Safe and efficient deep peak regulation coal-fired power generation system based on fused salt heat storage and operation method of safe and efficient deep peak regulation coal-fired power generation system

Abstract

The invention discloses a safe and efficient deep peak regulation coal-fired power generation system based on fused salt heat storage and an operation method thereof, and the system comprises a traditional coal-fired power generation unit and a fused salt heat storage system coupled with the traditional coal-fired power generation unit. According to the fused salt heat storage system, heat storage is carried out in the mode that fused salt is sequentially heated through exhaust steam of a pressure cylinder in a split-flow turbine and reheated steam, heat release is carried out through a boiler water supply bypass scheme, and the steam split-flow rate in the heat storage process is increased through an SSS clutch. In the heat storage process of the system, under the condition that the lowest stable combustion load of a boiler is guaranteed, part of steam turbine medium-pressure cylinder exhaust steam and reheated steam of the coal-fired power generation unit are distributed to the fused salt heat storage system, and fused salt in a low-temperature fused salt tank is sequentially heated through the two streams of steam; through cooperation of the SSS clutch, exhaust steam of the intermediate pressure cylinder of the steam turbine is completely shunted for heat storage; in the heat release process of the system, under the condition that the coal feeding amount of the boiler is not increased, the molten salt heat storage system is used for heating part of condensed water of the coal-fired power generation unit, and the variable load rate of the coal-fired power generation unit is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexibility improvement and transformation of coal-fired power generation, and specifically relates to a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage and an operation method thereof. Background Art

[0002] In recent years, with the implementation of the "dual carbon" goals, 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, and its proportion has exceeded 50% of my country's total installed power generation capacity. However, renewable energy such as solar energy and wind power has strong volatility and intermittency, which requires coal-fired units to frequently participate in the peak and frequency regulation of the power grid, but the regulation capacity of traditional coal-fired units is limited, and it is difficult to meet the needs of larger-scale renewable energy power access, which has an adverse effect on the grid to maintain frequency stability. Therefore, in order to give full play to the "ballast stone" role of coal-fired power generation in my country's power industry, how to achieve efficient and flexible operation is the most urgent technical demand facing coal-fired power generation.

[0003] At present, the minimum power load rate of coal-fired units is generally around 30%. To further reduce the power load rate, measures such as oil injection and supplementary combustion are needed, resulting in a waste of high-quality energy. The existing technology integrates a heat storage system in a traditional coal-fired unit to further reduce its minimum power load rate. However, due to limitations such as the pinch point temperature difference in the superheated steam heat exchange process and the minimum condensing gas flow rate of the steam turbine, it is difficult to further increase the power load rate of the coal-fired unit. To this end, it is necessary to further transform the existing coal-fired power generation system with integrated heat storage to achieve its ultra-low load operation. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage and an operation method thereof, wherein the system comprises a traditional coal-fired power generation unit and a molten salt heat storage system coupled thereto, wherein the molten salt heat storage system adopts a method of diverting the exhaust steam of the intermediate pressure cylinder of the steam turbine and the reheated steam to heat the molten salt in sequence for heat storage and a boiler feed water bypass scheme for heat release, and in addition, an SSS clutch is used to increase the steam diversion flow rate in the heat storage process, thereby achieving an increase in the heat storage power. During the heat storage process, the system diverts part of the turbine intermediate pressure cylinder exhaust steam and reheat steam of the coal-fired generator set to the molten salt heat storage system while ensuring the minimum stable combustion load of the boiler. The two streams of steam are used to heat the molten salt in the low-temperature molten salt tank in turn, and the exhaust steam of the turbine intermediate pressure cylinder is completely diverted for heat storage through the cooperation 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, the system uses the molten salt heat storage system to heat part of the condensate of the coal-fired generator set without increasing the coal feed to the boiler, thereby rapidly increasing the working fluid flow in the turbine and improving the load change rate of the coal-fired generator set.

