Study On Discharge Characteristics Of Three-electrode DBD Rector And Its Application For Benzene Degradation

Dielectric barrier discharge（DBD）can generate stable plasma at normal temperature and pressure.Because of its simple device configuration and higher energy utilization rate,it has become one of the most commonly methods which used plasma production.According to the spatial distribution of discharge plasma,there are two basic DBD configurations which can be divided into surface dielectric barrier discharge（SDBD）and volume dielectric barrier discharge（VDBD）.VDBD generates discharge plasma in the gas gap between electrodes,but the initial discharge voltage is relatively high;The discharge electrode of SDBD is covered on its dielectric surface,and SDBD generates plasma in the surface electrode and propagates along the dielectric surface,which causes the plasma chemical reaction to occur near the surface of the dielectric and affects the gas treatment ability.However,for SDBD configuration,it has a lower initial discharge and higher energy yield.Therefore,in this paper,two kind of three-electrode surface/volume DBD hybrid discharge configurations were built by combining the discharge structures of SDBD and VDBD.One is to form the V-SDBD system by adding a grounding electrode above the SDBD,and the other is to add a grounding electrode under the plate-to-plate DBD to form an S-VDBD system.By analyzing the electrical characteristics,optical characteristics and active species pruduced of the systems,the effects of the additional grounding electrode on the structure of the original single DBD configuration were studied.Finally,the benzene degradation performance of the three-electrode DBD hybrid structure was investigated.The specific experimental results were shown below:（1）By comparing the electrical signals,emission spectra,and active species pruduced capabilities of the SDBD and V-SDBD systems,the effects of the grounding electrode on the DBD system along the surface was studied,including voltammetric characteristics,charge characteristics,power characteristics,and active species.The discharge current pulse number and amplitude of the V-SDBD system increased significantly.When the voltage was 16 kV and the discharge gap was 2.8 mm,the number of micro-discharges along the surface in the V-SDBD system increased by two times,and the amount of discharge charge increased by 21%,the suface discharge power in the V-SDBD system is 1.18 times that of the SDBD alone.The V-SDBD configuration generates plasma more fully along the surface of the dielectric and the air gap,the ozone concentration produced and the energy efficiency are higher.At the applied voltage of 16 kV,the ozone concentration and energy efficiency of V-SDBD were 3.66 mg/L and 27.6 g/kW·h that were 4.3 times and 1.76 times that of SDBD configuration respectively.（2）By analyzing the plate-to-plate DBD and S-VDBD systems,when the voltage was 9 kV,the S-VDBD system had generated a number of larger amplitude current pulses,but the VDBD system had not discharged nearly.At the voltage of 16 kV,compared with VDBD,the discharge charge of the volume DBD in the S-VDBD system was increased to 1.39 times,the peak-to-peak charge was increased by 43%,the discharge power was increased by 3.85 W,and the dielectric capacitance was increased by 19%.The number of generated active species increased significantly.When the S-VDBD system used a grounding electrode with a mesh size of 60 meshes,the volume DBD exhibited a"relatively uniform"stable filament discharge.（3）The benzene degradation performance of the two hree-electrode surface/volume DBD hybrid discharge configurations were discussed,and the influence of relevant parameters on benzene degradation performance was explored by comparing SDBD with V-SDBD systems.When the initial concentration of benzene was 150 ppm,the applied voltage was 16 kV,and the gas flow rate was 1 L/min,the degradation efficiency of the V-SDBD and S-VDBD system was55.3%and 53%respectively,the maximum energy efficiency of those were 1.29 g/kW·h and0.75 g/kW·h.As the gas flow rate increased,the energy yield of benzene increased first and then decreased.When the gas flow rate was 1 L/min,the energy yield of the experimental system reached the optimal.The V-SDBD system was less affected by the gas gap than the SDBD system.The higher initial concentration of benzene gas can improve the energy efficiency of benzene degradation to a certain extent.The products of benzene degradation are mainly H₂O,O₃,CO,N₂O,HCOOH,and CO₂.