Dielectric Barrier Discharge Reactor Research Articles

Optimisation of CuO/AC, Fe2O3/AC synergistic multi-electrode DBD reactor for degradation of ATZ in water

Atrazine (ATZ) is a synthetic triazine herbicide and has become a new pollutant in environment water. In this study, a multi-high-voltage, double-grounded- pole dielectric barrier discharge (DBD) reactor was designed to degrade ATZ in water. The effects of different factors, such as input voltage, air flow rate, and pH, on the degradation of ATZ in the DBD reactor were compared using response surface methodology. The optimal reaction conditions for the degradation of ATZ by DBD were determined by fitting the model to the experiment: air flow rate of 100 L/h, input voltage of 32 kV and pH of 10. The degradation efficiency obtained was 97.89%, which closely matched the simulation, indicating that the model had good correlation and consistency with the measured data. In this experiment, catalysts such as activated carbon loaded with CuO and Fe2O3 were added to DBD reactor to improve the utilisation of active substances and enhance the degradation of ATZ. The catalysts were characterized by FT-IR, XRD, XPS and SEM, proving that they promoted the degradation of ATZ.

Plasma‐Catalytic CO2 Methanation Over Supported Ni–Co Catalysts Prepared by Solution Combustion Synthesis

ABSTRACTIncorporating suitable promoters into nickel‐based catalysts for carbon dioxide methanation proves to be a successful strategy for enhancing catalyst structure, optimizing surface properties, mitigating deactivation, and ultimately boosting catalytic performance. This study focuses on the synthesis of Co‐modified Ni/CaCO3 catalysts using the solution combustion synthesis method. The catalytic activity of the afforded catalysts has been evaluated for CO2 methanation in a dielectric barrier discharge reactor operating at a gaseous hourly space velocity of 11,320 h−1 and an H2:CO2 ratio of 4:1. The catalyst exhibits optimal performance at a Ni:Co ratio of 13:2, achieving a CO2 conversion rate of 57.5% and CH4 selectivity of 92.4%. Characterization techniques such as X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, programmed temperature‐raising hydrogen reduction, carbon dioxide desorption, and in situ plasma DRIFTS are employed to evaluate the catalysts. The results indicate that the addition of Co to Ni‐based catalysts leads to an increase in moderately basic sites, thereby enhancing the catalytic activity and stability of catalysts for CO2 methanation. Notably, the combination of the plasma and the Ni–Co catalyst offers a novel pathway for CO2 methanation, featuring higher energy efficiency and superior synergistic effects compared to monometallic catalysts.

Study on the parameters of non-thermal plasma degradation process based on the combination of simulation and experiment

The destruction of benzene in a dielectric barrier discharge (DBD) reactor was studied in this work. The effects of specific energy density, initial concentration and oxygen content on benzene degradation efficiency were investigated by experiment and matrix correlation analysis. The results showed that specific energy density was the most important factor on benzene removal with a Pearson's coefficient of 0.7, meanwhile both initial concentration and oxygen content presented the inverse influence. In addition, a model to study the plasma discharge process was developed by COMSOL simulation software and surface reactions were included in the model. The behavior of the plasma was described by the coupled equations of electron density, heavy matter density and electron mean energy, and the drift-diffusion equation was calculated. When the peak voltage is 30 kV, the terminal current obtained by the simulation is 0.03 A, and the corresponding output current measured by the experiment is 0.013 A. Simulated and experimental current change trends are the same, indicating that the method simulation is correct and reasonable.

Plasma-Assisted Synthesis of Methanol Through Hydrogenation of Carbon Dioxide With Non-Noble Metal Mixed Oxide Catalysts.

The utilization of carbon dioxide through chemical conversion is a promising approach for the recycling of carbon resources. Despite well-developed industrial processes for CO2 hydrogenation to methanol, the effective use of CO2 as a feedstock remains challenging because of the costly requirements of high temperature and reaction pressure. In this paper, we report the methanol synthesis from CO2 and hydrogen using a dielectric barrier discharge (DBD) reactor under atmospheric pressure with a nickel-cerium-aluminum mixed oxide (Ni/Ce-Al MOx) catalyst. The combined use of plasma and the Ni/Ce-Al MOx catalyst was observed to yield 13.3±0.4 % of methanol, favorably compared to the 2.6±0.5 % yield of the case without catalyst. Microscopy images, selected area electron diffraction patterns, and energy-dispersive X-ray analysis confirmed the presence of fluorite-structured ceria, aluminium, nickel, and nickel oxide particles in the catalyst. The reaction mechanism for the plasma-assisted hydrogenation of CO2 was hypothesized to involve a carbide formation pathway due to the presence of carbide confirmed by X-ray photoelectron spectroscopic characterization.

