真空碳热还原煅白制取金属镁的冷凝实验研究

Vapor Condensation of Magnesium in Vacuum Carbothermic Reduction of Calcined Dolomite

简要分析了真空碳热还原煅白制取金属镁过程中镁蒸气冷凝所遇到的主要问题,并通过理论计算和实验提出了解决方案。首先从实验结果的对比中发现,真空碳热还原煅白的冷凝产物会发生燃烧甚至爆炸主要是钠钾等碱金属的自燃所引起的。在对冷凝区的热量分布进行计算分析后,对相应设备进行了改造,结果表明,改造后的冷凝设备对金属镁的直收率有很大提升。最后,对现存的传统真空冷凝设备提出了多级冷凝的改造方案,实验结果表明冷凝产物形貌发生明显改善,晶粒尺寸加大、氧化率降低,钾钠蒸气与镁蒸气分级冷凝,达到安全生产的要求。

The major technical problems, involving Mg vapor condensation in vacuum carbothennic reduction of cal- cined dolomite, were theoretically and experimentally studied. We found that the serf-ignition of alkali meals, such as Na and K,results in burning and/or explosion of the condensed products, the crystalline grains of Mg in particular. A novel multistage condensation technique （by condensing Na, K, and Mg, separately） was developed, based on the calculation of the temperature field distribution. The results show that the newly-developed multistage condensation eliminated the burning-loss problem,and significantly improved the quality of Mg powder. For example, a higher and more stable Mg recovery efficiency, a bigger grain size with better surface morphology, and a lower oxidation rate.