EP1929134A1

EP1929134A1 - Device for eliminating harmful constituents from exhaust gases of internal combustion engines

Info

Publication number: EP1929134A1
Application number: EP06805300A
Authority: EP
Inventors: Bernhard Nibbrig
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-09-16
Filing date: 2006-09-15
Publication date: 2008-06-11
Also published as: JP2009508047A; US20090208393A1; WO2007031074A1; DE102005044494B3

Abstract

The invention relates to a device for eliminating harmful constituents from exhaust gases of internal combustion engines, having a first housing, wherein in the front region, a first structure comprising a plurality of interconnected cavities covers the cross section of the first housing at least in regions, which first structure is followed in the housing, in any order, by: at least one second structure which comprises a plurality of interconnected cavities and comprises at least one first metal oxide and/or is at least partially coated with said metal oxide, at least one third structure which comprises a plurality of interconnected cavities and comprises at least one catalyst for converting or decomposing pollutants and/or is at least partially coated with said catalyst, and at least one fourth structure which covers the cross section of the first housing at least in regions, comprises a plurality of interconnected cavities and comprises at least one second metal oxide, wherein the first housing is made of in particular porous aluminium oxide, mullite, cordierite, silicon nitride, tialite, steatite, zircon, zircon dioxide and/or silicon carbide, or is coated with aluminium oxide, mullite, cordierite, silicon nitride, tialite, steatite, zircon, zircon dioxide and/or silicon carbide.

Description

Lothar Wenzel

Steinebacher Street 41

57627 Hachenburg

Device for removing harmful components from exhaust gases of fueling machines

description

The present invention relates to a device for removing harmful components from exhaust gases of internal combustion engines, in particular of diesel engines.

The elimination of harmful components from exhaust gases from internal combustion engines has long been of great interest for obvious reasons. It is known that sulfur-containing residues, carbon monoxide, polycyclic aromatic compounds and soot particles can cause lasting damage to humans and the environment. Accordingly, a variety of new methods and devices have already been developed for reducing pollutants in exhaust gases. More recent efforts are in particular to exhaust gases from diesel engines even more complete and efficient of pollutants, such as soot particles, especially known is that soot organic residues, such as hydrocarbons, binds. There are a variety of methods available for this purpose.

For example, with the aid of exhaust gas recirculation, as described in DE 699 06 586 T2, the formation of nitrogen oxides (NOx) is reduced. In this case, exhaust gas is generally taken from the exhaust manifold via an exhaust gas recirculation valve and the charge air (fresh gas) mixed in, thereby lowering the combustion temperature and, in response thereto, reducing the proportion of NO x. Since the oxygen content in the exhaust gas also decreases, can not at optimum setting, the levels of carbon monoxide, unburned hydrocarbons and soot increase.

In SCR (Selective Catalytic Reduction) technology, nitrogen oxides are reduced to nitrogen on a suitable catalyst in the presence of ammonia. Ammonia is obtained in the catalyst system from urea, which is always carry in the form of an aqueous solution with the motor vehicle and metered in the required amounts. The aqueous urea solution is mixed, for example, in a manner known from WO 96/36797 A1 with compressed air in a mixing chamber and injected into the exhaust gas stream via an atomizer nozzle arranged in the exhaust gas stream. SCR catalysts are generally based on one element from the group Pt, Pd, Rh, Ir, Au, Ag and Ru. Details of the use of SCR catalysts can be found, inter alia, also in DE 197 49 607 C1, DE 103 48 799 A1 and DE 102 57 113 A1.

In general, in exhaust systems of diesel engines, the temperature is not so high that filtered soot particles, even when present on a suitable catalyst surface, are burned immediately. In order to avoid clogging of the filter and to reduce soot levels in the exhaust gases, the accumulated soot particles have to be periodically burned. The temperature required for burning soot with the oxygen from the exhaust gas is approximately 500 to 600 ^° C. A temporary increase in temperature can be achieved by injecting an additive, for example a cerium additive, as described in DE 100 20 170 C1 described be performed. Although the soot content can be markedly lowered in this way, additive residues in the filter system still remain to a not inconsiderable extent. Such a discontinuous regeneration can also be effected by connecting an oxidation catalyst to which unsaturated or unburned hydrocarbons are fed, ie by post-injection (see also DE 103 21 105 A1). Instead of increasing the temperature periodically by adding additives or fuels to the combustion temperature of soot in the short term, DE 101 03 771 A1 proposes collecting soot particles and hydrocarbons on the surface of an oxidation catalyst, so that an increase in temperature to 450 ^° C. would suffice. to eliminate the mentioned residues. This temperature can be brought about by external heating according to DE 101 03 771 Al. DE 197 48 561 A1 discloses for this purpose an electric heating element. The continuous regeneration of particle filters can be carried out according to the so-called CRT method (continuous regeneration trap), as described in DE 199 55 324 A1 and DE 103 21 105 A1. Thereafter, the particle filter in the exhaust pipe upstream of an oxidation catalyst which oxidizes the nitrogen oxide NO contained in the exhaust gas to nitrogen dioxide, which is then used for the oxidation of carbon monoxide or carbon black. Naturally, with this technology it is difficult to keep the proportion of NOx in the excreted exhaust gases low.

Suitable soot particle filters are regularly produced according to DE 103 48 799 A1 from a high-temperature oxide ceramic or silicon carbide.

As described above, not least because of the very complex interactions between the components to be removed, the problem of exhaust gas purification has not yet been satisfactorily resolved. On the one hand pollutants such as carbon monoxide, hydrocarbons and soot are rendered harmless by oxidation. On the other hand, nitrogen oxides can only be eliminated by means of reduction. In addition, if you burn soot at its conventional combustion temperature of about 500 to 600 ° C, the materials used for exhaust systems can be irreparably damaged.

The present invention therefore an object of the invention to provide a device for the removal of pollutants from internal combustion engines, which is not subject to the disadvantages of the prior art and in particular the continuous combustion of filtered soot particles allows, without, for example, the continuous or periodic addition of additives or fuel needs.

