A molten salt peak shaving system for a combined heat and power unit and a method thereof

Abstract

The present application relates to a kind of cogeneration unit molten salt peak shaving system and method thereof, its cogeneration unit molten salt peak shaving system of the present application includes: boiler, steam turbine unit and heat storage device, steam generated by the boiler enters the steam turbine unit and generates power and does work, and the heat storage device includes high-temperature molten salt operation loop and low-temperature molten salt operation loop;The high-temperature molten salt operation loop includes high-temperature molten salt hot tank, molten salt heat-releasing superheater, high-temperature molten salt cold tank, high-temperature molten salt circulating electric pump and high-temperature molten salt heating assembly;The low-temperature molten salt operation loop includes low-temperature molten salt hot tank, molten salt heat-releasing steam generator, molten salt heat-releasing make-up water heater, low-temperature molten salt cold tank, low-temperature molten salt circulating electric pump and low-temperature molten salt heating assembly.The technical scheme of the present application has mutually isolated molten salt loop, can realize the comprehensive utilization of different temperature domain operating characteristics molten salt, and improves the wide temperature range operating ability of system.

Description

Technical Field

[0001] This invention relates to the field of molten salt energy storage technology, and in particular to a molten salt peak-shaving system and method for cogeneration units. Background Technology

[0002] Molten salt thermal energy storage technology uses molten salt as a medium to store solar thermal energy, industrial waste heat, and off-peak electricity as thermal energy, releasing it when needed. It aims to solve the problem of mismatch between thermal energy supply and demand in terms of time, space, or intensity, and to maximize the energy utilization rate of the entire system. Molten salt thermal energy storage technology has advantages such as large storage capacity, long storage period, and low cost, making it more suitable for large-scale energy storage needs compared to other energy storage technologies. Molten salt thermal energy storage technology is gradually gaining attention and is beginning to be used in the flexible peak-shaving retrofit of combined heat and power (CHP) units to improve the deep peak-shaving and peak-load operation capabilities of the units.

[0003] However, since the operating temperature range of molten salt is relatively narrow, the use of a single type of molten salt to establish a thermal storage system cannot match the temperature of the steam generated by the cogeneration unit, resulting in a weak temperature load operation capability of the entire system. Summary of the Invention

[0004] The purpose of this invention is to provide a molten salt peak-shaving system for cogeneration units, which has mutually isolated molten salt circuits, can realize the comprehensive utilization of molten salt with different operating characteristics in different temperature ranges, and improve the system's wide temperature range operating capability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A molten salt peak-shaving system for a combined heat and power unit includes: a boiler, a steam turbine unit, and a thermal storage device. The steam generated by the boiler enters the steam turbine unit to perform work and generate electricity. The thermal storage device includes a high-temperature molten salt operating circuit and a low-temperature molten salt operating circuit.

[0007] The high-temperature molten salt operating circuit includes a high-temperature molten salt hot tank, a molten salt heat release superheater, a high-temperature molten salt cold tank, a high-temperature molten salt circulating electric pump, and a high-temperature molten salt heating assembly;

[0008] The molten salt outlet of the high-temperature molten salt hot tank is connected to the molten salt inlet of the molten salt heat release superheater, the molten salt outlet of the molten salt heat release superheater is connected to the molten salt inlet of the high-temperature molten salt cold tank, the molten salt outlet of the high-temperature molten salt cold tank is connected to the molten salt inlet of the high-temperature molten salt heating assembly, the high-temperature molten salt circulating electric pump is installed at the molten salt inlet of the high-temperature molten salt heating assembly, and the molten salt outlet of the high-temperature molten salt heating assembly is connected to the molten salt inlet of the high-temperature molten salt hot tank.

[0009] The cryogenic molten salt operating circuit includes a cryogenic molten salt hot tank, a molten salt heat release steam generator, a molten salt heat release water heater, a cryogenic molten salt cold tank, a cryogenic molten salt circulating electric pump, and a cryogenic molten salt heating assembly;

[0010] The molten salt outlet of the low-temperature molten salt hot tank is connected to the molten salt inlet of the molten salt heat release steam generator; the molten salt outlet of the molten salt heat release steam generator is connected to the molten salt inlet of the molten salt heat release water heater; the molten salt outlet of the molten salt heat release water heater is connected to the molten salt inlet of the low-temperature molten salt cold tank; the molten salt outlet of the low-temperature molten salt cold tank is connected to the molten salt inlet of the low-temperature molten salt heating assembly; the low-temperature molten salt circulating electric pump is installed at the molten salt inlet of the low-temperature molten salt heating assembly; and the molten salt outlet of the low-temperature molten salt heating assembly is connected to the molten salt inlet of the low-temperature molten salt hot tank.

[0011] The steam outlet of the boiler is connected to the steam inlet of the high-temperature molten salt heating component, and the steam outlet of the high-temperature molten salt heating component is connected to the steam inlet of the low-temperature molten salt heating component.

[0012] Preferably, the turbine unit includes a steam reheater, and the steam outlet of the steam reheater is connected to the steam inlet of the low-temperature molten salt steam heater.

[0013] Preferably, the system further includes a molten salt steam supply circuit, which includes a feed water pump and an industrial steam supply pipe. The feed water inlet of the feed water pump is connected to the water supply pipe and the feed water outlet of the low-temperature molten salt heating component. The feed water outlet of the feed water pump is connected to the feed water inlet of the molten salt heat release water supply heater. The feed water outlet of the molten salt heat release water supply heater is connected to the feed water inlet of the molten salt heat release steam generator. The steam outlet of the molten salt heat release steam generator is connected to the steam inlet of the industrial steam supply pipe.

