Water Vapor Partial Pressure Research Articles

Technical and economic evaluations of the triethylene glycol regeneration processes in natural gas dehydration plants

A conventional natural gas dehydration plant and one based on striping gas concept, which employs triethylene glycol (TEG) as the dehydrating agent, were simulated using a steady state simulator (UniSim Design). The main units were included in the flowsheets, namely: absorber, flash units, heat exchangers, regenerator, and reboiler. All simulations were performed of about 25 L TEG/kg water absorbed. The equation of state (EOS) used in the simulation is the Peng Robinson (PR). The reboiler temperature of conventional regenerator and then the hot stripping gas flowrate, have been studied for their response to changes in the regenerated TEG concentration, dew point of sale gases, TEG losses (make-up), regenerator overhead vapor flowrate, and partial pressure of water vapor. Despite the increase in plant complexity, the fixed capital investment estimation proves an insignificant costs increase of the stripping gas configuration over the benchmark. It appears that stripping gas is a more effective way to improve the regenerated TEG concentration and entire dehydration plant performance.

A Thermochemical Long‐Term Heat Storage System Based on a Salt/Zeolite Composite

AbstractFor the purpose of a long‐term heat storage system based on water sorption, a composite material consisting of CaCl2 and zeolite Ca‐X, obtained by ion exchange with Ca2+ and subsequent impregnation with CaCl2 of a binder‐free granulated zeolite Na‐X, was prepared on a technical scale. In a lab‐scale apparatus, the heat storage density of the composite material reaches values up to 260 kWh m−3 for water vapor partial pressures up to 33 mbar. As compared to the pure zeolites Ca‐X and Na‐X, this corresponds to an increase in heat storage density of 45 % and 68 %, respectively. An engineering concept based on the mechanical transport of the composite heat storage material through a prereactor and a main reactor was demonstrated in a hardware‐in‐the‐loop test bench.

Photocatalytic reduction of CO 2 with H 2 O over graphene oxide-supported oxygen-rich TiO 2 hybrid photocatalyst under visible light irradiation: Process and kinetic studies

Abstract The photoreduction of carbon dioxide (CO2) into hydrocarbon fuels was studied in a homemade photocatalytic system over 5 wt.% graphene oxide-doped oxygen-rich TiO2 (5GO-OTiO2) photocatalyst. The CO2 transformation process is a sequential combination of both water oxidation and CO2 reduction. As these processes can be affected by parameters such as radiant flux intensity and the partial pressures of both CO2 and water vapour, these factors were systematically varied and studied in order to determine the most suitable process conditions for achieving high photocatalytic activity. Based on results from the CO2 photoreduction experiments, a total methane (CH4) yield of 3.450 μmol gcat−1 was successfully attained over 5GO-OTiO2 after 8 h of reaction time under visible light irradiation. The experimental data obtained was then fitted into the Langmuir-Hinshelwood surface reaction mechanism, wherein both CO2 and H2O adsorbed simultaneously on the photocatalyst surface to form the CH4 product. Regression fitting was performed to determine the kinetic parameters such as reaction rate constant and adsorption equilibrium constants. The reaction rate as well as CO2 and H2O adsorption equilibrium constants were determined to be 84.42 μmol gcat−1 h−1, 0.019 bar−1 and 8.07 bar−1, respectively. The significantly smaller CO2 adsorption equilibrium constant implied that the adsorption of CO2 was very weak while water strongly adsorbed on the photocatalyst surface.

Thermal and Chemical Stability of Micron Aluminum Powders Subjected to Gaseous Water

The paper studies the impact of gaseous water on the stability of micron aluminum powders in time at room temperature using the method of gravimetric analysis. The stability was studied using methods of thermal analysis during heating up to 1200 °С in air. The composition of products was analyzed using X-ray diffraction analysis. It was found out that the stability of micron aluminum powders depends on partial pressure of water vapor: the increase of pressure results in decreased stability of powders. The work gives recommendations for storing micron aluminum powders.

