DE10005954A1 - Desulfurization of a storage catalytic converter by heating - Google Patents

Desulfurization of a storage catalytic converter by heating

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Publication number
DE10005954A1
DE10005954A1 DE10005954A DE10005954A DE10005954A1 DE 10005954 A1 DE10005954 A1 DE 10005954A1 DE 10005954 A DE10005954 A DE 10005954A DE 10005954 A DE10005954 A DE 10005954A DE 10005954 A1 DE10005954 A1 DE 10005954A1
Authority
DE
Germany
Prior art keywords
exhaust gas
catalytic converter
catalyst
heating
storage catalytic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
DE10005954A
Other languages
German (de)
Inventor
Eberhard Schnaibel
Oliver Wiemers
Matthias Dall
Andreas Kufferath
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Priority to DE10005954A priority Critical patent/DE10005954A1/en
Priority to PCT/DE2001/000270 priority patent/WO2001059271A1/en
Priority to JP2001558586A priority patent/JP2003522874A/en
Priority to EP01911381A priority patent/EP1257736A1/en
Priority to KR1020027010151A priority patent/KR20020076289A/en
Priority to US10/203,446 priority patent/US20030131588A1/en
Priority to BR0108148-9A priority patent/BR0108148A/en
Publication of DE10005954A1 publication Critical patent/DE10005954A1/en
Withdrawn legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/008Controlling each cylinder individually
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404Removing only nitrogen compounds
    • B01D53/9409Nitrogen oxides
    • B01D53/9431Processes characterised by a specific device
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495Controlling the catalytic process
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust 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
    • F01N13/009Exhaust 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust 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
    • F01N13/011Exhaust 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 purifying devices arranged in parallel
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828Exhaust 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
    • F01N3/0842Nitrogen oxides
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/025Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by changing the composition of the exhaust gas, e.g. for exothermic reaction on exhaust gas treating apparatus
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/0275Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
    • F02D41/028Desulfurisation of NOx traps or adsorbent
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1438Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1439Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
    • F02D41/1441Plural sensors
    • F02D41/1443Plural sensors with one sensor per cylinder or group of cylinders
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/04Sulfur or sulfur oxides
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Health & Medical Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

A method for heating a main catalyst arranged behind at least one pre-catalyst is disclosed, whereby unburnt fuel generated by the engine is introduced into the exhaust gas, before the main catalyst with the simultaneous presence of an excess of air before the main catalyst. The generation of unburnt fuel by the engine is temporally and/or spatially coupled to the generation of an excess of air in the exhaust gas by the engine.

Description

Stand der TechnikState of the art

Bei Verbrennungsmotoren in Kraftfahrzeugen wird bei magerem Motorbetrieb (λ < 1) zur Erfüllung gesetzlich vorgegebener Abgasgrenzwerte ein sogenannter Speicherkatalysator für die bei der Verbrennung entstehenden Stickoxide NOx benötigt. Bei der Verbrennung entstehen weiterhin Schwefeloxide. Durch die große Affinität der aktiven Zentren, d. h. der Speicherplätze des NOx-Speicherkatalysators gegenüber den bei der Verbrennung des Kraftstoffs entstehenden Schwefeloxiden (SOx), werden primär die aktiven Zentren durch das SOx belegt. Diese dabei entstehenden Sulfate sind thermisch so stabil, daß sie im normalen Fahrbetrieb nicht wieder freigesetzt werden. Als Folge sinkt mit zunehmender Schwefelbeladung die Speicherfähigkeit des Katalysators für die Stickoxide. Bei einer erhöhten Temperatur im Katalysator (T < 600°C), bei gleichzeitig reduzierenden Bedingungen (λ < 1) sind die Sulfate thermodynamisch nicht mehr stabil und werden als Schwefelwasserstoff (H2S) und Schwefeldioxid (SO2) freigesetzt. Um die Speicherfähigkeit zu erhalten, bzw. wieder herzustellen, muß in bestimmten Abständen der Speicherkatalysator kurzzeitig fett bei erhöhten Temperaturen betrieben werden. Dies ist beispielsweise aus der EP 580 389 bekannt. In internal combustion engines in motor vehicles with lean engine operation (λ <1), a so-called storage catalytic converter for the nitrogen oxides NO x produced during combustion is required to meet legally prescribed exhaust gas limit values. Sulfur oxides continue to be generated during combustion. Due to the high affinity of the active centers, ie the storage locations of the NO x storage catalytic converter with respect to the sulfur oxides (SO x ) formed during the combustion of the fuel, the active centers are primarily occupied by the SO x . The resulting sulfates are so thermally stable that they are not released during normal driving. As a result, the storage capacity of the catalyst for the nitrogen oxides decreases with increasing sulfur loading. At an elevated temperature in the catalyst (T <600 ° C), with simultaneously reducing conditions (λ <1), the sulfates are no longer thermodynamically stable and are released as hydrogen sulfide (H 2 S) and sulfur dioxide (SO 2 ). In order to maintain or restore the storage capacity, the storage catalytic converter must be operated briefly in bold at elevated temperatures at certain intervals. This is known for example from EP 580 389.

