EP2352911A1 - Device for eliminating sulphur oxides in a system for capturing nitrogen oxides - Google Patents

Device for eliminating sulphur oxides in a system for capturing nitrogen oxides

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Publication number
EP2352911A1
EP2352911A1 EP09784389A EP09784389A EP2352911A1 EP 2352911 A1 EP2352911 A1 EP 2352911A1 EP 09784389 A EP09784389 A EP 09784389A EP 09784389 A EP09784389 A EP 09784389A EP 2352911 A1 EP2352911 A1 EP 2352911A1
Authority
EP
European Patent Office
Prior art keywords
fuel
trapping system
hydrogen sulphide
oxides
air
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP09784389A
Other languages
German (de)
French (fr)
Inventor
Pascal Barrillon
Axel Vannier
Emmanuel Poilane
Pierre-Yves Le Morvan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Renault SAS
Original Assignee
Renault SAS
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 SAS filed Critical Renault SAS
Publication of EP2352911A1 publication Critical patent/EP2352911A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/085—Sulfur or sulfur oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
    • F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/24—Hydrogen sulfide (H2S)
    • 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 device for removing sulfur oxides in a nitrogen oxide trapping system disposed in the exhaust line of a motor vehicle internal combustion engine. It also relates to a process for removing sulfur oxides.
  • a NO x trap post-processing system is broken down into two stages. Firstly, one proceeds to the accumulation of nitrogen oxides emitted by the engine in the NO x trap. After a certain time, the available space for the storage of NO x decreases, and a regeneration step is then required, which makes it possible on the one hand to transform the NO x stored in non-polluting compounds and to evacuate, and secondly, to recover some of the storage capacity, in order to resume the storage process.
  • the regeneration step is obtained by a change in the operating mode of the engine, which during this period makes it possible to obtain gaseous conditions in which the quantities of reducing elements are considerably increased. We speak of wealth greater than 1.
  • the elimination of nitrogen oxides is therefore conceivable only in a context of alternating storage periods of NO x , occurring during normal operation of the engine, and long duration, and regeneration phases, requiring a tilting of the motor to obtain a richness greater than 1, and whose durations are 10 to 1000 times lower than those of the previous phases.
  • the fuel and oil of internal combustion engines contain a non-zero proportion of sulfur.
  • the oxidation process and the favorable thermodynamic conditions will transform the sulfur species into SO 2 compounds, which are in the form of exhaust gas, next to the nitrogen oxides.
  • the nitrogen oxides (NO x ) and the sulfur species formed (SO 2 ) then have very similar properties, and the SO 2 will store on the NO x trap, instead of the nitrogen oxides.
  • the storage capacity of the latter normally dedicated to nitrogen oxides, will then gradually decrease until it becomes zero if sulfur poisoning is allowed to continue. Indeed, during the NO x reduction steps mentioned above, the conditions generated are not sufficient to allow parallel destocking of the sulfur species, which are much more stable. The NO x species are therefore removed from the trap surface, but the sulfur species remain in place. As the process is cumulative, the sequencing of these steps means that the storage capacity dedicated to NO x will gradually decrease, up to a potential complete cancellation.
  • This desulfurization process is obtained by combining at the level of the NO x trap conditions of high temperatures with an excess of reducing compounds. These conditions are generally achieved by modifying the engine calibration, although it is possible to inject the necessary reducing compounds directly into the exhaust line and / or to use an auxiliary heating device to provoke the engine. temperature rise of the exhaust gas. Under these conditions, the sulfur species are effectively removed from the NO x trap, mainly in the form of SO 2 (sulfur dioxide), but can be in the form of a particularly malodorous compound: I 1 H 2 S or sulfide d 'hydrogen. Depending on the quantities of 2 S and the driving conditions of the vehicle, the formation of H 2 S can be experienced as inconvenient for the driver, the follower vehicles or the environment.
  • Document FR 2 881 177 discloses a vehicle engine comprising a trap for nitrogen oxides, as well as means for introducing into an exhaust pipe downstream of the trap an oxidant capable of converting hydrogen sulphide into dioxide. of sulfur, using an air pump injecting into the exhaust line of atmospheric air.
  • the present invention aims to overcome these disadvantages.
  • the invention proposes a device for treating in a simple and economical way the hydrogen sulphide emitted during desulphurization.
  • the proposed device also allows optimal conditions for the treatment of hydrogen sulfide and effectively prevents the appearance of foul odors.
  • the invention thus relates to a device for removing sulfur oxides in a nitrogen oxide trapping system disposed in the exhaust line of a motor vehicle internal combustion engine, the engine being powered in air and fuel, the device comprising control means capable of triggering a removal of sulfur oxides from the nitrogen oxide scavenging system, by heating the nitrogen oxide scavenging system beyond a predetermined temperature and by adjusting the fuel richness of the mixture of air and fuel to a value greater than 1, the removal of sulfur oxides accompanied by the emission of hydrogen sulfide.
  • the device according to the invention further comprises a system for trapping emitted hydrogen sulphide, means for oxidation of trapped hydrogen sulphide, and means for measuring or estimating the temperature of the sulphide trapping system. hydrogen.
  • said control means are able to trigger the elimination of sulfur oxides when the measured or estimated temperature of the hydrogen sulfide trapping system is greater than or equal to a threshold value.
  • the device thus makes it possible to ensure that the hydrogen sulfide trapping and oxidation system is at a sufficiently high temperature to be able to effectively treat the first H 2 S emissions leaving the NO x trap, when triggers the removal of sulfur oxides from the NO x trap. Indeed, the conversion rate from SO 2 to H 2 S increases with the temperature of the gases that pass through the H 2 S trap.
  • the fuel richness of the air and fuel mixture is greater than 1, ie the fuel is in stoichiometric excess. relative to the oxygen of the air.
  • the threshold value of the measured or estimated temperature of the hydrogen sulfide trapping and oxidation system is preferably greater than or equal to 350 ° C., and in particular greater than or equal to at 400 ° C. It is more preferentially between 400 ° C. and 600 ° C.
  • the oxidation means of the trapped hydrogen sulphide preferably comprise means for controlling the fuel richness of the mixture of air and fuel to a value of less than 1.
  • the exhaust line may include a particulate filter.
