Low energy efficient self-balancing reliquefaction system for ship fuel storage tank

Abstract

The utility model discloses a kind of low-energy high-efficiency self-balancing liquefaction system of ship fuel storage cabin, LNG barge pump is connected with lower spray pipe through first control valve, daily-use tank is sequentially connected with LNG booster pump, SBR heat exchanger, around pipe gasifier, LNG barge pump is connected with upper spray pipe through first control valve, upper spray control valve, LNG storage tank is connected with compressor unit through second control valve, compressor unit is connected with low-pressure user through third control valve, compressor unit is sequentially connected with daily-use tank through pre-cooler, SBR heat exchanger, control valve, LNG barge pump is connected with low-pressure user through first control valve.The utility model utilizes low-temperature BOG flash steam to carry out cooling, utilizes LNG booster pump to discharge the cold energy of low-temperature LNG gasification and is formed to the shell side BOG flash steam cooling, and it is realized liquefaction again to spray in daily-use tank bottom.

Description

Technical Field

[0001] This utility model relates to the field of marine technology, and in particular to a low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks. Background Technology

[0002] In recent years, global air pollution has continued to worsen, and the standards for controlling ship emissions have become increasingly stringent. Achieving global carbon neutrality has become a consensus and action plan among countries.

[0003] When ships use natural gas as fuel, carbon and nitrogen oxide emissions can be reduced by more than 30%, and sulfur oxide emissions can be reduced by more than 98%. Based on this significant emission reduction advantage, switching to LNG fuel has become one of the most direct and effective ways for ships to achieve energy conservation, emission reduction, and improved transportation efficiency. Currently, almost all newly built mainstream ship types adopt dual-fuel or single-fuel LNG propulsion designs, with a significant increase in the proportion of ships using LNG as the primary fuel. This aims to ensure that ships can compliantly use LNG in emission control areas of various countries and throughout the entire voyage, in order to meet increasingly stringent emission regulations.

[0004] However, in the LNG storage stage, ships equipped with high-pressure main engines face significant challenges in handling BOG (Boiled Air Gaseous) gases. Using conventional reliquefaction systems would significantly increase shipbuilding costs; compressing BOG directly to 300 bar would require not only expensive high-pressure compressors but also necessitate larger generators due to their enormous power consumption. Furthermore, the piping for 300 bar high-pressure gas is lengthy, posing significant risks to personnel and gas leaks. This clearly exceeded the shipowner's expectations. Utility Model Content

[0005] To solve the above problems, this utility model provides a low-energy, high-efficiency, self-balancing reliquefaction system for ship fuel storage tanks.

[0006] To solve the above-mentioned technical problems, the technical solution of this utility model is: a low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks, including an LNG transfer pump. The LNG transfer pump is connected to a lower spray pipe via a first control valve. The lower spray pipe is located inside a day tank. The day tank is sequentially connected to an LNG booster pump, an SBR heat exchanger, and a coiled vaporizer. The LNG transfer pump is connected to an upper spray pipe via a first control valve and an upper spray control valve. The LNG transfer pump and the upper spray pipe are located inside an LNG storage tank. The LNG storage tank is connected to a compressor unit via a second control valve. The compressor unit is connected to a low-pressure user via a third control valve. The compressor unit is sequentially connected to the day tank via a precooler, an SBR heat exchanger, and a control valve. The LNG transfer pump is connected to the low-pressure user via the first control valve.

[0007] Furthermore, the compressor unit includes a preheater, a compressor, and an aftercooler connected in sequence.

[0008] Furthermore, the coiled gasifier is connected to the fuel supply pipe of the main unit.

[0009] Furthermore, a safety valve is installed between the LNG storage tank and the daytime use tank.

[0010] Furthermore, a low-pressure heat exchanger is connected between the first control valve and the low-pressure user.

[0011] Furthermore, the daily use tank is equipped with heat exchange tubes, and the first control valve is connected to the low-pressure heat exchanger through the heat exchange tubes inside the daily use tank.

[0012] When low-pressure users cannot consume all the compressed BOG flash vapor, the excess high-temperature BOG flash vapor bypasses through a control valve and first enters the precooler tube side, where it is cooled by the low-temperature BOG flash vapor. Then, in the shell side of the SBR heat exchanger, the cold energy generated by the vaporization of low-temperature LNG discharged from the LNG booster pump further cools the shell-side BOG flash vapor, which is then sprayed at the bottom of the day tank for reliquefaction. This reliquefaction system reliquefies excess BOG flash vapor in the LNG storage tank while simultaneously utilizing the cold energy generated by LNG vaporization in the gas supply system to reduce the LNG storage tank pressure and increase the LNG storage tank's port accumulation time. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of this utility model;

[0014] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of this utility model.

