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 Production with Dielectric Barrier Discharge from Air: The Influence of Pulse Polarity

ABSTRACT

This research aims to study the effects of different pulse modes of the power supply on ozone production from air. Single positive, negative as well as the bipolar voltage pulses (positive–negative and negative–positive) with a repetition rate of 300 Hz have been applied to coaxial dielectric barrier discharge arrangement. Results reveal that at fixed specific input energy (SIE), which is defined as the ratio of power to gas flow rate, the ozone generation efficiencies for different pulse modes are in the sequence of positive > positive–negative > negative–positive > negative, and the difference between positive and positive–negative pulse becomes considerable with SIE higher than 500 J/L. Results also reveal that the maximum NO₂ concentration is obtained at 400 J/L. Moreover, utilizing bipolar pulse can reduce N₂O production with SIEs higher than 250 J/L and hinder NO₂ production with SIEs higher than 350 J/L.     

Ozone Generation by Hybrid Discharge Combined with Catalysis

In this paper, combining hybrid discharge with pellet alumina catalyst is used for ozone generation. The hybrid discharge including corona discharge (CD), surface discharge (SD) and dielectric barrier discharge (DBD) may happen in the device. Factors that affect the ozone production efficiency and concentration are studied, such as energy density, power, gas flow rate, frequency, peak voltage and catalysts.     

Optimal Sizing of a DBD Ozone Generator Using Response Surface Modeling

Dielectric barrier discharge (DBD) reactors used as ozone generators are well known today and widely used for water treatment and air disinfection. The purpose of this article is to propose an experimental procedure based on the response surface modeling in order to optimize the geometrical dimensions of the cylindrical shape ozone generator, i.e., the discharge gap and the electrodes length. Because an effective ozone generator is expected to give high ozone concentration with a minimum of power requirements, the applied high voltage was associated with the geometrical parameters to carry out a composite centered faces design. Obtained results indicate that for an efficient ozone generator, length of the electrodes needs to be optimized while the discharge gap should be minimized.     

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.     

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.     

Development and Experimental Analysis of a New “Serpentine-Shape” Surface-DBD Ozone Generator—Comparison with a Cylindrical Volume-DBD Ozone Generator

Ozone generators used in the industry for water treatment are almost all based on volume dielectric barrier discharge (DBD). The generation of ozone by surface DBD is also possible. However, there are not enough studies devoted to this solution. The objective of this article is the development of a new patent-pending “serpentine” model in which the gas circulates in a channel having the shape of a serpentine. The developed model is made of 10 parallel channels engraved in a Bakelite plate of 4-mm thickness. The ground electrode is an adhesive aluminum tape placed on the lower surface of the plate, while the high voltage electrode is constituted of narrow tapes of 1-mm width of the same material, placed in the bottom of each channel. The surface DBD is produced inside each channel that measures 1-cm width, 3-mm depth, and 10-cm length. The obtained results showed that the ozone rate (in g/hr) is much higher in the case of surface DBD compared to a cylindrical volume-DBD generator, which is the most used reactor in ozone technology. Furthermore, the energy efficiency of the “serpentine” model is better than the cylindrical model.     

Experimental Study of Ozone Generation by Negative Corona Discharge in Mixtures of N2 and O2

Ozone generation by negative DC corona discharge in N₂-O₂ mixtures has been experimentally investigated using a coaxial wire-cylinder corona reactor operating at room temperature and atmospheric pressure. The experiments have been carried out under different gas flows (15 cm³ min^?1 to 200 cm³ min^?1) and gas compositions (5% to 90% of O₂), and the effect of these parameters on the corona current, the ozone density and the efficiency of the ozone generator have been analyzed. The global rate coefficients for ozone formation and destruction have also been evaluated, and their values compared with those reported by other authors. The maximum efficiency for ozone production was found in gas mixtures with oxygen content about 70–80%.     

Ozone Production Influenced by Increasing Gas Pressure in Multichannel Dielectric Barrier Discharge for Positive and Negative Pulse Modes

This paper describes the influence of gas pressure on the conversion of O₂ to O₃ and the ozone production efficiency in a multichannel dielectric barrier discharge (DBD) reactor utilizing positive and negative pulses. Results show that conversion of O₂ to O₃ is continuously enhanced by the increase of gas pressure (0.1–0.24 MPa) while the rising speed of oxygen conversion with the increasing gas pressure at fixed specific input energy is reduced above 0.15 MPa. The maximum ozone generation efficiency is increased with increasing gas pressure (0–0.2 MPa) while positive pulse exhibits higher energy efficiency. The maximum ozone generation efficiency is suppressed with further increase of gas pressure (0.2–0.24 MPa) while no significant difference in ozone generation efficiency is observed for two unipolar pulse modes. Results also show that 0.2 MPa is the optimal working gas pressure to obtain the maximum ozone generation efficiency and increasing gas pressure would lead to remarkable increase of ozone generation efficiency for ozone production at high energy densities in multichannel DBD.     

