Countercurrent column crystallization of ternary mixtures with different mutual solubilities of components in the solid state

Abstract

Characteristic features of the mass transfer in separation of ternary organic mixtures of two types and different compositions in a countercurrent crystallization column are studied. In a mixture of the first type, all the components form continuous series of solid solutions of each other, and in mixtures of the second type, only one pair of components does. The temperature and concentration distributions along the height of a modernized column in the startup period and steady-state operation are experimentally investigated. It is found that the concentration profile of the component with an intermediate melting point in the separation of a mixture of the first type has an extremum. Mixtures of the second type behave as pseudobinary mixtures if the crystallization occurs in the field of the component that forms simple eutectics with the two other components. The results of separation of ternary and binary mixtures of the same components are compared. It is shown that it is possible to increase the efficiency of separation of binary mixtures with solid solutions by controlled introduction of a third component.