Ammonia vapor reliquefaction system, ammonia fuel system and ship

Abstract

The invention belongs to the technical field of ships, and discloses an ammonia vapor reliquefaction system, an ammonia fuel system and a ship. The ammonia vapor reliquefaction system comprises a heater, a buffer tank, a first-stage compressor, a first-stage cooler, a second-stage compressor, a second-stage cooler and a liquid ammonia collecting tank, an inlet of the heater is used for being communicated with an ammonia vapor outlet of the liquid ammonia storage tank, an outlet of the heater is communicated with the buffer tank, an outlet of the buffer tank is communicated with an inlet of the first-stage compressor, a first outlet pipeline of the first-stage compressor is in heat exchange connection with the first-stage cooler, and an outlet of the first outlet pipeline is communicated with an inlet of the second-stage compressor. A second outlet pipeline of the second-stage compressor is in heat exchange connection with the second-stage cooler, an outlet of the second outlet pipeline is communicated with a liquid ammonia collecting tank, and an outlet of the liquid ammonia collecting tank is used for being communicated with an inlet of the liquid ammonia collecting tank. According to the ammonia vapor reliquefaction system, the compression efficiency of ammonia vapor can be improved, the energy consumption is reduced, the ammonia vapor is liquefied again and stored at low cost, and the waste of ammonia fuel is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and in particular to an ammonia vapor reliquefaction system, an ammonia fuel system and a ship. Background Art

[0002] Existing ships typically operate on traditional fossil fuels such as fuel oil, with some using alternative fuels such as LNG and methanol. These fuels produce significant amounts of the greenhouse gas carbon dioxide upon combustion. To reduce the environmental impact of carbon dioxide emissions, research is underway to use ammonia as an alternative fuel on ships. Ammonia, which does not produce carbon dioxide upon combustion, is a gas at room temperature and pressure. Compared to conventional fuels, ammonia has a lower calorific value. Therefore, to conserve storage space on board, it is necessary to consider storing it in liquid form.

[0003] However, ammonia fuel requires low-temperature, high-pressure storage: liquid ammonia must be stored at approximately -33°C and 8 to 12 bar. Heat leaks cause a continuous generation of boil-off gas (BOG). Improper handling can lead to fuel waste and the risk of tank overpressure. Directly discharging ammonia to maintain tank pressure within limits can pollute the environment and waste energy. Existing BOG reliquefaction systems suffer from low energy efficiency and poor adaptability (unable to cope with flow fluctuations or extreme environments), making it difficult for ammonia-fueled vessels to operate stably over long distances or in extreme climates.

[0004] Therefore, there is an urgent need to provide a new ammonia vapor reliquefaction system, an ammonia fuel system and a ship to solve the above-mentioned technical problems in the prior art. Summary of the Invention

[0005] The object of the present invention is to provide an ammonia vapor reliquefaction system that can improve the compression efficiency of ammonia vapor, reduce energy consumption, reliquefy and store ammonia vapor at low cost, and reduce the waste of ammonia fuel.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The ammonia vapor reliquefaction system includes a heater, a buffer tank, a first-stage compressor, a first-stage cooler, a second-stage compressor, a second-stage cooler, and a liquid ammonia collecting tank; the inlet of the above-mentioned heater is used to communicate with the ammonia vapor outlet of the liquid ammonia storage tank, the outlet of the above-mentioned heater is connected to the above-mentioned buffer tank, the outlet of the above-mentioned buffer tank is connected to the inlet of the above-mentioned first-stage compressor, the first outlet pipeline of the above-mentioned first-stage compressor is connected to the above-mentioned first-stage cooler for heat exchange, the outlet of the above-mentioned first outlet pipeline is connected to the inlet of the above-mentioned second-stage compressor, the second outlet pipeline of the above-mentioned second-stage compressor is connected to the above-mentioned second-stage cooler for heat exchange, the outlet of the above-mentioned second outlet pipeline is connected to the above-mentioned liquid ammonia collecting tank, and the outlet of the above-mentioned liquid ammonia collecting tank is used to communicate with the inlet of the liquid ammonia collecting tank.

[0008] Optionally, the ammonia vapor reliquefaction system further includes a seawater pipeline system, and the primary cooler and the secondary cooler are respectively connected to the seawater pipeline system for heat exchange.

[0009] Optionally, the heater is a heat exchanger or an electric heater.

[0010] Optionally, the heater is a heat exchanger, and the heat exchanger is connected to the seawater pipeline system for heat exchange.

[0011] Optionally, the outlet of the second outlet pipeline is connected to a gas-liquid separator, the liquid outlet of the gas-liquid separator is connected to the liquid ammonia collection tank, and the gas outlet of the gas-liquid separator is connected to the inlet of the heater.

