As the stirrer speed directly affects the motion of grinding media, and hence the interactions with material particles to be ground, the rotation speed of a stirred mill is well recognised as one of the most important factors affecting the grinding performance.
In this work, the effect of stirrer speed on grinding performance in terms of grinding rate and grinding energy efficiency was quantitatively investigated. Batch wet grinding tests of quartz powder at different stirrer speeds were performed, using a self-made horizontal stirred mill with alumina balls as grinding media. Grinding time, operating power and the sizes of ground product were recorded to analyse the grinding performance. The test results showed that grinding processes followed the first order grinding kinetics. The grinding rate constant increased with the increasing stirrer speed. Based on the grinding kinetics, the grinding energy equation was established. The energy utilisation coefficient in the energy equation can be used as an indicator of energy efficiency. The energy efficiency decreased with the increasing stirrer speed. Quantitatively, with the stirrer tip speed increasing from 4.25 m/s to 9.35 m/s, the grinding rate constant was improved by 441.47%, whereas the energy utilisation coefficient was decreased by 39.35%.
The grinding rate constant and energy utilisation coefficient can be used to evaluate the grinding performance when the grinding conditions need to be adapted. The adjustment of grinding conditions would be optimal when grinding rate get significant improved with little decrease in energy efficiency.
This aper was presented at IMPC 2014