Study On Degradation Of Indoor Benzene By Complex Dielectric Barrier Discharge Plasma

Volatile organic compounds (VOCs) are the main pollutants of indoor environment including workshop. However, because of incomplete protection facilities and non-professional installation and debugging, VOCs always lead to unqualified of the work environment, which threats to workers’health ultimately. So it is of great significance to research indoor VOCs purification technology which has the advantages of high-efficiency, low energy consumption and no secondary pollution. Non-thermal plasma technology is a new advanced oxidation technology, and has broad application prospects for indoor VOCs treatment.In this paper, an innovative complex dielectric barrier plasma (CDBD) reactor was proposed to degrade benzene. The simultaneous surface discharge and packed-bed discharge were successfully realized in this reactor. Between the high voltage electrodes of two discharge regions was the common low voltage electrode, forming an electrode parallel structure. Benzene, a typical indoor VOCs, was used as the target pollutant. The study mainly focuses on studying the degradation efficiency and energy efficiency of benzene, and proposes the mechanism by Fourier Transform Infrared Spectroscopy and carbon balance analysis. The main research results are as follows:(1) In order to optimize the structure parameters of CDBD reactor and experimental parameters, the study investigated the degradation of benzene in terms of structural parameters, electrical parameters and gas parameters of S-P reactor and PBD reactor. The experimental result showed that, for S-P reactor, increasing the discharge length and dielectric tube diameter, decreasing initial concentration and gas flow rate contributed to higher degradation efficiency of benzene. In S-P reactor, when the benzene initial concentration was100ppm, the degradation rate of benzene was42.5%and the energy efficiency was10.1g/kWh. For PBD reactor, compared with the smooth cylindrical electrode, the threaded cylindrical electrode was more benefit for energy injection, and reducing discharge gap and diameters of glass beads contributed to the degradation of benzene. In PBD reactor, when the benzene initial concentration was100ppm, the degradation rate of benzene was30.7%and the energy efficiency was8.0g/kWh. (2) CDBD reactor was an efficient and cost-effective method for benzene degradation under the optimized experimental parameters. The benzene degradation efficiency and energy yield in the CDBD reactor were52.8%and13.80g/kWh, respectively, which was10.3%and3.8g/kWh higher than in the S-P reactor and22.1%and5.76g/kWh higher than in the PBD reactor, respectively operated at53J/L. The result proved degradation of benzene by CDBD reactor was feasible.(3) By quantitative analysis of carbon balance during benzene degradation and analysis of benzene degradation intermediates by FTIR, benzene degradation pathway in CDBD reactor was proposed. The results showed that the carbon balance of three reactors were60.0%,49.0%and37.0%, respectively, indicating a proportion of benzene was converted into intermediates in all the three reactors. The decomposition products of benzene includes formic acid, CO2, CO and H2O and so on. In CDBD reactor, benzene is converted into some intermediates and C-containing products via reactions with the reactive species generated in the S-P region. Subsequently, the unreacted benzene can further interact with the plasma in PBD region to achieve a higher degradation efficiency than expected. The main degradation pathway of low concentrations of benzene in this experiment is reacted directly with radical.