Accordingly, a device for eliminating harmful components, in particular soot, from exhaust gases of internal combustion engines, in particular of diesel engines, found comprising a first housing, suitable for passing exhaust gases, with at least one inlet and at least one outlet and containing a front, middle and at least one inlet, in particular in the front region, and at least one outlet, in particular in the rear region, is present, wherein in the front region at least a first structure containing a plurality of contiguous cavities at least partially, in particular completely completeness, the cross section of the first housing - dig, covering what is arranged in the housing in any order, in particular one after the other, follow: at least one second, the cross-section of the first housing at least partially, in particular completely, covering structure containing a plurality of contiguous cavities containing at least a first metal oxide and / or at least partially coated therewith, at least one third, the cross-section of the first housing at least partially, in particular completely, covering structure containing a plurality of contiguous cavities, the at least one catalyst for the reaction or decomposition of pollutants, in particular a Oxidationskata - Lysator, contains and / or at least partially coated therewith, and at least a fourth, the cross section of the first housing at least partially, in particular completely, covering structure containing a plurality of contiguous cavities, ie e contains at least a second metal oxide and / or at least partially coated therewith, wherein the first housing at least partially and / or the inner wall of the housing at least partially made of, in particular porous, alumina, mullite, Cordie- rit, silicon nitride, tialite, steatite, Zirconium, zirconium dioxide and / or silicon carbide or is coated with, in particular porous, alumina, mullite, cordierite, silicon nitride, tialite, steatite, zirconium, zirconium dioxide and / or silicon carbide.

Preferably, at least a first, at least one second, at least one third and at least one fourth structure are present in the first housing in the direction from the inlet to the outlet, in this order.

The first housing of the device according to the invention is preferably a silicon carbide housing or coated on the inner wall with silicon carbide. Although it is already sufficient if the inner wall of the first housing is coated to more than 50% with silicon carbide, but preferably such housing are used, the inner wall is completely or almost completely coated with silicon carbide. To protect against damage, the first housing may also have an outer sheath made of metal. This metal outer sheath is preferably made of, in particular coated, zinc sheet or steel, in particular Cr / Ni steel.

Silicon carbide in the context of the present invention should in particular also comprise carbon fiber-reinforced silicon carbide (C / SiC). Carbon fiber reinforced silicon carbide It has extremely good thermal conductivity and is characterized by high thermal shock resistance. Also, density and porosity can be adjusted according to needs during manufacture. Details relating to this can be found, for example, in DE 198 58 197 A1.

The silicon carbide used according to the invention preferably also comprises such silicon carbide, the additions of inorganic binders, in particular clay, zirconium zirconate, zirconium dioxide and / or alumina, and / or organic binders, in particular in the form of an additive to carbon black, which are added to the manufacturing process can, contains.

Suitable Siliziumcarbidformkörper can be obtained for example from a Schlickervorstufe. This may be e.g. to act an aqueous dispersion, in addition to silicon carbide, preferably ground, additives to organic binders such as carbon black, inorganic binders such as clay and optionally containing surfactants. Suitable clay binders include e.g. Kaolinite, halloysite, serpentine, muscovite, mit, talc, vermiculite, montmorillonite, beidelite, smectite, saponite and hectorite. Alternatively or in addition to carbon black, various synthetic or semisynthetic polymers are also suitable as organic binders, such as polyvinyl alcohol, polyvinyl butyrate, cellulose or cellulose derivatives and, in particular, starch products as described in DE 44 00 131 A1. The silicon carbide molding can here u.a. via slip casting, film casting, die casting or extrusion. For example, the aqueous slip dispersion is poured into a plaster mold from which, after the dispersion water has been taken up by the plaster mold, the Siliziumcarbidrohmasse is removed and fed to a sintering process. At the temperatures of the sintering process, the organic or inorganic binders within the Siliziumcarbidformkörpers often form a substantially contiguous, the moldings again reinforcing structure.

The coating material of the first housing or the housing material is preferably substantially equipped with open pores. The housing or inner coating, in particular containing porous silicon carbide helps to prevent deposits. Further, a housing wall configured in this manner contributes to the observed beneficial flow characteristics. Help in the construction of the devices according to the invention is further that the first housing described above, in particular those containing silicon carbide, show little or no thermal expansion and are therefore extremely dimensionally stable.

For the present in the front region of the housing first structure is preferably used materials and moldings, as they are known from the Porenbreimertechnik. These are mostly structures with spatially contiguous cavities over which a defined flame zone can form. In addition, these pore burner structures can be used to precisely set the desired flow profile over a wide range. Embodiments of such known pore burners can be found e.g. in US 5,522,723, WO 95/01532, DE 199 39 951 A1 and DE 199 04 921 C2. Suitable porous pore-burning materials may also be obtained from loosely-laid, granular bulk material which has been subjected to a sintering process. By way of example, reference should be made to EP 0 840 061 A1 and DE 2 211 297 OS. In this context, also sintered metal powder comes into question. Furthermore, metal wire knits are also suitable, as are foam ceramics, metal foams or sponges, such as e.g. in DE 10 2004 006 824 Al and DE 198 04 267 Al discloses. Furthermore, the porous material of the first structure may be based on an alumina or silicon carbide ceramic as described in DE 102 28 411 C1.

In a preferred embodiment, the first structure comprises a metal wire mesh, an open-cell foam ceramic, in particular based on silicon carbide, or in particular an open-cell metal foam, which preferably has a so-called washcoat coating comprising, in particular, oxides of aluminum, titanium, zirconium, iron, nickel, Germanium, barium, hafnium and / or oxides of rare earth metals such as lanthanum oxide and cerium oxide. Titanium dioxide and aluminum oxides and mixtures thereof are particularly preferred as coating materials. Alternatively or additionally, a coating with phosphoric acid can be carried out. The voids or pores in the first structure generally have a size sufficient to allow particulate exhaust gas constituents such as soot particles to enter the first housing. The porosity is, for example, in the range of 5 to 35, in particular 10 to 25 ppi (pores per inch). In one embodiment, the porosity of the first structure is about 20 ppi. By attaching the first structure, as described above, in the front region of the housing, ie following the inlet, it is ensured that the incoming exhaust gas flows through the inventive exhaust gas purification device laminar. The cleaning result impairing cross flows are completely prevented from the outset. Also for this reason, there is also no deposition of soot particles or other pollutants on the inner wall of the housing or on the first structure as such.

