Dry Carbon Monoxide Research Articles

Influence of water vapor concentration on photoacoustic spectroscopy‐based characteristic gas analysis of transformer faults

AbstractThe water vapor in the ambient air affects the accuracy of the photoacoustic (PA) dissolved gas analysis system for transformer health monitoring. A laser PA system was evaluated by dry and humidified standard gases to study the influence of water vapor concentration on PA gas detection. Theoretical analysis was conducted on the effect of gas molecule relaxation on PA signal detection. A high‐frequency resonant PA cell and a low‐frequency nonresonant PA cell were used to detect acetylene (C2H2) and carbon monoxide (CO), respectively. The experimental results show that the PA signal of humidified CO is about 12 times higher than PA signal of dry gas for the resonant PA detection system, respectively. In addition, as the frequency is increased from 30 to 980 Hz, the PA signals of humidified and dry CO attenuate by 1.5 and 6.9 times, respectively.

The Effects of Cigarette Filter Ventilation on Delivery and Retention of Organic Acids

Summary A method for simultaneous identification and quantitative determination of 30 organic acids was established. The smoke yields and filter retentions of organic acids and routine smoke components, total particulate matter (TPM), nicotine-free dry particulate matter (NFDPM), nicotine and carbon monoxide (CO) at different filter ventilation levels were determined under both International Organization for Standardization (ISO) and Health Canadian Intense (HCI) smoking regimes. As a result of smoke dilution during filter ventilation, the yields of all organic acids were reduced in mainstream cigarette smoke. The spatial distribution pattern of the concentration of each organic acid in the filter was investigated at different ventilation levels and their filter retention determined. On one hand, the concentration of organic acids with a lower boiling point (BP) and lower molecular weight (MW) was relatively higher at the smoking end and the periphery part of the filter and spatial concentration distributions within the filter were significantly affected by smoke diffusion. On the other hand, those acids with high BPs and high MW were mainly distributed at the tobacco rod end and central part of the filter and spatial concentration distributions were only slightly influenced by their smoke diffusion within the filter whilst air compression around the filter vents also led to less change. This way, different acids in mainstream cigarette smoke were reduced to different extents which can also influence the acid-base equilibrium and sensory quality of the smoke. Compared with ISO smoking regime, the vent blocking and more intense smoking HCI regime led to different extents of yield increase for each of the studied acids. The effect of filter ventilation in the HCI smoking regime was not investigated, as the HCI smoking regime requires blocked ventilation holes. [Contrib. Tob. Nicotine Res. 30 (2021) 199–211]

Preparation, Characterization and CO Oxidation Performance of Ag2O/γ-Al2O3 and (Ag2O+RuO2)/γ-Al2O3 Catalysts

This research dealt with the preparation and characterization of silver oxide (SLO) nanomaterials (NMs) and their composite catalysts (i.e., silver and ruthenium oxide (SLORUO)). The prepared materials were tested for their catalytic performance in carbon monoxide (CO) oxidation. Generally, silver in its pure state is not widely used for CO oxidation due to stability and structural issues. However, the usage of subsurface oxygen and oxygen-induced reconstruction could be effective as an oxidation catalyst at a slightly high temperature. The low-temperature reaction of highly active RuO2 (RUO) is a well-known phenomenon. Thus, the possibility of using it with SLO to observe the combined catalytic behavior was investigated. The wet chemically prepared SLO and SLORUO NMs exhibited spherical and rods in spherical aggregate-type surface morphology belonging to cubic and rutile crystalline structures, respectively. The NMs and catalysts (i.e., the NMs on γ-Al2O3 catalyst support at 0.5 and 1.0 wt.% ranges) showed good thermal stability. The dry and wet CO oxidation using RUO and SLO showed concentration-dependent catalytic activity. The RUO, SLO, and SLORUO composites using 0.5 wt.% showed full CO oxidation at 200, 300, and 225 °C, respectively. The reasons for the observed activity of the catalysts are explained based on the pore characteristics, chemical composition, and dispersion using H2 temperature-programmed reduction (TPR) behaviors.

