DE102016113375A1 - Method for operating an internal combustion engine and internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine (1) with an exhaust gas charging system (2) and with an exhaust aftertreatment system (3), wherein the exhaust gas charging system (2) comprises an exhaust gas turbocharger (8) with a turbine (10) and a compressor (9), wherein the exhaust aftertreatment system (3) having a catalyst (12), upstream of and downstream of the catalyst (12) positioned shut-off devices (14, 15) and a bypass (13) with a further shut-off device (16) to the catalyst (12), and wherein for preventing an exhaust gas flow closed by the catalyst (12) the upstream and downstream of the catalyst (12) positioned shut-off devices (14, 15) and the further shut-off device (16) of the bypass (13) is opened. Then, when the upstream and downstream of the catalyst (12) positioned shut-off devices (14, 15) are closed, the catalyst (12) in the compressor (9) of the exhaust gas turbocharger (8) compressed charge air is applied.

Description

The invention relates to a method for operating an internal combustion engine with an exhaust gas charging system and an exhaust gas aftertreatment system. Furthermore, the invention relates to an internal combustion engine, a system of several internal combustion engines and a method for operating such a system.

In combustion processes in stationary internal combustion engines, which are used for example in power plants, as well as combustion processes in non-stationary internal combustion engines, which are used for example on ships, resulting in nitrogen oxides, these nitrogen oxides typically in the combustion of sulfur-containing fossil fuels, such as coal, hard coal , Brown coal, petroleum, heavy fuel oil or diesel fuels. Therefore, such internal combustion engines are assigned exhaust aftertreatment systems that serve the cleaning, in particular the denitrification, of the exhaust gas leaving the internal combustion engine.

To reduce nitrogen oxides in the exhaust gas, so-called SCR catalysts are used in practice in exhaust gas aftertreatment systems known from practice. In a SCR catalyst, a selective catalytic reduction of nitrogen oxides, wherein for the reduction of nitrogen oxides as a reducing agent ammonia (NH ₃ ) is required. The ammonia (NH ₃ ) or an ammonia precursor substance, such as urea, for this purpose, is introduced into the exhaust gas upstream of the SCR catalyst in liquid form, wherein the ammonia or the ammonia precursor substance upstream of the SCR catalyst with the exhaust gas is mixed. For this purpose, mixing paths between the introduction of the ammonia or of the ammonia precursor substance and the SCR catalyst are provided according to the practice.

Then, when such an internal combustion engine is used with an exhaust gas charging system and an exhaust aftertreatment system, for example, on a ship, the internal combustion engine is operated in areas with different emission legislations and emission limits to be observed differently. If, for example, an internal combustion engine of a ship is operated in regions with low nitrogen oxide emission requirements, such as on the high seas, the nitrogen oxide limit values to be observed can already be met by purely engine measures so that the exhaust gas does not have an SCR catalytic converter to comply with the emission limit values must be led. In this case, the exhaust aftertreatment system, in particular an SCR catalytic converter of the exhaust aftertreatment system, can then be deactivated.

In this case, in order to avoid aging of the catalysts when the catalysts are deactivated, in this case catalysts are shut off from the exhaust gas stream via shut-off devices positioned upstream and downstream of the catalyst, and then bypass the exhaust gas past the catalyst. However, since such shut-off devices do not always close completely, exhaust gas leakage into the catalytic converter may occur. In particular, if in the engine heavily sulfur-containing fuels, such as heavy oil or residual oil, are burned, it can be damaged by a flowing into the catalyst exhaust gas leakage, in particular by the fact that the sulfuric acid contained in the exhaust gas condenses and causes corrosion in the catalyst. This is a disadvantage.

From the WO 2015/158948 A1 a system for protecting an SCR catalyst is known, the system comprising a heating system for the SCR catalyst, and wherein the heating system comprises a compressed air supply. Starting from the compressed air supply, the SCR catalytic converter can be supplied with compressed air. About the heating system, the modules of the catalyst can be heated.

