WO1992006768A1

WO1992006768A1 - Process and device for purifying exhaust gases

Info

Publication number: WO1992006768A1
Application number: PCT/DE1991/000806
Authority: WO
Inventors: Herrmann Gerstenmeier
Original assignee: Herrmann Gerstenmeier
Priority date: 1990-10-18
Filing date: 1991-10-12
Publication date: 1992-04-30

Abstract

The invention concerns a process for purifying exhaust gases, in particular for the removal by filtration of carbon particles from exhaust gases produced by diesel engines and by heating installations in buildings, as well as a device for carrying out this process. The exhaust gases are passed through a special high-temperature-resistant filter material disposed in a filter chamber surrounded by a gas-permeable sheath, preferably also made of high-temperature-resistant material, through which the purified gas emerges.

Description

Method and device for cleaning

of exhaust gases

The present invention relates to a method and a device for carrying out the method for cleaning exhaust gases, in particular for the filtering removal of soot particles from the exhaust gases of diesel internal combustion engines and building heating systems, the exhaust gas being passed through a special filter material which is resistant to high temperatures and is in a filter space is located, which is surrounded on the outside by a gas-permeable covering, preferably also made of high-temperature resistant material, through which the cleaned exhaust gas exits.

The increasing environmental awareness has been around for a long time, e.g. In the United States of America since 1978, that has led to automobiles with Otto engines

Catalysts are required to be in the exhaust gases

Minimize emissions of hydrocarbons, carbon monoxide and NO _x .

Diesel vehicles have also been criticized for a number of years after it was suspected that the soot particles contained in the exhaust gas of these vehicles could be carcinogenic.

Numerous vehicle manufacturers and other experts have therefore intensively dealt with possible solutions over the past few years to avoid or reduce the emissions of soot particles. For this purpose, filters are installed in the exhaust gas flow, on which the soot particles are deposited. As a result of the deposition, the back pressure in the exhaust gas flow increases, and with it the consumption of the fuel or fuel producing the exhaust gas.

It is therefore necessary to regenerate the exhaust gas filter, ie the to remove deposited soot. This happens through

Burning of the soot with electrical heating or with burners fed with fuel or gas.

Numerous property rights are known, which the

Remove soot, carbon monoxide, hydrocarbons and NO _x . Only part of the prior art can therefore be cited in the following section.

A catalyst which only relates to the oxidation of CO and hydrocarbons is disclosed in DE-OS 21 55 338.

It can contain lanthanum and rare earths, 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 which contains manganese oxide and platinum and / or palladium.

Catalysts which only serve to reduce NO 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 an annealed aluminum oxide support.

DE-OS 21 40 852 also discloses a reduction catalyst which consists of palladium and rhodium on an annealed support.

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 is used, the cerium,

Contains lanthanum, rhodium, platinum, palladium and phosphorus on a refractory inorganic support.

According to DE-OS 23 06 395 and DE-OS 24 16 753 there is a 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 shockproof, weakly porous,

ceramic material.

Also in DE-OS 26 02 286 a catalyst is open-bart, the simultaneous reduction and Oxidatioh

of pollutants. The active metals are

Palladium, platinum, cerium oxide, zirconium oxide and nickel oxide.

DE-OS 32 223 500 discloses a catalyst which consists of rhodium, palladium, cerium oxide and iron oxide on aluminum oxide as a carrier.

Finally, DE-OS 33 25 292 discloses a catalyst made of iron, nickel and cobalt on ceramic

Aluminum oxide or titanium oxide.

Patents and patent applications and publications relating to the removal of soot are sold in the

the following section.

In DE-OS 25 19 609 a device for separating soot is described with a pleated filter in which the initiator and

Temperature sensors. By measuring the differential pressure upstream and downstream of the filter, a specific measurement is made

Set the ignition in motion so that in this

The soot area burns down.

Since the filters used here are materials with only limited thermal load capacity, the temperature sensors mentioned above are used for

When a bypass is reached at a certain temperature, part of the exhaust gas flows out unfiltered.

DE-OS 30 17 784 describes a soot filter made of porous ceramic which has a heating coil embedded in it which is connected to the filter.

DE-OS 30 24 539 discloses a device for

Eliminate soot from exhaust gases, essentially consists of a filter, which according to the example given consists of SiO ₂ fibers. The deposited soot is burned off by microwaves, wall elements on the clean gas side being arranged on the filter, which are impermeable to microwaves.

