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.

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.

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.

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 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.

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.

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.

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.