Experimental Research On Low Temperature SCR Denitrification Of Oxy-fuel Combustion Flue Gas

At present, the method of the selective catalytic reduction (SCR) with the reductantNH3, is one of the most effective applications of NOXremoval technology. The NOconversion can reach80%-90%with reasonable arrangement and temperature range. Thetraditional SCR device must be installed at the upstream of the desulfurization andparticulate control devices as a result of the restriction of the active temperature of thecatalyst, which can reduce catalyst activity and service life. Therefore, researches on thelow temperature SCR which makes SCR unit be installed at the downstream of thedesulfurization and particulate control devices are of significant practical importance.Five catalysts, Ce/AC, Mn/AC, Mn-Ce/AC, V2O5/AC and V2O5/CNTs, have beenprepared by impregnation method in this paper. On the catalytic activity testing, the effectsof catalysts carrier, active component type and active component capacity on NOconversion have been studied in the atmospheres of CO2and N2respectively. Results showthat, in the research scopes, SCR reactivity of all kinds of catalysts increases at first thendecreases with the increase of active components. The catalyst of Mn-Ce/AC has thehighest SCR reactivity in the atmospheres of CO2and N2respectively. The catalyst whenthe mole ratio of Mn to Ce is2:1has the highest NO conversion in CO2atmosphere, and itsNO conversion reaches to94.0%at250℃. While the catalyst when the mole ratio of Mn toCe is1:1has the highest NO conversion in N2atmosphere whose NO conversion is90.9%at250℃.The influences of space velocity and O2concentration on NO conversion also havebeen studied in this paper. The results show that space velocity has a great influence onSCR reactivity. The NO conversions of all kinds of catalysts reduce with the improvementof space velocity. The NO conversion reduces slowly when space velocity is in the range of3408h-1to6816h-1, while it begins to descent fast when space velocity is greater than6816h-1. O2concentration can also significantly influence the NO conversion. NOconversion of each catalyst is small in the low O2concentration and it rapidly increaseswhen the O2concentration increases from1%to6%. After that, the NO conversion almost no longer changes with the increase of O2concentration, and the NO conversion of eachcatalyst is above65%.The effects of SO2and H2O on NO conversion have been studied in the atmospheresof CO2and N2respectively. The results show that the existence of SO2and H2O restrainsthe SCR activity. And the higher the concentrations of SO2and H2O, the more obviousinhibitory effects.