PREFACE

Modem civilization cannot exist without sources of power. Coal is an energy resource of great abundance, and population growth and technological development intensify its use. The increasing use of coal on one hand, and the need for decreasing environmental pollution on the other, place ever-growing demands on clean coal technologies, a task impossible to achieve without a clear understanding of coal beneficiation and utilization principles.

Coal, an organic sedimentary rock, is upgraded in coal preparation unit operations which reduce its content of impurities. Traditionally, in designing coal preparation plants, crushing was eliminated as much as possible to reduce the yield of fines and the cost of fine coal processing, dewatering and handling. However, separation results depend directly on the degree of liberation which is improved with a decrease in particle size. This and intensifying mechanization continuously increase the yield of fines in the coal preparation plant feed that end up in flotation circuits. The utilization of fine coal in the form of coal-water slurries eliminates the necessity of dewatering and drying it, and makes fine coal's transport possible without dusting, storage and spontaneous combustion problems by pipelining or shipping it in tankers.

Almost all coal cleaning processes are carried out using water as a medium, so an understanding of the coal/water interface is of utmost importance in dealing with fine coal cleaning and utilization. Surface chemistry plays a very important role in all unit operations handling fine coal; the finer the particles, the more profound the effect of their surface properties on the behavior of fine particle systems. The main objective of this book has been to combine in a single volume the engineering aspects of coal flotation and fine coal utilization with the fundamental principles of colloid and surface chemistry and coal surface chemistry, the fundamentals on which coal flotation technology and fine coal utilization are based.

This book is a result of copious notes employed in teaching short courses on fine coal flotation and utilization in Poland, Canada, Brazil and South Africa, as well as various undergraduate courses taught at the Silesian University of Technology in Poland and at the University of British Columbia in Canada. The author had the opportunity to spend one year as a post-graduate student in Professor Klassen's laboratories at the Mining Institute in Moscow during which he translated his monograph on coal flotation from Russian into Polish (which appeared in Poland in 1966), and since then has been collecting data for his own monograph on the subject. One year with the University of California, Berkeley, in 1981 and participation in the coal surface chemistry-related research projects carried out at that time by prof. D.W. Fuerstenau made it clear that a new monograph on this topic would be very useful for many research centers around the world.

The unit operations, fine and coarse coal processing circuits, and the role of surface chemistry in fine coal processing and utilization are defined in Chapter 1. Coal

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classification, petrography, mineral matter chemistry and distribution, and the liberation of mineral matter are discussed in Chapter 2. Chapter 3 considers those aspects of the coal surface and its interactions with water that determine coal surface wettability. The relevant theoretical and practical aspects of electrical phenomena associated with the coal/water interface, as well as experimental methods, including those used to characterize wettability of heterogeneous solid surfaces, are discussed in Chapter 3. Coal floatability and experimental techniques used to characterize it are dealt with in Chapter 4. Flotation cannot exist without reagents, and the chemistry of reagents utilized in coal flotation and the mode of their action are described in Chapter 5. Coal flotation technology is addressed in Chapter 6, and fine coal cleaning circuits in Chapter 7. Chapter 8 surveys flotation machines utilized in coal preparation plants. While decreasing the size of particles improves coal/mineral matter liberation (and thus separation results), dewatering, handling, transportation and storage are much more difficult for fine particles. Therefore, particle size enlargement is an important issue in coal utilization. The principles of these processes are also based on coal surface chemistry and are discussed in Chapter 9. The final chapter is concerned with traditional dewatering-utilization schemes, and with utilization of fine coal in the form of coal- water slurries. The latter, an exciting application of colloid chemistry, is going to entirely revolutionize many facets of coal technology as we know it today.

It is hoped that this book will be used by many groups of readers: those practic- ing mineral processing, chemical engineering, mining and metallurgical engineering; technical personnel working for reagent suppliers; and scientists researching the field of coal surface chemistry, flotation and fine coal utilization. The book was intended to be written as a text which could also be used in teaching graduate and specialized undergraduate courses, as well as the short courses which are so popular today. For those readers who may require more detail in some of these subject areas, bibliographies have been appended to each chapter.

Thanks are due to a number of people. I am particularly grateful to the late Professor V.I. Klassen who stimulated my early interests in flotation theory and in coal flotation in particular, and to whom I owe much of my conceptual understanding of the subject. I would like to thank all my students and post-docs for the stimulating discussions and for their hard and not always acknowledged work. I am indebted to many colleagues who have been very generous in providing detailed criticism. The whole book was read by Professor Jan Leja; Professor Jerry Luttrell's constructive comments have been particularly helpful. Chapter 3 was critically reviewed by Dr. Jaroslaw Drelich. I thank Mrs. Sally Finora for her ability to deal with what appeared to be an endless sequence of revisions of figures; without her computer touch this book would probably have never materialized. The help offered by Mrs. Elizabeth Fedyczkowski in drawing some figures is also gratefully acknowledged.

Another debt is owed to several persons who worked hard to ease my "Polishisms". Cameron Lilly's help, and my sons' Cyprian's and Komel's assistance in this respect have been invaluable.

This text was started many years ago. Parts of this book were written when I was on sabbatical leaves with l~cole National Sup6rieure de Geologi6, Nancy, France, and with the University of Cape Town in South Africa. This note of appreciation would be

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incomplete without acknowledging the patience of my wife, Barbara, during these long years abroad and at home.

Janusz S. Laskowski Vancouver, November 2000.