Kinetics of Silicon Production by Aluminothermic Reduction of Silica Using Aluminum and Aluminum Dross as Reductants

A silicon alloy was produced by reduction of silica in a calcia-silica (CaO-SiO2) slag using aluminium (Al) metal or aluminium dross as reductant. The aluminothermic reduction was conducted in a laboratory scale induction furnace with an argon atmosphere. The reductant and 300 g of 51.3CaO-46.7SiO2 (wt%) pre-fused slag, were heated and held at 1650 °C for 20, 30, 40, 60 and 180 minutes. For the dross material, the metallic Al content was estimated to 75 wt% by melting in salt flux. The kinetics of reduction was investigated by evaluating the Si-alloy and product slag composition against simulated thermodynamic equilibrium obtained from FactSage 7.3. The Al dross was demonstrated to be as effective reductant as pure Al and analysis of the results indicate a rapid aluminothermic reduction as well as good Si-alloy/slag separation for both reductants. The composition of the produced Si-alloys, mainly dependent on the reductant type, were above 70 wt%Si, 8-15 wt%Al, 13-19 wt%Ca and with low (<0.3 wt%) content of other elements such as Fe and P.