DE102006043081A1 - Emission control device for after-treatment of exhaust gas of internal combustion engine of motor vehicle, has reducing agent generating system with valve system, with which part of gas mixture can be fed to heating gas route - Google Patents

Abstract

An emission control device includes a reducing agent generating system (10) having a valve system, with which a part of a gas mixture carried in the standard gas route (16) can be fed to a heating gas route (21) with a heat exchanger (24). An emission control device comprises a reducing agent generating system. Ammonia produced by the reducing agent generating system for the reduction of nitrogen oxides can be delivered to an exhaust gas duct of the internal combustion engine in front of a selective catalytic reduction-catalytic converter. The reducing agent generating system along a standard gas route is constructed from a nitrogen oxide production unit (14), an oxidation reformation unit, and a combined nitrogen oxide storage/ammonia production unit. Source materials for production of ammonia can periodically be delivered to the nitrogen oxide production unit by an air/exhaust gas feed and a fuel feed. The reducing agent generating system has a valve system, with which a part of a gas mixture carried in the standard gas route can be fed to a heating gas route with a heat exchanger.

Description

was standing of the technique

A method of assisting in starting an exhaust aftertreatment system of an internal combustion engine having an exhaust gas conduit in which an SCR catalyst is provided in the flow direction of the exhaust gas, wherein a reductant generation system comprises a multitron unit comprising a NO _x production unit, a mixture formation chamber and an oxidation reforming unit ( cPOx), as a combined NO _x storage / ammonia generating unit in the standard gas path of the reducing agent generation system, and is supplied to reduce nitrogen oxides before the SCR catalyst from the reducing agent generation system ammonia as a reducing agent, the Multitron unit are fed via an air / exhaust gas supply and a fuel supply starting materials for generating the ammonia, at least temporarily. The invention further relates to a corresponding device.

In connection with future legal requirements regarding the nitrogen oxide emission of motor vehicles, a corresponding exhaust aftertreatment is required. The selective catalytic reduction (SCR) can be used to reduce the NO _x emission (denitrification) of internal combustion engines, in particular diesel engines, with temporally predominantly lean, ie oxygen-rich exhaust gas. In this case, a defined amount of a selectively acting reducing agent is added to the exhaust gas. This can be, for example, in the form of ammonia, which is added directly in gaseous form, or is also obtained from a precursor substance in the form of urea or from a urea-water solution (HWL). Such HWL-SCR systems have been used for the first time in the commercial vehicle segment.

In the DE 10139142 A1 is described an exhaust gas purification system of an internal combustion engine, in which an SCR catalyst is used to reduce the NO _x emission, which reduces the nitrogen oxides contained in the exhaust gas ent with the reagent ammonia to nitrogen. The ammonia is recovered in a urea-water solution (HWL) hydrolysis catalyst upstream of the SCR catalyst. The hydrolysis catalyst converts the urea contained in the HWL to ammonia and carbon dioxide. In a second step, the ammonia reduces the nitrogen oxides to nitrogen, with water being produced as a by-product. The exact procedure has been adequately described in the specialist literature (see WEISSWELLER in CIT (72), pages 441-449, 2000). The HWL is provided in a reagent tank.

adversely in this method is that HWL in the operation of the internal combustion engine is consumed. The consumption is about 4% of fuel consumption. The supply of urea-water solution should correspondingly large area, for Example at gas stations, be assured. Another disadvantage of the method is in the necessary operating temperature range. The hydrolysis reaction for the reaction of water and urea on Hydrolysis catalyst to ammonia takes place only in the range of 200 ° C to 220 ° C. These temperatures in the exhaust gas are, for example, in diesel engines only after a long time Operating time reached. Due to deposits, it can be at temperatures below from 200 ° C come to blockages on the dosing unit, which the supply the urea-water solution at least hinder in the exhaust tract. Furthermore, a metered addition the urea-water solution at temperatures below 200 ° C due to the formation of deposits to inhibit the necessary catalytic properties on the hydrolysis catalyst or on the SCR catalyst to lead.

