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1
Wierzba, I., and G. A. Karim. "A Predictive Approach for the Flammability Limits of Methane-Nitrogen Mixtures." Journal of Energy Resources Technology 112, no. 4 (December 1, 1990): 251–53. http://dx.doi.org/10.1115/1.2905768.
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The present contribution describes a relatively simple procedure for predicting the lean and rich flammability limits of methane-nitrogen mixtures in air from a knowledge of the composition of the fuel mixture and the corresponding limit for methane. It is shown that this approach can be extended similarly to consider the limits of natural gas-nitrogen mixtures yielding relatively good agreement with experimental values over a relatively wide range of composition and pressure.
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Sizova, A. A., S. A. Grintsevich, M. A. Kochurin, V. V. Sizov, and E. N. Brodskaya. "Molecular Simulations of CO2/CH4, CO2/N2 and N2/CH4 Binary Mixed Hydrates." Colloid Journal 83, no. 3 (May 2021): 372–78. http://dx.doi.org/10.1134/s1061933x21030145.
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Abstract Grand canonical Monte Carlo simulations were performed to study the occupancy of structure I multicomponent gas hydrates by CO2/CH4, CO2/N2, and N2/CH4 binary gas mixtures with various compositions at a temperature of 270 K and pressures up to 70 atm. The presence of nitrogen in the gas mixture allows for an increase of both the hydrate framework selectivity to CO2 and the amount of carbon dioxide encapsulated in hydrate cages, as compared to the CO2/CH4 hydrate. Despite the selectivity to CH4 molecules demonstrated by N2/CH4 hydrate, nitrogen can compete with methane if the gas mixture contains at least 70% of N2.
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Borodin, Stanislav L., and Denis S. Belskikh. "The Current State of Researches Related to the Extraction of Methane from a Porous Medium Containing Hydrate." Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy 4, no. 4 (December 17, 2018): 131–47. http://dx.doi.org/10.21684/2411-7978-2018-4-4-131-147.
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In the next few decades due to a depletion of traditional gas deposits, a question of using alternative sources of natural gas, such as gas hydrates deposits, might arise. Besides, there is a problem of existing greenhouse effect, which is constantly aggravated by increasing carbon dioxide emissions into the atmosphere. At the same time, carbon dioxide can replace methane in gas hydrates and remain in its stable hydrate state in the reservoir. Therefore, available deposits of hydrates are not only potential sources of energy, but also allow a sequestration (“burial”) of carbon dioxide with simultaneous extraction of methane.<br> Several “classical” approaches to extract gas from its hydrate are discussed in the article: depressurization method (pressure reduction), thermal impact (temperature increase), and inhibitors’ use. Laboratory and practical experience of those approaches is reviewed, and their advantages and disadvantages are briefly described. Next, the most promising exchange method for simultaneous sequestration of the greenhouse gas and the production of energy is studied. The paper includes the results of this method’s use in the laboratory and the only practical application currently. The advantage of using a mixture of nitrogen and carbon dioxide for the exchange method was demonstrated, which significantly increases methane extraction degree from its hydrates, which was tested on the first well using this method. Comparing to previous studies reviewing this subject, additional studies related to methane exchange method in hydrates over the last two years were studied.<br> The exchange method is acknowledged the most effective since it ensures a successful extraction of methane from gas hydrate deposits and a “burial” of greenhouse carbon dioxide. In this case, the highest percentage of methane extraction is observed when a mixture of carbon dioxide and nitrogen is injected into the formation. An additional advantage is the exchange can be combined with depressurization and thermal impact. The most promising for research and further application is the combined method for obtaining energy and disposing of the resulting greenhouse carbon dioxide gas. First, a hot mixture of carbon dioxide and nitrogen from combustion of methane on a power plant is pumped into the reservoir through the first well. Then, decomposition/exchange of methane hydrates occurs in the formation. Methane and associated products of its decomposition/exchange are extracted through the second well by depressurization method, and then the methane is cleaned and fed to the power plant for further combustion.
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Avramenko, Andrii. "The impact of oxidiser humidity on methane combustion in a gas burner." French-Ukrainian Journal of Chemistry 8, no. 2 (2020): 48–59. http://dx.doi.org/10.17721/fujcv8i2p48-59.
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The improvement of thermodynamic and environmental indicators of energy facilities is a vital and topical problem. Numerical simulation methods are used to investigate the processes of combustion and formation of hazardous substances by computation, and to work out recommendations on increasing the effectiveness of fuel combustion. The paper examines the impact of atmospheric air humidity on the process of combustion of a stoichiometric methane-air mixture in a burner. The combustion process is simulated in the 3D unsteady statement in Cartesian coordinates. In the investigation, the combustion of the methane-air mixture is considered in one stage. Air humidity is considered in the 0 to 100% range. The monoxide nitrogen formation process is described using the extended Zeldovich-Fenimore mechanism. A comparative study has found that increasing air humidity up to 100% reduces the mass emission of monoxide nitrogen by a factor of 1.27, as compared to dry air. The study results can be used for designing equipment that uses methane as fuel.
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Mazánková, V., L. Töröková, D. Trunec, F. Krčma, S. Matejčík, and N. J. Mason. "Diagnostics of Nitrogen-methane Atmospheric Glow Discharge Used for a Mimic of Prebiotic Atmosphere." PLASMA PHYSICS AND TECHNOLOGY 4, no. 1 (2017): 83–86. http://dx.doi.org/10.14311/ppt.2017.1.83.
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The exploration of planetary atmosphere is being advanced by the exciting results of the Cassin-Huygens mission to Titan. The complex chemistry revealed in such atmospheres leading to the synthesis of bigger molecules is providing new insights into our understanding of how life on Earth developed. This work extends our previous investigation of nitrogen-methane (N<sub>2</sub>-CH<sub>4</sub>) atmospheric glow discharge for simulation chemical processes in prebiotic atmospheres. In presented experiments 2 % of water vapor were addet to nitrogen-methane gas mixture. Exhaust products of discharge in this gas mixture were in-situ analysed by Fourier Transform Infra Red spectroscopy (FTIR). The major products identified in spectra were: hydrogen cyanide, acetylene and acetonitrile.
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Budak, Paweł, and Tadeusz Szpunar. "Dobór wydajności gazów propan-butan dodawanych w celu wspomagania efektywnego spalania gazu ziemnego niskometanowego z użyciem flary." Nafta-Gaz 77, no. 1 (January 2021): 26–32. http://dx.doi.org/10.18668/ng.2021.01.04.
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The paper discusses the problems related to the burning of gas mixtures containing flammable and non-flammable gases using a flare. Before being burned, such a gas mixture must be “enriched” with other flammable gases before it can be directed to the flare. In the case of some Polish gas reservoirs such as Cychry or Sulęcin, the composition of the gas mixture doesn’t make it possible to burn it using the flare because the content of inflammable components is too high and the gas mixture is inflammable. The gas from the reservoirs mentioned above contains above 90 percent of nitrogen and small percentages of flammable components. Sometimes, besides nitrogen, the gas mixture contains other inflammable gases like carbon dioxide, helium, and oxygen. Usually, the propane/butane is used for that purpose. The possibility of burning the gas mixture using the flare is particularly important if the toxic gases are present in the mixture – hydrogen sulfide in particular. The propane/butane gases are added to the stream of gas mixture meant for burning using a special appliance. The typical arrangement of a gas-burning installation (i.e. the flare) is shown and the destination of its components is discussed. The empirical formula is provided which allows us to recognize if the gas mixture is flammable or not. The composition of the gas mixture must be known to calculate the propane/butane flow rate, including percentages of flammable and inflammable components. The algorithm constructed for calculating the propane/butane flow rate is presented, which must be maintained to assure the flammability of the gas mixture destined for burning using the flare. The results of the calculations for four gas mixtures from the Polish gas reservoirs are provided. The presented method of determining the flammability of gas mixtures (or its inability to be burned) and the flow rate of the propane/butane mixture required for complete combustion is based on empirical relationships, which are provided in the paper and may be helpful in planning the assisted combustion of low methane gases (not suitable for further use) using a flare.
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Minkov, Leonid, and Kseniya Moiseeva. "Combustion peculiarities of coal-methane-air mixtures in a recuperative burner." MATEC Web of Conferences 243 (2018): 00007. http://dx.doi.org/10.1051/matecconf/201824300007.
