WO2013100846A1 - Procédé et système pour réduire des dépôts dans un système de post-traitement - Google Patents

Procédé et système pour réduire des dépôts dans un système de post-traitement Download PDF

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Publication number
WO2013100846A1
WO2013100846A1 PCT/SE2012/051448 SE2012051448W WO2013100846A1 WO 2013100846 A1 WO2013100846 A1 WO 2013100846A1 SE 2012051448 W SE2012051448 W SE 2012051448W WO 2013100846 A1 WO2013100846 A1 WO 2013100846A1
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WIPO (PCT)
Prior art keywords
content
coating
reduction
compound
catalyst
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PCT/SE2012/051448
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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 EP12861669.5A priority Critical patent/EP2798168B1/fr
Publication of WO2013100846A1 publication Critical patent/WO2013100846A1/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
    • F01N3/10—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
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • 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]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • 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]
    • 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
    • F01N9/00—Electrical control of exhaust gas treating 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • 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
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • 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
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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 an exhaust flow 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.
  • a commonly applied way to post-treat exhaust gases from a combustion engine is a so-called catalytic cleaning process, so vehicles equipped with a combustion engine are usually also provided with at least one catalyst.
  • catalysts there are various types of catalysts, since different types may be required for different fuels and/or to clean different types of pollutants in the exhaust flow, and with regard at least to nitrous gases (nitrogen monoxide, nitrogen dioxide) , hereinafter called nitrogen oxides N0 X heavy vehicles are often provided with a catalyst where an additive is supplied to the exhaust flow
  • SCR selective catalytic reduction
  • SCR catalysts usually use ammonia (NH 3 ) , or a compound from which ammonia may be generated/formed, as additive for reduction of the amount of nitrogen oxides (NO x ) .
  • the additive is injected, upstream of the catalyst, into the exhaust flow arising from the engine.
  • the additive supplied to the catalyst is adsorbed (stored up) in the catalyst, and nitrogen oxides in the exhaust gases react with the additive stored in the catalyst.
  • An object of the present invention is to propose a method for reduction of at least one coating in a post-treatment system. This object is achieved by a method according to the
  • the present invention relates to a method for reduction of a first coating in a post-treatment system which is intended to treat an exhaust flow arising from combustion in a combustion engine, said first coating being formed by an additive
  • the method at commencement of reduction of said first coating, comprises
  • the present invention is thus applicable in post-treatment systems where an additive is supplied to the exhaust flow.
  • SCR systems are an example of such a system.
  • These types of systems have certain disadvantages.
  • One problem with for example SCR systems and injecting their additives, e.g. urea or AdBlue, is that the supply of additive may cause a coating build-up such as a crystal build-up, e.g. of urea, in the post-treatment system, e.g. in pipes/catalysts/silencers at or downstream of the location where the injection takes place.
  • the coating may for example take the form of a urea build-up or a build-up of a combination from/with which urea may form.
  • the coating may also damage components of the post- treatment system if for example crystal formations, e.g. in the form of lumps, become detached from the location where they have formed and are then carried by the exhaust flow to, for example, a downstream SCR catalyst.
  • the build-up of the coating may for example occur when for example a vehicle and hence its combustion engine run in static conditions, e.g. if for example a vehicle is run for a lengthy period in such a way that the resulting exhaust flow temperature is kept relatively low.
  • the present invention prevents this by determining a first content of at least one compound which is normally reduced by using the additive, which content is determined at a location downstream of said first catalyst. Comparing this first content with a second content which may be a
  • An SCR catalyst usually reduces nitrogen oxides NO x comprising mainly nitrogen monoxide and nitrogen dioxide.
  • NO x comprising mainly nitrogen monoxide and nitrogen dioxide.
  • the additive stored in the crystals will react with the passing exhaust flow so that a reduction of said first compound continues to take place to a certain extent.
  • the content of said first compound will rise and eventually reach undesirable and, in cases where emissions of said first compound are regulated, perhaps even impermissible levels.
  • the invention prevents this by monitoring the content of said first compound in the exhaust flow discharged and taking a remedial measure to lower the content of the first compound when the emission becomes undesirably large.
  • the remedial measure is taken so that the content of said first compound downstream of said first catalyst is reduced.
