Chemical beneficiation of Hingula coal

Mineral matter can be reduced by using chemical demineralisation techniques. In this study beneficiation of Hingula coal from Talcher coal field, Odisha, India, having 29.6% ash is reported. Physical beneficiation of the Hingula coal reduced the ash content to 13.3%. To further reduce the ash content, Hingula coal was chemically treated in a two-stage leaching process i.e. alkali leaching followed by acid leaching. Various process parameters such as concentration of alkali, time, and temperature required for optimum demineralisation have been investigated. It was found that by leaching with 0.25N Na₂ CO₃ for 60 min at a temperature of 85°C and a pulp density of 10% followed by leaching with 10% HCl at 95°C for 60 min, ash content of this coal was reduced to 9.8%. It was also observed that when this coal was leached only with 10% H₂ SO₄ at 95°C for 60 min ash content was reduced to 9.8%. The calorific value of the chemically treated coal was also determined.