A method of investigating rod motion in a laboratory rod mill

Abstract

The work reported here measured the position of a rod in a laboratory mill at 1/25 second time intervals using an active light source in the rod and a video camera. The detailed picture of the charge movement which was obtained was used to calculate mill power using rod lift and torque arm models. Theoretical analysis showed that the presence of slip does not change the mill power because the lower power required for lift in the presence of slip is counterbalanced by the extra power required to overcome friction. Power predicted from a simple slip surface treatment is not correct because media emerging through the slip surface has to rise further to over-ride media emerging lower in the surface. The powers calculated from the lift model and the torque arm model (assuming all rods contribute to torque) were almost identical, but did not predict the correct variation in power with mill rotational speed. It was concluded that a valid fundamentally based prediction of mill power is still not available.