Exhaust aftertreatment system of an engine designed as a gas engine or dual-fuel engine, engine and method for operating the same

Abstract

Exhaust aftertreatment system (1) of an engine designed as a gas engine or as a dual-fuel engine, with a catalyst (3) which is permeable to exhaust gas, with a control tube (4) extending through a recess (5) in the catalyst (3), which is displaceable relative to the catalyst (3) and which is also permeable to exhaust gas, with an actuator (6) configured to displace the control pipe (4) relative to the catalyst (3) depending on at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system (1), such that in a first relative position of the control pipe (4) relative to the catalyst (3) the catalyst (3) is open to exhaust gas flow but not the control pipe (4), and that in a second relative position of the control pipe (4) relative to the catalyst (3) the control pipe (4) is open to exhaust gas flow but not the catalyst (3), wherein the control tube (4) carries a first closure body (13) radially outside on a first section (4a), which in the first relative position of the control tube (4) allows the flow of exhaust gas through the catalyst (3) and which in the second relative position of the control tube (4) prevents the flow of exhaust gas through the catalyst (3).

Description

[0001] The invention relates to an exhaust aftertreatment system for an engine designed as a gas engine or as a dual-fuel engine. Furthermore, the invention relates to an engine designed as a gas engine or dual-fuel engine and a method for operating the exhaust aftertreatment system or the engine.

[0002] Large engines, such as those used on ships as internal combustion engines, are increasingly being designed as gas engines or dual-fuel engines. Gas engines burn a gaseous fuel, such as natural gas. Dual-fuel engines can burn a gaseous fuel, such as natural gas, in a gas fuel operating mode and a liquid fuel, such as diesel fuel, in a liquid fuel operating mode.

[0003] The exhaust gas from such large engines must be cleaned. For this purpose, engines are equipped with exhaust aftertreatment systems. There is a need for a compact exhaust aftertreatment system for an engine designed as a gas engine or dual-fuel engine, particularly a large engine that is preferably used as a propulsion unit on a ship.

[0004] Documents DE 692 19 485 T2 and WO 2004 / 053 313 A1 describe exhaust aftertreatment systems.

[0005] Based on this, the invention aims to create a novel exhaust aftertreatment system for an engine designed as a gas engine or as a dual-fuel engine, and an engine with such an exhaust aftertreatment system.

[0006] This problem is solved by an exhaust aftertreatment system according to claim 1.

[0007] The exhaust aftertreatment system according to the invention has a catalyst through which exhaust gas can flow.

[0008] The exhaust aftertreatment system according to the invention further comprises a control tube extending through a recess in the catalyst, which is movable relative to the catalyst and which is also permeable to exhaust gas.

[0009] The exhaust aftertreatment system according to the invention further comprises an actuator which is configured to displace the control pipe relative to the catalyst depending on at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system, such that in a first relative position of the control pipe relative to the catalyst the catalyst can be permeated by exhaust gas but not the control pipe, and that in a second relative position of the control pipe relative to the catalyst the control pipe can be permeated by exhaust gas but not the catalyst.

[0010] In the exhaust aftertreatment system according to the invention, the control pipe is integrated into the catalyst in such a way that the control pipe penetrates a recess in the catalyst and is movable relative to the catalyst. In the first relative position of the control pipe, it allows exhaust gas flow through the catalyst; in the second relative position of the control pipe, it prevents exhaust gas flow through the catalyst but allows exhaust gas flow through itself. Such an exhaust aftertreatment system requires little installation space. Bypass pipes, insulation, flaps, rupture discs, and control valves for the bypass pipes can be omitted.

[0011] Preferably, the catalyst is a ring catalyst, radially bounded on the inside in the region of the recess accommodating the control tube by a first catalyst tube, and radially bounded on the outside by a second catalyst tube and / or a pressure reactor, which has a flow inlet for exhaust gas at a first axial end and a flow outlet for exhaust gas at a second axial end. Such a catalyst is particularly preferred to ensure a compact design of the exhaust aftertreatment system.

[0012] According to the invention, the control pipe carries a first closure element on a first section, which, in the first relative position of the control pipe, allows flow through the catalyst and, in the second relative position of the control pipe, prevents flow through the catalyst. This also serves to provide a compact design for the exhaust aftertreatment system.

