EXHAUST AFTER TREATMENT SYSTEM WITH A PASSIVE NOx ADSORBER AND A HEATABLE SCR CATALYTIC CONVERTER

Abstract

The invention relates to an exhaust after treatment system with a passive NOx adsorber and a heatable SCR catalytic converter. The exhaust gas after treatment system according to the invention for an internal combustion engine comprises an exhaust pipe, a passive NOx adsorber arranged in the exhaust pipe, an injector arranged in the exhaust pipe, a mixer arranged in the exhaust pipe, an SCR catalytic converter arranged in the exhaust pipe and a heating device arranged in the exhaust pipe, wherein the heating device is set up in such a way that at exhaust gas temperatures below a start-up temperature of the SCR catalytic converter, the temperature in the SCR catalytic converter can be brought to a temperature above the start-up temperature within a period of time by means of the heating device.

1 . Exhaust after treatment system for an internal combustion engine, comprising an exhaust pipe, a passive NO x  adsorber arranged in the exhaust pipe, an injector arranged in the exhaust pipe, a mixer arranged in the exhaust pipe, an SCR catalytic converter arranged in the exhaust pipe and a heating device arranged in the exhaust pipe, wherein the heating device is set up that so at exhaust gas temperatures below a start-up temperature of the SCR catalytic converter, the temperature in the SCR catalytic converter can be brought to a temperature above the start-up temperature within a period of time by the heating device. 
     
     
         2 . Apparatus according to  claim 1 , wherein the heating device is attached directly to the SCR catalytic converter. 
     
     
         3 . Apparatus according to  claim 1 , wherein the heating device is arranged upstream of the SCR catalytic converter between the passive NO x  adsorber and the mixer. 
     
     
         4 . Apparatus according to  claim 1 , wherein the heating device is arranged upstream of the SCR catalytic converter between the mixer and the SCR catalytic converter. 
     
     
         5 . Apparatus according to  claim 1 , wherein the heating device as an electric heat source. 
     
     
         6 . Apparatus according to  claim 1 , wherein the NO x  adsorber is a low-temperature adsorber. 
     
     
         7 . Apparatus according to  claim 1 , including a control unit having a structure performing the following steps:
 switching on the heating device,   determining the temperature in the SCR catalytic converter,   switching off the heating device if the temperature in the SCR catalytic converter has exceeded a temperature threshold.   
     
     
         8 . Apparatus according to  claim 7 , wherein the control unit switches on the heating device immediately when the engine is started. 
     
     
         9 . Apparatus according to  claim 7 , wherein the control unit switches on the heating device if it is recognized that desorption of the NO x  adsorber is required at a point in time and that the temperature in the SCR catalytic converter will not exceed a temperature threshold by that point in time without heating. 
     
     
         10 . Apparatus according to any one of  claim 7 , wherein the control unit regulates the power of the heating device depending on the load state of the NO x  adsorber and the temperature in the SCR catalytic converter.