DE4012719A1 - Engine esp. diesel engine exhaust gas purificn. by complete filtration - with gas permeable filter of refractory fibres to remove solid particles, e.g. soot - Google Patents

Abstract

Elimination of harmful constituent from engine exhaust gas, esp. from diesel engines, involves passing the gas through a gas-permeable filter consisting (partly) of fibres withstanding high temp. These fibres contain metal oxide(s) and/or metalloid oxide(s) and opt. binder, additives, support and catalyst for oxidn. of combustible particles, esp. soot, hydrocarbons and/or CO and/or reducing NOx. The gas is passed into chamber(s) of a filter having inner filter(s) surrounded by an outer filter; this chamber is closed on the outlet side; the filtered gas is delivered from chamber(s) closed on the inlet side; and the filter has a density of 0.03-1.5, pref. 0.06-1, esp. 0.06-0.5 g/cc. The gas is pref. through a filter surrounded by a support suited to the gas flow. A gas-permeable cloth- or mat-type sheath. The filter fibres consist (mainly) of Al2O3, SiO2 and metal(loid) oxide(s), pref. ZrO2 and/or TiO2 fibres, is used on the outlet side. When the filter is laden with combustible particles, a heater, pref. a burner, is switched on, to burn these. ADVANTAGE - The process is highly effective and very economical. The construction of the filter ensures that all the gas passes through it.

Description

The present invention relates to a method and a device for Elimination of harmful components from exhaust gases of internal combustion engines, in particular of diesel engines in which the exhaust gases through a filter assembly be guided, which consists of at least one inner and one outer Filter consists, wherein the filter material at least partially made of thermal consists of highly resilient fibers containing at least one metal oxide and / or Semi-metal oxide included.

The increasing environmental awareness has long been such. For example, in the United States of America since 1978, catalytic converters have been mandated for cars with petrol engines to minimize emissions of hydrocarbons, carbon monoxide, and NO _x in the exhaust gases.

Diesel vehicles have come under criticism only for a few years, after the suspicion was expressed that contained in the exhaust of these vehicles Soot particles may be carcinogenic.

Numerous vehicle manufacturers and other professionals have therefore during In recent years, there has been a great deal of possible solutions, the issue To avoid or at least largely avoid soot particles.

Although as a consequence numerous patent applications in this field are known no solution has been found to date that is secure and, above all, for diesel car driver economically portable way the soot emission completely or almost completely prevented.

There are also very many patent applications and patents known which relate to catalysts and devices for the reduction of NO _x , oxidation of hydrocarbons and carbon monoxide.

Only part of the state of the art can therefore be found in the following section  be quoted.

A catalyst that only affects the oxidation of CO and hydrocarbons, is disclosed in DE-OS 21 55 338. He can be lanthanum and rare Earth, strontium, barium, nickel, cobalt, iron, zinc, copper, ruthenium, Osmium, titanium, molybdenum, tungsten, niobium, manganese, vanadium, tantalum and the like. a. contain.

DE-OS 23 03 695 discloses an oxidation catalyst containing manganese oxide and platinum and / or palladium. Catalysts which serve only for the reduction of NO _x , are disclosed in DE-OS 21 33 271. They consist of manganese oxide, palladium and iron oxide or nickel, cobalt, copper, zinc or cerium oxide on a calcined alumina support. Also DE-OS 21 40 852 discloses a reduction catalyst consisting of palladium and rhodium on a annealed carrier.

DE-OS 21 58 877 discloses a two-bed system consisting of a reduction and an oxidation bed. Reduction catalysts are rhodium, iridium or palladium. The reduction catalyst in DE-OS 23 55 418 is nickel-copper. A catalyst for the simultaneous removal of NO _x , hydrocarbons and carbon monoxide is disclosed in DE-OS 29 28 249. A catalyst comprising cerium, lanthanum, rhodium, platinum, palladium and phosphorus on a refractory inorganic support is used.

According to DE-OS 23 06 395 and DE-OS 24 16 753, such a catalyst from a metal from the group ruthenium, rhodium, palladium and platinum and a metal from the group aluminum, titanium, chromium, manganese, cobalt, Nickel. Carrier is a shock-resistant, weakly porous, ceramic material. The disclosed in DE-OS 26 02 286 catalyst allows the simultaneous reduction and oxidation of pollutants. The active metals are palladium, platinum, ceria, zirconia and nickel oxide. Carrier is Silica and / or alumina.

DE-OS 3 22 23 500 discloses a catalyst consisting of palladium, rhodium, Ceria and iron oxide on alumina as a carrier. After all  DE-OS 33 25 292 discloses a catalyst of iron, nickel and Cobalt on ceramics of alumina or titania. Patent applications and Publications concerning the removal of soot are to be described in US Pat briefly describe the following section. Only in a few cases will according to this prior art in the soot combustion with an oxidation Catalyst worked.

In DE-OS 25 19 609 a device for separating soot is described, in which a folded filter is described, in which at several Make initial igniter and temperature sensor are located. By differential pressure measurement in front of and behind the filter, the ignition is at a certain point set in motion, so that the soot burns in this area. As it is The materials used here are of limited scope thermal load capacity (page 8, paragraph 2) is determined by the above Temperature sensor opens a bypass when a certain temperature is reached, so that a portion of the exhaust gas flows unfiltered.

In DE-OS 30 17 784 a soot filter made of porous ceramic is described, in which a heating coil is inserted, which is in communication with the filter stands. The filter is tubular, with the unpurified exhaust gas inside the tube is passed, in which there is a helical baffle, so that the soot due to its higher specific gravity by Centrifugal force is deposited on the inner wall of the filter.

DE-OS 30 24 539 discloses a device for removing soot from Exhaust gases, which consists essentially of a filter, according to the stated Example consists of SiO₂ fibers. The burning off of the deposited soot is done by microwaves, with wall elements arranged on the clean gas side of the filter are impermeable to microwaves.

