Increase In Water Vapor Concentration Research Articles

Experimental investigation on the high-temperature corrosion of 12Cr1MoVG boiler steel in waste-to-energy plants: Effects of superheater operating temperature and moisture

Waste-to-energy (WTE) technology via municipal solid waste incineration (MSWI) have developed very rapidly with the advantages of achievement on waste disposal and energy conversion. This technology is developing towards higher capacity and efficiency. Therefore, the operation parameters of WTE boilers must be improved. However, higher steam parameters means higher surface temperature of exchange tube in superheaters and reheaters in WTE boilers, resulting higher risk of engineering failure due to high-temperature corrosion. Additionally, the incineration of MSW releases flue gas with a high content of corrosive species and water vapor, which can cause severe high-temperature corrosion. This experimental investigation details the effect of surface temperature and water vapor concentration on the high-temperature corrosion behavior of 12Cr1MoVG boiler steel under an atmosphere mimicking MSWI. The corrosion test environment consists of high temperature, ash deposit and simulated flue gas of waste incineration according to a real WTE boiler. The experiment was conducted using a two-zone bench-scale tube furnace with a gas temperature of 600℃ and the sample temperatures of 380℃, 430℃, and 480℃. For the investigation of water vapor concentration effect, 18 % vol and 23 % vol were set up in this study. After 240 hours of exposure, the corrosion weight curves illustrated that the corrosion kinetics was highly dependent on the surface temperature of corrosion samples. Furthermore, an increase in water vapor concentration exacerbated the high-temperature corrosion. XRD analysis identified the corrosion products as metal chlorides and metal oxides. Cross-sectional SEM images and EDS analysis revealed that an increase in water vapor accelerated the corrosion rate of the steel samples due to chromium dilution behavior.

Magnetized Seeds and Structured Water: Effects on Resilience of Velvet Bean Seedlings (Mucuna pruriens) under Deficit Irrigation

A custom-built water generator supplied structured water (SW) for applying the deficit irrigation treatments to velvet bean plants (Mucuns pruriens). The objectives of the study were to 1) determine the effects of magnetized seed treatment on velvet bean plants, 2) determine the effects of magnetized and hydroxylated water treatments on velvet bean plants, and 4) determine the effects of deficit irrigation, using three soil moisture levels, on velvet bean plants. The optimal water-saving treatment was magnetized seeds plus 10 MT + HWT. This treatment had a 226% increase in transpiration and a 22% increase in water vapor concentration in the intercellular airspace for the low soil moisture watering schedule. The three study factors in the optimal seed and water treatment had a synchronistic effect for enhancing metabolic efficiency by increasing whole plant WUE by 87% and carbon assimilation efficiency by 66% in the low soil moisture schedule. Plants irrigated with SW water and grown from magnetized seeds had enhanced resilience to high water stress conditions by maintaining adequate levels of biologically structured water. The rapid deactivation of a suite of highly interconnected defense activities in the optimal seed and water treatments implies that the plants exhibit macroscopic coherence properties. Coherence at the macroscopic level resulted in complex synchronization between metabolic efficiency, plant health, and deactivation of a suite of regulatory defenses in plants exposed to high water stress.

Adsorption performance of multi-walled carbon nanotube-SiO2 adsorbent for toluene

In this study, multi-walled carbon nanotube (MWCNTs)-SiO2 composite adsorbents MWCNTs-SiO2-2, MWCNTs-SiO2-4, MWCNTs-SiO2-6 (CS2, CS4, CS6) with molar percentages of MWCNTs of 38%, 52%, and 66% were synthesized using the sol-gel method. The effects of the MWCNT content, temperature (30−60°C), water vapor concentration (1%−5%), and the number of cycles on the adsorption capacity of toluene were studied, and an adsorption kinetics analysis was performed. The results showed that the adsorption capacity for toluene at 30−60°C was AC (activated carbon) < CS2 < CS4 < CS6, and the adsorption capacity of CS6 to toluene was up to 50.28 mg/g. For every 10°C increase in temperature, the penetration time decreased by 10−20 min, and the adsorption content decreased by 3.5% for every 1% increase in water vapor concentration. The phase with the fastest mass transfer rate of toluene could be described by the quasi-secondary adsorption kinetics model, in which intraparticle diffusion plays a major role. The mole percentage of MWCNTs ranged from 38% to 66%, the higher the content was, the easier it was to adsorb toluene. The functional group types of the MWCNTs-SiO2 adsorbent after regeneration did not change, and the adsorbent maintained good adsorption performance.

