A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage and its operation method

Abstract

This invention discloses a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal storage and its operation method. The system includes a conventional coal-fired generator set and a coupled molten salt thermal storage system. The molten salt thermal storage system uses a method of sequentially heating molten salt with exhaust steam from the intermediate-pressure cylinder of the turbine and reheat steam for thermal storage, and a boiler feedwater bypass scheme for heat release. An SSS clutch is also used to increase the steam diversion flow rate during the thermal storage process. During thermal storage, under the condition of ensuring the minimum stable combustion load of the boiler, a portion of the exhaust steam from the intermediate-pressure cylinder of the coal-fired generator set and reheat steam are diverted to the molten salt thermal storage system. The two steam streams are used to sequentially heat the molten salt in the low-temperature molten salt tank. The complete diversion of the turbine intermediate-pressure cylinder exhaust steam for thermal storage is achieved through the SSS clutch. During heat release, without increasing the boiler coal feed rate, the system uses the molten salt thermal storage system to heat a portion of the condensate from the coal-fired generator set, thereby improving the load change rate of the coal-fired generator set.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power generation flexibility improvement and retrofit technology, specifically involving a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal storage and its operation method. Background Technology

[0002] In recent years, with the implementation of the "dual carbon" target, the proportion of coal-fired power generation capacity has been decreasing year by year, while the installed capacity of renewable energy power generation such as photovoltaic and wind power has developed rapidly, accounting for more than 50% of my country's total installed power generation capacity. However, renewable energy sources such as solar and wind power have strong volatility and intermittency, which requires coal-fired units to frequently participate in grid peak shaving and frequency regulation. However, the regulation capacity of traditional coal-fired units is limited, making it difficult to meet the needs of larger-scale renewable energy power grid connection, which has an adverse impact on the grid's frequency stability. Therefore, in order to give full play to the "ballast" role of coal-fired power generation in my country's power industry, how to achieve efficient and flexible operation is the most urgent technical requirement facing coal-fired power generation.

[0003] Currently, the minimum load factor of coal-fired power units is generally around 30%. Further reducing the load factor requires measures such as oil injection for supplemental combustion, resulting in the waste of high-quality energy. Existing technologies integrate thermal storage systems into traditional coal-fired power units to further reduce their minimum load factor. However, limitations such as the pinch-point temperature difference in the superheated steam heat exchange process and the minimum condensate flow rate of the turbine make it difficult to further increase the load factor of coal-fired power units. Therefore, it is necessary to further technically modify existing coal-fired power generation systems with integrated thermal storage to achieve ultra-low load operation. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal storage and its operation method. The system includes a conventional coal-fired generator set and a coupled molten salt thermal storage system. The molten salt thermal storage system uses a method of sequentially heating the molten salt with exhaust steam from the intermediate-pressure cylinder of the split-flow turbine and reheat steam for thermal storage, and a boiler feedwater bypass scheme for heat release. In addition, an SSS clutch is used to increase the steam diversion flow rate during the thermal storage process, thereby improving the thermal storage power. During the heat storage process, under the condition of ensuring the minimum stable combustion load of the boiler, the system diverts part of the exhaust steam from the intermediate-pressure cylinder of the turbine of the coal-fired generator set and the reheat steam to the molten salt heat storage system. The two streams of steam are used to heat the molten salt in the low-temperature molten salt tank in sequence. The complete diversion of the exhaust steam from the intermediate-pressure cylinder of the turbine for heat storage is achieved through the engagement of the SSS clutch. This not only improves the deep peak-shaving capability of the coal-fired generator set, but also effectively improves the energy cascade utilization of the molten salt heat storage system. During the heat release process, without increasing the boiler coal feed, the system uses the molten salt heat storage system to heat part of the condensate of the coal-fired generator set, thereby rapidly increasing the working fluid flow rate in the turbine and improving the load change rate of the coal-fired generator set.

