Pyrolysis of low‐rank coal: Thermo‐kinetic analysis and product characterization

Abstract

AbstractPyrolysis, the primary process accompanying the thermal degradation of coal, is complicated, and understanding this process requires kinetic analysis followed by product characterization. In this context, the present work involves the study of kinetics and thermodynamics of low‐rank Indian coal from thermogravimetric analysis data followed by batch pyrolysis and subsequent analysis of the liquid products. The thermal degradation of the coal sample has been carried out using a thermogravimetric analyzer from ambient temperature to 1350 K at five different heating rates (5, 10, 15, 20, and 25⁰C/min) under N2 atmosphere. The kinetic triplets (E, A, and n) are evaluated using the order‐based model‐fitting method. The result of this work shows that coal pyrolysis satisfies the first‐order kinetics mechanism with an average activation energy of 62.141 kJ/mol and a pre‐exponential factor of 123.835 min–1. Thermodynamic parameters such as average enthalpy change (ΔH), entropy change (ΔS), and free energy change (ΔG) of coal pyrolysis are calculated to be 56.1716 kJ/mol, –225.524 kJ/mol/s, and 1.6212 × 105 kJ/mol, respectively. A Batch pyrolysis study of coal was carried out in a semi‐batch reactor at different temperatures with an optimum oil yield of 18.94 wt% at 450°C. The chemical composition of pyrolytic oil was investigated by the FTIR and GC‐MS analysis confirmed the presence of D‐Limonene as the major constituent in the coal pyrolytic oil.