The Direct Alloying of Steel through Silicothermic Self-Reduction of Chromite Ore Utilizing Si-Containing Solid Waste

Abstract

Organosilicon materials generate copious amounts of Si-containing solid waste during production, leading to severe environmental pollution and substantial resource squandering. In pursuit of the resource utilization of Si-containing solid waste, this study conducted experimental research on the direct alloying of molten steel through the silicothermic self-reduction of chromite ore using Si-containing solid waste as a reducing agent. Additionally, thermodynamic analysis was performed, employing the thermodynamic calculation software FactSage 8.2 (Thermfact Ltd., Montreal, QC, Canada and GTT-Technologies, Aachen, Germany), to examine the equilibrium reactions of the silicothermic reduction of chromite ore and the variations in the thermodynamic equilibrium compositions of slag and metal phases. The results indicate a reduction sequence for the reducible components in chromite ore as Fe2O3 → Cr2O3. The introduction of CaO and Al2O3 into the silicothermic self-reduction compacts altered the forms of Fe and Cr oxides in equilibrium, significantly reducing the standard Gibbs free energy (ΔG0) of the silicothermic reduction reaction. The initial slag melting point decreased from 1700 °C without the addition of CaO and Al2O3 to 1500 °C with the addition of CaO and Al2O3. Correspondingly, the slag viscosity at 1600 °C decreased from 134.1 Pa·s without CaO and Al2O3 addition to 1.81 Pa·s with CaO and Al2O3 addition. The addition of CaO and Al2O3 accelerated the reduction of Cr oxide in chromite ore and enhanced the recovery of Cr, consistent with the thermodynamic calculation results. In the process of steelmaking through the direct alloying of chromite ore silicothermic self-reduction compacts, the final recovery rate of Cr increased from 86.4% without CaO and Al2O3 addition to 95.4% with CaO and Al2O3 addition.