DE2313837A1 - DEVICE FOR CATALYTIC EXHAUST GAS TREATMENT - Google Patents

Description

23581/2

Chemical Construction Corporation, New York, N.Y. / UNITED STATES

Device for catalytic exhaust gas treatment

The invention relates to a device for treating exhaust gases from prime movers, comprising a container with two consecutive catalyst chambers with an air inlet in between.

The invention is concerned with preventing air pollution by nitrogen oxides, carbon monoxides and unburned or thermally degraded hydrocarbons, those in the exhaust gases of drive machines, e.g. internal combustion engines for vehicles such as automobiles, trucks, Omnibuses, tractors and motorcycles emanate from it. In recent years it has been recognized that the incineration

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Exhaust gases from engines are a source of harmful emissions Air pollution, especially in metropolitan areas. In some areas, due to atmospheric inversions and accumulation of such exhaust gases in the atmosphere, the so-called smog. Recent attempts to prevent such air pollution have focused on the Destruction or elimination of certain constituents through catalysis concentrated, in particular through admixture of Secondary air in the exhaust gases after the first catalytic reduction of the nitrogen oxides, followed by catalytic Oxidation of residual hydrocarbons, carbon monoxide in various types of devices specially built for this purpose or catalytic silencers.

The invention particularly relates to a device for catalytic exhaust gas treatment, whereby nitrogen oxides are catalytically reduced to nitrogen, air supplied to the exhaust gas and the resulting mixture is brought into contact with a catalyst, thus toxic unburned or thermally oxidize degraded hydrocarbon vapors or other organic vapors to harmless products such as carbon dioxide or water vapor through catalysis. The term hydrocarbons here includes remaining unburned hydrocarbons, thermally degraded hydrocarbons and other organic ones Vapors in the exhaust gas flow. The catalytic oxidation process results in and when the hot engine is running steadily Hot exhaust gas normally eliminates a substantial amount of these harmful components originally in the exhaust gases external and internal combustion engines, e.g. Jet engines, gas turbines, diesel engines or gasoline-burning automobiles, buses or truck engines are present so that the leakage of these toxic components including unburned hydrocarbons, other organic vapors and carbon monoxide in the air and with it

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air pollution is prevented.

Numerous catalytic converters, catalytic devices and silencers and treatment systems have been proposed for processing exhaust gases emitted from prime movers, in order to control the exhaust emissions from prime movers and prevent the release of toxic components into the air. From dealing with catalysis and catalytic compositions Employing many United States patents include the following numbers: 3. »053 * 773J 3,429,65b; 3,316,057; 3,398,101; 3, ^ 77,893 and 3, ^ 76,508. Apparatus for carrying out the process is disclosed in US Pat. Nos. 3,380,810; 3,325,256; 3,255,123; 3.222, 14o; 3, Ι86, δθ6; 3, 18o, 712; 3, ^ 69,836; 3,168,806; 3,146 073 and 3,086,839. In one embodiment, there is an apparatus with two stages for performing the method provided with air injection between the steps. A programmed Injection during various phases of the prime mover's operating cycle may be provided.

The object on which the invention is based is achieved in that a central gas passage element with a cell structure and an annular gas passage member having a cell structure is provided around the first cell structure member wherein the elements have a plurality of parallel running parallel to the central axis of the container linear gas passage cells have that at one end of the container an inlet for delivery to the central element and a discharge for gases emerging from the annular element, and at the other end of the container a from the central one to the annular element leading passage is provided which contains an air inlet, and that the cell walls the inner element with a catalyst to reduce nitric oxide to nitrogen and the cell walls of the annular elements are covered with a catalyst for oxidizing carbon monoxide and hydrocarbons.