Anodic Dissolution of Tungsten from Super Hard Alloys in Molten Sodium Hydroxide

Anodic dissolution of tungsten in a molten sodium hydroxide bath was investigated at 723K in order to simplify a tungsten dissolution step during tungsten recycling process from secondary resources like used super hard alloy tools. Cyclic voltammetry using tungsten, tungsten carbide and cobalt, which is used as binder in super hard alloys, electrodes suggested that tungsten is easily oxidized and dissolves into the melt. Cobalt was also oxidized and formed oxide or hydroxide film. When water vapor was introduced into the system, the obtained cyclic voltammograms changed with the partial pressure of water vapor. Based on the above mentioned results, anodic dissolution was carried out at constant voltage using throw-away tips as actual secondary resources. When the throw-away tip was anodically oxidized, both the tungsten carbide and binder metal of cobalt were dissolved at constant voltage of 1.0 V, and whole the tips were dissolved by a long-term electrolysis of 20 hours. Although the dissolved tungsten remained in the melt, the greater part of dissolved cobalt deposited as metal powder on the cathode. The current efficiencies of tungsten carbide dissolution were calculated to be 96%. When 0.7 atm of water vapor was introduced, the electrolysis was terminated within 5 hours, which indicates the effectiveness of water vapor pressure control in the present process.

Processing of Solid Oxide Fuel Cell Anodes for Enhanced Intermediate Temperature Catalytic Activity at High Fuel Utilization

Despite many years of research on solid oxide fuel cell (SOFC) electrolyte and electrode materials, the conventional anode formulation of nickel and yttria-stabilized zirconia (Ni-YSZ) cermet has not changed much, which highlights the effectiveness of nickel as a catalyst for the fuel oxidation reaction occurring at the triple phase boundaries (TPBs). However, most studies on single cells report results only under fuel rich atmospheric conditions in the anode, which is not representative of how fuel cell stacks are operated. SOFC stacks can easily reach fuel utilizations of 85%. High fuel utilization conditions result in lower hydrogen and higher water vapor partial pressures and an increase in anodic polarization, reducing the electrochemical performance of SOFC anodes. It is postulated that fuel oxidation reaction kinetics can be improved by increasing the TPB length via the deposition of sub-micron sized nickel particles in the cermet anode. This research analyzes the effects of various such nickel infiltration and deposition processes on the performance of anode-supported SOFC over a wide range of hydrogen and water vapor partial pressures at intermediate temperatures (600-800 Celsius). Infiltration and stability or coarsening of sub-micron nickel particles in Ni-YSZ cermets is a well-documented problem. So the impacts of various processing techniques derived from literature and developed internally were examined through long-term or accelerated testing. The cell performance was characterized using I-V and EIS techniques. The cell microstructure was characterized using SEM and image analysis techniques. Out-of-cell measurements on electrodes were also conducted to model its performance. The results were then all combined to identify the role of the sub-micron size nickel particles and the deposition process in enhancing the anode performance at high fuel utilization.

Anodic Dissolution of Tungsten from Super Hard Alloys in Molten Sodium Hydroxide

Anodic dissolution of tungsten in a molten sodium hydroxide bath was investigated at 723K in order to simplify tungsten recycling process from secondary resources like used super hard alloy tools. Cyclic voltammograms suggested that tungsten is easily oxidized and dissolves into the melt. Cobalt, which is used as binder metal, was also oxidized and formed passive film having certain solubility in the melt. When water vapor was introduced into the system, the obtained cyclic voltammograms changed with the partial pressure of water vapor. Based on the above mentioned results, anodic dissolution was carried out at constant cell voltage using throw-away tips as an actual super hard alloy tool. When water vapor was introduced into the system, the cell voltage and duration required to dissolve whole the tips were reduced.

