scholarly journals Sorption and Micro-Scale Strength Properties of Coals Susceptible to Outburst Caused by Changes in Degree of Coalification

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5807
Author(s):  
Katarzyna Godyń ◽  
Barbara Dutka
Keyword(s):  
Sorption Capacity ◽  
Effective Diffusion ◽  
Gravimetric Method ◽  
Strength Properties ◽  
Methane Content ◽  
Warning Sign ◽  
Micro Scale ◽  
Effective Diffusion Coefficients ◽  
Upper Silesian Coal Basin ◽  
Methane Sorption

Coals from the south-western part of the Upper Silesian Coal Basin have a strong outburst susceptibility. The objective of this study was to identify the influence of coalification degree on methane sorption and micro scale strength properties of 24 coals from Jastrzębie Zdrój. Coal samples showed a reflectance Ro between 0.98 and 1.25%. Sorption measurements were carried out by gravimetric method. Sorption capacities were determined at mean deposit temperature of 35 °C. Using the unipore model and solution of Fick’s second law, the effective diffusion coefficients of methane in the studied coals were obtained. The Vickers method was used to study the microhardness and the modulus of elasticity. It has been shown that the increase in the coalification degree reduces the sorption capacity of coal and also reduces the rate of methane emission. Coals the most susceptible to outbursts, were the most brittle. With the increase in Ro, the methane seam pressure p increased as well as desorbable methane content DMC, both due to the reduction in the sorption capacity of coal. The increased dp index is a warning sign indicating an increased total methane content of coal seam, an increased seam pressure or an alternation of coal structure.

THE EFFECT OF TEMPERATURE ON THE SORPTION PROPERTIES OF COAL FROM UPPER SILESIAN COAL BASIN, POLAND / WPŁYW ZMIAN TEMPERATURY NA WŁASNOŚCI SORPCYJNE NA PODSTAWIE BADAŃ WYBRANYCH WĘGLI Z GÓRNOŚLĄSKIEGO ZAGŁĘBIA WĘGLOWEGO

2013 ◽  
Vol 58 (4) ◽  
pp. 1163-1176 ◽  
Author(s):  
Mirosław Wierzbicki
Keyword(s):  
Coal Seam ◽  
Sorption Capacity ◽  
Gravimetric Method ◽  
Geothermal Gradient ◽  
Effect Of Temperature ◽  
Coal Basin ◽  
Equilibrium Pressure ◽  
Rock Temperature ◽  
Upper Silesian Coal Basin ◽  
Nonlinear Increase

Abstract This paper presents the results of studies on gas sorption performed by means of the gravimetric method. The tests were performed on two coal samples of different metamorphism degrees, came from two regions of Upper Silesian Coal Basin, Poland. The changes in sorption capacity of coals were measured in the pressure range from 0.1 MPa to 17 MPa and in temperatures ranging from 291K to 333K. Coal of a lower coalification degree was a better methane sorbent. Changes in sorption capacity of tested coals were linearly dependent on the temperature. The increase in temperature of 10K reduces the Langmuir sorption of about 0.7-0.8 [cm3/g]. Such increase of temperature causes a nonlinear increase of the Langmuir pressure (b-1). These results showed that the rise of rock temperature, caused by geothermal gradient, can induce a significant increase of equilibrium pressure of methane in coal seam. An increase of coal seam temperature may cause an increase of gas and coal outburst risk in a coal mine.

scholarly journals Evaluation of the Presence of Methane in Złoczew Lignite: Comparison with Other Lignite Deposits in Poland

2020 ◽  
Vol 29 (6) ◽  
pp. 3841-3856 ◽  
Author(s):  
Jan Macuda ◽  
Paweł Baran ◽  
Marian Wagner
Keyword(s):  
Bearing Capacity ◽  
Sorption Capacity ◽  
Nitrogen Adsorption ◽  
Isosteric Heat ◽  
Heat Of Adsorption ◽  
Methane Content ◽  
Mining Operations ◽  
Mining Areas ◽  
Statistical Correlations ◽  
Methane Sorption

