Influence of matrix size and pore damage path on the size dependence of gas adsorption capacity of coal

Abstract

Gas adsorption laws of coal particles are vital to the natural gas science and engineering. It is commonly believed that coal particle size exerts an important influence on the gas adsorption capacity. However, different trends of adsorption capacities versus particle sizes were reported in literature. The main purpose of this study is to explain the mechanism of gas sorption behaviors occurred in previous experiments and to clarify the relationship between the pore system damage path and the adsorption capacity. First, experiments including proximate analysis, scanning electron micropore test, mercury porosimetry test and low-temperature liquid N2 adsorption test were conducted for obtaining an accurate pore damage path. Then, the matrix size was investigated according to the theory of fractal dimension. Furthermore, based on the experimental results of isothermal adsorption and desorption, critical desorption particle size was obtained to verify the matrix size applied in the theoretical analysis. Finally, an improved Langmuir model was proposed to calibrate the influence of particle size. The results can help improve the accuracy of the evaluation of adsorption capacity for coal.