Twin screw granulation : a detailed study

Granulation is the process by which a large number of fine particles (primary particles) are agglomerated together in the presence of a liquid to form a smaller number of larger particles (granules). The process of granulation can be carried out as dry or wet depending upon process conditions. Dry granulation is where the powdered particles, with or without the binder, are compressed together under high pressure to form granules. Wet granulation begins with the addition of a liquid binder to the powders that are to be granulated. There are well known and established techniques such as high shear mixers and fluidised beds which are currently used for the wet granulation of materials. Being batch processes these techniques can process material of variable quality and consistency. In the pharmaceutical industry the production of granules is still mostly based on a batch concept. Continuous process forms are considered to be feasible for only large volume productions and too inflexible for product changes which can occur daily. However, it is gaining in popularity recently since it provides several advantages over batch processes. Techniques such as roller compaction and spray drying are used for the continuous production of granules. In this context, twin-screw granulation can be seen as the latest process form for continuous wet granulation. Some studies have reported the utility of this equipment in continuous wet granulation. However, there are many other possibilities still left undiscovered. The present study was targeted to characterize the process of wet granulation in a twin screw granulator. The effect of variables like powder feed rate, liquid to solid ratio, screw speed, viscosity of granulation liquid on the granulation behavior and granular properties were studied. To determine the effect that each of these had on the properties of the granules, analysis was carried out to determine the size, shape, flowability and strength of the granules. The flow of powder in the twin screw granulator was studied using PIV. Finally, the granulation process along the length of screw was studied. The data will be useful to map the process of granulation using a twin screw granulator.EThOS - Electronic Theses Online ServiceGBUnited Kingdo