From the same applicant in DE-OS 31 11 228 a soot filter also disclosed SiO₂ fibers, wherein after loading the deposited soot with Help a powdered or liquid soot removal agent for burning is brought. As such agent is called copper (I) chloride. This invention seeks to solve the problem  the field of soot removal from exhaust gases of diesel internal combustion engines, the Lower the temperature for combustion of the deposited soot to <600 ° C.

Another method for separation and combustion of the separated Carbon black is described in DE-OS 36 22 623. The filter is made of spun Quartz glass or ceramic fibers or of open-cell foam ceramic or fine oxide ceramic granules. Essential innovative feature is the combustion of the soot deposited on the filter by the use of electric Conductivity of the carbon black itself.

DE-OS 36 35 038 discloses soot filters, as described by the same applicant in DE-OS 36 22 623 are described, but in addition fine and coarse mesh Sieves contain, wherein the filter granules used by Compressed air is compressed.

The DE-OS 23 53 346 describes a method and apparatus for removing combustible particulate matter from exhaust gases of internal combustion engines. Filters made of refractory polycrystalline material are used, wherein the temperature of the exhaust gases conducted into the filter must be so high that at least a portion of the filtered-out solid particles burns. The filter may also contain catalysts for improving combustion, as well as catalysts for removing CO, NO _x and hydrocarbons. In order to be able to maintain sufficiently high exhaust gas temperatures in the case of soot combustion, the filter is generally mounted as close as possible behind the engine. Under cold start conditions, soot initially collects in the filter, which then burns at high load after reaching the required temperature. The filter materials may be in the form of staple fibers, paper, towels, sheets, sheets and felts but may also be cylinders, plugs or pads of fibers, the latter having a relatively small surface area. Hollow cylinders are made by winding the former materials on a tubular mandrel which may also remain in the filter.

Too high a back pressure with appropriate deposition of solid particles and to avoid damaging the filter is in one part  In the prior art, a bypass valve is provided to exhaust in this case unfiltered to be able to pass the filter.

In DE-OS 34 44 397 is a process for the production of refractory Moldings disclosed, which are also suitable for use as filter elements for Exhaust gases from internal combustion engines are suitable. The moldings are made from a slurry refractory fibers and additional finely divided refractory Materials made. It claimed fibers of a certain length. The finely divided materials are deposited on the fibers by flocculants. The water is sucked out of the slurry and onto the molded part Pressure of 2 bar exerted by pressing a punch. The suction takes place from a provided with sieve bottom molding box, is essential however, that pressure is applied simultaneously. The refractory fibers are conventional ceramic fibers with Al₂O₃ contents of 45 wt .-%. The finely divided Materials may be: SiO₂, Al₂O₃, chamotte, kaolin, ZrO₂, Zirkonsilikat, TiO₂ and Cr₂O₃. By applying pressure will be desired Densities up to 1 g / cm³ received. As a binder, inorganic Phosphates and organic binders used.

In DE-OS 24 47 678 a device for the removal of pollutants from car exhaust, namely NO _x , CO and hydrocarbons is described in which a ceramic body of refractory fibers is mounted in a housing. On the catalyst body, the actual catalyst is applied. The fiber material is preferably polycrystalline alumina or zirconia.

None of the described filter systems has so far been used in the art found, as cost-effectiveness and, if necessary, also the technical usability are not given.

European patents EP-B-0089751 and EP-B-0089756 disclose soot filters described, which consist of a ceramic block, by injection molding produced and contains many channels, with the channels, in which the exhaust gas to be cleaned flows on the output side are closed and Parallel channels are closed on the input side and open on the output side.  

These ceramic bodies developed by Corning Glass Works in the USA will be technically used as a soot filter.

The largest ceramic block of 38 cm length and a diameter of 38 cm contains in one direction about 17 600 channels and just as many parallel Channels. The canals have a square shape with a side of about 0.2 mm. The exhaust gas flows through the very thin porous walls of the input channels in the output side open gas channels. The full filtering effect the filter, it is the filter available on the market Depending on the type between 65 to 95% of the unpurified exhaust existing Soot, is reached after at least one hour of operation, since then enough carbon black is deposited to act as a filter.

Depending on the type of filter, the back pressure rises after just 1.5 to 4 hours 130-150 mbar.

Since the channel walls are very thin, cracking and pressure occur easily on, with unfiltered exhaust gas emerges. The material sensitivity is increased by crystallization processes in the ceramic material, in particular in Regenerate, causing additional embrittlement.

The filters and their properties are described in detail in the Corning Glass Described font "diesel filter from Corning".

Related to this is of great interest that from Daimler-Benz Soot filter is tested for trucks, the copper oxide as a combustion catalyst contains, wherein additionally acetylacetone is injected. For the device 20 000 DM are estimated ("Auto, Motor, Sport", January 1989). In "Auto-Zeitung" March 1989, p. 84, development work by VW is described, in which a soot filter made of ceramic material is used and as the combustion catalyst, iron oxide is added to the fuel.

It should be noted that with continuous supply of an oxidation catalyst, the oxidant itself can be emitted or  that unwanted by incomplete combustion of combustion aids Emissions occur.

The described prior art makes it clear that the skilled person still far from a technically and economically optimal solution.

