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Artículos de revistas sobre el tema "Coal Extraction (Chemistry)"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 13 de febrero de 2022

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1

Kozłowski, Mieczysław, Helena Wachowska y Jan Yperman. "Composition of extraction products from alkylated high-sulphur coals". Open Chemistry 1, n.º 4 (1 de diciembre de 2003): 366–86. http://dx.doi.org/10.2478/bf02475223.

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AbstractProducts of reductive and non-reductive methylation of two high-sulphur coals (Mequinenza and Illinois No. 6) have been extracted by dichloromethane. It has been established that the efficiency of the transformation of coal to the products soluble in CH2Cl2 is higher for coals subjected to non-reductive methylation by the Liotta method than for those after reduction in the potassium/liquid ammonia system. The extracts and the extraction residues were subjected to elemental analysis, IR spectroscopy, and AP-TPR (Atmospheric Pressure-Temperature Programmed Reduction) measurements. It has been shown that the main species undergoing extraction by CH2Cl2 are aliphatic compounds or aromatic structures of low degree of condensation. The effect of the extraction on the sulphur groups in coal has been discussed.

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2

Tasic, Aleksandra, Ivana Sredovic-Ignjatovic, Ljubisa Ignjatovic, Danijel Djuranovic y Malisa Antic. "Aqueous extraction of anions from coal and fly ash followed by ion-chromatographic determination". Journal of the Serbian Chemical Society 81, n.º 12 (2016): 1441–53. http://dx.doi.org/10.2298/jsc160223086t.

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Three different techniques were applied for the aqueous extraction of anions from coal and fly ash: rotary mixer- and ultrasonic-assisted extraction with different duration time, and microwave-assisted extraction at different temperatures. Validation showed that the ion-chromatographic method was suitable for the analysis of anions in coal and fly ash extracts. The variations in the amounts of anions using different extraction times during rotary-assisted extraction were minimal for all investigated anions. The efficiency of ultrasound-assisted extraction of anions from coal depended on the sonication time and was highest at 30 min. The ultrasound-assisted extraction was less efficient for the extraction of anions from fly ash than rotary-assisted extraction. Increase of temperature in the microwave-assisted extraction had a positive effect on the amounts of all anions extracted from coal and sulphate from fly ash, while the amounts of fluoride and chloride in fly ash extracts decreased. The microwave-assisted extraction of coal at 150?C was compared with standard ASTM methods, and results were in good agreement only for chloride. Changes in the pH value and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of coal particles in contact with water and different processes that occur under environmental conditions.

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3

Antonovits, Ábel Dániel y József Molnár. "3D modelling of coal seams for optimization of extraction". MATEC Web of Conferences 342 (2021): 02008. http://dx.doi.org/10.1051/matecconf/202134202008.

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Underground coal mining was finished in the north-eastern region of Hungary after its operation of more than two centuries, as a result of economic, technical, environmental and political reasons. A fairly significant part of the reserve is still available to extract. With a different perspective of coal mining, considering different ways of utilization (such as coal chemistry, etc.) the extraction of the material can still be cost effective. In the past few years, several studies were conducted regarding the possible utilization of the available reserve. The properties of the coal are highly mutable, therefore, comprehensive knowledge about the geology is indispensable. Two and three-dimensional modelling of the coal seam is discussed in this paper, with the optimal coal face height, and the expected quality of mining products taken into consideration. Applying the method presented, the production can fulfil the desired properties, regarding to the utilization of the coal.

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4

Cooke, Norman E., O. Maynard Fuller y Rajendra P. Gaikwad. "Ultrasonic extraction of coal". Fuel 68, n.º 10 (octubre de 1989): 1227–33. http://dx.doi.org/10.1016/0016-2361(89)90234-2.

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5

Nishioka, Masaharu. "Multistep extraction of coal". Fuel 70, n.º 12 (diciembre de 1991): 1413–19. http://dx.doi.org/10.1016/0016-2361(91)90007-w.

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6

Pietrzak, Robert, Helena Wachowska y Piotr Nowicki. "The effect of flame coal oxidation on the solid and soluble products of its extraction". Open Chemistry 3, n.º 4 (1 de diciembre de 2005): 852–65. http://dx.doi.org/10.2478/bf02475208.

