DE102019202943A1 - Method for operating an SCR catalytic converter with a bypass flow channel - Google Patents

Abstract

A method for operating an exhaust gas aftertreatment device (5) which comprises an SCR catalytic converter (8) with an inlet (16), an outlet (17) and a bypass flow channel (40), wherein upstream of the inlet (16) comprises a SCR inlet valve (41) is arranged, an inlet into the bypass flow channel (40) is arranged upstream of the inlet (16) and the bypass flow channel (40) comprises a bypass valve (42). The method comprises the following steps: determining (51) the temperature of the exhaust gas upstream of the SCR catalytic converter (8); if the temperature exceeds a predetermined threshold value (54), opening the bypass valve (42) and closing the SCR inlet valve (41); if the temperature falls below a defined threshold value (53), closing the bypass valve (42) and opening the SCR inlet valve (41).

Description

The present invention relates to a method for operating an exhaust gas aftertreatment device which comprises an SCR catalytic converter. The invention also relates to an exhaust gas aftertreatment device, an engine arrangement, a vehicle and a computer program product.

With exhaust gas aftertreatment devices, combustion gases are cleaned mechanically, catalytically or chemically after they have left the combustion chamber or the combustion chamber of an internal combustion engine in order to be able to comply with statutory pollutant limits. In connection with the increasingly strict legal requirements for emissions from vehicles, especially motor vehicles, there are far-reaching challenges for exhaust gas aftertreatment.

The nitrogen oxide emissions (NOx emissions) that occur when an internal combustion engine is operated under high load and / or at high engine speeds represent a major challenge. an aqueous urea solution (urea) being injected into the exhaust gas flow upstream of the SCR catalytic converter. However, the performance of an SCR catalytic converter decreases at high exhaust gas temperatures as a result of oxidation effects within the SCR system, mainly due to oxidation effects on the coating. In particular, there is the effect that, due to the increasing proportion of urea supplied, the ammonia produced oxidizes directly instead of contributing to the reduction of nitrogen oxides. A simple solution to the problem described is to arrange the SCR catalytic converter further away from the internal combustion engine, where the temperatures are lower, but this reduces the performance under cold start conditions and the operating temperature of the SCR catalytic converter of at least 200 degrees Celsius is reached much later.

In the document US 2014/0010744 A1 For example, an SCR catalytic converter with a bypass flow channel is described, with exhaust gas being passed through the bypass flow channel when the exhaust gas temperature falls below a threshold value and the hydrocarbon content in the exhaust gas exceeds a threshold value.

Against the background described, the object of the present invention is to provide an improved method for operating an exhaust gas aftertreatment device with an SCR catalytic converter, which in particular counteracts the disadvantages described above in connection with a high exhaust gas temperature.

This object is achieved by a method for operating an exhaust gas aftertreatment device in accordance with claim 1, an exhaust gas aftertreatment device in accordance with claim 6, an engine arrangement in accordance with claim 8, a vehicle in accordance with claim 9 and a computer program product in accordance with claim 10. The dependent claims contain further advantageous developments of the present invention.

The method according to the invention for operating an exhaust gas aftertreatment device relates to an exhaust gas aftertreatment device which comprises an SCR catalytic converter with an inlet, an outlet and a bypass flow channel. An SCR inlet valve is arranged upstream of the inlet with respect to an exhaust gas flow. An inlet into the bypass flow channel is arranged upstream of the inlet. The bypass flow channel includes a bypass valve.

The method according to the invention comprises the following steps: The temperature of the exhaust gas upstream of the SCR catalytic converter is determined, in particular measured. If the temperature exceeds a set threshold, the bypass valve is opened and the SCR inlet valve is closed. In other words, in this case the exhaust gas flow is directed past the SCR catalytic converter. If the temperature falls below a specified threshold value, the bypass valve is closed and the SCR inlet valve is opened. In this case, the exhaust gas flow is passed through the SCR catalytic converter. Urea or urea is preferably injected into the exhaust gas flow upstream of the SCR catalytic converter.

The method according to the invention has the advantage that, at high exhaust gas temperatures, undesired oxidations of the urea on hot coatings in the SCR catalytic converter are avoided. Furthermore, the conversion of nitrogen oxides is ensured even at high exhaust gas temperatures, for example by arranging and using a further SCR catalytic converter further downstream of the SCR catalytic converter.

