Internal combustion engines and methods for managing ammonia in them

Abstract

This application provides a large two-stroke, single-flow scavenging turbocharged internal combustion engine and a method for managing ammonia in the engine, the engine having at least one operating mode where ammonia is the primary fuel. The engine includes: at least one cylinder having a cylinder liner, a reciprocating piston located within the cylinder liner, and a cylinder head covering the cylinder; a combustion chamber formed inside the cylinder and located between the reciprocating piston and the cylinder head; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed in the cylinder head or cylinder liner; and an ammonia discharge flow path connecting the outlet of the ammonia fuel system to the inlet of an ammonia absorption system, the ammonia absorption system containing water during use for absorbing ammonia supplied through the discharge path into the water, thereby forming ammonia water.

Description

[0001] This application is a divisional application of Chinese invention patent application filed on May 25, 2022, with application number 2022105800652 and entitled "Internal Combustion Engine and Method for Managing Ammonia Therein". Technical Field

[0002] This disclosure relates to a large two-stroke, single-flow scavenging turbocharged internal combustion engine that operates in at least one mode using ammonia as fuel for combustion in the engine. Background Technology

[0003] Large, two-stroke, single-flow, scavenging, turbocharged, compression-ignition, internal combustion crosshead engines are typically used in the propulsion systems of large ships or as prime movers in power plants. Their enormous size, weight, and power output make them fundamentally different from ordinary combustion engines, thus classifying large, two-stroke, turbocharged, compression-ignition internal combustion engines as a separate category.

[0004] In the past, internal combustion engines primarily operated on hydrocarbon fuels, such as fuel oils like diesel, or fuel gases like natural gas or petroleum gas. The combustion of hydrocarbon fuels releases carbon dioxide (CO2) and other greenhouse gases that contribute to air pollution and climate change. Unlike fossil fuel impurities that result in byproduct emissions, CO2 is an unavoidable byproduct of hydrocarbon combustion. The energy density and CO2 footprint of a fuel depend on the length of the hydrocarbon chain and the complexity of its molecules. Therefore, gaseous hydrocarbon fuels have a lower footprint than liquid hydrocarbon fuels, which also presents challenges in handling and storage. To reduce CO2 footprint, non-hydrocarbon fuels are being researched.

[0005] Ammonia is a synthetic product obtained from fossil fuels, biomass, or renewable resources (wind, solar, water, or heat). When ammonia is generated from renewable resources, it has almost no carbon cover when burned, or emits almost no CO2, SOx, particulate matter, or unburned hydrocarbons.

[0006] Ammonia has been tested and used on a small scale in small spark-ignition internal combustion engines, but it has not yet been used to power compression-ignition internal combustion engines.

[0007] Ammonia is hazardous and has an irritating odor. Therefore, ammonia escaping from the engine should be prevented. When operations using ammonia are stopped and changed to, for example, conventional fuel, the ammonia in the fuel system needs to be purged, and the purged ammonia cannot simply be released into the atmosphere / environment. Other situations requiring the handling of excess ammonia may include those caused by engine leaks or other malfunctions. In these and similar situations, a solution to terminate ammonia is needed.

[0008] CN112696289 discloses a marine liquid ammonia fuel supply and recovery system. The system includes an ammonia fuel engine, a liquid ammonia supply system, a liquid ammonia circulation system, and a liquid ammonia nitrogen removal and emission system. According to this system, high-pressure liquid ammonia fuel supply (70 bar, 45±10 degrees Celsius) is achieved, and unconsumed liquid ammonia fuel in the pipeline can be recovered, thereby saving a significant amount of fuel. Simultaneously, it reduces ammonia fuel emissions to the ventilation mast and improves the safety of the ship and its personnel. Summary of the Invention

[0009] The aim is to provide a large two-stroke single-flow scavenging turbocharged internal combustion engine that overcomes or at least reduces the aforementioned problems.

[0010] The foregoing and other objectives are achieved through the features of the independent claims. Further implementations are apparent from the dependent claims, the specification, and the drawings.

[0011] According to a first aspect, a large two-stroke single-flow scavenging turbocharged internal combustion engine is provided, the engine having at least one operating mode in which ammonia is the primary fuel, the engine comprising: At least one cylinder, the cylinder having a cylinder bushing, a reciprocating piston located in the cylinder bushing, and a cylinder head covering the cylinder. The combustion chamber is formed inside the cylinder and located between the reciprocating piston and the cylinder head (22). The ammonia fuel system is configured to supply pressurized ammonia to a fuel valve, which is located in the cylinder head or, alternatively, in the cylinder liner. Ammonia absorption system 60, and The ammonia discharge flow path connects the outlet of the ammonia fuel system to the inlet of the ammonia absorption system. The ammonia absorption system contains water during operation to absorb the ammonia supplied through the discharge path, thereby forming ammonia water.

