Double Dielectric Barrier Research Articles

Remediation of pyrene contaminated soil by double dielectric barrier discharge plasma technology: Performance optimization and evaluation

Polycyclic aromatic hydrocarbons (PAHs) in soil are not only detrimental to environment but also to human health. Double dielectric barrier discharge (DDBD) plasma reactor used for the remediation of pyrene contaminated soil was studied. The performance of DDBD reactor was optimized with influential parameters including applied voltage, type of carrier gas, air feeding rate as well as pyrene initial concentration. The analysis of variance (ANOVA) results showed that input energy had a great effect on pyrene remediation efficiency followed by pyrene initial concentration, while, the effect of air feeding rate was insignificant. More specifically, the remediation efficiency of pyrene under air, nitrogen and argon as carrier gas were approximately 79.7, 40.7 and 38.2% respectively. Pyrene remediation efficiency is favored at high level of applied voltages and low level of pyrene initial concentration (10 mgkg−1) and air feeding rate (0.85 L/min). Moreover, computation of the energy efficiency of the DDBD system disclosed that an optimal applied voltage (35.8 kV) and higher initial pyrene concentration (200 mgkg−1) favored the high energy efficiency. A regression model predicting pyrene remediation under DDBD plasma condition was developed using the data from a face-centered central composite design (FCCD) experiment. Finally, the residual toxicity analysis depicted that the respiratory activity increased more than 21 times (from 0.04 to 0.849 mg O2 g−1) with a pyrene remediation efficiency of 81.1%. The study demonstrated the DDBD plasma technology is a promising method not only for high efficiency of pyrene remediation, but also recovering biological function without changing the physical-chemical properties of soil.

Comparison of single and double dielectric barrier discharge non-thermal plasma for toluene removal

In order to investigate the effect of dielectric barrier discharge (DBD) reactor structure on toluene degradation in non-thermal plasma, reactors with single and double barrier were designed. The discharge characteristics, toluene removal efficiency, mineralization rate, CO2 selectivity and energy efficiency of the two rectors were compared, and the effects of voltage and initial concentration on toluene degradation were analyzed. The results indicated that DDBD reactor had higher electric field strength and SDBD reactor had higher power under the same applied voltage. The removal efficiency of toluene in the DDBD reactor ranged from 9.4%~100%, 7.4%~99%, 5.1%~64% and that in the SDBD reactor ranged from 67%~98%, 46%~90%, 26%~59%, when the initial toluene concentration and the applied voltage were 616, 1 027, 1 848 mg·m−3 and were 14~24 kV, respectively. It showed that SDBD has a higher toluene removal efficiency at low applied voltage, while the removal efficiency is higher in DDBD at a higher applied voltage. Moreover, the decrease of toluene concentration and the increase of applied voltage were favorable for toluene degradation. In SDBD, the energy efficiency decreased with the increase of applied voltage, while that of the DDBD reactor first increased and then decreased. The energy efficiency of the DDBD reactor was higher than that of the SDBD reactor at 16~24 kV. The present study could provide reference for the application of DBD in VOCs abatement.

Post-plasma-catalytic degradation of toluene using atmosphere double dielectric barrier discharge combined MnOx-based catalysts

Post-plasma catalytic system with Mn-based has shown potential performance in terms of air pollution degradation, in which Ce was induced into MnOx/Al2O3 mixed with 1:1 weight ratio by the impregnation method to increase the capacity of toluene degradation. The catalytic ability of prepared catalysts was analyzed by characterizations of XRD, SEM, XPS, and BET. The effects of the SIE and initial concentration on toluene and CO2 production were discussed in this work. The results showed that the toluene removal efficiency and CO2 selectivity increased with the promotion of SIE. With the addition of 15% Ce1Mn1/A2O3, the PPC system displayed the potential performance in the enhancement of toluene conversion and CO2 generation, and suppression of ozone and NO2 compared with plasma alone. At the SIE level of 504 J/L, the system showed better performance in terms of toluene removal efficiency (90.1%), CO2 selectivity (67.3%), O3 suppression (79.3%), and NO2 prohibition (61.8%). Also, the organic by-products generated by the PPC system were discussed.