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

[0006] A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage includes a coal-fired generator set and a thermal storage circuit and a heat release circuit of a molten salt thermal energy storage system coupled to the coal-fired generator set. The coal-fired generator set includes a boiler 1, a high-pressure turbine cylinder 2, a medium-pressure turbine cylinder 3, a low-pressure turbine cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10, and a high-pressure heater 11. The main steam outlet of the boiler 1 is connected to the steam inlet of the high-pressure turbine cylinder 2. The extraction steam outlet of turbine 2 is connected to the steam inlet of high-pressure heater 11, and the steam outlet of turbine high-pressure cylinder 2 is connected to the reheat steam inlet of boiler 1. The reheat steam outlet of boiler 1 is divided into two paths: one path is connected to the water inlet of steam-molten salt heat exchanger 19 of the heat storage circuit of molten salt heat storage system via reheat steam control valve 13, and the other path is connected to the steam inlet of turbine intermediate-pressure cylinder 3 via reheat steam control valve 12. The extraction steam outlet of turbine intermediate-pressure cylinder 3 is connected to the steam inlet of deaerator 9, and the steam outlet of turbine intermediate-pressure cylinder 3 is divided into two paths. There are two paths: one path connects to the water inlet of the No. 2 steam-molten salt heat exchanger 18 in the heat storage circuit of the molten salt thermal storage system via the No. 2 intermediate-pressure cylinder exhaust control valve 15; the other path connects to the steam inlet of the turbine low-pressure cylinder 4 via the No. 1 intermediate-pressure cylinder exhaust control valve 14. The extraction steam outlet of the turbine low-pressure cylinder 4 is connected to the steam inlet of the low-pressure heater 8, and the steam outlet of the turbine low-pressure cylinder 4 is connected to the steam inlet of the condenser 6. The water outlet of the condenser 6 is connected to the water inlet of the low-pressure heater 8 via the condensate pump 7. The water inlet of the low-pressure heater 8... The outlet is divided into two paths: one leads to the condensate flow control valve 21, and the other is connected to the water inlet of the deaerator 9. The water outlet of the deaerator 9 is connected to the water inlet of the high-pressure heater 11 via the feed water pump 10. The water outlet of the high-pressure heater 11 and the water outlet of the water-molten salt heat exchanger 23 of the heat storage circuit of the molten salt heat storage system are combined and connected to the feed water inlet of the boiler 1. The high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4 of the turbine are connected by a rotating shaft and jointly drive the generator 5 to output electrical power.

[0007] The thermal storage circuit of the molten salt thermal storage system includes a low-temperature molten salt tank 16, a low-temperature molten salt pump 17, a high-temperature molten salt tank 20, a second reheat steam control valve 13, a second intermediate-pressure cylinder exhaust control valve 15, a first steam-molten salt heat exchanger 19, and a second steam-molten salt heat exchanger 18. A portion of the reheat steam diverted by the second reheat steam control valve 13 is exchanged with heat in the first steam-molten salt heat exchanger 19 and then flows into the water inlet of the deaerator 9. The second intermediate-pressure cylinder exhaust control valve 15 diverts... The steam from the outlet of the intermediate pressure cylinder 3 of the steam turbine is also fed into the water inlet of the deaerator 9 after heat exchange in the No. 2 steam-molten salt heat exchanger 18; the molten salt outlet of the low-temperature molten salt tank 16 is connected to the molten salt inlet of the No. 2 steam-molten salt heat exchanger 18 via the low-temperature molten salt pump 17; the molten salt outlet of the No. 2 steam-molten salt heat exchanger 18 is connected to the molten salt inlet of the No. 1 steam-molten salt heat exchanger 19; the molten salt outlet of the No. 1 steam-molten salt heat exchanger 19 is connected to the molten salt inlet of the high-temperature molten salt tank 20.

[0008] The heat release circuit of the molten salt thermal storage system includes a high-temperature molten salt pump 24, a condensate diversion control valve 21, a condensate bypass pump 22, and a water-molten salt heat exchanger 23. A portion of the condensate diverted by the condensate diversion control valve 21 is connected to the water inlet of the water-molten salt heat exchanger 23 via the condensate bypass pump 22. The water outlet of the water-molten salt heat exchanger 23 flows into the feedwater inlet of the boiler 1. The molten salt outlet of the high-temperature molten salt tank 20 is connected to the molten salt inlet of the water-molten salt heat exchanger 23 via the high-temperature molten salt pump 24. The molten salt outlet of the water-molten salt heat exchanger 23 is connected to the inlet of the low-temperature molten salt tank 16.

[0009] Furthermore, the No. 1 steam-molten salt heat exchanger 19, the No. 2 steam-molten salt heat exchanger 18, and the water-molten salt heat exchanger 23 are all indirect-contact water-molten salt heat exchangers.

