Molten salt energy storage system for thermoelectric decoupling of power plant and working method of molten salt energy storage system

Abstract

The invention belongs to the field of thermoelectric unit thermoelectric decoupling, and discloses a fused salt energy storage system for thermoelectric decoupling of a power plant and a working method thereof, and the fused salt energy storage system comprises a fused salt electric heating subsystem, a fused salt heat storage subsystem and a fused salt-steam-water heat exchange subsystem which are connected in sequence. The fused salt electric heating subsystem is used for heating low-temperature fused salt by utilizing high-plant electric energy; the fused salt heat storage subsystem realizes high-temperature and low-temperature fused salt circulating transmission and high-temperature fused salt storage; and the fused salt-steam-water heat exchange subsystem exchanges heat with water through high-temperature fused salt to generate steam which is supplied to the corresponding mother pipe. Thermoelectric decoupling is achieved through fused salt energy storage, fused salt energy storage is not limited by geography, arrangement can be flexible, and power transmission loss is low. Energy is released during the peak of power demand and stored during the valley of power demand, so that the loss of a system power transmission network is effectively reduced, peak clipping and valley filling are realized, the peak regulation and difference adjustment capabilities of a power plant unit are enhanced, the flexible demand of peak-valley difference of a power grid can be better adapted, stable power supply of a region is ensured, and efficient utilization of energy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoelectric decoupling of thermoelectric generator sets, and in particular relates to a molten salt energy storage system for thermoelectric decoupling of a power plant and a working method thereof. Background Art

[0002] With the continuous growth of energy demand and the increasing demand for energy efficiency, optimizing power plant operations faces numerous challenges. In traditional power plant operations, heat and electricity are produced in a coupled manner, meaning that the power generation process inevitably generates heat for heating or industrial applications. However, this coupled production method leads to energy waste, especially when electricity and heat demand are out of sync. For example, in northern winter, when electricity demand is low but heating demand is high, excess electricity may not be effectively utilized, resulting in reduced system efficiency.

[0003] Currently, most power plants are experiencing numerous operational issues. During the heating season, certain thermal-electric coupling characteristics exist, significantly limiting the units' ability to meet heating demand and adjust peak and valley power. During the off-season, however, they are subject to minimum stable combustion requirements, resulting in a certain amount of excess zero-cost electricity generation. In today's spot electricity market, the demand for flexible power generation to accommodate peak and valley power levels is increasingly prominent, but this plant's units are unable to adapt, negatively impacting the region's stable power supply and efficient energy utilization. This also severely impacts the company's economic profitability and market competitiveness. Energy storage is usually used to address the above issues. That is, energy storage devices can absorb or release power in real time, effectively reducing system transmission network losses, achieving peak shaving and valley filling, and thus improving the flexible adaptability of power plants. Traditional energy storage devices mostly use pumped storage, compressed air storage, flywheel storage, water heat storage technology, electric boiler solid energy storage and electrochemical energy storage. However, due to the many geographical restrictions, high transmission losses, weak emergency response capabilities and poor thermal and electric decoupling performance of the above energy storage methods, they cannot meet the needs of power plants to significantly improve the operating flexibility of units, and thus cannot achieve a stable supply of regional electricity and efficient use of energy.

[0004] It can be seen that the existing energy storage methods are unable to meet the needs of power plants to significantly improve the operating flexibility of units due to many geographical restrictions, high transmission losses, weak emergency capabilities and poor thermal and electric decoupling performance, and thus cannot achieve a stable supply of regional electricity and efficient use of energy. Summary of the Invention

[0005] The present invention provides a molten salt energy storage system for thermal-electric decoupling in power plants and its operating method. This system is based on molten salt energy storage technology, uses electrically heated molten salt, and has rapid power regulation capabilities. The heat from the molten salt can be returned to the system for power generation and can also be used for industrial steam supply or heating steam supply, greatly improving the operational flexibility of the unit.

[0006] In order to achieve the above object, the present invention adopts the following technical contents:

[0007] A molten salt energy storage system for thermal-electric decoupling of a power plant, comprising: a molten salt electric heating subsystem, a molten salt heat storage subsystem, and a molten salt-steam-water heat exchange subsystem connected in sequence;

[0008] The molten salt electric heating subsystem is used to heat the low-temperature molten salt by electric heating using high-voltage power plant transformers;

[0009] The molten salt heat storage subsystem is used to realize the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt;

[0010] The molten salt-steam-water heat exchange subsystem is used to exchange heat with water through high-temperature molten salt, and supply the generated steam to the auxiliary steam or steam supply main pipe.

