DE19850762A1 - Device and method for aftertreatment of engine exhaust gases from an internal combustion engine - Google Patents

Abstract

The invention relates to a method and device for post-treating the exhaust gases of an internal combustion engine. The inventive device comprises a body (4) through which exhaust gases flow and which is rotatably placed in the flow of said exhaust gases, as well as a filter (6) which can rotate with said body (4). The rotation speed of the body (4) is selected so that a major part of the temperature front which forms in the body remains in said body. Preferably, said body is in the form of a cylinder with an axial cavity (7) which houses the filter (6) and through which channels (3) extend in the radial direction (3). The rotation axis of said cylinder is perpendicular to the direction of flow of the exhaust gases. When the body is in the form of a NOx accumulating catalyst, removal of nitric oxide can be achieved by cyclic enrichment of the exhaust gases or by introduction of extra fuel in the inventive device. Thus, desulfurization of the catalyst is triggered by a corresponding command of rotation of said catalyst.

Description

The invention relates to a device and a method for aftertreatment of the Engine exhaust gases from an internal combustion engine, and particularly relates to a device and a Process for the aftertreatment of soot particles and / or nitrogen oxides in the exhaust gas stream.

Known NOx catalysts absorb that during the lean operation of an engine generated nitrogen oxides and reduce the stored NOx during a rich operation of the Motors, the known methods are discontinuous and the storage and Reduction of nitrogen oxides occurs in different phases. To such a thing To be able to carry out procedures, the memory has to wait for a certain time its finite absorption capacity can be emptied. This happens either after expiration a predetermined time or the degree of filling of the catalyst must be determined become. If the memory is regenerated after a fixed predetermined time, this has the disadvantage that the storage capacity of the catalyst is not full for safety reasons is exploited so that no optimal engine operation in terms of consumption and Emission behavior is possible. The memory is regenerated when a certain Degree of filling of the memory is reached, this has the disadvantage that an additional Device is required that determines the degree of filling of the NOx storage catalyst. The exact determination of the degree of filling of the memory is difficult, so that too here is switched to regenerative operation if the memory is not yet is completely filled. Ultimately, this also leads to less than optimal operation of the Motors. Furthermore, it applies to both methods that none during the rich operation of the engine optimal exhaust gas behavior achieved and a complicated for cyclic engine operation Motor control is needed.

Furthermore, for a sufficiently good function of a NOx storage catalyst Minimum temperature of approx. 250 ° C is required. If the exhaust gas coming from the engine is too cold,  the process can only work if the catalyst is at this minimum temperature is heated. This causes heat losses, which greatly increases the energy requirement.

In addition, soot particles occur in the exhaust gas of diesel engines that are not released to the environment can be delivered. For the aftertreatment of those with soot particles In a known device, the soot particles are retained and cyclically with reaching a certain filling level of the soot filter this either replaced or the retained soot particles with an appropriate Heater ignited and burned. Both approaches are for one continuous use unsatisfactory.

The invention is therefore based on the object of a device and a method for Treatment of the exhaust gas flow of an internal combustion engine to develop a enable optimal engine operation.

The invention is solved by the features of claims 1, 24 and 27. Preferred Embodiments of the invention are the subject of the dependent claims.

The device according to the invention for the aftertreatment of the engine exhaust gases Internal combustion engine has a body or monolith with the exhaust gas flowing through it Channels, which is rotatably arranged in the exhaust gas flow. Monolith is a body here understood the one-piece from ceramic, from metallic carrier materials or from ceramic or metallic segments, which are arranged in a receiving structure, can exist.

Furthermore, the device has an inflow channel which is connected to a part (B1) of the channels of the Body is in fluid communication. A flow connection is also provided, that on the output side with the part B1 of the channels flowed against by the inflow channel Connection is established and connects this in terms of flow to part B2 of the channels, which is not in flow connection with the inflow channel.

Preferably, the body or monolith is divided into two areas B1, B2, the exhaust gas entering the first area B1 on the front face of the body, exiting on the rear face of the first area B1, passing through the filter attached there, into one End face of the second area B2 enters and leaves the second area B2 on the other end face 2 , the body 4 rotating during the flow around an axis substantially perpendicular to the flow direction of the exhaust gas flow.

