DD155389A5 - CATALYTIC FILTER FOR DIESEL EXHAUST PURIFICATION - Google Patents

Abstract

1. A catalytic filter for the purification of diesel engine exhaust gas, consisting of layers which are arranged in a pile to produce a gas-permeable package, or are wound up spirally to produce a gas-permeable body, the package or the wound body being sealed at the opposite front faces by cover means so that a sealed front face section is opposite an open front face section, characterised in that the layers consist of temperature- and corrosionresistant metal, and either a) in each case one layer of a wavy or folded screen cloth alternates with in each case one flat, closed cover layer, or b) in each case one layer of a wavy or folded screen cloth alternates with in each case one flat perforated cover layer, or c) in each case one layer of a wavy or folded sheet alternates with in each case one flat perforated cover layer and the filter is coated with a catalysis-promoting metal oxide, with filling of the cross-sections of the openings defined according to a), b) and c), and the oxide layer is designed to be permeable to gas.

Description

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Siebgewebeanordnung

Field of application of the invention

The invention relates to a catalytic filter for diesel exhaust gas purification.

Characteristic of the known technical solutions

In the course of the shortage of world oil reserves, petroleum products and thus also fuels for internal combustion engines are becoming increasingly expensive. It is therefore desirable to constrict engines that have the lowest possible fuel consumption. An alternative solution to this problem is the diesel engine with at least about 5% higher efficiency than engines powered by gasoline. "Exceptions are so-called lean concepts for gasoline engines, but these are not yet fully developed.

With most diesel engines are without catalyst all z. Z. to comply with valid exhaust emission standards. However, this does not exclude that diesel engines often cause environmental pollution and that a percentage increase in the number of registrations can give rise to a real problem.

Diesel engines emit in addition to the also emitted by gasoline engines pollutants, such as CO, hydrocarbons and nitrogen oxides, due to their operation and soot particles or finest condensate droplets or a

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Conglomerate of "particulates". "These" particulates "are particularly rich in condensed polynuclear hydrocarbons, some of which have been recognized to be carcinogenic. Aldehydes also belong to the emitted substances and contribute to the odor nuisance of the environment.

In some countries, such as As in the US, is now intended to introduce limit values for pollutants and particulates in diesel exhaust, which can not be achieved by engine-side measures. With exhaust gas recirculation (EGR) may e.g. a reduction in the ITO emission is achieved, but at the same time leads to a disproportionate increase in particulates.

Other solutions for reducing pollutants from diesel engine exhaust gases suggest trapping particulate traps and condensate particles. However, since the temperatures of diesel exhaust gases are normally insufficient to burn off soot, since at least 450 ° C is necessary, an increase in the exhaust gas temperature must be used to regenerate the trap to prevent accumulation of soot and condensate and congestion. This can u. a, have happened so that the air / Kraft.st off mixture is periodically enriched and thereby result in higher exhaust gas temperatures. An enrichment of the air / fuel mixture is associated with additional fuel consumption and would partially offset an advantage of the diesel engine.

In addition, igniting an accumulation of -Kuß- and condensate particles to an uncontrolled, even explosive burning and thus the destruction of the trap or 'the whole

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Exhaust system lead, ^ i e contained in the diesel exhaust gas volatile hydrocarbons, carbon monoxide and odor-causing substances, such. For example, aldehydes can not be deposited by means of traps or the like. For their elimination, the catalytic reaction is required.

It would be possible, for the degradation of said pollutants, a catalyst, e.g. based on a monolithic ceramic amplifier body (US-PS 3,597,165) to use, but such arrangements are already after a short period of operation due to their relatively distant from the engine attachment gradually occupied by uB and thus often lose their activity quickly. The "pärticulates" but can pass through the channels of the amplifier without being degraded.