From the same applicant is in DE-OS 31 11 228

Soot filter also disclosed from SiO ₂ fibers, wherein

after loading the separated soot with the help of one

powdery or liquid soot removing agent for burning. As such an agent is called copper (I) chloride. This invention endeavors to

Solution to the task of lowering the temperature for burning the separated soot to 600ºC.

Another process for the separation and combustion of the separated soot is described in DE-OS 36 22 623. The filter consists of spun quartz glass or ceramic fibers or of open-pore foam ceramic or fine oxide ceramic granulate. An essential inventive feature is the combustion of the soot deposited on the filter by using the electrical conductivity of the carbon black.

DE-OS 23 53 346 also describes a method and a device for removing combustible, particulate substances from exhaust gases from internal combustion engines.

In order to obtain sufficiently high exhaust gas temperatures, the filter is placed as close as possible behind the engine.

In the European patents EP-B-0 089 751 and 0 089 756 soot filters are described, which consist of a ceramic block, which is produced by injection molding and contains very many channels, the channels into which

Exhaust gas flows in and is closed on the outlet side, so that the exhaust gas has to pass through the thin walls of the channels, which Cornng Glass Works wrapped ceramic bodies are technically used as soot filters.

Since the channel walls are very thin, they are easy to walk on

Cracking and back pressure on, being unfiltered

The sensitivity of the material is increased due to crystallization processes in the ceramic material, in particular when regenerating by burning, whereby embrittlement also occurs.

In connection with this, it is of great interest that Daimler-Benz is testing a soot filter for trucks that contains copper oxide as a combustion catalyst, with additional acetvlacetone being injected. 20,000 DM are estimated for such a device

(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 a soluble iron compound is added to the fuel as a combustion catalyst.

It should be borne in mind here that if an oxidation catalyst is fed in continuously, the oxidizing agent itself can be emitted or that incomplete combustion of combustion aids

unwanted emissions occur.

The described state of the art makes it clear that the person skilled in the art is still far from technically and economically optimal regeneration of exhaust gas filters loaded with soot.

Surprisingly, the applicant has now found a solution to the problem described, characterized in that the exhaust gas is passed through a filter material containing 30-99.8% by weight, preferably 50-95% by weight, of Al ₂ O ₃ and 0, 2-70% by weight, preferably 5-50% by weight of SiO ₂ or SiO ₂ + ZrO ₂ contains that the ZrO ₂ content 0.05-75 % By weight of the total amount of SiO ₂ + ZrO ₂ can be such that the density of the material is 0.01-1.5 g / cm ³ , preferably 0.03-

1 g / cm ³ and particularly preferably 0.06-05 g / cm ³ and that the exhaust gas flows after flowing through the filter material through a gas-permeable envelope surrounding it and containing SiO ₂ and Al ₂ O ₃ .

The present invention further relates to a device for cleaning exhaust gases, in particular for the filtering removal of soot particles from the exhaust gases of diesel internal combustion engines and building heating systems, which has a space into which the exhaust gas to be cleaned is introduced, which is open on the input side and closed on the output side and a room in which there is high-temperature resistant filter material, characterized in that a gas-permeable covering is arranged around the filter material, that the filter material 30-99.8% by weight, preferably 50-95% by weight Al ₂ O ₃ , and 0.2-70 wt .-%, preferably 5-50 wt .-% SiO ₂ or SiO ₂ + ZrO ₂ contains and that the ZrO ₂ portion 0.05-75 wt .-% of the sum of the SiO ₂ +

ZrO ₂ amount can be and that the density of the material

0.01-1.5 g / cm ³ , preferably 0.03-1 g / cm ³ and particularly preferably 0.06-0.5 g / cm ³ .

The applicant has also found that the result according to the invention is also obtained if the filter material in addition to Al ₂ O ₃ , SiO ₂ or ZrO ₂ > 0-10% by weight of at least one metal or semimetal oxide from the Group alkali oxides, alkaline earth oxides, gallium oxide, indium oxide, thallium oxide, boron oxide, germanium oxide, tin oxide, lead oxide, phosphorus oxide, arsenic oxide, antimony oxide, bismuth oxide, selenium oxide, tellurium oxide and oxides of the sub-group elements of the periodic table, preferably from the group Fe ₂ O ₃ , TiO ₂ , Contains Cr ₂ O ₃ , manganese oxide, rare earth oxide (s), whereby the total amount of all components is 100% complementary.

