Effects of Supercritical CO2 on the Pore Structure Complexity of High-Rank Coal with Water Participation and the Implications for CO2 ECBM

To reveal how mineralchanges affect a coal pore structure in thepresence of water, an autoclave was used to carry out the supercriticalCO(2) (ScCO2)-H2O-coal interactionprocess. To reveal the changes in pore complexity, mercury intrusioncapillary pressure (MICP), low-pressure nitrogen adsorption, CO2 adsorption, and field emission scanning electron microscopy(FESEM) experiments were combined with fractal theory. The experimentaldata of MICP show that the MICP data are meaningful only for the porefractal dimension with pore sizes >150 nm. Therefore, the poreswereclassified into the classes >150, 2-150, and 150 nm. Themorphologiesof these pores are controlled by the morphologies of the completedissolution carbonate particles. The pore morphologies were relativelyuniform, and the fractal dimensions decreased. However, the incompletedissolution of calcite leads to irregular variations in the morphologiesfor the pores in the 2-150 nm pore size range. The pore morphologiesthat are produced by incompletely dissolved calcite particles aremore complex, which increases the fractal dimensions after the reaction.The fractal dimensions of the pores <2 nm decreased after the reaction,indicating that the newly generated micropores were more uniform andhad regular pore morphologies.

Automated summary

An autoclave was used to study the effect of mineral changes on coal pore structure in the presence of water. The pore complexity was analyzed using various experimental techniques, such as mercury intrusion capillary pressure, low-pressure nitrogen adsorption, CO2 adsorption, and field emission scanning electron microscopy. The results showed that the pore morphologies were controlled by the dissolution of carbonate particles, and the newly generated micropores had more uniform and regular shapes.