真空碳热还原红土镍矿制取金属镁的热力学分析及实验研究

通过热力学计算,得出红土镍矿被C还原的化学反应自由能和各还原反应临界温度,表明真空可有效降低化学反应自由能,确定了碳热还原氧化镁制取金属镁的反应温度为1200~1350℃,同时存在氧化镁的硅热还原反应。对实验反应剩余物的元素含量计算分析表明,镁元素成功脱除,脱除率达到99.96%;Ni元素几乎全部回收,直收率达99.67%;绝大部分的Fe、Si也得到了回收,直收率分别为83.98%以及85.35%。冷凝物主要为金属镁,元素质量比达到95.59%,由于冷凝区发生逆反应Mg(g)+CO(g)=MgO(s)+C(s),得到的冷凝物经检测含有少量氧化镁。

Magnesium Extraction from Nickel Laterite by Carbothermic Reduction in Vacuum

We addressed the extraction of magnesium metal from nickel laterite by carbothermic reduction in vacuum.The Gibbs free energy and critical temperature in the nickel laterite de-oxidation by carbon were calculated in thermodynamics.The calculated results show that low pressure significantly lowers the curve of Gibbs free energy and temperature,and that the magnesium carbothermic reduction occurs at the critical temperature ranging from 1200℃ to 1350℃,coinciding with magnesia silicothermic reduction.The contents in the slag were analyzed.The results show that the Mg removal rate was over 99.96%,the direct recovery rate of Ni was 99.67%,and that the recovery rates of Fe and Si were 83.98% and 85.32%,respectively.Mg metal,95.59% pure,dominated in the condensate.X-ray diffraction results show that small amount of magnesia existed in the slag possibly because of the reverse reaction:Mg(g)+CO(g)=Mg(s)+C(s).