A steam ejector coupled single-tank molten salt heat storage system and method for power plant peak shaving

Abstract

This invention discloses a thermal power peak-shaving system and method using a steam ejector coupled to a single-tank molten salt thermal storage system, belonging to the field of thermal power peak-shaving technology. The system includes: a superheater, a reheater, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a low-pressure heater, a deaerator, a high-pressure heater, a steam ejector, an integrated molten salt thermal storage and exchange tank, a separator, a steam booster pump, and a feedwater booster pump. During periods of low electricity or heating demand, exhaust steam from the main steam ejector turbine is mixed through the steam ejector and enters the molten salt tank, storing the heat of the steam in the high-temperature molten salt. During periods of high electricity or heating demand, the high-temperature molten salt is used to heat boiler feedwater or municipal heating return water. This method achieves both power peak-shaving and thermal-electrical decoupling. The use of a single-tank molten salt system effectively avoids the drawbacks of high investment and complex equipment in traditional dual-tank systems, while the steam ejector enables the cascaded utilization of steam energy, achieving energy conservation.

Description

Technical Field

[0001] This invention belongs to the field of thermal power peak shaving technology, specifically relating to a thermal power plant peak shaving system and method that couples a steam ejector with a single-tank molten salt thermal storage. Background Technology

[0002] Molten salt thermal energy storage has become a research hotspot in energy storage technology in recent years. Coupled with coal-fired power plant systems, the molten salt thermal storage / release process is used to regulate the unit load, which is one of the effective ways to achieve flexible peak shaving for coal-fired power units. For example, Chinese patent CN 113669715 B discloses an energy storage peak shaving system suitable for reheat units that uses steam to heat molten salt. This system adopts a dual-tank arrangement of hot and cold molten salt tanks, storing the heat of high-pressure steam from the boiler in high-temperature molten salt. This allows for decoupling of the boiler's output power from the turbine's power generation, thus meeting the grid's demand for peak shaving capacity. However, traditional molten salt energy storage technologies often use a dual-tank arrangement, with each tank designed to store the entire power plant's thermal storage medium. In actual operation, the actual amount of molten salt in each tank at the same time will not exceed half of its designed volume, resulting in high power plant thermal storage costs. Molten salt tanks account for more than 20% of the total investment in the thermal storage system. Meanwhile, in the dual-tank molten salt system, the heat storage and heat exchange processes of molten salt are carried out separately in the tank and the heat exchanger. Therefore, it is also necessary to equip the system with a variety of auxiliary equipment such as molten salt pumps, molten salt electric heaters, and heat tracing systems. The system is complex and has many potential failure points.

[0003] Furthermore, current technical solutions for applying molten salt energy storage technology to peak shaving in thermal power plants mostly involve directly using the high-temperature, high-pressure steam from the power plant to heat the molten salt. For example, Chinese patent CN 108426238 A discloses a molten salt thermal storage heating system for thermal power plants that utilizes main steam for heating, where the boiler's main steam is used to heat the molten salt through a molten salt heat exchanger. However, boiler steam in thermal power plants is typically high-parameter steam, and currently commonly used shell-and-tube heat exchangers are limited by the high-temperature, high-pressure heat exchange medium, making supercritical heat exchange very difficult. If the parameters of the boiler steam are reduced before entering the heat exchanger, for example, by using a desuperheating and pressure-reducing valve, the high-grade steam produced by the boiler will be wasted, resulting in energy waste. Summary of the Invention

[0004] Based on the above background, this invention discloses a thermal power peak-shaving system and method using a steam ejector coupled with single-tank molten salt thermal storage. During periods of low electricity or heating demand, the boiler operates at full load. Exhaust steam from the main steam ejector turbine is mixed through the steam ejector and then fed into several single molten salt tanks, storing the heat of the steam in high-temperature molten salt. During periods of high electricity or heating demand, the high-temperature molten salt is used to heat boiler feedwater or municipal heating return water. This invention can be applied to condensing thermal power units or back-pressure thermal power units.

