Vertical Milling; Why 44 is the Meaning of Life, the Universe, and Everything

  • Rhymer, Daniel (University of Birmingham)
  • Ingram, Andy (University of Birmingham)
  • Windows-Yule, Kit (University of Birmingham)

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Grinding and comminution is one of the most demanding and widespread processes in industry, with mining alone contributing approximately 1.8% of global energy usage [1]. Most of this energy is waste from unfruitful collisions, so the opportunity for improving efficiency is highly possible. With the UK energy crisis becoming increasingly significant, and the global climate crisis being an ongoing concern, it is becoming more important to run processes as optimally as possible. One way of researching this is by conducting parametric studies and the talk discusses several which have been carried out on a Vertical Attritor Mill using DEM simulation. Computing has enabled a more detailed understanding into engineering systems, as it lets researchers go beyond the "black box" theory which complex equipment is often portrayed as in experimentation, and into the microscopic detail of the individual regions. Of the studies conducted, the first shows that media sliding friction has a greater effect on milling efficacy than restitution coefficient [2]. At near-frictionless conditions, the presence of single-body motion could be seen, as the media resistance was almost completely removed. It was also proven that changing media size ratios has an effect, with potential that multiple bead sizes within the chamber would be best for performance. Bead segregation becomes a large factor, so there needs to be design consideration for optimal flow of process material. Finally, it was shown that the surface area created by the attritor profile was of much greater influence that the pin configuration, meaning that more durable impellers could be manufactured. One way of showing this is by calculating granular temperature, a measure of media chaos. What this showed is that when the overall pin area is kept constant, the media chaos is more evenly distributed and independent of configuration.