Gas Bath Research Articles

Recovery of Multicomponent Shale Gas from Single Nanopores

The adsorption of multicomponent gas mixtures in shale formations and their recovery are of great interest to the shale gas industry. Here we report molecular dynamics simulations of the adsorption of methane/ethane mixtures in 2 and 4 nm-wide nanopores and their recovery from these nanopores. Surface adsorption contributes significantly to the storage of methane and ethane inside the pores, and ethane is enriched inside the nanopores in equilibrium with bulk methane–ethane mixtures. The enrichment of ethane is enhanced as the pore is narrowed but is weakened as the pressure increases due to entropic effects. These effects are captured by the ideal adsorbed solution (IAS) theory, but the theory overestimates the adsorption of both gases. Upon opening the mouth of the nanopores to gas baths with lower pressure, both gases enter the bath. The production rates of both gases show only weak deviation from the square root scaling law before the gas diffusion front reaches the dead end of the pores. The ratio of...

Simultaneous Visualization of Hydrogen Peroxide and Water Concentrations Using Photofragmentation Laser-Induced Fluorescence

A concept based on photofragmentation laser-induced fluorescence (PFLIF) is for the first time demonstrated for simultaneous detection of hydrogen peroxide (H2O2) and water (H2O) vapor in various mixtures containing the two constituents in a bath of argon gas. A photolysis laser pulse at 248 nm dissociates H2O2 into OH fragments, whereupon a probe pulse, delayed 100 ns and tuned to an absorption line in the A2Σ+ (v = 1) ← X2Π(v = 0) band of OH near 282 nm, induces fluorescence. The total OH fluorescence reflects the H2O2 concentration, while its spectral shape is utilized to determine the H2O concentration via a model predicting the ratio between the fluorescence intensities of the A2Σ+ (v = 1) → X2Π(v = 1) and the A2Σ+ (v = 0) → X2Π(v = 0) bands. The H2O detection scheme requires that the bath gas has a collisional cross-section with OH(A) that is significantly lower than that of H2O, which is the case for argon. Spectrally dispersed OH fluorescence spectra were recorded for five different H2O2/H2O/Ar mixtures; the H2O2 concentration in the range of 30-500 ppm and the H2O concentration in the range of 0-3%. Fluorescence intensity ratios predicted by the model for these mixtures agree very well with corresponding experimental data, which thus validates the model. The concept was also demonstrated for two-dimensional imaging, using two intensified charge-coupled device (CCD) cameras for signal detection. Water content was here sensed through the different temporal characteristics of the two fluorescence bands by triggering the two cameras so that one captures the total OH fluorescence while the other one captures only the early part, which mainly stems from A2Σ+ (v = 1) → X2Π(v = 1) fluorescence. Hence, the H2O2 concentration is reflected by the image of the camera recording the total OH fluorescence, whereas H2O concentration is extracted from the ratio between the two camera images. Quantification of the concentrations was carried out based on calibration measurements performed in known mixtures of H2O2 (30-500 ppm) and H2O (0-3%) in bulk argon. The detection limits for single-shot imaging are estimated to be 20 ppm for H2O2 and 0.05% for H2O. The authors believe that the concept provides a valuable asset in, for example, pharmaceutical or aseptic food packaging applications, where H2O2/H2O vapor is routinely used for sterilization.

High Pressure Shock Tube Ignition Delay Time Measurements During Oxy-Methane Combustion With High Levels of CO2 Dilution

Ignition delay times and methane species time-histories were measured for methane/O2 mixtures in a high CO2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 6 and 31 atm. The test mixtures were at an equivalence ratio of 1 with CH4 mole fractions ranging from 3.5% to 5% and up to 85% CO2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (gri 3.0 and aramco mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against measured ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into account the different parameters showing the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane/CO2/O2 under these conditions. Current data provides crucial validation data needed for the development of future kinetic mechanisms.

Size analysis of slag eye formed by gas blowing in ladle refining

The formation of slag eye in a gas stirred ladle was studied through cold models and industrial trials. In the cold model, water and sodium tungstate solution were employed to simulate liquid steel, and silicon oil was employed to simulate slag. The simulation results revealed that the gas flow rate and bath height had strong effects on the slag eye size. In particular, the thickness of slag layer played a strong role in the slag eye size. In addition, the slag eye could not be formed when the thickness of the top layer was more than 4 cm in water-silicone oil model. Besides, the section area of vessel had a great impact on the slag eye size. Industrial trials results showed a similar trend that the gas flow rate was very significant on the slag eye size. The predictions of the existing models showed larger predictions deviations compared with the experimental data. Moreover, a new model without fitting parameters was developed based on force balance and mathematical derivation, and verified by the experimental data. The new model provides the prediction with small deviations by comparing with the data acquired from cold models and industrial trials.