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AbstractSolid and soluble products of THF and CH2Cl2 extraction of flame coal oxidised by four different oxidising agents (peroxyacetic acid (PAA), 5% HNO3, O2/Na2CO3, air/125 °C) were studied by elemental analysis and FTIR. The extraction yield with THF was much higher than that with CH2Cl2 for all samples. The greatest changes in elemental composition were in the extracts from coal oxidised by nitric acid. The sulphur content was lowest in extracts from coal oxidised with 5% HNO3 and PAA. FTIR confirmed that coal treatment with nitric acid incorporates nitrogen into the coal structure.

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7

Smith, Aidan M. y Andrew B. Ross. "The Influence of Residence Time during Hydrothermal Carbonisation of Miscanthus on Bio-Coal Combustion Chemistry". Energies 12, n.º 3 (7 de febrero de 2019): 523. http://dx.doi.org/10.3390/en12030523.

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Miscanthus was treated by hydrothermal carbonisation in a 2-L batch reactor at 200 °C and 250 °C with residence times ranging between 0 and 24 h to understand the impact of residence time has on the resulting bio-coal combustion chemistry. Increasing the residence time results in dehydration of the bio-coal and increased repolymerisation; however, temperature has the greatest influence on bio-coal properties. After 24 h at 200 °C, bio-coal has similar properties to that of the 250 °C + 0 h bio-coal. After 1 h at 250 °C, the cellulose present in the raw biomass appears to be largely removed. The removal of cellulose and the associated dehydration and repolymerisation results in bio-coal having a ‘coal like’ combustion profile, which exhibits a decreasing reactivity with increasing residence time. At 200 °C + 0 h, 75% of the alkali metal is removed, increasing to 86% with increasing residence time. Further extraction is seen at 250 °C. Phosphorus and sulphur appear to undergo substantial extraction at 200 °C + 0 h but then are reincorporated with increasing residence time. The calcium content increases in the bio-coal with increasing residence time at 200 °C but then reduces after 1 h at 250 °C. Increasing temperature and residence time has been shown to decrease the fuels’ fouling and slagging propensity.

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8

Yao, Jian, Huaijun Ji, Huazhang Lu y Tongtong Gao. "Effect of Tetrahydrofuran Extraction on Surface Functional Groups of Coking Coal and Its Wettability". Journal of Analytical Methods in Chemistry 2019 (26 de junio de 2019): 1–8. http://dx.doi.org/10.1155/2019/1285462.

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Coking coal was extracted with tetrahydrofuran solvent using ultrasonic and microwave-assisted method at 50°C and atmospheric pressure. Wettability of raw coal and its residue (residual coal) was tested with capillary penetration method. The raw and residual coals were studied by Fourier transform infrared spectroscopy (FTIR) with curve-fitting analysis. The variation of main surface functional groups of coking coal before and after extraction and its effect on wettability were analyzed. The results were obtained as the following: after extraction with tetrahydrofuran, hydroxyl, ether oxygen, and carbonyl in the coal structure were dissolved, the content of hydrophilic functional groups reduced, and then the hydrophobicity of coal enhanced. At the same time, part of aliphatic hydrocarbon dissolved, the length of aliphatic chains (I2) decreased from 3.961 of raw coal to 3.636 of residual coal, the length of aliphatic chains became shorter, aliphatic CH2 side-chains decreased and aliphatic CH3 side-chains increased, and hydrophobic functional groups content increased. In the aromatic structure, four hydrogens per ring increased and two, three, and five hydrogens per ring decreased. Reduction of substitution functional groups and aliphatic hydrocarbon decreased with the side-chains breakage produce more active sites, which increases the degree of condensation of the aromatic ring (I3). The combined action of the decrease of the hydrophilic functional groups and the increase of the hydrophobic functional groups made the wettability of the coking coal become weak.

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9

Xie, Heng-Shen, Zhi-Min Zong, Yu-Gao Wang, Pei-Zhi Zhao, Shi-Hua Zhang, Jun-Qiang Wang, Hong Fu, Shuang-Hua Liang, Ling Su y Xian-Yong Wei. "Conversion of Organic Matter in Coal by Photocatalytic Oxidation with H2O2 over SFC/TiO2 in Isolated Oxygen System". Journal of Chemistry 2019 (24 de octubre de 2019): 1–12. http://dx.doi.org/10.1155/2019/1768351.