[0010] Furthermore, the maximum steam diversion flow rate of the second intermediate pressure cylinder exhaust control valve 15 is 100% of the total exhaust flow rate of the intermediate pressure cylinder.

[0011] Furthermore, an SSS clutch 18 is provided between the intermediate pressure cylinder 3 and the low pressure cylinder 4 of the steam turbine.

[0012] Furthermore, the generator 5 is arranged on one side of the high-pressure cylinder 2 of the steam turbine, and is connected to the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 of the steam turbine via a rotating shaft.

[0013] Furthermore, the temperature of the low-temperature molten salt tank 16 is 115℃~120℃, and the temperature of the high-temperature molten salt tank 20 is 300℃~450℃.

[0014] An operation method for a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage is as follows:

[0015] 1) When the coal-fired power generation unit is running at low load, the heat storage circuit of the molten salt thermal storage system is opened and the heat release circuit is closed. The No. 2 reheat steam control valve 13 and the No. 2 intermediate pressure cylinder exhaust control valve 15 are opened, and the low-temperature molten salt pump 17 is started. The low-temperature molten salt is heated in sequence by the diverted intermediate pressure cylinder exhaust steam and reheat steam. The molten salt in the low-temperature molten salt tank 16 is heated in sequence in the No. 2 steam-molten salt heat exchanger 18 and the No. 1 steam-molten salt heat exchanger 19 and then sent to the high-temperature molten salt tank 20 for storage. The operating objective at this stage is to reduce the external power output of the coal-fired power generation unit by diverting reheat steam for thermal storage and intermediate pressure cylinder exhaust steam for thermal storage, while ensuring the minimum stable combustion load of the boiler.

[0016] 2) When the coal-fired power generation unit needs to operate at ultra-low load, the exhaust steam from the intermediate pressure cylinder 3 of the turbine is completely diverted to the No. 2 steam-molten salt heat exchanger 18 to heat the molten salt. At this time, the SSS clutch 18 is further disengaged, and the low pressure cylinder 4 of the turbine is disconnected from the coal-fired power generation unit and does not perform external work. The operating objective at this stage is to achieve ultra-low load operation of the coal-fired power generation unit while ensuring the minimum stable combustion load of the boiler.

[0017] 3) When the coal-fired power generation unit needs to rapidly increase its load rate, the heat release circuit of the molten salt thermal storage system is opened and the thermal storage circuit is closed. The condensate diversion control valve 21 is opened, and the condensate bypass pump 22 and the high-temperature molten salt pump 24 are started. The heat stored in the molten salt is used to heat the diverted condensate through the water-molten salt heat exchanger 23. The heated condensate flows into the feedwater inlet of the boiler 1. The molten salt in the high-temperature molten salt tank 20 is sent to the low-temperature molten salt tank 16 for storage after heat exchange. The operating objective at this stage is to rapidly increase the steam flow rate in the turbine and improve the load change rate of the coal-fired power generation unit by heating the bypass condensate with molten salt without increasing the boiler load.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] (1) By integrating a molten salt thermal storage system into a coal-fired power generation unit and using the exhaust steam from the intermediate pressure cylinder of the split turbine and reheat steam to heat the molten salt in sequence, the present invention can significantly reduce the minimum electrical load rate of the coal-fired power generation unit and realize the cascade utilization of energy.

[0020] (2) The present invention sets an SSS clutch between the intermediate pressure cylinder and the low pressure cylinder of the steam turbine, which ensures the safety of the low pressure cylinder of the steam turbine and realizes the complete diversion of the exhaust steam of the intermediate pressure cylinder, thereby greatly reducing the minimum electrical load rate of the coal-fired power generation unit.

[0021] (3) In the process of heat storage, the output power of coal-fired units that are difficult to connect to the grid is stored in the form of heat energy. When the coal-fired unit needs to quickly increase the load rate, the rapid heat release of the molten salt heat storage system effectively improves the load change rate of the coal-fired unit and can achieve a better transformation effect. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, the present invention provides a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal storage, including a coal-fired generator set and a thermal storage circuit and a heat release circuit of the molten salt thermal storage system coupled to the coal-fired generator set.

