Ozone Synthesis Research Articles

Use electrodes with high active electrical resistance as a way to increase the productivity of an ozone generator based on dielectric barrier discharge

The study is focused on the synthesis of ozone in discharge cells of dielectric barrier discharge (DBD), in which electrodes with high active electrical resistance are used. It is shown that such ozone generators have higher productivity in comparison with traditional devices in which metal electrodes with low active electrical resistance are used. The physical laws leading to such result were analyzed. Also, the paper presents the results of comparative experimental studies of the basic performance of ozone generators with high and low active electrical resistances of electrodes.

Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater

The whole process of biofuel production from Desmodesmus sp. EJ 8-10 cultivated in anaerobic digested wastewater (ADW) under the optimal temperature was evaluated by using the method of Life Cycle Assessment (LCA). The energy efficiency and environment emissions were under considerable for the corresponding parametric study. The functional unit was 1 kg microalgae. It was concluded that the harvest stage was responsible for the main energy consumption during the microalgal whole pyrolysis process. The energy conversion efficiency of the whole process was larger than 1, which indicated that the process was profitable. The environmental impact of the whole process was 1165.67 mPET2000, among which the primary impact on the environment was eutrophication that accounts for 57.36%, followed by photochemical ozone synthesis (22.56%), acidification (17.36%); and global warming (2.73%), respectively. Keywords: microalgae, fast pyrolysis, life cycle assessment (LCA), anaerobic digested wastewater (ADW), biofuel production DOI: 10.25165/j.ijabe.20201301.4178 Citation: Li G, Lu Z T, Zhang J, Li H, Zhou Y G, Zayan A M I, et al. Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater. Int J Agric & Biol Eng, 2020; 13(1): 241–246.

Ozone synthesis from oxygen in narrow‐gap hybrid discharge integrated with oxide coating: The role of surface catalytic reactions

AbstractIntegrating oxide coatings with narrow‐gap hybrid discharge (HD) can modulate ozone (O3) synthesis. O3 concentration () and energy yield (η) for HD can be enhanced by single‐valent oxides, whereas they are reduced by multivalent oxides. The discharge and oxide characterizations suggest that surface catalytic reactions play a crucial role in the synthesis of O3: single‐valent oxide coatings facilitate O3 production by offering abundant catalytic sites for surface catalytic reactions; surface catalytic reactions on multivalent oxide coatings suppress O3 production because of the dominating O3 decomposition over highly active sites of oxygen vacancies. This study is inspirational for designing and fabricating high‐efficiency O3 generators.

Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater

The whole process of biofuel production from Desmodesmus sp. EJ 8-10 cultivated in anaerobic digested wastewater (ADW) under the optimal temperature was evaluated by using the method of Life Cycle Assessment (LCA). The energy efficiency and environment emissions were under considerable for the corresponding parametric study. The functional unit was 1 kg microalgae. It was concluded that the harvest stage was responsible for the main energy consumption during the microalgal whole pyrolysis process. The energy conversion efficiency of the whole process was larger than 1, which indicated that the process was profitable. The environmental impact of the whole process was 1165.67 mPET2000, among which the primary impact on the environment was eutrophication that accounts for 57.36%, followed by photochemical ozone synthesis (22.56%), acidification (17.36%); and global warming (2.73%), respectively. Keywords: microalgae, fast pyrolysis, life cycle assessment (LCA), anaerobic digested wastewater (ADW), biofuel production DOI: 10.25165/j.ijabe.20201301.4178 Citation: Li G, Lu Z T, Zhang J, Li H, Zhou Y G, Zayan A M I, et al. Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater. Int J Agric & Biol Eng, 2020; 13(1): 241–246.

Characteristic of DBD plasma for ozone synthesis and its application on disinfection of chilli

The main objectives of this work are to study effect of high voltage power supply on plasma dielectric barrier discharge (DBD) system to amount of ozone concentration and to preliminary study effect of ozone on disinfection of microorganism. The amount of ozone concentration generated by the plasma DBD was determined by the KI standard ASTM method while on-site research work, ozone concentration was measured by the Liverbond test kit. The experimental result showed that ozone concentration was relatively dependent on the voltage supply. The produced ozone concentration was varied between 10 and 100 mg/l of air flow rate relating to voltage supply. The characteristics of plasma discharges was also presented. For feasibility study of disinfection of microorganism on chili by ozonated water bubbling, the results showed that the dissolved ozone with 8 kV can reduce E.coli from 9×105 MPN/100 ml to 1×105 MPN/100 ml in 120 min duration time.