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The above-mentioned catalytic reactions can expediently Use of cell structure elements are carried out, which a large number of individual parallel running have linear gas flow cells as a carrier for the active catalyst, in most cases is used for both reduction and oxidation. The cell structure elements are in a container arranged of preferably cylindrical shape. A central gas passage element in cell structure is in the container provided, and this element has individual cells that contain an active reduction catalyst are covered by oxides of nitrogen to form nitrogen. The exhaust gases of the prime movers get into the container and are guided through the central cell structure element. The partially treated Exhaust gases are added to air and the mixture of air and exhaust gases is then passed through an annular cell structural member out, which is arranged in the container around the central element. The ring-shaped cell structure possesses individual cells or passages that contain an active catalyst to oxidize carbon monoxide and Hydrocarbons to generate non-toxic products such as carbon dioxide and water vapor. The done treated exhaust gases from which the toxic components have now been removed, or which are now essentially non-toxic can then be removed from the container and safely without causing air pollution Air.

An advantage of the device of the present invention is that the device generally stores heat and becomes quickly warmed to normal operating temperature by heat exchange between the central and the annular Cell structural element, with an exothermic oxidation reaction taking place. When the machine is started, the external Cell structure act as an insulator and heat for the first

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Save reactions of the inner layer. Heat losses contribute to bringing the outer element to operating temperature bring. While the machine is running smoothly, heat is conducted from the outer line structure to the inner component, whereby its average temperature is raised and the nitric oxide elimination reaction is somewhat accelerated.

Another advantage can be seen in the fact that the gas pressure drop of the device is generally low and the back pressure therefore essentially reduced in the machine.

Yet another advantage is that the device is of relatively simple construction and can be easily manufactured and is therefore usually cheaper than known such devices.

Another advantage is that the flow is even and a uniform distribution of the exhaust gases contacting the catalytic converter is achieved regularly, without channeling or secondary line, and the exhaust gases are normally treated uniformly and completely over long periods of use, without the risk of failure during long machine runtimes. The device is also advantageous in that as the cell structure elements neither wear nor decompose during operation in moving vehicles, what is a characteristic shortcoming of known catalytic devices in which, consisting of loose carrier particles, layers covered or impregnated with catalyst compositions are used. The cell structure is uniform rigid body and consequently no physical losses due to movements and friction between individuals Subjected to parts, as is the case, for example, with packed catalyst layers.

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Further details of the invention should be based on exemplary embodiments will be explained and described in more detail, reference being made to the accompanying drawings.

Pig. 1 is a longitudinal section through a preferred embodiment of the invention,

FIG. 2 is an enlarged section through FIG. 1 according to FIG Line 2-2, in which the coaxial and concentric arrangement of the cell structure elements is shown is and

FIGS. 5 and 4 show modified cell structure forms.

Reference is then made to FIG. 1. A fuel stream 1, which usually consists of a flowing hydrocarbon fuel such as gasoline, and a primary air stream 2 are fed into a prime mover j5, which is usually an internal combustion engine installed in a car or the like. The fuel stream 1 is burned in the engine J5 and produces usable energy and engine exhaust that is typically collected in the exhaust manifold 4. This gas collected in the manifold 4 usually contains poisonous components including nitrogen oxides, hydrocarbons and carbon monoxide. A stream of air 5 may in some cases be introduced into manifold -4 so that manifold 4 serves as an afterburner to partially burn the hydrocarbon in place. In any case, the exhaust gas flow 6 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 support or retaining ring 8 in which the compressible seal 9 is mounted. This seal 9 consists of asbestos or another mineral fiber material or the like suitable for operation at elevated temperatures

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Materials.

The central cylindrical partition Io extends out of the seal 9 and serves to divide the component into a central and an annular chamber. The central cylindrical gas passage element 1I in cell structure extends coaxially within the partition wall lo, and the diffuser ¹ J serves to distribute the exhaust gas flow b evenly into the plurality of parallel linear gas passage cells in the component 11. These cells in element 11 are covered and soaked with a suitable catalyst for the catalytic reduction of nitrogen oxides to nitrogen by reaction with oxidizable components in the gas stream, such as hydrogen, carbon monoxide and / or hydrocarbons. Any catalyst for the reaction can in practice be selected from any catalyst or any combination of catalysts, for example zinc, nickel, platinum, copper, manganese, vanadium, cobalt, chromium or iron, or catalytically promoted oxides of these metals, or catalytically promoted mixtures of these metals . A combination of catalytic components including copper, cobalt, nickel and manganese is preferred. The preferred building material for the cell structure element 11 is lithium aluminum silicate, but other heat-resistant materials such as aluminum oxide can also be used. The element 11 is produced by extrusion, molding or other known manufacturing methods, 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 acid salts of the above-mentioned catalytically active metals. Before being installed in the device, the element II is then usually dried at an elevated temperature, usually in a hydrogen atmosphere or other reducing gas atmosphere, and in some cases multiple dipping and drying stages can be provided before use. The aqueous solution of the salts of the catalytically active metals can also be ammonium nitrate or others