[0025] The coal-fired power generation unit includes a boiler 1, a high-pressure turbine cylinder 2, a medium-pressure turbine cylinder 3, a low-pressure turbine cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10, and a high-pressure heater 11; the main steam outlet of the boiler 1 is connected to the steam inlet of the high-pressure turbine cylinder 2; the extraction steam outlet of the high-pressure turbine cylinder 2 is connected to the steam inlet of the high-pressure heater 11, and the steam outlet of the high-pressure turbine cylinder 2 is connected to the reheat steam inlet of the boiler 1; the boiler 1 The reheat steam outlet is divided into two paths. One path connects to the water inlet of the No. 1 steam-molten salt heat exchanger 19 in the heat storage circuit of the molten salt heat storage system via the No. 2 reheat steam control valve 13. The other path connects to the steam inlet of the intermediate pressure cylinder 3 of the turbine via the No. 1 reheat steam control valve 12. The extraction steam outlet of the intermediate pressure cylinder 3 of the turbine is connected to the steam inlet of the deaerator 9. The steam outlet of the intermediate pressure cylinder 3 of the turbine is divided into two paths. One path connects to the No. 2 intermediate pressure cylinder exhaust control valve 15 in the heat storage circuit of the molten salt heat storage system via the No. 2 reheat steam control valve 19. The water inlet of the steam-molten salt heat exchanger 18 is connected, and the other path is connected to the steam inlet of the low-pressure cylinder 4 of the turbine via the exhaust control valve 14 of the first intermediate-pressure cylinder. The extraction steam outlet of the low-pressure cylinder 4 of the turbine is connected to the steam inlet of the low-pressure heater 8, and the steam outlet of the low-pressure cylinder 4 of the turbine is connected to the steam inlet of the condenser 6. The water outlet of the condenser 6 is connected to the water inlet of the low-pressure heater 8 via the condensate pump 7. The water outlet of the low-pressure heater 8 is divided into two paths, one of which leads to the condensate flow control valve 14. The valve 21 is connected to the water inlet of the deaerator 9; the water outlet of the deaerator 9 is connected to the water inlet of the high-pressure heater 11 via the feed water pump 10; the water outlet of the high-pressure heater 11 and the water outlet of the water-molten salt heat exchanger 23 of the heat release circuit of the molten salt heat storage system are combined and connected to the feed water inlet of the boiler 1; the high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4 of the steam turbine are connected by a rotating shaft and jointly drive the generator 5 to output electrical power.

[0026] The thermal storage circuit of the molten salt thermal storage system includes a low-temperature molten salt tank 16, a low-temperature molten salt pump 17, a high-temperature molten salt tank 20, a second reheat steam control valve 13, a second intermediate-pressure cylinder exhaust control valve 15, a first steam-molten salt heat exchanger 19, and a second steam-molten salt heat exchanger 18. A portion of the reheat steam diverted by the second reheat steam control valve 13 is exchanged with heat in the first steam-molten salt heat exchanger 19 and then flows into the water inlet of the deaerator 9. The second intermediate-pressure cylinder exhaust control valve 15 diverts... The steam from the outlet of the intermediate pressure cylinder 3 of the steam turbine is also fed into the water inlet of the deaerator 9 after heat exchange in the No. 2 steam-molten salt heat exchanger 18; the molten salt outlet of the low-temperature molten salt tank 16 is connected to the molten salt inlet of the No. 2 steam-molten salt heat exchanger 18 via the low-temperature molten salt pump 17; the molten salt outlet of the No. 2 steam-molten salt heat exchanger 18 is connected to the molten salt inlet of the No. 1 steam-molten salt heat exchanger 19; the molten salt outlet of the No. 1 steam-molten salt heat exchanger 19 is connected to the molten salt inlet of the high-temperature molten salt tank 20.

[0027] The heat release circuit of the molten salt thermal storage system includes a high-temperature molten salt pump 24, a condensate diversion control valve 21, a condensate bypass pump 22, and a water-molten salt heat exchanger 23. A portion of the condensate diverted by the condensate diversion control valve 21 is connected to the water inlet of the water-molten salt heat exchanger 23 via the condensate bypass pump 22. The water outlet of the water-molten salt heat exchanger 23 flows into the feedwater inlet of the boiler 1. The molten salt outlet of the high-temperature molten salt tank 20 is connected to the molten salt inlet of the water-molten salt heat exchanger 23 via the high-temperature molten salt pump 24. The molten salt outlet of the water-molten salt heat exchanger 23 is connected to the inlet of the low-temperature molten salt tank 16.