Chemical processes in the discharge chamber of an ozone generator

The aim of this work was to study the effect of chemical reactions occurring in the discharge chamber of an ozone generator on the concentration of oxygen and ozone when working with medical oxygen as a working gas. This will allow to adjust the parameters of the electrical energy that the discharge chamber feeds for more efficient ozone generation. The article deals with the chemical processes that occur in the discharge gap of the discharge chamber of an ozone generator during synthesis. The main chemical reactions that are responsible for the decay of molecular oxygen under the influence of a discharge, ozone synthesis and its decay are presented. Literature analysis of the sources showed that there are a large number of such chemical reactions, the main are three reactions. The given rate constants of these reactions. The effect of temperature on the concentration of ozone in the ozone-oxygen mixture is justified. It was shown that with increasing temperature, the speed of the reaction group, which is responsible for the synthesis of molecular oxygen from atomic oxygen, significantly increases, and vice versa, the rate of reactions that are responsible for the synthesis of ozone decreases. A study was made of the influence of the course of chemical reactions on the parameters of electric energy supplying the discharge chamber during operation of the ozone generator. It is proved that the operating frequency of the AC voltage should not exceed the value of 20 kHz, as this will reduce the ozone concentration obtained. The study of gas parameters in the discharge interval was determined by applying the method of representative elementary volume, which allowed to break the discharge gap into volumes that are quasi-stationary in concentration. The processes occurring between these elemental volumes during ozone synthesis are described, as well as the processes of diffusion and the diffusion rate between two tangent elementary volumes with different ozone concentrations are determined.

Promoting ozone synthesis from oxygen by a high performance volume-surface hybrid discharge

A high performance hybrid discharge reactor with a flat-plate configuration, in which volume and surface discharges can occur simultaneously, is designed to achieve a high ozone energy yield at high concentrations. Compared with the single volume/surface dielectric barrier discharge, this hybrid discharge acquires much higher discharge voltage, number density of current pulses, and thus discharge power at the same input power. The optical emission spectroscopy diagnosis indicates that the designed reactor possesses a relatively high electron density, excitation temperature, and low rotational temperature, which facilitates the production of ozone. The excellent performance of the hybrid discharge in ozone production from oxygen demonstrates its high energy efficiency and reliability for the practical application of the ozone synthesis.

Hysteresis characteristics of the initiating and extinguishing boundaries in a nanosecond pulsed DBD

The dielectric barrier discharge (DBD) is presently used in many fields, including plasma medicine, surface modification, and ozone synthesis; the influence of airflow on the DBD is a widely investigated topic. In this work, a hysteresis characteristic on the initiating and extinguishing boundaries is observed in a nanosecond pulsed DBD, which is sensitive to the variation in the airflow velocities and pulse repetition frequencies (PRFs). It is found that, at a certain airflow velocity, the initiating PRF is higher than the extinguishing PRF. This difference between the initiating PRF and the extinguishing PRF leads to a hysteresis phenomenon on the initiating and extinguishing boundaries. When the airflow velocity is increased, both the initiating and extinguishing PRFs are increased and the difference between the initiating PRF and the extinguishing PRF also increased. The hysteresis width between the initiating and extinguishing boundaries is enhanced. To explain these results, the physical processes involved with the seed particles and the mechanisms of forming discharge channels are discussed.

Analysis and Experimentation of a New Half-Bridge High-Frequency Resonant Inverter for DBD Type Ozonizer

ABSTRACTThe peak voltage across the dielectric barrier discharge (DBD) type ozonizer is a key factor for ozone synthesis, and it is hard to be kept stable in widely used high-frequency resonant inverters within the entire working range. The soft switching conditions of power switches in these resonant inverters cannot always be satisfied within the entire working range, too. To address the two questions, a new half-bridge high-frequency resonant inverter is proposed in the paper, and the expressions that accurately describe the behavior of the inverter are derived by analyzing different operating modes. The simulation and experimental results show that the peak voltage across DBD type ozonizer is kept stable, moreover, zero current switching of power switches is realized within the entire working range.

