Effect of Ferrosilicon on Reduction of Cr2O3 in Steelmaking Slags

Abstract

The stainless steel slag as the by-product of steel-making plants contains 2–10 wt% Cr2O3, and the potential elution of hexavalent chromium impedes the utilization as a secondary resource. The reduction of chromium oxide in steelmaking slag containing Cr2O3 by FeSi at 1550 °C was investigated in the laboratory. The experiments were performed in a carbon-tube furnace, and the samples collected during tests were analyzed using X Ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) equipped Energy Dispersive Spectroscopy (EDS). The results show that the FeSi addition could efficiently enhance the reduction and recovery of chromium. When the amount of FeSi ranged from 2 upto 9 wt%, the recovery increased from 65.60% to 84.19%. The occurrence of residual chromium was metal particles, which dispersedly distributed in silicate phases owing to the size limitation. The sufficient FeSi could easily reduce chromium oxides into metal, but the critical factor of chromium recovery is the precipitation of suspending metal particles from the molten slag. Thus, some measures should be proposed in order to make sure that the suspending particles are adequate to aggregate into bigger ones.