Ternary Gas Mixtures Research Articles

ISOCONCENTRATION DISTRIBUTIONS OF COMPONENTS IN TERNARY GAS MIXTURES IN THE PRESENCE OF SPECIAL DIFFUSION MIXING MODES

The features of the formation of convective flows arising in three-component gas mixtures in the presence of special diffusion mixing regimes are investigated. The time variation of the isoconcentration lines of the heavy component of the mixture and the average kinetic energy are consideredas characteristics of convective flows. A numerical model based on the splitting scheme in physical parameters is used to calculate the characteristics of convective flows arising in a vertical cylindrical channel. It is shown that nonmonotonic distributions of component concentrations and kinetic energy can occur in ternary gas mixtures, where special diffusion regimes are manifested. The time of stability loss of the mechanical equilibrium of the mixture and the time of developed convective flows are determined.

CONVECTIVE MIXING IN AN INCLINED CHANNEL CAUSED BY TERNARY DIFFUSION UNDER CONDITION OF INCREASING DENSITY OF THE MIXTURE WITH HEIGHT

Using methods of numerical simulation, we studied the quasi-stationary mass transfer of isothermal ternary gas mixtures in the vertical and inclined channels for the zone of flow exit from a given channel into the lower flask of a diffusion cell. Convective mixing is considered under conditions involving an increase in the density of the mixture with the height of the channel. The characteristic features of structured flows were studied at a certain content of the component with the highest molecular weight in the mixture. The convective formations in the vertical and inclined channels are compared. The dynamics of structured convective flows at various inclination angles is analysed. Estimates of the lifetime of a structural formation consisting mainly of the component with the highest molecular weight moving in a gas mixture with a lower density value are given.

Electron swarm coefficients and critical field strength of the gaseous ternary mixtures CF3I-SF6-N2 and CF3I-SF6-CO2

The electron drift velocity, longitudinal diffusion and effective ionization coefficients in the gaseous ternary mixtures CF3I-SF6-N2 and CF3I-SF6-CO2 have been measured using a pulsed Townsend apparatus over the density-normalized electric field intensity, E/N, from 230 to 470 Td and 230 to 430 Td, respectively (1 Td = 10−17 V cm2). Several ternary gas mixture compositions containing 10% to 50% CF3I or SF6 and either N2 or CO2 have been studied. Also, we have measured the critical field strength, E/Ncrit, for all of these gaseous mixtures, finding out that the 40% CF3I–40% SF6–20% N2 and 40% CF3I–40% SF6–20% CO2 have an E/Ncrit value smaller by only 4.0% and 1.0%, respectively than that of pure SF6 (360 Td). Provided that both CF3I, CO2 and N2 are environmentally friendly, its addition to SF6 may be highly advantageous over other binary SF6 mixtures with gases having relatively high warming potentials, since these mixtures have only 40% SF6 and behave, from the swarm physics point of view as good candidates to ameliorate impact of SF6 when released into the atmosphere. An interesting synergetic effect has been found for the CF3I-SF6 mixture when N2 added and has been interpreted in terms of the efficient low-energy electron scattering of N2 at low collision energies up to 2 eV.

Investigation of the performance of CF3I/c-C4F8/N2 and CF3I/c-C4F8/CO2 gas mixtures from electron transport parameters

CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas, owing to their excellent insulating performance. This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis, compared with SF6 gas mixtures. The results confirm that the critical electric field strength of CF3I/c-C4F8/70 % CO2 is greater than that of 30% SF6/70% CO2 when the CF3I content is greater than 17%. Moreover, a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field, and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures. The synergistic effects for CF3I/c-C4F8/70 % N2 were most obvious when the c-C4F8 content was approximately 20%, and for CF3I/c-C4F8/70 % CO2 when the c-C4F8 content was approximately 10%. On the basis of this research, CF3I/c-C4F8/70 % N2 shows better insulation performance when the c-C4F8 content is in the 15%–20% range. For CF3I/c-C4F8/70 % CO2, when the c-C4F8 content is in the 10%–15% range, the gas mixtures have excellent performance. Hence, these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.

