Patent ID: 8904760

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 hydrocarbon selective catalytic reduction catalyst (HC-SCR) in direct fluid communication with the diesel oxidation catalyst through a first conduit that extends directly from the diesel oxidation catalyst to the HC-SCR to receive the exhaust gas flow therefrom; a two-way catalyst in direct fluid communication with the HC-SCR through a second conduit that extends directly from the HC-SCR to the two-way catalyst to receive the exhaust gas flow therefrom, the two-way catalyst comprising a urea selective catalytic reduction (two-way) catalyst and a diesel particulate filter (DPF); 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, wherein the diesel oxidation catalyst, HC-SCR and two-way catalyst are the only catalyst devices used in the exhaust gas treatment system; a second injection device that is configured to inject urea or ammonia, or a combination thereof, into the exhaust gas flow between the HC-SCR and the two-way catalyst; and a controller configured to periodically reduce the reliance on the HC-SCR by the use of the two-way catalyst to balance NOx conversion load of the exhaust gas treatment system.