Patent ID: 8375700

Claim:
A method of evaluating an ammonia conversion efficiency of an ammonia oxidation (AMOX) catalyst for reducing ammonia and hydrocarbons present in an exhaust gas stream, the AMOX associated with an exhaust gas after-treatment system having a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen (NO X ) present in the exhaust gas stream and a dosing system for introducing a reductant into the exhaust gas stream for reacting with the NO X in the presence of the SCR catalyst, the AMOX catalyst arranged downstream of the SCR catalyst, the method comprising the steps of: a) introducing the reductant into the exhaust gas stream at a first dosing rate per original NO X reduction requirement; b) introducing the reductant into the exhaust gas stream at a second dosing rate sufficient to cause ammonia in the exhaust gas stream to slip the SCR catalyst; c) determining a first ammonia concentration rate of the exhaust gas stream at a location downstream of the SCR catalyst and upstream of the AMOX catalyst while introducing the reductant at the first dosing rate; d) determining a second ammonia concentration rate of the exhaust gas stream at a location downstream of the AMOX catalyst while introducing the reductant at the first dosing rate; e) determining a third ammonia concentration rate of the exhaust gas stream at a location downstream of the SCR catalyst and upstream of the AMOX catalyst while introducing the reductant at the second dosing rate; f) determining a fourth ammonia concentration rate of the exhaust gas stream at a location downstream of the AMOX catalyst while introducing the reductant at the second dosing rate; and g) determining an ammonia conversion efficiency of the AMOX catalyst based on the determined first, second, third and fourth ammonia concentration rates.