Effect of Temperature on Permeability and Mechanical Characteristics of Lignite

Shao, Jixi; Hu, Yue; Meng, Tao; Song, Su; Jin, Peihua; Gui, Feng

doi:10.1155/2016/1430641

Cited by 10 publications

(5 citation statements)

References 22 publications

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“…To sum up, the mechanical parameters of the coal indicate a weakening trend with an increase in temperature, which is consistent with the research results of Xu et al [19] and Shao et al [20].…”

Section: Influence Of Temperature On the Mechanical Properties Of Dee...supporting

confidence: 91%

Experimental Study on Permeability Evolution of Deep Coal Considering Temperature

Wang

Zhang

2022

Sustainability

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With the depletion of shallow mineral resources, the sustainable development and utilization of deep mineral resources will become a normal activity. As a type of clean energy to promote sustainable development, gas in deep coal seams has attracted wide attention. A better understanding of the permeability evolution induced by mining disturbance and the geological environment is of great importance for underground coal exploitation and gas extraction. In order to analyze the evolution of the mechanical properties and permeability of deep coal that are induced by high ground temperature, coal of the Pingdingshan Coal Mine has been investigated, and the seepage tests were carried out by keeping the confining pressure constant and loading and unloading axial stress under different temperature conditions. The effect of temperature on the peak strength and the initial elastic modulus of coal samples is analyzed. The evolution of permeability, which is estimated with the transient pulse method, based on fractional derivative and fracture connectivity, are discussed by establishing the relationship between fracture connectivity and fractional derivative. Meanwhile, the damage variable that is caused by stress and temperature is introduced and the contribution of thermal damage on coal damage accumulation is discussed. A theoretical model is proposed regarding permeability evolution with temperature and stress based on the Cui–Bustin model, which is verified by experimental data. It has been found that the strength and elastic modulus of deep coal decrease nonlinearly with increasing temperature, which demonstrates that temperature has a weakening effect on the mechanical properties of coal. The fracture connectivity and permeability evolution trends with axial strain are consistent under different temperatures, which decrease slowly in the compaction and linear elastic stages, reach the minimum at the volumetric dilation point, gradually increase in the yield stage, then have a sharp increasing trend in the post-peak stage and, finally, become steady in the residual stage. The damage induced by temperature increases with rising temperatures under different external load conditions. When the external load increases gradually, the thermal damage still accumulates, but the thermal damage variable ratio decreases. The proposed permeability model considering temperature and stress can describe the trend of the experimental data. With axial stress increasing, the influence of temperature on permeability decreases, and its leading effect is mainly reflected in the compaction stage and the linear elastic stage of coal.

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Section: Influence Of Temperature On the Mechanical Properties Of Dee...supporting

confidence: 91%

Experimental Study on Permeability Evolution of Deep Coal Considering Temperature

Wang

Zhang

2022

Sustainability

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“…This behavior was also observed in the literature, where, according to Ifelebuego and Momoh [29], who studied the sorption capacity of coconut residues with vegetable oil and diesel oil, this parameter decreased with increasing temperature. According SHAO et al [30], this is due to the reduction of permeability that occours with materials when the temperature rises. This increase generates the dilatation of the sorbent medium and reduces the porous volume of the material, reducing the permeable channels and, consequently, the surface area of oil adsorption and absorption.…”

Section: Sorbent Materials T (Min) T (°C) S (G/g) -Average Standard Dementioning

confidence: 99%

Comparative study of diesel sorption performance between Chorisia speciosa fibers and a commercial polyurethane foam

et al. 2021

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The objective of this work was to evaluate and compare the potential of polyurethane and kapok (Chorisia speciosa) residues as sorbent materials in the treatment of diesel spillage. To determine the sorption capacity, gravimetric tests were performed in static medium at room temperature and at different temperatures (10, 15 and 28 °C) and varying the time of contact between the sorbent material and diesel. It was observed that the sorption process occurs at a high velocity, with saturation point achieved in the first 5 minutes of contact, and the natural fiber presents higher sorption capacity compared to the polyurethane residue due to the low viscosity of diesel oil, that contributes to reduce de entrapment inside the porous foam. It has also been observed that the polyurethane residue exhibits an increase in sorption capacity with time and temperature increase. Scanning electron microscopy (SEM) analysis have shown that the main morphological property involved in smooth oil sorption was the high porosity associated with a small porous diameter. The kapok presented sorption capacity of 37 g/g in equilibrium demonstrating its great potential of application as a sorbent material for the treatment of diesel spillage.

