Vacuum distillation refining of crude lithium (I)──Thermodynamics on separating impurities from lithium

Thermodynamics on vacuum refining process of the crude lithium has been studied by using separation coefficients of impurities in the crude lithium and vapor liquid equilibrium composition diagrams of Li i binary alloy (i stands for an impurity) at different temperatures. Behaviors of impurities in the vacuum distillation process have been examined. The results show that fractional vacuum distillation should be taken to obtain metal lithium with high purity more than 99.99% Li, in which metal K, Na and partial Mg are volatilized at lower temperature of 673 ～ 873?K. Lithium is distilled from the residual liquid containing other impurities, such as Ca, Mg, Al, Si, Fe and Ni at higher temperature of 873 ～ 1?073?K and the chamber pressure is less than the critical pressure of lithium.