WO2013100845A1 - Procédé et système pour la désulfuration d'un système de post-traitement - Google Patents

Procédé et système pour la désulfuration d'un système de post-traitement Download PDF

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Publication number
WO2013100845A1
WO2013100845A1 PCT/SE2012/051446 SE2012051446W WO2013100845A1 WO 2013100845 A1 WO2013100845 A1 WO 2013100845A1 SE 2012051446 W SE2012051446 W SE 2012051446W WO 2013100845 A1 WO2013100845 A1 WO 2013100845A1
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WIPO (PCT)
Prior art keywords
temperature
component
fuel
post
level
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PCT/SE2012/051446
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English (en)
Inventor
Carl-Johan Karlsson
Klas Telborn
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Scania Cv Ab
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Application filed by Scania Cv Ab filed Critical Scania Cv Ab
Priority to EP12863269.2A priority Critical patent/EP2798169A4/fr
Publication of WO2013100845A1 publication Critical patent/WO2013100845A1/fr

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Classifications

    • 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
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
    • 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
    • F01N13/02—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 silencers 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
    • 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
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • 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
    • 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
    • F02D41/029—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 particulate filter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/02—Combinations of different methods of purification filtering and catalytic conversion
    • 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
    • F01N2260/00—Exhaust treating devices having provisions not otherwise provided for
    • F01N2260/04—Exhaust treating devices having provisions not otherwise provided for for regeneration or reactivation, e.g. of catalyst
    • 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
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/02—Catalytic activity 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/04—Sulfur or sulfur 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
    • 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
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1602—Temperature of exhaust gas apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0818—SOx storage amount, e.g. for SOx trap or NOx trap
    • 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
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/405—Multiple injections with post injections
    • 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
    • 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
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a method pertaining to treatment of exhaust flows arising from a combustion process by using a post-treatment system.
  • the invention relates also to a system and a vehicle and to a computer programme and a computer programme product.
  • N0 X nitrogen oxides
  • HC hydrocarbons
  • CO carbon monoxide
  • post-treatment systems e.g. on vehicles and other means of transport, usually comprise at least one catalyst.
  • Post-treatment systems may also comprise other components, e.g. particle filters, as alternatives to or in combination with one or more catalysts.
  • Combustion of fuel in an engine's combustion chambers results in the formation of soot particles.
  • Particle filters used to capture these particles work in such a way that the exhaust flow is led through a filter structure whereby soot particles are captured from the passing exhaust flow and are stored in the filter.
  • the particle filter As it progressively fills with soot when the vehicle is travelling, the particle filter has sooner or later to be emptied of soot, which is usually achieved by so-called regeneration .
  • Regeneration involves the soot particles, consisting mainly of carbon particles, being converted to carbon dioxide and/or carbon monoxide in one or more chemical processes, and may be conducted in various ways.
  • N0 2 - based regeneration affords the advantage that desired reaction rates, and hence the rate at which the filter is emptied, may be achieved at relatively low temperatures, which is
  • the post-treatment system comprises temperature-sensitive components.
  • N0 2 -based regeneration does however depend greatly on the supply of nitrogen dioxide. If the supply of nitrogen dioxide is reduced, the regeneration rate will also be reduced.
  • the supply of nitrogen dioxide may for example be reduced if its formation is hindered, which may for example be due to one or more components of the post-treatment system being poisoned by sulphur, which is normally present in certain kinds of fuel, e.g. diesel fuel.
  • An object of the present invention is to propose a method for desulphuration of at least one component of a post-treatment system. This object is achieved by a method according to the characterising part of claim 1.
  • the present invention relates to a method for desulphuration of a post-treatment system which is intended to treat an exhaust flow arising from combustion in a combustion engine and comprises at least one first component and one second component. If sulphur has accumulated in said first component of said post-treatment system, the method comprises
  • the sulphur which fuels such as diesel fuel normally contain will react chemically with the active coating, often consisting of noble or other metals, with which components of the post-treatment system are usually provided.
