The investigation of grinding kinetics of power plant solid fossil fuel in ball mill

Abstract

The kinetics of batch dry grinding of power plant solid fossil fuel, from the feeds of sieve sizes −3.350 + 2.360, −2.360 + 1.700, −1.180 + 0.850, −0.425 + 0.300 and −0.212 + 0.150 mm have been determined using a Bond ball mill with a mixture of five ball sizes. The mill used has a diameter of 30.5 cm, length of 30.5 cm, providing a total mill volume of 22.272 cm 3 with a total mass of 20.125 g steel ball mixtures of 38.10, 31.75, 25.40, 19.05 and 12.70 mm diameters. The balls occupied 22% of mill volume. The speed of rotation of the mill was chosen as 70 rpm. The specific rates of breakage ( S i ) and primary breakage distribution ( B i , j ) values, called as grinding breakage parameters, were determined for those feed size fractions to simulate the product size distributions for comparison to the experimentally obtained data. As the feed sizes increase, the S i values also increase, that is, faster breakage values from higher to lower values were in the order of solid fossil fuel by comparing to its α values. Breakage distribution functions were found non-normalizable. It is dependent upon the initial feed particle sizes. In other words, the simulations of product size distributions for fossil fuels were in good agreement with the experimental data using a ball mill simulation program, called JKSimMet.