A Mechanistic Model for Granule Breakage in Twin Screw Granulation

Wet granulation is a particle size enlargement process commonly used in solids handling industries to alleviate issues related to fine powder handling such as powder segregation, dust hazards, and poor flowability. Twin Screw Granulation provides several advantages over other methods of wet granulation, such as compact size, flexible design, flexible throughput, and robust performance, and is thus becoming increasingly common in several industries.

Granule breakage has been shown to be an important rate process in controlling the formation of large agglomerates as well as providing good liquid distribution. This presentation describes a mechanistic model for granule breakage in Twin Screw Granulation. Breakage-isolating experiments were performed at various screw speeds and powder feed rates using model granules having a wide range of dynamic yield strengths. The breakage probability and daughter size distribution were measured as functions of the formulation and process parameters. The process parameter dependence was quantified using the dimensionless powder feed number. Breakage probability was observed to be a strong function of the dynamic yield strength and the powder feed number. Breakage rate and daughter size distribution models were proposed based on fundamental understanding of the breakage mechanisms in Twin Screw Granulation.