Experimental Study On Simultaneous Desulfurization And Denitrification By UV/H₂O₂ Through A Pre-oxidation Gas-phase-likeness Method

SO₂ and NO_x discharged by coal-fired power plant are main reasons for the production of haze. At present, the major technologies for desulfurization and denitrification are wet flue gas desulfurization system and selective catalytic reduction system. Although the mode of series stage treatment process can meet the emission standards, we should face to the problem of complicated systems、unstable operation、high costs、difficult disposal of waste catalyst and the NH3 escape. Therefore, simultaneous desulfurization and denitrification technology become a hot issue of multi-pollutants control.Considering the defects of the traditional UV /H₂O₂ reaction system and the basis of the previous studies on pre-oxidation by research group, this article firstly proposed a method for simultaneous desulfurization and denitrification by UV/H₂O₂. The features of this system is the oxidant vaporization process. Before ultraviolet catalyzing reaction, we set a self-made nebulizer which boiled the liquid oxidant and made it vaporized into the state of steam instantly. The flue gas mixed with steam oxidation agent entered the ultraviolet catalyzing reaction to oxidize NO. The final oxidation product was absorbed by HA-Na solution.Several influencing factors were investigated in this article, such as concentration and pH of hydrogen peroxide solution, nebulizer temperature, reaction temperature, UV wavelength and light energy intensity, then we find the optimal experimental conditions. Results of simultaneous desulfurization and denitrification experiment show that the SO₂ removal mainly depended on the absorption by HA-Na. which can contribute removal efficiency of over 98% for SO₂ without the any other oxidation. Otherwise, under 4L/min simulated flue gas, nearly 100% for SO₂、86.2% for NO were obtained in the process of pre-oxidation combining with post-absorption in this conditions: hydrogen peroxide solution concentration of 15% and pH of 5、addition rate of 200μL/min; the reactor temperature of 363K; nebulizer temperature of 403K; ultraviolet light wavelength of 254 nm and energy density of 80μW/cm3. We also explored the performance in different flue gas parameters. From the phenomena, it could be concluded that SO₂ concentration would be good to denitrification in a certain concentration, and inhibit if over range; O2 concentration had some positive impact; With NO concentration increasing, the NO removal efficiency went up first and then down. In addition, this article analyzed the result of characterization of the product and revealed the reaction mechanism for simultaneous desulfurization and denitrification by UV/H₂O₂ through a pre-oxidation gas-phase-likeness.