Research On Low Temperature Denitrification Performance Of Mn-Ce/FA-TiO₂ Catalysts Under Oxy-fuel Combustion Flue Gas Atmosphere

Selective catalytic reduction（SCR）is one of the most effective technologies to solve NOx problem of stationary place like boiler.Nowdays,commercial SCR catalysts are easy to lost activity because there are plent of fly ash and SO₂ in the flue gas,which would poison the catalysts.Oxygen enriched combustion technology is benifit to reduce CO₂ emissions and there is a large amount of CO₂ in the flue gas under the condition of oxygen enriched combustion.It is of very significance to study low temperature SCR under CO₂ atmosphere.By the way,fly ash is a kind of solid particle discharged from power plant,which could cause land resources waste and the pollution of soil.In this work,fly ash was used as SCR catalyst supporter and a variety of catalysts were prepared by acetic acid modification,compounding with TiO2 and other other treatment process.The effects of acetic acid modified fly ash and the change of active components on the performance of the catalyst were tested under both N2 and CO2atmospheres.The experimental results proved that denitrification efficiency of each catalyst was improved after modified by acetic acid.At 300℃,under CO₂ atmosphere,Mn and Ce molar ratio of 1:1,the catalyst’s denitrification rate increased from 68.43%to 74.29%.When Mn acted as the active component,with the increase of the temperature of the NO conversion rate rised first then deduced later.Ce acted for the active component,the NO conversion rate increased with the temperature.Mn-Ce molar ratio has a great influence on the denitrification effect of the catalyst.The molar ratio of Mn-Ce 1:1 is better than the other molar ratio,and the catalyst’s NO conversion can reach 84.28%and 74.29%in both atmospheres respectively.Under N₂ and CO₂ atomspheres,the denitrification rate increased with the riasing of TiO2 proportion of the carrier and reached 91.91%and 81.47%when TiO₂ acted as supporter,active component was 8%Mn:Ce=1:1.BET results show that ACFA-20%TiO₂ obtained the minimum specific suface.There is no MnOx and CeOx diffraction peaks which suggests that MnOx and CeOx are highly dispersed on the carriers.SEM results show that the micro structure of fly ash was destroyed and a large number of pore structures are formed on the surface of fly ash after acetic acid modification.At 180℃,330℃,490℃the 8%Mn-Ce（1:1）/ACFA-20%TiO₂catalyst displays three acid sites according to NH3-TPD results.The effects of NH₃:NO,O₂ concentration and space velocity were studied.NO conversion was increased with the rising of NH₃:NO ratio and O₂ concentration in both atmospheres.Under CO₂ atomsphere when the NH₃ to NO tatio is above 1.2 the NO conversion was beyond60%and when O₂ concentration was more than 7%the denitrification rate increased slowly.The denitrification rate decreased with the increasing of space velocity.In the atmosphere of N₂,8%Mn-Ce（1:1）/ACFA-20%TiO₂ deduced about 50%NO conversion compared 16800h^-1space velocity with 4200h^-1.The effect of 200ppm SO₂ and 6%H₂O on the performance of the catalyst were also tested.No matter one of them existence or both existence can inhibit the performance of the catalyst.