HEAT-POWER DECOUPLING SYSTEM COUPLED WITH MOLTEN SALT ENERGY STORAGE AND METHOD FOR IMPROVING EFFICIENCY OF HEAT-POWER DECOUPLING SYSTEM

[0001] This patent application claims the benefit and priority of Chinese Patent Application No. CN202510021751.X, entitled “HEAT-POWER DECOUPLING SYSTEM COUPLED WITH MOLTEN SALT ENERGY STORAGE AND METHOD FOR IMPROVING EFFICIENCY OF HEAT-POWER DECOUPLING SYSTEM” filed on Jan. 7, 2025, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.

[0002] The present disclosure belongs to the field of thermal energy storage for peak shaving in power generation, and in particular to a heat-power decoupling system coupled with molten salt energy storage and a method for improving efficiency of the heat-power decoupling system.

[0003] At the present stage, implementing the clean replacement of renewable energy has become a primary pathway for the green and low-carbon transition in the energy sector. However, due to the significant influence of natural environmental factors on renewable sources such as wind and solar energy, and the natural properties of renewable energy, such as obvious fluctuation and intermittence, create inherent power generation properties of poor output stability and regulation. In addition, spatiotemporal mismatch between “source and load” leads to widespread phenomena of “wind curtailment” and “solar curtailment”, causing substantial waste of resources. Therefore, in order to improve the absorptive capacity of a new energy power generation system and stabilize the fluctuation of a power grid, it is necessary to enhance the flexible operational capabilities of coal-fired power units, including a load response rate and a peak-shaving depth, while also addressing issues such as increased coal consumption and equipment wear caused by frequent peak-shaving operations.

[0004] The coupling of an energy storage system with the coal-fired power unit enables “boiler-turbine decoupling”, which is a critical approach to enhance the flexible operational capabilities of such power generation power units. Molten salt energy storage is an only energy storage mode which is not limited by geographical factors and can achieve long-term, large-scale and low cost. At present, there are two mainstream molten salt energy storage modes adopted in thermal power units: the first is steam extraction for energy storage, which extracts high-temperature steam from the steam turbine system to exchange heat with low-temperature molten salt and transfers heat to high-temperature molten salt; and the second is power-to-heat energy storage, which uses electric energy at a generator outlet, the low-temperature molten salt is heated through an electric heater to convert the electric energy into heat energy to be stored in the high-temperature molten salt. These two energy storage modes both can effectively reduce an output load of the power unit.

[0005] However, most molten salt thermal energy storage systems adopt a mode of extracting a small amount of main steam or a larger amount of reheated steam as a heat source for storage, and cooling and depressurizing the steam after heat exchange into condensate water to return to the steam turbine system. This approach results in significant condensation heat loss when the steam after heat exchange is condensed into water, which leads to the economic decline of the entire system. Additionally, there is a problem of overheating of the reheater tube, leading to the limited the peak-shaving depth.

[0006] In view of the foregoing elements, the present disclosure provides a heat-power decoupling system coupled with molten salt energy storage and a method for improving efficiency of the heat-power decoupling system.

[0007] For the disadvantages in the prior art, the technical problem to be solved by the present disclosure is to provide a heat-power decoupling system coupled with molten salt energy storage and a method for improving efficiency of the heat-power decoupling system.

[0008] The present disclosure employs the following technical solutions to solve the technical problem.

[0009] In a first aspect, the present disclosure provides a heat-power decoupling system coupled with molten salt energy storage, including a steam boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a generator, a condenser, a condensate pump, a low-temperature molten salt tank and a high-temperature molten salt tank. The system further includes a buffer tank, a steam-molten salt heat exchanger, a main steam-molten salt heat exchanger, a reheat steam-molten salt heat exchanger, a steam ejector, a heat exchanger, a steam superheater and a brine dual-media thermal storage tank. A steam outlet of the steam boiler 1 is connected with a steam inlet of the high-pressure cylinder 2 and a steam end inlet of the main steam-molten salt heat exchanger 12. A steam outlet of the high-pressure cylinder 2 is connected with a reheater inlet of the steam boiler 1, and a reheater outlet of the steam boiler 1 is connected with a steam inlet of the medium-pressure cylinder 3, a steam inlet of the brine dual-media thermal storage tank 16 and a steam end inlet of the reheat steam-molten salt heat exchanger 13.

