Sorption Hysteresis Characterization of CH4 and CO2 on Anthracite, Bituminous Coal, and Lignite at Low Pressure

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Zhenjian Liu ◽  
Zhenyu Zhang ◽  
Yiyu Lu ◽  
Sing Ki Choi ◽  
Xiaoqian Liu
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Bituminous Coal ◽  
Gravimetric Method ◽  
Sorption Isotherms ◽  
Low Pressure ◽  
Wide Distribution ◽  
Co2 Sorption ◽  
Sorption Hysteresis

Sorption hysteresis characterization of CH4 and CO2 on lignite, bituminous coal, and anthracite were studied to improve the understanding of the interaction between gas molecules and different ranks of coal and further improve the precision of the adsorption methods in characterizing pore structure at low pressure. Pore structure of three ranks of coal was investigated with scanning electron microscopy (SEM) and nitrogen (N2) adsorption. Then, CH4 and CO2 sorption isotherms were measured using the gravimetric method under 288, 308, and 328 K. The N2 sorption isotherms show that a wide distribution of pore size existed in three coal samples, and with the process of coalification, the specific surface area (SSA) decreased and then increased, while the pore size of coal monotonically decreased. This is confirmed by SEM observation. The measured sorption isotherms were then decomposed into simultaneously running adsorption and absorption branches based on the assumption that the former is totally reversible and the latter completely irreversible. The reconstructed adsorption branches can be well described by both Langmuir model and Dubinin–Radushkevich (D–R) equation. The absorption, which represents the sorption hysteresis portion, increased with pressure, but decreased with temperature. The absorbed amount of gas increased with pressure, but the absorption of CO2 increased concavely with gas pressure while CH4 followed an upward exponential function. Also, the absorption varied with coal rank, following a U-shaped function. This study can provide new insights to CH4 and CO2 sorption hysteresis on coal and other organic geomaterials.

scholarly journals Sorption of CO2 and CH4 on Raw and Calcined Halloysite—Structural and Pore Characterization Study

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 917 ◽  
Author(s):  
Anna Pajdak ◽  
Norbert Skoczylas ◽  
Arkadiusz Szymanek ◽  
Marcin Lutyński ◽  
Piotr Sakiewicz
Keyword(s):  
Surface Area ◽  
Structural Parameters ◽  
Mercury Porosimetry ◽  
Effective Diffusion ◽  
Gravimetric Method ◽  
Sorption Isotherms ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
High Rate ◽  
Co2 Sorption

The article presents comparative characteristics of the pore structure and sorption properties of raw halloysite (R-HAL) and after calcination (C-HAL) at the temperature of 873 K. Structural parameters were determined by optical scanning and transmission electron microscopy methods as well as by mercury porosimetry (MIP, Hg) and low-pressure nitrogen adsorption (LPNA, N2, 77 K). The surface area parameter (LPNA) of halloysite mesopores before calcination was 54–61 m2/g. Calcining caused the pore surface to develop to 70–73 m2/g. The porosity (MIP) of halloysite after calcination increased from 29% to 46%, while the surface area within macropores increased from 43 m2/g to 54 m2/g. The total pore volume within mesopores and macropores increased almost twice after calcination. The course of CH4 and CO2 sorption on the halloysite was examined and sorption isotherms (0–1.5 MPa, 313 K) were determined by gravimetric method. The values of equilibrium sorption capacities increased at higher pressures. The sorption capacity of CH4 in R-HAL was 0.18 mmol/g, while in C-HAL 0.21 mmol/g. CO2 sorption capacities were 0.54 mmol/g and 0.63 mmol/g, respectively. Halloysite had a very high rate of sorption equilibrium. The values of the effective diffusion coefficient for methane on the tested halloysite were higher than De > 4.2 × 10−7 cm2/s while for carbon dioxide De > 3.1 × 10−7 cm2/s.