Development of pilot-scale plasma bubble reactors for efficient antibiotics removal in wastewater

Plasma bubble (PB) is a promising technology to control antibiotic wastewater pollution. However, the practical implementation of PB technology at the industrial-scale is still underdeveloped. In addition, the influence of different discharge modes for PB on wastewater treatment is largely unknown. This study designed pilot-scale PB reactors with different discharge modes to investigate the degradation effect of norfloxacin (NOR) and tetracycline (TC) in bulk tap water. Results indicate that the dielectric barrier discharge (DBD) mode with low average discharge power demonstrates superior degradation ability and higher production of O3(g) and .O2−(aq) compared to the spark mode which exhibits the high-intensity spark discharge in the tip area of the tube. After 40 min of treatment in a Double DBD reactor, 97.4% and 100% of NOR and TC are removed from 2 L tap water, attributed to the accumulation of antibiotic molecules by PBs and the in-situ generation of O3(g) and .O2−(aq) produced by plasma. Furthermore, a larger-scale PB reactor is developed by creating an array of four DBD reactors, effectively degrading 8 L mixed antibiotics solution. This study provides valuable insights for PB reactor design and the degradation performance of antibiotic wastewater, which will contribute to the further development of synergistic systems for plasma degradation.

Plasma-mediated mercury vapor generation after microwave-induced combustion of fish tissue with detection by atomic absorption spectrometry

Mercury determination in fish tissues by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) was performed using microwave-induced combustion (MIC) for sample preparation, and plasma-mediated vapor generation (PMVG) in a tubular dielectric barrier discharge (DBD) as a sample introduction system. The main goal was to develop a method for Hg determination using very low amount of reagents being at the same time virtually free of interferences. The operational parameters of the PMVG step in the DBD reactor were optimized as follows: 70 mL min−1 Ar as the discharge gas, 20 mm electrode distance, primary voltage at 60 V and 50 μL as digested sample volume (in 0.1 mol L−1 HNO3 matrix). The effect of HNO3 concentration on the PMVG efficiency was studied. No differences in signal intensity were observed for HNO3 concentration up to 0.1 mol L−1, while a signal decrease by 25 % and 40 % was observed when the acid concentration increased to 1 and 5 mol L−1, respectively. Accuracy of the proposed method was evaluated using certified reference material (CRM) of dogfish liver (DOLT-4) and by Hg spikes on the sample prior to MIC. By using 500 mg of sample (or 250 mg of CRM) and 6 mL of 0.5 mol L−1 HNO3 as absorbing solution in MIC, recoveries of 104 % and 97 % were observed for spikes and CRM values, respectively. A limit of detection of 0.16 μg g−1 Hg (160 pg Hg absolute) was obtained. A comparison of the results for Hg determination in the CRM by PMVG-AAS and chemical cold vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS) was performed with no significant differences in the results. Finally, an efficient, low-cost and low-volume reagent consumption sample introduction system for Hg determination by AAS was successfully combined with the advantages of MIC and subsequent PMVG by DBD.

Ozone Plasma Nanobubble (OPN) Reactor Combined with Coagulation-Flocculation Process: A Promising Technology for Leachate Treatment

According to World Bank data, approximately 2.01 billion tons of urban waste is produced annually, with approximately 33% of waste being improperly managed, leading to concentrated and toxic leachate. This poses a global challenge due to its varied characteristics influenced by climate, landfill age, and waste composition, resulting in groundwater and surface water pollution with severe impacts on human health, ecosystems, and biodiversity, necessitating stringent treatment measures. To address this, a study integrated coagulation-flocculation and advanced oxidation processes (AOPs) using a dielectric barrier discharge (DBD) ozone plasma nanobubble (OPN) reactor to degrade leachate. Gas flow rate, plasma voltage, and gas sources are variated. This research uses O2 or air as a gas source that produces plasma. The leachate is fed into the DBD reactor, so the bubble will burst and produce further ROS. Optimal results were observed after 60 min, with oxygen gas feed reducing total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD) by 100, 93.93, and 74.12%, respectively, alongside a decrease in pH. This study indicates the promising potential of this technology for leachate treatment and demonstrates the potential for nitrate production using both types of gas feed.

