Adaptive Desulfation Control Algorithm

Abstract

The exhaust from a diesel-fueled internal combustion engine is treated by a lean NO X trap. The maximum temperature used for desulfating the lean NO X trap is kept relatively lower during early life and progressively increased as the trap ages. Designing for adequate late life performance entails excess capacity during early life. The method utilizes the excess capacity available during early life to slow aging of the trap and thereby extend the trap lifetime. The method facilitates meeting durability requirements for diesel-powered vehicles with exhaust aftertreatment.

1 . A method of operating a diesel power generation system in which the exhaust from a diesel-fueled internal combustion engine is treated using a lean NO X  trap, the method comprising:
 operating the engine to produce a lean exhaust comprising NO X  and SO X ;   treating the exhaust using the lean NO X  trap;   determining when to denitrate the lean NO X  trap and denitrating the lean NO X  trap accordingly;   from time-to-time, desulfating the lean NO X  trap by heating the lean NO X  trap to within a desulfating temperature range having an upper limit temperature and exposing the heated lean NO X  trap to rich conditions under which the lean NO X  trap desulfates;   aging the lean NO X  trap through many desulfations; and   in response to the lean NO X  trap's aging, increasing the upper limit temperature.   
     
     
         2 . A diesel power generation adapted, configured, and functional to operate according to the method of  claim 1 . 
     
     
         3 . The method of  claim 1 , wherein:
 heating the lean NO X  trap to within a desulfating temperature range having an upper limit temperature consists of controlling the heating of the lean NO X  trap to bring a characteristic temperature for the lean NO X  trap to a predetermined target value; and   increasing the upper limit temperature consists of increasing the target value.   
     
     
         4 . The method of  claim 1 , wherein:
 the aging takes place over two or more consecutive time intervals, each interval comprising at least 1,000 hours of operating the engine and at least 10 desulfations; and   the highest upper limit temperature used within each interval after the first is at least 5° C. greater than the highest upper limit temperature used within of the preceding interval.   
     
     
         5 . The method of  claim 4 , wherein the highest upper limit temperature used within the last interval is at least 30° C. greater than the highest upper limit temperatures used within the first interval. 
     
     
         6 . The method of  claim 4 , wherein the highest upper limit temperature within the last interval is at least 50° C. greater than the highest upper limit temperature within the first interval. 
     
     
         7 . The method of  claim 4 , wherein there are three or more of the intervals. 
     
     
         8 . The method of  claim 4 , wherein there are five or more of the intervals. 
     
     
         9 . A method of operating a diesel power generation system in which the exhaust from a diesel-fueled internal combustion engine is treated using a lean NO X  trap, the method comprising:
 operating the engine to produce a lean exhaust comprising NO X  and SO X ;   treating the exhaust using the lean NO X  trap;   determining when to denitrate the lean NO X  trap and denitrating the lean NO X  trap accordingly;   from time-to-time, desulfating the lean NO X  trap by heating the lean NO X  trap to a desulfating temperature and providing the heated lean NO X  trap with a reducing environment;   aging the lean NO X  trap through many desulfations; and   compensating for the effects of the aging by increasing the desulfating temperature.   
     
     
         10 . A vehicle comprising a diesel power generation system adapted, configured, and functional to operate according to the method of  claim 9 . 
     
     
         11 . The method of  claim 9 , wherein the increases to the desulfating temperature are made incrementally and progressively over the lifetime of the lean NO X  trap, whereby the lifetime is appreciably extended. 
     
     
         12 . The method of  claim 9 , wherein the desulfating temperature is a main desulfating temperatures and further comprising:
 between the foregoing desulfations, performing mild desulfations that comprise heating the lean NO X  trap to a mild desulfating temperature that is less than the main desulfating temperature and providing the lean NO X  trap at the mild desulfating temperature with a reducing environment.   
     
     
         13 . The method of  claim 12 , wherein the mild desulfating temperature is also increased to compensate for the LNT's aging. 
     
     
         14 . A method of operating a diesel power generation system in which the diesel exhaust is treated using a lean NO X  trap, the method comprising:
 operating an engine to produce a lean exhaust comprising NO X  and SO X ;   treating the exhaust using the lean NO X  trap;   from time-to-time, denitrating the lean NO X  trap;   from time-to-time, desulfating the lean NO X  trap by heating the lean NO X  trap to within a desulfating temperature range having an upper limit temperature and providing the heated lean NO X  trap with reductants;   determining the efficacy of the desulfations; and   in response to the efficacy determination, increasing the upper limit temperature, whereby the upper limit temperature increases as the LNT ages.   
     
     
         15 . A vehicle comprising a diesel power generation system adapted, configured, and functional to operate according to the method of  claim 14 . 
     
     
         16 . The method of  claim 14 , wherein determining the efficacy of the desulfations comprises evaluating NO X  mitigation data collected between desulfations. 
     
     
         17 . The method of  claim 14 , wherein determining the efficacy of a desulfation comprises comparing the performance of the lean NO X  trap after the desulfation to the performance of the lean NO X  trap before the desulfation. 
     
     
         18 . The method of  claim 14 , wherein determining the efficacy of a desulfation comprises determining whether the desulfation brings the lean NO X  trap to a satisfactory level of performance, wherein performance relates to NO X  storage capacity or NO X  trapping efficiency. 
     
     
         19 . The method of  claim 14 , wherein a duration for the desulfations is adapted according to the efficacy determination and the upper limit temperature is not increased unless the duration is at an upper limit. 
     
     
         20 . The method of  claim 14 , wherein a duration for the desulfations is adapted according to the efficacy determination and the upper limit temperature is not increased unless increasing the duration at the current upper limit temperature has failed to satisfactorily increase the efficacy of the desulfations.