DE2313837B2 - Device for treating exhaust gases from internal combustion engines - Google Patents

Description

The invention relates to a device for treating exhaust gases from internal combustion engines, consisting of a cylindrical container, at one end of which has an inlet for exhaust gas to a central one Gas passage element and an outlet for a ring-shaped one surrounding the central gas passage element Gas passage element coming gases are provided and at the other end of a central one Gas passage element is provided for the annular gas passage element leading passage, which has an air inlet, the inner gas passage member having a catalyst for reducing Nitrogen oxides to nitrogen and the ring-shaped gas passage element a catalyst for the oxidation of Contain carbon monoxide and hydrocarbons.

Such a device has become known, for example, from US Pat. No. 3,544,264. In this Document is a device of the type in question with a central and a central one surrounding, annular gas passage element described, wherein the gas passage elements made of beads. Cylinders, granules or impregnated fibers can exist, which are arranged like a mat. Partition walls are arranged between the central and the annular gas passage element, which keep the gas flows in the gas passage elements separated from one another. In this setup, the Replacement of the material of the gas passage elements or the entire gas passage elements extraordinary difficult, and the construction of the entire device is complex and expensive.

Furthermore, DT-OS 14 42 587 carriers for catalyst materials have become known, which the shape of tubes with a regular hexagonal cross-section, so that when assembling several such tubes result in a honeycomb structure.

ίο The invention is based on the object of a To improve the device of the type mentioned in such a way that it has the simplest possible structure has and the gas passage elements can be easily exchanged or replaced if the or the

Catalysts, with which the gas passage element or the gas passage elements are impregnated, are consumed are.

This object is achieved according to the invention in that the central gas passage element and the ringför mig ^ gas passage element made of a multitude of linear, There are gas flow cells aligned parallel to the central longitudinal axis of the container, which have hexagonal cross-sections have and their walls with the peep The corresponding catalysts are coated, and that that

central and the annular gas passage element are parts of a single unit, with the cells between the central and the annular gas passage element are sealed against the passage of the gases. As can be seen, the device according to the invention offers the advantage of a simple structure and can be made easily. This usually makes them cheaper than known ones Manufacture devices. Another advantage is that the pressure drop in the exhaust gases through the channel-like formation in the device is generally low and the back pressure in the internal combustion engine is significantly reduced.

Another advantage of the device according to the invention is that the uniform flow

and the even distribution of the exhaust gases in contact with the catalyst without major Effort a uniform catalysis is achieved and the exhaust gases uniformly and over relatively long times be treated completely without being during

longer running times of the internal combustion engine there is a risk of failure. Another advantage the device according to the invention is that the gas passage elements during operation in neither wear nor decompose while moving vehicles, which is characteristic of known catalytic devices in which consisting of loose carrier particles, covered with catalyst compositions or soaked layers can be used. The two gas passage elements consist of a one-piece rigid body and therefore there are no physical losses due to movement and friction subject between individual parts, as it is, for. B. is the case with packed catalyst layers.

Appropriate embodiments and developments of the invention emerge from the subclaims.

In the following, the invention is illustrated by means of an exemplary embodiment with reference to the drawing explained and described in more detail. It shows Fig.l a longitudinal section through a preferred one Embodiment of the invention and

Fig. 2 shows an enlarged section through Fig.l along line 2-2, in which the coaxial and concentric

Ie arrangement of the gas passage elements is shown.

A fuel flow 1, which generally consists of a liquid hydrocarbon fuel such as gasoline, and a primary air flow 2 are fed into a combustion engine 3, which is usually installed in a car or the like. The fuel flow I »v is burned in the internal combustion engine 3 and generates usable energy and an engine exhaust gas, which is usually collected in the exhaust manifold 4. This gas collected in the manifold 4 usually contains toxic components including nitrogen oxides, hydrocarbons and carbon monoxide. A stream of air 5 may in some cases be introduced into the manifold 4 so that the manifold 4 serves as an afterburner to partially burn the hydrocarbon in place. In any case, the exhaust gas flow t> emerging from the manifold 4 is guided into a conical diffuser 7, which extends centrally into the device of the present invention. The diffuser 7 is held in place by a circular retaining ring 8 in which the compressible seal 9 is attached. This seal 9 consists of asbestos or another Mincralfaserstolf or similar materials suitable for operation at elevated temperatures.

The partition wall 10 extends away from the seal 9 and serves to divide the component into a central and a split annular chamber. The central gas passage element 11 extends in a cell structure coaxially within the partition wall 10, and the diffuser 7 serves to distribute the exhaust gas flow 6 evenly in the To distribute a plurality of parallel linear gas passage cells in the gas passage element 11. These gas flow cells are covered and soaked with a suitable catalyst for catalytic reduction from nitrogen oxides to nitrogen by reaction with oxidizable components in the gas stream, such as. B. Hydrogen, carbon monoxide and / or hydrocarbons. As a catalyst for the reaction can be used in the Practice any catalyst or combination of catalysts can be chosen, e.g. B. zinc, nickel, platinum. Kupier. Manganese, vanadium, cobalt, chromium or iron, or. Catalytically active oxides of these metals or Mixtures of these metals. A combination of catalytic components including copper, cobalt, nickel and manganese is preferred. The preferred building material for the gas permeable element 11 is lithium aluminum silicate, however, other heat-resistant materials, such as e.g. B. aluminum oxide is used will. The gas passage member 11 is formed by extrusion molding, molding or other known manufacturing methods generated, and the finished unitary component can be sintered or fired or annealed followed by immersion in an aqueous solution of the carbonates, nitrates, or organic Acids of the above-mentioned catalytically active metals. Before being installed in the device, the Gas passage element 11 then usually dried at an elevated temperature, usually in a Hydrogen atmosphere or other reducing gas atmosphere, and in some cases multiple Immersion and drying stages may be provided prior to use. The aqueous solution of the salts of the catalytically active metals can also contain ammonium nitrate or other suitable accelerators. In in any case, any suitable and effective catalyst or combination of catalysts can be used any suitable method can be stored on and in the gas passage cells of the gas passage element 11.