Influence of tropopause height on inversion of greenhouse gas column concentration in Lhasa, China

The tropopause, as a transition layer between the troposphere and the stratosphere, has a significant influence on the inversion of trace gas concentration. Theoretical analysis of the influence of tropopause on the vertical distribution of atmospheric molecular content, combined with Lhasa observation data, is presented, and the quantitative analysis of the influence of tropopause on the inversion of column-averaged dry air mole fractions (DMFs) is given as well. The comparison results show that the tropopause height has a great influence on the inversion results. First, its height variation has a little effect on XH<sub>2</sub>O, but it has a great influence on XCO<sub>2</sub>, XCH<sub>4</sub> and XCO. The XCO<sub>2</sub> and XCH<sub>4</sub> have positive correlation with tropopause height variation, but for XCO, negative correlation with the tropopause height variation is observed. The correlation coefficient of XCO<sub>2</sub>, XCH<sub>4</sub> and XCO are 0.998, 0.78 and 0.994, respectively. When the tropopause height is varied by 3 km, XCO<sub>2</sub>, XCH<sub>4</sub> and XCO are varied by 8.64%、0.0354% and 0.0488%, respectively. The column-averaged dry air mole water vapor, carbon dioxide, carbon monoxide and methane in Lhasa are observed based on ground-based Fourier transform infrared spectrometer EM27/SUN. The time series of XH<sub>2</sub>O, XCO<sub>2</sub>, XCH<sub>4</sub> and XCO in a period from August 6 to August 16, 2018 in Lhasa were obtained. The main achievements are as follows. In the observation period, the daily average value of XH<sub>2</sub>O, XCO<sub>2</sub>, XCH<sub>4</sub> and XCO vary between 3432 and 4287 ppmv, 406.1 and 408.2 ppmv, 1.673 and 1.720 ppmv, and 0.082 and 0.095 ppmv, respectively. The average value of XH<sub>2</sub>O, XCO<sub>2</sub>, XCH<sub>4</sub> and XCO are 3919.70, 406.887, 1.689, and 0.091 ppmv, res[ectively. Comparison between XCO<sub>2</sub> and XCH<sub>4</sub> time series shows that XCO<sub>2</sub> and XCH<sub>4</sub> time series have similar daily trends, the correlation coefficient between XCO<sub>2</sub> and XCH<sub>4</sub> time serires is higher than 0.5. In particular, the correlation coefficient reached about 0.86 on August 7, 8, 13, 2018. High correlation coefficient indicates that CO<sub>2</sub> and CH<sub>4</sub> molecules come from the same source. Compared with the WACCM simulation values, the XCO<sub>2</sub> and XCH<sub>4</sub> of the ground-based observations are small. The observation results can provide reference and first-hand direct observation data for the study of the temporal and spatial distribution of greenhouse gases in the temperate zone of the plateau in China.

Numerical model for the chemical adsorption of oxygen and reducing gas molecules in presence of humidity on the surface of semiconductor metal oxide for gas sensors applications

Charge transfer between the interacting gas molecules and the surface of the sensing layer is the main mechanism for the detection of gases in semiconductor metal oxides. In the presented work, the Wolkenstein's theory of adsorption is used instead of the conventional Langmuir isotherm for the numerical modelling of adsorption of oxygen, reducing gas (CO) molecules and water vapours. A numerical model of chemical adsorption of these gas species at the surface of tin oxide (SnO2) semiconductor gas sensor is presented in this paper. Using this model, quantitative calculation of the combined effect of environmental oxygen, reducing gas(CO) and water vapor adsorption on various electronic properties like electrical conductivity, surface potential and the work function of the metal oxide surface has been carried out. The surface coverage of the chemically adsorbed oxygen gas molecules is simulated as a function of oxygen gas pressure, the temperature of the sensor surface and bulk doping level of the n-type SnO2 semiconductor. Along with oxygen, the adsorption of CO gas is simulated as a function of CO gas pressure at constant atmospheric pressure of Oxygen gas. Furthermore, the sensor response is simulated and compared both in presence of dry Carbon Monoxide (CO) gas as well in the humid environment. It is shown that in the presence of water vapor there is an increase in the conductivity due to the decrease in the surface potential barrier at the semiconductor surface.

Temperature-programmed technique accompanied with high-throughput methodology for rapidly searching the optimal operating temperature of MOX gas sensors.

