A supercritical carbon dioxide source-storage integrated power generation system and operation method

Abstract

The present invention discloses a supercritical carbon dioxide source-storage integrated power generation system and an operation method thereof. The system includes a super-recompression reheat power generation system, a heat pump energy storage system, and a heat release system. A bypass flue is arranged at the tail of the boiler, and a flue gas heat exchanger is arranged in the bypass flue. During energy storage, the bypass flue is opened, and the heat pump energy storage system is started. The surplus power of the unit is used to drive the heat pump cycle to convert the heat of the diverted flue gas in the bypass flue into higher-grade heat energy, which is stored in the molten salt energy storage tank to reduce the output power of the unit. During heat release, the heat stored in the molten salt tank is released to heat a part of the working medium diverted at the inlet of the high-temperature recuperator, and then it is merged into the high-pressure turbine to increase the output power of the unit. The supercritical carbon dioxide source-storage integrated power generation system proposed by the present invention can broaden the load regulation range of coal-fired power generation units, realize the ultra-low load operation of the units, improve the load change rate, enhance the flexibility of the system, and promote the consumption of new energy power generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation, and particularly relates to a supercritical carbon dioxide source-storage integrated power generation system and an operation method thereof. Background Art

[0002] The supercritical carbon dioxide cycle is a new power cycle with great potential for coal-fired power generation, and is expected to replace the traditional steam Rankine cycle. The critical parameters of carbon dioxide are low, and it is easy to achieve the supercritical state. Moreover, the physical properties of carbon dioxide change violently near the critical point. When approaching the critical point, the density increases sharply, the compressibility decreases, and the power consumption of the compressor decreases. Therefore, the system cycle efficiency is relatively high.

[0003] For coal-fired power generation units, in addition to continuously improving the energy utilization efficiency, it is also necessary to enhance the flexibility of the units to provide peak shaving services for large-scale new energy consumption. The flexibility of the units is usually manifested in the variable load range, variable load rate, start-stop time, etc. However, supercritical carbon dioxide coal-fired power generation units are also restricted by the minimum stable combustion load of the boiler and the strong coupling between the turbine and the boiler, resulting in insufficient flexibility. Summary of the Invention

[0004] In order to broaden the operating load range of coal-fired power generation units and increase the system flexibility to better serve the power grid peak shaving and frequency modulation, the present invention proposes a supercritical carbon dioxide source-storage integrated power generation system and an operation method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A supercritical carbon dioxide source-storage integrated power generation system, comprising a recompression and reheat power generation system, a heat pump energy storage system, and a heat release system;

[0007] The recompression reheating power generation system includes a gas-cooled wall, a superheater 2, a reheater 3, an economizer 4, a high-pressure turbine 16, a low-pressure turbine 17, a high-temperature recuperator 24, a low-temperature recuperator 23, a recompressor 19, a main compressor 20, and a cooler 22. The outlet of the main compressor 20 is connected to the inlet of the cold side of the low-temperature recuperator 23. The outlet of the cold side of the low-temperature recuperator 23 is connected to the inlet of the cold side of the high-temperature recuperator 24. The outlet of the cold side of the high-temperature recuperator 24 is connected to the inlet of the gas-cooled wall and the superheater 2. The working medium outlet of the gas-cooled wall and the superheater 2 is connected to the high-pressure turbine 16. The working medium outlet of the high-pressure turbine 16 is connected to the inlet of the reheater 3. The working medium outlet of the reheater 3 is connected to the inlet of the low-pressure turbine 17. The outlet of the low-pressure turbine 17 is successively connected to the hot side of the high-temperature recuperator 24 and the hot side of the low-temperature recuperator 23. The outlet of the hot side of the low-temperature recuperator 23 is respectively connected to the inlet of the recompressor 19 and the inlet of the cooler 22. The outlet of the recompressor 19 is connected to the outlet of the cold side of the low-temperature recuperator 23. The outlet of the cooler 22 is connected to the inlet of the main compressor 20. The inlet of the cold side of the high-temperature recuperator 24 is further connected to the inlet of the economizer 4. The outlet of the economizer 4 is connected to the inlet of the gas-cooled wall and the superheater 2.

