Study On The Catalytic Oxidation Of NO In Flue Gas By Ozone Combined Catalyst

The nitrogen oxide in flue gas emitted from coal-fired power plants is one of the main sources of air pollution.Since 2015,the Environmental Protection Bureau has put forward the requirements of ultra-low emission.while there are some problems in the traditional SCR?selective catalytic reduction?technology,such as secondary pollution caused by the escape of ammonia gas.Therefore,we need to develop a new and efficient way of denitration technology.This topic has tried a new way of denitration,using ozone combined with catalyst to catalyze oxidation of NO to remove nitrogen oxides from flue gas.This method does not produce the two pollution problems of ammonia gas escape,and has high oxidation efficiency at low and middle temperature.It has important guiding significance for the new denitrification technology in the future industrial development.The research ideas and methods of this subject are as follows.First,the NO experiment of ozone alone oxidation and the oxidation of NO by the catalyst were carried out separately,then the NO experiment was carried out by the combined ozone with catalyst.The first two groups were used as the reference for the combined oxidation test to analyze the role of ozone and the catalyst in the process of joint removal.The catalysts used in this paper are titanium dioxide as a carrier,and catalysts supporting the corresponding metal oxides of Mn,Ce,Cr,and Co are prepared by impregnation.Under the condition of ozone injection,the effects of different catalysts on the oxidation efficiency of NO under different reaction conditions were investigated by a fixed bed reactor.In the combined oxidation NO experiment,the oxidation activity of MnO_x is the highest,the active window is the most in the four,and the overall oxidation activity of the four catalysts is MnO_x>CoO_x>CrO_x>CeO_x.The Mn based catalyst was optimized by changing the load and calcining temperature.The experiment showed that the activity of 15%MnO_x-TiO₂?400 ^oC?catalyst was the highest.Under the conditions of[O₃]/[NO]=0.7,oxygen content 5%and airspeed 24000 h^-1,the reaction temperature was in the range of 200 ^oC-300^oC,the oxidation rate of the catalyst was above 75%.At last,the influence of reaction temperature,air velocity and O₂ content on the oxidation efficiency of NO was investigated for the better catalyst 15%MnO_x-TiO₂?400 ^oC?,which provided theoretical guidance for the engineering application.In this paper,the physicochemical properties of the catalysts were characterized by means of XRD,BET,H₂-TPR,O₂-TPD,XPS and In Suit-FRITS,and the relationship between the micro properties of different catalysts and the macro reaction efficiency was discussed.The BET specific surface area,average pore diameter,and pore volume of the four catalysts are close to each other,and the specific surface area is about 90 m²/g.and the15%MnO_x-TiO₂?400 ^oC?catalyst has a lower reduction temperature and a stronger oxygen storage capacity.In situ IR characterization showed that the adsorption of NO on the surface of 15%MnO_x-TiO₂?400 ^oC?catalyst would form a nitro peak site and the decomposition of nitro group occurred at high temperature.MnO_x-O₂ was formed by Oxygen chemisorption between MnO_x,then reacts with NO to form an intermediate MnO_x-?NO₂?₂.The intermediate product decomposes into NO₂ at high temperature and completes the NO oxidation process.The above study shows that the oxidation of NO by the ozone combined catalyst can realize the high efficiency oxidation of NO in the middle and low temperature segments,which provide a new path for the removal of nitrogen oxides from the flue gas of the power plant.