Study On The Scale-Up Of Fluidized Bed Crystallizer

Industrial crystallization has been widely used in the fields of chemical, medicine and environmental protection. In practical production, crystallization process faces a tricky difficulty that is scaling-up from lab to industrialization because of the complicated process. Comparing the crystallization process in the laboratory scale crystallizer with that in the industrial crystallizer, the big difference is the flow field in the crystallizer. Concerning the crystallization process, the different flow fields in different scales of crystallizer produce different concentration distributions for different sizes of crystals, which provides different local environment for the crystal nucleation and crystal growth, the different sizes of product crystals will be obtained. Therefore, concentration distribution of the crystals in the crystallizer has to be taken into account in the scale up of the crystallization process.It was proved that the solid suspension distribution in the crystallizer had a high relativity with the state of flow. The effect of solid suspension on crystallization is very complicated and difficult to be obtained with general experimental method.Computational Fluid Dynamics (CFD) used computer as a tool to study the effect of fluid flow on processes of mass transfer, heat transfer and other transformation in different processes, through the numerical method of motion equations. And now, CFD was considered as a powerful tool for simulating the process of industrial crystallization.The aim of this paper was to study the scale-up process of crystallization with CFD. Different scales of fluidized bed crystallizers were selected as geometry models, and multiphase model was Euler-Euler. In the work, standard k-ε model was employed to describe turbulent fluid flow, since it was widely used in the industrial cases. The content are as following:The variation of specific energy input in scale-up process was investigated, and set up a new scale-up criterion with empirical equation. As well, the flow field was studied with variable particle sizes and summarized the effect of particle size on crystallization scale-up.