Surprisingly, the Applicant has now found a solution to the described problem, which leads to a highly effective and particularly very economical method for removing harmful components from exhaust gases of internal combustion engines and to a device for performing the method, namely by a method for eliminating harmful components Exhaust gases of internal combustion engines, in particular of diesel engines, in which the exhaust gases are passed through a permeable to gases, at least partially made of thermally highly resilient fibers existing filter material whose fibers contain at least one metal oxide and / or metalloxide and if necessary. Binders and, if necessary, thermally high strong additives and, if necessary, supporting materials and possibly at least one catalyst for the oxidation of combustible particles, in particular of carbon black and / or of hydrocarbons and / or of CO and / or for the reduction of NO _x contains, characterized gekenn characterized in that the exhaust gas to be purified is directed into at least one space of a filter assembly consisting of at least one inner and one outer filter disposed around the inner filter (s), and that the space into which the exhaust gas to be purified is introduced is is closed on the output side and that the filtered exhaust gas is discharged from at least one space of the filter assembly, which is closed on the input side and that the filter material has a density of 0.03-1.5 g / cm³, preferably from 0.06-1 g / cm³ and particularly preferably from 0.06 to 0.5 g / cm³.

The present invention further relates to a device for removing harmful components from exhaust gases of internal combustion engines, in particular of diesel engines, containing filter material for passing the exhaust gas to be cleaned, which consists at least partially of thermally highly resilient fibers containing at least one metal oxide and / or metalloxide If necessary, at least one catalyst for the oxidation of combustible particles, in particular of carbon black and / or of hydrocarbons and / or of CO and / or for the reduction of NO _x contains, characterized in that the exhaust gas purification takes place in a filter assembly, which consists of at least one inner filter and an outer filter disposed around the (the) inner filter and at least one space for introducing the exhaust gas to be cleaned and at least one space for discharging the filtered exhaust it exists and that the space into which the exhaust gas to be purified is introduced is closed on the outlet side and the space from which the filtered exhaust gas is discharged is closed on the input side and that the filter material has a density of 0.03-1.5 g / cm³, preferably from 0.06-1 g / cm3 and especially from 0.06-0.5 g / cm3.

The invention is illustrated in more detail in the following figures:

In Fig. 1, the input side of a filter assembly according to the invention of 2 filters is exemplified.

FIG. 2 shows, by way of example, the input side of a filter arrangement according to the invention consisting of 3 filters.

FIG. 3 shows by way of example a longitudinal section of a filter arrangement according to the invention.

FIGS. 4 and 5 illustrate electrical heaters for regeneration with soot loaded filters.

It is well known that both catalytic converters for gasoline engines and soot filters with or without oxidation catalysts for diesel engines only develop full activity at a sufficiently high temperature.

Diesel vehicles achieve an exhaust gas temperature in short-distance traffic and city driving at best 300 ° C. Only with faster and longer lasting Motorway travel can be reached 500-600 ° C. This temperature is however at least necessary for burning the soot particles in exhaust filters, unless an additional oxidation catalyst is used. With the help of these catalysts, a combustion temperature of about 250-300 ° C.  

As the described state of the art shows, the experts are concerned intense with action, either high enough temperatures even at slower To achieve driving style, such as by temporary use from burners, through initial firings distributed across the filter, or in another method by using the soot as an electrical conductor, so that reaches the required temperatures by the electrical resistance become. As a further alternative, adding catalysts to the fuel or you arrange the filter so close behind the engine that the combustion temperature of the carbon black is achieved.

The Applicant has now surprisingly found that the inventive Filter assembly with its specific structure excellent for removal the soot particles contained in the exhaust gas is suitable, wherein the to be cleaned Exhaust gas is directed into a space in the filter assembly, the output side is closed, so that the entire exhaust gas flows through the filter. The filters of the filter arrangement according to the invention are preferably tubular, however, the cross-section of such a tube is arbitrarily shaped may be, such as round, oval, square, rectangular, trapezoidal or irregular. These forms are exemplified. The filters can also have different shapes along the length of the filter, d. H. run conically, or over the entire length or certain Rejuvenate or extend sections. At one from an inner one and an outer filter existing filter arrangement, it is advantageous in a space lying between inner filter and outer filter, the output side is closed to initiate the exhaust gas to be cleaned. The cleaned Exhaust gas can then pass through the inner filter into a room that closed on the input side of the exhaust gas to be cleaned and on the output side is open, and may further through the outer filter into a this lying room occur, which is also closed on the input side and output side is open.

In an arrangement consisting of 3 filters, the exhaust gas to be cleaned enters preferably in a centrally arranged space, located in the interior of inner filter is located as well as in the space between the 2nd and 3rd  Filter, while the filtering exhaust gas from the space between the inner and 2. Filter and outside of the third filter flows.

Due to the filter arrangement according to the invention, the exhaust gas to be cleaned must pass completely through the filters.

Analogously constructed filter arrangements according to the invention, which consist of more than 3 filters exist. Length, wall thickness and inside diameter of the filter tubes can vary within wide limits depending on the engine type. In dependence of Engine power, generally with increasing engine power, can be larger or several filters are used.

The filters of the invention can be lengths of a few centimeters to the Have the order of magnitude of meters. Usual lengths are 30-60 cm. Also the diameters of the inflow and outflow spaces and the filter walls can be a few millimeters to many centimeters thick. Here is the automotive specialist a wide room, according to important points of view to select these values. It should be noted that the Density of the material used according to the invention and the wall thickness of the Filters can complement.

In connection with the specific structure of the filter arrangement according to the invention the density of the material is an important inventive feature. It is 0.03-1.5 g / cm³, preferably 0.06-1 g / cm³ and especially preferably at 0.06-0.5 g / cm³, the density in the specified range in Filter may also be different locally.

Although high temperature resistant fiber materials with densities in this Area are known, it has not been recognized that the inventive Filter with the densities of the invention a complete removal Allow solid particles by filtering without an undesirable high pressure, which contributes to fuel economy Exhaust-producing vehicle leads.

In the filter material densities according to the invention are common filter wall thicknesses  at about 3 to 15 mm, wherein in the case of high densities these thicknesses fell short of these thicknesses in the case of lower densities can be.

