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WO2008116618A1 - Système de post-traitement des gaz d'échappement d'un moteur à combustion interne et procédé de fonctionnement d'un système de post-traitement des gaz d'échappement - Google Patents

Système de post-traitement des gaz d'échappement d'un moteur à combustion interne et procédé de fonctionnement d'un système de post-traitement des gaz d'échappement Download PDF

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Publication number
WO2008116618A1
WO2008116618A1 PCT/EP2008/002311 EP2008002311W WO2008116618A1 WO 2008116618 A1 WO2008116618 A1 WO 2008116618A1 EP 2008002311 W EP2008002311 W EP 2008002311W WO 2008116618 A1 WO2008116618 A1 WO 2008116618A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst
exhaust gas
aftertreatment system
main catalyst
precatalyst
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.)
Ceased
Application number
PCT/EP2008/002311
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German (de)
English (en)
Inventor
Achim Dittler
Alexander Massner
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.)
Mercedes Benz Group AG
Original Assignee
Daimler AG
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 Daimler AG filed Critical Daimler AG
Publication of WO2008116618A1 publication Critical patent/WO2008116618A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • F01N3/033—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 in combination with other devices
    • F01N3/035—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 in combination with other devices with catalytic reactors
    • 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
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features having two or more separate purifying devices arranged in series
    • 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
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features having two or more separate purifying devices arranged in series
    • F01N13/0093—Exhaust or silencing apparatus characterised by constructional features having two or more separate purifying devices arranged in series the purifying devices are of the same type
    • 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
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features 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
    • F01N3/02—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
    • F01N3/023—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 using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—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 using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—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 using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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
    • F01N3/24—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 constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2892—Exhaust flow directors or the like, e.g. upstream of catalytic device
    • 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
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration
    • 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
    • F01N2340/00—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the exhaust apparatus; Spatial arrangements of exhaust apparatuses
    • 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
    • F01N2340/00—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the exhaust apparatus; Spatial arrangements of exhaust apparatuses
    • F01N2340/02—Distance of the exhaust apparatus to the engine or between two exhaust apparatuses
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/14—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics having more than one sensor of one kind
    • 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
    • Y02T10/40—Engine management systems

Definitions

  • the invention relates to an exhaust aftertreatment system having the features of the preamble of claim 1 and to an exhaust aftertreatment method having the features of the preamble of claim 14.
  • An exhaust aftertreatment system of an internal combustion engine is known from WO 2006/023091, which has a precatalyst configured as an oxidation catalyst, a main catalytic converter arranged downstream of the primary catalytic converter in the exhaust gas flow direction and designed as an oxidation catalytic converter, and a particle filter arranged downstream of the main catalytic converter in the exhaust gas flow direction.
  • a fuel injector which can deliver fuel upstream of the precatalyst into exhaust gas expelled from the internal combustion engine.
  • the exhaust aftertreatment system is particularly adapted to produce the high exhaust gas temperatures required for thermal particulate filter regeneration. This is done by combustion or oxidation of exhaust gas discharged through the fuel injector into the exhaust gas at the pre- or HauptkataIysator.
  • the object of the invention is to provide a cost-effective exhaust aftertreatment system, which allows a further improved thermal particle filter regeneration. It is another object of the invention to provide a reliable and specify simple operating method for a corresponding exhaust aftertreatment system.
  • the exhaust aftertreatment system according to the invention is distinguished by a precatalyst which has a higher volume-related noble metal loading than the main catalyst.
  • a precatalyst which has a higher volume-related noble metal loading than the main catalyst.
  • particulate filter regeneration is reliably enabled even under unfavorable conditions. Due to the comparatively low noble metal loading of the main catalyst, this is on the one hand particularly cost-effective, on the other hand, it has an improved thermal stability. This is particularly advantageous if the main catalyst, as is preferably provided, is provided for releasing an increased amount of heat compared to the primary catalyst.
  • both the precatalyst and the main catalyst are designed as so-called supported catalysts with a mechanical support.
  • the mechanical support has a geometric surface enlarging, so called washcoat coating on.
  • This noble metal loading is usually referred to the installation volume and in g / ft 3 (grams per cubicfoot) indicated.
  • the noble metal loading of the pre-catalyst is in the range of 40 g / ft 3 to 120 g / ft. 3 More preferably, a noble metal loading is between 50 g / ft 3 to 90 g / ft 3 .
