US20100037597A1 - Exhaust emission control system for lean engines and method for operating the system - Google Patents
Exhaust emission control system for lean engines and method for operating the system Download PDFInfo
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- US20100037597A1 US20100037597A1 US12/519,989 US51998907A US2010037597A1 US 20100037597 A1 US20100037597 A1 US 20100037597A1 US 51998907 A US51998907 A US 51998907A US 2010037597 A1 US2010037597 A1 US 2010037597A1
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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
- 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
- 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 emission control system for the cleaning of the exhaust gases of lean burn engines with two or more cylinders and to a method for operating the system.
- lean burn engines refer to diesel engines and lean burn petrol engines.
- This emission control system has a crucial drawback: during the regeneration of a nitrogen oxide storage catalyst, considerable amounts of ammonia can be generated when the storage catalyst is regenerated for longer than necessary. This risk exists particularly in the case of aged storage catalysts.
- the ammonia formed flows together with the other exhaust gases over the oxidation catalyst in the combined exhaust leg and is oxidized again to nitrogen oxides, which reduces the control performance of the exhaust gas system with regard to the nitrogen oxide. This is the case especially at relatively high exhaust gas temperatures in the case of oxidation catalysts with high oxidation activity.
- Such catalysts are used in order to oxidize the hydrocarbons and carbon monoxide present in the exhaust gas at as early as possible a stage at low exhaust gas temperatures, for example after a cold start.
- WO 2006/008625 describes an exhaust gas treatment system for a lean burn engine with an SCR reactor downstream of an NOx adsorber (nitrogen oxide adsorber).
- the nitrogen oxide adsorber is regenerated with syngas from a fuel reforming reactor.
- the nitrogen oxide adsorber preferably possesses a catalytic function for converting the nitrogen oxides during the 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 convert the nitrogen oxides during the lean operating mode of the engine.
- an oxidation catalyst is arranged downstream of the SCR reactor.
- WO 2004/090296 discloses, in FIG. 1 , a single-line exhaust gas aftertreatment unit. It comprises, in the exhaust gas flow direction, downstream of an internal combustion engine, in the full flow of the exhaust gas line, in succession, a reforming unit which simultaneously acts as a particulate filter, a nitrogen oxide storage catalyst and an SCR catalyst as emission control components.
- a reforming unit which simultaneously acts as a particulate filter, a nitrogen oxide storage catalyst and an SCR catalyst as emission control components.
- hydrogen is obtained by steam reforming, partial oxidation of hydrocarbons and/or mixed forms thereof.
- U.S. Pat. No. 6,732,507 B1 likewise describes a single-line nitrogen oxide aftertreatment system in which a nitrogen oxide adsorber is combined with an SCR catalyst.
- the nitrogen oxide aftertreatment system is operated alternately with rich and lean air/fuel mixtures.
- the SCR catalyst stores the ammonia generated by the nitrogen oxide absorber during the regeneration in the rich exhaust gas and converts, with the ammonia stored, the nitrogen oxides which have not been adsorbed during the lean operation of the nitrogen oxide adsorber to harmless products.
- the SCR catalyst possesses a first end which is directly connected to the second end of the nitrogen oxide adsorber.
- the engines may be configured as in-line engines in which all cylinders are arranged in series in a single cylinder bank. Alternatively, each group of cylinders may be combined in a separate cylinder bank.
- the invention utilizes the storage action of SCR catalysts for ammonia in order to store any ammonia formed in the regeneration of the nitrogen oxide storage catalysts.
- a nitrogen oxide storage catalyst is understood to mean a catalyst which oxidizes the nitrogen monoxide present in a lean exhaust gas to nitrogen dioxide during a storage phase and then stores it in the form of nitrates.
- the mode of operation of nitrogen oxide storage catalysts is described in detail in the SAE document SAE 950809.
- a storage catalyst usually contains platinum, with or without palladium, as catalytically active components.
- the materials used for storage of the nitrogen oxides as nitrates include 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 of strontium.
- Storage phase and regeneration phase alternate regularly.
- the storage phase usually lasts between 60 and 120 seconds, whereas the duration of the regeneration phase is only between 1 and 10% of that of the storage phase and hence is only a few seconds.
