The best objective function for seeded batch crystallization

Although many researchers have optimized the operation of seeded batch crystallization, there remains little understanding of the effect of the choice of objective function on the optimization and no consensus on which objective function is best. In this work, different objective functions for seeded batch crystallization are compared by calculating the supersaturation trajectory that minimizes each objective function and then comparing the results of each trajectory. We show that some objective functions lead to trajectories that cause excessive nucleated mass and should be avoided. We conclude that the best objective function in most cases is to minimize the nucleated mass. This also corresponds to maximizing the growth of seeds, and leads to a product with a large volume mean size. We also show that the width of the product crystal size distribution can be controlled much more effectively by manipulating seed properties than by adjusting the supersaturation trajectory. © 2012 American Institute of Chemical Engineers AIChE J, 59: 390–398, 2013