Improvement of a Measurement System for Surface Loss Rate of Ozone

Ozone molecules present in high-purity oxygen as a feed gas interact with surfaces and oxygen molecules in an enclosed container. Therefore, some of the ozone molecules are destroyed and the density of ozone decreases with time. An experimental system has been constructed to monitor the temporal decrease in ozone density in a container based on the HgI 254 nm photoabsorption method. Our investigation is focused on the dependence of the effective lifetime of ozone on the wall material at various gas pressures. During the experiments, distortion of the measured decay curves often caused by instabilities in the mercury lamp intensity. We thus attempted to build a simple setup that eliminates the effect of long-term intensity drift. This setup is based on light source intensity monitoring by a separate photodetector and data correction software. This article describes the setup of the experimental apparatus, the results including some preliminary experiments and the temporal variation of the surface loss rate of ozone by repeated measurement along with inspections of the wall surface by Auger electron spectroscopy.     

The Use of Gaseous Ozone as a Cleaning Agent on Stainless Steel Surfaces Fouled with Bovine Protein

Facilitation of cleaning of stainless steel particles fouled with heat-treated bovine serum albumin (BSA) was studied using gaseous ozone generated from a pure oxygen-fed ozonizer at concentrations of 0.1 to 0.5% (v/v). Ozone pretreatment markedly accelerated the rate of BSA desorption during subsequent caustic alkali cleaning. The effect of ozone pretreatment depended on the concentration of ozone and it was attributed to partial decomposition of BSA molecules into some fragments. It was also found that the surface charge property of stainless steel particles was modified by ozone oxidation, resulting in the improvement of the cleanability of stainless steel surfaces.     

The Effect of Gaseous Diluents on Ozone Generation from Oxygen

Ozone generation in a negative corona discharge has been experimentally investigated using both a pure oxygen and in binary mixtures of oxygen with several gases. The concentration of ozone (O₃) in such mixtures is found to be dependent both on the input energy density η, dissipated in unit volume of gas mixture and on the type and the concentration of the additives. The experimentally measured dependencies of ozone concentration on the input energy density (O₃) = f(η) have been fitted using the Vasiliev–Kobozev–Eremin formula and the specific rate coefficients for ozone formation K_f and ozone decomposition K_d have been calculated. Using Ar, N₂ or CO₂ as admixtures, an increase in the specific rate coefficient for ozone generation was observed for increasing concentrations of added gaseous impurity into oxygen. In contrast, admixtures with SF₆ or CCl₂F₂ caused a substantial reduction of K_f values. The absolute values of ozone concentration at constant input energy density were observed to decrease with decreasing concentrations of oxygen in all mixtures.     

Corrosion Resistance of Ozone Generator Electrode

Materials used for the discharge tubes of ozone generators and also their method of production are examined, focusing on the conductive film characteristics. In comparison with the aluminum hot spray method, the stainless steel sputtering method can form a thinner and denser amorphous conductive thin film with corrosion resistance. It has higher durability exposed under discharge species than other materials ever before used.     

Experimental Investigations On Production Of Excited Ozone Species From A Silent Discharge Ozone Generator

Ozone decomposition kinetics are investigated together with the influence of energy input to an ozone generator. Decomposition is considered in a solid bed reactor, a gas phase reactor and a bubbling reactor. Ozone is produced at the same concentration and gas flow rate using two methods: 1) from the generator at a higher power giving higher ozone concentration, then ozone is diluted by oxygen before entering the decomposition reactor, and 2) at a lower power without dilution.     

Evaluation of Solubility and the Gas-Liquid Equilibrium Coefficient of High Concentration Gaseous Ozone to Water

Solubility and the gas-liquid equilibrium coefficient of gaseous ozone to water were examined under higher concentrations of supplied gaseous ozone up to 100 mg/L. The experimental and modeling approach was employed to evaluate the gas-liquid equilibrium coefficients and mass transfer of ozone. The gas-liquid equilibrium coefficients were evaluated as 0.35, 0.31 and 0.25 (mg/L-liquid)/(mg/L-gas) at 15, 20 and 30 °C, respectively. These gas-liquid equilibrium coefficients are applicable for the wide concentration range of supplied ozone gas up to 100 mg/L. The calculation result by a model which has terms of the mass transfer of ozone, the gas-liquid equilibrium coefficient and the rate of ozone self-decomposition, was examined and had a good agreement with the experimental data over the wide range of temperatures, pHs, inorganic carbon concentrations and supplied ozone gas concentrations. The rate of ozone self-decomposition evaluated separately from this study was employed for the calculation. We can conclude that absorption of gaseous ozone to water is expressed by the three terms mentioned above when the rate of ozone self-decomposition is evaluated properly. In sensitive analysis, we elucidated that the rate of ozone self-decomposition affected strongly on the concentration of dissolved ozone at steady-state under higher concentration of supplied gaseous ozone.     