The second structure is preferably based on an open-cell foam ceramic, a wire mesh or in particular an open-cell metal foam. It expediently also covers the entire cross section of the first housing and accordingly extends to the inner wall. Incorporated into this second structure, for example in the form of a coating, is at least one first metal oxide, optionally in combination with a platinum group metal such as Pt, Rh, Pd, Ir, Os and Ru. Suitable first metal oxides include lithium oxide, barium oxide, titanium oxide, cerium oxide, manganese oxide, zirconium oxide, magnesium oxide, lithium, sodium, potassium, silver and cervanadates, vanadium oxide / alkali metal oxide combinations and perrhenates. Cerium / zirconium mixed oxides are also suitable. It has proved to be particularly advantageous that the second structure contains at least one vanadate, in particular silver and / or potassium vanadate, and / or is coated with at least one vanadate, in particular silver and / or potassium vanadate. Potassium vanadate is particularly preferred. It has been found that even this second structure significantly contributes to the elimination of soot.

According to a further preferred embodiment, the coating of the second structure comprises in addition to a first metal oxide, in particular potassium vanadate, a metal nitrate, for example an alkali or alkaline earth nitrate such as sodium, lithium, potassium, barium, calcium, magnesium and strontium nitrate, and / or a compound based on a waterglass compound such as sodium and potassium silicates, in particular soda waterglass. Particularly preferably, the proportion of the coating, based on the total weight of the second structure, in the range of 0.01 to 10 wt .-%, preferably in the range of 0.1 to 5 wt .-%.

The porosity of the second structure is preferably in the range of 5 to 40 ppi, preferably 10 to 35 ppi. Suitable porosities are for example also in the range of 10 to 20 ppi. In one embodiment, the porosity of the second structure is about 20 ppi.

It has proved to be particularly advantageous if at least two, in particular successive, optionally separated by a gap, coated second structures are present in the first housing, in particular in the central region of this housing.

The third structure is preferably also in the form of an open-cell foam ceramic, in particular made of silicon carbide, a wire mesh and in particular an open-cell metal foam, which extends over the entire cross-sectional area of the first housing. This structure has a catalyst which promotes the oxidation of components of the passed exhaust gas by means of the oxygen still contained in the exhaust gas. A particularly good cleaning effect is also achieved in that the third structure comprises a catalyst comprising palladium, rhodium and / or silver, and / or coated with a catalyst comprising palladium, rhodium and / or silver. If the catalyst additionally contains at least slight traces of iron, nickel, iron oxide, in particular Fe ₂ O ₃ and Fe ₃ O ₄ , the cleaning result can be optimized once more. Iron oxides are particularly suitable as an additive. Residues of carbon monoxide, hydrocarbons or other oxidizable harmful components are completely or almost completely eliminated from the exhaust gas of the internal combustion engine. According to a further embodiment, the coating or the catalyst of the third structure further contains at least one metal nitrate, for example an alkali or alkaline earth nitrate such as potassium nitrate, and / or a compound based on a water glass compound such as sodium or potassium silicates, in particular sodium water glass. Like the first structure, the third structure is preferably pre-coated with a washcoat. Suitable washcoat coatings comprise, in particular, oxides of aluminum, titanium, zirconium, hafnium, oxides of alkali metals and alkaline earth metals such as barium oxide or magnesium oxide and / or oxides of lanthanides or rare earth metals such as lanthanum oxide, praseodymium oxide, terbium oxide, ytterbium oxide, samarium oxide, gadolinium oxide or cerium oxide. Titanium dioxide or aluminum oxides are particularly preferred as coating materials. Alternatively or additionally, a coating with phosphoric acid can be carried out.

The open-cell third structure preferably has cell widths of 6 to 50 ppi, especially 20 to 45 ppi. Suitable porosities are for example also in the range of 20 to 40 ppi. In one embodiment, the porosity of the third structure is about 40 ppi.

If, for example, soot particles or hydrocarbons which have not yet been burned or oxidized when passing the exhaust gas through the first housing to the third structure, are converted to carbon dioxide at the latest at a fourth structure, preferably separated by a gap from the third structure. The fourth structure preferably represents a metal wire mesh, an open-celled foam ceramic, in particular silicon carbide-based, or in particular an open-cell metal foam, and preferably, like the first, second and third structures, covers the entire cross section of the first housing, but is different from the first one , Second and third structure, preferably not in the front or middle area, but housed in the rear of the first housing. The fourth structure comprises or is coated with at least one second metal oxide, such as tungsten oxide, silicon oxide, titanium dioxide, boron oxide, aluminum oxide, zirconium oxide, in particular lanthanum-containing, barium oxide, magnesium / aluminum mixed oxide and / or silicon / aluminum mixed oxide. Alumina is particularly preferred as the second metal oxide. In a particularly preferred embodiment, in addition to the second metal oxide, in particular aluminum oxide, at least one rare earth metal oxide such as yttrium oxide, praseodymium oxide, terbium oxide, gadolinium oxide, lanthanum oxide, samarium oxide, ytterbium oxide or cerium oxide is present. Cerium oxide is particularly preferred. In addition to cerium oxide as the preferred rare earth metal oxide, preference may alternatively or additionally be given to lanthanum oxide. In a further preferred embodiment, zeolites are present in or on the fourth structure in addition to the second metal oxide, in particular aluminum oxide, especially in combination with at least one rare earth metal oxide, in particular cerium oxide. With the device according to the invention it is readily possible to maintain a temperature in the range of 300 to 450 ° C between the third and fourth structure. These temperatures are completely sufficient under the circumstances of the device according to the invention for the degradation of soot and / or hydrocarbons in the fourth structure.

The porosity of the fourth structure may be, for example, in the range of 10 to 65, especially 15 to 60 ppi. In one embodiment, the porosity of the fourth structure is about 50 ppi.

