Oxygen Water System Research Articles

The Effect of Impeller–Sparger Geometry on the Gas Holdup in an Oxygen–Water System Using an Agitated and Sparged Tank Contactor

The Effect of Impeller–Sparger Geometry on the Gas Holdup in an Oxygen–Water System Using an Agitated and Sparged Tank Contactor

Estimation of Gas Holdup Using the Gassed to Ungassed Power Ratio of an Oxygen-Water System in a Stirred and Sparged Tank Contactor.

Gas holdup (εg) and power correlations in gas–liquid (G–L) systems, apart from the physicochemical properties of the liquid phase, are dependent on impeller–sparger–vessel geometry. To date, reported correlations do not specifically address this issue, and it must be investigated with a unified approach. Here, we propose a correlation via the use of a normalized εg that involves the impeller–sparger system geometry for a vessel of standard geometry expressed as a function of an easily measurable and independent operational parameter, that is, (1 – Pg/Pl), where Pg/Pl is the gassed to ungassed power ratio. Furthermore, our work demonstrates that Pg/Pl can be used as a tool for the identification of hydrodynamic regimes. Radial and axial impellers with ring spargers were used in a stirred and sparged contactor (SSTC) of 0.25 m diameter containing 1 × 10–2 m3 water. The oxygen flowrate (Qg) was varied from 2.5 to 40 LPM or (4.17 to 66.7) × 10–5 m3 s–1, and the agitation intensity (N0) was varied from 1.67 to 50 rps at the temperature (θ) = 313 K under atmospheric pressure. This novel correlation is easy to use, offers reasonable precision, and can serve as a valuable alternative to more complex correlation models.

Fuel‐Free Bio‐photoelectrochemical Cells Based on a Water/Oxygen Circulation System with a Ni:FeOOH/BiVO4 Photoanode

AbstractA bio‐photoelectrochemical cell (BPEC) based on a fuel‐free self‐circulation water–oxygen–water system was fabricated. It consists of Ni:FeOOH modified n‐type bismuth vanadate (BiVO4) photoanode and laccase catalyzed biocathode. In this BPEC, irradiation of the photoanode generates photocurrent for photo‐oxidation of water to oxygen, which is reduced to water again at the laccase biocathode. Of note, the by‐products of two electrode reactions could continue to be reacted, which means the H2O and O2 molecules are retained in an infinite loop of water–oxygen–water without any sacrificial chemical components. As a result, the assembled fuel‐free BPEC exhibits good performance with an open‐circuit potential of 0.97 V and a maximum power density of 205 μW cm−2 at 0.44 V. This BPEC based on a self‐circulation system offers a fuel‐free model to enhance multiple energy conversion and application in reality.

Emitters of chemiluminescence occurring during autoxidation of substituted hydroquinones in water

A mathematical processing method for determination of spectral parameters of chemiluminescence emitters during the autoxidation of phenolic compounds in aqueous-alkaline media has been developed. The presence of a single luminescence emitter (the corresponding p-benzoquinone in the triplet state) has been demonstrated in the hydroquinone–oxygen–water system. The emitters spectra have been obtained.

Interaction between phases in the liquid–gas system

This work analyzes the equilibrium between a liquid and a gas over this liquid separated by an interface. Various gas forms exist inside the liquid: dissolved gas molecules attached to solvent molecules, free gas molecules, and gaseous bubbles. Thermodynamic equilibrium is maintained between two phases; the first phase is the liquid containing dissolved and free molecules, and the second phase is the gas over the liquid and bubbles inside it. Kinetics of gas transition between the internal and external gas proceeds through bubbles and includes the processes of bubbles floating up and bubble growth as a result of association due to the Smoluchowski mechanism. Evolution of a gas in the liquid is considered using the example of oxygen in water, and numerical parameters of this system are given. In the regime under consideration for an oxygen–water system, transport of oxygen into the surrounding air proceeds through micron-size bubbles with lifetimes of hours. This regime is realized if the total number of oxygen molecules in water is small compared with the numbers of solvated and free molecules in the liquid.