[0012] By providing a purge flow path and an ammonia absorption system, incidents requiring the handling of excess ammonia from the engine can be addressed, such as purge events or leaks occurring when operations using ammonia fuel cease. Large quantities of ammonia can be temporarily stored in water by dissolving it in an aqueous absorption system, producing ammonia water. Ammonia water can be used as fuel in the engine or as a reducing agent in an SCR reactor to clean exhaust gases.

[0013] The inventors realized that the solubility of ammonia typically increases as water temperature decreases. By adding a cooling loop facility to cool the water, the actual amount of ammonia recovered in the recovery system (tank) could be increased, thereby improving the recovery rate.

[0014] In a possible implementation of the first aspect, the ammonia absorption system includes at least one container that is at least partially filled with water during use; preferably, the at least one container includes a water inlet for connection to a water source; and preferably, the at least one container includes an ammonia outlet for the discharge of ammonia water.

[0015] In a possible implementation of the first aspect, the engine is a dual-fuel engine, which preferably includes a fuel system for supplying conventional fuel to the cylinders of the engine.

[0016] In a possible implementation of the first aspect, the ammonia outlet is connected to the ammonia fuel system for combustion of ammonia within the engine.

[0017] In a possible implementation of the first aspect, the engine includes an SCR reactor located in the exhaust gas flow path of the engine, wherein an ammonia outlet is connected to a reducing agent inlet associated with the SCR reactor.

[0018] In a possible implementation of the first aspect, the ammonia absorption system includes a pressure vessel that is at least partially filled with water during use. Preferably, the pressure vessel is provided with a cooling system for reducing the temperature of the pressure vessel. Preferably, the pressure vessel includes a gaseous ammonia inlet for introducing gaseous ammonia. Preferably, the pressure vessel is connected to a water source. Preferably, the pressure vessel has an ammonia outlet for discharging ammonia water.

[0019] In a possible implementation of the first aspect, the ammonia absorption system includes a packed absorption tower, preferably, the packed absorption tower includes a gaseous ammonia inlet for introducing gaseous ammonia, preferably, the packed absorption tower is connected to a water source, and preferably, the packed absorption tower has an ammonia outlet for discharging ammonia water.

[0020] In a possible implementation of the first aspect, the ammonia absorption system includes a cascade of water tanks that are at least partially filled with water during use. Preferably, the first water tank includes a gaseous ammonia inlet and a gaseous ammonia outlet, a water inlet and an ammonia outlet. Preferably, subsequent water tanks include a gaseous ammonia inlet connected to the gaseous ammonia outlet of the first water tank and an ammonia outlet connected to the water inlet of the first water tank. Preferably, the cascade of water tanks is configured to allow water to flow in the opposite direction to the flow of gaseous ammonia. The water in the upstream tank has the highest concentration of ammonia during the gaseous ammonia flow and is provided with an ammonia outlet. The water in the downstream tank has the lowest concentration of ammonia during the gaseous ammonia flow. Preferably, the downstream tank is provided with a discharge outlet for discharging gaseous material from the tank.

[0021] In a possible implementation of the first aspect, the ammonia fuel system includes a scavenging system configured to remove ammonia from the fuel system to an ammonia absorption system. Preferably, the scavenging system includes a pressurized nitrogen source, which is connected to the fuel system via a scavenging valve. Preferably, the scavenging system uses an ammonia removal flow path to remove ammonia from the ammonia fuel system to the ammonia absorption system.

[0022] In a possible implementation of the first aspect, the ammonia fuel system includes: a medium-pressure ammonia supply line; an ammonia return line; a first purging line connecting the medium-pressure ammonia supply line to the ammonia absorption system; a second purging line connecting the ammonia return line to the ammonia absorption system; and preferably, the ammonia fuel system includes a valve for selectively connecting the medium-pressure ammonia supply valve and the ammonia return line to the ammonia absorption system.

[0023] In a possible implementation of the first aspect, a separation drum is arranged in a first purging line and / or a second purging line. The separation drum is configured to separate liquid ammonia from gaseous ammonia. The separation drum includes a gaseous ammonia outlet and a liquid ammonia outlet. The gaseous ammonia outlet is connected to an ammonia absorption system. Preferably, the liquid ammonia outlet is connected to a recovery tank, which in turn is connected to an ammonia fuel system.

[0024] In a possible implementation of the first aspect, the ammonia fuel system includes a supply line and a return line, wherein the pipes forming the supply line and the return line include double-walled pipes, and wherein the space between the inner pipe and the outer pipe of the double-walled pipe is fluidly connected to the ammonia absorption system via an ammonia discharge path.

