• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a device for the after-treatment of the exhaust gases of a heat engine (M) comprising, from upstream to downstream: • a mouth of an ammonia introduction means (2) or an ammonia precursor for selective catalytic reduction of SCR nitrogen oxides; A selective catalytic reduction catalyst member SCR (3) in the form of a member dedicated to selective catalytic reduction catalysis SCR (NOx nitrogen oxides and / or a particulate filter (4) equipped with a catalytic selective catalytic reduction catalyst SCRF of NOx nitrogen oxides • an ammonia leak treatment unit (5), such that said ammonia leak treatment unit (5) is equipped with ammonia purge means .
    公开号:FR3057020A1
    申请号:FR1659498
    申请日:2016-10-03
    公开日:2018-04-06
    发明作者:Alejandro Yarce；Faycal Souidi；Thomas Le Tallec；Dimitri Bastaert
    申请人:Peugeot Citroen Automobiles SA；
    IPC主号:
    专利说明:

    Holder (s): PEUGEOT CITROEN AUTOMOBILES SA Société anonyme.
    Extension request (s)
    Agent (s): PEUGEOT CITROEN AUTOMOBILES SA Public limited company.
    DEVICE FOR AFTER-TREATMENT OF THE EXHAUST GASES OF A THERMAL ENGINE.
    FR 3 057 020 - A1
    The invention relates to a device for post-treating the exhaust gases of a heat engine (M) which comprises, from upstream to downstream:
    a mouth of a means of introduction (2) of ammonia or of an ammonia precursor for the selective catalytic reduction of nitrogen oxides SCR;
    a selective catalytic reduction catalyst SCR member (3) in the form of a member dedicated to the selective catalytic reduction catalysis SCR (nitrogen oxides NO X and / or a particulate filter (4) provided with a catalyst coating for selective catalytic reduction SCRF of nitrogen oxides NO X an ammonia leakage treatment device (5), such that said ammonia leakage treatment device (5) is provided with ammonia purge means .
    Illllllllllllllllllllllllllllllllllllllllllllll
    DEVICE FOR AFTER-TREATMENT OF EXHAUST GASES OF A THERMAL ENGINE [001] The invention relates to means for treating pollutants of exhaust gases from heat engines.
    Pollutant emissions from combustion engines fitted to motor vehicles are regulated by standards. The regulated pollutants are, depending on the combustion engine technology considered, carbon monoxide (CO), unburnt hydrocarbons (HC), nitrogen oxides (NOx, i.e. NO and NO 2 > and particles (PM), which are formed during the combustion of fuel in the combustion chamber and then emitted to the exhaust.
    It is known to use a number of depollution means in the exhaust line of combustion engines to limit emissions of regulated pollutants. An oxidation catalyst allows the treatment of carbon monoxide, unburnt hydrocarbons, and under certain conditions nitrogen oxides; a particulate filter can be used to treat soot particles.
    This type of device is generally designated by the term "post-treatment" device for the exhaust gases.
    To meet the anti-pollution standards on nitrogen oxide (NOx) emissions, a specific post-treatment system can be introduced into the exhaust system of vehicles, especially vehicles equipped with Diesel engines. For the treatment of nitrogen oxides (NOx), there are known technologies of selective catalytic reduction, or "SCR" for "Selective Catalytic Reduction" in English, which consist in reducing NOx by introduction of a reducing agent ( or a precursor of such a reducing agent) in the exhaust gas by catalyzed reactions. It may for example be a urea solution, the decomposition of which will make it possible to obtain ammonia which will serve as a reducing agent, but also a reducing agent or a precursor of such a reducing agent under gaseous form. In the remainder of this document, we generally speak of a "reducing agent" to designate a reducing agent or a precursor of a reducing agent.
    The reducing agent generated makes it possible to reduce the nitrogen oxides by reaction in an SCR catalyst, that is to say a substrate carrying a catalytic impregnation capable of promoting the reduction of NOx by the reducing agent.
    European standards, in particular, are becoming more and more stringent. And solutions to reduce pollutant emissions at the exhaust line to meet current standards will prove to be insufficient given the changes in standards planned beyond 2017.
    Indeed, the first step of the standard, Euro 6b (entered into force in September 2014) has led car manufacturers to choose between different options to more specifically reduce NOx emissions: - reduction of NOx "to the source >>, at the level of the very functioning of the engine, via technologies of type recycling of exhaust gases in the engine, recycling also called EGR technology according to the acronym of the English term corresponding to "Exhaust Gas Recirculation >> high and low pressure, for example; - reduction of NOx at the exhaust line via a sequential catalytic treatment technology called "NOx trap"; - reduction of NOx at the exhaust line also, via a continuous treatment technology called "selective catalytic reduction" as briefly described above (SCR); or even by combining several of these solutions.
