Large two-stroke uniflow scavenged turbocharged internal combustion engine with water regeneration system for ammonia absorption system, and method for managing ammonia for such engine

Abstract

To provide a large two-stroke uniflow scavenged turbocharged internal combustion engine and a method of managing ammonia in such engine.SOLUTION: A method of managing ammonia in a large two-stroke uniflow scavenged turbocharged internal combustion engine comprises conveying excess gas phase ammonia from an ammonia fuel system (30) to an ammonia absorption system (60) and absorbing the excess gas phase ammonia in water thereby forming ammonia water, conveying the ammonia water to a distillation apparatus (80), and separating water and ammonia in the distillation apparatus (80).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 on ammonia.

[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 powered primarily by hydrocarbon fuels, such as fuel oils like diesel and fuel gases like natural gas or petroleum gas. Combustion of hydrocarbon fuels produces greenhouse gases, including carbon dioxide, which can contribute to air pollution and climate change. Unlike impurities in petroleum fuels, which produce by-product emissions, CO2 emissions are inevitable when hydrocarbons are burned. The energy density and CO2 footprint 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 synthetic compound derived from petroleum, biomass, and renewable energy sources. Ammonia produced using renewable energy sources has virtually zero carbon emissions when burned, and produces no CO2 or SO 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 large compression-ignition internal combustion engines.

[0006] Ammonia is toxic and has a pungent odor. For this reason, it must be prevented from escaping from the engine. When operation on ammonia is stopped and changed to, for example, operation on conventional fuel, 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 disposed of can arise, for example, due to leaks or engine failure. There is a need to provide the engine with a solution for ammonia in such scenarios.

[0007] DK181016B1 discloses an engine as set forth in the preamble of claim 1. The engine includes an ammonia absorption system that contains water during use to absorb ammonia into the water to form aqueous ammonia. However, the system requires an external supply of fresh water for use in the ammonia absorption system. Fresh water, present on ships such as those in which the engine is typically used, is a scarce resource and must be produced in a fresh water generator. The aqueous ammonia produced by the ammonia absorption system must be disposed of. When the engine is used on a ship, if the aqueous ammonia is not available on the ship, it must be removed at great expense. Abstract

[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 problems are solved by the features of the independent claims. More specific implementations will become apparent from the dependent claims, the 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. at least one cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; 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; · With an ammonia absorption system; · Ammonia excretion pathways; the ammonia exhaust 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 to form aqueous ammonia during use; The institution further: a distillation apparatus associated with the ammonia absorption system for separating ammonia from aqueous ammonia; Equipped with.

[0011] By including a distillation unit that separates the ammonia water into nearly pure water and nearly pure ammonia, the water can be reused in the ammonia absorption system without the need to use fresh fresh water, such as from the ship's fresh water generator. In other words, the distillation unit forms part of the water reclamation system.

[0012] In one implementation of the first aspect, the distillation apparatus comprises a distillation column.

[0013] In one implementation of the first aspect, the distillation apparatus comprises a heat exchanger coupled to a cooling medium path of the engine, the heat exchanger preferably being disposed in a distillation column.

[0014] In one implementation of the first aspect, the ammonia absorption system includes at least one vessel that is at least partially filled with water during use, the vessel including a water inlet for connecting to a water source and an ammonia water outlet for discharging the ammonia water.

[0015] In one implementation of the first aspect, the ammonia water outlet is connected to the ammonia water inlet of the distillation apparatus.

[0016] In one implementation of the first aspect, the water outlet of the distillation device is connected to the water inlet.

[0017] In one example of an implementation form of the first aspect, the engine includes a heat exchanger that performs heat exchange between ammonia water flowing from the ammonia water outlet to the ammonia water inlet and water flowing from the water outlet to the water inlet.

