KR20230030937A - Ammonia Treatment System And Method For Ship Engine - Google Patents

Abstract

Disclosed are a system and a method for treating ammonia of a vessel engine. In accordance with the present invention, the system for treating ammonia of a vessel engine, includes: a service tank storing ammonia to be supplied as engine fuel in a vessel equipped with an engine supplied with ammonia; a fuel supply line supplying liquid ammonia as fuel from the service tank to the engine; a fuel supply unit supplying the ammonia from the service tank to the engine at pressure and temperature adjusted to a level required by the engine; a fuel return line recovering ammonia not consumed in the engine, to the upstream of the fuel supply unit; and a cooling line in which a refrigerant cooling the service tank is circulated. The cooling line can receive ammonia gas produced from the service tank and circulate the gas to the refrigerant, wherein the ammonia discharged from a fuel pipe of the engine and the fuel supply unit can be supplied to the cooling line. Therefore, the present invention is capable of securing safety by quickly discharging ammonia from each pipe and a fuel supply unit.

Description

Ammonia Treatment System And Method For Ship Engine

The present invention relates to a system and method for treating ammonia in a marine engine, and more particularly, for a marine engine that recovers ammonia discharged from a fuel pipe and a fuel supply unit of an engine and then cools a service tank in which the ammonia is stored or returns it to the service tank for treatment. It relates to an engine ammonia treatment system and method.

Efforts are being made to reduce greenhouse gas emissions worldwide as the global warming phenomenon intensifies, and as the Kyoto Protocol in 1997, which contained the obligations of developed countries to reduce greenhouse gases, expired in 2020, the conference was held in Paris, France in December 2015. According to the Paris Climate Change Accord, which was adopted in the 21st United Nations Framework Convention on Climate Change and entered into force in November 2016, the 195 Parties participating in the agreement are making various efforts to reduce greenhouse gases.

Along with this global trend, interest in renewable energy (or renewable energy) such as wind power, solar power, solar heat, bioenergy, tidal power, and geothermal heat has increased and various technologies have been developed as pollution-free energy that can replace fossil fuels and nuclear power. are losing

Liquefied gas, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so it can be seen as an eco-friendly fuel with less air pollutant emissions during combustion. Accordingly, in recent years, consumption of liquefied gas such as liquefied natural gas (LNG) has been rapidly increasing worldwide. Since liquefied gas obtained by liquefying gas at a low temperature has a very small volume compared to gas, it has the advantage of increasing storage and transfer efficiency.

Liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component by cooling it to about -162 ° C, and has a volume of about 1/600 compared to natural gas. Therefore, when the natural gas is liquefied and transported, it can be transported very efficiently.

Liquefied petroleum gas has a difference in liquefaction temperature depending on its composition, but in the case of petroleum gas whose main component is propane, it is liquefied at a low temperature of about -42 ℃ at atmospheric pressure, up to about 45 ℃ at 18 bar, and liquid up to 20 ℃ at 7 bar. state can be stored.

On the other hand, conventional LPG carriers adopt a fuel supply system using heavy oil such as bunker C oil, which is relatively inexpensive as a propulsion fuel for ships. Due to stricter regulations, a separate heavy fuel oil fuel tank (LSHFO tank) with low sulfur content had to be installed, and the demand for an eco-friendly fuel supply system that meets international environmental regulatory standards has increased.

In recent years, the application of fuel supply systems that use LPG or LNG and boil-off gas generated from them as propulsion fuel in LPG or LNG carriers is increasing, and in accordance with the strengthening of international exhaust gas emission regulations, general ships in addition to LPG or LNG carriers are also using LNG. Ships using it as a propulsion fuel are increasing.

In particular, LPG is easier to store than LNG, which is liquefied at cryogenic temperatures, and does not fall significantly in SPECIFIC ENERGY and ENERGY DENSITY compared to existing HFO, and has excellent effects in reducing SOX, NOX, CO2, PM, etc. compared to existing HFO.

