Dielectric Barrier Discharge Plasma Reactor Research Articles

Plasma‐catalytic reforming of biogas over supported Ni catalysts in a dielectric barrier discharge reactor: Effect of catalyst supports

In this study, plasma‐catalytic reforming of simulated biogas for the production of value‐added fuels and chemicals (e.g., H2) has been carried out in a coaxial dielectric barrier discharge (DBD) plasma reactor. The influence of four Ni catalysts (Ni/γ‐Al2O3, Ni/MgO, Ni/SiO2, and Ni/TiO2) on the plasma‐catalytic biogas reforming has been investigated in terms of the conversion of reactants, the yield and selectivity of target products, the carbon deposition on the catalysts, and the energy efficiency of the plasma‐catalytic process. The use of plasma combined with these Ni catalysts enhanced the performance of the biogas reforming. A maximum CO2 conversion of 26.2% and CH4 conversion of 44.1% were achieved when using the Ni/γ‐Al2O3 catalyst at a specific energy density (SED) of 72 kJ l−1. Compared to other Ni catalysts, placing the Ni/γ‐Al2O3 catalyst in the DBD produced more syngas and C3C4 hydrocarbons, but less C2H6. The lowest energy cost (EC) for biogas conversion and syngas production, as well as the highest energy efficiency and fuel production efficiency (FPE), were achieved when using the Ni/γ‐Al2O3 catalyst in the plasma process. The Ni/γ‐Al2O3 catalyst also showed the lowest surface carbon deposition of 3.8%, after catalysing the plasma biogas reforming process for 150 min at a SED of 60 kJ l−1. Compared to other Ni catalysts, the enhanced performance of the Ni/γ‐Al2O3 catalyst can be attributed to its higher specific surface area, higher reducibility and more, stronger basic sites on the catalyst surface.

Investigation of the Arrayed Dielectric Barrier Discharge Reactor for PM2.5 Removal in Air

Low-temperature plasma treatment is a promising technology for particulate matter (PM). In this paper, the arrayed dielectric barrier discharge (DBD) plasma reactor for PM2.5 removal is investigated at atmospheric pressure. In order to reveal the interaction between experimental findings and simulation results, the equivalent electrical circuit is used. The electrical model is implemented on the PSIM software. To calculate the capacitance of the arrayed DBD reactor, the capacitor expressions are developed. Considering the experimental elements, such as plasma-generated configuration and the power source, a topological equivalent circuit is given. Finally, the simulation results are compared with the experimental ones, and they agree well. In addition, the designed DBD reactor was used to investigate PM2.5 removal. PM2.5 removal after 4 min of plasma treatment found to be about 53.8%.

Dielectric barrier discharge plasma reactor

A dielectric barrier discharge plasma reactor has been designed and constructed. The space discharge regime has been implemented. The reactor operating conditions for the desired reaction have been calculated using the dissociation of water molecules as a model reaction. The operating conditions have been selected for the dissociation of water vapor via excitation of vibrational levels of the molecule by a single electron impact.

Study of Humidity Effect on Benzene Decomposition by the Dielectric Barrier Discharge Nonthermal Plasma Reactor**supported by National Natural Science Foundation of China (Nos. 11205007 and 11205029)

The humidity effects on the benzene decomposition process were investigated by the dielectric barrier discharge (DBD) plasma reactor. The results showed that the water vapor played an important role in the benzene oxidation process. It was found that there was an optimum humidity value for the benzene removal efficiency, and at around 60% relative humidity (RH), the optimum benzene removal efficiency was achieved. At a SIE of 378 J/L, the removal efficiency was 66% at 0% RH, while the removal efficiency reached 75.3% at 60% RH and dropped to 69% at 80% RH. Furthermore, the addition of water inhibited the formation of ozone and NO2 remarkably. Both of the concentrations of ozone and NO2 decreased with increasing of the RH at the same specific input energy. At a SIE of 256 J/L, the concentrations of ozone and NO2 were 5.4 mg/L and 1791 ppm under dry conditions, whereas they were only 3.4 mg/L and 1119 ppm at 63.5% RH, respectively. Finally, the outlet gas after benzene degradation was qualitatively analyzed by FT-IR and GC-MS to determine possible intermediate byproducts. The results suggested that the byproducts in decomposition of benzene primarily consisted of phenol and substitutions of phenol. Based on these byproducts a benzene degradation mechanism was proposed.