[0028] Furthermore, the No. 1 steam-molten salt heat exchanger 19, the No. 2 steam-molten salt heat exchanger 18, and the water-molten salt heat exchanger 23 are all indirect-wall water-molten salt heat exchangers, which can improve the deep peak-shaving capacity and load change rate of coal-fired power generating units through the molten salt thermal storage system.

[0029] Furthermore, the maximum steam diversion flow rate of the second intermediate-pressure cylinder exhaust control valve 15 is 100% of the total exhaust flow of the intermediate-pressure cylinder, which significantly reduces the output power of the coal-fired power generator set by cutting off the low-pressure cylinder.

[0030] Furthermore, an SSS clutch 18 is provided between the intermediate pressure cylinder 3 and the low pressure cylinder 4 of the steam turbine. By controlling the SSS clutch, the low pressure cylinder can be disconnected, which greatly reduces the output power of the coal-fired unit.

[0031] Furthermore, the generator 5 is arranged on one side of the high-pressure cylinder 2 of the steam turbine, and it is connected to the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 of the steam turbine through a rotating shaft, so that the generator can continue to operate even after the low-pressure cylinder is cut off.

[0032] Furthermore, the temperature of the low-temperature molten salt tank 16 is 115℃~120℃, and the temperature of the high-temperature molten salt tank 20 is 300℃~450℃. This temperature range can achieve good temperature matching between the molten salt thermal storage system and the reheat steam, intermediate pressure cylinder exhaust steam, and boiler feedwater bypass in the coal-fired power generation unit, thereby improving the system's energy efficiency.

[0033] like Figure 1 As shown, a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage is operated as follows:

[0034] 1) When the coal-fired power generation unit is running at low load, the heat storage circuit of the molten salt thermal storage system is opened and the heat release circuit is closed. The No. 2 reheat steam control valve 13 and the No. 2 intermediate pressure cylinder exhaust control valve 15 are opened, and the low-temperature molten salt pump 17 is started. The low-temperature molten salt is heated in sequence by the diverted intermediate pressure cylinder exhaust steam and reheat steam. The molten salt in the low-temperature molten salt tank 16 is heated in sequence in the No. 2 steam-molten salt heat exchanger 18 and the No. 1 steam-molten salt heat exchanger 19 and then sent to the high-temperature molten salt tank 20 for storage. The operating objective at this stage is to reduce the external power output of the coal-fired power generation unit by diverting reheat steam for thermal storage and intermediate pressure cylinder exhaust steam for thermal storage, while ensuring the minimum stable combustion load of the boiler.

[0035] 2) When the coal-fired power generation unit needs to operate at ultra-low load, the exhaust steam from the intermediate pressure cylinder 3 of the steam turbine is completely diverted to the No. 2 steam-molten salt heat exchanger 18 to heat the molten salt. At this time, the SSS clutch 18 is further disengaged, and the low pressure cylinder 4 of the steam turbine is disconnected from the coal-fired power generation unit and does not perform external work. The operating objective at this stage is to achieve ultra-low load rate operation of the coal-fired power generation unit while ensuring the minimum stable combustion load of the boiler.

[0036] 3) When the coal-fired power generation unit needs to rapidly increase its load rate, the heat release circuit of the molten salt thermal storage system is opened and the thermal storage circuit is closed. The condensate diversion control valve 21 is opened, and the condensate bypass pump 22 and the high-temperature molten salt pump 24 are started. The heat stored in the molten salt is used to heat the diverted condensate through the water-molten salt heat exchanger 23. The heated condensate flows into the feedwater inlet of the boiler 1. The molten salt in the high-temperature molten salt tank 20 is sent to the low-temperature molten salt tank 16 for storage after heat exchange. The operating objective at this stage is to rapidly increase the steam flow rate in the turbine and improve the load change rate of the coal-fired power generation unit by heating the bypass condensate with molten salt without increasing the boiler load.

[0037] In summary, this invention, by integrating a molten salt thermal storage system into a coal-fired power generation unit and using intermediate-pressure cylinder exhaust steam and reheat steam to sequentially heat the molten salt, can significantly reduce the minimum electrical load rate of the coal-fired power generation unit and achieve cascaded energy utilization. Furthermore, an SSS clutch is installed between the intermediate-pressure cylinder and the low-pressure cylinder of the turbine, ensuring the safety of the low-pressure cylinder while achieving complete diversion of the intermediate-pressure cylinder exhaust steam, thereby greatly reducing the minimum electrical load rate of the coal-fired power generation unit. Through the rapid heat release of the molten salt thermal storage system, the load change rate of the coal-fired unit is effectively improved, achieving good retrofit results.

