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WO2013160712A1 - Système et procédé de traitement d'oxydes d'azote contenus dans des gaz d'échappement - Google Patents

Système et procédé de traitement d'oxydes d'azote contenus dans des gaz d'échappement Download PDF

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Publication number
WO2013160712A1
WO2013160712A1 PCT/IB2012/001024 IB2012001024W WO2013160712A1 WO 2013160712 A1 WO2013160712 A1 WO 2013160712A1 IB 2012001024 W IB2012001024 W IB 2012001024W WO 2013160712 A1 WO2013160712 A1 WO 2013160712A1
Authority
WO
WIPO (PCT)
Prior art keywords
ammonia
unit
units
gaseous ammonia
release
Prior art date
Application number
PCT/IB2012/001024
Other languages
English (en)
Inventor
Jean-Pascal Petit
Original Assignee
Renault Trucks
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Renault Trucks filed Critical Renault Trucks
Priority to PCT/IB2012/001024 priority Critical patent/WO2013160712A1/fr
Publication of WO2013160712A1 publication Critical patent/WO2013160712A1/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
    • F01N3/2066—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
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/02—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a heat exchanger
    • 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
    • F01N2610/01—Adding substances to exhaust gases the substance being catalytic material in liquid form
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/06—Adding substances to exhaust gases the substance being in the gaseous form
    • 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
    • F01N2610/10—Adding substances to exhaust gases the substance being heated, e.g. by heating tank or supply line of the added substance
    • 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
    • F01N2610/10—Adding substances to exhaust gases the substance being heated, e.g. by heating tank or supply line of the added substance
    • F01N2610/105—Control thereof
    • 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
    • F01N2610/11—Adding substances to exhaust gases the substance or part of the dosing system being cooled
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1406—Storage means for substances, e.g. tanks or reservoirs
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1406—Storage means for substances, e.g. tanks or reservoirs
    • F01N2610/142—Controlling the filling of the tank
    • 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

Definitions

  • the present invention relates to a system and a method for treating nitrogen oxides contained in exhaust gases flowing in an exhaust line of an engine, especially but not exclusively in a vehicle.
  • Exhaust gases formed in the combustion of fuel in an internal combustion engine, in particular in industrial vehicles, may contain a proportion of undesirable components, in particular nitrogen oxides (NOx).
  • NOx nitrogen oxides
  • a selective catalytic reduction (SCR) system has been a standard feature in engine arrangements for many years, in order to treat said nitrogen oxides and reduce air pollution.
  • exhaust gases, mixed with ammonia as a reducer are treated in a specific catalytic converter where nitrogen oxides are converted into water and nitrogen which are both non-toxic substances.
  • ammonia may be introduced in the form of urea in aqueous solution from which ammonia is obtained through hydrolysis.
  • the urea solution is usually nebulised in the exhaust gases upstream from the catalytic converter.
  • a urea injection nozzle is fitted on the exhaust line upstream from the catalytic converter.
  • urea can crystallize before it has transformed into ammonia.
  • the aqueous solution of urea which is sprayed through the nozzle inside the exhaust pipe, according to a direction which may be angled with respect to the exhaust gases flow direction, tends to form a solid deposit on the exhaust pipe wall, on the internal side thereof, for example opposite of the injection point.
  • the aqueous solution of urea could also be vaporized into the exhaust line, i.e.
  • ammonia could be introduced in the exhaust line in the form of gaseous ammonia.
  • this implementation is less preferred because of the safety issues related to the storage of ammonia in high pressure tanks.
  • containers containing a solid on which ammonia has been previously absorbed or adsorbed In use, ammonia can be released under certain operating conditions, and directed towards the exhaust line upstream from the catalytic converter.
  • This implementation is advantageous in that it avoids crystallization that occurs when injecting liquid urea solution.
  • the containers need to be exchanged by the customer when all ammonia retained on the solid has been released, so as to meet legal requirements in terms of NOx emissions. This solution therefore proves inconvenient.
