Direct smelting

Ironmaking refers to those processes which reduce iron oxides to iron. By the nature of the processes, the iron produced usually contains carbon and/or other impurities which are removed in downstream processing. There are three principal categories of ironmaking processes, in order of commercial importance blast furnace, direct reduction, and direct smelting. 

Second, development efforts ia direct reduction and direct smelting processes have also iacreased. Whereas these developmeats require significant commitment of finances and labor to achieve commercialization, the rewards promised by avoiding cokemaking and hy utilizing smaller scale units which have relatively low capital costs make the commitment worthwhile. 

Processes operating ia the range of 1300—1530°C produce molten iron, called hot metal or pig iron. These processes are classified as direct smelting processes. Processes operating above 1530°C produce molten steel (qv) and are called direct steehnakiag processes. 

Metafile arsenic can be obtained by the direct smelting of the minerals arsenopyrite or loeUingite. The arsenic vapor is sublimed when these minerals are heated to about 650—700°C in the absence of air. The metal can also be prepared commercially by the reduction of arsenic trioxide with charcoal. The oxide and charcoal are mixed and placed into a horizontal steel retort jacketed with fire-brick which is then gas-fired. The reduced arsenic vapor is collected in a water-cooled condenser (5). In a process used by Bofiden Aktiebolag (6), the steel retort, heated to 700—800°C in an electric furnace, is equipped with a demountable air-cooled condenser. The off-gases are cleaned in a sembber system. The yield of metallic arsenic from the reduction of arsenic trioxide with carbon and carbon monoxide has been studied (7) and a process has been patented describing the gaseous reduction of arsenic trioxide to metal (8). 

Hardie, G. J., Wright, J. K., and Batterham, R. J., Pulverised Coal Based Direct Smelting The HIsmelt Process, VDEh Blast Furnace Committee Meeting, Use of Coal for Hot Metal Production, Duesseldorf, March (1993)... 

Direct-sheet carbon steel casting, 23 269 Direct smelting ironmaking processes,... 

Ironmaking processes, 14 498-521 blast furnace, 14 498-509 direct reduction, 14 509-520 direct smelting, 14 520-521 Iron-manganese-silicon steels, 22 712 Iron melting channel melting furnaces, 12 316... 

Direct Smelting. Direct smelting processes use coal directly instead of coke. Several processes are under development which effectively divide the functions of the blast furnace into two separate but connected unit operations. First, the iron ore is prereduced in a shaft furnace or a fluidized bed, depending on the process and the type of ore used. Second, the prereduced ore is charged into a molten bath into which coal and oxygen or air are also introduced. The gases leaving the smelter are used to perform the reduction in the prereduction vessel. 

Long-term development work is focusing on direct smelting technologies. Multimillion dollar development programs are underway in the United States (AISI Direct Ironmaking process), Australia (HIsmelt process), and Japan (DIOS process). A direct smelting process, called the COREX process, already is in commercial operation in South Africa. 

Roasting. Copper and lead sulfides are directly smelted but not zinc sulfide. However, theoretical calculations are encouraging (20) and, if an efficient means of condensing zinc rapidly from 1600 K in the presence of carbon dioxide, sulfur dioxide, and steam can be devised, the process may be feasible. The reaction of zinc vapor to yield zinc oxide or zinc sulfide presents the main difficulty. 

Nevertheless, the last-generation plants designed for the production of primary lead are able to treat sulphur-bearing lead from spent batteries. These are direct-smelting plants which are suitable to treat lead sulphates, which, after the addition of lead concentrates, are directly reduced to metallic lead without problems. In Europe, there are three plants of this kind. Although based on different technologies, a feedmg mix... 

R. Li, J. G. Peacey and P. J. Hancock, Direct Smelting of Zinc Concentrate and Residues , The Howard Womer International Symposium on Injection in Pvrometallurgv. M. Nihnani and T. Lehner, Eds., The Minerals, Metals and Materials Society, Warrendale, PA, U.S.A., 1996,107-121. 

N.A. Warner, Direct Smelting of Zinc-Lead Ore , Trans. Institution of Minina and Metallurgy, 1983, Sect C, C147-152. 

NICKEL, COBALT AND COPPER RECOVERY FROM SEA NODULES BY DIRECT SMELTING PROCESS... 

Nickel, Cobalt and Copper Recovery from Sea Nodules by Direct Smelting... 

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