[0018] In one implementation of the first aspect, the ammonia absorption system comprises: a cascade of water tanks or columns each of which is at least partially filled with water during use; The first water tank or column preferably has a vapor-phase ammonia inlet and a vapor-phase ammonia outlet, a water inlet, and an aqueous ammonia outlet; a subsequent water tank having a vapor-phase ammonia inlet connected to the vapor-phase ammonia outlet of the first water tank, an ammonia water outlet connected to the water inlet of the first water tank, and a vapor-phase ammonia outlet; the cascade is preferably 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 the gaseous ammonia during use has the highest ammonia concentration in the water in the tank and is provided with an ammonia water outlet; During use, the water tank furthest downstream in the flow of gaseous ammonia has the lowest ammonia concentration in the water therein; The water tank most downstream in the flow of the vapor phase ammonia is preferably provided with a vent for discharging the vapor phase material from the tank, and the ammonia water outlet is connected to the ammonia water inlet of the distillation apparatus.

[0019] In one implementation of the first aspect, the engine includes a condenser disposed downstream of an ammonia outlet of the distillation device, the condenser condensing vapor-phase ammonia from the ammonia outlet.

[0020] In one example 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 implementation of the first aspect, the ammonia fuel system comprises 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 comprises valves for selectively connecting the medium-pressure ammonia supply line and the ammonia return line to the ammonia absorption system.

[0022] In one example implementation of the first aspect, the engine preferably includes 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 knockout drum including a gas-phase ammonia outlet and a liquid-phase ammonia outlet, the gas-phase ammonia outlet of the knockout drum connected to the ammonia absorption system, and the liquid-phase ammonia outlet connected to a recovery tank connected to the ammonia fuel system.

[0023] In one example of an implementation of the first aspect, the ammonia fuel system includes a supply line and a return line, wherein piping forming the supply line and the return line includes a double-walled pipe, and a 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 discharge flow path.

[0024] In one example implementation of the first aspect, the ammonia fuel system includes a liquid-phase ammonia fuel tank and a fuel 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 fuel pump.

[0025] In one implementation of the first aspect, the distillation column is provided with a condenser downstream of the ammonia outlet to condense residual water vapor in the ammonia exiting the distillation column, thereby improving reflux for steady-state operation of the distillation process.

[0026] 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 and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; 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; wherein the method comprises: conveying excess gas phase ammonia from the ammonia fuel system to an ammonia absorption system and absorbing the excess gas phase ammonia in water to form aqueous ammonia; sending the aqueous ammonia to a distillation device; separating the water and ammonia in said distillation apparatus; Includes.

[0027] In one implementation of the second aspect, the method includes using separated water in the ammonia absorption system.

[0028] In one implementation of the second aspect, the method includes using a cooling medium of the engine to heat the distillation apparatus.

[0029] In one implementation of the second aspect, the method includes exchanging heat between aqueous ammonia fed to the distillation apparatus and separated water discharged from the distillation apparatus.

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

[0031] Various aspects, embodiments, and implementations will be described in detail below with reference to exemplary embodiments shown 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] This shows an overview of the engine in Figure 1 seen from the rear. [Figure 3] 2 is a schematic representation of the engine in FIG. 1. [Figure 4] 1 is a schematic representation of an engine according to a first embodiment, the engine having an ammonia fuel system, an ammonia purge system, an ammonia absorption system, and an ammonia-water separation system. [Figure 5] 1 is a schematic representation of an engine according to a second embodiment, also including an ammonia fuel system, an ammonia purge system, an ammonia absorption system, and an ammonia-water separation system. Detailed explanation

[0032] In the following detailed description, the internal combustion engine will be described with reference to an exemplary 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. A large, two-stroke, slow-speed, uniflow-scavenged, turbocharged internal combustion engine may be a compression-ignition (i.e., high-pressure) engine, in which fuel is injected near or at top dead center of the piston. Or, it may be a spark-ignition (i.e., low-pressure) engine, in which scavenging air is mixed with fuel before or during compression. In the latter case, a pilot ignition with an additive (e.g., fuel oil) is usually used to ensure ignition.

