Twin screw wet granulation: Granule properties

Abstract

Granulation is an important particle size enlargement process, used in many applications. Granulation has, for many years, been a batch process because of a greater knowledge base. However, the technique of using a twin screw granulator has been found to be very effective at granulating and is an attractive proposition for manufacturing processes because it can be operated continuously. The acceptability of the granules produced varies depending on a number of different parameters. The effect on the properties of granules caused by varying the screw speed, powder feed rate and the ratio of liquid to solid were investigated. This work focuses on the effect that process variables have on the properties of granules and shows that all three-process variables (screw speed, powder feed rate and liquid to solid ratio) had varying influences on residence time and torque, which in turn affected the distribution of size, strength, shape and structure of the granules. For all three-process variables, it was found that by varying the process variables mentioned above resulted in changes to the average particle size distribution. The granules that were produced, however, were irregular, non-spherically shaped granules. The properties of the granules produced by changing each variable in turn were tested and compared in order to determine the optimal conditions for agglomeration using a twin screw granulator, for the used formulation. The ideal conditions will produce to meet the predefined target criteria of mechanically strong and consistent granules, which is important for reliable process operation.