SCR - Selective Catalytic Reduction

Selective Catalytic Reduction (SCR) is the most effective way to eliminate nitrogen oxides by converting them in to inoffensive compounds like nitrogen (N2) and water (H2O).

Unfortunately the required chemical reaction does not happen spontaneously in the contaminated exhaust gas. Two more actors are needed to render the transformation possible: Ammonia and the catalyst.

If ammonia (NH3) is added to the NOx and Oxygen (O2) which are already present in the exhaust gas, the atoms of this three reaction partners will be rearranged to form new safe molecules.

In the presence of the catalyst these reactions start to happen already at temperatures above 250°C.