Rate Constants of Wet and Dry Ball Mill Grinding

Abstract

To investigate ball mill grinding from the kinetic point of view, the effects of hardness of samples, feed weight and feed size on the rate constant of weight fraction increase in the ground product have been studied.
The samples used were silica glass, borosilicate glass, quartz, feldspar, limestone, marble and talc. The pebble mill consisted of a 13.2cm-long cylinder of 12.8cm diameter and 40 balls of 3cm diameter having the total weight of 1180g. In the case of wet grinding, 400 cc-water was added to the mill. The tests were done at the speed of 88.1% of critical one. The experiments were performed on the samples of 5 different particle sizes from 14 to 65 mesh for dry grinding and 4 different ones from 20 to 65 mesh for wet grinding to obtain the grinding rate constant. The following results were obtained.
Dry: K_x=0.024H_V^-0.47(W_S/W_B)^-1.5·(x/x_f)·(x_f/x_o)^0.7 (x_o=0.119cm)
Wet: K_x=0.05H_V^-0.47(W_S/W_B)^-1·(x/x_f)·(x_f/x_o)^0.5 (x_o=0.084cm)
where K_x is the zero order increasing rate constant of weight fraction less than size x, H_V the dimensionless Vickers hardness, W_S the feed weight, W_B the ball weight, x_f the feed size and x_o the optimum feed size.