[0013] Preferably, the control pipe carries a second sealing element on a second section, which seals a gap between the control pipe and the catalyst in the first relative position of the control pipe. This advantageously reduces the required installation space of the exhaust aftertreatment system.

[0014] Preferably, the control pipe has recesses on a third section that are blocked in the first relative position of the control pipe and open in the second relative position. These also serve to reduce the installation space required for the exhaust aftertreatment system.

[0015] Preferably, the exhaust aftertreatment system includes a spray device for a regeneration agent, via which a regeneration agent can be introduced into the catalyst in the first relative position of the control pipe relative to the catalyst and in the second relative position of the control pipe relative to the catalyst. The spray device makes it possible to introduce regeneration agents into the catalyst while maintaining a compact design for the exhaust aftertreatment system.

[0016] Preferably, the exhaust aftertreatment system comprises at least one sensor and one control unit to detect the at least one operating condition of the engine and / or the at least one operating condition of the exhaust aftertreatment system, and to control the actuator depending on the at least one operating condition of the engine and / or the at least one operating condition of the exhaust aftertreatment system. This allows for particularly advantageous operation of the exhaust aftertreatment system, either to direct exhaust gas through the catalyst or to route the exhaust gas around the catalyst via the control pipe in a bypass mode. Thus, depending on the at least one operating condition of the exhaust aftertreatment system and / or the at least one operating condition of the engine, the exhaust aftertreatment system can be automatically adjusted to operate either in catalyst mode or in catalyst bypass mode.

[0017] The motor according to the invention is defined in claim 8.

[0018] The inventive method for operating the exhaust aftertreatment system is defined in claim 9.

[0019] Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1 an exhaust aftertreatment system according to the invention in a first state; Fig. 2 the exhaust aftertreatment system of the Fig. 1 in a second state.

[0020] The invention relates to an exhaust aftertreatment system for an engine designed as a gas engine or as a dual-fuel engine, and to such an engine with a fuel supply system. Furthermore, the invention relates to an engine designed as a gas engine or dual-fuel engine and a method for operating the exhaust aftertreatment system or the engine.

[0021] Fig. 1 and Fig. Figure 2 shows a schematically preferred embodiment of an exhaust gas aftertreatment system 1 according to the invention of a gas engine or dual-fuel engine which is not shown in detail, in particular a large engine which is used as a propulsion unit on a ship.

[0022] Fig. 1 and Fig. Figure 2 shows an exhaust pipe 2, which leads from the engine (not shown) towards the exhaust aftertreatment system 1.

[0023] The exhaust aftertreatment system 1 has a catalyst 3. The catalyst 3 is permeable to exhaust gas.

[0024] Furthermore, the exhaust aftertreatment system 1 has a control pipe 4 which extends through a recess 5 in the catalyst 3. The control pipe 4 is displaceable relative to the catalyst 3 and is also permeable to exhaust gas. The control pipe 4 is guided axially displaceably within the recess 5 of the catalyst 3.

[0025] The exhaust aftertreatment system 1 also has an actuator 6. The actuator 6 is configured to move the control pipe 4 relative to the catalyst 3 depending on at least one operating condition of the engine and / or depending on at least one operating condition of the exhaust aftertreatment system 1.

[0026] In a first relative position I (see Fig. 1) of the control pipe 4 relative to the catalyst 3, the catalyst 3 is permeable to exhaust gas, but not the control pipe 4.

[0027] In a second relative position II (see Fig. 2) of the control pipe 4 relative to the catalyst 3, the control pipe 4 is permeable to exhaust gas, but not the catalyst 3.

[0028] The catalyst 3 is a ring catalyst. Radially on the inside of the catalyst 3, in the region of the recess 5 accommodating the control tube 4, it is bounded by a first catalyst tube 7. Radially on the outside, the catalyst 3 is bounded by a second catalyst tube 8 and / or by a pressure reactor 9. Fig. 1 and Fig. 2 A section 9a, 9b of the pressure reactor 9 adjoins both axial sides of the catalyst 3 or second catalyst tube 8.

[0029] The catalyst 3 has two opposing axial ends. At a first axial end 10 of the catalyst 3, a flow inlet side for exhaust gas is formed. At an opposing second axial end 11 of the catalyst 3, a flow outlet side for exhaust gas is formed.