  • an object of the present invention is to provide such a system and method which can be effective, even at low temperatures, which avoids crystallization in the exhaust line and which is convenient for the vehicle operator.
  • the invention relates to a system to be fitted on an automotive vehicle for treating nitrogen oxides contained in exhaust gases flowing in an exhaust line of an engine of the vehicle, wherein the system comprises:
  • a dosing device for dosing gaseous ammonia to be introduced in the exhaust line upstream from a selective catalytic reduction device;
  • the ammonia storage and release arrangement comprises at least a first and a second unit, each unit including a container containing a material which, depending on the operating conditions, is capable of retaining gaseous ammonia supplied by the conversion device, in order to store gaseous ammonia, and of releasing previously retained gaseous ammonia towards the dosing device;
  • system comprises a control system capable of operating each of the first and second units:
  • the invention does not require specific arrangement for this part of the system, nor does it involve the hazards related to the storage of liquid or gaseous ammonia;
  • the invention avoids crystallization problems.
  • the containers can be fairly small, and can be used for a long period. An exchange of said containers is not needed between two normal services of the vehicle.
  • the containers can be made in various sizes and shapes, which makes their fitting on the vehicle easier.
  • gaseous ammonia can always be available and ready to use, whatever the engine operating conditions, either in the first unit or in the second unit. Indeed, during the storage mode of one unit, gaseous ammonia can be released from the other unit.
  • a significant advantage of the invention over the prior art is that there is no need to provide a real time management of the converting process, i.e. of the production of ammonia, to always have available ammonia for treating the exhaust gases.
  • the first and second units can be arranged in parallel between the conversion device and the dosing device.
  • one unit can be operated in the storage mode while the other unit is operated in the release mode.
  • the units can then be switched respectively to the release mode and the storage mode. Switching can occur for example when the unit in the storage mode reaches a certain high level of accumulated ammonia or when the unit in the release mode reaches a certain low level of remaining ammonia.
  • both units be operated in the release mode, or in the storage mode. In the latter case, it may be preferred to provide gaseous ammonia to the dosing device through another device, so as to enable the continuous treatment of nitrogen oxides in the exhaust gases.
  • Another significant advantage of the invention is that the system performance is high even at low temperatures, insofar as gaseous ammonia is directly introduced in the exhaust line. Moreover, the dosing of gaseous ammonia proves simple and effective.
  • the invention relates to a method for treating nitrogen oxides contained in exhaust gases flowing in an exhaust line of an engine of an automotive vehicle, the method comprising:
  • each unit including a container containing a material which, depending on the operating conditions, is capable of retaining gaseous ammonia supplied by the conversion device, in order to store gaseous ammonia, and of releasing previously retained gaseous ammonia towards a dosing device which is intended for dosing gaseous ammonia to be introduced in the exhaust line upstream from a selective catalytic reduction device;
  • both units can be operated in the release mode, or in the storage mode.
  • Figure 1 is a schematic representation of a system according to a first embodiment of the invention
  • FIGS. 2 to 6 show the system of Figure 1 in various operating phases
  • Figure 7 is a schematic representation of a system according to a second embodiment of the invention.
  • FIG. 1 schematically shows a first embodiment of a system 1 for treating nitrogen oxides (NOx) contained in the exhaust gases produced by an automotive vehicle engine, especially by an internal combustion engine 3.
  • An exhaust line 2 carries exhaust gases from an engine 3 towards the atmosphere.
  • a selective catalytic reduction (SCR) device 4 in which NOx can be converted essentially into water and nitrogen by means of ammonia used as a reductant.
  • the system 1 comprises a tank 5 which contains a precursor of ammonia, i.e. a substance which is chemically separable into gaseous ammonia and possible other components.
  • the tank can be considered a source of a precursor of ammonia.