[0014] Preferably, the turbine unit includes a high-pressure turbine cylinder, a steam reheater, and a low-pressure turbine cylinder. The steam outlet of the boiler is connected to the steam inlet of the high-pressure turbine cylinder, the steam outlet of the high-pressure turbine cylinder is connected to the steam inlet of the steam reheater, the steam outlet of the steam reheater is connected to the steam inlet of the low-pressure turbine cylinder, and the steam outlet of the low-pressure turbine cylinder is connected to the condenser. The steam outlet of the molten salt heat release superheater is connected to the steam inlet of the high-pressure turbine cylinder.

[0015] Preferably, the high-temperature molten salt heating assembly includes a high-temperature molten salt electric heater, a high-temperature electric heating bypass pipe, a high-temperature molten salt steam heater, and a high-temperature steam bypass pipe. The high-temperature electric heating bypass pipe is disposed between the molten salt inlet and molten salt outlet of the high-temperature molten salt electric heater. The high-temperature steam bypass pipe is disposed between the molten salt inlet and molten salt outlet of the high-temperature molten salt steam heater. The molten salt outlet of the high-temperature molten salt cold tank is connected to the molten salt inlet of the high-temperature molten salt electric heater. The high-temperature molten salt circulating electric pump is installed at the molten salt inlet of the high-temperature molten salt electric heater. The molten salt outlet of the high-temperature molten salt electric heater is connected to the molten salt inlet of the high-temperature molten salt steam heater. The molten salt outlet of the high-temperature molten salt steam heater is connected to the molten salt inlet of the high-temperature molten salt hot tank.

[0016] Preferably, the low-temperature molten salt heating assembly includes a low-temperature molten salt electric heater, a low-temperature electric heater bypass pipe, a low-temperature molten salt steam heater, and a low-temperature steam bypass pipe. The low-temperature electric heater bypass pipe is disposed between the molten salt inlet and the molten salt outlet of the low-temperature molten salt electric heater. The low-temperature steam bypass pipe is disposed between the molten salt inlet and the molten salt outlet of the low-temperature molten salt steam heater. The molten salt outlet of the low-temperature molten salt cold tank is connected to the molten salt inlet of the low-temperature molten salt electric heater. The low-temperature molten salt circulating electric pump is installed at the molten salt inlet of the low-temperature molten salt electric heater. The molten salt outlet of the low-temperature molten salt electric heater is connected to the molten salt inlet of the low-temperature molten salt steam heater. The molten salt outlet of the low-temperature molten salt steam heater is connected to the molten salt inlet of the low-temperature molten salt hot tank.

[0017] The present invention also provides a method for the molten salt peak-shaving system of the aforementioned cogeneration unit, comprising the following steps:

[0018] When the system participates in power peak shaving, it determines whether it is necessary to reduce the output power load.

[0019] If it is necessary to reduce the output electrical load, part of the steam generated by the boiler will enter the turbine unit to do work and generate electricity, and the other part of the steam will heat the molten salt in the heat storage device for heat storage.

[0020] If an increase in output electrical load is required, all the steam generated by the boiler will enter the turbine unit to do work and generate electricity. At the same time, the heat in the heat storage device will heat the feedwater to generate steam, and this part of the steam will also be fed into the turbine unit to drive the turbine unit to do work.

[0021] Preferably,

[0022] If it is necessary to reduce the output electrical load, a portion of the steam generated by the boiler is used to heat the molten salt in the thermal storage device for heat storage. The specific steps are as follows:

[0023] Determine whether heat storage is being performed simultaneously by both high-temperature molten salt operating circuit and low-temperature molten salt operating circuit;

[0024] If so, the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit simultaneously perform heat storage; the high-temperature molten salt circulation electric pump and the low-temperature molten salt circulation electric pump are started, so that the high-temperature molten salt in the high-temperature molten salt operating circuit flows out from the high-temperature molten salt cold tank, absorbs heat through the high-temperature molten salt heating component, and is stored in the high-temperature molten salt hot tank; at the same time, the low-temperature molten salt in the low-temperature molten salt operating circuit flows out from the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank;

[0025] If not, then only the low-temperature molten salt operating circuit stores heat. In this case, the low-temperature molten salt circulating electric pump is started, so that the low-temperature molten salt in the low-temperature molten salt operating circuit flows out from the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank.

[0026] Preferably,

[0027] If an increase in output electrical load is required, the molten salt stored in the high-temperature molten salt tank and the low-temperature molten salt tank in the thermal storage device is used to heat the feedwater to generate steam. This steam is then fed into the turbine unit to drive the turbine unit to perform work. The specific steps are as follows:

[0028] Start the low-temperature molten salt circulating electric pump, so that the hot low-temperature molten salt in the low-temperature molten salt operating circuit flows out of the low-temperature molten salt hot tank, flows through the molten salt heat release steam generator and the molten salt heat release water heater, and heats the feedwater into steam for industrial steam supply; start the high-temperature molten salt circulating electric pump, so that the hot high-temperature molten salt in the high-temperature molten salt operating circuit flows out of the high-temperature molten salt hot tank, flows through the molten salt heat release superheater, and further heats the steam, and the steam is fed back to the steam turbine unit.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The molten salt peak-shaving system for cogeneration units provided in the above technical solution utilizes a high-temperature molten salt operating loop and a low-temperature molten salt operating loop in the thermal storage device. The molten salt in the high-temperature molten salt operating loop has a higher temperature range, while the molten salt in the low-temperature molten salt operating loop has a lower temperature range. The molten salt loops formed by the high-temperature molten salt operating loop and the low-temperature molten salt operating loop are isolated from each other, and the temperature ranges between the high-temperature molten salt operating loop and the low-temperature molten salt operating loop do not affect each other. This enables the comprehensive utilization of molten salts with different operating characteristics in different temperature ranges, thereby improving the system's wide-temperature-range operating capability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a molten salt peak-shaving system for a combined heat and power unit in an embodiment of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. High-temperature molten salt hot tank; 2. Molten salt heat release superheater; 3. High-temperature molten salt cold tank; 4. High-temperature molten salt circulating electric pump; 5. Valve No. 2; 6. High-temperature molten salt electric heater; 7. Valve No. 3; 8. Valve No. 5; 9. High-temperature molten salt steam heater; 10. Valve No. 6; 11. Valve No. 7; 12. Valve No. 4; 21. Low-temperature molten salt hot tank; 22. Molten salt heat release steam generator; 23. Molten salt heat release makeup water heater; 24. Low-temperature molten salt cold tank; 25. Low-temperature molten salt circulating electric pump; 26. Valve No. 8; 27. Low-temperature molten salt electric heater; 28. Valve No. 9; 29. ​​Valve No. 12; 30. Low-temperature molten salt steam heater; 31. Valve No. 13; 32. Valve No. 11; 33. Valve No. 10; 41. Valve No. 1; 42. Steam turbine high-pressure cylinder; 43. Steam reheater; 44. Steam turbine low-pressure cylinder; 45. Valve No. 16; 46. ​​Water pump; 47. Valve No. 14; 48. Valve No. 15; 49. Valve No. 17. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] This invention provides a molten salt peak-shaving system for a combined heat and power (CHP) unit. This system utilizes a high-temperature molten salt operating loop and a low-temperature molten salt operating loop within a thermal storage device. The molten salt in the high-temperature molten salt operating loop has a higher temperature range, while the molten salt in the low-temperature molten salt operating loop has a lower temperature range. The molten salt loops formed by the high-temperature and low-temperature molten salt operating loops are isolated from each other, and their temperature ranges do not affect each other. This allows for the comprehensive utilization of molten salts with different operating characteristics in different temperature ranges, enhancing the system's wide-temperature-range operating capability.