  • the active coating often consisting of noble or other metals, with which components of the post-treatment system are usually provided.
  • sulphur molecules e.g. in the form of sulphates, bind to metal atoms/ions which can then no longer take part in desired chemical reactions, i.e. the component becomes poisoned by sulphur deposition.
  • N0 2 -based regeneration depends on nitrogen dioxide NO 2 , and sulphur poisoning has adverse effects on the characteristics of the post-treatment system with regard to N0 2 conversion, i.e.
  • the decreased N0 2 conversion i.e. the changed balance between NO and N0 2 in the exhaust flow, may also adversely affect the exhaust cleaning in other ways.
  • the post-treatment system may for example comprise an SCR catalyst which is for example situated downstream of a particle filter and depends on N0 2 formation to achieve total NO x conversion.
  • the present invention reduces problems of sulphur poisoning of components in the post-treatment systems by responding to the detection of sulphur poisoning by cyclically raising the temperature of the component where sulphur deposition has been found. Cyclic raising and lowering of the temperature causes "pulsing" of the temperature of components of the post- treatment system.
  • the component primarily subject to the poisoning is, from the engine onwards, the first component coated with (noble) metal which the exhaust flow meets, e.g. an oxidation catalyst.
  • the cyclic raising of the temperature affords the advantage that where the desulphuration is very temperature-dependent a high temperature may be achieved in the component primarily poisoned, and subsequently allowing the temperature to drop to a lower level before it is again raised will result in the temperature of downstream components of the post-treatment system not being raised to the same extent, owing to their thermal inertia.
  • the temperature of a sulphur-poisoned component may be raised to a
  • Fig. 1A depicts schematically a vehicle with which the
  • Fig. IB depicts a control unit in the control system for the vehicle depicted in Fig. 1.
  • Fig. 2 depicts the post-treatment system in more detail for the vehicle depicted in Fig. 1.
  • Fig. 3 depicts an example of the regeneration (soot burnout) rate as a function of the amount of soot in the particle filter, and its temperature dependency.
  • Fig. 4 depicts the temperature dependency of the oxidation of nitrogen oxide to nitrogen dioxide in an oxidation catalyst, and the temperature dependency of the reaction rate when oxidising carbon by means of O 2 .
  • Fig. 5 depicts a method according to an embodiment example of the present invention.
  • Fig. 6 is a temperature diagram of a desulphuration process according to the present invention.
  • Fig. 1A depicts schematically a power train of a vehicle 100 according to an embodiment of the present invention.
  • the vehicle depicted has only one axle provided with tractive wheels 113, 114 but the invention is also applicable on vehicles in which more than one axle is provided with tractive wheels, and on vehicles with one or more further axles, e.g. one or more tag axles.
  • the power train comprises a combustion engine 101 connected in a conventional way, via an output shaft of the engine, usually via a flywheel 102, to a gearbox 103 via a clutch 106.
  • the engine is controlled by the vehicle's control system via a control unit 115.
  • the clutch 106 which may for example be automatically operated, and the gearbox 103 are also
  • the vehicle's control system may of course also be of some other kind, e.g. a type with conventional automatic gearbox etc.
  • An output shaft 107 from the gearbox 103 drives the tractive wheels 113, 114 via a final gear 108, e.g. a conventional differential, and driveshafts 104, 105 which are connected to said final gear 108.
  • a final gear 108 e.g. a conventional differential, and driveshafts 104, 105 which are connected to said final gear 108.
  • the vehicle 100 further comprises a post-treatment (exhaust cleaning) system 200 for treatment (cleaning) of exhaust emissions arising from combustion in the engine's combustion chambers (e.g. cylinders).
  • the post-treatment system is depicted in more detail in Fig. 2, showing the vehicle's engine 101 from which the exhaust gases (the exhaust flow) generated by the combustion being led through a turbo unit 220.
  • turbo engines the exhaust flow arising from the combustion often drives a turbo unit which compresses the incoming air for the combustion in the
  • turbo unit may for example be of compound type.