  • the conversion of the precursor into gaseous ammonia takes place in a conversion device 6 which is supplied with the precursor of ammonia from the tank 5 by a supply line 7 which may comprise a pump and a dosing system.
  • the conversion device 6 can be thermally connected to the exhaust line 2, therefore using the thermal energy of hot exhaust gases to convert the precursor of ammonia into gaseous ammonia and other components.
  • the conversion device 6 may be located next to the exhaust line, and can be located upstream of a turbine driven by the exhaust gases so as to benefit from high temperature of the gases upstream of the turbine.
  • the only interaction between the exhaust gases and the conversion device consists in a heat transfer.
  • an additional heating device not relying on the heat generated by the engine, could also be provided to provide heat to the conversion device in certain operating conditions.
  • Such heating device could include an electric heater, a fuel burner, etc...
  • the precursor of ammonia can comprise an aqueous solution of urea. Then, in the conversion device 6, both an evaporation and an hydrolysis of the aqueous solution of urea take place, resulting essentially in the production of gaseous ammonia, C0 2 and water vapour.
  • the precursor of ammonia could be of a different chemical nature, for example aqueous ammonia. It could be in a different state such as in the case of urea in solid state, in the form of a block or in the form of pellets.
  • the precursor could even comprise ammonium salts such as ammonium carbonate or ammonium carbamate. In such a case, the conversion device would be adapted accordingly.
  • a feed line 8 carries the gases resulting from the conversion of the precursor of ammonia towards an ammonia storage and release arrangement 10 which is intended to be able to send gaseous ammonia towards a dosing device 111 substantially permanently in a steady state phase of the system.
  • the dosing device 1 1 then doses gaseous ammonia to be introduced in the exhaust line 2 upstream from the SCR device 4.
  • a nozzle 112 capable of injecting gaseous ammonia in the exhaust line 2.
  • the shown arrangement 10 comprises a first unit 11 and a second unit 12.
  • Each unit comprises a container 13 having an inlet connected to the feed line 8 and an outlet connected to the dosing device 1 1.
  • the container 13 of each unit contains a material which, depending on the operating conditions, is capable of retaining gaseous ammonia supplied by the conversion device 6, in order to store gaseous ammonia, and of releasing previously retained gaseous ammonia towards the dosing device 111.
  • the supply line 8 may be equipped with a compressor to supply pressurized gases to the arrangement 10.
  • ammonia is retained in the container by being absorbed and/or adsorbed by the material contained in the container and/or by forming a chemical complex with the material stored in the container.
  • the material can be solid. It can take several forms, including that of a powder, of granules or pellets, of open-cell foam, of a block, etc.... Such type of storage and release units has several advantages over conventional pressurized tanks:
  • the gas which is stored is essentially pure ammonia which can be easily dosed when released and injected in the exhaust line.
  • said material can comprise a material which is capable of retaining gaseous ammonia under certain operating conditions, for example below a threshold temperature or in a low range of temperatures, and of releasing previously retained ammonia under different operating conditions, for example above said threshold temperature or in a high range of temperatures.
  • gaseous ammonia can be absorbed in the material or adsorbed at the material surface depending on the temperature of the material and/or of the ammonia and depending on the pressure of gaseous ammonia. In such a case, operating the units in a storage mode or in a release mode can be controlled simply by controlling the temperature of said units.
  • suitable materials include materials based on MgCI 2,
  • SrCI 2 or CaCI 2 may include ammine complexes such as calcium ammine chloride Ca(NH 3 ) 8 CI 2 or Strontium ammine chloride Ca(NH 3 ) 8 CI 2 .
  • ammine complexes such as calcium ammine chloride Ca(NH 3 ) 8 CI 2 or Strontium ammine chloride Ca(NH 3 ) 8 CI 2 .
  • Suitable materials for retaining gaseous ammonia are described for example in US-
  • the materials contained in the containers 13 of the first and second units 1 1 , 12 can have one and the same optimum ammonia release temperature. Said materials can furthermore be identical.