Investigation on the Behavior of Electrons in the Bullet as Well as Its Dependence on Applied Voltage and H2O Concentration in the Atmospheric-Pressure Ar/H2O Plasma Jets

This article presents a systematic investigation on the behavior of electrons in the bullet in the Ar/H2O plasma jet in increasing the applied voltage and water vapor concentration based on a needle-plate discharge configuration and a 1-D particle-in-cell Monte Carlo method. The scattering angle of the electron in the bullet is described using the angle between the electron scattering direction and the bullet propagation direction. The following results are obtained. The evolution characteristic of the angle spectrum of electrons in the bullet in increasing the applied voltage is the same as that in increasing water vapor concentration, namely, the electrons scattered toward the target get increasingly less. When increasing the applied voltage, the OH density, the electron density, and the average electron energy $E_{\mathrm {ave}}$ increase. However, the increase in water vapor concentration leads to an evidently increasing OH density and a decrease in both the electron density and $E_{\mathrm {ave}}$ . In the range of electron scattering angles below 90° in the bullet, the percentage of electrons with energy above 3.27 eV (the threshold of inducing dissociative electron attachment to water molecule) increases with increasing applied voltage but presents a slight decrease in increasing water vapor concentration. The majority of electrons to most probably interact with the target are of energies higher than 3.27 eV. Finally, a notable effect of H2O admixture is that it gives rise to the decrease in not only $E_{\mathrm {ave}}$ but also the electron density in the bullet, especially the latter decreases evidently.

In-situ measurement of water-vapor in fire environments using a real-time tunable diode laser based system

A robust tunable diode laser absorption spectroscopy (TDLAS) based system is developed and deployed to make real-time water-vapor concentration measurements in quasi-controlled live-fire experiments conducted in firefighter training props. This system targets the 1392.5 nm (7181.15 cm−1) water-vapor absorption line while employing a multi-tier detection sensitivity scheme that allows for measurements at multiple locations in fire environment through varying smoke obscuration levels. Temperature-corrected absorbance values are compared to HITRAN simulations to quantify water-vapor concentration. Upon validation in laboratory setting, the impact of firefighter hose stream application on water-vapor concentration is studied. Comparative effects of training structures (metal, concrete and drywall-lined) and fuel-loads (pallet/straw, lightweight furnishings and pallet/straw/oriented-strand-board (OSB)) on water-vapor concentration are characterized. Despite small increase in water-vapor concentration due to suppression, the post-suppression concentrations are found to be comparable or lower than the corresponding maximum pre-suppression concentrations in all scenarios except the metal structure. Irrespective of the structure, highest temperature and water-vapor concentrations are measured with pallet/straw/OSB fuel-load. Under identical fuel-loads, the drywall structure scenarios generate highest water-vapor concentration. Peak water-vapor concentrations are measured post-suppression in typical training structures (near-floor and crawling levels), but prior to suppression in the structure/fuel package combination that simulated a typical residential fire scenario.

Heterogeneous Ozonolysis of Squalene: Gas-Phase Products Depend on Water Vapor Concentration.

