Carbothermic smelting of high carbon ferrochromium alloy from low and high grade chromite ores

Abstract

The objective of this study is to investigate some of the parameters affecting the possible utilisation of Egyptian chromite ores for the production of high carbon ferrochromium. Pilot plant experimental heats were carried out to determine the optimum condition to get the highest recovery and metallic yield using the carbothermic smelting process in 100 kVA submerged electrical furnace. Different amounts of nut coke, as well as different fluxes, were used in these melts. Chromium recovery and metallic yield were related to the excess reductant and slag composition. The results showed that 50% of coke in excess of the stoichiometric amount should be added. Both MgO/Al₂O₃ and slag basicity must be controlled by flux addition. Acidic slag having (CaO+MgO)/(SiO₂+Al₂O₃) weight ratio equal to 0·74 and MgO/Al₂O₃ weight ratio in the range of 0·9–1·1 ensure higher chromium recovery and metallic yield. With the optimum reductant addition and slag condition, chromium recovery and metallic yield of ∼82% can be attained, and ferrochromium alloy containing 66% chromium and 7% carbon can be produced from these chromite ores without concentration.

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