In a further embodiment of the device according to the invention, at least one further, fifth structure, comprising a plurality of contiguous cavities, is present in the first housing, which covers the cross section of this housing at least in areas, in particular completely. The main body of this fifth structure is preferably constructed as the first to fourth structures and is in particular in the form of an open-cell foam ceramic, a metal wire mesh or in particular an open-cell metal foam. This fifth structure contains and / or is at least partially coated with platinum and / or rhodium as a catalyst. This coating can also contain, for example, in the form of a precoat as washcoat, titanium dioxide, zirconium oxide, silicon dioxide, aluminum oxide and / or aluminum silicate. In the present case, the use of a catalyst mixture comprising platinum and rhodium as the relevant components has proven to be particularly effective. Here are very satisfactory results in particular when the weight ratio of platinum to rhodium in the range of 10: 1 to 1:10, in particular in the range of 6: 1 to 1.5: 1 and more preferably in the ratio of about 4: 1 is set. The fifth structure is preferably mounted between the first and second structures. Conveniently, the fifth structure directly follows the first structure, i. without allowing a gap.

In a further embodiment of the device according to the invention, at least one further, sixth structure, comprising a plurality of contiguous cavities, is provided in the first housing, which at least partially covers the cross-section of this housing, in particular special completely covers. The sixth structure preferably represents a metal wire trick as well as in particular a metal foam. Alternatively, this structure may for example also be based on a ceramic foam or other known support materials or structures. The sixth structure contains a so-called SCR catalyst and / or is at least partially coated therewith. SCR catalysts for the reduction of nitrogen oxides in the exhaust gas to nitrogen with ammonia as a reducing agent, which is generally produced in the system from urea in solution, are well known to those skilled in the art. These are, for example, platinum, vanadium oxide, iron oxide, copper oxide, manganese oxide, chromium oxide or molybdenum oxide, preferably applied to a support such as, for example, aluminum oxide or titanium oxide. As an example, reference may be made to DE 102 57 113 A1, EP 0 376 025 B1, EP 0 385 164 B1 and EP 1 321 641 B1. The sixth structure may be present in one embodiment together with the fourth structure as a common, unitary structure.

As far as the first to sixth structures are to be coated, be it with an intermediate coating, e.g. In the form of a washcoat, or with a final coating, it is basically possible to resort to all conventional coating methods such as galvanic or wet-chemical coating or sputtering. Preferably, the wet chemical variant is used. As a rule, this is sufficient, for example. when the respective structure is immersed once, preferably at least twice, in a corresponding immersion bath containing the coating components in solution, dispersion or suspension.

The first to sixth, in particular the second to sixth, structure are generally so-called wall-flow filters. Such wall-flow filters are usually equipped with a porous, open-cell filter wall. The particles remain in these filter structures mainly due to adhesion phenomena mainly adhere to the surface of the filter wall or by means of depth filtration in the interior of the filter wall.

According to the invention may accordingly be provided that the first, second, third, fourth, fifth and / or sixth structure open-cell foam ceramic, a porous metal foam, an open-cell metal sponge, a heat-resistant porous or cellular foam plastic, a wire mesh and / or sintered includes bulk material. The first to sixth structures are regularly designed such that a gaseous fluid can readily pass through the contiguous cavities or open pores. Preferably, the first, second, third, fourth, fifth and / or sixth structure completely cover the cross section of the housing. These structures are accordingly enclosed in the housing interior and are in a practicable embodiment in direct contact with the inner wall of the housing. These structures are also designed in such a way that a uniform passage of gases is ensured.

According to a further embodiment, the first, second and third and optionally the fifth and / or sixth structure can be realized on a uniform permeable or porous body, for example a metal wire mesh, a foamed ceramic or in particular a metal foam. The individual structures then form e.g. discrete zone sections on such a unitary body. In an alternative embodiment, the first, second, third and fourth and optionally the fifth and / or sixth structure on a uniform permeable or porous body, such as a metal wire mesh, a foam ceramic or in particular a metal foam can be realized, for example as stated above. For example, this uniform structure may be incorporated, in particular, in register with the first housing, wherein free spaces may be provided in particular in the inlet and outlet areas. In particular, this uniform structure may also have at least one free or hollow space between the third and fourth structures. With regard to the arrangement of the first to sixth structures within the first housing, the details of the separate structures can be applied accordingly.

Open cell ceramics include cordierite, silicate, alumina, aluminum nitride, aluminum titanate, glass, zirconia, silicon carbide, and silicon nitride ceramics. Suitable open-cell foam ceramics include in particular those of zirconium oxide, silicon carbide, silicon nitride, aluminum nitride, mullite (magnesium aluminum silicate) and α-aluminum oxide. These ceramics and their preparation are known in the art. The same applies to metal foams and sponges. Suitable metal foams are preferably formed from chromium / nickel steels or ferro-chromium / aluminum alloys. Nitride-based metal foams are generally less suitable.

As a wire material for the wire body is used in particular alumium-containing steel.

Optionally, the first structure, preferably if present as a metal wire mesh or as a metal foam, previously coated with a solder material, preferably on aluminum-chromium, in particular aluminum-chromium-nickel base.

It is of particular advantage in terms of flow technology if the front region of the first housing widens toward the middle region and / or if the rear region tapers toward the outlet, in particular in the form of a cone. In this context, it is also important in an optimized embodiment that the surface of the first structure, which faces the inlet, is curved in the direction of the interior of the first housing, in particular substantially spherical.

According to one embodiment of the device according to the invention, the first, second, third and fourth structures can each follow one another directly. Alternatively it can be provided that between the first and second structure, a first space, between adjacent second structures, a second space, between the second and third structure, a third space between adjacent third structures, a fourth space and / or between the third and fourth structure there is a fifth gap. The spaces between the individual structures serve primarily as expansion or swirling spaces. In this context, it has been found that particularly satisfactory results set when there is a fifth gap. This fifth gap is in particular at least partially disposed in the tapered portion of the first housing, ie in the transition from the middle to the rear of the first housing. It can be provided that the fifth structure is mounted between the first and the second structure, in particular directly follows the first structure. According to one embodiment, there may be a gap between the first structure and the fifth structure and / or between the second structure and the fifth structure, for example over the entire cross-section of the device. Alternatively, the first and fifth structures may also be in the form of a unitary body, ie without gap, or be arranged as separate structures without gaps.

Further, the invention provides that the sixth structure is arranged in the direction from the inlet to the outlet before and / or after the fourth structure.

