DE2121158A1 - Catalytic exhaust converter - Google Patents

Description

DIl. ING. E. HOFFMANN DIPL. ING. W. EITLE · DR. HBH. NAT. K. HOFFMANN O.8000 MUNICH 81ARABEUASTRASSE 4 TELEPHONE (0811) 911087

Chemical Construction Corporation

New York, N.Y./ USA

Catalytic exhaust converter

The invention relates to catalytic converters. In particular, it relates to converters with a or several catalyst beds through which the gas flows one after the other. The converters are used for switching off of harmful components used in the exhaust gases from combustion engines, e.g. from diesel engines or contained in gasoline engines to prevent these harmful components, such as nitrogen oxides, unburned hydrocarbon vapors and carbon dioxide escape into the atmosphere and pollute the air.

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21211

In the last few years it has been recognized * that the exhaust gases from burners, especially in urban areas, represent a serious source of air pollution. In some areas, due to atmospheric inversions and accumulation of such exhaust gases in the atmosphere, what is known as smog is created. More recent attempts to avoid such air pollution have concentrated on the destruction or elimination of harmful components by catalytic means, in particular by adding secondary air to the exhaust gas, followed by catalytic oxidation of the remaining hydrocarbons of carbon monoxide and the like. Various types of devices have been developed for this purpose. Improvements to the catalytic agents for their function are described, for example, in U.S. Patents 3,053,773, 3,429,656, 3,316,057, 3,398,101, 3,477,893, and 3,476,508. Devices for carrying out this process are described in US Patents 3 38O 8IO, 3,325,256, 3,255,123 "3222 l40, 3 I86 806 3180712 _A 3,169,836, 3,168,806, 3,146,073 and 3,086,839 described.

According to the present invention, a catalytic converter with a container rait one or more, arranged therein catalyst beds, through which the öas napheinander is passed, with an inlet for heated air between the beds and with a heat exchanger in which the exhaust gas from the second Bed heats the incoming air.

Thus · a catalytically operating »device for the Treatment of exhaust gases created by combustion gases, in which the catalytic action in r.w@i stages within

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of the same unitary container is made and in which a heat exchanger is installed for preheating the air, which is then transferred to the exhaust gas between the first reduction stage, wherein the nitrogen oxides are catalytically reduced, and the second catalytic stage, wherein the remaining Hydrocarbons and carbon monoxide catalytically turn into harmless components such as carbon dioxide and water vapor are oxidized, is added. For the reaction in the first and the second stage, inclined upper and lower catalyst beds can be used. For every level the conventional catalysts such as those described in the above references can be used. PUr each stage can also use different catalysts can be used. However, for reasons of economy and simplicity, it is preferred in both catalytic Stages to use the same catalyst. The shallow sloped catalyst beds are the same Containers aligned and are preferably arranged substantially parallel. The zone of indirect heat exchange, which reacted completely with the hot air to preheat the reaction air through indirect heat exchange Exhaust gas is provided is centrally located in the container and is coaxial with the central axis of the substantially horizontal container aligned.

The main advantage of the device according to the invention is in that a unitary combination of devices is provided which is easy to manufacture and can be easily assembled and the combined punctures of the in a single device unit catalytic reduction, the preheating of the air, the loss of the preheated air in the catalytically reduced Exhaust gas and the catalytic oxidation performs.

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Another advantage is that the device has a low total pressure drop, and hence the availability a high initial exhaust pressure or a high back pressure is not required. Another benefit is seen therein that the device has a damping effect on noise and pulsation of the exhaust gas from the internal combustion engine and that the device thus acts as a muffler.

The invention is explained in more detail in the drawings. It means:

Fig. 1 is an elevation of an embodiment of the invention,

Pig. FIG. 2 is an end elevation of the embodiment of FIG Fig. 1, taken in zone 2-2, showing internal parts

Fig. 3 is an elevation of a further embodiment Invention,

Figure k is an end elevational view of the embodiment of Figure 1t taken in zone 4-4 showing the exhaust and air inlet portions;

Fig. 5 shows the two air inlet pipes in plan, added in zone 5-5 of Fig. 4,

Fig. 6 is an elevation of the embodiment of Fig. 3 # taken in zone 6-6, showing internal parts.