    If these solutions make it possible to satisfy this first stage in the evolution of the standard (Euro6b), they are not necessarily capable of satisfying the second stage which promises to be even more severe (Euro 6c, entry into force planned for September 2017), with measurements of pollutants on a new rolling cycle called "WLTC >> (for" Worldwide Harmonized Light vehicles Test Cycle >> in English, or harmonized test cycle for light vehicles in French), containing more phases transient than the current homologation cycle (known as “MVEG >> for Motor Vehicle Emissions Group in English, or group of emissions for motorized vehicles in French), but also non-cycle measures (called“ RDE ”for Real Driving Emission or emissions under real driving conditions) should be introduced.
    To respond in particular to the risk of excessively high NOx emissions outside the cycle, different technological solutions and architectures can be envisaged. They have their pros and cons. But the most effective nitrogen oxides treatment technology is selective catalytic reduction (SCR) because it is effective in wider temperature and gas flow ranges than that of a NOx trap, the other solution. post-processing.
    In addition, there are constraints on the location of the post-processing device. In fact, in general, the catalytic systems used are all the more efficient as the temperature of the exhaust gases passing through them is high (up to a certain point). They will then prime faster after the engine starts as the temperature of the exhaust gases increases rapidly. It is therefore advantageous to install the post-treatment devices as close as possible to the engine, that is to say as close as possible to the exhaust gas collector, under the hood, even though this environment is generally very congested. Post-processing devices must therefore be as compact as possible without affecting their performance.
    It is, for example, known from patent application WO 2011/089330 a post-treatment device grouping together in the same envelope several members which will be successively crossed by the exhaust gases. It is proposed, in particular, a series of organs comprising from upstream to downstream: - an oxidation catalyst, - an injector of urea-type reducing agent, - a mixer whose role is to intimately mix the droplets d urea injected into the envelope through which the gases pass, so as to decompose into ammonia as homogeneously as possible over the entire cross section of the envelope, - an SCR member, - a particle filter (called FAP by the after). An alternative is also proposed, consisting in replacing the SCR member and the FAP, by a FAP which is impregnated with a NOx reduction catalyst and which thus fulfills both the function of soot filter and reduction of NOx (hereafter called SCRF).
    However, a dedicated SCR member as described in this document may not start early enough for reasons of unfavorable thermal conditions, in particular in urban driving conditions during which the temperatures in the exhaust line are quite low. . However, it is precisely during this type of urban driving that changes to the European standard (in particular) will become restrictive in terms of reducing NOx emissions.
    In addition, additional constraints appear when the motor vehicle is a so-called "heavy" vehicle (over 1500 kg), whether it is a vehicle for individuals or of the utility type. Indeed, under the same driving conditions as a lighter vehicle, the "heavy" vehicle will have higher temperature conditions at the exhaust to manage, and larger quantities to be treated with NOx generated in the engine. To compensate for these higher NOx emissions, the quantities of reducing agent to be injected into the exhaust line (for example urea decomposing into ammonia) will have to be greater too, since these quantities are dictated by the stoichiometry of the NOx reactions with ammonia. The higher temperatures of the gases leaving the engine also favor the thermo-desorption of the ammonia stored in the SCR (and / or SCRF) organs, and can also contribute to the degradation of their active catalytic phases which can induce a reduction in their ammonia storage capacity. The combination of higher temperatures and a greater quantity of urea (or ammonia) to be injected onto the line induces an increased risk of ammonia emissions which would not have reacted at the end of the exhaust line. . However, ammonia leaks at the end of the exhaust line are smelly, and can be inconvenient, especially if the vehicle is in a confined space such as a closed parking lot.
    It is known from patent application WO 2016/092170 a pollution control architecture which offers a first response, by adding at the end of the exhaust line a member dedicated to the treatment of a possible excess of unreacted ammonia before let it escape at the end of the line. It is in particular a body which treats excess ammonia by oxidation of ammonia to NOx then by reduction of said NOx into nitrogen, and which we will be able to designate in the following of this text under the term ASC . "ASC" is the English acronym for "Ammonia Slip Catalyst" or catalyst for ammonia leaks in French.
    However, this type of ammonia leakage treatment device requires reaching a certain temperature to be effective. And it is through the heat of the exhaust gases passing through it that it can heat up to the threshold temperature required to make it operational. However, it is rather arranged at the end of the line, when the exhaust gases already have a lowered temperature, and, under certain operating conditions, it may not fulfill its role properly.
    The invention then aims to improve the post-treatment devices, and more particularly to improve the functioning of the ammonia leakage treatment organs which are part of it.
    The invention firstly relates to a device for post-treating the exhaust gases of a heat engine which comprises, from upstream to downstream:
    • a mouthpiece of a means for introducing ammonia or an ammonia precursor for the selective catalytic reduction of nitrogen oxides SCR;
    • a selective catalytic reduction catalyst SCR member in the form of a member dedicated to the selective catalytic reduction catalysis SCR of nitrogen oxides NO X and / or a particulate filter provided with a selective catalytic reduction catalyst coating SCRF of nitrogen oxides NO X ;
    • an ammonia leakage treatment device, and such that said ammonia leakage treatment device is provided with means for purging ammonia.
