FR2872199A1 - METHOD AND DEVICE FOR REDUCING / ELIMINATING THE QUANTITY OF PARTICLES CONTAINED IN THE EXHAUST GASES OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The invention relates to the reduction of harmful emissions from lean-burn internal combustion engines, using particulate filters arranged in the exhaust circuit and implementing chemical (catalytic) assistance for the combustion of carbonaceous particles. The aim of the invention is to optimize the reduction / elimination of soot in the exhaust gases by providing a solution to the problem of premature clogging of the filtration means, that is to say by improving the regeneration of these. To do this, the method according to the invention essentially consists of o collecting all or part of the particles contained in said exhaust gas using filtration means; o seeding the particles before and / or during and / or after '' they have been collected by the filtration means, with at least one combustion catalyst comprising nanoparticles; o and to regenerate the filtration means by combustion of the particles in the presence of the nanoparticulate combustion catalyst (CNPC), o and to obstruct a part of the filtration means as soon as the temperature of the exhaust gases drops below a threshold of 200-250 ° C, so as to keep this blocked part of the filtration means at a temperature above 200-250 ° C and thus allow when the temperature of the exhaust gases becomes greater than θs again, accelerated regeneration of at least this blocked part of the filtration means. The invention also relates to the device for the mid is implemented by this method.

Description

METHOD AND DEVICE FOR REDUCING / ELIMINATING QUANTITY

  OF PARTICLES CONTAINED IN THE EXHAUST GASES OF A

INTERNAL COMBUSTION ENGINE

  The present invention generally relates to the field of reducing or eliminating the contained particles (e.g. soot) in the exhaust gases of internal combustion engines, for example diesel engines.

  More specifically, the invention relates to a method and a device for reducing or even eliminating the harmful emissions of internal combustion engines and in particular those with lean mixture: The harmful emissions more specifically targeted are soot, that is to say say carbon emissions in particulate form.

  It is known that in combustion engines, the combustion of the carbonaceous or hydrocarbon products contained in the fuel (or fuel) leads to combustion by-products including carbon particles (soot).

  These, on the one hand, are harmful, both for the environment and health, and, on the other hand, are deposited on all internal walls of the engine, which can cause malfunctions, particularly in turbochargers.

  As a result, governments have introduced increasingly stringent standards to force car manufacturers to develop engines that produce fewer and fewer polluting emissions. Manufacturers are therefore seeking to develop spark-ignition engines, particularly diesel engines and lean-burn engines, whose emissions of unburned particles are as limited as possible.

  As the modification of the combustion of the engines is no longer sufficient to meet these "green" requirements, the implementation of exhaust gas filtration method and device with regeneration of the filters by combustion, is now unavoidable.

  The search for processes and devices for reducing soot produced by internal combustion engines, especially diesel engines, is accompanied by another constraint, which is not to increase the emission of carbon oxides or other harmful gases. and mutagens, such as nitrogen oxides.

  To reduce the emission of unburned pollutants and solid particles, car manufacturers have developed and extended the use of catalytic converters or catalysts, usually consisting of a stainless steel casing, thermal insulation and a honeycomb support impregnated with catalytic precious metals, such as platinum, palladium, rhodium or others.

  An evolution of these catalytic converters was to further provide a particulate filter disposed in the exhaust system and to reduce at least 85% by mass soot emissions.

  But, the problem to be solved was then moved to those filters subject to clogging by soot, which subsequently leads to a loss of performance of the internal combustion engine considered.

  In addition, this reduction in engine performance caused by clogging of the filter, due to a pressure drop, another damaging phenomenon occurs. In fact, the engine disturbance induced by the clogging causes, moreover, an increase in the exhaust temperature, which causes a combustion of a large mass of particles, combustion just as fast, violent and instantaneous as unexpected, of so that the temperature rises to values well above 1000 C. It is easy to imagine the deleterious consequences of such a thermal shock on the filter.

  To fight against this clogging, it has been proposed to carry out an operation called burning or regeneration of the filter, by burning soot. This operation is extremely difficult to predict and implement, in particular because of the often incomplete and uncontrolled combustion of the particles retained on the filter media.

  Indeed, for example for urban conditions of use of the engine, the temperature reached for the exhaust gas is insufficient to cause the combustion of soot and limit clogging of the filter.

  Therefore, to reduce the combustion temperature (ignition or oxidation) temperature of the order of 500 to 600 C-, it is essential to resort to chemical assistance and, more specifically, to combustion catalysts.

  An earlier technical proposal is to take advantage of the composition of the exhaust gases from lean-burn engines, especially diesel engines. Generally, these exhaust gases comprise, in significant amounts, nitrogen oxides (NO, NO2), oxygen, carbon monoxide ... and, where appropriate, sulfur dioxide. However, the NO has the property of oxidizing the carbon particles starting from 250 C. To increase the oxidizing capacity by means of NO2, it is possible to transform the nitric oxide NO to NO2, with the aid of a catalyst and at a temperature greater than or equal to 250 C. This is the principle of the technique called "Continuous Regenerating Trap" (CRT), for example EP-B-341 832-. This technique is effective only to the extent that the exhaust gas or the combustion chamber are at a temperature greater than 250 ° C for at least 50% of the engine running time, and also provided that the NO2 present is formed either in sufficient amounts, usually a NO2 / soot ratio greater than 7.66 in theory, but greater than 31 in practice (reference Eminox Ltd., SAE 2004-01-0078) compared to the carbon particles to be burned. In addition, the oxidation of carbon with NO2 is strongly inhibited as soon as the sulfur concentration in the fuel fuel is higher than 50 ppm. This concentration generates an inhibitory content of sulfur dioxide in the exhaust gas.