[0015] The components are: 1. LNG transfer pump, 1a. First control valve, 2. LNG storage tank, 3a. Second control valve, 4. LNG booster pump, 5. Daily use tank, 5a. Lower spray pipe, 5b. Safety valve, 6. SBR heat exchanger, 7. Wrapped pipe vaporizer, 8. Low-pressure user, 8a. Third control valve, 9. Control valve, 10. Upper spray pipe, 10a. Upper spray control valve, 13. Preheater, 14. Compressor, 15. Aftercooler, 16. Precooler, 17. Low-pressure heat exchanger. Detailed Implementation

[0016] The following is in conjunction with the appendix Figure 1 , 2 The specific embodiments of this utility model will be further described below.

[0017] Example 1

[0018] The ship's fuel storage tank features a low-energy, high-efficiency, self-balancing reliquefaction system, comprising an LNG storage tank 2 with an internal LNG transfer pump 1 and an upper spray pipe 10, and a day tank 5 with an internal lower spray pipe 5a. The LNG transfer pump 1 is connected to the lower spray pipe 5a via a first control valve 1a, and to the upper spray pipe 10 via the first control valve 1a and the upper spray control valve 10a. The LNG storage tank 2 is connected to a compressor unit via a second control valve 3a, and the compressor unit is connected to a low-pressure user 8 via a third control valve 8a. The compressor unit is connected to the day tank 5 sequentially via a precooler 16, an SBR heat exchanger 6, and a control valve 9. The day tank 5, LNG booster pump 4, SBR heat exchanger 6, and a coiled vaporizer 7 are sequentially connected, and the coiled vaporizer 7 is connected to the main engine's fuel supply pipe. The compressor unit includes a preheater 13, a compressor 14, and an aftercooler 15 connected sequentially. A safety valve 5b is installed between the LNG storage tank 2 and the day tank 5. LNG transfer pump 1 is connected to low-pressure heat exchanger 17 via first control valve 1a, and low-pressure heat exchanger 17 is connected to low-pressure user 8.

[0019] Working principle:

[0020] (a) The compressor unit compresses the BOG flash vapor in the LNG storage tank 2 to 12-16 bar, cools it to 40-45°C by the aftercooler 15, and supplies it to the low-pressure user 8 after pressure reduction.

[0021] (b) The LNG transfer pump 1 continuously operates to transfer LNG liquid from LNG storage tank 2 to day tank 5. A portion of the LNG liquid flows back into LNG storage tank 2 through the upper spray control valve 10a and upper spray pipe 10, adjusting the flow rate into day tank 5 to maintain a constant liquid level. The pressure in day tank 5 depends on the excess BOG flash vapor flow rate discharged from the compressor unit. When the pressure exceeds 14 bar, day tank 5 adjusts the pressure to LNG storage tank 2, maintaining the pressure between 9 and 14 bar.

[0022] (c) The LNG booster pump 4 pressurizes the LNG liquid in the daily use tank 5 to 300 bar and then discharges it into the SBR heat exchanger 6 and the coiled vaporizer 7 for heating / vaporization, and finally supplies it to the main unit. The gas supply pressure is 300 bar and the gas supply temperature is 45°C.

[0023] When the SBR liquefaction temperature is ≤-110℃, control valve 9 opens, allowing excess BOG flash vapor that cannot be consumed by low-pressure user 8 to first enter the suction precooler 16 to exchange heat with the low-temperature BOG flash vapor in LNG storage tank 2, cooling the BOG flash vapor to -45℃. The cooled BOG flash vapor then passes through the shell side of SBR heat exchanger 6 and exchanges heat with the low-temperature LNG liquid discharged from LNG booster pump 4, cooling the BOG flash vapor to -110℃. The cooled BOG flash vapor is then sprayed with liquid from LNG transfer pump 1 for further cooling, completing self-balancing reliquefaction in day tank 5.

[0024] The cryogenic gas compressor 14 employs one or more stages of oil-free reciprocating, oil-free screw, or oil-free centrifugal compressors. When a two-stage compressor 14 is used, the exhaust gas and / or intermediate stage heat energy can be used to heat the intake gas. The advantage of using a multi-stage compressor 14 is that the energy required to compress the same unit to reach the set value is far less than the energy consumed by a single-stage compressor 14. Furthermore, multi-stage heating of the intake gas using the exhaust gas and intermediate stages allows the intake cryogenic natural gas to reach a more stable temperature. This compressor unit extracts and compresses BOG flash vapor from the LNG storage tank 2 before sending it to the heat exchanger. An interstage cooler is also provided to reduce the intake temperature of the subsequent compressor 14, effectively protecting the compressor 14 for continuous and efficient operation.

