EP0258813A1 - Catalytic granule converter - Google Patents

Abstract

Bulk catalyst for cleaning exhaust gases from an internal combustion engine, which is arranged in the exhaust pipe and consists of a cylindrical housing (25) in which the catalyst bed (26) is enclosed by radially arranged sieve plates (31, 32), one of which (32) is axially displaceable by the action of an armature (34) made of ferromagnetic material and a magnet arrangement (20) provided outside the exhaust gas flow.

Description

The invention relates to a bulk catalyst for cleaning exhaust gases of an internal combustion engine which is arranged in the exhaust pipe and has a catalyst bed enclosed by a cylindrical wall of a housing and by sieve plates arranged radially therewith, a sieve plate being axially displaceable to compensate for the operational shrinkage of the granular catalyst material .

The problem with such catalysts is to offer the largest possible reaction surface in the smallest space with the lowest possible flow resistance, the reaction surface being understood to mean the catalytically active surface. The flow resistance is critical in the case of porous solid catalysts and in the case of honeycomb arrangements in the case of favorable flow conditions however, the reaction surface is limited. In bulk catalysts, depending on the grain size of the granular catalytic material, a favorable ratio between the reaction surface offered and the flow resistance can be achieved in the smallest space, especially if the internal reaction surface of the grains is large. This is particularly the case with zeolitic material. Granular catalytic material has the disadvantage, however, that it is consumed during operation under the action of the pulsations of the exhaust gases of the internal combustion engine due to mutual abrasion of the grains, so that until the catalytic effect is exhausted, this material wears considerably, with the greater degrees of freedom of the individual which then arise Grains this effect is increasingly intensified. Unless the abrasion is blown out by the flow of the medium to be cleaned, the reaction surfaces, in particular the inner surfaces of the catalytic packing, become clogged and thus the catalytic performance is reduced. The vibrations generated by the exhaust impacts of the internal combustion engine are significantly increased in land vehicles by the vibrations caused by driving. An attempt was therefore made to compensate for the shrinkage of the bulk goods package by pressing one of the radial sieve plates of the catalyst bed elastically and thus to keep the catalyst grains always in contact with one another in order to prevent the relative movements of the grains with one another. DE-OS 17 67 532 shows an example of a catalytic packing made of granular material, in which the shrinkage of the catalyst material is not taken into account spatially.

DE-PS 644 734 has already attempted to achieve constant filling of the catalyst bed by spring pressure on a refill container for the granular catalytic material. Although this has the advantage that the spring exerting pressure on the catalyst pack is somewhat outside the heat range of the actual catalyst, such a device is unsuitable for vehicles solely for reasons of space and the pressure exerted can only be used for refilling, but not for producing one constant close contact between the grains is sufficient.

DE-OS 22 42 888 describes a spring arrangement which is arranged outside the actual catalytic converter and acts axially on the sieve plates delimiting the catalytic bed. Although this allows the spring to be moved out of the hot area of the catalytic converter, this requires a radial supply and removal of the hot medium to be cleaned. In addition, bushings for the linkage transmitting the contact pressure with the seals exposed to the thermal load are necessary in order to exclude secondary air. In addition, the heat conduction via the linkage will shortly reach the contact springs with reasonable room dimensions of such a system. Just because of this Given the spatial conditions proposed, such an arrangement for vehicles is virtually impossible.

DE-OS 23 10 843 describes another such spring-operated system in which the sieve plates, which are axially displaceable on both sides, are pressed against the catalyst packing by a tension spring arranged in the axial center of the catalyst bed. This avoids the need for spring rods to penetrate the housing walls. However, this tension spring is fully exposed to the heat of the exhaust gas flow, which is increased in the catalytic converter by the consumption of the flow energies, so that even at a greater distance from the internal combustion engine and the cooling of the exhaust gases that can be achieved thereby, temperatures above 800 ° C. must be expected. In any case, the spring material cannot withstand such thermal exposure in the long run and such catalysts have therefore not proven themselves in operation.

The object of the invention is therefore a device that receive the catalyst packing made of granular material in the catalyst bed regardless of the resulting heat load and without openings in the walls of the housing for rods in continuous operation in accordance with the increasing shrinkage of the catalyst material in constant close contact of the grains of the catalyst material can. The task is also one such an arrangement, which can be used in motor vehicles, ie that withstands the shaking loads of the driving operation and has a spatial extent that allows mounting on the underside of the motor vehicle.

This object is achieved in bulk catalysts of the type described in the introduction with the arrangements characterized in the claims.

The arrangement of permanent magnets on the outside of the catalyst, in particular the outside of the housing for the catalyst bed, makes it possible to exert the necessary contact pressure on the movable sieve plate without mechanical passages in the housing wall, and all the dangers of accessing secondary air or the failure of seals on the bushings to avoid for spring rods.

