Energy Distribution In A Commercial Ozone Generating System

A model of energy flow in an ozone generating commercial installation using atmospheric air is presented in this paper. An analysis of the model operation has been presented in a system approach. Correctness of the model has been verified for the data of a real installation of output capacity mO₃ ~5 kg O₃/h. Results obtained give encouragement to follow examinations in this field.     

New High-Power Ozone Generators and Their Application In Industry

BBC ozone generators, with their high efficiency and high production density, have opened up for the exceptionally strong oxidizing agent ozone, a wide range of new possibilities in industrial applications. The article reports on measurements carried out on type OH ozone generators and on their use in industrial processes. An indication of future developments is given.     

Ozone Generation from Oxygen and Air: Discharge Physics and Reaction Mechanisms

Industrial ozone generation uses a special high pressure, low temperature electrical discharge which is referred to as the dielectric barrier discharge or silent discharge. The filamentary structure of this discharge and the properties of individual microdischarges are discussed. The main reaction paths for the excited atomic and molecular species in oxygen and air are identified. Possible approaches to obtain high power densities, high ozone generating efficiencies or high ozone concentrations are discussed.     

Medium frequency pulse train ozone generation

In this paper an ozone generation system that uses square bipolar pulses at 1900 Hz frequency (carrier signal) modulated with low frequency square wave is presented. The optimization of the carrier was done by sweeping the frequency from 500 to 2400 Hz and the duty cycle from 20 to 100 %, obtaining the best results at 1900 Hz and 80 % respectively. The experiment was done using a corona discharge generator with glass dielectric, 2 mm gap, water‐cooling at 26 °C and oxygen as the feed gas. Different levels of ozone production were obtained by changing the duty cycle of the modulator signal. The modulator signal works on a discrete way with whole numbers of pulses. The priority of the pulse polarity can be set so the beginning of the pulses may be either positive or negative. A dead time between pulse trains is always present with a minimum value of 10% of the modulator signal. The dead time contributes to the generator cooling because no energy is applied.

A comparative study between the proposed system and a 60 Hz traditional source generator shows an increase in the ozone concentration and ozone production rate, as well as a reduction of the voltage required to produce the corona discharge by using a pulse train at medium frequency.     

The Treatment of Spa Water with Ozone Produced by UV Light

Some North American manufacturers are selling devices which produce ozone from UV radiation, which is pumped or sucked into spas, presumably to disinfect the water, without having to use chlorine. To test this claim, a private spa used by two people at least once a day was equipped with a UV radiation unit and an ozone (generating by UV) unit. Bacterial analyses were conducted during experiments carried out using chlorine alone, ozone generated by UV radiation, unit and an ozone (generating by UV) unit. Bacterial analyses were conducted during experiments carried out using chlorine alone, ozone generaed by UV radiation, and ozoen in combination with UV radiation.

Heterotrophic plate counts, and counts of Staphyiococcus aureus and Pseudomonas aeruginosa were lowest when using chlorine, next lowest when using ozone #x002B; UV radiation, and highest when using UV-generated ozone. It is concluded that insufficient dissolved ozone is present for a sufficient reaction time to effect disinfection of these organisms by ozone generated by UV radiation. The fact that the odor of ozone was present above the spa water indicates that contacting also was inefficient.     

Ozone Production: Economical Operation of a Cold Plasma Reactor

For a fixed value of the reduced electrical field, the economical operation of a cold plasma reactor generating ozone is determined by a particular value of the energy supplied by the field per molecule of reactant. Evidences are given in the ozone formation from air and oxygen. Moreover, influence of the flow and reduced electrical field upon the production is emphasized.     

Ozone Generation Using Plate Rotating Electrode Ozonizer- Effect Of Electrode Rotation And Discharge Analysis Method

An attempt to explain the phenomenon of the effect of electrode rotation on the ozone generation process is presented. A discharge photography method was applied and computer analysis method was used to find discharge differences between electrode rotational and non-rotational cases. The research presented shows that with electrode rotation the discharge was more uniform and the ozone generation efficiency increased about 15% compared to an ozonizer with a non-rotating electrode. In addition, during the research, the most suitable electrode rotational speed for the ozone generation process was estimated.     

Optimal Ozone Production From Air

In this paper, another achieved example of Lunt's theory of chemical reactions in electrical discharges is emphasized. From an economic viewpoint, it is shown for a given mean value of the plasma temperature that the ozone yield of an air-fed cold plasma reactor presents an optimal value depending on the reduced electrical field, as expected from theoretical developments.     

The Photochemical Generation of Ozone : Present State–of–the–Art

This paper reflects an investigation of the feasibility of photochemical generation of ozone by irradiating gases containing oxygen with Hg lamps of the highest performance emitting the 185 nm line. Besides the expected photostationary equilibrium, determining factors for practical yields in ozone generation by the 185 nm wavelength are : the reactor and gas temperature, the reactor geometry, and the gas composition, as well as the pressure.

Further developments are expected in the field of lamp construction and also improvement of reactor geometry. A better knowledge of the aging of the lamps is required, as well as of the photochemical reactions of oxygen in the technologies applied.

Systems presently available are most promising for application on small scale or in areas of public water distribution which have no developed structure.