Zur Aufheizung auf die geforderte Temperatur zum Entschwefeln des Speicherkatalaysators kann ein später Zündwinkel eingestellt werden, was über eine Verschlechterung des Wirkungsgrades des Verbrennungsmotors zu einer erhöhten Abgastemperatur führt, die zur Aufheizung des Speicherkatalysators führt. Der Aufheizeffekt kann durch das Erzeugen von brennbarem Gemisch vor dem Katalysator verstärkt werden. Bevorzugt erfolgt das Erzeugen von brennnarem Gemisch durch eine Erhöhung der unverbrannten HC- Rohemissionen des Motors vor den Katalysatoren in Verbindung mit einem Sauerstoffüberschuß im Abgas. Das so vor dem Katalysator entstehende brennbare Gemisch reagiert im Katalysator exotherm und heizt diesen auf.For heating to the required temperature for Desulphurization of the storage catalyst can be done later Ignition angle can be set, what about a Deterioration of the efficiency of the internal combustion engine leads to an increased exhaust gas temperature, which leads to heating of the storage catalytic converter. The heating effect can be caused by generating combustible mixture in front of the catalyst be reinforced. The generation of preferably takes place combustible mixture by increasing the unburned HC Raw engine emissions in front of the catalytic converters with an excess of oxygen in the exhaust gas. That before The resulting combustible mixture reacts in the Catalyst exothermic and heats it up.

Moderne Abgasreinigungsanlagen weisen neben dem Speicherkatalysator weitere Katalysatoren, insbesondere einen motornah angeordneten Vorkatalysator auf.Modern exhaust gas cleaning systems have in addition to that Storage catalyst other catalysts, in particular a pre-catalytic converter arranged close to the engine.

Durch die konventionell eingesetzte Aufheizung des Speicherkatalysators kann der Vorkatalysator thermisch stark belastet werden. Dies kann zu einer frühzeitigen Deaktivierung des Katalysators führen.Due to the conventionally used heating of the Storage catalytic converter, the pre-catalyst can be thermally strong be charged. This can be premature Deactivate the catalyst.

Die Aufgabe der Erfindung liegt darin eine Aufheizung des Speicherkatalysators zu ermöglichen, die eine unzulässige Aufheizung des Vorkatalysators vermeidet.The object of the invention is to heat the To enable storage catalytic converter, which is an impermissible Avoid heating the pre-catalyst.

Diese Aufgabe wird mit den Merkmalen des Anspruchs 1 gelöst.This object is achieved with the features of claim 1.

