基于ReaxFF的水煤浆反应过程中自由基反应机理研究OA

Oxy-fuel combustion of coal-water slurry(CWS)is an important technological routes for the clean and efficient utilization of coal.However,its microscopic reaction processes are strongly governed by the generation and evolution of free radicals,which are difficult to resolve precisely under high-temperature,highly nonequilibrium conditions using conventional experimental techniques.In this study,a reactive molecular dynamics framework based on the ReaxFF force field was employed to construct a CWS reaction system based on Guozhuang coal,enabling a systematic atomistic investigation of coal macromolecular decomposition and oxidative conversion dominated by free radicals.The results show that the energy evolution of the CWS oxy-fuel combustion process exhibits a pronounced stage-dependent behavior.In the initial stage,atomization,evaporation,and heating of coal particles dominate,and the system is endothermic characteristic.Subsequently,with the rapid cleavage and oxidation of coal molecular structures,the process transitions to a strongly exothermic regime.Under high-temperature conditions,large amounts of oxygen-centered radicals(O,OH,and OOH)are continuously generated and become the dominant reactive species.Their strong oxidative activity preferentially attacks bridge bonds and side chains in coal molecules,inducing the rupture of C-C and C-H bonds and driving the progressive disintegration of the aromatic backbone.Carbon-containing radicals continuously evolve from complex organic moieties into simpler oxygen-containing radicals such as CHO and CHO2,and through successive dehydrogenation and rearrangement reactions,coal macromolecules are ultimately converted efficiently into small molecular products,mainly CO and CO2.A clear temporal correlation is observed between radical evolution and product formation:the peak appearance time of·OH radicals is highly correlated with the maximum CO generation rate,while the sustained activity of·O radicals correspond to the acceleration stage of CO2 formation,reflecting the regulatory role of different radical species on product selectivity.This work elucidates the fundamental driving mechanism of CWS oxy-fuel combustion and provides a microscopic theoretical basis for process optimization and improved energy conversion efficiency.