Surface Dielectric Barrier Discharge Reactor Research Articles

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.

Plasma characteristics and de-icing of three-electrode double-sided pulsed surface dielectric barrier discharge

Ice accumulation on aircraft can lead to aerodynamic performance degradation and even trigger security incidents. However, traditional surface dielectric barrier discharge (SDBD) reactors cannot work while covered by glaze ice. In the present work, a novel three-electrode double-sided SDBD is proposed and employed for glaze ice deicing. Compared with traditional SDBD reactor, three-electrode double-sided SDBD introduces an additional discharge area and grounding electrode. On one hand, the heat generated in the additional discharge area can melt the glaze ice covered on the high-voltage electrode, providing a discharge gap for the subsequent discharge. On the other hand, the introduction of the additional grounding electrode can also dramatically enhance the upper discharge and thermal effect. As a result, compared with the three-electrode single-sided SDBD and two-electrode double-sided SDBD, the three-electrode double-sided SDBD has the highest deposited energy, maximal temperature, and deicing rate. To further optimize the structural design, the effect of air gap length below the dielectric on three-electrode double-sided SDBD is investigated. And it is found that the best deicing performance can be obtained at the air gap length of 1 mm.

The effect of toluene trace admixtures on the plasma‐assisted oxygen trace removal from hydrogen‐rich gas mixtures in a surface dielectric barrier discharge reactor

AbstractA surface dielectric barrier discharge reactor was applied in the removal of oxygen traces from coke oven gas (COG), to which toluene was added as a model hydrocarbon contaminant. The adverse effect of toluene on O2 conversion was observed in a H2/N2/O2 mixture, while in synthetic COG consisting of H2, CH4, N2, CO, CO2, and O2, it remained unchanged. Online gas chromatography (GC) showed that the reactivity of toluene is mainly driven by H2/N2/O2. The accumulated residue was dissolved and analyzed by GC coupled with mass spectrometry. The identified reaction products suggest that toluene undergoes ring‐opening and functionalization.

A novel two-stage kinetic model for surface DBD simulations in air

In this work, a novel 0D model for the evaluation of O3 and NO2 produced by a surface dielectric barrier discharge (SDBD) in a closed environment is presented. The model is composed by two coupled sub-models, a discharge sub-model and an afterglow one. The first one, simulating the discharge regime and consequently including electron impact reactions, aims to calculate the production rates of a set of key species (atomic oxygen, excited states of molecular oxygen and molecular nitrogen). These latter are the input of the afterglow sub-model, that simulates the afterglow regime. We introduce a methodology to relate the production rates of the above mentioned species to the input power of the SDBD reactor. The simulation results are validated by a comparison with experimental data from absorption spectroscopy. The experimental measurements are carried out as follows. First, the discharge is turned on until the NO2 number density reaches steady state. Then, the discharge is turned off for several minutes. Finally, the discharge is turned on again to observe the effects of the NO2 concentration on ozone dynamics. The entire process is done without opening the box. The system operating in all the above-listed conditions is simulated for three different levels of input power.

OZONE GENERATOR BASED ON SURFACE DIELECTRIC BARRIER DISCHARGE WITH PULSE POWER SUPPLY

A pilot model of an ozone generator with a pulsed power supply has been developed. The ozone generator can be used for disinfection of domestic and industrial premises, in medicine and the chemical industry. Ozone is generated by a surface dielectric barrier discharge reactor (SDBD), consisting of 18 parallel-connected quartz tubes, inside and outside of which spiral the stainless steel high-voltage electrodes are wound. The measurements of the main parameters of the ozone generator showed that the ozone concentration reached 57 mg/l, and the output ozone concentration is 9.4 g/h. The developed design takes into account the technical features of the implementation of a particular type of discharge used, allows reducing energy consumption for ozone generation, having improved output parameters.

UV-C photon integrated surface dielectric barrier discharge hybrid reactor: A novel and energy-efficient route for rapid mineralisation of aqueous azo dyes