PMMA Surface Functionalization Using Atmospheric Pressure Plasma for Development of Plasmonically Active Polymer Optical Fiber Probes

In this paper, we demonstrate the development of plasmonically active PMMA optical fiber probes by the attachment of gold nanoparticles to the probe surface functionalized by means of flowing post-discharges from dielectric barrier discharge (DBD) plasmas for the first time. Polymer optical fiber (POF) probes (U shape to improve absorbance sensitivity) were subjected to reactive gas atmospheres in the post-discharge region of a coaxial DBD plasma reactor run at atmospheric pressure in different gases (Ar, Ar + 10 % O2, O2, N2, N2 + 0.5 % H2). Plasma treatments in Ar or N2 gave rise to water-stable electrophilic functional groups on PMMA surface, whereas the amine groups generated by N2-containing plasmas were not stable. Subsequently, PMMA surfaces were treated with hexamethylene diamine (HMDA) to obtain stable amine groups through the reaction of electrophilic groups. Gold nanoflowers (AuNF, 37 nm, peak 570 nm) binding to the amine functionalized fiber probes was monitored in real-time by recording the optical absorbance changes at 570 nm with the help of a UV–vis spectrometer. Absorbance response from Ar or N2 plasma treated probes are 100 and 60 times, respectively, that of untreated control probes. A 25 fold improvement in absorbance response was obtained for Ar plasma treated POF in comparison with only HMDA treated POF. The shelf life of the hence fabricated plasmonically active probes was found to be at least 3 months. In addition, plasmonic activity of U-bent fiber probes treated in Ar plasma is better than the conventional wet-chemical activation by environmentally hazardous acid pre-treatment approaches.

Parametric analysis of the operation of a non-thermal plasma reactor for the remediation of NAPL-polluted soils

A new metallic plane-to-grid dielectric barrier discharge (DBD) reactor was designed for the efficient remediation of polluted soils at atmospheric pressure. A synthetic NAPL composed of equal mass fractions of n-C10, n-C12 and n-C16 was mixed with soil at a high initial NAPL concentration equal to 100g/kg-soil. The NAPL was removed after a few minutes of plasma treatment, depending on NAPL composition, air flow rate and applied voltage. At 28kV peak-to-peak, the NAPL was completely removed from soil very fast (1–3min) for a flow rate ranging from 1.0 to 4.0Lmin−1. At a constant flow rate (i.e. 2.0Lmin−1) the NAPL removal efficiency was 99%, 61.4% and 18.8% for applied voltage 28, 25 and 22kV, respectively, after 2min of plasma treatment. NOx and O3 were detected as the main gaseous plasma active molecules, with the NOx concentration being an increasing function of the applied voltage and air flow rate. The intermediates of the NAPL oxidation in soil were identified as ketones and alcohols regardless of the experimental conditions (i.e. air flow rate and applied voltage). The temperature in the vicinity of the soil found to be varied in the range 285–340°C stimulating the evaporation of NAPL. The total carbon content of initial NAPL detected in exhaust gas in the form of COx increased from 25.5% to 99% when the air flow rate decreased from 4.0 to 0.15Lmin−1, minimizing the release of VOCs and environmental fingerprint. Except of the pollutant remediation efficiency and electric energy consumption, the process sustainability associated with the composition of exhaust gases should be taken into account when designing DBD plasma reactors and determining the optimal operational window.

