EP2104782A1 - Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en uvre de l'installation - Google Patents
Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en uvre de l'installationInfo
- Publication number
- EP2104782A1 EP2104782A1 EP07857042A EP07857042A EP2104782A1 EP 2104782 A1 EP2104782 A1 EP 2104782A1 EP 07857042 A EP07857042 A EP 07857042A EP 07857042 A EP07857042 A EP 07857042A EP 2104782 A1 EP2104782 A1 EP 2104782A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- exhaust
- lean
- storage
- exhaust gas
- catalyst
- 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- Withdrawn
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Classifications
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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
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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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
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
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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
- 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
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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
- 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
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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
- 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
- F01N13/011—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 purifying devices arranged in parallel
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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
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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
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0842—Nitrogen oxides
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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
- F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
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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
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
- F01N3/2073—Selective catalytic reduction [SCR] with means for generating a reducing substance from the exhaust gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/008—Controlling each cylinder individually
- F02D41/0082—Controlling each cylinder individually per groups or banks
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/32—Controlling fuel injection of the low pressure type
- F02D41/34—Controlling fuel injection of the low pressure type with means for controlling injection timing or duration
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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
- F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
- F01N2570/18—Ammonia
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
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- 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
- the invention relates to an exhaust gas purification system for the purification of the exhaust gases of lean-burn engines with a plurality of cylinders and a method for operating the plant.
- lean-burn engines are diesel engines and lean-burn gasoline engines.
- the exhaust gas purification system includes a first exhaust pipe for the exhaust gases of a first group of cylinders and a second exhaust pipe for the exhaust gases of a second group of cylinders.
- a nitrogen oxide storage catalyst is arranged in each exhaust pipe.
- Both exhaust pipes are combined downstream of the storage catalytic converters at a junction to a common exhaust pipe.
- the common exhaust pipe contains an oxidation catalyst.
- the composition of the exhaust gases in the first and second exhaust passages is independently adjusted by the electronic engine controller, so that the exhaust gas in one conduit for regeneration of the storage catalyst is enriched while the exhaust gas in the other conduit is lean. Enrichment and emaciation are adjusted so that after the merging of the two exhaust gas streams in the common exhaust pipe, a lean exhaust gas is present and a possible slip of the reducing agent is oxidized on the oxidation catalyst.
- This emission control system has a decisive disadvantage: during the regeneration of a nitrogen oxide storage catalyst, significant amounts of ammonia can be generated when the storage catalyst is regenerated longer than necessary. This danger exists especially with aged storage catalytic converters.
- the generated ammonia flows together with the other exhaust gases via the oxidation catalyst in the common exhaust pipe and is oxidized again to nitrogen oxides, which reduces the cleaning performance of the exhaust system with respect to the nitrogen oxides. This is especially true at higher exhaust gas temperatures in the case of oxidation catalysts with high oxidation activity.
- Such catalysts are used to oxidize at low exhaust gas temperatures, for example after a cold start, the hydrocarbons and carbon monoxide contained in the exhaust gas as early as possible.
- US 6,047,542 describes an exhaust system for an engine having first and second cylinder groups.
- the first cylinder group is connected to a three-way catalyst.
- the second group of cylinders and the three-way catalyst are connected via a common exhaust pipe with an ammonia absorbing and oxidizing catalyst.
- the three-way catalyst converts the nitrogen oxides contained in the rich exhaust gas of the first cylinder group into ammonia, which reduces the nitrogen oxides emitted by the second cylinder group on the ammonia absorbing and oxidizing catalyst in the common exhaust gas line.
- a nitrogen oxide storage catalytic converter inserted in the exhaust gas line between the second cylinder group and the common exhaust gas line reduces the amount of nitrogen oxide flowing into the ammonia absorbing and oxidizing catalyst.
- WO 2006/008625 describes an exhaust gas treatment system for a lean-burn engine with an SCR reactor behind a NOx adsorber (nitrogen oxide adsorber).
- the nitrogen oxide adsorber is regenerated with water gas from a fuel reforming reactor.
- the nitrogen oxide absorber preferably has a catalytic function for converting the nitrogen oxides during regeneration.