  • the invention also relates to a motor vehicle comprising a device described above.
  • the invention also relates to a method that can implement a device described above.
  • the method according to the invention comprises:
  • the triggering if the measured or estimated temperature is greater than or equal to a threshold value, of removal of the sulfur oxides from the nitrogen oxide scavenging system, by heating the nitrogen oxide scavenging system; beyond a predetermined temperature and by adjusting the fuel richness of the mixture of air and fuel to a value greater than 1, hydrogen sulfide being produced during this step, and
  • the oxidation of hydrogen sulphide is advantageously carried out by regulating the fuel richness of the mixture of air and fuel to a value of less than 1.
  • the threshold value of the measured or estimated temperature of the hydrogen sulfide trapping system is preferably greater than or equal to 350 ° C.
  • FIG. 1 schematically illustrates a device according to the invention, according to a first embodiment
  • FIG. 1 schematically illustrates a device according to the invention, according to a second embodiment.
  • the heat engine 1 as shown in FIG. 1, is a diesel type explosion engine. It conventionally comprises a cylinder head 3 comprising a plurality of combustion chambers 4, for example four in number.
  • a fuel injection system 2 is connected to each of the combustion chambers 4.
  • the engine 1 is supplied with air via an intake zone A.
  • the exhaust gases produced by the combustion of air and fuel in the combustion chambers combustion chambers 4 are routed to an exhaust line E.
  • the circulation of burnt gases, symbolized by arrows, is carried out from left to right in the figure.
  • the exhaust line E of the flue gas is provided with a nitrogen oxide trap 5 and a flue gas post-treatment assembly comprising a particulate filter 6 and a hydrogen sulfide trap 7 disposed in downstream of the particulate filter 6.
  • the particulate filter 6 is disposed downstream of the nitrogen oxide trap 5 and is for example housed in the same casing 11.
  • the particulate filter 6 is advantageously used for the removal of particles responsible black fumes from a diesel engine.
  • the particulate filter 6 could also be disposed upstream of the nitrogen oxide trap 5, or downstream of the hydrogen sulfide trap 7.
  • the hydrogen sulphide trap 7 is an independent monolith, distinct from the particulate filter 6.
  • the hydrogen sulphide trap 7 is thus housed in a specific envelope 12.
  • the trap The hydrogen sulfide 7 comprises a composition capable, on the one hand, of trapping the hydrogen sulphide from the nitrogen oxide trap 5 in a medium of richness greater than 1 (the fuel is in stoichiometric excess with respect to the oxygen of the air), and secondly, able to convert it to sulfur dioxide, in a poor environment, of less than 1 richness (including excess oxygen), and then to release it in this state.
  • the hydrogen sulfide trap 7 may for example comprise a cordierite or aluminum titanate substrate.
  • the trapping may advantageously be by adsorption of hydrogen sulphide on the composition.
  • a control device 8 is capable of triggering removal of the sulfur oxides from the nitrogen oxide scavenging system 5 by heating the nitrogen oxide scavenging system 5 beyond a predetermined temperature and by an adjustment of the fuel richness of the mixture of air and fuel to a value greater than 1.
  • the heating of the nitrogen oxide scavenging system 5 can advantageously be carried out by controlling the fuel richness of the air and fuel mixture, for example by increasing the flow rate of the fuel. fuel. It is thus possible to control the temperature of the nitrogen oxide trap 5 by alternating wealth greater than 1 and wealth less than 1.
  • the temperature setting and / or temperature control at the time of the desulfurization can also be ensured or supplemented by means of an auxiliary heating system arranged upstream or at the level of the nitrogen oxide trap 5.
  • the predetermined temperature is preferably greater than or equal to 650 ° C., and still more preferably greater than or equal to 700 ° C.
  • a temperature sensor 9 is intended to measure the temperature of the hydrogen sulfide trap 7. This temperature can also be estimated. It is indeed possible to estimate the temperature of the hydrogen sulfide trap 7 as a function of the architecture of the exhaust line E, as described for example in the documents FR 2 877 043 and FR 2 853 691.
  • the temperature estimate of the hydrogen sulfide trap 7 may be to wait for a calibrated time after setting the predetermined temperature of the nitrogen oxide trap 5. This time can be set as a function of the thermal inertia due to the distance and the post-treatment volumes between the nitrogen oxide trap 5 and the hydrogen sulphide trap 7.
  • the temperature sensor 9 is connected to the control device 8.
  • control 8 is able to trigger the removal of sulfur oxides when the measured or estimated temperature of the hydrogen sulfide trap 7 is greater than or equal to a threshold value.
  • the hydrogen sulphide trap 7 is at a sufficiently high temperature to be able to effectively treat the hydrogen sulphide emissions coming out of the trap. Nitrogen oxides 5. If the threshold temperature is not reached, the desulphurisation is not initiated.
  • the desulfurization is started by the control device 8.
  • the richness of the mixture passing through the exhaust circuit (E) is then greater than 1.
  • An additional device 10 The fuel injection nozzle is advantageously used to deconstruct the engine 1 during this phase.
  • the additional device 10 thus makes it possible to burn fuel and increase the temperature in the vicinity of the nitrogen oxide trap 5.
  • the reducing species are in excess and a part of between them will react with the sulfur species, in particular SO 2 , stored in the nitrogen oxide trap 5, to convert it in part to H 2 S.
  • the compound H 2 S is then released from the nitrogen oxide trap 5, and is transferred into the hydrogen sulfide trap 7.
  • the oxygen is found in excess in the exhaust gases. Exhaust that runs through the exhaust line E. This oxygen then reacts with the H 2 S stored to form SO 2 and other sulfur species that are toxic or smelly. These sulfur species can be evacuated out of the exhaust line E without risk of pollution.
  • the control device 8 stops the specific injection strategies to return to normal operation. The process is reiterated periodically according to the desulphurization requirements of the exhaust line E.
  • FIG. 2 in which the elements identical to those of FIG. 1 bear the same references, it is the particle filter 6 itself which is impregnated with the composition of the hydrogen sulfide trap 7, so that it also constitutes the catalytic system.
  • the nitrogen oxide trap 5 and the particulate filter 6 and hydrogen sulfide trap 7 are housed in a common envelope 11.

