Research On Micro-discharge Mode And Oxygen Plasma Reaction Efficiency Near Atmosphere

With the help of high frequency excitation strong electric field discharge,the Advanced Oxidation Processes（AOPs）is qualified for the treatment of ballast water and drinking water where the oxygen plasma reactor module is the core component,because water treatment efficiency is directly affected by oxygen plasma reaction efficiency.In practical application,when the intake air volume of the oxygen plasma reactor module does not match the running speed of Venturi,the operating pressure of oxygen plasma reactor module,the pressure in the reactor will be lower（60-100 kPa）or higher than atmospheric pressure（100-150 kPa）,which affects the production of the oxygen active particles,and ultimately affects the water treatment efficiency.In this paper,oxygen active particles reaction efficiency was studied based on self-designed high frequency excited oxygen plasma reactor under the pressure of 60-100 kPa and 100-150 kPa,respectively.The effect of pressure on the micro-discharge state and its discharge mode was analyzed with pin-plate Dielectric Barrier Discharge（DBD）.The results demonstrate that the discharge mode in single micro-discharge is micro-streamer discharge for the first half cycle of the excitation voltage,while for the second half cycle it is micro-glow discharge.The equivalent electric field strength in discharge gap changes with the operating pressure and excitation power,which results in different discharge characteristics and plasma chemical reaction efficiency with different power applied,The equivalent electric field strength is the main factor affecting the reaction efficiency of oxygen active particles in the reactor,which can be changed through adjusting the air pressure and the input power.When the pressure in reactor is lowered,O₂ ionization degree increases,the micro-discharges scale is magnified,and the discharge intensity enhances,the equivalent electric field strength of the discharge gap is enhanced,the ignition voltage of gas is decreased,the number of discharge current pulse per unit time increases,the current pulse amplitude is decreased,the time for the first discharge current to occur is brought forward,the equivalent capacitance of the discharge gap is decreased while the equivalent capacitance of the dielectric layer is increased.For a certain amount of O₂,it requires certain equivalent electric field strength to get the supreme oxygen active particles yield.The production efficiency grows with the increase of the electric field strength when the electric field strength is lower than that strength,when the equivalent electric field strength is higher than that,its yield declines with the increase of electric field strength due to the increasing of reaction heat.In practical application,different excitation power needs to be used according to pressure conditions to get the maximum oxygen active particles production efficiency,so that the reactor can work in the best working condition in relevant water treatment technology.When the reactor operates at normal pressure,the excitation power 250-300 W is suitable,when the pressure is reduced to 60 kPa,the best excitation power is 150 W,when the pressure rises to 150 kPa,the excitation power 400 W is appropriate.