[0025] A significant change has been made to the heat exchanger, which has been changed from a shell-and-tube type to a shell-and-tube type. The heat exchanger in this system is divided into two sections. One section is the SBR heat exchanger 6, where the tube-side medium is liquid LNG, and the shell-side medium is BOG flash vapor processed by compressor 14. This heat exchanger is designed for a pressure of 300 bar. Heat exchange is performed between the ambient or cryogenic BOG flash vapor in the shell side and the cryogenic LNG liquid in the tube side from the LNG booster pump 4, reducing the temperature of the BOG flash vapor gas to -110°C. The other side is the coiled-tube vaporizer 7, where the tube-side medium is LNG / NG from the tube-side outlet of the SBR heat exchanger 6, and the shell-side medium is water-glycol. This heat exchanger is designed for a pressure of 300 bar. The heat exchange through the coiled-tube heat exchanger raises the temperature of the NG gas to 45°C.

[0026] This system can also use shell-and-tube, plate, printed circuit board, and other types of heat exchangers.

[0027] The coiled vaporizer 7 in this system is an independently developed product and has obtained a patent: CN 207848967U.

[0028] LNG transfer pump 1 transfers LNG liquid from LNG storage tank 2 to day tank 5 and maintains it at a set liquid level. The injection volume of LNG transfer pump 1 into day tank 5 is adjusted by the upper spray control valve 10a. LNG booster pump 4 pressurizes the LNG liquid in day tank 5 to 300 bar and discharges it into SBR heat exchanger 6 and coiled vaporizer 7 to supply the main unit.

[0029] The LNG transfer pump 1 inside the LNG storage tank 2 pumps the LNG to the low-pressure heat exchanger 17, which can supply the low-pressure user 8 either alone or in conjunction with the compressor unit.

[0030] Example 2

[0031] The ship's fuel storage tank features a low-energy, high-efficiency, self-balancing reliquefaction system, comprising an LNG storage tank 2 equipped with an internal LNG transfer pump 1 and an upper spray pipe 10, and a day-use tank 5 equipped with an internal lower spray pipe 5a. A safety valve 5b connects the LNG storage tank 2 and the day-use tank 5. The LNG transfer pump 1 is connected to the lower spray pipe 5a via a first control valve 1a, and to the upper spray pipe 10 via the first control valve 1a and the upper spray control valve 10a. The LNG storage tank 2 is connected to the upper spray pipe 10 via a second control valve 3. The compressor unit is connected to the compressor unit via the third control valve 8a. The compressor unit is then connected to the day tank 5 via the precooler 16, SBR heat exchanger 6, and control valve 9. The day tank 5, LNG booster pump 4, SBR heat exchanger 6, and coiled vaporizer 7 are connected in sequence. The coiled vaporizer 7 is connected to the fuel supply pipe of the main unit. The LNG transfer pump 1, first control valve 1a, heat exchange pipes in the day tank 5, low-pressure heat exchanger 17, and low-pressure user 8 are connected in sequence. The compressor unit includes a preheater 13, compressor 14, and aftercooler 15 connected in sequence.

[0032] Working principle:

[0033] (a) The compressor unit compresses the BOG flash vapor in the LNG storage tank 2 to 12-16 bar, cools it to 40-45°C by the aftercooler 15, and supplies it to the low-pressure user 8 after pressure reduction.

[0034] (b) The LNG transfer pump 1 continuously operates to transfer LNG liquid from LNG storage tank 2 to day tank 5. A portion of the LNG liquid flows back into LNG storage tank 2 through the upper spray control valve 10a and upper spray pipe 10, adjusting the flow rate into day tank 5 to maintain a constant liquid level. The pressure in day tank 5 depends on the excess BOG flash vapor flow rate discharged from the compressor unit. When the pressure exceeds 14 bar, day tank 5 adjusts the pressure to LNG storage tank 2, maintaining the pressure between 9 and 14 bar.

[0035] Another portion of the cooler LNG liquid exchanges heat with the warmer LNG outside through the heat exchange tubes inside the day tank 5, utilizing its latent heat of vaporization. It is then discharged into the tube side of the low-pressure heat exchanger 17 for further heat exchange with the shell-side water and glycol. Finally, it is supplied to the low-pressure user 8.

[0036] (c) The LNG booster pump 4 pressurizes the LNG liquid in the daily use tank 5 to 300 bar and then discharges it into the SBR heat exchanger 6 and the coiled vaporizer 7 for heating / vaporization, and finally supplies it to the main unit. The gas supply pressure is 300 bar and the gas supply temperature is 45°C.

[0037] When the SBR liquefaction temperature is ≤-110℃, control valve 9 opens, allowing excess BOG flash vapor that cannot be consumed by low-pressure user 8 to first enter the suction precooler 16 to exchange heat with the low-temperature BOG flash vapor in LNG storage tank 2, cooling the BOG flash vapor to -45℃. The cooled BOG flash vapor then passes through the shell side of SBR heat exchanger 6 and exchanges heat with the low-temperature LNG liquid discharged from LNG booster pump 4, cooling the BOG flash vapor to -110℃. The cooled BOG flash vapor is then sprayed with liquid from LNG transfer pump 1 for further cooling, completing self-balancing reliquefaction in day tank 5.

