A COMPLETE MODEL OF SCR MONOLITH REACTORS FOR THE ANALYSIS OF INTERACTING NOX REDUCTION AND SO2 OXIDATION REACTIONS

A previous one-dimensional model of the SCR monolith reactor has been extended to include the treatment of the undesired SO2 oxidation react ion. A redox rate expression has been fitted to data, which accounts f or the variable order of SO2, the asymptotic zeroth order behavior wit h respect to O-2, the inhibiting effects of water and ammonia and the slight promoting effect of NO. The complete model successfully reprodu ces the interaction between DeNO(x), and SO2 oxidation reactions, as e videnced by the match between the experimental and predicted dependenc es of SO2 conversion on the NH3/NO feed ratio. Applications of the mod el to catalyst design are investigated. The optimal monolithic SCR cat alysts have very thin walls, large fractions of macropores to promote diffusion of NO and NH3, but low specific surface areas to prevent SO2 oxidation. According to a dedicated analysis, under industrial condit ions it is not possible to modify the catalyst morphological propertie s in order to induce an NH3 excess inside the catalyst to inhibit SO2 oxidation.