Der Kern der Erfindung liegt darin, unverbranntes Gemisch durch motorische Maßnahmen bereitzustellen und gleichzeitig dafür zu sorgen, daß dies nicht oder nur in geringem Umfang im Vorkatalysator exotherm reagieren kann. The essence of the invention is unburned mixture through motor measures and at the same time to ensure that this is not or only to a small extent can react exothermically in the pre-catalyst.  

Dies wird durch eine zeitliche oder räumliche Entkopplung der Emission von Luftüberschuß im Abgas und HC-Überschuß im Abgas erreicht.This is achieved through a temporal or spatial decoupling the emission of excess air in the exhaust gas and excess HC in Exhaust gas reached.

Damit kann relativ unabhängig von den Temperaturen in den Vorkatalysatoren und dem aktuellen Lastpunkt des Motors, die benötigte Temperatur im Hauptkatalysator eingestellt werden. Die bei den konventionell eingesetzten Methoden auftretende hohe thermische Belastung des Vorkatalysators, die zu einer Deaktivierung führen kann, wird vermieden.This can be relatively independent of the temperatures in the Pre-catalysts and the current load point of the engine, the required temperature can be set in the main catalyst. The one that occurs with the conventionally used methods high thermal load on the pre-catalyst, which leads to a Deactivation can be avoided.

Ausführungsbeispiele der Erfindung sind in den Figuren dargestellt und werden weiter unten beschrieben.Embodiments of the invention are in the figures are shown and are described below.

Fig. 1 repräsentiert den Stand der Technik. Fig. 1 represents the prior art.

Fig. 2 zeigt ein erstes Ausführungsbeispiel der Erfindung und Fig. 2 zeigt ein zweites Ausführungsbeispiel. Fig. 2 shows a first embodiment of the invention and Fig. 2 shows a second embodiment.

Die 1 in der Fig. 1 stellt einen Verbrennungsmotor dar, der aus einem Ansaugrohr 2 mit Luft und aus einer Einspritzdüsenanordnung 3 mit Kraftstoff versorgt wird. Die Einspritzdüsenanordnung wird von einem Steuergerät 4 mit Einspitzimpilsbreiten angesteuert. Dabei werden die Einspritzimpulsbreiten auf der Basis erfaßter Betriebsparameter des Verbrennungsmotors berechnet. Beispiele solcher Betriebsparameter sind die Menge der angesaugten Luft, die von einem Sensor 5 erfaßt wird, die Drehzahl des Motors, die von einem Sensor 6 erfaßt wird und die Zusammensetzung des Abgases, bspw. dessen Sauerstoffgehalt, der von einem Sensor 7 erfaßt wird. Neben der Einspritzventilanordnung steuert das Steuergerät die Zündvorrichtung 8, um das Kraftstoff/Luftgemisch in den einzelnen Motorzylindern 9-12 jeweils zum richtigen Zeitpunkt zu zünden. 1 in FIG. 1 represents an internal combustion engine which is supplied with air from an intake pipe 2 and with fuel from an injection nozzle arrangement 3 . The injection nozzle arrangement is controlled by a control unit 4 with injection peak widths. The injection pulse widths are calculated on the basis of detected operating parameters of the internal combustion engine. Examples of such operating parameters are the amount of air drawn in which is detected by a sensor 5 , the speed of the engine which is detected by a sensor 6 and the composition of the exhaust gas, for example its oxygen content, which is detected by a sensor 7 . In addition to the injection valve arrangement, the control unit controls the ignition device 8 in order to ignite the fuel / air mixture in the individual engine cylinders 9-12 at the right time in each case.

Die Ziffer 13 bezeichnet einen Vorkatalysator und die Ziffer 14 einen Speicherkatalysator.The number 13 denotes a pre-catalytic converter and the number 14 a storage catalytic converter.