[0025] In a possible implementation of the first aspect, the ammonia fuel system includes a liquid ammonia fuel tank and a low-pressure ammonia supply line, the low-pressure ammonia supply line connecting the liquid ammonia fuel tank to the inlet of a medium-pressure fuel pump via the action of a low-pressure pump. Preferably, the fuel system includes a medium-pressure fuel line connecting the outlet of the medium-pressure pump to the inlet of a fuel valve. Preferably, the fuel system includes a return line connecting the outlet of the fuel valve to the inlet of the medium-pressure fuel pump.

[0026] In a possible implementation of the first aspect, at least one cylinder is provided with a scavenging port located in the lower region of the cylinder.

[0027] In a possible implementation of the first aspect, the cylinder head is provided with a central exhaust valve, with two or more fuel valves surrounding the central exhaust valve.

[0028] According to a second aspect, a method for managing ammonia in a large two-stroke, single-flow scavenging turbocharged internal combustion engine is provided, the engine having at least one operating mode in which ammonia is the primary fuel, the engine comprising: At least one cylinder, the cylinder having a cylinder bushing, a reciprocating piston located in the cylinder bushing, and a cylinder head covering the cylinder. The combustion chamber is formed inside the cylinder and located between the reciprocating piston and the cylinder head. The ammonia fuel system is configured to supply pressurized ammonia to a fuel valve, which is located in the cylinder head or, alternatively, in the cylinder liner. The method includes: conveying excess gaseous ammonia from the fuel system to an ammonia absorption system; and absorbing the gaseous ammonia into water to form ammonia water.

[0029] In a possible implementation of the second aspect, the method includes separating liquid ammonia from gaseous ammonia derived from excess ammonia, preferably using a separation drum to separate liquid ammonia from gaseous ammonia derived from excess ammonia; conveying gaseous ammonia to an ammonia absorption system; and absorbing ammonia into water to form ammonia water.

[0030] In a possible implementation of the second aspect, the method includes: using ammonia water as fuel for an engine, or using ammonia water as a reducing agent for the SCR reactor of an engine.

[0031] These and other aspects will become apparent from the implementation methods described below. Attached Figure Description

[0032] In the following detailed sections of this disclosure, aspects, implementation methods, and forms will be described in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which: Figure 1This is a top front view of a large two-stroke diesel engine according to an example embodiment; Figure 2 yes Figure 1 A top-down side view of a large two-stroke engine; Figure 3 It is based on Figure 1 A schematic diagram of a large two-stroke engine; Figure 4 This is a schematic diagram of an engine having an ammonia fuel system, an ammonia removal system, and an ammonia absorption system according to the first embodiment; Figure 5 This is a schematic diagram of an engine having an ammonia fuel system, an ammonia removal system, and an ammonia absorption system according to the second embodiment. Detailed Implementation

[0033] In the following detailed description, the internal combustion engine will be described with reference to a large, two-stroke, low-speed, single-flow scavenging turbocharged internal combustion engine with a crosshead in an example embodiment. However, it should be understood that the internal combustion engine can be other types of engines. The large, two-stroke, low-speed, single-flow scavenging turbocharged internal combustion engine can be either a (high-pressure) or (low-pressure) type engine. In the (high-pressure) type, fuel is injected at or near the top dead center of the piston, i.e., compression ignition; in the (low-pressure) type, fuel is mixed with scavenging air before or during scavenging air compression, i.e., spark ignition. In the case of the (low-pressure) type, an ignition fluid such as fuel oil is typically used for "leader" ignition to ensure reliable ignition.

[0034] Figure 1 , Figure 2 and Figure 3 A large, low-speed, turbocharged, two-stroke diesel engine with a crankshaft 8 and a crosshead 9 is shown. Figure 3 A schematic diagram of a large, low-speed turbocharged two-stroke diesel engine with an intake and exhaust system is shown. In this example embodiment, the engine has six inline cylinders. Large, low-speed turbocharged two-stroke diesel engines typically have between four and fourteen inline cylinders supported by a cylinder block 23, which is carried by an engine frame 11. The engine can be used, for example, as a main engine in a ship or as a stationary engine in a power plant for operating generators. The total output of the engine can, for example, range from 1,000 kW to 110,000 kW.

[0035] In this example embodiment, the engine is a two-stroke, direct-fired, dual-fuel compression ignition engine with a scavenging port 18 located in the lower region of the cylinder liner 1 and a central exhaust valve 4 located at the top of each cylinder liner 1. The engine has at least one ammonia mode and at least one conventional fuel mode. In ammonia mode, the engine operates using ammonia fuel or amino fuel, and in conventional fuel mode, the engine operates using conventional fuels such as fuel oil (marine diesel) or heavy fuel oil.

