Theoretical estimation of mass transfer coefficients in solution crystallization

Abstract

Generally, diffusion through film thickness is used for correlating data in the industrial crystallization processes. Furthermore, mass transfer is an important phenomenon in most chemical processes and studies involving determination of mass transfer coefficients are necessary for a better estimation of equipment performance. Solid-liquid mass transfer coefficients in stirred systems have received substantial attention in the past due to their practical applications. In contrast, little information is available on solid-liquid mass transfer in crystallization systems, despite the importance of crystallization. In this work, an expression for the mass transfer coefficients in solution crystallization has been developed based on the Stefan problem formulation. The model is able to predict a finite mass transfer coefficient when the layer thickness vanishes. The obtained mass transfer coefficients agree with previously reported experimental data. Furthermore, it is found that the stagnant film for mass transfer has oscillatory behavior, and this behavior is a function of residence time.