Comparison of Energy Requirements for Conventional and Stirred Ball Milling of Coal-Water Slurries

This paper presents the results of an investigation of energy requirements for grinding of coal-water slurries in conventional and high speed stirred ball mills. The high speed stirred ball mill, featuring a rotor-stator type of stirring device, has been found to outperform a tumbling ball mill for wet grinding of minus 12 mesh coal to a fineness meeting the requirements of utility fuel. Grinding tests showed that the energy reduction which is possible with stirred mills increases linearly with the percentage of material passing 325 mesh up to 90% and beyond this point, energy reduction is even higher. A direct comparison of stirred ball mill and tumbling ball mill performance resulted in grinding minus 12 mesh (1400μm) coal to approximately 96% passing 325 mesh (45 μm) with a specific energy input of 32.6kWh/T (l.0min retention time) and 58.8kWh/T (60min retention time) respectively.