Insight into fast infrared-assisted and coal rank on pyrolysis kinetics and products distribution

An infrared rapid heating reactor was employed to investigate the effect of coal rank on pyrolysis product distribution and pyrolysis behavior among different coals. The dynamic analysis demonstrated that the average E_α decreased with the coal rank increased, with values of 438.89 kJ/mol for lignite (LGC), 388.83 kJ/mol for long flame coal (LFC), and 338.20 kJ/mol for lean coal (LNC). The tar yields of LGC, LFC and LNC increased initially and then decreased. Notably, the LGC yield reached the highest yield of 23.20 % at 700 °C, but LFC and LNC got the maximum yields at 600 °C with yields of 13.10 % and 5.10 %, respectively. GC-MS analysis revealed that hydrocarbon content in pyrolysis tar increased with coal rank. Specifically, LGC exhibited a hydrocarbon content of 39.13 %, LFC showed 48.44 %, and LNC reached 57.86 %. Different coals displayed distinct pyrolysis mechanisms, with LGC generating H₂ and CH₄ through the breaking of straight and branched aromatic hydrocarbons at low temperatures, whereas LNC produced these gases through the cracking and condensation of aromatic rings. Raman spectroscopy revealed that LGC exhibited a higher content of aromatic hydrocarbons in char compared to LFC and LNC.