Carbothermic Reduction of Synthetic Chromite with/without the Addition of Iron Powder

Abstract

Carbothermic reduction of chromite is an important industrial process for extracting chromium from the chromite. To have a better understanding of the effect of iron on the carbothermic reduction of chromite, the reduction of synthetic chromite (FeCr₂O₄) by graphite with/without the addition of iron powder was investigated in this paper by Thermogravimetric Analysis (TGA) in argon atmosphere. The fractional reduced samples were examined by SEM/EDS and XRD analysis, and the reduction process was thermodynamically and kinetically evaluated. The experimental results show that the iron powder addition enhances the reduction of FeCr₂O₄ and this effect increases when increased amounts of iron powder are added. This phenomenon is attributed to the in situ dissolution of chromium into the iron and mixed carbide (Cr,Fe)₇C₃, which can decrease the activity of the nascent chromium formed by the reduction of the FeCr₂O₄. The experimental results indicate that the reduction of FeCr₂O₄ with up to 80 wt.% iron powder addition is likely to be a single-step process and the kinetic analysis suggests that the reduction reaction is likely to be either (a) chemical reaction at the surface of FeCr₂O₄ or (b) diffusional dissolution of the product (FeCr₂) into the iron/alloy particles or the mixed control of (a) and (b).