Experimental Study Of The Degradation Of Toluene By Using Pulse Modulated Plasma

In recent years,using the low-temperature plasma technology to deal with volatile organic compounds becoming a popular technology to the governance of gas environment.It is a new technology compromise of physical,chemical,environmental sciences.The treatment of volatile organic compounds (VOCs) emissions by using low-temperature plasma is a hot research topic around the world.The study of this thesis is mainly focus on reducing the energy consumption of plasma processing of VOCs and avoiding the second pollution of the byproducts generation during the processing which the two important problems of the plasma VOCs degradation.Toluene is selected as the imitation of VOCs,by using coaxial dielectric barrier discharge,the affect of the continue discharge, the pulse modulation and the using of catalyst on VOCs degradation are studied and compared.The results show that the energy density required to achieve the same removal rate in the continue discharge is almost1to4times of pulse modulated one, the energy efficiency of pulse modulated discharge is nearly2to3times of the continue one; at the same time, the pulse modulated discharge effectively reduce the temperature rise of the DBD discharge chamber,the equilibrium temperature of the pulse modulated discharge is70℃,which in the case of unmodulated is about200℃.While.The removal of toluene in the case of pulse modulation increased with the increase of peak voltage, until saturated finally. The removal rate of toluene is increased first and then decreased with the increasing of the modulation frequency. It is increased with the increasing of duty cycle.Toluene degradation rate decreased with the increase of the initial concentration while the energy efficiency is increased with the increase of the initial concentration.with the increase of the discharge length,the toluene removal rate is increased first and then decreased. The improvement of catalyst on the toluene degradation efficiency are studied. The results show that in the case of catalyzed,the energy efficiency is almost1.5to2times compared the one without catalysts,especially in the condition of low energy density.The catalyst also effectively change the formation of products during the processing.The concentration of ozone was from1.2mg/L reduced to0.3mg/L;the amount of CO2has increased,and the amount of CO significantly reduced.These implies that the catalyst effectively increases the VOCs gas oxidation process.The amount of the benzene derivative in the yellow oil coking was generated in the reaction chamber is significantly reduced in the case of catalyst.Finally, the treatment byproduct are detected by the IR and GC-MS.Based on the possible structure and kind of the products, toluene degradation mechanism is analyzed simply.