Method and device for improving flexibility of thermal power plant by coupling small pulverized coal bunker and molten salt energy storage

Abstract

The application provides a method and device for improving the flexibility of a thermal power plant by coupling a small coal bunker and a molten salt energy storage, comprising establishing a small coal bunker flexible storage and supply system and a molten salt energy storage system, coupling the small coal bunker flexible storage and supply system and the molten salt energy storage system to a coal-fired thermal power unit to enhance the flexible peak regulation capacity of the coal-fired thermal power unit, wherein the small coal bunker flexible storage and supply system is coupled to a combustion system to shorten the fuel supply response time of a boiler, one end of the molten salt energy storage system is connected to a generator through a molten salt electric heating module to convert the excess power energy in the flexible peak regulation process of the coal-fired thermal power unit into the form of molten salt sensible heat for storage, and the other end of the molten salt energy storage system is connected to a steam-water system through a molten salt-steam heat exchange module to shorten the steam turbine response time by using high-temperature molten salt to heat steam working medium. The small coal bunker flexible storage and supply system and the molten salt energy storage system are coupled to the coal-fired thermal power unit, which can effectively improve the rapid load rising and falling capacity of the coal-fired thermal power unit and realize efficient energy utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible peak regulation in thermal power plants, and in particular to a method and device for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage. Background Art

[0002] Under the dual pressures of fossil fuel depletion and rising environmental concerns, renewable energy generation has become the most promising option for the power system. However, renewable energy generation is intermittent and unstable, leading to widespread phenomena such as wind and solar power curtailment. To meet the application and development of renewable energy, the power grid is increasingly demanding the flexible peak-shaving capabilities of coal-fired power plants. However, existing units were not designed with deep peak-shaving in mind, resulting in significant limitations in low-load operation and the ability to rapidly ramp up and down loads. Therefore, upgrading thermal power units to provide greater flexibility is a major trend in power generation transformation and a pressing priority.

[0003] On the one hand, utilizing molten salt energy storage technology to achieve thermoelectric decoupling, thermal / electrical energy storage, and delayed reuse, thereby enhancing unit flexibility, is a relatively mature solution. In recent years, molten salt energy storage technology has rapidly advanced. High-temperature molten salts can maintain chemical stability at temperatures of 600°C and above under normal pressure, which is a good match for the steam temperature parameters required for turbine operation. Existing molten salt energy storage technology utilizes molten salt heat release to heat feedwater, enabling rapid frequency modulation of the unit. However, this technology, which uses molten salt energy storage to heat boiler feedwater and increase boiler exhaust gas temperature, has limited effectiveness in rapidly increasing and decreasing the load capacity of coal-fired units.

[0004] On the other hand, large-capacity power station boilers are currently generally equipped with direct-blowing pulverizing systems. The ability to quickly increase or decrease loads is an important part of the flexible peak regulation of coal-fired power plants. The lag in coal powder supply in direct-blowing pulverizing systems seriously restricts the load change rate of coal-fired units. Summary of the Invention

[0005] The purpose of the present invention is to address the problems raised in the above background technology and provide a method and device for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage, so as to solve the limitations of coal-fired thermal power units in the prior art in terms of low-load operation stability and rapid load increase and decrease capabilities.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The method for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage includes the following steps:

[0008] Establish a flexible storage and supply system for small powder silos and a molten salt energy storage system;

[0009] The flexible storage and supply system of the small powder silo and the molten salt energy storage system are simultaneously coupled to the coal-fired thermal power unit to enhance the flexible peak-shaving capability of the coal-fired thermal power unit. The coal-fired thermal power unit includes a combustion system, a steam-water system, and an electrical system. The flexible storage and supply system of the small powder silo is coupled to the combustion system, and one end of the molten salt energy storage system is connected to the generator through a molten salt power module, and the other end is connected to the steam-water system through a molten salt-steam heat exchange module.

[0010] When the coal-fired power unit is operating at a stable load, the amount of pulverized coal in the small pulverized coal silo flexible storage and supply system is adjusted to maintain at a first preset threshold, and the heat of the molten salt energy storage system is adjusted to maintain at a second preset threshold;

[0011] During the rapid load reduction process of the coal-fired thermal power unit, the molten salt energy storage system converts the excess power energy of the generator into molten salt sensible heat through the molten salt electric heating module and stores it, quickly reducing the external load of the coal-fired thermal power unit. At the same time, the small powder silo flexible storage and supply system stores the redundant pulverized coal of the combustion system, quickly reducing the heat provided by the combustion system to the steam-water system, thereby reducing the load of the steam-water system. When the steam-water system drops to the target load state, the small powder silo flexible storage and supply system stops storing pulverized coal, and the combustion system and steam-water system maintain stable load operation. At the same time, the molten salt electric heating module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation, and the coal-fired thermal power unit completes the rapid load reduction process;

[0012] During the rapid load increase process of the coal-fired power unit, the pulverized coal in the small pulverized coal silo flexible storage and supply system is supplied to the combustion system for combustion, which quickly increases the steam production rate of the steam-water system. At the same time, the molten salt energy storage system uses the molten salt-steam heat exchange module to exchange part of the steam working fluid in the steam-water system with high-temperature molten salt in the molten salt-steam heat exchanger, thereby shortening the response time of the steam turbine during the flexible peak regulation process. When the steam-water system reaches the target load state, the small pulverized coal silo flexible storage and supply system stops supplying pulverized coal to the combustion system, and the combustion system and the steam-water system maintain stable load operation. At the same time, the molten salt-steam heat exchange module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation. The coal-fired power unit completes the rapid load increase process.

[0013] Furthermore, a flexible storage and supply system for a small powder silo is coupled with the primary air duct of the combustion system to shorten the fuel supply response time of the combustion system. The flexible storage and supply system for a small powder silo includes an inlet control valve, a gas-powder separator, a small powder silo, and an outlet control valve connected in sequence. The inlet control valve is connected to one end of the primary air duct, and the outlet control valve is connected to the other end of the primary air duct. The gas-powder separator introduces exhaust gas into the furnace through a pipeline.

[0014] When the coal-fired power unit is operating at a stable load, the pulverized coal content in the small pulverized coal silo is obtained. If the pulverized coal in the small pulverized coal silo is lower than a first preset threshold, the outlet control valve is closed and the inlet control valve is adjusted to maintain a first opening threshold until the pulverized coal in the small pulverized coal silo reaches the first preset threshold, at which point the inlet control valve is closed.

