Introduction Of Gas Research Articles

Studies of Isotopic Fractionation of D/H Water Ice in Lunar Regolith

In order to study the processes related to the origin and retention of water on the surface of the Moon, an experimental setup has been created at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), for the analysis of (re)sublimation processes of water ice in a vacuum at low temperatures. The temperature range for (re)sublimation varies from –100 to 0°C. The setup is connected to an Isotope Ratio Mass Spectrometer (IRMS), which allows for measuring the isotopic composition of the vapor of the evaporating substance and providing an estimation of the (re)sublimation rate under specific physicochemical conditions. The direct introduction of gases into the mass spectrometer in real-time mode sets the developed setup apart from foreign counterparts. The setup is equipped with a transparent quartz window through which the surface of the studied substance can be heated using a halogen lamp, simulating the movement of solar rays on the surface of mineral grain compositions under conditions similar to those on the lunar surface. In addition to studying gas (de)sorption on the surfaces of mineral grains of various compositions, the setup can also be used for researching the (re)sublimation of gas hydrates and CO2.

Determination of change in enthalpy and entropy for hydride formation and decomposition of palladium using in-situ electrical resistance measurement with various hydrogen pressures

Detection of hydride formation and decomposition of palladium is performed on pure palladium in the hydrogen gas atmosphere up to 0.5 MPa between room temperature and 673 K using an in-situ electrical resistance measurement system. Introduction of hydrogen gas increases the electrical resistance about 1.1 time higher than that in vacuum. Electrical ratio-temperature plot gives a peak during heating and cooling with the temperature changing ration of 0.067 K/s under hydrogen gas, which are associated with the hydride composition and decomposition. Change in enthalpy ΔH and entropy ΔS are determined using van't Hoff plot, and the values were comparable to the reported ones obtained by pressure-composition-temperature measurements. Those for hydride decomposition are 45.6±2.6 (kJ/mol) and 104.8±5.3 (J/mol), respectively, and those for hydride formation are -29.4±2.1 (kJ/mol) and 73.8±4.6 (J/mol), respectively. Furthermore, the measurement method is relatively simple and easy compared with pressure-composition-temperature measurements.

Process Considerations for the Production of Hydrogen via Steam Reforming of Oxygenated Gases from Biomass Pyrolysis and Other Conversion Processes

AbstractIn 2021, average CO2 emissions was 9.7 g CO2/g H2 produced, primarily based on steam methane reforming (SMR) technology that currently dominates hydrogen production. The substitution of natural gas (NG) and other fossil feedstocks in SMRs with renewable gases may be considered as an option for reducing greenhouse gas emissions. This analysis explores process impacts and constraints associated with the potential introduction of biogenic gases into SMRs. The results indicate that replacing NG in the fuel train of the SMR, followed by partial replacement of NG in the feed train may be a feasible approach. For the CO‐ and CO2‐rich gas compositions assumed in this analysis the results indicate that feed train may accommodate up to 25 mole % of biogenic gases using allowances in existing designs and/or with small modifications, while maintaining similar hydrogen output. NG substitution in higher proportions require more major changes because of increased flow rates and heat exchange requirements in the system. Biogenic gases with lower CO2 and higher calorific values are advantageous for NG substitution, and dry reforming using the CO2 present in the feed gas can reduce steam consumption and increase process efficiency within limits where coking does not become a new constraint.

Optimization of biodiesel yield and performance investigations on diesel engine powered with hydrogen and acetylene gas injected with enriched Jojoba biodiesel blend