In the embodiment of ^Fig.% L is the hot exhaust x 8 tr on 1 ■ '/ oil a Verbreririungsm & s chine, such as a Bensin-

cars or a diesel engine. The stream 1 contains typically noxious components such as nitrogen oxides, residual hydrocarbon vapor and carbon monoxide as well Carbon dioxide and nitrogen. The stream 1 is through the inlet pipe 2 in the generally horizontally oriented Container passed through an end wall J5 * a side or Top and bottom wall 4 and the other end wall 5 is defined. A vertically oriented liquid seal Partition 6 hangs from the top wall 4 outside the pipe 2 and directs the exhaust gas flow 1 through the enclosed Sieve 7 and into the first catalyst bed 8, in which the selective reduction of all or the largest nitrogen oxides Part of it is made to elemental nitrogen. The catalyst bed 8 can typically be of any known number Catalyst for the treatment of exhaust gases, e.g. consisting of the agents, compounds or mixtures, which are mentioned in the publications described above. The bed 8 is preferably made of elemental metallic Zinc, nickel, platinum, copper, manganese, vanadium, cobalt, chromium or iron or their mixtures, as well as mixtures, which include the oxides of these metals. These catalysts can suitably be formed by alkali or alkaline earth metal oxides or carbonates, e.g. oxides or carbonates of sodium, potassium, calcium, magnesium. the Catalysts are preferably applied to a suitable support, such as kaolin, silicon dioxide, aluminum oxide or zeolite. A catalytic reduction of the nitrogen oxides takes place by reacting the nitrogen oxides in the bed 8 with reducing ones Compounds in the gas stream, forming nitrogen, water vapor and / or carbon dioxide. The bed 8 is preferably substantially flat and inclined to the horizontal at an angle of 2 to 45 ° and it extends from the partition 6 upwards and ends at the end wall 5 ·

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The downflowing hot, partially converted gas stream discharged below bed 8 is essentially freed from nitrogen oxides, but also contains other harmful components, as explained above, which are caused by a High-temperature oxidation reaction are destroyed. The after The gas stream flowing below is horizontal and laterally below the bed 8 through the essentially horizontal partition 9, which extends through the container from a liquid-impermeable connection to the lower end the partition 6 extends. A preheated hot air stream is in the partially converted exhaust gas between the Wall 5 and the end of the partition wall 9 »which adjoins the wall 5 and is spaced therefrom, discharged via the widening outlet of the transition channel 10. The resulting hot mixture of the exhaust gas with the air flows downward between the wall 5 and the gas baffle 11, which TOssi end of the partition or sheet metal hanging down adjacent to the wall 5. The hot gas mixture then flies through the catalyst retention screen 12 and naeli up through the catalyst bed 13 This is a well-known addition and serves to do this Oxidation of hydrocarbon that »?. Carbon monoxide etc.

^ in the exhaust gas au dlieli @ R comp © H © afesn _e such as carbon dioxide and water vapor to catalyze. Is Izimn ? Lt the oen called catalysts or catalyst mixtures be filled.

The get hot © vollkoasnsn! © set AbgasstroRj · discharged upwards out of bed I3, now has a suitable ZusaiuBiensetzung UNAE is Essentially won achäd-

Korap © n®nt @ o ΐΐ "ΘΪ _Β so that © r © fen® äi-s- danger © lessened

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The hot fully reacted gas is directed laterally and horizontally towards the end wall 3J below the partition 9 deflected and the hot gas then flows into the substantially horizontal channel 14, which is generally is coaxial with the horizontal container defined by wall 4 and end walls 3 and 5 will. As will be explained in more detail, the hot gas flowing through the channel 14 is caused by indirect heat exchange with air that flows outside to the channel 14 «and the cooled, completely converted and harmless Exhaust gas flow is discharged from channel 14 as flow 15. This can go through an exhaust pipe to an auxiliary silencer (not shown) or released directly into the atmosphere.

The air stream that is preheated according to the invention, comes from a stream 16 from a suitable fan or the like (not shown) passing through a roller which can be rotated by the fan belt of the motor. In any case it will the flow into the facility through the transition tube or Element 17 passed, which preferably consists of ambient air stream 16 tangentially over a tangential Transition piece leads into an annular channel between the channel 14 and the outer concentric channel is formed. In this way, the air flows through the annular channel between the channels 14 and 18 in one spiral flow path. The spirally flowing air is through indirect heat exchange with the hot completely converted exhaust gases which flow within the channel 14 are indirectly heated. The resulting preheated Air gets out of the annular channel between the channels 14 and 18 via a tangential transition piece or a

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Zone of the tube 10 removed, the tangential © removal of the preheated air over the element 10 the spiral flow of the. Air supports. The heated air is introduced from the pipe or duct 10 into the partially converted exhaust gas as described above.