  • the remedial measure may for example take the form of
  • the engine may be controlled so that a lower content is delivered. Controlling the content delivered by the engine may be
  • an amount of additive may be supplied to lower said first content, the amount supplied being less than that normally required for reducing the content of said first compound when there is no contribution to the reduction from burning of the coating.
  • 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 a dosing system for supply of additive to the exhaust flow.
  • Fig. 4 depicts a method according to an embodiment example of the present invention.
  • Fig. 5 depicts an example of a time pattern for released
  • Fig. 6 depicts an example of a time pattern for the content of nitrogen oxides N0 X generated by the engine's combustion according to an embodiment of 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.
  • 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
  • Combustion in the engine results in the formation of soot particles, and the particle filter 202 is used to intercept them.
  • 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 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, e.g. urea, as additive to reduce the amount of nitrogen oxides NO x in the exhaust flow.
  • NH 3 ammonia
  • urea compounds from which ammonia may be generated/formed, e.g. urea
  • the post-treatment system may generally be of various kinds and for example need not comprise a particle filter 202 or an oxidation catalyst 205 so long as the post-treatment system is of a type which supplies additive to a catalytic exhaust cleaning process, as in the case of said SCR catalyst 201.
  • the post-treatment system may also comprise further undepicted components, e.g. an ASC (ammonia slip catalyst) .
  • the components DOC 205, DPF 202 and the SCR catalyst 201 may also be integrated in a combined exhaust cleaning unit or be separate units.
  • the SCR catalyst requires additive to reduce the concentration of a first compound such as nitrogen oxides in the exhaust gases from the engine.
  • This additive is often urea-based, e.g. in the form of AdBlue, which is in principle urea diluted with water. Urea forms ammonia when heated .
  • FIG. 3 An example of a system for supply of additive is depicted in more detail in Fig. 3 showing from among the above components only the particle filter 202 and the SCR catalyst 201, which system comprises as well as said SCR catalyst a urea tank 302 connected to a urea dosing system (UDS) 303.
  • UDS urea dosing system
  • the UDS system comprises or is controlled by a UDS control unit 304 which generates control signals to control the supply of additive so that by means of an injection nozzle 305 upstream of the SCR catalyst desired amounts of additive are injected from the urea tank 302 into the exhaust flow arising from the combustion in the cylinders of the engine 101.
  • Fig. 3 also shows an NO x sensor 308 situated downstream of the SCR catalyst .
  • injection points/SCR catalysts needs to be at least 200-250°C, preferably over 300°C, to achieve desired reaction rates and hence desired reduction of said first compound, e.g. one or more types of nitrogen oxides.
  • this crystal build-up will not grow unacceptably large before the crystals are burnt away by the passing exhaust flow. If conversely the vehicle runs for a time in relatively static conditions at relatively light loads, resulting in low temperatures in the exhaust system, this crystal build-up may proceed until the vehicle' s
  • the crystal build-up may also affect the ability of the SCR system to convert N0 X if the supply of urea (e.g. spray pattern, amount) is disrupted by a coating in lump form. In such situations, remedial measures have therefore to be taken to prevent problems of far-reaching crystal build-up.
  • the crystal build-up may be reduced by raising the temperature of the exhaust flow while at the same time halting the supply of additive. During this reduction of crystals, however, increased and unacceptable emissions of said first compound, e.g. ⁇ , may occur.
  • the present invention proposes a method for preventing such unacceptable emissions.
  • a method example 400 according to the invention is illustrated in Fig. 4.
  • Control systems in modern vehicles generally consist of a communication bus system comprising one or more communication buses to connect a number of electronic control units (ECUs), e.g. the control units or controllers 115, 208, 304 to various components on board the vehicle.
  • ECUs electronice control units
  • Such a control system may comprise a large number of control units, and taking care of a specific
  • control unit 208 which in this embodiment also takes care of other functions in the post-treatment system. It may for example take care of so-called regeneration, i.e. emptying of the particle filter 202. Control unit 208 may also take care of urea injection, i.e. the function which as above is performed by control unit 304.
  • control unit 208 may depend on signals from one or more NOx sensors 210, 308, and also on one or more temperature sensors 211-212 for determination of temperatures in the post- treatment system.
  • control unit will probably also depend 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.