Density and wall thickness are not only of special importance for the fact that the soot in the exhaust gas is completely absorbed immediately after starting the engine but also with respect to the very important through the filter caused pressure build-up. As is known, increasing pressure causes motor output side before the filter, increasing fuel consumption or at Maintaining a low pressure Frequent burning off of the filtered soot deposit.

With sufficient wall thickness according to the invention filter materials a density <0.2 g / cm³ be particularly favorable. Basically, arrangement can and number of filter tubes, shape, wall thickness, diameter and Length of the filter tubes and the control of the heating for regeneration the filter according to soot loading be adapted to the respective vehicle type.

As is known in the art, very many materials are known which as high-temperature-resistant fibers for filtering off solid particles hot exhaust gases are suitable. The fibers generally consist of the high temperature resistant oxide fiber material itself, from binders and others In general, very fine-grained additives, but can only from Fiber material or fiber material and binder exist. According to the invention are high fiber fractions or filters, which consist only of fibers, preferably. The fibers can be glassy or crystalline. Glassy fibers are in general more brittle than crystalline fibers. The filter materials according to the invention can contain only crystalline or polycrystalline fibers or only glassy or mixtures of the two. The fibers can also work with others Be coated materials.

Fibers of crystalline and vitreous material, in particular mixtures These fibers can be fused together by heating, so that bonds between the fibers arise and the strength of the filter material is increased at high porosity. Exemplary are materials  called alone or as consisting of at least 2 components Mixtures for the production of fibers are suitable: aluminum silicates, aluminum silicates high alumina, chromium oxide, silica, alumina, Zirconium oxide, iron oxides, silicates, such as alkaline earth silicates, Alkaline earth and alkali oxides, titanium oxide, boron oxide, aluminum borosilicates, natural aluminum silicates such as rock formers, clays, clays and other aluminum silicate minerals, carbon, carbides, such as. B. Silicon and boron carbide, manganese oxides, germanium oxide, rare earth oxides. The Enumeration of suitable materials is exemplary. Also other components can be used in the prior art. According to the invention It is also possible to use coated fibers, as known from the prior art Technics are known or can be rebuilt. Prefers are fibers based on aluminum silicate, in addition to Al₂O₃ and SiO₂ at least contain an additional metal or semimetal oxide. Preferred additional Metal oxides are zirconia or titania. An example is at a combination of Al₂O₃, SiO₂ and additional metal or Halbmetalloxid the Al₂O₃ amount 30-40 wt .-%, the amount of SiO₂ 40-50 wt .-% and the additional Metal or Halbmetalloxidmenge 10-20 wt .-%. Another exemplary Composition consists of 15-70 wt .-% Al₂O₃, 30-80 wt .-% SiO and 5-35% by weight of metal or semimetal oxide, respectively. In principle, the inventive Compositions are chosen within very wide limits, namely between 0.5-99.5 wt .-% Al₂O₃, 0.5-99.5 wt .-% SiO₂ and 0.1-75 wt .-% other oxides, wherein the individual amounts are chosen so that they are too 100% complete.

According to the invention for the production of the filter materials and mixtures usable from at least two of said fibers. In the high temperature resistant Fibers and filter materials can, as known in the art, organic and inorganic binders are used, the Burn organic binder during later firing. exemplary may be mentioned: clays, alumina, sulfite liquor, phosphates such as Alkali and aluminum phosphates, boron oxide, phosphorus pentoxide, artificial and natural aluminum silicates, colloidal silicic acid, alkali silicates, porcelain flour, colloidal alumina, alumina hydrates and hydroxide, aluminates, such as As calcium aluminate, fireclay, cements, glass materials  u. a., carboxymethyl cellulose, starch, cellulose, molasses, organic plastics, such as polyvinyl alcohol, polyacrylamide, polyethers and many others, as can be seen from the prior art.

Examples of finely distributed additional materials in fibers and filter materials are:
Aluminum powder, silicon powder, silica, alumina hydrate, magnesium oxide, titanium oxide, zirconium oxide, chromium oxide, porcelain flour, fireclay powder, artificial and natural aluminum silicates, clays and clays, corundum, other aluminum oxides, carbides, such as. As silicon and boron carbide, calcined bauxite, quartz, cobalt oxides, iron oxides, manganese oxides, zirconium silicates, aluminum borosilicates, carbon, such as. As graphite, coke and carbon black and many other elemental and oxidic materials.

It should be noted that the properties of the invention materials are largely retained, even if small other admixtures are contained therein, the essential ingredients however, these compounds are. By way of example, a method for Production of aluminum silicate fibers and other thermally stable Fibers described. The oxides are mixed, if necessary. An inorganic and / or organic binder and sprayed this mixture into fibers. The product is fired. Mashes can be made from these fibers Produce further processing. Also different aluminum silicates can be processed to such materials. There are many methods for the production of fibers used according to the invention described in the specialist literature, so that they do not need to be explained here. Known Methods for producing fibers are the drawing, spinning, blowing, blowing Pull and spin blow process. The thermal conductivity of the invention For example, material can be between 0.03 and 1.5 at 200-1200 ° C W / mk, since this depends strongly on the type of materials used. A typical range is 0.05-0.6 W / mk, preferably 0.05-0.4 W / mk.

The filters according to the invention can be prepared by all known methods become. So the filters can be made out of fiber mats Fiber wadding or by vacuum forming. Particularly effective filters that  In addition, by low pressure build-up between the exhaust outlet on the engine and Filters can be characterized by loose stratification of the fibers in one Cage-like support device, wherein the layering in the desired density by simply blowing the fibers into the support device can be generated. Support devices are also advantageous if you put the filters in by inserting fiber mats or cotton wool in makes the support device. Such support devices are intended to high gas flow allow and even not to appreciable additional pressure build-up contribute. They are made of thermally stable materials, such as Metals, ceramics, temperature resistant inorganic fiber fabric, temperature resistant Plastic fibers and the like. They can be used both at the Inside as well as on the outside wall, as well as inside and outside wall in form a highly permeable cage be arranged.

Different fiber materials can also be used to make the filters are used, which then layer or segment present in the filter. The surfaces of the filters can also be defined by certain designs such as Ridges, grooves, grooves and the like are increased.

By way of example, a method for vacuum forming known per se is described.

The finely divided filter material is preferred with a liquid Water, mashed. By means of a tube, the later inner diameter corresponds to the filter and which has fine openings, the Mash which may be stirred or otherwise mixed by applying vacuum to the interior of the tube on the same deposited down to the desired filter thickness.

Then the tube is removed and the filter is dried and fired. The tube can remain in the filter, but can also be removed.

The individual filters can then be used on the input side and on the output side closed lid-like devices are in which there are grooves in which the individual filters are used. With the help of a  in the center of the filter assembly present rod, which at both ends with threaded, the lid-like shutter plates can be on both sides be tightened on the filter assembly. The shutter plates Contain the required exhaust gas and filtered exhaust gas to be cleaned Inputs and outputs.

The closure plates may also contain the container in which the entire filter assembly is included. Basically, one can also be on one side closed filter are already made in the production, where the closure consists of the filter material. Support materials can also be arranged inside the filter material, such as. B. tissue, grid, Longitudinal and transverse ribs and the like. In addition, between the filters and the closure plates seals are attached.

It is also advantageous according to the invention on the surface of the filter on which the filtered exhaust gas emerges, a thin, textile-like, temperature-resistant Material existing on the filter layer z. In Form of a fiber cloth or a fiber mat to install. This should be here be so dense that fine or finest fiber material from the filter not entrained with the filtered exhaust stream, but otherwise in the smallest possible extent an additional pressure buildup occurs.

The filters according to the invention can also be carriers for oxidation catalysts for the oxidation of carbon monoxide, hydrocarbons and carbon black and for reduction catalysts for the reduction of NO _x .

It is well known that the so-called uncontrolled catalytic converters in the case of gasoline engines remove about 50% of the pollutants NO _x , CO and hydrocarbons. Suction. Controlled three-way catalytic converters, which use a probe to regulate the required oxygen supply and consist of a catalyst system that catalyzes both the reduction of NO _x and the oxidation of CO and hydrocarbons, can contain about 90% of the hydrocarbons and CO and Remove 83% of NO _x . Great problems still exist when starting with cold catalysts. At low temperatures, the full activity of the catalyst is not achieved. Only at temperatures, as they adjust after a long drive, even up to 91% of the pollutants can be removed. It is therefore of great importance that the catalyst comes up to operating temperature quickly. Due to the temporarily low activity of the cold catalyst, relatively large amounts of pollutants still reach the atmosphere.

In the catalysts of the prior art, the exhaust gas is generally passed over the surface of the catalyst-bearing material. Therefore, very expensive constructions are sometimes used to increase the surface carrying the catalyst and to redirect the exhaust gas in order to bring about intimate contact between the exhaust gas and the catalyst. Thus, for example, in DE-OS 31 16 967 discloses a metallic winding body. According to DE-OS 27 59 559 corrugated coated metal strips are used or in DE-OS 29 05 241 and DE-OS 29 47 694 a combination of wound honeycomb bodies and smooth metal bands is used, which are coated with catalyst. According to the present invention, the catalysts are introduced in finely divided form on and / or in the filter according to the invention with its specific structure, wherein the exhaust gas is passed completely through the filter. The catalyst may also be in and on the surface of the fibrous material itself. Due to its uniform, highly porous structure of only low density, an extremely intimate contact between the exhaust gas and the catalyst material is brought about. With the material according to the invention the full activity of the catalyst and thus high conversions of the pollutants are achieved shortly after the engine is put into operation, so that according to the invention overall a substantial removal of pollutants CO, NO _x , hydrocarbons and soot can be achieved. Another advantage of the method and the device according to the invention is the result that the removal of catalyst from the material according to the invention is substantially lower than in the case of catalysts which are located on surfaces according to the prior art, in particular when the catalysts in the Fiber material are incorporated itself.

It should not be further explained here, such as such catalysts or in the material or introduced, since this very numerous  Methods are accessible to the skilled person and readily in the Under the present invention can be applied. According to the invention can all reduction and oxidation catalysts or their combinations be used. Numerous examples, but they are by no means limiting, since the prior art is not fully reproduced here are given in the described prior art. It deals For example, without this enumeration being complete, the following Elements, their compounds and other compounds: ruthenium, rhodium, Osmium, iridium, platinum, palladium, vanadium, chromium, manganese, tin, cobalt, Nickel, molybdenum, tungsten, niobium, tantalum, rare earths and others as well as around Vanadates, Chromates, Chromites, Manganates, Manganites, Stannates, Molybdate, Tungstates, niobates, tantalates of Fe, Co, Ni, Cr, Mn, Cu, Zn, Ag, Cd, rare earths and numerous other compounds, such as those from the state known in the art.

The filters according to the invention are outstandingly suitable for the removal of the pollutants NO _x , carbon monoxide and hydrocarbons and soot, that they separate the soot completely and with only very low pressure build-up, allow intimate contact between pollutants and catalyst, quickly to the temperature of the full Activity of the catalyst can be brought and can be brought very quickly to the combustion temperature of the soot in the separation process of soot with low heat consumption and also the removal of catalyst is very low. The present invention accordingly leads to previously unattainable properties of devices for the removal of pollutants from exhaust gases.

Soot filters have to be used after a certain period of operation Soot deposits on or in the filter the back pressure up to a certain Pressure limit has increased, be regenerated, d. H. the deposited soot must to be burned.