Previous work examining the condensed-phase products of squalene particle ozonolysis found that an increase in water vapor concentration led to lower concentrations of secondary ozonides, increased concentrations of carbonyls, and smaller particle diameter, suggesting that water changes the fate of the Criegee intermediate. To determine if this volume loss corresponds to an increase in gas-phase products, we measured gas-phase volatile organic compound (VOC) concentrations via proton-transfer-reaction time-of-flight mass spectrometry. Studies were conducted in a flow-tube reactor at atmospherically relevant ozone (O3) exposure levels (5-30 ppb h) with pure squalene particles. An increase in water vapor concentration led to strong enhancement of gas-phase oxidation products at all tested O3 exposures. An increase in water vapor from near zero to 70% relative humidity (RH) at high O3 exposure increased the total mass concentration of gas-phase VOCs by a factor of 3. The observed fraction of carbon in the gas-phase correlates with the fraction of particle volume lost. Experiments involving O3 oxidation of shirts soiled with skin oil confirms that the RH dependence of gas-phase reaction product generation occurs similarly on surfaces containing skin oil under realistic conditions. Similar behavior is expected for O3 reactions with other surface-bound organics containing unsaturated carbon bonds.

Photocatalytic Oxidation of Toluene on Fluorine Doped TiO2/SiO2 Catalyst Under Simulant Sunlight in a Flat Reactor

Improving the capacity of TiO2 semiconductors for visible light response is a key problem for utilization of solar energy in photo-catalytic degradation of organic pollutants. Both catalyst character and reactor conditions are important for the reaction efficiency. The fluorine ion doped TiO2/SiO2 catalyst was prepared by sol-gel method using HF solution as fluorine source. The activity test and UV–vis results indicated that this catalyst was superior to TiO2 P25 in photocatalytic oxidation of gaseous toluene under simulant sunlight irradiation due to the enhancement of visible and ultraviolet light absorbance. GC-MS results indicated that the main intermediates accumulated on active sites included benzoic acid, benzaldehyde, and phenol. A flat interlaid reactor was designed for continuous treatment of the stream with F-TiO2/SiO2 film. The results showed that coating the catalyst on the surface of both top and bottom glass substrates, through the knife coating method with an optimal reactor height, attained the highest efficiency. In addition, the presence of water and oxygen enhanced the oxidation of toluene due to the generation of hydroxyl radicals and peroxy radicals, respectively. The toluene oxidation rate increased with the increase in water vapor concentration in the range of 0~60 vol.%.

Analysis of photosynthetically active radiation and applied parameterization model for estimating of PAR in the North China Plain

As photosynthetically active radiation (PAR) variability and PAR estimating methods play an important role in climate change and ecological process research, PAR variation trends and broadband global solar radiation (R s ) ratios (PAR/R s ) in the North China Plain (NCP) are examined using in situ PAR and R s observed data for 2005 to 2011. The annual average PAR value found in the NCP is 22.9 mol m−2 d−1. The highest and lowest values were recorded at Changwu and Luancheng sites, respectively. The highest PAR/R s value was found in Jiaozhouwan due to large water vapor volumes present in this area. PAR/R s levels have increased in the NCP due to a decrease in fine aerosols and increase in water vapor concentration. From these analysis results, a parameterization model that can be applied to all sky conditions was checked. Empirical estimation model comparisons for obtaining PAR values indicate that model was least accurate when R s was used independently. When the model included R s, the clearness index (K s) and the solar zenith angle, the model estimated PAR values with acceptable accuracy. A parameterization model was constructed by considering K s and attenuation factors of PAR under clear weather conditions (ρ clear). The improved parameterization model more accurately predicts values for local sites and for various observation sites.

Atmospheric pressure plasma jet utilizing Ar and Ar/H2O mixtures and its applications to bacteria inactivation

An atmospheric pressure plasma jet generated with Ar with H2O vapor is characterized and applied to inactivation of Bacillus subtilis spores. The emission spectra obtained from Ar/H2O plasma shows a higher intensity of OH radicals compared to pure argon at a specified H2O concentration. The gas temperature is estimated by comparing the simulated spectra of the OH band with experimental spectra. The excitation electron temperature is determined from the Boltzmann's plots and Stark broadening of the hydrogen Balmer Hβ line is applied to measure the electron density. The gas temperature, excitation electron temperature, and electron density of the plasma jet decrease with the increase of water vapor concentration at a fixed input voltage. The bacteria inactivation rate increases with the increase of OH generation reaching a maximum reduction at 2.6% (v/v) water vapor. Our results also show that the OH radicals generated by the Ar/H2O plasma jet only makes a limited contribution to spore inactivation and the shape change of the spores before and after plasma irradiation is discussed.

