Large two-stroke uniflow scavenged turbocharged internal combustion engine with ammonia absorption system

Abstract

To provide a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operation mode in which ammonia is used as main fuel.SOLUTION: An engine comprises: at least one cylinder having a cylinder liner, a reciprocating piston in the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber formed between the reciprocating piston in the cylinder and the cylinder cover; an ammonia fuel system (30) configured to supply pressurized ammonia to fuel valves disposed in the cylinder cover or the cylinder liner; and an ammonia evacuation flow path (42, 44, 47) that connects an outlet of the ammonia fuel system to an inlet of an ammonia absorption system. The ammonia absorption system makes ammonia water during use by causing ammonia supplied through the ammonia evacuation flow path to be absorbed in water.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The subject matter disclosed herein relates to a large, two-stroke, uniflow-scavenged, turbocharged internal combustion engine in at least one mode operating with ammonia as the fuel burned for a period of time.

[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. Their size, weight, and power output set them apart from other combustion engines, placing this type of compression ignition engine in a unique category.

[0003] Internal combustion engines have traditionally been run primarily on hydrocarbon fuels, such as fuel oils, like diesel oil, or fuel gases, like natural gas or petroleum gas. Combustion of hydrocarbon fuels produces carbon dioxide (CO 2 ), which can contribute to air pollution and climate change. Unlike impurities in petroleum fuels that produce by-product emissions, CO 2 The generation of CO is inevitable in the combustion of hydrocarbons. 2 The footprint depends on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Therefore, gaseous hydrocarbon fuels have a smaller footprint than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are more difficult and expensive to handle and store. 2 In order to reduce the footprint, non-hydrocarbon fuels have been considered.

[0004] Ammonia is a synthetic product derived from petroleum, biomass, and renewable energy sources (wind, solar, hydroelectric, geothermal). Ammonia produced using renewable energy sources has a virtually zero carbon footprint when burned, or CO 2 or SO x , particulate matter and unburned hydrocarbon emissions are virtually zero.

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

[0006] Ammonia is hazardous and has a pungent odor. For this reason, it must be prevented from escaping from the engine. When operation with ammonia is stopped and changed to, for example, operation with conventional fuels, the ammonia in the fuel system must be purged (removed), but the removed ammonia cannot simply be released into the surrounding environment. Other scenarios where excess ammonia must be treated can arise, for example, due to leaks, engine failure, etc. There is a need to provide the engine with an ammonia solution for such scenarios.

[0007] CN112696289 discloses a liquid ammonia fuel supply system and a fuel recycling system for ships. The system includes an ammonia fuel engine, a liquid ammonia supply system, a liquid ammonia recycling system, and a liquid ammonia nitrogen purge ventilation system. The system realizes high-pressure (70 bar, 45+ / -10°C) liquid supply of liquid ammonia fuel for ships. The unconsumed liquid ammonia fuel in the pipeline is recycled, which can save a large amount of fuel, while the amount of ammonia fuel discharged to the ventilation tower is reduced, improving the safety of the ship and personnel. Summary of the Invention

[0008] The object is to provide a large two-stroke uniflow scavenged turbocharged internal combustion engine which solves or at least mitigates the above mentioned problems.

[0009] These and other objects are achieved by means of the features set forth in the independent claims. More particular implementations will become apparent from the dependent claims, the detailed description and the drawings.

[0010] According to a first aspect, there is provided a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which the primary fuel is ammonia. The engine comprises: at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder liner; a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed in the cylinder cover or the cylinder liner; an ammonia absorption system; the ammonia exhaust flow path connecting an outlet of the ammonia fuel system to an inlet of the ammonia absorption system; the ammonia absorption system having water for absorbing ammonia supplied through the ammonia discharge passage in use into the water to form aqueous ammonia.

[0011] The use of an exhaust flow path and an ammonia absorption system allows for the sudden need to deal with excess ammonia from the engine, such as when an ammonia-fueled operation is shut down or leaks occur, requiring the ammonia to be vented. By dissolving the ammonia in an absorption system with water, a significant amount of ammonia can be stored in water and ammonia water can be produced. The ammonia water can be used as a fuel in the engine or as a reducing agent in an SCR reactor to clean the exhaust.

