Nucleation, growth, and aggregation kinetics of KCI produced by stirred crystallization

Crystallization kinetics serve as the foundation for understanding crystallization behavior and designing crystallizer scale-ups. This study investigates the crystallization kinetics of Potassium Chloride (KCl) during the cooling crystallization process, utilizing the intermittent dynamic method under varying experimental conditions within a continuous mixed-suspension mixed-product-removal (MSMPR) crystallizer. Concurrently, the study explores the functional relationship between particle size and crystal growth rate. Kinetic rates were determined using a least-squares method for multivariate linear regression, and the validity of the kinetic model was confirmed through experimental testing. The findings suggest that the KCl crystallization process is governed by surface reaction, and that coalescence occurs between particles. It was observed that an increase in suspension density, supersaturation ratio, and stirring rate enhances both the nucleation rate and growth rate of KCl. The factors influencing the nucleation rate of KCl crystals, in order of significance, are stirring rate, supersaturation, and suspension density. Additionally, an increase in stirring rate was found to inhibit aggregation. Further investigation revealed that the growth rate of KCl crystals is size-dependent. Consequently, growth rate equations for KCl during the cooling crystallization process were derived using two particle-size-dependent growth rate models. When compared to the CR model, the MJ2 model demonstrated superior relevance and adaptability to experimental results in describing the population density distribution of KCl, with an average relative error of approximately 13.37% between model values and experimental data. This research offers valuable theoretical guidance for optimizing the crystallization process and designing industrial crystallizers.