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Dzurňák, Róbert, Augustín Varga, Ján Kizek, Gustáv Jablonský i Ladislav Lukáč. "Influence of Burner Nozzle Parameters Analysis on the Aluminium Melting Process". Applied Sciences 9, nr 8 (18.04.2019): 1614. http://dx.doi.org/10.3390/app9081614.
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The paper presents the results of the optimisation of burner nozzle diameters during the combustion of natural gas under the conditions of increasing oxygen concentrations in the oxidizer in aluminium melting processes in drum rotary furnaces. The optimisation of outlet nozzle diameters was performed employing the method of experimental measurements, the results of which can be used for aluminium melting in hearth furnaces. The measurements were carried out using an experimental upstream burner with 13.5 kW input power. The monitored oxygen concentrations in the oxidizer ranged from 21% to 50%. The measurements were performed and evaluated in two variations of the burner configuration (geometry). In the first study, the impact of the enriched oxidizer on the melting of aluminium ingots was evaluated with the defined diameter of the air nozzle, which resulted in a reduction of the aluminium charge melting time by 50% at 45.16% oxygen concentration in the oxidizer, thus achieving savings in the consumption of fuel used for melting. In the second study, the diameter was optimised depending on the combustion rate of the natural gas and oxidizer mixture. The optimisation of the nozzle parameters resulted in the reduction of the charge melting time by 23.66%, while the same 25% enriched oxidizer was used. With the rise of the enrichment level to 35%, further reduction by approximately 12% was observed. The measurement results prove considerable influence of the parameter (geometry) optimisation of the outlet nozzles and oxidizer enrichment. Appropriately selected parameters of the burner can contribute to achieving comparable results at a lower enrichment of the oxidizer. The obtained results demonstrate the intensification of the heat transfer in the current thermal aggregates. The research conclusions confirm that oxygen-enhanced combustion and modification of existing burners reduces the specific energy consumption on the process and reduces CO2 emissions.
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Soroka, B. S., i V. V. Horupa. "ANALYSIS OF THE PROCESS OF WATER VAPOR CONDENSATION WITHIN GAS ATMOSPHERES AND COMBUSTION PRODUCTS". Energy Technologies & Resource Saving, nr 1 (20.03.2017): 3–18. http://dx.doi.org/10.33070/etars.1.2017.01.
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Water vapor is the most important working medium by the processes of energy generation and conversion. The H2O content in gases and gas mixtures serves as a standard of their desiccation by technological processes. The presence of vapor in the air-oxidizer provides a reduction of harmful substances formation by combustion. The values characterizing the saturation state: the dew point tdew and the wet bulb thermometer twb temperature are used to evaluate an approximation degree of the wet gas system (any air, gas mixtures or combustion products) to the condensation state. The values of these parameters have been determined for moist air in dependence on the basic temperature and the relative humidity of an air. The lower are the temperature values tdew, twb, the wider is the region of H2O existence in the vapor phase. The EUROSTAT’s gas fuels list includes the natural gas (NG), blast furnace gas (BFG), coke oven gas (COG). Calculations of dew point values of the combustion products for the gas fuels: NG, COG, BFG has been carried out in dependence on the characteristics of the combustion air: the oxidizer excess factor l, the temperature ta and the relative humidity ja. The dew point tdew values have been found under standard conditions for the combustion products of the listed gas fuels, presented by stoichiometric (l = 1.0) mixtures with dry air: pure methane, NG, COG, BFG. The tdew values make — respectively 59.3; 58.5; 11.1; 61.5. In the case of saturated air as an oxidizer at temperature of 25 °C, the dew point for the combustion products of the listed fuels makes the folloving values: 62.0; 61.5; 25.6; 64.0 °C respectively. The fractions of H2O in the vapor and liquid phases of natural gas combustion products are determined as a function of temperature by condition that the 100 % content of H2O in from of vapor state (without water) corresponds to the saturation temperature (or dew point).This temperature has value of about 60°C for combustion products under stoichiometric air/gas ratio. Bibl. 31, Fig. 10, Tab. 3.
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Ермолаев, Денис Васильевич, i Айрат Заудатович Даминов. "INFLUENCE OF THE OXIDIZER ON THE FORMATION AND PURIFICATION EFFICIENCY OF ACID GASES PRODUCED DURING ASPHALTENE GASIFICATION". Bulletin of the Tomsk Polytechnic University Geo Assets Engineering 333, nr 4 (20.04.2022): 215–23. http://dx.doi.org/10.18799/24131830/2022/4/3474.
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Link for citation: Ermolaev D.V., Daminov A.Z. Influence of the oxidizer on the formation and purification efficiency of acid gases produced during asphaltene gasification. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 4, рр. 215-223. In Rus.
The relevance of the study is determined by the need to understand the influence of the oxidizer on the formation of acid gases (CO2, H2S, COS and CS2) during thermal decomposition of high-viscosity hydrocarbons. This is important for predicting the purification efficiency of the produced gasification products and estimating the economic costs. The aim: using the simulation to study the effect of an oxidizer in the form of steam on the composition and properties of asphaltene gasification products obtained from natural bitumen, as well as to determine the cleaning efficiency depending on the amount of steam and the absorbent based on NaOH water-alkaline solution. Object: asphaltene of natural bitumen of Ashalchinskoe field of the Tatarstan Republic (Russia), oxidizer in the form of steam, the value of which varied from 0,1 to 1 depending on the amount of asphaltene. Methods: simulation of asphaltene gasification and acid gas absorption taking into account influence of an oxidizer in a form of steam with regard for basic chemical kinetics, ultimate analysis and TGA. Simulation results of gasification and absorption showed that steam used as an oxidizer during asphaltene gasification has a significant influence on the composition and properties of gasification products, as well as on the purification of syngas. With the increase of steam, a parabolic dependence of the concentrations of syngas components is observed, which values decrease with time, except for CO2. The calorific value of syngas decreases from 11,3 to 7,2 MJ/m3 and the cold gas efficiency increases from 53,4 to 62,5 % due to growth of syngas yield. As the amount of steam increases, the amount of absorbent decreases and the purification efficiency of acid gases rises. Thus, the amount of absorbed CO2 increases by 20,7 % while the absorbent decreases by 6,7%. At the same time the amount of absorbed H2S increased by 0,39 % with decrease of NaOH by 40,9 %.
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Landfahrer, M., C. Schluckner, H. Gerhardter, T. Zmek, J. Klarner i C. Hochenauer. "Numerical model incorporating different oxidizer in a reheating furnace fired with natural gas". Fuel 268 (maj 2020): 117185. http://dx.doi.org/10.1016/j.fuel.2020.117185.
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Sigal, Aleksandr, i Dmitri Paderno. "EFFECT OF MOISTURE ON NITROGEN DIOXIDE FORMATION IN LAMINAR FLAME OF NATURAL GAS". Journal of Environmental Engineering and Landscape Management 29, nr 3 (15.09.2021): 287–97. http://dx.doi.org/10.3846/jeelm.2021.15492.