In the prior art, this can be achieved by switching on an electrical Heating, for example, as a heating coil in a filter body can be done or by turning on a burner, the Burner with fuel or with fuel gas from an additional compressed gas tank  can be operated. Does the filter have the combustion temperature? of the soot can, if necessary, by means of a mini-compressor Air or oxygen are supplied via a capillary system. After reaching the temperature, if necessary. With air supply, can already after a few Minutes the heater will be turned off and the filter stands for the next use ready.

Burners are generally mounted on the input side in front of the filter assembly. They serve both to the exhaust gas flowing into the filter so To heat up that the soot burns, as well as for direct firing the filter, wherein the burner can also protrude into the filter. you can also be adapted to the space between the filters and be designed for example as a ring burner.

Due to the presence of oxidation catalysts in the filter or on the Filter for the oxidation of the soot to CO₂ can even be achieved in the best case be that the exhaust gas temperature itself already for the combustion of Sooty enough.

This may be the case in particular when the filters are close to the exhaust gas outlet are arranged from the engine.

In any case, the oxidation catalyst has the effect, the combustion temperature to reduce the soot.

The regeneration can be carried out in such a way that two parallel filter arrangements of which one is in Abgasfiltrierbetrieb and the others is regenerated. However, it can also be regenerated in the way in the presence of only one filter arrangement during the filtering operation is regenerated.

Finally, in addition to a filter arrangement according to the invention additionally a simple switchable filter tube be present on the during the in a few minutes running regeneration of the filter assembly according to the invention is switched to filtration mode, with a brief increase in pressure  due to the smaller surface of the single filter tube occurs. Since several filter arrangements can be used depending on the vehicle, are preferred in such cases by a clock circuit or a Time relay controlled, heated one after the other.

When using an electric heater, the heating coils or others Heating devices, such as rods, grids and the like., As from the state of Technique is known to consist of different materials. One good suitable material is for example nickel wire. You can see the voids in the filter assemblies also in addition with a temperature-resistant, fill porous material. Example is called expanded clay. The material must not be electrically conductive, should a low heat consumption Have heating, good Rußabscheideeigenschaften, the combustion of the deposited Promote soot and do not tend to slagging.

Even fiber materials or filter materials themselves can in so-called. Wirrer or disordered arrangement in the white space.

The commissioning of the heating can be done by pressure difference measurement before and take place behind the filter, so that at a certain pressure difference the Heating goes into operation. In principle, the commissioning can also after a specific mileage or a specified time. However, these circuits are less preferred since they are different Driving modes quite different amounts of soot are formed.

The input and output side attached to the filter assembly closure plates can with electrical heating for the ground connection of the Heating conductor can be used.

Table 1 summarizes results obtained with 100 hours of operation a tube filter according to the invention determined behind a diesel engine were.

For this purpose, a white test paper filter was used, which at the output of Filter assembly was attached. The test paper filter was 1 liter  cleaned exhaust gas passed and checked the discoloration of the test paper.

For comparison, the unpurified exhaust gas of the diesel engine with the test paper Filter tested. After passage of a liter of exhaust gas was the filter black.

As a diesel engine, a 2-liter, 4-cylinder engine, built in 1981 was used.

The length of the filter assembly was 300 mm, the diameter 70 mm. The used test paper filters were also under the test after the test Microscope examined. In almost all cases, no soot particles could be determined after cleaning according to the invention.  

Table 1

In Table 2, the efficiency of an inventive Filter F with efficiencies in the market Filters A, B and C are shown as a function of the operating time, the filter F being at 100% efficiency the soot particles are 100% filtered off, while A, B and C when reaching 100% efficiency, the soot particles too Filter off 90%, 75% and 65%. Only the invention Filter therefore removes existing in the exhaust gas to be cleaned Soot particles completely.

filter type 100% efficiency F immediately after commissioning A after about 1.5 hours B after about 1.5 hours C after about 3.5 hours

Table 3 shows the buildup of backpressure in mbar during of the filtration operation with the filters as shown in Table 2. The density of the filter F was 0.28 g / cm3. Similar good results were obtained at other densities.

Table 3

Table 3 shows that in comparison filter A, which maximum 90% of the carbon black filtered off, after 2 hours, a back pressure of 150 mbar is reached. The further increase after more than 2 hours is not accessible from the accessible literature determine. Only in the case of the comparison filter C, the maximum Filtered off 65% of the carbon black, there is a pressure increase, the after 3 hours of operation about the rise of the invention Filters F corresponds.

From Tables 2 and 3, the superiority of the invention Filters compared to the prior art clearly. Another important feature of soot filters is the Regenerability of the filter after reaching a certain Counterpressure as a result of deposited soot. In Table 4, the burning time in an inventive Filter arrangement shown, which consists of 2 filters. The exhaust gas to be cleaned was in the space between initiated inside and outside filter, in which in the Try 1-3 heating coils arranged in 3 segments, brought to the burning temperature by battery operation were, with the distance between the inner and outer filter 4 mm, 8 mm and 10 mm. The heating power was 300 W. The filter length was 300 mm. In experiment 4 was with a on the filter gap regenerated burner fueled has been.

Table 4

During the burning process air was introduced through a capillary blown the filter inside. According to the invention, the air be sucked in from the outlet of the filter device, so no additional emissions during burning occur. For further testing the regenerability of the invention Filter was a filter tube of 300 mm in length and a Distance between inner and outer filter of 10 mm each 30 Operated minutes and then with a burner respectively 2 minutes regenerated. In total, 1000 (thousand) times were regenerated. Partially was heated to 1200 ° C (one thousand two hundred). After completion of the experiment, the filter assembly was in perfect condition. Abrasion and mechanical damage were not detectable. The filter test with the test paper filter resulted in a completely white paper filter.

With the help of the figures, the invention is additionally explained.