    We understand by the terms "upstream" and "downstream" as a function of the normal direction of flow of the exhaust gases in the exhaust line, from the exhaust gas manifold at the outlet of the engine up to '' to the end cannula of the exhaust line.
    The invention therefore proposes to improve the operation of the ammonia leakage treatment device by adding to it purging means, that is to say means making it possible to de-saturate and to release ammonia in an oxidized form (nitrogen) at the end of the line, which allows the organ to maintain its efficiency even when the conditions encountered (significant leaks, low temperatures) are not favorable.
    Preferably, the purging means are controllable electric heating means. It is in fact by heating the gases which will pass through the organ, or directly the organ, that it becomes possible to purge it when the temperature conditions are not sufficient for the treatment and the salting out of the ammonia. treated are done correctly.
    According to one embodiment, the controllable heating means are an electrically heated catalyst (also called "EHC >> for" Electrically Heated Catalyst >> in English, or even "electrically heated catalyst >> in French), which is arranged upstream of the ammonia leakage treatment unit. It can be an entirely metallic or partially metallic component or it can be mineral and doped.
    Advantageously, this electrically heated EHC catalyst is placed in the same casing as the ammonia leakage treatment device. It is notably very close. This limits any heat loss from the exhaust gases between the area where they are heated and the area where the ammonia leakage treatment device is located.
    Alternatively, the electrically heated EHC catalyst comprises an electrically conductive mineral matrix intended to be traversed by the exhaust gases and which is connected to an electrical supply. This mineral matrix may or may not be entirely made of metal, for example based on doped SiC, be porous, have channels, be in the form of a network of conductive wires, etc.
    According to another variant, the controllable heating means are integrated into the ammonia leakage treatment device: the ammonia leakage treatment device comprises a porous matrix on which catalytic compositions are deposited, and said matrix is electrically conductive, in particular by being based on doped SiC or on metal. It is the matrix of the organ which heats directly this time, with the ad hoc current leads, possibly with the support of heating elements which also completely surround it (sheath) or partially (network of wires, strips conductors distributed around its perimeter).
    Advantageously, the ammonia leakage treatment unit is a catalyst for treating ammonia ASC leaks by oxidizing ammonia to NOx and then reducing said NOx to nitrogen.
    The invention also relates to an assembly comprising the post-processing device described above and which also comprises an electrical supply for the heating means and a control unit controlling the electrical supply of the heating means according to the temperature of the ammonia leakage treatment unit.
    The invention also relates to a method of implementing the assembly described above, such that the control unit activates the electrical supply of the heating means when the temperature of the leakage treatment member ammonia is less than or equal to 150 or 200 ° C.
    Advantageously, one can determine the temperature of the ammonia leakage treatment device by measurement using a sensor at said device, or upstream or downstream of the device on the line. escapement, or by estimation or by mapping.
    Preferably, the control unit controls the all or nothing heating means or in a modulated manner.
    The invention also relates to an exhaust line which includes the post-processing device described above, as well as the powertrain incorporating this exhaust line, and also the motor vehicle incorporating this powertrain.
    This architecture of post-processing device has proven to be extremely favorable in several aspects.
    It improves the performance of the device, in particular as regards the reduction of NOx under the least favorable conditions, namely, as mentioned above, in urban driving conditions (where the temperature of the gases d exhaust remains less than a road or motorway type rolling); or even aggressive driving conditions, with high exhaust gas flows to be treated in spurts.
    It has also been shown that this architecture makes it possible to limit ammonia releases / leaks as far as possible at the end of the exhaust line (which is also known in English as "NH 3 slip", releases of ammonia coming either from the reducing agent injected upstream of the member carrying the SCR catalyst but which have not reacted, or formed during the purging of the LNT) this thanks to the addition of a member for treating these ammonia leaks. This is very advantageous, especially for heavy vehicles which require the injection of a greater quantity of reducing agent, with therefore an increased risk of salting out of ammonia in the end.
    The device according to the invention will treat gaseous and particulate pollutants as they pass through the depollution organs: they therefore first enter a first organ, according to a first embodiment, in the form an oxidation catalyst, where CO and HC are oxidized to water (H 2 O) and carbon dioxide (CO 2 ). The products of the oxidation of CO and HC, namely H 2 O and CO 2 , as well as nitrogen oxides and particles, emerge from this first DOC body. The residual NOx, and the particles re-enter the SCR organ and / or the SCRF organ, which will (will) operate the reduction of NOx by NH 3 and eliminate the particles by storing them before burning them during regeneration.