According to the invention, the filter material can also be used very effectively to remove carbon monoxide, hydrocarbons and NO _x from exhaust gases, in particular from Internal combustion engines are used when it is

preferably contains at least one catalyst from the group on the surface: oxidation catalyst for removing carbon monoxide, oxidation catalyst for removing hydrocarbons, oxidation catalyst for removing carbon monoxide and hydrocarbons, reduction catalyst for removing NO _x from exhaust gases.

It is generally known that the so-called uncontrolled exhaust gas catalysts remove approximately 50% of the pollutants NO _x , CO and hydrocarbons in the case of Otto engines. So-called regulated three-way catalytic converters, in which the required oxygen supply is regulated with the aid of a probe and which consist of a catalytic converter system which both

Reduction of NO _x as well as the oxidation of CO and coal

Hydrogen catalyzed can remove about 90% of the hydrocarbons and CO and about 83% of the NO _x .

Big problems still exist when starting with cold catalysts. At low temperatures, the full activity of the catalytic converter is not achieved. Only at temperatures such as those which arise after long driving operation can up to 91% of the pollutants be removed. It is therefore very important that the catalytic converter quickly reaches operating temperature. Due to the temporarily low activity of the cold catalyst, relatively large amounts of pollutants still get into the atmosphere.

In the case of the catalysts of the prior art, the exhaust gas is generally passed over the surface of the material carrying the catalyst. In some cases, very complex structures are used to enlarge the catalyst surface and to redirect the exhaust gas in order to bring about intimate contact between the catalyst and the exhaust gas . For example, 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 one

Combination of wound honeycomb bodies and smooth

Metal strips are used, which are coated with catalyst. According to the present invention, the catalysts are in finely divided form on and / or in the filter material according to the invention with its specific

Structure introduced, the exhaust gas completely through

the filter is directed. The catalyst can also be located in and on the surface of the filter material itself. Due to its uniform structure of only low density and the device according to the invention, there is an extremely intimate contact between exhaust gas and catalyst material

The material according to the invention is used shortly after the internal combustion engine is started up

the full activity of the catalyst and thus high sales of the pollutants reached, so that according to the invention

overall, extensive removal of the pollutants

CO, NO _x , hydrocarbons and soot can be achieved.

A further advantage of the method according to the invention or the device according to the invention is the result that the removal of catalyst from the material according to the invention is significantly less than with catalysts which are located on surfaces according to the prior art, in particular when the catalysts are in the filter material itself is incorporated.

It is not to be further explained here how such

Catalysts are applied to or in the material, because there are very many processes for this

Are accessible to a person skilled in the art and can be used without further ado within the scope of the present invention. According to the invention, all reduction and oxidation catalysts or their combinations can be used. Numerous examples, but they are by no means limiting,

since the prior art cannot be reproduced here in full, the described prior art are specified. For example, without this list being complete, the following elements, their compounds and, other compounds: ruthenium, rhodium,

Osmium, iridium, platinum, palladium, vanadium, chrome, manganese, tin, cobalt, nickel molybdenum, tungsten, niobium, tantalum, rare earths as well as vanadates, chromates, chromites, manganates, manganites, stannates, molybdates, tungstates, niobates, tantalates , Compounds of Fe, Co, Ni, Cr, Mn, Cu, Zn, Ag, Cd, rare earths and numerous other compounds as are known from the prior art.

The filters according to the invention are for removing the

Pollutants NO _x , carbon monoxide and hydrocarbons as well as soot are ideally suited because they completely separate the soot and build up only very little pressure, allow intimate contact between the pollutants and the catalyst, can be brought quickly to the temperature of the full activity of the catalyst and during the separation process soot can be brought to the combustion temperature of the soot very quickly with only a small amount of heat and the removal of catalyst is also very low. The present invention accordingly leads to previously unachieved properties of methods and devices for removing pollutants from exhaust gases.

According to the present invention, it is also possible to pretreat the filter material in such a way that it can be regenerated or. Removing the soot deposited on the filter does not require the use of burners and heaters. This is achieved in that the filter material is preferably pretreated with a soluble iron compound in such a way that the iron compound is sprayed onto the filter material in dissolved form. However, other treatment methods are also possible according to the invention, such as, for example, immersing the filter material in a dilute solution of the iron compound.