The body preferably has a cylindrical shape, the channels being radial Extend direction. The body has a cylindrical recess in the axial direction, with in other words, the cylinder is hollow in the axial direction. The body can be made of metal or ceramic, where it can be assembled in one piece or from segments can be trained. If the body consists of segments, these are channels that the channels are radial after assembling the segments Extend direction with respect to the axis of symmetry of the cylinder.

Preferably, the device comprises a filter which can be rotatably arranged, wherein the filter can rotate in particular with the monolith, whereby in the case of cylindrical body with the axial cavity of the filter is arranged in this. The The filter can be fixed or can rotate with the body, the Speed of rotation does not have to be identical to the speed of rotation of the body.

Furthermore, the internal combustion engine has a direct fuel injection into the combustion chamber and / or is a diesel fuel machine.

The filter preferably has a heating element which serves to filter the filter after a Bring cold start to operating temperature. After reaching the required temperature the heating element can be switched off. Basically, additional heating is required only provided if the engine conditions (exhaust gas temperature) do not increase soot burn. In particular, the temperature required for Alternative or supportive implementation of pollutants also by suitably chosen Engine parameters (injection quantity, injection process, post-injection) quickly reached here, too, the motor parameters are based on their normal conditions returned when the desired temperature is reached.

Furthermore, the body can reduce pollutants, in particular to reduce NOx, HC and / or CO, at least partially coated catalytically.  

The device also has a fixed housing ( 12 ) in which the body rotating about its longitudinal axis is arranged. The housing is preferably made of a non-metallic material.

The body is preferably rotated by a drive unit. The drive unit can be formed by an electric motor. It is also possible for the drive unit to be formed by an external magnetic field and magnets arranged inside the housing. Furthermore, the body can also be rotated through the exhaust gas flow in the manner of a turbine. The speed of rotation of the body ( 4 ) is preferably approximately 0.3 to 10 rpm, the speed of rotation being selected so that the maximum of the temperature distribution which arises remains inside the body, preferably at the location of the filter.

Furthermore, the device can have a means for introducing additional fuel, to cause a reduction in the NOx exhaust gas component when the engine is lean can be operated. Preferably, the means for introducing additional Fuel is arranged in the axis of rotation of the body.

The method according to the invention for the aftertreatment of the exhaust gas of an internal combustion engine, a body being arranged in the exhaust gas flow and having channels in the exhaust gas flow direction and being divided into two areas, has the following steps:
Directing the exhaust gas flow into the front end face of a first area,
Directing the exhaust gas flow at the rear end face of the first area into an end face of a second area and releasing the exhaust gas flow at the other end face of the second area, and
Rotating the body around an axis during operation so that the channels change from the first area to the second area.

Furthermore, the body is rotated about its axis at such a speed that a heating of the second region by the exhaust gas flow to a heating of the Exhaust gas flow leads through the first area.

The soot particles of the exhaust gas stream are preferably retained on a filter is that between the exhaust gas outlet side face of the first region and the Exhaust gas inlet-side end face of the: second region is arranged, and the The speed of rotation is chosen so that the maximum of the temperature front is in is located on the filter.

The body used in the method is preferably at least partially catalytic coated so that a NOx storage of the exhaust gas during the lean phases of the Internal combustion engine is effected. By adding reducing agents to the body a continuous NOX storage regeneration process can be effected.

The method according to the invention for desulfating the device according to the invention for aftertreatment of the exhaust gases of an internal combustion engine, the device being designed as a NOx storage device, has the following steps:
Slowing or stopping the rotation of the body while simultaneously increasing the amount of pollutants in the exhaust gas at the beginning of the desulfation until a temperature maximum has migrated into or through the second region, in particular near the end face of the second region on the exhaust outlet side,
Rotating the body until the second area at least predominantly takes the place of the first area, so that the temperature maximum is predominantly in the first area, and suspending the rotation until the temperature maximum has reached at least the second area,
Decrease post-injection and re-rotate the body.

It may be necessary for the rotation to slow down or stop is repeated several times until essentially all areas have been desulfurized. The  continuous rotation of the body will resume when that Temperature maximum is approximately at the interface of the two areas.

A preferred embodiment of the invention is described below with reference to the drawings explained in more detail.