Time-resolved characterization of non-thermal plasma-assisted photocatalytic removal of nitric oxide

We performed time-resolved characterization of plasma-photocatalytic removal of nitric oxide (NO) in a ceramic foam packing double dielectric barrier discharge reactor using mid-infrared laser absorption spectroscopy. Non-thermal plasma (NTP) was generated in the porous ceramic foam coated with mesoporous TiO2 thin film. Real-time NO monitoring was performed using a quantum cascade laser at 5.26 µm combined with a custom-designed multipass gas cell, leading to a sub-ppm detection limit at 0.1 s measurement time. By analyzing the feed gas of 90 ppm NO/1% O2 balanced in N2, the plasma treatment without TiO2 photocatalyst had no effect on NO removal when the discharge power was below 45 W. In comparison, the NTP-TiO2 system achieved an efficiency of 49% for NO removal even at the relatively low discharge power of 18 W. The synergy between NTP and TiO2 photocatalyst effectively promotes the NO removal at low plasma discharge powers. However, we also observed a negative effect of TiO2 photocatalyst on NO removal at a relatively high discharge power of 135 W.

Construction of a power electronic source for cold plasma generation

This paper presents the development of a high voltage and high-frequency power electronics source, for plasma generation, at atmospheric pressure and vacuum, using helium and air as working gases. The source design consists of an inductive (L) full bridge series resonant inverter at high frequency, where the control implemented allows varying duty cycle and frequency. Plasma generation is made by high voltage with the power signal applied on two electrodes, which provides a strong electric field that excites, and thus, ionize helium particles or air particles. The power electronic source operation was tested in different plasma reactor configurations (dielectric barrier discharge, double dielectric barrier discharge, and jet type discharge). The developed power electronics source shows a correct performance and generate a strong electric field to achieve the plasma discharges desired.

Effects of Dielectric Barrier Discharge Plasma on the Combustion Performances of Reverse-Flow Combustor in an Aero-Engine

In order to apply plasma assisted combustion (PAC) into a reverse-flow aero-engine and verify the improvement of combustion performance, a feasible approach was proposed in this work. In this approach, based on the structure characteristics of the reverse-flow combustor, a parallel plate double dielectric barrier discharge (DBD) PAC actuator was designed to generate plasma. It was installed at the front of combustor. When the actuator is driven, the original air flow is not disturbed for the device's structure and installation. Using aviation kerosene as fuel, the effects of plasma on ignition boundary and outlet temperature of the combustor were experimentally investigated at atmosphere pressures. Through the dual high voltage differential power supply, the large gap, large area and uniform plasma discharge was achieved. The results of PAC actuator discharge indicate that inlet air temperature has a small increase of 4–9 K. After PAC is applied, the combustion performances of reverse-flow combustor in an aero-engine are remarkably improved. Experimental results indicate that ignition boundary is widened by 3.7%-12.5% because of the impact of plasma. Outlet highest temperature of combustor is raised by 19–75 K; outlet temperature distribution coefficient is reduced by 11.1%-26.6%. This research provides an effective and practicable way to implement the application of PAC in aero-engine combustor and has some engineering application significance.

A novel array of double dielectric barrier discharge combined with TiCo catalyst to remove high-flow-rate toluene: Performance evaluation and mechanism analysis.

A novel array double dielectric barrier discharge (ADDBD) combined with a TiO2/Al2O3-Co3O4/AC (TiCo) catalyst was applied to remove toluene. The effects of catalyst setting distance, catalyst combination mode, and process factors (including specific input energy, initial toluene concentration, and relative humidity) were investigated in terms of the toluene degradation efficiency (ηtoluene) and the selectivity of CO2 (SCO2). When the specific input energy was 65 J·L-1, the initial toluene concentration was 100 mg·m-3, and the relative humidity was 30%, the highest ηtoluene of 72% and SCO2 of 44% could be achieved with TiO2/Al2O3 10 cm and Co3O4/AC 20 cm downstream of the ADDBD. Based on the determination of active substances (e.g., O3, OH) and the catalyst activation mode, a synergistic effect of active substances and photon between the ADDBD and the TiCo catalyst was proposed for the removal of toluene. Finally, the biodegradability and toxicity of the outlet gas were evaluated, and the results showed that the outlet gas was more convenient for subsequent biopurification and less toxic to the surroundings after the treatment by the ADDBD combined with the TiCo catalyst.

