Addition Of Ethane Research Articles

The effect of ethane on the chain reaction characteristics of methane–air mixtures explosions

In order to study the effect of ethane on gas explosions, the macroscopic properties, thermodynamics and kinetics of gas explosions were investigated using Chemkin numerical simulation software with the GRI-Mech 3.0 mechanism. Ethane was added to methane-air mixtures at seven different concentrations, such as 0%, 0.1%, 0.3% and so on, at constant initial temperature (1200 K) and pressure(0.9atm), respectively. The results show that the maximum explosion pressure, explosive power and ·H content was all maximized when the volume fraction of ethane was 3%, which was the most effective volume addition to promote gas explosion. Ethane reduced the time to peak energy of key radical reactions from 0.049s to 0.003s and reduced the sensitivity factors for reactions such as R155 and R158. When the added ethane was 8%, R158 and R98 shifted from inhibiting methane consumption to promoting methane consumption. Calculated by Arrhenius and Lindemann formulae found that ethane can act as the third molecule in unimolecular reactions, increasing the reaction rate constant and decreasing the activation energy, so accelerating the reaction. Due to the low addition of ethane, there was still a large amount of N2 acting as the third molecule, so the decrease in activation energy was small.

Experimental and kinetic modeling study of the autoignition and oxidation of ammonia/ethane mixtures in a rapid compression machine and a jet-stirred reactor

Ignition delay times and speciation data of ammonia/ethane (NH3/C2H6) fuel blends were measured in a rapid compression machine (RCM) and in a jet-stirred reactor coupled with molecular beam mass spectrometry (JSR-MBMS), respectively. Specifically, the RCM experiments were conducted at elevated pressures of 20 and 40 bar, intermediate temperatures between 890 and 1110 K, three equivalence ratios of 0.5, 1.0 and 2.0 and for three C2H6 mole fractions from 1% to 10%. Besides, the JSR measurements were conducted at atmospheric pressure, intermediate temperatures between 700 and 1180 K, three equivalence ratios of 0.5, 1.0 and 2.0 and three C2H6 mole fractions from 10% to 50%. The experimental results demonstrate that adding C2H6 into NH3 leads to a more reactive mixture. A kinetic model from our recent work on ammonia/ethanol fuel blends (M. Li et al., Proc. Combust. Inst., 2022) has been updated and validated with the new data obtained in this work. The updated model (PTB-NH3/C2 mech) can reproduce the effects of ethane fraction and equivalence ratio on IDT/speciation and show an overall satisfactory agreement between experimental results and predictions. Based on the kinetic analyses, for all conditions investigated in this study, the generation of OH radicals from HO2 and H radicals dominates the characteristic of the auto-ignition process in the RCM and the NH3 consumption process in the JSR, respectively. Apart from that, the addition of ethane provides additional OH from a relatively low temperature (e.g., around 850 K in a JSR condition) and triggers the interactions between hydrocarbon and ammonia systems, e.g., the reactions of C2H6/C2H4/CH3+NH2, which play an important role in the combustion of ammonia.

Study of methane oxycondensation reaction (mn2o3)x∙ (na2moo4)y ∙ (zro2)z and textural characteristics of the catalyst

In the study, the effect of temperature, methane: air ratio, specific volume velocity, and various other factors on the yield of target products, methane conversion, and process selectivity of the methane catalytic oxycondensation reaction were studied. The effect of volumetric velocity was studied at a temperature of 800°C and a volumetric ratio of CH4:air = 1:2. The effect of temperature on the oxycondensation reaction of methane was studied in the presence of a catalyst of optimal composition at intervals of 50°C in the range of 600–850°C, at a constant volumetric velocity (1000 h-1) and a ratio of CH4:air = 1:2. CN4: The effect of air ratio was studied at a temperature of 800°C and a volumetric velocity = 1000 h-1. As a result of kinetic studies, an improvement in process performance was observed with increasing contact time and temperature rise. An increase in the CH4:O2 ratio leads to a decrease in methane and oxygen conversion. The addition of ethane, ethylene, СО, and СО2 to the reactor has been shown to reduce the formation of products. The work aims to study the kinetic laws of the reaction of oxidation of methane in a catalyst containing (Mn2O3)x·(Na2MoO4)y ·(ZrO2)z and to evaluate the texture characteristics of the catalyst.

