Discrete particle simulations predicting mixing behavior of solid substrate particles in a rotating drum fermenter

A soft-sphere discrete particle model was used to simulate mixing behavior of solid substrate particles in a slow rotating drum for solid-state fermen tation. In this approach, forces acting on and subsequent motion of individ ual particles can be predicted. The (2D) simulations were qualitatively and quantitatively validated by mixing experiments using video and image analy sis techniques. It was found that the simulations successfully predicted th e mixing progress as a function of the degree of filling and size of the dr um. It is shown that only relatively large, straight baffles perpendicular to the drum wall (67% of the drum radius) increase the mixing performance o f the rotating drum. Considering the different aspects of mixing dealt with in this work, it is concluded that the soft sphere discrete particle model can serve as a valuable tool for investigating mixing of solid substrate p articles. Finally, it is expected that this model may evolve into a potenti al tool for design and scale-up of mixed solid-state fermenters. (C) 2001 J ohn Wiley & Sons, Inc.