[0010] A steam outlet of the medium-pressure cylinder 3 is connected with a steam inlet of the low-pressure cylinder 4. A steam outlet of the low-pressure cylinder 4 is connected with an inlet of the condenser 6 and the generator 5. An outlet of the condenser 6 is connected with an inlet of the condensate pump 7. An outlet of the condensate pump 7 is connected with a feedwater inlet of the steam boiler 1 and a feedwater end inlet of the heat exchanger 15.

[0011] A steam end outlet of the main steam-molten salt heat exchanger 12 is connected with a steam end inlet of the steam-molten salt heat exchanger 11 and an inlet of the steam ejector 14. A steam end outlet of the steam-molten salt heat exchanger 11 is connected with the feedwater inlet of the steam boiler 1. A steam end outlet of the reheat steam-molten salt heat exchanger 13 is connected with the inlet of the steam ejector 14 and the steam inlet of the low-pressure cylinder 4. An outlet of the steam ejector 14 is connected with the reheater inlet of the steam boiler 1.

[0012] An outlet of the low-temperature molten salt tank 8 is connected with a molten salt end inlet of the steam-molten salt heater exchanger 11. A molten salt end outlet of the steam-molten salt heat exchanger 11 is connected with an inlet of the buffer tank 10. An outlet of the buffer tank 10 is connected with a molten salt inlet of the main steam-molten salt heat exchanger 12 and a molten salt inlet of the reheat steam-molten salt heat exchanger 13.

[0013] A molten salt outlet of the main steam-molten salt heat exchanger 12 is connected with an inlet of the high-temperature molten salt tank 9. A molten salt outlet of the reheat steam-molten salt heat exchanger 13 is connected with the inlet of the high-temperature molten salt tank 9. An outlet of the high-temperature molten salt tank 9 is connected with a molten salt end inlet of the heat exchanger 15. A molten salt end outlet of the heat exchanger 15 is connected with an inlet of the low-temperature molten salt tank 8. A feedwater end outlet of the heat exchanger 15 is connected with the feedwater inlet of the steam boiler.

[0014] A steam outlet of the brine dual-media thermal storage tank 16 is connected with a steam end inlet of the steam superheater 17. A steam end outlet of the steam superheater 17 is connected with the steam inlet of the low-pressure cylinder 4. An outlet of the high-pressure molten salt tank 9 is connected with a molten salt end inlet of the steam superheater 17. A molten salt end outlet of the steam superheater 17 is connected with the inlet of the buffer tank 10.

[0015] Further, the brine dual-media thermal storage tank includes a steam collection pipeline, a surrounding pipeline and serpentine pipeline. The steam collection pipeline is supplied with steam. The surrounding pipeline and the serpentine pipeline are filled with phase-change salt. The thermal storage tank is filled with a water medium which occupies no more than 80% of an inner cavity space.

[0016] Further, the steam collection pipeline includes multiple annular pipelines which are horizontally arranged, horizontal flow-guiding pipelines arranged on a diameter of a corresponding one of the plurality of the annular pipelines and vertical flow-guiding pipelines communicating with the horizontal flow-guiding pipelines and an inlet of the thermal storage tank. The surrounding pipe is uniformly wrapped around the steam collection pipeline. The serpentine pipeline is disposed on a central axis plane of the thermal storage tank. The steam collection pipeline, the surrounding pipeline and the serpentine pipeline do not interfere with each other. The steam collection pipeline is uniformly provided with nozzles, and the nozzles and the surrounding pipelines do not interfere with each other.

[0017] Further, the molten salt may employ ternary molten salt widely used in a thermal power station as an energy storage medium, which has the advantages of wide temperature range, high thermal stability and low price, and preferably, the ternary molten salt is KNO₃—NaNO₂—NaNO₃ (53%-40%-7%). The ternary molten salt is decomposed slightly above 427° C., and additionally, excessively low temperature presents a risk of molten salt solidification, potentially causing blockage in the flow channel. Therefore, an operating temperature of the high-temperature molten salt tank is designed to be 425° C. and an operating temperature of the low-temperature molten salt tank is designed to be 190° C. During energy storage, due to inconsistent heat in the two-stage heat exchange process, a demand for molten salt in a low-temperature heat exchange zone is slightly higher than that in a high-temperature zone. A buffer tank is disposed to store excess medium-temperature molten salt, with an operating temperature of 305° C.