[0036] Scavenging air is delivered from scavenging air receiver 2 to the scavenging port 18 of each cylinder 1. The piston 10, reciprocating between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1, compresses the scavenging air. Fuel (ammonia in ammonia mode) is injected at or near the TDC into the combustion chamber in the cylinder liner 1 via (high-pressure) fuel valves 50 arranged in the cylinder head 22. Combustion continues, generating exhaust gases. Each cylinder head 22 is provided with two or more fuel valves 50. The fuel valves 50 are configured to inject only one specific type of fuel, such as ammonia, and in this case, two or more fuel valves 54 are also provided to inject conventional fuel into the combustion chamber. Therefore, the engine will have four or more fuel valves. In cases where the fuel valves 50 are adapted to inject both ammonia and conventional fuel, each cylinder may be provided with two or more fuel valves 50. The fuel valves 50 are arranged in the cylinder head 22 and surround the central exhaust valve 4. Furthermore, in this embodiment, an additional, typically smaller fuel valve (not shown) is provided in the cylinder head for injecting ignition fluid, thereby ensuring reliable ignition of the ammonia fuel. The ignition fuel is, for example, dimethyl ether (DME) or fuel oil, but may also be another form of ignition enhancer such as hydrogen. Since the engine can be a dual-fuel engine, it may also be provided with a conventional fuel supply system (not shown) for supplying conventional fuel to the fuel valve 50. In this embodiment, the fuel valve 50' is arranged along the cylinder liner (shown by the interrupted line) and allows fuel to enter the cylinder liner before the piston 10 passes through the fuel valve 50' during its journey from the BDC to the TDC. Thus, the piston 10 compresses the mixture of scavenging air and fuel. Timing ignition at or near the TDC is triggered by a spark, laser, ignition fluid injection, etc. In the embodiment with the fuel valve 50', the pressure at which fuel is allowed to enter is substantially lower than the pressure at which fuel is injected in the embodiment where the fuel valve 50 is located in the cylinder head 22. Therefore, the pressure required for the fuel supply system 30 to deliver fuel can be significantly reduced, and / or, the turbocharger commonly used in the fuel valve 50 located in the cylinder head can be avoided.

[0037] When the exhaust valve 4 is open, the exhaust gas flows into the exhaust gas receiver 3 through the exhaust pipe associated with the cylinder, and continues through the selective catalytic reduction (SCR) reactor 28 through the first exhaust duct 19 to the turbine 6 of the turbocharger 5. From the turbine, the exhaust gas flows out through the second exhaust duct via the economizer 20 to the outlet 21 and into the atmosphere. The SCR reactor reduces emissions, specifically NOx emissions.

[0038] Turbine 6 drives compressor 7 via a shaft, and compressor 7 is supplied with fresh air through intake port 12. Compressor 7 delivers pressurized scavenging air to scavenging air duct 13 leading to scavenging air receiver 2. Scavenging air in scavenging air duct 13 passes through intercooler 14 for cooling scavenging air.

[0039] When the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2, i.e., under low or partial engine load, the cooled scavenging air is propelled by an auxiliary blower 16 that pressurizes the scavenging air flow, driven by an electric motor 17. Under higher engine load, the turbocharger compressor 7 delivers sufficient compressed scavenging air, and the auxiliary blower 16 is bypassed via a one-way valve 15 and the electric motor 17 is deactivated.

[0040] In ammonia mode, the engine operates using ammonia as the primary fuel, which is supplied to ammonia valve 50 at a relatively stable pressure and temperature. Ammonia can be supplied to ammonia valve 50 in either a liquid or gaseous phase. Liquid ammonia can be aqueous ammonia (an ammonia-water mixture).

[0041] Conventional fuel systems are known and are not shown or described in detail elsewhere. The ammonia fuel system 30 supplies liquid ammonia to the fuel valve 50 at an intermediate supply pressure (e.g., 30 to 80 bar). Alternatively, ammonia fuel is supplied to the ammonia valve 50 in the gaseous phase at a relatively lower supply pressure (e.g., 30 to 80 bar). In the case of a compression-ignition engine, the fuel valve 50 includes a booster that significantly increases the pressure of the ammonia fuel from intermediate to high pressure, allowing the ammonia fuel to be injected at a pressure higher than the engine's compression pressure. Typically, the injection pressure for compression-ignition engines is above 300 bar.

[0042] Reference Figure 4 The ammonia fuel system 30, including a scavenging and ammonia absorption system 60, is disclosed in more detail. Ammonia is stored in the liquid phase in a pressurized storage tank 31 at approximately 17 bar. Ammonia can be stored in the liquid phase in the ammonia storage tank 31 at a pressure above 8.6 bar and an ambient temperature of 20°C. However, ammonia is preferably stored at a pressure of approximately 17 bar or higher to maintain it in the liquid phase when the ambient temperature rises.