[0030] Then, when the head tube 4 is in Fig. When the exhaust gas A, which flows via the exhaust pipe 2 to the exhaust aftertreatment system 1, assumes the first relative position shown in Figure 1, it can initially flow into section 9a of the pressure reactor 9 and from there into the catalyst 9 via the flow inlet side formed at the first axial end 10. After passing through the catalyst 3, the exhaust gas A exits the catalyst 3 via the flow outlet side formed at the opposite second axial end 11, enters section 9b of the pressure reactor 9, and from this section 9b can flow towards a further exhaust pipe 12 to be discharged by the exhaust aftertreatment system 1.

[0031] The control tube 4 has a first closure element 13 at a first section 4a. This first closure element 13 allows, in the first relative position of the control tube 4 relative to the catalyst 3 (see Fig. 1) the flow of exhaust gas A through the catalyst 3; the first closure element 13 therefore, in this position, opens the flow inlet side of the catalyst 3, formed at the first axial end 10, to the exhaust gas flow. In the second relative position (see Fig. 2) In contrast, the first closure element 13 of the control tube 4 prevents the flow of exhaust gas through the catalyst 3. In this position, the first closure element 13 therefore blocks the flow inlet side of the catalyst 3, which is formed at the first axial end 10, from the exhaust gas flow. The first section 4a of the control tube 4, on which the first closure element 13 is radially attached, projects from the catalyst 3 at the first axial end 10 of the catalyst 13. The first section 4a of the control tube 4 therefore protrudes from the catalyst 3 at its first axial end 10.

[0032] The control tube 4 has a second sealing element 14 on a second section 4b. In the first relative position of the control tube 4 relative to the catalyst 3, this second sealing element 14 seals a gap 15 formed between the control tube 4 and the radially inner catalyst tube 7. This is the case in the second relative position (see Fig. 2) of the control tube 4 relative to the catalyst 3 is not required.

[0033] The head tube 4 has recesses 16 in a third section 4c. In the first relative position (see Fig. 1) of the control tube 4 relative to the catalyst tube 3, these recesses 16 are blocked, in particular by the inner catalyst tube 7 and the second sealing element 14. In the second relative position (see Fig. 2) between control tube 4 and catalyst 3, however, these recesses 16 are released in the third section 4c of the control tube 4.

[0034] In the state of Fig. 2, that is, when the control pipe 4 assumes the second relative position relative to the catalyst 3, exhaust gas A, which is fed to section 9a of the pressure reactor 9 via the exhaust pipe 2, can flow into the control pipe 4 and thus flow past the catalyst 3, in order to then enter the second part 9b of the pressure reactor 9 via the recesses 16 of the control pipe 4 and from there be discharged via the exhaust pipe 12 by the exhaust aftertreatment system 1.

[0035] The exhaust aftertreatment system 1 further comprises a spray device 17 for a regeneration agent. This spray device 17 is positioned adjacent to the flow inlet end of the catalyst 3, which is formed at the first axial end 10 of the catalyst 3, and reducing agent can be supplied to the spray device 17 from a metering valve 18.

[0036] The spray device 17 is preferably designed as a circular spray tube, by means of which the regeneration agent can be applied uniformly to the flow inlet side of the catalyst 10 formed at the first axial end 10.

[0037] In the illustrated embodiment, the actuator 6 of the exhaust aftertreatment system 1 has a pressure-medium-operated piston 19, which is slidably guided in a pressure-medium cylinder 20. A piston rod 21 engages this piston 19 and is in operative connection with the second sealing element 14.

[0038] Pressure medium can be supplied to the pressure medium cylinder 20 from a pressure medium reservoir 22 in order to displace the pressure medium piston 19 and, via the pressure medium piston 19, the control tube 4 in an axial direction relative to the catalyst 3.

[0039] The exhaust aftertreatment system 1 also has at least one sensor to detect at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system.

[0040] This shows Fig. 1. A sensor 23, which is assigned to the exhaust pipe 2, is designed to detect, for example, engine misfires. For this purpose, the sensor 23 can, for example, be designed as a temperature sensor which, when fuel is burned in the engine and a temperature drop is detected, can infer misfires in the engine.

[0041] Fig. 1, Fig. Figure 2 further shows a temperature sensor 24 in the area of ​​the second section 9b of the pressure reactor 9 to detect the exhaust gas temperature of the exhaust gas flowing out of the catalyst 3.

