JP2022183044A - Large two-stroke uniflow scavenged turbocharged internal combustion engine with ammonia absorption system - Google Patents

Abstract

To provide a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which ammonia is used as main fuel.SOLUTION: The large two-stroke uniflow scavenged turbocharged internal combustion engine includes: a 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 and the cylinder cover in the cylinder; an ammonia fuel system 30 configured to supply pressurized ammonia to a fuel valve located in the cylinder cover or cylinder liner; and ammonia evacuation flow paths 42, 44, 47 connecting an outlet of the ammonia fuel system 30 to an inlet of an ammonia absorption system 60. The ammonia absorption system 60 contains water during use for absorbing ammonia supplied through the ammonia evacuation flow paths 42, 44, 47 into the water thereby forming ammonia water.SELECTED DRAWING: Figure 4

Description

The subject matter disclosed herein relates to a large two-stroke uniflow scavenging turbocharged internal combustion engine in at least one mode operating with ammonia as the fuel to be combusted for a period of time.

background

Large two-stroke uniflow scavenging turbocharged internal combustion engines are typically used as propulsion systems for large marine vessels and as prime movers in power plants. Its size, weight and power set large two-stroke turbocharged compression ignition internal combustion engines far apart from other combustion engines and place this type of compression internal combustion engine in a unique class.

Internal combustion engines have traditionally been driven primarily by hydrocarbon fuels, such as fuel oil, such as diesel oil, or fuel gas, such as natural gas or petroleum gas. Combustion of hydrocarbon fuels is associated with the production of greenhouse gases such as carbon dioxide ( _CO2 ), which can contribute to air pollution and climate change. Unlike petroleum fuel impurities that produce by-product emissions, _CO2 production is inevitable in the combustion of hydrocarbons. A fuel's energy density and _CO2 footprint depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Thus, gaseous hydrocarbon fuels have a smaller footprint than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are more difficult and costly to handle and store. Non-hydrocarbon fuels have been explored to reduce the _CO2 footprint.

Ammonia is a synthetic product obtained from petroleum, biomass and renewable energy sources (wind, solar, hydro, geothermal). Ammonia produced using renewable energy sources has a virtually zero carbon footprint when burned, or virtually zero emissions of _CO2 , _SOx , particulate matter and unburned hydrocarbons. .

Ammonia has been tested and used on a small scale in spark ignited internal combustion engines. However, it has not yet been used to operate a compression ignition internal combustion engine.

Ammonia is harmful and has a pungent odor. Therefore, ammonia must be prevented from leaking out of the engine. When ammonia operation is stopped and, for example, changed to conventional fuel operation, the ammonia in the fuel system must be purged, but the removed ammonia cannot simply be released to the environment. Other scenarios in which excess ammonia must be disposed of can occur, for example, due to leaks, engine failures, and the like. There is a need to provide agencies with solutions for ammonia in such scenarios.

CN112696289 discloses a marine liquid ammonia fuel supply system and fuel recycling system. 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. This system provides a high pressure (70 bar, 45+/-10°C) liquid supply of liquid ammonia fuel for ships. Unconsumed liquid ammonia fuel in the pipeline can be recycled, saving a large amount of fuel while reducing the amount of ammonia fuel discharged to the ventilation tower, improving vessel and personnel safety.

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

The above objects and other objects are achieved by the features of the independent claims. More specific implementations will become apparent from the dependent claims, the detailed description of the invention and the drawings.

According to a first aspect, a large two-stroke uniflow scavenging turbocharged internal combustion engine having at least one mode of operation in which the main fuel is ammonia is provided. This institution
- at least one cylinder having a cylinder liner, a reciprocating piston in said cylinder liner and a cylinder cover covering it;
a combustion chamber defined between the reciprocating piston in the cylinder 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 discharge channel connecting the outlet of the ammonia fuel system to the inlet of the ammonia absorption system;
wherein, in use, said ammonia absorption system comprises said water for absorbing ammonia supplied through said ammonia discharge channel into water to form aqueous ammonia.