[0018] Further, an operating temperature of the high-temperature molten salt tank is not higher than a decomposition temperature of the ternary molten salt, an operating temperature of the low-temperature molten salt tank is 185° C.-200° C., and a temperature of middle-medium molten salt in the buffer tank is 300° C.-320° C.

[0019] In a second aspect, the present disclosure provides a method for improving efficiency of a heat-power decoupling system coupled with molten salt energy storage, including: arranging a buffer tank between a molten salt tank and a high-temperature molten salt tank and a low-temperature molten salt tank, arranging a steam-molten heat exchanger between the buffer tank and the low-temperature molten salttank, arranging a reheat steam-molten salt heat exchanger between the buffer tank and the high-temperature molten salt tank, and arranging a main steam-molten salt heat exchanger between the buffer tank and a steam boiler; wherein both steam after heat exchange in the reheat steam-molten salt heat exchanger and main steam after heat exchange in the main steam-molten salt heat exchanger are subjected to pressurization and flow rate increase by a steam ejector and then enter a pipeline of a reheater of the steam boiler;

• • [0020] arranging a temperature detection point on the pipeline of the reheater, wherein parameters, comprising pressure, temperature and flow rate, of steam output from the steam ejector match required steam parameters in the pipeline of the reheater, thereby preventing the pipeline of the reheater from overheating during an energy storage condition;
  • [0021] preferably supplying reheated steam output from a reheater to medium-pressure cylinder steam according to a load, and then enabling the steam to enter the reheat steam-molten salt heat exchanger 13 to provide for molten salt heat exchange, and then storing the steam in the reheat steam-molten salt heat exchanger 13; and
  • [0022] arranging a heat exchanger 15 between a low-pressure cylinder and the steam boiler, connecting a steam superheater to a steam outlet of a brine dual-media thermal storage tank to exchange heat with high-temperature molten salt.

[0023] In a heat release condition: under a stable load condition of the steam boiler, high-pressure feedwater is extracted from a feedwater portion of the steam boiler 1 to enter a heat exchanger, and high-temperature molten salt in the high-temperature molten salt tank 9 and the buffer tank 10 is used as a heat source to heat the high-pressure feedwater to a high temperature, then the high-pressure feedwater is sent into the steam boiler, steam expansion work efficiency decreases progressively in each stage within the high-pressure, medium-pressure, and low-pressure cylinders, making the work efficiency of the high-pressure cylinder and the medium-pressure cylinder higher than that of the low-pressure cylinder, the heat carried by medium-temperature molten salt and high-temperature molten salt is configured to heat the high-pressure feedwater to 275° C.-285° C., thereby increasing thermal efficiency obtained from the increased steam flow rate through the high-pressure cylinder and the medium-pressure cylinder, and ultimately improving efficiency of power generation by a generator 5 of a steam turbine system.

[0024] A high-temperature and high-pressure water medium in a brine dual-media thermal storage tank 16 is subjected to flash evaporation through a steam outlet in the brine dual-media thermal storage tank 16 and is regulated to medium-temperature steam with appropriate parameters through a pressure regulating valve. The high-temperature molten salt makes steam passing through the steam superheater 17 become superheated steam with appropriate superheat, and then the superheated steam enters the low-pressure cylinder 4 to do work, thereby ensuring operation safety of the steam turbine. The high-temperature molten salt after heat exchange is returned to the buffer tank 10, in heat release engineering of the brine dual-media thermal storage tank 16, the water medium continuously cools down, and the high-temperature molten salt in a surrounding pipeline 1602 and a serpentine pipeline 1603 continuously transfers heat to the water medium through the heat exchange across a pipe wall, thereby reducing a cooling speed of the water medium and timely regulating fluctuation of a load and electricity.