A combinatorial high-throughput temperature-programmed method to obtain the optimal operating temperature (OOT) of gas sensor materials is demonstrated here for the first time. A material library consisting of SnO2, ZnO, WO3, and In2O3 sensor films was fabricated by screen printing. Temperature-dependent conductivity curves were obtained by scanning this gas sensor library from 300 to 700 K in different atmospheres (dry air, formaldehyde, carbon monoxide, nitrogen dioxide, toluene and ammonia), giving the OOT of each sensor formulation as a function of the carrier and analyte gases. A comparative study of the temperature-programmed method and a conventional method showed good agreement in measured OOT.

The effect of current density and temperature on the degradation of nickel cermet electrodes by carbon monoxide in solid oxide fuel cells

The oxidation of dry carbon monoxide (CO) in intermediate temperature solid oxide fuel cells (IT-SOFCs) has been studied using a three electrode assembly. Ni/CGO:CGO:LSCF/CGO three electrode pellet cells at 500, 550 and 600 °C were exposed to dry carbon monoxide for fixed periods of time, at open circuit and under load at 50 and 100 mA cm −2, in an aggressive test designed to accelerate electrode degradation. It is shown that if the anode is kept under load during exposure to dry CO, degradation in anode performance can be minimised, and that under most conditions the anode showed significant irreversible degradation in performance after subsequent load cycling on dry H 2. Only at 500 °C and at 100 mA cm −2 was the degradation in performance after operation on dry CO and subsequent load cycling on dry H 2 within the background degradation rates measured. Where anode performance was compromised, this appeared to be caused by a reduction in the exchange current density for hydrogen oxidation, and the relatively large degradation after load cycling on dry H 2 was primarily caused by an increase in the series resistance of the anode. It is suggested that this increase in series resistance is associated with the removal of carbon deposited in the non-electrochemically active region of the electrode during operation on dry CO, and that operation under load inhibits carbon deposition in the active region.

A method to simultaneously image two-dimensional mixture fraction, scalar dissipation rate, temperature and fuel consumption rate fields in a turbulent non-premixed jet flame

A new imaging technique was developed that provides two-dimensional images of the mixture fraction (ξ), scalar dissipation rate (χ), temperature (T), and fuel consumption rate \((\dot{\omega}_{\rm F})\) in a turbulent non-premixed jet flame. The new method is based on “seeding” nitric oxide (NO) into a particular carbon monoxide–air flame in which it remains passive. It is first demonstrated that the mass fraction of NO is a conserved scalar in the present carbon monoxide–air flame configuration, using both laminar flame calibration experiments and computations with full chemistry. Simultaneous planar laser-induced fluorescence (PLIF) and planar Rayleigh scattering temperature imaging allow a quantitative determination of the local NO mass fraction and hence mixture fraction in the turbulent jet flame. The instantaneous mixture fraction fields in conjunction with the local temperature fields are then used to determine quantitative scalar dissipation rate fields. Advantages of the present technique include an improved signal-to-noise ratio over previous Raman scattering techniques, improved accuracy near the stoichiometric contour because simplifying chemistry assumptions are not required, and the ability to measure ξ and χ in flames experiencing localized extinction. However, the method of measuring ξ based on the passive NO is restricted to dry carbon monoxide–air flames due to the well-controlled flame chemistry. Sample imaging results for ξ, χ, T, and \(\dot{\omega}_{\rm F}\) are presented that show high levels of signal-to-noise while resolving the smallest mixing scales of the turbulent flowfield. The application, accuracy, and limitations of the present technique are discussed.

A closed-loop control "playback" smoking machine for generating mainstream smoke aerosols.

A first generation smoking machine capable of reading and replicating detailed puffing behavior from recorded smoking topography data is presented. Unlike standard smoking machines, which model human puffing behavior as a steady periodic waveform with a fixed puff frequency, volume, and duration, this novel machine generates a mainstream smoke aerosol by automatically "playing-back" puff topography recordings. Because combustion chemistry is highly non-linear, representing real smoking behavior with a smoothed periodic waveform may result in a tobacco smoke aerosol with a significantly different chemical composition and physical properties than that generated by a smoker. The machine presented here utilizes a rapid closed-loop control algorithm coded in Labview to generate smoke aerosols for toxicological assessment and inhalation studies. To illustrate its use, dry particulate matter and carbon monoxide yields generated using the playback and equivalent periodic puffing regimens are compared for a single smoking session by a 26-year-old male narghile water-pipe smoker. It was found that the periodic puffing regimen yielded 20% less carbon monoxide (CO) than the played-back smoking session, indicating that steady periodic smoking regimens, which are widely used in tobacco smoke research, may not produce realistic smoke aerosols.

