DE102021005095A1 - Control device for controlling a hydrogen content of an exhaust gas of an internal combustion engine - Google Patents

Abstract

The invention relates to a control device for a drive train, comprising an internal combustion engine, for controlling the internal combustion engine so that a hydrogen content of an exhaust gas is adjusted.
The control device (1) according to the invention for a drive train (2), comprising an internal combustion engine (3) and an exhaust gas aftertreatment system (4), wherein the internal combustion engine (3) is designed as a hydrogen engine and the exhaust gas aftertreatment system (4) includes a first DeNOx system (5). , is trained and equipped to perform the following steps:
- detecting a content (S10) of a component of an exhaust gas upstream or downstream of the first DeNOx system (5) and
- Control (S40) of the internal combustion engine (3) so that an H2 content of the exhaust gas is adjusted based on the detected content (S10).

Description

The invention relates to a control device for a drive train, comprising an internal combustion engine, for controlling the internal combustion engine so that a hydrogen content of an exhaust gas is adjusted.

From the DE 10 2007 021 827 A1 there is known an exhaust gas purification system for a hydrogen engine, wherein hydrogen gas is introduced into the exhaust gas based on detection of an exhaust element upstream of a catalyst of the exhaust gas purification system to improve purification of the exhaust element.

• - Erfassen eines Gehalts einer Komponente eines Abgases stromauf oder stromab des ersten DeNOx Systems und
• - Steuern des Verbrennungsmotors, so dass ein Gehalt an Wasserstoff (H2) des Abgases basierend auf dem erfassten Gehalt angepasst wird.

The control unit according to the invention for a drive train, comprising an internal combustion engine and an exhaust gas aftertreatment system, wherein the internal combustion engine is designed as a hydrogen engine and the exhaust gas aftertreatment system includes a first DeNOx system, is designed and set up to carry out the following steps:

• - detecting a content of a component of an exhaust gas upstream or downstream of the first DeNOx system and
• - controlling the internal combustion engine so that a hydrogen (H2) content of the exhaust gas is adjusted based on the detected content.

Because the control device controls the internal combustion engine in such a way that an H2 content of the exhaust gas is adjusted based on the detected content, the invention makes it possible for an H2 content required for exhaust gas cleaning by the first DeNOx system to be provided. This has the advantage that the H2 content of the exhaust gas can be adjusted without requiring an additional dosing device to provide hydrogen upstream of the first DeNOx system.

A DeNOx system is understood to mean a system for reducing NOx emissions. This can be an SCR catalytic converter or a NOx storage catalytic converter, for example.

Here, detection is understood to mean both measuring using a sensor arranged upstream and/or downstream of the first DeNOx system and, alternatively or additionally, calculating the content of the component of the exhaust gas using a model and/or a map. A NOx or H2 probe, for example, but also a lambda probe can be used as a sensor.

The control device preferably detects a hydrogen content upstream of the first DeNOx system. By comparing it with a required hydrogen content stored in a characteristic map, for example, the control unit controls the internal combustion engine to adjust the hydrogen content.

Alternatively or in addition, the control device detects a level of nitrogen oxides (NOx) downstream of the first DeNOx system. By comparing with a target value for a nitrogen oxide emission, the control unit causes the internal combustion engine to be controlled so that the hydrogen content of the exhaust gas is adjusted.

Control is understood here to mean control with an open or temporarily closed path of action as well as regulation with a closed course of action.

• - Erfassen eines ersten Gehalts einer Komponente eines Abgases stromauf des ersten DeNOx Systems,
• - Erfassen eines zweiten Gehalts der Komponente des Abgases stromab des ersten DeNOx Systems,
• - Vergleichen des ersten und des zweiten erfassten Gehalts der Komponente und
• - Steuern des Verbrennungsmotors, so dass ein H2 Gehalt des Abgases basierend auf dem Ergebnis des Vergleichens angepasst wird.

The control unit is preferably designed and set up to carry out the following steps:

• - detecting a first content of a component of an exhaust gas upstream of the first DeNOx system,
• - detecting a second content of the component of the exhaust gas downstream of the first DeNOx system,
• - comparing the first and second detected content of the component and
• - controlling the internal combustion engine so that an H2 content of the exhaust gas is adjusted based on the result of the comparison.

