DE19845381C1 - Purifying apparatus for exhaust gas of an internal combustion engine - Google Patents

Abstract

IC engine exhaust gas is purified using an apparatus with rotating disks. The purifying apparatus for an IC engine exhaust gas comprises a container (1) with an axial drive shaft (11), upper inlet (12) and a lower outlet (13) for the exhaust gas stream with at least two rotating disks (2) in the container filled with catalyst material. The disks have numerous openings on their upper and lower sides for gas to permeate and are connected to the drive shaft. Corrugated covers (22) lie opposite the upper and lower sides of the disks and there is a larger opening (23) in the cover between the first and second disk. The larger opening is the outlet for the first stage as well as the inlet for the second stage.

Description

The invention relates to a novel arrangement of catalysts for catalytic cleaning of the Exhaust gases from internal combustion engines.

When burning hydrocarbons in internal combustion engines arise because of Presence of nitrogen in the combustion air and nitrogen oxides and such remain in the exhaust gas Internal combustion engines due to the incomplete combustion of hydrocarbons and Carbon monoxide. Since the components mentioned both human health and It is necessary to remove or reduce nature damage.

Since complete removal is not possible for scientific reasons, a possible, effective reduction through fuel selection or through catalytic cleaning sought.

Regulated three-way catalysts are usually used for this, the shape, Duct arrangement and coating mainly depend on the application criteria Flow resistance, breaking strength, large active surface and good starting behavior orientate. Precious metals such as platinum, rhodium and palladium are predominantly used as the active material used. With these three-way catalytic converters of the known type can be used in a very narrow Setting the stoichiometric fuel-air mixture of lambda close to 1 hydrocarbons, 90% of carbon monoxide and nitrogen oxides are removed. These catalysts are disadvantageous the sluggish starting behavior during cold starts, control difficulties at full load and the Largest possible restriction on petrol engines.

There has been no shortage of attempts to significantly improve catalytic exhaust gas purification.

However, these attempts encounter a number of natural ones when using single-bed catalysts Limits: The larger amount of oxygen or higher temperature required for better oxidation would lead directly to the formation of new nitrogen oxides, increasing the effectiveness of the catalyst enlarged by larger catalytically active surfaces over the amount or surface of the catalyst the back pressure and the increase in temperature the risk of thermal damage.

Numerous works focus on reducing the content of nitrogen oxides in the exhaust gas by adsorption, subsequent partial desorption and feeding the desorption gas containing NO _x into the intake line. Such exhaust gas purifications are known from the patents DE 43 19 294 C1, DE 196 28 796 C1, J 050781331 A, J 09177546 A and J 05195756 A. A disadvantage of these solutions is the relatively high expenditure on equipment by means of two-bed adsorber systems or a rotatable adsorber with segments through which hot exhaust gas flows. In systems of this type, it is particularly difficult to restore the adsorption capacity by cooling the discharged adsorber.

Analog arrangements for the adsorption of hydrocarbons in the cold start phase and their Desorption and catalytic combustion after heating the catalyst are in J 07208156 A. described. Avoiding high hydrocarbon emissions is advantageous with this solution the reaching of the light-off temperature of the catalyst and the buffering effect of the adsorber uneven load. The additional effort of an adsorber and itself is disadvantageous rotating catalytic converter through which the exhaust duct flows twice.

Uchida Tomoyuki (J 08260943 A) suggests the suppression of nitrogen oxide formation by recycling of carbon dioxide, which was obtained via an exhaust gas centrifuge, into the intake air. Thereby a reduction in carbon dioxide emissions is advantageously achieved at the same time. Disadvantageous  This method involves a high outlay on equipment in addition to a conventional one Exhaust gas cleaning must be applied.

WO 9524226 describes an arrangement in which the exhaust gas is mixed with ozone and is then passed over a catalyst. One advantage of this method is a higher one Oxidation of hydrocarbons and carbon monoxide, on the other hand, the disadvantage is that in addition ozone must be added. The expenditure on equipment for generating a is also considerable uniform mixing of exhaust gas and ozone.

An improved cleaning during cold starts is achieved in DE 39 07 776 A1 in that a small one upstream catalytic converter is only switched into the exhaust gas path at low exhaust gas temperature.

EP 0 741 236 A1 describes the removal of soot from the exhaust gas of internal combustion engines proposed a targeted spiral design of the flow in the exhaust duct Centrifugal separation of the soot and this in a coaxial around the catalyst ordered collectors to direct where it is burned. Also by a rotating movement of the Exhaust gas flow in WO 94/167561 and WO 94/10430 are the current gas flow from the particle flow separately and passed through a catalyst coaxially disposed in the combustion chamber, wherein the rotational movement through the arrangement of the inflow channel in the combustion chamber and is generated by internals. A significant reduction in the soot value was achieved. A disadvantage of The arrangements mentioned are the relatively voluminous arrangements, with which the separation effect is achieved becomes.

