Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/247—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the cells
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2474—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the walls along the length of the honeycomb
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2478—Structures comprising honeycomb segments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2482—Thickness, height, width, length or diameter
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2484—Cell density, area or aspect ratio
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2486—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure characterised by the shapes or configurations
  • B01D46/2488—Triangular
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2486—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure characterised by the shapes or configurations
  • B01D46/249—Quadrangular e.g. square or diamond
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2486—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure characterised by the shapes or configurations
  • B01D46/2492—Hexagonal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2486—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure characterised by the shapes or configurations
  • B01D46/2494—Octagonal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2418—Honeycomb filters
  • B01D46/2498—The honeycomb filter being defined by mathematical relationships
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
  • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
  • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2279/00—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses
  • B01D2279/30—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses for treatment of exhaust gases from IC Engines
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the invention relates to the field of filter structures possibly comprising a catalytic component, for example used in an exhaust line of a diesel type internal combustion engine.
• Filters for the treatment of gases and the removal of soot typically from a diesel engine are well known in the prior art.
• These structures all most often have a honeycomb structure, one of the faces of the structure allowing the admission of the exhaust gas to be treated and the other side the evacuation of the treated exhaust gas.
• the structure comprises, between the intake and discharge faces, a set of adjacent ducts or channels, most often of square section, axes parallel to each other separated by porous walls.
• the ducts are closed at one or the other of their ends to delimit inlet chambers opening on the inlet face and outlet chambers opening along the discharge face.
• the channels are alternately closed in an order such that the exhaust gases, during the crossing of the honeycomb body, are forced to pass through the sidewalls of the inlet channels to join the outlet channels. In this way, the particles or soot are deposited and accumulate on the porous walls of the filter body.
• porous ceramic filters for example cordierite, alumina, in particular aluminum titanate, mullite silicon nitride, are used for the filtration of gases.
• silicon / silicon carbide or silicon carbide mixture are used for the filtration of gases.
• the particulate filter is subjected to a succession of filtration phases (accumulation of soot) and regeneration
• soot particles emitted by the engine are retained and are deposited inside the filter.
• soot particles are burned inside the filter, in order to restore its filtration properties.
• the porous structure is then subjected to intense radial and tangential thermomechanical stresses, which can lead to micro-cracking likely over time to cause a severe loss of filtration capacity of the unit, or even its complete deactivation. This phenomenon is particularly observed on monolithic filters of large diameter.
• the assembled filters currently marketed for light vehicles typically comprise approximately 10 to 20 unit elements having, in a cross section, a square or rectangular section and whose surface elemental section is between about 13 cm 2 and about 25 cm 2 . These elements consist of a plurality of channels of usually square section.
• an obvious solution could be to reduce the number of unit elements in the assembly by increasing their individual size. Such an increase, however, is not currently possible, particularly with SiC filters, without unacceptably reducing the thermomechanical strength of the filter.
• the larger section filters are made by assembling with a grouting cement of elements of a size similar to those constituting the filters intended for light vehicles.
• the number of unit elements of truck filter type is then very high and can have up to 30 or even 80 elements.
• Such filters then have an overall mass and a loss of charge that is too high.
• the object of the present invention is a filter or a filter element having all at once:
• a low pressure loss caused by the filtering structure in operation that is to say typically when it is in an exhaust line of an internal combustion engine, both when said structure is free of particles of soot (initial pressure drop) than when it is loaded with particles, - an increase in the pressure drop of the filter during said reasonable operation, ie an increase in the pressure drop measured as a function of time of use or, more exactly, depending on the level of soot loading of the filter, - a high specific filtration area, a mass of the monolithic element adapted to ensure a thermal mass sufficient to minimize the maximum regeneration temperature and the gradients caused by the filter, which can themselves cause cracks on the element,
• thermomechanical resistance that is to say allowing a prolonged life of the filter
• EP 1495791 discloses structures whose input channels have a generally octagonal cross-sectional cross-section, the outlet channels being of square section.
• the tests carried out by the applicant have shown that such structures present a substantially deteriorated compromise between the thermomechanical resistance and the pressure drop generated by such a filter on the exhaust line.
• the present invention relates to a filtration structure of particles-loaded gases of the honeycomb type and comprising a set of longitudinal adjacent channels of mutually parallel axes separated by porous filtering walls.
