Large dual-fuel two stroke uniflow-scavenged turbocharged internal combustion engine with exhaust gas cleaning system for two fuels

Abstract

A large two stroke uniflow-scavenged turbocharged internal combustion engine having an ammonia mode and a heavy oil mode is disclosed.SOLUTION: The cylinder has a cylinder liner 1, a reciprocating piston 10, and a cylinder cover 22, and forms a combustion chamber. The ammonia fuel system 30 supplies pressurized ammonia to the ammonia fuel valve 50, and the heavy oil fuel system 31 supplies pressurized heavy oil to the heavy oil fuel valve 51. The turbocharging system has a compressor 7 and a turbine 6. A wet scrubber 40 on the downstream side of a turbine functions as an ammonia scrubber using a first cleaning liquid in an ammonia mode, and functions as a sulfur oxide scrubber using a second cleaning liquid in a heavy oil mode, so that the scrubber can be applied to a large-sized internal combustion engine switching two kinds of fuels, and reliability and robustness can be improved for SCR or the like.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This application relates to a large, two-stroke, uniflow-scavenged, turbocharged internal combustion engine having at least one mode that uses ammonia as the fuel to be burned and another mode that operates on fuel oil.

[0002] Large two-stroke, uniflow-scavenged, turbocharged internal combustion engines are typically used in the propulsion systems of large ships and as prime movers in power plants. The size, weight, and power output of this type of engine are quite different from typical internal combustion engines, placing it in a class of its own.

[0003] Until now, internal combustion engines have primarily been powered by hydrocarbon fuels, such as fuel oils like diesel and fuel gases like natural gas or petroleum gas. Combustion of hydrocarbon fuels results in the production of greenhouse gases, including carbon dioxide (CO2), which can contribute to air pollution and climate change. Unlike impurities in petroleum fuels, which result in by-product emissions, the production of CO2 is inevitable when hydrocarbons are burned. The energy density and CO2 emissions of a fuel depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Therefore, gaseous hydrocarbon fuels emit less CO2 than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult and expensive to handle and store. Research into non-hydrocarbon fuels is ongoing to reduce CO2 emissions.

[0004] Ammonia is a compound derived from petroleum, biomass, and renewable energy sources (wind, solar, hydroelectric, and geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when burned, and produces no CO2 or SO4. x It does not emit any particulate matter or unburned hydrocarbons.

[0005] Ammonia has been tested and used on a small scale in small spark-ignition internal combustion engines, but has not yet been used to operate a compression-ignition internal combustion engine.

[0006] Large two-stroke, uniflow-scavenged, turbocharged, compression-ignition, internal combustion crosshead engines capable of running on ammonia need to have an alternative operating mode for running on more conventional fuels, such as fuel oil (heavy fuel oil). This is necessary, for example, if the ammonia supply from the ammonia fuel system is interrupted.

[0007] SCR systems are currently proposed for ammonia engines to reduce ammonia (NH3) slip in ammonia operation mode and to ensure compliance with International Maritime Organization (IMO) Tier III in fuel oil operation mode. However, SCR systems are sensitive to changes in operating conditions and are expensive. Furthermore, SCR systems require NOx to reduce ammonia slip. x and NH3 must be balanced.

[0008] DK202270087 discloses a large two-stroke uniflow scavenged turbocharged internal combustion engine configured to remove nitrous oxide from the exhaust gas using an electrically generated mediator in a wet scrubber, and a method for removing nitrous oxide from the exhaust gas of a large two-stroke uniflow scavenged turbocharged internal combustion engine by wet electroscrubbing.

[0009] It is an object to provide a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one mode using ammonia as the fuel to be burned and another mode operating on fuel oil, which overcomes or at least mitigates the above mentioned drawbacks.

[0010] The features of the independent claims achieve the above-mentioned objects and also other objects. The dependent claims, the description and the drawings show further implementations.

[0011] According to a first aspect, there is provided a large two-stroke uniflow scavenged turbocharged internal combustion engine having an ammonia operating mode in which the main fuel is ammonia, and a fuel oil operating mode in which the main fuel is fuel oil. at least one cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder liner; a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a plurality of ammonia fuel valves disposed in the cylinder cover in the ammonia operation mode; a fuel oil fuel system configured to, in the fuel oil operating mode, supply pressurized fuel oil to a plurality of fuel oil fuel valves disposed in the cylinder cover; and a turbocharging system comprising at least one compressor for compressing scavenged air, the compressor being located in the intake system of the engine, and at least one turbine located in the exhaust system of the engine and driven by the exhaust gases; a wet scrubber located downstream of the at least one turbine for scrubbing at least a portion of the exhaust gases exiting the at least one turbine with a scrubbing liquid; and the wet scrubber functions as an ammonia scrubber configured to absorb ammonia from the flue gas flowing through the wet scrubber using a first scrubber liquor in the ammonia operation mode; In the fuel oil mode of operation, the wet scrubber functions as a sulfur oxide scrubber configured to absorb sulfur oxides and / or sulfuric acid from the exhaust gas flowing through the wet scrubber using a second scrubber liquor.