In the DE 199 22 961 C2 is an exhaust gas purification system for purifying the exhaust gas of a combustion source, in particular an automotive internal combustion engine, at least nitrogen oxides contained therein with an ammonia generation catalyst for generating ammonia using constituents of at least a portion of the exhaust gas emitted from the combustion source during ammonia generation operating phases and downstream of the ammonia generation catalyst Nitrogen oxide reduction catalyst for the reduction of nitrogen oxides contained in the emitted exhaust gas of the combustion source using the generated ammonia described as a reducing agent. In this case, a combustion-source-external nitrogen oxide generation unit is provided for enriching the exhaust gas supplied to the ammonia generation catalyst with nitrogen oxide produced by it during the ammonia generation operating phases. As a nitrogen oxide generating unit, for example, a plasma generator for plasma-technical oxidation of nitrogen contained in a gas stream supplied in nitrogen oxide is proposed. The hydrogen required for ammoniation generation is generated during the ammonia generation operating phases by the operation of the combustion source with a rich, ie fuel-rich air ratio.

A disadvantage of this method is the relatively high fuel consumption during the necessary rich operating phases. Furthermore, a high energy requirement for the external emission of the nitrogen oxide is required, in particular, since nitric oxide Herge during the shortest possible ammonia generating operating phases in high concentration must be set and the remaining residual oxygen to produce ammonia must be removed energy consuming. If the hydrogen is generated via a POx catalyst by a partial oxidation reforming (POx), another disadvantage lies in the still insufficient dynamics of hydrogen production.

One Plasmachemisches process for producing a hydrogen-rich Gas mixture is described in WO 01/14702 A1. It will be in an arc a rich fuel-air mixture, preferably under POx conditions.

Around to carry with you to avoid another fuel has now been in an unpublished one Document of the applicant a plasma method for on-board generation proposed by reducing agents. This will be the reduction The nitrogen oxides required ammonia from non-toxic substances as needed produced in the vehicle and then fed to the SCR process. A in terms of the fuel consumption acceptable solution offers a discontinuous operated method for ammonia production, as well proposed in this document. This procedure is hereafter as RGS (Reductant Generating System) or reducing agent called generating system.

A disadvantage of this method is that especially in the start phase, the reducing agent generation system (RGS) a sufficiently high operating temperature is reached only very slowly, in which an optimal operation is guaranteed. The previous strategy provides a burner functionality, which makes it possible to make the system, in particular the catalytic components at about 650 ° C and the ammonia generating unit at about 250 ° C ready for operation. For this, diesel fuel combustion in a flame, possibly assisted by catalytic combustion within the catalytic components to raise the temperature in the area of the plasma reactor within the NO _x production unit is provided. A disadvantage is the additional energy consumption until the operational readiness of the reducing agent generation system (RGS), which results in a rather high fuel consumption.

It It is therefore an object of the invention to provide a method on the one hand the fast achievement of an optimal operating temperature the RGS unit allows and on the other hand, the necessary energy requirement is minimized. It is a further object of the invention to provide a suitable device provide.

Disclosure of the invention

Advantages of the invention

These Task is in the method with the features of the claim 1 and solved in the device with the features of claim 11.

The The object of the invention relating to the method is solved by at least temporarily over at least one valve part of the exhaust gas from the exhaust system behind taken from the internal combustion engine and the reducing agent generation system supplied becomes.

The The object of the invention relating to the device is achieved in that the exhaust aftertreatment system has at least one valve over which a portion of the exhaust gas from the exhaust system behind the internal combustion engine can be fed to the reducing agent generation system.

With the method and the device according to the invention can be achieved be that contained in the exhaust stream from the engine heat in certain Operating phases and in particular for the system start of the reducing agent generation system (RGS) to increase the temperature of RGS components or the whole Reducing agent generation system can be used. Thereby can be a faster heating of the reductant generation system to be achieved with its components, resulting in a faster System startup of the exhaust aftertreatment system is made possible. This is special advantageous with regard to a sufficiently high nitrogen oxide reduction of Exhaust gases, especially in the starting phase of the internal combustion engine. By Use of the hot Exhaust gas as a heat source becomes an otherwise additional Fuel consumption significantly minimized.