The study describes developing an energy-efficient and scalable alternative to conventional non-thermal plasma systems by integrating surface dielectric barrier discharge (SDBD) and UV-C radiation sources. The unprecedented enhancement in the mineralisation rate of an azo dye (brilliant red 5B) by the hybrid reactor (photo-SDBD) is demonstrated thoroughly as a function of dye concentrations, pH, and background salts. The photo-SDBD is 1.25 – 4.9 times more energy efficient than SDBD under similar experimental conditions. The photo-SDBD could overcome the problems such as the recombination of hydroxyl radicals and scavenging of radicals by salts (NaCl, Na2SO4, Na2CO3) observed in conventional non-thermal plasma systems. The TOC and HR-MS analysis establish the complete mineralisation potential and chemical mineralisation pathway. Besides, the phytotoxicity of the treated water is tested and demonstrated its utility as a liquid fertiliser for enhanced germination of mung bean seeds. The optical emission spectroscopy measurements were performed to estimate the plasma's electron temperature (1.6 ± 0.2 eV) and density (1021/m3). The emission line ratio (I763.5/I738.3) approach is used to compare the influence of UV-C on plasma parameters in the SDBD reactor. The study opens a new pathway for developing energy-efficient and scalable plasma-assisted mineralisation of complex and emerging organic pollutants.

Surface dielectric barrier discharge plasma–treated pork cut parts: bactericidal efficacy and physiochemical characteristics

Maintaining agro-food product safety remains a significant challenge for satisfying local and global consumers in tropical countries. This issue has been growing due to new pathogen strains, low infectious doses, increased virulence, antibiotic resistance, cross-contamination or recontamination of foods, food-contact surfaces, and biocontamination of water within the food production chain. To respond to this situation, we studied the inactivation efficacy of surface dielectric barrier discharge (SDBD) plasma against pathogens on the surface of various pork cut parts, including the loin, hip, belly, liver, and intestine. The SDBD plasma was operated at 0.30 W/cm2 in ambient air, with a gap of 5.0 mm between the plasma generator and the sample surface. Up to 96% germicidal efficiency against surface pathogens were observed, showing after 1 min of SDBD plasma exposure. Visualization of reactive species deposition on the treated surface using KI–starch agar gel reagent indicated a non-uniform distribution of the SDBD-generated reactive species on the treated surface. Following the indirect plasma treatment by the SDBD reactor, the overall color of pork cut samples after plasma treatment was significantly different compared with before. However, the surface morphology and structural characterization of the treated pork cut samples were not significantly altered, and residual nitrites and nitrates were lower than the restriction level for safe consumption. The SDBD reactor should be developed further to produce a uniform distribution of reactive species on the meat surface for the improvement of the decontamination effect without undesirable effects on meat quality parameters.

Advances on aerodynamic actuation induced by surface dielectric barrier discharges

Surface Dielectric Barrier Discharge (SDBD) is a well-known technology for active aerodynamic flow control with low power consumption. It is a type of plasma actuation for flow control with no moving parts and very fast response times. Research on SDBD flow control over the years has shown great potential for flow separation, boundary layer transition, drag reductions and suppression of local heating. A major area of research on SDBD flow control lies in increasing the effectiveness of SDBD actuators with new electrode configurations, surface materials, and plasma array designs. This review aims to provide a comprehensive report of research performed on SDBD flow control over the last 2 decades with a focus on SDBD reactor designs. Aspects of SDBD flow control including discharge morphology and actuation mechanism through momentum and energy transfer have been discussed in depth. Additionally, the future of research in SDBD actuated flow control has been explored. This review can serve as the baseline to develop new SDBD reactor designs for specific applications with improved effectiveness and advanced systems.

Feasibility of surface dielectric barrier discharge in wastewater treatment: Spectroscopic modeling, diagnostic, and dye mineralization

The paper investigates the ability of a surface dielectric barrier discharge (SDBD) based reactor to mineralize complex organic molecules such as azo dyes in water. The high operational flexibility, low maintenance, and energy efficiency of SDBD over most of the other plasma systems motivated its selection. Also, SDBD produces even discharge over a relatively large surface area. This could enhance plasma-liquid interaction and the production of reactive chemical species. Optical emission spectroscopy coupled with the collision radiative model and temperature measurements reveals the non-equilibrium nature of the plasma. Through plasma diagnostics, the study established the ability of SDBD to generate high energetic electrons with an electron temperature of 1.6 eV at a moderate sample temperature. The data supports the effective generation of reactive chemical species by SDBD reactor and its suitability for wastewater treatment with less energy consumption. The enhanced ability of the SDBD to mineralize azo dye (Brilliant Red 5B) in water is demonstrated under ambient conditions. The reactor is operated as a function of initial dye concentration, pH, and background salts such as NaCl, Na2SO4, and Na2CO3 to understand their effect on dye degradation. Faster degradation and mineralization of Brilliant Red 5B were observed due to the enhanced generation of •OH and H2O2 in the liquid medium. The degradation and complete mineralization of 50 mg/L of dye was achieved at hydraulic retention times of 20 min and 72 min, respectively. Compared to other plasma reactors reported, the present system showed a high energy yield of 247 mg/kWh at an operating power of 60 W and initial dye concentration of 50 mg/L. In short, the studies address two significant challenges of using plasma in wastewater treatment, i.e., energy efficiency and scalability.

