Supercritical CO 2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

Zhenjian Liu, Zhenyu Zhang, Xiaoqian Liu, Tengfei Wu and Xidong Du
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Zhenjian Liu: College of Civil Engineering, Yancheng Institute of Technology, Yancheng 221051, China
Zhenyu Zhang: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Xiaoqian Liu: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Tengfei Wu: China Coal Technology and Engineering Group Shenyang Research Institute, Fushun 113122, China
Xidong Du: School of Earth Sciences, East China University of Technology, Nanchang 330013, China

Energies, 2019, vol. 12, issue 17, 1-14

Abstract: Carbon dioxide (CO 2 ) has been used to replace coal seam gas for recovery enhancement and carbon sequestration. To better understand the alternations of coal seam in response to CO 2 sequestration, the properties of four different coals before and after supercritical CO 2 (ScCO 2 ) exposure at 40 °C and 16 MPa were analyzed with Fourier Transform infrared spectroscopy (FTIR), low-pressure nitrogen, and CO 2 adsorption methods. Further, high-pressure CO 2 adsorption isotherms were performed at 40 °C using a gravimetric method. The results indicate that the density of functional groups and mineral matters on coal surface decreased after ScCO 2 exposure, especially for low-rank coal. With ScCO 2 exposure, only minimal changes in pore shape were observed for various rank coals. However, the micropore specific surface area (SSA) and pore volume increased while the values for mesopore decreased as determined by low-pressure N 2 and CO 2 adsorption. The combined effects of surface property and pore structure alterations lead to a higher CO 2 adsorption capacity at lower pressures but lower CO 2 adsorption capacity at higher pressures. Langmuir model fitting shows a decreasing trend in monolayer capacity after ScCO 2 exposure, indicating an elimination of the adsorption sites. The results provide new insights for the long-term safety for the evaluation of CO 2 -enhanced coal seam gas recovery.

Keywords: super-critical CO 2; coal rank; surface property; pore structure; adsorption (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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