Sintering of chromite ore fines for its utilization in arc furnace for ferrochrome production

Abstract

Production of a better quality ferro-chrome requires using high-grade chromite ores; but these are fragile and tend to form fines during handling. Agglomeration of these fines is needed before charging in electric arc furnace. The present study aims at producing sinter directly (like iron ore sintering) from the available chromite ore fines (-10 mm) without any grinding in presence of coke breeze. Sintering was carried out in 10 kg scale in a sintering pot at maximum flame temperature ~1600 C. Result indicated that a good amount of (20%) molten phase formed for bonding. It decreased the spinel phases of chromite fines, forming molten phases such as Fe2SiO4, Ca2Al2SiO7, and MgCa2Si2O7. As it is a prefused mass, reduces faster in subsequent electric arc furnace smelting. It has >85% shatter index, >75% Tumbler index and ~5% abrasion index. Produced chromite sinter was utilized for ferrochrome production in 50 kVA EAF in presence of coke as reductant and flux (silica) on 10 kg scale. Smelting parameters viz. tapping temperature, specific power consumption, flux requirement, metallic recovery has been studied. The slag tapping temperature measured 1761°C and was appeared to be sufficiently fluid. The obtained Fe-Cr alloy has metallic yield of 75%, chromium recovery of 88%. Produced ferrochrome has composition 55%Cr, 36% Fe, 7.8%C and the final slag Cr and Fe was very low (0.76% Cr2O3, 0.98% FeO).