    In one embodiment; the first DOC oxidation catalyst type member is replaced by a NOx trap, the presence, upstream of the SCR member, of the NOx trap, furthermore guarantees that at least part of the NOx will be treated even before entering the SCRF selective catalytic reduction unit. It is recalled that the NOx traps are sequential NOx treatment systems, with storage in a poor mixture of NOx (excess oxygen), then destocking and reduction of NOx in rich mixture (excess of reducing agents): - in mixture poor, the NOx are stored in the form of nitrates on active sites (in general in the form of simple or mixed oxides such as barium oxide or aluminate); - in a rich mixture, the NOx are destocked and reduced to N 2 by the reducing agents (CO, HC and H 2 ), this is called purging of NOx. To ensure this NOx trapping and reduction function, the active phase of the catalyst generally comprises noble metals, of the Pt, Pd type, ensuring the oxidation of NO to NO 2 and of CO / HC, thus playing the same role. than a conventional oxidation catalyst, rhodium allowing the reduction of NOx in a rich mixture, and a simple or mixed oxide allowing the storage of NOx in a lean mixture. The operation of the NOx trap therefore requires periodic wealth switching, the trap storing until NOX saturation, and then being periodically "purged" by a change in wealth.
    Finally, any excess ammonia is treated by the ad hoc treatment member, at the downstream end of the post-treatment device, According to a first variant, the DOC oxidation catalyst member or the NOx trap, the mouthpiece, and the particulate filter member provided with a SCRF selective catalytic reduction catalyst coating of nitrogen oxides NOx are grouped in a single envelope, and the leakage treatment member d ammonia is disposed outside said single envelope. It is thus possible to distribute the various organs of the post-treatment device, as a function of the space available under the hood: thus, the organs except that treating the ammonia leakage remain grouped at the engine output under the hood, while the organ of ammonia leakage treatment can be carried further downstream on the exhaust line, and thus be in the underbody area of the vehicle.
    Optionally, the action of the ammonia leakage treatment device is supplemented by an ammonia leakage treatment coating integrated into the particle filter, preferably in its downstream part.
    In another variant, all the organs and mouth are grouped in a single envelope: This architecture preserves the compactness of the assembly, which is contained in a single envelope, and which can thus be advantageously housed as close as possible to the collector exhaust gases at the engine outlet on the exhaust line, and in particular under the hood.
    Preferably, the ammonia leakage treatment device is a catalyst for the treatment of ammonia leaks by oxidation of ammonia to NOx and then the reduction of said NOx to nitrogen, which may be described below. of this text designate under the term ASC. "ASC" is the English acronym for "Ammonia Slip Catalyst" or catalyst for ammonia leaks in French.
    Advantageously, the oxidation catalyst member can also comprise a nitrogen oxide adsorber material, also called PNA which is the acronym for the expression "Passive NOx Adsorber".
    The role of a PNA type material is to be able to store during the cold phases the nitrogen oxides emitted by the engine, as long as the organs catalyzing the reduction of NOx (the SCR member and the particle filter with SCRF catalytic coating) are not yet functional. Indeed, it is necessary to wait 180 to 200 ° C to be able to inject the reducer (urea) in the exhaust line and form the ammonia which will then convert the NOx. With NH 3 "pre-stored" in the SCR coating, the conversion of NOx can take place a few tens of degrees before (around 140 ° C). PNA works by storing NOx "cold" (thanks, in particular, to the addition, in the "classic" impregnation of an oxidation catalyst, of simple or mixed oxides of basic character such as, for example , cerium or barium oxides) before returning them at a higher temperature when the SCR is fully operational (between 200 and 300 ° C). To ensure correct operation of the PNA, purging phases are provided to clean its surface which has been sulphated over time, in known manner.
    The invention also relates to, in a first embodiment, a motor vehicle delimiting a space under the hood, which contains what is usually designated by the term engine compartment, and a space under the body, and comprising a combustion engine connected to the previous exhaust line, such that the engine and the exhaust line after-treatment device are arranged in the space under the hood. There are thus all the pollution control devices grouped together, compactly, as close as possible to the engine.
    The invention also relates to, in a second embodiment, a motor vehicle delimiting a space under the hood and a space under the body, and comprising a heat engine connected to the previous exhaust line, such as the engine , the DOC oxidation catalyst component or the LNT NOx trap, the mouthpiece, and the SCR component and the particulate filter fitted with a SCRF selective catalytic reduction catalyst coating of the NOx nitrogen oxides of the aftertreatment of the exhaust line are arranged in the space under the hood, and such that the ammonia leakage treatment device is arranged in the space under the body. In this way, the pollution control devices needing a high exhaust gas temperature are brought together as close as possible to the engine, and the ammonia leakage treatment device is moved away from the engine to protect it from excessively severe thermals which could cause degradation of its effectiveness.
    The invention is described in more detail below with reference to the figures relating to a non-limiting embodiment relating to a device for post-treating the exhaust gases of a diesel engine:
    - Figure 1 very schematically shows an engine and its exhaust line of a motor vehicle comprising the post-processing device according to an example of the invention;
    - Figure 2 shows the structure of the catalysts of the ammonia leakage treatment device belonging to the post-treatment device of Figure 1;
    - Figure 3 shows a first variant of ammonia leakage treatment device belonging to the post-treatment device of Figure 1;
    - Figure 4 shows a second variant of ammonia leakage treatment device belonging to the post-treatment device of Figure 1.
