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

摘要

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 (FeCr_2O_4) 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 thermo-dynamically and kinetically evaluated. The experimental results show that the iron powder addition enhances the reduction of FeCr_2O_4 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)_7C_3, which can decrease the activity of the nascent chromium formed by the reduction of the FeCr_2O_4. The experimental results indicate that the reduction of FeCr_2O_4 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 FeCr_2O_4 or (b) diffusional dissolution of the product (FeCr_2) into the iron/alloy particles or the mixed control of (a) and (b).