According to the invention, it is also possible, inter alia, for there to be no gap between the fourth and sixth structures, in particular the fourth and the sixth structure to form a uniform structure.

A further advantage is that at least between two adjacent, in particular between all adjacent structures, there is a gap, in particular over the entire cross-sectional area of adjacent structures.

Furthermore, according to a further embodiment it can be provided that the average distance between adjacent structures, measured along the longitudinal axis in the direction from the inlet to the outlet, in the range of 5 mm to 50 mm, in particular in the range of 10 mm to 40 mm.

According to a further embodiment of the invention, the average width of the first and / or second and / or third and / or fourth and / or fifth and / or sixth structure in the range of 5 mm to 50 mm, in particular from 10 mm to 40 mm, measured along the longitudinal axis in the direction from the inlet to the outlet.

Devices of the invention are also distinguished in an advantageous embodiment in that the distance from the inlet to the first structure in the range of 20 mm to 100 mm, in particular from 30 mm to 80 mm, and / or that the distance from the outlet (12) nearest structure to the outlet in the range of 20 mm to 120 mm, in particular from 30 mm to 90 mm ,

According to another exemplary embodiment of the device according to the invention for removing harmful components from exhaust gases of Brennlcraftmaschinen the average width of the first and / or second and / or third and / or fourth and / or fifth and / or sixth structure is about 25 mm to 35 mm , preferably about 30 mm. As a rule, it suffices here if the average distance from the inlet to the structure closest to the inlet is about 50 mm to 70 mm, in particular about 60 mm. Furthermore, in a further embodiment, a distance between the structure closest to the outlet and the outlet can be selected from about 40 mm to 90 mm, in particular from 50 mm to 80 mm and particularly preferably from 60 mm to 70 mm.

According to a preferred embodiment, the device according to the invention has, essentially in sections, an oval or elliptical cross-sectional structure. According to a preferred embodiment, the device according to the invention has, in particular over the region in which the structures mentioned above, an extension transverse to the longitudinal axis of this device extending from the inlet to the outlet in the range of 100 mm to 400 mm, preferably from 150 mm 300 mm and more preferably from 200 mm to 250 mm and may for example assume a value of about 220 mm. If the cross-section of the structures described above is oval or ellipse-shaped, the device can extend in the direction of the longitudinal axis in the range from 100 mm to 400 mm, preferably from 150 mm to 300 mm and more preferably from 200 mm to 250 mm, for example about 220 mm and / or the transverse axis has an extension in the range from 50 mm to 300 mm, preferably from 70 mm to 200 mm and particularly preferably from 90 mm to 150 mm, for example about 100 mm.

According to a further aspect of the present invention, the device according to the invention further comprises a second housing, in particular of metal, in which the first housing is arranged at least in regions. It can be provided that the inlet of the first housing outside and the outlet of the first housing are present within the second housing.

Advantageously, the inner wall of the second housing and the outer wall of the first housing are at least partially spaced.

It is preferably provided that at least a first connecting element, in particular in the form of, e.g. metallic, support bearing, between the inner wall of the outer, second housing and the outer wall of the inner, first housing is present.

Preferably, at least one layer containing, in particular synthetic, mineral fibers such as, in particular refractory, ceramic fibers and / or glass fibers is present between the first connecting element and the outer wall of the first housing. Furthermore, a second connecting element can be attached directly between the outer wall of the first housing and the inner wall of the second housing, comprising at least one layer containing, in particular synthetic, mineral fibers such as, in particular refractory, ceramic fibers and / or glass fibers.

The layer containing ceramic fibers may, for example, be a woven layer, a nonwoven or felt layer, a cast or formed layer, a plate, a molded article or a paper. Ceramic fibers in the context of the present invention should also comprise fibrous mineral wool. Fibrous mineral wool again comprises fibrous glass wool and fibrous rockwool. Suitable ceramic fibers are also known under the trade name Refractory Ceramic Fibers (RCF).

Particularly preferably, the layer comprising ceramic fibers additionally comprises clay minerals, in particular phyllosilicates. Among the phyllosilicates, for example, mica, talc, serpentine and especially vermiculite are suitable. In a preferred embodiment, the said layers may each contain between 30 and 70% by weight of ceramic fibers, in particular refractory ceramic fibers, and clay minerals, in particular vermiculite. Such layers have proven to be particularly advantageous, which additionally contain organic and / or inorganic binders. A suitable product is for example in the Trade under the name XPE ^® Expanding mat from the company Unifrax GmbH, Dusseldorf, Germany, available. •

The connecting elements described above dampen vibrations and other mechanical stresses well and contribute to a reliable bond between the first and second housing. Of course, at least one layer containing ceramic fibers, as described above, also be present or attached between the connecting element and the inner wall of the second housing.

A further development provides that before the outlet of the second housing at least one retaining device, which prevents the unimpeded outlet of the exhaust gas freed of pollutants, in particular a pinhole, is arranged. The retaining device preferably has a graphite coating at least in regions.

Advantageously, the entire passage area of the pinhole corresponds approximately to the area of the inlet of the first housing, via which the exhaust gas to be cleaned enters the housing.

According to a further embodiment, the system according to the invention is integrated into an exhaust gas recirculation system (EGR). It can be provided that follows the outlet at least one return line for returning in particular a portion of the filtered exhaust gas into the engine. The return line may be connected, for example, to an air inlet duct for fresh air via a valve arrangement. The mixture of recirculated and fresh air optionally set via an EGR control arrangement can then be supplied to the air inlet opening of an engine.

According to an expedient embodiment, the device according to the invention further comprises at least one lambda probe, at least one first temperature and / or pressure sensor before or at the inlet or in the front region of the first housing and at least one second temperature and / or pressure sensor on or outside the Outlet or in the rear of the first or second housing. With the inventive device for the elimination of harmful components from exhaust gases of internal combustion engines of Neufalirzeugen the limits for carbon monoxide, nitrogen oxides, hydrocarbons + nitrogen oxides, and particulate constituents can be complied with according to the Euro 5 standard. Even with a diesel car end-of-life vehicle with a mileage of about 240,000 km, the following measured values according to RL 70/220 / EWG (test cycle MVEG) could be achieved with a device according to the invention: HC 0.17 g / km, NOx 0.61 g / km, HC + NOx 0.78 g / km, CO 0.92 g / km, CO ₂ 185.15 g / km and particles 0.035 g / km.