Although LNG or LPG is evaluated as an eco-friendly fuel compared to other fossil fuels previously used as ship fuel, carbon dioxide is still generated when burned, and ships that use it as fuel still emit carbon dioxide during operation.

IMO (International Maritime Organization), a UN specialized organization established to internationally unify ship routes, traffic rules, port facilities, etc., also reduced greenhouse gas emissions by 50% in 2050 compared to 2008 and 100% in 2100. % reduction (GHG Zero Emission) is presented as a goal, and regulations in each country and region are expected to be strengthened accordingly.

According to EEDI (Energy Efficiency Design Index), a compulsory carbon dioxide reduction regulation applied by IMO to new ships, in the initial EEDI announcement, CO2 emissions in 2015 were reduced by 10% based on the CO2 emissions from 2013 to 2015 EEDI Phase 1 was applied, and it was scheduled to apply Phase 3 in 2025 by strengthening and applying one step every 5 years. are making it As such, regulations on carbon dioxide emissions are rapidly being strengthened, and in the case of LPG carriers of 15,000 DWT or more, if the standards of Phase 4 (40% reduction in carbon dioxide emissions) or higher are applied in the future, LPGCs that use LPG as fuel will not be able to achieve carbon dioxide emission regulations. It can be difficult.

Accordingly, various studies on eco-friendly ship fuels capable of reducing carbon dioxide emissions have been conducted, and recently, technologies related to ship engines capable of using ammonia as a fuel along with fuels such as LNG or LPG have been developed.

Ammonia (NH ₃ ) is a substance in which three hydrogens are bonded to one nitrogen, and it is easy to liquefy because it can form a strong hydrogen bond between molecules, and has a boiling point of -33.34 ° C and a melting point of -77.73 ° C under normal pressure.

This ammonia is easier to store than LNG, and although it is slightly lower in SPECIFIC ENERGY and ENERGY DENSITY compared to existing HFO, it does not emit carbon dioxide at all, so it is attracting attention as an eco-friendly ship fuel that can respond to the strengthening trend of international greenhouse gas emission standards.

The present invention proposes a method for effectively treating ammonia discharged from fuel supply pipes and fuel supply systems and ammonia in exhaust gas when the engine is stopped or tripped while supplying ammonia as fuel for a ship engine. want to do

According to one aspect of the present invention for solving the above problems, a service tank for storing ammonia to be supplied as engine fuel in a ship equipped with an engine receiving ammonia;

a fuel supply line supplying liquid ammonia as fuel from the service tank to the engine;

a fuel supply unit supplying ammonia from the service tank to the engine at a pressure and temperature required by the engine;

a fuel return line for recovering ammonia not consumed in the engine upstream of the fuel supply unit; and

A cooling line through which a refrigerant cooling the service tank circulates;

The cooling line receives ammonia gas generated from the service tank and circulates it as a refrigerant, and supplies ammonia discharged from the fuel pipe and fuel supply unit of the engine to the cooling line. is provided.

Preferably, the cooling line includes a compressor for receiving and compressing ammonia gas; a cooling device that cools and liquefies the ammonia gas compressed by the compressor; And an expansion device for receiving liquefied ammonia from the cooling device and expanding and cooling it: may be provided.

Preferably, an ammonia recovery line branched from the cooling line at the rear end of the cooling device and connected to the service tank; an ammonia recovery selection valve opening and closing the ammonia recovery line; And an ammonia heat exchanger provided in the ammonia recovery line and receiving liquefied ammonia from the cooling device for additional cooling, wherein in the ammonia heat exchanger, the ammonia liquefied in the cooling device passes through the expansion device for expansion and cooling. It can be cooled by heat exchange with the ammonia gas of the cooling line.

