Study On Mercury Oxidize By Non-thermal Plasma Of Dielectric Barrier Discharge

China's coal-rich and oil-poor energy structure determines that the main way of power generation is burning coal.But a large number of coal used in power generation causes huge pollution.Among these pollutions,mercury pollution is one of the outstanding problems.As a new way of mercury removal,mercury oxidize by non-thermal plasma has the advantages of high efficiency,without residue and secondary pollution.In this paper,the mechanism of plasma mercury removal is studied in the laboratory by dielectric barrier discharge.Influences of the structure of the reactor,the gas characteristics and different gases compositions are mainly studied.The effect of the structure of the reactor on the mercury removal efficiency was studied.It was found that the oxidation efficiency of mercury was about 2%-8% higher than that of the anode when the internal electrode was used as cathode.This is because when the internal electrode as a cathode,the cathode surface has the largest electric field strength.And the breakdown voltage at this time is the lowest.The longer the effective discharge time in a cycle,the higher the efficiency of mercury oxidation.The mercury removal efficiency of the internal electrode is higher than that of using the fluorescent tube.When the input voltage is more than 4k V,the oxidation efficiency of threaded tube is about 20% higher than the oxidation efficiency of fluorescent tube.This is due to that the helical tube facilitates the discharge of the tip and can produce more reactive groups to react with the mercury.The gas flow rate in the reactor also has a significant effect on the oxidation efficiency of mercury.When the gas flow rate from 1L / min down to 7L / min,the oxidation efficiency of mercury decreases from 85% to 50%.The oxidation efficiency decreases 35%.This is because the higher the gas flow rate,the shorter the residence time of the gas in the reactor and the lower the oxidation efficiency of the mercury.However,the concentration of Hg has no significant effect on Hg oxidation.Because the Hg content is too small for the active group content and therefore does not substantially affect the overall chemical equilibrium.After changing the Hg concentration,Hg O and Hg concentrations remain at the same rate,so that the rate of oxidation of mercury is essentially unchanged.It is found that oxygen has a significant effect on the oxidation of mercur y.When the input voltage is 15 k V and the oxygen content is 10%,the oxidation efficiency of mercury is only 55%.When the oxygen content increases to 30%,the mercury oxidation efficiency reaches 78% and the oxidation efficiency increases 23%.Because the higher the oxygen concentration,the more active substances generated,and the corresponding the higher the efficiency of mercury oxidation.Sulfur dioxide has an inhibitory effect on the oxidation of mercury.When the SO₂ concentration reached 1500 ppm,the oxidation efficiency of mercury is 30% lower than that without SO₂.This is because sulfur dioxide consumes the reactive groups in the reactor.Nitric oxide also consumes reactive groups in the reactor,thus inhibiting the oxidation of mercury.When the NO concentration reaches 1500 ppm,the oxidation efficiency of mercury is 58% lower than that without NO.NO₂ has no significant effect on the oxidation of mercury,since nitrogen dioxide reacts with the reactive groups in the reactor,but the generated nitrogen oxides have a strong oxidizing ability to mercury.In the air atmosphere,steam has an inhibitory effect on mercury oxidation.Moreover,it is found that the oxida tion efficiency of mercury is still very high even when the oxygen content is only about 10 pp m.When the input voltage is 15 k V,the oxidation efficiency of mercury can reach 42.62 %.Argon does not react with mercury,but argon gas can stabilize the gas discharge,reducing the thermal conductivity of the gas.So that it can improve the oxidation efficiency of mercury.The experimental results show that the oxidation efficiency of mercury is up to 61.66% when the concentration of oxygen reaches 50%,while the content level of oxygen is only ppm.