DE4125686C2 - Exhaust gas filters for fuel engines and manufacturing methods - Google Patents

Description

The invention relates to an exhaust gas filter for fuel engines according to the preamble of claim 1 and a process for its manufacture.

Filters for fuel engines are used for reduction the environmental pollution caused by the combustion exhaust gases puts. There are different requirements put the filter that partially contradict each other.

On the one hand, the filter should be used especially when Diesel engines have the most efficient filtering possible ensure the soot particles from the combustion gases.

On the other hand, the filter should be as permeable as possible be because of an increased exhaust back pressure the efficiency of the diesel engine is reduced, which in turn ne has a negative impact on the environment.

DE 38 23 205 filter candles with a Keramikfa serschicht described, which, however, by the soot dense, especially in full load operation, and thus to a reduction in permeability or to a Contributes to increasing the exhaust gas back pressure.

Furthermore, dimensionally stable filters, e.g. B. foam ceramic fil ter, known from DE 35 41 444, in which no Ver sealing of the filter material with a high soot load occurs, which in turn is very sensitive to ther mixing and mechanical influences. Furthermore, one  Adaptation of such filter structures to individual for very expensive for different vehicle models.

DE 35 45 762 A1 describes an exhaust gas filter with a alternating arrangement of a ceramic fiber mat and a metal mesh mat known. Fiber mat and metal knitted mat, which is rolled up tightly on top of each other and under radial tension in a cylindrical housing are concentric to the housing axis arranged. The exhaust gas flow essentially becomes guided parallel to the housing axis and penetrates the Fiber mat metal knitted roll covering the entire case can fill or formed as a hollow cylinder is, in the longitudinal direction.

This exhaust filter is also variable, the respective one Shape adapted to requirements only very limited possible.

It is an object of the invention to provide an efficient to create the most permeable filter possible has good dimensional stability, largely against thermal and is insensitive to mechanical influences and can be inexpensively manufactured in various forms.

The object is achieved by the characterizing Features of claim 1 and by a method according to claim 11 solved. Advantageous developments of the invention are the subject of the subclaims.

The advantage of the invention is in a compo Sitfilter made from an alternating filter layer made of a fiber material and a metal structure the mechanical stability the filter system by a defined composition and Training without increasing the thermal shock  The sensitivity of this situation increases. The increase continues the dimensional stability by a special simple process realized for the production of the filter layer, wherein the filter layer resiliently adapts to different filter shapes can be adjusted.

According to the filter effect and the support we in the filter layer of different materials perceived, the filter layer being made of a fiber material with a high specific surface, which but does not need to have a supporting function with fiber like support elements is interspersed, as a support material act and are statistically distributed. This Support material has no filter effect, but should only lead to the dimensional stability of the fil remains intact and no compression of the filter layer, especially with higher soot loading. The The filter therefore remains permeable  even with a stronger soot load in full load operation of the Diesel engine guaranteed.

Ceramic fibers can preferably be used as the fiber material of the filter layers Fiber materials, especially zeolites with a very high use specific surface. These fiber materials represent a very large attachment area for soot particles available and are also thermally resistant, so that the catalytic burnout to oxidize Survive the soot particles without damage. Particularly advantageous the zeolite forms natrolite, mesolite and murders are important not. A filter layer made of this fiber material and mixed, statistically distributed, fibrous support elements preferably has a thickness of 1 to 5 mm and a width of 20 to 100 mm. This filter layer will with a gas permeable metal structure, e.g. B. a me tallgewebe, a perforated sheet, an expanded metal or a Sieve connected, the flat metal structure, for example, a thickness from 0.03 to 0.5 mm and a width from 40 to 220 mm points. The filter layer is inserted into this metal structure beat so that you get a composite composite that is very easy to filter with different shapes, e.g. B. round, oval or conical cylinders.

The support elements are preferably made of metal fibers det, which is statistical and homogeneous in a cost-effective manner be mixed into the fiber material of the filter layers. This metal fibers give the filter layers the necessary stability, to counteract their compression.

Preferably the fiber material and / or the support element elements with catalytically active substances on the base be impregnated with precious and / or base metals, around the Exhaust filters operate at a lower load level can. The soot particles are oxidized here even at lower temperatures, making it too strong Clogging of the filter is prevented.  