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Numerical modeling of the combustion of a lean methane-air mixture containing fine coal particles entering the “Swiss-roll” type recuperative burner is considered. The mathematical model is constructed under the following assumptions: the flow field is two-dimensional; the gas mixture is an ideal incompressible gas consisting of oxygen, methane, coal volatile substances, carbon monoxide, carbon dioxide, water vapor, hydrogen and nitrogen. In the gas phase four oxidation reactions, in which methane, volatile matter of coal, carbon monoxide, hydrogen participate and the reaction of carbon dioxide decomposition take place. On the surface of the coal particle, there are three oxidation reactions involving oxygen, carbon dioxide and water vapor, resulting in the formation of carbon monoxide. It is assumed that coal contains 8% of ash, 12.9% of volatile substances and 79.1% of carbon. It is shown that for a two percent methane-air mixture the reaction zone shifts toward the center of the burner as the feed rate of the mixture increases. An increase in the content of coal particles leads to a shift of the reaction zone into the inlet part of the burner, and the heat release in the burner increases.
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Karp, I. M. "HYDROGEN IN MUNICIPAL ENERGY." Energy Technologies & Resource Saving, no. 1 (March 20, 2021): 23–26. http://dx.doi.org/10.33070/etars.1.2021.02.
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The use of hydrogen in the municipal energy sector is currently inappropriate due to its high cost. Production of hydrogen by electrolysis requires more energy than it is emitted during its combustion. Thermophysical properties of hydrogen and natural gas are compared. Heat value of hydrogen in a unit of volume is 3.3 times lower than that of methane. The cost per unit of energy in hydrogen is more than 10 times higher than in natural gas. Distribution gas networks are not suitable for transportation of pure hydrogen. The possibility of transporting hydrogen in mixtures with natural gas is being studied. The efficiency of fuel use in a heating gas boiler decreases with increasing hydrogen concentration in a mixture with natural gas up to 50 %. The concentration of nitrogen oxides does not depend on the hydrogen content in the mixture. Bibl. 4, Table 1.
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Wang, S. G., Q. Zhang, D. J. Yang, S. F. Yoon, J. Ahn, and B. Gan. "EFFECTS OF HYDROGEN GAS FLOW RATIO ON THE QUALITY OF NANO-DIAMOND FILMS." International Journal of Modern Physics B 16, no. 06n07 (March 20, 2002): 876–80. http://dx.doi.org/10.1142/s0217979202010543.
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In this paper, we studied the effects of hydrogen gas flow ratio of [H2]/[N2 + CH4 + H2] on the quality of nanometer diamond (nano-diamond) films prepared by microwave plasma enhanced chemical vapor deposition method. Nano-diamond films were deposited on the silicon substrates from a gaseous mixture of nitrogen, methane and hydrogen. The experimental results show that if only using a gaseous mixture of nitrogen and methane, although we can obtain nano-diamond films with a grain size of about 5nm, the diamond films contain much non-diamond components. With hydrogen addition, and with increasing the hydrogen gas flow ratio from 1 to 10%, the non-diamond components in the films are significantly reduced and the grain size of the films increases from 5nm to 60nm. However optical transmittance of the films increases with increasing hydrogen gas flow ratio from 1 to 7% because of an improvement of film quality, and then decreases with further increasing hydrogen gas flow ratio owing to the increase of film roughness.
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Bhadra, S. J., and S. Farooq. "Separation of Methane–Nitrogen Mixture by Pressure Swing Adsorption for Natural Gas Upgrading." Industrial & Engineering Chemistry Research 50, no. 24 (December 21, 2011): 14030–45. http://dx.doi.org/10.1021/ie201237x.
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Karim, G. A., and V. Panlilio. "Flame Propagation and Lean-Limit Extinction Within Stratified Mixtures Involving a Diluent Gas." Journal of Energy Resources Technology 114, no. 3 (September 1, 1992): 216–20. http://dx.doi.org/10.1115/1.2905944.
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Flame propagation within confined, stratified gaseous environments were investigated experimentally. The diluents nitrogen and helium were used in turn to overlay initially combustible methane-air or hydrogen-air mixtures. Gas stratification was achieved by allowing the two initially homogeneous gases to interdiffuse for a certain period of time at constant temperature and pressure within a long, vertical, smooth, closed, circular tube. Upward flame propagation was examined following spark ignition while the tube was closed at the top but open at the bottom. Near-extinction flame speeds, lower than those predicted according to Davies and Taylor (1950), were obtained with helium dilution. Moreover, estimated reactant concentrations at the observed location of flame extinction indicated, in specific instances, that mixture stratification appears to slightly enhance locally the lean flammability limit. Nonuniform, stratified combustible gaseous mixtures and flame propagation within such mixtures are found in many situations, including in numerous technical applications, as well as in various potentially hazardous circumstances. The leakage of a fuel from storage tanks or pipelines, the formation of layered combustible mixtures within rooms, corridors, or elevator shafts of buildings, the formation of gas pockets in coal mine galleries, and the inerting of flammable mixtures through diluent gas addition are some examples. Some relevant information about the stratification process and the flame propagation characteristics in these specific circumstances has already been reported in the literature by Bakke and Leach (1962), James and Purdy (1962), Girard et al. (1979), Karim and Lam (1986) and Karim et al. (1987). This investigation considers some aspects of flame propagation and mass transfer within confined, stratified gaseous environment. The diluents nitrogen and helium were used in turn to overlay initially combustible methane-air or hydrogen-air mixtures. Mixture stratification was produced by permitting the two initially homogeneous gaseous systems to interdiffuse at constant temperature within a long, vertical, smooth, closed, circular tube. Only upward flame propagation was examined, as this mode is expected to involve the widest flammability limits and the fastest propagation for both homogeneous and stratified methane-air mixtures when confined in tubes (Liebman et al., 1971).
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Mazankova, V., I. Manduchová, F. Krcma, L. Prokes, and D. Trunec. "GC-MS and GC-FID Analysis of Products from Glow Discharge in N2 + CH4 Mixture." PLASMA PHYSICS AND TECHNOLOGY 5, no. 3 (2018): 103–6. http://dx.doi.org/10.14311/ppt.2018.3.103.
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This work extends our previous investigation of nitrogen-methane atmospheric glow discharge for the simulation of chemical processes in prebiotic atmospheres. Also reactions on surfaces of solid state bodies can be important. So in presented experiments the electrodes with different shapes and different surface areas were used. Exhaust products of discharge in this gas mixture were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS) and Gas Chromatography - Flame Ionization Detector (GC-FID). The major products identified in chromatograms were hydrogen cyanide and acetylene.
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Stateva, Roumiana P., and Stefan G. Tsvetkov. "Modelling of the Multiphase Behavior of Methane-Ethane-Nitrogen Mixture at Low Temperatures with an Equation of State." Collection of Czechoslovak Chemical Communications 57, no. 7 (1992): 1362–72. http://dx.doi.org/10.1135/cccc19921362.
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The paper discusses modelling of the multiphase behavior of the methane-ethane-nitrogen mixture, which is of a considerable interest for the natural gas and oil industries. The thermodynamic model is a modified Redlich-Kwong-Soave equation of state. The computer algorithm is based on a new approach to solving the isothermal multiphase flash problem, when the number and identity of the phases present at equilibrium are unknown in advance. The results demonstrate that Redlich-Kwong-Soave equation of state and the algorithm applied predict with reasonable accuracy the complicated phase behavior and the region of L1L2V equilibrium, observed in the experiment, of the methane-ethane-nitrogen system.
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Wu, Zhenkuo, Christopher J. Rutland, and Zhiyu Han. "Numerical evaluation of the effect of methane number on natural gas and diesel dual-fuel combustion." International Journal of Engine Research 20, no. 4 (February 22, 2018): 405–23. http://dx.doi.org/10.1177/1468087418758114.
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Natural gas and diesel dual-fuel combustion is a promising technology for efficiently utilizing natural gas in a compression ignition engine. Natural gas composition varies depending on the geographical source, which affects engine performance. The methane number is an indicator of natural gas fuel quality to assess the variation in composition. In this study, the influences of methane number on natural gas/diesel dual-fuel combustion were numerically examined using computational fluid dynamic simulations. The differences between natural gases with the same methane number but different components were also compared. Two dual-fuel combustion strategies, diesel pilot ignition, and reactivity controlled compression ignition were evaluated. The results show that for both diesel pilot ignition and reactivity controlled compression ignition, the ignition delay increases and the combustion duration decreases as the methane number is increased. The retarded trend of ignition of reactivity controlled compression ignition is more significant than that of diesel pilot ignition, while the decreased trend in combustion duration is less significant. To understand this trend, a chemical kinetics study of ignition delay characteristic of natural gas and n-heptane mixture was conducted. The result reveals that introducing ethane, propane, or an ethane–propane mixture into pure methane shortens the ignition delay in the entire temperature range. However, for the methane and n-heptane mixture, adding ethane, or propane, or an ethane–propane mixture shortens the ignition delay in the high temperature range, while increases the ignition delay in the low temperature range. These observations in combination with the analysis of air–fuel mixture formation and combustion provide the evidence to interpret the different ignition and combustion behaviors between diesel pilot ignition and reactivity controlled compression ignition combustion. In addition, a temperature A-factor sensitivity study was carried out to explain the result of the chemical kinetics study. Furthermore, the responses of emissions to methane number were also investigated. The results show that for diesel pilot ignition, the hydrocarbon and carbon monoxide emissions decrease with the decreased methane number. However, for reactivity controlled compression ignition, the variations of hydrocarbon and carbon monoxide emissions with the methane number are not so obvious as for diesel pilot ignition combustion. For both diesel pilot ignition and reactivity controlled compression ignition combustion, the nitrogen oxides emissions show a strong dependence on combustion phasing rather than natural gas composition. Overall, to control diesel pilot ignition combustion, the methane number should be considered together with other parameters. However, attention should be paid to other control parameters for the reactivity controlled compression ignition combustion. The engine performance of reactivity controlled compression ignition is not sensitive to the variation of natural gas composition, so it can adapt to the natural gas from different sources.
