Secondary Nucleation from Nuclei Breeding and Its Quantitative Link with Fluid Shear Stress in Mixing: A Potential Approach for Precise Scale-up in Industrial Crystallization

Abstract

The development of robust process scale-up involves a clear understanding of mixing hydrodynamics in crystallization. In the present work, particle imaging velocimetry (PIV) was used to determine the fluid turbulent shear stress (TSS) as a function of scale-up involving cooling crystallization experiments at different agitation rates. At a given scale, with increased agitation rate from 300 to 370 rpm, the secondary nucleation threshold (SNT) and product mean particle size were observed to decrease due to increased TSS. In nuclei breeding, the nucleated crystals at the seed surface are readily sheared off by the increased fluid shear stress. This catalytic process enhanced the rate of secondary nucleation, and hence a decrease in SNT. The SNT and mean particle size increased with scale size due to a decrease in average turbulent dissipation rate which resulted from a decrease in TSS. Secondary nucleation due to nuclei breeding was found to have a quantitative link with TSS. This resulted in a constant SNT...