The material is then thermally treated at a temperature at which the material dries or

the temperature can be varied within wide limits, for example from room temperature to 2000 ° C. Stoving can take place according to the invention, but is not required. For example, the filter material treated with the solvent can be used after the solvent has largely or completely evaporated use directly in the device according to the invention.

All solvents are suitable, but in the case of water-soluble iron compounds such as FeSO ₄ , green salt, FeCl ₂ , Fe (NO ₃ ) ₂ and other water, preference is given to those with relatively low water in the case of organic iron compounds

Boiling point, such as the lower alcohols and ketones and their mixtures. However, ethers, cyclic compounds containing heteroatoms, aromatics and numerous others can also be used. All soluble iron compounds can be used according to the invention. Organic iron compounds are e.g. B. Ferrocene, iron acetylacetonate, iron acetates and many others. Preference is given to ferrocene and derivatives, which can be dissolved, for example, in methanol. The pretreatment described leads to the fact that when a certain counterpressure is reached when the filter or the device according to the invention is operated, the soot burns off automatically without any further action. The back pressure goes back to the outlet pressure or up to the vicinity of the outlet pressure. Then the back pressure builds up again, followed by another burning of the soot. So far, the applicant has not noticed a decrease in this burning cycle even after burning over 100 times.

The invention is explained by way of example in the figures. FIG. 1 shows a filter and / or catalyst device in cross section, FIG. 2 shows one in longitudinal section. Figure 3 shows a further filter and / or catalyst device.

Figure 4 also shows an example of a filter and / or catalyst device.

Figures 5-7 show the pressure build-up depending on the flow time and the filter construction.

FIG. 8 shows a further arrangement according to the invention. Mullite is a preferred constituent in the filter material according to the invention, particularly in the range of high temperatures up to 2000 ° C. It can be present in any proportion. Preferred are 20-100% by weight, more preferred

60-100 wt. -5 and particularly preferred are 80-100 wt.%. At high temperatures up to 2000 ° C., polycrystalline or predominantly polycrystalline material which does not recrystallize even at temperatures up to 2000 ° C. is also preferred according to the invention.

However, to reduce brittleness, the material can also contain amorphous components.

The filter material is preferably used in fiber form, but it can also have numerous other configurations, such as, for example, granulate form, mat form, woven form, cloth form and others, the latter forms also

can be made from yarns that can also be made from the material according to the invention with reinforcements on the inside such as glass fibers or inconel.

The fibers used in the invention can be made in various ways, e.g.

by converting primary fibers through tempering

or by extrusion-sintering processes or spin-sintering processes. The fibers can be produced, for example, by mixing the starting material into a slurry in the presence of an organic or inorganic binder, the oxides used preferably being in a gel-like composition. The fibers are drawn from the slurry, annealed after being pulled and then fired at at least 1 400 ° C, but below

2000 ° C.

Another method of production can be such that alumina and silicon dioxide are melted in an arc furnace and the melt mixture is poured into threads or threads are drawn from the melt, which are then refined into fibers.

The methods given are to be regarded as examples, but are not limiting.

In connection with the specific structure of the material used according to the invention, the density of the material is important. It is 0.01-1.5

g / cm ³ , preferably 0.03-1 g / cm ³ and particularly preferably 0.06-0.5 g / cm ³ .

The filter device according to the invention is preferably tubular. The exhaust gas is introduced into a space which is located inside the device, preferably arranged centrally, e.g. as a tubular space with, for example, a round or oval cross section, the entire filter device also being able to have a round or oval cross section, but this is not absolutely necessary. Other cross sections can also be used according to the invention, such as e.g. rectangular, square, irregular, trapezoidal, etc.

The central room is preferably

an empty space that is open on the input side and closed on the output side. It can also contain internals. The diameter of the room is generally 1-30 cm. The room is delimited to the outside by a dimensionally stable wall that is gas-permeable. Prefers

the wall consists of a sheet provided with openings, such as a perforated sheet or a wire basket. The material can be steel, stainless steel, copper or another metal or alloy. According to the invention, the wall can also consist of ceramic material or other dimensionally stable, temperature-resistant materials. Around the wall there is a room in which the actual filter material is located.

Accordingly, the exhaust gas to be cleaned must pass through the

flow through the central room, then through the wall and then through the actual filter material. By doing

Filter material can also be embedded in other temperature-resistant materials, for example gas-permeable metal or ceramic body or metal fibers.

