nitrogen oxides emerge during the combustion of waste or inside a diesel engine. This oxides are harmful for the ozon layer. With ammonia (NH3) and a catalyst it is possible to reduce the nitrogen oxides.
A chemical reaction can be:
4NO + 4NH3 + O2 --> 4N2 + 6H2O
2NO2 + 4NH3 + O2 --> 3N2 + 6H2O
The better the inflow of the catalyst the higher the efficiency of the reaction. A good inflow means a homogenous velocity- and ammonia concentarion field in front of the catalyst. Typical values:
Ammonia concentration: +/- 10%
Velocity mean deviation: + / - 15%
To reach this tolerances the implementation of baffle plates, static mixers etc. are necessary. With cfd the implementation/adjustment is economiclal compared to building a prototype.
The pictures below are showing the evaporation of ammonia and the Streamlines inside the duct.