Liquid concentration profile and mass transfer efficiency for an aerotank-sedimentation tank system

Analytical solutions are obtained for the liquid concentration profile along the length of an aerotank in the case of the oxygen-water system and for the mass transfer efficiency in the absorption of oxygen by water to calculate the mass transfer kinetics and sizes of an aerotank and to determine its optimal operating modes.

Effect of Bottom Bubbling Conditions on Surface Reaction Rate in Oxygen–Water System

In secondary steelmaking, the enhancement of the reaction rate in the low carbon period during the decarburization of steel is considered the most effective method to produce ultralow carbon steel. In a previous study, it was revealed that the surface reaction is dominant during the final stage of the actual refining process. In order to improve the surface reaction rate, it is necessary to enlarge the reaction region, which is usually achieved by increasing the plume eye area. In this study, water model experiments were carried out to estimate the influence of bottom stirring conditions on the gas-liquid reaction rate; for this purpose, the deoxidation rate during the bottom bubbling process was measured. Five types of nozzle configurations were used to study the effect of the plume eye area on the reaction rate at various gas flow rates. The results reveal that the surface reaction rate is influenced by the gas flow rate and the plume eye area. An empirical correlation was developed for the reaction rate and the plume eye area. This correlation was applied to estimate the gas-liquid reaction rate mat the bath surface.

Phase equilibria for the oxygen–water system up to elevated temperatures and pressures

A new thermodynamic model was presented to calculate the phase equilibria for the oxygen–water system. The modified Redlich–Kwong equation of state with a new correlated cross-interaction parameter was used to calculate fugacity coefficients for the vapor phase. The dissolved oxygen followed Henry’s law. A new expression was correlated from the experimental data to calculate Henry’s constant of oxygen. The calculated results of equilibrium composition were compared with the available experimental data and those calculated by other models with different parameters. The comparison revealed that the new model is suitable for calculating both liquid and vapor compositions while the empirical method is only suitable for estimating the liquid composition. Furthermore, compared to the model proposed by Rebenovich and Beketov, the calculated results of the vapor composition with the new model are better.

Saturated thermodynamic properties for the air–water system at elevated temperatures and pressures

A new thermodynamic model is proposed to calculate the thermodynamic properties for the air–water system in which the dry air was assumed to be a mixture of nitrogen and oxygen with the mole fractions of 0.7812 and 0.2188, respectively. For the vapor phase, fugacity coefficients were calculated with the modified Redlich–Kwong equation of state in which a new interaction parameter of oxygen and water was correlated from the experimental data of oxygen–water system. The dissolved gas followed Henry's law. Henry's constant of nitrogen was calculated with the Helgeson equation of state and that for oxygen was correlated from the experimental data of oxygen–water system. The proposed model was verified by comparing the calculated results with the available experimental data. It is shown that the proposed model is suitable for predicting saturated thermodynamic properties for the air–water system up to 300°C and 200 atm . Furthermore, the prediction results of the proposed model are better than those calculated with the model of Rabinovich and Beketov (Moist Gases, Thermodynamic Properties. Begell: House, 1995), and the application range is wider than that of the model of Hyland and Wexler (ASHRAE Trans. 89(2A) (1983a, b) 500–519, 520–535) which are among the best of today's models.

Intensification of random packing via CFD simulation, PIV measurement and traditional experiments

AbstractIt is shown from CFD simulation and particle image velocimetry (PIV) measurements that the flow field around ring packing is impacted by their height/diameter ratio and inclination. The results indicate that it is better to decrease the height/diameter ratio of ring packing to intensify the separation processes in the packing bed. Based on a systematic study, a new Plum Flower Mini Ring (PFMR) was developed to meet the demands of separation column intensification.A comparison of the PFMR, Pall Ring and Intalox Saddle in a 600 mm diameter column with an air–oxygen–water system over a wide range of liquid loads is presented. It was shown from the experiments that the PFMR had a much lower pressure drop, much larger throughput and better mass transfer efficiency than Pall Rings and Intalox Saddles.© 2003 Society of Chemical Industry

