EP1837497B1 - Système de purification de gaz d'échappement comprenant un piège à polluants et un filtre à particules ainsi qu'un procédé de fabrication d'un tel système - Google Patents

Système de purification de gaz d'échappement comprenant un piège à polluants et un filtre à particules ainsi qu'un procédé de fabrication d'un tel système Download PDF

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Publication number
EP1837497B1
EP1837497B1 EP20060111594 EP06111594A EP1837497B1 EP 1837497 B1 EP1837497 B1 EP 1837497B1 EP 20060111594 EP20060111594 EP 20060111594 EP 06111594 A EP06111594 A EP 06111594A EP 1837497 B1 EP1837497 B1 EP 1837497B1
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EP
European Patent Office
Prior art keywords
exhaust
honeycomb filter
aftertreatment system
filter
exhaust gas
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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.)
Expired - Fee Related
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EP20060111594
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German (de)
English (en)
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EP1837497A1 (fr
Inventor
Matthew Schneider
Mario Balenovic
Alexei Dubkov
Brendan Carberry
Yasser Mohammed Sayed Yacoub
Jan Harmsen
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Ford Global Technologies LLC
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Ford Global Technologies LLC
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Priority to DE200650002485 priority Critical patent/DE502006002485D1/de
Priority to EP20060111594 priority patent/EP1837497B1/fr
Publication of EP1837497A1 publication Critical patent/EP1837497A1/fr
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—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
    • F01N3/022—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • 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
    • 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
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/18—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an adsorber or absorber
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/14—Combinations of different methods of purification absorption or adsorption, and filtering
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details

Definitions

  • the invention relates to an exhaust aftertreatment system comprising a storage catalytic converter and a particle filter for after treatment of the exhaust gas of an internal combustion engine, which flows through the exhaust aftertreatment system substantially in the direction of its longitudinal axis, wherein the storage catalytic converter for storing and reducing the nitrogen oxides (NO x ) and exhaust gas in the exhaust gas Collecting and burning the soot particles located in the exhaust gas are integrally formed as a structural unit, wherein the particulate filter is a honeycomb filter and this honeycomb filter also serves as a carrier substrate for forming the storage catalyst.
  • the invention relates to a method for producing such an exhaust aftertreatment system.
  • Thermal reactors attempt to achieve a substantial post-oxidation of HC and CO in the exhaust system by providing heat insulation and a sufficiently large volume in the exhaust pipe of the exhaust system.
  • the thermal insulation should ensure the highest possible temperature level by minimizing the heat losses, whereas a large exhaust pipe volume ensures a long residence time of the exhaust gases. Both the long residence time as well as the high temperature level support the desired post-oxidation.
  • the disadvantage is the poor efficiency in substoichiometric combustion and high costs. For diesel engines, thermal reactors are not effective because of the generally lower temperature level.
  • the nitrogen oxides NO x are reduced by means of the existing unoxidized exhaust gas components, namely the carbon monoxides and the unburned hydrocarbons, wherein at the same time these exhaust gas components are oxidized.
  • the nitrogen oxides located in the exhaust gas can by principle - d. H. due to the lack of reducing agents - can not be reduced.
  • an oxidation catalyst is provided in the exhaust system.
  • a certain operating temperature is required.
  • the so-called light-off temperature can be 120 ° C to 250 ° C.
  • selective catalysts - so-called SCR catalysts - are used, in which targeted reducing agents are introduced into the exhaust gas to selectively reduce the nitrogen oxides.
  • a reducing agent not only ammonia and urea but also unburned hydrocarbons are used.
  • the latter is also referred to as HC enrichment, the unburned hydrocarbons are introduced directly into the exhaust system or by internal engine measures, namely be supplied by a post injection of additional fuel into the combustion chamber after the actual combustion.