The threshold value for the exhaust gas temperature can be between 400 degrees Celsius and 600 degrees Celsius, for example between 450 degrees Celsius and 550 degrees Celsius, preferably 500 degrees Celsius.

In a further variant, downstream of the SCR catalytic converter, in the following also as the first SCR catalytic converter for better understanding referred to, a particle filter, for example a diesel particle filter, and / or a further SCR catalytic converter is arranged. After passing through the first SCR catalytic converter or the bypass flow channel, the exhaust gas can thus be passed through the particle filter and / or the further SCR catalytic converter. No separate urea injection device is required for the further SCR catalytic converter if a urea injection device is already arranged upstream of the first SCR catalytic converter and urea or urea has already been injected into the exhaust gas flow by means of this. However, a second urea injection device can also be arranged upstream of the further SCR catalytic converter.

The further SCR catalytic converter can be arranged, for example, in the underbody area of a motor vehicle. Such an arrangement has the advantage that the further SCR catalytic converter can thus be placed at a greater distance from the internal combustion engine, where lower temperatures prevail and thus the exhaust gas temperature is also lower than in the area of the first SCR catalytic converter. At high exhaust gas temperatures, the nitrogen oxides can be converted by the additional SCR catalytic converter in this embodiment.

The computer program product according to the invention comprises commands which, when the program is executed by a computer, leave the computer to execute a previously described method according to the invention. The computer program product according to the invention has the advantages already mentioned in connection with the method according to the invention.

The exhaust gas aftertreatment device according to the invention comprises an SCR catalytic converter with an inlet, an outlet and a bypass flow channel. An SCR inlet valve is arranged upstream of the inlet. An inlet into the bypass flow channel is arranged upstream of the SCR inlet valve, and the bypass flow channel comprises a bypass valve. The exhaust gas aftertreatment device comprises a device for determining the temperature of the exhaust gas upstream of the SCR catalytic converter and a control device. The control device is designed to carry out a method according to the invention as described above. The exhaust gas aftertreatment device according to the invention has the features and advantages already mentioned.

In an advantageous variant, a device for injecting urea or urea is arranged upstream of the SCR catalytic converter. Additionally or alternatively, a particle filter, in particular a diesel particle filter, and / or a further SCR catalytic converter can be arranged downstream of the SCR catalytic converter. The advantages of such a configuration have already been explained above. In a further embodiment, the diesel particulate filter itself can have an SCR coating. If the bypass then acts as a cooler due to the design or even contains a cooler, the injection can be continued. Since it can get too hot in extreme situations with this arrangement, a second urea injector in front of the SCR catalytic converter located in the underbody area makes sense.

The engine arrangement according to the invention comprises an internal combustion engine and an exhaust gas aftertreatment device according to the invention described above. The vehicle of the invention includes an engine assembly of the invention. The engine arrangement according to the invention and the vehicle according to the invention have the advantages already mentioned. The vehicle according to the invention can be a motor vehicle or a ship. The motor vehicle can be a motorcycle, a passenger car, a truck, a bus or a minibus.

• 1 zeigt schematisch eine erfindungsgemäße Motoranordnung mit einer erfindungsgemäßen Abgasnachbehandlungsvorrichtung.
• 2 zeigt schematisch ein erfindungsgemäßes Verfahren in Form eines Flussdiagramms.
• 3 zeigt schematisch ein erfindungsgemäßes Kraftfahrzeug.

The figures show:

• 1 shows schematically an engine arrangement according to the invention with an exhaust gas aftertreatment device according to the invention.
• 2 shows schematically a method according to the invention in the form of a flow chart.
• 3 shows schematically a motor vehicle according to the invention.

The ones in the 1 engine arrangement shown schematically 1 includes an internal combustion engine 2 , an exhaust gas aftertreatment device according to the invention 5 , a high pressure exhaust gas recirculation device 6th and / or a low pressure exhaust gas recirculation device 7th . The motor assembly also includes 1 a turbocharger 9 . The turbocharger 9 includes a compressor 11 and a turbine 12 .

