WO2015007306A1 - Particle filter designed as a wall-flow filter with duct structure - Google Patents

Particle filter designed as a wall-flow filter with duct structure Download PDF

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Publication number
WO2015007306A1
WO2015007306A1 PCT/EP2013/064941 EP2013064941W WO2015007306A1 WO 2015007306 A1 WO2015007306 A1 WO 2015007306A1 EP 2013064941 W EP2013064941 W EP 2013064941W WO 2015007306 A1 WO2015007306 A1 WO 2015007306A1
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WO
WIPO (PCT)
Prior art keywords
substrate
filter
substrates
filter according
particle
Prior art date
Application number
PCT/EP2013/064941
Other languages
German (de)
French (fr)
Inventor
Klaus Schrewe
Simon Steigert
Original Assignee
Hjs Emission Technology Gmbh & Co. Kg
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 Hjs Emission Technology Gmbh & Co. Kg filed Critical Hjs Emission Technology Gmbh & Co. Kg
Priority to PCT/EP2013/064941 priority Critical patent/WO2015007306A1/en
Priority to CN201380077694.2A priority patent/CN105324167A/en
Publication of WO2015007306A1 publication Critical patent/WO2015007306A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/247—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/0084—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours provided with safety means
    • B01D46/0087—Bypass or safety valves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/2429—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material of the honeycomb walls or cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24492—Pore diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2474—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the walls along the length of the honeycomb
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2482—Thickness, height, width, length or diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2484—Cell density, area or aspect ratio
    • 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
    • F01N3/031—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 having means for by-passing filters, e.g. when clogged or during cold engine start
    • 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, e.g. catalysed diesel particulate filters
    • 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