The use of an exhaust channel and an ammonia absorption system also allows for contingencies such as having to deal with excess ammonia from the engine. For example, when ammonia fuel operation stops or a leak occurs, ammonia must be discharged, and such situations can be handled. By dissolving ammonia in an absorption system containing water, a substantial amount of ammonia can be temporarily stored in water and ammonia water can be produced. Aqueous ammonia can be used as a fuel in the engine and can also be used to clean the exhaust by utilizing it as a reductant in the SCR reactor.

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 arrangement to cool the water, the effective amount of ammonia regenerated in the regeneration system (tank) is increased and a high regeneration rate can be realized.

In an example of implementation of said first aspect, said ammonia absorption system comprises at least one container which in use is at least partially filled with water, said at least one container being water for connecting a water source. An inlet is preferably provided, and an ammonia water outlet for discharging the ammonia water is preferably provided.

In one example of implementation of said first aspect, said engine is a dual fuel engine, preferably comprising a fuel system that supplies conventional fuel to the cylinders of the engine.

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

In one example of implementation of the first aspect, an SCR reactor is provided in the exhaust flow path of the engine, and the aqueous ammonia outlet is connected to a reductant inlet associated with the SCR reactor.

In one example of an implementation of said first aspect, said ammonia absorption system comprises a pressure vessel which in use is at least partially filled with water, said pressure vessel preferably containing water to reduce the temperature of said pressure vessel. wherein said pressure vessel preferably comprises a vapor phase ammonia inlet for taking in vapor phase ammonia, said pressure vessel is preferably connected to a water source, said pressure vessel discharging ammonia water It is preferable to have an ammonia water outlet for

In one example of implementation of said first aspect, said ammonia absorption system preferably comprises a bundled absorption tower, said absorption tower comprising a vapor phase ammonia inlet for taking in vapor phase ammonia, said The absorption tower is preferably connected to a water source, said absorption tower preferably comprising an aqueous ammonia outlet for discharging the aqueous ammonia.

In one example of implementation of said first aspect, said ammonia absorption system comprises a cascade of water tanks each at least partially filled with water in use, a first water tank containing gaseous ammonia a subsequent water tank preferably having an inlet and a gas phase ammonia outlet, a water inlet and an aqueous ammonia outlet, the subsequent water tank having a gas phase ammonia inlet connected to said gas phase ammonia outlet of said first water tank; Preferably having an aqueous ammonia outlet connected to said water inlet of said first water tank and a vapor phase ammonia outlet, said cascade for water flow in the opposite direction to the flow of vapor phase ammonia. Preferably, the water tank most upstream in the flow of the gas phase ammonia during use has the highest ammonia concentration in the water in the tank, is provided with an ammonia water outlet, and during use the gas phase The water tank furthest downstream in the ammonia flow has the lowest concentration of ammonia in the water in the tank and is preferably provided with a vent for venting vapor phase material from that tank.

In one example of implementation of the first aspect, the ammonia fuel system comprises a purge system configured to expel ammonia from the ammonia fuel system to the ammonia absorption system, the purge system preferably a pressurized nitrogen source, said pressurized nitrogen source preferably connected to said ammonia fuel system via a purge valve, said purge system for purging ammonia from said ammonia fuel system to said ammonia absorption system; It is preferred to use channels.

In one example implementation of the first aspect, the ammonia fuel system includes an intermediate pressure ammonia supply line and an ammonia return line, a first purge line connecting the intermediate pressure ammonia supply line to the ammonia absorption system, and a second purge line connecting an ammonia return line to the ammonia absorption system, and preferably valves for selectively connecting the medium pressure ammonia supply line and the ammonia return line to the ammonia absorption system. Prepare.

