EP1461515A1

EP1461515A1 - Method for regenerating particulate filters by ammonium nitrate injection and device therefor

Info

Publication number: EP1461515A1
Application number: EP02799087A
Authority: EP
Inventors: Jean-Claude Fayard
Original assignee: CRMT
Current assignee: CRMT
Priority date: 2001-12-03
Filing date: 2002-12-03
Publication date: 2004-09-29
Anticipated expiration: 2022-12-03
Also published as: EP1461515B1; WO2003048534A1; FR2833036A1; DE60215052T2; AU2002364313A1; DE60215052D1; FR2833036B1

Abstract

The invention essentially concerns a method for regenerating a device for filtering exhaust gases produced by an engine, said method being of the type whereby the particles, retained on a filtering means of said filtering device, are burnt by the action of a combustion catalyst. Said method is characterized in that it essentially consists in using an ammonium nitrate solution, so as to produce an intimate mixture between the nitrate and the carbon particles and cause said particles to be burnt. The invention also concerns a device for implementing said method, which mainly comprises means for filtering (22) exhaust gases contained in a reaction chamber (18), in the path of the exhaust gas streams produced by an engine (10) and means for injecting the ammonium nitrate solution connected to said reaction chamber (18).

Description

METHOD FOR REGENERATING PARTICLE FILTERS BY INJECTION OF AMMONIUM NITRATE AND DEVICE FOR CARRYING OUT SAID METHOD

The present invention relates generally to the field of particle filters and more particularly to a method of regenerating particle filters. More particularly still, the present invention relates to a method for regenerating a particulate filter for a diesel engine, integrated in the exhaust line of a vehicle, based on the use of an aqueous solution of ammonium nitrate. In addition, the present invention also relates to a device allowing the implementation of the present method.

The reduction of polluting emissions linked to the operation of diesel engines is the objective that all manufacturers have set themselves.

Various systems have already been developed in order to reduce the level of these polluting emissions, in particular by integrating a particulate filter on the exhaust line. However, a major challenge in the development of these techniques consists in developing solutions so that the carbon particles trapped on the filter can burn or oxidize as they are deposited and thus avoid the clogging of the latter. The techniques currently used involving particle filters all face the major problem of incomplete combustion of the particles once retained on the filter. In fact, in urban use conditions, the temperature of the exhaust gases reached is not high enough to cause the complete combustion of the carbon particles and thereby significantly limit the clogging of the filter.

Without chemical assistance, the carbonaceous particles from the combustion of diesel fuel in diesel engines do not start to oxidize significantly above 500 ° C. However, these temperatures are almost never reached in urban driving conditions, it is necessary to use a chemical process to eliminate them.

Document FR-A-2 549 135 describes a process for eliminating the soot produced by a diesel engine, contained in the exhaust gases and deposited on a filtration means. This process mainly involves the use of copper chloride to remove carbonaceous particles. This copper chloride is combined with ammonium nitrate, in order to reduce the ignition temperature of the soot particles and to slow down the deposition of copper oxide on the filtration means. Copper chloride and ammonium nitrate, both in powder form, are brought to the level of the filtration means, in mixture or separately, distributed in the compressed air.

Such a process is now obsolete since the use of copper chloride is now prohibited, due to its toxicity. In addition, the use of solid product does not make it possible to obtain the homogeneous mixture necessary to lead mainly to the combustion of carbonaceous materials.

To obtain the oxidation of these particles, other methods are currently used. Thus, some systems propose to have upstream of the particulate filter, an oxidation catalysis means allowing the transformation of nitrogen monoxide NO, contained in the exhaust gases, into nitrogen dioxide NO ₂ from 250 ° C. This technique, called "Continuous Regenerating Trap" (CRT), combines the effects of the particle filter and the NO oxidation catalyst. This means consists of a catalytic support on which is fixed the catalyst, which is generally a precious metal such as platinum or rhodium. The NO ₂ produced by the action of the latter has the property of oxidizing the carbon particles from 250 ° C. However, the proper functioning of the filter depends on the average temperature reached and the ratio of particles emitted relative to the NO ₂ formed.

