Experimental Study On Degradation Of Ethyl Acetate By Strong Ionization Discharge Plasma

In recent years,with the rapid development of China’s economy and the accelerating development of industrialization,toxic and harmful gases emitted by various types of enterprises have increased year by year,accelerating the deterioration of the ecological environment.Among them,NOx,SOx and volatile organic compounds（VOCs）as typical atmospheric pollutants pose a serious threat to China’s atmospheric environment.With regard to the removal technologies of NOx and SOx compounds,which have become increasingly mature,VOCs have a variety of types,and the vast majority of VOCs have certain toxicities.Therefore,the research on the control technology of VOCs is of great significance,so the treatment of VOCs was an important part of’13th Five-Year Plan’ the air pollution prevention and control work.In this paper,ethyl acetate,which is a typical organic solvent in industrial production,is selected as the target contaminant.Experimental study was conducted using strong ionization discharge non-thermal plasma technology.The discharge characteristics of the reactor were investigated.The effects of various factors such as specific input energy（SIE）,discharge frequency,initial concentration,space velocity,humidity,and temperature on the degradation efficiency were investigated.The variation of O₃,NOx,CO and CO₂ production in degradation products with reactor SIE was studied by ozone analyzer,CO/CO₂ meter and flue gas analyzer.GC and GC-MS analysis methods were used to analyze and detect other by-products produced during the degradation of ethyl acetate,and the possible reaction pathways for the degradation of ethyl acetate were explored and inferred in conjunction with the measured intermediates.Experimental studies can lead to the following conclusions:（1）The characteristic of the reactor current output is not the performance of a purely resistive circuit,and its value will fluctuate and change greatly.And the reactor has a good discharge characteristics,the discharge frequency does not change,and the specific input energy increases with the increase of the voltage.The degradation rate of ethyl acetate rises rapidly when the specific input energy is 40-100 J/L,and when the input energy is greater than 100 J/L,it begins to slow down,and the final degradation efficiency is close to 91%;The energy yield is highest at a specific input energy in the range of 100-110 J/L.The ethyl acetate degradation efficiency and discharge frequency are not a simple linear relationship but an optimal value and the optimal discharge frequency is 5.71 kHz.（2）Keeping the voltage constant,as the concentration increases,the removal efficiency decreases,and the optimum applied voltage for different concentrations is slightly different.The approximate range of the best applied voltage is 2.6-3.4 kV;with space velocity from 442 h-1 Increased to 973 h"1,the removal rate of ethyl acetate was reduced at any applied voltage and the effect of space velocity on ethyl acetate was more pronounced at lower voltages.With the increase of humidity,the degradation rate of ethyl acetate increases first and then decreases.The degradation efficiency reaches its maximum value at a relative humidity of 20%.When the temperature rises from 20 °C to 150 °C,the degradation efficiency of ethyl acetate at each specific input energy increases.There are different degrees of increase.When the specific input energy is 90 J/L,the degradation efficiency increases from 71%to 98.6%.When the specific input energy is low,the degradation efficiency is increased by 38%.（3）With the increase of the voltage,the TOC content in the degradation products gradually decreases,and the decreasing trend is obvious.When the voltage is 3.2 kV,the organic carbon content in the reaction products is very small.And the use of solution to absorb the reaction products,the pH showed a decreasing trend,proved that most of the organic carbon in the reaction products were converted into CO₂ and other inorganic carbon,and the degradation effect was good.The results of gas chromatography showed that the peak areas of ethyl acetate in the decomposition products at the voltages of 0.4,2.0,2.5,2.9,and 3.5 kV showed a declining trend,which further validated the good degradation performance of ethyl acetate in the strong ionization discharge reactor.The degradation rate calculated by the peak area is basically consistent with the results of the chapter 3.（4）The output of O₃ increases with the increase of specific input energy.When the specific input energy is greater than 120 J/L,the 03 output is greater than 750 mg/m³,indicating that the reactor discharge performance is extremely strong,the average electron energy is high,and the chemical reaction efficient.A small amount of nitrogen oxides was detected in the reactor,but its production was lower than the industrial minimum emission standard（80 mg/m³）.In addition to CO₂,there is a very small amount of CO produced in the reaction product,but the CO₂ selectivity is far greater than that of CO,which proves that the reactor not only has a high degradation efficiency for ethyl acetate,but also has a very thorough oxidation degree.The ethyl acetate waste gas is directly oxidized to CO₂ with only a very small amount of CO and other incomplete oxidation products.（5）Qualitative analysis of ethyl acetate by GC-MS,other intermediate products of the reaction were determined:ethanol,formic acid,and acetic acid.Based on the theoretical analysis,the possible degradation pathways of ethyl acetate were analyzed using the detected intermediates.