Investigating the Effects of Particle's Parameters and Operating Conditions on the Flow Hydrodynamics in a Wurster Type Fluidized Bed Based on DEM-CFD Simulation

Wurster type fluidized beds are widely used in the pharmaceutical industry in which incorporation of various sub-processes such as wetting, granulation, and circulation of particles for coating tablets and small particles. During the coating and granulation processes, numbers of parameters can influence the flow hydrodynamic behavior which plays an important role to control the coating quality. In this research, a DEM-CFD (Discrete Element Method, Computational Fluid Dynamics) coupled model is used to develop an understanding of the effects of particle’s parameters including size, density, and moisture and operating conditions including temperature and velocity on the flow hydrodynamic behavior in a Wurster type fluidized bed coater. For this purpose, the drying and wetting conditions in a laboratory scale Wurster fluid bed coater are modeled and key process parameters including particle circulation, particle Cycle Time Distributions (CTD), Residence Time Distributions (RTD), the average solids concentration in the chamber, and the solid concentration in a cross-sectional area are given and analyzed. By designating appropriate operating and particle’s parameters, the CTD and concentration in the chamber and cross-sectional area can be controlled. Based on the CFD simulation results, the optimum range of the operating condition and the particle’s parameters for the Wurster fluidization process is discussed.