The magnetic properties of both the magnets and the armature material are not canceled or reduced by the thermal load. Magnetic material is available under economic conditions, which can be exposed to temperatures significantly above 1000 ° C without significant reductions in its magnetic properties for the present purpose, as is not possible with contact springs.

The catalyst bed of the proposed arrangements, if zeolitic catalytic material is used, can be proportionate in its axial extent be kept briefly at radial expansions acceptable for motor vehicle conditions, so that the flow resistance remains as small as possible. Replacing the used catalyst pack is possible without difficulty by removing the outlet pipe and the stationary sieve plate, so that it is not necessary to replace the entire catalyst if its catalytic action fails. The granular catalytic material can be inserted into prefabricated packs or cartridges.

• Fig. 1 einen schematischen Axialschnitt durch den erfindungsgemäßen Katalysator
• Fig. 2 einen teilweisen Axialschnitt durch einen erfindungsgemäßen Katalysator
• Fig. 3 eine Draufsicht auf den Katalysator gemäß Figur 2 in Strömungsrichtung
• Fig. 4 einen Radialschnitt durch den Katalysator gemäß Figur 2 in Ebene IV - IV
• Fig. 5 eine Draufsicht auf den Katalysator gemäß Figur 2 entgegen der Strömungsrichtung.

Embodiments of the invention are described below with reference to the drawings. Show it

• Fig. 1 shows a schematic axial section through the catalyst according to the invention
• Fig. 2 shows a partial axial section through a catalyst according to the invention
• 3 shows a plan view of the catalytic converter according to FIG. 2 in the flow direction
• 4 shows a radial section through the catalyst according to FIG. 2 in plane IV-IV
• 5 shows a top view of the catalytic converter according to FIG. 2 against the flow direction.

In the catalytic converter shown in FIG. 1, between the inlet pipe 1 for the uncleaned exhaust gases connected to the exhaust pipe of the internal combustion engine, which is not shown, and the outlet pipe 2 for the cleaned exhaust gases, an expanded, cylindrical, coaxial housing made of non-magnetic material is provided with the catalyst bed 4 filled with granular catalyst material. This is closed on the outlet side by the screen plate welded to its periphery on the inside of the housing in the form of a perforated plate 5. On the inlet side, an axially displaceable sieve plate in the form of a perforated plate 6 is arranged, which is connected to a ring armature 7 made of ferromagnetic material, which is provided on its circumference in the drawing above this perforated plate 6 and is axially displaceable on the inner wall of the housing 3 in the axial direction. This ring armature 7 can have the shape of a hollow cylinder or, as shown in the drawing, can be connected for its guidance to a cylindrical carriage 8 made of ferromagnetic sheet metal sliding on the inner wall of the housing 3. This perforated plate 6 closes off the catalyst bed on the inlet side.

In the area of the ring armature 7, a plurality of rod-shaped permanent magnets 9 are arranged on the outside of the housing 3. These are held axially by rings 10 and 11 of ferromagnetic material lying around the housing 3, which form right-angled triangles in axial section, which have a cathode on the housing 3, with them the other catheter under pressure exerted by the legs of a clamping ring 12 against the end faces of the permanent magnets 9.

The action of the magnets 9 causes the ring armature 7 and thus the perforated plate 6 to be displaced in the direction of the outlet side, the gas pressure of the incoming exhaust gas participating.

The rings 10 and 11 have the primary task of transmitting the magnetic field forces to the ring armature 9 or the slide 8 forming a magnetic unit with it and thereby magnetically bridging the gap between the permanent magnets 9 and the housing 3.

The permanent magnets 9 are provided at a height of the housing 3 which corresponds to the end position of the perforated plate 6 when the catalytic granulate in the catalyst bed 4 is used up. By moving the permanent magnets downwards, which is possible by opening the clamping ring 12, the magnetic forces acting on the perforated plate 6 can be increased.

