Exhaust gas aftertreatment system

Abstract

An exhaust gas aftertreatment system. The invention relates to an exhaust gas aftertreatment system for an internal combustion engine, an internal combustion engine and a method for reducing fuel emissions of an internal combustion engine. An exhaust gas aftertreatment system of an internal combustion engine having at least one cylinder having an inner diameter of at least 200 mm is operable in at least a first mode in which the engine is fueled with a first fuel and a second mode in which the engine is fueled with at least one of methanol, ethanol, ammonia, LNG or LPG, the exhaust aftertreatment system includes an SCR catalyst and a fuel escape catalyst disposed upstream or downstream of the SCR catalyst, and further includes: a bypass line for bypassing the fuel escape catalyst, branching downstream of the SCR catalyst if the fuel escape catalyst is disposed downstream of the SCR catalyst, diverting upstream of the SCR catalyst if the fuel escape catalyst is disposed upstream of the SCR catalyst; and a control unit and a bypass regulation device to control the passage of the bypass line and / or the fuel escape catalyst.

Description

Technical Field

[0001] The invention relates to an exhaust gas aftertreatment system for an internal combustion engine having at least one cylinder with an inner diameter of at least 200 mm, to an internal combustion engine and to a method for reducing fuel emissions of an internal combustion engine.

[0002] The present invention relates to the technical field of internal combustion engines and to reducing their emissions.

[0003] In particular, the invention relates to internal combustion engines that can be fueled by a secondary or "green fuel" (eg LNG, LPG, ammonia, ethanol or methanol) and can also operate on a primary fuel (eg a conventional type of fuel such as diesel).

[0004] The invention preferably relates to an internal combustion engine, such as a large ship or marine engine or a stationary engine, whose cylinder has an internal diameter of at least 200 mm. The engine may be a four-stroke engine, and preferably a two-stroke engine or a two-stroke crosshead engine. The engine may be a diesel or gas engine, a dual fuel or a multi-fuel engine. Combustion of liquid and / or gaseous fuels in such an engine, and self-ignition or forced ignition are possible.

[0005] The internal combustion engine may be a longitudinally scavenged two-stroke engine. Background Art

[0006] The term internal combustion engine also refers to large engines that can be operated not only in diesel mode (characterized by self-ignition of the fuel) but also in Otto mode (characterized by positive ignition of the fuel) or a mixture of the two. Furthermore, the term internal combustion engine particularly includes dual-fuel engines and large engines in which the self-ignition of a fuel is used for the positive ignition of another fuel.

[0007] The engine speed is preferably below 800 RPM (4-stroke), and more preferably below 200 RPM (2-stroke), which indicates the designation of a low speed engine.

[0008] The first fuel may be a conventional fuel such as diesel, marine diesel, heavy fuel oil, emulsion or slurry, and the second fuel may be a green fuel such as ammonia, methanol or ethanol and a gas such as liquid natural gas (LNG), liquid petrol gas (LPG) and the like.

[0009] Other possible second fuels that can be used: LBG (liquid biogas), biofuels (eg oil obtained from algae), hydrogen, synthetic fuels from CO2 (eg made from power-gas or power-liquid).

[0010] Large ships, especially those used to transport cargo, are usually powered by internal combustion engines, especially diesel and / or gas engines, mainly two-stroke crosshead engines. The exhaust gases from this combustion process should be cleaned to comply with existing regulations, such as IMO Tier III.

[0011] IMO emission standards are commonly referred to as Tier I…III standards, and in particular define NOx emission standards for existing and new marine engines.

[0012] For large ships, emission requirements have increased, in particular with regard to nitrogen oxide emissions.Therefore, there is a need to reduce the amount of nitrogen oxides in the exhaust gases emitted by the internal combustion engines of these ships.

[0013] SCR (selective catalytic reduction) technology is used to reduce the level of nitrogen oxides (NOx) in the exhaust gas of combustion engines. SCR is commonly used in land-based engines, such as heavy vehicles, industrial plants and other applications. SCR technology has also been used in marine environments in conjunction with two-stroke diesel engines. Due to regulatory requirements for marine diesel engines and land-based engines, the demand for efficient SCR systems has increased.

[0014] SCR can be based on the reduction of nitrogen oxides in the exhaust gas using ammonia (NH3) in the SCR catalyst. Ammonia can be produced by injecting an ammonia precursor substance (such as urea solution) into the exhaust gas of an internal combustion engine. The urea solution is injected into the hot exhaust gas, for example, via a nozzle, wherein the liquid urea solution reacts with ammonia, carbon dioxide and water vapor. The ammonia then reduces the nitrogen oxides to nitrogen (N2) and water (H2O) under the influence of the catalyst in the SCR reactor.