The fibers of the filter material according to the invention are preferably arranged in a tangled position. However, they can also be mat-like, cotton-like, fleece-like, layer-by-layer, vacuum-shaped or shaped or arranged differently, and they can also be directional.

A covering is arranged around the filter material, which is preferably fabric-like. The casing preferably also consists of the filter material according to the invention. However, it can also consist of other high-temperature resistant materials. It is known to the person skilled in the art that numerous materials have high-temperature resistant properties, e.g. Aluminum silicates in general, aluminum silicates with a high proportion of aluminum oxide, chromium oxides, silicon dioxide, aluminum oxide, zirconium oxide, iron oxides, silicates such as alkaline earth silicates, titanium oxide, boron oxide, aluminum borosilicates, natural silicates such as rock formers, clays, clays, carbides, manganese oxides, germanium oxide and rare earth oxides Combinations of the materials mentioned.

The fabric-like sheath is gas-permeable, so that the exhaust gas can flow through and can flow out cleaned. The filter device is located in a muffler-like device, which is usually made of sheet steel or stainless steel sheet and is open on the output side. Between the steel sheet and the casing, rib-like or other holders or steel wool, ceramic material or the like can be arranged to fix the filter device, so that a space is present through which the cleaned exhaust gas can flow to the outlet of the silencer-like container. The filter device in the container has a strong sound-absorbing effect, so that an additional silencer is generally not necessary. A solid, gas-permeable wall, such as, for example, a perforated plate or a wire cage, is generally arranged around the fabric-like covering.

The investigations by the applicant have shown that a particularly low pressure build-up is observed during filter operation if the filter material is in direct contact with the casing, i.e. if there is no, for example, a grid-like or perforated sheet-like wall between the filter material and casing. This is shown in FIGS. 5-7 shown.

The covering, which is preferably fabric-like, prevents the passage of even the smallest fiber particles in the μ range, despite the very good permeability for the cleaned gas. In principle, the exhaust gas can also flow from the outside inwards in the manner according to the invention. However, the flow path from the inside to the outside is preferred according to the invention.

A so-called

Wet mat can be used. Here, a high temperature resistant mat in water-wet condition from

Manufacturer supplied. It works particularly well

to form. Such a mat can be 30-75, for example

Wt .-% Al ₂ O ₃ and and 25-70 wt .-% SiO _{2 in} addition to small

Amounts of other oxides such as ZrO ₂ ,

Fe ₂ O ₃ and Na ₂ O included. It can consist at least predominantly of mullite. The permeability to the exhaust gases can be increased by driving an inert gas stream under pressure through the mat before use. The effect of driving with N _{2 is} shown by the following

Results:

a, the wet mat was exposed to 2 bar N _{2 for} 5 minutes

drive through and dried at 150 ° C.

Back pressure difference: 3m mbar

b, the wet mat was at 2.5 bar for 15 minutes

Drive through N ₂ and dry at 150 ° C.

Back pressure difference: 20 mbar.

c, the wet mat was treated with 3 bar N _{2 for} 45 minutes

drive through and dried at 150 ° C.

Back pressure difference: 10 mbar.

The results show that the permeability of the mat is not affected by the emergence of fine particles

can significantly improve the pretreatment.

Because of the device according to the invention, the

Pass exhaust gas completely through the filter.

The length, wall thickness and inner diameter of the filter tubes can vary within wide limits depending on the motor type.

Depending on the motor strength, larger or multiple filters can be used.

The devices according to the invention can have lengths of a few centimeters to the order of magnitude of meters. Usual lengths are 15-80 cm

Diameter of the inflow and outflow spaces and the

Filter walls can be a few millimeters to many cm thick. The motor vehicle specialist has a wide range here to select these values from the points of view which are important to him. It must be taken into account here that the density of the material used according to the invention and the wall thickness of the filter can complement one another.

With the filter material densities according to the invention, customary filter wall thicknesses are approx. 5-300, preferably 10-150 mm, in the case of the high densities these thicknesses may be undershot and in the case of the low densities these thicknesses may be exceeded.

Density and wall thickness are not only special

This means that the soot is completely caught in the exhaust gas immediately after starting the engine, but also with regard to the very important pressure build-up caused by the filter. As is known, increasing pressure on the engine outlet side causes increasing fuel consumption in front of the filter.

A comparison with the technically used soot filter from Corning Glass Works shows the particularly advantageous behavior of the filter according to the invention, namely that complete filtration is achieved immediately after commissioning.

