Marine liquid ammonia fuel supply system capable of cooling ammonia ejector

Abstract

A marine liquid ammonia fuel supply system capable of cooling an ammonia injector is provided with a dual-fuel main engine capable of using liquid ammonia or diesel oil as fuel, the system is provided with a variable-frequency low-pressure fuel pump and a variable-frequency high-pressure fuel pump to supply the liquid ammonia to the dual-fuel main engine, and the frequency can be changed along with the load of the main engine. Liquid ammonia is heated and pressurized to 40 DEG C and 85 barg required by a dual-fuel main engine through a heater and a high-pressure fuel pump, liquid ammonia fuel enters the main engine, and after operation in an ammonia fuel mode is finished, the liquid ammonia fuel is purged and refluxed, so that the liquid ammonia fuel can be recycled, ammonia gas can be absorbed, and residual nitrogen is discharged into the atmosphere. By slightly improving the existing liquid ammonia supply system, the function of cooling the ammonia injector in the main engine ammonia fuel mode can be realized, and the cost and the space are greatly saved. The liquid ammonia fuel replaces fresh water to cool the ammonia ejector, and due to the fact that the temperature of liquid ammonia is lower and the specific heat capacity is larger than that of water, the cooling effect is better.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid ammonia fuel supply systems, and particularly relates to a marine liquid ammonia fuel supply system capable of cooling ammonia injectors. BACKGROUND

[0002] The demand for green and environmentally friendly ships in the shipping industry is growing, and it is urgent to develop and introduce innovative technologies and alternative fuels for emission reduction measures in the shipping industry. Using low-carbon or even zero-carbon fuels to replace traditional marine fuels is an important measure for the shipping industry to reduce emissions. Among many new types of fuels, ammonia is one of the potential zero-carbon fuels, which can be stored on ships at a temperature of minus 33 degrees Celsius, has an acceptable energy density, does not produce carbon and sulfur compounds when burned, is easy to store and transport, has abundant energy and low price, and has become the focus of industry research.

[0003] At present, diesel / liquid ammonia dual-fuel main engines that can be applied to large ships and use ammonia fuel are still in the research and development process. When a prototype test is conducted, it is found that when the main engine is running in ammonia fuel mode, the ammonia injector that injects ammonia fuel into the cylinder has a continuously rising temperature due to contact with high-temperature and high-pressure servo oil and liquid ammonia fuel, and is located adjacent to the combustion chamber. Therefore, the temperature eventually exceeds the material's bearing capacity, and thus appropriate cooling measures need to be taken for the ammonia injector. According to the traditional method, a separate fresh water cooling system is configured for the ammonia injector. Although this can solve the problem of cooling the ammonia injector, since the cooling power required by the ammonia injector is not large, the separate configuration of a complete cooling system including a pressure water tank, a delivery pump, pipelines, corresponding valves, instruments, a control system, etc. not only increases the cost, but also occupies a large space and increases the complexity and failure rate of system configuration. SUMMARY

[0004] To solve the above problems, the application provides a marine liquid ammonia fuel supply system capable of cooling ammonia injectors, which aims to achieve the purpose of cooling the ammonia injectors without separately configuring a fresh water cooling system when the main engine is running in ammonia fuel mode. The technical solution adopted by the application is as follows:

[0005] A marine liquid ammonia fuel supply system capable of cooling ammonia injectors, wherein a liquid ammonia fuel tank is provided with a low-pressure fuel pump, the low-pressure fuel pump is connected with a buffer tank, a heater, a high-pressure fuel pump, a double filter and a fuel valve group unit in sequence through pipelines, the fuel valve group unit is connected with an ammonia injector through a supply double-wall pipe, and the ammonia injector is installed at the top of a cylinder and used for spraying liquid ammonia fuel into the cylinder.

[0006] The dual-fuel main engine is connected with the fuel valve group unit, an ammonia gas treatment unit, an ammonia gas absorption device and a gas permeable mast in sequence through a return double-wall pipe.