Jojoba biodiesel has turned into one of the best adequate renewable energy sources owing to its ability to substitute traditional fossil fuels in IC engines. Even though Jojoba biodiesel (JOBD) mitigates destructive pollutants, engine performance is not comparable to that of regular diesel. To correct this limitation, the impacts of hydrogen and acetylene gas introduction with Jojoba biodiesel blend (JB20) on the combustion, emission, and performance features of a CI engine were investigated. The properties of fuel (JB20) were determined and different experiments on the engine were performed in dual fuel mode using hydrogen gas and acetylene gas at diverse flow rates, and the outcomes were compared. The hydrogen gas and acetylene gas were introduced separately at the inlet manifold of the engine with a volume flow rate of 4 p.m. and 8 lpm respectively. According to the results of the experiments, JB20 + 8 lpm of H2 had a higher BTE of 7.18% and 3.14% when compared to JB20 and diesel fuel correspondingly and acetylene mixed JB20 fuel was improved by 2.61% percent with 8 lpm in comparison with JB20 fuel sample. The addition of hydrogen (4 lpm and 8 lpm) into the JB20 fuel bsec was reduced by 6.78% and 13.71% compared to the diesel, 28.65%, and 34.96% than the JB20 fuel. The induction of hydrogen and acetylene gas to the JB20 fuel improved the heat release rate (HRR) and cylinder pressure (CP) equated with JB20 fuel. Further, a considerable reduction was found in CO, HC, and smoke exhaust pollutants at 11.85% 18.4% % and 7.52% respectively but NOx emissions were significantly improved by 2.55% compared to JB20 with hydrogen injection at 8lpm. It concludes that hydrogen and acetylene gas are feasible diesel engine fuel substitutes.

A sustainable, high-quality method for machining film cooling holes: Cryogenic airflow-assisted electrochemical discharge drilling

Film cooling hole is an essential part of aero-engines, necessitating without recast layer, no stray corrosion, and high machining efficiency. Its sustainable manufacturing has been at the forefront of industrial focus. Existing machining methods have problems such as low efficiency and environmental hazards. In order to achieve the production requirements of precision, quality, and green simultaneously, an external cryogenic airflow-assisted electrochemical discharge drilling (ECDD) is proposed. Compared with the current electrochemical drilling (ECD) or electrical discharge drilling (EDD), a glycol working fluid with ultra-low conductivity neutralizing salt replaces the high conductivity of acidic solution or spark oil to realize green machining without a recast layer. Compared to existing ECDD, the introduction of cryogenic gas with glycol can significantly reduce stray corrosion and achieve exceptionally high surface quality. In the theoretical part, the influence mechanism of a low-temperature environment on the electrochemical interface was analyzed by using the electrochemical analysis technique. In addition, a multi-physical field simulation model was established, which was finally verified by experiments. Finally, the surface characteristics were analyzed by using TEM. The results demonstrate that the cryogenic environment enhances the passivation effect, as evidenced by a 35% reduction in taper at 258 K and a 28.2% decrease in stray corrosion. The hole side has nano-roughness (Ra 0.512 μm). Notably, the material removal rate does not significantly diminish at low temperatures and achieves 0.1 mm/s, superior to EDD. As there is no need for an additional machining step after drilling, this method proves its characteristic to attain sustainability, efficiency, and high quality, indicating promising application prospects.

Atomistic insight into the shock-induced bubble collapse in water

Atomistic simulations are employed to investigate the dynamics of shock-induced bubble collapse in water. Two types of bubbles (an empty bubble and a bubble filled with N2 gas) in water are considered in this study. Apart from the manifestation of a rise in temperature and pressure due to implosion energy released upon bubble collapse; distinct differences in response could be observed for the case of empty bubble to that of the case of the bubble with N2 gas. It is observed that the mechanism of the bubble associated with bubble dissociation as well as the time taken for collapse are changed with the introduction of N2 gas within the bubble. Numerous new chemical species are also observed as the N2 within the bubble reacts with water molecules upon shock compression which can be correlated with the differences in observation between an empty bubble system and a system containing N2 gas. This study is anticipated to lead to further improvements in continuum theories for cavitation bubble collapse in which the effects of chemical reactions need to be incorporated.

Numerical investigation of hydrogen-rich gas and pulverized coal injection in the raceway of a blast furnace with lower carbon emissions

