Capillary-like condensation of sorbed gases in coals

Aстахов, А. В.; Shirochin, D. L.

doi:10.1016/0016-2361(91)90094-q

Cited by 9 publications

(3 citation statements)

References 2 publications

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“…The shape of the adsorption isotherm changes from more Langmuir-like to more rectilinear as the rank of the coal decreases. Hysteresis is seen often between adsorption and desorption isotherms, and typically the hysteresis becomes larger as the coal rank decreases. − Although hysteresis is generally associated with mesoporous adsorbents, at the low CO 2 pressures ( P / P s < 0.95) studied here, this origin of the hysteresis is unlikely . As noted in previous studies, − coal swelling may be the origin of the hysteresis as well as the rectilinear shape of the adsorption isotherms.…”

Section: Resultssupporting

confidence: 48%

Importance of Volume Effects to Adsorption Isotherms of Carbon Dioxide on Coals

2003

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Attempts to describe high-pressure carbon dioxide (CO2) adsorption isotherm data using conventional adsorption equations to model the coal behavior have been only partially successful. Because swelling of the coal organic matrix in the presence of adsorbing gases is a well-known phenomenon and because traditional isotherm models assume a rigid structure, an adsorption isotherm equation was derived to account for the volume effects which may occur when an adsorbate alters the structure of an adsorbent. The equation, which accounts for volume change in general, was applied to the particular example of CO2 adsorption on coal. In some cases, significantly better fits were obtained when the adsorption data were fit to the swelling-modified model. The modified model partitions the experimentally determined adsorption into a surface adsorption term, which is important at lower pressure, and a rectilinear term, related to volume effects, which is important at higher pressures. This is particularly significant to the problem of CO2 sequestration in coal seams where high pressures of CO2 will be used.

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Section: Resultssupporting

confidence: 48%

Importance of Volume Effects to Adsorption Isotherms of Carbon Dioxide on Coals

2003

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“…The adsorption isotherm analysis revealed a hysteresis loop within the range of 0.5<P/P 0 <0.99, indicating that the evaporation in the pore differs from the condensation within it, reflecting the capillary condensation phenomenon in the presence of mesopores [ 67 ]. The hysteresis type of coal samples, classified according to the ISO 9277:2022 recommendations by IUPAC [ 68 ], was identified as H3 type.…”

Section: Resultsmentioning

confidence: 99%

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal

Li,

et al. 2024

PLoS ONE

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The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

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“…Larson and co-workers suggested that rearrangement will induce substantial increase in the self-diffusivity of CO 2 in the coal matrix, although it also appears that as the structure undergoes volumetric relaxation, the excess free volume associated with the glassy state is reduced, resulting in lower diffusion (Duda et al, 1994). The absorption of CO 2 allows the relaxation of the structure network and results in the weakening or softening of the internal structure of coal (Astakhov and Shirochin, 1991). This may contribute to local lithotype compression and compaction due to the heterogeneous and layered structure of most bituminous coal.…”

Section: Introductionmentioning

confidence: 96%