[0012] Replacing the relatively delicate and less robust SCR system with a low-pressure system using a wet scrubber on the low-pressure side of the turbocharger improves system reliability and robustness. Furthermore, low-pressure wet scrubber systems are less expensive than SCR systems for reducing ammonia slip when the engine is operated on ammonia. SCR systems for reducing ammonia slip may require the addition of an ammonia-oxygen catalyst to the system, further increasing the system's cost and complexity. Furthermore, by using a wet scrubber to scrub exhaust gases in ammonia operation mode (removing ammonia from the exhaust gas to avoid or at least reduce ammonia slip) and the same wet scrubber to scrub recirculated exhaust gases in fuel oil operation mode, the dual use of the wet scrubber further reduces the number of system components and reduces engine complexity and space requirements. During fuel oil operation, the scrubber liquor leaving the wet scrubber absorbs H2SO4 and becomes acidic (low pH). This allows it to be used as scrubber liquor to neutralize ammonia water in the wet scrubber in ammonia operation mode. This reduces operating costs in terms of both the amount of NaOH and H2SO4 that needs to be added to the scrubber liquor in each operating mode.

[0013] However, in one implementation of the first aspect, NaOH is added to the scrubber liquor to neutralize the H2SO4 to prevent the scrubber liquor from becoming too acidic. (Neutralizing the H2SO4 with NaOH results in the addition of NaOH to the water.) + , SO4 2- , leaving H2O.)

[0014] In one implementation of the first aspect, the first scrubber liquor has a pH of 7 or less and the second scrubber liquor has a pH of 7 or more.

[0015] In one implementation of the first aspect, the first scrubber liquor includes fresh water or seawater in combination with an acidic agent, which preferably includes sulfuric acid.

[0016] In one implementation of the first aspect, the second scrubber liquor includes freshwater or seawater combined with an alkaline agent, preferably including one of ammonium hydroxide, sodium hydroxide, sodium carbonate, and magnesium oxide.

[0017] In one implementation of the first aspect, the engine comprises a conduit and valve system, the conduit and valve system comprising: in the ammonia operation mode, directing the exhaust gas exiting the at least one turbine to the wet scrubber and directing the exhaust gas exiting the wet scrubber to an outlet to the atmosphere; In the fuel oil operating mode, a first portion of the exhaust gas exiting the at least one turbine is directed to the wet scrubber, the exhaust gas exiting the wet scrubber is recirculated to the air intake system, and a remaining second portion of the exhaust gas exiting the at least one turbine is directed to an outlet to atmosphere. However, the first portion is preferably 0 to 40% of the exhaust gases leaving the at least one turbine.

[0018] In one implementation of the first aspect, the engine is compression ignition in both the ammonia and fuel oil modes of operation.

[0019] In one implementation of the first aspect, the institution: a first tank for storing the first scrubber liquor; a second tank for storing the second scrubber liquor; a conduit and scrubber liquor pump and scrubber liquor valve system; In the ammonia operation mode, the conduit, the scrubber liquid pump, and the scrubber liquid valve system guide the first scrubber liquid from the first tank to the scrubber liquid inlet of the wet scrubber, and guide the scrubber liquid from the outlet of the wet scrubber to the second tank; In the fuel oil operation mode, the second scrubber liquid is guided from the second tank to a scrubber liquid inlet of the wet scrubber, and the scrubber liquid is guided from an outlet of the wet scrubber to the first tank. It is configured as follows.

[0020] In one implementation of the first aspect, NaOH is added to the scrubber liquor to neutralize the H2SO4 to prevent the scrubber liquor from becoming too acidic. (Neutralizing the H2SO4 with NaOH results in the release of Na in the water.) + , SO4 2- , leaving H2O.)

[0021] In one implementation of the first aspect, the wet scrubber has at least two stages, an upstream stage being a cooling stage and a downstream stage being a scrubbing stage.

[0022] In one example of implementation of the first aspect, the engine includes a cooler for reducing the temperature of the exhaust gas, the cooler being arranged between the at least one turbine and the wet scrubber or between the wet scrubber and the intake system, and the cooler is preferably a condenser.

[0023] In one implementation of the first aspect, the engine includes an electronic control unit configured to control an ammonia fuel system, a fuel oil fuel system, a valve system, and a scrubber liquid valve system.

[0024] In one implementation of the first aspect, the electronic control unit: controlling the ammonia fuel system to supply ammonia to the combustion chamber in the ammonia operation mode; controlling the fuel oil fuel system to supply fuel oil to the combustion chamber in the fuel oil operating mode; controlling the valve system to direct exhaust gas exiting the at least one turbine to the wet scrubber and to direct exhaust gas exiting the wet scrubber to an outlet to atmosphere in the ammonia operation mode; and controlling the valve system to, in the fuel oil operating mode, direct a first portion of the exhaust gases exiting the at least one turbine to the wet scrubber, recirculate the exhaust gases exiting the wet scrubber to the air intake system, and direct a remaining second portion of the exhaust gases exiting the at least one turbine to an outlet to atmosphere, wherein the first portion is preferably between 0 and 40% of the exhaust gases exiting the at least one turbine; In the ammonia operation mode, controlling the scrubber liquor valve system so as to direct first scrubber liquor from the first tank to a scrubber liquor inlet of the wet scrubber and direct scrubber liquor from an outlet of the wet scrubber to the second tank; In the fuel oil operation mode, the scrubber liquid valve system is controlled so as to direct second scrubber liquid from the second tank to a scrubber liquid inlet of the wet scrubber and direct scrubber liquid from an outlet of the wet scrubber to the first tank. It is configured as follows.

