US20100064665A1 - Method and desulfurizing nitrogen oxide storage catalysts in the exhaust gas system of a lean mix engine - Google Patents

Method and desulfurizing nitrogen oxide storage catalysts in the exhaust gas system of a lean mix engine Download PDF

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US20100064665A1
US20100064665A1 US12/520,606 US52060607A US2010064665A1 US 20100064665 A1 US20100064665 A1 US 20100064665A1 US 52060607 A US52060607 A US 52060607A US 2010064665 A1 US2010064665 A1 US 2010064665A1
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exhaust
exhaust gas
desulphurization
nitrogen oxide
catalyst
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Stephan Eckhoff
Susanne Philipp
Wilfried Mueller
Thomas Kreuzer
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Umicore AG and Co KG
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Umicore AG and Co KG
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Assigned to UMICORE AG & CO. KG reassignment UMICORE AG & CO. KG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PHILIPP, SUSANNE, MUELLER, WILFRIED, ECKHOFF, STEPHAN, KREUZER, THOMAS
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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
    • 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
    • F02D41/028—Desulfurisation of NOx traps or adsorbent
    • 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
    • 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
    • F01N13/0093—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 of the same type
    • 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
    • F01N13/04—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 silencers in parallel, e.g. having interconnections for multi-cylinder engines
    • 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
    • F01N13/08—Other arrangements or adaptations of exhaust conduits
    • F01N13/10—Other arrangements or adaptations of exhaust conduits of exhaust manifolds
    • F01N13/107—More than one exhaust manifold or exhaust collector
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • 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
    • 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
    • F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • 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
    • F01N3/101—Three-way catalysts
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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
    • 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
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F01N3/2033—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using a fuel burner or introducing fuel into exhaust duct
    • 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
    • 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
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
    • 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
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/08—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing
    • 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
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/08—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing
    • F01N2430/085—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing at least a part of the injection taking place during expansion or exhaust stroke
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/025—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting O2, e.g. lambda sensors
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/14—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics having more than one sensor of one kind
    • 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 a method for desulphurizing nitrogen oxide storage catalysts in the exhaust gas system of a lean burn engine with two or more cylinders.
  • nitrogen oxygen storage catalysts can be used.
  • a nitrogen oxide storage catalyst oxidizes the nitrogen monoxide present in the lean exhaust gas to nitrogen dioxide 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 publication SAE 950809.
  • a storage catalyst contains, as catalytically active components, usually platinum with or without palladium.
  • basic oxides, carbonates or hydroxides of alkali metals, alkaline earth metals and rare earth metals are used; preference is given to using basic compounds of barium and of strontium.
  • a storage catalyst After exhaustion of its storage capacity, a storage catalyst has to 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 nitrogen over the catalytically active components with the aid of the rich exhaust gas constituents.
  • the storage catalyst usually contains rhodium in addition to the platinum.
  • Storage phase and regeneration phase alternate regularly.
  • the alternation of storage phase and regeneration phase is referred to as alternating rich/lean operation.
  • the storage phase usually lasts between 60 and 200 seconds, whereas the duration of the regeneration phase is only between 1 and 10% of the storage phase and thus comprises only a few seconds.
  • nitrogen oxide storage catalysts The function of nitrogen oxide storage catalysts is impaired by sulphur compounds which are present in the fuel and motor oil and get into the exhaust gas essentially in the form of sulphur dioxide in the course of combustion, and are bound by the nitrogen oxide storage catalysts in the form of very stable sulphates. This is at the expense of the nitrogen oxide storage capacity. At high sulphur contents in the fuel (>10 ppm), nitrogen oxide storage catalysts therefore frequently have to be desulphurized. To this end, the exhaust gas has to be brought to desulphurizing conditions, i.e. it has to be enriched and its temperature has to be raised.
  • the air/fuel ratio lambda ⁇ of the exhaust gas should be lowered to a value below 0.98, preferably to below 0.95, and the exhaust gas temperature should be brought to a value between 600 and 750° C. Under these conditions, the sulphates formed are decomposed and emitted as hydrogen sulphide or preferably as sulphur dioxide.
  • the storage catalyst When a nitrogen oxide storage catalyst is contacted with a sulphur-containing exhaust gas, the storage catalyst thus, as well as the regular regeneration to remove the nitrogen oxides stored, also has to be desulphurized from time to time in order to reverse a continuous deterioration in the nitrogen oxide storage capacity as a result of sulphates formed.
  • the interval between two desulphurizations depends on the sulphur content of the fuel, but even at high sulphur contents is generally still several operating hours of the engine and is thus significantly greater than the interval between two regenerations to remove the nitrogen oxides stored.
  • For the desulphurization usually 2 to 10 minutes are required. It thus likewise lasts longer than the nitrogen oxide regeneration of the storage catalyst.
  • the method requires a lean burn engine with two or more cylinders, which are divided into a first group and a second group.
  • the exhaust gases of the two cylinder groups are released into exhaust legs assigned to each.
  • Each exhaust leg contains at least one nitrogen oxide storage catalyst for removal of the nitrogen oxides in the exhaust gas.
  • the two exhaust legs open downstream of the storage catalysts into a common exhaust leg at a confluence.
  • the common exhaust leg contains a catalyst which, under stoichiometric conditions, has a three-way function, which allows it to simultaneously remove hydrocarbons, ammonia, nitrogen oxides and carbon monoxide from the stoichiometric exhaust gas. This catalyst is referred to hereinafter as three-way catalyst for short.
  • the lean burn engine can be configured as an in-line engine in which all cylinders are arranged in succession in a single cylinder bank. Alternatively, each group of cylinders can be combined in a separate cylinder bank.