The largest of these filters consists of a ceramic block 38 cm long and 38 cm in diameter. It contains approximately 17,000 channels in one direction, which are open on the input side and just as many channels, which are closed on the input side and open on the output side. The channels have an approximately square shape with a side length of approximately 0.2 mm. The exhaust gas flows through the very thin, porous walls of the input channels into the output channels. The full filtering effect of the channels, which in the case of the filters available on the market, depending on the type, is between 65 and 95% of the soot present in the exhaust gas, is only achieved after at least 1 hour of operation, since enough soot is then deposited to be used as a filter to act.

The back pressure increases depending on the filter type

1.5-4 hours at 130-150 mbar.

Since the channel walls are very thin, it occurs easily

Crack formation, so that unfiltered exhaust gas emerges. Furthermore, recrystallization processes occur with embrittlement of the material. These disadvantages of the prior art are overcome by the present invention.

With sufficient wall thickness, filter materials with a density of 0.06-0.5 can be very cheap according to the invention. Basically, the arrangement and number of filter tubes, shape, wall thickness, diameter and length of the filter tubes can be adapted to the respective vehicle type.

The externally closed areas of the filter device according to the invention can be conventional

Be closed with lids, plates and the like. According to the invention, the fabric-like covering can also be closed by sewing.

The importance of the present invention is made clear by measurements carried out by the Rhineland Technical Monitoring Association in Cologne-Porz on August 14-17, 1990. As a motor vehicle, a car of the type Daimler-Benz 190D, built in 1986 with a mileage of 106,162 was used. The passage of soot through the filter was 0.009 g / km. This value was reached immediately after the engine was started. The fiber material contained only 20% by weight mullite. The device corresponded to that shown in FIG.

This value was not quite achieved in a comparative test with a fiber filter drawn from the melt. However, the arrangement according to the invention also achieved the very good value of 0.012 g / km. Comparative measurements with soot filters of the prior art

Technology result in values of 0.08-0.09 g / km.

The result shows that not only the US standard of

0.124 g / km, but also the currently strictest standard of the state of California in the USA of 0.05 g / km.

It was completely unpredictable and surprising for the person skilled in the art that a relatively thin layer of the according filter material in the inventive

Arrangement would improve the results of the soot filter of the prior art by a power of 10.

According to the invention, the filter material apparently act in conjunction with the arrangement according to the invention in which the filter material is in direct contact with the

Wrapping and in connection with the density of the material according to the invention in a synergistic manner that in particular soot particles with their

specific properties are bound in a particularly favorable manner.

It is generally known that, despite the economy of diesel vehicles, the soot emission is a serious disadvantage. This situation is improved by the present invention by leaps and bounds, the type of production of the fibers and the arrangement according to the invention, in particular the filter material lying on the casing and the density of the Filter material play an essential role.

To determine the very important criterion of the pressure increase during the driving operation of a diesel engine, the above-mentioned vehicle was under full load two

Driven for hours. Only a slight increase in pressure could be measured. No increase in the CO content in the exhaust gas was found during this driving period. This means that no higher fuel consumption has occurred. For comparison, the same driving time was used with a filter as currently used by third parties in test runs. After 2 hours of driving, the back pressure had increased by 160 mbar.

In a further comparison test, the device according to the invention was used, but a highly permeable perforated plate was arranged between the fibrous filter material and the casing. After 2 hours of driving, the back pressure had increased by 60 mbar. This result clearly shows that due to the direct contact of the filter material with the casing, in this case tissue-like, one filtration and one

Flow entering the pressure increase in the filter

minimize.

The filter according to the invention can not only be used for cleaning engine exhaust gases, it also gives good results when used for cleaning exhaust gases from building heating systems. However, it is advantageous here to press the heating exhaust gas through the filter by means of a fan.

To determine the thermal stability of the filter material used in the present invention, the influence of mullite was investigated. The filter device according to the invention was heated to 2000 ° C. with a burner and then cooled to room temperature. The results are summarized in the following table.

The present invention is explained in more detail with the aid of the figures.

Figure 1

In Figure 1, the filter area is represented by (1).

(2) is the centrally located space for introducing the exhaust gas to be cleaned. (3) is a perforated plate attached between this and the filter bottom. (4) represents the envelope. (5) is the outer space through which the cleaned exhaust gas flows out.

(6) is a gas-permeable, supporting wall around the casing (4).

(7) is the silencer-like casing.