  According to other prior techniques, the catalyst is deposited directly on the particulate filter. However, only certain materials constituting the particulate filters are able to fix the catalysts. This is particularly the case of cordierite and other supports based on oxides, nitrides and carbides. However, materials of this type are known to be particularly sensitive to increases in temperature and thermal shock. Consequently, the violent and instantaneous combustions resulting from clogging are such as to irreversibly damage such filter media. This strikes unacceptably the cost of such a technique, which is also disqualified by the fact that its effectiveness depends on a temperature threshold.

  Other known techniques for regeneration of particulate filters include adding to the fuel a catalytic additive selected from transition metal derivatives, alkaline earth, alkali or rare earths. EP-B-0 599 717 is an illustration of this kind of technique. The combustion of soot clogging the filters is thus significantly improved. However, for the oxidation of these soot is optimal, it remains necessary that the temperature of the exhaust gas to be treated is at least of the order of 300 C. However, these catalytic additives organometallic added to diesel (cerium oxide) iron, strontium, calcium or other) have the major disadvantage of clogging the filters, like the soot they can eliminate.

  To correct this, catalysts formed by particles of rare earth oxide (e.g. cerium) and metal oxide particles (e.g. copper, manganese or iron) have been developed. Patent applications EP-A-671,205, EP-A-737,236 and WO-A-97/18022 disclose organic colloidal solutions, based on these mixtures of cerium oxide and iron oxide particles. There are also on the market several catalytic additives marketed under the trademark EOLYSTM by RHODIA, such as, for example, colloidal solutions based on iron and cerium whose concentration of active ingredient varies according to the composition of iron and cerium and the field of application. By way of example, mention may be made of EOLYSTM-DPX9 based on cerium oxide colloid, whose concentration in weight of cerium metal is 25% and EOLYSTM176, based on iron and cerium colloids, the concentration by weight of total metals is 6.5%.

  To improve somewhat the effectiveness of this type of catalytic additive for iron oxide and cerium oxide based fuel, it is proposed in the patent application FR-A-2,780,096 to associate said additive. to the CRT catalysis system by NO2.

  These techniques based on the use of catalytic additive for fuel based on cerium oxide and iron oxide, have not proved entirely satisfactory, with regard to the fight against the premature clogging of the filter induced by said oxides. . Thus, it has been shown in car tests with an additive based on cerium oxide used at diesel concentrations between 25 and 30, that significant clogging of filters occurs at mileages of around 80 000 km. for a particle filter size compatible with the vehicle application.

  The effective concentrations of rare earth oxide and metal oxide are therefore still too high in the current state of the techniques mentioned above.

  In another register which is no longer based on chemical assistance by catalysis of combustion, the patent application WO-A-03/102389 describes a method and a device for filtering exhaust gases for diesel engines, in which soot is well burned by the action of a combustion catalyst, combining this with a partial obstruction of the filter means as soon as the temperature of the exhaust gas becomes less than or equal to 200-250 C, so to limit or even prevent the cooling of the obstructed part and thus maintain it at a temperature greater than or equal to 300 C and close to the regeneration temperature. This allows when the temperature of the exhaust gas returns to greater than 200-250 C, to have an accelerated regeneration of this part of the filtration means which is interrupted at this time, the obstruction.

  In this device, the filtering means consist of filter cartridges upstream of each of which is arranged the combustion catalyst fixed on a support. It can be provided a diesel injection post and / or an exhaust gas recirculation system, to promote the combustion of soot according to this WO-A-03/102389.

  In such a technical context, the objective of the present invention is to provide a method and a device for reducing / eliminating the amount of particles (soot) contained in the exhaust gases of a lean-burn internal combustion engine. (eg the diesel engine), on the one hand, by overcoming the drawbacks of the various existing techniques and, on the other hand, by improving them, in particular as regards the regeneration of the filters, so as to provide a satisfactory solution to the problems of clogging said filters.

  Another essential object of the invention is to provide a method and a device for reducing or even eliminating harmful emissions from internal combustion engines (eg lean mix engines and / or diesel engines).

  Another essential objective of the invention is to provide a method and a device for reducing / eliminating the soot contained in the exhaust gas, by providing a regular, high-performance and continuous regeneration thanks to the introduction of oxidation at from 300 C and a complete combustion to less than 400 C, so that there is thus avoided any risk of accumulation of particles in the filtration means and, therefore, any risk of uncontrolled regeneration.

  Another essential objective of the invention is to provide a method and a device for reducing / removing soot contained in the engine exhaust gases, for example diesel, by using particulate combustion catalysts based on rare earth and metal oxide, at sufficiently low concentrations to prevent premature clogging of the filters by said catalytic additives.

  Another essential object of the invention is to provide a method and a device for reducing / eliminating soot contained in the exhaust gas of an internal combustion engine in which the filtering means are regenerated by catalytic combustion in a homogeneous manner. complete, fast and minimizing the energy needs to do this.