The application of hydrogen-rich gas in the pulverized coal injection technology represents a precious solution to mitigate carbon emissions. In this research, a three-dimensional physical model has been constructed based on the actual dimensions of the gas lance, coal lance, blowpipe, tuyere and raceway of a prominent blast furnace in China. A comparative analysis of the tuyere and raceway status, along with the coal combustion behaviors, is conducted using numerical simulation method after the injection volume of the two hydrogen-rich gases changes. The simulation outcomes demonstrate that the introduction of natural gas into the blast furnace has a comparatively larger influence on the temperature within the raceway, in contrast to the injection of coke oven gas, leading to a more noticeable temperature reduction. Additionally, the average temperature at the tuyere outlet is about 20 K higher with coke oven gas injection compared to natural gas injection under equivalent coal ratios. Furthermore, the burnout of particles is lower in the case of natural gas injection compared to coke oven gas injection. When the injection rates of natural gas and coke oven gas increase, and the coal ratio decreases from 170 kg/t to 140 kg/t, the burnout of coal powder decreases from 68.11% to 64.12% and 64.73%, respectively. The impact of injecting natural gas on coal powder combustion is more pronounced. The research offers a theoretical guide for advancing the mixed application of natural gas, coke oven gas, and particles in the blast furnace, serving as a valuable guide for practical implementation.

Optimization of deposition conditions to tune optoelectronic properties of MoO3-x films prepared by RF-sputtering technique

Tunable optoelectronic properties of Molybdenum oxide (MoO3-x) make it a suitable applicant for its use as a catalyst and a hole transport layer. Oxygen vacancies play a vital role in deciding the properties of MoO3-x. In this article, the influence of deposition conditions like substrate temperature and gaseous environment on optoelectronic properties of MoO3-x films are investigated. Increase in substrate temperature have formed oxygen deficient MoO3-x films having lesser transmission (∼30%) and higher conductivity (15-200 Ω−1cm−1). Films prepared at the substrate temperature of 400 °C and rf-power 80 W are mostly crystalline and have led to the formation of MoO2 along with MoO3-x which results in highly conducting less transparent film suitable for catalysis application. Further, introduction of oxygen gas during deposition led to the formation of highly transparent (∼80%) and resistive (10−6 Ω−1cm−1) thin films suitable for hole transport layer application. An increase in oxygen concentration and decrease in oxygen vacancy is confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy measurement respectively for films deposited in presence of oxygen gas. These studies imply that stoichiometry of molybdenum oxide can be controlled by varying the film preparation conditions and thus optoelectronic properties can be tuned accordingly.

Operational and engineering experiences of gas injection to JET for TT and DT operational campaigns

Following the first deuterium–tritium experiment (DTE1) at UKAEA, modifications were investigated to the Joint European Torus’ (JET) gas introduction (GI) systems to increase the gas feed capabilities of the JET facility to better support future campaigns. The GI systems comprise the GI and gas distribution system in the Active Gas Handling System (AGHS), and neutral beam injection and the tritium injection modules on the torus. During DTE1 about 100 g of tritium was supplied from AGHS to JET users. During the second deuterium–tritium experiment (DTE2) and the tritium–tritium experiment (TT) just over 373 g and 630 g of tritium respectively was supplied to JET users for the campaigns. The tritium and deuterium gas supply systems of the fuel cycle can be underestimated as having fewer technical or scientific challenges based on the mechanical simplicity of equipment that they consist of. However, operational experience has shown these systems have the potential to bottleneck a campaign programme. This publication outlines the upgrade requirements foreseen, following DTE1, for operations in the DTE2 and TT campaigns, how these changes impacted the gas supply operations, and where limitations were encountered. The areas discussed include—challenges of upgrading and maintaining equipment designed for a short operating life; the impact of having differences between user requirements and gas supply capabilities; the logistics of gas supply involving multiple control room locations; communication routes between gas supply systems and teams; and safely controlling and tracking tritium gas movements. The latest JET tritium campaigns highlighted a number of challenges for future facilities looking to operate in both batch and continuous gas injection operational modes. The recommendations from this publication intend to provide a starting point for how to address these challenges and optimise gas supply in support of future fusion programmes. This work has been carried out within the framework of the contract for the operation of the JET Facilities and has received funding from the European Union’s Horizon 2020 research and innovation programme. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Effectiveness of hyperbaric chamber ventilation.