[0025] These and other aspects will become more apparent from the examples and embodiments described below. [Brief explanation of the drawings]

[0026] Various aspects, embodiments and implementations will now be described in detail with reference to exemplary embodiments illustrated in the drawings. [Figure 1] 1 shows a front view of a large two-stroke diesel engine according to an exemplary embodiment; FIG. [Figure 2] Figure 1 shows an overview of the large two-stroke engine as seen from the rear. [Figure 3]3 is a schematic representation of one embodiment of the large two-stroke engine of Figures 1 and 2, including an ammonia fuel system, a fuel oil fuel system, and a wet scrubber that scrubs exhaust gas in an ammonia mode of operation or recirculated exhaust gas in a fuel oil mode of operation. [Figure 4] 3 is a schematic representation of another embodiment of the large two-stroke engine of Figures 1 and 2, also including an ammonia fuel system, a fuel oil fuel system, and a wet scrubber that scrubs exhaust gas in an ammonia mode of operation or recirculated exhaust gas in a fuel oil mode of operation. [Figure 5] 5 is a schematic representation of a scrubber liquor system used in the embodiment of FIGS. 3 and 4. Detailed explanation

[0027] In the following detailed description, the internal combustion engine will be described with reference to an example crosshead type large, slow-speed, two-stroke, uniflow-scavenged, turbocharged internal combustion engine. Note that in some cases, the internal combustion engine may be of another type. The illustrated large, two-stroke, slow-speed, uniflow-scavenged, turbocharged internal combustion engine may be of the type in which fuel is injected at or near top dead center of the piston (i.e., high-pressure type), or may be of the compression ignition type.

[0028] The present disclosure provides a large two-stroke, uniflow-scavenged, turbocharged internal combustion engine that is designed to operate in two distinct modes: ammonia and fuel oil. In ammonia, the engine utilizes ammonia as the primary fuel, while in fuel oil, the engine operates on fuel oil as the primary fuel. In ammonia, pilot injection can be performed to facilitate ignition with a pilot liquid (e.g., fuel oil).

[0029] 1 and 2 show isometric views of a large, slow-speed, turbocharged, two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a large, slow-speed, turbocharged, two-stroke diesel engine according to a first embodiment, along with its intake and exhaust systems. In this example, the engine has six in-line cylinders. Large, slow-speed, turbocharged, two-stroke diesel engines typically have four to fourteen in-line cylinders. These cylinders are supported by a cylinder frame 23, which is supported by an engine frame 11. The engine structure is supported by the engine frame 11, which forms the foundation of the engine structure. The cylinder frame 23 is mounted on top of the engine frame 11 and provides support for the cylinder liners 11 and other upper components. The illustrations show the integration of these components into a compact, efficient engine design. Such an engine can be used, for example, as a main engine on a ship or as a stationary engine for driving a generator in a power plant. The total engine power output may be in the range of, for example, 1,000 to 110,000 kW.

[0030] The engine of this embodiment is a two-stroke uniflow compression ignition dual-fuel engine. The cylinder liner 1 has a scavenging port 18 in its lower region and an exhaust valve at the top center. This engine has at least one ammonia mode and at least one conventional fuel mode. In the ammonia mode, the engine is operated on ammonia fuel or an ammonia-based fuel. In the conventional fuel mode, the engine is operated on conventional fuels, such as fuel oil (marine diesel fuel) or heavy oil.

[0031] The engine includes two different fuel systems: an ammonia fuel system 30 configured to supply pressurized ammonia to a plurality of ammonia fuel valves 50 located on the cylinder cover 22 in an ammonia operating mode, and a fuel oil fuel system 31 configured to supply pressurized fuel oil to a plurality of fuel oil fuel valves 51 located on the cylinder cover 22 in a fuel oil operating mode.

[0032] Scavenging air is guided to the scavenging ports 18 of each cylinder 1 through the scavenging air receiver 2. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1, compressing the scavenging air. In the ammonia operation mode, high-pressure liquid ammonia is supplied by the ammonia fuel system 30 and injected at high pressure into the combustion chamber in the cylinder liner 1 at or near TDC through multiple ammonia fuel valves 50 arranged on the cylinder cover 22 (Diesel principle). Following fuel injection, combustion occurs and exhaust is generated. The cylinder cover 22 is provided with two or more fuel valves 50. In the fuel oil operation mode, high-pressure fuel oil is supplied by the fuel oil fuel system 31 and injected at high pressure into the combustion chamber in the cylinder liner 1 at or near TDC through multiple ammonia fuel valves 51 arranged on the cylinder cover 22 (Diesel principle). Following fuel injection, combustion occurs and exhaust is generated. The cylinder cover 22 is provided with two or more fuel valves 51. The ammonia fuel valve 50 and the fuel oil fuel valve 51 are each configured to inject only one specific type of fuel: ammonia, and fuel oil. The fuel valves 50 and 51 are arranged in the cylinder cover 22 around the exhaust valve 4, which is located in the center of the cylinder cover 22. However, it is also possible to use fuel valves that are compatible with both types of fuel, in which case only one type of fuel valve would be located in the cylinder cover 22. Although not shown, in some embodiments, the cylinder cover 22 may be provided with an additional (usually small) fuel valve configured to inject ignition fluid to ensure ignition of the ammonia fuel. The ignition fluid may be, for example, dimethyl ether (DME) or fuel oil. However, other forms of ignition enhancers, such as hydrogen, may also be used.

[0033] When the exhaust valve 4 opens, the exhaust gases flow through an exhaust duct connected to the cylinder to the exhaust receiver 3 and then through a first exhaust pipe 19 to the turbine 6 of the turbocharger 5. From there, the exhaust gases exit through a second exhaust pipe 28 to the low pressure side of the exhaust gas access system, which will be described in more detail below.

[0034] A turbine 6 of the turbocharger 5 drives a compressor 7 via a shaft. Outside air is supplied to the compressor 9 through an air intake 12. The compressor 7 sends compressed scavenging air into a scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air in the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

[0035] The turbocharging system may have two or more turbochargers 5 .