The exhaust gas aftertreatment device according to the invention 5 includes an SCR catalytic converter 8th with an inlet 16 and an outlet 17th . Upstream of the inlet 16 is an inlet valve 41 arranged. Upstream of the inlet valve 41 is an inlet into an SCR bypass flow channel bridging the SCR catalytic converter 40 arranged. The SCR bypass flow channel 40 includes an SCR bypass valve 42 . The SCR bypass flow channel 40 leads immediately downstream of the outlet 17th of the SCR catalytic converter 8th into the exhaust flow channel 18th . Upstream of the SCR bypass flow channel 40 is a device for injecting urea 15th in the flow channel 18th arranged.

The ones in the 1 Exhaust aftertreatment device shown 5 also includes a pure oxidation catalytic converter or a NOx storage catalytic converter 13 and one downstream of the NOx storage catalytic converter 13 arranged particle filter 14th . Downstream of the particulate filter 14th is another SCR catalytic converter 31 arranged.

The internal combustion engine 2 includes a number of cylinders 3 , in the variant shown four cylinders, one flywheel 4th , an intake manifold 20th and an exhaust manifold 21st . Furthermore is in the internal combustion engine 2 an oil cooler 22nd and a high pressure fuel pump 23 arranged.

When operating the internal combustion engine 2 becomes the cylinders 3 via the fuel pump 23 Fuel supplied. Furthermore, it is through an air filter 24 Charge air 46 by means of the compressor 11 sucked in. In the variant shown, the air filter comprises 24 an air mass sensor 39 . The one from the air filter 24 to the compressor 11 leading flow channel is with the reference number 25th marked. The one by the compressor 11 Compressed charge air or the exhaust gas mixed with the charge air in the case of exhaust gas recirculation is passed through a flow channel 26th to a thrush 27 and further through an intercooler 28 to the intake manifold 21st and to the cylinders 3 directed.

In the variant shown is a high pressure exhaust gas recirculation flow channel 29 present, which from the exhaust manifold 21st branches off and immediately upstream of the intake manifold 20th flows into this. The flow channel 29 also includes a high pressure exhaust gas recirculation valve 30th .

That the internal combustion engine 2 Exiting exhaust is through the exhaust manifold 21st to the turbine 12 directed, causing the compressor 11 is driven. The exhaust gas is then passed through the flow channel 18th routed to the exhaust aftertreatment components already mentioned. After passing the exhaust aftertreatment device 5 the cleaned exhaust gas is directed to an outlet. The direction of flow of the exhaust gas is indicated by the reference number 32 marked.

Upstream of the further SCR catalytic converter 31 is a low pressure exhaust gas recirculation flow passage 33 arranged. This low pressure exhaust gas recirculation flow passage 33 includes a dirt filter 34 and a cooler 35 , as well as a valve 36 . In the variant shown, the exhaust gas recirculation cooler 35 from a bypass flow channel 37 with a low pressure exhaust gas recirculation bypass valve 38 bridged. The low pressure exhaust gas recirculation duct 33 is also via an exhaust gas recirculation combination valve 43 with the flow channel 25th connected.

In the following, a method according to the invention based on the in the 2 shown in the flowchart. In a first step 51 becomes the exhaust gas temperature upstream of the SCR catalyst 8th determined, for example detected by means of a temperature sensor. In step 52 it is checked whether the in step 51 certain exhaust gas temperature exceeds a specified threshold value, for example 500 degrees Celsius. If this is not the case, step 53 the SCR inlet valve 41 opened and the SCR bypass valve 42 closed. The exhaust gas is therefore through the SCR catalytic converter 8th directed. If the exhaust gas temperature is at step 52 above the threshold temperature, step 54 the SCR inlet valve 41 closed and the SCR bypass valve 42 open. The exhaust gas is therefore sent to the SCR catalytic converter 8th passed by.

The 3 shows schematically a motor vehicle according to the invention 10 . The motor vehicle according to the invention 10 includes a motor assembly according to the invention 1 , for example one based on the 1 described motor arrangement 1 . The engine assembly includes 1 an exhaust gas aftertreatment device according to the invention 5 with a control device 60 which is designed to carry out the method according to the invention. The engine assembly according to the invention 1 is thus designed to carry out a method according to the invention, for example a method in connection with the in 2 explained method according to the invention.