[0038] The cryogenic gas compressor 14 employs one or more stages of oil-free reciprocating, oil-free screw, or oil-free centrifugal compressors. When a two-stage compressor 14 is used, the exhaust gas and / or intermediate stage heat energy can be used to heat the intake gas. The advantage of using a multi-stage compressor 14 is that the energy required to compress the same unit to reach the set value is far less than the energy consumed by a single-stage compressor 14. Furthermore, multi-stage heating of the intake gas using the exhaust gas and intermediate stages allows the intake cryogenic natural gas to reach a more stable temperature. This compressor unit extracts and compresses BOG flash vapor from the LNG storage tank 2 before sending it to the heat exchanger. An interstage cooler is also provided to reduce the intake temperature of the subsequent compressor 14, effectively protecting the compressor 14 for continuous and efficient operation.

[0039] A significant change has been made to the heat exchanger, which has been changed from a shell-and-tube type to a shell-and-tube type. The heat exchanger in this system is divided into two sections. One section is the SBR heat exchanger 6, where the tube-side medium is liquid LNG, and the shell-side medium is BOG flash vapor processed by compressor 14. This heat exchanger is designed for a pressure of 300 bar. Heat exchange is performed between the ambient or cryogenic BOG flash vapor in the shell side and the cryogenic LNG liquid in the tube side from the LNG booster pump 4, reducing the temperature of the BOG flash vapor gas to -110°C. The other side is the coiled-tube vaporizer 7, where the tube-side medium is LNG / NG from the tube-side outlet of the SBR heat exchanger 6, and the shell-side medium is water-glycol. This heat exchanger is designed for a pressure of 300 bar. The heat exchange through the coiled-tube heat exchanger raises the temperature of the NG gas to 45°C.

[0040] This system can also use shell-and-tube, plate, printed circuit board, and other types of heat exchangers.

[0041] The fuel tank of this system can be of type C, type B, membrane tank, or other types of marine fuel tank.

[0042] The coiled vaporizer 7 in this system is an independently developed product and has obtained a patent: CN207848967U.

[0043] LNG transfer pump 1 transfers LNG liquid from LNG storage tank 2 to day tank 5 and maintains it at a set liquid level. The injection volume of LNG transfer pump 1 into day tank 5 is adjusted by the upper spray control valve 10a. LNG booster pump 4 pressurizes the LNG liquid in day tank 5 to 300 bar and discharges it into SBR heat exchanger 6 and coiled vaporizer 7 to supply the main unit.

[0044] The LNG transfer pump 1 inside the LNG storage tank 2 pumps the LNG into the heat exchange pipe inside the day use tank 5 and discharges it into the low-pressure heat exchanger 17. It can be supplied to the low-pressure user 8 alone or in conjunction with the compressor unit.

[0045] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the scope of the technology disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks, characterized in that: The system includes an LNG transfer pump (1), which is connected to a lower spray pipe (5a) via a first control valve (1a). The lower spray pipe (5a) is located inside a day tank (5). The day tank (5) is connected in sequence to an LNG booster pump (4), an SBR heat exchanger (6), and a coiled vaporizer (7). The LNG transfer pump (1) is connected to an upper spray pipe (10) via a first control valve (1a) and an upper spray control valve (10a). The LNG transfer pump (1) and the upper spray pipe (10) are located inside an LNG storage tank (2). The LNG storage tank (2) is connected to a compressor unit via a second control valve (3a). The compressor unit is connected to a low-pressure user (8) via a third control valve (8a). The compressor unit is connected to the day tank (5) via a precooler (16), an SBR heat exchanger (6), and a control valve (9). The LNG transfer pump (1) is connected to the low-pressure user (8) via a first control valve (1a).

2. The low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks according to claim 1, characterized in that, The compressor unit includes a preheater (13), a compressor (14), and an aftercooler (15) connected in sequence.

3. The low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks according to claim 1, characterized in that, The coiled gasifier (7) is connected to the fuel supply pipe of the main unit.

4. The low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks according to claim 1, characterized in that, A safety valve (5b) is provided between the LNG storage tank (2) and the daily use tank (5).

5. The low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks according to claim 1, characterized in that, A low-pressure heat exchanger (17) is connected between the first control valve (1a) and the low-pressure user (8).

6. The low-energy, high-efficiency self-balancing reliquefaction system for ship fuel storage tanks according to claim 5, characterized in that, The daily use tank (5) is equipped with a heat exchange tube, and the first control valve (1a) is connected to the low-pressure heat exchanger (17) through the heat exchange tube in the daily use tank (5).

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