Using non-thermal plasma for decomposition of toluene adsorbed on γ-Al2O3 and ZSM-5: Configuration and optimization of a double dielectric barrier discharge reactor

A novel hybrid system was established to degrade adsorbed toluene efficiently. A double dielectric barrier discharge (DDBD) reactor was filled with two common adsorbents, γ-Al2O3 and ZSM-5, in various combinations. Packing material, high-voltage electrode structure, and gas-flow mode were investigated to optimize this reactor. The reactor packed with a mixture of γ-Al2O3 and ZSM-5 provided a mineralization rate 6.1% to –14.1% greater than one using a single material. Specifically, the highest mineralization rate was obtained in a DDBD reactor packed with γ-Al2O3 in the inner tube and ZSM-5 in the outer tube. Using the optimal combination of packing material, two high-voltage electrodes were compared. A higher mineralization rate was observed in the reactor with a rod electrode (63.3%) than in one equipped with a coil electrode (53.7%), The total amounts of O3 and N2O generated were much less in the reactor with a rod electrode. The effect of gas-flow mode on toluene decomposition was investigated and the result showed that mode 1 (with the gas flowing from the inner tube into the outer tube during both adsorption and discharge phases) could not only improve the degradation of toluene, but could also suppress the generation of O3 and N2O. A possible mechanism for toluene decomposition in the packed-bed DDBD reactor was proposed based on the analysis of organic intermediates remaining in the adsorbents.

Double dielectric barrier discharge cells for promoting the catalytic degradation of volatile organic compound released by industrial processes.

In this study, the recycling of gas flow was added to oxidize mixture (toluene and xylene) in the post-plasma catalysis (PPC) system, and the MnOx catalysts using impregnation method were used to further oxidize the VOC mixture. The circulation and catalysts were of enhancement for the plasma degradation on both toluene and xylene. The improvement of CO2 selectivity and the reduction of NO, NO2, and O3 were 64.4%, 92.0%, 62.2%, and 51.9%, respectively. The fresh and used catalysts were characterized for the ozone decomposition and mixture degradation in the NTP-REC-CATAL system with the 15wt% loading amount of catalysts. The results showed that OH groups, lattice oxygen, and manganese sites were potential and significant for the catalytic ability for O3 and mixture conversion. Aldehyde was detected from FT-IR characterization after treating, which indicates that it is the main intermediate NTP-REC-CATAL process. The air plasma was employed to reactive catalytic activity.

DDBD ozone plasma reactor generation: the proper dose for medical applications

Double Dielectric Barrier Discharge (DDBD) ozone plasma reactor generation are presented in this paper. The generation of this reactor generates ozone concentration which can be arranged upon the proper dose for medical applications. AC high voltage is applied to the range of 0-3 kV and the frequency of 50 Hz. Pure oxygen gas was piped into the DDBD reactor with flow rate variations of 2, 4 and 6 L/min. The results showed that current as a function of voltage where the current is increased with the increasing of voltage. Ozone productivity is shown by the significant increase of current. Ozone concentration is increasing as the increase of the voltage provided, but rather the concentration of ozone is decreasing as the increasing of flow rate. The Ozone capacity is affected by ozone concentration and flow rate, and can be used to determine the ozone dose. The proper dose of ozone can be ozone therapy for various kinds of diseases.

Electrical model and experimental analysis of a double spiral structure surface dielectric barrier discharge

A surface dielectric barrier discharge (SDBD) can discharge at atmospheric pressure and produce a large area of low-temperature plasma. An SDBD plasma reactor based on the double spiral structure is introduced in this paper. To study the discharge mechanism of SDBD, an equivalent circuit model was proposed based on the analysis of the micro-discharge process of SDBD. Matlab/Simulink is used to simulate and compare the voltage–current waves, Lissajous and discharge power with the experimental results. The consistency of the results verifies the validity of the SDBD equivalent circuit model. Maxwell software based on the finite elements method is used to analyze the electrostatic field distribution of the device, which can better explain the relationship between the discharge image and the electrostatic field distribution. The combination of equivalent circuit simulation and electrostatic field simulation can provide better guidance for optimizing a plasma generator. Finally, the device is used to treat PM2.5 and formaldehyde. The test results show that the degradation rate of PM2.5 can reach 78% after 24 min, and formaldehyde is about 31.5% after 10 min of plasma treatment.

Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO2/Al2O3 catalyst

A new reactor of array double dielectric barrier discharge (DDBD) combined with catalysis was prepared, and the effect of different factors on removal efficiency of toluene at pilot scale were investigated. The possible degradation mechanism was explored. The results indicate that the removal efficiency of toluene in the exhaust gas decreases with the increasing of the toluene initial concentration and the gas flow rate, but increases with the increasing of the specific energy density. When the air relative humidity is 55%, the removal efficiency of toluene is higher than that of the relative humidity by 85%. The results of XPS, FT-IR and GC-MS analysis show that the main intermediate products of removing toluene by DDBD combined with TiO2/Al2O3 catalyst are phenol, benzaldehyde, benzyl alcohol, benzoic acid, N-benzyl formamide, dimethyl terephthalate, dimethyl isophthalate and other substances. There are five possible pathways to degrade toluene by DDBD combined with TiO2/Al2O3.

A review on application of dielectric barrier discharge plasma technology on the abatement of volatile organic compounds

Volatile organic compounds (VOCs) released from the waste treatment facilities have become a significant issue because they are not only causing odor nuisance but may also hazard to human health. Non-thermal plasma (NTP) technologies are newly developed methods and became a research trend in recent years regarding the removal of VOCs from the air stream. Due to its unique characteristics, such as rapid response at room temperature, bulk homogenized volume, high reaction efficiency, dielectric barrier discharge (DBD) plasma technology is considered one of the most promising techniques of NTP. This paper reviews recent progress of DBD plasma technology for abatement of VOCs. The principle of plasma generation in DBD and its configurations (electrode, discharge gap, dielectric barrier material, etc.) are discussed in details. Based on previously published literature, attention has been paid on the effect of DBD configuration on the removal of VOCs. Effect of various process parameters such as initial concentration, gas feeding rate, oxygen content and input power on VOCs removal are also considered. Moreover, the role of catalysis and inhibitors in VOCs removal by DBD system are presented. Finally, a modified configuration of the DBD reactor, i.e. double dielectric barrier discharge (DDBD) for the abatement of VOCs is discussed. It was suggested that the DDBD plasma reactor could be used for higher conversion efficiency as well as for avoiding solid residue deposition on the electrode. These depositions can interfere with the performance of the reactor.

Development of DDBD and plasma jet reactors for production reactive species plasma chemistry

A novel Double Dielectric Barrier Discharge (DDBD) and an atmospheric pressure plasma jet (APPJ) was generated with a dielectric barrier discharge (DBD) column by AC high voltage have been developed. This reactor can produce cold atmospheric plasmas (CAP) that formed in air reactive oxygen species (ROS). These species among others are O3, H2O2, was quantified in the outlet of reactors. The analysis for ROS has been conducted by using medium that we call Plasma-Activated Medium (PAM). Some analysis conducted including variation of exposure times by ROS to the plasma-activated medium. In addition, concentration-voltage characteristics of ozone production. Peroxide Value, Acid Value and Viscosity of virgin coconut oil (VCO, as PAM) increased with increasing exposure time of O3. The concentration of hydrogen peroxide in water (as PAM) has been measured. The concentration of H2O2 179 μM with exposure time for 1 minute. The concentration of H2O2 in the study is quite high when compared with some other research results. The results showed that increased exposure time resulted in increased concentrations of ozone and hydrogen peroxide.

New development of double dielectric barrier discharge (DBD) plasma reactor for medical

Effect of gas source and flowrate to ozone concentration and capacity was investigated using double DBD plasma reactor with cylinder-cylinder configuration. The high AC voltage was applied in the range of 200-500 Volts and the frequency of 50 Hz. Gas sources; i.e. free air and pure oxygen; flowed into the reactor with several variations in flow rate, i.e. 2 to 24 L/min. The results showed that the ozone concentration decreased with increasing gas flow rate. Free air sources produced smaller ozone concentration and capacity compared to those produced using a pure oxygen source (O2). While the ozone capacity increases with increasing gas flow rate. The pure oxygen (O2) with a flow rate of 24 L/min had produced ozone concentration of 2.2 mg/liter and ozone capacity of 52.8 mg/min. A number of further studies need to be conducted related to the effect of voltage, diameter, and length of the electrode to obtain lower ozone concentration and capacities, for ozone applications in medical therapy. The suitable dose of ozone therapy for medical can be used for wound healing and chronic disease.

