초록 ▼

Exhaust gas post treatment system for nitrogen oxide reduction of internal combustion engines operated with excess air. A partial exhaust gas stream is branched off upstream of an SCR catalytic converter for reducing nitrogen oxides. A metering device delivers to the partial exhaust gas stream reduc

Exhaust gas post treatment system for nitrogen oxide reduction of internal combustion engines operated with excess air. A partial exhaust gas stream is branched off upstream of an SCR catalytic converter for reducing nitrogen oxides. A metering device delivers to the partial exhaust gas stream reduction agent, which is ammonia or a material that releases ammonia downstream of the supply location as a result of the hot exhaust gas. The partial exhaust gas stream is returned to the exhaust gas stream downstream of the supply location and upstream of the SCR catalytic converter, which reduces the 1J nitrogen oxides in the exhaust gas stream with the aid of the ammonia or released ammonia, by selective catalytic reduction, to nitrogen and water vapor. At engine operating conditions at which reversal of the exhaust gas stream toward the engine occurs, an oxidation catalytic converter, disposed in the partial exhaust gas stream upstream of the supply location for the reduction agent, oxidizes ammonia and/or reduction agent decomposition products that flow back.

대표청구항 ▼

What I claim is: 1. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partia

What I claim is: 1. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; and an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back. 2. An exhaust gas post treatment system according to claim 1, wherein said oxidation catalytic converter for the oxidation of ammonia in said partial exhaust gas stream is simultaneously provided with SCR activity for nitrogen oxides. 3. An exhaust gas post treatment system according to claim 1, wherein an NH3-oxidation catalytic converter or catalyst is disposed downstream of said SCR catalytic converter. 4. An exhaust gas post treatment system according to claim 1, wherein a plurality of at least one of catalytic converters and separation devices are accommodated in a common housing. 5. An exhaust gas post treatment system according to claim 1, wherein said oxidation catalytic converter is embodied in such a way that, in addition to the at least one of ammonia and the reduction agent decomposition products that flow back, at engine operating conditions at which the exhaust gas flows away from the internal combustion engine, said oxidation catalytic converter is also adapted to oxidize at least one of the materials selected from the group consisting carbon monoxide, nitric oxide, and hydrocarbons that are carried along in the exhaust gas. 6. An exhaust gas post treatment system according to claim 5, wherein said oxidation catalytic converter for the oxidation of ammonia is provided with different properties, as viewed along a direction of flow of said exhaust gas, such that a side that is adjacent to said supply location for the reduction agent oxidizes ammonia, preferable selectively, to nitrogen and water, and an opposite side oxidizes at least one of the materials selected from the group consisting of carbon monoxide, nitric oxide and hydrocarbons, carried along is said exhaust gas, in a conversion-optimized manner. 7. An exhaust gas post treatment system according to claim 6, wherein that side of said oxidation catalytic converter for the oxidation of ammonia that is adjacent to the supply location for the reduction agent has a greater charge of at least one of the materials selected from the group consisting of palladium, iridium, and zeolites than does the side that faces the internal combustion engine. 8. An exhaust gas post treatment system according to claim 6, wherein that side of said oxidation catalytic converter for the oxidation of ammonia that is adjacent to the supply location for the reduction agent has a lower charge of at least one of the materials selected from the group consisting of platinum and oxides thereof than does the side that faces the internal combustion engine. 9. An exhaust gas post treatment system according to claim 1, wherein a further SCR catalytic converter, for a selective reduction of nitrogen oxides with the aid of ammonia that flows back, is disposed in said partial exhaust gas stream downstream of said oxidation catalytic converter and upstream of said supply location for the reduction agent. 10. An exhaust gas post treatment system according to claim 9, wherein said oxidation catalytic converter in said partial exhaust gas stream, and said further SCR catalytic converter that is disposed downstream of said oxidation catalytic converter, are combined to form a single component. 