[0011] Furthermore, the molten salt electric heating subsystem includes at least one group of high-voltage transformers; the transmission end of the high-voltage transformer is connected to an electric heater; the low-temperature molten salt of the molten salt heat storage subsystem is converted into high-temperature molten salt after flowing through the electric heater to achieve heat storage.

[0012] Furthermore, the molten salt electric heating subsystem also includes an intelligent power allocation device, which is connected between the high-voltage transformer and the electric heater and is used to automatically allocate the output electric power according to a preset power.

[0013] Furthermore, the electric heater is arranged vertically, with the lower end being the molten salt inlet and the upper end being the molten salt outlet.

[0014] Furthermore, the molten salt heat storage subsystem includes a low-temperature tank and a high-temperature tank;

[0015] The output end of the low-temperature tank is connected to the input end of the high-temperature tank through the molten salt electric heating subsystem;

[0016] The high-temperature tank is connected to the molten salt-steam-water heat exchange subsystem via a high-temperature molten salt pump;

[0017] The output end of the low-temperature tank is sequentially provided with a low-temperature molten salt pump and a low-temperature molten salt control valve.

[0018] Furthermore, the low-temperature molten salt control valve includes a control valve body;

[0019] The control valve body includes a valve stem and a valve seat;

[0020] A first electric heating tape is wound around the valve stem;

[0021] The inner wall of the valve seat is paved with a second electric heating tape;

[0022] The first electric heating tape and the second electric heating tape are both connected to the molten salt electric heating subsystem.

[0023] Furthermore, a high-temperature molten salt control valve is provided between the high-temperature molten salt pump and the molten salt-steam-water heat exchange subsystem.

[0024] Furthermore, the molten salt-steam-water heat exchange subsystem includes a brine heat exchanger; the first inlet of the brine heat exchanger is connected to the high-temperature molten salt output end of the molten salt heat storage subsystem, the second inlet is connected to the deaerator inlet, the first outlet is connected to the low-temperature molten salt input end of the molten salt heat storage subsystem, and the second outlet is connected to the auxiliary steam or steam supply main pipe.

[0025] Furthermore,

[0026] A water inlet control valve and a booster pump are connected in sequence between the second inlet of the brine heat exchanger and the deaerator;

[0027] A gas supply control valve is connected between the second outlet of the brine heat exchanger and the auxiliary steam or steam supply main pipe.

[0028] A method for operating a molten salt energy storage system for thermal and electric decoupling in a power plant, based on the above-mentioned molten salt energy storage system for thermal and electric decoupling in a power plant, comprising:

[0029] The molten salt electric heating subsystem is used to heat the low-temperature molten salt by electric heating with high-voltage power plant transformer energy;

[0030] The molten salt heat storage subsystem realizes the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt;

[0031] The high-temperature molten salt is exchanged with water through the molten salt-steam-water heat exchange subsystem, and the generated steam is then supplied to the auxiliary steam or steam supply main pipe.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a molten salt energy storage system for thermal-electric decoupling in power plants. The system comprises a molten salt electric heating subsystem, a molten salt heat storage subsystem, and a molten salt-steam-water heat exchange subsystem, which are connected in sequence. The molten salt electric heating subsystem uses high-voltage power plant transformers to heat and raise the temperature of low-temperature molten salt; the molten salt heat storage subsystem realizes the circulation transmission of high-temperature and low-temperature molten salt and the storage of high-temperature molten salt; the molten salt-steam-water heat exchange subsystem generates steam through heat exchange between high-temperature molten salt and water to supply the corresponding main pipe. The energy storage system achieves thermal-electric decoupling through molten salt energy storage. Molten salt energy storage is not subject to geographical restrictions, can be flexibly arranged, and has low transmission losses. It releases energy during peak power demand and stores energy during valley power demand, effectively reducing system transmission network losses and achieving peak shaving and valley filling. It enhances the peak-shaving and valley-shaving capabilities of power plant units, can better adapt to the flexible peak-valley demand of the power grid, ensure the stable supply of regional power, improve the efficient use of energy, and thus enhance the economic benefits and market competitiveness of enterprises.

[0034] In addition, the low-temperature molten salt is heated by electric heating. Compared with the general steam heating method, it does not require a large amount of steam extraction and is not restricted by the safety and stability of steam turbines and boilers. It can ensure the stable and reliable operation of the molten salt heating process.