[0012] The inventors of the present application have realized that the solubility of ammonia generally increases when the water temperature is low. By adding a cooling circuit device to cool the water, the actual amount of ammonia regenerated in the regeneration system (tank) is increased, and high regeneration rates can be achieved.

[0013] In one example of an implementation of the first approach, the ammonia absorption system comprises at least one container that is at least partially filled with water during use, the at least one container preferably comprising a water inlet for connecting a water source, and preferably comprising an ammonia water outlet for discharging the ammonia water.

[0014] In one implementation of the first aspect, the engine is a dual fuel engine, preferably with a fuel system that supplies conventional fuels to the engine cylinders.

[0015] In one example implementation of the first aspect, the ammonia water outlet is connected to the ammonia fuel system to combust the ammonia water within the engine.

[0016] In one embodiment of the first aspect, the engine includes an SCR reactor in an exhaust flow path, and the ammonia water outlet is connected to a reductant inlet associated with the SCR reactor.

[0017] In one example of an implementation of the first aspect, the ammonia absorption system comprises a pressure vessel that is at least partially filled with water during use, the pressure vessel preferably being equipped with a cooling system for reducing a temperature of the pressure vessel, the pressure vessel preferably comprising a gas phase ammonia inlet for taking in gas phase ammonia, the pressure vessel preferably being connected to a water source, and the pressure vessel preferably comprising an ammonia water outlet for discharging ammonia water.

[0018] In one example implementation of the first aspect, the ammonia absorption system comprises a bracketed absorption tower, the absorption tower preferably comprising a gas phase ammonia inlet for taking in gas phase ammonia, the absorption tower preferably being connected to a water source, and the absorption tower preferably comprising an aqueous ammonia outlet for discharging aqueous ammonia.

[0019] In one example of an implementation of the first aspect, the ammonia absorption system comprises a cascade of water tanks each at least partially filled with water in use, a first water tank preferably having a gas phase ammonia inlet and a gas phase ammonia outlet, a water inlet, and an aqueous ammonia outlet, a subsequent water tank preferably having a gas phase ammonia inlet connected to the gas phase ammonia outlet of the first water tank, an aqueous ammonia outlet connected to the water inlet of the first water tank, and a gas phase ammonia outlet, the cascade preferably configured for water flow in a counter direction to the flow of gas phase ammonia, the water tank most upstream of the gas phase ammonia flow in use has the highest ammonia concentration in the water in the tank and is provided with an aqueous ammonia outlet, and the water tank most downstream of the gas phase ammonia flow in use has the lowest ammonia concentration in the water in the tank and is preferably provided with a vent for exhausting gas phase material from the tank.

[0020] In one example of an implementation of the first aspect, the ammonia fuel system includes a purge system configured to exhaust ammonia from the ammonia fuel system to the ammonia absorption system, the purge system preferably including a pressurized nitrogen source, the pressurized nitrogen source preferably connected to the ammonia fuel system via a purge valve, and the purge system preferably uses the ammonia exhaust flow path to purge ammonia from the ammonia fuel system to the ammonia absorption system.

[0021] In one example of an implementation of the first aspect, the ammonia fuel system includes a medium-pressure ammonia supply line and an ammonia return line, a first purge line connecting the medium-pressure ammonia supply line to the ammonia absorption system, and a second purge line connecting the ammonia return line to the ammonia absorption system, and preferably includes a valve for selectively connecting the medium-pressure ammonia supply line and the ammonia return line to the ammonia absorption system.

[0022] In one example of an implementation form of the first approach, it is preferable that the first purge line and / or the second purge line are provided with a knockout drum, the knockout drum is configured to separate gas phase ammonia from liquid phase ammonia, the knockout drum has a gas phase ammonia outlet and a liquid phase ammonia outlet, the gas phase ammonia outlet of the knockout drum is connected to the ammonia absorption system, and the liquid phase ammonia outlet is connected to a recovery tank that is connected to the ammonia fuel system.

[0023] In one example of an implementation form of the first aspect, the ammonia fuel system includes a supply line and a return line, the piping forming the supply line and the return line has a double-walled pipe, and the space between an inner tube and an outer tube of the double-walled pipe is fluidly connected to the ammonia absorption system by the ammonia exhaust flow path.