[0015] During the rapid load reduction process of the coal-fired power unit, the outlet control valve remains closed, and the opening of the inlet control valve is increased to the second opening threshold, so that the excess pulverized coal in the combustion system is stored in the small pulverized coal bin. When the steam-water system reaches the target load state, the inlet control valve is closed;

[0016] During the rapid load increase of the coal-fired power unit, the inlet control valve remains closed, and the outlet control valve opening is increased to the third opening threshold so that the pulverized coal in the small pulverized coal bin is supplied to the combustion system. When the steam-water system reaches the target load state, the outlet control valve is closed.

[0017] Furthermore, the steam working medium discharged from the outlet of the high-pressure cylinder in the steam-water system is divided into two sub-paths, so that the steam working medium from the high-pressure cylinder can enter the reheater through the first sub-path controlled by the steam regulating valve 1 for heating and then be transported to the medium-pressure cylinder, and can also enter the molten salt-steam heat exchange module of the molten salt energy storage system through the second sub-path controlled by the steam regulating valve 2. The molten salt-steam heat exchange module is used to heat the steam working medium from the high-pressure cylinder to a first preset temperature range and then transport it to the medium-pressure cylinder to perform work. The time required for the steam working medium to be transported to the medium-pressure cylinder after heat exchange through the second sub-path is shorter than the time required for the steam working medium to be transported to the medium-pressure cylinder after being heated through the first sub-path;

[0018] At the same time, the electricity generated by the generator is divided into two circuits for transmission. The first circuit is used to supply power to the external power grid, and the second circuit is used to supply power to the molten salt electric heating module.

[0019] When the coal-fired power unit is operating at a stable load, the steam regulating valve 2 is closed, and the molten salt-steam heat exchange module is in a closed state. When the high-temperature molten salt stored in the molten salt energy storage system is below a second preset threshold, the molten salt electric heating module is controlled to switch to a low-power state until the high-temperature molten salt stored in the molten salt energy storage system reaches the second preset threshold, at which point the molten salt electric heating module stops working.

[0020] During the rapid load reduction process of the coal-fired power plant, the second steam regulating valve is closed, the molten salt-steam heat exchange module is in the closed state, and the molten salt electric heating module is controlled to switch to a high-power state to operate, reducing the power supply of the first circuit to the outside, so that more electricity generated by the generator enters the second circuit. The molten salt in the low-temperature molten salt tank is heated to a second preset temperature range by the molten salt electric heating module and then pumped directly to the high-pressure molten salt tank for storage. When the steam-water system reaches the target load state, the molten salt electric heater is controlled to switch to a low-power state to operate, reducing the amount of electricity entering the second circuit until the power generation of the generator drops to the target load, and the molten salt electric heating module stops working;

[0021] During the rapid load increase process of the coal-fired power unit, the molten salt electric heating module is in the closed state, the steam control valve 2 is opened to the fourth opening threshold, and the opening of the steam control valve 1 is reduced to the fifth opening threshold, so that part of the steam working medium enters the molten salt-steam heat exchange module through the second sub-path for heating and then directly enters the intermediate pressure cylinder to perform work, shortening the load increase response time of the steam turbine. When the steam-water system reaches the target load state, the opening of the steam control valve 1 is increased to the sixth opening threshold, and the opening of the steam control valve 2 is reduced to the seventh opening threshold to control the steam working medium flow entering the molten salt-steam heat exchange module. After the opening of the steam control valve 1 is adjusted to the eighth opening threshold and the steam control valve 2 is reduced to the closed state, the molten salt-steam heat exchange module stops working.

[0022] Furthermore, the molten salt-steam heat exchange module and the molten salt electric heating module are partially connected in series to form a loop to realize the conversion of electrical energy and thermal energy. The molten salt-steam heat exchange module transfers the heat in the high-temperature molten salt to the steam working medium, and the high-temperature molten salt is converted into low-temperature molten salt for storage. The molten salt electric heating module converts the low-temperature molten salt into high-temperature molten salt after electric heating, so that the energy of excess electricity is converted into sensible heat for storage.

[0023] A device for coupling a small powder silo with molten salt energy storage to improve the flexibility of a thermal power plant comprises:

[0024] Coal-fired power units, including combustion systems, steam-water systems, and electrical systems;

[0025] The small pulverized coal silo flexible storage and supply system is coupled with the combustion system. The small pulverized coal silo flexible storage and supply system is used to store the redundant pulverized coal in the combustion system, or the small pulverized coal silo flexible storage and supply system supplies the internally stored pulverized coal to the combustion system for combustion;

[0026] The molten salt energy storage system includes a molten salt electric heating module and a molten salt-steam heat exchange module. The molten salt electric heating module is connected to the generator, and the molten salt-steam heat exchange module is connected to the steam-water system.

[0027] Furthermore, the combustion system includes a raw coal hopper, a coal feeder, a pulverizer, a coarse powder separator, a primary fan, and an air preheater. The raw coal hopper, the coal feeder, the pulverizer, and the coarse powder separator are connected in sequence. One outlet of the primary fan is connected to the pulverizer to deliver cold air, and the other outlet is connected to the pulverizer through the air preheater to deliver hot air. The mixed air formed by the cold air and the hot air carries the pulverized coal through the coarse powder separator and the primary air duct into the furnace for combustion.

[0028] The flexible storage and supply system of the small powder silo includes an inlet control valve, a gas-powder separator, a small powder silo and an outlet control valve connected in sequence, wherein the inlet control valve is connected to one end of the primary air duct, and the outlet control valve is connected to the other end of the primary air duct. The gas-powder separator introduces the exhaust gas into the furnace through the pipeline.

[0029] Furthermore, the steam-water system includes a high-pressure cylinder, a reheater, an intermediate-pressure cylinder, and a low-pressure cylinder arranged in sequence, and the electrical system includes a generator, a main transformer, and an external power grid arranged in sequence, and the bearings of the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder on the steam-water system are coaxially connected to the generator;

[0030] The molten salt electric heating module includes a plant transformer, a power regulator, a molten salt electric heater, a low-temperature molten salt pump and a low-temperature molten salt tank, which are arranged in sequence. The plant transformer, the power regulator and the molten salt electric heater are connected in sequence, the low-temperature molten salt tank, the low-temperature molten salt pump and the molten salt electric heater are connected in sequence, and the molten salt-steam heat exchange module includes a high-temperature molten salt tank, a high-temperature molten salt pump and a molten salt-steam heat exchanger which are connected in sequence.