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Qiu, Wei, Yogesh K. Vohra, and Samuel T. Weir. "Role of nitrogen in the homoepitaxial growth on diamond anvils by microwave plasma chemical vapor deposition." Journal of Materials Research 22, no. 4 (April 2007): 1112–17. http://dx.doi.org/10.1557/jmr.2007.0118.
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The catalytic effect of nitrogen during the homoepitaxial diamond growth on a diamond anvil was investigated using isotopically enriched carbon-13 methane in a feed-gas mixture in a microwave plasma chemical vapor deposition reactor. The use of isotopically enriched carbon-13 allows us to precisely measure the film thickness in this homoepitaxial growth process by Raman spectroscopy. It is found that the addition of 0.4 sccm of nitrogen to an H2/CH4/O2 gas-phase mixture increases the growth rate by a factor of 2.3. This enhanced growth rate with the addition of trace amounts of nitrogen allows for a quick encapsulation of embedded sensors in the designer diamond anvils and is a key control parameter in the fabrication process. Photoluminescence spectroscopy reveals nitrogen-vacancy defect centers in the high-growth-rate diamonds. Atomic force microscopy reveals dramatic changes in the surface microstructure as is indicated by a total loss of step-flow growth morphology on the addition of nitrogen in the plasma.
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Samudrala, Gopi K., and Yogesh K. Vohra. "Multivariable study on homoepitaxial diamond growth using isotopically enriched carbon-13 gas mixtures." Journal of Materials Research 24, no. 2 (February 2009): 493–98. http://dx.doi.org/10.1557/jmr.2009.0052.
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We report our observations on the homoepitaxial diamond growth by microwave plasma chemical vapor deposition (MPCVD) experiments on Type Ib diamond substrates conducted by varying three independent variables. In a feed gas mixture of H2, N2, O2, and 13CH4, the amount of nitrogen was varied in the range of 0 to 4000 ppm, the amount of methane was varied from 2% CH4/H2 to 6% CH4/H2, and the substrate temperature was varied in the range of 850 to 1200 °C. We used isotopically enriched carbon-13 methane gas as the source of carbon in the plasma to clearly distinguish the grown diamond layer from the underlying substrate using Raman spectroscopy. The x-ray rocking curve measurements confirmed the homoepitaxial nature of the deposited layers with a slight increase in the full width at half-maximum for sample grown with the highest nitrogen content in the plasma. Optical and atomic force microscopy revealed dramatic changes in surface morphology with variation in each parameter. The nitrogen incorporation in carbon-13 diamond layers was monitored through photoluminescence spectroscopy of nitrogen–vacancy complexes. A twentyfold increase in diamond growth rate was clearly achieved in this multivariable study.
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Ojha, Varun Kumar, and Paramartha Dutta. "Performance analysis of neuro swarm optimization algorithm applied on detecting proportion of components in manhole gas mixture." Artificial Intelligence Research 1, no. 1 (July 5, 2012): 31. http://dx.doi.org/10.5430/air.v1n1p31.
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The article presents performance analysis of the neuro swarm optimization algorithm applied for the detection of proportion of the component gases found in manhole gas mixture. The hybrid neuro swarm optimization technique is used for implementing an intelligent sensory system for the detection of component gases present in manhole gas mixture. The manhole gas mixture typically contains toxic gases such as Hydrogen Sulfide, Ammonia, Methane, Carbon Dioxide, Nitrogen Oxide, and Carbon Monoxide. A semiconductor based gas sensor array used for sensing the gas components consists of many sensor elements, where each sensor element is responsible for sensing particular gas component. Presence of multiple gas sensors for detecting multiple gases results in cross-sensitivity. The central theme of this article is the performance analysis of the algorithm which offers solution to multiple gas detection issue. The article also presents study on the computational cost incurred by the algorithm.
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Torokova, Lucie, Vera Mazankova, Frantisek Krcma, Nigel J. Mason, and Stefan Matejcik. "Atmospheric pressure glow discharge generated in nitrogen-methane gas mixture: PTR-MS analyzes of the exhaust gas." European Physical Journal Applied Physics 71, no. 2 (July 2015): 20806. http://dx.doi.org/10.1051/epjap/2015150072.
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Anggono, Willyanto, I. N. G. Wardana, M. Lawes, K. J. Hughes, Slamet Wahyudi, and Nurkholis Hamidi. "Laminar Burning Velocity and Flammability Characteristics of Biogas in Spark Ignited Premix Combustion at Reduced Pressure." Applied Mechanics and Materials 376 (August 2013): 79–85. http://dx.doi.org/10.4028/www.scientific.net/amm.376.79.
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Biogas as a “Powergas” is an alternative fuel produced in digestion facilities, that is sustainable and renewable. Based on chemical analysis, the composition of the biogas produced in East Java is 66.4% methane, 30.6% carbon dioxide and 3% nitrogen. Methane is a flammable gas, whereas, nitrogen and carbon dioxide are inhibitors. Given it has a different composition to traditional fuels, a fundamental study of biogas flame propagation characteristics is desirable to quantify this important fuel property. Spherically expanding flames propagating at constant pressure are employed to measure the laminar burning velocity and flammability characteristics as mixture function of the mixture composition. These important parameters were measured using a photographic technique in a high pressure fan-stirred bomb. The characteristics of biogas-air flames were initially studied at reduced pressure and at various equivalence ratios from the lower flammable limit to the upper flammable limit. The results were compared with those from biogas-air flames at atmospheric pressure. Based on this experimental investigation, the laminar burning velocities of biogas-air mixtures at reduced pressure were 0.218 m/s for ϕ=0.75, 0.246 m/s for ϕ=0.80 and 0.269 m/s for ϕ=0.85 respectively and only for these biogas mixtures propagated at reduced pressure. At the same equivalence ratio (ϕ), the laminar burning velocities of the biogas-air mixtures at reduced pressure are higher than those at atmospheric pressure. The flammable region of biogas became narrower by reducing initial pressure. The dilution effect is stronger at reduced pressure. Therefore, the flammable composition mixture areas of biogas-air mixtures are more limited at reduced pressure than those at atmospheric pressure.
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Fen, Chiu-Shia, Yu-Ro Lin, and Chia-Yu Chen. "Methane transport in a soil column: experimental and modeling investigation." Environmental Engineering Research 26, no. 5 (October 12, 2020): 200311–0. http://dx.doi.org/10.4491/eer.2020.311.
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This study explored two diffusion approaches, Fick’s law and the dusty gas model (DGM), to assess their differences on modeling methane transport in porous systems. Laboratory experiments were also conducted for methane transport through a nitrogen gas-dry soil column from different source densities. Gas pressures and methane densities at transient state were measured along the column for two transport configurations (horizontal and vertically upward) and compared with the predictions obtained from the DGM- and Fickian-based models. The retardation factor is the only parameter used in the model calibration. The results showed that the methane density profiles predicted by these models fairly matched the measured data and are quite consistent for vertically upward transport of methane. However, the predictions were over the measured ones for horizontal transport of methane. We suspected it is due to incomplete mixing of gas mixture in the inlet chamber since high pressure variations were observed in the horizontal transport experiments. Further, we found that the methane density profile predicted by the Fickian-based model is lagged behind the DGM result for at most 15% of difference in methane density for horizontal transport of methane from a pure methane source.horizontal transport experiments. Further, we found that the methane density profile predicted by the Fickian-based model lagged behind the DGM result for at most 15% of difference in methane density for horizontal transport of methane from a pure methane source.
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Christensen, Jesper B., Lasse Høgstedt, Søren M. M. Friis, Jui-Yu Lai, Ming-Hsien Chou, David Balslev-Harder, Jan C. Petersen, and Mikael Lassen. "Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning." Sensors 20, no. 17 (August 21, 2020): 4725. http://dx.doi.org/10.3390/s20174725.