[0015] It is desirable to minimize the emission of ammonia because ammonia is harmful. Therefore, ammonia cannot simply be vented to the atmosphere / surroundings. This is especially true when the fuel is ammonia.

[0016] Although at least a portion of the slipped ammonia is partially consumed in the NOx reduction reaction in the SCR, the excess ammonia may require special treatment. Therefore, an ammonia reduction system may be required downstream of the SCR (preferably based on the specific case of an ammonia slip catalyst - ASC - oxidation catalyst - OC).

[0017] ASC is susceptible to sulfur poisoning.

[0018] Furthermore, other green fuels that avoid CO2 emissions may result in undesirable emissions. For example, during the combustion of methanol, formaldehyde and HCN may occur.

[0019] EP3670856 A1 discloses an exhaust gas aftertreatment system comprising a first catalyst and a second catalyst, wherein the first catalyst may have a different chemical composition from the second catalyst. The first catalyst and the second catalyst may be arranged in series, and the exhaust gas aftertreatment system comprises a control unit for individually controlling the passing of the catalysts.

[0020] DE102017011300 A1 discloses an exhaust system for an internal combustion engine of a motor vehicle. An oxidation catalyst is arranged downstream of a first SCR catalyst and upstream of a second SCR catalyst in the exhaust system. The exhaust system has a bypass line, via which the exhaust gas can be fed to the second SCR catalytic converter while bypassing the oxidation catalytic converter.

[0021] US9624874 B2 discloses an exhaust gas recirculation device, which includes an engine, an intake line, an exhaust gas line and a post-treatment unit. The circulation line guides a portion of the exhaust gas from the downstream side of the post-treatment unit to the intake line. A bypass line branches from the upstream side of the circulation line and merges with the downstream side of the circulation line, wherein ammonia exhausted from the post-treatment unit is prevented from escaping and guided to the intake line.

[0022] EP2808512 A1 discloses an exhaust gas aftertreatment system for reducing nitrogen oxide (NOx) emissions. However, the system is not designed for dual fuel engines, and the AOC reduces the excess urea injected for SCR operation.

[0023] WO2022 / 219458A1 relates to a pollutant reduction system for an internal combustion engine. However, the system is not designed for dual-fuel engines and the DOC oxidizes diesel slip. Summary of the invention

[0024] The object of the present invention is therefore to prevent the disadvantages of the prior art and to create an exhaust gas aftertreatment system, an internal combustion engine and a method for reducing emissions of an internal combustion engine, which ensure a compact design and reduced operating costs.

[0025] The object of the present invention is achieved by an exhaust gas aftertreatment system for an internal combustion engine, which has at least one cylinder with an inner diameter of at least 200 mm, and the cylinder can be operated in at least a first mode and a second mode. In the first mode, the engine uses a first fuel (first fuel) as fuel, and in the second mode, the engine uses a second fuel (second fuel) as fuel, wherein the second fuel includes at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG.

[0026] The first fuel is a fuel such as diesel, which causes CO2 emissions.

[0027] In this application, a "green fuel" is a fuel that may be carbon-free, carbon-neutral, and / or does not cause additional CO 2. Carbon content may also be removed from a green fuel if the carbon content comes from carbon already in the atmosphere rather than from fossil deposits in the ground (such as oil).

[0028] Green fuels can be carbon neutral or even carbon-free alternatives to fossil fuels. Produced from hydrogen and electricity from renewable sources, they can be considered essential for decarbonizing heavy industry, especially the transportation industry. In areas where direct electrification is not feasible, green fuels allow a smooth transition from fossil to sustainable energy sources because they can be used in existing storage and propulsion systems.

[0029] For example, ammonia does not contain any carbon molecules, so it does not contain carbon.

[0030] Methanol is considered carbon neutral when the carbon content comes from carbon capture technology.

[0031] For combustion of the second fuel, for example a pilot injection of a first fuel such as diesel may be required.

[0032] Therefore, also for a second fuel like LNG, ammonia or methanol, a small amount of diesel fuel may be injected into the cylinder to assist the combustion of the methanol or ammonia.

[0033] The exhaust gas aftertreatment system includes an SCR catalyst, a fuel slip catalyst arranged upstream or downstream of the SCR catalyst for processing fuel slip of a second fuel, and a bypass line for bypassing the fuel slip catalyst. If the fuel slip catalyst is arranged downstream of the SCR catalyst, the bypass line branches downstream of the SCR catalyst, and if the fuel slip catalyst is arranged upstream of the SCR catalyst, the bypass line turns upstream of the SCR catalyst.

