Heat pump coupling fused salt energy storage system and method suitable for peak regulation of thermal power generating unit

Abstract

The invention provides a heat pump coupling fused salt energy storage system and method suitable for peak regulation of a thermal power generating unit, a thermal power generating unit comprises a boiler and a multi-stage steam turbine assembly, the output end of the boiler is communicated with the multi-stage steam turbine assembly, and a heat storage subsystem comprises a high / low-temperature fused salt storage tank and a first / second heat exchanger assembly. The output end of the boiler further communicates with a steam-water channel inlet of the second heat exchanger assembly, an outlet of the multi-stage steam turbine assembly communicates with a water supply pipeline, and the water supply pipeline communicates with the input end of the boiler and a steam-water channel inlet of the first heat exchanger assembly. In the heat storage period, part of high-temperature steam output by the boiler is conveyed to the multi-stage steam turbine assembly, and the remaining high-temperature steam is distributed to the second heat exchanger assembly to be used for heating the low-temperature fused salt. In the heat release period, steam output by the multi-stage steam turbine assembly is condensed to form feed water, the feed water is transmitted to the first heat exchanger assembly, high-temperature steam is formed and flows back to the multi-stage steam turbine assembly, and the multi-stage steam turbine assembly is driven to do work to generate power.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal energy storage peak shaving for thermal power generating units, and particularly relates to a heat pump coupled molten salt energy storage system and method suitable for peak shaving of thermal power units. Background Art

[0002] The technology of deep peak shaving transformation of the main equipment of coal-fired power plants refers to a series of technical transformations carried out on traditional coal-fired generating units in order to meet the changing demand of the power grid load, especially to increase the power grid's ability to absorb renewable energy (such as wind energy and solar energy). This transformation aims to enable coal-fired power plants to adjust their output power more flexibly and achieve deep peak shaving operation while maintaining stability and safety.

[0003] However, under the existing technology, due to the differences in the peak shaving capacity limits of main equipment such as boilers and steam turbines, the actual peak shaving capacity of coal-fired power plants has not been fully released, resulting in technical problems such as low electro-electric conversion efficiency in the existing electric heating molten salt technology, and only the sensible heat part of steam can be utilized for steam heating molten salt, with low heat utilization rate, leading to excessive exergy loss in the system. Summary of the Invention

[0004] The present invention provides a heat pump coupled molten salt energy storage system and method suitable for peak shaving of thermal power units to solve the technical problems of insufficient peak shaving depth and low peak shaving thermal energy utilization rate in conventional thermal power generating units under the existing technology.

[0005] To solve the above problems, the technical solution of the present invention is: A heat pump coupled molten salt energy storage system suitable for peak shaving of thermal power units, comprising: A thermal power generating unit, the thermal power generating unit includes a boiler and a multi-stage steam turbine assembly, and a first branch at the output end of the boiler is communicated with the inlet of the multi-stage steam turbine assembly; A heat storage subsystem, the heat storage subsystem includes a high-temperature molten salt storage tank and a low-temperature molten salt storage tank. A first heat exchanger assembly is provided on the molten salt pipeline from the high-temperature molten salt storage tank to the low-temperature molten salt storage tank side, and a second heat exchanger assembly is provided on the molten salt pipeline from the low-temperature molten salt storage tank to the high-temperature molten salt storage tank side. A second branch at the output end of the boiler is communicated with the steam-water channel inlet of the second heat exchanger assembly through a steam heating flow regulating valve; The outlet of the multi-stage steam turbine assembly is communicated with the feed water pipeline of the thermal power generating unit, and the feed water pipeline includes a connection to the input end of the boiler and the steam-water channel inlet of the first heat exchanger assembly; During the heat storage period, a part of the high-temperature steam output by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to perform work and generate electricity. Moreover, a part of the high-temperature steam output by the boiler is diverted to the second heat exchanger assembly to heat the low-temperature molten salt. During the heat release period, the steam output by the multi-stage steam turbine assembly is condensed to form feed water and transmitted to the first heat exchanger assembly. The feed water is reheated by the high-temperature molten salt to form high-temperature steam again, and the high-temperature steam is enabled to flow back to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to perform work and generate electricity.

[0006] Preferably, it further includes a high-temperature heat pump subsystem. The high-temperature heat pump subsystem is provided with a heat pump steam condenser and a compression assembly. The steam-water channel inlet of the heat pump steam condenser is communicated with the steam-water channel outlet of the second heat exchanger assembly. The steam-water channel outlet of the heat pump steam condenser is communicated with the water supply pipeline. The heat pump medium channel of the heat pump steam condenser is communicated with the heat pump medium pipeline of the compression assembly. The high-temperature heat pump subsystem is configured such that during the heat storage period, after the sensible heat of the high-temperature steam is exchanged with the low-temperature molten salt in the second heat exchanger assembly, the steam flows through the heat pump steam condenser, condenses and flows back into the water supply pipeline. Moreover, the heat pump medium in the heat pump medium pipeline absorbs the latent heat of the steam in the heat pump steam condenser and is heated under the compression of the compression assembly.

[0007] Preferably, the second heat exchanger assembly includes a steam-salt high-temperature heater, a heat pump salt heater, and a steam-salt low-temperature heater. The steam-water channel inlet of the steam-salt high-temperature heater is communicated with the second branch of the output end of the boiler. The steam-water channel outlet of the steam-salt high-temperature heater is communicated with the steam-water channel inlet of the steam-salt low-temperature heater. The steam-water channel outlet of the steam-salt low-temperature heater is communicated with the steam-water channel inlet of the heat pump steam condenser. The heat pump medium channel of the heat pump salt heater is communicated with the heat pump medium pipeline of the compression assembly. The molten salt pipeline from the low-temperature molten salt storage tank to the high-temperature molten salt storage tank sequentially passes through the molten salt channels of the steam-salt low-temperature heater, the heat pump salt heater, and the steam-salt high-temperature heater. The second heat exchanger assembly is configured such that during the heat storage period, the high-temperature steam and the low-temperature molten salt flow through the steam-salt high-temperature heater and the steam-salt low-temperature heater, enabling the heat of the steam to be transferred to the molten salt in a stepped manner. Moreover, the high-temperature heat pump medium and the low-temperature molten salt flow through the heat pump salt heater, enabling the heat of the heat pump medium to be transferred to the molten salt.

[0008] Preferably, the water supply pipeline extends with a third branch and a fourth branch. The third branch of the water supply pipeline is connected to the input end of the boiler through a boiler feed water flow regulating valve, and the fourth branch of the water supply pipeline is connected to the steam-water channel inlet of the first heat exchanger assembly through a molten salt feed water flow regulating valve.

[0009] Preferably, the first heat exchanger assembly is provided with a molten salt feed water heater; The steam-water channel inlet of the molten salt feed water heater is connected to the fourth branch of the water supply pipeline, and the steam-water channel outlet of the molten salt feed water heater is connected to the inlet of the boiler; The molten salt channel inlet of the molten salt feed water heater is connected to the output end of the high-temperature molten salt storage tank, and the molten salt channel outlet of the molten salt feed water heater is connected to the input end of the low-temperature molten salt storage tank.

