Analysis of energy requirements in stirred media mills

Vertically stirred media mills represent an important tool for the comminution of a range of industrial minerals. In this work, calcium carbonate is ground to size ranges below 2 μm in an Imerys stirred media mill. The role of grinding media on the efficiency is considered, and with the use of a novel, rod shaped grinding media, significant energy savings in ultrafine wet grinding are seen. This is proven to be an effect attributable to the shape of the grinding media, rather than the density of the grinding media. After a comprehensive efficiency analysis of the performance of a range of spherical and rod shaped media, further investigations are made through analysis of flow patterns within the mill using Positron Emission Particle Tracking (PEPT). Data collected from PEPT has given new insights into the distribution of material and kinetic energy within the mill, as well as an understanding of the effect of media density and motor speed in relation to the efficiency of the grinding. Furthermore, investigations are made into dry grinding of talc using the stirred media mill, which is subsequently soaked in water to give a low energy route to high surface area of the mineral.