There is a similar means constituting a variant of the latter, in which the catalyst is fixed directly to the particle filter. However, only certain materials constituting the particle filter are capable of fixing the metal catalysts. This is particularly the case for cordierite. However, materials of this type are known to be particularly sensitive to an increase in temperature. It then appears that sudden increases in temperature which can occur in the particulate filter when it is clogged, are liable to cause irreversible deterioration of the latter. It is then necessary to replace the particulate filter and more generally the exhaust device, which represents an absolutely prohibitive cost. On the same principle as catalysis by precious metals, it has been described the use of organometallic additives, introduced into diesel, so that the carbon particle formed during the combustion of fuel is impregnated by this catalyst.

These additives are alkalis, alkaline earths or metals which are often used in admixture.

A first drawback of these techniques is the prohibitive cost of the additives used. Another major drawback lies in the fact that it is necessary to provide an additional additivation device.

Another drawback of these organometallic additives is that they entail an even greater risk of clogging of the filtration means and therefore of the reactions which result therefrom, if the temperatures reached in operation are not high enough to burn it.

However, none is really satisfactory, given the results obtained. In addition, the implementation of these methods leads to a significant additional operating cost by the additives they require or by the precious metal content required at the level of the support.

It also turned out that the implementation of these different types of procedures in severe urban use, was at the origin of incidents which led to the complete destruction of the filtration means. Expertise has shown that before its destruction, the filtration means gradually became clogged, thus modifying the driving conditions by gradually increasing the exhaust temperatures until the correct temperature was obtained to suddenly ignite all the particles deposited, the sudden increase in temperature causing destruction thereof either by thermal shock or simply because of the excessive temperature level reached. In such a technical context, the primary objective of the present invention is therefore to provide a simple, efficient and inexpensive process for regenerating the filtration means contained in the exhaust lines of motor vehicles.

Another objective is to provide a regeneration process avoiding any risk of accumulation of particles in the filtration means and therefore any risk of uncontrolled regeneration.

Yet another objective of the present invention is to provide a process which does not entail any significant additional cost for the user.

Yet another objective is to provide a method which can be implemented directly on the vehicle, but also by the use of a regeneration device independent of the vehicle.

Finally, a final objective of the invention is to provide a filtration device making it possible to implement the regeneration process according to the invention.

To achieve these objectives, the Applicant has had the merit of demonstrating that an aqueous solution of pure or quasi-pure ammonium nitrate could be used to regenerate the means of filtration of exhaust gases.

This is how the present invention satisfies the above objectives by first proposing a method for regenerating a gas filtration device. exhaust produced by an engine, this method being of the type in which particles, retained on a filtration means of said filtration device, are burned by the action of a combustion catalyst. This process is characterized in that it consists essentially in using an aqueous solution of ammonium nitrate, in order to allow an intimate mixture between the nitrate and the carbon particles and to cause the combustion of said particles.

According to a variant, the method according to the invention comprises the following steps: measuring a temperature θ _m in the filtration device, - comparing θ _m to a temperature θ _r corresponding to the temperature successively allowing the vaporization of the solvent and the crystallization of the nitrate of ammonium, the fusion of the crystals formed and the combustion of the carbon particles by decomposition of the ammonium nitrate, if θ _m is greater than or equal to θ _r , trigger an injection of the aqueous solution of ammonium nitrate, by through an appropriate injection means, into the filtration device, for a determined period, in order to cause the complete combustion of the particles retained on the filtration means.

