Effect Of Oxygen Addition Research Articles

Effects of oxygen addition to argon glow discharges: A hybrid Monte Carlo-fluid modeling investigation

A hybrid model is developed for describing the effects of oxygen addition to argon glow discharges. The species taken into account in the model include Ar atoms in the ground state and the metastable level, O 2 gas molecules in the ground state and two metastable levels, O atoms in the ground state and one metastable level, O 3 molecules, Ar +, O +, O 2 + and O − ions, as well as the electrons. The hybrid model consists of a Monte Carlo model for electrons and fluid models for the other plasma species. In total, 87 different reactions between the various plasma species are taken into account. Calculation results include the species densities and the importance of their production and loss processes, as well as the dissociation degree of oxygen. The effect of different O 2 additions on these calculation results, as well as on the sputtering rates, is discussed.

Effect of oxygen addition on catalytic performance of Ni/SiO2·MgO toward carbon dioxide reforming of methane under periodic operation

Abstract This work investigates the catalytic performance of an industrial steam reforming Ni/SiO2·MgO catalyst toward dry reforming of CH4 under periodic operation. The effects of cracking/regeneration temperatures and O2 addition during regeneration on the catalyst stability and activity were determined and various characterizations i.e. BET, SEM, XRD, and TPO were employed to relate the catalyst performance with its physical properties. It was found that, without O2 addition, the catalyst showed good stability at 650 °C but observed high deactivation at 750 °C due to the formation of encapsulating carbon. The addition of O2 along with CO2 can eliminate all deactivation at 750 °C and no significant loss of catalyst activity was observed for at least 12 cracking/regeneration cycles. The optimal performance for periodic operation was found at the condition with 5 min of the cracking step followed by 5 min of the regeneration step at 750 °C with CO2/O2 ratio of 7/3.

Shielding Gas Oxygen Additions as a Means of Curbing Nitrogen Degassing During the Autogenous Arc Welding of Nitrogen-Alloyed Stainless Steel

This study examined the influence of oxygen additions (0.5% to 2.0%) to argon-rich shielding gas on nitrogen degassing during the autogenous arc welding of a high-manganese nitrogen-alloyed austenitic stainless steel, previously commercially available under the trade name of Cromanite. Autogenous arc welding of this steel in inert shielding gas results in considerable nitrogen losses from the weld pool, characterised by an unstable arc, spattering and violent metal expulsion from the weld pool. Oxygen additions to the shielding gas stabilise the arc and curb nitrogen-induced porosity, but at least 2.0% oxygen (by volume) is required to maintain the weld metal nitrogen content at the level of the parent material prior to welding. The beneficial effect of oxygen additions to the shielding gas is attributed to the formation of a solid MnCr2O4 spinel phase on the weld pool surface during welding, which retards nitrogen degassing by reducing the area available for the adsorption of nitrogen atoms prior to their recombination to form N2. This layer has a granular, irregular appearance and presents a less effective barrier to nitrogen degassing than the continuous, uniform liquid slag layer that forms when the Cr-Ni 300-series austenitic stainless steels are welded in oxygen-containing shielding gas mixtures.

Effects of oxygen addition to the electrochromic properties of WO 3 − z thin films sputtered on flexible PET/ITO substrates

An investigation was conducted on electrochromic properties of WO 3 − z (tungsten oxide) thin films sputtered on 60 Ω/□ flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates at various oxygen flow rates. A metallic W target, sputtered by radio frequency (r.f.) power with argon gases and reacted with oxygen gases at room temperature (23 °C), was proven to provide extraordinary electrochromic properties. Cyclic voltammetry measurement demonstrated that only low driving voltages from − 1 V to 1 V were needed to provide Li + ion insertion and extraction to and from a working electrode. The flexible PET/ITO/WO 3 − z film was mounted on the working electrode and dipped in a 0.1 M LiClO 4–PC (propylene carbonate) electrolyte. The electrochromic properties of flexible PET/ITO/WO 3 − z were investigated by cyclic potentiostatic switching and ultraviolet (UV)–visible spectroscopy. An oxygen flow rate of 0.71 sccm with a low O/W-ratio of 2.916, an oxygen deficiency z of 0.084 and an insertion coefficient x of 0.150 can offer an excellent light modulation of up to 73.1% of transmittance variation, optical density change of 0.89 and color efficiency of 62.4 cm 2/C at a wavelength of 650 nm in 14 s of Li + insertion and extraction.