Fig. 1 illustrates a filter arrangement consisting of an inner and an outer filter. ( 3 ) and ( 5 ) are inner and outer filters. The exhaust gas to be filtered enters ( 7 ) characterized in the space ( 4 ) between the inner and outer filter. The filtered exhaust gas exits space ( 1 ) via ( 8 ) and outwardly via ( 9 ) from the filter assembly. ( 2 ) and ( 6 ) are cloth-like materials that prevent the removal of fine and fine fiber particles. ( 10 ) represents the housing around the filter assembly.

Fig. 2 shows a filter arrangement consisting of 3 filters. The exhaust gas to be cleaned enters the spaces ( 1 ) and ( 7 ) according to arrows ( 10 ) and ( 11 ) in the filter arrangement.

The filtered exhaust gas exits the space ( 4 ) and around the filter assembly indicated by the arrows ( 12 ) and ( 13 ). ( 2 ), ( 6 ) and ( 8 ) represent the filters, ( 3 ), ( 5 ) and ( 9 ) the cloth-like sheaths. ( 14 ) is the housing around the filter assembly.

Fig. 3 shows a cross section through a filter arrangement consisting of 3 filters. Exhaust gas to be filtered enters the rooms ( 1 ) and ( 5 ) = ( 6 ) via ( 14 ), ( 15 ) and ( 16 ). The purified exhaust gas flows out of ( 4 ) = ( 10 ) and around the filter assembly ( 7 ) according to arrows ( 19 ), ( 20 ), ( 21 ) and ( 22 ) from the housing at ( 26 ). The filters are represented by ( 2 ), ( 8 ) and ( 13 ), the cloth-like sheaths by ( 3 ), ( 11 ) and ( 12 ). ( 17 ), ( 18 ) and ( 23 ) represent the covers of the filter assembly, ie in total on both sides a plate with the required perforations. ( 24 ) is the screw of the threaded rod ( 25 ) with which the cover plates and the filter assembly are firmly connected. ( 9 ) is the housing wall around the filter assembly.

FIG. 4 shows, by way of example, a circuit for the regeneration of 5 filter assemblies after soot loading, wherein the heating takes place electrically. In principle, other circuits known to those skilled in the art can also be used. ( 1 ) are the filter assemblies. ( 2 ) is the power supply. ( 3 ) is a square-wave generator, ( 4 ) represents resistors. ( 5 ) is a capacitor, ( 6 ) are transistors, ( 7 ) electronic fuses, and ( 8 ) relays. Finally, ( 9 ) is a timing chain for driving the transistors. The pulse duration is determined by ( 3 ) via the dimensioning of ( 10 ) and ( 5 ). The square wave signal arrives ( 9 ). Via ( 9 ) a signal is applied via a resistor ( 4 ) to a transistor ( 6 ). ( 6 ) becomes conductive, after which a relay ( 8 ) attracts. The heating of a filter arrangement ( 1 ) is for example at 12 volts. The next pulse blocks ( 6 ), a second transistor ( 6 ) becomes conductive and the heating of a second filter arrangement goes into operation, etc. At clock 6 ( 9 ) is reset. In this way all filter arrangements are regenerated. A changeover to a second combination of filter arrangements can take place after release of the first combination via a magnetic switch flap control. This backup control can be installed for the first and second combination, ie if multiple relays are energized, the electronic fuse ( 7 ) will respond and switch to the backup system via a relay contact. The few components can be accommodated on a plug-in module. To indicate a defective filter part or a changeover of the control system, a signaling for the driver of the diesel vehicle can be provided. In Fig. 4 is further exemplified a circular arrangement of the 5 filter assemblies, equipped with 5 heating conductors shown, wherein the deposited soot does not cause short circuits. To achieve even burn-off of the filters, a timebase clock control can be used. Here, the single-time clock is set to a certain period of time. During this time, the accumulated soot burns completely in a filter. Also a step circuit is possible. The clock control is, as already described above, a decade counter, with a series of power transistors driving a relay chain. The control of the decade counter is performed by a clock generator. The pulse duration of the clock generator can be determined. The advantage of this control is that only ever a relay is controlled and thus the electrical system is not overloaded. In the unlikely event of a disturbance resulting in high current flow, this system can be installed in duplicate with the first system disconnected and the second system taking control. The individual heaters can be monitored via mains fuses. Since the described regeneration is a two-way system, the control of the heating system of the respective filter arrangement can be effected via a pressure difference circuit, depending on the soot load. In principle, a regeneration can also take place alternately, timed. If in extreme cases the entire system should fail, the system can be bypassed via a bypass and a sealed safety valve.

Fig. 5 shows a clock-controlled arrangement of 4 heating coils ( 1 ). The control is carried out via a clock generator and a decadic counter, as shown in Fig. 4, which supplies only one output with voltage in rapid order. Although such circuits are basically known to the person skilled in the art, the present new use results in a particularly high degree of efficiency. Embedded or initiated heating coils within tubes, which consist of thermally stable fibers of oxides, ceramics or similar materials, which have a poor thermal conductivity, can be heated in a short time almost simultaneously, with only one heating coil loaded the electrical system. Due to the low heat losses within a tube, a heat pumping effect is observed in numerous experiments, whereby each tube could be heated up to almost 1200 ° C at an on-board voltage of 12 V and a load current of approx. Through the tubes unfiltered exhaust gas is directed towards the filter. The starting temperatures were at an inlet temperature of 230-300 ° C almost 680-700 ° C, which then leads to combustion of the accumulated soot particles.

The clock frequencies used can be in the range of kilohertz, but also only a few hertz or megahertz. The connections ( 2 ) of the heating coils can be screwed in, for example, as is known with spark plugs. Ground connection is located centrally on a connection ( 3 ) on the housing ( 4 ) of the filter. The power electronics ( 5 ) can be easily accommodated on the vehicle floor, the wind provides sufficient cooling. The filter arrangement is represented by ( 6 ). The exhaust gas to be cleaned enters at ( 7 ), the filtered exhaust gas exits at ( 8 ).

