Research on the grinding characteristics of lignite based on grinding kinetics

Aiming to explore the limitation of Hardgrove Grindability Index (HGI) and broken behavior of lignite, coal samples were ground for different minutes in the Hardgrove mill. Experiments show that the grinding kinetics can describe the grinding process of coal well. For the same kind of coal, the grinding kinetic parameters k and m of a certain particle size can be regarded as constants. The particle size of the particles to be ground R has a power function relationship with the parameter k. The initial particles appeared selective grinding during the grinding process. From the perspective of the index T-10 (a size of 1/10 of the initial particle size) and grinding rate, HGI has a poor description of continuous lignite grinding. In this case, the grinding kinetic parameter k of the same size of lignite can be used to discuss the grindability of different coal samples. Generally, the larger the k of the same size coal, the higher the grindability. The lattice size and mosaic morphology of ash forming minerals affect the grinding rate of coal samples. Raw coal with low ash content is more likely to liberate a large amount of minerals in the early stage of grinding.