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The paper contains the results of experimental studies of the effect of moisture on nitrogen dioxide formation and on oxidation of NO to NO2 in laminar premixed flame of natural gas. The water vapor is shown to be the third very influential participant, along with fuel and oxidizer, in the combustion process. Injection of moisture into the combustion zone has an effect due to the insertion of additional quantities of HO2- and OH– radicals into the process, which contributes to the intensification of the oxidation of NO to NO2. Introduction of the concept of the “excess moisture ratio” in the combustion process is proposed. The studies were executed at the laboratory installation in conditions of formation of the V-shaped laminar flame of natural gas behind a transverse cylindrical steel stabilizer, with determining the concentrations of flue gas components.
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Soroka, B. S., i N. V. Vorobyov. "Efficiency of the Use of Humidified Gas Fuel and Oxidizing Mixture". ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 62, nr 6 (29.11.2019): 547–64. http://dx.doi.org/10.21122/1029-7448-2019-62-6-547-564.
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The influence of hydration of the components of combustion (air-oxidizer and – in some cases – fuel) including hydration in the conditions of substitution of natural gas by alternative gas fuels, viz. by coke blast furnace mixture and natural blast furnace mixture – on energy efficiency of the use of different fuels has been determined. Calculations of fuel saving for substitution of natural gas (NG) by wet process gas (blast furnace gas (BFG), coke gas (CG), their mixtures) were performed taking into account real technological parameters (on the example of a specific metallurgical plant). All the calculations were performed within the framework of the author’s methodology on fuel substitution grounded on the 1st and the 2nd laws of thermodynamics. The analysis of possibility for saving or overspending NG is performed in the conditions of preservation of the flow of the used total enthalpy (as the main requirement of the methodology that had been proposed) and of taking into account the corresponding efficiency of fuel use. The calculation of the required heat flow of natural gas combustion depending on the content of wet blast furnace gas in NG + BFG mixtures for the cases of NG substitution by process gases has been carried out. It is established that the presence of moisture in the fuel-oxidation mixture always reduces the efficiency of the combustion chamber or the energy process and the unit. In order to increase the efficiency of a high-temperature furnace (boiler), it is necessary to provide heating of combustion components when utilizing the heat of the outgoing combustion products. It is shown that the efficiency of the fuel-using system can be significantly increased when the potential (excess total enthalpy) of the working fluid (combustion products) is activated. There are additiоnal benefits due to the fact that the existing heat of products of combustion with humid air in a full range of temperatures – from the theoretical combustion temperature to ambient temperature under conditions of equilibrium, including account of the heat of condensation – increases with increasing moisture content of the initial components of combustion, viz. air-oxidizer and/or fuel gas.
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Ahn, Joon, i Hyouck-Ju Kim. "Combustion Characteristics of 0.5 MW Class Oxy-Fuel FGR (Flue Gas Recirculation) Boiler for CO2 Capture". Energies 14, nr 14 (18.07.2021): 4333. http://dx.doi.org/10.3390/en14144333.
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A 0.5 MW class oxy-fuel boiler was developed to capture CO2 from exhaust gas. We adopted natural gas as the fuel for industrial boilers and identified characteristics different from those of pulverized coal, which has been studied for power plants. We also examined oxy-fuel combustion without flue gas recirculation (FGR), which is not commonly adopted in power plant boilers. Oxy-fuel combustion involves a stretched flame that uniformly heats the combustion chamber. In oxy-natural-gas FGR combustion, water vapor was included in the recirculated gas and the flame was stabilized when the oxygen concentration of the oxidizer was 32% or more. While flame delay was observed at a partial load for oxy-natural-gas FGR combustion, it was not observed for other combustion modes. In oxy-fuel combustion, the flow rate and flame fullness decrease but, except for the upstream region, the temperature near the wall is distributed not lower than that for air combustion because of the effect of gas radiation. For this combustion, while the heat flux is lower than other modes in the upstream region, it is more than 60% larger in the downstream region. When oxy-fuel and FGR combustion were employed in industrial boilers, more than 90% of CO2 was obtained, enabling capture, sequestration, and boiler performance while satisfying exhaust gas regulations.
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Serbin, Serhiy, Kateryna Burunsuz, Daifen Chen i Jerzy Kowalski. "Investigation of the Characteristics of a Low-Emission Gas Turbine Combustion Chamber Operating on a Mixture of Natural Gas and Hydrogen". Polish Maritime Research 29, nr 2 (1.06.2022): 64–76. http://dx.doi.org/10.2478/pomr-2022-0018.
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Abstract This article is devoted to the investigation of the characteristics of a low-emission gas turbine combustion chamber, which can be used in Floating Production, Storage and Offloading (FPSO) vessels and operates on a mixture of natural gas and hydrogen. A new approach is proposed for modelling the processes of burning out a mixture of natural gas with hydrogen under preliminary mixing conditions in gaseous fuel with an oxidizer in the channels of radial-axial swirlers of flame tubes. The proposed kinetic hydrocarbon combustion scheme is used in three-dimensional calculations for a cannular combustion chamber of a 25 MW gas turbine engine for two combustion models: the Finite-Rate/Eddy-Dissipation and the Eddy Dissipation Concept. It was found that, for the investigated combustion chamber, the range of stable operations, without the formation of a flashback zone in the channels of radial-axial swirlers, is determined by the hydrogen content in the mixture, which is less than 25-30% (by volume). For the operating modes of the chamber without the formation of a flashback zone inside the swirler channels, the emissions of nitrogen oxide NO and carbon monoxide CO do not exceed the values corresponding to modern environmental requirements for emissions of toxic components by gas turbine engines.
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Director, L. B., K. A. Homkin, I. L. Maikov, Yu L. Shekhter, G. F. Sokol i V. M. Zaichenko. "Theoretical and Experimental Investigations of Substantiating Technologies for Carbon Materials Production from Natural Gas". Eurasian Chemico-Technological Journal 5, nr 1 (12.07.2017): 29. http://dx.doi.org/10.18321/ectj587.
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The results of theoretical and experimental investigations on methane pyrolysis with infiltration through a heated porous matrix generated from various carbon materials are presented. The features of mathematical<br />models, kinetic relationships of process are discussed. The mathematical model of process shares on external problem (a flow of particles in an external stream) and internal problem (reaction in particle porous). The<br />heat and mass transfer for the average (over the reactor cross section) parameters, ignoring the heat transfer in gas by thermal conductivity, is described by unsteady-state one-dimensional differential equations in<br />partial derivatives. For the mathematical description of process kinetics of methane decomposition the approach is used by which the soot formation is treated as a chain radical process. The porous media is represented by a system of large enough particles. In its turn, every macroparticle consists of finer particles, which are also composed of microparticles, etc. Calculating programs were used for modeling and efficiency analysis of technological installations for technical carbon production in a regenerative heater, filled by a ceramic nozzle and for similar purposes concerning carbon (oven soot) in autothermal torch process of partial gas oxidation by air at a surplus factor of oxidizer in relation to stoichiometry 0.4-0.5 at pressure close to atmospheric on Sosnogorsk Gas-Processing Plant. Experiment descriptions and techniques for experimental realization are given. These results are used as fundamentals for new technologies considering pyrocarbon materials production in the continuous operation reactor.
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Mathieu, P., i R. Nihart. "Zero-Emission MATIANT Cycle". Journal of Engineering for Gas Turbines and Power 121, nr 1 (1.01.1999): 116–20. http://dx.doi.org/10.1115/1.2816297.