Abstract Catastrophic cases of methane explosion during exploratory drilling within the Bełchatów ortholignite deposit have led to testing for methane in other Polish ortholignite mining areas, as well as in the Złoczew deposit, where it is planned to begin mining operations. Initial tests have shown Złoczew lignite to have the highest methane content among the Polish deposits so far studied, comparable with lignite from the Bełchatów deposit, with a methane capacity in excess of 2.5 dcm3/kg at a pressure of 10 bar. Based on the computed values of the Langmuir constant, a determination was made of the quantity of methane that can be desorbed from a pressure of 10 bar to 1 bar, as well as the residual methane content. For all of the tested samples, the residual methane content is between 30 and 50% of the sorption capacity at a pressure of 10 bar. The thermal sorption equations were used to compute values of the limiting isosteric heat of adsorption. Higher values of the heat of adsorption at zero surface capacity may indicate the presence of a small quantity of micro-pores. In the case of the samples with the highest sorption capacity, the limiting isosteric heats of adsorption are low, indicating a low proportion of micro-pores in the lignite. This was confirmed by tests of nitrogen adsorption at 77 K. The proportion of micro-pores in the studied lignites is 2–3%, while the dominant pore fraction is the meso-pores, which in lignite from the Złoczew and Bełchatów deposits account for 50–66% of total pores. It is concluded that the significant adsorption of methane in the ortholignite occurs chiefly in meso-pores because of compression of the gas under increased orogenic pressure. A link is made between the higher methane-bearing capacity of the ortholignite deposits and the degree of gelification of the huminite components, based on simple statistical correlations between the methane sorption capacity and the content of humic gelified maceral. The results concerning methane sorption in lignite from the Złoczew deposit have enabled a preliminary classification of the methane-bearing capacity of Polish ortholignite deposits, which may also be of significance for similar deposits in other countries.

scholarly journals Synergy of Parameters Determining the Optimal Properties of Coal as a Natural Sorbent

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1967 ◽  
Author(s):  
Katarzyna Godyń ◽  
Barbara Dutka ◽  
Monika Chuchro ◽  
Mariusz Młynarczuk
Keyword(s):  
Multiple Regression ◽  
Sorption Capacity ◽  
Vitrinite Reflectance ◽  
Sorption Property ◽  
Effective Diffusion ◽  
Gravimetric Method ◽  
Low Rank ◽  
Petrographic Analysis ◽  
Natural Sorbent ◽  
Specific Pore Volume

Selection of the optimal properties of coal as a natural sorbent, both as a sample collected from a seam or of the coal seam itself, requires various parameters to be determined and may not be based on the knowledge of metamorphism degree only. In order to improve the predictions of sorption capacity and the kinetics, analyses of correlation and multiple regression based on the results of laboratory studies were performed for 15 coal samples with various coal rank. The maximum vitrinite reflectance (R0) for low-rank coals was 0.78%–0.85%, and 0.98%–1.15% and 1.85%–2.03% for medium- and high-rank coals, respectively. Coal samples were subjected to technical and petrographic analysis. The gravimetric method was used to perform sorption tests using methane, in order to determine the sorption capacity and the effective diffusion coefficient for each of the coals. Pycnometric methods were used to determine the textural parameters of coals, such as the percentage porosity and specific pore volume. The studies were further supplemented with an evaluation of the mechanical properties of the coals, Vickers micro-hardness, and elastic modulus. This work shows that the statistical multiple regression method enables a computational model including the selected petrophysical parameters displaying synergy with the specific sorption property—capacity or kinetics—to be created. The results showed the usefulness of this analysis in providing improved predictions of the optimal sorption properties of coal as a natural sorbent.

scholarly journals Estimation of Coal’s Sorption Parameters Using Artificial Neural Networks

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5422
Author(s):  
Marta Skiba ◽  
Mariusz Młynarczuk
Keyword(s):  
Diffusion Coefficient ◽  
Sorption Capacity ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Gravimetric Method ◽  
Neural Models ◽  
Petrographic Composition ◽  
Artificial Neural ◽  
Sorption Parameters ◽  
Maximal Sorption Capacity

This article presents research results into the application of an artificial neural network (ANN) to determine coal’s sorption parameters, such as the maximal sorption capacity and effective diffusion coefficient. Determining these parameters is currently time-consuming, and requires specialized and expensive equipment. The work was conducted with the use of feed-forward back-propagation networks (FNNs); it was aimed at estimating the values of the aforementioned parameters from information obtained through technical and densitometric analyses, as well as knowledge of the petrographic composition of the examined coal samples. Analyses showed significant compatibility between the values of the analyzed sorption parameters obtained with regressive neural models and the values of parameters determined with the gravimetric method using a sorption analyzer (prediction error for the best match was 6.1% and 0.2% for the effective diffusion coefficient and maximal sorption capacity, respectively). The established determination coefficients (0.982, 0.999) and the values of standard deviation ratios (below 0.1 in each case) confirmed very high prediction capacities of the adopted neural models. The research showed the great potential of the proposed method to describe the sorption properties of coal as a material that is a natural sorbent for methane and carbon dioxide.

