CH712344B1 - Exhaust aftertreatment system and internal combustion engine. - Google Patents

Abstract

Exhaust gas aftertreatment system for an internal combustion engine, with a catalytic converter (9), with an exhaust gas feed line (8) leading to the catalytic converter (9) and with an exhaust gas discharge line (11) leading away from the catalytic converter (9), the exhaust gas feed line (8) having a downstream end (15 ) opens into a reactor space (10) accommodating the catalyst (9), with this end (15) of the exhaust gas feed line (8) cooperating with an impact element (19) which can be displaced relative to the downstream end (15) of the exhaust gas feed line (8). In particular, the catalytic converter is an SCR catalytic converter. The exhaust gas aftertreatment system is preferably provided with an introduction device (16) assigned to the exhaust gas feed line (8) for introducing a reducing agent, in particular ammonia or an ammonia precursor substance, into the exhaust gas, and with one of the exhaust gas feed line (8) downstream of the introduction device (16) Mixing section (18) for mixing the exhaust gas with the reducing agent upstream of the SCR catalytic converter (9).

Description

The invention relates to an exhaust gas aftertreatment system for an internal combustion engine and an internal combustion engine with an exhaust gas aftertreatment system according to the preambles of the independent claims.

In combustion processes in stationary internal combustion engines, which are used, for example, in power plants, as well as in combustion processes in non-stationary internal combustion engines, which are used, for example, on ships, nitrogen oxides arise, these nitrogen oxides typically during the combustion of sulfur-containing fossil fuels, such as Coal, hard coal, lignite, crude oil, heavy oil or diesel fuels are produced. Such internal combustion engines are therefore assigned exhaust gas aftertreatment systems which serve to clean, in particular denitrify, the exhaust gas leaving the internal combustion engine.

To reduce nitrogen oxides in the exhaust gas, so-called SCR catalytic converters are primarily used in exhaust gas aftertreatment systems known from practice. A selective catalytic reduction of nitrogen oxides takes place in an SCR catalytic converter, whereby ammonia (NH3) is required as a reducing agent for the reduction of the nitrogen oxides. For this purpose, the ammonia or an ammonia precursor substance, such as urea, is introduced into the exhaust gas in liquid form upstream of the SCR catalytic converter, the ammonia or the ammonia precursor substance being mixed with the exhaust gas upstream of the SCR catalytic converter. For this purpose, according to practice, mixing sections are provided between the introduction of the ammonia or the ammonia precursor substance and the SCR catalytic converter.

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

Based on this, the present invention is based on the object of creating a novel exhaust gas aftertreatment system for an internal combustion engine.

This object is achieved by an exhaust gas aftertreatment system for an internal combustion engine according to claim 1. According to the invention, the exhaust gas feed line opens with a downstream end into a reactor chamber accommodating the catalyst, with this end of the exhaust gas feed line cooperating with an impact element that can be displaced relative to the downstream end of the exhaust gas feed line. The impact element, which is arranged at the downstream end of the exhaust gas feed line opening into the reactor chamber, can ensure good mixing of the exhaust gas with the reducing agent and a defined flow of the SCR catalytic converter on the one hand with a shortened mixing section. With a compact design, effective exhaust gas aftertreatment can be guaranteed.

According to an advantageous development, the baffle element is displaceable relative to the downstream end of the exhaust gas feed line in order to either shut off the exhaust gas feed line at the downstream end or to release the exhaust gas feed line at the downstream end, the relative position of the baffle element preferably relative to the downstream end of the exhaust gas feed line when the exhaust gas feed line is to be released depends on the exhaust gas mass flow and / or on the exhaust gas temperature and / or on the amount of the reducing agent introduced into the exhaust gas mass flow. This enables particularly effective exhaust gas aftertreatment with a compact design of the exhaust gas aftertreatment system.

According to an advantageous development, the downstream end of the exhaust gas feed line widens in a funnel shape to form a diffuser. The impact element is arched, in particular arched like a bell, on a side facing the downstream end of the exhaust gas feed line, on which the exhaust gas flow and the reducing agent impinge, to form a flow guide surface. These details also allow effective exhaust gas aftertreatment with a short mixing section as a result of the defined flow guidance in the area of the impact element and the downstream end of the exhaust gas feed line facing the same.

