Integrated method for controlling diesel engine emissions in CRT-LNT system

A method of reducing the amount of NOx and carbonaceous particulate matter in exhaust from an internal combustion engine, said NOx having nitric oxide as one component thereof, the method comprising:

• receiving the exhaust into a first stage, the first stage having a NOx oxidation catalyst adapted to oxidize the nitric oxide to nitrogen dioxide and discharge a gaseous stream containing reduced exhaust;
• positioning a second stage in fluid communication with said first stage and adapted to receive said gaseous stream from said first stage, said second stage having a carbon trap adapted to store carbonaceous particulate material contained in the gaseous stream, to reduce a portion of the nitrogen dioxide contained in the gaseous stream, to oxidize the carbon component of the carbonaceous particulate matter contained in the gaseous stream, and to discharge a gaseous stream containing at least nitrogen, carbon dioxide, and any residual nitrogen dioxide;
• interposing a bypass valve between the engine and the first stage, operable to bypass a portion of the exhaust around the first stage and into the second stage;
• positioning a third stage in fluid communication with said second stage and adapted to receive said gaseous stream from said second stage, said third stage having a lean NOx trap adapted to store nitrogen dioxide discharged from said second stage and to reduce at least a portion of the nitrogen dioxide by reaction with the carbonaceous particulate matter and to oxidize at least a portion of the carbonaceous particulate matter;
• sensing when regeneration of the third stage is to be performed;
• and
• bypassing at least a portion of the exhaust around the first stage in response to the sensing step.