SCR De-NOx Activity Study And Catalyst Characterization With Modified Fly Ash Catalyst

Selective Catalytic Reduction (SCR) de-NOx technology is the mainNOx control method from stationary resource. SCR research focuses oncatalytic chemistry and engineering application. In the search, study oncatalytic character with some kind of catalyst is the key. SCR catalyst whichusing moldified fly ash as catalyst support had been inferred and the studycontinued with the modified fly ash catalyst in the fields of catalyticcharacter and catalyst engineering application research.Four types of SCR catalysts were prepared, CuO/moldified fly ash(FA),CuO/modified fly ash-γ -Al2O3, CuO(Fe2O3)/Al2O3 /cordierite honeycombceramics catalyst, and V2O5-WO3/TiO2 catalyst. The de-NOx activities of thefour types of SCR catalysts were studied in one or two different conditions.One was pure mixed gases condition using piston-flow tubular fixed reactorsystem, and the other was real flue gas condition using pilot plant fixed bedreactor system.The work studied the contribution of some factors to SCR de-NOx activities.The factors included catalysts preparing method and preparing parameters, activeelements content, reaction space velocity (SV), existence of alkali metal, et al. InSCR reaction with modified fly ash catalyst, the feature of NO2 formation was alsodiscussed. At last, SCR de-NOx activities of the different catalysts with temperaturechanging were compared and discussed. Then improved method of preparing andmolding was designed. Some other questions were also involved, specific surfacearea and pore distribution changing in the course of molding and adding activeelement onto catalyst support, catalyst component changing after reacting in fluegas.The experiments showed that high de-NOx activity (higher than 90%)could be acquired with modified fly ash catalyst in pure mixed gasescondition. The activity was sensitive to temperature and space velocity. ForCuO/modified fly ash-γ-Al2O3 catalyst, the available temperature window ofde-NOx activity was extended and the activity was higher than CuO/modified fly ashcatalyst and CuO/Al2O3 catalyst. The presence of alkali metal element Na, whichwas put into the mixture before it was molded, could reduce SCR activity. So thealkali metal should be washed out after molding. Formation of NO2 was related withsome factors in high temperature (especially higher than 350℃), these factorsconcluded SCR catalyst support features, the presence of alkali metal element andthe content of active elements. The CuO/modified fly ash-γ-Al2O3 tube catalystwas also sensitive with space velocity. Determinate de-NOx activity was obtained influe gas experiment with tube catalyst.The highest SCR activity could be obtained using V2O5-WO3/TiO2 catalyst. Atlast, the improved preparing method of molding and loading was discussed withmodified fly ash catalyst.