Fig. 1a shows a horizontal cross-sectional view through a first embodiment of the inventive device for the aftertreatment of the exhaust gas of an internal combustion engine,

Fig. 1b shows a vertical cross section through the device of Fig. 1a, and

Fig. 2 shows a horizontal cross-sectional view through a second embodiment of the inventive device for the aftertreatment of the exhaust gas of an internal combustion engine

Fig. 1a shows a horizontal cross section through a first preferred embodiment of a device for the aftertreatment of the exhaust gas of an internal combustion engine. Raw exhaust gas from an engine (not shown) flows through an exhaust gas supply 1 into an outer end face 2, a first region B1 of a cylindrical body 4 , which is traversed by channels 3 . The channels 3 run in the radial direction with respect to the axis of rotation 9 formed by the axis of symmetry of the cylinder. The channels 3 arranged perpendicular to the axis of rotation 9 are at least partially catalytically coated, as has already been mentioned above. After the exhaust gas emerges from the inner end face 5 of the body 4 , which is formed by an axial cavity 7 formed centrally in the body, the exhaust gas passes through a particle filter 6 arranged in the cavity 7 and passes through the outer end face 5 into an opposite second one Area B2 and enters an outflow channel 8 on the outer end face 2 of the second area B2. FIG. 1 a shows that the first area and the second area are limited to three channels 3 by the inflow channel 1 and the outflow channel 8 . This is not absolutely necessary. Another construction of the housing 10 enclosing the body 4 can ensure that the inflowing and outflowing exhaust gas each reach a first and second region B1, B2 of a maximum of 180 °. In other words, the first and the second region can comprise at most half of the body 4 .

FIG. 1b shows a vertical section through the inventive device. The filter 6 , which generally rotates synchronously with the body 4, is arranged in the interior of the body 4 through which the channels 3 pass. The body 4 and the filter 6 are arranged in a corresponding housing 10 . The rotation takes place about an axis of rotation 9 , which can serve as the supply of additional fuel for combustion in a catalytically active filter or in the rotor matrix, ie the body 4 .

As a result of the filter 6 flowing through the body 4, the temperature rises on the inlet side due to the catalytic conversion of CO and HC present in the exhaust gas during the passage through the catalytically coated channels 3 . At the same time, nitrogen oxides can be chemically absorbed if the channels 3 are coated with a NOx-absorbing catalyst. The temperature maximum is reached in the middle of the device, in the particle filter 6 . Upon further passage through the body 4 or rotor, the exhaust gas releases its heat again and leaves the rotor 4 at approximately the same temperature as on the inlet side. Without rotation, the temperature front, ie the maximum temperature, would be driven out of the device. By turning the rotor 4 , the temperature font is driven back into the system again and again. On average, a periodically stationary profile is created, the maximum of which lies in the area of the filter 6 .

Fig. 2 shows a horizontal cross-sectional view through a second embodiment of the inventive device for the aftertreatment of the exhaust gas of an internal combustion engine in which the device is operated as a pure NOx storage catalyst.

Fig. 2 shows a body 4 rotating about its longitudinal axis, which is coated as a NOx storage catalytic converter, which is used as a regenerative heat exchanger. The body 4 has a large number of fine channels 3 in the radial direction and the exhaust gas flows radially through it, namely the exhaust gas is supplied to it via an inflow channel 1 and is discharged via an outflow channel 8 , as a result of which first and second regions B1, B2, as in the case of the first Embodiment are formed. Furthermore, the body has an axial cavity 7 which is delimited by the inner end face 5 of the body 4 . The axial cavity serves for the fluidic connection of the channels 3 of the first and the second area B1, B2. Advantageously, there is no flow deflection, which keeps the pressure loss low. The inner part, represented as a circular ring T1, of the channels 3 is coated with a NOx-storing catalyst. The outer part of the channels, represented by a circular ring T2, is not coated and does not take part in the catalysis, it only functions as a heat exchanger. Due to the radial flow with simultaneous rotation, a temperature profile can be set in the body 4 , which is located on the inlet and outlet sides of the outer end face 2 of the body approximately at the exhaust gas temperature and rises steeply towards approximately 350 to 400 ° C. towards the center . This means that part of the catalytic converter is always in an optimal temperature range for NOx storage. The rotating arrangement of the catalyst, ie the body 4 , ensures the best possible heat recovery according to the regenerator principle. With ideal thermal insulation and correct dimensioning and rotation speed, the heat once entered will no longer leave the system. The heat losses actually occurring are compensated for by the heat of reaction which is released in the T1 area during the pollutant oxidation.