Probe Measurements and Optical Emission Spectroscopy in Inductively Coupled Ar/CF4, Ar/NF3, and Ar/SF6 Discharges

Experiments of inductive Ar/CF4, Ar/NF3, and Ar/SF6 discharges with a Langmuir probe and optical emission spectroscopy are carried out in the total pressure range of 8–30 mTorr, changing the ratio of the partial pressure of reactive gas to the total pressure (the fraction of the reactive gas) from 0 to 30%. The structure of the measured electron energy probability functions (EEPFs) deviates from the Maxwellian distribution owing to the large depletion of high-energy electrons at any reactive gas fraction. The electron density markedly decreases with increasing reactive gas fraction in the fraction range below 10%, whereas the electron temperature gradually increases. The density of the ground state fluorine atoms in the Ar/SF6 and Ar/NF3 discharges is about 5 times higher than that in the Ar/CF4 discharges. The effects of oxygen addition on the plasma parameters in those discharges are also investigated. The plasma parameters, such as electron density and temperature, do not depend on the fraction of oxygen for the fixed fraction of Ar. On the other hand, the dependence of the fluorine atom density on the fraction of oxygen differs among the inductive Ar/CF4, Ar/NF3, and Ar/SF6 discharges.

Effect of oxygen addition on the hydrogen production from ethanol steam reforming in a Pd–Ag membrane reactor

In this communication, a porous stainless steel (PSS) tube was electrolessly plated into Pd–Ag membrane reactor which was used for separating hydrogen produced in an ethanol steam reforming reaction with the addition of oxygen, which has not been reported before. Palladium and silver were deposited on porous stainless steel tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. Ethanol–water mixture ( n water/ n ethanol = 1 or 3) and oxygen ( n oxygen/ n ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with MDC-3. The reaction temperatures were set at 593–723 K and the pressures 3–10 atm. The effect of oxygen addition plays a vital role on the ethanol steam reforming reaction, especially for the Pd–Ag membrane reactor in which a higher flux of hydrogen is required. If oxygen in the feed is not sufficient, it would be possible that steam reforming reaction prevails. Inversely, high O 2 addition will shift the reaction scenario to be partial oxidation dominating, and selectivity of CO 2 increases with increasing oxygen feed. At high pressure, autothermal reaction of ethanol would be easily reached.

Theoretical study of DI diesel engine performance and pollutant emissions using comparable air-side and fuel-side oxygen addition

The present work examines the effects of oxygen addition on diesel combustion parameters and pollutant emissions. Oxygen is added either by increasing the partial pressure of oxygen in the intake air or by oxygenating the fuel. This is a predominately computational study, where the effect of oxygen addition is addressed using a two-dimensional multi-zone model. The validity of model calculations was assessed against pertinent experimental data generated in this laboratory from a single cylinder DI diesel engine using neat diesel oil and oxygenated fuels. The comparison of the two techniques was conducted at comparable oxygen mole fractions (21–22.5%) in the fuel–air mixture (charge) of the combustion chamber. For all cases, engine torque was retained the same by adjusting fuelling rate. At fixed engine load, in-cylinder pressure, temperature, soot and NO concentration histories, which were calculated for a conventional diesel fuel, are compared with corresponding data, which were derived using either oxygenated fuels or oxygen-enhanced air. Results showed that both techniques produce an increase of cylinder pressure and reduction of soot compared to the normal diesel operation, with the fuel oxygenation being the most effective. However, both techniques increase NO x emissions, with the fuel oxygenation being more detrimental. Fuel-side oxygenation gave higher soot reductions for a given NO increase compared to air-side oxygen-enhancement. The higher sensitivity of soot reduction and NO x deterioration to fuel-side oxygen-addition is attributed to higher oxygen availability inside each combustion zone. Model computations revealed “linearity” between engine out pollutant emissions and oxygen content of the intake air. To the contrary, “non-linearity” was evident between emissions and oxygen content in oxygenated fuels. This indicates that engine performance characteristics and pollutant emissions are easier to predict when enriching the air rather than the fuel with oxygen, since in the latter case changes in performance and emissions are attributed not only to fuel oxygen content but also to fuel molecular structure and properties.

Oxidative steam reforming of ethanol over Ni/CeO2-ZrO2 catalyst

Abstract Catalytic steam reforming of ethanol for hydrogen production in presence and absence of oxygen has been studied over Ni-CeO 2 -ZrO 2 catalyst. The effect of oxygen addition and space time on conversion and product selectivities has been investigated in a down-flow tubular fixed bed reactor at atmospheric pressure with an ethanol/water molar ratio of 1:8, over a temperature range of 400–650 °C. The O 2 /EtOH molar ratio was varied from 0.5 to 1.5. In the presence of oxygen, the catalytic activity was significantly higher and the effect was more at lower temperature ( 2 /EtOH molar ratio of 0.5, whereas at higher temperatures, higher hydrogen yields were obtained in absence of oxygen. Higher oxygen content in the feed (O 2 /EtOH ≥ 0.5) reduced the hydrogen yield.

