Investigation of the Effect of Raw Material Properties on the Breakage Rate Process in a Twin Screw Granulator

Granulation is often used as a size enlargement unit operation in various solid handling and powder processing industries. Granulation helps to mitigate issues related to poor flowability, dust hazards, and powder segregation. Twin screw granulation (TSG) is becoming increasingly relevant due to its compact size, continuous and robust mode of operation, flexible and customizable design, and flexible production capacity.

Granule breakage has been shown to be an important rate process in TSG. This presentation describes the experiments designed to explore granule breakage in TSG. Cylindrical pellets were prepared from model powders of varying particle sizes and binders of varying viscosity. The powder and binder systems were chosen such that the pellets had a range of dynamic yield strengths (DYS). The breakage probability and daughter size distribution of the pellets was measured as a function of the DYS of the powder/binder system as well as for different screw designs. It was observed that for conveying screw elements, the breakage probability is a strong function of the DYS, whereas for distributive mixing screw elements, breakage is governed mainly by geometric effects.