(99c) Optimizing the Reduction of Segregation in Baffled-Tumbler Mixers

Segregation is a major problem for many solids processing industries. A small difference in any mechanical properties like particle size or density can lead to flow-induced segregation. Recently, our group has proposed a method of thwarting segregation in surface-dominated flows whereby segregation is dramatically reduced via periodic inversion of the surface/flowing layers. In this study we use the discrete element method (DEM) to systematically investigate how this approach may be used to enhance the mixing in a tumbler mixer, probing such operating parameters as baffle shape, baffle placement and the tumbler filling level. Previous work has suggested that a simple design heuristic may be used to effectively discriminate between a host of tumbler/baffle geometries. The detailed flow profiles that result from our simulations allow us to exhaustively test the proposed link between the asymptotic mixing behavior of the system and the suggested design heuristic -- the probability distribution of the number of layer passes a particle takes per tumbler rotation.