[0005] In order to achieve the above object, 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 heat storage, comprising a coal-fired generator set and a heat storage circuit of a molten salt heat storage system coupled to the coal-fired generator set and a heat release circuit of the molten salt heat storage system; the coal-fired generator set comprises a boiler 1, a steam turbine high-pressure cylinder 2, a steam turbine intermediate-pressure cylinder 3, a steam turbine low-pressure 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 steam turbine high-pressure cylinder 2; the steam turbine high-pressure cylinder The steam extraction outlet of the steam turbine high-pressure cylinder 2 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 reheat steam inlet of the boiler 1; the reheat steam outlet of the boiler 1 is divided into two paths, one of which is connected to the water medium inlet of the No. 1 steam-molten salt heat exchanger 19 of the heat storage circuit of the molten salt heat storage system through the No. 2 reheat steam control valve 13, and the other is connected to the steam inlet of the steam turbine intermediate pressure cylinder 3 through the No. 1 reheat steam control valve 12; the steam extraction outlet of the steam turbine intermediate pressure cylinder 3 is connected to the steam inlet of the deaerator 9, and the steam outlet of the steam turbine intermediate pressure cylinder 3 is divided into There are two routes, one of which is connected to the water working medium inlet of the No. 2 steam-molten salt heat exchanger 18 of the heat storage circuit of the molten salt heat storage system through the No. 2 intermediate pressure cylinder exhaust control valve 15, and the other is connected to the steam inlet of the turbine low pressure cylinder 4 through the No. 1 intermediate pressure cylinder exhaust control valve 14; the steam extraction 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 working medium outlet of the condenser 6 is connected to the water working medium inlet of the low pressure heater 8 through the condensate pump 7; the water working medium of the low pressure heater 8 The outlet is divided into two routes, one route leads to the condensate diversion control valve 21, and the other route is connected to the water working medium inlet of the deaerator 9; the water working medium outlet of the deaerator 9 is connected to the water working medium inlet of the high-pressure heater 11 through the feed water pump 10; the water working medium outlet of the high-pressure heater 11 and the water working medium outlet of the water-molten salt heat exchanger 23 of the heat storage loop of the molten salt heat storage system are combined and then connected to the feed water inlet of the boiler 1; the high-pressure cylinder 2 of the steam turbine, the medium-pressure cylinder 3 of the steam turbine and the low-pressure cylinder 4 of the steam turbine are connected through a rotating shaft, and jointly drive the generator 5 to output electrical power to the outside;

[0007] The heat storage circuit of the molten salt heat 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 No. 2 reheat steam control valve 13, a No. 2 intermediate pressure cylinder exhaust control valve 15, a No. 1 steam-molten salt heat exchanger 19 and a No. 2 steam-molten salt heat exchanger 18; part of the reheat steam diverted by the No. 2 reheat steam control valve 13 is heat exchanged in the No. 1 steam-molten salt heat exchanger 19 and then merged into the water working medium inlet of the deaerator 9; part of the reheat steam diverted by the No. 2 intermediate pressure cylinder exhaust control valve 15 is diverted to the water working medium inlet of the deaerator 9; Part of the outlet steam of the steam turbine intermediate pressure cylinder 3 is also merged into the water working medium inlet of the deaerator 9 after heat exchange through 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 through 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 heat 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; part of the condensate diverted by the condensate diversion control valve 21 is connected to the water working medium inlet of the water-molten salt heat exchanger 23 via the condensate bypass pump 22; the water working medium outlet of the water-molten salt heat exchanger 23 merges into the feed water 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 wall-type water working medium-molten salt heat exchangers.

[0010] Furthermore, the maximum steam diversion flow rate of the No. 2 intermediate pressure cylinder exhaust control valve 15 is 100% of the total intermediate pressure cylinder exhaust volume.

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

[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 medium-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°C to 120°C, and the temperature of the high-temperature molten salt tank 20 is 300°C to 450°C.

