Kinetic characteristics and reactive behaviors of HSW vitrinite coal pyrolysis: A comprehensive analysis based on TG-MS experiments, kinetics models and ReaxFF MD simulations

Abstract

Currently it is highly desired to study coal pyrolysis based on weight loss behavior, mathematical model of pyrolysis kinetics and advanced multi-scale molecular simulations to realize clean utilization of coal. This work presents a comprehensive analysis of HSW vitrinite coal pyrolysis based on thermogravimetric mass spectrometry (TG-MS) experiments, kinetics models and reactive force field molecular dynamics (ReaxFF MD) simulations. The weight loss and gas release behavior of HSW vitrinite coal at different heating rates was investigated by TG-MS. The kinetic parameters of coal pyrolysis were analyzed by Coats-Redfern model and distributed activation energy model (DAEM). The pyrolysis reactive behaviors and thermal decomposition process of HSW vitrinite coal was observed and analysis with ReaxFF MD simulations at atomic scale. The results show that the weight loss rate of pyrolysis decreased with increased heating rate. The trend of higher heating rate delayed the release of pyrolysis gas was consistent with TG results. The pyrolysis activation energy increases from 12.30 to 25.83 kJ/mol with further pyrolysis stage by Coats-Redfern model, and from 59.85 to 328.24 kJ/mol with higher carbon conversion hate by DAEM model. The results of ReaxFF MD simulations give complex initial chemical process of coal pyrolysis process, which agrees with the actual and expected coal pyrolysis process. Also the secondary reaction of tar in later stage of pyrolysis is observed clearly via ReaxFF MD simulations.