According to a further advantageous development, a bypass line to the SCR catalytic converter is between the exhaust gas feed line and the exhaust gas discharge line. switched to the reactor space, wherein a shut-off element is connected in the bypass line, the position of which is dependent on the position of the impact element relative to the downstream end of the exhaust gas feed line. Excess exhaust gas can be led past the SCR catalytic converter via the bypass, in particular if, after the internal combustion engine has been started, there are still cold assemblies to be heated in the area of the internal combustion engine's turbocharger.

According to a further advantageous development, the impact element carries a catalytic coating, at least on the side facing the downstream end of the exhaust gas feed line. This can further improve the exhaust gas aftertreatment.

The internal combustion engine according to the invention is defined in claim 13.

Preferred developments of the invention emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. 1 shows a schematic, perspective view of an internal combustion engine with an exhaust gas aftertreatment system according to the invention; FIG. 2: a detail of the exhaust gas aftertreatment system of FIG. 1; FIG. 3: a detail of FIG. 2; and FIG. 4: a further detail of the exhaust gas aftertreatment system according to the invention.

The present invention relates to an exhaust gas aftertreatment system of an internal combustion engine, for example a stationary internal combustion engine in a power plant or a non-stationary internal combustion engine used on a ship. In particular, the exhaust gas aftertreatment system is used on a marine diesel engine operated with heavy fuel oil. The method is explained in more detail below in connection with SCR technology, but it is not restricted to this, but can also be used with CH4 and HCHO oxidation catalysts, such as those used in gas engines, for example.

1 shows an arrangement of an internal combustion engine 1 with an exhaust gas turbocharging system 2 and an exhaust gas aftertreatment system 3.

The internal combustion engine 1 can be a transient or stationary internal combustion engine, in particular a transiently operated marine internal combustion engine. Exhaust gas that leaves the cylinder of the internal combustion engine 1 is used in the exhaust gas charging system 2 in order to obtain mechanical energy from the thermal energy of the exhaust gas for compressing the charge air to be supplied to the internal combustion engine 1.

1 shows an internal combustion engine 1 with an exhaust gas turbocharging system 2 which comprises several 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 leaves the cylinder of the internal combustion engine 1, first flows through a high pressure turbine 6 of the first exhaust gas turbocharger 1 and is relaxed in the same, the energy obtained in this case being used in a high pressure compressor of the first exhaust gas turbocharger 4 to compress charge air.

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

The method is not limited to two-stage supercharged engines, but can also be used in single-stage supercharged engines, the AGN system then advantageously being mounted upstream of the turbine.

In addition to the two exhaust gas turbochargers 4 and 5 having exhaust gas charging system 2, the internal combustion engine 1 includes the exhaust gas aftertreatment system 3, which is an SCR exhaust gas aftertreatment system. The SCR exhaust gas aftertreatment system 3 is connected between the high pressure turbine 6 of the first compressor 5 and the low pressure turbine 7 of the second exhaust gas turbocharger 5, so that exhaust gas leaving the high pressure turbine 6 of the first exhaust gas turbocharger 4 can initially be routed through the SCR exhaust gas aftertreatment system 3 before the same reaches the area of the low-pressure turbine 7 of the second exhaust gas turbocharger 5. 1 shows an exhaust gas feed line 8, via which exhaust gas, starting from the high pressure turbine 6 of the first exhaust gas turbocharger 4, can be guided in the direction of an SCR catalytic converter 9 which is arranged in a reactor chamber 10. 1 also shows an exhaust gas discharge line 11, which is used to discharge the exhaust gas from the SCR catalytic converter 9 in the direction of the low-pressure turbine 7 of the second exhaust gas turbocharger 5. Starting from the low-pressure turbine 7, the exhaust gas flows via a line 26, in particular into the open.

The exhaust gas feed line 8 leading to the reactor chamber 10 and thus to the SCR catalytic converter 9 positioned in the reactor chamber 10 and the exhaust gas discharge line 11 leading away from the reactor chamber 10 and thus from the SCR catalytic converter 9 are coupled via a bypass line 12 into which a shut-off element 13 is integrated is. When the shut-off element 13 is closed, the bypass line 12 is closed so that no exhaust gas can flow through it. Then, on the other hand, when the shut-off element 13 is open, exhaust gas can flow via the bypass line 12, namely past the reactor space 10 and thus past the SCR catalytic converter 9 positioned in the reactor space 10.