  • the function of various kinds of turbo unit is well-known and is therefore not described in more detail here.
  • the exhaust flow is then led via a pipe 204 (indicated by arrows) to a diesel particle filter (diesel particulate filter, DPF) 202 via an oxidation catalyst (diesel oxidation catalyst, DOC) 205.
  • DPF diesel particulate filter
  • DOC oxidation catalyst
  • the oxidation catalyst DOC 205 has various functions and is normally used primarily, as part of the post-treatment, to oxidise remaining hydrocarbons and carbon monoxide in the exhaust flow to carbon dioxide and water.
  • the oxidation of hydrocarbons i.e. oxidation of fuel results also in the formation of heat which may be utilised to raise the
  • the oxidation catalyst may also oxidise to nitrogen dioxide (N0 2 ) a large proportion of the nitrogen monoxides (NO) present in the exhaust flow.
  • N0 2 nitrogen dioxide
  • NO nitrogen monoxides
  • the post-treatment system further comprises an SCR (selective catalytic reduction) catalyst 201 situated downstream of the particle filter 202.
  • SCR catalysts use ammonia (NH 3 ) , or compounds from which ammonia may be generated/formed, as additive to reduce the amount of nitrogen oxides NO x in the exhaust flow. The effectiveness of this reduction does however depend on the ratio between NO and NO2 in the exhaust flow, so this reaction too is adversely affected by lowered O2 conversion .
  • the components DOC 205, DPF 202 and the SCR catalyst 201 are integrated in a combined exhaust cleaning unit. It should however be noted that these components DOC 205, DPF 202 and the SCR catalyst 201 are integrated in a combined exhaust cleaning unit. It should however be noted that these components DOC 205, DPF 202 and the SCR catalyst 201 are integrated in a combined exhaust cleaning unit. It should however be noted that these components DOC 205, DPF 202 and the SCR catalyst 201 are integrated in a combined exhaust cleaning unit. It should however be noted that these
  • Fig. 2 shows also temperature sensors 210-212 and a differential pressure sensor 209.
  • Control systems in modern vehicles generally comprise a
  • ECUs electronice control units
  • controllers 115, 208 electronice control units
  • Such a control system may comprise a large number of control units and the responsibility for a specific function may be shared by two or more of them. For the sake of simplicity, only control units 115 and 208 appear in Figs. 1A-B.
  • control unit 208 which in the embodiment depicted takes care as above of other functions in the post- treatment system, e.g. the regeneration (emptying) of the particle filter 202, although the invention might equally well be implemented in a control unit dedicated to it, or wholly or partly in one or more other control units with which the vehicle is already provided, e.g. the engine control unit 115.
  • the function according to the present invention of control unit 208 (or the control unit or units in which the present invention is implemented) will depend not only on signals from one or more of the temperature sensors 110-112 but probably also on, for example, information received from, for example, the control unit or units which control engine functions, i.e. in the present example control unit 115.
  • Control units of the type depicted are normally adapted to receiving sensor signals from various parts of the vehicle.
  • Control unit 208 may for example receive sensor signals as above and also from other control units than the engine control unit 115.
  • Such control units are also usually adapted to delivering control signals to various parts and components of the vehicle, e.g. control unit 208 may for example deliver signals to the engine control unit 115.
  • Control is often governed by programmed instructions
  • the computer programme usually forms part of a computer programme product which comprises a digital storage medium 121 (see Fig. IB) which has the computer programme 109 stored on it and may for example take the form of any from among ROM (read-only memory) , PROM (programmable read-only memory) , EPROM (erasable PROM) , flash memory, EEPROM (electrically erasable PROM), a hard disc unit etc., and be situated in or in communication with the control unit, in which case the computer programme is executed by the control unit.
  • ROM read-only memory
  • PROM programmable read-only memory
  • EPROM erasable PROM
  • flash memory erasable PROM
  • EEPROM electrically erasable PROM
  • control unit 208 depicted
  • a calculation unit 120 may for example take the form of any suitable kind of processor or microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP) , or a circuit with a predetermined specific function (Application Specific
  • the calculation unit is connected to a memory unit 121 which provides it with, for example, the stored programme code 109 and/or the stored data which the calculation unit needs for it to be able to perform
  • the calculation unit is also arranged to store partial or final results of calculations in the memory unit 121.
