Yan Wu

Dalian University of Technology, Lü-ta-shih, Liaoning, China

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Publications (74)129.32 Total impact

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    ABSTRACT: The discharge uniformity and area of surface dielectric barrier discharge (DBD) has recently attracted lots of attention. In this study, morphological images of surface DBD are acquired by an intensified charge-couples device (ICCD) camera from the top view of the exposed electrode. Spatial and transient characteristics of plasma have been visualized with the gate width of 5 μs and 120 μs The discharge uniformity and discharge area are respectively estimated by calculating the number of pixels and the full width at half maximum (FWHM) of gray frequency by MATLAB software with microsecond time scale. The results offer a new estimated method for the characteristics of homogenous discharge. The formation of diffuse plasma mainly depends on an increase of the ionization coefficient and a creation of sufficient seed electrons by the Penning Effect at low electric fields. Accordingly, experimental measurements show that the diffuse discharge with a larger area behaves a good uniformity and stability comparing with the filamentary discharge. Applied frequency is not capable of exerting significant influence on the discharge uniformity and area. By adding noble gases into N2, the diffuse discharge is more likely to form. And the diffuse discharge also can be stabilized by the helium flow with gas velocity of 0.6-0.8 cm/s.
    No preview · Article · Jan 2016 · Vacuum
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    ABSTRACT: Pulsed electric discharge over water surface/in water has been used to generate reactive species for decomposing the organic compounds in water, and hydrogen peroxide (H2O2) is one of the strong reactive species which can be decomposed into another stronger oxidative species, hydroxyl radical. The production efficacy of H2O2 by a gas phase pulsed discharge over water surface and an underwater bubbling pulsed discharge was evaluated through diagnosis of H2O2 by a chemical probe method. The experimental results show that the yield and the production rate of H2O2 increased with the input energy regardless of the electric discharge patterns, and the underwater bubbling pulsed discharge was more advantageous for H2O2 production considering both the yield and the production rate of H2O2. Results also indicate that the electric discharge patterns also influenced the water solution properties including the conductivity, the pH value and the water temperature.
    No preview · Article · Jan 2016 · Japanese Journal of Applied Physics
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    ABSTRACT: The purpose of this paper is to develop a high-efficiency air-cleaning system for volatile organic compounds (VOCs) existing in the workshop of a chemical factory. A novel parallel surface/packed-bed discharge (PSPBD) reactor, which utilized a combination of surface discharge (SD) plasma with packed-bed discharge (PBD) plasma, was designed and employed for VOCs removal in a closed vessel. In order to optimize the structure of the PSPBD reactor, the discharge characteristic, benzene removal efficiency, and energy yield were compared for different discharge lengths, quartz tube diameters, shapes of external high-voltage electrode, packed-bed discharge gaps, and packing pellet sizes, respectively. In the circulation test, 52.8% of benzene was removed and the energy yield achieved 0.79 mg kJ−1 after a 210 min discharge treatment in the PSPBD reactor, which was 10.3% and 0.18 mg kJ−1 higher, respectively, than in the SD reactor, 21.8% and 0.34 mg kJ−1 higher, respectively, than in the PBD reactor at 53 J l−1. The improved performance in benzene removal and energy yield can be attributed to the plasma chemistry effect of the sequential processing in the PSPBD reactor. The VOCs mineralization and organic intermediates generated during discharge treatment were followed by COx selectivity and FT-IR analyses. The experimental results indicate that the PSPBD plasma process is an effective and energy-efficient approach for VOCs removal in an indoor environment.
    No preview · Article · Oct 2015 · Journal of Physics D Applied Physics
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    ABSTRACT: Removal of polycyclic aromatic hydrocarbon (PAH) in soil by pulsed corona discharge plasma with γ-Al2O3-supported catalysts was studied at normal temperature and atmospheric pressure. Phenanthrene (Phe) was used as the model pollutant. Spontaneous CuO/γ-Al2O3, MnO2/γ-Al2O3, Fe2O3/γ-Al2O3 or TiO2/γ-Al2O3 was added into plasma system. Phe removal, energy efficiency and catalytic property were investigated. The results showed that prepared γ-Al2O3-supported catalysts all exhibited catalytic effects on Phe removal from soil. Removal efficiencies of Phe were improved by 14.1%, 21.4%, 16.5% and 9.1% in 40 min at 5 wt% amount of CuO/γ-Al2O3, MnO2/γ-Al2O3, Fe2O3/γ-Al2O3 and TiO2/γ-Al2O3, respectively. The energy efficiency increased when pulsed corona discharge plasma was combined with catalysts. As each catalyst dosage was increased from 5 wt% to 23 wt%, the energy efficiency of the reactor with discharge alone was further increased by approximately 20%–40%. Furthermore, the catalysts kept stable activity in Phe removal after five times reuse cycle. Effect of pulsed corona discharge plasma on physicochemical properties of catalysts were evaluated through XRD and BET characterization. This study implied a promising combined-application of γ-Al2O3-supported catalysts and pulsed corona discharge plasma for the removal of PAH in soil.
