Exhaust gas aftertreatment system

Abstract

To provide an exhaust gas aftertreatment system for an internal combustion engine, an internal combustion engine, and a method for reducing fuel discharge of an internal combustion engine.SOLUTION: An exhaust gas aftertreatment system 10 for an internal combustion engine includes: a SCR catalyst 1; and a fuel slip catalyst 2 arranged upstream or downstream the SCR catalyst. The exhaust gas aftertreatment system further comprises: a bypass-line 12 for bypassing the fuel slip catalyst, which branches off downstream the SCR catalyst when the fuel slip catalyst is arranged downstream the SCR catalyst, and which turns in upstream the SCR catalyst when the fuel slip catalyst is arranged upstream the SCR catalyst; and a control unit 5 and a bypass adjustment device 4 for controlling a throughput of the bypass-line and / or the fuel slip catalyst, in particular depending on a second fuel content of exhaust gas, a sulfur content of the exhaust gas, temperature of the exhaust gas, temperature and pressure of the fuel slip catalyst, and / or an engine load.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention is directed 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 combustion engines and the reduction of their emissions. In particular, the present invention relates to internal combustion engines that can be fueled with a second fuel or "green fuel", for example LNG, LPG, ammonia, ethanol or methanol, and to conventional types of internal combustion engines, for example diesel, that can also be operated with a first fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent No. 3670856(A1) [Patent Document 2] German Patent No. 102017011300(A1) [Patent Document 3] US Patent No. 9624874(B2) [Patent Document 4] European Patent No. 2808512(A1) [Patent Document 5] International Publication No. 2022 / 219458(A1) Summary of the Invention

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

[0005] The internal combustion engine may be a two-stroke engine with longitudinal rejection of waste materials.

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

[0007] The engine speed is preferably less than 800 RPM (4 stroke), more preferably less than 200 RPM (2 stroke), indicating a low speed engine designation.

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

[0009] Further possible second fuels that can be used are: LBG (Liquefied Biogas), biological fuels (e.g. oil obtained from algae), hydrogen, synthetic fuels from CO2 (e.g. made by Power-to-Gas or Power-to-Liquids).

[0010] Large ships, especially those for transporting goods, are usually powered by internal combustion engines, especially diesel and / or gas engines, mostly two-stroke, cross-head engines. The exhaust gases from this combustion process must be cleaned in order to comply with existing rules such as IMO Tier III.

[0011] IMO emission standards, commonly referred to as Tier I...III standards, among others, define NOx emission standards for existing and new marine engines.

[0012] For larger ships, emission requirements are increasing, particularly with regard to nitric oxide emissions. There is therefore a need to reduce the amount of nitric oxide in the exhaust gases emitted by the internal combustion engines of these ships.

[0013] Selective catalytic reduction (SCR) technology is used to reduce the levels of nitrogen oxides (NOx) in the exhaust gases of combustion engines. SCR is commonly used in land-based engines, such as heavy vehicles, factories and other applications. SCR technology has also been used in marine environments in combination with two-stroke diesel engines. Regulatory requirements for the marine diesel engines and land-based engines have increased the need for efficient SCR systems.

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

[0015] Since ammonia is harmful, it is desirable to minimize the release of ammonia gas. Therefore, ammonia cannot simply be released into the atmosphere / ambient. This is especially true when the fuel is ammonia.

[0016] At least some of the leaking ammonia is partially consumed in the NOx reduction reactions in the SCR, but excessive ammonia may require special treatment. Therefore, an ammonia reduction system (preferably based on an ammonia slip catalyst - ASC (ammonia slip catalyst) - in the specific case of an oxidation catalyst - OC (oxidation catalyst) - may be required downstream of the SCR.

[0017] ASC is prone to sulfur poisoning.

[0018] Other green fuels that avoid emitting CO2 may also cause unnecessary emissions. For example, during the combustion of methanol, formaldehyde and HCN may appear.

[0019] EP 3670856 A1 discloses an exhaust gas aftertreatment system comprising a first catalyst and a second catalyst, where the first catalyst may have a different chemical composition than the second catalyst. The first and second catalysts may be arranged in series, and the exhaust gas aftertreatment system comprises a control unit for individually controlling the throughput through the catalysts.