[0034] A bypass line is provided for bypassing only the fuel slip catalyst so that the exhaust gas is directed through the SCR catalyst or through the SCR catalyst and the fuel slip catalyst.

[0035] In this context, the terms upstream and downstream refer to the direction of flow of the exhaust gases exiting the cylinders.

[0036] The fuel slip catalyst used to treat fuel slip of the second fuel is a catalyst that removes or reduces residues of the second fuel. These residues may include the second fuel itself, such as ammonia residues, or substances produced during combustion of the second fuel, such as formaldehyde or HCN that may be produced during combustion or treatment of methanol in the SCR.

[0037] The fuel slip catalyst may also be adapted to remove or reduce substances that may be produced when the exhaust gas resulting from the combustion of the second fuel passes through another catalyst, such as an SCR catalyst. For example, formaldehyde (CH2O) may be formed by exposure of methanol to an SCR catalyst. Hydrogen cyanide (HCN) may be generated by the reaction of formaldehyde with a quantity of ammonia on the SCR.

[0038] The exhaust gas aftertreatment system comprises a control unit and a bypass regulating device for controlling the passage of a bypass line and / or a fuel slip catalyst.

[0039] The control unit may be adapted to set the pass-through depending on the second fuel content of the exhaust gas, the sulphur content of the exhaust gas, the temperature of the exhaust gas, the temperature of the fuel slip catalyst, the pressure and / or the engine load.

[0040] The second fuel content may correspond to a second fuel slip which escapes the cylinder, for example, after incomplete combustion. However, slip may also occur in the case of complete combustion. In this case, the fuel slip occurs due to the slip of fuel remaining in the pocket volume of the injector.

[0041] The control unit may comprise an inlet line for receiving data relating to the second fuel content of the exhaust gas, the sulphur content of the exhaust gas, the temperature of the exhaust gas, the temperature of the fuel slip catalyst, pressure, regulation level and / or engine load.

[0042] The control unit may be part of an engine control unit for controlling the operation of the internal combustion engine.

[0043] The fuel slip catalyst may only be required when the engine is operating in the second mode, otherwise no fuel slip of the second fuel occurs.

[0044] On the other hand, when the engine is operated with the first fuel, particularly a fuel with a high sulfur content above 0.1 %wt, the fuel slip catalyst may not be allowed to be hit with exhaust gas to avoid or reduce poisoning of the fuel slip catalyst.

[0045] However, since any level of sulfur may damage the catalyst, even 10 ppm (which is the case in the automotive industry), it is preferred to avoid the use of a fuel slip catalyst whenever possible in the first mode.

[0046] Chemical ageing processes of the catalyst (eg by exposure to sulphur) reduce its useful life. Preferably the catalyst operates for at least 5 years, which is a typical interval in marine vessel service.

[0047] The bypass line ensures that the exhaust gases cannot pass through the fuel slip catalyst but instead pass through the SCR catalyst.

[0048] For example, if the internal combustion engine is a dual fuel engine that can operate with diesel and ammonia, the fuel slip catalyst may be an AOC, which may be bypassed in diesel mode.

[0049] In certain operating modes, it is undesirable for the fuel slip of the second fuel (eg ammonia slip) to exceed regulatory levels. Therefore, in these modes, the control unit may be adapted to bypass the fuel slip catalyst to improve life.

[0050] The exhaust aftertreatment system may include a temperature sensor for providing temperature data indicative of the temperature of the fuel slip catalyst. The temperature data may then be used to control the throughput of the bypass line and / or the fuel slip catalyst. This enables the fuel slip catalyst to operate only at a sufficiently high temperature for proper operation.

[0051] The exhaust aftertreatment system may include a pressure sensor for providing pressure data representative of the exhaust pressure, which may be representative of the load.

[0052] Typically, fuel slip catalysts (e.g. AOCs) only produce their catalytic effect at elevated temperatures, e.g. at temperatures above 200° C. The temperature sensor may provide data to the control unit, which may be adapted to allow passage of the fuel slip catalyst only when the fuel slip catalyst has a temperature above a predetermined temperature, e.g. a corresponding light-off temperature, in particular at least 200° C., in particular at a conservable load or full load.

[0053] The control unit may be adapted to allow passing through the fuel slip catalyst in case the internal combustion engine is operated in the second mode and in case the temperature of the fuel slip catalyst is above a respective light-off temperature, in particular above 200°C.

