Upgrading Effects of Supercritical Carbon Dioxide Extraction on Physicochemical Characteristics of Chinese Low-Rank Coals

Li, Hongjun; Chang, Qinghua; Dai, Zhenghua; Chen, Xueli; Yu, Guangsuo; Wang, Fuchen

doi:10.1021/acs.energyfuels.7b02228

Cited by 9 publications

(3 citation statements)

References 34 publications

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“…According to Wang et al [27], the decrease in surface functional group density may be attributable to the extracting effect or reactivity of ScCO2 fluid. The decrease of -OH groups may be related to the dissolution of ScCO2 to the inherent moisture in the coal samples; however, the elimination of the amide carbonyl groups may be related to the extraction of the organic volatile corresponds from coal with ScCO2 exposure, as demonstrated by Li et al [28]. In addition, a decrease in the distribution of mineral matter content in the coal samples was observed after ScCO2 exposure.…”

Section: Effect Of Scco 2 Exposure On Coal Surface Propertymentioning

confidence: 89%

Supercritical CO2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

et al. 2019

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Carbon dioxide (CO2) 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 CO2 sequestration, the properties of four different coals before and after supercritical CO2 (ScCO2) exposure at 40 °C and 16 MPa were analyzed with Fourier Transform infrared spectroscopy (FTIR), low-pressure nitrogen, and CO2 adsorption methods. Further, high-pressure CO2 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 ScCO2 exposure, especially for low-rank coal. With ScCO2 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 N2 and CO2 adsorption. The combined effects of surface property and pore structure alterations lead to a higher CO2 adsorption capacity at lower pressures but lower CO2 adsorption capacity at higher pressures. Langmuir model fitting shows a decreasing trend in monolayer capacity after ScCO2 exposure, indicating an elimination of the adsorption sites. The results provide new insights for the long-term safety for the evaluation of CO2-enhanced coal seam gas recovery.

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Section: Effect Of Scco 2 Exposure On Coal Surface Propertymentioning

confidence: 89%

Supercritical CO2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

et al. 2019

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“…On the one hand, the interactions change the coal pore structure. − Some studies have reported that scCO 2 decreased the micropore surface area and the volume of dry coals. − Similar trends were also found in the meso- and macropores of dry bituminous coals. Conversely, the scCO 2 increased the meso- and macropore structure parameters of anthracites. ,− On the other hand, the interactions change the surface chemistry properties of coal. ,− scCO 2 could extract some polycyclic aromatic hydrocarbons and aliphatic hydrocarbons from the coal matrix. , Moreover, scCO 2 typically reduces the content of weak polar functional groups of coal, including lipids, epoxies, and hydrocarbons ,,,, and, finally, alters the ratio of aromatic carbon to alkyl carbon . The pore structure and surface chemistry properties are the two main factors affecting the adsorption, diffusion, and flow of fluids within coal reservoirs. ,, Aiming to better understand the practical CO 2 –ECBM, it is of great significance to further explore the influence of scCO 2 on the physicochemical properties of coal.…”

Section: Introductionmentioning

confidence: 99%

“…13,21−24 scCO 2 could extract some polycyclic aromatic hydrocarbons and aliphatic hydrocarbons from the coal matrix. 11,13 Moreover, scCO 2 typically reduces the content of weak polar functional groups of coal, including lipids, epoxies, and hydrocarbons 13,19,21,23,24 and, finally, alters the ratio of aromatic carbon to alkyl carbon. 22 The pore structure and surface chemistry properties are the two main factors affecting the adsorption, diffusion, and flow of fluids within coal reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Zhang

et al. 2021

Energy Fuels

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Regarding CO2 geologic sequestration in the coal seam, injected CO2 in the coal reservoir at an optimum depth often presents as supercritical fluid (scCO2), which is capable of changing the physicochemical properties of coal and further affecting its CO2 storage capacity. Aiming to better explore the aforementioned influences, we conducted a long-term scCO2–H2O–coal static interaction in the laboratory. The influences of scCO2 exposure on the pore structure characteristics, the main oxygenic functional groups, and the high-pressure CO2 adsorption and desorption capabilities of four rank coals were explored. The results show that long-term scCO2–H2O exposure has minor effects on the coal micropore surface area and volume. On the contrary, it remarkably decreases the mesopore of all of the coals. The alterations in the coal pore structure parameters are mainly relevant to coal matrix swelling and mineral dissolution due to long-term scCO2–H2O exposure. In general, long-term scCO2–H2O exposure increases the Neimark fractal dimension of coals, further implying an elevated pore surface roughness and a more complex pore structure. Moreover, the main oxygenic functional groups, including C–O, CO, and −COOH, of coals after long-term scCO2 exposure are reduced. The aforementioned changes in the physicochemical properties of coals further affect their CO2 adsorption and desorption capabilities. In particular, the maximum CO2 adsorption capacity of high-rank coals decreases after exposure, whereas that of low-rank coals increases. Furthermore, the CO2 adsorption and desorption hystereses of coals become pronounced after long-term scCO2–H2O exposure, implying more stable CO2 sequestration in the coal seam. In conclusion, the implementation of CO2 sequestration in the coal seam should focus on the long-term scCO2–H2O–coal interaction.

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Effects of supercritical carbon dioxide under different conditions on mechanical properties and energy evolution of coal

Wang

Yang

Meng

et al. 2022

Geomech. Geophys. Geo-energ. Geo-resour.

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Upgrading Effects of Supercritical Carbon Dioxide Extraction on Physicochemical Characteristics of Chinese Low-Rank Coals

Cited by 9 publications

References 34 publications

Supercritical CO2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

Supercritical CO2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Effects of supercritical carbon dioxide under different conditions on mechanical properties and energy evolution of coal

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