DE102016003742A1 - Exhaust after-treatment system, internal combustion engine and method for operating the same - Google Patents

Abstract

Exhaust gas aftertreatment system (3) of an internal combustion engine, namely SCR exhaust aftertreatment system of an internal combustion engine, with an SCR catalytic converter (9), with an exhaust gas feed line (8) leading to the SCR catalytic converter (9) and with an exhaust gas outlet leading away from the SCR catalytic converter (9) ( 11), with one of the exhaust gas supply line (8) associated introduction device (16) for introducing a reducing agent, in particular ammonia or an ammonia precursor substance, in the exhaust gas, and with one of the exhaust gas supply line (8) downstream of the introduction device (16) provided mixing section (18) for mixing the exhaust gas with the reducing agent upstream of the SCR catalyst (9), wherein the exhaust gas inlet (8) and the exhaust gas outlet (11) on a common side (19) of the SCR catalyst (9) receiving the reactor chamber (10 ) and / or extend on the common side (19) in the reactor space (10), wherein between the exhaust gas inlet (8) and the exhaust gas outlet (11) a Bypass (12) to the SCR catalyst (9) or reactor space (10) is formed, and wherein in the bypass (12) a shut-off element (13) is connected.

Description

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

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 takes place, whereby ammonia (NH ₃ ) is required as reducing agent for the reduction of the nitrogen oxides. The ammonia 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, with the ammonia or the ammonia precursor substance being mixed with the exhaust gas upstream of the SCR catalytic converter. 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.

Although exhaust gas aftertreatment, in particular nitrogen oxide reduction, can already be successfully carried out using exhaust gas aftertreatment systems which comprise an SCR catalytic converter known from practice, there is a need to further improve the exhaust aftertreatment systems. In particular, there is a need to allow for a compact design of such exhaust aftertreatment systems effective exhaust aftertreatment.

On this basis, the present invention has the object to provide a novel exhaust aftertreatment system of an internal combustion engine, an internal combustion engine with an exhaust aftertreatment system and a method for operating such an internal combustion engine.

This object is achieved by an exhaust aftertreatment system of an internal combustion engine according to claim 1. According to the exhaust gas supply line and the exhaust gas discharge on a common side of the SCR catalyst receiving reactor space and / or extend on the common side of the reactor chamber into the reactor space inside, between the exhaust gas inlet and the exhaust gas outlet a bypass to the SCR catalyst or Reactor space is formed, and wherein in the bypass a shut-off element is connected. This design of an exhaust aftertreatment system allows effective exhaust aftertreatment in a compact design. It can be dispensed with a long bypass line, which extends around the reactor space around.

According to an advantageous development of the bypass branches downstream of the introduction device in the region of the mixing section of the exhaust gas supply line in the direction of the exhaust gas discharge. This design enables a particularly compact design and effective exhaust aftertreatment.

According to an advantageous development, the shut-off element connected in the bypass is a shut-off valve or a rupture disk. This design enables a particularly compact design and effective exhaust aftertreatment.

According to a further advantageous embodiment, the exhaust gas inlet opens with a downstream end into the reactor space, with this downstream end of the exhaust gas supply line, a baffle element cooperates, which is displaceable relative to the downstream end of the exhaust gas supply line. The impact element allows a still compact design and an even more effective exhaust aftertreatment.

According to a further advantageous embodiment, the exhaust gas outlet at least partially surrounds the exhaust gas outside preferably concentric, wherein the bypass to the SCR catalyst or reactor space is formed in or adjacent to the area in the exhaust gas outlet and exhaust gas supply outside surrounds, preferably concentric with each other. This design enables a particularly compact design and effective exhaust aftertreatment.

The internal combustion engine according to the invention is defined in claim 11. Inventive methods for operating the internal combustion engine are defined in claims 13 and 14.

