(116f) Scaling of Continuous Twin Screw Wet Granulation

Continuous twin screw granulation has been the subject of much interest in the past few years. The influence of process parameters on granule properties (size distributions, shape, porosity and strength) has been studied by several researchers [1]–[3]. Their findings, however, are applicable only to the equipment scale on which the experiments were conducted leading to difficulties during scale up. The approach taken here was to identify key dimensionless groups that control granule properties and develop a model to map the operating space of the Thermo Fisher 11 mm, 16 mm, and 24 mm twin screw granulators (TSGs). While the process parameters themselves are scale dependent, these dimensionless groups are scale independent.

Three dimensionless groups for scaling were identified and tested. A distributive feed screw (DFS) was used as the screw configuration in all three TSG scales. The DFS configuration is not reported to have been previously characterized, thus this study also served to mechanistically understand the effect of a DFS as the screw configuration. The results from the DFS configuration were compared in all three TSG scales. In addition, the effect of the DFS configuration was compared to the effect of the distributive mixing elements [4] and kneading elements [5] configurations, which were previously characterized in our group.

[1]      D. Djuric and P. Kleinebudde, “Continuous granulation with a twin-screw extruder: Impact of material throughput,” Pharm. Dev. Technol., 15, pp. 518–525, 2010

[2]      R. M. Dhenge, J. J. Cartwright, D. G. Doughty, M. J. Hounslow, and A. D. Salman, “Twin screw wet granulation: Effect of powder feed rate,” Adv. Powder Technol., 22, pp. 162–166, 2011

[3]      R. M. Dhenge, R. S. Fyles, J. J. Cartwright, D. G. Doughty, M. J. Hounslow, and A. D. Salman, “Twin screw wet granulation: Granule properties,” Chem. Eng. J., 164, pp. 322–329, 2010

[4]      R. Sayin, A.S. El Hagrasy, J.D. Litster, "Distributive mixng elements: Towards improved granule attributes from a twin screw granulation process.," Chem. Eng. Sci., 125, pp. 165-175, 2015

[5]      A.S. El Hagrasy, J.D. Litster, "Granulation rate processes in the kneading elements of a twin screw granulator.," AIChE J.., 59, pp. 4100-4115, 2013