    The references taken from one figure to another denote the same components, and the different components shown are not necessarily to scale. The figures remain very schematic to facilitate reading.
    In the invention, and as shown in Figure 1 in the manner of a block diagram, there is provided a treatment device according to the invention of the exhaust gases of a heat engine M. This device is integrated into the exhaust line L connected to the exhaust gas collector (not shown) of the engine Μ. It comprises, depending on the direction of flow of the exhaust gases (from upstream to downstream), represented by the arrow F, a member 1 oxidation catalyst or a NOx trap according to one or the other of the modes. of embodiment of the invention, a mouthpiece of a means 2 for introducing a reducing agent (or a precursor of reducing agent), a mixer not shown, a dedicated SCR member 3, a particle filter 4 SCRF provided with an SCR impregnation coating and an ammonia leakage treatment catalyst 5. At least one NOx sensor (not shown) is also provided between the filter 4 and the ammonia treatment catalyst 5.
    Note that all of these organs can be arranged in the same envelope coming to be connected to the line L. As a variant, certain organs can have a dedicated envelope connected to the line. Thus, we can group organs 1 to 4 in a common envelope, and have organ 5 for treating ammonia leaks further down the line, in a dedicated envelope.
    According to a first embodiment, the first “brick” of this post-treatment device is an oxidation catalyst member 1, which oxidizes the reducing species that are carbon monoxide (CO) and unburnt hydrocarbons (HC ). The reactions it promotes are as follows:
    CO + 1/2 O 2 -> CO 2 (R1) Oxidation reaction of carbon monoxide
    C x H y + (x + y / 4) O 2 -> x CO 2 + (y / 2) H 2 O (R2) Oxidation reaction of unburnt hydrocarbons [0051] It consists of a nest support cordierite type bee on which is deposited a catalytic active phase ("washcoat") containing precious metals to catalyze the oxidation reactions of CO, HC and NO. This phase also includes oxides such as alumina doped with different stabilizers (lanthanum, cerium, zirconium, titanium, silicon, etc.). Precious metals (platinum, palladium) are deposited on these oxides in order to catalyze the oxidation reactions from low temperatures. Acid compounds such as zeolites are also added. Their aptitude for the storage of hydrocarbons at low temperature and their destocking at high temperature makes it possible to improve the treatment of HC during cold phases. We can add to these functions (oxidation of carbon monoxide and unburnt hydrocarbons and storage of the latter at low temperature) a storage function of nitrogen oxides, NOx also at low temperature. This storage function is ensured by the introduction of simple or mixed oxide materials of a basic nature such as, for example, cerium or barium oxides, among others.
    According to another embodiment, the oxidation catalyst is replaced by a NOx trap. It consists of a honeycomb-type cordierite support on which is deposited a catalytic phase comprising elements promoting storage such as, but not only, simple or mixed oxides of barium and / or magnesium.
    In lean mixture, the NOx trap will store the NOx by carrying out two reactions in series:
    NO + 1/2 O 2 NO 2
    NO 2 + "Ba >> Ba (NO 3 ) 2 In a rich mixture, the NOx trap destocks and processes at least part of the NOx by carrying out two other reactions in series:
    Ba (NO 3 ) 2 NOx + "Ba >>
    NOx + "reducers" (HC, CO ..) -> N 2 [0055] The urea injector 2 or the mixer (also called mixing box), already described and known, is not described in detail here, in particular from the aforementioned patent application WO 2011/089330. We just remember that the mixing box supplied by an injector 3, itself supplied by a gauge-pump module which draws urea in aqueous solution from a tank of approximately 20 liters (it may contain less because the volume onboard urea depends on the consumption strategy adopted), ensures a mixture between the urea drops and the exhaust gases sufficient for the thermolysis reaction (R3) to take place completely and for the reaction (R4) to hydrolysis takes place in part. Reactions (R3) and (R4) are explained below.
    The dedicated SCR 3 member and the SCRF 4 particulate filter treat nitrogen oxides. The principle of reducing these NOx by SCR (by the dedicated body and by coating the particle filter 4) can be broken down into two main steps:
    > Formation of the reducing agent (NH 3 ) from Adblue ® which is a mixture of 32.5% urea and water (NH 2 ) 2 CO NH 3 + HNCO (R3) thermolysis of urea
    HNCO + H 2 O -> NH 3 + CO 2 (R4) hydrolysis of isocyanic acid The decomposition of urea, injected by injector 3 into the mixing box, takes place in two stages: a first called "thermolysis" which forms a molecule of NH 3 and an isocyanic acid molecule (HNCO) and a second which forms the second molecule of NH 3 from the hydrolysis of isocyanic acid. These two stages, but especially the vaporization of the water contained in the mixture, require temperatures of at least 180 to 200 ° C, hence the advantage that the injector and the gas-liquid mixing box (urea ) are close to the output of the motor M. This step makes it possible to form the reducer essential for the operation of the SCR reduction.
