Investigation and Model Validation of Media Motion in a Vertical Stirred Mill Using Positron Emission Particle Tracking

J. Conway-Baker1, R.W. Barley1, R.A. Williams1, A.J. Clarke1, J.A. Kostuch2 and D.J. Parker3

1Camborne School Of Mines, University Of Exeter, Redruth, Cornwall, TR15 3SE,UK, email : jcbaker@csm.ex.ac.uk

2 English China Clays International, John Keay House, St Austell, Cornwall, PL25 4DJ, UK

3 University Of Birmingham Positron Imaging Centre, Edgbaston, Birmingham, B15 2TT, UK

Abstract - One of the major growth areas within the minerals industry has been that of ultra-fine grinding. This Paper considers modelling the behaviour of a vertical stirred mill at a particulate level using distinct element analysis, with the first stage being the characterisation of the motion of the media within the mill. The analysis seeks to predict the motion of the grinding beads which determines the frequency and energy of the media collisions and so is crucial to the energy dissipation and breakage behaviour within the mill. Here we report on the use of positron emission particle tracking as a means of validation of the model. Initially two modes of motion were identified directly from the PEPT data and results are presented here showing the effect of impeller speed on the mode of motion. From the data directly a link between the media motion and the grinding action can be seen. The effect of different operating conditions including the media loading, slurry density and filling ratio will also be studied to allow validation of the model.

Keywords: Modelling, Stirred Mill, Comminution, Positron Tracking