Surface activation of textile fibers by plasma DBD for dyeing with teak leaf

The use of natural dyes is a field of great interest to solve the problems related to environment pollution and health risks. The objective of this research was to study the plasma discharge of double dielectric barrier (DDB) to modify the fabrics surfaces of polyamide 6.6 (PA66), silk (SK) and cotton (CO) dyed with leaf extract of teak (Tectona grandis). It was also aimed the improvement in the penetration and fixation properties to the natural dyes even without using metal mordants, which are toxic and usually used in this type of dyeing. The dye extract obtained from the teak leaves was chemically characterized by using UHPLC/QTOF-MS. The color parameters were calculated by means of spectroscopy to evaluate the color intensity (K/S) and its fastness was evaluated for washing, friction and perspiration.

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.

Kinetics of plasma-assisted oxidation of highly diluted hydrocarbon mixtures excited by a repetitive nanosecond pulse discharge

Plasma-assisted oxidation of atmospheric pressure hydrogen- and hydrocarbon-oxygen mixtures diluted in argon is analyzed by kinetic modeling, over a wide range of temperatures. In the experiments, preheated reactant mixtures are excited by a repetitively pulsed, double dielectric barrier ns discharge in plane-to-plane geometry, at near-isothermal conditions. Plasma images and temperature distributions in the discharge indicate that the reactant flow is nearly uniform, justifying the use of quasi-0D approximation in kinetic modeling. The kinetic model is based on a plasma chemistry mechanism combined with a conventional combustion reaction mechanism. The model does not contain adjustable parameters such as reduced electric field in the plasma, used in a number of previous 0D modeling studies. Comparison of the modeling predictions with the experimental data for hydrogen and methane oxidation exhibits good agreement between measured and predicted fuel concentrations over a wide range of temperatures, showing that the yield of primary radicals generated in the plasma is predicted accurately. Concentrations of intermediate hydrocarbon species predicted by the model are also in good agreement with the experiments, with the exception of acetylene below the hot ignition point. For ethylene and propane oxidation, the model overpredicts fuel consumption at low temperatures, also overpredicting concentration of CO, the dominant oxidation product, and underpredicting acetaldehyde concentration. This indicates that low-temperature pathways of formaldehyde formation, a major precursor for CO, as well as low-temperature reactions of several radicals which are precursors for formaldehyde and acetaldehyde, are not represented accurately in both conventional reaction mechanisms used. Although concentrations of intermediate hydrocarbon species in ethylene and propane are predicted relatively well, kinetics of formation and decay of acetylene remains not understood. This may be due to inaccurate branching ratio for dissociative quenching of metastable argon by heavy hydrocarbon species, as well as deficiencies of the conventional reaction mechanisms.

Process for Chloroform Decomposition: Nonthermal Plasma Polymerization with Methane and Hydrogen

This paper describes an alternative process for chloroform decomposition via nonthermal plasma polymerization at atmospheric pressure and investigates the effect of methane and hydrogen addition on the process. The effect of both additives was assessed separately, where experiments were conducted in a double dielectric barrier discharge reactor under nonoxidative conditions. The most profound impact of the additives was a significant increase in the yield of non-cross-linked polymer produced compared to that in their absence. The addition of methane resulted in a 120% increase in polymer yield, while in hydrogen the increase was 31%. Critical parameters such as effect of the methane and hydrogen concentration on the conversion of chloroform at various applied voltages, the product distribution, mass balance, and polymer characterization are elucidated in this paper. Single pass conversions of 61% and 68% (with corresponding mass balances of 98% and 95%, respectively) were achieved for CHCl3 + CH4 and CHCl3 + H2 feed scenarios, respectively. Furthermore, a polymerization mechanism which explains the formation of major chain structures as well as structural defects in the polymer is expounded upon in the paper.

Effects of Reduced Electric Field on Sulfur Hexafluoride Removal for a Double Dielectric Barrier Discharge Reactor

Sulfur hexafluoride (SF6) is a greenhouse gas with very high global warming potential. This paper investigated the effects of reduced electric field, E/N, on SF6 abatement by using a coaxial double-layer dielectric barrier discharge (DBD) reactor. The concentration of SF6 was 2%, and the remaining 98% of the feed gas is He/water vapor. The reduced electric field of the discharge region was calculated. The effects of different reduced electric fields on SF6 removal and the mechanisms were studied in terms of the removal efficiency and energy yield (EY). The experimental results showed that higher removal efficiency was achieved when the reduced electric field was higher than 126 Td and as the E/N increased; the time for removing SF6 completely was shortened. However, the EY at different reduced electric fields did not change much. SO2F2, SOF4, SOF2, and SO2 were the main products after the plasma removal process.