Fig. 2 illustrates with arrows 14 the flow of the exhaust gas through the exhaust gas aftertreatment system 3 with the bypass line 12 closed by the shut-off device 13, FIG. 2 it can be seen that the exhaust gas feed line 8 opens into the reactor chamber 10 with a downstream end 15, wherein the exhaust gas experiences a flow deflection by approximately 180 ° or approximately 180 ° in the area of this end 15 of the exhaust gas feed line 8, the exhaust gas being guided over the SCR catalytic converter 9 after the flow deflection.

The exhaust line 8 of the exhaust gas aftertreatment system 3 is assigned an introduction device 16, via which a reducing agent can be introduced into the exhaust gas flow, in particular ammonia or an ammonia precursor substance that is required to define nitrogen oxides of the exhaust gas in the area of the SCR catalytic converter 9 to implement.

This introduction device 16 of the exhaust gas aftertreatment system 3 is preferably an injection nozzle, via which the ammonia or the ammonia precursor substance is injected into the exhaust gas stream within the exhaust gas feed line 8. With a cone 17, FIG. 2 illustrates the injection of the reducing agent into the exhaust gas flow in the region of the exhaust gas feed line 8.

The section of the exhaust gas aftertreatment system 3, which, viewed in the flow direction of the exhaust gas, is located downstream of the introduction device 16 and upstream of the SCR catalytic converter 9, is referred to as the mixing section. In particular, the exhaust gas feed line 8 provides a mixing section 18 downstream of the introduction device 19, in which the exhaust gas can be mixed with the reducing agent upstream of the SCR catalytic converter 9.

The downstream end 15 of the exhaust gas feed line 8 opens into the reactor chamber 10. This downstream end 15 of the exhaust gas feed line 8 is assigned a baffle element 19 which can be displaced relative to the downstream end 15 of the exhaust gas feed line 8.

In the preferred embodiment shown, the impact element 19 is linearly displaceable relative to the end 15 of the exhaust gas line 8, which opens into the reactor chamber 10, in the direction of the double arrow 25, in particular with the aid of a pneumatic actuating cylinder 20, which is connected to the impact element via a piston rod 21 19 engages and extends through a wall 22 of the reactor space 10. A seal 23 seals the piston rod 21 of the pneumatic cylinder 20 where it penetrates the wall 22 of the reactor space 10.

The impact element 19 is displaceable relative to the downstream end 15 of the exhaust gas feed line 8 in order to either shut off the exhaust gas feed line 8 at the downstream end 15 or to release the same at the downstream end 15. Then, when the impact element 19 shuts off the exhaust gas feed line 8 at the downstream end 15, the shut-off element 13 of the bypass line 12 is preferably opened in order to then lead the exhaust gas completely past the SCR catalytic converter 9 or the reactor chamber 10 receiving the SCR catalytic converter 9. Then, when the impact element 19 releases the downstream end 15 of the exhaust gas feed line 8, the shut-off element 13 of the bypass line 12 can either be completely closed or also at least partially open.

When the impact element 19 releases the downstream end 15 of the exhaust gas line 8, the relative position of the impact element 19 relative to the downstream end 15 of the exhaust gas line 8 is in particular of the exhaust gas mass flow through the exhaust gas line 8 and / or of the exhaust gas temperature of the exhaust gas in the Exhaust gas feed line 8 and / or dependent on the amount of the reducing agent introduced into the exhaust gas flow via the introduction device 16.

About the relative position of the impact element 19 to the downstream end 15 of the exhaust gas line 8 when the downstream end 15 is released, it can be determined in particular whether the exhaust gas that is deflected in the area of the downstream end 15 of the exhaust gas line 8 in the area of the impact element 19 is stronger Direction of radially inwardly positioned sections or more in the direction of radially outwardly positioned sections of the SCR catalytic converter 9 is guided or steered.

According to a particularly preferred embodiment of the invention, the exhaust gas feed line 8 is widened in the form of a funnel in the region of its downstream end 15 to form a diffuser. This increases the flow cross-section of the exhaust gas feed line 8 in the area of the downstream end 15, whereby, as can be seen in particular from FIG. 2, it can be provided that, viewed in the flow direction of the exhaust gas, the flow cross-section of the exhaust gas feed line 8 is initially reduced upstream of the downstream end 15 of the exhaust gas feed line 8 . 2 shows that the flow cross-section of the exhaust gas feed line 8, viewed in the flow direction of the exhaust gas, is initially approximately constant downstream of the introduction device 16 for the reducing agent, then initially gradually tapers and finally widens in the area of the downstream end 15. This expansion of the flow cross-section at the downstream end 15 of the exhaust gas feed line 8 is preferably carried out over a shorter section of the exhaust gas feed line 8 than the section over which the exhaust gas feed line 8 initially tapers in front of the downstream end 15.