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

1 a schematic, perspective view of an internal combustion engine with an exhaust aftertreatment system according to the invention;

2 : a detail of the exhaust aftertreatment system of 1 ; and

3 : a detail of 2 ,

The present invention relates to an exhaust aftertreatment system of an internal combustion engine, such as a stationary internal combustion engine in a power plant or on a ship used, non-stationary internal combustion engine. In particular, the exhaust aftertreatment system is used on a heavy fuel oil marine diesel engine. Furthermore, the invention relates to an internal combustion engine with such an exhaust aftertreatment system and a method for operating the internal combustion engine.

1 shows an arrangement of an internal combustion engine 1 with an exhaust charging system 2 and an exhaust aftertreatment system 3 , In the internal combustion engine 1 it may be unsteady or stationary internal combustion engine, in particular a transiently operated marine engine. Exhaust gas, which is the cylinder of the internal combustion engine 1 leaves is in the exhaust charging system 2 used to extract from the thermal energy of the exhaust gas mechanical energy for compression of the internal combustion engine 1 to gain supplied charge air.

So shows 1 an internal combustion engine 1 with a Abgasaufladungssystem or Abgasturboaufladungssystem 2 , which comprises a plurality of exhaust gas turbochargers, namely a first, high pressure side exhaust gas turbocharger 4 and a second, low pressure side exhaust gas turbocharger 5 ,

Exhaust gas, which is the cylinder of the internal combustion engine 1 leaves, first flows through a high-pressure turbine 6 of the first exhaust gas turbocharger 1 and is relaxed in the same, wherein this energy recovered in a high-pressure compressor of the first exhaust gas turbocharger 4 is used to compress charge air.

In the flow direction of the exhaust gas is seen downstream of the first exhaust gas turbocharger 4 the second turbocharger 5 arranged over which exhaust gas, which is already the high-pressure turbine 6 of the first exhaust gas turbocharger 4 has passed through, namely, a low-pressure turbine 7 the second exhaust gas turbocharger 5 , In the low-pressure turbine 7 the second exhaust gas turbocharger 5 the exhaust gas is further expanded and thereby recovered energy in a low-pressure compressor of the second exhaust gas turbocharger 5 used also to the cylinders of the internal combustion engine 1 to compress supplied charge air.

In addition to the two exhaust gas turbochargers 4 and 5 having exhaust gas charging system 2 includes the internal combustion engine 1 the exhaust aftertreatment system 3 which is, for example, an SCR, CH4, HCHO, or oxidation exhaust aftertreatment system. The exhaust aftertreatment system 3 is between the high pressure turbine 6 of the first compressor 5 and the low-pressure turbine 7 the second exhaust gas turbocharger 5 switched, so therefore exhaust, which is the high-pressure turbine 6 of the first exhaust gas turbocharger 4 leaves, first via the exhaust aftertreatment system 3 can be performed before the same in the field of low-pressure turbine 7 the second exhaust gas turbocharger 5 arrives.

1 shows an exhaust gas supply line 8th , about the exhaust, starting from the high-pressure turbine 6 of the first exhaust gas turbocharger 4 towards an SCR catalyst 9 can be performed in a reactor room 10 is arranged.

Further shows 1 an exhaust gas discharge 11 , the discharge of the exhaust gas from the SCR catalyst 9 towards the low-pressure turbine 7 the second exhaust gas turbocharger 5 serves.

Starting from the low-pressure turbine 7 the exhaust gas flows through a pipe 21 especially outdoors.

The to the reactor room 10 and thus to the reactor room 10 positioned SCR catalyst 9 leading exhaust gas supply 8th as well as from the reactor room 10 and thus from the SCR catalyst 9 leading exhaust gas discharge 11 are over a bypass 12 coupled, in a shut-off 13 is integrated.