Cyclic Detonation of the Ternary Gas Mixture Propane–Oxygen–Steam for Producing Highly Superheated Steam

Systematic experiments were performed on an innovative pulse detonation steam superheater (PDSS) for determining the concentration limits of detonation of the ternary mixtures propane–oxygen–steam at normal atmospheric pressure. The experiments were carried out while varying the fuel–oxygen equivalence ratio (from 0.3 to 1.7) and the volume fraction of steam (from 0 to 0.7). Cyclic detonation of ternary mixtures was shown to be able to create a high-temperature gas medium that has a temperature above 2250 K and contains to 80% highly superheated steam and to 20% CO2, and also CO, O2, and H2 at low concentrations at atmospheric pressure. Such medium was proposed to be used for advanced treatment of household and industrial organic waste to produce a gas mixture of CO and H2. Because the filling of PDSS with the “cold” ternary gas mixture is periodic, the increase in the temperature of its walls and internals is insignificant, and PDSS can be built from conventional (not necessarily refractory) construction materials.

On-Line Mixture Quantification to Track Temporal Change of Composition Using FAIMS.

This paper reports on-line mixture quantification with FAIMS. Ternary gas mixtures composed of acetone, ethanol, and diethyl ether were used for quantification. We succeeded in an on-line quantification of ppm-level concentration and even sub-ppm-level gases using the gradient descent method. It took 10 minutes to quantify the ternary mixture. However, it was too long, because we aim to track the temporal change of each component concentration in the mixture. Then, an algorithm based on feedback control was introduced to reduce the quantification time. The feedback method successfully tracked concentrations in three cases. The simulation result shows that the proposed method can reduce the quantification time.

Hydrate Phase Equilibrium of CH4-Rich Binary and Ternary Gas Mixtures in the Presence of Tetra-n-butyl Ammonium Bromide

In this work, binary gas mixtures of 92 mol % CH4/CO2 and ternary gas mixtures of 87 mol % CH4/5 mol % C2H6/CO2 were studied as simulate associated petroleum gas. It mainly consists of two parts: o...

An experimental study of the density of the helium – neon – nitrogen gas system at low temperatures

An experimental installation has been created at the Department of TOT to measure the density of ternary gas mixtures from 100 to 300 K and pressures up to 16 MPa. The experimental density for the He–Ne–N2 system is determined by the constant volume piezometer method. The amount of substance in the piezometer is measured by the volumetric method. He–Ne–N2 mixtures are prepared in a special mixer at 20°C for the p-v-T series of experiments, the concentrations are calculated using the equations of state of pure components. In the experiment, 3 mixtures were prepared, which had mole concentrations: (xHe = 0.24; xN2 = 0.17), (xHe = 0.33; xN2 = 0.34), (xHe = 0.16; xN2 = 0.60). 70 experimental points on 7 isotherms were obtained.

Effect of the Channel Inclination Angle on Convective Mixing Caused by Instability of Mechanical Equilibrium of Ternary Gas Mixture at Isothermal Diffusion

The peculiarities of a convective regime aroused due to instability of mechanical equilibrium of a ternary helium–argon–nitrogen gas mixture at isothermal diffusion are experimentally investigated. The effect of the inclination angle of diffusion channel on the intensity of convective flows is considered. The intensity of the partial transport of components in the inclined channel was measured at increased pressures. The nonlinear dependence of the mixing rate of components on the inclination angle is discovered. It is established that the observed transport of components atypical for diffusion is possible at a certain composition of the gas mixture.