- the SCR reactor increases the conversion of the nitrogen oxides by storing the ammonia formed during the regeneration and using the stored ammonia to react the nitrogen oxides during the lean operation of the engine. To avoid slippage of ammonia, an oxidation catalyst is placed behind the SCR reactor.
- WO 2004/090296 discloses in Figure 1 a single-strand exhaust aftertreatment device. It includes in the exhaust gas flow direction behind an internal combustion engine in the full flow of the exhaust line successively a reforming unit, which also acts as a particle filter, a nitrogen oxide storage catalyst and an SCR catalyst as exhaust gas cleaning components. In the reforming unit, hydrogen is generated by steam reforming, partial oxidation of hydrocarbons, and / or mixed forms thereof.
- US Pat. No. 6,732,507 B1 likewise describes a single-stranded nitrogen oxide after-treatment system in which a nitrogen oxide adsorber is combined with an SCR catalyst.
- the nitrogen oxide aftertreatment system is operated alternately with lean and rich air / fuel mixture.
- the SCR catalyst stores the ammonia produced by the nitrogen oxide adsorber during the regeneration in the rich exhaust gas and reacts with the stored ammonia during the lean operation of the Nitrogen oxide adsorbers do not adsorb nitrogen oxides to harmless products.
- the SCR catalyst has a first end which is in direct communication with the second end of the nitric oxide adsorber.
- Object of the present invention is to modify the known exhaust system of WO 2004/020807 Al in the way that the unintentionally formed in the regeneration of the storage catalysts ammonia is neither oxidized to nitrogen oxides nor discharged to the environment.
- the slip of reducing agents during regeneration should be made harmless.
- Claim 5 describes a method for operating the exhaust system.
- the invention relates to lean burn engines with at least two cylinders.
- the lean-burn engines preferably have four, six or more cylinders, which are combined in a first and in a second group of cylinders, which can be supplied with an air / fuel mixture independently of each other.
- the engines may be designed as in-line engines in which all cylinders are arranged in a single cylinder bank one behind the other. Alternatively, each group of cylinders may be grouped together in a separate cylinder bank.
- the exhaust gas purification system of these lean-burn engines includes a first exhaust pipe for the exhaust gases of the first group of cylinders and a second exhaust pipe for the exhaust gases of the second group of cylinders.
- Each exhaust pipe contains at least one nitrogen oxide storage catalyst. Both exhaust pipes are combined downstream of the storage catalytic converters at a junction to a common exhaust pipe.
- This emission control system is characterized in that the common exhaust pipe includes an SCR catalyst.
- the invention utilizes the storage effect of SCR catalysts for ammonia in order to store any ammonia formed during the regeneration of the nitrogen oxide storage catalysts.
- an SCR catalyst When storing the nitrogen oxides on the nitrogen oxide storage catalysts and the regeneration of the storage catalysts, it may unintentionally lead to a slip of nitrogen oxides during the storage phase.
- This slip of nitrogen oxides can be converted by the SCR catalyst with the stored ammonia to nitrogen.
- an SCR catalyst has sufficient oxidation activity to len slip of reducing agents (hydrocarbons, carbon monoxide and hydrogen) with the oxygen content of the exhaust gases to harmless components implement.
- a nitrogen oxide storage catalyst is understood as meaning a catalyst which, during a storage phase in a lean exhaust gas, oxidizes the nitrogen monoxide contained to form nitrogen dioxide and then stores it in the form of nitrates.
- the operation of nitrogen oxide storage catalysts is described in detail in SAE SAE 950809.
- a storage catalyst as catalytically active components usually contains platinum and optionally palladium.
- For storing the nitrogen oxides as nitrates serve basic oxides, carbonates or hydroxides of alkali metals, alkaline earth metals and rare earth metals; Preference is given to using basic compounds of barium and strontium.
- a storage catalytic converter After exhaustion of its storage capacity, a storage catalytic converter must be regenerated during a regeneration phase.
- the exhaust gas is briefly enriched, for example by operating the engine with a rich air / fuel mixture.
- the nitrogen oxides are desorbed again and reduced to the catalytically active components using the rich exhaust gas constituents to nitrogen.
- the storage catalyst usually contains rhodium in addition to platinum.
- the fat constituents of the exhaust gas are converted into harmless components in an exothermic reaction with the nitrogen oxides stored in the catalyst and with any oxygen stored and residual oxygen remaining in the exhaust gas.