[0025] In an energy storage condition: under a stable combustion load condition of the steam boiler 1, main steam generated by the steam boiler 1 exchanges heat with the molten salt from the buffer tank 10 through the main steam-molten salt heat exchanger 12, such that the medium-temperature molten salt in the buffer tank 10 is heated to a temperature of the high-temperature molten salt and is stored in the high-temperature molten salt tank 9. A portion of the main steam cooled after heat exchange exchanges heat with low-temperature molten salt from the low-temperature molten salt tank 8 through a steam-molten salt heat exchanger 11. The low-temperature molten salt from the low-temperature molten salt tank 8 is stored in the buffer tank 10 after being heated through heat exchange, and steam after heat exchange becomes high-pressure condensate water and enters a feedwater portion of the steam boiler 1.

[0026] Exhaust steam generated by a high-pressure cylinder 2 enters the reheater of the steam boiler 1 and is reheated, and a portion of the reheated steam exchanges heat with the molten salt from the buffer tank 10 through the reheat steam-molten salt heat exchanger 13, such that the medium-temperature molten salt in the buffer tank 10 is heated to the temperature of the high-temperature molten salt and then enters the high-temperature molten salt tank 9 for storage again. Another portion of the main steam after heat exchange by the main steam-molten salt heat exchanger 12 and the reheated steam after heat exchange by the reheat steam-molten salt heat exchanger 13 are ejected by the steam ejector 14 to obtain mixed steam with a steam pressure of 1.6 MPa-1.7 MPa and a temperature of 300° C.-310° C. The mixed steam matches parameters including temperature and pressure required by the reheater, upon entering the reheater of the steam boiler 1. A steam flow rate of the reheater is compensated to ensure that the pipeline of the reheater is prevented from overheating under the energy storage condition, and a portion of the reheated steam enters the brine dual-media thermal storage tank 16 for energy storage.

[0027] Compared with the prior art, the embodiment have beneficial effects as follows.

[0028] A power unit extracts a portion of main steam and reheated steam to store energy in the form of heat-heat conversion under a stable combustion load condition of a boiler to ensure low-load safe and stable operation of the boiler and a generation load of the power unit. In a heat release condition, the boiler operates at a stable load to release heat energy from the high-temperature molten salt and the dual-media thermal storage tank to heat boiler feedwater, thereby increasing steam inlet flow rate of the steam turbine, improving the work capacity of the power unit, and acquiring extra output power. The heat-power decoupling system according to the embodiments utilizes high-temperature molten salt, medium-temperature molten salt and low-temperature molten salt, along with the brine dual-media thermal storage tank, for peak shaving through thermal energy storage. The system can effectively achieve “boiler-turbine decoupling” in a thermal power unit, which means that the boiler and the generating power unit can operate independently. The energy storage system is configured to provide steam for the generating power unit for power generation, such that the flexible operation capacity can be improved without depending on the boiler. In addition, the range of upward and downward peak shaving of the power unit is broadened, thereby providing a broader space for consuming new energy power. In the system according to the embodiments, high-pressure main steam after heat storage and heat exchange is adopted to eject reheated steam after heat exchange to obtain new steam with consistent parameters to compensate the steam flow rate at an inlet of a reheater, and the compensated flow can keep a temperature of the reheater in an interval, thereby solving the problem of overheating of the pipeline of the reheater caused by extracting large amounts of main steam for thermal storage during low-load operation of the power unit. In addition, substantial condensation heat loss caused by returning the water condensed from the steam after heat exchange in a cooling and depressurizing mode to the steam turbine system is avoided, and the condensation heat loss appeared in steam extraction thermal storage in a deep peak shaving condition is effectively reduced. The steam extraction energy storage mode in the embodiments is higher than an electric heating energy storage mode under the same conditions in terms of energy storage capacity, the whole heat storage-release process, thermal efficiency and the like. In the heat release process of molten salt systems, the steam flow rate required by the steam turbine system (including medium-pressure, high-pressure and low-pressure cylinders and generators) can be directly increased, or regenerative extraction steam can be reduced to indirectly increase the steam flow rate within a turbine cylinder. From the energy point of view, the exergy of the high-pressure and medium-pressure cylinders is higher than that of the low-pressure cylinder, and the exergy of steam expansion in each stage in the cylinder decreases in turn. When boiler feedwater is directly heated, the heat carried by the molten salt increases the thermal efficiency obtained by steam flow rate of the high-pressure cylinder and the medium-pressure cylinder, which is significantly better than that obtained by increasing steam flow rate of the low-pressure cylinder. In the embodiments, heat-power decoupling coupled with ternary molten salt is adopted, the ternary molten salt is decomposed slightly above 427° C., and additionally, excessively low temperature presents a risk of molten salt solidification, potentially causing blockage in the flow channel. Therefore, an operating temperature of the high-temperature molten salt tank is designed to be 425° C., and an operating temperature of the low-temperature molten salt tank is 190° C. During energy storage, due to inconsistent heat in the two-stage heat exchange process, a demand for molten salt in a low-temperature heat exchange zone is slightly higher than that in a high-temperature zone. A buffer tank is disposed to store excess medium-temperature molten salt, with an operating temperature of 305° C.