Statistical analysis of detonation wave structure

Hydrocarbon fueled detonations are imaged in a narrow channel with simultaneous schlieren and broadband chemiluminescence at 5 MHz. Mixtures of stoichiometric methane and oxygen are diluted with various levels of nitrogen and argon to alter the detonation stability. Ethane is added in controlled amounts to methane, oxygen, nitrogen mixtures to simulate the effects of high-order hydrocarbons present in natural gas. Sixteen unique mixtures are characterized by performing statistical analysis on data extracted from the images. The leading shock front of the schlieren images is detected and the normal velocity is calculated at all points along the front. Probability distribution functions of the lead shock speed are generated for all cases and the moments of distribution are computed. A strong correlation is found between mixture instability parameters and the variance and skewness of the probability distribution; mixtures with greater instability have larger skewness and variance. This suggests a quantitative alternative to soot foil analysis for experimentally characterizing the extent of detonation instability. The schlieren and chemiluminescence images are used to define an effective chemical length scale as the distance between the shock front and maximum intensity location along the chemiluminescence front. Joint probability distribution functions of shock speed and chemical length scale enable statistical characterization of coupling between the leading shock and following reaction zone. For more stable, argon dilute mixtures, it is found that the joint distributions follow the trend of the quasi-steady reaction zone. For unstable, nitrogen diluted mixtures, the distribution only follows the quasi-steady solution during high-speed portions of the front. The addition of ethane is shown to have a stabilizing effect on the detonation, consistent with computed instability parameters.

Comparative investigation of Ga- and In-CHA in the non-oxidative ethane dehydrogenation reaction

Ga- and In-exchanged chabazite (CHA) zeolites with same Si/Al and metal/Al ratios were prepared via the incipient wetness impregnation method, were characterized using N2 adsorption, electron microscopy, temperature-programed reactions and were evaluated for the ethane dehydrogenation reaction using flow microreactors. Ga-CHA has higher reaction rates and a lower activation energy of 107 kJ/mol than In-CHA (Ea = 175 kJ/mol). Rietveld refinement of the X-ray powder diffraction pattern shows that the In+ cation is predominantly located above the 6-ring of the CHA cage. It is proposed that the reaction proceeds through the alkyl mechanism based on stability of alkyl hydride intermediates as determined using DFT calculations. The oxidative addition of ethane to the metal shows much lower Gibbs free energy for Ga-CHA (+27.95 kJ/mol) vs In-CHA (+124.85 kJ/mol). These results indicate that oxidative addition may be the rate-limiting step of ethane dehydrogenation in these materials.

Effect of steam addition and distance between inlet nozzles on non-catalytic POX process under MILD combustion condition

Moderate or intensive low-oxygen dilution (MILD) combustion is a novel combustion technology with high efficiency and low emissions. Few studies have been performed on the application of this technology for partial oxidation processes. In this research, a Computational Fluid Dynamics study for the effect of different parameters on the natural gas partial oxidation under MILD combustion conditions has been carried out. The combustion chamber was in the form of cylinder with a diameter of 300 mm and a length of 1500 mm. The effect of parameters such as different kinetic mechanisms, adding ethane and propane to methane (shale gas feed), adding steam to the feed and distance (interval) between methane and oxygen nozzles were investigated. Results showed that addition of ethane and propane to methane increased the mole fraction of CO and C2H2 so that, in the case of mixed methane with ethane and propane compared to the case of pure methane, an increase of 18.75% and 12.93% was observed for CO and C2H2, respectively. In addition, with increasing the percentage of steam in the inlet feed at a constant flow rate, methane conversion increased so that it in the case of 30% inlet steam was 77.17%, which showed 11% promotion compared to the pure methane case. Also, increasing the distance between the fuel and oxidizer nozzles led to an increase in the maximum temperature in the combustion chamber.

Development of Natural Gas Chemical Kinetic Mechanisms and Application in Engines: A Review.

In this paper, the brief development of chemical kinetic modeling of natural gas is discussed, with emphasis on the development of chemical kinetic mechanisms describing fuel oxidation. The addition of ethane and/or propane to natural gas not only decreases the ignition delay times but also increases flame speeds. Thus, the mixture of methane, ethane, and propane rather than bare methane obtains more accurate predictions for the combustion and emission characteristics of natural gas. This paper also evaluates different comprehensive mechanisms employed for natural gas engines and pointed out their advantages and disadvantages, giving guidance for the selection of mechanisms during the development of natural gas engines.

