Ammonia flash vapor reliquefaction system for cold energy supply

Abstract

The application provides an ammonia flash vapor liquefaction system for realizing cold energy supply, which comprises ammonia fuel tank, ammonia gas storage tank, compressor, condenser pipe, cooling tank and other devices connected in sequence. The ammonia gas flowing out of the ammonia fuel tank is converted into high-pressure liquid ammonia after being compressed and condensed. The high-pressure liquid ammonia is divided into three branches after flowing out of the cold exchanger. The first branch flows into the cooling tank after being depressurized and cooled by the high-pressure throttle valve, so as to realize internal cooling of the cooling tank. The second branch enters the liquid ammonia evaporator in the cold storage after being depressurized and cooled by the cold storage throttle valve, so as to realize cooling of the cold storage. The third branch flows back to the ammonia fuel tank after being depressurized and cooled by the back tank throttle valve. Meanwhile, the liquid ammonia in the cooling tank is also used for cooling the refrigerant water, so as to realize refrigeration of the user room. The liquefaction system fully utilizes the cold energy contained in the high-pressure liquid ammonia in the liquefaction process, different refrigeration schemes are formulated for the cold storage and the user room respectively, and the whole pipeline design is more rational.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia fuel reliquefaction treatment on board ships, and in particular to an ammonia flash steam reliquefaction system for realizing cold energy supply and a control method thereof. Background Art

[0002] While most existing dual-fuel vessels use natural gas as a clean fuel, a large number of equipment manufacturers, shipyards, and liquid cargo designers have begun researching ammonia-fueled vessels and equipment. Ammonia has a condensation temperature of only -33°C and can be easily liquefied at normal pressure. Furthermore, the hydrogen content per unit mass of ammonia fuel is approximately 18%. Ammonia fuel offers significant advantages in terms of energy density and safety. Ammonia has a higher energy density than hydrogen per unit volume, allowing it to transport more energy within a storage container of the same volume.

[0003] As a fuel for ship engines, ammonia is usually stored in fuel tanks in the form of liquid ammonia at -33°C. Once stored in the fuel tanks, the liquid ammonia will continue to vaporize into ammonia gas. If this ammonia gas is not liquefied or consumed by users, it will cause the tank pressure to rise. Unlike LNG dual-fuel engines, ammonia fuel engines developed by engine manufacturers mainly consume liquid ammonia and cannot consume ammonia gas evaporated from the ship's fuel tanks. When an ammonia fuel tank ship is equipped with a reliquefaction system to handle ammonia vapor, a large amount of liquid ammonia will be produced on board. This part of liquid ammonia contains a large amount of cold energy. How to utilize this part of cold energy has become another difficult problem facing technicians. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides an ammonia flash steam reliquefaction system for realizing cold energy supply, wherein the reliquefaction system includes an ammonia fuel tank, the top outlet of the ammonia fuel tank is connected to an ammonia gas storage tank, the top outlet of the ammonia gas storage tank is connected to a compressor, the high-pressure ammonia gas at the outlet of the compressor flows into a condenser, and the outlet of the condenser is connected to a subcooling heat exchanger inside a cooling tank;

[0005] The cooling tank is filled with liquid ammonia, and the subcooling heat exchanger is immersed in the liquid ammonia in the cooling tank, so that the high-pressure liquid ammonia after condensation and liquefaction can achieve heat exchange with the low-pressure liquid ammonia in the cooling tank; the high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger is divided into three branches, and the first branch flows into the cooling tank after being reduced in pressure and temperature by the high-pressure throttle valve, thereby cooling the interior of the cooling tank.

[0006] Optionally, a refrigerant water cooler is further provided in the cooling tank, and the refrigerant water cooler is immersed in the liquid ammonia in the cooling tank. The refrigerant water flowing out of the refrigerant water cooler outlet flows back to the inlet of the refrigerant water cooler through an external refrigeration pipeline, forming a closed refrigeration cycle. The liquid ammonia in the cooling tank provides cold energy for the refrigerant water, and the refrigeration pipeline passes through the refrigerant water heat exchanger located in the user's room.

[0007] Optionally, a refrigerant water pump is installed in the refrigeration pipeline.

[0008] Optionally, the second branch of high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger is reduced in pressure and temperature after passing through the cold storage throttle valve and then enters the liquid ammonia evaporator located in the cold storage. The liquid ammonia in the liquid ammonia evaporator absorbs heat and turns into ammonia gas, which then flows through the pipeline to the ammonia storage tank.

[0009] Optionally, the third branch of the high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger is reduced in pressure and temperature by a return-to-tank throttle valve and then flows back to the ammonia fuel tank.

[0010] Optionally, the compressor includes a primary compressor and a secondary compressor, the top outlet of the ammonia storage tank is connected to the primary compressor, and the outlet of the primary compressor is connected to the secondary compressor.

