Swelling and acoustic emission behaviour of unconfined and confined coal during sorption of CO2

Majewska, Z.; Majewski, S.A.; Ziętek, Jerzy

doi:10.1016/j.coal.2013.06.001

Cited by 32 publications

(5 citation statements)

References 63 publications

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“…The swelling of coal, which accompanies sorption processes, reduces coal permeability [12,19,20], while the shrinking of coal, accompanying desorption processes, increases coal permeability [21][22][23]. The number of the available studies of the swelling-sorption relationship in stress-affected coal is relatively small, and the available results show that stress applied to coal limits a coal's sorption swelling [13,24].…”

Section: Introductionmentioning

confidence: 99%

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Kudasik

2019

Energies

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Among the numerous factors that have an impact on coal permeability, coal porosity is one of the main parameters. A change in the mechanical stress applied to coal results in a change of porosity. The main objective of the conducted research was to answer the following question: is a decline in coal permeability a direct effect of a decrease in coal porosity, and does mechanical stress result solely in a porosity change? A study of coal porosity under mechanical stress conditions was conducted using a uniquely constructed measurement stand. The coal samples used were briquettes prepared from a granular coal material (middle-rank coal of type B—meta bituminous, upper carboniferous formation) from the “Zofiówka” coal mine, in Poland. In order to describe coal permeability, the Klinkenberg equation was used, as it takes into consideration the slippage effect, typical of porous media characterized by low permeability. On the basis of the obtained results, it was established that the values of the Klinkenberg permeability coefficient decrease as the mechanical stress and the corresponding reduction in porosity become greater. As the briquette porosity increased, the Klinkenberg slippage effect: (i) disappeared in the case of nitrogen, (ii) and was minor for methane. The briquettes used were characterized by various porosities and showed that mechanical stress results mainly in a change in coal porosity, which, in turn, reduces coal permeability.

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Section: Introductionmentioning

confidence: 99%

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Kudasik

2019

Energies

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“…Coal mass gets ductile as the coal becomes plasticized in the process of CO 2 adsorption, and this phenomenon is more notable under the condition of Sc-CO 2 adsorption. It has been put forward that physical and molecule microstructures of coal can be altered by the interaction between CO 2 and coal induced by sorption-induced swelling, pore size reset, hydrocarbon extraction, and macromolecular rearrangement [23][24][25][26][27]. However, the link between the weakening of coal strength and the microcosmic physical-chemical alterations of Sc-CO 2 -treated coal is still rarely reported.…”

Section: Introductionmentioning

confidence: 99%

Time-Dependence of Mechanical Property Alterations on Anthracite Coals Treated by Supercritical Carbon Dioxide

Pang

et al. 2019

Geofluids

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The injection of supercritical carbon dioxide (Sc-CO2) into coal seams remarkably changes the physical-chemical structures of coal mass and thereby improves coal mechanical properties. In this study, a series of unconfined and triaxial compressive strength tests were performed on anthracite coal samples under the pressure of 8 MPa at the temperature of 35°C for 24 h and 48 h, respectively. Besides, experiments with longer Sc-CO2 treatment time were carried out on coal mass without stress constraint to observe the damage mode of coal. The results show that Sc-CO2 treatment obviously alters time-dependent mechanical properties of anthracite coal. The coal samples treated with Sc-CO2 for 240 h and 960 h show different damage modes from limited fractures to a complicated fracture network. The time-dependence of the mechanical weakening model on Sc-CO2-treated coal was proposed to explain the link between CO2 flow and mechanical weakening effect by means of physical-chemical effects on time scales.

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“…e gas in the coal pillar is mainly in the free state and adsorbed state. e free-state gas takes the form of pore pressure as the volume force to affect the mechanical property of coal, while the adsorbed gas affects the constitutive relation of the coal through adsorption and desorption [16][17][18][19]. During longwall mining, the gas in the coal pillar is in a dynamic change process of adsorption and desorption due to the variations of natural fractures, stress state, and gas migration in the coal pillar.…”

Section: Introductionmentioning

confidence: 99%

Effect of Gas on Burst Proneness and Energy Dissipation of Loaded Coal: An Experimental Study Using a Novel Gas‐Solid Coupling Loading Apparatus

Wang

et al. 2021

Shock and Vibration

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Deep coal mining is seriously affected by a combined dynamic disaster of rock burst and coal and gas outburst, but the influence mechanism of gas on this combined dynamic disaster is still not very clear, which is significantly different from the single type disasters. In this study, to explore the effect of gas on the coal-rock burst, a novel gas-solid coupling loading apparatus is designed to realize gas adsorption of coal sample with burst proneness and provide uniaxial loading environment under different gas pressure. A series of uniaxial compression tests of gas-containing coal with different gas pressure is carried out, and the energy dissipation process is monitored by an acoustic emission (AE) system. Results show that the macroscopic volume strain of the coal sample increases as gas adsorption and gas pressure increase under constant uniaxial loading pressure. Gas has the ability to expand the pores and natural fractures in coal sample by mechanical and physicochemical effects, which leads to a degradation in microstructure integrity of coal sample. With the increase of gas pressure, both the macrouniaxial compression strength (UCS) and elastic modulus show a downward trend; the UCS and elastic modulus of coal samples with 2 MPa gas pressure reduce by 58.78% and 48.82%, respectively, compared to those of the original coal samples. The main reason is that gas changes the pore-fissure structure and the mesoscopic stress environment inside the coal sample. Owing to the gas, the accumulated elastic energy of the gas-containing coal samples before failure reduces significantly, whereas the energy dissipated during loading increases, and the energy release process in the postpeak stage is smoother, indicating the participation of gas weakens the burst proneness of the coal sample. This study is of important scientific value for revealing the mechanism of combined dynamic disaster and the critical occurrence conditions of coal-rock burst and coal and gas outburst.

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Swelling and acoustic emission behaviour of unconfined and confined coal during sorption of CO2

Cited by 32 publications

References 63 publications

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Time-Dependence of Mechanical Property Alterations on Anthracite Coals Treated by Supercritical Carbon Dioxide

Effect of Gas on Burst Proneness and Energy Dissipation of Loaded Coal: An Experimental Study Using a Novel Gas‐Solid Coupling Loading Apparatus

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