2):211. https://doi.org/10.1051/metal/2017102 Toll H, Kohler I, Nelles L (2000) CSQ coke stabilization quenching process. Stahl und Eisen 120(4):95–99 Tong Y, Zhang Q, Cai J, Gao C, Wang L, Li P (2018) Water consumption and wastewater discharge in China’s steel industry. Ironmak Steelmak 45(10):868–877. https://doi.org/10. 1080/03019233.2018.1538180 Uribe-Soto W, Portha JF, Commenge JM, Falk L (2017) A review of thermochemical processes and technologies to use steelworks off-gases. Renew Sustain Energy Rev 74:809–823. https:// doi.org/10.1016/j.rser.2017.03.008 Valente A, Iribarren D, Gálvez-Martos J-L, Dufour J (2019) Robust eco-efficiency assessment of hydrogen from biomass gasification as an alternative to conventional hydrogen: a life-cycle study with and without external costs. Sci Total Environ 650:1465–1475. https://doi.org/10. 1016/j.scitotenv.2018.09.089 Valia HS (2019) Nonrecovery and heat recovery cokemaking technology. In: New trends in coal conversion-combustion, gasification, emissions, and coking, pp 263–292. https://doi.org/10. 1016/B978-0-08-102201-6.00010-8 Vega F, Alonso-Farinas B, Baena-Moreno FM, Rodriguez JA, Navarrete B (2019) Technologies for control of sulfur and nitrogen compounds and particulates in coal combustion and gasification. In: New trends in coal conversion-combustion, gasification, emissions, and coking, pp 141–173. https://doi.org/10.1016/B978-0-08-102201-6.00006-6 Veit G, D’Lima PFX (2002) Combining stamp charging with the heat recovery process. AISE Steel Technol:22–24 Wang X, Wang T (2012) Hydrogen amplification from coke oven gas using a CO2 adsorption enhanced hydrogen amplification reactor. Int J Hydrogen Energy 37:4974–4986. https://doi.org/ 10.1016/j.ijhydene.2011.12.018 Wang S, Wang G, Jiang F, Luo M, Li H (2010) Chemical looping combustion of coke oven gas by using Fe2O3/CuO with MgAl2O4 as oxygen carrier. Energy Environ Sci 3:1353–1360. https://doi.org/10.1039/B926193A Wang J, Liang B, Parnas R (2013) Manganese-based regenerable sorbents for high temperature H2S removal. Fuel 107:539–546. https://doi.org/10.1016/j.fuel.2012.10.076 Wen-wu L, Xiu-ping W, Xue-yan T, Chang-yong W (2014) Treatment of pretreated coking wastewater by flocculation, alkali out, air stripping, and three-dimensional electrocatalytic oxidation with parallel plate electrodes. Environ Sci Pollut Res 21(19):11457–11468. https:// doi.org/10.1007/s11356-014-3124-0 Worrell E, Blinde P, Neelis M, Blomen E, Masanet E (2010) Energy efficiency improvement and cost saving opportunities for the U.S. Iron and steel industry. An ENERGY STAR guide for energy and plant managers

110

2 Coke Making: Most Efficient Technologies for Greenhouse Emissions Abatement

Wu ZH, Liu B, Yin JS, Kang N, Zhao LJ (2017) Study on coal moisture control technology using superheated steam. Adv Eng Res 111:189–193 Xiang D, Yang S, Mai Z, Qian Y (2015) Comparative study of coal, natural gas, and coke-oven gas based methanol to olefins processes in China. Comput Chem Eng 83:176–185. https://doi. org/10.1016/j.compchemeng.2015.03.007 Xiang D, Huang W, Huang P (2018) A novel coke-oven gas-to-natural gas and hydrogen process by integrating chemical looping hydrogen with methanation. Energy 165:1024–1033. https:// doi.org/10.1016/j.energy.2018.10.050 Xing X, Rogers H, Zulli P, Hockings K, Ostrovski O (2019) Effect of coal properties on the strength of coke under simulated blast furnace conditions. Fuel 237:775–785. https://doi.org/10.1016/j. fuel.2018.10.069 Yang Y, Raipala K, Holappa L (2014) Ironmaking. Treatise on process metallurgy-volume 3: industrial processes, pp 2–88. https://doi.org/10.1016/B978-0-08-096988-6.00017-1 Yang Z, Huang J, Song S, Wang Z, Fang Y (2019) Insight into the effects of additive water on caking and coking behaviors of coal blends with low-rank coal. Fuel 238:10–17. https://doi. org/10.1016/j.fuel.2018.10.099 Zhang H (2019) Relationship of coke reactivity and critical coke properties. Met Trans B50(1):204–209. https://doi.org/10.1007/s11663-018-1438-x Zhang G, Dong Y, Feng M, Zhang Y, Zhao W, Cao H (2010) CO2 reforming of CH4 in coke oven gas to syngas over coal char catalyst. Chem Eng J 156:519–523. https://doi.org/10.1016/j. cej.2009.04.005 Zhang H, Dong L, Li H, Fujita T, Ohnishi S, Tang Q (2013) Analysis of low carbon industrial symbiosis technology for carbon mitigation in a Chinese iron/steel industrial park: a case study with carbon flow analysis. Energy Policy 61:1400–1411. https://doi.org/10.1016/j.enpol.2013. 05.066 Zhang F, Bournival G, Ata S (2019) The influence of process water chemistry on coal thermoplastic properties. Powder Technol 345:468–477. https://doi.org/10.1016/j.powtec.2019.01.002 Zhao Y, Hao R, Wang T, Yang C (2015) Follow-up research for integrative process of pre-oxidation and post-absorption cleaning flue gas: absorption of NO2, NO and SO2. Chem Eng J 273:55–65. https://doi.org/10.1016/j.cej.2015.03.053

Chapter 3

Sintering: Most Efficient Technologies for Greenhouse Emissions Abatement

3.1

Introduction

Iron ore in its natural state occurs as lump ore or fine ore. Lump ore is crushed and screened before shipment from the mine. It must meet certain quality restrictions (>62% iron) and physical characteristics in terms of size and handling since it is fed directly into the BF. The energy needs of the BF depend to some extent on the quality of the ore (Mou and Morrison 2016). The higher the metal content is, the lower the energy consumption results. Variations in the ore chemical composition can make a difference of about 10–15% in BF energy use. Lump ore is more expensive than ore fines. About 25% of all iron ore is used directly, without agglomeration. Fine ore must be converted into larger aggregates for use in BFs. These aggregates are often a better feedstock than lump ore. Blast furnaces are able to improve their performances once burden is characterized by excellent physical and metallurgical properties leading to high permeability and reducibility. The sintering process is finalized to transform the small grained raw material into larger grained iron ore sinter of the right dimensions to be used in the blast furnace. Achieving an adequate sintered product depends on the adequate raw materials supply and the previous stage to the sintering process, granulation (Fernández-González et al. 2017a). Sintering acts on a porous bed necessary for the permeability and to improve the reduction reactions (Fig. 3.1). The sinter is of high quality if, after the process, it has an high reducibility that reduces the intensity of the blast furnace operations and the coke consumption (Jursova et al. 2018). So, the sintering process main objectives are to increase the size of ore additives to a level acceptable to the blast furnace for improving permeability of burden inside the BF; to form a strong agglomerate with high bulk reducibility; to remove volatile matter like CO2 from carbonates, H2O from hydroxides, and sulfur from sulfide type of ore fines along with their agglomeration; to incorporate flux in the burden; to utilize certain wastes containing iron, fuel, and flux; and to engineer the © Springer Nature Switzerland AG 2019 P. Cavaliere, Clean Ironmaking and Steelmaking Processes, https://doi.org/10.1007/978-3-030-21209-4_3

111

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3 Sintering: Most Efficient Technologies for Greenhouse Emissions Abatement

Fig. 3.1 Sintering operations

characteristics ferrous feed toward ideal blast furnace burden and partial reduction of iron ore from Fe+3 stages to Fe+2 stages. Sintering is a heat exchange process. In a static sinter bed, there are various zones like cold sinter, hot sinter, combustion zone, preheating zone, drying zone, and cold charge (Fig. 3.2). There is a downward movement of each zone with the forward movement of the pellet throughout the entire length during sintering. A mix of iron ores and coke (coke breeze) particles are deposited on the grate; coke breeze (0.5 MPa 5/40
C, >1 MPa

504

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

by the use of four compressors. The outlet temperature of the compressor is limited to 150
C, since higher outlet temperatures will damage the compressor equipment. After the first three compressors, the gas is cooled to 50
C by cooling water. After the fourth compressor, the blast furnace gas reached a temperature of 141.3
C and a pressure of 21 bars. The gas then enters a heat exchanger where it is heated by the hot outlet stream of the water-gas shift reactor which has a temperature of 499.7
C. After this heat exchanger, the gas has reached a temperature of 325.7
C and still has a pressure of 21 bars. The gas now enters the COS hydrolysis reactor. Under the presence of a CoMo catalyst (cobalt and molybdenum), the present COS is being transformed to H2S, as shown in: COS þ H2 O $ H2 S þ CO2 The COS is being transformed to H2S which will be removed later. The gas experiences a pressure drop of 1 bar during this reactor. After that the gas enters the chloride removal reactor, where the hydrogen chloride is removed. Under the presence of Na2O/Al2O3 catalyst, the hydrogen chloride is removed from the stream. The following two reactions take place: HCl þ NaAlO2 $ AlOOH þ NaCl 2HCl þ 2NaAlO2 $ Al2 O3 þ 2NaCl þ H2 O The gas experiences a pressure drop of 1 bar during this reactor. Finally, the gas enters the hydrogen sulfide removal reactor. In this reactor H2S is removed under the presence of a ZnO catalyst: H2 S þ ZnO $ H2 O þ ZnS Now the blast furnace gas is compressed and heated, and the present contaminants have been removed. The blast furnace gas has exactly the same composition; only H2S, COS, and HCl have been removed. This gas, with a temperature of 321.1
C and a pressure of 18 bars, is now sent to further treatment. A MEA scrubber system is used to capture CO2 from the shifted stream. The shifted BFG stream led into the absorber column. In this absorber column, the BFG comes in contact with MEA and water. The CO2 that enters the system ends up in the Rich MEA stream. The Rich MEA stream is pumped by the Rich MEA pump to ensure the flow speed needed for the system to operate. The pumped Rich MEA stream enters a heat exchanger where it is heated to 120
C. The heated Rich MEA stream enters the stripper column. In the stripper column, steam is used to separate the CO2 from the stream. This CO2 leaves the stripper column at the top and enters a compression section where two compressors and one cooler are used to compress the CO2 to 100 bar and 137
C. The compressed CO2 can now be transported via a pipeline. The stripped amine flow, consisting mostly of MEA, water, and some CO2, which is not stripped, is pumped back in the system, cooled by the Rich/Lean heat

9.4 Chemical/Physical Adsorption

505

exchanger, mixed in the makeup to ensure the right composition, further cooled by the Lean MEA cooler, and eventually recycled back in the absorber column. The recycle stream is vital for ensuring a high efficiency of the system. The MEA used in the absorber is highly selective to CO2; the sweet gas to methanol synthesis stream therefore is mainly CO, H2, N2, and a small proportion of CO2. This stream is sent to the methanol synthesis section. The sweet gas stream that leaves the stripper column of the MEA absorber system is available to produce methanol. The stream optimal ratio is H2/CO ¼ 2. First, the stream enters a compressor, a cooler, and a separator to remove liquid H2O. Finally the stream enters the last compressor which ensures it reaches 80 bars and 150
C. Now the stream has the right pressure, temperature, and H2/CO to produce methanol efficiently. In the methanol synthesis reactor: CO þ 2H2 $ CH3 OH After equilibrium is reached in the reactor, the temperature continuously rises as conversion proceeds (exothermic reaction). This means that the outlet temperature of the stream is higher than the inlet temperature. The stream then has to be cooled to enter the next reactor. This cooling generates MP steam that can be reused in the system to drive down utility cost. New blends of amine are continuously developed in order to improve the performances. As a matter of fact, the addition of piperazine by 15% increases the process efficiency (Cheng et al. 2010). Sodium and potassium carbonates are less expensive than amine and have lower corrosion inconveniences (Yoon et al. 2011). There are some differences between power plant and ironmaking plant such as the gas composition in exhaust gas, the usage of CO2-lean gas recovered from CO2 removal, and the utilization of waste heat utilization. The difference can be explained as follows: In exhaust gas, the CO2 concentration of ironmaking process is 20–23 vol.%, but the one of power plant is 10–15 vol.%. CO2 concentration of feeding gas gives effect to the absorption rate and efficiency; in ironmaking process, CO2-lean gas recovered from CO2 removal is reused as fuel gas of power plant. After removing the CO2, recovered gas has higher combustion energy per volume and so can be used effectively to generate electricity; in iron and steelmaking industry, much low- and medium-temperature waste heat, not recovered due to the economic feasibility, exist. Using these waste heats as regeneration energy of CO2 capture process, the energy cost of CO2 capture process will be decreased remarkably. For these reasons, ammonia-based processes are developed to capture CO2 from blast furnace gas (BFG) which contains high-concentration CO2 and is the major CO2emitting source at ironmaking industries. Ammonia plants are largely developed in Korea, with high efficiency, low cost, and low energy consumption (Fig. 9.5). Possible reactions between NH3 and CO2 are the following. The total reaction of CO2 in aqueous ammonia can be described as the equation:

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.5 Aqueous ammonia plant (Rhee et al. 2011)

2NH3ðlÞ þ CO2ðgÞ þ H2 OðlÞ $ ðNH4 Þ2 CO3ðaqÞ NH3ðlÞ þ CO2ðgÞ þ H2 OðlÞ $ NH4 HCO3ðaqÞ CO2 and NH3 react to generate NH2COONH4, and then NH2COONH4 hydrolyzes in solution instantaneous.  CO2ðgÞ þ 2NH3ðaqÞ ! NH2 COO ðaqÞ þ NH4ðaqÞ

Then, NH4+ and NH2COO have an irreversible reaction in solution: þ NH2 COO ðaqÞ þ NH4ðaqÞ þ 2H2 O ! NH4 HCO3ðaqÞ þ NH3  H2 OðaqÞ

At the same time, the balances of solute ionizing and ion reactions are occurring in the solution, and the reaction equations are:  NH3ðaqÞ þ H2 OðlÞ $ NHþ 4ðaqÞ þ OHðaqÞ  NH4 HCO3ðaqÞ $ NHþ 4ðaqÞ þ HCO3ðaqÞ 2þ ðNH4 Þ2 CO2 ðaqÞ $ 2NHþ 4ðaqÞ þ CO3ðaqÞ

9.4 Chemical/Physical Adsorption

507

Table 9.4 Comparisons of amine-based and ammonia CO2 capture systems Absorbent feature CO2 absorption Regeneration energy Absorbent cost Loss of absorbent Corrosion Influence of impurities (SOx) Operation condition

Technical issues

Amines 1 1

Ammonia 2.4 0.3

1 1 Large  Formation of heat stable salt  Regeneration of heat stable salts by reclaimer  Absorption at ambient pressure  Absorption: ~50
C  Regeneration: 110–130
C  Anti-corrosion agent needed  High regeneration energy  Salt formation during operation  Thermal degradation

0.17 2.5 Small  Possible to use as a fertilizer of ammonium sulfate  Absorption at room temperature  Absorption: ~40
C  Regeneration: 80–90
C  Salt formation during operation  Highly volatile  Utilization of low-temp. waste heat

 2þ OH ðaqÞ þ HCO3ðaqÞ $ CO3ðaqÞ þ H2 O  CO2þ 3ðaqÞ þ CO2ðgÞ þ H2 OðlÞ $ 2HCO3ðaqÞ

Among the conventional CO2 chemical removal processes, the monoethanolamine (MEA) process has been comprehensively studied and successfully used in chemical plants for CO2 recovery. Although the MEA process is a promising system for the control of CO2 emissions from massive discharging plants, it is an expensive option since the cost of CO2 separation may range from US$ 40 to 70/ton of CO2 removed. CO2 capture using ammonia solution offers several advantages over the commercially available amine-based process for CO2 capture from coalfired power plants. The following items can be compared, CO2 loading capacity, equipment corrosion, absorbent degradation, makeup rate and cost, energy consumption during regeneration, etc., and summarized in Table 9.4. Data were published comparing maximum CO2 loading capacity in MEA solution and in ammonium hydroxide solution on an equal weight-of-absorbent basis. It was concluded that the maximum CO2 removal efficiency by NH3 absorbent can reach ~99% and the CO2 loading capacity can approach 1.2 kg CO2/kg NH3. On the other hand, the maximum CO2 removal efficiency and loading capacity by MEA absorbent are 94% and 0.40 kg CO2/kg MEA, respectively, under the same test conditions. In other words, ammonia’s CO2 loading is three times that of MEA’s. Usually H2 is recovered from the gas and then is mixed with N2 to manufacture ammonia, according to the reaction:

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

N2 þ 3H2 $ 2NH3 Δr H∘ ð298KÞ ¼ 45:9 kJ=mol For the urea synthesis, a CO2 source is needed. In some plants, the BFG is used as CO2 source. Then, the urea synthesis is made in two steps, according to the following reactions: CO2 þ 2NH3 $ NH2 COONH4 Δr H∘ ð298KÞ ¼ 637:1 kJ=mol NH2 COONH4 $ COðNH2 Þ2 þ H2 O Δr H∘ ð298KÞ ¼ 134 kJ=mol It has a potential of 90% of reduction with 9% of ammonia in the pilot plant of 50 m3/h. In the steel mill of Thyssenkrupp Steel in Duisburg, it is possible to achieve a urea capacity of 3500 t/day, which is comparable with common capacities. For increasing the reduction, additional green hydrogen, e.g., from water electrolysis, is necessary. By this means, up to 45% of the steel mill carbon dioxide can be used chemically, and a urea capacity of 29,000 t/day can be reached. It was shown that urea plants can make an incredible impact on the reduction of full-scale steel mill carbon dioxide emissions (Yildirim et al. 2018). Physical adsorption is applied at high CO2 partial pressure and low temperatures. Its high capacity makes it the preferred method for CO2 concentrations higher than 15%. The combination of shift reactor and Selexol™ or Rectisol® is believed to reach an adsorption of 99.5%. Rectisol method is one of the most mature technologies used in CO2 capture process (Sun and Smith 2013). It has been widely used for CO2 and sulfide capture in coal-based chemical processes because of high CO2 solubility, high selectivity for CO2, no degradation of the solvent, and low operation cost. The crude syngas from coal gasification is fed into the water scrubber for removal of ammonia and ash and then sent to the acid gas absorber. Acid gas (CO2 and H2S) are absorbed by low-temperature methanol. The clean syngas is obtained from the top of the absorber, and the acid gas with methanol is obtained from the bottom of the absorber. This methanol is then fed into the desorber to separate CO2 and H2S. CO2 and methanol are separated by flash separation. Recovered CO2 is compressed to 15 MPa. With CO2 capture process, 90% of CO2 is captured, and the rest CO2 is emitted out from the H2S acid gas removal tower. The energy penalty for this solution is high, in the order of 1500 kJ/kg CO2 (Ho et al. 2011). The concentration of the capture CO2 is able to be increased to as high as 99% by adjusting the stages number of desorber column, the temperature, and pressure of the CO2/methanol flash separation. In Gielen (2003) a case study taking into account gas cleaning, gas pressurization (at 20 bar), shift reaction to convert CO into CO2 and H2, CO2 capture through Selexol, H2 usage for power generation and CO2 pressurization (at 100 bar), and storage in oil or gas fields is presented. Also the cost analysis is performed in order to make a comparison with IGCC costs (35$/t CO2). The scheme of the proposed solution is shown in Fig. 9.6. In the shift reaction, the carbon monoxide reacts with the steam (at 623 K) to produce CO2 and H2 through an exothermic reaction. The capture is performed by

9.4 Chemical/Physical Adsorption

509

Fig. 9.6 CO2 capture and storage system process flow Table 9.5 CCS costs using Selexol

Electricity consumption (GJ/t CO2) Investment ($/t CO2 year) O&M costs ($/t CO2 year) Storage costs ($/t CO2 year) Electricity production from CO2 (tCO2/ t CO2) Total costs ($/t CO2 year)

BF 0.62 16–25 1.25 5 0.062 17.6– 18.8

Oxygen-blown BF 0.59 13–20 2 5 0.07

Corex 0.59 25 1.25 5 0.07

CCF 0.59 25 1.25 5 0.038

DRI 0.34 1 0.05 5 0.021

17.5–18.5

18.4

18.4

10.3

Selexol at a temperature of 293 K and a pressure of 20–30 bar. 99.5% of CO2 is removed. The CO2 pressurization depends on the storage depth. For oil and gas lands, 80 bar are necessary to store the gas at 1500 m; 100 bar are necessary for a storage depth of 2600 m. Less pressure is required for oceanic storage (50 bar for 500 m). With the indicated configuration, the cost estimation results are listed in Table 9.5. The physical absorption process may be a useful method of CO2 removal from metallurgical fuel gases on a large industrial scale. However, such a process is always accompanied by a high power consumption. The optimization of parameters concerning the absorption process is necessary to keep the energy demand at a minimum level. Different CO2 contents in Corex and blast furnace gases result in a

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

510

Table 9.6 Direct emissions for a 5 Mt/year integrated steel mill Iron production Power plant stack COG 3.69 1.73

CO2 (Mt/year) Flow rate 400 (Nm3/s) Pressure 101.3 (kPa) Temperature 300 (
C) Composition (Vol.%) N2 68 H2O 8 CO2 23 O2 1 CO – H2 – SOx >200 NOx >200

Steel production BF stoves 1.94

Sinter plant stack 1.67

Lime kiln stack 0.05

BOF stack 0.28

Hot strip mill stack 0.14

Plate mill stack 0.06

159

14

337

16

194

47

41

101.3

101.3

101.3

101.3

101.3

101.3

101.3

100

300

100

300

300

300

300

67 5 27 1 – – 120 300

68 10 21 1 – – 100 150

70 21 8 – 1 – >200 >200

70 21 7 2 – – >200 >200

13 2 15 – 70 – 200

70 21 7 2 – – >200 >200

higher power consumption in the case of blast furnace gas treatment. Changing the pressure level in the absorber is possible within specified limits (Lampert and Ziebik 2007). Increased LHV due to the CO2 removal and increased content of combustible components bring many new possibilities of utilization of treated fuel gas. The gas may be used inside iron works or may be sent to the external users. Particularly, one of the most interesting options is using of the gas as the source of additional reducing agents in blast furnace process. This concerns especially the treated Corex gas, as it contains about 90% of CO and H2. A further increase of CO2 removal effectiveness would require a shift reactor to convert some part of CO into CO2 and simultaneously increase the H2 content in the gas. Another very interesting and complete study from the emission analyses to the solutions and the consequent costs is developed by Ho et al. (2013). The flow rate, temperature, pressure, and compositions of all the direct CO2 emissions for a 5 Mt/ year primary steel plant are summarized in Table 9.6. The same data collected for ISM, TGRBF, HIsmelt, and Corex iron and steel mill are listed in Table 9.7. For the given plants, the CO2 captured by employing MEA or VPSA is listed in Table 9.8. It is clear how the MEA adsorption is more effective in BF and HIsmelt plants. Anyway the energy penalty is 50% higher with respect to the VPSA. The principle of the PSA CO2 scrubbing technology is shown in Fig. 9.7.

9.5 Solid Adsorbents Capture

511

Table 9.7 Direct emissions for a 5 Mt/year ISM, TGRBF, HIsmelt, and Corex

Conventional ISM TGRBF HIsmelt Corex

Iron production Power plant stack COG 3.7 1.7 2.9 4.4 7.6

0.8 N/A N/A

Steel production BF stoves 1.9

Sinter plant stack 1.7

Lime kiln stack 0.05

BOF stack 0.3

Hot strip mill stack 0.1

Plate mill stack 0.1

N/A 3.9 N/A

1.1 N/A N/A

0.05 0.06 0.15

0.3 0.1 0.1

0.1 0.1 0.1

0.1 0.1 0.1

Table 9.8 CO2 captured for the studied plants, costs, and energy consumption for the different adopted solutions

CO2 emitted (Mt/year) CO2 captured (Mt/year) Capital costs ($/t CO2) Energy penalty (kJe/kg CO2)

BF MEA 3.6 3.2 140 1510

VPSA 3.6 2.9 85 1045

TGRBF MEA VPSA 2.9 2.9 2.6 2.6 125 86 1440 930

HIsmelt MEA 4.7 4.2 130 1495

Corex VPSA 4.7 4 95 1085

MEA 5.2 4.7 110 1400

VPSA 5.2 4.5 85 825

Another solution is represented by Steelanol developed by ArcelorMittal in Ghent (Fig. 9.8). The process allows to synthesize ethanol from steel gases. The process for ethanol production employs a technology developed by LanzaTech, whereby gases produced during the chemistry of steel production are fermented by microbes that secrete ethanol. The capture and reuse of a portion of carbon emitted by the steel mill will be achieved with minimal rebuilding of the plant and will produce highgrade biofuel (Lucas and Rossetti di Valdalbero 2018). This technology could entail the production of 2.5 million tons of bioethanol in Europe with emissions reductions of 65% compared to fossil fuels and at a competitive cost.

