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The blends of a high ash Indian coal with three coals of different foreign origins -Australia, Russia and Indonesia were subjected to HGI testing as per ASTM D 409 and the resulted fractions obtained in the coarser and finer portions of ASTM 200 mesh (75 microns) were assessed for their characteristics in respect of proximate and ultimate parameters, alpha quartz and combustion reactivity. The similar studies were also carried out for the parent coals. HGI values were found additive in case of Indian-Indonesian coal blends and the same was found non-additive in respect of Indian-Russian and Indian-Australian coal blends. Considerable variation in properties was observed in the coarser and finer fractions of the ASTM 200 mesh for parent Indian and Indonesian coals compared to parent Australian and Russian coals. This indicates the disproportion of the coals and coal blends particles during the sieving process after subjecting to HGI test. The variation of alpha quartz content in the coarser and finer fractions indicate that there is a segregation of free minerals in the coarser and finer fractions. The conversion plots obtained through TGA for the coarser and finer fractions indicate that there is no maceral segregation.

Keywords

Blended coal, Disproportionation, Hardgrove Grindability Index (HGI), Non-Additive, Thermogravimetric Analysis (TGA)

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