DE2302746A1 - CARRIER MATRIX FOR A CATALYTIC REACTOR FOR EXHAUST GAS CLEANING IN COMBUSTION MACHINES, ESPEC. GASOLINE ENGINES OF MOTOR VEHICLES AND A MANUFACTURING PROCESS - Google Patents

Description

Company Süddeutsehe Kühlerfabrik Julius Pr. Behr 7 Stuttgart 30, Mauserstr. 5

"Support matrix for a catalytic reactor for exhaust gas purification for internal combustion engines, especially gasoline engines of motor vehicles, as well as a manufacturing process "

The invention relates to a carrier matrix for a catalyzer ti see reactor for exhaust gas purification of internal combustion engines, especially gasoline engines of motor vehicles.

Due to the modern emissions legislation in various countries, it is necessary to control the exhaust gases from vehicle engines largely rid of pollutants. For this it is important to use carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (N0 ") through post-combustion to convert into non-toxic burn practices.

The measures, with the help of a corresponding operating method of the internal combustion engine, the pollutant emissions Keeping them low is not enough. In order to be able to comply with the required limit values, thermal or catalytically acting reactors used.

In the case of catalytic reactors, to reduce the Pollutants in the exhaust gases, reduction catalytic converters and oxidation catalytic converters may be used together used in the form of so-called double bed catalysts.

Platinum, palladium, copper and nickel oxides and the like are used as catalysts. The catalyst needed a catalyst carrier that offers the catalyst the required size or surface area and the whole System holds together and gives strength. Known catalyst carriers consist of aluminum oxides. you will be used as a honeycomb body and as bulk material. In the case of bulk goods, it is also known to use metal supports in ring shape or saddle shape, mainly made of materials with a high nickel content (Monel), which is catalytic after conversion into nickel oxide and copper oxide Shows effectiveness.

Honeycomb bodies made of aluminum oxide are known as a so-called carrier matrix for catalytic converters. However, aluminum oxide is a very brittle material, which results in disadvantages in terms of fatigue strength. The material crumbles relatively soon in the event of the vibrations occurring during operation due to shock waves in the exhaust gas jet or due to driving movements and engine vibrations. It is therefore necessary to protect the catalyst carrier against mechanical vibrations of the vehicle and / or the engine by means of elastic suspensions. Alumina also has an over steel lower thermal expansion coefficient. Since the carrier matrix has to be embedded in a metal housing for assembly purposes, constant relative movements between the housing and the matrix result from the fluctuating temperatures from -2o to + 900 ° C which have to be absorbed by elastic members. Tem-

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Thermal stresses and play occurring due to slackening of the elastic material lead to the destruction of the Carrier material. Due to the elastic assembly of the Honeycomb bodies in the reactor housing occur sealing problems that have to be remedied by special seals and should have the effect that all exhaust gas is pushed through the honeycomb body and not past it flows between the honeycomb body and the housing.

In addition, aluminum oxide is a porous body, the porosity of which depends on the sintering temperature. the The sintering temperature therefore also has a great influence on the later catalytic effectiveness. In the event of excess temperatures If the coated carrier continues to sinter out, it closes its pores and thus reduces the surface available for the catalytic effectiveness. In addition, the porosity depending on impurities in the gasoline.

Aluminum oxide is also a poor conductor of heat. With local accumulations of especially unburned HC therefore local overheating occurs, which leads to local burnout of the carrier.

The strength of aluminum oxide is low, so that the honeycomb wall thicknesses of at least 0.2 mm are selected Need to become.

Bulk goods are mainly made of aluminum oxide and for this reason have the same disadvantages as the aluminum oxide honeycomb, which is based on the properties of the material. In addition, bulk goods exhibit a very high pressure drop.

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Among the gas and mechanical ones used in operation Vibrations changes the bulk density, so that the cohesion between individual grains of the bulk material is no longer given, hit individual grains together and grind themselves in the process.

Another disadvantage, as in the case of aluminum oxide honeycomb bodies, is the different expansion coefficient of the bulk material compared to the steel jacket.

