Indian coal pyrolysis behaviour and kinetics study using covalent bond information

Abstract

Coal pyrolysis is a critical step of coal thermal conversion, impacting the downstream utilisation of coal, such as combustion and gasification. The understanding of this complex process plays a crucial role to predict the products, operation optimisation and reactor design. Indian coals typically have 25–52% (as received) ash yields. There is little knowledge about the pyrolysis kinetics of Indian high-ash coals, which are widely used in Indian power plants. In this work, five Indian thermal coals were investigated using thermogravimetric analysis (TGA) at heating rates varying from 278 to 773 K/min to provide pyrolysis kinetic data. The common single reaction kinetic model (Friedman) was used to analyse the pyrolysis behaviour of the coals and estimate the kinetic parameters. The activation energies ranged from 428.78 to 520 kJ/mol. Six Gaussian functions were used to analyse the DTG curves, each presenting a group of covalent bonds. The variation of pyrolysis behaviour is highly correlated to the distribution of aliphatic and aromatic carbon structures in the coal. The activation energy of coal pyrolysis can be estimated using the chemical bonds information obtained from the curve-fitting results of the DTG curve.