Ball motion, axial segregation and power consumption in a full scale two chamber cement mill

Grinding of clinker for cement production is often performed in a two chamber ball mill. In the first shorter chamber, raw feed is ground using media consisting of large balls. The ground product of the first chamber exits through a discharge grate and enters the second longer chamber. Here smaller balls are used to grind the product material even finer. In this paper we analyse the charge motion, short term ball segregation processes and energy utilisation in a 4 m diameter cement ball mill using DEM. The power draw predicted is consistent with the rated power of the mill. The energy dissipation in the mill is dominated by shear interaction. The gentle liner profiles ensure that few balls move on cataracting trajectories. The distribution of energy utilisation between the different size media fractions is explored as are differences in the collisional environment between the two mill chambers.