WO2012001296A1

WO2012001296A1 - Device with expanded metal walls for treating a particle-laden gaseous medium

Info

Publication number: WO2012001296A1
Application number: PCT/FR2011/051505
Authority: WO
Inventors: Daniel Teboul
Original assignee: Daniel Teboul
Priority date: 2010-06-28
Filing date: 2011-06-28
Publication date: 2012-01-05
Also published as: FR2961852A1

Abstract

Device for treating a particle-laden gaseous medium, comprising at least one filtering element (22) for trapping the particles of the gaseous medium, characterized in that each filtering element comprises a plurality of non-flattened expanded metal thin walls positioned adjacent to one another to form a monolithic partitioning structure made up of these perforated walls, so as to form obstacles to the passage of the particle-laden gaseous medium, so as to hold these particles back inside the structure.

Description

The present invention relates to a device for treating a gaseous medium loaded with particles. . A particular, but not exclusive, application is the purification of the exhaust gases of a diesel engine.

Another application is the industrial sector.

Pollutants leaving the exhausts include: - carbon components: CO, CO2;

- Nitrogen compounds: NO, NO2 (generally called nitrogen oxides NOx) ...;

organic compounds, such as hydrocarbons (HC);

sulfur compounds: SO2, SO3;

organic particles;

- etc.

The emissions of organic particles are especially characteristic of diesel engines and consist of a carbonaceous material (soot), on which are adsorbed various organic species (SOF: Soluble Organic Fraction).

Numerous processes and devices for treating the exhaust gases of an internal combustion engine have already been proposed in the past.

It is notably known to use particulate support or monolithic support oxidation catalysts, in particular for oxidizing CO and unburned hydrocarbons.

For particles of diesel engines, there are also regenerable trapping systems.

For some time, the interest of researchers has focused mainly on the problem of limiting the mass of particulate matter released by the exhaust gases of diesel engines and other internal combustion engines. In the case of diesel engines, great efforts are made to develop practical and effective devices and processes to reduce particulate emissions, mainly carbon, and gaseous pollutants released with exhaust gases.

It is known that a method for achieving this result is to mount suitable filters or other types of particle traps in the exhaust system of an engine or vehicle. In view of this fact, it is sought to find the most effective and practical means to collect and dispose of soot-like particulate matter emitted by diesel engines before the exhaust gases are released into the engine. atmosphere.

If today a material based on SiC (silicon carbide) is the most frequently used, it should be noted that all players are also continuously looking for alternative materials, more efficient and less expensive.

The main technologies in the field of depollution of thermal engines are thus, currently:

The two-way catalytic purifiers: they are composed of a ceramic support on which is deposited a metal catalyst. This allows a reduction in the temperature necessary for the oxidation of carbon monoxide and organic compounds. The efficiency of the catalytic scrubbers for the different pollutants depends a lot on the temperature of the exhaust gas.

Particulate filters: they are designed to retain the particles emitted by diesel engines. There are several types of filters available on the market.

Consumable filters: they consist of fibers. The particles are retained in the filter volume. They make it possible to retain 80 to 90% of the particles. To prevent their degradation, the temperature of the exhaust gases must not exceed a temperature depending on the nature of the fibers. They are gradually clogged with retained particles and must be replaced after a certain period of operation of the engine. Regenerable filters: the filter medium consists of either a porous ceramics (usually cordierite or silicon carbide) or ceramic or metallic fibers. These materials withstand temperatures high enough to be regenerated by burning carbon particles.

The ceramic filters with deposited catalyst: they are manufactured with a porous ceramic in the middle of which a catalyst is deposited, allowing the combustion of the carbon particles for exhaust gas temperatures of at least about 350 ° C, dependent on the technology used.

The ceramic filters with catalyst added to the fuel: the catalyst is added to the fuel in liquid form, either directly on the vehicle via a metering pump during each filling of the tank, or directly in the tank used to make the full. The catalysts used are based on cerium, iron, strontium or platinum. They allow the lowering of the combustion temperature to 300 to 400 ° C, depending on the nature of the catalyst and the temperature needed to burn the carbon particles.

The coupling of a filter and a catalytic scrubber: such a system consists of a catalytic scrubber followed by a particulate filter. The scrubber allows the oxidation of CO, organic compounds as well as a part of the nitric oxide. The nitrogen dioxide formed will allow oxidation of the carbon particles retained in the particulate filter. Such a device provides good efficiency vis-à-vis the particles and carbon monoxide but leads to an increase in nitrogen dioxide emissions.