- the exhaust gas is heated during the regeneration of the storage catalyst.
- An additional heating of the exhaust gas takes place in that during the rich operation, the air content in the cylinder is greatly reduced by Andros- the engine and thus the exhaust gas is not cooled as in lean operation by high excess air. Both effects together can lead to a temperature increase of the exhaust gas from 50 to 150 0 C during regeneration at the storage catalytic converter.
- Storage phase and regeneration phase alternate regularly.
- the storage phase usually lasts between 60 and 120 seconds, while the duration of the regeneration phase only amounts to between 1 and 10% of the storage phase and thus only comprises a few seconds.
- the short regeneration period increases the risk that the storage catalytic converter regenerates longer than required, that is, is supplied with rich exhaust gas. Under these conditions, the storage catalyst from the nitrogen oxides forms ammonia.
- Oxidation catalyst such catalysts are referred to here, which oxidize hydrocarbons and carbon monoxide in the lean exhaust gas to carbon dioxide and water.
- Oxidation catalysts contain for this purpose as the catalytically active component platinum and optionally palladium. These oxidation catalysts also oxidize ammonia to nitrogen and nitrogen oxides.
- SCR catalysts are understood to mean catalysts which, under lean exhaust gas conditions, react nitrogen oxides selectively with the addition of ammonia as a reducing agent to form nitrogen. These catalysts contain acidic oxides and can store ammonia. Typical SCR catalysts include, for example, vanadium oxide and / or tungsten oxide on titanium oxide. Alternatively, zeolites exchanged with copper and / or iron are used. Usually, such catalysts do not contain catalytically active platinum metals, since these metals would oxidize the ammonia in the lean exhaust gas to nitrogen oxides. Preferably SCR catalysts are used for the erfmdungswashe emission control system containing zeolites. Zeolites have a particularly large storage capacity for ammonia and hydrocarbons. They are therefore ideally suited for the storage and conversion of these components of the exhaust gas with nitrogen oxides.
- the storage effect of the SCR catalysts for ammonia depends very much on the temperature. Especially after aging of the catalysts in real operation, the storage effect above 300 0 C is very strong and is barely noticeable at temperatures above 400 0 C. Therefore, especially at higher exhaust gas temperatures there is a risk that too much metered ammonia leaves the SCR catalyst with the exhaust gas before it can react with the nitrogen oxides.
- a so-called ammonia blocking catalyst is usually arranged behind the SCR catalyst. In the simplest case, this is an oxidation catalyst which, however, under adverse operating conditions can oxidize the ammonia again to nitrogen oxides.
- the nitrogen oxide storage catalysts, oxidation catalysts and SCR catalysts used in the context of this invention are known to the person skilled in the art.
- the catalysts are preferably applied in the form of a coating to inert honeycomb bodies made of ceramic or metal.
- An advantage of the SCR catalyst in the common exhaust pipe is that it does not or hardly oxidizes any nitrogen monoxide which may break through to nitrogen dioxide, in contrast to the oxidation catalyst. This property is particularly important in view of the expected exhaust emission legislation for the emission of nitrogen dioxide.
- Nitric oxide harms the environment less than nitrogen dioxide.
- Another advantage of the exhaust gas purification system according to the invention is the fact that the SCR catalyst due to the design of the system due to a large distance between the nitrogen oxide storage catalytic converter and the SCR catalyst has.
- the exhaust gas line between the storage catalytic converter and the SCR catalytic converter can be 0.5 to 1.5 meters. During the flow through this exhaust pipe, the exhaust gas cools about 50 0 C per meter of exhaust pipe.
- Another crucial advantage of the method is that storage and regeneration phase of the two cylinder groups are offset from each other in time, whereby the exhaust gas in the common exhaust system less high temperature fluctuations and lower maximum temperatures in the storage ZRegenerations concede than it directly behind the nitrogen oxide storage in the catalysts individual exhaust gas strands would be the case.
- the SCR catalyst has a temperature over long operating ranges of the engine, at which the catalyst has a high storage efficiency for ammonia and is thus able to neutralize the stored with the stored ammonia during the lean phase through the storage catalytic converters nitrogen oxides Implement products.
