High Pressure Adsorption Behaviors of CO2/CH4 Mixture On Korean Coal

High pressure adsorption behaviors of CO₂/CH₄ mixture on Korean coal

Hae Jung Kim, Hyeon Hui Lee and Chang-Ha Lee^*

Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul, Korea

^*E-mail: leech@yonsei.ac.kr, Tel: +82-2-2123-2762

CO₂ storage in geological formations has been regarded as one of the promising methods to reduce anthropogenic CO₂ emissions. Among geological sequestration sites, un-mineable coal seams offer attractive sites because it can have a chance for the recovery of CH₄ from a coal seam (ECBM) in addition to CO₂ sequestration. Due to the higher adsorption affinity of CO₂ to coal, the injected CO₂ displaces the pre-adsorbed CH₄ being stored in the coal seams.

To evaluate preferential CO₂ adsorption on coals, adsorption and desorption behaviors of pure CO₂ and CH₄ on Kyungdong coal (anthracite coal, South Korea) were measured and competitive adsorption experiments with CO₂/CH₄ mixture gas were performed in this study. Adsorption behavior of anthracite with a significant amount of mineral matter was measured at 318 and 338 K up to 150 atm. To evaluate the moisture effect, a set of experiments on dry and wet coal was carried out by a volumetric method.

The water dissolved in the CO₂-rich (or CH₄-rich) gas phase as well as coal swelling should be considered in evaluating the sorption capacity of a wet coal seam. In the mixture, the mole ratio of CO₂ to CH₄ was lower in the equilibrium phase than in the source gas at both temperatures throughout all pressures. It indicated the preferential CO₂ adsorption in competitive adsorption condition, and it could also be confirmed from higher CO₂ adsorbed amounts than CH₄ from the mixture. When the adsorption isotherms of mixture gas were compared with pure gas, those showed similar behaviors with pure CO₂ rather than CH₄.

References

[1] D. Li, Q. Liu, P. Weniger, Y. Gensterblum, A. Busch, B.M. Krooss, Fuel, 89 (2010) 569-580.

[2] J. He, Y. Shi, S. Ahn, J.W. Kang, C.-H. Lee, J. Phys. Chem. B, 114 (2010) 4854-4861.

[3] H.J. Kim, Y. Shi, J. He, H.-H. Lee, C.-H. Lee, Chem. Eng. J. (2011), doi: 10.1016/j.cej.2011.03.035