Degradation of triclocarban in water by dielectric barrier discharge plasma combined with TiO2/activated carbon fibers: Effect of operating parameters and byproducts identification

The removal of triclocarban (TCC) in aqueous solution by dielectric barrier discharge (DBD) plasma combined with TiO2 coated activated carbon fibers (TiO2/ACFs) catalysts was investigated at atmospheric pressure and room temperature. The effects of output power, initial concentration, radius of TiO2/ACFs catalysts and recyclability of catalysts on the removal rate of triclocarban were explored. The results showed that the addition of TiO2/ACFs catalysts with radius of 3cm into DBD plasma reactor could improve mineralization efficiency of TCC by 12% as compared with sole DBD system and the acute toxicity of TCC solution decreased from 64% to 32% after 30min degradation in DBD/TiO2/ACFs system. The mechanism experiments indicated that oxygen and OH radical played an important role during the degradation process. Moreover, a possible reaction pathway was proposed based on stable products identified by gas chromatography–mass spectrometer. The results confirmed that DBD/TiO2/ACFs might be a promising method for effectively removing TCC from water.

Remediation of pyrene-contaminated soil by active species generated from flat-plate dielectric barrier discharge

In this study, soil polluted with pyrene was remediated using a dielectric barrier discharge (DBD) plasma reactor at atmospheric pressure. Influencing factors, including treatment time, discharge voltage, electrode gap, gas flow rate, initial pyrene concentration, and pH of the soil, were studied. Experimental results showed that pyrene degradation efficiency was influenced on a small scale by soil pH: the pyrene removal rate reached 76% in alkaline condition (pH of 11.69), i.e., 8% higher than in neutral conditions (pH of 7.76) and 13.7% higher than in acidic conditions (pH of 5.67). The removal of pyrene increased as the applied voltage increased and the electrode gap decreased. The optimal airflow rate was 1.0L/min. The more pyrene that was coated on soil particles the higher was the energy efficiency, but the plasma penetrating pyrene layers faded by approximately 25% when the layers doubled. Optical Emission Spectrometer (OES), FT-IR and GC–MS data indicated that the excited atomic nitrogen, atomic oxygen and NOx were abundant in the plasma, and that the active species containing oxygen and nitrogen both contributed to the decomposition of pollutants. The possible pyrene degradation pathway was suggested. The experimental results showed that the DBD technique was able to effectively degrade pyrene over a broad pH range.

Hybrid plasma-catalytic methanation of CO2 at low temperature over ceria zirconia supported Ni catalysts

A hybrid plasma-catalytic system was used in for the hydrogenation of carbon dioxide (CO2) into methane (methanation) at atmospheric pressure and very low temperature using a dielectric barrier discharge (DBD) plasma reactor packed with Ni-CexZr1−xO2 catalysts. Three catalysts were prepared by a conventional wet impregnation method, using 15 wt% of Ni loading over ceria-zirconia mixed oxides having different Ce/Zr ratios. The physico–chemical features of both catalysts and supports were evaluated by means of X-Ray Diffraction (XRD), Temperature-Programmed Reduction of H2 (H2-TPR), Temperature Programmed-Desorption of CO2 (CO2-TPD) and Transmission Electron Microscopy (TEM). The methanation experiments in the absence or in the presence of plasma were carried out in the temperature range of 90–420 °C. The hybrid plasma 15NiCZ5842 catalyst combination was found to efficiently convert CO2 into methane even at low temperature. Indeed, CO2 conversions as high as 80%, together with 100% selectivity toward methane was measured in the presence of plasma at 90 °C. On the contrary in the absence of plasma, the same conversion and selectivity were only achieved at much higher temperatures around 300 °C, for the same catalyst.

Dielectric barrier discharge plasma induced degradation of aqueous atrazine.

