Pulsed Corona Discharge Reactor Research Articles

Degradation of perfluorosurfactant in aqueous solution using non-thermal plasma generated by nano-second pulse corona discharge reactor

Perfluorosurfactants (PFS) are global environmental pollutants and are considered as a new anthropogenic type of carcinogenic contaminant that remains untreated by conventional wastewater treatment plants. These organic surfactants are typically refractory, non-biodegradable, and pose great threats to environmental safety and human health. The gradual increase in PFS product consumption by various industries resulted in their abundant occurrence in the ecosystem. Non-thermal plasma-based advanced oxidation processes with powerful oxidation ability appeared to be applicable for the degradation of refractory organic pollutants and enhancing biodegradability. In this work, the decomposition of Perfluorooctanesulfonic acid (PFOS) in water by the application of nano-second pulse corona discharge under oxygen was examined. Working corona discharge under oxygen, argon, and helium has no effects on the decomposition rate. The energy yields at 50% conversion (G 50 ) of about 1 mg L −1 initial PFOS concentration was estimated as 22 mg/kWh under argon or oxygen and 27 mg/kWh under helium. The energy yield G 50 for initial concentrations of 7.5 and 18.5 µg L −1 in helium and oxygen was estimated as 0.20 and 0.33 mg/kWh, respectively. A considerable difference in the generation of short perfluoroalkyl acids by-products and fluoride ions was observed when corona discharge was conducted under oxygen and much more of these by-products are formed. A synergistic effect was observed in the presence of other surface-active compounds. Degradation efficiency was enhanced by 10% after the addition of surface-active sulfobetaine into the medium following the same experimental procedure.

Gasoline degradation and nitrogen fixation in soil by pulsed corona discharge plasma

Gasoline contaminated soil poses an environmental and human health problem, which may be partially solved by the emerging non-thermal plasma technology. In this study a pulse corona discharge (PCD) reactor was employed to degrade gasoline in soil and simultaneously to fix nitrogen in soil. The gasoline removal rates were influenced by input power, electrode gap, gas flow rate, initial gasoline concentration, soil pH, and soil moisture. This technology produced no secondary pollution. Ozone, NOx, and hydroxyl radicals, generated directly on the soil surface, were identified as the primary agents responsible for gasoline degradation. The role of the major active agents was determined by ventilating different gases during the corona discharges. In addition, the concentration of nitrate and wettability of soil was increased after the treatment. Safety and fertility of treated soil were investigated by planting lettuce. Thus, soil pollution was remediated using this non-thermal plasma treatment, while simultaneously improving soil nitrogen content and physical characteristics. This process potentially enhances soil fertility and revegetation, since this environmentally-friendly method does not involve other chemicals injections.

Continuous flow pulse corona discharge reactor for the tertiary treatment of drinking water: Insights on disinfection and emerging contaminants removal

The widespread occurrence of emerging contaminants (ECs) and pathogens in potable water sources has led to the need of an efficient alternative method for water treatment. Three pharmaceuticals and two pesticides were selected for the ECs degradation study in a continuous flow pulse corona discharge reactor. For a power dissipation of 58.67 W, ECs were completely removed from lake water with a flow rate of 10 mL/min. Whereas, 91–100% ECs degradation was achieved in river water after a hydraulic retention time (HRT) of 24 min. Initial bacterial concentrations were determined in lake and river water samples and subsequently, disinfection studies were carried out. With the same power input, complete disinfection (3 log reduction in river water) was achieved within HRT of 10 min. The toxicities of the ECs were completely eliminated after the plasma treatment. Several other water quality parameters were also monitored and an increase in nitrate concentration and decrease in pH value was observed after treatment. The problem of increased nitrate concentrations in the plasma treated water was tackled, thus making the plasma treated water suitable for drinking purpose. Using oxygen as a feed gas instead of atmospheric air, nitrate concentration was brought down significantly. Energy efficiency of the reactor was also compared in terms of electrical energy per order (EEO) and G value. Depending on the nature of the ECs, the EEO values ranged between 20 and 86 kWh/m3 and G-value between 8.4 and 36.8 mg/kWh in different potable water sources. The operating cost for treating ECs from contaminated water was found to be as low as 4.3 $/m3.

