Energy-Size Reduction of Coals in the Hardgrove Machine.

To simulate the grinding process in an industrial vertical spindle mill, the Hardgrove mill was fitted with a power-measuring meter to investigate the breakage characterizations of different narrow size fractions of coal. Power consumption in the grinding process was precisely recorded at the sampling frequency of 1 second with the help of sampling software for power. The experimental results indicated that the energy input for grinding decreased with increases in time for each sample. Changes in the weight percentage in the top-size interval showed that the first-order law was not satisfied to describe the total grinding process. The new produced fine coal had a negative effect on the breakage behavior of coarse particles. But removal of −0.09 mm size can help to increase the energy input for grinding and the generating rate of −0.09 mm also accelerated in turn. The relationship between t10and energy input can be described by the classical breakage function. Specific energy consumed by raw coal with a small size was higher when subjected to the same value of t10, due to the relatively higher specific surface area of ground coal at the same breakage ratio of 10. [ABSTRACT FROM AUTHOR]