Two experimental simulations of underground coal gasification (UCG) processes, using large bulk samples of lignites, were conducted in a surface laboratory setup. Two different lignite samples were ...used for the oxygen-blown experiments, i.e., “Velenje” meta-lignite (Slovenia) and “Oltenia” ortho-lignite (Romania). The average moisture content of the samples was 31.6wt.% and 45.6wt.% for the Velenje and Oltenia samples, respectively. The main aim of the study was to assess the suitability of the tested lignites for the underground coal gasification process. The gas composition and its production rates, as well as the temperatures in the artificial seams, were continuously monitored during the experiments. The average calorific value of gas produced during the Velenje lignite experiment (6.4 MJ/Nm3) was much higher compared to the result obtained for the experiment with Oltenia lignite (4.8 MJ/Nm3). The Velenje lignite test was also characterized by significantly higher energy efficiency, i.e., 44.6%, compared to the gasification of Oltenia lignite (33.4%). The gasification experiments carried out showed that the physicochemical properties of the lignite used considerably affect the in situ gasification process. Research also indicates that UCG can be considered as a viable option for the extraction of lignite deposits; however, lignites with a lower moisture content and higher energy density are preferred, due to their much higher process efficiency.
Coal is one of the main fossil fuel resources and remains the most important contributor to global power generation but coal utilization has severe negative impacts, mostly due to the release of CO2 ...and toxic elements into the environment. This means that determining the quality of coal is important to address the environmental and health problems related to coal combustion. Coal samples from the Velenje coalmine, one of the largest actively mined coal basins in Central Europe, were divided into organic rich and inorganic rich fractions according to the percentage of carbon. Oxides of the major elements (SiO2, Al2O3, Fe2O3 MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3), toxicologically and environmentally relevant elements (As, Ba, Co, Cu, Hg, Mo, Ni, Pb, Th, U, V, Zn, Se) and other trace elements (Ce, Cs, Dy, Er, Eu, Gd, La, Nb, Nd, Pr, Rb, Sm, Sr, Tb, Y, Zr) were measured in sample digests using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the majority of analyzed elements were either equal to or below the global average for coal. Exceptions were Sr (1090 ± 510 μg g−1, 9 times higher), Ba (301 ± 184 μg g−1, 2 times higher) and Pb (9.12 ± 17.0 μg g−1, 1.4 times higher) in inorganic rich coal and Mo (7.76 ± 4.76 μg g−1, 3.5 times higher) and U (5.24 ± 3.23 μg g−1, 1.8 times higher) in organic rich samples. Eighteen elements (Ag, Au, Be, Bi, Cd, Ga, Hf, Ho, Lu, Sb, Sc, Se, Sn, Ta, Ti, Tm, Yb, W) were below the limit of detection in >70% of the samples. Speciation analysis revealed the presence of several organoarsenic compounds in the organic rich samples, with the tetramethylarsonium ion (TETRA, 0.01–1.10 μg g−1) and trimethylarsine oxide (TMAO, 0.01–0.29 μg g−1) as the most abundant. A comparison with coal samples from the Senovo, Kanižarica, and Trbovlje coal mines in Slovenia and from the Sokolov Basin, (Czech Republic) revealed that Velenje contains much higher amount of organoarsenic compounds (34.8 ± 16.9%) in comparison to the others (4.45 ± 4.19%).
•We investigated element composition in inorganic and organic rich lignite.•Major, minor and trace elements were determined in Velenje lignite.•Values of measured elements are comparable to world coal, except U and Mo.•Unexpected organoarsenic compounds were found in Velenje lignite.•Organoarsenic compounds in Velenje lignite are related to bacterial activity.
The Velenje coal mine (VCM) is situated on the largest Slovenian coal deposit and in one of the thickest layers of coal known in the world. The thickness of the coal layer causes problems for the ...efficiency of extraction, since the majority of mining operations is within the coal layer. The selected longwall coal mining method with specific geometry, increasing depth of excavations, changes in stress state and naturally given geomechanical properties of rocks induce seismic events. Induced seismic events can be caused by caving processes, blasting or bursts of coal or the surrounding rock. For 2.5D visualization, data of excavations, ash content and calorific value of coal samples, hanging wall and footwall occurrence, subsidence of the surface and coal burst source locations were collected. Data and interpolation methods available in software package Surfer®12 were statistically analyzed and a Kriging (KRG) interpolation method was chosen. As a result 2.5D visualizations of coal bursts source locations with geomechanical properties of coal samples taken at different depth in the coal seam in the VCM were made with data-visualization packages Surfer®12 and Voxler®3.
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
Glasilo je nadaljevanje Velenjskega rudarja, izhajalo je mesečno. Zajemalo je problematiko občine, krajevne skupnosti, delavskih organizacij in društev. S tem naj bi dalo možnost občanom, da izrazijo ...svoja mnenja in podajo predloge
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