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

Abstract

One subject of the invention is a device for eliminating sulphur oxides in a system (5) for capturing nitrogen oxides positioned in the exhaust line (E) of an internal combustion engine (1) of a motor vehicle, the engine (1) being fed with air and with fuel, the device comprising control means (8) capable of initiating an elimination of sulphur oxides from the system (5) for capturing nitrogen oxides, by heating the system (5) for capturing nitrogen oxide above a predetermined temperature and by adjusting the richness, in terms of fuel, of the air/fuel mixture to a value greater than 1, the elimination of the sulphur oxides being accompanied by the emission of hydrogen sulphide, characterized in that the device also comprises a system (7) for capturing the hydrogen sulphide emitted, means for oxidizing the captured hydrogen sulphide, and means for measuring or estimating the temperature of the system (7) for capturing hydrogen sulphide, and in that said control means (8) are capable of initiating the elimination of the sulphur oxides when the measured or estimated temperature of the system (7) for capturing hydrogen sulphide is greater than or equal to a threshold value.

Description

DISPOSITIF D'ELIMINATION D'OXYDES DE SOUFRE DANS UN SYSTEME DE DEVICE FOR REMOVING SULFUR OXIDES IN A SYSTEM OF
PIEGEAGE D'OXYDES D'AZOTETRAPPING NITROGEN OXIDES
La présente invention concerne un dispositif d'élimination d'oxydes de soufre dans un système de piégeage d'oxydes d'azote disposé dans la ligne d'échappement d'un moteur à combustion interne de véhicule automobile. Elle concerne également un procédé d'élimination d'oxydes de soufre.The present invention relates to a device for removing sulfur oxides in a nitrogen oxide trapping system disposed in the exhaust line of a motor vehicle internal combustion engine. It also relates to a process for removing sulfur oxides.
Les oxydes d'azote NOx provoquent des infections et des allergies respiratoires et jouent un rôle dans la formation de pluies acides, de sorte que la plupart des pays ont imposé des normes limitant l'émission d'oxydes d'azote NOx par les véhicules automobiles.Nitrogen oxides NO x cause respiratory infections and allergies and play a role in the formation of acid rain, so that most countries have imposed standards limiting the emission of NO x oxides by motor vehicles.
Aussi, la plupart des véhicules automobiles, et notamment les véhicules à moteur de type Diesel, sont pourvus de systèmes de piégeage catalytique d'oxydes d'azote. Le fonctionnement d'un système de post-traitement de type piège à NOx se décompose en deux étapes. Tout d'abord, on procède à l'accumulation des oxydes d'azote émis par le moteur dans le piège à NOx. Au bout d'un certain temps, l'espace disponible pour le stockage des NOx diminue, et il faut alors procéder à une étape de régénération, qui permet d'une part de transformer les NOx stockés en composés non polluants et de les évacuer, et d'autre part, de retrouver une partie de la capacité de stockage, afin de pouvoir reprendre le processus de stockage. L'étape de régénération est obtenue par un changement de mode de fonctionnement du moteur, qui permet pendant cette période d'obtenir des conditions gazeuses dans lesquelles les quantités d'éléments réducteur sont considérablement augmentées. On parle de richesse supérieure à 1.Also, most motor vehicles, including diesel-type motor vehicles, are equipped with catalytic systems for the capture of nitrogen oxides. The operation of a NO x trap post-processing system is broken down into two stages. Firstly, one proceeds to the accumulation of nitrogen oxides emitted by the engine in the NO x trap. After a certain time, the available space for the storage of NO x decreases, and a regeneration step is then required, which makes it possible on the one hand to transform the NO x stored in non-polluting compounds and to evacuate, and secondly, to recover some of the storage capacity, in order to resume the storage process. The regeneration step is obtained by a change in the operating mode of the engine, which during this period makes it possible to obtain gaseous conditions in which the quantities of reducing elements are considerably increased. We speak of wealth greater than 1.
L'élimination des oxydes d'azote ne se conçoit donc que dans un contexte d'alternance de phases de stockage des NOx, s'opérant lors du fonctionnement normal du moteur, et de durée longue, et de phases de régénération, nécessitant un basculement du moteur pour obtenir une richesse supérieure à 1 , et dont les durées sont 10 à 1000 fois inférieures à celles des phases précédentes. Le carburant et l'huile des moteurs à combustion interne contiennent une proportion non nulle de soufre. Lors de la combustion dans la chambre de combustion, le processus d'oxydation et les conditions thermodynamiques favorables vont transformer les espèces soufrées en composés SO2, qui se retrouvent sous forme de gaz à l'échappement, à coté des oxydes d'azote. Les oxydes d'azote (NOx) et les espèces soufrées formées (SO2) possèdent alors des propriétés très proches, et le SO2 va se stocker sur le piège à NOx, en lieu et place des oxydes d'azote. La capacité de stockage de ce dernier, normalement dédiée aux oxydes d'azote, va alors diminuer progressivement, jusqu'à devenir nulle, si on laisse l'empoisonnement au soufre se prolonger. En effet, lors des étapes de réduction des NOx évoquées ci-dessus, les conditions générées ne sont pas suffisantes pour permettre un déstockage en parallèle des espèces soufrées, beaucoup plus stables. Les espèces NOx sont donc éliminées de la surface du piège, mais les espèces soufrées restent en place. Le processus étant cumulatif, l'enchaînement de ces étapes fait que la capacité de stockage dédiée aux NOx va progressivement diminuer, jusqu'à une potentielle annulation complète.The elimination of nitrogen oxides is therefore conceivable only in a context of alternating storage periods of NO x , occurring during normal operation of the engine, and long duration, and regeneration phases, requiring a tilting of the motor to obtain a richness greater than 1, and whose durations are 10 to 1000 times lower than those of the previous phases. The fuel and oil of internal combustion engines contain a non-zero proportion of sulfur. During combustion in the combustion chamber, the oxidation process and the favorable thermodynamic conditions will transform the sulfur species into SO 2 compounds, which are in the form of exhaust gas, next to the nitrogen oxides. The nitrogen oxides (NO x ) and the sulfur species formed (SO 2 ) then have very similar properties, and the SO 2 will store on the NO x trap, instead of the nitrogen oxides. The storage capacity of the latter, normally dedicated to nitrogen oxides, will then gradually decrease until it becomes zero if sulfur poisoning is allowed to continue. Indeed, during the NO x reduction steps mentioned above, the conditions generated are not sufficient to allow parallel destocking of the sulfur species, which are much more stable. The NO x species are therefore removed from the trap surface, but the sulfur species remain in place. As the process is cumulative, the sequencing of these steps means that the storage capacity dedicated to NO x will gradually decrease, up to a potential complete cancellation.
