Heat Exchange in Shaft Furnaces PDF
Preview Heat Exchange in Shaft Furnaces
Heat Exchange in Shaft Furnaces B. I. Kitaev, Yu. G. Yaroshenko and V. D. Suchkov Translated from the Russian by M. M. PAGE and H. SIMONS and edited by P. A. YOUNG PERGAMON PRESS OXFORD • LONDON • EDINBURGH - NEW YORK TORONTO • SYDNEY . PARIS • BRAUNSCHWEIG Pergamon Press Ltd., Headington Hill Hall, Oxford 4 & 5 Fitzroy Square, London W.l Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1 Pergamon Press Inc., 44-01 21st Street, Long Island City, New York 11101 Pergamon of Canada, Ltd., 6 Adelaide Street East, Toronto, Ontario Pergamon Press (Aust.) Pty. Ltd., 20-22 Margaret Street, Sydney, N.S.W. Pergamon Press S.A.R.L., 24 rue des Ecoles, Paris 5© Vieweg & Sohn GmbH, Burgplatz 1, Braunschweig Copyright © 1967 Pergamon Press Ltd. First English edition 1967 This is translation from the original Russian TeriAOodMen e Maxmnux nemx published by MeTaJiJiyprH3ji;eT, Moscow and contains corrections and revisions made by the Author. Library of Congress Catalog Card No. 67-20053 2907/67 Authors9 Preface to the English Edition THIS book is devoted to the special question of the theory of heat exchange in shaft furnaces, and most of the examples are drawn from the field of blast furnace operation. The path of research which we followed is justified by the general tendency of science towards specialization and by the hope that, with time, the thermophysics of the blast furnace might merge with other aspects, and serve as a means of strengthening the general and unifying theory of the blast furnace process. The results with which the reader will become acquainted in this book were, by 1964, confirmed by experiments of all categories, from laboratory to industrial scale, and emerged as the sum of the joint work of a great collective of scientific workers and plant researchers. It was only thanks to this collaboration that the age long barrier between theory and practice was overcome. The bridges from theory to practice were built by the combined ef forts of research workers at the institutes and plants mentioned. Of course, in 1944 we were not beginning research in the de sert—the work of Academician M. A. Pavlov, of Furnas, of Saunders and Ford, of Kinney, of Schumann, and others, had already been published. Afterwards C. C. Furnas, apparently, stepped over into another field of science, and, as with other workers, never returned to his researches on heat transfer in blast furnaces, so successfully begun. In the last 5 years the very energetic French workers at I.R.S.I.D. have included Michard, Rist and Dutilloy. In Belgium, at C.N.R.M., there have been Decker, Poos and Firket. In the Federal Republic of Germany Zischkale, Heynert, Ischebeck and Schuzmann. Earlier still, Baake —the famous scientist from the German Democratic Republic — working in the field of low shaft furnaces. IX Authors' Preface to the English Edition At the Troisiemes Journees Internationales de Siderurgie, which took place in Luxemburg in October 1962, interest was rightly shown by blast furnace operators in the question of heat exchange. The problem was discussed not only in our paper, but also in many others read at the congress. Today many results can already be noted which not only ex plained remarkable advances in practice, but also assisted in bringing them about. The theory of heat exchange in shaft fur naces not only concluded the contemporary stage of development of the theory of shaft smelting, but also introduced such theoret ical sciences as the thermodynamics and kinetics of the reduction of oxides. This occurred because the theory of heat transfer pro vides the link between temperatures and spatial dimensions of the blast furnace. These results are reflected in numerous books, pamphlets and papers, and in the proceedings of conferences and congresses, which we have tried, to the best of our ability, to include, without omission, in the bibliography. x Editor's Preface THE English version of this book arose from a meeting between the editor and Professor Kitaev at the Journees Internationales de Siderurgie 1962 at Luxemburg. At that time the writer was Director of Research for the firm of Head Wrightson, who have been builders of blast furnaces for the last hundred years, and it seemed important that constructors of capital plant should be concerned with process requirements as well as with mechanical principles. At the same time the writer was himself active in the general field of heat and mass transfer in packed beds. The translation and editing of the book was then undertaken, very much on a spare-time basis, within the Research and De velopment Division of Head Wrightson & Co. Ltd. (to whose generosity the publication of the book is, indeed, due). Miss H. Simons translated Chapters I, II, III and IV, and Miss M. M. Page Chapters V, VI and VII and the Appendices. Miss Page has been responsible for checking the entire translation as need arose, and for checking the references against originals wherever possible. The editor has checked the English of the entire text, and any responsibility for obscurities or errors not in the original Russian, or for any infelicities of style, must be his. It has been difficult to achieve a simple, coherent and meaning ful set of symbols. Cyrillic characters have been changed through out, but Roman or Greek symbols have not been changed except where the Russian usage is clearly at variance with British engi neering practice. It is hoped that the mathematical text can be read without too much re-learning of symbols. The term "water equi valent" is not as frequently met with in modern British parlance as in French or German —in the translation "water equivalent" and "thermal capacity" are used indifferently. XI Editor's Preface Professor Kitaev has brought the book up to date by providing an entire new chapter (Chapter VI) and an enlarged bibliography, and a few other small changes from the Russian text have been made in consultation with him. The great achievements of Russian scientists in the blast fur nace field are well known, and were appreciated in a practical sense by the British Iron and Steel Research Association visit of 1962. This book presents the scientific basis for these