  • both platinum (Pt) and palladium (Pd) are provided as noble metal components. Additions of rhodium may also be provided. In this case, a Pt / Pd ratio of 0.1 to 10 can be provided. Preference is given to a comparatively high Pt content of at least 50%, in particular of at least 75%. Also advantageous may be the use of a so-called platinum-only coating.
  • a lower noble metal loading is provided, which is typically in the range of 10 g / ft 3 to 70 g / ft 3 . More preferably, a noble metal loading is between 20 g / ft 3 to 50 g / ft 3 .
  • the type of noble metal loading is preferably selected to be analogous or similar to that of the precatalyst.
  • any suitable for the retention of particles exhaust emission control component can be used.
  • sintered metal filters or so-called wallflow filters constructed from cordierite, silicon carbide or aluminum titanate ceramics, with a multitude of elongated gas ducts.
  • sintered metal filters with sintered metal pockets or sintered metal plates are advantageous.
  • foam-like depth filters or so-called open filter bodies with a plurality of gas chambers are also possible. clauses.
  • catalytically coated particle filters can be designed, for example, with regard to promoting soot oxidation and / or nitrogen oxide oxidation.
  • a coating with nitrogen oxide storage properties or an SCR catalyst coating comes into consideration.
  • the particulate filter can assume a nitrogen oxide reduction function, as a result of which it is possible to dispense with a downstream nitrogen oxide reduction catalyst.
  • the coatings can be applied in succession in two or more layers on contact surfaces of the particulate filter or in the exhaust gas flow direction.
  • a coating may be provided on the gas inlet side and / or on the gas outlet side contact surfaces, wherein it is advantageous to provide the coating only on partial regions, in particular only on the end side.
  • the fuel injector may be configured to introduce a gaseous fuel, such as a liquid fuel that has been vaporized or appropriately conditioned by an external reformer.
  • a gaseous fuel such as a liquid fuel that has been vaporized or appropriately conditioned by an external reformer.
  • an injector which is suitable for injecting liquid fuel in particular the diesel fuel itself used by the internal combustion engine, which is typically designed as a diesel engine, is preferred.
  • the exhaust aftertreatment system according to the invention is primarily advantageous for predominantly lean-burn internal combustion engines, in particular for diesel engines.
  • the exhaust aftertreatment system is preferably carried out in a single-flow.
  • Pre-catalyst, a main catalyst and a particulate filter are thus arranged in an unbranched executed exhaust line, which permits a low outlay on components and a ⁇ times the operation of the exhaust aftertreatment system.
  • the single-flow design of the exhaust system is not precluded that two or more similar components are arranged in parallel flow parallel within a housing for one of said components and are flowed through by exhaust gas of the same composition.
  • optimum NO oxidation can be achieved on the one hand by means of the precatalyst and the main catalyst.
  • continuous soot regeneration of the particulate filter at low temperatures below 400 ° C. is possible in wide operating ranges.
  • the particulate filter can be kept to a thermal regeneration by soot combustion required temperature of 550 0 C or more and heated at this temperature level reliably even under adverse conditions if necessary.
  • the two-stage fuel oxidation caused by the precatalyst and the main catalyst the local density of the temperature load on both components is reduced and the total amount of precious metal used is reduced.
  • the exhaust aftertreatment system according to the invention can have further, in particular catalytic, exhaust gas purification components.
  • Advantageous is a downstream of the particulate filter oxidation catalyst.
  • an oxidation of reducing exhaust gas components is made possible, which can remain in the exhaust gas during a thermal particle filter regeneration (fuel slippage).
  • a nitrogen oxide reduction catalytic converter may be upstream or downstream of the particle filter. This is in addition to the removal of particles in addition to a removal of the pollutant nitric oxide allows.
  • the nitrogen oxide reduction catalyst may be formed as a so-called Denox catalyst, which can reduce nitrogen oxides under oxidizing conditions using a hydrocarbon or hydrogen-containing reducing agent.
  • an embodiment is preferred as a so-called SCR catalyst, which can reduce nitrogen oxides under oxidizing conditions with ammonia or another nitrogen-containing reducing agent.
  • the precatalyst and the main catalyst are designed as honeycomb bodies, wherein the main catalyst has a cell density at least twice as high as the precatalyst and a volume which exceeds the precatalyst by a multiple.