[0010] Preferably, the first heat exchanger assembly is further provided with an evaporator and a superheater; A fifth branch is also divergently provided in the steam-water pipeline on one side of the steam-water channel outlet of the molten salt feed water heater. A steam generator inlet regulating valve is provided in the fifth branch. The steam-water channel outlet of the molten salt feed water heater is connected to the steam-water channel inlet of the evaporator through the steam generator inlet regulating valve. The steam-water channel outlet of the evaporator is connected to the steam-water channel inlet of the superheater, and the steam-water channel outlet of the superheater is connected to the inlet of the multi-stage steam turbine assembly; The first heat exchanger assembly is configured that during the heat release period, when the steam generator inlet regulating valve is closed, high-temperature molten salt and low-temperature feed water flow through the molten salt feed water heater, so that the heat of the molten salt is transferred to the feed water, and then the high-temperature feed water is transmitted to the boiler; when the steam generator inlet regulating valve is opened, high-temperature molten salt and part of the feed water flow through the molten salt feed water heater, the evaporator and the superheater, so that the heat of the molten salt is transferred to part of the steam in a stepped manner to generate high-temperature steam, and then the high-temperature steam is transmitted to the multi-stage steam turbine assembly.

[0011] Preferably, the first heat exchanger assembly is further provided with a reheater; A sixth branch is also divergently provided in the molten salt pipeline on one side of the output end of the high-temperature molten salt storage tank. The molten salt channel inlet of the reheater is connected to the sixth branch of the output end of the high-temperature molten salt storage tank, and the molten salt channel outlet of the reheater is connected to the molten salt channel inlet of the evaporator; The multi-stage steam turbine assembly includes at least a high-pressure cylinder and an intermediate-pressure cylinder; The steam-water channel inlet of the reheater is connected to the outlet of the high-pressure cylinder, and the steam-water channel outlet of the reheater is connected to the high-pressure heater extraction steam channel of the intermediate-pressure cylinder; The first heat exchanger assembly is further configured such that, during the heat release period, the low-temperature steam output by the high-pressure cylinder and the high-temperature molten salt flow through the reheater, enabling the heat of the molten salt to be transferred to the steam, and then the high-temperature steam is transmitted to the intermediate-pressure cylinder.

[0012] Preferably, the steam-water passage outlet of the superheater is communicated with the extraction steam passage of the high-pressure cylinder. In the steam-water pipeline between the steam-water passage outlet of the superheater and the extraction steam passage of the high-pressure cylinder, a superheater outlet stop valve, a superheater outlet check valve, and a superheater outlet regulating valve are sequentially provided; In the steam-water pipeline between the outlet of the high-pressure cylinder and the steam-water passage inlet of the reheater, a reheater inlet regulating valve is provided; In the steam-water pipeline between the steam-water passage outlet of the reheater and the extraction steam passage of the intermediate-pressure cylinder, a reheater outlet stop valve, a reheater outlet check valve, and a reheater outlet regulating valve are sequentially provided.

[0013] Preferably, the extraction steam passage of the high-pressure cylinder is also shunted with a seventh branch, which is communicated with the first high-pressure heat exchanger assembly. A first extraction steam stop valve and a first extraction steam check valve are provided in the seventh branch; The extraction steam passage of the intermediate-pressure cylinder is also shunted with an eighth branch, which is communicated with the second high-pressure heat exchanger assembly. A second extraction steam stop valve and a second extraction steam check valve are provided in the eighth branch; The high-pressure cylinder and the intermediate-pressure cylinder are configured such that, during the heat storage period, the first extraction steam stop valve and the second extraction steam stop valve are opened, steam is extracted from the high-pressure cylinder and the intermediate-pressure cylinder, and the high-temperature steam flows through the first high-pressure heat exchanger assembly and the second high-pressure heat exchanger assembly respectively for heating feed water.

[0014] Based on the same concept, the present invention further provides a heat pump-coupled molten salt energy storage method applicable to peak shaving of thermal power units, which is applied to the heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units as described in any one of the above, and includes the following steps: S11: During the heat storage period, the power grid outputs a peak shaving and load reduction instruction, the steam heating flow regulating valve is opened, a part of the high-temperature steam generated by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to maintain low-load power generation, and a part of the high-temperature steam generated by the boiler is transmitted to the second heat exchanger assembly; S12: The cold molten salt pump is started, enabling the molten salt to be transmitted from the low-temperature molten salt storage tank to the high-temperature molten salt storage tank through the steam-molten salt low-temperature heater, the heat pump molten salt heater, and the steam-molten salt high-temperature heater. The high-temperature steam flows through the steam-molten salt high-temperature heater to achieve primary heating of the molten salt, and then the high-temperature steam flows through the steam-molten salt low-temperature heater to achieve secondary heating of the molten salt; S13: The steam flows through the heat pump steam condenser, condenses and then returns to the water supply pipeline. The heat pump medium in the heat pump medium pipeline absorbs the remaining heat of the steam in the heat pump steam condenser and is heated under the compression of the compression assembly. The high-temperature heat pump medium flows through the heat pump molten salt heater to heat the molten salt three times; S14: The high-temperature molten salt is stored in the high-temperature molten salt storage tank; S21: During the heat release period, the power grid outputs a peak shaving and load increasing instruction, and the steam heating flow regulating valve is closed. All the high-temperature steam generated by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to do work and generate electricity; S22: Start the hot molten salt pump to enable the molten salt to be transmitted from the high-temperature molten salt storage tank to the low-temperature molten salt storage tank through the reheater, superheater, evaporator and molten salt feed water heater; Open the molten salt feed water flow regulating valve, steam generator inlet regulating valve, reheater inlet regulating valve, reheater outlet regulating valve and superheater outlet regulating valve to enable part of the exhaust steam output from the high-pressure cylinder to be transmitted to the reheater. The high-temperature molten salt flows through the reheater to heat the exhaust steam, and then enable the reheated exhaust steam to be transmitted to the intermediate-pressure cylinder to drive the intermediate-pressure cylinder to do work and generate electricity; The high-temperature molten salt flows through the molten salt feed water heater to heat the feed water once. Part of the high-temperature feed water is transmitted to the boiler. The high-temperature molten salt flows through the evaporator to heat the feed water twice to generate steam. Subsequently, the high-temperature molten salt flows through the superheater to heat the steam three times, and then enable the high-temperature steam to be transmitted to the high-pressure cylinder to drive the high-pressure cylinder to do work and generate electricity; S23: The low-temperature molten salt is stored in the low-temperature molten salt storage tank.

[0015] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art: The present invention provides a heat pump coupled molten salt energy storage system and method suitable for peak shaving of thermal power units, which are provided with a thermal power generating unit, a heat storage subsystem and a high-temperature heat pump subsystem. During the heat storage period, the power grid outputs a peak shaving and load reduction instruction. The high-temperature steam generated by the boiler will be shunted and transmitted to the multi-stage steam turbine assembly and the heat storage subsystem respectively, reducing the real-time power generation and storing part of the heat energy. Among them, the high-temperature steam flows through the steam-molten salt high-temperature heater and the steam-molten salt low-temperature heater, which can realize the efficient absorption of the sensible heat of the high-temperature steam by the molten salt. The heat pump molten salt heater cooperates with the high-temperature heat pump subsystem to realize the deep absorption of the latent heat of the high-temperature steam by the molten salt, thereby realizing the full and effective recovery of heat. During the heat release period, the power grid outputs a peak shaving and load increase instruction. The high-temperature steam generated by the boiler is all used to drive the multi-stage steam turbine assembly to do work. The exhaust steam and condensate water output or formed after the multi-stage steam turbine assembly does work flow through the reheater, molten salt feed water heater, evaporator and superheater, which can realize the full absorption of the heat of the high-temperature molten salt by the low-temperature steam-water, and regenerate it into high-temperature steam and flow back to the boiler and the multi-stage steam turbine assembly, enabling the multi-stage steam turbine assembly to generate electricity by doing work. Through the efficient utilization of heat during the heat storage period and the heat release period, the purpose of the peak shaving depth of the thermal power generating unit is achieved, effectively increasing the power generation flexibility of the thermal power generating unit and reducing the fuel consumption required during boiler operation. Description of the Drawings

[0016] Figure 1 Schematic structural diagram of a heat pump coupled molten salt energy storage system suitable for peak shaving of thermal power units provided by the present invention.

[0017] Description of the reference numerals: 1: Thermal power generating unit; 1.1: Boiler; 1.2: High-pressure cylinder; 1.3: Intermediate-pressure cylinder; 1.4: Boiler feed water flow regulating valve; 1.5: Molten salt feed water flow regulating valve; 1.6: Steam heating flow regulating valve; 1.7: First high-pressure heater extraction steam stop valve; 1.8: First high-pressure heater extraction steam check valve; 1.9: Second high-pressure heater extraction steam stop valve; 1.10: Second high-pressure heater extraction steam check valve; 2: Heat storage subsystem; 2.1: High-temperature molten salt storage tank; 2.2: Low-temperature molten salt storage tank; 2.3: Steam-molten salt high-temperature heater; 2.4: Steam-molten salt low-temperature heater; 2.5: Steam generator inlet regulating valve; 2.6: Molten salt feed water heater; 2.7: Evaporator; 2.8: Superheater; 2.9: Reheater; 2.10: Reheater inlet regulating valve; 2.11: Reheater outlet regulating valve; 2.12: Reheater outlet check valve; 2.13: Reheater outlet stop valve; 2.14: Superheater outlet regulating valve; 2.15: Superheater outlet check valve; 2.16: Superheater outlet stop valve; 2.17: Cold molten salt pump; 2.18: Hot molten salt pump; 3: High-temperature heat pump subsystem; 3.1: Heat pump steam condenser; 3.2: Heat pump molten salt heater. Detailed Embodiments

[0018] The following further describes in detail a heat pump coupled molten salt energy storage system and method applicable to peak shaving of thermal power units according to the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description and the claims, the advantages and features of the present invention will be clearer.

[0019] First Embodiment Refer to Figure 1 , this embodiment provides a heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units, which is used to realize the deep peak shaving function of the thermal power generating unit 1 and fully and efficiently realize the storage and off-peak use of thermal energy.

[0020] Among them, the heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units at least includes a thermal power generating unit 1 and a heat storage subsystem 2.

[0021] The thermal power generating unit 1 is provided with a boiler 1.1 and a multi-stage steam turbine assembly. The boiler 1.1 is used to heat low-temperature steam and water to a high-temperature steam state, and the multi-stage steam turbine assembly is used to convert the thermal energy and pressure energy of the high-temperature steam into mechanical energy, thereby driving a generator device to generate electric energy. In this embodiment, the output end of the boiler 1.1 is provided with a branched first branch and a second branch, and the first branch at the output end of the boiler 1.1 is communicated with the inlet of the multi-stage steam turbine assembly.

[0022] The heat storage subsystem 2 is provided with a high-temperature molten salt storage tank 2.1 and a low-temperature molten salt storage tank 2.2. The high-temperature molten salt storage tank 2.1 and the low-temperature molten salt storage tank 2.2 are respectively used to store high-temperature and low-temperature molten salts. A first heat exchanger assembly is provided on the molten salt pipeline on one side from the high-temperature molten salt storage tank 2.1 to the low-temperature molten salt storage tank 2.2, and a second heat exchanger assembly is provided on the molten salt pipeline on one side from the low-temperature molten salt storage tank 2.2 to the high-temperature molten salt storage tank 2.1. Generally speaking, the first heat exchanger assembly and the second heat exchanger assembly are respectively provided with interactive molten salt channels and steam and water channels. When different media flow through the molten salt channels and the steam and water channels respectively, due to the temperature difference between different media, heat exchange can be realized between the different media in the molten salt channels and the steam and water channels. In this embodiment, the second branch at the output end of the boiler 1.1 is communicated with the inlet of the steam and water channel of the second heat exchanger assembly through a steam heating flow regulating valve 1.6.

[0023] At the same time, a water supply pipeline is also provided in the thermal power generating unit 1. The outlet of the multi-stage steam turbine assembly is communicated with the water supply pipeline of the thermal power generating unit 1. The low-temperature steam discharged after the multi-stage steam turbine assembly does work can be recovered to the water supply pipeline after condensation and other treatments. The water supply pipeline is further communicated to the input end of the boiler 1.1 and the inlet of the steam and water channel of the first heat exchanger assembly, that is, through the water supply pipeline, the low-temperature steam and water can be returned to the boiler 1.1 for reheating operations, or returned to the first heat exchanger assembly for heat exchange operations.

[0024] Specifically, during the heat storage period, that is, when the power grid issues a peak shaving and load reduction command, by opening the steam heating flow regulating valve 1.6, a part of the high-temperature steam output by the boiler 1.1 is still transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to maintain low-load power generation. The remaining part of the high-temperature steam output by the boiler 1.1 is shunted to the second heat exchanger assembly. In the second heat exchanger assembly, the high-temperature steam exchanges heat with the low-temperature molten salt, and the heat in the high-temperature steam is transferred to the low-temperature molten salt, and the heated high-temperature molten salt is stored in the high-temperature molten salt storage tank 2.1, thereby realizing the functions of reducing power generation and storing heat energy. During the heat release period, that is, when the power grid issues a peak shaving and load increase command, first, by closing the steam heating flow regulating valve 1.6, all the high-temperature steam output by the boiler 1.1 is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to perform conventional high-power power generation. At the same time, the low-temperature steam output by the multi-stage steam turbine assembly is condensed to form feed water and transmitted to the first heat exchanger assembly. In the first heat exchanger assembly, the low-temperature feed water exchanges heat with the high-temperature molten salt, and the heat in the high-temperature molten salt is transferred to the low-temperature steam and water to generate high-temperature feed water and high-temperature steam, so that the high-temperature feed water and high-temperature steam are re-circulated to the boiler 1.1 and the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to perform power generation.

[0025] Next, the specific structure and function of the heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units provided in this embodiment will be further described in detail: Preferably, in one embodiment, a high-temperature heat pump subsystem 3 is further included. The high-temperature heat pump subsystem 3 is provided with a heat pump steam condenser 3.1 and a compression assembly. Similarly, the heat pump steam condenser 3.1 is provided with an interactive steam-water channel and a heat pump medium channel. When different media flow through the steam-water channel and the heat pump medium channel respectively, due to the temperature difference between different media, heat exchange can be realized between the different media in the steam-water channel and the heat pump medium channel. In this embodiment, the inlet of the steam-water channel of the heat pump steam condenser 3.1 is communicated with the outlet of the steam-water channel of the second heat exchanger assembly, the outlet of the steam-water channel of the heat pump steam condenser 3.1 is communicated with the water supply pipeline, and the heat pump medium channel of the heat pump steam condenser 3.1 is communicated with the heat pump medium pipeline of the compression assembly. Among them, the compression assembly can be understood as a structural body formed by combining devices such as a compressor, an expander, and a heat exchanger. A heat pump medium pipeline is provided in the compression assembly, and the compression assembly is used to compress the heat pump medium in the heat pump medium pipeline to increase the heat of the heat pump medium. In this embodiment, the specific composition method of the compression assembly is not specifically limited, and the heat pump medium can be air or carbon dioxide gas.

[0026] In this embodiment, the high-temperature heat pump subsystem 3 is configured such that during the heat storage period, high-temperature steam flows through the second heat exchanger assembly. Among them, after the sensible heat of the high-temperature steam is exchanged with the low-temperature molten salt in the second heat exchanger assembly, the steam flows through the heat pump steam condenser 3.1, condenses to form low-temperature feed water and then returns to the feed water pipeline. At the same time, the heat pump medium in the heat pump medium pipeline flows through the heat pump steam condenser 3.1, and the latent heat of the steam is exchanged with the heat pump medium in the heat pump steam condenser 3.1, enabling the heat pump medium to absorb the latent heat of the steam and heat up under the compression of the compression assembly. The heat of the heat pump medium can be further used to heat the low-temperature molten salt.

[0027] Specifically, the second heat exchanger assembly includes a steam-salt high-temperature heater 2.3, a heat pump salt heater 3.2, and a steam-salt low-temperature heater 2.4. The steam-salt high-temperature heater 2.3 and the steam-salt low-temperature heater 2.4 are respectively provided with an interactive steam-water channel and a molten salt channel, and the media flowing in the steam-water channel and the molten salt channel can achieve heat exchange. The heat pump salt heater 3.2 is provided with an interactive heat pump medium channel and a molten salt channel, and the media flowing in the heat pump medium channel and the molten salt channel can also achieve heat exchange.

[0028] In this embodiment, the steam-water channel inlet of the steam-salt high-temperature heater 2.3 is connected to the second branch of the output end of the boiler 1.1, the steam-water channel outlet of the steam-salt high-temperature heater 2.3 is connected to the steam-water channel inlet of the steam-salt low-temperature heater 2.4, and the steam-water channel outlet of the steam-salt low-temperature heater 2.4 is connected to the steam-water channel inlet of the heat pump steam condenser 3.1.

[0029] The heat pump medium channel of the heat pump salt heater 3.2 is connected to the heat pump medium pipeline of the compression assembly.

[0030] The molten salt channels of the steam-salt low-temperature heater 2.4, the heat pump salt heater 3.2, and the steam-salt high-temperature heater 2.3 are connected in sequence, and the molten salt pipeline from the low-temperature molten salt storage tank 2.2 to the high-temperature molten salt storage tank 2.1 passes through the molten salt channels of the steam-salt low-temperature heater 2.4, the heat pump salt heater 3.2, and the steam-salt high-temperature heater 2.3 in sequence.

[0031] In this embodiment, the second heat exchanger assembly is specifically configured that during the heat storage period, the low-temperature molten salt in the low-temperature molten salt storage tank 2.2 is driven by the cold molten salt pump 2.17 and transferred to the high-temperature molten salt storage tank 2.1. The high-temperature steam first flows through the steam-molten salt high-temperature heater 2.3. In the steam-molten salt high-temperature heater 2.3, the high-temperature steam exchanges heat with the low-temperature molten salt for the first time. Then, the high-temperature steam flows through the steam-molten salt low-temperature heater 2.4. In the steam-molten salt low-temperature heater 2.4, the high-temperature steam exchanges heat with the low-temperature molten salt for the second time, that is, the steam heat is transferred to the molten salt in a stepped manner. Finally, the steam output from the steam-molten salt low-temperature heater 2.4 is transferred to the heat pump steam condenser 3.1. During this process, the heat pump medium in the heat pump medium pipeline of the high-temperature heat pump subsystem 3 also flows through the heat pump steam condenser 3.1. In the heat pump steam condenser 3.1, the high-temperature steam also exchanges heat with the heat pump medium. The heat pump medium absorbs the remaining heat of the high-temperature steam and generates heat under the compression operation of the compression assembly. Finally, the high-temperature heat pump medium flows through the heat pump molten salt heater 3.2. In the heat pump molten salt heater 3.2, the high-temperature heat pump medium exchanges heat with the molten salt for the third time.

[0032] It should be noted that the real-time temperature of the molten salt itself in the steam-molten salt low-temperature heater 2.4, the heat pump molten salt heater 3.2 and the steam-molten salt high-temperature heater 2.3 has a gradually increasing corresponding relationship with the heat value that can be provided by the high-temperature steam and the high-temperature heat pump medium. That is, the temperature of the molten salt in the steam-molten salt low-temperature heater 2.4 is lower than that in the heat pump molten salt heater 3.2, and lower than that in the steam-molten salt high-temperature heater 2.3. And the temperature of the steam or the heat pump medium in the steam-molten salt low-temperature heater 2.4 is lower than that in the heat pump molten salt heater 3.2, and lower than that in the steam-molten salt high-temperature heater 2.3. Therefore, the steam-molten salt low-temperature heater 2.4, the heat pump molten salt heater 3.2 and the steam-molten salt high-temperature heater 2.3 as a whole still maintain the function of stepped heating of the molten salt, realizing the efficient temperature rise of the molten salt.