Because the controller controls the internal combustion engine so that an H2 content of the exhaust gas is adjusted based on the result of the comparison, the invention enables an H2 content required for exhaust gas purification by the first DeNOx system taking into account a change in the content of the component can be provided via the first DeNOx system.

The control device preferably records a first and a second NOx content of the exhaust gas. Based on comparing the first and second NOx levels, the controller may determine a NOx conversion rate of the first deNOx system. If the NOx conversion rate is too low, the internal combustion engine can be controlled in such a way that the H2 content of the exhaust gas is adjusted.

The control unit particularly preferably detects the second NOx content using a sensor arranged downstream of the first DeNOx system and the first NOx content using a model. So one sensor can be saved and costs reduced. The sensor arranged downstream of the first DeNOx system can be designed, for example, as a NOx probe or lambda probe.

A NOx conversion rate of less than 85%, preferably less than 90%, particularly preferably less than 95%, is understood here as being too low.

The internal combustion engine is preferably designed as a direct-injection hydrogen engine and the control unit is designed and set up to supply hydrogen to the internal combustion engine when controlling the internal combustion engine in an exhaust stroke of the internal combustion engine, so that the H2 content of the exhaust gas is adjusted based on the detected content or based on the result of the comparison can.

Because the control unit causes hydrogen to be supplied in the exhaust stroke of the internal combustion engine, the invention enables the H2 content of the exhaust gas to be adjusted based on the detected content or based on the result of the comparison without a significant change in the combustion process.

Supplying hydrogen in the exhaust stroke means that the hydrogen is introduced into the cylinder well after top dead center, but before an exhaust valve of a cylinder of the internal combustion engine opens. As a result, the hydrogen introduced in this way takes little or no part in chemical reactions and is largely unburned in the exhaust gas.

The control unit is preferably designed and set up to control a fuel/air ratio, an ignition point, an injection point, an EGR rate and/or an intake pressure when controlling the internal combustion engine.

Due to the fact that the control unit controls a fuel-air ratio, an ignition timing, an injection timing, an EGR rate and/or an intake pressure when controlling, the invention enables a combustion process to be adjusted in such a way that the H2 content is based on the recorded content or adjusted based on the result of the comparison.

The internal combustion engine preferably includes a spark plug for igniting the hydrogen-air mixture. As a result, reliable ignition can be achieved and by adjusting the ignition point, a combustion focus and thus also H2 emissions can be directly influenced.

The control device is preferably designed and set up to take into account a knock limit, a combustion focus, a load requirement and/or NOx emissions of the internal combustion engine when controlling.

Because the control unit takes into account a knock limit, a combustion focus, a load requirement and/or NOx emissions of the internal combustion engine when controlling, the invention enables knocking combustion to be avoided or at least reduces the probability of knocking combustion occurring, a desired power to be provided and fuel consumption and NOx emissions can be limited.

Preferably, the control unit can control a ratio of a content between H2 and NOx, so that sufficient H2 is present in the exhaust gas to reduce NOx emissions in the first DeNOx system produced in the internal combustion engine. The H2/NOx ratio in the exhaust gas is particularly preferably greater than or equal to seven.

The first DeNOx system preferably includes a dosing unit, the dosing unit being designed and set up to supply a reducing agent containing H2 or NH3 to the exhaust gas aftertreatment system. The control unit is designed and set up to cause the reducing agent to be supplied by the dosing unit.

Because the control unit causes the reducing agent to be supplied by the dosing unit, a hydrogen content in the exhaust gas can be adjusted based on the detected content or based on the result of the comparison without intervention in the control of the internal combustion engine.

The control unit preferably only initiates the supply of the reducing agent if controlling the internal combustion engine is not sufficient to adjust the H2 content of the exhaust gas and/or if supplying the reducing agent is more favorable than controlling the internal combustion engine for energy reasons or with regard to an emission to be considered is.

Furthermore, the dosing unit is preferably designed and set up to introduce the reducing agent at at least two positions relative to the cross-sectional area of the exhaust gas aftertreatment system, so that mixing of reducing agent and exhaust gas can be improved. Also preferably, the exhaust gas aftertreatment system comprises one downstream of the dosing unit Mixer so that mixing of reducing agent and exhaust gas can be improved.

The first DeNOx system is preferably designed as an H2-SCR system or as an NH3-SCR system.

Because the first DeNOx system is designed as an H2-SCR system or as an NH3-SCR system, NOx emissions can be reduced by the exhaust aftertreatment system.