Figure 2 is an elevational view of the front end of the device of Figure 1 showing selected internal elements as seen from the front wall 3 '. Figure 2 shows the general elliptical cross-section of the device across the wall element 4, the vertical axis of the elliptical element 4 being longer than the horizontal axis. The tangential entry of the stream. 16 via the pipe 17 into the annular channel between the channels 14 and 18 is shown, as well as the tangential removal of the preheated air from the tangential channel via the pipe 10. Finally, the figure shows the horizontal partition 9, which extends between the outer channel 18 and the wall 4 extends. In the figure, parts of the catalyst bed 8 and the screen have been omitted for the sake of clarity. In this regard it will be seen from Fig. 2 that the elements 8 and 7 can extend laterally between the upper half of the channel 18 and the wall 4 downwards to a lower end of the partition wall 9. Similar considerations also apply to the upper rear of the catalyst bed 13 and the screen 12, which may extend to an upper end which abuts the partition 9 on either side between the lower half of the channel 18 and the wall 4 adjacent to the sheet 11.

3 shows an alternative and simplified embodiment of the invention in which rectangular elements

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and channels are provided. The unit 19 is an internal combustion engine, e.g., a gasoline-burning automobile and the exhaust gas stream 20 flows from the unit 19 into the pipe 21 which extends through the front wall 22 and which the exhaust gas into the right-angled device this embodiment gives off. The device is made up of a front wall 22, top wall 23, bottom wall 24 and rear wall 25 formed. The exhaust gas flows down through the flat inclined inlet screen 26 at an angle which typically 2 to 45 degrees from horizontal. The reduction catalyst bed 27 extends between the sieve 26 and the lower sieve 28, which is preferably arranged essentially parallel to the sieve 26. The nitrogen oxide content of the hot exhaust gas flowing down through the bed 27 becomes catalytically harmless Constituents such as elemental nitrogen and water vapor and / or carbon dioxide reduced.

The resulting exhaust gas, which is discharged down through the sieve 28, is laterally and horizontally through the im substantial horizontal partition 29 and deflected towards the rear of the device where the exhaust gas between the end of the partition wall 29 and the wall 25 and outside of the discharge pipe 30 flows downwards. It flows further down between the substantially vertical plate 32 and the wall 25. The plate 32 hangs from the end of the Partition 29 down. A preheated air stream is injected into the downward flowing exhaust gas stream through the pipe 31. The resulting downward-flowing mixture of the hot exhaust gas and preheated air flows downward and horizontally under the lower end of the sheet 32 and is up through the bottom or bottom wall 24

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diverted. The hot gas mixture then flows laterally and at the top through the sieve 33 and through the oxidation catalyst bed 34, in which the harmful ingredients, such as Hydrocarbon gases or vapors and carbon monoxide to harmless components such as water vapor and carbon dioxide be oxidized. The hot gas mixture obtained flows upwards from the catalyst bed 34 through the upper retention screen 35. Screens 34 and 35 are preferably arranged in parallel and they can be inclined at a greater angle to the horizontal, than screens 26 and 28. Screens 34 and 35 can also in some cases the screens 26 and 28 may be arranged substantially parallel to each other. In any case, extend the screens 34 and 35 from the lower front end wall 22 to above and laterally to the lower end of the sheet metal 32.

The hot gaseous mixture discharged upwards from the sieve 35 is now suitable for being able to be discharged into the atmosphere without the risk of air pollution, but the hot gas mixture according to the invention is used to preheat the reaction air by indirect heat exchange The rising hot gas mixture is diverted horizontally under the lower, essentially horizontal partition wall and flows upwards between the end of the partition wall 36 and the conveying wall 22. The hot gas mixture then flows horizontally through the channel defined between the partition walls 36 and 29 , and heats the air flowing inside the pipe 31, which is arranged between the horizontal partition walls 36 and 29. The preheated air is discharged from the pipe 3I as described above. The somewhat cooled gas mixture flows out of the channel between the partition walls 36 and 29

the tube 30 delivered. The mixture can now be released into the atmosphere or, as described above, transferred to another silencer.

The preheated air derives from the ambient air flow 38 from which via a fan or blower 39 is passed as stream 4o to the main inlet pipe 4l. from part of the air is directed to this through a shoulder tube connection 42 to a tube 31 in order, as described, to be preheated and recycled.

Fig. 4 shows an elevation of the front end or exhaust and air inlet end of the device. The Pig. 4 shows the top wall 23, the bottom wall 24 and the side walls 43 and 44 of the right angle device of Fig. 3. Furthermore, Fig. 4 shows a second air preheat tube 45 which is arranged parallel to the pipe 31 and that the air to Preheating via the central tube 41 and the shoulder tube connection 46 is obtained.

The Fig. 5 is a plan view of Fig. 4, received in the Zone 5-5 represents, and shows the parallel Luftvorerhitzungsrohre 31 and 45, 4o receive the flow of air through the tube Hl and the shoulder pipe joints or transition portions 4l and 46 and the Release hot air into the partially converted hot exhaust gas between the sheet metal or the partition 32 and the rear wall 25. In practice, one or more than two air preheating tubes such as elements 31 and 45 can be provided. The pipe 30, which serves to discharge the completely converted and harmless exhaust gas from the device outside the rear wall 25, is also shown.