  • the nacheingespritzte fuel is not ignited in the combustion chamber by the still running main combustion or by - even after completion of the main combustion - high combustion gas temperatures, but are introduced during the charge exchange in the exhaust system.
  • the nitrogen oxide emissions can also be reduced with so-called nitric oxide storage catalysts (LNT - L ean N O x T rap).
  • the nitrogen oxides are first - during a lean operation of the internal combustion engine - absorbed in the catalytic converter, ie stored and stored, and then reduced during a regeneration phase, for example by means of a substoichiometric operation (for example, ⁇ ⁇ 0.95) of the internal combustion engine in deoxygenation (deNO x ) ,
  • Further internal engine options for realizing a rich ie a stoichiometric operation of the internal combustion engine provides the exhaust gas recirculation (EGR) and - in diesel engines - the throttling in the intake system.
  • EGR exhaust gas recirculation
  • In-engine measures can be dispensed with if the reducing agent is introduced directly into the exhaust tract, for example by injecting additional fuel.
  • the nitrogen oxides are released and converted essentially into nitrogen dioxide (N 2 ), carbon dioxide (CO 2 ) and water (H 2 O.
  • the frequency of the regeneration phases is determined by the total emission of nitrogen oxides and the storage capacity of the LNT.
  • the temperature of the storage catalyst (LNT) should preferably be in a temperature window between 200 ° C and 450 ° C, so that on the one hand a rapid reduction of nitrogen oxides is ensured and on the other hand no desorption takes place without converting the re-released nitrogen oxides, which is triggered by excessive temperatures can be.
  • a difficulty in the use and in particular in the arrangement of the LNT in the exhaust system results from the sulfur contained in the exhaust gas, which is also absorbed in the LNT and in a so-called desulfurization (deSO x ) ie a Desulphurization must be removed on a regular basis.
  • the LNT to high temperatures, usually between 600 ° C and 700 ° C, heated and supplied with a reducing agent, which in turn can be achieved by the transition to a rich operation of the internal combustion engine.
  • the higher the temperature of the LNT the more effectively the desulphurisation will take place, whereby a maximum permissible temperature should not be exceeded, because then the desulfurization of the LNT contributes to the thermal aging of the catalyst due to too high temperatures.
  • the desired conversion of the nitrogen oxides towards the end of the life of the catalyst is adversely affected, in particular, the storage capacity decreases due to thermal aging.
  • so-called regenerative particulate filters are used in the prior art, which filter the soot particles from the exhaust gas and store, these soot particles are intermittently burned during the regeneration of the filter (deSoot).
  • the intervals of the regeneration are determined, inter alia, by the exhaust backpressure, which occurs as a result of the increasing flow resistance of the filter due to the increasing particle mass in the filter.
  • the combustion of the particles can be effected by additional combustion burner provided in the exhaust duct or by a post-injection of additional fuel into the combustion chamber, the nacheingespritzte fuel is already ignited in the combustion chamber, resulting in the expiring main combustion or the present in the combustion chamber towards the end of the combustion high temperatures can happen, so that the exhaust gas temperature of the exhaust gases pushed into the exhaust tract is raised by the engine.
  • Disadvantages of this procedure are, in particular, the heat losses which are to be feared in the exhaust gas tract on the way to the filter and the associated temperature reduction of the hot ones Exhaust gases.
  • the filter can easily be located a meter and more away from the outlet of the combustion chamber in the exhaust system.
  • the compensation of the heat losses by the generation of correspondingly high exhaust gas temperatures are limited by the temperature resistance of other components provided in the exhaust system, in particular the temperature resistance of an exhaust gas turbine arranged in the exhaust gas turbocharger, a three-way catalyst or a storage catalyst.
  • the turbine is subjected to the highest temperatures, since it is located closest to the outlet of the combustion chamber.
  • the nacheingespritzte fuel can also be unburned and possibly already processed pushed out into the exhaust system and then selectively oxidized locally there in the exhaust system, where high exhaust gas temperatures are necessary, namely in the particulate filter or in its immediate vicinity.
