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Plasma Sci. Technol.  
  Plasma Sci. Technol.--2017, 19 (6)   Published: 02 May 2017
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Special Issue on Selected Papers from the HVDP 2016

Special issue on selected papers from HVDP 2016

Zhi FANG (方志) and Cheng CHENG (程诚)
Plasma Sci. Technol. 2017, 19 (6): 060101 ;  doi: 10.1088/2058-6272/aa6a29
Full Text: PDF (109KB) ( 558 )
Show Abstract ( 165 )

This special issue contains selected papers from the 2016 National Conference on
High Voltage and Discharge Plasmas (HVDP), which was hosted by the Plasmas
and their Applications Committee, China Electrotechnical Society, and held in
Beijing, China, on 26 and 27 November 2016. The conference was attended by
over 430 delegates from 110 universities, research institutes and enterprises. In
total, 280 abstracts and 132 full papers have been submitted, giving a wonderful
assembly of technical contributions from around China.
Discharge plasmas have attracted increasing interest from both fundamental
and applied points of view, because of the unique advantages and promising
applications in fields such as energy, environment, materials, medicine etc.
Significant advances in the related fundamentals and applications of discharge
plasmas including theory, modeling and simulation, measurement and diagnostic
techniques, plasma sources and applications have progressed concurrently during
the past two decades. Discharge plasmas and applications have become increasingly
interdisciplinary fields closely related to plasma physics and chemistry,
pulsed power technology and high voltage insulation. It has been noticed that
these related topics are a rapidly evolving field, which is a point of focus in many
international conferences. The HVDP conference was first held in 2016, and will
be held biennially (in even-numbered years). The primary purpose of the HVDP
conference was to provide a platform for the discussion, interchange, and presentation
of research on discharge plasma and applications. Besides this, the
conference sought to promote the interaction between discharge plasma
researchers and facilitate interactions between the fields of discharge plasmas and
the other related interdisciplinary research areas.
Seventeen papers from the 2016 HVDP conference appear in this special issue
covering the topics of generation, diagnostics, and various applications of
discharge plasmas. The objective of this special issue is to bring the most up-todate
developments reported at the HVDP conference to the readership of Plasma
Science and Technology (PST). Contributions cover a variety of discharge plasma
technologies and include papers discussing various experimental diagnostics for
discharge plasma and related pulsed power technologies. We have also included
several papers on the applications of discharge plasmas to VOC and water
purification/treatment, and plasma treatment for coating and surface modifications.
The quality of the research in this area can easily be seen in this special
issue, and we hope it will help to advance our knowledge of discharge plasma and
cultivate future scientific collaboration among those who participated in the
HVDP conference.
As Guest Editors, we would like to thank all the authors for their excellent
papers in this special issue. We also thank the anonymous referees for their time
spent in providing careful and thoughtful comments on the manuscripts. The guest
editors would like to thank the PST journal and Editor, Dr Ping Xu, for his support
and help with details pertaining to the preparation of this special issue. Special
thanks go to the conference chairman of HVDP, Professor Tao Shao, Institute ofElectrical Engineering Chinese Academy of Sciences, for his hard work in making
the HVDP conference a success and his interactions with the Editor and Guest
Editors. We hope this special issue will encourage the publication of similarly
high-quality papers from future HVDP conferences. We look forward to the
continued success of the next HVDP conference!

The influence of grounded electrode positions on the evolution and characteristics of an atmospheric pressure argon plasma jet Hot!

Bo ZHANG (张波), Ying ZHU (朱颖), Feng LIU (刘峰) and Zhi FANG (方志)
Plasma Sci. Technol. 2017, 19 (6): 064001 ;  doi: 10.1088/2058-6272/aa629f
Full Text: PDF (2318KB) ( 730 )
Show Abstract ( 223 )

An atmospheric pressure plasma jet (APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ. Electrical and optical methods are used to characterize the plasma properties. The discharge modes of the APPJ with respect to applied voltage are studied for grounded electrode positions of 10 mm, 40 mm and 80 mm, respectively, and the main discharge and plasma parameters are investigated. It is shown that an increase in the distance between the grounded electrode and high-voltage electrode results in a change in the discharge modes and discharge parameters. The discharges transit from having two discharge modes, dielectric barrier discharge (DBD) and jet, to having three, corona, DBD and jet, with increase in the distance from the grounded to the high-voltage electrodes. The maximum length of the APPJ reaches 3.8 cm at an applied voltage of 8 kV. The discharge power and transferred charges and spectral line intensities for species in the APPJ are influenced by the positions of the grounded electrode, while there is no obvious difference in the values of the electron excited temperature (EET) for the three grounded electrode positions.