[0038] It should be noted that the high-temperature molten salt operating circuit can use molten salt with a temperature range of 300-750℃, meaning the melting point of the molten salt used is 300℃ and the decomposition temperature is 750℃; the low-temperature molten salt operating circuit can use molten salt with a temperature range of 150-550℃, meaning the melting point of the molten salt used is 150℃ and the decomposition temperature is 550℃. The entire system can operate within a temperature range of 150-750℃.

[0039] Please see Figure 1 A molten salt peak-shaving system for a combined heat and power (CHP) unit includes a boiler, a steam turbine, a thermal storage device, and a molten salt steam-water supply circuit. The thermal storage device includes a high-temperature molten salt operating circuit and a low-temperature molten salt operating circuit. The system operates primarily in two modes: thermal storage mode and thermal release mode. The steam generated by the boiler can be used to power the steam turbine, or it can be used to heat the molten salt working fluid in the thermal storage device.

[0040] Loop 1: This is the operating loop of the high-temperature molten salt operating loop. The high-temperature molten salt operating loop includes a high-temperature molten salt hot tank 1, a molten salt heat release superheater 2, a high-temperature molten salt cold tank 3, a high-temperature molten salt circulating electric pump 4, and a high-temperature molten salt heating assembly. The high-temperature molten salt heating assembly includes a high-temperature molten salt electric heater 6, a high-temperature electric heating bypass pipe, a high-temperature molten salt steam heater 9, and a high-temperature steam bypass pipe.

[0041] Specifically, the high-temperature electric heating bypass pipe is located between the molten salt inlet and molten salt outlet of the high-temperature molten salt electric heater 6, the high-temperature steam bypass pipe is located between the molten salt inlet and molten salt outlet of the high-temperature molten salt steam heater 9, the molten salt outlet of the high-temperature molten salt hot tank 1 is connected to the molten salt inlet of the molten salt heat release superheater 2, the molten salt outlet of the molten salt heat release superheater 2 is connected to the molten salt inlet of the high-temperature molten salt cold tank 3, the molten salt outlet of the high-temperature molten salt cold tank 3 is connected to the molten salt inlet of the high-temperature molten salt electric heater 6, the high-temperature molten salt circulating electric pump 4 is installed at the molten salt inlet of the high-temperature molten salt electric heater 6, the molten salt outlet of the high-temperature molten salt electric heater 6 is connected to the molten salt inlet of the high-temperature molten salt steam heater 9, and the molten salt outlet of the high-temperature molten salt steam heater 9 is connected to the molten salt inlet of the high-temperature molten salt hot tank 1. It should be noted that either the high-temperature molten salt steam heater 9 or the high-temperature molten salt electric heater 6 in the high-temperature molten salt heating assembly can be used. Both electric heating and steam heating can be used to heat the high-temperature molten salt working medium to achieve heat storage, and the system has diverse heat storage operation modes.

[0042] Understandably, the high-temperature molten salt hot tank 1 is used to store high-temperature molten salt in a high-temperature state, and the molten salt heat release superheater 2 is activated during the molten salt heat release operation to heat steam using the high-temperature molten salt in a high-temperature state, thereby improving its temperature quality; the high-temperature molten salt cold tank 3 is used to store high-temperature molten salt in a low-temperature state, and the high-temperature molten salt circulating electric pump 4 is used to drive the flow of molten salt; the high-temperature molten salt electric heater 6 uses electrical energy to heat the high-temperature molten salt in a low-temperature state, and the high-temperature molten salt steam heater 9 uses steam heat energy to heat the high-temperature molten salt in a low-temperature state.

[0043] When using electric heating for heat storage, open and adjust valves 41, 5, 7, and 12, and close valves 8, 10, and 11. Valve 41 is installed at the steam outlet of the boiler; valve 5 is installed at the molten salt inlet of the high-temperature molten salt electric heater 6; valve 7 is installed at the molten salt outlet of the high-temperature molten salt electric heater 6; and valve 11 is installed on the electric heating bypass pipe. Valve 8 is installed at the molten salt inlet of the high-temperature molten salt steam heater 9; valve 10 is installed at the molten salt outlet of the high-temperature molten salt steam heater 9; and valve 12 is installed on the high-temperature steam bypass pipe. Low-temperature high-temperature molten salt is introduced into the high-temperature molten salt electric heater 6 and heated to a high-temperature state. Then, the high-temperature molten salt is directly stored in the high-temperature molten salt hot tank 1 through the high-temperature steam bypass pipe.

