Hardgrove_Grindability_Index
Hardgrove Grindability Index
Measure for the grindability of coal
Hardgrove Grindability Index (short HGI) is a measure for the grindability of coal. Grindability is an index, therefore it has no unit. The smaller the HGI, the harder is coal texture and less grindable is the coal.
Grindability is an important factor for the design a coal mill. As grindability depends on many unknown factors, HGI is determined empirically using a sample mill according to the following procedure: