Simultaneous oxidation of NO,SO_2 and Hg^0 from flue gas by pulsed corona discharge

A process capable of simultaneously oxidizing NO, SO2, and Hg^0 was proposed, using a nigh-voltage and short-duration positive pulsed corona discharge. By focusing on NO, SO2, and Hg^0 oxidation efficiencies, the influences of pulse peak voltage, pulse frequency, initial concentration, electrode number, residence time and water vapor addition were investigated. The results indicate that NO, SO2 and Hg^0 oxidation efficiencies depend primarily on the radicals （OH, HO2, O） and the active species （O3, H2O2, etc.） produced by the pulsed corona discharge. The NO, SO2 and Hg^0 oxidation efficiencies could be improved as pulse peak voltage, pulse frequency, electrode number and residence time increased, but they were reduced with increasing initial concentrations. By adding water vapor, the SO2 oxidation efficiency was improved remarkably, while the NO oxidation efficiency decreased slightly. In our experiments, the simultaneous NO, SO2, and Hg^0 oxidation efficiencies reached to 40%, 98%, and 55% with the initial concentrations 479 mg/m^3, 1040 mg/m^3, and 15.0 μg/m^3, respectively.

Removal of SO_2 and NO_x by Pulsed Corona Combined with in situ Ca(OH)2 Absorption

Removal of SO2 and NOx by pulsed corona combined with in situ alkali absorption was experimentally investigated.In the reactor,a plate-wire-plate combination is devised for generating pulsed corona and then alkaline absorbent slurries were introduced into the reactor by a continuous band conveying system to capture the gaseous reaction products.It was found that both SO2 and NO could be removed by corona combined with in situ alkali absorption.The removal of SO2 increased to 75%with the corona discharge,compared with 60%removal only with Ca(OH)2 absorption.About 40%removal of NO was reached by pulsed corona combined with in situ Ca(OH)2 absorption.It was found that SO2 and NO in the gas stream are oxidized to SO3 and NO2 by pulsed corona respectively,and then absorbed by the alkali in the reactor.The removals of SO2 as well as NO were higher with Ca(OH)2 as the absorbent,compared with using CaCO3 or ZnO.

Factors Influencing the Electron Yield of Needle-Ring Pulsed Corona Discharge Electron Source for Negative Ion Mobility Spectrometer

A simple negative ion mobility spectrometer （IMS） is designed and used to investi- gate the factors that influence the number and efficiency of electrons generated by the needle-ring pulsed corona discharge electron source. Simulation with Ansoft Maxwell 12 is carried out to analyze the electric field distribution within the IMS, and to offer the basis and foundation for analyzing the measurement results. The measurement results of the quantities of electrons show that when the drift electric field strength and the ring inner diameter rise, both the number of ef- fective electrons and the effective electron rate are increased. When the discharge voltage becomes stronger, the number of effective electrons goes up while the effective electron rate goes down. In light of the simulation results, mechanisms underlying the effects of drift electric field strength, ring inner diameter, and discharge voltage on the effective electron number and effective electron rate are discussed. These will make great sense for designing negative ion mode IMS using the needle-ring pulsed corona discharge as the electron source.

Electrical Characteristics of Pulsed Corona Discharge Plasmas in Chitosan Solution

Pulsed discharge plasma has exhibited active potential to prepare low molecular weight chitosan. In the present study, the viscosity of ehitosan solution was decreased noticeably after treated with pulsed corona discharge plasma. An experimental investigation on electrical characteristics of pulsed corona discharge plasma in chitosan solution was conducted with a view toward getting insight into discharge process. Factors affecting I-V curve, single pulse injec- tion energy and pulse width were studied. Experimental results showed positive effect of pulsed peak voltage on discharge plasma in chitosan solution. Pulse-forming capacitor greatly influenced the discharge form, and 4 nF was observed as a suitable value for efficiently generating stable discharge plasmas. As the electrode distance was larger than 10 ram, it had slight impact on dis- charge plasma due to the excellent conductive-property of chitosan solution. The injection energy significantly increased with air flow rate, while the pulse width hardly changed as the air flow rate increased from 0.5 m^3/h to 1.0 m^3/h. This study is expected to provide reference for promoting the application of pulsed corona discharge plasma to ehitosan solution treatment.

Conversion of Methane to Hydrogen via Pulsed Corona Discharge

Experiments are performed to develop a pulsed corona discharge system for the conversion of methane to hydrogen at atmospheric pressure (≈760 Torr) without using a catalyst. The corona discharge was energized by 10-12 μs wide voltage pulses (≤7 kV) at a repetition rate of about 1.0-1.5 kHz. The residual gases were characterized by mass spectrometry. The conversion of methane is as high as 50.8% producing the 70% yield of hydrogen. The influences of argon on the discharge of methane were studied. This result could be useful for the mass production of hydrogen in both academic and industrial point of view.

Decontamination of 2-Chloroethyl Ethyl Sulfide by Pulsed Corona Plasma

Decontamination of 2-chloroethyl ethyl sulfide （2-CEES, CH_3CH_2SCH_2CH_2C1） by pulsed corona plasma was investigated. The results show that 212.6 mg/m^3 of 2-CEES, with the gas flow rate of 2 m^3/h, can be decontaminated to 0.09 mg/m^3. According to the variation of the inlet and outlet concentration of 2-CEES vapor with retention time, it is found that the reaction of 2-CEES in a pulsed corona plasma system follows the first order reaction, with the reaction rate constant of 0.463 s^-1. The decontamination mechanism is discussed based on an analysis of the dissociation energy of chemical bonds and decontamination products. The C-S bond adjacent to the C1 atom will be destroyed firstly to form CH3CH2S. and .CH2CH2C1 radicals. CH3CH2S. can be decomposed to .C_2H_5 and .S..S can be oxidized to SO_2, while .C_2H_5 can be finally oxidized to CO_2 and H_2O. The C-Cl bond in the .CH_2CH_2C1 radical can be destroyed to form .CH_2CH_2. and .C1, which can be mineralized to CO_2, H_2O and HCl. The H atom in the .CH_2CH_2C1 radical can also be substituted by -C1 to form CHCl_2-CHCl_2.

Treatment of Dyeing Wastewater by Using Positive Pulsed Corona Discharge to Water Surface

This study investigated the treatment of textile-dyeing wastewater by using an electrical discharge technique （positive pulsed corona discharge）. The high-voltage electrode was placed above the surface Of the wastewater while the ground electrode was submerged in the wastewater. The electrical discharge starting at the tip of the high voltage electrode propagated toward the surface of the wastewater, producing various oxidative radicals and ozone. Oxygen was used as the working gas instead of air to prevent nitrogen oxides from forming. The simulated wastewater was made up with amaranth, which is a kind of azo dye. The results obtained showed that the chromaticity of the wastewater was almost completely removed within an hour. The ultraviolet/visible spectra of the wastewater treated by the electrical discharge revealed that the total hydrocarbon level also decreased significantly.

The Study of Active Atoms in High-Voltage Pulsed Coronal Discharge by Optical Diagnostics

In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.

Generation of reactive atomic species of positive pulsed corona discharges in wetted atmospheric flows of nitrogen and oxygen

The emission spectra of excited radicals（OH（A^2E）,O（3p^3 P）,Hα（3P）） and emissive species（N2^＋（B^2∑u^＋）,N2（C3Πu）） produced by positive pulsed high-voltage needle-plane corona discharges in atmospheric N2 and O2 flows wetted with 10%H2O at 80 ℃ are used to investigate the relative concentrations of the produced radicals.The results indicate that the tendencies of the concentrations of radicals with discharge conditions are similar to each other due to their similar excitation processes by electron collision.The influence of oxygen flow mixed with the nitrogen flow on the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2S）,N2＋（B^2∑u^＋ → X^2∑g＋0-0）,and N2（C^3Πu → B^3Πg 1-0） is presented.When the flow rate of oxygen addition is varied from 0-30 ml min^-1,the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2s）,and N2^＋（B^2∑u^＋ →X^2∑g 0-0） increase and reach a maximum.Then,if the oxygen flow rate increases further,the emission intensities tend to decrease.However,the intensity of N2（C^3Πu → B^3Πg1-0） decreases monotonously with the increasing oxygen flow,which indicates that the electron density decreases with the increasing oxygen flow.By the tendencies of the relative intensities to N2（C^3Πu → B^3Πg 1-0）,the concentrations of the total produced O,H,and N2^＋ are shown to increase with the oxygen flow.Based on the reactions for the production of H and O without and with the addition of O2,the analytic solutions for H and O production are derived in accordance with the experimental results.

The characteristics of negative corona discharge and radio interference at different altitudes based on coaxial wire-cylinder gap

The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.

Experimental study of NO_2 reduction in N_2/Ar and O_2/Ar mixtures by pulsed corona discharge

Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density （SED）, and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar 〉 Ar 〉 02/Ar. The highest energy yield of 3.31 g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals.

Investigations on removal of SO_2 from flue gas by aerosol formation in pulsed corona discharge process

The removal of SO 2 from flue gas by pulsed corona discharge in presence of ammonia was experimentally investigated. The results showed that the SO 2 removal mainly depends on thermal reaction of SO 2 with NH 3 and enhancements of 0%—25% by pulsed corona discharge in the range of the specific energy 0—5 Wh/Nm 3. The aerosol mass concentration, mainly composed of ammonium sulfate, increased with specific energy dissipated into the reactor. With an initial concentration of 2000—2100 ppmv SO 2 and energy consumption of 3 Wh/Nm 3, when a stoichiometric amount of ammonia is injected, the removal efficiency of SO 2 and percentage of ammonium sulfates in reaction products are all ≥80%. The collection efficiency of the reactor for aerosol is about 74% at a flue gas temperature of 60 to 65℃ and a water vapor content of 9% to 11% volume.

Study on the Methane Coupling under Pulse Corona Plasma by Using CO_2 as Oxidant

In this paper, the conversion of CO2/CH4 by using pulse corona plasma was studied at atmospheric pressure and ambient temperature. The effects of ratio of CO2/CH4, pulse voltage and repeated frequency of plasma discharge were first studied in the system.

The Experimental Investigations of Dielectric Barrier Discharge and Pulse Corona Discharge in Air Cleaning

The dielectric barrier discharge (DBD) and pulse corona discharge(PCD) plasma generator was used to remove NH3, H2S, C7H8 etc. from atmosphere. The principle and characteristic of the two ways was discussed in the article. The test shows the result of PCD is better than that of DBD.

A novel simulation method for positive corona current pulses

A novel two-dimensional （2D） simulation method of positive corona current pulses is proposed. A control-volume- based finite element method （CV-FEM） is used to solve continuity equations, and the Galerkin finite element method （FEM） is used to solve Poisson＇s equation. In the proposed method, photoionization is considered by adopting an exact Helmholtz photoionization model. Furthermore, fully implicit discretization and variable time step are used to ensure the time-efficiency of the present method. Finally, the method is applied to a positive rod-plane corona problem. The numerical results are in agreement with the experimental results, and the validity of the proposed method is verified.

Comparative Analysis of Experiment Treating Benzene and CEES by Pulse Corona Plasma

Based on an experiment treating benzene and 2-chloroethyl ethyl sulfide （CEES） by pulse corona induced-plasma, the simiarities and differences found in the experimental data and analytical results are analyzed in a comparative manner in this paper. The theory applied is also discussed.

Two-Phase Flow Regimes and Discharge Characteristics of a Plasma Electrohydrodynamic Atomization

Experimental investigation was conducted to study the flow regimes and discharge characteristics of plasma electrohydrodynamic atomization （EHDA） for decane （CloH22） under pulsed applied negative voltage. The experimental parameters were set as the flow rate of decane from 0 mL/min to 10 mL/min and the DC charging voltage from DC 0 V to 12 V with a pulse repetition rates of 200 Hz. The flow regime of decane was observed and the volume-to-electrical charge ratio was measured. Unlike a conventional EHDA system, the results show that a corona discharge was initiated at the edge of the hollow electrode at a specific corona on-set voltage of -17 kV or -20 kV in the case with or without decane flow, respectively. This phenomenon was defined as plasma EHDA.

Experimental study on toluene removal by a two-stage plasma-biofilter system

Volatile organic compounds(VOCs) are typical pollutants that affect air quality.Discharge plasma is thought to be a potential method that can remove VOCs from flue gas.In this experiment,pulsed corona discharge plasma combined with a biological tower was carried out to remove the benzene series,and toluene was selected as the typical VOC.The results indicated that the removal efficiency of toluene by pulsed corona plasma was slightly higher than that of direct current(DC) corona plasma,while its energy efficiency was much higher than DC corona plasma.Under the optimal experimental conditions of pulse voltage 8.5 kV,initial toluene concentration 1400 mg m^(-3),and toluene flow rate of 121h^(-1),the toluene removal efficiency reached 77.11% by the single method of pulsed corona discharge plasma,and the energy efficiency was up to 1.515 g/(kW·h) under the pulse voltage of 4.0 kV.The trickling biofilter was constructed by using the screened and domesticated Acinetobacter baumannii,and the highest toluene removal efficiency by the pulsed corona discharge plasma combined with the trickling biofilter rose up to 97.84%.Part of the toluene was degraded into CO_(2),H_(2)O,and some intermediate products such as o-diphenol under the influence of Acinetobacter baumannii.When the remaining waste gas passed through the discharge plasma reactor,the benzene ring structure could be directly destroyed by the collision between toluene and plasma.Meanwhile,O·,OH·,and some other oxidizing radicals generated by the discharge also join into the oxidative decomposition of toluene and its intermediate products,thereby further improving the removal efficiency of toluene.Therefore,the two-stage plasma-biofilter system not only showed a high toluene removal efficiency,but also had a good energy efficiency.The results of this study will provide theoretical support and technical reference for industrial VOC treatment.

Methane Coupling Using Hydrogen Plasma and Pt/γ-Al_2O_3 Catalyst

In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/g-Al2O3 catalyst. Experimental results showed that Pt/g-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.

Decomposition of dimethyl sulfide in a wire-cylinder pulse corona reactor

Decomposition of dimethyl sulfide (DMS) in air was investigated experimentally by using a wire-cylinder dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure.A new type of high pulse voltage source with a thyratron switch and a Blumlein pulse-forming network (BPFN) was adopted in our experiments.The maximum power output of the pulse voltage source and the maximum peak voltage were 1kW and 100kV,respectively.The important parameters affecting odor decomposition,including peak voltage,pulse frequency,gas flow rate,initial concentration,and humidity,which influenced the removal efficiency,were investigated.The results showed that DMS could be treated effectively and almost a 100% removal efficiency was achieved at the conditions with an initial concentration of 832mg/m3 and a gas flow rate of 1000ml/min.Humidity boosts the removal efficiency and improves the energy yield (EY) greatly.The EY of 832mg/m3 DMS was 2.87mg/kJ when the relative humidity was above 30%.In the case of DMS removal,the ozone and nitrogen oxides were observed in the exhaust gas.The carbon and sulfur elements of DMS were mainly converted to carbon dioxide,carbon monoxide and sulfur dioxide.Moreover,sulfur was discovered in the reactor.According to the results,the optimization design for the reactor and the matching of high pulse voltage source can be reckoned.