Effect of Mean Specific Gravity on Combustion Characteristics of Selected High Ash Indian Coal

The present research shows the combustion characteristics of different specific gravity fractions of high ash thermal coal. Coal with different mean specific gravity (SG_M) ranging from 1.25 to 2.0 was produced using the float–sink experiment. All SG_M coals were characterized with proximate analysis, ultimate analysis, higher heating value, ash analysis, Brunauer–Emmett–Teller analysis and Fourier-transform infrared spectroscopy (FTIR). Combustion experiments were performed with thermogravimetric analysis to identify the impact of SG_M. Experimental results inferred that ignition temperature ranged from 285 to 408 °C as SG_M varied from 1.25 to 2.0. The combustion rate of 1.25 SG_M coal was found to be the highest due to the strong or moderate presence of hydrocarbons like alkane, alkene, aldehyde and alcoholic, as observed from FTIR. Activation energy ranged from 121.81 to 54.60 kJ/ mol as SG_M of coal increased from 1.25 to 2.0. Thermodynamic analysis inferred that 1.65 SG_M coal had the highest ΔS (− 158.21 J/mol. K) and minimum ΔH (48.93 kJ/ mol), inferring ease of decomposition and higher combustion reactivity.