[0031] Among them, the outlet of the high-pressure cylinder is connected to the first sub-circuit and the second sub-circuit, the first sub-circuit is controlled by steam regulating valve 1 and the end is connected to the inlet of the reheater, the outlet of the reheater is connected to the inlet of the medium-pressure cylinder, the second sub-circuit is controlled by steam regulating valve 2 and the end is connected to the first fluid inlet of the molten salt-steam heat exchanger, the first fluid outlet of the heat exchanger is connected to the inlet of the medium-pressure cylinder, the second fluid inlet of the heat exchanger is connected to the high-temperature molten salt pump, the second fluid outlet of the heat exchanger is connected to the low-temperature molten salt tank, the molten salt inlet in the molten salt electric heater is connected to the low-temperature molten salt pump, the molten salt outlet in the molten salt electric heater is connected to the high-temperature molten salt tank, the generator is electrically connected to the main transformer through the first circuit, the main transformer adjusts the voltage to supply power to the external power grid, the generator is electrically connected to the plant transformer through the second circuit, and supplies power to the molten salt electric heater after adjusting the voltage and power respectively through the plant transformer and the power regulator.

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

[0033] (1) The present invention provides a method and device for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage. Compared with the use of a molten salt energy storage system alone for peak regulation, this solution is more flexible. The molten salt energy storage system equipment and the molten salt itself are expensive, and can only allow the steam-water system to respond quickly, but cannot improve the rapid response of the entire coal-fired thermal power unit. Existing large-capacity power station boilers are mostly equipped with direct-blowing pulverizing systems, which have lags. Therefore, relying solely on the molten salt energy storage system is difficult to meet the rapid peak regulation needs of thermal power units.

[0034] (2) The method and device provided by the present invention for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage technology couples the flexible storage and supply technology of the small powder silo and the molten salt energy storage technology with existing coal-fired thermal power units to form a new system. By combining the flexible storage and supply system of the small powder silo and the molten salt energy storage system, deep peak regulation is performed on the existing coal-fired thermal power units, which can meet the needs of rapid peak regulation of the power grid.

[0035] (3) The method and device provided by the present invention for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage. The flexible storage and supply system of the small powder silo is coupled with the combustion system, and has a simple structure. Existing coal-fired thermal power units can be directly modified. Compared with the use of a single molten salt energy storage technology for peak regulation, the cost is low and the rapid peak regulation effect is better.

[0036] (4) The method and device provided by the present invention for improving the flexibility of thermal power plants by coupling a small powder silo and molten salt energy storage can store redundant coal powder in the flexible storage and supply system of the small powder silo during the low-load operation process of the coal-fired thermal power unit in the "valley" period, and at the same time convert the excess electrical energy into molten salt sensible heat for storage through the molten salt electric heating module, thereby ensuring the minimum output of the coal-fired thermal power unit at the "valley" period, improving the safety and economy of the coal-fired thermal power unit, and not easily causing waste of coal powder and loss of steam heat, thereby ensuring the stable operation of the coal-fired thermal power unit at low load. When the coal-fired thermal power unit is operating at high load at "peak", the coupling of the flexible storage and supply system of the small powder silo and the combustion system can shorten the coal powder supply time, so that the steam-water system responds to the load requirements more quickly. At the same time, part of the steam working medium in the steam-water system of the molten salt-steam heat exchange module is heated by high-temperature molten salt, thereby shortening the response time of the steam turbine in the flexible peak-shaving process, so that the electrical system responds more quickly. The combination of the two can make the entire thermal power system respond, and expand the peak-shaving range of the unit more quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 Schematic diagram of the method of coupling a small powder silo and molten salt energy storage to improve the flexibility of a thermal power plant according to the present invention.

[0039] Figure 2 This is a schematic diagram of the device for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to the present invention.

[0040] Figure 3 This is an overall schematic diagram of the device for coupling a small powder silo and molten salt energy storage to improve the flexibility of a thermal power plant.

[0041] 1. Raw coal hopper; 2. Coal feeder; 3. Coal mill; 4. Coal powder separator; 5. Primary fan; 6. Air preheater; 7. Inlet control valve; 8. Air-powder separator; 9. Small coal silo; 10. Outlet control valve; 11. Primary air duct; 12. Economizer; 13. Water-cooled wall; 14. Superheater; 15. Reheater; 16. High-pressure cylinder; 17. Medium-pressure cylinder; 18. Low-pressure cylinder; 19. Generator; 20. Main transformer; 21. External power grid; 22. Condenser; 23. Condensate pump; 24. Low-pressure heater; 25. Deaerator; 26. Feedwater pump; 27. High-pressure heater; 28. Steam regulating valve 1; 29. ​​Plant transformer; 30. Power regulator; 31. Molten salt electric heater; 32. High-temperature molten salt tank; 33. High-temperature molten salt pump; 34. Low-temperature molten salt tank; 35. Low-temperature molten salt pump; 36. Heat exchanger; 37. Steam regulating valve 2. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0044] Example 1

[0045] Example 1 provides a method for coupling a small powder silo and molten salt energy storage to improve the flexibility of a thermal power plant, such as Figure 1 As shown, the following steps are included:

[0046] Establish a flexible storage and supply system for small powder silos and a molten salt energy storage system;

[0047] The flexible storage and supply system of the small powder silo and the molten salt energy storage system are simultaneously coupled to the coal-fired thermal power unit to enhance the flexible peak-shaving capability of the coal-fired thermal power unit. The coal-fired thermal power unit includes a combustion system, a steam-water system, and an electrical system. The flexible storage and supply system of the small powder silo is coupled to the combustion system, and one end of the molten salt energy storage system is connected to the generator through a molten salt power module, and the other end is connected to the steam-water system through a molten salt-steam heat exchange module.