- an oxidation catalytic converter is located behind the SCR catalytic converter in the common exhaust gas line.
- SCR catalyst and oxidation catalyst can be arranged one behind the other in separate housings. In this arrangement, the exhaust gas must heat the two separate catalysts to operating temperature. This is made more difficult by heat losses between the two catalysts. It is therefore preferred for thermal reasons to apply both catalysts in the form of coatings on a common honeycomb body as a carrier of the coatings.
- This combined SCR and oxidation catalyst can be constructed as a so-called zone catalyst, that is, the SCR catalyst is applied to an upstream part of the honeycomb body and the oxidation catalyst on a downstream part of the honeycomb body.
- the oxidation catalyst in the form of a first layer on a honeycomb body and on this first layer, the SCR- Apply catalyst as a second layer.
- This arrangement has an outstanding blocking effect for ammonia and also converts even remaining nitrogen oxides.
- the nitrogen oxide storage catalysts can be preceded by oxidation catalysts or three-way catalysts, for example in a position close to the engine, in order to reduce the cold-start emissions and to support the oxidation of nitrogen monoxide to nitrogen dioxide during normal operation.
- oxidation catalysts or three-way catalysts for example in a position close to the engine, in order to reduce the cold-start emissions and to support the oxidation of nitrogen monoxide to nitrogen dioxide during normal operation.
- the exhaust gas purification system described here operates as follows: the two nitrogen oxide storage catalysts are respectively traversed by lean exhaust gas during a storage phase and by rich exhaust gas during a regeneration phase, the storage phase and regeneration phase alternating cyclically.
- the regeneration phase of one of the two storage catalytic converters is always initiated when the other storage catalytic converter is in its storage phase.
- Lean and rich exhaust are coordinated so that after the merging of the exhaust gases in the common exhaust pipe results in a lean exhaust gas.
- Lean and rich exhaust gases are preferably generated by operating the two storage cylinders associated cylinders with lean or rich air / fuel mixture and discharged into the corresponding exhaust pipes.
- the engine may also be operated constantly with lean air / fuel mixture.
- the exhaust gas is enriched in the two exhaust pipes respectively by injecting reducing agents for the regeneration of the storage catalysts.
- Suitable reducing agents are, for example, fuel or other hydrocarbons. This mode of operation may be particularly advantageous in diesel engines.
- the correct course of these processes is preferably monitored by an electronic engine control.
- This engine control regulates the composition of the exhaust gases in the two exhaust pipes independently. It supplies, for example, the first group of cylinders associated with the first exhaust pipe during the lean air / fuel mixture storage phase and during this phase initiates the regeneration of the nitrogen oxide storage catalyst in the second exhaust pipe by second grouping of the second exhaust pipe associated with Cylinders for a short time with supplied with a rich air / fuel mixture. This process is repeated periodically in reverse order.
- FIG. 1 emission control system according to the invention with an SCR catalyst in the common exhaust pipe
- FIG. 2 emission control system according to the invention with an SCR catalyst in the common exhaust pipe and an oxidation catalyst arranged behind it
- FIG. 3 emission control system according to the invention with an SCR catalyst and an oxidation catalyst on a honeycomb body in the common
- FIG. 4 Exhaust gas purification system according to the invention with a combination catalyst comprising a layer of an SCR catalyst over a layer of an oxidation catalytic converter in the common exhaust gas line
- Figure 5 Schematic representation of the time course of the air ratio ⁇ in the first and second exhaust pipe and in the common exhaust pipe
- Figures 1 to 4 show four embodiments of the emission control system. Like reference numerals designate like components.
- Reference numeral (1) denotes a lean-burn engine with two cylinder banks (2) and (2 '). The exhaust gases of these cylinder banks are discharged into the two exhaust pipes (3) and (3 '). At the junction (4), the two exhaust pipe (3) and (3 ') to a common exhaust pipe
- the nitrogen oxide storage catalysts are in the exhaust pipes (3) and (3 ')
- an SCR catalytic converter (7) is located in the common exhaust pipe (5). It stores the unintentionally produced during the regeneration of the storage catalytic converter ammonia.
- the correct sequence of storage phase and regeneration phase is preferably monitored by an electronic engine controller.