[0033] In summary, in this embodiment, through the stepped heating of the molten salt, the heat exchange efficiency can be effectively improved. And in the prior art, the lower limit of the operating temperature of the molten salt is usually higher than the condensation temperature of the steam. Therefore, the molten salt cannot directly absorb the latent heat in the steam, resulting in waste of heat. However, in this application, the sensible heat in the steam is transferred to the molten salt through the steam-molten salt low-temperature heater 2.4 and the steam-molten salt high-temperature heater 2.3, and further by using the heat pump steam condenser 3.1 and the compression assembly, the latent heat in the steam is absorbed through the heat pump molten salt heater 3.2 and then transferred to the molten salt, effectively increasing the utilization rate of thermal energy during the peak shaving of the thermal power generating unit 1.

[0034] Preferably, in one embodiment, the water supply pipeline extends with a third branch and a fourth branch. The third branch of the water supply pipeline is connected to the input end of the boiler 1.1 through the boiler feed water flow regulating valve 1.4, and the fourth branch of the water supply pipeline is connected to the steam-water channel inlet of the first heat exchanger assembly through the molten salt feed water flow regulating valve 1.5.

[0035] In this embodiment, by controlling the opening and closing of the boiler feed water flow regulating valve 1.4 and the molten salt feed water flow regulating valve 1.5, the flow direction and flow rate of the feed water in the water supply pipeline can be efficiently controlled, and then the supply of steam and water can be flexibly adjusted according to the actual power generation demand of the thermal power generating unit 1.

[0036] Furthermore, the first heat exchanger assembly is provided with a molten salt feed water heater 2.6. In the molten salt feed water heater 2.6, there are interactive steam-water channels and molten salt channels, and the media flowing in the steam-water channels and the molten salt channels can achieve heat exchange.

[0037] In this embodiment, the steam-water channel inlet of the molten salt feed water heater 2.6 is connected to the fourth branch of the water supply pipeline, and the steam-water channel outlet of the molten salt feed water heater 2.6 is connected to the inlet of the boiler 1.1.

[0038] The molten salt channel inlet of the molten salt feed water heater 2.6 is connected to the output end of the high-temperature molten salt storage tank 2.1, and the molten salt channel outlet of the molten salt feed water heater 2.6 is connected to the input end of the low-temperature molten salt storage tank 2.2.

[0039] During the heat release period, the high-temperature molten salt in the high-temperature molten salt storage tank 2.1 is driven by the hot molten salt pump 2.1 to be transferred to the low-temperature molten salt storage tank 2.2. Open the molten salt feed water flow regulating valve 1.5, and all or part of the low-temperature feed water can flow through the molten salt feed water heater 2.6. In the molten salt feed water heater 2.6, the low-temperature feed water exchanges heat with the high-temperature molten salt, and the high-temperature molten salt transfers heat to the low-temperature feed water, and then the preheated feed water directly returns to the boiler 1.1, thereby reducing the amount of steam used for regenerative heating in the thermal power generating unit 1 and reducing the fuel consumed by the boiler.

[0040] Even further, the first heat exchanger assembly is also provided with an evaporator 2.7 and a superheater 2.8. Similarly, in the evaporator 2.7 and the superheater 2.8, there are respectively interactive steam-water channels and molten salt channels, and the media flowing in the steam-water channels and the molten salt channels can achieve heat exchange.

[0041] The steam pipe on the outlet side of the steam-water channel of the molten salt feed water heater 2.6 is also shunted with a fifth branch. A steam generator inlet regulating valve 2.5 is provided in the fifth branch. The outlet of the steam-water channel of the molten salt feed water heater 2.6 is connected to the inlet of the steam-water channel of the evaporator 2.7 through the steam generator inlet regulating valve 2.5. The outlet of the steam-water channel of the evaporator 2.7 is connected to the inlet of the steam-water channel of the superheater 2.8. The outlet of the steam-water channel of the superheater 2.8 is connected to the multi-stage steam turbine assembly.

[0042] In this embodiment, during the heat release period, when the steam generator inlet regulating valve 2.5 is opened, first, the low-temperature feed water flows through the molten salt feed water heater 2.6, and the high-temperature molten salt and the low-temperature feed water perform a primary heat exchange. Then, a part of the preheated feed water is directly transmitted to the boiler 1.1, and the remaining feed water flows through the evaporator 2.7 through the fifth branch. In the evaporator 2.7, the high-temperature molten salt and the feed water perform a secondary heat exchange to generate steam. Then, the steam flows through the superheater 2.8 again. In the superheater 2.8, the high-temperature molten salt and the steam perform a tertiary heat exchange, that is, the heat of the molten salt is also transferred to the steam in a stepped manner. Finally, the formed high-temperature steam is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to do work and generate electricity.

[0043] It should be noted that the real-time temperature of the steam and water itself in the molten salt feed water heater 2.6, the evaporator 2.7, and the superheater 2.8 has a gradually increasing corresponding relationship with the heat value that the high-temperature molten salt can provide. That is, the temperature of the molten salt in the molten salt feed water heater 2.6 is lower than that in the evaporator 2.7, and lower than that in the superheater 2.8. And the temperature of the steam and water is also lower in the molten salt feed water heater 2.6 than in the evaporator 2.7, and lower than in the superheater 2.8. Therefore, the molten salt feed water heater 2.6, the evaporator 2.7, and the superheater 2.8 as a whole still maintain the function of stepwise heating the steam and water, realizing the efficient temperature rise of the steam and water.

[0044] Furthermore, the first heat exchanger assembly is also provided with a reheater 2.9. Similarly, the reheater 2.9 is provided with an interactive steam-water channel and a molten salt channel, and the media flowing in the steam-water channel and the molten salt channel can achieve heat exchange.

[0045] In this embodiment, the molten salt pipeline on one side of the output end of the high-temperature molten salt storage tank 2.1 is also shunted with a sixth branch. The inlet of the molten salt channel of the reheater 2.9 is connected to the sixth branch at the output end of the high-temperature molten salt storage tank 2.1, and the outlet of the molten salt channel of the reheater 2.9 is connected to the inlet of the molten salt channel of the evaporator 2.7.

[0046] Moreover, the multi-stage steam turbine assembly includes at least a high-pressure cylinder 1.2 and an intermediate-pressure cylinder 1.3.

[0047] In this embodiment, the inlet of the steam-water passage of the reheater 2.9 is communicated with the outlet of the high-pressure cylinder 1.2, and the outlet of the steam-water passage of the reheater 2.9 is communicated with the high-pressure feedwater extraction passage of the intermediate-pressure cylinder 1.3.

[0048] During the heat release period, the exhaust steam output by the high-pressure cylinder 1.2 and the high-temperature molten salt flow through the reheater 2.9. In the reheater 2.9, heat exchange occurs between the low-temperature steam and the high-temperature molten salt, and the high-temperature molten salt transfers heat to the low-temperature steam. Then, the heated steam is transmitted to the intermediate-pressure cylinder 1.3 through the high-pressure feedwater extraction passage of the intermediate-pressure cylinder 1.3 to do work.

