The Degradation Of Toluene Reinforced By Microporous Insulating Low-voltage Electrode In Corona Discharge Plasma

Volatile organic compounds?VOCs?have caused great pollution on the environment due to numerous emission sources and large emission load.VOCs has become a difficulty problem in environmental pollution treatment,and the focus in the field of environmental pollution control in our country for the characters of complicated composition and degradation-resistant.However,the traditional control technologies are not economically effective for low concentration and high air volume due to the technique level and investment cost.Non-thermal plasma has become a prospect VOCs degradation technology for the advantages of low energy consumption,high degradation efficiency and no selectivity to pollutants.In this paper,DC corona discharge induced low-voltage electrode micro-discharge to enhance the plasma strength was proposed,the degradation efficiency of VOCs was increased accordingly.Main research work and results are as follows:1.The feasibility of micro-discharge on the low-voltage electrode was investigated.The results show that when the porous insulating material was coated on the surface of the low-voltage electrode,charge will accumulate on the insulating layer,and form an electric field in the insulated micro-channel.Micro-discharge in the insulating layer will be induced when the electric field intensity reaches a certain intensity,and the discharge plasma strength was enhanced.Among the materials used in this paper,porous polytetrafluoroethylene?PTFE?showed the best improvement on the plasma strength.Under the conditions of film thickness was 50 ?m,the number of pores was 100 /dm-2 and the pore size was 10 ?m,the discharge current reached 1296 ?A,and the ozone concentration was 3.11 mg/L when the voltage was 12 kV,increased by 4.5 times and 2.2 times respectively compared with the use of uncovered electrodes.2.The research of toluene degradation by corona discharge reinforced by porous insulating material micro-discharge was carried out,and the effects of gas phase parameters on toluene degradation rate,energy efficiency and mineralization rate were investigated.The results show that the degradation efficiency of toluene in O₂,N2 and Air was: N2>Air>O₂;Increasing the oxygen content and carrier gas humidity in a certain range can improve the degradation efficiency of toluene.The degradation effect of toluene was reduced as the increase of carrier gas flow rate and initial concentration of toluene,on the contrary,the utilization energy efficiency of the system was improved.The toluene degradation efficiency of optimized discharge system up to 58%,which is 31% higher than using corona discharge with no optimized.3.The mechanism of toluene degradation by the DC corona discharge reinforced by low-voltage electrode porous insulating material micro-discharge was discussed.The emission spectra of the discharge system and the degradation products of toluene were analyzed.The results show that the emission spectrum of discharge system is mainly N2 second positive transition line N2?C3?u?B3?g?.Compared to the other active substances,N2?C3?u?plays a key role in the degradation of toluene due to its relatively long life.Except the main degradation products of CO₂ and H₂ O,the products of toluene degradation also consist of organic acids and benzene derivatives.According to the determined results,it can be speculated that the degradation process of toluene mainly start with high energy electrons and high excited state molecules attack the benzene ring and make it to break,which generate a series of intermediates,then these intermediates were further degraded into organic acid under the action of oxygen-active substances,and ultimately decomposed into CO₂ and H₂ O.