To start the cold system, the ignition temperature of approx. 200 ° C must be reached in the catalytically active area T2. For this purpose, an electrical heating element 11 can be provided in the middle of the body 4 . As an alternative and / or as a support, the temperature required for the conversion of pollutants can also be achieved by suitably selected engine parameters (in particular in the case of common rail injection, for example by varying the injection timing, the injection process, the injection quantity, and / or post-injection). The measures are ended after the ignition temperature has been reached. The further temperature increase only takes place by a brief increase in the pollutant concentrations, which raises the catalyst temperature through the heat of reaction released in the area T1 during the conversion of the pollutants. This increase in the pollutant concentration can either be done by a separate fuel metering in the middle of the body 4 , or can also be brought about by motor parameters.

The rotation of the body 4 is realized by a suitable electrical or mechanical drive (not shown). For this purpose, the body 4 is mounted on a rotatably mounted shaft or axis of rotation 9 , which is set in rotation by the above-mentioned drive. The additional fuel can also be introduced through this shaft 9 . When using an electric motor, the rotational speed can be adapted to the operating state of the vehicle engine using suitable information from the engine control unit. Furthermore, the body 4 is arranged in a suitable fixed housing 10 .

The regeneration of the NOx storage catalytic converter is carried out in the known manner motor enrichment of the exhaust gas.

When using sulfur-containing fuel, desulfation must be carried out from time to time of the catalyst can be carried out, as already described in the previous has been. This is done thermally at temperatures above 600 ° C. How Already mentioned above, in the system described almost any Temperature increase by increasing the concentration of pollutants or their oxidation can be achieved. By appropriately controlling the speed of rotation and the The catalyst can pollutant concentration for the required time of several minutes are kept at the required high temperatures. As already described above the energy consumption compared to conventional systems is significantly lower.

The following embodiments of the device described above using two examples are therefore possible:
Device with a body 4 rotatable in the exhaust gas flow without catalytic coating and without filter for generating a temperature maximum in the device;
Device with a body 4 rotatable in the exhaust gas flow and a filter 6 arranged in the body 4 for burning off the soot particles;
Device with a body 4 rotatable in the exhaust gas flow and an at least partial catalytic coating of the body 4 ;
Device with a body 4 rotatable in the exhaust gas flow, as well as a filter 6 arranged in the body 4 and an at least partial catalytic coating of the body.

Reference list

1

Inflow channel

2nd

outer face

3rd

channels

4th

Body or rotor

5

inner face

6

filter

7

axial cavity

8th

Outlet channel

9

Axis of rotation

10th

casing

11

electric heating element
B1 first area
B2 second area
T1 inner ring
T2 outer ring

Claims (32)