Design and Analysis of Nano-Pulse Generator for Industrial Wastewater Application

Recently, the application of a pulsed power system is being extended to environmental and industrial fields. The non-dissolution wastewater pollutants from industrial plants can be processed by applying high-voltage pulses with a fast rising time (a few nanoseconds) and short duration (nano to microseconds) in a pulsed corona discharge reactor. The high-voltage nano-pulse generator with a magnetic switch has been developed. It can be used for a spray type water treatment facility. Its corona current in load can be adjusted by pulse width and repetition rate. We investigated the performance of the nano-pulse generator by using the dummy load that is composed of resistor and capacitor equivalent to the actual reactor. In this paper, the results of design, construction and characterization of a high-voltage nano-pulse generator for an industrial wastewater treatment are reported. Consequently, a pulse width of 1.1 μs at the repetition rate of 200 pps, a peak voltage of 41 kV for the nano-pulse generator were achieved across a 640 Ω load. The simulation results on magnetic switch show reasonable agreement with experimental ones.

Effect of recycling overhead gases on pollutants degradation efficiency in gas-phase pulsed corona discharge treatment

In the present study, pollutant degradation efficiency was investigated by recycling of overhead gases from gaseous phase to aqueous phase in gas-liquid interface pulsed corona discharge reactor. Methylene blue (MB) was used as a model pollutant and its degradation was compared by recycling and non-recycling of oxygen, air and argon gases. The degradation rate constants of MB were 0.28 and 0.23 min−1 in recycled condition which was decreased to 0.22 and 0.21 min−1 in non-recycled condition in oxygen and argon gas, respectively. On contrary, in air medium, comparatively higher MB degradation rate (0.21 min−1) was achieved in non-recycled condition compared to recycled condition (0.11 min−1). The long-lived reactive oxygen species (ROS) such as hydrogen peroxide and ozone were quantified in both conditions. We observed that the concentration of ozone present in the aqueous solution was slightly higher in recycling conditions as compared to that of non-recycled condition in all the gases. Moreover, higher hydrogen peroxide concentration was detected in recycled condition (185 and 168 mg/L) compared to non-recycled condition (112 and 40 mg/L) in the presence of oxygen and argon, respectively, and vice-versa in air medium. The economic comparison revealed that up to 33% of electrical energy could be saved by recycling overhead oxygen gas.

Integrated CO2 Capture and Utilization Using Non-Thermal Plasmolysis

In the presented work, 2 simple processes for carbon dioxide (CO2) capture and utilisation have been combined to form a whole systems approach to carbon capture and utilisation (CCU). The first stage utilises a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times whilst employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance towards impurities in the feed, in the form of nitrogen (N¬2) for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%).

Removal of Acid Black 1 from water by the pulsed corona discharge advanced oxidation method

Water pollution is a major global problem. Organic pollutants are one of the major groups of toxic and carcinogenic contaminants that, due to their complex structures, show resistance to biodegradation processes. The pulsed corona discharge (PCD) advanced oxidation technology, with a point-to-point configuration of the electrodes immersed in the aqueous solution, was used for decomposing Acid Black 1 (AB1) as a representative of synthetic organic azo dyes. The effects of electrical field frequencies (60 and 120Hz) and electrode gap spaces (2, 4 and 6mm) on decomposition of AB1 were investigated. The largest decomposition achieved was 99.93% with optimal conditions of electrical field frequencies of 120Hz and an 8mm electrode gap space. Also, the effect of the catalytic properties of titanium dioxide nanoparticles on the treatment process of the PCD reactor was investigated. Different concentrations of TiO2 NPs (0.075, 0.3, 0.08 and 3gL−1) were tested. A concentration of 0.08gL−1 TiO2 was found to be the optimal concentration that increased the dye degradation from 52.62% (with no titanium dioxide nano particles) to 94.14% in 15min. However, a higher concentration of TiO2 showed the adverse effect and decreased the degradation level of AB1. Finally, the pulsed corona discharge as an oxidation process was compared with the photocatalytic processes of UV, UV/H2O2 and UV/TiO2 in terms of removing AB1 from an aqueous solution, and promising results were reported.