According to another variant, the method according to the invention also consists in: measuring a pressure P _m inside the filtration device, said pressure P _m reflecting the degree of obstruction of the filtration means by the particles, measuring the temperature θ _m , - compare said pressure P _m with a reference pressure P _r corresponding to the maximum acceptable degree of obstruction,

- if P _m is greater than or equal to the pressure P _r , compare θ _m to θ _r ,

- if θ _m is greater than or equal to θ _r , initiate the injection of the aqueous ammonium nitrate solution. Advantageously, the method according to the invention comprises a preliminary step, consisting in triggering an injection of ammonium nitrate into the filtration device, when the temperature θ _m is less than or equal to θ _r , so that the nitrate ammonium, in aqueous form, impregnates in a particularly homogeneous manner, the particles deposited on the filtration means. Thus, the injection of ammonium nitrate is preferably triggered if

P _m is greater than or equal to the pressure P _r . An alternative consists in a method implementing a device for regenerating ex-situ filtration means, consisting in: connecting the filtration means to said regeneration device, injecting against the current an aqueous solution of ammonium nitrate in said means filtration, so that it impregnates the particles retained on the filtration means, and - generate a stream of hot air counter-current in said filtration means so as to bring the temperature inside said filtration means at a temperature at least equal to the decomposition temperature of ammonium nitrate, in order to trigger the combustion of the particles retained on the filtration means and the separation of the latter. Advantageously, this alternative process comprises an additional step consisting in carrying out one or more successive injections of the aqueous ammonium nitrate solution against the current, in the filtration means maintained at a temperature at least equal to the decomposition temperature of the nitrate. ammonium.

The aqueous ammonium nitrate solution used has an ammonium nitrate concentration, less than 128 g / 100 ml, and preferably between 10 and 100 g / 100ml. It can advantageously also contain soluble salts of alkali metals, alkaline earth metals, metals in the form of nitrates, acetates or other anions at concentrations of less than 10 grams per liter.

Another object of the invention relates to a filtration device allowing the implementation of the regeneration process according to the invention, which mainly comprises a means of filtering the exhaust gases contained in a reaction vessel, in the trajectory of the flow of exhaust gases produced by an engine and a means for injecting the ammonium nitrate solution connected to said reaction enclosure. Advantageously, this device also comprises an electronic device controlling the means for injecting the solution of the ammonium nitrate solution.

Preferably, the device also comprises at least one temperature probe placed inside the reaction enclosure, capable of measuring the temperature θ _m , within it and connected to the electronic control device. According to a remarkable variant, it also includes at least one pressure probe, placed inside said enclosure, capable of measuring the pressure P _m within it and connected to the electronic control device.

Advantageously, the means for injecting the ammonium nitrate solution mainly comprises a reservoir for said solution, connected to a nozzle for injecting said solution inside the reaction vessel, at the level of the filtration means.

Said injection nozzle is supplied on the one hand with ammonium nitrate solution via a first conduit connecting the reservoir to said nozzle, and on the other hand with compressed air via a second conduit connecting said nozzle to the engine.

According to another remarkable characteristic, the conduits connecting the injection nozzle to the tank of the ammonium nitrate solution and to the engine are each equipped with a solenoid valve controlled by the electronic control device.

According to yet another remarkable characteristic, the device also comprises a means for catalyzing the combustion of the particles retained on the filtration means.

Advantageously, this means of catalysis consists of a support on which is fixed an oxidation catalyst.

Preferably, the filtration means of said device consists of at least one set of at least one filtering unit.

The present invention will be better understood on reading the description which follows, made with reference to the single figure which represents, in a non-limiting manner, an exemplary embodiment of the filtration device according to the invention according to a general schematic view, within of a system comprising an engine 10 of a motor vehicle. This engine 10 is supplied with fuel from a tank 12, via a supply duct 14. The engine 10 produces exhaust gases in operation. These gases are recovered by means of a manifold (not shown) at the outlet of the engine and are evacuated via an exhaust duct 16. This duct joins an enclosure 18 of the filtration device. This enclosure contains a means of catalysis 20 and a means of filtration 22.