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In this paper, a novel technology based on the zero CO2 emission MATIANT (contraction of the names of the two designers MAThieu and IANTovski) cycle is presented. This latter is basically a gas cycle and consists of a supercritical CO2 Rankine-like cycle on top of regenerative CO2 Brayton cycle. CO2 is the working fluid and O2 is the fuel oxidizer in the combustion chambers. The cycle uses the highest temperatures and pressures compatible with the most advanced materials in the steam and gas turbines. In addition, a reheat and a staged compression with intercooling are used. Therefore, the optimized cycle efficiency rises up to around 45 percent when operating on natural gas. A big asset of the system is its ability to remove the CO2 produced in the combustion process in liquid state and at high pressure, making it ready for transportation, for reuse or for final storage. The assets of the cycle are mentioned. The technical issues for the predesign of a prototype plant are reviewed.
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Makaryan, Iren A., Eugene A. Salgansky, Vladimir S. Arutyunov i Igor V. Sedov. "Non-Catalytic Partial Oxidation of Hydrocarbon Gases to Syngas and Hydrogen: A Systematic Review". Energies 16, nr 6 (22.03.2023): 2916. http://dx.doi.org/10.3390/en16062916.
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The review contains a comparative analysis of studies on the production of hydrogen and syngas based on the processes of partial oxidation of natural gas and other types of gas feedstock. The results presented in the literature show the high potential of non-catalytic autothermal processes of partial oxidation of hydrocarbons for the development of gas chemistry and energetics. The partial oxidation of hydrocarbons makes it possible to overcome such serious shortcomings of traditional syngas production technologies as technological complexity and high energy and capital intensity. The features of non-catalytic partial oxidation of hydrocarbon gases, the obtained experimental results and the results of kinetic modeling of various options for the implementation of the process, which confirm the adequacy of the kinetic mechanisms used for the analysis, are considered in detail. Examples of industrial implementation of processes based on partial oxidation and proposed alternative options for its organization are considered. Designs of reactors used to ensure stable conversion of rich mixtures of hydrocarbons with an oxidizer are presented. The possibility of obtaining other chemical products by partial oxidation of hydrocarbons is discussed.
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Vusikhis, Alexander S., Leopold I. Leontiyev, Victor P. Chentsov i Evgeny N. Selivanov. "Process modeling of the nickel and iron reduction from oxide melts by converted natural gas". Butlerov Communications 57, nr 2 (28.02.2019): 151–58. http://dx.doi.org/10.37952/roi-jbc-01/19-57-2-151.
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The converted natural gas using possibility to reduce iron and nickel from oxide melts in bubbled layer has been considered. The thermodynamic modeling technique has been applied to describe the kinetic features of the multicomponent oxide melts interaction processes with various compositions reducing gases. Various types of conversion is used to obtain it (oxygen, steam, carbon dioxide) are considered. Influence of the natural gas/oxidizer gas ratio and the temperatures at which the conversion is carried out to the converted gases compositions is estimated. It is shown that temperature increase from 1725 to 2273 K has little effect to the converted gases compositions. The hydrogen concentration in the products of oxygen conversion at CH4/O2 = 2 is 66.5%; steam (CH4/H2O = 1) is 75.0%; carbon dioxide (СН4/СО2 = 1) is 49.9% (the rest is CO), respectively. Oxidant addition leads to СО2 and water vapor appearance in the mixture. Bubbling kinetics is described by means of thermodynamic calculation. Reducing gas content and quantity (injected in oxide melt) affect to it properties is considered. The melt content changing, elements reduction degree, oxide and metal phases mass ratio, equilibrium contents of exhaust gases, etc are analyzed on this base. As was obtained, Nickel oxide residual content in the final melt have been decreasing to 0.03% and Nickel share in the ferronickel (formed in reducing process) is 70% in the case of oxidant absent. Residual NiO content in the oxide melt is higher, and degree of reduction is less in the presence of CO2 and H2O. The results obtained allow us to predict the metals reduction process parameters in the oxide systems melt babbling treatment. It has been found that the most efficient gas is steam reformed.
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DEONISE, Dumitru, Adrian IOANA, Lucian PAUNESCU, Massimo Pollifroni, Costin Alexandru DEONISE, Florin-Stefan PETCU i Ionela Luminita CANUTA. "EXPERIMENTAL RESULTS ON THE IMPLEMENTATION AND USE OF RECOVERY BURNERS". European Journal of Materials Science and Engineering 7, nr 4 (20.12.2022): 284–87. http://dx.doi.org/10.36868/ejmse.2022.07.04.284.
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The article presents the main aspects of the implementation, use and pilot and industrial experiments of some self-contained recovery burners. The results of pilot and industrial experiments of these burners have argued and quantified their energy efficiency. This efficiency consists mainly in an economy of specific fuel consumption (natural gas and / or coke gas) of approx. 25-35%. Other advantages of using recuperative burners are: ensuring a higher temperature in the hearth, reducing the duration of the processing cycle and thus increasing labor productivity. All these advantages of using recuperative burners are based on their operating principle, which consists in preheating the oxidizer (combustion air) by recovering an important part of the enthalpy of its own flue gases. This recovery is done in an energy recuperator designed right in the body of the recuperative burner. Due to this important aspect, the recovery burner is part of the Primary Energy Recovery (REP) category.
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Skryja, Pavel, Igor Hudak, Jiří Bojanovsky, Zdeněk Jegla i Lubomír Korček. "Effects of Oxygen-Enhanced Combustion Methods on Combustion Characteristics of Non-Premixed Swirling Flames". Energies 15, nr 6 (21.03.2022): 2292. http://dx.doi.org/10.3390/en15062292.
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The objective of the present study was to experimentally investigate and compare the characteristics of three oxygen-enhanced combustion (OEC) methods; premix enrichment (PE), air-oxy/fuel combustion (AO), and additionally also oxygen lancing (OL) method. The overall oxygen concentration varied from 21% to 38%. Combustion tests were carried out using the gas burner with the thermal input of 750 kW fired by natural gas. The characteristics of OEC methods, such as the concentration of nitrogen oxides and carbon monoxide in flue gas, in-flame temperatures distribution in the horizontal symmetry plane of the combustion chamber, heat flux to the combustion chamber wall, flue gas temperature, and the stability of flame were investigated. NOx emissions increased by more than 40 times and by 20 times for the PE method. The tests using the AO and OL methods with NOx emissions below 150 mg/Nm3 at all oxygen concentrations showed significantly better results. For all OEC methods, radiative heat transfer increased with increasing oxygen concentration. The available heat was 20% higher at 38% O2 than at 21% O2. The flue gas temperature decreased with increasing oxygen concentration, which was affected by a decrease in N2 concentration in the oxidizer and a simultaneous increase in radiant heat flux.
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Schmitz, Nico, Lukas Sankowski, Elsa Busson, Thomas Echterhof i Herbert Pfeifer. "NOx Emission Limits in a Fuel-Flexible and Defossilized Industry—Quo Vadis?" Energies 16, nr 15 (27.07.2023): 5663. http://dx.doi.org/10.3390/en16155663.