Impedance matching for repetitive high voltage all-solid-state Marx generator and excimer DBD UV sources

Yonggang WANG (王永刚), Liqing TONG (童立青) and Kefu LIU (刘克富)
Plasma Sci. Technol. 2017, 19 (6): 064002 ;  doi: 10.1088/2058-6272/aa6153
Full Text: PDF (3043KB) ( 514 )
Show Abstract ( 157 )

The purpose of impedance matching for a Marx generator and DBD lamp is to limit the output current of the Marx generator, provide a large discharge current at ignition, and obtain fast voltage rising falling edges and large overshoot. In this paper, different impedance matching circuits (series inductor, parallel capacitor, and series inductor combined with parallel capacitor) are analyzed. It demonstrates that a series inductor could limit the Marx current. However, the discharge current is also limited. A parallel capacitor could provide a large discharge current, but the Marx current is also enlarged. A series inductor combined with a parallel capacitor takes full advantage of the inductor and capacitor, and avoids their shortcomings. Therefore, it is a good solution. Experimental results match the theoretical analysis well and show that both the series inductor and parallel capacitor improve the performance of the system. However, the series inductor combined with the parallel capacitor has the best performance. Compared with driving the DBD lamp with a Marx generator directly, an increase of 97.3% in radiant power and an increase of 59.3% in system efficiency are achieved using this matching circuit.

Influence of the axial magnetic field on sheath development after current zero in a vacuum circuit breaker

Yi CHEN (陈毅), Fei YANG (杨飞), Hao SUN (孙昊), Yi WU (吴翊),Chunping NIU (纽春萍) and Mingzhe RONG (荣命哲)
Plasma Sci. Technol. 2017, 19 (6): 064003 ;  doi: 10.1088/2058-6272/aa65c8
Full Text: PDF (652KB) ( 677 )
Show Abstract ( 162 )

After current zero, which is the moment when the vacuum circuit breaker interrupts a vacuum arc, sheath development is the first process in the dielectric recovery process. An axial magnetic field (AMF) is widely used in the vacuum circuit breaker when the high-current vacuum arc is interrupted. Therefore, it is very important to study the influence of different AMF amplitudes on the sheath development. The objective of this paper is to study the influence of different AMF amplitudes on the sheath development from a micro perspective. Thus, the particle in cell-Monte Carlo collisions (PIC-MCC) method was adopted to develop the sheath development model. We compared the simulation results with the experimental results and then validated the simulation.We also obtained the speed of the sheath development and the energy density of the ions under different AMF amplitudes. The results showed that the larger the AMF amplitudes are, the faster the sheath develops and the lower the ion energy density is, meaning the breakdown is correspondingly more difficult.

Influence of electrical parameters on H2O2 generation in DBD non-thermal reactor with water mist

Di XU (徐迪), Zehua XIAO (肖泽铧), Chunjing HAO (郝春静), Jian QIU (邱剑) and Kefu LIU (刘克富)
Plasma Sci. Technol. 2017, 19 (6): 064004 ;  doi: 10.1088/2058-6272/aa61f6
Full Text: PDF (1815KB) ( 636 )
Show Abstract ( 205 )

A dielectric barrier discharge (DBD) reactor is introduced to generate H2O2 by non-thermal plasma with a mixture of oxygen and water mist produced by an ultrasonic atomizer. The results of our experiment show that the energy yield and concentration of the generated H2O2 in the pulsed discharge are much higher than that in AC discharge, due to its high energy efficiency and low heating effect. Micron-sized liquid droplets produced by an ultrasonic atomizer in water mist have large specific surface area, which greatly reduces mass transfer resistance between hydroxyl radicals and water liquids, leading to higher energy yield and H2O2 concentration than in our previous research. The influence of applied voltage, discharge frequency, and environmental temperature on the generated H2O2 is discussed in detail from the viewpoint of the DBD mechanism. The H2O2 concentration of 30 mg l−1, with the energy yield of 2 g kW−1h−1 is obtained by pulsed discharge in our research.

