Investigating the trigger mechanism of Shenfu bituminous coal pyrolysis

Abstract

This work aims at exploring the trigger mechanism of Shenfu bituminous coal pyrolysis. Flash pyrolysis technique combined with gas chromatography-mass spectrometry (Py-GC/MS), thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy (TGA-FTIR), and reactive molecular dynamic simulations (ReaxFF MD) were employed in elucidating the trigger mechanism of coal pyrolysis. The proposed coal model was C1328H1130N21O245S7, whose pyrolysis was simulated using ReaxFF MD. Simulation results showed that the pyrolysis process could be divided into activation, decomposition and recombination stages, which agreed well with the experimental weight loss. Based on evolutions of gas species, it was found that the generation of gases was caused by the cleavage of oxygen-containing groups during the activation stage. Simulation results with the unimolecular of Shenfu coal showed that the order of chemical bond cleavage was C-O-C<CO<aromatic-CH<COOH in the activation stage. The variation of chemical bond agreed well with those from TGA-FTIR and Py-GC/MS analyses, indicating that the simulated results are valid and convincing. Therefore, it was concluded that the free radical reactions responsible for gas generation were caused by the cleavage of oxygen-containing functional groups, and this was also the trigger mechanism of coal pyrolysis.