[0011] Optionally, the outlet of the secondary compressor is connected to an oil separation device, and the high-pressure ammonia gas from the outlet of the secondary compressor first passes through the oil separation device and then enters the condenser.

[0012] Optionally, the top outlet of the cooling tank is also connected to the inlet of a secondary compressor, and the ammonia gas from the top outlet of the cooling tank is merged with the ammonia gas from the outlet of the first compressor and then connected to the inlet of the second compressor.

[0013] Optionally, the first-stage compressor and the second-stage compressor are driven by a motor, and the outlet pressure of the second-stage compressor is greater than the outlet pressure of the first-stage compressor.

[0014] Optionally, the cooling medium of the condenser is cooling water.

[0015] As described above, the present invention provides an ammonia flash steam reliquefaction system for realizing cold energy supply. The reliquefaction system includes an ammonia fuel tank, an ammonia gas storage tank, a compressor, a condenser, a cooling tank and other devices connected in sequence. The ammonia gas flowing out of the ammonia fuel tank is compressed and condensed to be converted into high-pressure liquid ammonia. After flowing out through the cold heat exchanger, the high-pressure liquid ammonia is divided into three branches. The first branch is reduced in pressure and temperature by a high-pressure throttle valve and flows into the cooling tank to achieve internal cooling of the cooling tank; the second branch is reduced in pressure and temperature by a cold storage throttle valve and enters the liquid ammonia evaporator located in the cold storage, thereby achieving cooling of the cold storage; the third branch is reduced in pressure and temperature by a return tank throttle valve and flows back to the ammonia fuel tank. At the same time, the liquid ammonia in the cooling tank is also used to cool the refrigerant water, thereby achieving refrigeration of the user's room. The reliquefaction system fully utilizes the cold energy contained in the high-pressure liquid ammonia during the reliquefaction process, formulates different refrigeration plans for the cold storage and user's room respectively, takes into account refrigeration efficiency and operational safety, and makes the entire pipeline design more rational. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a schematic diagram of the pipeline connections of the reliquefaction system in Example 1 of the present invention.

[0017] Component number description

[0018] 1. Ammonia fuel tank; 2. Ammonia storage tank; 3. Primary compressor; 4. Secondary compressor; 5. Motor; 6. Oil separation device; 7. Condenser; 8. Subcooling heat exchanger; 9. High-pressure throttle valve; 10. Return tank throttle valve; 11. Return cabin throttle valve; 12. Cooling tank; 13. Liquid ammonia evaporator; 14. Cold storage; 15. Refrigerant water pump; 16. Refrigerant water heat exchanger; 17. User room; 18. Refrigerant water cooler; 19. Water-cooled heat exchanger. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] For example, when describing the embodiments of the present invention, cross-sectional views of device structures may be partially enlarged to scale for ease of explanation. Furthermore, these schematic views are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual manufacturing, three-dimensional dimensions, including length, width, and depth, should be included.

[0021] For ease of description, spatially relative terms such as "under," "below," "below," "below," "above," and "on" may be used herein to describe the relationship of one element or feature to other elements or features shown in the drawings. It will be understood that these spatially relative terms are intended to encompass orientations of the device in use or operation in addition to the orientation depicted in the drawings. Additionally, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may be present. As used herein, "between" is inclusive of both endpoints.

[0022] In the context of the present application, a structure described as a first feature being "above" a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where an additional feature is formed between the first and second features, such that the first and second features may not be in direct contact.

[0023] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0024] Example 1

[0025] like Figure 1 As shown, this embodiment provides an ammonia flash steam reliquefaction system for realizing cold energy supply, specifically comprising:

[0026] An ammonia fuel tank 1 has its top outlet connected to an ammonia storage tank 2, which in turn has its top outlet connected to a compressor. The compressor includes a primary compressor 3 and a secondary compressor 4. The top outlet of the ammonia storage tank 2 is connected to the primary compressor 3, which in turn has its outlet connected to the secondary compressor 4. The outlet pressure of the secondary compressor 4 is greater than that of the primary compressor 3. The outlet of the secondary compressor 4 is connected to an oil separator 6, and the high-pressure ammonia gas from the outlet of the secondary compressor 4 enters the oil separator 6 for filtration. The oil separator 6 is used to separate grease and moisture from the gas, while filtering out particulate matter and impurities in the gas, thereby purifying the ammonia gas.

[0027] Furthermore, the outlet of the oil separation device 6 is connected to the left inlet of the condenser 7, so that the high-pressure ammonia gas from the oil separation device 6 is condensed into high-pressure liquid ammonia. The cooling medium of the condenser 7 is preferably cooling water.

[0028] The right outlet of the condenser pipe 7 is connected to the subcooling heat exchanger 8 inside the cooling tank 12.

