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.     

Ozone and Nitrogen Oxides Generation in Gas Flow Enhanced Hollow Needle to Plate Discharge In Air

Siemens made the first ozone generation system by corona discharge about hundred and fifty years ago. At present mainly two types of atmospheric pressure electrical discharges - corona discharge and dielectric barrier discharge are used for production of ozone. Another type of discharge, which can be used for this purpose, is multineedle to plate electrical discharge enhanced by the gas flow. Contrary to the conventional arrangement when the gas is flowing around the needles we studied the discharge in which the gas was pumped through the needles. Results of studies of ozone and nitrogen oxides production by DC electrical discharge in air at atmospheric pressure with a single hollow needle to plate electrode configuration enhanced by the flow of air through the needle for both polarities of the needle, different airflow rates and currents are presented in this paper.     

A Study of Ozone Synthesis in Coaxial Cylinder Pulse Streamer Corona Discharge Reactors

Synthesis of ozone in coaxial cylinder non-thermal plasma reactors with different structures was investigated in this paper. With digital measuring technology, the absorption energy of non-thermal plasma reactors induced by pulse streamer corona was estimated. In the view of energy absorption of non-thermal plasma reactors, pulse input energy depended on reactor structures, as well as pulse parameters, such as pulse amplitude and DC bias. With coaxial cylinder reactors energized by pulse voltage, the influences on ozone generation of pulse voltage polarity, pulse amplitude, and pulse repetition rate were studied. It was found that positive pulse voltage induced higher ozone generation than negative pulse voltage and higher amplitude pulses generated more ozone. Increasing the pulse repetition rate at a low level increased ozone generation to some extent, but then leveled off with further increasing. A critical repetition rate was found at which the ozone synthesis was the most efficient. Lower pulse amplitude was associated with higher critical repetition rate. Superimposing DC bias on pulse voltage was an effective method to enhance ozone generation. Besides, discharge modes and electrode structures of reactors affect ozone generation. A mixed discharge mode of volume and surface discharges was the most effective mode to generate ozone in all of the experimental discharge modes, namely volume, surface, volume and surface mixed discharge modes. Moreover, helix-cylinder reactors were better than wire-to-cylinder reactors in generating ozone.     

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.%.     

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.     

Ozone Generation in Air by a DC-Excited Multi-Pin-to-Plane Plasma Source

In the fields of material processing and environmental technology, atmospheric pressure non-thermal plasmas embrace a broad range of applications. Ozone generation is one of them. This paper discusses a DC-excited atmospheric pressure glow discharge in a multi-pin-to-plane electrode configuration for the production of ozone in air. The influence of discharge current, temperature, flow rate and air humidity is investigated. A simple model is proposed to predict the experimental results for the ozone production and ozone concentrations.     

A Study of the Physical and Chemical Processes Active in Corona Discharges Fed by Carbon Dioxide

Ozone generation in both positive and negative corona discharges DC corona, both operated in glow regime, feed by dry CO₂ has been studied. Higher ozone concentrations were observed in negative corona discharges. Ozone formation was found to be strongly dependent upon both the flow rate of the gas and on the radius of the outer electrode. The physical characteristics of the discharge were monitored through measurement of the discharge current. Small increases in the gas flow rate were observed to cause a significant increase in the discharge current of a negative corona discharge but little/no effect was observed in positive corona.     

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.     

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.     

Productivity and Efficiency of Ozone Synthesis in Coplanar Discharge Arrangements

In order determine the potential of coplanar discharge arrangements with short electrode distances for the production of ozone, a numerical model of the discharge behavior has been developed. The temporal and spatial distributions of the discharge parameters e.g. those of the field strength, the densities of the charged particles in the gas region and on the dielectric surface and that of the energy release reveal that the ozone production results from the electron phase of the discharge. Quantitative data of the productivity and efficiency of the ozone yield in a certain system are presented, which are in agreement with experimental results.     