[0005] The technical problem solved by this invention is achieved through the following technical solution:

[0006] A thermal power peak-shaving system with a steam ejector coupled to single-tank molten salt thermal storage is disclosed. The thermal power peak-shaving system includes a main unit and a steam ejector unit. The main unit includes a reheater, a superheater, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a low-pressure heater, a deaerator, and a high-pressure heater. The thermal power peak-shaving system also includes a molten salt thermal storage unit. The steam ejector unit includes a main steam regulating valve, a waste steam regulating valve, and a steam ejector. The molten salt thermal storage unit includes several molten salt tanks, a separator, a steam booster pump, and a feedwater booster pump. The several molten salt tanks are connected in parallel between the steam ejector and the separator.

[0007] Furthermore, in the steam ejector unit, the main flow inlet of the steam ejector is connected to the main steam regulating valve, which is connected to any main steam pipeline from the superheater; the secondary flow inlet of the steam ejector is connected to the exhaust steam regulating valve, which is connected to one exhaust steam pipeline from the low-pressure cylinder; and the mixed steam outlet of the steam ejector is connected to the steam inlet of the molten salt tank.

[0008] Furthermore, the steam inlets of the molten salt tanks in the molten salt thermal storage unit are all connected to the mixed steam outlet of the steam ejector, and the steam outlet of the molten salt tanks is connected to the separator; the water-side inlet of the molten salt tanks is connected to the boiler feedwater from the low-pressure heater, and the water-side outlet of the molten salt tanks is connected to the feedwater pipeline entering the deaerator; the water-side outlet of the separator is connected to the feedwater booster pump, and the feedwater booster pump is connected to the feedwater pipeline entering the deaerator; the steam-side outlet of the separator is connected to the steam booster pump, and the steam booster pump is connected to the exhaust pipe of the high-pressure cylinder.

[0009] Furthermore, the molten salt tank has an integrated cylindrical structure. The molten salt tank is equipped with heat storage and heat exchange tubes, heat release and heat exchange tubes, and baffles. The tank is filled with molten salt. The heat storage and heat exchange tubes are located inside the baffles. High-temperature steam flows through the heat storage and heat exchange tubes used to heat the molten salt. The heat storage and heat exchange tubes are connected to the steam inlet and steam outlet. The heat release and heat exchange tubes are located outside the baffles. Feed water flows through the heat release and heat exchange tubes used to cool the molten salt. The heat release and heat exchange tubes are connected to the water-side inlet and water-side outlet.

[0010] Furthermore, the shape of the partition matches the shape of the molten salt tank.

[0011] Furthermore, the number of molten salt tanks shall not be less than two.

[0012] A method for peak shaving in thermal power plants using a steam ejector coupled with a single-tank molten salt thermal storage system is disclosed. This method is applicable to condensing thermal power units or back-pressure thermal power units. The specific method is as follows:

[0013] In condensing thermal power units, power output is adjusted by regulating the steam volume of the turbine to achieve peak power regulation: During off-peak hours, the main steam regulating valve is opened, allowing some main steam to flow into the main flow inlet of the steam ejector, and the exhaust steam regulating valve is opened, allowing some exhaust steam to enter the secondary flow inlet of the steam ejector. The two steam components entering the steam ejector mix and then enter several parallel molten salt tanks through the mixed steam outlet for heat exchange. This heats the low-temperature molten salt in the molten salt tanks into high-temperature molten salt, storing the heat of the steam in the high-temperature molten salt. During peak hours, the main steam regulating valve and the exhaust steam regulating valve are closed to maintain normal boiler operation. Boiler feedwater from the low-pressure heater enters the molten salt tanks to exchange heat with the high-temperature molten salt. The resulting hot water enters the deaerator, thereby reducing the amount of steam extracted from the high-pressure cylinder by the high-pressure heater, which in turn increases the turbine output power, thus achieving peak power regulation.