Aqueous Benzene Oxidation in Low-Temperature Plasma of Pulsed Corona Discharge

AbstractWastewaters polluted with non-biodegradable volatile organic compounds (VOCs), such as aromatic substances, present a growing problem meeting no adequately affordable technological response. Low-temperature plasma generated in the gas-phase pulsed corona discharge (PCD) presents competitive advanced oxidation technology in abatement of various classes of pollutants, although the process parameters, the pulse repetition frequency and the liquid spray rate, require optimization. The experimental research into aqueous benzene oxidation with PCD was undertaken to establish the impact of the parameters to the energy efficiency. The oxidation reaction was found under the experimental conditions to mostly proceed in the gas phase showing little influence of the pulse repetition frequency and the gas-liquid contact surface. Oxidation of benzene and, presumably, other volatile pollutants in the volume of PCD reactor compartment presents an effective strategy of aqueous VOCs abatement.

Energy Injected in Multi-tip Pulsed Corona Discharge Reactor in Air at Atmospheric Pressure for Pollution Control

This work is devoted to the analysis of experimental and calculated results obtained in dry air at atmospheric pressure in positive pulsed multi-tip corona discharges. The maximum corona current is analysed as a function of several parameters such as the gap distance, the applied voltage and the anodic tip number. The energy injected in the discharge is also calculated as a function of the above parameters for to optimize the most efficient configuration for the pollution control. Also, the average propagation velocity is discussed as a function of the same operating parameters (gap distance, applied voltage and anodic tip number). Intensified Charged-coupled device pictures are shown to prop up the results obtained in this study.

High Voltage Pulse Generator Using Transformer Parasitic Components for Pulsed Corona Discharge Generation

This paper proposes a new topology of a nanosecond, high voltage pulse generator devoted to pulsed corona discharge (PCD) reactor supply. The proposed topology is based on solid state, semiconductor switches and uses parasitic components of transformers. A prototype construction of the proposed generator loaded with a PCD reactor with 6.4-pF capacitance is able to generate high voltage pulses with maximum amplitude of 14 kV (using 5.4-kV supply and up to six modules of proposed topology, each equipped with a MOSFET transistor with 1-kV blocking capability) with voltage steepness of 730 V/ns. Obtained pulses are 65-ns long. The peak power delivered to the PCD reactor is ${>}{\rm 0.3}~{\rm MW}$ while the energy consumed reaches 7 mJ/pulse. This paper also compares two different mechanical constructions of such generators and gives an overview of analytical and numerical voltage waveform analyzes.

Oxidation of ammonium sulfite by a multi-needle-to-plate gas phase pulsed corona discharge reactor

The oxidation of ammonium sulfite in the ammonia-based flue gas desulfurization (FGD) process was investigated in a multi-needle-to-plate gas phase pulsed corona discharge reactor in this paper. The effect of several parameters, including capacitance and peak pulse voltage of discharge system, electrode gap and bubbling gas flow rate on the oxidation rate of ammonium sulfite was reviewed. The oxidation rate of ammonium sulfite could reach 47.2% at the capacitance, the peak pulse voltage, electrode gap and bubbling gas flow rate equal to 2 nF, −24.6 k V, 35 mm and 4 L min−1 within treatment time of 40 min The experimental results indicate that the gas phase pulsed discharge system with a multi-needle-to-plate electrode can oxide the ammonium sulfite. The oxidation rate increased with the applied capacitance and peak pulse voltage and decreased with the electrode gap. As the bubbling gas flow rate increased, the oxidation rate increased first and then tended to reach a stationary value. These results would be important for the process optimization of the (NH4)2SO3 to (NH4)2SO4 oxidation.