[0008] The heat pump energy storage system includes a flue gas heat exchanger 6, a No. 1 molten salt heat exchanger 10, a heat pump turbine 8, a heat pump compressor 14, a low-temperature molten salt tank 11, and a high-temperature molten salt tank 13. The outlet of the low-temperature molten salt tank 11 is connected to the inlet of the cold side of the No. 1 molten salt heat exchanger 10. The outlet of the cold side of the No. 1 molten salt heat exchanger 10 is connected to the inlet of the high-temperature molten salt tank 13. The hot side of the No. 1 low-temperature recuperator 10 is successively connected to the heat pump turbine 8, the flue gas heat exchanger 6, and the heat pump compressor 14.

[0009] The heat release system includes a No. 2 molten salt heat exchanger 12. The inlet of the hot side of the No. 2 molten salt heat exchanger 12 is connected to the outlet of the high-temperature molten salt tank 13. The outlet of the hot side of the No. 2 molten salt heat exchanger 12 is connected to the inlet of the low-temperature molten salt tank 11. The inlet of the cold side of the No. 2 molten salt heat exchanger 12 is connected to the outlet of the cold side of the low-temperature recuperator 23. The outlet of the cold side of the No. 2 molten salt heat exchanger 12 is connected to the inlet of the high-pressure turbine 16.

[0010] The system further includes a boiler 1. A gas-cooled wall, a superheater 2, a reheater 3, an economizer 4, and a flue gas heat exchanger 6 are arranged in the boiler 1. A bypass flue damper 5 is further arranged in the boiler 1, dividing the flue into a main flue and a bypass flue 7. The economizer 4 is arranged in the main flue, and the flue gas heat exchanger 6 is arranged in the bypass flue 7.

[0011] The system further includes a generator 18 coaxially connected to the high-pressure turbine 16 and the low-pressure turbine 17, a motor 21 coaxially connected to the main compressor 19 and the recompressor 20, a heat pump generator 9 connected to the heat pump turbine 8, and a heat pump motor 15 connected to the heat pump compressor 14.

[0012] A first valve 251 is provided on the connecting pipeline between the low-temperature molten salt tank 11 and the first molten salt heat exchanger 10, a third valve 253 is provided on the connecting pipeline between the high-temperature molten salt tank 13 and the second molten salt heat exchanger 12, and a second valve 252 is provided on the connecting pipeline between the second molten salt heat exchanger 12 and the cold-side outlet of the low-temperature recuperator 23.

[0013] The inlet temperature of the main compressor 20 is 32 - 42 °C.

[0014] The inlet pressure of the main compressor 20 is 7.5 - 9.0 MPa.

[0015] An operation method of the supercritical carbon dioxide source-storage integrated power generation system includes a normal operation mode, a heat pump energy storage operation mode, and a heat release operation mode;

[0016] In the normal operation mode, all valves and the bypass flue gas baffle 5 are in the default closed state. The high-temperature and high-pressure carbon dioxide working medium at the outlets of the gas-cooled wall and the superheater 2 in the boiler 1 enters the high-pressure turbine 16 to do work. After the working medium at the outlet of the high-pressure turbine 16 is reheated by the reheater 3, it enters the low-pressure turbine 17 to do work. The working medium at the outlet of the low-pressure turbine 17 is successively cooled by the high-temperature recuperator 24 and the low-temperature recuperator 23 and then divided into two parts: one part is compressed and boosted by the recompressor 19; the other part is cooled by the cooler 22 and then enters the main compressor 20 to be compressed and boosted. The working medium at the outlet of the main compressor 20 enters the low-temperature recuperator 23 for heating. The working medium at the cold-side outlet of the low-temperature recuperator 23 converges with the working medium at the outlet of the recompressor 19, is heated by the high-temperature recuperator 24, and then enters the boiler 1; there is a flow split before the cold-side inlet of the high-temperature recuperator 24, and a part of the working medium is diverted to enter the economizer 4 of the boiler 1 to absorb the heat of the medium and low-temperature flue gas, and then converges into the main flow before the inlets of the working media of the gas-cooled wall and the superheater 2;

[0017] In the heat pump energy storage operation mode, based on the normal operation mode, the bypass flue gas baffle 5 is opened, and the first valve 251 is opened; a bypass flue is formed inside the boiler 1 to divert part of the flue gas to heat the low-temperature and low-pressure carbon dioxide working medium at the outlet of the heat pump turbine 8. The working medium at the outlet of the flue gas heat exchanger 6 is further compressed to a higher temperature state, and the heat is stored in the high-temperature molten salt tank 13 via the molten salt heat exchanger 10; the heat pump compressor 14 is driven by the surplus power of the power station, that is, the surplus power is used to convert the heat of the medium and low-temperature flue gas into high-temperature heat for storage, reducing the output power of the unit;