The catalyst means 20 is preferably a metal support, in the form of a cartridge, on which is fixed a metal catalyst of the oxidation catalyst type, such as platinum.

This filtration means 22 is constituted by a set of filter units. These filter units are preferably of rectangular parallelepiped shape. Their structure is of the honeycomb type. They are advantageously made of silicon carbide.

However, it is possible to use filter units made of other metals or ceramics, such as cordierite. The filter units are separated by a seal, making the latter thermally independent from each other and also allowing their expansion. This seal can occupy only part of the interstitial space of the filter units, thus allowing the circulation of the exhaust gases therebetween. At the inlet of the enclosure 18, a temperature probe 24 and a pressure probe 26 are arranged. These probes have the function of measuring the temperature and the pressure at the inlet of the enclosure. The data relating to these measurements are transmitted to an electronic control device 28 and are analyzed by the latter. This device is also connected to two solenoid valves 30 and 32, arranged respectively on two conduits 34 and 36.

The function of the conduit 34 is to supply compressed air to an injection nozzle 38, fixed against the wall of the enclosure 18 and a part of which projects inside the said enclosure.

The conduit 36 connects said injection nozzle 38 to a reservoir 40 containing an aqueous solution of ammonium nitrate. At the outlet from the reservoir 40 is arranged a pump 42, of any suitable design, intended to take the ammonium nitrate from the reservoir and to send it into the conduit 36.

The capacity of the tank 40 is chosen according to the type of vehicle on which the device according to the invention is installed. Indeed, it must not be too bulky to be able to be installed easily. However, it should not be too small to avoid overly regular refills.

The method according to the invention and the device making it possible to implement it are based on the injection of an aqueous ammonium nitrate solution into the enclosure, at the level of the filtration means, in order to optimally burn the carbon particles retained during the use of the vehicle.

To do this, the temperature at the inlet of the enclosure 18 is measured, using the probe 24. The temperature value θ _m measured is collected by the electronic device 28. The latter will compare this value θ _m to a value of reference de _r , corresponding to the temperature at which the ammonium nitrate contained in the aqueous solution causes the combustion of these particles.

If the temperature θ _m measured is greater than or equal to the reference value θ _r , the electronic device triggers the opening of the solenoid valves 30 and 32, in order to supply the injection nozzle 38 with ammonium nitrate solution and pressurized air. The compressed air and the ammonium nitrate solution mix in the injection nozzle 38. This mixture is then sprayed on the filtration means 22. When the volume of ammonium nitrate solution, predetermined by the electronic device, has been injected, the supply is cut off by closing the solenoid valve 32.

The ammonium nitrate solution is sprayed on the filter units as an aerosol. Given the temperature prevailing in the enclosure, the ammonium nitrate crystallizes by vaporization of the water used in the solution as solvent. The ammonium nitrate crystals formed then disperse over the entire surface of the filter units, then melt at a temperature of 173 ° C, optimally impregnating the carbon particles. They decompose abruptly above 210 ° C to cause the instant ignition of particles impregnated with ammonium nitrate. Finally, the combustion energy released propagates the combustion step by step to neighboring particles.

The filtration means is then found free of deposits and recovers its full filtration capacity. A variant of this method consists in simultaneously measuring the temperature and the pressure at the inlet of the enclosure 18, using the temperature probe 24 and the pressure probe 26. The pressure value P _m measured reflects the degree d obstruction of the filtration means 22 by the particles. In fact, if the filtration means 22 is clogged, the exhaust gases pass more difficultly and then exert a back pressure. Thus, the measurement of the pressure P _m corresponds to the best means of controlling the degree of clogging of the filtration means 22. The electronic device 28 compares the value P _m measured with a reference value P _r , corresponding to the maximum degree of obstruction acceptable filtration means 22. If P _m is greater than or equal to P _r , the electronic device 28 compares θ _m to θ _r . If θ _m is greater than or equal to θ _r , the device 28 then triggers the post-injection of diesel which leads to the regeneration of the filtration means 22. This operational mode has the advantage of triggering post-injection only when the means of filtration has reached a specific degree of clogging, which limits the consumption of ammonium nitrate solution.