- This engine control and the necessary sensors for determining the air ratio in the two exhaust pipes are not shown in the figures for the sake of simplicity.
- Electronic engine controls and the necessary sensors to operate a Lean-burn engines with nitrogen oxide storage catalysts are known to the person skilled in the art.
- the control program For the operation of the exhaust system according to the invention according to the described method, the control program must be adapted accordingly.
- an oxidation catalytic converter (8) is inserted into the common exhaust gas line.
- FIG. 3 shows the structure of the exhaust gas purification system according to a preferred embodiment of the invention.
- the SCR and oxidation catalyst are now arranged directly behind one another.
- This combination of SCR and oxidation catalyst may, for example, be implemented as a zone catalyst on a single continuous honeycomb body.
- FIG. 4 shows a further embodiment of the invention.
- the catalyst (9) is constructed in the common exhaust pipe as a combined SCR and oxidation catalyst.
- the catalyst has an oxidation catalyst as a first layer on an inert honeycomb body.
- the SCR catalyst is applied as a second layer. This second layer is in direct contact with the exhaust gas.
- FIG. 5 schematically shows the time profile of the air ratio lambda ( ⁇ ) in the first exhaust gas line (curve a) relative to the curve in the second exhaust gas line (curve b)) and in the common exhaust gas line (curve c)).
- the air ratio ⁇ is the air / fuel ratio normalized to stoichiometric conditions.
- the storage phase with ⁇ > 1 (lean exhaust gas) alternates regularly in the two exhaust gas lines with the regeneration phase with ⁇ ⁇ 1 (rich exhaust gas).
- the regeneration phase is significantly shorter than the storage phase.
- the phase angle of the two lambda curves a) and b) to each other is largely variable as long as the exhaust gas in the common exhaust pipe is always lean (curve c)), that is, has a lambda value greater than 1.
- a particular advantage of the proposed emission control system and the method for their operation is the fact that the accidentally generated during the regeneration of the storage catalysts ammonia is stored by the downstream SCR catalyst. With the stored ammonia are nitrogen oxides, which during the Storage phase, the storage catalysts pass, selectively converted to nitrogen. As a result, the nitrogen oxide emission is additionally reduced.
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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)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP07857042A EP2104782A1 (fr) | 2006-12-23 | 2007-12-21 | Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en uvre de l'installation |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP06026858 | 2006-12-23 | ||
EP07857042A EP2104782A1 (fr) | 2006-12-23 | 2007-12-21 | Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en uvre de l'installation |
PCT/EP2007/011319 WO2008077602A1 (fr) | 2006-12-23 | 2007-12-21 | Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en œuvre de l'installation |
Publications (1)
Publication Number | Publication Date |
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EP2104782A1 true EP2104782A1 (fr) | 2009-09-30 |
Family
ID=38042844
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP07857042A Withdrawn EP2104782A1 (fr) | 2006-12-23 | 2007-12-21 | Installation d'épuration des gaz d'échappement pour moteurs à mélange pauvre et procédé de mise en uvre de l'installation |
Country Status (7)
Country | Link |
---|---|
US (1) | US20100037597A1 (fr) |
EP (1) | EP2104782A1 (fr) |
JP (1) | JP2010514968A (fr) |
KR (1) | KR20090094466A (fr) |
BR (1) | BRPI0721036A2 (fr) |
CA (1) | CA2673628A1 (fr) |
WO (1) | WO2008077602A1 (fr) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102008039112A1 (de) * | 2008-08-21 | 2010-02-25 | Deutz Ag | Abgasnachbehandlungssystem |