Properties of CrC+(Ni-W) Duplex Layers Produced in Vacuum Chromizing Process Combined With Galvanic Treatment

Abstract Diffusion chromizing was applied to increase the durability of tools, which operate under wear conditions. Vacuum chromizing, as opposed to other known methods, i.e., powder pack, gas, and molten salt baths, is ecological on account of non-toxic substrates, as well as absence of harmful wastes. Vacuum chromizing of tool steel results in hard and wear resistant chromium carbide coatings. However, the obtained carbide layers exhibited rather poor corrosion resistance in chloride media. To improve their corrosion resistance, Ni-W alloy was deposited electrolytically on the steel surface before the chromizing process. This resulted in the formation of CrC+(Ni-W) type duplex layers with modified characteristics. The objective of this paper was to determine the structure of these duplex layers on tool steel surface, their tribological properties and corrosion resistance in chloride solutions. Investigations of layers’ thickness, their morphology, phase composition, hardness, and depth profiles of elements in the layer diffusion zone have been carried out. The chemical composition and distribution of the phases formed in the surface region of the samples were examined by a SEM microscope, equipped with a BSE detector and an EDS spectrometer. Wear resistance tests were carried out by the three-cylinder-cone method. Electrochemical corrosion measurements of obtained layers were performed in a 0.5 M NaCl solution. The tests proved that the wear resistance of duplex layers of the CrC+(Ni-W) type, produced by vacuum chromizing of electrolytically coated steel, is as good as that of carbide layers of the CrC type, produced on bare steel surface, but their corrosion resistance is higher.

Electrochemical CO2 Reduction in Ionic Liquid Using Two Compartment Cell Separated with Proton-Conducting Membrane

Electrochemical conversion of CO2 to CH4 using EMIM-TFSI ionic liquid bath was investigated. EMIM-TFSI can absorb much CO2 gas and thus used as an electrolyte solution. To maximize conversion efficiency, two compartment cell was developed in which ionic liquid bath containing Cu mesh working electrode bubbled with CO2 gas and KCl aqueous solution bath containing counter electrode were separated by proton conducting Nafion membrane. Suitable condition of water content in the ionic liquid bath and polarization potential for efficient conversion was investigated by using gas chromatography. Spatial arrangement working electrode and membrane was also shown to be an important factor for efficient conversion from CO2 to CH4.

Ozone Gas Bath Combined with Endovenous Laser Therapy for Lower Limb Venous Ulcers: A Randomized Clinical Trial

ABSTRACTBackground: Endovenous laser therapy (EVLT) is safe and effective for lower limb venous ulcers. However, severe necrosis and infection in the ulcer area are contraindications of puncture and EVLT. Local bath with ozone gas has been shown to improve the condition of ulcer areas. The aim of this study was to evaluate the clinical efficacy of ozone gas bath combined with EVLT in comparison with EVLT alone for the treatment for lower limb venous ulcers. Patients and Methods: Ninety-two patients with venous ulcers were randomized to receive ozone gas bath combined with EVLT (OEVLT group) or EVLT alone (EVLT group). In the OEVLT group, the venous ulcers were preconditioned with ozone gas bath prior to EVLT. The minimum follow-up time was 12 months. The two groups were compared in terms of complete occlusion of the treated veins, ulcer healing ratio, ratio of ulcer recurrence, patient satisfaction, complications, and side effects. Results: There was no significant difference in venous occlusion between the two groups. The ratio of ulcer healing in the OEVLT group was significantly higher than the EVLT group at 12 months follow-up. Patients in the OEVLT group showed better satisfaction and a lower recurrence ratio than the OEVLT group. No severe complications or side effects occurred in either groups. Conclusions: Ozone gas bath combined with EVLT showed improved efficacy for the treatment of lower limb venous ulcers and lower recurrence ratio comparison with EVLT alone. This procedure is a safe and technically feasible.