[0014] In back-pressure thermal power units, when thermoelectric decoupling is required, it is achieved by adjusting the flow rate of the main steam: When heating demand is low, the main steam regulating valve is opened, allowing a portion of the main steam to flow into the main inlet of the steam ejector; the exhaust steam regulating valve is opened, allowing a portion of the exhaust steam to enter the secondary inlet of the steam ejector; the mixed steam then enters the molten salt tank for heat exchange after passing through the mixed steam outlet, heating the low-temperature molten salt in the molten salt tank into high-temperature molten salt, storing the heat of the steam in the high-temperature molten salt; when heating demand is high, the main steam regulating valve and the exhaust steam regulating valve are closed to maintain normal boiler operation; the return water from the heat users enters the molten salt tank for heat exchange with the high-temperature molten salt, and the resulting high-temperature hot water is sent to the heat users to meet their heating needs; when power peak shaving is required, the regulation method of pure condensing thermal power units is adopted, changing the turbine extraction steam rate and adjusting the turbine power output to meet the power plant's peak shaving needs.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The molten salt thermal energy storage unit of this invention utilizes multiple molten salt tanks connected in parallel. The molten salt filling these tanks facilitates heat storage and release, enabling peak power regulation and thermoelectric decoupling in thermal power units, thus improving their flexibility. Compared to traditional dual-tank systems, the integrated molten salt storage and heat exchange tank offers advantages such as lower investment costs and system simplicity. The use of a steam ejector enables cascaded utilization of steam energy, improving energy efficiency and achieving energy conservation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a peak-shaving system for a pure condensing thermal power unit provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a back-pressure thermal power unit thermoelectric decoupling system provided in an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of a single molten salt tank integrating heat storage and exchange;

[0020] Figure 4 for Figure 3 AA section view in the image.

[0021] In the diagram: 1 is the main unit, 2 is the steam ejector unit, 3 is the molten salt thermal storage unit, 10 is the heating network water heat exchanger, 11 is the reheater, 12 is the superheater, 13 is the high-pressure cylinder, 14 is the medium-pressure cylinder, 15 is the low-pressure cylinder, 16 is the condenser, 17 is the low-pressure heater, 18 is the deaerator, 19 is the high-pressure heater, 21 is the main steam regulating valve, 22 is the exhaust steam regulating valve, 23 is the steam ejector, 31 is the molten salt tank, 311 is the steam inlet, 312 is the steam outlet, 313 is the water-side inlet, 314 is the water-side outlet, 315 is the thermal storage heat exchanger tube, 316 is the heat release heat exchanger tube, 317 is the baffle plate, 318 is the molten salt, 32 is the separator, 33 is the steam booster pump, 34 is the feedwater booster pump, 35 is the return water for heat users, and 36 is the heat user. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications or equivalent substitutions made within the spirit of the present invention are within the protection scope of the present invention.

[0023] This invention provides a thermal power peak-shaving system and method with steam ejector coupled to single-tank molten salt thermal storage, which can be applied to pure condensing thermal power units or back-pressure thermal power units.

[0024] like Figure 1 and Figure 2 As shown, the present invention discloses a thermal power peak-shaving system with a steam ejector coupled to a single-tank molten salt thermal storage system. The system includes a main unit 1, a steam ejector unit 2, and a molten salt thermal storage unit 3.

[0025] Furthermore, combined Figure 1 and Figure 2 The main unit 1 specifically includes a reheater 11, a superheater 12, a high-pressure cylinder 13, an intermediate-pressure cylinder 14, a low-pressure cylinder 15, a condenser 16 or a heat exchanger for the heating network water 10, a low-pressure heater 17, a deaerator 18, and a high-pressure heater 19; the steam ejector unit 2 specifically includes a main steam regulating valve 21, a waste steam regulating valve 22, and a steam ejector 23; the molten salt thermal storage unit 3 specifically includes a molten salt tank 31, a separator 32, a steam booster pump 33, and a feedwater booster pump 34.