[0043] The low-pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 31 to the inlet of the medium-pressure supply pump 35. The low-pressure supply pump 33 forces liquid ammonia from the tank 31 through the filter device 34 to the inlet of the medium-pressure supply pump 35. The medium-pressure supply pump 35 forces the liquid ammonia through the medium-pressure ammonia supply line 36 to the fuel valve 50. A portion of the liquid ammonia supplied to the fuel valve 50 is injected into the engine's combustion chamber, while another portion of the liquid ammonia supplied to the fuel valve 50 returns to the ammonia return line 38, which connects the return port of the fuel valve 50 to the low-pressure supply line 32. Therefore, a portion of the liquid ammonia fuel is recycled to the inlet of the medium-pressure supply pump 35.

[0044] When operations using ammonia fuel are interrupted, for example, due to a malfunction in the ammonia fuel system 30 or other reasons requiring a switch to conventional fuel, the ammonia fuel system 30 is purged to remove ammonia from the system. At this point, the pressurized nitrogen source 40, such as the pressurized nitrogen container 40, is connected to the medium-pressure ammonia supply line 36 via a purge valve 41. Preferably, the pressurized nitrogen source 40, such as the pressurized nitrogen container 40, is connected to the medium-pressure ammonia supply line 36 immediately downstream of the medium-pressure supply pump 35 via the purge valve 41.

[0045] A first purge line 42, including a second purge valve 43, connects a medium-pressure ammonia supply line 36 to a knockout drum 46. A second purge line 44, including a third purge valve 45, connects an ammonia return line 38 to the knockout drum 46. During the purge operation, the first purge valve 41, the second purge valve 43, and the third purge valve 45 are opened, and pressurized nitrogen drives residual ammonia fuel from the ammonia fuel supply line 36 and the ammonia fuel return line 38 into the knockout drum 46. The knockout drum 46 is configured to separate liquid-phase ammonia fuel from gaseous-phase ammonia. A nitrogen discharge line 48, including a nitrogen discharge valve 49, connects the interior of the knockout drum 46 to the surrounding environment for discharging nitrogen from the knockout drum 46. A liquid-phase ammonia outlet is located in the lower region of the knockout drum 46 and connected to a recovery tank 57. In an embodiment, the liquid ammonia in the recovery tank 57 is delivered to an ammonia storage tank 31 for use as ammonia fuel. The gaseous-phase ammonia outlet of the knockout drum 46 is connected to an ammonia absorption system 60 via the third purge line 47.

[0046] The ammonia absorption system 60 includes at least one container that is at least partially filled with water during use to allow ammonia to be absorbed into the water to form ammonia solution. Ammonia solution—also known as aqueous ammonia—is a solution of ammonia in water.

[0047] This embodiment includes a pressure vessel 58 that is at least partially filled with water during use. The pressure vessel 58 is preferably cooled (cooling device not shown) because heat is generated when ammonia dissolves in water and the water's ability to absorb ammonia decreases as the water temperature increases. Therefore, the cooling device is configured to continuously lower the temperature of the water in the pressure vessel to optimize the water's ability to absorb ammonia in the pressure vessel 58.

[0048] Pressure vessel 58 has a gaseous ammonia inlet for receiving gaseous ammonia via pressure vessel ammonia supply conduit 59. Pressure vessel ammonia supply conduit 59 includes a check valve 73 to prevent fluid from returning from pressure vessel 58 to the third purge line 47. Pressure vessel 58 has an inlet for (fresh) water, which is connected via a conduit to a (fresh) water pressurization source 71. Herein, fresh water is water in which no significant amount of ammonia is dissolved and therefore it can still almost completely absorb ammonia. The water level in pressure vessel 58 is regulated between an upper and lower water level. Gaseous ammonia supplied to pressure vessel 58 is absorbed into the water to form ammonia water. The pressure in the pressure vessel is regulated and maintained at a suitable high pressure because water can absorb a higher amount of gaseous ammonia at higher pressures. Pressure vessel 58 is provided with an ammonia water outlet. The amount of fresh water allowed to enter pressure vessel 58 and the amount of ammonia water discharged from pressure vessel 58 are controlled to ensure sufficient capacity for ammonia absorption. The ammonia water outlet is connected via an ammonia water discharge conduit 75 to the third return line 55. The ammonia discharge conduit 75 includes a valve 76 for controlling the flow from pressure vessel 58 to the third return line 55. Ammonia is supplied from the third return line 5 to SCR reactor 28 to be used as a reducing agent in SCR reactor 28, or from the third return line 5 to low-pressure ammonia supply line 32 to be used as fuel in an engine, as described in more detail below. The third scavenging line 47 includes a pressure regulating valve 74 that opens when a predetermined pressure in the third scavenging line 47 has been exceeded. This predetermined pressure corresponds to the maximum pressure at which pressure vessel 58 can operate, ensuring that gaseous ammonia is directed to a cascade of three absorbers connected in series: first absorber 61, intermediate absorber 63, and final absorber 65. In another embodiment, the flow of gaseous ammonia from the third scavenging line 47 to pressure vessel 58 or to the cascade of water tanks 61, 63, 65 is controlled by an electronically controlled valve (not shown) instead of the pressure regulating system shown.

