Enhancing mixing of particles by baffles in a rotating drum mixer

Baffles with shape of "-" (single baffle), "+" (cross-baffles with four arms) and "*" (baffles with 6 arms) are used to enhance the mixing of particles in a rotating drum mixer. A micro-dynamics study of mixing and segregation of a bi-disperse system of two particle sizes in the rotating drum with these three kinds of baffles is carried out using the discrete element method (DEM). The effect of the baffles on mixing, and the mechanisms of mixing enhancement by the baffles are discussed and analyzed. Simulation results show that in an unbaffled drum mixer, particle convection, particle diffusion, and size segregation of bi-disperse particles, all play important roles in the mixing process; whereas size segregation will be largely restrained when the drum mixer has a baffle, regardless of its shape, and the degree of mixing is higher than that in an unbaffled drum mixer. The different mixing characteristics for "-" shaped baffle, "+" baffle, and "*" baffle are revealed by the simulation results. For "+" or "*" style baffles, there is an optimal size of baffles for the mixing of particles, and the optimal mixing efficiency is higher than that for "-" baffle. (C) 2011 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.