Ozone Zero Phenomenon in Ozone Generator Equiped with Coaxial Cylinder Electrodes Covered by Dielectrics

A gradual decrease in the concentration of ozone produced by the continuous operation of a large-scale dielectric barrier discharge-type ozone generator (OG) was observed under the supply of a constant discharge power and high-purity oxygen as the feed gas. This finding was named the ‘ozone zero phenomena’ on the basis of our experiments demonstrating that the ozone molecules disappeared at the surface of the electrodes in the OG, in which both the formation and decomposition of ozone occur simultaneously. To clarify the cause of the phenomena, we performed new experiments with an OG separated functionally into two parts to avoid the effects of the discharge, which also oxidizes stainless-steel and increases the temperature in the generator, although the discharge is indispensable for ozone generation. The first part was an OG supplying ozone to the following part. The second part was an ozone destructor that simulated an OG in which only the ozone zero phenomena occurred. The ozone destructor was an incubator with pipes made of stainless-steel or borosilicate glass in them and maintained at a constant temperature of up to 473 K. The generator and destructor were connected serially with a gas flow line. Ozone–oxygen mixtures with constant ozone concentrations produced by the first part were introduced into the ozone destructor, and the ozone concentrations at the inlet and outlet of the pipes were monitored simultaneously. Using the two ozone concentrations, the decomposition rate of ozone was evaluated as functions of time, the pipe material, the pipe temperature, and the concentration of ozone introduced into the pipe. We concluded that in this model experiment the ozone zero phenomena are induced by the thermal decomposition of ozone in the pipes which is installed in the heated incubator to provide ambient temperature conditions for the conversion of ozone molecules.

Ozone treatment in the food and horticulture product capitalization sectors is widely acknowledged as completely safe for human use, in accordance with the most recent rules of the relevant authorities. Ozone-generating devices for research and education are known to allow the introduction of ozone gas for many uses, especially in food and agricultural applications. Despite their usefulness, their high cost prevents them from being widely available in research and educational institutions in underdeveloped nations, limiting practical training and the development of local applications to support the capacities of the food and agriculture sectors. In this study a device was constructed to generate ozone (O3) using the high-voltage principal circuit. An Arduino board was used to accomplish the control operation. An MQ-131 ozone sensor was utilized to measure the ozone concentration with a measuring unit of (%); however, the detecting range of the MQ-131 sensor is 10~1000 ppb, so in the present study, a formula to covert the measuring units between ppm and (%) for the concentration of the generated ozone (Y) as (Y, %) = 0.0333 × (Y, ppm) was presented. Different ozone concentrations are generated by varying the high voltage level from 20 to 35 kV with an increment of 5 kV and flow rate variations of 1.5, 2, 2.5, and 3 L/min. It was found that ozone concentration increases with increasing applied high voltage and decreases with increasing oxygen flow rate at a fixed applied high voltage. This study uses experimental data in a multiple linear regression analysis to predict ozone concentration based on levels of high voltage and oxygen flow rate, with a coefficient of determination of 0.7686 using a testing dataset. The findings provide evidence of the viability of constructing an inexpensive ozone generator with inexpensive parts, thereby promoting sustainable technological advancement. Drawing from our research, we can highlight the educational value and cost-effective benefits of employing an ozone-generating device, which can be used to produce ozone for a variety of purposes.

Electrochemical system with moderate ozone generation and catalytic enhancement for efficient organic wastewater treatment.

Ozone is a powerful disinfectant and oxidizing agent, and it is used in a wide range of applications, such as waste water treatment, food processing, etc.. There is also a great potential of using ozone in new emerging medical applications, such as ozone dentistry and ozone oxygen therapy. For these purposes, simple, small, compact and efficient sources of ozone are needed.BR In this study, in order to increase the current-voltage range of the discharge and to avoid the overheating of the gas in the ozonizer we suggested ozonizer of injection needle and plate electrode type(INP Type) with the gas through the needle. A ozonizer of INP type have been investigated by focusing on ozone concentration and yield according to flow rates and Gap of two electrodes. The results of studies of ozone production for DC corona discharge in oxygen at atmospheric pressure about the ozonizer of INP type. The ozone concentration and the generation yield increased as the gap of two electrodes and gas flow were decreased. Also, when the gap of two electrodes and gas flow with no change, the ozone concentration and generation yield each have variation of direct proportion and inverse proportion with discharge voltage.

