| In recent years, the volatile organic compounds emission from industrial sources has raised serious air pollution problems. Non-thermal plasma (NTP) technology as a new developed technology has received much research attention owing to the advantages as low investment cost, easy operation and wide applicability especially for the VOCs with low concentration and large air flow rate. In this thesis, the needle-plate corona discharge reactor coupled with the high voltage DC power supply was employed and the VOCs degradation performances has been investigated under different catalysis assistant mode.Firstly, the effects of the discharge features of NTP on the VOCs degradation performances have been studied. The experimental results showed that the positive corona discharge has a more narrow discharge range, faster streamer development, and more active group generated compared with negative corona discharge, resulting in a higher VOCs degradation rate. When the energy density is 324.9 J/L, the removal efficiency of toluene is 58%. The gas-phase products of this process include the small organic molecules, O3, CO and CO2. When the voltage U= 19 kV, the outlet concentration of O3 was 230 ppm and aerosol deposition on the electrode was found during the discharging process.Secondly, the VOCs degradation performances with combined NTP and post catalysis have been investigated. The results indicated that the removal efficiency of VOCs could be greatly improved and the by-products like O3 emission was well controlled. For instance, when the voltage was 19 kV with 5wt%CoOx/Al2O3 used as the catalyst, the removal efficiency of toluene could reach 98%, which was around twice higher than that with NTP used solely. And the residue O3 in tail gas has been almost decomposed completely. However, the aerosols particles may block the micro-pores of the catalyst and cover the active sites, thereby leading to the deactivation of the catalysts.Furthermore, the catalysis section loaded with transition metal oxides based catalysts was put in NTP reactor and the VOCs degradation performances were then investigated. It could be found that VOCs removal efficiency could remain a high value in this in-situ NTP-catalysis mode, and the durability of the catalysts and COx selectivity were enhanced compared to post catalysis assistant mode. For 1%MnOx-4%CoOx/Al2O3, the removal efficiency of toluene could reach 98% with outlet O3 concentration and COx selectivity being ca.20 ppm and 51%, respectively. In addition, the catalysis section was employed as a suspension type in-between the two electrodes. The energy efficiency was improved and COx selectivity was further increased. For examples, The COx selectivity could approach 82.3% over 1%MnOx-4%CoOx/SiC catalyst under U=26 kV.Finally, the investigations on VOCs degradation performances for combined NTP and two-stage catalysis process were carried out in this dissertation. Compared with one-stage catalysis assistant process, the durability of the catalysts and the emission of the byproducts was improved. In addition, the mineralization rate and the COx selectivity were increased as well. The optimal catalysts of the insitu catalytic section were the oxides of Mn, Co and Ni or Ag. And as for the post catalytic section, the oxides of Mn, Ce, Co, etc. have better performances due to their high decomposition efficiency of O3. Moreover, the VOCs degradation performances of NTP and different catalytic assistant NTP mode have been investigated, by considering degradation rate, mineralization rate, COx selectivity and the energy yield. It was found that the mineralization rate and the COx selectivity of NTP combined with two-stage suspended catalysis process could both approach 92% at a voltage of 26kV. And this NTP-catalysis mode can remain a high degradation rate and a high yield at low energy density. For instance, the removal efficiency of toluene and energy yield at a energy densisty of 50J/L were 80% and 18.04 g/kWh, respectively. And O3 emission could not be detected in the tail gas. |
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