9.5

Solid Adsorbents Capture

CO2 is passed through a bed of solid sorbents such as zeolites or activated carbons. The main employed processes are PSA and VPSA. They require gas compression, so the process is related to the energy consumption. In the Lulea large-scale pilot plant, CO2 is removed from the TGRBF through VSPA. It allows to reduce CO2 by 3%, CO recovery is 88%, and the total CO2 emissions are reduced by 76% (Danloy et al. 2009). Pérez-Fortes et al. (2014) presented a validated conceptual model of a reference iron and steel plant to observe its performance in terms of CO2, energy, and mass

512

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.7 Principle of the PSA CO2-scrubbing techniques and various domains of application and performances of the variant techniques, PSA, VPSA, and VSA

balances. The technology selected as the most immediate (retrofitting) solution implementable at the industrial scale was the top gas recycling blast furnace (TGRBF), with CO2 capture in a PSA. This configuration, instead of hot blast, uses low-purity O2 to produce the reducing gases from pulverized coal injection (PCI) coal. The BF is converted into an OBF. The gas obtained directly from the OBF is the top gas (TG) or the oxygen blast furnace gas (OBFG), and the reducing gas resulting after CO2 capture is called process gas (PG) (van der Stel et al. 2014). The reference plant for the base case is a classical steelmaking plant with a production of 4 Mt of hot rolled coil (HRC) per year. A standard configuration route consists in coke oven or coking plant, sinter plant, BF, basic oxygen furnace (BOF), and hot rolling mill. In this work, only the coke oven and BF are considered as being the two units on which modifications are required (1) for injecting of oxygen in the BF instead of air (OBF) and (2) for PG recycling, since the blast furnace gas (BFG) is treated in the PSA, and coke production diminishes due to the reducing gases recirculated into the BF. The gases produced in the iron and steel plant have an important calorific value and can be used for different purposes. In the base case, COG is mainly used to meet the energy needs of the rest of the plant. In

9.5 Solid Adsorbents Capture

513

Fig. 9.8 Steelanol schematic

the coke oven, it is utilized to produce the pyrolysis gases and in the BF to (1) dry the PCI coal and to (2) heat up the cold blast. The BFG is used in the coke oven supporting the COG for the production of the pyrolysis gases and, in the BF, also with COG, to heat up the cold blast. The remaining is sent to the power plant. Figure 9.9 shows a detailed distribution of the by-product gases among the simulated units. The production of gases changes in the plant configuration with carbon capture (Fig. 9.10). However, the needs satisfied by the base case gases must be also fulfilled when capture is used. The main concepts that differ from the base case are O2 injection in the BF instead of air. Therefore, hot blast is not produced, and hot stoves are not required; gas from BF is recycled to the own BF, as a reducing agent for the iron ore. Since this gas must be at high temperature (i.e., adapted temperatures according to the injection zone), PG gas is preheated before entering the tuyeres and the shaft with hot gases from natural gas combustion; use of CO2 capture and CO2 purification techniques; and extra combustible needs (i.e., to cover the demand of BFG that is not satisfied with the change of configuration) are covered by natural gas. Capture was performed using a PSA with tested pressures between 4.2 and 5.5 bar. The last CO2 purification unit before compression and transportation is a cryogenic distillation column that mainly separates CO2 and CO. In this plant, the TG is cleaned and compressed to PSA working pressure. After the PSA, the tail gas is fed to a cryogenic purification unit, to obtain pure CO2. The non-condensable gases are

Fig. 9.9 Block diagrams that outline the modeling blocks and the COG, BFG, OBFG, and PG connections: base case

514 9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.10 Block diagrams that outline the modeling blocks and the COG, BFG, OBFG, and PG connections: CO2 capture case

9.5 Solid Adsorbents Capture 515

516

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

recycled back to the compressed gases before the PSA, and the PSA product gas, the reducing gas, is reinjected into the OBF. In the CO2 capture case, the hot blast is replaced by oxygen. The recycled PG enters the furnace through tuyeres and shaft, at 1250
C and 900
C, respectively. COG production, which is lower due to a minor need of coke, is used again to supply all the needs of the rest of the plant that does not change with the addition of the capture configuration, to dry the PCI coal, and to produce the pyrolysis gases. PG is used to supply reducing agents to the BF and to produce the pyrolysis gas. The main gas distributions for the two simulated cases were presented. Natural gas consumption in the CO2 capture case is 61,170 kg/h. Coking coal consumption decreases by around 25% in mass terms (73,700 kg/h). The emissions of CO2 are 0.621 tCO2/tHRC for the base case and 0.333 tCO2/tHRC for the CO2 capture case. The flow rate of the captured CO2 stream is 445.2 t/h.

9.6

Membrane Separation

Gas separation through membranes can reach an efficiency of 80%. The main advantages of membranes for gas purification are low capital investment, good weight and space efficiency, ease of scale-up, minimal associated hardware, no moving parts, ease of installation, flexibility, minimal utility requirements, low environmental impact, reliability, and, finally, the ease of incorporation of new membrane developments (Ramírez-Santos et al. 2018). The disadvantages are that a clean feed is required (particulates and in most cases entrained liquids must be removed), there is little economy of scale, and, finally, the energy requirements for gas compression are high. In order to be a good separator, it is important that the membrane has a high permeance [mol/(m2 bar h)] for CO2 and a high selectivity for CO2 over the other gases in the blast furnace gas. Also, the partial pressure level of CO2 is important. The comparison of the three separation technologies, chemical absorption (MEA), pressure swing adsorption, and membrane separation, showed that the chemical absorption was the best at flue gas compositions (low partial pressures), while membrane separation was the best at the blast furnace conditions. At high pressures, e.g., for natural gas treating plants, CO2 removal by membranes is even more suitable, and most industrial applications are found in this area. Membrane technology, as applied to gases, involves the separation of individual components on the basis of the difference in their rates of permeation through a thin membrane barrier. The rate of permeation for each component is determined by the characteristics of the component, the characteristics of the membrane, and the partial pressure difference of the gases across the membrane. The membranes normally employed in the natural gas utilization can be employed for the BFG. Carbon membranes have the ability to separate gases based on small differences in the size and shape of the gas molecules. Their separation performance is superior to conventional polymeric membranes. In addition, carbon membranes have high chemical and thermal stability. Two different types are normally employed: adsorption selective carbon and sieving selective

9.6 Membrane Separation

517

carbon. ASCM is a semicommercial membrane, with average pore size of about 5 A
. The flux through the membrane is characterized by a high degree of surface diffusion. Carbon molecular sieving membrane (CMSM) is an in-house made membrane with average pore size of about 3.5 A
. The separation is dominated by molecular sieving. The precursor is kraft pulp, i.e., a mixture of cellulose and hemicellulose. By considering the principle transport mechanisms of carbon membranes, Knudsen diffusion and surface diffusion may take place in the same pore, and the extent depends on conditions like temperature and partial pressure. This may be exploited for enhanced CO2 diffusion in the ASCM membrane. In the CMS membrane, the narrowest pore constrictions are approaching molecular dimensions, resulting in the sieving mechanism. The sieving kinetic diameters of N2, CO, CO2, and H2, as calculated via adsorption in zeolites, are 3.6, 3.8, 3.3, and 2.9 A
, respectively. A dry gas feed is preferred for carbon membranes, since the separation performance of carbon membranes is deteriorated when introducing water vapor, mainly due to pore blocking. The fixed site carrier membrane (FSCM) is a polymeric membrane which has active amine groups bound to the polymer backbone, acting as carriers for a CO2-water complex. The membrane has to be humidified, and the water in the feed gas is an advantage. A further advantage of this kind of membrane is the ease of production and handling. A number of articles have been published on polymeric membranes containing an amine moiety for the facilitated transport of CO2. According to these studies, for the CO2 hydration reaction in the water-swollen membranes, CO2 does not interact directly with the amino groups fixed to the membrane, but rather CO2 is carrier-transported in the form of HCO3 (exchanging H+ between water and amine group). This mechanism may provide the possibility of enhanced permeability and selectivity in favor of CO2 for the aminated fixed site carrier membranes. The role of fluoride ions in water-swollen membranes may be significant and may increase the reactivity between CO2 and water. The water molecules become more basic compared to pure water, and the fluoride creates highly polar sites in the membrane. The basic water molecules have a higher affinity for CO2, which leads to an increased concentration of HCO3 in the membrane and, consequently, an increased transport rate of CO2. Thus, the number of available carrier sites for transport of CO2 in the membrane is a function of the degree of amination and the amount of cross-linking agent used. Permeation of more permanent gases like CH4, N2, CO, and H2 is retarded by the highly polar sites, and increased selectivity is expected. In general, the FSC membrane selectivity decreases as temperature is increased. This may be explained by reduced sorption of CO2, and, for temperatures approaching 100
C, progressive dehydration of the membrane occurs. A very high efficiency has been reached with polymeric membranes with amine groups (Lie et al. 2007). The main results of the study are listed in Table 9.9. 97% CO2 recovery was achieved for the O2-blown BFs. Electricity consumption ranged from 0.24 GJ/tCO2 captured for just the membrane section increasing to 0.5–0.9 GJ/tCO2 captured when the CO2 was compressed to 11 MPa for pipeline transport. Estimated costs range from 15 euro/tCO2 for case 2a to 17.5 A/tCO2 for case 1b (euro year 2005).

518

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Table 9.9 Performances of the described cases; Case 1, includes compression to 11 MPa for pipeline transport; Case 1, taken as the compressor duties from where feed enters battery limits up to and including compression of CO2 product to 0.15 MPa; Case 2, adiabatic efficiency of 75% used; Case 2, energy recovered in expander taken into account CO2 in feed (t/h) CO2 recovery (%) Feed temperature, pressure stage 1, (
C; MPa) Feed temperature, pressure stage 2, (
C; MPa) Membrane area (m2) Plant compression duty (MWe) Membrane section compression duty (MWe) Expander energy (MWe) Total compression duty (GJe/CO2 recovered) Membrane section duty (GJe/CO2 recovered)

9.7

Case 1 420 97 30, 0; 48 – 1.3  106 93 48 3.6 0.8 0.4

Case 1 420 97 30, 0; 48 22, 0; 26 3  106 103 59 3.4 0.9 0.5

Case 2 299 79 30, 0; 45 – 4.9  106 62 37 14.3 0.5 0.24

Case 2 299 83 30, 0; 48 22, 0; 26 1.2  106 73 48 14.3 0.6 0.33

Cryogenics Separation

The basic concept is the CO2 separation from other gases through cooling and re-condensation. It is obviously a high energy-consuming process, even if the cooled gas can be easily compressed for the transport or direct use (Lampert et al. 2010). The advantages are that no chemical ab- or adsorbents or large pressure differences are needed and that high-purity products can be obtained. At atmospheric pressures CO2 will go directly from its gas phase to its solid phase (desublimation). In order to be able to carry out the CO2 removal from flue gases as a gas-liquid separation, it is necessary to compress the gas to pressures above the triple point of CO2, which is at 5.2 bar and  56.6
C for pure CO2 (Fig. 9.11). Compressing flue gases to high pressures is too energy-intensive. When a gas mixture consisting of N2, CO2, and H2O is being fed at a relatively high temperature to an initially cryogenically refrigerated packed bed, an effective separation between these components can be accomplished, due to differences in dew and sublimation points. The gas mixture will cool, and the packing material will heat, until H2O starts to condense at the packing surface. A certain amount of H2O per volume of packing material will condense, until a local equilibrium is reached. Actually a very small part of the H2O at the front will be frozen to ice, but simulations have revealed that this is a very small part of the H2O and has negligible influence on the resulting axial temperature and mass deposition profiles. The cold energy stored in the packing will be consumed, and a front of condensing H2O will move through the bed toward the outlet of the bed. At the same time, previously condensed H2O will evaporate due to the incoming relatively hot gas mixture. Therefore, two fronts of evaporating and condensing water will move through the bed, with a faster moving condensing front. After all water being condensed, the gas mixture will be cooled further until CO2 starts to change phase. At atmospheric pressure CO2 will desublimate directly from gas to solid, and therefore solid CO2 is deposited onto the packing surface. Similar as

9.7 Cryogenics Separation

519

Fig. 9.11 Phase diagram of pure CO2

for H2O, two CO2 fronts will move through the bed: an evaporation and a desublimation front. Again an equilibrium is reached; a certain amount of CO2 is deposited at the packing surface. In this way an effective separation between CO2 and H2O is accomplished. N2 will not undergo any phase change (as long as T0 is not chosen too low) and will therefore move through the bed unaffected. When the CO2 desublimation front reaches the end of the bed, CO2 may break through, and the bed should be switched to a recovery step just before that. The first zone of the bed has been heated during the capture step. This heat is used in the recovery step to evaporate the condensed H2O and desublimated CO2. A gas flow consisting of pure CO2 is fed to the bed. When feeding a pure CO2 gas flow to the packed bed, the gas will be heated, and all fronts will move through the bed. However, during the initial period of the recovery step, the ingoing CO2 will deposit onto the packing. Due to the increase in CO2 partial pressure compared to the capture step, more CO2 is able to desublimate at the packing surface, and the bed temperature will slightly increase. Pure CO2 is obtained at the outlet of the bed after this new equilibrium is reached. Part of the outgoing CO2 should be compressed for transportation and sequestration, while the other part can be used to recycle to the inlet of the bed at a temperature which is slightly higher due to the heat production associated with the compression in the recycle blower and some unavoidable heat leaks. When all CO2 has been recovered, the bed is switched to a step in which H2O is removed and the bed is cooled simultaneously. Alternatively, the deposited CO2 could be recovered as a liquid, avoiding expensive compression costs required for transportation and storage. This could be accomplished by closing the valves connected to the bed and by introducing heat into the bed. CO2 evaporation occurs, and pressure builds up until the system reaches the triple point of pure CO2 and liquid CO2 will be formed.

520

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

The drawbacks of this process alternative are that pressure vessels are required and that heat should be introduced into the bed, for example, by means of internal tubes. Both measures will result in a significant increase in capital costs. Furthermore not all liquid CO2 might be recovered from the packing, due to the static liquid holdup in the bed. In the last step, the bed is cooled down using a gas flow refrigerated. The cleaned flue gas can be used for this purpose. Cooling can be performed using a cryogenic refrigerator. H2O is evaporated and removed from the bed during the first period of the cooling step. The N2/H2O mixture can be released to the atmosphere, and when all H2O is recovered, the outgoing flow can be recycled to the inlet of the bed, via a cooler. Simulations performed on the cryogenic CO2 capture concept based on dynamically operated packed beds show several advantages compared to cryogenic separation based on conventional heat exchangers. In the first place, plugging is intrinsically avoided. Due to the limited amount of cold stored in the packing material, also a limited amount of CO2 is desublimated. It can, for example, be observed that the amount of CO2 during the recovery step is approximately 80 kg/ m3, which is corresponding to a volume fraction of approximately 0.06, depending on the density of solid CO2. The gas void fraction of the used packing was much higher (0.7), and plugging or an increase in pressure drop is therefore avoided. Another advantage of the proposed concept is the very high purity of the treated gas. An initial bed temperature of 140
C will result in a CO2 fraction in the outlet of less than 0.1% during the capture step. The proposed concept can therefore recover more than 99% of the CO2 when feeding a mixture containing 10 vol.% CO2, while, for example, scrubbing technology is only able to capture 90% of CO2 at acceptable absorber sizes. Another possible advantage of the proposed concept is that other pollutants such as NOx, SOx, and H2O can be captured simultaneously, avoiding expensive pre-treatment. H2O and CO2 can be captured simultaneously. However, it was also explained that the allowed water content in the flue gas is limited, due to the heat required for evaporation of the condensed H2O in the recovery step. Finally, an additional advantage of the concept is that simple low-pressure vessels packed with low-cost inert packing material can be used, reducing capital costs. A dedicated experimental setup was designed to measure CO2 deposition rates under well-defined conditions. The results showed that heat transfer through the formed frost layer plays an important role in the deposition rates. Furthermore, it was shown that diluting CO2 with N2 has a large effect on the mass deposition rate, due to the introduction of mass transfer limitations from the gas bulk toward the frost surface. Under the packed bed conditions, heat transfer through the solid frost layer plays no significant role, and the process was mainly determined by mass transfer of CO2 toward the particle. The entire process cycle including the cooling, recovery, and capture step was demonstrated in an advanced fully automated experimental pilot setup. Three beds were operated in parallel, therefore enabling the option to operate the process continuously. The walls of the packed bed caused temperature differences measured in the radial center and close to the wall and also a much more dispersed temperature front closer to the wall, especially for the cooling step. The costs of cryogenic CO2 capture using dynamically operated packed beds depend strongly on initial bed temperatures and CO2 concentrations in the feed gas.

9.8 Carbonization

521

At lower initial temperatures, the cold stored in the bed can be used more efficiently, resulting in more CO2 deposited per unit of bed volume. At low CO2 inlet concentrations, the relative costs for the amount of CO2 avoided increase strongly. Due to high flow rates required during the process, the pressure drops over the system substantially influence the CO2 avoidance costs. It is expected that required gas distribution plays an important role in the resulting pressure drop. In the comparison with other technologies, it was found that the preferred technology depends heavily on the availability of utilities. The cryogenic concept requires a cold source, such as the evaporation of LNG at a regasification terminal, while amine scrubbing requires low-pressure steam in order to strip the solvent. When both LNG and steam are not available at low costs, membrane technology shows advantages. When steam is available at low costs, especially when using an advanced amine, scrubbing is the preferred technology. The cryogenic concept could be the preferred option, when LNG is available at low costs. Especially when pressure drops can be decreased and the simultaneous removal of impurities can be incorporated in one process, the concept could become a serious candidate for capturing CO2 from flue gases.

9.8

Carbonization

The alkaline rare hearth rich slags can be used to capture and store the CO2. Calcium oxide and magnesium oxide in the slags react with CO2 to form stable calcium carbonate. Carbonization can be direct when the reactions act in the aqueous phase or at the gas-solid interphase (Richards et al. 2008). It can be indirect when the alkaline metals are firstly extracted from the slag and then they precipitate as carbonates (Kunzler et al. 2011). The theoretical storage capacity is around 25% (0.25 kgCO2/kg slag), with a global potential reduction by 11%. Table 9.10 compares the mature CO2 capture technologies for the steel industry. Although PSA and VPSA have the lowest energy consumption, the captured CO2-rich gas is not of a high enough purity for storage. Adding a cryogenics unit is required. The total energy consumption of this setup is still lower than an amine system. For a TGRBF, the PSA and VSPA, with cryogenics, schemes are best in terms of technical performance and cost, both operating and capital. Kuramochi et al. (2011) provided an estimation of steel production costs coupled with the CO2 emissions levels by applying different CCS technologies (Fig. 9.12). For the BF route, CO2 emissions strongly decrease once the CO in the BF gas is shifted or TGRBF are employed. Advanced CO2 capture technologies do not seem to have significant economic advantages over conventional technologies. The COREX process allows to reduce both the production costs and the greenhouse emissions. However, the reduction in specific CO2 emissions compared to the reference BF-based process is only 15%. Advanced smelting reduction process shows very promising results: reducing crude steel production cost by 15% and specific CO2 emissions by 90% compared to the reference BF-based process (last bar).

Recycled gas CO yield (%) CO volume (%) CO2 volume (%) N2 volume (%) H2 volume (%) H2O volume (%) CO2-rich gas captured CO volume (%) CO2 volume (%) N2 volume (%) H2 volume (%) Suitable for transport and storage? CCS process Electricity consumption (kWh/tCO2) Capture process (kWh/tCO2) Compression to 11 MPa for storage (kWh/tCO2) Low-pressure steam consumption (GJ/tCO2) Total energy consumption (GJ/tCO2) 90.4 68.2 3 15.7 13 0 10.7 87.2 1.6 0.6 No 105 105 – 0 0.38

12.1 79.7 5.6 2.5 No

100 100 –

0

0.36

VPSA

88 71.4 2.7 13.5 12.4 0

PSA

Table 9.10 Mature CO2 capture technologies

1.05

0

292 160 132

3.3 96.3 0.3 0.1 Yes

97.3 68.9 3 15.6 12.6 0

VPSA+compression and cryogenic flash

3.81

3.2

170 55 115

0 100 0 0 Yes

99.9 67.8 2.9 15.1 12.1 2.1

Amines + compression

1.12

0

310 195 115

0 100 0 0 Yes

100 69.5 2.7 15.4 12.4 0

PSA + cryogenic distillation + compression

522 9 Carbon Capture and Storage: Most Efficient Technologies for. . .

9.8 Carbonization

523

Fig. 9.12 Costs and CO2 emissions for different capture technologies applied to various processing routes (Kuramochi et al. 2011)

A recently proposed technology allows to capture CO2 directly from the air of industrial plants (Keith et al. 2018). The authors developed a system capable of capturing 1 MtCO2/year in a continuous process using an aqueous KOH sorbent coupled to a calcium caustic recovery loop (Fig. 9.13). The system consumes 8.81 GJ of natural gas or 366 kWh of electricity per ton of carbon dioxide capture. The costs are estimated in 94–232 US dollars per ton. The process comprises two connected chemical loops (Fig. 9.14); the first loop captures CO2 from the atmosphere using an aqueous solution with ionic

524

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.13 Fans capture scheme of the proposed technology

Fig. 9.14 Proposed process chemistry

concentrations of roughly 1.0 M OH, 0.5 M CO32, and 2.0 M K+. In the second loop, CO32 is precipitated by reaction with Ca2+ to form CaCO3, while the Ca2+ is replenished by dissolution of Ca(OH)2. The CaCO3 is calcined to liberate CO2 producing CaO, which is hydrated or “slaked” to produce Ca(OH)2. The overview of the process is shown in Fig. 9.15. Obviously, the results belong to very recent studies performed on a pilot plant (1 tCO2/day); this is the main reason for the broad cost range precision. A full-scale wet scrubbing air contactor was developed (Holmes et al. 2013) as one of the last DAC solutions. The prototype featured the air contactor (Fig. 9.16), which used a hydroxide solution on structured packing to capture CO2 and produce carbonate, then a causticizer to react this solution with lime to precipitate calcium carbonate and regenerate the hydroxide for further capture, and finally a filter to separate out the calcium carbonate as a wet cake.

Liquid stream

Air contactor basin

Air contactor

CO2 adsorber

Gaseous stream

Solid strea

0.4MW

9.2MW

Fig. 9.15 Industrial scheme of the plant

21°C 251000t/h 0.06%CO2 23%O2 75.96%N2 0.98%H2O

Fines to calciner

CaCO3 21.5t/h

21°C 35000t/h 2[K+] 1.1[OH-] 0.45[CO32-]

CaCO3 3.4t/h

Fines to disposal

19°C 252000t/h 0.016%CO2 22.96%O2 75.83%N2 1.2%H2O

112 t of captured CO2

CWS

2.6MW

AUX

31°C 3200t/h 2.01[K+] 0.68[OH-] 0.66[CO32-]

93°C 121t/h 14.43% CO2 0.91% O2 72% N2 12.66% H2O

0.2MW

85°C

300°C 0.3t/h H2O 24.7t/h CaO 186t/h Ca(OH)3

Quick time mix tank

567t/h 0.14[K+] 0.08[OH-] 0.03[CO32-]

773t/h 4.56[Ca(OH)3] 0.23[K+] 0.06[OH-] 0.06[CO32-]

Pellet Reactor 3.4MW

CaCO3 seed From calciner

6t/h

Separation

CaCO3 makeup 3.4t/h

Cooling water hx

Fines filter

CWR

21°C 369000t/h 2[K+] 1.1[OH-] 0.45[CO32-]

4.5t/h CaCO3

HSRG -46MW

50°C

Gas turbine

Condenser

CWR

Lime cooler

253°C 4.2MPa 70.2t/h

Steam slaker 3.6MW

6.3t/h 315GJ/h 100% CH4

CWS

674°C 170t/h 165t/h CaO 5t/h K2CO3

300°C 306t/h 300t/h CaO 5.4t/h K2CO3

CaCO3 seed to pellet reactor 6t/h

650°C

ASU 13.3MW

13.4t/h 670GJ/h 100% CH4

900°C

Preheat 1

58.5t/h 96.6% O2 4.4% N2

674°C

Steam superheat

171t/h 97.12% CO2 1.36% O2 1.51% N2 0.01% H2O

40°C 151bar

454°C 201t/h 82.57% CO2 1.16% O2 1.28% N2 14.99% H2O

CO2 compressor 22MW

Oxygen preheat

Steam turbine -0.8MW

415°C 4.2MPa

531t/h H2O

9.8 Carbonization 525

526

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.16 Prototype module capable of capturing 100 kt CO2/year

In the full system design, the calcium carbonate would be heated in an oxy-fired calciner to liberate CO2 for subsequent cleanup and compression. The calciner also reforms the lime required by the causticizer, thus closing the chemical loop. This is a commonly used chemical cycle in the pulp and paper industry. The designers did not build the high-temperature calciner into the pilot due to cost restrictions, so the pilot required a lime feed to run and produced CaCO3 for disposal. The outdoor contractor was designed to examine the core packing wetting, mass transfer, and potential particulate fouling phenomena that underpin the performance of air contractor design. A quantitative understanding of these phenomena is critical for our scale-up efforts and for continual revision and improvement of the design itself. The packed volume was 1.8 m tall and 0.9 m wide and could be set up with an air travel distance of 4.5–6.0 m. Air travel distance is the distance which air travels through wetted packing. The 1.8 m height of the packing was chosen to allow uniform liquid flow conditions to develop as the solution passed down through the packing. This was important, as proper flow conditions ensure that the surface wetting in the packed volume represents what would be achieved in a larger-scale system. At least 20 cm of height was required to achieve uniform liquid distribution, and then the rest of the height served to mimic the realistic wetting conditions of a full-scale contactor. Packing wetting phenomena is a key driver of overall contactor performance. Directly above the structured packing volume is a set of spray nozzles used to distribute the hydroxide solution over the packing. Each module, covering a top area of packing of 1 m2, had nine nozzles for liquid distribution, which immediately fell on what is termed a distribution pad—a device commonly used in the cooling tower industry to push the solution laterally before it fell into the actual packing volume. After flowing down through the packing volume, the liquid fell

9.9 CHG Capture

527

through a grated floor back into the main sump. A combination of pumps and flow control valves allowed us to supply this liquid over the packing at a wide range of flow rates. It was also from this sump that a small stream of liquid was removed for processing by our solution management system, which removed some of the constituent CO2 in order to reform the OH to allow continued capture. When run in steady-state operation, the removal rate of CO2 from solution matches our capture rate of CO2 from the air, allowing us to maintain steady OH and CO32 concentrations in the sump. At the inlet of the contractor, an inlet louver was used to catch debris in the air before it passes into the packing volume, where it could cause clogging or increased pressure drop. At downstream end of the contactor, a drift eliminator was installed that passes the air through a tortuous path that strains out any small, entrained hydroxide droplets.