If in this case the part of the exhaust gas from the exhaust system is introduced in an RGS heating gas path upstream of the oxidation reforming unit of the reducing agent generation system, there is the advantage that in particular the rapid heating of the oxidation reforming unit and the downstream combined NO _x storage / ammonia production unit within the reducing agent Generation system is supported, so that full operational readiness can be achieved quickly. An additional advantage is that in particular the catalytic component of the oxidation reforming unit can be heated very quickly. If they have reached a sufficiently high temperature for initial oxidation reactions, the temperature can be significantly increased and exceeded by means of a coordinated fuel injection and the reaction in the catalyst the Katbrennerfunktionalität possible thereby bring the entire system to operating temperature.

Becomes the portion of exhaust gas from the exhaust passage in an RGS heating gas path in front of the Multitron unit of the reducing agent generation system can also be achieved that the Multitron unit is additionally heated, so that these are also speedy can be brought to their required operating temperature. This can advantageously with a corresponding embodiment for the Device happen at which the reducing agent generation system a valve over that by means of a connector a portion of the exhaust gas from the exhaust system behind the internal combustion engine in the flow direction the standard gas path of the reducing agent generation system the Multitron unit or before the oxidation reforming unit can be introduced.

In The variants of the method is provided that the initiation of a Part of the exhaust gas from the exhaust system by means of one or more 2/2 valves or by means of a 3/2 or 3/3 valve is performed. With that you can pursued different heating concepts with different functionality become.

In a preferred embodiment is provided that the introduction of a part of the exhaust gas the exhaust system after reaching an optimum operating temperature of the components the reductant generation system or the entire reductant generation system is stopped. This can be achieved that the components of the reductant generation system should not be overheated. advantageously, is provided in this connection that the reducing agent generation system one or more temperature sensors whose signals for Control of the process can be used.

there can after completion of the introduction of the exhaust gas from the exhaust system in the reductant generation system is one for heating Amount of fuel over the fuel feeder in the Multitron unit is injected. This will then be in the catalytic components within the oxidation reforming unit oxidized. The resulting heat Then, the oxidation reforming unit continues to heat until the unit the for a pulse operation necessary Operating temperature has. additionally heats up by this measure the downstream within the reductant generation system, ammonia generator unit to the required operating temperature.

Especially It is advantageous if the method with previously described method variants in Cold start and / or restart of the exhaust aftertreatment system carried out which makes an energetically sensible and cost-effective system start the reducing agent generation system due to reduced fuel consumption allows becomes.

In addition, can in a variant of the method within the cold start and / or the Restart phases in the Multitron unit additionally by means of the Multitron unit included igniters ignited a fuel / air mixture become, whereby an additional heat source for rapid heating of the reducing agent generation system to disposal stands.

Becomes the method applied to diesel engines or lean-burn engines, which is a reducing agent generation system have, so can the nitrogen oxide load especially during Cold start can be significantly reduced, which is especially true for diesel engines is important. But also with other lean-burn engines, which with normal or super fuel can be operated, the process in conjunction with the reducing agent generation system advantages in minimizing the pollutants while reducing fuel consumption Offer.

A particularly simple and inexpensive embodiment provides that the valve is designed as a 2/2 valve.

In a preferred embodiment, the reductant generation system comprises a multi-way valve between the oxidation reforming unit and the combined NO _x storage / ammonia generating unit, wherein the multi-way valve is additionally connected via a connecting piece to the exhaust gas duct behind the internal combustion engine. With this arrangement can be achieved that can be selected between different gas paths within the reducing agent generation system and thus the gas path of the respective operating phase of the internal combustion engine can be adjusted.

is the multi-way valve at this location as a 3/2-valve or as two 2/2 valves can run between the standard gas path for the normal gas flow within the reductant generation system while the normal operating phase and an RGS heating path during the Cold start or restart phases, with the RGS heating path the introduction of a portion of the exhaust stream into the reductant generation system allowed.

