DE102015201902B4 - exhaust aftertreatment arrangement - Google Patents
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- DE102015201902B4 DE102015201902B4 DE102015201902.0A DE102015201902A DE102015201902B4 DE 102015201902 B4 DE102015201902 B4 DE 102015201902B4 DE 102015201902 A DE102015201902 A DE 102015201902A DE 102015201902 B4 DE102015201902 B4 DE 102015201902B4
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- 239000003054 catalyst Substances 0.000 claims abstract description 61
- 238000003860 storage Methods 0.000 claims abstract description 52
- 230000003197 catalytic effect Effects 0.000 claims abstract description 48
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000007789 gas Substances 0.000 claims abstract description 39
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 29
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000001301 oxygen Substances 0.000 claims abstract description 23
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 23
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 7
- 230000003647 oxidation Effects 0.000 claims abstract description 4
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 4
- 239000000758 substrate Substances 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims description 11
- 238000010276 construction Methods 0.000 claims 1
- 238000011144 upstream manufacturing Methods 0.000 description 9
- 239000000446 fuel Substances 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 239000011593 sulfur Substances 0.000 description 5
- 239000011449 brick Substances 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- 230000008929 regeneration Effects 0.000 description 4
- 238000011069 regeneration method Methods 0.000 description 4
- 238000010531 catalytic reduction reaction Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910001868 water Inorganic materials 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
- F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0842—Nitrogen oxides
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0864—Oxygen
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Emergency Medicine (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
Abgasnachbehandlungsanordnung, mitwenigstens einem NOx-Speicherkatalysator (LNT), wobei der NOx-Speicherkatalysator (LNT) einen ersten Katalysatorabschnitt und einen zweiten Katalysatorabschnitt aufweist, wobei der zweite Katalysatorabschnitt bezogen auf den Abgasstrom stromabwärts des ersten Katalysatorabschnitts angeordnet ist; undeinem SCR-Katalysator (140) oder einem SDPF-System mit einem auf einem Dieselpartikelfiltersubstrat angeordneten SCR-Washcoat,wobei der SCR-Katalysator (140) bzw. das SDPF-System bezogen auf den Abgasstrom stromabwärts des zweiten Katalysatorabschnitts (130) angeordnet ist und dazu ausgelegt ist, im Abgas enthaltene Stickoxide mittels Ammoniak zu Stickstoff (N2) zu reduzieren,dadurch gekennzeichnet, dassder erste Katalysatorabschnitt (120) zumindest eine Sauerstoffspeicherkomponente (OSC) aufweist, undder zweite Katalysatorabschnitt (130) zur Vermeidung einer Oxidation des Ammoniaks auf Seiten des zweiten Katalysatorabschnitts (130) keinerlei Sauerstoffspeicherkomponenten (OSC) aufweist.Exhaust gas aftertreatment arrangement, comprising at least one NOx storage catalyst (LNT), the NOx storage catalyst (LNT) having a first catalyst section and a second catalyst section, the second catalyst section being arranged downstream of the first catalyst section with respect to the exhaust gas flow; andan SCR catalyst (140) or an SDPF system with an SCR washcoat arranged on a diesel particulate filter substrate,wherein the SCR catalyst (140) or the SDPF system is arranged downstream of the second catalyst section (130) with respect to the exhaust gas flow and is designed to reduce nitrogen oxides contained in the exhaust gas to nitrogen (N2) by means of ammonia, characterized in that the first catalytic converter section (120) has at least one oxygen storage component (OSC), and the second catalytic converter section (130) to prevent oxidation of the ammonia on the part of the second catalyst section (130) has no oxygen storage components (OSC).
Description
Die Erfindung betrifft eine Abgasnachbehandlungsanordnung für ein Kraftfahrzeug.The invention relates to an exhaust aftertreatment arrangement for a motor vehicle.
Die Einführung immer strengerer NOx-Grenzwerte hat zur Entwicklung diverser Abgasnachbehandlungstechnologien geführt, um eine Kontrolle der NOx-Emissionen (= Stickoxid-Emissionen) im Abgas eines Dieselmotors zu erzielen.The introduction of increasingly stringent NOx limits has led to the development of various exhaust aftertreatment technologies to achieve control of NOx (=nitrogen oxides) emissions in the exhaust gas of a diesel engine.