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“…32,33 Taiyuan University of Technology studied the physical characteristics of coal during pyrolysis under high-temperature triaxial stress using an in situ developed high-temperature and high-pressure rock triaxial testing machine, 34 and the porosity of coal decreased with increasing pore pressure under in situ underground pyrolysis. 35,36 Duan et al 37 used a high-temperature and highpressure rheometer to study the pyrolysis characteristics of coal under different stress conditions. The results showed that the gas and semicoke yields increased with increasing stress, while the tar yield decreased.…”

Section: Introductionmentioning

confidence: 99%

“…Research on in situ underground pyrolysis of coal is still in the laboratory stage. The University of Utah has studied the pyrolysis behavior of coal in the underground environment using chemical permeation devolatilization (CPD) model simulations and a high-pressure reactor. , The results indicate that the product of subsurface coal thermal treatment technology is mainly light crude oil. , Taiyuan University of Technology studied the physical characteristics of coal during pyrolysis under high-temperature triaxial stress using an in situ developed high-temperature and high-pressure rock triaxial testing machine, and the porosity of coal decreased with increasing pore pressure under in situ underground pyrolysis. , Duan et al used a high-temperature and high-pressure rheometer to study the pyrolysis characteristics of coal under different stress conditions. The results showed that the gas and semicoke yields increased with increasing stress, while the tar yield decreased.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Analysis of In Situ Underground Pyrolysis of Tar-Rich Coal: Primary Reactions

Yang

Gao

et al. 2023

ACS Omega

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In situ underground pyrolysis of tar-rich coal is significant for alleviating the scarcity of oil and gas resources and realizing the green and efficient development and utilization of coal in China. Tar-rich coal is often subjected to high axial pressure, surrounding pressure, and pore pressure in the in situ underground pyrolysis environment. Consequently, laboratory simulation conditions are difficult to meet the actual needs. This paper conducts a thermodynamic study of the pyrolysis characteristics of tar-rich coal under an in situ environment. Typical thermodynamic functions of tar-rich coal, including the standard enthalpy of formation, standard formation Gibbs free energy, and standard entropy, were determined. Ten representative primary reactions were constructed with typical tar-rich coal pyrolysis oil components as a guide. The Gibbs free energy and equilibrium constant change laws of the above reactions were analyzed for pyrolysis temperatures from 200 to 800 °C and pyrolysis pressures from atmospheric pressure to 10 MPa. The results showed that the standard enthalpy of formation of tar-rich coal was −72.27 kJ·mol–1, the standard entropy was −37.79 J·mol–1·K–1, and the standard formation Gibbs free energy was −60.01 kJ·mol–1. When the reaction pressure increased from atmospheric pressure to 10 MPa, the thermodynamically feasible initial temperature fractions of the primary reaction of tar-rich coal pyrolysis all showed different degrees of increase. In the underground environment, the initial temperature of the primary reaction of in situ underground pyrolysis of tar-rich coal moves to a higher-temperature gradient to some extent, so the adjustment of the reaction temperature and pressure could guide the directional regulation of the in situ underground pyrolysis products of tar-rich coal.

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Effect of Temperature on Permeability and Mechanical Characteristics of Lignite

Cited by 10 publications

References 22 publications

Experimental Study on Permeability Evolution of Deep Coal Considering Temperature

Experimental Study on Permeability Evolution of Deep Coal Considering Temperature

Comparative study of diesel sorption performance between Chorisia speciosa fibers and a commercial polyurethane foam

Thermodynamic Analysis of In Situ Underground Pyrolysis of Tar-Rich Coal: Primary Reactions

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