In one example of implementation of said first aspect, said first purge line and/or said second purge line comprises a knockout drum, said knockout drum being configured to separate gas phase ammonia from liquid phase ammonia. wherein said knockout drum comprises a vapor phase ammonia outlet and a liquid phase ammonia outlet, said vapor phase ammonia outlet of said knockout drum being connected to said ammonia absorption system and said liquid phase ammonia outlet being connected to said ammonia fuel system. It is preferably connected to the tank.

In one example of implementation of the first aspect, the ammonia fuel system comprises a supply line and a return line, the piping forming the supply line and the return line comprises double-walled pipe, and the double-walled The space between the inner tube and the outer tube of the pipe is fluidly connected to the ammonia absorption system by the ammonia discharge channel.

In one example implementation of the first concept, the ammonia fuel system includes a liquid ammonia fuel tank and a low pressure ammonia supply line connecting the liquid ammonia fuel tank to the inlet of a medium pressure fuel pump by operation of a low pressure pump. and said ammonia fuel system preferably comprises a medium pressure fuel line connecting said medium pressure fuel pump outlet to said fuel valve inlet, said ammonia fuel system preferably comprising said fuel valve outlet to the inlet of said medium pressure fuel pump.

In an example of implementation of said first aspect, said at least one cylinder is provided with a scavenging port in its lower region.

In one example of implementation of the first conception, an exhaust valve is provided in the middle of the cylinder, and two or more fuel valves are arranged around the exhaust valve.

A second aspect provides a method of managing ammonia in a large two-stroke uniflow scavenge turbocharged internal combustion engine having at least one mode of operation in which the primary fuel is ammonia. wherein said agency:
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
a combustion chamber defined between the reciprocating piston in the cylinder 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;
Prepare. The method then includes transporting excess vapor phase ammonia from the ammonia fuel system to the ammonia absorption system and absorbing the excess vapor phase ammonia in water to form aqueous ammonia.

In an example of implementation of the second aspect, the method comprises separating liquid and gas phase ammonia obtained from the excess gas phase ammonia, preferably using a knockout drum; transferring vapor phase ammonia to the ammonia absorption system; and absorbing the transferred ammonia in water to form aqueous ammonia.

In one example of implementation of the second aspect, the method includes using the aqueous ammonia as a fuel for the engine or as a reductant for an SCR reactor of the engine.

These and other ways of thinking will become clearer with the examples described below.

Hereinafter, various concepts, embodiments, and implementation examples will be described in detail with reference to exemplary embodiments shown in the drawings.
1 is a frontal view of a large two-stroke diesel engine in accordance with certain exemplary embodiments; FIG. FIG. 2 is a diagram showing an overview of the large two-stroke engine of FIG. 1 as viewed from the rear; 2 is a schematic representation of the large two-stroke engine of FIG. 1; 1 is a schematic representation of an engine according to a first embodiment; This engine has an ammonia fuel system, an ammonia purge system and an ammonia absorption system. Fig. 4 is a schematic representation of an engine according to a second embodiment; This engine also has an ammonia fuel system, an ammonia purge system and an ammonia absorption system.

Detailed explanation

In the following detailed description, the internal combustion engine will be described with reference to an exemplary crosshead, low speed, two-stroke, uniflow scavenge turbocharged internal combustion engine. Note that in some cases the internal combustion engine could be another type of engine. A large two-stroke low speed uniflow scavenging turbocharged internal combustion engine can be a compression ignition type (ie, high pressure type) engine in which fuel is injected near or at top dead center of the piston. Or it can be a spark ignited (ie low pressure) 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 fluid (e.g., fuel oil) is typically used to ensure ignition.

1-3 depict a turbocharged large low speed two-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9 . FIG. 3 is a schematic representation of a turbocharged large low-speed two-stroke diesel engine with its intake and exhaust systems. In this example, the engine has six cylinders in series. Turbocharged large slow speed two-stroke diesel engines typically have 4 to 14 cylinders arranged in series. These cylinders are carried on a cylinder frame 23 . The cylinder frame 23 is carried by the engine frame 11 . Such an engine can also be used, for example, as a main engine on ships or as a stationary engine for powering generators in power plants. The total engine power can be, for example, 1000 kW to 110000 kW.