Definitions

  • Particle filter designed as a wall-flow filter with a channel structure
  • the invention relates to a particle filter designed as a wall-flow filter with a channel structure for removing particles entrained in the exhaust gas of an internal combustion engine, in particular soot particles, which particulate filter has a substrate with a multiplicity of filter channels enclosed by filter walls and via at least one bypass for providing flow pathability of the filter Upstream on the downstream side of the substrate, without having to flow through a filter wall features.
  • a particle filter is switched on in the exhaust gas line of such an internal combustion engine. This serves to remove entrained in the exhaust gas of the internal combustion engine particles, in particular of soot particles.
  • the particulate filters are designed as full filters.
  • Such full filters are wall-flow filters, ie: filters in which the medium to be filtered - here: that the particles, and indeed the soot particles entrained exhaust - must flow through a filter wall to get from the upstream side of the substrate on the downstream side - the clean side.
  • the substrate of such a particulate filter comprises a multiplicity of filter channels which run parallel to one another and are enclosed by filter walls.
  • a ceramic material is often used.
  • the filter channels in the manner of honeycombs are each separated by a filter wall and alternately upstream and closed flow side.
  • Particle filters are also known from sintered metal materials.
  • Such particulate filters are designed so that the exhaust gas backpressure does not increase too much as a result of this, even with increasing accumulation of soot. For this reason, it is necessary that such a substrate is regenerated with sufficient soot loading.
  • a regeneration of the accumulated soot is oxidized, which is also addressed as a controlled Rußabbrand.
  • Such regeneration can be done passively and thus automatically or actively controlled upon reaching a certain temperature of the soot. In a passive regeneration is fed to the soot accumulated on the upstream side N0 2 , whereby the oxidation of the carbon black is allowed at lower temperatures.
  • such particle filter or its substrate are designed so that they have a relatively small pore size of typically only 5 ⁇ to 15 ⁇ and a porosity of not more than 50%.
  • the substrate is designed so that, starting from an unloaded substrate, the filtration process adjusts as quickly as possible to a surface filtration. Before a surface filtration takes place at least to a significant degree, the pores in the filter walls must have added something with soot, whereby the effective porosity compared to that of the substrate is further reduced. During the duration of the depth filtering, the desired separation efficiency of more than 98% can not yet be realized with such filters. Therefore, it is endeavored to design such particle filters so that they quickly reach the state of their intended surface filtration.
  • soot emission of an internal combustion engine is reduced by 50% or even only 20% to 25%.
  • Partial filters have a maximum nominal degree of separation of the desired order of magnitude. This means that such filters can absorb the proportion of the entrained in the exhaust gas of an internal combustion engine particles, in particular soot particles.
  • Partial filters can be designed as a wall-flow filter. In such a case, the substrate used for a full filter is used and one or more, usually a plurality of bypass channels are formed by different measures. The bypass channels provide a flow path from the upstream side of the substrate to the downstream side, without having to flow through a filter wall of the exhaust gas. Such a bypass is established by connecting a filter channel sealed off on the outlet side with one or more filter channels that are open on the outflow side.
  • the flow-through cross-sectional area of the bypass flow path is designed to allow a particular flow Share of the exhaust stream flows through this unfiltered.
  • the degree of separation that can be achieved with such a sub-filter is determined.
  • the invention is therefore the object of proposing a designed as a wall-flow filter particulate filter as a partial filter, which not only allows greater freedom in its design, but preferably also has a lower weight.
  • the object is achieved according to the invention by an aforementioned, generic particle filter, in which the filter walls of the substrate have a porosity between about 55% and about 75% and a pore size between about 20 ⁇ and 35 ⁇ .
  • a substrate is used, which has a, compared to the porosity of conventional substrates, significantly higher porosity.
  • this substrate has a pore size that is also significantly greater than that found in conventionally used substrates.
  • properties of the particle particle filter to be produced from the substrate are already introduced into the design of the substrate.
  • the significant Fikant higher porosity and also significantly larger pore size allows a lower resistance flow through the filter wall formed from such a substrate.
  • the partial filter designed as a wall-flow filter with a channel structure in the inventive embodiment of the depth filtration effect remains significantly longer.
  • the free cross-sectional area of the bypass flow path can thus be dimensioned smaller than previously known particle wall filters designed as wall-flow filters. As a result, this results in the same substrate volume to improve the efficiency of the separation efficiency. At the same time, the significantly higher porosity of the substrate significantly reduces its weight compared with previously known substrates.
  • the degree of separation of such a particle-part filter can be increased if the porosity is between 60% and 70%.
  • the porosity of the filter walls of the substrate is about 65%, while the pore size is preferably not greater than 30 ⁇ , in particular about 22 ⁇ .
  • a particulate filter designed as a wall-flow filter is particularly effective for the purposes mentioned, when the substrate has a diameter-to-length ratio between 1 and 1.5, in particular about 1.4. This means that these substrates can be designed much shorter compared to conventional substrates, which brings about advantages in the temperature resistance of the substrate during regeneration.
  • a plurality of substrates can be connected in series in the direction of the exhaust gas, should a larger overall substrate length be desired or needed. In such a case, in the context of these embodiments, the multiple substrates in their entirety are also addressed by the term "the particle filter”.
  • the flow velocity is too small-that is to say the diameter of the substrate is large-this leads to the fact that the exhaust gas preferably flows through the bypass pathway and the desired degree of separation can not be achieved. It is thus preferable to adapt the diameter of the at least one substrate of the particle filter to the volume flow of the exhaust gas to be cleaned and thus to the engine size.
  • the degree of separation of such a particle filter is also determined by the filter channel density.
  • This feature also referred to as cell density, is preferably between about 180 cpsi and about 225 cpsi (cpsi: cells per square inch).
  • cpsi cells per square inch.
  • Especially effective Particle Filters have about 200 cpsi, considering the design criteria already mentioned above.
  • the filter channel density already taken into account for the purpose of the substrate in the interpretation of the same. If the filter channel density is lower, it has been shown that the flow velocity through the filter walls is relatively high, thus reducing the depth filtration desired in the design of such a particle filter and thus decreasing the separation efficiency. In addition, then the cross-sectional area of the bypass flow path is relatively large. With higher cell density, the cross-sectional area of the bypass pathway is relatively small. In addition, it has been shown that a depth filtration in the filter walls then takes place only subordinate, which leads to too rapid Rußakkumulation alone on the surface.
  • a thus designed partial particle filter is due to the desired depth filtration effect, especially the filter wall as used for filtering out entrained in the exhaust stream particles.
  • Wall thicknesses between 0.3 mm and 0.7 mm, in particular of approximately 0.4 mm, have proved to be particularly expedient in order to meet the requirements imposed on such a partial filter.
  • particulate filter As a wall-flow filter designed particulate filter allow the formation of the use of the particulate filter with a plurality of such substrates, which are then connected in series in the flow direction of the exhaust gas. These at least two or even several subdivisions connected in series then determine the overall degree of separation of the particulate filter.
  • a particle filter comprising a single substrate in front of a conventional full filter or a particle filter of conventional design.
  • the use of such a first partial filter arranged upstream of a particle filter is particularly expedient if it is preceded by an oxidation catalytic converter or by an oxidation-catalytic coating of its upstream surface.
  • Such a first partial particle filter can have a much smaller volume compared with the main filter connected downstream in the flow direction of the exhaust gas and therefore be arranged very close to the engine, typically directly to the exhaust manifold or, in the event that a turbocharger is provided downstream of the turbocharger.
  • this arrangement close to the engine ensures that this particulate filter, since it is designed to work passively, works in an optimal degree of separation even when the internal combustion engine is exposed to different dynamic loads.
  • part of the ejected particles is already effectively removed, which relieves the filter action of the downstream main particle filter.
  • this downstream particulate filter is actively regenerated, this also means a reduction in the energy consumption required for this purpose, for example of fuel that would be required by a burner to raise the exhaust gas temperature.
  • a particle filter having such a first substrate in its own housing is directly close to the engine and thus within the first section of the exhaust gas.
  • This particulate filter may be one with a degree of separation of about 20%.
  • the substrate has only a small volume, which allows the above-described close-coupled arrangement.
  • the actual main particle filter is then located at an appropriate distance from the engine, at a point on the vehicle, where a corresponding space is available.
  • This second filter is also a partial filter, for example of the type described above with a separation efficiency of 40%.
  • the first substrate is equipped on the inflow side with an oxidation-catalytic coating and is therefore subject to a passive regeneration strategy.
  • the oxidation-catalytic coating is designed in such a way that it can be used to generate N0 2 sufficiently to supply N0 2 to the main filter arranged further back in the exhaust gas line or the soot accumulated thereon for regeneration of the substrate.
  • the nominal cumulative degree of separation of these two successive particle partial filters is 52%.
  • An advantage of such an embodiment is, above all, that the oxidation catalyst used for the N0 2 supply even of the main particle filter or the relevant oxidation-catalytic coating is arranged very close to the motor, and thus is very quickly at the operating temperature. Therefore, the soot accumulated on the downstream second particulate filter also receives the N0 2 needed for the regeneration after a very short operating time of the engine.
  • the very close to the engine arrangement of the oxidation catalyst or serving for this purpose upstream of the first substrate applied oxidation catalytic coating also requires that after a short period of operation and thus rapidly reaching its operating temperature further emissions, such as entrained HCs are decomposed in the exhaust. As a result of this reaction, which is exothermic on the oxidation-catalytic surface, the oxidation catalyst is brought to operating temperature even faster. It is understood that, when providing a plurality of substrates forming such a particle filter, they can be arranged in a common housing. In the application described above, for example, in which a first substrate is arranged directly close to the motor, while a second is located elsewhere in the exhaust system, the first substrate is in a separate housing, while the one or more downstream substrates are enclosed in a separate housing.
  • the at least one substrate of the particulate filter is designed for passive regeneration.
  • the design of the respective substrate is designed and arranged within the exhaust line, that a regeneration of the substrate takes place after the degree of separation of the substrate has reached its nominal maximum degree of separation, but before the degree of separation by successive further accumulation of soot on its minimum separation efficiency is lowered.
  • the configuration of the substrate is such that a regeneration has taken place before the actual degree of separation is reduced by 50% of the difference between the nominal maximum degree of separation and the minimum degree of separation.
  • the regeneration window to be maintained for maintaining the effectiveness of the particle sub-filter or its substrate is therefore significantly larger compared to those of full filters. This means that the operation of the particulate filter with the desired degree of separation is maintained without significant increase in the exhaust backpressure, even if regeneration can take place only considerably delayed due to possibly not given regeneration conditions.
  • the substrate is a silicon carbide material.
  • other materials for example ceramic materials or sintered metal, for producing a substrate for such a particle filter.

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  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)
  • Filtering Materials (AREA)

Abstract

A particle filter designed as a wall-flow filter with duct structure serves for the removal of particles, in particular soot particles, entrained in the exhaust gas of an internal combustion engine. The particle filter has a substrate with a multiplicity of filter ducts enclosed by filter walls. Furthermore, said particle filter has at least one bypass for providing a flow path from the inflow side to the outflow side of the substrate without the need for flow to pass through a filter wall. The filter walls of the substrate have a porosity of between approximately 55% and approximately 75% and a pore size of greater than approximately 20 µm to at most 35 µm.

