Plasma Technology in Ferroalloy Processing

Plasma technology has come a long way since the early reported applications to metallurgy by Sir W. Siemens(1878) and H. Moissan(1897) about a century back(1). Major attraction of using plasma in metallurgical smelting oper-ations, especially in the last two to three decades, have emerged from its ability to deliver high grade heat to any environment independently of oxygen potential. Further more, compact unit of high throughput, due to high power flux and higher reaction rates attained, and ability to handle cheaper fine feed without causing pollution problems have been the other important attractions. Although, the development of plasma technology in the area of nonferrous extractivepetallurgy is still confined to the laboratory and pilot plant research stage, applications in ferrous metallurgy have entered the stage of commercialization. Table 1' lists some of the high capacity iron and steel installations. Ferroalloys production, using carbothermic smelting reduction of oxide ores and by remelting of ferro-alloys fines, has been a major driving force in fostering the development of plasma technology, As indicated in Table 1, both ferro manganese and ferro chromiuin are being produced at present on industrial scale. Research and development in the production of other ferroalloys, e.g. ferro silicon, ferro vanadium, ferro molybdenum, is in an advanced stage. A brief review is presented in this paper on the applicat-ion of plasma technology for ferroalloys production. We begin with the definition of plasma in general, followed by a discussion on various plasma furnaces, process funda-mentals, i.e. chemistry and transport phenomena in plasma environment, and energy conSiderations involved in plasma smelting. Finally, the advantages of the technology, vis-a-vis the conventional processing using submerged arc fur-nace, and relevance of the technology in 'the Indian con-text are brought into focus. Specific examples of ferro-alloys are cited wherever possible. The reader may refer to the reviews [1-6] for detail