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Shenfu bituminous coal (SFBC), Geting coal (GTC), Shengli lignite (SLL), and Holingola coal (HLGLC) were oxidized by UV light radiation with aqueous H2O2 over SFC/TiO2 in a closed suspension system (CSS) to understand structural characteristics of 4 typical Chinese coals. Raw and oxidized coals were dried and extracted with acetone thoroughly to ensure residue extraction. Meanwhile, the extracts were analyzed using a gas chromatograph/mass spectrometer. The results show that organic matters (OMs) in coals can be converted into a large number of oxygen-containing organic compounds (OCOCs), mainly containing ketones, esters, alcohols, etc. Oxidizing species such as hydroxyls, hydroperoxyl, and alkyl radicals are excited by light irradiation and substitute for hydrogen atoms of methyls and methylenes of acenes or branched-chain alkanes in coals. Acetic acid and acetaldehyde can be formed and dissolved in aqueous solution in the oxidation reaction. The yields can be improved with the enhancement of the oxidation effect.

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10

MATSUBARA, Kenji y Mamoru YANAGIUCHI. "The Application of Supercritical Fluid Extraction for Petroleum and Coal Chemistry". Journal of Japan Oil Chemists' Society 35, n.º 4 (1986): 287–92. http://dx.doi.org/10.5650/jos1956.35.287.

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11

Zhang, Xiaodong, Shuo Zhang, Xianzhong Li y Shuai Heng. "Dynamic Evolution of Nanoscale Pores of Different Rank Coals Under Solvent Extraction". Journal of Nanoscience and Nanotechnology 21, n.º 1 (1 de enero de 2021): 450–59. http://dx.doi.org/10.1166/jnn.2021.18458.

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During the coalification process, coalbed methane (CBM) is formed and mainly adsorbed in the pores of coal. Pore structure evolution is critical to CBM adsorption/desorption and extraction. This paper puts forward two parameters, namely the variety degree x and variety gene σ, for characterizing pore structure through mercury injection tests. Then, under extraction with different solvents, the dynamic evolution characteristics of nanoscale pores are addressed and quantified by taking four different rank coals (lignite, medium-volatile bituminous coal, low-rank anthracite and mediumrank anthracite) from different coal mines of China as the study object. The results indicate that the content of meso- and macropores after solvent extraction is much larger, but that there is no obvious law with the content of transition pores and micropores in the size range of 50–7.2 nm, according to the basic data sets of specific surface area (SSA) and pore volume (PV) of all coal samples. This phenomenon can be explained by the pore increase and expansion effects in nanoscale pores during solvent extraction. Generally, with the increasing of the solvent extraction degree, the difference in variety degree x with respect to the total PV and total SSA of different coals shows a significant decreasing trend, which expresses a homogeneous development in the change in pore structure. In regard to different solvents, benzene mainly causes pore expansion in meso- and macropores, and CS2 has a great effect on micropores. Whereas acetone plays an important role in mesopores and transition pores with pore expansion, THF has various effects on different size pores. Further study with higher variety gene σ values shows that the total PV mainly depends on the change in the absolute content of meso- and macropores. While the change in the absolute content of transition pores and micropores (less than 50 nm) has a great influence on the total SSA. As the extraction degree increases, the influence of the transition pores and micropores on the total PV is increased, and then, the content of meso- and macropores also plays an important role on the total SSA. However, this effect is highly different for raw coals of different ranks.

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12

Sunol, Aydin K. y Gerhard H. Beyer. "Mechanism of supercritical extraction of coal". Industrial & Engineering Chemistry Research 29, n.º 5 (mayo de 1990): 842–49. http://dx.doi.org/10.1021/ie00101a019.

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13

Mishra, S. y D. K. Sharma. "Solvent extraction and extractive disintegration of coal in anthracene oil". Fuel 69, n.º 11 (noviembre de 1990): 1377–80. http://dx.doi.org/10.1016/0016-2361(90)90118-a.

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14

Chan, Melissa, M. Granger Morgan y H. Scott Matthews. "It Is Time to Clean up Coal Extraction". Environmental Science & Technology 44, n.º 13 (julio de 2010): 4845–46. http://dx.doi.org/10.1021/es100534f.

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15

Yu, Xiaobing, Xiaoping Wang, Richard Bartha y Joseph D. Rosen. "Supercritical fluid extraction of coal tar contaminated soil". Environmental Science & Technology 24, n.º 11 (noviembre de 1990): 1732–38. http://dx.doi.org/10.1021/es00081a017.

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16

Adschiri, Tadafumi, Shinji Abe y Kunio Arai. "Mechanism of supercritical fluid extraction of coal." JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 24, n.º 6 (1991): 715–20. http://dx.doi.org/10.1252/jcej.24.715.