[0054] Alternatively or additionally, the control unit may be adapted to allow passage of the fuel slip catalyst when the internal combustion engine is operated in the second mode and during loads when no fuel slip of the second fuel occurs, in particular when the engine is operated at a load below 80%, preferably below 75%, more preferably below 60%, more preferably below 50%.

[0055] When the internal combustion engine is operated in the second mode and in a case where the temperature of the fuel slip catalyst is higher than 200° C., the fuel slip catalyst may remove or reduce the fuel residue of the second fuel.

[0056] When the internal combustion engine is operated in the second mode and at a load at which no fuel slip of the second fuel occurs, no second fuel residue is present and must be removed. Regardless, the exhaust gas may be directed through the fuel slip catalyst to heat the fuel slip catalyst.

[0057] In case the internal combustion engine is operated in the first mode, the control unit may be adapted to bypass the fuel slip catalyst.

[0058] The control unit may be adapted to provide a warning to the operator in the event that the internal combustion engine is operated in the second mode (eg above 75% load) when fuel slip occurs and the fuel slip catalyst still has a temperature that is too low for efficient or reliable operation.

[0059] The control unit may provide for displaying a warning to the operator that fuel slip of the second fuel may occur before the light-off temperature of the fuel slip catalyst (eg, ASC or OC) is achieved.

[0060] The control unit may be adapted to provide a warning to the operator if the fuel slip catalyst still has a low temperature, and the internal combustion engine will operate in a second mode when fuel slip occurs (e.g. at loads above 75%) and the fuel slip catalyst still has a temperature that is too low for efficient or reliable operation.

[0061] The control unit may be adapted to provide a displayed warning, for example of the type "if you increase the engine load further it may lead to emissions limits being exceeded for NH3-slip".

[0062] If the operator wants to further increase the engine load without waiting for the light-off temperature, the control unit may be adapted to receive a confirmation from the operator.

[0063] The exhaust gas aftertreatment system may comprise a tempering device for raising the temperature of the fuel slip catalyst to a temperature of preferably at least 200°C and / or for maintaining the temperature of the fuel slip catalyst, preferably at least 200°C.

[0064] In particular, the exhaust gas aftertreatment system may comprise a tempering device comprising a thermostat for ensuring that the temperature of the fuel slip catalyst is within a preset temperature range, preferably at least 150°C.

[0065] The thermostatic device may comprise a temperature setting device and / or a cooling device.

[0066] The control unit may be adapted to control the flashback device, in particular to set the temperature of the fuel slip catalyst.

[0067] The control unit may comprise an inlet line for receiving data and / or may have a memory for storing data relating to a preset temperature and / or a preset temperature range in order to set and / or maintain the temperature of the fuel slip catalyst accordingly.

[0068] The tempering arrangement can include a heat exchanger which uses the exhaust gas from the bypass line, from the SCR catalyst and / or from the exhaust gas receiver for temperature regulation, in particular as temperature control medium.

[0069] Typically, exhaust gases, for example from a plurality of cylinders, are collected in an exhaust gas receiver and conducted from there to a fuel slip catalyst, a bypass line and / or an SCR catalyst.

[0070] At least a portion of a surface of the fuel slip catalyst may be in direct or indirect thermal contact with a surface of at least one of the bypass line, the SCR catalyst, and / or the exhaust receiver.

[0071] The heat exchanger may include a thermally conductive material disposed between the fuel slip catalyst and at least one of the bypass line, the SCR catalyst and / or the exhaust receiver, the thermally conductive material having a thermal conductivity of at least 15 W / (mK) so that the exhaust gas can be used as a temperature control medium in an effective manner.

[0072] Exhaust gases directed through the bypass line, through the SCR catalyst and / or through the exhaust gas receiver, in particular during the first mode, can be used to heat the fuel slip catalyst.The fuel slip catalyst will then be ready for use when the internal combustion engine switches to the second mode.

[0073] The tempering device may comprise a separate heating device.

[0074] The separate heating device may include a heat exchanger using a temperature control medium which may be heated outside the exhaust gas aftertreatment system.

[0075] The separate heating device may be an electric heating device.

[0076] The flashback device may include an insulating cover, such as an insulating housing. The housing may surround the fuel slip catalyst and another part of the internal combustion engine, such as an SCR catalyst, a bypass line and / or an exhaust gas collector.

[0077] The temperature setting device may also comprise a temperature-introducing contact wall between the fuel slip catalyst and another part of the internal combustion engine, such as an SCR catalyst, a bypass line and / or an exhaust gas collector.

