Insights into granular mixing in vertical ribbon mixers

In this research, granular mixing in vertical ribbon mixers was studied by means of discrete element method (DEM) simulations. Time-averaged velocity distributions, granular mixing, mean square displacement of tracer particles, diffusion coefficients, and Peclet number in axial and azimuthal directions were used to find the flow pattern of particles and the dominant mixing mechanisms. Strong azimuthal motion of particles was observed, and it was found that by decreasing the height in the mixer, this azimuthal motion becomes stronger. The effects of rotating speed, fill level, and filling method were studied on the quality of mixing, where the quality of mixing was assessed using relative SD mixing index. It was found that by increasing the rotation speed from omega(s) = 60 rpm-120 rpm, the mixing quality improves in a linear trend. Decreasing the fill level from 12 cm-11 cm did not change the mixing quality, while with further decrease of the fill level to 10 cm, the mixing quality was improved. The mixing quality was also much better when the powder was inserted side-to-side instead of in axial layers.

Automated summary

The research focused on granular mixing in vertical ribbon mixers using discrete element method simulations. It was found that decreasing the mixer height strengthens the azimuthal motion of particles. Increasing rotation speed and inserting powder side-to-side improved mixing quality.