[0014] A method for operating a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat 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 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 steam 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 the No. 2 steam-molten salt heat exchanger 18 and the No. 1 steam-molten salt heat exchanger 19 in sequence and then sent to the high-temperature molten salt tank 20 for storage; the operation goal of this stage is: under the condition of ensuring the minimum stable combustion load of the boiler, the external output power of the coal-fired power generation unit is reduced by diverting the reheat steam heat storage and the intermediate pressure cylinder exhaust steam heat storage;

[0016] 2) When the coal-fired generator set needs to operate at ultra-low load, the exhaust steam of the steam turbine intermediate pressure cylinder exhaust 3 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 steam turbine low pressure cylinder 4 is disconnected from the coal-fired generator set and does not work externally; the operation goal of this stage is to achieve ultra-low load rate operation of the coal-fired generator set under the condition of ensuring the minimum stable combustion load of the boiler;

[0017] 3) When the coal-fired power generation unit needs to quickly 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, and 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 is merged into the water feed inlet of the boiler 1, and 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 goal of this stage is: without increasing the boiler load, the bypass condensate is heated by molten salt, the steam flow rate in the turbine is quickly increased, and the load change rate of the coal-fired power generation unit is improved.

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

[0019] (1) The present invention integrates a molten salt heat storage system in a coal-fired power generation unit and uses the exhaust steam from the intermediate pressure cylinder of the split steam turbine and the reheated steam to heat the molten salt in sequence, thereby significantly reducing the minimum power load rate of the coal-fired power generation unit and realizing 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, thereby ensuring the safety of the low pressure cylinder of the steam turbine and achieving complete diversion of the exhaust steam of the intermediate pressure cylinder, thereby greatly reducing the minimum electrical load rate of the coal-fired generator set.

[0021] (3) During the heat storage process, the output power of the coal-fired units that are difficult to connect to the grid is stored in the form of thermal energy. When the coal-fired units need 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 units, thereby achieving better transformation effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the system of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with 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 heat storage, comprising a coal-fired power generation unit, a heat storage circuit of a molten salt heat storage system coupled to the coal-fired power generation unit, and a heat release circuit of the molten salt heat storage system;

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

[0026] The heat storage circuit of the molten salt heat 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 No. 2 reheat steam control valve 13, a No. 2 intermediate pressure cylinder exhaust control valve 15, a No. 1 steam-molten salt heat exchanger 19 and a No. 2 steam-molten salt heat exchanger 18; part of the reheat steam diverted by the No. 2 reheat steam control valve 13 is heat exchanged in the No. 1 steam-molten salt heat exchanger 19 and then merged into the water working medium inlet of the deaerator 9; part of the reheat steam diverted by the No. 2 intermediate pressure cylinder exhaust control valve 15 is diverted to the water working medium inlet of the deaerator 9; Part of the outlet steam of the steam turbine intermediate pressure cylinder 3 is also merged into the water working medium inlet of the deaerator 9 after heat exchange through 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 through 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 heat 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; part of the condensate diverted by the condensate diversion control valve 21 is connected to the water working medium inlet of the water-molten salt heat exchanger 23 via the condensate bypass pump 22; the water working medium outlet of the water-molten salt heat exchanger 23 merges into the feed water 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 wall-type water working medium-molten salt heat exchangers, which can improve the deep peak-shaving capacity and load variation rate of the coal-fired power generation unit through the molten salt heat storage system.

[0029] Furthermore, the maximum steam diversion flow rate of the No. 2 intermediate pressure cylinder exhaust control valve 15 is 100% of the total intermediate pressure cylinder exhaust volume, and the output power of the coal-fired generator set is significantly reduced by cutting off the low pressure cylinder.

[0030] Furthermore, an SSS clutch 18 is provided between the steam turbine intermediate pressure cylinder 3 and the steam turbine low pressure cylinder 4. The low pressure cylinder is cut off by controlling the SSS clutch, thereby greatly reducing 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 is connected to the high-pressure cylinder 2 and the medium-pressure cylinder 3 of the steam turbine via a rotating shaft, so that the generator can still keep running after the low-pressure cylinder is cut off.

[0032] Furthermore, the temperature of the low-temperature molten salt tank 16 is 115°C to 120°C, and the temperature of the high-temperature molten salt tank 20 is 300°C to 450°C. This temperature range can achieve good temperature matching between the molten salt heat storage system and the reheated steam, medium-pressure cylinder exhaust steam, and boiler feed water bypass in the coal-fired power generation unit, thereby improving the system energy efficiency.