[0018] In the heat release operation mode, based on the normal operation mode, the first valve 251 is closed, and the second valve 252 and the third valve 253 are opened; the high-temperature molten salt stored in the high-temperature molten salt tank 13 is released to heat the working medium diverted from the outlet of the low-temperature recuperator 23 in the second molten salt heat exchanger 12. The low-temperature molten salt after heat release returns to be stored in the low-temperature molten salt tank 11, and the working medium heated in the second molten salt heat exchanger 12 flows into the inlet of the high-pressure turbine 16, thereby increasing the working medium flow rate of the high-pressure turbine to improve the unit output power.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1) By adopting a redundant power-driven heat pump energy storage cycle, the present invention realizes rapid load reduction and increases the high-pressure turbine flow rate to improve the load increase rate.

[0021] 2) The present invention integrates a heat pump energy storage system, which can reduce the minimum operating load of a coal-fired power generation unit through heat storage and increase the unit output power through heat release, broaden the unit operating load range, and enhance flexibility.

[0022] 3) The present invention arranges a split flue at the tail of the boiler. When the unit operates at low load, the flue gas temperature is increased by mixing the main path and bypass flue gas to avoid low-temperature corrosion. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the supercritical carbon dioxide source-storage integrated power generation system of the present invention.

[0024] Figure 2(a) is a schematic diagram of the normal operation mode of the supercritical carbon dioxide source-storage integrated power generation system.

[0025] Figure 2(b) is a schematic diagram of the heat storage mode of the supercritical carbon dioxide source-storage integrated power generation system.

[0026] Figure 2(c) is a schematic diagram of the heat release mode of the supercritical carbon dioxide source-storage integrated power generation system. Detailed Embodiments

[0027] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0028] The supercritical carbon dioxide cycle is a very promising new power cycle that can be used for coal-fired power generation and is expected to replace the traditional steam Rankine cycle. However, it is also restricted by the minimum stable combustion load of the boiler, and the flexibility of the unit is insufficient. For this reason, the present invention proposes a supercritical carbon dioxide source-storage integrated power generation system and operation method.

[0029] Such as Figure 1As shown in the figure, a supercritical carbon dioxide integrated power generation system includes a recompression reheating power generation system, a heat pump heat storage system, and a heat release system; the recompression reheating power generation system includes a gas-cooled wall, superheater 2, reheater 3, economizer 4, high-pressure turbine 16, low-pressure turbine 17, high-temperature recuperator 24, low-temperature recuperator 23, recompressor 19, main compressor 20, and cooler 22; the outlet of the main compressor 20 is connected to the cold-side inlet of the low-temperature recuperator 23, the cold-side outlet of the low-temperature recuperator 23 is connected to the cold-side inlet of the high-temperature recuperator 24, the cold-side outlet of the high-temperature recuperator 24 is connected to the inlet of the gas-cooled wall and superheater 2, the working medium outlet of the gas-cooled wall and superheater 2 is connected to the high-pressure turbine 16, the working medium outlet of the high-pressure turbine 16 is connected to the inlet of the reheater 3, the working medium outlet of the reheater 3 is connected to the inlet of the low-pressure turbine 17, the outlet of the low-pressure turbine 17 is sequentially connected to the hot side of the high-temperature recuperator 24 and the hot side of the low-temperature recuperator 23, the hot-side outlet of the low-temperature recuperator 23 is respectively connected to the inlet of the recompressor 19 and the inlet of the cooler 22, the outlet of the recompressor 19 is connected to the cold-side outlet of the low-temperature recuperator 23, and the outlet of the cooler 22 is connected to the inlet of the main compressor 20; the cold-side inlet of the high-temperature recuperator 24 is also connected to the inlet of the economizer 4, and the outlet of the economizer 4 is connected to the inlet of the gas-cooled wall and superheater 2;

