| Nitrogen oxides(NOx)are one of the main three pollutants emitted by coal-fired power plants,which are against human wellbeing and ecological surroundings under certain circumstances.Selective catalytic reduction(SCR),whose key falls to catalysts’share,is the most popular method to remove NOx from flue gas in the world.As of now,V2O5-WO3(MoO3)/TiO2 has obtained the favor of most global users.The existing SCR denitration reactor is usually arranged between the coal economizer and the air preheater.The impurities such as sulfur dioxide and fly ash in the flue gas will have adverse effects on the denitration effect and catalyst life expectancy.The reactor of low-temperature SCR flue gas denitration technology is arranged behind the desulfurization device,which avoids many problems such as equipment failure and catalyst poisoning.It is an ideal flue gas denitration technology,and the key to implement this technology is the development and application of low-temperature SCR denitration catalyst.According to the recent researches,Mn-based catalyst has a bright future of application,but efforts must be made to enhance its low-temperature denitration and sulfur resistance abilities.In this paper,the low-temperature denitration and sulfur resistance ability of a series of Mn/TiO2 and Fe-Mn/TiO2 catalysts which were prepared under various conditions were studied in order to select their best conditions of preparation and application.In the meantime,the physicochemical properties of Mn/TiO2 and Fe-Mn/TiO2 were elaborated by N2 adsorption and desorption,XRD,SEM,XPS and NH3-TPD.In this paper,a series of Mn/TiO2 catalysts were prepared by incipient wetness impregnation method,and the best preparation and application conditions of the catalysts were explored.The experimental results showed that the optimum preparation condition was 15%of Mn mass percentage and 450℃ of calcination temperature,and the optimum application condition was 30,000 h-1 of gas hourly space velocity,2%of oxygen concentration and 1:1 of ratio of ammonia to nitrogen.Under these conditions,the catalyst showed the best denitration performance.When the test temperature was 240℃,the NO removal rate could reach 87.5%.In this paper,a series of Fe-Mn/TiO2 catalysts were prepared by incipient wetness impregnation method,and the best preparation and application conditions of the catalysts were explored.The experimental results showed that the optimum preparation condition was 15%of Fe mass percentage,15%of Mn mass percentage and 450℃ of calcination temperature,and the optimum application condition was 30,000 h-1 of gas hourly space velocity,5%of oxygen concentration and 1:1 of ratio of ammonia to nitrogen.Under these conditions,the catalyst showed the best denitration performance.When the test temperature was 240℃,the NO removal rate could reach 100%.NOx concentration in flue gas could meet national standard regarding coal-fired power plant emission by utilizing Fe0.15-Mn0.15/TiO2 during 160～280℃.The characterization results showed that high calcination temperature would change the crystal structure of the catalysts,enhance the agglomeration,and reduce the BET surface area of the catalysts.All of those resulted in a poor denitration performance.On the other hand,Fe doping increased the BET surface area of the catalysts,enhanced the acidity of the catalyst,and increased the content of Mn4+on the catalysts’ surface.The sulfur resistance ability of Fe0.15-Mn0.15/TiO2 and Mn0.15/TiO2 were explored.The test results showed that Fe0.15-Mn0.15/TiO2 catalyst had better SO2 resistance ability.The characterization results showed that ammonium sulfite and manganese sulfate were formed on the surface of the catalysts in the flue gas containing SO2.Those substances covered the surface of the catalysts,thus,reducing the BET surface area of the catalysts,the number of active sites and the content of more active components on the surface of the catalysts,which was an important reason for the decline of the denitration performance of the catalysts. |
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