When the shut-off device is closed 13 is the bypass 12 closed so that no exhaust gas can flow over the same. Then, however, when the obturator 13 opened, can over the bypass 12 Exhaust gas flow, past the reactor room 10 and therefore past the reactor room 10 positioned SCR catalyst 9 ,

2 illustrated with arrows 14 the flow of exhaust gas through the exhaust aftertreatment system 3 at over the obturator 13 closed bypass 12 , in which 2 it can be seen that the exhaust gas supply line 8th in the reactor room 10 with a downstream end 15 opens, with the exhaust gas in the region of this end 15 the exhaust gas supply line 8th a flow deflection around about 180 ° or approximately 180 ° experiences, the exhaust after the flow deflection over the SCR catalyst 9 to be led.

The exhaust gas supply line 8th the exhaust aftertreatment system 3 is a loading device 16 assigned, can be introduced via the in the exhaust stream, a reducing agent, in particular ammonia or an ammonia precursor substance, which is needed to in the range of the SCR catalyst 9 Defined to implement nitrogen oxides of the exhaust gas. In this introduction device 16 the exhaust aftertreatment system 3 it is preferably an injection nozzle, via which the ammonia or the ammonia precursor substance into the exhaust gas stream within the Abgaszuführleitung 8th is injected. 2 illustrated with a cone 17 the injection of the reducing agent into the exhaust gas flow in the region of the exhaust gas supply line 8th ,

The route of the exhaust aftertreatment system 3 , seen in the flow direction of the exhaust gas downstream of the introduction device 16 and upstream of the SCR catalyst 9 is, is referred to as a mixing section. In particular, the exhaust gas supply line 8th downstream of the introduction device 16 a mixed route 18 in which the exhaust gas with the reducing agent upstream of the SCR catalyst 9 can be mixed.

As stated, the exhaust gas supply line 8th as well as the exhaust gas discharge 11 over a bypass 12 can be coupled to open bypass 12 Exhaust gas at the reactor room 10 and therefore on the SCR catalyst 9 passing out. It is envisaged that the exhaust gas inlet 8th and the exhaust gas discharge 11 on a common page 19 of the SCR catalyst 9 receiving reactor space 10 attack and / or join this common side 19 of the reactor space 10 in the reactor room 10 extend. This allows for a long bypass line between the exhaust gas supply line 8th and the exhaust gas discharge 11 , which is about the the SCR catalyst 9 receiving reactor space 10 extends around, be waived. The bypass 12 can therefore be made short and compact, so that in a compact design effective exhaust aftertreatment is possible.

As 2 can be removed, the exhaust gas supply line extends 8th over the bottom 19 of the reactor space 10 into the same, with a downstream end 15 the exhaust gas supply line 8th adjacent to one of the bottom 19 opposite top 23 of the reactor space 10 flows into it. The exhaust gas discharge 11 attacks at the bottom 19 of the reactor space 10 on and encloses sections of concentric radially outside the exhaust gas supply line 8th , in an area outside the reactor room 10 adjacent to the bottom 19 the same goes. The bypass 12 is in the embodiment of 2 formed in a region which is positioned adjacent to the region in which the exhaust gas discharge 11 the exhaust gas supply line 8th concentrically surrounds. This makes a compact design possible. In contrast, it is also possible that the bypass 12 is formed in the area in which the exhaust gas discharge 11 the exhaust gas supply line 8th concentric outside surrounds.

As already stated, is in the bypass 12 a shut-off element 13 switched or integrated. After a first variant that can be in the bypass 12 switched shut-off element 13 be designed as a shut-off valve, which is preferably open or closed depending on the operating situation. Then, if the internal combustion engine, such an exhaust aftertreatment system 3 is operated, for example in a cold start operating mode and / or when a sudden, dynamic load increase is requested for the internal combustion engine, the shut-off is 13 preferably open to cold start, bypassing the SCR catalyst 9 To heat turbines of the exhaust gas turbocharger and handle handling of a dynamic load change or a dynamic load request amount of exhaust gas safely.

