scholarly journals Coalbed methane adsorption capacity related to maceral compositions

2019 ◽  
Vol 38 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Langtao Liu ◽  
Chao Jin ◽  
Lei Li ◽  
Chenyang Xu ◽  
Pengfei Sun ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Coalbed Methane ◽  
Functional Group ◽  
Methane Adsorption ◽  
Low Rank ◽  
Low Rank Coal ◽  
Great Role ◽  
Adsorption Volume ◽  
Isothermal Adsorption ◽  
Enhanced Adsorption

Maceral compositions take a great role in coalbed methane adsorption. Two controversial viewpoints coexist on the effect of maceral compositions to coalbed methane adsorption. One is vitrinite has better adsorption capacity than inertinite and the other is inertinite has enhanced adsorption capacity than vitrinite. In order to clarify this issue, a series of coal samples were collected and highly purified vitrinite and inertinite concentrates were gained by heavy-fluid flotation and centrifugal separation. Isothermal adsorption experiments of methane were performed to these concentrates with equilibrium moisture and their ultimate adsorption volume were obtained finally. The results show that the adsorption capacity of vitrinite is weaker and the capacity of inertinite is stronger for low-rank coal. For high-rank coal, the adsorption capacity of vitrinite is stronger and the capacity of inertinite is weaker. Along with the increase of coal rank, the adsorption capacity of vitrinite rises gradually and the adsorption capacity of inertinite declines little by little. This result shows that the adsorption capacity of coal to methane not only relates to contents of vitrinite and inertinite, but also relates to metamorphic grade of the coal, because with the increase of metamorphism of coal, molecular structure, functional group and pore characteristic of vitrinite and inertinite change gradually, which results in tremendous changes in the adsorption capacity of coal.

scholarly journals Variation of Petrophysical Properties and Adsorption Capacity in Different Rank Coals: An Experimental Study of Coals from the Junggar, Ordos and Qinshui Basins in China

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 986 ◽  
Author(s):  
Yingjin Wang ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Xiawei Li
Keyword(s):  
Adsorption Capacity ◽  
Vitrinite Reflectance ◽  
Inhibitory Effect ◽  
Proximate Analysis ◽  
Methane Adsorption ◽  
Low Rank ◽  
Petrophysical Properties ◽  
Isothermal Adsorption ◽  
Variation Rule ◽  
Moisture Absorbent

The petrophysical properties of coal will vary during coalification, and thus affect the methane adsorption capacity. In order to clarify the variation rule and its controlling effect on methane adsorption, various petrophysical tests including proximate analysis, moisture measurement, methane isothermal adsorption, mercury injection, etc. were carried out on 60 coal samples collected from the Junggar, Ordos and Qinshui basins in China. In this work, the boundary values of maximum vitrinite reflectance (Ro,m) for dividing low rank, medium rank and high rank coals are set as 0.65% and 2.0%. The results show that vitrinite is the most abundant maceral, but the maceral contents are controlled by sedimentation without any relation to coal rank. Both the moisture content and porosity results show higher values in the low ranks and stabilized with Ro,m beyond 1%. Ro,m and VL (daf) show quadratic correlation with the peak located in Ro,m = 4.5–5%, with the coefficient (R2) reaching 0.86. PL decrease rapidly before Ro,m = 1.5%, then increase slowly. DAP is established to quantify the inhibitory effect of moisture on methane adsorption capacity, which shows periodic relationship with Ro,m: the inhibitory effect in lignite is the weakest and increases during coalification, then remains constant at Ro,m = 1.8% to 3.5%, and finally increases again. In the high metamorphic stage, clay minerals are more moisture-absorbent than coal, and the inherent moisture negatively correlates with the ratio of vitrinite to inertinite (V/I). During coalification, micro gas pores gradually become dominant, fractures tends to be well oriented and extended, and clay filling becomes more common. These findings can help us better understand the variation of petrophysical properties and adsorption capacity in different rank coals.

