Effect of supercritical CO₂ on pore structure and desorption characteristics of tectonic coal

In order to analyze the influence of supercritical CO₂ on pore structure and desorption characteristics of tectonic coal, a high-temperature and high-pressure geological environment simulation system was used to treat primary coal and tectonic coal with supercritical CO₂, and then mercury injection method and coal sample desorption experimental system were used to quantitatively characterize the pore structure and desorption characteristics of coal. The results show that the total pore volume of coal samples increases after supercritical CO₂ treatment, and the pore expansion effect of supercritical CO₂ on tectonic coal is more obvious. Due to the extraction and dissolution effect of supercritical CO₂, the pore size of structural coal increases to a certain extent, and the changes of small hole and large hole are the most obvious. The increment of hysteresis loop of treated tectonic coal is significantly higher than that of primary coal, indicating that the pore network of treated structural coal is more developed and the connectivity is better. At equilibrium pressures of 0.74 MPa and 3.00 MPa, the increase in the desorption capacity of tectonic coal after supercritical CO₂ treatment is significantly higher than that of primary coal, which is caused by the increase in the total pore volume of tectonic coal after supercritical CO₂ treatment.