  Another essential objective of the invention is to provide a method and a device for reducing / eliminating soot contained in the exhaust gases of internal combustion engines, in which the integrated regeneration of the filtration means used does not lead to no significant overconsumption of fuel, and more generally, does not entail additional financial cost for the user.

  Another essential objective of the invention is to provide a method and a device for reducing / eliminating the quantity of particles contained in the exhaust gases of an internal combustion engine, in which the integrated regeneration of the filtration means used implement, does not enter the performance of the engine, including losses due to the back pressure exerted by the exhaust gas on the engine, due to a clogging of the aforesaid filter means.

  Another essential object of the invention is to provide a method and a device for reducing / eliminating soot contained in the exhaust gas of an internal combustion engine, this method and this device having to be economical, reliable , flexible in its application conditions, delaying the clogging of the filter as much as possible, even eliminating it, whatever the use regimes (even urban use regimes), and without being affected by the possible presence of compounds sulfur, in particular of sulfur dioxide in the exhaust gas.

  These objectives, among others, are achieved by the present invention which firstly relates to a method for reducing / eliminating the amount of particles contained in the exhaust gas of an internal combustion engine, characterized in that it essentially consists in: o collecting all or part of the particles contained in said exhaust gas by means of filtration means; o Seeding the particles before and / or during and / or after they have been collected by the filtration means, with at least one combustion catalyst comprising nanoparticles also called nanoparticulate combustion catalyst (CNPC); and / or to ensure that the CNPC is present on at least one solid support in and / or near the filtration means; o and to regenerate the filtering means by combustion of the particles in the presence of CNPC, and in that it also consists in clogging at least part of the filtering means as soon as the temperature 0 g of the exhaust gas to be filtered becomes lower or equal to a threshold temperature Os, so as to limit, or even avoid, the cooling of the obstructed part and to maintain it at a temperature 0o greater than or equal to bone until 0g will become greater than es, and then allow a accelerated regeneration of at least this obstructed portion of the filtration means; excluding or excluding processes in which the CNPC is an additive automatically incorporated into the fuel of the tank and independently of the full, this fuel being the fuel contained in the tank and supplying the engine considered.

  The present invention is based in particular on the synergistic implementation of a particular catalyst in nanoparticulate form (hereinafter referred to as CNPC) and a filter with particles with variable filtration area.

  This variable filtration system consists, for example, in filtering the exhaust gases on filtering means consisting of at least two cartridges arranged in an envelope, one of the two cartridges being switched off each time the engine operates without load or at idle, in order to maintain in the insulated cartridge and without exhaust gas flow, a sufficient temperature to cause a significant continuous regeneration speed, since the engine will again be solicited more significantly and thus produce gas hot exhaust. Each cartridge is preferably in turn turned off so that it regenerates continuously. In the filter units thus isolated and maintained at high temperatures in the absence of less hot exhaust gas, the regeneration process continues to continue slowly thanks to the low flow that is maintained. But above all, these filter units are at a temperature maintained at an optimum until the engine is again solicited consistently and thus hot exhaust gases are again admitted to the filter means. The process in these cartridges thus isolated can thus take place continuously, avoiding any risk of clogging.

  It is the merit of the inventors to have proposed, in a completely non-obvious manner, the combination of these two known means but hitherto used separately to reduce or eliminate the amount of particles, including soot, contained in the exhaust gas of an internal combustion engine and more specifically of a diesel engine and to have observed synergistic effects between these two distinct processes.

  The synergistic combination CNPC / variable capacity filtration is particularly but not limited to poorly mixed internal combustion engines because it optimizes the combustion of the carbonaceous particles in a significantly wider temperature range, without the the possible presence of sulfur compounds, in particular sulfur dioxide in the exhaust gas, is a handicap. The method according to the invention thus enjoys excellent flexibility in a wide field of application.

  Said method also makes it possible to extend the operating time of the filtration means by ensuring a regeneration of the filters which is homogeneous, complete, fast and economical.

  Another advantage of the synergistic combination CNPC / variable capacity filtration (or variable geometry) is to minimize the amount of CNPC useful for the regeneration of the filtration means compared to conventional use of current applications: this not only has an effect positive on the cost of the process but also on the reduction of the harmful side effect known for NCPCs based on rare earth oxide and metal oxide and / or alkaline oxide and / or oxide of alkaline earth that is contributing to clogging filters. This energy saving allowed by the method of the invention is all the more expressed in the variants where it is implemented an assistance to the regeneration of the filters by supply of thermal energy, for example by post-injection of diesel fuel in the exhaust system and / or by the use of a heating resistor and / or a fuel burner. It also makes it possible to limit the maintenance operations of the filters used (washing, removing residues, etc.).

  The invention thus provides a reliable, durable, high-performance and cost-effective solution to the problem of clogging the filtering means for particles, especially soot contained in the exhaust gases of thermal engines, for example diesel engines.

  Thanks to the invention, the combustion of the particles is carried out in a significantly enlarged temperature range, which corresponds in particular to that encountered for the exhaust gases of diesel engines. Thus, unlike other processes, the method of the invention is effective at very low exhaust temperature, that is to say less than 250 C and in particular in the range 200-250 C. It does not not less effective at temperatures above 400 C.