  • the control unit is further provided with respective devices 122, 123, 124, 125 for receiving and sending input and output signals. These signals may comprise waveforms, pulses or other attributes which the input signal receiving devices 122, 125 can detect as information for processing by the
  • the output signal sending devices 123, 124 are arranged to convert calculation results from the calculation unit 120 to output signals for conveying to other parts of the vehicle's control system and/or the
  • Each of the connections to the respective devices for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus or some other bus configuration, or a wireless connection.
  • a data bus e.g. a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus or some other bus configuration, or a wireless connection.
  • a data bus e.g. a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus or some other bus configuration, or a wireless connection.
  • CAN Controller Area Network
  • MOST Media Oriented Systems Transport
  • soot particles are captured by the particle filter 202, which works in such a way that the exhaust flow is led through a filter structure whereby soot particles are captured from the passing exhaust flow in order to be stored in the filter.
  • the filter makes it possible for a very large proportion of the particles to be separated from the exhaust flow.
  • the particles separated from the exhaust flow from the filter 202 progressively accumulate in the filter, which thus fills with soot over time.
  • soot /particles will take place more or less quickly, but when the filter reaches a certain level of fullness it needs to be "emptied". If the filter is filled to too high a level, the vehicle's performance may be affected, while at the same time fire hazards may also arise from soot accumulation in
  • the emptying of the particle filter 202 is effected by regeneration whereby soot particles, carbon particles, take part in a chemical process. Over time, the filter is
  • determination of suitable times for regenerating it may for example be by means of a control unit 208 which may for example determine appropriate times at least partly on the basis of signals from a pressure sensor 209 which measures the differential pressure across the filter. The fuller the filter becomes, the higher the pressure difference across it.
  • Regeneration may be conducted in mainly two different ways.
  • One is so-called oxygen (0 2 ) based regeneration, also called active regeneration, involving a chemical process
  • Oxygen-based regeneration thus converts carbon plus oxygen gas to carbon dioxide plus heat.
  • This chemical reaction is highly temperature-dependent and requires high particle filter temperatures to enable appreciable rates of reaction to take place at all.
  • the temperature tolerance of the components of the exhaust system is often limited, which means that active regeneration may be subject to a maximum permissible temperature which is low relative to the
  • the particle filter 202 and/or any downstream SCR catalyst are for example often subject to design limits with regard to the maximum temperature to which they may be allowed to be exposed.
  • N0 2 + C NO + CO.
  • N0 2 -based regeneration is highly dependent specifically on 0 2 .
  • N0 2 - based regeneration affords the advantage that desired reaction rates, and hence the rate at which the filter is emptied, may be achieved at substantially lower temperatures.
  • N0 2 -based regeneration of particle filters typically takes place at temperatures within the range 200-500°C, although temperatures in the upper part of this range are normally preferable.
  • Fig. 3 illustrates an example of regeneration (soot burn-out) rates in N0 2 -based regeneration as a function of the amount of soot in the particle filter in operating situations at two different temperatures (350°C and 450°C).
  • the regeneration rate is also exemplified for respective low and high
  • the burn-out rate is low at low temperature (350°C) and low concentration of nitrogen dioxide.
  • the temperature- dependency of the regeneration rate is indicated by the fact that the burn-out rate is relatively low even at high
  • the burn-out rate is substantially higher at 450°C even in cases where a low concentration of nitrogen dioxide prevails, but a high temperature in combination with high contents of N0 2 is preferable.
  • passive regeneration depends not only on the temperature of the particle filter and the amount of soot as in Fig. 3 and as indicated by the chemical processes above, but also on the supply of nitrogen dioxide.
  • the proportion of nitrogen dioxide N0 2 to the total amount of nitrogen oxides NO x generated by the engine's combustion amounts to only 0 - 10% of the total amount of nitrogen oxides NO x in the exhaust flow.
