The Effect Of Flow Pattern On The Ozone Generation In Surface Dielectric Barrier Discharge

As China's energy consumption is getting larger and larger,there is a strong demand for air pollutant removal technology.The technology“Simultaneous removal of NO_x,SO₂ and Hg by ozone active molecules”,which has many merits such as easy access to reconstruction project,rapid reaction rate and good pollutant removal effect,has been widely used.But the high cost of ozone hinders wider application of this technology.Nowadays,most of the commercial ozone generators use dielectric barrier discharge.Surface dielectric barrier discharge?SDBD?is a new arrangement of dielectric barrier discharge.Surface dielectric barrier discharge,which can produce a relatively high reactive volume near the dielectric layer due to the strong normal electric field generated by putting a counter polarity electrode on the other side of the dielectric sheet,is a very hopeful way for many applications.Therefore,SDBD can promote the plasma chemical reaction process,which is considered to be a very promising way to increase ozone yield.Temperature and flow pattern are two very important parameters in the surface dielectric barrier discharge process.They can influence the chemical reaction rate,electric field distribution and dissociation rate during the discharge process.However,to the best of our knowledge,there is no comprehensive study about the temperature distribution and the effect of flow patterns on ozone genetation in surface dielectric barrier discharge.In this paper,the temperature distribution in surface dielectric barrier discharge reactor is studied.Based on this,both in air and oxygen source,the effect of the flow patterns on ozone generation characteristics in surface dielectric barrier discharge is studied.The study of temperature distribution in the surface dielectric barrier discharge shows that the gas temperature?T_g?is significantly lower than the temperature?T_p?of the reactive plasma region in the surface dielectric barrier discharge.The temperature of the electrode?T_e?is almost the same as the temperature?T_p?.The temperature in the surface dielectric barrier discharge increases continuously until it reaches a steady state.T_p,T_e,and T_g all follow a first-order model.The temperature of the forepart and flanks of the surface dielectric barrier discharge reactor is higher than the central part of the reactor.The flow rate has little effect on the temperature of the plasma reactive region,and the impedance characteristic is more stable in the surface dielectric barrier discharge than that in the volume dielectric barrier discharge.A small increase in temperature?from 26?to 43.9??results in a large drop in ozone concentration?from1.96 g/m³ to 1.50 g/m³?.Studies in oxygen sources show that ozone yield can be improved by these three ways:?1?Increasing the uniformity of gas flow in a surface dielectric barrier discharge reactor?2?Distributing gas flow rate according to the plasma reaction intensity in each part of surface dielectric barrier discharge reactor,matching the flow rate with the intensity of plasma reaction.?3?Adding disturbances to the gas flow,destroying the gas flow boundary layerIn SDBD reactor,ozone production in lateral flow is significantly higher than that in vertical flow parallel to the electrode.When input energy is higher,the optimized flow pattern can increase the ozone yield and concentration more than when the input energy is lower.In surface dielectric barrier discharge,when the flow rate exceeds“critical flow rate”,the ozone yield does not vary with the flow rate.And as the voltage increases,this“critical flow rate”also increases.Studies in air sources have shown that an increase in flow uniformity can increase the ozone yield,but different from the case in oxygen source,adding a transversal flow or employing transversal flow perpendicular to the electrode cannot increase the ozone yield.