A scalable twin surface dielectric barrier discharge system for pollution remediation at high gas flow rates

Investigation of conversion of volatile organic compounds by a scaled-up surface dielectric barrier discharge reactor designed for industrial applications.

Degradation of toluene in surface dielectric barrier discharge (SDBD) reactor with mesh electrode: Synergistic effect of UV and TiO2 deposited on electrode

Combing with photo-catalysis and photo-catalyst, a surface dielectric barrier discharge (SDBD) reactor with a mesh electrode was applied for toluene degradation and a high mineralization was achieved. The degradation performance comparison between SDBD reactors with a mesh and a spring electrode was carried out as well. A significant improvement in carbon balance and CO2 selectivity were obtained in mesh SBDB reactor compared with that of spring's one. For instance, when only plasma was applied, the carbon balance and CO2 selectivity of mesh SDBD reactor were 84% and 42.6%, while only 64.5% and 31.8% in spring one, the carbon balance and CO2 selectivity were improved by 30.3% and 34% at SIE of 300 J L−1, respectively. Synergistic effects of photo-catalysis and photo-catalyst were conducted with a 254 nm UV lamp and TiO2 deposited on the mesh electrode by atmospheric pressure (AP) plasma technology. The results showed that TiO2 and UV irradiation both presented promoting effect on toluene degradation in SDBD reactor with mesh electrode. According to the experimental results, the carbon balance rose to 89.5% and 93.9% at SIE of 300 J L−1, when UV or TiO2 was applied. With the application of TiO2 and UV together, a highest carbon balance of 95.9% was obtained at the same SIE. At the same SIE, the CO2 selectivity was promoted by 42.8% or 55.3% with the application of UV or TiO2, and the promotion finally reached at 59.1% when TiO2 and UV were applied together. Additionally, the degradation efficiency of toluene was also enhanced with the introduction of TiO2 and UV irradiation. Increases in toluene degradation efficiency of 19. 7% and 26.8% were obtained at SIE of 300 J L−1, respectively. When both TiO2 and UV were applied, the enhancement could rise to 41.6%.

Liquid oxygenated hydrocarbons produced during reforming of CH4 and CO2 in a surface dielectric barrier discharge: Effects of steam on conversion and products distribution

We have developed a low-temperature atmospheric surface dielectric barrier discharge reactor that transforms biogas into liquid chemicals. The influence of steam on the conversion of methane and carbon dioxide and the distribution of products vs specific energy input was investigated. The conversion rates of 44% for CH4 and 22% for CO2 were reached based on our operational conditions. The lowest energetic cost of 26 eV/molecule was reached when steam was added at the in-feed. The selectivity of 3 wt. % for liquid hydrocarbon was achieved. More than 12 chemicals were produced as a result of biogas (CH4 + CO2) transformation. Methanol, ethanol, isopropanol, and acetone constituted the most abundant oxygenated hydrocarbon liquids at room temperature. The main gaseous products were H2, CO, C2H4, and C2H6.

Experimental research on denitrification and elemental mercury removal by Surface Dielectric Barrier Discharge

A spiral Surface Dielectric Barrier Discharge reactor was employed to remove both NO and Hg from the flue gas. The effects of O2 and peak voltage were extensively studied. Only NO, NO2 and N2O were observed using FTIR at the outlet of the reactor in the atmosphere of NO/O2/N2. A desired NO conversion efficiency of 99.2% at 7 kV was obtained in the absence of O2 with low energy cost. The presence of O2 can suppress the reduction reaction while accelerating the oxidization of NO, consequently restraining the NO reduction to N2 and promoting the NO2 generation. O2 is necessary for the oxidation of Hg. At peak voltage of 7.0 kV, the Hg conversion reached above 94% at O2 concentration higher than 4%. It decreased to lower than 55% at 3.5 kV. Different concentrations of CO2, C2H4, SO2, HCl and H2O were also introduced to study their effect on NO and Hg conversions. When the CO2 concentration was increased from 0% to 5 and 10%, the NO conversion decreased from 81.0% to 74.1% and 73.6% respectively. At peak voltage of 7 kV and 500 ppm and 1000 ppm of C2H4 were introduced, the NO conversion increased from 78.7% to 85.4% and 93.8% accordingly, while Hg removal efficiency declined. With HCl concentration increasing to 30 and 60 ppm, the Hg oxidation rate increased significantly to above 90% at peak voltage of 9 kV. A strong inhibition effect of SO2 and H2O on NO and Hg conversion were observed.