Bulk goods made of nickel alloys (monel), have the disadvantage that Monel has too low a temperature resistance. Merge bulk goods from this material when higher temperatures occur, so that the entire reactor is destroyed.

In the case of bulk goods, however, the coating with the catalyst material be carried out in a continuous process, only after this coating the reactor housing is filled with the coated bulk material.

The invention is based on the object of creating a carrier matrix which has the disadvantages of the known carriers does not have and moreover combines the advantages of a honeycomb structure with those of the bulk goods.

According to the invention, this object is essentially achieved in a carrier matrix of the type explained at the beginning solved that it is made of high temperature resistant steel, and that it is formed from corrugated and smooth sheet steel is, which are arranged alternately and coated with catalyst material.

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In the case of bulk catalysts, it is known that the catalyst particles to be arranged in close packing in each catalyst bed. As a support for the catalyst material Wires, pasers, corrugated tapes, foils, spirals, sheaths, Pipes or the like. Has already been proposed. In a known exhaust gas cleaning process, particles are used, which are manufactured by metal cutting. However, there is a high loss of pressure on and a relatively high risk of pollution. The system settles slowly, as the desired closest packing cannot be achieved in advance.

A catalytic converter is also known in which the catalyst bed consists of at least one first channel limiting part and at least one a second Kaäal limiting part consists and wherein the first and second parts are flat and corrugated plates, which on their Surface carry a catalyst, wherein the first and second parts are crossed one above the other. The Gas flow deflected several times, so that high pressure losses also occur. Furthermore, the manufacture is this Converter difficult and expensive.

Another known method for reducing nitrogen oxides uses a catalytic part, the has a mesh-like structure and is made of steel can be. The catalytic part must be traversed transversely, which leads to high pressure losses and, because of the requirement to keep the passage channels open, leads to assembly difficulties. The gas ducts are not regularly but randomly arranged chaotically.

In known catalytic converters made of steel, various steels have a self-reducing effect on NO. in the

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In contrast, the present invention proposes to use high-temperature-resistant steel as a support matrix for the catalyst materials.

High-temperature steel has only small proportions at Pe and Cu on; It is particularly advantageous that the steel used is itself catalytically inactive.

In order to obtain a large effective surface, it is particularly useful if the width and height of the Cross-section of the individual honeycombs are smaller than 1.5 mm.

It is particularly advantageous to choose the wall thickness of the carrier plates to be less than 0.1 mm. This leads to a relatively firm association.

Hub bodies according to the invention change at high temperatures their surface structure does not. By separating the functions of a carrier, namely strength and cohesion on the one hand, on the function of catalytic activity on the other hand, there are significant advantages. The small wall thicknesses lead to much smaller print lists. The individual honeycomb cells can be built smaller, so that high geometric surfaces per building volume can be installed.

For the production it is particularly advantageous if the profile of the corrugation of the corrugated part of the carrier matrix corresponds to an involute toothing. This achieves a very compact structure for the honeycomb and avoids that local catalyst accumulations result, which leads to an increased requirement for catalyst material, without the effective surface is increased.

The carrier matrix can advantageously be designed in this way be that the carrier of the honeycomb are ribbons that are wound spirally to form a cylinder are. But it is also possible to design the carrier plate-shaped in a manner known per se and to be flat and alternately stacking corrugated tapes or plates on top of one another, the corrugation always running parallel.

It is particularly useful to coat the steel sheets with a catalytically active one before stacking or winding them up Metal e.g. B. to coat copper, nickel or the like and then to oxidize.

But it is also possible, the steel sheets with a catalytically active metal oxide z. B. copper oxide, nickel oxide or the like. To be coated directly.

The individual layers of the steel sheets can be spot welded or soldered to one another. It is also possible to weld or solder them to one another as a whole. The elasticity and strength of the matrix thus results in high operational reliability, in particular with regard to gas and mechanical vibrations.

The catalyst supports are in any length and shape manufacturable.