9.9

CHG Capture

Coke oven gas (COG) is a point of high interest to enhance energy efficiency and reduce GHG emissions in the steel industry. In spite of the reduction of coke consumption in the blast furnace (and therefore COG production), during the past few decades, blast furnaces cannot operate without coke which implies COG will continue to be produced in large quantities in the future. COG has a very complex composition after leaving the coke oven. Firstly, the gas is cooled down to separate tars to subsequently undergo different scrubbing processes to eliminate NH3, H2S, and BTX. After these conditioning stages, cold COG comprises H2 (~55–60%), CH4 (~23–27%), CO (~5–8%), N2 (~3–6%), and CO2 (less than 2%) along with other hydrocarbons in small proportions. Currently 20–40% of COG produced is normally utilized as fuel in the actual coke ovens. The remaining COG generated is generally employed in alternative processes of the steel mills, but most surplus is currently burned off in torches and even in some cases directly emitted to the air. These vary due to the highly dynamic nature of the steelmaking process. In addition, COG approximately accounts for 18% of the energy output of a coking plant due to its large low calorific value, which varies from 17 to 18 MJ/m3. Both COG energetic properties and production excess lead to large GHG emissions, energy inefficiency, and most importantly a significant environmental impact which in turn is also reflected in a clearly improvable economic efficiency. During the past few decades, various alternatives to valorize COG have been proposed, including its use for energy production, a direct utilization in the blast furnace to produce “pig iron,” or gas treatment for the production of chemicals and fuels. Bermudez et al. (2013) reviewed the main advantages and disadvantages of all the technologies for exploiting the COG surplus (Table 9.11). These alternatives can be divided in three main blocks: hydrogen separation, synthesis gas production, and other technologies. Hydrogen separation has a huge potential since COG is a H2-rich gas, which would allow a “green” production of H2, since, instead of the pollution and GHG emissions characteristic of conventional H2

Syngas production

Process Hydrogen separation

High purity of H2

Cryogenic

Lower CO2 emissions than conventional processes Whole exploitation of COG surplus High versatility for the production of chemicals

Mild operating conditions

Hydrates

Steam reforming

Well developed Easy industrial implementation

Easy industrial implementation

Advantages Well developed

Membranes

Technology PSA

Table 9.11 Mature COG usage technologies

High operation and capital costs

Catalysts well developed

Possible use of hot COG (but Quick catalyst deactivation)

High H2/CO ratio

High energy requirements

Disadvantages Need of other technologies for whole exploitation of COG surplus

Most used and known technology

High H2 purity Easy operation Low capital and operation costs Low energy requirement No need of removing light hydrocarbons

Low operating costs

Low energy requirement

With cold COG the complete elimination of BTX, NH3, and H2S is needed

Low H2 concentration Needs additives Complicated Low stage of development The high H2O/CH4 ratios Avoiding catalyst deactivation Decrease energy efficiency Mild pressures

Low stage of development

H2 purity limited to 95% Less studied for H2 separation from COG

Previous separation of tar, BTX, H2S, NH3, and light hydrocarbons

528 9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Other technologies

Chemicallooping combination

Methanol production

Partial oxidation

Dry reforming

Optimal use of COG surplus

Easier CO2 capture

Economically competitive Easier to handle than H2

Possible partial recycling of CO2 Industrially implanted

High reaction rates Possible use of hot COG (but quick catalyst deactivation)

Requires lower pressure and energy Consumption of CO2 H2/CO  2 (FischerTropsch) Possible to avoid total H2S Elimination High energy efficiency

Low stage of development

Low operation margin in the O2/ CH4 ratio Recovery of unreacted H2 to adjust the H2/CO ratio Higher cost and more complex facilities

Cold COG needs complete elimination of BTX, NH3, and H2S High temperatures High costs (reduced with membrane technology)

Needs complete elimination of BTX and NH3 No commercial catalyst

9.9 CHG Capture 529

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

production technologies, using COG as H2 source would eliminate the pollution resulting from its combustion. Hydrogen separation has been one of the most studied alternatives for using the COG surplus. Moreover, some of these technologies, such as PSA and membrane separation, are already in use in other industrial processes, so their implantation in coking plants would not present any special difficulty. However, the H2 recovery from COG surplus has an important drawback that needs to be overcome. With these technologies, no advantage is taken of the other gases, especially those containing carbon, i.e., CH4, CO, CO2, and light hydrocarbons. For this reason, H2 separation needs to be combined with other technologies in order to exploit all of the components of the COG surplus. For syngas production, COG is upgraded by means of the different technologies currently available (steam reforming, dry reforming, and partial oxidation), making these processes interesting alternatives for H2 amplification of the original COG or for the production of chemicals, thereby supplanting conventional production from natural gas or petroleum. Synthesis gas, or syngas, is a fuel gas mixture composed primarily of CO, H2, and often some CO2. The mixture is combustible and can be used as a fuel for internal combustion engines or for chemical synthesis. Synthesis gas provides the building block upon which an entire field of fuel science and technology is based. Syngas is produced by steam reforming, partial oxidation, or a combination of both processes. The syngas composition, most importantly the H2/ CO ratio, differs per production technology and input material. The desired H2/CO can be adjusted by conversion or CO/H2 separation. Synthesis gas production from COG surplus seems to be the most interesting alternative for the use of this interesting source. The large number of processes available (steam reforming, dry reforming, partial oxidation) allows obtaining a wide variety of H2/CO ratios (from 2 in dry reforming to nearly 5 in steam reforming), making the COG alternative highly versatile for obtaining different final chemical products. Moreover, even for the production of H2, COG is a more interesting alternative than H2 separation, since the hydrocarbons (CH4 and CnHm) are also used. However, reforming processes are energy-intensive technologies, so their industrial implantation needs to study in depth the energetic requirements and benefits. Besides, the construction of reforming plants requires a high level of capital investments. Special attention has been paid to methanol production, due to the interest of this product as a gasoline substitute or H2 carrier. In this case, dry reforming of COG seems to be the preferable technology, since it will require fewer process units than the other thermal upgrading technologies. In the particular case of methanol, it is already industrially implanted. Besides, by using dry reforming as the method for the production of synthesis gas, it will be possible to partially recycle the CO2 produced when methanol has been consumed. Moreover, the economic studies carried out on this matter suggest that it would be economically competitive with classical methanol synthesis processes. Even so, the complete process of methanol production will require a higher level of investment and more complex facilities. Other interesting alternatives, such as COG chemical-looping combustion or the combination of two or more of the previous technologies, have been proposed,

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531

though research into these systems is still in its initial stages and will need further research before considering their implantation at industrial level. Energy penalty is the primary challenge facing CO2 capture and storage (CCS) technology. One possible solution to this challenge is gas switching combustion (GSC): a promising technology for gaseous fuel combustion with integrated CO2 capture at almost no direct energy penalty (Arnaiz del Pozo et al. 2019). The most efficient plant evaluated in the study achieved 50.9% efficiency with 80.7% CO2 capture. The GSC integrated with IGCC power plant can solve the most fundamental challenge facing CCS. Based on the industrial technology from coke oven gas to synthetic natural gas, a process of CO2 recycle assistance with coke oven gas to synthetic natural gas is proposed, simulated, and optimized (Yi et al. 2017). The effects of key parameters on the performance of new system are investigated, and the optimum parameters are determined. The coke oven gas reacts with the recycled CO2 separated from the CO2-rich exhaust gas to produce syngas for synthetic natural gas production. This CO2 recycle can significantly improve the hydrogen utilization efficiency in coke oven gas, which does not only increase the synthetic natural gas production and thus enhancing energy efficiency but also reduce the CO2 emission simultaneously. Pure O2 generated from ASU is sent to combustor chamber to produce CO2-rich flue gas. The exhaust gas is split into two streams after being cooled and recovered moisture content. Part of the dry exhaust gas as working medium is recycled to the combustor chamber of the coke oven to control the temperature within a reasonable range. The rest gas is sent to CO2 separation unit where CO2 can be easily separated from the CO2-rich exhaust gas (about 80 vol.% CO2) by methyldiethanolamine (MDEA) technology with very low energy penalty. Part of the separated CO2 is captured directly, and the rest CO2 as supplementary carbon mixes with the cleaned COG to adjust the H/C mole ratio to be approximately 3.0. The adjusted syngas is used for SNG production. In comparison with the traditional process, the most significant feature of the proposed one is that the new process uses CO2 generated from the coking plant itself to supply carbon source to improve the utilization of COG; thus it will lead to the increase of SNG production. CO2 is totally recycled and captured in a very low energy consumption way. This highly integrated plant simplifies the production process and has great potentials in energy efficiency improvement and CO2 emissions reduction. The results show that the energy and exergy efficiency (79.0% and 81.1%) of the new process is increased by 6.3% and 6.6% points, synthetic natural gas production cost and direct CO2 emission reduced by 0.05 US$/m3 and 99.9%, whereas the synthetic natural gas output increased by 20%, in comparison with the conventional coke oven gas to synthetic natural gas process. The proposed system provides a promising way for future improvements of coke oven gas to synthetic natural gas process and can also be a guide for CO2 utilization or CO2 emissions reduction in coking industry. Ho et al. (2013) analyzed the opportunities existing to capture CO2 at different process units during iron production with the relative cost estimation. At a conventional iron and steel mill, the four major point sources during the iron production that

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

may be considered for CO2 capture in the future include the on-site power plant, sinter plant, coke oven batteries, and the blast furnace stoves. The estimated cost to capture CO2 from these emission sources ranges from A$ 80 to A$ 100 per ton CO2 avoided. Capture of CO2 from other emission point source such as the lime kiln or during steel production is estimated to cost over A$ 110 per ton. The analysis also found that although the capture cost at each of the individual point sources varied widely, the overall capture cost for the iron and steel mill is approximately A$ 85 per ton CO2 avoided. Further, the results showed that it is not always necessary to capture at all emission point sources to achieve deep cuts in CO2 emissions but rather to capture at the major point sources. In doing so, the overall capture cost for the iron and steel mill is approximately A$ 80 per ton CO2 avoided with a reduction of CO2 emissions from 10 Mtpa to less than 2 Mtpa. Opportunities for CO2 capture were also investigated for emerging steel process technologies such as the HIsmelt, Corex, and MIDREX processes. The study found that the opportunities to capture from direct CO2 emissions at a HIsmelt mill and Corex mill are similar to that for a conventional integrated steel mill except that the HIsmelt and Corex processes eliminate the requirement of the coke ovens and sinter plant, thereby reducing the number of emission sources of a plant. For the HIsmelt and Corex iron and steel mills, deep cuts in CO2 emissions of almost 7.5 Mtpa of CO2 could be achieved by capturing from key process units with overall capture costs of A$ 80 per ton CO2 avoided. For the HIsmelt mill, capture should be at the on-site power plant and stoves, while for the Corex mill, capture only at the power plant is required. Capture of CO2 from the only direct emission sources of the MIDREX plant (the exhaust stack gas) is estimated to be comparable to the cost of capturing from the on-site power plants at other iron and steel mills. Implementing CO2 capture at the blast furnace or smelt reduction vessel appears to be an attractive option; the CO2 concentrations are high coupled with large volumes of exhaust gas. The cost for capture at the blast furnace using MEA solvent absorption is shown to be comparable with the cost of capture at the on-site power plant. Using VPSA to capture the concentrated flue gases results in lower cost due to the lower energy penalty associated with the adsorption process. Process-specific capture technologies, such as the TGRBF, appear to be an attractive capture option. It may allow the implementation of CO2 capture at the blast furnace to be undertaken with less impact on the interlinked energy than simply deploying a capture facility at the existing blast furnace. The use of oxyfuel firing in the blast furnace produces an exhaust gas with a higher calorific value than in a conventional blast furnace. However, deployment of this technology on a commercial scale may be several years away as technical feasibility testing is still being completed at the pilot scale. Other key issues associated with the deployment of this technology are the large capital costs required to retrofit existing steel mills and the uncertainties and risks of deploying a new technology. At current prices the implementation of CO2 capture is comparable to or at the lower end of cost estimates for capturing CO2 at pulverized coal power plants. As this paper only evaluates the costs of CO2 capture, future work should include the costs for the entire CCS network including transport and storage. Assessing

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533

opportunities for integration of the capture technology with the iron and steel plant to utilize low-grade heat thereby reducing capture costs as well as investigating how this would influence the interlinked energy system and the oxygen production system would also be beneficial. The economic analysis would also be expanded to assess impact of capture on estimating the cost of steel production. Kuramochi et al. (2011) have shown that for the short midterm, a CO2 avoidance cost of less than 50 €/ton at a CO2 avoidance rate around 50% is possible. TGRBF with VPSA seems to be the best option from an economic point of view. TGRBF showed a potential for relatively low-cost CO2 capture because of significant reduction in coking coal consumption. However, large additional power consumption for CO2 removal and oxygen generation, and reduction in BF gas export, makes the economic performance of the technology very sensitive to energy prices. Add-on CO2 capture for air-blown blast furnace using VPSA or Selexol will also enable CO2 capture at similar costs (40–50 €/tCO2 avoided), but the CO2 avoidance rate will be only about 15% of the specific CO2 emissions. For the long-term future, although there are large uncertainties, advanced CO2 capture technologies do not seem to have significant economic advantages over conventional technologies. Selective carbon membranes will enable CO2 capture from air-blown BF at around 30 €/ton, but this still was found to be more expensive than using VPSA for oxygen-blown BF. When a new plant is considered, smelting reduction technologies such as the Corex process may become a strong competitor to conventional blast furnace-based steelmaking process in a carbon-constrained society when equipped with CO2 capture. Moreover, the results show that smelting reduction technologies can achieve considerable reduction in CO2 emissions compared to the BF process while keeping the steel production cost on par. Although conventional iron- and steelmaking using BF is expected to dominate the market in the long term, strong need for drastic CO2 emissions reduction may drive the sector toward large-scale implementation of advanced smelting reduction technologies. Recent studies on the application of this technology on large scale find that the total costs for air contacting alone—no regeneration—can be of the order of $60 per ton CO2 (Holmes and Keith 2016). Carbon capture and sequestration is the most efficient way to reduce CO2 emissions. However, introducing CO2 capture techniques to coal-based chemical process requires more investment and energy consumption. Meanwhile, whether to sequestrate or utilize the captured CO2 also needs to be discussed. Technical, environmental, and economic performance of conventional coal gasification process, coal gasification process with CCS, and coal gasification process with CCU has been conducted (Man et al. 2014). For element efficiency, coal gasification process with CCS is slightly less, while the process with CCU increases about 19% more than the conventional coal gasification process. For energy efficiency, coal gasification process with CCS decreases about 11%, while the process with CCU is very close to the conventional process. The environmental performance results indicate that the reduction of CO2 emissions of coal gasification process is 28% and 45% for CCS and CCU from life cycle point of view. For economic performance, production cost

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

of the process with CCS and CCU rises nearly 10% and 38% compared to the conventional coal gasification process. However, the disadvantage in production cost of the process with CCS and CCU is getting smaller and smaller by the increasing carbon tax. The production cost of the three processes is almost the same when carbon tax is about 15 USD/t CO2. The development of coal-based chemical processes faces the problems of high energy consumption and CO2 emissions.

9.10

Post-combustion

Different possibilities for reducing carbon dioxide emissions at an integrated steel mill by applying post-combustion capture (PCC) were studied (Arasto et al. 2013); a schematic view of the system is shown in Fig. 9.17. The parts of the steel mill under investigation were the hot stoves and the power plant. There were no significant differences between the flue gases of the power plant and the hot stoves regarding composition, CO2 content, and impurities. A single capture island could be used thanks to the close location of the flue gas stream sources and the steady operation of the both source process units. In addition to this, only a single location suitable for constructing a capture island could be found within a reasonably close proximity of the sources. This also justifies the combination of the two flue gas streams into a single capture island. When these flue gases are combined, the total maximum CO2 flow to the capture unit is 103 kg/s. The starting point for capturing carbon dioxide from the flue gases was a conventional MEA-based solvent scrubbing process. Blast furnace gas is purified with a wet scrubber prior to utilization in the hot stoves and the power plant boiler. This leads to a rather low SOx concentration in the flue gases of the power plant and the hot stoves. The capture process consists of an absorber unit and a stripper unit, pumps, and heat exchangers. The flue gas is cooled down with a wet scrubber before the absorber unit. In the absorber, the CO2 of the flue gas is absorbed by the MEA solvent to form stable chemical compounds. The absorber is operated near atmospheric pressure. The rich solvent from the absorber is led into the stripper unit via a

Fig. 9.17 Prototype module capable of capturing 100 kt CO2/y

9.10

Post-combustion

535

cross heat exchanger. In the stripper unit, the chemically bound CO2 is released from the solvent by heating it to 122
C with low-pressure steam at 133–160
C (3.0–6.2 bar). The CO2 exiting from the top of the stripper is led to a condenser to remove the water and solvent from the gas and return it for use in the process. Part of the water is removed from the process at this stage. The lean solvent is then led back to the absorber unit via cross heat exchanger. The stripper is operated at approximately 2 bar pressure. A small amount of solvent and water is lost from the process with the exiting flue gas flow from the absorber unit. In addition, a small amount of solvent is removed from the system to remove impurities and degraded solvent. Because of this, water and solvent makeup is added to the process. The evaluation of an alternative solvent is based on amino acid salt CO2 capture technology. The most significant benefit with this solvent in comparison to MEA solvents is the low regeneration energy requirements of 2.7 MJ/kg CO2. In addition, the operational costs associated are expected to be slightly lower compared to baseline MEA. This was mainly due to a lower solvent makeup consumption, estimated to be only 13% of the consumption estimated for MEA. The larger capture amounts studied (2–3 MtCO2/a) account for approximately 50–75% of the CO2 emissions from the site. If larger amounts of emissions were to be captured, it would be technically and economically significantly less feasible in comparison to only applying CCS for the largest emission sources on the site. This is due to the large number of small stacks scattered around the fairly large production site. There are other carbon abatement options for iron and steel production. CO2 emissions can be lowered, for example, by utilizing bio char as a reducing agent, applying different energy-saving measures, etc. The high level of integration typical in modern steel plants makes further energy-saving measures of any significant extent difficult. Large-scale bio char utilization is restricted by constrained resources and sustainability questions. Generally, also other CO2 emissions reduction options, such as electric arc furnaces or DRI processes, exist, but these are only applicable for certain types of steel mills. While being important and cost-effective at best, these measures are generally of smaller scale, when compared to the order of millions of tons of CO2 emissions reductions that are possible with CCS. The results showed that the costs for CCS are heavily dependent not only on the characteristics of the facility and the operational environment but also on the chosen system boundaries and assumptions. Especially the assumed impacts on electricity production in the network affect strongly the amount of avoided CO2 emissions. In the long term, the impacts on the electricity production system is an ambiguous issue due to, for instance, complex rebound effects on fuel, electricity and EUA prices and investment decisions. Capturing and storing smaller amounts of CO2 (in the range of 0.3 Mt CO2/a) could be realized with very low operational costs, due to the waste heat available at the site of the steel mill. However, the total costs would still be in the same range as with the larger amounts captured due to the relatively higher investment costs for the smaller size equipment and higher transportation costs per ton of CO2. The cost optimum depends on various factors, but in general, heat integration is a major contributor to the overall efficiency and economics of CCS installation (Tsupari et al. 2013).

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Capture processes using more developed solvent processes were the most feasible solutions studied. A solvent, which could be regenerated using low-temperature process heat, would probably result in significant advantages in the overall economics of CCS in the process industry, where substantial amounts of process heats are available in liquid phase. If the studied “low-t” solvent could be developed and commercialized, even more low level waste heat could be available in the mill in comparison to heat streams above 130
C. This might lead to improvements in the feasibility of CCS if heat recovery can be implemented with low investment. In certain applications, such as in industrial processes and combined heat and power plants, significant improvements can be achieved with heat integration, for instance, in the production of district heat. The feasibility could also be optimized by using new operational options that CCS brings. For instance, CO2 capture could be bypassed during periods of peak electricity prices. The optimal solution from the mill owner’s point of view depends on multiple factors with electricity price and CO2 price being the dominant ones. The final result of the cost estimation is driven by the relationship between CO2 emission prices and electricity prices. High CO2 prices increase the electricity prices making the CCS less profitable because the value gained from the carbon allowances must exceed the value of the electricity production lost in the capture process in order to make CCS feasible. Analyses performed on OBF with and without CCS to an integrated steel mill show that the CO2 emission from an iron and steel mill can be significantly reduced by application of an oxygen blast furnace and CCS. OBF is a blast furnace fired with pure oxygen instead of oxygen-enriched air. In principle the process resembles a conventional blast furnace process, but a part of the top gas is recycled back to the furnace to reuse the carbon in top gas as a reducing agent. Because of this the top gas of the blast furnace contains very little nitrogen. The CO2 of the top gas is separated and the hydrogen and carbon monoxide recycled back to the blast furnace to act as reductant and improve the energy balance. The separated CO2 is purified, compressed, and sent to a permanent storage via ship transportation. Oxygen for the OBF is produced by an air separation unit (ASU). The ASU is utilizing conventional cryogenic technology for oxygen production. Similar ASUs are currently operating on the existing site to produce oxygen, for instance, for oxygen enrichment in the conventional blast furnaces. The current oxygen consumption of blast furnaces is 70 Nm3/t-HM, and the oxygen consumption is estimated to rise to 220 Nm3/t-HM with an oxygen blast furnace. The top gas exiting from the OBF and going to the VPSA for CO2 separation is cooled down to 30
C before the compressors. Before cooling down, 10% of the top gas is taken to combustion to heat up the recycle gas stream before injection to the blast furnace. Hot gas is directed to the combustion to take advantage of the sensible heat in the gas. The CO2 stream exiting from the VPSA is not pure enough for storage purposes and needs to be purified. Purification is done by cryogenic distillation at 26 bar similar to oxyfuel CO2 purification processes developed (Fig. 9.18). This produces CO2 with a purity of 99.0%. After purification CO2 is compressed to meet the conditions needed in ship transportation (52
C, 6.5 bar). Cooling of the CO2 stream is done by first pressurizing the stream up to 64.3 bar and flashing the

9.10

Post-combustion

537

Fig. 9.18 Oxyfuel combustion scheme

stream to 6.5 bar in several stages. The evaporated part is recirculated back to the compressors. Purified and recycled top gas needs to be heated before injected into the blast furnace to secure the process conditions in the blast furnace. The gas is heated with a pebble heater from 88 to 900
C. The gas boiler is fueled with blast furnace top gas (10% side stream), mixed gas (from coke ovens and converter), and LPG for additional fuel. Part of the flue gas is directed to PCI drying and the heat left in rest of the flue gases recovered as low-pressure steam. PCI drying by flue gases would replace PCI drying by flue gases of hot stoves in reference case. The heat requirement of drying is 390 TJ/a. The direct CO2 emissions from the system are reduced from 3.2 Mt/a to 1.96 Mt/a by only applying the oxygen blast furnace (Arasto et al. 2014). This is mainly due to the reduced coke consumption in the blast furnace. With application of CCS to the system, the emissions can be further reduced to 0.55 Mt/a. In OBF process, electricity production decreases, and consumption increases in comparison with the reference case. Also consumption of LPG or LNG increases. OBF process enables selling of coke due to smaller coke consumption, and further savings are achieved from reduced CO2 emissions even if CCS would not be applied. If CCS is applied, economic savings due to avoided purchase of CO2 emission allowances would be significant, depending on price of the allowances. However, utilization of CCS would introduce additional costs due to electricity consumption in CO2 compression and costs of transportation (Tsupari et al. 2015). The CCS installation at Boundary Dam coal power plant in Canada (in operation since 2014) is able to capture one million tons of CO2 per year. It is expected that the second-generation plants will reduce the overall costs by 67% (Rogala 2019).

538

9.11

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Chemical Looping

Different chemical-looping cycles have been proposed for CO2 capture including both the transference of CO2 or oxygen. Commonly, the term chemical looping is referred to those processes transporting oxygen. Thus, the term “chemical looping” has been used for cycling processes that use a solid material as oxygen carrier containing the oxygen required for the conversion of the fuel. To close the loop, the oxygen-depleted solid material must be re-oxidized before starting a new cycle. The final purpose of the conversion of the fuel can be the combustion or the hydrogen production. For combustion purposes, the oxygen-depleted solid material must be regenerated by oxygen in air. In general, these processes are known with the general term “chemical-looping combustion” (CLC). CLC processes can address gaseous or solid materials as primary fuels. In CLC of gaseous fuels, the oxygen carrier reacts directly with the fuel, e.g., natural gas, refinery gas, etc. Other processes use the property of some oxygen-depleted materials to react with steam to produce hydrogen, also known as “water splitting.” In this category the chemicallooping hydrogen (CLH) or “one-step decarbonization” (OSD) process and the so-called “chemical-looping gasification” technologies, the syngas chemicallooping process (SCL) and the coal-direct chemical-looping process (CDCL), can be found. Usually these processes need several oxidation steps using air for the final regeneration of the oxygen carrier (Adanez et al. 2012). Both pre-combustion and post-combustion applications of the calcium looping cycle follow similar principles, in that a calcium oxide (CaO) sorbent—usually but not exclusively derived from limestone—is repeatedly cycled between two vessels. In one vessel (the carbonator), carbonation of CaO occurs, stripping the flue gas of its CO2. The CaCO3 formed is then passed to another vessel where calcination occurs (the calciner) and the CaO formed is passed back to the carbonator leaving a pure stream of CO2 suitable for sequestration (Blamey et al. 2010). This cycle is continued, and spent (unreactive) sorbent is continuously replaced by fresh (reactive) sorbent. The carbonation can either occur in situ (i.e., within the gasifier/combustor) or ex situ (i.e., on the product gases), with the former resulting in a reduction in plant complexity at the expense of a higher rate of degradation of sorbent due to contact with ash, sulfur, and other impurities in the fuel burned. Heat from the exothermic carbonation of lime can be used to run a steam cycle, making up for some of the energy losses elsewhere. The conditions in the calciner must be a compromise between the increased rate of reaction obtained at higher temperatures and the reduced rate of degradation of sorbent at lower temperatures. The conditions in the carbonator must strike a balance between the increased equilibrium conversion obtained at lower temperatures and the increased rate of reaction at higher temperatures. One major advantage of both calcium looping and a similar technology, chemical looping, is that these hightemperature solid looping cycles utilize technologies that have been demonstrated at large scale (fluidized beds): large (460 MWe) atmospheric and pressurized systems exist; there is no need to vastly scale up existing technologies such as the solvent scrubbing towers required for amine scrubbing.