Eine dieser Lösungen ist der sogenannte NOx-Speicherkatalysator (LNT), dessen Funktionsprinzip darauf beruht, Stickoxide (NOx) unter mageren Abgasbedingungen zunächst zu speichern und dann unter Einstellung eines fetten, reduzierenden Abgasgemischs in einer Regenerationsphase (welche typischerweise wenige Sekunden andauert) in unschädliche Komponenten, vor allem Stickstoff, Kohlendioxid und Wasserdampf, umzuwandeln. Die Häufigkeit, mit der diese Regenerationsphase durchgeführt wird, wird im Wesentlichen durch die NOx-Emissionen und die Speicherkapazität des NOx-Speicherkatalysators bestimmt, wobei diese Speicherkapazität wiederum von der Abgastemperatur abhängig ist.One of these solutions is the so-called NO x storage catalytic converter (LNT), the functional principle of which is based on first storing nitrogen oxides (NO x ) under lean exhaust gas conditions and then in a regeneration phase (which typically lasts a few seconds) while setting a rich, reducing exhaust gas mixture to convert harmless components, primarily nitrogen, carbon dioxide and water vapour. The frequency with which this regeneration phase is carried out is essentially determined by the NOx emissions and the storage capacity of the NOx storage catalytic converter, this storage capacity in turn being dependent on the exhaust gas temperature.
Eine zweite Technologie ist die selektive katalytische Reduktion in einem sogenannten SCR-Katalysator (SCR = „Selective Catalytic Reduction“ = „selektive katalytische Reduktion“), wobei am SCR-Katalysator die im Abgas enthaltenen Stickoxide mittels Ammoniak zu Stickstoff (N2) reduziert werden. Darüber hinaus ist der SCR-Katalysator dazu in der Lage, das z.B. stromaufwärts des SCR-Katalysators direkt dem Abgasstrom zugeführte Ammoniak bei niedrigen Abgastemperaturen zu speichern.A second technology is selective catalytic reduction in a so-called SCR catalytic converter (SCR = “Selective Catalytic Reduction” = “selective catalytic reduction”), whereby the nitrogen oxides contained in the exhaust gas are reduced to nitrogen (N 2 ) using ammonia at the SCR catalytic converter . In addition, the SCR catalytic converter is able to store the ammonia that is fed directly to the exhaust gas flow, for example upstream of the SCR catalytic converter, at low exhaust gas temperatures.
Des Weiteren ist es bekannt, in NOx-Speicherkatalysatoren (LNT) Sauerstoffspeicherkomponenten (OSC = „oxygen storage components“) einzusetzen, um eine CO/HC-Steuerung bei niedrigen Temperaturen sowie eine Erhöhung der Schwefeltoleranz zu erzielen.Furthermore, it is known to use oxygen storage components (OSC) in NOx storage catalytic converters (LNT) in order to achieve low temperature CO/HC control and an increase in sulfur tolerance.
Allerdings wird durch diese Sauerstoffspeicherkomponenten das Potential zur Ammoniak (NH3)-Erzeugung während der vergleichsweise kurzen Betriebsphasen mit fettem Luft-Kraftstoffgemisch (d. h. einem Verbrennungsluftverhältnis λ<1) bzw. in den Regenerationsphasen verringert. Diese verringerte Ammoniak (NH3)-Erzeugung ist darauf zurückzuführen, dass der in einer Betriebsphase mit fettem Luft-Kraftstoffgemisch in einem bezogen auf die Richtung des Abgasstroms vorderen bzw. stromaufwärtigen Bereich eines NOx-Speicherkatalysators (LNT) erzeugte Ammoniak (NH3) im hinteren bzw. stromabwärtigen Bereich des NOx-Speicherkatalysators (LNT), welcher immer noch einen mageren Bereich bildet (in dem Bedingungen entsprechend einem mageren Luft-Kraftstoffgemisch vorliegen), oxidiert werden kann. Ursache hierfür ist, dass die im hinteren bzw. stromabwärtigen Bereich des NOx-Speicherkatalysators (LNT) befindlichen Sauerstoffspeicherkomponenten (OSC) noch immer Sauerstoff enthalten.However, these oxygen storage components reduce the potential for ammonia (NH 3 ) production during the comparatively short operating phases with a rich air-fuel mixture (ie a combustion air ratio λ<1) or in the regeneration phases. This reduced ammonia (NH 3 ) production is due to the fact that the ammonia (NH 3 in the rear or downstream region of the NOx storage catalyst (LNT), which still forms a lean region (where conditions corresponding to a lean air-fuel mixture exist). This is because the oxygen storage components (OSC) located in the rear or downstream of the NOx storage catalyst (LNT) still contain oxygen.