• said channels being alternately plugged at one or other end of the structure so as to define inlet channels and outlet channels for the gas to be filtered, and to force said gas to pass through the walls porous separating the inlet and outlet channels,
• said structure being characterized in that: the inlet and outlet channels share with each other at least one wall of constant average thickness over the entire length of the filtration structure, the inlet or outlet channels share with each other at least one wall of constant average thickness over the entire length of the filtration structure, the ratio e / d is strictly greater than ur to 1.
• each outlet channel consists of at least three walls of substantially identical width, so as to form a channel whose section has a substantially regular shape
• each output channel has a common wall with several input channels, each common wall constituting one side of said output channel, at least two input channels share a common wall of width b and of average thickness e.
• the input and output channels are hexagonal.
• the input channels are triangular and the output channels are hexagonal.
• the input channels are octagonal and the output channels are square.
• the channels have, in a cross section, a general shape that can be respectively in a polygon with 3, 4, 6 or 8 sides.
• the ratio of the thicknesses e / d is greater than 1 and less than or equal to 10, preferably greater than or equal to 1.05 and less than or equal to 4, and very preferably greater than or equal to 1.1 and less than or equal to 2 and even more preferably greater than or equal to 1.1 and less than or equal to 1.5.
• the walls constituting the input and output channels are planar.
• the walls constituting the inlet and / or outlet channels are corrugated, that is to say that they have, in cross-section and with respect to the center of a channel, at least one concavity or a convexity.
• the output channels have walls convex relative to the center of said output channels.
• the output channels may have concave walls with respect to the center of said output channels.
• the maximum distance, in a cross-section, between an end point of the concave or convex wall or walls and the line segment connecting the two ends of said wall, is typically greater than 0 and less than 0.5 a.
• the thickness d is constant over the entire width at common walls between the inlet and outlet channels and / or the thickness e is constant over the entire width b of the common walls between the inlet channels.
• These thicknesses d or / and e may also have, in cross-section, a variable thickness, it being understood that the ratio of the average thicknesses d and e remains strictly greater than 1. More precisely, it is possible, without departing from the scope of the According to the invention, the ratio e / d is not always greater than 1 in the entire volume of the filter, provided that said ratio e / d remains overall greater than 1 when it is integrated over the widths a and b of the corresponding walls.
• the channels preferably those of exit, may have rounded corners so as to further reduce the pressure drop and improve the mechanical and thermomechanical strength of the structure according to the invention.
• the density of channels is typically between about 1 and 280 cm 2 channels and preferably between 15 and 65 channels per cm 2 .
• the average wall thickness is typically between 100 and 1000 microns, and preferably between 100 and 700 microns.
• the width has output channels is between 0.05 and 4.00mm, and preferably between 0.10mm and 2.50mm, and very preferably between 0.20mm and 2.00mm.
• the width b of the inlet channels is between 0.05 and about 4 mm, and preferably between 0.10 mm and 2.50 mm, and very preferably between 0.20 mm and 2.00 mm.
• the walls are based on silicon carbide, and / or aluminum titanate and / or cordierite and / or mullite and / or silicon nitride and / or sintered metals.
• the invention relates in particular to an assembled filter comprising a plurality of filtering structures as previously described, said structures being bonded together by a cement, preferably of ceramic and refractory nature.
• the invention further relates to the use of a filter structure or an assembled filter as previously described as a device on an exhaust line of a Diesel engine or Gasoline preferably Diesel.
• Figures 1 to 5 illustrate 5 non-limiting embodiments of a filter structure having a configuration of the channels according to the invention.
• FIG. 1 is a front view in elevation of the front face of a filter according to a first embodiment according to the invention, comprising six-wall inlet and outlet channels and in which said walls are flat and of constant thickness.
• FIG. 2 is a front view in elevation of the front face of a filter according to a second embodiment according to the invention, comprising six-wall inlet and outlet channels and in which said walls are corrugated, the channels of outlet being made of convex walls relative to the center of an exit channel.
• Figure 2a illustrates a more detailed view of Figure 2.
• FIG. 3 is a front view in elevation of the front face of a filter according to a third embodiment according to the invention, comprising three-walled inlet channels and six-wall outlet channels and in which said walls are corrugated, the outlet channels being concave walls relative to the center of an outlet channel.
