An assessment of grindability index of coal

Grindability index of coal is an important technological parameter to understand the behaviour and assess the relative hardness of coals of varying ranks and grades during comminution. This is usually determined by Hardgrove Grindability Index (HGI), which involves requirement of a costly grinding equipment and accessories not readily available and affordable. Due to heterogeneous character of coals as regards maturity, petrological constituents, mineral impurities, etc. as well as mechanism of comminution render such determination rather difficult, leading to poor reproducibility and repeatability of HGI value, contrary to other analyses for coal characterisation. As such, it often gives misleading results to understand and explain properties emerging from other analyses and testing. In view of such problems, many attempts have been done in the past to develop correlation of HGI with simple analytical composition of coal. In this perspective a fresh attempt in arriving at a more reliable and reproducible correlation with proximate analysis alone is reported. Such an index termed as Statistical Grindability Index (SGI), may be found useful in assessment of coal behaviour not only in crushing and grinding of coal but also its friability vis-à-vis dust emission during comminution.