  • the range of temperatures at which the material or each of the materials releases gaseous ammonia can be comprised between 100 and 140°C, with- an optimum of for example around 120°C.
  • Such a temperature is fairly high, which means that there is no need to excessively cool the gaseous ammonia flowing from the conversion device 6 to maintain it in a low range of temperatures to allow it to be retained in the material, i.e. stored in the corresponding unit 11 , 12.
  • this release temperature is not too high, and therefore there is no need to excessively heat the material to allow gaseous ammonia to be released.
  • the units 1 1 , 12 are similar, in particular contain the same material, and are arranged in parallel. This material may have an optimum release temperature of around 120°C. In the shown embodiment, both units have approximately the same capacity in terms of the amount of ammonia which can be retained.
  • one unit has a larger capacity than the other.
  • Each unit 11 , 12 can further comprise a heater 14 which is capable of raising the temperature in the container 13 up to an optimum release temperature in order for the material to release gaseous ammonia.
  • the heater is therefore intended to change the operating conditions of the corresponding unit 1 1 , 12, so that the unit can be operated either in a storage mode or in a release mode.
  • the heater 14 can be operated by the heat generated by the engine 2, either directly or indirectly.
  • the heater 14 could take advantage of the heat contained in exhaust gases, in an engine cooling fluid or in a lubrication fluid.
  • the arrangement 10 can comprise a cooler 17 located between the conversion device 6 and the units 11 , 12.
  • said cooler 17 can be located in the feed line 8 before it divides into a first branch 15 and a second branch 16 respectively connected to the container inlet of the first and second unit 1 , 12.
  • the aim of the cooler 17 is to lower the temperature of gaseous ammonia down to an optimum storage range of temperatures, for example below the threshold temperature, before gaseous ammonia enters the container(s) 13, to enable the material to retain said gaseous ammonia.
  • a valve system is provided in order to direct the gas flow towards the appropriate unit(s) 11 , 12.
  • the valve system may comprise a three way valve 18 provided at the junction between the feed line 8 and the branches 15, 16.
  • the valve system could alternatively comprise two valves, one in each branch 15, 16.
  • the outlet of the containers 13 of each of the first and second units 11 , 12 come out into a respective release line 21 , 22 connected to the inlet of the dosing device 111.
  • the release lines 21 , 22 can be distinct or, alternatively, could comprise common portions, in particular just upstream from the dosing device 111.
  • the material of the first and second units 11 , 12 can be capable of retaining essentially only gaseous ammonia among the gases produced in the conversion device 6.
  • the precursor of ammonia is an aqueous solution of urea which converts into ammonia, C0 2 and water vapour, C0 2 and H 2 0 are not retained by the material in the storage mode.
  • the ammonia storage and release arrangement 10 may comprise a purification or discharge line 20 connected to the outlet of each of the containers 13 of the first and second units 11 , 12.
  • the purification line 20 is used, when the corresponding unit is operated in the storage mode to carry said gases produced in the conversion device 6 in addition to ammonia - and which have not been retained in the material of the unit - from said containers 13 towards the exhaust line 2, in the storage mode.
  • the purification line 20 bypasses the dosing device 11 1.
  • a valve system ensures that the outlet of each unit 1 1 , 12 is either connected to the purification line 20 or to the dosing device 1 1 1 , depending on whether the unit is in the storage mode or in the release mode.
  • a three way valve 24, respectively 25 may be provided at the junction between the purification line 20 and the release line 21 , 22 of the first unit 1 1 , respectively the second unit 12.
  • the ammonia storage and release arrangement 10 can comprise a third unit 23 including a container 26 containing a material which, depending on the operating conditions, is capable of retaining gaseous ammonia supplied by the conversion device 6, in order to store gaseous ammonia, and of releasing previously retained gaseous ammonia towards the dosing device 1 1 1.