Lifetime of nitric oxide produced by surface dielectric barrier discharge in controlled atmospheres: Role of O2 content

Nitric oxide (NO) is an invaluable multifunctional chemical in agri-food applications; for example, it plays a role in plant growth, development, and stress tolerance. One of the interesting implications of NO is the suppression of fruit ripening and the resulting increase in shelf life. Since a high concentration of NO is producible in atmospheric plasmas, increasing attempts in plasma agriculture have been made to study several types of plasma reactors operated in air. However, as NO is rapidly oxidized by oxygen (O2) and/or ozone (O3), the use of NO produced in atmospheric plasmas is naturally nontrivial, and the lifetime of NO is highly sensitive to the reactor environments. Here, we investigated the time development of O3 and nitrogen oxides (NOx=1–3) in a surface dielectric barrier discharge (sDBD) reactor with respect to the O2 content of the controlled atmosphere (N2+O2). In situ optical absorption spectroscopy enabled the observation of the dynamics of O3 and NOx under gas-tight conditions. In these plasma reactors, NO became a dominant species after the chemical mode transition from O3 to NO occurred. We found that a lower O2 content correlated to a faster appearance of NO in the plasma reactor. The NO lifetime significantly increased as the O2 content decreased from 20 to 5 % in the plasma reactor, while the maximum concentration of NO decreased. Our findings indicated that the appropriate control of the O2 content is essential in atmospheric plasma reactors dependent on O3 and/or NOx applications.

Enhancing CO2 conversion in a temperature-controlled DBD plasma reactor with HKUST-1 catalyst: Water removal and CuO/Cu2O-derived approach

Due to a synergy effect, using dielectric barrier discharge (DBD) plasma technology combined with catalysts for CO2 decomposition, a major contributor to global warming, is recognized as an effective approach to transforming CO2 into valuable products such as CO, which is a crucial feedstock for chemical synthesis. Herein, HKUST-1 was synthesized using the hydrothermal method for CO2 conversion in the DBD reactor. To enhance catalyst performance in the plasma region, HKUST-1 was treated with O2 plasma to increase its specific surface area. Additionally, HKUST-1 was calcined at 300 °C to produce the CuO/Cu2O catalyst. Since the recombination reaction in the CO2 conversion is increased at higher temperatures, the reactor heat is removed using fan cooling and a water circulation system. In the presence of the HKUST-1 catalyst, the CO2 conversion rate significantly increased by 132 %, 82 %, and 12 % in reactors operating without cooling, with fan cooling, and with water cooling circulation, respectively compared to the reactors without catalyst, at a flow rate of 50 ml/min and maximum input power. The catalysts have been characterized using a comprehensive suite of analytical techniques, including FTIR, XRD,TEM, SEM, EDS, and BET analysis. The BET analysis indicates that the specific surface area of HKUST-1 after O2 plasma treatment is increased by 52 %, which causes an increasing conversion rate of up to 18 %. The CuO/Cu2O catalyst demonstrated maximum CO2 conversion of 21 % at an input power of 140 W and achieved energy efficiency of 8.6 % at 40 W. The presence of oxygen vacancies within this catalyst enhances the process of CO2 decomposition.

Non-Oxidative Coupling of Methane via Plasma-Catalysis Over M/γ-Al2O3 Catalysts (M = Ni, Fe, Rh, Pt and Pd): Impact of Active Metal and Noble Gas Co-Feeding

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:{\ ext{m}\ ext{o}\ ext{l}}_{\ ext{C}{\ ext{H}}_{4}}^{-1}$$\\end{document} and from 9 to 4.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:\ ext{m}\ ext{o}{\ ext{l}}_{{\ ext{C}}_{2+}}^{-1}$$\\end{document}. Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Non-thermal plasma-catalytic ammonia synthesis over alumina-supported iron catalyst: Insights into the effect of alumina calcination temperature

