De-mixing of binary particle mixtures during unloading of a V-blender

The V-blender is an industrial batch mixing device which is used to blend granular mixtures in the food, household products, agricultural and pharmaceuticals industries. The mixing characteristics of this device have been previously studied both experimentally and numerically. When emptying the device, de-mixing of this granular mixture can occur due to segregation produced by the flow. This reverses some fraction of the mixing produced by the blender. In this study we consider the de-mixing that occurs when the particles flow out of the device. We begin with close to a perfectly mixed state and measure the change in particle homogeneity during discharge. In this initial study, we consider only the simplest case of a binary mixture with components only differing by size. The extent of de-mixing is evaluated as a function of the size ratio of the mixture components. Different unloading scenarios are considered and it is shown that the presence of additional transferring surfaces can greatly increase the segregation of the mixture. We also consider how to optimise the set-up so as to minimise any de-mixing.

► De-mixing that occurs during unloading of a V-blender is significant.
► Sloping walls of V-blender lead to shear induced segregation during unloading.
► Shear induced segregation occurs on the surface of heaped granular matter.
► For particles which differ in size percolation drives de-mixing.