Effect of longitudinal heat conduction on the catalytic ignition of carbon monoxide in a boundary layer

The catalytic ignition of dry carbon monoxide and air in a boundary layer flow over a palladium plate is studied in this paper. The heterogeneous reaction mechanism is modelled with the dissociative adsorption of the molecular oxygen and the non-dissociative adsorption of CO, together with a surface reaction of the Langmuir-Hinshelwood type and the desorption reaction of the adsorbed product, CO2(s). The critical condition for catalytic ignition, represented by the ignition Damköhler number, has been deduced using high activation energy asymptotics of the desorption kinetics of the most efficiently adsorbed reactant, CO(s). Longitudinal heat conduction along the plate has been considered and its influence on the ignition temperature has been evaluated. This influence is rather weak, indicating that the flat plate boundary layer flow configuration is a robust device to determine the critical conditions for catalytic ignition.

FTIR Study of CO Oxidation on Au/TiO2 at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers

An FTIR study of CO adsorption and oxidation on Au/TiO2 is reported. At 90 K different CO−18O2 interactions have been performed, with preadsorbed carbon monoxide or preadsorbed isotopically labeled oxygen, with dry or wet carbon monoxide. From the experimental results it can be inferred that (i) at 90 K carbon monoxide and oxygen are molecularly adsorbed on gold particles, (ii) the reaction occurs if carbon monoxide is preadsorbed (it is almost completely inhibited if oxygen is preadsorbed), and (iii) the reaction occurs more easily in the presence of water. It is proposed that dissociation of oxygen is needed in order to observe the oxidation reaction.

Catalytic combustion of dry carbon monoxide by external power activation

The catalytic combustion of dry carbon monoxide and air in a planar stagnation-point flow over a platinum foil with external power is studied in this paper. The reduced heterogeneous kinetics are modelled with the dissociative adsorption of the molecular oxygen and the non-dissociative adsorption of CO, together with a surface reaction of the Langmuir–Hinshelwood type and the desorption reaction of the adsorbed product, CO 2(s). The resulting governing equations have been numerically integrated and the whole S-shaped response curve has been obtained as a function of the mixture initial concentration. The critical conditions for the catalytic ignition and extinction are deduced using high activation energy asymptotics of the desorption kinetics of the most efficient adsorbed reactant, CO(s). We obtained a very good agreement between the numerical and asymptotic results for the ignition and extinction conditions. In general, the ignition process can be well modelled without reactant consumption, while extinction occurs in the partial diffusion-controlled regime, with a finite non-zero concentration of carbon monoxide close to the plate.

Catalytic ignition of dry carbon monoxide in a stagnation-point flow

The catalytic ignition of dry carbon monoxide and air in a planar stagnation-point flow over a platinum foil is studied in this paper. The heterogeneous reaction mechanism is modeled with the dissociative adsorption of the molecular oxygen and the nondissociative adsorption of CO, together with a surface reaction of the Langmiur-Hinshelwood type and the desorption reaction of the adsorbed product, CO 2( s). The critical conditions for the catalytic ignition are deduced using high activation energy asymptotics of the desorption kinetics of the most efficient adsorbed reactant, CO( s). When using the appropriate activation energy of the desorption reaction of CO( s), the ignition temperature obtained in closed form compares very well with experimental results.

Some photometric observations of trace additives in dry carbon monoxide flames

Nitric oxide, iodine, cyanogen, and lithium bromide have been added to CO/N 2 /O 2 flames containing less than .007% of hydrogen-containing impurities. Relative oxygen atom concentrations, derived from measured intensities of emission bands of CO 2 , NO 2 , and IO, are compared. Addition of NO produced a significant reduction in the O-atom concentration, the effect being greatest in O 2 -rich flames. Measurements of the resonance absorption by lithium atoms indicate that LiO is the major compound formed by lithium in O 2 -rich flames, but they do not rule out the possibility that significant amounts of LiO 2 are also formed. A recalculation of earlier data yields D o Na-O 2 = 234 ± 13 kJ mol −1 ; we estimate D o Li-O 2 = 222 ± 25 kJ mol − .