[0029] The cooling tank 12 is filled with liquid ammonia, and the subcooling heat exchanger 8 is immersed in the liquid ammonia in the cooling tank 12, allowing the high-pressure liquid ammonia from the condenser 7 to exchange heat with the liquid ammonia in the cooling tank 12. The liquid ammonia flowing out of the outlet of the subcooling heat exchanger 8 is divided into three branches. The first branch is reduced in pressure and temperature by the high-pressure throttle valve 9 before flowing into the cooling tank 12 to cool the interior of the cooling tank 12. This is achieved by absorbing heat from the high-pressure liquid ammonia in the subcooling heat exchanger 8 and the refrigerant water in the refrigerant water cooler 18.

[0030] The cooling tank 12 is also provided with a refrigerant water cooler 18, which is immersed in the liquid ammonia in the cooling tank 12. The refrigerant water flowing out of the refrigerant water cooler 18 outlet is returned to the inlet of the refrigerant water cooler 18 through the external refrigeration pipeline, forming a closed refrigeration cycle. The liquid ammonia in the cooling tank 12 provides cold energy for the refrigerant water. The refrigeration pipeline passes through the refrigerant water heat exchanger located in the user room 17, thereby achieving cooling for the living and working areas of personnel. A refrigerant water pump 15 is installed in the refrigeration pipeline to provide power for the circulation of the refrigerant water.

[0031] At the same time, the top outlet of the cooling tank is also connected to the inlet of the compressor, specifically to the inlet of the secondary compressor 4, that is, the ammonia from the top outlet of the cooling tank is combined with the ammonia from the outlet of the first compressor 3 and then connected to the inlet of the secondary compressor 4, so that the ammonia formed in the cooling tank due to the heat absorption and evaporation of the liquid ammonia itself can be discharged in time.

[0032] Furthermore, the second branch of liquid ammonia flowing out from the outlet of the subcooling heat exchanger 8 is reduced in pressure and temperature through the cold storage throttle valve 10 and then enters the liquid ammonia evaporator 13 located in the cold storage. The liquid ammonia in the liquid ammonia evaporator 13 absorbs heat and turns into ammonia gas, which then flows through the pipeline to the ammonia storage tank 2, and then enters the compressor and condenser again to be liquefied.

[0033] Since the cooling capacity required by the cold storage is much greater than that required by the user's room, liquid ammonia can be directly connected to the cold storage for heat exchange to ensure maximum cooling efficiency. For the user's room, refrigerant water is used as the heat exchange medium, that is, the refrigerant water is first cooled by liquid ammonia, and then the refrigerant water is passed to the user's room for cooling. The entire heat exchange process is more moderate, avoiding the temperature in the room being too low. In addition, considering the risk of ammonia leakage, it is not suitable to pass liquid ammonia directly to the user's room to avoid liquid ammonia leakage causing the dangerous area to spread to the user's room. This application is based on the existing reliquefaction system, which makes full use of the cold energy contained in the high-pressure liquid ammonia in the reliquefaction process, reducing the need for additional refrigeration systems for the cold storage and user's room. Different refrigeration plans are formulated for the cold storage and user's room. For the cold storage, the cooling efficiency is preferably guaranteed, while for the user's room, the safety is first guaranteed. The entire pipeline design is more rational.

[0034] Furthermore, the third branch of liquid ammonia flowing out of the outlet of the subcooling heat exchanger 8 is reduced in pressure and temperature through the return throttle valve 11 and then flows back to the ammonia fuel tank 1 for storage.

[0035] It should be noted that in each pipeline, components such as barometers, control valves, flow meters, etc. can be installed according to actual needs, and in each tank body, components such as barometers and liquid level gauges can be installed to monitor the status of pipelines and storage tanks in real time, and make corresponding flow adjustments to ensure the smooth operation of the entire system.

[0036] The operation process of the above reliquefaction system is as follows:

[0037] The heat-absorbing, vaporized ammonia flows from the ammonia fuel tank 1 into the ammonia storage tank 2. It is then drawn into the primary compressor 3 from the top of the tank 2 through a pipeline. The compressed ammonia from the primary compressor 3 merges with the ammonia from the cooling tank 12 and is further compressed by the secondary compressor 4. After exiting the secondary compressor 4, the high-temperature, high-pressure ammonia enters the oil separator 6. From the oil separator 6, the ammonia flows into the condenser 7. The high-pressure liquid ammonia flowing out of the condenser enters the cooling tank 12, where it exchanges heat with the low-pressure liquid ammonia outside the subcooling heat exchanger 8 inside the cooling tank 12, further cooling the ammonia within the pipe. After flowing out of the subcooling heat exchanger 8, the liquid ammonia is divided into three branches. The first branch is reduced in pressure and temperature through the high-pressure throttle valve 9 and flows into the cooling tank 12, where it evaporates and absorbs the heat of the high-pressure liquid ammonia in the subcooling heat exchanger 8 and the refrigerant water in the refrigerant water cooler 18. The ammonia gas generated by evaporation is extracted by the secondary compressor 4; the liquid ammonia of the third branch flows into the ammonia fuel tank 1 after passing through the return tank throttle valve 11, completing the reliquefaction of the ammonia gas in the tank.

