Reactive force field molecular dynamics (ReaxFF MD) simulation of coal oxy-fuel combustion

Understanding the reaction mechanism of oxy-coal combustion is fundamentally important to the CO₂ capture and storage in coal-fired industrial processes. In this paper, the microscopic reactive behaviors of brown coal combustion in O₂/CO₂ atmosphere were simulated by combining the molecular dynamics (MD) simulations and the reactive force field (ReaxFF). With thoroughly tracing the motion trajectories of atoms, as well as the formation, transition and breaking of bonds between atoms, the generation pathways of CO₂ and the effects of temperature (1600–2000 K) and oxygen concentration (21%~30%) on the coal oxy-fuel combustion process were studied. Results showed that the main process of CO₂ generation consists of the decomposition, oxygenation, and dehydrogenation. The atmosphere with a high concentration of CO₂ can accelerate the reaction rate of coal combustion and reduce the consumption of O₂. The higher temperature will promote the production of major intermediates with more fragments being released earlier, and finally increase the generation of CO₂. The increase of O₂ concentration obviously hastens the decomposition of coal molecule and the generation of H₂O, but shows very weak influence on the distributions of other major products and intermediates.