  • the proportion of N0 2 may even be as low as 2 - 4%.
  • the burn-out rate (the regeneration rate) thus increases with the amount of N0 X in the exhaust flow, the temperature of the exhaust flow (the temperature of the particle filter) and the prevailing amount of soot in the filter.
  • the NO 2 content of the total amount of NO x in the exhaust flow may be markedly increased by means of the oxidation catalyst 205, whereby the resulting NO 2 content after the oxidation catalyst depends greatly on the temperature.
  • the conversion of NO to NO 2 by means of the oxidation catalyst depends not only on the temperature of the catalyst but also on whether it has been poisoned by undesirable coating.
  • the temperature of the exhaust flow arising from the combustion will vary. If the engine is working hard, the exhaust flow will maintain a higher temperature, whereas when the vehicle is running with a relatively low load upon the engine the temperature of the exhaust flow will be substantially lower. If the vehicle is run for a lengthy period in such a way that the temperature of the exhaust flow stays relatively low, e.g. below 300-350°C, degradation of the function of the oxidation catalyst will occur because the sulphur in various forms which is usually present in the fuel reacts with the active coating, which usually comprises one or more noble or other suitable metals, e.g. aluminium. This has adverse effects upon the active coating.
  • the sulphur may react with the coating and may for example form sulphates, e.g. aluminium sulphate, platinum sulphate and palladium sulphate, depending on which type of metal is present in the coating. These sulphates occupy the surface of the active coating and prevent desired reactions, e.g. oxidation of NO to N0 2 . Compared with the case of an oxidation catalyst which is not affected, N0 2 conversion in an oxidation catalyst with sulphur coating will therefore deliver a lower proportion of N0 2 in otherwise similar conditions.
  • sulphates e.g. aluminium sulphate, platinum sulphate and palladium sulphate
  • the reduced NO2 conversion may also have further disadvantages.
  • the post-treatment system may as above comprise an SCR
  • the SCR catalyst usually situated downstream of the oxidation catalyst and the particle filter.
  • the SCR catalyst depends for its function on a good supply of O2 to enable the overall N0 2 conversion in the post-treatment system to fulfil stated requirements.
  • oxidation catalyst without risk of damage to downstream components which are more temperature-sensitive.
  • a method 500 illustrated in Fig. 5 beginning with a step 501 of determining whether unacceptable sulphur coating of the oxidation catalyst has occurred, which may be done in various different ways. It may for example be determined during the course of an N0 2 -based regeneration that the regeneration rate is unacceptably low. This determination may for example be by means of the differential pressure sensor 209 depicted in Fig. 2 which measures the differential pressure across the particle filter 202.
  • the differential pressure across the particle filter will decrease progressively as the filter is emptied of soot particles and the throughflow resistance therefore decreases. If this differential pressure decrease takes place more slowly than expected during regeneration, which may for example be determined by comparing the rate of decrease relative to the prevailing regeneration conditions, it may be determined that the regeneration rate is unacceptably low despite prevailing temperature conditions, indicating sulphur coating in the oxidation catalyst.
  • Whether sulphur coating has occurred or not may also be determined in other ways. It is for example possible to use suitable models to estimate a degree of sulphur coating on the basis of the type of fuel used and a temperature history representing for example that of the oxidation catalyst. As mentioned above, the lower the temperature of the oxidation catalyst, the more quickly sulphur coating will take place. The sulphur coating rate depends also on the exhaust flow, and the greater the flow the more quickly will the active surfaces of the oxidation catalyst be coated with sulphur. Sulphur coating of the oxidation catalyst may also be determined in other suitable ways.
