Influence of selected factors of Polish coking coals on the Hardgrove Grindability Index (HGI)

This paper presents the results of a study on the influence of selected parameters of coal on the Hardgrove Grindability Index (HGI). The samples used in the investigation came from the same Polish coking-coal mine. The samples varied in terms of their quality parameters, i.e., volatile matter, ash content, chemical composition, maceral composition, and vitrinite reflectance). The influence of the aforementioned parameters on HGI was assessed. It was found that, among the investigated coals, the mean random vitrinite reflectance value, a measure of the coal rank, was the parameter that had the most significant effect on coal grindability (positive correlation). Such a correlation was also found for the carbon and vitrinite content. However, for volatile matter, liptinite, and total sulfur content, a negative correlation was found. The content and chemical composition of ash (as a reflection of mineral matter) has no significant effect on HGI. There were some weak negative correlations observed between HGI and the SO₃ and the TiO₂ content of ash. Of the tested parameters, vitrinite reflectance has the greatest effect on HGI.