Exhaust Gas Aftertreatment System and Exhaust Gas Cleaning Method

Abstract

An exhaust gas aftertreatment system, and a method for exhaust gas purification, has a first oxidation catalyst device, a NOx catalyst device for removing nitrogen from the exhaust gas, a device for actively increasing an exhaust gas temperature with at least one second oxidation catalyst device, and a device for removing particles. The devices are arranged one behind the other in the flow direction of the exhaust gas of an internal combustion engine, so that the exhaust gas flows through them. A respective operating temperature of the NOx catalyst device and of the device for removing particles can be set independently of an exhaust gas temperature at an outlet of the internal combustion engine.

1 - 24 . (canceled) 
     
     
         25 . An exhaust-gas aftertreatment system having, arranged in series in the flow direction of exhaust gas of an internal combustion engine, and traversed by exhaust gas, a first oxidation catalytic converter device, a NOx catalytic converter device for the denitrogenization of the exhaust gas, a device for actively raising an exhaust-gas temperature with at least one second oxidation catalytic converter device, and a device for particle removal, wherein a respective operating temperature of the NOx catalytic converter device and of the device for particle removal can be set independently of an exhaust-gas temperature at an outlet of the internal combustion engine. 
     
     
         26 . The exhaust-gas aftertreatment system of  claim 25 , further comprising a unit for generating a heat tone to control the temperature of the NOx catalytic converter device. 
     
     
         27 . The exhaust-gas aftertreatment system of  claim 26 , wherein the unit for generating a heat tone is arranged upstream of the NOx catalytic converter device and downstream of the first oxidation catalytic converter device. 
     
     
         28 . The exhaust-gas aftertreatment system of  claim 26 , wherein the unit for generating a heat tone is arranged upstream of the first oxidation catalytic converter device. 
     
     
         29 . The exhaust-gas aftertreatment system of  claim 25 , wherein the device for actively raising an exhaust-gas temperature comprises at least one fuel metering apparatus upstream of the second oxidation catalytic converter device. 
     
     
         30 . The exhaust-gas aftertreatment system of  claim 29 , wherein the oxidation catalytic converter device has a twin-strand configuration. 
     
     
         31 . The exhaust-gas aftertreatment system of  claim 30 , wherein a fuel metering apparatus is provided separately for each oxidation catalytic converter. 
     
     
         32 . The exhaust-gas aftertreatment system of  claim 30 , wherein a single fuel metering apparatus supplies all of the oxidation catalytic converters of the device for actively raising an exhaust-gas temperature together. 
     
     
         33 . The exhaust-gas aftertreatment system of  claim 25 , wherein the NOx catalytic converter device has a twin-strand configuration. 
     
     
         34 . The exhaust-gas aftertreatment system of  claim 25 , wherein the device for particle removal has at least one particle filter. 
     
     
         35 . The exhaust-gas aftertreatment system of  claim 34 , wherein the device for particle removal has a twin-strand configuration. 
     
     
         36 . The exhaust-gas aftertreatment system of  claim 35 , wherein the oxidation catalytic converter of the device for actively raising the exhaust-gas temperature or the first oxidation catalytic converter is integrated into the device for particle removal. 
     
     
         37 . The exhaust-gas aftertreatment system of  claim 36 , wherein a third oxidation catalytic converter device is provided downstream of the device for particle removal. 
     
     
         38 . The exhaust-gas aftertreatment device of  claim 37 , wherein the third oxidation catalytic converter device has a single-strand configuration. 
     
     
         39 . The exhaust-gas aftertreatment device of  claim 37 , wherein the third oxidation catalytic converter device has a twin-strand configuration. 
     
     
         40 . The exhaust-gas aftertreatment device of  claim 25  wherein at least one temperature sensor is provided upstream of the first oxidation catalytic converter unit or downstream of the unit for generating a heat tone or upstream of the NOx catalytic converter device or downstream of the NOx catalytic converter device or upstream of the device for actively raising the exhaust-gas temperature or upstream of the device for particle removal or downstream of the device for particle removal. 
     
     
         41 . The exhaust-gas aftertreatment device of  claim 25 , wherein an ammonia sensor is provided downstream of the NOx catalytic converter device. 
     
     
         42 . The exhaust-gas aftertreatment device of  claim 25 , wherein a NOx sensor is provided downstream of the NOx catalytic converter device or upstream of the first oxidation catalytic converter unit. 
     
     
         43 . The exhaust-gas aftertreatment device of  claim 25 , wherein one pressure sensor is arranged upstream and downstream of the device for particle removal. 
     
     
         44 . A method for exhaust-gas purification in an exhaust-gas aftertreatment system having, arranged in series in the flow direction of exhaust gas of an internal combustion engine, a first oxidation catalytic converter device, a NOx catalytic converter device for the denitrogenization of the exhaust gas, a device for actively raising an exhaust-gas temperature with at least one second oxidation catalytic converter device, and a device for particle removal, said method comprising the steps of:
 operating the NOx catalytic converter device and the device for particle removal independently of the exhaust-gas temperature at an outlet of the internal combustion engine and according to demand.   
     
     
         45 . The method of  claim 44 , further comprising the steps of activating the unit for generating a heat tone to control the temperature of the NOx catalytic converter device if regulated operation of a metering of reducing agent into the NOx catalytic converter device or regulated operation of the device for actively raising an exhaust-gas temperature is required and the NOx catalytic converter device or one or more oxidation catalytic converters of the device for actively raising an exhaust-gas temperature are outside a respective preferred temperature range. 
     
     
         46 . The method as claimed in  claim 44 , further comprising activating a regulated operation of the device for actively raising an exhaust-gas temperature if the device for particle removal exceeds a pressure loss increase or a temperature to be expected in the device for particle removal when the device for raising the exhaust-gas temperature is active exceeds a limit value, or if a loading of the device for particle removal exceeds an admissible limit value. 
     
     
         47 . The method as claimed in  claim 45 , further comprising activating regulated operation of the device for actively raising an exhaust-gas temperature if the device for particle removal exceeds a pressure loss increase or a temperature to be expected in the device for particle removal when the device for raising the exhaust-gas temperature is active exceeds a limit value, or a loading of the device for particle removal exceeds an admissible limit value. 
     
     
         48 . The method as claimed in  claim 44 , further comprising
 activating the unit for generating a heat tone to control the temperature of the NOx catalytic converter device if regulated operation of a metering of reducing agent into the NOx catalytic converter device or regulated operation of the device for actively raising an exhaust-gas temperature is required and the NOx catalytic converter device or one or more oxidation catalytic converters of the device for actively raising an exhaust-gas temperature are outside a respective preferred temperature range;   and activating regulated operation of the device for actively raising an exhaust-gas temperature if the device for particle removal exceeds a pressure loss increase or a temperature to be expected in the device for particle removal when the device for raising the exhaust-gas temperature is active exceeds a limit value, or a loading of the device for particle removal exceeds an admissible limit value;   wherein when the device for raising an exhaust-gas temperature is active, a mean temperature of the device for particle removal is between 550° C. and 850° C., preferably between 600° C. and 800° C.   
     
     
         49 . The method as claimed in  claim 44 , wherein in regulated operation of the device for raising an exhaust-gas temperature, the temperature of its oxidation catalytic converter device is higher than 250° C., preferably higher than 300° C.