[0030] The heat pump heat storage part of the system includes a flue gas heat exchanger 6, a No. 1 molten salt heat exchanger 10, a heat pump turbine 8, a heat pump compressor 14, a low-temperature molten salt tank 11, and a high-temperature molten salt tank 13; the outlet of the low-temperature molten salt tank 11 is connected to the cold-side inlet of the No. 1 molten salt heat exchanger 10, and the cold-side outlet of the No. 1 molten salt heat exchanger 10 is connected to the inlet of the high-temperature molten salt tank 13; the hot side of the No. 1 low-temperature recuperator 10 is sequentially connected to the heat pump turbine 8, the flue gas heat exchanger 6, and the heat pump compressor 14;

[0031] The heat release part of the system is a No. 2 molten salt heat exchanger 12. The hot-side inlet of the No. 2 molten salt heat exchanger 12 is connected to the outlet of the high-temperature molten salt tank 13, and the hot-side outlet of the No. 2 molten salt heat exchanger 12 is connected to the inlet of the low-temperature molten salt tank 11; the cold-side inlet of the No. 2 molten salt heat exchanger 12 is connected to the cold-side outlet of the low-temperature recuperator 23, and the cold-side outlet of the No. 2 molten salt heat exchanger 12 is connected to the inlet of the high-pressure turbine 16.

[0032] The system also includes a boiler 1. Inside the boiler 1, a gas-cooled wall, superheater 2, reheater 3, economizer 4, and flue gas heat exchanger 6 are arranged along the flue gas flow direction; a bypass flue baffle 5 is also arranged inside the boiler 1, dividing the flue into a main flue and a bypass flue 7. The economizer 4 is arranged in the main flue, and the flue gas heat exchanger 6 is arranged in the bypass flue 7.

[0033] The system also includes a generator 18 coaxially connected to the high-pressure turbine 16 and the low-pressure turbine 17, a motor 21 coaxially connected to the main compressor 19 and the recompressor 20, a heat pump generator 9 connected to the heat pump turbine 8, and a heat pump motor 15 connected to the heat pump compressor 14.

[0034] A first valve 251 is provided on the connecting pipeline between the low-temperature molten salt tank 11 and the first molten salt heat exchanger 10, a third valve 253 is provided on the connecting pipeline between the high-temperature molten salt tank 13 and the second molten salt heat exchanger 12, and a second valve 252 is provided on the connecting pipeline between the second molten salt heat exchanger 12 and the cold-side outlet of the low-temperature recuperator 23.

[0035] The inlet temperature of the main compressor 20 is 32 - 42 °C; the inlet pressure of the main compressor 20 is 7.5 - 9.0 MPa.

[0036] The operation method of the supercritical carbon dioxide source-storage integrated power generation system described above mainly includes a normal operation mode, a heat pump energy storage operation mode, and a heat release operation mode:

[0037] Normal operation mode: All valves and the bypass flue gas damper 5 are in the default closed state, as shown in Figure 2(a). The high-temperature and high-pressure carbon dioxide working medium at the outlet of the gas-cooled wall and the superheater 2 in the boiler 1 enters the high-pressure turbine 16 to do work. After the working medium at the outlet of the high-pressure turbine 16 is reheated by the reheater 3, it enters the low-pressure turbine 17 to do work. The working medium at the outlet of the low-pressure turbine 17 is successively cooled by the high-temperature recuperator 24 and the low-temperature recuperator 23 and then divided into two parts: one part is compressed and boosted by the recompressor 19; the other part is cooled by the cooler 22 and then enters the main compressor 20 to be compressed and boosted. The working medium at the outlet of the main compressor 20 enters the low-temperature recuperator 23 for heating. The working medium at the cold-side outlet of the low-temperature recuperator 23 converges with the working medium at the outlet of the recompressor 19, is heated by the high-temperature recuperator 24, and then enters the boiler 1; there is a flow split before the cold-side inlet of the high-temperature recuperator 24, and a part of the working medium is diverted to the economizer 4 of the boiler 1 to absorb the heat of the medium and low-temperature flue gas, and then converges into the main flow before the inlet of the working medium of the gas-cooled wall and the superheater 2;