Ozone Gas Scrubbing for Air-Operated Ozone Generation Systems

In laboratory testing as well as in tests using a semi-technical plant it was found that removal of the gaseous N₂O₅ as a by-product of ozone generation from air can be realized from a chemical point of view by gas scrubbing using treated drinking water, and forming nitric acid. At the same time this measure accomplishes a reduction of the trichloronitromethane (TCNM = chloropicrin) concentration in the treated water from Lake Constance by 30%. Surprisingly it was also found that the material used herein (stainless steel DIN 1.4571) will be attacked under conditions such as these.     

A Study of Ozone Formation on the Surfaces of Electrodes

It had been previously thought that ozone production occurred in gaseous space, especially the space between electrodes. However, based on our research, we believe that may only be one of the ozone-producing processes. In this study, we aimed to confirm that a third body, which is present at the interface between oxygen gas and a metal electrode, works to compose ozone. Ozone was not observed in pure oxygen (400x10^?6 Nm³/min flow rate) when electrical discharge was supplied after approximately 6 months. The concentration of ozone increased (approximately 0.07 ppm) when nitrogen (approximately 20x10^?6 Nm³/min flow rate) was added to a gas-mixing chamber. A third body was required to produce ozone when an oxygen molecule and an oxygen atom collided. The same phenomenon was observed on the surface of a copper anode. A simulation confirmed this. Using an industrial ozone generator which utilized ceramic dielectrics and expanded metal electrodes, an increase in the temperature of the cooling water led to a proportional decrease in ozone concentration. After changing from the titanium electrode to a nickel electrode and an antimony electrode, we observed the difference in the enthalpy changes which were calculated using van't Hoff's formula. The antimony electrode increases the efficiency of the ozone generator to produce ozone. We have come to believe that ozone can be composed on the surface of a metal electrode.     

Optimizing Factors on High Concentration of Ozone Production with Dielectric Barrier Discharge

The gap distance, electrode material, voltage and gas flow velocity were optimized with gas pressure variation of dielectric barrier discharge (DBD) for producing high concentration of ozone. There exists an optimum gas pressure at which the highest ozone concentration is produced with other parameters being fixed. This optimum gas pressure value changes accordingly as the other parameters changed. As the discharge continues at the optimum pressure, the ozone concentration could increase or decrease slowly. This aging effect has different characteristics with the metal electrode material and the impurity level of the oxygen gas used for ozone generation. The aging effect is supposed to be related with the catalytic effect of metal oxide, which is generated in the discharge zone. The change in the characteristic of optimum pressure by the other parameters, indicate that the ozone concentration is deeply related with the filament self-organization characteristics of DBD. At the final optimized condition, the ozone concentration was higher than 22.5 wt.%.     

Ozone decomposition on glass and silica

Ozone decomposition on glass and silica surfaces is studied by means of non‐porous particles in a fixed bed (sand, glass bead, crushed glass bead, silica). Influences of gas velocity, particle diameter and reactor volume are investigated. Ozone is produced by a silent discharge generator. A model considering the geometric characteristics of material is used so that the ozone decomposition rate per unit of surface area is identified. The decomposition reaction is represented by means of an apparent first‐order kinetic constant. The high dependency of the apparent kinetic constant on the surface area, for given flow rates, suggests that the ozone decomposition mechanism is not simple. Due to the values of the apparent first order kinetic constant, the existence of catalytic species produced by the ozone generator, as well as excited ozone and/or oxygen species, are considered, by means of several models, to explain the experimental results.     

On the Performance of Ozone Generators Working with Dielectric Barrier Discharges

The parameters, which determine the performance of ozone generators, are efficiency and maximum ozone concentration. The efficiency from oxygen has been found to be nearly independent on the kind of barrier discharge arrangement (volume, surface, coplanar), while the ozone concentration saturation level depends on the specific design of the generator. These phenomena are explained with features of the discharge process and the properties of chemical reactions, respectively. The importance of a limit in the energy density of the discharge is highlighted.     

Role of Ozone Concentrations and Exposure Times in Extending Shelf Life of Strawberry

Efficiency of three aqueous ozone concentrations (0.075 ppm, 0.15 ppm, 0.25 ppm) and two exposure times (2 and 5 min) were investigated for maintaining strawberry quality. Exposure to 0.075 ppm and 0.15 ppm ozone delayed the changes in pH, total soluble solids, firmness and electrical conductivity. All ozone treatments prevented mold growth during storage. However, the 0.25 ppm ozone treatment caused loss of strawberry quality due to high ozone concentration. The results have shown that; low (0.075 ppm) and middle (0.15 ppm) ozone concentrations can be applied to extend the shelf-life of strawberries by at least 3 weeks under refrigerated conditions.     

Effects of surface roughness and the chemical structure of materials of construction on wall slip behavior of linear low density polyethylene in capillary flow

The presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion. © 1993 John Wiley & Sons, Inc.     