11. An exhaust gas post treatment system according to claim 9, wherein said SCR catalytic converter and said further SCR catalytic converter for the reduction of nitrogen oxides with the aid of ammonia contain at least one of the materials selected from the group consisting of vanadium, vanadium pentoxide, titanium dioxide, tungsten oxide, copper-containing zeolites, iron-containing zeolites, and cobalt-containing zeolites as active component. 12. An exhaust gas post treatment system according to claim 1, wherein a hydrolysis catalytic converter is disposed downstream of said supply location for the reduction agent, and wherein said hydrolysis catalytic converter facilitates release of ammonia from the reduction agent. 13. An exhaust gas post treatment system according to claim 12, wherein said hydrolysis catalytic converter for the release of ammonia contains at least one of the materials selected from the group consisting of titanium dioxide, silicon dioxide, aluminum oxide, and zeolites as active component. 14. An exhaust gas post treatment system according to claim 1, wherein at least one separation device, for a separation of particles from said exhaust gas, is disposed in at least one of said partial exhaust gas stream and in said exhaust gas stream downstream of said supply location for the reduction agent. 15. An exhaust gas post treatment system according to claim 14, wherein said at least one separation device is disposed in said exhaust gas stream upstream or downstream of said SCR catalytic converter. 16. An exhaust gas post treatment system according to claim 14, wherein at least one of an exhaust gas temperature and a content of nitrogen dioxide at said separation device for separation of particles is adapted to be varied upstream of a further oxidation catalytic converter by adjustment of engine parameters and/or by raising a hydrocarbon concentration with the aid of an adjustment of engine parameters and/or by a supply of hydrocarbon into said exhaust gas stream. 17. An exhaust gas post treatment system according to claim 14, wherein at least one separation device is constructed such that it is adapted to be exchanged or removed. 18. An exhaust gas post treatment system according to claim 1, wherein a further oxidation catalytic converter is disposed upstream of said return location of said partial exhaust gas stream to said exhaust gas stream, and wherein during a normal direction of flow of said exhaust gas away from the internal combustion engine said further oxidation catalytic converter at least partially converts the nitric oxide contained in said exhaust gas stream to nitrogen dioxide. 19. An exhaust gas post treatment system according to claim 18, wherein at least one of the materials from the group consisting of platinum, palladium, iridium, oxides thereof, IrTiOx, and zeolites is used as active component for said oxidation catalytic converter for at least one of the oxidation of ammonia and for said further oxidation catalytic converter. 20. An exhaust gas post treatment system according to claim 18, wherein active components of said oxidation catalytic converter for the oxidation of at least one of ammonia and reduction agent decomposition products that flow back, and active components of said further oxidation catalytic converter, differ from one another and are respectively optimized to subsequent chemical reactions. 21. An exhaust gas post treatment system according to claim 1, wherein at least one turbine of at least one exhaust gas turbocharger is disposed in said exhaust gas stream, and wherein a branching-off of said partial exhaust gas stream, to which the reduction agent is supplied, is effected upstream of said at least one turbine of said exhaust gas turbocharger. 22. An exhaust gas post treatment system according to claim 21, wherein said turbine is a double-flow turbine, further wherein one channel thereof is supplied with exhaust gas from at least one first cylinder of the internal combustion engine and the other channel thereof is supplied with exhaust gas from at least one second cylinder of the internal combustion engine, and wherein said partial exhaust gas stream is branched off from one of said two channels. 23. An exhaust gas post treatment system according to claim 22, wherein the cylinders of that channel of the turbine from which the partial exhaust gas stream is branched off is adapted to be operated with other engine parameters than are the cylinders of the other channel. 24. An exhaust gas post treatment system according to claim 21, wherein two exhaust gas turbochargers are provided, further wherein the turbine of one of said turbochargers is supplied with exhaust gas from a first bank of cylinders of the internal combustion engine and the turbine of the other turbocharger is supplied with exhaust gas from a second bank of cylinders of the internal combustion engine, and wherein said partial exhaust gas stream is branched off from said exhaust gas stream upstream of the turbine of one of said two exhaust gas turbochargers. 