Synthesis of Silicon Carbide from Technogenic Waste: A Large-Scale Laboratory Study

This study presents the results of an investigation into the carbothermic synthesis of silicon carbide (SiC) from microsilica and petroleum coke. The research combines thermodynamic modeling with experimental validation conducted in an ore-thermal furnace. Thermodynamic calculations were performed using the HSC Chemistry 10 software package to evaluate the influence of temperature and the SiO₂/C ratio on phase formation and the conditions of SiC synthesis. The results show that the synthesis process exhibits a strong dependence on temperature and is largely governed by the carbon balance of the charge. At an SiO₂/C ratio of 1, the system is carbon-rich, which promotes effective reduction of silicon dioxide. However, at elevated temperatures, these conditions intensify gas-phase reactions and lead to increased silicon losses. The most favorable conditions for silicon carbide formation were achieved at an SiO₂/C ratio of 1.5, which is close to the stoichiometric value. This conclusion is confirmed by the maximum degree of SiC recovery obtained under experimental conditions. In contrast, at an SiO₂/C ratio of 2, carbon deficiency results in incomplete reduction in SiO₂ and a lower yield of the target product. The phase composition of the synthesized samples was analyzed by X-ray diffraction, revealing β-SiC as the dominant crystalline phase. The morphology and structure of the materials were examined using scanning electron microscopy, which confirmed the formation of SiC particles and aggregates with characteristic features. A comparison between calculated and experimental results demonstrates that thermodynamic modeling adequately describes the main trends of the process and can be effectively applied to optimize SiC synthesis conditions during the processing of technogenic silica-containing waste.