[0049] Meanwhile, specifically, the outlet of the steam-water passage of the superheater 2.8 is communicated with the high-pressure feedwater extraction passage of the high-pressure cylinder 1.2. During the process of realizing cascade heating of steam and water in the molten salt feedwater heater 2.6, the evaporator 2.7 and the superheater 2.8, the steam temperature output by the superheater 2.8 reaches the highest, up to 540 °C. Therefore, the high-temperature steam can be transmitted to the high-pressure cylinder 1.2 through the high-pressure feedwater extraction passage of the high-pressure cylinder 1.2 to do work.

[0050] Moreover, in the steam-water pipeline between the outlet of the steam-water passage of the superheater 2.8 and the high-pressure feedwater extraction passage of the high-pressure cylinder 1.2, a superheater outlet stop valve 2.16, a superheater outlet check valve 2.15 and a superheater outlet regulating valve 2.14 are successively provided.

[0051] In the steam-water pipeline between the outlet of the high-pressure cylinder 1.2 and the inlet of the steam-water passage of the reheater 2.9, a reheater inlet regulating valve 2.10 is provided.

[0052] In the steam-water pipeline between the outlet of the steam-water passage of the reheater 2.9 and the high-pressure feedwater extraction passage of the intermediate-pressure cylinder 1.3, a reheater outlet stop valve 2.13, a reheater outlet check valve 2.12 and a reheater outlet regulating valve 2.11 are successively provided.

[0053] Thus, the one-way flow, sealing safety of steam and water in the steam-water pipeline and flexible and controllable adjustment of the steam and water flow can be realized.

[0054] Preferably, in one embodiment, the high-pressure feedwater extraction passage of the high-pressure cylinder 1.2 is also shunted with a seventh branch, and the seventh branch is communicated with the first high-pressure heat exchanger assembly. A first high-pressure feedwater extraction stop valve 1.7 and a first high-pressure feedwater extraction check valve 1.8 are provided in the seventh branch.

[0055] The high-pressure feedwater extraction passage of the intermediate-pressure cylinder 1.3 is also shunted with an eighth branch, and the eighth branch is communicated with the second high-pressure heat exchanger assembly. A second high-pressure feedwater extraction stop valve 1.9 and a second high-pressure feedwater extraction check valve 1.10 are provided in the eighth branch.

[0056] It should be noted that in the high-pressure cylinder 1.2 and the intermediate-pressure cylinder 1.3, the high-pressure feedwater extraction channels are two-way flow channels. The first high-pressure heat exchanger assembly and the second high-pressure heat exchanger assembly are structures formed by combining heat exchange devices, condensation devices, deaerators, etc. The first high-pressure heat exchanger assembly and the second high-pressure heat exchanger assembly are used to selectively extract some of the steam that has completed work in the intermediate stages of the high-pressure cylinder 1.2 and / or the intermediate-pressure cylinder 1.3 and directly exchange heat with the feedwater to achieve the purpose of heating the feedwater. Therefore, in this embodiment, during the heat storage period, the first high-pressure feedwater extraction stop valve 1.7 and the second high-pressure feedwater extraction stop valve 1.8 can be opened, and some of the high-temperature steam that has completed work is extracted from the high-pressure cylinder 1.2 and the intermediate-pressure cylinder 1.3. The high-temperature steam flows through the first high-pressure heat exchanger assembly and the second high-pressure heat exchanger assembly respectively to heat the feedwater. During the heat release period, the first high-pressure feedwater extraction stop valve 1.7 and the second high-pressure feedwater extraction stop valve 1.8 are closed. At this time, the high-temperature steam formed by heating through the second heat exchanger assembly can be reversely transmitted to the high-pressure cylinder 1.2 and the intermediate-pressure cylinder 1.3 respectively.

[0057] Second Embodiment Based on the same concept, the present invention also provides a heat pump-coupled molten salt energy storage method applicable to peak shaving of thermal power units, which is applied to the heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units as described in the first embodiment, and includes the following steps: S11: During the heat storage period, the power grid issues a peak shaving and load reduction command, and the steam heating flow regulating valve 1.6 is opened. Part of the high-temperature steam generated by the boiler 1.1 is transmitted to the multi-stage steam turbine assembly through the first branch to drive the multi-stage steam turbine assembly to maintain low-load power generation, and part of the high-temperature steam generated by the boiler 1.1 is shunted and transmitted to the second heat exchanger assembly through the second branch.

[0058] S12: The cold molten salt pump 2.17 is started, so that the enabled molten salt is transmitted from the low-temperature molten salt storage tank 2.2 to the high-temperature molten salt storage tank 2.1 through the steam-molten salt low-temperature heater 2.4, the heat pump molten salt heater 3.2, and the steam-molten salt high-temperature heater 2.3.

[0059] During this process, the high-temperature steam first flows through the steam-molten salt high-temperature heater 2.3, and the sensible heat of the high-temperature steam is used to perform primary heating on the low-temperature molten salt. Then the high-temperature steam flows through the steam-molten salt low-temperature heater 2.4, and the secondary sensible heat of the high-temperature steam is also used to perform secondary heating on the low-temperature molten salt.

[0060] The steam output from the steam-molten salt low-temperature heater 2.4 is transmitted to the heat pump steam condenser 3.1. The heat pump medium in the heat pump medium pipeline in the high-temperature heat pump subsystem 3 flows through the heat pump steam condenser 3.1. The heat pump medium absorbs the latent heat of the steam and is further heated under the compression of the compression assembly. Then the high-temperature heat pump medium flows through the heat pump molten salt heater 3.2 to perform tertiary heating on the low-temperature molten salt.

[0061] S14: Store the high-temperature molten salt after heating is completed in the high-temperature molten salt storage tank 2.1.

[0062] S21: During the heat release period, the power grid outputs a peak shaving and load increasing command, closes the steam heating flow regulating valve 1.6, and all the high-temperature steam generated by the boiler 1.1 is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to do work and generate electricity.

[0063] S22: Start the hot molten salt pump 2.18 to enable the molten salt to be transmitted from the high-temperature molten salt storage tank 2.1 to the low-temperature molten salt storage tank 2.2 through the reheater 2.9, superheater 2.8, evaporator 2.7, and molten salt feed water heater 2.6.

[0064] Open the molten salt feed water flow regulating valve 1.5, steam generator inlet regulating valve 2.5, reheater inlet regulating valve 2.10, reheater outlet regulating valve 2.11, and superheater outlet regulating valve 2.14.

[0065] During this process, part of the exhaust steam output after the high-pressure cylinder 1.2 does work is transmitted to the reheater 2.9, the high-temperature molten salt flows through the reheater 2.9 to heat the exhaust steam, and then enables the reheated exhaust steam to be transmitted to the intermediate-pressure cylinder 1.3 to drive the intermediate-pressure cylinder 1.3 to do work and generate electricity.

[0066] At the same time, the high-temperature molten salt flows through the molten salt feed water heater 2.6 to achieve primary heating of the low-temperature feed water, part of the preheated high-temperature feed water is directly transmitted to the boiler 1.1, then the high-temperature molten salt flows through the evaporator 2.7 to achieve secondary heating of part of the feed water to generate steam, then the high-temperature molten salt flows through the superheater 2.8 to achieve tertiary heating of the steam, and finally enables the high-temperature steam to be transmitted to the high-pressure cylinder 1.2 to drive the high-pressure cylinder 1.2 to do work and generate electricity.