[0012] Optionally, the gas-liquid separator is provided with a pressurizing device, which can re-liquefy the gaseous ammonia in the gas-liquid separator.

[0013] Optionally, both the first-stage compressor and the second-stage compressor are scroll compressors.

[0014] Optionally, the liquid ammonia collection tank is a C-type pressure-resistant low-temperature storage tank or a non-pressure-resistant low-temperature storage tank.

[0015] Another object of the present invention is to provide an ammonia fuel system, which includes a liquid ammonia storage tank and an ammonia vapor reliquefaction system as described in any of the above schemes, wherein the inlet of the above-mentioned heater is connected to the ammonia vapor outlet of the above-mentioned liquid ammonia storage tank, and the outlet of the above-mentioned liquid ammonia collecting tank is connected to the inlet of the above-mentioned liquid ammonia storage tank.

[0016] Another object of the present invention is to provide a ship, comprising a hull and an ammonia fuel system as described in the above scheme, wherein the ammonia fuel system is arranged on the hull.

[0017] Beneficial effects:

[0018] The ammonia vapor reliquefaction system of the present invention first uses a heater to heat the ammonia vapor evaporated in the liquid ammonia storage tank, so that the temperature of the ammonia vapor entering the buffer tank remains constant, so that the temperature of the ammonia vapor is maintained in a constant range before entering the primary compressor, ensuring the stable operation of the primary compressor and the secondary compressor; before entering the primary compressor, the ammonia vapor is first stored in the buffer tank, which can reduce the flow fluctuation of the ammonia vapor entering the primary compressor and the secondary compressor, avoid the ammonia vapor directly entering the primary compressor, maintain the flow stability at the inlet of the primary compressor and the secondary compressor, ensure the low load operation of the compressor, and have high working efficiency; after the ammonia vapor flows out of the primary compressor or the secondary compressor, the high-pressure ammonia vapor is cooled by the primary cooler and the secondary cooler, so that it is liquefied into liquid ammonia as soon as possible, with higher liquefaction efficiency. At the same time, the two-stage compression and two-stage cooling can optimize the compression process, control the exhaust temperature of each stage, avoid the efficiency loss caused by high temperature, improve the operating efficiency of the compressor, and reduce the operating energy consumption. The ammonia vapor reliquefaction system can improve the compression efficiency of ammonia vapor, reduce energy consumption, liquefy and store ammonia vapor again at a low cost, and reduce the waste of ammonia fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of an ammonia fuel system provided in accordance with a specific embodiment of the present invention.

[0020] In the picture:

[0021] 10. Liquid ammonia storage tank; 11. Heater; 12. Buffer tank; 13. Primary compressor; 14. Primary cooler; 15. Secondary compressor; 16. Secondary cooler; 17. Gas-liquid separator; 18. Liquid ammonia collection tank. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0023] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0024] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0025] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0026] like Figure 1 As shown, the ammonia vapor reliquefaction system in this embodiment includes a heater 11, a buffer tank 12, a primary compressor 13, a primary cooler 14, a secondary compressor 15, a secondary cooler 16, and a liquid ammonia collecting tank 18; the inlet of the above-mentioned heater 11 is used to communicate with the ammonia vapor outlet of the liquid ammonia storage tank 10, the outlet of the above-mentioned heater 11 is connected to the above-mentioned buffer tank 12, the outlet of the above-mentioned buffer tank 12 is connected to the inlet of the above-mentioned primary compressor 13, the first outlet pipeline of the above-mentioned primary compressor 13 is connected to the above-mentioned primary cooler 14 for heat exchange, the outlet of the above-mentioned first outlet pipeline is connected to the inlet of the above-mentioned secondary compressor 15, the second outlet pipeline of the above-mentioned secondary compressor 15 is connected to the above-mentioned secondary cooler 16 for heat exchange, the outlet of the above-mentioned second outlet pipeline is connected to the above-mentioned liquid ammonia collecting tank 18, and the outlet of the above-mentioned liquid ammonia collecting tank 18 is used to communicate with the inlet of the liquid ammonia collecting tank 18.