Bei der dargestellten Anordnung wird das Problem der Aufheizung des Speicherkatalysators durch motorische Maßnahmen deutlich: Die Erhöhung der Abgastemperatur durch Spätzündung und die Erzeugung von brennbarem Gemisch mit einer Gemischzusammensetzung von Lambda 1a direkt hinter dem Verbrennungsmotor wirkt sich nicht nur im Speicherkatalysator aus, sondern unerwünschtermaßen bereits im Vorkatalysator.In the arrangement shown, the problem of heating the storage catalytic converter through engine measures becomes clear: the increase in the exhaust gas temperature through spark ignition and the generation of a combustible mixture with a mixture composition of lambda 1 a directly behind the internal combustion engine not only has an effect in the storage catalytic converter, but also undesirably in the pre-catalyst.

Eine Abhilfe zeigt Fig. 2: Die Fig. 2 zeigt als wesentlichen Unterschied zu der Fig. 1 zwei getrennte Vorkatalysatoren, wobei jeweils ein Vorkatalysator einer bestimmten Zylindergruppe zugeordnet ist. Die Zuordnung wird dabei durch eine Trennung der Abgasrohre erreicht.A remedy is shown in FIG. 2: As an essential difference from FIG. 1, FIG. 2 shows two separate precatalysts, one precatalyst being assigned to a specific cylinder group. The assignment is achieved by separating the exhaust pipes.

Aus Gründen der Übersichtlichkeit ist hier wie auch in der folgenden Fig. 3 die Peripherie der Sensorik und der Kraftstoff- sowie Luftzuführung aus der Fig. 1 nicht dargestellt. Diese Peripherie ist aber sowohl bei dem Gegenstand der Fig. 2 als auch bei dem Gegenstand der Fig. 3 vorhanden, so diese beiden Figuren insoweit in Verbindung mit der Fig. 1 zu betrachten sind.For reasons of clarity, the periphery of the sensors and the fuel and air supply from FIG. 1 are not shown here, as in FIG. 3 below. This periphery is present both in the subject of FIG. 2 and in the subject of FIG. 3, so these two figures are to be considered in connection with FIG. 1.

Die Trennung der Abgasführung verschiedener Zylindergruppen ermöglicht erfindungsgemäß eine Zusammenführung eines mageren und eines fetten Abgasstromes vor dem Speicherkatalysator.The separation of the exhaust gas routing of different cylinder groups enables a merger of a lean and a rich exhaust gas flow before Storage catalytic converter.

Dazu wird beispielsweise die Zylindergruppe, deren Abgas den Vorkatalysator 1 (V.Kat. 1) durchströmt mit fettem Gemisch ohne Luftüberschuß (Lambda 1b) betrieben. Als Folge enthält das Abgas dieser Zylindergruppe unverbrannten Kraftstoff bei gleichzeitigem Mangel an Sauerstoff. Aufgrund des Sauerstoffmangels kann der überschüssige Kraftstoff in dem Vorkatalysator 1 nicht exotherm reagieren. Vorkatalysator 1 wird daher nicht aufgeheizt.For this purpose, the cylinder group, for example, whose exhaust gas flows through the pre-catalytic converter 1 (V. cat. 1) is operated with a rich mixture without excess air (lambda 1 b). As a result, the exhaust gas from this group of cylinders contains unburned fuel with a lack of oxygen. Due to the lack of oxygen, the excess fuel in the pre-catalytic converter 1 cannot react exothermically. Pre-catalyst 1 is therefore not heated.