Degradation of herbicide atrazine in aqueous solution was investigated using a plate type dielectric barrier discharge (DBD) plasma reactor. DBD plasma was generated at the gas-liquid interface of the formed water film. At discharge time of 14min, atrazine was degradated effectively with a degradation rate of 99% at the discharge power of 200W. The experimental data fitted well with first-order kinetics and the energy efficiency for 90% degradation of atrazine (G value) was calculated, obtaining a rate constant of 0.35min(-1) and a G value of 1.27 × 10(-10)molJ(-1) (98.76mgkW(-1)h(-1)) at a discharge power of 200W, respectively. The addition of Fe(2+) increased the rate constant and G value dramatically, and a significant decrease of the rate constant and G value was observed with the addition of radical scavengers (tert-butyl alcohol, isopropyl alcohol, or Na2CO3). The generated aqueous O3 and H2O2 were determined, which promoted the degradation of herbicide atrazine. Dechlorination was observed and the experimentally detected Cl(-) was 1.52mgL(-1) at a discharge time of 14min. The degradation intermediates of atrazine were detected by means of liquid chromatography-mass spectrometry; dechlorination, hydroxylation, dealkylation, and alkyl oxidation processes were involved in the degradation pathways of atrazine.

Pesticide degradation in water using atmospheric air cold plasma

A high voltage dielectric barrier discharge plasma reactor using atmospheric air as the inducer gas was studied for the degradation of pesticides (dichlorvos, malathion, endosulfan) in water. The degradation kinetics of the pesticides were studied using GC–MS as a function of plasma control parameters. Electrical characterisation of the plasma revealed that the plasma discharge consisted of filamentary streamers. Excited nitrogen, reactive oxygen species and OH radicals generated in the dielectric barrier discharge (DBD) plasma reactor were identified using optical emission spectroscopy. Ozone, used as an indicator for metastable oxygen species, was quantified within the reactor at concentrations of 1600, 2200, 2800ppm after 8min of plasma treatment for applied voltages of 60, 70, and 80kV respectively. The degradation efficacy of pesticides after 80kV and 8min of plasma treatment were found to be 78.98±0.81% for dichlorvos, 69.62±0.14% for malathion and 57.71±0.58% for endosulfan. Degradation was found to follow first order kinetics. GC–MS analyses showed that the degraded compounds and intermediates formed were less toxic than the parent pesticide. A proposed mechanism of degradation of these pesticides is suggested.

Direct conversion of methanol to n-C4H10 and H2 in a dielectric barrier discharge reactor

A direct conversion of methanol to n-C4H10 and H2 by limiting CO and CO2 formation was achieved in a coaxial dielectric barrier discharge plasma reactor without a catalyst.

Oxidation characteristics of mixed NO and Hg0 in coal-fired flue gas using active species injection generated by surface discharge plasma

The oxidation characteristics of mixed NO and Hg0 were investigated using active species injection under oxygen atmosphere, namely, a surface dielectric barrier discharge plasma (SDBD) reactor inserted in simulated flue duct was used to generate and inject the oxygen-based active species into the flue gas to simultaneously oxidize NO and Hg0 at 110°C. Approximately 92.5% and 99.1% of NO and Hg0 were oxidized at 301.8JL−1, respectively, a reaction competition between NO and Hg0 with active species existed, and the NO oxidation was faster. The effects of important flue gas components on NO and Hg0 oxidation were investigated. H2O enhanced the NO oxidation, but inhibited the Hg0 oxidation. HCl exhibited a promotional effect on the Hg0 oxidation, but displayed no effect on the NO oxidation. SO2 and H2O showed obviously inhibitory effect on the NO and Hg0 oxidation. Ozone and O2 metastable states contributed to the NO and Hg0 oxidation. NO2, HNO3 and N2O5 were observed by Fourier transform infrared spectroscopy (FTIR).