• • [0031] 1 steam boiler; 2 high-pressure cylinder; 3 medium-pressure cylinder; 4 low-pressure cylinder; 5 generator; 6 condenser; 7 condensate pump; 8 low-temperature molten salt tank; 9 high-temperature molten salt tank; 10 buffer tank; 11 steam-molten salt heat exchanger; 12 main steam-molten salt heat exchanger; 13 reheat steam-molten salt heat exchanger; 14 steam ejector; 15 heat exchanger; 16 brine dual-media thermal storage tank; 1601 steam collection pipeline; 1602 surrounding pipeline; 1603 serpentine pipeline; and 17 steam superheater.

[0032] Specific embodiments are provided below in conjunction with embodiments and accompanying drawings. The specific embodiments are only used to describe the technical solution of the present disclosure in detail, without limiting the scope of protection of the present disclosure.

[0033] With reference to FIG. 1, the present disclosure provides a heat-power decoupling system coupled with molten salt energy storage, including a steam boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-temperature molten salt tank 8, a high-temperature molten salt tank 9, a buffer tank 10, a steam-molten salt heat exchanger 11, a main steam-molten salt heat exchanger 12, a reheat steam-molten salt heat exchanger 13, a steam ejector 14, a heat exchanger 15, a brine dual-media thermal storage tank 16 and a steam superheater 17.

[0034] A steam outlet of the medium-pressure cylinder 3 is connected with a steam inlet of the low-pressure cylinder 4, a steam outlet of the low-pressure cylinder 4 is connected with an inlet of the condenser 6 and the generator 5, an outlet of the condenser 6 is connected with an inlet of the condensate pump 7, and an outlet of the condensate pump 7 is connected with a feedwater inlet of the steam boiler 1 and a feedwater end inlet of the heat exchanger 15.

[0035] A steam end outlet of the main steam-molten salt heat exchanger 12 is connected with a steam end inlet of the steam-molten salt heat exchanger 11 and an inlet of the steam ejector 14, a steam end outlet of the steam-molten salt heat exchanger 11 is connected with the feedwater inlet of the steam boiler 1, a steam end outlet of the reheat steam-molten salt heat exchanger 13 is connected with the inlet of the steam ejector 14 and the steam inlet of the low-pressure cylinder 4, and an outlet of the steam ejector 14 is connected with the inlet of the reheater of the steam boiler 1.

[0036] An outlet of the low-temperature molten salt tank 8 is connected with a molten salt end inlet of the steam-molten salt heater exchanger 11, a molten salt end outlet of the steam-molten salt heat exchanger 11 is connected with an inlet of the buffer tank 10, and an outlet of the buffer tank 10 is connected with a molten salt inlet of the main steam-molten salt heat exchanger 12 and a molten salt inlet of the reheat steam-molten salt heat exchanger 13.

[0037] A molten salt outlet of the main steam-molten salt heat exchanger 12 is connected with an inlet of the high-temperature molten salt tank 9, a molten salt outlet of the reheat steam-molten salt heat exchanger 13 is connected with the inlet of the high-temperature molten salt tank 9, an outlet of the high-temperature molten salt tank 9 is connected with a molten salt end inlet of the heat exchanger 15, a molten salt end outlet of the heat exchanger 15 is connected with an inlet of the low-temperature molten salt tank 8, and a feedwater end outlet of the heat exchanger 15 is connected with the feedwater inlet of the steam boiler.