  • step 501 determines that sulphur coating in the oxidation catalyst has occurred, e.g. to some appropriate extent which may for example be controlled by regeneration rate, calculated coating or the like as above, the method moves on to step 502 for determination of a temperature T of the post-treatment system 200, e.g. a temperature representing that of the oxidation catalyst 205. This temperature is then compared at step 503 with a minimum temperature T3 at which oxidation of unburnt fuel to a desired extent in the oxidation catalyst is regarded as possible. If the post-treatment system temperature T (the oxidation catalyst temperature) is below said temperature T3, the method moves on to step 504 to try by engine control to achieve this oxidation catalyst temperature. It is in principle sufficient that the oxidation catalyst reaches a temperature of about 250°C. When engine control has begun, the method goes back to step 502 to see whether a desired temperature has been reached.
  • a temperature T of the post-treatment system 200 e.g. a temperature representing that of the oxidation catalyst
  • the oxidation catalyst temperature is above said minimum temperature T3, which may therefore be of the order of about 250°C, and oxidation of unburnt fuel in the oxidation catalyst to a desired extent is therefore regarded as
  • a raising of the temperature of the oxidation catalyst commences, which may be achieved as described below. Its temperature needs to be over 400°C to enable the
  • the binding of the sulphur to the metals of the coating may thus be broken, which may at least partly be by the oxidation of hydrocarbons (fuel) reacting with oxygen atoms in, for example, sulphates so that sulphur in new molecule form becomes detached from the catalyst coating and is then carried by the exhaust flow through the post-treatment system and/or becomes attached again downstream of the previous location.
  • the chemical process in this respect may be conducted in various ways and is not described in more detail here, but when the bonding of the sulphur with the coating metal is broken the released/newly formed sulphur molecule, e.g.
  • sulphur dioxide sulphuric acid or sulphite
  • sulphur dioxide is carried by the exhaust flow out of the oxidation catalyst or becomes attached again.
  • the same sulphur atom may become attached and be released many times during its passage through the post- treatment system.
  • Heating may thus result in the oxidation catalyst being detoxified and recovering its original performance as regards NO2 conversion.
  • the desulphuration process follows the Arrhenius equation, so the process rate increases with rising temperature. In other words, for best desulphuration effectiveness, as high a temperature as possible needs to be achieved in the oxidation catalyst. As mentioned above, however, there are often different temperature tolerances with respect to the
  • the temperature rise is achieved by supplying unburnt fuel to the exhaust flow, in which, since the temperature T of the oxidation catalyst is above said minimum temperature T3, it then at least partly oxidises, with the associated release of heat.
  • Step 505 therefore determines an appropriate amount of fuel for supply to the exhaust flow, and fuel injection then commences.
  • the amount of fuel supplied may for example depend on oxidation catalyst temperature, current volume of exhaust flow, engine load, current vehicle speed etc., or may also be some predetermined constant amount, in which case the supply of fuel is controlled on the basis of the oxidation catalyst's temperature T with the object of reaching a first temperature Tl, the supply of fuel being halted when a desired first oxidation catalyst temperature Tl is or will be reached.
  • the supply of unburnt fuel to the exhaust flow may take place in various different ways, e.g. the post-treatment system may comprise, in the exhaust system upstream of the oxidation catalyst, an injector (not depicted) which may be used to inject fuel into the exhaust flow.
  • an injector not depicted
  • fuel may be supplied to the exhaust flow by injection in the engine's combustion chambers (e.g. the engine's cylinders) so late during the combustion cycle that none or only some of the fuel intended for the regeneration burns in the cylinders, in which case fuel will accompany the exhaust flow to the post-treatment system.
  • the present invention is suited to both types of fuel injection.
  • step 506 determines whether the oxidation catalyst's temperature T is above a first temperature Tl which is substantially higher than said minimum temperature T3.
  • This first temperature Tl would result in the possibility of downstream components being damaged by reaching it.
  • a cyclic raising of the temperature is effected for the component where sulphur storage has been found, i.e. in this case the oxidation catalyst 205, and the cyclic temperature rise means that the temperature of downstream components will not rise to
  • step 505 the method goes back to step 505 to continue fuel supply. If Tl is reached, the supply of fuel to the exhaust flow is halted and the method moves on to step 507 to
  • Said first temperature Tl and said second temperature T2 are determined/chosen such that the temperature at components situated downstream of the oxidation catalyst, e.g. the particle filter 202 and the SCR catalyst 201, will not rise above permissible levels.
