Effect of coal grade and heating rate on the thermal degradation behavior, kinetics, and thermodynamics of pyrolysis of low-rank coal

The work investigates the thermal degradation characteristics, kinetics, and thermodynamics of low-rank coals of three different grades selected from coal mines of Odisha, India by thermogravimetric analysis in temperatures ranging from 30 degrees C to 1000 degrees C under a nitrogen atmosphere at five heating rates of 5, 10, 15, 20, and 25 degrees C min(-1). The kinetic parameters are computed using model-fitting methods assuming first-order kinetics in the 250-635 degrees C temperature range of major weight loss. The average activation energy of the reaction at different heating rates is found to be in the range of 55-65 kJ/mol. The average entropy change is found to vary from -180.03 to -165.887 J/K/mol(1), the average enthalpy change varies from 51.1758 to 57.574 kJ/mol and that of free energy change varies from 189.718 to 177.9 kJ/mol. In addition, the composition of the oil obtained by pyrolysis of the coal in a semi-batch reactor at different temperatures is analyzed by FTIR and GC-MS techniques. The composition of the oil is found to be affected by the pyrolysis temperature.