Effect of ethane and ethylene on catalytic non oxidative coupling of methane.

The effect of addition of ethane and ethylene (C2) on methane coupling at 1000 °C was investigated. A Fe/SiO2 catalyst was used to determine the contributions of catalytic as well as C2 initiated methane activation. The catalyst load as well as the residence times at 1000 °C downstream of the catalyst bed were varied. C2 addition significantly increases methane conversion rates, similarly for both ethane and ethylene, although ethylene is more effective when operating with long residence times in the post-catalytic volume. Methane activation via C2 addition proceeds dominantly in the gas-phase whereas catalytic C2 activation is negligible. The catalyst has no effect on methane conversion when the feed contains more than 2 vol% C2. Product selectivity distribution as well as total hydrocarbon yield at 10% conversion is not influenced by C2 addition, but is influenced by the amount of catalyst as well as residence time in the post-catalytic volume at high temperature. It is proposed that C2 impurities in natural gas change from a nuisance to an advantage by enhancing methane conversion and simplifying purification of the natural gas feed. A process is proposed in which ethylene is recycled back into the reactor to initiate methane coupling, leading to a process converting methane to aromatics.

Large eddy simulation for the rapid phase transition of LNG

The environmental concerns on the use of fossil fuels have incentivized the utilization of cleaner solutions for energy supply. Natural gas in the form of a liquid (LNG) is considered a promising and highly attractive alternative due to the high density and relatively low cost of transportation.In the case of accidental release on water, elevated heat transfer causes rapid evaporation that has the potential to lead to a rapid phase transition (RPT), thus producing significant overpressures.In this work, the effects of composition, release rate, and the fluid dynamic regime of water on the RPT of LNG are analyzed by means of detailed analysis based on computational fluid dynamics and large eddy simulation for the turbulence model. The thermodynamic properties at ultra-low temperature related to the species considered in the mixtures are estimated by using an approach based on quantum mechanics.Results are compared with experimental analysis, quite satisfactorily. A preliminary conclusion shows that calm water, as within port facilities, decreases the likelihood of the RPT or its magnitude to a negligible intensity. On the contrary, the addition of ethane or propane may dramatically affect the explosive phenomenon.

Numerical simulation of small-scale pool fires of LNG

Liquefied natural gas (LNG) has been largely indicated as a promising alternative solution for the transportation and storage of natural gas. In the case of accidental release on the ground, a pool fire scenario may occur. Despite the relevance of this accident, due to its likelihood and potential to trigger domino effects, accurate analyses addressing the characterization of pool fires of LNG are still missing.In this work, the fire dynamic simulator (FDS) has been adopted for the evaluation of the effects of the released amount of fuel and its composition (methane, ethane, and propane), on the thermal and chemical properties of small-scale LNG pool fire. More specifically, the heat release rate, the burning rate, the flame height, and thermal radiation, at different initial conditions, have been evaluated for pool having diameter smaller than 10 m. Safety distances have been calculated for all the investigated conditions, as well.Results have also been compared with data and correlations retrieved from the current literature. The equation of Thomas seems to work properly for the definition of the height over diameter ratio of the LNG pool fire for all the mixture and the investigated diameters.The addition of ethane and propane significantly affects the obtained results, especially in terms of radiative thermal radiation peaks, thus indicating the inadequacy of the commonly adopted assumption of pure methane as single, surrogate species for the LNG mixture.

Modeling natural gas-carbon dioxide system for solid-liquid-vapor phase behavior

With the shale gas boom, natural gas has become one of the main energy sources in the United States. But in the cryogenic processes of this natural gas, the formation of solid carbon dioxide remains a concern because it can cause the blockage of equipment. Accurately modeling the rich phase behavior of carbon dioxide in methane is helpful for optimizing the industrial processes, especially where experimental data are lacking at the operation conditions. In this work, the Perturbed Chain-SAFT (PC-SAFT) equation of state is applied to model the phase behavior of hydrocarbon (i.e., methane, ethane, butane) + carbon dioxide systems over a wide range of temperatures and pressures. It is observed that the PC-SAFT equation of state can accurately predict the vapor-liquid equilibria (VLE), solid-vapor equilibria (SVE), and solid-liquid equilibria (SLE) of hydrocarbon + carbon dioxide systems using a single set of temperature and pressure independent binary interaction parameters. In the end, the effect of addition of ethane and butane on SLE of methane + carbon dioxide is also investigated which has applications in reducing the carbon dioxide solidification conditions.

