Model-based analysis of stirred cooling crystallizer of high aspect ratio crystals with linear and nonlinear breakage

Abstract

Abstract 2D population balance model is presented for stirred cooling crystallizer of high aspect ratio crystals including primary and secondary nucleation, size-dependent growth of the two characteristic crystal facets and linear and nonlinear breakage along the crystal length. Three breakage mechanisms are modelled: crystal-impeller and crystal-wall collisions linear and crystal–crystal collisions nonlinear breakage processes. The 2D population balance equation is reduced into a system of moment equations for the mixed moments of length and width variables which is closed applying the quadrature method of moments and solved by using a three point QMOM-ODE method. It was shown that strong interactions exist between the secondary nucleation, crystal growth and breakage processes connected by the CSD. The stirring rate has strong impact on crystallization of high aspect ratio crystals forming the crystalline product directly by breakage. The crystal-impeller breakage proved to be the dominant process but the crystal–crystal breakage also play significant role.