Description

Als Wandstromfilter mit Kanalstruktur ausgelegter Partikelfilter  Particle filter designed as a wall-flow filter with a channel structure
Die Erfindung betrifft einen als Wandstromfilter mit Kanalstruktur ausgelegter Partikelfilter zum Entfernen von in dem Abgas einer Brennkraftmaschine mitgeführten Partikeln, insbesondere Rußpartikeln, welcher Parti- kelfilter ein Substrat mit einer Vielzahl von durch Filterwände eingefassten Filterkanälen aufweist und über zumindest einen Bypass zum Bereitstellen einer Strömungswegsamkeit von der Anströmseite auf die Abströmseite des Substrate, ohne eine Filterwand durchströmen zu müssen verfügt. Zur Reduzierung der Emissionen einer Brennkraftmaschine, beispielsweise eines Dieselmotors wird in den Abgasstrang einer solchen Brennkraftmaschine ein Partikelfilter eingeschaltet. Dieser dient zum Entfernen von in dem Abgas der Brennkraftmaschine mitgeführten Partikeln, insbesondere von Rußpartikeln. Dabei ist man in aller Regel bestrebt, die Rußparti- kelemission möglichst vollständig zu unterdrücken, weshalb in vielen Fällen die Partikelfilter als Vollfilter ausgeführt sind. Derartige Vollfilter sind Wandstromfilter, also: Filter, bei denen das zu filternde Medium - hier: dass die Partikel, und zwar die Rußpartikel mitführende Abgas - eine Filterwand durchströmen muss, um von der Anströmseite des Substrates auf die Abströmseite - die Reinseite - zu gelangen. Das Substrat eines solchen Partikelfilters umfasst eine Vielzahl von parallel zueinander verlaufenden, durch Filterwände eingefasste Filterkanäle. Als Material wird vielfach ein keramisches Material eingesetzt. Bei diesem sind die Filterkanäle nach Art von Waben jeweils durch eine Filterwand voneinander getrennt und wechselweise anströmseitig bzw. strömseitig verschlossen. Partikelvollfilter sind auch aus Sintermetallwerkstoffen bekannt. The invention relates to a particle filter designed as a wall-flow filter with a channel structure for removing particles entrained in the exhaust gas of an internal combustion engine, in particular soot particles, which particulate filter has a substrate with a multiplicity of filter channels enclosed by filter walls and via at least one bypass for providing flow pathability of the filter Upstream on the downstream side of the substrate, without having to flow through a filter wall features. To reduce the emissions of an internal combustion engine, for example a diesel engine, a particle filter is switched on in the exhaust gas line of such an internal combustion engine. This serves to remove entrained in the exhaust gas of the internal combustion engine particles, in particular of soot particles. As a rule, the aim is to suppress the soot particle emission as completely as possible, which is why in many cases the particulate filters are designed as full filters. Such full filters are wall-flow filters, ie: filters in which the medium to be filtered - here: that the particles, and indeed the soot particles entrained exhaust - must flow through a filter wall to get from the upstream side of the substrate on the downstream side - the clean side. The substrate of such a particulate filter comprises a multiplicity of filter channels which run parallel to one another and are enclosed by filter walls. As a material, a ceramic material is often used. In this case, the filter channels in the manner of honeycombs are each separated by a filter wall and alternately upstream and closed flow side. Particle filters are also known from sintered metal materials.
Ausgelegt werden derartige Partikelfilter, dass durch diese auch bei einer zunehmenden Rußakkumulation der Abgasgegendruck nicht zu weit an- steigt. Aus diesem Grunde ist es erforderlich, dass ein solches Substrat bei hinreichender Rußbeladung regeneriert wird. Im Zuge einer solchen Regengeneration wird der akkumulierte Ruß oxidiert, was auch als kontrollierter Rußabbrand angesprochen wird. Eine solche Regeneration kann passiv und somit bei Erreichen einer bestimmten Temperatur des Rußes selbsttätig oder aktiv gesteuert erfolgen. Bei einer passiven Regeneration wird dem auf der Anströmseite akkumulierten Ruß N02 zugeführt, wodurch die Oxidation des Rußes bei niedrigeren Temperaturen ermöglicht wird. Um den vorgenannten Anforderungen zu genügen, werden derartige Partikelfilter bzw. deren Substrat ausgelegt, dass diese eine relativ kleine Porengröße von typischerweise nur 5 μιτι bis 15 μιτι und eine Porosität von nicht mehr als 50% aufweisen. Darüber hinaus ist das Substrat ausgelegt, damit sich ausgehend von einem unbeladenen Substrat der Filtrati- onsprozess möglichst rasch auf eine Oberflächenfiltration einstellt. Bevor eine Oberflächenfiltration zumindest in nennenswertem Maße stattfindet, müssen sich die in den Filterwänden befindlichen Poren mit Ruß etwas zugesetzt haben, wodurch die effektive Porosität gegenüber derjenigen des Substrates nochmals herabgesetzt wird. Während der Zeitdauer der Tiefenfilterung kann mit derartigen Filtern der gewünschte Abscheidegrad von mehr als 98% noch nicht realisiert werden. Daher ist man bestrebt, derartige Partikelfilter so auszulegen, dass diese rasch in den Zustand der ihnen zugedachten Oberflächenfiltration gelangen. Such particulate filters are designed so that the exhaust gas backpressure does not increase too much as a result of this, even with increasing accumulation of soot. For this reason, it is necessary that such a substrate is regenerated with sufficient soot loading. In the course of such a regeneration of the accumulated soot is oxidized, which is also addressed as a controlled Rußabbrand. Such regeneration can be done passively and thus automatically or actively controlled upon reaching a certain temperature of the soot. In a passive regeneration is fed to the soot accumulated on the upstream side N0 2 , whereby the oxidation of the carbon black is allowed at lower temperatures. To meet the above requirements, such particle filter or its substrate are designed so that they have a relatively small pore size of typically only 5 μιτι to 15 μιτι and a porosity of not more than 50%. In addition, the substrate is designed so that, starting from an unloaded substrate, the filtration process adjusts as quickly as possible to a surface filtration. Before a surface filtration takes place at least to a significant degree, the pores in the filter walls must have added something with soot, whereby the effective porosity compared to that of the substrate is further reduced. During the duration of the depth filtering, the desired separation efficiency of more than 98% can not yet be realized with such filters. Therefore, it is endeavored to design such particle filters so that they quickly reach the state of their intended surface filtration.
Für einige Anwendungen wird eine vollständige Reduzierung der Rußemission nicht gefordert. Bei diesen Anwendungen ist es mitunter ausrei- chend, wenn die Rußemission einer Brennkraftmaschine um 50% oder auch nur 20% bis 25% reduziert ist. For some applications, a complete reduction in soot emissions is not required. In these applications it is sometimes sufficient if the soot emission of an internal combustion engine is reduced by 50% or even only 20% to 25%.