According to a particular embodiment, the electronic device 28 can be programmed in order to trigger an injection of cold ammonium nitrate solution at a determined time interval. For example, such an injection can occur every morning when the vehicle is started. This embodiment is of particular interest insofar as the filtration means being at a temperature more or less equal to the outside temperature, the ammonium nitrate solution remains in liquid form. It then uniformly permeates the carbon particles. In addition, given the time required for the enclosure to reach the temperature θ _m , the solution of ammonium nitrate can permeate particles deep down. Therefore, when the temperature θ _m is reached, the combustion of the particles is optimized.

Advantageously, the electronic device can be programmed to trigger this cold injection only on condition that a sufficient degree of clogging has been detected, at the end of the previous period of use.

In the case of the use of a filtration means made of a more fragile material than silicon carbide, for example cordierite, It may be preferable to program the electronic device so that the regeneration frequency is greater . In fact, an excessively high degree of clogging of the filtration means risks provoking a strongly exothermic regeneration, which can damage the filtration means.

An alternative regeneration process to that described above consists, in general, of using a device for regenerating ex-situ filtration means. More specifically, this alternative process consists of:

- connect the filtration means to the regeneration device,

- inject the aqueous ammonium nitrate solution against the current in the filtration means, so that it comes to impregnate the particles retained on the filtration means, and - generate a stream of hot air against- current in said filtration means so as to bring the temperature inside the filtration means to a temperature at least equal to the decomposition temperature of ammonium nitrate, in order to trigger the combustion of the particles retained on the filtration means and the detachment of the latter.

Such a regeneration device is described in document FR-A-2 787 343. With reference to the single figure of this document, this device essentially comprises:

- means for supplying a hot air stream (27, 26, 22) connected to the exhaust line in order to circulate the air stream against the current to bring it through the filter,

- means (29) for recirculating the stream of hot air,

- And a regenerator (35) capable of causing combustion of the particles in suspension in the vein and of filtering the latter and which is interposed between the means for supplying the vein and those ensuring its recirculation. The means for injecting the ammonium nitrate can be adapted on the device described above. Indeed, a reservoir, equivalent to the reservoir 40 according to the invention, can advantageously be connected to the injector referenced 49 in the single figure of document FR-A-2 787 343, via a conduit. At the outlet of this tank, a pump can be arranged, equivalent to the pump 42 according to the invention. The ammonium nitrate propagates in the pipeline to the filtration device. It then impregnates the particles which detach from the filtration means under the action of the hot air stream. These particles then join the regenerator by the recirculation means, in which they are burned. A variant of this regeneration process consists in recovering the filtration means after deposition of the vehicle exhaust line and in mounting the filtration means directly on the regeneration device. Such a variant has the advantage of not providing an exhaust line having a recirculation circuit of the hot air stream in the direction of the regeneration device, after passage through the filtration means. Another interest is related to security. Indeed, the stream of hot air reaching relatively high temperatures (of the order of 500 ° C), by radiation, the vehicle being stopped, the whole of the particle filter can overheat the engine parts or surrounding bodywork.

Once the filter is mounted on the machine, the temperature of the filtration medium is raised to more than 210 ° C by placing the stream of hot air against the current, so as to cause the combustion of all the particles impregnated with ammonium nitrate. It may be wise to monitor the outlet temperature of the vein in particular, so as to be able to control the regeneration and, if necessary, be able to slow down the phenomenon by very significantly increasing the air flow. According to this latter variant, it may be judiciously provided for a prior step of injecting the ammonium nitrate solution into the filtration means, before that is mounted on the regeneration device. Such a step allows better impregnation of the carbon particles with the aqueous ammonium nitrate solution and therefore better combustion of the latter, once retained on the regenerator.