Optimizing an Intermediate Ozone System Used for Primary Disinfection at a 55 MGD Surface Water Treatment Plant

The Henrico County VA Water Treatment Facility has been in operation since April 2004, making use of intermediate ozone for primary disinfection to take advantage of both the disinfection and DBP benefits. Since the summer of 2007 the staff at the Henrico WTF has embarked on an optimizing journey with their ozone system. This paper overviews the significant milestones accomplished on this journey as well as ongoing improvements. Optimizing efforts to reduce operating costs while achieving disinfection goals included: Staff training workshops; Automating ozone data collection and access; Operating system at optimum ozone concentration; Selecting optimum contactor sampling locations and number of contactors; Overcoming minimum gas flow limitations; Solenoid contactor sampling system issues and improvements; Disinfection calculation constraints; Excessive buildup of liquid oxygen (LOX) tank pressure. Each of these items is discussed following an overview of this 55 MGD surface water treatment facility.     

Pool boiling of water-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and water-Cu nanofluids on horizontal smooth tubes

Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al₂O₃ and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al₂O₃ and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al₂O₃ or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density.     

Treatment of Water Contaminated with Chlorinated Organic Herbicide 2,4-D by an Ozone/Gamma Process

Radiation-induced degradation of 50 ppm 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated in different ozonation times. Co-60 gamma-source was used as a gamma-source with a dose rate of 0.07 kGy/h. Ozonized samples were irradiated for the 0.2 kGy dose. It is observed that irradiation enhances the degradation of 2,4-D with ozone. The amount of passed ozone from samples is between 0.0695 g/L and 8.33 g/L with a flow rate of ozone at 0.078 L/min (10 g/h), from 10 s to 1200 s with the ozone generator. Aliphatic acids and chloride were determined with ion chromatography. Formaldehyde, dissolved oxygen, pH and total acidity were also measured. Both species and amounts of radiolytic intermediates were determined. 2,4-dichloro phenol (2,4-DCP) is one of the toxic intermediates of 2,4-D observed with GC/MS and it decomposes at further ozonation times. It is observed that combination of ozone/gamma irradiation is more effective for degradation of 2,4-D and its intermediate 2,4-DCP. Chloride ions are observed as completely released with combined processes at lower ozonation times although nearly 98% are released with 20 min' ozonation. Intermediate 2,4-DCP decomposes at earlier ozonation times than 2,4-D.     

The Basic Clinical Applications of Ozone Therapy

Medical ozone is a mixture of ozone and oxygen, prepared via silent electrical discharge, within a concentration range of 0.05 volume % O₃ to max. 5.0 volume % O₃.

In order to exclude its toxic effect on the pulmonary epithelium, the medical ozone/oxygen mixture is administered so that exposure of the respiratory tract is avoided at all times, i.e., without the disturbing effects of its odor.     

水源热泵用换热设备常用金属的腐蚀性能

目前有关金属腐蚀的研究多集中在探讨影响腐蚀的因素以及防腐蚀相关技术,有关换热器金属腐蚀经济性的文献较少。本文采用挂片失重试验,结合电镜分析,分别研究了碳钢10^#、不锈钢316L、紫铜T2和铝合金LF21在海水和污水中的腐蚀速率、电偶腐蚀速率以及微观腐蚀形貌;并运用模糊综合评价法进行评价,为合理选择换热设备金属材料提供依据。结果表明,根据金属均匀腐蚀耐蚀性十级标准,不锈钢316L、紫铜T2与铝合金LF21都属于耐蚀金属,不锈钢316L在静止和流动水环境中,均具有最好的耐蚀性;在严格避免与电位较正金属偶合使用的前提下,铝合金LF21比碳钢10^#和紫铜T2耐蚀,其经济性也较为优秀;碳钢10^#虽耐蚀性差但胜在价格优势,是实际工程最常用的金属材料。     

Super-Hydrophilicity of Stainless Steel Surface Induced by Heat Treatment with Gaseous Ozone

The hydrophilic states of stainless steel surface treated by the separate or combined use of gaseous ozone and heat were investigated by measuring the contact angle of a water droplet, the content of the surface carbon contaminants, and the adsorption isotherm of water vapor. Super-hydrophilic states of stainless steel plates were achieved only by the combined gaseous ozone/heat treatment. The contact angle of a water droplet on the plate decreased from 81° to less than 5° after treating at 120 to 180 °C under 2 vol% ambient gaseous ozone. It was found that the super-hydrophilization proceeded according to two different mechanisms. One is the decomposition of surface contaminants. There was a good correlation between the surface carbon content and the water contact angle over the range of 15 to 81°. The other is the once removal of surface hydroxyl groups followed by chemisorption of water on these dehydroxylated sites. As a result of the removal of contaminants and the rehydration, the total number of surface hydroxyl groups on stainless steel became larger than that on the original surface.     

Ozone Synthesis and Decomposition in Oxygen-Fed Pulsed DBD System: Effect of Ozone Concentration,Power Density,and Residence Time

The process of ozone production in pure oxygen was studied. It was shown how the ozone concentration changes along the discharge gap, both during its generation and decomposition processes. The effect of ozone inlet concentration, power, and gas residence time on ozone concentration was analyzed. It has been shown that concentrated ozone is easily decomposed at very low discharge powers, i.e., when the increase of the average gas temperature in the gap is negligibly small. It was hypothesized that the most intense decomposition takes place in the microdischarge channels, because the process of gas heating in the gap begins inside them.