[0042] Furthermore, it shows Fig. 1, Fig. 2 a pressure sensor 25, which has a first measuring point upstream of an aperture 26 and a second measuring point downstream of the aperture 26 on the exhaust pipe 12.

[0043] Furthermore, the exhaust aftertreatment system 1 has at least one control unit by means of which the actuator 6 can be controlled depending on at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system in order to direct the control pipe 4 either into the Fig. 1 shown position or in the Fig. To move to the position shown in point 2.

[0044] The exhaust aftertreatment system according to the invention therefore comprises the catalyst 3, which is preferably designed as a ring catalyst, the control tube 4 integrated into the catalyst 3, which can be displaced in the axial direction relative to the control tube 4, and the actuator 6.

[0045] Preferably, the exhaust aftertreatment system 1 further comprises the spray device 17 for the regeneration agent and at least one sensor 23, 24, 25.

[0046] The control tube 4 is movably arranged within the catalyst 3, specifically inside the inner catalyst tube 7, and can be axially displaced via the actuator 6. Absolute tightness of the control components is not required. Effective exhaust aftertreatment can be ensured even with limited installation space.

[0047] The catalyst 3 has a ring-shaped cross-section and therefore features the recess 5, within which the control pipe 4 is guided. Exhaust gas can be routed past the catalyst 3 through the control pipe 4. The catalyst 3 can be preheated by exhaust gas routed through the control pipe 4 even before any exhaust gas flows over it.

[0048] Particularly during engine start-up, high concentrations of ignitable residual gases containing gaseous fuel are present in the exhaust gas. These can then bypass the catalyst 3 via the control pipe 4 without an oxidative reaction within the catalyst 3.

[0049] The control tube 4 is moved axially by means of the actuator 6. The movement of the control tube 4 can, for example, depend on the exhaust gas pressure and / or the exhaust gas temperature. Temperatures and pressures can be measured using sensors 24 and 25.

[0050] The control tube 4 carries the closures 13, 14. Depending on the relative position of the control tube 4 relative to the catalyst 3, either the first closure body 13 or the second closure body 14 is effective.

[0051] Preferably, the closure bodies 13, 14 are conically contoured. This conical contouring of the closure bodies 13, 14 allows them to ensure an effective seal in their respective closure positions without the need for separate seals.

[0052] Exhaust gas can be supplied to the exhaust aftertreatment system 1 via exhaust line 2. Cleaned exhaust gas can be discharged via exhaust line 12. During the regeneration process of the catalyst 3, regeneration fluid can be discharged from the exhaust aftertreatment system 1 via a further line 27.

[0053] For the regeneration of the catalyst 3, the exhaust aftertreatment system 1 includes the spray device 17, by means of which regeneration agent can be applied to the catalyst 3 in the region of the first axial end 10, and thus in the region of the flow inlet side. In particular, regeneration of the catalyst 3 is carried out when exhaust gas is not flowing through it. In this case, effective regeneration of the catalyst 3 can be ensured with very small quantities of regeneration agent. Regeneration can then take place at lower temperatures in the catalyst 3. Regeneration can also be carried out during engine shutdown or other operating conditions.

[0054] Catalyst 3 is preferably a methane catalyst. Ethanol, ethane, or nitrogen are suitable regenerants.

[0055] The invention further relates to an engine with the exhaust aftertreatment system 1 described above and to a method for operating the exhaust aftertreatment system 1.

[0056] Then, when the head tube 4 is in the first relative position of the Fig. The exhaust gas is cleaned in catalyst 3, which occupies position 1. This first position of the Fig. The control pipe 4 therefore assumes the position of the control pipe 4 during catalyst operation when gaseous fuel is burned in the engine. The exhaust gas A then flows through the catalyst 3 and can be discharged via the exhaust pipe 12. The temperature sensor 24 can be used, for example, to detect a permissible exhaust gas temperature downstream of the exhaust catalyst 3. The pressure sensor 25 can detect an exhaust gas pressure downstream of the catalyst 3. Depending on this, the control pipe 4 can be adjusted relative to the position of the Fig. 1 into the relative position of the Fig. 2 are shifted, whereby the relative position of the Fig. 2 corresponds to a catalyst bypass operation in which no exhaust gas is routed over the catalyst 3, but rather the exhaust gas is routed past the catalyst 3 through the flow pipe 4.