List of reference symbols

1

Motor arrangement

2

Internal combustion engine

3

cylinder

4th

flywheel

5

Exhaust aftertreatment device

6th

High pressure exhaust gas recirculation device

7th

Low pressure exhaust gas recirculation device

9

turbocharger

8th

SCR catalytic converter

10

Motor vehicle

11

compressor

12

turbine

13

NOx storage catalytic converter

14th

Particle filter

15th

Urea injection device

16

inlet

17th

Outlet

18th

Flow channel

19th

Fuel injector

20th

Intake manifold

21st

Exhaust manifold

22nd

oil cooler

23

High pressure fuel pump

24

Air filter

25th

Flow channel

26th

Flow channel

27

throttle

28

Intercooler

29

High pressure exhaust gas recirculation flow channel

30th

High pressure exhaust gas recirculation valve

31

SCR catalytic converter

32

Direction of flow

33

Low pressure exhaust gas recirculation flow passage

34

Dirt filter

35

cooler

36

Valve

37

Bypass flow channel

38

Low pressure exhaust gas recirculation bypass valve

39

Air mass sensor

40

SCR bypass flow channel

41

SCR inlet valve

42

SCR bypass valve

43

Exhaust gas recirculation combination valve

44

Direction of flow of recirculated exhaust gas

45

Direction of flow of the mixture of fresh air and recirculated exhaust gas

46

Direction of flow

51

Detecting the exhaust gas temperature

52

Does the exhaust gas temperature exceed a specified threshold?

53

Closing the SCR bypass valve, opening the SCR inlet valve

54

Open the SCR bypass valve, close the SCR inlet valve

60

Control device

J

Yes

N

No

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2014/0010744 A1 [0004]

Claims (10)

Method for operating an exhaust gas aftertreatment device (5) comprising an SCR catalytic converter (8) with an inlet (16), an outlet (17) and a bypass flow channel (40), an SCR inlet upstream of the inlet (16) Valve (41) is arranged, an inlet into the bypass flow channel (40) is arranged upstream of the inlet (16) and the bypass flow channel (40) comprises a bypass valve (42), characterized in that the method is as follows Steps include: - determining (51) the temperature of the exhaust gas upstream of the SCR catalytic converter (8), - if the temperature exceeds a defined threshold value (54), opening the bypass valve (42) and closing the SCR inlet valve ( 41), - if the temperature falls below a specified threshold value (53), close the bypass valve (42) and open the SCR inlet valve (41). Procedure according to Claim 1 , characterized in that the threshold value is between 400 degrees Celsius and 600 degrees Celsius. Procedure according to Claim 2 , characterized in that the threshold value is between 450 degrees Celsius and 550 degrees Celsius. Method according to one of the Claims 1 to 3 , characterized in that a particle filter (14) and / or a further SCR catalytic converter (31) is arranged downstream of the SCR catalytic converter (8) and exhaust gas after passing through the SCR catalytic converter (8) or the bypass flow channel (40 ) is passed through the particle filter (14) and / or the further SCR catalytic converter (31). Method according to one of the Claims 1 to 4th , characterized in that urea is injected into the exhaust gas flow upstream of the SCR catalytic converter (8). Exhaust gas aftertreatment device (5) which comprises an SCR catalytic converter (8) with an inlet (16), an outlet (17) and a bypass flow channel (40), an SCR inlet valve (41) being upstream of the inlet (16) ) is arranged, upstream of the SCR inlet valve (41) an inlet is arranged in the bypass flow channel (40) and the bypass flow channel (40) comprises a bypass valve (42), characterized in that the exhaust gas aftertreatment device ( 5) comprises a device for determining the temperature of the exhaust gas upstream of the SCR catalytic converter (8) and a control device (60), the control device (60) being designed to implement a method according to one of the Claims 1 to 5 execute. Exhaust aftertreatment device (5) after Claim 6 , characterized in that upstream of the SCR catalytic converter (8) a device for injecting urea (15) and / or downstream of the SCR catalytic converter (8) a particle filter (14) and / or another SCR catalytic converter (31) is arranged is. Motor arrangement (1), which comprises an internal combustion engine (2) and an exhaust gas aftertreatment device (5) according to one of the Claims 6 to 7th includes. Vehicle (10) having an engine arrangement (1) according to Claim 8 includes. Computer program product, comprising instructions which cause the program to be executed by a computer, a method according to one of the Claims 1 to 5 execute.

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