Patent ID: 8505279

Claim:
An exhaust gas treatment system for a diesel engine, comprising: a diesel oxidation catalyst (DOC) in fluid communication with the diesel engine to receive an exhaust gas flow therefrom, the DOC disposed in a DOC housing; a hydrocarbon injection device located between the engine and the DOC that is configured to inject a hydrocarbon, CO, or H 2 material, or combination thereof, into the exhaust gas flow; a urea selective catalytic reduction (U-SCR) catalyst in fluid communication with the DOC to receive the exhaust gas flow therefrom, the U-SCR catalyst disposed in a U-SCR catalyst housing a second injection device that is configured to inject urea or ammonia, or a combination thereof, into the exhaust gas flow between the diesel engine and the U-SCR; a four-way catalyst in fluid communication with the U-SCR catalyst to receive the exhaust gas flow therefrom, the four-way catalyst comprising a monolithic substrate having a plurality of porous cell walls that incorporates a lean nitrogen oxide (NO X )Atrap disposed on the porous cell walls and a diesel particulate filter; and a controller that is configured to control operation of the exhaust gas aftertreatment system and periodic and selective injection of the hydrocarbon, CO or H 2 material, or combination thereof, using the hydrocarbon injection device, and periodic and selective injection of the urea or ammonia, or combination thereof using the second injection device, and determine an amount of NO x in the exhaust gas flow, the controller configured to operate in a first mode to minimize consumption of the urea or ammonia, or a combination thereof, and minimize NO X conversion in the U-SCR catalyst or in a second mode to minimize consumption of the hydrocarbon, CO or H 2 material, or combination thereof, and minimize NO X conversion in the four-way catalyst.