| The properties, the application and the consumption of metal lithium and its compounds are discussed in the thesis. The preparation methods of crude lithium and high purity lithium are overviewed. The principles involved in the process of vacuum distillation refining of crude lithium, vacuum thermal decomposition of Li2CO3 with carbon and vacuum carbothermic reduction of L120 have been analyzed with thermodynamic and kinetic calculation. The refining process of crude lithium by vacuum distillation was experimentally studied. In particular, the preliminary study on the process of producing metal lithium from Li20 by vacuum carbothermic reduction was also carried out experimentally and a novel process for preparing metal lithium has been proposed. The thermodynamics and kinetics on the refining process of crude lithium by vacuum distillation are studied. The separation coefficients of the impurities in crude lithium are calculated. The liquid-vapor equilibrium composition diagram of Li-K, Li-Na, Li-Mg, Li- Ca, Li-Al, Li-Si, Li-Fe and Li-Ni binary system are worked out in a range of 573K to 1273 from which the quality of distillated lithium is how to be influenced by contents of impurities and distillation temperature is shown obviously. The maximum evaporation rates of K, Na, Li, Mg, Ca, Al, Si, Fe and Ni, the critical pressure and the accommodation coefficient of lithium during the process of distillation are also calculated respectively. The distillation process of metal in vacuum is discussed. The influences on distillation by distillation temperature, chamber pressure and condensation parameter are studied. The results from thermodynamic and kinetic analyses on lithium refining process by vacuum distillation indicate that the impurities in lithium can be classified as three kinds according to the separation coefficient: P >1 as K and Na. P <1 as Al, Si, Fe and Ni, P ~ 1 as Ca and Mg. The former two kinds of impurities can be removed easily from lithium by vacuum distillation while the removal of the impurities of Ca and Mg shows more difficult. In order to separate the impwities of crude lithium more completely in vacuum, fractional distillation should be adopted in the process. That is the impurities such as low boiling point elements of K and Na are distillated at lower temperature, then Li is distillated at higher temperature while the high boiling elements of Al, Si, Fe and Ni are remained in residue. By controlling the parameters, Ca and Mg can also be separated with Li more completely. The distillation rate of lithium can't increase infinitely as the chamber pressure decreases because there is a known critical pressure during the process lithium's vacuum distillation. The maximum chamber pressure should be controlled just a little less than the critical pressure to ensure the higher distillation rate of lithium during the evaporation process. With the feedstock of industry-grade lithium, the refining process of lithium by vacuum distillation was approached in more details. The principal parameters involved inthis process are the first phase (lower temperature) distillation temperature and distillation time, the second phase (higher temperature) distillation temperature, the varieties and quantities of the additives were examined. The optimized technical parameters of vacuum distillation refining have been obtained: the first step distillation temperature ~?50C, the first phase distillation period is 60mins, the second phase distillation temperature 700(2, the additive is B203 and its quantity is 2.0%(wt.). On this condition, the metal lithium with a h...
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