[0038] Heat pump energy storage operation mode: The valves and the bypass flue gas damper 5 are in the default closed state. On the basis of the normal operation mode, the bypass flue gas damper 5 is opened, and the first valve 251 is opened, as shown in Figure 2(b). A bypass flue is formed inside the boiler 1 to divert part of the flue gas to heat the low-temperature and low-pressure carbon dioxide working medium at the outlet of the heat pump turbine 8. The working medium at the outlet of the flue gas heat exchanger 6 is further compressed to a higher temperature state, and the heat is stored in the high-temperature molten salt tank 13 via the molten salt heat exchanger 10; the heat pump compressor 14 is driven by the surplus power of the power station, that is, the surplus power is used to convert the heat of the medium and low-temperature flue gas into high-temperature heat for storage;

[0039] Heat release operation mode, the valves and the bypass flue gas damper 5 are in the default closed state. On the basis of the conventional operation mode, the first valve 251 is closed, the second valve 252 and the third valve 253 are opened, as shown in Figure 2(c). The high-temperature molten salt stored in the high-temperature molten salt tank 13 is released to heat the working medium diverted from the outlet of the low-temperature recuperator 23 in the second molten salt heat exchanger 12. The low-temperature molten salt after heat release returns to be stored in the low-temperature molten salt tank 11. The working medium heated in the second molten salt heat exchanger 12 flows into the inlet of the high-pressure turbine 16, thereby increasing the working medium flow rate of the high-pressure turbine to improve the unit output power.

Claims

1. A supercritical carbon dioxide source-storage integrated power generation system, characterized in that: It includes a recompression reheating power generation system, a heat pump energy storage system, and a heat release system; The recompression reheating power generation system includes a gas-cooled wall and a superheater (2), a reheater (3), an economizer (4), a high-pressure turbine (16), a low-pressure turbine (17), a high-temperature recuperator (24), a low-temperature recuperator (23), a recompressor (19), a main compressor (20), and a cooler (22); the outlet of the main compressor (20) is connected to the cold-side inlet of the low-temperature recuperator (23), the cold-side outlet of the low-temperature recuperator (23) is connected to the cold-side inlet of the high-temperature recuperator (24), the cold-side outlet of the high-temperature recuperator (24) is connected to the inlet of the gas-cooled wall and the superheater (2), the working medium outlet of the gas-cooled wall and the superheater (2) is connected to the high-pressure turbine (16), the working medium outlet of the high-pressure turbine (16) is connected to the inlet of the reheater (3), the working medium outlet of the reheater (3) is connected to the inlet of the low-pressure turbine (17), the outlet of the low-pressure turbine (17) is sequentially connected to the hot side of the high-temperature recuperator (24) and the hot side of the low-temperature recuperator (23), the hot-side outlet of the low-temperature recuperator (23) is respectively connected to the inlet of the recompressor (19) and the inlet of the cooler (22), the outlet of the recompressor (19) is connected to the cold-side outlet of the low-temperature recuperator (23), and the outlet of the cooler (22) is connected to the inlet of the main compressor (20); the cold-side inlet of the high-temperature recuperator (24) is also connected to the inlet of the economizer (4), and the outlet of the economizer (4) is connected to the inlet of the gas-cooled wall and the superheater (2); The heat pump energy storage system includes a flue gas heat exchanger (6), a No. 1 molten salt heat exchanger (10), a heat pump turbine (8), a heat pump compressor (14), a low-temperature molten salt tank (11), and a high-temperature molten salt tank (13); the outlet of the low-temperature molten salt tank (11) is connected to the cold-side inlet of the No. 1 molten salt heat exchanger (10), and the cold-side outlet of the No. 1 molten salt heat exchanger (10) is connected to the inlet of the high-temperature molten salt tank (13); the hot side of the No. 1 low-temperature recuperator (10) is sequentially connected to the heat pump turbine (8), the flue gas heat exchanger (6), and the heat pump compressor (14); The heat release system includes a No. 2 molten salt heat exchanger (12), the hot-side inlet of the No. 2 molten salt heat exchanger (12) is connected to the outlet of the high-temperature molten salt tank (13), and the hot-side outlet of the No. 2 molten salt heat exchanger (12) is connected to the inlet of the low-temperature molten salt tank (11); the cold-side inlet of the No. 2 molten salt heat exchanger (12) is connected to the cold-side outlet of the low-temperature recuperator (23), and the cold-side outlet of the No. 2 molten salt heat exchanger (12) is connected to the inlet of the high-pressure turbine (16).

