Chemical Beneficiation of Indian Non-Coking Coal

Abstract

Indian coals are of poor quality, often containing 30-50% ash. In addition, the calorific values of thermal coals in India have deteriorated because of depleted reserves of the better quality coal and surface mining. Low-quality coal also creates problems for power stations, including erosion in equipments, difficulty in pulverization, and producing excessive amounts of fly ash containing large amounts of unburnt carbon. In view of this physically beneficiated Hingula coal with 13.3% ash from Talcher coal field was treated for demineralisation. The effects of alkali and acid concentration, time and temperature on the demineralisation have been investigated. It was found that leaching with 0.25N Na2CO3 followed by treatment with 10% HCl at 85oC for 60 min the ash content of coal was reduced from 13.3% to 9.5% and calorific value increased from 5355 kcal/kg to 5857 kcal/kg. Similar results were obtained with 10% H2SO4 leaching at 95oC for 15 min. The treated coal was characterized by SEM and XRD.