The Influences of the Rank of Coal on Methane Sorption Capacity in Coals/Wpływ Rzędu Węgla Na Pojemność Sorpcyjną Metanu W Węglach

2014 ◽  
Vol 59 (2) ◽  
pp. 509-516
Author(s):  
Andrzej Olajossy
Keyword(s):  
Sorption Capacity ◽  
Coalbed Methane ◽  
Vitrinite Reflectance ◽  
Sorption Isotherms ◽  
Volatile Matter ◽  
Low Rank ◽  
Hard Coal ◽  
Petrographic Composition ◽  
Methane Sorption ◽  
Indian Coals

Abstract Methane sorption capacity is of significance in the issues of coalbed methane (CBM) and depends on various parameters, including mainly, on rank of coal and the maceral content in coals. However, in some of the World coals basins the influences of those parameters on methane sorption capacity is various and sometimes complicated. Usually the rank of coal is expressed by its vitrinite reflectance Ro. Moreover, in coals for which there is a high correlation between vitrinite reflectance and volatile matter Vdaf the rank of coal may also be represented by Vdaf. The influence of the rank of coal on methane sorption capacity for Polish coals is not well understood, hence the examination in the presented paper was undertaken. For the purpose of analysis there were chosen fourteen samples of hard coal originating from the Upper Silesian Basin and Lower Silesian Basin. The scope of the sorption capacity is: 15-42 cm3/g and the scope of vitrinite reflectance: 0,6-2,2%. Majority of those coals were of low rank, high volatile matter (HV), some were of middle rank, middle volatile matter (MV) and among them there was a small number of high rank, low volatile matter (LV) coals. The analysis was conducted on the basis of available from the literature results of research of petrographic composition and methane sorption isotherms. Some of those samples were in the form (shape) of grains and others - as cut out plates of coal. The high pressure isotherms previously obtained in the cited studies were analyzed here for the purpose of establishing their sorption capacity on the basis of Langmuire equation. As a result of this paper, it turned out that for low rank, HV coals the Langmuire volume VL slightly decreases with the increase of rank, reaching its minimum for the middle rank (MV) coal and then increases with the rise of the rank (LV). From the graphic illustrations presented with respect to this relation follows the similarity to the Indian coals and partially to the Australian coals.

scholarly journals Methane Emission during Gas and Rock Outburst on the Basis of the Unipore Model

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1999 ◽  
Author(s):  
Skoczylas Norbert ◽  
Anna Pajdak ◽  
Katarzyna Kozieł ◽  
Leticia Teixeira Palla Braga
Keyword(s):  
Coal Mine ◽  
Effective Diffusion ◽  
Measurement Data ◽  
Sorption Isotherms ◽  
Sieve Analysis ◽  
Measurement Systems ◽  
Upper Silesian Coal Basin ◽  
Tectonic Disturbances ◽  
Concentration Changes ◽  
Time Courses

The goal of this paper is to analyze the phenomenon of gas emission during a methane and coal outburst based on the unipore Crank diffusion model for spherical grains and plane sheets. Two occurrences in the Upper Silesian Coal Basin were analyzed: an outburst in a Zofiówka coal mine in 2005 and an outburst in a Budryk coal mine in 2012. Those two outbursts differed considerably. The first one was connected with an unidentified tectonic disturbance in the form of a triple, interlocking fault, and the other one is an example of an outburst in an area free from tectonic disturbances. The model analysis required laboratory tests in order to determine the sorption properties of coals from post-outburst masses. Sorption isotherms and the values of the effective diffusion coefficient were specified. The post-outburst masses were subjected to sieve analysis and the grain composition curves were plotted. The researchers also used the measurement data provided by proper mine services, such as the methane content, the volume of post-outburst masses, and the time courses of CH4 concentration changes in excavations. They were recorded by methane measurement systems in the mines.

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