A novel pathway for the preparation of Mg metal from magnesia

High-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride. The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pinpointed. The effect of sample dimension on the above critical stages was investigated respectively. The purity guarantee mechanism of anhydrous magnesium chloride was proposed. After that, magnesium metal was obtained via electrolyzing the anhydrous magnesium chloride-containing molten salt. The new process for the continuous production of magnesium metal from magnesia was proposed and discussed. The incomplete chlorination reaction and the hydrolysis of anhydrous magnesium chloride are the two critical stages affecting the purity of the anhydrous magnesium chloride. The dimension of the sample can influence reaction process and reaction mechanism, and thus the problems of incomplete chlorination reaction and hydrolysis can be solved together. The magnesia content in anhydrous magnesium chloride was below 0.1 wt.% when the ratio of height to diameter of the sample was over 2.43. The content of impurities in the magnesium metal obtained met the specifications of the product Mg9980. The current efficiency was (94.7±1.8)% and the electricity consumption was (9107±97) kW h/t.