Experimental study on ozone generation from oxygen in double surface dielectric barrier discharge

Double surface dielectric barrier discharge (DSDBD) can simultaneously form two uniform plasma zones for ozone synthesis with an AC power supply, thus exhibiting great advantages in achieving high energy yield at high ozone concentration. However, effects of the experimental parameters on DSDBD is urgently to be investigated to optimize the discharge reactor and provide references for high-efficiency ozone generator design. Here we present a systematical experimental study of the DSDBD in oxygen for ozone generation. The effects of important parameters (gas-flow mode, dielectric, discharge gap, etc.) on DSDBD in oxygen were studied, and the optimal DSDBD reactor was screened out. The optimal DSDBD reactor can achieve ozone energy yield of 317.7–130.0 g/kWh within ozone concentration of 12.7–56.2 g/Nm3 and exhibit an excellent stability during a 2-h continuous test, demonstrating its much better performance in ozone synthesis than other conventional DBDs. The discharge characteristics and the optimization results suggest that the superior performance of the optimal DSDBD reactor lies in its complete interaction of oxygen and plasma, large numbers of reactive species and electrons as well as favorable energy distribution of the reactive species.

Effects of nitrogen on ozone synthesis in packed-bed dielectric barrier discharge

The effects of nitrogen on ozone synthesis are studied in a coaxial cylinder generator with dielectric barrier discharge (DBD) and pack-bed dielectric barrier discharge (PB-DBD). A series of 10 h discharge experiments are conducted adopting a bare stainless electrode and bare copper electrode. Results show that the material of the electrode can affect the ozone synthesis. It is inferred that the ozone zero phenomenon (OZP) may be induced from ozone decomposing by metallic oxide catalysis. Packing dielectric particles can reduce the OZP. Adding a certain amount of nitrogen into the oxygen feed gas can further eliminate the OZP, and increase the ozone concentration significantly, but decreases the maximum energy efficiency of ozone generators. Initial analysis indicates that the optimal proportion of nitrogen addition is inversely related to the average reduced electric field strength in the discharge region.

A High-Efficiency Double Surface Discharge and Its Application to Ozone Synthesis

Surface discharge with the flat plate configuration tends to generate a uniform and high-density plasma during ozone synthesis, but suffers from relatively low energy yield at high ozone concentration. Here we report that a double surface discharge reactor can produce, at the same input power, two uniform plasma zones that locate two sides of the thin dielectric layer simultaneously, which results in a high ozone energy yield at high ozone concentration. Discharge characteristics confirm that reducing dielectric thickness and discharge gap favors the achievement of high plasma-density and energy efficiency. The optical emission spectroscopy diagnosis suggests that the double surface discharge with thinner dielectric thickness and narrower discharge gap possesses much higher electron density, as well as higher excitation temperature and low rotational temperature, which is responsible for the excellent performance in ozone synthesis. The optimal parameters of 0.25 mm dielectric thickness and 2 mm discharge gap enable ozone synthesis to proceed with an energy yield of 295.2–108.7 g/kWh at ozone concentration of 11.1–48.3 g/Nm3 and exhibit a good stability during a 4-h test. This performance surpasses the performance of many other typical discharge processes for ozone synthesis.

Hydrogen Evolution at the Buried Interface between Pt Thin Films and Silicon Oxide Nanomembranes

This paper reports the performance of hydrogen evolution reaction (HER) electrocatalysts based on Pt thin film electrodes that are encapsulated by silicon oxide (SiOx) nanomembranes. This membrane-coated electrocatalyst (MCEC) architecture offers a promising approach to enhancing electrocatalyst stability while incorporating advanced catalytic functionalities such as poison resistance and tunable reaction selectivity. Herein, a room-temperature ultraviolet (UV) ozone synthesis process was used to systematically control the thickness of SiOx overlayers with nanoscale precision and evaluate their influence on the electrochemically active surface area (ECSA) and HER performance of the underlying Pt thin films. Through detailed characterization of the physical and electrochemical properties of the SiOx-encapsulated electrodes, it is shown that proton and H2 transport occur primarily through the SiOx coating such that the HER takes place at the buried Pt|SiOx interface. Increasing the thickness of the SiOx ove...

