Integrated system for controlling diesel engine emissions

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 catalyzed soot filter adapted to reduce the carbon content of the exhaust and to discharge exhaust containing at least nitrogen dioxide and reduced carbonaceous particulate matter;
• 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 lean NOx trap adapted to store nitrogen dioxide in the exhaust, to reduce at least a portion of the nitrogen dioxide, 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;
• sensing when regeneration of the first stage is to be performed;
• regenerating the first stage by increasing the exhaust gas temperature;
• wherein regeneration of the first stage occurs without bypass of the first stage;
• sensing when regeneration of the second stage is to be performed regardless whether the step of regenerating the first stage is performed;
• bypassing a portion of the exhaust around the first stage in response to the step of sensing when regeneration of the second stage is to be performed;
• during the bypassing step, regenerating the second stage by performing one or both of the following operations:
• increasing the carbon monoxide in the exhaust from the engine or post-injecting hydrocarbon fuel into the exhaust;
• and
• wherein regeneration of the second stage may occur even if the first stage does not require regeneration.