Experimental Study On SCR Denitrification Of Oxy-fuel Combustion Flue Gas

Oxy-fuel combustion technology not only can enrich CO₂,but also reduce NO_x emissions unit weight of fuel.But in order to use the CO₂ more safety,and make the flue gas meet the higher level of nitrogen oxide emission standard at the same time,it is necessary to have a gas denitration process in the oxygen-enriched combustion flue gas.This paper studies the influences of different atmosphere on the V₂O₅-WO₃/TiO₂ catalyst activity,and discuss effects of the atmosphere on the surface reactions through some characterization experiments.The catalytic activity performance experiments show that CO₂ only has little effect on the catalyst activity.And with the increase of CO₂ concentration,the efficiency of denitrification does not change regularly.The water vapor inhibits the efficiency of catalyst obviously.With the increase of water vapor concentration,the inhibitory effect is more significant.When adding CO₂ and water vapor at the same time,the denitrification efficiency is a linear superposition of CO₂ and water vapor inhibition.According to the results of XRD and BET,we can see that the physical structure characteristics of catalysts does not change obviously before and after the reaction.The XPS data shows that the valence state of the active sites on the catalysts has changed after the reaction in different conditions.When the water vapor is simulated,the content of V³⁺on the catalysts surface increase obviously.The lattice oxygen and the content of W⁶⁺decrease at the same time.It shows that CO₂ and water vapor can affect the distribution of active substances on the catalyst surface and the existence of the valence state,then inhibit the catalysts activity.In order to investigate the effect of CO₂ and water vapor on SCR reaction,the NH₃-TPD is used to study desorption amount and intensity of NH₃ after adsorbing NH₃ in the CO₂ and water vapor atmosphere.It shows that when NH₃ was adsorbed under CO₂condition,desorption peak of NH₃ was broadened,but the desorption amount is less than under Ar condition.When water vapor is in the adsorption condition,desorption amount increase with the increase of water vapor concentration,and desorption peak shifts to higher temperature.That means water vapor makes more acid sites on the catalysts surface.The TPSR experiment under different adsorption of NH₃ conditions has carried out,and it shows that the NH₃ adsorbed on the catalysts surface only partially involves in the SCR reaction when adsorbed in the water vapor condition.The adsorption of water vapor on catalysts surface will occupy the active site,so NH₃ can not be activated effectively.The catalytic efficiency decreased finally.