Preferably, a fuel valve train (FVT) in which a service valve for controlling ammonia supply between the fuel supply line and the fuel return line and the engine is disposed; a first drum for recovering ammonia discharged from the fuel supply unit; And a second drum for recovering ammonia discharged from the fuel valve train: further comprising, in the fuel valve train, the fuel supply line and the fuel return line are double block valves for controlling the supply of ammonia, respectively. valve) can be installed.

Preferably, a first vent line connected to the first drum from the fuel supply unit; a first vent return line branched off from the first vent line and connected upstream of the compressor of the cooling line; a first three-way valve provided at a branch point of a first vent return line from the first vent line; and a vent purging selection valve opening and closing the first vent return line.

Preferably, a second vent line connected to the second drum between double shutoff valves provided in the fuel supply line in the fuel valve train; a third vent line connected to the second drum between double shut-off valves provided in the fuel return line in the fuel valve train; and a fourth vent line connected to the second drum upstream of the double shutoff valve of the fuel return line in the fuel valve train.

Preferably, a second vent recovery line branched off from the fourth vent line and connected upstream of the vent purging selection valve of the first vent recovery line; a second three-way valve provided at a branch point of a second vent return line from the fourth vent line; a third vent recovery line branched off from the third vent line and connected upstream of the vent purging selection valve of the first vent recovery line; and a third three-way valve provided at a branch point of the third vent return line from the third vent line.

Preferably, when the ammonia fuel mode of the engine is stopped, the double shutoff valves of the fuel supply line and the fuel return line are closed and the pressure between the valves is relieved through the second and third vent lines, and the first and second shutoff valves are closed. 4 The ammonia remaining in the fuel supply unit and the engine may be discharged through the vent line, and the ammonia discharged from the fuel pipe and the fuel supply unit may be supplied to the cooling line by opening the vent purging selection valve.

Preferably, when venting is completed by discharging ammonia remaining in the fuel pipe and the fuel supply unit, the vent purging selection valve is closed and nitrogen is supplied to the fuel pipe and the fuel supply unit to perform purging.

Preferably, water is injected into the first drum and the second drum to generate ammonia water, and the presence or absence of liquid inside the first drum and the second drum is detected by a level sensor to restart the engine in the ammonia fuel mode. can determine whether

According to another aspect of the present invention, in a ship equipped with an engine receiving ammonia, ammonia is supplied at a pressure and temperature required by the engine through a fuel supply unit from a service tank,

While recovering ammonia not consumed in the engine upstream of the fuel supply unit,

Ammonia gas generated in the service tank is discharged to a refrigerant line and circulated as a refrigerant to cool the service tank, and the ammonia discharged from the fuel pipe and fuel supply unit of the engine can be supplied to the cooling line. A method for ammonia treatment of an engine is provided.

Preferably, the cooling line includes a compressor for receiving and compressing ammonia gas; a cooling device that cools and liquefies the ammonia gas compressed by the compressor; and an expansion device for receiving liquefied ammonia from the cooling device and expanding and cooling the ammonia.

In the present invention, ammonia, which is an eco-friendly fuel, is supplied as fuel for a ship engine to reduce greenhouse gas emissions during ship operation and to meet regulatory standards set by international agreements.

In particular, when an engine stops or a trip occurs, ammonia is quickly discharged from each pipe for supplying fuel and a fuel supply unit to ensure safety.

In addition, by sending the discharged ammonia to the cooling line and using it as a refrigerant for cooling the service tank, vaporization of ammonia in the service tank can be prevented and the tank pressure can be adjusted.

1 schematically shows an ammonia treatment system for a marine engine according to an embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

Hereinafter, the ship in the present invention refers to all types of ships in which an engine capable of using ammonia as a fuel for an inboard engine is installed, and is representative of an LPG carrier, an LNG carrier, a liquid hydrogen carrier, and a liquid hydrogen carrier. Carriers, ammonia carriers, container carriers, crude oil carriers, bulk carriers such as minerals or grains, ships with self-propelled capabilities such as Ro-Ro (Roll on/Roll off) ships, etc. Offshore structures under construction may also be included.