According to a preferred embodiment of the invention, the smooth and the corrugated steel sheets are in one Steel jacket arranged under prestress. If the individual layers of the steel sheets are welded or soldered, can the coat is also omitted. Since the jacket and the carrier matrix can consist of the same material, none of them occur Installation difficulties due to different thermal expansion coefficients. So there won't be any complex elastic connections are required.

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According to a development of the invention, the sheets of the matrix are metallically connected to the jacket. The connection can be effected by screws; the sheets of the matrix can also be welded to the jacket or be soldered.

In the case of a cartridge consisting of a carrier matrix and jacket, the carrier matrix in the jacket can preferably be through holding means arranged in front of the end face of the matrix can be fixed.

The holding means expediently consist of intersecting struts made of wires or webs. The striving are advantageously designed or arranged to be elastically resilient.

According to a modified embodiment of the invention, the holding means can also be wire grids are formed.

To achieve the bias, it is advantageous according to a further feature of the invention if the jacket is cone-shaped is trained.

The preload can also be achieved using an insertion cone as an assembly aid.

According to a modified embodiment of the invention, the outer tape end is inclined to the longitudinal axis of the tape cut. This also results in a pressing effect during assembly, which brings about the preload. Particularly it is advantageous for the length of the beveled end to correspond approximately to the circumference of the inside of the jacket Select.

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The invention also comprises a catalytic reactor with a support matrix according to the invention and a housing with connections for exhaust gas inlet, exhaust gas outlet and possible secondary air supply, whereby according to the invention the carrier matrix is fastened with its jacket in a sealed manner in the housing via flange rings. Between cartridge and reactor housing, there are no sealing problems, as the matrix is directly in the housing with the help of the axial rings can be screwed or welded. In the case of a carrier matrix that is soldered or welded to itself, the matrix also directly, i.e. H. without a jacket, be fastened in the housing.

The facing rings can have a U-shaped cross-section, wherein the legs of the U are connected to the housing on the one hand and the shell of the cartridge on the other hand. The connection can be made by screwing, soldering or welding.

According to a modified embodiment of the invention, the face rings are Z-shaped and between The inner edge of the Z-profile and jacket of the carrier matrix is the exhaust gas inlet pipe and / or the exhaust gas outlet pipe attached.

In a manner known per se, a carrier matrix can be placed in a housing be arranged as a reduction catalyst and a second support matrix as an oxidation catalyst, and the The carrier matrix for the reduction catalyst and the carrier matrix for the oxidation catalyst are in one place Coat housed.

It is advantageous here if spacer test struts are arranged between the reduction catalytic converter and the oxidation catalytic converter

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and the secondary air connection is connected to the jacket in the area of the spacer struts.

The space between the outermost ring flanges and the inner wall of the housing on the one hand and the jacket of the carrier matrix or the carrier matrix itself is filled with insulating material, for example glass wool, asbestos or the like ..

Another advantage of the carrier matrix according to the invention or a catalytic reactor according to the invention proves the high thermal conductivity of the steel carrier material, which makes local overheating better at colder Parts of the matrix can be derived and local burn-through is largely excluded. Further lead the usable small wall thicknesses lead to very low heat capacity, so that the heating-up time until it starts of the catalyst is smaller than in the case of the previously known catalysts.

The invention also encompasses a method of making the carrier matrix described above. In doing so, according to the invention two endless sheet steel belts fed to a bath; one of the belts is in itself is known to be previously corrugated, and the smooth and the corrugated tape are in spiral or alternating in level layers arranged one above the other and connected to one another.

It is particularly advantageous if the coating of the strips with the catalyst material is continuous and before the stacking or rolling up to the carrier matrix takes place.

The carrier matrix is then, for example with the help of a multi-jaw chuck, in a jacket with prestress pressed in.