The advantage of the two 2/2 valves over a 3/2 valve is, if they are just behind the Oxi dationsreformierungseinheit before a then necessary T-piece or directly in the supply line before the exhaust gas flow behind the T-piece are used, that in addition to a shutdown of the gas flow for the entire reducing agent generation system via a shutdown of the gas supply directly to a compressor, compressor or blower a shutdown by closing the first 2/2-valve in the gas stream is made possible behind the Oxidationreformierungseinheit. The pure functionality of the reducing agent generation system and the presented start strategy can also be realized in a simplified manner with a 2/2 valve, which is then inserted directly in the supply line upstream of the exhaust gas flow behind the T piece. However, this presupposes that the air path of the reducing agent generation system is closed, for example, by the air compressor.

In particularly preferred embodiment the multi-way valve designed as a 3/3-valve or as three 2/2 valves. Thereby becomes an additional gas flow path allows. This feature can be achieved through the three 2/2 valves, if these are used in the gas passages around a T-piece then to be inserted are.

So are preferred with the multi-way valve within the reductant generation system Operating modes with the standard gas path, with the RGS heating path or with a DPF regeneration gas path selectable wherein the first position of the multi-way valve is the standard gas path, with the second position the DPF regeneration path and with the third Position of the RGS heating path chosen can be.

In the operating mode "DPF regeneration" (2nd valve position) for regeneration of a diesel particulate filter (DPF) NO ₂ , which is generated in the multitron unit, into the exhaust system upstream of the diesel particulate filter or possibly before a diesel oxidation catalyst ( DOC) can be initiated, it being possible to achieve via the so-called CRT effect (oxidation of soot by means of NO ₂ ) that the diesel particle filter is regenerated and thus the soot can be broken down again. A regeneration of the diesel particle filter can also be effected by means of H ₂ / CO which is generated from the reducing agent generation system within an extended fat phase within the Multitron unit. the H ₂ / CO is in the oxidation of the diesel oxidation catalyst (DOC) or coated diesel particulate filter (DPF) releases heat, which raises the temperature up to the Soot ignition temperature raises.

In the operating mode "RGS heating", part of the gas flow from the exhaust gas is conducted directly into the combined NO _x storage / ammonia production unit, in particular during the cold start or restart phase, whereby in particular the ammonia generator unit until reaching a sufficiently high temperature can be heated for the nO _x storage capacity. it is not necessary at this stage to bring the entire thermal mass in this area to operating temperature. Due to the convective heating a fuel consumption is particularly avoided. If a sufficiently high temperature for the complete nO _x storage achieved within the ammonia generating unit, the nO _x generating can be operated because the arc plasma generated _NOx can be sufficiently stored now without the system encounters a _NOx slip. the heat generated in the plasma means no additional energy and thus forces toffverbrauch for the system consideration of the reducing agent generation system, since the offered nitrogen oxide can be used completely for ammonia production. During the plasma operation, the oxidation reforming unit is heated and the ammonia generating unit can be maintained at operating temperature.

By passing a portion of the exhaust gas full flow can be stored as a further advantage proportionate to completely present therein NO _x mass flow in the ammonia generating unit of the reducing agent generation system and used for conversion to ammonia. If, for example, one assumes a 10% proportion of the exhaust gas mass flow through the reducing agent generation system for heating the ammonia generating unit, then a 20% reduction of the nitrogen oxides in the exhaust gas with respect to the operating point can be achieved. This results because, due to the 10% exhaust gas mass flow, this NO _x mass flow can be reduced from the full flow in the ammonia generating unit of the reducing agent generation system to ammonia, which then after metering into the exhaust gas full flow again 10% of the NO _x mass flow in the exhaust gas in the SCR catalyst can reduce.

In preferred embodiment the exhaust aftertreatment system has a control unit, with the valves are reversible, the control unit on the input side with at least one temperature sensor within the reductant generation system or a component of the reducing agent generation system connected is. This can on the one hand a monitoring of the temperature in the Reducing agent generation system and on the other hand a scheme take place, in which the introduction of a part of the exhaust gas stopped is when the components of the reductant generation system their required Operating temperatures have reached. Temperaturüberschreitungen can thus be avoided.

is the control unit integrated in the reducing agent generation system or part of a parent Motor control, can also complex control tasks within the exhaust aftertreatment system be realized, including signals from additional sensors in the control unit can be processed.