Mineral Characteristics of Low-Rank Coal and the Effects on the Micro- and Nanoscale Pore-Fractures: A Case Study from the Zhundong Coalfield, Northwest China

2021 ◽  
Vol 21 (1) ◽  
pp. 460-471 ◽  
Author(s):  
Sandong Zhou ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Yingjin Wang ◽  
Detian Yan
Keyword(s):  
Adsorption Capacity ◽  
Coalbed Methane ◽  
Mineral Content ◽  
Northwest China ◽  
Low Rank ◽  
Low Rank Coal ◽  
Mineral Characteristics ◽  
Type D ◽  
Coal Reservoir ◽  
Nuclear Magnetic

The mineral characteristics (occurrence, type, and content) of low-rank coal and their influence on coalbed methane (CBM) reservoirs are investigated at the micro- and nanoscales. Six coal samples of three representative coalmines were used to demonstrate the uniform tectonization from the Zhundong coalfield, NW China. Based on optical microscopy and scanning electron microscopyenergy dispersive spectrum (SEM-EDS) analysis, the mineral composition and occurrence characteristics were discussed. The micro- and nanoscale reservoir characteristics in low-rank coal (pore size distribution and adsorption capability) were studied by diverse methods, including lowtemperature N2 adsorption/desorption, mercury intrusion porosimetry and CH4 isotherm adsorption analysis. The coal reservoir nuclear magnetic T2 spectra of porosity and movable fluid were obtained by combining low-field nuclear magnetic resonance (NMR) analysis, which has an advantage of determining pore fluid technology. The mineral content is highly variable (4˜16 vol.%) in the Xi Heishan prospecting area of the Qitai region. Kaolinite, goyazite, ankerite and anorthosite were microscopically observed to be filling in coal pores and microfractures, and the minerals are given priority to silicate minerals. There is a greater content of mesopores (100–1000 nm) and transition pores (10–100 nm), and they are well connected. The micropores (0–10 nm) are dominated by parallel plate, closed or wedge-shaped pores. Furthermore, the microfractures are mainly observed for types B (width ≥ 5 μm and length≤ 10 mm) and D (width<5 μm and length<300 μm). The results show that microfractures B and C (width< 5 μm and length ≥ 300 μm) are better connected, but the orientation and connectivity of type D are worse. The Langmuir volume and mesopore content decreased with increasing mineral content, which shows that the low-rank coal minerals filled some adsorption space; the reduced CBM adsorption capacity and cellular pore and intergranular pore filled with minerals affect the mesopore content. Therefore, mineral characterization significantly influences methane adsorption capacity and pore structure.

scholarly journals Surface Chemical Heterogeneity of Low Rank Coal Characterized by Micro-FTIR and Its Correlation with Hydrophobicity

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 239
Author(s):  
Wei Wang ◽  
Long Liang ◽  
Yaoli Peng ◽  
Maria Holuszko
Keyword(s):  
Surface Chemistry ◽  
Functional Group ◽  
Group Composition ◽  
Contact Angles ◽  
Low Rank ◽  
Surface Chemical ◽  
Carbonyl Groups ◽  
Low Rank Coal ◽  
Different Types ◽  
Aliphatic Carbon

Micro-Fourier transform infrared (micro-FTIR) spectroscopy was used to correlate the surface chemistry of low rank coal with hydrophobicity. Six square areas without mineral impurities on low rank coal surfaces were selected as testing areas. A specially-designed methodology was applied to conduct micro-FTIR measurements and contact angle tests on the same testing area. A series of semi-quantitative functional group ratios derived from micro-FTIR spectra were correlated with contact angles, and the determination coefficients of linear regression were calculated and compared in order to identify the structure of the functional group ratios. Finally, two semi-quantitative ratios composed of aliphatic carbon hydrogen, aromatic carbon hydrogen and two different types of carbonyl groups were proposed as indicators of low rank coal hydrophobicity. This work provided a rapid way to predict low rank coal hydrophobicity through its functional group composition and helped us understand the hydrophobicity heterogeneity of low rank coal from the perspective of its surface chemistry.