The zinc–vanadium–oxygen–water system: hydrothermal synthesis and characterization

Abstract Zinc forms a variety of structures with vanadium oxide. We review and report here on four compounds formed by mild hydrothermal synthesis in the presence of the tetramethyl ammonium ion, which tends to stabilize layered vanadium oxide structures. These invariably contain protons either in the form of hydroxyl ions or as structural water. The compounds include Zn 3 (OH) 2 (V 2 O 7 )•2H 2 O, which contains V 2 O 7 pillars, Zn 2 (OH) 3 (VO 3 ), and the two related double sheet vanadium oxides δ -Zn 0.8 V 4 O 10 •0.6H 2 O and [N(CH 3 ) 4 ] 4 [Zn 4 V 21 O 58 ]. We report the new structure of the last, which was determined from micron size crystals, and compare it to other double sheet structures. These compounds provide model systems to study ionic mobility and reversible redox chemistry.

Solubility of oxygen and inert substances in water

The solubility of oxygen in water at different temperatures has been analysed in the light of a statistical thermodynamic model. According to the model, the oxygen–water system is considered as a convoluted ensemble consisting of a reacting system, formed by oxygen molecules and structured solvent with enthalpy difference Δ H φ between discrete enthalpy levels, and of a non-reacting system with continuous distribution of enthalpy levels. The enthalpy change of the reaction between oxygen and water, as determined either by measuring the solubility of substances in water at different temperatures either by measuring heat calorimetrically, is partially absorbed by some n w water molecules. The relaxed water molecules occupy part of the cavity formed around solute. The part of heat absorbed, Δ H w depends linearly upon the temperature and causes the observed changes with temperature of apparent enthalpy Δ H app for the dissolution of oxygen and many other inert substances in water. The number n w is proportional to the size of solute as shown by comparison with noble gases and other inert substances slightly soluble in water. The solubilization process of all these substances is clearly analogous.

Water Cluster Ions: Formation and Decomposition of Cluster Ions in the Oxygen-Water System

Drift-tube techniques have been employed to determine rate constants in the reaction sequence leading to formation of the hydronium ion hydrates H3O+(H2O)n starting from O2+ ions in O2–H2O gas mixtures at 310°K. Total pressures used ranged from 0.5 to 2 torr with water partial pressures from 0.15 to 1.2%. Measured three-body clustering rate constants declined in all cases as E/P0 increased in the range 5–30 V cm−1· torr−1. Thermal rate constants were deduced from the low E/Po data. Mobilities for O2+ and H3O+(H2O)n in oxygen are given as a function of E/Po in the range 5–60 V cm−1· torr−1 and for O2+ and H3O+ in argon from 4 to 20 V cm−1· torr−1. In oxygen, quasiequilibrium studies were conducted in which a cluster ion H3O+(H2O)n loses one or more water molecules during drift, successive ions from n=3 to 0 becoming dominant as E/Po increased from 5 to 60 V cm−1· torr−1. A simple analytical model for treating sequential reactions in drift experiments is presented.

PROTON SPIN RELAXATION BY PARAMAGNETIC MOLECULAR OXYGEN

The proton spin–lattice relaxation time, T1, was measured for oxygen solutions of water, methanol, and acetone at different temperatures and resonance frequencies of 10.8, 20.0, and 29.8 Mc/s. The contribution of O2 to the relaxation was assumed to be due to the dipole–dipole and hyperfine interaction between the proton spins and the unpaired spins of the O2 molecule. The correlation times of the two interactions were related to the motion and the size of the polymeric cluster of the solvent. Activation energies for the two correlation times were obtained for the oxygen–water system from the dependence of the relaxation time on the resonance frequency. No separation of the two terms was possible for either the oxygen–methanol or oxygen–acetone systems because of their independence of magnetic field variations. The correlation time of the hyperfine term was postulated to be a measure of the extent of solvent–oxygen hydrogen bond strength in all the measured systems.