US8443587B2 (en) | 2009-02-23 | 2013-05-21 | GM Global Technology Operations LLC | Method for exhaust aftertreatment in an internal combustion engine |
FR2964696A1 (fr) * | 2010-09-13 | 2012-03-16 | Renault Sa | Systeme et procede de traitement des oxydes d'azote pour ligne d'echappement d'un vehicule automobile |
EP2428659B1 (fr) | 2010-09-13 | 2016-05-18 | Umicore AG & Co. KG | Catalyseur destiné à supprimer les oxydes d'azote contenus dans les gaz d'échappement de moteurs diesel |
DE102011012799A1 (de) | 2010-09-15 | 2012-03-15 | Umicore Ag & Co. Kg | Katalysator zur Entfernung von Stickoxiden aus dem Abgas von Dieselmotoren |
WO2012065933A1 (fr) | 2010-11-16 | 2012-05-24 | Umicore Ag & Co. Kg | Catalyseur destiné à supprimer les oxydes d'azote contenus dans les gaz d'échappement de moteurs diesel |
US9222420B2 (en) * | 2012-08-02 | 2015-12-29 | Ford Global Technologies, Llc | NOx control during cylinder deactivation |
US8862370B2 (en) | 2012-08-02 | 2014-10-14 | Ford Global Technologies, Llc | NOx control during engine idle-stop operations |
JP5920368B2 (ja) * | 2014-01-17 | 2016-05-18 | トヨタ自動車株式会社 | 内燃機関の制御装置 |
DE102015007908A1 (de) * | 2015-06-20 | 2016-12-22 | Man Truck & Bus Ag | Verfahren zum Betreiben eines Gasmotors |
US10337374B2 (en) * | 2017-03-15 | 2019-07-02 | Ford Global Technologies, Llc | Methods and systems for an aftertreatment catalyst |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2004061278A1 (fr) * | 2003-01-02 | 2004-07-22 | Daimlerchrysler Ag | Dispositif et procede de post-traitement de gaz d'echappement |
Family Cites Families (9)
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KR100287051B1 (ko) * | 1995-11-17 | 2001-09-07 | 와다 아끼히로 | 엔진의 배기가스 정화 방법 및 장치 |
JP3456408B2 (ja) * | 1997-05-12 | 2003-10-14 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
US7055311B2 (en) * | 2002-08-31 | 2006-06-06 | Engelhard Corporation | Emission control system for vehicles powered by diesel engines |
DE10244137A1 (de) * | 2002-09-23 | 2004-04-08 | Bayerische Motoren Werke Ag | Abgasreinigungsanlage für eine Brennkraftmaschine |
US6732507B1 (en) * | 2002-12-30 | 2004-05-11 | Southwest Research Institute | NOx aftertreatment system and method for internal combustion engines |
DE10308288B4 (de) * | 2003-02-26 | 2006-09-28 | Umicore Ag & Co. Kg | Verfahren zur Entfernung von Stickoxiden aus dem Abgas eines mager betriebenen Verbrennungsmotors und Abgasreinigungsanlage hierzu |
DE10315593B4 (de) * | 2003-04-05 | 2005-12-22 | Daimlerchrysler Ag | Abgasnachbehandlungseinrichtung und -verfahren |
US7213395B2 (en) * | 2004-07-14 | 2007-05-08 | Eaton Corporation | Hybrid catalyst system for exhaust emissions reduction |
FR2873158B1 (fr) * | 2004-07-15 | 2008-11-14 | Peugeot Citroen Automobiles Sa | Ligne d'echappement d'un moteur a combustion interne, et systeme d'epuration des gaz d'echappement la comprenant |
-
2007
- 2007-12-21 BR BRPI0721036-1A patent/BRPI0721036A2/pt not_active IP Right Cessation
- 2007-12-21 KR KR1020097015405A patent/KR20090094466A/ko not_active Application Discontinuation
- 2007-12-21 WO PCT/EP2007/011319 patent/WO2008077602A1/fr active Application Filing
- 2007-12-21 EP EP07857042A patent/EP2104782A1/fr not_active Withdrawn
- 2007-12-21 JP JP2009541903A patent/JP2010514968A/ja active Pending
- 2007-12-21 US US12/519,989 patent/US20100037597A1/en not_active Abandoned
- 2007-12-21 CA CA002673628A patent/CA2673628A1/fr not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2004061278A1 (fr) * | 2003-01-02 | 2004-07-22 | Daimlerchrysler Ag | Dispositif et procede de post-traitement de gaz d'echappement |
Non-Patent Citations (1)
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See also references of WO2008077602A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2008077602A1 (fr) | 2008-07-03 |
KR20090094466A (ko) | 2009-09-07 |
US20100037597A1 (en) | 2010-02-18 |
CA2673628A1 (fr) | 2008-07-03 |
JP2010514968A (ja) | 2010-05-06 |
BRPI0721036A2 (pt) | 2014-07-29 |
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