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Further features and advantages of the invention are explained in more detail with reference to the drawing, which schematically shows exemplary embodiments of the devices according to the invention and a scheme of the method according to the invention. It shows:

1 shows a carrier matrix according to the invention in a spiral shape wrapped condition,

Pig. 2 a cartridge with a carrier matrix in a jacket,

Pig. 3 a partial section from a stacked carrier matrix,

Fig. 4 schematically shows a catalytic reactor

a carrier matrix according to the invention in an oblique view, partially cut,

Pig. 5 shows a cross section through a reactor according to a modified embodiment,

6 shows a detail of a modified reactor, and

7 schematically shows a device for implementation of the method according to the invention.

In Fig. 1, a carrier matrix 13 according to the invention is wound State shown. The carrier matrix 13 is made of high temperature resistant steel, and consists of a smooth intermediate sheet 1 and a corrugated tape 2, which are coated with catalyst material. In an embodiment according to FIG. 1, a smooth intermediate belt 1 and a corrugated tape 2 wound spirally on a core 3. After the desired diameter has been reached, the rolled-up carrier matrix 13 is surrounded by a jacket 4, as follows that a cartridge 2o is formed.

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In Fig. 2 holding means 21 are shown in the form of crossed webs that for fixing the Tragermatι ix 13th serve in the jacket 4 of the cartridge 2o. The webs 21 are bent in order to elastically absorb any thermal expansions of the jacket 4 to be able to adapt. The arrangement and number of webs 21 is arbitrary, it can only one, preferably diagonal, web may be provided, but preferably two crosswise arranged; the webs can consist of sheet metal strips or wires in a straight line or, as shown, be arched.

The diameter of the support matrix I3 and its length can be, as well as the length of the cartridge 2o, depend on the respective requirements.

In the embodiment of FIG. 3, a sandwich-like construction is shown schematically, with Alternate smooth intermediate belts 1 or plates and corrugated belts one on top of the other. The outer contours of the stack can be arbitrary, preferably rectangular or cutx-shaped be.

In Fig. 4 is a schematic, partially sectioned catalytic reactor with two support matrices or cartridges shown according to the invention. The reactor 23 exists from a housing 16 with an exhaust gas inlet pipe 14 and an exhaust gas outlet pipe 15 · between the two support matrices A secondary air connection 17 is provided. the Cartridges 20 can be fastened in the housing 16 with screws 18. But you can also use a Flange 19 to be soldered or welded to the housing 16. The flange 19 can be L-shaped, U-shaped or Be designed in a Z-shape, the fastening screws on an angled flange part or in the case of a U-profile

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or Z-profile are attached to both flange parts. A seal in the housing 16 between the cartridges 2o and the inside of the housing is achieved by the planch 19.

As can be seen from FIG. 4, there are no sealing problems between the cartridges 20 and the housing 16 because the cartridges are fastened directly in the housing l6 via the flanges 19.

In the embodiment shown in Fig. 4 is it is a so-called two-bed catalyst, whereby the catalyst at the front in the direction of flow as a reduction catalyst and the one behind (right) second catalyst is designed as an oxidation catalyst. Between the reduction catalyst 25 and the Oxidation catalytic converter 26 is a secondary air connection I7 intended.

As mentioned, the carrier matrix I ^ is advantageously below Introduced bias in their jacket 4. This can be achieved, for example, in that, as in the case of the right Catalyst 26 indicated in Fig. 4, the jacket of the cartridge is conical. When pressing in the wound The carrier matrix then achieves the required pressure to generate the prestress. But it is also possible to use a push-in cone (not shown), with the help of which the corresponding preload is achieved.

Another way to achieve the desired preload is shown in Fig. 2, wherein the outer end of the wound support matrix Ij5 is not perpendicular to the

of the tape
Longitudinal direction / but is cut obliquely, whereby an inclined edge 24 is formed. The angle of the obliquely cut edge 24 to the longitudinal axis is chosen such that the

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The length of the cut edge corresponds approximately to the inner circumference of the jacket 4, so that the cut edge is practically once on Runs along the outer circumference. Due to the different diameter, if a corresponding pressing force is used Introducing the carrier matrix I ^ in the jacket 4, the desired bias is achieved.