[0026] Specifically, such as Figure 1 and 2As shown, in the steam ejector unit 2, the main flow inlet 231 of the steam ejector 23 is connected to the main steam regulating valve 21, which is connected to a main steam pipeline from the superheater 12; the secondary flow inlet 232 of the steam ejector 23 is connected to the exhaust steam regulating valve 22, which is connected to an exhaust steam pipeline from the low-pressure cylinder 15; and the mixed steam outlet 233 of the steam ejector 23 is connected to the steam inlet 311 of the molten salt tank 31. The steam ejector in the steam ejector unit utilizes high-pressure main steam to extract turbine exhaust steam. This device replaces some of the functions of the traditional desuperheating and pressure-reducing valve, while simultaneously realizing the cascade utilization of steam energy, improving energy efficiency, and achieving energy conservation.

[0027] Similarly, as Figure 1 and 2 As shown, in the illustrated embodiment, the molten salt thermal storage unit 3 includes several molten salt tanks 31, which are connected in parallel between the steam ejector 23 and the separator 32. The number of molten salt tanks 31 is not less than two, and in this embodiment, the number of molten salt tanks 31 is three. The number can be adjusted according to actual needs during actual use. The mixed steam outlet 233 of the steam ejector 23 is connected to the steam inlet 311 of each molten salt tank 31, and the steam outlet 312 of the molten salt tank 31 is connected to the separator 32. The water-side inlet 313 of the molten salt tank 31 is connected to the boiler feedwater from the low-pressure heater 17, and the water-side outlet 314 of the molten salt tank 31 is connected to the feedwater pipeline entering the deaerator 18. The water-side outlet 321 of the separator 32 is connected to the feedwater booster pump 34, which is connected to the feedwater pipeline entering the deaerator 18; the steam-side outlet 322 of the separator 32 is connected to the steam booster pump 33, which is connected to the exhaust pipe of the high-pressure cylinder 13.

[0028] Furthermore, such as Figure 1 and 2 As shown, the molten salt thermal storage unit 3 adopts a parallel connection of multiple cylindrical molten salt tanks 31. The number of molten salt tanks required can be set according to the required thermal storage power. Compared with a dual-tank system, a single-tank thermal storage system has advantages such as simple and compact structure, convenient use, and low maintenance cost, and has good economic performance.

[0029] Specifically, such as Figure 3As shown, the molten salt tank 31 adopts an integrated heat storage and heat exchange single tank structure. The internal structure includes heat storage and heat exchange tube 315, heat release and heat exchange tube 316, baffle 317, and molten salt 318. The shape of the baffle 317 matches the shape of the molten salt tank 31. In this embodiment, the molten salt tank 31 adopts a cylindrical structure, wherein the heat storage heat exchange tube 315 is placed inside the partition 317, and high-temperature steam flows through the heat storage heat exchange tube 315 to heat the molten salt. The heat storage heat exchange tube 315 is connected to the steam inlet 311 and the steam outlet 312. The heat release heat exchange tube 316 is placed outside the partition 317, and feed water flows through the heat release heat exchange tube 316 to cool the molten salt. The heat release heat exchange tube 316 is connected to the water side inlet 313 and the water side outlet 314. In this embodiment, the heat storage heat exchange tube 315 and the heat release heat exchange tube 316 are spirally placed inside and outside the partition 317, respectively. Molten salt 318 fills the entire molten salt tank 31.