[0035] Preferably, the molten salt electric heating subsystem in the present invention comprises at least one high-voltage transformer and an electric heater. Low-temperature molten salt flows through the electric heater and is converted into high-temperature molten salt for heat storage. This subsystem facilitates stable system operation and provides a reliable heat source for subsequent heating or power generation.

[0036] Preferably, the present invention includes an intelligent power allocation device that automatically adjusts the output power according to the preset power. This enables the system to precisely control heating power according to actual needs, avoiding energy waste and improving energy efficiency. It also ensures the safety and stability of system operation and better adapts to operating requirements under different working conditions.

[0037] Preferably, in the present invention, the electric heater is arranged vertically, with the molten salt inlet at the bottom and the molten salt outlet at the top. This arrangement facilitates the natural flow of the molten salt during the heating process, reduces flow resistance, improves heat exchange efficiency, and enables the low-temperature molten salt to more fully absorb heat, rapidly heating up and enhancing the overall performance of the system. Furthermore, in the event of a system failure, the molten salt can be smoothly discharged from the electric heater through the inlet by gravity, preventing condensation and blockage of the equipment.

[0038] Preferably, in the present invention, the molten salt heat storage subsystem includes a low-temperature tank and a high-temperature tank. The low-temperature molten salt in the low-temperature tank is heated by the electric heating subsystem and then enters the high-temperature tank for storage. The high-temperature tank is connected to the heat exchange subsystem through a high-temperature molten salt pump. A low-temperature molten salt pump and a low-temperature molten salt control valve are provided at the output end of the low-temperature tank to ensure stable circulation and precise control of the molten salt in the system, which is conducive to the effective storage and release of heat.

[0039] Preferably, in the present invention, the valve stem and valve seat of the low-temperature molten salt control valve are equipped with electric heating cables connected to the molten salt electric heating subsystem. In low-temperature environments, the electric heating cables prevent the control valve from freezing or clogging due to the low temperature of the molten salt, ensuring the normal opening and closing of the control valve, maintaining the stable flow of molten salt at the output of the cryogenic tank, and improving the reliability and stability of the system.

[0040] Preferably, in the present invention, a high-temperature molten salt control valve is provided between the high-temperature molten salt pump and the heat exchange subsystem; the control valve can accurately control the flow of high-temperature molten salt entering the heat exchange subsystem, and flexibly adjust it according to the actual heating or power generation needs to ensure the stability and efficiency of the heat exchange process, and avoid problems such as poor heat exchange effect or equipment damage due to unstable flow.

[0041] Preferably, in the present invention, the molten salt-steam-water heat exchange subsystem includes a brine heat exchanger, which transfers the heat of the high-temperature molten salt to water, generates steam to supply auxiliary steam or the steam supply main pipe, thereby realizing the effective utilization of thermal energy; this connection method is simple and reliable, can meet the actual heating or power generation needs of the power plant, and improve the comprehensive utilization efficiency of energy.

[0042] Preferably, in the present invention, a water inlet control valve and a booster pump are connected sequentially between the water inlet of the brine heat exchanger and the deaerator, and an air supply control valve is connected between the steam outlet and the auxiliary steam or steam supply main. The water inlet control valve and booster pump precisely control the amount and pressure of water entering the heat exchanger, ensuring a stable heat exchange process. The air supply control valve flexibly adjusts steam output to meet the steam needs of different users, improving the system's automation control level and operational flexibility.

[0043] The present invention also provides a working method of a molten salt energy storage system for thermoelectric decoupling in power plants. Based on the above-mentioned energy storage system, the molten salt electric heating subsystem is first used to convert high-voltage power plant electricity into thermal energy to heat the low-temperature molten salt. The molten salt heat storage subsystem is then used to realize molten salt circulation transmission and high-temperature molten salt storage. Finally, the molten salt-steam-water heat exchange subsystem transfers the heat of the high-temperature molten salt to water to generate steam. Molten salt energy storage can be flexibly arranged without geographical restrictions, reducing power transmission losses. During the heating period, thermoelectric decoupling is achieved by storing and releasing thermal energy, breaking through the thermoelectric coupling limitations and enhancing the peak-shaving and differential adjustment capabilities of the unit. During the non-heating period, the molten salt energy storage characteristics are used to reduce the generation of zero-price electricity. This method is used to effectively improve the flexible adaptability of power plants, adapt to the peak-valley difference requirements of the power grid, ensure the stable supply of regional electricity, improve the efficient use of energy, and enhance the economic benefits and market competitiveness of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A structural block diagram of a molten salt energy storage system for thermal and electrical decoupling in a power plant provided by an embodiment of the present invention;

[0045] Figure 2 A schematic structural diagram of a molten salt energy storage system for thermal and electrical decoupling in a power plant according to an embodiment of the present invention;

[0046] Figure 3 A schematic structural diagram of a molten salt control valve provided in an embodiment of the present invention.

