Behavior Analysis of CaF2 in Magnesia Carbothermic Reduction Process in Vacuum

Abstract

Magnesium production by carbothermic reduction of magnesia with CaF2 in vacuum was investigated experimentally by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermodynamic analysis. Thermodynamic calculations indicate that magnesium was generated by a carbothermic reduction among MgO-C system, which should be above 1500 K (1227 °C) (50 Pa). According to the carbothermic reduction analysis, the CaF2 does not participate in the carbothermic process. The experimental results demonstrated that the mass loss increased along with increasing CaF2. The percentage was up to 92 pct with 5 pct CaF2.The reduction degree increased with CaF2 more than it without CaF2 obviously. Considering the reduction degree and economic benefit, 5 pct CaF2 was the optimal choice. The purity of metal magnesium reached 95.59 wt pct, which has perfect crystallization and lamellar structure. CaF2 did not participate in magnesia carbothermic reduction in vacuum; instead, it played a catalytic role during the process.