Figure 2

FIG. 2 shows an example of a device according to the invention in longitudinal section.

The exhaust gas to be cleaned enters the room (2), flows through the gas-permeable wall (3) and enters the

Filter space (1) and then passes through the casing (4) and

the supporting wall (6).

Figure 3

The exhaust gas to be cleaned flows into the room (2) through which

gas-permeable wall (3) in the filter chamber (1). The covering is sewn like sacks. Around the wrapper is the

Support wall (6) arranged. At (9) is the sheath (4)

on the inlet pipe (10) tight, but releasably attached.

Figure 4

Figure 4 represents one of an inner and an outer

Filters existing filter arrangement. (3) and (5) are

inner and outer filter. The exhaust gas to be filtered enters through (7) the space (4) between the inner and outer filter. The filtered exhaust gas exits the filter arrangement from room (1) via (8) and outside via (9). (2) and (6) are cloth-like materials that prevent the removal of the finest fiber particles. (10) represents the housing around the filter assembly.

Figures 5-7

In FIG. 5, the filter consists only of an envelope (4) surrounded by a gas-permeable support plate (6). The exhaust gas to be cleaned enters the interior (2).

Curve (a) shows a relatively quick build-up of pressure.

A counter pressure of 110 mbar is already achieved after 2 hours.

FIG. 6 shows a filter which consists of an inner space (2) into which the exhaust gas to be cleaned enters, a gas-permeable solid wall (3), the actual filter space (1), which contains the filter material according to the invention, the casing ( 4), to which the filter material lies directly and the outer, supporting, gas-permeable wall (6).

Curve (b) shows that the back pressure rises only very slowly and then rises less. After 2 hours of driving, the back pressure is only approx. 40 mbar.

FIG. 7 shows a filter in which a gas-permeable perforated plate (8) is located between the filter material and the casing 4).

Curve (c) shows the surprising effect of this changed structure, although the pressure increase is less than in curve (a), but much stronger than in

Curve (b) .After 2 hours the back pressure is 60 mbar.

In Figures 5-7, the wrapper consisted of

fabric-like, high temperature resistant material with 80% by weight mullite.

Figure 8

In Figure 8 (1) indicates that

cleaning exhaust gas. (2) represents the passage of the exhaust gas through the filter zone and casing. (3) is the filter space in which the filter material is located.

(4) is the wrapper. (5) is the space through which the cleaned exhaust gas flows out. (6) represents the direction of the exhaust gas flowing out. (7) is the closed space on the outlet side into which the exhaust gas to be cleaned flows.

In contrast to FIGS. 1-4, the arrangement represents an arrangement in which the filter zone and the envelope have a rectangular shape.

Claims

1. Process for cleaning exhaust gases, in particular for

filtering removal of soot particles from the exhaust gases of diesel internal combustion engines and building heating systems, characterized in that the exhaust gas is passed through a filter material containing 30-99.8% by weight, preferably 50-95% by weight Al ₂ O ₃ and 0.2 -70% by weight, preferably 5-50% by weight of SiO ₂ or SiO ₂ + ZrO ₂ contains that the ZrO ₂ content 0.05

75 wt .-% of the sum of the SiO ₂ + ZrO ₂ amount can be that the density of the material 0.01-1.5 g / cm ³ , preferably 0.03-

1 g / cm ³ and particularly preferably 0.06-0.5 g / cm ³ and that the exhaust gas after flowing through the filter material flows through a gas-permeable envelope surrounding it and containing SiO ₂ and Al ₂ O ₃ .

2. The method according to claim 1, characterized in that the exhaust gas is passed through a filter material in which the Al ₂ O ₃ and SiO ₂ are 20-100%, preferably 60-100% and particularly preferably 80-100% .

3. The method according to claims 1 and 2, characterized in that the exhaust gas is passed through a filter material that 0-10 wt .-% of at least one metal and / or semimetal oxide from the group alkali oxides, alkaline earth oxides, gallium oxide, indium oxide, Thallium oxide, boron oxide, germanium oxide tin oxide, lead oxide, phosphorus oxide, arsenic oxide, antimony oxide, bismuth oxide, selenium oxide, tellurium oxide and oxides of the subgroups of the periodic table, preferably from the group FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , TiO ₂ , Cr ₂ O ₃ , contains manganese oxides, rare earth oxides, whereby the total amount of all components is 100% complementary.

