Comprehensive energy storage system based on step heat storage of flue gas waste heat and steam heat energy

Abstract

The invention discloses a comprehensive energy storage system based on flue gas waste heat and steam heat energy cascade heat storage. The comprehensive energy storage system comprises a coal power unit, a fused salt heat storage module and a solid heat storage module. The fused salt heat storage unit comprises a flue gas-fused salt heat exchanger and a fused salt-feed water heat exchanger, a first flow path and a second flow path which exchange heat with each other are arranged in the flue gas-fused salt heat exchanger, a third flow path and a fourth flow path which exchange heat with each other are arranged in the fused salt-feed water heat exchanger, and the first flow path and the fourth flow path are respectively connected in series in the coal power unit; the solid heat storage unit comprises a solid heat storage tank, a fifth flow path and a sixth flow path which exchange heat with the heat storage medium are arranged in the solid heat storage tank, and the fifth flow path and the sixth flow path are connected in the coal power unit in series. According to the comprehensive energy storage system based on flue gas waste heat and steam heat energy cascade heat storage, cascade recovery and time-sharing utilization of flue gas waste heat can be achieved, the smoke exhaust loss can be reduced, and the energy utilization rate and the flexible peak regulation capacity of a coal power unit are improved.

Description

Technical Field

[0001] This invention relates to the field of deep peak shaving and waste heat recovery technology for thermal power generating units, and in particular to a comprehensive energy storage system based on the cascade storage of flue gas waste heat and steam thermal energy. Background Technology

[0002] In related technologies, with the adjustment of the global energy structure, thermal power units play an important role in peak shaving and grid stabilization in the power system. However, thermal power units face significant challenges in the process of deep peak shaving and flexibility transformation. Traditional coal-fired power plants experience reduced boiler combustion efficiency and increased unit coal consumption rates during low-load operation, while frequent start-ups and shutdowns exacerbate equipment wear and thermal stress damage. During the operation of thermal power units, the large amount of high-temperature flue gas emitted by the boiler contains abundant waste heat resources. This waste heat is mainly distributed near the economizer and air preheater; direct emission not only results in significant energy waste but may also further reduce the exhaust temperature due to flue gas dew point corrosion. Existing waste heat recovery methods are mostly limited to low-temperature feedwater heating or air preheating, with limited heat storage and energy cascade utilization capabilities, resulting in significant waste of waste heat. This makes it difficult to meet the needs of deep peak shaving and rapid start-up and shutdown of thermal power units, leading to unsatisfactory peak shaving efficiency and economic performance. Summary of the Invention

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an integrated energy storage system based on the cascaded storage of flue gas waste heat and steam thermal energy. The integrated energy storage system based on the cascaded storage of flue gas waste heat and steam thermal energy can realize the cascaded recovery and time-sharing utilization of flue gas waste heat, reduce exhaust losses, and improve the energy utilization rate and flexible peak-shaving capability of coal-fired power units.

[0004] According to an embodiment of the present invention, a comprehensive energy storage system based on the cascaded thermal energy storage of flue gas waste heat and steam includes: a coal-fired power unit, a molten salt thermal energy storage module, and a solid thermal energy storage module. The coal-fired power unit includes a boiler and a steam turbine; the molten salt thermal energy storage unit circulates molten salt and includes a flue gas-molten salt heat exchanger and a molten salt-feedwater heat exchanger. The flue gas-molten salt heat exchanger has a first flow path and a second flow path for mutual heat exchange, and the molten salt-feedwater heat exchanger has a third flow path and a fourth flow path for mutual heat exchange. The second flow path and the third flow path are connected and circulate molten salt. The first flow path and the fourth flow path are respectively connected in series within the coal-fired power unit, and one end of the first flow path is connected to the... The boiler is connected, and one end of the fourth flow path is connected to the steam turbine. The molten salt thermal storage unit also includes a molten salt pump for driving the molten salt circulation. The solid thermal storage unit includes a solid thermal storage tank, which stores a thermal storage medium. The solid thermal storage tank is provided with a fifth flow path and a sixth flow path that exchange heat with the thermal storage medium, respectively. The fifth flow path and the sixth flow path are connected in series in the coal-fired power unit. One end of the fifth flow path is connected to the boiler, and one end of the sixth flow path is connected to the steam turbine.