Hyperbaric chamber ventilation (HCV) refers to the intentional introduction of fresh gas, whether air, oxygen, or heliox, into a pressurised hyperbaric chamber in order to remove stale or otherwise compromised gas. The minimum required continuous HCV rate is usually determined by mathematical models derived from the contaminant mass balance within a well-stirred compartment. Non-uniform contaminant distribution patterns inside a hyperbaric chamber could emerge and invalidate the predictions of well-stirred models. Contaminant distribution was investigated inside a clinical hyperbaric chamber with the aim of comparing well-stirred model predictions with the actual contaminant concentration measurements. Local ventilation effectiveness inside a clinical hyperbaric chamber may be compromised, leading to higher contaminant concentration values compared to the predictions of a mathematical model with a well-stirred assumption. A well-stirred assumption in mathematical models is a useful simplification that allows reasonably accurate estimates of HCV requirements. However, local ventilation effectiveness values in a particular hyperbaric chamber might vary, with the potential for hazardous contaminant accumulation in under-ventilated zones.

Design of a chamber for the characterization of gas sensors in dynamic flow

In the present work, the description of a design is presented, as a proposal, for the evaluation or characterization of gas sensors. The proposed design allows the introduction of gas into a chamber at one end and its exhaust at the other, so that a flow of this is generated during the evaluation of the sensors. The gas to be evaluated in the first instance is ethanol. On the other hand, the use of peltiers was contemplated to heat the chamber at different temperatures, with a series of heatsinks and fans for its regulation, for which the use of a temperature sensor and a humidity sensor were incorporated. In total, eight gas sensors manufactured specifically with QCM crystals and an ethyl-cellulose film are contemplated. So, also, the corresponding electronic circuit is shown. Finally, the results of the simulation, in Abaqus, of the temperature distribution inside the chamber for a certain value in the peltiers and the variation of the gas flow along the duct inside the chamber are shown.

Activity-based molecular CO2 detection by amine-free polymers in organic and aqueous media

Many machineries have been developed to detect and monitor the ubiquitous molecule “CO2” in a global warming essay. CO2 detection in water with amine-free functionalities and N-heterocyclic carbene (NHC)-based systems remains of interest in the sensing community. This manuscript introduces a unique fluorescent polymeric system capable of CO2 detection in organic and water media. The imidazolium-based ionic polymer controls fluorescence using an ON/OFF mechanism. The formation of the complex NHC-CO2- turns “ON” fluorescence in organic media and solid films through the photo-induced transmission “OFF” photophysical phenomenon. In contrast, fluorescence quenching was observed in the water medium due to aggregation-caused quenching (ACQ) of polymeric nanoparticles upon CO2 gas introduction, which resulted in the formation of carbamate anions in water. The single ionic polymer P1 works in a multimode pathway and detects CO2 gas in various phases such as organic solvents, water, and solid films, through fluorometric analysis.

An innovative gas inlet design in a microwave plasma chemical vapor deposition chamber for high-quality, high-speed, and high-efficiency diamond growth

A novel design of the gas inlet system in a diamond microwave plasma chemical vapor deposition growth chamber has been reported in this paper. The design is targeting for high-quality, high-speed, and high-efficiency diamond material fabrication. By introducing a gas inlet hole into the susceptor, we expand the ways of gas introduction for diamond growth. After extensive numerical and experimental investigation, we have found that the introduction of methane and doping gas inlet from the hole of below while the hydrogen from the top is feasible for realizing the target. The growth and doping species could be confined around the substrate, making efficient usage of the precursors. The plasma state change caused by the difference of the gas inlet modes has been ascribed to the resulted gas distribution in the chamber. The measured growth rate has been increased to 32 μm h−1, which is 16 times higher than traditional gas inlet configuration. Meanwhile, a large improvement of the nitrogen doping concentration has been achieved. Besides, with the increase of growth rate and nitrogen incorporation efficiency, the crystal quality and surface morphology keep in an acceptable degree. In this mode, the dual gas flow system can perfectly solve the contradiction among the crystal quality, growth rate, and doping efficiency, commonly existing during the material fabrication process, the chamber contamination could be significantly suppressed due to the constrained distribution of methyl and doping species, making the fabrication cost much lower. The results of repetitive experiments indicate that other residual impurities present in the chamber of microwave plasma chemical vapor deposition could likely regulate the threshold concentration of nitrogen required for accelerating the growth rate during the nitrogen doped diamond growth, which have a significant effect on the diamond growth.