4. The method according to claims 1-3, characterized in that the exhaust gas to be cleaned is passed into a room which is open on the input side, closed on the output side and on the wall between the entrance and exit is gas-permeable.

5. The method according to claims 1-4, characterized in that the exhaust gas is passed through a room in which there is fibrous, high temperature resistant filter material.

6. The method according to claims 1-5, characterized in that the exhaust gas to be cleaned is passed through a filter material, which preferably on the surface, at least one catalyst from the group: oxidation catalyst for removing carbon monoxide from exhaust gases, oxidation catalyst for removing hydrocarbons from exhaust gases, contains an oxidation catalyst for removing carbon monoxide and hydrocarbons and a reduction catalyst for removing NO _x from exhaust gases.

7. The method according to claims 1-6, characterized in that the exhaust gas to be cleaned is passed through a filter material which has been pretreated with a soluble iron compound.

8. The method according to claims 1-7, characterized in that the exhaust gas flows through a gas-permeable envelope, which consists of high temperature resistant material and preferably contains mullite.

9. The method according to claims 1-8, characterized in that the exhaust gas is passed through a mat-like, gas-permeable covering.

10. The method according to claims 1-9, characterized in that the exhaust gas is passed through a mat-like, gas-permeable casing pretreated by flowing through it with inert gas under pressure.

11. The method according to claims 1-10, characterized in that the exhaust gas is passed through a filter material arranged in turbulence.

12. The method according to claims 1-11, characterized in that the exhaust gas is passed through a filter material which bears directly on the casing.

13. Device for cleaning exhaust gases, in particular for the filtering removal of soot particles from the exhaust gases of diesel internal combustion engines and building heating systems, which has a space into which the exhaust gas to be cleaned is introduced, which is open on the inlet side, closed on the outlet side and on the wall between the inlet and Output is gas-permeable and a room in which there is high-temperature-resistant filter material, characterized in that a gas-permeable covering containing Al ₂ O ₃ and SiO ₂ is arranged around the filter material, that the filter material 30-99.8% by weight. , preferably 50-95% by weight of Al ₂ O ₃ and 0.2-70% by weight, preferably 5-50% by weight of SiO ₂ , or SiO ₂ + ZrO ₂ contains that the ZrO ₂ content is 0 , 05-75% by weight of the sum of the SiO ₂ + ZrO ₂ amount can be that the

Density of the material 0.01-1.5 g / cm ³ , preferably 0.03-

1 g / cm ³ and particularly preferably 0.06-0.5 g / cm ³ .

14. The device according to claim 13, characterized in that the Al ₂ O ₃ and SiO ₂ to 20-100 wt .-%, preferably to 60-100 wt .-% and particularly preferably to 80-100 wt .-% as mullite available.

15. Device according to claims 13 and 14, characterized in that the filter material 0-10 wt .-% of at least one metal and / or semimetal oxide from the group: alkali oxides, alkaline earth oxides, gallium oxide, indium oxide, thallium oxide, boron oxide, germanium oxide, Tin oxide, lead oxide, phosphorus oxide, arsenic oxide, antimony oxide, bismuth oxide, selenium oxide, tellurium oxide and oxides of the subgroups of the periodic table, preferably from the group: FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , Cr ₂ O ₃ , Contains manganese oxides, rare earth oxides, whereby the total amount of all components is 100% complementary.

16. The device according to claims 13-15, characterized in that the filter material is fibrous and resistant to high temperatures.

17. Device according to claims 13-16, characterized in that the filter material preferably on the surface, at least one catalyst from the

Group: Oxidation catalyst for the removal of

Carbon monoxide from exhaust gases, Ox.-Katal. for removing hydrocarbons from exhaust gases, oxidation catalyst for removing carbon monoxide and hydrocarbons from exhaust gases, reduction catalyst for removing NO _x from exhaust gases.

18. Device according to claims 13-17, characterized in that the filter material is pretreated with a soluble iron compound.

19. Device according to claims 13-18, characterized in that the gas-permeable covering consists of high-temperature resistant material and preferably contains mullite.

20. Device according to claims 13-19, characterized in that the gas-permeable covering is mat-like.

21. Device according to claims 13-20, characterized in that the gas-permeable casing is pretreated by flowing inert gas under pressure.

22. Device according to claims 13-21, characterized in that the filter material is arranged in tangled layers.

23. Device according to claims 13-22, characterized in that the filter material lies directly on the casing.