System of multi-stage rankine power generation cycle coupled with hydrate energy storage using lng cold energy

Abstract

The application discloses a system for utilizing LNG cold energy and multi-stage Rankine power generation cycle coupling hydrate energy storage, and is characterized in that the system comprises a combustion power generation system, an organic Rankine cycle system, a transcritical carbon dioxide cycle system, a carbon dioxide hydrate energy storage system and a seawater ice making cycle system; wherein LNG sequentially passes through the organic Rankine cycle system, the transcritical carbon dioxide cycle system, the carbon dioxide hydrate energy storage system and the seawater ice making cycle system; and high-temperature waste heat generated by the combustion power generation system sequentially passes through evaporators of the transcritical carbon dioxide cycle and the organic Rankine cycle to provide heat. Based on the consideration of the actual situation of the use of LNG cold energy, the great utilization potential of industrial waste heat is determined, the cascade utilization mode is adopted, the irreversible loss of the system caused by a large temperature difference is greatly reduced, the efficiency of the system is improved, and the performance of the system is enhanced.

Description

Technical Field

[0001] This invention relates to the field of LNG cold energy recovery and utilization technology, and in particular to a system that utilizes LNG cold energy for multi-stage Rankine power generation cycle coupled with hydrate energy storage. Background Technology

[0002] For long-distance natural gas transportation, it is mostly converted into a liquefied state and transported via pipelines. Liquefied natural gas is generally stored at an ultra-low temperature of -162℃. The energy consumption of this liquefaction process ranges from 700 to 850 kWh / kg, depending on the liquefaction method. However, when supplied to users, the liquefied natural gas needs to be regasified. Due to the large temperature difference, the regasification process releases a large amount of usable cold energy. If this large amount of cold energy is not used properly, it will not only cause significant energy loss but may also pollute the environment.

[0003] LNG cold energy utilization can be divided into two types: direct utilization and indirect utilization. Common direct utilization methods include cryogenic power generation, air separation, dry ice production, and cold storage refrigeration. Indirect utilization methods include cryogenic pulverization and transporting refrigerated food. Using LNG cold energy in a single manner has a limited suitable temperature range and involves significant irreversible energy loss. However, cascaded utilization of LNG cold energy can significantly improve system performance, making the system more efficient and reducing energy loss.

[0004] LNG cold energy power generation technology is relatively mature, with the Rankine cycle being particularly widely used. The choice of working fluid has a significant impact on the performance of the Rankine cycle. Through a series of studies, propane and carbon dioxide have been selected as the two working fluids for multi-stage Rankine cycles, exhibiting significantly better performance and economic efficiency than other working fluids. Meanwhile, gas hydrate energy storage technology, as a promising energy storage technology, has great research potential; however, there are still significant gaps in its application research. Based on the aforementioned problems, this invention proposes a system that utilizes a multi-stage Rankine power generation cycle coupled with hydrate energy storage to efficiently recover and utilize LEG cold energy. Summary of the Invention

[0005] To improve the efficiency of LNG cold energy utilization systems, this invention provides a system that utilizes LNG cold energy through a multi-stage Rankine power generation cycle coupled with hydrate energy storage. This system combines an organic Rankine cycle, a transcritical carbon dioxide cycle, a carbon dioxide hydrate energy storage cycle, and a seawater ice-making cycle to recover and utilize LNG cold energy and the high-temperature waste heat from gas combustion power generation.

[0006] This invention provides a multi-stage Rankine cycle power generation system coupled with hydrate energy storage utilizing LNG cold energy, comprising: a combustion power generation system, an organic Rankine cycle system, a transcritical carbon dioxide cycle system, a carbon dioxide hydrate energy storage system, and a seawater ice-making cycle system; wherein, LNG sequentially passes through the organic Rankine cycle system, the transcritical carbon dioxide cycle system, the carbon dioxide hydrate energy storage system, and the seawater ice-making cycle system; the high-temperature waste heat generated by the combustion power generation system sequentially provides heat through the evaporators of the transcritical carbon dioxide cycle and the organic Rankine cycle.