[0044] When steam heat storage is required, open and adjust valves 41 (1), 8 (5), 10 (6), and 11 (7), and close valves 5 (2), 7 (3), and 12 (4). The high-temperature molten salt output from the high-temperature molten salt hot tank 1 is cooled by the molten salt heat release superheater 2, and then the low-temperature high-temperature molten salt is introduced into the high-temperature molten salt cold tank 3. The high-temperature molten salt circulation electric pump 4 is started, directly introducing the low-temperature high-temperature molten salt into the high-temperature electric heating bypass pipe, and then into the high-temperature molten salt steam heater 9. The main steam generated by the boiler is input into the high-temperature molten salt steam heater 9 to heat the low-temperature high-temperature molten salt, resulting in high-temperature molten salt, which is then stored in the high-temperature molten salt hot tank 1.

[0045] Loop Two: This is the operating loop for the cryogenic molten salt operation loop. The cryogenic molten salt operation loop includes a cryogenic molten salt hot tank 21, a molten salt heat release steam generator 22, a molten salt heat release makeup water heater 23, a cryogenic molten salt cold tank 24, a cryogenic molten salt circulating electric pump 25, and a cryogenic molten salt heating assembly. The cryogenic molten salt heating assembly includes a cryogenic molten salt electric heater 27, a cryogenic electric heating bypass pipe, a cryogenic molten salt steam heater 30, and a cryogenic steam bypass pipe. It should be noted that either the cryogenic molten salt electric heater 27 or the cryogenic molten salt steam heater 30 can be used in the cryogenic molten salt working fluid to achieve heat storage, allowing the system to operate in diverse heat storage modes.

[0046] Specifically, the low-temperature electric heating bypass pipe is disposed between the molten salt inlet and molten salt outlet of the low-temperature molten salt electric heater 27, the low-temperature steam bypass pipe is disposed between the molten salt inlet and molten salt outlet of the low-temperature molten salt steam heater 30, the molten salt outlet of the low-temperature molten salt hot tank 21 is connected to the molten salt inlet of the molten salt heat release steam generator 22, the molten salt outlet of the molten salt heat release steam generator 22 is connected to the molten salt inlet of the molten salt heat release water heater 23, and the molten salt heat release water heater 23... The molten salt outlet of valve 3 is connected to the molten salt inlet of the cryogenic molten salt cold tank 24. The molten salt outlet of the cryogenic molten salt cold tank 24 is connected to the molten salt inlet of the cryogenic molten salt electric heater 27. The cryogenic molten salt circulating electric pump 25 is installed at the molten salt inlet of the cryogenic molten salt electric heater 27. The molten salt outlet of the cryogenic molten salt electric heater 27 is connected to the molten salt inlet of the cryogenic molten salt steam heater 30. The molten salt outlet of the cryogenic molten salt steam heater 30 is connected to the molten salt inlet of the cryogenic molten salt hot tank 21. It should be noted that either the cryogenic molten salt electric heater 27 or the cryogenic molten salt steam heater 30 in the cryogenic molten salt heating assembly can be used.

[0047] Understandably, the low-temperature molten salt hot tank 21 is used to store low-temperature molten salt in a high-temperature state. The molten salt heat release steam generator 22 and the molten salt heat release water heater 23 are activated in the low-temperature molten salt heat release operation, using the low-temperature molten salt in a high-temperature state to heat the water in stages, turning it into steam. The low-temperature molten salt cold tank 24 is used to store low-temperature molten salt in a low-temperature state. The low-temperature molten salt circulating electric pump 25 is used to drive the flow of molten salt. The low-temperature molten salt electric heater 27 uses electrical energy to heat the low-temperature molten salt in a low-temperature state. The low-temperature molten salt steam heater 30 uses steam heat energy to heat the low-temperature molten salt in a low-temperature state.

[0048] When electric heating is required for heat storage, open and adjust valves 41 (1), 26 (8), 28 (9), and 33 (10), and close valves 32 (11), 29 (12), and 31 (13). Valve 26 (8) is installed at the molten salt inlet of the low-temperature molten salt electric heater 27, valve 28 (9) is installed at the molten salt outlet of the low-temperature molten salt electric heater 27, and valve 32 (11) is installed on the low-temperature electric heating bypass pipe; valve 29 (12) is installed at the molten salt inlet of the low-temperature molten salt steam heater 30, valve 31 (13) is installed at the molten salt outlet of the low-temperature molten salt steam heater 30, and valve 33 (10) is installed on the low-temperature steam bypass pipe. The low-temperature molten salt output from the low-temperature molten salt hot tank 21 is cooled by passing through the molten salt heat release steam generator 22 and the molten salt heat release water heater 23. The low-temperature molten salt in the low-temperature state is then introduced into the low-temperature molten salt cold tank 24. The low-temperature molten salt circulation electric pump 25 is started to transfer the low-temperature molten salt in the low-temperature state to the low-temperature molten salt electric heater 27 to heat the low-temperature molten salt in the low-temperature state, so as to obtain the low-temperature molten salt in the high-temperature state. The high-temperature molten salt is then directly stored in the low-temperature molten salt hot tank 21 through the low-temperature steam bypass pipe.

[0049] When steam heat storage is required, open and adjust valves 41 (number 1), 32 (number 11), 29 (number 12), and 31 (number 13), and close valves 26 (number 8), 28 (number 9), and 33 (number 10). The low-temperature molten salt output from the low-temperature molten salt hot tank 21 is cooled sequentially by the molten salt heat release steam generator 22 and the molten salt heat release water heater 23. The low-temperature molten salt is then introduced into the low-temperature molten salt cold tank 24. The low-temperature molten salt circulation electric pump 25 is started, and the low-temperature molten salt is directly transferred to the low-temperature molten salt steam heater 30 through the low-temperature electric heating bypass pipe. Steam with a lower heat exchange temperature from the high-temperature molten salt heating component is input into the low-temperature molten salt steam heater 30 to heat the low-temperature molten salt, resulting in high-temperature molten salt, which is then stored in the low-temperature molten salt hot tank 21.