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Quartz-enhanced photoacoustic sensing is a promising method for low-concentration trace-gas monitoring due to the resonant signal enhancement provided by a high-Q quartz tuning fork. However, quartz-enhanced photoacoustic spectroscopy (QEPAS) is associated with a relatively slow acoustic decay, which results in a reduced spectral resolution and signal-to-noise ratio as the wavelength tuning rate is increased. In this work, we investigate the influence of wavelength scan rate on the spectral resolution and signal-to-noise ratio of QEPAS sensors. We demonstrate the acquisition of photoacoustic spectra from 3.1 μm to 3.6 μm using a tunable mid-infrared optical parametric oscillator. The spectra are attained using wavelength scan rates differing by more than two orders of magnitude (from 0.3 nm s−1 to 96 nm s−1). With this variation in scan rate, the spectral resolution is found to change from 2.5 cm−1 to 9 cm−1. The investigated gas samples are methane (in nitrogen) and a gas mixture consisting of methane, water, and ethanol. For the gas mixture, the reduced spectral resolution at fast scan rates significantly complicates the quantification of constituent gas concentrations.
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Hao, Xiaofei, Hongjie Hu, Zhen Li, Limei Wu, Xueqin Liu, and Yinnian Zhang. "Adsorption Properties of Modified Clinoptilolite for Methane and Nitrogen." Materials 11, no. 10 (October 18, 2018): 2024. http://dx.doi.org/10.3390/ma11102024.
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Coalbed methane (CBM) is a kind of unconventional gas. CBM often contains a great deal of air when it comes out of the well. So, it must be condensed and purified before it can be applied. In this paper, raw clinoptilolite (Cp) was treated with grinding, gravimetric concentration, and ion-exchange using different aqueous solutions of salts. Then, the modified Cp powder was prepared into particles as adsorbents. Then, the adsorbents were used for nitrogen/methane separation in pressure swing adsorption (PSA) at the same condition of 0.2 MPa and 298 K. Research results indicated that there were micropores and lots of mesopores in the Cp, and the pores were mainly slit holes formed by sheet stacking. The adsorbents of NH4-Cp, Cs-Cp, and Cu-Cp showed good equilibrium selectivity for CH4, and the equilibrium separation factors of CH4 and N2 were 2.56, 2.31, and 1.95, respectively. The adsorbents of Na-Cp and Ag-Cp showed good equilibrium selectivity for N2, and the equilibrium separation factors of N2 and CH4 were 7.25 and 6.53, respectively. Consequently, the adsorbent of Na-Cp was suitable for nitrogen/methane mixture separation, which could make the concentration of methane concentrated from 19.7% to 30.72%.
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van Hemert, Patrick, Karl-Heinz A. A. Wolf, and E. Susanne J. Rudolph. "Output gas stream composition from methane saturated coal during injection of nitrogen, carbon dioxide, a nitrogen–carbon dioxide mixture and a hydrogen–carbon dioxide mixture." International Journal of Coal Geology 89 (January 2012): 108–13. http://dx.doi.org/10.1016/j.coal.2011.07.010.
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Almeida, Alcino R. "A Model To Calculate the Theoretical Critical Flow Rate Through Venturi Gas Lift Valves." SPE Journal 16, no. 01 (August 19, 2010): 134–47. http://dx.doi.org/10.2118/126184-pa.
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Summary A model to calculate the theoretical critical flow rate of nitrogen (N2) or natural gas through a Venturi gas lift valve is described herein. This new model considers real-gas effects not only in density calculations but also in other thermodynamic properties that are relevant during gas isentropic evolution. For the properties of N2, the Bennedict, Webb, and Rubin (BWR) equation of state and an accurate correlation for the ideal-gas isobaric heat capacity were used. For natural gas, the Dranchuk and Abou-Kassem equation, which reproduces the well-known Standing and Katz chart, was used, and, for the ideal-gas isobaric heat capacity, it was assumed that the natural gas was a mixture of methane and ethane only, their individual ideal-gas heat capacity being calculated by updated correlations. To validate the use of the proposed equations of state, a comparison of calculated with experimental or reference data on properties of N2 and natural gas (including pure methane and some relevant mixtures) was performed with very good results for N2 and for natural-gas compositions usual in gas lift operations (dry gas with very small amounts of contaminants). For natural gas with moderate amounts of N2 and carbon dioxide (CO2), accurate results were obtained after correction of critical conditions and of ideal heat capacity. The model was also compared with other theoretical models found in the literature, which use compositional approaches for natural gas, with excellent results. Some experimental results obtained with commercial Venturi valves manufactured in Brazil are also presented.
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Vambol, S., V. Vambol, O. Kondratenko, V. Koloskov, and Y. Suchikova. "Substantiation of expedience of application of high-temperature utilization of used tires for liquefied methane production." Journal of Achievements in Materials and Manufacturing Engineering 2, no. 87 (April 1, 2018): 77–84. http://dx.doi.org/10.5604/01.3001.0012.2830.
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Purpose: The purpose of this investigation is to substantiate by means of numerical simulation the expedience of high-temperature utilization of used tires with subsequent methanation of fuel gases and separation of multicomponent hydrocarbon mixtures to drain the liquefied methane. Design/methodology/approach: The investigation was carried out by means of numerical simulation. In mathematical description of gas processes relations of thermodynamics and heat and mass transfer were used. To determine the coefficients of thermal and physical parameters of working bodies the Peng-Robinson equation of state was used through the computer program REFPROP. The system of equations is represented as the interrelations between the functional elements according to the principle "output from the element A – input into the element B". Its solution was obtained by the method of successive approximations, namely by the Newton-Raphson iteration method. Using this method we have determined the values of temperature, pressure, mass flow rate and mass content of the hydrocarbon gas mixture components in each reference cross-section of the power facility. Findings: As a result of numerical simulation, it is determined that when the multicomponent hydrocarbon mixtures are separated, three flows of energy resources may be obtained: with a high mass content of methane of 91.5% and 83.4%, which may be used as motor fuel, and a gas flow suitable for maintaining the process of waste gasification. However, to remove heat in the condenser of the rectification column, it is necessary to use expensive liquid nitrogen. The cost of methane production may be reduced if the condenser is removed from the rectification column. However, such approach reduces the overall yield of commercial products almost in four times and significantly reduces the methane with the third product (molar percentage of 35%). Research limitations/implications: The investigation was carried out for the material of used tires without a metal frame. Practical implications: The implementation of the technology of high-temperature recycling of used tires gives the opportunity to use the generated synthetic gas to maintain the process of utilization, and gives the opportunity to produce liquefied methane, suitable for storage. Originality/value: The main problem of high-temperature recycling of tires is the emission of toxic gas to the atmosphere. It is proposed to allocate methane energy resource from this gas. For the first time an attempt was made to justify the expedience of the technology of high-temperature utilization of tires for liquefied methane production.
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Henglein, A. "Sonolysis of Carbon Dioxide, Nitrous Oxide and Methane in Aqueous Solution." Zeitschrift für Naturforschung B 40, no. 1 (January 1, 1985): 100–107. http://dx.doi.org/10.1515/znb-1985-0119.
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Water was irradiated with ultrasonic waves under an argon atmosphere which contained small amounts of carbon dioxide, nitrous oxide or methane. The yield of the products was measured as a function of the composition of the gas atmosphere. Maximum yields were observed at a few per cent of the added polyatomic gas. No chemical effects occurred in the irradiation under an atmosphere of pure CO2 , N2O or CH4. It is concluded that the gas mixture in the tiny gas bubbles, in which the chemical effects are brought about, is not in Henry’s equilibrium with the aqueous gas solution.The main product of the sonolysis of CO2 is CO, a small amount of formic acid also being formed. The sonolysis is explained by both the attack of H atoms from the sonolysis of water and direct decomposition of CO2 due to the high temperatures existing in compressed gas bubbles. The main products of the sonolysis of N2O are nitrogen, nitrite and nitrate. N2O enhances the rate of various oxidations such as that of iodide, nitrite and propanol-2. In the methane containing solution, a lot of hydrogen is produced, the main oxidation products being ethane, ethylene, C3- and C4-hydrocarbons and carbon monoxide. A mechanism is postulated which involves both the attack on methane by radicals from the decomposition of water and thermal decomposition of methane. The local radical concentrations are so high that a methane molecule may undergo multiple radical attack. The similarity between sonolytic reactions and reactions occurring in flames is emphasized
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Roy, Sandip K., Konstantin V. Vassilevski, Christopher J. O'Malley, Nick G. Wright, and Alton B. Horsfall. "Discriminating High k Dielectric Gas Sensors." Materials Science Forum 778-780 (February 2014): 1058–62. http://dx.doi.org/10.4028/www.scientific.net/msf.778-780.1058.