  • said material has essentially the same properties as that of the first and second units 1 1 , 12, and can comprise a material which is capable of retaining gaseous ammonia by absorption, and/or adsorption and/or formation of chemical complexes, under certain operating conditions, for example below a threshold temperature Tth or in a low range of temperatures, and of releasing previously retained ammonia under different operating conditions, for example above said threshold temperature or in a high range of temperatures.
  • One purpose of the third unit 23 is to more easily allow the release of gaseous ammonia for cold start of the engine 3.
  • an optimum release temperature or range of temperatures, or a threshold temperature of the material of the third unit 23 be lower than an optimum release temperature or range of temperatures, or lower than a threshold temperature, of the material of at least one of the first and second units 1 1 , 12.
  • said optimum release temperature or range of temperatures of the third unit 23 could be comprised between 60 and 100°C, for example around 80°C if the optimum release temperature or range of temperatures of the material of the first and second units 1 1 , 12 is comprised between 100 and 140°C, for example around 120°C.
  • Such an optimum release temperature or range of temperatures is fairly low, which means that there is no need to provide a lot of heat to the material to allow gaseous ammonia to be released, which is advantageous during cold start of the engine 2.
  • the material of the third unit 23 can be CaCI 2 , which has an optimum release temperature of around 80°C.
  • the third unit 23 can further comprise a heater 27 which is capable of raising the temperature in the container 26 above the optimum release temperature or range of temperatures (or above threshold temperature ) in order for the material to release gaseous ammonia.
  • the heater 27 is therefore intended to change the operating conditions of the unit 13 so that the unit is operated either in a storage mode or in a release mode.
  • the heater 27 is a heater which does not depend only on the heat generated by the engine 2, so as to be able to provide enough heat even during cold start.
  • the heater 27 may comprise for example an electric heater or a fuel burner.
  • the container 26 of the third unit 23 is connected to the outlet of the containers 13 of the first and second units 11 , 12, and to the inlet of the dosing device 11 1.
  • an additional line 28 branching from each release line 21 , 22 and connected to the inlet of the container 26.
  • a valve system may be provided to selectively connect the inlet of container to the outlet of the containers 13 of the first and second units 11 , 12.
  • the valve system may comprise for example three way valves 29, respectively 30, provided at the junction of the additional line 28 and of the release line 21 , respectively 22.
  • An additional release line 31 connects the outlet of the container 26 to the inlet of the dosing device 111.
  • the third unit 23 can be operated in a storage mode during the release mode of at least one of the first and second units 11 , 12.
  • a cooler (not shown) can be provided in the additional line 28 to lower the temperature of gaseous ammonia released from the first or second unit 11 , 12. Indeed, said gaseous ammonia has been heated by heater 4 and its temperature when entering the container 26 of the third unit 23 could be too high to allow the material of the third unit 23 to retain it.
  • the third unit 23 could possibly be operated in a storage mode during the storage mode of at least one of the first and second units 1 1 , 12, provided a dedicated purification line be provided for the third unit 23, in order to remove the gases produced in the conversion device 6 in addition to ammonia from the gas flow before it enters the dosing device 111.
  • the third unit 23 could be arranged in parallel with the first and second units 11 , 12, and therefore connected to the conversion device, to the dosing device and to a purification line through an adequate valve system.
  • the system 1 further includes a control system 32 which can control cooler 17, heaters 14, 27, valves 18, 24, 25, 29, 30 as well as the supply of the precursor of ammonia towards the conversion device 6, in order to operate the system 1 according to the appropriate operating phases, as will now be explained.
  • a control system 32 which can control cooler 17, heaters 14, 27, valves 18, 24, 25, 29, 30 as well as the supply of the precursor of ammonia towards the conversion device 6, in order to operate the system 1 according to the appropriate operating phases, as will now be explained.
  • the control system 32 can also control the dosing device 111 for introducing the appropriate quantity of gaseous ammonia in the exhaust line 2 depending on the quantity of NOx to be treated.