An engine supplied with ammonia as a fuel of an engine means to be supplied as fuel together with other marine fuel such as LNG, LPG, HFO, and Diesel Oil, and to be supplied with ammonia alone as fuel, and is used for propulsion of a ship. Includes both engines and engines for power generation.

1 schematically shows an ammonia treatment system for a marine engine according to an embodiment of the present invention.

As shown in FIG. 1, the ammonia treatment system of the present embodiment includes a service tank for storing ammonia to be supplied as engine fuel in a ship equipped with an engine E that receives ammonia, a pressure required by the engine for ammonia in the service tank, and It includes a fuel supply unit (LFS) supplying fuel according to the temperature, and ammonia recovery drums (D1, D2) for recovering ammonia discharged from the fuel pipe and fuel supply unit of the engine and ammonia in the exhaust.

To supply fuel to the marine engine, a fuel supply line supplying liquid ammonia to the engine from the service tank is connected.

In the service tank (ST), ammonia is stored in a liquid state, and liquefied ammonia can be stored at room temperature by pressurizing, for example, around 5 to 20 bar. A safety valve (STV) for preventing an increase in tank pressure may be provided in the service tank.

Ammonia stored in the service tank is supplied to the engine (E) along the fuel supply line (FSL) through the transfer pump 10, and the fuel supply line supplies fuel according to fuel supply conditions such as pressure and temperature required by the engine. A fuel supply unit (LFS) for supplying is provided.

In the fuel supply unit (LFS), a compression pump 20 compresses ammonia transferred from the transfer pump to a pressure required by the engine, and a temperature controller 30 heats or cools the fuel compressed by the compression pump to adjust the temperature required by the engine. ), and a filter 40 for filtering out foreign substances contained in the fuel to protect the engine.

Liquid ammonia supplied from the service tank through the transfer pump is compressed, for example, to around 50 to 85 bar by the compression pump, and after the temperature is adjusted to around 45°C through a temperature controller, foreign substances are filtered out and sent to the engine as a high-pressure liquid. The engine may be operated by being injected into the nozzle at a pressure of 600 to 700 bar by hydraulic pressure from the engine.

When an incompressible fluid having little or no change in volume even when pressure is applied, that is, fuel in a liquid state is supplied to the engine, excess fuel is supplied to the engine to respond to engine load fluctuations and prevent cavitation. Among the fuel supplied to the engine, the remaining fuel after being consumed as fuel is recovered upstream of the engine.

To this end, the system of this embodiment is provided with a fuel return line (FRL) for recovering ammonia not consumed by the engine upstream of the fuel supply unit, and the fuel return line is provided upstream of the fuel supply unit from the engine, for example, the service tank (ST). ) can be connected.

When the fuel supply line and the fuel return line pass through the safe area of the engine room, they may be configured as double pipes to prevent danger in case of ammonia leakage from the pipe.

Service valves are disposed in the fuel valve train (FVT) to control the supply of ammonia between the fuel supply line and the fuel return line and the engine. A double block and bleed valve (DV1, DV2) is installed to supply ammonia to the engine, and when the ammonia fuel supply is stopped due to engine fuel oil conversion, ammonia fuel mode stop, trip, etc., ammonia due to temperature rise When is not in a liquid state but is gasified, each pipe is double-blocked and the pressure in the pipe is relieved.

In the present embodiment, the ammonia discharged from the fuel supply unit and each pipe for pressure relief is recovered to the ammonia recovery drums D1 and D2 without being discharged into the atmosphere.

The ammonia recovery drum includes a first drum D1 for recovering ammonia discharged from the fuel supply unit LFS and a second drum D2 for recovering ammonia discharged from the fuel valve train FVT.