CO2 removal from synthesized ternary gas mixtures used hydrate formation with sodium dodecyl sulfate(SDS) as additive

In order to investigate the hydrate formation kinetics of the ternary gas mixtures containing sodium dodecyl sulfate (SDS) and evaluate the applicability of hydrate based gas separation (HBGS) technology to biogas, synthesized ternary gas mixture (CH4/CO2N2) hydrate formation processes with different concentrations of SDS were investigated comprehensively in this work. The changes in the gas composition during the hydrate formation process, the gas consumption of the hydrate, the effective reaction time, the recovery factor of CH4, the split ratio of CO2, and the microscopic promotion mechanism of SDS for the hydrate were studied. The results indicated that the addition of SDS increased the hydrate reaction rate and gas consumption compared with those in a pure water system. The promotional effect of SDS improved with an increase in its concentration. The maximum CO2 split ratio was 0.95, at a driving force of 4.4 MPa and 0.05% SDS concentration. The maximum CH4 recovery factor was 3.18, at a driving force of 6.4 MPa and 0.03% SDS concentration. SDS promoted the formation of CO2 hydrate more strongly than that of CH4 and N2 for the ternary gas mixture. In summary, HBGS technology exhibited a good separation effect under two experimental conditions.

Versatile Paschen's model for the dielectric strength estimation of binary and ternary gas mixtures

The dielectric strength of various binary and ternary gas mixtures is accurately estimated by using the proposed versatile Paschen's model. Unlike the conventional Paschen's models, the new model is based on the improved regression process of the ionization coefficients that results in enhanced accuracy in the dielectric strength estimations of pure gases as well as binary and ternary gas mixtures. Compared to the conventional models, the dielectric strength values estimated by the proposed model and the experimental breakdown measurements show more close and consistent agreement. The results confirm the effectiveness, versatility, and veracity of the proposed Paschen's model in estimating the dielectric strength of gas media.

Experimental Installation used for Preparation of Breathing Mixtures Needed for Professional Diving

Starting from the mathematical modelling of the gas dynamics processes and, of course, from the needs of the Diving Center, several schemes of experimental installations were developed. These schemes are used for the preparation of binary or ternary gas mixtures, specific: for autonomous professional diving, for the system diving, respectively for those simulated or real which are performed in the hyperbaric chambers of the Diving Center or in the diving turrets.The principle of preparing breathing gas mixtures in the experimental installation ensures that an invariable flow rate (with the pressure of the gaseous mixture from a pressurized cylinder) is injected (constant mass flow) while ensuring the permanent control of this flow. The installation delivers an invariable gas mixture flow regardless of the gas pressure value inside the storage cylinder.Depending on the number of components from which the binary or ternary breathable mixture is to be prepared, the design of the plant has been structured in two parts or in the case of a more complex ternary structure of the gaseous mixture, the plant has three distribution-injection lines active. Each of these lines independently carries the three pure component gases used to continuously produce the required respiratory mixture.Finally, the tests of the gas-dynamical processes related to the plant were presented very succinctly, following a comprehensive testing and evaluation plan in the summer of last year.

Ternary Gas Mixture Quantification Using Field Asymmetric Ion Mobility Spectrometry (FAIMS).

Gas mixture quantification is essential for the recording and reproducing odors, because an odor consists of multiple chemical compounds. Gas mixture quantification using field asymmetric ion mobility spectrometry (FAIMS) was studied. Acetone, ethanol, and diethyl ether were selected as components of a ternary gas mixture sample as representatives of the ketone, alcohol, and ether chemical classes, respectively. One hundred and twenty-five points with different concentrations were measured. The results were evaluated by error hypersurface, variance, and the coefficient of variation. The error hypersurface showed that it is possible to reach the target composition by following the error-hypersurface gradient. Successful convergence was achieved with the gradient descent method in a simulation based on the measurement data. This result verified the feasibility of the quantification of a gas mixture using FAIMS.

