Continuous Granulation in a Twin Screw Granulator

Dr. James Litster, Professor of Chemical Engineering,Professor of Industrial and Physical Pharmacy, Director, Center for Particulate Processes and Products, Purdue University

28 October 2015 at 11:30

Location: BSB 137

A Twin Screw Granulator (TSG) is the preferred equipment for continuous wet granulation in the pharmaceutical industry owing to its flexible design, optimum throughput, and robustness toward variation in raw material attributes.  It also offers the opportunity for regime separated granulation where different granulation processes are individually optimized in different sections of the screw.  However, the inherent flexibility of the TSG means a very large number of degrees of freedom in the operating space related to the powder feed, liquid feed and the equipment itself such as screw speed, shaft length and screw configuration.  This talk will firstly present an overview of the principles of wet granulation, especially the rate processes which control granule attributes.  Experimental results from a careful study of the rate processes occurring in each type of screw element: conveying elements, kneading elements and distributive mixing elements will then be presented.  The impact of each mixing element on granule size and liquid distribution, shape and density is described.  Default screw configurations borrowed from application of the twin screw as an extruder perform poorly as granulator configurations.  Implications for optimizing the TSG, developing predictive models and scaling rules are discussed.  Testing of an on-line image analysis system for real time granule size measurement is also presented.



Jim Litster is Professor of Chemical Engineering and Professor of Industrial and Physical Pharmacy at Purdue University.  Prior to his appointment at Purdue in 2007, he spent 20 years in academic positions at The University of Queensland including Head of Chemical Engineering and Head of School of Engineering. His research area is Particulate Products and Processes.  He is an international leading expert on wet granulation with over 25 years experience in the field.  His key contributions include the development of key regime maps for granulation processes and the development of mathematical models for engineering design and scaling of granulation processes. He is the co-author ofthe well known monograph in this area - The Science and Engineering of Granulation Processes and his approaches are now widely used in engineering practice in industry. He is author of over 150 refereed publications.  In recognition of his contribution to the field, he was awarded the Achievement Award for Excellence in Granulation Research, 9th International Symposium on Agglomeration (2009), was elected a Fellow of the Australian Academy of Technological Sciences and Engineering (equivalent to the Royal Academy of Engineering) in 2010, and was awarded the Thomas Barron Award in Fluid-Particle Systems from the American Institute of Chemical Engineers in 2012. 

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