Aus der
Aus der US 2007 / 0 056 268 A1 ist u. a. eine Abgasnachbehandlungsanordnung bekannt, welche zwei separate NOx-Speicherkatalysatorträger („LNT-Bricks“) aufweist, die in einer parallelen Anordnung derart konfiguriert sind, dass sie gleichzeitig separate Abgasanteile aufnehmen.US 2007/0 056 268 A1 discloses, inter alia, an exhaust gas aftertreatment arrangement which has two separate NO x storage catalyst carriers (“LNT bricks”) which are configured in a parallel arrangement in such a way that they simultaneously absorb separate exhaust gas components.
Aus der US 2004 / 0 076 565 A1 ist u. a. eine Abgasnachbehandlungsanordnung mit einem stromaufwärts eines SCR-Katalysators angeordneten NOx-Speicherkatalysator (LNT) bekannt, wobei die Ammoniak (NH3)-Erzeugung auf Seiten des NOx-Speicherkatalysators (LNT) dadurch optimiert wird, dass die Sauerstoffspeicherkapazität des NOx-Speicherkatalysators (LNT) vermindert wird.US 2004/0 076 565 A1 discloses, among other things, an exhaust gas aftertreatment arrangement with a NO x storage catalytic converter (LNT) arranged upstream of an SCR catalytic converter, with the ammonia (NH 3 ) generation on the side of the NO x storage catalytic converter (LNT) thereby being reduced is optimized that the oxygen storage capacity of the NO x storage catalyst (LNT) is reduced.
Aus der
Die
Aus der
Die US 2006 / 0 272 316 A1 beschreibt einen NOx-Absorptions- und Reduktionskatalysator, in welchem der Anteil an Sauerstoffspeicherkomponenten in einem vorderen bzw. einlassseitigen Halbabschnitt geringer ist als in einem hinteren bzw. auslassseitigen Halbabschnitt.US 2006/0 272 316 A1 describes a NO x absorption and reduction catalyst, in which Chem, the proportion of oxygen storage components in a front or inlet-side half section is lower than in a rear or outlet-side half section.
Es ist eine Aufgabe der vorliegenden Erfindung, eine Abgasnachbehandlungsanordnung bereitzustellen, welche eine verbesserte Reduzierung von Stickoxiden im Abgas ermöglicht.It is an object of the present invention to provide an exhaust gas aftertreatment arrangement which enables an improved reduction of nitrogen oxides in the exhaust gas.
Diese Aufgabe wird durch die Abgasnachbehandlungsanordnung gemäß den Merkmalen des unabhängigen Anspruchs 1 gelöst.This object is achieved by the exhaust gas aftertreatment arrangement according to the features of independent claim 1 .
Vorteilhafte Ausgestaltungen der Erfindung sind in den abhängigen Patentansprüchen beschrieben.Advantageous refinements of the invention are described in the dependent patent claims.
Der vorliegenden Erfindung liegt insbesondere das Konzept zugrunde, in einer Abgasnachbehandlungsanordnung mit einem NOx-Speicherkatalysator (LNT) einen mit Sauerstoffspeicherkomponenten (OSC) versehenen ersten Katalysatorabschnitt des NOx-Speicherkatalysators (LNT) mit einem von solchen Sauerstoffspeicherkomponenten (OSC) freien zweiten Katalysatorabschnitt des NOx-Speicherkatalysators (LNT) zu kombinieren, wobei der zweite Katalysatorabschnitt bezogen auf den Abgasstrom stromabwärts des ersten Katalysatorabschnitts angeordnet ist. In dieser Anordnung kann aufgrund des ersten (Sauerstoffspeicherkomponenten aufweisenden) Katalysatorabschnitts die erforderliche Funktionalität hinsichtlich Schwefeltoleranz sowie auch CO/HC-Steuerung gewährleistet werden, wobei zugleich über den zweiten (von Sauerstoffspeicherkomponenten freien) Katalysatorabschnitt eine hinreichende Ammoniak (NH3)-Erzeugung in Betriebsphasen mit fettem Luft-Kraftstoff-Gemisch (d.h. mit einem Verbrennungsluftverhältnis λ < 1), also insbesondere in Regenerations- bzw. Reinigungsphasen erzielt werden kann.The present invention is based in particular on the concept, in an exhaust gas aftertreatment arrangement with an NO x storage catalytic converter (LNT), a first catalytic converter section of the NO x storage catalytic converter (LNT) provided with oxygen storage components (OSC) with a second catalytic converter section of the NO x storage catalytic converter (LNT) free of such oxygen storage components (OSC). NO x storage catalyst (LNT) to combine, wherein the second catalyst section is arranged relative to the exhaust gas flow downstream of the first catalyst section. In this arrangement, due to the first catalytic converter section (having oxygen storage components), the required functionality in terms of sulfur tolerance and also CO/HC control can be ensured, while at the same time sufficient ammonia (NH 3 ) production in operating phases with the second catalytic converter section (free of oxygen storage components). rich air-fuel mixture (ie with a combustion air ratio λ <1), so can be achieved in particular in regeneration or cleaning phases.