Electrostatic precipitators: there are also particle filters on the market that operate on the principle of the electrostatic precipitator. The gases and particles circulate between two electrodes between which a high potential difference is maintained. Under the effect of these, the particles agglomerate, load negatively and are attracted by the positive electrode on which they come to stick. Some types of electrostatic precipitators also use additional devices to retain agglomerated particles (cyclone or filter). These filters have an efficiency that can exceed 90%. The saturation of the filter does not cause a loss of charge. These filters need to be cleaned regularly to maintain their effectiveness

The ultimate solution is so-called 4-way catalysis that eliminates 4 pollutants:

NOx, HC, CO and particles simultaneously.

The invention aims to improve the known treatment devices, especially as regards their effectiveness.

It also aims to achieve a device that is compact, inexpensive and easy to manufacture.

It proposes a device for treating a particle-laden gaseous medium, comprising at least one filtering element for trapping the particles of the gaseous medium, each filtering element comprising a plurality of thin non-flattened stretched metal walls arranged adjacent to form a monolithic partitioning structure formed of these perforated walls, so as to form obstacles to the passage of the gaseous medium loaded with particles, in order to retain them inside the structure.

The invention consists in replacing the known filtering elements, in particular made of ceramic, with monolithic micro-stretched metal elements with perforated walls forming a new structure and configuration to effectively stop the particles emitted by the diesel engines. These elements are arranged to form compact units with high efficiency having an extremely large filter surface for their volume. They can be cleaned by heating the monolithic micro-stretched metal structure or parts of this structure to the incineration temperature of the collected particles, thereby removing the particles by combustion. The invention also relates to several different arrangements for the construction of monolithic micro-stretched metal filter elements with perforated walls and several methods of manufacturing these elements.

The monolithic micro-stretched metal filter option allows greater permeability and generates lower back pressure, in temperature more easily by its metallic nature and offers a development potential quite relevant.

The invention relates more particularly to exhaust gas filtration devices comprising catalytic filter elements made of micro-stretched metal, with perforated walls placed successively so as to form a monolithic block forming a catalytic filter.

According to other provisions, which can be implemented for reasons of convenience of manufacture, of operating efficiency, ... and which can possibly be combined:

- The plates are arranged parallel to each other, vertically or horizontally.

- The plates are offset relative to each other, transversely to the direction of the parallel alignment, preferably arranged staggered.

- The filter element comprises a pleated metal structure not drawn flat, forming said thin walls, preferably star or accordion.

the star-pleated structure extends around a central passage, open at an inlet end of the gaseous medium, to which the pleated structure is closed, while the opposite end of the passage is closed and that of the structure pleated open for the exit of gases from the purified gaseous medium.

the stretched metal is micro-stretched metal.

the average opening dimension of the drawn metal is between 200 microns and 2000 microns.

the meshes of the drawn metal are in the shape of a diamond, square, triangle, rectangle, hexagon or round.

each thin wall of drawn metal has perforations forming baffles with salient relief.

the walls are mounted in a clamping frame,

the device comprises two filter elements arranged one behind the other and separated by a free transition space forming a relaxation chamber. the device comprises means for thermal or catalytic regeneration of the filter element.

the device comprises an electrical resistance adapted to raise the temperature of the gaseous medium and to burn the particles accumulated on the thin walls of the filter element.

the thin walls have perforations dimensioned so as to generate a back pressure, these walls being further impregnated with precious metal catalyst.

the thin walls have perforations dimensioned so as to avoid backpressure and which are impregnated with precious metal catalyst, so that the filter element also acts as oxidation catalyst.

precious metals include platinum, palladium and rhodium.

the device comprises at least one longitudinal housing envelope of the filter element or elements.

the device comprises, successively from the inlet to the outlet of the treatment device, an oxidation catalyst, an electrostatic precipitator, preferably spikes, and a filter element as defined above.

the oxidation catalyst is as defined above.

the device further comprises an electrostatic precipitator and / or a device for selective catalytic reduction of NOx.