The first vent line (VL1) is connected from the fuel supply unit (LFS) to the first drum (D1), and between the double shutoff valve (DV1) provided in the fuel supply line (FSL) in the fuel valve train (FVT), the second drum (D2), the second vent line (VL2) is connected to the second drum (D2) between the double shutoff valve (DV2) provided in the fuel return line (FRL) in the fuel valve train (FVT), and the third vent line (VL3) In the fuel valve train (FVT), the fourth vent line (VL4) is respectively connected to the second drum (D2) upstream of the double shutoff valve of the fuel return line (FRL). Venting valves VV1 and VV2 for controlling discharge of ammonia to the first or second drum are provided on the first to fourth vent lines, respectively.

For example, when the ammonia fuel mode of the engine is stopped, the double shutoff valves (DV1, DV2) of the fuel supply line and fuel return line are closed, and the second drum (D2) is discharged through the second and third vent lines (VL2, VL3). Ammonia is released to relieve the pressure between the valves, and the ammonia remaining in the fuel supply unit (LFS) and the engine is discharged to the first and second drums by opening the venting valves (VV1, VV2) of the first and fourth vent lines, respectively. This can reduce the risk of fuel explosion.

In this way, ammonia water may be generated by supplying water to ammonia discharged from the fuel supply unit and respective pipes and recovered to the ammonia recovery drums D1 and D2.

That is, ammonia is discharged from the fuel supply unit and each pipe and recovered to the ammonia recovery drum, and the pressure is lowered to change the phase from liquid to gas. Ammonia has a very high solubility in water. Therefore, fresh water is sprayed on gaseous ammonia recovered in the ammonia recovery drum through an injection unit (not shown) to generate ammonia water, which can be used on board or discharged overboard as necessary.

A level sensor LS for detecting liquid inside the drum is provided on each of the ammonia recovery drums D1 and D2, and whether or not the engine is restarted in the ammonia fuel mode is determined based on the presence or absence of liquid inside the ammonia recovery drum detected by the level sensor. can

On the other hand, ammonia stored in the service tank (ST) is vaporized to generate boil-off gas and the internal pressure of the tank may increase. It includes a circulating cooling line (CL).

The cooling line CL of this embodiment may receive ammonia gas generated from the service tank ST and circulate it as a refrigerant.

In the cooling line CL, a compressor 100 for receiving and compressing ammonia gas, a cooling device 200 for cooling and liquefying the ammonia gas compressed in the compressor, and an expansion device for receiving liquefied ammonia from the cooling device to expand and cool it. 300 is provided.

The ammonia gas generated in the service tank is supplied to the refrigerant line from the service tank and circulated as a refrigerant before the safety valve (STV) of the service tank bursts.

The ammonia gas discharged from the service tank is compressed in the compressor and then liquefied while being cooled in the cooling device. As the refrigerant of the cooling device, for example, seawater, glycol water, or the like can be used.

The liquefied ammonia cooled in the cooling device changes its phase to gas as it expands in the expansion device, and is cooled by the Joule-Thomson effect. The ammonia cooled in the expansion device is supplied to the service tank along the cooling line to cool the service tank.

When the service tank is sufficiently cooled, ammonia in the cooling line may be liquefied and recovered into the service tank.

To this end, an ammonia recovery line (ARL) branched from the cooling line and connected to the service tank is connected at the rear end of the cooling device, and an ammonia recovery selection valve (SV2) for opening and closing the ammonia recovery line is connected to the ammonia recovery line. An ammonia heat exchanger 400 for additional cooling by receiving the supplied ammonia is provided. In the ammonia heat exchanger 400, ammonia liquefied in the cooling device 200 and branched to the ammonia recovery line (ARL) is further cooled by heat exchange with ammonia gas in the cooling line (CL) expanded and cooled through the expansion device 300 After that, it can be transferred to the service tank (ST).

Meanwhile, ammonia discharged from the fuel pipe and fuel supply unit of the engine may also be supplied to the cooling line CL and circulated as a refrigerant for cooling the service tank.

