Twin-screw wet granulation offers the possibility to granulate continuously. A drying step after wet granulation is required to realize a full continuous manufacturing line. Aim of this study was to gain insights into the drying behavior of a continuous vibrated fluidized bed dryer intended for pharmaceutical research and development. A Design of Experiment was conducted to examine the influence of process parameters during the drying of granules using drying temperature, air flow, and vibration acceleration as factors. The obtained temperature and humidity profiles during the drying of lactose-MCC and mannitol granules displayed the first and second drying stage which is spatially resolved. With a higher drying temperature or higher air flow, the second drying stage was achieved earlier. An increase in vibration acceleration shortened the residence time and by this, the second drying stage was reached later at a lower granule temperature and thus higher residual moisture of the granules. Formulation-dependent impact of the drying parameters was observed as lactose-MCC led to smaller granules when increasing the temperature or air flow.
Keywords: Continuous manufacturing; design of experiment; drying behavior; horizontal vibrated fluidized bed dryer; temperature profiles.