[0048] When the coal-fired power unit is operating at a stable load, the amount of pulverized coal in the small pulverized coal silo flexible storage and supply system is adjusted to maintain at a first preset threshold, and the heat of the molten salt energy storage system is adjusted to maintain at a second preset threshold;

[0049] During the rapid load reduction process of the coal-fired thermal power unit, the molten salt energy storage system converts the excess electrical energy of the electrical system into molten salt sensible heat through the molten salt electric heating module and stores it, quickly reducing the external load of the coal-fired thermal power unit. At the same time, the small powder silo flexible storage and supply system stores the redundant pulverized coal of the combustion system, quickly reducing the heat provided by the combustion system to the steam-water system, thereby reducing the load of the steam-water system. When the steam-water system drops to the target load state, the small powder silo flexible storage and supply system stops storing the pulverized coal generated by the combustion system, and the combustion system and the steam-water system maintain stable load operation. At the same time, the molten salt electric heating module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation. The coal-fired thermal power unit completes the rapid load reduction process;

[0050] During the rapid load increase process of the coal-fired power unit, the pulverized coal in the small pulverized coal silo flexible storage and supply system is supplied to the combustion system for combustion, which quickly increases the steam production rate of the steam-water system. At the same time, the molten salt energy storage system uses the molten salt-steam heat exchange module to heat part of the steam working medium in the steam-water system using high-temperature molten salt, thereby shortening the response time of the steam turbine during the flexible peak regulation process. When the steam-water system reaches the target load state, the small pulverized coal silo flexible storage and supply system stops supplying pulverized coal to the combustion system, and the combustion system and the steam-water system maintain stable load operation. At the same time, the molten salt-steam heat exchange module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation. The coal-fired power unit completes the rapid load increase process.

[0051] The method provided in this embodiment for coupling a small powder silo with molten salt energy storage to improve the flexibility of a thermal power plant is more flexible than equipping coal-fired thermal power units with a molten salt energy storage system for peak regulation. First, the equipment and molten salt of the molten salt energy storage system are expensive. When the molten salt energy storage system is used alone to quickly increase or decrease the load, the cost is relatively high. Second, the molten salt energy storage system can only enable the electrical system to respond quickly, but cannot improve the rapid response of the entire coal-fired thermal power unit. In addition, currently existing large-capacity power station boilers are generally equipped with a direct-blowing pulverizing system, which has a certain hysteresis. For example, when the load needs to be reduced quickly, the molten salt energy storage system is continuously recovering the heat of the steam, while the direct-blowing pulverizing system is still supplying pulverized coal for combustion, which will result in a large amount of pulverized coal being wasted. When the load needs to be increased quickly, the direct-blowing pulverizing system cannot quickly increase the pulverized coal supply. It is difficult to meet the rapid peak regulation requirements by relying solely on the molten salt energy storage system. Therefore, equipping coal-fired thermal power units with a molten salt energy storage system for peak regulation has certain limitations.

[0052] This embodiment couples the flexible storage and supply technology of small powder silos and molten salt energy storage technology with existing coal-fired thermal power units to form a new system. By combining the flexible storage and supply system of small powder silos and the molten salt energy storage system, deep peak regulation is performed on the existing coal-fired thermal power units, which can meet the needs of rapid peak regulation of the power grid.

[0053] Moreover, the small powder silo flexible storage and supply system of this embodiment is coupled with the combustion system, has a simple structure, and can be directly modified for existing coal-fired power units. Compared with the use of a single molten salt energy storage technology for peak regulation, it has low cost and better rapid peak regulation effect.

[0054] This embodiment can store excess coal powder during the "valley" low-load operation of the coal-fired power unit in a small powder bin flexible storage and supply system, and at the same time convert the excess electricity into molten salt sensible heat through the molten salt electric addition module and store it, thereby ensuring the minimum output of the coal-fired power unit during the "valley", improving the safety and economy of the coal-fired power unit, and not easily causing waste of coal powder and loss of steam heat, ensuring the stable operation of the coal-fired power unit at low load. When the coal-fired power unit is operating at a "peak" high load, the coupling of the small powder bin flexible storage and supply system and the combustion system can shorten the coal powder supply time, so that the steam-water system responds to load requirements more quickly. At the same time, part of the steam working fluid in the steam-water system of the molten salt-steam heat exchange module is heated by high-temperature molten salt, thereby shortening the response time of the steam turbine in the flexible peak-shaving process, making the electrical system respond faster. The combination of the two can make the entire thermal power system respond, and expand the peak-shaving range of the unit more quickly.

[0055] In Example 1, the small powder silo flexible storage and supply system is coupled with the combustion system, and the load adjustment method for the coal-fired power unit is as follows:

[0056] The small powder silo flexible storage and supply system is coupled with the primary air duct 11 of the combustion system to shorten the fuel supply response time of the combustion system. The small powder silo flexible storage and supply system includes an inlet control valve 7, an air-powder separator 8, a small powder silo 9 and an outlet control valve 10 connected in sequence, wherein the inlet control valve 7 is connected to one end of the primary air duct 11, and the outlet control valve 10 is connected to the other end of the primary air duct 11. The air-powder separator 8 introduces the exhaust gas into the furnace through a pipeline;

[0057] When the coal-fired power unit is operating at a stable load, the pulverized coal content in the small pulverized coal bin 9 is obtained. If the pulverized coal content in the small pulverized coal bin 9 is lower than a first preset threshold, the outlet control valve 10 is closed and the inlet control valve 7 is adjusted to maintain the first opening threshold until the pulverized coal content in the small pulverized coal bin 9 reaches the first preset threshold, and the inlet control valve 7 is closed.

[0058] During the rapid load reduction process of the coal-fired power unit, the outlet control valve 10 remains closed, and the opening of the inlet control valve 7 is increased to the second opening threshold, so that the excess pulverized coal in the combustion system is stored in the small pulverized coal bin 9. When the steam-water system reaches the target load state, the inlet control valve 7 is closed;

[0059] During the rapid load increase of the coal-fired power unit, the inlet control valve 7 remains closed, and the opening of the outlet control valve 10 is increased to the third opening threshold so that the pulverized coal in the small pulverized coal bin 9 is supplied to the combustion system. When the steam-water system reaches the target load state, the outlet control valve 10 is closed.

[0060] Among them, the first preset threshold range is 40% to 60%, the second preset value range is 60% to 80%, the first opening threshold range is 10% to 30%, and the second opening threshold and the third opening threshold range are both 70% to 90%.