  • the nitrogen oxide storage catalysts in the two exhaust legs are desulphurized offset in time with respect to one another.
  • the desulphurization conditions needed for this purpose can be established by engine measures or by external measures.
  • the engine measures include the operation of the group of cylinders assigned in each case with a rich air/fuel mixture, the postinjection of fuel, a late combustion position or a multistage combustion. These measures can also be combined with one another.
  • the exhaust gas can be enriched by injecting fuel into the particular exhaust leg upstream of the nitrogen oxide storage catalyst, and its temperature can be raised to desulphurization temperature, for example, by external heating.
  • the external heating can also be undertaken by means of oxidation catalysts arranged upstream of the nitrogen oxide storage catalysts and combustion of the fuel injected on these catalysts.
  • the other nitrogen oxide storage catalyst is operated under lean exhaust gas conditions of the lean burn engine.
  • the air/fuel ratios of the exhaust gases in the two exhaust legs are adjusted with respect to one another such that the exhaust gas in the common exhaust leg ideally has an air/fuel ratio lambda of 1 over the entire desulphurization time, i.e. is of stoichiometric composition.
  • the air/fuel ratio in the common exhaust leg will deviate downward or upward from the ideal value, to a greater or lesser degree, variably with time, owing to the dynamic operating conditions of the engines.
  • the other nitrogen oxide storage catalyst is desulphurized in a corresponding manner offset in time with respect to the first nitrogen oxide storage catalyst. Between two desulphurizations, the two nitrogen oxide storage catalysts are operated in the known alternating operation between storage phase and regeneration phase.
  • the exhaust gas is enriched to an air/fuel ratio lambda of ⁇ 1, preferably to ⁇ 0.98 and particularly to ⁇ 0.95.
  • the second storage catalyst is operated at an air/fuel ratio of the exhaust gas lambda of >1, preferably >1.1.
  • a further advantage of the invention is that the desulphurization can be performed under constantly rich exhaust gas conditions. This is because the hydrogen sulphide formed is converted to sulphur dioxide over the three-way catalyst in the common exhaust leg.
  • the exhaust gas is usually switched back and forth between lean and rich in rapid alternation, in order to suppress the formation of hydrogen sulphide.
  • this alternating operation requires high exhaust gas temperatures for the desulphurization and leads to higher fuel consumption and longer desulphurization times compared to the method described here.
  • the second storage catalyst can be operated with constantly lean exhaust gas.
  • the regular nitrogen oxide regeneration of the second storage catalyst during the desulphurization of the first storage catalyst is unnecessary.
  • the storage capacity of the second storage catalyst for nitrogen oxides is already exhausted about 1 to 2 minutes after the start of desulphurization of the first storage catalyst, the nitrogen oxides which therefore break through the nitrogen oxide storage catalyst are completely converted by the downstream three-way catalyst.
  • the catalyst in the common exhaust leg must be able to fulfil the function of a three-way catalyst under stoichiometric exhaust gas conditions.
  • it contains at least one noble metal from the group of platinum, palladium and rhodium.
  • the catalyst preferably contains palladium and/or rhodium.
  • the catalyst may contain so-called oxygen storage materials, particularly cerium oxide or a mixed oxide containing cerium oxide. Preference is given to using a catalyst configured specially as a three-way catalyst.
  • the storage catalyst may contribute additionally to the conversion of nitrogen oxides by storing them during the lean phase and converting them to nitrogen by means of short rich pulses.
  • a slightly lean exhaust gas in the common exhaust leg may be advantageous when the hydrogen sulphide formed in the desulphurization is to be oxidized to sulphur dioxide over the three-way catalyst.
  • a slightly rich exhaust gas can prevent the sulphur dioxide or hydrogen sulphide formed in the desulphurization from being absorbed by the nitrogen oxide storage catalyst in the common exhaust leg to form sulphates.
  • an oxygen probe upstream and/or downstream of the three-way catalyst.
  • This probe passes its lambda signal on to an engine control system.
  • the combustion in the two cylinder groups is conducted such that a very substantially stoichiometric exhaust gas mixture is present in the common exhaust leg.
  • Suitable oxygen probes are linear lambda probes or so-called jump probes. Nitrogen oxide probes can also be used to measure the oxygen content.
  • rich or lean exhaust gas mixtures in the particular exhaust legs can also be established during the desulphurization by direct injection of fuel into the particular exhaust legs.
  • FIGS. 1 and 2 The invention is illustrated in detail with reference to FIGS. 1 and 2 .
  • the figures show:
  • FIG. 1 emission control system for performing the method for desulphurization with reduced emission of pollutants
  • FIG. 2 a further embodiment of the emission control system for performance of the method for desulphurization with reduced emission of pollutants
  • FIG. 3 schematic diagram of the offset operation of the two cylinder banks of the emission control systems according to FIGS. 1 and 2
  • FIG. 1 shows an emission control system for performing the desulphurization method with reduced pollutant emission.
  • 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 gas lines ( 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 ′).
  • the three-way catalyst or nitrogen oxide storage catalyst ( 7 ) is present in the common exhaust leg.
  • Reference numerals ( 8 ) and ( 8 ′) denote the possible positions of an oxygen probe (lambda probe).
  • the cylinders of the cylinder bank ( 2 ) are operated with a rich air/fuel mixture by an engine control system which is not shown. This leads to an exhaust gas with an air/fuel ratio less than 1, whose temperature is raised to the necessary desulphurization temperature of about 700° C., for example by postinjection. Over the entire desulphurization period of about 2 to 10 minutes, the cylinders of the second cylinder bank ( 2 ′) are operated with a lean air/fuel mixture.
  • the correspondingly lean exhaust gas with lambda greater than 1 has a temperature of 300 to 400° C. which is optimal for the nitrogen oxide storage catalyst.
  • the two exhaust gas streams are mixed and lead to a combined exhaust gas with a temperature between the desulphurization temperature and the normal exhaust gas temperature.
  • the oxygen content of the combined exhaust gas is measured with the oxygen probes ( 8 ) and/or ( 8 ′) and regulated with the aid of the engine control system to give a value of the air/fuel ratio as close as possible to 1.
  • FIG. 2 shows a variant of the emission control system for performing the method.
  • a further catalyst ( 9 ) and ( 9 ′) is inserted into each exhaust leg.
  • This may be a further nitrogen oxide storage catalyst, a three-way catalyst or an oxidation catalyst. All three catalyst types can further reduce the pollutant emission of the emission control system.
  • it may be advantageous to arrange a diesel particulate filter, with or without a catalytic coating, between the catalysts ( 9 ) and ( 6 ), and between ( 9 ′) and ( 6 ′), or beyond each of catalysts ( 6 ) and ( 6 ′).
  • FIG. 3 is a schematic diagram of the offset operation of the two cylinder banks ( 2 ) and ( 2 ′) of the emission control systems of FIGS. 1 and 2 as a function of the operating time t.
  • the brief desulphurization of catalyst ( 6 ) is always undertaken during the normal rich/lean alternating operation of catalyst ( 6 ′), and vice versa.
  • the mode of operation of the two cylinder banks ( 2 ) and ( 2 ′) is correspondingly switched as described above.