9.11

Chemical Looping

539

Fig. 9.19 Principle of CaL process

CaL is based on the reversible reaction of the CO2 of the flue gases with calcium oxide (Shimizu et al. 1999): CO2ðgÞ þ CaOðsÞ ! CaCO3ðsÞ The process is carried out in a dual fluidized bed (DFB). The two reactors, known as carbonator and regenerator, are connected with a solid looping system which transports the CaO and the CaCO3 between them (Fig. 9.19). In the first of them, the carbonation reaction takes place, and the CO2 of the gas to be treated is absorbed at a temperature between 600 and 700
C. The reaction of the CO2 with the CaO is exothermic, and the exiting solids with a certain conversion of CaO converted to CaCO3 are transported to the regenerator. The flue gas flow exiting the carbonator has a low content of CO2 and can be released into the atmosphere or, in this case, recirculated into the blast furnace. In the regenerator, the CaCO3 created in the carbonator is calcined by the reverse reaction obtaining CaO, which can be used again in the carbonator. The reaction is highly endothermic, and it takes place at a temperature of 900
C. Extra coal is needed in the regenerator to provide the required heat for the calcination reaction and to heat the gas and solid streams up to 900
C. The combustion of the coal is done with pure oxygen in order to avoid the contamination of nitrogen of captured CO2 stream. The hot CO2-rich gas exiting the regenerator has a high purity and can be directly processed and sent to storage. In addition, a makeup flow of sorbent has to

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

be injected in the regenerator to neutralize the sorbent deactivation through multiple cycles. A large amount of energy is introduced into the system to heat the gas and solid streams up to the regenerator temperature and to provide the necessary heat for the endothermic reaction. Nevertheless, unlike in other CO2 capture methods, calcium looping enables the recovery of part of this heat. The flue gases leaving the carbonator and the regenerator are at 650 and 900
C, respectively, and also extra energy can be recovered in the carbonator due to the heat produced in the exothermic carbonation reaction. Besides the application of post-combustion CO2 capture technology, CaL can be used as a pre-combustion capture technology. This is the case of adsorptionenhanced reforming (AER). This technology is based on the capture of the CO2 in situ in the steam gasifier in order to enhance the water-gas shift reaction, increasing the hydrogen production. The operation of the AER is similar to the one of the CaL cycle. The CaCO3 used as a bed material in the DFB biomass gasification process has a double function: heat carrier and selective CO2 transport from the gasification reactor to the combustion reactor. As a matter of fact, BFG has a high content of CO but does not have water. Thus, if steam were introduced in the carbonator fluidized bed reactor (or gasifier), the water-gas shift reaction could take place producing a gas with a high content of hydrogen. This case is similar then to a CO2 capture to increase the H2 production after the gasification step, with the difference that the gas comes from a blast furnace instead of being the syngas derived from a biomass gasification (Mandova et al. 2018). The stoichiometric CO2 capture efficiency of a CaO particle is 78.6 wt.%. However, it has been experimentally observed that the carrying capacity of the particles decreases rapidly in the first 20 cycles to a residual value. It is well known that the decay in the reactivity of the sorbent through multiple CO2 capture and release cycles affects the cost and efficiency of the process. This sorbent reactivity decay is associated to different factors including sintering, attrition, and reaction with impurities with the flue- or fuel gas, especially sulfur species such as SO2 or H2S. The sintering of small CaO grains toward larger grains reduces the free surface of CaO, affecting the rate of carbonation. Sintered particles have lower porosity, which is characterized by a reduced number of large pores, whereas fresh particles have a high porosity due to a large number of small pores. Another parameter that affects the reactivity of the sorbent is the content of sulfur. The sulfur particles disable the sorbent capture potential reacting with the CaO and reducing the amount of CaO available for CO2 capture. This can be substantial in gasification of coal (containing S) or in post-combustion CO2 capture process without previous desulfuration. The combustion in the calciner is carried out in an O2/CO2 atmosphere, avoiding the presence of nitrogen in order to obtain a flue gas of pure CO2 directly available for compression and storage. However, the combustion with only oxygen would produce too high temperatures (nearly 3500
C). For this reason part of the CO2 is redirected to the regenerator at a lower temperature after heating other streams, decreasing the temperature in the combustor reactor without affecting the CO2 purity.

9.11

Chemical Looping

541

Fig. 9.20 Simulated CaL process

Simulations once parameters are described in Fig. 9.20 have been performed. The energy produced in the carbonator reactor and the energy of the flue gases are utilized for heating up other streams of the process or steam production. In the process proposed, there are two main heat sources: energy in the carbonator due to the exothermic reaction and energy of the CO2 flow leaving the regenerator at 900
C. On the other hand, the CO2-lean flue gas has to be split and heated up before its reinjection into the blast furnace through the tuyeres. The CO2-lean gas is reinjected into the blast furnace in 56% through the shaft tuyeres at approximately 900
C and 44% into the hearth of the blast furnace at higher temperature (1200
C). The energy extracted in the carbonator due to the exothermic reaction at 650
C will be used to produce steam. The energy of the CO2 flue gas at 900
C will be used to heat in a first step the process gas that leaves the carbonator at 650
C. However, after this first step, the CO2-rich flow is still having a lot of energy that can be extracted in the following steps, as represented in flow diagram presented in Fig. 9.21. For steam production the temperature of the flue gas has been reduced until 370
C. For realistic heat exchanger dimensions, the temperature gradient (ΔT) has been taken of minimum 40
C. In addition, the outlet temperature of the flue gas has been considered 120
C. Lower temperatures would require as well too big heat exchangers with unrealistic exchange surfaces. The heat integration can have a certain influence in the coal consumption and, as a result, in the oxygen required

Heater

Heater Slagl Hot metal

1200°C

850°C

Q45

370°C

Fig. 9.21 Energy integration of the CaL treating BFG

Coal oxygen

Ore coke

1179 Nm3/h BFG: CO 48%; CO2 38%; H2 8%; N2 6% @ 110°C

120°C

319°C

776°C

Q2

Q12

850°C

Heater

CaO

CaCO3, CaO

776 Nm3/h: CO 72.95%; CO2 5.78%; H2 12.16%; N2 9.12% @ 650°C

CARBONATOR T=650°C

Q1

Qnet

CaCO3

Coal

REGENERATOR T=900°C

Ash

ASU

778 Nm3/h: O2 3.52%; CO2 95.76%; H2O 0.18%; SO2 0.13%; N2 0.42% @ 900°C 401 Nm3/h: O2 @ 20°C

542 9 Carbon Capture and Storage: Most Efficient Technologies for. . .

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543

in the regenerator. The coal consumption is expected to decrease because of the preheating of the BFG. The CO2-lean stream has been heated up until 850
C with the pure CO2 flow exiting the calciner at 900
C. However, a higher temperature is necessary for the reinjection of the gas rich in CO and H2 into the hearth of the blast furnace (1200
C). For this reason, it is proposed to burn a fraction of this gas to heat the rest of the stream up to 1200
C. The combustion only with oxygen is not possible because too high flame temperatures are achieved. In a real facility, the calcination should be carried out with a certain amount of CO2 recirculated in the regenerator. A 50% of recirculation of the CO2-rich flow has been proposed. The stream is recirculated after extracting the heat for steam production. The main consequence of this change will be higher coal consumption. The reason for this is that more energy will be required to heat up again the cold CO2-rich flow reinjected into the calcinery. If the coal consumption is higher, the oxygen required for the oxyfuel combustion will be obviously also higher. At the same time, higher steam will be produced. The simulation has been carried out for the treatment of the gas generated in the production of 1 ton of hot metal during 1 h. Thus, the energy that can be produced by the treatment of the BFG in the CaL is 366.5 kWh/t-HM for the first scenario without CO2 recirculation and 481 kWh/t-HM for the second scenario with CO2 recirculation. One of the particularities of the CaL process is that unlike the other CCS technologies, it enables the recovery of energy for steam production. When this process is used as a post-combustion CO2 capture unit in a power plant, a significant increase of the electricity produced is achieved. The other energy recovery in the process is the heating of the CO2-lean gas up to 850
C previous its reinjection in the blast furnace. This energy comes from the CO2 flue gas and has to be subtracted from the total energy input because it is not an inherent process of the calcium looping capture. If this preheating were not done, like in the case of the other capture methods, more steam would be produced, but an extra heater would be required. Once this is done, the resulting energy input will be considered as energy for CO2 capture. Part of this energy is used for heating up streams and solids, another part is required for the endothermic reaction, and some energy is just lost in the flue gases and in the purge. The other point of the calcium looping process with large energy consumption is the air separation unit, which requires electricity for the production of oxygen used in the oxyfuel combustion. The air separation unit, which is an essential unit in an oxygen blast furnace, will have a higher electricity consumption in order to provide this necessary extra oxygen for the CaL. The CaL process offers similar energetic penalties than the amine absorption. The amine method requires steam and electricity that have to be produced elsewhere in the steel mill, whereas the only consumption of the CaL is the coal that is burned in the process. Compared to the VPSA technology, the energetic cost of capture with the CaL process, including the required energy for the ASU, is higher. However, the VPSA technology is based on membranes and consumes electricity that has to be imported from the grid or has to be produced in a power plant adding economic penalties or complexity to the process. In addition, the sorbents used in the VPSA

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

technology are not very resistant toward impurities in the off-gas. In contrast, the sorbent used in the CaL process is very robust and cheap. Although the VPSA method offers lower energy penalties of capture than CaL process, in terms of complexity, economic viability, or CO2 emission, the CaL process could be considered as an alternative solution. Unlike the MDEA technology, the CaL and the VPSA capture plants do not require steam for the capture. Thus, the steam demand of the steel mill is substantially lower than the steel mill with MDEA, and the steam generation plant, necessary in the steel mill with MDEA, can be avoided in both cases. In the VPSA CO2 capture plant steam is avoided, but the electricity consumption is higher than the MDEA. Therefore, the total electricity demand of the steel mill is increased, and the power plant required for the VPSA steel mill has been resized to meet the higher demand. The direct consequence of the different conceptions of the steel mill is the difference in the CO2 emissions. The steel mill with TGRBF and using MDEA for capture reduce the CO2 emissions by 46.6% compared to the steel mill without capture. The emissions of the VPSA steel mill have been calculated taking into account the avoidance of the steam generation plant but a higher CO2 emission in the power plant (which has a larger electricity generation). The CO2 emissions for this case were reduced by 58%. In the CaL steel mill, the CO2 emissions were reduced by almost 70%. Calcium looping generates electricity without emissions to the atmosphere since CO2 is generated in a pure flow that can be stored. In addition, unlike in the other two methods, CaL CO2 capture technology does not have associated extra CO2 emissions (MDEA requires steam and VPSA electricity that are produced by a power plant generating CO2). The cost of the CaL was estimated, and an economical comparison of the three capture methods was done. The investment costs for the steel mill using CaL for capture resulted higher than for the other capture technologies due to the higher cost of the CO2 capture plant. However, the operating costs were lower. The avoidance of the power plant and steam generation plant leads to lower maintenance, labor, and other costs. Moreover, the CaL steel mill does not require natural gas (which is burned in the other steel mills), and, although the coal consumption is high, the fuel costs of the steel mill are reduced. The cost of steel production was slightly lower for CaL than for other cases with CO2 capture. This fact, together with a higher rate of CO2 avoided, results in lower cost of CO2 avoidance (approximately 25 $/t CO2). It has to be remarked that these costs are the cost of CO2 avoidance for this reference steel mill that is producing its own electricity in the boundary limits of the plant and under the economic assumptions considered. An additional advantage that the CaL process implemented in the steel mill could offer is the production of hydrogen through the adsorption-enhanced reforming. Two post-combustion CO2 capture technologies, a conventional chemical absorption technology using monoethanolamine (MEA) and a more innovative one based on calcium looping (CaL), were evaluated and compared against the benchmark case represented by the integrated steel mill without CCS. All results are reported on the basis of one metric ton of hot rolled coil (HRC) produced. Analyzing the most significant environmental impact categories leads to the conclusion that

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545

integrating CCS into the steel production route decreases the global warming potential in the range of 47.98–75.74%. Here, the considered impact categories were global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), ozone depletion potential (ODP), aquatic depletion potential (ADP), freshwater aquatic ecotoxicity potential (FAETP), human toxicity potential (HTP), photochemical oxidation potential (PCOP), terrestrial ecotoxicity potential (TEP), and marine ecotoxicity potential (MAETP). Generally, the decrease of CO2 emissions goes along with an increase of the other impact categories regardless of the technology used, as the adoption of CCS technologies leads to efficiency losses, which, in turn, brings additional fuel demand and related other emissions. Among the investigated capture technologies, CaL shows significantly better environmental performance than the conventional amine-based CO2 capture technology as the decrease observed in eight of the environmental indicators, other than GWP, is between 2.90% and 48.87% compared to the case when MEA is applied (Chisalita et al. 2019). Ca-based sorbents suffer from a decline of the capture capacity over multiple sorption/desorption cycles, mainly due to sintering, and from a markedly heterogeneous fluidization behavior due to the strength of interparticle attractive forces as compared to particle weight. The development of novel synthetic CaO/Al2O3 sorbents for CO2 capture with enhanced CaL performance and fluidizability by dry mixing with flow conditioner nanopowders has been presented (Azimi et al. 2019). The influence of initial precursors on the sorbents multicycle activity at realistic CaL conditions has been investigated. The formation of a stable Ca9Al6O18 mixedphase during the preparation of the sorbents promotes the multicycle capture capacity. The type of Ca and Al precursors, either soluble or insoluble, can significantly affect the dispersion of this stabilizer (Ca9Al6O18) in the sorbent matrix and, consequently, may affect the carbonation activity of the materials. The sorbent prepared from soluble aluminum nitrate and calcium nitrate precursors by sol-gel method exhibits a very stable multicycle capture capacity with a capture capacity around 0.2 g of CO2/g of sorbent after 21 cycles keeping a 72% of its initial capture capacity. Fluidization experiments confirmed the positive effect of using hydrophilic alumina and hydrophobic silica nanoparticles on improving the fluidizability of the synthesized sorbents. Tian et al. (2018) propose a new decarbonization concept which exploits the inherent potential of the iron and steel industry through calcium looping lime production. They find that this concept allows steel mills to reach the 2050 decarbonization target by 2030. Moreover, only this concept is revealed to exhibit a CO2 avoidance cost (12.5–15.8 €2010/t) lower than the projected CO2 trading price in 2020, while the other considered options are not expected to be economically feasible until 2030. They conclude that the proposed concept is the best available option for decarbonization of this industrial sector in the mid- to long term. The application of pre-combustion capture systems based on CO2 separation in steel industry, such as the sorption-enhanced water-gas shift (SEWGS), can be particularly attractive to decarbonize the blast furnace gas (BFG), while a higherLHV fuel gas is produced that can be easily integrated throughout the steel mill

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

(van Dijk et al. 2017). In the SEWGS, a high-temperature sorbent (typically a hydrotalcite-like material) that also acts as WGS catalyst removes the CO2 from the gaseous phase as soon as it is produced. The WGS equilibrium is then shifted toward a higher production of H2 according to the Le Chatelier’s principle. As a result, the almost total conversion of CO can be achieved at temperatures above 400
C. The CO2 sorbent is then regenerated by a thermal swing procedure or by purging with steam at low pressure. An integrated full system to decarbonize a steelworks plant is described using high-temperature Ca-Cu chemical-looping reactions (Martínez et al. 2018). A H2-enriched gas is produced through sorptionenhanced water-gas shift (SEWGS) of blast furnace gas (BFG) using a CaO-based CO2 sorbent (Fig. 9.22). The resulting CaCO3 is regenerated with heat from CuO reduction with N2-free steel mill off-gases. The high-temperature operation allows for an effective integration of a power steam cycle that replaces the steel mill power plant. The proposed fluidized bed process facilitates a solid segregation step to separate the O2 solid carrier from the CO2 sorbent. The CaO-rich stream separated could be used in the steelmaking process thereby removing the lime plant. Balances of a steel mill integrated with the Ca-Cu process are solved and compared with those obtained for a reference steelworks plant with post-combustion CO2 capture through amine absorption. Using exclusively steel mill off-gases in the Ca-Cu process can reduce CO2 emissions by 30%. Moreover, the H2 gas could produce about 10% of additional iron through a direct reduced iron process. In contrast, by adding natural gas for CuO reduction, almost all the BFG can be decarbonized, and an overall CO2 capture efficiency in the steel plant of 92% can be achieved.

Fig. 9.22 Simplified scheme of the Ca-Cu looping process

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Conclusions

547

The Energy Transition Commission has carried out a very recent study on the cost trade-offs and overall economic impact to deep decarbonization in steel sector (Delasalle 2019). Estimates from the Global Carbon Capture and Storage Initiative (GCCSI) suggest that current costs for capturing CO2 from steel furnaces could be around $65–70 per ton of CO2, potentially falling to around $55 in the future. McKinsey analysis (Fig. 9.23) suggests that, if the total cost of carbon capture and storage varies from around $50 to $100 per ton of CO2 as the electricity price increases, electricity prices would have to be below $40/MWh before hydrogen reduction became more economic than the carbon capture for greenfield plants ($20/MWh for plants using biomass). For brownfield plants, this breakeven point between hydrogen reduction and carbon capture with BF-BOF goes down to $25/MWh ($20/MWh for plants using biomass). In general, the costs depend on the region because of electricity prices, technical issues and social acceptance, and sites available for CCS. It is believed that in some regions renewable electricity will be available at below $20/MWh. Also biomass availability and prices strongly vary by region.

9.12

Conclusions

Study on the resource utilization of CO2 is vital for the reduction of CO2 emissions to cope with global warming and bring a beneficial metallurgical effect. The present chapter reviews the current CO2 capture and usage solutions that are available or under development. The necessity of the broader application of these solutions is due to the fact that the BF-BOF route (responsible for the 70% of the main dangerous emissions) is destined to remain the main production way in the next future due to cost issues. The SR-BOF route development and diffusion are not so clear also because the DRI-EAF production is continuously growing and under deep development in terms of modern gasification technologies or hydrogen reduction. Studies from IEA show that at the moment, only the scrap-EAF route is capable of reaching the goals described by the Blue scenario for 2050. The improvement of energy efficiency will reduce the CO2 emissions at least by 15–20%. For the DRI-EAF route, the main problems are represented by the natural gas availability and the indirect emissions. The development of alternative solutions to be applied to the BF-BOF route could only achieve CO2 reduction of 10–25%. Only the capture of CO2 will be responsible for the achievement of the goals of the Blue scenario. The main CO2 reduction options related to the blast furnace operations are based on development of alternative reductants to reduce the carbon consumption, separation, and capture of BF top gas, improvement of coke, and/or metal burden mainly through optimized innovative coke making operations. Intergovernmental Panel on Climate Change (IPCC) scenarios associated with a more than even chance of achieving the 2
C target are characterized by average capture rates of 10 GtCO2 per year in 2050, 25 GtCO2 per year in 2100, and cumulative storage of 800–3000 GtCO2 by the end of the century. CCS and CCU are recognized as crucial

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9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Fig. 9.23 Cost comparison of different steel production decarbonization technologies depending on price of zero-carbon electricity (adapted from Delasalle 2019)

in climate change mitigations and in particular in a NET contest to limit warming well below the 2
C scenario. The capture technologies are grouped as chemical/ physical absorption, solid adsorbents capture, membranes or molecular sieves physical separation, cryogenics separation, and carbonation. Obviously, this best

References

549

available technology could be applied globally at current production levels taking into account precise energy balances, economic feasibility, transition rates, and regulatory and social factors. Water-gas shift processes are under development with lower-energy consumption, such as the water-gas shift membrane reactor, which converts CO to CO2 and separates the H2 from CO2 in a single reactor. This increases the heating value of the fuel gas (H2), which could be used for power generation with the same efficiency as natural gas. Chemical solvents are mainly used in those gases with low CO2 concentration with low partial pressure. The most largely used are the monoethanolamine (MEA). These are highly efficient compounds; anyway, they lead to equipment corrosion and are subjected to fat degradation due to the presence of SOx and O2 in the gas. The process can be largely improved once these compounds are eliminated before the amine treatment. Among the conventional CO2 chemical removal processes, the monoethanolamine (MEA) process has been comprehensively studied and successfully used in chemical plants for CO2 recovery. Although the MEA process is a promising system for the control of CO2 emissions from massive discharging plants, it is an expensive option. The physical absorption process may be a useful method of CO2 removal from metallurgical fuel gases on a large industrial scale. Physical adsorption is applied at high CO2 partial pressure and low temperatures. Its high capacity makes it the preferred method for CO2 concentrations higher than 15%. The combination of shift reactor and Selexol™ or Rectisol® is believed to reach an adsorption of 99.5%. Another solution is represented by Steelanol developed by ArcelorMittal in Ghent. The process allows to synthesize ethanol from steel gases. Gas separation through membranes has high efficiency with low capital investment, good weight and space efficiency, ease of scale-up, minimal associated hardware, no moving parts, ease of installation, flexibility, minimal utility requirements, low environmental impact, reliability, and, finally, the ease of incorporation of new membrane developments. Cryogenic separation is obviously a high energy-consuming process, even if the cooled gas can be easily compressed for the transport or direct use. Many DAC technologies have been developed or are under development; the field is broadly open in terms of efficiency and plant costs. Chemical-looping solutions are also largely approached with high efficiency.