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contain suitable accelerators. In any event, any suitable and effective catalyst or combination of catalysts can be used be stored on and in the cells of the cell structure element 11 by any suitable method.

The gas stream 6 flows through the linear cells of the cell structure element 11, and at least some of the nitrogen oxides contained in the exhaust gases or essentially the quite a lot of them are catalytically reduced to nitrogen. The partially treated exhaust gas flows through the circular support ring 12 from the cell structure 11.

A secondary air flow Ij5> which may be preheated, is passed through the blower 14 as blown air 15 into the pipe 16, which extends into a perforated air outlet portion within the device. The through the Air flowing out of openings in tube 16 mixes with the partially treated air flowing out of cell structure 11 Exhaust gases and a uniform mixture of air and exhaust gases is produced through the openings in the cylindrical perforated supporting partition wall 17 flows out, which is located between the support ring 12 and the disk-shaped Container end wall 18 extends. The mixture of air and exhaust gases then flows in the opposite direction Direction through an annular opening between the support ring 12 and the outer annular support strip 19; those at the Inner wall of the cylindrical outer wall · of the container 2o is attached. .

The mixture of air and exhaust gases then flows through the annular gas passage element with cell structure, the one with a plurality of linear gas passage cells running in parallel is provided, which are covered with a suitable catalyst for the catalytic oxidation of carbon monoxide and hydrocarbons to non-toxic products like

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Carry out carbon dioxide and water vapor * .The ring-shaped Cell structural member 21 is generally made of a building material similar in composition to that of that described above Element 11 is similar or the same, specifically lithium aluminum silicate or aluminum oxide. Besides that The active catalyst applied to the wall surfaces of the individual cells of the element 21 is preferable the same one used in element 11. This type of catalyst is commonly known as a redox catalyst, a catalyst that undergoes a reduction or oxidation reaction is able to accelerate, depending on the state and composition of the operating stream contacting the catalyst .

The mixture of air and exhaust gases flowing through the cells of the annular cell structure element 21 is inside the Cells converted catalytically, the oxygen content of the supplied secondary air stream 13 serving to reduce the carbon monoxide and to at least partially or substantially wholly non-toxic the hydrocarbons in the exhaust gases To oxidize products such as carbon dioxide and water vapor. This exothermic catalytic reaction is used to generate of heat which rapidly raises the temperature of the entire device to an optimal temperature range approximately between 500 and can rise to 900 ° C.

The reservoir 2o is provided with an end flange or an annular closure element 22 at the outlet end of the device for the treated exhaust gases. A mating flange 23 is also provided, to which the exhaust gas outlet manifold is attached. An annular seal 2k is provided between the elements 22 and 23, which is preferably made of asbestos, a similar mineral fiber mass or some other suitable heat-resistant sealing composition. In most cases the seal 24 is made

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be composed of the same material as the seal described above. Those from the cells of element 21 exiting, fully treated final exhaust gases are now essentially free of toxic Components and are directed by the gas outlet manifold 25, which is between flange 2 ^ and the outside of the element 7 extends and serves to lead the completely treated exhaust gases to the discharge pipe 26, which the May be an automobile exhaust pipe or the like. The treated exhaust gases can exit the pipe 26 as a stream 27 to the atmosphere without causing air pollution.

