WO2008071730A1 - Procédé et système de mesure d'une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur - Google Patents

Procédé et système de mesure d'une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur Download PDF

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Publication number
WO2008071730A1
WO2008071730A1 PCT/EP2007/063768 EP2007063768W WO2008071730A1 WO 2008071730 A1 WO2008071730 A1 WO 2008071730A1 EP 2007063768 W EP2007063768 W EP 2007063768W WO 2008071730 A1 WO2008071730 A1 WO 2008071730A1
Authority
WO
WIPO (PCT)
Prior art keywords
solution
precursor
tank
ammonia
metering
Prior art date
Application number
PCT/EP2007/063768
Other languages
English (en)
Inventor
Francois Dougnier
Joel Op De Beeck
Jules-Joseph Van Schaftingen
Original Assignee
Inergy Automotive Systems Research (Société Anonyme)
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
Priority claimed from FR0610912A external-priority patent/FR2909900B1/fr
Priority claimed from FR0610913A external-priority patent/FR2909901B1/fr
Application filed by Inergy Automotive Systems Research (Société Anonyme) filed Critical Inergy Automotive Systems Research (Société Anonyme)
Publication of WO2008071730A1 publication Critical patent/WO2008071730A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/90—Injecting reactants
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—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
    • F01N2610/02—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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • 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
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • 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
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0412—Methods of control or diagnosing using pre-calibrated maps, tables or charts
    • 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
    • F01N2900/08—Parameters used for exhaust control or diagnosing said parameters being related to the engine
    • 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
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • 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
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • F01N2900/1811—Temperature
    • 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 method and system for metering an aqueous ammonia precursor solution into the exhaust gases of an engine.
  • the change in legislation relating to emissions from diesel vehicles especially stipulates a significant reduction in releases of nitrogen oxide in exhaust gases.
  • the SCR (Selective Catalytic Reduction) process in which nitrogen oxides (NO x ) are reduced by ammonia is one of the technologies of choice for achieving this pollution control objective.
  • An aqueous solution of an ammonia precursor (generally of urea or of a mixture of urea and ammonium formate) is then injected into the exhaust line upstream of the SCR catalyst.
  • the operation of this catalyst requires precise metering of the amount of solution sprayed. This is because both overmetering (leading to a release of ammonia into the atmosphere) and undermetering (leading to an expulsion of untreated nitrogen oxides into the atmosphere) are harmful.
  • the present invention relates to a method for metering an aqueous ammonia precursor solution stored in a ventilated and/or pressure- calibrated tank into the exhaust gases of an internal combustion engine, said method consisting in determining the precursor concentration of the solution based on a measurement of the temperature of the solution in the tank and on nomograms obtained by ageing of reference solutions and establishing, for various temperatures, the change in the precursor concentration as a function of the calibration pressure of the tank.
  • This method has the advantage of being simple and of not adding a specific sensor to the system, a temperature sensor often being present already (especially for thermal conditioning of the solution).
  • ammonia precursor in aqueous solution may be suitable within the context of the invention.
  • the invention gives good results with eutectic solutions of urea for which there is a standard quality: for example, according to the standard DIN 70070, in the case of the AdBlue ® solution (commercial solution of urea), the urea content is between 31.8% and 33.2% (by weight) (i.e. 32.5 +/- 0.7% by weight) hence an available amount of ammonia between 18.0% and 18.8%.
  • the invention may also be applied to the urea/ammonium formate mixtures sold under the trade name DenoxiumTM and of which one of the compositions (Denoxium-30) contains an equivalent amount of ammonia to that of the Adblue ® solution.
  • the present invention may be applied to any internal combustion engine likely to generate NO x in its exhaust gases. It may be an engine with or without a fuel return line (that is to say, a line returning the surplus fuel not consumed by the engine to the fuel tank). It is advantageously applied to diesel engines, and in particular to vehicle diesel engines and particularly preferably to the diesel engines of heavy goods vehicles.
  • One advantageous variant of the invention consists in taking into account all the forms of ammonia available directly or indirectly in the solution (in the form of precursor, ammonia and ammonium hydroxide), and not solely that derived from the precursor. It takes into account the fact that: - urea hydrolyses according to the following overall reaction:
  • ammonium formate which, in solution, may release ammonia and formic acid and which decomposes at high temperature to form ammonia, carbon monoxide and carbon dioxide.
  • the concentrations of precursor (urea and/or ammonium formate for example), and optionally of ammonia and of ammonium hydroxide, are first determined for reference solutions that have been intentionally left to age at various temperatures, so as to obtain nomograms.
  • the total nitrogen is metered by an analytical chemistry method and the corresponding number of moles OfNH 3 per litre of solution are deduced therefrom.
  • Methods which are particularly suitable for this purpose are the Kjeldahl method and a pyrometry/chemiluminescence combination such as applied, for example, by analysers of the ANTEK 9000 NS type.
  • the precursor solution is stored in a tank that is ventilated and/or of which the pressure is calibrated so that only the temperature, and not the pressure, is to be considered as a parameter for establishing the nomograms.
  • the method according to the invention uses a computer designed to be able to combine the conditioning times when the temperature of the solution varies over time (or in other words: that it can jump from one nomogram to another when the temperature varies and this with a view to combining the thermal ageing effects at the various temperatures).
  • the tank could be equipped with a conditioning system that ensures a constant temperature in the tank, but this variant is more difficult and expensive to carry out in practice.