Finally, a final evolution of this variant may consist in carrying out final successive injections of aerosol at a temperature in the region of 200 ° C. to finish the regeneration of the filter until there is no combustion phenomenon.

In the case of ex-situ regeneration, the advantage of using the ammonium nitrate solution lies mainly in the fact that it makes it possible to greatly reduce the time necessary for the regeneration of the filtration means. The aqueous ammonium nitrate solution used can be made from ammonium nitrate of ammonitrate quality, used as fertilizer and available at very attractive costs.

By filtration or centrifugal separation, the ammonium nitrate is freed from the anti-flaking additives it contains such as calcium and magnesium carbonates.

The ammonium nitrate is dissolved in a solvent, which is preferably water.

It is preferable that the concentration of ammonium nitrate in the solution is less than the water saturation threshold at 0 ° C, or less than 128 g / 100 ml. Preferably, this concentration will be less than 100 g / 100 ml.

The solution may contain only ammonium nitrate. However, it may be judiciously added soluble salts of alkali metals, alkaline earth metals, metals in the form of nitrates or acetates or other anions without disadvantage in this aqueous solution.

For example, a mixture of iron nitrate, calcium nitrate and cerium nitrate could judiciously be added to the ammonium nitrate solution, each of these constituents having a metal concentration of 1 gram per liter.

These salts are added in very small quantities so that their total concentration in the ammonium nitrate solution remains below 10 grams / liter.

The composition of the solution is chosen so as to have the best reactivity with respect to the oxidation temperature of carbonaceous materials.

Example: Use of the method according to the invention on a bus equipped with a 10 liter cylinder diesel engine operating in urban use.

The reference pressure P _r , corresponding to the maximum degree of clogging of the filter, at which regeneration must take place, is fixed at 200 mbar. During the start-up phase, as soon as the engine was started, an injection of the ammonium nitrate solution was programmed for 3 minutes corresponding to an injection of 150 cm ³ of the ammonium nitrate solution, which is a quantity sufficient to wet and permeate any trapped particles on the filter.

The rise in temperature of the exhaust gases firstly causes the water contained in the solution to vaporize and crystallize the ammonium nitrate. This results in a dispersion of the ammonium nitrate crystals formed. These then melt at a temperature above 165 ° C and transform into a very fluid liquid which exhibits excellent wettability with the carbon particles retained on the filter. A homogeneous paste of carbon particles and ammonium nitrate is then formed.

This homogeneous paste ignites by itself above 210 ° C, which corresponds to the decomposition temperature of ammonium nitrate, causing the combustion, gradually, of approximately 90% of the carbon particles retained on the filter.

Claims

1. Method for regenerating a device for filtering the exhaust gases produced by an engine (10), this method being of the type in which particles, retained on a filter means (22) of said filter device, are burned by the action of a combustion catalyst, characterized in that it consists essentially in using an aqueous solution of ammonium nitrate in order to cause the combustion of said particles.

2. Method according to the preceding claim, characterized in that it comprises the following steps:

- measure a temperature θ _ra in the filtration device,

- compare θ _m at a temperature θ _r corresponding to the temperature allowing successively the vaporization of the solvent and the crystallization of ammonium nitrate, the melting of the crystals formed and the combustion of carbon particles by decomposition of ammonium nitrate,

- if θ _m is greater than or equal to θ _r , initiate an injection of the aqueous ammonium nitrate solution, by means of an appropriate injection means, into the filtration device, for a determined period, in order to to cause the complete combustion of the particles retained on the filtration means (22).

3. Method according to the preceding claim, characterized in that it also consists in:

measuring a pressure P _m inside the filtration device, said pressure P _m reflecting the degree of obstruction of the filtration means (22) by the particles,

- measure the temperature θ _m , - compare said pressure P _m with a reference pressure P _r corresponding to the maximum acceptable degree of obstruction,

- if θ _m is greater than or equal to θ _r , initiate the injection of the aqueous ammonium nitrate solution.