Proceeding from this, the present invention has the object, a novel method for operating an internal combustion engine with an exhaust gas charging system and an exhaust aftertreatment system and a method for operating a system of several such internal combustion engines, such an internal combustion engine and to create a system of several such internal combustion engines.

This object is achieved by a method for operating an internal combustion engine according to claim 1. According to the invention, when the shut-off devices positioned upstream and downstream of the catalytic converter are closed, the catalytic converter is charged with charge air compressed in the compressor of the exhaust gas turbocharger.

The invention uses charge air to protect the catalyst. Charge air is available anyway. Therefore, no separate compressed air source is required. The invention makes it possible to protect catalysts from aging in a particularly advantageous manner with little device complexity, namely, when they are deactivated and exhaust gas is conducted past the same. The catalysts are then flushed with charge air.

According to an advantageous development, a pressure in the catalytic converter is detected and a charge air flow supplied to the catalytic converter is adjusted in such a way that in the catalytic converter relative to one of the catalytic converter leading exhaust gas supply line and / or relative to the exhaust gas leading away from the catalyst and / or an overpressure of at least 2 mbar, preferably an overpressure of at least 4 mbar, particularly preferably an overpressure of at least 8 mbar. Then, when such an overpressure in the catalyst is adjusted via the charge air, an exhaust gas leak into the catalyst can be prevented in a particularly effective manner and thus the catalyst can be protected from aging.

According to an advantageous development of the catalyst charge air at a temperature of at least 120 ° C, preferably at a temperature of at least 140 ° C, more preferably at a temperature of at least 200 ° C, respectively. This is advantageous to keep assemblies of the catalyst at a desired temperature. More preferably, the temperature of the charge air, which is supplied to the catalyst, at more than 132 ° C and therefore above a sulfuric acid dew point. If, in spite of the charging of the catalyst with charge air, exhaust gas leakage enters the catalyst, then condensation of sulfuric acid can be avoided at this temperature.

In particular, the charge air supplied to the catalyst is heated, preferably in a heat exchanger, via which, on the one hand, the charge air supplied to the catalyst and, on the other hand, exhaust gas is conducted. Here, the thermal energy of the exhaust gas is used to heat the charge air to a corresponding temperature. This allows a particularly advantageous, efficient operation of the internal combustion engine.

The inventive method for operating a system of several internal combustion engines is defined in claim 8. The internal combustion engine according to the invention is in claim 10 and the inventive system of internal combustion engine is defined in claim 14.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 a block diagram of a first internal combustion engine according to the invention to illustrate the inventive method for operating the same;

2 a block diagram of a second internal combustion engine according to the invention to illustrate the inventive method for operating the same;

3 a block diagram of a third internal combustion engine according to the invention to illustrate the inventive method for operating the same; and

4 a block diagram of a system according to the invention of several internal combustion engine to illustrate the inventive method for operating the same.

1 schematically shows an internal combustion engine 1 with an exhaust charging system 2 and an exhaust aftertreatment system 3 , The internal combustion engine 1 includes several cylinders 4 , wherein the internal combustion engine 1 on the one hand fuel 5 and on the other hand charge air 6 is fed to the combustion, and wherein during the combustion of the fuel 5 resulting exhaust gas 7 from the internal combustion engine 1 is dissipated.

The exhaust charging system 2 includes an exhaust gas turbocharger 8th , the one compressor 9 and a turbine 10 includes. In the turbine 10 the exhaust gas turbocharger 8th the exhaust charging system 2 becomes the exhaust 7 Relaxed and used this energy used to the charge air 6 in the compressor 9 the exhaust gas turbocharger 8th to condense. In the compressor 9 compressed charge air is before feeding to the engine 1 via a charge air cooler 11 guided and cooled down.

The exhaust aftertreatment system 3 includes a catalyst 12 , which is in particular an SCR catalyst. Exhaust gas, which is in the turbine 10 the exhaust gas turbocharger 8th has been relaxed, the exhaust aftertreatment over the catalyst 12 led, wherein the exhaust aftertreatment system 3 also via a bypass 13 over which bypasses the catalyst 12 Exhaust gas on the catalyst 12 can be passed.