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The reduction of CO2 emissions in hard-to-abate industries is described in several proposals on the European and National levels. In order to meet the defined goals, the utilization of sustainable, non-fossil fuels for process heat generation in industrial furnaces needs to be intensified. The focus mainly lies on hydrogen (H2) and its derivates. Furthermore, biofuels, e.g., dimethyl ether (DME), are considered. Besides possible changes in the process itself when substituting natural gas (NG) with alternative fuels, the emission of nitrogen oxides (NOx) is a major topic of interest. In current European standards and regulations, the NOx emissions are specified in mg per m3 of dry off-gas and refer to a reference oxygen concentration. Within this study, this limit specification is investigated for its suitability for the use of various fuel-oxidizer combinations in industrial combustion applications. Natural gas is used as a reference, while hydrogen and DME are considered sustainable alternatives. Air and pure oxygen (O2) are considered oxidizers. It is shown that the current specification, which is built on the use of fossil fuels, leads to non-comparable values for alternative fuels. Therefore, alternative NOx limit definitions are discussed in detail. The most suitable alternative was found to be mg per kWh. This limit specification is finally being investigated for its compliance with current regulations on various aspects of Continuous Emission Monitoring Systems.
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Mizher, Usama J., i Peter A. Velmisov. "Mathematical modeling of a swirling jet in applications to low-emission combustion of low-grade fuels". Zhurnal Srednevolzhskogo Matematicheskogo Obshchestva 23, nr 3 (30.09.2021): 308–17. http://dx.doi.org/10.15507/2079-6900.23.202103.308-317.
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Abstract. The search for new solutions in the field of energy, preventing negative impact on the environment, is one of the priority tasks for modern society. Natural gas occupies a stable position in the demand of the UES of Russia for fossil fuel. Biogas is a possible alternative fuel from organic waste. Biogas has an increased content of carbon dioxide, which affects the speed of flame propagation, and a lower content of methane, which reduces its heat of combustion. However, the combined combustion of natural gas and biogas, provided that the mixture of fuel and oxidizer is well mixed, can, on the one hand, reduce the maximum adiabatic temperature in the combustion chamber of power boilers at TPPs, and, on the other, increase the stability of biogas combustion. For the combined combustion of natural gas and biogas in operating power boilers, it is necessary to reconstruct the existing burners. For a high-quality reconstruction of burners capable of providing stable and low-toxic combustion of fuel, it is important to have theoretical data on the combustion effect of combustion of combinations of organic fuels on the temperature distribution in the combustion zone and on its maximum value. In this paper, self-similar solutions of the energy equation for axisymmetric motion of a liquid (gas) in a model of a viscous incompressible medium are obtained. Basing on them, a stationary temperature field in swirling jets is constructed. A set of programs based on the ANSYS Fluent software solver has been developed for modeling and researching of thermal and gas-dynamic processes in the combustion chamber. On the basis of the k - ϵ (realizable) turbulence model, the combustion process of a swirling fuel-air mixture is simulated. The results of an analytical and numerical study of the temperature and carbon dioxide distribution in the jet are presented.
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Shilova, Alyona, Nikolay Bachev i Roman Bulbovich. "COMPUTATIONAL AND EXPERIMENTAL STUDIES OF THE AREA OF SUSTAINABLE COMBUSTION OF NATURAL GAS WITH AIR". Perm National Research Polytechnic University Aerospace Engineering Bulletin, nr 66 (2021): 47–55. http://dx.doi.org/10.15593/2224-9982/2021.66.05.
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One of the rational ways of creating low-emission combustion chambers is the organization of low-temperature lean combustion with external heating of the components before they are fed into the combustion chamber. When organizing lowtemperature lean combustion with large excess air ratios, problems may arise with ensuring a stable position of the flame front. Combustion stability to a large extent depends on the ratio of the average flow rate and the rate of turbulent combustion. The rate of turbulent combustion depends on the composition, pressure and temperature of the components supply and the degree of turbulence in the combustion chamber. The average flow rate depends on the excess air ratio (oxidizer and fuel consumption) and the geometric dimensions of the chamber. Earlier it was shown that when developing a low-emission combustion chamber with low-temperature lean combustion, it is advantageous to use the relative flow rate as a generalized characteristic of the intra-chamber process, which takes into account the consumption, geometric and thermodynamic parameters in the combustion chamber. This work is devoted to the analysis of stable combustion of a fuel composition natural gas + air based on the experimental data available in the public domain by the authors from the University of Michigan (USA). With the help of the methods developed by the authors, the experimental data on the limiting feed rates of the components into the atmospheric burner were processed. The limiting flow rates of air and natural gas, the limiting values of the excess air ratio, the longitudinal values of the speed of the fuel-air mixture and the limiting values of the relative flow rate are obtained and analyzed. Areas of stable combustion by the listed parameters at different degrees of air swirl are graphically presented.
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Fedyukhin, Alexander V., Konstantin V. Strogonov, Olga V. Soloveva, Sergei A. Solovev, Irina G. Akhmetova, Umberto Berardi, Mark D. Zaitsev i Daniil V. Grigorev. "Aerogel Product Applications for High-Temperature Thermal Insulation". Energies 15, nr 20 (21.10.2022): 7792. http://dx.doi.org/10.3390/en15207792.
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This paper presents the results of theoretical and experimental studies to determine the optimal thickness of thermal insulation from basalt fiber and aerogel products for pipelines at temperatures of 300 and 600 °C. We carried out a comparison of the key thermophysical characteristics of the claimed heat-insulating materials. We performed a thermal imaging survey of the furnace chimney, insulated with basalt fiber and aerogel, while controlling the temperature of the flue gases by establishing the required ratio of the flow rate of natural gas and oxidizer. The temperature gradient along the thickness of the thermal insulation was obtained using a numerical tool developed in ANSYS. The results show that aerogel surpasses basalt fiber in all key thermophysical characteristics. At the same time, the only barrier to widespread industrial production and use of aerogel in the high-temperature thermal insulation segment is its market cost, which is still several times higher than that of basalt fiber in terms of an equivalent performance.
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Dzurňák, Róbert, Augustín Varga, Gustáv Jablonský, Miroslav Variny, Marcel Pástor i Ladislav Lukáč. "Analyzing the Formation of Gaseous Emissions during Aluminum Melting Process with Utilization of Oxygen-Enhanced Combustion". Metals 11, nr 2 (1.02.2021): 242. http://dx.doi.org/10.3390/met11020242.
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Oxygen-enhanced combustion (OEC) is a useful method for improving the efficiency of thermal plants and for decreasing greenhouse gas (GHG) emissions. Basic and modified burner designs utilizing OEC in the aluminum melting process in a rotary tilting furnace were studied. A combined approach comprising experimental measurement and simulation modeling was adopted aimed at assessing GHG emissions production. Reduction of up to 60% fuel consumption of the total natural gas used in the laboratory-scale furnace was achieved. The optimal oxygen concentration in the oxidizer regarding the amount of total GHG emissions produced per charge expressed as CO2 equivalent was 35% vol. Its further increase led only to marginal fuel savings, while the nitrogen oxide emissions increased rapidly. Using the modified burner along with OEC led to around 10% lower CO2 emissions and around 15% lower total GHG emissions, compared to using a standard air/fuel burner. CFD simulations revealed the reasons for these observations: improved mixing patterns and more uniform temperature field. Modified burner application, moreover, enables furnace productivity to be increased by shortening the charge melting time by up to 16%. The presented findings demonstrate the feasibility of the proposed burner modification and highlight its better energy and environmental performance indicators, while indicating the optimal oxygen enrichment level in terms of GHG emissions for the OEC technology applied to aluminum melting.