If the first DeNOx system is designed as an NH3-SCR system, it preferably includes a three-way catalytic converter or a NOx storage catalytic converter. This has the advantage that emissions of unburned hydrocarbons and NOx emissions contained in the exhaust gas can be converted in the three-way catalytic converter or in the NOx storage catalytic converter, if the latter is regenerated, with the formation of NH3. The NH3 can be used in the NH3-SCR system to reduce NOx emissions or stored in the NH3-SCR system for later reduction of NOx emissions. This enables the NH3-SCR system to be designed as a passive SCR system, i.e. without a dosing device.

Furthermore, the exhaust gas aftertreatment system preferably includes a second DeNOx system, the second DeNOx system being arranged downstream of the first DeNOx system. This has the advantage that sufficient NOx conversion can be achieved even at operating points with very high NOx emissions.

The first DeNOx system is particularly preferably designed as an H2-SCR system and the second SCR system as an NH3-SCR system. This has the advantage that NOx conversion can be made possible over a large temperature range, since the NH3-SCR system has sufficient NOx conversion rates in a different temperature range than the H2-SCR system.

The dependent claims describe further advantageous embodiments of the invention.

• 1 ein Ausführungsbeispiel eines Antriebstrangs mit einem Steuergerät,
• 2 ein Ausführungsbeispiel von durch ein Steuergerät ausgeführten Schritten zum Steuern eines H2 Gehalts im Abgas,
• 3 ein Ausführungsbeispiel eines Abgasnachbehandlungssystems eines Antriebsstrangs und
• 4 ein weiteres Ausführungsbeispiel ein Abgasnachbehandlungssystem eines Antriebsstrangs

Preferred exemplary embodiments are explained in more detail with reference to the following figures. while showing

• 1 an embodiment of a drive train with a control unit,
• 2 an embodiment of steps executed by a control device for controlling an H2 content in the exhaust gas,
• 3 an embodiment of an exhaust aftertreatment system of a powertrain and
• 4 another exemplary embodiment, an exhaust aftertreatment system of a drive train

1 shows a drive train 2 for a vehicle. The drive train 2 includes an intake section 9, an internal combustion engine 3, an exhaust section 10 and a first 11 and a second 12 exhaust gas recirculation section. In this case, the intake path 9 is arranged upstream of the internal combustion engine 3 . The exhaust line 10 is arranged downstream of the internal combustion engine 3 and includes an exhaust gas purification system 4.

The internal combustion engine 3 is designed as a supercharged, direct-injection and spark-ignited hydrogen engine with four cylinders 13 . For this purpose, the internal combustion engine 3 includes an exhaust gas turbocharger 14. The exhaust gas turbocharger 14 includes a compressor 15 arranged in the intake section 9 and a turbine 16 arranged in the exhaust section 10. The turbine 16 and the compressor 15 are coupled to one another, so that the through the turbine 16 from Exhaust energy absorbed can be used by the compressor 15 to compress the fresh gas to an increased pressure level.

The internal combustion engine 3 includes an injection device 30 for introducing the hydrogen into the cylinders 13. The injection device 30 includes an injector for each cylinder 13, feed lines and a fuel supply.

The internal combustion engine includes an ignition device 40 for igniting the hydrogen-air mixture. The ignition device 40 includes a spark plug for each cylinder 13 and an ignition system connected to the spark plugs.

The exhaust gas purification system 4 includes an H2-SCR catalyst 5, an NH3-SCR system and an ammonia slip catalyst (ASC) 7. The H2-SCR catalyst 5 is designed to reduce nitrogen oxide emissions using H2.

The NH3-SCR system is arranged downstream of the H2-SCR catalyst 5 and comprises an NH3-SCR catalyst 6, a metering unit 19 and a mixer 20. The metering unit 19 is designed and set up ammonia (NH3) upstream of the NH3-SCR catalyst 6 in to introduce the exhaust line 10. The introduced ammonia and the exhaust gas are mixed in the mixer 20 arranged between the dosing unit 19 and the NH3-SCR catalytic converter 6 . The NH3-SCR catalytic converter 6 is designed and set up to reduce NOx emissions using the ammonia.

A NOx sensor 22 is arranged downstream of the exhaust gas aftertreatment system 4 for detecting NOx emissions.