[0049] The final absorption tank 65 is provided with a fourth discharge port 66 connecting the final absorption tank 65 to the surrounding environment. In an embodiment, more than three absorption tanks are provided to obtain a lower concentration of ammonia in the atmosphere above water in the final absorption tank 65, and thus obtain a lower concentration of ammonia in the gas discharged through the fourth discharge port 66.

[0050] The absorption efficiency of the cascaded absorption tanks is maintained by periodically replacing the water in the final absorption tank 65 using a pressurized (desalinated) water source 71 and by reusing slightly contaminated water from upstream tanks. Therefore, water replaced by water from the water source 71 in the final tank 65, where some ammonia has been absorbed, is transported to the intermediate absorption tank 63 via a first water return line 67 controlled by a first water return valve 68. Similarly, water from the intermediate absorption tank 63 is transported to the first absorption tank 61 via a second water return line 69 controlled by a second water return valve 70. The system is configured to compensate for water evaporation in absorption tanks 61, 63, 65, and 66, and the water level in absorption tanks 61, 63, and 65, where ammonia water removed from the first ammonia tank 61 is maintained... Figure 4 The area between the minimum and maximum values ​​indicated by the dashed line.

[0051] Ammonia gas above the water in the first absorption tank 61 flows to the intermediate absorption tank 63 via the first ammonia discharge line 62. Ammonia gas above the water in the intermediate absorption tank 63 flows to the final absorption tank 65 via the second ammonia discharge line 64. This process is preferably driven by the pressure of the purging process.

[0052] The ammonia concentration in the fourth discharge unit 66 is low enough to allow discharge into the surrounding environment. However, if compliance with regulations is required, ammonia emissions from the exhaust mast can be further reduced by introducing an additional absorbent column with an acidic absorbent medium. The acid protonates NH3(aq) through the formation of ammonium hydroxide, thereby reducing the amount of ammonia released into the atmosphere.

[0053] The ammonia concentration in the water produced in the first absorption tank 61 is higher than the ammonia concentration in the water in the intermediate absorption tank 63, and the ammonia concentration in the water in the intermediate absorption tank 63 is higher than the ammonia concentration in the water in the final ammonia absorption tank 65.

[0054] Ammonia water from the first absorption tank 61 is removed from the first absorption tank 61 via a first ammonia water return line 51, which includes a return pump 52. A second ammonia water return line 53, which includes a first return valve 54, connects the first ammonia water return line 51 to a low-pressure ammonia supply line 32. Therefore, when the first return valve 54 is open, ammonia water with a relatively high ammonia concentration from the first absorption tank 61 mixes with fuel from the ammonia storage tank 31, and the ammonia absorbed by the ammonia absorption system 60 is reused as fuel for the engine. A third ammonia water return line 55, which includes a second return valve 56, connects the first ammonia water return line 51 to a reductant inlet associated with the SCR reactor 28. The reductant inlet may be part of the SCR reactor 28 or located in the exhaust gas flow path upstream of the SCR reactor 28. Therefore, when the second return valve 56 is open, the ammonia absorbed by the ammonia absorption system 60 is used as a reductant in the SCR reactor 28.

[0055] The cascade of tanks 61, 63, and 65 is entirely passive, meaning that no pumps or other auxiliary systems are required when ammonia absorption needs to be shut down. Therefore, the system is inherently reliable and available when needed.

[0056] In this embodiment, the low-pressure ammonia fuel line 32, the medium-pressure ammonia fuel line 36, and the ammonia return line 38 are wholly or partially constructed of double-walled pipes having a space between an inner and an outer pipe. In this embodiment, the space between the inner and outer pipes is connected to a purging system, thereby connecting any ammonia fuel accidentally leaking into the space between the inner and outer pipes to an ammonia absorption system 60 for absorption. Therefore, absorption in the ammonia absorption system 60 can prevent the accidental entry of ammonia into the surrounding environment in the event of any fuel line leak. Preferably, a detection system is provided that detects the presence of ammonia in the space between the inner and outer pipes, thereby allowing the ammonia operation to be stopped upon detection of ammonia in the space, followed by purging of the ammonia fuel system and absorption of residual ammonia into the absorption and purging system 60.

[0057] The electronic control unit 100 is connected via signal lines or wirelessly to the pumps and valves of the fuel system 30, the scavenging system, and the ammonia absorption system 60. The electronic control unit 100 is configured to control these components, for example, by adjusting the pump speed and by controlling the opening and closing of the various valves, to ensure the operation of the aforementioned fuel system and the scavenging and absorption system.

