On Multiple Distillation or Crystallization Refining at Given Yield

Abstract

A comparison is made of the Cn concentration of the impurity with a separation coefficient β < 1 in the product of n-fold refining by simple distillation or normal directed crystallization with the concentration of C1 impurity in the product of 1-fold refining with the same initial concentration and the same final yield G. The dependence Cn/C1 from the process parameters n, G, and β allowing to evaluate the feasibility of using n-fold refining instead of a single one is shown. The excess of Cn over the minimum achievable level increases with a decrease in β < 1 and with an increase in n and G.