[0005] According to an embodiment of the present invention, a comprehensive energy storage system based on the cascaded thermal energy storage of flue gas waste heat and steam heat energy is constructed by setting up a coal-fired power unit, a molten salt thermal energy storage module, and a solid thermal energy storage module. The coal-fired power unit includes a boiler and a steam turbine. Molten salt is circulated within the molten salt thermal energy storage unit, which includes a flue gas-molten salt heat exchanger and a molten salt-feedwater heat exchanger. The solid thermal energy storage unit includes a solid heat storage tank, which stores a heat storage medium. This system enables solid thermal energy storage in the solid thermal energy storage module and molten salt thermal energy storage in the molten salt thermal energy storage module, thereby achieving cascaded recovery and time-sharing utilization of flue gas waste heat. This facilitates deep peak shaving of the coal-fired power unit, reduces flue gas losses, improves the energy utilization rate and flexible peak shaving capability of the coal-fired power unit, thereby improving the flexibility of the coal-fired power unit, reducing thermal stress damage caused by frequent start-ups and shutdowns, and achieving energy conservation, emission reduction, and green low-carbon goals.

[0006] In some embodiments of the present invention, the boiler includes a burner, a furnace, a flue, an economizer, and an air preheater. The burner is disposed on the side wall, top, or bottom of the furnace. The flue is connected to the furnace and is used to discharge flue gas. The economizer and the air preheater are disposed in the flue. One end of the first flow path is connected to the economizer, and one end of the fourth flow path is connected to the burner or the furnace.

[0007] In some embodiments of the present invention, the coal-fired power unit further includes a dust collector, a fan, a desulfurization device, and a chimney. The inlet of the dust collector is connected to the tail end of the flue, the outlet of the dust collector is connected to the inlet of the fan, the outlet of the fan is connected to the inlet of the desulfurization device, the outlet of the desulfurization device is connected to the inlet of the chimney, the other end of the first flow path is connected to the inlet of the dust collector, and the other end of the fifth flow path is connected to the inlet of the dust collector.

[0008] In some embodiments of the present invention, the steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder, and the coal-fired power unit further includes a deaerator. One end of the fourth flow path is connected to the inlet of the high-pressure cylinder, the intermediate-pressure cylinder, or the low-pressure cylinder, and the other end is connected to the deaerator; and / or, one end of the sixth flow path is connected to the inlet of the high-pressure cylinder, the intermediate-pressure cylinder, or the low-pressure cylinder, and the other end is connected to the deaerator.

[0009] In some embodiments of the present invention, the steam turbine includes a high-pressure cylinder and an intermediate-pressure cylinder, the coal-fired power unit also includes a deaerator, and the molten salt thermal storage unit also includes a steam-molten salt heat exchanger. The steam-molten salt heat exchanger is provided with a seventh flow path and an eighth flow path for mutual heat exchange. The seventh flow path, the second flow path, and the third flow path are connected in sequence to form a loop. The eighth flow path is connected in series in the coal-fired power unit. One end of the eighth flow path is connected to the outlet of the high-pressure cylinder or the intermediate-pressure cylinder, and the other end is connected to the deaerator.

[0010] In some embodiments of the present invention, the molten salt thermal storage module further includes a first valve, which is connected between the eighth flow path and the steam turbine, and is used to control the on / off state of the eighth flow path.

[0011] In some embodiments of the present invention, the molten salt thermal storage module further includes a second valve and a third valve. The second valve is located on the side of the fourth flow path away from the steam turbine and is used to control the opening and closing of the fourth flow path. The third valve is located between the first flow path and the boiler and is used to control the opening and closing of the first flow path.

[0012] In some embodiments of the present invention, the solid thermal energy storage module further includes a fourth valve and a fifth valve. The fourth valve is located between the fifth flow path and the boiler and is used to control the on / off state of the fifth flow path. The fifth valve is located on the side of the sixth flow path away from the turbine and is used to control the on / off state of the sixth flow path.

[0013] In some embodiments of the present invention, the boiler is provided with a flue gas diversion baffle to control the flow direction and flow rate of the flue gas.

[0014] In some embodiments of the present invention, the heat storage medium is ceramic particles, high-temperature rock, or concrete block.

[0015] 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

[0016] 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: Figure 1 This is a schematic diagram of the structure of an integrated energy storage system based on the cascaded thermal energy storage of flue gas waste heat and steam according to an embodiment of the present invention.

[0017] Figure label: 1. Burner; 2. Furnace; 3. Economizer; 4. Air preheater; 5. Dust collector; 6. Fan; 7. Desulfurization unit; 8. Chimney; 9. Steam turbine; 10. Generator; 11. Condenser; 12. Condensate pump; 13. Low-pressure heater group; 14. Deaerator; 15. Feedwater pump; 16. High-pressure heater group; 17. First valve; 18. Steam-molten salt heat exchanger; 19. Flue gas-molten salt heat exchanger; 20. Molten salt-feedwater heat exchanger; 21. Molten salt tank; 22. Molten salt pump; 23. Second valve; 24. Third valve; 25. Fourth valve; 26. Fifth valve; 27. Solid heat storage tank. Detailed Implementation

[0018] 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.

