Particle filling and size effects on the ball load behaviour and power in a dry pilot mill: Experimental study

The ball load behaviour in a pilot mill is studied under conditions of increasing particle filling, for coarse silica feed (0.8–1.8 mm) and fine silica feed (0.075–0.3 mm), at the mill speeds of 63, 78, 88 and 98% of the critical. An inductive probe is used to obtain the ball load behaviour independent of particles present in the mill. The difference in mill power draw obtained from the coarse and fine particle charges are explained via their load behaviour signals. The effect of particle filling and size on the ball load behaviour is quantified through the toe and shoulder angular positions. Radial segregation of the coarse silica particles to the periphery of the charge occurs. A radial segregation index related to the extent of drop in the inductive probe's signal has been defined and used to quantify radial segregation as a function of particle filling and mill speed.

This study presents an experimental investigation into the effects that both particle filling and size have on the ball load behaviour and net power in a dry batch pilot mill. Measurements of the ball load behaviour were obtained using an inductive proximity probe. An understanding of the various power curves was brought about using their respective load behaviour signals. Conditions such as cataracting, centrifuging and radial segregation were easily detected and their effects on the power draw deduced. Radial segregation was quantified as a function of particle filling and mill speed.Figure optionsDownload as PowerPoint slide