Plasma-catalytic destruction of xylene over Ag-Mn mixed oxides in a pulsed sliding discharge reactor.

Plasma-assisted catalytic degradation of xylene was performed in a pulsed sliding dielectric barrier discharge (SLDBD) reactor based on three-electrode geometry over Ag-Mn bimetallic oxides catalysts at room temperature. Experimental results showed that more active species were distributed uniformly in the SLDBD plasma than traditional surface dielectric barrier discharge (SDBD), contributing to higher degradation and energy performance. The xylene degradation efficiency and energy yield in the SLDBD reactor driven by both +pulse (+18 kV) and -DC (-10 kV) were 40% and 2.3 g/kWh higher, respectively, than in the SDBD reactor energized by +pulse alone. The combination of SLDBD plasma with catalysts significantly improved the xylene degradation efficiency and CO2 selectivity than the plasma-only system. The incorporation of Ag into Mn oxide further enhanced its catalytic activity for xylene degradation, and the catalytic activity of Ag-Mn oxides was closely correlated with the Ag/Mn molar ratio. Ag-Mn/γ-Al2O3 (1:2) presented the best performance in plasma-catalysis process, with 91.5% of degradation efficiency and 80.1% of CO2 selectivity at 4.6 W. The higher proportion of surface Oads and better reducibility through the interaction between Ag and Mn species can explain the excellent reactivity of Ag-Mn/γ-Al2O3 (1:2).

Improved Performance for Toluene Abatement in a Continuous-Flow Pulsed Sliding Discharge Reactor Based on Three-Electrode Configuration

The degradation of toluene by non-thermal plasma has been evaluated in a continuous-flow sliding dielectric barrier discharge (SLDBD) reactor based on three-electrode configuration and compared with a traditional surface dielectric barrier discharge reactor. In order to optimize the electrical and geometry parameters of the SLDBD reactor, the effects of positive pulsed high-voltage (U+pulse), negative DC voltage (U−DC), pulse-forming capacitance (Cp)), inter-electrode gap, discharge length, and dielectric material have been systematically investigated. Morphological characterizations demonstrate that the steamer channels can propagate more homogeneously along the dielectric surface when a sufficient U−DC is applied under the condition of slight increase in energy. The average discharge power of the SLDBD reactor mainly depends on U+pulse, while which is less affected by U−DC. Unexpectedly, both toluene degradation efficiency and energy yield using the SLDBD increase significantly as U−DC, indicating that VOC degradation is not only determined by the energy primarily provided by U+pulse, but also depends on the drift of the ionized species induced by U−DC. Increasing Cp enhances the energy injected into the SLDBD reactor and leads to a higher toluene degradation efficiency, but lowers the energy yield when the other parameters remains unchanged. The optimal Cp is 0.67 nF. Shorter inter-electrode gap and longer discharge length appear to be more advantageous in terms of toluene degradation and energy yield. Quartz plate exhibits remarkably better degradation and energy performance than ceramic and polytef ones, leading to the maximum toluene degradation efficiency of 58% and energy yield of 0.85 g/kWh in this work.

Enhancing the Wetting Properties of Polypropylene and Polyethylene Nonwoven Fabrics Using a Cost-Effective Surface Dielectric Barrier Discharge

An atmospheric pressure surface dielectric barrier discharge (SDBD) was used for surface treatment of Polypropylene (PP) and Polyethylene (PE) nonwoven fabrics which are widely used in filtration media, oil adsorbents, biomedical textiles, etc. The SDBD reactor has been built using the Printed Circuit Board (PCB) which is an inexpensive material available in the local market. The use of the PCB led to the ease of fabrication of a low-cost discharge electrode system that can be scaled up without difficulty. The effect of the plasma treatment on the hydrophilic behavior of the treated samples was studied using water contact angle (WCA) measurements. The microstructure of the PP and PE nonwoven fabrics before and after plasma treatment was characterized by Scanning Electron Microscopy (SEM). The results showed that the plasma treatment converted the fiber surface from smooth to textured surface. This resulted in enhancing the wettability of both materials but with more pronounced effect on the PP.