The features and advantages of the invention will become apparent from the following description, with reference to the accompanying drawings, given solely by way of example, in which:

FIG. 1 is a perspective view of a portion of a vehicle chassis comprising a diesel engine and an exhaust system equipped with exhaust particle traps according to the invention;

FIG. 2 and FIGS. 2a to 2c are perspective and sectional views of different scales and showing the construction of monolithic micro-stretched metal filter elements used in the particle traps of the arrangement of FIG. FIG. I; FIG. 3 is a partial perspective view of a vehicle chassis on which is mounted an alternative embodiment of the exhaust particle trap according to the invention for a diesel engine,

FIG. 4 is a partial sectional view illustrating the construction of a pleated monolithic micro-stretched metal filter element used in the particulate trap device of FIG. 3

- Figs. 5a to k, m, n, and p are front views which illustrate a number of possible wall and pass configurations for monolithic micro-stretched metal filter elements of the general type shown in Figs. 2a to 2c.

FIG. 6 schematically illustrates an example of a method of manufacturing a metal plate and Figures 6b to 6e show different views of the resulting plate.

Fig. 1 shows a vehicle chassis 10 comprising a chassis proper 1 1 on which is mounted a diesel engine 12 of the V-type, itself having two rows of cylinders, each of which carries an exhaust manifold 14 interposed in a circuit d exhaust, the collector on the right being the only visible on the drawing.

Each exhaust manifold is connected via an exhaust pipe 15 to an exhaust particle trap 16 mounted in the chassis of the vehicle by means not shown and which is adapted to collect the particles contained in the exhaust gas and which are sent to the traps by the cylinders of the corresponding row of cylinders. The outputs of the traps 16 are connected by a tube 18 Y to a muffler or muffler 19 which, in turn, is connected to the rear of the vehicle by an outlet pipe 20 for rejecting the exhaust in the air.

Each of the particle traps 16 comprises an envelope which may be of any shape and configuration suitable for this purpose, for example: round, oval, square, rectangular, diamond. In the casing is housed at least one filter element made of monolithic (ie forming a block) micro-stretched (deployed) metal - with high efficiency and cleanable by incineration or regeneration, which may have any one of several possible configurations, such as, for example, that of the element 22 shown in Fig.2 and Fig.2a to 2c. The filter element 22 is made here, in the form of a monolithic micro-stretched metal element having a cylindrical outer wall 23 forming the envelope of the trap 16, and internally braced by a large number of inner plates or walls. thin perforated 24, which intersect each other. It is more precisely discs, here in number of 120 for 5 cm in length (in general the length of the filtering element is between 5 cm and 10 cm, but can be longer as necessary. diameter is here about 13 cm The stretched metal is not flattened The inside walls internally delimit globally two groups of parallel passages with respect to their median plane and because of their non-flattened stretched structure, which respectively comprise passages of inlet 26 in the wall and outlet passages 27 of the wall, successively extending from one to the other of the opposite ends of the element 22. The inlet and outlet passages are, because of the structure of the adjacent non-flattened expanded metal plates, either open or partially open (thus partially closed) due to the presence of one or more strips of the adjacent obstacle plate (a kind of entanglement). Thus, the inlet passages 26 may be open at the inlet end 28 of the element and partially closed at the outlet end 30 thereof, while the outlet passages 27 may be partially closed on the input end 28 side of the element and open towards the outlet end 30 of this element. In the embodiment of Fig. 2, the passages have a square section, although as will be described more fully below, many other configurations can also be used.

Furthermore, the inlet passages and the outlet passages are grouped in vertical rows or in horizontal rows (sectional view Fig.2b and 2c where the plates are arranged respectively horizontally and vertically), the alternating inlet passages, preferably, with the outlet passages in a staggered arrangement. It is therefore visible that each inner wall portion of the element is interposed between an inlet passage and an outlet passage at each point of its surface except where it meets another wall as occurs at the corners of the passages. For example, except at corner meeting points, the inlet passages are isolated from each other by interposed exit passages and vice versa.