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

The scavenging air is led through the scavenging air receiver 2 to the scavenging air port 18 of each cylinder 1 . Piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in cylinder liner 1 to compress scavenging air. Fuel (ammonia in ammonia mode) is injected into the combustion chamber in the cylinder liner 1 through a plurality of (high pressure) fuel valves 50 arranged in the cylinder cover 22 at or near TDC. Following the injection of fuel, combustion occurs and exhaust is produced. Each cylinder cover 22 is provided with two or more fuel valves 50 . Fuel valve 50 may be configured to inject only one particular type of fuel (eg, ammonia). In that case, more than one fuel valve 54 would also be provided for injecting conventional fuel into the combustion chamber. In such a case, the engine would therefore 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 for each cylinder may be two or more. The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4 arranged in the central portion of the cylinder cover 22 . Although not shown, in some embodiments an additional (usually small) fuel valve may be located in the cylinder cover configured to inject ignition fluid to ensure ignition of the ammonia fuel. The ignition liquid may be, for example, dimethyl ether (DME) or fuel oil. However, other forms of ignition accelerators, such as hydrogen, are also possible. Since the engine may be a dual engine, the engine may be equipped with a conventional fuel supply system for supplying conventional fuel to fuel valve 50 (not shown). In some embodiments, along the cylinder liner is a fuel valve 50' (shown in dashed lines). The fuel valve 50' introduces fuel into the cylinder liner before the piston 10 passes through the fuel valve 50' on its way from BDC to TDC. In that case, the piston 10 compresses the mixture of scavenging air and fuel. Ignition is timed at or near TDC. Ignition may be by spark, laser, injection of igniter liquid, 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 such, the pressure required for fuel delivery system 30 to deliver fuel may be significantly lower and/or the pressure booster often used in fuel valve 50 located in cylinder cover 22 may be unnecessary. .

When the exhaust valve 4 opens, the exhaust flows through an exhaust duct provided in the cylinder 1 to the exhaust receiver 3, further through a selective catalytic reduction reactor (SCR reactor) 28, through a first exhaust pipe 19, and into the turbo. Proceed to turbine 6 of supercharger 5 . From there, the exhaust flows through a second exhaust pipe 25 to the economizer 20 and out the outlet 21 to the atmosphere. SCR reactors reduce emissions in the exhaust, especially NOx emissions.

Turbine 6 drives compressor 7 via a shaft. Outside air is supplied to the compressor 9 through an air intake 12 . The compressor 7 sends the compressed scavenging air to the scavenging pipe 13 connected to the scavenging receiver 2 . The scavenging air in the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

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 receiver 2, ie when the engine is under low or part load. When the engine load is high, the turbocharger compressor 7 can supply sufficiently compressed scavenging air so that the auxiliary blower 16 is bypassed by the non-return valve 15 and the electric motor 17 is stopped. .

In ammonia mode, the engine is operated with ammonia as the main fuel. Ammonia is supplied to the ammonia valve 50 at approximately constant pressure and temperature. Ammonia can be supplied to the ammonia valve 50 in liquid or gas phase. The liquid phase ammonia may be aqueous ammonia, ie an aqueous solution of ammonia.

Since conventional fuel systems are well known, they are not shown and will not be described in detail. The ammonia fuel system 30 supplies liquid phase ammonia to the ammonia valve 50 at an intermediate supply pressure (eg 30-80 bar). Alternatively, the ammonia fuel is supplied to the ammonia valve 50 in vapor phase at a relatively low supply pressure (eg 8-30 bar). For compression ignition engines, the fuel valve 50 includes a pressure booster that significantly increases the pressure of the ammonia fuel. The pressure booster raises the pressure of the ammonia fuel from an intermediate pressure to a high pressure, thereby allowing the ammonia fuel to be injected at a pressure higher than the compression pressure of the engine. Compression ignition engines typically have injection pressures higher than 300 bar.