[0078] The temperature conducting contact wall may be made of or comprise a material having a thermal conductivity of at least 15 W / (mK), in particular a metal, such as stainless steel or carbon steel.

[0079] The temperature conducting contact wall may comprise a cavity for conducting a temperature control medium.

[0080] The fuel slip catalyst may be an oxidation catalyst (OC), in particular an ammonia slip catalyst (ASC). The fuel slip catalyst eliminates fuel slip and its byproducts from combustion or products generated in an upstream catalyst such as an SCR catalyst.

[0081] The fuel slip catalyst may be an ASC and may comprise cordierite or a metallic monolith, metal foam or similar material, preferably coated on a substrate or in extruded form.

[0082] The fuel slip catalyst may include PGM, platinum, palladium and / or rhodium.

[0083] This catalyst can oxidize methanol or formaldehyde slip upstream of the SCR. It can also be placed downstream of the SCR to eliminate formaldehyde and HCN before the exhaust escapes into the atmosphere.

[0084] The bypass regulating device may include at least one valve arranged upstream and / or downstream of the fuel slip catalyst and / or at least one valve arranged in the bypass line.

[0085] The bypass regulation device may include at least one three-way valve for directing the exhaust gas to a bypass line or a fuel slip catalyst.

[0086] The exhaust gas aftertreatment system may include a main bypass line and a main bypass regulating device for bypassing the SCR, the fuel slip catalyst and the bypass line. The main bypass allows bypassing both catalysts.

[0087] A main bypass may be required to bypass the SCR system in situations where operation with regard to emissions legislation is not required (e.g. Tier II in ammonia mode without ammonia slip), when the exhaust gas temperature is too low for SCR operation (e.g. below 10% in diesel mode) and / or when the SCR system is damaged (e.g. when the catalyst element is damaged), in particular to prevent turbocharger damage.

[0088] A bypass may also be allowed for maintenance purposes for certain concepts (eg SCR shut down engine) in order to prevent exhaust gas leakage into the engine room during maintenance work on an open reactor.

[0089] The control unit may be adapted to set a main bypass regulation for opening and / or closing the main bypass line.

[0090] The object of the present invention is also achieved by an internal combustion engine, which has at least one cylinder with an inner diameter of at least 200 mm, and the at least one cylinder can be operated in at least a first mode and a second mode. In the first mode, the engine uses a first fuel as fuel, and in the second mode, the engine uses a second fuel as fuel, wherein the second fuel includes at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG, and the engine includes an exhaust gas after-treatment system as described above.

[0091] The internal combustion engine may include a turbocharger having a turbine and a compressor. An SCR catalyst, a fuel slip catalyst for treating fuel slip of the second fuel, and a bypass line may be arranged upstream of the turbine.

[0092] Alternatively, the SCR catalyst may be arranged downstream of the turbine and upstream of the funnel.

[0093] The internal combustion engine may be adapted to use ammonia or methanol as the second fuel.

[0094] The object of the present invention is also achieved by a method for reducing fuel emissions (such as ammonia emissions) of an internal combustion engine, which is preferably as described above, and has at least one cylinder with an inner diameter of at least 200 mm, which cylinder can be operated in at least a first mode and a second mode, in which the engine uses a first fuel as fuel and in which the engine uses a second fuel as fuel, wherein the second fuel includes at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG in the exhaust gas aftertreatment system as described above.

[0095] Exhaust gases are discharged through outlets of the cylinders of the internal combustion engine.

[0096] The method comprises the following steps: a bypass regulating device is arranged so as to (i) direct the exhaust gas through an SCR catalyst and a fuel slip catalyst for treating a fuel slip of a second fuel arranged upstream or downstream of the SCR catalyst, or (ii) only through the SCR catalyst. Alternatively or additionally, the bypass regulating device controls the passage of the fuel slip catalyst and / or a bypass line for bypassing the fuel slip catalyst. Thus, the amount of exhaust gas directed through the fuel slip catalyst and / or the bypass line can be controlled.

[0097] The setting step may be dependent on the second fuel content of the exhaust gas, the sulfur content of the exhaust gas, the temperature of the exhaust gas, the temperature of the fuel slip catalyst, the pressure and / or the engine load.

[0098] The method may include the following steps: allowing passage of the fuel slip catalyst when the engine is operating in the second mode and the temperature of the fuel slip catalyst is above 200°C and / or when the engine is operating in the second mode and at a load at which fuel slip of the second fuel does not occur (for example, at a load below 80%).