Effects of sequence stratigraphy on coal characteristics and CH4 adsorption capacity of the low-rank coal in Santanghu Basin, China

2020 ◽  
Vol 81 ◽  
pp. 103467
Author(s):  
Liwei Zhang ◽  
Detian Yan ◽  
Shuguang Yang ◽  
Hassan Nasir Mangi ◽  
Haijiao Fu ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Sequence Stratigraphy ◽  
Low Rank ◽  
Low Rank Coal ◽  
Ch4 Adsorption

scholarly journals Effects of Pore Structures of Different Maceral Compositions on Methane Adsorption and Diffusion in Anthracite

2019 ◽  
Vol 9 (23) ◽  
pp. 5130 ◽  
Author(s):  
Jincheng Zhao ◽  
Yong Qin ◽  
Jian Shen ◽  
Binyang Zhou ◽  
Chao Li ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Pore Diameter ◽  
Fractal Theory ◽  
Effective Diffusion ◽  
Low Pressure ◽  
Methane Adsorption ◽  
Isothermal Adsorption ◽  
Diffusion Capacity ◽  
Pore Structures ◽  
Study Results

The pore structure of coal reservoirs is the main factor influencing the adsorption–diffusion rates of coalbed methane. Mercury intrusion porosimetry (MIP), low-pressure nitrogen adsorption (LP-NA), low-pressure carbon dioxide adsorption (LP-CA), and isothermal adsorption experiments with different macerals were performed to characterize the comprehensive pore distribution and methane adsorption–diffusion of coal. On the basis of the fractal theory, the pore structures determined through MIP and LP-NA can be combined at a pore diameter of 100 nm to achieve a comprehensive pore structural splicing of MIP, LP-NA, and LP-CA. Macro–mesopores and micro-transitional pores had average fractal dimensions of 2.48 and 2.18, respectively. The Langmuir volume (VL) and effective diffusion coefficients (De) varied from 31.55 to 38.63 cm3/g and from 1.42 to 2.88 × 10−5 s−1, respectively. The study results showed that for super-micropores, a higher vitrinite content led to a larger specific surface area (SSA) and stronger adsorption capacity but also to a weaker diffusion capacity. The larger the average pore diameter (APD) of micro-transitional pores, the stronger the diffusion capacity. The diffusion capacity may be controlled by the APD of micro-transitional pores.

scholarly journals Characteristics and Origin of Methane Adsorption Capacity of Marine, Transitional, and Lacustrine Shales in Sichuan Basin, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xianglu Tang ◽  
Wei Wu ◽  
Guanghai Zhong ◽  
Zhenxue Jiang ◽  
Shijie He ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Adsorption Capacity ◽  
Clay Minerals ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Thermal Evolution ◽  
Methane Adsorption ◽  
Isothermal Adsorption ◽  
Xujiahe Formation

Adsorbed gas is an important component of shale gas. The methane adsorption capacity of shale determines the composition of shale gas. In this study, the methane adsorption capacity of marine, transitional, and lacustrine shales in the Sichuan Basin was analyzed through its isothermal adsorption, mineral composition, water content, etc. The results show that the methane adsorption capacity of marine (Qiongzhusi Formation and Longmaxi Formation), transitional (Longtan Formation), and lacustrine (Xujiahe Formation and Ziliujing Formation) shales is significantly different. The Longtan Formation has the strongest methane adsorption capacity. This is primarily related to its high organic matter and organic matter type III content. The methane adsorption capacity of the lacustrine shale was the weakest. This is primarily related to the low thermal evolution degree and the high content of water-bearing clay minerals. Smectite has the highest methane adsorption capacity of the clay minerals, due to its crystal structure. The water content has a significant effect on methane adsorption largely because water molecules occupy the adsorption site. Additionally, the temperature and pressure in a specific range significantly affect methane adsorption capacity.

scholarly journals Hydrogen Adsorption Capacity Reduction of Activated Carbon Produced from Indonesia Low Rank Coal by Pelletizing