[0020] German Patent No. 102017011300(A1) discloses an exhaust gas system for an internal combustion engine of a motor vehicle. An oxidation catalyst is arranged in the exhaust gas system downstream of a first SCR catalyst and upstream of a second SCR catalyst. The exhaust gas system has a bypass line, via which exhaust gas can be fed to the second SCR catalytic converter while bypassing the oxidation catalytic converter.

[0021] US Patent No. 9,624,874 (B2) discloses an exhaust gas recirculation device including an engine, an intake line, an exhaust line and an aftertreatment unit. The circulation line directs a portion of the exhaust gas from the downstream side of the aftertreatment unit to the intake line. A bypass line branches off from the upstream side of the circulation line and joins with the downstream side of the circulation line, where ammonia slip discharged from the aftertreatment unit is prevented from being directed to the intake line.

[0022] EP 2808512 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 excessive urea injected for SCR operation.

[0023] WO 2022 / 219458 A1 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.

[0024] It is therefore an object of the present invention to obviate the drawbacks of the prior art and to create an exhaust gas aftertreatment system, an internal combustion engine, and a method for reducing the emissions of an internal combustion engine that ensures a compact design and reduced operating costs.

[0025] This object is achieved by an exhaust gas aftertreatment system for an internal combustion engine having at least one cylinder with an inner diameter of at least 200 mm, operable at least in a first mode in which the engine is fuelled with a first fuel and in a second mode in which the engine is fuelled with a second fuel, the second fuel comprising at least one of the group consisting of methanol, ethanol, ammonia, LNG, or LPG.

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

[0027] In this application, a "green fuel" is a fuel that does not contain carbon, may be carbon neutral, and / or does not cause the emission of additional CO2. Carbon can also be released from green fuels if it comes from carbon already in the atmosphere, even if it is not derived from underground fossil deposits, as with oil.

[0028] Green fuels can be carbon-neutral or carbon-free alternatives to fossil fuels. Generated from hydrogen and electricity from renewable sources, they can be considered crucial to decarbonizing heavy industry, and especially shipping. In sectors where direct electrification is not feasible, green fuels can be used in existing storage and propulsion systems, thus allowing a smooth transition from fossil to sustainable energy sources.

[0029] For example, ammonia does not contain carbon molecules and is therefore carbon-free.

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

[0031] For combustion of a second fuel, such as of a first fuel, such as diesel, a pilot injection may be necessary.

[0032] Thus, even with a second fuel such as LNG, ammonia or methanol, a small amount of diesel fuel may be injected into the cylinder to aid in the combustion of the methanol or ammonia.

[0033] The exhaust gas aftertreatment system includes an SCR catalyst, a fuel slip catalyst for treating a fuel slip of a second fuel, located upstream or downstream of the SCR catalyst, and a bypass line for bypassing the fuel slip catalyst, the bypass line branching downstream of the SCR catalyst if the fuel slip catalyst is located downstream of the SCR catalyst, and redirecting upstream of the SCR catalyst if the fuel slip catalyst is located upstream of the SCR catalyst.

[0034] The bypass line allows the exhaust gases to bypass only the fuel slip catalyst, so that the exhaust gases are routed 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 exhaust gas flow emerging from the cylinder.

[0036] A fuel slip catalyst for treating a fuel slip of a second fuel is a catalyst that removes or reduces residuals of the second fuel. These residuals may include the second fuel itself, such as ammonia residuals, or substances produced during combustion of the second fuel, such as formaldehyde or HCN, which may be produced during methanol combustion or processing in an SCR.

[0037] The fuel slip catalyst may also be adapted to remove or reduce substances that may be created when exhaust gases from the combustion of the second fuel pass through a further catalyst, such as an SCR catalyst. For example, formaldehyde (CHO) may be formed by exposure of methanol to an SCR catalyst. Hydrogen cyanide (HCN) may be produced by reaction of formaldehyde with ammonia dosed on the SCR.

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

[0039] The control unit may be adapted to set the throughput 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, pressure and / or the engine load of the fuel slip catalyst.

[0040] The second fuel content may correspond to a second fuel slip that escapes from the cylinder, for example after incomplete combustion. However, slip can also occur in the case of complete combustion. In this case, the fuel slip originates from a slip of fuel remaining in the injector suck-hole volume.

[0041] The control unit may be provided with 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, pressure, regulatory levels and / or engine load of the fuel slip catalyst.

