International Series on MATERIALS SCIENCE AND TECHNOLOGY Volume 32-Editor: D. W. HOPKINS PERGAMON MATERIALS ADVISORY COMMITTEE Sir Montague Finniston, Ph.D., D.Sc., F.R.S., Chairman Dr. George Arthur Professor J. W. Christian, M.A., D.Phil., F.R.S. Professor R. W. Douglas, D.Sc. Professor Mats Hillert, Sc.D. D. W Hopkins, M.Sc. Professor H. G. Hopkins, D.Sc. Professor W. S. Owen, D.Eng., Ph.D. Professor G. V. Raynor, M.A., D.Phil., D.Sc, F.R.S. Other Titles in the Series CHRISTIAN The Theory of Transformations in Metals and Alloys, Part 1, 2nd Edition HULL Introduction to Dislocations, 2nd Edition SCULLY Fundamentals of Corrosion, 2nd Edition SARKAR Wear of Metals HEARN Mechanics of Materials GILCHRIST Fuels, Furnaces and Refractories MARSCHALL & MARINGER Dimensional Stability—An Introduction DOWSON & HIGGINSON Elasto-Hydrodynamic Lubrication, SI Edition KUBASCHEWSKI & ALCOCK Metallurgical Thermochemistry, 5th Edition UPADHYAYA & DUBE Problems in Metallurgical Thermodynamics & Kinetics PARKER An Introduction to Chemical Metallurgy, 2nd Edition COUDURIER, HOPKINS & WILKOMIRSKY Fundamentals of Metallurgical Processes GABE Principles of Metal Surface Treatment and Protection, 2nd Edition WILLS Mineral Processing Technology GILCHRIST Extraction Metallurgy, 2nd Edition PEACEY & DAVENPORT The Iron Blast Furnace, Theory and Practice Extractive Metallurgy of Copper by A. K. BISWAS University of Queensland, Brisbane, Australia and W. G. DAVENPORT McGill University, Montreal, Canada SECOND EDITION PERGAMON PRESS OXFORD · NEW YORK · TORONTO · SYDNEY PARIS · FRANKFURT UK Pergamon Press Ltd., Headington Hill Hall, Oxford OX3 OBW, England USA Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York 10523, USA CANADA Pergamon of Canada, Suite 104, 150 Consumers Road, Willowdale, Ontario M2J 1P9, Canada AUSTRALIA Pergamon Press (Aust.) Pty. Ltd., P.O. Box 544, Potts Point, NSW 2011, Australia FRANCE Pergamon Press SARL, 24 rue des Ecoles, 75240 Paris, Cedex 05, France FEDERAL REPUBLIC Pergamon Press GmbH, 6242 Kronberg-Taunus, OF GERMANY Pferdstrasse 1, Federal Republic of Germany Copyright © 1980 A. K. Biswas and Patricia Margaret Davenport All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means : electronic, electrostatic, magnetic tape, mechanical photocopying, recording or otherwise, without permission in writing from the publishers First edition 1976 Second edition 1980 British Library Cataloguing in Publication Data Biswas, Anil Kumar Extractive metallurgy of copper—2nd ed. (Pergamon international library: international series on materials science and technology ; vol. 32) 1. Copper—Metallurgy I. Title II. Davenport, W. G. 669'.3 TN780 79-40505 ISBN 0-08-024736-9 (Hard cover) ISBN 0-08-024735-0 (Flexi cover) Printed and bound in Great Britain by William Clowes (Beccles) Limited Beccles and London PREFACE TO THE SECOND EDITION For this edition we have concentrated mainly on bringing the operating data and process descriptions of the first edition up to date. Typo­ graphical errors have been corrected and several passages have been rewritten to avoid misinterpretation. Since most of the new data have come directly from operating plants, very few new references have been added. For collections of recent published information, the reader is directed to the excellent symposium publications: Extractive Metal lurgy of Copper, Volumes I and II, Yannopoulos, J. C. and Agarwal, J. C, editors, A.I.M.E., New York, 1976, Copper and Nickel Con verters, Johnson, R. E., Editor, A.I.M.E., New York, 1979, and to the reviews of copper technology and extractive metallurgy published annually in the Journal of Metals (A.I.M.E., New York). Most of the credit for this edition should go to the many industrial engineers and scientists who almost without exception responded to our requests for new information on their processes. We would like in particular to single out Jan Matousek of INCO, Keith Murden of Outokumpu Oy and John Schloen of Canadian Copper Refiners (now a metallurgical consultant) for their help. September 1979 A. K. Biswas W. G. Davenport PREFACE TO THE FIRST EDITION This book describes the extraction of copper from its ores. The starting point is with copper ores and minerals and the finishing point is the casting and quality control of electrical grade copper. Techniques for recovering copper from recycled scrap are also discussed. The main objectives of the book are to describe the extractive metallurgy of copper as it is today and to discuss (qualitatively and quantitatively) the reasons for using each particular process. Arising from these descriptions and discussions are indications as to how copper-extraction methods will develop in the future. Control of air and water pollution is of tremendous importance when considering future developments and these are discussed in detail for each process. Likewise, the energy demands of each process are dealt with in detail. Costs are mentioned throughout the text and they are considered in depth in the final chapter. The book begins with an introductory synopsis (for the generalist reader) of the major copper-extraction processes. It then follows copper extraction in a step-wise fashion beginning with mineral beneficiation and advancing through roasting, smelting, converting, refining, casting and quality control. Hydrometallurgy and its asso­ ciated processes are introduced just before electrorefining so that electrowinning and electrorefining can be discussed side by side and the final products of each method compared. The last two chapters are not in sequence--they are devoted to the sulphur pollution problem and to economics. As far as possible, the length of each chapter is