Research On Oxidation Of Mercury With Non-thermal Plasma Coupled With A Wet Process

Mercury is one of hazardous trace elements in coal,because of its highly toxic,highly volatile and cumulative in the food chain,has become a global circulation contamination element caused widespread concern in the international community.To address this problem,non-thermal plasma(NTP)has been proposed,which can remove NO,SO2 and trace elements simultaneously.The oxidation of gas-phase elemental mercury(Hg0)by non-thermal plasma coupled with a wet process has been studied.A dielectric barrier discharge(DBD)was used to produce non-thermal plasma.Simulated flue gas was prepared by direct mixing of N2,O2,NO and SO2 in a gas mixing chamber.The simulated gas was made to pass through the DBD reactor and the bubble reactor in tandem.Effects of oxygen content,supplied voltage,gas temperature,wet process residence time and flue gas composition on Hg0 oxidation were investigated using a dielectric barrier discharge(DBD)reactor.The main contents are as follows:Results indicate that both O and O3 generated by O2 during the discharge process contribute to the oxidation of Hg0.The increase of O2 content improves the Hg oxidation efficiency.The 97% of Hg oxidation efficiency was obtained when the O2 content was 30%.It is noted that the Hg oxidation efficiency declines when the supplied voltage is too high,there was an optimal voltage level for Hg0 oxidation.High temperatures promote oxidation of Hg0.The main reason for this is that the high temperature increases the generation of O atoms and the reaction rate of O3 with Hg0.Compared with the NTP process only,the Hg oxidation efficiency increases from 43% to 82% after adding a wet process when the supplied voltage was 8kV at room temperature.The active substance in this system is excessive,and the Hg oxidation efficiency increases with an increasing residence time.The flue gas composition has an effect on the oxidation of mercury by DBD combined with wet process.The presence of NO remarkably hindered mercury oxidation due to competitive consumption of O3.With the addition of 750 ppm of NO,only about 12% Hg oxidation efficiency was obtained.While SO2 was found to enhance oxidation of Hg0,because of the positive effect of SO3 generated in the NTP environment.CO2 can slightly inhibit the oxidation of mercury by NTP.But CO2 can stabilize the discharge,which can weaken the negative effect of high supplied voltage discharge.