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High temperature gas sensors for the detection of harmful gases under extreme conditions have been demonstrated. Here, we show the detection and selective response of two SiC based MIS sensor structures with HfO2and TiO2high κ dielectric layers to two different hydrogen containing gases. The structures utilise a Pt catalytic gate contact and a high-κ dielectric that was grown on a thin SiO2layer, which was thermally grown on the Si face of epitaxial 4H SiC. The chemical characteristics of MIS capacitors have been studied in N2, O2, H2and CH4ambients at 573K. The data show a positive flatband voltage shift for oxygen and methane with respect to the nitrogen baseline, whilst hydrogen shows a negative shift. The response for the TiO2based sensor is significantly larger than that of the HfO2based device for hydrogen, enabling discrimination of gases within a mixture.
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Choi, Bong Geun, Jae Kwang Kim, Won Jae Yang, Koichi Niihara, Jong Won Yoon, and Kwang Bo Shim. "The Effects of Nitrogen and Annealing on the Electrical Property of the Diamond-Like Carbon (DLC) Films." Key Engineering Materials 317-318 (August 2006): 589–92. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.589.
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The nitrogenated diamond-like carbon films (a-C:H:N) were deposited on Si-wafer by the rf-PECVD method with the addition of nitrogen to the mixture gas of methane and hydrogen. We were investigating the effect of the additive nitrogen gases and annealing in relationship between bonding structure and electrical properties of the deposited films. The electrical conductivity of films increased with the flow rate of nitrogen increasing up to 10 sccm. Also as annealing temperature was increased, the electrical conductivity of films increased. The structure analysis results show that an increase of the flow rate of nitrogen and annealing temperature favor the formation of sp2 bonding in the films. Therefore, we confirmed that the increase of the electrical conductivity is due to structure change by graphitization of the films.
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Cha, Minjun, Kyuchul Shin, Huen Lee, Igor L. Moudrakovski, John A. Ripmeester, and Yutaek Seo. "Kinetics of Methane Hydrate Replacement with Carbon Dioxide and Nitrogen Gas Mixture Using in Situ NMR Spectroscopy." Environmental Science & Technology 49, no. 3 (January 21, 2015): 1964–71. http://dx.doi.org/10.1021/es504888n.
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Soroka, B. S., and V. V. Horupa. "Environmental Characteristics of Modern Systems of Domestic Use of Fuel. Part 1." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no. 4 (August 7, 2020): 340–54. http://dx.doi.org/10.21122/1029-7448-2020-63-4-340-354.
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The analysis of the environmental component of the processes of natural gas burning in atmospheric burners of domestic gas stoves has been carried out. The computational and experimental studies of the harmful substances formation by combustion of natural gas have been performed. The chemical equilibrium of the NO–O2–NO2 system was considered. The thermodynamic analysis of transformation of the system during a process of natural gas (methane-air mixture) combustion has been tested. Despite an essential (sometimes – by the order(s)) difference between the thermodynamically equilibrium concentration of the nitrogen oxides [NOx]eq and the local, actually measured values [NOx] = [NO] + [NO2], the [NO]eq values could be served as the qualitative indicators of actual values of [NOx] concentrations. In the combustion processes natural gas and other fuels combustion at high temperatures [NO] >> [NO2] for both equilibrium and measured concentrations. By moderate and low local temperatures up to 600 K the equilibrium concentration [NO2]eq → [NO]eq in order of magnitude. Under some compositions of burning mixture the correlation could be set as [NO2] >> [NO], resulting in great danger for the human health. With regard to the formation of particularly toxic NO2 effluents observed in some cases, an influence of the reaction temperature and the composition of the combustible mixture on the possibility of nitrogen dioxide formation in the combustion products have been analyzed. A methodology for the experimental study of the harmful emissions formation has been proposed while the computerized firing rig has been developed for studying the combustion of hydrocarbon gases in burners of household stoves. An influence of the coefficient of primary air excess on the СО, NO, NO2 formation has been revealed and the possibility of appearance the emissions of a high concentration of nitrogen dioxide has been demonstrated.
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Leu, Jai Houng, and Ay Su. "Structure of Combustion Enhancement on Impinging Diffusion Flame." Applied Mechanics and Materials 152-154 (January 2012): 872–76. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.872.
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For the purpose to clear obverse the impingement and entrainment of the impinging diffusion flame, numbers of the tests are executed under various sets of momentum ratios in this paper. The oxidizer-fuel impinging flames shorten the fully development length. The peak temperature distributions are also greater than that of pure methane impinging flame. Furthermore, its flame width in YZ plane is thicker than that of the pure impinging flame. This effect is more obvious under lean combustion condition. Also, nitrogen gas in the mixture can increase the mixing rate.
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Wahid, Abdul, Fariz Adriansyah Putra, Muhamad Taufiq Hidayat, and Muhammad Yusuf. "Enhanced coal bed methane (ECBM) recovery: optimization of CBM production using different injected gas composition and rate for south sumatra CBM field, Indonesia." E3S Web of Conferences 67 (2018): 03015. http://dx.doi.org/10.1051/e3sconf/20186703015.
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Indonesia, whose 453 TCF potential coal bed methane (CBM) reserves, rank the 6th largest CBM reserves around the world. However, the technical limitation is amongst the major issues slowing down the exploitation progress of the resources which current national CBM production only reach up to 1 MMSCFD. This paper provides a newly enhanced coal bed methane (ECBM) recovery method to improve the methane production. Scenarios of nitrogen (N2) and carbon dioxide (CO2) injection were used in this study to perform 25 years production simulation and compared with CBM primary production. Created hypothetical model based on the characteristic of coal seams CBM field in South Sumatra, Indonesia, was used to analyze the increasing methane production by using N2 and CO2 injection with different compositions and rates. The result observed about 3,52% incremental methane production by injecting N2 into CBM reservoir. In other words, this new method has an impact on enhancing the CBM national production, particularly South Sumatra CBM field, which could be useful for further CBM development in Indonesia. Mixture injection seemed to be unfavorable for the field due to the difference of gas mechanism. Thus
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Santos, Nazir M., Tatiane M. Arantes, Neidênei G. Ferreira, and Mauricio R. Baldan. "Characterization of Nitrogen Doped Diamond Electrodes Produced by Hot Filament Chemical Vapor Deposition." Materials Science Forum 802 (December 2014): 180–85. http://dx.doi.org/10.4028/www.scientific.net/msf.802.180.
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The purpose of this work is to study the structural and morphological modification of the surface of the n-type diamond electrodes as a function of nitrogen doping. The characterizations of these electrodes were made using Raman Spectroscopy, Contact Angle, X-ray diffraction and Scanning Electron Microscopy (SEM). The nitrogen-doped diamond (NDD) electrodes were produced using Hot Filament-assisted Chemical Vapor Deposition method (HFCVD) from methane, hydrogen and nitrogen in the gas mixture. The results from Raman spectroscopy show that the diamond films obtained with nitrogen addition presented one large band at 1100-1700 cm-1. The SEM images showed that the variation in the nitrogen doping influenced the growth rate of films by promoting changes in the sizes of grains from microcrystalline to nanocrystalline texture. This behavior supported the results obtained from X-ray diffraction analyses. It was possible to verify a decrease in the crystallite size as a function of the nitrogen increase.
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Shi, Ji-Quan, and S. Durucan. "A Model for Changes in Coalbed Permeability During Primary and Enhanced Methane Recovery." SPE Reservoir Evaluation & Engineering 8, no. 04 (August 1, 2005): 291–99. http://dx.doi.org/10.2118/87230-pa.
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Summary The natural fracture network of a dual-porosity coalbed reservoir is made up of two sets of orthogonal, and usually subvertically oriented, cleats. Coalbed permeability has been shown to vary exponentially with changes in the effective horizontal stress acting across the cleats through the cleat-volume compressibility, which is analogous to pore compressibility in porous rocks. A formulation for changes in the effective horizontal stress of coalbeds during primary methane recovery, which includes a Langmuir type curve shrinkage term, has been proposed previously. This paper presents a new version of the stress formulation by making a direct link between the volumetric matrix strain and the amount of gas desorbed. The resulting permeability model can be extended readily to account for adsorption-induced matrix swelling as well as matrix shrinkage during enhanced methane recovery involving the injection of an inert gas or gas mixture into the seams. The permeability model is validated against a recently published pressure-dependent permeability multiplier curve representative of the San Juan basin coalbeds at post-dewatering production stages. The extended permeability model is then applied successfully to history matching a micropilot test involving the injection of flue gas (consisting mainly of CO2 and N2) at the Fenn Big Valley, Alberta, Canada. Introduction Over the past 2 decades, coalbed methane (CBM) has become an important source of the (unconventional) natural gas supply in the U.S. On the basis of this experience, CBM has attracted worldwide attention in recent years as a potential clean energy source. Current commercial CBM production occurs almost exclusively through reservoir-pressure depletion, which is simple but considered to be rather inefficient, with an estimated total recovery of generally around 50% (this figure appears to be pessimistic; mature coal plays in the U.S. have now seen recovery of 60 to 80%) of the gas in place. In recent years, enhanced CBM (ECBM) recovery techniques have been proposed as a more efficient means for the recovery of a larger fraction of methane in place. There are two principal variants of ECBM recovery, namely N2 and CO2injection, which use two distinct mechanisms to enhance methane desorption and production. Unlike the primary recovery method, ECBM allows the maintenance of reservoir pressure. The mechanism used in N2 injection is somewhat similar to inert gas stripping because nitrogen is less adsorbing than methane. Injection of nitrogen reduces the partial pressure of methane in the reservoir, thus promoting methane desorption without lowering the total reservoir pressure. On the other hand, CO2 injection works on a different mechanism because it is more adsorbing on coal compared with methane. Carbon dioxide ECBM recovery thus has an added benefit that a potentially large volume of greenhouse gas can be sequestrated in deep coal seams globally.