Referring to FIG. 4, ammonia fuel system 30 is shown in detail along with ammonia purge system and ammonia Kyushu system 60 . Ammonia is stored in the liquid phase in pressure storage tank 31 at about 17 bar. Ammonia can be stored in the liquid phase in the ammonia storage tank 31 at an ambient temperature of 20° C. and above 8.6 bar. However, it is preferable to store the ammonia at 17 bar or more in order to keep the liquid phase even when the ambient temperature rises.

A low pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 31 and the inlet of the medium pressure supply pump 35 . Low pressure feed pump 33 pressurizes liquid phase ammonia from tank 31 through filter device 34 to the inlet of medium pressure feed pump 35 . Medium pressure feed pump 35 pumps liquid phase ammonia from medium pressure ammonia feed line 36 to fuel valve 50 . A portion of the liquid phase ammonia supplied to fuel valve 50 is injected into the combustion chamber of the engine while another portion is returned to ammonia return line 38 . An ammonia return line 38 connects the return port of the fuel valve 50 to the low pressure supply line 32 . A portion of the liquid phase ammonia fuel is therefore recycled to the inlet of the intermediate pressure feed pump 35 .

When ammonia fuel operation is terminated, 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 pressurized nitrogen source 40 (eg, a pressurized nitrogen container 40) is connected via a purge valve 41 to the medium pressure ammonia supply line 36, preferably immediately downstream of the medium pressure supply pump 35. .

A first purge line 42 including a second purge valve 43 connects medium pressure ammonia supply line 36 to 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 purge operation, first purge valve 41 , second purge valve 43 , and third purge valve 45 are opened and pressurized nitrogen forces residual ammonia fuel from ammonia supply line 36 and ammonia return line 38 to knockout drum 46 . Knockout drum 46 is configured to separate liquid phase ammonia from gas phase ammonia. A nitrogen vent line 48 containing a nitrogen vent valve 49 connects the interior and exterior of the knockout drum 46 for venting nitrogen from the knockout drum 46 . A liquid phase ammonia outlet is provided in the lower region of the knockout drum 46 and leads to a recovery tank 57 . In some embodiments, liquid phase ammonia in recovery tank 57 is conveyed to 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 third purge line 47 .

Ammonia absorption system 60 comprises at least one vessel. The container is at least partially filled with water when in use. This is because ammonia is absorbed by water to form aqueous ammonia.

Ammonia water (Aqueous ammonia) is an aqueous solution of ammonia.

This embodiment includes a pressure vessel 58 that is at least partially filled with water when in use. Pressure vessel 58 is preferably chilled. Cooling means are not shown. This is because heat is generated when ammonia dissolves in water, and the ability of water to absorb ammonia decreases as the water temperature rises. Therefore, a cooling means is configured to keep the temperature of the water in the pressure vessel 58 low so as to optimize the ammonia absorption capacity of the water in the pressure vessel 58 .

Pressure vessel 58 has a vapor phase ammonia inlet for receiving vapor phase ammonia through pressure vessel ammonia feed 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 . Pressure vessel 58 has an inlet for water (fresh water). This inlet is connected to a source 71 of pressurized water (fresh water) through a tube. As used herein, "fresh water" means water that has substantially no dissolved ammonia and has a nearly complete ability to absorb ammonia. The height of the water in pressure vessel 58 is adjusted between upper and lower limits. Vapor phase ammonia supplied to the pressure vessel 58 is absorbed by water to form aqueous ammonia. The pressure within the pressure vessel is adjusted and kept at a suitably high pressure so that the water can absorb a greater amount of gas 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 ammonia water 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 the ammonia water discharge pipe 75 . Aqueous ammonia drain 75 has a valve 76 to control flow from pressure vessel 58 to third return line 55 . Aqueous ammonia is sent from the third return line 55 to the SCR reactor 28 for use as a reductant in the SCR reactor 28 or to the low pressure ammonia supply line 32 for use as fuel in the engine. This will be explained in more detail later. The third purge line 47 has a pressure control valve 74 . Pressure control valve 74 opens when the pressure in third purge line 47 exceeds a predetermined value. This predetermined pressure corresponds to the maximum pressure at which pressure vessel 58 can operate. Above this predetermined pressure, the vapor phase ammonia is sent to a cascade of three sequential absorption tanks (first absorption tank 61, intermediate absorption tank 63, final absorption tank 65). In another embodiment, a controlled flow of vapor phase ammonia from the third purge line 47 to the pressure vessel 58 or cascade of water tanks 61, 63, 65 is not shown in place of the pressure control system shown. Controlled by an electronic control valve.

