High pressure steam supply system coupled with molten salt thermal storage

Abstract

The application discloses a high-pressure steam supply system coupled with fused salt heat storage, which comprises a coal-fired unit and a high-pressure steam supply system. The high-pressure steam supply system comprises a back pressure turbine, a main steam outlet of a boiler is communicated with a steam inlet of the back pressure turbine, the boiler is provided with a primary reheating intermediate reheater and a primary reheating secondary reheater, steam outlets of the primary reheating intermediate reheater are respectively communicated with steam inlets of the primary reheating secondary reheater and the back pressure turbine; a main steam shunt valve is used for controlling the on-off between the main steam outlet and the steam inlet of the back pressure turbine; and a reheated steam shunt valve is used for controlling the on-off between the steam outlet of the primary reheating intermediate reheater and the steam inlet of the back pressure turbine. According to the high-pressure steam supply system coupled with fused salt heat storage, the high-pressure steam supply system coupled with fused salt heat storage can realize energy cascade utilization, reduce the auxiliary power consumption rate of the unit, and effectively improve the peak shaving capacity of the unit.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, and in particular to a high-pressure steam supply system coupled with molten salt thermal storage. Background Technology

[0002] In related technologies, the installed capacity of renewable energy sources such as wind power and photovoltaics is increasing year by year. Renewable energy power generation output exhibits strong time-varying characteristics, and large-scale grid connection of renewable energy power creates significant peak-valley differences on the grid supply side, while also adversely affecting the grid's frequency stability. To ensure the safe and stable operation of the power system under high-proportion renewable energy penetration, coal-fired power generating units need to leverage their excellent load regulation performance. Simultaneously, coal-fired power generating units are the main heat source for urban district heating and industrial heating. Ensuring heating supply while simultaneously fulfilling grid peak-shaving tasks and reducing wind and solar curtailment are significant challenges facing coal-fired power generating units.

[0003] When a coal-fired power unit is operating under heating load, its deep peak-shaving capacity decreases due to safety operating limits such as the boiler's minimum stable combustion load and the turbine's minimum cooling flow rate. When operating under high-pressure industrial steam load, the coal-fired power unit faces the risk of not being able to guarantee steam supply parameters at low loads under constant-slip-constant operation mode. It can only reduce the pressure by extracting steam with higher parameters, resulting in a waste of high-quality energy. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a high-pressure steam supply system coupled with molten salt thermal storage. This high-pressure steam supply system coupled with molten salt thermal storage can realize energy cascade utilization, reduce the unit's power consumption rate, and effectively improve the unit's peak-shaving capacity.

[0005] A high-pressure steam supply system with coupled molten salt thermal storage according to an embodiment of the present invention includes: a coal-fired power unit and a high-pressure steam supply system. The high-pressure steam supply system includes a back-pressure turbine, and the coal-fired power unit includes: a boiler, a turbine ultra-high-pressure cylinder, a turbine high-pressure cylinder, a main steam diversion valve, and a reheat steam diversion valve. The boiler is equipped with a main steam outlet, which is connected to the steam inlet of the back pressure turbine. The boiler contains a primary reheat intermediate reheater and a primary reheat secondary reheater. The steam outlet of the primary reheat intermediate reheater is connected to the steam inlets of both the primary and secondary reheaters and the back pressure turbine. The main steam outlet is connected to the steam inlet of the turbine's ultra-high pressure cylinder, and the steam outlet of the turbine's ultra-high pressure cylinder is connected to the steam inlet of the primary reheat intermediate reheater. The steam outlet of the primary reheat secondary reheater is connected to the steam inlet of the turbine's high pressure cylinder. The main steam diversion valve controls the connection between the main steam outlet and the steam inlet of the back pressure turbine. The reheat steam diversion valve controls the connection between the steam outlet of the primary reheat intermediate reheater and the steam inlet of the back pressure turbine.

[0006] According to an embodiment of the present invention, a high-pressure steam supply system with coupled molten salt thermal storage can achieve energy cascade utilization, reduce the unit's power consumption rate, and effectively improve the unit's peak-shaving capacity by setting a back pressure turbine in the high-pressure steam supply system, setting a primary reheat intermediate reheater and a primary reheat secondary reheater in the boiler, connecting the steam outlet of the primary reheat intermediate reheater to the steam inlet of the primary reheat secondary reheater and the steam inlet of the back pressure turbine, and setting a main steam diversion valve for controlling the on / off connection between the main steam outlet and the steam inlet of the back pressure turbine, and a reheat steam diversion valve for controlling the on / off connection between the steam outlet of the primary reheat intermediate reheater and the steam inlet of the back pressure turbine.

[0007] According to some embodiments of the present invention, the coal-fired unit further includes a steam turbine intermediate pressure cylinder and a deaerator. The extraction steam outlet of the steam turbine intermediate pressure cylinder is connected to the steam inlet of the deaerator, and the water outlet of the deaerator is connected to the feedwater inlet of the boiler. The high-pressure steam supply system further includes a desuperheating and pressure reducing device. The desuperheating and pressure reducing device has a steam inlet and a liquid inlet. The steam outlet of the back pressure turbine is connected to the steam inlet, and the liquid inlet is connected to the water outlet of the deaerator. The steam outlet of the desuperheating and pressure reducing device is connected to the steam supply header for heating.

