EXPERIMENTAL INVESTIGATION INTO THE INFLUENCE OF THE PARTICLE-SIZE DISTRIBUTION UPON THE LOCAL MIXING MECHANISMS IN A FLOWING BULK MATERIAL

The small-scale mixing of densely packed bulk material was modelled by Buggisch and Loffelmann in 1989, starting from a diffusion approach w hich had been developed previously. An equation could be deduced from which the diffusion coefficient appears to be proportional to the shea r rate. This model conception was confirmed through shearing experimen ts using a Couette apparatus. The model bulk consisted of vertically p acked metal rods of various diameters, parts of which were marked by c olours. The present paper investigates the influence of the particle s ize distribution upon the mixing process. It is to be expected that th e distribution of the particle size has an influence upon the package structure of the bulk and hence, amongst other things, upon the shear rate, and, eventually, upon the intensity of the diffusion. It has bee n possible to confirm this prediction through shearing experiments wit h the model bulk in the Couette apparatus.