Dabei wird die hinreichende Ammoniak (NH3)-Bereitstellung in der Abgasnachbehandlungsanordnung - insbesondere für einen stromabwärts des NOx-Speicherkatalysators bzw. dessen zweiten Katalysatorabschnitts angeordneten SCR-Katalysator - dadurch erreicht, dass in Betriebsphasen mit fettem Luft-Kraftstoff-Gemisch im Wesentlichen keine Oxidation mehr auf Seiten des zweiten (d.h. bezogen auf den Abgasstrom stromabwärts angeordneten) Katalysatorabschnitts des NOx-Speicherkatalysators (LNT) erfolgt.The sufficient provision of ammonia (NH 3 ) in the exhaust gas aftertreatment arrangement - in particular for an SCR catalytic converter arranged downstream of the NO x storage catalytic converter or its second catalytic converter section - is achieved in that, in operating phases with a rich air-fuel mixture, essentially no Oxidation takes place more on the part of the second (ie based on the exhaust gas flow arranged downstream) catalyst section of the NO x storage catalyst (LNT).
Der erfindungsgemäß somit in ausreichender Menge zur Verfügung gestellte Ammoniak (NH3) kann insbesondere in einem stromabwärts des NOx-Speicherkatalysators (LNT) angeordneten SCR-Katalysator dazu genutzt werden, die im Abgas enthaltenen Stickoxide zu Stickstoff (N2) zu reduzieren.The ammonia (NH 3 ) made available according to the invention in sufficient quantity can be used in particular in an SCR catalytic converter arranged downstream of the NOx storage catalytic converter (LNT) to reduce the nitrogen oxides contained in the exhaust gas to nitrogen (N 2 ).
Gemäß einer Ausführungsform weist der NOx-Speicherkatalysator (LNT) zwei separate Katalysatorträger (Katalysator-Bricks) auf. Der erste Katalysatorträger ist mit einem LNT-Washcoat beschichtet, welches Sauerstoffspeicherkomponenten (OSC) aufweist, um die erwünschte Erhöhung der Schwefeltoleranz sowie die CO/HC-Steuerung bei niedrigen Temperaturen zu erzielen. Bei diesen Sauerstoffspeicherkomponenten (OSC) kann es sich beispielsweise um eine CeO2/ZrO2-Mischung handeln.According to one embodiment, the NO x storage catalyst (LNT) has two separate catalyst supports (catalyst bricks). The first catalyst support is coated with an LNT washcoat containing oxygen storage components (OSC) to achieve the desired increase in sulfur tolerance and CO/HC control at low temperatures. These oxygen storage components (OSC) can be, for example, a CeO 2 /ZrO 2 mixture.
Der zweite Katalysatorträger weist keinerlei Sauerstoffspeicherkomponenten (OSC) auf, so dass jeglicher Ammoniak, welcher stromaufwärts des zweiten Katalysatorträgers produziert wird, in Reinigungsphasen mit fettem Luft-Kraftstoff-Gemisch nicht oxidiert wird. Hierdurch kann eine erhöhte Ammoniak (NH3)-Ausbeute erzielt werden, welche wiederum z. B. in einem stromabwärts angeordneten SCR-Katalysator zur weiteren NOx-Umwandlung genutzt werden kann.The second catalyst support does not have any oxygen storage components (OSC) so that any ammonia produced upstream of the second catalyst support is not oxidized during rich air-fuel mixture purge phases. This allows an increased ammonia (NH 3 ) yield can be achieved, which in turn z. B. can be used in a downstream SCR catalyst for further NO x conversion.