Pour éradiquer le phénomène, il faut donc périodiquement générer un processus de désulfuration qui permet de libérer de la surface du piège à NOx le soufre retenu. Ce processus de désulfuration, connu en lui-même, est obtenu en combinant au niveau du piège à NOx des conditions de températures élevées avec un excès de composés à caractère réducteur. Ces conditions sont en règle générale atteintes par modification de la calibration du moteur, bien qu'il soit possible d'injecter directement dans la ligne d'échappement les composés réducteurs nécessaires et/ou d'utiliser un artifice de chauffage annexe pour provoquer l'élévation en température des gaz d'échappement. Dans ces conditions, les espèces soufrées sont effectivement évacuées du piège à NOx, principalement sous forme de SO2 (dioxyde de soufre), mais peuvent l'être sous forme d'un composé particulièrement malodorant : I1H2S ou sulfure d'hydrogène. En fonction des quantités dΗ2S et des conditions de roulage du véhicule, la formation d'H2S peut être vécue comme gênante pour le conducteur, les véhicules suiveurs ou l'environnement.To eradicate the phenomenon, it is therefore necessary periodically to generate a desulfurization process that allows the sulfur retained to be released from the surface of the NO x trap. This desulfurization process, known in itself, is obtained by combining at the level of the NO x trap conditions of high temperatures with an excess of reducing compounds. These conditions are generally achieved by modifying the engine calibration, although it is possible to inject the necessary reducing compounds directly into the exhaust line and / or to use an auxiliary heating device to provoke the engine. temperature rise of the exhaust gas. Under these conditions, the sulfur species are effectively removed from the NO x trap, mainly in the form of SO 2 (sulfur dioxide), but can be in the form of a particularly malodorous compound: I 1 H 2 S or sulfide d 'hydrogen. Depending on the quantities of 2 S and the driving conditions of the vehicle, the formation of H 2 S can be experienced as inconvenient for the driver, the follower vehicles or the environment.
Il est connu du document FR 2 881 177 un moteur de véhicule comprenant un piège à oxydes d'azote, ainsi que des moyens pour introduire dans un conduit d'échappement en aval du piège un oxydant apte à transformer du sulfure d'hydrogène en dioxyde de soufre, à l'aide d'une pompe à air injectant dans la ligne d'échappement de l'air atmosphérique.Document FR 2 881 177 discloses a vehicle engine comprising a trap for nitrogen oxides, as well as means for introducing into an exhaust pipe downstream of the trap an oxidant capable of converting hydrogen sulphide into dioxide. of sulfur, using an air pump injecting into the exhaust line of atmospheric air.
L'ajout d'une pompe à air pose toutefois des problèmes de coût et d'encombrement.The addition of an air pump, however, poses problems of cost and space.
La présente invention a pour objectif de remédier à ces inconvénients.The present invention aims to overcome these disadvantages.
L'invention propose un dispositif permettant de traiter de manière simple et économique le sulfure d'hydrogène émis lors de la désulfuration. Le dispositif proposé permet en outre des conditions optimales pour le traitement du sulfure d'hydrogène et évite efficacement l'apparition d'odeurs nauséabondes.The invention proposes a device for treating in a simple and economical way the hydrogen sulphide emitted during desulphurization. The proposed device also allows optimal conditions for the treatment of hydrogen sulfide and effectively prevents the appearance of foul odors.
L'invention a ainsi pour objet un dispositif d'élimination d'oxydes de soufre dans un système de piégeage d'oxydes d'azote disposé dans la ligne d'échappement d'un moteur à combustion interne de véhicule automobile, le moteur étant alimenté en air et en carburant, le dispositif comprenant des moyens de commande aptes à déclencher une élimination des oxydes de soufre du système de piégeage d'oxydes d'azote, par chauffage du système de piégeage d'oxydes d'azote au-delà d'une température prédéterminée et par un réglage de la richesse en carburant du mélange d'air et de carburant à une valeur supérieure à 1 , l'élimination des oxydes de soufre s'accompagnant de l'émission de sulfure d'hydrogène.The invention thus relates to a device for removing sulfur oxides in a nitrogen oxide trapping system disposed in the exhaust line of a motor vehicle internal combustion engine, the engine being powered in air and fuel, the device comprising control means capable of triggering a removal of sulfur oxides from the nitrogen oxide scavenging system, by heating the nitrogen oxide scavenging system beyond a predetermined temperature and by adjusting the fuel richness of the mixture of air and fuel to a value greater than 1, the removal of sulfur oxides accompanied by the emission of hydrogen sulfide.
Le dispositif selon l'invention comprend en outre un système de piégeage du sulfure d'hydrogène émis, des moyens d'oxydation du sulfure d'hydrogène piégé, et des moyens de mesure ou d'estimation de la température du système de piégeage du sulfure d'hydrogène. En outre, lesdits moyens de commande sont aptes à déclencher l'élimination des oxydes de soufre lorsque la température mesurée ou estimée du système de piégeage du sulfure d'hydrogène est supérieure ou égale à une valeur seuil.The device according to the invention further comprises a system for trapping emitted hydrogen sulphide, means for oxidation of trapped hydrogen sulphide, and means for measuring or estimating the temperature of the sulphide trapping system. hydrogen. In addition, said control means are able to trigger the elimination of sulfur oxides when the measured or estimated temperature of the hydrogen sulfide trapping system is greater than or equal to a threshold value.