Study of Geometry Structure on a Wire–Plate Pulsed Corona Discharge Reactor

The wire-plate pulsed corona discharge reactor has been regarded as the plasma reactor with highest efficiency for controlling pollutants such as NO and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in flue gas with high-voltage and short-duration positive pulsed corona discharge. A laboratory-scale pulsed corona discharge reactor with wire-plate electrode configuration is established for optimizing the geometry structure of the wire-plate plasma reactor. In this paper, three different methods are used to optimize the wire-to-wire distance and wire-to-plate distance of the plasma reactor. There are experiments with different conditions including various electrical parameters, streamer parameters, and NO oxidation efficiency. The same results are obtained from all the three experiments. The results indicate that short wire-to-plate distance should be adopted to increase the input energy of the plasma reactor but not too short to cause spark discharge in the reactor. Moreover, the wire-to-wire distance should be at least twice as large as wire-to-plate distance, to reduce the interferences between adjacent wire electrodes.

Plasma steam reforming of E85 for hydrogen rich gas production

E85 (85 vol% ethanol and 15 vol% gasoline) is a partly renewable fuel that is increasing in supply availability. Hydrogen production from E85 for fuel cell or internal combustion engine applications is a potential method for reducing CO2 emissions. Steam reforming of E85 using a nonthermal plasma (pulse corona discharge) reactor has been exploited at low temperature (200–300 °C) without external heating, diluent gas, oxidant or catalyst in this work. Several operational parameters, including the discharge current, E85 concentration and feed flow rate, have been investigated. The results show that hydrogen rich gases (63–67% H2 and 22–29% CO, with small amounts of CO2, C2 hydrocarbons and CH4) can be produced by this method. A comparison with ethanol reforming and gasoline reforming under identical conditions has also been made and the behaviour of E85 reforming is found to be close to that of ethanol reforming with slightly higher C2 hydrocarbons yields.

Effect of gas mixture composition on tar removal process in a pulsed corona discharge reactor

Results of simulation of naphthalene removal from nitrogen and its mixture with water vapour by a sequence of corona discharge pulses are presented. A comparison of the data calculated on the basis of two approaches is presented: with approximate and detailed account of reactions involving charged species. It is shown that approximate account gives the efficiency of naphthalene removal close to that obtained basing on more detailed approach.

The Characteristic of Decomposition of LAS in a Water Droplets Spray by Pulsed Power Discharge in Air

A method for decomposing organic compound by spraying water solution into non-equilibrium plasma in gas phase was investigated using a pulsed-corona discharge reactor. The corona reactor used consists of a discharge wire and a cylindrical electrode. Water solution of sodium dedecylbenzensulfonate (C12-LAS) with a concentration of 100mg/L was sprayed into the reactor from a showerhead. The sprayed water solution was circulated into the reactor. C12-LAS was decomposed up to about 90 % by one time exposure in the discharge for the discharging power of 6 W. C12-LAS was mostly decomposed for 30 minutes of a treatment. However by-products were generated by the treatment. It is speculated that the by-product after treating for 300 minutes was CH3(CH2)2-O-(CH2)4-O-(CH2)3CH3.

Energy efficiency of hydrogen sulfide decomposition in a pulsed corona discharge reactor

A novel pulsed corona wire-in-tube reactor with quartz view-ports allowed visual observation of the effect of charge voltage and gas composition on the corona distribution. The H 2 S conversion and energy efficiency of H 2 S decomposition in this pulsed corona discharge reactor varied at constant power (100 W) due to the selected values of the electrical parameters of pulse forming capacitance (720–2880 pF), charge voltage (11–21 kV), and pulse frequency (157–961 Hz). Low pulse forming capacitance, low charge voltage, and high pulse frequency operation produces the highest energy efficiency for H 2 S conversion at constant power. H 2 S conversion is more efficient in Ar–N 2 gas mixtures than in Ar or N 2 . These results can be explained by corona discharge observations, the electron attachment reactions of H 2 S at the streamer energies, and a proposed reaction mechanism of H 2 S dissociation in the Ar–N 2 gas mixture. The energy consumption per molecule of converted H 2 S in an equimolar mixture of Ar and N 2 (4.9 eV/H 2 S) is the lowest that has been reported for any plasma reactor operated at non-vacuum pressures. The results reveal the potential for energy efficient H 2 S decomposition in pulsed corona discharge reactors.

