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, 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 exhaust;
• positioning a second stage in fluid communication with said first stage and adapted to receive said exhaust from said first stage, said second stage having a carbon trap adapted to store carbonaceous particulate material contained in the exhaust, and to discharge a gaseous stream containing at least nitrogen and carbon 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 upstream the second stage;
• positioning a third stage in fluid communication with said second stage and adapted to receive said exhaust 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;
• sensing when regeneration of the second stage is to be performed;
• regenerating the second stage, wherein regeneration of the second stage occurs without bypass of the first stage;
• sensing when regeneration of the third stage is to be performed regardless whether the step of regenerating the second stage is performed;
• and
• bypassing at least a portion of the exhaust around the first stage in response to the step of sensing when regeneration of the third stage is to be performed;
• during the bypassing step, regenerating the third stage;
• wherein regeneration of the third stage may occur even if the second stage does not require regeneration.