The first exhaust gas recirculation path 11 is arranged upstream of the exhaust gas purification system 4 and is designed to discharge exhaust gas from the exhaust gas path 10 upstream of the turbine 16 of the exhaust gas turbocharger 14 and to feed it to the intake path 9 downstream of the compressor 15 of the exhaust gas turbocharger 14 . The second exhaust gas recirculation path 12 is designed to discharge exhaust gas from the exhaust path 10 downstream of the H2-SCR system 5 and to feed it to the intake path 9 upstream of the compressor 15 of the exhaust gas turbocharger 14 . With the first 11 and the second 12 exhaust gas recirculation route, preferred exhaust gas recirculation rates can be provided for the operation of the internal combustion engine 3 and the most efficient possible operation of the internal combustion engine 3 can be achieved.

• - Erfassen eines ersten NOx Gehalts S10 des Abgases stromauf des Abgasnachbehandlungssystems 4 mittels eines Modells,
• - Erfassen eines zweiten NOx Gehalts S20 des Abgases stromab des Abgasnachbehandlungssystems 4 mittels des NOx Sensors 22,
• - Vergleichen des ersten und des zweiten erfassten S10,S20 NOx Gehalts und
• - Steuern S40 des Verbrennungsmotors 3, so dass ein H2 Gehalt des Abgases basierend auf dem Ergebnis des Vergleichens S30 angepasst wird.

The drive train 2 includes a control unit 1. The control unit 1 is designed and set up to execute a control program. The control program includes commands to perform the following steps:

• - detecting a first NOx content S10 of the exhaust gas upstream of the exhaust gas aftertreatment system 4 by means of a model,
• - detecting a second NOx content S20 of the exhaust gas downstream of the exhaust gas aftertreatment system 4 by means of the NOx sensor 22,
• - Comparing the first and the second recorded S10,S20 NOx content and
• - Control S40 of the internal combustion engine 3 so that an H2 content of the exhaust gas is adjusted based on the result of the comparison S30.

In order to record the first NOx content S10, the control program includes commands to run the model. The model is designed to determine a NOx content of the exhaust gas at an outlet of the internal combustion engine 3 (engine-out NOx).

In order to record the second NOx content S20, the control program includes commands to read in measurement data from the NOx sensor 22 and to process them.

For comparison S30, the control program includes commands to determine a NOx conversion rate for the NH3-SCR system 6 and the H2-SCR catalytic converter 5 based on the detected first NOx content S10 and the detected second NOx content S20.

To control S40 the internal combustion engine 3, the control program includes commands to adjust a fuel-air ratio, an ignition timing and an intake pressure or to supply hydrogen to the cylinders 13 in an exhaust stroke of the internal combustion engine 3 so that the H2 content of the exhaust gas based on the result of the comparison S30 is adjusted. The H2 contained in the exhaust gas is then used in the H2-SCR catalytic converter to reduce NOx emissions.

For example, if the comparison indicates that the H2 content needs to be increased, the control program adjusts the air-fuel ratio, spark timing, and/or intake pressure accordingly. Characteristic fields are stored in the control program for the adjustment. In alternative exemplary embodiments, measurement data and/or a model are used additionally or alternatively for the adaptation.

The control program includes commands to take into account a knock limit, a combustion center and a load requirement of the internal combustion engine 3 as well as resulting NOx emissions when adjusting, so that knocking combustion is avoided as far as possible, the necessary performance is provided with the lowest possible fuel consumption and NOx emissions are limited.

If controlling the fuel-air ratio, the ignition timing and the intake pressure is not sufficient to provide a desired H2 content in the exhaust gas and/or cannot be implemented in a sensible manner for energy reasons or emission specifications, the control program initiates the injection of hydrogen in an exhaust stroke Cylinder 13, so that the injected hydrogen is largely present without participating in chemical reactions in the exhaust gas.

When operating the internal combustion engine 3 with a high load, the control program includes commands to introduce ammonia via the dosing unit 19 into the exhaust line 10 upstream of the NH3-SCR catalyst 6 . Using the NH3, the NH3-SCR catalyst 6 reduces NOx emissions in the exhaust. In this way, NOx emissions can be effectively reduced over a large operating range of the internal combustion engine 3 .

3 shows an alternative exemplary embodiment of the exhaust gas aftertreatment system 4. Here the NH3-SCR system is designed as a passive system and only includes the NH3 catalytic converter 6. However, a NOx storage catalytic converter (NSK) 8 is arranged upstream of the NH3 catalytic converter.