- the short regeneration time increases the risk that the storage catalyst regenerates for longer than required, i.e. is supplied with rich exhaust gas. Under these conditions, the storage catalyst forms ammonia from the nitrogen oxides.
- Oxidation catalysts refer here to those catalysts which oxidize hydrocarbons and carbon monoxide to carbon dioxide and water in the lean exhaust gas.
- oxidation catalysts comprise, as the catalytically active component, platinum with or without palladium. These oxidation catalysts also oxidize ammonia to nitrogen and nitrogen oxides.
- SCR catalysts are understood to mean catalysts which convert nitrogen oxides selectively to nitrogen under lean exhaust gas conditions with addition of ammonia as a reducing agent. These catalysts contain acidic oxides and can store ammonia. Typical SCR catalysts contain, for example, vanadium oxide and/or tungsten oxide on titanium oxide. Alternatively, it is also possible to use copper- and/or iron-exchanged zeolites. Usually, such catalysts do not contain any catalytically active platinum group metals since these metals would oxidize the ammonia in the lean exhaust gas to nitrogen oxides. For the inventive emission control system, preference is given to using SCR catalysts which comprise zeolites. Zeolites have a particularly high storage capacity for ammonia and for hydrocarbons. They are therefore outstandingly suitable 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 greatly on the temperature. In particular after ageing of the catalysts in real operation, the storage effect declines very greatly above 300° C. and is barely perceptible any longer at temperatures above 400° C. Therefore, particularly at high exhaust gas temperatures, there is the risk that too much ammonia metered in leaves the SCR catalyst with the exhaust gas before it can react with the nitrogen oxides.
- a so-called ammonia barrier catalyst is usually arranged downstream of the SCR catalyst. In the simplest case, this is an oxidation catalyst which, however, can also reoxidize the ammonia to nitrogen oxides under unfavourable operating conditions.
- a further advantage of the inventive emission control system is the fact that the SCR catalyst, caused by the design of the system, has a large distance between the nitrogen oxide storage catalysts and the SCR catalyst.
- the exhaust leg between the storage catalysts and the SCR catalyst may be 0.5 to 1.5 metres. In the course of flow through this exhaust leg, the exhaust gas cools down by about 50° C. per metre of exhaust leg.
- a further crucial advantage of the process according to the invention is that storage and regeneration phases of the two cylinder groups are offset in time with respect to one another, as a result of which the exhaust gas in the common exhaust line has temperature variations of lesser magnitude and lower maximum temperatures in storage/regeneration operation than would be the case directly downstream of the nitrogen oxide storage catalysts in the individual exhaust lines.
- SCR catalyst and oxidation catalyst may be arranged in series in separate housings. In this arrangement, the exhaust gas must heat the two separate catalysts to operating temperature. This is additionally complicated by heat losses between the two catalysts. It is therefore preferred for thermal reasons to apply both catalysts in the form of coatings to a common honeycomb as a support of the coatings.
- This combined SCR and oxidation catalyst may be designed as a so-called zone catalyst, which means that the SCR catalyst is applied on an inflow part of the honeycomb and the oxidation catalyst on an outflow part of the honeycomb.
- oxidation catalyst in the form of a first layer to a honeycomb and to apply the SCR catalyst as a second layer to this first layer.
- This arrangement has an outstanding barrier effect for ammonia and additionally also converts residual nitrogen oxides.
- the nitrogen oxide storage catalysts may be connected upstream of oxidation catalysts or three-way catalysts, for example in a position close to the engine, in order to reduce cold start emissions and to promote the oxidation of nitrogen monoxide to nitrogen dioxide in normal operation. Combination with a diesel particulate filter is also possible.
- the emission control system described here is operated as follows: lean exhaust gas flows through the two nitrogen oxide storage catalysts during a storage phase, and rich exhaust gas during a regeneration phase, storage phase and regeneration phase alternating cyclically.
- the regeneration phase of one of the two storage catalysts is initiated whenever the other storage catalyst is in its storage phase.
- Lean and rich exhaust gas are adjusted with respect to one another so as to result in a lean exhaust gas after the combination of the exhaust gases in the combined exhaust leg.
- Lean and rich exhaust gases are preferably obtained by operating the cylinders assigned to the two storage catalysts with lean or rich air/fuel mixtures and releasing them into the corresponding exhaust legs.
