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 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.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

scholarly journals Thermodynamics of Methane Adsorption on Copper HKUST-1 at Low Pressure

2015 ◽  
Vol 6 (13) ◽  
pp. 2439-2443 ◽  
Author(s):  
Di Wu ◽  
Xiaofeng Guo ◽  
Hui Sun ◽  
Alexandra Navrotsky
Keyword(s):  
Low Pressure ◽  
Methane Adsorption

Role of chemical structures in coalbed methane adsorption for anthracites and bituminous coals

Adsorption ◽  
2017 ◽  
Vol 23 (5) ◽  
pp. 711-721 ◽  
Author(s):  
Yongshuai Fu ◽  
Xianfeng Liu ◽  
Boqing Ge ◽  
Zhenghong Liu
Keyword(s):  
Coalbed Methane ◽  
Methane Adsorption ◽  
Chemical Structures ◽  
Bituminous Coals

FRACTAL PORE STRUCTURE MODEL AND MULTILAYER FRACTAL ADSORPTION IN SHALE

Fractals ◽  
2014 ◽  
Vol 22 (03) ◽  
pp. 1440010 ◽  
Author(s):  
LIEHUI ZHANG ◽  
JIANCHAO LI ◽  
HONGMING TANG ◽  
JINGJING GUO
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Saturated Vapor ◽  
Adsorption Property ◽  
Fractal Theory ◽  
Complex Structure ◽  
Structure Model ◽  
Adsorption Model ◽  
Adsorption Volume ◽  
Isothermal Adsorption

The complex structure and surface property of porous media have significant impact on its accumulation and adsorption capacity. Based on the fractal theory, this paper presents a fractal pore structure model for shales. The effect of different pore structures on fractal dimension is discussed, and the influence of fractal dimension and pore size distribution on porosity is also analyzed. It is shown that the fractal dimension D decreases with the increase of structure parameter q/m for a certain pore diameter ratio, and porosity has positive relationship with fractal dimension. This paper also presents a multilayer fractal adsorption model which takes into account the roughness of adsorption surface by using fractal theory. With the introduction of pseudo-saturated vapor pressure in the supercritical temperature condition, the proposed adsorption model can be applied into a wider range of temperature. Based on the low-pressure nitrogen adsorption and methane isothermal adsorption experiments, the effect of fractal dimension on the adsorption behavior of shales is discussed. Fractal dimension has significant impact on the surface adsorption property and adsorption layer number n. The monolayer saturated adsorption volume Vm increases with the increase of D, while parameter C has the opposite variation trend. Finally, the optimal combination of fractal parameters for describing pore structure of shale samples is selected.

scholarly journals The influence of temperature on methane adsorption in coal: A review and statistical analysis

2019 ◽  
Vol 37 (9-10) ◽  
pp. 745-763 ◽  
Author(s):  
Zhijun Wang ◽  
Xiaojuan Wang ◽  
Weiqin Zuo ◽  
Xiaotong Ma ◽  
Ning Li
Keyword(s):  
Coalbed Methane ◽  
Methane Adsorption ◽  
Gas Content ◽  
Future Research ◽  
Temperature Dependent ◽  
Current State ◽  
Influence Of Temperature On ◽  
State Of Research ◽  
Increasing Temperature ◽  
The Relationship

The capacity of coal to adsorb methane is greatly affected by temperature and, in recent years, temperature-dependent adsorption has been studied by many researchers. Even so, comprehensive conclusions have not been reached and conflicting experimental results are common. This paper reviews the current state of research regarding the temperature-dependent adsorption of methane in coal and catalogs the conclusions from experiments conducted on that subject by 28 researchers, as published between 1995 and 2017. Probability theory and statistics are used to show that the conclusion generally accepted by most researchers is that the amount of methane adsorbed by coal decreases with increasing temperature. It is highly likely that the Langmuir volume decreases as the temperature rises, and it is also probable that the Langmuir pressure increases at higher temperatures. Equations are presented that express the relationships between methane adsorption, Langmuir volume, Langmuir pressure, and temperature. Future research should be directed toward determining the relationship between Langmuir pressure and temperature. The results of the study presented herein provide a theoretical basis for predicting the gas content in coal seams and improving the efficiency of coalbed methane development.

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.

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