CO Release Characteristics and Generation Pathways during High-Temperature Oxidation of Coal under Forced Rapid Heating

Forced rapid heating leads to significantly higher concentrations of carbon oxides during the high-temperature oxidation of coal compared to slow spontaneous combustion. A sudden release of large amounts of carbon monoxide frequently leads to serious poisoning accidents. This study employed a combined approach of oxidation experiments (30–300 °C at heating rates of 10, 20, 30, and 40 °C/min) and ReaxFF molecular dynamics simulations. The influence of the heating rate on the release characteristics of CO during coal oxidation was systematically investigated, and the generation pathways were elucidated. The results show that when the temperature exceeds 150 °C, higher heating rates significantly increase both the concentration and the release rates of carbon oxides. Under forced rapid heating conditions, the concentration of carbon oxides increases explosively during high-temperature oxidation, and the growth trend conforms to the exponential function. ReaxFF molecular dynamics simulations reveal that the high-temperature oxidation of coal under rapid heating is predominantly driven by pyrolysis. Forced rapid heating causes the accumulation of unreacted small molecular fragments in the system. This leads to a highly incomplete and locally oxygen-lean oxidation process. In addition to oxidation involving aldehyde radicals, new decomposition pathways of C2HO3· and C2HO2· radicals are identified as major molecular transformation routes contributing significantly to the high CO yield observed under rapid heating. This study is helpful to guide the dry drilling process of gas extraction for preventing CO poisoning and exceedance incidents.