Research On VOCs Toxic Air Treatment By Pulsed Discharge And Purification Effectiveness Evaluation

Research on the air purification technology by discharge plasma has two merits on science discovery and practical application, one is to help people to realize some characteristics and laws of the combination of discharge physics and discharge chemistry under some certain conditions, the other is to supply a prospective way to purify air for indoor environments such as workshops, offices, sitting rooms, saloon cars, space stations and submarine cabins. Toluene was chosen as the target pollutant and the VOCs decomposition effectiveness induced by pulsed discharge plasma was investigated under experimental conditions. The main subjects and results are as follows: 1) Followed the analysis for the structures and characteristics of some designed discharge reactors, the basic principles, especially the synergy optimization combining electric field analysis and flow field analysis for reactor optimization were discussed, based on the basic principles of VOCs decomposition induced by discharge plasma. A novel ejection wire-cylinder reactor was set up. Field synergy analysis and experiments which related with two different air supply ways were carried out consequently. 2) For the field synergy problems of air purification by discharge plasma, some preliminary experiments were conducted via changing pulse polarity or air supply ways. The results indicated that the field synergy degree affected decomposition efficiency largely, and the biggest difference reached at 42.5%. The top of toluene decomposition efficiency induced by pulsed discharge reached at 90%. 3) The development process of reaction field was investigated by analyzing the changes of the concentrations of C₇H₈,CO and CO₂. The phenomenon which CO concentration trail presented a hump and CO₂ concentration increased gradually to a upper limit showed that reaction field was activated immediately when high pulsed voltage was turned on, and developed gradually to maximize decomposition capacity subsequently. A majority of toluene was not decomposed to such simple carbon compounds as CO and CO₂ when concentration was higher. 4) The experiments about toluene decomposition efficiency induced by pulsed discharge combined with nanometer-sized TiO2 catalyst film were carried out. The decomposition efficiency was higher than 90% , at 0-400ppm. Field synergy effect still existed when the catalyst strengthened the decomposition capacity of plasma. 5) For the problem that the current indexes cannot evaluate purification effectiveness for equipment accurately, briefly and effectively, two new evaluation indexes, i. e. equivalent toxic concentration and total purification degree,are proposed in this paper. A simple application example are also presented. The two new indexes contain double information of qualitative change and quantitative change for decomposed pollutants, and have the practical value introduced to the similarly environment treatment field.