The one in Pig. The modified exemplary embodiment shown in FIG. 5 are the support matrices for the reduction catalytic converter and the oxidation catalyst arranged or pushed into a common jacket 27. For spacer bracket A web 28 is used, which is designed similar to the web or webs 21 in FIG. 2. In the bridge area the secondary air connection 17 is attached.

In Fig. 6 a detail of the connection between cartridge 2o, housing 16 and exhaust gas inlet pipe 14 is shown schematically. A Z-shaped flange 19 and its bent flange ends are used to fasten the jacket 4 of a cartridge 2o in the housing are fastened by means of screws 18 on the one hand to the jacket 4 of the cartridge 2o and on the other hand to the housing 16. Included the training is made so that between the bent to the right flange of the annular flange 19 and the Jacket 4, the end of the exhaust gas inlet pipe 14 is clamped. A particularly favorable exhaust gas routing is achieved in this way. From Fig. 6 it can also be seen that the space between the jacket 4 of the cartridge (s) 2o and the housing 16 with a Isolation 22 is filled. This insulation can consist of asbestos, glass fibers or the like.

The production of a carrier matrix according to FIG. 1 or 2 can be carried out in an advantageous manner with a device according to FIG. DabA is fed with the smooth intermediate strip 1 from a supply roll and a strip from another roll,

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which is shaped into the corrugated tape 2 in a corrugating machine 5. Intermediate belt 1 and corrugated belt 2 are then fed via guide rollers or guide rollers 7 to Io and a deflection roller 11 to a coating bath 12 in which the catalyst material is applied to the two belts. After the coating, the strips 1, 2 are wound onto a core 3 in a winding machine 6 up to the diameter desired in each case. With the aid of scissors (not shown) or the like, the strips 1, 2 can then be cut after the desired diameter of the carrier matrix IJ has been reached, the cut either perpendicular to the longitudinal axis or, as in connection with FIG. 2 explained, can be guided obliquely to the longitudinal axis. The tapes 1 and 2 are then wound up again accordingly on a next core J>. The carrier matrix 1J> is then introduced into a jacket 4 under prestress. A corresponding tensile stress is already applied to the tapes during winding in order to achieve the tightest possible winding.

The profile of the rollers in the corrugating machine 5 is preferably an involute toothing.

The height of the corrugation and the distance between the wave troughs, for example in the case of a carrier matrix according to FIG. 1 or 2 are chosen such that the width and height of the Individual honeycombs are smaller than 1.5 millimeters. The intermediate strip and the corrugated strip 2 preferably have a smaller wall thickness than 0.1 millimeters.

The invention is not restricted to the exemplary embodiments shown. It is possible, for example, instead the webs 21 also a suitable wire mesh

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use. The bands 1 and 2 can be soldered or welded to one another at points or as a whole. The support matrices IJ> can be fastened in their associated sheaths by screws or by soldering or also by welding.

The invention thus also includes all specialist modifications and all partial and sub-combinations of features and measures described or illustrated.

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Claims (1)

