The Response Characteristics of Pore Volume and Specific Surface Area of Different Phases of Carbon Dioxide Injection into Anthracite Coal Pores

Abstract

After the coal sample reacts with CO₂, the porosity and pore volume change. Compared with dry raw coal sample, the porosity of coal after CO₂ adsorption is increased. With the increase of CO₂ injection pressure, the porosity of coal will gradually increase, especially when CO₂ enters the supercritical phase. In terms of pore capacity of coal samples, CO₂ adsorption time, CO₂ adsorption pressure and CO₂-H₂O treatment do not show obvious regularity in the changes of pore capacity of coal samples, but in general, the increase of CO₂ adsorption pressure and CO₂-H₂O treatment have a positive effect on the increase of pore capacity of coal samples, especially ScCO₂-H₂O. The mesoporous pore capacity increased by 137.1%. In terms of macro pore volume of coal sample, the change of macro pore volume after CO₂ adsorption is more regular. Extending CO₂ adsorption time, increasing CO₂ adsorption pressure and CO₂-H₂O treatment all have positive effects on the increase of macro pore volume of coal sample. Under 8MPaScCO₂-H₂O, macro pore volume reaches a maximum of 0.016462ml/g. The increase also reached 130.4 percent. On the mesoporous specific surface area of coal sample, increasing CO₂ adsorption pressure, prolongating CO₂ adsorption time and CO₂-H₂O treatment can increase the mesoporous specific surface area of the sample. The mesoporous specific surface area of the sample at 8 MPa ScCO₂-H₂O is 0.631 m²/g, which reaches the maximum in this experiment, with an increase of 334.27%.