According to a further alternative of the invention, this can be in the bypass 12 switched shut-off element 13 be designed as a rupture disk. Such a rupture disk is destroyed during opening, so it can not be closed again after opening unlike a shut-off valve. Then, when the shut-off element 13 designed as a rupture disk, the same opens in particular depending on a pressure difference between the pressure in the exhaust gas supply line 8th and the pressure in the exhaust gas outlet 11 , Increases, for example, as a result of a dynamic load request in the exhaust gas supply line 8th the pressure jumps, so the rupture disk is destroyed and thus opened depending on the pressure increase. Further, the rupture disk may be associated with a means, not shown, to open the rupture disk, such means being, for example, a compressed air device which directs compressed air toward the rupture disk to open it. The device for opening the rupture disk can also open the rupture disk mechanically.

The exhaust gas supply line 8th flows with the downstream end 15 in the reactor room 10 , This downstream end 15 the exhaust gas supply line 8th is a baffle element 20 assigned, which is relative to the downstream end 15 the exhaust gas supply line 8th is relocatable.

In the embodiment shown, the baffle element 20 relative to the end 15 the exhaust gas supply line 8th which is in the reactor room 10 flows, linearly displaceable. The impact element 20 is relative to the downstream end 15 the exhaust gas supply line 8th relocatable to either the exhaust gas supply 8th at the downstream end 15 shut off or the same at the downstream end 15 release. Then, if the baffle element 20 the exhaust gas supply line 8th at the downstream end 15 shut off, is preferably the obturator 13 of the bypass 12 then open the exhaust completely on the SCR catalyst 9 or on which the SCR catalyst 9 receiving reactor space 10 passing out. Then, if the baffle element 20 the downstream end 15 the exhaust gas supply line 8th releases, the obturator can 13 of the bypass 12 either completely closed or at least partially open. Then, if the baffle element 20 the downstream end 15 the exhaust gas supply line 8th releases, is the relative position of the impact element 20 relative to the downstream end 15 the exhaust gas supply line 8th in particular of the exhaust gas mass flow through the exhaust gas supply line 8th and / or the exhaust gas temperature of the exhaust gas in the exhaust gas supply line 8th and / or the amount of the via the introduction device 16 in the exhaust gas flow introduced reducing agent dependent. Another function of the impact element 20 with released, downstream end 15 the exhaust gas supply line 8th is that possibly present in the exhaust stream drops of liquid reducing agent on the impact element 20 get trapped and atomized there to avoid such drops of liquid reducing agent in the area of the SCR catalyst 9 reach. About the relative position of the impact element 20 to the downstream end 15 the exhaust gas supply line 8th with the downstream end enabled 15 In particular, it can also be determined whether the exhaust gas which is in the region of the downstream end 15 the exhaust gas supply line 8th in the area of the impact element 20 is deflected, more toward radially inwardly positioned sections or more towards radially outwardly positioned sections of the SCR catalyst 9 is directed or directed.

According to a preferred embodiment, the exhaust gas supply line 8th in the region of its downstream end 15 widened funnel-shaped formation of a diffuser. As a result, the flow cross section of the exhaust gas supply line increases 8th in the area of the downstream end 15 , where, in particular 2 can be taken, it can be provided that seen in the flow direction of the exhaust gas upstream of the downstream end 15 the exhaust gas supply line 8th the flow cross section of the same initially reduced. So shows 2 in that the flow cross section of the exhaust gas supply line 8th seen in the flow direction of the exhaust gas downstream of the introduction device 16 is initially approximately constant for the reducing agent, then initially gradually tapers and finally in the region of the downstream end 15 extended. This extension of the flow cross-section at the downstream end 15 the exhaust gas supply line 8th takes place vorzugwseise over a shorter section of the exhaust gas supply line 8th , as the section over which the exhaust gas supply line 8th in front of the downstream end 15 initially rejuvenated.

