Experimental Study on the Reversion Reaction Between Magnesium and CO Vapor in the Carbothermic Reduction of Magnesia Under Vacuum

The mechanism of magnesia production was investigated experimentally in reversion reaction process in vacuum. Condensation temperature and temperature gradient which effected on the condensation of the magnesium vapor produced by magnesia carbothermic reduction in vacuum have been investigated by Mg recovery efficiency, XRD, SEM and EDS. The results show that the higher recovery efficiency was obtained when the condensing temperature which is closer to the dew point of magnesium in the constant temperature gradient. Under the condition of appropriate condensation temperature, the lower the temperature gradient is, the better the crystallization of magnesium vapor is. The XRD patterns of the profile and undersurface of the condensation product of 1873 K show that the profile of the condensation contains Mg only and the purity of the metal magnesium is high. But the undersurface of the condensation contains Mg and MgO. The SEM and EDS images of the profile and undersurface of condensation indicate that the microstructure of the undersurface of condensation is largely flocculent structure and irregular arrangement and the crystal morphology was poor and particles were also tiny. This is due to magnesium vapor reacted with CO vapor at cooling phase, MgO and C obtained covered the undersurface and stopped magnesium vapor condensing.