  • the honeycomb bodies have a multiplicity of parallel gas passages which are separated from one another by a carrier material of the honeycomb body provided with catalytic coating.
  • the number of gas channels related to the cross-sectional area is referred to as cell density, which is usually given in cpsi (cells per square inch).
  • a cell density of the precatalyst of less than 100 cpsi is preferred. Particularly preferred is a cell density of about 50 cpsi.
  • L / D ratio a ratio of length to diameter
  • a particularly uncritical and uniform temperature distribution during thermal regeneration and a particularly favorable back pressure behavior can be achieved.
  • a cell density of 300 cpsi to 400 cpsi and an L / D ratio in the range of 1.5 to 2.25 are preferably selected.
  • the volume design according to the invention makes it possible for only a partial conversion of the fuel delivered by the fuel injector to be carried out at the primary catalytic converter. As a result, its temperature load is reduced and increases the aging stability. Preference is given to an interpretation of the volume ratio of the primary catalyst and catalyst such that less than 50%, preferably about 20% of the fuel are reacted at the primary catalyst. Particularly advantageous is a volume ratio of main catalyst and precatalyst in the range of 15 to 20. It is particularly advantageous if the volumes of precatalyst and main catalyst are adapted to the displacement of the internal combustion engine designed as a reciprocating engine.
  • Particularly advantageous with respect to a desired fuel part conversion is a design of the precatalyst such that under idle conditions of the internal combustion engine results in a space velocity of about 230000 l / h.
  • the space velocity is to be understood as meaning an exhaust gas flow rate based on the catalyst volume and on standard conditions.
  • the precatalyst has a volume which is less than 10% of the engine displacement.
  • the main catalytic converter has a volume that is greater than the engine displacement.
  • the light-off catalyst has a lower light-off temperature at least 50 0 C with respect to an oxidation of fuel delivered by the fuel injector than the main catalytic converter.
  • the precatalyst is designed so that it has a light-off temperature of 200 0 C or less. In this way, a catalytic activity of the precatalyst and thus a thermal particle filter regeneration even at low load or idle the engine allows. On the other hand, a risk of its age-related increase is reduced with the light-off temperature of the main catalytic converter selected from the outset.
  • a further embodiment of the invention is provided between the delivery point of fuel through the fuel injector and an abgaseintritt feature end of the precatalyst for flowing exhaust gas of the internal combustion engine to a multiple times longer than between a exhaust outlet end of the precatalyst and a exhaust gas entry end of the main catalyst.
  • the fuel injector is thus arranged comparatively far away from the exhaust gas inlet of the primary catalytic converter, whereas the primary catalytic converter and the main catalytic converter are arranged at a small distance from each other. In this way, on the one hand a good or almost complete evaporation of liquid introduced into the exhaust gas in the liquid state allows fuel, on the other hand, the heat losses on the way between the primary catalyst and catalytic converter are low.
  • An arrangement of the fuel injector that is close to the internal combustion engine is advantageous, in particular at a small distance in front of or behind a turbine of an exhaust gas turbocharger.
  • the distance between the fuel injector and the primary catalytic converter is selected so that the transit time for flowing exhaust gas between the delivery point of fuel through the fuel injector and the exhaust gas inlet end of the primary catalytic converter under idling conditions of the internal combustion engine is between 0.1 seconds and 0.3 seconds.
  • the precatalyst is formed as a metal foil catalyst. This embodiment has proved to be particularly advantageous with respect to temperature loads.
  • the main catalyst is designed as a ceramic catalyst.
  • a cost advantage arises in the case of a typically large-volume main catalytic converter with several liters of installation volume.
  • Preferred is an embodiment with a Cordieritnic.
  • the precatalyst is arranged in a form-fitting and / or material fit in a front pipe for a housing of the main catalyst. This eliminates complex mat storage and the space is used optimally.
  • the main catalytic converter and the particle filter are arranged in a common housing, wherein the housing is designed to be double-walled in the area of the main catalytic converter and / or in the region of the particle filter, at least in sections. This will be Heat loss minimized. It is particularly advantageous if the main catalyst and particulate filter are arranged at a small distance of preferably less than 500 mm from each other.
  • the main catalytic converter and the particle filter are arranged in a common housing, wherein the housing has a separation in the form of a detachable connection in the region between the main catalytic converter and the particle filter.