OPERATION FEATURES OF ENVIRONMENTALLY EFFICIENT BOILER PLANTS OF MUNICIPAL THERMAL POWER ENGINEERING

The work is devoted to research on the improvement of thermal energy production technologies in gas-consuming heating boiler installations while improving their environmental performance and increasing the operation reliability. The work purpose is to study the heat and humidity modes of the air-supply ducts of boiler plants with exhaust gases recirculation systems into the blown air. The main objectives of the study are: to determine the thermal parameters of a heating boiler with a 2 MW heating capacity with a exhaust gases recirculation system mixed with blown air into its furnace space under conditions of using heat recovery technologies and without them; determination and analysis the heat and humidity parameters of this mixture in different operating modes of boiler plants. Known thermal calculation methods of boiler plants and data from our own experimental studies of heat transfer during deep cooling of boiler plant exhaust gases were used. The thermal calculation results of the heating boiler with a system for exhaust gas recirculation into its furnace space mixed with blown air are presented. The regularities of changes in the adiabatic combustion temperature and heat-humidity characteristics of the above mixture depending on the boiler heat load in different its operation modes during the heating period and the share of flue gas recirculation from 10 to 20 % were established. The research results show that the introduction of recirculation gases leads to a decrease by 150 – 250 °С of the adiabatic combustion temperature tad due to the need to consume fuel heat for heating the introduced ballast and the greater of the recirculation share s the lower the level of the indicated temperature. The research results also showed that gas recirculation causes insignificant (in the range of 0.5 – 4.7 °С) changes in the temperature of the boiler exhaust gases. Based on the data obtained, the change regularities in the heat-humidity characteristics (temperature and dew point) of the mixture of recirculated gases and air in different boiler operating modes during the heating period and under the studied recirculation shares were established. It is shown that recirculation causes condensate formation on the surfaces of air ducts in all operating modes of boiler and in some modes their icing is possible. To prevent these negative phenomena, it is necessary to apply measures to increase the temperature of the gas-air mixture by a value not less than Δtsum = 15 – 35 °С.

Colorimetric Signal Readout for the Detection of Volatile Organic Compounds Using a Printable Glass-Based Dielectric Barrier Discharge-Type Helium Plasma Detector.

In this paper, we report on a printable glass-based manufacturing method and a new proof-of-concept colorimetric signal readout scheme for a dielectric barrier discharge (DBD)-type helium plasma photoionization detector. The sensor consists of a millimeter-sized glass chamber manufactured using a printable glass suspension. Plasma inside the chip is generated using a custom-built power supply (900 V and 83.6 kHz), and the detector uses ∼5 W of power. Our new detection scheme is based on detecting the change in the color of plasma after the introduction of target gases. The change in color is first captured by a smartphone camera as a video output. The recorded video is then processed and converted to an image light intensity vs retention time plot (gas chromatogram) using three standard color space models (red, green, blue (RGB), hue, saturation, lightness (HSL), and hue, saturation, value (HSV)) with RGB performing the best among the three models. We successfully detected three different categories of volatile organic compounds using our new detection scheme and a 30-m-long gas chromatography column: (1) straight-chain alkanes (n-pentane, n-hexane, n-heptane, n-octane, and n-nonane), (2) aromatics (benzene, toluene, and ethylbenzene), and (3) polar compounds (acetone, ethanol, and dichloromethane). The best limit of detection of 10 ng was achieved for benzene at room temperature. Additionally, the device showed excellent performance for different types of sample mixtures consisting of three and five compounds. Our new detector readout method combined with our ability to print complex glass structures provides a new research avenue to analyze complex gas mixtures and their components.

Micromixing intensification by gas introduction in a miniaturized annular rotating flow mixer (MARFM)

Micromixing intensification by gas introduction in a miniaturized annular rotating flow mixer (MARFM)

Investigation of C2H6, C2H4, CO and H2 on the explosion pressure behavior of methane/blended fuels