[0036] The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging air flow when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging air receiver 2, i.e. when the engine is at low or partial load. When the engine load is high, the turbocharger compressor 7 can provide sufficiently compressed scavenging air, so the auxiliary blower 16 is bypassed by the check valve 15 and the electric motor 17 is switched off.

[0037] In the ammonia operating mode, the engine is operated using ammonia as the primary fuel. Ammonia is supplied to the ammonia valve 50 by the ammonia fuel system 30 at a substantially constant pressure and temperature. The ammonia may be supplied to the ammonia valve 50 in either the liquid or gas phase. The liquid phase ammonia may be aqueous ammonia, i.e., an aqueous ammonia solution.

[0038] Fuel supply systems 31 for conventional fuel oils are well known and are not shown or described in detail.

[0039] The engine can operate in two broadly different modes: an ammonia mode of operation and a fuel oil mode of operation. In the ammonia mode of operation, the engine's primary fuel can be ammonia. Conversely, in the fuel oil mode of operation, the engine's primary fuel can be fuel oil. The engine or engine operator can switch between these two modes based on a variety of factors, including fuel availability, environmental conditions, and operating requirements.

[0040] In some embodiments, the ammonia fuel system 30 and the fuel oil fuel system 31 may be separate systems, each with its own set of fuel valves 50, 51. In some embodiments, the ammonia fuel system 30 and the fuel oil fuel system 31 may share some components, such as fuel pumps and fuel lines. The specific configurations of the ammonia fuel system 30 and the fuel oil fuel system 31 will vary based on factors such as the engine design, the type of fuel used, or the engine operating requirements.

[0041] The electronic control unit 100 is connected via signal lines or wirelessly to the pumps and valves of the engine system and is configured to control these elements, for example by adjusting the speed of the pumps or controlling the opening and closing of the valves, thereby enabling the fuel system and exhaust gas purification system to operate as described in detail below.

[0042] A wet scrubber 40 is disposed downstream of the turbine 6. The wet scrubber 40 is designed to scrub at least a portion of the exhaust gases exiting the turbine 6 with a scrubber liquid. In an ammonia operation mode, the wet scrubber 40 functions as an ammonia scrubber, using a first scrubber liquid to absorb ammonia from the exhaust gases flowing through the wet scrubber 40. In a fuel oil operation mode, the wet scrubber 40 functions as a sulfur oxide scrubber, using a second scrubber liquid to absorb sulfur oxides and / or sulfuric acid from the exhaust gases flowing through the scrubber.

[0043] The first scrubber liquor may comprise freshwater or seawater combined with an acidic agent, preferably sulfuric acid. The second scrubber liquor may comprise freshwater or seawater combined with an alkaline agent, preferably ammonia hydroxide, sodium hydroxide (NaOH), sodium carbonate (NaCO), or magnesium oxide (MgO).

[0044] The wet scrubber 40 is disposed in the exhaust system and is connected to a scrubber liquid supply line 48 and a scrubber liquid return line 49 .

[0045] The exhaust system is provided with a plurality of control valves, such as a first control valve 24, a second control valve 25, a third control valve 26, a fourth control valve 35, and a fifth control valve 36.

[0046] A low pressure EGR pipe 29 connects the exhaust system to the intake system.

[0047] The wet scrubber 40 is disposed downstream of the turbine 6. The wet scrubber 40 may be configured to scrub at least a portion of the exhaust gases exiting the turbine 6 with a scrubber liquor. In some embodiments, the wet scrubber 40 may function as an ammonia scrubber in an ammonia mode of operation. In this mode, the wet scrubber 40 may use a first scrubber liquor to absorb ammonia from the exhaust gases flowing through the scrubber 40.

[0048] The wet scrubber 40 may function as a sulfur oxide scrubber in a fuel oil operating mode. In this mode, the wet scrubber 40 may use a second scrubber liquor to absorb sulfur oxides and / or sulfuric acid from the exhaust gas flowing through the wet scrubber 40. The first and second scrubber liquors may be different and may be selected based on the operating mode of the engine.

[0049] The engine may include a system of conduits and valves configured to direct the exhaust gas flow, which in an ammonia mode of operation directs the exhaust gases exiting the turbine 6 to a wet scrubber 40. After exiting the wet scrubber 40, the exhaust gases are released to the atmosphere through an atmospheric outlet 21.

[0050] The conduit and valve system may be configured to direct a first portion of the exhaust gases exiting the turbine 6 to the wet scrubber 40 in a fuel oil operating mode. The exhaust gases exiting the wet scrubber 40 may be recirculated to the air intake system. A second portion of the exhaust gases exiting the turbine 6 is directed towards the atmospheric outlet 21. The first portion may be between 0 and 40% of the exhaust gases exiting the turbine 6, depending on various factors such as engine operating requirements and environmental conditions.

[0051] In some embodiments, the conduits and valve system are controlled by an electronic control unit 100. The electronic control unit 100 may be configured to control the direction of exhaust gas flow and scrubber liquid flow in both ammonia and fuel oil operating modes, allowing for flexible and efficient operation of the engine in different modes.

[0052] The wet scrubber 40 may have at least two stages: an upstream cooling stage and a downstream scrubbing stage. The exhaust gas may be cooled in the cooling stage to reduce the temperature of the exhaust gas before entering the scrubbing stage. In the scrubbing stage, the exhaust gas may be scrubbed with a scrubber liquor to remove certain components from the exhaust gas. The specific configuration of each stage of the wet scrubber 40 will vary depending on factors such as the design of the wet scrubber 40, the type of exhaust gas being treated, and the engine operating requirements.

