Influence of sub-supercritical CO2 on pore structure and fractal characteristics of anthracite: An experimental study

Wang, Xiaolei; Geng, Jiabo; Zhang, Dongming; Xiao, Weijing; Chen, Yu; Zhang, Hao

doi:10.1016/j.energy.2022.125115

Cited by 13 publications

(10 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mechanisms of Sc-CO 2 extraction affecting coal pore structure are attributed to the dissolution of small organic molecules in Sc-CO 2 fluid. In order to describe the pore structure evolution characteristics of coal based on Sc-CO 2 extraction, according to the related previous research results (Chen et al, 2017;Su et al, 2018;Wang et al, 2022) and the analysis of results of this study, the evolution model of pore structure of coal by Sc-CO 2 extraction was established (Figure 11). In the process of coalification, under the influence of coalification, temperature, and pressure, the branches and side chains in the macromolecular structure of organic matter present in coal continuously fall off to form small organic molecules in coal, which get filled in the pore structure of coal to form closed or semi-closed organic filling pores (Figure 11A).…”

Section: Pore Structure Evolution Modelmentioning

confidence: 99%

“…However, supercritical (Sc)-CO 2 that offers a better ability to transform the pore structure of coal, resulting in significant changes in pore structure, has not been extensively investigated to date. Notably, Sc-CO 2 can extract small organic molecules from the coal matrix, change the pore structure characteristics of coal, and affect the recovery and storage effect of CO 2 -enhanced coal bed recovery (CO 2 -ECBM) (Wang, 2018;Zhang, 2019;Sampath et al, 2020;Wang et al, 2022). In this study, five sets of coal samples before and after the second coalification (R o,max = 1.3%) were selected from the eastern margin of Ordos Basin to simulate the process of Sc-CO 2 extraction of small organic molecules from coal under geological conditions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Chen

Hu²,

Lv³

et al. 2023

Front. Earth Sci.

View full text Add to dashboard Cite

Abundant pore space in coal is not only the place for the accumulation of coalbed methane (CBM), but also the tunnel for gas migration. In this study, five sets of coal samples before and after the second coalification were selected from the eastern margin of Ordos Basin to simulate supercritical CO2 (Sc-CO2) extraction in supercritical extraction equipment. The evolutions of pore structure and porosity were tested by mercury intrusion porosimetry and nuclear magnetic resonance spectroscopy to compare the changes of pore structure and porosity due to the Sc-CO2 extraction, and to explain the related mechanism. The results show that: (1) Pore volume, pore specific surface area, and connectivity characteristics changed significantly due to Sc-CO2 extraction, and the increment of pore volume and pore specific surface area presented a law of increase–decrease–increase with the increase in the coal rank, and the turning point was near the second coalification. (2) The porosity increment change trend due to Sc-CO2 extraction was increase–decrease–increase with increasing coal rank, and the turning point was again near the second coalification, which supports the mercury intrusion porosimetry results. (3) The changes were observed in the porosity characteristics due to Sc-CO2 extraction through pore-increasing and expanding effects. Before the second coalification, the pore-increasing and expanding effects co-existed in the micropores, and after the second coalification, the pore-expanding effect mainly existed in the transitional pores and above. (4) The variation model for the pore structure of coal due to Sc-CO2 extraction was established. The conclusions offer not only important theoretical significance for the CO2-enhanced CBM (CO2-ECBM) mechanism but also important significance for CO2-ECBM engineering.

show abstract

Section: Pore Structure Evolution Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Chen

Hu²,

Lv³

et al. 2023

Front. Earth Sci.

View full text Add to dashboard Cite

show abstract

“…The adsorption of SCO 2 caused the expansion of the coal matrix in the early stage of interaction, resulting in a decrease in porosity. Similarly, Wang et al treated coal samples with SCO 2 and found that the total porosity increased by 1.25, 4.53, and 5.82% after treatment at 4, 8, and 12 MPa and 35 °C for 4 days. Additionally, the micropore volume increased by 10.1, 42.2, and 42.7% at these pressures.…”

