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1282
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Energy & Fuels 1996, 10, 1282
Book Reviews Power from CoalsWhere To Remove Impurities? By Gordon R. Couch. IEACR/82; IEA Coal Research: London, 1995; 87 pp. £450. From a power production standpoint, impurities in coal are usually considered to be those minerals or elements that affect power station operations and emissions. This book takes a broader view and explores the entire coal to electricity chain and the opportunities for removing impurities along the way. It also discusses the nature of coal impurities; emissions, effluents, and residues that are produced; and what happens to impurities during combustion and postcombustion control. The book also addresses impurities during gasification, a topic that has not received much attention but one that is important as increasing amounts of electricity are generated using gas turbines. Coal impurities consist of both the minerals present in coal and the elements that are organically associated. Impurities can be found in relatively large quantities, as the ash-forming minerals may constitute up to 50% by weight of some raw coals. They are also found in trace quantities. Trace elements, such as mercury or arsenic, may be the next target of emissions regulations. These impurities can be removed through selective mining and coal cleaning or preparation, during the combustion process, or by cleaning the gaseous emissions from combustion. The amount of solid residues produced worldwide from coal used for heating and steam production is over 800 Mt/y, with a little over half produced from power generation. While a description of conventional coal-cleaning technologies is absent, the book offers brief descriptions of some of the advanced technologies: micronized magnetite cycloning; flotation columns; selective agglomeration; dry processes such as electrostatic, electrodynamic, and magnetic; and advanced chemical or biological methods. Comprehensive references are provided for the reader to obtain detailed data on these and other processes discussed throughout the book. These processes beneficiate fine or ultrafine particlessnatural fines as well as fines generated through crushing of the coal to liberate impurities. The wet processes produce a fine clean coal stream that is difficult to dewater. Options for this stream are considered: advanced dewatering techniques; addition of the dewatered stream back to the coarse stream to produce an acceptable moisture content overall; use of the fine coal as a coal water fuel; and reconstitution of the coal through briquetting or pelletizing. Some dry processes are also being evaluated for the incorporation of coal cleaning at pulverized coal-fired power plants in conjunction with the pulverizer. Since the coal is ground to very fine sizes in the pulverizer, some liberation of mineral matter will occur. A high-ash, high-pyrite stream can be removed using, for example, magnetic separators. The transformation of minerals in the combustion process is quite complex, forming bottom ash, boiler deposits, and fly ash for disposal or, sometimes, for use in building products. Some impurities are volatilized so that postcombustion removal is required for some of these elementssmost notably sulfur. Sorbents are added to capture sulfur (and perhaps some trace elements), resulting in another stream either for disposal or, in the case of wet limestone/gypsum scrubbers, for sale. Some processes use sorbents that can be regenerated. This book should prove especially useful to electric utilities
operating in the international market and those that purchase coals from a wide variety of sources. Perhaps the most important point of the book is that it is difficult to generalize about coal and coal impurities and that each coal must be evaluated on its own and in blends. Coal market conditions and emissions regulations also vary from country to country and play an important role in the overall cost of impurities removalsnot only in the cost of coal cleaning or postcombustion control but in the cost of disposal of the rejected impurities. Computer software for comparing different coals and different processes is reviewed, showing how these programs can be used to develop cost benefit analyses for removing coal impurities. While costs are very specific to the locale of the coal mine, transportation mode, or power plant, costs are given throughout the book that provide the basis for comparison of processes or techniques for impurities removal. By reviewing the options presented in this book, utilities can begin to optimize impurities removal in the coal to electricity chain. B. J. Arnold, CQ Inc., Homer City, Pennsylvania 15748 EF960043U S0887-0624(96)00043-6
Asphaltenes: Fundamentals and Applications. By E. Y. Sheu and O. C. Mullins. Plenum Press, New York, 1995; 236 pages plus Index. $79.50. ISBN No. 0-306-45191-3. Asphaltenes are an extremely complex, difficult to characterize, fraction of petroleum. They are responsible for sediment formation during petroleum recovery operations, coke production in thermal processes, and sludge formation during petroleum storage. However, over the past several decades, major inroads have been made into understanding the nature of asphaltenes and to solving to the problems that arise when asphaltenes are present in feedstocks. This book provides an overview of the development of the techniques used to examine asphaltenes. The book contains chapters on (I) Colloidal Properties of Asphaltenes in Organic Solvents; (II) Sulfur and Nitrogen Molecular Structures in Asphaltenes and Related Materials Quantified by XANES Spectroscopy; (III) Solubility and Phase Behavior of Asphaltenes in Hyrocarbon Media; (IV) A Unified View of the Colloidal Nature of Asphaltenes; (V) The effects of Asphaltenes on the Chemical and Physical Characteristics of Asphalt; (VI) Asphalt Emulsion Generators for Use in Oil Wells and Heavy Crude Oil/Bitumen Transportation Facilities; (VII) New Methods of Petroleum Sludge Disposal and Utilization. The book makes an excellent complementary volume to the earlier volume Asphaltenes and Asphalts, 1, by T. F. Yen and G. V. Chilingarian. Both books are very worthy additions to the bookshelves of those involved in this important area of science and technology. Dr. James G. Speight, Western Research Institute, Laramie, Wyoming 82070-3380 EF960070K S0887-0624(96)00070-9
