Experimental Investigation On Denitration Of Coal-fired Flue Gas By NO Oxidation Combining Wet Absorption

The atmospheric pollution problem caused by coal combustion has been received as a major concern.The NO_x pollutants in air mainly come from the emission of coal-fired flue gas.China has published a more strict emissions standard of NO_x,so we should control the emission of coal-fired flue gas.At present,wet denitrification technology is adopted for coal-fired flue gas,which has the advantages of low investment operation cost and low pollution,and it has important practical significance for NO_x removal.Therefore,this paper mainly studied two wet denitrification methods:gas phase and liquid phase oxidation denitrification,and the main results were as follows:Firstly,O₂ was used as an oxidant for flue gas denitrification.The effects of NO inlet concentration,flue gas temperature,O₂ concentration and SO₂ inlet concentration on denitration efficiency were studied.The optimum experimental conditions were gas flow rate 1 L·min^-1,NO inlet concentration 896 ppm,O₂ concentration 50%,flue gas temperature 25°C,and SO₂ had no effect,and the denitration efficiency was 60.10%.Under the optimal experimental conditions,the gas component of oxygen oxidation of NO was NO₂ by an infrared spectrometer.Secondly,H₂O₂ was used as an oxidant for flue gas denitrification.The effects of NO inlet concentration,H₂O₂ solution concentration,H₂O₂ solution temperature,H₂O₂ solution pH and O₂ concentration on denitration efficiency were studied.When H₂O₂ is used as the oxidant,the optimum experimental conditions were gas flow rate 1 L·min^-1,NO inlet concentration 300 ppm,the H₂O₂ solution concentration 5%,H₂O₂ solution temperature45°C,the pH 8,O₂ concentration 6%,reaction time 40 s and the denitration efficiency was52.37%.Under the optimal experimental conditions,the liquid phase product was NO₃^-by liquid chromatography,and the concentration was 12.21 mg/L.Finally,the reaction gas was absorbed into a sodium sulfite solution.The absorption reaction products were characterized and analyzed by XRD and FTIR.The results showed that the gas products after H₂O₂oxidation of NO were NO₂ or higher NO_x.Finally,Fenton was used as an oxidant for flue gas denitrification.The effects of NO inlet concentration,Fe²⁺to H₂O₂ molar ratio,Fenton solution temperature,Fenton solution pH and O₂ concentration on denitration efficiency were studied.When Fenton was used as the oxidant,the optimum experimental conditions were gas flow rate 1 L·min^-1,NO inlet concentration 715 ppm,Fe²⁺to H₂O₂ molar ratio 0.003,Fenton solution temperature 50°C,the Fenton solution pH 3,the O₂ concentration 4%,and the denitration efficiency was74.00%.Under the optimal experimental conditions,the liquid phase product was NO₃^-and NO₂^-by liquid chromatography,and the concentration was 16.20 mg/L and 17.95 mg/L,respectively.Finally,the reaction gas was absorbed into a sodium sulfite solution.The absorption reaction products were characterized and analyzed by XRD and FTIR.The results showed that the gas products after Fenton oxidation of NO were NO₂ or higher NO_x.Compared with O₂ and H₂O₂ solutions,Fenton solution could be used as an excellent oxidant in wet denitrification technology.Its advantages were short reaction time and high denitrification efficiency.