1. Device for the aftertreatment of the engine exhaust gases of an internal combustion engine, characterized in that the device has a body ( 4 ) with channels ( 3 ) through which the exhaust gas flows, which is rotatably arranged in the exhaust gas flow. 2. Device according to claim 1, characterized in that an inflow channel is provided which is in flow connection with a part (B1) of the channels ( 3 ) of the body ( 4 ). 3. Apparatus according to claim 2, characterized in that a flow connection is provided which is connected on the outlet side to the part (B1) of the ducts ( 3 ) which is flown against by the inflow duct and which is flow-related to a part (B2) of the ducts ( 3 ) connects that is not in flow connection with the inflow channel. 4. Device according to one of the preceding claims, characterized in that the body ( 4 ) is divided into two areas (B1, B2), the exhaust gas on the front end face ( 2 ) of the body ( 4 ) in the first area (B1 ) occurs, exits at the rear end face ( 5 ) of the first area (B1), enters an end face ( 5 ) of the second area (B2) and leaves the second area (B2) at the other end face ( 2 ), the body ( 4 ) rotates about an axis substantially perpendicular to the direction of flow of the exhaust gas stream during the flow. 5. Device according to one of the preceding claims, characterized in that the device has a filter ( 6 ). 6. The device according to claim 5, characterized in that the filter is rotatably arranged, in particular together with the body ( 4 ). 7. Apparatus claim 4 and according to one of claims 5 or 6, characterized in that the filter ( 6 ) between the rear end face ( 4 ) of the first region (B1) and the end face ( 5 ) of the second region (B2) is arranged . 8. Device according to one of the preceding claims, characterized in that the body ( 4 ) for pollutant reduction, in particular for the reduction of NOx, HC and / or CO, is at least partially (T1) catalytically coated. 7. Device according to one of the preceding claims, characterized in that the body ( 4 ) has a cylindrical shape, the channels ( 3 ) extending in the radial direction. 8. The device according to claim 7, characterized in that the body ( 4 ) has a cylindrical recess ( 7 ) in the axial direction, 9. The device according to claim 8, characterized in that the filter ( 6 ) is arranged in the cylindrical recess ( 7 ). 10. Device according to one of the preceding claims, characterized that the engine has direct fuel injection into the combustion chamber has and / or is a diesel fuel machine. 11. Device according to one of the preceding claims, characterized in that the device has a heating element ( 11 ). 12. Device according to one of the preceding claims, characterized in that the device has a fixed housing ( 12 ) in which the body ( 4 ) rotating about its longitudinal axis is arranged. 13. The apparatus according to claim 11, characterized in that the housing is a non-metallic material. 15. Device according to one of the preceding claims, characterized in that the body ( 4 ) is rotated by a drive unit ( 9 ). 16. The apparatus according to claim 15, characterized in that the drive unit ( 9 ) is formed by an electric motor. 17. The apparatus according to claim 15, characterized in that the drive unit by an external magnetic field and arranged within the housing Magnet is formed. 18. Device according to one of the preceding claims, characterized in that the rotational speed of the body ( 4 ) is approximately 0.3 to 10 U / min. 19. Device according to one of the preceding claims, characterized in that the body ( 4 ) is made of metal or ceramic. 20. Device according to one of the preceding claims, characterized in that the body ( 4 ) is a monolith. 21. Device according to one of the preceding claims, characterized in that the body ( 4 ) consists of segments which are traversed by channels ( 3 ). 22. Device according to one of the preceding claims, characterized in that that the device has a means for introducing additional fuel. 23. The device according to claim 19, characterized in that the means for introducing additional fuel is arranged in the axis of rotation ( 9 ) of the body ( 4 ). 24. A method for the aftertreatment of the exhaust gas flow of an internal combustion engine, characterized in that a body ( 4 ) is arranged in the exhaust gas flow, which is traversed in the exhaust gas flow direction with channels ( 3 ) and is divided into two areas (B1, B2), the exhaust gas flow into the front End face ( 2 ) of the first area (B1) is directed, the exhaust gas flow is directed at the rear end face ( 5 ) of the first area (B1) into an end face ( 5 ) of the second area (B2) and at the other end face ( 2 ) of the second area (B2) emerges, and the body ( 4 ) is rotated about an axis during operation, so that the channels ( 3 ) change from the first area (B1) to the second area (B2). 25. The method according to claim 24, characterized in that the body ( 4 ) is rotated about its axis at such a speed that heating of the second region (B2) by the exhaust gas flow leads to heating of the exhaust gas flow through the first region. 26. The method according to any one of claims 24 or 25, characterized in that a retention of the soot particles of the exhaust gas flow is effected on a filter ( 6 ) which between the rear end face ( 5 ) of the first region (B1) and the exhaust gas inlet end face ( 5th ) of the second region (B2) is arranged, and the speed of rotation is selected so that the maximum of the temperature front is approximately at the filter ( 6 ). 27. The method according to any one of claims 24 to 26, characterized in that a NOx storage on correspondingly catalytically coated parts (T1) of the body is carried out. 28. The method according to claim 27, characterized in that by additional supply of reducing agent a continuous reduction of the stored NOx is carried out. 29. A method for desulfating a device designed as a NOx storage catalyst for aftertreatment of the exhaust gases of an internal combustion engine according to one of the preceding claims, characterized in that at the beginning of the desulfation, the rotation of the body ( 4 ) is slowed down or suspended while increasing the amount of pollutants in the exhaust gas The body ( 4 ) is rotated until an emerging maximum of temperature has migrated into or through the second region (B2), in particular near the end face ( 2 ) of the second region (B2) on the exhaust gas outlet side, until the second region (B2) takes the place of the first Area occupies at least predominantly, so that the temperature maximum is predominantly in the first area, and the rotation is suspended until the temperature maximum has reached at least in the second area (B2), the post-injection is reduced and the body ( 4 ) is rotated again. 30. The method according to claim 29, characterized in that the slowdown of the rotation or the stop is repeated several times until substantially the body ( 4 ) are desulfurized. 31. The method according to claim 29 or 30, characterized in that the continuous rotation of the body ( 4 ) is resumed when the temperature maximum is approximately at the interface of the two areas (B1, B2).