  • the combustion of the post-injected fuel can be catalytically initiated by means of a catalyst positioned in front of the filter. But it can also be provided an electric ignition in or on the soot filter.
  • fuel can also be introduced directly into the exhaust gas tract.
  • the further procedure corresponds to that described above, in which the additionally injected fuel enters the exhaust system unburned and is specifically oxidized in the vicinity of the particle filter.
  • the present invention has, for example, a combined exhaust aftertreatment system, ie a system in which the storage catalytic converter for storing and reducing the nitrogen oxides (NO x ) present in the exhaust gas and the particle filter for collecting and burning the soot particles located in the exhaust gas are formed integrally, ie as a structural unit ,
  • the particle filter is a honeycomb filter and this honeycomb filter also serves as a carrier substrate for forming the storage catalyst.
  • the honeycomb filter is coated with a catalytic material which is suitable for storing and reducing the nitrogen oxides (NO x ) present in the exhaust gas.
  • Such an exhaust aftertreatment system is for example in EP 1 486 248 described.
  • Such a system is distinguished from conventional systems in which the particulate filter and the storage catalyst each form an independent component, by its compact design.
  • the number of carrier substrates can be halved, since the carrier substrate of the particulate filter is used simultaneously to form the storage catalyst.
  • the honeycomb filter serving as a particle filter comprises a multiplicity of channels, which are generally mutually closed, ie in a checkerboard pattern, so that the exhaust flows into the channels open at the inlet of the honeycomb filter and flows through the channel walls of these channels which are closed towards the exit on the way to the outlet in order to get into a channel that is open to the outlet of the honeycomb filter (see also FIG. 1 ).
  • the pore diameters of the carrier substrate are so small that the soot particles do not penetrate into the filter material, but deposit themselves as filter cakes on the surface of the filter.
  • the current exhaust back pressure or the non-exceeding of a maximum allowable exhaust back pressure essentially form the relevant parameters by which it is decided whether or when a particulate filter regeneration is performed.
  • the storage catalytic converter is to be heated, for example, to the high temperatures required for the desulfurization between 600 ° C. and 700 ° C.
  • an inhomogeneous temperature distribution in the system is generally present during the heating of the system.
  • the temperature inside the honeycomb filter can already be 650 ° C, while in the outer regions of the filter temperatures around 550 ° C prevail.
  • the heating process could be continued until the temperature in the outer regions is sufficiently high for desulfurization.
  • the temperature inside the exhaust aftertreatment system would have to be raised to a level which would at least lead to the thermal deterioration of the honeycomb filter for thermal destruction. Therefore, the prior art dispenses with excessive heating of the system and instead accepts the decrease in storage capacity, especially in the outer regions.
  • the resulting inhomogeneous temperature distribution as a result of heating in the system also proves disadvantageous in terms of filter regeneration. If the filter is heated for the purpose of a filter regeneration, the temperature of about 550 ° C. required for the soot oxidation can already be present in the interior of the system, while the outer regions do not yet have a sufficiently high temperature for the regeneration. Consequently, the soot in the outer regions is not oxidized, the exhaust back pressure increases, and the storage capacity of the outer regions also decreases.
  • an exhaust aftertreatment system of the generic type d. H According to the preamble of claim 1, which is optimized with regard to the problems known from the prior art - inhomogeneous temperature distribution, thermal aging or damage, cost efficiency, pollutant conversion.
  • Another object of the present invention is to provide a method for producing such an exhaust aftertreatment system.