[0007] The nitrogen supply unit is connected with the fuel valve group unit to provide nitrogen for purging the liquid ammonia fuel supply system and the main engine.

[0008] The fuel valve group unit is connected with the ammonia treatment unit and the buffer tank through pipelines, and the fourth remote control valve is arranged on the passage of the fuel valve group unit to the ammonia treatment unit, and the fifth remote control valve is arranged on the passage of the fuel valve group unit to the buffer tank.

[0009] When the main engine operates in the ammonia fuel mode, a part of the liquid ammonia fuel is used as the cooling medium of the ammonia injector, so that the existing liquid ammonia fuel supply system is improved to serve as the ammonia injector cooling system.

[0010] The ammonia injector is installed on the top of the cylinder in the dual-fuel main engine, and the heat exchange coil is wound outside the ammonia injector.

[0011] When the dual-fuel main engine operates in the ammonia fuel mode, the low-pressure fuel pump is used to deliver the liquid ammonia to the buffer tank, and the heater and the high-pressure fuel pump are used to warm and pressurize the liquid ammonia, and then the liquid ammonia is filtered through the double filter, and then sequentially passes through the fuel valve group unit and the supply double-wall pipe to the dual-fuel main engine.

[0012] The supply double-wall pipe is connected with the ammonia injector, the second remote control valve is arranged on the passage of the supply double-wall pipe to the ammonia injector, the cooling branch pipeline is extended from the passage of the supply double-wall pipe to the ammonia injector, the third remote control valve is arranged on the cooling branch pipeline, most of the liquid ammonia is injected into the cylinder through the ammonia injector for combustion and work, a small part of the liquid ammonia enters the cooling branch pipeline of the ammonia injector, and the liquid ammonia exchanges heat with the ammonia injector when passing through the heat exchange coil, and then the cooled liquid ammonia is returned to the buffer tank through the return double-wall pipe.

[0013] After the ammonia fuel mode operation is completed, the nitrogen is used to purge the fuel supply pipeline and the dual-fuel main engine, the gas-liquid mixture is purged to the ammonia treatment unit through the return double-wall pipe for gas-liquid separation, the separated liquid ammonia is returned to the buffer tank through the first remote control valve, and the separated gas is introduced into the ammonia gas absorption device.

[0014] The above-mentioned ship liquid ammonia fuel supply system capable of cooling the ammonia injector further warms the liquid ammonia to 40℃ through the heater and the high-pressure fuel pump, and pressurizes the liquid ammonia to 85bar.

[0015] The above-mentioned ship liquid ammonia fuel supply system capable of cooling the ammonia injector further absorbs the ammonia gas in the ammonia gas absorption device through water.

[0016] The ship liquid ammonia fuel supply system capable of cooling ammonia ejector further has a bypass pipeline connected with the buffer tank and provided with an adjusting valve at the pipeline, and the excess fuel can be returned to the buffer tank to adjust the fuel amount supplied to the main engine.

[0017] The ship liquid ammonia fuel supply system capable of cooling ammonia ejector further has the liquid ammonia heater taking water glycol as an intermediate medium and steam as a heat source.

[0018] The ship liquid ammonia fuel supply system capable of cooling ammonia ejector further has the double filter with an absolute mesh accuracy of 10 mu m.

[0019] The present application has the following advantages:

[0020] 1. The present application realizes the cooling function of the ammonia ejector in the ammonia fuel mode of the main engine by slightly improving the existing liquid ammonia supply system, thereby greatly saving the cost and space.

[0021] 2. The present application uses liquid ammonia fuel to replace fresh water to cool the ammonia ejector, and since the liquid ammonia has a lower temperature and a larger specific heat capacity than water, the cooling effect is better.

[0022] 3. The present application returns the liquid ammonia with a higher temperature after cooling the ammonia ejector to the liquid ammonia supply system, which is equivalent to preheating the liquid ammonia fuel by using the excess heat of the ammonia ejector, thereby greatly saving energy and improving the energy efficiency of the ship.

