NOx REDUCTION SYSTEM

Abstract

A system and method for reducing the nitrogen oxides found in the exhaust produced by a vehicle engine, the system comprising a NOx trap and a first adding means for adding a reducing agent to the exhaust gas. The first adding means is positioned downstream of the engine and either upstream of or within the NOx trap.

1 . A system for reducing nitrogen oxides of an exhaust gas produced by an engine of a vehicle, the system comprising:
 a NOx trap;   a first adding means for adding a reducing agent to the exhaust gas, the first adding means being positioned downstream of the engine and either upstream of or within the NOx trap;   a first Selective Catalytic Reduction unit, the first Selective Catalytic Reduction unit being located downstream of the NOx trap;   
       wherein the reducing agent is ammonia. 
     
     
         2 . The system of  claim 1 , wherein the NOx trap and the first Selective Catalytic Reduction unit are located within a same canning. 
     
     
         3 . The system of  claim 1 , wherein the system further comprises a second Selective Catalytic Reduction unit; wherein the second Selective Catalytic Reduction unit is located downstream of the first Selective Catalytic Reduction unit. 
     
     
         4 . The system of  claim 2 , wherein the system further comprises a second adding means for adding a reducing agent to the exhaust gas; wherein the second adding means is located upstream of at least one Selective Catalytic Reduction unit. 
     
     
         5 . The system of  claim 1 , wherein the system further comprises:
 at least one sensor; and   a controller configured to receive sensed data from the at least one sensor and to control at least one of the adding means based on the sensed data from the at least one sensor.   
     
     
         6 . The system of  claim 5 , wherein the system comprises:
 a NOx sensor located downstream of the NOx trap; and   the controller is configured to receive sensed data from the NOx sensor and to control at least one of the adding means based on the sensed data from the NOx sensor.   
     
     
         7 . The system of  claim 5 , wherein the system comprises:
 a second adding means for adding a reducing agent to the exhaust gas; wherein the second adding means is located upstream of at least one Selective Catalytic Reduction unit;   a temperature sensor; and   the controller is configured to control at least one of the adding means based on the temperature sensed by the temperature sensor.   
     
     
         8 . The system of  claim 4 , wherein at least one of the adding means is configured to inject the reducing agent in the gas phase. 
     
     
         9 . The system of  claim 1 , wherein the first adding means are arranged to spray the reducing agent in an exhaust line extending between the engine and the NOx trap. 
     
     
         10 . The system of  claim 1 , wherein the system is located within an exhaust line of the vehicle. 
     
     
         11 . A controller configured to:
 receive data indicative of a measured parameter in an exhaust system; and   control adding a reducing agent upstream of a NOx trap or within a NOx trap and downstream of an engine based on the received data.   
     
     
         12 . The controller of  claim 11 , wherein the controller is configured to:
 receive data indicative of a NOx content in an exhaust gas; and   control the adding of a reducing agent upstream of a NOx trap or within a NOx trap, based on the received NOx content data.   
     
     
         13 . The controller of  claim 11 , wherein the controller is configured to:
 receive data indicative of the temperature of the exhaust system; and   control the adding of a reducing agent upstream of a NOx trap or within a NOx trap, based on the received temperature data.   
     
     
         14 . A method for reducing nitrogen oxides of an exhaust gas produced by an engine, the method comprising:
 storing nitrogen oxides produced by an engine in a NOx trap positioned downstream of the engine;   adding a reducing agent into the exhaust gas upstream of or within the NOx trap and downstream of the engine; and   using this reducing agent to reduce the NOx absorbed in the NOx trap and purge the NOx trap.   
     
     
         15 . The controller of  claim 12 , wherein the controller is configured to:
 receive data indicative of the temperature of the exhaust system; and   control the adding of a reducing agent upstream of a NOx trap or within a NOx trap, based on the received temperature data.