  • the first sub-task is solved by an exhaust aftertreatment system comprising a storage catalytic converter and a particle filter for the aftertreatment of the exhaust gas of an internal combustion engine, which flows through the exhaust aftertreatment system substantially in the direction of its longitudinal axis, wherein the storage catalytic converter for storing and reducing the nitrogen oxides (NO x ) and the particulate filter for collecting and burning the soot particles located in the exhaust gas are integrally formed as a structural unit, wherein the particulate filter is a honeycomb filter and this honeycomb filter serves as a carrier substrate for forming the storage catalyst, and which is characterized in that an inner to the longitudinal axis of Systems arranged portion of the honeycomb filter for storing and reducing the exhaust gases in the nitrogen oxides (NO x ) is coated with a catalytic material, whereas an outer portion of the honeycomb filter such Beschic does not have.
  • the exhaust aftertreatment system is not the entire honeycomb filter coated with catalytic material, but only an inner area, which is characterized, inter alia, that it can be heated more easily ie faster and with less effort than the outlying areas of the system.
  • Only the inner region of the honeycomb filter has a dual function as a particle filter and storage catalyst, whereas the outer region merely serves as a particle filter due to the lack of a catalytic coating.
  • the exhaust aftertreatment system according to the invention has further advantages resulting from the targeted coating of only the inner region and the deliberate omission of the coating in the outer region.
  • the storage capacity of the storage catalytic converter can be increased or the decrease in the storage capacity caused by the omission of the coating in the outer regions can be compensated for again.
  • the exhaust aftertreatment system according to the invention also allows a higher loading of the outer regions with soot or soot particles.
  • the first object of the invention is achieved, namely to provide a system according to the preamble of claim 1, which is in terms of known from the prior art problem - inhomogeneous temperature distribution, thermal aging or damage, cost efficiency, pollutant conversion - optimized.
  • the inner region and the outer region do not necessarily have to form a coherent filter volume in each case, but can be composed of a plurality of non-interconnected partial regions or partial volumes.
  • the outer region can be made up of two separate, i.e. be constructed not contiguous subvolume.
  • Embodiments of the exhaust gas aftertreatment system in which the honeycomb filter is provided with an additional coating at least in the outer region, which accelerates the ignition and / or the oxidation of the soot or the soot particles or reduces the ignition temperature for the regeneration of the filter are advantageous. especially the outer regions which, depending on the particular embodiment of the system, are heated to a greater or lesser extent than the inner region, ie reach a predetermined temperature with respect to the inner central region of the honeycomb filter with a time delay, benefit from a catalytic coating , which supports the regeneration of the particulate filter.
  • Embodiments of the exhaust aftertreatment system in which the honeycomb filter is of cylindrical shape and has an outer diameter D are advantageous.
  • a cylindrical shape of the honeycomb filter offers advantages in the heating, thereby advantages in the regeneration or cleaning and thus turn basically advantages in terms of pollutant conversion.
  • the cylindrical shape has proven to be particularly favorable to make a given system volume usable as effectively as possible.
  • Systems which have an oval cross-section have the advantages mentioned in a slightly attenuated form. However, in comparison to systems with polygonal, for example rectangular or square, cross sections, they again offer noticeable advantages with regard to the relevant and relevant temperature distribution within the system.
  • the decision as to whether a system having a cylindrical or oval cross section is used is also determined by the available installation space or the arrangement of the system, which is usually arranged below the floor of the motor vehicle.
  • Embodiments of the exhaust aftertreatment system in which the inner coated region forms a tubular section which has an outer diameter d ⁇ D and is surrounded by the outer uncoated region are advantageous.
  • the inner region must have a smaller outer diameter than the honeycomb filter.
  • the inner region is tubular and thus symmetrical to the longitudinal axis of the system. Assuming a temperature distribution at which the temperature assumes its maximum value in the center of the system ie on the longitudinal axis and decreases continuously towards the outer regions, an approximately equal local temperature prevails over the entire circumference at the transition from the inner region to the outer region.
  • the tubular formation of the inner region is fundamentally advantageous d.
  • H. an inner region arranged symmetrically about the longitudinal axis offers advantages in terms of temperature distribution, regardless of the specific outer shape of the honeycomb filter.