DE 41 19 156 A1 eliminates the soot contained in the exhaust gas from diesel engines a porous or honeycomb rotating filter made during the rotation in a Sector is burned with a hydrogen oxidation burner. This method is disadvantageous in addition to the complex arrangement, the additional need for hydrogen peroxide.

The improvement of the active surface of catalysts has been attempted by special To allow arrangements such as the use of spherical, dust and rod-shaped catalysts. WO 93/24207 describes an arrangement in which, by introducing the catalyst material into a rapidly rotating drum built a stable catalyst layer on the jacket side becomes. The advantage of this arrangement is the possibility of using very different ones Forming the catalyst material. A disadvantage is the relatively voluminous design of the System and the change of operation or transition from rotation to standstill and vice versa occurring mechanical loads on the catalyst material and the associated abrasion.

For engines whose exhaust gases contain oil, salt or dirt, the exhaust gas inlet side of the Catalyst often through these substances or through deposition of the resulting chemical Connections blocked. To prevent this, an arrangement of the Reverse gas path through the catalyst. The disadvantage is that this procedure only the loose sedentary deposits can be removed.

In DE 40 04 424 C2, the soot that arises especially at full load is generated from the exhaust gas of a diesel engine removed by means of a soot filter, which is switched on and off at full load using a rotary switch cleans itself by thermal contact. The disadvantage of this method is the design effort and the soot removal that only takes place at full load.

In DE 39 22 019 A1, the soot is removed by means of an additional burner in the exhaust gas path.

In EP 0382700 A3, soot is first removed from the exhaust gas stream by means of a filter and then regeneration of the filter by means of combustion using an additional burner. A disadvantage of both Arrangements is the additional burner required and the related one  Fuel consumption. In EP 0304762 A1, the particle removal takes place analogously, but by means of a rotating porous ceramic filter, so that a continuous regeneration is possible. The Pores of these filters house catalytically active components for further gas cleaning d. H. the Removal of nitrogen oxides or carbon monoxide. The switching of the gas path takes place, for. B. about a Bowden cable and a built-in flap.

Solutions are also known in which the active components are applied to rotor blades and the rotor is driven by the exhaust gas flow. This solution is e.g. B. in DE 35 19 543 A1 proposed, the effectiveness of catalytic combustion by the number of cells that Size and coverage of the rotor blades and the residence time of the exhaust gas in the rotor is determined. common are also solutions in which the exhaust gas energy is used to compress the intake air and to feed part of it into the exhaust gas stream for better combustion (JP 61160511 A, DE 34 43 200 A1, DE 34 35 201 A1)

All of the solutions mentioned have the disadvantage that the ratio of the exhaust gas space to the catalyst space is unfavorable in the exhaust gas path and leads to relatively voluminous systems. This ratio can change are made by making the catalyst bed larger or denser. This increases however, the back pressure and there is sometimes channeling of the flow through the Catalyst. This leads to a reduction in performance and a reduction in the cleaning effect especially at high engine speeds.

To solve this also in the scientific investigation of reaction equilibrium Problems occurring were reported by Nelles (DD 281353 B5 and Chem. Techn. 39 (6) 1987, 237) Minimal space reactor for the investigation of chemical equilibria developed a new one Basic principle with effective mixing of the catalyst bed with a small size of guaranteed catalyst-free space in the reaction vessel. One rotates with catalyst material filled disc with axially perforated catalyst basket in an inclined ring Cavity. The advantage of this arrangement is that the gas turns due to the rotation of the disk alternately flows through the rotating disc, mixing well and the active surface the flow of the catalyst is good. A disadvantage of this type of reactor for use as Exhaust gas catalytic converter is the fact that due to the rotating movement and entrained gas molecules faster transport through the catalyst bed and the process is only comparatively low loads works effectively. The average residence time of the individual gas molecules in the plant was therefore high, the corresponding flow rate very low.

The invention is therefore based on the object of a device for catalytic cleaning of the Exhaust gases from internal combustion engines to develop which reduce pollutants and Soot particles in the exhaust gas cause cold start, warm-up and full load.

This object is achieved by the characterizing part of claim 1 specified features solved.

The solution according to the invention then has the following features:

• - A container 1 with an axial drive shaft 11 , upper inlet opening 12 and lower outlet opening 13 for the exhaust gas flow with at least two rotatable disks 2 arranged in the container 1 and filled with catalyst material, the disks 2 on the top and bottom being designed to be gas-permeable through numerous openings 21 and are firmly connected to the drive shaft 11 and
• - Corrugated covers 22 fixed in container 1 opposite the upper and lower sides of the panes 2 and a larger opening 23 in the corrugated cover arranged between the first and second panes such that the opening 23 is both the exit opening of the first and the entrance opening of the second stage , in which
• - The lower wave-shaped cover of the first stage simultaneously the upper cover of the second stage is and
• - The lower wave-shaped cover of the second stage has an opening 23 analogous to the first stage, which is directly connected to the lower outlet opening 13 of the container 1 .

A further advantageous embodiment is specified in claim 2.

