A DEM model-based study to quantitatively compare the effect of wet and dry binder addition in high-shear wet granulation processes

Abstract

Wet granulation is widely used in many particulate industries for its capability to improve flowability and handling of powder substances. A mathematical model using discrete element methodology (DEM) was developed to study two kinds of binder addition approaches commonly used during wet granulation in a batch high-shear granulator: wet binder addition (WBA) and dry binder addition (DBA). To define the complex interactions in the systems, a novel integrated DEM algorithm that incorporates powder wetting behavior, capillary and viscous liquid bridge formation as well as binder dissolution was developed. DEM simulation results show a significant difference between the viscous regions in the particle bed for the two systems: the WBA approach quickly wets the majority of the particle bed with a low viscosity fluid, while in the DBA approach fewer particles with higher viscous surface liquid are generated that are responsible for a delayed but faster granule growth rate. The difference in the viscosity of the surface liquid in the two systems lead to varying strengths and numbers of the liquid bridge formed between particles as well as particle velocities. In general, the high viscous areas are dependent on the binder and liquid dispersion which are affected by the mechanical agitation.