References Adanez J, Abad A, Garcia-Labiano F, Gayan P, De Diego LF (2012) Progress in chemical-looping combustion and reforming technologies. Prog Energy Combust Sci 38(2):215–282. https://doi. org/10.1016/j.pecs.2011.09.001 Air Products (2011) BF Plus offers steelmakers the complete package . . . lower costs, improved iron-making productivity and a cleaner environment. Available from: www.airproducts.com/ blastfurnace Allentown, PA, USA Arasto A, Tsupare E, Karki J, Pisila E, Sorsamaki L (2013) Post-combustion capture of CO2 at an integrated steel mill – part I: technical concept analysis. Int J Greenhouse Gas Control 16:271–277. https://doi.org/10.1016/j.ijggc.2012.08.018

550

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Arasto A, Tsupari E, Karki J, Lilja J, Sihvonen M (2014) Oxygen blast furnace with CO2 capture and storage at an integrated steel mill—part I: technical concept analysis. Int J Greenhouse Gas Control 30:140–147. https://doi.org/10.1016/j.ijggc.2014.09.004 Ariyama T, Takahashi K, Kawashiri Y, Nouchi T (2019) Diversification of the ironmaking process toward the long-term global goal for carbon dioxide mitigation. J Sustain Metall. https://doi.org/ 10.1007/s40831-019-00219-9 Arnaiz del Pozo C, Cloete S, Cloete JH, Alvaro AJ, Amini S (2019) The potential of chemical looping combustion using the gas switching concept to eliminate the energy penalty of CO2 capture. Int J Greenhous gas Contrl 83:265–281. https://doi.org/10.1016/j.ijggc.2019.01.018 Azimi B, Tahmasebpoor M, Sanchez-Jimenez PE, Perejon A, Valverde JM (2019) Multicycle CO2 capture activity and fluidizability of Al-based synthesized CaO sorbents. Chem Eng J 358:679–690. https://doi.org/10.1016/j.cej.2018.10.061 Bains P, Psarras P, Wilcox J (2017) CO2 capture from the industry sector. Prog Energy Combust Sci 63:146–172. https://doi.org/10.1016/j.pecs.2017.07.001 Bermudez JM, Arenillas A, Luque R, Menendez JA (2013) An overview of novel technologies to valorise coke oven gas surplus. Fuel Precess Technol 110:150–159. https://doi.org/10.1016/j. fuproc.2012.12.007 Birat J-P (2010a) Steel sectoral report. Contribution to the UNIDO roadmap on CCS—fifth draft Birat J-P (2010b) Carbon dioxide (CO2) capture and storage technology in the iron and steel industry. In: Developments and innovation in carbon dioxide (CO2) capture and storage technology, vol 1: carbon dioxide (CO2) capture, transport and industrial applications. Woodhead Publishing Ltd, Cambridge, UK Blamey J, Anthony EJ, Wang J, Fennell PS (2010) The calcium looping cycle for large-scale CO2 capture. Prog Energy Combust Sci 36(2):260–279. https://doi.org/10.1016/j.pecs.2009.10.001 Bui M, Adjiman CS, Bardow A, Anthony EJ, Boston A, Brown S, Fennell PS, Fuss S, Galindo A, Hackett LA, Hallett JP, Herzog HJ, Jackson G, Kemper J, Krevor S, Maitland GC, Matuszewski M, Metcalfe IS, Petit C, Puxty G, Reimer J, Reiner DM, Rubin ES, Scott SA, Shah N, Smit B, Trusler JPM, Webley P, Wilcox J, Mac Dowell N (2018) Carbon capture and storage (CCS): the way forward. Energy Environ Sci 11(5):1062–1176. https://doi.org/10.1039/ c7ee02342a Cavaliere P (2016) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. https://doi.org/10.1007/978-3-319-39529-6 Chen L, Yang B, Shen X, Xie Z, Sun F (2015) Thermodynamic optimization opportunities for the recovery and utilization of residual energy and heat in China's iron and steel industry: a case study. Appl Therm Eng 86:151–160. https://doi.org/10.1016/j.applthermaleng.2015.04.026 Cheng H-H, Shen J-F, Tan C-S (2010) CO2 capture from hot stove gas in steel making process. Int J Greenhouse Gas Control 4(3):525–531. https://doi.org/10.1016/j.ijggc.2009.12.006 Chisalita D-A, Petrescu L, Cobden P, van Dijk HAJE, Cormos A-M, Cormos C-C (2019) Assessing the environmental impact of an integrated steel mill with post-combustion CO2 capture and storage using the LCA methodology. J Clean Prod 211:1015–1025. https://doi.org/10.1016/j. jclepro.2018.11.256 Chowdhury JI, Hu Y, Haltas I, Balta-Ozkan N, Matthew G Jr, Varga L (2018) Reducing industrial energy demand in the UK: a review of energy efficiency technologies and energy saving potential in selected sectors. Renew Sustain Energy Rev 94:1153–1178. https://doi.org/10. 1016/j.rser.2018.06.040 Cormos CC (2016) Evaluation of reactive absorption and adsorption systems for post-combustion CO2 capture applied to iron and steel industry. Appl Therm Eng 105:56–64. https://doi.org/10. 1016/j.applthermaleng.2016.05.149 Danloy G, Berthelemot A, Grant M et al (2009) ULCOS - pilot testing of the low-CO2 blast furnace process at the experimental BF in Luleå. Revue de Metallurgie - Cahiers d’Informations Techniques 106(1):1–8. https://doi.org/10.1051/metal/2009008 Davidson R M (2007) Post-combustion carbon capture from coal fired plants - solvent scrubbing. IEA Clean Coal Centre, CCC/125, London

References

551

Delasalle F (2019) Steel in the global value chain and in the circular economy. Steel and coal: a new perspective, Bruxelles, 28 Mar 2019 Dong K, Wang X (2019) CO2 utilization in the ironmaking and steelmaking process. Metals 9:273. https://doi.org/10.3390/met9030273 Ghanbari H, Helle M, Saxen H (2012) Process integration of steelmaking and methanol production for suppressing CO2 emissions—a study of different auxiliary fuels. Chem Eng Process 61:58–68. https://doi.org/10.1016/j.cep.2012.06.008 Gielen D (2003) CO2 removal in the iron and steel industry. Energy Convers Manag 44:1027–1037. https://doi.org/10.1016/S0196-8904(02)00111-5 Ho MT, Allinson GW, Wiley DE (2011) Comparison of MEA capture cost for low CO2 emissions sources in Australia. Int J Greenhouse Gas Control 5(1):49–60. https://doi.org/10.1016/j.ijggc. 2010.06.004 Ho MT, Bustamante A, Wiley DE (2013) Comparison of CO2capture economics for iron and steel mills. Int J Greenhouse Gas Control 19:145–159. https://doi.org/10.1016/j.ijggc.2013.08.003 Holappa LEK (2017) Energy efficiency and sustainability in steel production. Minerals, metals and materials series 9783319510903, pp 401–410. https://doi.org/10.1007/978-3-319-51091-0_39 Holmes G, Keith DW (2016) An air–liquid contactor for large-scale capture of CO2 from air. Philos Trans R Soc 370:4380–4403. https://doi.org/10.1098/rsta.2012.0137 Holmes G, Nold K, Walsh T, Heidel K, Henderson MA, Ritchie J, Klavins P, Singh H, Keith DW (2013) Outdoor prototype results for direct atmospheric capture of carbon dioxide. Energy Procedia 37:6079–6095. https://doi.org/10.1016/j.egypro.2013.06.537 IEA (2007) Tracking industrial energy efficiency and CO2 emissions Keith DW, Holmes G, St. Angelo D, Heidel K (2018) A process for capturing CO2 from the atmosphere. Joule. https://doi.org/10.1016/j.joule.2018.05.006 Khallaghi N, Hanak DP, Manovic V (2019) Staged oxy-fuel natural gas combined cycle. Appl Therm Eng 153:761–767. https://doi.org/10.1016/j.applthermaleng.2019.03.033 Koytsoumpa EI, Bergins C, Kakaras E (2018) The CO2 economy: review of CO2 capture and reuse technologies. J Supercrit Fluids 132:3–16. https://doi.org/10.1016/j.supflu.2017.07.029 Kunzler C, Alves N, Pereira E, Nienczewski J, Ligabue R, Einloft S, Dullius J (2011) CO2 storage with indirect carbonation using industrial waste. Energy Procedia 4:1010–1017. https://doi.org/ 10.1016/j.egypro.2011.01.149 Kuramochi T, Ramírez A, Turkenburg W, Faaij A (2011) Techno-economic assessment and comparison of CO2 capture technologies for industrial processes: preliminary results for the iron and steel sector. Energy Procedia 4:1981–1988. https://doi.org/10.1016/j.egypro.2011. 02.079 Kuramochi T, Ramírez A, Turkenburg W, Faaij A (2013) Comparative assessment of CO2 capture technologies for carbon-intensive industrial processes. Prog Energy Combust Sci 38:87–112. https://doi.org/10.1016/j.pecs.2011.05.001 Lampert K, Ziebik A (2007) Comparative analysis of energy requirements of CO2 removal from metallurgical fuel gases. Energy 32:521–527. https://doi.org/10.1016/j.energy.2006.08.003 Lampert K, Ziebik A, Stanek W (2010) Thermoeconomical analysis of CO2 removal from the Corex export gas and its integration with the blast-furnace assembly and metallurgical combined heat and power (CHP) plant. Energy (Oxford) 35(2):1188–1195. https://doi.org/10.1016/j. energy.2009.05.010 Lie JA, Vassbotn T, Hägg M-B, Grainger D, Kim T-J, Mejdell T (2007) Optimization of a membrane process for CO2 capture in the steelmaking industry. Int J Greenhouse Gas Control 1(3):309–317. https://doi.org/10.1016/S1750-5836(07)00069-2 Lucas N, Rossetti di Valdalbero D (2018) Energy in future steelmaking, steel in the energy market applications, greening European steel. European steel, the wind of change, Bruxelles, 31 Jan 2018 Man Y, Yang S, Xiang D, Li X, Quian Y (2014) Environmental impact and techno-economic analysis of the coal gasification process with/without CO2 capture. J Clean Prod 71:59–66. https://doi.org/10.1016/j.jclepro.2013.12.086

552

9 Carbon Capture and Storage: Most Efficient Technologies for. . .

Mandova H, Gale WF, Williams A, Heyes AL, Hodgson P, Miah KH (2018) Global assessment of biomass suitability for ironmaking – opportunities for co-location of sustainable biomass, iron and steel production and supportive policies. Sustain Energy Technol Assess 27:23–39. https:// doi.org/10.1016/j.seta.2018.03.001 Mandova H, Patrizio P, Leduc S, Kjärstad J, Wang C, Wetterlund E, Kraxner F, Gale W (2019) Achieving carbon-neutral iron and steelmaking in Europe through the deployment of bioenergy with carbon capture and storage. J Clean Prod 218:118–129. https://doi.org/10.1016/j.jclepro. 2019.01.247 Martínez I, Fernández JR, Abanades JC, Romano MC (2018) Integration of a fluidised bed ca–cu chemical looping process in a steel mill. Energy 163:570–584. https://doi.org/10.1016/j.energy. 2018.08.123 Pérez-Fortes M, Moya MJA, Vatopoulos K, Tzimas E (2014) CO2 capture and utilization in cement and iron and steel industries. Energy Procedia 63:6534–6543. https://doi.org/10.1016/j.egypro. 2014.11.689 Ramírez-Santos ÁA, Castel C, Favre E (2018) A review of gas separation technologies within emission reduction programs in the iron and steel sector: current application and development perspectives. Sep Purif Technol 194:425–442. https://doi.org/10.1016/j.seppur.2017.11.063 Rhee CH, Kim JY, Han K, Ahn CK, Chun HD (2011) Process analysis for ammonia-based CO2 capture in ironmaking industry. Energy Procedia 4:1486–1493. https://doi.org/10.1016/j. egypro.2011.02.015 Richards V L, Peaslee K, Smith J D (2008) Geological sequestration of CO2 by hydrous carbonate formation with reclaimed slag. Office of Scientific and Technical Information, TRP 9955, Oak Ridge, TN Riley M F, Rosen L, Drnevich R (2009) Mitigating CO2 emissions in the steel industry: a regional approach to a global need. In: AISTech 2009, proceedings of the iron and steel technology conference, St. Louis, MO, USA, 4–7 May 2009, vol 1. Association for Iron and Steel Technology (AIST), Warrendale, PA, pp 89–101 Rogala T (2019) European coal – technological and socio-economic challenges. Steel and coal: a new perspective, Bruxelles 28 Mar 2019 Shimizu T, Hirama T, Hosoda H, Kitano K, Inagaki M, Tejima K (1999) A twin fluid-bed reactor for removal of CO2 from combustion processes. Chem Eng Res Des 77(1):62–68. https://doi. org/10.1205/026387699525882 Sun L, Smith R (2013) Rectisol wash process simulation and analysis. J Clean Prod 39:321–328. https://doi.org/10.1016/j.jclepro.2012.05.049 Suopajarvi H, Kemppainen A, Haapakangas J, Fabritius T (2017) Extensive review of the opportunities to use biomass-based fuels in iron and steelmaking processes. J Clean Prod 148:709–734. https://doi.org/10.1016/j.jclepro.2017.02.029 Tian S, Jiang J, Zhang Z, Manovic V (2018) Inherent potential of steelmaking to contribute to decarbonisation targets via industrial carbon capture and storage. Nat Commun 9(1):4422. https://doi.org/10.1038/s41467-018-06886-8 Treadgold C (2015) Opportunities for adding value to Tata Steels works arising gases. Tata Steel, IJmuiden Tsupari E, Karki J, Arasto A, Pisila E (2013) Post-combustion capture of CO2 at an integrated steel mill – part II: economic feasibility. Int J Greenhouse Gas Control 16:278–286. https://doi.org/ 10.1016/j.ijggc.2012.08.017 Tsupari E, Karki J, Arasto A, Lilja J, Kinnunen K, Sihvonen M (2015) Oxygen blast furnace with CO2 capture and storage at an integrated steel mill – part II: economic feasibility in comparison with conventional blast furnace highlighting sensitivities. Int J Greenhouse Gas Control 32:189–196. https://doi.org/10.1016/j.ijggc.2014.11.007. Tzirakis F, Tsivintzelis I, Papadopoulos AI, Seferlis P (2019) Experimental measurement and assessment of equilibrium behaviour for phase change solvents used in CO 2 capture. Chem Eng Sci:20–27. https://doi.org/10.1016/j.ces.2018.12.045 van der Stel J, Hirsch A, Janhsen U, Sert D, Grant M, Delebecque A, Diez-Brea P, Adam J, Ansseau O, Feiterna A, Lin R, Zagaria AM, Küttner W, Schott R, Eklund N, Pettersson M, Boden A, Sköld B-E, Sundqvist L, Simoes J-P, Edberg N, Lövgren J, Bürgler T, Feilmayr C,

References

553

Sihvonen M, Kerkkonen O, Babich A, Born S (2014) ULCOS top gas recycling blast furnace process (ULCOS TGRBF). Research fund for coal and steel (EC), EUR 26414, Luxembourg van Dijk HAJ, Cobden PD, Lundqvist M, Cormos CC, Watson MJ, Manzolini G, van der Veer S, Mancuso L, Johns J, Sundelin B (2017) Cost effective CO2 reduction in the Iron & Steel Industry by means of the SEWGS technology: STEPWISE project. Energy Procedia 114:6256–6265. https://doi.org/10.1016/j.egypro.2017.03.1764 Vlek M (2007) Feasibility study of CO2 capture and storage at a power plant fired on production gas of the steel industry. Master thesis, Department of Technology Management, Eindhoven University of Technology, Eindhoven Wiley DE, Ho MT, Bustamante A (2011) Assessment of opportunities for CO2 capture at iron and steel mills: an Australian perspective. Energy Procedia 4:2654–2661. https://doi.org/10.1016/j. egypro.2011.02.165 Yi W, Wu G-S, Gong M-H, Huang Y, Feng J, Hao Y-H, Li WY (2017) A feasibility study for CO2 recycle assistance with coke oven gas to synthetic natural gas. Appl Energy 193:149–161. https://doi.org/10.1016/j.apenergy.2017.02.031 Yildirim O, Nölker K, Büker K, Kleinschmidt R (2018) Chemical conversion of steel mill gases to urea: an analysis of plant capacity. Chemie-Ingenieur-Technik 90(10):1529–1535. https://doi. org/10.1002/cite.201800019 Yoon Y, Nam S, Jung S, Kim Y (2011) K2CO3/hindered cyclic amine blend (SEFY-1) as a solvent for CO2 capture from various industries. Energy Procedia 4:267–272. https://doi.org/10.1016/j. egypro.2011.01.051

Chapter 10

Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse Emissions Abatement

10.1

Introduction

Electrolysis is a well-established processing route to produce metals such as aluminum or lithium. In this technology electrons, provided by electricity, are used as the reducing agent. Electrolysis of iron ore has not been developed in the past because of the energetic balance and energy expenses. In addition, until now its application in iron production has been hindered due to the difficulty in finding a suitable anode material capable of weathering the challenging conditions. The basic principle is based on iron ore placed in a solution (termed the electrolyte) and an electric current passing through it. Negatively charged oxygen ions migrate to the positively charged anode, where the O2 bubbles out and is captured. Positively charged iron ions are transported to the negatively charged cathode where they are reduced to elemental iron. Up to now, the iron production through electrolysis has been hindered because of the unavailability of suitable cathode materials able to weather the challenging conditions (withstanding temperatures of over 1500
C and absence of corrosion by the molten oxides or the oxygen released in the process). Two electrolysis routes are currently being investigated: – An electrowinning process, ULCOWIN (an ULCOS project), in which iron ore grains are suspended in an alkaline sodium hydroxide solution at a temperature of 110
C (Junjie 2018). The result is a solid iron product. A pilot plant with a capacity of 5 kg iron/d has been proposed (Cavaliere 2016). – Molten oxide electrolysis, where the iron ore is dissolved in a mixed oxide solvent, such as silicon oxide and calcium oxide, at ~1600
C. The resultant molten iron collects at the bottom of the cell and is siphoned off. In MOE processes, iron ore is dissolved in a molten oxide mixture at 1823–1973 K (1550–1700
C). The anode, made of a material inert towards the oxide mixture, is dipped in this solution. Electrical current is passed between this © Springer Nature Switzerland AG 2019 P. Cavaliere, Clean Ironmaking and Steelmaking Processes, https://doi.org/10.1007/978-3-030-21209-4_10

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anode and a liquid iron pool connected to the circuit as the cathode. Oxygen evolves as a gas at the anode, and iron is produced as a liquid metal at the cathode. The oxygen generated in the process is a marketable by-product, thereby decreasing the overall cost of the process. The most promising options for electrolysis are ULCOWIN, also called electrowinning, and iron ore ULCOLYSIS (similar to the MOE process). Both technologies have already been demonstrated at a small scale. In the ULCOLYSIS process, iron ore is dissolved in a molten oxide mixture at 1600
C. This electrolyte medium can sustain a temperature above the melting point of iron metal. The anode, made of a material inert in relation to the oxide mixture, is dipped in this solution. An electric current flows between this anode and a liquid iron pool that is connected to the circuit to act as the cathode. O2 evolves as a gas at the anode, and iron is produced as a liquid metal at the cathode. The development of ULCOWIN is, however, more advanced. A prototype plant has been proposed that could produce 5 kg/day. Since electrolysis produces no CO2, it could theoretically be zero-carbon, but only if the electricity needed to power, the process is produced without generating CO2 emissions. The energy consumption is dependent on the cell configuration, the chemistry of the electrolyte, and the process temperature. Several engineering problems still need to be solved before electrolysis becomes economically viable. This includes the development of a cheap, carbon-free inert anode that is resistant to the corrosive conditions in molten oxide electrolysis. Molten oxide electrolysis (MOE) has been identified by the American Iron and Steel Institute (AISI) as one of four possible breakthrough technologies to alleviate the environmental impact of iron and steel production. MOE produces iron by electrolysis of an iron oxide containing electrolyte. The electrolysis results in the production of pure iron metal at the cathode and pure oxygen gas at the anode. Because of the low vapor pressure of the electrolyte at temperatures above 1538
C, MOE can be performed above the melting temperature of iron. The production of liquid metal, ready for continuous casting, is a prerequisite for any industrial-scale extractive metallurgical process. Therefore, if an inert anode can be identified, MOE could provide an industrial process to produce iron from its ore with pure oxygen gas as the only direct emission (Paramore 2010). The development of this process is motivated by the production of iron metal from an iron oxide containing electrolyte as a carbon neutral approach to replace current pyrometallurgical processes that result in copious amounts of greenhouse gas emissions. Iron ore electrolysis, as well as hydrogen direct reduction, has been recognized as the preferred future steelmaking technology across different perspectives (Weigel et al. 2016). In fact, taking into account the technology development of the solution, the social acceptance and the regulations development, the safety issues, the process economy, and the ecology, the different scores shown in Fig. 10.1 have been developed.

10.2

Molten Oxide Electrolysis

557

Fig. 10.1 Scoring criteria (with equally distributed weighting)

10.2

Molten Oxide Electrolysis

MOE appears very promising in order to reach a deep CO2 reduction in ironmaking. This consists in the electrolysis process of oxides mixture leading to the separation of liquid iron and oxygen gas through the electric current application. It is a metal extraction process that exhibits an exceptionally high productivity in comparison with other electrowinning techniques. Furthermore, MOE has the ability to generate oxygen as an environmentally benign by-product, which is a key asset to improve metal extraction sustainability. Performing direct electrolysis of iron oxide at temperatures above the melting point of iron (1538
C) requires resilient supporting electrolytes, particularly mixtures of molten metal oxides. Consequently, the structure and properties of molten oxide electrolytes are of critical importance in electrochemical engineering of an iron oxide electrolysis process. From an electrochemical engineering standpoint, the high concentration of metal cations dissolved in the electrolyte justifies cathode current densities above 10,000 A m2. At the anode, the available data suggest a mechanism of oxidation of the free oxide anions which concentration in oxide melts is reported to be limited. In this context, the application of available mass transfer correlations for the anodic oxygen evolution suggests a key role of convection induced by gas bubbles evolution (Allanore 2013). The

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Fig. 10.2 Electrical energy required per ton of liquid iron as a function of the electrical conductivity of the molten oxide electrolyte

temperature levels below the melting point of iron and the direct route from iron oxide to molten iron lead to high energy saving (Allanore et al. 2011). The basic reaction is: 1 3 Electrolysis 3 Fe2 O3 ðs 298KÞ $ Fe3þ þ O2 Feðl 1863KÞ þ O2 ðg 1863KÞ 2 2 ! 4 Obviously, the process must be energy efficient in order to be appealable for large-scale production. The variation of the electrical energy required per ton of liquid iron as a function of the electrical conductivity of the molten oxide 95 electrolyte, for a range of G factor between 0.5 and 6 Acm1, is plotted. (Fig. 10.2). Electrolysis cell is believed to produce a heat loss of 40%. As comparison, the blast furnace energy requirement is indicated (17.9 MJ/t Fe; 4980 kWh/t Fe). From the authors’ calculations, the minimum practical electrical energy requirement should be 10 MJ/t Fe (2780 kWh/t Fe). If the system energy is below this value, the cell will be under-heated and will cool to the point where the process is quenched and reaction ceases. Any energy value in excess of the required value will imply more heat loss and reduced energy efficiency. The indicated promising approach is the development of a cell of very low G factor by reducing the inter-electrode gap which enables the use of low conductivity electrolytes, at around 0.3 Scm1. The advantage of such electrolytes is that they are less aggressive on refractories and

10.2

Molten Oxide Electrolysis

559

Fig. 10.3 CO2 mitigation factor for the MOE technology

readily available in steelmaking. Anyway, it is recognized that the energy requirement for the process is, for any realistic conductivity and G factor, less than the energy requirement in an actual carbon-based route (Allanore et al. 2010). The consequent CO2 mitigation factor is plotted in Fig. 10.3. First of all, Fig. 10.3 shows that for a G factor of 4 A.cm1, which corresponds to todays’ Hall-Heroult cell technology, a reduction in CO2 emissions can be obtained for a conductivity slightly above 2 Scm1 whatever the mode of electricity generation. A combination of an advanced electrolysis cell with a low G factor and electricity generation with a fairly high CO2 content as long as the conductivity of the electrolyte is higher than 0.2 Scm1. If carbon-free electricity is available (nuclear or high-power renewables), the cell design has a marginal influence on the CO2 impact of the process. Finally, for a G factor of 0.5 Acm1, the CO2 emissions mitigation can be drastic when the electrolyte conductivity is increased, no matter which mode of electricity generation is employed. The development of new electrolysis cell configuration, as achieved recently for low-temperature electrolysis processes, will provide a versatile ironmaking process. Such process CO2 impact would then be decoupled from the electricity production mode. The E-logpO2 diagrams for ironmaking by molten oxide electrolysis were determined at different temperatures (Judge et al. 2017). The iron-oxygen phase diagram is plotted in Fig. 10.4. Each of these oxides is characterized by a region of stability under different oxygen partial pressures and temperatures, as shown by the T-logpO2 diagram in Fig. 10.5, but this provides no information regarding the influence of electric potential.

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Fig. 10.4 Iron-oxygen phase diagram

Fig. 10.5 T-logpO2 diagram for iron and its oxides

10.2

Molten Oxide Electrolysis

561

Fig. 10.6 E-logpO2 diagram for iron and its oxides for the 1473 and 1873 K isotherms. The solid lines indicate phase boundaries, while the dashed lines indicate iso-activity lines for some solid solutions of oxygen in the oxides

The authors calculated the E-logpO2 for the isotherms at 1473 and 1873 K (Fig. 10.6). At 1473 K, the stability regions of metallic iron, wüstite, magnetite, and hematite were determined, and the effect of electric potential and oxygen partial pressure on

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Fig. 10.7 Valence distribution diagram of iron in liquid oxide at the 1873 K isotherm. The solid lines indicate phase boundaries, while the dashed lines indicate iso-pressure contours of oxygen

their stoichiometry was explored. The practical implication of these results is predicting the solid-state chemistry of the sidewall of frozen electrolyte in the iron electrolysis cell. At 1873 K, the stability regions of liquid iron and its liquid oxide were determined, and the relationship between the electric potential and oxygen partial pressure and the valence distribution of iron was established (Fig. 10.7). The authors conclude that thanks to the high temperature of operation mandated by the desire for a liquid metal product, most of the energy needed to produce iron is in the form of heat, which is efficiently provided by electricity. Contrary to conventional wisdom, the energy consumption for electrolysis is low, provided that faradaic efficiency is high and best available cell design is adopted. In such circumstances, the process’s CO2 impact is related to the carbon content of the electricity and the conductivity of the electrolyte. The development of an advanced cell configuration that features a low anode-cathode distance and runs with a high-conductivity electrolyte could result in a decoupling of the CO2 impact of the process from the mode of electricity production. This would lead to new opportunities for the deployment of electricity-based steel production. Such development is however possible provided that a number of fundamental aspects of the MOE process are understood: the influence of electrolyte composition on the electrochemical reactions and the invention of a new inert anode design for gas production and recovery at high temperature in highly aggressive melts. In recent studies from Wiencke et al. (2018), the implementation of MOE in a controlled way and at steady state has been carried out with a small-scale experimental device at 1823 K. An electrolyte composed of molten oxides has been derived, from thermodynamic considerations, to flow electric current ionically and

10.2

Molten Oxide Electrolysis

563

Fig. 10.8 Electrolysis of molten oxides

to overcome the problem of the multiple valence states of the oxidized iron element. The production of liquid iron samples has been accomplished relying on the sole application an electrical voltage surpassing the minimum thermodynamic requirement (Fig. 10.8). The faradaic character of the cathodic reaction was checked by following the accompanying anodic oxygen gas evolution. Afterward, the observation and analysis of the samples confirmed the reduction of iron into metal. The current chosen was large enough to produce macroscopic iron samples during the time of the experiment and to evolve oxygen gas at a rate significantly higher than the thermally generated oxygen; however, the corresponding voltages were exceeding the thermodynamic threshold of decomposition of constituents of the electrolyte. If compared to the Hall-Heroult cell used to produce aluminum, the MOE process is characterized by its unique parameters: high-operating temperatures leading to the corrosion reaction acceleration, highly oxidizing environment due to the evolution of pure oxygen and anodic potential, the presence of metal-solubilizing liquid metal product, and the presence of ceramic-solubilizing molten oxide electrolyte. So, in order to overcome these inconveniences, the industrial cell must be designed with special characteristics, an inert anode capable of resisting the highly corrosive environment and thermal gradient to allow molten electrolyte to freeze at the

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Fig. 10.9 Industrial MOE cell (Gmitter 2008)

extremities of the cell, therefore protecting the refractories used to contain the bath. The schematic of the industrial cell is shown in Fig. 10.9. Iridium-based anode materials are demonstrated to be very promising for MOE (Wang et al. 2011). Iridium is seen as a candidate material for an oxygen-evolving anode only in acidic melts. Basic melts attack iridium owing to the high concentration of free oxide ion coupled with the low viscosity, which results in unimpaired mass transport (Kim et al. 2011). Molybdenum disks are employed as cathode materials. The cathode would never come in contact with the evolving oxygen bubbles or the oxygen-containing atmosphere of the furnace during electrolysis because of its susceptibility to oxidation. Furthermore, the cathodic potential should offer protection from oxidation during electrolysis. It was found that molybdenum crucibles, despite severe oxidation, would last considerably longer than their ceramic counterparts. The design uses a molybdenum crucible, which is connected to the current supply and supplies cathodic potential to the electrolyte by means of a molten copper pool. Zhou et al. (2017) showed the possibility to produce pure iron by electrolysis in CaO-MgO-SiO2-Al2O3-Fe2O3 at 1723 K. In this system, the pure iron had been obtained, and the current efficiency is about 46%, higher than the previous results. There is a molybdenum-iron transition layer between the deposition and the electrode, and a dense and uniform iron film confirms the considerable capacity of

10.2

Molten Oxide Electrolysis

565

CaO-MgO-SiO2-Al2O3 media for electrolytic iron. The Fe-Ni alloy deposits were derived from galvanostatic electrolysis in CaO-MgO-SiO2-Al2O3-Fe2O3-NiO. The results prove the formation of Ni-Mo-Fe ternary intermetallic compound and the feasibility of Fe-Ni alloy electro-deposition in such conditions. The results are still insufficient for the actual production process—current efficiency is low, products separation is difficult, and other issues still need to be addressed, but the more efficient direct production of Fe and Fe-Ni alloy can be expected by further investigation to optimize the electrolyte composition and finding the better electrode materials. Electrolytic reduction of dissolved iron oxide to metal iron in molten salts with an inert anode is an alternative short route for steelmaking without CO2 emissions. A novel and simple integrated yttria-stabilized zirconia (YSZ) cell was constructed from a YSZ tube with a closed end. The YSZ tube played multiple functions, including the container for the molten salts, the solid electrolyte membrane in the O2|YSZ|Pt|O2 (air) reference electrode (RE), and the solid electrolyte membrane between the working and counter electrodes (WE and CE). Electrochemical behavior of ferric ions (Fe3+) that were formed by dissolution of 0.5 wt pct Fe2O3 in the molten CaCl2-NaCl eutectic mixture was investigated on a Pt WE at 1273 K by various electrochemical techniques including cyclic voltammetry, linear scan voltammetry, square wave voltammetry, chronopotentiometry, chronoamperometry, and potentiostatic electrolysis (Hu et al. 2018). The test results of various electrochemical techniques, such as CV/V, LSV, SWV, CP/C, reversal CP/C, and CA, suggest that the reduction of Fe3+ to Fe on the Pt WE could be a single one-step and diffusion-controlled reaction that was also possibly reversible. The peak potential of the reduction of Fe3+ to Fe on the CV/V was observed at about 0.73 V, and the reduction product, Fe, was found to alloy with the Pt electrode. The diffusion coefficient of ferric ions was derived in satisfactory consistency from the CV/V, SWV, CP/C, reversal CP/C, and the CA analyses and also matched reasonably well with those values in related literature. It was found that there was another reduction reaction with potentials more negative than 1.2 V in CP/Cs. It was considered that the reduction reaction was most likely due to the reduction of Fe2+ ions from FeO. However, it still needs further investigation and confirmation. The transport of O2 ions in the YSZ membrane seemed to have no or little effect on the behavior of electroactive species on the Pt WE in the three-electrode cell at a sufficiently high temperature. Overall, this work has demonstrated the feasibility of electrochemical investigation of ferric ions in molten salts with the aid of the integrated cell with the “O2|YSZ|Pt|O2 (air)” RE. It should be noted that the integrated cell as reported in this work is not studied for direct industrial adaption, but the working principle, i.e., using the YSZ membrane for incorporation of RE and also separation of the anode and cathode should be applicable in a future continuous electrolytic steelmaking process, such as the MOE method.

