Exhaust gas purification system

Abstract

The invention relates to an exhaust gas purification system ( 1 ) for exhaust gases from an internal combustion engine, in particular from a diesel engine, said system being arranged in an exhaust tract ( 2 ) which has a primary exhaust gas treatment system ( 22 ) and an inlet line ( 3 ) with a metering device ( 19 ). In order to achieve higher efficiency in nitrogen conversion, it is proposed that the inlet line ( 3 ) together with the metering device ( 19 ) be arranged downstream of the exhaust gas treatment system ( 22 ) and that the inlet line ( 3 ) be divided downstream by the metering device ( 19 ) into two catalyst lines ( 13 ) which lead the exhaust gas stream from the internal combustion engine in each case to a catalyst element ( 6, 7 ), the exhaust gas stream being steerable into the first catalyst element ( 6 ) or the second catalyst element ( 7 ) by means of a control valve ( 14 ).

1 . A system for treating an exhaust gas from an internal combustion engine, comprising:
 a primary exhaust gas treatment system;   a first catalyst coupled downstream of said primary exhaust gas treatment system;   a second catalyst coupled downstream of said primary exhaust gas treatment system; an inlet line connecting said primary exhaust gas aftertreatment system to said first catalyst and said second catalyst, said inlet line having a valve and a reductant metering device; and   a controller adjusting said valve to control an amount of said exhaust gas entering said first catalyst and said second catalyst based on a temperature of said exhaust gas.   
     
     
         2 . The system as claimed in  claim 1 , wherein the engine is a diesel engine. 
     
     
         3 . The system as claimed in  claim 2 , wherein said first catalyst and said second catalyst are SCR catalysts. 
     
     
         4 . The system as claimed in  claim 3 , wherein said reductant metering device injects urea into the exhaust gas stream. 
     
     
         5 . The system as claimed in  claim 4  wherein said controller further controls an amount of said exhaust gas entering said first catalyst and said second catalyst based on a ratio of NH 3  to NOx at said inlet line. 
     
     
         6 . The system as claimed in  claim 5  wherein said controller adjusts said valve such that a major portion of total exhaust gas flow is directed to said first catalyst when said temperature of said exhaust gas is below a first predetermined threshold and an amount of ammonia stored in said first catalyst is above a second predetermined threshold. 
     
     
         7 . The system as claimed in  claim 5  wherein said controller adjusts said valve such that a major portion of total exhaust gas flow is directed to said second catalyst when said temperature of said exhaust gas is above said first predetermined threshold. 
     
     
         8 . The system as claimed in  claim 5  wherein when said temperature of said exhaust gas is below said predetermined threshold and said amount of ammonia stored in said first catalyst is below a second predetermined threshold, said controller adjusts said valve such that a major portion of total exhaust gas flow is directed to said second catalyst; said controller further controls said reductant metering device to allow said amount of ammonia stores in said first catalyst to reach said first predetermined threshold.