Claims

1. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage, characterized in that: This includes coal-fired power generating units and the heat storage circuit and heat release circuit of the molten salt thermal storage system coupled with the coal-fired power generating units. The coal-fired power generation unit includes a boiler (1), a high-pressure cylinder (2) of a steam turbine, an intermediate-pressure cylinder (3) of a steam turbine, a low-pressure cylinder (4) of a steam turbine, a generator (5), a condenser (6), a condensate pump (7), a low-pressure heater (8), a deaerator (9), a feedwater pump (10), and a high-pressure heater (11); the main steam outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (2) of the steam turbine; the extraction steam outlet of the high-pressure cylinder (2) of the steam turbine is connected to the steam inlet of the high-pressure heater (11), and the steam outlet of the high-pressure cylinder (2) of the steam turbine is connected to the reheater of the boiler (1). The steam inlet is connected; the reheat steam outlet of the boiler (1) is divided into two paths, one path is connected to the water medium inlet of the No. 1 steam-molten salt heat exchanger (19) of the molten salt heat storage system via the No. 2 reheat steam control valve (13), and the other path is connected to the steam inlet of the intermediate pressure cylinder (3) of the turbine via the No. 1 reheat steam control valve (12); the extraction steam outlet of the intermediate pressure cylinder (3) of the turbine is connected to the steam inlet of the deaerator (9), and the steam outlet of the intermediate pressure cylinder (3) of the turbine is divided into two paths, one path is connected to the heat storage circuit of the molten salt heat storage system via the No. 2 intermediate pressure cylinder exhaust control valve (15). The water inlet of the No. 2 steam-molten salt heat exchanger (18) is connected, and the other path is connected to the steam inlet of the low-pressure cylinder (4) of the turbine via the exhaust control valve (14) of the No. 1 intermediate-pressure cylinder; the extraction steam outlet of the turbine low-pressure cylinder (4) is connected to the steam inlet of the low-pressure heater (8), and the steam outlet of the turbine low-pressure cylinder (4) is connected to the steam inlet of the condenser (6); the water outlet of the condenser (6) is connected to the water inlet of the low-pressure heater (8) via the condensate pump (7); the water outlet of the low-pressure heater (8) is divided into two paths, one of which leads to the condensate diversion. The control valve (21) is connected to the water inlet of the deaerator (9) on the other side; the water outlet of the deaerator (9) is connected to the water inlet of the high-pressure heater (11) via the feed water pump (10); the water outlet of the high-pressure heater (11) and the water outlet of the water-molten salt heat exchanger (23) of the heat release circuit of the molten salt heat storage system are connected together to the feed water inlet of the boiler (1); the high-pressure cylinder (2), the intermediate-pressure cylinder (3) and the low-pressure cylinder (4) of the steam turbine are connected by a rotating shaft and jointly drive the generator (5) to output electrical power. The thermal storage circuit of the molten salt thermal storage system includes a low-temperature molten salt tank (16), a low-temperature molten salt pump (17), a high-temperature molten salt tank (20), a second reheat steam control valve (13), a second intermediate-pressure cylinder exhaust control valve (15), a first steam-molten salt heat exchanger (19), and a second steam-molten salt heat exchanger (18). A portion of the reheat steam diverted by the second reheat steam control valve (13) is exchanged with the first steam-molten salt heat exchanger (19) and then flows into the water inlet of the deaerator (9). The second intermediate-pressure cylinder exhaust control valve (15) further divides the reheat steam... The steam from the outlet of the intermediate pressure cylinder (3) of the steam turbine is exchanged for heat in the No. 2 steam-molten salt heat exchanger (18) and then flows into the water inlet of the deaerator (9); the molten salt outlet of the low-temperature molten salt tank (16) is connected to the molten salt inlet of the No. 2 steam-molten salt heat exchanger (18) via the low-temperature molten salt pump (17); the molten salt outlet of the No. 2 steam-molten salt heat exchanger (18) is connected to the molten salt inlet of the No. 1 steam-molten salt heat exchanger (19); the molten salt outlet of the No. 1 steam-molten salt heat exchanger (19) is connected to the molten salt inlet of the high-temperature molten salt tank (20); The heat release circuit of the molten salt thermal storage system includes a high-temperature molten salt pump (24), a condensate diversion control valve (21), a condensate bypass pump (22), and a water-molten salt heat exchanger (23). A portion of the condensate diverted by the condensate diversion control valve (21) is connected to the water inlet of the water-molten salt heat exchanger (23) via the condensate bypass pump (22). The water outlet of the water-molten salt heat exchanger (23) flows into the feedwater inlet of the boiler (1). The molten salt outlet of the high-temperature molten salt tank (20) is connected to the molten salt inlet of the water-molten salt heat exchanger (23) via the high-temperature molten salt pump (24). The molten salt outlet of the water-molten salt heat exchanger (23) is connected to the inlet of the low-temperature molten salt tank (16). The maximum steam diversion flow rate of the No. 2 intermediate pressure cylinder exhaust control valve (15) is 100% of the total exhaust flow rate of the intermediate pressure cylinder; An SSS clutch (18) is provided between the intermediate pressure cylinder (3) and the low pressure cylinder (4) of the steam turbine.