Weiterhin wird dann, wenn der Vorkatalysator 1 von Abgas mit Kraftstoffüberschuß durchströmt wird, die andere Zylindergruppe, deren Abgas den Vorkatalysator 2 (V.Kat. 2) durchströmt, mit Kraftstoffmangel und damit mit Sauerstoffüberschuß (Lambda 2b) betrieben. Daraus resultiert ein Sauerstoffüberschuß im Vorkatalysator 2, für den kein Kraftstoff als Reaktionspartner im Vorkatalysator 2 zur Verfügung steht. Damit findet auch im Vorkatalysator 2 keine exotherme Reaktion statt, so daß auch der Vorkatalysator 2 nicht aufgeheizt wird.Furthermore, if exhaust gas with excess fuel flows through the pre-catalyst 1 , the other cylinder group, the exhaust gas of which flows through the pre-catalyst 2 (V.Kat. 2), is operated with a lack of fuel and thus with an excess of oxygen (Lambda 2 b). This results in an excess of oxygen in the pre-catalyst 2 , for which no fuel is available as a reactant in the pre-catalyst 2 . So that there is no exothermic reaction in the pre-catalyst 2 , so that the pre-catalyst 2 is not heated.

Eine Zusammenführung des Luftüberschusses der zweiten Zylindergruppe mit dem Kraftstoffüberschuß der ersten Zylindergruppe zu einem Abgas, das einem Lambdawert Lambda 3b entspricht, findet findet erst hinter den beiden Vorkatalysatoren statt. Das Abgas mit Lambda 3b enthält damit sowohl unverbrannten Kraftstoff als auch den notwendigen Reaktionspartner Sauerstoff. Beide Bestandteile reagieren erst im Speicherkatalysator exotherm und heizen diesem damit erwünschtermaßen auf.A merging of the excess air of the second cylinder group with the excess fuel of the first cylinder group to form an exhaust gas that corresponds to a lambda value Lambda 3 b takes place only behind the two pre-catalysts. The exhaust gas with lambda 3b thus contains both unburned fuel and the necessary reaction partner oxygen. Both components only react exothermically in the storage catalytic converter and thus heat it up as desired.

Mit anderen Worten: Für die in diesem Ausführungsbeispiel aufgezeigte Erfindung sind mindestens zwei Vorkatalysatoren zur Realisierung notwendig. In der Aufheizphase werden die beiden Vorkatalysatoren mit unterschiedlichen Lambdas (λ1b und λ2b) beaufschlagt. Eine Realisierung ist durch die Bankweise (Bank 1/Bank 2) unterschiedlichen Einspritzmengen des Kraftstoffs problemlos möglich. Ein Lambdawert muß hierbei größer 1 sein (mager), der andere kleiner 1 (fett) sein. Das Gemischlambda (λ3b) sollte sich, resultierend aus den Einzellambdas (λ1b und λ2b) und den Abgasmassenströmen, auf einen Wert um λ3b = 1 einstellen. Im Speicherkatalysator erfolgt dann die Umsetzung des im Abgas vorliegenden Heizwertes, der hauptsächlich aus dem fetten Abgas nach V.Kat. stammt, mit dem vorhandenen Sauerstoff, der hauptsächlich dem mageren Abgas nach V.Kat. entstammt. Die Temperaturerhöhung im Hauptkatalysator resultiert aus der Umsetzung der nicht vollständig oxidierten Komponenten mit dem Sauerstoff.In other words: for those in this embodiment shown invention are at least two pre-catalysts necessary for realization. In the heating phase, the two pre-catalysts with different lambdas (λ1b and λ2b) acted upon. A realization is through the Bank way (bank 1 / bank 2) different Injection quantities of the fuel are possible without any problems. On Lambda value must be greater than 1 (lean), the other be less than 1 (bold). The mixture lambda (λ3b) should  resulting from the individual lambdas (λ1b and λ2b) and the Set exhaust gas mass flows to a value around λ3b = 1. in the Storage catalytic converter is then implemented in the exhaust gas present calorific value, mainly from the fat Exhaust gas according to V. Cat. comes with the available oxygen, which is mainly the lean exhaust gas according to V.Kat. originated. The temperature increase in the main catalyst results from the implementation of the not fully oxidized components with the oxygen.