A fourth vent 66 is provided in the final absorption tank 65 . A fourth vent 66 connects the final absorption tank 65 to the outside world. In some embodiments there are more than three absorption tanks. This is to create a lower concentration of ammonia above the water in the final absorption tank and thus a lower concentration of ammonia in the gas exiting the fourth vent 66 .

The absorption efficiency of the multiple absorption tank cascade is maintained by periodically exchanging the water in the final absorption tank 65 . This water is supplied from a source 71 of pressurized water (fresh water). Some ammonia-laden water is reused in upstream tanks. Thus, the water in the final tank 65 that has absorbed some ammonia is replaced by water from the water source 71 , but the displaced water in the final tank 65 is the first water controlled by the first water return valve 65 . It is sent to intermediate absorption tank 63 through return line 67 . 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 absorption tanks 61 , 63 , 65 and ammonia water removed from first absorption tank 61 . That is, the height of the water in the absorption tanks 61, 63, 65 is maintained between the minimum height and the maximum height indicated by the dashed lines in FIG.

Ammonia vapor above the water in the first absorption tank 61 flows through the first ammonia discharge line 62 to the intermediate absorption tank 63 . Ammonia vapor above the water in intermediate absorption tank 63 flows through second ammonia discharge line 64 to final absorption tank 65 . This process is preferably accomplished by the pressure of the purge process.

The concentration of ammonia in the fourth vent 66 is low enough to allow venting to the environment. However, if required to meet regulations, additional absorption columns can be used to further reduce ammonia emissions from the ventilator. The absorption medium used in such absorption columns is acid. The acid protonates ammonia in aqueous solution to form ammonium hydroxide. Therefore, the amount of ammonia released into the environment is reduced.

During operation, the ammonia concentration of the water in the first absorption tank 61 is higher than the ammonia concentration of the water in the intermediate absorption tank 63, and the ammonia concentration of the water in the intermediate absorption tank 63 is higher than the ammonia concentration of the water in the final absorption tank 65. high.

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 aqueous ammonia return line 52 having a first return valve 54 connects the first aqueous ammonia return line 51 to the low pressure ammonia supply line 32 . Therefore, when the first return valve 54 opens, the relatively high-concentration ammonia water from the first absorption tank 61 mixes with the fuel from the ammonia storage tank 31 . Therefore, the ammonia absorbed by the ammonia absorption system 60 is recycled to the engine as fuel. A third aqueous ammonia return line 55 having a second return valve 56 connects the first aqueous ammonia return line 51 to the 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 recycled to the SCR reactor 28 as a reductant.

The cascade of water tanks 61, 63, 65 is a purely passive element. That is, there are no pumps or the like, nor are there any auxiliary systems available when it is necessary to stop the absorption of ammonia. As such, the system is inherently reliable and available when needed.

In some embodiments, the low pressure ammonia supply line 32, medium pressure ammonia supply line 36, and ammonia return line 38 are configured wholly or partially 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 such that any ammonia fuel that inadvertently leaks into the space is connected to an ammonia absorption system 60 for absorption. ing. Therefore, even if these fuel lines leak, unintentional release of ammonia into the 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 tube and the outer tube. Then, when ammonia is detected in the space, it is possible to stop the operation of the engine with ammonia, followed by purging the ammonia fuel system and absorbing the residual ammonia by the ammonia absorption system 60. good too.