The present invention was based on the surprising finding that soot residues in the erfϊndungsgemäßen emission control system no longer accumulate in the realization of the claimed features. Rather, soot particles are constantly converted to carbon dioxide. Consequently, a continuous, active regeneration succeeds. Due to the complete and continuous removal of soot residues in the exhaust gas, the device according to the invention ensures that the pressure difference between inlet and outlet is never greater than 150 mbar and preferably never greater than 100 mbar, whereby a negative feedback on engine performance can be excluded. For example, with the devices according to the invention, a pressure difference between inlet and outlet of less than 60 mbar, for example 57 mbar, can easily be achieved. In this case, the volume passages can readily be in the range of 10 to 15 1 / sec, for example at about 12 1 / sec. An often occurring in known particulate filters, disadvantageous pressure build-up does not take place with the device according to the invention. A subsequent increase in fuel consumption is thus also excluded. In addition to the specific arrangement of the coated carrier structures and the specific coating materials, the "pore burner" structure attached to the front of the system also contributes to this, because in this way a laminar flow can be set and maintained without The device according to the invention is further surprised by its structurally very simple structure, which can be used without serious changes in any combustion engine, for example in the exhaust systems of passenger cars and trucks In addition, a very compact housing shape is made possible, so that the device according to the invention can be integrated in any exhaust systems, retrofitting is therefore completely unproblematic, for the elimination of soot particles that it is compatible with the acquired To the device according to the invention can set a temperature profile, after which the temperature in the rear area is higher than in the front area. It is also advantageous that the device according to the invention ages only very slowly, with the result that its service life corresponds at least to that of conventional internal combustion engines and replacement of the particulate filter according to the invention is generally no longer necessary. The use in particular of a housing or an inner coating of porous silicon carbide finally has the advantage that this material represents a suitable heat storage in the present application. Therefore, even with alternating load operation during a phase of low engine load, and concomitantly a low exhaust gas temperature, previously stored heat energy can be supplied to the first to sixth structures, so that passive regeneration of the filtered particles or other residues is always possible.

Further features and advantages of the invention will become apparent from the following description, are explained in the preferred embodiments of the invention by way of example with reference to schematic drawing.

Showing:

Figure 1 is a schematic cross-sectional view of a device according to the invention;

Figure 2 is a schematic cross-sectional view of an alternative embodiment of the inventive device;

Figure 3 is a schematic cross-sectional view of another alternative embodiment of the device according to the invention, and

Figure 4 is a schematic cross-sectional view of another alternative embodiment of the device according to the invention. 1 shows a device 1 according to the invention for the removal of pollutants from exhaust gases of Brennlcraftmaschinen comprising a housing 2 with a front, middle and rear region 4, 6 and 8. In the front region 4 of the inlet 10 and in the rear region 8 of the outlet 12th arranged. On the inlet 10 follows in the front region 4 of the housing 2, a first structure 14 made of a material, as is commonly used in pore burners. The adjoining the inlet 10 input area 16 is itself free of the pore burner structure 14. Rather, the inlet 10 facing surface 18 of the pore burner structure 14 surrounds the input portion 16 in approximately hemispherical. The first structure 14 is present mainly in the front region 4 of the device 1 according to the invention and covers the entire inner cross section of the housing 2. In the transition region between the front and middle region 4, 6, the housing diameter widens noticeably. The pore burner structure 14 ensures as laminar a flow as possible of the exhaust gas entering the device 1 and eliminates transverse flows, so that soot particles no longer accumulate on the inner walls 24 of the housing 1. Also, a consistent distribution of pollutants in the exhaust stream is ensured. Connected to the pore burner structure 14, separated by a first gap 22, is a second structure 20, comprising a metal foam, which is coated with potassium vanadate and extends over the entire cross section of the middle region 6 of the housing 2. The second structure 20 is followed, separated by the second gap 26, by a further second structure 20 ', which in construction and coating substantially coincides with the second structure 20, ie, this is likewise a potassium vanadate-coated metal foam which forms extends over the entire cross-sectional area of the central region 6 of the device 1. The second structures 20 and 20 'serve essentially to transfer nitrogen oxides contained in the exhaust gas by means of reduction into harmless components. The central region 6 is substantially closed by a third structure 28 based on a metal foam coated with a palladium / silver catalyst and used for the oxidation of carbon monoxide and hydrocarbons. The third structure 28 again extends over the entire cross-sectional area of the housing 2 and is separated from the second structure 20 'by a third gap 30 so that there is substantially no direct contact. In the rear region 8 of the housing 2, a fourth structure 32, again based on a metal foam, is applied, which extends over the entire cross-sectional area of the rear region and is coated with a mixture of aluminum oxide and cerium oxide. In the illustrated embodiment, the fourth structure 32 is separated from the third structure 28 by a fourth gap 34. The inner wall 24 of the housing 2 has, in the illustrated embodiment, a silicon carbide coating.

FIG. 2 shows a further development of the exhaust gas purification system 1 described in FIG. In this embodiment 1 ', the system 1, as shown in Figure 1 and as described above, surrounded by another, second housing 50. This second housing 50 is connected to the first housing 2 in the front region 4. Otherwise, the device 1 is substantially free of contact in the second housing 50 before. Accordingly, there is at least a fifth gap 54 between the outer wall of the first housing 2 and the inner wall 52 of the outer second housing 50. Of course, the device 1 can be supported in the outer housing 50 at one or more points, for example in the middle or preferably rear area 8 on the inner wall 52. The outer housing 50 has an outlet 56, which is arranged substantially in front of the outlet 12 of the device 1. Between the outlet 12 and the outlet 56, a pinhole 58 is attached. The exiting from the outlet 12 purified exhaust gas is thus prevented via the aperture 58 at a free outlet and depending on the size of the exit surface at least partially in the lying in front of the outlet 12 area 60 in the direction of the between the system 1 and the inner wall 52nd the outer, second housing 50 lying space 54 is deflected. In this way, the temperature of the exiting, purified exhaust gas can be used to ensure a constantly high operating temperature of the exhaust gas purification system 1.