THE THERAPY OF ELDERLY PATIENTS WITH ISCHEMIC HEART DISEASE USING OZONE-OXYGEN MIXTURE

The paper presents the results of application of ozone-oxygen mixture in the comprehensive treatment of 68 elderly patients with ischemic heart disease with stable I-II functional class angina. Ozone synthesis was carried out on the ozone therapeutic installation UOTA-60-01 «Medozon», Moscow. The therapy was carried out in the form of intravenous infusion of ozonized physiological solution with ozone concentration of 2-4 mg/l, 3 times per week, in the amount of 7 procedures in patients receiving nitrates, or beta blockers, or inhibitors of angiotensin converting enzyme. The results of the study indicate a high clinical efficacy of the method of ozone therapy, which is a qualitatively new approach in restorative treatment of elderly patients with ischemic heart disease.

Poison-Resistant Electrocatalysis Enabled By Encapsulation of Platinum with Silicon Oxide Nanomembranes

Improvement in the efficiency and lifetime of electrochemical technologies such electrolyzers and photoelectrochemical cells are critically important for the realization of storable chemical fuels.[1-5] Typically, the device lifetime relies on the durability of electrocatalyst nanoparticles. In an effort to reduce costs and catalyst loading, catalyst particle sizes are kept small (< 5 nm). However, decreasing particle size often leads to increased rates degradation mechanisms that generally reduce the electrochemically active surface area (ECSA).[1,6,7] To prevent this degradation, previous studies have encapsulated the active electrocatalyst material with an ultrathin, permeable or porous silica layer.[8,9] These encapsulated electrocatalysts exhibited greatly enhanced stability compared to silica-free electrocatalysts while still maintaining high electrochemical activity. It was hypothesized that transport of reactant and product species occurred through the silica layers, although direct evidence and detailed understanding of transport through the silica was lacking. This understanding is complicated by the complex electrode geometries studied in both reports, where the silica coatings had varying thickness and did not uniformly coat the electroactive Pt. This study removes this complexity by investigating well-defined Pt thin film electrodes that are encapsulated with silicon oxide (SiOx) nanomembranes. By systematically changing the SiOx thickness and evaluating hydrogen evolution reaction (HER) performance, we seek to gain deeper understanding of the structure-property relationships that affect the transport properties through SiOx nanomembranes. This membrane coated electrocatalyst (MCEC) architecture provides a promising approach to enhance electrocatalyst stability, improve poison resistance, and/or tune reaction selectivity. We use a room-temperature UV ozone synthesis process to systematically control the thickness of SiOx overlayers with nanoscale precision and evaluate the effects on the ECSA and HER performance of the underlying Pt thin films. Through detailed characterization of the SiOx overlayers this study shows that proton and H2 transport occur primarily through the SiOx coating. Notably, the SiOx nano-membranes exhibit high selectivity for proton and H2 transport compared to a HER poison species such as copper ions. These results demonstrate that MCECs are capable of multifunctional catalysis with poisoning resistance, still a more complete understanding of the structure-property-performance relationships will enable design improvements to further minimize efficiency losses due to mass-transport overpotential losses.

Macrokinetic study on ozone boundary concentration. Effect of temperature

The process of ozone production in pure oxygen using the tubular, high voltage pulse supplied ozonizer was studied. The unusual methodology of conducting kinetics measurements of the ozone synthesis process was presented. It was shown how the process rate changes along the discharge gap. The effect of power density and gas residence time in the discharge gap on the process rate was analysed. The temperature influence on the course of the process, particularly on the ozone boundary concentration and ozone decomposition rate constant, was discussed.