    > Selective catalytic reduction of NOx by NH 3 by the SCR coating of organs and 4:
    NO + O 2 + 4 NH 3 4 N 2 + 6 H 2 O (R5) SCR standard
    NO + NO 2 + 2 NH 3 -> 2 N 2 + 3 H 2 O (R6) SCR with fast kinetics
    6NO 2 + 8NH 3 -> 7 N 2 + 12 H 2 O (R7) SCR with slow kinetics [0058] Several reactions can take place (R5 to R7), but the optimal and desired conversion of NOx is obtained thanks to the reaction (R6) whose kinetics are the fastest but whose stoichiometry imposes a NO 2 / NOx ratio close to 0.5, especially at low temperatures (that is to say at most 250 ° C).
    The SCR catalyst of the dedicated SCR member 3 and of the particle filter 4 is based on copper zeolites, such as chabazite, β, copper-ferrierite, ZSM5 ... It is the best choice, in particular so that the catalyst of the particulate filter remains effective even at very high temperature (that it resists regeneration of the filter in particular). The porous support of the filter 7 is rather made of silicon carbide SiC.
    Let us now return to the operation of the ammonia leakage treatment catalyst 8. We have chosen here a catalyst member 5 of ASC type, the operating principle and structure of which are illustrated in FIG. 2. It has two layers of impregnation: a layer C2 which performs the oxidation function of NH 3 to NOx and a layer C1 which performs the function of reducing NOx by NH 3 .
    The composition of the ASC 8 catalysts is thus as follows: the upper layer C1 (that which is in contact with the exhaust gases) corresponds to a catalytic coating of SCR type and the lower layer C2 (that which is in contact with the walls of the substrate contains precious metals (preferably very small amount of palladium, between 0.5 and 5 g / ft3, ideally 1 to 2)) deposited on alumina. The functioning of the body 8 ASC is as follows: the residual ammonia enters the layer C1 and is stored in this layer in part. The rest of the ammonia crosses this layer C1 and enters the layer C2, the precious metals (Pd) of which favor the oxidation of the ammonia NH 3 to NOx. When the NOx emerge from the SCR catalytic coating of the layer C2, they necessarily pass through the layer C1 where the NH 3 is stored. The NOx reduction reaction with NH 3 can then take place. The NOx are thus converted into nitrogen (N 2 ) before leaving this catalyst 8.
    At the outlet of the exhaust line, there is therefore no, or almost no risk of ammonia emissions into the atmosphere thanks to this catalyst 5, even if the engine is fitted to a utility vehicle. with a strong need for NOx treatment, as explained below:
    If we take all of the reactions R3 to R7 explained above, we understand that there is a NH 3 storage phase in the catalytic coating of the SCRF filter 7, - prior to the conversion of NOx to N 2 thanks to this same NH 3 generated by the decomposition of urea. This ammonia storage represented by a criterion called "NH 3 storage capacity" evolves according to different parameters such as the intrinsic characteristics of the catalytic coating, its state (new or aged), the intra-catalyst temperature, or even to a lesser extent. measurement, the residence time of the gases in the catalyst ...
    There are thus SCR catalytic coatings which have greater or lesser NH 3 storage capacities: the ammonia storage capacity of SCR coatings based on copper is, for example, greater than that of coatings. based on Iron.
    As indicated in the preamble to the present application, the ammonia leakage treatment unit 5 (or ASC) loses its effectiveness in treating the ammonia and then releasing the N 2 resulting from its treatment as soon as it goes below a temperature of around 200 ° C, and even more significantly when it goes below 150 ° C. However, certain operating conditions of the engine (starting) or certain locations (when it is offset far enough from the rest of the exhaust gas treatment bodies on the exhaust line) mean that it can be saturated with ammonia, without be able to process it and release it.
    The invention therefore proposes to equip this member with purging means, in the form of electric heating means.
    A first variant of implementation of these heating means is shown in Figure 3, where the ASC 5 member is arranged in an envelope 51 which is dedicated to it, downstream of the other members 1 to 4, cylindrical envelope of diameter larger than that of the rest of the exhaust line and provided at each of its ends with a connection cone 52,53. Here, the matrix of the ASC 5 member on which the catalytic compositions are deposited has been modified to become electrically conductive. It is in particular a porous SiC matrix preferably doped with nitrogen. Current feeds are provided in the form of metal plates, in particular in the form of a metal sheath or of a network of metal wires coming to surround the matrix and supplied with electricity by a source of electricity S, in the occurrence the vehicle battery. Here, therefore, the entire matrix of the ASC organ heats up when it is supplied with electricity.