The impact element 20 is preferably at one of the exhaust gas supply line 8th facing side 22 is arched to form a flow guide for the exhaust, preferably curved like a bell. So can 3 to be taken that side 22 of the baffle element 20 that is the downstream end 15 the exhaust gas supply line 8th facing, at a radially inner portion of the impact member 20 a smaller distance to the downstream end 15 the exhaust gas supply line 8th as at a radially outer portion thereof. The impact element 20 is in the center of the page 22 towards the downstream end 15 the exhaust gas supply line 8th retracted or curved against the flow direction of the exhaust gas.

In the internal combustion engine 1 of the 1 is the exhaust aftertreatment system 3 standing above the exhaust gas charging system 2 positioned. Access to cylinders of the internal combustion engine 1 is free, the accessibility of the turbocharger 4 and 5 is limited. The reactor room 10 However, if necessary maintenance on the turbochargers 4 . 6 simply be dismantled.

Unlike the in 1 shown standing arrangement of the exhaust aftertreatment system 3 above the exhaust charging system 2 is also a horizontal, tilted by 90 ° arrangement of the exhaust aftertreatment system 3 next to the exhaust charging system 2 possible, but with such a lying arrangement, the length of the arrangement grows. Internal combustion engine 1 and exhaust charging system 2 However, then stand for maintenance without the need to disassemble the reactor space 10 unrestricted available.

The invention further relates to a method for operating an internal combustion engine 1 with an exhaust aftertreatment system described above 3 , When the internal combustion engine is operating in a cold start mode of operation and / or when a torque to be provided by the internal combustion engine is dynamically increased in the sense of a dynamic load request, and / or when the exhaust aftertreatment system 3 , in particular the SCR catalyst 9 , is clogged, that will be in the bypass 12 switched shut-off element 13 automatically open, then exhaust gas on the SCR catalyst 9 or on which the SCR catalyst 9 receiving reactor space 10 passing out. During the cold start, the thermal energy of the exhaust gas can be used, for example, to quickly heat the low-pressure turbine to operating temperature, without first having to heat up the cold AGN system. In the case of a dynamic load request to the internal combustion engine, an exhaust gas flow and thus an excessive exhaust gas pressure in the exhaust gas supply line can occur 8th be prevented.

In the preferred embodiment of the invention, in which the downstream end 15 the exhaust gas supply line 8th the impact element 20 is assigned to the bypass 12 over the shut-off element 13 then automatically open if that is the downstream end 15 the exhaust gas supply line 8th associated baffle element 20 the exhaust gas supply line 8th blocked. Then, on the other hand, if the baffle element 20 the exhaust gas supply line 8th releases, the bypass becomes 12 over the shut-off element 13 at least in part, outside a cold start mode of operation and outside the dynamic load request, preferably fully closed.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

Turbocharging System

3

aftertreatment system

4

turbocharger

5

turbocharger

6

High-pressure turbine

7

Low-pressure turbine

8th

exhaust lead

9

SCR catalyst

10

reactor chamber

11

Flue gas discharge

12

bypass

13

shutoff

14

exhaust system

15

The End

16

introducing device

17

Injection cone

18

mixing section

19

page

20

baffle

21

management

22

page

23

page

Claims (16)

