Suppression of Secondary Nucleation via Crystal Fluidization in a Modified DTB Crystallizer: Preparation of Large Crystals with Narrow Crystal Size Distribution

Large crystals with narrow crystal size distribution (CSD) are beneficial for filtration and drying and are the goals pursued by industrial crystallization. In traditional stirred crystallizers, the secondary nucleation caused by crystal–impeller collisions is the main reason for the small crystal size and uneven distribution. This study investigates the optimization of structural parameters in the draft tube baffle (DTB) crystallizer to promote crystal fluidization in the annular channel. The proposed design spatially separates the crystal suspension zone from the impeller zone, demonstrating the effective suppression of secondary nucleation. The influence of factors such as bottom suspension, structural parameters, particle size, and solid content on the solid–liquid phase distribution in the DTB crystallizer was studied through a CFD simulation. Based on the simulation optimization results, a laboratory-scale fluidized draft tube baffle (FDTB) crystallizer was designed and manufactured. The particle cloud height and suspension state in the FDTB crystallizer are in good agreement with the simulation results. The FDTB crystallizer yields crystals with an average particle size 6.8 times that obtained from a traditional stirred crystallizer, along with a 42% reduction in the coefficient of variation.