Exhaust gas purification system of an internal combustion engine and method for purifying the exhaust gases thereof

Abstract

An exhaust gas purification system for purifying the exhaust gas of an internal combustion engine, especially an internal combustion engine featuring auto-ignition and/or direct fuel injection, is provided. The system includes at least one oxidation catalytic converter disposed in an exhaust gas duct of the internal combustion engine, at least one device for selective catalytic reduction of the exhaust gases which is installed downstream of the oxidation catalytic converter, and a feed device for feeding reducing agent into the exhaust gas stream upstream of, or in, the device for selective catalytic reduction. A switch-over device is provided for selectively feeding reducing agent into the exhaust gas stream upstream of, or inside, the at least one oxidation catalytic converter. A corresponding method for purifying the exhaust gas of an internal combustion engine is also provided.

1 - 16 . (canceled)  
   
   
       17 . An exhaust gas purification system for purifying an exhaust gas stream of an internal combustion engine, comprising: 
 at least one oxidation catalytic converter provided in an exhaust gas duct of the internal combustion engine;    at least one device for selective catalytic reduction of the exhaust gas stream, the at least one device being provided downstream of the at least one oxidation catalytic converter; and    a feed device for feeding a reducing agent into the exhaust gas stream one of upstream of the at least one device for selective catalytic reduction and in the at least one device for selective catalytic reduction; and    a switch-over device for selectively feeding the reducing agent into the exhaust gas stream one of upstream of the at least one oxidation catalytic converter and in the at least one oxidation catalytic converter.    
   
   
       18 . The exhaust gas purification system as recited in  claim 17 , wherein the switch-over device is a valve.  
   
   
       19 . The exhaust gas purification system as recited in  claim 18 , wherein the switch-over device is a directional control valve.  
   
   
       20 . The exhaust gas purification system as recited in  claim 18 , wherein the switch-over device is a mixing valve.  
   
   
       21 . The exhaust gas purification system as recited in  claim 19 , wherein the switch-over device is temperature-controlled.  
   
   
       22 . The exhaust gas purification system as recited in  claim 20 , wherein the switch-over device is temperature-controlled.  
   
   
       23 . The exhaust gas purification system as recited in  claim 21 , wherein the feed device has a metering device and a nozzle for distributing and atomizing the reducing agent in the exhaust gas stream.  
   
   
       24 . The exhaust gas purification system as recited in  claim 22 , wherein the feed device has a metering device and a nozzle for distributing and atomizing the reducing agent in the exhaust gas stream.  
   
   
       25 . The exhaust gas purification system as recited in  claim 23 , wherein the at least one oxidation catalytic converter is disposed in the immediate vicinity of an exhaust gas outlet of the internal combustion engine.  
   
   
       26 . The exhaust gas purification system as recited in  claim 25 , wherein the at least one oxidation catalytic converter is a catalytically coated particle filter.  
   
   
       27 . The exhaust gas purification system as recited in  claim 25 , further comprising: 
 at least one particle filter provided between the at least one oxidation catalytic converter and the at least one device for selective catalytic reduction.    
   
   
       28 . A method for purifying an exhaust gas stream of an internal combustion engine, comprising: 
 passing the exhaust gas stream through at least one oxidation catalytic converter located in an exhaust gas duct of the internal combustion engine, and through at least one device for selective catalytic reduction located downstream of the at least one oxidation catalytic converter; and    selectively performing at least one of: a) feeding a reducing agent into the exhaust gas stream one of upstream of the at least one device for selective catalytic reduction and in the at least one device for selective catalytic reduction; and b) feeding the reducing agent to the exhaust gas stream one of upstream of the at least one oxidation catalytic converter and in the at least one oxidation catalytic converter.    
   
   
       29 . The method as recited in  claim 28 , wherein the reducing agent is fed into one of the at least one oxidation catalytic converter and the at least one device for selective catalytic reduction.  
   
   
       30 . The method as recited in  claim 28 , wherein the reducing agent is fed into the at least one oxidation catalytic converter and the at least one device for selective catalytic reduction simultaneously during a transition period.  
   
   
       31 . The method as recited in  claim 28 , wherein the reducing agent is fed by a nozzle.  
   
   
       32 . The method as recited in  claim 28 , wherein the selective feeding of the reducing agent is determined as a function of temperature.  
   
   
       33 . The method as recited in  claim 30 , wherein the reducing agent is fed into the at least one oxidation catalytic converter at an exhaust gas temperature of less than approximately 180° C. in the at least one oxidation catalytic converter.  
   
   
       34 . The method as recited in  claim 32 , wherein the reducing agent is fed into the at least one oxidation catalytic converter at an exhaust gas temperature of less than approximately 180° C. in the at least one oxidation catalytic converter.  
   
   
       35 . The method as recited in  claim 33 , wherein the reducing agent is fed into the at least one device for selective catalytic reduction at an exhaust gas temperature of more than approximately 180° C. in the at least one device for selective catalytic reduction.  
   
   
       36 . The method as recited in  claim 34 , wherein the reducing agent is fed into the at least one device for selective catalytic reduction at an exhaust gas temperature of more than approximately 180° C. in the at least one device for selective catalytic reduction.