Fig. 2 is a section along line 2-2 in Fig. 1 and shows the coaxial concentric arrangement of the central cell structure element 11, the "" cylindrical partition wall lo, the annular cell structure element and the cylindrical Outer wall of the container 2o in this preferred embodiment of the invention. The individual cell passages in the cell structure elements 11 and 21 have circular cross-sections.

In Fig. 3 is a modified embodiment of the invention shown, with a single unitary cell structure for both the central and the annular exhaust gas passage is provided and the individual Durehlasszellen of the common cell structure have hexagonal cross-sections. The delimitation of the central gas flow from the ring-shaped one Gas flow is controlled by providing an end seal or sealed cells between the central and of the annular group of cells. The intermediate cells clogged to prevent gas penetration can either use an inert material like aluminum oxide or an insulating intermediate mass completely filled or it can be at one or both ends of the sealing

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individual plugs or sealing gaskets be provided.

In Fig. 4 a further modification of the invention is shown, wherein the cell structure element consists of rows of waves arranged in a circle or alternating of cylindrical ones or curved elements.

In addition to the alternatives mentioned above, innumerable other alternatives can be found within the scope of the present invention to be provided by professionals. The invention is generally applicable to engine exhaust gases that are toxic Components such as nitrogen oxides, carbon monoxide or contain hydrocarbons. The container 2 and the Cell structural elements contained therein may have various shapes in practice and in some cases have a square or rectangular cross-section. Suitable accessories, e.g. radial or parallel running Retaining rings, carriers, clamping elements or various seals can be used, as can thermoelectric elements are provided, the latter being divided into the cell structure elements can extend to measure the operating temperature. Expansion joints, corrugated or bellows parts can if necessary be provided for the element 2o and other parts of the device to the thermal To accommodate expansion or contraction during various periods of the machine's operating cycle. the Device can by means of suitable spring or rubber retaining elements in a moving vehicle, for example one of the vehicles mentioned above, in order to avoid violent movements or effective displacements of the device Compensate while driving the vehicle on uneven roads or when passing potholes.

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Claims (9)

- fc - 23581/2 patent p. sayings- 1. Device for treating exhaust gases from prime movers, consisting of a container with two consecutive catalyst chambers with an air inlet in between, characterized by the fact that a central gas passage element (11) with cell structure and an annular gas passage element (21) with cell structure around the first 'cell structure element is provided, the elements being a plurality of parallel to the central axis of the container (2o) have aligned parallel linear gas passage points that at one end of the container an inlet (7) for exhaust gases to the central Element and a discharge line (26) for gases emerging from the annular element, and at the other end of the container a passage (17 * 18) leading from the central sum ring-shaped element is provided, which has an air inlet (16) contains, and that the wall panels of the inner element with ein'Katalysator zum.-Reduce γοη nitrogen oxide to Nitrogen and the cell wall thickness of the annular elements with a catalyst for the oscillation of carbon monoxide and Hydrocarbons are covered " 2. Apparatus according to claim l _s characterized geke η η I show η et that the container and the central elements with a cell structure are cylindrical _o j5. Device according to claim 1 and 2 characterized g- _S e ζ characterizing ei chnet _s that both elements with cell structure of lithium aluminum silicate are assembled. 4. Device according to one of claims 1 to J5, characterized characterized that the catalytic 309840/0897 ren on the inner and outer elements are the same. 5. The device according to claim 4, characterized in that the catalyst is at least one of the .Metals Zinc, nickel, platinum, copper, manganese, vanadium, cobalt, chromium or iron, a catalytically promoted oxide contains one of these elements or a mixture thereof. 6. Device according to one of claims 1 to 5, characterized in that an air inlet (5) to the exhaust gases entering the container is provided. 7. Device according to one of the preceding claims, characterized in that the central and the annular element in the container are separated by a partition (lo). 8. Device according to one of claims 1 to 6, characterized in that the central and the annular Cell structure elements are parts of a single cell structure, the central of which is the ring-shaped Element-separating cells are filled with an inert substance. 9. Device according to one of claims 1 to 7 * thereby denoted that the central and the ring-shaped cell structure are parts of a single cell structure unit are, the cells between the central and the annular element against the passage of flowing Media are sealed. 309840/0897