Effect Of SO₂ Concentration On Performance Of SCR DeNO_x Catalyst In Coal-fired Power Plant

In order to adapt to the increaseingly strict emission standards,coal-fired power plants begin to extensively construct DeNOx projects.NH3 selective catalytic reduction is the mainstream technology of flue gas denitration in coal-fired power plant.SCR catalysts are the core of the flue gas denitration system in coal-fired power plant.At present,the commercial catalysts(V2O5-WO3/TiO2)for this process are highly active within the narrow temperature window of 280?-400?.In order to satisfy the needs of the reactive temperature,denitration reactor is often distributed between the boiler economizer and air preheater,before the dust remover and desulfurization equipment,but this way requires that SCR catalyst can adapt to high sulfur and high fly ash gas environment.V2O5 catalytic reduction of NOx and SO2 oxidation into SO3,SO3 and NH3 reaction with H2O generated ammonium sulfate salt deposition on the catalyst surface easily when the temperature below 280? causing the catalyst surface clogging and fouling,so study the influence of SO2 on catalyst and its denitration system is very urgent.The article selects 18 X 18 hole SCR denitration catalyst from A,B,C power plant,which running 5000h,15000h,23000h and the SO2 concentration in the flue gas is 500?L/L,1500?L/L,and 4000p?L/L respectively.Using a test platform for the catalyst activity detection and taking some instruments to characterize the physical and chemical properties of the catalyst,we test the denitration efficiency and catalytic activity on different operating conditions,including space velocity,NH3 to NOx ratio,reaction temperature,H2O content.Using a*exp(b*x)of Exponential function model and a*exp(-(((x-b))/c)^2)of Gaussian function model provided by cftool fitting toolbox in Matlab software for inactivation curve fitting,we make a conclusion as follows:1.The effect of SO2 on the denitration catalyst has two sides.SO42-can be formed on the surface of the catalyst by SO2 to enhance the acid sites' acidity,thus improve the catalytic activity of TiO2.The competitive adsorption of SO2 and NH3 will reduce activity of catalyst after the NH3 into the flue gas.The specific surface area and pore volume of the catalyst are decreasing at the continuous operation and the rate of descent increases with the advance of SO2 concentration in the flue gas.2.Changing the operating conditions,we compared catalysts with the same SO2 flue gas concentration at different operating times.SO2 concentration for 500?L/L,the denitration efficiency of catalysts with operating time less than 15000h is less than that of the new catalyst;SO2 concentration for 1 500?L/L,the efficiency gap of the catalyst running at different times begins to widen;SO2 concentration for 4000?L/L,the denitration efficiency of catalysts with operating time more than 15000h is obviously lower than that of the new catalyst.3.The activity of denitration catalyst in A power plant declines slowly at the beginning continuous operation and compared to the new catalyst activity decreased by 13.33m/h;In the first two years of the catalyst continuous operation,the activity decreases by 2.9m/h within 8000h.After two years of the catalyst continuous operation,the activity decreases by 7.87m/h in 8000h;The activity of denitration catalyst in B power plant declines gently at the continuous operation and compared to the new catalyst activity decreased by 14.7m/h,the activity decreases by 5m/h within 8000h;The activity of denitration catalyst in C power plant declines sharply at the beginning continuous operation and compared to the new catalyst activity decreased by 16.52m/h;In the first two years of the catalyst continuous operation,the activity decreases by 7.3m/h within 8000h.After two years of the catalyst continuous operation,the activity decreases by 2.83m/h in 8000h.4.The relationship between catalyst activity and running time is exponential.Through the preliminary comparison between the predicted data of the deactivation curve and the measured resultsit,it is found that the prediction result is good and can be used to guide the relevant power plant in the catalyst replacement or the addition of the backup layer.