[0038] A steam outlet of the brine dual-media thermal storage tank 16 is connected with a steam end inlet of the steam superheater 17, a steam end outlet of the steam superheater 17 is connected with the steam inlet of the low-pressure cylinder 4, an outlet of the high-pressure molten salt tank 9 is connected with a molten salt end inlet of the steam superheater 17, and a molten salt end outlet of the steam superheater 17 is connected with the inlet of the buffer tank 10.

[0039] Further, the brine dual-media thermal storage tank 16 includes a steam collection pipeline 1601, a surrounding pipeline 1602 and a serpentine pipeline 1603. The steam collection pipeline 1601 includes multiple layers of horizontally arranged annular pipelines, a horizontal flow-guiding pipelines arranged on diameters of the annular pipelines, and vertical flow-guiding pipelines communicating with the horizontal flow-guiding pipelines and an inlet of the brine dual-media thermal storage tank 16. The surrounding pipeline 1602 is uniformly wrapped around the steam collection pipeline 1601, the serpentine pipeline 1603 is disposed on a central axis plane of the brine dual-media thermal storage tank 16, and the steam collection pipeline 1601, the surrounding pipeline 1602 and the serpentine pipeline 1603 do not interfere with each other.

[0040] Further, the steam collection pipeline 1601 is supplied with steam, the surrounding pipeline 1602 and the serpentine pipeline 1603 are filled with phase-change salt, the steam collection pipeline 1601 is uniformly provided with nozzles, and the nozzles and the surrounding pipeline 1602 do not interfere with each other. The brine dual-medial thermal storage tank 16 is filled with a water medium, accounting for no more than 80% of an inner cavity space.

[0041] Further, the molten salt may employ ternary molten salt widely utilized in a thermal power station as an energy storage medium, which has the advantages of wide temperature range, high thermal stability and low price. The ternary molten salt used in this embodiment is KNO₃—NaNO₂—NaNO₃ (53%-40%-7%), which can be decomposed slightly above 427° C., and additionally, excessively low temperature presents a risk of molten salt solidification, potentially causing blockage in the flow channel. Therefore, an operating temperature of the high-temperature molten salt tank 9 is set to be 425° C. (slight lower than a decomposition temperature of the ternary molten salt), and an operating temperature of the low-temperature molten salt tank 8 is set to be 190° C. During energy storage, due to inconsistent heat in the two-stage heat exchange process, a demand for molten salt in a low-temperature heat exchange zone is slightly higher than that in a high-temperature zone. A buffer tank 10 is disposed to store excess medium-temperature molten salt, with an operating temperature of 305° C. Specific attribute parameters of the ternary molten salt are as follows:

Item	Numerical value
Composition	KNO3—NaNO2—NaNO3(53%-40%-7%)
Melting point, boiling	142.2, 680.0
point/° C.
Operating temperature/° C.	180-430
Isobaric specific heat	1.507-0.1T(T is operating temperature)
capacity /(J*(kg*K)−1)
Heat conductivity	0.5
coefficient /(W*(m2*K)−1)
Density/(kg*m−3)	1938(150° C.), 1650(600° C.), linear
	decline within a temperature interval

[0042] The operating principle and flow of this embodiment are as follows.

[0043] In an energy storage condition: under a stable combustion load condition of the steam boiler 1, main steam (10 MPa, 560° C.) generated by the steam boiler 1 exchanges heat with the molten salt from the buffer tank 10 through the main steam-molten salt heat exchanger 12, the molten salt at 305° C. in the buffer tank 10 is heated to high-temperature molten salt at 425° C., and then enters the high-temperature molten salt tank 9 for storage, a portion of the main steam (10 MPa, 315° C.) cooled after heat exchange exchanges heat with low-temperature molten salt from the low-temperature molten salt tank 8 through a steam-molten salt heat exchanger 11, and the low-temperature molten salt at 190° C. from the low-temperature molten salt tank 8 is heated and then is stored in the buffer tank 10, and the steam after heat exchange becomes high-pressure condensate water and enters a feedwater portion of the steam boiler 1.