  For the purposes of the invention, the seeding of the particles to be burned off using CNPC means that said particles (e.g. carbonaceous particles of soot) are brought into contact with very fine particles of CNPC.

  As regards the first pillar of the synergy according to the invention, namely the CNPC combustion catalyst, it may be specified that according to the invention, the latter comprises at least one element chosen from transition metals, alkalis alkaline earths (such as manganese, iron, copper, sodium, nickel, scandium) rare earths and their mixtures, rare earths being preferred and those selected from cerium, yttrium, neodymium, gadolinium, praseodymium, lanthanum and their mixtures being more preferred still.

  Preferably, the constituent element (s) of the CNPC nanoparticles are in oxide form. Of course the NCPC may comprise a mixture of several elements, each element may be present independently of one another in the form of its corresponding oxide or not.

  According to a preferred embodiment of the invention, the CNPC comprises at least one element chosen from rare earths, that is to say from elements whose atomic number is between 57 and 71 as well as yttrium. Rare earths, especially rare earth oxides, especially those of cerium, effectively catalyze the combustion or oxidation of carbonaceous materials. In the particular case of rare earth mixtures, it is preferable that cerium and / or lanthanum be the majority.

  Can also be used in the context of this invention, an NCPC comprising cerium in admixture with at least one other element selected from zirconium, alkalis, alkaline earths, transition elements such as elements of columns 1B, VIIA and VIII of the Periodic Table, especially copper, manganese and iron.

  For the whole of the presentation, the periodic table is the one published in the supplement to the Bulletin of the Chemical Society of France N 1, January 1996.

  As indicated above, it is preferable that at least one of the CNPC constituents be in the form of oxide (s) or oxyhydroxide (s), which are the preferred forms for the expression of the catalytic function of the aforementioned elements.

  The CNPC catalyst useful for seeding particles, for example soot, is at least partly in the form of powder and / or organic colloidal suspension.

  According to a preferred feature of the invention, the CNPC (in the form of a powder and / or an organic colloidal suspension) is brought into the presence of the particles by at least one of the following routes: introduction into the fuel supplying the engine ; introduction into the post-injected fuel in the exhaust circuit upstream of the filtration means; o introduction into the exhaust circuit upstream of the filtration means; o introduction into the air at admission; o introduction into the gas recirculation circuit (EGR loop); o introduction into the engine lubricant.

  This bringing into play is carried out for example by dispersion of the CNPC nanoparticles on the soot particles collected on the filter and / or present in the exhaust circuit upstream of the filter.

  In place of or in addition to the various aforementioned inoculation routes, the NCPC particles could be arranged and / or fixed on a solid support in and / or in the vicinity of the filtration means.

  In accordance with the preferred embodiment, the CNPC is advantageously incorporated in the fuel supplying the engine, for example diesel fuel, and optionally post-injected into the exhaust circuit upstream of the filtration means. The colloidal suspension is the preferred form of CNPC incorporation into the fuel. The constituent element (s) of the nanoparticles of the CNPC, preferably in the form of oxide (s) or oxyhydroxide (s), may be, for example, in the form of salts or in the form of organic complexes.

  Organic colloidal suspensions which are particularly suitable in the process according to the invention are described in EP-A-0 671 205, EP-A-0 737 236 and WO-A-97/19022. As for the preparation of these colloidal suspensions, reference will also be made to the teaching of these titles.

  Another advantage of the method and the device according to the invention is to ultimately allow the reduction of fuel consumption due to the rapid and optimal regeneration of the filter.

  Quantitatively, the NCPC advantageously meets the following specifications: its concentration [CNPC], expressed in% by weight of total metals relative to the total mass of the particles to be removed collected by the filtration means, is such and more preferably still [CNPC] 0.5 In practice, this CNPC concentration is, for example, between 0.25% and 1.0%.

  According to an advantageous arrangement of the invention, the process is carried out with exhaust gases containing sulfur compounds, in particular sulfur dioxide, which gives more flexibility under the conditions of real applications.

  Indeed, it is particularly interesting that the soot reduction / elimination process of the invention is not sensitive to the presence of sulfur in the exhaust gas, as is the case in particular for prior methods of the CRT type.

  As will be understood from the foregoing, the particles that are to be eliminated in the exhaust gases of the combustion engines, preferably diesel engines, are at least partially constituted of carbonaceous particles, that is, to say soot.

  Regarding the second pillar of the synergistic composition according to the invention, namely the variable capacity filtration of the invention, it should be emphasized that the different parts of the filtration means are preferably successively each subject to the blockage sequence. regeneration for each variation of 0g between a value v1 greater than or equal to es, a value v2 less than or equal to bone and again a value v3 greater than or equal to Os, v1 = or v3, so as to allow a regular regeneration and continuous filtration means.

  According to a remarkable embodiment of the invention, the obstruction of part of the filtration means consists in preventing the circulation of the exhaust gases in at least 30%, preferably in at least 50% and even more preferably in 50 to 75% of the filtration means, this percentage expressing a percentage by volume.

  Preferably, Os is between 200 and 300 C, preferably between 200 and 250 C.