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Hamilton, T., R. G. Wilks, M. V. Yablonskikh, Q. Yang, M. N. Foursa, A. Hirose, V. N. Vasilets, and A. Moewes. "Determining the sp2/sp3 bonding concentrations of carbon films using X-ray absorption spectroscopy." Canadian Journal of Physics 86, no. 12 (December 1, 2008): 1401–7. http://dx.doi.org/10.1139/p08-063.
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The sp2 bonding concentrations of nitrogen-doped amorphous carbon samples and nanodiamond films were determined from their soft X-ray absorption spectra. The amorphous carbon (a-C) samples were deposited under atmospheres of varying nitrogen concentrations onto polytetrafluoroethylene (PTFE) polymer and silicon substrates. The nanodiamond films were synthesized on silicon substrates in a CH4/H2 gas mixture by microwave plasma chemical vapour deposition. The sp2 bonding concentrations in the a-C films (deposited on PTFE substrates) increase from 74% to 93% as nitrogen doping increases, with a step-like increase in sp2 fraction when nitrogen concentrations in the films exceed 27%. The a-C films on silicon substrates display the same trend of increasing sp2 concentration as a function of greater nitrogen concentration. Nanodiamond deposition conditions, such as bias voltage and methane concentration, affect the purity of the film. Our analysis reveals sp2 bonding concentrations in these samples ranging from a few percent to 11%.PACS Nos.: 78.70.Dm, 61.10.Ht, 61.46.+w, 81.05.Uw
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Qu, Donglei, Ying Yang, Zhiling Qian, Ping Li, Jianguo Yu, Ana Mafalda Ribeiro, and Alirio E. Rodrigues. "Enrichment of low-grade methane gas from nitrogen mixture by VPSA with CO2 displacement process: Modeling and experiment." Chemical Engineering Journal 380 (January 2020): 122509. http://dx.doi.org/10.1016/j.cej.2019.122509.
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Kosarev, I. N., M. M. Nudnova, P. N. Sagulenko, V. I. Khorunzhenko, and N. N. Kudryavtsev. "Measurement of the radiation intensity beyond the front of strong shock waves for a methane-nitrogen gas mixture." Doklady Physics 56, no. 12 (December 2011): 593–96. http://dx.doi.org/10.1134/s1028335811120093.
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Ridouane, El Hassan, and Antonio Campo. "Compounded Heat Transfer Enhancement in Enclosure Natural Convection by Changing the Cold Wall Shape and the Gas Composition." Journal of Heat Transfer 129, no. 7 (July 12, 2006): 827–34. http://dx.doi.org/10.1115/1.2712857.
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This article addresses compound heat transfer enhancement for gaseous natural convection in closed enclosures; that is, the simultaneous use of two passive techniques to obtain heat transfer enhancement, which is greater than that produced by only one technique itself. The compounded heat transfer enhancement comes from two sources: (1) reshaping the bounded space and (2) the adequacy of the gas. The sizing of enclosures is of great interest in the miniaturization of electronic packaging that is severely constrained by space and∕or weight. The gases consist in a subset of binary gas mixtures formed with helium (He) as the primary gas. The secondary gases are nitrogen (N2), oxygen (O2), carbon dioxide (CO2), methane (CH4), and xenon (Xe). The steady-state flow is governed by a system of 2-D coupled mass, momentum, and energy conservation equations, in conjunction with the ideal gas equation of state. The set of partial differential equations is solved using the finite volume method, for a square and a right-angled isosceles triangular enclosure, accounting for the second-order accurate QUICK and SIMPLE schemes. The grid layouts rendered reliable velocities and temperatures for air and the five gas mixtures at high Ra=106, producing errors within 1% were 18,500 and 47,300 elements for the square and triangle enclosures, respectively. In terms of heat transfer enhancement, helium is better than air for the square and the isosceles triangle. It was found that the maximum heat transfer conditions are obtained filling the isosceles triangular enclosure with a He–Xe gas mixture. This gives a good trade-off between maximizing the heat transfer rate while reducing the enclosure space in half; the maximum enhancement of triangle∕square went up from 19% when filled with air into 46% when filled with He–Xe gas mixture at high Ra=106.
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Ramesham, R., T. Roppel, C. Ellis, D. A. Jaworske, and W. Baugh. "Selective and low temperature synthesis of polycrystalline diamond." Journal of Materials Research 6, no. 6 (June 1991): 1278–86. http://dx.doi.org/10.1557/jmr.1991.1278.
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Polycrystalline diamond thin films have been deposited on single crystal silicon substrates at low temperatures (⋚ 600 °C) using a mixture of hydrogen and methane gases by high pressure microwave plasma-assisted chemical vapor deposition. Low temperature deposition has been achieved by cooling the substrate holder with nitrogen gas. For deposition at reduced substrate temperature, it has been found that nucleation of diamond will not occur unless the methane/hydrogen ratio is increased significantly from its value at higher substrate temperature. Selective deposition of polycrystalline diamond thin films has been achieved at 600 °C. Decrease in the diamond particle size and growth rate and an increase in surface smoothness have been observed with decreasing substrate temperature during the growth of thin films. As-deposited films are identified by Raman spectroscopy, and the morphology is analyzed by scanning electron microscopy.
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Kus, J., B. Cramer, and F. Kockel. "Effects of a Cretaceous structural inversion and a postulated high heat flow event on petroleum system of the western Lower Saxony Basin and the charge history of the Apeldorn gas field." Netherlands Journal of Geosciences - Geologie en Mijnbouw 84, no. 1 (April 2005): 3–24. http://dx.doi.org/10.1017/s0016774600022873.
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AbstractThermal history and evolution of the Palaeozoic petroleum system of the western Lower Saxony Basin as well as charge history of the Apeldorn gas field was reconstructed using 2-D forward basin modelling software. The Apeldorn gas field is located on an inverted western rim of the Lower Saxony Basin (LSB) and belongs with its relatively anomalous nitrogen content of 73.9 vol. % to one of the most unique gas accumulations in North Germany. Based on thermal calibration studies utilising both, vitrinite reflectance and corrected bottom hole temperatures as calibration parameters, a shallow burial model and an anomalous event of Coniacian high heat flow of 80 to 120 mW/m2was derived. As result, Lower Triassic and younger successions became subjected to slight changes in thermal maturity as opposed to Carboniferous and Permian successions, which show no assessable impact of the high heat flow event on the coalification pattern. The deep burial model in contrary to the shallow burial model is not supported by the structural reconstruction and backstripping in this more marginal setting. According to the modelling results, the key charge of the present Apeldorn gas field began in Tithonian (late Upper Jurassic) during the major phase of rifting in the Lower Saxony Basin. The present Westphalian coal-derived gas accumulations of the Lower Triassic Buntsandstein reservoir were sourced directly from modelled methane pools at top Rotliegend level. The hydrocarbon potential of the Westphalian source rocks became exhausted in Oxfordian (early Upper Jurassic). Reduction of the hydrostatic pressure during the Coniacian high heat flow event together with uplift during the Coniacian-Santonian inversion led to an extensive free gas exsolution. The resulting gas mixture between the exsolved free gas and the Westphalian coal-derived gas reached and saturated Buntsandstein reservoir. The structural trap became destroyed in course of the inversion leading to a sharp decrease of methane and nitrogen saturation.
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Mohd Saleh, Siti Shuhadah, Hazizan Md Akil, Ramdziah Md. Nasir, Muhammad Razlan Zakaria, and Muhammad Helmi Abdul Kudus. "Effect of Catalyst Calcination Temperature on the Synthesis of MWCNTs-Talc Hybrid Compound Using CVD Method." Key Engineering Materials 594-595 (December 2013): 63–67. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.63.
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Carbon nanotubes-talc (CNTs-talc) hybrid compound has been successfully synthesized via chemical vapour deposition (CVD) method. A gas mixture of methane/nitrogen (CH4/N2) was used as the carbon source and nickel as the metal catalyst for the growth of CNT hybrid compound. Talc works as substrate or support material which is combined with nickel to form a complex metal-talc catalyst that will react with carbon source to produce the hybrid compound. To study the effect of different calcinations temperature, four different calcinations temperature, 300 °C (C-talc300), 500 °C (C-talc500), 700 °C (C-talc700) and 900 °C (C-talc900) were used. Among these four calcination temperatures for synthesis the multi-walled carbon nanotubes (MWCNTs), C-talc500 is the most optimum calcination temperature to perform catalytic decomposition by reacting in methane atmosphere at 800 °C to produce the CNT-talc hybrid compound.
