Study on pyrolysis mechanism of coal in hydrogen-rich atmosphere based on reactive molecular dynamics simulation

Due to the co-combustion of hydrogen-rich atmosphere and coal in power plants has a great influence on NOX emission, it has been studied by more and more researchers. Therefore, the study of the effect of hydrogen-rich atmosphere on coal pyrolysis mechanism provides a theoretical basis for subsequent application in power plants. In this paper, reaction molecular dynamics simulation is used to investigate the pyrolysis mechanism of Henan anthracite coal within the temperature range of 300–3600 K. The consistency between the activation energy, TG curve, and gas release characteristics derived from the ReaxFF simulation and the experimental results provides evidence for the validity of this method in investigating the pyrolysis mechanism of coal. Furthermore, the pyrolysis behavior of Henan anthracite coal in N2, H2, and NH3 atmospheres with varying temperatures are studied. The pyrolysis of Henan anthracite coal can be categorized into three distinct stages under varying atmospheric conditions, as revealed by the simulation findings. Compared with N2 pyrolysis atmosphere, H2 and NH3 pyrolysis atmospheres can reduce the release of CO, reduce the activation energy, promote the degree of pyrolysis and accelerate the pyrolysis process. NH3 atmosphere has more obvious influence on the coal pyrolysis process. Also, HCN (NOX precursor) generation reactions during pyrolysis are revealed in N2, H2 and NH3 atmosphere. H2 and NH3 pyrolysis atmospheres can increase the number of HCN generation reactions and change the distribution of HCN generation reactions. The analysis of HCN formation reaction shows that CN and H2CN are the main precursors of HCN.