  Advantageously, the exhaust gases come from a supercharged diesel engine and the reference parameters, namely the exhaust gas temperature and the temperature Os, are given indirectly by the supercharging pressure and / or the origin of the engine. and / or by the back pressure upstream of the filtration means, the boost pressure (threshold) being preferably equal to 2.5% of the maximum boost pressure of the engine.

  The filtration means used in the process are preferably composed of at least two preferably at least three filter cartridges, each equipped with a shutter. In the preferred form with three cartridges, two of these three cartridges constitute the obstructed portion of the filtration means when 0g Os.

  According to another of its aspects, the subject of the invention is a device for reducing / eliminating the quantity of particles contained in the exhaust gases of an internal combustion engine, this device being: process of the type as described above, o and being of the type comprising at least one catalytic means, means 10 for filtering said exhaust gases, arranged in a reaction chamber 11 in the flow path of the gas streams. exhaust produced by a motor 8, of FIG. 1, said device being characterized in that: the filtering means 10 consist of at least two assemblies each comprising a filter cartridge equipped with a flow obstruction means 13, and in that it comprises: means for seeding the particles to be removed, before and / or during and / or after they have been collected by the filtration means, this seeding taking place with c at least one nano-particulate combustion catalyst (CNPC); and / or at least one solid support comprising CNPC; and alternating control means of the obstruction means, so as to allow the regeneration of or obstructed filter cartridges by combustion of the particles to be removed in the presence of the CNPC; and excluding or excluding devices in which the CNPC is an additive automatically incorporated into the fuel of the tank and independently of the full, this fuel being the fuel contained in the tank and supplying the engine considered.

  Advantageously, the device comprises an exhaust gas recirculation means at the intake of the engine whose operation is associated with the shutdown of the flow in one or more of the cartridges each time the engine is not accelerated, so that the increase of generated pressure against pressure automatically opens a valve that allows this recirculation of the exhaust gas.

  According to a preferred feature of the device of the invention, each of the filter cartridges has a means of obstruction of the flow, arranged upstream or downstream, controlled by at least one electronic calculator which takes into account all the engine operating conditions. , so as to isolate at least one cartridge each time the accelerator position will be zero (not accelerated).

  In an advantageous embodiment of the device according to the invention, the filtering means consists of at least three cartridges with a means of obstruction of flow on each of them, these obstruction means being controlled by at least one electronic computer which takes into account all the engine operating conditions, so as to isolate in turn, at least two cartridges when the engine is not accelerated, and to isolate the cartridge which filters the gases in non-accelerated position, each time that the engine will be accelerated.

  Advantageously, the flow obstruction means disposed on each filter cartridge, comprise a calibrated orifice of small size to maintain a very low flow rate.

  According to an advantageous variant, the device comprises a system for post-injection of diesel into the exhaust gas, via a sprayer, preferably arranged upstream of the filtration means and the CNPC as long as it is fixed on at least one solid support, said sprayer being controlled by at least one electronic computer which takes into account all the engine operating conditions, this diesel injection post-injection system possibly being associated with an exhaust gas recirculation system .

  In this variant, it may be appropriate for the post-injected gas oil to contain at least one CNPC, this diesel fuel coming from a specific tank or not.

  This post injection system can therefore allow the introduction into the exhaust of the CNPC (or other additives e.g organometallic) together or not with diesel.

  In the preferred embodiment, the filtration means consist of a set of at least two filter units each equipped with an obstruction means controlled by at least one computer that takes into account the engine operating conditions.

  When the device according to the invention comprises more than two filter units, each of said filtering units will comprise an obstruction means so as to be able to turn them off in turn.

  The obstruction means for each of the cartridges used will be disposed downstream of the filtration unit.

  According to a variant of the invention, the obstruction means may also be incorporated upstream of the filtration unit and the associated catalyst.

  According to another variant of the invention, said filtering units will each comprise upstream a catalyst slab, preferably on a metal support.

  The CNPC catalyst may optionally be combined with a conventional combustion catalyst, e.g. platinum-based, to achieve complete combustion / oxidation of hydrocarbons and CO. This optional conventional catalyst could also be based on Palladium or Palladium / Platinum insofar as the sulfur content in the fuel is low (typically less than 10 ppm).

  According to another variant of the invention, the device comprises a system allowing the recycling of exhaust gases whenever the filtration capacity will be reduced, thus taking advantage of the increase in the back pressure caused by this restriction to direct to through a non-return valve a part of the unfiltered exhaust gas in the intake duct.

  According to a variant of the invention, the device comprises more than three cartridges and a sufficient number so that for full load operating conditions one of the cartridges is isolated, this cartridge being reserved for the filtration of part-load or idle gases. . The objective being to maintain at high temperature, the filter medium and the catalyst of each of the cartridges used at full load. The cartridge used at idle will be swapped with one another when a start of clogging is detected.

  The present invention will be better understood on reading the description which follows, made with reference to the drawing which shows, in no way limiting, an embodiment of the device according to the invention.

  FIG. 1, according to a preferred embodiment of the invention, represents a general view of the device according to the invention comprising the filtration means with two cartridges 10, each having upstream a fixed metal support 9 of identical combustion catalyst or different from the CNPC, and downstream a valve 13 controlled to completely obstruct the flow of the gases to be filtered when necessary, the filtration means (10) being associated with a diesel fuel injection system.