Damage Mechanisms of Plasma, Gas and Salt Bath Nitrocarburized Steel in Lab-Scale Sliding Test

Nitrocarburized steel surfaces are often used in tribological forming applications due to their beneficial sliding properties. One typical application field can be found in bending machines where the nitrocarburized layer can withstand massive volume loss and prevent from adhesion of the work sheet material. However, under non-lubricated sliding conditions abrupt failure of the nitrocarburized layer can occur, which results in pronounced increase of friction and wear. In order to characterise the wear mechanisms of nitrocarburized surfaces under non-lubricated sliding conditions, a lab-scale study was carried out. Different nitrocarburizing processes including plasma, gas and salt bath nitrocarburizing were investigated. Oscillating sliding tests with DIN 100Cr6 bearing steel cylinder sliding against nitrocarburized plate were performed at contact pressures typical for bending machines. Evaluation of wear was performed by white-light interferometer with measurements of the wear-scar topography and a subsequent calculation of the average wear depth. A strong influence of the nitrocarburizing process on friction and wear behaviour was observed. This behaviour could be correlated with the microstructure of the compound layer.

Numerical Simulation of an Argon Stirred Ladle with Top and Bottom Injection

The stirring of a molten steel ladle with argon injection through a top submerged lance and a bottom nozzle is numerically studied here through Computational Fluid Dynamics (CFD) simulations. Three lance submergence depths and three injection velocities are considered in the CFD numerical experiments. The turbulent dissipation rate is employed to characterize the stirring phenomenon. The mixing times are determined from the gas flow rate, ladle geometry and bath depth using an empirical correlation.

Mixing Phenomena in a Bottom Blown Copper Smelter: A Water Model Study

The first commercial bottom blown oxygen copper smelting furnace has been installed and operated at Dongying Fangyuan Nonferrous Metals since 2008. Significant advantages have been demonstrated in this technology mainly due to its bottom blown oxygen-enriched gas. In this study, a scaled-down 1:12 model was set up to simulate the flow behavior for understanding the mixing phenomena in the furnace. A single lance was used in the present study for gas blowing to establish a reliable research technique and quantitative characterisation of the mixing behavior. Operating parameters such as horizontal distance from the blowing lance, detector depth, bath height, and gas flow rate were adjusted to investigate the mixing time under different conditions. It was found that when the horizontal distance between the lance and detector is within an effective stirring range, the mixing time decreases slightly with increasing the horizontal distance. Outside this range, the mixing time was found to increase with increasing the horizontal distance and it is more significant on the surface. The mixing time always decreases with increasing gas flow rate and bath height. An empirical relationship of mixing time as functions of gas flow rate and bath height has been established first time for the horizontal bottom blowing furnace.

Measuring Gaussian noise using a lock-in amplifier

Gaussian fluctuations (or Gaussian noise) appear in almost all measurements in physics. Here, a concise and self-contained introduction to thermal Gaussian noise is presented. Our analysis in the frequency domain centers on thermal fluctuations of the position of a particle bound in a one-dimensional harmonic potential, which in this case is a microcantilever immersed in a bath of room-temperature gas. Position fluctuations of the microcantilever, detected by the optical beam deflection technique, are then fed into a lock-in amplifier to measure the probability distribution and spectral properties of the fluctuations. The lock-in amplifier measurement is designed to emphasize the frequency-domain properties of Gaussian noise. The discussion here can be complementary to a discussion of Gaussian fluctuations in the time domain.

Theoretical and experimental study of measuring gas temperature in vacuum environment using tunable diode laser absorption spectroscopy

Measuring the temperature in vacuum environment is more complex than in atmospheric environment. For example, high vacuum will cause the thermocouple sensor surface desorption, and the mechanism of heat transfer is also different. Therefore, there are some uncertainties if the thermocouple is used to measure the gas temperature in vacuum condition. In the present paper, tunable diode laser absorption spectroscopy (TDLAS) is employed to measure the gas temperature and also explore the application prospect of TDLAS temperature measurement technology in vacuum environment. During the thermal vacuum experiments, the vacuum gas cell is immersed in the thermostatic bath, and the gas temperature is determined by TDLAS. Meanwhile, a standard Pt-resistance is used to measure the thermostatic bath temperature. The results show that the temperatures of the gas and thermostatic bath are highly consistent with each other, and the difference between the two temperatures is less than 0.2 ℃ when the thermostatic bath is stable.