Modeling investigation of wet tropospheric delay error and precipitable water vapor content in Egypt

A set of 1092 radio soundings was performed at the Egyptian stations in the south of Egypt, near the Mediterranean Sea, and near the Red Sea in 2005. These measurements are mean monthly data that were used to determine the mean vertical profiles of water vapor pressure and its effect on GPS signal propagation (wet tropospheric delay) in the troposphere and lower stratosphere. Temperature data were corrected for errors due to radiation, heat exchange processes, and for the lag errors of the sensor. Due to temperature dependence and other dry bias effects, the humidity errors were also taken into account. The results showed that partial water vapor pressure in Egypt varies from 6.43 to 23.19mb and decreases significantly with height. In addition, the quantity of water vapor pressure above 8km is negligible. Results showed that, in Egypt zenith wet delay varies from 66.84mm to 239.34mm. It can be concluded that, the best model to predict zenith wet tropospheric delay for the atmospheric conditions of Egypt is the Saastamoinen model with a mean error of 11mm and rms of 3.12mm.

Bismuth phosphates as intermediate temperature proton conductors: From polycrystalline powders to amorphous glasses

Proton conducting electrolyte materials operational in the intermediate temperature range of 200–400 °C are of special interest for applications in fuel cells and water electrolysers. Bismuth phosphates in forms of polycrystalline powders and amorphous glasses are synthesized and investigated by scanning electron microscopy, X-ray diffraction, FT-IR, thermogravimetric analysis and AC impedance. Under dry atmosphere the pure crystalline and amorphous phosphates exhibit an intrinsic conductivity of up to 10−5 S cm−1 at 250 °C. In the presence of atmospheric humidity the conductivity of both types of phosphates is significantly enhanced, reaching about 10−2 S cm−1 at a water vapor partial pressure above 0.5 atm. During a period of more than 100 h with four humidity cycles from zero to 0.58 atm of the water vapor partial pressure, the phosphates show good stability, suggesting the potential as an intermediate temperature electrolyte.

Effect of Nb Doping on Hydration and Conductivity of La27W5O55.5−δ

Hydration properties and electrical characteristics of the high‐temperature proton conductor La27(W0.85Nb0.15)5O55.5−δ are investigated by means of thermogravimetry, impedance spectroscopy, and the electromotive force (EMF) method as a function of temperature, water vapor, and oxygen partial pressures, as well as isotope exchange measurements in order to elucidate the mechanism and thermodynamics of protons formation and transport. The highest proton conductivity, 1.3 × 10‐3 S/cm, is achieved at 700°C in wet O2. Proton self‐diffusion coefficients are estimated from thermogravimetric measurements of hydration and conductivity data. Comparison of the conductivity characteristics between nominally pure and Nb‐substituted materials reveals that the ionic conductivity increases and the activation energy decreases with Nb doping. These differences are discussed to reflect changes in the structure promoting ionic transport rather than changing the concentration of defects to any large extent.

MATRIX, a multi activity test-room for evaluating the energy performances of ‘building/HVAC’ systems in Mediterranean climate: Experimental set-up and CFD/BPS numerical modeling

Technology transfer, scientific research and education could have a key role in Mediterranean regions, in order to reduce the environmental impact of the building sector.Recently, the Department of Engineering of University of Sannio has developed a laboratory suitable for performing researches on the dynamic interactions between building envelope components, indoor environment and mechanical systems for a typical climate of south of Italy.The work described within this paper is a part of this large-scale project. Its goals are: (a) to design, test and validate a poly-equipped test room, (b) to perform transient tests to determine performances of common and innovative building components and alternative HVAC systems. More in detail, this paper focuses on the first goal, with the aim to generalize the design approach, requirements and capabilities of calibrated outdoor test facilities, specifically thought for Mediterranean climate. The facility has undergone a substantial amount of characterization tests, aimed at determining its response under yearly operations. The primary conclusions are that the new test facility is usable for a wide range of environmental and indoor conditions, it is functional and has been validated through characterization and preliminary investigations of the behavior of the thermal envelope.Moreover, some experimental results are here analyzed, by evidencing the potentialities of vacuum insulation panels for improving the performances of the thermal envelope, for what concerns both winter and summer seasons. Then, some numerical analyses have been carried out. A 3D CFD model has been calibrated for studying the real distribution of temperatures and water vapor partial pressures within VIP panels. Furthermore, a dynamic energy model of the test cell has been developed by means of Energy Plus, with the aim to use its capability to compare potential configurations that would be installed in future researches, or to evaluate energy, environmental and economic issues.

