Scr reductant deposit removal

Abstract

An engine exhaust aftertreatment system including a selective catalytic reduction (SCR) system. The SCR system includes a reductant injection system configured to introduce a reductant into a exhaust stream of a engine, a SCR catalysts configured to reduce NOx in the presence of a reductant, and a SCR monitoring system configured to determine temperatures associated with the SCR system. The SCR system also includes a heat source configured to raise the temperature of the exhaust stream and a controller configured to operate the heat source to reach exhaust stream temperatures in the SCR system of at least about 400 degrees Celsius based on the temperature associated with the SCR system.

1 . An engine exhaust aftertreatment system comprising:
 a selective catalytic reduction (SCR) system including:
 a reductant injection system for introducing a reductant into a exhaust stream of a engine; 
 a SCR catalyst configured to reduce NOx in the presence of the reductant; and 
 a SCR monitoring system; 
   a heat source configured to increase the temperature of the exhaust stream; and   a controller operating the heat source to reach a temperature associated with the SCR system of at least about 400 degrees Celsius as determined by the SCR monitoring system.   
     
     
         2 . The engine exhaust aftertreatment system of  claim 1  wherein the controller operates the heat source to reach a temperature associated with the SCR system of at least about 450 degrees Celsius as determined by the SCR monitoring system. 
     
     
         3 . The engine exhaust aftertreatment system of  claim 1  wherein the controller operates the heat source to reach a temperature associated with the SCR system of at least about 450 degrees Celsius for at least about 15 minutes as determined by the SCR monitoring system. 
     
     
         4 . The engine exhaust aftertreatment system of  claim 1  wherein the controller operates the heat source to reach a temperature associated with the SCR system of at least about 650 degrees Celsius as determined by the SCR monitoring system. 
     
     
         5 . The engine exhaust aftertreatment system of  claim 1  wherein the controller operates the heat source to reach a temperature associated with the SCR system of at least about 650 degrees Celsius for at least about 5 minutes as determined by the SCR monitoring system. 
     
     
         6 . The engine exhaust aftertreatment system of  claim 1  wherein the heat source is a burner. 
     
     
         7 . The engine exhaust aftertreatment system of  claim 1  further including a diesel particulate filter upstream of the SCR system in the exhaust stream, wherein the heat source is upstream of the diesel particulate filter in the exhaust stream. 
     
     
         8 . The engine exhaust aftertreatment system of  claim 7  wherein the operation of the heat source by the controller coincides with a regeneration of the diesel particulate filter. 
     
     
         9 . The engine exhaust aftertreatment system of  claim 1  wherein the controller activates the operation of the heat source based on parameters measured by the SCR monitoring system. 
     
     
         10 . The engine exhaust aftertreatment system of  claim 1  wherein the controller activates the operation of the heat source based on an elapsed period of time. 
     
     
         11 . The engine exhaust aftertreatment system of  claim 1  wherein during the operation of the heat source, the controller at least partially suspends the introduction of the reductant by the reductant injection system. 
     
     
         12 . The engine exhaust aftertreatment system of  claim 1  wherein following the operation of the heat source, the controller assigns a value of about zero for an amount of reductant stored in the SCR catalyst for control of the reductant injection system. 
     
     
         13 . The engine exhaust aftertreatment system of  claim 1  wherein following the operation of the heat source and during an engine idle condition, the controller orders the introduction of reductant by the reductant injection system. 
     
     
         14 . A method for removing deposits from a selective catalytic reduction (SCR) system comprising:
 determining temperatures associated with the SCR system;   activating a heat source to increase exhaust stream temperatures to reach temperatures in the SCR system of at least about 400 degrees Celsius; and   controlling the heat source based on temperatures in the SCR system.   
     
     
         15 . The method of  claim 14  wherein the heat source is activated to reach temperatures in the SCR system of at least about 450 degrees for at least about 15 minutes. 
     
     
         16 . The method of  claim 14  wherein the heat source is activated to reach temperatures in the SCR system of at least about 650 degrees. 
     
     
         17 . The method of  claim 14  wherein the heat source is activated to reach temperatures in the SCR system of at least about 650 degrees for at least about 5 minutes. 
     
     
         18 . The method of  claim 14  further including at least partially suspending an introduction of a reductant in the SCR system. 
     
     
         19 . The method of  claim 14  further including assigning a value of about zero for an amount of reductant stored in a SCR catalyst for control of a reductant injection system in the SCR system. 
     
     
         20 . A selective catalytic reduction (SCR) system comprising:
 an injector configured to introduce a reductant into a exhaust stream of a engine;   a SCR catalyst configured to reduce NOx in the presence of the reductant; and   an injector heater associated with the injector and configured to prevent or remove deposits.