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

[0043] The fuel slip catalyst may only be required when the engine is operated in the second mode, where no fuel slip of the second fuel would otherwise occur.

[0044] On the other hand, the fuel slip catalyst may not be allowed to be affected by exhaust gases when the engine is operated on the first fuel, particularly a fuel having a high sulfur content of about 0.1% wt, in order to avoid or reduce poisoning of the fuel slip catalyst.

[0045] However, since any content of sulfur, even 10 ppm, can be harmful to the catalyst, which is the case in the automotive industry, the use of fuel slip catalysts is preferably avoided whenever possible in the first mode.

[0046] The process of chemical aging of the catalyst, for example by exposure to sulfur, reduces its useful life. Preferably, the catalyst is effective for at least five years, a typical interval for the service of a marine vessel.

[0047] The bypass line ensures that exhaust gas is passed through the SCR catalyst but not through the fuel slip catalyst.

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

[0049] In certain operating modes, fuel slip of the second fuel, e.g. ammonia slip, is not expected to exceed regulatory levels, so in these modes the control unit may be adapted to bypass the fuel slip catalyst to extend its life.

[0050] The exhaust gas aftertreatment system may include a temperature sensor for providing temperature data representative of the temperature of the fuel slip catalyst. The throughput of the bypass line and / or the fuel slip catalyst may then be controlled using said temperature data. This allows operation of the fuel slip catalyst only at temperatures high enough for proper operation.

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

[0052] Typically, fuel slip catalysts such as AOCs only initiate their catalytic effect at elevated temperatures, for example above 200° C. The temperature sensor may provide data to a control unit, which may be adapted to enable throughput to the fuel slip catalyst, particularly at a storable or full load, only when the fuel slip catalyst has a predetermined temperature, for example above the respective light-off temperature, in particular at least 200° C.

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

[0054] Alternatively, or in addition, the control unit may be adapted to enable throughput to the fuel slip catalyst when the internal combustion engine is operated in the second mode and at load when no fuel slip of the second fuel occurs, in particular when the engine is operated at a load of less than 80%, preferably less than 75%, more preferably less than 60%, more preferably less than 50%.

[0055] When the internal combustion engine is operated in the second mode and the temperature of the fuel slip catalyst exceeds 200°C, the fuel slip catalyst may remove or reduce the residual of the second fuel.

[0056] When the internal combustion engine is operated in the second mode and when the internal combustion engine is operated at load, no fuel slip of the second fuel occurs, so the second fuel residual does not occur and does not need to be removed, and exhaust gases may be directed through the fuel slip catalyst anyway to warm it.

[0057] When 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 operate the internal combustion engine in the second mode at a load when fuel slip occurs, for example at a load greater than 75%, and provide an alert to an operator if the fuel slip catalyst still has a temperature that is too low for efficient or reliable operation.

[0059] The control unit may be implemented to indicate a warning to an operator that a fuel slip of the second fuel may occur before the light-off temperature of the fuel slip catalyst, e.g. ASC or OC, is reached.

[0060] The control unit may be adapted to provide an alert to an operator if the fuel slip catalyst still has a low temperature and the internal combustion engine is to be operated in the second mode at a load when fuel slip occurs, for example at a load greater than 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 realise indicating a warning, for example of the type "If you further increase the engine load this may result in higher than the emission limit of NH3 slip".

[0062] The control unit may be adapted to receive a confirmation from the operator if he wishes to further increase the engine load without waiting for the light-off temperature.

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

[0064] In particular, the exhaust gas aftertreatment system may comprise a tempering arrangement comprising a thermostatic device for ensuring the temperature of the fuel slip catalyst in a set temperature range, preferably at least 150°C.

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

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

[0067] The control unit may have an inlet line for receiving data and / or may have storage for storing data relating to a set temperature and / or set temperature range for setting and / or maintaining the temperature of the fuel slip catalyst accordingly.

[0068] The tempering arrangement may comprise a heat exchanger which uses 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 multiple cylinders, are collected in an exhaust gas receiver from which they are directed 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 gas receiver.

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

[0072] In particular, during the first mode, exhaust gases routed through the bypass line, through the SCR catalyst and / or through the exhaust gas receiver can be used to heat a fuel slip catalyst, which is then ready for use when the internal combustion engine is switched to the second mode.

