Patent attributes
Various embodiments of an apparatus, system, and method are disclosed for reducing NOx emissions on an SCR catalyst. For example, according to one representative embodiment, an apparatus for reducing NOx emissions in an engine exhaust includes a NOx reduction target module that is operable to determine a NOx reduction requirement that includes an amount of NOx in the exhaust gas stream to be reduced on a selective catalytic reduction (SCR) catalyst. The apparatus also includes an ammonia target module that is operable to determine an ammonia addition requirement that includes an amount of ammonia added to the exhaust gas stream to achieve the NOx reduction requirement. The apparatus also includes a reductant target module that has a hydrolysis module and an inverse hydrolysis module. The hydrolysis module is operable to determine a predicted amount of ammonia and isocyanic acid entering the SCR catalyst. The inverse hydrolysis module is operable to determine a reductant injection requirement based at least partially on the predicted amount of ammonia and isocyanic acid entering the SCR catalyst.