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17

Baikenov, M. I., Sh K. Amerkhanova, G. G. Baikenova, R. M. Shlyapov y A. E. Tuktybaeva. "Cavitation extraction of phenols form coal tar". Solid Fuel Chemistry 47, n.º 1 (enero de 2013): 27–33. http://dx.doi.org/10.3103/s0361521912060031.

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18

Vasilakos, Nicholas P. y Daniel D. Lawson. "SOLUBILITY-PARAMETER SPECTROSCOPY IN COAL EXTRACTION". Liquid Fuels Technology 3, n.º 3 (enero de 1985): 305–22. http://dx.doi.org/10.1080/07377268508915387.

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19

Shilova, Tatiana y Sergey Serdyukov. "Permeability of Coking Coals and Patterns of Its Change in Leninsky Area, Kuznetsk Coal Basin, Russia". Applied Sciences 11, n.º 9 (27 de abril de 2021): 3969. http://dx.doi.org/10.3390/app11093969.

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A prediction of the permeability of gas-bearing coking coals in the Leninsky area, Kuznetsk coal basin (Kuzbass), which is promising for the production of coal methane, was performed. The results of laboratory studies of coal permeability and cleat compressibility under hydrostatic stress conditions are presented. As the confining pressure increased by 8 times (from 1 MPa to 8 MPa), the coal permeability perpendicular to the butt cleat direction decreased by 6.7 times (from 60 mD to 9 mD). The coal cleat compressibility was 0.085 MPa−1. On the basis of the results of filtration tests and microstructural analysis of the coking coals, we provide the estimation of the permeability anisotropy along the bedding planes (perpendicular to the face and butt cleat directions). The predicted dependences of gas-bearing coking coal permeability perpendicular to the butt and face cleat directions on depth and on features of coal seam bedding were determined under uniaxial strain conditions. It was found that in the coking coal depth intervals, as the depth increased, their permeability decreased by 61–82%. The obtained results can be used to select facilities and to design industrial works for the extraction of coal methane in the region.

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20

Zhao, Yuan, Shugang Cao, Yong Li, Zhenyu Zhang, Ping Guo, Hongyun Yang, Shuwen Zhang y Ruikai Pan. "The occurrence state of moisture in coal and its influence model on pore seepage". RSC Advances 8, n.º 10 (2018): 5420–32. http://dx.doi.org/10.1039/c7ra09346b.

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21

Tasic, Aleksandra, Ivana Sredovic-Ignjatovic, Ljubisa Ignjatovic, Ivan Andjelkovic, Malisa Antic y Ljubinka Rajakovic. "Investigation of different extraction procedures for the determination of major and trace elements in coal by ICP-AES and ion chromatography". Journal of the Serbian Chemical Society 81, n.º 4 (2016): 403–17. http://dx.doi.org/10.2298/jsc150429078t.

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This paper presents the extraction of major and trace elements from a coal sample, in deionized water, by using three different extraction techniques. Rotary mixing and ultrasonic extraction were examined for different extraction times, while the microwave assisted extraction was performed at different temperatures. Metal concentrations (Na, K, Ca, Mg, Al, Fe, Mn, Be, Cd, Co, Cr, Hg, As, Ni, Se, Sb and Pb) in a solution were determined by employing the inductively coupled plasma atomic emission spectrometry; whereas the results obtained for Na, K, Ca and Mg were compared employing ion chromatography. Comparing the rotary and ultrasonic-assisted extraction it is shown that the former is more efficient for the determination of Fe, Na and Pb, whereas the latter one has proven more efficient for the determination of Co and Cr ions. Microwave-assisted extraction has proven the most efficient method for any elements tested in coal. In addition, sequential extraction of elements was done using microwave digestion. The results of sequential extraction experiments indicated associations of investigated elements with a mineral phase and organic matrix. Sequential extraction provided information on possible leaching of As, Cd, Co, Cr, Ni, Pb, Fe and Mn in environmental conditions.

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22

Tasic, Aleksandra, Ivana Sredovic-Ignjatovic, Ljubisa Ignjatovic, Marija Ilic y Malisa Antic. "Comparison of sequential and single extraction in order to estimate environmental impact of metals from fly ash". Journal of the Serbian Chemical Society 81, n.º 9 (2016): 1081–96. http://dx.doi.org/10.2298/jsc160307038t.