[0061] This embodiment sets up a small powder silo flexible storage and supply system coupled with the primary air duct 11, and the small powder silo flexible storage and supply system includes an inlet control valve 7, an air-powder separator 8, a small powder silo 9 and an outlet control valve 10 connected in sequence. The inlet control valve 7 and the outlet control valve 10 can cooperate to quickly adjust the amount of coal powder entering the furnace, and cooperate with the molten salt energy storage system which is connected to the generator through a molten salt electric module at one end and connected to the steam-water system through a molten salt-steam heat exchange module at the other end. This shortens the response time of the steam turbine in the flexible peak-shaving process, which can not only ensure the stable load operation of the coal-fired power unit, but also quickly regulate the peak of the coal-fired power unit.

[0062] In Example 1, one end of the molten salt energy storage system is connected to the generator via a molten salt power module, and the other end is connected to the steam-water system via a molten salt-steam heat exchange module. The load regulation method for the coal-fired power unit is as follows:

[0063] The steam working medium discharged from the outlet of the high-pressure cylinder 16 in the steam-water system is divided into two sub-paths, so that the steam working medium from the high-pressure cylinder 16 can enter the reheater 15 through the first sub-path controlled by the steam regulating valve 1 28 for heating and then be transported to the intermediate-pressure cylinder 17, and can also enter the molten salt-steam heat exchange module of the molten salt energy storage system through the second sub-path controlled by the steam regulating valve 2 37. The molten salt-steam heat exchange module is used to heat the steam working medium from the high-pressure cylinder 16 to above a first preset temperature and transport it to the intermediate-pressure cylinder 17 to perform work. The time required for the steam working medium to be transported to the intermediate-pressure cylinder 17 after heat exchange through the second sub-path is shorter than the time required for the steam working medium to be transported to the intermediate-pressure cylinder 17 after being heated through the first sub-path;

[0064] At the same time, the electricity generated by the generator 19 is divided into two circuits for transmission, the first circuit supplies power to the external power grid 21, and the second circuit supplies power to the molten salt electric heating module;

[0065] When the coal-fired power unit is operating at a stable load, the steam regulating valve 2 37 is closed, and the molten salt-steam heat exchange module is in a closed state. When the high-temperature molten salt stored in the molten salt energy storage system is lower than the second preset threshold, the molten salt electric heating module is controlled to switch to a low-power state and operate until the high-temperature molten salt stored in the molten salt energy storage system reaches the second preset threshold, at which point the molten salt electric heating module stops working.

[0066] During the rapid load reduction process of the coal-fired thermal power unit, the steam regulating valve 2 37 is closed, the molten salt-steam heat exchange module is in a closed state, and the molten salt electric heating module is controlled to switch to a high-power state to operate, reducing the amount of power supplied to the outside by the first circuit, so that more electricity generated by the generator 19 enters the second circuit, and the molten salt in the low-temperature molten salt tank 33 is heated to a second preset temperature by the molten salt electric heating module and then pumped directly to the high-pressure molten salt tank 31 for storage. When the steam-water system reaches the target load state, the molten salt electric heater 30 is controlled to switch to a low-power state to operate, reducing the amount of electricity entering the second circuit until the power generation of the generator 19 drops to the target load, at which time the molten salt electric heating module stops working;

[0067] During the rapid load increase process of the coal-fired power unit, the molten salt electric heating module is in the closed state, the steam regulating valve 2 37 is opened to the fourth opening threshold, and the opening of the steam regulating valve 1 36 is reduced to the fifth opening threshold, so that part of the steam working medium enters the molten salt-steam heat exchange module through the second sub-path for heating and then directly enters the intermediate pressure cylinder 17 to perform work, shortening the load increase response time of the steam turbine. When the steam-water system reaches the target load state, the opening of the steam regulating valve 1 36 is increased to the sixth opening threshold, and the opening of the steam regulating valve 2 37 is reduced to the seventh opening threshold to control the steam working medium flow entering the molten salt-steam heat exchange module. After the opening of the steam regulating valve 1 36 is adjusted to the eighth opening threshold and the steam regulating valve 2 37 is reduced to the closed state, the molten salt-steam heat exchange module stops working.

[0068] Among them, the first preset temperature range is 530℃~550℃, the second preset temperature range is 580℃~620℃, the fourth opening threshold range is 20%~40%, the fifth opening threshold range is 60%~80%, the sixth opening threshold range is 80%, the seventh opening threshold range is 10%~30%, and the eighth opening threshold range is 90%~100%. In the low power state, the coal-fired power unit consumes its rated load range of 5%~10%, and in the high power state, it consumes its rated load range of 15%~30%.

[0069] In this embodiment, by adjusting steam regulating valve 1 36 and steam regulating valve 2 37, the time for the steam working medium to be heat exchanged through the second sub-path and heated through the first sub-path can be controlled, thereby shortening the response time of the steam turbine during the flexible peak regulation process, thereby ensuring not only stable load operation of the coal-fired thermal power unit but also rapid load increase and decrease of the coal-fired thermal power unit.

[0070] Preferably, in Example 1, in the molten salt energy storage system, the molten salt-steam heat exchange module and the molten salt electric heating module are connected in series to form a loop to realize the conversion of electrical energy and thermal energy. The molten salt-steam heat exchange module transfers the heat in the high-temperature molten salt to the steam working medium, and the high-temperature molten salt is converted into low-temperature molten salt for storage. The molten salt electric heating module converts the low-temperature molten salt into high-temperature molten salt after electrical heating, so that the energy of excess electricity is converted into sensible heat for storage.

[0071] Example 2

[0072] Example 2 provides a device for coupling a small powder silo with molten salt energy storage to improve the flexibility of a thermal power plant, such as Figure 2 Shown, including:

[0073] Coal-fired power units, including combustion systems, steam-water systems, and electrical systems;

[0074] The small pulverized coal silo flexible storage and supply system is coupled with the combustion system. The small pulverized coal silo flexible storage and supply system is used to store the excess pulverized coal in the combustion system, or the small pulverized coal silo flexible storage and supply system supplies the internally stored pulverized coal to the combustion system for combustion;

[0075] The molten salt energy storage system includes a molten salt electric heating module and a molten salt-steam heat exchange module. The molten salt electric heating module is connected to the generator, and the molten salt-steam heat exchange module is connected to the steam-water system.