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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)
  • Materials Engineering (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Saccharide Compounds (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
US12/520,606 2006-12-30 2007-12-19 Method and desulfurizing nitrogen oxide storage catalysts in the exhaust gas system of a lean mix engine Abandoned US20100064665A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP06027131.9 2006-12-30
EP06027131A EP1939420A1 (de) 2006-12-30 2006-12-30 Verfahren zum Entschwefeln von Stickoxid-Speicherkatalysatoren in der Abgasanlage eines Magermotors
PCT/EP2007/011175 WO2008080559A1 (de) 2006-12-30 2007-12-19 Verfahren zum entschwefeln von stickoxid-speicherkatalysatoren in der abgasanlage eines magermotors

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US20100064665A1 true US20100064665A1 (en) 2010-03-18

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EP (2) EP1939420A1 (ja)
JP (1) JP2010514970A (ja)
KR (1) KR20090094452A (ja)
AT (1) ATE504725T1 (ja)
BR (1) BRPI0720744A2 (ja)
CA (1) CA2673938A1 (ja)
DE (1) DE502007006908D1 (ja)
WO (1) WO2008080559A1 (ja)

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US8617495B1 (en) * 2012-11-08 2013-12-31 GM Global Technology Operations LLC Exhaust gas aftertreatment desulfurization control
US8763368B1 (en) * 2013-03-14 2014-07-01 EMIT Technologies, Inc. Systems and methods for controlling a combustion engine
US10975791B1 (en) * 2019-12-13 2021-04-13 Denso International America, Inc. System and method for particulate filter regeneration

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DE102013207709A1 (de) 2013-04-26 2014-10-30 Umicore Ag & Co. Kg Entschwefelung von NOX-Speicherkatalysatoren
FR3098249B1 (fr) * 2019-07-04 2021-06-04 Renault Sas Procédé de commande d’un véhicule automobile muni d’un piège à oxydes d’azote pour la désoxydation dudit piège

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EP2122135B1 (de) 2011-04-06
WO2008080559A1 (de) 2008-07-10
KR20090094452A (ko) 2009-09-07
BRPI0720744A2 (pt) 2014-01-14
JP2010514970A (ja) 2010-05-06
DE502007006908D1 (de) 2011-05-19
ATE504725T1 (de) 2011-04-15
EP1939420A1 (de) 2008-07-02
CA2673938A1 (en) 2008-07-10
EP2122135A1 (de) 2009-11-25

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