[0044] Exhaust steam generated by a high-pressure cylinder 2 enters the reheater of the steam boiler 1 and is reheated (the reheated steam has a pressure of 1.7 MPa and a temperature of 560° C.), and a portion of the reheated steam exchanges heat with the molten salt from the buffer tank 10 through the reheat steam-molten salt heat exchanger 13 (the steam after heat exchange has a pressure of 1.55 MPa and a temperature of 315° C.), such that the medium-temperature molten salt at 305° C. in the buffer tank 10 is heated to a temperature (425° C.) of the high-temperature molten salt and then enters the high-temperature molten salt tank 9 for storage again. Afterwards, another portion of the main steam (10 MPa and 315° C.) after heat exchange by the main steam-molten salt heat exchanger 12 and the reheated steam (1.55 MPa and 315° C.) after heat exchange by the reheat steam-molten salt heat exchanger 13 are ejected by the steam ejector 14 to obtain mixed steam with a steam pressure of 1.6 MPa and a temperature of 301° C. The mixed steam matches parameters including steam temperature and pressure required by a reheater, upon entering the reheater of the steam boiler 1, the steam flow rate of the reheater is compensated to ensure that the pipeline of the reheater is prevented from overheating under the energy storage condition, and a portion of the reheated steam enters the brine dual-media thermal storage tank 16 for energy storage. Finally, the heat-exchanged reheated steam that bypasses the steam ejector 14 is depressurized and is returned to the low-pressure cylinder 4 to do work.

[0045] The steam ejector operates on the principle of utilizing high-pressure steam for high-velocity jetting to pressurize low-pressure steam, thereby forming medium-pressure steam that meets the required parameters after energy exchange. Operating medium high-pressure steam may also be called operating steam, the ejected low-pressure steam may also be called ejected steam, and the mixed medium-pressure steam may also be called mixed steam.

[0046] The reheated steam enters the steam collection pipeline 1601 of the brine dual-media thermal storage tank 16, and the reheated steam in the steam collection pipeline 1601 exchanges heat with the molten salt in the surrounding pipe 1602 wrapped around the steam collection pipeline 1601 through a pipe wall to improve a temperature of the molten salt in the surrounding pipe 1602, and the reheated steam in the steam collection pipeline 1601 enters the brine dual-media thermal storage tank 16 through the nozzles on the steam collection pipeline 1601 to heat the water medium in the brine dual-media thermal storage tank 16. The heated water medium exchanges heat with the molten salt in the serpentine pipeline 1603 to improve the temperature of the molten salt in the serpentine pipeline 1603.

[0047] In a heat release condition: under a stable load condition of the steam boiler 1, high-pressure feedwater is extracted from a feedwater portion of the steam boiler 1 to enter the heat exchanger 15, where a temperature of the high-pressure feedwater is about 190° C. High-temperature molten salt in the high-temperature molten salt tank 9 and the buffer tank 10 is served as a heat source to heat the high-pressure feedwater to a high temperature of about 280° C., then the high-pressure feedwater is sent into the steam boiler. Then, cooled low-temperature molten salt is returned to the low-temperature molten salt tank 8 for storage.

[0048] A high-temperature and high-pressure water medium in a brine dual-media thermal storage tank 16 is subjected to flash evaporation through a steam outlet in the brine dual-media thermal storage tank, the steam is regulated to medium-temperature steam with appropriate parameters through a pressure regulating valve (not shown in the figure), the high-temperature molten salt makes the steam passing through the steam superheater 17 become superheated steam with appropriate superheat, and then the superheated steam enters the low-pressure cylinder 4 to do work, thereby ensuring operation safety of the steam turbine. The high-temperature molten salt after heat exchange is returned to the buffer tank 10. In the heat release engineering of the brine dual-media thermal storage tank, the water medium continuously cools down, and the high-temperature molten salt in the surrounding pipeline 1602 and the serpentine pipeline 1603 continuously transfers heat to the water medium through the heat exchange across a pipe wall, such that a cooling speed of the water medium is reduced, the stored thermal energy can be further utilized, and the energy utilization is improved.

[0049] The points not mentioned in the present disclosure are applicable to the prior art.