[0099] The method may include the steps of sensing a temperature of the fuel slip catalyst and controlling the bypass regulating device based thereon.

[0100] The method may include the step of setting the temperature of the fuel slip catalyst.

[0101] The method may include the step of maintaining the temperature of the fuel slip catalyst.

[0102] The temperature may be set and / or maintained by directing the second fuel through the fuel slip catalyst during load periods without fuel slip of the second fuel for heating the fuel slip catalyst or by using a temperature setting device such as a heat exchanger, a heating device, or an insulating housing.

[0103] The method may comprise the step of using the exhaust gas from the bypass line to heat a fuel slip catalyst from the SCR catalyst and / or from the exhaust gas receiver, in particular as a temperature control medium in a heat exchanger.

[0104] The method may comprise the step of providing a warning signal in the event that fuel slip of the second fuel occurs or is anticipated, for example when load increases and the fuel slip catalyst has not yet reached a light-off temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] In the following, the invention is further explained in the form of exemplary embodiments by means of the drawings, wherein functionally similar components are provided with the same reference numerals.

[0106] Figure 1 shows a schematic diagram of an internal combustion engine having a first example of an exhaust aftertreatment system;

[0107] Figure 2 shows a schematic diagram of an internal combustion engine having a second example of an exhaust aftertreatment system;

[0108] Figure 3 shows a schematic diagram of an internal combustion engine having a third example of an exhaust aftertreatment system;

[0109] Figure 4 a schematic diagram showing the arrangement of a fourth example of an exhaust gas aftertreatment system;

[0110] Figure 5 a schematic diagram showing the arrangement of a fifth example of an exhaust gas aftertreatment system;

[0111] Figure 6 a schematic diagram showing the arrangement of a sixth example of an exhaust aftertreatment system;

[0112] Figure 7 a schematic diagram showing the arrangement of a seventh example of an exhaust gas aftertreatment system;

[0113] Figure 8 A perspective view of another example of an exhaust aftertreatment system is shown. DETAILED DESCRIPTION

[0114] Figure 1 Shown is a schematic diagram of an internal combustion engine 20 having a first example of an exhaust gas aftertreatment system 10. The internal combustion engine 10 comprises a cylinder 21 having an inner diameter 23 of at least 200 mm.

[0115] The exhaust gas aftertreatment system 10 includes an SCR catalyst 1, a fuel slip catalyst 2 arranged upstream of the SCR catalyst 1, and a bypass line 3 for bypassing the fuel slip catalyst 2, wherein the bypass line 3 turns upstream of the SCR catalyst 1 so that the bypass line 3 only bypasses the fuel slip catalyst 2 but not the SCR catalyst 1.

[0116] The bypass regulating device 4 is adapted to set the passage of the bypass line 3 and the fuel slip catalyst 2 .

[0117] The exhaust gas aftertreatment system 10 comprises a control unit 5 for controlling the passage of the bypass line 3 and the fuel slip catalyst 2 .

[0118] The exhaust gas aftertreatment system 10 comprises a flashback device 6 which, in this example, comprises a heat exchanger which uses the exhaust gas from the bypass line 3 to temperature-regulate the fuel slip catalyst 2 .

[0119] Downstream of the exhaust gas aftertreatment system 10 , the internal combustion engine 20 comprises a turbocharger 26 having a turbine 27 and a compressor 28 .

[0120] Figure 2 A schematic diagram of an internal combustion engine 20 with a second example of an exhaust gas aftertreatment system 10 is shown, wherein a fuel slip catalyst 2 is arranged downstream of an SCR catalyst 1. The exhaust gas aftertreatment system 10 comprises a backfire device 6, which in this example comprises a heat exchanger which uses exhaust gas from the SCR catalyst 1 to temperature-regulate the fuel slip catalyst 2.

[0121] The bypass regulating device 4 comprises a valve 7 which, when closed, prevents passage through the bypass line 3 to the chimney 25 .

[0122] The second example of the exhaust gas aftertreatment system 10 includes a main bypass regulating device 11 and a main bypass line 12 for bypassing the SCR catalyst 1 and the fuel slip catalyst 2 .

[0123] Figure 3 A schematic diagram of an internal combustion engine 20 with a third example of an exhaust aftertreatment system 10 is shown.

[0124] In this example, the fuel slip catalyst 2 is arranged upstream of the SCR catalyst 1 .

[0125] The fuel slip catalyst 2 is attached to the SCR catalyst 1 to allow the fuel from the SCR reactor (eg Figure 2 ) heat transfer.