Non-thermal plasma-catalytic ammonia synthesis (NTPCAS) has been regarded as a promising route to store hydrogen by utilizing renewable electricity. Alumina is a suitable support of the catalysts in NTPCAS and its properties can influence the performance of catalysts remarkably. In this study, the influence of the alumina calcination temperatures (Tc) on the catalytic performance of Fe-Al-x (x represents the value of Tc) was analyzed in a dielectric barrier discharge (DBD) reactor for NTPCAS. The results suggested that an increase in Tc transforms the alumina crystalline from γ phase to α phase. The best performance with a synthesized ammonia concentration of 11833 ppm was achieved over Fe-Al-900 with coexisting γ and θ phases of alumina under N2: H2 = 1:1 and SEI = 37.05 kJ/L conditions, which was 37 % higher than that of Fe-Al-800 with only γ phase. In addition, the larger Tc (i.e. 1100 and 1200 °C) decreased the specific surface area, increased the mean catalyst particle size, and led to the non-uniform dispersion of Fe species. The NH3-TPD and XPS studies suggested that an increase in Tc could influence the surface acidity and oxygen vacancy concentration of Fe catalysts, which were crucial to adjusting the catalytic activity for NTPCAS. This study clarifies the value of a suitable design of support of catalysts for improving NTPCAS.

Mechanical and statistical pathway for the experimental investigation of the dairy industry effluent using non-thermal plasma

Globally, there is still a demand for effective removal of industrial pollutants using modern treatment technologies. Therefore, to achieve industrial implementation, treatment efficiency and energy demand, at present the new Non-Thermal Plasma (NTP) technology is adopted to treat the dairy industry pollutants. Falling Film Dielectric Barrier Discharge reactor (FF-DBD) is developed whereas the reactor is further characterized by the various operating parameters including electric field, gas source, flow rate and pH for the removal of COD and lactose content for different experimental conditions. In this present study, experimental works are carried out in ‘lab-scale experimental hardware to analyze the degradation efficiency of dairy effluent based on COD and lactose. For the maximum of 68 % and 75.56 % of COD and lactose removal is achieved at the maximum voltage of 30 k,Vp-p. Moreover, the interaction between COD and lactose is analyzed by using ANOVA and the p-value is < 0.001. Comparing to the air, oxygen as a discharge gas in a DBD reactor gives more treatment efficiency because it produces more oxygen-based oxidative species. Further the 2D - simulation model is employed to find the velocity profile of effluent inside the FF-DBD reactor.

Dielectric barrier discharge plasma for chlorobenzene removal: Performance optimization, process modeling, and toxicity evaluation

Bio-purification has been recognized as an effective method of removal of volatile organic pollutants (VOCs), yet exist a technical bottleneck of low removal efficiency in the treatment of high toxicity and low water-soluble VOCs, especially chlorobenzene (CB). Herein, dielectric barrier discharge (DBD) technology was used as a pre-treatment technology, and the effect of process parameters (specific input of energy (SIE), inlet concentration of CB, humidity, and discharge length) of DBD on the removal performance of CB was analyzed, in order to investigate the feasibility of DBD as a pre-treatment approach for bio-purification. Taking energy yield, by-product analysis and exhaust evaluation as considerations, an SIE of 1,131.57 J·L-1, an inlet CB concentration of 300 ppm, a humidity of 50 %, and a discharge length of 10 cm were selected as the most suitable experimental conditions for the air DBD reactor. The temperature of gas flow was analyzed. Results suggested that DBD have no adverse thermal effect on the subsequent biotechnology (decreased by about 8 K during the discharge process). The temperature change caused by the degradation of CB (e.g., phenyl ring-opening and other processes) accounts for about 90 % of the total temperature change, where remaining part of temperature decreased caused by the large number of active substances produced by electron excitation, collision and cracking during discharge. The regulation of short-life active substances (e.g., ·NO, ·NO2,·OH, and O2–·) further reduced the toxicity of the outlet gas generated by DBD through affect the contents the long-life active substances (e.g., H2O2, and O3). This study provides a better understanding of the feasibility of DBD as a treatment for bio-purification and a new coupling technology for the effective removal of CB.