Fluid modelling of a packed bed dielectric barrier discharge plasma reactor

A packed bed dielectric barrier discharge plasma reactor is computationally studied with a fluid model. Two different complementary axisymmetric 2D geometries are used to mimic the intrinsic 3D problem. It is found that a packing enhances the electric field strength and electron temperature at the contact points of the dielectric material due to polarization of the beads by the applied potential. As a result, these contact points prove to be of direct importance to initiate the plasma. At low applied potential, the discharge stays at the contact points, and shows the properties of a Townsend discharge. When a high enough potential is applied, the plasma will be able to travel through the gaps in between the beads from wall to wall, forming a kind of glow discharge. Therefore, the inclusion of a so-called ‘channel of voids’ is indispensable in any type of packed bed modelling.

플라즈마 공정을 이용한 고추역병균(Phytophthora capsici) 불활성화 모델의 적용

Ten empirical disinfection models for the plasma process were used to find an optimum model. The variation of model parameters in each model according to the operating conditions (first voltage, second voltage, air flow rate, pH, incubation water concentration) were investigated in order to explain the disinfection model. In this experiment, the DBD (dielectric barrier discharge) plasma reactor was used to inactivate Phytophthora capsici which cause wilt in tomato plantation. Optimum disinfection models were chosen among ten models by the application of statistical SSE (sum of squared error), RMSE (root mean sum of squared error), r 2 values on the experimental data using the GInaFiT software in Microsoft Excel. The optimum models were shown as Log-linear+Tail model, Double Weibull model and Biphasic model. Three models were applied to the experimental data according to the variation of the operating conditions. In Log-linear+Tail model, Log10(No), Log10(Nres) and kmax values were examined. In Double Weibull model, Log10(No), Log10(Nres), α, δ1, δ2, p values were calculated and examined. In Biphasic model, Log10(No), f, kmax1 and kmax2 values were used. The appropriate model parameters for the calculation of optimum operating conditions were kmax, α, kmax1 at each model, respectively.

Plasma Functionalized Multiwalled Carbon Nanotubes for Immobilization of Candida antarctica Lipase B: Production of Biodiesel from Methanolysis of Rapeseed Oil.

Surface modification of multiwalled carbon nanotubes (MWCNTs) through functionalization could improve the characteristics of these nanomaterials as support for enzymes. Carboxylation of MWCNTs (MWCNT-COOH) has been carried out in this study using the dielectric barrier discharge (DBD) plasma reactor through humidified air. The chemical method was also used for further functionalization of the MWCNT-COOH through which the amidation of the surfaces with either butylamine (MWCNT-BA) or octadecylamine (MWCNT-OA) was performed. By immobilization of Candida antarctica B lipase (CALB) on these nanoparticles, performance of the immobilized enzyme in catalyzing methanolysis of rapeseed oil was evaluated. The CALB loading on the MWCNT-BA and MWCNT-COOH was 20mg protein/g, while the value for MWCNT-OA was 11mg protein/g. The yield of biodiesel was determined as percentage of mass of fatty acid methyl ester (FAME) produced per initial mass of the oil, and the yield value for the two of these three supports namely, MWCNT-COOH and MWCNT-BA used for the CALB immobilization was similar at about 92%, while 86% was the yield for the reaction catalyzed by the lipase immobilized on MWCNT-OA. Thermal stability of the immobilized CALB and the catalytic ability of the enzyme in the repeated batch experiments have also been determined.

Experimental Investigation on the Effect of a Microsecond Pulse and a Nanosecond Pulse on NO Removal Using a Pulsed DBD with Catalytic Materials

In this study, an experimental investigation of the removal of NO from an atmospheric air stream has been carried out with a non-thermal plasma dielectric barrier discharge reactor filled with different catalytic materials. TiO $$_2$$ , CuO–MnO $$_2$$ –TiO $$_2$$ , CuO–MnO $$_2$$ –Al $$_2$$ O $$_3$$ catalysts were used to study the synergy between the plasma and the catalysts. The NO $$_\mathrm{{x}}$$ removal efficiency and by-products formation were studied as a function of energy density, pulse rise time and width using a plasma catalytic configuration. It was observed that the shorter pulses are more efficient for NO $$_\mathrm{{x}}$$ removal but at the expense of higher by-products formation such as N $$_2$$ O and O $$_3$$ . A comparison has been made between an in-plasma catalytic configuration and a post-plasma catalytic configuration. Among all the three catalysts that were studied, CuO–MnO $$_2$$ –TiO $$_2$$ catalyst showed the best performance with respect to the removal efficiency as well as the by-products formation in both the in-plasma and the post-plasma catalytic configuration. In general, the post-plasma configuration showed better results with respect to low by-products formation.