  The device comprises a diesel fuel tank 6 connected to a conventional diesel fuel injection system 5 in the engine. The pipe circuit connecting the tank 6 of the injection system 5 comprises a pipe 4 for returning diesel fuel to the tank 6.

  In this advantageous embodiment of the device according to the invention, the injection system of the CNPC additive, associated with the filtration means 10, 13, 14 with variable filtration surface, is able to perform a volume addition. of CNPC additive determined by taking into account the amount of fuel added, the metal concentration of the CNPC additive and the CNPC target concentration in soot seeding. This CPNC injection system consists of a low volume reservoir of additive 1, allowing an injection of a calibrated volume of additive from a volumetric pump 2 and the volume of the fuel to additiver, controlled by a calculator 3, with an injection directly into the diesel fuel tank 6 of the vehicle. Details of these additive systems are available in several articles, such as SAE 2004-01-0071 and SAE 2002-01-0436, but also in SAE 2004-01-0821 describing a non-additive system. - embedded, centralized and stationary usable for fleets of commercial vehicles.

  This automatic additive system is associated with a particle filter of the variable filtration surface type in which the exhaust gas at the outlet of the engine is introduced into the device through the pipe 8, then is directed to each catalyst slab on metal support 9, to be filtered on the two filter cartridges 10, these cartridges are preferably made of silicon carbide, but may also consist of a filtering medium cordierite or other ceramic materials. These cartridges 10 are disposed inside an enclosure 11 and are isolated therefrom through an insulator 12, so as not to be cooled by the ambient air.

  Valves 13 are arranged at the outlet of these filter cartridges 10, so as to completely isolate each cartridge 10 and completely obstruct the outlet channel. These valves 13 are controlled by pneumatic cylinders 14, the exhaust gases then being directed towards the outlet 15.

  The device operates in the following manner, each time the position of the accelerator will return to the zero position (not accelerated), an undescribed position detector will send the information to a computer, it alternately controls each cylinder 14 for completely block one of the two cartridges 10 and use only one for these particular operating conditions. The filtering medium of the cartridge obstructed by the valve 13 thus retains the high temperature it has reached during the last acceleration, the valve 13 does not fade to put it back into operation until the engine is again requested, so to again at high 0g exhaust temperatures. To allow each of them to regenerate in good conditions, it is the same cartridge that is obstructed for a time between 5 and 60 minutes e.g. and alternately. To control this rotation other possibilities are conceivable, such as that consisting in measuring the idle backpressure on the used cartridge 10 and controlling the openings of all the valves 13 as soon as a predetermined level of the backpressure (for example 100 mbar variable depending on the type of motor) is reached and close on the contrary when the value of counter pressure measured falls below this level. In the same manner for supercharged engines, this control of the valves 13 can be made by following a supercharging pressure sensor, or the cartridges 10 are obstructed as soon as the boost pressure value approaches the atmospheric pressure, for example to +50 mb, conversely this closing occurs when the supercharging pressure falls below this threshold.

  In this FIG. 1, the variant of the device represented shows the possibility of incorporating a diesel fuel injection system loaded in CNPC, upstream of the filtration means 10, controlled from the information collected on the pressure and temperature sensors 7. 16, arranged upstream of the filters 10, the computer can adapt the best strategy to keep each of the filters 10 clean, by injecting a metered quantity of diesel fuel through the sprayer 17, supplied with air by the pipe 18 and diesel by an injector 19 supplied with diesel fuel through the conduit 4 of diesel fuel in the tank 6. These injections are intended to increase the temperature of the exhaust gas 9g when the engine is at full power, so as to reach the auto-ignition temperature of the carbon on the filter medium, temperature close to 400 C thanks to the catalytic action of the nanoparticles of the CNPC, and completely burn the s deposited particles. These injections may for example be implemented whenever an abnormal increase in the back pressure of the filter is detected. This auto-ignition temperature of 400 C of the particles in the presence of CNPC additive is all the more easily achieved that a portion of the filter medium is already at a temperature of about 300 C and the injection of diesel fuel is carried out in exhaust gas at more than 300 C. It is the combination of this CNPC additive to a variable surface filtration system which makes it possible to obtain at each injection of diesel fuel the complete combustion of the carbon deposited.

  As we have seen the purpose of each of the valves 13 that equip each cartridge 10 is to be able to isolate them to maintain the high temperature level obtained during the full load of the previous engine and prevent them from cooling on the load partial or the following idling, this high temperature favoring the combustion reactions, there is a major interest in keeping closed flap a low flow of exhaust gas to maintain these combustion reactions which are very exothermic and which contribute to raising even these temperatures. This operation is possible by making valves provided with a calibrated hole of small diameter of less than 1 to a few millimeters, the size of which is a function of the displacement of the engine to allow the necessary flow to pass.

  In the same way, a superior efficiency of reduction of hydrocarbons in the official pollution cycles has been observed thanks to the temperature maintenance of at least one of the catalyst cakes for the devices where each cartridge is equipped with its catalyst.

  A variant of this control for a system comprising at least three cartridges, and the size of each of which will be provided so that exhaust gas filtration for full load conditions can be performed on only two of it consists in specializing two of the cartridges with full load operation and one reserved for idle and partial load operation so as to keep the filter media and the catalyst of the cartridges used at full load at high temperature, and obtain a maximum reduction of all pollutants. To allow each of them to regenerate in good conditions, the computer changes the cartridge used exclusively at idle and replaces it with a full-load used, as soon as a level of back pressure is detected.