[0050] In a preferred embodiment, the turbine unit includes a steam reheater 43, the steam outlet of which is connected to the steam inlet of the low-temperature molten salt steam heater 30. It is understood that the low-temperature molten salt steam heater 30 may also use the reheated steam from the steam reheater 43 as a heat source to heat the low-temperature molten salt at a low temperature, and recover the heat exchanged and cooled hot water.

[0051] Circuit 1 and Circuit 2 are in heat storage mode. As can be seen from Circuit 1 and Circuit 2, the main steam of the boiler first heats the high-temperature molten salt steam heater 9. The steam with a lower heat exchange temperature is further introduced to the low-temperature molten salt steam heater 30 for heating, realizing the cascade utilization of steam energy, preventing the waste of boiler heat energy, ensuring the heat energy required by the high-temperature molten salt operation circuit and the low-temperature molten salt operation circuit, and storing the energy in the boiler in the high-temperature molten salt operation circuit and the low-temperature molten salt operation circuit.

[0052] Loop 3: This loop is for heat release operation. The molten salt steam supply loop includes a feed water pump 46 and an industrial steam supply pipe. The feed water outlet of the feed water pump 46 is connected to the feed water inlet of the molten salt heat release water heater 23. The feed water outlet of the molten salt heat release water heater 23 is connected to the feed water inlet of the molten salt heat release steam generator 22. The steam outlet of the molten salt heat release steam generator 22 is connected to the steam inlet of the industrial steam supply pipe.

[0053] If used solely for supplying industrial steam, since the low-temperature molten salt operating circuit and the high-temperature molten salt operating circuit are isolated from each other, the low-temperature molten salt operating circuit can be used alone to supply industrial users. Specifically, open and adjust valve 14 47, close valve 15 48, and feed water is sequentially pumped by feed water pump 46 into the molten salt heat release water heater 23 and the molten salt heat release steam generator 22. The molten salt in the low-temperature zone, which is in a high-temperature state, is heated to a steam state and can be used to supply industrial steam.

[0054] The turbine unit includes a high-pressure turbine cylinder 42, a steam reheater 43, and a low-pressure turbine cylinder 44. The steam outlet of the molten salt heat release steam generator 22 is connected to the steam inlet of the molten salt heat release superheater 2. The steam outlet of the molten salt heat release superheater 2 is connected to the steam inlet of the high-pressure turbine cylinder 42. A valve 49 (No. 17) is installed at the steam outlet of the molten salt heat release superheater 2. The steam outlet of the high-pressure turbine cylinder 42 is connected to the steam inlet of the steam reheater 43. The steam outlet of the steam reheater 43 is connected to the steam inlet of the low-pressure turbine cylinder 44. The steam outlet of the low-pressure turbine cylinder 44 is externally connected to a condenser.

[0055] If the steam is used both to supply industrial steam and to power the turbine unit, open valves 47 (number 14) and 48 (number 15). Makeup water is sequentially pumped by feedwater pump 46 into the molten salt heat release makeup water heater 23 and the molten salt heat release steam generator 22. The molten salt, currently at a high temperature, is heated to a steam state in the low-temperature zone. This steam is then further heated to a high-temperature steam state by the molten salt heat release superheater 2, and subsequently returned to the turbine's high-pressure cylinder 42. This further realizes the cascade utilization of steam energy and improves efficiency. By combining the high-temperature and low-temperature molten salt operating circuits, the steam temperature is further increased, and the steam is then returned to the turbine's high-pressure cylinder 42, increasing the steam intake of the cogeneration unit's high-pressure cylinder and thus improving the unit's power generation capacity.

[0056] As can be seen from loop three, the heat stored in the low-temperature molten salt operating loop can be used to heat the makeup water to a steam state for supplying industrial steam; the high-temperature molten salt operating loop can be used to further heat the steam and feed it back to the turbine unit, thereby increasing the steam flow rate of the unit, enhancing the unit's work capacity, giving the cogeneration unit strong thermoelectric decoupling characteristics, and improving the unit's flexible operation capability.

[0057] Circuit 4: The steam generated by the boiler sequentially enters the high-pressure cylinder 42 of the steam turbine, the steam reheater 43, and the low-pressure cylinder 44 of the steam turbine to perform work and generate electricity. Alternatively, only the high-pressure cylinder 42 of the steam turbine can perform work and generate electricity.

[0058] Please continue reading. Figure 1 The present invention also provides a method for the molten salt peak-shaving system of the cogeneration unit, comprising the following steps:

[0059] When the system participates in power peak shaving, it determines whether it is necessary to reduce the output power load.

[0060] If it is necessary to reduce the output electrical load, part of the boiler heat will generate steam to enter the turbine unit to do work and generate electricity, while the other part of the boiler heat will heat the molten salt in the thermal storage device for thermal storage.

[0061] Part of the boiler heat generates steam which enters the turbine unit to do work and generate electricity. Specifically, the steam generated by the boiler enters the high-pressure cylinder 42, the steam reheater 43, and the low-pressure cylinder 44 of the turbine in sequence to do work and generate electricity.

[0062] Another portion of the boiler heat is used to heat the molten salt in the heat storage device for heat storage. Specifically, it is determined whether heat storage is carried out simultaneously by the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit. If heat storage is carried out simultaneously by the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit, it is determined whether steam heat storage or electric heating heat storage is used, because during the heat storage process, either steam heat storage or electric heat storage can be selected to achieve heat storage.