Calculation of electron-molecule reactions of NO decomposition in pulsed corona discharges

In recent years there has been increasing research interest in the removal of nitrogen-oxides from exhaust gases using a pulsed corona discharge reactor. The pulsed streamer corona produces energetic electrons that excite, ionize and dissociate gas molecules, and by forming radicals that enhance the gas-phase chemical reactions which reduce the pollutant's concentration. The decomposition ratio of these substances is dependant on the gas composition, concentration, energy distribution of fast electrons, and other parameters. For a detailed analysis of the phenomena, knowledge of chemical reaction mechanisms is essential. The reaction rates of possible molecule-molecule reactions can in most cases be found in the literature, but the rates of the electron-molecule collision reactions depend on the energy of free electrons. With the knowledge of the field distribution, the energy of the free electrons and the reaction rates can be found. In this paper the authors present a method, in which the reaction rates of the electron- molecule collision are determined. The model is based on a calculation of: the energy of free electrons in the time and space varying field, considering the mean free path and the energy-dependent reaction cross sections of molecules. Knowing the rates, it is possible to solve the reaction kinetic equations, and to get the time-evolution of byproducts, and the decomposition ratio of the pollutant gases.

Decomposition of Dye in Water Solution by Pulsed Power Discharge in a Water Droplet Spray

A method for decomposing dye by spraying water solution of dye into nonequilibrium plasma in gas phase was investigated using a pulsed-corona discharge reactor. The corona reactor consists of a discharge wire and a cylindrical electrode. The water solution of indigo carmine with a concentration of 20 mg/L was sprayed into the reactor from a showerhead. The sprayed water solution was circulated into the reactor. The dependence of the discharging power injected into the reactor on the decomposition rates of chromogenic and unsaturated bonds in indigo carmine was investigated. Indigo blue was decolored by 1-min circulation with the discharging power of 8.6 W. The nuclear magnetic resonance spectrometry showed that indigo carmine was decomposed completely by 60-min treatment. The chromogenic and unsaturated bonds were almost decomposed at 9 and 360 J/mg, respectively. As the discharging power increased, the decomposition rates of both bonds in indigo carmine increased. The decomposition rates of the chromogenic bond showed equal values in equal discharging power regardless of the difference of discharge repetition rate and charging voltage of the capacitor. In contrast, the higher repetitive pulses were more effective for the decomposition of the unsaturated bond rather than the magnitude of charging voltage in equal discharging power.

Modeling of the production of OH and O radicals in a positive pulsed corona discharge plasma

A mathematical model was applied to describe the behavior of OH and O radicals in positive pulsed corona discharge of N 2–H 2O mixture gas. The model takes into account the generation and disappearance of radials in a pulsed corona discharge reactor by a single pulse or continuous pulses. Their concentrations were derived by considering direct electron effect on the dissociation of gaseous molecules (O 2, N 2, H 2O) and subsequent excitation transfer reaction of excited oxygen atoms to produce OH radicals. The equations promoted could be solved numerically with the FORTRAN subroutine Treanor. So as to establish the validity of the model simulation, the calculated results were compared with the experimental data. Although there is some discrepancy between the calculation and experiment, the total trend is coincident.

Kinetic model of hazardous gas decomposition by pulsed corona discharge

In recent years there has been increasing research interest in the removal of nitrogen-oxides from exhaust gases using a pulsed corona discharge reactor. The pulsed streamer corona produces energetic electrons that excite, ionize and dissociate gas molecules, and by forming radicals that enhance the gas-phase chemical reactions which reduce the pollutant’s concentration.In this paper a method is presented, where the reaction rates of the electron-molecule collision are determined. The model is based on calculation of the energy of free electrons in the time and space varying field, considering the mean free path and the energy-dependent reaction cross sections of molecules. Knowing the rates, it is possible to solve the reaction kinetic equations, and to get the time-evolution of by-products, and the decomposition ratio of the pollutant gases.