[0067] S23: Store the low-temperature molten salt after heat transfer is completed in the low-temperature molten salt storage tank 2.2.

[0068] In summary, the present invention provides a heat pump coupled molten salt energy storage system and method applicable to peak shaving of thermal power units, which are provided with a thermal power generating unit 1, a heat storage subsystem 2 and a high-temperature heat pump subsystem 3. During the heat storage period, the power grid outputs a peak shaving and load reduction instruction. The high-temperature steam generated by the boiler 1.1 will be shunted and transmitted to the multi-stage steam turbine assembly and the heat storage subsystem 2 respectively, reducing the real-time power generation and storing part of the heat energy. Among them, the high-temperature steam flows through the steam-molten salt high-temperature heater 2.3 and the steam-molten salt low-temperature heater 2.4, which can realize the efficient absorption of the sensible heat of the high-temperature steam by the molten salt. The heat pump molten salt heater 3.2 cooperates with the high-temperature heat pump subsystem 3 to realize the deep absorption of the latent heat of the high-temperature steam by the molten salt, thereby realizing the full and effective recovery of heat. During the heat release period, the power grid outputs a peak shaving and load increase instruction. The high-temperature steam generated by the boiler 1.1 is all used to drive the multi-stage steam turbine assembly to do work. The condensed steam water and exhaust steam output after the multi-stage steam turbine assembly does work pass through the superheater 2.8, the evaporator 2.7, the molten salt feed water heater 2.6 and the reheater 2.9, which can realize the full absorption of the heat of the high-temperature molten salt by the low-temperature steam water and regenerate it into high-temperature steam, which flows back to the boiler 1.1 and the multi-stage steam turbine assembly, enabling the multi-stage steam turbine assembly to generate electricity by doing work. By efficiently utilizing heat during the heat storage period and the heat release period, the function of improving the deep peak shaving of the thermal power generating unit 1 is achieved, effectively increasing the power generation flexibility of the thermal power generating unit 1 and reducing the fuel consumption required during boiler operation.

[0069] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalent technologies, they still fall within the protection scope of the present invention.

Claims

1. A heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units, characterized in that, Comprising: A thermal power generating unit, which includes a boiler and a multi-stage steam turbine assembly. The first branch at the output end of the boiler is communicated with the inlet of the multi-stage steam turbine assembly; A heat storage subsystem, which includes a high-temperature molten salt storage tank and a low-temperature molten salt storage tank. A first heat exchanger assembly is provided on the molten salt pipeline from the high-temperature molten salt storage tank to the low-temperature molten salt storage tank side, and a second heat exchanger assembly is provided on the molten salt pipeline from the low-temperature molten salt storage tank to the high-temperature molten salt storage tank side. The second branch at the output end of the boiler is communicated with the steam-water channel inlet of the second heat exchanger assembly through a steam heating flow regulating valve; The outlet of the multi-stage steam turbine assembly is communicated with the water supply pipeline of the thermal power generating unit. The water supply pipeline includes a connection to the input end of the boiler and the steam-water channel inlet of the first heat exchanger assembly; During the heat storage period, part of the high-temperature steam output by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to generate electricity. And, part of the high-temperature steam output by the boiler is diverted to the second heat exchanger assembly to heat the low-temperature molten salt. During the heat release period, the steam output by the multi-stage steam turbine assembly is condensed to form feed water and transmitted to the first heat exchanger assembly. The feed water is re-formed into high-temperature steam based on the heating of the high-temperature molten salt, and the high-temperature steam is enabled to flow back to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to generate electricity.

2. The heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 1, wherein It further includes a high-temperature heat pump subsystem, which is provided with a heat pump steam condenser and a compression assembly. The steam-water channel inlet of the heat pump steam condenser is communicated with the steam-water channel outlet of the second heat exchanger assembly. The steam-water channel outlet of the heat pump steam condenser is communicated with the water supply pipeline. The heat pump medium channel of the heat pump steam condenser is communicated with the heat pump medium pipeline of the compression assembly; The high-temperature heat pump subsystem is configured such that during the heat storage period, after the sensible heat of the high-temperature steam is heat-exchanged with the low-temperature molten salt in the second heat exchanger assembly, the steam flows through the heat pump steam condenser, condenses and flows back into the water supply pipeline; and, the heat pump medium in the heat pump medium pipeline absorbs the latent heat of the steam in the heat pump steam condenser and is heated under the compression of the compression assembly.

3. The heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 2, wherein The second heat exchanger assembly includes a steam-molten salt high-temperature heater, a heat pump molten salt heater and a steam-molten salt low-temperature heater; The steam-water channel inlet of the steam-molten salt high-temperature heater is communicated with the second branch at the output end of the boiler. The steam-water channel outlet of the steam-molten salt high-temperature heater is communicated with the steam-water channel inlet of the steam-molten salt low-temperature heater. The steam-water channel outlet of the steam-molten salt low-temperature heater is communicated with the steam-water channel inlet of the heat pump steam condenser; The heat pump medium channel of the heat pump molten salt heater is communicated with the heat pump medium pipeline of the compression assembly; The molten salt pipeline from the low-temperature molten salt storage tank to the high-temperature molten salt storage tank sequentially passes through the molten salt channels of the steam-molten salt low-temperature heater, the heat pump molten salt heater and the steam-molten salt high-temperature heater; The second heat exchanger assembly is configured such that, during the heat storage period, high-temperature steam and low-temperature molten salt flow through the steam-molten salt high-temperature heater and the steam-molten salt low-temperature heater, enabling the heat of the steam to be transferred to the molten salt in a stepped manner. Moreover, high-temperature heat pump medium and low-temperature molten salt flow through the heat pump molten salt heater, enabling the heat of the heat pump medium to be transferred to the molten salt.

4. The heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 1, wherein A third branch and a fourth branch are provided in extension of the feed water pipeline. The third branch of the feed water pipeline is connected to the input end of the boiler through a boiler feed water flow regulating valve, and the fourth branch of the feed water pipeline is connected to the steam-water channel inlet of the first heat exchanger assembly through a molten salt feed water flow regulating valve.

5. The heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 4, characterized in that, The first heat exchanger assembly is provided with a molten salt feed water heater; The steam-water channel inlet of the molten salt feed water heater is connected to the fourth branch of the feed water pipeline, and the steam-water channel outlet of the molten salt feed water heater is connected to the inlet of the boiler; The molten salt channel inlet of the molten salt feed water heater is connected to the output end of the high-temperature molten salt storage tank, and the molten salt channel outlet of the molten salt feed water heater is connected to the input end of the low-temperature molten salt storage tank.