[0033] 1-3 illustrate 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, along with its intake and exhaust systems. In this embodiment, the engine has six cylinders arranged in series. Turbocharged, large, slow-speed, two-stroke diesel engines typically have four to fourteen cylinders arranged in series. These cylinders are supported on a cylinder frame 23, which is supported on an engine frame 11. Such an engine can also 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 power output of the engine can be, for example, in the range of 1,000 to 110,000 kW.

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

[0035] Scavenging air is introduced into 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 multiple (high-pressure) fuel valves 50 located in the cylinder cover 22. Following fuel injection, combustion occurs 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 50 for injecting conventional fuel into the combustion chamber would also be provided. Therefore, in such a case, the engine would have four or more fuel valves. If the fuel valves 50 are configured to inject both ammonia and conventional fuel, the number of fuel valves 50 provided in each cylinder may be two or more. The fuel valve 50 is located on the cylinder cover 22 around the exhaust valve 4, which is located in the center of the cylinder cover 22. Although not shown, in some embodiments, the cylinder cover may include 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 accelerators, such as hydrogen, may also be used. Since the engine may be a dual-fuel engine, the engine may include a conventional fuel supply system (not shown) for supplying conventional fuel to the fuel valve 50. In some embodiments, a fuel valve 50' (shown in dashed lines) is located along the cylinder liner. The fuel valve 50' introduces fuel into the cylinder liner as the piston 10 moves from BDC to TDC before passing the fuel valve 49'. The piston 10 then compresses the scavenging air / fuel mixture. Ignition is timed at or near TDC. Ignition can be achieved by a spark, laser, injected ignition fluid, or the like. In the embodiment with fuel valve 50', the pressure at which fuel is introduced is significantly lower than the pressure at which fuel is injected in the embodiment with fuel valve 50 in cylinder cover 22.As a result, the pressure required for the fuel supply system 30 to deliver fuel may be significantly lower and / or the pressure booster often used with fuel valves 50 located on the cylinder cover 22 may not be necessary.

[0036] When the exhaust valve 4 opens, the exhaust flows 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 flows through a second exhaust pipe 25 to an economizer 20 and is then released to the atmosphere through an outlet 21. The SCR reactor reduces the amount of emissions in the exhaust, particularly NO. X Reduce emissions.

[0037] The turbine 6 drives the 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 to cool 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. 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.

[0039] The engine is equipped with a cooling system, part of which is a jacket cooling system, which circulates cooling water through the space between the cylinder liner 1 and a jacket (not shown) surrounding the cylinder liner 1. The cooling water supplied to and exiting the cylinder liner / jacket is indicated by arrows 25.

[0040] In ammonia mode, the engine is operated using ammonia as the primary fuel. The ammonia is supplied to the fuel valve 50 at a substantially constant pressure and temperature. The ammonia may be supplied to the fuel valve 50 in either the liquid or gas phase. The liquid phase ammonia may be aqueous ammonia, i.e., an aqueous ammonia solution.

[0041] Conventional fuel systems are well known and are not shown or described in detail. The ammonia fuel system 30 supplies ammonia in liquid phase at an intermediate supply pressure (e.g., 30-80 BAR) to the ammonia fuel valve 50. Alternatively, the ammonia fuel is supplied to the fuel valve 50 in vapor 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 that 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 engine's compression pressure. Typically, the injection pressure of a compression ignition engine is greater than 300 BAR.

[0042] 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 a pressurized storage tank 31. Ammonia can be stored in liquid phase in the ammonia storage tank 31 at or above 8.6 BAR at an ambient temperature of 20°C. However, it is preferred to store the ammonia at or above 17 BAR to maintain the liquid phase as ambient temperatures increase.