Comparative research of plasma-assisted milling and traditional milling in synthesizing AlN

Sen WANG (王森), Wenchun WANG (王文春), Zhijie LIU (刘志杰) and Dezheng YANG (杨德正)
Plasma Sci. Technol. 2017, 19 (6): 064005 ;  doi: 10.1088/2058-6272/aa62f8
Full Text: PDF (2197KB) ( 660 )
Show Abstract ( 143 )

In this paper, traditional milling and discharge plasma-assisted milling are employed to synthesize aluminum nitride (AlN) powder at nanometer scale by milling the mixture of aluminum and lithium hydroxide monohydrate. AlN powders can be generated in traditional milling and plasma-assisted milling in an hour milling time. Differential thermal analysis curves show that the reaction temperature of the powders treated by plasma-assisted milling is lower than that of traditional milling. These results indicate that plasma-assisted milling has higher efficiency in the synthesis of AlN, getting smaller crystallite size and activating powder. Moreover, an optical emission spectrum is employed to demonstrate the active species in plasma. The different formation process of AlN in the two-milling process, and the promotion effects of plasma in the milling process are discussed.

Spatiotemporal characteristics of nanosecond pulsed discharge in an extremely asymmetric electric field at atmospheric pressure

Li ZHANG (张丽), Dezheng YANG (杨德正), Sen WANG (王森) and Wenchun WANG (王文春)
Plasma Sci. Technol. 2017, 19 (6): 064006 ;  doi: 10.1088/2058-6272/aa632d
Full Text: PDF (2616KB) ( 772 )
Show Abstract ( 165 )

In this paper, high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration. Temporal-spatial distributions of discharge images, the emission intensities of optical emission spectra, and plasma vibrational and rotational temperatures are investigated. By analyzing the evolution of vibrational and rotational temperatures in space and time dimensions, the energy distribution and energy transfer process in plasma are also discussed. It is found that a diffuse structure with high density plasma concentrated in the region near the needle tip can be presented in nanosecond pulsed discharge, and an obvious energy transfer from electronic energy to vibration energy can be observed in each discharge pulse.

Electrical characters and optical emission spectra of VBD coupled SBD excited by sine AC voltage in atmospheric air

Zilu ZHAO (赵紫璐), Dezheng YANG (杨德正), Wenchun WANG (王文春), Hao YUAN (袁皓), Li ZHANG (张丽) and Sen WANG (王森)
Plasma Sci. Technol. 2017, 19 (6): 064007 ;  doi: 10.1088/2058-6272/aa6679
Full Text: PDF (1596KB) ( 649 )
Show Abstract ( 156 )

In this paper, volume coupled surface barrier discharge (V-SBD) with three structures possessing different volumes is excited by sine AC power in atmospheric air. Discharge images, waveforms of applied voltage and discharge current, and optical emission spectra simulating rotational and vibrational temperatures are recorded and analyzed. The effects of applied voltage on emission intensities of N2 (C3Πu→B3Πg) and N2+ (B2Σ +u →X2Σ +g ), and rotational and vibrational temperatures are investigated. The results show that as applied voltage rises, emission intensities and rotational temperatures increase while vibrational temperatures decrease. In addition it is found that, as applied voltage varies, the rotational temperature of surface discharge changes faster than that of volume discharge.

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

Feng LIU (刘峰)1, Bo ZHANG (张波)1, Zhi FANG (方志)1,4 and Wenchun WANG (王文春)2,3
Plasma Sci. Technol. 2017, 19 (6): 064008 ;  doi: 10.1088/2058-6272/aa632f
Full Text: PDF (854KB) ( 574 )
Show Abstract ( 134 )

The emission spectra of excited radicals (OH (A2Σ), O (3p5 P), Hα (3P)) and emissive species (N2+(B2 Σu+) N2 (C3Πu)) produced by positive pulsed high-voltage needle-plane corona discharges in atmospheric N2 and O2 flows wetted with 10% H2O at 80 °C 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 (3p5P→3s5 S20), Hα (3P→2S), N2+ (B2 Σu+→X2 Σg+0-0), and N2 (C3Πu→B3Πg 1-0) is presented. When the flow rate of oxygen addition is varied from 0–30 ml min−1, the emission intensities of O (3p5P→3s5S20), Hα (3P→2s), and N2+(B2 Σ u+→X2Σ+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 (C3Πu→B3Πg1-0) 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 (C3Πu→B3Πg 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.