酸素添加の形態が予燃焼室式ディーゼル機関の排出ガス特性に及ぼす影響

Ships have many advantages in loading capacities compared with vehicles. If the amount of NOx can be reduced by some way, ships can be equipped with oxygen permeable membranes as an oxygen generator that has recently shown a remarkable improvement in the performance of producing more oxygen for the purpose of PM (Particulate Matter) reduction.Therefore, the objective of this study is to examine the effect of oxygen addition on exhaust gas emissions for marine diesel engines.In the experiment oxygen was added to the air suction pipe of a pre-combustion chamber type diesel engine. Then oxygen was added to the exhaust gas pipe before DPF (Diesel Particulate Filter) .The results were as follows:(1) Oxygen addition to the air suction pipe of a pre-combustion chamber type diesel engine decreases both ISF (Insoluble Organic Fraction) and SOF (Soluble Organic Fraction) . Oxygen addition works very well especially at all loads for reduction of ISF with an increase of 2% in oxygen concentration.(2) Although oxygen addition to the air suction pipe of a pre-combustion chamber type diesel engine increases NOx emission. The NOx emission of a pre-combustion chamber type diesel engine is not so much as that of a direct injection type engine. The increase of NOx emission is saturated with further increasing engine load.(3) DPF was effective even in an ordinary type engine that has mechanical fuel injection system and no supercharger. The reduction rate was superior in ISF compared to SOF.(4) Oxygen addition before DPF has almost no effect on PM reduction.

The Effect of Oxygen Addition on Oxidation Resistance and Cutting Performance of Si<sub>3</sub>N<sub>4</sub> Ceramics

The effect of oxygen addition on oxidation behavior of the β-Si3N4 ceramics with 5 mass% Y2O3 and 2 or 4 mass% Al2O3 was investigated by performing oxidation tests in air at 1300° to 1400°C and cutting performance tests. These tests were intended to clarify their ware resistance as cutting tools. The results of mass change, SEM observation and composition analysis of the specimens before and after oxidation test showed that as the Al2O3 content in the β-Si3N4 ceramics increased, mass changes resulted higher oxidation during which process pores and cracks formed due to the release of N2 gas. The values of hardness and bending strength of the specimens with relatively small amount of 2 mass% Al2O3, which formed solid solution in the Si3N4 structure [Si6-zAlzOzN8-z (z = 0.1)], showed larger than those of the specimen with 4 mass% Al2O3 (z = 0.2). The specimens group added with Al2O3 of 2 mass% (Z = 0.1) also showed high wear resistance. From this, we could conclude that the mechanical properties of β-Si3N4 ceramics depending on oxygen introduction is much effective on cutting performance improvements of the cutting performance of β-Si3N4 ceramics.

Effects of Oxygen Addition on Superconductivity of Sn Cluster-Assembled Films

Sn cluster-assembled films have been produced using a plasma-gas-condensation cluster deposition apparatus with and without O2 gas addition in a sputtering chamber. The Sn clusters prepared without O2 gas addition agglomerated on the substrate and formed larger islands. They exhibited a broad superconducting transition below 3.7 K, suggesting that their transition temperature Tc depends on their cluster size. When O2 gas was added to the cluster source, cluster size decreased and the agglomeration was prevented. The Sn cluster-assembled film prepared at an O2 gas flow rate RO2 =0.05 sccm showed a sharp superconducting transition at Tc=4.0 K, which was higher than the Tc of bulk β-Sn (Tcb=3.7 K). Magnetization measurements indicated that the Sn cluster-assembled films prepared at RO2 ≤0.1 sccm were type II superconductors.

Effect of oxygen addition to methane on growth of vertically oriented carbon nanotubes by radio-frequency plasma-enhanced chemical-vapor deposition

We have investigated the effect of oxygen addition to methane on the growth of vertically oriented carbon nanotubes (VCNTs) by radio-frequency plasma-enhanced chemical-vapor deposition (RFCVD). By adding moderate concentrations of oxygen to methane during RFCVD, highly crystalline VCNTs were densely grown at 430°C. With increasing oxygen concentration, the length of the VCNTs was increased and the linearity was degraded, whereas when excess oxygen was added to methane, no VCNTs were grown. Plasma states were investigated by optical emission spectroscopy during RFCVD. In the case of RFCVD with oxygen added to methane, peaks due to CO and OH radicals were dominant. The CO species appear to be one of the key factors in the growth of well-crystallized VCNTs. Moreover, VCNTs were grown at temperatures as low as 350°C with the addition of moderate amounts of oxygen to methane in RFCVD.