[0007] Furthermore, the combustion power generation system includes a first compressor, an intercooler heat exchanger, a second compressor, an air storage tank, a first shut-off valve, a burner, a first expander, and a first generator; wherein, the outlet side of the first compressor is connected to the heat flow inlet side of the intercooler heat exchanger, the heat flow outlet side of the intercooler heat exchanger is connected to the inlet side of the second compressor, the outlet side of the second compressor is connected to the inlet side of the air storage tank, the outlet side of the air storage tank is connected to the inlet side of the first shut-off valve, the outlet side of the first shut-off valve is connected to the inlet side of the burner, the outlet side of the burner is connected to the inlet side of the first expander, the outlet side of the first expander is connected to the heat flow inlet side of the second evaporator in the transcritical carbon dioxide cycle, and the heat flow outlet side of the second evaporator is connected to the heat flow inlet side of the first evaporator in the organic Rankine cycle; the first expander is electrically connected to the first generator.

[0008] Preferably, the fuel for the burner is methane; and the cold stream for the intercooler is water.

[0009] Furthermore, the organic Rankine cycle system includes a second expander, a second generator, a first regenerator, a first condenser, a first working fluid pump, and a first evaporator; wherein, the outlet side of the second expander is connected to the hot flow inlet side of the first regenerator, the hot flow outlet side of the first regenerator is connected to the hot flow inlet side of the first condenser, the hot flow outlet side of the first condenser is connected to the inlet side of the first working fluid pump, the outlet side of the first working fluid pump is connected to the cold flow inlet side of the first regenerator, the cold flow outlet side of the first regenerator is connected to the cold flow inlet side of the first evaporator, and the cold flow outlet side of the first evaporator is connected to the inlet side of the second expander; the second expander is electrically connected to the second generator.

[0010] Preferably, the working fluid of the first working fluid pump is propane, and the high pressure and low pressure of the organic Rankine cycle system are 6000 kPa and 100 kPa, respectively.

[0011] Furthermore, the transcritical carbon dioxide cycle system includes a third expander, a third generator, a second regenerator, a second condenser, a second working fluid pump, and a first evaporator; wherein, the outlet side of the third expander is connected to the hot flow inlet side of the second regenerator, the hot flow outlet side of the second regenerator is connected to the hot flow inlet side of the second condenser, the hot flow outlet side of the second condenser is connected to the inlet side of the second working fluid pump, the outlet side of the second working fluid pump is connected to the cold flow inlet side of the second regenerator, the cold flow outlet side of the second regenerator is connected to the cold flow inlet side of the second evaporator, and the cold flow outlet of the second evaporator is connected to the inlet side of the third expander; the third expander is electrically connected to the third generator.

[0012] Preferably, the working fluid of the second working fluid pump is carbon dioxide, and the high pressure and low pressure of the transcritical carbon dioxide cycle system are 21000 kPa and 4000 kPa, respectively.

[0013] Furthermore, the carbon dioxide hydrate energy storage system includes a separator, a water pump, a carbon dioxide compressor, a mixer, a second shut-off valve, a hydrate generation unit, and a hydrate separation unit; wherein, the outlet side of the separator is connected to the inlet side of the water pump and the carbon dioxide compressor, the outlet side of the water pump and the carbon dioxide compressor is connected to the inlet side of the mixer, the outlet side of the mixer is connected to the inlet side of the second shut-off valve, the outlet side of the second shut-off valve is connected to the hot flow inlet side of the hydrate generation unit, the hot flow outlet side of the hydrate generation unit is connected to the cold flow inlet side of the hydrate separation unit, and the cold flow outlet side of the hydrate separation unit is connected to the inlet side of the separator.