High concentration xylene decomposition and diagnostic analysis by non-thermal plasma in a DBD reactor

Zehua XIAO (肖泽铧), Di XU (徐迪), Chunjing HAO (郝春静), Jian QIU (邱剑) and Kefu LIU (刘克富)
Plasma Sci. Technol. 2017, 19 (6): 064009 ;  doi: 10.1088/2058-6272/aa632c
Full Text: PDF (804KB) ( 655 )
Show Abstract ( 168 )

Dielectric barrier discharge (DBD) is utilized to decompose xylene vapor in mobile gas under normal atmospheric pressure. The plasma is generated by an AC power source with a frequency of 6 kHz. In the experiment, the discharge power on the DBD reactor was calculated by a Lissajous figure, and the specific input energy (SIE) of different discharge voltage or residence time was obtained. The concentrations of xylene, carbon monoxide and carbon dioxide in the gas were analyzed by gas chromatography. The spectra of DBD were diagnosed using a spectrometer. We calculated the conversion rate (CR), mineralization rate (MR) and carbon dioxide selectivity. The relationship between these quantities and the SIE was analyzed. The experimental results show that high concentration xylene can be decomposed mostly by DBD plasma. The CR can reach as high as 90% with the main product of carbon dioxide.

Parametric study on the characteristics of a SDBD actuator with a serrated electrode

Guoqiang GAO (高国强), Kaisheng PENG (彭开晟), Lei DONG (董磊), Wenfu WEI (魏文赋)1 and Guangning WU (吴广宁)
Plasma Sci. Technol. 2017, 19 (6): 064010 ;  doi: 10.1088/2058-6272/aa5b39
Full Text: PDF (2115KB) ( 685 )
Show Abstract ( 173 )

Active flow control based on surface dielectric barrier discharge (SDBD) has become a focus of research in recent years, due to its unique advantages and diverse potential applications. Compared with the conventional SDBD with straight electrodes, the serrated electrode-based SDBD has a great advantage due to its 3D flow topology. It is believed that the boundary layer separation of moving objects can be controlled more effectively with this new type of SDBD. In SDBD with a serrated electrode, the R (tip sharpness) and N (tip number per unit length) have a great influence on the discharge and induced airflow characteristics. In this paper, a parametric study of the characteristics of SDBD with a serrated electrode has been conducted with different ranges of R and N. Aspects of the power consumption, the steady medium temperature distribution, and the maximum induced airflow velocity have been investigated. The results indicate that there is a critical value of R and N where the maximum power consumption and induced airflow velocity are achieved. The uniformity of the steady temperature distribution of the medium surface is found to be more dependent on N. We found that the accelerating effects of the induced airflow can be evaluated with the Schlieren technique, which agree well with the results from the pitot tube.

Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear

Yuanji CAI (蔡元纪), Yonggang GUAN (关永刚)1 and Weidong LIU (刘卫东)
Plasma Sci. Technol. 2017, 19 (6): 064011 ;  doi: 10.1088/2058-6272/aa65c7
Full Text: PDF (1945KB) ( 667 )
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Transient enclosure voltage (TEV), which is a phenomenon induced by the inner dielectric breakdown of SF6 during disconnector operations in a gas-insulated switchgear (GIS), may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage (UHV)substations. In this paper, the statistical characteristics of TEV at UHV level are collected from field experiments, and are analyzed and compared to those from a repeated strike process. The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first. Then, statistical characteristics, such as the pulse number, duration of pulses,frequency components, magnitude and single pulse duration, are extracted. The transmission line theory is introduced to analyze the TEV and is validated by the experimental results. Finally,the relationship between the TEV and the repeated strike process is analyzed. This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage. The results contribute to the definition of the standard testing waveform of the TEV, and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