[0076] In Example 2, Figure 3As shown, the combustion system includes a raw coal hopper 1, a coal feeder 2, a coal mill 3, a coarse powder separator 4, a primary fan 5, and an air preheater 6. The raw coal hopper 1, the coal feeder 2, the coal mill 3, and the coarse powder separator 4 are connected in sequence. One outlet of the primary fan 5 is connected to the coal mill 3 to deliver cold air, and the other outlet is connected to the coal mill 3 through the air preheater 6 to deliver hot air. The mixed air formed by the cold air and the hot air carries the pulverized coal, passes through the coarse powder separator 4, and enters the furnace through the primary air duct 11 for combustion.

[0077] like Figure 3 As shown, the small powder silo flexible storage and supply system includes an inlet control valve 7, an air-powder separator 8, a small powder silo 9 and an outlet control valve 10 connected in sequence, wherein the inlet control valve 7 is connected to one end of the primary air duct 11, and the outlet control valve 10 is connected to the other end of the primary air duct 38, and the air-powder separator 8 introduces the exhaust gas into the furnace through a pipeline.

[0078] In Example 2, Figure 3 As shown, the steam-water system includes an economizer 12, a water-cooled wall 13, a superheater 14, a high-pressure cylinder 16, a reheater 15, an intermediate-pressure cylinder 17, a low-pressure cylinder 18, a condenser 22, a condensate pump 23, a low-pressure heater 24, a deaerator 25, a feed water pump 26, and a high-pressure heater 27, which are connected in sequence. The outlet of the high-pressure heater 27 is connected to the inlet of the economizer 12, and the outlet of the economizer 12 is connected to the water-cooled wall 13, thereby realizing the water vapor circulation of the steam-water system.

[0079] like Figure 3 As shown, the electrical system includes a generator 19, a main transformer 20, and an external power grid 21 arranged in sequence. The bearings of the high-pressure cylinder 16, the medium-pressure cylinder 17, and the low-pressure cylinder 18 on the steam-water system are coaxially connected to the generator 19 on the electrical system.

[0080] like Figure 3 As shown, the molten salt electric heating module includes a plant transformer 29, a power regulator 30, a molten salt electric heater 31, a low-temperature molten salt pump 35 and a low-temperature molten salt tank 34 arranged in sequence, wherein the plant transformer 29, the power regulator 30 and the molten salt electric heater 31 are connected in sequence, the low-temperature molten salt tank 34, the low-temperature molten salt pump 35 and the molten salt electric heater 31 are connected in sequence, and the molten salt-steam heat exchange module includes a high-temperature molten salt tank 32, a high-temperature molten salt pump 33 and a molten salt-steam heat exchanger 36 connected in sequence;

[0081] Among them, the outlet of the high-pressure cylinder 16 is connected to the first sub-path and the second sub-path. The first sub-path is controlled by a steam regulating valve 28 and the end is connected to the inlet of the reheater 15. The outlet of the reheater 15 is connected to the inlet of the medium-pressure cylinder 17. The second sub-path is controlled by a steam regulating valve 37 and the end is connected to the first fluid inlet of the molten salt-steam heat exchanger 36. The first fluid outlet of the heat exchanger 36 is connected to the inlet of the medium-pressure cylinder 17. The second fluid inlet of the heat exchanger 36 is connected to the high-temperature molten salt pump 33. The second The fluid outlet is connected to the low-temperature molten salt tank 34, the molten salt inlet in the molten salt electric heater 31 is connected to the low-temperature molten salt pump 35, the molten salt outlet in the molten salt electric heater 31 is connected to the high-temperature molten salt tank 32, the generator 19 is electrically connected to the main transformer 20 through a first circuit, the main transformer 20 adjusts the voltage and supplies power to the external power grid 21, the generator 19 is electrically connected to the plant transformer 29 through a second circuit, and supplies power to the molten salt electric heater 31 after adjusting the voltage and power respectively through the plant transformer 29 and the power regulator 30.

[0082] In the specific implementation scheme of this embodiment, the first preset threshold is 50%, the second preset value is 70%, the first opening threshold is 20%, the second opening threshold and the third opening threshold are both 80%, the fourth opening threshold is 30%, the fifth opening threshold is 70%, the sixth opening threshold is 80%, the seventh opening threshold is 20%, and the eighth opening threshold range is 100%. The first preset temperature range is 540°C, and the second preset temperature range is 600°C. In the low power state, the molten salt energy storage system consumes 10% of the rated load of the coal-fired thermal power unit. In the high power state, the molten salt energy storage system consumes 30% of the rated load of the coal-fired thermal power unit. The operating conditions of the coal-fired thermal power unit operating stably at 80% of the rated load, rapidly decreasing from 100% of the rated load to 30% of the rated load, and rapidly increasing from 30% of the rated load to 100% of the rated load are discussed respectively.

[0083] When the coal-fired power unit is operating at a stable load of 80%, the small powder silo flexible storage and supply system obtains the coal powder content in the small powder silo 9. If the coal powder content in the small powder silo 9 is lower than 50%, the outlet control valve 10 is closed, and the inlet control valve 7 is adjusted to maintain an opening of 20% until the coal powder content in the small powder silo 9 reaches more than 50%. The inlet control valve 7 is closed, and at the same time, the steam regulating valve 2 37 of the molten salt energy storage system is closed, and the molten salt-steam heat exchange module is in a closed state. When the high-temperature molten salt stored in the molten salt energy storage system is lower than 70%, the molten salt electric heating module is controlled to switch to a low-power state. When the high-temperature molten salt stored in the molten salt energy storage system reaches 70%, the molten salt electric heating module stops working;

[0084] When the coal-fired thermal power unit is rapidly reduced from 100% rated load to 30% rated load, in the molten salt energy storage system, the steam regulating valve 2 37 is closed, the molten salt-steam heat exchange module is in the closed state, and the molten salt electric heating module is controlled to switch to the high power state to operate, and the external load of the coal-fired thermal power unit is rapidly reduced to 70%, so that more electricity generated by the generator 19 enters the second circuit, and the molten salt in the low-temperature molten salt tank 34 is heated to 600°C by the molten salt electric heating module and then pumped directly to the high-pressure molten salt tank 32 for storage. At the same time, the outlet control valve 10 of the small powder silo flexible storage and supply system Keep it closed, increase the opening of the inlet control valve 7 to 80%, quickly reduce the heat provided by the combustion system to the steam-water system, and then reduce the load of the steam-water system. When the load of the coal-fired thermal power unit drops to 60%, control the molten salt electric heater 31 to switch to low power state operation. When the steam-water system drops to 30% load state, the small powder bin flexible storage and supply system stops storing pulverized coal, and the combustion system and steam-water system maintain stable load operation. At the same time, the molten salt electric module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation. The coal-fired thermal power unit completes the rapid load reduction process;

