Patent ID: 8256208

Claim:
An apparatus for reducing NO x emissions in an engine exhaust gas stream of an engine system having a selective catalytic reduction (SCR) system with an SCR catalyst positioned downstream of a reductant injector, comprising: a NO x reduction target module configured to determine a NO x reduction requirement, the NO x reduction requirement comprising an amount of NO x in the exhaust gas stream to be reduced on the SCR catalyst; and a reductant module configured to determine the amount of reductant added to the exhaust gas stream to achieve the NO x reduction requirement; wherein the amount of reductant added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst, at least one reductant-to-ammonia conversion characteristic, and an ammonia conversion efficiency of an ammonia oxidation (AMOX) catalyst in exhaust receiving communication with the SCR catalyst.