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

[0074] The separate heating device may comprise a heat exchanger that uses a temperature control medium that may be heated outside the exhaust gas aftertreatment system.

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

[0076] The tempering arrangement may comprise an insulating cover, for example an insulating housing, which may enclose the fuel slip catalyst and further parts 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 further comprise a temperature inducing contact wall between the fuel slip catalyst and further parts of the internal combustion engine, such as an SCR catalyst, a bypass line and / or an exhaust gas collector.

[0078] The temperature-inducing contact wall may be made of or may include 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 inducing contact wall may include 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), which eliminates fuel slip and its by-products from combustion or products produced in an upstream catalyst, such as an SCR catalyst.

[0081] The fuel slip catalyst may be an ASC or may comprise cordierite or metal monoliths, metal foams, or similar materials, preferably coated on a substrate or in extruded form.

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

[0083] Such a catalyst could oxidize methanol or formaldehyde slip upstream of the SCR, or it could be placed downstream of the SCR to eliminate formaldehyde and HCN before the exhaust gas escapes to the atmosphere.

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

[0085] The bypass regulating device may include at least one three-way valve for directing exhaust gases to a bypass line or to 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] The main bypass may be required to bypass the SCR system when there is no need for operation due to emission legislation (e.g. Tier II in ammonia mode with no ammonia slip), when exhaust gas temperatures are too low for SCR operation (e.g. below 10% diesel mode) and / or when the SCR system is damaged (e.g. a broken catalytic element), especially to prevent damage to the turbocharger.

[0088] A bypass can also be made possible for maintenance purposes for certain concepts (e.g. SCR off engine) to prevent exhaust gas leakage into the engine compartment during maintenance work on an open reactor.

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

[0090] The object of the present invention is also achieved by an internal combustion engine having at least one cylinder with a bore of at least 200 mm, capable of operating at least in a first mode, in which the engine is fuelled with a first fuel, and in a second mode, in which the engine is fuelled with a second fuel, wherein the second fuel comprises at least one of the group consisting of methanol, ethanol, ammonia, LNG or LPG, the engine being equipped with an exhaust gas aftertreatment system as previously described.

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

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

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

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

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

[0096] The method includes configuring the bypass regulating device to direct exhaust gases through (i) the SCR catalyst and a fuel slip catalyst for treating a fuel slip of a second fuel, located upstream or downstream of the SCR catalyst, or (ii) only through the SCR catalyst. Alternatively or additionally, the bypass regulating device controls the throughput of the fuel slip catalyst and / or a bypass line for bypassing the fuel slip catalyst. Thus, the amount of exhaust gases 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, pressure and / or engine load of the fuel slip catalyst.

[0098] The method may include a step of enabling throughput to the fuel slip catalyst when the engine is operated in the second mode and the temperature of the fuel slip catalyst exceeds 200°C and / or when the engine is operated in the second mode and at a load where fuel slip of the second fuel does not occur, for example at a load less than 80%.

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

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

[0101] The method may include maintaining a 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 without a fuel slip of the second fuel to warm the fuel slip catalyst, or by using a temperature setting device, such as a heat exchanger, heating device or insulated enclosure.

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

[0104] The method may include the step of providing a warning signal when fuel slip of the second fuel occurs or is expected, for example when the load is increasing and the fuel slip catalyst has not yet reached light-off temperature.

[0105] In the following, the invention is further explained in examples using figures in which functionally similar parts have the same reference numbers. [Brief description of the drawings]

[0106] [Figure 1]1 shows a schematic diagram of an internal combustion engine together with a first example of an exhaust gas aftertreatment system. [Diagram 2] 2 shows a schematic diagram of an internal combustion engine with a second example of an exhaust gas aftertreatment system; [Diagram 3] 1 shows a schematic diagram of an internal combustion engine with a third example of an exhaust gas aftertreatment system. [Figure 4] 1 shows a schematic diagram of a fourth example arrangement of an exhaust gas aftertreatment system. [Diagram 5] 1 shows a schematic diagram of a fifth example arrangement of an exhaust gas aftertreatment system. [Figure 6] 13 shows a schematic diagram of a sixth example arrangement of an exhaust gas aftertreatment system. [Figure 7] 13 shows a schematic diagram of a seventh example arrangement of an exhaust gas aftertreatment system. [Figure 8] 1 shows a perspective view of a further example exhaust gas aftertreatment system; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0107] 1 shows a schematic diagram of an internal combustion engine 20 together with 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.