l \. 23-2746 Expectations Carrier matrix for a catalytic reactor for exhaust gas purification in internal combustion engines, especially gasoline engines of motor vehicles, characterized in that it is made of high temperature resistant steel and that it is formed from corrugated and smooth sheet steel, which are arranged alternately and coated with catalyst material. 2. Support matrix according to claim 1, characterized in that the steel is catalytically inactive. 3. Carrier matrix according to claim 1 or claim 2, characterized in that the width and height of the individual honeycombs are less than 1.5 millimeters. 4. carrier matrix according to claim 1 or the following, characterized in that the wall thickness of the carrier plates is less than 0.1 millimeters. 5. carrier matrix according to claim 1 or 2, 3 or 4, characterized in that the profile of the corrugation of the corrugated part of the matrix sprihht an involute toothing. 6. Carrier matrix according to one or more of claims 1 to 5, characterized in that the steel sheets are plate-shaped and stacked alternately on top of one another. 7. carrier mat according to one or more of claims 1 to 5, characterized in that the carriers consist of tapes which are spirally wound into a cylinder. - 2 - 403830/0575 230274S 8. carrier matrix according to one or more of claims 1 to 7> characterized in that the steel sheets prior to stacking or winding with a catalytically active metal z. B. copper and 'or nickel are coated and then oxidized. 9. Support matrix according to one or more of claims 1 to 7i, characterized in that the steel sheets with a catalytically active metal oxide z. B. copper oxide, nickel oxide or the like. Are coated. 10. Carrier matrix according to claim 6 or 7 or the following, characterized in that the individual layers of the steel sheets are welded or soldered to one another at points. 11. Support matrix according to claim 1 or the following, characterized in that the steel sheets are welded or soldered to one another as a whole. 12. Support matrix according to one or more of claims 1 to 9, characterized in that the smooth and the corrugated steel sheets are arranged in a steel jacket under prestress. IJi. Carrier matrix according to claim 12, characterized in that the jacket is conical. 14. Carrier matrix according to claim 12, characterized by an insertion cone as an assembly aid. 15 · Carrier matrix according to claim 12, characterized in that the outer end of the tape is cut obliquely to the longitudinal axis of the tape. 409830 / 0S7S 16. Carrier matrix according to claim 15, characterized in that the length of the beveled end corresponds approximately to the circumference of the inside of the jacket. 17. Support matrix according to claim 12 or the following, characterized in that the sheets are metallically connected to the jacket. 18. Carrier matrix according to claim I7, characterized in that the connection is effected by screws. 19. Carrier matrix according to claim 17, characterized in that the sheets of the matrix are welded or soldered to the jacket. 20. Carrier matrix according to claim 7 or the following, characterized by holding means which fix the position of the matrix in the jacket and are arranged in front of the end face. 21. Carrier matrix according to claim 2o, characterized in that the holding means are formed avoiding crossing struts. 22. Carrier matrix according to claim 2o or 21, characterized in that the struts are designed and / or arranged to be elastically resilient. 25. Carrier matrix according to claim 2o, characterized by a grid as holding means. 24 »Catalytic reactor with a support matrix according to one or more of claims 1 to 2 ^ and a housing with Connections for exhaust gas inlet, exhaust gas outlet and any 409830/0575 ■ ^{> -} ίο Secondary air supply, characterized in that the carrier matrix is fastened with its jacket in a sealed manner in the housing by means of flange rings. 25. Reactor according to claim 24, characterized in that the flanges are U-shaped and are connected at their U-legs to the housing on the one hand and the jacket of the carrier matrix on the other hand. 26. Reactor according to claim 24, characterized in that the flanges are Z-shaped and that the exhaust gas inlet pipe and / or the exhaust gas outlet pipe is attached between the inner edge of the Z-profiles and the jacket of the carrier matrix. 27. Reactor according to claim 24, characterized in that a support matrix as a reduction catalyst and a second support matrix are arranged as an oxidation catalyst in a housing in a manner known per se and that the support matrix for the reduction catalyst and the support matrix for the oxidation catalyst are housed in a common jacket . 28. Reactor according to claim 27 , characterized in that spacer struts are arranged between the reduction catalyst and oxidation catalyst, and that the secondary air connection is connected to the jacket in the region of the spacer struts. 29. Reactor according to claim 24 or following, characterized in that at least the space between the outermost flange rings, housing and jacket is filled with insulating material. 40Ö830 / OS75 J) O. Process for producing a carrier matrix according to one or more of Claims 1 to 7, characterized in that two endless sheet steel belts are fed to a coating bath, that one of the belts is previously corrugated in a manner known per se, and that the smooth and the corrugated belt are spiral shaped or alternately arranged in flat layers one above the other and connected to one another. 31. The method according to claim J> o , characterized in that the continuous coating of the strips with the catalyst material takes place before stacking or rolling up to form the carrier matrix. J2. Method according to Claim Jo or J> 1, characterized in that the carrier matrix is pressed into a jacket with prestressing with the aid of a multi-jaw chuck. 409830/0675