The construction of the monolithic micro-stretched metal member is such that the inner walls 24 are perforated so as to pass the exhaust gas from the inlet passages to the outlet passages through the walls. The perforation of the walls is determined so as to filter a large part of the particles of materials present in the exhaust gas of the diesel engines. At present, tests have shown that effective filtering is achieved with a micro-stretched metal wall structure having average perforations of about 10% (10% void relative to the total volume of the element, so % solid volume stopping the particles), with an average opening size of 200 microns to 2000 microns. This result is obtained in a monolithic micro-stretched metal structure having round, square, diamond, hexagonal passages of about 0.05 millimeter side or diameter, with a wall thickness of about 0.5 millimeter between the passages . In view of the fact that the entire surface of the internal partitioning between the inlet passages and the outlet passages constitutes an active filtering surface, it can be calculated that this partition provides more than 5 cm ² of filtering wall area per cm ³ of the monolithic filter structure. Thus, a filter is obtained which represents only a very small section throat and has a large filter surface in a device of very small dimensions. Of course, by increasing the perforation of the mean wall openings beyond 10% of the initial test samples, it can be expected to further reduce the flow resistance of the gases through the filter element, at least as far as possible. the surfaces of the inlet and outlet passages become limiting factors of the gas flow. In other words, to conceive the invention of this catalytic filter in a metal substrate, which is in practice a micro-stretched metal, which is similar to a shock filter, a series of blades is used. lattices or rigid plates of special design, which are perforated and stretched, thus forming baffles with salient relief successively installed vertically or horizontally, so as not to press against each other (which would have the disadvantage of obstructing the passage of gases ), all inserted into a clamping frame so as to make, here, a monolithic mass of sections which are separated by a free space of transition forming an expansion chamber for the gases, in which or which one can install systems of regeneration that allow the burning of particles.

This system is placed in the flow of exhaust gases, the shape of these perforated plates causing abrupt changes of direction of the air and gases charged with particles, which by turbulent flow projects the particles of soot (fat) against the inner faces of the plates or plates arranged in a baffle, which are introduced into the purification member.

If it is desired to use such a device in the form of a particulate filter, it is necessary to tighten the mesh size so as to cause a little more back pressure, which has the advantage of increasing the temperature of the gaseous medium. in the device.

If it is desired to implement such a device in the form of an oxidation catalyst filter, it is necessary to increase the mesh size, so as to avoid backpressure and to impregnate it with a catalytic solution based on metals. precious (platinum, palladium, rhodium).

In the operation of an engine which comprises in its exhaust circuit one or more of the compact and high efficiency particulate filter elements of the type described above, the exhaust gases are sent from the engine to each particle trap 16, into which they enter the filter element through the open ends of the inlet passages to the right of the inlet end 28 of the element. The incoming gases are distributed over the entire length of the entrance passages, from where they pass through all the perforated walls delimiting the various passages to enter the adjacent exit passages.

The carbonaceous particles contained in the diesel engine exhaust gases are thus largely retained and collected by impact on the internal surfaces of the walls of the inlet passages when the exhaust gases pass through these walls. The collected particles form on the surfaces of the walls a cake which accumulates until, finally, it reaches a thickness which begins to hinder the passage of gases through the walls. The purified gases that pass through the walls to reach the exit passages continue their path to the open ends at the outlet end of the element and then continue their path through the remainder of the exhaust system until they are released into the atmosphere.

When operating an engine equipped with an exhaust filter of the type described, the collected particles periodically reach a level beyond which the throttling of the gas flow becomes excessive. At this stage, or before this stage has been reached, it is necessary to regenerate by catalytic oxidation aftercombustion, by means of an injection of catalytic additive or impregnation of the catalyst filter (rhodium, platinum, palladium ) or by cleaning (injection of soapy water for example), so that the engine of the vehicle can continue to operate with its normal efficiency. Although the compact high-efficiency monolithic micro-stretched metal element according to the invention can be used in any desired way, it is believed that the cleaning of the element takes place under the best conditions by heating the element at a temperature at which the collected particles are incinerated by reaction with the oxygen contained in the exhaust gas stream. This incineration can also be obtained by heating the exhaust gas, by the forced passage of the gaseous medium in the treatment device associated with an electrical resistance adapted to burn the particles deposited on its structure. This thermal regeneration can, alternatively, also be obtained by means of a diesel burner. Such a filtering structure makes it possible to bring the gaseous medium to the operating temperature of the oxidation catalyst, but above all it makes it possible to achieve a particularly compact device by causing the combustion of the particles retained in the filter.

The micro-stretched metal plates are here impregnated with precious metal catalyst (platinum, rhodium, palladium), depending on the gases to be treated.

For their attachment, these metal plates are, for example, placed in a cylindrical insulating ceramic ring of different diameter and thickness follow the size of the discs, so as to ensure electrical continuity once the desired incineration temperature reached, during the operation of the engine, this being done naturally by appropriate methods of heating and adjusting combustion temperatures as indicated in particular above or by connecting the discs on electric current to heat them while isolating them electrically from the envelope of the trap. Alternatively, for cleaning the micro-stretched metal filter elements, and after several hours or kilometers of operation, these elements can be removed from the exhaust system and placed in a detergent solution.