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 generator by using dielectric barrier discharge plasma (DBDP) has been studied. DBDP reactor was constructed with spiral cylender configuration. We found that ozone concentration increased with increasing of voltage, number of spools coil. The ozone concentration decreases with increasing distance between spiral electrode and cylender electrode. We found something very interesting in the generation of ozone, where electrc current has been measured, in other words ionization has occurred, but ozone was not formed. It can be interpreted that although ionization has occurred but oxygen molecular dissociation has not happened or is not enough for the formation of ozone.

Sugar maple (Acer saccharum, Mill.) wood samples were exposed to the flowing afterglow of a N2 dielectric barrier discharge (DBD) open to ambient air. Freshly-sanded wood surfaces were hydrophilized by the treatment. The dynamic behaviour of water droplets on hardwood samples further reveals a volumetric effect of treatment as well as a modification of the topmost surface. Analysis of the discharge properties by optical emission spectroscopy (OES) indicates that the neutral gas temperature (determined from the rovibrational spectrum of N2) was close to room temperature, thus ruling out wood modification due to heat transfer. OES spectra combined with a collisional-radiative model also reveals significant concentration of metastable N2(A) states and UV photons (in particular those from the NOγ system in the 200–300 nm range) in the discharge. To better examine the role of UV irradiation, wood samples were exposed to the late afterglow of a low-pressure N2/O2 plasma optimized for UV emission from the NO systems. Wood hydrophilization was observed only for samples directly exposed to the late afterglow and not for those contained in a UV-transparent enclosure. Wood hydrophilization in the DBD is thus not directly related to UV irradiation; these energetic photons rather participate [along with N2(A) metastables] in the formation of other active species, in particular atomic oxygen and ozone due to the open-air configuration. The role of ozone was confirmed by treatments in an ozone generator, showing dynamic wettability comparable to the ones achieved after treatment in the flowing afterglows of the atmospheric-pressure N2 DBD and low-pressure N2–O2 plasma. FTIR spectra of wood samples treated in the three systems (DBD, N2–O2 plasma, and ozone generator) indicate an increased lignin content due to the possible development of lignin precipitates, corroborating the effect of atomic oxygen and ozone.

Design for high purity oxygen absorption and nitrogen stripping for fish culture

This paper presents an ozone generator by using a full-bridge inverter for applying in prolonging fruits process. The phase-shifted pulse width modulation (PSPWM) is used in the proposed circuit for adjusting the output power of inverter. In addition, the concentration of ozone will be controlled by adjusting the operating frequency of inverter. In order to prove the mentioned principle, the ozone generator was built and test in laboratory for prolonging mangoes. From the test, the 250 mg/hr of ozone concentration at 24 kHz of switching frequency can prolong the mangoes life satisfyingly more than the other concentrations and the maximum efficiency of inverter is 93.1 %.

During the production of ozone using needle & plate electrodes and a DC current in 99.5% oxygen, we noticed that the concentration of ozone decreased to 0 after several months in which the electrical discharge had produced ozone. The concentration of ozone increased due to the addition of nitrogen into a gas-mixing chamber located behind an electrical discharge. The concentration of ozone increased due to the addition of heat-energy to an anode located in an electrical discharge. The controlled heating cycles showed a change in the density of nitrogen on the surface of the anode. Simulations confirmed this pattern. We used an industrial ozone generator that consisted of ceramic dielectrics and a titanium expanded metal electrode. A change in the temperature of the cooling water led to the characteristic of ozone concentration making a linear line. It follows the formula of van't Hoff. The generator was supplied with 99% oxygen gas and produced ozone. The concentration of ozone increased from 98 g/m/sup 3/ to 120 g/m/sup 3/ under the same conditions. After reaching its peak, the concentration of ozone decreased to zero. Afterward, we produced ozone which was over 20% higher in concentration than primary state ozone due to change in the third element from nitrogen to antimony.