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Electrowinning

Unlike MOE, aqueous electrolysis uses an alkaline solution (mostly aqueous NaOH) as the electrolyte. In addition, two inert electrodes are used. On the cathode, the iron cations are reduced and iron is plated. Electrolysis still involves CO2 generation as the process relies intensively on electrical energy which is largely produced by the consumption of carbon-based fuels. Also, there are other obstacles to be overcome in MOE, such as the high temperature required to maintain the electrolyte liquid as well as the electrode material for large scale. For aqueous electrolysis, in addition to the requirement of electrical energy, the major challenge is the large-scale solution treatment and purification as well as other problems associated with hydrometallurgical processes. Iron oxide particles are reduced at solid state, which distinguishes this route from conventional electrowinning processes where the metal is deposited through the reduction of dissolved metal cations, with suspended hematite (α-Fe2O3) particles: high current yields of Fe deposition could be obtained from concentrated hematite suspensions in hot concentrated NaOH solutions, with a current density in the order of 1000 A/m2. It was evidenced that the reduction is only possible upon adsorption and contact of the oxide particle and the electrode contact, and intermediate formation of magnetite Fe3O4 at the hematite surface, in a shrinking core mechanism. Although most studies on this new electrowinning technique have been carried out with hematite, other iron oxide-hydroxide varieties could be considered, such as magnetite and goethite α-FeOOH, as long as they are available from natural resources. It is therefore of interest to compare their electrochemical reactivity to hematite’s as they could represent, either additional primary iron sources for this processing route or an opportunity to check postulated electrochemical mechanisms for the decomposition of iron oxides as derived from previous hematite reactivity studies. Decades ago, polarographic experiments were carried out on hematite and goethite suspensions with low concentration at 90
C (Picard et al. 1980). It was found that although the main reduction peak was observable at a similar potential for the two suspensions, goethite would turn into sodium ferrite, NaFeO2, after about 2.5 h in these conditions of high temperature and high alkalinity, and would be almost electrochemically inert. Recent studies however showed that iron deposits with high current efficiency could be obtained with higher concentration of goethite (Duchateau 2013). Other studies (Monteiro et al. 2016) demonstrated that iron could be deposited with high current efficiency and current densities from sintered magnetite in similar physical and chemical conditions. Though reduction of porous magnetite samples yields very porous and fragile metallic product, this offers good prospects for electrochemical conversion at much fast rate and with much higher faradaic efficiency. Direct in situ electrochemical reduction of magnetite precursor used as cathode in alkaline media at higher potentials that of hydrogen evolution is possible, metallic iron being the reaction product; relatively dense metallic iron films are produced on the magnetite pellet faced to the electrolyte; morphology of the Fe deposit is consistent with a key role of

10.3

Electrowinning

567

Fig. 10.10 Fe fraction vs. Fe3O4 density (a), current-time transients for magnetite samples recorded at E ¼ 1.15 V in 10 M NaOH and 90
C (b)

soluble species in reduction; a maximum Fe reduction current efficiency of 85% was achieved for magnetite oxides with porosities as high as 0.45 (Fig. 10.10). Because of the current extraction technique of iron ores and the fore treatments to remove the gangue, suspended solids appear as the simplest form of iron oxides to be considered in an industrial process for electrochemical reduction to iron metal.

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Fig. 10.11 Principle of iron electrowinning

This technology comprises alkaline electrolysis as a way to reduce CO2 by transforming the iron ore into metal and oxygen (O2) requiring electrical energy only. No direct CO2 would be emitted applying this technology, which is still in a development phase. The first obtained results were the definition of the influence of the operating parameters on the morphology of the iron deposits in order to obtain the most favorable conditions to reach high faradaic yield. The conditions for maximum faradaic yield have been determined as 40% of Fe2O3 in 50%NaOHH2O at 110
C, 1000 rpm and 0.2A/cm2 Fig. 10.11). The Fe2O3 particle suspended in the electrolyte is directly reduced by the cathodic reaction, and the metallic Fe phase is obtained on the surface of a rotating disk cathode. In this process, as shown in Fig. 10.12, the cathode limit of the electrolyte (H2 evolution) is shifted to a negative potential using a strong alkaline electrolyte so that electrowinning of iron can be conducted. The anodic reaction is the oxygen evolution. The morphology of the obtained Fe film was found to change as a result of electrolysis conditions such as the current

10.3

Electrowinning

569

Fig. 10.12 Pourbaix diagram for Fe-H2O at 110
C

density and the rotation rate of the disk cathode. As for the morphology of the electrodeposited Fe films, many investigations have been conducted on the electrolyte containing the dissolved iron ions, and it was found that the electrodeposited Fe columnar grows (grows in a columnar formation) and its morphology changes from tetragonal to trigonal pyramids as a result of changing electrolysis conditions such as the current density, the pH value of the electrolyte, and the applied magnetic field. The nucleated Fe grew by spiral dislocation according to the two-dimensional nucleation. The formation of heterogeneous film decreases current efficiency. Therefore, in order to industrialize this process as a novel iron production method, it is necessary to clarify and control the reduction process of the Fe2O3 particles and the growth process of the deposited Fe and to obtain a homogeneous Fe film. Then, to determine the appropriate conditions for obtaining Fe films with homogenous morphology, the relation between the morphology of the obtained Fe and electrolysis conditions such as current density and Fe2O3 particle content would be deeply investigated. Electrowinning was conducted in a 50 wt% (18 M) NaOH-H2O system (NaOH: 99.0% purity, VWR International, Ltd.) containing Fe2O3 particle (electrolyte) at 110
C. α-Fe2O3 particles (99.5% purity, 325 mesh, Alfa Aesar Gmbh & Co KG) with diameters of less than 0.2 μm were used as suspension. A graphite disk (ø8.0 mm) was used as a working electrode (cathode), and a Ni mesh (45  125 mm, 0.1 mmt) was used as a counter electrode (anode). The reference electrode was a HgO/Hg electrode immersed in a 0.1 M NaOH-H2O reference solution with a salt bridge connecting the electrolyte and the reference solution. All potential values were calibrated based on that of the dynamic hydrogen electrode (DHE), where hydrogen evolution starts on a Pt wire cathode. In order to confirm the

570

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Fig. 10.13 Efficiency of the iron reduction according to the production rate

direct reduction of Fe2O3 in 50 wt% NaOH-H2O electrolyte at 110
C, the electrowinning (1.0 A, 20,000 C) was conducted using an Fe2O3 pellet as a cathode. The electric yield reaches 97%. The current density window for efficient iron production extends from 0.1 to 0.3 A/cm2 (Fig. 10.13). The authors find that the Fe2O3 particle was directly reduced on the surface of the disk cathode and the deposited Fe atoms formed a cubic particle with a side length of around 0.1 μm. The aspect of the deposited iron is shown in Fig. 10.14. The crystal orientation of α-Fe depends on electrolysis conditions such as current density and Fe2O3 particle content, and the (211) face plane of α-Fe was preferentially orientated. Therefore, a cubic α-Fe particle columnar grows towards the (211) face direction by spiral dislocation after 2-D nucleation. In addition, the morphology of the obtained Fe films can be controlled by the current density and the transfer rate of the Fe2O3 particle content. At a high Fe2O3 particle content, the direct reduction of the Fe2O3 particle progresses on the cathode due to the fast transfer of the Fe2O3 particle to there. Thus, the transfer of the Fe nuclei is fast and hydrogen evolution is slow. This consideration agrees with the dependence of the average grain size of α-Fe on the current density. At 33 wt% of the Fe2O3 particle content, the size of α-Fe crystal grain decreases by increasing the current density, despite that the nucleation rate becomes fast due to increasing the overpotential. On the other hand, the grain size increases with higher current density at 40 wt.% Fe2O3 particle content. The transfer rate of the Fe2O3 particle affects the growth process of α-Fe crystal. These results suggest that the growth process of the deoxidated Fe depends on the transfer rate of the Fe2O3 particle. It is believed that this maximum current density means a division by a factor 3 of a large-scale plant compared to the assumed production rate (Tokushige et al. 2013).

10.3

Electrowinning

571

Fig. 10.14 Iron electrodeposited through electrowinning

Fig. 10.15 Anode materials

The approach comprises the development of a Ni-based electrode incorporating cobalt-based oxides in order to lower the anode potential (Fig. 10.15). The ULCOWIN steelmaking route is shown in Fig. 10.16 with the indications of the processing steps and the material/energy balance.

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Fig. 10.16 Electrowinning route

A lamellar anode was designed in order to conciliate the uniform current distribution with the efficient removal of oxygen bubbles developed during the process. Solutions for cathode materials have been selected based on Cupronickel10, magnesium, and graphite. The laboratory pilot cell has been adapted to treat electrochemically slurry based on alkaline solution with suspended ultrafine particles of iron oxide. The main obtained results were massive sample production (3605 g); straight, self-standing, and conveyable iron plates; 4.3-mm-thick metal deposit on a 770-mm-long plate; compact growth; 99% purity iron; low overall faradaic efficiency of 72%; and instantaneous efficiency of 91% (in Maizieres-les-Mets R&D ArcelorMittal Lab, France). By analyzing the conditions of operations at laboratory level of the hightemperature electrolysis of iron ore, the iron electrochemical reactivity in molten salt-molten slag was experienced. The results have shown that the cathodic reaction is reversible and limited by diffusional transport, the overwhelming contributor to the cathodic reaction of ferrous iron, and that ionic conduction in the molten slag prevails compared to electronic. The results of thermal expansion and electrical conductivity properties at high temperatures indicate that the most promising materials for consumable ceramic anodes in pyroelectrolysis are iron oxides substituted spinels Fe2.6Al0.2Mg0.2O4 and Fe2.6Ti0.2Mg0.2O4. The optimized composition of the slag, which guarantees high faradaic yield and facilitates oxygen gas and liquid steel extraction, is SiO2 66%, Al2O3 2%, and MgO 14%. Silica- and alumina-based refractories were employed. In very recent studies from the reduction of several iron oxide/hydroxides to iron through alkaline electrolysis has been investigated in a stirred electrochemical cell at the same constant cell voltage. Results converge towards the conclusion that

10.3

Electrowinning

573

Fig. 10.17 Current density along electrolysis time for hematite, goethite, magnetite, and NaOHH2O

hematite is the most easily reduced iron oxide, with about 85% as current efficiency at current density of about 1100 A/m2 (Fig. 10.17). Goethite reduction was obtained with a current density close to 650 A/m2 at the same voltage, but with a noticeably lower faradaic yield for iron formation: this could be the fact of different electrode reaction pathways between the two Fe-based minerals. Moreover, the very high viscosity of goethite slurry, likely because of the highly cohesive interactions between goethite particles, could be detrimental to the evolution of oxygen bubbles, usually larger than hydrogen bubbles. The reactivity of magnetite in form of a suspension proved to be extremely poor in these conditions, in terms of both available current density and faradaic yield. Results converge towards the conclusion that hematite is the most easily reduced iron oxide, with about 85% as current efficiency at current density of about 1100 A/ m2. Goethite reduction was obtained with a current density close to 650 A/m2 at the same voltage, but with a noticeably lower faradaic yield for iron formation: this could be the fact of different electrode reaction pathways between the two Fe-based minerals. Moreover, the very high viscosity of goethite slurry, likely because of the highly cohesive interactions between goethite particles, could be detrimental to the evolution of oxygen bubbles, usually larger than hydrogen bubbles. The reactivity of magnetite in form of a suspension proved to be extremely poor in these conditions, in terms of both available current density and faradaic yield.

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Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Haarberg and Yuan (2014) investigated the feasibility of the electrochemical reduction for iron metal production in concentrated sodium hydroxide solutions at a low temperature for iron production. In this process, a porous hematite powder pellet was manufactured by mechanical pressing followed by sintering. The sintered pellet was then immersed in a concentrated sodium hydroxide solution. A direct current was applied between the hematite pellet cathode and a nickel metal mesh anode at 110
C. The oxygen in the hematite was ionized and was diffused through the solid and the electrolyte to the anode and was discharged as oxygen gas. The electrolyte was a 50 wt. % NaOH-50 wt. % H2O sodium hydroxide solution contained in a cylindrical Teflon container. The highly concentrated solution provided the advantages such as a high conductivity, suppressed H2 evolution reaction, and possibility to apply higher temperature without considerable loss of water. A rectangular nickel mesh was attached to the wall of the container and was used as the inert anode for oxygen evolution. The powder pellet was suspended in the electrolyte corresponding to the geometric center of the anode for the sake of uniform current distribution. The reduction reaction front was carried forward in the oxide phase by the partially reduced oxide. Simultaneously with the propagation reaction, a complete conversion of the oxide core to the metal iron occurred through the shrinking of the oxide core. The electro-crystallization of the iron took place, and an incomplete twin-crystal pyramid was formed. The diffusion of the oxygen ions in the solid oxide phase was the rate-determining step in the electrochemical reduction process. This shows a high potential for the industrial production of pure electrochemical iron and iron alloys.

10.4

Conclusions

Electrolysis of iron ores has not been developed in the past because of the costs differences with the traditional integrated ironmaking route. From a technological point of view, the limit has always been the availability of a suitable anode material capable of weathering the challenging conditions. The principal electrolysis routes under investigation and development are the molten oxide electrolysis and the electrowinning. Since electrolysis produces no CO2, it could theoretically be zerocarbon, but only if the electricity needed to power, the process is produced without generating CO2 emissions (renewable sources). MOE consists in the electrolysis process of oxides mixture leading to the separation of liquid iron and oxygen gas through the electric current application at temperatures above the melting point of iron (1538
C) requiring resilient supporting electrolytes, particularly mixtures of molten metal oxides. In order to overcome MOE process inconveniences, the industrial cell must be designed with special characteristics, an inert anode capable of resisting the highly corrosive environment and thermal gradient to allow molten electrolyte to freeze at the extremities of the cell, therefore protecting the refractories used to contain the bath. As mentioned, the anode material issues are a crucial aspect of iron ores electrolysis. Iridium-based anode materials are demonstrated to be very

References

575

promising for MOE. Electrowinning uses an alkaline solution (mostly aqueous NaOH) as the electrolyte. In addition, two inert electrodes are used. On the cathode, the iron cations are reduced and iron is plated. The anodic reaction is the oxygen evolution. The morphology of the obtained Fe film was found to change as a result of electrolysis conditions such as the current density and the rotation rate of the cathode. In order to industrialize this process as a novel iron production method, it is necessary to clarify and control the reduction process of the Fe2O3 particles and the growth process of the deposited Fe and to obtain a homogeneous Fe film. The actual approach comprises the development of a Ni-based electrode incorporating cobalt-based oxides in order to lower the anode potential.

References Allanore A (2013) Electrochemical engineering of anodic oxygen evolution in molten oxides. Electrochim Acta 110:587–592. https://doi.org/10.1016/j.electacta.2013.04.095 Allanore A, Lavelain H, Birat JP, Valentin G, Lapicque F (2010) Experimental investigation of cell design for the electrolysis of iron oxide suspensions in alkaline electrolyte. J Appl Elctrochem 40:1957–1966. https://doi.org/10.1007/s10800-010-0172-0 Allanore A, Ortiz LA, Sadoway R (2011) Molten oxide electrolysis for iron production: identification of key process parameters for largescale development. In: Energy technology 2011: carbon dioxide and other greenhouse gas reduction metallurgy and waste heat recovery. Wiley, Hoboken, NJ, pp 120–129 Cavaliere P (2016) Ironmaking and steelmaking processes: greenhouse emissions, control, and reduction. Springer, New York, NY. https://doi.org/10.1007/978-3-319-39529-6 Duchateau A (2013) Réduction par électrolyse de nanoparticules d’oxydes de fer en milieu alcalin à 110
C. Dissertation, University ParisTech Gmitter AJ (2008) The influence of inert anode material and electrolyte composition on the electrochemical production of oxygen from molten oxides. Massachusetts Institute of Technology, Cambridge Haarberg GM, Yuan B (2014) Direct electrochemical reduction of hematite pellets in alkaline solutions. ECS Trans 58(20):19–28. https://doi.org/10.1149/05820.0019ecst Hu H, Gao Y, Lao Y, Qin Q, Li G, Chen GZ (2018) Yttria-stabilized zirconia aided electrochemical investigation on ferric ions in mixed molten calcium and sodium chlorides. Metall Mater Trans B B49:2794–2808. https://doi.org/10.1007/s11663-018-1371-z Judge WD, Allanore A, Sadoway DR, Azimi G (2017) E-logpO2 diagrams for ironmaking by molten oxide electrolysis. Electrochim Acta 247:1088–1094. https://doi.org/10.1016/j.electacta. 2017.07.059 Junjie Y (2018) Progress and future of breakthrough low-carbon steelmaking technology (ULCOS) of EU. Int J Miner Process Extract Metall 3(2):15–22. https://doi.org/10.11648/j.ijmpem. 20180302.11 Kim H, Paramore J, Allanore A, Sadoway DR (2011) Electrolysis of molten iron oxide with an iridium anode: the role of electrolyte basicity. J Electrochem Soc 158(10):E101–E105. https:// doi.org/10.1149/1.3623446 Monteiro JF, Ivanova YA, Kovalevsky AV, Ivanou DK, Frade JR (2016) Reduction of magnetite to metallic iron in strong alkaline medium. Electrochim Acta 193:284–292. https://doi.org/10. 1016/j.electacta.2016.02.058 Paramore JD (2010) Candidate anode materials for iron production by molten oxide electrolysis. Master Thesis, Massachusetts Institute of Technology

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10

Electrolysis of Iron Ores: Most Efficient Technologies for Greenhouse. . .

Picard G, Oster D, Tremillon B (1980) Electrochemical reduction of iron oxides in suspension in water-sodium hydroxide mixtures between 25 and 140
C. Part II. Experimental study. J Chem Res (S) 8:252–253 Tokushige M, Kongstein OE, Haarberg GM (2013) Crystal orientation of iron produced by electrodeoxidation of hematite particles. ECS Trans 50(52):103–114. https://doi.org/10.1149/ 05052.0103ecst Wang D, Gmitter AJ, Sadoway DR (2011) An inert anode for the production of oxygen gas by electrochemical decomposition of an oxide melt. Unpublished results from Massachusetts Institute of Technology Weigel M, Fischedick M, Marzinkowski J, Winzer P (2016) Multicriteria analysis of primary steelmaking technologies. J Clean Prod 112:1064–1076. https://doi.org/10.1016/j.jclepro. 2015.07.132 Wiencke J, Lavelaine H, Panteix PJ, Petitejean C, Rapin C (2018) Electrolysis of iron in a molten oxide electrolyte. J Appl Elctrochem 48(1):115–126. https://doi.org/10.1007/s10800-017-1143-5 Zhou Z, Jiao H, Tu J, Zhu J, Jiao S (2017) Direct production of Fe and Fe-Ni alloy via molten oxides electrolysis. J Electrochem Soc 164(6):E113–E116. https://doi.org/10.1149/2.0881706jes

Index

A Abatement potential, 488 Abrasion index, 85 ACARP (Sustainable Technology Australia), 100 Activated carbons (AcC), 395, 396 Activated coke method, 121, 122 Adsorption-enhanced reforming (AER), 540 Aeration tank, 45 Agglomerating agents, 315 Air emissions, 115 Air separation unit (ASU), 536 Air travel distance, 526 Aligned policies, 23 Alkali-activated fly ash, 314 Alkaline-binding systems, 313 Anaerobic degradation, 46 Anthracite/petroleum coke, 148 AOPs, 46 ArcelorMittal plant, 124 ArcSave stirring, 347–349 Ash, 311 Ash-based geopolymer systems, 314 Atmospheric emissions, 115 Automotive grade steels, 317 Auxiliary reducing agents (ARA), 437

B Basic oxygen furnace (BOF), 7, 20, 179, 222, 275, 512 bottom gas stirring (see Bottom gas stirring) by-products reuse, 287 capacities, 275

composition variation melt, 278 slag, 277, 278 contour censoring, 294, 295 dust recovery dedusting load, 287 electrostatic precipitators, 287 RecoDust plant, 288, 289 types, 288 energy consumption, 288 energy input (see Metallized iron usage) energy issues, 287–291 energy saving potential, 289–291 environmental issues, 279 exhaust gas analysis, 293 functions, 275, 276 gas blowing process, 288 gas dry dedusting technique, 290, 291 heat and gas recovery (see Energy recovery) in-furnace post-combustion, 296, 297 ladle preheating, 295, 296 materials flow and emission, 279, 280 melt composition variation, 277 off-gas composition, 279 reactions, 275–277 route, 14 slag (see BOF slags) steel/slag composition monitoring, 294 Basic oxygen steelmaking (BOS) process, 277–279 Baur-Glaessner type diagram, 469 Bessemer Thomas converter, 275 Best available techniques, 6 BF-BOF route, 426, 427 BF-MIDREX-EAF process, 426

© Springer Nature Switzerland AG 2019 P. Cavaliere, Clean Ironmaking and Steelmaking Processes, https://doi.org/10.1007/978-3-030-21209-4

577

578 Biochar, 156–158 Biological treatment method, 45 Biomass, 31, 32 coke making, 99–103 combustion BF injection, 225 biofuel production technologies, 227 bioreducers, 223, 231 Brazilian plants, 226 charcoal chemistry, 223 CO2 emissions, 223 coke and coal, 223 emission taxes, 230 flame temperature, 229 hard carbons, 227 HTC, 226 isotropic disordered material, 230 lignin, 226 morphology, 230 optimized carbonization, 231 price, 229 pulverized coal, 223 pyrolysis concept, 230 steelmaking process, 227 TP and WP, 228 tuyeres constant, 229 wood-based biomass, 224 wood-based materials, 225 in sintering activated carbon/lignite, 158 biochar, 156–158 cellulignin coal, 155 characterization techniques, 154 clean energy, 153 coke breeze fuel, 158 combustion efficiency, 154 corus, 153 CSIRO, 155, 156 environment impacts, 158, 159 ESP, 158 flame front speed, 155, 156 gas flow simulations, 155 hydrocarbons, 154 material types, 154 metallurgical properties, 156 micropores, 154 operation data, 158 reaction surfaces, 155 silica, 154 small-scale sinter pot experiments, 154 solid fuels properties, 153 SOx emission, 154 Tumble index, 155, 156