[0008] In some embodiments of the present invention, the high-pressure steam supply system coupled with molten salt thermal storage further includes a molten salt thermal storage system. Molten salt circulates within the molten salt thermal storage system. The molten salt thermal storage system includes a low-temperature molten salt tank, a high-temperature molten salt tank, a molten salt electric heater, and a low-temperature molten salt pump. The molten salt electric heater has a first flow path for heating the molten salt within the first flow path. The two ends of the first flow path are respectively connected to the outlet of the low-temperature molten salt tank and the inlet of the high-temperature molten salt tank to form a thermal storage circuit of the molten salt thermal storage system. The low-temperature molten salt pump is located between the low-temperature molten salt tank and the molten salt electric heater for driving the molten salt to circulate.

[0009] In some embodiments of the present invention, the coal-fired unit further includes a generator, and the cryogenic molten salt pump is driven by the generator.

[0010] In some embodiments of the present invention, the molten salt thermal storage system further includes: a feedwater-molten salt heat exchanger, a superheated steam-molten salt heat exchanger, a saturated steam-molten salt heat exchanger, a steam drum, and a high-temperature molten salt pump. The feedwater-molten salt heat exchanger has a first channel and a second channel for mutual heat exchange. The outlet of the first channel is connected to the inlet of the low-temperature molten salt tank, and the inlet of the second channel is connected to the water outlet of the deaerator. The superheated steam-molten salt heat exchanger has a third channel and a fourth channel for mutual heat exchange. The inlet of the third channel is connected to the outlet of the high-temperature molten salt tank, and the outlet of the fourth channel is connected to the steam inlet of the primary reheat intermediate reheater via a molten salt steam supply pipeline. The saturated steam-molten salt heat exchanger has a fifth channel and a sixth channel for mutual heat exchange. The fifth channel is connected to the outlet of the third channel and the inlet of the first channel at both ends, and the sixth channel is connected to the outlet of the second channel and the inlet of the fourth channel at both ends, respectively. The inlet of the steam drum is connected to the outlet of the sixth channel. The steam drum is used to separate saturated steam and water. The steam drum has a steam outlet and a liquid outlet. The steam outlet is connected to the inlet of the fourth channel, and the liquid outlet is connected to the inlet of the second channel. The high-temperature molten salt pump is located between the high-temperature molten salt tank and the superheated steam-molten salt heat exchanger to drive the molten salt to circulate. The high-temperature molten salt tank, the third channel, the fifth channel, the first channel, and the low-temperature molten salt tank form the heat release loop of the molten salt heat storage system.

[0011] In some embodiments of the present invention, the feedwater-molten salt heat exchanger, the saturated steam-molten salt heat exchanger, and the superheated steam-molten salt heat exchanger are all indirect-wall water-molten salt heat exchangers.

[0012] In some embodiments of the present invention, the molten salt thermal storage system further includes a feedwater bypass pump and a feedwater diversion valve. The feedwater bypass pump is used to drive water from the water outlet of the deaerator to the inlet of the second channel and the liquid inlet of the desuperheating and pressure reducing device. The feedwater diversion valve is used to control the connection and disconnection between the water outlet of the deaerator and the inlet of the second channel, and to control the connection and disconnection between the water outlet of the deaerator and the liquid inlet.

[0013] In some embodiments of the present invention, the high-pressure steam supply system coupled with molten salt thermal storage has a normal mode, a low-load mode, and a high-load mode. In the normal mode, the main steam diversion valve is closed, and the reheat steam diversion valve and the feedwater diversion valve are connected. In the low-load mode, the main steam diversion valve and the feedwater diversion valve are connected, the reheat steam diversion valve is closed, and the molten salt electric heater and the low-temperature molten salt pump are turned on. In the high-load mode, the main steam diversion valve is closed, the reheat steam diversion valve and the feedwater diversion valve are connected, and the high-temperature molten salt pump is turned on.

[0014] According to some embodiments of the present invention, the steam flow rate at the outlet end of the main steam diversion valve does not exceed 21% of the steam flow rate at the main steam outlet; and / or, the steam flow rate at the outlet end of the reheat steam diversion valve does not exceed 23% of the steam flow rate at the steam outlet of the primary reheat intermediate reheater; and / or, the exhaust back pressure of the back pressure turbine is in the range of 4.3MPa-4.5MPa.

[0015] According to some embodiments of the present invention, the coal-fired power unit further includes a turbine intermediate-pressure cylinder, a turbine low-pressure cylinder, a generator, a condenser, a condensate pump, a low-pressure heater, a deaerator, a feedwater pump, and a high-pressure heater. The extraction steam outlet of the turbine ultra-high-pressure cylinder is connected to the steam inlet of the high-pressure heater. The steam outlet of the turbine high-pressure cylinder is connected to the steam inlet of the boiler's secondary reheater. The steam outlet of the secondary reheater is connected to the steam inlet of the turbine intermediate-pressure cylinder. The extraction steam outlet of the turbine intermediate-pressure cylinder is connected to the steam inlet of the deaerator. The steam outlet of the turbine intermediate-pressure cylinder is connected to the steam inlet of the turbine low-pressure cylinder. The extraction steam outlet of the turbine is connected to the steam inlet of the low-pressure heater. The steam outlet of the turbine's low-pressure cylinder is connected to the steam inlet of the condenser. The water outlet of the condenser is connected to the water inlet of the low-pressure heater via a condensate pump. The water outlet of the low-pressure heater is connected to the water inlet of the deaerator. The water outlet of the deaerator is connected to the water inlet of the high-pressure heater via a feedwater pump. The water outlet of the high-pressure heater is connected to the feedwater inlet of the boiler. The turbine's ultra-high-pressure cylinder, high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder are connected by a rotating shaft and jointly drive the generator to generate electricity.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0018] Figure 1 This is a schematic diagram of a high-pressure steam supply system with coupled molten salt thermal storage according to an embodiment of the present invention.