Exhaust aftertreatment system ( 3 ) an internal combustion engine with a catalyst ( 9 ), with a catalyst ( 9 ) leading exhaust gas supply ( 8th ) and with a catalyst ( 9 ) leading off exhaust gas discharge ( 11 ), characterized in that the exhaust gas supply line ( 8th ) and the exhaust gas discharge ( 11 ) on a common page ( 19 ) of a catalyst ( 9 ) receiving reactor space ( 10 ) attack and / or on the common side ( 19 ) into the reactor space ( 10 ) and that between the exhaust gas supply line ( 8th ) and the exhaust gas discharge ( 11 ) a bypass ( 12 ) to the SCR catalyst ( 9 ) or reactor space ( 10 ) is formed, wherein in the bypass ( 12 ) a shut-off element ( 13 ) is switched. Exhaust aftertreatment system ( 3 ) according to claim 1, characterized in that it is for example an SCR, CH4, or HCHO oxidation catalyst. Exhaust after-treatment system according to claim 1, characterized in that the bypass ( 12 ) downstream of a feed device ( 16 ) for introducing a reducing agent, in particular ammonia or an ammonia precursor substance, into the exhaust gas in the region of a mixing zone ( 18 ) for mixing the exhaust gas with the reducing agent from the exhaust gas supply line ( 8th ) in the direction of the exhaust gas discharge ( 11 ) branches off. Exhaust after-treatment system according to one of claims 1 to 3, characterized in that the exhaust gas feed line ( 8th ) with a downstream end ( 15 ) into the reactor space ( 10 ) and that with this downstream end ( 15 ) of the exhaust gas supply line ( 8th ) an impact element ( 20 ), which is relative to the downstream end ( 15 ) of the exhaust gas supply line ( 8th ) is displaceable. Exhaust after-treatment system according to one of claims 1 to 4, characterized in that in the bypass ( 12 ) shut-off element ( 13 ) is a shut-off valve that is open or closed depending on the operating situation. Exhaust after-treatment system according to claim 4 and 5, characterized in that the position of the in the bypass ( 12 ) shut-off valve from the position of the impact element ( 20 ) relative to the downstream end ( 15 ) of the exhaust gas supply line ( 8th ) is dependent. Exhaust after-treatment system according to one of claims 1 to 4, characterized in that in the bypass ( 12 ) shut-off element ( 13 ) is a rupture disk. Exhaust after-treatment system according to claim 7, characterized in that the rupture disk is dependent on a pressure difference between the pressure in the exhaust gas supply line ( 8th ) and the pressure in the exhaust gas discharge ( 11 ) opens. Exhaust after-treatment system according to claim 7 or 8, characterized in that the rupture disk is associated with a device which opens the rupture disk. An exhaust after-treatment system according to claim 9, characterized in that the means for opening the rupture disk directs compressed air to the rupture disk. Exhaust gas aftertreatment system according to one of claims 1 to 10, characterized in that the exhaust gas discharge ( 11 ) at least in sections, the exhaust gas supply line ( 8th ) surrounds the outside, and that the bypass ( 12 ) to the catalyst ( 9 ) or reactor space ( 10 ) is formed in or adjacent to the region in which exhaust gas discharge ( 11 ) and exhaust gas supply line ( 8th ) surrounds outside. Internal combustion engine ( 1 ), in particular with a diesel fuel or with a heavy fuel oil-fueled internal combustion engine, with an exhaust aftertreatment system ( 3 ) according to one of claims 1 to 11. Internal combustion engine according to claim 12, characterized in that it has a multi-stage exhaust gas charging system ( 2 ) with a high-pressure turbine ( 6 ) comprehensive exhaust gas turbocharger ( 4 ) and a low-pressure turbine ( 7 ) second exhaust gas turbocharger ( 5 ), wherein the exhaust aftertreatment system ( 3 ) between the high-pressure turbine ( 6 ) and the low-pressure turbine ( 7 ) is switched. Internal combustion engine according to claim 12, characterized in that in single-stage supercharged engines, the AGN system is arranged upstream of the exhaust gas turbine. Method for operating an internal combustion engine according to claim 11 or 12, characterized in that in the bypass ( 12 ) shut-off element ( 13 ) is opened, the internal combustion engine is operated in a cold start operating mode and / or when a torque to be provided by the internal combustion engine is dynamically increased and / or when the exhaust gas aftertreatment system ( 3 ), in particular the SCR catalyst ( 9 ), is clogged. Method for operating an internal combustion engine according to Claim 11 or 12 with an exhaust aftertreatment system ( 3 ) according to claim 3, characterized in that in the bypass ( 12 ) shut-off element ( 13 ) is opened, if that with the downstream end ( 15 ) of the exhaust gas supply line ( 8th ) cooperating impact element ( 20 ) the exhaust gas supply line ( 8th ) blocked.

Images