Computational Fluid Dynamics Simulation for Controllable Residence Time Distribution in a Slug Flow Crystallizer

Abstract

Recently, slug-flow crystallizers have been proposed for controlling the product quality and generating uniform crystals. However, there is still a lack of understanding of the residence time distribution (RTD) of slug flow with liquid films. Herein, we developed a computational fluid dynamics model to simulate a gas−liquid slug flow with liquid film phenomenon to obtain the RTD. The proposed model was validated by comparing the resulting slug geometries and RTDs with experiments using various solvents. The results highlighted the appropriate solvent properties and operating conditions required to generate a narrow RTD. Unfavorable conditions yielded wide RTDs with multiple peaks due to liquid-film diffusion. Furthermore, the higher the flow rate, the lower the RTD variance, but the resulting slug formation was unstable and broken. In summary, analysis using the proposed methodology led to controllable slug formation with a sharp RTD, which facilitated the manufacture of high-quality uniform crystals.