  • embodiments of the exhaust gas aftertreatment system in which the inner region has a shape similar to the honeycomb filter can also be advantageous.
  • embodiments of the system are advantageous in which d / D> 0.5 or d / D> 0.65, but also embodiments in which d / D> 0.85 applies.
  • the concrete ratio of the outer diameter D of the honeycomb filter to the outer diameter d of the inner region depends on the individual application and often results from the primary objective.
  • the outer range can be extended comparatively far by the ratio d / D being chosen as small as possible. This means that only a small portion of the surface of the honeycomb filter is coated with a catalytic material, which on the one hand reduces the flow resistance and on the other hand, the costs - by saving catalytic material - lowers.
  • the exhaust stream which flows through the outer region of the exhaust aftertreatment system, not freed or purified from nitrogen oxides due to the lack of coating.
  • nitrogen oxides are neither stored in lean operation, nor are nitrogen oxides reduced under oxygen deficiency in rich operation.
  • the nitrogen oxides can escape unhindered - after flowing through the outer area - in the environment or the environment.
  • the proportion of these nitrogen oxides in the total nitrogen oxide emission of the internal combustion engine increases in principle with increasing outer area. with a reduction of the ratio d / D to.
  • the definition of the size of the inner and the outer region thus also depends on the original emissions (engine-out emissions) of the internal combustion engine and the statutory requirements to be observed.
  • the carrier substrate is formed essentially of silicon carbide and / or cordierite. Investigations have shown that carrier substrates produced from these materials can be heated or heated comparatively quickly due to the low specific heat capacity, which is advantageous with regard to the required energy requirement for heating the system. In addition, the heat is distributed more rapidly in the honeycomb filter or in the carrier substrate, which is useful for the most homogeneous possible temperature distribution in the system. Both offer advantages in terms of efficient pollutant conversion.
  • Embodiments of the exhaust aftertreatment system in which the carrier substrate has a porosity of 50 to 70% are advantageous.
  • an oxidation catalyst in particular for the oxidation of the exhaust gas in the carbon monoxide (CO) and the unburned hydrocarbons (HC), is provided, which forms a four-way catalyst together with the system according to the invention.
  • An exhaust aftertreatment system for the oxidation of CO and HC not only reduces the emissions of incompletely or not oxidized pollutants, but leads due to the Exothermic reactions in the context of the oxidation to a heating of the exhaust gas and the exhaust gas aftertreatment components through which the exhaust gas flows.
  • Advantageous embodiments are those in which the oxidation catalyst and the system according to the invention are connected in series, wherein the oxidation catalyst is arranged upstream of the system.
  • This embodiment is advantageous with regard to the temperatures which are required for the reduction of the individual pollutants.
  • the three-way catalysts are to be counted in the context of the present invention to the oxidation catalysts.
  • the oxidation catalyst By providing the oxidation catalyst upstream of the system, the oxidation catalyst is the exhaust aftertreatment component located closest to the engine exhaust and first traversed by the hot exhaust gases. Consequently, the heat losses and the associated reduction in temperature of the hot exhaust gases on the way to the oxidation catalyst are comparatively low. Accordingly, the oxidation catalyst reaches its so-called light-off temperature of about 250 ° C even after a cold start within a relatively short period of time.
  • both the preferred operating temperature of the storage catalyst and the regeneration temperature of the particulate filter is above the light-off temperature of the oxidation catalyst, so that here an additional heating of the exhaust gases in the oxidation catalyst is expedient or beneficial.
  • Embodiments of the system in which an end section of predefinable length .DELTA.l of the honeycomb filter is uncoated are advantageous.
  • the exhaust gas carries ash, which deposits on the closed ends of the inlet channels of the honeycomb filter.
  • the growing ash deposit at the channel ends shortens the usable channel length increasingly and thus also the usable length of the honeycomb filter.
