Optimization of a Two Step Batch-Cooling Crystallization Process

A population balance equation describing unseeded batch cooling crystallization processes was simplified with the method of moments, and the processes were simulated using kinetic models incorporating crystal growth, primary nucleation, and secondary nucleation. These models were used to predict the development of concentration and crystal size distribution (CSD) over time. A multi-objective optimization was solved in order to maximize mean crystal size as well as to decrease variance of the CSD. It is found that a two-step cooling strategy, which holds the temperature constant in the middle of the cooling to induce primary nucleation, can improve the process, in comparison with a linear cooling profile. Nucleation and growth kinetics were analyzed to discuss the reason for this advantage in the two-step cooling system.