As already stated, the baffle element 19 interacts with the downstream end 15 of the exhaust gas line 8, which in a particularly preferred embodiment of the invention is curved at least on one side facing the downstream end 15 of the exhaust gas line 8 to form a flow guide for the exhaust gas , preferably arched like a bell. 3 and 4, in particular, that the side 24 of the impact element 19, which faces the downstream end 15 of the exhaust gas feed line 8, is at a smaller distance from the downstream end 15 of the exhaust gas feed line 8 at a radially inner section of the impact element 19 than at a radially outer portion thereof. The impact element 19 is accordingly drawn in or arched in the center of the side 24 in the direction of the downstream end 15 of the exhaust gas feed line 8 against the direction of flow of the exhaust gas.

When the baffle element 19 releases the downstream end 15 of the exhaust gas feed line 8, the distance between the baffle element 19 and the downstream end 15 of the exhaust gas feed line 8 is in particular at least 100 mm in order to deflect the exhaust gas flow with as little pressure loss as possible in the area of the baffle element 19 to ensure, namely with a pressure loss of less than 10 mbar.

As already stated, the impact element 19 takes on several tasks, namely a shut-off function when the downstream end 15 of the exhaust gas supply line 8 is blocked and a flow guiding function when the downstream end 15 of the exhaust gas supply line 8 is open, depending on the exhaust gas flow and / or exhaust gas temperature and / or amount of reducing agent introduced into the exhaust gas flow. A further function of the impact element 19 when the downstream end 15 of the exhaust gas feed line 8 is released is that any drops of liquid reducing agent present in the exhaust gas flow reach the side 24 of the impact element 19 facing the downstream end 15 of the exhaust gas feed line 8 and are caught and atomized there. in order to prevent such drops of liquid reducing agent from getting into the area of the SCR catalytic converter 9. In addition, large particles, such as rust particles, which arise when the exhaust pipe is corroded, are crushed when it hits, so that they can no longer clog the EGR system.

The impact element 19 can have a catalytic coating in the region of the side 24 facing the downstream end 15 of the exhaust gas feed line 8 in order to improve the exhaust gas aftertreatment.

As can best be seen from Fig. 4, the expansion of the downstream end 15 of the exhaust gas line 8 and the bell-like contouring of the side 24 of the impact element 19 is preferably continuous, so without discontinuities.

In the internal combustion engine 1 of FIG. 1, the exhaust gas aftertreatment system 3 is positioned upright above the exhaust gas charging system 2. Access to the cylinders of the internal combustion engine 1 is free, but the accessibility of the exhaust gas turbochargers 4 and 5 is restricted. The reactor space 10 can, however, simply be dismantled when maintenance work is required on the exhaust gas turbochargers 4, 6.

In contrast to the standing arrangement of the exhaust gas aftertreatment system 3 shown in Fig. 1 above the exhaust gas charging system 2, a horizontal, 90 ° tilted arrangement of the exhaust gas aftertreatment system 3 next to the exhaust gas charging system 2 is possible, but with such a horizontal arrangement the length of the Arrangement grows. Internal combustion engine 1 and exhaust gas charging system 2 are then, however, available without restriction for maintenance work without the need to dismantle the reactor chamber 10.

List of reference symbols

1 Internal combustion engine 2 Exhaust gas charging system 3 Exhaust gas aftertreatment system 4 Exhaust gas turbocharger 5 Exhaust gas turbocharger 6 High pressure turbine 7 Low pressure turbine 8 Exhaust gas feed line 9 SCR catalytic converter 10 Reactor chamber 11 Exhaust gas discharge line 12 Bypass line 13 Shut-off element 14 Exhaust gas guide 15 End 16 Injection device 17 Injection cone 18 Mixing section 19 Impact element 20 Pneumatics 18 Mixing section 19 Impact element 20 Pneumatics Seal 24 Page 25 Direction of displacement 26 Cable

Claims (15)