Thermal radiation properties of PTFE plasma

Xiangyang LIU (刘向阳), Siyu WANG (王司宇), Yang ZHOU (周阳), Zhiwen WU (武志文), Kan XIE (谢侃) and Ningfei WANG (王宁飞)
Plasma Sci. Technol. 2017, 19 (6): 064012 ;  doi: 10.1088/2058-6272/aa65e8
Full Text: PDF (1659KB) ( 548 )
Show Abstract ( 165 )

To illuminate the thermal transfer mechanism of devices adopting polytetrafluoroethylene (PTFE) as ablation materials, the thermal radiation properties of PTFE plasma are calculated and discussed based on local thermodynamic equilibrium (LTE) and optical thin assumptions. It is clarified that line radiation is the dominant mechanism of PTFE plasma. The emission coefficient shows an opposite trend for both wavelength regions divided by 550 nm at a temperature above 15 000 K. The emission coefficient increases with increasing temperature and pressure.Furthermore, it has a good log linear relation with pressure. Equivalent emissivity varies complexly with temperature, and has a critical point between 20 000 K to 25 000 K. The equivalent cross points of the average ionic valence and radiation property are about 10 000 K and 15 000 K for fully single ionization.

Investigation of NO removal using a pulseassisted RF discharge

Qi WANG (王奇)1, Yanhui WANG (王艳辉)1, Haochen WANG (王灏宸)2, Zhanhui WANG (王占辉)3 and Hongbin DING (丁洪斌)1
Plasma Sci. Technol. 2017, 19 (6): 064013 ;  doi: 10.1088/2058-6272/aa607b
Full Text: PDF (1626KB) ( 533 )
Show Abstract ( 173 )

In this paper, removal of nitrogen oxide (NO) is investigated in capacitive atmospheric pressure discharges driven by both radio-frequency (RF) and trapezoidal pulsed power with a onedimensional self-consistent fluid model. The results show that the number density of NO could be reduced significantly once a short pulse of low duty ratio is additionally applied to the RF power. It is found that the process of NO removal by the pulse-modulated RF discharge could be divided into three stages: the quick reaction stage, the NO removal stage, and the sustaining stage. Furthermore, the temporal evolution of particle densities is analyzed, and the key reactions in each stage are discovered. Finally, the influence on the removal efficiency of the voltage amplitude of the pulse and the RF voltage amplitude is investigated.

Research of a fractional-turn ratio saturable pulse transformer and its application in a microsecond-range pulse modulator

Rong CHEN (陈绒), Jianhua YANG (杨建华), Xinbing CHENG (程新兵)1 and Zilong PAN (潘子龙)
Plasma Sci. Technol. 2017, 19 (6): 064014 ;  doi: 10.1088/2058-6272/aa6155
Full Text: PDF (2126KB) ( 620 )
Show Abstract ( 157 )

As a combination device for a step-up pulse transformer and a magnetic switch, the saturable pulse transformer is widely used in pulsed-power and plasma technology. A fractional-turn ratio saturable pulse transformer is constructed and analyzed in this paper. Preliminary experimental results show that if the primary energy storage capacitors are charged to 300 V, an output voltage of about 19 kV can be obtained across the capacitor connected to the secondary windings of a fractional-turn ratio saturable pulse transformer. Theoretical and experimental results reveal that this kind of pulse transformer is not only able to integrate a step-up transformer and a magnetic switch into one device, but can also lower the saturable inductance of its secondary windings, thus leading to the relatively high step-up ratio of the pulse transformer. Meanwhile, the application of the fractional-turn ratio saturable pulse transformer in a μs range pulse modulator as a voltage step-up device and main switch is also included in this paper. The demonstrated experiments display that an output voltage with an amplitude of about 29 kV, and a 1.6 μs pulse width can be obtained across a 3500 Ω resistive load, based on a pulse modulator, if the primary energy storage capacitors are charged to 300 V. This compact fractional-turn ratio saturable pulse transformer can be applied in many other fields such as surface treatment, corona plasma generation and dielectric barrier discharge.