     

Preliminary Investigations On The Reactivity Of Ozone Considering Energy Supplied To Ozone Generators

A simplified engineering analysis developed by investigations of the energy levels and the data of ozone decomposition is presented. Experiments have been conducted by generating ozone from the same ozone generator by two ways and keeping the hydrodynamic conditions identical during ozonation. Ozonation conducted in various media such as gas, gas-liquid and gas-solid supports the assumptions of the presence of excited ozone species and variation in reactivity. The variation in reactivity linked with ozone generation shows an increase in the case of sawdust bleaching. The reactivity is the same for the removal of total organic carbon from water, and a higher ozone decomposition without significant reaction with methyl red solutions and coliform inactivation is observed.     

Structure and Activity of Ni- and Sb–doped SnO2 Ozone Anodes

Data are presented on the effect of the loading of Ni/Sb-SnO₂ on the physical, structural and electrochemical characteristics of this highly active ozone electrocatalyst with the aim of understanding its catalytic activity. The data strongly suggest that, despite the ‘cracked earth’ morphology of the catalysts, the walls of the fissures do not contribute to the observed electroactivity, both in terms of ferrocyanide oxidation or O₃ and O₂ evolution. In addition, the data indicate that there is a surface enrichment of Ni, and hence active sites, with increasing loading.     

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.     

Ozone Generator with Cylindrical Type of Rotating Electrode

An ozone generator using a rotating electrode to improve ozone generation efficiency is proposed. The ozone generator electrode unit consists of a rotating electrode and fixed electrode. The rotating electrode has the grounded 36 pieces of tungsten wires fixed in parallel to the rotation axis on the rotating cylinder surface. A dielectric electrode is used as a fixed electrode located on the inside of the tube of the electrode unit. The width of the apparent discharge gap is 1mm. Alternating current with a frequency of 50 Hz is applied to the electrode unit. The rotation speed can be adjusted from 0 rpm to 1200 rpm by a variable speed motor. Oxygen gas is used as the material gas. Higher ozone concentration and higher ozone generation efficiency are obtained compared with that when the rotation speed is 0 rpm. The gas temperature is measured at the inlet and outlet of the ozone generator, and the rotation speed for the cooling effect is most effective at about 500 rpm. The maximum generation efficiency is estimated to be 61 g/kWh at 800 rpm, and this value is twice as large as in the case of 0 rpm.     

Comparative Experimental Study between Surface and Volume DBD Ozone Generator

Volume Dielectric Barrier Discharge (DBD) is nowadays considered the most effective way for ozone generation in the industry. Some papers were published only on surface discharge reactors applied for ozone generation. This article describes an experimental investigation for the comparison between these two reactor types of ozone generation. Two surface and volume DBD reactors of cylindrical shape were used in the same experimental conditions. Obtained results showed that although the majority of ozone generators are of volume discharge type, the surface DBD presents significant superiority in terms of ozone generation and energy efficiency.     

High Frequency Testing and Modeling of Silent Discharge Ozone Generators

This paper deals with high frequency modeling of silent discharge ozone generators (OGs). The electrical characteristics of two simple silent discharge OGs operated at low and high frequency are analyzed and compared. An equivalent electric model is proposed for the operation of the OG at high frequency. This model can be used to optimize the electronic power converter used to supply silent discharge OGs at high frequency. Experimental results measured in the laboratory for two particular OGs are presented to validate the proposed model.     

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.     

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.     

Kinetic Modeling of Ozone Generation via Dielectric Barrier Discharges

A mathematical model combining chemical kinetic and reactor geometry is developed for ozone synthesis in dry O₂ streams with a wire-tube dielectric barrier discharge (DBD) reactor. Good agreement is found between the predicted ozone concentrations and experimental data. Sensitivity analysis is conducted to elucidate the relative importance of individual reactions. Results indicate that the ground-state oxygen atom is the most important species for O₃ generation; however, ozone generation will be inhibited if the O atom is overdosed. The excited species, that is, O(¹ D) and O₂(b ¹Σ), can decompose O₃ and suppress ozone synthesis. The model developed is then applied to modify the original DBD reactor design for the enhancement of ozone yield. With a thinner dielectric thickness, more than 10% increase of ozone concentration is achieved.     

Investigation of Ozone Loss Rate Influenced by the Surface Material of a Discharge Chamber

Decay characteristics of ozone concentration in oxygen in a chamber with three types of wall material (stainless steel, copper, and aluminum) are measured using the 254 nm photoabsorption method. Effective lifetimes of ozone are estimated from decay curves of ozone concentration. These values depend on the wall material: They are largest for stainless steel and smallest for aluminum. The relationship between effective lifetime and gas pressure is investigated precisely to determine three values. The equivalent diffusion coefficient of ozone in oxygen and the reflection coefficient of ozone at the wall correspond to the loss rate of ozone at the wall. The collisional loss (quenching) rate coefficient of ozone in oxygen is also determined.     

Characterization of the ozone zero phenomenon by infrared spectroscopy

The presence of a small amount of nitrogen in the feed gas is necessary to generate ozone efficiently out of oxygen. Operating an ozone generator with ultra-pure oxygen for extended periods results in highly deteriorated ozone generation efficiency. In extreme cases, when the nitrogen levels in the feed gas are in the lower ppm range, the efficiency of the ozone generation process even drops to zero. In this article, we present our results concerning the correlation between the N₂O₅ concentration in the off-gas and the ozone generation efficiency. After the ozone generator is run for a well-defined amount of time with an oxygen–nitrogen mixture, the N₂ supply is shut off, and the behavior of the system is monitored by near-infrared spectroscopy. Different surface materials lead to different temporal behavior of both the nitrogen oxide levels and the ozone concentration after shutting down the nitrogen supply. The measurements show a good correlation between the evolution of ozone generation efficiency and the changes of the N₂O₅ concentration in the off-gas.