  • the method example 400 illustrated begins at step 401 by determining whether a reduction of coating, in this example a reduction of said crystal build-up, should commence. This determination is not of itself subject matter of the present invention and may be conducted in any suitable way. It is for example possible to make an estimate of the crystal build-up. Determining or estimating for example a temperature at the point/region where the additive is injected, or some other suitable location, makes it
  • this temperature as a basis for estimating an expected crystal build-up which may for example be determined by table consultation or appropriate calculation.
  • Calculation of said expected value may for example be by means of a suitable calculation model, and different calculation models may for example be used to represent different
  • the calculation model may for example take account of the volume of the exhaust flow, the amount/mass flow of additive supplied etc.
  • the model may for example be set up on the basis of practical tests or be arrived at in some other way.
  • the temperature at for example the location where the additive supplied encounters surrounding pipes or the like may be determined by means of any available temperature sensors or by means of a temperature model based for example on the
  • the calculation model may be refined by for example also taking account of further circumstances, e.g. outside temperature and vehicle speed.
  • One embodiment determines alternatively or additionally whether a predetermined operating state of said vehicle is fulfilled which relates to a state in which there is increased risk of coating build-up in the exhaust system, and if said state is fulfilled then at least one remedial measure is taken to counter the coating build-up.
  • Said operating state may for example be based on parameters as above, or it is for example possible to determine whether the vehicle has been running "statically" for a certain time. Such determination of the need for reduction of such coatings is described in
  • step 401 If it is determined at step 401 that the amount of additive which has crystallised and has formed a coating, e.g. a certain weight, exceeds some suitable amount/weight, e.g. a certain number of grams, the method moves on to step 402 to commence reduction/burning of the coating.
  • some suitable amount/weight e.g. a certain number of grams
  • the temperature in the post-treatment system is raised.
  • the supply of additive is halted.
  • the supply of additive is not halted until the temperature in the post-treatment system reaches a first temperature which is set at any suitable level, such as a suitable temperature within the range 250-400°C, e.g. within the range 300-350°C.
  • the crystal reduction is accelerated by the method according to the invention by the engine being set to deliver relatively high contents of nitrogen oxides (NO x HIGH ) in order to speed up reactions between the crystal build-up and passing nitrogen oxides.
  • the engine in one embodiment it is for example possible at step 402 for the engine to be set to deliver a relatively high NO x level (NO X HI G H ) , e.g. 1000-2000 ppm or a suitable content/level over 2000 ppm (it is generally the case that the ratio between emissions of nitrogen oxides NO x from a combustion engine is such that increased NO x most often results in better
  • a relatively high NO x level NO X HI G H
  • a relatively high NO x level e.g. 1000-2000 ppm or a suitable content/level over 2000 ppm
  • the temperature rise as above may for example be achieved by supplying the exhaust flow with unburnt fuel which then at least partly oxidises, with consequent release of heat. This oxidation may for example take place in the oxidation catalyst 205 or the particle filter 202 or in some other suitable way. Before unburnt fuel is supplied to the exhaust flow, it is possible to verify for example that the oxidation catalyst temperature is above a minimum level so that oxidation
  • the engine may first be directed to an operating mode of low efficiency and consequently deliver higher exhaust temperatures with the object of raising the temperature in the post-treatment system to a level which causes oxidation of fuel supplied.
  • the amount of fuel supplied may for example depend on such parameters as the temperature of the oxidation catalyst, current volume of exhaust flow, engine load, current vehicle speed etc. and/or be controlled so that desired temperatures are reached in the post-treatment system.
  • the supply of unburnt fuel to the exhaust flow may be effected in various different ways.
  • the post-treatment system may for example be provided with an injector in the exhaust system upstream of the oxidation catalyst, in which case fuel may injected into the exhaust flow by means of the injector.
  • fuel may be supplied to the exhaust flow by injection into the engine's combustion chambers at a late stage in the combustion cycle so that none or only some of the fuel intended for the regeneration burns in the cylinders, in which case unburnt fuel will accompany the exhaust flow to the post-treatment system. Raising the temperature in the post-treatment system and hence in the region or regions where crystal build-up has occurred will result in the crystals being burnt by the passing exhaust flow and the build-up thereby decreasing. During the burning of the crystals, ammonia/urea will be released and nitrogen oxides NO x will therefore continue to be reduced as above even if the supply of further additive is shut off.
  • Fig. 5 How the amount/content of reducing agent released by the crystal varies over time is illustrated in Fig. 5.