[0043] A low-pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 31 to the inlet of a medium-pressure supply pump 35. A low-pressure supply pump 33 applies pressure to liquid-phase ammonia from the tank 31 so that it passes through a filter device 34 and reaches the inlet of the medium-pressure supply pump 35. The medium-pressure supply pump 35 pumps liquid-phase ammonia from a medium-pressure ammonia supply line 36 to a fuel valve 50. A portion of the liquid-phase ammonia supplied to the fuel valve 50 is injected into the combustion chamber of the engine, while another portion is returned to an 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 portion of the liquid-phase ammonia fuel is recirculated to the inlet of the medium-pressure supply pump 35.

[0044] 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.

[0045] A first purge line 42 including a second purge valve 43 connects the medium-pressure ammonia supply line 36 to a 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. During purging, 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 into 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 transported to the ammonia storage tank 31 and used as ammonia fuel. The vapor phase ammonia outlet of knockout drum 46 is connected to ammonia absorption system 60 through a third purge line 47 .

[0046] The ammonia absorption system 60 comprises at least one vessel that, when in use, is at least partially filled with water to absorb ammonia with the water to form aqueous ammonia.

[0047] Ammonia water (Ammonia water) is also called aqueous ammonia, and is an aqueous solution of ammonia.

[0048] Purge line 47 delivers the purged ammonia to a cascade of three absorption tanks in series, including first absorption tank 61, intermediate absorption tank 63, and final absorption tank 65.

[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 achieve a lower ammonia concentration above the water in the final absorption tank, and thus a lower ammonia concentration in the gases exiting the final vent.

[0050] The absorption efficiency of the cascade of multiple absorption tanks is maintained by periodically replacing the water in the final absorption tank 65 with fresh water. To this end, the water in the final tank 65, which has absorbed a certain amount of ammonia, is replaced with water from the water source. The replaced water from the final tank 65 is sent to the intermediate absorption tank 63 through a first water return line 67 controlled by a first water return valve 68. 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 water evaporating from the absorption tanks 61, 63, and 65 and ammonia water removed from the first absorption tank 61. In other words, the water height in the absorption tanks 61, 63, and 65 is maintained between a minimum height and a maximum height.

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

[0052] The ammonia concentration in the fourth vent 66 is low enough to allow it to be released into the environment. However, if required to comply with regulations, the amount of ammonia released from the ventilation tower can be further reduced by using an absorption column. The absorption medium used in such an absorption column is an acid. The acid protonates the ammonia in aqueous solution, forming ammonium hydroxide. Thus, the amount of ammonia released into 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 an ammonia water discharge line 86 having a discharge pump 83. The ammonia water having a relatively high ammonia concentration originating from the first absorption tank 61 is discharged through the ammonia water discharge line 86 to a distillation system 80, which will be described in detail below.

[0055] The cascade of water tanks 61, 63, 65 is a completely passive element, i.e. there are no pumps 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 configured, completely or partially, as double-walled pipes with a space between the inner and outer pipes. In such embodiments, 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 the ammonia absorption system 60 for absorption. Thus, even if a leak occurs in 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. If ammonia is detected in the space, the engine may be shut down on ammonia, followed by purging the ammonia fuel system and absorbing any remaining ammonia with 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, purge system, ammonia absorption system 60, and separation system 80. 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, purge system, ammonia absorption system, and separation system to operate as described above.

[0058] The separation system (distillation apparatus) 80 includes a distillation column. The distillation column 81 has an ammonia water inlet connected to an ammonia discharge pipe 86. The ammonia water inlet is preferably located slightly above the middle of the height of the distillation column 81. A water outlet is provided near the bottom of the distillation column 81. The water outlet is connected to a water discharge pipe 85. The water discharge pipe 85 is connected to the water inlet of the final ammonia absorption tank 65 to supply fresh water to the absorption system 60. As used herein, "fresh water" refers to water that contains substantially no dissolved ammonia and has nearly complete ammonia absorption capacity. The distillation column 81 has an ammonia outlet near the top of the distillation column 81. The ammonia discharge outlet is connected to an ammonia discharge pipe 87. The ammonia discharge pipe 87 may be connected to a fuel system to be used as a fuel or to an SCR reactor of an engine to be used as a reducing agent therein.