[0057] The relative position of the Fig. 2. The control pipe 4 of a dual-fuel engine occupies position 2 when the engine is operating on liquid fuel, i.e., when diesel fuel is being burned in the engine. Exhaust gas from diesel fuel should not be routed through a methane catalyst. Furthermore, the exhaust aftertreatment system, namely its control pipe 4, occupies the relative position of Fig. 2. This occurs when the engine is started during an engine start and / or when the engine is stopped during an engine stop, and / or in emergency operation and / or in the event of an engine malfunction, for example in the event of misfires, and / or in the event of exhaust gas overheating.

[0058] The invention enables effective exhaust gas purification of a gas engine or a dual-fuel engine operating in gas fuel mode, while requiring minimal installation space for the exhaust aftertreatment system 1. Existing engines can be easily retrofitted using the exhaust aftertreatment system 1 according to the invention. The catalyst 3 can be subjected to effective regeneration with minimal regeneration agent requirements.

Claims

[1] Exhaust aftertreatment system (1) of an engine designed as a gas engine or as a dual-fuel engine, with a catalyst (3) which is permeable to exhaust gas, with a control tube (4) extending through a recess (5) in the catalyst (3), which is displaceable relative to the catalyst (3) and which is also permeable to exhaust gas, with an actuator (6) configured to displace the control pipe (4) relative to the catalyst (3) depending on at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system (1), such that in a first relative position of the control pipe (4) relative to the catalyst (3) the catalyst (3) is open to exhaust gas flow but not the control pipe (4), and that in a second relative position of the control pipe (4) relative to the catalyst (3) the control pipe (4) is open to exhaust gas flow but not the catalyst (3), wherein the control tube (4) carries a first closure body (13) radially outside on a first section (4a), which in the first relative position of the control tube (4) allows the flow of exhaust gas through the catalyst (3) and which in the second relative position of the control tube (4) prevents the flow of exhaust gas through the catalyst (3). [2] Exhaust aftertreatment system (1) according to claim 1, characterized by , that the catalyst (3) is a ring catalyst which is radially internally bounded in the area of ​​the recess (5) receiving the control tube (4) by a first catalyst tube (7), which is radially externally bounded by a second catalyst tube (8) and / or a pressure reactor (9), and which has a flow inlet side for exhaust gas at a first axial end (10) and a flow outlet side for exhaust gas at a second axial end (11). [3] Exhaust aftertreatment system (1) according to one of claims 1 to 2, characterized by, that the control tube (4) carries a second closure body (14) on a second section (4b) which, in the first relative position of the control tube (4), seals a gap (15) between the control tube (4) and the catalyst (3). [4] Exhaust aftertreatment system (1) according to any one of claims 1 to 3, characterized by , that the head tube (4) has recesses (16) on a third section (4c) which are blocked in the first relative position of the head tube (4) and which are released in the second relative position of the head tube (4). [5] Exhaust aftertreatment system (1) according to any one of claims 1 to 4, characterized by a spray device (17) for a regeneration agent, via which regeneration agent can be introduced into the catalyst (3) in the first relative position of the control tube (4) relative to the catalyst (3) and in the second relative position of the control tube (4) relative to the catalyst (3). [6] Exhaust aftertreatment system (1) according to any one of claims 1 to 5, characterized by at least one sensor (23, 24, 25) to detect at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system. [7] Exhaust aftertreatment system (1) according to any one of claims 1 to 6, characterized by a control unit to control the actuator (6) depending on at least one operating condition of the engine and / or at least one operating condition of the exhaust aftertreatment system. [8] Engine, namely gas engine or dual-fuel engine, with an exhaust aftertreatment system (1) according to any one of claims 1 to 7. [9] Method for operating the exhaust aftertreatment system (1) according to any one of claims 1 to 7, where, when a gaseous fuel is burned in the engine, the control tube (4) is or becomes displaced into the first relative position relative to the catalyst (3), wherein when liquid fuel is burned in the engine, and / or when an engine malfunction occurs, and / or when the engine is started, and / or when the engine is shut down, and / or when exhaust gas overheating occurs, and / or when the catalyst is regenerated, the control pipe (4) is or becomes moved into the second relative position relative to the catalyst (3).

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