Crystallization

Abstract This article provides an overview of crystallization that can be used by scientists and engineers, regardless of their familiarity with the operation. Key aspects of using crystallization for separation, purification, or other purposes are covered; especially noteworthy is the coverage relating product purity, morphology, polymorphs, solvates, and size distribution to the kinetic phenomena of crystal nucleation and growth. Variables such as mixing and the rate at which supersaturation is generated can influence the purity of recovered crystals. Crystal morphology can be affected by variables modifying inherent growth kinetics of crystal faces or by changing interfacial or solution properties. Theory is mixed with empiricism in showing the role of operating variables (supersaturation, magma density, and agitation) in determining crystallization kinetics. Methods are illustrated for coupling crystallization kinetics with population balances for continuous and batch crystallizers to determine crystal size distributions. In addition, the bases of using selective removal functions (clear‐liquor advance, classified fines removal, and classified product removal) to influence the characteristics of size distributions are presented. Qualitative characteristics of batch crystallizers are introduced, and the role nucleation plays in determining the general behavior of crystal size distributions from such system is described. Furthermore, a summary of industrial practice and equipment (solution and melt crystallization00) is presented. Finally, brief reviews are given of the importance of preferential crystallization, eutectic freeze crystallization as well as the crystallization of proteins.