[0059] Distillation column 81 includes trays 89 to facilitate separation of the ammonia water into ammonia and water. Thus, distillation column 81 is configured to separate the ammonia water received from ammonia outlet line 86 into substantially pure gaseous ammonia and substantially pure water. A lower portion of distillation column 81 is supplied with heat to drive the distillation process. This heat is preferably supplied by the engine cooling medium, i.e., engine waste heat, e.g., jacket cooling water, via heat conduit 88.

[0060] A heat exchanger 84 is provided to exchange heat between the ammonia water in the ammonia water discharge pipe 86 and the water in the water discharge pipe 85. A water pump 82 in the water discharge pipe 85 controls the flow rate of the water discharged from the distillation column 81 and supplied to the final ammonia absorption tank 65.

[0061] A condenser 90 is located downstream of the ammonia outlet of distillation column 81 to condense residual water vapor in the ammonia stream exiting distillation column 81, thereby improving reflux for steady-state operation of the distillation process. A first ammonia outlet line 87 connects the ammonia outlet of distillation column 81 to the inlet of condenser 90. A second ammonia outlet line 94 is connected to the ammonia outlet at or near the top of condenser 90. A condensed water conduit 92 connects a water outlet in the lower region of condenser 90 to the condensed water inlet of distillation column 81, thus increasing the amount of fresh water available to ammonia absorption system 60 and improving reflux for steady-state operation of the distillation process.

[0062] By separating ammonia and water from the ammonia water in separation system 80 and using the separated water in ammonia absorption system 60, an engine equipped with an ammonia absorption system is provided that eliminates or at least significantly reduces the need to add fresh water during operation of the ammonia absorption system.

[0063] Figure 5 shows a second embodiment of the engine, which also includes a fuel system, a purge system, an ammonia absorption system, and a separation system. In this embodiment, elements and features that are similar to elements and features already described or shown are given the same reference numerals as previously used. The embodiment according to Figure 5 is essentially the same as the embodiment according to Figure 4, except that the tray 89 is replaced by a packing 89'. The inlet of the condenser 90 is connected to an ammonia discharge pipe 87.

[0064] In both of the above embodiments, a further condenser (not shown) may be provided downstream of the condenser 90 to condense the gas phase ammonia into liquid phase ammonia, which is then conveyed to the liquid phase ammonia fuel tank 31 for use as fuel.

[0065] Various aspects and implementations of the invention have been described with reference to several examples. 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 examples 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 an explicit reference to a plurality of elements in a claim does not exclude the presence of a plurality of such elements.

[0066] Any 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, 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, at least one cylinder having a cylinder liner and a reciprocating piston within said cylinder liner, and a cylinder cover covering said cylinder; 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; - ammonia excretion pathway; the ammonia exhaust 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 to form aqueous ammonia during use; The institution further: a distillation apparatus comprising a distillation column, the distillation apparatus being associated with the ammonia absorption system for separating ammonia from the aqueous ammonia; An institution characterized by comprising:

2. 2. The engine of claim 1, wherein said distillation device comprises a heat exchanger associated with a cooling path of said engine.

3. 2. The engine of claim 1, wherein the heat exchanger is disposed in the distillation column.

4. 3. The engine of claim 1, wherein the ammonia absorption system comprises at least one container that is at least partially filled with water during use, the container comprising a water inlet for connecting a water source and an ammonia water outlet for discharging the ammonia water.

5. 5. The engine of claim 4, wherein said aqueous ammonia outlet is connected to an aqueous ammonia inlet of said distillation device.

6. 5. The engine of claim 4, wherein the water outlet of said distillation device is connected to said water inlet.