[0024] In one example of an implementation form of the first aspect, the ammonia fuel system includes a liquid phase ammonia fuel tank and a low pressure ammonia supply line connecting the liquid phase ammonia fuel tank to an inlet of a medium pressure fuel pump by operation of a low pressure pump, the ammonia fuel system preferably includes a medium pressure fuel line connecting an outlet of the medium pressure fuel pump to an inlet of the fuel valve, and the ammonia fuel system preferably includes a return line connecting an outlet of the fuel valve to the inlet of the medium pressure fuel pump.

[0025] In one example of an implementation of the first approach, the at least one cylinder is provided with a scavenging port in a lower region thereof.

[0026] In one example of an implementation form of the first aspect, an exhaust valve is provided in a center of the cylinder, and two or more fuel valves are arranged around the exhaust valve.

[0027] According to a second aspect, there is provided a method for managing ammonia in a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which the primary fuel is ammonia, said engine comprising: At least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder liner; a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed in the cylinder cover or the cylinder liner; And the method includes conveying excess gas phase ammonia from the ammonia fuel system to the ammonia absorption system and absorbing the excess gas phase ammonia in water to form aqueous ammonia.

[0028] In one example implementation of the second approach, the method includes separating liquid and gas phase ammonia obtained from the excess gas phase ammonia, preferably using a knockout drum, transferring the gas phase ammonia to the ammonia absorption system, and absorbing the transferred ammonia in water to form aqueous ammonia.

[0029] In one example implementation of the second aspect, the method includes using the aqueous ammonia as a fuel for the engine or as a reducing agent in an SCR reactor for the engine.

[0030] These and other aspects will become more apparent from the examples described below. [Brief description of the drawings]

[0031] Various concepts, embodiments, and implementation examples will be described in detail below with reference to exemplary embodiments shown in the drawings. [Figure 1] FIG. 1 shows a front view of a large two-stroke diesel engine according to an exemplary embodiment. [Diagram 2] FIG. 2 is a diagram showing an overview of the large two-stroke engine of FIG. 1 as seen from the rear. [Diagram 3] FIG. 2 is a schematic representation of the large two-stroke engine of FIG. [Figure 4] 1 is a schematic representation of an engine having an ammonia fuel system, an ammonia purge system, and an ammonia absorption system according to a first embodiment. [Diagram 5] 1 is a schematic representation of an engine according to a second embodiment, also having an ammonia fuel system, an ammonia purge system, and an ammonia absorption system. Detailed explanation

[0032] In the following detailed description, the internal combustion engine is described with reference to an example crosshead type large slow speed two-stroke uniflow scavenging turbocharged internal combustion engine. It should be noted that in some cases the internal combustion engine can be another type of engine. A large two-stroke slow speed uniflow scavenging turbocharged internal combustion engine can be a compression ignition type (i.e. high pressure type) engine, in which fuel is injected near or at the top dead center of the piston, or a spark ignition type (i.e. low pressure type) engine, in which the scavenging air is mixed with the fuel before or during compression. In the latter case, a pilot ignition with an additive liquid (e.g. fuel oil) is usually provided to ensure ignition.

[0033] 1-3 depict a turbocharged large slow-speed two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a turbocharged large slow-speed two-stroke diesel engine together with its intake and exhaust systems. In this embodiment, the engine has six cylinders in series. A turbocharged large slow-speed two-stroke diesel engine usually has 4 to 14 cylinders arranged in series. The cylinders are carried in a cylinder frame 23. The cylinder frame 23 is carried in an engine frame 11. Such an engine can also be used, for example, as a main engine of a ship or as a stationary engine for driving a generator in a power plant. The total power output of the engine can be, for example, between 1000 kW and 110000 kW.

[0034] The engine in this embodiment is a two-stroke uniflow compression ignition type binary engine, and each cylinder liner 1 is provided with a scavenging port 18 in its lower region and an exhaust valve in its top center. The engine has at least one ammonia mode and at least one conventional fuel mode. In the ammonia mode, the engine is operated with ammonia fuel or an ammonia-based fuel. In the conventional fuel mode, the engine is operated with conventional fuel, such as fuel oil (marine diesel fuel) or heavy oil.

