Study Of The Decomposition Of Mixed VOCs By Wire Tube Pulsed Corona Discharge

In recent years, the pollution problems of volatile organic compounds (VOCs) in air and the effective control of the pollution have already attracted people's attention. Among the treatment methods of VOCs, the nonthermal plasma (NTP) technology has such advantages as high removal efficiency, nonselective, wide using range and etc.,and exhibits promsing application perspective.The mixture gas of acetone/benzene/perchloroethylene (PCE)/m-xylene was chosen as the target pollutants in this study, and wire tube positive pulsed corona discharge was used to decompose the mixture gas. The degradation characteristics and carbon oxides formation characteristics of the mixture were investigated, and the interacton of the pollutions in degradation process was discussed. Meanwhile, the degradation performances of the four mixed VOCs between different reactors, which have been studied by our research group, were compared. The influences of plasma-Mn catalyst system on degradation characteristics and carbon oxides formation characteristics of the mixed VOCs were discussed. The main results are summarized as follows:1.Performance optimization of wire tube positive pulsed corona discharge reactor structure.The energy input and the degradation efficiency of the mixed VOCs, combining the practical operation of the reactor, were optimized to obtain the optimal reactor structure:the high voltage electrode diameter of 0.50 mm and the tube inner diameter of 32.00 mm. The optimal reactor structure is benefit to energy input and long-term stable operation of the reactor, which could achieve the maximum degradation effect of the mixed VOCs.2.Comparison of different discharge reactors'performance during the mixed VOCs decomposing.The degradation performance of the four mixed VOCs between the wire tube positive pulsed corona reactor and three different forms of DBD reactors (which has been studied by our research group) was mainly.The wire tube reactor showed better degradation performance than that of tube tube DBD reactor with AC power and wire tube DBD reactor with AC power for the decomposition of PCE/m-xylene mixture.Meanwhile, the wire tube reactor also showed better degradation performance than that of tube tube DBD reactor with bipolar pulsed power and tube tube DBD reactor with AC power for the decomposition of acetone/benzene/PCE/m-xylene mixture.This may be due to the wire tube positive pulsed corona discharge provided the sharp pulse edge, narrow pulse width and reaction in a large space, so that the degradation performance of the mixed VOCs decomposition was promoted.3.Degradation and mutual influence characteristics of the mixed VOCs decompositon. Both the decomposition of PCE and m-xylene mixture and the decomposition of acetone, benzene, PCE and m-xylene mixture, the total removal rate both became higher after the single VOC mixed, which was benefit to decompose (degradation rate of PCE/xylene mixture could be increased by 8.4%, degradation rate of acetone/benzene/PCE/xylene mixture could be increased by 33.8%).It's mainly due to the intermediate products, generated during the degradation, could interact with each other or with the target pollutions after the contaminants mixed, which could improve the degradation rate and energy efficiency of the mixed VOCs, promoting the degradation. The promotion between the each other contaminants play more important role than the competition between the pollutions with energy when the mixed VOCs decomposing.4.COx formation characteristics in the mixed VOCs decomposing. During the decomposition process of two or four kinds of VOCs,COx selectivity were both lower than that of single component decomposition process.Although the degradation imtermediate products promoted the mixed VOCs decomposition, they might react with each other or react with the target pollutions, so that the intermediate products could not be further oxidized to CO and CO2.5.Degradation characteristics of plasma-Mn catalyst system about the mixed VOCs decompition. The degradation efficiency of the four target pollutions was not significantly inprobed after adding Mn catalyst in the plasma afterglow region. But the CO selectivity and CO2 selectivity both increased significantly at the outlet and the O3 content reduced at the same time.This is mainly due to Mn catalyst could promot the the utilization of O3 by chemical reaction, while O3 played a major role in the further mineralizition of small molecule imtermediate products.