Denkbar sind auch Varianten, bei denen mehr als zwei Vorkatalysatoren eingesetzt werden. Das Sammel-lambda vor Sp. Kat. wird dann durch die Einzellambdas der V.Kat. wieder auf ungefähr 1 eingestellt. Ein Einsatz ist auch bei anderen Zylinderzahlen denkbar, wobei erfindungsgemäß immer mindestens eine Zweizylinderanordnung vorliegen muß.Variants are also conceivable in which more than two Pre-catalysts are used. The collecting lambda before Sp. Kat. Is then replaced by the single lambdas of the V.Kat. again set to about 1. An application is also with other numbers of cylinders conceivable, but always according to the invention there must be at least one two-cylinder arrangement.

Bei dem zweiten Ausführungsbeispiel, das in der Fig. 3 dargestellt ist, findet ebenfalls eine Vermischung fetter und magerer Abgaspakete erst nach dem Vorkatalysator statt.In the second exemplary embodiment, which is shown in FIG. 3, rich and lean exhaust gas packs likewise only mix after the pre-catalytic converter.

Bei diesem Ausführungsbeispiel wird dem aufzuheizenden Hauptkatalysator ein Mischelement (statischer Mischer) vorgeschaltet. Dieser besteht beispielsweise aus einem Hohlraum, der mit verwinkelt zueinander angeordneten Strömungsleitblechen versehen ist. Die Strömungsleitbleche lenken die einzelnen Strömungsvolumina ineinander und verlangsamen die Strömung. Dadurch wird eine Durchmischung einzelner Abgasportionen erreicht.In this embodiment, the is to be heated Main catalyst a mixing element (static mixer) upstream. This consists, for example, of a Cavity that is arranged with angled to each other Flow baffles is provided. The flow baffles direct the individual flow volumes into each other and slow down the flow. This creates a thorough mixing individual portions of exhaust gas reached.

Der Kern des 2. Ausführungsbeispiels liegt in der Vermischung der mageren und fetten Abgasportionen vor dem Speicherkatalysator, wobei die mageren und fetten Abgasportionen hier zeitlich getrennt voneinander motorisch erzeugt werden.The core of the second embodiment lies in Mixing the lean and rich portions of exhaust gas before Storage catalytic converter, the lean and fat  Exhaust gas portions here separated from each other by motor be generated.

Dazu wird der Motor in der Aufheizphase immer wechselnd fett (λ < 1) und mager (λ < 1) betrieben. Alternativ können auch einzelne Zylinder durch eine unterschiedliche Einspritzmenge fett und mager betrieben werden. Die damit entstehenden fetten und mageren Abgaspakete werden nur zum Teil im Vorkatalysator rückvermischt so daß auch noch nach dem Vorkatalysator magere und fette Abgaspakete vorliegen.For this purpose, the engine always becomes alternately rich in the heating phase (λ <1) and lean (λ <1) operated. Alternatively, you can individual cylinders due to a different injection quantity be operated fat and lean. The resulting fat and lean exhaust gas packages are only partially in the Pre-catalyst backmixed so that even after Pre-catalytic converter lean and rich exhaust gas packs are present.

In dem dem Vorkatalysator nachgeschalteten statischen Mischer erfolgt dann durch die dort erfolgende Rückvermischung eine Homogenisierung des Abgases (das Verhalten des statischen Mischers ähnelt durch die Verschmierung der Verweilzeit einem idealen Rührkessel mit kleinem Volumen).In the static downstream of the pre-catalyst Mixer then takes place through the one taking place there Backmixing a homogenization of the exhaust gas (the Behavior of the static mixer is similar due to the Smear the residence time with an ideal stirred tank small volume).

Im Speicherkatalysator erfolgt dann die Umsetzung des im Abgas vorliegenden Heizwertes, der hauptsächlich aus dem fetten Abgaspaketen stammt, mit dem vorhandenen Sauerstoff, der hauptsächlich aus den mageren Abgaspaketen stammt. Die Temperaturerhöhung im Hauptkatalysator resultiert aus der Umsetzung der nicht vollständig oxidierten Komponenten mit dem Sauerstoff.The conversion of the im takes place in the storage catalytic converter Exhaust gas calorific value, mainly from the fat exhaust packs comes with the available oxygen, which mainly comes from the lean exhaust gas packages. The Temperature increase in the main catalyst results from the Implementation of the not fully oxidized components the oxygen.