4. Method according to one of claims 2 or 3, characterized in that it comprises a prior step, consisting in triggering an injection of ammonium nitrate into the filtration device, when the temperature θ _m is less than or equal to θ _r , so that the ammonium nitrate, in aqueous form, uniformly impregnates the particles deposited on the filtration means.

5. Method according to the preceding claim, characterized in that said injection of ammonium nitrate is triggered if P _m is greater than or equal to the pressure P _r .

6. Method according to claim 1, characterized in that it consists in implementing a device for regenerating ex-situ filtration means, and comprises the following steps: connecting the filtration means (22) to a regeneration device such means, injecting against the current an aqueous solution of ammonium nitrate into said filtration means (22), so that it comes to impregnate the particles retained on the filtration means (22), and - generating a stream of countercurrent hot air in said filtration means (22) so as to bring the temperature inside said filtration means to a temperature at least equal to the decomposition temperature of ammonium nitrate, so to trigger the combustion of the particles retained on the filtration means and the detachment of the latter.

7. Method according to claim 6, characterized in that it comprises an additional step consisting in carrying out one or more successive injections of the aqueous ammonium nitrate solution against the current, in the filtration means (22) maintained at a temperature at least equal to the decomposition temperature of ammonium nitrate.

8. Method according to one of claims 1 to 7, characterized in that the aqueous ammonium nitrate solution has an ammonium nitrate concentration, less than 128 g / 100 ml, and preferably between 10 and 100 g / 100 ml.

9. Method according to claim 8, characterized in that the aqueous solution of ammonium nitrate also comprises soluble salts of alkali metals, alkaline earth metals, of metals in the form of nitrates, acetates or other anions at lower concentrations. at 10 grams per liter.

10. Filtration device allowing the implementation of the regeneration process according to one of claims 1 to 5, characterized in that it mainly comprises a means of filtration (22) of the exhaust gases contained in a reaction vessel ( 18), in the path of the flow of the exhaust gases produced by an engine (10) and a means for injecting the ammonium nitrate solution connected to said reaction enclosure (18).

11. Device according to the preceding claim, characterized in that it also comprises an electronic device (28) controlling the means for injecting the ammonium nitrate solution.

12. Device according to claim 10 or 11, characterized in that it also comprises at least one temperature probe (24) placed inside the reaction chamber (18), capable of measuring the temperature θ _m , in its breast and connected to the electronic control device (28).

13. Device according to one of claims 10 to 12, characterized in that it also comprises at least one pressure probe (26), placed inside said enclosure (18), capable of measuring the pressure P _m therein and connected to the electronic control device (28).

14. Device according to one of claims 10 to 13, characterized in that the means for injecting the ammonium nitrate solution mainly comprises a reservoir of said solution (40), connected to an injection nozzle (38 ) of said solution, inside the reaction enclosure (18), at the level of the filtration means (22).

15. Filtration device according to the preceding claim, characterized in that said injection nozzle (38) is supplied on the one hand with ammonium nitrate solution via a first conduit (36) connecting the reservoir (40) to said nozzle (38), and on the other hand by compressed air via a second conduit (34) connecting said nozzle (38) to the motor (10).

16. Device according to one of claims 14 or 15, characterized in that the conduits (36, 34) connecting the injection nozzle (38) respectively to the tank (40) of the ammonium nitrate solution and to the engine (10) are each equipped with a solenoid valve (32, 30) controlled by the electronic control device (28).

17. Device according to one of claims 10 to 16, characterized in that it also comprises a means of catalysis (20) of the combustion of the particles retained on the filtration means.

18. Device according to the preceding claim, characterized in that the catalysis means (20) consists of a support on which is fixed an oxidation catalyst.

19. Device according to one of claims 10 to 18, characterized in that the filtration means (22) consists of at least one set of at least one filter unit.