Process for controlled addition of a reducing agent into nitrogen oxides containing exhaust gas

Abstract

Process for controlled addition of a reducing agent into nitrogen oxides containing exhaust gas being contacted with a selective reducing catalyst for abatement of the nitrogen oxides by reaction with the reducing agent in contact with the catalyst, comprising the steps of determining mass flow of combustion air passed to the engine; determining concentration of nitrogen oxides in the exhaust gas prior to contact with the catalyst; determining temperature of the exhaust gas at inlet of the catalyst; determining temperature of the exhaust gas at outlet of the catalyst; and communicating determined values of the air mass flow, the nitrogen oxides concentration and the inlet and outlet temperature to an electronic control unit and calculating amount of reducing agent to be injected into the exhaust gas prior to contact with the catalyst.

1 . Improved process for controlled addition of a reducing agent into nitrogen oxides containing vehicle engine exhaust gas by reaction of nitrogen oxides with a reducing agent in contact with a selective reducing catalyst amount of the reducing agent being added to the exhaust gas is metered on base of exhaust gas values and/or engine values, which values are determined by means of sensors and sensor data being communicated to an electronic control unit for metering the amount of the reducing agent being added to the exhaust gas, the improvement of which comprises communicating the sensor data by means of a serial interface to the electronic control unit.  
     
     
         2 . Process of  claim 1 , wherein the reducing agent contains or is urea and/or ammonia.  
     
     
         3 . Process of  claim 1 , wherein the exhaust gas values being determined are at least one of nitrogen oxide concentration, exhaust gas temperature at inlet the reducing catalyst, exhaust gas temperature at outlet of the reducing catalyst and oxygen content in the exhaust gas.  
     
     
         4 . Process of  claim 1 , wherein the engine values comprise flow amount of engine intake air.  
     
     
         5 . Process of  claim 1 , wherein the electronic control unit is arranged in the vehicle engine compartment.  
     
     
         6 . Process of  claim 1 , wherein the electronic control unit is an existing unit for controlling operation of the engine.  
     
     
         7 . System for controlled addition of a reducing agent into nitrogen oxides containing vehicle engine exhaust gas comprising at least a sensor for providing data on exhaust gas composition and condition and/or a sensor for engine operation, and an electronic control unit for processing of the data and for metering the addition of the reducing agent into the exhaust gas, wherein the sensors are equipped with a serial interface for transmission of sensor data to the electronic control unit.