7. The engine according to claim 1 , further comprising a heat exchanger that performs heat exchange between the ammonia water flowing from the ammonia water outlet to the ammonia water inlet and the water flowing from the water outlet to the water inlet.

8. 10. The engine of claim 1, wherein the ammonia absorption system comprises a cascade of multiple water tanks or columns that are each at least partially filled with water during use.

9. 9. The engine of claim 8, wherein the first water tank or column has a vapor phase ammonia inlet and a vapor phase ammonia outlet, a water inlet, and an aqueous ammonia outlet.

10. 9. The engine of claim 8, wherein a subsequent water tank has a vapor phase ammonia inlet connected to the vapor phase ammonia outlet of the initial water tank, an ammonia water outlet connected to the water inlet of the initial water tank, and a vapor phase ammonia outlet.

11. the cascade is preferably 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 the gaseous ammonia during use has the highest ammonia concentration in the water in the tank and is provided with an ammonia water outlet; 9. An engine as claimed in claim 8, wherein in use the water tank furthest downstream in the flow of vapor phase ammonia has the lowest ammonia concentration in the water therein.

12. 9. The engine of claim 8, wherein the water tank most downstream in the flow of vapor-phase ammonia is provided with a vent for discharging vapor-phase material from the tank, and the ammonia water outlet is connected to the ammonia water inlet of the distillation device.

13. 2. The engine of claim 1, further comprising a condenser disposed downstream of the ammonia outlet of the distillation column for condensing residual water vapor in the ammonia at the ammonia outlet.

14. The engine of claim 1 , further comprising a purge system configured to vent ammonia from the ammonia fuel system to the ammonia absorption system.

15. 15. The engine of claim 14, wherein the purge system comprises a pressurized nitrogen source connected to the ammonia fuel system through a purge valve, the purge system using the ammonia vent path to purge ammonia from the ammonia fuel system to the ammonia absorption system.

16. 2. The engine of claim 1, wherein the ammonia fuel system comprises 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.

17. 16. The engine of claim 15, further comprising valves for selectively connecting the medium pressure ammonia supply line and the ammonia return line to the ammonia absorption system.

18. 17. The engine of claim 16, further comprising a knock-out drum in the first purge line and / or the second purge line, the knock-out drum configured to separate gas phase ammonia from liquid phase ammonia, the knock-out drum including a gas phase ammonia outlet and a liquid phase ammonia outlet, the gas phase ammonia outlet connected to the ammonia absorption system.

19. 19. The engine of claim 18, wherein the liquid phase ammonia outlet is connected to a recovery tank connected to the ammonia fuel system.

20. 2. The engine of claim 1, wherein the ammonia fuel system comprises a supply line and a return line, the piping forming the supply line and the return line comprising a double-walled pipe, the space between an inner tube and an outer tube of the double-walled pipe being fluidly connected to the ammonia absorption system by the ammonia exhaust path.

21. 10. The engine of claim 1, wherein the ammonia fuel system comprises a liquid phase ammonia fuel tank and a fuel pump, the ammonia fuel system comprises 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 comprises a return line connecting an outlet of the fuel valve to an inlet of the fuel pump.

22. 1. A method of 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 and a reciprocating piston within said cylinder liner, and a cylinder cover covering said cylinder; 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; wherein the method comprises: conveying excess gas phase ammonia from the ammonia fuel system to an ammonia absorption system and absorbing the excess gas phase ammonia in water to form aqueous ammonia; sending the aqueous ammonia to a distillation apparatus comprising a distillation column; separating water and ammonia in said distillation apparatus; A method comprising:

23. 23. The method of claim 22, including using the separated water in the ammonia absorption system.

24. 24. The method of claim 22 or 23, comprising using the engine's cooling medium to heat the distillation apparatus.

25. 23. The method of claim 22, comprising exchanging heat between the aqueous ammonia fed to the distillation apparatus and the separated water discharged from the distillation apparatus.

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