commensurate with the relative importance of the process it describes. Blast-furnace copper smelting is, for example, given a rather brief treatment because it is a dying process while newer techniques such as continuous copper- X11I xiv Preface making and solvent extraction are given extensive coverage because they may assume considerable importance in the near future. A word about units : the book is metric throughout, the only major exception to the Standard International Unit System being that energy is reported in terms of kilocalories and kilowatt-hours. The principal units of the book are metric tons (always written tonnes in the text), kilograms and metres. A conversion table is provided in Appendix I. A knowledge of thermodynamics is assumed in parts of the book, particularly with respect to equilibrium constants. For concise informa­ tion on the thermodynamic method as applied to metallurgy, the reader is directed to Metallurgical Thermochemistry by O. Kubas- chewski, E. L. Evans and C B. Alcock, an earlier volume in this series. The text of the book is followed by four appendixes which contain units and conversion factors ; stoichiometric data ; enthalpy and free energy data; and a summary of the properties of electrolytic tough pitch copper. Copper is one of man's most beautiful and useful materials. It has given us great satisfaction to describe and discuss the methods by which it is obtained. Both of our universities have had a long association with the copper industries of our countries, and it is hoped that, through this book, this association will continue. A. K. BISWAS W. G. DAVENPORT University of Queensland McGill University ACKNOWLEDGEMENTS We gratefully acknowledge the encouragement and assistance of our industrial and university colleagues during the preparation of this book. We thank especially our department chairmen, Professors R. L. Whitmore and W. M. Williams, who, by encouragement and coercion, have kept our pens on paper. We also acknowledge the contributions of our students, past and present, who through persistent debate and question have encouraged us to look for truth. Many companies have provided us with up to date information on their operations. Their contributions have been particularly useful because they have permitted us to include hitherto unpublished data. We thank them for their invaluable assistance. Our labours would not have come to fruition without the dedica­ tion and workmanship of: Anne Coeman and Ruth Griffith who typed the manuscript; Sue McKenzie who prepared the diagrams; and Margaret Davenport who proofread and scrutinized the writing. Their contributions are happily acknowledged. CHAPTER 1 SYNOPSIS 1.1 Introduction Copper is present in the Earth's crust mainly in the form of sulphide minerals such as chalcopyrite (CuFeS), bornite (Cu FeS ) 2 5 4 and chalcocite (CuS). The concentration of these minerals in an 2 orebody is low, and typical copper ores contain from 7% copper (open pit mines) to 1 or 2% copper (underground mines). The processes for recovering pure copper from these ores are outlined in Fig. 1.1. Copper also occurs in the form of oxidized minerals (carbonates, oxides, silicates, sulphates), but to a much lesser extent. Ores con­ taining these minerals are almost always treated by hydrometallurgical methods as is indicated by Fig. 1.2. This synopsis introduces the principal processes by which copper is extracted from ore and it outlines the relative importance of each process within the overall scheme of the copper-extraction industry. 1.2 Extraction of Copper from Sulphide Ores Approximately 90% of the world's primary copper originates in sulphide ores. Sulphides are not readily treated by hydrometallurgical methods (i.e. they are not easily leached) so that the vast majority of the extraction is by pyrometallurgical techniques starting with copper concentrates. The extraction consists of the following four steps : (a) concentration by froth flotation ; (b) roasting (an optional step) ; (c) matte smelting (in blast, reverberatory, electric or flash furnaces); (d) converting to blister copper. 1 2 Extractive Metallurgy of Copper Sulphide Ores ( ^ to 2%Cu) i/y \\J Comminution I Flotation Concentrates (20to30%Cu) Drying Drying Green Sintering concentrate epa -Roasting έ=^α Flash furnace Continuous Blast furnace processes J ^atte(30 to 55%Cy)^ ' -OHD Blister copper (9Θ 5·»·% Cu) Anode refining *=t and casting Anodes (99 5% Cu) Electrorefinmght Atttttttl Cathodes (99 99 + % Cu) ή Melting I A Open mould <^^ Continuous casting casting ^ g^ Fabrication and use Fig. 1.1. Principal processes for extracting copper from sulphide ores. Parallel lines indicate alternative processes. ( Rare; Under development.) Synopsis 3 Oxide Ores (Carbonates, Silicates, Sulphates) Ì Flotation 1—ûûûû- Lea1n(< l%Cu) Rich(lto2%Cu) Oxide concentrates and/or ! roasted sulphides (20to30%Cu) n Heap Leach with H2S04 wiVtha t Hle2aSc0h 4 PREGNANT SOLUTION (<5kg Cu m"3) Agitation Leach with H2S04 Electrolyte (40kg Cu m-3) Cementation on scrap iron Impure Cu precipitates to pyrometallurgica converter or smelting furnace Electrowinning Cathodes (999%Cu) To melting casting and fabrication Fig. 1.2. Principal processes for extracting copper from oxide ores. A recent development has been the combining of (b), (c) and (d) in a continuous process, several configurations of which have just reached the commercial stage. The final product of this succession of steps is impure blister copper which must be fire- and electro-refined before it is suitable for fabrica­ tion and use. The most important aspects of these processes are introduced here and each is discussed in detail in later chapters.