[0019] 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. 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.

[0020] The following is for reference. Figure 1 This invention describes an integrated energy storage system based on the cascaded thermal storage of flue gas waste heat and steam thermal energy according to an embodiment of the present invention.

[0021] like Figure 1 As shown, the integrated energy storage system based on the cascaded thermal energy storage of flue gas waste heat and steam according to an embodiment of the present invention includes a coal-fired power unit, a molten salt thermal energy storage module and a solid thermal energy storage module.

[0022] Specifically, the coal-fired power unit includes a boiler and a steam turbine 9. Molten salt circulates within the molten salt thermal storage unit, which includes a flue gas-molten salt heat exchanger 19 and a molten salt-feedwater heat exchanger 20. The flue gas-molten salt heat exchanger 19 has a first flow path and a second flow path for mutual heat exchange, and the molten salt-feedwater heat exchanger 20 has a third flow path and a fourth flow path for mutual heat exchange. The second and third flow paths are connected and circulate molten salt. The first and fourth flow paths are connected in series within the coal-fired power unit. One end of the first flow path is connected to the boiler, and one end of the fourth flow path is connected to the steam turbine 9. The molten salt thermal storage unit also includes a molten salt pump 22 for driving the molten salt circulation. The solid thermal storage unit includes a solid thermal storage tank 27, which stores a thermal storage medium. The solid thermal storage tank 27 is provided with a fifth flow path and a sixth flow path that exchange heat with the thermal storage medium. The fifth flow path and the sixth flow path are connected in series in the coal-fired power unit. One end of the fifth flow path is connected to the boiler, and one end of the sixth flow path is connected to the steam turbine 9.

[0023] The molten salt thermal energy storage module includes a flue gas-molten salt heat exchanger 19, a molten salt-feedwater heat exchanger 20, a molten salt tank 21, and a molten salt pump 22 connected in sequence. Both the flue gas-molten salt heat exchanger 19 and the molten salt-feedwater heat exchanger 20 are shell-and-tube heat exchangers. Further, the flue gas-molten salt heat exchanger 19 is a shell-and-tube heat exchanger for molten salt and flue gas. The flue gas flows along the tube side of the flue gas-molten salt heat exchanger 19 to form a first flow path, and the molten salt flows along the shell side of the flue gas-molten salt heat exchanger 19 to form a second flow path. The molten salt-feedwater heat exchanger 20 is a shell-and-tube heat exchanger for feedwater and molten salt. The feedwater flows along the tube side of the molten salt-feedwater heat exchanger 20 to form a third flow path, and the molten salt flows along the shell side of the molten salt-feedwater heat exchanger 20 to form a fourth flow path.

[0024] During periods of low load or off-peak electricity at night, the system enters the heat storage phase. In the solid heat storage module, pulverized coal combustion in the boiler generates high-temperature flue gas, some of which enters the fifth flow path of the solid heat storage tank 27. Within the solid heat storage tank 27, the high-temperature flue gas exchanges heat with a heat storage medium such as ceramic particles, high-temperature rock, or concrete blocks, storing sensible heat. The cooled flue gas then flows into the boiler's tail flue and, after treatment, is discharged into the atmosphere. Utilizing the waste heat of the boiler's tail flue gas for high-temperature sensible heat storage reduces exhaust gas temperature, minimizes energy waste, and simultaneously addresses environmental emissions concerns.

[0025] In the molten salt thermal storage module, a portion of the flue gas is controlled to enter the first flow path of the flue gas-molten salt heat exchanger 19. The cold molten salt in the molten salt tank 21 is pumped into the second flow path of the flue gas-molten salt heat exchanger 19 via the molten salt pump 22 to absorb heat from the flue gas, and finally returns to the molten salt tank 21. After releasing heat, the flue gas is treated in the boiler's tail flue and then discharged into the atmosphere, achieving ultra-low emission levels.

[0026] The flue gas-molten salt heat exchanger 19 and the solid heat storage tank 27 can be connected to different locations on the boiler to obtain flue gas at different temperatures. This allows for the storage of medium- and high-temperature flue gas heat energy across different time periods, reducing energy waste under low-load conditions in coal-fired power units and improving energy utilization. In this stage, the sensible heat of the medium- and high-temperature flue gas is stored in stages in the solid heat storage tank 27 and the molten salt tank 21, achieving energy capture under low-load conditions and providing energy reserves for peak shaving.