2. The safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage according to claim 1, characterized in that: The No. 1 steam-molten salt heat exchanger (19), the No. 2 steam-molten salt heat exchanger (18), and the water-molten salt heat exchanger (23) are all indirect-wall water-molten salt heat exchangers.

3. The safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage according to claim 1, characterized in that: The generator (5) is arranged on one side of the high-pressure cylinder (2) of the steam turbine, and is connected to the high-pressure cylinder (2) and the intermediate-pressure cylinder (3) of the steam turbine via a rotating shaft.

4. The safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage according to claim 1, characterized in that: The temperature of the low-temperature molten salt tank (16) is 115℃~120℃, and the temperature of the high-temperature molten salt tank (20) is 300℃~450℃.

5. The operation method of a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt thermal energy storage as described in any one of claims 1 to 4, characterized in that: Specifically as follows: 1) When the coal-fired power generation unit is running at low load, the heat storage circuit of the molten salt heat storage system is opened and the heat release circuit is closed. The No. 2 reheat steam control valve (13) and the No. 2 intermediate pressure cylinder exhaust control valve (15) are opened, and the low temperature molten salt pump (17) is started. The low temperature molten salt is heated in sequence by the diverted intermediate pressure cylinder exhaust steam and reheat steam. The molten salt in the low temperature molten salt tank (16) is heated in sequence in the No. 2 steam-molten salt heat exchanger (18) and the No. 1 steam-molten salt heat exchanger (19) and then sent to the high temperature molten salt tank (20) for storage. The operation objective at this stage is to reduce the external power output of the coal-fired power generation unit by diverting reheat steam heat storage and intermediate pressure cylinder exhaust heat storage under the condition of ensuring the minimum stable combustion load of the boiler. 2) When the coal-fired power generation unit needs to operate at ultra-low load, the exhaust steam of the intermediate pressure cylinder (3) of the steam turbine is completely diverted to the No. 2 steam-molten salt heat exchanger (18) to heat the molten salt. At this time, the SSS clutch (18) is further disconnected, and the low pressure cylinder (4) of the steam turbine is disconnected from the coal-fired power generation unit and does not perform external work. The operating objective of this stage is to achieve ultra-low load rate operation of the coal-fired power generation unit under the condition of ensuring the minimum stable combustion load of the boiler. 3) When the coal-fired power generation unit needs to rapidly increase the load rate, the heat release circuit of the molten salt heat storage system is opened and the heat storage circuit is closed. The condensate diversion control valve (21) is opened, and the condensate bypass pump (22) and the high-temperature molten salt pump (24) are started. The heat stored in the molten salt is used to heat the diverted condensate through the water-molten salt heat exchanger (23). The heated condensate flows into the feed water inlet of the boiler (1). The molten salt in the high-temperature molten salt tank (20) is sent to the low-temperature molten salt tank (16) for storage after heat exchange. The operation objective at this stage is to rapidly increase the steam flow rate in the turbine by heating the bypass condensate with molten salt without increasing the boiler load, thereby increasing the load change rate of the coal-fired power generation unit.

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