Upstream of the catalyst 12 is a shut-off device 14 arranged. Further, downstream of the catalyst 12 a shut-off device 15 positioned. Another shut-off device 16 is in the bypass 13 arranged.

Then, if exhaust over the bypass 13 bypassing the catalyst 12 should be performed, the shut-off devices 14 . 15 closed and the other shut-off device 16 will be opened.

Then, on the other hand, if all the exhaust gas of the internal combustion engine 1 over the catalyst 12 the exhaust aftertreatment system 3 should be performed, the shut-off devices 14 . 15 opened and the other shut-off device 16 of the bypass 13 will be closed.

In the internal combustion engine 1 of the 1 it is preferably an internal combustion engine of a ship, is burned as a fuel heavy oil or residual oil. Ships will operate in areas or regions with different emission limits, some of which can already be met by internal combustion engine or internal combustion engine measures, so that then the catalyst 12 the exhaust aftertreatment system 3 , which is preferably an SCR catalyst, can be stopped or deactivated. It then becomes the upstream and downstream of the catalyst 12 positioned shut-off devices 14 . 15 closed to the catalyst 12 to separate from the exhaust flow, whereas then the other shut-off device 16 of the bypass 13 is opened. This is to avoid that exhaust gas in the area of the SCR catalyst 12 sulfuric acid from the exhaust gas in the area of the SCR catalyst 12 condense and so corrosion in the SCR catalyst 12 can cause.

As the upstream and downstream of the catalyst 12 positioned shut-off devices 14 . 15 not 100% close and therefore despite closed shut-off devices 14 . 15 an exhaust gas leak into the SCR catalyst 12 can reach, is proposed according to the invention that, if when the internal combustion engine 1 the upstream and downstream of the catalyst 12 positioned shut-off devices 14 . 15 are closed, the catalyst 12 with in the compressor 9 the exhaust gas turbocharger 8th compressed charge air is applied.

For this purpose branches of a charge air line, which starts from the compressor 9 of the catalytic converter 8th towards the internal combustion engine 1 extends a line 17 off, over the charge air downstream of the compressor 9 branched off and the catalyst 12 can be supplied. This will be in the catalyst 12 set an overpressure, which prevents over the closed shut-off devices 14 . 15 Exhaust gas into the SCR catalyst 12 arrives.

1 shows a pressure sensor 18 over which the pressure in the catalyst 12 , in particular that in the catalyst 12 prevailing pressure, can be detected metrologically. Based on the metrologically detected pressure in the catalyst 12 can a choke 19 be driven in the line 17 positioned downstream of the compressor 9 branches off from the charge air line and the charge air in the direction of the catalyst 12 can be performed. In particular, the throttle 19 activated or opened or closed, that in the catalyst 12 a defined overpressure relative to the catalyst 12 leading exhaust gas supply line and / or relative to the catalyst 12 leading exhaust gas discharge and / or relative to the bypass 13 adjusts, this overpressure at least 2 mbar, preferably at least 4 mbar, more preferably at least 8th mbar. This is to avoid exhaust leakage into the SCR catalyst 12 particularly preferred.

In the embodiment of 1 is the charge air flowing through the line 17 towards the SCR catalyst 12 is guided, downstream of the compressor 9 and upstream of the intercooler 11 diverted. In this case, it is to be assumed that the charge air already has a temperature of at least 120 ° C., particularly preferably a temperature of at least 140 ° C., so that a separate heating of the charge air can be dispensed with.

If necessary, however, in the embodiment of the 1 be provided, the charge air, over the line 17 towards the SCR catalyst 12 is led to heat, and over a in 1 not shown heater, preferably the line 17 assigned.

2 shows a variant of the invention, in which the line 17 , via which charge air branched off from the charge air line and in the direction of the SCR catalytic converter 12 is guided, downstream of the intercooler 11 branches. In this case, therefore, the intercooler 11 cooled charge air 6 branched off, and towards the SCR catalyst 12 guided, in which case preferably the line 17 in addition to the throttle 19 a heating device 20 with the help of those in the direction of the SCR catalyst 12 Guided charge air can be heated or heated.