Boundary slip phenomena in multicomponent gas mixtures

The slip phenomena in multicomponent gas mixtures are studied. The moment equations, derived from the linearized Boltzmann equation by using the 13-moment approximation of the Grad’s method, are used to obtain the full (containing the contribution from the Knudsen layer) and asymptotic (valid far from the plane physical boundary of the domain) expressions for the nonequilibrium macroscopic parameters of the mixture species. The latter relations are employed to deduce the expressions for the mixture slip velocity and the viscous, thermal, and diffusion slip coefficients by using the modified Maxwell method and the diffuse-specular model of molecule scattering on the wall. The derived relations for the slip coefficients are given in the convenient form expressed in terms of basic transport coefficients, such as partial viscosity and thermal conductivity coefficients, diffusion and thermal diffusion coefficients, and coefficients of molecule momentum accommodation at the wall. The expressions found are used to calculate the slip coefficients for binary (He-Ar) and ternary (He-Ar-Xe) gas mixtures. The numerical results are in good agreement with the data calculated by using other methods.

Improved CO2 recovery from flue gas by layered bed Vacuum Swing Adsorption (VSA)

Performance of a two column five-step vacuum swing adsorption cycle is tested for CO2 enrichment and recovery from a simulated ternary flue gas mixture containing 13% CO2, 82% N2, and balance O2. The results are compared when a layered bed of commercial activated carbon (AC) (F-400, Calgon) and 13X zeolite (Z10-04, Zeochem) is employed with reference to an only single layer of AC and 13X adsorbent. With the layered bed, in which the first layer at the feed entry end is AC followed by 13X, the CO2 recovery obtained is 84% which is 42% more than that of pure 13X bed and the purity of CO2 is almost at the same level as that with 13X bed (∼90 mol%). The VSA is compared at same adsorption time, set as a 70% of CO2 breakthrough time. The CO2 purity obtained with the activated carbon bed was 76 mol% which is considerably lower compared to the bed with only zeolite 13X layer (90 mol%). The result can be explained due to higher CO2/N2 selectivity of the zeolite than activated carbon. The recovery of CO2 with activated carbon is, however, higher (97%) than zeolite (59%) due to its lower heat of CO2 adsorption compared to that with 13X. The lower heat of CO2 adsorption on the activated carbon surface implies weaker interaction and thus better desorption characteristics than 13X. VSA performance of the layered bed are also compared under different adsorption/evacuation time, bed temperature and evacuation level.

Reactive sputtering deposition of plasma polymerized nylon films with embedded NHx groups

Reactive magnetron sputtering deposition of plasma polymer film enriched by nitrogen-containing functional groups (NCFGs) was investigated. The main goal of our research is to obtain plasma polymerized nylon films prepared by rf magnetron sputtering with embedded –NHx functional groups in its volume. Those films can be used as “storage environment” for many chemical substances (for example, antibiotics) that need the presence of chemical grafts. Films were prepared in ternary process gas mixture of Ar (carrier gas), and N2:C2H2 (reactive component). We found that a small amount of acetylene added in the process gas results in an increased amount of NCFGs while keeping the deposited film stable in aqueous environments. However, an enhanced amount of acetylene in the process gas, above some certain limit, causes target poisoning and suppression of the nylon sputtering which practically results in the conversion of the deposition process to PECVD. When the deposition was done in a reactive atmosphere only (N2:C2H2), the required optimum flow of acetylene to incorporate maximum NCFGs into the film volume raised, but it had a negative effect on the film stability in water.

Quantitative analysis of SO2, H2S and CS2 mixed gases based on ultraviolet differential absorption spectrometry.

SO2, H2S and CS2 are the decomposition components of insulating gas SF6. The detection of these gases is significant for the online monitoring and fault diagnosis of SF6 electrical equipment. In this study, an ultraviolet differential optical absorption spectrometry (UV-DOAS) platform for detecting the concentration of SO2, H2S and CS2 mixed gases was established and a quantitatively detecting method was proposed. Firstly, the concentration of SO2 was calculated by the spectrum data at 300 nm band. Then the gas mixture spectra of H2S and CS2 at 200 nm band were obtained after linear deduction of SO2 spectrum. By wavelet extraction and fourier transform, the spectral information of H2S and CS2 was separated and the concentrations of the two gases were calculated. The method can detect the concentrations of SO2 (1-20 ppm), H2S (1-20 ppm) and CS2 (0.01-2 ppm) ternary gas mixture and the detection limits of SO2, H2S and CS2 are 0.44 ppm, 0.49 ppm and 3.23 ppb. This method has good detection sensitivity and high detection precision, which is suitable for the on-line monitoring of SF6 gas insulated equipment.