The NSK is designed to adsorb emissions of nitrogen oxides (NOx) and to reduce them in regeneration mode with the formation of NH3. The NH3-SCR catalyst 6 can do that Store the NH3 formed by the NSK 8 and use it directly or at a later point in time to reduce nitrogen oxide emissions.

Upstream of the NSK 8, the exhaust aftertreatment system 4 includes a dosing unit 19 and a mixer. The dosing unit 19 is designed and set up here to introduce H2 into the exhaust line 10 . Thus, at operating points of the internal combustion engine 3 where the H2 content in the exhaust gas upstream of the NSK 8 is not high enough to form sufficient amounts of NH3 in the NSK 8, the control program causes H2 to be supplied in order to reduce NOx emissions in the NH3-SCR catalytic converter 6 to reduce.

4 shows a further, alternative embodiment of the exhaust gas aftertreatment system 4. In this embodiment, the exhaust gas aftertreatment system 4 between the H2-SCR catalyst 5 and the NH3-SCR system has two flows with a first 51 and a second 52 exhaust gas flow. The exhaust gas aftertreatment system 4 includes a closing device 53 so that an exhaust gas stream flowing through the first 51 and the second exhaust gas flow 52 can be controlled.

The first 51 and the second 52 exhaust gas flow each include a NOx storage catalytic converter 8. The dosing unit 19 is designed and set up here to supply the first and/or the second exhaust gas flow H2 as a reducing agent.

The closing device 53 is designed and set up to at least partially close the first 51 and the second 52 exhaust gas flow by means of a slide. At least one of the two exhaust gas flows 51,52 remains fully open.

In 4 the second exhaust flow 52 is fully open. The NSK 8 in the second exhaust flow 52 stores NOx emissions in a temperature range of approximately 200 - 500°C. As the filling level of the NSK 8 increases, its efficiency decreases and it has to be regenerated by reducing the NOx.

For the regeneration of a NOx storage catalytic converter 8, the control program causes the corresponding exhaust gas flow 51, 52 to be closed by the closing device 53. In 4 this is shown for the first exhaust gas flow 51 . In addition, the control program causes hydrogen to be introduced by the dosing unit 19. The hydrogen is converted in the NSK 8 during the regeneration to form NH3.

The exhaust gas aftertreatment system 4 includes a metering section 54 which is designed to conduct the introduced hydrogen from the metering unit 19 to the first 51 and/or second 52 exhaust gas flow. For this purpose, the H2 metering section 54 is designed in such a way that a pressure drop from a pressure at a first point P1 to a pressure at a second point P2 is sufficient to direct a slight scavenging flow of exhaust gas with the metered H2 in the direction of the NSK 8 to be regenerated. so that part of the hydrogen can be oxidized with the oxygen in the exhaust gas. The oxidation of the hydrogen results in the release of heat, as a result of which cooling down of the NSK 8 to be regenerated can be avoided or at least reduced.

The NH3 formed during regeneration in the NSK 8 is used in the downstream NH3-SCR catalytic converter 6 for NOx reduction. This in 4 The exemplary embodiment of the exhaust gas aftertreatment system shown allows an amount of NH3 to be set by the hydrogen metering.

The control program may position the closure device 53 such that the first 51 and second 52 exhaust flows are fully open. By introducing hydrogen through the dosing unit 19 via the dosing section 54, both NSK's 8 can be regenerated. This operation is particularly advantageous when operating the internal combustion engine at medium loads.

In a further, alternative exemplary embodiment, the NH3-SCR system 6 includes a three-way catalytic converter. In the three-way catalytic converter, emissions of CO, HC and NOx are reduced, with NH3 also being formed, in particular when the internal combustion engine 3 is operated in a non-stoichiometric manner. The NH3 is stored in the NH3-SCR system 6 and used directly or at a later point in time to reduce nitrogen oxide emissions.

In further, alternative exemplary embodiments, the exhaust gas aftertreatment system comprises a particle filter and/or an oxidation catalytic converter. The particulate filter reduces soot emissions, the oxidation catalytic converter reduces unburned hydrocarbons and carbon monoxide in the exhaust gas. In one exemplary embodiment, the particle filter is designed with an oxidation coating.