[0019] Figure label:

[0020] 1. Boiler; 2. Ultra-high pressure cylinder of steam turbine; 3. High pressure cylinder of steam turbine; 4. Intermediate pressure cylinder of steam turbine; 5. Low pressure cylinder of steam turbine; 6. Generator; 7. Condenser; 8. Condensate pump; 9. Low pressure heater; 10. Deaerator; 11. Feedwater pump; 12. High pressure heater; 13. Main steam diversion valve; 14. Primary reheat intermediate reheater; 15. Reheat steam diversion valve; 16. Primary reheat secondary reheater; 17. 18. Feedwater diversion valve; 19. Low-temperature molten salt pump; 20. Low-temperature molten salt tank; 21. High-temperature molten salt tank; 22. Molten salt electric heater; 23. High-temperature molten salt pump; 24. Feedwater bypass pump; 25. Feedwater-molten salt heat exchanger; 26. Saturated steam-molten salt heat exchanger; 27. Steam drum; 28. Superheated steam-molten salt heat exchanger; 29. ​​Molten salt steam supply pipeline; 30. Back pressure compressor; 31. Steam supply header; 32. Desuperheating and pressure reducing device. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and 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, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] 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.

[0024] The following is for reference. Figure 1 A high-pressure steam supply system with coupled molten salt thermal storage according to an embodiment of the present invention is described.

[0025] like Figure 1 As shown, the high-pressure steam supply system with coupled molten salt thermal storage according to an embodiment of the present invention includes a coal-fired unit and a high-pressure steam supply system.

[0026] Specifically, the high-pressure steam supply system includes a back-pressure turbine 29, and the coal-fired unit includes: a boiler 1, a turbine ultra-high-pressure cylinder 2, a turbine high-pressure cylinder 3, a main steam diversion valve 13, and a reheat steam diversion valve 15. The boiler 1 has a main steam outlet, which is connected to the steam inlet of the back-pressure turbine 29. The boiler 1 contains a primary reheat intermediate reheater 14 and a primary reheat secondary reheater 16. The steam outlet of the primary reheat intermediate reheater 14 is connected to the steam inlets of the primary reheat secondary reheater 16 and the back-pressure turbine 29, respectively. The main steam outlet is connected to the steam inlet of the turbine ultra-high-pressure cylinder 2, and the steam outlet of the turbine ultra-high-pressure cylinder 2 is connected to the steam inlet of the primary reheat intermediate reheater 14. The steam outlet of the primary reheat secondary reheater 16 is connected to the steam inlet of the high-pressure cylinder 3 of the steam turbine. The main steam diversion valve 13 is used to control the connection and disconnection between the main steam outlet and the steam inlet of the back pressure machine 29. The reheat steam diversion valve 15 is used to control the connection and disconnection between the steam outlet of the primary reheat intermediate reheater 14 and the steam inlet of the back pressure machine 29.

[0027] The main steam outlet of boiler 1 is divided into two paths: one leads to the main steam diversion valve 13, and the other connects to the steam inlet of the ultra-high pressure cylinder 2 of the turbine. The extraction steam outlet of the ultra-high pressure cylinder 2 is connected to the steam inlet of the high-pressure heater 12, and the steam outlet of the ultra-high pressure cylinder 2 is connected to the steam inlet of the primary reheat intermediate reheater 14 of boiler 1. The steam outlet of the primary reheat intermediate reheater 14 of boiler 1 is divided into two paths: one leads to the reheat steam diversion valve 15, and the other connects to the steam inlet of the primary reheat secondary reheater 16.

[0028] When the coal-fired unit is in the normal operating load range, the main steam diversion valve 13 is closed and the reheat steam diversion valve 15 is opened. When the coal-fired unit is in normal operating condition, the reheat steam diversion valve 15 is open, and the steam from the outlet of the primary reheat intermediate reheater 14 enters the back pressure compressor 29 through the steam inlet pipe of the back pressure compressor 29 and does work. The exhaust steam from the back pressure compressor 29 is used to deliver heat users.

[0029] When the coal-fired unit is operating at low load and requires deep peak shaving, the main steam diversion valve 13 is opened and the reheat steam diversion valve 15 is closed. The main steam enters the back pressure turbine 29 through the steam inlet pipe of the back pressure turbine 29 via the main steam diversion valve 13 and performs work. The exhaust steam of the back pressure turbine 29 is used to deliver heat users.

[0030] When the coal-fired unit is operating at high load and needs to carry peak load, the main steam diversion valve 13 is closed and the reheat steam diversion valve 15 is opened. The steam from the outlet of the primary reheat intermediate reheater 14 enters the back pressure turbine 29 through the steam inlet pipe of the back pressure turbine 29 and does work. The exhaust steam from the back pressure turbine 29 is used to deliver heat to the heat user.