  • a means for flow equalization between the pre-catalyst and the main catalyst is provided.
  • a mixer is used.
  • the cross-sectional area of the main catalyst is uniformly exposed to exhaust gas, whereby it is optimally utilized.
  • sensory measurements of temperature and exhaust gas composition can be made representative.
  • the method according to the invention for operating an exhaust aftertreatment system of the type described above is characterized in that the fuel injector is operated in connection with a thermal regeneration of the particulate filter under predetermined conditions, wherein the conditions include that a main catalyst inlet temperature of exhaust gas entering the main catalyst exceeds a predetermined threshold.
  • the exhaust gas temperature or the particulate filter temperature is brought to a temperature necessary for soot combustion, which is achieved by delivery of force
  • Fuel is caused by the fuel injector and oxidation of the introduced fuel at the primary catalyst and the main catalyst.
  • a particulate filter regeneration is not possible or desired in every operating state of the exhaust aftertreatment system or the internal combustion engine.
  • predetermined conditions which must be fulfilled for an initiation of the particle filter regeneration and are polled at regular intervals or continuously.
  • these conditions include the presence of a predetermined threshold value for the temperature of the exhaust gas entering the main catalytic converter.
  • This main catalyst inlet temperature is preferably detected by means of a short distance before the inlet end of the main catalyst arranged temperature sensor.
  • a temperature threshold is chosen which corresponds to the light-off temperature of the main catalyst or slightly above it. This ensures that fuel released into the exhaust gas can be converted by the main catalytic converter, thus enabling exhaust gas heating.
  • the threshold is about 265 0 C.
  • an enable signal for the fuel injector is generated.
  • the fuel injector may then be put into operation to deliver fuel. If the release signal is not present, the fuel injector remains out of operation or is put out of operation.
  • the predetermined Conditions further include that a main catalyst outlet temperature exiting the main catalyst exhaust gas is higher than the reduced by a predetermined amount main catalyst inlet temperature. In this way it is ensured that the fuel injector is put into operation only when the main catalyst is sufficiently warmed through.
  • a release for the fuel injector takes place only when the main catalyst outlet temperature is higher than about 20 0 C to 40 0 C decreased main catalyst inlet temperature.
  • a maximum permissible temperature of 650 0 C in the precatalyst is exceeded.
  • the precatalyst is always kept below the maximum allowable temperature.
  • a temperature damage is avoided and the precatalyst is operated aging stable.
  • an age-related increase in its light-off temperature is avoided and a long service life is achieved.
  • a particularly aging-stable behavior of the precatalyst can also be a maximum allowable temperature of 600 0 C or only 550 0 C may be provided. This is achieved in particular by an optimally coordinated design of volume, L / D ratio, cell density and noble metal loading of the precatalyst.
  • the precatalyst By a coordinated design of the precatalyst whose sales capacity can be limited in terms of the fuel used and thus its heat load.
  • the design is preferably such that a specific, ie based on a catalyst volume of one liter heat release of 200 MJ per hour is reliably exceeded.
  • it is particularly advantageous if at least in a heating phase for heating the particulate filter to a regeneration temperature less than 50% of the fuel injected by the fuel injector and flowing through the precatalyst fuel at the primary catalyst is implemented.
  • the single figure shows an advantageous embodiment of the exhaust aftertreatment system according to the invention.
  • the illustrated in the figure preferred embodiment of the exhaust aftertreatment system 1 comprises in succession arranged in the exhaust gas flow direction 2 a fuel injector 7, designed as an oxidation catalyst precatalyst 3, designed as an oxidation catalyst main catalyst 4 and a particulate filter 5.
  • a fuel injector 7 designed as an oxidation catalyst precatalyst 3, designed as an oxidation catalyst main catalyst 4 and a particulate filter 5.
  • the reference numerals 3a and 4a assigned.
  • reference numerals 3b and 4b designate an exhaust gas exit side end of the pre-catalyst 3 and of the main catalyst 4.
  • temperature sensors 10, 11 are guided into the housing 9, with which the temperatures of entering into the main catalyst 4 or can be detected from this exiting exhaust gas.