Le dispositif permet ainsi de s'assurer que le système de piégeage et d'oxydation du sulfure d'hydrogène est à une température suffisamment élevée pour pouvoir traiter efficacement les premières émissions d'H2S sortant du piège à NOx, lorsqu'on déclenche l'élimination des oxydes de soufre du piège à NOx. En effet, le taux de conversion du SO2 en H2S augmente avec la température des gaz qui traversent le piège à H2S.The device thus makes it possible to ensure that the hydrogen sulfide trapping and oxidation system is at a sufficiently high temperature to be able to effectively treat the first H 2 S emissions leaving the NO x trap, when triggers the removal of sulfur oxides from the NO x trap. Indeed, the conversion rate from SO 2 to H 2 S increases with the temperature of the gases that pass through the H 2 S trap.
Pour déclencher une élimination des oxydes de soufre du système de piégeage d'oxydes d'azote, la richesse en carburant du mélange d'air et de carburant est supérieure à 1 , c'est-à-dire que le carburant est en excès stoechiométrique par rapport à l'oxygène de l'air.To trigger sulfur oxides removal from the nitrogen oxide scavenging system, the fuel richness of the air and fuel mixture is greater than 1, ie the fuel is in stoichiometric excess. relative to the oxygen of the air.
Pour une conversion optimale du SO2 en H2S, la valeur seuil de la température mesurée ou estimée du système de piégeage et d'oxydation du sulfure d'hydrogène est de préférence supérieure ou égale à 3500C, et notamment supérieure ou égale à 4000C. Elle est plus préférentiellement comprise entre 400° C et 6000C.For an optimal conversion of SO 2 to H 2 S, the threshold value of the measured or estimated temperature of the hydrogen sulfide trapping and oxidation system is preferably greater than or equal to 350 ° C., and in particular greater than or equal to at 400 ° C. It is more preferentially between 400 ° C. and 600 ° C.
Les moyens d'oxydation du sulfure d'hydrogène piégé comprennent de préférence des moyens de réglage de la richesse en carburant du mélange d'air et de carburant à une valeur inférieure à 1.The oxidation means of the trapped hydrogen sulphide preferably comprise means for controlling the fuel richness of the mixture of air and fuel to a value of less than 1.
La ligne d'échappement peut comprendre un filtre à particules.The exhaust line may include a particulate filter.
L'invention a également pour objet un véhicule automobile comprenant un dispositif décrit ci -dessus.The invention also relates to a motor vehicle comprising a device described above.
L'invention a également pour objet un procédé pouvant mettre en oeuvre un dispositif décrit ci-dessus.The invention also relates to a method that can implement a device described above.
Elle a ainsi pour objet un procédé d'élimination d'oxydes de soufre d'un système de piégeage d'oxydes d'azote disposé dans la ligne d'échappement d'un moteur à combustion interne de véhicule automobile, le moteur étant alimenté en air et en carburant, le système de piégeage d'oxydes d'azote étant susceptible de produire du sulfure d'hydrogène lors d'une élimination des oxydes de soufre du système de piégeage d'oxydes d'azote, le sulfure d'hydrogène produit étant apte à être piégé par un système de piégeage du sulfure d'hydrogène.It thus relates to a process for removing sulfur oxides from a nitrogen oxide trapping system disposed in the exhaust line of a motor vehicle internal combustion engine, the engine being supplied with fuel. air and fuel, the nitrogen oxide trapping system being capable of producing hydrogen sulphide during removal of the sulfur oxides from the nitrogen oxide trapping system, hydrogen sulphide product being capable of being trapped by a system for trapping hydrogen sulphide.
Le procédé selon l'invention comprend :The method according to the invention comprises:
- la mesure ou l'estimation de la température du système de piégeage du sulfure d'hydrogène,- measuring or estimating the temperature of the hydrogen sulphide trapping system,
- le déclenchement, si la température mesurée ou estimée est supérieure ou égale à une valeur seuil, d'une élimination des oxydes de soufre du système de piégeage d'oxydes d'azote, par chauffage du système de piégeage d'oxydes d'azote au-delà d'une température prédéterminée et par un réglage de la richesse en carburant du mélange d'air et de carburant à une valeur supérieure à 1 , du sulfure d'hydrogène étant produit lors de cette étape, etthe triggering, if the measured or estimated temperature is greater than or equal to a threshold value, of removal of the sulfur oxides from the nitrogen oxide scavenging system, by heating the nitrogen oxide scavenging system; beyond a predetermined temperature and by adjusting the fuel richness of the mixture of air and fuel to a value greater than 1, hydrogen sulfide being produced during this step, and
- le piégeage et l'oxydation du sulfure d'hydrogène ainsi produit. L'oxydation du sulfure d'hydrogène est avantageusement réalisée en réglant la richesse en carburant du mélange d'air et de carburant à une valeur inférieure à 1.trapping and oxidation of the hydrogen sulphide thus produced. The oxidation of hydrogen sulphide is advantageously carried out by regulating the fuel richness of the mixture of air and fuel to a value of less than 1.
La valeur seuil de la température mesurée ou estimée du système de piégeage du sulfure d'hydrogène est de préférence supérieure ou égale à 3500C. D'autres buts, caractéristiques et avantages de l'invention apparaîtront à la lecture de la description suivante, donnée uniquement à titre d'exemple non limitatif, et faite en référence aux dessins annexés sur lesquels :The threshold value of the measured or estimated temperature of the hydrogen sulfide trapping system is preferably greater than or equal to 350 ° C. Other aims, characteristics and advantages of the invention will become apparent on reading the following description. given only by way of non-limiting example, and with reference to the appended drawings in which:
- la figure 1 illustre de manière schématique un dispositif selon l'invention, conformément à un premier mode de réalisation, etFIG. 1 schematically illustrates a device according to the invention, according to a first embodiment, and
- la figure 2 illustre de manière schématique un dispositif selon l'invention, conformément à un deuxième mode de réalisation. Le moteur thermique 1 , tel qu'illustré à la figure 1 , est un moteur à explosion de type Diesel. Il comprend classiquement une culasse 3 comprenant plusieurs chambres de combustion 4, par exemple au nombre de quatre. Un système 2 d'injection de carburant est relié à chacune des chambres de combustion 4. Le moteur 1 est alimenté en air via une zone d'admission A. Les gaz d'échappement produits par la combustion d'air et de carburant dans les chambres de combustion 4 sont acheminés vers une ligne d'échappement E. La circulation des gaz brûlés, symbolisée par des flèches, s'effectue de gauche à droite sur la figure.- Figure 2 schematically illustrates a device according to the invention, according to a second embodiment. The heat engine 1, as shown in FIG. 1, is a diesel type explosion engine. It conventionally comprises a cylinder head 3 comprising a plurality of combustion chambers 4, for example four in number. A fuel injection system 2 is connected to each of the combustion chambers 4. The engine 1 is supplied with air via an intake zone A. The exhaust gases produced by the combustion of air and fuel in the combustion chambers combustion chambers 4 are routed to an exhaust line E. The circulation of burnt gases, symbolized by arrows, is carried out from left to right in the figure.