The exhaust gas stream 6 flows through the gas passage element 11, and at least a part of that in the exhaust gases Oxides of nitrogen contained therein or essentially the whole amount thereof is catalytically converted to nitrogen reduced. The partially treated exhaust gas flows within the support ring 12 from the gas passage element 11th

A secondary air flow 13, which can be preheated, is blown into the pipe 16 as blown air 15 by the blower 14 which extends to a perforated air outlet portion within the device in the same. the Air flowing out through the openings in the pipe 16 mixes with the air flowing out of the gas passage element ii partially treated exhaust gases flowing out and a mixture of air and exhaust gases is produced by the Openings in the perforated, load-bearing partition 17 flows out, which is located between the support ring 12 and the disk-shaped · 'Siiniwand 18 of the container extends. The mixture of air and exhaust gases then flows in the opposite direction through an annular Opening between the support ring 12 and the outer annular support strip 19 on the inner wall of the cylindrical wall of the container 20 is attached

The mixture of air and exhaust gases then flows through the annular gas passage element 21, the is seen with a plurality of parallel linear gas passage cells, which with a suitable Catalyst covered to catalytic oxidation of carbon monoxide and hydrocarbons to carry out non-toxic products such as carbon dioxide and water vapor. The annular gas passage element 21 is made of the same building material as the gas passage member 11 described above, i.e., made of Lithium aluminum silicate or aluminum oxide, and is formed in one piece with this. Besides, he's up the wall surfaces of the individual gas passage cells of the gas passage element 21 applied active The catalyst is preferably the same as that used in the gas passage member 11. This type of catalyst is commonly known as a redox catalyst, a catalyst that performs a reduction or oxidation reaction is able to accelerate, depending on the condition and composition of the contacting catalyst Operating current.

The mixture of air flowing through the gas passage cells of the annular gas passage element 21 and exhaust gases are catalytically converted within the gas passage cells, the oxygen content of the supplied secondary air stream 13 is used to remove the carbon monoxide and hydrocarbons in the Exhaust gases at least partially or essentially entirely to non-toxic products such as carbon dioxide and To oxidize water vapor. This exothermic catalytic reaction is used to generate heat that the Temperature of the whole device rapidly to an optimal temperature range approximately between 500 and lets rise to 900 ° C.

The container 20 is at the outlet end of the device for the treated exhaust gases with an annular flange 22 Mistake. A mating flange 23 is also provided, to which the exhaust gas outlet manifold is attached. Between the flanges 22 and 23 an annular seal 24 is provided, which is preferably made of asbestos, a similar mineral fiber paste or other suitable heat resistant sealing composition consists. In most cases, the seal 24 will be made from the same material as that described above

Seal 9 be assembled. The finally from the gas passage cells of the gas passage element 21 exiting, fully treated, final exhaust gases are now essentially free of toxic components and are directed from the gas outlet manifold 25, which is located between the counter flange 23 and the outside of the diffuser 7 and serves to the completely treated exhaust gases To lead discharge pipe 26, which od the exhaust pipe of an automobile. The like. Can be. The treated Exhaust gases can be fed to the discharge pipe 26 as flow 27 leak into the atmosphere without causing air pollution.

In Fig. 2 can be seen that both for the central As well as the annular exhaust gas passage, a single unitary cell structure is provided and the individual gas passage cells of the common cell structure have hexagonal cross-sections. the The central gas flow is delimited from the annular gas flow by providing a sealing seal or sealed cells between the central and annular groups of cells. The for Preventing gas penetration clogged intermediate cells can either use a wear Material like aluminum oxide or an insulating intermediate mass completely filled or it can be individual plugs or sealing seals are provided at one or both ends of the intermediate sealing cells be.

15th

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Device for treating exhaust gases from internal combustion engines, consisting of a cylindrical Container at one end of which has an inlet for exhaust gas to a central gas passage element and an outlet for an annular one surrounding the central gas passage element Gas passage element coming gases are provided and at the other end of a central one Gas passage element is provided for the annular gas passage element leading passage, which has an air inlet, the inner gas passage member having a catalyst for reduction from nitrogen oxides to nitrogen and the annular gas passage member a catalyst for the oxidation of carbon monoxide and hydrocarbons, characterized in that that the central gas passage element and the annular gas passage element from one A plurality of linear gas-permeable cells aligned parallel to the central longitudinal axis of the container (20) exist, which have hexagonal cross-sections and their walls with the corresponding catalysts are coated, and that the central and the annular gas passage element are parts of a single one Are unit, the cells between the central and the annular gas passage member are sealed against the passage of gases. 2. Device according to claim 1, characterized in that that both elements consist of lithium aluminum silicate. 3. Apparatus according to claim 1 or 2, characterized in that the cells between the central and the annular gas passage element are filled with an inert solid.