[0030] This invention also discloses a method for peak shaving of thermal power plants using a steam ejector coupled with a single-tank molten salt thermal storage system. This method is applied to condensing thermal power units or back-pressure thermal power units, and the specific adjustment process is as follows:

[0031] refer to Figure 1 The specific working process of the peak-shaving system of the pure condensing thermal power unit is as follows: During the off-peak electricity demand, the main steam regulating valve 21 is opened, allowing a portion of the main steam to flow into the main flow inlet 231 of the steam ejector 23. The exhaust steam regulating valve 22 is opened, allowing a portion of the exhaust steam to enter the secondary flow inlet 232 of the steam ejector 23. The mixed steam enters the molten salt tank 31 for heat exchange after passing through the mixed steam outlet 233. This heats the low-temperature molten salt in the molten salt tank 31 into high-temperature molten salt, storing the heat of the steam in the high-temperature molten salt. The heat-exchanged steam or water enters the separator 32, where steam-water separation is completed. The separated water enters the deaerator 18 after being pressurized by the feedwater booster pump 34 through the water side outlet 321. The separated steam enters the deaerator 18 after being pressurized by the steam booster pump 33 through the steam side outlet 322 and mixed with the exhaust steam from the high-pressure cylinder 13. The main steam and exhaust steam mix in the steam ejector 23 and then enter the molten salt thermal storage unit 3, simultaneously realizing the cascade utilization of the energy of the main steam and exhaust steam. Another portion of the main steam enters the turbine to perform work according to the power plant's original operating mode, that is, the main steam sequentially enters the high-pressure cylinder 13, the intermediate-pressure cylinder 14, and the low-pressure cylinder 15 to perform work, while another portion of the exhaust steam enters the condenser 16. During peak electricity demand, the main steam regulating valve 21 and the exhaust steam regulating valve 22 are closed to maintain normal boiler operation. Boiler feedwater from the low-pressure heater 17 enters the molten salt tank 31 to exchange heat with the high-temperature molten salt. The resulting hot water enters the deaerator 18, thereby reducing the amount of steam extracted from the high-pressure cylinder 13 by the high-pressure heater 19, thus increasing the turbine's output power and achieving peak power regulation.

[0032] refer to Figure 2 The specific working process of the back-pressure thermal power unit thermoelectric decoupling system is as follows: When thermoelectric decoupling is required, it can be achieved by adjusting the flow rate of the main steam: When the heating demand is low, the main steam regulating valve 21 is opened, allowing a portion of the main steam to flow into the main flow inlet 231 of the steam ejector 23. The exhaust steam regulating valve 22 is opened, allowing a portion of the exhaust steam to enter the secondary flow inlet 232 of the steam ejector 23. The mixed steam enters the molten salt tank 31 for heat exchange after passing through the mixed steam outlet 233. This heats the low-temperature molten salt in the molten salt tank 31 into high-temperature molten salt, storing the heat of the steam in the high-temperature molten salt. The heat-exchanged steam or water enters the separator 32, where steam-water separation is completed. The separated water enters the deaerator 18 after being pressurized by the feedwater booster pump 34 through the water side outlet 321. The separated steam enters the deaerator 18 after being pressurized by the steam booster pump 33 through the steam side outlet 322 and mixed with the exhaust steam of the high-pressure cylinder 13. The main steam and exhaust steam mix in the steam ejector 23 and then enter the molten salt thermal storage unit 3, simultaneously realizing the cascade utilization of the energy of the main steam and exhaust steam. Another portion of the main steam enters the turbine to perform work according to the power plant's original operating mode, that is, the main steam sequentially enters the high-pressure cylinder 13, the intermediate-pressure cylinder 14, and the low-pressure cylinder 15 to perform work. Another portion of the exhaust steam enters the heat exchanger 10 to heat the return water for heat users. When the heating demand is high, the main steam regulating valve 21 and the exhaust steam regulating valve 22 are closed to maintain normal boiler operation. The return water 35 for heat users enters the molten salt tank 31 to exchange heat with the high-temperature molten salt, and the resulting high-temperature hot water is sent to heat users 36 to meet the heating demand. When peak power regulation is required, the regulation method of pure condensing thermal power units is adopted, changing the turbine extraction steam rate and adjusting the turbine power output to meet the power plant's peak power regulation needs.