    A second variant of implementation of these heating means is shown in Figure 4: Here, the matrix of the 5 ASC member remains unchanged, mineral and not / not very conductive. On the other hand, a conductive disc 7 is attached to it, just upstream and in the same envelope 51. This disc 7 is made of metal and has openings to let the gases pass: it can consist of networks or of winding of metallic wires. . In this example, it consists of several windings of metal strips, which define channels allowing the exhaust gases to pass through it. It is very compact (between 8 and 12 mm, in particular between 9 and 11 mm thick only), and supplied with electricity via a current supply 8 connected to the electrical power source S, which is the vehicle battery or a dedicated battery. Electrically insulated pins 10 provide constant spacing between the disc 7 and the member 5, they ensure the mechanical strength of the disc. Here, the disc 7 therefore comes to heat the exhaust gases before they pass through the ASC 5 member.
    The control of the electrical supply of the heating means, whatever their implementation, is carried out by a command and control unit which controls the ON / OFF switch between the battery and the current leads of these means heated. The control unit controls the closing of the switch as long as the temperature of the ASC 5 member remains below 200 ° C and controls its opening above 200 ° C. The temperature of the ASC 5 member can be done by a temperature sensor connected to the control unit and located either in the immediate vicinity of the ASC 5 member, or further on the exhaust line, with a correction of temperature made, then, compared to the temperature actually measured. The temperature can also be entered in the control unit in the form of a map or estimated by the control unit itself according to the operating conditions of the engine M.
    In conclusion, thanks to the post-processing device of the invention, it is not only possible to meet the increasing requirements of future standards, in particular as regards the NOx emission levels, but it is also possible to reduce the discharge of ammonia at the end of the exhaust line in an extremely efficient way, even when the operating conditions of the treatment unit are not favorable.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    1. Device for post-processing the exhaust gases of a heat engine (M) comprising, from upstream to downstream:
    • a mouthpiece of a means of introduction (2) of ammonia or of an ammonia precursor for the selective catalytic reduction of nitrogen oxides SCR;
    • a selective catalytic reduction catalyst SCR (3) in the form of a body dedicated to the selective catalytic reduction catalysis SCR (nitrogen oxides NO X (6) and / or a particulate filter (4) fitted with a SCRF selective catalytic reduction catalyst coating of nitrogen oxides NO X ;
    • an ammonia leakage treatment device (5), characterized in that said ammonia leakage treatment device (5) is provided with means for purging ammonia.
    [2" id="c-fr-0002]
    2. Post-treatment device according to the preceding claim, characterized in that the purging means are controllable electric heating means (5,6,7).
    [3" id="c-fr-0003]
    3. Post-treatment device according to the preceding claim, characterized in that the controllable heating means are an electrically heated EHC catalyst (6) disposed upstream of the ammonia leakage treatment device (5).
    [4" id="c-fr-0004]
    4. Post-treatment device according to the preceding claim, characterized in that the electrically heated EHC catalyst is placed in the same casing (51) as the ammonia leakage treatment device (5).
    [5" id="c-fr-0005]
    5. Post-treatment device according to one of claims 3 or 4, characterized in that the electrically heated catalyst EHC comprises an electrically conductive mineral matrix, in particular metallic, intended to be traversed by the exhaust gases and which is connected to a power supply.
    [6" id="c-fr-0006]
    6. Post-treatment device according to claim 2, characterized in that the controllable heating means (6) are part of the ammonia leakage treatment device, in that the leakage treatment device ammonia comprises a porous matrix on which are deposited catalytic compositions, and in that said matrix is electrically conductive, in particular by being based on doped SiC or on metal.
    [7" id="c-fr-0007]
    7. Post-treatment device according to one of the preceding claims, characterized in that the ammonia leakage treatment member (5) is a catalyst for treating ammonia leaks ASC by ammonia oxidation to NOx and then the reduction of said NOx to nitrogen.
    [8" id="c-fr-0008]
    8. Assembly comprising the post-processing device according to one of claims 2 to 7, characterized in that it also comprises an electrical supply (S) for the
    10 heating means and a control unit controlling the electrical supply of the heating means as a function of the temperature of the ammonia leakage treatment unit (5).
    [9" id="c-fr-0009]
    9. Method of implementing the assembly according to the preceding claim, characterized in that the control unit activates the electrical supply of the means of
    15 heating when the temperature of the ammonia leakage treatment device (5) is less than or equal to 150 or 200 ° C.
    [10" id="c-fr-0010]
    10. A method of implementing the assembly according to claim 9, characterized in that the temperature of the ammonia leakage treatment device (5) is determined by measurement using a sensor at level of said organ or upstream or downstream of
    20 the organ on the exhaust line, or by estimation or by mapping.