To this end, a first vent return line RL1 branched off from the first vent line VL1 and connected upstream of the compressor 100 of the cooling line is provided, and a first vent return line RL1 is provided at a branch point of the first vent return line from the first vent line. 1 A three-way valve (TV1) is provided, and a vent purging selection valve (SV1) for opening and closing the first vent return line is provided.

In addition, a second vent recovery line RL2 branched from the fourth vent line VL4 and connected upstream of the vent purging selection valve of the first vent recovery line is provided, and the fourth vent line branches from the second vent recovery line. A second three-way valve (TV2) is provided at the branch, and a third vent return line (RL3) branched off from the third vent line (VL3) and connected upstream of the vent purging selection valve of the first vent return line is provided, A third three-way valve TV3 is provided at a branch point of the third vent return line from the third vent line.

When the ammonia fuel mode of the engine is stopped, the double shutoff valves (DV1, DV2) of the fuel supply line and the fuel return line are closed, the pressure between the valves is relieved through the second and third vent lines, and the first and fourth vent lines The ammonia remaining in the fuel supply unit and the engine is discharged through, but the first to third three-way valves (TV1, TV2, TV3) are adjusted to remove the ammonia discharged from the fuel supply unit and each pipe through the first to third vent recovery lines (RL1, RL2, RL3), and open the vent purging selection valve (SV1) to supply to the cooling line (CL).

Ammonia supplied to the cooling line is compressed in the compressor 100, cooled in the cooling device 200, expanded and cooled in the expansion device 300, and supplied to the service tank ST along the cooling line CL to be supplied to the service tank. can be cooled. The ammonia recovery selection valve (SV2) of the ammonia recovery line (ARL) may be opened, and the ammonia liquefied in the cooling device may be additionally cooled in the ammonia heat exchanger (400) and recovered to the service tank (ST).

When venting is completed by discharging ammonia remaining in the fuel supply unit and each pipe, the first to third three-way valves (TV1, TV2, TV3) are adjusted to return to the first to third vent recovery lines (RL1, RL2, RL3). block the flow of Nitrogen may be supplied to the fuel pipe and the fuel supply unit to perform purging.

If cooling of the service tank is continuously required to adjust the pressure of the service tank, the cooling line can be operated as a closed circuit after the vent purging selection valve (SV1) is closed.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be variously modified or modified without departing from the technical gist of the present invention. it did

E: engine
ST: service tank
FSL: fuel supply line
FRL: fuel return line
LFS: fuel supply
FVT: fuel valve train
D1, D2: ammonia recovery drum
VL1, VL2, VL3, VL4: first to fourth vent lines
RL1. RL2, RL3: first to third vent recovery lines
CL: cooling line
100: compressor
200: cooling device
300: expansion device
400: ammonia heat exchanger

Claims (12)

