Experimental and molecular dynamics study on combustion characteristics of non-stick coal

To investigate the combustion characteristics of non-stick coal and the formation patterns of main combustion products and radicals, this study initially conducted a TG-DSC experiment of non-stick coal. Subsequently, non-stick coal was characterized and analyzed using XPS and ¹³C NMR experiments, and a molecular model with the formula C₂₀₈H₁₉₉O₂₃N₃S was constructed. Subsequently, the ReaxFF MD method was employed to simulate the combustion molecular dynamics of the non-stick coal periodic mixing model under varying oxygen content and temperature conditions. The analysis focused on elucidating the formation patterns of free and primary products during combustion. Experimental findings indicate that the combustion of non-stick coal progresses through stages, including water evaporation and desorption (30-145.65 °C), dynamic equilibrium (145.65-181.76 °C), oxygen weight gain (181.76-263.56 °C), thermal decomposition (263.56-379.14 °C), combustion (379.14-562.04 °C) and burnout (562.04-800 °C). The ignition temperature of non-stick coal was determined to be 379.14 °C. The simulation results indicate that an increase in temperature and oxygen content further enhances the relatively stable peak production of CO₂. The peak increase of CO production is weaker than that of CO₂. The rise in temperature also promotes the formation of H₂O, while the increase in oxygen content initially enhances and subsequently inhibits the peak production of H₂O. H radicals, O radicals, and OH radicals are primarily generated through the decomposition reactions of small molecular compounds or other free radicals. Free radical polymerization and the decomposition of small molecular compounds represent the primary pathways for the formation of CO, CO₂, and H₂O.