Treatment Of Simulated Waste Gas From Painting By Micro-nano Bubble Spray And Low Temperature Plasma

As a key source of volatile organic gas(VOCs)emissions,coating waste gas is characterized by large air volume,low concentration and complex components.Substandard emissions of this type of exhaust gas seriously endanger the atmospheric environment and human health.Therefore,the treatment of painting exhaust gas has become the current research hotspots.In this paper,the removal experiments of benzene,toluene and xylene from the typical toxic and harmful waste gas of painting were carried out.According to the coating exhaust gas composition and characteristic concentration of a construction industry,the concentration ratio of benzene,toluene and xylene in the simulated gas was controlled to 1:2:3,a combination of micro-nano bubble spraying and non-therml plasma was used to deal with "triphenyl" waste gas.First,the best operating conditions and pollutant removal effects were explored by changing the operating parameters of a single device.Then,the two devices were operated in series to determine the applicable concentration range of pollutants.The main conclusions are as follows:(1)When the micro-nano bubble generating device was in operation,the instantaneous high temperature was generated along with the cavitation reaction of microbubbles and the energy was converted into heat energy by the releaser,the water temperature was gradually increased and the dissolved oxygen content was gradually reduced.After the continuous use of 10 min,the device runs stably,the dissolved oxygen content was 15.3 mg/L,and the average clarification time was 196 s.The effective gas-liquid mixture ratio was basically maintained at 1.2-1.5%.(2)When the removal rate of VOCs was investigated by using water and micro-nano bubbles as spraying fluids,it could be seen that the main effect on pollutant removal was the cavitation reaction when the bubbles collapse.When the concentration of benzene,toluene and xylene were 140 mg/m3,280 mg/m3,420 mg/m3 respectively,the inlet air volume was 471 m3/h(i.e.the residence time was 18 s)and the gas ratio was 4 L/m3 during the spraying process of micro-nano bubbles,the exhaust gas treatment effect is the best.The removal rates of benzene,toluene,and xylene reached 41.95%,49.63%,and 54.63%respectively.According to the detection value of circulating water quality,the concentration of COD increased with the increase of the operating time(3)DC corona discharge form of syringe electrode was installed in the Non-therml Plasma.When the concentrations of benzene,toluene and xylene were 100 mg/m3,200 mg/m3,and 300 mg/m3 respectively,the regulated voltage value was 30 kV,the current was 250 mA,the residence time was 2.4 s and the humidity was 30%,the effect of exhaust gas treatment was the best.The removal rates of benzene,toluene,and xylene reached 73.21%,84.22%and 85.9%.The energy utilization efficiency was 4.25 g/kWh,9.76 g/kWh and 15.14 g/kWh respectively.According to the analysis of concentration changes of COx,NOx and O3,the higher the power was,the stronger the ability of gas thorough degradation and ionization of the device was.(4)When micro-nano bubble spray and low temperature plasma run in series,the removal rate of the "triphenyl" combination gas decreased with increasing concentration When the gas flow was 500 m3/h(i.e.the residence time of the gas in the spray tower was 17 s and the residence time in the low-temperature plasma was 2.4 s),the spray liquid-gas ratio was 4 L/m3,the voltage was 30 kV,the current was 250 mA and the relative humidity was 37%,the "triphenyl" combination concentration could be treated in series device need to be lower than that of 101.21 mg/m3 of benzene,202.5 mg/m3 of toluene and 293.2 mg/m3 of xylene.