Interactions of Supercritical CO₂ with Coal

Abstract

Carbon dioxide sequestration on coal with enhanced coalbed methane recovery (CO 2 -ECBM) is acknowledged as a promising way to mitigate CO 2 emissions. For successfully understanding and implementing CO 2 -ECBM process, the potential interactions of CO 2 with coal during CO 2 sequestration in coal seams were investigated. Research methods consisting of lowtemperature nitrogen adsorption−desorption and chromatographic analysis were used to address the transformation of coal pore morphology and the capability of supercritical CO 2 extraction when coal contacts with high pressure CO 2 . According to the test results, interaction of coal with high pressure CO 2 does not create a significant influence on pore shape and mesoporous volume distribution of any rank of coal. However, this causes the coal surface fractal dimension and specific surface area to be changed, which implies that the coal's pore morphology change due to CO 2 sorption is irreversible. The results also indicate that the injection of high-pressure CO 2 does not only change the pore morphology of coal but also has the ability to extract the hydrocarbons present in the coal matrix. The extracted hydrocarbons are of biological toxicity and can be mobilized with gas or water to other geologic structures and aquifers. Thus, the potential environmental safety and health issues (ES&H issues) related to CO 2 sequestration in deep coal seams require thorough assessment.

Measurement of CO2Solubility in NaCl Brine Solutions at Different Temperatures and Pressures Using the Potentiometric Titration Method

“…The reaction between the solution and the NaOH was given 10 min before it was withdrawn. During the withdrawal, no gas bubble was generated because all types of the carbon species (including HCO 3 − and H 2 CO 3 ) were dissolved in the NaOH and converted to CO 3 2− as long as excess amounts of NaOH were available. 27,29 The NaOH preserved samples were then analyzed through the potentiometric titration method.…”

Multifractal analysis of Hg pore size distributions of tectonically deformed coals

“…The pore size distributions (PSDs) of coals have gained wide attention since they have a significant influence on the success of exploiting coalbed methane (CBM) from wells (Clarkson and Bustin, 1999;Zhang et al, 2013aZhang et al, , 2013b. The pore properties are related to the complex physical and chemical structures of coals (Bustin et al, 1995;Firouzi et al, 2014;Xu et al, 2014).…”

Experimental study of physical‐chemical properties modification of coal after CO2 sequestration in deep unmineable coal seams

“…Mining depths are more than 800 m. Below this depth, the temperature and pressure are far above the critical points of CO 2 (T c = 31.1°C, P c = 7.38 MPa). 35,36 In addition, the water in coal seams may be supplied from other sandstone formations, and there also will be some residual water in coal seams during drainage and pressure, lowering exploitation of CBM. Besides, some minerals contained in coal and some coal gangue layers exist in coal seams.…”