Crystallization with Sinusoidal Modulation of Stirrer Speed: Frequency Response Analysis and Secondary Nucleation Kinetics

In crystallization, obtaining the proper nucleation and growth parameters is essential to the design of crystallization processes. This paper studies the response of crystal size distribution (CSD) to periodic oscillations in the stirrer speed within a mixed suspension mixed product removal (MSMPR) crystallizer. We start from a model in which all processes are coupled. Stirrer speed oscillations drive oscillations in the secondary nucleation kinetics. Oscillations in the nucleation rate drive damped waves in the population distribution of growing crystals. Changes in the population of crystals drive changes in the supersaturation. Supersaturation along with the total mass of crystals influences the nucleation rate. At low frequencies, including the pseudo-steady-state limit, effects of a change in stirring rate are attenuated by the coupling to other processes. At high frequencies, stirring rate oscillations lead to pronounced waves in the CSD that might facilitate studies of secondary nucleation.