Study of mass transport kinetics in co-doped Ba0.9Sr0.1Ce0.85Y0.15O3 − δ by electrical conductivity relaxation

In this work, Sr2+ and Y3+ co-doped BaCeO3-based perovskite Ba0.9Sr0.1Ce0.85Y0.15O3−δ (BSCY) was synthesized by solid-state reaction method, and its mass transport behavior was studied using electrical conductivity relaxation (ECR) measurements in 600–800°C range with respect to variations in oxygen partial pressure (pO2) and water vapor pressure (pH2O). During oxidation/reduction process, the electrical conductivity showed a monotonic relaxation behavior and in −2.65≤log(pO2/atm)≤−0.67 range the values of oxygen chemical diffusivity (D˜vO) and surface exchange coefficient (κvO) varied in 10−6–10−4 cm2⋅s−1 and 10−4–10−2 cm⋅s−1 range, respectively. However, during hydration/dehydration process, the electrical conductivity showed a non-monotonic twofold relaxation behavior, and hydrogen, and oxygen chemical diffusivities (D˜iH) and (D˜vH) values were in 10−5–10−3 and 10−6–10−4 cm2⋅s−1 range, respectively, whereas hydrogen and oxygen surface exchange coefficient (κiH) and (κvH) values were in 10−3–10−2 and ~10−4–10−2 cm⋅s−1 range, respectively. The comparison of H and O diffusivities of BSCY with BaCe0.85Y0.15O3−δ (BCY) showed that during hydration/dehydration the diffusivities of BSCY were lower than that of BCY. The long-term electrical conductivity measurement for ~800h in humidified conditions showed a gradual decrease, which might be due to the gradual appearance of rhombohedral phase in otherwise orthorhombic BSCY, as confirmed by the X-ray diffraction (XRD) measurements.

On the significant enhancement of the continuum-collision induced absorption in H2O+CO2 mixtures

The IR spectra of water vapor–carbon dioxide mixtures as well as the spectra of pure gas samples have been recorded using a Fourier-transform infrared spectrometer at a resolution of 0.1cm−1 in order to explore the effect of colliding CO2 and H2O molecules on their continuum absorptions. The sample temperatures were 294, 311, 325 and 339K. Measurements have been conducted at several different water vapor partial pressures depending on the cell temperature. Carbon dioxide pressures were kept close to the three values of 103, 207 and 311kPa (1.02, 2.04 and 3.07atm). The path length used in the study was 100m. It was established that, in the region around 1100cm−1, the continuum absorption coefficient CH2O+CO2 is about 20 times stronger than the water–nitrogen continuum absorption coefficient CH2O+N2. On the other hand, in the far wing region (2500cm−1) of the ν3 CO2 fundamental band, the binary absorption coefficient CCO2+H2O appears to be about one order of magnitude stronger than the absorption coefficient CCO2+CO2 in pure carbon dioxide. The continuum interpretation and the main problem of molecular band shape formation are discussed in light of these experimental facts.

Effect of anode gas mixture humidification on the electrochemical performance of the BaCeO3-based protonic ceramic fuel cell

In this work a tape-calendering method has been adopted to fabricate an anode-supported proton ceramic fuel cell (PCFC) with a 50 μm BaCe0.89Gd0.1Cu0.01O3–δ proton-conducting electrolyte. In order to evaluate the feasibility of the method the PCFC's characteristics such as open-circuit voltage, power density, ohmic and polarization losses were investigated with special attention being given to the effects of water vapor partial pressure in an anode gas mixture on the PCFC's performance and the transport properties of the electrolyte. It was found that the proton transport number of the electrolyte increases significantly with increased water content which ensures greater efficiency of the PCFC due to more complete fuel utilization. The electrodes contribute 50% of the total voltage drop of the developed PCFC element at 600 °C and 25% at 750 °C. This is principally due to the tangible contact resistance between the cathode and the electrolyte as well as the low electrocatalytic activity of the Pt cathode. The anode atmosphere humidification can be considered as a perspective strategy for further enhancement of PCFC's performance.