In addition to the so far described system can take place before or in the combined NO _x storage / ammonia generating unit incorporates a particle filter be arranged, which makes it possible in the standard gas within the reducing agent generation system a particle-containing partial stream of the full flow of the exhaust gas of a diesel engine, if the Discharge of the partial flow before a diesel particulate filter (DPF) takes place, to filter. A purification or regeneration of the particulate filter within the reducing agent generation system can be achieved without problems, since at this point sufficiently high temperatures (> 600 ° C.) are achieved during grease phases during operation of the oxidation reforming unit, which is sufficient for regeneration with oxygen in subsequent lean phases are. In addition, a continuous regeneration via NO _{2 is achieved} via the CRT effect, since the NO produced in the plasmatron in the lean phase is converted into NO ₂ in the subsequent oxidation reforming unit in lean operation and this is available for the CRT effect. This particle filter also filters the particles that would form when using a burner as an additional heating measure in the area of the multitron unit of the reducing agent generation system.

The previously described features of the device according to the invention are in particular Use in diesel engines or other lean-burn engines advantageous, if this is a reductant generation system exhibit.

short Description of the drawings

The Invention will be described below with reference to the figures shown in the figures Embodiments explained in more detail. It demonstrate:

1 a schematic representation of an exhaust aftertreatment system of an internal combustion engine with a reducing agent generation system,

2 a schematic representation of the exhaust aftertreatment system with a reducing agent generation system in an alternative embodiment and

3 a schematic representation of the exhaust aftertreatment system with a further embodiment variant for the reducing agent generation system.

embodiments the invention

1 schematically shows the technical environment using the example of a diesel engine, in which the inventive method can be applied.

Shown is an exhaust aftertreatment system 1 for an internal combustion engine 10 whose exhaust gases via an exhaust system 20 be guided, wherein in the flow direction of the exhaust gas, a diesel oxidation catalyst 30 (DOC), a diesel particulate filter 40 (DPF) and a downstream SCR catalyst 50 are provided. For the reduction of nitrogen oxides is before the SCR catalyst 50 from a reductant generation system 60 Ammonia can be fed as a reducing agent. SCR catalysts 50 work on the principle of selective catalytic reduction, in which by means of the reducing agent ammonia in oxygen-containing exhaust gases nitrogen oxides are reduced to nitrogen and water.

The reductant generation system 60 has a multitron unit ( 61 ), which consists of a NO _x production unit, a mixture formation chamber and an oxidation reforming unit ( 62 ) (POx), such as a combined NO _x storage / ammonia production unit 63 (AGC unit) in a standard gas path 66 of the reductant generation system 60 on.

The multitron unit 61 are via an air / exhaust gas supply 70 and a fuel feeder 80 Starting materials for generating the ammonia, at least temporarily fed. The ammonia is generated from air, exhaust gas or a mixture of air and exhaust gas and in the example shown from diesel fuel. For this purpose, a hydrogen generating unit and a nitrogen oxide generating unit are provided. In the example shown, the nitrogen generation unit is a plasma reactor in the multitron unit 61 educated. In the hydrogen generating unit, hydrogen and carbon monoxide are generated from the hydrocarbons of the fuel by means of an oxidation reforming reaction. The required mixture-forming chamber is in this example together with the nitrogen oxide generating unit in a common Multitron unit 61 integrated, with the associated cPOx stage, the oxidation reforming unit 62 , listed separately.