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The aim of this paper was to simulate leaching of metals from fly ash in different environmental conditions using ultrasound and microwave-assisted extraction techniques. Single-agent extraction and sequential extraction procedures were used to determine the levels of different metals leaching. The concentration of metals (Al, Fe, Mn, Cd, Co, Cr, Ni, Pb, Cu, As, Be) in fly ash extracts were measured by Inductively Coupled Plasma-Atomic Emission Spectrometry. Single-agent extractions of metals were conducted during sonication times of 10, 20, 30, 40 and 50 min. Single-agent extraction with deionized water was also undertaken by exposing samples to microwave radiation at the temperature of 50?C. The sequential extraction was undertaken according to the BCR procedure which was modified and applied to study the partitioning of metals in coal fly ash. The microwave-assisted sequential extraction was performed at different extraction temperatures: 50, 100 and 150?C. The partitioning of metals between the individual fractions was investigated and discussed. The efficiency of the extraction process for each step was examined. In addition, the results of the microwave-assisted sequential extraction are compared to the results obtained by standard ASTM method. The mobility of most elements contained in fly ash is markedly pH sensitive.

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23

Kershaw, John R. y Laurence J. Bagnell. "Extraction of brown coals with supercritical fluid mixtures: Implications for coal structure". Fuel 66, n.º 12 (diciembre de 1987): 1739–41. http://dx.doi.org/10.1016/0016-2361(87)90374-7.

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24

Kershaw, J. "Supercritical gas extraction of Victorian brown coals The effect of coal properties". Fuel 64, n.º 8 (agosto de 1985): 1070–74. http://dx.doi.org/10.1016/0016-2361(85)90108-5.

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25

Suprapto, Suprapto, Zahrotul Istiqomah, Eko Santoso, Ahmad Anwarud Dawam y Didik Prasetyoko. "Alumina Extraction from Red Mud by Magnetic Separation". Indonesian Journal of Chemistry 18, n.º 2 (30 de mayo de 2018): 331. http://dx.doi.org/10.22146/ijc.25102.

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Alumina extraction from red mud has been investigated by magnetic separation with three-step treatment. First, the addition of red mud with Na2CO3 (12 wt%) and heated at 110 °C for 4 h. The second step was carbon reduction using coal with mass ratio of (red mud+Na2CO3) : coal was 1:3 then roasted at temperature of 850, 950, and 1050 °C for 1, 2, and 3 h. The third step was magnetic separation. The magnetic separation was carried out in order to remove magnetite produced during roasting process. Magnetic and non-magnetic phases obtained were characterized by XRD and SEM-EDX techniques. The non-magnetic phase obtained was leached using HCl 6 M, and then aluminum content was determined by Inductively Coupled Plasma (ICP). The result revealed that the highest aluminum oxide extracted from the red mud was 20.66 wt% obtained by roasting at temperature of 1050 °C for 2 h.

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26

Wu, Chunling, Yang Luo, Kai Zhao, Xiaobing Yu, Xian Zhang y Xuqiang Guo. "Recycling Molybdenum from Direct Coal Liquefaction Residue: A New Approach to Enhance Recycling Efficiency". Catalysts 10, n.º 3 (6 de marzo de 2020): 306. http://dx.doi.org/10.3390/catal10030306.

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In this paper, direct coal liquefaction residue was prepared from Shen-dong coal, and the solubility of the residue in five organic solvents was studied. Then, an experimental device was set up to recover molybdenum (Mo) compounds from the direct coal liquefaction residue after extraction, and the influences of sublimation temperature and duration on recycling efficiency were examined. The recycled Mo-based products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and a thermal analyzer. The results reveal that the optimum extraction conditions were obtained through ultrasonic extraction with a quinoline solvent and the highest recycling efficiency occurred for sublimation at 900 °C for 30 min. The recycled products are identified to be α-MoO3 crystals. Moreover, the α-MoO3 crystal is thermally stable before the temperature reaches its melting point.

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27

Dong, Jun, Yuanping Cheng y Pinkun Guo. "The dual deformation and remodeling of coal powders: implications for obtaining reliable stress-formed coal samples". RSC Advances 9, n.º 38 (2019): 22004–10. http://dx.doi.org/10.1039/c9ra03861b.

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The preparation of suitable specimens is important for obtaining credible mechanical and methane migration parameters for tectonic coal, which help to guide methane extraction and disaster prevention.