To withstand the operating and incineration temperatures and stresses that monolithic micro-stretched metal filter elements have to undergo under the indicated conditions, these elements must necessarily be made of a suitable metallic material, which may be carbon steel, steel stainless steel, refractory stainless steel, stainless steel inconel, copper, brass, titanium or other alloy, although many of these materials may be appropriate.

It is advantageous to form the metal elements by taking advantage of known technologies:

- using materials and processes which have been developed for the manufacture of elements for catalytic converters and the like,

a preferred series of phases of a manufacturing process applied to the formation of monolithic micro-stretched metal plates whose passages are more or less open and larger in their fields of application to catalytic converters and other devices they cause less back pressure in the exhaust line. After execution of these manufacturing phases, the structure is made of superimposed plates so as to make a monolithic assembly into a filter element.

A description of the fabrication of the micro-stretched metal and the procedures for producing the raw material is made with reference to FIGS. 6a to 6e. The product the drawn metal (or the micro-stretched metal) is a metal structure obtained by a method of deployment, applied to a metal sheet in which openings are created by shearing and stretching the metal (Fig 6a). Thus, it appears from FIG. 6a, the combination of different parameters - shape and dimensions of the knife, adjustment of the depth of penetration of the tool in the sheet metal, advance of the sheet between each cycle - gives rise to a specific grid composed of repetitive elements of which unit is called mesh. Each mesh is delimited by nodes.

The mesh is defined by: the long diagonal distance (LD) measured in the shearing direction of the metal, the short diagonal (CD), measured center distance in the stretching direction of the metal (Fig. 6b), the width of the thong ( av), dimension corresponding to the advance of the sheet between each cycle and the thickness (sp) measurement which corresponds to the thickness of the sheet (Fig 6c).

These manufacturing parameters result from complementary characteristics:

- the apparent thickness (Fig. 6d): Overall thickness of the drawn metal;

- the opening rate (or void percentage): if we want a high opening rate, we will choose a large dimension (CD) - see for example Fig. 6th - compared to a given dimension (LD) and a small strap. Conversely, if a low percentage of vacuum is desired, a product with a wide strap will be selected proportionally to the dimensions of the mesh.

Although the description given above has described a known method for manufacturing the micro-stretched metal which can advantageously be used in the context of the present invention, it goes without saying that it is possible to make various modifications to the structure and the manufacturing process while remaining within the scope of the inventive principles of the present invention. For example, Figs. 3 and 4 show the structure of an alternative embodiment of a micro-stretched metal filter element for diesel engine exhaust and its application in the exhaust system of a vehicle.

Fig. 3 shows parts of a vehicle chassis 32, which comprises a chassis 33 itself, in which is mounted a diesel engine 34 of the V-type. The engine comprises two rows of cylinders 35 which deliver exhaust gases 35, only the manifold of the row of cylinders on the right being shown. Along the right side of the engine, is mounted an exhaust particle trap 37 which comprises, here, a cubic envelope, or other configuration provided with front and rear entrances which are themselves connected to the pipes exhaust 38, 39 respectively corresponding to the left exhaust manifold and the exhaust manifold on the right. An exhaust outlet formed at the base of the casing is connected to an outlet pipe 44 which sends the purified exhaust gas to an exhaust pipe, not shown, and from there to the atmosphere.

As seen in Fig.4, in the casing of the particle trap 37 is disposed a filter element 45 for exhaust particles, of the micro-stretched and pleated metal type. In this case, the element 45 is constituted by a micro-stretched metal filter of another laminar flow configuration. The construction of this type of filter comprises a set of micro-stretched metal pleated walls, in one piece having several superimposed layers of longitudinal passages 46 and transverse or lateral passages 48, the different passages being separated from each other by the perforated inner walls or partitions 49 of the assembly.

In practice this set forms, in section, a star configuration around a central passage. Alternatively, an accordion pleating may also be considered.

In the illustrated construction, the longitudinal passages 46 are used as inlet interior passages while the lateral passages 48 are used as external outlet passages, and vertically arranged (the longitudinal passages) when the micro-stretched and pleated metal filter is mounted in the particle trap 37 of FIG. FIG. 4 shows that the partitions 49 are between the layers of longitudinal passages 46 and transverse outlet passages 48 and thus constitute filtering walls whose interior surfaces serve to collect the particles of the gases which pass from them. inlet passages to the outlet passages through these walls. When using this form of micro-stretched and pleated metal element for filtration, only about half of the inner walls are used as the filtering surface. The size of the filter element must therefore be about twice as large as that of the first embodiment described above, to give the same filtration area and an equivalent value of free passage section through the pierced walls.

