System and method for treating diesel exhaust gases

Abstract

A system for treating diesel exhaust gases includes an engine for producing a diesel exhaust stream, a diesel particulate filter downstream of the engine and adapted to remove particulates from the exhaust stream, a heater upstream of the filter adapted to deliver energy in sufficient amounts to the exhaust stream to cause active regeneration of the filter, and a diesel oxidation catalyst upstream of the heater adapted to cause passive regeneration of the filter when the exhaust stream is above a light-off temperature of the diesel oxidation catalyst. A NOx reduction catalyst can be provided downstream of the heater. Methods for treating diesel exhaust gases are also disclosed.

1 . A system for treating diesel exhaust gases, comprising:
 an engine for producing a diesel exhaust stream;   a diesel particulate filter downstream of the engine and adapted to remove particulates from the exhaust stream;   a heater upstream of the filter adapted to deliver energy in sufficient amounts to the exhaust stream to cause active regeneration of the filter; and   a diesel oxidation catalyst upstream of the heater adapted to cause passive regeneration of the filter when the exhaust stream is above a light-off temperature of the diesel oxidation catalyst.   
     
     
         2 . The system as set forth in  claim 1 , comprising a NOx reduction catalyst downstream of the heater. 
     
     
         3 . The system as set forth in  claim 2 , wherein the NOx reduction catalyst includes a catalyst downstream of the DPF. 
     
     
         4 . The system as set forth in  claim 2 , wherein the heater is adapted to elevate the exhaust stream temperature to a temperature in an optimal range for NOx reduction by the catalyst. 
     
     
         5 . The system as set forth in  claim 2 , comprising a controller for controlling operation of the heater and a temperature sensor for sensing a temperature in the exhaust stream and sending a signal corresponding to the temperature in the exhaust stream to the controller, the controller controlling the heater in response to the temperature signal. 
     
     
         6 . The system as set forth in  claim 1 , comprising an oxidation catalyst coating on the filter. 
     
     
         7 . A system for treating diesel exhaust gases, comprising:
 an engine for producing a diesel exhaust stream;   a diesel particulate filter downstream of the engine and adapted to remove particulates from the exhaust stream;   a heater upstream of the filter adapted to deliver energy to the exhaust stream; and   a NOx reduction catalyst downstream of the heater.   
     
     
         8 . The system as set forth in  claim 7 , comprising an oxidation catalyst coating on the filter. 
     
     
         9 . The system as set forth in  claim 7 , wherein the NOx reduction catalyst includes a catalyst downstream of the DPF. 
     
     
         10 . The system as set forth in  claim 7 , wherein the heater is adapted to elevate the exhaust stream temperature to a temperature in an optimal range for NOx reduction by the NOx reduction catalyst. 
     
     
         11 . The system as set forth in  claim 10 , wherein the heater is adapted to elevate the exhaust stream temperature to a temperature sufficient to cause active regeneration of the filter. 
     
     
         12 . The system as set forth in  claim 11 , comprising a controller for controlling operation of the heater and a temperature sensor for sensing a temperature in the exhaust stream and sending a signal corresponding to the temperature in the exhaust stream to the controller, the controller controlling the heater in response to the temperature signal. 
     
     
         13 . The system as set forth in  claim 10 , comprising a controller for controlling operation of the heater and a temperature sensor for sensing a temperature in the exhaust stream and sending a signal corresponding to the temperature in the exhaust stream to the controller, the controller controlling the heater in response to the temperature signal. 
     
     
         14 . The system as set forth in  claim 7 , comprising a diesel oxidation catalyst upstream of the heater adapted to cause passive regeneration of the filter when the exhaust stream is above a light-off temperature of the diesel oxidation catalyst. 
     
     
         15 . A method for treating diesel exhaust gases, comprising:
 producing a diesel exhaust stream with a diesel engine;   removing particulates from the exhaust stream with a diesel particulate filter downstream of the engine;   periodically delivering energy from a heater to the exhaust stream upstream of the filter in sufficient amounts to cause active regeneration of the filter; and   periodically heating a diesel oxidation catalyst upstream of the heater to a light-off temperature of the diesel oxidation catalyst to cause passive regeneration of the filter.   
     
     
         16 . The method as set forth in  claim 15 , comprising causing NOx reduction with a NOx reduction catalyst downstream of the heater. 
     
     
         17 . The method as set forth in  claim 15 , comprising sensing a temperature in the exhaust stream and sending a signal corresponding to the temperature in the exhaust stream to a controller for controlling operation of the heater, and controlling the heater in response to the temperature signal. 
     
     
         18 . A method for treating diesel exhaust gases, comprising:
 producing a diesel exhaust stream with a diesel engine;   removing particulates from the exhaust stream with a diesel particulate filter downstream of the engine;   causing NOx reduction in the exhaust stream with a NOx reduction catalyst; and   delivering energy from a heater upstream of the NOx reduction catalyst sufficient to raise a temperature of the NOx reduction catalyst to a temperature in an optimal range for NOx reduction by the NOx reduction catalyst.   
     
     
         19 . The method as set forth in  claim 18 , comprising delivering energy from the heater sufficient to elevate the temperature of the exhaust stream to a temperature sufficient to cause active regeneration of the filter. 
     
     
         20 . The method as set forth in  claim 18 , comprising sensing a temperature in the exhaust stream and sending a signal corresponding to the temperature in the exhaust stream to a controller for controlling operation of the heater, and controlling the heater in response to the temperature signal.