Ar/H2O大气压等离子体射流放电特性

The influences of water vapor concentration on discharge mechanisms and discharge efficiency of atmosphere pressure plasma jet (APPJ) are studied to generate highly active cold plasma and optimize its efficiency. The discharge characteristics of APPJ with different water vapor content are studied by means of electrical measurements on voltage and current waveforms and Lissajous figures, and the optical properties are diagnosed using optical emission spectra and light-emission pictures. The main discharge parameters, such as discharge power, transported charges, electronic excitation temperature, molecular vibrational temperature and molecular rotational temperature are calculated, and the changing tendencies of them with applied voltage are studied, with the experimental results being explained by analyzing the discharge mechanism. The results show that the APPJ in Ar/H2O produces N2, Ar, O, and OH. Gas temperature changes between 525 K and 720 K, which shows that the APPJ in Ar/H2O plasma is a typical non-thermal one. With the increase of water vapor concentration, the plasma plume, light intensity and discharge power decrease, and the rotational temperature and vibrational temperature increase. Under certain discharge power, the content of OH produced reaches maximum when the water vapor content is 0.5%. Accordingly, better results can be achieved under this condition for application in surface modification of polymer materials.

Investigation of Current Density Effect on Water Vapor Concentration Profile along PEMFC Channels by TDLAS

In this article, we applied tunable diode laser absorption spectroscopy (TDLAS) technique to measure variation of water vapor concentration in gas flow channels in an operating polymer electrolyte membrane fuel cell (PEMFC). TDLAS measurement offered an optical remote sensing to detect slight change of water vapor concentration, showing that electrochemical reaction in an operating PEMFC is not uniformly observed. We performed TDLAS measurement in gas flow channels in the anode and the cathode with variation of cell current density. We observed increase of water vapor concentration due to electrochemical reaction along the cathode channel as well as along the anode channel from the inlet, suggesting that generated water was exhausted through the both channels. It was also shown that less electrochemical reaction was observed in the upstream of the channel presumably due to less hydration of the membrane because of dry gas supply.

Temperature dependence of the rate of formation of active species in nanosecond streamer corona discharge between a solid electrode and water surface

The dependence of the yield of ozone in a nanosecond streamer electric corona discharge in the presence of oxygen and water vapor on temperature over the range 25–66°C was examined. It was found that the yield decreased to zero with an increase in temperature to 66°C. The decrease in the yield can be explained in terms of an increase of water vapor concentration in the discharge gap at elevated temperatures, as well as by an increase in the water ionization constant.

Study of TiO2 Deactivation during Gaseous Acetone Photocatalytic Oxidation

The kinetics of the deep photocatalytic oxidation of acetone was studied. Special attention was paid to the thermal deactivation process. The rate of the reaction reaches a peak at about 100°C. With increasing concentration of water vapor the peak shifts towards higher temperature, whereas with increasing acetone concentration the peak shifts towards lower temperature. An increase in water vapor concentration slightly decreases the rate of oxidation at 40°C and increases it at temperatures above the rate maximum. The presence of two types of acetone adsorption sites was deduced from two νC=O bands of adsorbed acetone at 1683 and 1710 cm−1 and can explain the dependence of the rate on acetone concentration. The rate of oxidation increases at temperatures below the peak, mainly because of the increase in the rate coefficient at the sites of the first type. This behavior has been ascribed to the thermal oxidation of an intermediate of the photocatalytic process. Abrupt drop in rate at temperatures above the peak is due to the partial oxidation products of acetone thermal oxidation that modify the TiO2 surface.