  • control system 32 is capable of operating each of the first and second units 11 , 12, as well as the third unit 23 when present:
  • the precursor of ammonia is supplied to the conversion device 6 which makes the conversion into gaseous ammonia and other components
  • the cooler 17 may be set on to lower the gaseous ammonia temperature in order to allow the storage, and the valve 18 allows the gas flow to enter the container 13.
  • the heater 14 is in most cases set off, and the valve 24 is preferably set so as to direct the flow of other components, not retained in the material, only towards the purification line 20 and exhaust line 2.
  • the valve 18 is preferably set so as to not allow a gas flow to enter the container 13. If said gas flow cannot be directed towards the second unit 12 for example because the second unit is fully loaded with ammonia, then, preferably, no gas flow is created in conversion device. To that end, no precursor of ammonia is supplied to the conversion device 6, and the conversion device 6 is not working.
  • the heater 14 is set on in order to raise the temperature at or above a minimum release temperature in order to allow the release of gaseous ammonia previously retained in the material, and the valve 24 is set to direct the flow of gaseous ammonia only towards the release line 21 and dosing device 111.
  • a full line indicates that gas flows in said line, contrary to dotted lines. Dotted arrows indicate that gas can optionally flow in the corresponding line. Cooler or heaters are illustrated with thick lines when they are on, and with thin lines when they are off.
  • first and second units 11 , 12 having an optimum ammonia release temperature of around 20°C
  • third unit 23 having an optimum ammonia release temperature of around 80°C.
  • other embodiments are possible.
  • Aqueous solution of urea is supplied through the supply line 7 from the tank 5 to the conversion device 6, where it is converted into gaseous ammonia and other components, especially C0 2 and H 2 0.
  • the gases flowing in the feed line 8 are cooled by cooler 17 below 120°C, preferably well below, and are exclusively directed towards the first unit 11 , the second unit 12 not being supplied with gases in this operating phase.
  • the heater 14 of the first unit 11 is set off, so that gaseous ammonia can be retained in the material.
  • C0 2 and H 2 0 go through the first unit 11 without being retained and are directed towards the purification line 20, no gas being sent from the first unit 1 neither towards the dosing device 111 nor towards the third unit 23.
  • the heater 14 of the second unit 12 is set on, allowing ammonia to be released from the material and directed towards the dosing device 1 11 through release line 22.
  • the third unit 23 may be envisaged, during this phase, to send part of the gaseous ammonia released from the second unit 12 towards the third unit 23, in order to be stored in said third unit 23, if not the whole amount of released gaseous ammonia is required to treat the NOx contained in the exhaust gases.
  • the third unit 23 is preferably used for cold start, it should preferably contain enough retained ammonia when the engine 2 is started, which means that the third unit 23 should preferably be loaded with retained ammonia as soon as possible after the system has reached a steady state phase.
  • the system 1 is operated in a transient phase, as depicted in Figure 3.
  • the heater 14 of the first unit 11 is set on and the valve 24 now directs the gas flow -containing essentially only ammonia - to the release line 21 and no more to the purification line 20.
  • the object of this transient phase is to ensure that ammonia is continuously provided to the dosing device 111 , taking into account that the rate of delivery of ammonia by the first unit 11 is dependent on the temperature in the first unit 11 , and that said temperature does not rise instantaneously to the optimum release temperature due to the thermal inertia of the unit.
  • Aqueous solution of urea is supplied through the supply line 7 from the tank 5 to the conversion device 6, where it is converted into gaseous ammonia and other components, especially C0 2 and H 2 0.
  • the gases flowing in the feed line 8 are cooled by cooler 17 below 120°C and are exclusively directed towards the second unit 12, the first unit 11 not being supplied with gases in this operating phase.
  • the heater 14 of the second unit 12 is set off, so that gaseous ammonia can be retained in the material.
  • C0 2 and H 2 0 go through the first unit 11 without being retained and are directed towards the purification line 20, no gas being sent from the second unit 12 neither towards the dosing device 111 nor towards the third unit 23.
