SEPARATION OF QUATERNARY CONJUGATE SALT SYSTEMS BY FRACTIONAL CRYSTALLIZATION

A method is presented that synthesizes fractional crystallization sepa ration processes to obtain pure solids from conjugate salt solutions. The method, which includes a procedure to generate phase diagrams by u sing solubility products, explains how to calculate concentrations of all components in a system given a point on a Janecke projection. Both multivalent ions and species that exhibit complex-ionic equilibrium a re considered. For solutions from which only simple salts crystallize, three separation classes are identified, The classification is based on the composition of the feed, the characteristics of the phase diagr am, and the product salts. Class I separates compatible salts, Class I I incompatible salts, and Class III two compatible salts and one incom patible salt. Process paths and design equations for each class are al so presented. Guidelines proposed select the separation sequence and t he stream compositions based on the effects of the design variables on stream flows and on total amount cost. The method is applicable to sy stems in which hydrates and double salts are present. An example given shows how to obtain simple salts from these systems.