Prediction of maximum ozone concentration is of great importance, especially to alert the population and to allow the authorities to take preventive measures soon enough. Ozone concentration and meteoro‐logical variables are now observed each hour or every 10 min so that we nearly get continuous observations along time, i.e. functions, as covariates. Much work has been done in the statistical community to propose effective models for predicting ozone concentration one day ahead, but there has been much less effort to study methods that take the functional nature of these data into account. We propose here two non‐linear models based on kernel estimators that handle the functional characteristics of the data by means of a measure of proximity between observed functions. In addition, we use additive ideas to take exogeneous variables into account without being too sensitive to dimensionality effects.Such procedures are called multivariate functional non‐parametric approaches, since our models/estimates are non‐parametric (because of the non‐linear structure linking the explanatory and the response variables), functional (because the variables are curves) and multi‐dimensional (because we can have many functional explanatory variables).These models are used to forecast maximum ozone concentration in Toulouse (France). We compare them to more classical techniques and the results are promising. Copyright © 2004 John Wiley & Sons, Ltd.

The influence of duty cycle on ozone generation and discharge characteristics was investigated experimentally using volume dielectric barrier discharge in both synthetic air and pure oxygen at atmospheric pressure. The discharge was driven by an amplitude-modulated AC high voltage–power supply producing TON (a single AC cycle) and TOFF periods with a widely variable duty cycle. The experimental results show that the energy delivered to the discharge during each AC cycle remains roughly constant and is independent of feed gas, duty cycle and TOFF. Both average discharge power and ozone concentration show an initial linear increase with duty cycle, and deviate gradually from linearity owing to an increase in gas temperature at higher duty cycles. Nevertheless, ozone yield remains nearly constant (45.7 ± 3.5 g/kWh in synthetic air and 94.7 ± 3.1 g/kWh in pure oxygen) over a wide range of applied duty cycles (0.02–1). This property can be conveniently employed to develop a unique ozone generator with a widely adjustable ozone concentration and simultaneously a constant ozone yield. Additionally, the discharges in synthetic air and pure oxygen have similar electrical characteristics; however, there are observable differences in apparent luminosity, which is weak and white-toned for synthetic air discharge, and bright and blue-toned for pure oxygen discharge.

The temperature dependence of the atmospheric ozone generation rate was studied based on measurements in a reference area. The type of this dependence is determined by the method based on the comparison of variations in the ozone concentration when a hot or cold wave passes above the measurement post. This approach allowed us to derive for the first time the quantitative, but not qualitative, dependence type. The coefficients of the expression used depend on both the air temperature and initial ozone concentration. Thus, at the long-term minimum of the surface ozone concentration (1999) at a temperature of 30°C, its increase of 5 μg/m3 corresponded to a temperature change of 1°C. At a maximal concentration (2001) and the same temperature, the increase is almost 25 μg/m3 per 1°C. In the intermediate periods (1997 and 2010), it was about 14 μg/m3 per 1°C. The analysis shows that the quadratic character of the given dependence is conditioned by the nonlinear increase in reaction constants and the quadratic increase in hydrocarbon emissions by vegetation with increasing air temperature.

This paper studies the influence of inert gases He, Ar, Kr and Xe on ozone generation in a dielectric barrier reactor fed by oxygen feed gas. Results show that inert gas additions would lead to lower applied voltage, discharge power and reduced field. The electron energy distribution function shifts to the right though inert gas addition would lead to a lower reduced field with He, Ar and Kr addition, but it shifts to the left with Xe addition. The effective electron density decreases with inert gas content. With respect to Ar/O2, Kr/O2 and Xe/O2 mixture, conversion ratio of oxygen into ozone and ozone yield would increase with increasing Ar, Kr or Xe content, the growth rates follow the order of Xe > Kr > Ar. Such behaviors can be ascribed to the fact that Ar*, Kr* and Xe* could provide another effective pathway to produce oxygen atom through penning dissociation of O2 and metastable species due to their relatively low excitation threshold and considerable rate coefficients.

Ozone generation in pure oxygen using a wire-to-cylinder corona discharge reactor is experimentally and numerically investigated. Ozone concentration is determined by means of direct UV spectroscopy and the effects of Joule heating and ozone decomposition on the electrodes are analysed for different discharge gaps. The numerical model combines the physical processes in the corona discharge with the chemistry of ozone formation and destruction. The chemical kinetics model and the electrical model are coupled through Poisson's equation, and the current–voltage (CV) characteristic measured in experiments is used as input data to the numerical simulation. The numerical model is able to predict the radial distributions of electrons, ions, atoms and molecules for each applied voltage of the CV characteristic. In particular, the evolution of ozone density inside the discharge cell has been investigated as a function of current intensity and applied voltage.