[0027] During periods of high load or grid peak shaving, the system enters a heat release phase. In the solid thermal storage module, a portion of the boiler feedwater from the coal-fired power unit flows into the sixth flow path of the solid thermal storage tank 27, where it is heated by the high-temperature solid. The heated water generates medium- or low-pressure steam, which is then piped to the turbine 9's high-pressure, medium-pressure, and low-pressure cylinders to supplement power output. The solid thermal storage module releases high-temperature sensible heat to quickly respond to load changes, providing supplementary steam to the turbine 9 and reducing fluctuations in the main steam regulating pressure.

[0028] In the molten salt thermal energy storage module, a portion of the boiler feedwater from the coal-fired power unit flows into the fourth flow path of the molten salt-feedwater heat exchanger 20. The molten salt pump 22 transports the hot molten salt from the molten salt tank 21 to the third flow path of the molten salt-feedwater heat exchanger 20. The molten salt in the third flow path transfers heat to the feedwater in the fourth flow path, generating medium-temperature steam or increasing the inlet steam temperature. The steam enters the corresponding cylinder section of the turbine 9 for power compensation, achieving flexible peak shaving. The molten salt thermal energy storage releases heat stably and controllably, allowing for continuous heat release to regulate the unit load. This improves the unit's deep peak shaving capability and reduces thermal stress caused by rapid load changes. This stage utilizes solid thermal energy storage modules and molten salt thermal energy storage modules to release heat energy in stages, achieving rapid load increase and deep peak shaving for the unit, meeting the peak demand of the power grid.

[0029] Throughout the entire operation, the solid thermal storage module and the molten salt thermal storage module are used to achieve the cascade recovery and time-sharing utilization of flue gas waste heat, thereby improving the flexibility of coal-fired power units, reducing thermal stress damage caused by frequent start-ups and shutdowns, improving energy utilization, reducing flue gas losses, and achieving energy conservation and emission reduction goals.

[0030] According to an embodiment of the present invention, a comprehensive energy storage system based on the cascaded thermal energy storage of flue gas waste heat and steam heat energy is constructed by setting up a coal-fired power unit, a molten salt thermal energy storage module, and a solid thermal energy storage module. The coal-fired power unit includes a boiler and a steam turbine 9. Molten salt is circulated within the molten salt thermal energy storage unit, which includes a flue gas-molten salt heat exchanger 19 and a molten salt-feedwater heat exchanger 20. The solid thermal energy storage unit includes a solid heat storage tank 27, which stores a heat storage medium. This system enables solid thermal energy storage in the solid thermal energy storage module and molten salt thermal energy storage in the molten salt thermal energy storage module, thereby achieving cascaded recovery and time-sharing utilization of flue gas waste heat. This facilitates deep peak shaving of the coal-fired power unit, reduces flue gas losses, improves the energy utilization rate and flexible peak shaving capability of the coal-fired power unit, thereby improving the flexibility of the coal-fired power unit, reducing thermal stress damage caused by frequent start-ups and shutdowns, and achieving energy conservation, emission reduction, and green low-carbon goals.

[0031] In some embodiments, such as Figure 1 As shown, the coal-fired power unit includes a boiler, a steam turbine 9, a generator 10, a condenser 11, a condensate pump 12, a low-pressure heater group 13, a deaerator 14, a feedwater pump 15, and a high-pressure heater group 16 connected in sequence. The low-pressure heater group 13 is composed of multiple low-pressure heaters connected in series, and the high-pressure heater group 16 is composed of multiple high-pressure heaters connected in series.

[0032] In some embodiments of the present invention, such as Figure 1 As shown, the boiler includes a burner 1, a furnace 2, a flue, an economizer 3, and an air preheater 4. The burner 1 is located on the side wall, top, or bottom of the furnace 2. The flue is connected to the furnace 2 and is used to discharge flue gas. The economizer 3 and the air preheater 4 are located inside the flue. One end of the first flow path is connected to the economizer 3, and one end of the fourth flow path is connected to the burner 1 or the furnace 2.

[0033] Specifically, one end of the fourth flow path can be connected to the vicinity of burner 1, the middle of furnace 2, or the front of convective heating, while one end of the first flow path can be connected to the inlet or outlet of economizer 3. The flue gas-molten salt heat exchanger 19 and the solid heat storage tank 27 are connected to different locations in the boiler, allowing for the acquisition of flue gas at different temperatures. This enables the storage of medium- and high-temperature flue gas heat energy across time periods, reducing energy waste under low load conditions and improving energy utilization. In this stage, the sensible heat of medium- and high-temperature flue gas is stored in stages in the solid heat storage tank 27 and the molten salt tank 21, achieving energy capture under low load conditions and providing energy reserves for peak shaving.