Investigating the solid–gas phase reaction between WO3 powder, NH3 and H2O vapors to prepare ammonium paratungstate

The solid–gas phase heterogeneous reaction between tungsten oxide powder, ammonia and water vapors was studied with the aim of preparing ammonium paratungstate (APT, (NH4)10[H2W12O42]·xH2O (X=4, 10)). The effects of the composition, crystal structure and particle size of the WO3 powder were investigated along with the effect of the partial pressure of ammonia and water vapor on the products. The as-prepared APT was characterized with powder XRD, FTIR, Raman, SEM, TEM and TG/DTA-MS measurements. At 43.40kPa and 12.23kPa ammonia partial pressures after one day two partially reduced intermediates, i.e. W5O14 and (NH4)2W2O7·0.5H2O, were identified, which transformed into APT·4H2O in 30days with a yield of almost 100%. (NH4)2W2O7·0.5H2O was produced for the first time ever, while for W5O14 this was a new preparation route, as it was only produced in great vacuum at high temperature before. At 1.56kPa ammonia partial pressure APT·10H2O was also a product of the reaction. At lower ammonia partial pressures the reaction was very slow, and only small changes were detected in the structure after 30days. The results showed that this novel synthesis of APT is not sensitive to the reaction conditions, in contrast to the previously only available wet chemical crystallization process. According to the measurements, the as-produced APT is equivalent to the commercial ones. As an additional feature, our method is capable to yield APT nanoparticles for the first time, which is important for both research and industry due to the greater surface area.

An experimentally validated numerical model of interface advance of the lithium sulfate monohydrate dehydration reaction

Interface advance plays an essential role in understanding the kinetics and mechanisms of thermal decomposition reactions such as the dehydration reaction of lithium sulfate monocrystals. However, many fundamental processes including mass transfer during interface advance are still not clear. In this work, the dynamics of interface advance, involving interaction between interfacial reaction and mass diffusion, is investigated numerically together with microscopy observations. A mathematical model is developed for interface advance with a moving boundary and then solved by using a conservative scheme. To examine the significance between the intrinsic chemical reaction and mass diffusion, a Damkohler number is defined as $$Da=k_{{\rm r}}L/(D_{{\rm e}} c_{0})$$ . Numerical results at various Da values are discussed to distinguish the limiting step of the dehydration reaction of lithium sulfate monocrystals. Moreover, experiments are carried out with a hot-stage microscopy system where the propagation of the reaction interface into the crystal bulk is followed in situ. By fitting the experimental results with the numerical results, the effective diffusivity of water through the dehydrated crystal is estimated to be in the order of $$10^{-8}\,\hbox {m}^2\,\hbox {s}^{-1}$$ . According to the corresponding Da values, it is found that, within the reaction temperature ranging from 110 to 130 °C and a partial water vapor pressure of 13 mbar, the rate of dehydration interface advance in the bulk of large crystals (typically in the order of millimeters) is not constant, but shows a small decrease over time due to the influence of mass diffusion.

Кристаллическая структура и дефектность перовскитоподобного протонного проводника Ba4Ca2Nb2O11

The crystal structure complex oxide Ba4Ca2Nb2O1 inanhydrous and hydrated forms was studied by the method of neutron diffraction, the preferred localization of protons were set. The hydration process with temperature variation and the partial pressure of water vapor was studied. It is established that the crystallographic non-equivalence OH-groups in the structure determines their different thermal stability. The quasi-chemical approach was proposed that describes the formation of proton defects in oxides with structural disordering.

A Novel Scale Up Model for Prediction of Pharmaceutical Film Coating Process Parameters.

