Rate Constants of Ball Mill Grinding
Effect of Feed Size on Rate Constants of Weight Fraction Decrease of Feed and Specific Surface Increase
1978 Volume 27 Issue 298 Pages 667-670
Details
1978 Volume 27 Issue 298 Pages 667-670
In the previous paper, the authors studied the effects of hardness of samples and feed weight on grinding rate constants from the kinetic point of view. In the present paper, we studied the effect of feed size on the rate constants of weight fraction decrease of feed and specific surface increase.
The samples used were silica glass, borosilicate glass, soda glass, quartz, feldspar, limestone, gypsum and talc. The pebble mill consisted of a 12.8cm-diameter by 13.2cm-long cylinder and 40 balls of 3cm diameter having the total weight of 1180g. The testes were done at the speed of 88.1% of critical one with several feed size ranges, 14∼20, 20∼28, 28∼35, 35∼48, 48∼65, 65∼100, 100∼150, 150∼200mesh. With an assumption that the shape factor was six, the specific surface of fine particles was measured by the permeability method and that of coarse ones was calculated from the size distribution. As the result, the following equations were obtained.
K1=0.02HV-0.23(WS/WB)-1.5(xf/x0)
KS=0.41HV-0.58(WS/WB)-1.5(xf/x0)
Where K1 is the first order decreasing rate constant of weight fraction of feed, HV the dimensionless Vickers hardness, WS the feed weight, WB the ball weight, xf the feed size, x0 the optimum feed size and KS the zero order increasing rate constant of specific surface. To obtain KS from K1, the following equation was derived.
KS=20HV-0.35K1