The production of ammonia occurs within the reductant generation system 60 , in which nitric oxide NO in a lean phase (λ> 1) in a plasma within the Multitron unit 61 is generated from air. These nitrogen oxides flow through the subsequent oxidation reforming unit 62 (POx) and are then in the example shown a combined NO _x storage / ammonia generating unit 63 supplied and stored. In a second phase of operation following the lean phase, the fat phase (0.33 <λ <1), becomes in the range of the multitron unit 61 metered liquid fuel in an evaporation and mixture forming zone and in the oxidation reforming unit 62 (POx) to a hydrogen and carbon monoxide-containing gas mixture, which then in the range of NO _x storage / ammonia generating unit 63 converts the previously stored nitrogen oxides to ammonia. This generated gaseous ammonia is then in the exhaust gas flow of the exhaust system 20 before the SCR catalyst 50 added.

Because the SCR catalyst 50 has an ammonia storage capacity, it is possible to continuously achieve via a batch process for ammonia production, the reduction of nitrogen oxides by means of the SCR process in the exhaust stream. In the temperature range between 150 ° C. and 450 ° C., catalysts of, for example, titanium dioxide (TiO ₂ ) and vanadium pentoxide (V ₂ O ₅ ) convert the nitrogen oxides with the ammonia produced at a high rate.

In the start phase, a rapid heating of the components of the reducing agent generation system 60 to reach, according to the invention comprises the exhaust aftertreatment system 1 at least one valve, via which a part of the exhaust gas from the exhaust system 20 behind the internal combustion engine 10 the reductant generation system 60 at least temporarily be fed. In the exemplary embodiment shown, the exhaust aftertreatment system 1 within the reductant generation system 60 a valve 65 on, via the means of a connector, a portion of the exhaust gas from the exhaust system 20 behind the internal combustion engine 10 in the flow direction of the standard gas path 66 of the reductant generation system 60 before the oxidation reforming unit 62 can be introduced. In the example shown, the valve 65 designed as a 2/2 valve, which is operated open in the starting phase.

With this start strategy, a rapid operational readiness of the reducing agent generation system 60 , in particular of the oxidation reforming unit 62 and the NO _x storage / ammonia generating unit 63 achieved so that a high ammonia production rate is achieved at a very early stage.

After reaching the corresponding optimum temperature (> 200 ° C) is in a process variant, the valve 65 closed and tuned for heating amount of diesel fuel through the fuel supply 80 into the Multitron unit 61 injected. This is in the oxidation reforming unit 62 oxidizes and heats them further until the unit has reached the temperature required for pulse operation. In addition, the downstream heats up within the reductant generation system 60 Combined NO _x storage / ammonia generating unit located 63 also to the required operating temperature.

The valve is activated 65 from a control unit 90 , the input side with at least one temperature sensor within the reducing agent generation system 60 or a component of the reducing agent generation system 60 connected is. The control unit 90 may be in the reductant generation system 60 be integrated or is part of a higher-level engine control.

2 shows a variant of the in 1 shown arrangement. Deviating from 1 takes place in 2 the introduction of a portion of the exhaust gas from the exhaust system 20 over the valve 65 in front of the Multitron unit 61 ,

The in the 1 and in the 2 shown variants allow over the open valve 65 a RGS heating gas path 67 , which is the quick start of the reductant generation system 60 can be used.

In 3 an embodiment of the device according to the invention is shown, in which the reducing agent generation system 60 a multi-way valve 64 between the oxidation reformation unit 62 such as the combined NO _x storage / ammonia production unit 63 having, wherein the multi-way valve 64 additionally via a connecting piece with the exhaust system 20 behind the internal combustion engine 10 connected is. The multi-way valve 64 can be designed as a 3/2 valve or as two 2/2 valves, bringing in two working positions between the standard gas path 66 and the RGS heating path 67 can be chosen.

In the in 3 variant shown is the multi-way valve 64 as a 3/3-valve or as three 2/2 valves. This will be within the reductant generation system 60 a switching between the modes with the standard gas path 66 , with the RGS heating path 67 or with a DPF regeneration gas path 68 allows. The RGS heating path 67 allows an effective heating of the combined NO _x storage / ammonia generating unit 63 , The operating mode with the DPF regeneration gas path 68 allows against also the use of the reducing agent generation system 60 for the regeneration of the diesel particulate filter 40 ,

As in 3 is shown, the valve position of the multi-way valve 64 or designed as 2/2 valves individual valves by means of the control unit 90 according to the operating phases of the internal combustion engine 10 be adjusted or adjusted. Is the control unit 90 with additional sensors and / or control units of the exhaust aftertreatment system 1 Connected or a higher-level engine control, so can complex operations within the exhaust aftertreatment system 1 be executed.