[0034] In some embodiments of the present invention, such as Figure 1As shown, the coal-fired power unit also includes a dust collector 5, a fan 6, a desulfurization device 7, and a chimney 8. The inlet of the dust collector 5 is connected to the tail end of the flue, the outlet of the dust collector 5 is connected to the inlet of the fan 6, the outlet of the fan 6 is connected to the inlet of the desulfurization device 7, the outlet of the desulfurization device 7 is connected to the inlet of the chimney 8, the other end of the first flow path is connected to the inlet of the dust collector 5, and the other end of the fifth flow path is connected to the inlet of the dust collector 5.

[0035] It should be noted that pulverized coal is injected into the furnace 2 through burner 1 for combustion and heat release. The high-temperature flame and flue gas generated by combustion transfer heat to the boiler's heating surfaces sequentially through different heat exchange mechanisms in the furnace 2 and flue. When the flue gas leaves the boiler, its temperature is already low, and it then enters the dust collector 5 to remove most of the ash particles. The flue gas cold end of the flue gas-molten salt heat exchanger 19 and the flue gas cold end of the solid heat storage tank 27 are both connected to the inlet of the dust collector 5. After heat exchange, the flue gas enters the dust collector 5 to remove most of the ash particles. The flue gas is driven by fan 6 into the desulfurization device 7 to remove most of the sulfur dioxide, and finally discharged into the atmosphere through chimney 8, achieving ultra-low emission levels.

[0036] In some embodiments of the present invention, such as Figure 1 As shown, the steam turbine 9 includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The coal-fired power unit also includes a deaerator 14. One end of the fourth flow path is connected to the inlet of the high-pressure cylinder, intermediate-pressure cylinder, or low-pressure cylinder, and the other end is connected to the deaerator 14. The pipe connection point between the molten salt-feedwater heat exchanger 20 and the steam turbine 9 is located at the inlet of the high-pressure cylinder, intermediate-pressure cylinder, or low-pressure cylinder. Steam can be introduced at single or multiple points, and a regulating valve is installed in the steam inlet pipeline for easy control.

[0037] During periods of high load or grid peak shaving, a portion of the boiler feedwater in the deaerator 14 flows into the fourth flow path of the molten salt-feedwater heat exchanger 20. The molten salt pump 22 transports the hot molten salt in the molten salt tank 21 to the third flow path of the molten salt-feedwater heat exchanger 20. The molten salt in the third flow path transfers heat to the feedwater in the fourth flow path, generating medium-temperature steam or increasing the inlet steam temperature. The steam then enters the corresponding cylinder section of the turbine 9 for power compensation, achieving flexible peak shaving.

[0038] In some embodiments of the present invention, such as Figure 1 As shown, the steam turbine 9 includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The coal-fired power unit also includes a deaerator 14. One end of the sixth flow path is connected to the inlet of the high-pressure cylinder, intermediate-pressure cylinder, or low-pressure cylinder, and the other end is connected to the deaerator 14. The pipeline connection point of the solid heat storage tank 27 to the steam turbine 9 is located at the inlet of the high-pressure cylinder, intermediate-pressure cylinder, or low-pressure cylinder. Steam can be introduced at one or more points, and a regulating valve is installed in the steam inlet pipeline for easy control.

[0039] During periods of high load or grid peak shaving, a portion of the boiler feedwater in the deaerator 14 flows into the sixth flow path of the solid thermal storage tank 27, where it is heated by high-temperature solids. The heated water generates medium- or low-pressure steam, which is then piped to the turbine 9's high-pressure, medium-pressure, and low-pressure cylinders to supplement power output. The solid thermal storage module releases high-temperature sensible heat to quickly respond to load changes, providing supplementary steam to the turbine 9, reducing main steam regulation pressure fluctuations, and achieving flexible peak shaving.

[0040] In some embodiments of the present invention, such as Figure 1 As shown, the steam turbine 9 includes a high-pressure cylinder and an intermediate-pressure cylinder. The coal-fired power unit also includes a deaerator 14. The molten salt heat storage unit also includes a steam-molten salt heat exchanger 18. The steam-molten salt heat exchanger 18 is provided with a seventh flow path and an eighth flow path for mutual heat exchange. The seventh flow path, the second flow path, and the third flow path are connected in sequence to form a loop. The eighth flow path is connected in series in the coal-fired power unit. One end of the eighth flow path is connected to the outlet of the high-pressure cylinder or the intermediate-pressure cylinder, and the other end is connected to the deaerator 14.

