A comparative study on the nucleation, growth, and agglomeration kinetics of potassium dihydrogen phosphate crystal in circulating fluidized-bed crystallizer

The crystallization in a fluidized-bed crystallizer has recently received increasing interest for separation and purification of crystals. Past investigations on potassium dihydrogen phosphate (KDP) crystallization mainly focused on process efficiency and thermodynamics and less on kinetics. In this paper, the fluidized crystallization technology is used to investigate a KDP crystallization process. The mechanisms involved in crystal formation have been explored by observation of a continuous withdrawal of a suspension containing target crystals having certain size distribution. The crystallization process of KDP is researched to investigate the key parameters (suspension density [M-T], solution supersaturation [Delta C], and fluid shear force [expressed by circulation flow rate; Re]) influencing crystal growth, nucleation, and agglomeration process. Three proposed crystallization kinetic models about crystals growth, nucleation, and agglomeration rates are developed and validated against data from the fluidized-bed crystallizer. Taking advantage of multivariate nonlinear regression analysis, crystallization kinetic parameters are obtained by adopting the kinetic model in fluidized-bed crystallization process. The comparative research of three crystallization kinetic rates is also studied. The results indicated that the parameters given by the kinetic mathematics model fit well with the experimental data. The error rate between the experimental and calculated value is also controlled within a reasonable range.