Mechanistic modelling of the drying behaviour of single pharmaceutical granules.

The trend to move towards continuous production processes in pharmaceutical applications enhances the necessity to develop mechanistic models to understand and control these processes. This work focuses on the drying behaviour of a single wet granule before tabletting, using a six-segmented fluidised bed drying system, which is part of a fully continuous from-powder-to-tablet manufacturing line. The drying model is based on a model described by Mezhericher et al. and consists of two submodels. In the first drying phase (submodel 1), the surface water evaporates, while in the second drying phase (submodel 2), the water inside the granule evaporates. The second submodel contains an empirical power coefficient, β. A sensitivity analysis was performed to study the influence of parameters on the moisture content of single pharmaceutical granules, which clearly points towards the importance of β on the drying behaviour. Experimental data with the six-segmented fluidised bed dryer were collected to calibrate β. An exponential dependence on the drying air temperature was found. Independent experiments were done for the validation of the drying model.