    类似技术:
    公开号 | 公开日 | 专利标题
    EP3230564B1|2019-01-02|Exhaust gas aftertreatment device for internal combustion engine
    EP3068987B1|2019-05-08|Method for purifying exhaust gases, particularly for an internal combustion engine, in particular for a motor vehicle, and installation using such a method
    FR3057020A1|2018-04-06|DEVICE FOR POST-PROCESSING EXHAUST GASES OF A THERMAL ENGINE
    EP3230563B1|2019-04-03|Exhaust gas aftertreatment device for internal combustion engine
    EP1617051B1|2011-09-07|Exhaust line for an internal combustion engine and purifying system of the exhaust gas
    EP3153677B1|2018-05-09|Device for after-treatment of exhaust gases from a combustion engine
    EP3149300B1|2018-08-15|Exhaust gas after-treatment device for an internal combustion engine
    FR3029970A1|2016-06-17|EXHAUST GAS POST-TREATMENT DEVICE OF A COMBUSTION ENGINE
    FR3062680A1|2018-08-10|DEVICE FOR POST-PROCESSING EXHAUST GASES OF A THERMAL ENGINE
    FR3041032A1|2017-03-17|EXHAUST GAS POST-TREATMENT DEVICE OF A COMBUSTION ENGINE
    FR3061742A1|2018-07-13|DEVICE FOR POST-PROCESSING EXHAUST GASES OF A THERMAL ENGINE
    FR3081921A1|2019-12-06|HEAT ENGINE EXHAUST SYSTEM COMPRISING AN UPSTREAM HEATING ELEMENT
    EP3369905A1|2018-09-05|Vehicle integrating post-treatment system for internal combustion engine exhaust gas
    FR3066408B1|2019-06-21|DEVICE FOR POST-PROCESSING EXHAUST GASES OF A THERMAL ENGINE
    FR3043430B1|2019-08-09|DEVICE FOR POST-PROCESSING EXHAUST GASES OF A THERMAL ENGINE
    EP1553272A1|2005-07-13|Method and device for controlling the temperature of a NOx trap in an exhaust line of a motor vehicle engine
    FR2895274A1|2007-06-29|CATALYST FOR ENGINE EXHAUST LINE, POLLUTANT EMISSION REDUCTION DEVICE INCLUDING THIS CATALYST AND USES OF THIS DEVICE
    FR3042813A1|2017-04-28|EXHAUST GAS POST-TREATMENT DEVICE OF A COMBUSTION ENGINE
    FR3100839A1|2021-03-19|Set comprising an internal combustion engine with an electric compressor and a heating element
    FR3066541A1|2018-11-23|EXHAUST GAS POST-PROCESSING SYSTEM OF AN INTERNAL COMBUSTION ENGINE
    FR2995349A1|2014-03-14|Device i.e. solid particle filter, for processing e.g. carbon monoxide emissions, in diesel engine exhaust line of car, has reducer compensating on-board reducer in its action of nitrogen oxide catalytic reduction during reduction catalysis
    FR3088958A1|2020-05-29|OPTIMIZED SYSTEM FOR AFTER-TREATMENT OF THE EXHAUST GASES OF A THERMAL ENGINE
    EP3194052A1|2017-07-26|Method for decontamination of nitrogen oxides
    FR2888614A1|2007-01-19|Heat engine exhaust gas treating device for motor vehicle, has support, for oxidation catalyst that is located in downstream of nitrogen oxide trap, impregnated with catalytic impregnation for oxidation of hydrocarbons and carbon monoxide
    EP2404045A1|2012-01-11|Device and method for processing nitrogen oxides contained in exhaust gases
    同族专利:
    公开号 | 公开日
    FR3057020B1|2020-09-11|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20110023463A1|2009-07-30|2011-02-03|Ford Global Technologies, Llc|Methods and systems for control of an emission system with more than one scr region|
    GB2493987A|2011-08-26|2013-02-27|Jc Bamford Excavators Ltd|An engine system|
    JP2014148908A|2013-01-31|2014-08-21|Toyota Motor Corp|Exhaust emission control device for internal combustion engine|
    WO2016092170A1|2014-12-10|2016-06-16|Peugeot Citroen Automobiles Sa|Device for post-treating exhaust gases of a combustion engine|WO2020159991A1|2019-01-29|2020-08-06|Watlow Electric Manufacturing Company|Virtual sensing system|
    EP3915679A1|2020-05-26|2021-12-01|UMICORE AG & Co. KG|Ammonia emissions reduction catalyst, catalyst system, and exhaust gas purification system|
    US11255244B2|2016-03-02|2022-02-22|Watlow Electric Manufacturing Company|Virtual sensing system|
    法律状态:
    2017-09-20| PLFP| Fee payment|Year of fee payment: 2 |
    2018-04-06| PLSC| Search report ready|Effective date: 20180406 |
    2018-09-19| PLFP| Fee payment|Year of fee payment: 3 |
    2019-09-19| PLFP| Fee payment|Year of fee payment: 4 |
    2020-10-20| PLFP| Fee payment|Year of fee payment: 5 |
    2021-09-22| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1659498|2016-10-03|
    FR1659498A|FR3057020B1|2016-10-03|2016-10-03|DEVICE FOR AFTER-TREATMENT OF THE EXHAUST GASES OF A THERMAL ENGINE|FR1659498A| FR3057020B1|2016-10-03|2016-10-03|DEVICE FOR AFTER-TREATMENT OF THE EXHAUST GASES OF A THERMAL ENGINE|
    [返回顶部]