When the element 45 is mounted in the envelope of the particle trap 37 of FIG. 3, the upper end of the inlet passages 46 (on the left in FIG. 4), which are now oriented vertically, is closed so that that the gaseous flow that leaves the passages must flow through the lower open ends to reach the exhaust pipe 44. The flow entering the inlet passages through 50 enters the two open ends of the trap when arriving from the row of cylinders on the left by the exhaust pipe 38 and the row of cylinders on the right by the exhaust pipe 39. The gas enters via the two ends into the inlet passages 46, obliquely (or transversely) to through the central passage closed at the lower end, and is filtered through the partitions 49, to pass through the exhaust passages 48 and escape through the lower open ends to the exhaust pipe 44.

Of course, one could also possibly use other arrangements for inserting the filter element described in a particle trap and, moreover, one could use another arrangement of the filter elements in the particle parts without going beyond the scope of the invention.

With the exception of the passage arrangement variants in the micro-stretched metal filter elements, for example the variant shown in FIGS. 3 and 4, it is also obvious that one can use passages having different configurations in the different general types elements. For example, Figs. 5a to 5k, 5m, 5n and 5p illustrate a number of configurations of the passages used in monolithic micro-stretched metal filters of the general type shown in Fig.2, i.e. monolithic elements which exhibit parallel passages partially closed alternately at one end and the other.

Fig. 5a, for example is a schematic sectional view of a portion of an element similar to that of Fig.2, wherein the walls are arranged in staggered rows. The input passages are shaded to indicate that they are closed at their output end while the output passages are clear to show that they are open at their output end. This view clearly shows the advantage of this arrangement, which is that all the inner walls are interposed between inlet passages and outlet passages, except at their points of contact with other walls, at the corners of the passages. square section. In this way, with this arrangement with parallel walls, a proportion of nearly 100% of the surface of the walls consists of a filtering surface.

Similar results are obtained in all the other embodiments shown in FIGS. 5b at 5k, 5m, 5n and 5p; however, some differences are apparent. Figs. 5b to 5e are similar to FIG. 5a in that the inlet and outlet passages which are parallel and adjacent are of equivalent section and are delimited by flat walls which intersect. The passages of FIG. 5b are of rectangular section while those of FIGS. 5c, 5d and 5e have different triangular shapes. Fig. 5f shows diamond shaped passages.

All the arrangements which have been described so far have in common the advantage that the entire surface of the inner walls forms an effective filtering surface between the inlet passages and the outlet passages, the inlet passages and the outlet passages being all of the same sectional area. However, it is obvious that since in operation the accumulation of cake-forming particles on the wall surfaces of the inlet passages results in ultimately reducing the effective flow section of these passages, it is possible to have advantage to making arrangements in which the sections of the inlet passages are larger than those of the adjacent outlet passages. The arrangements which will be described hereinafter include this improvement while retaining the advantage that all the inner walls are interposed between inlet passages and outlet passages except at their points of mutual contact and that, therefore, In fact, the entire surface of the inner walls forms an effective filtering surface.

This improvement is illustrated first by Figs. 5h, 5i and 5j in which planar inner walls are arranged to form different polygonal patterns. In FIG. At 5 o'clock, the entry passages are defined by sections presented as equilateral hexagons that border exit passages having sections that are equilateral triangles. In Figs. 5i and 5j, the drawings are different, with different configurations of non-equilateral hexagonal entry entrances adjacent to corresponding triangular section exit passages.

Each of the arrangements shown in Figs. 5h, 5i, 5j, 5k, 5m, 5n and 5p and which has been described as having sections of inlet passages larger than the corresponding sections of the outlet passages still retains the advantage that the surface of the straps The inner side is almost entirely effective for filtering since all these arrangements retain the fundamental advantage that the walls separate the inlet passages from the outlet passages except at their points of contact. However, it goes without saying that arrangements of polygonal or other cross sectional passages do not all have the advantage mentioned above. For example, it is possible to form a pattern of hexagonal section parallel passages which, when arranged in alternating inlet passages with exit passages, have substantial portions of wall sections that are not in contact with each other. which separate two inlet passages or two output passages. This lanyard surface is not effective for filtering. This would also be the case with many other reasons that could be proposed and suitable for the implementation of the catalysts. Nevertheless, the reasons described above should not be considered that as representative of those who provide the desired benefits and their enumeration does not exclude that there are other grounds falling within the scope of the invention.