  • the heater 14 of the first unit 11 is set on, allowing ammonia to be released from the material and directed towards the dosing device 111 through release line 21.
  • Figure 6 illustrates the system 1 during cold start of the engine 2.
  • gaseous ammonia is mainly, or even exclusively at the very beginning, provided by the third unit 23.
  • the third unit 23 is designed for this purpose since it contains a material having a quite low ammonia release temperature. This material therefore does not require to be heated a lot before releasing previously retained ammonia.
  • the third unit 23 is preferably provided with a heater 27 which does only not use the heat provided by the engine operation. Therefore, the heater 27 can be effectively operated even if the engine temperature has not reached the threshold temperature yet.
  • gaseous ammonia flows from the container 26 of the third unit 23 towards the dosing device 1 1 1 through the additional release line 31.
  • At least one of the first and second units 11 , 12 is progressively set on.
  • the corresponding heater 14 is switched on and, when the temperature has reached the threshold temperature, gaseous ammonia begins to be released by the material and to be sent towards the dosing device 111 through the corresponding release line 21.
  • ammonia is preferably entirely provided by said unit and the third unit 23 is no more used.
  • the system 1 is then operated as in Figure 2 or Figure 5, with a need in the short term to store ammonia in the third unit 23 in view of a subsequent cold start.
  • the converting device 6 may be set on to provide ammonia to be stored in the first or second unit 11 , 12. If the heat provided by the exhaust gases is not sufficient, an additional and dedicated heater may be provided for said converting device 6.
  • Figure 7 shows a second embodiment of the invention, where no third unit is provided, meaning that lines 28 and 31 are useless.
  • the third unit is no more present, another means is provided to allow the supply of gaseous ammonia during cold start of the engine 2.
  • the second unit 12 - comprises a main heater 14 operated by the heat generated directly or indirectly by the engine 2 and an additional heater 35 capable of supplying heat to the container 13 during the cold start of the engine.
  • the main heater 14 can be switched on from the beginning but it becomes effective only after a certain period of time, during which the additional heater 35 can allow the release of previously retained ammonia.
  • the two units can have a similar ammonia retaining material or can have different materials, especially having materials such that they start releasing ammonia at different temperature levels. Also the units could have the same capacity or be of different capacities.
  • this embodiment could also include a third unit, if necessary.
  • the system according to the invention can be easily integrally fitted on-board an automotive vehicle, especially on a truck. It can be noted that the system according to the invention requires only a single dosing device for metering the reductant, here gaseous ammonia, which is effectively injected in the exhaust line.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

Le système (1) comprend : - une source (5) d'un précurseur d'ammoniac ; - un dispositif de conversion (6) permettant de produire de l'ammoniac gazeux à partir dudit précurseur ; - un dispositif de dosage (111) permettant de doser l'ammoniac gazeux devant être introduit dans la conduite d'échappement (2) en amont d'un dispositif de réduction catalytique sélective (4) ; un agencement de stockage et de libération d'ammoniac (10) comprenant des première et seconde unités (11, 12), chaque unité comprenant un réceptacle (13) contenant un matériau, lequel, en fonction des conditions de fonctionnement, permet de retenir l'ammoniac gazeux fourni par le dispositif de conversion afin de stocker l'ammoniac gazeux et de libérer l'ammoniac gazeux retenu précédemment en direction du dispositif de dosage ; - et un système de commande (32) permettant d'actionner chacune des première et seconde unités (11, 12) soit dans un mode de stockage, soit dans un mode de libération.