[0041] Specifically, the cold end of the steam-molten salt heat exchanger 18 is connected to the inlet end of the deaerator 14, and the hot end of the steam-molten salt heat exchanger 18 is connected to the outlet of the high-pressure cylinder or the intermediate-pressure cylinder. The molten salt thermal storage module includes, in sequence, the steam-molten salt heat exchanger 18, the flue gas-molten salt heat exchanger 19, the molten salt-feedwater heat exchanger 20, the molten salt tank 21, and the molten salt pump 22. The steam-molten salt heat exchanger 18 is a shell-and-tube heat exchanger. Further, the steam-molten salt heat exchanger 18 is a shell-and-tube heat exchanger for molten salt and steam. Steam flows along the tube side of the steam-molten salt heat exchanger 18 to form an eighth loop, and molten salt flows along the shell side of the steam-molten salt heat exchanger 18 to form a seventh flow path.

[0042] During low load periods or off-peak electricity hours at night, the system enters the thermal storage phase. In the molten salt thermal storage module, a portion of the main steam or reheat steam from turbine 9 is drawn into the eighth flow path of the steam-molten salt heat exchanger 18 via a regulating valve. By controlling the flue gas diversion baffle, a portion of the medium- and high-temperature flue gas from the boiler enters the flue gas-molten salt heat exchanger 19. The cold molten salt in the molten salt tank 21 is pumped into the steam-molten salt heat exchanger 18 and the flue gas-molten salt heat exchanger 19 successively through the molten salt pump 22 to absorb heat from the steam and flue gas, finally returning to the molten salt tank 21. The main steam or reheat steam is then sent to the deaerator 14 after releasing heat. This process stores the thermal energy of medium- and high-temperature steam across time periods, reducing steam waste under low unit load and improving energy utilization. In this phase, the sensible heat of the high-temperature flue gas from the boiler and the thermal energy of the medium-temperature steam from turbine 9 are stored in stages in the solid thermal storage tank 27 and the molten salt tank 21, achieving energy capture under low load conditions and providing energy reserves for peak shaving.

[0043] By constructing a comprehensive energy storage system based on the cascaded storage of flue gas waste heat and steam thermal energy, the graded recovery and storage of medium- and high-temperature flue gas and medium- and low-temperature steam thermal energy can be realized, thereby improving the energy utilization rate and flexible peak-shaving capability of the unit and providing a new technical path for deep peak shaving, energy saving and consumption reduction and green and low-carbon operation of thermal power units.

[0044] In some embodiments of the present invention, such as Figure 1 As shown, the molten salt thermal storage module also includes a first valve 17, which is connected between the eighth flow path and the steam turbine 9 to control the opening and closing of the eighth flow path. The inlet end of the first valve 17 is connected to the steam turbine 9, and the outlet end of the first valve 17 is connected to the hot steam end of the steam-molten salt heat exchanger 18. The pipeline connection point between the first valve 17 and the steam turbine 9 is located at the inlet of the high-pressure cylinder or the intermediate-pressure cylinder, allowing for single or multiple steam intake points, with regulating valves installed on the steam intake pipelines. The first valve 17 on the pipelines enables flexible switching between steam or flue gas intake and feedwater heating, facilitating the control system to enter the heating or heat release stage.

[0045] In some embodiments of the present invention, such as Figure 1 As shown, the molten salt thermal storage module also includes a second valve 23 and a third valve 24. The second valve 23 is located on the side of the fourth flow path away from the turbine 9 and is used to control the on / off state of the fourth flow path. The third valve 24 is located between the first flow path and the boiler and is used to control the on / off state of the first flow path. The inlet end of the second valve 23 is connected to the outlet end of the deaerator 14, and the outlet end of the second valve 23 is connected to the cold end of the feedwater in the molten salt-feedwater heat exchanger 20. The inlet end of the third valve 24 is connected to the boiler, and the outlet end of the third valve 24 is connected to the hot end of the flue gas in the flue gas-molten salt heat exchanger 19. The pipeline connection point of the third valve 24 to the boiler is located at the inlet or outlet of the economizer 3, allowing for single or multiple gas intake points, with regulating valves installed on the intake pipelines. The second valve 23 and the third valve 24 are installed on the pipelines to achieve flexible switching between steam or flue gas intake and feedwater heating, facilitating the control system to enter the heating or cooling phase.

