Chemical structure of coal surface and its effects on methane adsorption under different temperature conditions

Zheng, Yuannan; Li, Qingzhao; Yuan, Desheng; Zhang, Guiyun; Liu, Junfeng; Yuan, Chuangchuang; Tao, Qinglin

doi:10.1007/s10450-018-9975-9

Cited by 17 publications

(11 citation statements)

References 42 publications

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“…The experimental data clearly demonstrate that the methane adsorption capacity is greatly affected by the coal rank. The good fits ( R 2 > 0.99) in Figure illustrate that the use of the Langmuir model for describing methane adsorption on coal surfaces is reasonable and convincing; therefore, the Langmuir volume ( V L ) and Langmuir pressure ( P L ) can be used to evaluate the methane adsorption capacity. − V L is a direct indicator of the CBM gas storage capacity and is proportional to the total number of available sites for adsorption. P L is closely related to the affinity of a gas on a solid surface and the energy stored in coal formation …”

Section: Resultsmentioning

confidence: 77%

Crystallite Structure Characteristics and Its Influence on Methane Adsorption for Different Rank Coals

Meng

Niu

2019

ACS Omega

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The ability of coal to adsorb methane depends on the coal microstructure; however, the research on its exploration is still underway. In this paper, a new method was adopted to investigate the evolution characteristics of the crystallite structure of eight different rank coals and its influence on the methane adsorption capacity. The crystallite lattice parameters, including d002, Lc, La, Nave, and fa, were determined by curve fitting analysis of X-ray diffraction (XRD) spectra. The methane adsorption experiments were carried out through a static capacity method, and the methane adsorption parameters (VL, PL) were measured. Correlations were established for the crystallite lattice parameters and the methane adsorption parameters. From the results obtained, there is a good negative linear relationship between VL and d002 and a good exponential relationship between PL and d002, indicating that the increasing d002 can weaken the methane adsorption capacity. VL displays an exponential increase with increasing Lc and Nave, whilePL presents a linear decrease, but reverse variations are emerged in the process of change for both, and the methane adsorption capacity is weaken temporarily. VL presents a lognormal distribution with increasing La, and the minimum value appears at La = 1.85–1.9 nm. VL and PL both obey lognormal distribution with increasing La/Lc, but their trends are completely opposite, and the methane adsorption capacity is the strongest at La/Lc = 0.85–0.9. As fa increases, VL and PL present an overall exponential increase and an overall exponential decrease, respectively, but reverse changes also emerge. The methane adsorption is related to the crystallite structure characteristics of coal. Finally, the influence mechanism of the crystallite structure evolution on the methane adsorption capacity was analyzed, which has great significance for prevention of gas disasters in underground coal mines.

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Section: Resultsmentioning

confidence: 77%

Crystallite Structure Characteristics and Its Influence on Methane Adsorption for Different Rank Coals

Meng

Niu

2019

ACS Omega

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“…The methane adsorption isotherms of coal can be characterized by the Langmuir model, Dubinin–Radushkevich (D-R) model, Dubinin–Asthakov (D-A) model, and BET model . Characterized by a simple expression, the Langmuir model is the most common method for analyzing gas adsorption in coal .…”

Section: Resultsmentioning

confidence: 99%

Microwave-Induced Microstructure Evolution of Coal and Its Effects on the Methane Adsorption Characteristic

Shi

et al. 2021

Energy Fuels

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Coalbed methane (CBM) reservoirs usually require stimulation to enhance the permeability. Characterized by the transformation of electromagnetic energy into thermal energy, microwave heating may be a promising CBM stimulation approach. In this work, the microstructure evolution of coal affected by microwave heating was investigated by Fourier transform infrared spectroscopy (FTIR), low-temperature nitrogen adsorption (LT-N2GA), and scanning electron microscopy (SEM). In addition, the methane adsorption property of coal was evaluated using a high-pressure adsorption instrument. The results indicate that microwave heating would cause the pyrolysis of ether groups, oxygen-containing groups, and aliphatic hydrocarbon in coal. After microwave treatment, the volume and connectivity between mesopores and micropores increase. The decrease in the methane adsorbability of coal may be attributed to the reduction of the methane adsorption site induced by microwave heating. The outcome of this study implies that microwave heating can be used to promote CBM recovery.

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“…In this paper, FTIR was used to study the molecular structure changes of coal before and after 3 h of ultrasonic treatment. We can qualitatively and quantitatively infer the molecular structure of a substance by comparing the absorption capacity of different groups to infrared light. , According to the characteristics of the infrared spectral absorption peak (position, intensity, shape, etc. ), the types and quantities of functional groups contained in coal can be inferred …”

Section: Resultsmentioning

confidence: 99%

Changes of Coal Molecular and Pore Structure under Ultrasonic Stimulation

Sun

et al. 2021

Energy Fuels

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In view of the limitation of the conventional coal seam fracturing method, an ultrasonic stimulation method was proposed. Utilizing the combined effects of ultrasonic cavitation, mechanical vibration, and thermal conditions, the coal will form a network of intertwined cracks, and the gas will desorb and flow more easily. Current research on the changes of coal molecular and pore structure under ultrasonic stimulation is not in-depth. In this paper, the coal samples were treated by ultrasonic stimulation at 30 kHz frequency, and the changes of temperature, molecular structure, and pore structure of different scales were captured by combining a temperature acquisition unit, an infrared spectrometer, a stereoscopic microscope, a low-field nuclear magnetic resonance apparatus, and a three-dimensional X-ray microscope. The main conclusions are as follows: The temperature rise of coal during ultrasonic stimulation can be divided into three stages, namely, rapid rise, slow rise, and fluctuating rise. Also, the maximum temperature within 1 h can reach 263.9 °C. The oxygencontaining functional groups were decomposed and removed under ultrasonic stimulation, thus reducing the methane adsorption capacity of coal. The main fractures parallel to the bedding direction and the secondary branch fractures perpendicular to the bedding direction were produced. Furthermore, the primary and secondary fractures were penetrated, and the surface porosity increased to 3.93% after 3 h of treatment. Ultrasonic stimulation had little effect on the micropores and transition pores, but it increased the mesopores, macropores, and fractures. The effective porosity and free fluid proportion increased significantly with the increase in ultrasonic processing time by 43.86 and 31.30%, respectively. After ultrasonic stimulation, the scanned pore-fracture network model was highly connected and showed an ordered network and cross-linking, thus providing space for gas desorption and seepage.

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Chemical structure of coal surface and its effects on methane adsorption under different temperature conditions

Cited by 17 publications

References 42 publications

Crystallite Structure Characteristics and Its Influence on Methane Adsorption for Different Rank Coals

Crystallite Structure Characteristics and Its Influence on Methane Adsorption for Different Rank Coals

Microwave-Induced Microstructure Evolution of Coal and Its Effects on the Methane Adsorption Characteristic

Changes of Coal Molecular and Pore Structure under Ultrasonic Stimulation

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