EP1837498A1 - 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
EP1837498A1
EP1837498A1 EP06111595A EP06111595A EP1837498A1 EP 1837498 A1 EP1837498 A1 EP 1837498A1 EP 06111595 A EP06111595 A EP 06111595A EP 06111595 A EP06111595 A EP 06111595A EP 1837498 A1 EP1837498 A1 EP 1837498A1
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EP
European Patent Office
Prior art keywords
exhaust
exhaust gas
honeycomb filter
filter
nitrogen oxides
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06111595A
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German (de)
English (en)
Inventor
Matthew Schneider
Jan Harmsen
Mario Balenovic
Brendan Carberry
Alexei Dubkov
Yasser Mohammed Sayed Yacoub
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Ford Global Technologies LLC
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Ford Global Technologies LLC
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Publication date
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Priority to EP06111595A priority Critical patent/EP1837498A1/fr
Publication of EP1837498A1 publication Critical patent/EP1837498A1/fr
Withdrawn legal-status Critical Current

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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 of length L 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 and 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, wherein the unburned hydrocarbons are introduced directly into the exhaust tract or by internal engine measures, namely by a post-injection of additional fuel into the combustion chamber after the actual combustion, be supplied.
  • 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.
  • 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 must be removed regularly in a so-called desulfurization (deSO x ) ie a desulfurization.
  • the LNT has to be 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 to be feared in the exhaust tract on the way to the filter and the associated reduction in temperature of the hot 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 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 plurality of channels, which are generally mutually d. H. closed in the checkerboard pattern, so that the exhaust gas flows into the channels open at the inlet of the honeycomb filter and on the way to the outlet, the channel walls of these exit-closed channels must flow through in order to enter a channel which 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 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 desulphurization of too low temperatures in the outer regions of the system means that these areas of the storage catalyst are not cleaned of sulfur, resulting in a decrease in the storage capacity of these outer areas and thus a decrease in the storage capacity of the LNT with increasing operating time or drives with increasing age. If the storage capacity of the outer areas completely stops, the exhaust gases flow through these outer areas, without the nitrogen oxides contained in the exhaust gas being stored or converted.
  • 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 respect to the problems known from the prior art, in particular the partial ashing of the system as a result of ash deposits.
  • 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 of length L and this honeycomb filter simultaneously serves as a carrier substrate for forming the storage catalyst, and which is characterized in that an initial portion of the honeycomb filter for storing and reducing the nitrogen oxides (NO x ) located in the exhaust gas along a vorgebaren length 1 1 at least partially coated with a catalytic material, whereas an end portion of predeterminable length ⁇ 1 of the honeycomb filter does not have such a coating.
  • the exhaust aftertreatment system according to the invention is not the entire honeycomb filter coated with catalytic material, but only an initial portion of a vorgebaren length l 1 , which is characterized in that here the risk of ash deposits is relatively low. Only this initial section of the honeycomb filter has a dual function as a particle filter and storage catalyst, whereas the end section only serves as a particle filter due to the lack of a catalytic coating.
  • the exhaust gas carries ash, which deposits at 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 disadvantage of this is - in addition to the reduction of the storage capacity of the system due to ashing - in particular, that the catalytic materials for forming the storage catalyst - as already mentioned - are very expensive and due to the deposition of ash at the closed channel ends in these areas are of limited use ie
  • the coating is after deposition of ash without value for the aftertreatment of the exhaust gases of the internal combustion engine.
  • the first object of the invention is achieved, namely to provide a system according to the preamble of claim 1, which is optimized in terms of known from the prior art problem, in particular the partial ashing of the system due to ash deposits.
  • Embodiments of the system in which ⁇ l / L> 0.75 or ⁇ l / L> 0.9 apply are advantageous.
  • 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 gas aftertreatment system in which an inner region of the initial section arranged to arrange the longitudinal axis of the system for storing and reducing the nitrogen oxides (NO x ) in the exhaust gas are coated with a catalytic material are advantageous, whereas an outer region of the initial section does not have such a coating having.
  • not all of the initial portion of the honeycomb filter is coated with catalytic material, but only an interior region which is characterized, inter alia, by being lighter in e.g. can be heated faster and with less effort than the outside areas of the system or the initial section. Only the inner region of the initial section has a dual function as a particle filter and storage catalyst, whereas the outer region only serves as a particle filter due to the lack of a catalytic coating.
  • the present embodiment of the exhaust aftertreatment system has further advantages resulting from the targeted coating of only the inner portion of the initial portion and the deliberate omission of the outer portion coating.
  • the fact that the outer regions for the exhaust gases are easier to pass due to the lack of catalytic coating or the lower flow resistance can also be used to apply more catalytic material in the inner region of the initial section, ie a thicker one Provide coating. Although this increases the flow resistance of the inner region and thus the flow resistance of the entire system, whereby the advantage of a lower exhaust back pressure is at least partially lost again.
  • 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 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.
  • the outer regions, which - depending on the particular embodiment of the system - compared to the inner region - more or less strongly - are heated delayed. 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 inner coated portion of the start portion forms a tubular portion having an outer diameter d ⁇ D and surrounded by the outer uncoated portion 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 in the center of the system, i. on the longitudinal axis assumes its maximum value and decreases continuously towards the outer regions, then prevails over the entire circumference at the transition from the inner region to the outer region in the initial section of an approximately equal local temperature.
  • the tubular formation of the inner region is basically advantageous, i. 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 portion of the initial section depends on the individual application and often results from the primary objective.
  • the outer range can be comparatively extended by the Ratio d / D is chosen as small as possible. This is equivalent to coating only a small portion of the surface area of the initial section of the honeycomb filter with a catalytic material, which reduces flow resistance and reduces costs by conserving catalytic material.
  • the exhaust gas flow which flows through the outer region of the initial section, is not freed or cleaned of 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.
  • Embodiments of the exhaust gas aftertreatment system in which an oxidation catalytic converter, in particular for the oxidation of the exhaust gas located in the exhaust gas, are advantageous Carbon monoxide (CO) and the unburned hydrocarbons (HC) is provided, which forms a four-way catalyst together with the storage catalyst (LNT) and the particulate filter of the system according to the invention.
  • CO Carbon monoxide
  • HC unburned hydrocarbons
  • 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 warming of the exhaust gas and the exhaust gas flowed through exhaust aftertreatment components.
  • 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 is the exhaust aftertreatment component that is 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.
  • the entire honeycomb filter not the entire honeycomb filter, but only an initial section of the honeycomb filter is at least partially coated with a catalytic material for storing and reducing the nitrogen oxides. This takes into account the problem of ashing.
  • FIG. 1 schematically shows a perspective view of a honeycomb filter 4 according to the prior art.
  • the honeycomb filter 4 serving as a particulate filter and as a carrier substrate for the storage catalyst comprises a plurality of channels 6, which are mutually closed in the checkerboard pattern, so that the exhaust gas flows into the channels 6 which are open at the inlet 7 of the honeycomb filter 4 and on the way to the outlet 8 the channel walls of these channels 8 closed towards the outlet 8 must flow through in order to get into a channel 6, which leads 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
  • Figure 2a shows schematically a first embodiment of the system 1 in cross section.
  • FIG. 2b shows this first embodiment in longitudinal 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 illustrated in FIG. 1 - which acts as a particle filter 3 and at the same time serves as a carrier substrate for forming a storage catalytic converter 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.
  • an initial portion 14 of the honeycomb filter 4 for storing and reducing the nitrogen oxides along a vorgebaren length 1 1 coated with a catalytic material whereas an end portion 13 with the length .DELTA.1 of the honeycomb filter 4 does not have such a coating.
  • Only the initial section 14 of the honeycomb filter 4 has a dual function as a particle filter 3 and a storage catalyst 2, whereas the end section 13 merely serves as a particle filter 3 due to the lack of a catalytic coating.
  • This catalytic material 11 is saved.
  • Figure 3a shows schematically a second embodiment of the system 1 in cross section.
  • FIG. 3b shows this second embodiment in longitudinal section.
  • not the entire starting section 14 is coated. Only an inner region 10 of the starting section 14, which is arranged around the longitudinal axis 9 of the system 1 and which can be heated more rapidly due to its central position within the system 1 or exhaust gas flow, is coated with a catalytic material 11 for storing and reducing the nitrogen oxides, whereas the outer region 12 of the starting portion 14 does not have such a coating.
  • 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 large amounts of heat - according to need - to be supplied. 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 of the starting portion 14 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 whose outer diameter d is smaller than the outer diameter D of the honeycomb filter 4.
  • d / D the diameter ratio of the second In the embodiment illustrated in FIGS. 3a and 3b: d / D ⁇ 0.77.
  • Figure 4a shows schematically a third embodiment of the system in cross-section.
  • FIG. 4b shows this third embodiment in longitudinal section.
  • the embodiment shown in FIGS. 4 a and 4 b has a honeycomb filter 4 with a square cross section.
  • the inner region 10 of the starting portion 14 also has a square cross-section.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Exhaust Gas After Treatment (AREA)
EP06111595A 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 Withdrawn EP1837498A1 (fr)