In the pharmaceutical tablet film coating process, we clarified that a difference in exhaust air relative humidity can be used to detect differences in process parameters values, the relative humidity of exhaust air was different under different atmospheric air humidity conditions even though all setting values of the manufacturing process parameters were the same, and the water content of tablets was correlated with the exhaust air relative humidity. Based on this experimental data, the exhaust air relative humidity index (EHI), which is an empirical equation that includes as functional parameters the pan coater type, heated air flow rate, spray rate of coating suspension, saturated water vapor pressure at heated air temperature, and partial water vapor pressure at atmospheric air pressure, was developed. The predictive values of exhaust relative humidity using EHI were in good correlation with the experimental data (correlation coefficient of 0.966) in all datasets. EHI was verified using the date of seven different drug products of different manufacturing scales. The EHI model will support formulation researchers by enabling them to set film coating process parameters when the batch size or pan coater type changes, and without the time and expense of further extensive testing.

Partial conductivities in perovskites CaZr1–x Sc x O3–α (x = 0.03–0.20) in an oxidation atmosphere

Partial (ionic, proton, and hole) conductivities of oxides CaZr1–xScxO3–α(x = 0.03–0.20) with the perovskite structure in air atmosphere have been studied as functions of temperature in the range of 600–900°C and partial water-vapor pressure in the range of \({P_{{H_2}O}}\)= 40–2500 Pa. The influence of the humidity of the atmosphere on the relative change in the concentration of oxygen vacancies as a function of temperature has been estimated.

Thin Water Films at Multifaceted Hematite Particle Surfaces.

Mineral surfaces exposed to moist air stabilize nanometer- to micrometer-thick water films. This study resolves the nature of thin water film formation at multifaceted hematite (α-Fe2O3) nanoparticle surfaces with crystallographic faces resolved by selected area electron diffraction. Dynamic vapor adsorption (DVA) in the 0-19 Torr range at 298 K showed that these particles stabilize water films consisting of up to 4-5 monolayers. Modeling of these data predicts water loadings in terms of an "adsorption regime" (up to 16 H2O/nm(2)) involving direct water binding to hematite surface sites, and of a "condensation regime" (up to 34 H2O/nm(2)) involving water binding to hematite-bound water nanoclusters. Vibration spectroscopy identified the predominant hematite surface hydroxo groups (-OH, μ-OH, μ3-OH) through which first layer water molecules formed hydrogen bonds, as well as surface iron sites directly coordinating water molecules (i.e., as geminal η-(OH2)2 sites). Chemometric analyses of the vibration spectra also revealed a strong correspondence in the response of hematite surface hydroxo groups to DVA-derived water loadings. These findings point to a near-saturation of the hydrogen-bonding environment of surface hydroxo groups at a partial water vapor pressure of ∼8 Torr (∼40% relative humidity). Classical molecular dynamics (MD) resolved the interfacial water structures and hydrogen bonding populations at five representative crystallographic faces expressed in these nanoparticles. Simulations of single oriented slabs underscored the individual roles of all (hydro)oxo groups in donating and accepting hydrogen bonds with first layer water in the "adsorption regime". These analyses pointed to the preponderance of hydrogen bond-donating -OH groups in the stabilization of thin water films. Contributions of μ-OH and μ3-OH groups are secondary, yet remain essential in the stabilization of thin water films. MD simulations also helped resolve crystallographic controls on water-water interactions occurring in the "condensation regime". Water-water hydrogen bond populations are greatest on the (001) face, and decrease in importance in the order (001) > (012) ≈ (110) > (014) ≫ (100). Simulations of a single (∼5 nm × ∼ 6 nm × ∼ 6 nm) nanometric hematite particle terminated by the (001), (110), (012), and (100) faces also highlighted the key roles that sites at particle edges play in interconnecting thin water films grown along contiguous crystallographic faces. Hydroxo-water hydrogen bond populations showed that edges were the preferential loci of binding. These simulations also suggested that equilibration times for water binding at edges were slower than on crystallographic faces. In this regard, edges, and by extension roughened surfaces, are expected to play commanding roles in the stabilization of thin water films. Thus, in focusing on the properties of nanometric-thick water layers at hematite surfaces, this study revealed the nature of interactions between water and multifaced particle surfaces. Our results pave the way for furthering our understanding of mineral-thin water film interfacial structure and reactivity on a broader range of materials.