Zu diesem Zweck sind so genannte Teilfilter entwickelt worden. Teilfilter haben einen maximalen nominalen Abscheidegrad in der gewünschten Größenordnung. Dieses bedeutet, dass derartige Filter dem den Abscheidegrad entsprechenden Anteil der in dem Abgas einer Brennkraftmaschine mitgeführten Partikel, insbesondere Rußpartikel auffangen können. Teilfilter können als Wandstromfilter ausgelegt sein. In einem solchen Fall wird das für einen Vollfilter eingesetzte Substrat verwendet und es werden durch unterschiedliche Maßnahmen ein oder mehrere, üblicherweise eine Vielzahl an Bypass-Kanälen ausgebildet. Die Bypass-Kanäle stellen eine Strömungswegsamkeit von der Anströmseite des Substrates zur Abströmseite hin, ohne dass von dem Abgas eine Filterwand durchströmt werden muss. Eingerichtet wird ein solcher Bypass durch Verbinden eines ab- strömseitig verschlossenen Filterkanals mit einem oder mehreren ab- strömseitig offenen Filterkanälen. Die durchströmbare Querschnittsfläche der Bypass-Strömungswegsamkeit ist ausgelegt, damit ein bestimmter Anteil des Abgasstromes diesen ungefiltert durchströmt. In Abhängigkeit von der durchströmbaren Querschnittsfläche der Bypass-Strömungsweg- samkeit bestimmt sich der mit einem solchen Teilfilter realisierbare Abscheidegrad. So-called sub-filters have been developed for this purpose. Partial filters have a maximum nominal degree of separation of the desired order of magnitude. This means that such filters can absorb the proportion of the entrained in the exhaust gas of an internal combustion engine particles, in particular soot particles. Partial filters can be designed as a wall-flow filter. In such a case, the substrate used for a full filter is used and one or more, usually a plurality of bypass channels are formed by different measures. The bypass channels provide a flow path from the upstream side of the substrate to the downstream side, without having to flow through a filter wall of the exhaust gas. Such a bypass is established by connecting a filter channel sealed off on the outlet side with one or more filter channels that are open on the outflow side. The flow-through cross-sectional area of the bypass flow path is designed to allow a particular flow Share of the exhaust stream flows through this unfiltered. Depending on the permeable cross-sectional area of the bypass flow path, the degree of separation that can be achieved with such a sub-filter is determined.
Neben derartigen, als Wandstromfilter ausgelegten Partikelteilfiltern sind auch solche bekannt geworden, bei denen eine Filterung allein durch Wandablagerungen des an einer Filterwand vorbeiströmenden Abgases erfolgt. Typischerweise sind derartige Filterwände mit Fangstrukturen aus- gerüstet, beispielsweise nach Art eines Metal Mieses oder dergleichen. In addition to such designed as a wall-mounted flow filter particle filters are also known, in which a filtering is done solely by wall deposits of passing past a filter wall exhaust gas. Typically, such filter walls are equipped with catch structures, for example in the manner of a Metal Mieses or the like.
Auch wenn mit diesen vorbekannten Filtertypen Teilfilter mit unterschiedliche Abscheidegraden realisiert werden können, wäre es wünschenswert, wenn eine Auslegung von einem solchen, als Wandstromfilter ausgelegten Teilfilter verbessert werden könnte. Zudem wäre es wünschenswert, wenn das Gewicht eines solchen Filters bzw. dessen Substrates reduziert werden könnte. Gerade im Kraftfahrzeugbau ist man bestrebt, so viel Gewicht wie möglich einzusparen. Ausgehend von diesem diskutierten Stand der Technik liegt der Erfindung somit die Aufgabe zugrunde, ein als Wandstromfilter ausgelegten Partikelfilter als Teilfilter vorzuschlagen, der nicht nur größere Freiheiten in seiner Auslegung gestattet, sondern vorzugsweise auch ein geringeres Gewicht aufweist. Even if partial filters with different degrees of separation can be realized with these previously known filter types, it would be desirable if a design of such a partial filter designed as a wall-flow filter could be improved. In addition, it would be desirable if the weight of such a filter or its substrate could be reduced. Especially in the automotive industry is anxious to save as much weight as possible. Based on this discussed prior art, the invention is therefore the object of proposing a designed as a wall-flow filter particulate filter as a partial filter, which not only allows greater freedom in its design, but preferably also has a lower weight.
Gelöst wird die Aufgabe erfindungsgemäß durch einen eingangs genannten, gattungsgemäßen Partikelfilter, bei dem die Filterwände des Substrates eine Porosität zwischen etwa 55% und etwa 75% sowie eine Porengröße zwischen etwa 20 μιτι und 35 μιτι aufweisen. The object is achieved according to the invention by an aforementioned, generic particle filter, in which the filter walls of the substrate have a porosity between about 55% and about 75% and a pore size between about 20 μιτι and 35 μιτι.
Bei diesem als Teilfilter ausgelegten Partikelwandstromfilter wird ein Substrat eingesetzt, welches ein, verglichen mit der Porosität herkömmlicher Substrate, deutlich höhere Porosität aufweist. Zudem verfügt dieses Substrat über eine Porengröße, die ebenfalls signifikant größer ist als diejeni- ge, welche bei herkömmlich eingesetzten Substraten anzutreffen ist. Insofern werden in die Auslegung des Substrates bereits Eigenschaften des aus dem Substrat herzustellenden Partikelteilfilters eingebracht. Die signi- fikant höhere Porosität und die ebenfalls signifikant größere Porengröße erlaubt eine widerstandsärmere Durchströmbarkeit der aus einem solchen Substrat gebildeten Filterwand. Infolge dessen bleibt der bei einem als Wandstromfilter mit Kanalstruktur ausgelegten Teilfilter in der erfindungs- gemäßen Ausführung der Tiefenfiltrationseffekt deutlich länger erhalten. Die freie Querschnittsfläche der Bypass-Strömungsweg-samkeit kann somit gegenüber vorbekannten, als Wandstromfilter ausgelegten Partikelteilfiltern kleiner bemessen sein. Im Ergebnis führt dieses bei gleichem Substratvolumen zu einer Effizienzverbesserung des Abscheidegrades. Zugleich ist durch die signifikant höhere Porosität des Substrates dessen Gewicht gegenüber vorbekannten Substraten nicht unerheblich reduziert. In this designed as a partial filter particle wall flow filter, a substrate is used, which has a, compared to the porosity of conventional substrates, significantly higher porosity. In addition, this substrate has a pore size that is also significantly greater than that found in conventionally used substrates. In this respect, properties of the particle particle filter to be produced from the substrate are already introduced into the design of the substrate. The significant Fikant higher porosity and also significantly larger pore size allows a lower resistance flow through the filter wall formed from such a substrate. As a result of this, the partial filter designed as a wall-flow filter with a channel structure in the inventive embodiment of the depth filtration effect remains significantly longer. The free cross-sectional area of the bypass flow path can thus be dimensioned smaller than previously known particle wall filters designed as wall-flow filters. As a result, this results in the same substrate volume to improve the efficiency of the separation efficiency. At the same time, the significantly higher porosity of the substrate significantly reduces its weight compared with previously known substrates.
