Solving granular segregation problems using a biaxial rotary mixer

Granular mixing is a critical but poorly understood aspect in the manufacture of many industrial products, for example, pharmaceuticals, food, cosmetics, ceramics, fertilizer and polymers. The mixing and segregation phenomenon occur in most systems of granular solids and have a significant influence on the quality and outcome of the final product. The usual approach to mix the powders is by using a tumbling blender which rotates around one axis, where, the radial convection is reported to be faster than axial dispersion transport, hindering the mixing performance. A double cone mixer is fabricated which rotates around two axes, causing axial mixing competitive to its radial counterpart. Samples are collected intrusively using the discrete pocket samplers to quantify the characteristics of mixing for millimeter sized glass beads. Digital video recording and MATLAB based image analysis techniques are used for non-intrusive characterization of mixing in micron sized art sands. A parametric study of the effect of particle size, vessel speeds on the granular mixing is accomplished. Incorporation of dual axis rotation enhances axial mixing by 70–90% in comparison to single axis rotation. Particles of smaller sizes (art sand) tend to mix quicker than the bigger particles (glass beads) due to mild cohesive effects.