Numerical Algorithm for Pore Size Distribution Characterization of Materials from 3D Images

2013 ◽  
Vol 699 ◽  
pp. 584-589 ◽  
Author(s):  
Neven Ukrainczyk ◽  
Eduard Koenders ◽  
Klaas van Breugel
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Numerical Algorithm ◽  
Digital Image ◽  
Medial Axis ◽  
Characterization Of Materials ◽  
2D And 3D

This paper presents an image based numerical method proposed to obtain information regarding pore structure and organization of pores within materials based on 3D digital image input. The output of the numerical algorithm is a pore size distribution of materials. The algorithm is based on the combination of the two digital image processing algorithms: 1) a medial axis thinning algorithm to obtain 3D skeleton of the pore structure, and 2) the distance transform of an image. The method is tested on simple 2D and 3D microstructures of packed spheres, demonstrating the performance of the proposed method.

Characterization of Pore Structure and Its Relationship with Methane Adsorption on Medium-High Volatile Bituminous Coal: An Experimental Study Using Nuclear Magnetic Resonance

2021 ◽  
Vol 21 (1) ◽  
pp. 515-528
Author(s):  
Baoxin Zhang ◽  
Xuehai Fu ◽  
Ze Deng ◽  
Ming Hao
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Adsorption Capacity ◽  
Size Distribution ◽  
Bituminous Coal ◽  
Methane Adsorption ◽  
Nuclear Magnetic

A number of studies have used the nuclear magnetic resonance (NMR) technique to analyse pore characteristics and to discuss the influencing mechanisms of pore structure on methane adsorption. However, there are few studies on the dynamic characteristics of methane adsorption over time under the same temperature and pressure conditions, especially by using the cylindrical coal samples. In this study, scanning electron microscopy (SEM), mercury injection porosimetry (MIP), isothermal adsorption and NMR techniques were carried out on the four medium-high volatile bituminous coal samples from Shanxi Province, China. The simulation of methane adsorption was carried out with the custom adsorption instruments. Based on the experimental results and the Hodot pore size classification standard, the pore size distribution of the samples was analysed. In addition, the influence of nanopore structure and water content on methane adsorption was discussed. The results show that the T2 relaxation diagram of the four coal samples has a bimodal-triple peak, which reflects the complexity of the pore structure. Due to the clay minerals filling microfractures in the sample HX, the connectivity of the nanopores is reduced, in addition there is an obvious gap between the peaks in the relaxation diagram. After calculation of the T2 relaxation diagrams of the coals, the results can be converted into the pore size distribution map. The pores in the four samples are mainly composed of the macropores, followed by the mesopores, and the ratio of micropores and transition pores is relatively small. At Sw (saturated in 5% brine for 24 h) and Sir (dried at 333 K for 3 h) conditions, the adsorption capacity of the four samples presented a positive correlation with the effective porosity and the ratio of micropores, and presented a negative correlation with the ratio of mesopores, while the macropores contribute less to the adsorption. Compared with samples at Sw conditions, the adsorption capacity of the samples at Sir conditions shows an overall increasing trend, which is approximately 1.6 times that of the samples at Sw conditions on average. When a large amount of liquid water invades the nanopores and fractures, the water occupies the adsorption space of the methane due to the wettability effects and capillary pressure, which reduces the adsorption capacity.

scholarly journals Multiscale Research on Pore Structure Characteristics and Permeability Prediction of Sandstone

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
M. A. Shi-Jia ◽  
L. I. N. Yuan-Jian ◽  
L. I. U. Jiang-Feng ◽  
Kundwa Marie Judith ◽  
Ishimwe Hubert ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Target Material ◽  
Future Research ◽  
Distribution Method ◽  
Binary Images ◽  
Permeability Prediction

