The Batch Ball Mill Experiment

This experiment is the simplest experiment that can be done to estimate the variation of the specific rate of breakage as a function of particle size in a ball mill.  The method is based on the observation that the breakage of the top size in a ball mill follows a simple kinetic law

where p1 is the fraction of materials in size class 1 in the ball mill. k1 is the specific rate of breakage for materials in size class 1.  Integration of this equation gives the logarithmic law

so that the plot of log p1(t) against time gives a straight line of slope -k1.  The value of k1 is obtained from such a plot.

The experiment will be done by loading four identical small batch ball mills with limestone that is screened to a specific known top size.  These four mills will be rotated simultaneously  on rollers in the laboratory for different time periods.  The size distribution of the mill charges will be determined using standard size distribution measurement techniques and the fraction remaining in the top size will be determined and plotted and the value of k1 determined.