  • the ash-covered area of the honeycomb filter can neither be used as a particle filter nor as a storage catalyst.
  • the catalytic material layer applied here can only contribute to the conversion and reduction of pollutants because of ashing.
  • the coating is after deposition of ash without value for the aftertreatment of the exhaust gases of the internal combustion engine.
  • Embodiments of the system are advantageous in which: ⁇ 1 / L> 0.75 or ⁇ 1 / L> 0.9.
  • the entire honeycomb filter not the entire honeycomb filter, but only a selected central region in the interior of the honeycomb filter is coated with a catalytic material for storing and reducing the nitrogen oxides.
  • Embodiments of the method in which the outer region of the honeycomb filter is provided with an additional coating which promotes the ignition and / or the oxidation of the soot or of the soot particles or reduces the ignition temperature for the regeneration of the filter are advantageous.
  • Embodiments of the method in which an end section of predefinable length ⁇ l of the honeycomb filter is not coated are advantageous. This takes into account the problem of ashing.
  • FIG. 1 schematically shows in perspective view a honeycomb filter 4 according to the prior art.
  • the honeycomb filter 4 which serves as a particle filter and as a carrier substrate for the storage catalyst, comprises a plurality of channels 6, which alternately d. H. are closed in the checkerboard pattern, so that the exhaust gas flows into the open at the inlet 7 of the honeycomb filter 4 channels 6 and on the way to the outlet 8, the channel walls of these channels 8 closed to exit 8 must flow through to get into a channel 6, the to the outlet of the honeycomb filter 4 is open.
  • the sealed at the outlet 8 of the honeycomb filter 4 channel ends bear the reference numeral. 5
  • FIG. 2a schematically shows a first embodiment of the system 1 in longitudinal section.
  • FIG. 2b shows this first embodiment in cross section.
  • the exhaust gas of the internal combustion engine to be cleaned of pollutants enters the exhaust aftertreatment system 1 at the inlet 7, flows through it in the direction of the longitudinal axis 9 and leaves the system 1 again at the outlet 8.
  • the illustrated exhaust aftertreatment system 1 or system 1 has a honeycomb filter 4 - as in FIG. 1 illustrated - on, which acts as a particle filter 3 and at the same time serves as a carrier substrate for forming a storage catalyst 2.
  • the storage catalyst 2 for storing and reducing the nitrogen oxides (NO x ) present in the exhaust gas and the particle filter 3 for collecting and burning the soot particles located in the exhaust gas are integrally formed as a structural unit.
  • the outer region 12 acts only as a particle filter 3 due to the lack of catalytic coating. Desulfurization of the outer region 12 is therefore not more necessary because this area 12 is not used for storing and converting nitrogen oxides.
  • the flow resistance of the outer region 12 is comparatively low due to the lack of catalytic coating for forming a storage catalyst. This reduces the exhaust back pressure. Due to the lower flow resistance of the outer region 12 compared to the inner region 10, a larger part of the hot exhaust gases will flow through the outer region 12. This results in a much more homogeneous temperature distribution in the system 1, since in this way the areas 10,12 different amounts of heat - are supplied - according to need. The more difficult to heat outer regions 12 are occupied by a larger exhaust gas mass flow. The required for the ignition and the oxidation of the filter 3 high temperature of about 550 ° for the purpose of filter regeneration is achieved comparatively quickly.
  • the honeycomb filter 4 has a cylindrical shape, which offers advantages in the heating.
  • the inner coated portion 10 forms a tubular portion which is formed symmetrically to the longitudinal axis 9 of the system 1 and surrounded by the outer uncoated portion 12 and the outer diameter d is smaller than the outer diameter D of the honeycomb filter 4.
  • D the outer diameter of the honeycomb filter 4.
  • FIG. 3a schematically shows a second embodiment of the system 1 in cross section.
  • FIG. 3b shows this second embodiment in longitudinal section.