Influence of N₂ on Formation Conditions and Guest Distribution of Mixed CO₂ + CH₄ Gas Hydrates.

In this contribution, a method based on a solid solution theory of clathrate hydrate for multiple cage occupancy, host lattice relaxation, and guest-guest interactions is presented to estimate hydrate formation conditions of binary and ternary gas mixtures. We performed molecular modeling of the structure, guest distribution, and hydrate formation conditions for the CO2 + CH4 and CO2 + CH4 + N2 gas hydrates. In all considered systems with and without N2, at high and medium content of CO2 in the gas phase, we found that CO2 was more favorable in occupying clathrate hydrate cavities than CH4 or N2. The addition of N2 to the gas phase increased the ratio concentration of CO2 in comparison with the concentration of CH4 in clathrate hydrates and made gas replacement more effective. The mole fraction of CO2 in the CO2 + CH4 + N2 gas hydrate rapidly increased with the growth of its content in the gas phase, and the formation pressure of the CO2 + CH4 + N2 gas hydrate rose in comparison to the formation pressure of the CO2 + CH4 gas hydrate. The obtained results agreed with the known experimental data for simple CH4 and CO2 gas hydrates and the mixed CO2 + CH4 gas hydrate.

Comparison of swarm and breakdown data in mixtures of nitrogen, carbon dioxide, argon and oxygen

Mixtures of atmospheric gases such as , , and Ar are seen as possible insulation gases in high-voltage equipment, both with and without the admixture of a fluorinated gas such as the C4F7N nitrile or C5F10O ketone. Therefore, the binary gas mixtures –, – and –, as well as some selected ternary gas mixtures, were measured with a pulsed Townsend experiment and a breakdown experiment. In order to compare the experimental results, the breakdown voltage was estimated applying the streamer criterion to the effective ionization coefficient obtained with a pulsed Townsend experiment. The comparison shows a very good agreement between the two methods, which implies that it is possible to predict the electric strength of atmospheric gases in homogeneous electric fields over a wide pd range (product of vessel pressure p and electrode gap separation d) from swarm parameters only. Our results show that an admixture of 5% to – mixtures increases the breakdown voltage by 1%–2% in the measured pd range compared to the basis gas mixture. –– mixtures with an concentration between 40% and 80% and 5% of show an increased breakdown strength of around 8% compared to synthetic air (i.e. – 80%:20%) without .

The dielectric strength of dissociated cryogenic gas media

The dielectric strength of dissociated binary and ternary gas mixtures containing helium, hydrogen, and nitrogen for cryogenic power applications is reported. The compositions of the dissociated gas species in the temperature range of 77–5000 K at 1.0–2.0 MPa are obtained by minimizing the Gibbs free energy assuming local chemical equilibrium. The resulting mole fractions of the dissociated gas species that vary as a function of temperature and pressure are used for calculating the density-reduced critical electric field representing the dielectric strength. The results suggest that the He-H2-N2 mixture has higher dielectric strength than the He-H2 and He-N2 mixtures, but NH3 would potentially accumulate over multiple arcing and cooling cycles and potentially cause long-term issues in cryogenic switchgear applications. On the other hand, the binary alternatives, the He-H2 and He-N2 mixtures, show lower dielectric strength than the ternary gas mixture but will maintain their original gas properties even over multiple arcing and cooling cycles. The results also show that the dielectric strength of the He-H2-N2 and He-H2 mixtures decreases substantially with increasing temperature whereas that of the He-N2 mixture stays nearly unchanged. The results of this study are useful for the fundamental understanding of gas dielectrics under arcing conditions in cryogenic switchgear applications and the development of resilient cryogenic power systems.