[0058] Figure 5 A second embodiment of the engine and its fuel system, scavenging system, and ammonia absorption system is shown. In this embodiment, structures and features that are identical or similar to those previously described or shown herein are indicated by the same reference numerals as previously used, for simplification. Figure 5 Implementation methods and basis Figure 4The implementation method is largely the same, except that the cascade of water tanks is replaced by a packed absorber 78. The packed absorber 78 is used for the absorption of ammonia gas and subsequent discharge of ammonia water. The gas-liquid (water) contact in the packed absorber 78 is continuous. Water flows downward through the packing surface in the tower, while gaseous ammonia moves upward countercurrently in the tower 78. The packed absorber 78 is a container with packed sections. The tower is filled with one or more stacked structured packing sections. The packed absorber 78 has an inlet for receiving ammonia gas, which is connected to a third purging line 47 via a pressure regulating valve 74. The packed absorber has an outlet for ammonia water, which is connected to a first ammonia water return line 51. A pressurized (dehydrated) water source 71 is connected to the packed absorber 78 and the inlet arranged above the structured packing sections. An exhaust 76 is provided for ventilating the space above the packing sections to the surrounding environment. The flow rate of water from the pressurized (fresh water) source 71 is adapted to the flow rate of gaseous ammonia entering the packed absorber 78. The amount of ammonia water collected at the bottom of the packed absorber 78 is regulated and delivered to an intermediate ammonia water storage tank (not shown) when necessary.

[0059] Various aspects and implementations have been described herein in conjunction with different embodiments. However, by studying the accompanying drawings, disclosure, and appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments in practicing the claimed subject matter. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0060] The reference numerals used in the claims should not be construed as limiting the scope. Unless otherwise stated, the drawings are intended to be read in conjunction with the specification (e.g., crosshairs, arrangement of parts, scale, extent, etc.) and will be considered an integral part of the entire written specification of this disclosure.

Claims

1. A large two-stroke, single-flow scavenging turbocharged internal combustion engine, the engine having at least one operating mode with ammonia as the main fuel, the engine comprising: - At least one cylinder having a cylinder bushing (1), a reciprocating piston (10) located in the cylinder bushing (1), and a cylinder cover (22) covering the cylinder. - A combustion chamber formed inside the cylinder (1) and located between the reciprocating piston (10) and the cylinder head (22). - An ammonia fuel system (30), the ammonia fuel system (30) being configured to supply pressurized ammonia to fuel valves (50, 50'), the fuel valves being disposed in the cylinder head (22), or, the fuel valves being disposed in the cylinder liner (1), - Ammonia absorption system (60). as well as - Ammonia discharge flow path (42, 44, 47). The ammonia discharge flow paths (42, 44, 47) connect the outlet of the ammonia fuel system (30) to the inlet of the ammonia absorption system (60). The ammonia absorption system (60) contains water during use to absorb ammonia supplied through the ammonia discharge path into the water, thereby forming ammonia water. The ammonia fuel system (30) includes a scavenging system configured to remove ammonia from the fuel system (30) to the ammonia absorption system (60). The ammonia fuel system (30) includes: a medium-pressure ammonia supply line (36); an ammonia return line (38); a first purging line (42) connecting the medium-pressure ammonia supply line (36) to the ammonia absorption system (60); and a second purging line (44) connecting the ammonia return line (38) to the ammonia absorption system (60).

2. The engine according to claim 1, wherein, The ammonia absorption system (60) includes at least one container (58, 61, 63, 65, 78), which is at least partially filled with water during use. Preferably, the at least one container (58, 61, 63, 65, 78) includes a water inlet for connection to a water source (71). Preferably, the at least one container (58, 61, 63, 65, 78) includes an ammonia outlet for discharge of the ammonia water.

3. The engine according to claim 2, wherein, The ammonia outlet is connected to the ammonia fuel system (30) for burning the ammonia in the engine.

4. The engine according to claim 2, comprising an SCR reactor (28) located in the exhaust gas flow path of the engine, wherein, The ammonia outlet is connected to the reducing agent inlet associated with the SCR reactor (28).

5. The engine according to claim 1, wherein, The ammonia absorption system (60) includes a pressure vessel (58) which is at least partially filled with water during use. Preferably, the pressure vessel (58) is provided with a cooling system for reducing the temperature of the pressure vessel (58). Preferably, the pressure vessel (58) includes a gaseous ammonia inlet for introducing gaseous ammonia. Preferably, the pressure vessel is connected to a water source (71). Preferably, the pressure vessel (58) has an ammonia outlet for discharging the ammonia water.

6. The engine according to claim 1, wherein, The ammonia absorption system (60) includes a packed absorption tower (78), preferably, the packed absorption tower (78) includes a gaseous ammonia inlet for introducing gaseous ammonia, preferably, the ammonia absorption system (60) is connected to a water source (71), and preferably, the ammonia absorption system (60) has an ammonia outlet for discharging the ammonia water.