Exhaust gas aftertreatment system (3) for an internal combustion engine, with a catalytic converter (9), with an exhaust gas feed line (8) leading to the catalytic converter (9) and with an exhaust gas discharge line (11) leading away from the catalytic converter (9), characterized in thatthe exhaust gas feed line (8 ) with a downstream end (15) opens into a reactor space (10) receiving the catalyst (9), with this end (15) of the exhaust gas feed line (8) a baffle element (19) cooperating, which relative to the downstream end (15) of the Exhaust gas feed line (8) can be displaced. 2. Exhaust aftertreatment system (3) according to claim 1, wherein the catalyst is an SCR catalyst (9), with an introduction device (16) assigned to the exhaust gas feed line (8) for introducing a reducing agent, in particular ammonia or an ammonia precursor substance, into the Exhaust gas, and with a mixing section (18) provided by the exhaust gas feed line (8) downstream of the introduction device (16) for mixing the exhaust gas with the reducing agent upstream of the SCR catalytic converter (9). 3. Exhaust aftertreatment system according to claim 1 or 2, characterized in that the impact element (19) can be displaced relative to the downstream end (15) of the exhaust gas feed line (8) in order to either shut off the exhaust gas feed line (8) at the downstream end (15) or the exhaust gas feed line ( 8) at the downstream end (15). 4. Exhaust aftertreatment system according to claim 3, characterized in that it is designed in such a way that when the exhaust gas feed line (8) is to be released the relative position of the impact element (19) relative to the downstream end (15) of the exhaust gas feed line (8) from the exhaust gas mass flow and / or from the exhaust gas temperature and / or depends on the amount of the reducing agent introduced into the exhaust gas mass flow. 5. Exhaust gas aftertreatment system according to one of Claims 1 to 4, characterized in that the baffle element (19) is linearly displaceable relative to the downstream end (15) of the exhaust gas feed line (8). 6. Exhaust gas aftertreatment system according to one of Claims 1 to 5, characterized in that the impact element (19) can be displaced via a pneumatic actuating cylinder (20, 21) relative to the downstream end (15) of the exhaust gas feed line (8). 7. Exhaust gas aftertreatment system according to one of claims 1 to 6, characterized in that the downstream end (15) of the exhaust gas feed line (8) expands in a funnel shape to form a diffuser. 8. Exhaust gas aftertreatment system according to one of claims 1 to 7, characterized in that the baffle element (19) is formed on a side (24) facing the downstream end (15) of the exhaust gas feed line (8) on which the exhaust gas flow and the reducing agent encounter during operation a flow guide surface is curved. 9. Exhaust aftertreatment system according to claim 8, characterized in that the impact element (19) is curved on the side (24) facing the downstream end (15) of the exhaust gas feed line (8) in such a way that on a radially inner section of the impact element (19) the distance to the downstream end (15) of the exhaust gas feed line (8) is smaller than at a radially outer section of the impact element (19). 10. The exhaust gas aftertreatment system according to claim 8 or 9, characterized in that the impact element (19) is curved like a bell on the side (24) facing the downstream end (15) of the exhaust gas feed line (8). 11. Exhaust aftertreatment system according to one of claims 1 to 10, characterized in that a bypass line (12) to the reactor space (10) is connected between the exhaust gas feed line (8) and the exhaust gas discharge line (11), a shut-off element (13) being connected in the bypass line (12) is, the position of which is dependent on the position of the impact element (19) relative to the downstream end (15) of the exhaust gas feed line (8). 12. Exhaust aftertreatment system according to one of Claims 1 to 11, characterized in that the impact element (19) has a catalytic coating. 13. Internal combustion engine (1), in particular with a diesel fuel or with a heavy oil fuel or a gas-operated internal combustion engine, with an exhaust gas aftertreatment system (3) according to one of claims 1 to 12. 14. Internal combustion engine according to claim 13, characterized in that it has a multi-stage exhaust gas charging system (2) with a first exhaust gas turbocharger (4) comprising a high pressure turbine (6) and a second exhaust gas turbocharger (5) comprising a low pressure turbine (7), the exhaust gas aftertreatment system (3 ) is connected between the high-pressure turbine (6) and the low-pressure turbine (7). 15. Internal combustion engine according to claim 13, characterized in that it has a single-stage exhaust gas charging system (2), the exhaust gas aftertreatment system (3) being connected upstream of the turbine.