Fractional crystallization process

Abstract

A single or multi-step fractional crystallization process and apparatus for separating fluid material having two or more components, the material flowing down a cooled wall surface and a component crystallizing thereon. Each step comprises a single crystallization and all steps of a complete cycle are conducted within a single crystallizer.

I claim: 
     
       1. A method of segregating a high melting point ingredient of an initial liquid mixture of high and low melting point ingredients by a fractional crystallization procedure carried out on amounts of said mixture of successively higher concentration of said high melting point ingredient contained in a corresponding series of vessels, comprising in a cycle of operation as a first step the passing of an amount of the mixture contained in the first vessel of said series of vessels over a cooled surface thereby causing formation of a layer of crystals of said high melting point ingredient on said cooled surface, and draining the remainder of said mixture into a vessel for mother liquor, as a second step for passing of .[.an.]. .Iadd.a .Iaddend.heated amount of the mixture contained in the second vessel of said series of vessels over said layer of crystals while suspending the cooling of said surface thereby melting said crystals, .Iadd.recommencing cooling of said surface and circulating the mixture to form a layer of crystals on the cooled surface, .Iaddend.and returning the resulting liquid mixture to said first vessel, repeating  .[.said second step.]. .Iadd.the same procedures beginning with the aforementioned second step but with mixture contained in each succeeding vessel of said series of vessels and .Iaddend.with mixture from each succeeding vessel returned to the respective preceding vessel until the contents of the next to the last vessel of said series of vessels has been crystallized on said cooled surface and the remaining mixture has been returned to the next preceding vessel, the layer of crystals on said cooled surface then being of the required concentration, passing the mixture contained in the last vessel of said series of vessels in heated condition over said last mentioned layer of crystals and returning a first portion of the resulting mixture to said next to the last vessel until filled, a second portion to the last vessel until filled, and a third portion to a place of use or storage, draining said vessel for mother liquor, filling said first vessel with another supply of said initial liquid mixture which completes said cycle of opertions, and repeating said cycle of operations as required. 
     
     
       2. The method according to claim 1, in which the mixtures from said successive vessels are passed as a descending film over said surface. 
     
     
       3. The method according to claim 1, in which solvents are added to at least some of said vessels.