Effect of Ethane and Propane Addition on Acetylene Production in the Partial Oxidation Process of Methane

Wet shale gas contains relatively high concentrations of heavier hydrocarbons. In industry, the cryogenic separation process is used to separate methane and heavier hydrocarbons for the downstream conversion. In this work, the feasibility of direct application of wet gas in the partial oxidation (POX) process was studied. Flat flame experiments of methane with addition of ethane and propane were conducted using a McKenna reactor. The results showed that the mole fractions of acetylene and CO increased by 15% and 25% when using wet gas as the feedstock. Four detailed chemical mechanisms were verified, and the Curran and modified GRI 3.0 mechanisms gave good predictions of the POX of wet gas. The modified GRI 3.0 was further used in the three-dimensional computational fluid dynamics (CFD) simulations of a 3-jet reactor at industrial conditions. The results showed that in the wet gas POX process a higher C2H2 yield was obtained, and the optimal equivalence ratio slightly increased from 4.0 to 4.07 and the op...

Enhancing aerobic biodegradation of 1,2-dibromoethane in groundwater using ethane or propane and inorganic nutrients

1,2-Dibromoethane (ethylene dibromide; EDB) is a probable human carcinogen that was previously used as both a soil fumigant and a scavenger in leaded gasoline. EDB has been observed to persist in soils and groundwater, particularly under oxic conditions. The objective of this study was to evaluate options to enhance the aerobic degradation of EDB in groundwater, with a particular focus on possible in situ remediation strategies. Propane gas and ethane gas were observed to significantly stimulate the biodegradation of EDB in microcosms constructed with aquifer solids and groundwater from the FS-12 EDB plume at Joint Base Cape Cod (Cape Cod, MA), but only after inorganic nutrients were added. Ethene gas was also effective, but rates were appreciably slower than for ethane and propane. EDB was reduced to <0.02μg/L, the Massachusetts state Maximum Contaminant Level (MCL), in microcosms that received ethane gas and inorganic nutrients. An enrichment culture (BE-3R) that grew on ethane or propane gas but not EDB was obtained from the site materials. The degradation of EDB by this culture was inhibited by acetylene gas, suggesting that degradation is catalyzed by a monooxygenase enzyme. The BE-3R culture was also observed to biodegrade 1,2-dichloroethane (DCA), a compound commonly used in conjunction with EDB as a lead scavenger in gasoline. The data suggest that addition of ethane or propane gas with inorganic nutrients may be a viable option to enhance degradation of EDB in groundwater aquifers to below current state or federal MCL values.

Comparative study on the laminar flame speed enhancement of methane with ethane and ethylene addition

A systematic analysis of the flame speed enhancement effects of ethane and ethylene addition to methane was performed. Flame speeds of outwardly propagating spherical flames were measured in a high-pressure, cylindrical flame speed vessel using schlieren photography. It was ensured that the measured data were outside the ignition- and chamber-confinement-affected radii. The unstretched, unburnt flame speeds were obtained using nonlinear extrapolation methods from the experimentally determined stretched flame speeds. The AramcoMech 1.3 kinetics mechanism was validated against flame speeds of ethane, ethylene, and acetylene over a wide range of pressures and equivalence ratios. Good agreement between the measured data and those reported in the literature was seen. The model agreed closely with the measurements at fuel-lean conditions, but a slight over prediction was observed for the fuel-rich cases. Flame speeds of 80/20 and 60/40 (by volume) CH4/C2Hx mixtures in air and in air with excess nitrogen were measured over a wide range of fuel concentrations. In all cases, the addition of ethylene increased the flame speed more than did an equivalent addition of ethane. The Arrhenius effect (predominantly kinetic effect) was the principal driver for flame speed enhancement of methane with ethane/ethylene addition. Sensitivity analysis revealed that thermal and diffusive pathways were equally contributing to the flame speed enhancement of CH4/C2H6 mixtures, but the latter played a comparatively minor role in the C2H4-based blends.