A model based on equations of kinetics to study nitrogen dioxide behavior within a plasma discharge reactor.

In this work, a zero-dimensional kinetics model is used to study the temporal behavior of different species such as charged particles, radicals and excited states inside a Dielectric Barrier Discharge plasma reactor. It is shown that, the reactor significantly reduces the concentration of nitrogen monoxide as an environmental pollutant. After a drastic increase, a decrease in the concentration of the NO2 molecules inside the reactor is seen. Nitrogen monoxide molecules with a very low concentration are produced inside the reactor and its quick conversion to other products is proved. The obtained results are compared with the existing experimental and simulation findings, whenever possible.

Roles of individual radicals generated by a submerged dielectric barrier discharge plasma reactor during Escherichia coli O157:H7 inactivation

A submerged dielectric barrier discharge plasma reactor (underwater DBD) has been used on Escherichia coli O157:H7 (ATCC 35150). Plasma treatment was carried out using clean dry air gas to investigate the individual effects of the radicals produced by underwater DBD on an E. coli O157:H7 suspension (8.0 log CFU/ml). E. coli O157:H7 was reduced by 6.0 log CFU/ml for 2 min of underwater DBD plasma treatment. Optical Emission Spectra (OES) shows that OH and NO (α, β) radicals, generated by underwater DBD along with ozone gas. E. coli O157:H7 were reduced by 2.3 log CFU/ml for 10 min of underwater DBD plasma treatment with the terephthalic acid (TA) OH radical scavenger solution, which is significantly lower (3.7 log CFU/ml) than the result obtained without using the OH radical scavenger. A maximum of 1.5 ppm of ozone gas was produced during the discharge of underwater DBD, and the obtained reduction difference in E.coli O157:H7 in presence and in absence of ozone gas was 1.68 log CFU/ml. The remainder of the 0.62 log CFU/ml reduction might be due to the effect of the NO (α, β) radicals or due to the combined effect of all the radicals produced by underwater DBD. A small amount of hydrogen peroxide was also generated but does not play any role in E. coli O157:H7 inactivation.

Degradation of triclosan in aqueous solution by dielectric barrier discharge plasma combined with activated carbon fibers.

The degradation of triclosan (TCS) in aqueous solution by dielectric barrier discharge (DBD) plasma with activated carbon fibers (ACFs) was investigated. In this study, ACFs and DBD plasma coexisted in a planar DBD plasma reactor, which could synchronously achieve degradation of TCS, modification and in situ regeneration of ACFs, enhancing the effect of recycling of ACFs. The properties of ACFs before and after modification by DBD plasma were characterized by BET and XPS. Various processing parameters affecting the synergetic degradation of TCS were also investigated. The results exhibited excellent synergetic effects in DBD plasma-ACFs system on TCS degradation. The degradation efficiency of 120 mL TCS with initial concentration of 10 mg L(-1) could reach 93% with 1 mm thick ACFs in 18 min at input power of 80 W, compared with 85% by single DBD plasma. Meanwhile, the removal rate of total organic carbon increased from 12% at pH 6.26-24% at pH 3.50. ACFs could ameliorate the degradation efficiency for planar DBD plasma when treating TCS solution at high flow rates or at low initial concentrations. A possible degradation pathway of TCS was investigated according to the detected intermediates, which were identified by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) combined with theoretical calculation of Gaussian 09 program.