• Figure 3a illustrates a more detailed view of Figure 3.
• FIG. 4 is a front view in elevation of the front face of a filter according to a fourth embodiment in which the walls common to the input channels have a variable thickness, in particular a maximum thickness e2 and a minimum thickness e1.
• FIG. 5 is a front elevational view of the front face of a filter according to a fifth embodiment according to the invention, comprising four-walled output channels on the one hand and eight-walled input channels.
• FIG. 6 is a front view in elevation of the front face of a filter not according to the invention, in which, unlike the filter described in relation with FIG. 2, the thickness e of the walls common to the channels of FIG. The input is identical to the thickness of common walls between the input and output channels.
• FIG. 6a illustrates a more detailed view of FIG. 6.
• FIG. 1 shows an elevational view of the gas inlet face of a piece of the monolithic filtration unit 1.
• the present unit input channels 3 and output channels 2.
• the output channels are conventionally clogged on the gas inlet face by plugs.
• the filtering structure is characterized by the presence of an outlet channel 2 whose cross section has a hexagonal and regular shape, that is to say that the six sides of the hexagon are of one substantially identical length and that two adjacent sides form an angle close to 120 °.
• a regular outlet channel 2 thus formed by six walls of identical width arranged at 120 °, is in contact with 6 input channels 3 of a general shape also hexagonal but irregular, that is to say formed by adjacent walls of which at least two have a different width, in a cross section.
• two adjacent inlet channels 3 also have a common wall of width b.
• the thickness e of the walls 10 common to the input channels is greater than the thickness of the walls 5 common between the input and output channels. More particularly, the structures are characterized in that the ratio e / d is greater than 1 and preferably less than or equal to 10, or even less than or equal to 4.
• the distances a and b are defined according to the invention as the distances connecting the two vertices S1 and S2. of the wall considered, said vertices S1 and S2 are inscribed on the central core 6 of said wall (see Figure 1 and following). In this way we obtain values of a and of b independent of the thickness of the walls.
• FIG. 2 represents the arrangement of a set of outlet and inlet channels 2 of the gases in an elevational view of the inlet face of the gases to be purified in a honeycomb structure according to the invention whose walls are corrugated.
• the maximum distance c in a cross section, is defined as the distance between the end point 7 on the central core 6 of a corrugated wall and the right segment. 8 connecting the two ends Sl and S2 of the wall.
• the thickness e of the walls common to the input channels is greater than the thickness of common walls between the input and output channels.
• FIG. 3 is a front view in elevation of the front face of a filter according to a third embodiment according to the invention, comprising three-walled inlet channels and six-wall outlet channels and in which the walls of the input and output channels are wavy, the output channels being concave walls with respect to the center of an output channel.
• the thickness e of the walls common to the input channels is greater than the thickness of common walls between the input and output channels.
• Figure 3a illustrates a more detailed view of Figure 3.
• FIG. 4 is a front view in elevation of the front face of a filter according to a fourth embodiment according to an embodiment of the invention similar to that already described in relation to FIG. 2, but the walls common to the channels; input 3 present this variable thickness, in particular a maximum thickness e2 at the ends of said wall 10 and a minimum thickness el in the middle of said wall 10.
• the average thickness e m of said wall 10 is, however, greater than the average thickness. d of the wall 5, even if the thickness el, taken in the middle of the wall 10, is locally smaller than the thickness d, as represented in FIG.
• Figure 5 is a front elevational view of the front face of a filter according to a fifth embodiment of the invention, comprising four-walled output channels on the one hand and eight-walled input channels.
• the input 3 and output 2 channels have four common walls which delimit said output channels, the walls of the input and output channels being flat.
• the walls common to the inlet channels 10 form an angle close to 45 ° with the common walls 5 between the inlet and outlet channels.
• the thickness e of the walls common to the input channels is greater than the thickness of common walls 5 between the input and output channels.
• the green monoliths obtained are dried by microwave for a time sufficient to bring the water content not chemically bound to less than 1% by weight.
• the channels of each face of the monolith are alternately blocked according to well-known techniques, for example described in application WO 2004/065088.
• the monoliths are then baked under Argon according to a rise in temperature of 20 ° C / hour until reaching a maximum temperature of 2200 ° C. which is maintained for 6 hours.