[0023] 4. The present application has simple and effective configuration, reliable operation and low failure rate. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a system schematic diagram of the present application;

[0025] 1-liquid ammonia fuel tank, 2-low pressure fuel pump, 3-buffer tank, 4-heater, 5-high pressure fuel pump, 6-adjusting valve, 7-double filter, 8-fuel valve group unit, 9-supply double-wall pipe, 10-dual fuel main engine, 11-ammonia ejector, 12-cylinder, 13-nitrogen supply unit, 14-return double-wall pipe, 15-ammonia gas treatment unit, 16-first remote control valve, 17-ammonia gas absorption device, 18-permeable mast, 19-second remote control valve, 20-third remote control valve, 21-heat exchange coil, 22-fourth remote control valve, 23-fifth remote control valve. DETAILED DESCRIPTION

[0026] The present application will be further described in conjunction with the drawings.

[0027] As Figure 1The ship liquid ammonia fuel supply system shown can cool the ammonia injector. The liquid ammonia fuel tank 1 is used to store low temperature liquid ammonia fuel at about -33℃. When the dual fuel main engine is running in ammonia fuel mode, the low pressure fuel pump 2 is used to first deliver the liquid ammonia to the buffer tank 3, and then through the heater 4, the high pressure fuel pump 5 warms and pressurizes the liquid ammonia to achieve the temperature and pressure required by the main engine for liquid ammonia fuel. The heater 4 is used to heat the liquid ammonia by using water glycol as an intermediate heat exchange medium, and steam as the heat source. Because the main engine load is variable, the required fuel consumption is also constantly changing, so the regulating valve 6 and the pipeline where it is located are provided. When the main engine load is small, the liquid ammonia fuel can be automatically returned to the buffer tank 3 through the regulating valve 6. The warmed and pressurized liquid ammonia then passes through the double filter 7 to filter out larger particulate impurities and protect the stable operation of the main engine. After that, the fuel passes through the fuel valve group unit 8, and from the fuel valve group unit, it is supplied to the dual fuel main engine 10 through the supply double wall pipe 9. The supply double wall pipe is connected to the ammonia injector, the outside of which is wrapped with a heat exchange coil 21. The supply double wall pipe has a second remote control valve 19 provided on the passage leading to the ammonia injector, and a cooling branch pipe extends from the passage of the supply double wall pipe leading to the ammonia injector. A third remote control valve 20 is provided on the cooling branch pipe. Most of the liquid ammonia is injected into the cylinder through the ammonia injector for combustion and work, and about 20% of the small part of the liquid ammonia enters the cooling branch pipe of the ammonia injector. When passing through the heat exchange coil, the liquid ammonia exchanges heat with the ammonia injector, cools the ammonia injector, and then the heated liquid ammonia is returned to the buffer tank through the return double wall pipe, to be used as fuel again, and is preheated by using the excess heat of the ammonia injector, improving energy utilization. When the main engine is running in ammonia fuel mode, a portion of the liquid ammonia fuel is used as a cooling medium for the ammonia injector, realizing the use of the existing liquid ammonia fuel supply system as a cooling system for the ammonia injector after improvement.

[0028] The liquid ammonia is injected into the cylinder 12 through the ammonia injector 11 for combustion and work. The annular space of the supply double wall pipe and the return double wall pipe is provided with a ventilation and leakage monitoring system to ensure that even if ammonia leaks occur, they will not endanger the safety area such as the engine room.

[0029] After the main engine ammonia fuel mode operation is completed, nitrogen gas is provided by the nitrogen gas supply unit 13 connected to the fuel valve group unit for purging, and the fuel supply pipeline and the inside of the main engine are purged. The liquid ammonia is purged to the ammonia gas treatment unit 15 through the return double wall pipe 14, and the gas-liquid mixture purged is separated into liquid ammonia and gas in the ammonia gas treatment unit 15. The liquid ammonia is returned to the buffer tank 3 through the first remote control valve 16 to be reused, and the gas is introduced into the ammonia gas absorption device 17. After the ammonia gas is absorbed by water in the ammonia gas absorption device 17, the remaining gas containing almost no ammonia is discharged into the atmosphere through the gas permeable mast 18.