PCT/IB2012/001024 2012-04-26 2012-04-26 Système et procédé de traitement d'oxydes d'azote contenus dans des gaz d'échappement WO2013160712A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015092469A1 (fr) 2013-12-19 2015-06-25 Volvo Truck Corporation Système de traitement de gaz d'échappement à monter sur un châssis d'un véhicule automobile
FR3027056A1 (fr) * 2014-10-10 2016-04-15 Peugeot Citroen Automobiles Sa Dispositif de reduction catalytique selective
WO2021198227A1 (fr) * 2020-03-31 2021-10-07 Plastic Omnium Advanced Innovation And Research Système de stockage et de délivrance d'ammoniac
JP2023546799A (ja) * 2020-09-30 2023-11-08 プラスチック・オムニウム・アドヴァンスド・イノベーション・アンド・リサーチ 車両用燃料電池システムの熱管理方法

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US6361754B1 (en) * 1997-03-27 2002-03-26 Clean Diesel Technologies, Inc. Reducing no emissions from an engine by on-demand generation of ammonia for selective catalytic reduction
US6387336B2 (en) 1997-07-03 2002-05-14 Robert Bosch Gmbh Method and device for selective catalytic NOx reduction
WO2006012903A2 (fr) 2004-08-03 2006-02-09 Amminex A/S Matiere de stockage d'ammoniac solide et matiere de distribution associee
WO2007049042A1 (fr) * 2005-10-26 2007-05-03 Imi Vision Limited Traitement de gaz d'echappement
DE102006061370A1 (de) * 2006-12-22 2008-06-26 Amminex A/S Verfahren und Vorrichtung zur Ammoniakspeicherung und -zufuhr unter Verwendung von in-situ-Wiedersättigung einer Zufuhreinheit
EP2333262A1 (fr) * 2009-12-11 2011-06-15 IFP Energies nouvelles Procédé de traitement de polluants contenus dans des gaz d'échappement, notamment d'un moteur à combustion interne, et installation utilisant un tel procédé

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Publication number Priority date Publication date Assignee Title
US6361754B1 (en) * 1997-03-27 2002-03-26 Clean Diesel Technologies, Inc. Reducing no emissions from an engine by on-demand generation of ammonia for selective catalytic reduction
US6387336B2 (en) 1997-07-03 2002-05-14 Robert Bosch Gmbh Method and device for selective catalytic NOx reduction
WO2006012903A2 (fr) 2004-08-03 2006-02-09 Amminex A/S Matiere de stockage d'ammoniac solide et matiere de distribution associee
WO2007049042A1 (fr) * 2005-10-26 2007-05-03 Imi Vision Limited Traitement de gaz d'echappement
DE102006061370A1 (de) * 2006-12-22 2008-06-26 Amminex A/S Verfahren und Vorrichtung zur Ammoniakspeicherung und -zufuhr unter Verwendung von in-situ-Wiedersättigung einer Zufuhreinheit
EP2333262A1 (fr) * 2009-12-11 2011-06-15 IFP Energies nouvelles Procédé de traitement de polluants contenus dans des gaz d'échappement, notamment d'un moteur à combustion interne, et installation utilisant un tel procédé

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015092469A1 (fr) 2013-12-19 2015-06-25 Volvo Truck Corporation Système de traitement de gaz d'échappement à monter sur un châssis d'un véhicule automobile
US11319851B2 (en) 2013-12-19 2022-05-03 Volvo Truck Corporation Exhaust gas treatment system to be fitted on a chassis of an automotive vehicle
FR3027056A1 (fr) * 2014-10-10 2016-04-15 Peugeot Citroen Automobiles Sa Dispositif de reduction catalytique selective
WO2021198227A1 (fr) * 2020-03-31 2021-10-07 Plastic Omnium Advanced Innovation And Research Système de stockage et de délivrance d'ammoniac
BE1028173B1 (fr) * 2020-03-31 2021-10-25 Plastic Omnium Advanced Innovation & Res Système de stockage et de délivrance d'ammoniac
JP2023546799A (ja) * 2020-09-30 2023-11-08 プラスチック・オムニウム・アドヴァンスド・イノベーション・アンド・リサーチ 車両用燃料電池システムの熱管理方法

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