Ammonia flash steam reliquefaction system for realizing cold energy supply

Abstract

The invention provides an ammonia flash steam reliquefaction system for realizing cold energy supply, the reliquefaction system comprises an ammonia fuel cabin, an ammonia gas storage tank, a compressor, a condenser pipe, a cooling tank and other devices which are connected in sequence, ammonia gas flowing out of the ammonia fuel cabin is converted into high-pressure liquid ammonia after being compressed and condensed, and the high-pressure liquid ammonia is divided into three branches after flowing out through a cold heat exchanger, the first branch flows into the cooling tank after being depressurized and cooled by the high-pressure throttle valve, so that the interior of the cooling tank is cooled; the second branch is depressurized and cooled by a refrigeration storage throttle valve and then enters a liquid ammonia evaporator in the refrigeration storage, so that the refrigeration storage is cooled; and the third branch flows back to the ammonia fuel cabin after being depressurized and cooled by a back-to-cabin throttle valve. And meanwhile, the liquid ammonia in the cooling tank is also used for cooling the refrigerant water, so that the refrigeration of a user room is realized. According to the reliquefaction system, cold energy contained in high-pressure liquid ammonia in the reliquefaction process is fully utilized, different refrigeration schemes are made according to the refrigeration house and the user room, and the whole pipeline design is more reasonable.

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 and a control method for realizing cold energy supply. Background Art

[0002] Most of the existing dual-fuel ships use natural gas as clean fuel, but a large number of equipment manufacturers, shipyards and liquid cargo design manufacturers have begun to study ship types and equipment that use ammonia as fuel. The condensation temperature of ammonia is only -33°C, and it can be easily liquefied under normal pressure; and the hydrogen content of ammonia fuel per unit mass is about 18%. From the perspective of energy density, safety and other standards, the advantages of ammonia fuel are also very obvious. At the same volume, ammonia has a higher energy density than hydrogen, and can transport more energy in the same volume of storage containers.

[0003] As a ship engine fuel, ammonia is usually stored in the fuel tank in the form of liquid ammonia at -33°C. After being stored in the fuel tank, the liquid ammonia will continue to gasify into ammonia. If this part of the ammonia is not liquefied or consumed by the user, the tank pressure will increase. Unlike the LNG dual-fuel main engine, the ammonia fuel main engine developed by the main engine manufacturer mainly consumes liquid ammonia and cannot consume the ammonia evaporated in the ship's fuel tank. When the ammonia fuel tank ship is equipped with a reliquefaction system for handling ammonia vapor, a large amount of liquid ammonia will be produced on board. This part of liquid ammonia contains a lot of cold energy. How to utilize this part of cold energy has become another difficult problem faced by 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 comprises an ammonia fuel tank, the top outlet of the ammonia fuel tank is connected to an ammonia storage tank, the top outlet of the ammonia 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 a high-pressure throttle valve, thereby cooling the inside of the cooling tank.

[0006] Optionally, a refrigerant water cooler is also 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 outlet of the refrigerant water cooler 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 enters the liquid ammonia evaporator located in the cold storage after being reduced in pressure and temperature by a cold storage throttle valve. The liquid ammonia in the liquid ammonia evaporator absorbs heat and turns into ammonia gas, which then flows to the ammonia storage tank through a pipeline.

[0009] Optionally, the third branch of high-pressure liquid ammonia flowing out from the outlet of the subcooling heat exchanger is reduced in pressure and temperature through 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 primary compressor and then connected to the inlet of the secondary 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, and 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 converted into high-pressure liquid ammonia after compression and condensation. The high-pressure liquid ammonia flows out through the cold heat exchanger and is divided into three branches. The first branch flows into the cooling tank after the high-pressure throttle valve is depressurized and cooled to realize the internal cooling of the cooling tank; the second branch enters the liquid ammonia evaporator located in the cold storage after the cold storage throttle valve is depressurized and cooled, thereby realizing the cooling of the cold storage; the third branch flows back to the ammonia fuel tank after the return throttle valve is depressurized and cooled. At the same time, the liquid ammonia in the cooling tank is also used to cool the refrigerant water, thereby realizing the refrigeration of the user's room. The reliquefaction system makes full use of the cold energy contained in the high-pressure liquid ammonia in the reliquefaction process, formulates different refrigeration schemes for the cold storage and the user's room, takes into account the refrigeration efficiency and operation safety, and the entire pipeline design is more reasonable. 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, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0021] For ease of description, spatial relational terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers. As used herein, "between..." means including the end point values.

[0022] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are 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 illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0024] Embodiment 1

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

[0026] Ammonia fuel tank 1, the top outlet of ammonia fuel tank 1 is connected to ammonia storage tank 2, the top outlet of ammonia storage tank 2 is connected to a compressor, the compressor includes a primary compressor 3 and a secondary compressor 4, the top outlet of ammonia storage tank 2 is connected to primary compressor 3, the outlet of primary compressor 3 is connected to secondary compressor 4, the outlet pressure of secondary compressor 4 is greater than the outlet pressure of primary compressor 3. The outlet of secondary compressor 4 is connected to oil separation device 6, and the high-pressure ammonia from the outlet of secondary compressor 4 enters oil separation device 6 for filtration. Here, oil separation device 6 is used to separate grease and moisture in gas, and filter particulate matter and impurities in gas, so as to achieve the purpose of purifying ammonia.