Other devices are used in addition to a catalyst with a filter for the separation of soot and condensate, the cleaning of this filter is done mechanically by shaking the particles (GB-PS.1 425 386). However, there still remains the problem that the particles are practically not reacted to a downstream catalyst.

Object of the invention

The aim of the invention is to avoid the disadvantages of the prior art.

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Presentation of the Invention

D _e r invention has for its object to provide a Siebgewebeanordnung of metal, which can be applied for purifying exhaust gas as a highly effective filter for the separation of the ^ uBteilchen from the exhaust of diesel engines and / or as carriers for catalysts, wherein the exhaust gas of the flow ^ö iebgewebeflachen is forced.

These Si _e bgewe "beanprdnung consists of temperature- and corrosion-resistant metal having alternately at least one layer of a corrugated or folded screen cloth or sheet and at least one flat, closed or perforated liner, said layers laminated to a gas permeable package or spiral oval into a cylindrical, , rectangular or polygonal gas permeable body are wound, and is characterized in that the package or the winding body is closed at the opposite end faces by covering means that a closed end face portion facing an open end face portion.

Here, the flat top layer a smooth S] _ _e ch or a metallic mesh. _; , ,

About one or the same geometric shape over several Siebgewebelagen can be pushed frontally adapted to their respective profile U-shaped enclosure, which is attached to it.

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To fix the Siebgewebeanordnung it has proven to be a good idea to weld the brackets punctiform or flat with the layers or to solder. A packing or winding produced alternately from at least one layer of a corrugated or folded screen fabric and at least one flat, closed or openwork cover layer is expediently welded or soldered on the end face for further mechanical consolidation.

The Siebgewebeanordnungen thus produced can be customary, eg by electroplating or impregnating with precious metal and / or base metal, occupied. But you can also be coated with a conventional support material for catalysts and. Solutions of active catalyst metals impregnable carrier matrix are processed. In this case, according to an embodiment of the invention, the individual layers on its surface with a catalysis-promoting support material, usually a metal oxide high surface area, such as active Al ₂ Oo, coated so far that a 'part of the opening cross-section of the perforated layers, ie the Siebgewebelagen preserved , The filter effect is set here via the mesh size.

Another embodiment with a particularly intensive filtering effect is characterized in that the Siebgewebeanordnung with a catalytic metal oxide under filling. the opening cross-section of the perforated layers is coated, wherein the oxide layer is gas-permeable. The filter effect is set here via the porosity of the oxide layer,.

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As a catalyst-promoting additives, the elements Ger, zirconium, iron, nickel, rare earths or a Korabination of these can be incorporated into this metal oxide. The carrier material intermediate layer is then provided by conventional methods with the actual catalyst.

The means used to cover the end faces is made of a temperature or corrosion resistant material. The covering means may consist of a ceramic mass, a welding or soldering application or of an abutting and / or fixed template, optionally as a part of the shell of the package or the winding encompassing shadow mask is formed.

As a covering means for the end face sections are particularly suitable plugs of a ceramic mass, which consists of talc and water glass. With this mass, the individual channels are so clogged on the Siebgewebeanordnungen described that abv / alternately a closed channel end is opposite to an open channel end, d. H. in the case of a spiral arrangement of the fabric layers, a closed end surface section is adjacent to two open end surface sections and vice versa.

The covering of the end surface portions may also be such that a fitting and / or attached to the end faces template is optionally formed as a part of the jacket of the package or the winding encompassing hole or slit mask, which ensures the closure of the respective channel ends.

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The mask can be designed so that it covers alternately sections in the width of twice the amplitude of the corrugation or convolution in a spiral wound and made exclusively of mesh fabric and leaves open, facing each other at opposite end faces open and closed sections. This ensures that exhaust gas entering an open end face section can not escape at the end face opposite this section but must pass through the gas-permeable partitions of the matrix.

The spiral-shaped opening segments can lead up to just around the circumference of a winding or a package, whereby it must be ensured that a corresponding overlap of the closed-surface portions is always given to prevent bypass action. Segment division of the spirally protected surfaces by odd numbers is also possible.