[0108] The exhaust gas aftertreatment system 10 comprises 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 which turns upstream of the SCR catalyst 1 such that the bypass line 3 bypasses only the fuel slip catalyst 2 and not the SCR catalyst 1.

[0109] A bypass regulating device 4 is adapted to set the throughput of the bypass line 3 and the fuel slip catalyst 2 .

[0110] The exhaust gas aftertreatment system 10 comprises a control unit 5 for controlling the throughput of the bypass line 3 and the fuel slip catalyst 2 .

[0111] In this embodiment the exhaust gas aftertreatment system 10 comprises a tempering arrangement 6 which comprises a heat exchanger which uses the exhaust gas from the bypass line 3 for temperature regulation of the fuel slip catalyst 2 .

[0112] Downstream of the exhaust gas aftertreatment system 10 , the internal combustion engine 20 is equipped with a turbocharger 26 having a turbine 27 and a compressor 28 .

[0113] 2 shows a schematic diagram of a second example of an exhaust gas aftertreatment system 10 and an internal combustion engine 20, in which a fuel slip catalyst 2 is arranged downstream of the SCR catalyst 1. The exhaust gas aftertreatment system 10 is provided with a tempering arrangement 6, in this example including a heat exchanger that uses exhaust gas from the SCR catalyst 1 for temperature regulation of the fuel slip catalyst 2.

[0114] The bypass regulating device 4 comprises a valve 7 which, when closed, prevents throughput through the bypass line 3 to the funnel 25 .

[0115] The second example of an exhaust gas aftertreatment system 10 comprises a main bypass regulating device 11 and a main bypass line 12 for bypassing the SCR catalyst 1 and the fuel slip catalyst 2 .

[0116] FIG. 3 shows a third example of an exhaust gas aftertreatment system 10 and a schematic diagram of an internal combustion engine 20 .

[0117] In this example, a fuel slip catalyst 2 is positioned upstream of the SCR catalyst 1 .

[0118] A fuel slip catalyst 2 is attached to the SCR catalyst 1 (as in FIG. 2) to allow heat transfer from the SCR reactor.

[0119] In this example, the exhaust gas aftertreatment system 10 also comprises a tempering arrangement 6 having a heat exchanger that uses the exhaust gases from the SCR catalyst 1 for temperature regulation of the fuel slip catalyst 2 .

[0120] In this case, the main bypass regulating device 11 also makes it possible to direct the exhaust gases only through the fuel slip catalyst 2 and not through the SCR catalyst 1, or to direct the exhaust gases directly to the funnel 25 via the main bypass line 12, bypassing the SCR catalyst 1 and the fuel slip catalyst 2.

[0121] FIG. 4 shows a schematic diagram of a fourth example of an exhaust gas aftertreatment system 10 and an internal combustion engine 20 in which a fuel slip catalyst 2 is also positioned downstream of the SCR catalyst 1 .

[0122] The fuel slip catalyst 2 and the SCR catalyst 1 are disposed within a thermally insulated housing 8 .

[0123] In addition, the fuel slip catalyst 2 is in contact with a separate heating device 9 .

[0124] FIG. 5 shows a schematic diagram of a fifth example configuration of exhaust gas aftertreatment system 10.

[0125] A fuel slip catalyst 2 is disposed immediately above the exhaust gas receiver 24. A heat conductive layer 13 is disposed between the fuel slip catalyst 2 and the SCR catalyst 1 so that exhaust gases directed through the SCR catalyst 1 can warm the fuel slip catalyst 2.

[0126] FIG. 6 shows a schematic diagram of a sixth example configuration of exhaust gas aftertreatment system 10.

[0127] The fuel slip catalyst 2 is disposed immediately above the exhaust gas receiver 24, and the SCR catalyst 1 is disposed immediately below the exhaust gas receiver 24. A heat conductive layer 13 is disposed between the fuel slip catalyst 2 and the exhaust gas receiver 24 so that exhaust gases in the exhaust gas receiver 24 can warm the fuel slip catalyst 2.