Nitric and nitrous acid formation in plasma-treated water: Decisive role of nitrogen oxides (NOx=1–3)

Nitrogen fixation using low-temperature plasma, particularly in relation to plasma-treated water (PTW) and its chemical and physical properties, has received a renewed research focus. Dissolving highly concentrated nitrogen oxides (NOx = 1–3) generated by air discharge into water results in the formation of two aqueous oxiacids (nitrous and nitric acids; HNOy = 2,3) and their conjugates (nitrate and nitrite ions; NOy-). Nonlinear formation of these species in PTW with respect to plasma conditions has been observed; however, the significance of the time-varying NOx on this nonlinearity has not yet been thoroughly investigated. Here, we demonstrate real-time observations of HNOy/NOy- as well as NOx production in a surface dielectric barrier discharge reactor containing distilled water. Synchronized two optical absorption spectroscopy systems were employed to simultaneously measure gas-phase NOx and liquid-phase HNOy/NOy- in the plasma reactor operated under different oxygen contents of 5, 20, and 50%. Our results showed that reducing the oxygen content in the reactor accelerated the chemical transition from O3 and NO3 to NO1,2, leading to a predominance of nitrite in PTW. Specifically, the NO3-rich period was extended with increasing O2 content, resulting in the production of nitrate-dominant PTW at low pH levels. Our findings highlight the potential for the selective generation of HNOy/NOy- in PTW through the active and passive control of NOx in a plasma reactor. The direct, real-time observation of NOx–HNOy/NOy- conversion presented here has potential for improving the control and optimization of PTW, thereby enhancing its applicability.

Enhancement of non-thermal plasma-catalytic CO2 reforming of CH4 using Ni/Mg–Al2O3 catalysts in a parallel plate dielectric barrier discharge reactor

CO2 and CH4 are converted to syngas by dry reforming of methane (DRM) reaction. This research investigated the effects of the Mg promoter on Al2O3-supported Ni catalysts and Mg calcination temperature on the DRM performance in a parallel plate dielectric barrier discharge reactor. The Mg promoter played a crucial role in the DRM performance, as increasing the Mg calcination temperature from 700 °C to 800 °C significantly improved the DRM performance and catalyst properties, including increased specific surface area, decreased total acidity, reduced crystallite and particle sizes, and more uniform dispersion of the Ni nanoparticles. Under these conditions, the H2 and CO selectivity were 77.0 % and 70.7 %, the CH4 and CO2 conversion were 25.1 % and 20.6 %, and the energy efficiency was 8.4 %. In addition, the catalyst was associated with a lower coking rate (0.5 mg C/gcat h), a relatively low carbon deposit of 1.5 %, and a carbon loss of 2.8 %, possibly because the weak acidity hindered the Boudouard reaction and CH4 decomposition. However, increasing the Mg calcination temperature to 900 °C increased the total acidity and Ni particle size, decreasing H2 and CO selectivities and increasing carbon deposits on the catalyst surface.

Degradation mechanism of atrazine in water by permutit loaded Fe and Cu oxides in a multi-electrode dielectric barrier discharge reactor

In this paper, the degradation of ATZ (Atrazine) in water by a catalyst-filler synergistic multi-electrode DBD (Dielectric barrier discharge) reactor was investigated.The results showed that 1O2, ·O2- and ·OH played a major role in the degradation process of ATZ. The addition of catalyst filler accelerated the removal efficiency of ATZ, and the removal efficiency of ATZ in Fe2O3/Permutit+DBD, CuO/Permutit+DBD, and Permutit+DBD were 95.76 % at the input voltage, gas flow rate, dosing volume, and processing time of 34 kV, 100 L/h, 1 g, and 15 min, respectively, 94.85 % and 91.54 %, which was 15 min shorter than the processing time of DBD system alone. Eight major degradation products were detected by high-resolution mass spectrometry, and their possible degradation pathways were inferred by combining with the DFT, and their intermediate products were found to be less acutely toxic and less chronically toxic than the parent ATZ by the ECOSAR toxicity analysis software.

