Energy & Fuels 1997, 11, 1313
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Book Reviews Developments Affecting Metallurgical Uses of Coal. IEACR/74; IEA Coal Research: London, UK, 1994; 92 pp, 163 refs. £255. This report produced by IEA is a handy commentary consisting of 85 pages of text along with the list of 163 references, describing the development of the metallurgical use of coal. In the abstract, the author states that nearly half the tonnage of internationally traded coal is accounted for by coking coal and coking coals command premium prices. However, if you consult chapter 7 concerning the metallurgical coal prospects, you can get a more precise knowledge about the situation of coking coal in worldwide coal consumption: in 1990, over 4.7 billion tonnes of coal was consumed (of this total, 3.6 billion tonnes was hard coal and 1.1 billion tonnes brown coal). Worldwide coal consumption for coking is estimated 535 Mt. Hence, coal for coking was a little over 11% of total world coal. As for world market demand for imported coal, metallurgical coal was estimated 168 Mt in 1993. From this, the fact is that coal is used indigenously and the market for internationally traded coal is comparatively small. It is interesting to note that Australia, Canada, and USA together account for more than three-quarters of coking coal exports and Japan is consuming more than 40% of the internationally traded coking coal (1993). Prediction about the future markets for metallurgical coal depends on how the volume of steel production will be and how the technologies will be improved and renewed. The report contains the following eight chapters with an additional chapter of references: (1) introduction, (2) the use of metallurgical coal in ironmaking, (3) the production of hard coke, (4) alternative processes for metallurgical coke production, (5) reducing coke rate; coal injection, (6) direct reduction and smelting reduction processes, (7) metallurgical coal prospects, and (8) conclusions. Introduction is only one page; however, if you read this chapter, you can get a perspective of the present state of iron and steel production: due to the large capital investment required for the large blast furnace and their ancillaries, the new direct reduction process under development will be competition for the existing blast furnace along with the electric arc furnace process. Of course this situation is for the developed countries, the situation being different in less developed countries. In Chapter 2, the use of coke in the blast furnace is outlined in a very instructive way: chemically coke indirectly reduces Fe2O3 to Fe3O4 and wu¨stite (FeO) via CO and H2; at the higher temperature near the furnace hearth, coke directly reduces FeO to iron; the reactivity of the coke to CO2 is important around 900-950 °C; low-reactivity coke tends to reduce the coke consumption of the furnace and so on. The reduction process of iron ore in the blast furnace is clearly explained in terms of reaction zones, 1 (drying and preheating cold materials), 2 (commencement of direct reduction), 3 (cohesive zone), 4 (fluid zone), and 5 (deadman). Chapter 3 treats the traditional coke ovens process. It is interesting to note that the use of beehive ovens has continued in South Africa and India. The details of a modern horizontal chamber oven with byproduct recovery are discussed in terms of coal preparation, carbonization, coke handling, and byproducts. Here we should pay attention to the following sentence: the modern stamp charged coke oven (a method of increasing charge bulk density) is said to be “in no way inferior to top charged ovens in terms of mechanical performance and environmental protection”. Air pollution as well as water pollution from coke oven operation is discussed
S0887-0624(95)00046-6 CCC: $14.00
carefully by referring to the emission of polycyclic aromatic compounds, BTX, SOx, NOx, particulates, and odors. As for the employment of dry quenching, the environmental benefits is decisive. Since the evolutionary development of conventional coke ovens is approaching its technological and economic limits, radical changes are required to secure further progress. Some of the possibilities of alternative processes for metallurgical coke production, such as modern nonrecovery coke oven, the “jumbo” coking reactor (JCR) which features large single chambers, and the briquetted fuel process (formed coke), are described and discussed in Chapter 4. The high cost of providing metallurgical coke has motivated steel producers to reduce the coke rate (consumption of coke in kilograms per tonne of hot metal) of their blast furnaces. In Chapter 5, coal injection technique, considered as the most effective technique for reduction of coke rate, its limits to coke replacements, and the quality requirements for injection coal are discussed in depth. On the other hand, the oxygen-coal injection, the full oxygen blast furnace, the balanced oxygen blast furnace, and the fine ore injection are also described and discussed in this chapter. The world demand for steel is static or declining and only modest growth is predicted into the next century. The new “world class” furnace may not appear financially attractive. Investment in smaller conventional furnace may also be unattractive because of their higher operating costs per ton of metal produced. Small steel plants based on recycled scrap materials have appeared and these are making an increasing contribution to steel production; however, first class scrap, suitable for the production of high-quality steel, is limited. Development of an economical process for the production of iron with suitable quality to replace premium quality scrap would increase the scope for scrap-based production of the higher grade steels. Iron, suitable for use in scrap materials, may be produced by the direct reduction of iron ore. Chapter 6 describes and discusses a number of commercial direct reduction processes and their development status: the coalbased direct reduction processes, such as rotary kiln, Fastmet, iron bath gasification, direct reduction, and Corex process. In addition, the requirement for a highly reducing gas for the direct reduction shaft limits the opportunities for recycling heat to the melter/gasifier. The new smelting reduction processes designed to avoid the dilemma by using a two-stage reduction process: the American Iron and Steel Institute (AISI) process, direct iron ore smelting reduction (DIOS) process developed by Japan, and high-intensity smelting process (Hismelt) developed by the Australian CRA Co. are also described and compared with each other in this chapter. The author of this book clearly outlines the advantages and disadvantages of each technique, not only in the technical aspect but also in view of the economics, environment, and market opportunities. The contents are well written, and reasonably clear, even to the nonspecialist. The literature listed in the references provides useful direction for the readers who wish to explore a topic in more detail. It is also unquestionable that this book will be a superb resource for iron/steel industrial and relative university teaching. It is a very worthy addition to libraries of any organization involved economic analysis of iron and steel production, effective utilization of coal resource, and environmental issues. Masakatsu Nomura and Hong Gao, Osaka University EF950046R S0887-0624(95)00046-6
© 1997 American Chemical Society