[0035] The scavenging air is led to the scavenging ports 18 of each cylinder 1 through the scavenging 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. Fuel (ammonia in the ammonia mode) is injected into the combustion chamber in the cylinder liner 1 at or near TDC through a number of (high pressure) fuel valves 50 arranged in the cylinder cover 22. Combustion occurs following the injection of the fuel, and exhaust is generated. Two or more fuel valves 50 are provided in each cylinder cover 22. The fuel valves 50 may be configured to inject only one specific type of fuel (e.g. ammonia). In that case, two or more fuel valves 54 for injecting conventional fuel into the combustion chamber would also be provided. In such a case, the engine would therefore have four or more fuel valves. If the fuel valves 50 are configured to be able to inject both ammonia and conventional fuel, the number of fuel valves 50 provided in each cylinder could be two or more. The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4, which is arranged in the center of the cylinder cover 22. Although not shown, in some embodiments, an additional (usually small) fuel valve may be arranged in the cylinder cover, 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, it may also be other forms of ignition enhancer, such as hydrogen. Since the engine may be a dual-engine engine, the engine may be equipped with a conventional fuel supply system (not shown) for supplying conventional fuel to the fuel valve 50. In some embodiments, a fuel valve 50' is arranged along the cylinder liner (shown in dashed lines). The fuel valve 50' introduces fuel into the cylinder liner when the piston 10 is on its way from BDC to TDC and before it passes the fuel valve 50'. The piston 10 then compresses the mixture of scavenging air and fuel. Ignition is timed at or near TDC. Ignition is achieved by a spark, a laser, injection of ignition fluid, etc. In the embodiment having the fuel valve 50', the pressure at which fuel is admitted is significantly lower than the pressure at which fuel is injected in the embodiment having the fuel valve 50 in the cylinder cover 22.As a result, the pressure required for the fuel supply system 30 to deliver fuel may be significantly lower and / or a pressure booster that is often used with the fuel valve 50 located in the cylinder cover 22 may not be necessary.

[0036] When the exhaust valve 4 opens, the exhaust passes through an exhaust duct in the cylinder 1 to an exhaust receiver 3, then through a selective catalytic reduction reactor (SCR reactor) 28, through a first exhaust pipe 19 and on to the turbine 6 of the turbocharger 5. From there, the exhaust passes through a second exhaust pipe 25 to an economizer 20 and is then discharged to the atmosphere through an outlet 21. The SCR reactor reduces the amount of emissions in the exhaust, particularly NOx.

[0037] The turbine 6 drives the compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12. The compressor 7 sends the compressed scavenging air to 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.

[0038] 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. At high engine loads, the turbocharger compressor 7 can provide sufficiently compressed scavenging air, so that the auxiliary blower 16 is bypassed by the non-return valve 15 and the electric motor 17 is switched off.

[0039] In ammonia mode, the engine is operated with ammonia as the primary fuel. Ammonia is supplied to the ammonia valve 50 at a nearly constant pressure and temperature. Ammonia may be supplied to the ammonia valve 50 in liquid or gas phase. Liquid phase ammonia may be aqueous ammonia, i.e., an aqueous ammonia solution.

[0040] Conventional fuel systems are not shown or described in detail since they are well known. The ammonia fuel system 30 supplies ammonia in liquid phase at an intermediate supply pressure (e.g. 30-80 bar) to the ammonia valve 50. Alternatively, the ammonia fuel is supplied to the ammonia valve 50 in gas phase at a relatively low supply pressure (e.g. 8-30 bar). In the case of a compression ignition engine, the fuel valve 50 includes a pressure booster which significantly increases the pressure of the ammonia fuel. The pressure booster increases the pressure of the ammonia fuel from intermediate pressure to high pressure, thereby allowing the ammonia fuel to be injected at a pressure higher than the compression pressure of the engine. Typically, the injection pressure of a compression ignition engine is higher than 300 bar.

[0041] Referring to Figure 4, the ammonia fuel system 30 is shown in detail along with the ammonia purge system and the ammonia Kyushu system 60. Ammonia is stored in liquid phase at approximately 17 bar in pressurized storage tank 31. Ammonia can be stored in liquid phase in ammonia storage tank 31 at 8.6 bar or higher at an ambient temperature of 20°C. However, it is preferred to store ammonia at 17 bar or higher to maintain the liquid phase even as ambient temperatures increase.