A service tank for storing ammonia to be supplied as engine fuel in a ship equipped with an engine receiving ammonia;
a fuel supply line supplying liquid ammonia as fuel from the service tank to the engine;
a fuel supply unit supplying ammonia from the service tank to the engine at a pressure and temperature required by the engine;
a fuel return line for recovering ammonia not consumed in the engine upstream of the fuel supply unit; and
A cooling line through which a refrigerant cooling the service tank circulates;
The cooling line receives ammonia gas generated from the service tank and circulates it as a refrigerant, and supplies ammonia discharged from the fuel pipe and fuel supply unit of the engine to the cooling line. . The method of claim 1, wherein the cooling line
A compressor for receiving and compressing ammonia gas;
a cooling device that cools and liquefies the ammonia gas compressed by the compressor; and
An ammonia treatment system for a marine engine, characterized in that an expansion device for receiving liquefied ammonia from the cooling device and expanding and cooling it. According to claim 2,
an ammonia recovery line branched from the cooling line at the rear end of the cooling device and connected to the service tank;
an ammonia recovery selection valve opening and closing the ammonia recovery line; and
An ammonia heat exchanger provided in the ammonia recovery line and receiving liquefied ammonia from the cooling device for additional cooling;
In the ammonia heat exchanger, the ammonia treatment system of the marine engine, characterized in that the ammonia liquefied in the cooling device is cooled by heat exchange with the ammonia gas of the cooling line expanded and cooled through the expansion device. According to claim 3,
a fuel valve train (FVT) in which a service valve controlling ammonia supply between the fuel supply line and the fuel return line and the engine is disposed;
a first drum for recovering ammonia discharged from the fuel supply unit; and
A second drum for recovering ammonia discharged from the fuel valve train;
Ammonia treatment system of a marine engine, characterized in that in the fuel valve train, a double block and bleed valve for controlling ammonia supply is installed in the fuel supply line and the fuel return line, respectively. According to claim 4,
a first vent line connected from the fuel supply unit to the first drum;
a first vent return line branched off from the first vent line and connected upstream of the compressor of the cooling line;
a first three-way valve provided at a branch point of a first vent return line from the first vent line; and
Ammonia treatment system of a marine engine further comprising: a vent purging selection valve for opening and closing the first vent return line. According to claim 5,
a second vent line connected to the second drum between double shut-off valves provided in the fuel supply line in the fuel valve train;
a third vent line connected to the second drum between double shut-off valves provided in the fuel return line in the fuel valve train; and
Ammonia treatment system of a marine engine further comprising a fourth vent line connected to the second drum upstream of the double shutoff valve of the fuel return line in the fuel valve train. According to claim 6,
a second vent recovery line branched off from the fourth vent line and connected upstream of the vent purging selection valve of the first vent recovery line;
a second three-way valve provided at a branch point of a second vent return line from the fourth vent line;
a third vent recovery line branched off from the third vent line and connected upstream of the vent purging selection valve of the first vent recovery line; and
Ammonia treatment system of a marine engine further comprising: a third three-way valve provided at a branch point of the third vent recovery line from the third vent line. According to claim 7,
When the ammonia fuel mode of the engine is stopped, the double shutoff valves of the fuel supply line and the fuel return line are closed, the pressure between the valves is relieved through the second and third vent lines, and the first and fourth vent lines are closed. Ammonia treatment system for a marine engine, characterized in that the ammonia remaining in the fuel supply unit and the engine can be discharged through the fuel supply unit and the ammonia discharged from the fuel supply unit by opening the vent purging selection valve to supply the ammonia discharged from the fuel pipe and the fuel supply unit to the cooling line. According to claim 8,
Ammonia treatment system of a marine engine, characterized in that when venting is completed by discharging ammonia remaining in the fuel pipe and fuel supply unit, the vent purging selection valve is closed and nitrogen is supplied to the fuel pipe and fuel supply unit for purging. According to any one of claims 4 to 9,
Water is sprayed into the first drum and the second drum to generate ammonia water,
The ammonia treatment system of a marine engine, characterized in that it is possible to determine whether the engine is restarted in the ammonia fuel mode by detecting the presence or absence of liquid inside the first drum and the second drum by a level sensor. In a ship equipped with an engine receiving ammonia, supply ammonia at the pressure and temperature required by the engine through the fuel supply unit from the service tank,
While recovering ammonia not consumed in the engine upstream of the fuel supply unit,
Ammonia gas generated in the service tank is discharged to a refrigerant line and circulated as a refrigerant to cool the service tank, and the ammonia discharged from the fuel pipe and fuel supply unit of the engine can be supplied to the cooling line. How to treat ammonia in an engine. The method of claim 11, wherein the cooling line
A compressor for receiving and compressing ammonia gas;
a cooling device that cools and liquefies the ammonia gas compressed by the compressor; and
Ammonia treatment method of a marine engine, characterized in that provided: an expansion device for receiving liquefied ammonia from the cooling device and expanding and cooling it.

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