  • the exhaust aftertreatment system 1 is connected via an exhaust pipe 6 to a preferably designed as a diesel engine in Hubkolbenbauweise internal combustion engine (not shown). If an exhaust gas turbocharger is provided, a connection to an outlet of the exhaust gas turbocharger turbine is preferred. Characteristically, the mentioned exhaust gas aftertreatment units 7, 3, 4, 5 are arranged in a single-flow, ie unbranched exhaust gas line.
  • the main catalyst 4 is housed with a small distance to the particle filter 5 with this together in a common housing 9. It is preferred if the housing 9 is designed in two parts with a detachable connection, not shown, in the region between the main catalytic converter 4 and the particle filter 5. Furthermore, it is preferably provided, the housing 9 at least partially double-walled in the region of the main catalyst 4 and / or in the region of the particulate filter 5, i. to perform air gap insulation. To further improve the thermal insulation is preferably provided for each of the main catalyst 4 and the particulate filter 5 an enclosing insulation and bearing mat, which is also not shown in detail.
  • a mixing element 12 is arranged to equalize the exhaust gas flow. This ensures that the exhaust gas flow entering the housing 9 via a delivery pipe 8 is distributed essentially uniformly over the cross section of the main catalytic converter 4.
  • the mixing element is preferably arranged in the inlet funnel of the housing 9, but it may also be arranged in an anteroom between the inlet funnel end and the exhaust gas inlet end of the main catalyst 4.
  • the pre-catalyst 3 is positively, ie arranged adjacent to the inner wall of the front pipe 8 fitting.
  • the precatalyst 3 is preferably formed as a coated supported catalyst. In this case, an embodiment is preferred as a metal foil catalyst.
  • An arrangement with a short distance from the main catalytic converter 4 is preferred.
  • the distance between the exhaust outlet side end 3b of the primary catalytic converter 3 and the exhaust gas inlet side end 4a of the main catalytic converter 4 is less than 200 mm. A distance of about 100 mm is preferred.
  • a particularly space-saving arrangement results when the precatalyst 3 protrudes into the inlet funnel of the housing 9.
  • the pre-catalyst 3 is preferably made relatively small with a volume of less than 10% of the stroke volume of the connected internal combustion engine and has a low cell density of preferably about 50 cpsi at an L / D ratio of less than 1.0. This results under idle conditions of the internal combustion engine, a high space velocity of about 230000 l / h, which in turn has the result that the Kraftstoffinj ector 7 discharged into the exhaust fuel at most 50%, above the idling range but typically to a much lower proportion, preferably about 20 % is implemented. This design makes it possible to limit the maximum temperature in the primary catalytic converter 3 and the exhaust gas backpressure caused by it.
  • the maximum temperature in the primary catalytic converter 3 to about 550 0 C is limited.
  • the back pressure typically remains below 30 mbar.
  • the coating of the precatalyst is designed so that a conversion of gaseous diesel fuel under typical diesel engine exhaust conditions already at about 200 ° C to a considerable extent occurs (light-off temperature).
  • a washcoat with a platinum-palladium content of about 90 g / ft 3 based on the catalyst volume and a Pt / Pd ratio of 10: 1 has proven to be particularly suitable for this purpose.
  • the main catalyst 4 is designed primarily for a complete conversion of fuel supplied and for a nitric oxide oxidation activity. On the one hand, this results in a low hydrocarbon slip in a thermal particle filter regeneration. On the other hand, under normal operating conditions, a high NO 2 production rate and thus a high continuous soot degradation rate in the downstream particulate filter 5 are achieved.
  • a design for high aging and temperature stability is also preferred for the main catalyst 4.
  • An optimized design with respect to the mentioned criteria provides an L / D ratio of about 1.5 to 2.25, a cell density of 300 cpsi to 400 cpsi and a volume which is about 1.1 to 2.2 times the Stroke volume of the connected internal combustion engine is, before.
  • a coating analogous to the coating of the precatalyst, but provided with a reduced noble metal loading has proven to be particularly advantageous.
  • a washcoat with a noble metal content of about 40 g / ft 3 based on the catalyst volume and a Pt / Pd ratio of 10: 1 has proven to be particularly advantageous.
  • a light-off temperature with respect to hydrocarbons or fuel which is thereby increased to about 250 ° C. in this case does not represent a disadvantage, since preheating by the precatalyst 4 can take place.
  • particle filter 5 is preferably a so-called wall-flow filter made of SiC, cordierite or aluminum titanate base is used, which can be provided with a preferably precious metal-containing catalytic coating.