Biomass gasification tar removal using dielectric barrier discharge reactor: Effect of reactor geometry and carrier gases

This study investigates the impact of reactor geometry (varying external electrode length) of Dielectric Barrier Discharge (DBD) reactors on the decomposition of toluene, a model compound for biomass gasification tar, using different carrier gases and various power levels. Results reveal that toluene decomposition is higher at longer electrode lengths (30 mm) at all power levels tested. Specifically, the toluene decomposition in H2 carrier gas at 30 mm electrode length increased from 67.2 % to 97.5 % with rising power from 5 to 40 W, while it ranged from 52 % to 97.4 % at 15 mm electrode length. The decomposition of toluene was found to be higher in N2 carrier gas than in H2 carrier gas at both discharge lengths. At 30 mm external electrode and with rising power from 5 to 40 W, toluene decomposition ranged from 90.5 % to 98.7 %. Similarly, when the electrode length was reduced from 30 to 15 mm for N2 carrier gas, the decomposition of toluene ranged from 74 % to 97.9 %. Thus, the results indicate that the decomposition of toluene is affected by both the electrode length and the nature of the carrier gas. The effect of electrode length was significant at lower power levels, and the difference between the conversion at both electrode lengths nearly disappeared at higher power levels.

Fiber laser tuning by means of nonthermal plasma as a temperature regulator

AbstractThis work presents a technique to obtain wavelength tuning for a fiber laser with a nonthermal plasma‐based temperature regulator system and a fiber Bragg grating (FBG). The plasma effect was generated in a dielectric barrier discharge (DBD) reactor filled with helium as the carrier gas for plasma generation. The temperature characterization of the DBD reactor had shown that the nonthermal heating mechanism of plasma could manipulate gas temperature from 25°C to around 145°C in ~10 min. By exploiting the rapid temperature change of plasma, the reflected wavelength of the FBG can be tuned accordingly. At a discharge voltage of 3 kV, the fiber laser was tuned within a range of 2 nm with 11.9 pm/°C tuning resolution. The fiber laser exhibits a thermally stable emission with very low shifting at a constant temperature value.

Effect of dielectric material on the uniformity of nanosecond pulsed dielectric barrier discharge

Dielectric barrier discharge (DBD) is considered as a promising technique to produce large volume uniform plasma at atmospheric pressure, and the dielectric barrier layer between the electrodes plays a key role in the DBD processes and enhancing discharge uniformity. In this work, the uniformity and discharge characteristics of the nanosecond (ns) pulsed DBD with dielectric barrier layers made of alumina, quartz glass, polycarbonate (PC), and polypropylene (PP) are investigated via discharge image observation, voltage-current waveform measurement and optical emission spectral diagnosis. Through analyzing discharge image by gray value standard deviation method, the discharge uniformity is quantitatively calculated. The effects of the space electric field intensity, the electron density (N e), and the space reactive species on the uniformity are studied with quantifying the gap voltage U g and the discharge current I g, analyzing the recorded optical emission spectra, and simulating the temporal distribution of N e with a one-dimensional fluid model. It is found that as the relative permittivity of the dielectric materials increases, the space electric field intensity is enhanced, which results in a higher N e and electron temperature (T e). Therefore, an appropriate value of space electric field intensity can promote electron avalanches, resulting in uniform and stable plasma by the merging of electron avalanches. However, an excessive value of space electric field intensity leads to the aggregation of space charges and the distortion of the space electric field, which reduce the discharge uniformity. The surface roughness and the surface charge decay are measured to explain the influences of the surface properties and the second electron emission on the discharge uniformity. The results in this work give a comprehensive understanding of the effect of the dielectric materials on the DBD uniformity, and contribute to the selection of dielectric materials for DBD reactor and the realization of atmospheric pressure uniform, stable, and reactive plasma sources.

Application of a Scaled‐up Dielectric Barrier Discharge Reactor in the Trace Oxygen Removal in Hydrogen‐Rich Gas Mixtures at Ambient and Elevated Pressure

AbstractDielectric barrier discharges (DBDs) are frequently utilized in various gas conversion processes. For industrial applications a low flow resistance and scalability are crucial. In this study a tenfold scaled‐up reactor based on a surface dielectric barrier discharge (SDBD) was employed for the removal of oxygen traces from H2/N2/O2 gas mixtures. The conversion efficiency of the reactor with ten electrode configurations was investigated for different admixtures of O2, and high degrees of conversion were observed that decreased with increasing flow rate, but remained constant when raising the pressure to 2 bar(g). A new generator based on silicon carbide field‐effect transistors (SiC‐FETs) was used and compared to a generator based on classical metal oxide semiconductor field‐effect transistors (MOS‐FETs).