[0042] A 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. A low-pressure supply pump 33 applies pressure to the liquid phase ammonia from the tank 31 to pass through a filter device 34 to the inlet of the medium-pressure supply pump 35. The medium-pressure supply pump 35 pumps the liquid phase ammonia from the medium-pressure ammonia supply line 36 to the fuel valve 50. A part of the liquid phase ammonia supplied to the fuel valve 50 is injected into the combustion chamber of the engine, while another part is returned to the ammonia return line 38. The ammonia return line 38 connects the return port of the fuel valve 50 to the low-pressure supply line 32. Thus, a part of the liquid phase ammonia fuel is recycled to the inlet of the medium-pressure supply pump 35.

[0043] When operation on ammonia fuel is stopped, for example due to a failure of the ammonia fuel system 30 or another reason to switch to conventional fuel, the ammonia fuel system 30 is purged to remove ammonia from the system. Here, a source of pressurized nitrogen 40 (e.g., pressurized nitrogen container 40) is connected through purge valve 41 to medium pressure ammonia supply line 36, preferably just downstream of medium pressure supply pump 35.

[0044] A first purge line 42 including a second purge valve 43 connects the medium pressure ammonia supply line 36 to the knockout drum 46. A second purge line 44 including a third purge valve 45 connects the ammonia return line 38 to the knockout drum 46. In a purging operation, the first purge valve 41, the second purge valve 43, and the third purge valve 45 are opened and pressurized nitrogen pushes residual ammonia fuel from the ammonia supply line 36 and the ammonia return line 38 to the knockout drum 46. The knockout drum 46 is configured to separate liquid phase ammonia from gas phase ammonia. A nitrogen vent line 48 including a nitrogen vent valve 49 connects the inside and outside of the knockout drum 46 and releases nitrogen from the knockout drum 46. A liquid phase ammonia outlet is provided in a lower region of the knockout drum 46 and connects to a recovery tank 57. In some embodiments, the liquid phase ammonia in the recovery tank 57 is conveyed to the ammonia storage tank 31 and used as ammonia fuel. The vapor phase ammonia outlet of knockout drum 46 is connected to an ammonia absorption system 60 through a third purge line 47 .

[0045] The ammonia absorption system 60 comprises at least one vessel which, when in use, is at least partially filled with water so that ammonia is absorbed by the water to form aqueous ammonia.

[0046] Ammonia water (aqueous ammonia) is an aqueous solution of ammonia.

[0047] This embodiment comprises a pressure vessel 58 which is at least partially filled with water when in use. The pressure vessel 58 is preferably chilled. Cooling means are not shown. This is because heat is generated when ammonia dissolves in water, and as the water temperature increases the ammonia absorption capacity of the water decreases. Thus, cooling means are arranged to keep the temperature of the water in the pressure vessel 58 low so as to optimise the ammonia absorption capacity of the water in the pressure vessel 58.

[0048] The pressure vessel 58 has a vapor phase ammonia inlet for receiving vapor phase ammonia through a pressure vessel ammonia supply line 59. The pressure vessel ammonia supply line 59 has a check valve 73 to prevent liquid from returning from the pressure vessel 58 to the third purge line 47. The pressure vessel 58 has an inlet for water (fresh water). This inlet is connected through a line to a source of pressurized water (fresh water) 71. As used herein, "fresh water" means water that is substantially free of dissolved ammonia and has a nearly complete capacity to absorb ammonia. The height of the water in the pressure vessel 58 is adjusted between an upper limit and a lower limit. The vapor phase ammonia supplied to the pressure vessel 58 is absorbed by the water to form aqueous ammonia. The pressure in the pressure vessel is adjusted and maintained at a suitable high pressure to allow the water to absorb a larger amount of vapor phase ammonia. The pressure vessel 58 is provided with an aqueous ammonia outlet. The amount of fresh water allowed to enter the pressure vessel 58 and the amount of aqueous ammonia discharged from the pressure vessel 58 are adjusted to ensure sufficient capacity to absorb ammonia. The ammonia water outlet is connected to the third return line 55 through an ammonia water discharge pipe 75. The ammonia water discharge pipe 75 has a valve 76 to control the flow from the pressure vessel 58 to the third return line 55. From the third return line 55, the ammonia water is sent to the SCR reactor 28 to be used as a reductant therein, or to the low pressure ammonia supply line 32 to be used as fuel in the engine, as will be explained in more detail below. The third purge line 47 has a pressure control valve 74. The pressure control valve 74 opens when the pressure in the third purge line 47 exceeds a predetermined value. This predetermined pressure corresponds to the maximum pressure at which the pressure vessel 58 can operate. When this predetermined pressure is exceeded, the gas phase ammonia is sent to a cascade of three absorption tanks (the first absorption tank 61, the intermediate absorption tank 63, and the final absorption tank 65) in series. In another embodiment, the controlled flow of gas phase ammonia from the third purge line 47 to the pressure vessel 58 or the cascade of water tanks 61, 63, 65 is controlled by an electronically controlled valve, not shown, instead of the pressure control system shown.