Index Bioreducers, 223 Blast furnace gas (BFG), 146–148, 155, 461, 503, 505, 534 Blast furnaces (BFs), 7, 14, 27, 39, 52, 53, 55, 57, 61, 64, 66, 84, 86, 87, 89, 95, 99– 101, 111, 499 air flow, 167 air moisture, 173 BF-BOF steelmaking system, 179 burden and reduction reaction, 191 carbon, 171 carbon dioxide emission, 173 CFD-DEM model, 199 CO2 abatement, 170 emissions, 170, 178 intensity, 169 potential reduction, 169 COG, 178 coke and iron-bearing materials, 179 reduction, 181 concepts, 172 conceptual system, 168 conventional blast furnace, 178 EMF, 194 energy consumer, 167 energy-efficient technologies, 168 equilibrium reduction reactions, 174 gas-phase equilibrium composition, 175 gas recycling, 170, 172 gas scrubbing, 168 GHG, 168 H2 and CO, 173 hematite, 175 hot waste gases, 167 hydrogen, 175 industrial process, 175 instrumentation, 194 iron ore, 167 iron oxides, 167 legal requirements, 199 mathematical simulation, 173 online tools, 199 optimized scheduling, 201 oxygen blast furnace, 172 oxygen enrichment, 178 oxygen gas volume, 170 parameters, 194 PCI, 173 performances, 179, 181 process control, 194 pulverized coal, 172

Index reactor, 196 reduction, 173 secondary emissions, 200 size, 169 small-scale steel production, 169 steel production, 176 techniques, 194 temperature curves, 174 tuyeres level, 197 WTCR, 191 wüstite reduction, 176 Blast furnace with CCS (BF-CCS), 463 BLUE scenario, 24, 25 BOF slags applications, 286, 287 cement clinker manufacturing process, 286 CRW, 286 CW-EDI, 286 holding time, 291 magnetic spinel phases, 291 oxidation behavior, 291 properties, 285 sensible heat recovery, 284, 285 BOF steelmaking, 311 Bottom gas stirring bottom-blowing intensity, 293 dephosphorization mechanism, 292 differential flow, 293 inert gas injection, 292 mass transfer, 293 nitrogen, 291 oxidation volume, 293 phosphorous removal, 293 Bottom stirring carbon content, 349 characteristics, 350 in EAF, 346 efficiency, 350 electromagnetic force, 350 EMS stirring, 347 gas, 291 inert gas, 346 new EAF process development, 347 practice, 346 reduced electrode current swings, 347 Bottom-up energy system models, 462 Breakthrough technologies, 22, 28, 29, 31, 32 Briquettes, 101 Burning waste plastic, 499 Burn-through point (BTP), 133 Business model, 17

579 C Ca-based sorbents, 545 Ca-based WFGD system, 60 Calcium-enriched system, 313 Calorific value (CV), 58, 281 Capture processes, 536 Carbon, 28, 307 Carbonation, 316 Carbon capture and sequestration, 533 Carbon capture and storage (CCS), 22, 23, 25, 27, 31, 432, 462, 479, 488–491 BF-BOF process, 498 biomass, 493 blast furnaces, 499, 501 and CCU, 490 chemical composition, 497 in China, 487 CO2 capture, 488, 495 emissions, 486–488, 490 Dutch greenhouse, 493 energy efficiency potential, 496 EOR, 493 in Europe, 497 gas treatment, 489 global emissions, 486 IEA statistics, 496 iron and steel industry, 497 manufacturing plants, 485 methanation, 492 mini steel mills, 491 mitigation options, 490 natural gas, 501 and oxygen atoms, 491 recycling, 501 RUREH, 486 sintering process, 499 Carbon capture and usage (CCU), 5 Carbon capture technologies, 491 Carbon capture use and storage (CCUS), 6 Carbon dioxide (CO2) emissions, 309, 310 Carbon direct avoidance (CDA), 5 Carbonization air contactor, 524 BF, 521 chemical loops, 523 coking industry, 531 COREX process, 521 designers, 526 emission sources ranges, 532 iron and steel mill, 532 liquid distribution, 526 outdoor contractor, 526

580 Carbonization (cont.) prototype module, 526 storage capacity, 521 TGRBF, 533 Carbon membranes, 516 Cellulignin coal, 155 Chamber walls, 82 Charcoal, 99, 100, 422 markets, 183 in sintering application, 151 biomass fuel, 149 characteristics, JSM sinter blend, 152 charred plant carbon structures, 149 CO and CO2 concentrations, 149, 150 coke breeze, 148 combustion behavior, 149 emission mechanisms, 153 energy-efficient and nonpolluting, 148 experimental results, 151 fuel rate, 152 gaseous fuel injection technology, 152 green granules, 152 higher volatile matter content, 151 iron ore, 149 JFE Steel Corporation, 152 lower fixed carbon content, 151 matching, 148 PCDD/Fs, 148–151 POPs, 148 portion replacement, 152 properties, 149 replacement of coke, 150 SO2 emissions reduction effect, 149 temperature zone, 152 toxic organic pollutants, 150 Charging carbon composite agglomerates (CCA) BF production, 233 biomass-iron oxide composites, 237 FeO-Fe, 232 fine iron ores, 232 gas generation rate, 235 gas utilization ratio, 239 HCMB, 233 hot briquetting process, 233 ICHB, 240 nonvolatile carbon, 237 reaction model/ratios, 234 wüstite and metallic iron, 234 Chemical-looping combustion (CLC), 78 Chemical-looping cycles advantage, 538

Index CaCO3, 538 CaL, 539, 543 carbonator, 539, 541 CO2-lean gas, 541 CO2/oxygen, 538 coal consumption, 543 decarbonization concept, 545 DFB biomass, 540 investment costs, 544 O2/CO2 atmosphere, 540 parameters, 541 regenerator, 539, 540 steam production, 541, 543 steel production, 544 VPSA, 543, 544 Chemical-looping hydrogen (CLH), 538 Chemical/physical adsorption blast furnace gas, 504 carbon monoxide, 508 CoMo catalyst, 504 crude syngas, 508 equilibrium, 505 MEA scrubber system, 504 NH3 and CO2, 505 power plant and ironmaking plant, 505 Rich MEA stream, 504 sodium and potassium carbonates, 505 solvents, 503 temperature and pressure, 503 urea synthesis, 508 Circofer®, 494 CIRCORED, 452, 453 Circular economy, 6, 7 Circulating fluidized bed (CFB), 452 Cleaner technology, 117 Climate change, 4, 13 Clinker-like agglomerate, 115 CO2 BFs, 100 chemical-looping hydrogen process, 66 coal gasification process, 68 emissions, 39, 55, 80, 99, 104 hydration reaction, 517 mitigation and H/C ratio, 67 price set, 22 reforming, 65, 70 utilization, 77 Coal-based DR processes, 422 Coal-based HYL technology, 432 Coal cake, 83 Coal-direct chemical-looping process (CDCL), 538 Coal fly ash, 315

Index Coal gasification, 378, 402 Coal gas production, 357 Coal market of Europe, 39, 41 Coal moisture control process (CMCP), 87, 88, 103 Coal stamp charging battery (CSCB) accommodation, particles, 82 blend quality and process control, 85 bulk density, 86 CDQ facility, 86 coal blends, 84 cake, 83 making, 84 production, 83 quality, 82, 84, 86 compressive strength, 85 densification, 82 density, 84, 86 dimensions, 83 dry bulk density, 86 elastic-plastic deformation, 83, 84 heat recovery ovens, 83 heat recovery stamp-charged coke making technology, 85 mechanical properties, 82, 84 mechanical strength, 84 operational efficiency, 85 parameters, 86 pre-carbonization technologies, 83 preparation, 82, 83 temperature, crude COG, 85 wet agglomerate, 84 wet bulk density, 86 Coal-tar pitch, 101 CO2 capture by slag carbonization (CCSC), 56 CO2 emissions, 117 Chinese iron and steel industry, 13 economic measures, 28 vs. energy consumption, 12 engaging, 16 factor, 20 global warming, 21, 22 levels, 20 steel, 13 steel mill, 16, 18 COG chemical-looping hydrogen- assisted COG-to-natural gas (CGCLHCGtNG), 66 Coherent, 309 Coke breeze, 112, 114, 140 Coke consumption, 499, 527 Coke cooler, 52

581 Coke dry quenching (CDQ), 498 advantages, 52, 55 application, 55 ash content, 54 carbon flow analyses, 56 CO2 emissions, 55 coke cooler, 52 coke losses, 53, 54 communication tool, 52 cooled coke temperature, 56 CSQ, 55 CWQ, 50, 51 DDQ, 57 development of designs, 54 dry-quenching unit (see Dry-quenching unit) dust emissions, 52, 55 energy/exergy analysis, 50, 51 energy recoveries, 50, 57, 58 energy-saving technology, 53 gas emissions, 54 gas volume, 57 heat exchange, 52 injection, 52 lower moisture content, 52 operating conditions, 54 plant, 52, 53 pollutant emissions, 53 prechamber flare, 54 quality indexes, 55, 56 reduce air pollution, 50 SDQ, 57 single-chamber, 55 SO2 emissions, 55 steam generation, 56 in steelmaking industry, 52 strength and size distribution, 50 temperature, 50 thermal energy, 51, 53 thermodynamic analysis, 51, 52 uniform quenching, 57 usable exergy, 51 Coke making, 311 biomass, 99–103 carbon porous material, 39 CDQ (see Coke dry quenching (CDQ)) CMCP, 87, 88 coal market of Europe, 39, 41 COG (see Coke oven gas (COG)) control systems, 79–82 CSCB (see Coal stamp charging battery (CSCB)) CSQ, 95, 96

582 Coke making (cont.) dust and SO2 emissions, 39 emissions reduction and energy efficiency, 104 environmental pressure, 39 GHG and CO2 emissions, 39 heating time, 39 HPALA, 87 materials flow and emission sources, 40, 42 non-recovery coke ovens (see Non-recovery coke ovens) SCOPE21, 97–99 SCS, 96, 97 temperature monitoring, 80, 81 thermal and physical role, 39 waste materials, 99–103 wastewater treatment (see Wastewater treatment) world production, 39, 40 Coke oven gas (COG), 178, 426, 461, 527 activated carbon and Ni/Al2O3 catalysts, 71 advantages, 61, 68, 70, 72 application, 72 BCFNO membranes, 73 BF, 202 and blast furnace, 57, 205 by-product, coal carbonization, 57 caloric value, 60 catalysts, 61 catalytic method, 72 CGtNG, 66 chemical reagents, 60 in China’s coke industry, 76 CLC, 78 CO2 adsorption technology, 79 emissions, 207 MES system, emissions reduction, 79, 80 coal char catalyst, 65 coal gasification reactions, 68 cohesive zone and permeability, 205 COI12 case, 205 coke powder, 207 composition, 58, 59 and CTM processes, 76, 77 CWHS, 74 carbon balance, 74, 75 energy balance, 74, 76 CWOHS carbon balance, 74, 75 energy balance, 74, 76 deactivation rate of catalyst, 64

Index desulfurized, 68 direct and indirect emissions, 77 disadvantages, 64, 68, 70 DMR, 68, 74 dry reforming, 69–71 electricity emission factor, 78 elevated cost, 73 energy balance, 58, 59 consumption, 204 saving in steelmaking, 58 utilization, 206 EUD methodology, 79 exothermic process, 72 FT synthesis, 71 GaCTO, 67–69 gasification processes, 79 gas injection, 202 gas-phase oxidizers, 60 gas recycling optimization operations, 204 gas utilization, 204 GHG generation, 77 global sensitivity analysis, 77 greenhouse gases, 70 H2/CO ratio, 71 H2S, 71 HECA facility process, 77, 78 hierarchical attribution management, 77 hot COG, 60 hydrogen separation, 68, 69 IGAR, 207 inner furnace status, 205 integrated COG-DRI plant, 66 IR, 64 iron-molybdenum hydrodesulphurization technology, 74 isothermal reduction, 203 LTIR, 204 mechanism, NOx removal, 60 membrane reactors, 73 methanol production, 65, 66 methanol steam, 74 MPO, 74 multifunctional energy system, 79 nitrogen-free blast furnace, 206 non-catalytic method, 72 O2/CH4 ratio, 73 onsite use/separate sale, 64, 65 optimal utilization, 79 oxygen carrier, 78 ozone generation, 60 partial oxidation of methane, 71, 72

Index performances, different CTM processes, 74, 77 production ratios annual H2 production, 64, 65 COG vs. coke, 64, 65 coke vs. coal, 64, 65 H2 vs. COG, 64, 65 properties, 58 proposed MES system, 79 PSA, 64, 65 pseudo-catalyst, 73 quantitative conversions, 73 reforming processes, 69 RWGS, 71 RWGS+SR pathway, 71 SCR, 58 sensitivity analysis, 66 sinter, 202 SMR, 74 space velocity, 73 SPARG, 71 SR, 63 steam reforming hot COG, 64 methane, 63, 64 superiorities, 60 synergetic effect, 71 syngas production, 69 synthesis gas (syngas), 63 technologies, 58, 68, 70 TI and SI, 205 top gas recycling, 207 TRM, 75 types of catalysts, 71, 72 utilization, 61–63 valorization, 73 VSD compressors, 95 WFGD, 58, 60 Coke oven gas (COG)-to-natural gas (CGtNG), 66 Coke quality, 497, 498 Coke stabilization quenching (CSQ), 55, 95, 96 Coke strength after reaction (CSR), 86, 90, 92, 94, 101, 102 Coke wastewater (CWW) treatment plant, 49 Coke wet quenching (CWQ), 50, 51 Cold DRI, 433, 434 Cold rolling wastewater (CRW), 286 Combined cycle power plant (CCPP), 56 Combustion gases, 115 Combustion/non-combustion processes, 282

583 Commonwealth of Independent States (CIS), 446 Composite burnout potential (CBP), 182 Computer control technologies, 159 Concentrated water from electro-deionization (CW-EDI), 286 Consteel, 306, 329, 330, 344 Contiarc furnace, 360, 366 Convection, 307 Convective heat transfer, 307 Conventional BF ironmaking system, 400 Conventional burners, 134 Conventional ignition system, 145–147 Cooled coke temperature, 56 Cooling and extra reduction reactor, 468 Copper, 322 Corex, 381, 383, 398, 421, 533 AcC, 395, 396 adsorbent and desulfurizer, 396 Bauer-Glaessner diagram, 383, 384 chemical reactions, 397 CO2 direct emission analysis, 389 coal consumption, 388 coal gas, 394 coke oven, BF and COREX gases, 400 conventional BF process, 398 COREX® shaft furnace export gas, 392 degree of metallization, 388 description, 381 desulfurizers, 398, 399 downstream CO2 emission, 389 dry desulfurization, 399 EAFs and BOFs, 386 exergy analysis, 388 gas, 510 generator gas composition, 388, 390 hydrogen reduction, 383 material consumption and CO2 emissions, 400, 401 melter-gasifier, 381, 384–387 metal and slag composition, 388, 390 metallization degree, 394 and Midrex, 393 oxidation, 397 oxygen, 386 phthalocyanine metal complexes, 395 proportion of H2, 393 reactions, 382 shaft furnace, 385 Si and P contents, 392 thermodynamic model, 388, 389 top gas composition, 388, 390 two-stage direct smelting process, 381

584 Corus, 153 Costs coke, 56 collection and treatment of material, 100 excessive energy, 81 investment, 74 low, 48 maintenance, 87 methanol production, 66 NOx control, 60 plant, 90, 98 COURSE 50, 240, 241, 243 CRI, 90, 101, 102 Cryogenics separation CO2 capture, 520 concept, 518 experimental setup, 520 flue gases, 518 gas-liquid separation, 518 high temperature, 518 LNG, 521 refrigerator, 520 CSIRO, 155, 156 CTM processes, 76, 77 Curtain flame burner, 134 Curtain flame ignition system, 145–147 CWHS, 74–76 CWOHS, 74–76

D Decarbonization technologies, 548 Deflector plate type feeder, 139 Dephosphorization mechanism, 292 Desulfurizer, 395, 396, 399 Diffusion-controlled mechanism, 456 Diffusion melting, 307 Digital control system, 133 Dioxins, 115–117, 121, 124, 125, 127, 130, 136, 137, 142, 144, 146, 148, 153, 158 Direct current (DC) arc furnace, 351 Direct emissions reduction, 24, 25 Direct reduced iron (DRI), 27, 28 agglomerates, 420 annual production scale, 420 BF, 424 charcoal, 422 CIRCORED, 452, 453 classification, 422, 424 vs. coal-based system, 422, 423 coal volatile matter, 422 CO2 emissions, 422

Index density and shape, 419 EAF, 15, 419 energy consumption, 420, 424 FASTMELT, 440, 441 FASTMET, 440, 441 feedstocks, reactors and agents, 419 FINMET process, 450 gasified coal, 419 global warming, 422 greenhouse emissions and energy consumption, 419 Hyl-energiron process (see Hyl-energiron process) iron carbide process, 450–452 and iron ore resources, 420, 421 ITmk3® process, 441, 442 metallization, 317 Midrex® process (see Midrex® process) MXCOAL™ process (see MXCOAL™ process) on natural gas, 419, 421, 422 plants, 419 porosity, 419 processing conditions, 422, 423 production, 422 Redsmelt, 452, 454, 455 rotary hearth processes, 421 scrap, 419 shaft furnace, 420 SL/RN process, 448, 449 smelting reduction processes, 421 types, 420, 421 volume capacity, 420 waste heat recovery, 449 Dissolving, 307 Dolomite, 159 Double dry quenching (DDQ), 57 Drop tube furnace (DTF) data, 182 Dry bulk density, 86 Dry granulation, 285, 335 Dry methane reforming (DMR), 67, 68, 74 Dry-quenching unit blast fan, 53 CO emissions, 53 coke losses, 54 design and operation, 53 excess gases emitted, 54 gas channel, 54 gas emissions, 54 operational efficiency, 54 utilization, 54 Dry slag granulation (DSG), 260

Index Dry-type top gas cleaning and recovery (DTCR), 191 Dust, 311 emission, 117 recovery and recycling, 287 Dynamic hydrogen electrode (DHE), 569

E EAFD treatment technologies, 311, 312 EBT opening frequency, 348 ECOARC, 329, 342, 343 Economic analysis, 533 Electric arc furnace (EAF), 419, 446 advantages and disadvantages, 306 bottom stirring/stirring gas injection (see Bottom stirring) burners, 323, 324, 326 carbon, 311 cations, 313 Consteel, 345, 359 cost and quality competitive, 303, 309 DC arc furnace, 351 dioxins, emissions, 329 direct and indirect GHG emission factors, 367 disposal, EAF dust, 311 electricity consumption, 318 with EMS, 348 energy efficiency, 305, 317, 366 energy-intensive process, 322 energy issues, 342 GHG reduction, 305, 367 iEAF system, 368 indirect CO2 emissions, 303 LIBS, 328 major technology developments, 310 modern electrical energy consumption, 304 modern steelmaking, 307 molten pool, 350 online LIBS measurement, 328 oxyfuel burners (see Oxyfuel burners) pilot flame, 308, 309 post-combustion, EAF flue gas, 364 power consumption, 303, 309 process optimization and control, 365–367 raw materials carbon steel quality, 317 classification, 317 DRI, 317, 319, 320 secondary material, 322 route, 14

585 scrap charging, 308 scrap melting, 307 scrap recycling process, 303 shaft furnace (see Shaft furnace) social wastes, 303 S/S, 313 stages, 304 steelmakers, 316, 324 steelmaking, 324 tapping temperature, 305 theoretical minimum energy requirements, 309, 310 tunnel furnace preheating, 344–345 twin-shell, 361–364 WHR approach (see Waste heat recovery (WHR)) Electric arc-melting process, 329 Electric energy consumption, 364 Electric furnaces, 303 Electricity, 303, 305, 317, 319, 320, 324, 329, 340 Electric power production, 89 Electric smelting, 379, 380 Electric steel production, 305 Electrolysis aluminum/lithium, 555 electrowinning process, 555 energy consumption, 556 iron ore, 555 MOE, 555 production, 556 reducing agent, 555 ULCOWIN, 556 zero-carbon, 556, 574 Electromagnetic force, 350 Electromagnetic stirring, 346, 347 Electrostatic precipitator (ESP), 158 vs. alkali input, 123, 124 capture PCDD/Fs, 124 capturing efficiency, 123 chlorine, 123 configurations and types, 123 and cyclone, 130 data, 124, 125 dedusting stage, 117 dust emission, 121 efficiency, 123 maximal dedusting efficiency, 123 solid-phase PCDD/Fs, 131 waste gases, 121 and WS, 131 Electrostatic space cleaner super (ESCS), 123

586 Electrowinning anode potential, 571 crystal orientation of α-Fe, 570 current density, 573 efficient iron production, 570 electrochemical reduction, 574 extraction technique, 567 faradaic yield, 568 Fe fraction vs. Fe3O4 density, 566, 567 goethite reduction, 573 H2 evolution, 568, 569 iron electrochemical reactivity, 572 iron electrodeposited, 570, 571 morphology changes, 569 NaOH-H2O system, 569, 570 principle of iron, 568 reduction of dissolved metal cations, 566 slag composition, 572 ULCOWIN steelmaking route, 571 Emerging technologies, 170 Emissions optimized sintering (EOS), 136, 137 Emissions reduction, 136, 138, 159–161 Encapsulation, 314 End-of-life (EoL), 6 Endothermic, 462 Energiron HYL technology, 432 Energy consumption, 420 Energy efficiency, 485 CCS, 23 CO2 emissions, 20, 27 cost, 6 energy consumption, 26 methods, 21 vs. raw material, 7 short- to medium-term approach, 24 steel production, 10 utilization, by-product gases, 11 Energy-intensive industry (EII), 1 Energy optimized sintering process, 142 Energy penalty, 531 Energy recovery CO concentration, 282 combustion/non-combustion processes, 282 gas composition, 282 open/closed hood vessels, 281, 282 open combustion systems, 284 suppressed combustion systems, 284 Energy saving, 349 Energy Transition Commission, 547 Enhanced oil recovery (EOR), 31 Environmental management system (EMSy), 8

Index EN 12457 test, 315 EPOSINT process, 137, 138, 160 ETC, 5 EUD methodology, 79 European blast furnaces, 198 European Commission (EC), 1 Excess oxygen, 470 Exergy of waste heat recovery (EWHR), 121 Exhaust gas treatment acid gases, 127 activated carbon adsorption of PCDD/Fs, 126 adsorption performance, 124, 126 dioxin, 124 and MWCNTs, 127 PCDD/Fs adsorption efficiency, 127 PCDDs and PCDFs, 125 RAC, 127, 128 activated coal, 124 activated coke method, 121, 122 additive injection and bag filter dedusting, 127, 129 adsorb and recover SOx, 121 characteristics of activated carbon, 130 desulfurization reagents, 129 electrostatic field, 123 ESCS, 123 ESP, 121, 123–125 hazardous organic pollutants, 127 heavy metals, 127 low-temperature plasma, 127, 129 MEEP, 123 MSFB, 130 PCDDs and PCDFs, 131 PM, 130 selective catalytic reduction, 121, 122, 124 system efficiency, 123 wet configuration, 123 wet fine scrubbers, 130 Exothermic process, 72

F Faradaic efficiency, 562 FASTMELT process, 440, 441 FASTMET process, 440, 441 Feasibility studies, 28 Fenton and EF-Feox methods, 48 FeO surface, 431 FGRS, 143 Fifth hole, 434 Final reduction reactor, 468 Final sinter temperature (FST), 121

Index FINEX, 402, 421 balance data, 405 BF and FINEX integration, 404 and blast furnace, 405 description, 402 dried ores, 403 export gas, 402 fluidized bed chemical reactions, 403 fuel consumption and savings, 405, 406 LRI and reduced gas, 404 plant, 403 Finger Shaft EAF, 343 FINMET, 450, 494 Fischer–Tropsch (FT) synthesis, 71 Flash ironmaking technology, 412 Flat flame burners, 134 Flue gas recirculation (FGR), 119, 142, 144, 145 Fluidized bed, 379–381, 385, 402, 412, 413 Fly ash-based geopolymerization systems, 314 Foamy slag basicity, 332 carbonaceous compounds, 333 chemical energy, 332 CO gas, production, 332 components, EAF slag, 333 control, 333 EAF, 343 economic practice, 332 energy-generating reactions, 332 energy recovery, 334 granules, 335 heat recovery, 334 ironmaking and steelmaking practices, 333 promotion, 332 thermal conductivity, 334 thermal efficiency, EAF, 334 thermodynamic predictions, 336 Food and Agriculture Organization of the United Nations, 183 Fossil media, 455 Free space post-combustion, 323, 325 Fresh water consumption (FWC), 40 Fuel arc furnace (FAF), 341 Fuel composition, 226 Fuel rate, 153 Fuel reductions, 117 Fugitive emissions, 115 Furans, 116, 124, 130, 137, 153, 158 Furnace conditions, 213 Furnace gas, 215

587 G Gangue, 311 Gas-assisted coal to olefins (GaCTO), 67–69 Gas-based DRI processes, 433 Gaseous fuel injection technology, 152 Gas flow rates, 119 Gas-phase equilibrium, 177 Gas recycling process, 186 Gas separation, 516 Gas-solid interphase, 521 Genetic algorithm (GA), 121 Geopolymerization, 313 Geopolymers, 313, 314 Global Carbon Capture and Storage Initiative (GCCSI), 547 Global sensitivity analysis, 77 Global warming, 13, 19, 21, 29, 33, 422 Goethite reduction, 573 Granulated into small particles (GBFS), 254 Graphite, 434 Greenhouse gas (GHG), 39, 57, 63, 68, 70, 77, 309 Greenhouse gas emission (GHG), 146, 221 breakthrough technologies, 28 CCS, 19 climate change, 4 data, 21 impacts, 9 ironmaking and steelmaking sector, 9 pathways, 19, 26 UNFCC, 16 Greenhouse gas regulations, 309

H Hall-Heroult cell technology, 559, 563 Heat balance, 186 Heat recovery, 159 coke making, 89 ovens, 83 stamp-charged coke making technology, 85 Heating value of mixture (HVM), 223 Heat-resistant diagnostic system, 82 Heavy metal emissions, 117 H2 economy, 458 High-carbon DRI, 435 High-carbon metallic briquettes (HCMB), 233 High-pressure ammonia liquor aspiration system (HPALA), 87 High-temperature operation, 546 HIsarna, 471 HIsmelt®, 378, 379, 406–408 Holistic ironmaking optimization, 7