[0085] When a coal-fired power unit rapidly increases its rated load from 30% to 100% of its rated load, in the small pulverized coal silo flexible storage and supply system, the inlet control valve 7 remains closed, and the outlet control valve opening is increased to 80%. This allows the pulverized coal in the small pulverized coal silo to be rapidly supplied to the combustion system, rapidly increasing the steam production rate of the steam-water system. Simultaneously, the molten salt electric heating module of the molten salt energy storage system is closed, steam regulating valve 2 is opened to 30%, and the opening of steam regulating valve 1 is reduced to 70%. This allows some steam to enter the molten salt-steam heat exchange module through the second sub-path for heating and then directly enter the intermediate pressure cylinder to perform work, shortening the turbine's load increase response time. When the steam-water system reaches 100% of its rated load, the opening of steam regulating valve 1 is increased to 80%, while the opening of steam regulating valve 2 is reduced to 20%. This controls the flow of steam entering the molten salt-steam heat exchange module until the opening of steam regulating valve 1 reaches the 100% opening threshold and steam regulating valve 2 is reduced to the closed state. The molten salt-steam heat exchange module then stops operating, and the coal-fired power unit completes its rapid load increase process.

[0086] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for improving the flexibility of thermal power plants by coupling small powder silos and molten salt energy storage, characterized in that: The following steps are involved: Establish a flexible storage and supply system for small powder silos and a molten salt energy storage system; The flexible storage and supply system of the small powder silo and the molten salt energy storage system are simultaneously coupled to the coal-fired thermal power unit to enhance the flexible peak-shaving capability of the coal-fired thermal power unit. The coal-fired thermal power unit includes a combustion system, a steam-water system, and an electrical system. The flexible storage and supply system of the small powder silo is coupled to the combustion system, and one end of the molten salt energy storage system is connected to the generator through a molten salt power module, and the other end is connected to the steam-water system through a molten salt-steam heat exchange module. When the coal-fired power unit is operating at a stable load, the amount of pulverized coal in the small pulverized coal silo flexible storage and supply system is adjusted to maintain at a first preset threshold, and the heat of the molten salt energy storage system is adjusted to maintain at a second preset threshold; During the rapid load reduction process of the coal-fired thermal power unit, the molten salt energy storage system converts the excess power energy of the generator into molten salt sensible heat through the molten salt electric heating module and stores it, quickly reducing the external load of the coal-fired thermal power unit. At the same time, the small powder silo flexible storage and supply system stores the redundant pulverized coal of the combustion system, quickly reducing the heat provided by the combustion system to the steam-water system, thereby reducing the load of the steam-water system. When the steam-water system drops to the target load state, the small powder silo flexible storage and supply system stops storing pulverized coal, and the combustion system and steam-water system maintain stable load operation. At the same time, the molten salt electric heating module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation, and the coal-fired thermal power unit completes the rapid load reduction process; During the rapid load increase process of the coal-fired power unit, the pulverized coal in the small pulverized coal silo flexible storage and supply system is supplied to the combustion system for combustion, which quickly increases the steam production rate of the steam-water system. At the same time, the molten salt energy storage system uses the molten salt-steam heat exchange module to exchange part of the steam working fluid in the steam-water system with high-temperature molten salt in the molten salt-steam heat exchanger, thereby shortening the response time of the steam turbine during the flexible peak regulation process. When the steam-water system reaches the target load state, the small pulverized coal silo flexible storage and supply system stops supplying pulverized coal to the combustion system, and the combustion system and the steam-water system maintain stable load operation. At the same time, the molten salt-steam heat exchange module of the molten salt energy storage system stops working, and the electrical system maintains stable load operation. The coal-fired power unit completes the rapid load increase process.

2. The method for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to claim 1 is characterized in that: The flexible storage and supply system of the small powder silo is coupled with the primary air duct of the combustion system to shorten the fuel supply response time of the combustion system. The flexible storage and supply system of the small powder silo includes an inlet control valve, an air-powder separator, a small powder silo and an outlet control valve connected in sequence. The inlet control valve is connected to one end of the primary air duct, and the outlet control valve is connected to the other end of the primary air duct. The air-powder separator introduces the exhaust gas into the furnace through the pipeline. When the coal-fired power unit is operating at a stable load, the pulverized coal content in the small pulverized coal silo is obtained. If the pulverized coal in the small pulverized coal silo is lower than a first preset threshold, the outlet control valve is closed and the inlet control valve is adjusted to maintain a certain opening until the pulverized coal in the small pulverized coal silo reaches the first preset threshold, at which point the inlet control valve is closed. During the rapid load reduction process of coal-fired power units, the outlet control valve remains closed and the inlet control valve opening is increased to store redundant pulverized coal in the combustion system into the small pulverized coal silo. When the steam-water system reaches the target load state, the inlet control valve is closed. During the rapid load increase of a coal-fired power unit, the inlet control valve remains closed and the outlet control valve opening is increased to supply the pulverized coal in the small pulverized coal bin to the combustion system. When the steam-water system reaches the target load state, the outlet control valve is closed.