[0046] In some embodiments of the present invention, such as Figure 1 As shown, the solid thermal storage module also includes a fourth valve 25 and a fifth valve 26. The fourth valve 25 is located between the fifth flow path and the boiler, and is used to control the on / off state of the fifth flow path. The fifth valve 26 is located on the side of the sixth flow path away from the turbine 9, and is used to control the on / off state of the sixth flow path. The inlet end of the fourth valve 25 is connected to the boiler, and the outlet end of the fourth valve 25 is connected to the flue gas inlet of the solid thermal storage tank 27. The inlet end of the fifth valve 26 is connected to the water outlet end of the deaerator 14, and the outlet end of the fifth valve 26 is connected to the feedwater inlet of the solid thermal storage tank 27.

[0047] The fourth valve 25 is connected to the boiler via piping near the burner 1, in the middle of the furnace 2, or before the convective heat exchanger. It draws gas from one or more points, and a regulating valve is installed on the gas intake pipeline. The solid heat storage tank 27 is connected to the turbine 9 via piping at the inlet of the high-pressure, intermediate-pressure, or low-pressure cylinder. It receives steam from one or more points, and a regulating valve is installed on the steam intake pipeline. The pipeline is equipped with the fourth valve 25 and the fifth valve 26 to control the flow of flue gas and feedwater into the solid heat storage tank 27.

[0048] In some embodiments of the present invention, a flue gas diversion baffle is provided in the boiler to control the flow direction and flow rate of the flue gas. By increasing the flue gas diversion, it is easier to coordinate with valve control and provide conditions for subsequent cascade heat storage.

[0049] In some embodiments of the present invention, the heat storage medium is ceramic particles, high-temperature rock, or concrete blocks. Ceramic particles, high-temperature rock, and concrete blocks are all low-cost, high-performance, and highly reliable solid heat storage media. They have extremely low raw material costs and are easy to obtain on a large scale. They also have excellent thermal stability and chemical inertness, and will not decompose or undergo phase changes at high temperatures, which can ensure the long-term cycle life of the solid heat storage module.

[0050] In the specific implementation process, the shape, structure, size, type, and location of the coal-fired power unit, steam-molten salt heat exchanger 18, flue gas-molten salt heat exchanger 19, molten salt-feed water heat exchanger 20, molten salt tank 21, molten salt pump 22, solid heat storage tank 27, dust collector 5, fan 6, desulfurization device 7, and chimney 8 can be determined according to the actual situation and needs.

[0051] To further illustrate the combined heat and power system of coupled steam-to-steam heat exchange and molten salt energy storage provided by the present invention, please refer to the following: Figure 1 The method of its use is described below. The following description is merely exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0052] During periods of low load or off-peak electricity at night, the system enters the heat storage phase. In the solid heat storage module, pulverized coal is burned in the furnace 2 via burner 1 to generate high-temperature flue gas. The fourth valve 25 is opened, controlling the flue gas diversion baffle, allowing a portion of the high-temperature flue gas near burner 1, in the middle of furnace 2, or near the convective heating surface to enter the solid heat storage tank 27 through the fourth valve 25. Within the solid heat storage tank 27, the high-temperature flue gas exchanges heat with the heat storage medium, such as ceramic particles, high-temperature rock, or concrete blocks, storing sensible heat. The cooled flue gas then flows into the boiler tail flue, passing through the dust collector 5, fan 6, desulfurization device 7, and chimney 8 before being discharged into the atmosphere. Utilizing the waste heat of the boiler tail flue gas for high-temperature sensible heat storage reduces the exhaust temperature, minimizes energy waste, and simultaneously addresses environmental emissions concerns. In the molten salt thermal storage module, the first valve 17 is opened, and a portion of the main steam or reheat steam from the turbine 9 is drawn through the regulating valve and enters the steam-molten salt heat exchanger 18 via the first valve 17. The third valve 24 is opened, and by controlling the flue gas diversion baffle, a portion of the medium- and high-temperature flue gas at the inlet and outlet of the economizer 3 enters the flue gas-molten salt heat exchanger 19 via the third valve 24. The cold molten salt in the molten salt tank 21 is pumped into the steam-molten salt heat exchanger 18 and the flue gas-molten salt heat exchanger 19 successively through the molten salt pump 22 to absorb heat from the steam and flue gas, and finally returns to the molten salt tank 21. After releasing heat, the main steam or reheat steam is sent to the deaerator 14, and the flue gas, after releasing heat, is sent to the dust collector 5 and the denitrification device for efficient removal of dust and pollutants, achieving ultra-low emission levels. Storing the thermal energy of medium- and high-temperature steam across time periods reduces steam waste under low unit load and improves energy utilization. In this stage, the sensible heat of the high-temperature flue gas from the boiler and the thermal energy of the medium-temperature steam from the turbine 9 are stored in solid heat storage tank 27 and molten salt tank 21 in stages to achieve energy capture at low loads and provide energy reserves for peak shaving.

