Modeling Of Selectrive Catalytic Reduction (SCR) For NO Removal Using Monolithic Honeycomb Catalyst

In this study, a monolithic honeycomb catalyst is being used in a SCR reactor rather than pellet catalyst in many conventional gas-solid catalytic processes because the advantages of honeycomb matrix are very low pressure drop, high geometric specific surface area, and resistance to deposition of carbon and dust. The three-dimensional computational fluid dynamics (CFD) simulation for SCR for NO removal in monolithic honeycomb reactor was performed. The mathematical model of monolithic SCR reactor, in which a Rideal-type DeNOx rate equation was incorporated, was established. The calculated results were compared with the experimental data to verify the reliability.Firstly, it was found that the lower gas inlet velocity, higher gas inlet temperature, and higher NH3/NO feed ratio lead to higher NO conversion. The square shape of the monolith channel has a better performance both in NO conversion and pressure drop. The appropriate space length between two catalyst layers under the investigated conditions is about 60 mm, which can result in good NO conversion and gas mixing. Secondly, the heat and mass transfer of selective catalytic reduction using monolithic honeycomb catalyst are investigated because monolithic honeycomb catalysts have been widely used in SCR. This model was proved to be reliable by comparing with experiment data. It is observed that the heat transfer of the pellet catalyst is superior to that of the monolithic honeycomb catalyst by investigating the heat transfer parameter (λer/λg). The comparison of heat and mass transfer with different shapes of the monolith channel is made, which indicates the round and square shape of the monolith channel have a better performance both in heat transfer and mass transfer. The simulation results also show the heat and mass transfer of the coating catalyst are better than that of the extruded catalyst, but the difference is small. Furthermore, the internal diffusion effect is obvious in the monolith honeycomb catalyst when the washcoat thickness is more than 0.1mm.The last, make use of the software FLUENT to simulate the operating parameters of different catalysts coating type. They are the surface reaction catalyst, the porous catalyst and extruded catalyst.