[0063] When using steam for heat storage, open and adjust valves 41 (1), 8 (5), 10 (6), and 11 (7), and close valves 5 (2), 7 (3), and 12 (4). The high-temperature molten salt output from the high-temperature molten salt hot tank 1 is cooled by the molten salt heat release superheater 2, and then the cooled high-temperature molten salt is introduced into the high-temperature molten salt cold tank 3. The high-temperature molten salt circulation electric pump 4 is started, directly introducing the cooled high-temperature molten salt into the high-temperature electric heating bypass pipe, and then into the high-temperature molten salt steam heater 9. The main steam generated by the boiler is input into the high-temperature molten salt steam heater 9 to heat the cooled high-temperature molten salt, resulting in high-temperature molten salt, which is then stored in the high-temperature molten salt hot tank 1. During this process, the high-temperature molten salt electric heater 6 needs to be isolated.

[0064] Simultaneously, open and adjust valves 11 (32), 12 (29), and 13 (31), and close valves 8 (26), 9 (28), and 10 (33). The low-temperature molten salt output from the low-temperature molten salt hot tank 21 is cooled sequentially by the molten salt heat release steam generator 22 and the molten salt heat release water heater 23. The low-temperature molten salt is then introduced into the low-temperature molten salt cold tank 24. The low-temperature molten salt circulation electric pump 25 is started, directly transferring the low-temperature molten salt to the low-temperature molten salt steam heater 30 via the low-temperature electric heating bypass pipe. Steam with a lower heat exchange temperature from the high-temperature molten salt heating component is input into the low-temperature molten salt steam heater 30 to heat the low-temperature molten salt, resulting in high-temperature molten salt, which is then stored in the low-temperature molten salt hot tank 21. During this process, the low-temperature molten salt electric heater 27 needs to be isolated.

[0065] When using electric heating for heat storage, open and adjust valves 41 (1), 5 (2), 7 (3), and 12 (4), and close valves 8 (5), 10 (6), and 11 (7). Pass the low-temperature high-temperature molten salt into the high-temperature molten salt electric heater 6, heat it to obtain a high-temperature molten salt, and then directly store the high-temperature molten salt in the high-temperature molten salt hot tank 1 through the high-temperature steam bypass pipe.

[0066] Simultaneously, valves 26 (number 8), 28 (number 9), and 33 (number 10) are opened and adjusted, while valves 32 (number 11), 29 (number 12), and 31 (number 13) are closed. The low-temperature molten salt output from the low-temperature molten salt hot tank 21 is cooled sequentially by the molten salt heat release steam generator 22 and the molten salt heat release water heater 23. The low-temperature molten salt is then introduced into the low-temperature molten salt cold tank 24. The low-temperature molten salt circulation electric pump 25 is started to transfer the low-temperature molten salt to the low-temperature molten salt electric heater 27 for heating, resulting in high-temperature molten salt. This high-temperature molten salt is then directly stored in the low-temperature molten salt hot tank 21 via the low-temperature steam bypass pipe.

[0067] When using steam for heat storage, if only the low-temperature molten salt operating circuit is used for heat storage, the steam from the steam outlet of the steam reheater 43 can flow through the low-temperature molten salt steam heater 30 to heat the low-temperature molten salt and achieve heat storage. To start the low-temperature molten salt operating circuit, open and adjust valve 16 45 to connect the steam outlet of the steam reheater 43 to the steam inlet of the low-temperature molten salt steam heater 30. The low-temperature molten salt steam heater 30 uses the reheated steam from the steam reheater 43 as a heat source to heat the low-temperature molten salt in a low-temperature state and recover the heat-exchanged, low-temperature hot water. At this time, the high-temperature molten salt steam heater 9 needs to be isolated, i.e., valve 4 12 is opened and adjusted, valves 5 8 and 6 10 are closed, and the high-temperature molten salt electric heater 6 and the low-temperature molten salt electric heater 27 are also isolated. The low-temperature molten salt steam heater 30 is then activated.

[0068] When using electric heating for heat storage, if heat storage is performed solely by the low-temperature molten salt operating circuit, the low-temperature molten salt operating circuit is activated, isolating the high-temperature molten salt electric heater 6, the high-temperature molten salt steam heater 9, and the low-temperature molten salt steam heater 30, and activating the low-temperature molten salt electric heater 27.

[0069] If an increase in output electrical load is required, all the steam generated by the boiler heat is fed into the turbine unit to perform work and generate electricity. Simultaneously, the heat in the thermal storage device is also used to drive the turbine unit to perform work and generate electricity. The thermal storage device can also be used to heat feedwater to generate steam for industrial steam supply, reducing steam extraction from the turbine unit and increasing the unit's power generation capacity.

[0070] Determine whether to activate the high-temperature molten salt operation circuit. If the high-temperature molten salt operation circuit is activated, determine whether to supply industrial steam.

[0071] If industrial steam is supplied, open valves 14 (47) and 15 (48) to activate the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit for heat release. Use the high-temperature molten salt circulating electric pump 4 and the low-temperature molten salt circulating electric pump 25 to isolate the high-temperature molten salt electric heater 6, the high-temperature molten salt steam heater 9, the low-temperature molten salt steam heater 30, and the low-temperature molten salt electric heater 27.

[0072] If industrial steam is not supplied, valve 47 (number 14) is closed, valve 48 (number 15) is opened, and the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit are activated for heat release (see Circuit 1 and Circuit 2 for specific heat release conditions). The high-temperature molten salt electric heater 6, the high-temperature molten salt steam heater 9, the low-temperature molten salt steam heater 30, and the low-temperature molten salt electric heater 27 are isolated. Makeup water is sequentially pumped into the molten salt heat release makeup water heater 23 and the molten salt heat release steam generator 22 by the feed water pump 46. The molten salt in the low-temperature zone, which is in a high-temperature state, is heated to a steam state. The steam is further heated to a high-temperature steam state by the molten salt heat release superheater 2 and then returned to the high-pressure cylinder 42 of the steam turbine. The high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit can be used in combination to further increase the steam temperature and then return it to the high-pressure cylinder 42 of the steam turbine. This increases the steam intake of the high-pressure cylinder of the cogeneration unit, thereby increasing the unit's power generation capacity. In other words, it increases the steam flow rate of the unit and enhances the unit's work capacity.

