A SIMPLIFIED APPROACH TO THE OPERATION OF A BATCH CRYSTALLIZER

A general model for a seeded cooling batch crystallizer based on first principles is developed, incorporating either size‐dependent or size‐independent growth rates. A simple approach is proposed to obtain temperature‐time trajectories at constant supersaturation or nucleation rate, without resorting to optimization techniques. Cooling curves at constant supersaturation, which lead to a substantial improvement (a smaller coefficient of variation and a larger mean size) of the terminal crystal size distribution, can be determined even in the absence of precise nucleation and growth kinetics, whereas properties related to the crystal size distribution are sensitive to such kinetics. Experimental results for the potassium sulfate‐water system, potash alum‐water system, and hexamethylenetetramine in ethanol, methanol, and 2‐propanol/water are predicted reasonably well by the model. Extension to any type of batch crystallization with super‐saturation induced by means other than cooling, such as reactive precipitation and salting out, is briefly discussed. Copyright © 1990 Canadian Society for Chemical Engineering