[0047] Reference numerals:

[0048] 1. High-voltage transformer; 2. Intelligent power allocation device; 3. Electric heater; 4. Cryogenic tank; 5. Cryogenic molten salt pump; 6. Cryogenic molten salt control valve; 7. High-temperature tank; 8. High-temperature molten salt pump; 9. High-temperature molten salt control valve; 10. Brine heat exchanger; 11. Booster pump; 12. Water inlet control valve; 13. Air supply control valve;

[0049] 101. Valve stem; 102. Valve seat; 103. First electric heating tape; 104. Second electric heating tape. DETAILED DESCRIPTION

[0050] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0052] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0053] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0054] In the description of the embodiments of the present invention, it should be noted that the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0055] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0056] The technical terms involved in the present invention are now explained:

[0057] High-voltage plant transformer, whose full name is high-voltage plant transformer, is a key equipment in power plants used to convert the high-voltage electric energy output from the generator into the voltage level required by the plant power system, providing power for the plant loads (such as motors, lighting, control systems, etc.) within the power plant.

[0058] As mentioned in the background technology, currently, traditional energy storage methods are unable to meet the needs of power plants to significantly improve the operating flexibility of units due to many geographical restrictions, high transmission losses, weak emergency capabilities, and weak thermal and electric decoupling performance, and thus cannot achieve a stable supply of regional electricity and efficient use of energy.

[0059] In order to solve the above problems, the present invention provides a molten salt energy storage system for thermal and electric decoupling of power plants. The molten salt energy storage system can effectively improve the flexibility and efficiency of energy utilization in power plants and realize precise control of thermal and electric decoupling.

[0060] The present invention will be further explained below with reference to the accompanying drawings and embodiments:

[0061] For example, Figure 1 As shown, this embodiment provides a molten salt energy storage system for thermal-electric decoupling of a power plant, which is composed of a molten salt electric heating subsystem, a molten salt heat storage subsystem and a molten salt-steam-water heat exchange subsystem connected in sequence.

[0062] For example, Figure 2 As shown in the figure, the specific structure of the molten salt energy storage system for thermal and electrical decoupling of this power plant includes:

[0063] The molten salt electric heating subsystem, serving as the energy input front end, includes at least one high-voltage transformer 1. The transmission end of the high-voltage transformer 1 is connected to an intelligent power allocation device 2, which in turn is connected to an electric heater 3. The electric heater 3 is arranged vertically, with the molten salt inlet at its lower end and the molten salt outlet at its upper end. After the low-temperature molten salt from the molten salt heat storage subsystem flows through the electric heater 3, it absorbs the heat energy converted from the electrical energy and becomes high-temperature molten salt, achieving heat storage. The intelligent power allocation device 2 precisely regulates the power supply of the electric heater 3 according to preset strategies based on the power plant's operating conditions, such as during nighttime periods with low electricity prices and periods of tight power supply, to maximize economic and operational benefits.

[0064] The molten salt heat storage subsystem is used for the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt, and is composed of a low-temperature tank 4 and a high-temperature tank 7. The output end of the low-temperature tank 4 is connected in sequence to the low-temperature molten salt pump 5 and the low-temperature molten salt control valve 6, and then connected to the input end of the high-temperature tank 7 through the molten salt electric heating subsystem. The low-temperature tank 4 is used to store molten salt at room temperature or an initial low-temperature state, the low-temperature molten salt pump 5 provides power for the flow of molten salt, and the low-temperature molten salt control valve 6 accurately regulates the flow of molten salt to the electric heater 3; for example, in order to ensure a more stable operation effect; Figure 3 As shown, the control valve body of the low-temperature molten salt pump 5 and the low-temperature molten salt control valve 6 includes a valve stem 101 and a valve seat 102. A first electric heating tape 103 is wrapped around the valve stem 101, and a second electric heating tape 104 is laid on the inner wall of the valve seat 102. The first electric heating tape 103 and the second electric heating tape 104 are both connected to the molten salt electric heating subsystem. The design principle here is that since molten salt has a certain melting point, the control valve part is prone to molten salt solidification and blockage in a low-temperature environment or during shutdown. The electric heating tape can use a small amount of electricity from the molten salt electric heating subsystem to maintain the temperature of the valve stem and the valve seat above the melting point of the molten salt, ensuring that the control valve can be flexibly opened and closed at any time, thereby ensuring the reliability of the entire molten salt circulation system. The high-temperature tank 7 is connected to the molten salt-steam-water heat exchange subsystem through a high-temperature molten salt pump 8, and a high-temperature molten salt control valve 9 is provided between the high-temperature molten salt pump 8 and the molten salt-steam-water heat exchange subsystem. The control valve is used to accurately regulate the flow of high-temperature molten salt entering the heat exchange subsystem, dynamically adjust the heat release rate of the high-temperature molten salt in combination with the downstream thermal demand, and coordinate with the power plant steam supply system to avoid large fluctuations in steam supply.

