Using DEM to investigate how shell liner can induce ball segregation in a ball mill

M. M. Bwalya, N. Chimwani
Minerals Engineering
Ball size, Discrete element method, Liner configuration, Liner profile, segregation

Sometimes it is desirable to segregate the ball load in a mill so as to allow for the possibility of larger balls dealing with coarser particles at the feed end and finer product being ground more efficiently at the discharge end. The Hardinge mill with cylindrical and conical sections has been used to achieve segregation quite effectively. The cylindrical section tends to retain the biggest balls while the smaller balls drift to the conical section. However, this is a complex design and we use the discrete element method (DEM) model to investigate if simply altering liner configuration on an ordinary cylindrical mill can lead to similar success. The study involves simulating a mill with 4 sections. Each section can be configured with distinct liner profiles. Three ball size classes are tracked for evidence of segregation at 75% and 60% of critical mill rotation speed. The ball distributions in the various segments at the end of 80 mill revolutions suggest that varying axial liner profile configuration can affect ball segregation, particularly for the mill running at 75% of critical speed. The convenience of using computer simulations to avoid costly plant trials is highlighted.

Keywords: Discrete element method, Segregation, Liner configuration, Liner profile, Ball size

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