Underground coal gasification (UCG): An analysis of gas diffusion and sorption phenomena

Ludwik-Pardała, Magdalena; Stańczyk, Krzysztof

doi:10.1016/j.fuel.2015.01.041

Cited by 13 publications

(6 citation statements)

References 15 publications

(25 reference statements)

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“…In considering the implications of diffusion on the transport of gaseous compounds through geologic materials, it is important to consider that transport may be along cracks and fissures within the rock. , In these cases, perhaps initially counterintuitive, higher rates of diffusion actually may result in a slower release of a compound from subsurface to above ground, as the molecule may diffuse into the walls of the fracture, thus reducing the amount of material reaching the surface …”

Section: Resultsmentioning

confidence: 99%

Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

et al. 2021

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The goal of this study was to determine the physicochemical properties of a variety of geologic materials using inverse gas chromatography (IGC) by varying probe gas selection, temperature, carrier gas flow rate, and humidity. This is accomplished by measuring the level of interaction between the materials of interest and known probe gases. Identifying a material’s physicochemical characteristics can help provide a better understanding of the transport of gaseous compounds in different geologic materials or between different geological layers under various conditions. Our research focused on measuring the enthalpy (heat) of adsorption, Henry’s constant, and diffusion coefficients of a suite of geologic materials, including two soil types (sandy clay-loam and loam), quartz sand, salt, and bentonite clay, with various particle sizes. The reproducibility of IGC measurements for geologic materials, which are inherently heterogeneous, was also assessed in comparison to the reproducibility for more homogeneous synthetic materials. This involved determining the variability of physicochemical measurements obtained from different IGC approaches, instruments, and researchers. For the investigated IGC-determined parameters, the need for standardization became apparent, including the need for application-relevant reference materials. The inherent physical and chemical heterogeneities of soil and many geologic materials can make the prediction of sorption properties difficult. Characterizing the properties of individual organic and inorganic components can help elucidate the primary factors influencing sorption interactions in more complex mixtures. This research examined the capabilities and potential challenges of characterizing the gas sorption properties of geologic materials using IGC.

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Section: Resultsmentioning

confidence: 99%

Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

et al. 2021

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“…The tests were carried out using representative samples of solid materials collected from the underground georeactor situated in the experimental mine 'Barbara' in southern Poland, within the administrative area of Mikołów city. The footprint plan of the mining area, places where char samples were collected, and groundwater sampling points surrounding the UCG reactor has been described elsewhere (Kapusta et al 2013;Ludwik-Pardała and Stańczyk 2015).…”

Section: Sample Preparation and Analysismentioning

confidence: 99%

“…Approximately 4 kg of each of the coal and char samples from the UCG georeactor area were collected and standardized by fragmentation in a laboratory crusher and then left to air dry for 7 days until a constant mass was obtained (difference in mass during subsequent weighing did not exceed 5% within 24 h). More details about sample collection is provided by Ludwik-Pardała and Stańczyk (2015). The dried samples were sieved through a 10 mm plastic sieve, yielding a target research material with a fraction of less than 10 mm.…”

Section: Sample Preparation and Analysismentioning

confidence: 99%

Comparison of Metal Adsorption from Aqueous Solutions on Coal and Char Remaining After In-situ Underground Coal Gasification (UCG)

Strugała-Wilczek

Stańczyk

Bebek³

2020

Mine Water Environ

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The aim of the study was to describe the sorption interactions between potentially toxic metals (Cd, Co, Cu, Pb) and materials from an underground coal gasification (UCG) experimental zone. These interactions seem to be significant in terms of the impact of in situ UCG on the groundwater environment. Sorption parameters were determined for two different sample types: subbituminous coal mined from the coal-bed and then subjected to gasification and coal char from the cavity formed by the UCG process. Laboratory-scale tests were carried out using deionized water and aqueous solutions of metals with increasing concentrations. The Freundlich isotherm model was applied to describe sorption phenomena due to nonlinear mass distribution of adsorbed metal ions as a function of equilibrium concentration and assuming physical interactions only. In addition, the efficiency of the tested sorbents for metal removal was calculated. In the case of subbituminous coal, the percent removal ranged from a minimum of 3.6-9.8% (for cobalt) to a maximum of 43.4-79.8% (for lead). Char removed metals more efficiently (min. 26.6-94.8% for cadmium; max. 98.5-99.9% for lead). Furthermore, the sorbates can be ranked according to the metal ion binding efficiency to sorbents in the following order: Co < Cd < Cu < Pb. The sorption characteristics of materials obtained from the post-UCG cavity may be used to evaluate the retardation parameters of inorganic pollutant migration in the environment around a georeactor.

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“…The heterogeneity and anisotropy of the physical and mechanical properties of the surrounding rock have a great influence on the thermal fracture of high-temperature rock formations [21]. Temperature heat transfer is not only related to the thermal conductivity of rocks but also has a coupling relationship with the seepage of gas in pore fractures in rock formations [22,23]. Due to the limitations of the physics applied by previous scholars to the problem of underground coal gasification and the relatively single material model, the inter-coupling factors in many physics are not really considered and can easily bring errors to the final results.…”

Section: Introductionmentioning

confidence: 99%

A Thermal-Hydrological-Mechanical-Chemical Coupled Mathematical Model for Underground Coal Gasification with Random Fractures

Zhang

Xiao²,

Shang³

et al. 2022

Mathematics

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In this paper, in order to understand the development process and influencing factors of coal underground gasification, taking the two-dimensional underground gasification area of the plane as the simulation object, the characteristics of the multi-physical field coupling process of exudate mass heat transfer and combustion gasification reaction in the process of horizontal coal seam underground gasification are analyzed, and a two-dimensional mathematical model of thermal-hydrological-mechanical-chemical coupling of a porous medium is established. The temperature distribution of coal rock from the gasification point, the distribution of gas water vapor pressure and stress-strain, the temperature contour distribution of fractured coal rocks of different densities of heterogeneity, and the influence of different water-oxygen ratios and different fractured coal rocks on the gas components generated by the gasification reaction were studied. The results show that the tensile damage caused by the tensile strain volume expansion of the coal underground gasification center, the shear damage caused by the compression of the edge compressive strain volume, and the temperature conduction rate decrease with the increase in the coal rock fracture, but in the heterogeneous coal rock, the greater the fracture density, the faster the temperature conduction rate, which has a certain impact on the gasification combustion reaction. The ratio of CO2, H2 and CO in the case of simulating that the water-to-oxygen ratio is 1:2, 1:1, and 2:1 is 1:0.85:0.73, 1:1.1:0.97, and 1:1.76:1.33, respectively. At a water-oxygen ratio of 2:1, the concentration ratio is the most ideal, and the main gases, CO, CO2, and H2, are 32%, 21%, and 37%. Furthermore, the reaction rate increases with the increase of fracture density. The gas component concentration simulated in this paper has good consistency with the results of the previous experimental data, which has important guiding significance for the underground coal gasification project.

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Underground coal gasification (UCG): An analysis of gas diffusion and sorption phenomena

Cited by 13 publications

References 15 publications

Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

Comparison of Metal Adsorption from Aqueous Solutions on Coal and Char Remaining After In-situ Underground Coal Gasification (UCG)

A Thermal-Hydrological-Mechanical-Chemical Coupled Mathematical Model for Underground Coal Gasification with Random Fractures

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