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The Pig. Figure 6 is an elevation of part of the Pig's facility. 3, taken in zone 6-6, and shows the arrangement of the pipes 31 and 45, of the central exhaust gas discharge pipe 30, which are all arranged between the horizontal partitions 29 and 36.

Numerous alternatives are conceivable within the scope of the invention. For example, the air blower can be driven by a fan belt of the motor. Thus can the fan belt or an auxiliary gear of the motor 19 move the fan 39. The catalyst beds could be in in the opposite direction sloping downwards from the front wall of the device to the rear wall.

The following is an example of examining a manufactured Facility according to Flg. 1 as applied to a commercial gasoline-burning truck engine described.

example

The facility according to Flg. 1 was manufactured and tested on a commercial truck machine. The catalyst area in the reducing zone was 0.058 m. The catalyst volume was 0.0045 nr *. The area of the catalyst in the oxidizing zone was 0.05 m, the catalyst volume 0.0039 m · the catalyst mass © consisted of a reduced mixture of the oxides of nickel, cobalt and manganese, based on alpha-aluminum oxide had been deposited. The preliminary reduction was carried out using hydrogen, which is a part which reduced the oxides to the metallic state. The same catalyst composition was used for both the reducing and the used the oxidizing catalyst. There were the following Test results obtained:

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Reducing zone

Engine speed, km / h 24 43 32 60 48 65 22nd 80 50 Gas volume, no 0, 0, 0.91 1, 1, Inlet speed, m / sec. 41 12th 58 17th 88 119 / 32 147 42 Speed in cataly- 0, 0, 0.25 0, 0,

G
Sator beds, m / sec.

Space velocity / h 58OO 8IOO 12300 I67OO 20500

cm of water 0.025 1.02 2.66 4.40 5.83

(Pressure drop)

24 48 32 68 48 65 80 0, 15th 0, 21st 1.03 1.39 1.73 0, 0, 0.32 0.42 0.53

Oxidising zone, 15 % excess air

Engine speed, km / h gas volume, no

Speed through the catalyst, m / sec.

Space velocity / h 7200 10200 15400 20600 25500

cm of water 0.76 1.90 3.93 6.10 8.13

(Pressure drop)

In the tests, all surfaces were provided with 1.27 Ω of insulation.

The inlet exhaust gas contained 1θ4θ ppm nitrogen oxides, which were less than 75 ppm in the final exhaust gas was reduced. There was essentially complete destruction in the oxidizing zone of hydrocarbon vapors and carbon monoxide. The treated exhaust gas was essentially free of these components.

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Claims (8)

Claims 1. Catalytic exhaust gas converter with a container with one or more catalyst beds arranged therein, in which the oas flows through the beds one after the other, marked by the fact that two Beds (8, 13) with an inlet (10) for the heated air between the beds and a heat exchanger (14, 17, 18), through which the exhaust gas flows from the last bed to heat the incoming air is provided. 2. Exhaust converter according to claim 1, characterized in that the container (4) is horizontal and the beds (8, 13) parallel and one above the other and inclined upwards from the front to the rear wall of the container, so that the inlet (2) for the gas is in the front wall above the first bed and that the heat exchanger is arranged between the beds. 3. Exhaust converter according to claim 2, characterized in that the beds (8, 13) in are inclined at an angle of 2 to 45 degrees from the horizontal. 4. 'Exhaust converter according to one of claims 1 to 3 # characterized in that the container has an upper and a lower part passing through a central Sheet metal (9) are separated, with a channel through the sheet metal is provided at the rear of the container, whereby the oas flows through the catalyst bed and at the back of the container and up and down through the lower one Bstt in the direction of the inlet (14) dea WKrxeauetaueohers ; located at the front end of the container. 209 8 ^ -6 / CH 9 5. Exhaust converter according to one of the preceding claims, characterized in that the container (4) is substantially elliptical and vertical in cross-section, the elliptical cross-section has a vertical axis longer than a horizontal axis. 6. Exhaust converter according to one of the preceding claims, characterized in that the heat exchanger comprises a central tube (31) and a coaxial channel (18) around it, the inlet for the hot oasis from the second bed to the tube located at the front of the container is the inlet for the air leads to the duct and the outlet (10) for the air from the duct is at the rear of the container. 7. Exhaust converter according to claim 6, characterized in that the air is admitted into the annular channel tangentially thereto and tangentially is removed to give a spiral flow through the annular channel 8. Exhaust converter according to one of claims 1 to k, characterized in that the container (23) is rectangular in the vertical cross-section and with a central rectangular duct (29 * 36) is provided in which at least one tube (11, 45) for the air is arranged is to provide the heat exchange. 2098A6 / 0491 Blank page