Selective Catalytic Reduction Facts -

Selective catalytic reduction (SCR), advanced emission-control technology for diesel vehicles, helps light, medium and heavy-duty diesel vehicles meet nitrogen oxide (NOx) emission regulations. In a SCR system, Diesel Exhaust Fluid (DEF) is combined with engine exhaust in the catalyst to convert harmful NOx into harmless Nitrogen and water vapor.

Beginning with ultra-low sulfur diesel fuel combusted in an optimized diesel engine, hot engine exhaust flows through the diesel particulate filter and then to the SCR catalyst. DEF is injected into the exhaust stream, then the exhaust and DEF enter the SCR catalyst together where they react to convert NOx to nitrogen and water vapor.

SCR has been used for decades in both marine and large stationary diesel engines and is used with heavy-duty highway vehicles in Europe and now, in North America as well. Test have shown that SCR can reduce NOx emissions by 75% - 90%.