[0033] refer to Figure 3 The specific working process of the molten salt tank is as follows: During heat storage, the hot fluid flows through the heat storage heat exchange pipe 315 and exchanges heat with the molten salt inside the partition 317. After being heated, the molten salt inside the partition 317 experiences a temperature increase and a density decrease, forming natural convection with the low-temperature molten salt outside the partition 317, thus realizing the heat storage process. During heat release, the cold fluid flows through the heat release heat exchange pipe 316 and exchanges heat with the molten salt outside the partition 317. After absorbing heat, the molten salt outside the partition 317 experiences a temperature decrease and a density increase, forming natural convection with the high-temperature molten salt inside the partition 317, thus realizing the heat release process.

[0034] Furthermore, in this embodiment of the invention, the molten salt thermal storage unit can be formed by integrating multiple molten salt single tanks in parallel. The number of molten salt single tanks required can be set according to the required thermal storage power. Compared with the traditional dual-tank system, the single-tank thermal storage system composed of multiple molten salt single tanks in parallel in the thermal power peak shaving system of the present invention has the advantages of simple structure, compactness, ease of use, and low maintenance cost, and has good economic performance.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A thermal power peak-shaving system with a steam ejector coupled to a single-tank molten salt thermal storage, the thermal power peak-shaving system comprising a main unit (1) and a steam ejector unit (2), the main unit (1) comprising a reheater (11), a superheater (12), a high-pressure cylinder (13), an intermediate-pressure cylinder (14), a low-pressure cylinder (15), a condenser (16), a low-pressure heater (17), a deaerator (18), and a high-pressure heater (19), characterized in that, The thermal power peak shaving system also includes a molten salt thermal storage unit (3); the steam ejector unit (2) includes a main steam regulating valve (21), a waste steam regulating valve (22) and a steam ejector (23); The molten salt thermal storage unit (3) includes several molten salt tanks (31), a separator (32), a steam booster pump (33), and a water supply booster pump (34). The several molten salt tanks (31) are connected in parallel between the steam ejector (23) and the separator (32). The molten salt tanks (31) are integral cylindrical structures. The molten salt tanks (31) are equipped with heat storage heat exchange tubes (315), heat release heat exchange tubes (316), and partitions (317) inside. The tanks of the molten salt tanks (31) are filled with molten salt. The heat storage heat exchange tube (315) is placed inside the partition (317). High-temperature steam flows through the heat storage heat exchange tube (315) used for heating molten salt. The heat storage heat exchange tube (315) is connected to the steam inlet (311) and the steam outlet (312). The heat release heat exchange tube (316) is placed outside the partition (317). Feed water flows through the heat release heat exchange tube (316) used for cooling molten salt. The heat release heat exchange tube (316) is connected to the water-side inlet (313) and the water-side outlet (314) of the molten salt tank (31). Molten salt thermal energy storage units utilize multiple molten salt tanks connected in parallel. The molten salt filling the tanks facilitates heat storage and release, enabling power peak regulation and thermal-electric decoupling for thermal power units. During periods of low electricity demand or low heating demand, the boiler operates at full load. The exhaust steam from the main steam ejector turbine is mixed with steam ejector and then enters several molten salt tanks, storing the heat of the steam in high-temperature molten salt. During periods of high electricity demand or high heating demand, the high-temperature molten salt is used to heat boiler feedwater or municipal heating return water. In the steam ejector unit (2), the main flow inlet (231) of the steam ejector (23) is connected to the main steam regulating valve (21), and the main steam regulating valve (21) is connected to any main steam pipe from the superheater (12); the secondary flow inlet (232) of the steam ejector (23) is connected to the exhaust steam regulating valve (22), and the exhaust steam regulating valve (22) is connected to one exhaust steam pipe from the low-pressure cylinder (15); the mixed steam outlet (233) of the steam ejector (23) is connected to the steam inlet (311) of the molten salt tank (31); The steam inlet (311) of the molten salt tank (31) in the molten salt thermal storage unit (3) is connected to the mixed steam outlet (233) of the steam ejector (23), and the steam outlet (312) of the molten salt tank (31) is connected to the separator (32); the water-side inlet (313) of the molten salt tank (31) is connected to the boiler feedwater from the low-pressure heater (17), and the water-side outlet (314) of the molten salt tank (31) is connected to the feedwater pipeline entering the deaerator (18); the water-side outlet (321) of the separator (32) is connected to the feedwater booster pump (34), and the feedwater booster pump (34) is connected to the feedwater pipeline entering the deaerator (18); the steam-side outlet (322) of the separator (32) is connected to the steam booster pump (33), and the steam booster pump (33) is connected to the exhaust pipe of the high-pressure cylinder (13).