achievements, and here Professor Kitaev is a central figure. The book seems of particular value in that it reviews a whole stream of work — American and European as well as Russian. It is, indeed, most interesting to find much of the discussion pre sented on the historical method, as part of a stream of develop ment going back to Bell in England and Le Chatelier in France. (Where in a modern British paper would we find reference to the "Bell reaction", or the results of Bell's work quoted?) The volume is, then, presented as an important contribution to the literature, and of value to the metallurgical and chemical engineer not merely as a source book, but as a practical design manual. Finally, it is too much to hope that a work of this complexity will find its way into print without errors of translation, or of interpretation, or of proof reading. The editor would be most grateful if such errors could be brought to his notice. Xll Introduction THE theory of the shaft furnace process brings many theoretical problems to light, and decisions taken at the XlXth and XXth Congresses of the Communist Party of theU.S.S.R. have led cer tain Soviet scientists to attempt to solve them. The shaft furnace is a convective heat transfer installation used not only for the extraction of ferrous and non-ferrous metals but also for other processes such as the roasting of limestone, mag- nesite, dolomite, etc. Scientists have worked on theories of the shaft furnace for many years. Thus, Le Chatelier applied thermodynamic principles to the theory of the shaft furnace process in 1926 and V. E. Grum- Grzhimailo attempted to apply his theories of fluid flow to shaft furnaces. The Soviet period has seen many contributions to the develop ment of the theory of the shaft furnace process, as various de partments of the Academy of Sciences of the U.S.S.R., together with other scientific institutions, and even industrial enterprises, have taken part in this work. Even so, the technical approach to the theory of the shaft furnace process was felt to be inadequate. This was shown by the preference given to studying the chemical side of the process up to even recent times. A systematic study of the related heat ex change processes was first undertaken by Academician M. A. Pavlov. When considering the question of heat production and utilization in a blast furnace, he clearly showed the very limited results of calculations depending on the thermal balance. Dis agreeing with Ledebur in this instance, M. A. Pavlov says (ref. 1, p. 542): "The thermal balance is only concerned with the utili zation or consumption of heat and its distribution; it does not by Xlll Introduction itself indicate the way by which we may achieve the best distri bution." M. A. Pavlov also shows that water cooling requirements are not entirely determined by considering the thermal balance alone; on the contrary, the dynamic situation must also be considered. He does, however, say that the development of water cooling in blast furnaces at the beginning of the twentieth century was a decisive step which enabled furnace campaigns to be extended. Judging from the thermal balance, the charging of hot sinter into the blast furnace must, obviously, lead to greater economy on coke. However, as M. A. Pavlov rightly says, this practice has not yet been fully confirmed. M. A. Pavlov shows the inadequacy of the present thermodynam- ic approach to the question when he considers the operation of blast furnaces with steam additions to the blast, calcination of limestone, preparation of the burden, etc. Professor I. A. Sokolov considered that all aspects of scientific research must be utilized in examining the blast furnace process. He has utilized kinetics as well as thermodynamics in his study of the blast furnace process and he was the first to publish papers on the reducibility of iron ores. I. A. Sokolov considered the question of moisture to be of the utmost importance in the study of heat exchange in blast fur naces. This was because it is not possible to determine how chem ical processes will develop without having established what the temperature will be at any level of the blast furnace. The attention paid to heat exchange processes in blast furnaces by Academician I. P. Bardin, and also by Professors A. N. Pokhvisnev and I. A. Sokolov, attracted a large number of research workers to study this subject. The work on the present-day theory of the blast furnace process under our Soviet conditions proved so absorbing that it not only attracted those engaged in work on blast furnaces but also many people from other departments. The study of heat exchange processes in blast furnaces has con tributed to the development of blast furnace techniques, espec ially in the case of low shaft blast furnaces which enable iron to be xiv Introduction melted with fuels other than "metallurgical coke". Considerable practical results were also obtained on gasifica tion after a study of heat exchange in gas generators had been made. During gasification of brown coal it was observed that, by reducing the height of the bed, the output of gas generators could be doubled and the composition of the gas improved. Many aspects of the shaft furnace process have not, however, yet been studied. More research must be carried out in this field, and this book will be helpful in this work. xv List of Symbols A Coefficient in the Furnas expression (eqn. (138)), char s acterizing material of a packed bed a Thermal diffusivity (m2/hr) h Surface heat transfer coefficient s (kcal/m2 hr °C) h Volumetric heat transfer coefficient v (kcal/m3 hr °C) h Overall surface heat transfer coefficient s (kcal/m2 hr °C) h Overall volumetric heat transfer coefficient v (kcal/m3 hr °C) h Radiative heat transfer coefficient r (kcal/m2 hr °C) ft Root of transcendental equation n tan£ _ 1 C Specific heat of lumps of burden material s (kcal/kg °C) y Density of lumps of burden material s (kg/m3) y Density of gas (kg/m3) g y Bulk density (kg/m3) B d Average diameter of lump (m) [D] Concentration of gas S Surface area (m2) e Porosity of bed C Coefficient of resistance of packing G Consumption of solids (kg/hr) s G Consumption of gases (kg/hr) g xvi
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