7. The engine according to claim 1, wherein, The ammonia absorption system (60) includes a cascade of water tanks (61, 63, 65), which are at least partially filled with water during use. Preferably, the first water tank (61) includes a gaseous ammonia inlet and a gaseous ammonia outlet, a water inlet and an ammonia water outlet. Preferably, the subsequent water tanks (62, 63) include a gaseous ammonia inlet connected to the gaseous ammonia outlet of the first water tank (61) and an ammonia water outlet connected to the water inlet of the first water tank (61), and the subsequent water tanks (62, 63) include a gaseous ammonia outlet. Preferably, the cascade of the water tanks (61, 62, 65) is configured to allow the water flow to flow in the opposite direction to the flow of gaseous ammonia, wherein the upstream tank (61) during the gaseous ammonia flow has the highest concentration of ammonia in the water and the upstream tank (61) is provided with an ammonia water outlet, and the downstream tank (65) during the gaseous ammonia flow has the lowest concentration of ammonia in the water, preferably, the downstream tank (65) during the gaseous ammonia flow is provided with a discharge section for discharging gaseous material from the tank (65).

8. The engine according to claim 1, wherein the purging system includes a pressurized nitrogen source (40), preferably connected to the fuel system via a purging valve (41), and preferably, the purging system uses the ammonia discharge flow path to remove ammonia from the ammonia fuel system (30) to the ammonia absorption system (60).

9. The engine according to claim 1, wherein, The ammonia fuel system (30) includes valves (43, 45) for selectively connecting the medium-pressure ammonia supply line (36) and the ammonia return line (38) to the ammonia absorption system (60).

10. The engine according to claim 9, comprising a separation drum (46) located in the first purging line (42) and / or the second purging line (44), the separation drum (46) being configured to separate liquid ammonia from gaseous ammonia, the separation drum (46) including a gaseous ammonia outlet and a liquid ammonia outlet, the gaseous ammonia outlet of the separation drum (46) being connected to the ammonia absorption system (60), and preferably, the liquid ammonia outlet of the separation drum (46) being connected to a recovery tank (57), the recovery tank being connected to the ammonia fuel system (30).

11. The engine according to claim 1, wherein, The ammonia fuel system (30) includes supply lines (32, 35) and return lines (38), wherein the pipes forming the supply lines (32, 35) and the return lines (38) include double-walled pipes, and wherein the space between the inner pipe and the outer pipe of the double-walled pipe is fluidly connected to the ammonia absorption system (60) through the ammonia discharge path.

12. The engine according to claim 1, wherein, The ammonia fuel system (30) includes a liquid ammonia fuel tank (31) and a low-pressure ammonia supply line (32). The low-pressure ammonia supply line (32) connects the liquid ammonia fuel tank (31) to the inlet of a medium-pressure fuel pump (35) through the action of a low-pressure pump (33). Preferably, the fuel system (30) includes a medium-pressure fuel line (36) connecting the outlet of the medium-pressure pump (35) to the inlet of the fuel valve (50, 50'). Preferably, the fuel system (30) includes a return line (38) connecting the outlet of the fuel valve (50, 50') to the inlet of the medium-pressure fuel pump (35).

13. A method for managing ammonia in a large two-stroke, single-flow scavenging turbocharged internal combustion engine, the engine having at least one operating mode in which ammonia is the primary fuel, the engine comprising: - At least one cylinder having a cylinder bushing, a reciprocating piston (10) located in the cylinder bushing (1), and a cylinder head (22) covering the cylinder (1). - Combustion chamber (15), which is formed inside the cylinder (10) and located between the reciprocating piston (10) and the cylinder head (22), and - An ammonia fuel system (30), the ammonia fuel system (30) being configured to supply pressurized ammonia to fuel valves (50, 50'), the fuel valves being disposed in the cylinder head (22), or, the fuel valves being disposed in the cylinder liner (1), The ammonia fuel system (30) includes a scavenging system configured to remove ammonia from the fuel system (30) to the ammonia absorption system (60). The ammonia fuel system (30) includes: a medium-pressure ammonia supply line (36); an ammonia return line (38); a first purging line (42) connecting the medium-pressure ammonia supply line (36) to the ammonia absorption system (60); and a second purging line (44) connecting the ammonia return line (38) to the ammonia absorption system (60). The method includes the following steps: - Excess gaseous ammonia from the fuel system (30) is transported to the ammonia absorption system (60); and the gaseous ammonia is absorbed into water to form ammonia water.

14. The method of claim 13, comprising: The liquid ammonia derived from the excess ammonia is separated from the gaseous ammonia, preferably by using a separation drum (46) to separate the liquid ammonia derived from the excess ammonia from the gaseous ammonia; The gaseous ammonia is delivered to the ammonia absorption system (60); and the ammonia is absorbed into water to form ammonia water.

15. The method according to claim 13 or 14, comprising: The ammonia water is used as fuel for the engine, or as a reducing agent for the SCR reactor (28) of the engine.

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