[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, so that the high-pressure liquid ammonia from the condenser 7 can achieve heat exchange 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, and the first branch flows into the cooling tank 12 after being reduced in pressure and temperature by the high-pressure throttle valve 9, so as to cool the inside of the cooling tank 12, including absorbing the heat of the high-pressure liquid ammonia in the subcooling heat exchanger 8 and the heat of 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 of the cooling tank 12. The refrigerant water flowing out of the outlet of the refrigerant water cooler 18 flows back 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 area of ​​the 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, and then flows to the ammonia storage tank 2 through the pipeline, and then enters the compressor and condenser again to achieve liquefaction.

[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 led to the user's room for cooling. The whole heat exchange process is more gentle, avoiding the temperature in the room being too low. In addition, considering the risk of ammonia leakage, it is not suitable to lead 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, and 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 in 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 refrigeration efficiency is preferably guaranteed, while for the user's room, the safety is first guaranteed, and the whole pipeline design is more rational.

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

[0035] It should be noted that in each pipeline, barometers, control valves, flow meters and other components can be installed according to actual needs, and in each tank, barometers, liquid level gauges and other components 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 ammonia gas that absorbs heat and vaporizes flows out of the ammonia fuel tank 1 to the ammonia storage tank 2, and is then sucked into the primary compressor 3 through the pipeline from the top of the ammonia storage tank 2. The ammonia gas compressed by the primary compressor 3 merges with the ammonia gas from the cooling tank 12, and is further compressed by the secondary compressor 4. After coming out of the secondary compressor 4, the high-temperature and high-pressure ammonia gas enters the oil separator 6. The ammonia gas flows into the condenser 7 from the oil separator 6, and the high-pressure liquid ammonia flowing out of the condenser enters the cooling tank 12, and exchanges heat with the low-pressure liquid ammonia outside the supercooling heat exchanger 8 in the cooling tank 12, thereby further cooling the ammonia gas in the tube. After the liquid ammonia flows out through the subcooling heat exchanger 8, it 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 through the return tank throttle valve 11 to complete the reliquefaction of the ammonia gas in the tank.

[0038] The liquid ammonia of the second branch flows through the cold storage throttle valve 10 and flows into the liquid ammonia evaporator 13 of the cold storage 14, and exchanges heat with the air in the cold storage to perform refrigeration. Finally, the ammonia gas after the heat exchange is completed 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, the refrigerant water will enter the refrigerant water heat exchanger 16 in the user's room 17 driven by the refrigerant water pump 15, exchange heat with the air in the room, and achieve the effect of cooling the user's room 17, and finally return to the cooling tank 12 along the pipeline, exchange heat with liquid ammonia, and then repeat 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, and the high-pressure liquid ammonia is divided into three branches after flowing out through the cold heat exchanger, the first branch is reduced in pressure and temperature through the high-pressure throttle valve and flows into the cooling tank to realize the internal cooling of the cooling tank; the second branch enters the liquid ammonia evaporator located in the cold storage after the pressure is reduced and the temperature is reduced through the cold storage throttle valve, thereby realizing the cooling of the cold storage; the third branch is returned to the ammonia fuel tank after the pressure is reduced and the temperature is reduced through the return throttle valve. At the same time, the liquid ammonia in the cooling tank is also used to cool the refrigerant water, thereby realizing the refrigeration of the user's room. The reliquefaction system makes full use of the cold energy contained in the high-pressure liquid ammonia in the reliquefaction process, formulates different refrigeration schemes for the cold storage and the user's room, takes into account the refrigeration efficiency and operation safety, and the entire pipeline design is 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still 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 comprises an ammonia fuel tank, the top outlet of the ammonia fuel tank is connected to the ammonia storage tank, the top outlet of the ammonia storage tank is connected to the compressor, the high-pressure ammonia gas at the outlet of the compressor flows into the condenser, and 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 flows into the cooling tank after being reduced in pressure and temperature by a high-pressure throttle valve, thereby cooling the inside of the cooling tank.

2. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: A refrigerant water cooler is also provided in the cooling tank. 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.

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

4. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: The second branch of high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger enters the liquid ammonia evaporator located in the cold storage after being reduced in pressure and temperature by the cold storage throttle valve. The liquid ammonia in the liquid ammonia evaporator absorbs heat and turns into ammonia gas, which then flows to the ammonia storage tank through a pipeline.

5. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: The third branch of high-pressure liquid ammonia flowing out of the outlet of the subcooling heat exchanger is reduced in pressure and temperature through the return tank throttle valve and then flows back to the ammonia fuel tank.

6. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 1, characterized in that: The compressor comprises 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.

7. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 6, characterized in that: The outlet of the secondary compressor is connected to the 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.

8. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 6, characterized in that: The top outlet of the cooling tank is also connected to the inlet of the 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 primary compressor and then connected to the inlet of the secondary compressor.

9. The ammonia flash steam reliquefaction system for realizing cold energy supply according to claim 6, 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.

10. 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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