In other words, certain mesh shapes may be suitable for oxidation catalysis and not for particle filtration.

For example, it will be possible, for example, to produce a treatment device with two filter blocks, with reinforced walls, one for the oxidation catalyst (CO and HC), the other for the particles.

A treatment device according to the invention may also be associated with an electrostatic precipitator, of the type described in European patent EP 1 212 141, for example by placing an oxidation catalyst filter behind one another. a spiked electrofilter (arranged vertically or horizontally with respect to the gas flow, see patent mentioned above) and a particulate filter as described above. It can also be associated with a NOx trap, for example a selective catalytic reduction device (SCR), with which is injected for example urea, preferably through the edge of the filter element.

Claims

18 Claims

1. Device for treating a particle-laden gaseous medium, comprising at least one filtering element (22) for trapping the particles of the gaseous medium, characterized in that each filtering element comprises a plurality of thin unstretched metal thin walls, arranged adjacent to each other so as to form a monolithic partitioning structure formed of these perforated walls, so as to form obstacles to the passage of the gaseous medium loaded with particles, in order to retain them inside the structure.

2. Device according to claim 1, characterized in that the plates are arranged parallel to one another, vertically or horizontally.

3. Device according to claim 2, characterized in that the plates are offset relative to each other, transversely to the direction of parallel alignment, preferably arranged staggered.

4. Device according to claim 1, characterized in that the filter element comprises a pleated structure of non-flattened drawn metal, forming said thin walls, preferably star or accordion.

5. Device according to the preceding claim, characterized in that the star-pleated structure extends around a central passage, open at an inlet end of the gaseous medium, to which the pleated structure is closed, while the opposite end of the passage is closed and that of the pleated structure open for the gas outlet of the purified gaseous medium.

6. Device according to any one of the preceding claims, characterized in that the stretched metal is micro-stretched metal.

7. Device according to any one of the preceding claims, characterized in that the average opening dimension of the drawn metal is between 200 microns and 2000 microns.

8. Device according to any one of the preceding claims, characterized in that the meshes of the drawn metal are diamond-shaped, square, triangle, rectangle, hexagon or round. 19

9. Device according to any one of the preceding claims, characterized in that each thin stretched metal wall has perforations forming baffles protruding relief.

10. Device according to any one of the preceding claims, characterized in that the walls are mounted in a clamping frame.

1 1. Device according to any one of the preceding claims, characterized in that it comprises two filter elements arranged one behind the other and separated by a free transition space forming an expansion chamber for the gaseous medium.

12. Device according to any one of the preceding claims, characterized in that it comprises means for thermal or catalytic regeneration of the filter element.

13. Device according to claim 12, characterized in that it comprises an electrical resistance adapted to raise the temperature of the gaseous medium and to burn the particles accumulated on the thin walls of the filter element.

14. Device according to the preceding claim, characterized in that the thin walls have perforations dimensioned so as to generate a back pressure, these walls being further impregnated with a catalyst based on precious metals.

15. Device according to any one of claims 1 to 13, characterized in that the thin walls have perforations dimensioned so as to avoid back pressure and which are impregnated with a catalyst based on precious metals, so that the element The filter also acts as an oxidation catalyst.

16. Device according to any one of claims 14 or 15, characterized in that the precious metals include platinum, palladium and rhodium.

17. Device according to any one of the preceding claims, characterized in that it comprises at least one longitudinal housing housing or filter elements. 20

18. Device according to any one of the preceding claims, characterized in that it comprises, successively from the inlet to the outlet of the treatment device, an oxidation catalyst, an electrostatic precipitator, preferably with points, and an element filter according to any one of claims 1 to 14.

19. Device according to the preceding claim, characterized in that the oxidation catalyst is as defined in claim 15 or 16.

20. Device according to any one of the preceding claims, characterized in that it further comprises an electrostatic precipitator and / or a device for selective catalytic reduction of NOx.

21. Use of a treatment device according to any one of the preceding claims, for the treatment of the exhaust gas of an internal combustion engine, in particular a diesel engine.