3. The method for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to claim 1 is characterized in that: The steam working medium discharged from the outlet of the high-pressure cylinder in the steam-water system is divided into two sub-paths, so that the steam working medium from the high-pressure cylinder can enter the reheater through the first sub-path controlled by the first steam regulating valve to be heated and then transported to the intermediate-pressure cylinder. It can also enter the molten salt-steam heat exchange module of the molten salt energy storage system through the second sub-path controlled by the second steam regulating valve. The molten salt-steam heat exchange module is used to heat the steam working medium from the high-pressure cylinder and transport it to the intermediate-pressure cylinder. The time required for the steam working medium to be transported to the intermediate-pressure cylinder after heat exchange in the second sub-path is shorter than the time required for the steam working medium to be transported to the intermediate-pressure cylinder after being heated in the first sub-path. At the same time, the electricity generated by the generator is divided into two circuits for transmission. The first circuit is used to supply power to the external power grid, and the second circuit is used to supply power to the molten salt electric heating module. When the coal-fired power unit is operating at a stable load, the steam regulating valve 2 is closed, and the molten salt-steam heat exchange module is in a closed state. When the high-temperature molten salt stored in the molten salt energy storage system is below a second preset threshold, the molten salt electric heating module is controlled to switch to a low-power state until the high-temperature molten salt stored in the molten salt energy storage system reaches the second preset threshold, at which point the molten salt electric heating module stops working. During the rapid load reduction process of the coal-fired power unit, the steam regulating valve 2 is closed, the molten salt-steam heat exchange module is in the closed state, and the molten salt electric heating module is controlled to switch to a high-power state to operate, reducing the power supply of the first circuit to the outside, so that the excess power of the generator enters the second circuit. The molten salt in the low-temperature molten salt tank is heated by the molten salt electric heating module and then pumped directly to the high-pressure molten salt tank for storage. When the steam-water system reaches the target load state, the molten salt electric heater is controlled to switch to a low-power state to reduce the power entering the second circuit until the power generation of the generator drops to the target load, at which time the molten salt electric heating module stops working; During the rapid load increase process of the coal-fired power unit, the molten salt electric heating module is in the closed state, the steam control valve 2 is opened, and the opening of the steam control valve 1 is reduced, so that part of the steam working medium enters the molten salt-steam heat exchange module through the second sub-path for heating and then directly enters the intermediate pressure cylinder to perform work, shortening the load increase response time of the steam turbine. When the steam-water system reaches the target load state, the opening of the steam control valve 1 is increased and the opening of the steam control valve 2 is reduced to control the steam working medium flow entering the molten salt-steam heat exchange module. After the opening of the steam control valve 1 is adjusted to the maximum and the steam control valve 2 is reduced to the closed state, the molten salt-steam heat exchange module stops working.

4. The method for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to claim 1 is characterized in that: The molten salt-steam heat exchange module and the molten salt electric heating module are partially connected in series to form a loop to realize the conversion of electrical energy and thermal energy. The molten salt-steam heat exchange module transfers the heat in the high-temperature molten salt to the steam working medium, and the high-temperature molten salt is converted into low-temperature molten salt for storage. The molten salt electric heating module converts the low-temperature molten salt into high-temperature molten salt after electrical heating, so that the energy of excess electricity is converted into sensible heat for storage.

5. A device for improving the flexibility of a thermal power plant by coupling a small powder silo and molten salt energy storage, used to implement the method for improving the flexibility of a thermal power plant by coupling a small powder silo and molten salt energy storage as claimed in any one of claims 1 to 4, characterized in that: include: Coal-fired power units, including combustion systems, steam-water systems, and electrical systems; The small pulverized coal silo flexible storage and supply system is coupled with the combustion system. The small pulverized coal silo flexible storage and supply system is used to store the excess pulverized coal in the combustion system, or the small pulverized coal silo flexible storage and supply system supplies the internally stored pulverized coal to the combustion system for combustion; The molten salt energy storage system includes a molten salt electric heating module and a molten salt-steam heat exchange module. The molten salt electric heating module is connected to the generator, and the molten salt-steam heat exchange module is connected to the steam-water system.

6. The device for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to claim 5 is characterized in that: The combustion system includes a raw coal hopper, coal feeder, coal mill, coarse powder separator, primary fan and air preheater. The raw coal hopper, coal feeder, coal mill and coarse powder separator are connected in sequence. One outlet of the primary fan is connected to the coal mill to deliver cold air, and the other outlet is connected to the coal mill through the air preheater to deliver hot air. The mixed air formed by the cold air and hot air carries the pulverized coal through the coarse powder separator and enters the furnace through the primary air duct for combustion. The flexible storage and supply system of the small powder silo includes an inlet control valve, a gas-powder separator, a small powder silo and an outlet control valve connected in sequence, wherein the inlet control valve is connected to one end of the primary air duct, and the outlet control valve is connected to the other end of the primary air duct. The gas-powder separator introduces the exhaust gas into the furnace through the pipeline.

7. The device for improving the flexibility of a thermal power plant by coupling a small powder silo with molten salt energy storage according to claim 5 is characterized by: The steam-water system includes a high-pressure cylinder, a reheater, an intermediate-pressure cylinder, and a low-pressure cylinder arranged in sequence; the electrical system includes a generator, a main transformer, and an external power grid arranged in sequence; the bearings of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder on the steam-water system are coaxially connected to the generator; The molten salt electric heating module includes a plant transformer, a power regulator, a molten salt electric heater, a low-temperature molten salt pump and a low-temperature molten salt tank, which are arranged in sequence. The plant transformer, the power regulator and the molten salt electric heater are connected in sequence, the low-temperature molten salt tank, the low-temperature molten salt pump and the molten salt electric heater are connected in sequence, and the molten salt-steam heat exchange module includes a high-temperature molten salt tank, a high-temperature molten salt pump and a molten salt-steam heat exchanger which are connected in sequence. Among them, the outlet of the high-pressure cylinder is connected to the first sub-circuit and the second sub-circuit, the first sub-circuit is controlled by steam regulating valve 1 and the end is connected to the inlet of the reheater, the outlet of the reheater is connected to the inlet of the medium-pressure cylinder, the second sub-circuit is controlled by steam regulating valve 2 and the end is connected to the first fluid inlet of the molten salt-steam heat exchanger, the first fluid outlet of the heat exchanger is connected to the inlet of the medium-pressure cylinder, the second fluid inlet of the heat exchanger is connected to the high-temperature molten salt pump, the second fluid outlet of the heat exchanger is connected to the low-temperature molten salt tank, the molten salt inlet in the molten salt electric heater is connected to the low-temperature molten salt pump, the molten salt outlet in the molten salt electric heater is connected to the high-temperature molten salt tank, the generator is connected to the main transformer through the first circuit, the main transformer adjusts the voltage and supplies power to the external power grid, the generator is connected to the plant transformer through the second circuit, and supplies power to the molten salt electric heater after adjusting the voltage and power respectively through the plant transformer and the power regulator.

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