[0126] In this example, the exhaust gas aftertreatment system 10 further comprises a flashback device 6 having a heat exchanger which uses the exhaust gas from the SCR catalyst 1 to temperature-regulate the fuel slip catalyst 2 .

[0127] In this case, the main bypass regulating device 11 also allows to direct the exhaust gas only through the fuel slip catalyst 2 without passing through the SCR catalyst 1 , or to direct the exhaust gas via the main bypass line 12 directly to the chimney 25 while bypassing the SCR catalyst 1 and the fuel slip catalyst 2 .

[0128] Figure 4 A schematic diagram of an internal combustion engine 20 with a fourth example of an exhaust gas aftertreatment system 10 is shown, wherein a fuel slip catalyst 2 is also arranged downstream of the SCR catalyst 1 .

[0129] The fuel slip catalyst 2 and the SCR catalyst 1 are arranged in an insulating housing 8 .

[0130] In addition, the fuel slip catalyst 2 is in contact with a separate heating device 9 .

[0131] Figure 5 A schematic diagram of the arrangement of a fifth example of an exhaust aftertreatment system 10 is shown.

[0132] The fuel slip catalyst 2 is arranged directly above the exhaust gas receiver 24. The heat conducting layer 13 is arranged between the fuel slip catalyst 2 and the SCR catalyst 1 so that the exhaust gas guided through the SCR catalyst 1 can heat up the fuel slip catalyst 2.

[0133] Figure 6 A schematic diagram of the arrangement of a sixth example of an exhaust aftertreatment system 10 is shown.

[0134] The fuel slip catalyst 2 is arranged directly above the exhaust receiver 24, and the SCR catalyst 1 is arranged directly below the exhaust receiver 24. The heat conductive layer 13 is arranged between the fuel slip catalyst 2 and the exhaust receiver 24 so that the exhaust gas in the exhaust receiver 24 can heat up the fuel slip catalyst 2.

[0135] Figure 7 A schematic diagram shows the arrangement of a seventh example of an exhaust gas aftertreatment system 10 . A fuel slip catalyst 2 is embedded in a heating device 9 .

[0136] Figure 8 A perspective view of another example of an exhaust aftertreatment system 10 is shown.

[0137] The exhaust gases are collected in an exhaust gas receiver 24. From there, the exhaust gases are led to the SCR reactor 1 arranged below the exhaust gas receiver 24. Depending on the setting of the bypass control device 4, the exhaust gases are either led through the fuel slip catalyst 2, which is arranged above the exhaust gas receiver 24 in this case, or directly to the turbocharger (not shown in the figure) via the bypass line 3.

[0138] The fuel slip catalyst 2 may be arranged in thermal contact with the exhaust gas receiver 24, such as Figure 6 shown.

Claims

1. An exhaust gas aftertreatment system (10) for an internal combustion engine (20), the internal combustion engine having at least one cylinder (21) having an inner diameter (23) of at least 200 mm, the cylinder being operable in at least a first mode and a second mode, in which the engine is fueled with a first fuel and in which the engine is fueled with a second fuel, wherein: The second fuel comprises at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG, The system comprises SCR catalyst (1), a fuel slip catalyst (2) for treating fuel slip of the second fuel, the fuel slip catalyst being arranged upstream or downstream of the SCR catalyst (1), a bypass line (3) for bypassing the fuel slip catalyst (2), wherein if the fuel slip catalyst (2) is arranged downstream of the SCR catalyst (1), the bypass line branches downstream of the SCR catalyst, and if the fuel slip catalyst (2) is arranged upstream of the SCR catalyst (1), the bypass line turns upstream of the SCR catalyst (1), A control unit (5) and a bypass regulating device (4) for controlling the passage of the bypass line (3) and / or the fuel slip catalyst (2), in particular depending on a second fuel content of the exhaust gas, a sulfur content of the exhaust gas, a temperature of the exhaust gas, a temperature of the fuel slip catalyst (2), a pressure and / or an engine load.

2. The exhaust gas aftertreatment system (10) according to claim 1, in, The exhaust gas aftertreatment system comprises a temperature sensor for providing temperature data representative of the temperature of the fuel slip catalyst (2), and wherein the temperature data is used to control the passage of the bypass line (3) and / or the fuel slip catalyst (2).

3. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 2, wherein: The control unit (5) is adapted to allow passage of the fuel slip catalyst (2) in the following situations: The engine is operated in the second mode and the temperature of the fuel slip catalyst is above the light-off temperature, in particular above 200° C., and / or In particular when the engine is operated at a load below 80%, preferably below 75%, more preferably below 60%, more preferably below 50%, the engine is operated in the second mode and at a load condition where no fuel slip occurs.

4. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, wherein: The exhaust gas aftertreatment system (10) comprises a tempering device (6), which is used to heat the fuel slip catalyst (2) to a temperature of preferably at least 200°C and / or to maintain the temperature of the fuel slip catalyst (2), preferably at least 200°C.

5. The exhaust gas aftertreatment system (10) according to claim 4, wherein: The tempering device (6) comprises at least one or a combination selected from the group consisting of: a heat exchanger which uses the exhaust gas from the bypass line (3), from the SCR catalyst (1) and / or from an exhaust gas receiver (24) for temperature regulation, in particular as a temperature control medium, a separate heating device (9), and Insulating housing (8).

6. The exhaust gas aftertreatment system (10) according to any one of the preceding claims, wherein: The fuel slip catalyst (2) is an oxidation catalyst, in particular an ammonia slip catalyst.

7. The exhaust gas aftertreatment system (10) according to any one of the preceding claims, wherein: The fuel slip catalyst (2) comprises cordierite or metal monolith, metal foam or similar material, in particular coated on a substrate or in extruded form.

8. An exhaust gas aftertreatment system (10) according to any one of the preceding claims, wherein: The bypass regulating device (4) comprises at least one valve (7) arranged upstream and / or downstream of the fuel slip catalyst (2) and / or at least one valve arranged in the bypass line (3).

9. An exhaust gas aftertreatment system (10) according to any one of the preceding claims, the exhaust gas aftertreatment system being configured to set the temperature of the fuel slip catalyst (2) and / or being configured to maintain the temperature of the fuel slip catalyst (2).

10. An internal combustion engine (20) having at least one cylinder (21) having an inner diameter (23) of at least 200 mm, the cylinder being operable in at least a first mode and a second mode, in which the engine is fueled by a first fuel and in which the engine is fueled by a second fuel, wherein: The second fuel comprises at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG, and the engine comprises the exhaust gas aftertreatment system (10) according to any one of claims 1 to 9.

11. The internal combustion engine (20) according to claim 10, wherein: The internal combustion engine (20) comprises a turbocharger (26) having a turbine (27) and a compressor (28), and wherein the SCR catalyst (1), the fuel slip catalyst (2) and the bypass line (3) are arranged upstream of the turbine.

12. A method for reducing fuel emissions of a second fuel of an internal combustion engine (20), the internal combustion engine (20) having at least one cylinder (21) with an inner diameter (23) of at least 200 mm, the at least one cylinder being operable in at least a first mode and a second mode by means of an exhaust gas aftertreatment system (10) according to any one of claims 1 to 9, in the first mode the engine is fueled by a first fuel and in the second mode the engine is fueled by a second fuel, wherein: The second fuel comprises at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG, wherein the exhaust gas is discharged through the outlet (22) of the cylinder (21) of the internal combustion engine (20), And wherein the method comprises the following steps: The bypass regulating device (4) is arranged so as to (i) directing the exhaust gas through the SCR catalyst (1) and the fuel slip catalyst (2) to treat the fuel slip of the second fuel, or (ii) only through the SCR catalyst (1), and / or (iii) In particular, the passage of the fuel slip catalyst (2) and / or the bypass line (3) for bypassing the fuel slip catalyst (2) is controlled based on a second fuel content of the exhaust gas, a sulfur content of the exhaust gas, a temperature of the exhaust gas, a temperature of the fuel slip catalyst (2), a pressure and / or an engine load.

13. The method according to claim 12, comprising the steps of: Passing of the fuel slip catalyst (2) is permitted under the following conditions: The internal combustion engine (20) is operated in the second mode and the temperature of the fuel slip catalyst is above the light-off temperature, in particular above 200° C., and / or In particular when the engine is operated at a load below 80%, preferably below 75%, more preferably below 60%, more preferably below 50%, the internal combustion engine (20) is operated in the second mode and during loads when no fuel slip of the second fuel occurs.

14. A method according to any one of claims 12 to 13, comprising the step of setting the temperature of the fuel slip catalyst (2) and / or comprising the step of maintaining the temperature of the fuel slip catalyst (2).

15. The method according to any one of claims 12 to 14, wherein: The exhaust gas from the bypass line (3) is used to heat the fuel slip catalyst (2) from the SCR catalyst (1) and / or from the exhaust gas receiver (24), in particular as a temperature control medium in a heat exchanger.

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