This heating device is doing this 20 vorzugswiese depending on the measurement signal of a temperature sensor 21 controlled, the temperature in the SCR catalyst 12 detected. Depends on the SCR catalyst 12 The prevailing actual temperature is the heating device 12 then controlled so that in the SCR catalyst 12 the actual temperature approaches a desired target temperature. For this purpose, the charge air is in the range of the heater 20 preferably to a temperature of at least 120 ° C, preferably to a temperature of at least 140 ° C, more preferably to a temperature of at least 200 ° C, heated.

3 shows a variant of the invention, in which the charge air downstream of the compressor 9 branched off and over the line 17 towards the SCR catalyst 12 is guided, in the area of a heat exchanger 22 is heated to a desired temperature, passing through the heat exchanger 22 on the one hand to the SCR catalyst 12 leading to charge air and on the other hand, the exhaust gas leaving the engine is guided. As a result, the thermal energy of the exhaust gas can be used in the direction of the SCR catalyst 12 to heat leading charge air. This allows a particularly efficient operation of the internal combustion engine.

Furthermore, it is possible to use other thermal energy of the internal combustion engine, in the direction of the catalyst 12 leading charge air 17 To heat, for example, thermal energy of a cooling water circuit and oil circuit.

In 1 to 3 are internal combustion engines 1 with an exhaust charging system 2 shown a single exhaust gas turbocharger 8th exhibit. It is of course possible that the exhaust gas charging system 2 includes a plurality of exhaust gas turbochargers, such as a high-pressure exhaust gas turbocharger and a low-pressure exhaust gas turbocharger.

In 1 to 3 is the SCR catalyst 12 the exhaust aftertreatment system 3 downstream of the turbine 10 the exhaust gas turbocharger 8th arranged. In contrast, it is also possible, the catalyst 12 upstream of an exhaust gas turbocharger 8th namely upstream of the turbine 10 the exhaust gas turbocharger 8th In order to position, by the then prevailing higher temperatures and higher pressures, the SCR reaction in the SCR catalyst 12 to improve. Then, if the SCR catalyst 12 positioned upstream of an exhaust gas turbocharger, the exhaust gas turbocharger should 8th be designed such that a pressure on the charge air side downstream of the compressor 9 greater than a pressure on the exhaust side upstream of the turbine 10 , This can then be a permanent charge air purge of the SCR catalyst 12 be guaranteed.

It is preferably provided that the from the to the cylinders 4 the internal combustion engine 1 Charge air line branching line 17 at a branch point 25 from the to the cylinders 4 the internal combustion engine 1 leading charge air line branches off and at a Zuführstelle 26 in the catalyst 12 flows, with this branch point 25 and this feeder 26 are selected and the exhaust charge via the exhaust gas turbocharger 8th is designed such that a pressure at the branch point 25 the line 17 always greater or higher than a pressure of the feed 26 the line 17 in the range of the catalyst 12 , This can be avoided over the line 17 Exhaust gas can reach the charge air side. Rather, it is then ensured that there is always fresh air in the direction of the SCR catalyst 12 is guided, so that a penetration of exhaust gas into the charge air tract can be safely avoided.

It can be provided on the shut-off devices 14 . 15 provide a bypass, then the charge air from the catalyst 12 past the shut-off device 14 in the exhaust gas inlet or past the shut-off device 15 flows into the exhaust gas outlet. This allows exhaust gas from the shut-off devices 14 . 15 be kept away to prevent corrosion on the same.

4 shows a system of several internal combustion engines, namely from the internal combustion engines 1a . 1b , wherein each internal combustion engine 1a . 1b one exhaust charging system each 2a . 2 B and an exhaust aftertreatment system, respectively 3a . 3b having. With regard to their basic structure and their basic operation, the two internal combustion engines 1a . 1b the internal combustion engine 1 of the 1 so that the same reference numerals are used to avoid unnecessary repetition for the same components and to the above comments on 1 is referenced.

