Textural changes during CO2 activation of chars: A fractal approach

Mahamud, Manuel María

doi:10.1016/j.apsusc.2006.12.109

Cited by 21 publications

(5 citation statements)

References 29 publications

(75 reference statements)

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“…The curve of ln( V p ) versus ln( T 2 / T 2max ) of the coal core is shown in Figure . Theoretically, the fractal dimension is an intrinsic property of a surface and does not depend on its size, and thus, the linear regression equation was used to calculate the fractal dimension. The slopes of curves in Figure were determined to obtain the fractal dimensions of coal cores pre- ( D pre ) and postmicrowave ( D post ) heating.…”

Section: Results and Discussionmentioning

confidence: 99%

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

et al. 2016

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The effect of microwave heating on the fractal dimension of coal cores is evaluated by an experimental work, which is carried out by nuclear magnetic resonance. This paper verifies that the membrane-bound water model is appropriate for explaining the state of bound-water in pores of coal samples. The paper also verifies fractal dimension as an intrinsic property of a surface that does not depend on porosity. The pore size, pore number, connectivity, and porosity increased after microwave irradiation. Furthermore, a theoretical equation was proposed to calculate fractal dimensions based on the transverse relaxation time (T 2 ). The fractal dimensions of coal cores decreased after microwave treatment along with the permeability increase. These results suggest that microwave irradiation is a potential method for degassing coal seams in the future.

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Section: Results and Discussionmentioning

confidence: 99%

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

et al. 2016

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“…The pore structure of the char particle also undergoes a lot of changes during gasification reaction with CO 2 . As explained by Mahamud, the opening of the pores of the reacting char during the course of gas–solid heterogeneous reaction results from the transformation of the micropores into the macropores through the intermediate formation of mesopores. As a result, the mass transfer resistance decreases due to the increase in accessible porosity, ε, and the effective diffusivity, D ke .…”

Section: Modelmentioning

confidence: 99%

Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle

et al. 2017

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Gasification study of a single Indian sub-bituminous coal char particle is carried out in the temperature range of 880−910 °C in a pure CO 2 atmosphere. Two temperatures, 900 and 800 °C, are used for char preparation, and the char obtained at higher temperature is found to be more reactive. A fully transient nonisothermal model is developed incorporating the reaction kinetics along with transport limitations. Spatial and temporal variation of thermo-physical properties like thermal conductivity, diffusivity, and density of the gas mixture and variable specific pore surface area and accessible porosity are included in the model. The model computation shows that the combined kinetics and heat transfer model is more effective to predict the experimental findings of the present authors and that reported in the literature. The simulation study is carried out to assess the effect of reaction temperature, particle size, and char reactivity on the particle temperature, conversion, gasification rate, and CO and CO 2 mass fractions within the porous volume of the particle.

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“…Current measurement methods to determine pore size distribution include small-angle X-ray scattering (SAXS) 15,16 , atom force microscopy (AFM) 17,18 , micro-focus X-ray computed tomography (μCT) 19–21 and scanning electron microscopy (SEM), categorized as physical methods 22,23 . Mercury intrusion porosimetry (MIP) and gas adsorption methods are adopted in terms of chemistry methods, and gas adsorption is mainly carbon dioxide adsorption (CA) and low-temperature liquid nitrogen adsorption (NA) 24–27 . Zhongwei W et al .…”

Section: Introductionmentioning

confidence: 99%

The fractal characteristics of pore size distribution in cement-based materials and its effect on gas permeability

Zhu

Zhang

et al. 2019

Sci Rep

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To study the influence of the pore structure of cement-based materials on macroscopic features (gas permeability), mercury intrusion porosimetry (MIP) and nitrogen adsorption (NA) were applied to 8 groups of paste and mortar samples (including adding mineral admixtures or not and standard or sealed curing conditions). Pore size distribution has a great influence on gas permeability. By calculating pore surface fractal dimensions based on Zhang’s fractal model, the obvious fractal characteristics of micropores (<100 nm) and macropores (> 105 nm) have been found. The pore diameter of the paste is mostly distributed in the micropores, and the average critical pore diameter is 82 nm. For mortar, the pore diameter is mostly distributed in the micropores and transition pores, and the average critical pore diameter is 121 nm, which means that the seepage pore diameters of the paste and mortar are 82 nm and 121 nm, respectively. The pore surface fractal dimensions of the visible pores are larger than those of the micropores, and there is an inverse relationship between the pore surface fractal dimensions and gas permeability. An important guide for engineering production is to use standard curing and add mineral admixtures to mortar materials to improve the impermeability as much as possible, while a contrary condition exists for paste materials.

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Textural changes during CO2 activation of chars: A fractal approach

Cited by 21 publications

References 29 publications

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle

The fractal characteristics of pore size distribution in cement-based materials and its effect on gas permeability

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Textural changes during CO2 activation of chars: A fractal approach

Cited by 21 publications

References 29 publications

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

Influence of Microwave Energy on Fractal Dimension of Coal Cores: Implications from Nuclear Magnetic Resonance

Modeling and Experimental Studies on CO2 Gasification of Coarse Coal Char Particle

The fractal characteristics of pore size distribution in cement-based materials and its effect on gas permeability

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Modeling and Experimental Studies on CO₂ Gasification of Coarse Coal Char Particle