The introduction of other combustible gases to methane could change accident consequences. This work aimed to experimentally compare the effects of blended fuels (C2H6, C2H4, CO, and H2 mix in different proportions) on the explosion pressure behavior of methane and blended fuels in air. The explosion pressure properties of the mixtures were tested. Principal component analysis was employed, and multiple regression models were developed to predict the influences of principal components on the maximum explosion pressure of CH4. In addition, the software was used to analyze and compare the sensitivity analysis. For the fuel-lean CH4-air mixture(φ = 0.72), the results demonstrated that the value of Pmax and (dP/dt)max of the mixed gases increased, as the volume fraction of the blended fuels increased. The effects of other gases followed the order C2H6>C2H4>H2>CO. For stoichiometric concentrations (φ = 1), the order of the influence degree was H2>CO > C2H6>C2H4, and the value of Pmax and (dP/dt)max of the mixed gases tended to decrease slightly. As the volume fraction of the blended fuels was increased to 2%, the Pmax and (dP/dt)max of CH4 showed a decreasing trend for the fuel-rich CH4-air mixture. The effects of blended fuels on the equivalence ratio of φ = 1.1 followed the order C2H4>H2>CO > C2H6. The sensitivity variation analysis and normalized sensitivity variation analysis indicated that the chain branching reaction 2CH3(+M)<=>C2H6(+M) was the most sensitive reaction under various conditions. However, it was not very susceptible to changes in the blended fuel ratio. Most reactions were susceptible to changes in the blended fuel ratio. The 10 most sensitive reactions were generally much more susceptible to changes in the blended fuel ratio in the 2% blended fuels than they were in the 0.4% blended fuels.

Discrimination of volatile organic compounds using a sensor array via a rapid method based on linear discriminant analysis

We investigated a discriminant method for volatile organic compounds (VOCs) in exhaled breath under contaminant air as well as purified air conditions using an array of multiple semiconductive gas sensors and the linear discriminant analysis (LDA) space. We analyzed the sensor signals of resistance changes employing our developed discriminant method in the LDA space. In particular, the sensor resistances at intervals at which a resistance change occurred owing to target gas introduction were used as test data. The linear discriminant (LD) scores from the test data in the two-dimensional (2-D) LDA space gradually shifted in the direction of the correct LD scores of the training data. Therefore, the target gases were discriminated using the angle of locus of the test data in the 2-D LDA space. Our results proved the viability of the proposed method to discriminate target gases under contaminant air conditions.

Method for Intensive Gas–Liquid Dispersion in a Stirred Tank

This article presents the results of hydrodynamics and mass exchange in a stirred tank upon the introduction of gas from an open gas vortex cavity into local liquid regions with reduced pressure. It establishes conditions for the intensive dispersion of gas. Velocity fields and liquid pressure behind the stirrer paddles are determined by numerical simulation in OpenFOAM. The gas content value, gas bubble diameters, and phase surface are determined experimentally. The stirrer power criterion is calculated by taking into account the gas content and power input. The experimental mass transfer data based on the absorption of atmospheric oxygen into water during the dispersion of gas from the open vortex cavity in the local liquid regions behind the rotating stirrer paddles are presented. In this case, the energy dissipation from the rotating stirrer reaches 25 W/kg, with a phase surface of 1000 m−1 and a surface mass transfer coefficient of up to 0.3·10−3 m/s. These parameters are obviously higher than the data obtained in the apparatus for mass exchange through surface vorticity. The advantage of the given method for gas dispersion in a liquid is the functional stability of the apparatus regardless of how deep the stirrer is immersed in the liquid or the temperature or pressure of the gas. Apparatuses based on the intensive gas dispersion method allow for varying the mass transfer coefficient and gas content across a broad range of values. This allows establishing a dependency between the experimentally obtained mass transfer coefficient, energy dissipation, and phase surface values. An equation for calculating the mass transfer coefficient is formulated by taking into account the geometric parameters of the stirrer apparatus based on the stirring power and phase surface values.

Gas Introduction by Permeation into Long Fluorinated Ethylene Propylene Capillaries with Slug Flow

AbstractDue to the density differences between gases and liquids, the gas supply often limits the conversion of gas‐liquid reactions in slug flows. This paper investigates the permeation of reacting gas into an existing gas‐liquid slug flow in fluorinated ethylene propylene capillaries of up to 40 m in length, representing a significant sizing‐up of tube‐in‐tube reactors (maximum 4 m). The amount of gas introduced can be estimated with permeation coefficients given in the literature. Moreover, existing gas bubbles serve as reservoirs for the permeating gas, maintaining the advantageous slug flow pattern.