The effect of sulphur dioxide and oxygen on the viability and culturability of a strain of Acetobacter pasteurianus and a strain of Brettanomyces bruxellensis isolated from wine

The objective of this study was to investigate the effects of free molecular and bound forms of sulphur dioxide and oxygen on the viability and culturability of a selected strain of Acetobacter pasteurianus and a selected strain of Brettanomyces bruxellensis in wine. Acetic acid bacteria and Brettanomyces/Dekkera yeasts associated with wine spoilage were isolated from bottled commercial red wines. One bacterium, A. pasteurianus strain A8, and one yeast, B. bruxellensis strain B3a, were selected for further study. The resistance to sulphur dioxide and the effect of oxygen addition on these two selected strains were determined by using plating and epifluorescence techniques for monitoring cell viability in wine. Acetobacter pasteurianus A8 was more resistant to sulphur dioxide than B. bruxellensis B3a, with the latter being rapidly affected by a short exposure time to free molecular form of sulphur dioxide. As expected, neither of these microbial strains was affected by the bound form of sulphur dioxide. The addition of oxygen negated the difference observed between plate and epifluorescence counts for A. pasteurianus A8 during storage, while it stimulated growth of B. bruxellensis B3a. Acetobacter pasteurianus A8 can survive under anaerobic conditions in wine in the presence of sulphur dioxide. Brettanomyces bruxellensis B3a is more sensitive to sulphur dioxide than A. pasteurianus A8, but can grow in the presence of oxygen. Care should be taken to exclude oxygen from contact with wine when it is being transferred or moved. Wine spoilage can be avoided by preventing growth of undesirable acetic acid bacteria and Brettanomyces/Dekkera yeasts through the effective use of sulphur dioxide and the management of oxygen throughout the winemaking process.

04/02293 Effect of oxygen addition to steam and dryreforming of methane on bed temperature profile over Pt and Ni catalysts: Tomishige, K. et al. Fuel Processing Technology, 2004, 85, (8–10), 1103–1120

04/02293 Effect of oxygen addition to steam and dryreforming of methane on bed temperature profile over Pt and Ni catalysts: Tomishige, K. et al. Fuel Processing Technology, 2004, 85, (8–10), 1103–1120

Comparison of the Impact of Intake Oxygen Enrichment and Fuel Oxygenation on Diesel Combustion and Emissions

Among continuing efforts to develop low-emission combustion engines, oxygen-enhanced combustion has long been considered a promising approach. A number of investigations have focused on the effects of oxygen addition on soot formation and oxidation by using various oxygen introduction techniques, such as blending different oxygen-containing fuels or direct oxygen addition into the intake air stream. The present study of oxygen addition was performed on a Volkswagen 1.9 L “TDI” turbodiesel engine to investigate and compare the relative effect of two oxygen addition methods on diesel emission and combustion: oxygen enrichment of the intake air and oxygenation of the fuel. The oxygen enrichment was accomplished by connecting an oxygen generator to the intake air surge tank, while fuel oxygenation was accomplished using two compounds with different cetane number and molecular structure. The key observations are that both intake oxygen enrichment and fuel oxygenation via linear structure oxygenated molecules ...

Effect of oxygen addition to steam and dry reforming of methane on bed temperature profile over Pt and Ni catalysts

The effect of oxygen addition to the steam and dry reforming of methane on the temperature profile of the fixed catalyst bed was investigated over Pt/Al 2O 3, Ni/Al 2O 3 with various metal loadings and commercial steam reforming Ni catalyst. The temperature profile of the catalyst bed was much dependent on the kind of metal and its loading. Especially the Pt/Al 2O 3 with higher loading than 1.2×10 −5 mol/g-cat gave the flat temperature profile and high methane conversion. From the profiles of bed temperature measurements under various reaction conditions, one sees that the distance between the combustion and reforming zones becomes very short. This is related to the high reducibility of Pt metal itself, and Pt maintains metallic state in the combustion zone even under the presence of oxygen. In this case, the heat of combustion can be supplied to the reforming reaction effectively. On the other hand, Ni/Al 2O 3 and commercial steam reforming catalyst gave high temperature at the catalyst bed inlet, and this indicates that the reaction zones exist separately.