  • a so-called wall-flow filter made of SiC, cordierite or aluminum titanate base is used, which can be provided with a preferably precious metal-containing catalytic coating.
  • the largest possible volume of about 1.5 times the engine displacement is advantageous.
  • an optimized design of the particulate filter 5 with regard to the exhaust gas counterpressure is preferred. Porosity and size are preferably determined so that at a soot loading of about 5 g / l in the vast operating range of the internal combustion engine, a back pressure of about 100 mbar is exceeded.
  • L / D ratio a ratio of length to diameter in the range of 0.8 to 2.0 is preferred.
  • L / D ratio 1.0 to 1.3, a particularly uncritical and even temperature distribution during thermal regeneration can be achieved.
  • a delivery of fuel through the fuel injector 7 to support a particulate filter regeneration takes place as far upstream of the precatalyst 3, that a largely evaporation of the supplied fuel along a feed line s is possible. It is advantageous in this context to provide a feed distance s of more than 600 mm, in particular more than 1000 mm in length. Depending on the available space and vehicle dimensions can be provided up to 2000 mm. At idle conditions, this results in a transit time of the fuel delivered from the fuel injector 7 to the precatalyst 3 of typically 0.08 s to 0.3 s, which is sufficient for evaporation of most of the fuel delivered. It is particularly advantageous to use an exhaust pipe part from the engine compartment to the vehicle underbody area for the feed line s. A heat-insulating sheath may be provided in particular for the exhaust-gas line section of the feed line s.
  • the fuel injector 7 is arranged close to the engine.
  • soot deposited under normal operating conditions can be continuously oxidized and removed by NO 2 contained in the exhaust gas, especially by the precatalyst 3 and the main catalyst 4 by oxidation, a need for thermal particulate filter regeneration by thermal soot erosion arises at more or less regular intervals. Since the required high temperatures of 550 0 C to 650 0 C are usually not achieved in normal driving, this is caused by a corresponding increase in the exhaust gas temperature by oxidation of the Kraftstoffinj ector 7 into the exhaust gas discharged fuel as needed.
  • the loading of the particulate filter with soot or particles is continuously determined or estimated for this purpose, which can be done by determining a differential pressure via an exhaust gas line containing the particulate filter 5 and / or via a loading model. It is preferably provided that total values are determined for specific operating parameters, such as engine operating time and / or vehicle travel distance and / or fuel consumption, which are decisive for the particle emission to evaluate a resulting soot loading of the particulate filter. Is a predeterminable load value or a predetermined, typically empirically determined and applicated limit value of one of the relevant operating parameters exceeded over ⁇ , this is interpreted as an impermissibly increased soot loading of the particulate filter and requested a thermal regeneration.
  • release conditions may include the presence of certain ranges of engine operating parameters. However, according to the invention, the release conditions include at least the presence of a main catalyst inlet temperature above a predetermined threshold.
  • a release for actuating the fuel injector 7 preferably takes place only when an exhaust gas temperature above the light-off temperature is measured by means of the temperature sensor 10 arranged on the input side of the main catalytic converter 4.
  • the fuel injector 7 is put into operation and diesel fuel preferably sprayed finely divided into the exhaust.
  • diesel fuel preferably sprayed finely divided into the exhaust.
  • the corresponding opening ratio and thus the amount of fuel delivered per unit time are preferably set as a function of the signal of the temperature sensor 11 arranged on the output side of the main catalytic converter 4.
  • the adjustment is made preferably by a regulating or controlling such a way that first a ramp-like increase in the main catalyst outlet temperature results onto a target value for the particulate filter regeneration in the range of from 525 0 C to 625 0 C.
  • a temperature rise rate of more than 1 K / min is set.
  • a combustion phase subsequent to the ramp-shaped heating phase into two, preferably approximately six phases with different rates of Rußabbrand effet or different main catalyst outlet temperatures.
  • a first Rußabbrandphase the regeneration is started after the rise of the main catalyst outlet temperature to a first target value of about 525 0 C.
  • the temperature in predetermined or predetermined levels gradually increased after the expiration of a respective predetermined steady time to a final target value of preferably about 600 0 C to 625 0 C.
  • the temperature target values and steady-state times of the respective temperature stages are preferably chosen taking into account the oxygen content of the exhaust gas, the exhaust gas mass flow and optionally further parameters influencing the soot combustion rate such that no uncontrollable reaction can take place, but nevertheless the best possible burnup takes place.