[0027] The ammonia vapor reliquefaction system in this embodiment first uses a heater 11 to heat the ammonia vapor evaporated in the liquid ammonia storage tank 10, so that the temperature of the ammonia vapor entering the buffer tank 12 remains constant, so that the temperature of the ammonia vapor is maintained in a constant range before entering the first-stage compressor 13, ensuring the stable operation of the first-stage compressor 13 and the second-stage compressor 15; before entering the first-stage compressor 13, the ammonia vapor is first stored in the buffer tank 12. The buffer tank 12 can reduce the flow fluctuation of the ammonia vapor entering the first-stage compressor 13 and the second-stage compressor 15, avoid the ammonia vapor directly entering the first-stage compressor 13, maintain the flow stability at the inlet of the first-stage compressor 13 and the second-stage compressor 15, ensure low-load operation of the compressor, and have high working efficiency; after the ammonia vapor flows out of the first-stage compressor 13 or the second-stage compressor 15, the first-stage cooler 14 and the second-stage cooler 16 are used to cool the high-pressure ammonia vapor, so that it is liquefied into liquid ammonia as soon as possible, with higher liquefaction efficiency. At the same time, two-stage compression and two-stage cooling can optimize the compression process, control the exhaust temperature of each stage, avoid efficiency loss caused by high temperature, improve the operating efficiency of the compressor, and reduce operating energy consumption. The ammonia vapor reliquefaction system can improve the compression efficiency of ammonia vapor, reduce energy consumption, reliquefy and store ammonia vapor at low cost, and reduce the waste of ammonia fuel.

[0028] Furthermore, the ammonia vapor reliquefaction system includes a seawater piping system, with the primary cooler 14 and the secondary cooler 16 respectively connected to the seawater piping system for heat exchange. In this embodiment, seawater is flowed into the seawater piping system to cool and exchange heat with the primary cooler 14 and the secondary cooler 16. This not only improves heat exchange efficiency, but also reduces cooling costs due to the readily available seawater.

[0029] Optionally, the heater 11 is a heat exchanger or an electric heater. The heat exchanger can be a tubular heat exchanger or a plate heat exchanger, and the electric heater can be an electric heating tube, an electric heating wire or a PTC heater, which will not be described in detail here.

[0030] Specifically, heater 11 is a heat exchanger connected to the seawater piping system for heat exchange. Using the seawater piping system to exchange heat with the heat exchanger allows heat generated by primary cooler 14 and secondary cooler 16 to be transferred to the heat exchanger, thereby fulfilling the function of heater 11 and heating ammonia vapor. This reduces heating costs and its simple structure, thereby reducing both heating costs and structural manufacturing costs.

[0031] Please continue to refer to Figure 1The outlet of the second outlet pipeline is connected to a gas-liquid separator 17. The liquid outlet of the gas-liquid separator 17 is connected to the liquid ammonia collection tank 18, and the gas outlet of the gas-liquid separator 17 is connected to the inlet of the heater 11. The provision of the gas-liquid separator 17 can separate the liquid ammonia flowing out of the secondary cooler 16 into gas and liquid, so that the pure liquid ammonia is collected and stored in the liquid ammonia collection tank 18, while the ammonia vapor is separated and discharged. This prevents excessive ammonia vapor pressure in the liquid ammonia collection tank 18, and avoids the risk of overpressure and ammonia vapor leakage in the liquid ammonia collection tank 18.

[0032] In this embodiment, the gas-liquid separator 17 is provided with a pressurizing device, which is capable of re-liquefying the gaseous ammonia in the gas-liquid separator 17. The pressurizing device can re-liquefy the ammonia vapor in the gas-liquid separator 17, reduce the generation of ammonia vapor during the gas-liquid separation process of the liquid ammonia, complete the conversion of the ammonia vapor, improve the liquefaction efficiency of the ammonia vapor, and realize the recovery and reuse of the ammonia vapor.

[0033] Optionally, both the first-stage compressor 13 and the second-stage compressor 15 are scroll compressors, which eliminate the clearance volume loss of traditional reciprocating compressors and avoid the extra power consumption caused by the pulsed flow fluctuations of reciprocating compressors.

[0034] Specifically, the liquid ammonia collection tank 18 is a Type C pressure-resistant cryogenic storage tank or a non-pressure-resistant cryogenic storage tank. There are no specific pressure requirements for the liquid ammonia collection tank 18 and it can be a Type C pressure-resistant cryogenic storage tank specified by the International Maritime Organization (IMO), or a non-pressure-resistant cryogenic storage tank specified by the IMO, such as a Type A, Type B, or other non-pressure-resistant cryogenic storage tank. The liquid ammonia collection tank 18 is also equipped with a thermal insulation layer for storing low-temperature liquid ammonia fuel. Furthermore, the liquid ammonia collection tank 18 is equipped with liquid level, pressure, and temperature monitoring devices to monitor the liquid level, pressure, and temperature within the liquid ammonia collection tank 18. Furthermore, the liquid ammonia collection tank 18 is also equipped with a safety valve for overpressure protection.