[0030] After the end of the ammonia fuel mode operation, the liquid ammonia fuel can be recovered by purging backflow, ammonia gas can be absorbed, and the remaining nitrogen gas can be discharged into the atmosphere. The fuel valve group unit is connected with the ammonia gas treatment unit and the buffer tank through pipelines. A fourth remote control valve is arranged on the passage of the fuel valve group unit to the ammonia gas treatment unit, and a fifth remote control valve is arranged on the passage of the fuel valve group unit to the buffer tank. At this time, the first remote control valve 16 and the fifth remote control valve 23 are closed, and the second remote control valve 19, the third remote control valve 20 and the fourth remote control valve 23 are opened for nitrogen purging, liquid ammonia recovery and gas discharge.

[0031] The application utilizes the liquid ammonia supply system matched with the dual-fuel main engine and the cold energy of the low-temperature liquid ammonia fuel, and after slight improvement, the cooling function of the ammonia injector of the main engine in the ammonia fuel mode can be realized. Compared with the traditional technical solution of separately configuring a set of fresh water cooling system, the application has the advantages of low cost, small additional occupied space, simple system configuration, good cooling effect, energy saving, reliable operation and the like.

Claims

1. A marine liquid ammonia fuel supply system that enables cooling of an ammonia injector, characterized by, The ammonia injector (11) is installed on the top of the cylinder (12) in the dual-fuel main engine, and the heat exchange coil (21) is wound outside the ammonia injector; The liquid ammonia fuel tank (1) is provided with a low-pressure fuel pump (2), which is connected with the buffer tank (3), the heater (4), the high-pressure fuel pump (5), the double filter (7) and the fuel valve group unit (8) through pipelines in sequence, the fuel valve group unit is connected with the ammonia injector through the supply double-wall pipe (9), the ammonia injector is installed on the top of the cylinder and used for spraying the liquid ammonia fuel into the cylinder; The dual-fuel main engine is connected with the fuel valve group unit, the ammonia gas treatment unit, the ammonia gas absorption device and the air permeable mast (18) through the backflow double-wall pipe in sequence; The nitrogen supply unit (13) is connected with the fuel valve group unit, and provides the nitrogen for purging the liquid ammonia fuel supply system and the main engine; The fuel valve group unit is connected with the ammonia gas treatment unit and the buffer tank through pipelines, the fourth remote control valve (22) is arranged on the passage of the fuel valve group unit leading to the ammonia gas treatment unit, and the fifth remote control valve (23) is arranged on the passage of the fuel valve group unit leading to the buffer tank.

2. A marine liquid ammonia fuel supply system capable of cooling an ammonia injector according to claim 1, characterized in that, The liquid ammonia is heated to 40 DEG C and pressurized to 85 bar by the heater and the high-pressure fuel pump.

3. A marine liquid ammonia fuel supply system capable of cooling ammonia injectors as claimed in claim 1, wherein, The ammonia gas is absorbed by water in the ammonia gas absorption device.

4. A marine liquid ammonia fuel supply system capable of cooling ammonia injectors as claimed in claim 1, wherein, The bypass pipeline is connected with the buffer tank at the outlet of the high-pressure fuel pump, and the adjusting valve (6) is arranged on the pipeline, so that the excess fuel can flow back to the buffer tank and used for adjusting the fuel amount supplied to the main engine.

5. A marine liquid ammonia fuel supply system capable of cooling ammonia injectors as claimed in claim 1, wherein, The liquid ammonia heater uses water glycol as intermediate medium and steam as heat source.

6. A marine liquid ammonia fuel supply system that cools ammonia injectors as set forth in claim 1, characterized in that, The absolute mesh accuracy of the double filter is 10 μm.

7. A marine liquid ammonia fuel supply system capable of cooling ammonia injectors as claimed in claim 1, wherein, The cooling branch pipeline is arranged on the liquid ammonia supply pipeline in the main engine, a small amount of liquid ammonia passes through the heat exchange coil of the pipeline, and the cooling function of the ammonia injector is realized.

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