588 Hot blast temperature BF operation, 201 COG, 201 Hot briquetted iron (HBI), 422, 424, 435, 446, 447, 461, 478, 479, 501 Hot rolled coil (HRC), 512 Hot stove process control combustion process control, 193 dome temperature, 193 energy saving, 191 gas consumption, 193 production situation, 193 Siemens VAI control system, 193 Hüttenwerke Krupp Mannesmann GmbH (HKM), 132 Hydrocarbons, 184, 322 Hydrogen, 31 economy, 462, 477 iron ore reduction technology, 241 separation, 527 and synthesis gas, 204 Hydrogen direct reduction (H-DRI), 463 Hydrogen Energy California (HECA) facility process, 77, 78 Hydrogen reduction, 246 Baur-Glaessner type diagram, 469 BFG, 461 biogas, 462 biomass, 462 bottom-up energy system models, 462 carbon-based reductant, 452 chemical potentials, 456 CO2 emissions, 452, 455, 458, 471, 475 COG, 461 coke-less processes, 471 coke-using processes, 471 cooling and carburizing process, 468 cooling and extra reduction reactor, 468 DAV, 471 decarbonization costs, 463 diffusion-controlled mechanism, 456 DRI, 458, 459 dynamic control, 456 EAF steelmaking practice, 461 economy development, 461 electrolysis cell, 468 electrolysis module parameters, 476, 477 endothermic, 462 end-to-end TGNs and TFNs, 471, 475 energy and emissions comparison, 467 energy balance, 456, 457 excess oxygen, 470 ferrous metallurgy, 455

Index flowsheet, 472, 476 fossil media, 455 and fuel cells, 462 H2/H2-CO mixtures, 458 high temperature, 456 HIsarna, 471 hydrogen economy, 462, 477 HYL technology, 468 IEA, 458 IJmuiden, 477 industrial sector, 463 innovative routes, 463 input-output description, 456 kinetic models, 457 kinetics analysis, 462 Midrex H2 process, 460 Midrex process, 458–460 natural gas-based plant, 458 plasma hydrogen, 463 power-to-gas solutions, 474 production costs, 463, 466 ranking TFN, 471, 475 TFN + TGN, 471, 475 TGN, 471, 475 renewable electricity, 477 renewable energy-powered water electrolysis, 477 renewable power integration, 466 sponge iron, 468, 469 steel industry global energy demand and emissions, 466, 467 techno-economic parameters, 463–465 TFN: EAF operating, 471 TGN and TFN, 471–475 three-zone model, 457 thyssenkrupp Industrial Solutions, 472 value chains by thyssenkrupp, 473, 474, 476 water electrolysis, 455, 472, 475 water hydrogen, 467 WGSR equilibrium, 470 zero-gap electrolysis technology, 473 Hydrogen-rich reductants, 422 Hyl-energiron process auxiliary energy demand, 437 CH4, 435 chemical absorption process, 432 CO2 emissions, 432 DRI, 433 CO2 emissions, 438, 439 EAFs, 435 high-carbon, 435 measurements and calculations, 435, 436

Index minimum CO2 measured, 438, 440 PMDR, 438–440 quantity, 438 use in BF, 435, 436 energy balance, 437, 438 Fe3C, 435 fifth hole, 434 furnace model, 437 gas-based DRI processes, 433 graphite, 434 hot blast, 437 isothermal equilibrium reactors, 437 operating conditions assumptions, 438 principles, 432 production of cold DRI, 433, 434 reducing gas, 432 shift reactor, 432

I iEAF system, 368 Ignition control system, 134–136 Ignition oven efficiency, 134–136 IJmuiden, 477 Improved charging method, sintering, 139–141 Impurities/alloying elements, 320 Indirect emissions, EAFs, 303, 329 Indirect reduction (IR), 64 Industrial energy, 485 Industrial-scale grinding mills, 187 In-furnace post-combustion, 296, 297 Initial reduction reactor, 468 Intensified sifting feeder (ISF), 139 Intergovernmental Panel on Climate Change (IPCC), 19 Internal carbon material acts, 139 International Energy Agency, 485 Iron and steel industry, 486, 496 Iron carbide process, 450–452 Iron coke hot briquette (ICHB), 240 Ironmaking BF/BOF route, 14 DRI/EAF route, 15 energy consumption, 10, 21 energy intensity, 20 GHG emissions, 9 LCA, 8 MFA, 8 optimization, 7 ore-based, 7 process, 13–15 reaction, 460

589 scrap/EAF route, 14 smelting reduction route, 15 Iron-molybdenum hydrodesulphurization technology, 74 Iron ore electrolysis (EW), 463 Iron ores, 111, 112, 114, 115, 117, 119, 130, 136, 139, 140, 144, 145, 147–149, 151, 152, 154, 156 Iron oxides, 167, 311 ITmk3® process, 441, 442

J Japan Iron and Steel Federation (JISF), 255 Japanese sintering plants, 120

K Kaolinite, 315 Key enabling technology (KET), 1

L Ladle preheating, 295 Lagrange extrapolation technique, 94 Langmuir adsorption equations, 431 Large-scale bio char utilization, 535 Laser-induced breakdown spectroscopy (LIBS), 327 Leachate pH, 315 Lean MEA cooler, 505 LEEP, 137 Life cycle analysis (LCA), 7–9 Lignin, 226 Limestone, 159 Limonite, 139 Linz–Donawitz (LD) process, 275 Liquefied natural gas (LNG), 447 Liquid phase ratio, 152 Long-term approaches, 24 Low-carbon innovations, 23 Low emissions sintering process, 142 Low-grade MgO (LGMgO), 312 Low levels of carbon, 434 LPM-derived carbons (LPMCs), 227 Lump ore, 111 Lurgi Rectisol® unit, 443

M Magnetically stabilized fluidized bed (MSFB), 130 Magnetic braking feeder (MBF), 139

590 Materials flow analysis (MFA), 8 Mathematical model, 214 Mature CO2 capture technologies, 522 Mature COG usage technologies, 528 Melter-gasifier, 379, 381, 385–387, 389, 402, 403, 413 Melting, 307 Metakaolinite, 315 Metallized iron usage calorific value, 281 DRI/HBI, 280 hot metal ratio, 280 post-combustion of CO to CO2, 280, 281 steelmaking cycle, 280, 281 Metallurgical coke manufacture, 102 Methanation, 492 Methane, 469 Methane partial oxidation (MPO), 74 Methane steam reforming reaction (MSR), 255, 336 Methanol synthesis reactor, 505 Middle East/North Africa (MENA), 446 Midrex® process amine-based plant, CO2, 426 BF-BOF route, 426, 427 BF-MIDREX-EAF process, 426 CO2 emissions analysis, 429 COG, 426 energy consumption analysis, 426, 430 energy use and productivity, 426, 428 FeO surface, 431 gas consumption, 426 gasification and CO2 removal equipment, 424, 425 gas mixtures, 424 HBI, 424 H2 process, 460 hydrogen reduction, 458–460 mass and heat balance, 431 NG, 426 process syngas, 426 reducing atmosphere, 424, 425 shaft furnace, 424, 431 technologies, 494 TRS, 426 used and wasted energies, 426, 427 Mined iron ore, 377 92 MJ/t-sinter, 143 MLSS, 45 Modern steelmaking, 307 Modules, 146 Molten oxide electrolysis (MOE), 556 advantage, 558

Index CO2 mitigation factor, 559 reduction, 557 current densities, 557 electrical energy variations, 558 electrochemical techniques, 565 electrolytic reduction, 565 E-logpO2, 561 energy consumption, 562 faradaic efficiency, 562, 563 vs. Hall-Heroult cell, 563 industrial cell, 564 iridium, 564 iron-oxygen phase, 559, 560 mass transfer correlations, 557 minimum practical electrical energy, 558 molybdenum crucibles, 564 molybdenum-iron transition, 564 range of G factor, 558, 559 reduction reaction, 565 structure and properties, 557 temperature levels, 557 T-logpO2, 559, 560 valence distribution, 562 YSZ, 565 Molybdenum crucibles, 564 Monitoring systems, 328 Monoethanolamine (MEA), 503, 507 Monolithic leaching test, 313 Moving bed biofilm reactor (MBBR), 45 Moving electrode electrostatic precipitator (MEEP), 123 Multi-slit burners, 134–136 Municipal solid waste (MSW), 257 MXCOAL™ process description, 443 emission allowance cost, 445 gas pipeline and distribution infrastructure, 444 gas prices, 444 global natural gas producers, 445 HBI, 446 iron ore, 446 Lurgi Rectisol® unit, 443 merchant HBI plant, 446, 447 reduction rate of oxidized pellets, 443, 444 seaborne trade, 446 syngas, 443 UBS studies, 444 world DRI production vs. region, 447

Index N Nanofiltration (NF), 46 Natural gas (NG), 419–422, 424, 426, 427, 431–433, 435, 437, 439, 443–448, 450, 452, 455, 458, 460, 461, 468, 469, 474, 478, 479 blast furnace, 211, 214 coke rate, 210 EISCO, 211 furnace conditions, 211 internal exergy, 215 mathematical models, 214 PCI, 209 prereduction ratios, 215 sub-process, 211 theoretical model, 215 tuyere area, 215 tuyeres level, 209 Natural gas (NG)-based MIDREX shaft model, 426 Near-term targets, 22 Nippon Steel, 82 Nitrogen reduction ratio (NRR), 145 Noise pollution, 115 Non-coking coal in blast furnace, 55 Non-coking coal resources, 440 Non-recovery coke making, 88 Non-recovery coke ovens annual emissions, 90, 92 applications, 89 carbonization process, 88 coal properties vs. emissions parameters, 91, 93 coke properties, 90, 91 coke quality, 91, 94 combusted gases, 88 crystallite size, 94 CSR, 92, 94 direct heating, 89 down-comer passages, 88 fuel consumption, 89 heat recovery coke making, 89 Lagrange extrapolation technique, 94 mathematical model, 94 off-gas, 89, 92 properties, 94 and recovery, 89, 90 secondary flux of air, 89 slot-oven coke, 94 statistical analysis, 91 TSP, 91 vibro-compaction, 89 Nuclear energy, 479 Nucor plant, 448

591 O Oil/waste oil fuel, 208 hydrogen, 209 thermal effect, 208 On-line switching control strategy, 82 Open combustion systems, 284 Operation guidance system (OGS), 133 Optical sensors, 326 Optical texture index (OTI), 240 Optimal disk atomization, 261 Ore agglomeration, 311 Oxidation reactions, 276 Oxyfuel burners, 369, 501 effect, 325 electrical energy consumption, 325 emissions, 324 energy saving, 326, 327 net methane reaction, 326 post-combustion strategies, 324 scrap melting, 326 temperature, 324 ultrahigh power EAFs, 323 Oxyfuel combustion scheme, 537 Oxygen blast furnace, 207, 215 Oxygen bottom-blowing (OBM), 275, 291 Oxygen carrier, 78 Oxygen injection, 331 Oxygen-supplying technology, 324 Oxy-oil injection burners, 221 CO2 reduction, 221 steelmaking, 221 Ozone, 46

P Packing wetting phenomena, 526 Parallel factor analysis (PARAFAC), 49, 50 Partial oxidation (POX), 461 Particulate matter (PM), 130 Pellets, 440 Persistent organic pollutants (POPs), 148 Photo-Fenton process, 48 Photosynthesis, 493 Physical absorption, 508, 509 Physical pre-treatment methods, 45 “Pipe inside a pipe” arrangement, 326 Plastic waste injection BF, 216, 217 char reactivity, 219 chlorine-containing plastics, 216 CO2 emissions, 220 coal and waste plastics, 220

592 Plastic waste injection (cont.) flame temperature, 216 furnace permeability, 219 HV coal, 219 injectants influence, 218 injecting coal, 220 PCI/WPI, 220 PVC, 216, 217 thermochemical and kinetic conditions, 216 transport, 219 tuyere level, 216 waste impurities, 217 Pollutant emissions, 53 Polychlorinated dibenzofurans (PCDFs), 116, 131, 148, 149 Polychlorinated dibenzo-p-dioxins (PCDDs), 116, 131, 148, 149 Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), 115, 159 Polycyclic aromatic hydrocarbons (PAHs), 41, 43, 148 Polyethylene terephthalate (PET), 100 Polymeric Si–O–Al framework, 313 Polymer injection technology, 324 Polyolefin-enriched wastes, 102 Polyolefins, 102, 103 Polyolefins to polystyrene (PS), 100 Polyvinylchloride (PVC), 148 Post-combustion, 323, 324, 378 Post-combustion capture (PCC) carbon abatement options, 535 CCS, 535–537 CO2 emissions, 535 conventional blast furnace process, 536 feasibility, 536 industrial processes, 536 MEA, 534, 535 prototype, 534 steel mill, 534 VPSA, 536 Post-combustion optimization, steelmaking, 328–331 Pre-combustion capture systems, 545 Pre-reduced agglomerates, 139, 141 Principal component analysis, 50 Process gas (PG), 512 Process-specific capture technologies, 532 Process syngas, 426 PSA, 64, 65 PSA CO2 scrubbing technology, 510 Pulverized coal injection (PCI), 189 BFG, 183 biomass, 183 bio-PCI, 188 carbon dioxide emissions, 185

Index CBP, 182 charcoal supply chains, 183 coal-charcoal mixtures, 188 coal devolatilization, 185 gaseous fuel, 186 global warming, 186 hydrocarbon fuel, 184 integrated steelworks, 185 ironmaking process, 187 iron oxides reduction, 181 non-coked coal, 181 oxygen consumption, 182 productivity, 187 profitability, 184 rate, 183 screening, 188 tuyere, 184 unconventional energy resources, 185 VIU, 187 Purified and recycled top gas, 537 Pyrolysis, 183 Pyrometallurgical processes, 556

R Radiation model, 334 Recovery and utilization of residual energy and heat (RUREH), 486 Rectisol®, 508 Recycling procedures, 7 Recycling wastes, 26 Redsmelt, 452, 454, 455 Reduction disintegration (RDI), 152 Reference electrode (RE), 565 Regenerated activated carbon system (RAC), 127, 128 Renewable electricity, 477 Residue injection scheme, 222 Reverse WGS (RWGS), 71 Rotary hearth furnace (RHF), 380–382, 440 Rotary hearth processes, 421 Rotary kiln direct reduction, 449

S Scrap grades, 316 “invested” energy, 309, 311 obsolete, 316 preheating, 337–339 quality, 322 Tecnored process, 409 Scrap heating, 306 Scrap melting, 306, 309 Seaborne trade, 446

Index Sectional gas recirculation environmental process optimized sintering, 144 FGR (see Flue gas recirculation (FGR)) FGRS, 143 function of composition, 143 hazardous substances, 142 iron ores, 144 limonite, 145 low emission and energy optimized sintering, 144 NO-CO catalytic reduction, 145 NOx reduction, 144 NRR, 145 properties, 143 selective waste gas recirculation, 144 thermal state of sintering bed, 144 Sedimentation tank, 45 Segregating slit wires (SSW) feeder, 139 Selective catalytic reduction (SCR), 58 Selective crystallization and phase separation (SCPS), 255 Selexol™, 508, 509 Sequential batch reactor (SBR), 45 Shaft furnace, 420, 431 air-gas burners, 341 COREX, 381, 385, 392, 393 ECOARC, 343 FAF, 341 Finger Shaft EAF, 343 heat transfer, 339 oxy-gas burner flames, 341 pellet and lump ore, 380 productivity, 339 scrap preheating, 340 Tecnored process, 408 Shaft injection (SI), 235 Shift reactions BFG, 502 CO2 and H2, 502 CO content, 502 Short- to medium-term approach, 24 SIMETAL, 132 Single-chamber CDQ, 55 Single-chamber system (SCS), 96, 97 Single dry quenching (SDQ), 57 Sinter feed ore, 377 Sintering air emissions, 115 atmospheric emissions, 115 BFs, 111 in biomass (see Biomass) centralized dedust system, 115 characteristics ferrous, 111 in charcoal (see Charcoal)

593 cleaner technology, 117 CO2 emissions, 117 coke breeze, 112, 114 coke combustion, 113 combustion gases, 115 combustion zone, 113 computer control technologies, 159 cooled sinter, 114 critical temperature, 116 curtain flame ignition system, 145–147 desulfurization and dust collection, 117 dioxins (see Dioxins) dust emission, 117 emissions, 115 limits, 117 reduction, 160, 161 energy consumption, 117 energy efficiency, 160, 161 energy optimized, 142 energy-saving solutions, 117, 118 environmental regulations, 115 EOS, 136, 137 EPOSINT process, 137, 138, 160 exhaust gas treatment (see Exhaust gas treatment) flexibility, 115 fuel reductions, 117 fugitive emissions, 115 heat exchange process, 112 heavy metal emissions, 117 ignition oven efficiency, 134–136 improved charging method, 139–141 iron ores (see Iron ores) limits for toxic emissions, 115, 116 low emissions, 142 lump ore, 111 materials, 112 multi-slit burners, 134–136, 160 noise pollution, 115 operations, 111, 112 PCDD/F, 115 process control, 131–133 quality assurance, 131–133 raw materials, 111 reaction zones vs. temperature, 114 sectional gas recirculation (see Sectional gas recirculation) selective waste gas recycling, 137, 138 stack emissions, 115 static sinter bed, 112, 113 sulfur emission, 115 traveling grate, 112 treatment of pollutants, 116 VOC, 117 waste fuels, 146–148

594 Sintering (cont.) waste heat recovery (see Waste heat recovery) wastes, 115 wastewater, 115 Sintering energy control system (SECOS), 133 Sinter plants, 15 Slag foaming, 197 Slag heat recovery chemical methods, 255, 259 JISF, 255 methane reforming, 257 MSR, 255 RCA, 256, 257 SCPS, 258 waste heat, 255 Small-scale sinter pot experiments, 154 Smelting, 379 charcoal substitutes, 379 processes, 378 and pre-reduction stages, 379 schematic and reactor, 378 Smelting reduction classification, 380 COREX process, 381, 398, 400, 402 FINEX process, 402 heat and CO-rich hot gas, 378 HIsmelt, 406 hot metal production, 377 processes comparison, 379, 421 route, 15 stage, 379 Smelting technologies, 27 Solid sorbents by-product gases, 513 coking coal consumption, 516 polymeric membranes, 517 PSA and VPSA, 511 water molecules, 517 zeolites, 511 Solid-state reduction, 424 Source device supersonic burner (SSB), 331 Space velocity, 73 Sponge iron, 419, 468, 469, 472, 473 SRe processes, 378–380 Stabilization/solidification (S/S), 311–314 Stack emissions, 115 Stamp charging process, 84 Steam methane reforming (SMR), 67, 74 Steam reforming (SR) of COG, 63 Steam stripping, 47 Steel artifacts, 3 complex mixture, elements, 9 EII, 1

Index emissions type, integrated steel mill, 17 energy consumption, 10 EU steel industry, 4 global industry, 1 heavily traded, 3 integrated steel plant, 15, 16 iron and carbon, 9 KET, 1 LCA, 8 off-gas dust, 7 off-gases, 16, 18 plant, 3, 7, 11, 15, 20, 21, 27, 28, 31 raw material efficiency, 7 recycled material, 4 Steelmakers, 28 Steelmaking, 527 BF-BOF-CC route, 11 BOF, 20 breakthrough technologies, 28 China, 3 companies, 3, 4 energy intensity, 20 ETC, 5 EU, 3, 4 hydrogen, 27 low-carbon technologies, 28 Net export-import per country, 3, 5 next-generation nuclear power plants, 32 policy mechanisms, 23 post-combustion optimization, 328–331 primary and secondary production, 1, 2 raw materials and reactants, 9 renewable energy storage technologies, 32 technologies, 4 TGR-BF, 28 wasted energy, 12 Steel production, 485 China crude, growing rate, 2, 3 energy efficiency and CO2 emissions reduction technologies, 10 global crude, 2 raw materials, 9 Steelwork off-gases, 16, 18 Stelco-Lurgi/Republic Steel-National Lead (SL/RN) process, 448, 449 Stove hot gas recovery, 200 Submerged CO2 and O2 mixed injection (S-COMI), 324 Sulfur emission, 115 Super Coke Oven for Productivity and Environment enhancement towards the twenty-first century (SCOPE21), 97–99 Super Detox technology, 353

Index Supplementary cementitious material (SCM), 261 Suppressed combustion systems, 284 Surplus sludge, 45 Swirlers, 146 Syngas, 443, 479, 530 Synthesis gas production, 527, 530

T Tammann furnace tests, 225 Technological greenhouse number (TGN), 471–475 Technology CCS, 26 DRI, 27, 28 energy consumption per each analyze, 21 innovation and diffusion policy approaches, 23, 24 LCA, 8 smelting, 27 top gas recycling blast furnace, 27 Tecnored process agglomerates, 408 carbon units, 410 consumptions, fuels, 411 description, 408 furnace, 408, 410 lumpy fuel, 410 plant, 409 Temperature, 324 Tenova’s evaporative cooling system technology, 357 TFN, 471–475 Theoretical combustion temperature (TCT), 206 Thermally treated biomass, 231 Thermal reactor system (TRS), 426 Thyssenkrupp Industrial Solutions, 472 Thyssenkrupp Steel, 508 Top gas recycling (TGR), 206, 494 Top gas recycling blast furnaces (TGR-BF), 21, 27 BF configuration, 246 carbon consumption, 247–249 Chinese mill, 244 CO2 removal, 243 CO2-stripped BFG, 243 COG composition, 245 furnace, 248 OBF, 248 PCI, 251 TGR, 251, 253 TGR-OBF, 244, 245 Top-pressure control system, 192 Top-pressure recovery turbine (TRT)

595 bio-CCS, 190 CO2 abatement, 189 emissions, 190 costs, 190 low-BTU gas turbine, 190 wet/dry, 189 Torrefied pellets (TP), 228 Total suspended particulates (TSP), 91 Toxicity characteristic leaching procedure (TCLP), 314, 315 Traveling grate, 112 Trend, 19 Tri-reforming of methane (TRM), 75 Tube-in-tube burners, 134 Tumble index, 155, 156 Turbulent burners, 134 Tuyere injection, 211 Twin-shell EAF, 361, 366

U ULCOWIN steelmaking route, 571 Usable exergy, 51

V Variable speed drive (VSD) COG compressors, 95 Vitrification, 311 Voest-Alpine Industrieanlagenbau (VAI), 132, 133 Volatile organic compounds (VOCs), 115, 117

W Waelz kiln, 354 Waste desulfurizer, 398 Waste energy recovery, 495 Waste fuels, sintering, 146–148 Waste gas recirculation, 119 Waste gas recycling, sintering, 137, 138 Waste heat recovery (WHR) effective recovery and utilization, 121 for EAF, 354 approach, 356 chemical and physical heat, furnace gas, 357 coal gas production, 357 CO gas, 360 CO2 recycling, 359 Consteel furnace, 358 energy balance, 353 exergy transfer, 355 flue gas exergy determination, 355

596 Waste heat recovery (WHR) (cont.) hot gas line, 356 molten salt testing plant, 356 off-gas heat recovery, 356 organic rankine cycle generators, 358 steam and power generation, 358 sustainability and resource conservation, 354 thermocline storage tank, 356 vaporization, 355 Waelz kiln, 354 electricity generation, 119 energy analysis, 121 EWHR, 121 exergy, 121 exhaust gas, 119 FGR, 119 heat consumed, 118 high-temperature flux vs. lower-temperature flux, 120 iron ore sintering bed, 119 operating parameters, 120 recirculation system, 119 rotary kiln direct reduction, 449 steam generation, 119, 120 traditional researches, 121 waste gas recirculation, 119 in WHRS system, 119, 120 Waste materials, coke making, 99–103 Waste plastics, 100 Wastewater treatment aeration tank, 45 ammonia salts, 41 anaerobic degradation, 46 AOPs, 46 average concentration, substances before and after treatment, 47 biological treatment method, 45 COD removal efficiency, 48, 49 coke dusts, 49 CWW, 49 discharges higher quantities, 40 documented values from EPB, 47 efficiency of A2/O system, 47 effluent discharge limits and typical emissions, 43, 44 Fenton and EF-Feox methods, 48 FWC, 40 MBBR, 45 MLSS, 45 NF, 46 ozone, 46

Index PAHs, 41, 43 PARAFAC, 49, 50 photo-Fenton process, 48 physical pre-treatment methods, 45 plant active at SSAB, 47, 48 pre-microfiltration step, 48 primary treatment, 45 principal component analysis, 50 sedimentation tank, 45 steam stripping, 47 steel industry, 40 substances classified as PHS, 43, 44 surplus sludge, 45 toxic compounds, 41 water FWC and TWC, plant sector, 40, 43 WFD, 41 Water capillary, 84 and carbon dioxide, 45 consumption, 43 cooling, 52 electrolysis, 435, 455, 458, 472, 474, 475, 477, 479 FWC, 40 hydrogen, 467 quenching, 55 RWGS+SR pathway, 71 velocity, 334 WFD, 41 World Steel Association, 40 Water-cooled panels (WCP), 332, 333 Water Framework Directive (WFD), 41 Water-gas shift reaction (WGSR), 178, 461, 470 Water-intensive industry processes, 40 Wet vs. dry cleaning systems, 287 Wet fine scrubbers (WS), 130, 131 Wet flue gas desulfurization (WFGD), 58, 60 Working and counter electrodes (WE and CE), 565 Wuhan Iron and Steel Company (WISCO), 133

Y Yttria-stabilized zirconia (YSZ) cell, 565

Z Zero-Gap electrolysis technology, 473 Zero/low-carbon technologies, 22 Zero reformer (ZR), 433, 434, 478 Zero waste, 287