[0031] The high-pressure steam supply system of coupled molten salt thermal energy storage in this application uses exhaust steam from back compressor 29 for steam supply, and the work done by back compressor 29 is used for plant power. Under low load conditions, the system uses bypass main steam to first perform work in back compressor 29 before supplying steam, achieving energy cascade utilization and simultaneously reducing the unit's plant power consumption rate. Under high load conditions, the back compressor 29 is driven by steam from the outlet of the single reheat intermediate reheater 14, and exhaust steam from back compressor 29 is used for steam supply.

[0032] This invention utilizes high-temperature, high-pressure steam to first power the back compressor 29 and then supply heat, achieving cascaded energy utilization. Under high load, the steam from the outlet of the single reheat intermediate-temperature reheater drives the back compressor 29, reducing the unit's load pressure and effectively improving its peak-shaving capacity. Under low load, the main steam is used to power the back compressor 29, providing some of the plant's auxiliary power and reducing the plant's power consumption rate.

[0033] According to an embodiment of the present invention, a high-pressure steam supply system with coupled molten salt thermal storage can achieve energy cascade utilization, reduce the unit's power consumption rate, and effectively improve the unit's peak-shaving capacity by setting a back pressure unit 29 in the high-pressure steam supply system, setting a primary reheat intermediate reheater 14 and a primary reheat secondary reheater 16 in the boiler 1, with the steam outlet of the primary reheat intermediate reheater 14 connected to the steam inlet of the primary reheat secondary reheater 16 and the steam inlet of the back pressure unit 29, and setting a main steam diversion valve 13 for controlling the on / off connection between the main steam outlet and the steam inlet of the back pressure unit 29, and a reheat steam diversion valve 15 for controlling the on / off connection between the steam outlet of the primary reheat intermediate reheater 14 and the steam inlet of the back pressure unit 29.

[0034] In some embodiments of the present invention, such as Figure 1 As shown, the coal-fired unit also includes a steam turbine intermediate pressure cylinder 4 and a deaerator 10. The steam extraction outlet of the steam turbine intermediate pressure cylinder 4 is connected to the steam inlet of the deaerator 10, and the water outlet of the deaerator 10 is connected to the feedwater inlet of the boiler 1. The high-pressure steam supply system also includes a desuperheating and pressure reducing device 31, which has a steam inlet and a liquid inlet. The steam outlet of the back pressure turbine 29 is connected to the steam inlet, and the liquid inlet is connected to the water outlet of the deaerator 10. The steam outlet of the desuperheating and pressure reducing device 31 is connected to the steam supply header 30 for heating.

[0035] Steam enters the back pressure compressor 29 through the steam inlet pipe and does work. The steam after doing work enters the desuperheating and pressure reducing device 31. Some of the water discharged from the water outlet of the deaerator 10 enters the desuperheating and pressure reducing device 31 to cool and reduce the pressure of the exhaust steam from the back pressure compressor 29. Then it enters the steam supply header 30 and is delivered to the heat users to meet the heating demand.

[0036] In some embodiments of the present invention, such as Figure 1As shown, the high-pressure steam supply system coupled with molten salt thermal energy storage also includes a molten salt thermal energy storage system. Molten salt circulates within the molten salt thermal energy storage system, which includes a low-temperature molten salt tank 19, a high-temperature molten salt tank 20, a molten salt electric heater 21, and a low-temperature molten salt pump 18. The molten salt electric heater 21 has a first flow path for heating the molten salt within it. The two ends of the first flow path are connected to the outlet of the low-temperature molten salt tank 19 and the inlet of the high-temperature molten salt tank 20, respectively, forming a thermal energy storage loop for the molten salt thermal energy storage system. The low-temperature molten salt pump 18 is located between the low-temperature molten salt tank 19 and the molten salt electric heater 21 to drive the molten salt circulation. This allows off-peak electricity to be converted into high-temperature thermal energy for storage and released on demand, effectively improving the unit's peak-shaving capacity. Simultaneously, energy cascade utilization improves heating economy, achieving a synergistic improvement in system economy and flexibility.

[0037] In some embodiments of the present invention, such as Figure 1 As shown, the coal-fired unit also includes a generator 6, and a cryogenic molten salt pump 18 is driven by the generator 6. Under low load conditions, off-peak electricity is used to heat the molten salt, converting electrical energy into thermal energy for storage, thereby enhancing the unit's deep peak-shaving capability.