Der Abscheidegrad eines solchen Partikelteilfilters kann gesteigert werden, wenn die Porosität zwischen 60% und 70% beträgt. The degree of separation of such a particle-part filter can be increased if the porosity is between 60% and 70%.
Gemäß einer bevorzugten Ausgestaltung beträgt die Porosität der Filterwände des Substrates etwa 65%, während die Porengröße vorzugsweise nicht größer als 30 μιτι, insbesondere etwa 22 μιη beträgt. Neben der Porosität und der Porengröße hat sich überraschend gezeigt, dass ein als Wandstromfilter ausgelegter Partikelteilfilter für die genannten Zwecke besonders effektiv ist, wenn das Substrat ein Durchmesser-zuLängen-Verhältnis zwischen 1 und 1 ,5 insbesondere von etwa 1 ,4 aufweist. Dieses bedeutet, dass diese Substrate verglichen mit herkömmli- chen Substraten sehr viel kürzer ausgelegt werden können, was vor allem Vorteile in der Temperaturbeständigkeit des Substrates bei einer Regeneration mit sich bringt. Ohne Weiteres können zur Verbesserung des Ge- samtabscheidegrades mehrere Substrate in Richtung des Abgases hintereinander geschaltet sein, sollte eine größere Substratgesamtlänge ge- wünscht oder benötigt sein. In einem solchen Fall werden im Rahmen dieser Ausführungen auch die mehreren Substrate in ihrer Gesamtheit mit dem Begriff "der Partikelfilter" angesprochen. According to a preferred embodiment, the porosity of the filter walls of the substrate is about 65%, while the pore size is preferably not greater than 30 μιτι, in particular about 22 μιη. In addition to the porosity and the pore size, it has surprisingly been found that a particulate filter designed as a wall-flow filter is particularly effective for the purposes mentioned, when the substrate has a diameter-to-length ratio between 1 and 1.5, in particular about 1.4. This means that these substrates can be designed much shorter compared to conventional substrates, which brings about advantages in the temperature resistance of the substrate during regeneration. Without further ado, in order to improve the overall degree of separation, a plurality of substrates can be connected in series in the direction of the exhaust gas, should a larger overall substrate length be desired or needed. In such a case, in the context of these embodiments, the multiple substrates in their entirety are also addressed by the term "the particle filter".
Verglichen mit Vollfiltern hat sich bei der Auslegung von Teilfiltern mit den bereits vorbeschriebenen Auslegungskriterien gezeigt, dass diese besonders effektiv arbeiten, wenn das oder die Substrate einen eher geringeren Durchmesser aufweisen, und zwar bezogen auf die Motorgröße bzw. den zu reinigenden Abgasmassenstrom. Der Durchmesser des Substrates ist neben den weiteren Auslegungskriterien eines solchen Partikelteilfilters für die Strömungsgeschwindigkeit des das Substrat durchströmenden Abgases verantwortlich. Eine zu große Strömungsgeschwindigkeit - also ein im Durchmesser relativ kleines Substrat - hat zur Folge, dass die Bypass- Wegsamkeit einen relativ hohen Strömungswiderstand darstellt, sodass der Abscheidegrad über dem Notwendigen liegt. Zudem wird vermutet, dass bei höheren Durchströmungsgeschwindigkeiten eine Umlenkung durch die Filterwände hindurch nicht ideal ausgeführt werden kann. Ist hingegen die Strömungsgeschwindigkeit zu klein - also der Durchmesser des Substrates groß - führt dieses dazu, dass das Abgas bevorzugt durch die Bypass-Wegsamkeit strömt und der gewünschte Abscheidegrad nicht erreicht werden kann. Somit ist bevorzugt, den Durchmesser des zumindest einen Substrates des Partikelfilters an den Volumenstrom des zu rei- nigenden Abgases und somit an die Motorgröße anzupassen. Compared with full filters, it has been found in the design of partial filters with the design criteria already described above that they work particularly effectively when the substrate (s) have a rather small diameter, based on the size of the motor or the motor to be cleaned exhaust gas mass flow. The diameter of the substrate is responsible for the flow rate of the exhaust gas flowing through the substrate, in addition to the further design criteria of such a particle partial filter. Too high a flow velocity - ie a relatively small diameter in the substrate - has the consequence that the bypass pathway is a relatively high flow resistance, so that the separation efficiency is above what is necessary. In addition, it is believed that at higher flow rates, a deflection through the filter walls can not be carried out ideally. If, on the other hand, the flow velocity is too small-that is to say the diameter of the substrate is large-this leads to the fact that the exhaust gas preferably flows through the bypass pathway and the desired degree of separation can not be achieved. It is thus preferable to adapt the diameter of the at least one substrate of the particle filter to the volume flow of the exhaust gas to be cleaned and thus to the engine size.
Der Abscheidegrad eines solchen Partikelteilfilters wird auch durch die Filterkanaldichte bestimmt. Dieses auch als Zellendichte angesprochene Merkmal liegt bevorzugt zwischen etwa 180 cpsi und etwa 225 cpsi (cpsi: cells per Square inch). Besonders effektive Partikelteilfilter verfügen unter Berücksichtigung der bereits vorstehenden Auslegungskriterien über etwa 200 cpsi. The degree of separation of such a particle filter is also determined by the filter channel density. This feature, also referred to as cell density, is preferably between about 180 cpsi and about 225 cpsi (cpsi: cells per square inch). Especially effective Particle Filters have about 200 cpsi, considering the design criteria already mentioned above.
Somit kann in die Filterkanaldichte bereits die zur Zweckbestimmung des Substrates bei der Auslegung desselben berücksichtigt werden. Ist die Filterkanaldichte geringer, hat sich gezeigt, dass die Strömungsgeschwindigkeit durch die Filterwände relativ hoch ist und somit die bei der Auslegung eines solchen Partikelteilfilters gewünschte Tiefenfiltration reduziert und somit der Abscheidegrad sinkt. Zudem ist dann die Querschnittsfläche der Bypass-Strömungswegsamkeit relativ groß. Bei höherer Zellendichte ist die Querschnittsfläche der Bypass-Wegsamkeit relativ klein. Zudem hat sich gezeigt, dass eine Tiefenfiltration in den Filterwänden dann nur mehr untergeordnet stattfindet, was zu einer zu raschen Rußakkumulation allein auf der Oberfläche führt. Thus, in the filter channel density already taken into account for the purpose of the substrate in the interpretation of the same. If the filter channel density is lower, it has been shown that the flow velocity through the filter walls is relatively high, thus reducing the depth filtration desired in the design of such a particle filter and thus decreasing the separation efficiency. In addition, then the cross-sectional area of the bypass flow path is relatively large. With higher cell density, the cross-sectional area of the bypass pathway is relatively small. In addition, it has been shown that a depth filtration in the filter walls then takes place only subordinate, which leads to too rapid Rußakkumulation alone on the surface.
