Experimental Study On VOCs Degradation By Strong Ionization Discharge Combined With Pulsed Corona Discharge Plasma

Volatile organic compounds（VOCs）are important pollutants that harm the atmospheric environment and human health in China.It is of great significance to strengthen the research of VOCs treatment technology.In order to solve the problems of low average electron energy and poor treatment effect of high concentration VOCs in traditional low temperature plasma,strong ionization discharge reactor,strong ionization discharge and pulse corona discharge combined strong ionization+pulse corona device were designed respectively,and their degradation effects on xylene and mixed VOCs（xylene,ethyl acetate,formaldehyde）were studied,The effects of different factors on VOCs treatment efficiency were revealed.At the same time,the output of O₃,NO_x,CO and CO₂in the tail gas after xylene degradation was studied with the applied voltage as the control parameter.The intermediate products of xylene degradation were determined by gas chromatography and gas chromatography-mass spectrometry,and the possible reaction pathway was deduced by theoretical analysis.It provides theoretical and experimental basis for the application of low temperature plasma.The main conclusions are as follows（1）Experimental study on Influencing Factors of xylene degradation by strong ionization discharge.The degradation efficiency of xylene was positively correlated with applied voltage,and reached 95.8%at 4.0 k V;The xylene removal rate first increased and then decreased with the increase of discharge frequency,reaching the maximum of 91.4%at 5.78 k Hz;When the applied voltage was constant,the xylene removal rate was negatively correlated with the concentration;The removal efficiency of xylene was positively correlated with residence time;With the increase of relative humidity,the removal rate of xylene first increased and then decreased,and the degradation efficiency reached the maximum of 83.9%when the relative humidity was about 54%;The degradation efficiency of xylene was positively correlated with temperature.（2）The degradation products and mechanism of xylene by strong ionization discharge were studied.The p H of the aqueous solution which absorbed the degradation products of xylene was negatively correlated with the voltage drop.With the increase of applied voltage,the production of O3 increased.In the process of xylene degradation,the reactor will produce a small amount of nitrogen oxides,and the amount of nitrogen oxides is positively correlated with the voltage,and negatively correlated with the concentration of xylene.In addition to ozone and nitrogen oxides,there are a large amount of CO₂and a small amount of CO in the strong ionization discharge reactor,and the selectivity of CO₂is very high,which indicates that the oxidation degree of xylene in the strong ionization discharge reactor is relatively thorough,and most of xylene is oxidized to inorganic substances.Through the analysis of xylene degradation products by GC-MS,the other intermediate products were benzoic acid,benzaldehyde,2,4-2 tert butylphenol,2-aminopentane,2-methyl-5-（2-aminopropyl）-phenol,Propionamide,3-methyl-5-aminohexane and ethyl acetate.Combined with theoretical analysis,the possible reaction pathway was deduced.（3）Experimental study on VOCs degradation by strong ionization+pulse corona discharge.Under different conditions,the degradation effect of VOCs by strong ionization+pulse corona discharge method is better than that by pulse corona discharge method,and the removal rates of xylene,ethyl acetate,formaldehyde and mixed VOCs by strong ionization+pulse corona discharge method are more than 90%,which indicates that it has good treatment effect on a variety of VOCs.