[0053] In some embodiments, the cooler 20 for cooling the exhaust gas may be located between the turbine 6 and the wet scrubber 40, as shown in FIG. 3, or between the wet scrubber 40 and the intake system, as shown in FIG. 4. The cooler 20 may be designed to reduce the temperature of the exhaust gas, which may improve the efficiency of the wet scrubber 40. The specific location and configuration of the cooler 20 will vary based on factors such as the engine design, the type of exhaust gas being treated, and the engine's operating requirements.

[0054] The engine may include an electronic control unit 100. The electronic control unit 100 may be configured to control the ammonia fuel system 30, the heavy fuel oil system 31, the valve system, and the scrubber liquid valve system, thereby enabling precise control of the operation of these systems and components, which may improve the overall performance of the engine.

[0055] In some embodiments, electronic control unit 100 may be configured to vary the control of various systems and components between an ammonia mode of operation and a fuel oil mode of operation. For example, in an ammonia mode of operation, electronic control unit 100 may control ammonia fuel system 30 to supply ammonia to the combustion chamber and may control a valve system to direct exhaust gases exiting turbine 6 to wet scrubber 40. The exhaust gases exiting wet scrubber 40 are then released to the atmosphere through atmospheric outlet 21.

[0056] In the fuel oil operating mode, the electronic control unit 100 may control the heavy oil fuel system 31 to supply fuel oil to the combustion chamber. The electronic control unit 100 may also control the valve system to direct a first portion of the exhaust gases exiting the turbine 6 to the wet scrubber 40 and recirculate the exhaust gases exiting the wet scrubber 40 to the intake system. A second remaining portion of the exhaust gases exiting the turbine 6 may be directed to the exhaust outlet 21 and released to the atmosphere.

[0057] In some embodiments, the electronic control unit 100 may control the scrubber liquid valve system to direct a first scrubber liquid from a first tank to the scrubber liquid inlet of the wet scrubber 40 in an ammonia mode of operation, and direct a second scrubber liquid from a second tank to the scrubber liquid inlet of the wet scrubber 40 in a fuel oil mode of operation. The specific functionality and configuration of the electronic control unit 100 will vary depending on factors such as engine design, the type of fuel used, and the mode of operation.

[0058] This configuration allows for selective circulation of different scrubber liquors and addition of acid to the liquor stream through the wet scrubber 40. This configuration also allows the system to accommodate different operating modes, allowing for treatment of a variety of exhaust gas compositions.

[0059] In the ammonia operating mode, the engine is operated without EGR or with an EGR rate of less than 40%, preferably less than 30%, and more preferably less than 20% of the exhaust gases being recirculated. The EGR rate is preferably adjusted by the electronic control unit 100 according to operating conditions and emission requirements. In the ammonia operating mode, the electronic control unit 100 transitions the first control valve 24 to its closed position, the second control valve 25 to its open position, the third control valve 26 to its closed position, the fourth control valve 35 to its closed position, and the fifth control valve 36 to its open position. The electronic control unit 100 also shuts down the EGR blower 27. Thus, exhaust gases leaving the turbine 6 pass through the wet scrubber 40 and from there to the atmosphere outlet 21.

[0060] The wet scrubber 40 is supplied with a first scrubber liquor having a pH of 7 or less from the scrubber liquor system 41 through a scrubber liquor supply pipe 48. The pH of 7 or less is to improve the absorption of ammonia into the scrubber liquor to form ammonia water. (Ammonia in the exhaust gas is dissolved in the scrubber liquor in the form of ammonium hydroxide.) The ammonia water is removed from the scrubber together with the scrubber liquor leaving the wet scrubber 40 and returned to the scrubber liquor system 41 through a scrubber liquor return pipe 49.

[0061] In fuel oil operation mode, the engine is operated with EGR. The EGR rate is NO x The EGR rate is preferably less than 40% to reduce emissions. The EGR rate is adjusted according to the operating conditions and emission requirements, preferably by the electronic control unit 100. Fuel oil contains sulfur, which is emitted in the exhaust gas in the form of sulfur oxide particles and / or sulfuric acid. Therefore, in the fuel oil operating mode, the wet scrubber 40 is used to remove sulfur oxide particles and / or sulfuric acid from the exhaust gas. The recirculated exhaust gas preferably has a low content of sulfur oxide particles and / or sulfuric acid to protect the engine, particularly the inner surfaces of the cylinder liner 1.

[0062] In the fuel oil operation mode, the electronic control unit 100 transitions the first control valve 24 to its open position, the second control valve 25 to its closed position, the third control valve 26 to its open position, the fourth control valve 35 to its open position, and the fifth control valve 36 to its closed position. The electronic control unit 100 also activates the EGR blower 27. Thus, a first portion of the exhaust gases leaving the turbine 6 passes through the wet scrubber 40 and then to the EGR pipe 29 connecting to the air inlet 12. The recirculated exhaust gases are drawn into the compressor 7 and recirculated to the combustion chamber together with fresh air drawn into the compressor 7. A second portion of the exhaust gases leaving the turbine 6 passes through the open valve 26 to the atmospheric exhaust port 21. The EGR rate is controlled by the electronic control unit 100 by adjusting the rotation speed of the EGR blower 27 and / or by adjusting the positions of the first control valve 24, the third control valve 26, and / or the fourth control valve 35. In this case, each control valve 24, 26, 35 involved is not a simple on-off valve, but instead is of a type which allows throttling control of the amount of exhaust gas passing through the valve.