[0014] Furthermore, the seawater ice-making circulation system includes a third working fluid pump, a third shut-off valve, an ice-making unit, and a third condenser; wherein, the outlet side of the third working fluid pump is connected to the inlet side of the third shut-off valve, the outlet side of the third shut-off valve is connected to the cold flow inlet side of the ice-making unit, the cold flow outlet side of the ice-making unit is connected to the hot flow inlet side of the third condenser, and the inlet side of the third condenser is connected to the inlet side of the third working fluid pump.

[0015] Furthermore, the LNG is stored in an LNG storage tank, the outlet side of which is connected to the inlet side of an LNG pump. The LNG pump is connected to the cold inlet side of the first condenser in the organic Rankine cycle system. The cold outlet side of the first condenser is connected to the cold inlet side of the second condenser in the transcritical carbon dioxide cycle system. The cold outlet side of the second condenser is connected to the cold inlet side of the hydrate generation unit in the carbon dioxide hydrate energy storage system. The cold outlet side of the hydrate generation unit is connected to the cold inlet side of the third condenser in the seawater ice-making cycle system. The cold outlet side of the third condenser is connected to the cold inlet side of the seawater heat exchanger. The cold outlet side of the seawater heat exchanger is connected to the user end.

[0016] Beneficial effects

[0017] This invention proposes a multi-stage Rankine power generation cycle coupled with hydrate energy storage system utilizing LNG cold energy. Specifically, it discloses a multi-functional integrated system with power generation, energy storage, and ice making capabilities, thereby recovering and utilizing the high-temperature waste heat from combustion power generation and the cold energy of LNG. The system offers the following advantages:

[0018] 1. Based on the practical considerations of LNG cold energy utilization, this invention recognizes the great potential for utilizing industrial waste heat and adopts multiple LNG cold energy utilization methods to match different temperature zones in the LNG regasification process, i.e., adopting a cascade utilization method. This greatly reduces the irreversible losses of the system caused by large temperature differences, improves the system efficiency, enhances the system performance, and increases the practicality of the system of this invention.

[0019] 2. This invention further increases power generation efficiency by incorporating a regenerator in a multi-stage Rankine power generation cycle; the system not only generates electricity but also obtains freshwater resources. Furthermore, the innovative carbon dioxide hydrate energy storage cycle combines gas hydrate energy storage technology with LNG cold energy recovery and utilization technology, providing guidance for further research in this direction. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the system of the present invention, which utilizes the cold energy of LNG to generate electricity in a multi-stage Rankine power generation cycle coupled with hydrate energy storage.

[0022] In the diagram: 1-First compressor; 2-Intermediate cooling heat exchanger; 3-Second compressor; 4-Air storage tank; 5-First shut-off valve; 6-Burner; 7-First expander; 8-First generator; 9-First regenerator; 10-First evaporator; 11-Second expander; 12-Second generator; 13-First condenser; 14-First working fluid pump; 15-Second regenerator; 16-Second evaporator; 17-Third expander; 18-Third generator; 19-Second condenser; 20-Second working fluid pump; 21-Second shut-off valve; 22-Hydrate generation unit; 23-Hydrate separation unit; 24-Separator; 25-Water pump; 26-Carbon dioxide compressor; 27-Third condenser; 28-Third working fluid pump; 29-Third shut-off valve; 30-Ice making unit; 31-LNG storage tank; 32-LNG pump; 33-Seawater heat exchanger. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] In the description of this invention, it should be noted that terms such as "connected" are to be interpreted broadly, meaning that the method of connection is not explicitly specified except where it is explicitly stated. Those skilled in the art can determine the specific understanding of the terms in this invention based on the specific circumstances.

[0025] Example

[0026] like Figure 1 As shown, this embodiment of the invention provides a system for multi-stage Rankine cycle power generation coupled with hydrate energy storage using LNG cold energy, comprising: a combustion power generation system, an organic Rankine cycle system, a transcritical carbon dioxide cycle system, a carbon dioxide hydrate energy storage system, and a seawater ice-making cycle system; wherein, LNG passes sequentially through the organic Rankine cycle system, the transcritical carbon dioxide cycle system, the carbon dioxide hydrate energy storage system, and the seawater ice-making cycle system; the high-temperature waste heat generated by the combustion power generation system is provided as heat through the evaporators of the transcritical carbon dioxide cycle and the organic Rankine cycle sequentially.