La ligne d'échappement E des gaz brûlés est munie d'un piège à oxydes d'azote 5 et d'un ensemble de post-traitement des gaz brûlés comprenant un filtre à particules 6 et un piège à sulfure d'hydrogène 7 disposé en aval du filtre à particules 6. Le filtre à particules 6 est disposé en aval du piège à oxydes d'azote 5 et est par exemple logé dans la même enveloppe 11. Le filtre à particules 6 est avantageusement utilisé pour l'élimination des particules responsables des fumées noires issues d'un moteur Diesel. Le filtre à particules 6 pourrait également être disposé en amont du piège à oxydes d'azote 5, ou en aval du piège à sulfure d'hydrogène 7.The exhaust line E of the flue gas is provided with a nitrogen oxide trap 5 and a flue gas post-treatment assembly comprising a particulate filter 6 and a hydrogen sulfide trap 7 disposed in downstream of the particulate filter 6. The particulate filter 6 is disposed downstream of the nitrogen oxide trap 5 and is for example housed in the same casing 11. The particulate filter 6 is advantageously used for the removal of particles responsible black fumes from a diesel engine. The particulate filter 6 could also be disposed upstream of the nitrogen oxide trap 5, or downstream of the hydrogen sulfide trap 7.
Dans le mode de réalisation illustré à la figure 1 , le piège à sulfure d'hydrogène 7 est un monolithe indépendant, distinct du filtre à particules 6. Le piège à sulfure d'hydrogène 7 est ainsi logé dans une enveloppe spécifique 12. Le piège à sulfure d'hydrogène 7 comprend une composition apte, d'une part, à piéger le sulfure d'hydrogène issu du piège à oxydes d'azote 5 en milieu de richesse supérieure à 1 (le carburant est en excès stoechiométrique par rapport à l'oxygène de l'air), et d'autre part, apte à le convertir en dioxyde de soufre, en milieu pauvre, de richesse inférieure à 1 (comprenant de l'oxygène en excès), puis de le libérer dans cet état. Le piège à sulfure d'hydrogène 7 peut par exemple comprendre un substrat en cordiérite ou en titanate d'aluminium.In the embodiment illustrated in FIG. 1, the hydrogen sulphide trap 7 is an independent monolith, distinct from the particulate filter 6. The hydrogen sulphide trap 7 is thus housed in a specific envelope 12. The trap The hydrogen sulfide 7 comprises a composition capable, on the one hand, of trapping the hydrogen sulphide from the nitrogen oxide trap 5 in a medium of richness greater than 1 (the fuel is in stoichiometric excess with respect to the oxygen of the air), and secondly, able to convert it to sulfur dioxide, in a poor environment, of less than 1 richness (including excess oxygen), and then to release it in this state. The hydrogen sulfide trap 7 may for example comprise a cordierite or aluminum titanate substrate.
Le piégeage peut avantageusement se faire par adsorption du sulfure d'hydrogène sur la composition.The trapping may advantageously be by adsorption of hydrogen sulphide on the composition.
Un dispositif de commande 8 est apte à déclencher une élimination des oxydes de soufre du système de piégeage d'oxydes d'azote 5, par chauffage du système de piégeage 5 d'oxydes d'azote au-delà d'une température prédéterminée et par un réglage de la richesse en carburant du mélange d'air et de carburant à une valeur supérieure à 1.A control device 8 is capable of triggering removal of the sulfur oxides from the nitrogen oxide scavenging system 5 by heating the nitrogen oxide scavenging system 5 beyond a predetermined temperature and by an adjustment of the fuel richness of the mixture of air and fuel to a value greater than 1.
Le chauffage du système de piégeage d'oxydes d'azote 5 peut avantageusement être effectué en contrôlant la richesse en carburant du mélange d'air et de carburant, par exemple en augmentant le débit de carburant. On peut ainsi contrôler la température du piège à oxydes d'azote 5 en alternant des richesses supérieures à 1 et des richesses inférieures à 1. La mise en température et/ou le contrôle de la température au moment de la désulfuration peuvent également être assurés ou complétés au moyen d'un système de chauffage annexe disposé en amont ou au niveau du piège à oxydes d'azote 5.The heating of the nitrogen oxide scavenging system 5 can advantageously be carried out by controlling the fuel richness of the air and fuel mixture, for example by increasing the flow rate of the fuel. fuel. It is thus possible to control the temperature of the nitrogen oxide trap 5 by alternating wealth greater than 1 and wealth less than 1. The temperature setting and / or temperature control at the time of the desulfurization can also be ensured or supplemented by means of an auxiliary heating system arranged upstream or at the level of the nitrogen oxide trap 5.
La température prédéterminée est de préférence supérieure ou égale à 6500C, et encore de préférence supérieure ou égale à 7000C.The predetermined temperature is preferably greater than or equal to 650 ° C., and still more preferably greater than or equal to 700 ° C.
Un capteur de température 9 est destiné à mesurer la température du piège à sulfure d'hydrogène 7. On peut également estimer cette température. Il est en effet possible d'estimer la température du piège à sulfure d'hydrogène 7 en fonction de l'architecture de la ligne d'échappement E, tel que décrit par exemple dans les documents FR 2 877 043 et FR 2 853 691.A temperature sensor 9 is intended to measure the temperature of the hydrogen sulfide trap 7. This temperature can also be estimated. It is indeed possible to estimate the temperature of the hydrogen sulfide trap 7 as a function of the architecture of the exhaust line E, as described for example in the documents FR 2 877 043 and FR 2 853 691.
