Patent ID: 8109079

Claim:
An apparatus for controlling ammonia slip from a selective catalytic reduction (SCR) catalyst in exhaust receiving communication with an exhaust gas stream produced by an engine system, the exhaust gas stream flowing from an engine of the engine system to a tailpipe of the engine system, 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; an ammonia target module configured to determine an ammonia addition requirement, the ammonia addition requirement comprising an amount of ammonia added to the exhaust gas stream to achieve the NO x reduction requirement; a reductant target module configured to determine a reductant injection requirement, the reductant injection requirement comprising an amount of reductant added to the exhaust gas stream to achieve the ammonia addition requirement; a reductant modifier module configured to determine a reductant modifier requirement, the reductant target module being further configured to adjust the amount of reductant added to the exhaust gas stream in response to the reductant modifier requirement; and an ammonia oxidation (AMOX) conversion module configured to determine a conversion capability of an AMOX catalyst in exhaust receiving communication with the SCR catalyst; wherein the reductant modifier module is communicable in data receiving communication with the AMOX conversion module to receive the conversion capability of the AMOX catalyst, the reductant modifier requirement being based at least partially on the conversion capability of the AMOX catalyst.