As in 3 as an option, can in the standard gas path 66 within the reductant generation system 60 before or in the combined NO _x storage / ammonia production unit 63 integrated a particle filter 69 be arranged. This makes it possible for a particle-containing partial flow of the exhaust gas from the exhaust system 20 if this before the diesel particulate filter 40 is discharged, to filter.

The method variants described above are described with the device embodiments described in particular during cold start and / or restart of the exhaust aftertreatment system 1 carried out. Supportive may be within the cold start and / or restart phases in Multitron unit 61 additionally by means of the multitron unit 61 Ignition devices ignited a fuel / air mixture are ignited. Furthermore, by means of the oxidation reforming unit 62 initiated a catalytic reaction whose exothermic energy balance is another source of heat.

Overall, with the process variants and the device embodiments described a rapid heating of the reducing agent generation system 60 be achieved with its components, resulting in a faster system startup of the exhaust aftertreatment system 1 is possible. By using the hot exhaust gas as a heat source, otherwise additional fuel consumption is significantly minimized.

In principle, the apparatus and method may be applied to all vehicles having diesel or other lean-burn engines operating on other fuels, including a reductant generation system 60 is used.

Claims (21)

Method for supporting the starting of an exhaust aftertreatment system ( 1 ) an internal combustion engine ( 10 ) with an exhaust system ( 20 ), in which in the flow direction of the exhaust gas, an SCR catalyst ( 50 ), wherein a reducing agent generation system ( 60 ) a multitron unit ( 61 ), which consists of a NO _x production unit, a mixture formation chamber and an oxidation reforming unit ( 62 ) (cPOx), such as a combined NO _x storage / ammonia production unit ( 63 ) in the standard gas path ( 66 ) of the reducing agent generation system ( 60 ) and for the reduction of nitrogen oxides before the SCR catalyst ( 50 ) of the reductant generation system ( 60 ) Ammonia is fed as a reducing agent, wherein the multitron unit ( 61 ) via an air / exhaust gas supply ( 70 ) and a fuel supply ( 80 ) Starting materials for generating the ammonia are at least temporarily supplied, characterized in that at least at times via at least one valve ( 64 . 65 ) a part of the exhaust gas from the exhaust system ( 20 ) behind the internal combustion engine ( 10 ) and the reductant generation system ( 60 ) is supplied. A method according to claim 1, characterized in that the part of the exhaust gas from the exhaust system ( 20 ) in an RGS heating gas path ( 67 ) in front of the oxidation reforming unit ( 62 ) of the reducing agent generation system ( 60 ) is initiated. Ancestors according to claim 1, characterized in that the part of the exhaust gas from the exhaust system ( 20 ) in an RGS heating gas path ( 67 ) in front of the Multitron unit ( 61 ) of the reducing agent generation system ( 60 ) is initiated. Method according to one of claims 1 to 3, characterized in that the introduction of a portion of the exhaust gas from the exhaust system ( 20 ) by means of one or more 2/2 valves or by means of a 3/2 or 3/3 valve. Method according to one of claims 1 to 4, characterized in that the introduction of a portion of the exhaust gas from the exhaust system ( 20 ) after reaching an optimum operating temperature of the components of the reducing agent generation system ( 60 ) or the entire reductant generation system ( 60 ) is stopped. Method according to one of claims 1 to 5, characterized in that after completion of the introduction of the exhaust gas from the exhaust system ( 20 ) into the reductant generation system ( 60 ) a tuned for heating amount of fuel through the fuel supply ( 80 ) into the Multitron unit ( 61 ) is injected. Method according to at least one of the preceding claims, characterized in that the method during cold start and / or when restarting the exhaust aftertreatment system ( 1 ) is carried out. A method according to claim 7, characterized in that within