[0027] The combustion power generation system includes a first compressor 1, an intercooler heat exchanger 2, a second compressor 3, an air storage tank 4, a first shut-off valve 5, a burner 6, a first expander 7, and a first generator 8. The outlet side of the first compressor 1 is connected to the heat inlet side of the intercooler heat exchanger 2; the heat outlet side of the intercooler heat exchanger 2 is connected to the inlet side of the second compressor 3; the outlet side of the second compressor 3 is connected to the inlet side of the air storage tank 4; the outlet side of the air storage tank 4 is connected to the inlet side of the first shut-off valve 5; the outlet side of the first shut-off valve 5 is connected to the inlet side of the burner 6; the outlet side of the burner 6 is connected to the inlet side of the first expander 7; the outlet side of the first expander 7 is connected to the heat inlet side of the second evaporator 16 in a transcritical carbon dioxide cycle; and the heat outlet side of the second evaporator 16 is connected to the heat inlet side of the first evaporator 10 in an organic Rankine cycle. The first expander 7 is electrically connected to the first generator 8. The working fluid of the first working fluid pump 14 is propane, and the high pressure and low pressure of the organic Rankine cycle system are 6000 kPa and 100 kPa, respectively.

[0028] In the specific implementation of the combustion power generation system, air is pressurized once by the first compressor 1, then flows into the intercooler heat exchanger 2 for intercooling with water. After being pressurized again by the second compressor 3, it becomes high-pressure gas and enters the air storage tank 4 for storage. When needed, the high-pressure air in the air storage tank 4 is burned with fuel methane in the burner 6 through the first shut-off valve 5, producing high-temperature flue gas. The high-temperature flue gas first enters the first expander 7 to expand and drive the first generator 8 to generate electricity and discharge it. The flue gas discharged by the first expander 7, carrying high-temperature waste heat, enters the second evaporator 16 in the transcritical carbon dioxide cycle and the first evaporator 10 in the organic Rankine cycle, providing heat for the organic Rankine cycle and the transcritical carbon dioxide cycle, driving the operation of these two-stage power generation cycles.

[0029] The organic Rankine cycle system includes a second expander 11, a second generator 12, a first regenerator 9, a first condenser 13, a first working fluid pump 14, and a first evaporator 10. The outlet side of the second expander 11 is connected to the hot flow inlet side of the first regenerator 9; the hot flow outlet side of the first regenerator 9 is connected to the hot flow inlet side of the first condenser 13; the hot flow outlet side of the first condenser 13 is connected to the inlet side of the first working fluid pump 14; the outlet side of the first working fluid pump 14 is connected to the cold flow inlet side of the first regenerator 9; the cold flow outlet side of the first regenerator 9 is connected to the cold flow inlet side of the first evaporator 10; and the cold flow outlet side of the first evaporator 10 is connected to the inlet side of the second expander 11. The second expander 11 is electrically connected to the second generator 12. The working fluid of the first working fluid pump 14 is propane. The high and low pressures of the organic Rankine cycle system are 6000 kPa and 100 kPa, respectively.

[0030] In the specific implementation of the organic Rankine cycle system, propane, the working fluid, is first pressurized by the first working fluid pump 14. The pressurized high-pressure working fluid first enters the first regenerator 9 and exchanges heat with the high-temperature working fluid discharged from the second expander 11 for a first temperature increase. Then, it enters the first evaporator 10 for a second heating and temperature increase, transforming into a high-temperature, high-pressure gas. The high-temperature, high-pressure working fluid enters the second expander 11 for expansion, driving the second generator 12 to generate electricity. The working fluid after power generation enters the first regenerator 9 and exchanges heat with the first working fluid pump 14 for a first cooling. Then, it enters the first condenser 13 for a second cooling by exchanging heat with LNG before returning to the first working fluid pump 14 to form a cycle.