6. The heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 5, characterized in that The first heat exchanger assembly is further provided with an evaporator and a superheater; A fifth branch is also provided in a split manner on the steam-water pipeline on one side of the steam-water channel outlet of the molten salt feed water heater. A steam generator inlet regulating valve is provided in the fifth branch. The steam-water channel outlet of the molten salt feed water heater is connected to the steam-water channel inlet of the evaporator through the steam generator inlet regulating valve. The steam-water channel outlet of the evaporator is connected to the steam-water channel inlet of the superheater, and the steam-water channel outlet of the superheater is connected to the inlet of the multi-stage steam turbine assembly; The first heat exchanger assembly is configured such that, during the heat release period, when the steam generator inlet regulating valve is closed, high-temperature molten salt and low-temperature feed water flow through the molten salt feed water heater, enabling the heat of the molten salt to be transferred to the feed water, and then the high-temperature feed water is transmitted to the boiler; when the steam generator inlet regulating valve is opened, high-temperature molten salt and a part of the feed water flow through the molten salt feed water heater, the evaporator and the superheater, enabling the heat of the molten salt to be transferred to a part of the steam in a stepped manner to generate high-temperature steam, and then the high-temperature steam is transmitted to the multi-stage steam turbine assembly.

7. The heat pump-coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 6, wherein The first heat exchanger assembly is further provided with a reheater; A sixth branch is also provided in a split manner on the molten salt pipeline on one side of the output end of the high-temperature molten salt storage tank. The molten salt channel inlet of the reheater is connected to the sixth branch of the output end of the high-temperature molten salt storage tank, and the molten salt channel outlet of the reheater is connected to the molten salt channel inlet of the evaporator; The multi-stage steam turbine assembly includes at least a high-pressure cylinder and an intermediate-pressure cylinder; The steam-water channel inlet of the reheater is connected to the outlet of the high-pressure cylinder, and the steam-water channel outlet of the reheater is connected to the high-pressure heater extraction steam channel of the intermediate-pressure cylinder; The first heat exchanger assembly is further configured such that, during the heat release period, the low-temperature steam output by the high-pressure cylinder and the high-temperature molten salt flow through the reheater, enabling the heat of the molten salt to be transferred to the steam, and then the high-temperature steam is transmitted to the intermediate-pressure cylinder.

8. The heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 7, characterized in that, The outlet of the steam-water passage of the superheater is communicated with the high-pressure heater extraction steam passage of the high-pressure cylinder. In the steam-water pipeline between the outlet of the steam-water passage of the superheater and the high-pressure heater extraction steam passage of the high-pressure cylinder, a superheater outlet stop valve, a superheater outlet check valve and a superheater outlet regulating valve are sequentially arranged; In the steam-water pipeline between the outlet of the high-pressure cylinder and the inlet of the steam-water passage of the reheater, a reheater inlet regulating valve is arranged; In the steam-water pipeline between the outlet of the steam-water passage of the reheater and the high-pressure heater extraction steam passage of the intermediate-pressure cylinder, a reheater outlet stop valve, a reheater outlet check valve and a reheater outlet regulating valve are sequentially arranged.

9. The heat pump coupled molten salt energy storage system applicable to peak shaving of thermal power units according to claim 7, wherein The high-pressure heater extraction steam passage of the high-pressure cylinder is also shunted with a seventh branch, and the seventh branch is communicated with the first high-pressure heat exchanger assembly. A first high-pressure heater extraction stop valve and a first high-pressure heater extraction check valve are arranged in the seventh branch; The high-pressure heater extraction steam passage of the intermediate-pressure cylinder is also shunted with an eighth branch, and the eighth branch is communicated with the second high-pressure heat exchanger assembly. A second high-pressure heater extraction stop valve and a second high-pressure heater extraction check valve are arranged in the eighth branch; The high-pressure cylinder and the intermediate-pressure cylinder are configured that, during the heat storage period, the first high-pressure heater extraction stop valve and the second high-pressure heater extraction stop valve are opened, steam is extracted from the high-pressure cylinder and the intermediate-pressure cylinder, and the high-temperature steam flows through the first high-pressure heat exchanger assembly and the second high-pressure heat exchanger assembly respectively to heat the feed water.

10. A heat pump coupled molten salt energy storage method applicable to peak shaving of thermal power units, characterized in that, Applied to the heat pump coupled molten salt energy storage system suitable for peak shaving of thermal power units as described in any one of claims 1-9, the following steps are included: S11: During the heat storage period, the power grid outputs a peak shaving and load reduction instruction, the steam heating flow regulating valve is opened, a part of the high-temperature steam generated by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to maintain low-load power generation, and a part of the high-temperature steam generated by the boiler is transmitted to the second heat exchanger assembly; S12: Start the cold molten salt pump, enable the molten salt to be transmitted from the low-temperature molten salt storage tank through the steam-molten salt low-temperature heater, the heat pump molten salt heater and the steam-molten salt high-temperature heater to the high-temperature molten salt storage tank. The high-temperature steam flows through the steam-molten salt high-temperature heater to realize primary heating of the molten salt, and then the high-temperature steam flows through the steam-molten salt low-temperature heater to realize secondary heating of the molten salt; S13: The steam flows through the heat pump steam condenser to condense and return to the feed water pipeline, and the heat pump medium in the heat pump medium pipeline absorbs the remaining heat of the steam in the heat pump steam condenser and is heated under the compression of the compression assembly. The high-temperature heat pump medium flows through the heat pump molten salt heater to realize tertiary heating of the molten salt; S14: The high-temperature molten salt is stored in the high-temperature molten salt storage tank; S21: During the heat release period, the power grid outputs a peak shaving and load increase instruction, the steam heating flow regulating valve is closed, all the high-temperature steam generated by the boiler is transmitted to the multi-stage steam turbine assembly to drive the multi-stage steam turbine assembly to generate power; S22: Start the hot molten salt pump, enable the molten salt to be transmitted from the high-temperature molten salt storage tank through the reheater, the superheater, the evaporator and the molten salt feed water heater to the low-temperature molten salt storage tank; Open the molten salt feed water flow regulating valve, steam generator inlet regulating valve, reheater inlet regulating valve, reheater outlet regulating valve and superheater outlet regulating valve, so that part of the exhaust steam output by the high-pressure cylinder can be transmitted to the reheater. The high-temperature molten salt flows through the reheater to heat the exhaust steam, and then enable the reheated exhaust steam to be transmitted to the intermediate-pressure cylinder to drive the intermediate-pressure cylinder to do work and generate electricity; The high-temperature molten salt flows through the molten salt feed water heater to heat the feed water once. Part of the high-temperature feed water is transmitted to the boiler. The high-temperature molten salt flows through the evaporator to heat the feed water twice to generate steam. Subsequently, the high-temperature molten salt flows through the superheater to heat the steam three times, and then enable the high-temperature steam to be transmitted to the high-pressure cylinder to drive the high-pressure cylinder to do work and generate electricity; S23: Store the low-temperature molten salt in the low-temperature molten salt storage tank.

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