  • the temperature rise in the post-treatment system begins at time TO, at which stage the amount /content of reducing agent released by burning R0 is substantially zero.
  • time Tl the temperature in the post-treatment system has risen to such a high level that the amount/content of reducing agent released during the burning begins to increase
  • Step 403 determines a first content of a first compound, in this case an NO x content Hi downstream of the SCR catalyst 201, by means of the NO x sensor 308.
  • This NO x content is then compared at step 404 with a predetermined second NO x content H 2 which is set at any suitable value. It is for example
  • said second NO x content H 2 can be set at any suitable value within the range 200-500 ppm. So long as the NO x content Hi determined at step 403 is below said second NO x content H 2 , the method stays at step 404. When conversely the NO x content Hi determined is greater than said second NO x content H 2 , which with reference to Fig. 5 may for example occur at time T3, the method moves on to step 405 to take at least one remedial measure in order to lower said first NO x content Hi to a below said second content H 2 .
  • Figure 6 illustrates in one embodiment of the invention how the engine's combustion is controlled in such a way that the proportion of nitrogen oxides NO x generated during the
  • Times T0-T4 in Figure 6 correspond to times T0-T4 in Figure 5.
  • the engine' s combustion is controlled in such a way that the proportion of nitrogen oxides generated during the combustion is any suitable content NO x l.
  • the engine' s combustion is controlled in such a way that the proportion of nitrogen oxides generated during the combustion is a relatively high content NO x HIGH.
  • the crystal reduction is here accelerated by the method according to the invention by the engine being set to deliver relatively high nitrogen oxide contents NO x HIGH and thereby speed up reactions between the crystal build-up and passing nitrogen oxides.
  • the engine's combustion is controlled in such a way that the proportion of nitrogen oxides generated during the combustion increases stepwise or
  • the engine's combustion is controlled in such a way that the proportion of nitrogen oxides generated during the combustion increases stepwise or gradually/continuously all the way from time TO to reach at time T2 the relatively high content NO x HIGH.
  • the content of nitrogen oxides in the exhaust flow discharged from the post-treatment system must not reach too high levels. If for example the O 2 content of the exhaust flow emitted amounts to or exceeds levels of the order of 300-500 ppm, nitrogen dioxide NO 2 released will generate a yellowish brown- red smoke which not only looks repulsive but also adversely affects the environment by forming undesirable compounds by reactions with the surroundings. There may also be statutory emission levels not to be exceeded. According to the present invention, remedial measures are therefore taken to regulate the discharge of nitrogen oxides NO x even during crystal reduction.
  • the engine's combustion may for example be
  • the engine may be set to deliver during reduction of the crystal build-up high contents of nitrogen oxides in order to accelerate the reduction.
  • one remedial measure may thus be to reduce the nitrogen oxide content delivered by the engine Hi to a level at which the content determined by the NOx sensor 308 is not greater than said second content H 2 .
  • the reduction may for example be achieved by continuous regulation to provide continual assurance that desired levels delivered from the vehicle 100 are not exceeded.
  • the engine's combustion may be controlled in such a way that the proportion of nitrogen oxides NO x generated during the combustion
  • combustion may be controlled in such a way that the proportion of nitrogen oxides N0 X generated during the combustion
  • the engine's combustion may be controlled in such a way that the proportion of nitrogen oxides NO x generated during the combustion at time T3 decreases
  • Said relatively low content NO x LOW may be less than 400 ppm. It may be within the range 100-300 ppm. It may be less than 300 ppm. It may be less than 100 ppm. It may depend on current legal requirements regarding emissions and may be determined/specified at least partly on the basis of said legal requirements. Alternatively, or in combination, additive may be supplied to an extent such that the combined reduction of nitrogen oxides by crystal burning and supply of additive results in said second content 3 ⁇ 4 not being exceeded.
  • the engine is caused to deliver a high NO x level NO x HIGH, e.g. 1000-2000 ppm or a suitable content over 2000 ppm, in which case the dosing of additive is then controlled so that the NO x content delivered downstream of the SCR catalyst 201 is below said second content.
  • a high NO x level NO x HIGH e.g. 1000-2000 ppm or a suitable content over 2000 ppm
  • the dosing of additive is then controlled so that the NO x content delivered downstream of the SCR catalyst 201 is below said second content.