LiO formation in dry carbon monoxide flames

The concentration of uncombined lithium atoms has been measured as a function of time from primary combustion in isothermal pairs of CO-rich and O 2-rich flames. The lower concentration of lithium atoms in the O 2-rich flames is accounted for by the balanced reaction

High‐temperature oxidation of aluminium in various gases

AbstractThe oxidation of high‐purity aluminium sheet in dry oxygen, moist oxygen, carbon dioxide and carbon monoxide (at total pressure 1.333 × 103 Nm−2) was studied in the range 673–923°K, using a vacuum microbalance to follow weight gains. 14CO2 and 14CO were used to elucidate the mechanism of the oxidation in these gases and to estimate the extent of carbon deposition in the oxide layer.The rate of oxidation in moist oxygen was similar to that in dry oxygen, the principle reaction being 2Al + 3H2O ← Al2O3 + 3H2.It is suggested that there are three steps in the reaction in CO2, viz. 2Al+3CO2 ← Al2O3 + 3CO, followed by 2Al + 3CO ← Al2O3 + 3C, and about 10% of the deposited carbon reacting further by 4Al + 3C ← Al4C3. Only the last two reactions are operative in carbon monoxide.The Arrhenius plots show a distinct break in the region 773–823°K for both carbon monoxide and carbon dioxide, but not for dry or moist oxygen. This is tentatively explained by a change in the rate‐determining process from diffusion via grain boundaries or cracks in the oxide, to lattice diffusion. It is suggested that carbon may become mobile in the oxide film between 773 and 823°K and may tend to congregate in the grain boundaries and cracks.The oxide film remained protective throughout the duration of the experiments in all the gases.

New studies on calcium oxalate monohydrate: A guide to the interpretation of thermogravimetric measurements

The pyrolysis of calcium oxalate monohydrate in air occupies a unique place in the literature of thermogravimetry. Not only was a thermogram for this reaction the first pyrolysis curve published by Duval and his collaborators, but Duval and others have suggested that it can be used as a reference substance for judging the performance of a thermobalance. However, the pyrolysis of calcium oxalate monohydrate under a variety of conditions gives rise to considerable differences in its thermograms. The effects of sample size, heating rate, atmosphere and container geometry are presented in a series of paired thermograms, and the differences are accounted for with the aid of additional evidence from differential thermal analysis and from combustion train experiments. Variations in atmosphere are particularly important, and the atmospheres studied are dry nitrogen, humidified nitrogen, dry air, humidified air, dry oxygen, dry carbon dioxide and dry carbon monoxide. Even subtle variations in the shape of a thermogram obtained on a reliable balance may reflect the complexity of the reactions that produce the more noticeable over-all weight changes. Results presented in this report thus delineate conditions for the use of calcium oxalate monohydrate as a thermogravimetric reference substance, and show that its behaviour under controlled conditions in a thermobalance can provide an unusually versatile guide to the interpretation of thermogravimetric measurements.

Explosion limits of the dry carbon monoxide + oxygen reaction

Download options Please wait... Article information DOI https://doi.org/10.1039/TF9646000539 Article type Paper Download Citation Trans. Faraday Soc., 1964,60, 539-552 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Explosion limits of the dry carbon monoxide + oxygen reaction P. G. Dickens, J. E. Dove and J. W. Linnett, Trans. Faraday Soc., 1964, 60, 539 DOI: 10.1039/TF9646000539 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author P. G. Dickens J. E. Dove J. W. Linnett

Effect of Atmospheres on the Sintering of Alumina

The grain growth of alumina at 1600°-1960°C in various atmospheres, such as vacuum, wet or dry hydrogen, carbon monoxide, argon and air was investigated.The accelerating effect of hydrogen was observed in the surface layer of the specimens sintered at the temperatures higher than 1700°C. Dry hydrogen proved to be the most effective, while that loaded with moisture gave a little lower values.The grain growth of alumina sintered in CO at higher temperatures than 1900°C was investigated with a result showing that the accelerating effect was next to hydrogen.Little difference could be observed in the grain growth of the specimens sintered in vacuum and in air.Argon accerelated the growth a little more than vacuum, although the effect was smaller than that of CO.The authors concluded that the mechanism could be represented byO2-(l)_??__??_o2-+1/2O2(g)+2_??_This equation shows that the rate of diffusion of O2- may be accelerated with the increasing number of O2- vacancies in the crystal which is liable to be affected by the atmospheric conditions.

The Dry Carbon Monoxide–Oxygen Flame

The Dry Carbon Monoxide–Oxygen Flame