Study the effect of O 2 addition on hydrogen incorporation in CVD diamond

The effect of a small amount of O 2 addition on film quality and hydrogen incorporation in chemical vapour deposition (CVD) diamond films was investigated and the films were grown using a 5-kW microwave plasma CVD reactor. Film quality and bonded hydrogen were characterized using micro-Raman and Fourier transform infrared (FTIR) spectroscopy, respectively. It was found that in general for films grown using CH 4/H 2 plasma both without and with O 2 addition, the hydrogen incorporation increases with increasing substrate temperature, while a small amount of O 2 addition (O 2/CH 4=0.1) into CH 4/H 2 (4%) plasma strongly suppresses the incorporation of hydrogen into the film. Raman spectra show that the added oxygen improved film quality by etching and suppressing the amorphous carbon component formed in the film. The above effect of oxygen addition on hydrogen incorporation and film quality is discussed according to the growth mechanism of CVD diamond. The CVD diamond specific hydrogen related IR vibration at 2828 cm −1 appears as a sharp and strong peak only in the FTIR spectra of poor quality films grown at high temperature both without and with O 2 addition, but it appears much stronger in the film grown without O 2 addition. This result experimentally excludes the assignment of the 2828 cm −1 peak arises from hydrogen bonded to oxygen related defect in the literature.

Hydrogen production by auto-thermal reforming of ethanol on Rh/Al2O3 catalyst

Abstract This study is focused to optimising a bio-ethanols auto-thermal reforming (ATR) process over 5% Rh/Al 2 O 3 catalyst homemade, to produce syn-gas for fuel cell application. The effect of oxygen addition for a given S/C molar ratio ranging from 2.1 to 6.3 at T =923 K was investigated, varying the O 2 /EtOH molar ratio between 0.2 and 1.1. The results have identified an optimum range where the ethanol conversion is 100%, CH 4 and CO productions go down and hydrogen yield reaches a maximum before decreasing because of the prevalent oxidizing action of oxygen. The obtained data, compared with those from steam reforming (SR) process, gave a very clear indication about the potentiality of ATR process.

The impact of thiosulfate oxidation products on the oxidation of gold in ammonia thiosulfate solutions

The continued use of cyanide in the recovery of gold is being questioned due to environmental and public concerns. The present paper describes research into the gold thiosulfate leaching system, which is considered to be the most promising alternative to cyanide. The thiosulfate system is complicated by the homogeneous reaction between two of the reactants, copper(II) and thiosulfate. This reaction produces copper(I) and polythionates. It is generally accepted that oxygen addition is thus required in order to regenerate copper(II) from copper(I). Despite this, no one has previously studied the effect of oxygen addition on the kinetics of gold leaching in thiosulfate solutions. This paper presents a study on gold leaching in thiosulfate solutions containing oxygen. It will be shown that the leaching reaction is severely hindered as the reaction between thiosulfate and copper(II) occurs in the presence of oxygen. It is postulated that an intermediate product of the oxidation of thiosulfate by copper(II) in the presence of oxygen is responsible for the slow leaching kinetics. This effect was not observed when oxygen is excluded from the solution. Disulfite (S 2O 5 2−) was identified as a possible cause of this effect, as experiments performed with the addition of disulfite also resulted in very low gold oxidation rates.

Effects of Oxygen Additions to Argon Shielding Gas on GTA Weld Shape

In order to investigate the effect of oxygen additions on the weld shape in gas tungsten arc welding, bead-on-plate specimens were made of SUS304 stainless steel using O2-Ar mixed shielding gas with oxygen additions from 1 000 to 10 000 ppm. The weld bead cross-sections and the weld surface oxide layer were observed by optical microscopy after welding. The oxygen content in the weld metal was measured using an Oxygen/Nitrogen Analyzer. The weld depth/width ratio increases substantially as a result from the additions of oxygen to the argon shielding gas in the range of 3 000 to 5 000 ppm both for the 10 and 20 L/min shielding gas flow rates. When the oxygen addition contents are below 2 000 ppm or over 6 000 ppm, the weld D/W ratio decreases to approximately 0.2. The oxygen in the weld pool plays an important role as an active element affecting the Marangoni convection mode. The inward Marangoni convection occurs on the liquid pool surface when the oxygen in the weld is over 100 ppm, and hence the D/W ratio increases suddenly. The thicker oxide layer on the weld pool surface is not only a barrier for the oxygen to transfer and become a solute in the weld pool, but also prevents the weld pool from moving freely, and hence changes the weld pool shape.