An impeller 14 is then additionally arranged in the container 1 at the level of the inlet opening 12 , with an opening 24 for the gas transfer between the impeller and the catalyst space.

The device according to the invention can be placed anywhere in the exhaust gas path in the motor vehicle installed and is only subject to the thermal limit conditions of the used Catalyst material. the containers with the catalyst mass are driven via the axial one Drive shaft electrically, mechanically or through the kinetic energy of the exhaust gas.

Due to the rotating surfaces of the panes, which are roughly designed on the cover surfaces, the over the entrance opening into the space between the upper undulating cover and the pane reached exhaust gas molecules and forced by the wave-shaped design, the disc to flow axially. This process is repeated in reverse on the underside of the pane Direction.

As a result, the exhaust gas flow is forced into a kind of undulating movement.

This leads to constant intensive mixing and a very good gas Catalyst surface contact. Soot particles in the gas stream succumb very much strong abrasion and are caused by the constantly changing flow direction of the Always removed the catalyst bed from its surface. There is a short time Contact between the soot particles becoming smaller and the catalyst surface, which leads to their leads to catalytic combustion.

This process is intensified by moving to a second stage. It is possible through Intermediate air feed in the second stage the oxidation of the hydrocarbons and To improve carbon monoxide while reducing the temperature of the exhaust gas flow and so the Avoid formation of new nitrogen oxides.

Different catalyst materials can be used in the first and in the second stage become.

The invention is explained in more detail below with reference to the drawings.

Show it

Fig. 1 - an embodiment of the device according to the invention

Fig. 2 - a further advantageous embodiment of the device according to the invention.

The invention is not limited to the embodiments described and illustrated here limited. Further embodiments are within the scope of the invention and do not result from the Scope of protection of the claims.

The exhaust gases from the engine pass through the upper inlet opening 12 into the container 1 in which at least two disks 2 filled with catalyst rotate, which are fastened on a drive shaft 11 . The upper and lower sides of the panes 2 are designed to be gas-permeable with numerous smaller openings 21 and are provided with gas-impermeable undulating covers 22 above and below the panes 2 . This results in a rapid gas exchange between the interior of the window filled with catalyst and the closed cavity between the windows and the undulating covers. Due to the rapid rotation of the rough discs on both ends, the gas molecules are entrained and the exhaust gas flow that has entered the cavity through the inlet opening 12 is forced into a wave-shaped movement, whereby it has to penetrate the discs filled with catalyst several times and this cavity only after an almost full rotation through the lower opening 23 can leave. The exhaust gas stream flowing through the lower opening 23 reaches the second, analog stage with a further rotating disk which is also filled with catalyst. The fillings of the disks can be filled with the same, but also with different catalyst material. The number of cleaning stages used or the number of disks filled with catalyst can be increased according to the basic pattern shown if necessary. The upper input opening 12 and the lower opening 23 of the first stage and the upper and lower opening 23 of the second stage are each offset between 200 degrees and 360 degrees in the direction of rotation. If there are several stages, the lower opening 23 is at the same time the entrance opening for a further cleaning stage.

According to a further advantageous embodiment shown in FIG. 2, the kinetic energy of the exhaust gas flow is used in order to set the disks 2 fastened on the same shaft to a rotating movement via an additional impeller 14 attached to the drive shaft 11 . From there, the exhaust gas passes through the opening 24 into the cavity described above.

The advantages of the invention consist in a very intensive contact of the exhaust gas flow with the Catalyst and thereby a substantial reduction in pollutants and an additional very intensive swirling of the exhaust gas flow. Another advantage is that the catalyst bed is flowed through with a constant change of direction, so that deposited soot and dirt particles be rinsed out immediately. The soot particles are subject to a constant mechanical Burden and are ground up. With a suitable choice of the catalyst, a Combustion of these soot particles, now broken down into the finest particles, takes place.

Claims (2)

1. Device for the catalytic emission control of internal combustion engines, characterized by the following features:

• 1. A container 1 with an axial drive shaft 11 , an upper inlet opening 12 and a lower outlet opening 13 for the exhaust gas flow with at least two rotatable disks 2 arranged in the container 1 and filled with catalyst material, the disks 2 being gas-permeable through numerous openings 21 on the top and bottom are and are firmly connected to the drive shaft 11 and fixed in the container 1 wavy covers 22 opposite the upper and lower sides of the disks 2 and a larger opening 23 in the undulating cover 22 arranged between the first and second disks such that the opening 23 both Is the exit opening of the first as well as the entrance opening of the second stage, the lower wavy cover of the first stage being at the same time the upper cover of the second stage and the lower wavy cover of the second stage having an opening 23 analogous to the first stage, which is connected to the lower exit openings 13 of the container 1 is directly connected.

2. Device according to claim 1, characterized in that in the container 1 , at the level of the upper inlet opening 12 , an impeller 14 is additionally arranged, wherein there is an opening 24 for the gas transfer between the impeller and the catalyst space.