  The proper functioning of the device associated with the catalytic and assistance means described above and the use of an NCPC additive do not require the use of a gas oil with a limited sulfur content of 50 ppm. The use of CNPC makes it possible to be satisfied with diesel containing up to 500 ppm of sulfur by adapting the quantity of CNPC injected into the fuel.

  By way of example, the following is described to illustrate the invention.

EXAMPLES

  The aim of the tests is to clarify the synergistic effects between the nano-particulate catalytic additive CNPC and the variable volume filtration.

  The CNPC additive in colloidal form is introduced directly and manually into the fuels used.

  The tests were conducted on the catalytic additive RHODIA, called EOLYSTM-DPX10 whose characteristics are reported in Table 1 below:

Table 1

  Product name EOLYSTM-DPX10 Viscosity at 20 C 3.06 mm2 / s Density at 20 C 0, 866 kg / liter Composition Iron + Cerium + organic solvent Concentration Fe + Ce (% m) 8 + 1- 0.4 Assays used of 5 at 20 ppm metal (Fe + Ce) The device used for these tests is confused with that shown in Figure 1 attached. This device comprises an engine is Renault Industrial Vehicles brand and type MIDR 62045. This engine is representative of a portion of the public transport fleet in circulation in France and meets Euro II standards, requiring an additivation of 25 to 30 ppm under normal conditions of use and for currently used filtration systems (paper reference SAE 2004-01-0821). Its main characteristics are specified in Table 2 below:

Table 2

  Type MIDR 62045 Total displacement 9.84 liters Number of cylinders 6 Volumetric ratio 17/1 Bore x stroke 120 mm x 145 mm Maximum power 190 kW at 2100 rpm Maximum torque 1070 Nm at 1400 rpm Fuel supply pump online Direct Injection Air Supply Cooled Supercharging The motor is installed in an automated test cell and coupled to a ZOLLNER eddy current brake to reproduce stabilized operating conditions encountered on the vehicle. A control software makes it possible to carry out the loading cycle, the acquisition being directly carried out by the software of the computer connected to a computer thus making it possible to follow all the parameters such as against pressure, temperature, speed, pressure of supercharging.

  Prior to each series of tests, the particulate filter portion is disassembled and blown with compressed air to avoid drifting of the results due to residual backpressure and the residue of soot and other compounds of the previous tests.

  The fuels used during the study are: - Standard fuel, meeting the EURO 2000 standards, whose main characteristics are presented in table n 3 below:

Table 3

  Fuel Diesel EURO 2000 Cetane number 50.4 Density 0.835% m / m C 85.67% mlm H 13.16% m / m O 0.55 H / C ratio 1.83 OIC ratio 0 A / F stoichiometric 14, Sulfur Content (ppm) 340 Low sulfur fuel, TOTAL Xeol type, containing less than 50 ppm of sulfur in the fuel; - Aqueous emulsion fuel, GECAM, marketed by CAM Technology.

  This is the device of Figure 1.

  To charge the filter without carbon combustion, a cycle combining idling and engine operation was carried out as follows: idling for 75 seconds, then passing to a point of 1600 rpm, with a torque of 750 Nm for a period of 25 seconds, this full load operating time possibly being adjusted so as not to exceed 250 C at the input of the system, just before breaking.

  It is at the end of acceleration that the level of back pressure is measured to follow the clogging of the filter.

  The backpressure level set at 350 mb is reached, the engine is maintained at 1600 rpm, with a torque of 750 N m so as to reach first the 330 C, temperature level where a post-injection of diesel fuel a duration of 30 seconds is triggered, then the engine is maintained under these operating conditions the time necessary to return to a level close to the back pressure measured initially before loading (around 200 mb) the operating time being noted when a level of back pressure (see Table 4, 3rd pass) greater than 40 mb of the initial counterpressure (200 mb) is achieved and this for each product experiment.

  Regeneration is thus followed by evolution of the back pressure.

  Table 4 below gives the conditions and the results of tests 1 to 8 carried out.

In this table 4:

  - the loading time corresponding to the duration to pass from 200 mb against initial pressure to 350 mb level retained for the experimentation the regeneration duration represents the duration to pass from 350 mb filter loaded to 240 mb level retained to consider the end of regeneration.

  The loading of the engine particulate filters is started at the loading point over a period of time to reach the loading pressure of 350 mbar.

  The motor is then stabilized at the operating point so as to regenerate the particulate filter. During regeneration, the pressure drop of the filter and different temperatures (inlet, outlet and internal filter) are measured and analyzed.

Table 4

  Fuels Tests Temperature Counter-Time Counter-pressure duration at regeneration injection loading Min. (C) (min) final (mbar) (mbar) pressure 1 Diesel 350 200 330 15 220 standard (350 ppm) S) 2 Diesel Xeol 350 400 330 15 210 (40 ppm S) 3 Diesel 350 600 330 4,200 standard + Eolys (20 ppm) 4 Xeol + 350 650 330 4,200 Eolys (20 ppm) Xeol + 350 650 330 4,200 Eolys (10 ppm) 6 Xeol + 350 600 330 5 200 Eolys (5 ppm) 7 GECAM 350 600 330 15 205 (aqueous) (40 ppm) 8 GECAM + 350 1000 330 4,200 Eolys (10 ppm) New filter 200 mb, against pressure measured for operating conditions at 1600 rpm and 750 Nm at 350 C.