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28

Lancas, Fernando, E. Carrilho, H. M. McNair y H. S. Karam. "STUDY OF EXTRACTION METHODS FOR HIGH-ASH COAL USING LOW-BOILING EXTRACTING AGENTS. I. SOLID PHASE EXTRACTION". Petroleum Science and Technology 6, n.º 1 (1988): 95–107. http://dx.doi.org/10.1080/08843758808915876.

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29

Zhao, Hua y Michael S. Franklin. "Ionic liquids for coal dissolution, extraction and liquefaction". Journal of Chemical Technology & Biotechnology 95, n.º 9 (20 de junio de 2020): 2301–10. http://dx.doi.org/10.1002/jctb.6489.

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30

Kershaw, John R. y Paul J. Smart. "Extraction of coal-tar pitch with supercritical toluene". Journal of Supercritical Fluids 6, n.º 3 (septiembre de 1993): 155–63. http://dx.doi.org/10.1016/0896-8446(93)90014-o.

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31

Kershaw, J. R. y P. J. Smart. "Extraction of coal-tar pitch and the effect on carbonization". Carbon 32, n.º 1 (1994): 85–92. http://dx.doi.org/10.1016/0008-6223(94)90012-4.

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32

Du, Song, Jikun Wang, Wenbiao Jin y Weimin Wu. "Complex Mechanism of Phenol Extraction of Coal Gasification Wastewater". Polish Journal of Environmental Studies 28, n.º 3 (28 de enero de 2019): 1105–13. http://dx.doi.org/10.15244/pjoes/87100.

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33

Rodríguez, Francisco, José C. Burillo, Luis F. Adrados y Julio F. Tijero. "Recovery of Anthracene from Coal Tar by Solvent Extraction". Separation Science and Technology 24, n.º 3-4 (marzo de 1989): 275–89. http://dx.doi.org/10.1080/01496398908049767.

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34

Andrews, Rodney J., Terry Rantell, David Jacques, James C. Hower, J. Steven Gardner y Mike Amick. "Mild coal extraction for the production of anode coke from Blue Gem coal". Fuel 89, n.º 9 (septiembre de 2010): 2640–47. http://dx.doi.org/10.1016/j.fuel.2010.04.027.

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35

Shishido, Masahiro, Takahiro Mashiko, Tadafumi Adschiri y Kunio Arai. "The gasification reactivity of residual coal chars from supercritical fluid extraction of coal". Fuel 70, n.º 4 (abril de 1991): 539–43. http://dx.doi.org/10.1016/0016-2361(91)90033-7.

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36

Bica, Marin, Marius Sorin Sofronie y Corina Dana Cernaianu. "Solid Fuels Behavior Revealed by Thermo-Gravimetric Analysis". Applied Mechanics and Materials 659 (octubre de 2014): 301–6. http://dx.doi.org/10.4028/www.scientific.net/amm.659.301.

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Thermogravimetric analysis is also used for the determination of mass composition changes of solid fuels caused by heating processes, coal, and wood or plant debris. Energy characteristics of coal depends on the age of their formation (geological age) and the transformations undergone by organic matter under the influence of geological chemistry (chemical age). Several classification criteria, excluding other problems that may arise in connection with the extraction, preparation and other use than combustion, several classifications have been proposed enabling the sharing of the multitude of solid fuels in groups so that each group members behave similarly during the combustion procedure. Wood and plant debris, combustible wastes, coal, have a heating value depending on their mass composition.

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37

RUSIN, E., A. RUSIN y W. POTYKA. "Influence of recycle solvent properties on coal extraction". Fuel 67, n.º 8 (agosto de 1988): 1143–49. http://dx.doi.org/10.1016/0016-2361(88)90385-7.

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38

Kodera, Yoichi, Koji Ukegawa, Yutaka Mito, Masashi Komoto, Etsuro Ishikawa y Tetsuo Nakayama. "Solvent extraction of nitrogen compounds from coal liquids". Fuel 70, n.º 6 (junio de 1991): 765–69. http://dx.doi.org/10.1016/0016-2361(91)90076-m.

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39

Sakaki, Tsuyoshi, Masao Shibata, Yoshio Adachi y Hideharu Hirosue. "Supercritical fluid extraction of coal under pyrolysis conditions". Fuel 73, n.º 4 (abril de 1994): 515–20. http://dx.doi.org/10.1016/0016-2361(94)90034-5.

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40

Wang, Shengcheng, Haijian Li y Lanying Huang. "Permeability Evolution of Naturally Fractured Coal Injected with High-Temperature Nitrogen: Experimental Observations". Processes 9, n.º 2 (3 de febrero de 2021): 296. http://dx.doi.org/10.3390/pr9020296.