Effect of pulse voltage rising time on discharge characteristics of a helium–air plasma at atmospheric pressure

Muyang QIAN (钱沐杨)1, Gui LI (李桂)1, Sanqiu LIU (刘三秋)1, Yu ZHANG (张羽)1, Shan LI (李杉)1, Zebin LIN (林泽斌)1 and Dezhen WANG (王德真)2
Plasma Sci. Technol. 2017, 19 (6): 064015 ;  doi: 10.1088/2058-6272/aa6154
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In this paper, the influence of voltage rising time on a pulsed-dc helium–air plasma at atmospheric pressure is numerically simulated. Simulation results show that as the voltage rising time increases from 10 ns to 30 ns, there is a decrease in the discharge current, namely 0.052 A when the voltage rising time is 10 ns and 0.038 A when the voltage rising time is 30 ns. Additionally, a shorter voltage rising time results in a faster breakdown, a more rapidly rising current waveform, and a higher breakdown voltage. Furthermore, the basic parameters of the streamer discharge also increase with voltage rise rate, which is ascribed to the fact that more energetic electrons are produced in a shorter voltage rising time. Therefore, a pulsed-dc voltage with a short rising time is desirable for efficient production of nonequilibrium atmospheric pressure plasma discharge.

Experimental study of rotating wind turbine breakdown characteristics in large scale air gaps

Yu WANG (王羽), Lu QU (屈路), Tianjun SI (姒天军), Yang NI (倪阳), Jianwei XU (徐建伟) and Xishan WEN (文习山)
Plasma Sci. Technol. 2017, 19 (6): 064016 ;  doi: 10.1088/2058-6272/aa6743
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When a wind turbine is struck by lightning, its blades are usually rotating. The effect of blade rotation on a turbine’s ability to trigger a lightning strike is unclear. Therefore, an arching electrode was used in a wind turbine lightning discharge test to investigate the difference in lightning triggering ability when blades are rotating and stationary. A negative polarity switching waveform of 250/2500 μs was applied to the arching electrode and the up-and-down method was used to calculate the 50% discharge voltage. Lightning discharge tests of a 1:30 scale wind turbine model with 2, 4, and 6 m air gaps were performed and the discharge process was observed. The experimental results demonstrated that when a 2 m air gap was used, the breakdown voltage increased as the blade speed was increased, but when the gap length was 4 m or longer, the trend was reversed and the breakdown voltage decreased. The analysis revealed that the rotation of the blades changes the charge distribution in the blade-tip region, promotes upward leader development on the blade tip, and decreases the breakdown voltage. Thus, the blade rotation of a wind turbine increases its ability to trigger lightning strikes.

Activation of peroxydisulfate by gas–liquid pulsed discharge plasma to enhance the degradation of p-nitrophenol

Kefeng SHANG (商克峰)1,2, Hao WANG (王浩)1, Jie LI (李杰)1,2, Na LU (鲁娜)1,2, Nan JIANG (姜楠)1,2 and Yan WU (吴彦)1,2
Plasma Sci. Technol. 2017, 19 (6): 064017 ;  doi: 10.1088/2058-6272/aa6616
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Pulsed discharge in water and over water surfaces generates ultraviolet radiation, local high temperature, shock waves, and chemical reactive species, including hydroxyl radicals, hydrogen peroxide, and ozone. Pulsed discharge plasma (PDP) can oxidize and mineralize pollutants very efficiently, but high energy consumption restricts its application for industrial wastewater treatment. A novel method for improving the energy efficiency of wastewater treatment by PDP was proposed, in which peroxydisulfate (PDS) was added to wastewater and PDS was activated by PDP to produce more strong oxidizing radicals, including sulfate radicals and hydroxyl radicals, leading to a higher oxidation capacity for the PDP system. The experimental results show that the increase in solution conductivity slightly decreased the discharge power of the pulse discharge over the water surface. An increase in the discharge intensity improved the activation of PDS and therefore the degradation efficiency and energy efficiency of p-nitrophenol (PNP). An increase in the addition dosage of PDS greatly facilitated the degradation of PNP at a molar ratio of PDS to PNP of lower than 80:1, but the performance enhancement was no longer obvious at a dosage of more than 80:1. Under an applied voltage of 20 kV and a gas discharge gap of 2 mm, the degradation efficiency and energy efficiency of the PNP reached 90.7% and 45.0 mg kWh−1 for the plasma/PDS system, respectively, which was 34% and 18.0 mg kWh−1 higher than for the discharge plasma treatment alone. Analysis of the physical and chemical effects indicated that ozone and hydrogen peroxide were important for PNP degradation and UV irradiation and heat from the discharge plasma might be the main physical effects for the activation of PDS.

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