The random existence of many irregular pore structures in geotechnical materials has a decisive influence on its permeability and other macroscopic properties. The analysis and characterization of the micropore structure of the material and its permeability are of great significance for geotechnical engineering. In this study, digital images with different magnifications were used to examine the pore structure and permeability of sandstone samples. The image processing method is used to obtain binary images, and then, the pore size distribution method is used to calculate the pore size distribution. Therefore, based on the Hagen-Poiseuille formula, we get the prediction value of material’s permeability and compare it with the value obtained from mercury intrusion porosimetry (MIP). It is found that different microscopic images with different magnification and various statistical methods of pore size have a specific influence on the characterization of pore structure and permeability prediction. The porosity of different magnifications is not the same, and the results obtained at higher magnifications are more consistent with the results obtained with MIP. With the increase of magnification, we can observe more pores in large sizes. The effect of CPSD (continuous pore size distribution) in pore size statistics is better than that of DPSD (discrete pore size distribution). In permeability prediction, the prediction result of higher magnification images are closer to the instrument test value, and the value of DPSD is more significant than that of CPSD. In future research, an appropriate method should be selected to obtain a reasonable prediction of the permeability of the target material.

Characterization of Pore Structure of Hardened Cement-Asphalt Paste by Mercury Intrusion Porosimetry

2014 ◽  
Vol 1004-1005 ◽  
pp. 1589-1593 ◽  
Author(s):  
Sheng Zhang ◽  
Xi Ling Zhou ◽  
Ke Ren Zheng ◽  
You Jun Xie ◽  
Qiang Fu
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Mercury Intrusion Porosimetry ◽  
Total Porosity ◽  
Pore Distribution ◽  
Hardened Cement ◽  
Volume Distribution ◽  
Mercury Intrusion ◽  
Two Peaks

To know the pore structure of cement-asphalt pastes, mercury intrusion porosimetry was applied to measure the total porosity, pore distribution and accumulative volume distribution of pore size and the pore structures were analyzed. The results show that the total porosities decline with increase in ages and reduction in A/C ratio. The total porosities declines from 28% at 1d, to 15.8%~17.2% at 28d; the most probable pore size declines from 20nm at 1d to 5nm at 28d.At 28d, there is an increase in the magnitude of pore size between100nm and 5μm; the volume faction of smaller than 5μm is 40~50%; and the amount of pore size smaller than 5nm account for 6%.There are two peaks (5μm & 50μm) in the curves of pore distribution.

scholarly journals Fuzzy Random Characterization of Pore Structure in Frozen Sandstone: Applying Improved Niche Genetic Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yao Ya-feng ◽  
Lin Jian ◽  
Ge Jian ◽  
Peng Shi-long ◽  
Yin Jian-chao ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Conversion Coefficient ◽  
Nmr T2 Spectrum ◽  
Rock And Soil ◽  
Fuzzy Random

Nuclear magnetic resonance (NMR) technology provides an innovative method employed in detecting the porous structures in frozen rock and soil masses. On the basis of NMR relaxation theory, fuzzy random characteristics of the NMR T2 spectrum and pore structure are deeply analyzed in accordance with the complex and uncertain distribution characteristics of the underground rock and soil structure. By studying the fuzzy random characteristics of the NMR T2 spectrum, the fuzzy random conversion coefficient and conversion method of the T2 spectrum and pore size distribution are generated. Based on the niche principle, the traditional genetic algorithm is updated by the fuzzy random method, and the improved niche genetic algorithm is proposed. Then, the fuzzy random inversion of the conversion coefficient is undertaken by using the improved algorithm. It in turn makes the conversion curve of the T2 spectrum and pore size distribution align with the mercury injection test curve in diverse pore apertures. Compared with the previous least square fitting method, it provides a more accurate approach in characterizing complicated pore structures in frozen rock and soil masses. In addition, the improved niche genetic algorithm effectively overcomes the shortcomings of the traditional genetic algorithm, such as low effectiveness, slow convergence, and weak controllability, which provides an effective way for parameter inversion in the section of frozen geotechnical engineering. Finally, based on the T2 spectrum test of frozen sandstone, the fuzzy random characterization of frozen sandstone pore distribution is carried out by using this transformation method. The results illustrate that the conversion coefficient obtained through the improved algorithm indirectly considers the different surface relaxation rates of different pore sizes and effectively reduces the diffusion coupling effects, and the pore characteristics achieved are more applicable in engineering practices than previous methods.

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