Bei einem solchermaßen ausgelegten Partikelteilfilter wird aufgrund des gewünschten Tiefenfiltrationseffektes vor allem auch die Filterwand als solche für das Herausfiltern von im Abgasstrom mitgeführter Partikel genutzt. Als besonders zweckmäßig haben sich Wandstärken zwischen 0,3 mm und 0,7 mm, insbesondere von etwa 0,4 mm erwiesen, um den an einen solchen Teilfilter gestellten Anforderungen zu genügen. In a thus designed partial particle filter is due to the desired depth filtration effect, especially the filter wall as used for filtering out entrained in the exhaust stream particles. Wall thicknesses between 0.3 mm and 0.7 mm, in particular of approximately 0.4 mm, have proved to be particularly expedient in order to meet the requirements imposed on such a partial filter.
Als Wandstromfilter ausgeführte Partikelfilter erlauben die Ausbildung des Einsatzes des Partikelfilters mit mehreren derartigen Substraten, die dann in Strömungsrichtung des Abgases hintereinander geschaltet sind. Diese zumindest zwei oder auch mehreren, hintereinander geschalteten Substra- te bestimmten dann den Gesamtabscheidegrad des Partikelfilters. As a wall-flow filter designed particulate filter allow the formation of the use of the particulate filter with a plurality of such substrates, which are then connected in series in the flow direction of the exhaust gas. These at least two or even several subdivisions connected in series then determine the overall degree of separation of the particulate filter.
Durchaus möglich ist es, einen ein einziges Substrat umfassenden Partikelfilter vor einem herkömmlichen Vollfilter oder einen Partikelteilfilter herkömmlicher Bauart zu schalten. Besonders zweckmäßig ist der Einsatz eines solchen, einem Partikelfilter vorgeschalteten ersten Teilfilters dann, wenn diesem ein Oxidationskatalysator vorgeschaltet oder seine anström- seitige Oberfläche oxidationskatalytisch beschichtet ist. Ein solcher erster Partikelteilfilter kann verglichen mit dem in Strömungsrichtung des Abgases nachgeschalteten Hauptfilter ein sehr viel kleineres Volumen aufwei- sen und daher sehr motornah, typischerweise unmittelbar dem Abgaskrümmer oder, für den Fall, dass ein Turbolader vorgesehen ist, dem Turbolader nachgeschaltet, angeordnet sein. Diese motornahe Anordnung gewährleistet, dass dieser Partikelteilfilter, da passiv arbeitend ausgelegt, in einem optimalen Abscheidegrad auch bei unterschiedlichen dynami- sehen Beanspruchungen der Brennkraftmaschine arbeitet. Hierdurch wird bereits ein Teil der ausgestoßenen Partikel wirksam entfernt, was die Filtertätigkeit des nachgeschalteten Partikelhauptfilters entlastet. Insofern braucht dieser erst nach längeren Zeitintervallen als herkömmliche Partikelfilter oder Partikelfilteranordnungen regeneriert zu werden. Sollte dieser nachgeschaltete Partikelfilter aktiv regeneriert werden, bedeutet dieses auch eine Reduzierung des hierfür benötigten Energieverbrauches, beispielsweise von Brennstoff, der von einem Brenner zum Anheben der Abgastemperatur benötigt werden würde. In einem konkreten Ausführungsbeispiel ist vorgesehen, einen ein solches erstes Substrat in einem eigenen Gehäuse aufweisenden Partikelfilter unmittelbar motornah und somit innerhalb des ersten Abschnittes des Ab- gasstranges anzuordnen. Bei diesem Partikelteilfilter kann es sich um einen solchen mit einem Abscheidegrad von etwa 20% handeln. Das Substrat weist nur ein geringes Volumen auf, was die vorbeschriebene motornahe Anordnung ermöglicht. Der eigentliche Hauptpartikelteilfilter befindet sich sodann mit entsprechendem Abstand vom Motor, und zwar an einer Stelle am Fahrzeug, wo ein entsprechender Bauraum vorhanden ist. Bei diesem zweiten Filter handelt es sich ebenfalls um einen Teilfilter, beispielsweise der vorbeschriebenen Art mit einem Abscheidegrad von 40%. Das erste Substrat ist anströmseitig mit einer oxidationskatalytischen Be- Schichtung ausgerüstet und unterliegt daher einer passiven Regenerationsstrategie. Dabei ist die oxidationskatalytische Beschichtung derart ausgeführt, dass von dieser hinreichend N02 generiert werden kann, um auch den im Abgasstrang weiter hinten angeordneten Hauptfilter bzw. den darauf akkumulierten Ruß zur Regeneration des Substrates mit N02 zu versorgen. Der nominal kumulierte Abscheidegrad dieser beiden hintereinander geschalteten Partikelteilfilter beträgt 52%. It is entirely possible to switch a particle filter comprising a single substrate in front of a conventional full filter or a particle filter of conventional design. The use of such a first partial filter arranged upstream of a particle filter is particularly expedient if it is preceded by an oxidation catalytic converter or by an oxidation-catalytic coating of its upstream surface. Such a first partial particle filter can have a much smaller volume compared with the main filter connected downstream in the flow direction of the exhaust gas and therefore be arranged very close to the engine, typically directly to the exhaust manifold or, in the event that a turbocharger is provided downstream of the turbocharger. This arrangement close to the engine ensures that this particulate filter, since it is designed to work passively, works in an optimal degree of separation even when the internal combustion engine is exposed to different dynamic loads. As a result, part of the ejected particles is already effectively removed, which relieves the filter action of the downstream main particle filter. In this respect, it only needs to be regenerated after longer time intervals than conventional particle filters or particle filter arrangements. Should this downstream particulate filter be actively regenerated, this also means a reduction in the energy consumption required for this purpose, for example of fuel that would be required by a burner to raise the exhaust gas temperature. In a concrete exemplary embodiment, it is provided that a particle filter having such a first substrate in its own housing is directly close to the engine and thus within the first section of the exhaust gas. arrange gas string. This particulate filter may be one with a degree of separation of about 20%. The substrate has only a small volume, which allows the above-described close-coupled arrangement. The actual main particle filter is then located at an appropriate distance from the engine, at a point on the vehicle, where a corresponding space is available. This second filter is also a partial filter, for example of the type described above with a separation efficiency of 40%. The first substrate is equipped on the inflow side with an oxidation-catalytic coating and is therefore subject to a passive regeneration strategy. In this case, the oxidation-catalytic coating is designed in such a way that it can be used to generate N0 2 sufficiently to supply N0 2 to the main filter arranged further back in the exhaust gas line or the soot accumulated thereon for regeneration of the substrate. The nominal cumulative degree of separation of these two successive particle partial filters is 52%.