• the porous material obtained has an open porosity of 47% and a median pore distribution diameter of about 15 microns.
• Table 1 The dimensional characteristics of the elements thus obtained are given in Table 1 below, the structure having a periodicity, that is to say a distance between two adjacent channels, equal to 2.02 mm.
• An assembled filter was then formed from the monoliths. Sixteen elements from the same mixture were assembled together according to conventional techniques by bonding using a cement of the following chemical composition: 72% by weight of SiC, 15% by weight of Al 2 O 3, 11% by weight of SiO 2 , the remainder consisting of impurities mainly Fe2O3 and alkali and alkaline earth metal oxides. The average thickness of the joint between two adjacent blocks is of the order of 1 to 2 mm. The assembly is then machined in order to form assembled filters of cylindrical shape of about 14.4 cm in diameter.
• pressure loss is meant within the meaning of the present invention the differential pressure existing between the upstream and downstream of the filter.
• the pressure drop was measured according to the techniques of the art, for a gas flow rate of 250 kg / h and a temperature of 250 ° C., on the new filters.
• thermomechanical resistance B- Measurement of the thermomechanical resistance
• the filters are mounted on an exhaust line of a direct injection diesel 2.0 L engine running at full power (4000 rpm) for 30 minutes and then disassembled and weighed to determine their initial mass.
• the filters are then reassembled on the engine bench with a speed of 3000 rpm and a torque of 50 Nm for different times to obtain a soot loads of 8 g / liter (by volume of the filter).
• the filters thus loaded are reassembled on the line to undergo a severe regeneration thus defined: after stabilization at an engine speed of 1700 revolutions / minute for a torque of 95 Nm for 2 minutes, a post-injection is performed with 70 ° phasing for a post-injection flow rate of 18mm 3 / stroke.
• the engine speed is lowered to 1050 revolutions / minute for a torque of 40 Nm for 5 minutes to accelerate the combustion of soot .
• the filter is then run at 4000 rpm for 30 minutes to remove the remaining soot.
• the regenerated filters are inspected after cutting to reveal the possible presence of cracks visible to the naked eye.
• the thermomechanical resistance of the filter is appreciated in view of the number of cracks, a small number of cracks reflecting a thermomechanical resistance acceptable for use as a particulate filter.
• the storage volume was determined according to the usual techniques well known in the art.
• the open front area is obtained by calculating the percentage ratio of the area covered by the sum of the cross sections of the input channels of the front face of the monolithic unitary elements (except the walls and plugs) on the total area of the corresponding cross section of said unitary elements.
• the amount of storage of residues is greater the higher the percentage.
• the WALL is the ratio, in cross-section and in percentage, between the area occupied by all the walls of a monolithic unitary element (except plugs) and the total area of said cross-section.
• the specific filtering surface of the filter corresponds to the internal surface of all the walls of the filter inlet channels expressed in m 2 , relative to the volume in m 3 of filter, integrating if necessary its external coating.
• the soot storage volume is all the higher as the specific surface thus defined is large.
• the loading slope is even lower than the specific filtration surface is large.
• results reported in Table 2 show that the filters according to Examples 3 and 6 according to the invention have the best compromise between the different properties sought in an application as a particulate filter in an automobile exhaust line. More particularly, the results show that the filters according to the invention have, for an identical WALL factor, a significantly lower pressure drop, while nevertheless maintaining a filtration surface and an OFA (representative of the soot storage volume) while acceptable.
• the results in Table 2 also show that the filters according to the invention have improved thermomechanical resistance compared to comparative filters having an identical internal wall thickness.
• the filter according to Example 6 additionally exhibits the lowest fresh state pressure drop at the same time as the highest filtration area of the examples provided.
• the results reported in Table 2 indicate that the filter structures obtained according to the invention have the best compromise, in particular between the two essential characteristics necessary for an application as a particulate filter in an exhaust line. that is to say the thermomechanical resistance and the pressure drop.
• Such an improvement results in greater potential lifetimes of the filters, in particular in an automotive application, where the residues resulting from the successive combustion of the soot, during the phases of regeneration, tend to accumulate until finally make the filter unusable.

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• Physics & Mathematics (AREA)
• Geometry (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Filtering Materials (AREA)
• Filtering Of Dispersed Particles In Gases (AREA)
• Exhaust Gas After Treatment (AREA)

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