[0065] The molten salt-steam-water heat exchange subsystem converts heat energy from molten salt to steam, precisely matching the thermal load requirements of the power plant. It includes a brine heat exchanger 10, a core heat exchange component. This utilizes the large temperature difference between high-temperature molten salt and water for efficient heat exchange, heating the water to steam. Water from the deaerator absorbs heat from the molten salt through the heat exchanger, transforming it into high-quality steam. This steam is then fed to the auxiliary steam or steam supply mains as needed, meeting the thermal process requirements of different areas of the power plant. The first inlet of the brine heat exchanger 10 is connected to the high-temperature molten salt output of the molten salt heat storage subsystem, that is, the output of the high-temperature tank 7 after passing through the high-temperature molten salt pump 8 and the high-temperature molten salt control valve 9. The second inlet is connected to the deaerator inlet, and the water inlet control valve 12 and the booster pump 11 are connected in sequence between the two to adjust the water inlet flow and pressure according to the heat load demand of the heat exchanger to ensure stable and efficient heat exchange. The first outlet of the brine heat exchanger 10 is connected to the low-temperature molten salt input of the molten salt heat storage subsystem, that is, connected back to the low-temperature tank 4. The second outlet is connected to the auxiliary steam or steam supply main pipe, and the gas supply control valve 13 is connected between the two to accurately control the output steam flow direction and flow, prevent pressure shocks and thermal imbalances from adversely affecting the power plant steam supply network, and ensure accurate steam supply. The various components of the entire molten salt energy storage system operate in coordination, effectively improving the flexibility and efficiency of energy utilization in the power plant and achieving precise control of thermal decoupling.

[0066] Illustratively, this embodiment further provides a method for operating a molten salt energy storage system for thermal-electric decoupling in a power plant, including:

[0067] The molten salt electric heating subsystem is used to heat the low-temperature molten salt through electric heating with high-voltage power plant transformer energy. The power plant operating conditions and energy storage requirements are monitored in real time through the power intelligent allocation device, and the power of the electric heater is adjusted. The low-temperature molten salt enters from the bottom of the electric heater, and naturally rises due to the heat under the vertical arrangement structure, and is converted into high-temperature molten salt and flows out to the molten salt heat storage subsystem.

[0068] The molten salt heat storage subsystem realizes the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt; the low-temperature molten salt pump extracts molten salt from the low-temperature tank, and is sent to the electric heater after precise flow control by the low-temperature molten salt control valve, and the high-temperature molten salt flows into the high-temperature tank for storage. The high-temperature molten salt pump sends the high-temperature molten salt to the molten salt-steam-water heat exchange subsystem through the high-temperature molten salt control valve as needed. During this period, the low-temperature molten salt control valve and the high-temperature molten salt control valve dynamically adjust the opening according to the system temperature, pressure and thermal load feedback.

[0069] The high-temperature molten salt is exchanged with water through the molten salt-steam-water heat exchange subsystem, and the generated steam is then supplied to the auxiliary steam or steam supply main pipe; the water from the deaerator is regulated by the water inlet control valve and the booster pump and enters the brine heat exchanger, where it exchanges heat with the high-temperature molten salt to generate steam. The steam is then replenished to the auxiliary steam or steam supply main pipe as needed through the gas supply control valve to meet the thermal needs of all links in the power plant. Throughout the entire process, the subsystems work closely together to achieve flexible regulation of thermal and electrical decoupling based on real-time changes in electrical and thermal loads.

