Patent ID: 8635855

Claim:
An exhaust gas treatment system for a diesel engine, comprising: a diesel oxidation catalyst in fluid communication with a diesel engine to receive an exhaust gas flow therefrom; a first injection device that is configured to inject a hydrocarbon, CO or H 2 material, or a combination thereof, into the exhaust gas flow between the engine and the diesel oxidation catalyst; a lean nitrogen oxides (NO X ) trap catalyst in fluid communication with the diesel oxidation catalyst to receive the exhaust gas flow therefrom; a two-way catalyst in fluid communication with the lean NO X trap catalyst to receive the exhaust gas flow therefrom, the two-way catalyst comprising a first urea selective catalytic reduction (U-SCR) catalyst and a diesel particulate filter (DPF); and a second injection device that is configured to inject urea or ammonia, or a combination thereof, into the exhaust gas flow between the LNT catalyst and the two-way catalyst; 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 a combination thereof, using the first injection device, and periodic and selective injection of the urea or ammonia, or a 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 two-way 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 lean NO X trap catalyst.