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Lahaye, Domenico, Prajakta Nakate, Kees Vuik, Franjo Juretić i Marco Talice. "Modeling Conjugate Heat Transfer in an Anode Baking Furnace Using OpenFoam". Fluids 7, nr 4 (23.03.2022): 124. http://dx.doi.org/10.3390/fluids7040124.
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The operation of large industrial furnaces will continue to rely on hydrocarbon fuels in the near foreseeable future. Mathematical modeling and numerical simulation is expected to deliver key insights to implement measures to further reduce pollutant emissions. These measures include the design optimization of the burners, the dilution of oxidizer with exhaust gasses, and the mixing of natural gas with hydrogen. In this paper, we target the numerical simulation of non-premixed turbulent combustion of natural gas in a single heating section of a ring pit anode baking furnace. In previous work, we performed combustion simulations using a commercial flow simulator combined with an open-source package for the three-dimensional mesh generation. This motivates switching to a fully open-source software stack. In this paper, we develop a Reynolds-Averaged Navier-Stokes model for the turbulent flow combined with an infinitely fast mixed-is-burnt model for the non-premixed combustion and a participating media model for the radiative heat transfer in OpenFoam. The heat transfer to the refractory brick lining is taken into account by a conjugate heat transfer model. Numerical simulations provide valuable insight into the heat release and chemical species distribution in the staged combustion process using two burners. Results show that at the operating conditions implemented, higher peak temperatures are formed at the burner closest to the air inlet. This results in a larger thermal nitric-oxide concentration. The inclusion of the heat absorption in the refractory bricks results in a more uniform temperature on the symmetry plane at the center of the section. The peak in thermal nitric-oxides is reduced by a factor of four compared to the model with adiabatic walls.
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Gaber, Christian, Christoph Schluckner, Philipp Wachter, Martin Demuth i Christoph Hochenauer. "Experimental study on the influence of the nitrogen concentration in the oxidizer on NOx and CO emissions during the oxy-fuel combustion of natural gas". Energy 214 (styczeń 2021): 118905. http://dx.doi.org/10.1016/j.energy.2020.118905.
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Imanbayev, Ye, Ye Tileuberdi, Ye Ongarbayev, Z. Mansurov, A. Batyrbayev, Ye Akkazin, E. Krivtsov, A. Golovko i S. Rudyk. "Changing the Structure of Resin-Asphaltenes Molecules in Cracking". Eurasian Chemico-Technological Journal 19, nr 2 (30.06.2017): 147. http://dx.doi.org/10.18321/ectj645.
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In the paper, structural changing of resin-asphaltene molecules in cracking process of oil sand bitumen are investigated. Cracking process to natural bitumen carried out in an open-to-air reactor, which extracted from oil sand by organic solvent. Reaction temperature was 450 °С and process duration was 60 min. The reactor was heated at a rate of 10 °C/min up to the desired temperature. Di-tert-butyl peroxide was used as radical formation additive. When limiting oxygen, it can be used catalyst molecule supplies as the oxidizer. The thermal destruction processes of heavy hydrocarbons with the catalyst make it possible to increase the yield of low boiling liquid products with the formation of coke and gas as by-products. High temperature leads to increase the oil content, and decrease the total resinasphaltene components in bitumen. Monte Carlo method used for construction the molecular structure of resin-asphaltene components. The calculations data determined the most stable conformation of resins and asphaltenes molecules, that the stability of the molecules affect structural characteristics such as the number of structural blocks, their size and spatial arrangement of atoms with respect to each other. Microscopic images showed that the asphaltenes have around 40‒50 nm of particle size, which large monolithic switching, weakly focused on a major surface, provided with amorphous carbon.
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Liang, Feng, Ghaithan Al-Muntasheri, Hooisweng Ow i Jason Cox. "Reduced-Polymer-Loading, High-Temperature Fracturing Fluids by Use of Nanocrosslinkers". SPE Journal 22, nr 02 (5.10.2016): 622–31. http://dx.doi.org/10.2118/177469-pa.
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Summary In the quest to discover more natural-gas resources, considerable attention has been devoted to finding and extracting gas locked within tight formations with permeability in the nano- to microdarcy range. The main challenges associated with working in such formations are the intrinsically high-temperature and high-pressure bottom conditions. For formations with bottomhole temperatures at approximately 350–400°F, traditional hydraulic-fracturing fluids that use crosslinked polysaccharide gels, such as guar and its derivatives, are not suitable because of significant polymer breakdown in this temperature range. Fracturing fluids that can work at these temperatures require thermally stable synthetic polymers such as acrylamide-based polymers. However, such polymers have to be used at very-high concentrations to suspend proppants. The high-polymer concentrations make it very difficult to completely degrade at the end of a fracturing operation. As a consequence, formation damage by polymer residue can reduce formation conductivity to gas flow. This paper addresses the shortcomings of the current state-of-the-art high-temperature fracturing fluids and focuses on developing a less-damaging, high-temperature-stable fluid that can be used at temperatures up to 400°F. A laboratory study was conducted with this novel system, which comprises a synthetic acrylamide-based copolymer gelling agent and is capable of being crosslinked with an amine-containing polymer-coated nanosized particulate crosslinker (nanocrosslinker). The laboratory data have demonstrated that the temperature stability of the crosslinked fluid is much better than that of a similar fluid lacking the nanocrosslinker. The nanocrosslinker allows the novel fluid system to operate at significantly lower polymer concentrations (25–45 lbm/1,000 gal) compared with current commercial fluid systems (50–87 lbm/1,000 gal) designed for temperatures from 350 to 400°F. This paper presents results from rheological studies that demonstrate superior crosslinking performance and thermal stability in this temperature range. This fracturing-fluid system has sufficient proppant-carrying viscosity, and allows for efficient cleanup by use of an oxidizer-type breaker. Low polymer loading and little or no polymer residue are anticipated to facilitate efficient cleanup, reduced formation damage, better fluid conductivity, and enhanced production rates. Laboratory results from proppant-pack regained-conductivity tests are also presented.
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Jacobs, Trent. "Canadian Operator Works To Transform an Oil Field Into a Hydrogen Factory". Journal of Petroleum Technology 73, nr 03 (1.03.2021): 38–40. http://dx.doi.org/10.2118/0321-0038-jpt.
