Distillative freezing process for separating volatile mixtures and apparatuses for use therein

A crystallization separation process for separating a multicomponent mixture that is at least partly in a liquid state and has two key volatile components, denoted as A-component, that volatile noncrystallizing component present in the greatest amount, and B-component, the volatile crystallizing component, into a B-enriched portion and a B-lean portion through formation of a B-enriched solid mass, comprising a determination that the two key volatile components form a binary system

• (a) whose characteristic vapor pressure ratio defined as the ratio of the vapor pressure of A-component to that of B-component both evaluated at the triple point temperature of B-component is in the range of 0.1 to 10 and is less than the ratio of the heat of sublimation to the heat of melting of B-component evaluated at the triple point temperature of B-component, and
• (b) whose constant pressure phase diagram that includes a three phase (B-enriched solid, liquid and vapor) state has a two phase (B-enriched solid and vapor) region covering a substantial concentration range above the temperature of the three phase state and a two phase (B-enriched solid and liquid) region below the temperature of the three phase state,
• and a first step of forming a first vapor mixture and a first condensed mass that comprises a mother liquor and a solid phase mass enriched in B-component by concurrently vaporizing the volatile components from the mixture in a first zone under a first temperature and a first pressure that are respectively lower than the triple point temperature and the triple point pressure of the pure B-component, and a second step of separating at least a major fraction of the A-component from the first condensed mass to thereby produce a B-enriched first condensed mass.