Physicochemical effects of varying fuel composition on knock characteristics of natural gas mixtures

The physicochemical origins of how changes in fuel composition affect autoignition of the end gas, leading to engine knock, are analyzed for a natural gas engine. Experiments in a lean-burn, high-speed medium-BMEP gas engine are performed using a reference natural gas with systematically varied fractions of admixed ethane, propane and hydrogen. Thermodynamic analysis of the measured non-knocking pressure histories shows that, in addition to the expected changes arising from changes in the heat capacity of the mixture, changes in the combustion duration relative to the compression cycle (the combustion “phasing”) caused by variations in burning velocity dominate the effects of fuel composition on the temperature (and pressure) of the end gas. Thus, despite the increase in the heat capacity of the fuel–air mixture with addition of ethane and propane, the change in combustion phasing is actually seen to increase the maximum end-gas temperature slightly for these fuel components. By the same token, the substantial change in combustion duration upon hydrogen addition strongly increases the end-gas temperature, beyond that caused by the decrease in mixture heat capacity. The impact of these variations in in-cylinder conditions on the knock tendency of the fuel have been assessed using autoignition delay times computed using SENKIN and a detailed chemical mechanism for the end gas under the conditions extant in the engine. The results show that the ignition-promoting effect of hydrogen is mainly the result of the increase in end-gas temperature and pressure, while addition of ethane and propane promotes ignition primarily by changing the chemical autoignition behavior of the fuel itself. Comparison of the computed end-gas autoignition delay time, based on the complete measured pressure history of each gas, with the measured Knock-Limited Spark Timing shows that the computed delay time accurately reflects the measured knock tendency of the fuels.

Technologies for gas turbine power generation with CO2 mitigation

A review of the state of the art gas turbine power plants designs with CO2 capture was performed to set up a list of technologies to be considered in a conceptual process superstructure. It has been found that the efficiency and economics of carbon dioxide capture in gas turbine combined cycle power plants can be remarkably improved by introducing Flue Gas Recirculation (FGR) so as to increase the CO2 concentration in the flue gas and to reduce the volume of the flue gas treated in a CO2 capture plant. Thus, this process was chosen as the main focus of the thermo-economic modeling and the combustion system related experimental testing. Combustion studies were performed to quantify the impact of reduced oxygen content (caused by flue gas recirculation) on combustion stability and emission characteristics (NOx, CO). Tests were performed with methane, methane/ethane (simulated natural gas), methane/hydrogen and natural gas (as distributed in Switzerland) at different FGR ratios. For all conditions the addition of ethane or hydrogen shows beneficial effects (restoration of flame reactivity) on flame stability and CO emission. Using PSI’s high pressure test rig, it has been shown, that by redirecting up to 30% of exhaust gas volume back to the combustor, the CO2 concentration in the exhaust can be increased to 8% vol. while keeping the flame temperature constant (Tad=1750K) and meeting the emission requirements (CO, NOx< 25 ppm @ 15% O2). Benchmark tests of catalytic partial oxidation reactors were performed to determine whether sufficient H2 could be produced in situ by reaction of a slip stream of natural gas with extracted compressor oxidant. The work confirmed that FGR has the potential to significantly reduce the energy penalty connected with postcombustion carbon capture techniques and still meet the requirements on NOx and CO emissions.

Combustion of methane, ethane and propane and of mixtures of methane with ethane or propane on Pd/γ-Al2O3 catalysts

