Comparison of Extraction Behavior of Magnesium from Magnesite/Magnesia by Aluminothermic Process in Flowing Argon

The reduction process of extracting magnesium directly from low-grade magnesite by aluminothermic method in flowing argon was investigated. Then the difference between this process and the process of extracting magnesium directly from magnesia was compared and analyzed. The results indicated that the reduction percentage of magnesium oxide was higher when extracting magnesium from MgCO 3 –Al pellets at the same temperature and time compared to MgO–Al pellets. The reduction percentage of magnesium oxide could reach more than 70% at 1523 K for 2 h. The kinetic models of extracting magnesium from MgCO 3 –Al and MgO–Al systems in flowing argon could be explained by three-dimensional diffusion (D3) and first-order reaction model (F1), respectively. The apparent activation energies were 232.68 kJ/mol and 110.01 kJ/mol, respectively. SEM analysis showed that the reduction products of MgCO 3 –Al pellets formed MgO·Al 2 O 3 phase with regular octahedral structure at high temperature. For MgO–Al pellets, because MgO was easy to absorb moisture and deteriorate, with the progress of reduction reaction, layered double hydroxide compounds would be formed in the reduction products. Graphical Abstract