Section: Introductionmentioning

confidence: 95%

Study of the Mechanical Properties and Damage Characteristics of Coal after Interaction with Supercritical Carbon Dioxide

et al. 2023

View full text Add to dashboard Cite

The injection of CO 2 into deep unrecoverable coal seams can serve the dual purpose of facilitating the efficient extraction of coal-bed methane (CBM) and geological storage of CO 2 . However, due to the nonhomogeneous and anisotropic nature of coal seams, which are influenced by depositional environment, geological structure, and hydrogeology, the anisotropy of the deep unrecoverable coal seams can affect the CO 2 − water−coal reaction. The mechanical properties and damage of coal after the physical and chemical reactions of supercritical CO 2 (SCO 2 )−water−coal at different seam inclinations have not been extensively studied. In this study, we analyze the mechanical properties and damage of coal before and after the reaction by utilizing noncontact full-field strain, acoustic emission, ultrasonic nondestructive testing, and nuclear magnetic techniques. The results demonstrate that the mechanical properties of the coal underwent significant changes after SCO 2 treatment, with the largest decreases in compressive strength and elastic modulus observed in the 90°coal samples at 62.7 and 67.4%, respectively. Furthermore, the strain distribution of the treated coal samples exhibited distinct characteristics of laminar dip angle. Acoustic emission analysis revealed that the damage variable D 1 of the 45°coal sample had the largest value, while the acoustic emission damage variable D 1 of the 90°coal sample had the largest increase of 99.5%. The longitudinal wave velocity of a coal sample is highest at 0°, followed by 45°, and lowest at 90°. At 90°, the maximum value of the wave velocity damage factor is 0.577. Additionally, as the total porosity of the coal increases, the maximum increase observed after testing a coal sample at 90°is 1%. Moreover, the pore structure undergoes changes during this process. The number of micropores decreases, while the number of mesopores and macropores increases. The findings of this study provide theoretical guidance for CO 2 injection into deep unrecoverable coal-bed methane.

show abstract

“…Some of the ways to obtain the fractal dimensions of coal include mercury intrusion capillary pressure (MICP), low-pressure nitrogen/carbon dioxide adsorption, scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). − Current research on the changes in the fractal dimensions of coal after CO 2 injection shows that the fractal dimension of the pores will increase, and the surface pores will be rougher after the reaction. These factors combine to make the coal layers more conducive to CO 2 sequestration. , The fractal dimension is also affected by the burial depth and maturation degree of the coal. The deeper the coal is buried, the larger the temperature increase and the less the coal fractal dimension .…”

Section: Introductionmentioning

confidence: 99%

“…These factors combine to make the coal layers more conducive to CO 2 sequestration. 30 , 31 The fractal dimension is also affected by the burial depth and maturation degree of the coal. The deeper the coal is buried, the larger the temperature increase and the less the coal fractal dimension.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

ACS Omega

View full text Add to dashboard Cite

To reveal how mineral changes affect a coal pore structure in the presence of water, an autoclave was used to carry out the supercritical CO2 (ScCO2)-H2O-coal interaction process. To reveal the changes in pore complexity, mercury intrusion capillary pressure (MICP), low-pressure nitrogen adsorption, CO2 adsorption, and field emission scanning electron microscopy (FESEM) experiments were combined with fractal theory. The experimental data of MICP show that the MICP data are meaningful only for the pore fractal dimension with pore sizes >150 nm. Therefore, the pores were classified into the classes >150, 2–150, and <2 nm. The results show that the pore volume and specific surface area of the coal increased significantly after the reaction. ScCO2-H2O can cause the formation of many new pores and fractures in the coal. The presence of H2O may increase the potential for the injection of CO2 into the coal seam. The complete dissolution of calcite surfaces caused a significant increase in the pore volume and specific surface area of the pores >150 nm. The morphologies of these pores are controlled by the morphologies of the complete dissolution carbonate particles. The pore morphologies were relatively uniform, and the fractal dimensions decreased. However, the incomplete dissolution of calcite leads to irregular variations in the morphologies for the pores in the 2–150 nm pore size range. The pore morphologies that are produced by incompletely dissolved calcite particles are more 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 and had regular pore morphologies.

show abstract

Influence of sub-supercritical CO2 on pore structure and fractal characteristics of anthracite: An experimental study

Cited by 13 publications

References 50 publications

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Study of the Mechanical Properties and Damage Characteristics of Coal after Interaction with Supercritical Carbon Dioxide

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

Contact Info

Product

Resources

About

Influence of sub-supercritical CO2 on pore structure and fractal characteristics of anthracite: An experimental study

Cited by 13 publications

References 50 publications

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Effect of supercritical CO2 extraction on pore characteristics of coal and its mechanism

Study of the Mechanical Properties and Damage Characteristics of Coal after Interaction with Supercritical Carbon Dioxide

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

Contact Info

Product

Resources

About

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