- the engine can also be operated constantly with lean air/fuel mixture.
- the exhaust gas in the two exhaust legs is enriched in each case by injecting reducing agents for regeneration of the storage catalysts.
- Suitable reducing agents are, for example, fuel or other hydrocarbons. This mode of operation may be advantageous particularly in diesel engines.
- the correct running of these operations is preferably monitored by an electronic engine control system.
- This engine control system regulates the compositions of the exhaust gases in the two exhaust legs independently of one another. It supplies, for example, the first group of cylinders assigned to the first exhaust leg with lean air/fuel mixture during the storage phase and initiates the regeneration of the nitrogen oxide storage catalyst in the second exhaust leg during this phase by briefly supplying the second group of cylinders assigned to the second exhaust leg with rich air/fuel mixture. This operation is repeated periodically in the reverse sequence in each case.
- FIGS. 1 to 5 The invention is illustrated in detail by FIGS. 1 to 5 .
- the figures show:
- FIG. 1 Emission control system according to the invention with an SCR catalyst in the common exhaust leg
- FIG. 2 Emission control system according to the invention with an SCR catalyst in the common exhaust leg and an oxidation catalyst arranged downstream thereof
- FIG. 3 Emission control system according to the invention with an SCR catalyst and an oxidation catalyst on a honeycomb in the common exhaust leg
- FIG. 4 Emission control system according to the invention with a combination catalyst composed of a layer of an SCR catalyst atop a layer of an oxidation catalyst in the common exhaust leg
- FIG. 5 Schematic diagram of the air ratios ⁇ against time in the first and second exhaust leg and in the common exhaust leg
- FIGS. 1 to 4 show four embodiments of the emission control system.
- the same reference numeral denotes components of the same type.
- Reference numeral ( 1 ) denotes a lean burn engine with two cylinder banks ( 2 ) and ( 2 ′). The exhaust gases of these cylinder banks are released into the two exhaust legs ( 3 ) and ( 3 ′). At the confluence ( 4 ), the two exhaust legs ( 3 ) and ( 3 ′) are combined to form a common exhaust leg ( 5 ).
- the nitrogen oxide storage catalysts ( 6 ) and ( 6 ′) are arranged in the exhaust legs ( 3 ) and ( 3 ′).
- an SCR catalyst ( 7 ) is present in the common exhaust leg ( 5 ). It stores the unwanted ammonia which forms in the course of regeneration of the storage catalysts.
- the correct running of storage phase and regeneration phase is preferably monitored by an electronic engine control system.
- This engine control system and the necessary sensors for the determination of the air ratio in the two exhaust legs are not shown in the figures for the sake of simplicity.
- Electronic engine control systems and the necessary sensors for operation of a lean burn engine with nitrogen oxide storage catalysts are known to those skilled in the art.
- the control programme has to be adjusted correspondingly.
- an oxidation catalyst ( 8 ) is inserted into the common exhaust leg downstream of the SCR catalyst ( 7 ).
- FIG. 3 shows the design of the emission control system in a preferred embodiment of the invention.
- the SCR and oxidation catalysts are now arranged in direct succession.
- This combination of SCR and oxidation catalysts can be configured, for example, as zone catalyst on a single continuous honeycomb.
- FIG. 4 shows a further embodiment of the invention.
- the catalyst ( 9 ) in the common exhaust leg is designed as a combined SCR and oxidation catalyst.
- the catalyst has an oxidation catalyst as a first layer on an inert honeycomb.
- the SCR catalyst is applied as a second layer to this oxidation catalyst. This second layer is in direct contact with the exhaust gas.
- FIG. 5 shows, in schematic form, the air ratio lambda ( ⁇ ) against time in the first exhaust leg (curve a)) relative to that in the second exhaust leg (curve b)) and in the common exhaust leg (curve c)).
- the air ratio ⁇ is the air/fuel ratio normalized to stoichiometric conditions.
- the storage phase with ⁇ >1 (lean exhaust gas) alternates regularly with the regeneration phase with ⁇ 1 in the two exhaust legs.
- the regeneration phase is significantly shorter than the storage phase.
- the phase position of the two lambda curves a) and b) relative to one another is substantially variable, provided that the exhaust gas in the combined exhaust leg is always lean (curve c)), i.e. has a lambda value greater than 1.