[0070] For example, the molten salt energy storage system for thermal-electric decoupling of a power plant provided in this embodiment is applied and implemented in combination with actual scenarios. The specific implementation process is as follows:

[0071] Example 1:

[0072] At a coal-fired power plant with an installed capacity of 600MW, during peak daytime electricity load, the power plant generates electricity to meet the grid's power needs. During this time, the thermal load is relatively stable, and the molten salt energy storage system is in a heat-maintaining standby mode. In the molten salt thermal storage subsystem, the high-temperature tank stores high-temperature molten salt, which has been heated electrically during the nighttime off-peak hours. The high-temperature molten salt pump is stopped, the high-temperature molten salt control valve is closed, and the low-temperature molten salt pump operates at a low frequency to maintain slow circulation of the molten salt in the low-temperature tank to prevent local solidification. The low-temperature molten salt control valve is slightly open to maintain a certain amount of cold salt flow, ensuring the basic fluidity of the entire molten salt system.

[0073] As night falls, electricity demand reaches a low point and grid electricity prices drop significantly. The power plant activates the molten salt electric heating subsystem to fully utilize heat storage. The output voltage of the high-voltage transformer stabilizes at an appropriate level, and the intelligent power allocation device adjusts the electric heater to maximum power according to the preset economic operation strategy. Driven by the powerful low-temperature molten salt pump, the low-temperature molten salt flows at a high flow rate through the low-temperature molten salt control valve, which is opened to its maximum stroke, and enters the bottom of the vertical electric heater. The heating wire inside the heater rapidly converts electrical energy into heat. The low-temperature molten salt decreases in density as it rises along the heater, flowing out of the upper outlet as high-temperature molten salt and into a high-temperature tank for storage. Due to the low thermal load demand at night, the molten salt-steam-water heat exchange subsystem maintains only a minimum water flow. The water inlet control valve is minimally opened, the booster pump operates at a low frequency, and the brine heat exchanger operates at a low load, generating a small amount of steam just to maintain the basic temperature of the auxiliary steam network. The air supply control valve limits the output current to ensure stable steam pressure and avoid energy waste. Simultaneously, the high-temperature molten salt control valve is tightly closed to prevent the high-temperature molten salt from prematurely entering the heat exchange process. In this way, a large amount of electricity can be stored in the form of high-temperature molten salt thermal energy using the night-time off-peak electricity, thus reserving energy for subsequent decoupled operation of heating and power supply during peak electricity consumption.

[0074] Example 2:

[0075] A gas-steam combined cycle power plant with an installed capacity of 400MW must meet both grid-connected power demand and the large-scale heating needs of the surrounding area during the winter heating season, necessitating a critical need for thermal decoupling. During peak daytime heating hours, when power load is moderate, the molten salt electric heating subsystem operates at medium power to maintain sufficient thermal storage. An intelligent power allocation device monitors grid electricity prices, power generation, and heating load in real time to dynamically adjust the power of the electric heaters.

[0076] In the molten salt heat storage subsystem, both the low-temperature and high-temperature molten salt pumps operate at variable frequency according to heat load demand. The low-temperature and high-temperature molten salt control valves finely adjust their openings based on feedback from the inlet and outlet water temperatures and steam pressure of the brine heat exchanger, ensuring a steady flow of high-temperature molten salt into the brine heat exchanger and providing sufficient heat for heating. Water from the deaerator flows through the inlet control valve, which adjusts its opening according to the heat exchanger's inlet water temperature. A booster pump increases the water pressure to ensure sufficient heat exchange within the heat exchanger. The resulting large amount of high-temperature steam is fully replenished to the steam main via the gas supply control valve, meeting the heating network's heat demand.

[0077] When power demand suddenly spikes, such as when surrounding industrial enterprises collectively start up large equipment and the power grid urgently requests the power plant to increase its power generation capacity, the molten salt-steam-water heat exchange subsystem responds swiftly. The gas supply control valve is slightly closed, reducing steam output to the heating network and retaining some heat energy in the molten salt system. Simultaneously, the molten salt electric heating subsystem's intelligent power allocation device instantly reduces the power of the electric heater to maintain only the basic power input required to keep the molten salt cool. The high-temperature molten salt pump increases flow, rapidly pumping more high-temperature molten salt from the high-temperature tank into the brine heat exchanger. The molten salt energy storage rapidly replenishes the steam-water circulation heat during power generation, ensuring efficient operation of the steam turbine and achieving a significant jump in power generation in a short period of time to meet peak power demand. Once the power load stabilizes, the systems resume coordinated heating and heat storage operation. This dynamic thermal and electrical decoupling control ensures efficient and stable operation of the power plant under complex operating conditions.