    No preview · Article · Oct 2015 · Separation and Purification Technology
  • Lijuan Duan · Jie Li · Kefeng Shang · Lu Na · Yan Wu

    No preview · Article · Sep 2015 · Separation and Purification Technology
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    ABSTRACT: Ozonation of p-nitrophenol adsorbed on activated carbon fiber (ACF) was conducted in a semi-wet atmosphere, and its effect on the textural and chemical characteristics of ACF was examined. The decomposition kinetics of p-nitrophenol followed a pseudo first order reaction, and an increase in inputted O3 enhanced the removal of p-nitrophenol. Ozone slightly etched ACF and resulted in a decrease in the pores volume of ACF, but slightly different changes in pores diameter also occurred on virgin and spent ACF. An increase in the surface oxygen-containing groups (C=O, COOH, etc.) after ozonation might have influence on the adsorption capacity of ACF.
    No preview · Article · Jul 2015 · Ozone Science and Engineering
  • Na Lu · Yingchun Feng · Jie Li · Kefeng Shang · Yan Wu
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    ABSTRACT: The electrical characteristics of pulsed-discharge plasma for decoloration of dyes in water were systematically investigated with a view toward getting insight into discharge process. Methylene blue (MB) dye water was selected as the target object. The discharge behavior was found to depend on the power supply voltage, conductivity of MB solution, and pulse-forming capacity. A strong positive linear relationship existed between power supply voltage and initial capacitor voltage. The injection energy per pulse increased when increasing the power supply voltage and a maximal energy efficiency of injection of approximately 85% was obtained at power supply voltage of 50 V. The conductivity of MB solution had appreciable impact on the voltage-current characteristics and discharge time of pulse-forming capacitor. Remarkable increase of pulse current was observed as the pulse-forming capacity increasing, while it had slight effect on the pulse voltage. The pulsed corona discharge in MB solution could change into spark discharge by way of increasing the air flow rate and reducing the electrode distance. Increasing pulse-forming capacity and pulse frequency significantly accelerated the decoloration rate of MB in solution. This paper is expected to provide reference for improving the application of pulsed-discharge plasma in treating dye solution.
    No preview · Article · Feb 2015 · IEEE Transactions on Plasma Science
  • Na Lu · Jing Lou · Cui Hua Wang · Jie Li · Yan Wu
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    ABSTRACT: The remediation of dye-contaminated soil using silent discharge plasma in dielectric barrier discharge (DBD) reactor was reported in this study. Acid scarlet GR was selected as the representative of azo dye pollutants. Effects of applied voltage, discharge frequency, and gas flow rate on Acid scarlet GR treatment effect which were characterized by degradation efficiency and the change of chemical oxygen demand (COD) during the degradation were investigated. The decolorization rate of Acid scarlet GR in the soil increased with the applied voltage and discharge frequency, and the optimal gas flow rate was obtained at 1.0 L min(-1). The energy efficiency was clearly enhanced by way of increasing the amount of contaminated soil in the DBD reactor finitely. The degradation efficiency of Acid scarlet GR and the removal of COD value were achieved 93% and 74 % after 25-min discharge treatment, respectively. The results indicated that the DBD remediation system was able to degrade Acid scarlet GR in the soil quickly and efficiently. This study is expected to provide a possible pathway of Acid scarlet GR degradation in soil.
    No preview · Article · Jun 2014 · Water Air and Soil Pollution
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    ABSTRACT: The oxidation of elemental mercury (Hg-0) by dielectric barrier discharge reactors was studied at room temperature, where concentric cylinder discharge reactor (CCDR) and surface discharge plasma reactor (SDPR) were employed. The parameters (e.g. Hg-0 oxidation efficiency, energy constant, energy yield, energy consumption, and O-3 concentration) were discussed. From comparison of the two reactors, higher Hg-0 oxidation efficiency and energy constant in the SDPR system were obtained by using lower specific energy density. At the same applied voltage, energy yield in the SDPR system was larger than that in the CCDR system, and energy consumption in the SDPR system was much less. Additionally, more O-3 was generated in the SDPR system. The experimental results showed that 98% of Hg-0 oxidation efficiency, 0.6 J.L-1 of energy constant, 13.7 mu g.kJ(-1) of energy yield, 15.1 eV.molecule(-1) of energy consumption, and 12.7 mu g.J(-1) of O-3 concentration were achieved in the SDPR system. The study reveals an alternative and economical technology for Hg-0 oxidation in the coal-fired flue gas.