[0038] In some embodiments of the present invention, the molten salt thermal storage system further includes: a feedwater-molten salt heat exchanger 24, a superheated steam-molten salt heat exchanger 27, a saturated steam-molten salt heat exchanger 25, a steam drum 26, and a high-temperature molten salt pump 22. The feedwater-molten salt heat exchanger 24 has a first channel and a second channel for mutual heat exchange. The outlet of the first channel is connected to the inlet of the low-temperature molten salt tank 19, and the inlet of the second channel is connected to the water outlet of the deaerator 10. The superheated steam-molten salt heat exchanger 27 has a third channel and a fourth channel for mutual heat exchange. The inlet of the third channel is connected to the outlet of the high-temperature molten salt tank 20, and the outlet of the fourth channel is connected to the steam inlet of the primary reheat intermediate reheater 14 via a molten salt steam supply pipe 28. The saturated steam-molten salt heat exchanger 25 has... The fifth and sixth channels exchange heat with each other. The two ends of the fifth channel are connected to the outlet of the third channel and the inlet of the first channel, respectively. The two ends of the sixth channel are connected to the outlet of the second channel and the inlet of the fourth channel, respectively. The inlet of the steam drum 26 is connected to the outlet of the sixth channel. The steam drum 26 is used to separate saturated steam and water. The steam drum 26 has a steam outlet and a liquid outlet. The steam outlet is connected to the inlet of the fourth channel, and the liquid outlet is connected to the inlet of the second channel. The high-temperature molten salt pump 22 is located between the high-temperature molten salt tank 20 and the superheated steam-molten salt heat exchanger 27. It is used to drive the molten salt circulation. The high-temperature molten salt tank 20, the third channel, the fifth channel, the first channel, and the low-temperature molten salt tank 19 form the heat release loop of the molten salt heat storage system.

[0039] As the electrical load decreases, the outlet steam pressure of the intermediate reheater 14, which operates under sliding pressure, also decreases. To ensure high-pressure steam supply, high-temperature molten salt is used to heat the feedwater into steam, which is then introduced into the intermediate reheater 14 to raise the outlet pressure of the intermediate reheater 14 to meet the steam pressure required to drive the back pressure turbine 29, thus ensuring high-pressure steam supply under all operating conditions. Molten salt steam supply replaces part of the reheat steam from boiler 1, achieving round-trip coal savings.

[0040] This invention achieves round-trip coal savings by replacing reheat steam with molten salt steam supply under high loads and reduces plant power consumption under low loads. It couples a coal-fired unit with a molten salt thermal storage system, employing a low-load thermal storage and high-load heat release operation. Under medium and high loads, the thermal storage system enters heat release mode, replacing reheat steam with molten salt steam supply to increase reheat pressure and prevent a drop in steam supply pressure due to a decrease in unit load.

[0041] This invention couples a coal-fired power unit with a molten salt thermal storage system, employing a low-load thermal storage and high-load thermal release operation. Under medium and high loads, the thermal storage system enters a thermal release mode, and molten salt steam is introduced into the primary reheat intermediate reheater 14 to increase the reheat pressure, preventing a drop in steam supply pressure due to a decrease in unit load. Under low loads, bypass main steam first enters the back pressure turbine 29 to perform work before being supplied with steam. This ensures high-pressure steam supply under all operating conditions.

[0042] In some embodiments of the present invention, the feedwater-molten salt heat exchanger 24, the saturated steam-molten salt heat exchanger 25, and the superheated steam-molten salt heat exchanger 27 are all indirect-wall water-molten salt heat exchangers, which can ensure the heat exchange effect between molten salt and water, saturated steam, and superheated steam, thereby ensuring the heat release efficiency of the molten salt heat storage system.

[0043] In some embodiments of the present invention, the molten salt thermal storage system further includes a feedwater bypass pump 23 and a feedwater diversion valve 17. The feedwater bypass pump 23 is used to drive water from the water outlet of the deaerator 10 to the inlet of the second channel and the liquid inlet of the desuperheating and pressure reducing device 31. The feedwater diversion valve 17 is used to control the on / off connection between the water outlet of the deaerator 10 and the inlet of the second channel, and to control the on / off connection between the water outlet of the deaerator 10 and the liquid inlet.

[0044] The feedwater diversion valve 17 can control the opening and closing between the water outlet of the deaerator 10 and the inlet of the second channel. When the molten salt thermal storage system needs to release heat, the feedwater diversion valve 17 is opened, and the feedwater bypass pump 23 can provide driving force for the water flow.

[0045] The feedwater diverted by the feedwater diversion valve 17 is connected to the feedwater bypass pump 23. After being pressurized, the bypass feedwater is heated by the feedwater-molten salt heat exchanger 24 and then enters the steam inlet of the saturated steam-molten salt heat exchanger 25. After heat exchange, it enters the steam drum 26. The steam drum 26 separates the saturated steam into water. The water returns to the feedwater-molten salt heat exchanger 24 for reheating. The steam enters the superheated steam-molten salt heat exchanger 27. After heat exchange, the steam enters the molten salt steam supply pipeline 28. The molten salt steam supply pipeline 28 is connected to the steam inlet of the intermediate reheater 14 of the boiler 1.

[0046] In some embodiments of the present invention, the high-pressure steam supply system coupled with molten salt thermal storage has a normal mode, a low-load mode, and a high-load mode. In the normal mode, the main steam diversion valve 13 is closed, and the reheat steam diversion valve 15 and the feedwater diversion valve 17 are connected. In the low-load mode, the main steam diversion valve 13 and the feedwater diversion valve 17 are connected, the reheat steam diversion valve 15 is closed, and the molten salt electric heater 21 and the low-temperature molten salt pump 18 are turned on. In the high-load mode, the main steam diversion valve 13 is closed, the reheat steam diversion valve 15 and the feedwater diversion valve 17 are connected, and the high-temperature molten salt pump 22 is turned on.