[0078] Example 3:

[0079] A small cogeneration plant with 100MW of installed capacity primarily supplies electricity and heating to surrounding industrial parks. During the spring transition season, large temperature swings between day and night lead to fluctuating electricity demand during the day, while heat demand is relatively low and concentrated during specific periods. During normal daytime operation, the molten salt electric heating subsystem employs an intermittent operation strategy based on real-time electricity prices and power load forecasts. During periods of low electricity prices, the molten salt is centrally heated for thermal storage. High-voltage transformers are used for power supply, and an intelligent power allocation device adjusts the electric heater power to an appropriate level. The low-temperature molten salt is then heated and stored in a high-temperature tank.

[0080] When a chemical company within the industrial park requested an increase in steam usage, the molten salt-steam-water heat exchange subsystem quickly activated its emergency response. The inlet control valve quickly opened wide, and the booster pump increased its power to ensure inlet flow. The high-temperature molten salt in the brine heat exchanger efficiently exchanged heat with the water. The high-temperature molten salt control valve precisely adjusted the steam flow demand, ensuring stable output steam pressure that met the chemical company's process requirements. Simultaneously, the low-temperature molten salt pump in the molten salt heat storage subsystem accelerated the extraction of low-temperature molten salt and delivered it to the electric heater. The high-voltage transformer appropriately increased its power supply, allowing the electric heater to rapidly heat up and replenish the high-temperature molten salt. This maintained the stability and continuity of the entire system's heat supply, enabling flexible heat and power supply to different users within the industrial park at different times, effectively improving the energy flexibility and economic benefits of small cogeneration plants.

[0081] In this embodiment, the operation of the molten salt energy storage system is divided into two working processes: a molten salt heat storage cycle and a molten salt heat release cycle. Molten salt heat storage cycle: The low-temperature molten salt in the low-temperature molten salt tank enters the molten salt electric heater through a low-temperature molten salt pump. The molten salt is heated in the electric heater using wind power, photovoltaic power, and nighttime off-peak electricity through an intelligent complementary system. The heated high-temperature molten salt enters the high-temperature molten salt tank for storage, completing the molten salt heat storage cycle. Molten salt heat release cycle: The high-temperature molten salt in the high-temperature molten salt tank enters the heat exchange system through a high-temperature molten salt pump to exchange heat with the feed water. The feed water is heated into steam. The molten salt after heat release enters the cold salt tank for storage, completing the molten salt heat release cycle.

[0082] Through the above-mentioned actual application cases of power plants of different types and under different operating conditions, it can be seen that the molten salt energy storage system and working method of the present invention can accurately achieve thermal and electric decoupling according to the characteristics of each plant, operating time, and changes in electricity / heat load. Whether it is a large-scale thermal power plant, a combined cycle power plant or a small cogeneration plant, it can play a significant role in improving energy utilization efficiency, reducing operating costs, and ensuring the reliability of power supply and heating, and has broad market promotion prospects.

[0083] In summary, this embodiment provides a molten salt energy storage system for thermoelectric decoupling in a power plant and its operating method. Compared with existing thermoelectric decoupling methods, this system has the following advantages:

[0084] First, efficient thermal decoupling: Through the sophisticated architecture and intelligent operation methods of the molten salt energy storage system, the changes in power and thermal loads are accurately matched, breaking the limitations of the strong coupling of electricity and heat in traditional power plants. Heat can be stored during low-power consumption, used during peak hours, or flexibly switched to heating and power supply modes on demand, greatly improving the comprehensive energy utilization efficiency and reducing energy waste.

[0085] Second, operational economic optimization: With the help of intelligent power allocation devices, the power of electric heaters is dynamically adjusted according to electricity price fluctuations and load demand, making full use of cheap electricity storage during off-peak electricity price periods, reducing power generation costs, improving the economic benefits of power plants, and enhancing market competitiveness.

[0086] Third, the system has high reliability: the molten salt heat storage subsystem has a reasonable layout of high and low temperature tanks and comprehensive pump and valve design, such as the precise flow regulation of the low-temperature molten salt control valve and the high-temperature molten salt control valve, and the electric heating tape to prevent the molten salt from solidifying. Combined with the stable heat exchange and precise steam supply of the molten salt-steam-water heat exchange subsystem, the stability and reliability of the entire system under complex working conditions and long-term operation are guaranteed, reducing the risk of failure and shutdown, and ensuring the continuous operation of the power plant.

