Thermodynamics of high-purity calcium production

We present the results of thermodynamic analysis of the behavior of gaseous and gas-forming impurities at different stages of calcium production, including electrolysis of calcium chloride, vacuum distillation of calcium from copper–calcium alloy, mechanical dispersing, and remelting and granulation of distilled calcium from the melt. The mechanisms of transfer of H, C, N, and O impurities at all stages of the processes under study are discussed. It is shown that in order to produce high-purity calcium, deep degassing needs to be performed when heating the materials loaded at the distillation, remelting, and granulation stages under condition that the equipment is highly air-tight. Distillation of calcium is recommended to be carried out at temperatures that exceed the process start temperature by no more than 20 K.