Theoretical and experimental studies on magnesite smelting for co-producing forsterite via silicothermic magnesium production under relative vacuum

As a magnesium ore resource with abundant reserves and excellent cost-effectiveness, the efficient utilization of magnesite in the magnesium smelting process is of great significance to the green and low-carbon development of the magnesium metallurgical industry. In this paper, a systematic theoretical and experimental study was carried out on the in-situ reduction and phase change dissipation of magnesium prepared by relative vacuum silicothermic reduction of magnesite without the addition of calcium. A process for silicothermic magnesium production from magnesite under relative vacuum without calcium addition, which co-produces forsterite (RVMS-CF), was proposed. Meanwhile, the Gibbs free energy, equilibrium temperature of the reduction reaction were calculated based on the laws of thermodynamics. The reaction mechanism of RVMS-CF was elucidated through experimental investigations. The effects of different molar ratios of magnesium oxide to silicon on the magnesium reduction rate and the products of reduction slag were investigated. The experimental results show that when the molar ratio of magnesium oxide to silicon is 1.8:1, the magnesium reduction rate reaches the maximum of 82.26%. Furthermore, the energy consumption of the new process can be reduced by >40% compared with the Pidgeon process, and the production cost per ton of magnesium can be cut by >3000 CNY relative to the latter, representing excellent economic benefits. This study provides a theoretical basis and technical support for the engineering application of the RVMS-CF process, and offers insights for the development of continuous magnesium smelting technologies.