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The permeability of more than 70% of coal seams in China is less than 1 mD, creating difficulties in recovering underground coal methane. Therefore, a new technology of high-temperature nitrogen (HTN2) injection into the coal seam was proposed to improve the coal permeability and gas extraction rate. In this paper, the effects of the N2 temperature, injection pressure and cycle number on the permeability of naturally fractured coking coal has been investigated. When HTN2 was injected into coal samples, the results indicated that the permeability decreased over time in the beginning, suddenly increased to a large value, and was subsequently maintained in a relatively stable range. The maximum permeability ratio increased with the rise of the N2 temperature and injection pressure. An analysis indicated that the increase of coal permeability was the result of the increase of the global coal strain caused by thermal expansion and the adsorption-induced expansion. The maximum permeability ratios in various cycles of multicycle N2 injection into the coal sample were all greater than 1.0 while progressively declining. Obviously, the alternating stress was conducive to the further expansion of the coal fractures to increase the coal permeability. However, on the basis of the first period of expansion, re-expansion was difficult and required more energy. The effects of multicycle N2 injection on coal permeability have been considerably improved when compared with N2 injection with only one cycle. The research results are helpful for rapidly extracting methane and guaranteeing mine safety.

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41

Cox, James A. y Raaidah Saari. "Extraction method for the determination of total chlorine in coal". Analyst 112, n.º 3 (1987): 321. http://dx.doi.org/10.1039/an9871200321.

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42

Savic-Bisercic, Marjetka, Lato Pezo, Ivana Sredovic-Ignjatovic, Ljubisa Ignjatovic, Andrija Savic, Uros Jovanovic y Velibor Andric. "Ultrasound and shacking-assisted water-leaching of anions and cations from fly ash". Journal of the Serbian Chemical Society 81, n.º 7 (2016): 813–27. http://dx.doi.org/10.2298/jsc151222027b.

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Two mechanical extraction techniques were used for the extraction of environmentaly interesting elements from coal fly ash: shaking, in which the extraction process lasted from 6 to 24 hours, and ultrasonic sonication during 15 to 60 minutes, with water as extractant. The concentration of anions in fly ash extracts were determined by ion chromatography, while atomic absorption spectrometry was used for determination of: As, Pb, Cd, Ni, Cr, Zn, Cu, Fe, Mn and Al. The ultrasonic sonication yielded slightly higher amounts of extracted anions and Pb, Al, Mn and Fe, while shaking-assisted extraction was more efficient for the Cr, As, Zn and Ni ions. The changes in pH value, particle size distribution in colloid, zeta potential and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of fly ash particles in contact with water and different processes (adsorption, ion exchange, flocculation) that occur in environmental conditions. Principal Component Analysis were used for assessing the effect of observed process parameters. Essential from a practical point of view is a quantitative evaluation of these elements leachable from coal fly ash to surface waters in environmental conditions and contamination of the environment.

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43

Milicic, Ljiljana, Anja Terzic, Lato Pezo, Nevenka Mijatovic, Ilija Brceski y Nikola Vukelic. "Assessment of efficiency of rare earth elements recovery from lignite coal combustion ash via five-stage extraction". Science of Sintering 53, n.º 2 (2021): 169–85. http://dx.doi.org/10.2298/sos2102169m.

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Rare earth elements (REE) are frequently referred to as ingredients for enhancements in modern industry, as they are extensively applied in many industrial branches due to their accented electro-magnetic and optical properties. REE have end-utilizations as catalysts, magnets, and as dopants for ceramic materials. Rare earth minerals are scarce therefore the unconventional REE-containing resources such as waste materials and industrial byproducts are continuously being investigated. Coal combustion products comprise REE concentrations varying between 200 ppm and 1500 ppm. This quantity can be isolated though the extraction procedure. In this study, the five stages extraction was conducted on the coal combustion ash from the selected landfill site. The extractions of 32 elements (As, Ga, Ce, Be, Ge, Nd, Cr, Zr, Eu, Cu, Nb, Gd, Co, Mo, Dy, Li, Ag, W, Mn, Cd, Au, Ni, In, Hg, Pb, Sn, Tl, V, Sb, Th, Zn, and La) were conveyed. Chemical analyses were conducted via XRF, ICP-OES, ICP-MS, and AAS techniques. The complexity of the obtained data was examined by Principal component analysis and Cluster analysis in order to derive interconnections between quantity of elements and landfill characteristics, as well as mutual relationships among the elements of interest, and to assess the accomplishment of REE recovery from the coal ash.