  • the present invention also relates to a system for metering an aqueous ammonia precursor solution and injecting it into the exhaust gases of an internal combustion engine, said system comprising at least one ventilated and/or pressure-calibrated tank, equipped with a temperature sensor and intended for storing the solution; a line for injecting the solution into the exhaust gases; and a computer that makes it possible to calculate the amount of solution to be injected into said gases as a function of at least one operating parameter of the engine and of the amount of precursor present in the solution obtained based on information from the temperature sensor and on nomograms obtained by ageing of reference solutions and establishing, for various temperatures, the change in the precursor concentration as a function of the calibration pressure of the tank.
  • the system according to the invention comprises at least one tank intended for storing the additive (precursor solution).
  • This tank may be made from any material, preferably one that is chemically resistant to the additive in question. In general, this is metal or plastic. Polyolefin resins, in particular polyethylene (and more particularly HDPE or high-density polyethylene), constitute preferred materials.
  • the system according to the invention generally comprises a pump that is used to bring the additive solution to the pressure required for metering and injecting it.
  • Various types of pumps may be suitable for the application: gear pump, piston pump, diaphragm pump, etc.
  • This pump may be located in the additive tank (with the advantage of forming, with it, a compact and integrated module) or, considering the corrosive environment, be located outside of the additive tank. Its constituent materials will preferably be chosen from corrosion- resistant metals (especially certain grades of stainless steel and aluminium). The use of copper, even for connection components, is undesirable.
  • the tank is ventilated (i.e. vented to the atmosphere) and/or the pressure in the latter is calibrated by means of a suitable device.
  • a suitable device i.e. vented to the atmosphere
  • the latter may consist of a simple calibrated valve.
  • this valve can direct vapours that create an overpressure in the tank towards a canister so that these vapours are not expelled as they are into the atmosphere but are first purified by the ammonia.
  • This variant (with overpressure) also has the advantage that the solubility of the ammonia is increased and that therefore, a large part of the ammonia derived from the degradation of the precursor in the end remains available for the SCR reaction.
  • the overpressure range generally extends from 100 mbar to 1 bar, with a preferred interval between 250 and 500 mbar.
  • the pressure inside the tank is atmospheric pressure. After closing the tank, the internal pressure results from the autogenous overpressure (resulting from the decomposition of the urea, a function of the temperature) and may not reach the calibration value of the valve.
  • the system according to the invention also comprises an injection line intended to bring the additive to the exhaust pipe of the engine and in order to do this connecting the tank and an injector generally located at the end of the injection line that opens into or near the exhaust pipe.
  • This injector may be of any known type. It may be a so-called “active” injector, i.e. that includes a metering function, or a so-called “passive” injector then coupled to an additional metering device, such as a metering valve for example. It is advantageously a passive injector, and in particular a nozzle or spray gun making it possible to obtain drops of solution having a diameter between 5 and 100 ⁇ m.
  • Such a nozzle is advantageously equipped with an orifice having a diameter of around 150 ⁇ m - 250 ⁇ m.
  • This orifice is preferably supplied by a system of narrow channels (3-4) producing a "swirl" phenomenon (vortex) of the solution upstream of the nozzle. Clogging could be avoided by the purge which removes the last droplets of urea; there is therefore no crystallization by evaporation.
  • the amount of solution is preferably metered by regulating the opening frequency and duration of the metering valve.
  • This valve may be a piezoelectric or solenoid valve, the regulation of which may be electronic.
  • the system according to the invention comprises a computer connected to the metering device and enabling the amount of additive required, as a function of the state of ageing of the solution and of at least one engine operating parameter which may be chosen from the emission level and degree of conversion of the NO x ; temperature and/or pressure; engine speed and/or load, etc., to be brought to the injector.
  • this computer has a memory, in which nomograms are stored that give the change, as a function of time, of the concentration of precursor and of ammonia/ammonium hydroxide of the solution (expressed as they are or in the form of total available ammonia) for which the system is intended and this at various temperatures or even at various pressures corresponding to the different calibration devices (valves) that it is possible to use in this type of system.
  • the system according to the invention finally comprises a sensor for the temperature in the tank.
  • this temperature sensor may also fulfil another role in the system (for example, for thermal conditioning of the solution).
  • Figure 1 illustrates a system according to a preferred variant of the invention.
  • the flow direction of the exhaust gases is indicated therein by an arrow marked "G".
  • This system comprises a tank (1) containing the ammonia precursor solution. This tank is equipped with a system for maintaining an overpressure
  • the overpressure has the advantage of increasing the solubility of the ammonia produced by degradation of the precursor.
  • the ammonia precursor is conveyed by the action of a pump (4) towards a nozzle (6) located in the line (9) for discharging the exhaust gases of the engine, upstream of an SCR catalyst (8).
  • the amounts injected are controlled by a metering valve (5), the opening of which is operated by an electronic control unit or ECU (7).
  • a temperature sensor (3) supplies data for input into the control unit
  • the temperature of the precursor solution is recorded over time. For given temperature levels, the conditioning times are combined.
  • the ECU then refers to the changes in the concentration of urea and of ammonia/ammonium hydroxide and establishes the equivalent amount of ammonia available in the precursor solution at any point in the ageing. This equivalent amount is then compared to the initial amount, for which there is a standard quality: for example, according to the standard DIN 70070, in the case of the AdB lue ® solution, the urea content is between 31.8% and 33.2% (by weight), hence an amount of available ammonia between 18.0% and 18.8%, and the correction factor for the volume to be injected is thus determined.