[0031] The transcritical carbon dioxide cycle system includes a third expander 17, a third generator 18, a second regenerator 15, a second condenser 19, a second working fluid pump 20, and a second evaporator 16. The outlet side of the third expander 17 is connected to the hot flow inlet side of the second regenerator 15; the hot flow outlet side of the second regenerator 15 is connected to the hot flow inlet side of the second condenser 19; the hot flow outlet side of the second condenser 19 is connected to the inlet side of the second working fluid pump 20; the outlet side of the second working fluid pump 20 is connected to the cold flow inlet side of the second regenerator 15; the cold flow outlet side of the second regenerator 15 is connected to the cold flow inlet side of the second evaporator 16; and the cold flow outlet of the second evaporator 16 is connected to the inlet side of the third expander 17. The third expander 17 is electrically connected to the third generator 18. The working fluid of the second working fluid pump 20 is carbon dioxide. The high and low pressures of the transcritical carbon dioxide cycle system are 21000 kPa and 4000 kPa, respectively.

[0032] In the specific implementation of the transcritical carbon dioxide cycle system, the working fluid carbon dioxide is pressurized by the second working fluid pump 20. The pressurized high-pressure working fluid then enters the second regenerator 15 for a second heating, and then enters the second evaporator 16 to exchange heat with the high-temperature flue gas generated after combustion and power generation in the combustion power generation system, transforming it into a high-temperature and high-pressure gas. The high-temperature and high-pressure working fluid enters the third expander 17 to expand and drive the third generator 18 to generate electricity. After power generation, the working fluid enters the second regenerator 15 to exchange heat with the low-temperature and high-pressure gas discharged from the second working fluid pump 20 for a first cooling, and then enters the second condenser 19 to exchange heat with LNG for further cooling before returning to the second working fluid pump 14 to form a cycle.

[0033] The carbon dioxide hydrate energy storage system includes a separator 24, a water pump 25, a carbon dioxide compressor 26, a mixer, a second shut-off valve 21, a hydrate generation unit 22, and a hydrate separation unit 23. The outlet of the separator 24 is connected to the inlet of the water pump 25 and the carbon dioxide compressor 26; the outlets of the water pump 25 and the carbon dioxide compressor 26 are connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the second shut-off valve 21; the outlet of the second shut-off valve 21 is connected to the hot flow inlet of the hydrate generation unit 22; the hot flow outlet of the hydrate generation unit 22 is connected to the cold flow inlet of the hydrate separation unit 23; and the cold flow outlet of the hydrate separation unit 23 is connected to the inlet of the separator 24. The heat source of the hydrate separation unit 23 is air. The hydrate generation and separation pressures in the carbon dioxide hydrate energy storage system are 2500 kPa and 250 kPa, respectively, and the generation and separation temperatures are -9.688℃ and 6.85℃, respectively.

[0034] In the carbon dioxide hydrate energy storage cycle, water and carbon dioxide flowing from separator 24 are pressurized by water pump 25 and carbon dioxide compressor 26 respectively before entering the mixer for mixing. The mixed fluid then enters the hydrate generation unit 22 through the second shut-off valve 21 to exchange heat with LNG and cool down, generating carbon dioxide hydrate. When in use, the stored cold energy is released through the hydrate separation unit 23. In the hydrate separation unit 23, the hydrate is separated back into water and carbon dioxide and then enters separator 24 for further separation.

[0035] The seawater ice-making circulation system includes a third working fluid pump 28, a third shut-off valve 29, an ice-making unit 30, and a third condenser 27. The outlet side of the third working fluid pump 28 is connected to the inlet side of the third shut-off valve 29, the outlet side of the third shut-off valve 29 is connected to the cold flow inlet side of the ice-making unit 30, the cold flow outlet side of the ice-making unit 30 is connected to the hot flow inlet side of the third condenser 27, and the inlet side of the third condenser 27 is connected to the inlet side of the third working fluid pump 28. The working fluid of the third working fluid pump 28 is R410a. The high and low pressures of the seawater ice-making circulation system are 2000 kPa and 420 kPa, respectively. The heat flow type of the ice-making unit 30 is water.