Von Vorteil bei einer solchen Ausgestaltung ist vor allem auch, dass für die N02-Versorgung auch des Hauptpartikelfilters eingesetzte Oxidations- katalysator bzw. die diesbezügliche oxidationskatalytische Beschichtung sehr motornah angeordnet ist, mithin sehr rasch auf Betriebstemperatur ist. Daher erhält auch der auf dem nachgeschalteten zweiten Partikelteilfilter akkumulierte Ruß bereits nach sehr kurzer Betriebsdauer des Motors das für die Regeneration benötigte N02. An advantage of such an embodiment is, above all, that the oxidation catalyst used for the N0 2 supply even of the main particle filter or the relevant oxidation-catalytic coating is arranged very close to the motor, and thus is very quickly at the operating temperature. Therefore, the soot accumulated on the downstream second particulate filter also receives the N0 2 needed for the regeneration after a very short operating time of the engine.
Die sehr motornahe Anordnung des Oxidationskatalysators bzw. die diesem Zweck dienende anströmseitig auf das erste Substrat aufgebrachte oxidationskatalytische Beschichtung bedingt auch, dass bereits nach kurzer Betriebsdauer und somit raschem Erreichen seiner Betriebstemperatur weitere Emissionen, etwa mitgeführte HCs im Abgas zersetzt werden. Durch diese an der oxidationskatalytischen Oberfläche exotherme Reaktion wird der Oxidationskatalysator noch rascher auf Betriebstemperatur gebracht. Es versteht sich, dass bei Vorsehen von mehreren, einen solchen Partikelfilter ausbildenden Substraten, diese in einem gemeinsamen Gehäuse angeordnet sein können. In dem zuvor beschriebenen Anwendungs- beispiel, bei der ein erstes Substrat unmittelbar motornah angeordnet ist, während ein zweites sich an anderer Stelle im Abgasstrang befindet, wird das erste Substrat in einem eigenen Gehäuse, während das oder die nachgeschalteten Substrate in einem eigenen Gehäuse eingefasst sind. The very close to the engine arrangement of the oxidation catalyst or serving for this purpose upstream of the first substrate applied oxidation catalytic coating also requires that after a short period of operation and thus rapidly reaching its operating temperature further emissions, such as entrained HCs are decomposed in the exhaust. As a result of this reaction, which is exothermic on the oxidation-catalytic surface, the oxidation catalyst is brought to operating temperature even faster. It is understood that, when providing a plurality of substrates forming such a particle filter, they can be arranged in a common housing. In the application described above, For example, in which a first substrate is arranged directly close to the motor, while a second is located elsewhere in the exhaust system, the first substrate is in a separate housing, while the one or more downstream substrates are enclosed in a separate housing.
In einem bevorzugten Ausführungsbeispiel ist vorgesehen, dass das zumindest ein Substrat des Partikelfilters für eine passive Regeneration ausgelegt ist. Dabei ist die Auslegung des jeweiligen Substrates derart ausgeführt und innerhalb des Abgasstranges angeordnet, dass eine Regenera- tion des Substrates stattfindet, nachdem die Abscheidegrad des Substrates seine nominale maximale Abscheidegrad erreicht hat, allerdings bevor die Abscheidegrad durch sukzessiv weitere Akkumulation von Ruß auf seine minimale Abscheidegrad herabgesetzt ist. Bevorzugt ist die Ausgestaltung des Substrates dergestalt, dass eine Regeneration stattgefunden hat, bevor die IST-Abscheidegrad um 50% des Differenzbetrages zwischen der nominalen maximalen Abscheidegrad und der minimalen Abscheidegrad herabgesetzt ist. Das zur Aufrechterhaltung der Effektivität des Partikelteilfilters bzw. seines Substrates einzuhaltende Regenerationsfenster ist daher verglichen mit denjenigen von Vollfiltern signifikant grö- ßer. Dieses bedeutet, dass ohne nennenswerte Erhöhung des Abgasgegendruckes der Betrieb des Partikelfilters mit dem gewünschten Abscheidegrad aufrechterhalten wird, auch wenn eine Regeneration aufgrund möglicherweise nicht gegebener Regenerationsbedingungen erst erheblich verzögert stattfinden kann. In a preferred embodiment, it is provided that the at least one substrate of the particulate filter is designed for passive regeneration. In this case, the design of the respective substrate is designed and arranged within the exhaust line, that a regeneration of the substrate takes place after the degree of separation of the substrate has reached its nominal maximum degree of separation, but before the degree of separation by successive further accumulation of soot on its minimum separation efficiency is lowered. Preferably, the configuration of the substrate is such that a regeneration has taken place before the actual degree of separation is reduced by 50% of the difference between the nominal maximum degree of separation and the minimum degree of separation. The regeneration window to be maintained for maintaining the effectiveness of the particle sub-filter or its substrate is therefore significantly larger compared to those of full filters. This means that the operation of the particulate filter with the desired degree of separation is maintained without significant increase in the exhaust backpressure, even if regeneration can take place only considerably delayed due to possibly not given regeneration conditions.
In einem bevorzugtem Ausführungsbeispiel ist vorgesehen, dass das Substrat ein Siliziumkarbidwerkstoff ist. Grundsätzlich können auch andere Materialien, beispielsweise Keramikmaterialien oder Sintermetall zum Herstellen eines Substrates für einen solchen Partikelfilter verwendet wer- den. In a preferred embodiment it is provided that the substrate is a silicon carbide material. In principle, it is also possible to use other materials, for example ceramic materials or sintered metal, for producing a substrate for such a particle filter.
Die Erfindung ist anhand von Ausführungsbeispielen beschrieben worden. Ohne den Umfang der geltenden Ansprüche zu verlassen, ergeben sich für einen Fachmann zahlreiche weitere Möglichkeiten, die Erfindung zu verwirklichen. The invention has been described with reference to embodiments. Without departing from the scope of the applicable claims, numerous other ways for the skilled person to realize the invention will become apparent.