In the embodiment shown in FIGS. 2 to 5, the permanent magnets 20 are arranged in the region of the inlet tube 21 on a jacket 23 placed around it and welded to it with an annular cover disk 22, which, after a conical widening 24, encloses the housing 25 for the catalyst bed 26 forms. At the left end of the housing 25, a flange 27 is provided, which is screwed to a flange 28 of a conical extension 29 of the outlet pipe 30. The catalyst bed 26 is closed on the outlet side by a sieve plate in the form of a perforated plate 31, on the inlet side by a sieve plate in the form of the perforated plate 32. Both perforated plates 31 and 32 are loose and axially displaceable, but their circumference lies closely against the inside of the housing 25. The sieve plate 31 can be removed after unscrewing the outlet pipe 30 on the flanges 27 and 28 for filling or refilling the catalyst bed 26. It is secured in its position as the end of the filled catalyst bed 26 by a spacer 33 which is supported on the conical extension 29 of the outlet pipe 30. Between the inlet pipe 21, which ends in front of the catalyst bed 26, and the casing 23, the hollow cylindrical ring anchor 34 is arranged on the inner wall of the casing 23 in a sliding and axially displaceable manner. Fifteen rod-shaped permanent magnets 20 are provided on the outside of the jacket 23, which is made of non-magnetic material. These permanent magnets 20 are inserted with their end faces on the outlet side in bores in a ring 35 placed around and axially displaceable on this ring 35, with their inlet end faces in bores of a similar ring 36. Both rings 35 and 36 are made of ferromagnetic material and are used simultaneously for Introduction of the magnetic forces on the ring armature 34. The inlet-side rings 36 have a cuff-shaped Extension 37 with which it can be fixed on the jacket 23 by means of clamping screws 38. Between the magnets 20 axially directed clamping screws 39 are provided, which are screwed through arm-shaped flanges 39 of the cover plate 22 into the displaceable ring 35 and press it against the permanent magnets and the fixed ring 36.

The ring armature 34 is supported on the outlet side at 40 against a tube 41, which in turn widens conically within the conical extension 24 of the jacket 23, and which lies with its outlet-side edge 42 against the edge of the perforated plate 31 and this under the action of the permanent magnets 20 against the pack of Catalyst bed 26 presses. By moving the ring 37 after loosening the clamping screws 39, the axial position of the magnets can be changed with the corresponding adjustment of the clamping screws 39, and the effect of the magnets 20 can thus be adjusted.

List of reference symbols Figure 1

• 1 feed pipe
• 2 outlet pipe
• 3 housing
• 4 catalyst bed
• 5 lower perforated plate
• 6 movable perforated plate
• 7 ring anchors
• 8 sledges
• 9 permanent magnets
• 10.11 rings
• 12 tension ring

Figure 2 to 5

• 20 permanent magnets
• 21 inlet pipe
• 22 annular cover plate
• 23 coat
• 24 conical extension
• 25 housing
• 26 catalyst bed
• 27.28 flanges
• 29 conical extension
• 30 outlet pipe
• 31 perforated plate on the outlet side
• 32 perforated plate on the inlet side
• 33 spacers
• 34 ring anchors
• 35 sliding ring
• 36 fixed ring
• 37 cuff-shaped extension
• 38 clamping screws
• 39 arms on 22
• 40 starting point
• 41 pipe
• 42 outlet-side edge of 41

Claims (10)

1. bulk catalyst for cleaning exhaust gases of an internal combustion engine which is arranged in its exhaust pipe and has a catalyst bed enclosed by a cylindrical wall of a housing and by sieve plates arranged radially to the latter, a sieve plate being axially displaceable to compensate for the operational shrinkage of the granular catalyst material,
characterized in that the movable sieve plate (6, 32) lying in the inflow direction is pressed against the filling of the catalyst bed (4, 26) by the armature (7, 34) of a magnet arrangement (9, 20) arranged on the outside of the catalyst. 2. bulk catalyst according to claim 1,
characterized in that the anchor is a ring anchor (7) which rests on the edge of the movable screen plate (6). 3. bulk catalyst according to claim 1, 2,
characterized in that the ring anchor (7) is attached to a slide (8) made of ferromagnetic material sliding on the inner wall of the catalyst housing (3). 4. bulk catalyst according to claim 1, 2,
characterized in that the ring maker (7, 34) is a hollow cylinder. 5. bulk catalyst according to claim 1, 4,
characterized in that the hollow cylindrical ring anchor (34) is arranged between the inlet pipe (21) for the exhaust gases to be cleaned and a jacket (23) lying around this inlet pipe (21). 6. bulk catalyst according to claim 1, 2, 3, 4, 5,
characterized in that the magnets (9, 20) are permanent magnets. 7. bulk catalyst according to claim 1, 2, 3, 4, 5, 6, 7,
characterized in that the magnet arrangement (9, 20) consists of a plurality of bar magnets which are arranged axially directed around the housing (3) or the casing (23). 8. bulk catalyst according to claim 1, 7,
characterized in that the end faces of the magnets (9, 20) lie on rings which lie around the housing (3) or the casing (23) and are made of ferromagnetic steel. 9. bulk catalyst according to claim 1,
characterized in that the housing (3) and the casing (23) consist of non-magnetic material. 10. bulk catalyst according to claim 1, 4, 5,
characterized in that the magnet arrangement (20) and the ring armature (34) are arranged in the flow direction of the exhaust gases to be cleaned before the expansion (24) of the housing (25) of the catalyst bed (26) and in that between the ring armature (34) and the inlet side axially displaceable sieve plate (32), a funnel-shaped tube (41) is provided for transmitting the contact pressure to the edge of the sieve plate (32).

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