Dans une variante, l'estimation de la température du piège à sulfure d'hydrogène 7 peut consister à attendre une durée calibrée après l'établissement de la température prédéterminée du piège à oxydes d'azote 5. Cette durée peut être établie en fonction de l'inertie thermique due à la distance et aux volumes de post-traitement entre le piège à oxydes d'azote 5 et le piège à sulfure d'hydrogène 7. Le capteur de température 9 est relié au dispositif de commande 8. Le dispositif de commande 8 est apte à déclencher l'élimination des oxydes de soufre lorsque la température mesurée ou estimée du piège à sulfure d'hydrogène 7 est supérieure ou égale à une valeur seuil. Ainsi, on peut s'assurer qu'au moment de lancer un milieu de richesse supérieure à 1 , le piège à sulfure d'hydrogène 7 est à une température suffisamment élevée pour pouvoir traiter efficacement les émissions de sulfure d'hydrogène sortant du piège à oxydes d'azote 5. Si la température seuil n'est pas atteinte, la désulfuration n'est pas lancée.Alternatively, the temperature estimate of the hydrogen sulfide trap 7 may be to wait for a calibrated time after setting the predetermined temperature of the nitrogen oxide trap 5. This time can be set as a function of the thermal inertia due to the distance and the post-treatment volumes between the nitrogen oxide trap 5 and the hydrogen sulphide trap 7. The temperature sensor 9 is connected to the control device 8. control 8 is able to trigger the removal of sulfur oxides when the measured or estimated temperature of the hydrogen sulfide trap 7 is greater than or equal to a threshold value. Thus, it can be ensured that at the moment of launching a medium of richness greater than 1, the hydrogen sulphide trap 7 is at a sufficiently high temperature to be able to effectively treat the hydrogen sulphide emissions coming out of the trap. Nitrogen oxides 5. If the threshold temperature is not reached, the desulphurisation is not initiated.
Lorsque la température seuil est atteinte, la désulfuration est lancée par le dispositif de commande 8. La richesse du mélange passant dans le circuit d'échappement (E) est alors supérieure à 1. Un dispositif additionnel 10 d'injecteur de carburant à l'échappement est avantageusement utilisé pour décontraindre le moteur 1 durant cette phase. Le dispositif additionnel 10 permet ainsi de brûler du carburant et d'augmenter la température à proximité du piège à oxydes d'azote 5. Dans ces conditions de richesse (richesse supérieure à 1 ), les espèces réductrices sont en excès et une partie d'entre elles va réagir avec les espèces soufrées, en particulier le SO2, stockées dans le piège à oxydes d'azote 5, pour le convertir en partie en H2S.When the threshold temperature is reached, the desulfurization is started by the control device 8. The richness of the mixture passing through the exhaust circuit (E) is then greater than 1. An additional device 10 The fuel injection nozzle is advantageously used to deconstruct the engine 1 during this phase. The additional device 10 thus makes it possible to burn fuel and increase the temperature in the vicinity of the nitrogen oxide trap 5. In these conditions of richness (richness greater than 1), the reducing species are in excess and a part of between them will react with the sulfur species, in particular SO 2 , stored in the nitrogen oxide trap 5, to convert it in part to H 2 S.
Le composé H2S est alors libéré du piège à oxydes d'azote 5, et est transféré dans le piège à sulfure d'hydrogène 7. Lorsque le moteur 1 repasse en mélange pauvre, l'oxygène se retrouve en excès dans les gaz d'échappement qui parcourent la ligne d'échappement E. Cet oxygène réagit alors avec le H2S stocké pour former du SO2 et d'autres espèces soufrées qui ne sont toxiques ni malodorantes. Ces espèces soufrées peuvent être évacuées hors de la ligne d'échappement E sans risque de pollution. Dès que la désulfuration est terminée, le dispositif de commande 8 procède à l'arrêt des stratégies d'injection spécifiques pour revenir à un fonctionnement normal. Le processus est réitéré périodiquement en fonction des besoins en désulfuration de la ligne d'échappement E.The compound H 2 S is then released from the nitrogen oxide trap 5, and is transferred into the hydrogen sulfide trap 7. When the engine 1 returns to a lean mixture, the oxygen is found in excess in the exhaust gases. Exhaust that runs through the exhaust line E. This oxygen then reacts with the H 2 S stored to form SO 2 and other sulfur species that are toxic or smelly. These sulfur species can be evacuated out of the exhaust line E without risk of pollution. As soon as the desulfurization is complete, the control device 8 stops the specific injection strategies to return to normal operation. The process is reiterated periodically according to the desulphurization requirements of the exhaust line E.
Dans un deuxième mode de réalisation, tel qu'illustré à la figure 2, sur laquelle les éléments identiques à ceux de la figure 1 portent les mêmes références, c'est le filtre à particules 6 lui-même qui est imprégné de la composition du piège à sulfure d'hydrogène 7, de sorte qu'il constitue aussi le système catalytique. Le piège à oxyde d'azote 5 et l'ensemble filtre à particules 6 et piège à sulfure à hydrogène 7 sont logés dans une enveloppe commune 11. In a second embodiment, as illustrated in FIG. 2, in which the elements identical to those of FIG. 1 bear the same references, it is the particle filter 6 itself which is impregnated with the composition of the hydrogen sulfide trap 7, so that it also constitutes the catalytic system. The nitrogen oxide trap 5 and the particulate filter 6 and hydrogen sulfide trap 7 are housed in a common envelope 11.