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As the oil and gas industry scans the known universe for ways to diversify its portfolio with alternative forms of energy, it might want to look under its own feet, too. For inside every oil reservoir, there may be a hydrogen reservoir just waiting to get out. The concept comes courtesy of Calgary-based Proton Technologies. Founded in 2015, the young firm is the operator of an aging heavy oil field in Saskatchewan. There, on a small patch of flat farm-land, Proton has been producing oil to pay the bills. At the same time, it has been experimenting with injecting oxygen into its reservoir in a bid to produce exclusively hydrogen. Proton says its process is built on a technical foundation that includes years of research and works at the demonstration scale. Soon, the firm hopes to prove it is also profitable. While it produces its own hydrogen, Proton is licensing out the technology to others. In January, fellow Canadian operator Whitecap Resources secured a hydrogen production license of up to 500 metric tons/day from Proton. Whitecap produces about 48,000 B/D, and thanks to carbon sequestration, the operator has claimed a net negative emissions status since 2018. Proton says it has struck similar licensing deals with other Canadian operators but that these companies have not yet made public announcements. Where these projects go from here may end up representing the ultimate test for Proton’s innovative twist on the in-situ combustion process known so well to the heavy-oil sector. “In-situ combustion has been used in more than 500 projects worldwide over the last century. And, they have all produced hydrogen,” said Grant Strem, a cofounder and the CEO of Proton. Strem is a petroleum geologist by back-ground who spent the majority of his career working on heavy-oil projects for Canadian producers and research analysis with the banks that fund the upstream sector. While his new venture remains registered as an oil company, the self-described explorationist has come to look at oil fields very differently than he used to. “In an oil field, you have oil—hydrocarbons, which are made of hydrogen and carbon. The other fluid down there is H2O. So, an oil field is really a giant hydrogen-rich, energy-dense system that’s all conveniently accessible by wells,” Strem explained. But, in those past examples, the hundreds of other in-situ combustion projects, hydrogen production was merely a byproduct, an associated gas of sorts. It was the result of several reactions generated by air injections that producers use an oxidizer to heat up the heavy oil and get it flowing. What Proton wants to do is to super-charge the hydrogen-generating reactions by using the oil as fuel while leaving the carbon where it is. That ambition includes doing so at a price point that is roughly five times below that of Canadian natural gas prices and an even smaller fraction of what other hydrogen-generation methods cost.
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Lahaye, Domenico, Franjo Juretić i Marco Talice. "Modelling a Turbulent Non-Premixed Combustion in a Full-Scale Rotary Cement Kiln Using reactingFoam". Energies 15, nr 24 (19.12.2022): 9618. http://dx.doi.org/10.3390/en15249618.
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No alternatives are currently available to operate industrial furnaces, except for hydrocarbon fuels. Plant managers, therefore, face at least two challenges. First, environmental legislation demands emission reduction. Second, changes in the origin of the fuel might cause unforeseen changes in the heat release. This paper develops the hypothesis for the detailed control of the combustion process using computational fluid dynamic models. A full-scale mock-up of a rotary cement kiln is selected as a case study. The kiln is fired by the non-premixed combustion of Dutch natural gas. The gas is injected at Mach 0.6 via a multi-nozzle burner located at the outlet of an axially mounted fuel pipe. The preheated combustion air is fed in (co-flow) through a rectangular inlet situated above the attachment of the fuel pipe. The multi-jet nozzle burner enhances the entrainment of the air in the fuel jet. A diffusion flame is formed by thin reaction zones where the fuel and oxidizer meet. The heat formed is transported through the freeboard, mainly via radiation in a participating medium. This turbulent combustion process is modeled using unsteady Favre-averaged compressible Navier–Stokes equations. The standard k-ϵ equations and standard wall functions close the turbulent flow description. The eddy dissipation concept model is used to describe the combustion process. Here, only the presence of methane in the composition of the fuel is accounted for. Furthermore, the single-step reaction mechanism is chosen. The heat released radiates throughout the freeboard space. This process is described using a P1-radiation model with a constant thermal absorption coefficient. The flow, combustion, and radiative heat transfer are solved numerically using the OpenFoam simulation software. The equations for flow, combustion, and radiant heat transfer are discretized on a mesh locally refined near the burner outlet and solved numerically using the OpenFoam simulation software. The main results are as follows. The meticulously crafted mesh combined with the outlet condition that avoids pressure reflections cause the solver to converge in a stable manner. Predictions for velocity, pressure, temperature, and species distribution are now closer to manufacturing conditions. Computed temperate and species values are key to deducing the flame length and shape. The radiative heat flux to the wall peaks at the tip of the flame. This should allow us to measure the flame length indirectly from exterior wall temperature values. The amount of thermal nitric oxide formed in the flame is quantified. The main implication of this study is that the numerical model developed in this paper reveals valuable information on the combustion process in the kiln that otherwise would not be available. This information can be used to increase fuel efficiency, reduce spurious peak temperatures, and reduce pollutant emissions. The impact of the unsteady nature of the flow on the chemical species concentration and temperature distribution is illustrated in an accompanying video.
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Abuelnuor, A. A. A., Mazlan A. Wahid i M. Osman. "Characterization of a Low NOx Flameless Combustion Burner Using Natural Gas". Jurnal Teknologi 66, nr 2 (1.01.2014). http://dx.doi.org/10.11113/jt.v66.2497.
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Flameless combustion is a method that has a great potential in reducing pollutant emission from combustion process. In this work, the operation and emission of a laboratory scale furnace under the flameless combustion regime using natural gas as a fuel was examined. In the experimental setup, the combustor was equipped with parallel jet burner systems with controlled gas fuel and oxidizer. Several ports have been integrated in the combustor to allow for temperature and combustion emission measurement. In the study, a comparison between flameless combustion with and without preheated combustion air has been made. The atmospheric air was heated to near the auto ignition temperature by a coil placed within the furnace assembly. The results show that flameless combustion mode could be obtained with and without preheated combustion air. The results also revealed that the laboratory scale furnace could successfully operate in flameless combustion regime using natural gas as fuel. In terms of emission, it was found that flameless combustion was more effective than the conventional combustion in reducing the rate of NOX emission.
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Zhang, Na, i Noam Lior. "Comparative Study of Two Low CO2 Emission Power Generation System Options With Natural Gas Reforming". Journal of Engineering for Gas Turbines and Power 130, nr 5 (13.06.2008). http://dx.doi.org/10.1115/1.2904895.
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Two power plant schemes that reduce CO2 emission and employ natural gas reforming were analyzed and discussed. The first one integrates natural gas reforming technology for efficiency improvement with an oxy-fuel combined power system (OXYF-REF), with water as the main work fluid. The reforming heat is obtained from the available turbine exhaust heat, and the produced syngas is used as fuel with oxygen as the oxidizer. The turbine working fluid can expand down to a vacuum, producing a high-pressure ratio and thus more net work. The second system integrates natural gas reforming in a precombustion decarbonization scheme using chemical absorption technology for the CO2 removal (PCD-REF). The gas turbine is the conventional air-based one with compressor intercooling. Supplementary combustion is employed to elevate the turbine exhaust temperature and thus achieve a much higher methane conversion rate (96.9%). Both systems involve internal heat recuperation from gas turbine exhausts, and particular attention has been paid to the integration of the heat recovery chain to reduce the related exergy destruction. The systems are simulated and their thermal efficiency, overall and component exergy losses, and CO2 removal capacity are compared. The OXYF-REF system has a higher energy efficiency, of 51.4%, and higher CO2 removal, but the product CO2 has lower purity, of 84%. The PCD-REF system has a thermal efficiency of 46%, the captured CO2 is 99% pure, and the CO2 specific emission is 58.5g∕kWh.
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Nagy, Thomas Robert. "Scale Control in Oilfield Applications". Proceedings of the West Virginia Academy of Science 90, nr 1 (2.04.2018). http://dx.doi.org/10.55632/pwvas.v90i1.329.