Dielectric barrier micro-plasma reactor with segmented outer electrode for decomposition of pure CO2

Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the non-catalytic decomposition of pure CO₂ into CO and O₂ at low temperature and ambient pressure. The influence of segmented outer electrodes on the electrical characteristics and the reaction performance was investigated. Experimental results indicated that the introduction of segmented outer electrodes can significantly promote the decomposition of CO₂. Encouragingly, the highest conversion of 13.1% was obtained at an applied voltage of 18 kV, which was a substantial increase of 39.4% compared to the traditional device. Compared with other types of dielectric barrier discharge plasma reactors, the proposed segmented outer electrode micro-plasma reactor can give a higher CO₂ conversion and acceptable energy efficiency. The increase in conversion can be attributed mainly to the enhanced corona discharge caused by the fringe effect at electrode edges, the increase in energy density and the increase in the number of micro-discharges. In addition, detailed electrical characterization was performed to reveal some trends in the electrical behavior of proposed reactors.     

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.     

气液冷等离子体多相反应器基础研究与应用进展

等离子体作为物质存在的一种基本形态,因其特有的高活性而不同于固、液、气三种形态,逐渐应用于多个领域,并发展成了一门新兴学科。由于冷等离子体参与的气液化学反应能产生更多的活性物质,而且液体的流动性能够强化活性物质的传递,因此,气体放电产生的冷等离子体与液相反应在许多领域表现出重要的应用价值,更具有探究意义。综述了几种冷等离子体的放电形式以及表征技术,重点阐述了气液冷等离子体多相反应器的不同结构以及应用,并对气液冷等离子体技术发展进行了展望。     

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

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.     

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.     

脉冲放电等离子体协同Mn/TiO2-分子筛、Fe/TiO2-分子筛、Cu/TiO2-分子筛催化剂降解甲醛

为进一步提高脉冲放电等离子降解甲醛的效率,增加CO₂选择性,降低O₃产生量,研究采用放电等离子体和催化剂协同技术。实验以分子筛为载体,分别制备了Mn/TiO₂-分子筛、Fe/TiO₂-分子筛和Cu/TiO₂-分子筛3种催化剂,并利用XRD、SEM、EDS、FT-IR方法对催化剂进行表征分析。进行了脉冲放电等离子体协同3种催化剂降解甲醛的研究,比较了不同催化剂协同等离子体对甲醛去除率、CO₂选择性、O₃产生量的影响。结果表明,3种催化剂与脉冲放电等离子体都存在协同作用,并能有效地提高甲醛去除率,增加CO₂选择性,降低O₃产生量。当脉冲电压为20kV、放电频率为40Hz、气体流量为0.5L/min时,Mn/TiO₂-分子筛催化剂协同效果最佳,甲醛去除率为94.4%,CO₂选择性为42.2%。催化剂表征结果显示Mn/TiO₂-分子筛的活性组分颗粒分布均匀,锐钛矿相的TiO₂和微晶状态的MnO_x的存在有效促进了甲醛的氧化分解。研究还对放电等离子体协同Mn/TiO₂-分子筛催化剂降解甲醛的机理进行了探讨。     

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.     

Experimental Study on Ozone Synthesis via Dielectric Barrier Discharges

The characteristics of ozone generation using a dielectric barrier discharge reactor were investigated experimentally. Results indicate that ozone concentration increases with increasing applied voltage and gas residence time. In addition to applied voltage, ozone generation rate varies with reactor configuration as well. Optimum ozone generation rates can be reached at the specific gas residence time for a given applied voltage and gas composition. At the same applied voltage, the reactor with a single dielectric barrier results in a higher ozone generation rate in comparison with the reactor having double dielectric barriers. Given a constant N₂/O₂ ratio in the feed gas, NO_x concentration increases as applied voltage and gas residence time increase. Results indicate that maximum NO_x concentration is reached when the N₂/O₂ ratio of feed gas is 4.     

Ozone Production by an Ultra-Short Triggered Dielectric Barrier Discharge.

This work was motivated by the ozone production improvement by a dielectric barrier discharge supplied with a high voltage triggered pulsed generator. Particular attention was focused on the ozone generator cell geometry and on the type of electrical generator. A comparative parametrical analysis on two configurations of reactor was performed: an annular and a surface configuration. This study emphasizes that surface discharges coupled to ultra-short triggered high voltage generators stand out as an efficient process to produce ozone in large quantities.     

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.     

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.