Abstract

L'invention concerne un procédé permettant de mesurer une solution de précurseur d'ammoniac aqueux, stockée dans un réservoir (1) ventilé et/ou étalonné selon la pression, dans les gaz d'échappement (9) d'un moteur thermique. Ledit procédé consiste à déterminer la concentration du précurseur de la solution sur la base d'une mesure de la température de la solution dans le réservoir et sur les nomogrammes obtenus par vieillissement de solutions témoins et à établir, pour différentes températures, le changement au niveau de la concentration du précurseur en fonction de la pression d'étalonnage du réservoir.
PCT/EP2007/063768 2006-12-14 2007-12-12 Procédé et système de mesure d'une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur WO2008071730A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR0610912A FR2909900B1 (fr) 2006-12-14 2006-12-14 Methode et systeme pour le dosage d'une solution aqueuse de precurseur d'ammoniac dans des gaz d'echappement d'un moteur
FR0610913 2006-12-14
FR0610912 2006-12-14
FR0610913A FR2909901B1 (fr) 2006-12-14 2006-12-14 Methode et systeme pour le dosage d'une solution aqueuse de precurseur d'ammoniac dans des gaz d'echappement d'un moteur

Publications (1)

Publication Number Publication Date
WO2008071730A1 true WO2008071730A1 (fr) 2008-06-19

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PCT/EP2007/063764 WO2008071727A1 (fr) 2006-12-14 2007-12-12 Procédé et système pour mesurer une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur
PCT/EP2007/063768 WO2008071730A1 (fr) 2006-12-14 2007-12-12 Procédé et système de mesure d'une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur

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Application Number Title Priority Date Filing Date
PCT/EP2007/063764 WO2008071727A1 (fr) 2006-12-14 2007-12-12 Procédé et système pour mesurer une solution de précurseur d'ammoniac aqueux dans les gaz d'échappement d'un moteur

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130144505A1 (en) * 2011-12-01 2013-06-06 Robert Bosch Gmbh Method for operating an exhaust gas system of an internal combustion engine

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6408619B1 (en) * 1997-12-17 2002-06-25 Siemens Aktiengesellschaft Method and device for reducing the nitrogen oxides in the exhaust gas of a combustion system
US20030033799A1 (en) * 2001-08-09 2003-02-20 Gerd Scheying Exhaust gas treatment unit and measuring instrument for ascertaining a concentration of a urea-water solution

Family Cites Families (2)

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Publication number Priority date Publication date Assignee Title
DE19940298A1 (de) * 1999-08-25 2001-03-01 Bosch Gmbh Robert Verfahren und Vorrichtung zur Bestimmung eines Reduktionsmittels und/oder der Reduktionsmittelkonzentration einer Reduktionsmittellösung in einem Katalysatorsystem zugeordneten Reduktionsmitteltank
AU2003262057A1 (en) * 2002-09-10 2004-04-30 Mitsui Mining And Smelting Co., Ltd. Urea concentration identifying system, method for identifying urea concentration and automobile exhaust gas reducing system using same, and method for reducing automobile exhaust gas

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6408619B1 (en) * 1997-12-17 2002-06-25 Siemens Aktiengesellschaft Method and device for reducing the nitrogen oxides in the exhaust gas of a combustion system
US20030033799A1 (en) * 2001-08-09 2003-02-20 Gerd Scheying Exhaust gas treatment unit and measuring instrument for ascertaining a concentration of a urea-water solution

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130144505A1 (en) * 2011-12-01 2013-06-06 Robert Bosch Gmbh Method for operating an exhaust gas system of an internal combustion engine

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