2. The supercritical carbon dioxide integrated power generation system according to claim 1, wherein It also includes a boiler (1), in which a gas-cooled wall and a superheater (2), a reheater (3), an economizer (4), and a flue gas heat exchanger (6) are arranged; a bypass flue baffle (5) is also provided in the boiler (1) to divide the flue into a main flue and a bypass flue (7), the economizer (4) is arranged in the main flue, and the flue gas heat exchanger (6) is arranged in the bypass flue (7).

3. The supercritical carbon dioxide integrated power generation system according to claim 1, wherein It further includes a generator (18) coaxially connected to the high-pressure turbine (16) and the low-pressure turbine (17), a motor (21) coaxially connected to the main compressor (20) and the recompressor (19), a heat pump generator (9) connected to the heat pump turbine (8), and a heat pump motor (15) connected to the heat pump compressor (14).

4. The supercritical carbon dioxide integrated power generation system according to claim 1, wherein A first valve (251) is provided on the connecting pipeline between the low-temperature molten salt tank (11) and the first molten salt heat exchanger (10), a third valve (253) is provided on the connecting pipeline between the high-temperature molten salt tank (13) and the second molten salt heat exchanger (12), and a second valve (252) is provided on the connecting pipeline between the second molten salt heat exchanger (12) and the cold-side outlet of the low-temperature recuperator (23).

5. The supercritical carbon dioxide source-storage integrated power generation system according to claim 1, characterized in that The inlet temperature of the main compressor (20) is 32 - 42 °C.

6. The supercritical carbon dioxide integrated power generation system according to claim 1, wherein The inlet pressure of the main compressor (20) is 7.5 - 9.0 MPa.

7. A method for operating a supercritical carbon dioxide source-storage integrated power generation system according to any one of claims 1 to 6, characterized in that, It includes a normal operation mode, a heat pump heat storage operation mode, and a heat release operation mode; In the normal operation mode, all valves and the bypass flue gas damper (5) are in the default closed state. The high-temperature and high-pressure carbon dioxide working medium at the outlets of the gas-cooled wall and the superheater (2) in the boiler (1) enters the high-pressure turbine (16) to do work. After the working medium at the outlet of the high-pressure turbine (16) is reheated by the reheater (3), it enters the low-pressure turbine (17) to do work. The working medium at the outlet of the low-pressure turbine (17) is successively cooled by the high-temperature recuperator (24) and the low-temperature recuperator (23) and then divided into two parts: one part is compressed and boosted by the recompressor (19); The other part is cooled by the cooler (22) and then enters the main compressor (20) to be compressed and boosted. The working medium at the outlet of the main compressor (20) enters the low-temperature recuperator (23) for heating. The working medium at the cold-side outlet of the low-temperature recuperator (23) converges with the working medium at the outlet of the recompressor (19), and after being heated by the high-temperature recuperator (24), it enters the boiler (1); there is a flow split before the cold-side inlet of the high-temperature recuperator (24), and a part of the working medium is diverted to enter the economizer (4) of the boiler (1) to absorb the heat of the medium- and low-temperature flue gas, and then converges into the main flow before the inlets of the working media of the gas-cooled wall and the superheater (2); In the heat pump heat storage operation mode, based on the normal operation mode, the bypass flue gas damper (5) is opened, and the first valve (251) is opened; a bypass flue is formed inside the boiler (1) to divert part of the flue gas to heat the low-temperature and low-pressure carbon dioxide working medium at the outlet of the heat pump turbine (8). The working medium at the outlet of the flue gas heat exchanger (6) is further compressed to a higher temperature state, and the heat is stored in the high-temperature molten salt tank (13) via the molten salt heat exchanger (10); the heat pump compressor (14) is driven by the surplus power of the power station, that is, the surplus power is used to convert the heat of the medium- and low-temperature flue gas into high-temperature heat for storage, reducing the output power of the unit; In the heat release operation mode, based on the normal operation mode, the first valve (251) is closed, and the second valve (252) and the third valve (253) are opened; the high-temperature molten salt stored in the high-temperature molten salt tank (13) is released into the No. 2 molten salt heat exchanger (12) to heat the working medium diverted from the outlet of the low-temperature recuperator (23). The low-temperature molten salt after heat release returns to be stored in the low-temperature molten salt tank (11). The working medium heated in the No. 2 molten salt heat exchanger (12) flows into the inlet of the high-pressure turbine (16), thereby increasing the working medium flow rate of the high-pressure turbine to improve the unit output power.

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