Die Periodendauer der Fett- und Magerzyklen richtet sich nach den Verhältnissen von zu erwartendem Abgasvolumenstrom und dem Volumen des statischen Mischers, bzw. der geforderten Güte der Rückvermischung. Eine möglichst geringe Sauerstoffspeicherfähigkeit des Vorkatalysators ist anzustreben, damit nicht eine unnötige Totzeit bezüglich der fetten und mageren Abgaspakete in das System eingeführt wird. The period of the fat and lean cycles is determined according to the ratios of the expected exhaust gas volume flow and the volume of the static mixer, or the required quality of backmixing. The lowest possible Oxygen storage capacity of the pre-catalyst is to strive to avoid unnecessary dead time regarding the rich and lean exhaust gas packages introduced into the system becomes.  

Alternativ zu der Aufheizung eines Speicherkatalysators kann die Erfindung auch zur Aufheizung eines Dreiwegekatalysators verwendet werden, der hinter wenigstens einem Vorkatalysator angeordnet ist. Der Begriff Hauptkatalysator im Anspruch 1 soll diese beiden Alternativen abdecken.As an alternative to heating a storage catalytic converter the invention also for heating a three-way catalyst be used behind at least one pre-catalyst is arranged. The term main catalyst in claim 1 should cover these two alternatives.

Claims (1)

Verfahren zur Aufheizung eines hinter wenigstens einem Vorkatalysator angeordneten Hauptkatalysators durch Zufuhr von motorisch erzeugtem unverbrannten Kraftstoff im Abgas vor dem Hauptkatalysator bei gleichzeitigem Vorhandensein von Luftüberschuß vor dem Hauptkatalysator, dadurch gekennzeichnet, daß die motorisch Erzeugung von unverbranntem Kraftstoff zeitlich und/oder räumlich von der motorischen Erzeugung von Luftüberschuß im Abgas entkoppelt ist.Method for heating a main catalytic converter arranged behind at least one pre-catalytic converter by supplying motor-generated unburned fuel in the exhaust gas upstream of the main catalytic converter with the simultaneous presence of excess air in front of the main catalytic converter, characterized in that the motor-driven production of unburned fuel is temporally and / or spatially dependent on the motor production is decoupled from excess air in the exhaust gas.
DE10005954A 2000-02-09 2000-02-09 Desulfurization of a storage catalytic converter by heating Withdrawn DE10005954A1 (en)

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DE10005954A DE10005954A1 (en) 2000-02-09 2000-02-09 Desulfurization of a storage catalytic converter by heating
PCT/DE2001/000270 WO2001059271A1 (en) 2000-02-09 2001-01-24 Desulphurisation of a storage catalyst by heating
JP2001558586A JP2003522874A (en) 2000-02-09 2001-01-24 Desulfurization of storage catalyst by heating
EP01911381A EP1257736A1 (en) 2000-02-09 2001-01-24 Desulphurisation of a storage catalyst by heating
KR1020027010151A KR20020076289A (en) 2000-02-09 2001-01-24 Desulphurisation of a storage catalyst by heating
US10/203,446 US20030131588A1 (en) 2000-02-09 2001-01-24 Desulphurisation of a storage catalytst by heating
BR0108148-9A BR0108148A (en) 2000-02-09 2001-01-24 Sulfurization of a catalyst-accumulator by heating

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EP1257736A1 (en) 2002-11-20
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US20030131588A1 (en) 2003-07-17
BR0108148A (en) 2003-01-21
WO2001059271A1 (en) 2001-08-16

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