Claims

Patentansprüche claims
1. Als Wandstromfilter mit Kanalstruktur ausgelegter Partikelfilter zum Entfernen von in dem Abgas einer Brennkraftmaschine mitgeführten Partikeln, insbesondere Rußpartikeln, welcher Partikelfilter ein Substrat mit einer Vielzahl von durch Filterwände eingefassten Filterkanälen aufweist und über zumindest einen Bypass zum Bereit- stellen einer Strömungswegsamkeit von der Anströmseite auf die1. Particle filter designed as a wall-flow filter with a duct structure for removing particles carried in the exhaust gas of an internal combustion engine, in particular soot particles, which particle filter has a substrate with a multiplicity of filter channels enclosed by filter walls, and via at least one bypass for providing a flow path from the upstream side the
Abströmseite des Substrate, ohne eine Filterwand durchströmen zu müssen, verfügt, dadurch gekennzeichnet, dass die Filterwände des Substrates eine Porosität zwischen etwa 55% und etwa 75% sowie eine Porengröße zwischen etwa 20 μιτι und 35 μιτι aufwei- sen. Downstream of the substrates, without having to flow through a filter wall, has, characterized in that the filter walls of the substrate have a porosity between about 55% and about 75% and a pore size between about 20 μιτι and 35 μιτι aufwei- sen.
2. Partikelfilter nach Anspruch 1 , dadurch gekennzeichnet, dass die Porosität der Filterwände des Substrates etwa 65% beträgt. 2. Particle filter according to claim 1, characterized in that the porosity of the filter walls of the substrate is about 65%.
3. Partikelfilter nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Porengröße der Filterwände des Substrates nicht mehr als 30 μιτι, insbesondere etwa 22 μιη beträgt. 3. Particle filter according to claim 1 or 2, characterized in that the pore size of the filter walls of the substrate is not more than 30 μιτι, in particular about 22 μιη.
4. Partikelfilter nach einem der Ansprüche 1 bis 3, dadurch gekenn- zeichnet, dass das Substrat ein Durchmesser-zu-Längen-4. Particle filter according to one of claims 1 to 3, characterized in that the substrate is a diameter-to-length
Verhältnis zwischen 1 und 1 ,5, insbesondere von etwa 1 ,4 aufweist. Ratio between 1 and 1, 5, in particular from about 1, 4.
5. Partikelfilter nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass das Substrat eine Filterkanaldichte (Zellendichte) zwischen etwa 180 cpsi und etwa 225 cpsi (cpsi: cells per Square inch), insbesondere von etwa 200 cpsi aufweist. 5. Particle filter according to one of claims 1 to 4, characterized in that the substrate has a filter channel density (cell density) between about 180 cpsi and about 225 cpsi (cpsi: cells per square inch), in particular of about 200 cpsi.
6. Partikelfilter nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die Wandstärke der Filterwände zwischen 0,3 mm und 0,7 mm, insbesondere etwa 0,4 mm beträgt. 6. Particle filter according to one of claims 1 to 5, characterized in that the wall thickness of the filter walls between 0.3 mm and 0.7 mm, in particular about 0.4 mm.
7. Partikelfilter nach einem der Ansprüche 1 bis 6, dadurch gekenn- zeichnet, dass der Partikelfilter zwei oder mehr, in Strömungsrichtung des Abgases hintereinander geschaltete Substrate umfasst, wobei der Abscheidegrad des einem ersten Substrat in Strömungsrichtung des Abgases nachgeschalteten zweiten Substrates größer ist als der Abscheidegrad des vorgeschalteten Substrates. 7. Particulate filter according to one of claims 1 to 6, characterized shows that the particle filter comprises two or more, in the flow direction of the exhaust gas in series connected substrates, the degree of separation of a first substrate in the flow direction of the exhaust gas downstream second substrate is greater than the separation efficiency of the upstream substrate.
Partikelfilter nach Anspruch 7, dadurch gekennzeichnet, dass der Abscheidegrad des nachgeschalteten Substrates zumindest 10% höher ist als derjenige des vorgeschalteten Substrates. Particle filter according to claim 7, characterized in that the separation efficiency of the downstream substrate is at least 10% higher than that of the upstream substrate.
Partikelfilter nach Anspruch 7, dadurch gekennzeichnet, dass der Partikelfilter zwei Substrate umfasst und der Abscheidegrad des ersten Substrates etwa 20 % und derjenige des nachgeschalteten Substrates etwa 40% beträgt. Particle filter according to claim 7, characterized in that the particle filter comprises two substrates and the degree of separation of the first substrate is about 20% and that of the downstream substrate is about 40%.
Partikelfilter nach einem der Ansprüche 7 bis 9, dadurch gekennzeichnet, dass die Substrate in einem gemeinsamen Gehäuse angeordnet sind. Particulate filter according to one of claims 7 to 9, characterized in that the substrates are arranged in a common housing.
Partikelfilter nach einem der Ansprüche 7 bis 9, dadurch gekennzeichnet, dass ein erstes Substrat von dem oder den weiteren Substraten getrennt in einem eigenen Gehäuse und mit Abstand zu den weiteren Substraten angeordnet ist und eine geringeres Substratvolumen aufweist als in der Summe das oder die weiteren, diesem ersten Substrat nachgeschalteten weiteren Substrate. Particulate filter according to one of claims 7 to 9, characterized in that a first substrate of the one or more further substrates is arranged separately in a separate housing and at a distance from the other substrates and has a smaller substrate volume than the sum of the one or more, downstream of this first substrate further substrates.
Partikelfilter nach Anspruch 1 1 , dadurch gekennzeichnet, dass das erste Substrat in unmittelbarer Nähe zum Motorausgang in dem Abgasstrang angeordnet ist. Particulate filter according to claim 1 1, characterized in that the first substrate is arranged in the immediate vicinity of the engine outlet in the exhaust line.
Partikelfilter nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, dass das Substrat bzw. zumindest eines der mehreren Substrate katalytisch beschichtet ist, etwa mit einer oxidationskata- lytischen Beschichtung ausgerüstet ist. Particle filter according to one of claims 1 to 12, characterized in that the substrate or at least one of the plurality of substrates is catalytically coated, for example, is equipped with an oxidation-catalytic lytic coating.
Partikelfilter nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, dass das oder die Substrate des Partikelfilters zur passi- ven Regeneration dergestalt ausgelegt sind, dass eine passive Regeneration bei einer Rußbeladung des jeweiligen Substrates stattfindet, nachdem die Abscheidegrad des jeweiligen Substrates seine nominale maximale Abscheidegrad erreicht hat und bevor die Abscheidegrad durch sukzessive Akkumulation von weiterem Ruß auf seine minimale Abscheidegrad reduziert ist. Particulate filter according to one of claims 1 to 13, characterized in that the one or more substrates of the particulate filter for passive ven regeneration are designed such that a passive regeneration takes place at a soot loading of the respective substrate, after the degree of separation of the respective substrate has reached its nominal maximum degree of separation and before the degree of separation is reduced by successive accumulation of further soot to its minimum separation efficiency.
Partikelfilter nach einem der Ansprüche 1 bis 14, dadurch gekennzeichnet, dass das oder die Substrate des Partikelfilters aus einem porösen Siliziumkarbidwerkstoff hergestellt sind. Particulate filter according to one of claims 1 to 14, characterized in that the one or more substrates of the particulate filter are made of a porous silicon carbide material.
PCT/EP2013/064941 2013-07-15 2013-07-15 Particle filter designed as a wall-flow filter with duct structure WO2015007306A1 (en)

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CN201380077694.2A CN105324167A (en) 2013-07-15 2013-07-15 Particle filter designed as a wall-flow filter with duct structure

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1304152A1 (en) * 2001-10-19 2003-04-23 J. Eberspächer GmbH & Co. KG Exhaust system with particle filter for an internal combustion engine
EP1696109A2 (en) * 2005-02-23 2006-08-30 Ngk Insulators, Ltd. Method of manufacturing plugged honeycomb structure and plugged honeycomb structure
DE102005023518A1 (en) * 2005-05-21 2006-11-23 Umicore Ag & Co. Kg Blockage-free filter unit with high efficiency
EP2364765A1 (en) * 2010-03-11 2011-09-14 NGK Insulators, Ltd. Honeycomb catalyst body

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPWO2005064128A1 (en) * 2003-12-25 2007-07-19 イビデン株式会社 Exhaust gas purification device and method for regenerating exhaust gas purification device
DE102009010307A1 (en) * 2009-02-24 2010-08-26 Daimler Ag Exhaust gas treatment device and method for operating an exhaust gas treatment device
US8444752B2 (en) * 2009-08-31 2013-05-21 Corning Incorporated Particulate filters and methods of filtering particulate matter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1304152A1 (en) * 2001-10-19 2003-04-23 J. Eberspächer GmbH & Co. KG Exhaust system with particle filter for an internal combustion engine
EP1696109A2 (en) * 2005-02-23 2006-08-30 Ngk Insulators, Ltd. Method of manufacturing plugged honeycomb structure and plugged honeycomb structure
DE102005023518A1 (en) * 2005-05-21 2006-11-23 Umicore Ag & Co. Kg Blockage-free filter unit with high efficiency
EP2364765A1 (en) * 2010-03-11 2011-09-14 NGK Insulators, Ltd. Honeycomb catalyst body

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