Molecular simulation of CO production and adsorption in a coal–kaolinite composite gangue slit model

Abstract

To reveal the mechanism of CO gas generation and adsorption in coal gangue slits at the microscopic level, a new composite kaolinite–coal–kaolinite (KCK) slit model was constructed by combining the Hongqingliang (HQL) coal molecular model and the Bish kaolinite model to characterize the crack structure of the gangue. It is compared with the kaolinite model (TriK) commonly used in gangue research. Molecular dynamics was used to study the production of CO in different oxygen environments and variation in the adsorption amount, adsorption sites and diffusion coefficient in the temperature range from 293.15 K to 333.15 K. The results indicate that CO mainly comes from the decomposition of ether and phenol in organic structures, and the lower the oxygen concentration, the lesser the CO production time. The KCK model has a higher average adsorption capacity and weaker diffusion capacity mainly due to the additional adsorption sites provided by the carbon-containing structural layer, and CO is mainly adsorbed near the oxygen-containing functional groups. Although kaolinite exhibits bonding adsorption on the Al–O plane, its adsorption site is limited to the surface. The slit model with the carbon structure can better reflect the complex conditions of gas motion in the gangue, thus providing a reference to determine the spontaneous combustion conditions of the gangue hill via the index gas.