The interaction mechanism between the CO2 adsorption characteristics and the coal pore structures

This paper investigates the interaction mechanism between the CO2 adsorption characteristics and the coal pore structures by performed the isothermal adsorption experiments with high-pressure CO2 and the pore structures determined experiments comprehensive the low-temperature N2 adsorption method (LTGA-N2) and the low-pressure CO2 adsorption method (LPGA-CO2). The results show that the LTGA-N2 and LPGA-CO2 methods exhibit exactly opposite patterns in the obtained pore structure parameters as the coal rank varies, which can be attributed to the distinct pore ranges measured by each method. By collectively considering the parameters of coal pore structures determined via the two methods, the adsorption is affected by the intricate interplay of three factors: the total Vp (pore volume), total SSA (specific surface area), and Da (average diameter) of coal micropores. Increasing the first two factors enhances coal adsorption, while increasing the Da inhibits adsorption. The D-A model proves to be more suitable in explaining the adsorption behavior of coal samples compared the Langmuir model, and it Vmax (saturated adsorption amount) also shows a trend of "decreasing-increasing-decreasing" with the coal rank increases. The high-pressure CO2 isothermal adsorption experiment will change the pore structure and enhances the pore connectivity, resulting in an S-shaped feature in the adsorption curve.