In weiteren Ausführungsformen kann das erfindungsgemäße Konzept auch mit einem einzigen Katalysatorträger realisiert werden, welcher zwei unterschiedliche, zueinander in axialer Richtung versetzte Zonen aufweist.In further embodiments, the concept according to the invention can also be implemented with a single catalyst support, which has two different zones offset from one another in the axial direction.
Im Ergebnis kann durch die Erfindung die Ammoniak (NH3)-Menge, welche von einem NOx-Speicherkatalysator in Reinigungsphasen mit fettem Gemisch erzeugt wird, erhöht werden. Der zusätzliche Ammoniak (NH3) kann dazu dienen, Stickoxide (NOx), welche von dem NOx-Speicherkatalysator (LNT) entweichen, in einem stromabwärts vom NOx-Speicherkatalysator angeordneten SCR-Katalysator umzuwandeln.As a result, the amount of ammonia (NH 3 ) generated by a NO x storage catalytic converter in cleaning phases with a rich mixture can be increased by the invention. The additional ammonia (NH 3 ) may serve to convert nitrogen oxides ( NOx ) escaping from the NOx trap catalyst (LNT) in an SCR catalyst located downstream of the NOx trap catalyst.
Weitere Ausgestaltungen der Erfindung sind der Beschreibung sowie den Unteransprüchen zu entnehmen.Further configurations of the invention can be found in the description and in the dependent claims.
Die Erfindung wird nachstehend anhand eines in der beigefügten Abbildung dargestellten Ausführungsbeispiels näher erläutert.The invention is explained in more detail below with reference to an exemplary embodiment shown in the accompanying figure.
Die einzige
Gemäß
In dem dargestellten Ausführungsbeispiel von
Von den besagten beiden Katalysatorabschnitten weist der stromaufwärtige erste Katalysatorabschnitt 120 Sauerstoffspeicherkomponenten (OSC) auf, welche z. B. eine CeO2/ZrO2-Mischung aufweisen können. Hingegen ist der zweite, stromabwärtige Katalysatorabschnitt 130 frei von solchen Sauerstoffspeicherkomponenten. Durch diese Ausgestaltung wird erreicht, dass zum einen aufgrund der in dem ersten Katalysatorabschnitt 120 vorhandenen Sauerstoffspeicherkomponenten (OSC) im Betrieb eine ausreichende Schwefeltoleranz sowie CO/HC-Steuerung gewährleistet werden kann, wohingegen aufgrund des Umstandes, dass der zweite Katalysatorabschnitt 130 keine Sauerstoffspeicherkomponenten (OSC) enthält, eine ausreichende Ammoniak (NH3)-Bereitstellung durch den NOx-Speicherkatalysator 110 gegeben ist, da auf Seiten des zweiten Katalysatorabschnitts 130 keine signifikante Oxidation des Ammoniaks (NH3) mehr erfolgt.Of the said two catalyst sections, the upstream
Der erfindungsgemäß somit in ausreichender Weise stromabwärts des NOx-Speicherkatalysators 110 bereitgestellte Ammoniak (NH3) kann insbesondere in einem stromabwärts des zweiten Katalysatorabschnitts 130 befindlichen SCR-Katalysator 140 zur Reduktion der im Abgas enthaltenen Stickoxide zu Stickstoff (N2) genutzt werden.The ammonia (NH 3 ) provided according to the invention in a sufficient manner downstream of the NO x storage
In weiteren Ausführungsformen kann anstelle des SCR-Katalysators 140 auch ein SDPF-System (mit einem SCR-Washcoat auf einem Dieselpartikelfiltersubstrat) verwendet werden. Mit „135“ ist eine optionale Reduktionsmittelzufuhr (z.B. zur Zufuhr von Harnstoff) in den Bereich stromaufwärts des SCR-Katalysators 140 bezeichnet.In further embodiments, an SDPF system (with an SCR washcoat on a diesel particulate filter substrate) can also be used instead of the SCR
Im Ergebnis wird durch die erfindungsgemäße Abgasnachbehandlungsanordnung unter Gewährleistung einer hinreichenden Schwefeltoleranz eine verbesserte Ammoniak (NH3)-Bereitstellung und damit insgesamt eine verbesserte Reduzierung von Stickoxiden im Abgas ermöglicht.As a result, the exhaust gas aftertreatment arrangement according to the invention enables improved ammonia (NH 3 ) provision and thus an overall improved reduction in nitrogen oxides in the exhaust gas, while ensuring sufficient sulfur tolerance.
Claims (5)
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