[0128] 7 shows a schematic diagram of a seventh example arrangement of an exhaust gas aftertreatment system 10. A fuel slip catalyst 2 is integrated into a heating device 9.

[0129] FIG. 8 shows a perspective view of a further example of an exhaust gas aftertreatment system 10 .

[0130] The exhaust gases are collected in an exhaust gas receiver 24. From there, they are led to an SCR reactor 1 arranged below the exhaust gas receiver 24. Depending on the setting of the bypass regulating device 4, the exhaust gases are led either through a fuel slip catalyst 2, arranged in this case above the exhaust gas receiver 24, or directly via a bypass line 3 to a turbocharger (not shown).

[0131] The fuel slip catalyst 2 may be disposed in heat conducting contact with the exhaust gas receiver 24, as shown in FIG.

Claims

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

2. 2. The exhaust gas aftertreatment system (10) of claim 1, wherein the exhaust gas aftertreatment system comprises a temperature sensor for providing temperature data representative of a temperature of the fuel slip catalyst (2), and the throughput of the bypass line (3) and / or the fuel slip catalyst (2) is controlled using the temperature data.

3. The control unit (5) and / or when the engine is operated in the second mode and the temperature of the fuel slip catalyst exceeds the light-off temperature, in particular exceeds 200° C. When no fuel slip occurs, in particular when the engine is operated at a load of less than 80%, preferably less than 75%, more preferably less than 60%, more preferably less than 50%, when the engine is operated in the second mode and load regime, 3. An exhaust gas aftertreatment system (10) according to any one of claims 1 to 2, adapted to allow a throughput of fuel to said slip catalyst (2).

4. 4. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, comprising a tempering arrangement (6) for warming the fuel slip catalyst (2) to a temperature, preferably of at least 200°C, and / or for maintaining the temperature of the fuel slip catalyst (2), preferably of at least 200°C.

5. The tempering arrangement (6) A heat exchanger using 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 Insulated housing (8) The exhaust gas aftertreatment system (10) of claim 4, comprising at least one or a combination selected from the group consisting of:

6. 6. Exhaust gas aftertreatment system (10) according to any one of claims 1 to 5, wherein the fuel slip catalyst (2) is an oxidation catalyst, in particular an ammonia slip catalyst.

7. 7. An exhaust gas aftertreatment system (10) according to any one of claims 1 to 6, 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. 8. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 7, 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. 9. An exhaust gas aftertreatment system (10) according to any one of the preceding claims, configured to set the temperature of the fuel slip catalyst (2) and / or configured to maintain the temperature of the fuel slip catalyst (2).

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

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

12. 10. A method for reducing fuel emissions of a second fuel of an internal combustion engine (20) having at least one cylinder (21) having an inner diameter (23) of at least 200 mm, the method being operable at least in a first mode in which the engine is fuelled with a first fuel and in a second mode in which the engine is fuelled with a second fuel, the second fuel comprising at least one of the group consisting of methanol, ethanol, ammonia, LNG, or LPG, using an exhaust gas aftertreatment system (10) according to any one of claims 1 to 9, comprising: Exhaust gases are discharged through an outlet (22) of the cylinder (21) of the internal combustion engine (20), and the method comprises the steps of: (i) through said SCR catalyst (1) and a fuel slip catalyst (2) for treating a fuel slip of said second fuel; or (ii) to direct the exhaust gases exclusively through the SCR catalyst (1); and / or (iii) to control the throughput of the fuel slip catalyst (2) and / or the bypass line (3) for bypassing the fuel slip catalyst (2), In particular, depending on the second fuel content of the exhaust gas, the sulfur content of the exhaust gas, the temperature of the exhaust gas, the temperature, pressure and / or engine load of the fuel slip catalyst (2), The method includes the step of configuring the bypass regulation device (4).

13. and / or when the internal combustion engine (20) is operated in the second mode and the temperature of the fuel slip catalyst exceeds the light-off temperature, in particular exceeds 200° C. When the internal combustion engine (20) is operated in the second mode and at load when no fuel slip of the second fuel occurs, in particular when the engine is operated at a load of less than 80%, preferably less than 75%, more preferably less than 60%, more preferably less than 50%, 13. The method of claim 12, comprising the step of enabling fuel throughput to the slip catalyst (2).

14. 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 maintaining the temperature of the fuel slip catalyst (2).

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

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