Modeling Crystallization from Solution with Heat Effects

The influence of latent heat of crystallization and the crystal-solution heat transfer in solution crystallization is analyzed by modeling the distribution of the released heat between the crystals and solution. The analysis is based on comparing two population balance models of a batch cooling crystallizer in both exothermic and endothermic crystallization: a bivariate model, characterizing the crystals by their size and mean temperature that allows differentiating the crystals mean temperature from the average temperature of solution, and the corresponding univariate model assuming fully homogeneous temperature field of the crystal suspension. The models include primary and secondary nucleation, and crystal growth taking into consideration the temperatures at which they occur. The numerical analysis was performed using the quadrature methods of moments. The computations revealed that the difference between the mean temperatures of crystals and the average temperature of solution under high rate dynamical conditions may be significant causing observable differences between the numbers of crystals and the mean crystal size. Endothermic crystallization resulted in significantly less number of crystals than the exothermic process produced. The growth and secondary nucleation, and the cooling rate proved to be the determining factors of the process.