Ozone Production With Dielectric Barrier Discharge: Effects of Power Source and Humidity

Ozone synthesis in air dielectric barrier discharge (DBD) was studied with an emphasis on the effects of power sources and humidity. Discharge characteristics were investigated to understand the physical properties of plasma and corresponding system performance. It was found that 10-ns pulsed DBD produced a homogeneous discharge mode, while ac DBD yielded an inhomogeneous pattern with many microdischarge channels. At a similar level of the energy density (ED), decreasing the flowrate is more effective in the production of ozone for the cases of the ac DBD, while increased voltage is more effective for the pulsed DBD. Note that the maximum ozone production efficiency (110 g/kWh) was achieved with the pulsed DBD. At the ED of $\sim 85$ J/L, the ozone concentrations with dry air were over three times higher than those with the relative humidity of 100% for both the ac DBD and pulsed DBD cases. A numerical simulation was conducted using a global model to understand a detailed chemical role of water vapor to ozone production. It was found HO2 and OH radicals from water vapor significantly consumed O atoms, resulting in a reduction in ozone production. The global model qualitatively captured the experimental trends, providing further evidence that the primary effect of humidity on ozone production is chemical in nature.

Low Cost Compact Nanosecond Pulsed Plasma System for Environmental and Biomedical Applications

Nanosecond pulsed non-thermal atmospheric-pressure plasmas are promising for numerous applications including air and water purification, ozone synthesis, surface sterilization, material processing, and biomedical care. However, the high cost of the nanosecond pulsed power sources has hindered adaptation of the plasma-based technologies for clinical and industrial use. This paper presents a low cost ( 10 kV, a 3 ns rise time (10 to 90 %), and a 10 ns pulse duration (full width at half maximum) at a pulse repetition rate of up to 500 Hz were achieved in the present study. It has been successfully tested to power three different plasma reactors to form pulsed corona discharges, dielectric barrier discharges, and sliding discharges. The energy efficiency of such a nanosecond pulsed sliding discharge system was assessed in the context of ozone synthesis using air or oxygen as the feed gas, and was found comparable to a previously reported non-thermal plasma system that used commercial high voltage pulsed power sources. This study demonstrated that this low-cost nanosecond pulsed power source can prove to be an energy efficient and simple supply to drive various non-thermal atmospheric-pressure plasma reactors for environmental, medical and other applications.

A barrierless pulse discharge cell

A barrierless plasmachemical ozone generator, operating on the corona discharge, is studied. A high-voltage pulse power source and a discharge chamber are its basic elements. For obtaining high-voltage pulses with duration of several tens nanoseconds, a rotating discharger is connected to the output of a highvoltage direct-current source. The studied barrierless discharge chamber is characterized by a high efficiency of ozone synthesis, design simplicity, and minimal sizes. As compared to discharge chambers of other types, its advantage is that a corona discharge virtually fully fills its volume. Due to this fact, ozone is synthesized almost in the whole volume of the discharge chamber, resulting in attaining its high concentration at the chamber output. A productivity equal to 30 g/m3 and higher was reached in the experiments.

Ozone synthesis improves by increasing number density of plasma channels and lower voltage in a nonthermal plasma

Improvements in ozone synthesis from air and oxygen by increasing the number density of plasma channels and lower voltage for the same specific input energy (SIE) were explored in a nonthermal plasma based on a sliding discharge. The number of plasma channels and energy per pulse increased in direct proportion to the increase in the effective length of the anode (the high voltage electrode). Decreasing the discharge gap increased the energy per pulse for the same length and allowed the installation of more electrode pairs in the same space. It allowed the increase of the number of plasma channels in the same space to achieve the same SIE at a lower peak voltage with less energy per plasma channel. The ozone concentration gradually increased to ~1500 ppmv (140 to 50 g kWh−1) from air and to ~6000 ppmv (400 to 200 g kWh−1) from oxygen with a gradual increase in the SIE to ~200 J L−1, irrespective of the variations in electrode geometry, applied voltage or flow rate of the feed gas. A gradual increase in SIE beyond 200 J L−1 gradually increased the ozone concentration to a certain maximum value followed by a decline, but the rate of increase and the maximum value was higher for the greater number of plasma channels and lower peak voltage combination. The maximum ozone concentration was ~5000 ppmv (~30 g kWh−1) from air and ~22 000 ppmv (~80 g kWh−1) from oxygen. The results are explained on the basis of characteristics of the plasma and ozone synthesis mechanism.