Comparative experimental analysis of ozone generation between surface and volume DBD generators

Ozone generation by dielectric barrier discharge (DBD) is widely used in industry. Several DBD configurations can be used to generate ozone, which are classified in two main types depending on the geometry of the electrodes: volume DBD and surface DBD models. The aim of this work is to conduct a comparative experimental analysis between surface DBD and volume DBD ozone generators having a cylindrical geometry. This comparative investigation is carried out not only in terms of ozone concentration and energy efficiency, but also in terms of cooling performance. Two experimental setups were used in this work, one for measuring the ozone concentration (in mg/L) and the ozone rate production (in g/h) and a second for cooling experiments. The obtained results show that although the volume DBD model is the most frequently used in industry, the surface DBD reactor gives better results in terms of ozone rate production and cooling.

Impact of Argon in Reforming of (CH4 + CO2) in Surface Dielectric Barrier Discharge Reactor to Produce Syngas and Liquid Fuels

The aim of this work is to study the role of argon during plasma reforming of methane and carbon dioxide in order to convert Biogas into liquid fuels. Mixtures of synthetic CH4 and CO2, representing typical biogas compositions, were processed in a surface dielectric barrier discharge reactor in the presence of argon, which is considered to improve the discharge conditions. Our measurements showed that at constant feed flow rate and constant applied power, increasing the argon percentage from 0 to 66% in the feed, leads to increase the electron density up to 60% and the electron mean energy up to 50%. In these conditions, the absolute conversions of CH4 and CO2 are improved respectively from 19 to 43% and from 11 to 25%, the H2/CO ratio enhances up to 0.9. However, despite these improvements, the addition of argon beyond 33% decreases the carbon balance by deposition of black carbon and soot, decreases the selectivity of liquid products and finally lowers the energy efficiency of CH4 + CO2 mixture conversion. Meanwhile the selectivity of 10 liquid fuels principally alcohols, ketones and light organic acids, obtained in a yield of 3 wt%, depends also on the flow rate of argon in the feed mixture.

Combination of VOC degradation and electro-hydrodynamic pumping actions in a surface dielectric barrier discharge reactor

This paper concerns the study of a surface dielectric barrier discharge (SDBD) reactor designed for offering simultaneously chemical (VOC degradation) and mechanical (electro-hydrodynamic pumping) actions. It takes the form of a channel composed of active faces on which surface plasma is generated in AC sinusoidal mode with a resonant power-supply. The chemical application targeted is the flexible and low energy-cost abatement of VOC present in air at low concentration, which is a major current industrial concern for safety and environmental reasons. Regarding the mechanical action, the SDBD acts as a pump. It is able to induce flow rates reaching up to 153L/min for a 60W consumption with an electro-mechanical yield of 0.0133% in open configuration, while as any pump, it falls down in connected configuration; 39L/min connected to our air treatment bench. Regarding the chemical action, five VOC are tested, two ketones: acetone and butanone, two esters: methyl-butyrate and methyl-valerate, one aldehyde: butyraldehyde. They are injected at low concentration in a continuous air flow according to two modes of injection: (i) separately at 25ppmv, or (ii) together at 10ppmv each one, i.e. 50ppmv total. The air flow rate is modulated via an additional pump for investigating an extended range: 8.5–179L/min. Thus, for a fixed 60W consumption, the specific input energy (SIE) goes from 20J/L to 423J/L. As expected, the results show that as the SIE is increased, better conversion rates are achieved. Based on the experimental results, a chemical model of the SDBD reactor is proposed for providing a physical interpretation while giving information for helping the design of an optimized double-action reactor.

Influence of applied voltage waveforms on the performance of surface dielectric barrier discharge reactor for decomposition of naphthalene

This paper is aimed at investigating the effect of applied voltage waveform on the surface dielectric barrier discharge (SDBD) in order to improve its capability in decomposing naphthalene in air. Five symmetric waveforms (sine, sinc, square, pulse and triangle) are used in this study in addition to two asymmetric waveforms (positive- and negative- ramp). The results show that the discharge activity is strongly affected by the applied voltage waveform, where the SDBD in case of the sine and triangle waveforms is more filamentary when compared with the other waveforms. Although the discharge period of the sine and triangle waveforms is high, the rms value of its current is lower than that in the case of the square and pulse waveforms. The SDBD reactor is more efficient to decompose the naphthalene when it operates in filamentary mode than that in diffuse-like mode. This is why the highest decomposition efficiency and energy efficiency are achieved in sine and triangle waveforms. Furthermore, the positive- and the negative-ramp applied-voltage waveforms have a similar effect on the decomposition process.