Relative rate coefficients of OH radical reactions with CF3CF[dbnd]CClCF3 and CF3CH[dbnd]CHCH2OH. Ozone depletion potential estimate for CF3CF[dbnd]CClCF3

The relative rate method was used to determine the rate coefficients for the reactions of OH radicals with CF3CFCClCF3 (k1) and CF3CHCHCH2OH (k2). Experiments were carried out at (298 ± 2) K and atmospheric pressure using ultra pure air or ultra pure nitrogen as the gas bath. The k1 value was measured relative to those of chloroethane and ethane, and the k2 value was measured relative to those of cyclohexene and 1-pentene. The following rate coefficients were derived in units of cm3 molecule−1 s−1: k1 = (3.3 ± 0.9) × 10−13 and k2 = (3.3 ± 0.9) × 10−11. This is the first experimental determination of k1 and k2. The rate coefficients were used to estimate the atmospheric lifetimes for the studied haloalkenes considering the OH-initiated oxidation process. The ozone depletion potential (ODP) for CF3CFCClCF3 was estimated following a recently-developed technique based on Lagrangian trajectories, which takes into account the time and location of the release of the short-lived halogenated species.

Métodos de abate e qualidade da carne de peixe

Apesar do abate ser um dos maiores fatores de estresse na produção de animais, não existe neste âmbito, legislação específica para os peixes no Brasil. Os métodos de abate ou atordoamento mais utilizados são a imersão em água e gelo, asfixia no ar, eletricidade, narcose por gases e atordoamento percussivo. No entanto, o abate ideal é aquele procedimento que considera o bem estar animal e a qualidade da carne. O estresse perimortem pode levar a uma situação de pânico, medo e fuga fazendo com que os peixes utilizem suas reservas energéticas, diminuindo os teores de glicose e ATP post mortem e conseqüentemente o encurtamento do tempo de rigor mortis, e reduzindo o pH muscular. Essas reações também promovem mudanças indesejáveis nas características sensoriais como cor e textura do pescado, além de facilitar o desenvolvimento de micro- organismos deteriorantes, diminuindo a vida de prateleira. De maneira geral, observa-se que os métodos de atordoamento/abate por choque elétrico, percussão craniana e super dosagem de anestésico, quando aplicados de maneira correta, causam pouco sofrimento e melhor qualidade da carne. Os abates de peixes por asfixia no ar ou com gelo, choque térmico, narcose com gases e banho de sal, com exceção de alguns casos, causam muito estresse e piora na qualidade da carne. De acordo com a revisão bibliográfica observa-se que não é possível fazer reco-mendação de uma única metodologia de abate a ser empregada nas varias espécies de peixes, sendo assim necessário ampliar as pesquisas nesta área de maneira a determinar melhores técnicas de abate, visando à diminuição do sofrimento e obtendo desta maneira um produto ético de qualidade superior. Este trabalho foi elaborado com o objetivo de revisar os trabalhos mais recentemente publicados sobre o efeito dos diferentes métodos do abate sobre o estresse e a qualidade do pescado.

Effects of nitrocarburizing on fatigue property of medium carbon steel in very high cycle regime

Abstract In this study the medium carbon steel was nitrocarburized in gas and salt bath, forming three layers (oxide layer, compound layer and diffusion layer) on the surface of the specimen. The very high cycle fatigue (VHCF) tests were carried out and the results show that fatigue limits of the specimens treated in gas and salt bath are improved by 120% and 100%, respectively, compared to that of the untreated specimens. For the specimens treated in gas, from which the oxide layer was removed or both the oxide layer and compound layer were removed, the S–N curve of the former shows a step-wise shape while the latter continuously decreases and both of them show no fatigue limit in VHCF regime. However, all the specimens treated in salt bath have the same fatigue strength and show the fatigue limit in VHCF regime whether both the oxide layer and compound layer are removed or only the former is removed.

Ozone therapy: A clinical review

Ozone (O3) gas discovered in the mid-nineteenth century is a molecule consisting of three atoms of oxygen in a dynamically unstable structure due to the presence of mesomeric states. Although O3 has dangerous effects, yet researchers believe it has many therapeutic effects. Ozone therapy has been utilized and heavily studied for more than a century. Its effects are proven, consistent, safe and with minimal and preventable side effects. Medical O3 is used to disinfect and treat disease. Mechanism of actions is by inactivation of bacteria, viruses, fungi, yeast and protozoa, stimulation of oxygen metabolism, activation of the immune system. Medication forms in a gaseous state are somewhat unusual, and it is for this reason that special application techniques have had to be developed for the safe use of O3. In local applications as in the treatment of external wounds, its application in the form of a transcutaneous O3 gas bath has established itself as being the most practical and useful method, for example at low (sub-atmospheric) pressure in a closed system guaranteeing no escape of O3 into the surrounding air. Ozonized water, whose use is particularly known in dental medicine, is optimally applied as a spray or compress. Diseases treated are infected wounds, circulatory disorders, geriatric conditions, macular degeneration, viral diseases, rheumatism/arthritis, cancer, SARS and AIDS.