2015 ◽  
Vol 44 (5) ◽  
pp. 747-752
Author(s):  
Sri Harjanto ◽  
Latifa N. Noviana ◽  
Mia Diniati ◽  
Stefanno W. Yunior ◽  
Nasaruddin .
Keyword(s):  
Activated Carbon ◽  
Adsorption Capacity ◽  
Hydrogen Adsorption ◽  
Low Rank ◽  
Low Rank Coal ◽  
Capacity Reduction

scholarly journals Contribution of Ash Content Related to Methane Adsorption Behaviors of Bituminous Coals

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Yanyan Feng ◽  
Wen Yang ◽  
Wei Chu
Keyword(s):  
Adsorption Capacity ◽  
Coalbed Methane ◽  
Textural Properties ◽  
Isosteric Heat ◽  
Micropore Volume ◽  
Ash Content ◽  
Heat Of Adsorption ◽  
Methane Adsorption ◽  
Adsorbed Phase ◽  
Adsorption Processes

Methane adsorption isotherms on coals with varying ash contents were investigated. The textural properties were characterized by N2adsorption/desorption isotherm at 77 K, and methane adsorption characteristics were measured at pressures up to 4.0 MPa at 298 K, 313 K, and 328 K, respectively. The Dubinin-Astakhov model and the Polanyi potential theory were employed to fit the experimental data. As a result, ash content correlated strongly to methane adsorption capacity. Over the ash range studied, 9.35% to 21.24%, the average increase in methane adsorption capacity was 0.021 mmol/g for each 1.0% rise in ash content. With the increasing ash content range of 21.24%~43.47%, a reduction in the maximum adsorption capacities of coals was observed. In addition, there was a positive correlation between the saturated adsorption capacity and the specific surface area and micropore volume of samples. Further, this study presented the heat of adsorption, the isosteric heat of adsorption, and the adsorbed phase specific heat capacity for methane adsorption on various coals. Employing the proposed thermodynamic approaches, the thermodynamic maps of the adsorption processes of coalbed methane were conducive to the understanding of the coal and gas simultaneous extraction.

Pyrolysis characteristic of coals with different metamorphic grades and its instruction to coalbed methane development

2017 ◽  
Vol 14 (5) ◽  
pp. 423-432 ◽  
Author(s):  
Peng Xia ◽  
Kunjie Li ◽  
Fangui Zeng ◽  
Xiong Xiao ◽  
Jianliang Zhang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Adsorption Capacity ◽  
Coalbed Methane ◽  
Shanxi Province ◽  
Maximum Temperature ◽  
Coal Pyrolysis ◽  
Gas Generation ◽  
Isothermal Adsorption ◽  
Content Type ◽  
Cbm Production

Purpose Pyrolysis for coal gas generation changes the composition, pore structure, permeability and adsorption capacity of coal. This work aims to discuss the utilization of coal pyrolysis on enhancing coalbed methane (CBM) production in the Gujiao area, Shanxi province, China. Design/methodology/approach This research was conducted mainly by the methods of thermogravimetry mass spectrometry (TG-MS) analysis, liquid nitrogen adsorption experiment and methane isothermal adsorption measurement. Findings The results can be concluded as that 400-700°C is the main temperature range for generating CH4. Pore volume and specific surface area increase with increasing temperature; however, the proportion of micro pore, transition pore and macro pore has no difference. The optimum temperature for enhancing CBM production should be letter than 600°C because the sedimentation of tar and other products will occupy some pores and fissures after 600°C. Originality/value Here in, to accurately recognize the suitable maximum temperature for heating development, a method enhancing CBM production, TG-MS, was adopted to analyze the products and the weight loss of coals with different ranks in the Gujiao area at temperature of 30-1,100°C. And then the pore structure, porosity, permeability, methane adsorption capacity and thermal maturity of coals during pyrolysis were investigated with increased temperature from 30°C to 750°C. On these bases, the favorable condition for enhancing CBM production and the thermal evolution of coal were recognized.

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