  • system 1 is an end portion 13 of predeterminable length .DELTA.1 of the honeycomb filter 4 uncoated.
  • the ash carried by the exhaust gas deposits at the closed ends of the inlet channels of the honeycomb filter 4.
  • the growing ash deposit at the channel ends increasingly shortens the usable channel length and thus also the useful length of the honeycomb filter 4.
  • the ash-covered surface of the honeycomb filter 4 can be used neither for collecting soot particles nor for storing nitrogen oxides. An application of catalytic material in this asbestos-threatened area is therefore not useful.
  • FIG. 4a schematically shows a third embodiment of the system in cross section.
  • FIG. 4b shows this third embodiment in longitudinal section.
  • the inner region 10 also has a square cross-section.

Claims (11)

  1. Système de purification de gaz d'échappement (1) comprenant un piège à polluants (2) et un filtre à particules (3) pour le post-traitement des gaz d'échappement d'un moteur à combustion interne traversant le système de purification de gaz d'échappement (1) pour l'essentiel en direction de son axe longitudinal (9), dans lequel le piège à polluants (2) servant à piéger et réduire les oxydes d'azote se trouvant dans les gaz d'échappement et le filtre à particules (3) servant à rassembler et brûler les particules de suie se trouvant dans les gaz d'échappement sont intégralement réalisés comme une unité de construction, le filtre à particules (3) étant un filtre en nids d'abeille (4) et ce filtre en nids d'abeille (4) servant en même temps de couche de support pour former le piège à polluants (2), caractérisé en ce qu'une zone (10) du filtre en nids d'abeille (4) intérieure disposée autour de l'axe longitudinal (9) du système (1) est recouverte d'un matériau catalytique (11) pour piéger et réduire les oxydes d'azote se trouvant dans les gaz d'échappement, tandis qu'une zone (12) extérieure du filtre en nids d'abeille (4) ne comporte pas de tel revêtement.
  2. Système de purification de gaz d'échappement (1) selon la revendication 1, caractérisé en ce que le filtre en nids d'abeille (4) est de forme cylindrique et présente un diamètre extérieur D.
  3. Système de purification de gaz d'échappement (1) selon la revendication 2, caractérisé en ce que la zone (10) intérieure recouverte forme une section en forme de tuyau qui a un diamètre extérieur d < D et est entourée par la zone (12) sans revêtement.
  4. Système de purification de gaz d'échappement (1) selon la revendication 3, caractérisé en ce que d/D > 0,5.
  5. Système de purification de gaz d'échappement (1) selon la revendication 3 ou 4, caractérisé en ce que d/D > 0,65.
  6. Système de purification de gaz d'échappement (1) selon l'une quelconque des revendications 3 à 5, caractérisé en ce que d/D > 0,85.
  7. Système de purification de gaz d'échappement (1) selon l'une quelconque des revendications précédentes, caractérisé en ce que la couche de support est pour l'essentiel formée à partir de carbure de silicium et/ou de cordiérite.
  8. Système de purification de gaz d'échappement (1) selon l'une quelconque des revendications précédentes, caractérisé en ce que la couche de support présente une porosité de 50 à 70 %.
  9. Système de purification de gaz d'échappement (1) selon l'une quelconque des revendications précédentes, caractérisé en ce qu'un catalyseur d'oxydation est prévu, notamment pour l'oxydation du monoxyde de carbone se trouvant dans les gaz d'échappement et des hydrocarbures non brûlés, ledit catalyseur formant avec le système (1) un catalyseur à quatre voies.
  10. Système de purification de gaz d'échappement (1) selon l'une quelconque des revendications précédentes, caractérisé en ce qu'un segment terminal (13) de longueur Δl prédéfinie du filtre en nids d'abeille (4) reste sans revêtement.