The Effect of Solid Particles on Liquid Viscosity

AbstractThe viscosities of solid‐liquid mixtures were experimentally determined for silicon oil‐paraffin system at room temperature and solid‐liquid oxide mixture at steelmaking temperature. The use of oil‐paraffin systems was to confirm the results of high temperature measurements, the experimental conditions being very difficult to control. The silicon oil‐ paraffin mixtures behaved Newtonian until the particle fraction reached 0.15. At this fraction, the mixture started deviate from Newtonian flow; though some average values could still be collected with very high uncertainty. Liquid‐2CaO.SiO2 mixtures and liquid‐MgO mixtures were studied at steelmaking temperature with carefully prepared particle fractions and well controlled conditions. Liquid‐2CaO.SiO2 mixture behaved Newtonian even when the particle fraction reached 0.1. The results of both room temperature measurements and steelmaking temperature measurements were used to examine the applicability of the existing models. Einstein‐Roscoe equation was found to be the only model applicably for the systems studied. No modification of the model parameter was found necessary, though the particles were not spherical.

Bath mixing behaviour in top–bottom–side blown converter

The influence of blowing process parameters on bath stirring was investigated in a model of a top–bottom–side blown converter using physical modelling experiments. It was shown that the side blowing gas flowrate has an important influence on bath mixing time which decreases as side tuyere gas flowrate increases up to a critical flowrate and then plateaus. Bottom gas injection is favourable for bath mixing for top–bottom–side blown converters; however, top lance height, top gas flowrate and bath level have little influence.

Kinetic Study of OH Radical Reactions with CF3CClCCl2, CF3CClCClCF3 and CF3CF=CFCF3

The relative rate technique has been used to determine the rate constants of the reactions of OH radicals with CF(3)CCl=CCl(2) (k(1)), CF(3)CCl=CClCF(3) (k(2)) and CF(3)CF=CFCF(3) (k(3)). Experiments were carried out at (298±2) K and atmospheric pressure using ultrapure nitrogen as gas bath. The decay rates of the organic species were measured relative to those of ethane, methanol, acetone, chloroethane and 2-butanone. The following rate constants were derived in units of cm(3) molecule(-1) s(-1): k(1)= (10±1)×10(-13), k(2)=(2.1±0.2)×10(-13) and k(3)=(3.7±0.2)×10(-13). This is the first experimental determination of k(1) and k(2). The rate constants obtained are compared with previous literature data to establish reactivity trends and are used to estimate the atmospheric lifetimes of the studied perhaloalkenes. From the calculated lifetimes, using an average global concentration of hydroxyl radicals, the atmospheric loss of these compounds by the OH-initiated oxidation was determined. Also, estimations have been made of the ozone depletion potential (ODP), the radiative forcing efficiency (RE), the halocarbon global warming potential (HGWP) and the global warming potential (GWP) of the perhaloalkenes. The approximate nature of these values is stressed considering that these are short-lived compounds for which these atmospheric parameters may vary according to latitude and season.

Theoretical study of the bonding in Mn+-RG complexes and the transport of Mn+ through rare gas (M=Ca, Sr, and Ra; n=1 and 2; and RG=He–Rn)

We present high level ab initio potential energy curves for the M(n+)-RG complexes, where n=1 and 2; RG=He-Rn; and M=Ca, Sr, and Ra. Spectroscopic constants have been derived from these potentials and are compared with a wide range of experimental and previous theoretical data, and good agreement is generally seen. Large changes in binding energy, D(e), and bond length, R(e), between M(+)-He, M(+)-Ne, and M(+)-Ar, also found previously in the analogous Ba(+)-RG complexes [M. F. McGuirk et al., J. Chem. Phys. 130, 194305 (2009)], are identified and the cause investigated; the results shed light on the previous Ba(+)-RG results. These unusual trends are not observed for the dicationic complexes, which behave in a fashion similar to the isoelectronic alkali metal ion complexes. The potentials have also been employed to calculate transport coefficients for M(n+) moving through a bath of rare gas (RG) atoms.