FIG. 3 shows a further embodiment of a device according to the invention, which is essentially a further development of the system 1 'shown in FIG. The emission control system 1 is in turn embedded in an outer housing 50. In the front region 4, the first structure 14 is made of a pore burner material. This is immediately followed by a second structure 20, as described for FIG. 1, omitting the first intermediate space. A gap 26 is then present between the second and third structures 20, 28. The third structure 28 here corresponds to the variant described under FIG. Immediately adjacent to the third structure 28, again omitting a gap, is the fourth structure 32, which is a metal oxide coated with alumina and ceria. While the second and the third structure 20, 28 in the central region 6 of the device 1 present gen, the fourth structure 32 substantially completely fills the rear area 8 of the device 1. Between the inner wall 52 of the outer, second housing 50 and the wall 2 of the first housing 2 of the device 1, there is a gap 54 for receiving exiting from the outlet 12 exhaust gases. The device 1 is in the present case for better storage in the middle and rear regions 6 and 8 in contact with the inner wall 52 of the outer housing 50, via corresponding connecting elements or support bearings 62, 62 'and 64, 64', for example made of metal. Between the support bearing 62, 62 "and the outer wall of the first housing 2, in particular for the purpose of better and easier connection and damping purposes, there is a fiber layer 90 containing ceramic fibers and optionally a binder a fiber layer containing ceramic fibers and optionally a binder, as a second connecting element 88 between the first and second housings (2, 50) Following the outlet 12 of the device 1 in the second housing 50, a pinhole 58 'is mounted over the entire Cross-sectional area extends in the rear region of the housing.

FIG. 4 shows a further development of the device 1 shown in FIG. 1. This further development is equipped with temperature and pressure sensors 80 and 82 in the region of the inlet 10 and of the outlet 12. In addition, upstream of the inlet 10 there is a lambda probe 84, with which the oxygen content of the incoming exhaust gas can be determined. The values recorded with these sensors are forwarded to an evaluation unit 86 and used, for example, for optimized operation of the internal combustion engine.

The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential in any combination for the realization of the invention in its various embodiments. LIST OF REFERENCE NUMBERS

, T Device for removing harmful components from exhaust gases of

Brennlcraftmaschinen first housing front portion of the first housing middle portion of the first housing rear portion of the first housing 0 inlet of the first housing 2 outlet of the first housing 4 first structure 6 section which is free from the first structure 14 in the front region 4 8 front surface of first structure 14 0, 20 ^Λ second structure 2 first interspace 4 inner wall of the first housing 2 6 second interspace 8 third structure 0 third interspace fourth structure fifth interspace 0 second housing inner wall of the second housing sixth interspace 6 outlet of the second housing 8, 58 "retention device Area between outlet 12 and retaining device 58, 62 'rear support bearing (first connecting element), 64' middle support bearing (first connecting element) temperature sensors pressure sensors Lambda probe evaluation unit second connecting element 90 fiber layer containing ceramic fibers

Claims

claims

Device (1) for removing harmful components, in particular soot, from exhaust gases of internal combustion engines, in particular of diesel engines, comprising a first housing (2), suitable for passing exhaust gases, with at least one inlet (10) and at least one outlet ( 12) and comprising a front, middle and rear region (4, 6, 8), wherein at least one inlet (10) in the front region (4) and at least one outlet (12) in the rear region (8) is present, wherein in the front Area (4) at least a first structure (14) containing a plurality of contiguous cavities, the cross-section of the first housing (2) at least partially covers, whereupon in the housing (2) follow in any order: at least a second, the cross section at least partially covering the structure of the first housing (20), comprising a plurality of contiguous cavities, which contains at least one first metal oxide and / or with this zuminde St is partially coated, at least a third, the cross section of the first housing (2) at least partially covering structure (28) containing a plurality of contiguous cavities containing at least one catalyst for the reaction or decomposition of pollutants and / or with this at least partially coated, and at least a fourth, the cross section of the first housing (2) at least partially covering structure (32) containing a plurality of contiguous cavities containing at least one second metal oxide and / or at least partially coated therewith the first housing (2) is at least partially and / or the inner wall (24) of the housing (2) at least partially made of, in particular porous, alumina, mullite, cordierite, silicon nitride, tialite, steatite, zirconium, zirconium dioxide and / or silicon carbide or with , in particular porous, alumina, mullite, cordierite, silicon nitride, tialite, steat it is zirconium, zirconium dioxide and / or silicon carbide coated.

2. Device (1) according to claim 1, characterized in that in the first housing (2) in the direction from the inlet (10) to the outlet (12), in this order, at least one first (14), at least one second (20), at least a third (28) and at least a fourth (32) structure.

3. Device (1) according to claim 1 or 2, characterized in that the first housing (2) at least in sections and / or the inner wall (24) of the housing (2) at least partially made of, in particular porous, silicon carbide or with, in particular porous, silicon carbide is coated.

4. Device (1) according to any one of the preceding claims, characterized in that, the inner wall (24) of the first housing (2) to more than 50%, in particular substantially completely, of porous silicon carbide or is coated with porous silicon carbide.

5. Device (1) according to one of the preceding claims, characterized in that the silicon carbide comprises carbon fiber reinforced silicon carbide (C / SiC).

6. Device (1) according to any one of the preceding claims, characterized in that the silicon carbide additives to inorganic binders, in particular clay, zirconium silicate, zirconium dioxide and / or alumina, and / or organic binders, in particular carbon black comprises.

7. Device (1) according to one of the preceding claims, further comprising at least a fifth, the cross-section of the first housing at least partially covering structure containing a plurality of contiguous cavities containing platinum and / or rhodium and / or with platinum and / or Rhodium is at least partially coated.

8. Device (1) according to one of the preceding claims, further comprising at least a sixth, the cross-section of the first housing at least partially covering structure containing a plurality of contiguous cavities containing at least one SCR catalyst and / or coated at least partially is.

9. Device according to one of the preceding claims, characterized in that the first, second, third, fourth, fifth and / or sixth structure (14, 20, 28, 32) a open-cell or cellular foam ceramic, an open-pore or cellular metal foam, an open-pore or cellular metal sponge, a heat-resistant, open-pore or cellular foam plastic, a wire mesh and / or sintered bulk material.