  • soot burning rates are set corresponding to a decrease in soot load by 1 g per liter of filter volume in about 0.5 minutes to 4 minutes. It is advantageous to carry out the changeover from one stage or phase to the next in a time-controlled manner after the expiry of a predefined or predefinable period taking into account the aforementioned influencing factors.
  • the switching is performed by the fuel injector 7 is controlled so that there is an increase in the main catalyst outlet temperature to the respective temperature target value.
  • the regeneration is terminated when a predetermined end criterion is met.
  • the end criterion can be determined by a loading model estimating the soot loading of the particulate filter 5 or a differential pressure measurement over the particulate filter 5.
  • the regeneration is terminated after a predetermined or predefinable period of typically about 25 minutes and the fuel injector 7 is put out of operation.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)

Abstract

L'invention concerne un système de post-traitement des gaz d'échappement, dans lequel un injecteur de carburant (7), un précatalyseur (3), un catalyseur principal (4) ainsi qu'un filtre à particules (5) sont placés les uns derrière les autres, dans le sens de passage (2) des gaz d'échappement. Selon l'invention, le précatalyseur (3) présente une charge volumique de métaux nobles supérieure à celle du catalyseur principal (4). Le procédé de fonctionnement d'un système de post-traitement des gaz d'échappement (1) correspondant selon l'invention est caractérisé en ce que l'injecteur de carburant (7) est mis en service dans le cadre d'une régénération thermique du filtre à particules (5) à certaines conditions, notamment à la condition qu'une température d'entrée de gaz d'échappement entrant dans le catalyseur principal (4) excède une première valeur seuil prédéfinie.
PCT/EP2008/002311 2007-03-27 2008-03-22 Système de post-traitement des gaz d'échappement d'un moteur à combustion interne et procédé de fonctionnement d'un système de post-traitement des gaz d'échappement Ceased WO2008116618A1 (fr)

Applications Claiming Priority (2)

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DE102007015164A DE102007015164A1 (de) 2007-03-27 2007-03-27 Abgasnachbehandlungssystem einer Brennkraftmaschine und Verfahren zum Betreiben eines Abgasnachbehandlungssystems
DE102007015164.2 2007-03-27

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WO2008116618A1 true WO2008116618A1 (fr) 2008-10-02

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US8763369B2 (en) * 2010-04-06 2014-07-01 GM Global Technology Operations LLC Apparatus and method for regenerating an exhaust filter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030167756A1 (en) * 2002-03-07 2003-09-11 Szymkowicz Patrick G. After-treatment system and method for reducing emissions in diesel engine exhaust
WO2004099578A1 (fr) * 2003-05-09 2004-11-18 Emitec Gesellschaft Für Emissionstechnologie Mbh Regeneration d'un piege a particules
WO2006023091A2 (fr) * 2004-08-02 2006-03-02 Catalytica Energy Systems, Inc. Chambres de combustion prealable pour moteurs a combustion interne et systemes et procedes correspondants
DE102006025131A1 (de) * 2005-06-03 2006-12-07 GM Global Technology Operations, Inc., Detroit Abgasbehandlungsdiagnose unter Verwendung eines Temperatursensors
WO2008052756A1 (fr) * 2006-11-03 2008-05-08 Daimler Ag Système de retraitement de gaz d'échappement d'un moteur à combustion

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030167756A1 (en) * 2002-03-07 2003-09-11 Szymkowicz Patrick G. After-treatment system and method for reducing emissions in diesel engine exhaust
WO2004099578A1 (fr) * 2003-05-09 2004-11-18 Emitec Gesellschaft Für Emissionstechnologie Mbh Regeneration d'un piege a particules
WO2006023091A2 (fr) * 2004-08-02 2006-03-02 Catalytica Energy Systems, Inc. Chambres de combustion prealable pour moteurs a combustion interne et systemes et procedes correspondants
DE102006025131A1 (de) * 2005-06-03 2006-12-07 GM Global Technology Operations, Inc., Detroit Abgasbehandlungsdiagnose unter Verwendung eines Temperatursensors
WO2008052756A1 (fr) * 2006-11-03 2008-05-08 Daimler Ag Système de retraitement de gaz d'échappement d'un moteur à combustion

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