Effect of ash reduction on the grindability of some Turkish brown coals

Coal can be regarded as an aggregation of organic and inorganic materials. Most of the minerals associated with the inorganic material are mainly clay minerals, quartz, carbonates, sulfides, and sulfates. In this study, brown coal samples were collected from 10 different brown coal pits in Turkey. Firslty, these coal samples were cleaned in terms of density seperation. Secondly, ash contents of original and clean coal samples were determined. Thirdly and finally, HGI (Hard Groove Index) values were determined for each sample of clean and run of mine coals. According to obtained HGI results for the run of mine coal samples; Gürmin-Merzifon brown coal has the highest HGI value as 68.5, while Saray-Tekirdaǧ brown coal has the lowest HGI value as 43.5, respectively. HGI results for the clean coal samples; Ilgin-Konya brown coal has the highest HGI value as 84.4, while Orhaneli-Bursa brown coal has the lowest HGI value as 40.8, respectively. Evaluating the all results of HGI and ash content analysis, as ash making minerals reduce down with density seperation, HGI values are tend to increase. Coals containing higher mineral contents are more difficult to fracture compared to the ones having less mineral content.