Competitive Adsorption Mechanism of CH<sub>4</sub>, CO<sub>2</sub>, and N<sub>2</sub> in Different Coal Slit Pores Based on GCMC and MD
Yinghuan Xing, Jinzhang Jia
Abstract
It is essential to elucidate the meaning of the mechanism of gas adsorption, diffusion, and seepage in the coal microscopic pore structure for efficient gas extraction, disaster prevention and control, coalbed methane resource assessment, and CO 2 geological storage. This paper aims to examine the competitive adsorption mechanisms of CH 4, CO 2, and N 2 across different slit pore sizes. The study focuses on the competitive adsorption behaviors of these gases within various slit pore sizes, utilizing Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The effects of pressure, slit pore size, and molar volume fraction on CH 4, CO 2, and N 2 adsorption, energy distribution, and adsorption volumetric strain were analyzed. The results indicated that as the slit pore size increased from 0.4 to 8.0 nm, the saturated adsorption capacities showed an increase for CH 4 from 12.58 to 53.65 mL/g, for CO 2 from 16.94 to 144.5 mL/g, and for N 2 from 12.25 to 51.93 mL/g. When the pressure was 10 MPa, the volume strains of pure CO 2, CH 4 and N 2 were 4.73, 1.42, and 1.27%, and the adsorption and swelling capacities of CO 2 were 3.33 times those of CH 4 and 3.72 times those of N 2 .