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While the Northern Panhandle of West Virginia has a long history in the businesses of coal mining and steel production, advancing technologies have allowed hydraulic fracturing to arise as an effective method for extracting natural gas and oil in this area. Despite the abundance of natural gas deposits in the Marcellus Shale of northern West Virginia, using hydraulic fracturing to extract natural resources is not without its drawbacks. When HF flowback water moves through oilfield pipelines, it is highly saturated with metal cations from bedrock minerals which dissolved in solution during the fracturing process. These cations tend to precipitate out of solution as salts, therefore lining the insides of the pipes with scale and slowing the overall flow rate within the piping system. Since this issue can be very expensive to fix if not dealt with quickly, it is safer to simply avoid the chance of scale altogether by utilizing scale inhibitors. The goal of this experiment was to pre-treat the produced water with an oxidizer (Klear’s organic-based peroxide 4035) to reduce the amount of metals in solution and then proceed to treat with scale inhibitor 5210 to reduce the scaling potential of any remaining metal cations.
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Nicodemus, Julia Haltiwanger, Morgan McGuinness i Rijan Maharjan. "A Thermodynamic and Cost Analysis of Solar Syngas From the Zn/ZnO Cycle". Journal of Solar Energy Engineering 137, nr 1 (25.08.2014). http://dx.doi.org/10.1115/1.4028189.
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We present a thermodynamic and cost analysis of synthesis gas (syngas) production by the Zn/ZnO solar thermochemical fuel production cycle. A mass, energy, and entropy balance over each step of the Zn/ZnO syngas production cycle is presented. The production of CO and H2 is considered simultaneously across the range of possible stoichiometric combinations, and the effects of irreversibilities due to both recombination in the quenching process following dissociation of ZnO and incomplete conversion in the fuel production step are explored. In the cost analysis, continuous functions for each cost component are presented, allowing estimated costs of syngas fuel produced at plants between 50 and 500 MWth. For a solar concentration ratio of 10,000, a dissociation temperature of 2300 K, and a CO fraction in the syngas of 1/3, the maximum cycle efficiency is 39% for an ideal case in which there is no recombination in the quencher, complete conversion in the oxidizer, and maximum heat recovery. In a 100 MWth plant, the cost to produce syngas would be $0.025/MJ for this ideal case. The effect of heat recuperation, recombination in the quencher, and incomplete conversion on efficiency and cost are explored. The effects of plant size and feedstock costs on the cost of solar syngas are also explored. The results underscore the importance improving quencher and oxidizer processes to reduce costs. However, even assuming the ideal case, the predicted cost of solar syngas is 5.5 times more expensive than natural gas on an energy basis. The process will therefore require incentive policies that support early implementation in order to become economically competitive.
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Ullal, Ankith, Youngchul Ra, Jeffrey D. Naber, William Atkinson, Satoshi Yamada, Yuji Oda, Kenji Hiraoka i Kazutoshi Nomura. "Numerical investigation of oil droplet combustion using single particle ignition cell model". International Journal of Engine Research, 27.01.2020, 146808741989693. http://dx.doi.org/10.1177/1468087419896939.
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Pre-ignition in internal combustion engines is an abnormal combustion phenomenon which often results in structural damage to the engine. It occurs when an ignition event takes place in the combustion chamber before the designed ignition time. In this work, a numerical study was done to investigate the pre-ignition with potential application to natural gas marine engines. This was done by simulating experiments of lube oil–induced ignition and subsequent combustion in a constant volume combustion chamber using an in-house version of the KIVA4-CFD code. Initial conditions of the chamber gases are obtained from the pre-burn process of a known composition of C2H2/oxidizer mixture. Natural gas was injected from a single-hole injector at an injection temperature and pressure of 300 K and 105 Pa, respectively. A rotating fan was modeled, as is in the experimental setup. Oil droplet of known size and velocity is injected into the constant volume combustion chamber. For accurate prediction of oil droplet ignition, the computational cells that contain the droplets are to be refined. Combustion calculations are then carried out on the refined grid. Ignition delay times of both lube oil and methane/air mixtures were calculated. Parametric studies were also conducted by varying droplet conditions, and their results are also presented.
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Rahman, Ramees K., Samuel Barak, K. R. V. (Raghu) Manikantachari, Erik Ninnemann, Ashvin Hosangadi, Andrea Zambon i Subith S. Vasu. "Probing the Effects of NOx and SOx Impurities on Oxy-Fuel Combustion in Supercritical CO2: Shock Tube Experiments and Chemical Kinetic Modeling". Journal of Energy Resources Technology 142, nr 12 (12.06.2020). http://dx.doi.org/10.1115/1.4047314.
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Abstract The direct-fired supercritical carbon dioxide cycles are one of the most promising power generation methods in terms of their efficiency and environmental friendliness. Two important challenges in implementing these cycles are the high pressure (300 bar) and high CO2 dilution (>80%) in the combustor. The design and development of supercritical oxy-combustors for natural gas require accurate reaction kinetic models to predict the combustion outcomes. The presence of a small amount of impurities in natural gas and other feed streams to oxy-combustors makes these predictions even more complex. During oxy-combustion, trace amounts of nitrogen present in the oxidizer is converted to NOx and gets into the combustion chamber along with the recirculated CO2. Similarly, natural gas can contain a trace amount of ammonia and sulfurous impurities that get converted to NOx and SOx and get back into the combustion chamber with recirculated CO2. In this work, a reaction model is developed for predicting the effect of impurities such as NOx and SOx on supercritical methane combustion. The base mechanism used in this work is GRI Mech 3.0. H2S combustion chemistry is obtained from Bongartz et al. while NOx chemistry is from Konnov. The reaction model is then optimized for a pressure range of 30–300 bar using high-pressure shock tube data from the literature. It is then validated with data obtained from the literature for methane combustion, H2S oxidation, and NOx effects on ignition delay. The effect of impurities on CH4 combustion up to 16 atm is validated using NOx-doped methane studies obtained from the literature. In order to validate the model for high-pressure conditions, experiments are conducted at the UCF shock tube facility using natural gas identical mixtures with N2O as an impurity at ∼100 bar. Current results show that there is a significant change in ignition delay with the presence of impurities. A comparison is made with experimental data using the developed model and predictions are found to be in good agreement. The model developed was used to study the effect of impurities on CO formation from sCO2 combustors. It was found that NOx helps in reducing CO formation while the presence of H2S results in the formation of more CO. The reaction mechanism developed herein can also be used as a base mechanism to develop reduced mechanisms for use in CFD simulations.
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Nijman, Thomas P. A., Thomas A. Davidson, Stefan T. J. Weideveld, Joachim Audet, Chiara Esposito, Eti E. Levi, Adrian Ho, Leon P. M. Lamers, Erik Jeppesen i Annelies J. Veraart. "Warming and eutrophication interactively drive changes in the methane-oxidizing community of shallow lakes". ISME Communications 1, nr 1 (5.07.2021). http://dx.doi.org/10.1038/s43705-021-00026-y.