  • Said first temperature Tl is preferably set to a level which is as high as possible but which, in combination with the lowering of the oxidation catalyst' s temperature T to the chosen second level T2, provides assurance that the
  • the most temperature-sensitive component in the present example may be the SCR catalyst 201, and the method according to the invention makes it possible to ensure that the temperature after the particle filter/at the SCR catalyst's inlet 203 does not reach unacceptable levels.
  • Said second temperature T2 may be determined/chosen on the basis of calculation/modelling of a temperature pattern for the oxidation catalyst 205 and/or appropriate temperatures at components situated downstream of the oxidation catalyst, e.g. the particle filter 202 and the SCR catalyst 201.
  • said second temperature T2 may be determined/chosen on the basis of measurements of temperature pattern of the oxidation catalyst and/or appropriate temperatures at components situated
  • the oxidation catalyst e.g. the particle filter and the SCR catalyst.
  • Said second temperature T2 is determined/chosen such as to provide assurance that when the method according to the invention is employed the temperature at components situated downstream of the oxidation catalyst, e.g. the particle filter and the SCR catalyst, will not rise above permissible levels.
  • Step 508 determines whether the desulphuration has been completed. If such is the case, the method ends at step 509. This determination may be done in any suitable way, e.g. by determining the amount of time t for which desulphuration has proceeded, and stopping it when it has proceeded for at least an appropriate first amount of time tl. Alternatively, this may for example be determined by a requirement that heating to the temperature Tl must take place a certain number of times. The determination may also be based on the differential pressure change across the particle filter during an attempted regeneration.
  • the differential pressure decrease which occurs during regeneration over for example a certain amount of time has to be of at least some appropriate magnitude, otherwise the regeneration rate is regarded as too slow and desulphuration is therefore not regarded as effected to the desired extent.
  • the method according to the present invention affords the advantage that a higher desulphuration rate may be achieved by raising the oxidation catalyst's temperature T to a first level Tl which is above a temperature tolerance of at least one of the components situated downstream of the
  • oxidation catalyst e.g. the particle filter 202 and the SCR catalyst 201, in the post-treatment system 200. Stopping this temperature rise when the temperature Tl is reached, i.e.
  • Pulsing the oxidation catalyst's temperature T thus makes it possible locally to allow substantially higher temperatures, with associated increase in reaction rate, while at the same time this heat wave will be damped by subsequent portions of the oxidation catalyst and, for example, a particle filter 202, so that for example an SCR catalyst 201 situated downstream of the filter is exposed to a substantially lower temperature than the oxidation catalyst.
  • the method according to the present invention may thus be used to raise the maximum temperature in the oxidation catalyst by a relatively large number of degrees without neglecting other requirements, while at the same time also creating potential for desorbing as much stored sulphur as possible.
  • the SCR catalyst 201 represents the temperature after the particle filter 202 and hence at the inlet to the SCR catalyst.
  • the SCR catalyst 201 will be exposed to a substantially lower temperature than the oxidation catalyst because of the damping to which the heat wave is subjected by the thermal inertia of the components.
  • the engine 101 may also be adjusted to run at different lambda values.
  • the engine is run at the least possible lambda, in which case fuel is then supplied as far as possible without exceeding temperature requirements for arriving at nearly stoichiometric ratios. This may entail keeping the oxygen level at the inlet to the oxidation catalyst to a minimum, in which case
  • hydrocarbons will to the greatest possible extent react with oxygen atoms in sulphur/metal combinations.
  • said engine and/or fuel supply are controlled in such a way as to achieve a lambda value below 1.5 at the inlet to the oxidation catalyst.
  • metal/sulphur disassociate and are desorbed at different rates .
  • the rate at which the temperature T is raised which may be varied by the rate at which fuel is supplied, and lambda values may be adapted according to the metals present in the post-treatment system in order to achieve as optimum
  • the invention is exemplified above in relation to the system depicted in Fig. 2.