  • the supply required may at least initially be very limited, since NO x reduction will largely be effected by the crystal build-up.
  • step 406 determines whether the reduction in the crystal build-up has taken place to the desired extent and can therefore be halted. So long as such is not the case, the method goes back to step 403 for fresh determination of said first content ⁇ . If the reduction has been completed, the method ends at step 407.
  • Whether the reduction of the coating has taken place to a sufficient extent may be determined in any suitable way.
  • the reduction may for e,xample be regarded as completed when it has proceeded for a first amount of time during which the
  • Said first amount of time may for example be a
  • the amount of additive injected may alternatively be compared with NO x conversion measured.
  • the NO x sensor 308 may be used in conjunction with a content H 3 determined from a second NO x sensor 210 situated upstream of the SCR catalyst 201. So long as the sensor values indicate that a higher NO x conversion has been achieved than the amount of additive supplied can achieve, at least part of the crystal build-up remains.
  • the NO x content delivered by the engine is lowered while at the same time the dosing of additive is halted, whereupon signals from respective NO x sensors before and after the SCR catalyst 201 are compared to see whether they show equal values.
  • Both of these solutions require NO x sensors both upstream and downstream of the SCR catalyst.
  • the sensor situated upstream of the catalyst may alternatively be replaced by a model of the NO x contents generated by the engine at different operating points in order to determine said content H3.
  • 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)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

La présente invention concerne un procédé visant à réduire un premier revêtement dans 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). Le premier revêtement est formé par l'apport d'un additif audit système de post-traitement (200), cet additif étant fourni à un premier catalyseur (201) en vue de réduire au moins un premier composé (NOx) dans ledit flux de gaz d'échappement. Le procédé comporte, pendant la réduction dudit premier revêtement, les étapes consistant à déterminer une première concentration (Hi) du premier composé (NOx) en un point se situant en aval dudit premier catalyseur (201), et à prendre une première mesure corrective visant à réduire la concentration du premier composé (NOx) quand celle-ci (H1) est supérieure à une deuxième concentration (H2). L'invention concerne aussi un système et un véhicule.
PCT/SE2012/051448 2011-12-28 2012-12-20 Procédé et système pour réduire des dépôts dans un système de post-traitement WO2013100846A1 (fr)

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SE1251469A SE536798C2 (sv) 2011-12-28 2012-12-20 Förfarande och system för reduktion av en beläggning i ett efterbehandlingssystem

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US10054023B2 (en) 2014-02-28 2018-08-21 Scania Cv Ab Exhaust treatment system and method for treatment of an exhaust stream
US10495569B2 (en) 2015-06-05 2019-12-03 Scania Cv Ab Method and a system for determining a composition of a gas mix in a vehicle
US10344647B2 (en) 2015-08-27 2019-07-09 Scania Cv Ab Method and system for a first and a second supply of additive to an exhaust gas stream from an internal combustion engine
US10724460B2 (en) 2015-08-27 2020-07-28 Scania Cv Ab Method and system for treatment of an exhaust gas stream
US10807041B2 (en) 2015-08-27 2020-10-20 Scania Cv Ab Exhaust treatment system and method for treatment of an exhaust gas stream
US10837338B2 (en) 2015-08-27 2020-11-17 Scania Cv Ab Method and exhaust treatment system for treatment of an exhaust gas stream
US10920632B2 (en) 2015-08-27 2021-02-16 Scania Cv Ab Method and exhaust treatment system for treatment of an exhaust gas stream
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SE2050257A1 (en) * 2020-03-06 2021-09-07 Scania Cv Ab A method and a control arrangement for a process of selective catalytic reduction after-treatment of an exhaust gas
WO2021177875A1 (fr) * 2020-03-06 2021-09-10 Scania Cv Ab Procédé et agencement de commande pour un processus de post-traitement par réduction sélective catalytique d'un gaz d'échappement
SE544027C2 (en) * 2020-03-06 2021-11-09 Scania Cv Ab A method and a control arrangement for a process of selective catalytic reduction after-treatment of an exhaust gas
US11719150B2 (en) 2020-03-06 2023-08-08 Scania Cv Ab Method and a control arrangement for a process of selective catalytic reduction after-treatment of an exhaust gas

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SE1251469A1 (sv) 2013-06-29
SE536798C2 (sv) 2014-08-26

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