DEM-DDM Investigation of the Tablet Coating Process Using Different Particle Shape Models

Tablets are usually spray-coated in the pharmaceutical industry, and coating uniformity is important for the coating process. In this study, discrete element method-discrete droplet method (DEM-DDM) is applied for the investigation of the coating process, tablets are described by different particle shape models, and the influence of different particle shape models on inter-tablet coating uniformity is investigated. Multi-sphere approach with two accuracies, multi-super-ellipsoid approach, and polyhedron approach are applied to describe the biconvex cylinder tablet. The proposed model is verified by a lab-scale coating experiment within a coating pan first. And then, the coating process in a coating drum with baffles is investigated. It can be found that inter-tablet coating uniformity is almost the same for the polyhedron and multi-super-ellipsoid approaches, and the inter-tablet coating uniformity obtained by the multi-sphere approach is lower than both of them. The influence of different parameters on inter-tablet coating uniformity is also studied, including the droplet diameter, the drum rotation speed, the spray range angle, and the nozzle number, which can provide guidance for the tablet coating process.