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

[0034] 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 steam 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 the No. 2 steam-molten salt heat exchanger 18 and the No. 1 steam-molten salt heat exchanger 19 in sequence and then sent to the high-temperature molten salt tank 20 for storage; the operation goal of this stage is: under the condition of ensuring the minimum stable combustion load of the boiler, the external output power of the coal-fired power generation unit is reduced by diverting the reheat steam heat storage and the intermediate pressure cylinder exhaust steam heat storage;

[0035] 2) When the coal-fired generator set needs to operate at ultra-low load, the exhaust steam of the steam turbine intermediate pressure cylinder exhaust 3 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 steam turbine low pressure cylinder 4 is disconnected from the coal-fired generator set and does not work externally; the operation goal of this stage is to achieve ultra-low load rate operation of the coal-fired generator set under the condition of ensuring the minimum stable combustion load of the boiler;

[0036] 3) When the coal-fired power generation unit needs to quickly 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, and 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 is merged into the water feed inlet of the boiler 1, and 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 goal of this stage is: without increasing the boiler load, the bypass condensate is heated by molten salt, the steam flow rate in the turbine is quickly increased, and the load change rate of the coal-fired power generation unit is improved.

[0037] In summary, the present invention integrates a molten salt heat storage system in a coal-fired generator set and uses the exhaust steam of the intermediate pressure cylinder and reheated steam to heat the molten salt in turn, which can significantly reduce the minimum power load rate of the coal-fired generator set and realize the cascade utilization of energy; in addition, an SSS clutch is arranged between the intermediate pressure cylinder of the steam turbine and the low pressure cylinder of the steam turbine, which realizes the complete diversion of the exhaust steam of the intermediate pressure cylinder while ensuring the safety of the low pressure cylinder of the steam turbine, thereby greatly reducing the minimum power load rate of the coal-fired generator set; through the rapid heat release of the molten salt heat storage system, the load change rate of the coal-fired unit is effectively improved, and a better transformation effect can be achieved.

Claims

1. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage, characterized by: It includes a coal-fired power generation unit and a heat storage circuit of a molten salt heat storage system coupled with the coal-fired power generation unit and a heat release circuit of the molten salt heat storage system; The coal-fired power generation unit comprises a boiler (1), a high-pressure cylinder of a steam turbine (2), an intermediate-pressure cylinder of a steam turbine (3), a low-pressure cylinder of a steam turbine (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 cylinder of the steam turbine (2); the extraction steam outlet of the high-pressure cylinder of the steam turbine (2) is connected to the steam inlet of the high-pressure heater (11), and the steam outlet of the high-pressure cylinder of the steam turbine (2) is connected to the reheat outlet of the boiler (1). The steam inlet of the steam turbine intermediate pressure cylinder (3) is connected; the reheat steam outlet of the boiler (1) is divided into two paths, one of which is connected to the water working medium inlet of the No. 1 steam-molten salt heat exchanger (19) of the heat storage circuit of the molten salt heat storage system through the No. 2 reheat steam control valve (13), and the other is connected to the steam inlet of the steam turbine intermediate pressure cylinder (3) through the No. 1 reheat steam control valve (12); the steam extraction outlet of the steam turbine intermediate pressure cylinder (3) is connected to the steam inlet of the deaerator (9), and the steam outlet of the steam turbine intermediate pressure cylinder (3) is divided into two paths, one of which is connected to the heat storage circuit of the molten salt heat storage system through the No. 2 intermediate pressure cylinder exhaust control valve (15) The first steam-molten salt heat exchanger (18) is connected to the water medium inlet of the second steam-molten salt heat exchanger (18), and the other is connected to the steam inlet of the low-pressure cylinder (4) of the steam turbine through the first medium-pressure cylinder exhaust control valve (14); the steam extraction outlet of the low-pressure cylinder (4) of the steam 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 steam turbine is connected to the steam inlet of the condenser (6); the water medium outlet of the condenser (6) is connected to the water medium inlet of the low-pressure heater (8) through the condensate pump (7); the water medium outlet of the low-pressure heater (8) is divided into two paths, one of which leads to the condensate flow branch The control valve (21) has one path connected to the water working medium inlet of the deaerator (9); the water working medium outlet of the deaerator (9) is connected to the water working medium inlet of the high-pressure heater (11) via the feed water pump (10); the water working medium outlet of the high-pressure heater (11) and the water working medium outlet of the water-molten salt heat exchanger (23) of the heat release circuit of the molten salt heat storage system are combined and then connected to the feed water inlet of the boiler (1); the high-pressure cylinder (2) of the steam turbine, the intermediate-pressure cylinder (3) of the steam turbine and the low-pressure cylinder (4) of the steam turbine are connected via a rotating shaft and jointly drive a generator (5) to output electrical power to the outside; The heat storage circuit of the molten salt heat storage system comprises a low-temperature molten salt tank (16), a low-temperature molten salt pump (17), a high-temperature molten salt tank (20), a No. 2 reheat steam control valve (13), a No. 2 intermediate pressure cylinder exhaust steam control valve (15), a No. 1 steam-molten salt heat exchanger (19) and a No. 2 steam-molten salt heat exchanger (18); part of the reheat steam diverted by the No. 2 reheat steam control valve (13) is exchanged in the No. 1 steam-molten salt heat exchanger (19) and then flows into the water working medium inlet of the deaerator (9); part of the reheat steam diverted by the No. 2 reheat steam control valve (13) is exchanged in the No. 1 steam-molten salt heat exchanger (19) and then flows into the water working medium inlet of the deaerator (9); part of the reheat steam diverted by the No. 2 intermediate pressure cylinder exhaust steam control valve (15) is diverted to the water working medium inlet of the deaerator (9); The steam at the outlet of the intermediate pressure cylinder (3) of the steam turbine flows through the No. 2 steam-molten salt heat exchanger (18) and is also introduced into the water medium 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 a 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 heat storage system comprises 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); part of the condensate diverted by the condensate diversion control valve (21) is connected to the water working medium inlet of the water-molten salt heat exchanger (23) via the condensate bypass pump (22); the water working medium outlet of the water-molten salt heat exchanger (23) is merged into the feed water 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); and 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).

2. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat 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 partition-type water working medium-molten salt heat exchangers.

3. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage according to claim 1, characterized in that: The maximum steam diversion flow rate of the No. 2 intermediate pressure cylinder exhaust control valve (15) is 100% of the total amount of intermediate pressure cylinder exhaust steam.

4. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage according to claim 1, characterized in that: An SSS clutch (18) is provided between the steam turbine intermediate pressure cylinder (3) and the steam turbine low pressure cylinder (4).

5. A safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat 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 medium-pressure cylinder (3) of the steam turbine via a rotating shaft.

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

7. A method for operating a safe and efficient deep peak-shaving coal-fired power generation system based on molten salt heat storage according to any one of claims 1 to 6, characterized in that: The details are as follows: 1) When the coal-fired power generation unit is running at a 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 steam control valve (15) are opened, the low-temperature molten salt pump (17) is started, and the diverted intermediate pressure cylinder exhaust steam and reheat steam are used to heat the low-temperature molten salt in sequence, and the molten salt in the low-temperature molten salt tank (16) is heated in the No. 2 steam-molten salt heat exchanger (18) and the No. 1 steam-molten salt heat exchanger (19) in sequence and then sent to the high-temperature molten salt tank (20) for storage; the operation goal of this stage is: under the condition of ensuring the minimum stable combustion load of the boiler, the external output power of the coal-fired power generation unit is reduced by diverting the reheat steam heat storage and the intermediate pressure cylinder exhaust steam heat storage; 2) When the coal-fired power generation unit needs to operate at an ultra-low load, the exhaust steam of the steam turbine intermediate pressure cylinder exhaust (3) 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 steam turbine low pressure cylinder (4) is disconnected from the coal-fired power generation unit and does not perform external work. The operating goal 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 increase the load rate rapidly, 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, and 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 is then fed into the feed water inlet of the boiler (1), and 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 goal of this stage is: without increasing the boiler load, the bypass condensate is heated by molten salt, the steam flow rate in the turbine is rapidly increased, and the load change rate of the coal-fired power generation unit is improved.

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