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

Abstract

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 V_p (pore volume), total SSA (specific surface area), and D_a (average diameter) of coal micropores. Increasing the first two factors enhances coal adsorption, while increasing the D_a 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 V_max (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.