[0049] The final absorption tank 65 is provided with a fourth vent 66 which connects the final absorption tank 65 to the outside world. In some embodiments there are more than three absorption tanks. This is to provide a lower ammonia concentration above the water in the final absorption tank and thus a lower ammonia concentration in the gas exiting the fourth vent 66.

[0050] The efficiency of absorption by the cascade of absorption tanks is maintained by periodically replacing the water in the final absorption tank 65. This water is supplied from a source 71 of pressurized water (fresh water). The water containing some ammonia is reused in the upstream tanks. Thus, the water in the final tank 65 that has absorbed some ammonia is replaced by water from the water source 71, which is sent to the intermediate absorption tank 63 through a first water return line 67 controlled by a first water return valve 65. Similarly, water from the intermediate absorption tank 63 is sent to the first absorption tank 61 through a second water return line 69 controlled by a second water return valve 70. The system is configured to compensate for the water that evaporates from the absorption tanks 61, 63, 65 and the ammonia water that is removed from the first absorption tank 61. That is, the water height in the absorption tanks 61, 63, 65 is maintained between a minimum height and a maximum height, as shown by the dashed lines in FIG. 4.

[0051] The ammonia vapor above the water in the first absorption tank 61 flows through a first ammonia discharge line 62 to the intermediate absorption tank 63. The ammonia vapor above the water in the intermediate absorption tank 63 flows through a second ammonia discharge line 64 to the final absorption tank 65. This process is preferably accomplished under the pressure of the purge process.

[0052] The ammonia concentration in the fourth vent 66 is low enough that it can be permitted to be discharged to the environment. However, if necessary to comply with regulations, the amount of ammonia released from the ventilation tower can be further reduced by using additional absorption columns. The absorption medium used in such absorption columns is an acid. The acid adds protons to the ammonia in aqueous solution, forming ammonium hydroxide. Thus, the amount of ammonia released to the environment is reduced.

[0053] During operation, the ammonia concentration of the water in first absorption tank 61 is higher than the ammonia concentration of the water in intermediate absorption tank 63 , which in turn is higher than the ammonia concentration of the water in final absorption tank 65 .

[0054] The ammonia water in the first absorption tank 61 is removed from the first absorption tank 61 through a first ammonia water return line 51 having a return pump 52. A second ammonia water return line 52 having a first return valve 54 connects the first ammonia water return line 51 to the low pressure ammonia supply line 32. Thus, when the first return valve 54 is opened, the relatively high concentration ammonia water from the first absorption tank 61 mixes with the fuel from the ammonia storage tank 31. Thus, the ammonia absorbed by the ammonia absorption system 60 is reused as fuel in the engine. A third ammonia water return line 55 having a second return valve 56 connects the first ammonia water return line 51 to a reductant inlet associated with the SCR reactor 28. This reductant inlet may be part of the SCR reactor 28 or may be provided in the exhaust path upstream of the SCR reactor 28. When the second return valve 56 is opened, the ammonia absorbed by the ammonia absorption system 60 is reused as a reductant in the SCR reactor 28.

[0055] The cascade of water tanks 61, 63, 65 is a completely passive element, i.e. there are no pumps etc. or any auxiliary systems available in case it is necessary to stop the absorption of ammonia, making the system inherently reliable and available when needed.