    No preview · Article · Jan 2014 · Plasma Science and Technology
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    ABSTRACT: The use of non-thermal plasma (NTP) injection approach to oxidize elemental mercury (Hg(0)) in simulated flue gas at 110°C was studied, where a surface discharge plasma reactor (SDPR) inserted in the simulated flue duct was used to generate and inject active species into the flue gas. Approximately 81% of the Hg(0) was oxidized and 20.5μgkJ(-1) of energy yield was obtained at a rate of 3.9JL(-1). A maximal Hg(0) oxidation efficiency was found with a change in the NTP injection air flow rate. A high Hg(0) oxidation efficiency was observed in the mixed flue gas that included O2, H2O, SO2, NO and HCl. Chemical and physical processes (e.g., ozone, N2 metastable states and UV-light) were found to contribute to Hg(0) oxidation, with ozone playing a dominant role. The deposited mercury species on the internal surface of the flue duct was analyzed using X-ray photoelectron spectroscopy (XPS) and electronic probe microanalysis (EPMA), and the deposit was identified as HgO. The mercury species is thought to primarily exist in the form of HgO(s) by adhering to the suspended aerosols in the gas-phase.
    No preview · Article · Jan 2014 · Journal of hazardous materials
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    ABSTRACT: A surface dielectric barrier discharge plasma reactor was employed to study Hg0 oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg0 oxidation efficiency and 13.7 μg kJ−1 of energy yield were obtained under a specific energy density (SED) of 7.9 J L−1. Increasing SED was beneficial for Hg0 oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg0 oxidation efficiency, but higher amount of Hg0 oxidation. Water vapor inhibited Hg0 oxidation because the generation of O3 was suppressed. The presence of NO remarkably restrained Hg0 oxidation, while SO2 showed little effect on Hg0 oxidation. Roles of active species in Hg0 oxidation were examined under different gas atmospheres (O2 and air), indicating that O3 played an important role in Hg0 oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.
    Preview · Article · Jan 2014 · Plasma Chemistry and Plasma Processing
  • Yi Hong · Jing Pan · Na Lu · Kefeng Shang · Jie Li · Yan Wu
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    ABSTRACT: A low temperature air plasma jet was generated by syringe needle-ring electrodes dielectric barrier discharge at atmospheric pressure. It was found that the air plasma jet length reached about 25 mm and the gas temperature was close to the room temperature. Besides, the optical emission spectrum showed that a large number of active species, such as O* (777.2 nm), O* (794.7 nm), O* (799.5 nm), O* (844.6 nm), N-2* (C-B), N-2* (B-A), N-2(+) (B-X), N* (750.7nm), N* (812.9 nm), etc., existed in the air plasma plume.
    No preview · Article · Dec 2013 · Thin Solid Films
  • Nan Jiang · Na Lu · Kefeng Shang · Jie Li · Yan Wu
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    ABSTRACT: In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants.
    No preview · Article · Sep 2013 · Journal of hazardous materials
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    ABSTRACT: Active species injection generated by a surface discharge plasma reactor (SDPR) was studied to oxidize elemental mercury (Hg0) in the flue gas. The reactor was inserted in the simulated flue duct. The effects of several operational parameters, such as applied voltage, inlet Hg0 concentration, applied frequency and air injection flow rate, were well investigated. Experimental results showed that Hg0 oxidation efficiency of 83.8% was achieved at specific energy density of 4.0 J L-1 and the flow rate of 1.6 L min-1. Increasing applied voltage and air injection flow rate was beneficial for Hg0 oxidation due to higher production of active species. Lower Hg0 oxidation efficiency was observed with an increase of initial concentration. With an increase of applied frequency, Hg0 oxidation efficiency significantly increased, but the energy yield dropped.
    No preview · Article · Sep 2013
  • Yi Hong · Na Lu · Jing Pan · Jie Li · Yan Wu · Ke Feng Shang
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    ABSTRACT: Atmospheric argon plasma jets are generated with the rod-tube/tube high voltage electrode and a ring ground electrode at 8 kHz sinusoidal excitation voltage. It is found that the vibrational temperature, electronic excitation temperature, atomic oxygen density and spectral intensity with the rod-tube high voltage electrode are enhanced significantly than that with the tube high voltage electrode. The atomic oxygen density, molecular nitrogen density, and average electronic density are about magnitude of 1016 cm−3, 1015 cm−3, and 1012 cm−3 respectively, and the excited Ar, N2, OH and O are presented in the plasma plume with the rod-tube/tube high voltage electrode.
