Coalescence of deformable granules in wet granulation processes

In this work coalescence of deformable granules in wet granulation processe s is modelled. The model accounts for both the mechanical properties of the granules and the effect of the liquid layer at the granule surface. It is an extension to the model of Ennis ct al. (1991) to include the possibility of grannule plastic deformation during collisions. The model is written in dimensionless groups such as viscous and deformation Stokes numbers and th e ratio of granule dynamic yield strength to granule Young's modulus (Y-d/E *). These variables are bulk parameters of the powder-binder mixture and al so functions of the process intensify. The model glues the conditions for t wo types of coalescence - type I and type II. Type I coalescence occurs whe n granules coalesce by viscous dissipation in the surface liquid layer befo re their surfaces touch. Type II coalescence occurs wizen granules are slow ed to a halt during rebound after their surfaces have made contact. The mod el explains some of the trends observed in the literature, ale pi prelimina ry validation of the coalescence criterion with drum granulation data is en couraging. An extension is also made to the case of surface dry granules, w here liquid is squeezed to the surface during granule information.