The results show that the inventive Device and the method performed therewith for Exhaust gas purification of internal combustion engines, in particular of Diesel engines without the prior art There are thousands of channels in the filter that are light clog and their very thin partitions, which are light break and get damaged, clearly superior results be achieved. The soot becomes instantaneous at the time completely filtered out during commissioning. The pressure build-up takes place despite complete soot removal slower instead of at present technically used Filtering, so that less frequent regeneration, The fiber material used according to the invention is extraordinary temperature resistant, although at very frequent, strong temperature fluctuations no harmful crystallization processes take place, which makes the material useless The soot deposits can be quick and complete be removed and the filters are easily replaceable. Due to the inexpensive fibers, the simple filter construction and very common, possible without material damage Regeneration is especially the diesel car driver a far superior to the prior art exhaust filter made available. However, it should be emphasized that the inventive method and the invention Device also excellent for the emission control of Otto engines are suitable.

Claims (20)

1. A method for eliminating harmful components from exhaust gases of internal combustion engines, in particular of diesel engines, in which the exhaust gases are passed through a permeable for gases, at least partially made of thermally highly resilient fibers existing filter material whose fibers contain at least one metal oxide and / or half metal oxide and the optionally binder and optionally thermally highly stable additives and, if necessary, supporting materials and possibly at least one catalyst for the oxidation of combustible particles, in particular of carbon black and / or hydrocarbons and / or of CO and / or for the reduction of NO _x contains, characterized characterized in that the exhaust gas to be purified is directed into at least one space of a filter assembly consisting of at least one inner and one outer filter disposed around the inner filter (s) and that the space into which the exhaust gas to be purified is introduced is output side is closed and that the filtered Abg as is derived from at least one space of the filter assembly which is closed on the input side and that the filter material has a density of 0.03-1.5 g / cm³, preferably 0.06-1 g / cm³ and particularly preferably 0.06 0.5 g / cm³ has. 2. The method according to claim 1, characterized in that the exhaust gas to be cleaned is passed through filters, around which suitable for gas flow support material is arranged. 3. Process according to claims 1 and 2, characterized in that that the exhaust gas to be cleaned passed through filters is made by introducing the thermally high resilient fibers have been produced in the support material are.   4. Process according to claims 1-3, characterized that the exhaust gas to be cleaned by filters is directed to the side where the filtered Exhaust gas exits, a cloth or mat-like, gas-permeable Have wrapping made of thermal highly resilient material. 5. Process according to claims 1-4, characterized in that that the exhaust gas to be purified is passed through filters, by blowing the thermally highly resilient Fibers have been produced in the support material. 6. Process according to claims 1-5, characterized in that that the exhaust gas to be purified is passed through filters, in which the thermally highly resilient fibers completely or predominantly as Al₂O₃, SiO₂ and at least one further metal oxide and / or semimetal exist. 7. Process according to claims 1-6, characterized in that that the exhaust gas to be purified is passed through filters, in which the thermally highly resilient fibers completely or predominantly of Al₂O₃, SiO₂ and ZrO₂ and / or TiO₂ consist. 8. Process according to claims 1-7, characterized in that that after loading the filter with solid, combustible Particles a heating device for burning off the the filter material deposited, combustible particles is turned on and at least part of it is burned. 9. Process according to claims 1-8, characterized in that a burner is used as the heating device.   10. The method according to claims 1-9, characterized that the exhaust gas to be cleaned by filters is passed, whose filter material in the preamble Catalysts mentioned by claim 1 individually or in every possible out of at least two catalysts may have existing combination. 11. A device for removing harmful components from exhaust gases of internal combustion engines, in particular of diesel engines, the filter material for passing the exhaust gas to be cleaned, which consists at least partially of thermally highly resilient fibers containing at least one metal oxide and / or half metal oxide, wherein the filter material if necessary, binder and optionally thermally highly loadable additives and optionally supporting materials and possibly at least one catalyst for the oxidation of combustible particles, in particular carbon black and / or hydrocarbons and / or CO and / or for the reduction of NO _x , characterized in that the exhaust gas purification takes place in a filter arrangement consisting of at least one inner filter and an outer filter arranged around the inner filter (s) and at least one space for introducing the exhaust gas to be cleaned and at least one space for discharging the filtered exhaust gas, and that the room in that too cleaning exhaust gas is introduced, the output side is closed and the space from which the filtered exhaust gas is discharged, input side is closed and that the filter material has a density of 0.03-1.5 g / cm³, preferably from 0.06-1 g / cm³ and especially from 0.06 to 0.5 g / cm³. 12. The device according to claim 11, characterized that around the filter for gas flow suitable support material is arranged. 13. Device according to claims 11 and 12, characterized that the thermally highly resilient fibers are introduced into the support material. 14. Device according to claims 11-13, characterized that the filters are on the side where the filtered Exhaust gas exits, a cloth or mat-like envelope have, made of thermally highly resilient material consists. 15. Device according to claims 11-14, characterized that is the thermally highly resilient fibers in blown form in the support material. 16. Device according to claims 11-15, characterized that exist in the filters thermally highly resilient fibers wholly or predominantly of Al₂O₃, SiO₂ and at least one further metal oxide and / or Consist of semimetal oxide. 17. Device according to claims 11-16, characterized that exist in the filters thermally highly resilient fibers wholly or predominantly as Al₂O₃, SiO₂ and ZrO₂ and / or TiO₂ exist. 18. Device according to claims 11-17, characterized that for burning off the on or in the filters deposited soot a heater available is.   19. Device according to claims 11-18, characterized that the heater is a burner. 20. Device according to claims 11-19, characterized that the filter material in the preamble of claim 1 mentioned catalysts individually or in every possible combination of at least two Catalysts.