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44

An, Jung-Chul, Seong-Young Lee, Joo-Il Park, Manyoul Ha, Joongpyo Shim y Ikpyo Hong. "Study of Quinoline Insoluble (QI) Removal for Needle Coke-Grade Coal Tar Pitch by Extraction with Fractionalized Aliphatic Solvents and Coke Formation Thereof". Applied Sciences 11, n.º 7 (24 de marzo de 2021): 2906. http://dx.doi.org/10.3390/app11072906.

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Various fractionalized solvents with different paraffinicities were adopted to maximize the efficiency of the quinoline insoluble (QI) extraction process for coal tar pitch. In addition, highly pressurized conditions combined with raised temperature (4 bar at 300 °C) were used to accelerate the reaction kinetics of the extraction process. The QI content of purified coal tar pitch was analyzed to be 0.1% at a process yield of up to 72% as a solvent with a K-factor of 10 and above was used. Purified coal tar pitch was then processed to form anisotropic coke using a lab-scale tube bombe reactor. The texture observed under a polarized light microscope showed an anisotropic flow domain, a unique morphological feature of needle coke. The additives and reaction conditions used in this study for QI extraction for coal tar pitch were found to be effective and feasible as preliminary processing in needle coke production.

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45

DENG, Zhi-gan, Chang WEI, Gang FAN, Min-ting LI, Cun-xiong LI y Xing-bin LI. "Extracting vanadium from stone-coal by oxygen pressure acid leaching and solvent extraction". Transactions of Nonferrous Metals Society of China 20 (mayo de 2010): s118—s122. http://dx.doi.org/10.1016/s1003-6326(10)60024-6.

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46

Peiravi, M., L. Ackah, R. Guru, M. Mohanty, J. Liu, B. Xu, X. Zhu y L. Chen. "Chemical extraction of rare earth elements from coal ash". Minerals & Metallurgical Processing 34, n.º 4 (1 de noviembre de 2017): 170–77. http://dx.doi.org/10.19150/mmp.7856.

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47

Liu, A., Z. Shi, K. Xie, X. Hu, B. Gao, M. Korenko y Z. Wang. "Extraction of Al-Si master alloy and alumina from coal fly ash". Journal of Mining and Metallurgy, Section B: Metallurgy 53, n.º 2 (2017): 155–62. http://dx.doi.org/10.2298/jmmb160616006l.

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Coal fly ash from coal power plants is a potential raw material for the production of alumina. An objective aluminothermic reduction method for the preparation of Al-Si master alloy and alumina from coal fly ash was investigated. The kinetic analysis using non-isothermal differential scanning calorimetry indicated that the reduction of Al6Si2O13, Fe2O3, and TiO2 by aluminum in coal fly ash occurs at 1618 K, 1681 K, and 1754 K, respectively. Moreover, the influence of reaction temperature on product composition was studied. The phases and morphologies of the products obtained by the aluminothermic reduction of coal fly ash at 1373-1773 K were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, respectively. The results from X-ray diffraction show that no oxide reduction has taken place at 1373 K and 1473K, the compositions of the product obtained by aluminothermic reduction of fly ash at 1573K- 1673 K are Al2O3, mullite, Al and Si, while the compositions of the product at 1773 K are Al2O3, Al, and Si. In addition, the chemical compositions of Al-Si alloy obtained at 1773 K are 86.81 wt% Al and 13.19 wt% Si.

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48

Park, Jung hoon y Sang do Park. "Extraction of Low Rank Coal with Sub- and Supercritical Water". JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 41, n.º 7 (2008): 590–96. http://dx.doi.org/10.1252/jcej.07we070.

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49

Riley, Kenneth W., Harry N. S. Schafer y Helen Orban. "Rapid acid extraction of bituminous coal for the determination of phosphorus". Analyst 115, n.º 11 (1990): 1405. http://dx.doi.org/10.1039/an9901501405.

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50

Adschiri, T., T. Sato, H. Shibuichi, Z. Fang, S. Okazaki y K. Arai. "Extraction of Taiheiyo coal with supercritical water–HCOOH mixture". Fuel 79, n.º 3-4 (febrero de 2000): 243–48. http://dx.doi.org/10.1016/s0016-2361(99)00158-1.

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