    No preview · Article · Apr 2013 · Journal of Electrostatics
  • Yue Li · Kefeng Shang · Na Lu · Jie Li · Yan Wu
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    ABSTRACT: How to deal with unstable ammonium sulfite, the byproduct of flue gas desulfuration by ammonia absorption methods, has been a difficult problem in recent years. Oxidation of ammonium sulfite in aqueous solutions using ozone produced by a surface discharge system was investigated in the paper. The oxidation efficiency of ammonium sulfite by ozone and traditional air aeration were compared, and the factors including ozone concentration, gas flow rate, initial concentration of ammonium sulfite solution and reaction temperature were discussed. The results show that the oxidation efficiency of ammonium sulfite by ozone technology reached nearly 100% under the optimum conditions, which had a significant increase compared with that by air aeration.
    No preview · Article · Mar 2013 · Journal of Physics Conference Series
  • Hua Ren · Na Lu · Kefeng Shang · Jie Li · Yan Wu
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    ABSTRACT: 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.
    No preview · Article · Mar 2013 · Journal of Physics Conference Series
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    ABSTRACT: Soil contamination by organic compounds has become an issue of concern around the world. Currently, non-thermal plasma, especially pulsed corona discharge, has received a great attention in environmental protection field. As a result, the matching between a pulsed-power and corona discharge reactor containing different thickness of soil was a significant aspect in optimizing the pulse corona discharge. In this paper, some methods have been adopted to achieve the matching, including choosing a suitable capacity, adjusting the frequency, providing a suitable soil thickness and comparing the energy and energy utilization efficiency. The details of the matching and optimization discussed were based upon the theories of streamer formation and experimental results as well. The results indicated that energy injected into the reactor increased with the pulse forming capacity and pulse frequency. There existed an optimal energy utilization efficiency with the change of soil thickness and pulse frequency under the pulse forming capacity of 100 pF. The SED at pulse voltage of 19 kV and pulse frequency of 70 Hz was achieved 0.11 J g-1soil at the soil thickness of 3 mm, which was only 0.064 J g-1soil at the soil thickness of 9 mm; meanwhile, with the increase of pulse frequency from 50 Hz to 90 Hz, the SED increased from 0.075 J g-1soil to 0.146 J g-1soil at 19 kV and soil thickness of 3 mm. This study is expected to provide reference for the matching between a pulsed-power and reactor containing different thickness of soil for producing corona discharge.
    No preview · Article · Mar 2013 · Journal of Physics Conference Series
  • Shoufeng Tang · Na Lu · Jie Li · Kefeng Shang · Yan Wu
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    ABSTRACT: A catalytic method using titanium dioxide (TiO2) under a dielectric barrier discharge (DBD) plasma was studied to improve the decomposition of phenol adsorbed on granular activated carbon (GAC) and the simultaneous regeneration of the saturated GAC. The TiO2–GAC hybrid was fabricated by an impregnation-desiccation method and characterised by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherms and Boehm titration to investigate its adsorption and catalytic characteristics before and after the adsorption and DBD processes. The adsorption experiments showed that the GAC and TiO2–GAC both followed pseudo-second-order kinetic models with adsorption isotherms that were well represented by the Langmuir model. TiO2–GAC exhibited remarkable catalytic activity, increasing the phenol degradation by 19% and TOC removal by 8.7% relative to GAC in DBD treatment. TiO2–GAC also exhibited better regeneration efficiency than GAC, and the reusability of the hybrid material was examined over four consecutive adsorption-regeneration cycles. The above results may be due to the enhanced generation of active species, such as hydroxyl radicals and hydrogen peroxide, on TiO2–GAC relative to GAC during the discharge process, and the main intermediate products were analysed to explore the mechanisms involved in DBD plasma.
    No preview · Article · Mar 2013 · Carbon
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    ABSTRACT: A surface Dielectric Barrier Discharge (DBD) reactor was utilized to degrade phenol in water. Different power supplies applied to the DBD reactor affect the discharge modes, the formation of chemically active species and thus the removal efficiency of pollutants. It is thus important to select an optimized power supply for the DBD reactor. In this paper, the influence of the types of power supplies including alternate current (AC) and bipolar pulsed power supply on the ozone generation in a surface discharge reactor was measured. It was found that compared with bipolar pulsed power supply, higher energy efficiency of O3 generation was obtained when DBD reactor was supplied with 50Hz AC power supply. The highest O3 generation was approximate 4 mg kJ-1 moreover, COD removal efficiency of phenol wastewater reached 52.3% after 3 h treatment under an AC peak voltage of 2.6 kV.
    No preview · Article · Mar 2013 · Journal of Physics Conference Series