[0087] Fourth, wide adaptability: Whether it is large-capacity thermal power, combined cycle power generation or small cogeneration plants, the present invention can flexibly adapt to different seasons, day and night, and changes in user demand. It can achieve efficient operation of each plant through thermoelectric decoupling optimization and has universal promotion value.

[0088] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention.

Claims

1. A molten salt energy storage system for thermal and electrical decoupling in a power plant, characterized in that: include: A molten salt electric heating subsystem, a molten salt heat storage subsystem and a molten salt-steam-water heat exchange subsystem connected in sequence; The molten salt electric heating subsystem is used to heat the low-temperature molten salt by electric heating using high-voltage power plant transformers; The molten salt heat storage subsystem is used to realize the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt; The molten salt-steam-water heat exchange subsystem is used to exchange heat with water through high-temperature molten salt, and supply the generated steam to the auxiliary steam or steam supply main pipe.

2. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 1, characterized in that: The molten salt electric heating subsystem comprises at least one group of high-voltage transformers (1); the transmission end of the high-voltage transformer (1) is connected to an electric heater (3); the low-temperature molten salt of the molten salt heat storage subsystem flows through the electric heater (3) and is converted into high-temperature molten salt to achieve heat storage.

3. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 2, characterized in that: The molten salt electric heating subsystem further comprises a power intelligent allocation device (2), which is connected between the high-voltage transformer (1) and the electric heater (3) and is used for automatically allocating the output electric power according to a preset power.

4. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 2, characterized in that: The electric heater (3) is arranged vertically, with a molten salt inlet at the lower end and a molten salt outlet at the upper end.

5. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 1, characterized in that: The molten salt heat storage subsystem comprises a low-temperature tank (4) and a high-temperature tank (7); The output end of the low-temperature tank (4) is connected to the input end of the high-temperature tank (7) through the molten salt electric heating subsystem; The high-temperature tank (7) is connected to the molten salt-steam-water heat exchange subsystem via a high-temperature molten salt pump (8); The output end of the low-temperature tank (4) is provided with a low-temperature molten salt pump (5) and a low-temperature molten salt control valve (6) in sequence.

6. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 5, characterized in that: The low-temperature molten salt control valve (6) comprises a control valve body; The control valve body comprises a valve stem (101) and a valve seat (102); A first electric heating tape (103) is wound around the valve stem (101); The inner wall of the valve seat (102) is paved with a second electric heating tape (104); The first electric heating tape (103) and the second electric heating tape (104) are both connected to the molten salt electric heating subsystem.

7. The molten salt energy storage system for thermal-electric decoupling of a power plant according to claim 5, characterized in that: A high-temperature molten salt control valve (9) is provided between the high-temperature molten salt pump (8) and the molten salt-steam-water heat exchange subsystem.

8. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 1, characterized in that: The molten salt-steam-water heat exchange subsystem comprises a brine heat exchanger (10); a first inlet of the brine heat exchanger (10) is connected to a high-temperature molten salt output end of the molten salt heat storage subsystem, a second inlet is connected to a deaerator inlet, a first outlet is connected to a low-temperature molten salt input end of the molten salt heat storage subsystem, and a second outlet is connected to an auxiliary steam or steam supply main pipe.

9. The molten salt energy storage system for thermal and electrical decoupling of a power plant according to claim 8, characterized in that: A water inlet control valve (12) and a booster pump (11) are sequentially connected between the second inlet of the brine heat exchanger (10) and the deaerator; A gas supply control valve (13) is connected between the second outlet of the brine heat exchanger (10) and the auxiliary steam or steam supply main pipe.

10. A method for operating a molten salt energy storage system for thermal and electric decoupling of a power plant, based on the molten salt energy storage system for thermal and electric decoupling of a power plant according to any one of claims 1 to 9, characterized in that: include: The molten salt electric heating subsystem is used to heat the low-temperature molten salt by electric heating with high-voltage power plant transformer energy; The molten salt heat storage subsystem realizes the circulation transmission of high-temperature molten salt and low-temperature molten salt and the storage of high-temperature molten salt; The high-temperature molten salt is exchanged with water through the molten salt-steam-water heat exchange subsystem, and the generated steam is then supplied to the auxiliary steam or steam supply main pipe.

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