the cold start and / or the restart phases in the Multitron unit ( 61 ) additionally by means of the Multitron unit ( 61 ) ignited igniters a fuel / air mixture is ignited. Method according to one of claims 7 or 8, characterized in that by means of the oxidation reforming unit ( 62 ) (cPOx) a catalytic reaction is initiated. Application of the method according to one of claims 1 to 9, characterized in that the method is applied to diesel engines or to lean-burn engines which use a reducing agent generation system ( 60 ) exhibit. Device for assisting the starting of an exhaust aftertreatment system ( 1 ) an internal combustion engine ( 10 ) with an exhaust system ( 20 ), in the flow direction of the exhaust gas, an SCR catalyst ( 50 ), wherein the reducing agent generation system ( 60 ) a multitron unit ( 61 ), which consists of a NO _x production unit, a mixture formation chamber and an oxidation reforming unit ( 62 ) (cPOx), such as a combined NO _x storage / ammonia production unit ( 63 ) in the standard gas path ( 66 ) of the reducing agent generation system ( 60 ) and for the reduction of nitrogen oxides before the SCR catalyst ( 50 ) of the reductant generation system ( 60 ) Ammonia can be fed as a reducing agent, wherein the multitron unit ( 61 ) via an air / exhaust gas supply ( 70 ) and a fuel supply ( 80 ) Starting materials for generating the ammonia are at least temporarily fed, characterized in that the exhaust aftertreatment system ( 1 ) at least one valve ( 64 . 65 ), via which a part of the exhaust gas from the exhaust system ( 20 ) behind the internal combustion engine ( 10 ) the reductant generation system ( 60 ) can be fed. Apparatus according to claim 11, characterized in that the reducing agent generation system ( 60 ) a valve ( 65 ), via which by means of a connecting piece a part of the exhaust gas from the exhaust system ( 20 ) behind the internal combustion engine ( 10 ) in the flow direction of the standard gas path ( 66 ) of the reducing agent generation system ( 60 ) in front of the Multitron unit ( 61 ) or before the oxidation reforming unit ( 62 ) can be introduced. Device according to claim 12, characterized in that the valve ( 65 ) is designed as a 2/2 valve. Apparatus according to claim 11, characterized in that the reducing agent generation system ( 60 ) a multi-way valve ( 64 ) between the oxidation reforming unit ( 62 ) as well as the combined NO _x storage / ammonia production unit ( 63 ), wherein the multi-way valve ( 64 ) additionally via a connecting piece with the exhaust gas duct ( 20 ) behind the internal combustion engine ( 10 ) connected is. Apparatus according to claim 14, characterized in that the multi-way valve ( 64 ) is designed as a 3/2 valve or as two 2/2 valves. Apparatus according to claim 14, characterized in that the multi-way valve ( 64 ) is designed as a 3/3-valve or as three 2/2 valves. Apparatus according to claim 16, characterized in that with the multi-way valve ( 64 ) within the reductant generation system ( 60 ) Operating modes with the standard gas path ( 66 ), with an RGS heating path ( 67 ) or with a DPF regeneration gas path ( 68 ) are selectable. Device according to one of claims 11 to 17, characterized in that the exhaust aftertreatment system a control unit ( 90 ), with which the valves ( 64 . 65 ) are switchable, wherein the control unit ( 90 ) on the input side with at least one temperature sensor within the reducing agent generation system ( 60 ) or a component of the reducing agent generation system ( 60 ) connected is. Device according to claim 18, characterized in that the control unit ( 90 ) in the reductant generation system ( 60 ) is integrated or is part of a higher-level engine control. Device according to one of claims 11 to 19, characterized in that in the standard gas path ( 66 ) within the reductant generation system ( 60 ) before or in the combined NO _x storage / ammonia production unit ( 63 ) integrates a particle filter ( 69 ) is arranged. Use of the device according to one of claims 11 to 20, characterized in that the device is used in diesel engines or lean-burn engines, which use a reducing agent generation system ( 60 ) exhibit.