In a further embodiment of the invention, the end faces in the already described steps can be closed by welding or soldering.

The screen mesh used can be a web having a mesh size of 0.25 to 0.025 mm, preferably 0.1 to 0.05 mm and a thread thickness of 0.15 to 0.025 mm, preferably 0.1 to 0.05 mm, in particular 0.07 mm.

As closed cover layers find metal strips with a wall thickness below 0.15 mm use.

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The width and height of the cells enclosed by the alternately arranged smooth and corrugated or folded layers should not be less than 0.5 mm.

The corrugated layer can be shaped differently. It is favorable if it has a sinusoidal shape or the shape of an involute, or a rectangular or square shape.

The screen fabric arrangement used is particularly suitable for sheets and screen fabrics which consist of an alloy of iron, iron, aluminum and optionally cerium or yttrium and the usual alloying accompanying elements or other heat-resistant and scale-resistant materials.

The Siebgewebeanordnungen invention in package or winding form can be arranged for mechanical stabilization in a steel shell open at the front and firmly connected thereto by soldering or welding. Thermal insulation of the steel jacket with high-temperature insulating material may be advantageous,

Must the catalytic converter, ζ. B. for reasons of space, to be installed at locations of colder exhaust gas temperatures or should already during the cold start phase with. The Aiybau of soot and "particulates" are started, it may be advantageous for the jpiiterkatalysator power supply to install permanent or periodic galvanic heating of the layers.

The Siebgewebeanordnung invention can in exhaust gas purification systems, especially for internal combustion engines, as

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Filters for dusts and / or aerosols and / or used as' i'rägermatrix for catalysts «, As a preferred application, the cleaning of exhaust gases from diesel engines is envisaged. Here, a filter catalyst in the exhaust manifold is placed directly on the engine block. Degradation of the oxidizable volatiles of the exhaust gas may be accomplished by providing a suitable catalytic coating in parallel thereto. However, it is also possible for an embodiment designed exclusively as a filter arrangement to be followed by a normal or inventive catalyst.

embodiment

The invention will be explained below with reference to various effective embodiments, which are illustrated in the drawing. In the drawing show:

Fig. 1: Basic and - ufriß a cylindrical bobbin, in which a sealed with stopper end face portion facing an open end face portion;

Fig. 2: two possible forms of Abdeckmasl ^ en, when a wound matrix except the outer sheath consists entirely of screen fabric, and the partial view of a section through such a winding cylinder;

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Pig. 3: various combinations of mesh or Blechj

Pig. 4 is a schematic representation of a Siebgewebeanordnung invention with power supply for galvanic heating of the layers.

Like from Pig. 1, an embodiment of the invention consists of spirally wound-up layers of smooth mesh or of smooth metal foil and corrugated mesh. The channels formed thereby are closed at one end face at 1 and open at the other end face at 2. The closure is a plug 3 made of ceramic material, consisting for example of a hardened talc / water glass mass. The exhaust gas 4 enters through the end face at the open channels of the filter, penetrates the porous side walls 5 and exits at the other end at the open sides of the channels again. For use in ^A exhaust systems of motor vehicles, the winding body is fitted in a metal casing 6 and thus firmly connected.

But as a covering means sum partial closing of face portions are also hole or slit masks as in Pig. 2 shown. Figures 2a and 2c illustrate alternative forms of a slit mask. With them, circular segments 7; 11 covered the end faces, while the uncovered segments 8; 10 are closed at the opposite end face. Pig. FIG. 2b shows a section through a cylindrical arrangement of woven fabrics, wherein the course of the exhaust gas flow 4 through the screen fabric layers 5 is shown schematically.

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The slot mask used for the cover can be designed as a cap 9 and firmly connected to the winding body by welding or soldering.