Priority Applications (1)

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EP06111595A EP1837498A1 (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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EP06111595A EP1837498A1 (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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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1974795A1 (fr) * 2007-03-30 2008-10-01 Ibiden Co., Ltd. Filtre en nids d'abeilles

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003154223A (ja) * 2001-07-18 2003-05-27 Ibiden Co Ltd 触媒つきフィルタ、その製造方法及び排気ガス浄化システム
FR2849670A1 (fr) * 2003-01-07 2004-07-09 Peugeot Citroen Automobiles Sa Filtre a particules pour ligne d'echappement d'un moteur a combustion interne et ligne d'echappement le comprenant
WO2004070177A1 (fr) * 2003-01-07 2004-08-19 Peugeot Citroen Automobiles Sa Systeme d'aide a la regeneration d'un filtre a particules d'une ligne d'echappement d'un moteur diesel
EP1486248A1 (fr) * 2003-06-11 2004-12-15 Delphi Technologies, Inc. Filtre à particule diesel comprenant au moins deux revêtements catalytiques

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003154223A (ja) * 2001-07-18 2003-05-27 Ibiden Co Ltd 触媒つきフィルタ、その製造方法及び排気ガス浄化システム
FR2849670A1 (fr) * 2003-01-07 2004-07-09 Peugeot Citroen Automobiles Sa Filtre a particules pour ligne d'echappement d'un moteur a combustion interne et ligne d'echappement le comprenant
WO2004070177A1 (fr) * 2003-01-07 2004-08-19 Peugeot Citroen Automobiles Sa Systeme d'aide a la regeneration d'un filtre a particules d'une ligne d'echappement d'un moteur diesel
EP1486248A1 (fr) * 2003-06-11 2004-12-15 Delphi Technologies, Inc. Filtre à particule diesel comprenant au moins deux revêtements catalytiques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 2003, no. 09 3 September 2003 (2003-09-03) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1974795A1 (fr) * 2007-03-30 2008-10-01 Ibiden Co., Ltd. Filtre en nids d'abeilles

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