25. An exhaust gas post treatment system according to claim 24, wherein the bank of cylinders, from the exhaust gas section of which said partial exhaust gas stream is branched off, is adapted to be operated with other engine parameters than is the other bank of cylinders. 26. An exhaust gas post treatment system according to claim 1, wherein a flow-control element is disposed in said partial exhaust gas stream for control or regulation of at least one of a volume velocity and quantity of said exhaust gas in said branched-off portion. 27. An exhaust gas post treatment system according to claim 26, wherein said flow-control element is a check valve or a controllable or regulatable shut off element disposed in said partial exhaust gas stream upstream of the supply location for the reduction agent. 28. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, and wherein a further SCR catalytic converter, for a selective reduction of nitrogen oxides with the aid of ammonia that flows back, is disposed in said partial exhaust gas stream downstream of said oxidation catalytic converter and upstream of said supply location for the reduction agent. 29. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, and wherein said oxidation catalytic converter for the oxidation of ammonia in said partial exhaust gas stream is simultaneously provided with SCR activity for nitrogen oxides. 30. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, and wherein at least one separation device, for a separation of particles from said exhaust gas, is disposed in at least one of said partial exhaust gas stream and in said exhaust gas stream downstream of said supply location for the reduction agent. 31. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, and wherein a further oxidation catalytic converter is disposed upstream of said return location of said partial exhaust gas stream to said exhaust gas stream, and wherein during a normal direction of flow of said exhaust gas away from the internal combustion engine said further oxidation catalytic converter at least partially converts the nitric oxide contained in said exhaust gas stream to nitrogen dioxide. 32. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, wherein said oxidation catalytic converter is embodied in such a way that, in addition to the at least one of ammonia and the reduction agent decomposition products that flow back, at engine operating conditions at which the exhaust gas flows away from the internal combustion engine, said oxidation catalytic converter is also adapted to oxidize at least one of the materials selected from the group consisting carbon monoxide, nitric oxide, and hydrocarbons that are carried along in the exhaust gas, and wherein said oxidation catalytic converter for the oxidation of ammonia is provided with different properties, as viewed along a direction of flow of said exhaust gas, such that a side that is adjacent to said supply location for the reduction agent oxidizes ammonia, preferable selectively, to nitrogen and water, and an opposite side oxidizes at least one of the materials selected from the group consisting of carbon monoxide, nitric oxide and hydrocarbons, carried along is said exhaust gas, in a conversion-optimized manner. 33. An exhaust gas post treatment system for nitrogen oxide reduction of an internal combustion engine operated with excess air, comprising: an SCR catalytic converter disposed in the exhaust gas stream of the internal combustion engine for reducing nitrogen oxides, wherein a partial exhaust gas stream is branched off from said exhaust gas stream upstream of said SCR catalytic converter; a supply tank for a reduction agent; a metering device for receiving said reduction agent from said supply tank and for adding said reduction agent to said partial exhaust gas stream at a supply location, wherein said reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location as a result of the hot exhaust gas, and wherein said partial exhaust gas stream is returned to said exhaust gas stream at a return location downstream of said supply location and upstream of said SCR catalytic converter, and wherein said SCR catalytic converter reduces the nitrogen oxides contained in said exhaust gas stream with the aid of the ammonia or released ammonia, by way of selected catalytic reduction, to nitrogen and water vapor; an oxidation catalytic converter disposed in said partial exhaust gas stream upstream of said supply location for said reduction agent, wherein at engine operating conditions at which a reversal of said exhaust gas stream in a direction toward the internal combustion engine occurs, said oxidation catalytic converter is adapted to oxidize at least one of ammonia and reduction agent decomposition products that flow back, wherein at least one turbine of at least one exhaust gas turbocharger is disposed in said exhaust gas stream, and wherein a branching-off of said partial exhaust gas stream, to which the reduction agent is supplied, is effected upstream of said at least one turbine of said exhaust gas turbocharger.