Analysis of Magnesia Carbothermic Reduction Process in Vacuum

The mechanism of magnesia carbothermic reduction was investigated experimentally in a reduction reaction process in vacuum. The thermodynamic calculation results showed that the initial reduction temperature between MgO and C was 1500 K (1227 °C) at 50 Pa. Other reduction reactions did not occur between the temperature 300 K and 1900 K (27 °C and 1627 °C) and 30 to 100 Pa. Based on the analysis of experimental results, the initial reduction reaction temperature was 1553 K (1280 °C), and it matched well with the thermodynamic calculations. The gas–solid reaction between MgO and CO did not occur at 1723 K (1450 °C), 30 to 100 Pa. Therefore, the main reduction reaction was MgO (s) + C (s) = Mg (g) + CO (g) in vacuum. This reaction belonged to the solid–solid reaction type, the condensing product was obtained in the condensation zone, and the main component of the product was metal magnesium. A little magnesia was also obtained in the condensing product due to the reverse reaction.