[0056] In some embodiments, the low pressure ammonia supply line 32, the medium pressure ammonia supply line 36, and the ammonia return line 38 are fully or partially configured as double walled pipes with a space between the inner and outer pipes. In such an embodiment, the space between the inner and outer pipes is connected to a purge system, and any ammonia fuel that unintentionally leaks into the space is connected to an ammonia absorption system 60 for absorption. Thus, even if a leak occurs from these fuel lines, unintentional release of ammonia into the surrounding environment is prevented through absorption by the ammonia absorption system 60. A detection system is preferably provided to detect the presence of ammonia in the space between the inner and outer tubes. Then, when ammonia is detected in the space, it is possible to stop the engine from running on ammonia, followed by purging the ammonia fuel system and absorbing the remaining ammonia by the ammonia absorption system 60.

[0057] An electronic control unit 100 is connected, by wire or wirelessly, to the pumps and valves of the fuel system 30, the purge system, and the ammonia absorption system 60. The electronic control unit 100 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, the purge system, and the ammonia absorption system to operate as described above.

[0058] FIG. 5 shows a second embodiment of the engine, which also includes a fuel system, a purge system, and an ammonia absorption system. In this embodiment, features and structures similar to those already described or illustrated are given the same reference numerals as before. The embodiment of FIG. 5 is essentially the same as the embodiment of FIG. 4, except that the cascade of water tanks is replaced by a bundled absorption tower 78. The absorption tower 78 is used for the absorption of ammonia and the subsequent discharge of the ammonia water. The contact between the gas and the liquid (water) in the absorption tower 78 is continuous. In the tower 78, the water flows downwards over the bundled surface, while the gas phase ammonia moves in the opposite direction, upwards, in the tower 87. The absorption tower 78 is a vessel with a packed section. The absorption tower 78 has one or more packed structures, which are stacked. The absorption tower 78 has an inlet for receiving ammonia gas, which is connected to the third purge line 47 via the pressure control valve 74. The absorber tower 78 also has an outlet for aqueous ammonia, the outlet being connected to the first aqueous ammonia return line 51. The inlet is disposed above the packing structure. A source of pressurized water (fresh water) 71 is connected to the inlet of the absorber tower 78. A vent 76 is provided to ventilate the space above the packing structure. The flow rate of water from the source of pressurized water (fresh water) 71 is adapted to match the flow rate of gas-phase ammonia to the absorber tower 78. The amount of aqueous ammonia collected at the bottom of the absorber tower 78 is regulated and transferred to an intermediate aqueous ammonia storage tank (not shown) as required.

[0059] Many aspects and implementations have been described with some examples. However, upon review of 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 examples in implementing the claimed invention. The words "comprise", "have", and "include" in the claims do not exclude the presence of elements or steps not recited. Even if the number of elements recited in the claims is not explicitly stated as being plural, it does not exclude the presence of the elements in plural.

[0060] Any 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 and are an integral part of this disclosure.

Claims

1. 1. A large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which the primary fuel is ammonia, said engine comprising: at least one cylinder having a cylinder liner, a reciprocating piston within said cylinder liner, and a cylinder cover thereover; a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve located in the cylinder cover or the cylinder liner; a purge system for purging the ammonia fuel system; a separation means for separating gaseous ammonia from residual ammonia fuel discharged by purging through said purge system; Along with providing Equipped with an ammonia absorption and ammonia water generation system, The ammonia absorption / ammonia water production system is configured to be supplied with the gaseous ammonia separated by the separation means, and is configured to supply water for absorbing the gaseous ammonia into water to form ammonia water from a source of fresh water. institution.

2. The engine of claim 1 , configured to utilize the aqueous ammonia produced by the ammonia absorption and aqueous ammonia production system as a reducing agent in an SCR reactor.

3. 2. An engine as set forth in claim 1 wherein said separating means is a knockout drum.

4. 10. The engine of claim 1, wherein the ammonia absorption and aqueous ammonia generation system comprises a pressure vessel that is at least partially filled with water during use, the pressure vessel being equipped with a cooling system for reducing the temperature of the pressure vessel.

5. 5. An engine according to claim 1, wherein the ammonia absorption and ammonia-water production system comprises a cascade of multiple water tanks, each of which is at least partially filled with water during use, the cascade of multiple water tanks having a first water tank and a subsequent water tank, the first water tank having a water inlet and an ammonia-water outlet, the subsequent water tank having an ammonia-water outlet connected to the water inlet of the first water tank, and a vapor-phase ammonia outlet.

