Abstract
Chromite reduction by carbon dissolved in a high carbon ferrochromium alloy melt has been investigated in the temperature range 1580-1640°C using a slag system based on CaO2-FeO-Cr2O3-SiO2-Al2O3. Although the reduction is essentially first order with respect to Cr2O3 concentration, it exhibits both zero order and first order reaction kinetics. The zero order period is occupied by the preferential reduction of iron oxide, during which time there is no significant change in the concentration of Cr2O3. The predominance of the divalent chromium oxide in the slag phase is seen to provide further evidence that the reduction of chromite occurs by a stagewise process, involving the thermodynamically stable CrO species. While high basicity slags may be recommended to minimise the generation of CrO, and hence improve reaction kinetics and the extent of Cr2O3 reduction, there is a limitation imposed by chemical erosion of the alumina crucible as the slag basicity is increased above unity, with the dissolving Al2O3 further retarding the reduction kinetics. There is also evidence to suggest the participation of a reductant other than carbon (possibly silicon) in the reduction of chromite.