Reduction rate of Cr₂O₃ in a solid powder state and in CaO-SiO₂-Al₂O₃-CaF₂ Slags by Fe-C-Si melts

In order to understand effective conditions to recover chromium from stainless steel-making slags, the kinetic behavior of Cr₂O₃ reduction by iron-carbon melts were investigated at various conditions by using solid Cr₂O₃ powder and Cr₂O₃-CaO-SiO₂-Al₂O₃- CaF₂ slags. The effect of temperature on the reduction rate of solid Cr₂O₃ was fairly large and the apparent activation energy was about 180 kJ mol^-1. The overall reduction of solid Cr₂O₃ was considered to be controlled by a chemical reaction step. For reduction of Cr₂O₃ in slag, the addition of CaF₂ to slag and of silicon to iron melt promoted the reduction rate, but the reduction of Cr₂O₃ powder was retarded by the silicon addition. The kinetic behavior of reduction of Cr₂O₃ in slag could be well simulated by the kinetic reaction model proposed previously. As a result, it was found that the overall reduction rate of Cr₂O₃ in slag was controlled by the mass transport in the slag phase.