  This table No. 4 shows the CNPC / variable capacity filtering synergy effect in the tests for which the regeneration time is reduced very strongly in the presence of additive, even at low dosage, and complete (back to the backpressure of origin). In addition, the loading speed of the filters is slower, and therefore more interesting for the application, the additive is present in the fuel. Finally, these tests show a good behavior in the presence of additive, in the presence of fuel with high sulfur content.

Claims (13)

  A method of reducing / eliminating the amount of particles contained in the exhaust gas of an internal combustion engine, characterized in that it consists essentially of: o collecting all or part of the particles contained in said exhaust gases; exhaust using filtration means; o Seeding the particles before and / or during and / or after they have been collected by the filtration means, with at least one combustion catalyst comprising nanoparticles also called nano-particulate combustion catalyst (CNPC); and / or to ensure that the CNPC is present on at least one solid support in and / or near the filtration means; o and to regenerate the filtering means by combustion of the particles in the presence of CNPC, and in that it also consists in clogging at least part of the filtering means as soon as the temperature 0 g of the exhaust gas to be filtered becomes lower or equal to a threshold temperature Os, so as to limit, or even avoid, the cooling of the obstructed part and maintain it at a temperature 0o greater than or equal to es until 0g will become greater than es, and then allow a accelerated regeneration of at least this obstructed portion of the filtration means; excluding or excluding processes in which the CNPC is an additive automatically incorporated into the fuel of the tank and independently of the full, this fuel being the fuel contained in the tank and supplying the engine considered.   2. Method according to claim 1, characterized in that the CNPC comprises at least one element selected from transition metals, alkalis, alkaline earths (such as manganese, iron, copper, sodium, nickel). Rare earths and mixtures thereof, rare earths being preferred and those selected from cerium, yttrium, neodymium, gadolinium, praseodymium, lanthanum and mixtures thereof being more preferred.   3. Method according to claim 2, characterized in that the CNPC comprises cerium mixed with at least one other element chosen from zirconium, alkalis, alkaline earths, transition elements such as elements of columns IB, VIIA and VIII of the Periodic Table, especially copper, manganese and iron.   4. Method according to one of the preceding claims, characterized in that at least one of the constituent elements of the CNPC is in oxide form.   5. Method according to one of the preceding claims, characterized in that the CNPC is at least partly in the form of powder and / or organic colloidal suspension: "soil".   6. Method according to one of the preceding claims, characterized in that the CNPC is brought into the presence of the particles by at least one of the following routes: o introduction into the fuel supplying the engine; o introduction into the post-injected fuel in the exhaust circuit upstream of the filtration means; o introduction into the exhaust circuit upstream of the filtration means; o introduction into the air at admission; o introduction into the engine lubricant.   7. Method according to one of the preceding claims, characterized in that the CNPC concentration, expressed in% by weight on a dry basis relative to the total mass of the particles to be removed collected by the filtering means, is such that: and more preferentially still [CNPC] 0.5 8. Method according to one of the preceding claims, characterized in that it is implemented with exhaust gas containing sulfur compounds, in particular sulfur dioxide.   9. Method according to one of the preceding claims, characterized in that the particles to be removed are at least partially made of soot.   10. Method according to claim 1, characterized in that the different parts of the filtering means are each successively subjected to the blocking / regeneration sequence for each variation of 0g between a value v1 greater than or equal to es, a value v2 less than or equal to at os and again a value v3 greater than or equal to Os, v1 = or v3, so as to allow a regular and continuous regeneration of the filtration means.   11. The method of claim 10, characterized in that the obstruction of a portion of the filtration means is to prevent the circulation of the exhaust gas in at least 30%, preferably in at least 50% and more preferably still in 50 to 75% of the filtration means, this percentage expressing a percentage by volume.   12. The method of claim 10 or 11, characterized in that Os is between 200 and 300 C, preferably between 200 and 250 C.   13. A device for reducing / eliminating the quantity of particles contained in the exhaust gas of an internal combustion engine, this device being in particular provided for carrying out the method according to any one of the claims. 1 to 12, and being of the type comprising at least one catalytic means, means (10, 13) for filtering said exhaust gases, arranged in a reaction vessel (11) in the path of the flow of gases exhaust systems produced by a motor, said device being characterized in that the filtering means (3) consist of at least two assemblies each comprising a filter cartridge equipped with a flow obstruction means, and in that it comprises: means for seeding the particles to be removed, before and / or during and / or after they have been collected by the filtration means, this seeding taking place with at least one nano-particulate catalyst; combustion area (CNPC); and / or at least one solid support comprising CNPC; and alternating control means of the obstruction means, so as to allow the regeneration of or obstructed filter cartridges by combustion of the particles to be removed in the presence of the CNPC; and excluding or excluding devices in which the CNPC is an additive automatically incorporated into the fuel of the tank and independently of the full, this fuel being the fuel contained in the tank and supplying the engine considered.