Like Pig. 3, there are various possible combinations of screen fabric 12 and sheet 13. Thus, the corrugated or folded layers of screen fabric and the cover layers may consist of smooth metal foil or the corrugated or folded: and the cover layers

Sieve fabric, but it is also possible to produce the corrugated or folded layers of sheet metal and to use as a cover layer a corresponding screen fabric.

As mentioned, it may be advantageous to pre-heat the filter catalyst before starting the engine via the ignition lock and time relay and thereby reduce the soot quantities and "particulates" that occur especially in the cold start phase of a diesel engine. Also, this can during normal operating phases, eg. B. too low exhaust gas temperature or excessive Rußansarnmlung on the filter and thereby caused increased pressure loss in the exhaust system, ·

In Pig,.-4 is shown schematically the possibility to electrically heat a ilterkatalysator invention with the help of a normal car battery. Thus, e.g. the circuit will automatically be turned on for 30 seconds, for example, during the power-up process. Subsequently, either a time relay or a differential pressure switch takes over. Control function over the current flow,

Claims (15)

1. Siebgewebeanordnung of temperature and corrosion-resistant metal from alternately at least one layer of a corrugated or folded screen fabric or sheet and at least one flat closed or openwork cover layer, the layers layered into a gas-permeable package or spiral to a cylindrical, oval, rectangular or polygonal gas-permeable body are wound, characterized in that the package or the winding body is closed at the opposite end faces so by covering that a closed end face portion facing an open end face portion. 2. Siebgewebeanordnung according to item 1, characterized in that the flat cover layer is a metal or a metallic mesh, 3. Siebgewebeanordnung according to item 1 or 2, characterized in that pushed over one or the same geometric shape over several Siebgewebelagen the front side adapted to their respective profile U-shaped enclosure and secured thereto. 4. Siebgewebeanordnung according to item 3, characterized in that the borders with the layers are punctiform or flat welded or soldered. 22g 20 f -1.3-20.11.1980 58 177/13 5. Siebgewebeanordnung according to the points 1 to 4, characterized in that the package or winding is welded or soldered frontally. 6. Siebgewebeanordnung according to the points 1 to 5> gekennr characterized characterized in that the package or the winding body is coated with a catalyst. 7. Siebgewebeanordnung according to the items 1 to 6, characterized in that the catalyst is applied to a catalytic metal oxide. 8. screen fabric arrangement according to the items 1 to 7, characterized in that it is coated with a catalyzing metal oxide so far that a 5 e part of the opening cross section of the perforated layers is maintained. 9 · Siebgewebeanordnung according to the points 1 to 7, characterized in that it is coated with a catalytic metal oxide promoting the opening cross-section of the perforated layers, wherein the'Oxidschicht is gas permeable · 10. Siebgewebeanordnung according to the points 1 to 9, characterized in that the covering means of teniperatur- or corrosion resistant material. 11. Siebgewebeanordnung according to item 10, characterized in that the covering means of a ceramic 58 177 13 ²²⁶² Ot -η- Mass, a welding or soldering application or an adjacent and / or fixed template, which is optionally formed as a part of the jacket of the package or the winding encompassing shadow mask consists. 12 »Siebgewebeanordnung according to the points 1 to 11, characterized in that the package or the windings a frontally open, optionally provided externally provided with a thermal insulation steel jacket and is firmly connected to this« -12- 20.11.1980 58 177/13 invention claim 13 · Siebgewebeanordnung according to item 12, characterized in that the package or the winding is soldered or welded to the steel jacket. 14 · Siebgewebeanordnung according to the points 1 to 13, characterized in that the package or the Y / icklung is provided with power supply lines for galvanic heating of the layers. 15 · Siebgewebeanordnung according to the preceding claims, characterized in that it is used in exhaust gas purification systems, in particular for internal combustion engines, as a filter for dusts and / or aerosols and / or as a support matrix for catalysts. See 3 .. pages drawings