In further, alternative exemplary embodiments, the H2-SCR catalytic converter 5, the NH3-SCR catalytic converter 6 or the ASC 7 is designed as a particle filter with a corresponding coating.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102007021827 A1 [0002]

Claims (12)

Control unit (1) for a drive train (2), comprising an internal combustion engine (3) and an exhaust gas aftertreatment system (4), the internal combustion engine (3) being designed as a hydrogen engine, the exhaust gas aftertreatment system (4) including a first DeNOx system (5) and wherein the control unit (1) is designed and set up to carry out the following steps: - detecting a content (S10) of a component of an exhaust gas upstream or downstream of the first DeNOx system (5) and - Control (S40) of the internal combustion engine (3) so that an H2 content of the exhaust gas is adjusted based on the detected content (S10). Control unit (1) for a drive train (2), comprising an internal combustion engine (3) and an exhaust gas aftertreatment system (4), the internal combustion engine (3) being designed as a hydrogen engine, the exhaust gas aftertreatment system (4) including a first DeNOx system (5) and wherein the control unit (1) is designed and set up to carry out the following steps: - detecting a first content (S10) of a component of an exhaust gas upstream of the first DeNOx system (5), - detecting a second content (S20) of the component of the exhaust gas downstream of the first DeNOx system (5), - comparing (S30) the first and the second recorded (S10, S20) content of the component and - Controlling (S40) the internal combustion engine (3) so that an H2 content of the exhaust gas is adjusted based on the result of the comparison (S30). Control unit (1) after claim 1 or 2 , wherein the internal combustion engine (3) is designed as a direct-injection hydrogen engine and wherein the control unit (1) is designed and set up, when controlling (S40) the internal combustion engine (3), to supply hydrogen to the internal combustion engine (3) in an exhaust stroke of the internal combustion engine (3), so that the H2 content of the exhaust gas is adjusted based on the detected content (S10) or based on the result of the comparison (S30). Control unit (1) according to one of the preceding claims, wherein the control unit (1) is designed and set up, when controlling (S40) the internal combustion engine (3), a fuel-air ratio, an ignition point, an injection point, an EGR rate and/or or to control an inlet pressure. Control unit (1) according to one of the preceding claims, wherein the control unit (1) is designed and set up to take into account a knock limit, a combustion focus, a load requirement and/or NOx emissions of the internal combustion engine (3) during control (S40). Control unit (1) according to one of the preceding claims, wherein the exhaust gas aftertreatment system (4) comprises a dosing unit (19), wherein the dosing unit (19) is designed and set up to supply a reducing agent containing H2 or NH3 to the exhaust gas aftertreatment system (4) and wherein the control unit (1) is designed and set up to cause the reducing agent to be supplied by the dosing unit (19). Control device (1) according to one of the preceding claims, wherein the first DeNOx system (5) is designed as an H2-SCR system or as an NH3-SCR system. Control unit (1) according to one of Claims 1 until 6 , wherein the exhaust gas aftertreatment system (4) comprises a second DeNOx system (6), the second DeNOx system (6) being arranged downstream of the first DeNOx system (5), the first DeNOx system (5) being designed as an H2-SCR system and wherein the second DeNOx system (6) is designed as an NH3-SCR system. Control unit (1) after claim 7 or 8th , wherein the NH3-SCR system comprises a three-way catalytic converter or a NOx storage catalytic converter. Control unit (1) after claim 8 or 9 combined with claim 6 , wherein the control unit (1) is designed and set up to detect a loading condition of the NH3-SCR system (6) and to take the detected loading condition into account when supplying reducing agent through the dosing unit (19). Control unit according to one of Claims 8 until 10 combined with claim 6 , wherein the exhaust gas aftertreatment system (4) between the H2-SCR system (5) and the NH3-SCR system (6) has two flows with a first (51) and a second (52) exhaust gas flow, wherein - the exhaust gas aftertreatment system (4) has a closing device (53) so that an exhaust gas stream flowing through the first (51) and the second (52) exhaust gas flow can be controlled, - the first (51) and the second (52) exhaust gas flow each comprise a NOx storage catalytic converter (8) and - the Dosing unit (19) is designed and set up to supply a reducing agent to the first (51) and/or second (52) exhaust gas flow. Control device according to one of the preceding claims, wherein the exhaust gas aftertreatment system system (4) comprises a particle filter and/or an oxidation catalyst.

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