[0036] In the specific implementation of the seawater ice-making circulation system, the working fluid R410a is pressurized by the third working fluid pump 28. The pressurized working fluid enters the third shut-off valve 29, and the outlet side of the third shut-off valve 29 is connected to the inlet side of the ice-making unit 30. The working fluid flowing out from the outlet side of the third shut-off valve 29 enters the ice-making unit 30 to exchange heat with the external environment. Then, the working fluid at the outlet side of the ice-making unit 30 enters the third condenser 27 to exchange heat with LNG and cool down. The cooled working fluid is then pressurized by the third working fluid pump 28 to form a cycle.

[0037] In the LNG cold energy recovery and utilization system provided in this embodiment, the high-temperature flue gas waste heat generated by combustion power generation in the combustion power generation system provides primary waste heat for the second evaporator 16 in the transcritical carbon dioxide cycle system and secondary waste heat for the first evaporator 10 in the organic Rankine cycle system.

[0038] In the LNG cold energy recovery and utilization system provided in this embodiment, LNG flows out from LNG storage tank 31, is pressurized by LNG pump 32, and the pressurized LNG flows through first condenser 13, second condenser 19, hydrate generation unit 22, third condenser 27, and then enters seawater heat exchanger 33 to exchange heat with seawater and be heated to become room temperature natural gas for supply to the user end.

[0039] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A system for utilizing LNG cold energy through a multi-stage Rankine power generation cycle coupled with hydrate energy storage, characterized in that, include: The system consists of a combustion power generation system, an organic Rankine cycle system, a transcritical carbon dioxide cycle system, a carbon dioxide hydrate energy storage system, and a seawater ice-making cycle system. LNG is sequentially processed through the organic Rankine cycle system, the transcritical carbon dioxide cycle system, the carbon dioxide hydrate energy storage system, and the seawater ice-making cycle system. The high-temperature waste heat generated by the combustion power generation system is sequentially supplied as heat through the evaporators of the transcritical carbon dioxide cycle and the organic Rankine cycle. The carbon dioxide hydrate energy storage system includes a separator (24), a water pump (25), a carbon dioxide compressor (26), a mixer, a second shut-off valve (21), a hydrate generation unit (22), and a hydrate separation unit (23). The outlet side of the separator (24) is connected to the inlet side of the water pump (25) and the carbon dioxide compressor (26), the outlet side of the water pump (25) and the carbon dioxide compressor (26) is connected to the inlet side of the mixer, the outlet side of the mixer is connected to the inlet side of the second shut-off valve (21), the outlet side of the second shut-off valve (21) is connected to the hot flow inlet side of the hydrate generation unit (22), the hot flow outlet side of the hydrate generation unit (22) is connected to the cold flow inlet side of the hydrate separation unit (23), and the cold flow outlet side of the hydrate separation unit (23) is connected to the inlet side of the separator (24). The LNG is stored in an LNG storage tank (31). The outlet side of the LNG storage tank (31) is connected to the inlet side of the LNG pump (32). The LNG pump (32) is connected to the cold flow inlet side of the first condenser (13) in the organic Rankine cycle system. The cold flow outlet side of the first condenser (13) is connected to the cold flow inlet side of the second condenser (19) in the transcritical carbon dioxide cycle system. The cold flow outlet side of the second condenser (19) is connected to the cold flow inlet side of the hydrate generation unit (22) in the carbon dioxide hydrate energy storage system. The cold flow outlet side of the hydrate generation unit (22) is connected to the cold flow inlet side of the third condenser (27) in the seawater ice-making cycle system. The cold flow outlet side of the third condenser (27) is connected to the cold flow inlet side of the seawater heat exchanger (33). The cold flow outlet side of the seawater heat exchanger (33) is connected to the user end.

2. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 1, characterized in that, The combustion power generation system includes a first compressor (1), an intercooler heat exchanger (2), a second compressor (3), an air storage tank (4), a first shut-off valve (5), a burner (6), a first expander (7), and a first generator (8); wherein, the outlet side of the first compressor (1) is connected to the heat flow inlet side of the intercooler heat exchanger (2), the heat flow outlet side of the intercooler heat exchanger (2) is connected to the inlet side of the second compressor (3), the outlet side of the second compressor (3) is connected to the inlet side of the air storage tank (4), and the air storage tank (4) The outlet side of the first evaporator (5) is connected to the inlet side of the first shut-off valve (5), the outlet side of the first shut-off valve (5) is connected to the inlet side of the burner (6), the outlet side of the burner (6) is connected to the inlet side of the first expander (7), the outlet side of the first expander (7) is connected to the hot flow inlet side of the second evaporator (16) in the transcritical carbon dioxide cycle, and the hot flow outlet side of the second evaporator (16) is connected to the hot flow inlet side of the first evaporator (10) in the organic Rankine cycle. The first expander (7) is electrically connected to the first generator (8).

3. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 2, characterized in that, The fuel type of the burner (6) is methane; the cold flow type of the intermediate cooling heat exchanger (2) is water.

4. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 1, characterized in that, The organic Rankine cycle system includes a second expander (11), a second generator (12), a first regenerator (9), a first condenser (13), a first working fluid pump (14), and a first evaporator (10); wherein, the outlet side of the second expander (11) is connected to the hot flow inlet side of the first regenerator (9), the hot flow outlet side of the first regenerator (9) is connected to the hot flow inlet side of the first condenser (13), the hot flow outlet side of the first condenser (13) is connected to the inlet side of the first working fluid pump (14), the outlet side of the first working fluid pump (14) is connected to the cold flow inlet side of the first regenerator (9), the cold flow outlet side of the first regenerator (9) is connected to the cold flow inlet side of the first evaporator (10), and the cold flow outlet side of the first evaporator (10) is connected to the inlet side of the second expander (11); the second expander (11) is electrically connected to the second generator (12).

5. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 4, characterized in that, The working fluid of the first working fluid pump (14) is propane, and the high pressure and low pressure of the organic Rankine cycle system are 6000 kPa and 100 kPa, respectively.

6. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 1, characterized in that, The transcritical carbon dioxide cycle system includes a third expander (17), a third generator (18), a second regenerator (15), a second condenser (19), a second working fluid pump (20), and a second evaporator (16); wherein, the outlet side of the third expander (17) is connected to the hot flow inlet side of the second regenerator (15), the hot flow outlet side of the second regenerator (15) is connected to the hot flow inlet side of the second condenser (19), the hot flow outlet side of the second condenser (19) is connected to the inlet side of the second working fluid pump (20), the outlet side of the second working fluid pump (20) is connected to the cold flow inlet side of the second regenerator (15), the cold flow outlet side of the second regenerator (15) is connected to the cold flow inlet side of the second evaporator (16), and the cold flow outlet of the second evaporator (16) is connected to the inlet side of the third expander (17); the third expander (17) is electrically connected to the third generator (18).

7. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 6, characterized in that, The working fluid of the second working fluid pump (20) is carbon dioxide, and the high pressure and low pressure of the transcritical carbon dioxide cycle system are 21000 kPa and 4000 kPa, respectively.

8. The system for multi-stage Rankine power generation coupled with hydrate energy storage using LNG cold energy according to claim 1, characterized in that, The seawater ice-making circulation system includes a third working fluid pump (28), a third shut-off valve (29), an ice-making unit (30), and a third condenser (27); wherein, the outlet side of the third working fluid pump (28) is connected to the inlet side of the third shut-off valve (29), the outlet side of the third shut-off valve (29) is connected to the cold flow inlet side of the ice-making unit (30), the cold flow outlet side of the ice-making unit (30) is connected to the hot flow inlet side of the third condenser (27), and the inlet side of the third condenser (27) is connected to the inlet side of the third working fluid pump (28).

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