Dissolution and Reduction Behaviors of Chromite Ore in Molten Slag

Abstract

Experiments have been done on the smelting reduction of powdered chromite ore by graphite in the molten slag of CaO-MgO-Al₂O₃-SiO₂ system at the temperatures between 1 550 and 1 650°C.
The dissolution of chromite grains in slag proceeded usually from the grain surface and the surface became progressively enriched in MgO and Al₂O₃. However, the slag having the composition far remote from liquidus line penetrated into the inside of chromite grain and promoted the dissolution. The reduction took place mainly at the surface of graphite grain and proceeded more rapidly in the slag with higher concentration of SiO₂and with lower concentration of MgO. Temperature dependence of the reduction rate decreased with the increase of temperature, because of change in the rate-determining step of smelting reduction with temperature. Besides, the chromium and iron contents of slag and the oxidation state of chromium in slag were examined.