Then, if both internal combustion engines 1a . 1b of the 4 can run, both internal combustion engines 1a . 1b be operated in the manner described above, so then at each running internal combustion engine 1a . 1b and with closed shut-off devices 14a . 15a . 14b . 15b Exhaust gas at the respective SCR catalytic converter 12a . 12b is passed and the same over the line 17a . 17b Charge air is applied to the flushing of exhaust gas into the SCR catalyst 12a . 12b to prevent.

4 can be found in that 4 from the line 17a , via which charge air from the compressor 9a the SCR catalyst 12a can be supplied, a line 23 branches, in a shut-off device 24 integrated, being over this line 23 Charge air of the internal combustion engine 1a towards the catalyst 12b the internal combustion engine 1b can be performed.

At the plant of 4 is it possible that if the internal combustion engine 1b stands still, in the same so no fuel is burned and if the exhaust gas turbocharger 8b no charge air 6b provides, charge air 6a the internal combustion engine 1a to use the same over the line 23 with open shut-off device 24 towards the SCR catalyst 12b the internal combustion engine 1b to lead and so in the catalyst 12b to set a defined overpressure and to temper the same, ie to heat to a defined temperature.

In the event that so the internal combustion engine 1b stands still, but the catalyst 12b the same, for example, rinsed for rapid cooling or to be purged for preheating, charge air of the internal combustion engine 1b be used to the catalyst 12b the internal combustion engine 1b to charge with charge air.

The invention is used in particular in internal combustion engines operated with excess air, preferably in marine diesel engines operated with heavy oil or residual oil.

Although the invention has been described in the context of SCR catalysts, the exhaust aftertreatment systems 3 . 3a . 3b also have other catalysts, such as catalysts, which are used for the decomposition of methane and / or formaldehyde and / or carbon monoxide and / or hydrocarbons. Also in this case, the invention can be used. However, particularly preferred is the use of the invention in exhaust aftertreatment systems whose catalysts are designed as SCR catalysts.

LIST OF REFERENCE NUMBERS

1, 1a, 1b

Internal combustion engine

2, 2a, 2b

Turbocharging System

3, 3a, 3b

aftertreatment system

4, 4a, 4b

cylinder

5, 5a, 5b

fuel

6, 6a, 6b

charge air

7, 7a, 7b

exhaust

8, 8a, 8b

turbocharger

9, 9a, 9b

compressor

10, 10a, 10b

turbine

11, 11a, 11b

Intercooler

12, 12a, 12b

catalyst

13, 13a, 13b

bypass

14, 14a, 14b

shut-off

15, 15a, 15b

shut-off

16, 16a, 16b

shut-off

17, 17a, 17b

management

18, 18a, 18b

pressure sensor

19, 19a, 19b

throttle

20

heater

21

temperature sensor

22

heat exchangers

23

management

24

shut-off

25, 25a, 25b

branching point

26, 26a, 26b

induct

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• WO 2015/158948 A1 [0006]

Claims (14)