Effective Ozone Generation in Oxygen Using a Mesh Electrode in an Ozonizer with Variable Linear Velocity

Results of studies on ozone synthesis under discharges proceeding in a metal mesh-ceramic dielectric system have been presented. The experiments were carried out in the reactor with unique reaction space geometry, in which the reacting gas flew with consequently increasing linear velocity. The high voltage electrode was made of a metal mesh, which caused intensification of the gas mixing in the reaction space. Using a simple reactor with one-side cooling of the reaction space, high ozone maximum concentrations (100 g/Nm³) and energy efficiencies (180–200 g/kWh) were obtained at 25 °C.     

Basic Parameters of Coplanar Discharge Ozone Generator

Coplanar discharge is a new type of barrier discharge, and has some advantages for high-concentration ozone generation. In this article, basic parameters of coplanar discharge are clarified by experimental and theoretical approaches. Coplanar electrodes consist of many pairs of line electrodes printed on a glass plane, and are covered with dielectric layer. The discharge properties, ozone diffusion process, and surface reaction are discussed. Finally, the scaling rule of a coplanar discharge ozone generator is demonstrated by fabrication of a 3 kg/h ozone generator.     

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.     

Influence of Field Strength and Energy Distribution of Different Barrier Discharge Arrangements on Ozone Generation

Because of different field strength and energy density distributions in volume (VD), surface (SD) and coplanar discharge (CD) arrangements the ozone yield will differ in general. While in VD configurations the initial field strength distribution is rather uniform, the situation is quite different in CD and especially SD devices. The distributions change during discharge development as well as the energy density in the discharge region and by this the ozone yields. The situation in SD arrangements is discussed in detail and is compared with those in VD and CD configurations.     

Polarity Effect Of Silent Discharge

The polarity effect of microdischarge and the characteristics of ozone generation were studied using electrical and optical methods, paying attention to the distribution of microdischarges in terms of time and space and the effect of dielectric surface on microdischarge. As a result, the phenomenon in which a chain of microdischarges occurs in a brief period of time could be observed for the first time. In addition, it was found that the microdischarge characteristic, collective microdischarge phenomenon, and ozone yield vary according to the surface condition of the dielectric electrode used. The ozone yield was high with a glass surface and low with a ceramic surface.     

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.     

Ozone Production in a High Frequency Dielectric Barrier Discharge Generator

Factors that affect the performance of an expanded-mesh dielectric barrier discharge ozone cell were investigated. A gas feed pf 94% O₂, 4% Ar and 1% N₂ was used. An improvement in the productivity (g ozone/kWh) of about 20 % was achieved by doubling the gas flow rate through the cell. Decreasing the cell operating frequency (in the range 72 kHz to 19 kHz) increased the productivity of the ozone generator at constant power. The ozone production increased approximately in proportion to the input power; however productivity did not vary significantly with power above a minimum level. As the cell voltage was increased the dependence of productivity on power or frequency was reduced. Changing the feed gas temperature between ? 5^°C and + 42^°C had no effect on productivity. Finer meshes drew more power than coarser ones for a given voltage. Using a thinner mesh for the centre electrode increased productivity. The best results were obtained with a 6 × 3 × 1.86 mm titanium mesh giving a productivity of 110 g ozone/kWhr at 30–60 W, 1500–1900V and 23 KHz.     

Response Surface Methodology Applied to Ozone Generation

In this work, a strategy is presented to optimize the ozone generation by response surface methodology. A dielectric barrier discharge ozone generator was developed in which it is possible to control electrical current frequency and gas flow entering the generator. Response surface methodology was used to identify ozone generator optimum operational conditions, that is, those that permit considerable ozone productivity and high concentration of ozone gas.     

The Development of Ozone Generators with the Analysis of the Field Distribution of the Electrode Arrangements

The authors have investigated the field distribution of different electrode arrangements and voltage supply systems. The characteristics of the electric field of the electrode arrangements have been calculated using the finite element method for the potential and the Donor-Cell method for the space charge calculation, and those form a convergent iterative loop. The authors developed a method of analysis concerning the calculated field characteristics, which provides two index numbers. According to previous experiments, ozone production depends significantly on the electrode arrangement and the voltage supply system. The aim of this paper is to highlight the reasons for these differences in ozone production as related to the potential and electric field distribution. It is also shown that the index numbers of the analysis and the ozone production capacity has a strong regression.     

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.