电极结构对多孔陶瓷孔内微放电特性及苯降解的影响

Effect of Electrode Configuration on Microdischarge Characteristics in Porous Ceramics and Benzene Degradation

微放电可在小的空间中产生高密度等离子体,有利于气体污染物的高效处理。该文研究了电极结构及电极形状对多孔陶瓷孔内微放电特性及苯降解的影响。结果表明:在相同外加电压条件下,与二电极结构相比,三电极结构可生成更多的丝状放电通道,峰-峰电荷Qpk-pk提高了3.2倍,放电电荷Qd提高了4.4倍,放电功率从0.8W提高到8.6W,苯降解效率提高了35.1%;网高压电极结构相比于弹簧电极,能够增加有效放电面积并增强放电强度,放电功率相较于弹簧电极构型提高约4W,丝状放电通道能够充满放电空间,显著提高苯降解效率。

Dielectric barrier discharge(DBD),which is characterized by numerous microdischarge channels in narrow gas gap,can stably produce discharge plasma at atmospheric pressure and room temperature.DBD process is simple and easy to operate,leading to a wide range of applications such as waste gas/water treatment,material surface modification,biomedicine and so on.Especially DBD has been hotly studied for volatile organic compounds(VOCs)treatment because of its low breakdown voltage,high electron density and reactive species.Previous studies have found that the electrode configuration of DBD device would change the plasma distribution and the generation characteristics of reactive species.However,few studies have focused on how to enhance the microdischarge in DBD reactor for promoting the degradation of VOCs.In this paper a coaxial tri-electrode DBD device filled with a porous ceramic tube with micron pore size is proposed for benzene degradation.The coaxial DBD reactor has a three electrode configuration which was named surface-volume hybrid DBD.The mesh or spring type high-voltage electrode was tightly pasted at the inside wall of a quartz tube tightly and then a porous ceramic tube with 60μm pore size was put in the quartz tube(QTⅠ)and acted as a barrier dielectric.The high voltage electrode was powered by an AC(0~60 kV,50 Hz)power supply.A rod-like electrode wrapped in a quartz tube(QTⅡ)was put in the middle of ceramic tube to act as one of ground electrode as well as an aluminum foil sheet was wrapped on the outside of QTⅠto act as another ground electrode.Firstly,the effect of electrode configuration and electrode geometry on the microdischarge characteristics including voltage and current waveforms,microdischarge channel distribution,Lissajous figures was measured.The three-electrode configuration presented stronger microdischarge which was characterized by more current pulses on the current waveforms,more and brighter microdischarge channels on the discharge images and larger Lissajous figure area,and mesh electrode also presented stronger microdischarge than spring electrode,but a decrease in the spring gap of spring electrode can effectively enhance the microdischarge intensity.The dielectric equivalent capacitance and charge characteristics calculated from Lissajous figures showed that the dielectric equivalent capacitance,the peak-peak charge and discharge charge of the three-electrode configuration was 3.5 times,3.2 and 4.4 times that of the two-electrode configuration.In addition,mesh high-voltage electrode configuration can further improve the effective discharge area compared to spring electrode configuration.Moreover,the discharge power was increased from 0.8 W(two-electrode configuration)to 8.6 W(three-electrode configuration)and the benzene degradation efficiency was correspondingly increased by 35.1%.Compared to spring electrode,the mesh high-voltage electrode can enlarge the discharge area and intensity,and enhance the electric discharge power by 4 W,leading to higher benzene degradation efficiency and comparable energy efficiency to spring electrodes,moreover,the energy efficiency of spring electrode with smaller spring gap(4 mm gap)was slightly higher than that of 9mm gap.The study is helpful for understanding how to strengthen the generation of microdischarges and then promotes the application of microdischarges in gaseous pollutant treatment and ozone generation.