[0063] The wet scrubber 40 is supplied with a second scrubber liquor having a pH of 7 or higher from the scrubber liquor system 41 through a scrubber liquor supply line 48. The pH of 7 or higher is necessary to improve absorption of sulfur-based combustion products into the scrubber liquor in the scrubber 40 and form sulfuric acid dissolved in the water in the scrubber liquor. (Sulfur oxides and / or sulfuric acid dissolve in the scrubber liquor.) These sulfur combustion products are then removed from the wet scrubber 40 along with the scrubber liquor exiting the wet scrubber 40 and returned to the scrubber liquor system 41 through a scrubber liquor return line 49. During fuel oil operation, the scrubber liquor exiting the wet scrubber absorbs H2SO4 and becomes acidic (low pH). This allows it to be used as a scrubber liquor to neutralize ammonia water in the wet scrubber during ammonia operation, and vice versa. This reduces operating costs in terms of both the amount of NaOH and H2SO4 that must be added to the scrubber liquor in each operation mode. In some embodiments, NaOH is added to the scrubber liquor to neutralize the H2SO4 to prevent the scrubber liquor from becoming too acidic. (Neutralizing the H2SO4 with NaOH results in Na in the water. + , SO4 2- , leaving H2O.)

[0064] FIG. 4 is a schematic representation of a large, low-speed, turbocharged, two-stroke diesel engine according to a second embodiment, together with its intake and exhaust systems. In this embodiment, components and features similar to those already described or illustrated are designated by the same reference numerals as previously used. This embodiment differs from the first embodiment in that the EGR blower 27 is disposed downstream of the wet scrubber 40, i.e., the EGR blower 27 is disposed in the EGR pipe 29. Therefore, the second embodiment does not have or require the first control valve 24. The cooler 20 (preferably a condenser) is disposed in the EGR pipe 29, i.e., between the wet scrubber 40 and the intake system.

[0065] In the ammonia operating mode, the engine is operated without EGR or with an EGR rate of less than 40%, preferably less than 30%, and more preferably less than 20%. The EGR rate is preferably adjusted by the electronic control unit 100 according to operating conditions and emission requirements. In the ammonia operating mode, the electronic control unit 100 transitions the second control valve 25 to its open position, the third control valve 26 to its closed position, the fourth control valve 35 to its closed position, and the fifth control valve 36 to its open position. The electronic control unit 100 also shuts down the EGR blower 27. Thus, exhaust gases leaving the turbine 6 pass through the wet scrubber 40 and from there to the atmosphere outlet 21.

[0066] If the ammonia mode operation requires EGR operation, the electronic control unit 100 commands the fourth control valve 35 to transition to its open position, actuating the EGR blower 27, and preferably thereafter controls the operation of the EGR blower 27 to obtain the desired EGR rate.

[0067] The wet scrubber 40 is supplied with a first scrubber liquor having a pH of 7 or less from the scrubber liquor system 41 through a scrubber liquor supply line 48. The pH of 7 or less is to improve the absorption of ammonia to form aqueous ammonia. (Ammonia is dissolved in the scrubber liquor in the form of ammonium hydroxide.) The aqueous ammonia is removed from the scrubber together with the scrubber liquor exiting the wet scrubber 40 and returned to the scrubber liquor system 41 through a scrubber liquor return line 49.

[0068] In fuel oil operation mode, the engine is operated with EGR. The EGR rate is NO xThe EGR rate is preferably less than 40% to reduce emissions. The EGR rate is adjusted according to the operating conditions and emission requirements, preferably by the electronic control unit 100. Fuel oil contains sulfur, which is emitted in the exhaust gas in the form of sulfur oxide particles and / or sulfuric acid. Therefore, in the fuel oil operating mode, the wet scrubber 40 is used to remove sulfur oxide particles and / or sulfuric acid from the exhaust gas. The recirculated exhaust gas preferably has a low content of sulfur oxide particles and / or sulfuric acid to protect the engine, particularly the inner surfaces of the cylinder liner 1.

[0069] In the fuel oil operation mode, the electronic control unit 100 transitions the second control valve 25 to its open position, the third control valve 26 to its open position, the fourth control valve 35 to its open position, and the fifth control valve 36 to its closed position. The electronic control unit 100 also activates the EGR blower 27. Thus, a first portion of the exhaust gases leaving the turbine 6 passes through the wet scrubber 40 and then to the EGR pipe 29 connecting to the air inlet 12. The recirculated exhaust gases are drawn into the compressor 7 and recirculated to the combustion chamber together with fresh air drawn into the compressor 7. A second portion of the exhaust gases leaving the turbine 6 passes through the open third control valve 26 to the atmosphere outlet 21. The EGR ratio is controlled by the electronic control unit 100 by adjusting the rotation speed of the EGR blower 27 and / or by adjusting the positions of the second control valve 25, the third control valve 26, and / or the fourth control valve 35. In this case, each control valve 25, 26, 35 involved is not a simple on-off valve, but instead is of a type which allows throttling control of the amount of exhaust gas passing through the valve.

[0070] All other aspects of the operation and construction of the engine according to the second embodiment are the same as those of the engine according to the first embodiment.

[0071] Referring to FIG. 5 , the engine may have a scrubber liquid system 41 for the wet scrubber 40. The scrubber liquid system 41 may be used in both the first and second embodiments described above. The scrubber liquid system 41 may include a first scrubber liquid tank 45 and a second scrubber liquid tank 46. In some embodiments, the first scrubber liquid tank 45 may be configured to store a first scrubber liquid, and the second scrubber liquid tank 46 may be configured to store a second scrubber liquid. The first scrubber liquid and the second scrubber liquid may be different and may be selected based on the operating mode of the engine.