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Komarov, I. I., D. M. Kharlamova, A. N. Vegera, and V. Y. Naumov. "Study on effect CO2 diluent on fuel cоmbustion in methane-oxygen combustion chambers." Vestnik IGEU, no. 2 (April 30, 2021): 14–22. http://dx.doi.org/10.17588/2072-2672.2021.2.014-022.
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Studying closed gas turbine cycles on supercritical carbon dioxide is currently a promising issue in the development of power energy sector in terms of increasing energy efficiency and minimizing greenhouse gas emissions into the atmosphere. Combustion of methane with oxygen in the combustion chamber occurs not in the nitrogen environment, but in the environment of carbon dioxide, that is the working fluid of the cycle, which is an inhibitor of chemical reactions. A large mass content of such a diluent of the reaction mixture in the volume of the chamber leads to the risks of significant chemical underburning, efficiency decrease of the combustion chamber and the cycle as a whole. The aim of the research is to study the kinetic parameters of the combustion of methane with oxygen in a supercritical CO2 diluent medium to ensure reliable and stable combustion of fuel by assessing the degree of the inhibitory effect of CO2 and determining its permissible amount in the active combustion zone of the combustion chamber. The research method is a numerical simulation of turbulent-kinetic processes of methane combustion in the combustion chamber using the reduced methane combustion mechanism. Ansys Fluent software package has been used. The authers have studied the impact of CO2 diluent on fuel cоmbustion in methane-oxygen combustion chambers. It is found that the combustor flame stabilization takes place if the content of СО2 diluent supplied to the mixture with oxidizer is 0,46–0,5 of mass fraction; additional СО2 diluent forms local low temperature zones which slow down the combustion process. When this happens, adding cooling СО2 into the flame stabilization zone should be eliminated. The study has found that no more than 20 % of the total carbon dioxide content should be supplied to the combustion chamber; to stabilize the flame and reduce its length, it is necessary to install blades to swirl the fuel and oxidizer mixed with CO2 at the inlet of the combustion chamber; CO2 supply for cooling should be carried out not less than 130 mm away from the burner mouth.
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Jaworski, Jacek, and Adrian Dudek. "Study of the Effects of Changes in Gas Composition as Well as Ambient and Gas Temperature on Errors of Indications of Thermal Gas Meters." Energies 13, no. 20 (October 17, 2020): 5428. http://dx.doi.org/10.3390/en13205428.
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Thermal gas meters represent a promising technology for billing customers for gaseous fuels, however, it is essential to ensure that measurement accuracy is maintained in the long term and in a broad range of operating conditions. The effect of hydrogen addition to natural gas will change the physicochemical properties of the mixture of natural gas and hydrogen. Such a mixture will be supplied through the gas system, to consumers, including households, where the amounts of received gas will be metered. The physicochemical properties of hydrogen, including the specific density or viscosity, differ significantly from those of the natural gas components, such as methane, ethane, propane, nitrogen, etc. Therefore, it is of utmost importance to establish the impact of the changes in the gas composition caused by the addition of hydrogen to natural gas on the metrological properties of household gas meters, including thermal gas meters. Furthermore, since household gas meters can be installed outdoors and, taking into account the fact that household gas meters are good heat exchangers, the influence of ambient and gas temperature on the metrological properties of those meters should be investigated. This article reviews a test bench and a testing method concerning errors of thermal gas meter indicators using air and natural gas, including the type containing hydrogen. The indication errors for thermal gas meters using air, natural gas and natural gas with an addition of 2%, 4%, 5%, 10% and 15% hydrogen were determined and then subjected to metrological analysis. Moreover, the test method and test bench are discussed and the results of tests on the impact of ambient and gas temperatures (‒25 °C and 55 °C, respectively) on the errors of indications of thermal gas meters are presented. Conclusions for distribution system operators in terms of gas meter selection were drawn based on the test results.
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CHEN, YAN, E. G. WANG, FENG CHEN, and LIPING GUO. "SYNTHESIS OF HIGH QUALITY CRYSTALLINE C-N FILMS ON SILICON." Modern Physics Letters B 10, no. 12 (May 20, 1996): 567–71. http://dx.doi.org/10.1142/s0217984996000626.
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High quality crystalline C–N films have been synthesized via hot filament chemical vapor deposition using a gas mixture of nitrogen and methane. Scanning electron microscopy images show that a high density of crystalline clusters has been achieved. The clusters are composed of small columnar crystals (20–200 nm across) with hexagonal facets. Energy dispersive X ray analysis indicates a relative nitrogen:carbon composition of 1.30–2.5. X ray diffraction results indicate the films composed of β- and α- C 3 N 4 phases. Together with transmission electron microscopy analyses, we suggest that an interfacial layer C 3−x Si x N 4 is formed between the silicon substrate and the crystalline carbonnitride films.
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Barki, Hadjer, Latifa Khaouane, and Salah Hanini. "Modelling of Adsorption of Methane, Nitrogen, Carbon Dioxide, Their Binary Mixtures, and Their Ternary Mixture on Activated Carbons Using Artificial Neural Network." Kemija u industriji 68, no. 7-8 (2019): 289–302. http://dx.doi.org/10.15255/kui.2019.002.
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This work examines the use of neural networks in modelling the adsorption process of gas mixtures (CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>) on different activated carbons. Seven feed-forward neural network models, characterized by different structures, were constructed with the aim of predicting the adsorption of gas mixtures. A set of 417, 625, 143, 87, 64, 64, and 40 data points for NN1 to NN7, respectively, were used to test the neural networks. Of the total data, 60 %, 20 %, and 20 % were used, respectively, for training, validation, and testing of the seven models. Results show a good fit between the predicted and experimental values for each model; good correlations were found (<i>R</i> = 0.99656 for NN1, <i>R</i> = 0.99284 for NN2, <i>R</i> = 0.99388 for NN3, <i>R</i> = 0.99639 for <i>Q</i><sub>1</sub> for NN4, <i>R</i> = 0.99472 for <i>Q</i><sub>2</sub> for NN4, R = 0.99716 for <i>Q</i><sub>1</sub> for NN5, <i>R</i> = 0.99752 for <i>Q</i><sub>3</sub> for NN5, <i>R</i> = 0.99746 for <i>Q</i><sub>2</sub> for NN6, <i>R</i> = 0.99783 for <i>Q</i><sub>3</sub> for NN6, <i>R</i> = 0.9946 for <i>Q</i><sub>1</sub> for NN7, <i>R</i> = 0.99089 for <i>Q</i><sub>2</sub> for NN7, and <i>R</i> = 0.9947 for <i>Q</i><sub>3</sub> for NN7). Moreover, the comparison between the predicted results and the classical models (Gibbs model, Generalized dual-site Langmuir model, and Ideal Adsorption Solution Theory) shows that the neural network models gave far better results.
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Kennelly, C., E. Clifford, S. Gerrity, R. Walsh, M. Rodgers, and G. Collins. "A horizontal flow biofilm reactor (HFBR) technology for the removal of methane and hydrogen sulphide at low temperatures." Water Science and Technology 66, no. 9 (November 1, 2012): 1997–2006. http://dx.doi.org/10.2166/wst.2012.411.
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A novel horizontal flow biofilm reactor (HFBR) has been adapted and tested for its efficiency in treating hydrogen sulphide (H2S) and methane (CH4) gas. Six pilot-scale HFBR reactors were commissioned, three each treating CH4 and H2S respectively. The reactors were operated at 10 °C, often typical of ambient temperatures in Ireland, and were simultaneously dosed with an air mixture containing the gas in question and with synthetic wastewater (SWW). Three reactors (HFBR 1, 2 and 3), treating an air mixture containing CH4, were operated over three phases (Phases 1–3) lasting 180 days in total. During each phase the air mixture flow rate (AFR) and the plastic media top plan surface area (TPSA) loading rate to HFBR 1, 2 and 3 were 1.2 m3/m3/h and 0.6 m3/m2 TPSA/h respectively. In Phase 1 the reactors were operated in triplicate and were loaded with 8.6 g CH4/m3 reactor/h (4.3 g CH4/m2 TPSA/h) and a synthetic wastewater (SWW) similar to domestic sewage at 10 °C. During Phase 2 (reactors also operated in triplicate) the effect of temperature on the reactor performance was examined. During Phase 3 the reactors were operated independently in order to examine the effects of omitting organic carbon and adding additional nitrogen in the form of nitrate-nitrogen (NO3-N), rather than ammonium-nitrogen (NH4-N). During Phase 3, CH4 removal efficiencies (RE) of up to 92.8% were achieved at an empty bed retention time (EBRT) of 50 min, equating to a maximum removal of 8.0 g CH4/m3 reactor/h. Three additional reactors (HFBR 4, 5 and 6) were used to treat an air mixture containing H2S and were loaded at an AFR of 15 m3/m3 reactor/h (7.5 m3/m2 TPSA/h) with an average H2S loading rate of 3.34 g H2S/m3 reactor/h (1.67 g H2S/m2 TPSA/h). After 50 days of operation, the RE reached 100% for all three reactors at an EBRT of 4 min. In each reactor, profile samples of biofilm, air and liquid were taken periodically from various regions of the HFBR. These allowed detailed description of removal processes and optimisation of the reactors by detailing changes in air, liquid and biofilm composition as air moved through the reactor.