2. The thermal power peak-shaving system with steam ejector coupled to single-tank molten salt thermal storage according to claim 1, characterized in that, The shape of the partition (317) matches the shape of the molten salt tank (31).

3. The thermal power peak-shaving system with steam ejector coupled to a single-tank molten salt thermal storage according to claim 1, characterized in that, The number of molten salt tanks (31) shall not be less than two.

4. A method for peak shaving in thermal power plants using a steam ejector coupled with a single-tank molten salt thermal storage system, characterized in that, A thermal power peak-shaving system using a steam ejector coupled to a single-tank molten salt thermal storage as described in any one of claims 1 to 3, characterized in that the thermal power peak-shaving method is applied to pure condensing thermal power units or back-pressure thermal power units, and the specific method is as follows: In a pure condensing thermal power unit, the unit output is changed by adjusting the steam volume of the steam turbine to achieve peak power regulation: during off-peak hours, the main steam regulating valve (21) is opened, allowing a portion of the main steam to flow into the main flow inlet (231) of the steam ejector (23), and the exhaust steam regulating valve (22) is opened, allowing a portion of the exhaust steam to enter the secondary flow inlet (232) of the steam ejector (23). After the two portions of steam entering the steam ejector (23) are mixed, they enter several parallel molten salt tanks (31) through the mixed steam outlet (233) for heat exchange. This allows the low-temperature molten salt in the molten salt tank (31) to be heated into high-temperature molten salt, storing the heat of the steam in the high-temperature molten salt. During peak electricity demand, the main steam regulating valve (21) and the exhaust steam regulating valve (22) are closed to maintain the normal operation of the boiler. Boiler feedwater from the low-pressure heater (17) enters the molten salt tank (31) to exchange heat with the high-temperature molten salt. The resulting hot water enters the deaerator (18), thereby reducing the amount of steam extracted from the high-pressure cylinder (13) by the high-pressure heater (19), which in turn increases the output power of the steam turbine and achieves peak power regulation. In back-pressure thermal power units, when thermoelectric decoupling is required, it is achieved by adjusting the flow rate of the main steam: when the heating demand is low, the main steam regulating valve (21) is opened, allowing a portion of the main steam to flow into the main flow inlet (231) of the steam ejector (23), and the exhaust steam regulating valve (22) is opened, allowing a portion of the exhaust steam to enter the secondary flow inlet (232) of the steam ejector (23). The mixed steam then enters the molten salt tank (31) for heat exchange after passing through the mixed steam outlet (233), so that the molten salt tank (31) contains heat exchanged heat. Low-temperature molten salt is heated into high-temperature molten salt, storing the heat of steam in the high-temperature molten salt; when the heating demand is high, the main steam regulating valve (21) and the exhaust steam regulating valve (22) are closed to keep the boiler running normally, and the return water (35) of the heat user enters the molten salt tank (31) to exchange heat with the high-temperature molten salt, and the generated high-temperature hot water is sent to the heat user (36) to meet the heating demand; when power peak shaving is required, the regulation method of pure condensing thermal power unit is adopted to change the steam extraction of the turbine and adjust the power output of the turbine to meet the peak shaving demand of the power plant.

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