[0072] In some embodiments, the pH of the first scrubber liquor may be equal to or less than 7. A pH of 7 or less may make the first scrubber liquor suitable for absorbing ammonia from the exhaust gas in an ammonia mode of operation. The first scrubber liquor may include fresh water or seawater in combination with an acidic agent. In some embodiments, the acidic agent may be sulfuric acid, although other acidic agents may be used.

[0073] Alternatively, the pH of the second scrubber liquor may be equal to or greater than 7. A pH of 7 or greater may make the second scrubber liquor suitable for absorbing sulfur oxides and / or sulfuric acid from the exhaust gas in a fuel oil operation mode. The second scrubber liquor may include fresh water or seawater in combination with an alkaline agent. In some embodiments, the alkaline agent may be ammonium hydroxide, sodium hydroxide, sodium carbonate, or magnesium oxide. However, other alkaline agents may also be used.

[0074] The scrubber liquor system 41 may include a scrubber liquor pump 58. The scrubber liquor pump 58 may be connected to both the first scrubber liquor tank 45 and the second scrubber liquor tank 46 via a network of conduits and valves. The scrubber liquor pump 58 may be configured to pump scrubber liquor from the tanks 45, 46 to the wet scrubber 40. In some embodiments, the scrubber liquor pump 58 may be controlled by an electronic control unit 100, thereby allowing precise control of the flow rate (e.g., size and / or pressure) of the scrubber liquor. That is, the flow rate of the scrubber liquor can be adapted to the operating conditions of the engine (e.g., fuel mode, engine load, ambient conditions, etc.).

[0075] The scrubber liquor system 41 may further include a network of conduits and valves, which may include a first scrubber liquor valve 42 and a second scrubber liquor valve 43. The valves 42 and 43 may control the flow of scrubber liquor from the first and second tanks, respectively, to the wet scrubber 40. Additionally, a third scrubber liquor valve 44 and a fourth scrubber liquor valve 47 may control the return flow of scrubber liquor from the wet scrubber 40 to the tanks 45 and 46.

[0076] In the ammonia operation mode, the scrubber liquid system 41 may be configured to direct first scrubber liquor from the first tank 45 to the scrubber liquor inlet of the wet scrubber 40. To achieve this, the electronic control unit 100 transitions the first scrubber liquor valve 42 to its open position and the second scrubber liquor valve 43 to its closed position. The scrubber liquid leaving the outlet of the wet scrubber 40 may then be directed to the second tank 46. To achieve this, the electronic control unit 100 transitions the third scrubber liquor valve 44 to its closed position and the fourth scrubber liquor valve 47 to its open position.

[0077] Conversely, in the fuel oil operating mode, the scrubber liquid system 41 may be configured to direct second scrubber liquid from the second tank 46 to the scrubber liquid inlet of the wet scrubber 40. To achieve this, the electronic control unit 100 transitions the first scrubber liquid valve 42 to its closed position and the second scrubber liquid valve 43 to its open position. The scrubber liquid leaving the outlet of the wet scrubber 40 may then be directed to the first tank 45. To achieve this, the electronic control unit 100 transitions the third scrubber liquid valve 44 to its open position and the fourth scrubber liquid valve 47 to its closed position.

[0078] A scrubber liquor supply line 48 connects a scrubber liquor pump 58 to the wet scrubber 40, allowing scrubber liquor to flow from the pump to the scrubber. A scrubber liquor return line 49 allows scrubber liquor to return from the scrubber to the tank. This configuration may allow different scrubber liquors to be selectively circulated through the wet scrubber 40, allowing for treatment of various exhaust gas compositions.

[0079] In the scrubber liquid system 41 as described above, the scrubber liquid returned from the wet scrubber 40 in the ammonia operation mode can be reused as the second scrubber liquid in the fuel oil operation mode, and the scrubber liquid returned from the wet scrubber 40 in the fuel oil operation mode can be reused as the first scrubber liquid in the ammonia operation mode. Therefore, by operating the engine alternately between the ammonia operation mode and the fuel oil operation mode, the scrubber liquid can be reused to a large extent, reducing the need for a system to treat used scrubber liquid.

[0080] In some embodiments, an acid source 59 is incorporated into the scrubber liquor system 41 and is connected to the second tank 46. The acid provided by the acid source 59 may be, for example, sulfuric acid (H2SO4) or other suitable acid, to neutralize NH3 in the scrubber liquor returned to the second tank 46 during operation in the ammonia mode of operation.

[0081] Various aspects and implementations of the invention have been described with reference to several exemplary embodiments. However, upon reviewing the specification, drawings, and claims of this application, those skilled in the art will understand and be able to embody many variations in addition to the described embodiments in implementing the claimed invention. The words "comprise," "have," and "include" in the claims do not exclude the presence of unrecited elements or steps. The absence of a claim expressly stating a plurality of elements does not exclude the presence of a plurality of such elements. The functions of several elements recited in the claims may be performed by a single processor or electronic control unit. The fact that several items are recited in separate dependent claims does not exclude them from being implemented in combination, and may be advantageously implemented in combination.

[0082] Reference signs used in the claims should not be construed as limiting the scope of the invention. Unless otherwise noted, the drawings are intended to be read together with the specification, which is an entire part of this disclosure. Throughout the specification, the terms "horizontal," "vertical," "left," "right," "upper," "lower," and their adjectival and adverbial forms (e.g., "horizontally," "rightwardly," "upwardly," etc.) merely refer to the orientation of the illustrated structure in the direction of the reader's view. Similarly, the terms "inwardly" and "outwardly" generally refer to the orientation of a surface relative to a longitudinal axis or axis of rotation, as the context requires.