An additional emission-reducing effect is achieved if an oxidation catalytic converter is installed in front of the exhaust gas filter which is by pre-oxidation of gaseous hydrocarbons material connections with that which is sufficiently present in the exhaust gas Oxygen raises the exhaust gas temperature and thus a Bela dungs / regeneration equilibrium in the soot filter at low according to the back pressure level and thus an economical engine drive enabled.

Oxidation catalysis can also be carried out downstream of the exhaust gas filter sator be attached, which pass through the exhaust filter the gaseous hydrocarbon is oxidized and thus too converts environmentally friendly connections. The cat gate can therefore be arranged before and / or after the exhaust gas filter his.

The exhaust gas filter according to the invention enables filter efficiencies from approx. 95% for particle sizes down to 0.1 µm. The Temperature resistance is given up to 1000 ° C, whereby the exhaust filter has a high resistance to thermal shock and aggressive media. The exhaust filter has a high through casualness and enables easy regeneration, d. H. Oxidation of the accumulated soot particles.

The filter layers of the exhaust filter are only very shallow, thus only a correspondingly low particle load locally occurs. That is why the loosely laid is condensed with fibrous Support elements penetrated Fiber material of the filter layers hardly and an increase in the exhaust Back pressure is largely avoided. Through a sandwich construction multi-stage filtering can still be achieved.

Because the filter belt for different filter shapes can be used is a reduction in effort possible for storage.  

The one used for the filter layers Fiber material with the fibrous or ribbon-like Structure should have a pore volume of 40 to 80%. The fiber material should form one with the support bodies or support elements homogeneous mixture to be mixed to a large extent Uniform filter and support function over the entire Filter position remains guaranteed.

The molecular material makes it suitable as a fiber material Structure, its associated catalytic activity and its large specific surface and with it associated properties that lower the ignition temperature

Natrolite Na₁₆ (AlO₂) ₁₆ (SiO₂) ₂₄ × 16 H₂O,
Mordenite Na₈ (AlO₂) ₈ (SiO₂) ₄₀ × 24 H₂O or
Mesolite Na₂Ca₂ (Al₂SO₃O₁₀) ₃ × 8 H₂O

in fibrous training.

These fibers increase in addition to the egg mentioned above properties the temperature in the exhaust gas filter through the Adsorption of water vapor from the exhaust gas in the hydrophilic Cavity of their molecular structure and thus enable the better regeneration of the soot load. The adsorbed what This is achieved by regeneration of the zeolites at temperatures expelled again above 300 ° C.

The production of an exhaust gas or soot filter is simple possible if the components of the filter layer, d. H. the fiber mat rial and the fibrous support elements together with a binder be mixed in an immersion bath. By introducing a finely perforated support tube in the immersion bath becomes liquid aspirated so that the fibers and the fibrous support elements around attach the support tube. Then the support tube is dried net. This creates a flexible, gas-permeable tall body. With this manufacturing process is a völ lig free shaping of the soot filter possible.  

The support elements can be made of modified fibers Glass, machined or atomized steel alloy or made of atomize ceramic fibers with a diameter of 6 to 15 µm his. These fibers ensure, among other things a very good shape due to its high elasticity resistance of the filter layer.

The invention is described below, for example, in the schematic drawing described. In this shows:

Fig. 1 shows a longitudinal section through a cylindrical gas filter;

FIG. 2 shows a cross section II-II from FIG. 1;

Fig. 3 shows a longitudinal section through a wound ker zeniform exhaust filter and

FIGS. 4a and 4b show two embodiments of a cartridge filter produced by dipping and

Fig. 4c shows a cross section CC of Fig. 4b.

Figs. 1 and 2 show a cylindrical wound filter as an exhaust gas filter 10 machine for the exhaust gases of a diesel powered Verbrennungskraftma. The exhaust gas filter 10 consists of a gas-permeable metal outer cylinder 12 in which a composite structure of the filter layer 14 and a flat metal structure 16 are wound into a hollow cylindrical filter body. The hollow cylinder is in turn closed off by a gas-permeable metal cylinder 18 . This hollow cylindrical filter body is arranged in a filter housing in such a way that the exhaust gas flow A flows in on an end face of the inner cylinder 18, flows through the layers 14 , 16 and the outer cylinder 12 according to the arrows B from FIG. 1. To achieve this flow pattern, an end face 20 of the inner cylinder 18 is closed by a cover plate 20 . The filter layer 14 is formed from a ceramic fiber material which is interspersed with thicker fibrous support elements made of metal, glass or ceramic. The dimensional stability of the filter layer 14 is ensured by these supporting fibers. The metal structure 16 is formed by a 0.2 mm thick metal mesh. The filter 10 is very insensitive to mechanical and chemical stress and also allows regeneration at burn-out temperatures up to 1000 ° C. A further embodiment of an exhaust gas filter is shown in FIG. 3.