- a particular advantage of the proposed emission control system and of the method for operation thereof is the fact that unwanted ammonia which forms in the regeneration of the storage catalysts is stored by the downstream SCR catalyst.
- the ammonia stored selectively converts nitrogen oxides which pass through the storage catalysts during the regeneration phase to nitrogen. This additionally reduces nitrogen oxide emission.
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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)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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EP06026858.8 | 2006-12-23 | ||
EP06026858 | 2006-12-23 | ||
PCT/EP2007/011319 WO2008077602A1 (de) | 2006-12-23 | 2007-12-21 | Abgasreinigungsanlage für magermotoren und verfahren zum betreiben der anlage |
Publications (1)
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US20100037597A1 true US20100037597A1 (en) | 2010-02-18 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/519,989 Abandoned US20100037597A1 (en) | 2006-12-23 | 2007-12-21 | Exhaust emission control system for lean engines and method for operating the system |
Country Status (7)
Country | Link |
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US (1) | US20100037597A1 (de) |
EP (1) | EP2104782A1 (de) |
JP (1) | JP2010514968A (de) |
KR (1) | KR20090094466A (de) |
BR (1) | BRPI0721036A2 (de) |
CA (1) | CA2673628A1 (de) |
WO (1) | WO2008077602A1 (de) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110182789A1 (en) * | 2008-08-21 | 2011-07-28 | Deutz Aktiengesellschaft | Exhaust gas aftertreatment system |
US20140039781A1 (en) * | 2012-08-02 | 2014-02-06 | Ford Global Technologies, Llc | Nox control during engine idle-stop operations |
CN103573344A (zh) * | 2012-08-02 | 2014-02-12 | 福特环球技术公司 | 汽缸停用期间的NOx控制 |
US8753596B2 (en) | 2010-09-13 | 2014-06-17 | Umicore Ag & Co. Kg | Catalyst for removing nitrogen oxides from the exhaust gas of diesel engines |
US9095816B2 (en) | 2010-11-16 | 2015-08-04 | Umicore Ag & Co. Kg | Catalyst for removing nitrogen oxides from the exhaust gas of diesel engines |
US20160369678A1 (en) * | 2015-06-20 | 2016-12-22 | Man Truck & Bus Ag | Method for Operating a Gas Engine |
US10337374B2 (en) * | 2017-03-15 | 2019-07-02 | Ford Global Technologies, Llc | Methods and systems for an aftertreatment catalyst |
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Publication number | Priority date | Publication date | Assignee | Title |
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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 |
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- 2007-12-21 JP JP2009541903A patent/JP2010514968A/ja active Pending
- 2007-12-21 WO PCT/EP2007/011319 patent/WO2008077602A1/de active Application Filing
- 2007-12-21 EP EP07857042A patent/EP2104782A1/de not_active Withdrawn
- 2007-12-21 US US12/519,989 patent/US20100037597A1/en not_active Abandoned
- 2007-12-21 CA CA002673628A patent/CA2673628A1/en not_active Abandoned
- 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
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US8372364B2 (en) * | 2008-08-21 | 2013-02-12 | Deutz Aktiengesellschaft | Exhaust gas aftertreatment system |
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US8753596B2 (en) | 2010-09-13 | 2014-06-17 | Umicore Ag & Co. Kg | Catalyst for removing nitrogen oxides from the exhaust gas of diesel engines |
US9095816B2 (en) | 2010-11-16 | 2015-08-04 | Umicore Ag & Co. Kg | Catalyst for removing nitrogen oxides from the exhaust gas of diesel engines |
US8862370B2 (en) * | 2012-08-02 | 2014-10-14 | Ford Global Technologies, Llc | NOx control during engine idle-stop operations |
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US9518287B2 (en) | 2012-08-02 | 2016-12-13 | Ford Global Technologies, Llc | NOx control during engine idle-stop operations |
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Also Published As
Publication number | Publication date |
---|---|
WO2008077602A1 (de) | 2008-07-03 |
CA2673628A1 (en) | 2008-07-03 |
KR20090094466A (ko) | 2009-09-07 |
EP2104782A1 (de) | 2009-09-30 |
BRPI0721036A2 (pt) | 2014-07-29 |
JP2010514968A (ja) | 2010-05-06 |
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