[0073] If the high-temperature molten salt operating circuit is not activated, and only the low-temperature molten salt operating circuit is activated for heat release (see Circuit 2 for specific heat release conditions), then open valve 14 47 and close valve 15 48. Use the low-temperature molten salt circulating electric pump 25 to isolate the high-temperature molten salt electric heater 6, the high-temperature molten salt steam heater 9, the low-temperature molten salt steam heater 30, and the low-temperature molten salt electric heater 27.

[0074] This method utilizes a high-temperature molten salt operating loop and a low-temperature molten salt operating loop within the thermal storage device. The molten salt in the high-temperature molten salt operating loop has a higher temperature range, while the molten salt in the low-temperature molten salt operating loop has a lower temperature range. The molten salt loops formed by the high-temperature and low-temperature molten salt operating loops are isolated from each other, ensuring that their temperature ranges do not interfere with each other. This allows for the comprehensive utilization of molten salts with different temperature range operating characteristics, enhancing the system's wide-temperature-range operating capability. Furthermore, it enables the cascaded utilization of steam energy, improving efficiency. By combining the high-temperature and low-temperature molten salt operating loops, the steam temperature is further increased, which is then drawn back into the high-pressure cylinder 42 of the steam turbine, increasing the steam intake of the high-pressure cylinder of the cogeneration unit and thus improving the unit's power generation capacity.

[0075] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A molten salt peak-shaving system for a combined heat and power unit, characterized in that, include: The boiler, the steam turbine unit, and the thermal storage device are provided. The steam generated by the boiler enters the steam turbine unit to perform work and generate electricity. The thermal storage device includes a high-temperature molten salt operating circuit and a low-temperature molten salt operating circuit. The high-temperature molten salt operating circuit includes a high-temperature molten salt hot tank, a molten salt heat release superheater, a high-temperature molten salt cold tank, a high-temperature molten salt circulating electric pump, and a high-temperature molten salt heating assembly; The molten salt outlet of the high-temperature molten salt hot tank is connected to the molten salt inlet of the molten salt heat release superheater, the molten salt outlet of the molten salt heat release superheater is connected to the molten salt inlet of the high-temperature molten salt cold tank, the molten salt outlet of the high-temperature molten salt cold tank is connected to the molten salt inlet of the high-temperature molten salt heating assembly, the high-temperature molten salt circulating electric pump is installed at the molten salt inlet of the high-temperature molten salt heating assembly, and the molten salt outlet of the high-temperature molten salt heating assembly is connected to the molten salt inlet of the high-temperature molten salt hot tank. The cryogenic molten salt operating circuit includes a cryogenic molten salt hot tank, a molten salt heat release steam generator, a molten salt heat release water heater, a cryogenic molten salt cold tank, a cryogenic molten salt circulating electric pump, and a cryogenic molten salt heating assembly; The molten salt outlet of the low-temperature molten salt hot tank is connected to the molten salt inlet of the molten salt heat release steam generator; the molten salt outlet of the molten salt heat release steam generator is connected to the molten salt inlet of the molten salt heat release water heater; the molten salt outlet of the molten salt heat release water heater is connected to the molten salt inlet of the low-temperature molten salt cold tank; the molten salt outlet of the low-temperature molten salt cold tank is connected to the molten salt inlet of the low-temperature molten salt heating assembly; the low-temperature molten salt circulating electric pump is installed at the molten salt inlet of the low-temperature molten salt heating assembly; and the molten salt outlet of the low-temperature molten salt heating assembly is connected to the molten salt inlet of the low-temperature molten salt hot tank. The steam outlet of the boiler is connected to the steam inlet of the high-temperature molten salt heating component, and the steam outlet of the high-temperature molten salt heating component is connected to the steam inlet of the low-temperature molten salt heating component; the high-temperature molten salt operating circuit uses high-temperature molten salt with a temperature range of 300-750℃, and the low-temperature molten salt operating circuit uses low-temperature molten salt with a temperature range of 150-550℃. The system also includes a molten salt steam supply circuit, which includes a water supply pump and an industrial steam supply pipe. The water supply inlet of the water supply pump is connected to the water replenishment pipe and the water supply outlet of the low-temperature molten salt heating component. The water supply outlet of the water supply pump is connected to the water supply inlet of the molten salt heat release water replenishment heater. The water supply outlet of the molten salt heat release water replenishment heater is connected to the water supply inlet of the molten salt heat release steam generator. The steam outlet of the molten salt heat release steam generator is connected to the steam inlet of the industrial steam supply pipe. The turbine unit includes a high-pressure turbine cylinder, a steam reheater, and a low-pressure turbine cylinder. The steam outlet of the boiler is connected to the steam inlet of the high-pressure turbine cylinder, the steam outlet of the high-pressure turbine cylinder is connected to the steam inlet of the steam reheater, the steam outlet of the steam reheater is connected to the steam inlet of the low-pressure turbine cylinder, and the steam outlet of the low-pressure turbine cylinder is connected to the condenser. The steam outlet of the molten salt heat release superheater is connected to the steam inlet of the high-pressure turbine cylinder. If it is necessary to reduce the output electrical load, a portion of the steam generated by the boiler is used to heat the molten salt in the thermal storage device for heat storage. The specific steps are as follows: Determine whether heat storage is being performed simultaneously by both high-temperature molten salt operating circuit and low-temperature molten salt operating circuit; If so, the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit simultaneously perform heat storage; the high-temperature molten salt circulation electric pump and the low-temperature molten salt circulation electric pump are started, so that the high-temperature molten salt in the high-temperature molten salt operating circuit flows out from the high-temperature molten salt cold tank, absorbs heat through the high-temperature molten salt heating component, and is stored in the high-temperature molten salt hot tank; at the same time, the low-temperature molten salt in the low-temperature molten salt operating circuit flows out from the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank; If not, then only the low-temperature molten salt operating circuit is used for heat storage. In this case, the low-temperature molten salt circulating electric pump is started, so that the low-temperature molten salt in the low-temperature molten salt operating circuit flows out of the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank. If used only for supplying industrial steam, the low-temperature molten salt operating circuit is used alone. Open and adjust valve 14, close valve 15, and the water is pumped into the molten salt heat release water heater and molten salt heat release steam generator in sequence by the water supply pump. The molten salt in the low-temperature zone, which is in a high-temperature state, is heated to a steam state and used to supply industrial steam. If it is used to supply industrial steam and to power the turbine unit, open valves 14 and 15, and the makeup water is sequentially pumped into the molten salt heat release makeup water heater and the molten salt heat release steam generator by the feed water pump. The molten salt in the low temperature zone at high temperature is heated to the steam state, and the steam is further heated to the high temperature steam state by the molten salt heat release superheater and then led back to the high pressure cylinder of the turbine.