[0047] When the coal-fired unit is in its normal operating load range, the main steam diversion valve 13 is closed, and the reheat steam diversion valve 15 and feedwater diversion valve 17 are opened. Under normal operating conditions, the reheat steam diversion valve 15 is open, and the steam from the outlet of the primary reheat intermediate reheater 14 enters the back pressure turbine 29 via the back pressure turbine 29 inlet pipe. After performing work, it enters the desuperheating and pressure reducing device 31. Part of the feedwater enters the desuperheating and pressure reducing device 31 via the feedwater diversion valve 17 to desuperheat the exhaust steam from the back pressure turbine 29. After desuperheating and pressure reducing, the exhaust steam from the back pressure turbine 29 enters the steam supply header 30 and is delivered to heat users.

[0048] When the coal-fired unit is operating at low load and requires deep peak shaving, the molten salt thermal storage system enters the thermal storage stage. The molten salt electric heater 21 and the cryogenic molten salt pump 18 are started, using a portion of the unit's output power to drive the molten salt electric heater 21, heating the molten salt from the cryogenic molten salt tank 19 for thermal storage. The main steam diversion valve 13 and the feedwater diversion valve 17 are opened, while the reheat steam diversion valve 15 is closed. Main steam enters the back pressure turbine 29 through the main steam diversion valve 13 via the inlet pipe to perform work, and then enters the desuperheating and pressure reducing device 31. A portion of the feedwater enters the desuperheating and pressure reducing device 31 through the feedwater diversion valve 17 to desuperheat the exhaust steam from the back pressure turbine 29. After desuperheating and pressure reducing, the exhaust steam from the back pressure turbine 29 enters the steam supply header 30 and is delivered to the heat users.

[0049] When the coal-fired unit is operating at high load and requires peak load, the molten salt thermal storage system enters the heat release stage. The high-temperature molten salt pump 22 is turned on, and the high-temperature molten salt heats the feedwater from the feedwater bypass pump 23 in the feedwater-molten salt heat exchanger 24. After heat exchange, the feedwater enters the steam drum 26, where the saturated steam undergoes steam-water separation. The water returns to the feedwater-molten salt heat exchanger 24 for reheating, while the steam enters the superheated steam-molten salt heat exchanger 27. After heat exchange, the steam enters the steam inlet of the boiler 1 primary reheat intermediate reheater 14 via the molten salt steam supply pipeline 28. In the boiler 1 primary reheat intermediate reheater 14, it is heated by the flue gas. The main steam diversion valve 13 is closed, and the reheat steam diversion valve 15 is opened. Molten salt steam entering the intermediate reheater 14 of boiler 1 is heated by flue gas and then enters the steam inlet pipe of the back compressor 29 from the outlet of the intermediate reheater 14. After the back compressor 29 performs work, it enters the desuperheating and pressure reducing device 31. Part of the feedwater enters the desuperheating and pressure reducing device 31 through the feedwater diversion valve 17 and the feedwater bypass pump 23 to desuperheat the exhaust steam from the back compressor 29. After desuperheating and pressure reducing, the exhaust steam from the back compressor 29 enters the steam supply header 30 and is delivered to the heat users.

[0050] The high-pressure steam supply system coupled with molten salt thermal storage in this application uses exhaust steam from the back compressor 29 for steam supply. The back compressor 29 performs work for plant power consumption, while simultaneously integrating a molten salt dual-tank thermal storage system to ensure high-pressure steam supply under all operating conditions. Under low load, the system uses off-peak electricity to heat the molten salt, converting electrical energy into thermal energy for storage, thus enhancing the unit's deep peak-shaving capability. Bypass main steam is used to perform work on the back compressor 29 before being supplied as steam, achieving cascaded energy utilization and reducing the unit's plant power consumption rate. Under high load, steam from the outlet of the primary reheat intermediate reheater 14 drives the back compressor 29, and exhaust steam from the back compressor 29 is used for steam supply. When the electrical load decreases, to ensure high-pressure steam supply, high-temperature molten salt is used to heat feedwater into steam, which is then introduced into the primary reheat intermediate reheater 14 to raise the outlet pressure of the intermediate reheater to meet the steam pressure required to drive the back compressor 29, ensuring high-pressure steam supply under all operating conditions. Molten salt steam supply replaces part of the reheat steam from boiler 1, achieving round-trip coal savings.

[0051] In some embodiments of the present invention, the steam flow rate at the outlet of the main steam diversion valve 13 does not exceed 21% of the steam flow rate at the main steam outlet. If too much main steam is drawn into the back pressure unit 29, the working efficiency of the turbine will be reduced, thereby affecting the power generation of the generator 6.

[0052] In some embodiments of the present invention, the steam flow rate at the outlet of the reheat steam diversion valve 15 does not exceed 23% of the steam flow rate at the steam outlet of the primary reheat intermediate reheater 14. The primary reheat intermediate reheater 14 is surrounded by high-temperature flue gas, which heats the pipes of the primary reheat intermediate reheater 14, causing the pipe temperature to rise. To ensure that the pipe temperature remains within the permissible range of the material, the pipes of the primary reheat intermediate reheater 14 need to contain sufficient steam (at a temperature much lower than the flue gas) to absorb the heat from the high-temperature flue gas and cool the primary reheat intermediate reheater 14, thus maintaining the pipe temperature within the permissible range. If the steam flow rate within the pipes of the primary reheat intermediate reheater 14 is too low, the steam's heat absorption capacity is insufficient to cool the pipe temperature to the permissible range, resulting in reheater overheating.

