Seeded granulation process in twin-screw granulators: A DEM approach

Twin-screw granulation is a promising continuous manufacturing technique for producing granules with tailored properties. This study investigates the impact of screw configuration and speed on seeded granule formation using discrete element method (DEM) simulations. The aim is to identify optimal screw designs and operating conditions that yield desirable granule characteristics, such as high coordination, fine particle coverage, and throughput. DEM simulations were performed using Altair's EDEM software, employing Hertz-Mindlin and JKR contact models to capture particle-particle interactions and binder liquid effects. Five screw configurations (C1, C2, C3, C4, and CI) with varying conveying zone lengths and kneading elements were investigated, and screw speed was varied from 300 to 800 RPM. The Results show that screw configuration plays a crucial role in determining seeded granule characteristics. Increasing screw speed had a detrimental effect on granule properties, with lower speeds of 300 RPM yielding the granules with the greatest coordination number with the highest fine coverage. The study highlights the complex interplay between screw configuration, conveying zone length, kneading elements, and residence time in determining granule properties. Recommendations are provided for selecting suitable screw configurations and operating conditions for specific applications. Further research is suggested to investigate granule size distribution and morphology at different liquid properties screw speeds, and liquid-to-solid ratios.