2. The system as described in claim 1, characterized in that, The turbine unit includes a steam reheater, the steam outlet of which is connected to the steam inlet of the low-temperature molten salt steam heater.

3. The system as described in claim 1, characterized in that, The high-temperature molten salt heating assembly includes a high-temperature molten salt electric heater, a high-temperature electric heating bypass pipe, a high-temperature molten salt steam heater, and a high-temperature steam bypass pipe. The high-temperature electric heating bypass pipe is located between the molten salt inlet and molten salt outlet of the high-temperature molten salt electric heater. The high-temperature steam bypass pipe is located between the molten salt inlet and molten salt outlet of the high-temperature molten salt steam heater. The molten salt outlet of the high-temperature molten salt cold tank is connected to the molten salt inlet of the high-temperature molten salt electric heater. The high-temperature molten salt circulating electric pump is installed at the molten salt inlet of the high-temperature molten salt electric heater. The molten salt outlet of the high-temperature molten salt electric heater is connected to the molten salt inlet of the high-temperature molten salt steam heater. The molten salt outlet of the high-temperature molten salt steam heater is connected to the molten salt inlet of the high-temperature molten salt hot tank.

4. The system as described in claim 1, characterized in that, The cryogenic molten salt heating assembly includes a cryogenic molten salt electric heater, a cryogenic electric heater bypass pipe, a cryogenic molten salt steam heater, and a cryogenic steam bypass pipe. The cryogenic electric heater bypass pipe is located between the molten salt inlet and the molten salt outlet of the cryogenic molten salt electric heater. The cryogenic steam bypass pipe is located between the molten salt inlet and the molten salt outlet of the cryogenic molten salt steam heater. The molten salt outlet of the cryogenic molten salt cold tank is connected to the molten salt inlet of the cryogenic molten salt electric heater. The cryogenic molten salt circulating electric pump is installed at the molten salt inlet of the cryogenic molten salt electric heater. The molten salt outlet of the cryogenic molten salt electric heater is connected to the molten salt inlet of the cryogenic molten salt steam heater. The molten salt outlet of the cryogenic molten salt steam heater is connected to the molten salt inlet of the cryogenic molten salt hot tank.

5. A method for a molten salt peak-shaving system in a cogeneration unit as described in claim 1, characterized in that, Includes the following steps: When the system participates in power peak shaving, it determines whether it is necessary to reduce the output power load. If it is necessary to reduce the output electrical load, part of the steam generated by the boiler will enter the turbine unit to do work and generate electricity, and the other part of the steam will heat the molten salt in the heat storage device for heat storage. If an increase in output electrical load is required, all the steam generated by the boiler will enter the turbine unit to do work and generate electricity. At the same time, the heat in the heat storage device will heat the feedwater to generate steam, and this part of the steam will also be fed into the turbine unit to drive the turbine unit to do work.

6. The method as described in claim 5, characterized in that, If it is necessary to reduce the output electrical load, a portion of the steam generated by the boiler is used to heat the molten salt in the thermal storage device for heat storage. The specific steps are as follows: Determine whether heat storage is being performed simultaneously by both high-temperature molten salt operating circuit and low-temperature molten salt operating circuit; If so, the high-temperature molten salt operating circuit and the low-temperature molten salt operating circuit simultaneously perform heat storage; the high-temperature molten salt circulation electric pump and the low-temperature molten salt circulation electric pump are started, so that the high-temperature molten salt in the high-temperature molten salt operating circuit flows out from the high-temperature molten salt cold tank, absorbs heat through the high-temperature molten salt heating component, and is stored in the high-temperature molten salt hot tank; at the same time, the low-temperature molten salt in the low-temperature molten salt operating circuit flows out from the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank; If not, then only the low-temperature molten salt operating circuit stores heat. In this case, the low-temperature molten salt circulating electric pump is started, so that the low-temperature molten salt in the low-temperature molten salt operating circuit flows out from the low-temperature molten salt cold tank, absorbs heat through the low-temperature molten salt heating component, and is stored in the low-temperature molten salt hot tank.

7. The method as described in claim 6, characterized in that, If an increase in output electrical load is required, the molten salt stored in the high-temperature molten salt tank and the low-temperature molten salt tank in the thermal storage device is used to heat the feedwater to generate steam. This steam is then fed into the turbine unit to drive the turbine unit to perform work. The specific steps are as follows: Start the low-temperature molten salt circulating electric pump, so that the hot low-temperature molten salt in the low-temperature molten salt operating circuit flows out of the low-temperature molten salt hot tank, flows through the molten salt heat release steam generator and the molten salt heat release water heater, and heats the feedwater into steam for industrial steam supply; start the high-temperature molten salt circulating electric pump, so that the hot high-temperature molten salt in the high-temperature molten salt operating circuit flows out of the high-temperature molten salt hot tank, flows through the molten salt heat release superheater, and further heats the steam, and the steam is fed back to the steam turbine unit.

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