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Nampoothiri, Vinu M., Madhu Mohini, Bilal Ahmad Malla, Goutam Mondal, and Sujata Pandita. "Animal performance, and enteric methane, manure methane and nitrous oxide emissions from Murrah buffalo calves fed diets with different forage-to-concentrate ratios." Animal Production Science 60, no. 6 (2020): 780. http://dx.doi.org/10.1071/an17727.
Full textAbstract:
The present study aimed to evaluate the effects of dietary forage:concentrate ratios on growth performance and enteric and faecal greenhouse-gas emissions from growing buffalo calves. Fifteen Murrah male calves (bodyweight = 233.35 ± 30.92 kg; 8–12 months age) were randomly assigned to three dietary groups that were fed a mixture of berseem fodder, wheat straw and concentrate at the ratios of 20:60:20 (C20), 20:40:40 (C40) and 20:20:60 (C60) respectively, for 120 days. Enteric methane (CH4) production was estimated by the sulfur hexafluoride tracer technique. Faeces were stored for 12 weeks and CH4 and nitrous oxide (N2O) fluxes from stored faeces were estimated every 14 days. Dry-matter intake, feed conversion efficiency and nitrogen retention were not affected (P > 0.05) but average daily gain and urinary nitrogen loss (g/day) were higher for C60 than the C20 diet (P < 0.05). Daily enteric CH4 emission (g/day) was not affected but CH4 yield (g/kg dry-matter intake) and energy loss through CH4 as a proportion of energy intake were lower for C60 than the C20 diet (P < 0.05). Faeces composition was not affected, and large variations of greenhouse-gas emissions were observed for first 10 days of storage. Methane emissions from stored faces were 1.28 ± 0.40, 1.94 ± 0.34 and 3.90 ± 0.27 mg/kg faeces per day for C20, C40 and C60 diets respectively, being higher for C60 than the C40 and C20 diets (P < 0.05). Methane-flux rate from faeces was greater for C60 than the C20 and C40 diets (0.75 vs 0.26 and 0.37 g/animal respectively; P < 0.05). Diet C60 increased N2O fluxes from stored faeces by 63% and 58% respectively, expressed in mg/kg faeces per day and mg/animal per day, compared with C20 diet (P < 0.05). Overall, dietary concentrate proportion of up to 60% in growing buffalo calf diets improved growth performance without increasing enteric CH4 emission, but CH4 and N2O production from faeces were increased. This work has provided information for gas emissions factors from open storage of faeces. More detailed studies on gaseous emissions from open lots on farms are required.
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Norizan, Ali, Yoshimitsu Uemura, N. Omar Wissam, and Toshio Tsutsui. "Bio-Oil Derived from Palm Kernel Shell in Fluidized Bed Reactor: Effect of Particle Size." Advanced Materials Research 917 (June 2014): 63–71. http://dx.doi.org/10.4028/www.scientific.net/amr.917.63.
Full textAbstract:
Bio-oil production from pyrolysis of 0.15-0.5 mm and 1-2 mm palm kernel shell (PKS) has been investigated in a fluidized bed reactor under the nitrogen gas flow rate of 25 L(NTP)/min, with reactor temperature of 450°C. The pyrolysis unit has six successive condensers. Thus, six fractions of bio-oil samples were acquired from the six condensers. The calorific value, water content, ash content, and element content of each bio-oil samples were determined. The bio-oil yield from palm kernel shell with the size of 0.15-0.5 mm and 1-2 mm were 20 % and 26 %, respectively. The highest calorific value among the six bio-oil samples was 25.1 MJ/kg which was drawn from the forth condenser from pyrolysis of 0.15-0.5 mm of palm kernel shell. The incondensable gas was a mixture of hydrogen, methane, carbon dioxide and ethane.
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Soroka, B. S. "WET BURNING – THE MODERN TREND IN ENVIRONMENTAL BENIGN FUEL COMBUSTION AND IN SOLUTION TO THE PROBLEM OF SUSTAINABLE DEVELOPMENT OF THE POWER GENERATION." Alternative Energy and Ecology (ISJAEE), no. 25-30 (December 7, 2018): 96–117. http://dx.doi.org/10.15518/isjaee.2018.25-30.096-117.
Full textAbstract:
The article considers the role and place of water and water vapor in combustion processes with the purpose of reduction the effluents of nitrogen oxides and carbon oxide. We have carried out the complex of theoretical and computational researches on reduction of harmful nitrogen and carbon oxides by gas fuel combustion in dependence on humidity of atmospheric air by two approaches: CFD modeling with attraction of DRM 19 chemical kinetics mechanism of combustion for 19 components along with Bowman’s mechanism used as “postprocessor” to determine the [NO] concentration; different thermodynamic models of predicting the nitrogen oxides NO formation. The numerical simulation of the transport processes for momentum, mass and heat being solved simultaneously in the united equations’ system with the chemical kinetics equations in frame of GRI methane combustion mechanism and NO formation calculated afterwards as “postprocessor” allow calculating the absolute actual [CO] and [NO] concentrations in dependence on combustion operative conditions and on design of furnace facilities. Prediction in frame of thermodynamic equilibrium state for combustion products ensures only evaluation of the relative value of [NO] concentration by wet combustion the gas with humid air regarding that in case of dry air – oxidant. We have developed the methodology and have revealed the results of numerical simulation of impact of the relative humidity of atmospheric air on harmful gases formation. Range of relative air humidity under calculations of atmospheric air under impact on [NO] and [CO] concentrations at the furnace chamber exit makes φ = 0 – 100%. The results of CFD modeling have been verified both by author’s experimental data and due comparing with the trends stated in world literature. We have carried out the complex of the experimental investigations regarding atmospheric air humidification impact on flame structure and environmental characteristics at natural gas combustion with premixed flame formation in open air. The article also proposes the methodology for evaluation of the nitrogen oxides formation in dependence on moisture content of burning mixture. The results of measurements have been used for verification the calculation data. Coincidence of relative change the NO (NOx) yield due humidification the combustion air revealed by means of CFD prediction has confirmed the qualitative and the quantitative correspondence of physical and chemical kinetics mechanisms and the CFD modeling procedures with the processes to be studied. A sharp, more than an order of reduction in NO emissions and simultaneously approximately a two-fold decrease in the CO concentration during combustion of the methane-air mixture under conditions of humidification of the combustion air to a saturation state at a temperature of 325 K.
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Ahmed, Rand R. "Produced The Compost by Recycling The Municipality Waste." Association of Arab Universities Journal of Engineering Sciences 27, no. 1 (March 31, 2020): 140–47. http://dx.doi.org/10.33261/jaaru.2019.27.1.015.
Full textAbstract:
Around 5000 tons of food waste are prooduced every day in Iraq, accounts for about (50%) of the waste that we get rid of .Waste sent to landfill for disposal may breakdown and produce methane gas that causes greenhouse effect ,as well as odour , epidemics , and disease because of the disintegration. The aims of the research are to produce organic fertilizer through the recycling of domestic refuse. It has been working through this research to collect the domestic food waste which represent the nitrogen source, as well as the remains of cleaning and trimming of various trees and the remains of lawn mowers, and use of sawdust white wood which represent the carbon source. Working on dried and arranged in layers of perforated plastic containers for the purpose of ventilation, it was moisturized with two different types of water and monitored fertilizer maturity for four months. Previously the fresh water was used for the purpose for moisturizing the mixture (tap water) later the domestic wastewater have been used. The comparison was made between the results of tests performed; the test has come up with the resalt that the use of "domestic wastewater" rich in living organisms and bacteria to hydrate the mixture is better than the use of "tap water". The felicitous fertilizer is rich with nutrient nitrogen 2.3%, phosphorus 13% and potassium 20% etc. There are a number of important factors affecting the process of production of fertilizer, including air ventilation, temperature, and moisture content in the mixture, which ranges from 40-60% to provide a suitable medium for microorganisms within the mixture. Where less than 40% lead to dry mixture and kill organisms.