Claims

1. 1. A large two-stroke uniflow scavenging turbocharged internal combustion engine having an ammonia operation mode in which ammonia is used as a main fuel, and a fuel oil operation mode in which fuel oil is used as a main fuel, the engine comprising: at least one cylinder having a cylinder liner and a reciprocating piston within said cylinder liner, and a cylinder cover covering said cylinder liner; a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a plurality of ammonia fuel valves disposed in the cylinder cover in the ammonia operation mode; a fuel oil fuel system configured to, in the fuel oil operating mode, supply pressurized fuel oil to a plurality of fuel oil fuel valves disposed in the cylinder cover; a turbocharging system comprising at least one compressor for compressing scavenged air, the compressor being located in the intake system of the engine, and at least one turbine located in the exhaust system of the engine and driven by the exhaust gases; a wet scrubber located downstream of said at least one turbine for scrubbing at least a portion of the exhaust gases leaving said at least one turbine with a scrubbing liquid; and the wet scrubber functions as an ammonia scrubber in the ammonia operation mode, configured to absorb ammonia from the exhaust gas flowing through the wet scrubber using a first scrubber liquor; the wet scrubber functions as a sulfur oxide scrubber in the fuel oil mode of operation, configured to absorb sulfur oxides and / or sulfuric acid from the exhaust gas flowing through the wet scrubber using a second scrubber liquor; institution.

2. 2. The engine of claim 1, wherein said first scrubber liquor has a pH of 7 or less and said second scrubber liquor has a pH of 7 or more.

3. The engine of claim 1 , wherein the first scrubber liquor comprises fresh water or seawater combined with an acidic agent.

4. The engine of claim 2 , wherein the second scrubber solution comprises fresh water or seawater in combination with an alkaline agent.

5. The alkaline agent is selected from the group consisting of ammonia hydroxide, sodium hydroxide (NaOH), sodium carbonate (Na ２ CO ３ 5. The engine of claim 4, further comprising either magnesium oxide (MgO).

6. and a conduit and valve system, said conduit and valve system comprising: in the ammonia operation mode, directing the exhaust gas exiting the at least one turbine to the wet scrubber and directing the exhaust gas exiting the wet scrubber to an outlet to the atmosphere; In the fuel oil operating mode, a first portion of the exhaust gases exiting the at least one turbine are directed to the wet scrubber, the exhaust gases exiting the wet scrubber are recirculated to the air intake system, and a remaining second portion of the exhaust gases exiting the at least one turbine are directed to an outlet to atmosphere.

6. An engine according to any one of claims 1 to 5, configured so as to

7. The engine of claim 6, wherein said first portion is between 0 and 40% of the exhaust gases exiting said at least one turbine.

8. 2. The engine of claim 1, wherein the engine is compression ignition in both the ammonia and fuel oil operating modes.

9. a first tank for storing the first scrubber liquor; a second tank for storing the second scrubber liquor; a conduit and scrubber liquor pump and scrubber liquor valve system; The conduit and the scrubber liquor pump and scrubber liquor valve system are In the ammonia operation mode, a first scrubber liquid is guided from the first tank to a scrubber liquid inlet of the wet scrubber, and the scrubber liquid is guided from an outlet of the wet scrubber to the second tank; In the fuel oil operation mode, the second scrubber liquid is guided from the second tank to a scrubber liquid inlet of the wet scrubber, and the scrubber liquid is guided from an outlet of the wet scrubber to the first tank.

7. The engine of claim 6, configured to:

10. 10. The engine of claim 1, wherein the wet scrubber has at least two stages, an upstream stage being a cooling stage and a downstream stage being a scrubbing stage.

11. 2. The engine of claim 1, further comprising a cooler for reducing the temperature of the exhaust gases, the cooler being disposed between the at least one turbine and the wet scrubber, or between the wet scrubber and the intake system.

12. The engine of claim 9 , comprising an electronic control unit configured to control the ammonia fuel system, the fuel oil fuel system, the valve system, and the scrubber liquid valving system.

13. The electronic control unit controlling the ammonia fuel system to supply ammonia to the combustion chamber in the ammonia operation mode; controlling the fuel oil fuel system to supply fuel oil to the combustion chamber in the fuel oil operating mode; controlling the valve system to direct exhaust gas exiting the at least one turbine to the wet scrubber and to direct exhaust gas exiting the wet scrubber to an outlet to atmosphere in the ammonia operation mode; controlling the valve system to, in the fuel oil operating mode, direct a first portion of the exhaust gases exiting the at least one turbine to the wet scrubber, recirculate the exhaust gases exiting the wet scrubber to the air intake system, and direct a remaining second portion of the exhaust gases exiting the at least one turbine to an outlet to atmosphere; In the ammonia operation mode, controlling the scrubber liquor valve system to direct first scrubber liquor from the first tank to a scrubber liquor inlet of the wet scrubber and direct scrubber liquor from an outlet of the wet scrubber to the second tank; In the fuel oil operation mode, the scrubber liquid valve system is controlled so as to direct second scrubber liquid from the second tank to a scrubber liquid inlet of the wet scrubber and direct scrubber liquid from an outlet of the wet scrubber to the first tank.

13. The engine of claim 12 configured to:

14. The engine of claim 13, wherein the first portion is between 0 and 40% of the exhaust gases exiting the at least one turbine.

Images