[0035] like Figure 1 As shown, this embodiment also provides an ammonia fuel system, which includes a liquid ammonia storage tank 10 and an ammonia vapor reliquefaction system as described in any of the above schemes, the inlet of the above-mentioned heater 11 is connected to the ammonia vapor outlet of the above-mentioned liquid ammonia storage tank 10, and the outlet of the above-mentioned liquid ammonia collecting tank 18 is connected to the inlet of the above-mentioned liquid ammonia storage tank 10.

[0036] The ammonia fuel system uses an ammonia vapor reliquefaction system as described in any of the above schemes, thereby having all the beneficial effects of the ammonia vapor reliquefaction system described in any of the above schemes. Specifically, the ammonia fuel system can liquefy the evaporated ammonia vapor in the liquid ammonia storage tank 10. At the same time, the two-stage compression and two-stage cooling can optimize the compression process, control the exhaust temperature of each stage, avoid efficiency losses caused by high temperature, improve the operating efficiency of the compressor, and reduce operating energy consumption. The ammonia vapor reliquefaction system used by the ammonia fuel system can improve the compression efficiency of ammonia vapor, reduce energy consumption, re-liquefy and store ammonia vapor at a low cost, and reduce the waste of ammonia fuel.

[0037] This embodiment further provides a vessel comprising a hull and an ammonia fuel system as described in the above embodiment, the ammonia fuel system being mounted on the hull. The ammonia fuel system employed in this vessel utilizes an ammonia vapor reliquefaction system to liquefy and reuse ammonia vapor, thereby improving ammonia vapor compression efficiency, reducing energy consumption, and enabling low-cost reliquefaction and storage of ammonia vapor, thereby minimizing ammonia fuel waste and achieving energy conservation and emission reduction.

[0038] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. Ammonia vapor reliquefaction system, characterized in that: The invention comprises a heater (11), a buffer tank (12), a primary compressor (13), a primary cooler (14), a secondary compressor (15), a secondary cooler (16), and a liquid ammonia collecting tank (18); the inlet of the heater (11) is used to communicate with the ammonia vapor outlet of the liquid ammonia storage tank (10), the outlet of the heater (11) is connected to the buffer tank (12), the outlet of the buffer tank (12) is connected with the inlet of the primary compressor (13), the first outlet pipeline of the primary compressor (13) is connected to the primary cooler (14) for heat exchange, the outlet of the first outlet pipeline is connected to the inlet of the secondary compressor (15), the second outlet pipeline of the secondary compressor (15) is connected to the secondary cooler (16) for heat exchange, the outlet of the second outlet pipeline is connected to the liquid ammonia collecting tank (18), and the outlet of the liquid ammonia collecting tank (18) is used to communicate with the inlet of the liquid ammonia collecting tank (18).

2. The ammonia vapor reliquefaction system according to claim 1, characterized in that: The ammonia vapor reliquefaction system further comprises a seawater pipeline system, and the primary cooler (14) and the secondary cooler (16) are respectively connected to the seawater pipeline system for heat exchange.

3. The ammonia vapor reliquefaction system according to claim 2, characterized in that: The heater (11) is a heat exchanger or an electric heater.

4. The ammonia vapor reliquefaction system according to claim 3, characterized in that: The heater (11) is a heat exchanger, and the heat exchanger is connected to the seawater pipeline system for heat exchange.

5. The ammonia vapor reliquefaction system according to claim 1, wherein: The outlet of the second outlet pipeline is connected to a gas-liquid separator (17), the liquid outlet of the gas-liquid separator (17) is connected to the liquid ammonia collection tank (18), and the gas outlet of the gas-liquid separator (17) is connected to the inlet of the heater (11).

6. The ammonia vapor reliquefaction system according to claim 5, characterized in that: The gas-liquid separator (17) is provided with a pressurizing device, and the pressurizing device is capable of re-liquefying the gaseous ammonia in the gas-liquid separator (17).

7. The ammonia vapor reliquefaction system according to any one of claims 1 to 6, characterized in that: The first-stage compressor (13) and the second-stage compressor (15) are both scroll compressors.

8. The ammonia vapor reliquefaction system according to any one of claims 1 to 6, characterized in that: The liquid ammonia collecting tank (18) is a C-type pressure-resistant low-temperature storage tank or a non-pressure-resistant low-temperature storage tank.

9. Ammonia fuel system, characterized in that The invention comprises a liquid ammonia storage tank (10) and an ammonia vapor reliquefaction system according to any one of claims 1 to 8, wherein the inlet of the heater (11) is connected to the ammonia vapor outlet of the liquid ammonia storage tank (10), and the outlet of the liquid ammonia collecting tank (18) is connected to the inlet of the liquid ammonia storage tank (10).

10. A vessel, characterized in that The invention comprises a hull and the ammonia fuel system according to claim 9, wherein the ammonia fuel system is arranged on the hull.

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