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AbstractFreshwater ecosystems are the largest natural source of the greenhouse gas methane (CH4), with shallow lakes a particular hot spot. Eutrophication and warming generally increase lake CH4 emissions but their impacts on the sole biological methane sink—methane oxidation—and methane-oxidizer community dynamics are poorly understood. We used the world’s longest-running freshwater climate-change mesocosm experiment to determine how methane-oxidizing bacterial (MOB) abundance and composition, and methane oxidation potential in the sediment respond to eutrophication, short-term nitrogen addition and warming. After nitrogen addition, MOB abundance and methane oxidation potential increased, while warming increased MOB abundance without altering methane oxidation potential. MOB community composition was driven by both temperature and nutrient availability. Eutrophication increased relative abundance of type I MOB Methyloparacoccus. Warming favoured type II MOB Methylocystis over type I MOB Methylomonadaceae, shifting the MOB community from type I dominance to type I and II co-dominance, thereby altering MOB community traits involved in growth and stress-responses. This shift to slower-growing MOB may explain why higher MOB abundance in warmed mesocosms did not coincide with higher methane oxidation potential. Overall, we show that eutrophication and warming differentially change the MOB community, resulting in an altered ability to mitigate CH4 emissions from shallow lakes.
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Mi, Jianchun, Mengwei Wu i Minyi Xu. "On molecular unmixedness between the ejected original and entrained ambient fluids in a turbulent jet". Physics of Fluids 35, nr 7 (1.07.2023). http://dx.doi.org/10.1063/5.0154723.
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The present study investigates the molecular unmixedness between the injected and entrained fluids in a turbulent jet as well as its dependence on the initial conditions. This unmixedness can be quantified as the parameter of molecular segregation between the ejecting “fuel” fluid (A) and the entrained “oxidizer” fluid (B), defined by α≡cAcB¯/C¯AC¯B (overbar denotes time-averaging). For the first time, an expression of the parameter has been derived for the two-fluid mixing in a heated turbulent nonreactive jet. That is, α=−θ2¯/Θo−Θ¯Θ¯−Θa, where Θo and Θa denote the ejected “warm” and entrained “cold” fluid temperatures, whereas Θ and θ are the instantaneous and fluctuating temperatures of the local fluid mixture. This expression of α is well validated by comparing the measured natural-gas flames from a smooth-contraction nozzle with those from a long-pipe nozzle. Moreover, the jet-nozzle configuration is found to show a strong effect on α. Likewise, the jet density ratio (Rρ) is a highly influential factor: e.g., an increase in Rρ reduces α substantially. In contrast, the effect of the jet-exit Reynolds number is less significant. In the present paper, we try to explain these observations.
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Pinto, Ameet J., Daniel N. Marcus, Umer Zeeshan Ijaz, Quyen Melina Bautista-de lose Santos, Gregory J. Dick i Lutgarde Raskin. "Metagenomic Evidence for the Presence of Comammox Nitrospira-Like Bacteria in a Drinking Water System". mSphere 1, nr 1 (30.12.2015). http://dx.doi.org/10.1128/msphere.00054-15.
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ABSTRACT Nitrification plays an important role in regulating the concentrations of inorganic nitrogen species in a range of environments, from drinking water and wastewater treatment plants to the oceans. Until recently, aerobic nitrification was considered to be a two-step process involving ammonia-oxidizing bacteria or archaea and nitrite-oxidizing bacteria. This process requires close cooperation between these two functional guilds for complete conversion of ammonia to nitrate, without the accumulation of nitrite or other intermediates, such as nitrous oxide, a potent greenhouse gas. The discovery of a single organism with the potential to oxidize both ammonia and nitrite adds a new dimension to the current understanding of aerobic nitrification, while presenting opportunities to rethink nitrogen management in engineered systems. We report metagenomic evidence for the presence of a Nitrospira-like organism with the metabolic potential to perform the complete oxidation of ammonia to nitrate (i.e., it is a complete ammonia oxidizer [comammox]) in a drinking water system. This metagenome bin was discovered through shotgun DNA sequencing of samples from biologically active filters at the drinking water treatment plant in Ann Arbor, MI. Ribosomal proteins, 16S rRNA, and nxrA gene analyses confirmed that this genome is related to Nitrospira-like nitrite-oxidizing bacteria. The presence of the full suite of ammonia oxidation genes, including ammonia monooxygenase and hydroxylamine dehydrogenase, on a single ungapped scaffold within this metagenome bin suggests the presence of recently discovered comammox potential. Evaluations based on coverage and k-mer frequency distribution, use of two different genome-binning approaches, and nucleic acid and protein similarity analyses support the presence of this scaffold within the Nitrospira metagenome bin. The amoA gene found in this metagenome bin is divergent from those of canonical ammonia and methane oxidizers and clusters closely with the unusual amoA gene of comammox Nitrospira. This finding suggests that previously reported imbalances in abundances of nitrite- and ammonia-oxidizing bacteria/archaea may likely be explained by the capacity of Nitrospira-like organisms to completely oxidize ammonia. This finding might have significant implications for our understanding of microbially mediated nitrogen transformations in engineered and natural systems. IMPORTANCE Nitrification plays an important role in regulating the concentrations of inorganic nitrogen species in a range of environments, from drinking water and wastewater treatment plants to the oceans. Until recently, aerobic nitrification was considered to be a two-step process involving ammonia-oxidizing bacteria or archaea and nitrite-oxidizing bacteria. This process requires close cooperation between these two functional guilds for complete conversion of ammonia to nitrate, without the accumulation of nitrite or other intermediates, such as nitrous oxide, a potent greenhouse gas. The discovery of a single organism with the potential to oxidize both ammonia and nitrite adds a new dimension to the current understanding of aerobic nitrification, while presenting opportunities to rethink nitrogen management in engineered systems.
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Hu, Min, Fangbai Li, Jiangtao Qiao, Chaolei Yuan, Huanyun Yu i Li Zhuang. "New Arsenite Oxidase Gene (aioA) PCR Primers for Assessing Arsenite-Oxidizer Diversity in the Environment Using High-Throughput Sequencing". Frontiers in Microbiology 12 (6.10.2021). http://dx.doi.org/10.3389/fmicb.2021.691913.
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Gene encoding the large subunit of As(III) oxidase (AioA), an important component of the microbial As(III) oxidation system, is a widely used biomarker to characterize As(III)-oxidizing communities in the environment. However, many studies were restricted to a few sequences generated by clone libraries and Sanger sequencing, which may have underestimated the diversity of As(III)-oxidizers in natural environments. In this study, we designed a primer pair, 1109F (5′-ATC TGG GGB AAY RAC AAY TA−3′) and 1548R (5′-TTC ATB GAS GTS AGR TTC AT−3′), targeting gene sequence encoding for the conserved molybdopterin center of the AioA protein, yielding amplicons approximately 450 bp in size that are feasible for highly parallel amplicon sequencing. By utilizing in silico analyses and the experimental construction of clone libraries using Sanger sequencing, the specificity and resolution of 1109F/1548R are approximated with two other previously published and commonly used primers, i.e., M1-2F/M3-2R and deg1F/deg1R. With the use of the 1109F/1548R primer pair, the taxonomic composition of the aioA genes was similar both according to the Sanger and next-generation sequencing (NGS) platforms. Furthermore, high-throughput amplicon sequencing using the primer pair, 1109F/1548R, successfully identified the well-known As(III)-oxidizers in paddy soils and sediments, and they also revealed the differences in the community structure and composition of As(III)-oxidizers in above two biotopes. The random forest analysis showed that the dissolved As(III) had the highest relative influence on the Chao1 index of the aioA genes. These observations demonstrate that the newly designed PCR primers enhanced the ability to detect the diversity of aioA-encoding microorganisms in environments using highly parallel short amplicon sequencing.