[0053] Therefore, the steam flow rate at the outlet of the reheat steam diversion valve 15 does not exceed 23% of the steam flow rate at the steam outlet of the primary reheat intermediate reheater 14. This can prevent too much steam from being drawn out at the outlet of the main steam diversion valve 13, ensuring that there is enough steam in the pipeline of the primary reheat intermediate reheater 14 and avoiding overheating of the primary reheat intermediate reheater 14.

[0054] In some embodiments of the present invention, the exhaust back pressure of the back pressure unit 29 is in the range of 4.3MPa-4.5MPa, which can ensure the heating effect and at the same time avoid heat source waste.

[0055] In some embodiments of the present invention, the operating temperature range of the molten salt thermal storage system is 290℃-560℃, the steam supply pressure range of the molten salt thermal storage system is 7.6MPa-10.3MPa, and the steam supply temperature is higher than 500℃, so as to meet the parameter requirements of the back pressure compressor 29 driving steam, and keep the exhaust steam of the back pressure compressor 29 above 4.3MPa.

[0056] In some embodiments of the present invention, such as Figure 1As shown, the coal-fired unit also includes a turbine intermediate-pressure cylinder 4, a turbine low-pressure cylinder 5, a generator 6, a condenser 7, a condensate pump 8, a low-pressure heater 9, a deaerator 10, a feedwater pump 11, and a high-pressure heater 12. The extraction outlet of the turbine ultra-high-pressure cylinder 2 is connected to the steam inlet of the high-pressure heater 12. The steam outlet of the turbine high-pressure cylinder 3 is connected to the steam inlet of the secondary reheater of the boiler 1. The steam outlet of the secondary reheater is connected to the steam inlet of the turbine intermediate-pressure cylinder 4. The extraction outlet of the turbine intermediate-pressure cylinder 4 is connected to the steam inlet of the deaerator 10. The steam outlet of the turbine intermediate-pressure cylinder 4 is connected to the steam inlet of the turbine low-pressure cylinder 5. The turbine low-pressure cylinder 5... The extraction steam outlet of the turbine is connected to the steam inlet of the low-pressure heater 9. The steam outlet of the turbine's low-pressure cylinder 5 is connected to the steam inlet of the condenser 7. The water outlet of the condenser 7 is connected to the water inlet of the low-pressure heater 9 via the condensate pump 8. The water outlet of the low-pressure heater 9 is connected to the water inlet of the deaerator 10. The water outlet of the deaerator 10 is connected to the water inlet of the high-pressure heater 12 via the feedwater pump 11. The water outlet of the high-pressure heater 12 is connected to the feedwater inlet of the boiler 1. The turbine's ultra-high-pressure cylinder 2, high-pressure cylinder 3, intermediate-pressure cylinder 4, and low-pressure cylinder 5 are connected by a rotating shaft and jointly drive the generator 6 to generate electricity. This ensures the circulation of steam and water within the coal-fired unit, thereby guaranteeing power supply.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A high-pressure steam supply system coupled with molten salt thermal storage, characterized in that, include: A coal-fired power unit and a high-pressure steam supply system, wherein the high-pressure steam supply system includes a back pressure turbine, and the coal-fired power unit includes: The boiler is provided with a main steam outlet, which is connected to the steam inlet of the back pressure machine. The boiler has a primary reheat intermediate reheater and a primary reheat secondary reheater. The steam outlet of the primary reheat intermediate reheater is connected to the steam inlet of the primary reheat secondary reheater and the steam inlet of the back pressure machine, respectively. The turbine ultra-high pressure cylinder has its main steam outlet connected to the steam inlet of the turbine ultra-high pressure cylinder, and its steam outlet connected to the steam inlet of the primary reheat intermediate reheater. The steam outlet of the primary reheat and secondary reheater is connected to the steam inlet of the high-pressure cylinder of the steam turbine. The main steam diversion valve is used to control the connection and disconnection between the main steam outlet and the steam inlet of the back pressure unit. A reheat steam diversion valve is used to control the connection and disconnection between the steam outlet of the primary reheat intermediate reheater and the steam inlet of the back pressure machine. The coal-fired unit also includes a steam turbine intermediate pressure cylinder and a deaerator. The steam extraction outlet of the steam turbine intermediate pressure cylinder is connected to the steam inlet of the deaerator, and the water outlet of the deaerator is connected to the feedwater inlet of the boiler. The high-pressure steam supply system also includes a desuperheating and pressure reducing device, which has a steam inlet and a liquid inlet. The steam outlet of the back pressure turbine is connected to the steam inlet, and the liquid inlet is connected to the water outlet of the deaerator. The steam outlet of the desuperheating and pressure reducing device is connected to the steam supply header for heating. The high-pressure steam supply system coupled with molten salt thermal storage further includes a molten salt thermal storage system, in which molten salt circulates. The molten salt thermal storage system includes: The system includes a low-temperature molten salt tank, a high-temperature molten salt tank, and a molten salt electric heater. The molten salt electric heater has a first flow path for heating the molten salt in the first flow path. The two ends of the first flow path are respectively connected to the outlet of the low-temperature molten salt tank and the inlet of the high-temperature molten salt tank to form a heat storage circuit of the molten salt heat storage system. A cryogenic molten salt pump is provided between the cryogenic molten salt tank and the molten salt electric heater to drive the molten salt to circulate. A feedwater-molten salt heat exchanger has a first channel and a second channel for mutual heat exchange. The outlet of the first channel is connected to the inlet of the low-temperature molten salt tank, and the inlet of the second channel is connected to the water outlet of the deaerator. A superheated steam-molten salt heat exchanger has a third channel and a fourth channel for mutual heat exchange. The inlet end of the third channel is connected to the outlet of the high-temperature molten salt tank, and the outlet end of the fourth channel is connected to the steam inlet of the primary reheat intermediate reheater through a molten salt steam supply pipeline. A saturated steam-molten salt heat exchanger has a fifth channel and a sixth channel for mutual heat exchange. The two ends of the fifth channel are respectively connected to the outlet end of the third channel and the inlet end of the first channel, and the two ends of the sixth channel are respectively connected to the outlet end of the second channel and the inlet end of the fourth channel. A steam drum, the inlet of which is connected to the outlet of the sixth channel, the steam drum being used to separate saturated steam and water, the steam drum having a steam outlet and a liquid outlet, the steam outlet being connected to the inlet of the fourth channel, and the liquid outlet being connected to the inlet of the second channel; A high-temperature molten salt pump, located between the high-temperature molten salt tank and the superheated steam-molten salt heat exchanger, is used to drive the molten salt circulation. The high-temperature molten salt tank, the third channel, the fifth channel, the first channel, and the low-temperature molten salt tank form the heat release circuit of the molten salt thermal storage system.

2. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 1, characterized in that, The coal-fired unit also includes a generator, and the cryogenic molten salt pump is driven by the generator.

3. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 1, characterized in that, The feedwater-molten salt heat exchanger, the saturated steam-molten salt heat exchanger, and the superheated steam-molten salt heat exchanger are all indirect-contact water-molten salt heat exchangers.

4. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 1, characterized in that, The molten salt thermal storage system also includes: A water supply bypass pump is used to drive water from the water outlet of the deaerator to the inlet of the second channel and the liquid inlet of the desuperheating and pressure reducing device. The feedwater diversion valve is used to control the connection and disconnection between the water outlet of the deaerator and the inlet of the second channel, and to control the connection and disconnection between the water outlet of the deaerator and the liquid inlet.

5. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 4, characterized in that, The high-pressure steam supply system coupled with molten salt thermal storage has normal mode, low-load mode and high-load mode. In the normal mode, the main steam diversion valve is closed, and the reheat steam diversion valve and the feedwater diversion valve are connected. In the low-load mode, the main steam diversion valve and the feedwater diversion valve are connected, the reheat steam diversion valve is closed, and the molten salt electric heater and the cryogenic molten salt pump are turned on. In the high-load mode, the main steam diversion valve is closed, the reheat steam diversion valve and the feedwater diversion valve are connected, and the high-temperature molten salt pump is turned on.

6. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 1, characterized in that, The steam flow rate at the outlet of the main steam diversion valve shall not exceed 21% of the steam flow rate at the main steam outlet; And / or, the steam flow rate at the outlet of the reheat steam diversion valve does not exceed 23% of the steam flow rate at the steam outlet of the primary reheat intermediate reheater; And / or, the exhaust back pressure of the back pressure machine is in the range of 4.3MPa-4.5MPa.

7. The high-pressure steam supply system with coupled molten salt thermal storage according to claim 1, characterized in that, The coal-fired power unit also includes a steam turbine intermediate-pressure cylinder, a steam turbine low-pressure cylinder, a generator, a condenser, a condensate pump, a low-pressure heater, a deaerator, a feedwater pump, and a high-pressure heater. The steam extraction outlet of the ultra-high pressure cylinder of the steam turbine is connected to the steam inlet of the high-pressure heater; the steam outlet of the high-pressure cylinder of the steam turbine is connected to the steam inlet of the secondary reheater of the boiler; the steam outlet of the secondary reheater is connected to the steam inlet of the intermediate pressure cylinder of the steam turbine; the steam extraction outlet of the intermediate pressure cylinder of the steam turbine is connected to the steam inlet of the deaerator; the steam outlet of the intermediate pressure cylinder of the steam turbine is connected to the steam inlet of the low-pressure cylinder of the steam turbine; the steam extraction outlet of the low-pressure cylinder of the steam turbine is connected to the steam inlet of the low-pressure heater; and the steam outlet of the low-pressure cylinder of the steam turbine... The steam inlet of the condenser is connected to the steam outlet of the condenser, and the water outlet of the condenser is connected to the water inlet of the low-pressure heater via a condensate pump. The water outlet of the low-pressure heater is connected to the water inlet of the deaerator, and the water outlet of the deaerator is connected to the water inlet of the high-pressure heater via a feedwater pump. The water outlet of the high-pressure heater is connected to the feedwater inlet of the boiler. The ultra-high pressure cylinder, the high pressure cylinder, the intermediate pressure cylinder, and the low pressure cylinder of the turbine are connected by a rotating shaft and jointly drive the generator to generate electricity.

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