Study of correlation among total silica, free silica and HGI in different specific gravity fractions of coals from Karanpura coalfields and its impact in thermal power station

摘要

Coal samples from Balkundra, Bansgara, Hathidari, and Sounda block of Karanpura coalfields were washed at different specific gravity (1.40 to 1.80) and each gravity fraction is analysed for chemical composition of ash, Hardgrove Grindability Index (HGI) and other chemical properties with a focus on the correlation of free silica (a -quartz) with HGI. Quantitative data on quartz are important, as quartz endows coal with an abrasive propensity by virtue of its hardness (7.0 on Mohs hardness scale). Free silica is responsible for erosion of the boilers unit in thermal power stations and also responsible for abrasion effect in mining and grinding equipment. It was observed that with the increase in the value of free silica, HGI value decreases with some exception and in those cases it may be due to higher amount of fusinite in this coal as it has highest grindability value in comparison to other macerals.The data generated on total silica, free silica of coal ash and HGI of the coal studies have been subjected to regression and correlation analysis. Positive correlation have been found between free silica and HGI (R~2 = 0.84).