Sintering Characteristics of Indian Chrome Ore Fines
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TRODUCTION
IN order to produce ferrochrome and charge chrome, chrome ore is an essential raw material. The demand for ferrochrome and charge chrome is continuing to increase because of an increase in the manufacturing of alloy steel components. India has approximately 180 million tonnes of chromite ore reserves, which are largely confined to the Sukinda–Nausahi belt, and most of them are of the ferruginous type. From the point of view of chromium extraction, the associated gangue minerals in chrome ore can be classified into two types, namely, ferruginous and siliceous. During the selective mining of lumpy chrome ore from the siliceous-type deposits, approximately 50,000 tpa of low-grade siliceous ores is also produced. This material requires a
BIKASH NANDY, Senior Manager, is with IMTG, Tata Steel Limited, Jamshedpur-831001, Jharkhand, India. Contact e-mail: [email protected] MANOJ KUMAR CHAUDHURY, Researcher, and D. BHATTACHARJEE, Director, Research, Development & Technology, are with the R&D Division, Tata Steel Limited, Jamshedpur-831007, Jharkhand, India. JAGANNATH PAUL, Scientist, is with the National Metallurgical Laboratory, Jamshedpur-831007, Jharkhand, India. Manuscript submitted March 15, 2008. Article published online August 11, 2009. 662—VOLUME 40B, OCTOBER 2009
value addition for the effective marketing of this product. Currently, the ore is ground to below 75 lm for beneficiation and subsequent pelletization. Green pellets are hardened through a carbothermic reaction at 1300 C to 1400 C and then charged along with lumpy ore and briquettes into the submerged arc furnace for ferroalloy production. The physical properties of the chrome ore pellet, even after hardening, are found to be inconsistent; this is similar to the case of the briquettes. This leads to the generation of more fines during melting and causes increased electricity consumption while producing ferrochrome/charge chrome. An alternative route, using chrome ore concentrates/chips from lumps through agglomeration and then feeding to the arc furnace for ferrochrome production, is being practiced elsewhere. An attempt was made to produce chrome ore sinter at a low temperature using a pot-grate sinter machine and, subsequently, the electrical resistivity was determined. Deqing[1] has found that the agglomeration of chromite sinter consists of approximately 20 pct liquid phase of olivine along with the solid-state reactions and recrystallization of chromium oxides contributing to the sinter strength; this is quite different from the sintering of iron ores that contain approximately 35 to 40 pct liquid phase. METALLURGICAL AND MATERIALS TRANSACTIONS B
Table I. Source of Chrome Ore
Composition of Chromite Ore Available in Different Countries
Cr2O3 (Pct)
Fe (Pct)
SiO2 (Pct)
Al2O3 (Pct)
MgO (Pct)
44.5 48.5 50.5 48.0
18.5 8.5 11.4 11.2
5.0 10.5 4.4 3.5
14.5 7.5 10.8 12.0
10.5 20.0 17.5 17.0
South Africa Kazakhstan Turkey Pakistan
All chromite ores are smelted in electric arc furnaces (EAFs), which consume electrical energy to the exte
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