Studies On Removal Of Toluene Using Sliding Surface Discharge By Double Power Supplies And Combination With Catalysis

With the rapid development of industrialization in China,the emission of volatile organic pollutants?VOCs?has gradually increased,causing serious harm to human health and the environment.Among the many methods of removal VOCs,the plasma method has the advantages of rapidness,high efficiency,non-selectivity compared to some conventional methods,and has received extensive attention at home and abroad.Among them,surface discharge is a main form of plasma technology,but the traditional surface discharge plasma has several problems,such as small area of the extended area and low high-energy electron density,but which has low degradation efficiency and low mineralization efficiency when treating pollutants.In this thesis,a pulsed/negative DC coupled dual-power is used to stimulate the sliding surface discharge in order to improve the degradation efficiency and energy efficiency of the pollutants treated by plasma.In this thesis,the high voltage electrode of the plate-plate surface discharge system is excited by the nanosecond pulse power to increase the electric field intensity of the discharge and increase the number of high-energy electrons and active particles.In addition,a third electrode is respectively introduced on both sides of the high-voltage electrode and is driven by a negative DC power to form a parallel electric field to dielectric,and the streamer is extended by the Coulomb force to form a sliding surface discharge system to increase the discharge area and the probability of collisions between active particles and contaminants.This paper demonstrates the advantages of sliding surface discharges in terms of electrical characteristics,optical properties,and toluene degradation effects compared to traditional surface discharges,and explores the influence of electrical parameters,structural parameters,and gas phase parameters on sliding surface discharge,and synergistic effects of plasma and catalysts for removal of toluene.The main research content and the results obtained are as follows:?1?Discharge characteristics,optical characteristics,and degradation of toluene are compared in traditional surface discharge and sliding surface discharges.The results show that when the pulse voltage is 20 kV,the pulse peak current and the discharge power of the sliding surface discharge are 6 A and 0.53 W higher than that of the traditional surface discharge,respectively.The sliding surface discharge is stronger and more uniform than the traditional surface discharge and penetrate the entire discharge area.In addition,the sliding surface discharge has better degradation effect and mineralization effect on toluene.In the sliding surface discharge,when the input power is 6.5 W,the degradation efficiency,energy yield,and CO₂ selectivity of degradation the 100 ppm toluene with a flow rate of 300 mL/min are higher 11.5%,0.1 g/kWh and 23%than the traditional surface discharge;?2?The electrical parameters,structural parameters and gas phase parameters of the sliding surface discharge reactor were optimized.Effects on toluene degradation efficiency,energy efficiency,and mineralization rate of the polarity of the pulsed power supply,the forming capacitance,the negative DC voltage,the electrode spacing and length,the dielectric material and the toluene-containing air concentration and flow rate were examined.The results show that the positive polarity pulse has a better degradation effect than the negative polarity pulse,0.67 nF is the best forming capacitance of the nanosecond pulse power supply,negative DC voltage 5 kV,electrode spacing 40 mm,electrode length 80 mm,initial The concentration of 100 ppm and the total flow rate of 150 ml/min can make toluene degradation and energy efficiency the best.Quartz is a good dielectric material for sliding surface discharge.?3?The toluene-containing gas was degraded by a plasma synergistic Co_xCe_y/?-Al₂O₃catalyst.The degradation efficiency,energy efficiency and ozone generation of the toluene-containing gas were investigated for the catalysts with different metal proportions,and the catalysts with different space velocity were used.The infrared spectrum of the degradation product of the plasma synergistic catalytic system was analyzed.At 20 kV,the degradation efficiency and CO₂ selectivity of toluene were 20.2%and 22.1%higher by sliding surface discharge with Co_7.5Ce_2.5/?-Al₂O₃ catalyst than the sliding surface discharge reactor alone used.When the Co_7.5Ce_2.5/?-Al₂O₃ catalyst had a space velocity of 17456 h^-1,a good degradation effect could be achieved.