  11. Procédé de fabrication d'un système de purification de gaz d'échappement (1) selon l'une quelconque des revendications précédentes, caractérisé en ce que :
    le filtre à particules (3) utilisé est un filtre en nids d'abeille (4) ;
    ce filtre en nids d'abeille (4) sert de couche de support pour former le piège à polluants (2) ;
    une zone (10) intérieure du filtre en nids d'abeille (4) disposée autour de l'axe longitudinal (9) du système (1) servant à piéger et à réduire les oxydes d'azote se trouvant dans les gaz d'échappement étant recouverte d'un matériau catalytique (11) tandis qu'une zone (12) extérieure du filtre en nids d'abeille (4) reste sans revêtement.
EP20060111594 2006-03-23 2006-03-23 Système de purification de gaz d'échappement comprenant un piège à polluants et un filtre à particules ainsi qu'un procédé de fabrication d'un tel système Expired - Fee Related EP1837497B1 (fr)

Priority Applications (2)

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DE200650002485 DE502006002485D1 (de) 2006-03-23 2006-03-23 Abgasnachbehandlungssystem umfassend einen Speicherkatalysator und einen Partikelfilter sowie Verfahren zur Herstellung eines derartigen Systems
EP20060111594 EP1837497B1 (fr) 2006-03-23 2006-03-23 Système de purification de gaz d'échappement comprenant un piège à polluants et un filtre à particules ainsi qu'un procédé de fabrication d'un tel système

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EP1837497B1 true EP1837497B1 (fr) 2008-12-31

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DE102010033689A1 (de) 2009-08-28 2011-03-03 Umicore Ag & Co. Kg Abgasnachbehandlungssystem mit katalytisch aktivem Wall-Flow-Filter mit NOx-Speicherfunktion vor Katalysator mit gleicher Speicherfunktion
CN102482971B (zh) 2009-08-28 2014-10-29 尤米科尔股份公司及两合公司 在具有相同存储功能的催化转化器上游具有具有存储功能的催化活性壁流式过滤器的尾气后处理体系
DE102010033688A1 (de) 2009-08-28 2011-03-03 Umicore Ag & Co. Kg Abgasnachbehandlungssystem mit katalytisch aktivem Wall-Flow-Filter mit Speicherfunktion vor Katalysator mit gleicher Speicherfunktion
DE102011101079B4 (de) 2011-05-10 2020-08-20 Umicore Ag & Co. Kg Verfahren zur Regeneration von NOx-Speicherkatalysatoren von Dieselmotoren mit Niederdruck-AGR
DE102011107692B3 (de) 2011-07-13 2013-01-03 Umicore Ag & Co. Kg Verfahren zur Reaktivierung von Abgasreinigungsanlagen von Dieselmotoren mit Niederdruck-AGR
DE102013207709A1 (de) 2013-04-26 2014-10-30 Umicore Ag & Co. Kg Entschwefelung von NOX-Speicherkatalysatoren
DE102013218234B4 (de) 2013-09-11 2015-05-28 Umicore Ag & Co. Kg Verwendung unterschiedlicher Strategien bei der Regeneration von Stickoxidspeicherkatalysatoren zur Verminderung der N2O-Bildung
US10781735B2 (en) 2018-05-18 2020-09-22 Umicore Ag & Co Kg Exhaust emission reduction system having an HC-trap and NOx-trap combination designed for operating under strategic lean conditions

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DE602004029979D1 (de) * 2003-01-07 2010-12-23 Peugeot Citroen Automobiles Sa Unterstützungssystem zur regeneration einesteilchenfilters in einer auslassleitung eines dieselmotors
US7119044B2 (en) * 2003-06-11 2006-10-10 Delphi Technologies, Inc. Multiple washcoats on filter substrate

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US11813569B2 (en) 2021-03-29 2023-11-14 Andreas Stihl Ag & Co. Kg Exhaust muffler, two-stroke engine or four-stroke engine having an exhaust muffler, and catalytic converter for an exhaust muffler

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