Continuous twin screw wet granulation: The combined effect of process parameters on residence time, particle size, and granule morphology

In this study, a set of 24 experiments was designed to understand the combined effect of different process parameters, i.e. material feed rate, liquid-to-solid (L/S) ratio, screw speed, and screw configuration on the residence time distribution, granule morphology, and particle size distribution in twin screw wet granulation of microcrystalline cellulose. It was shown that residence times were longer at higher L/S and lower screw speeds. However, the most dominant effect on mean residence time had screw configuration, with longer residence times observed with increasing complexity of the screws employed. Scanning electron microscopy and laser diffraction measurements showed accordingly that the most important quality attribute affecting size of granules is L/S ratio. The relationships between input and output parameters observed for our low throughput setup generally match those concerning higher throughput granulators described in literature.