Extraction of magnesium from garnierite by carbothermal reduction in vacuum

The aim of the traditional pyrometallurgical processes is to extract nickel and iron in garnierite, but it is difficult to extract magnesium of higher value in minerals. Aimed at solving this problem, the extraction of magnesium from garnierite is proposed and studied in this study. The effects of different reduction temperatures, different reduction times and dosage of CaO additions in experiments were investigated. The experimental results indicate that the extraction rate of magnesium can reach 93.23% when the mass ratio of mineral/reductant is 100:28.3, system pressure is 50 Pa, reduction temperature is 1823 K, and reduction time is 120 min, and, at the same time, the purity of metal magnesium in the condensate can be up to 91.88%. Under these conditions, the extraction rate of magnesium can increase to 99.45% by adding 25 wt% CaO, and the purity of the metal magnesium in the condensate exceeds 90%. CaO as the additive can effectively improve the extraction rate of magnesium and promote the recovery and utilization of magnesium. The mechanism is that CaO replaces -O-Mg- in the -O-Mg-O-Si-O- structure to form free MgO, which is reduced to Mg vapor by carbon and condensed into magnesium metal in the condensation zone to achieve the purpose of removing and collecting Mg from the garnierite. At the same time, the reduced slag is rich in Ni and Fe, which can be used for the extraction of Ni and Fe. Compared with the traditional pyrometallurgical process, the process can extract magnesium from garnierite, and the process is short and its operation is simple, which is a potential technology.