This exhaust gas filter 30 consists of a support body 31 , on which a composite composite of a filter layer 32 and a metal fabric layer 34 is wound. The layers 32, 34 who moved axially during the winding, so that there is always a maximum of three Kompositlagen 32 come to lie, 34 to each other. Such an exhaust filter has a very low exhaust back pressure and can be easily integrated into smaller diameter exhaust pipes.

FIGS. 4a to 4c show a Herge the dipping method presented candle filter as an exhaust gas filter 40 in a stretched and curved design. Since the exhaust gas filters 40 differ only in their shape, identical parts of these filters are subsequently provided with identical reference numerals.

The exhaust gas filters 40 have a conical, dimensionally stable and gas-impermeable filter body 42 . This is immersed in an immersion bath containing ceramic fiber material, metallic support fibers and a binder. The fibers attach to the filter body 42 and form a filter layer 44 when they are dried after being removed from the immersion bath. To increase the stability, a thin, gas-permeable metal structure 46 is applied to this filter layer 44 and again immersed in the immersion bath. This process is repeated three times, so that three fiber layers 44 are formed on the filter body 42 , which alternate with three layers of the metal structures 46 . The gas inlet opening 48 is located on the larger diameter end face of the cone. The filter body 42 with the Fil terlagen 44 and metal structure layers 46 is installed in a metal housing 50 so that the exhaust gas flow from the inside of the filter body is passed 42 through the filter layers 44 and metal structure layers 46 a arranged at the outside of the filter body 42 gas outlet opening 52nd

The advantage of this immersion process for the production of exhaust gas filters is that any filter shapes can be implemented without technical difficulties. It should also be noted here that the candle filter 40 shown allows accommodation in exhaust pipes with a small diameter, with the possibility of the production of curved filters also an accommodation under spatially confined conditions in a motor vehicle is possible.

Claims (11)

1. Exhaust filter for in particular diesel-powered fuel engines with alternating arrangement of at least one filter layer made of a fiber material and at least one layer of a planar, porous metal structure, characterized in that the fiber material of the filter layers ( 14, 32, 44 ) is interspersed with fibrous support elements, which the Fiber material of the filter layers ( 14, 32, 44 ) are mixed and are statistically distributed in the fiber material. 2. Exhaust filter according to claim 1, characterized, that the support elements consist of metal, glass or ceramic. 3. Exhaust filter according to one of the preceding claims, characterized in that the fiber material of the filter layers ( 14, 32, 44 ) is formed from ceramic fibers. 4. Exhaust filter according to claim 3, characterized in that the fiber material of the filter layers ( 14, 32, 44 ) consists of zeolites, in particular natrolite, mesolite or mordenite. 5. Exhaust filter according to one of the preceding claims, characterized in that the fiber material of the filter layers ( 14, 32, 44 ) is provided with a binder. 6. Exhaust filter according to one of the preceding claims, characterized in that the filter layer ( 44 ) is attached to the metal structure ( 46 ). 7. Exhaust filter according to one of the preceding claims, characterized in that the fiber material and / or the support elements of the filter layers ( 14, 32, 44 ) are coated catalytically effectively on the basis of precious or base metals. 8. Exhaust filter according to one of the preceding claims, characterized in that the filter layers ( 32 ) and the metal structure ( 34 ) are spirally wound in several layers on a load-bearing, gas-permeable support body ( 31 ). 9. Exhaust filter according to one of the preceding claims, characterized in that the filter layers ( 32 ) and the layers of the metal structure are superimposed as a folded stack and bent at an acute angle in the middle and form the shape of a pocket. 10. Exhaust filter according to one of the preceding claims, characterized in that the fiber material of the filter layers ( 14, 32, 44 ) is designed in the manner of a fleece. 11. A method suitable for producing an exhaust gas filter according to claim 1, characterized in that fiber material and support elements for a filter layer are homogeneously distributed in an immersion bath provided with a binder and that a filter body ( 42 ) made of a porous metal structure coated with the filter layer in the immersion process becomes.