Analysis of adsorption tests of gases emitted in the coal self-heating process

Dudzińska, Agnieszka; Cygankiewicz, J.

doi:10.1016/j.fuproc.2015.04.008

Cited by 34 publications

(24 citation statements)

References 23 publications

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“…The lowest volumes of propylene were sorbed on coal samples 6 and 7, characterized by the lowest porosity and low micropore surface area (see Table 2). The grade of metamorphism [25][26][27], porosity, and chemical characteristics of coal surface [10,11] are the most important properties of coals in terms of their sorption characteristics. The increase in the grade of metamorphism and decrease in coal porosity resulted in the deterioration of sorption capacity of tested coals with respect to propylene.…”

Section: Resultsmentioning

confidence: 99%

“…This in turn causes the underestimation of the concentrations of gaseous indicators of the self-heating process and an incorrect assessment of the development of this process. The gases adsorbed on coal in the highest amounts include the unsaturated hydrocarbons-such as ethylene, propylene, and acetylene-which reduces their applicability in the assessment of the self-heating process progress [9][10][11]. This is particularly important in the case of coals with high sorption capacity, and with long distances between the self-heating center and the measurement point of concentrations of gaseous process indicators.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

2017

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Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed on coal, while migrating through the mine workings. Coal crushed during the mining process is characterized by a high sorption capacity, which facilitates the sorption phenomena. This results in the decrease in hydrocarbons content in mine air, and in the subsequent incorrect assessment of the development of the self-heating process. The results of the experimental study on propylene and acetylene sorption on Polish coals acquired from operating coal mines are presented in this paper. Bituminous coal is characterized by a high sorption capacity with respect to unsaturated hydrocarbons, like propylene and acetylene. The sorbed volumes depend on the grade of metamorphism, porosity, and chemical characteristics of coal. Low level of metamorphism, increased porosity, and oxygen content result in higher sorption capacity of coals. The reduction in grain size of coals also results in the increased sorption capacity with respect to hydrocarbons. The most significant increase in the volumes of sorbed propylene and acetylene with the decrease in grain class was observed for coals of low porosity, high grade of metamorphism, and low to medium sorption capacities. The 10-fold decrease in coal grain size resulted in the 3 to 6-fold increase in the volume of sorbed propylene, and 2-fold increase for acetylene. The decrease in grain size results in higher accessibility of pore structure, increased pore volume and area, and higher number of active centers interacting with hydrocarbons of dipole characteristics. For coals with low grade metamorphism, high porosity, and high sorption capacity the volumes of sorbed propylene and acetylene increased only slightly with the decrease in coal grain size.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

2017

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“…Krzysztof Stanczyk et al [13] applied the underground coal gasification technique at temperatures above 700 o C to produce a hydrogen-rich gas. Li et al [14] conducted open-system non-isothermal pyrolysis experiments on selected immature and mature carbonaceous coals and found considerable amounts of H 2 being released at temperatures up to 1200 o C. However generation mechanism and release rule responsible for H2 generation at low temperature(T<200 oC) have not been fully conducted and elucidated because of its low release content, ease of leaking, and difficult of monitoring Agnieszka Dudzińska [15] analyzed the absorbency of hard coals with respect to different gases (i.e., carbon monoxide, carbon dioxide, hydrogen, ethylene, and propylene) with hydrogen and carbon dioxide being the least and the most absorbed gases, respectively. Grossman [16][17][18] conducted a series of studies on molecular hydrogen evolution during low-temperature coal oxidation.…”

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confidence: 99%

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

Wang

Xue

et al. 2017

Energy Fuels

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Although H2 gas is used in coal mines as an important indicator to reflect the state of coal spontaneous combustion, the gas production of H2 at low temperature has been scarcely reported in the literature. In this paper, the modes and release mechanism of molecular hydrogen were investigated for three different coal ranks below 200 °C. Batch reactor tests were performed in combination with chromatographic analysis of the coal oxidation process. The experimental results showed that molecular hydrogen release mainly originated from coal oxidation rather than thermal decomposition of inherent hydrogen-containing groups. The amount of hydrogen released increased with the coal rank. The H2 release process during low-temperature oxidation typically proceeds in two phases, namely H2 slow release (T < 100 °C) and H2 accelerated release (T > 100 °C) phases. Experiments with model compounds revealed aldehyde compounds to noticeably produce H2. Coal plays a positive role in promoting the aldehyde groups to release H2 and CO2, but an opposite trend was observed in the case of CO. As revealed by Fourier transform infrared (FTIR) spectroscopy, the amount of aliphatic structures significantly decreased with the oxidation intensity, and a drastic increase in the aldehyde content was found at temperatures above 120 °C. Additionally, the path for the formation of H2 during low-temperature oxidation of coal was provided.

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“…The exception was sample 2 with grain size at the range of 0.25 to 0.50 mm, for which propylene and ethylene were absorbed in an equal amount, however, smaller than propane while the sorption value of propane was higher. The experimental results obtained in the sorption test as regards single gases on coals with the grain size of 0.5 to 0.7 mm demonstrated a higher sorption capacity of ethylene than propylene and saturated hydrocarbons . The reason for the higher amount of sorbed propylene in comparison with ethylene is that during the flow of the multicomponent mixture, a competitive adsorption process takes place.…”

Section: Resultsmentioning

confidence: 91%

The effect of coal grain size on the sorption of hydrocarbons from gas mixtures

2019

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Summary The flow of gas mixtures through coal, accompanied by sorption, is one of the natural processes occurring in the spontaneous heating of coal in underground mines. So far, studies on the sorption of mine gases have been mostly performed with regard to single components. In turn, sorption measurements with the use of gaseous mixtures were performed only on coals with grain size at the narrow range of 0.5 to 0.7 mm. In this paper, a dynamic sorption of a mixture of propylene, ethylene, propane, and ethane in a fixed‐bed column was investigated. Coal samples of various grain classes, ie, 0.25 to 0.50, 0.7 to 1.00, and 1.00 to 2.00 mm, were used as an adsorbent. The sorption tests were conducted at a constant gas flow rate of 2.17·10−7 m3/s and the pressure of approximately 1 atm. Next, the results of the sorption tests were compared with parameters characterizing the porous structure of the materials used. The total amount of sorbed gases decreases as the grain size becomes larger. The samples characterized by a lower carbon content (<70% w/w), a slightly higher oxygen content, and a larger surface area dominated by micropores at the range of 0.6 to 2.0 nm and mesopores with diameter of 2.0 to 10.0 nm had a higher sorption capacity than samples with the structure determined mainly by mesopores. It has been noticed that a high sorption ability of ethane results from its highest concentration in the mixture at the inlet of the sorption column. In most cases, propylene was sorbed in larger amount than ethylene, independently of grain size of coal and pore size distribution.

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Analysis of adsorption tests of gases emitted in the coal self-heating process

Cited by 34 publications

References 23 publications

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

The effect of coal grain size on the sorption of hydrocarbons from gas mixtures

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