  • the post-treatment system set-up depicted in Fig. 2 is commonly employed in heavy vehicles, at least in jurisdictions where stricter emission requirements prevail.
  • the particle filter comprises instead noble metal coatings so that the chemical processes taking place in the oxidation catalyst take place instead in the particle filter, in which case the post-treatment system will therefore not have a DOC.
  • the invention is nevertheless applicable here too, with for example the temperature Tl adapted to suit this system instead.
  • the post-treatment system 200 may also comprise more
  • components than exemplified above, e.g. it may, in addition to, or instead of, said DOC 205 and/or SCR 201, comprise an ASC (ammonia slip catalyst) (not depicted) , in which case appropriate temperature adaptation may here too be effected.
  • ASC ammonia slip catalyst
  • the present invention is exemplified above in relation to vehicles.
  • the invention is nevertheless also applicable to any other means of transport /processes in which particle filter systems as above are applicable, e.g. watercraft or aircraft with combustion processes as 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)
  • Processes For Solid Components From Exhaust (AREA)

Abstract

La présente invention concerne un procédé de désulfuration d'un système de post-traitement (200), ledit système servant à traiter un flux de gaz d'échappement produit par la combustion dans un moteur à combustion (101) et comprenant au moins un premier composant (202, 205). Quand le soufre s'est accumulé dans ledit premier composant (202, 205) du système de post-traitement (200), le procédé comporte les étapes consistant à : augmenter la température (T) dudit premier composant (202, 205) en fournissant du carburant au flux de gaz d'échappement afin de produire une oxydation dans le système de post-traitement (200), arrêter de fournir du carburant au flux de gaz d'échappement quand la température (T) du premier composant (202, 205) atteint un premier niveau (T1), et fournir à nouveau du carburant au système de post-traitement (200) pour produire une oxydation quand la température (T) du premier composant (202, 205) est tombée à un deuxième niveau (T2), inférieur au premier niveau (T1).
PCT/SE2012/051446 2011-12-28 2012-12-20 Procédé et système pour la désulfuration d'un système de post-traitement WO2013100845A1 (fr)

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SE1251468A SE1251468A1 (sv) 2011-12-28 2012-12-20 Förfarande och system för avsvavling av ett efterbehandlingsssystem

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113790094A (zh) * 2021-09-29 2021-12-14 潍柴动力股份有限公司 一种后处理***硫中毒确定方法、装置、车辆及介质

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070006573A1 (en) * 2005-07-07 2007-01-11 Eaton Corporation Thermal management of hybrid LNT/SCR aftertreatment during desulfation
US20070012032A1 (en) * 2005-07-12 2007-01-18 Eaton Corporation Hybrid system comprising HC-SCR, NOx-trapping, and NH3-SCR for exhaust emission reduction
FR2933445A1 (fr) * 2008-07-01 2010-01-08 Renault Sas Gestion combinee de la regeneration et de la desulfuration pour vehicule automobile
US20100126150A1 (en) * 2008-11-21 2010-05-27 Hyundai Motor Company Diesel Oxidation Catalyst and Exhaust System Provided with the Same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070006573A1 (en) * 2005-07-07 2007-01-11 Eaton Corporation Thermal management of hybrid LNT/SCR aftertreatment during desulfation
US20070012032A1 (en) * 2005-07-12 2007-01-18 Eaton Corporation Hybrid system comprising HC-SCR, NOx-trapping, and NH3-SCR for exhaust emission reduction
FR2933445A1 (fr) * 2008-07-01 2010-01-08 Renault Sas Gestion combinee de la regeneration et de la desulfuration pour vehicule automobile
US20100126150A1 (en) * 2008-11-21 2010-05-27 Hyundai Motor Company Diesel Oxidation Catalyst and Exhaust System Provided with the Same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113790094A (zh) * 2021-09-29 2021-12-14 潍柴动力股份有限公司 一种后处理***硫中毒确定方法、装置、车辆及介质

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