An electronic control unit 100 is wired or wirelessly connected to the pumps and valves of the fuel system 30, the purge system, and the ammonia absorption system 60. FIG. Electronic control unit 100 is configured to control these elements, for example, by regulating the speed of pumps and controlling the opening and closing of valves. This allows the fuel system, purge system, and ammonia absorption system to operate as described above.

FIG. 5 shows a second embodiment of the engine. This engine also has a fuel system, a purge system and an ammonia absorption system. In this embodiment, structures and features that are similar to structures and features already described or illustrated are labeled with the same reference numerals as before. The embodiment of FIG. 5 is essentially the same as the embodiment of FIG. Absorption tower 78 is used for absorption of ammonia and subsequent discharge of aqueous ammonia. The gas-liquid (water) contact within the absorption tower 78 is continuous. Within tower 78, water flows downward over the consolidating surfaces, and vapor phase ammonia travels upward within tower 87, reversing the flow. Absorption tower 78 is a vessel having a filled portion. The absorption tower 78 has one or more packing structures, which are stacked. Absorption tower 78 has an inlet connected to third purge line 47 via pressure control valve 74 for receiving ammonia gas. The absorption tower 78 also has an outlet for aqueous ammonia that is connected to the first aqueous ammonia return line 51 . The inlet is arranged above the filling structure. A source of pressurized water (fresh water) 71 is then connected to the inlet of absorption tower 78 . A vent 76 is provided to ventilate the space above the filling structure. The flow rate of water from source 71 of pressurized water (fresh water) is adapted to match the flow rate of vapor phase ammonia to absorption tower 78 . The amount of aqueous ammonia collected at the bottom of absorption tower 78 is regulated and transferred to an intermediate aqueous ammonia storage tank (not shown) as needed.

A number of aspects and implementations have been described with some examples. However, many variations in addition to those described exist in the practice of the claimed invention by one of ordinary skill in the art upon review of the specification, drawings, and claims of this application. understand and be able to implement it. The verbs "comprising," "having," and "including" in the claims do not exclude the presence of elements or steps not recited. The absence of an explicit plural number of an element in a claim does not exclude the presence of a plurality of such elements.

Any reference signs used in the claims shall not be construed as limiting the scope of the invention. Unless otherwise noted, the drawings are intended to be read in conjunction with the specification and are part of the entire disclosure of this application.

Claims (15)