6. 6. The engine of claim 5, wherein the first water tank has a vapor phase ammonia inlet and a vapor phase ammonia outlet, and the subsequent water tank has a vapor phase ammonia inlet connected to the vapor phase ammonia outlet of the first water tank.

7. 7. An engine as claimed in claim 6, wherein the cascade is configured for a flow of water in a counter direction to the flow of gaseous ammonia, the water tank most upstream in the flow of gaseous ammonia in use having the highest ammonia concentration in the water tank and being provided with an ammonia-water outlet, and the water tank most downstream in the flow of gaseous ammonia in use having the lowest ammonia concentration in the water tank.

8. 8. An engine as set forth in claim 7, wherein said most downstream water tank is provided with a vent for venting vapor phase materials therefrom.

9. 5. The engine of claim 1, wherein the ammonia absorption and ammonia water generation system comprises a unitary absorption tower for counter-flow contact of vapor-phase ammonia and water.

10. 5. An engine according to any preceding claim, wherein the purge system comprises a pressurized nitrogen source connected to the ammonia fuel system through a purge valve.

11. 5. The engine according to claim 1, wherein at least a portion of the ammonia fuel system comprises a double-walled pipe, and a space between an inner pipe and an outer pipe of the double-walled pipe is connected to the ammonia absorption and ammonia water production system to discharge leaked ammonia.

12. 1. A large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which the primary fuel is ammonia, said engine comprising: at least one cylinder having a cylinder liner, a reciprocating piston within said cylinder liner, and a cylinder cover thereover; a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve located in the cylinder cover or the cylinder liner; - Ammonia absorption and ammonia water generation system; an ammonia discharge path connecting an outlet of the ammonia fuel system to an inlet of the ammonia absorption and ammonia water production system; a purge gas supply; Equipped with the ammonia absorption and ammonia water production system has water for absorbing ammonia supplied through the ammonia discharge path into the water during use to form ammonia water; The ammonia fuel system comprises: a medium pressure ammonia supply line and an ammonia return line; a first purge line branching off from the medium-pressure ammonia supply line downstream of a point where the purge gas supply source is connected to the medium-pressure ammonia supply line, and connecting the medium-pressure ammonia supply line to the ammonia absorption / ammonia water production system; a second purge line connecting the ammonia return line to the ammonia absorption and aqueous ammonia production system; Equipped with institution.

13. 13. An engine as set forth in claim 12 wherein said purge gas source comprises a pressurized nitrogen source connected to said medium pressure ammonia supply line through a purge valve.

14. 13. The engine of claim 12, further comprising a knockout drum in the first purge line and / or the second purge line, the knockout drum configured to separate gas phase ammonia from liquid phase ammonia, the gas phase ammonia being directed to the ammonia absorption and aqueous ammonia production system, and the liquid phase ammonia being directed to a recovery tank.

15. 13. The engine of claim 12, wherein the first purge line and the second purge line include valves for selectively connecting the medium pressure ammonia supply line and the ammonia return line to the ammonia absorption and aqueous ammonia generation system.

16. 13. The engine of claim 12, further comprising an electronic control unit configured to control operation of pumps and valves in the ammonia fuel system, the purge gas supply, and the ammonia absorption and aqueous ammonia production system.

17. 17. An engine according to any one of claims 12 to 16, wherein the ammonia absorption and aqueous ammonia production system comprises a pressure vessel which is at least partially filled with water during use, the pressure vessel being provided with cooling means for reducing the temperature of the water to increase the solubility of ammonia.

18. 17. An engine according to any one of claims 12 to 16, wherein the ammonia absorption / ammonia-water production system includes a cascade of multiple water tanks, the cascade is configured so that gas-phase ammonia and water flow in opposite directions to each other, thereby causing the gas-phase ammonia to be absorbed by the water, and a vent is provided in the most downstream water tank of the cascade.

19. 17. The engine of claim 12, wherein the ammonia absorption and ammonia-water production system comprises a block of absorption towers configured to counter-flow and contact vapor-phase ammonia and water.

20. 17. An engine according to any one of claims 12 to 16, wherein the ammonia fuel system has a double-walled pipe for at least a portion of the medium-pressure ammonia supply line and / or the ammonia return line, and a space between an inner tube and an outer tube of the double-walled pipe is fluidly communicable between the ammonia absorption and ammonia-water production system.

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