The influence of adding ethane or propane in the feed during catalytic combustion of methane on Pd(2 wt.%)/γ-Al 2 O 3 catalyst was investigated. The addition of ethane or propane inhibits the ignition of methane. Palladium particles sinter during reaction. Palladium seems to be slightly less oxidized in presence of ethane or propane. Catalytic combustion of methane on a Pd(2 wt.%)/γ-Al 2 O 3 catalyst (♢, dotted line). Effect of the addition of increasing concentrations of ethane (500 (♦), 1000 (■), 1500 (▴) and 2000 ppm (●)) on the conversion of methane (solid lines). In a first step, the catalytic combustion of methane, ethane and propane on a Pd(2 wt.%)/γ-Al 2 O 3 catalyst was investigated. The order of reactivity of these three gases is propane > ethane > methane. In a second step, the influence of adding ethane or propane in the feed during the catalytic combustion of methane was studied. At low temperature, the addition of ethane or propane inhibits the ignition of methane. This inhibition could be explained by a competition for the surface oxygen species on the surface of palladium. At high temperature, the same competitive effect would explain the inhibition observed at high ethane concentration. In the presence of propane, a thermal effect seems to have an important role. This effect is minor in the presence of ethane. In all cases, palladium particles sinter during reaction and their surface is more oxidized after test than before running the reaction. However, when ethane or propane is added in the methane feed, palladium seems to be slightly less oxidized than in the presence of pure methane. In this last case the sintering effect seems to be more pronounced. The migration of oxygen species from the bulk seems to play an important role in the oxidation of palladium. These results support previous studies using H 2 -assisted methane combustion. Implications of the presence of ethane and propane in the combustion of natural gas are also discussed.

Measurement of Carbon Dioxide Freezing in Mixtures of Methane, Ethane, and Nitrogen in the Solid−Vapor Equilibrium Region

A non-sampling visual observation technique was used to measure solid−vapor equilibria of carbon dioxide in mixtures of light natural gas constituents. Frost points for the carbon dioxide + methane binary were determined for mixtures containing 1.00 %, 1.91 %, and 2.93 % moles of carbon dioxide at pressures ranging from (962.1 to 3008.2) kPa and temperatures ranging from (168.6 to 187.7) K. The addition of ethane and nitrogen to the carbon dioxide + methane binary system was also examined while keeping the carbon dioxide composition constant to determine the effect on the frost point.

Double Conjugate Addition of Dithiols to Propargylic Carbonyl Systems To Generate Protected 1,3-Dicarbonyl Compounds

The work describes the efficient double conjugate addition of ethane and propane dithiols in the presence of sodium methoxide to a wide variety of propargylic carbonyl containing compounds. The products of these reactions are differentiated, 1,3-dicarbonyl systems useful for various synthesis programs. By judicious use of hydroxylated substrates tandem cyclization occurs to afford tetrahydropyran lactols or, in the case of hydroxy-substituted propargylic esters, lactones. The corresponding amino-substituted propargylic aldehydes gives piperidine derivatives upon double conjugate addition tandem cyclization.

DRIFTS study of the nature and chemical reactivity of gallium ions in Ga/ZSM-5: II. Oxidation of reduced Ga species in ZSM-5 by nitrous oxide or water

The oxidation of reduced Ga species in ZSM-5 zeolite modified via anchoring of trimethyl gallium or by incipient wetness impregnation with a solution of gallium nitrate was studied. Reduction of such materials in hydrogen and evacuation at high temperature resulted in quantitative replacement of the Brønsted acidic protons by Ga + ions. However, the extent of dealumination of the material prepared by incipient wetness impregnation was higher. Oxidation of univalent gallium species by nitrous oxide at 673 K by either preparation method led to the quantitative formation of charge-compensating [Ga 3+(O 2−)] + fragments. Ga + ions can also be oxidized at 573 K by water vapor, whereupon approximately 25% of the Ga + ions are transformed into [GaO] + with concomitant release of molecular hydrogen. Dissociative chemisorption of molecular hydrogen via oxidative addition of hydrogen atoms to Ga + cations at 773 K resulted in the formation of gallium dihydride species, which are very stable and are decomposed only in vacuum above 673 K. Oxidation of such [Ga 3+(H −) 2] + cations by N 2O at 573 K gave positively charged [Ga 3+(H −)(OH) −] + species. At higher temperature (673 K), the latter are further oxidized by nitrous oxide, giving neutral GaOOH species and Brønsted acidic protons. The similarity of infrared spectra of ethane adsorbed on Ga/ZSM-5 and HZSM-5 at 298 K indicates weak polarization of ethane molecules by Ga + cations. However, oxidative addition of ethane at 523 K led to the formation of [Ga 3+(H −)(C 2 H 5 − )] + species. Above 573 K the grafted ethyl fragments decomposed to gallium hydride species and ethylene. Indications were also found for subsequent oligomerization and aromatization of the resulting olefin.