Claims

REVENDICATIONS
1. Dispositif d'élimination d'oxydes de soufre dans un système de piégeage d'oxydes d'azote (5) disposé dans la ligne d'échappement (E) d'un moteur à combustion interne (1 ) de véhicule automobile, le moteur (1 ) étant alimenté en air et en carburant, le dispositif comprenant des moyens de commande (8) aptes à déclencher une élimination des oxydes de soufre du système de piégeage (5) d'oxydes d'azote, par chauffage du système de piégeage (5) d'oxydes d'azote au-delà d'une température prédéterminée et par un réglage de la richesse en carburant du mélange d'air et de carburant à une valeur supérieure à 1 , l'élimination des oxydes de soufre s'accompagnant de l'émission de sulfure d'hydrogène, caractérisé en ce que le dispositif comprend en outre un système de piégeage (7) du sulfure d'hydrogène émis, des moyens d'oxydation du sulfure d'hydrogène piégé, et des moyens de mesure (9) ou d'estimation de la température du système de piégeage (7) du sulfure d'hydrogène, et en ce que lesdits moyens de commande (8) sont aptes à déclencher l'élimination des oxydes de soufre lorsque la température mesurée ou estimée du système de piégeage (7) du sulfure d'hydrogène est supérieure ou égale à une valeur seuil.1. A device for removing sulfur oxides in a nitrogen oxide trapping system (5) arranged in the exhaust line (E) of an internal combustion engine (1) of a motor vehicle, the motor (1) being supplied with air and fuel, the device comprising control means (8) able to trigger a sulfur oxide removal from the nitrogen oxide trapping system (5) by heating the heating system; trapping (5) nitrogen oxides above a predetermined temperature and adjusting the fuel richness of the mixture of air and fuel to a value greater than 1, the removal of sulfur oxides s accompanying emission of hydrogen sulfide, characterized in that the device further comprises a trapping system (7) of emitted hydrogen sulphide, oxidation means trapped hydrogen sulphide, and means measuring (9) or estimating the temperature of the trapping system (7) of the sulphide of hydrogen, and in that said control means (8) are capable of triggering the removal of the sulfur oxides when the measured or estimated temperature of the hydrogen sulfide trapping system (7) is greater than or equal to a threshold value.
2. Dispositif selon la revendication 1 , caractérisé en ce que la valeur seuil de la température mesurée ou estimée du système de piégeage (7) du sulfure d'hydrogène est supérieure ou égale à 3500C.2. Device according to claim 1, characterized in that the threshold value of the measured or estimated temperature of the trapping system (7) of the hydrogen sulphide is greater than or equal to 350 0 C.
3. Dispositif selon la revendication 1 ou 2, caractérisé en ce que moyens d'oxydation du sulfure d'hydrogène piégé comprennent des moyens de réglage de la richesse en carburant du mélange d'air et de carburant à une valeur inférieure à 1.3. Device according to claim 1 or 2, characterized in that oxidation means trapped hydrogen sulphide include means for adjusting the fuel richness of the mixture of air and fuel to a value less than 1.
4. Dispositif selon l'une des revendications 1 à 3, caractérisé en ce que la ligne d'échappement (E) comprend un filtre à particules (6). 4. Device according to one of claims 1 to 3, characterized in that the exhaust line (E) comprises a particle filter (6).
5. Véhicule automobile, caractérisé en ce qu'il comprend un dispositif selon l'une des revendications 1 à 4.5. Motor vehicle, characterized in that it comprises a device according to one of claims 1 to 4.
6. Procédé d'élimination d'oxydes de soufre d'un système de piégeage (5) d'oxydes d'azote disposé dans la ligne d'échappement (E) d'un moteur à combustion interne (1 ) de véhicule automobile, le moteur (1 ) étant alimenté en air et en carburant, le système de piégeage (5) d'oxydes d'azote étant susceptible de produire du sulfure d'hydrogène lors d'une élimination des oxydes de soufre du système de piégeage (5) d'oxydes d'azote, le sulfure d'hydrogène produit étant apte à être piégé par un système de piégeage (7) du sulfure d'hydrogène, caractérisé en ce que le procédé comprend :6. Process for removing sulfur oxides from a nitrogen oxide trapping system (5) arranged in the exhaust line (E) of an internal combustion engine (1) of a motor vehicle, the engine (1) being supplied with air and fuel, the nitrogen oxide trapping system (5) being capable of producing hydrogen sulphide during removal of the sulfur oxides from the trapping system (5); ) of nitrogen oxides, the produced hydrogen sulfide being capable of being trapped by a hydrogen sulfide trapping system (7), characterized in that the process comprises:
- la mesure ou l'estimation de la température du système de piégeage (7) du sulfure d'hydrogène,the measurement or estimation of the temperature of the trapping system (7) of the hydrogen sulphide,
- le déclenchement, si la température mesurée ou estimée est supérieure ou égale à une valeur seuil, d'une élimination des oxydes de soufre du système de piégeage (5) d'oxydes d'azote, par chauffage du système de piégeage d'oxydes d'azote (5) au-delà d'une température prédéterminée et par un réglage de la richesse en carburant du mélange d'air et de carburant à une valeur supérieure à 1 , du sulfure d'hydrogène étant produit lors de cette étape, etthe triggering, if the measured or estimated temperature is greater than or equal to a threshold value, of removal of the sulfur oxides from the nitrogen oxide trapping system (5) by heating the oxide trapping system nitrogen (5) above a predetermined temperature and by adjusting the fuel richness of the air and fuel mixture to a value greater than 1, hydrogen sulfide being produced in this step, and
- le piégeage et l'oxydation du sulfure d'hydrogène ainsi produit.trapping and oxidation of the hydrogen sulphide thus produced.
7. Procédé selon la revendication 6, caractérisé en ce que l'oxydation du sulfure d'hydrogène est réalisée en réglant la richesse en carburant du mélange d'air et de carburant à une valeur inférieure à 1.7. Method according to claim 6, characterized in that the oxidation of hydrogen sulfide is carried out by adjusting the fuel richness of the mixture of air and fuel to a value less than 1.
8. Procédé selon la revendication 6 ou 7, caractérisé en ce que la valeur seuil de la température mesurée ou estimée du système de piégeage (7) du sulfure d'hydrogène est supérieure ou égale à 3500C. 8. The method of claim 6 or 7, characterized in that the threshold value of the measured or estimated temperature of the trapping system (7) of hydrogen sulphide is greater than or equal to 350 0 C.
EP09784389A 2008-07-24 2009-05-18 Device for eliminating sulphur oxides in a system for capturing nitrogen oxides Withdrawn EP2352911A1 (en)

Applications Claiming Priority (2)

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FR0855092A FR2934314B1 (en) 2008-07-24 2008-07-24 DEVICE FOR REMOVING SULFUR OXIDES IN A SYSTEM FOR TRAPPING NITROGEN OXIDES.
PCT/FR2009/050921 WO2010010260A1 (en) 2008-07-24 2009-05-18 Device for eliminating sulphur oxides in a system for capturing nitrogen oxides

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FR2934314B1 (en) 2013-02-15
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