Method for operating an internal combustion engine ( 1 ) with an exhaust gas charging system ( 2 ) and with an exhaust aftertreatment system ( 3 ), wherein the exhaust gas charging system ( 2 ) an exhaust gas turbocharger ( 8th ) with a turbine ( 10 ) and a compressor ( 9 ), wherein the exhaust aftertreatment system ( 3 ) a catalyst ( 12 ), upstream and downstream of the catalyst ( 12 ) positioned shut-off devices ( 14 . 15 ) and a bypass ( 13 ) with a further shut-off device ( 16 ) to the catalyst ( 12 ), and wherein for preventing an exhaust gas flow through the catalyst ( 12 ) upstream and downstream of the catalyst ( 12 ) positioned shut-off devices ( 14 . 15 ) and the further shut-off device ( 16 ) of the bypass ( 13 ), characterized in that when the upstream and downstream of the catalyst ( 12 ) positioned shut-off devices ( 14 . 15 ) are closed, the catalyst ( 12 ) with in the compressor ( 9 ) of the exhaust gas turbocharger ( 8th ) compressed charge air is applied. Process according to claim 1, characterized in that the catalyst ( 12 ) is charged with charge air such that in the catalyst ( 12 ) relative to an exhaust gas feed line leading to the catalyst and / or relative to an exhaust gas lead leading away from the catalyst and / or relative to the bypass ( 13 ) there is an overpressure. Process according to claim 2, characterized in that a pressure in the catalyst ( 12 ) and a catalyst ( 12 ) is adjusted in such a way that in the catalyst ( 12 ) relative to the exhaust gas feed line and / or relative to the exhaust gas outlet and / or relative to the bypass ( 13 ) is an overpressure of at least 2 mbar, preferably of at least 4 mbar, more preferably of at least 8 mbar. Method according to one of claims 1 to 3, characterized in that the catalyst ( 12 ) is supplied heated charge air. A method according to claim 4, characterized in that the charge air in a heat exchanger ( 22 ) is heated over which on the one hand the catalyst ( 12 ) supplied charge air and on the other hand, exhaust gas is performed. Method according to one of claims 1 to 5, characterized in that the catalyst ( 12 ) Charge air at a temperature of at least 120 ° C, preferably at a temperature of at least 140 ° C, more preferably at a temperature of at least 200 ° C, is supplied. Method according to one of claims 1 to 6, characterized in that the catalyst ( 12 ) supplied charge air upstream or downstream of a charge air cooler ( 11 ) is taken. Method for operating a system with several internal combustion engines ( 1a . 1b ), characterized in that when an internal combustion engine ( 1a . 1b ) runs, the respective internal combustion engine ( 1a . 1b ) is operated according to one of claims 1 to 7. Method according to claim 8, characterized in that when an internal combustion engine ( 1a . 1b ), the catalyst ( 12a . 12b ) of the stationary internal combustion engine ( 1a . 1b ) with charge air of a running internal combustion engine ( 1a . 1b ) is applied. Internal combustion engine ( 1 ) with an exhaust gas charging system ( 2 ) and with an exhaust aftertreatment system ( 3 ), wherein the exhaust gas charging system ( 2 ) an exhaust gas turbocharger ( 8th ) with a turbine ( 10 ) and a compressor ( 9 ), wherein the exhaust aftertreatment system ( 3 ) a catalyst ( 12 ), upstream and downstream of the catalyst ( 12 ) positioned shut-off devices ( 14 . 15 ) and a bypass ( 13 ) with a further shut-off device ( 16 ) to the catalyst ( 12 ), Characterized in that downstream of the compressor ( 9 ) of the exhaust gas turbocharger ( 8th ) a line ( 17 ) from one to cylinders ( 4 ) of the internal combustion engine ( 1 branched off leading charge air line, over which, when the upstream and downstream of the catalyst ( 12 ) positioned shut-off devices ( 14 . 15 ) are closed, the catalyst ( 12 ) with in the compressor ( 9 ) of the exhaust gas turbocharger ( 8th ) compressed charge air can be acted upon. Internal combustion engine according to claim 10, characterized in that in the branched off from the charge air line line ( 17 ) an adjustable throttle ( 19 ) is integrated. Internal combustion engine according to claim 10 or 11, characterized in that the branching off from the charge air conduit line ( 17 ) at a branch point ( 25 ) branched off from the charge air line in such a way and at a Zuführstelle ( 26 ) in the catalyst ( 12 ) such that a pressure of the charge air at the branch point ( 25 ) is greater than a pressure in the region of the feed point ( 26 ).  Internal combustion engine according to one of Claims 10 to 12, characterized by a control device for carrying out the method according to one of Claims 1 to 9. Plant of several internal combustion engines ( 1a . 1b ) according to any one of claims 10 to 13, wherein via a line ( 23 ) obtained from a charge air of a first internal combustion engine ( 1a ) leading line ( 17a ), the catalyst ( 12b ) a second internal combustion engine ( 1b ) can be acted upon with charge air.

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