10. Device (1) according to one of the preceding claims, characterized in that the first structure (14) is coated at least partially with aluminum oxide and / or titanium oxide.

11. Device (1) according to one of the preceding claims, characterized in that the second structure (20) as the first metal oxide at least one vanadate, in particular potassium and / or silver vanadate, and / or with at least one vanadate, in particular potassium and / or silver vanadate, coated.

12. Device (1) according to one of the preceding claims, characterized in that the second structure (20) in addition to the first metal oxide at least one metal nitrate and / or at least one water glass compound.

13. Device (1) according to one of the preceding claims, characterized in that the third structure (28) contains a palladium / silver catalyst and / or coated with a palladium / silver catalyst.

14. Device (1) according to one of the preceding claims, characterized in that the catalyst of the third structure (28) contains iron, nickel, iron oxide and / or nickel oxide and / or coated with iron, nickel, iron oxide and / or nickel oxide.

15. Device (1) according to one of the preceding claims, characterized in that the fourth structure (32) contains alumina, ceria and / or zeolites and / or is coated with alumina, ceria and / or zeolites.

16. Device (1) according to any one of the preceding claims, characterized in that the front region (4) of the first housing (2) widens towards the central region (6) and / or that the rear region (8) extends to the outlet (12), in particular conical, tapered.

17. Device (1) according to one of the preceding claims, characterized in that the surface (18) of the first structure (14) which faces the inlet (10), in the direction of the interior of the first housing (2), in particular is substantially spherical, curved.

18. Device (V) according to one of the preceding claims, further comprising a second housing (50), in particular of metal, in which the first housing (2) at least partially, in particular with a peripheral connection in the front or middle region (4, 6 ) is arranged.

19. Device (V) according to claim 18, characterized in that the inlet (10) of the first housing (2) outside and the outlet (12) of the first housing (2) within the second housing (50 ') are present.

20. Device (1 ^Λ ) according to claim 18 or 19, characterized in that the inner wall (52) of the second housing (50) and the outer wall of the first housing (2) are at least partially spaced.

21. Device (l ^Λ ) according to any one of claims 18 to 20, further comprising at least a first connecting element (62, 62 ", 64, 64"), in particular in the form of a support bearing, between the inner wall (52) of the outer second housing (50) and the outer wall of the inner, first housing (2).

22. Device (V) according to claim 21, further comprising between the first connecting element (62, 62 \ 64, 64 ') and the outer wall of the first housing (2) at least one layer containing mineral fibers, in particular glass and / or ceramic fibers, and / or between the first connecting element (62, 62 ', 64, 64') and the inner wall (52) of the second housing (50) at least one layer containing mineral fibers, in particular glass and / or ceramic fibers, and / or at least one second connecting element between the outer wall of the first housing and the inner wall of the second housing, comprising at least one layer containing mineral fibers, in particular glass and / or ceramic fibers.

23. Device (1 '') according to claim 22, characterized in that the layer containing ceramic fibers, additionally at least one clay mineral, in particular phyllosilicates, and / or at least one organic and / or inorganic binder.

24. Device (V) according to any one of claims 18 to 23, characterized in that in front of the outlet (56) of the second housing (50) at least one retaining device (58), which prevents the unimpeded discharge of the exhaust gas freed of pollutants, in particular a Aperture plate, is arranged.

25. Device (V) according to claim 24, characterized in that the retaining device (58) at least region-wise comprises a graphite coating.

26. Device (1, V) according to one of the preceding claims, further comprising at least one lambda probe (84), at least one first temperature (80) and / or pressure sensor (82) before or at the inlet or in the front region of the first housing and at least one second temperature (80) and / or pressure sensor (82) on or outside the outlet (12) or in the rear region of the first or second housing (2, 50).

27. Device (1, V) according to one of the preceding claims, comprising at least two, in particular successive, second structures (20, 20 ').

28. Device (1, V) according to one of the preceding claims, characterized in that between the first and second structure (14, 20) a first intermediate space (22), between adjacent second structures (20, 20 ^Λ ) a second space ( 26), between the second and third structures (20, 20 \ 28) a third gap (30), between adjacent third structures (20, 20 ', 28) a fourth gap and / or between the third and fourth structures (28, 32) there is a fifth intermediate space (34).

29. Device (1, V) according to any one of claims 7 to 28, characterized in that the fifth structure is mounted between the first and the second structure, in particular directly follows the first structure.

30. Device (1, V) according to any one of claims 8 to 29, characterized in that the sixth structure is arranged in the direction from the inlet to the outlet before and / or after the fourth structure.

31. Device (1, V) according to claim 30, characterized in that there is no gap between the fourth and sixth structure, in particular the fourth and the sixth structure form a unitary structure.

32. Device (1, V) according to any one of the preceding claims, characterized in that at least between two adjacent, in particular between all adjacent structures, there is a gap, in particular over the entire cross-sectional area of adjacent structures.

33. Device (1, V) according to one of the preceding claims, characterized in that the average distance between adjacent structures, measured along the longitudinal axis in the direction from the inlet to the outlet, in the range of 5 mm to 50 mm, in particular in the range of 10th mm to 40 mm.

34. Device (1, V) according to one of the preceding claims, characterized in that the average width of the first and / or second and / or third and / or fourth and / or fifth and / or sixth structure in the range of 5 mm to 50 mm, in particular from 10 mm to 40 mm, measured along the longitudinal axis in the direction from the inlet to the outlet, is located.

35. Device (1, V) according to any one of the preceding claims, characterized in that the distance from the inlet (10) to the first structure in the range of 20 mm to 100 mm, in particular from 30 mm to 80 mm, is located and / or the distance from the structure closest to the outlet (12) to the outlet (12) is in the range from 20 mm to 120 mm, in particular from 30 mm to 90 mm.

36. The device (1, 1 ') according to one of the preceding claims, further comprising on the outlet (12) following at least one return line for returning, in particular a part, of the filtered exhaust gas into the engine.

37. Use of the device according to one of the preceding claims for the purification of exhaust gases of internal combustion engines of ships, passenger cars, trucks, stationary combustion units, and tractors.