A large two-stroke uniflow scavenging turbocharged internal combustion engine having at least one mode of operation in which the main fuel is ammonia,
- at least one cylinder having a cylinder liner, a reciprocating piston in said cylinder liner and a cylinder cover covering it;
a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed in the cylinder cover or the cylinder liner;
- an ammonia absorption system;
- an ammonia discharge channel;
with
the ammonia discharge channel connects the outlet of the ammonia fuel system to the inlet of the ammonia absorption system;
The ammonia absorption system, in use, comprises the water to absorb ammonia supplied through the ammonia discharge channel to form aqueous ammonia.
institution. Said ammonia absorption system preferably comprises at least one vessel which in use is at least partially filled with water, said at least one vessel preferably comprising a water inlet for connecting a water source and discharging said aqueous ammonia. 2. An engine according to claim 1, preferably comprising an aqueous ammonia outlet for 3. The engine of claim 2, wherein the aqueous ammonia outlet is connected to the ammonia fuel system to combust the aqueous ammonia within the engine. 3. The engine of claim 2, comprising an SCR reactor in an exhaust flow path of said engine, said aqueous ammonia outlet being connected to a reductant inlet associated with said SCR reactor. Said ammonia absorption system comprises a pressure vessel which in use is at least partially filled with water, said pressure vessel is preferably provided with a cooling system for reducing the temperature of said pressure vessel, said pressure vessel being in the vapor phase. 4. Preferably comprising a vapor phase ammonia inlet for taking in ammonia, said pressure vessel preferably being connected to a water source, said pressure vessel preferably comprising an aqueous ammonia outlet for discharging said aqueous ammonia. 1. Agency. Preferably said ammonia absorption system comprises an aggregated absorption tower, said absorption tower comprising a vapor phase ammonia inlet for taking in vapor phase ammonia, said ammonia absorption system preferably being connected to a water source, 2. An engine according to claim 1, wherein said ammonia absorption system preferably comprises an ammonia water outlet for discharging ammonia water. The ammonia absorption system comprises a cascade of water tanks each at least partially filled with water in use, a first water tank comprising a vapor phase ammonia inlet and a vapor phase ammonia outlet, a water inlet and an ammonia gas outlet. a water outlet, wherein a subsequent water tank is connected to the gas phase ammonia inlet connected to the gas phase ammonia outlet of the first water tank and to the water inlet of the first water tank. and a gas phase ammonia outlet, said cascade preferably being configured for water flow in a counter direction to the flow of gas phase ammonia, said gas phase in use The water tank furthest upstream in the flow of phase ammonia has the highest concentration of ammonia in the water in the tank, and is provided with an ammonia water outlet. 2. An engine as claimed in claim 1, wherein water has the lowest concentration of ammonia and a vent is preferably provided for discharging gaseous substances from said tank. Said ammonia fuel system comprises a purge system configured to exhaust ammonia from said ammonia fuel system to said ammonia absorption system, said purge system preferably comprising a source of pressurized nitrogen, said source of pressurized nitrogen preferably is connected to the ammonia fuel system via a purge valve, and the purge system preferably uses the ammonia discharge flow path to purge ammonia from the ammonia fuel system to the ammonia absorption system. Agency listed. The ammonia fuel system includes an intermediate pressure ammonia supply line and an ammonia return line, a first purge line connecting the intermediate 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 a valve for selectively connecting said intermediate pressure ammonia supply line and said ammonia return line to said ammonia absorption system. A knockout drum is provided 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 having a gas phase ammonia outlet and a liquid phase ammonia outlet. 10. An engine according to claim 9, preferably comprising an outlet, said vapor phase ammonia outlet being connected to said ammonia absorption system and said liquid phase ammonia outlet being connected to a recovery tank connected to said ammonia fuel system. 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 the inner and outer pipes of the double-walled pipe being 2. An engine according to claim 1, fluidly connected to said ammonia absorption system by said ammonia discharge channel. Said ammonia fuel system comprises a liquid phase ammonia fuel tank and a low pressure ammonia supply line connecting said liquid phase ammonia fuel tank to an inlet of a medium pressure fuel pump by operation of a low pressure pump, said ammonia fuel system preferably comprising: A medium pressure fuel line connecting the outlet of the medium pressure fuel pump to the inlet of the fuel valve, the ammonia fuel system preferably comprising a return line connecting the outlet of the fuel valve to the inlet of the medium pressure fuel pump. 2. The engine of claim 1, comprising: 1. A method of managing ammonia in a large two-stroke uniflow scavenging turbocharged internal combustion engine having at least one mode of operation in which the primary fuel is ammonia, said engine comprising:
- at least one cylinder having a cylinder liner, a reciprocating piston in said cylinder liner and a cylinder cover covering it;
a combustion chamber defined between the reciprocating piston in the cylinder 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
The method includes transporting excess vapor phase ammonia from the ammonia fuel system to the ammonia absorption system and absorbing the excess vapor phase ammonia in water to form aqueous ammonia. separating liquid phase ammonia and gas phase ammonia obtained from said excess gas phase ammonia, preferably using a knockout drum; transferring said gas phase ammonia to said ammonia absorption system; transferring ammonia; into water to form aqueous ammonia. 15. A method according to claim 13 or 14, comprising using said aqueous ammonia as fuel for said engine or as a reductant for an SCR reactor of said engine.

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