[0038] The liquid ammonia in the second branch flows through the cold storage throttle valve 10 and flows into the liquid ammonia evaporator 13 of the cold storage 14, exchanging heat with the air in the cold storage to perform refrigeration. Finally, the ammonia gas after heat exchange flows into the ammonia storage tank 2 through the pipeline.

[0039] After the refrigerant water in the refrigerant water cooler 18 dissipates heat and cools down in the cooling tank 12, it is driven by the refrigerant water pump 15 to enter the refrigerant water heat exchanger 16 in the user's room 17, exchange heat with the air in the room, and achieve the effect of cooling the user's room 17. Finally, it returns to the cooling tank 12 along the pipeline to exchange heat with liquid ammonia, and then repeats this process.

[0040] In summary, the present invention provides an ammonia flash steam reliquefaction system for realizing cold energy supply. The reliquefaction system includes an ammonia fuel tank, an ammonia storage tank, a compressor, a condenser, a cooling tank and other devices connected in sequence. The ammonia gas flowing out of the ammonia fuel tank is converted into high-pressure liquid ammonia after compression and condensation. The high-pressure liquid ammonia is divided into three branches after flowing out through the cold heat exchanger. The first branch is depressurized and cooled by the high-pressure throttle valve and flows into the cooling tank to realize internal cooling of the cooling tank; the second branch enters the liquid ammonia evaporator located in the cold storage after depressurization and cooling by the cold storage throttle valve, thereby realizing cooling of the cold storage; the third branch returns to the ammonia fuel tank after depressurization and cooling by the return tank throttle valve. At the same time, the liquid ammonia in the cooling tank is also used to cool the refrigerant water, thereby realizing refrigeration of the user's room. The reliquefaction system makes full use of the cold energy contained in the high-pressure liquid ammonia during the reliquefaction process, formulates different refrigeration schemes for the cold storage and the user's room, takes into account both refrigeration efficiency and operational safety, and makes the entire pipeline design more rational.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An ammonia flash steam reliquefaction system for realizing cold energy supply, characterized in that: The reliquefaction system includes an ammonia fuel tank, the top outlet of the ammonia fuel tank is connected to the ammonia storage tank, the compressor includes a primary compressor and a secondary compressor, the top outlet of the ammonia storage tank is connected to the primary compressor, and the outlet of the primary compressor is connected to the secondary compressor; The outlet of the secondary compressor is connected to the oil separation device. The high-pressure ammonia gas from the outlet of the secondary compressor first passes through the oil separation device and then enters the condenser. The outlet of the condenser is connected to the subcooling heat exchanger inside the cooling tank. The cooling tank is filled with liquid ammonia, and the subcooling heat exchanger is immersed in the liquid ammonia in the cooling tank, so that the high-pressure liquid ammonia after condensation and liquefaction can achieve heat exchange with the low-pressure liquid ammonia in the cooling tank; the high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger is divided into three branches, and the first branch is reduced in pressure and temperature by the high-pressure throttle valve and then flows into the cooling tank to cool the interior of the cooling tank; The cooling tank is also provided with a refrigerant water cooler, which is immersed in the liquid ammonia in the cooling tank. The refrigerant water flowing out of the refrigerant water cooler outlet flows back to the inlet of the refrigerant water cooler through the external refrigeration pipeline, forming a closed refrigeration cycle. The liquid ammonia in the cooling tank provides cold energy for the refrigerant water, and the refrigeration pipeline passes through the refrigerant water heat exchanger located in the user's room. The second branch of high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger passes through the cold storage throttle valve to reduce pressure and temperature, and then enters the liquid ammonia evaporator located in the cold storage. The liquid ammonia in the liquid ammonia evaporator absorbs heat and turns into ammonia gas, and then flows to the ammonia storage tank through the pipeline; the third branch of high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger passes through the return tank throttle valve to reduce pressure and temperature, and then flows back to the ammonia fuel tank; The top outlet of the cooling tank is also connected to the inlet of the secondary compressor. The ammonia gas from the top outlet of the cooling tank is merged with the ammonia gas from the outlet of the first compressor and then connected to the inlet of the second compressor.

2. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: A refrigerant water pump is installed in the refrigeration pipeline.

3. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: The primary compressor and the secondary compressor are driven by a motor, and the outlet pressure of the secondary compressor is greater than the outlet pressure of the primary compressor.

4. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: The cooling medium of the condenser is cooling water.

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