Molecular simulation of gases competitive adsorption in lignite and analysis of original CO desorption

Abstract

To study the adsorption characteristics of CO, CO2, N2, O2, and their binary-components in lignite coal, reveal the influence of CO2 or N2 injection and air leakage on the desorption of CO in goafs, a lignite model (C206H206N2O44) was established, and the supercell structure was optimized under temperatures of 288.15–318.15 K for molecular simulation. Based on molecular dynamics, the Grand Canonical Monte Carlo method was used to simulate the adsorption characteristics and the Langmuir equation was used to fit the adsorption isotherms of gases. The results show that for single-components, the order of adsorption capacity is CO2 > CO > O2 > N2. For binary-components, the competitive adsorption capacities of CO2 and CO are approximate. In the low-pressure zone, the competitive adsorption capacity of CO2 is stronger than that of CO, and the CO is stronger than N2 or O2. From the simulation, it can be seen that CO2, N2 or O2 will occupy adsorption sites, causing CO desorption. Therefore, to prevent the desorption of the original CO in the goaf, it is not suitable to use CO2 or N2 injection for fire prevention, and the air leakage at the working faces need to be controlled.

Investigation of Competitive Adsorption Properties of CO/CO2/O2 onto the Kailuan Coals by Molecular Simulation

“…When the adsorption capacity of O 2 is higher than that of CO, air leakage should be controlled to prevent CO in coal seams containing primary CO from desorbing to improve the accuracy of predicting spontaneous coal combustion when CO is used as the index gas. 40 For no. 2 coal, compared with the CO 2 competitive adsorption capacity, the stronger adsorption capacity is shown by CO 2 .…”

“…38,39 Therefore, it is necessary to study the adsorption of CO in coal. Although Zhang et al 40 analyzed the competition between CO and other small molecules in lignite by molecular simulation, there is a lack of comparison of adsorption selectivity between CO and other small molecules. Therefore, we aimed to clarify the competitive characteristics and adsorption capacity between O 2 , CO 2 , and CO of bituminous coal, aiming at the occurrence and diffusion behavior of CO in coal seams.…”

“…It is also common to use CO as an index gas to determine coal seam spontaneous combustion in the actual production process. , Therefore, it is necessary to study the adsorption of CO in coal. Although Zhang et al analyzed the competition between CO and other small molecules in lignite by molecular simulation, there is a lack of comparison of adsorption selectivity between CO and other small molecules.…”

Molecular Dynamics Simulation and Gas Generation Tracking of Pyrolysis of Bituminous Coal

“…The parameter settings of geometry optimization, energy optimization, and annealing optimization are shown in Table 1. 28,29 2.2. AMS Molecular Dynamics Simulation.…”

Study of Adsorption Characteristics of CO2, O2, and N2 in Coal Micropores and Mesopores at Normal Pressure

“…The allelic adsorption heat of CO 2 is nearly twice that of O 2 or N 2 , it occupies a stronger adsorption site without being affected by O 2 or N 2 , and the interaction energy between CO 2 and coal is greater than that of O 2 or N 2 . Zhang et al 20 found that the adsorption amount of a single component in coal is in the order of CO 2 > CO > O 2 > N 2 through simulation research. Bahamon, 21 Hauchhum et al 22 used MD to simulate the adsorption behavior of gases on activated carbon.…”