[0053] During periods of high load or grid peak shaving, the system enters the heat release phase. In the solid thermal storage module, valve 25 is closed and valve 26 is opened. Feedwater from the deaerator 14 outlet flows into the heat exchange channel of the solid thermal storage tank 27, where it is heated by the high-temperature solid. The heated water generates medium- or low-pressure steam, which is then piped to the high, medium, and low-pressure cylinders of the turbine 9 to supplement power output. The solid thermal storage module releases high-temperature sensible heat to quickly respond to load changes, providing supplementary steam to the turbine 9 and reducing main steam regulation pressure fluctuations. In the molten salt thermal storage module, valves 17 and 24 are closed and valve 23 is opened. Molten salt pump 22 transports hot molten salt from molten salt tank 21 to the molten salt-feedwater heat exchanger 20. The molten salt transfers heat to the feedwater at the deaerator 14 outlet, generating medium-temperature steam or increasing the inlet steam temperature. The steam enters the corresponding cylinder section of the turbine 9 for power compensation, achieving flexible peak shaving. The molten salt thermal storage releases heat energy stably and controllably, allowing for continuous heat release to regulate unit load. To improve the deep peak-shaving capability of generating units and reduce thermal stress caused by rapid load changes, this stage utilizes solid thermal storage modules and molten salt thermal storage modules to release heat energy in stages, enabling rapid load increase and deep peak shaving of generating units to meet the peak demand of the power grid.

[0054] Throughout the entire operation, solid thermal storage and molten salt thermal storage are used to achieve cascade recovery and time-sharing utilization of flue gas waste heat and steam thermal energy, improve the flexibility of coal-fired power units, reduce thermal stress damage caused by frequent start-ups and shutdowns, improve energy utilization, reduce flue gas losses, and achieve energy conservation and emission reduction goals.

[0055] 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.

[0056] 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 comprehensive energy storage system based on flue gas waste heat and steam thermal energy cascade heat storage, characterized in that, Comprise: Coal power unit, the coal power unit includes a boiler and a steam turbine; A molten salt heat storage module, molten salt is circulated in the molten salt heat storage unit, the molten salt heat storage unit includes a flue gas-molten salt heat exchanger and a molten salt-feedwater heat exchanger, the flue gas-molten salt heat exchanger is provided with a first flow path and a second flow path that exchange heat with each other, the molten salt-feedwater heat exchanger is provided with a third flow path and a fourth flow path that exchange heat with each other, the second flow path and the third flow path are connected and circulate molten salt, the first flow path and the fourth flow path are connected in series in the coal power unit, one end of the first flow path is connected with the boiler, one end of the fourth flow path is connected with the steam turbine, the molten salt heat storage unit further comprises a molten salt pump for driving molten salt to circulate and flow; A solid heat storage module, the solid heat storage unit includes a solid heat storage tank, the solid heat storage tank stores a heat storage medium, the solid heat storage tank is provided with a fifth flow path and a sixth flow path that exchange heat with the heat storage medium respectively, the fifth flow path and the sixth flow path are connected in series in the coal power unit, one end of the fifth flow path is connected with the boiler, one end of the sixth flow path is connected with the steam turbine.

2. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade heat storage according to claim 1, wherein The boiler comprises a burner, a furnace, a flue, an economizer and an air preheater, the burner is arranged on the side wall, top or bottom of the furnace, the flue is connected with the furnace for discharging flue gas, the economizer and the air preheater are arranged in the flue, One end of the first flow path is communicated with the economizer, and one end of the fourth flow path is communicated with the burner or the furnace.

3. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade thermal storage according to claim 2, characterized in that, The coal power unit further comprises: A dust collector, a fan, a desulfurization device and a chimney, the inlet of the dust collector is communicated with the tail of the flue, the outlet of the dust collector is connected with the inlet of the fan, the outlet of the fan is connected with the inlet of the desulfurization device, and the outlet of the desulfurization device is connected with the inlet of the chimney, The other end of the first flow path is communicated with the inlet of the dust collector, and the other end of the fifth flow path is communicated with the inlet of the dust collector.

4. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, The steam turbine comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, and the coal power unit further comprises a deaerator, One end of the fourth flow path is connected with the inlet of the high-pressure cylinder, the medium-pressure cylinder or the low-pressure cylinder, and the other end is connected with the deaerator; And / or, one end of the sixth flow path is connected with the inlet of the high-pressure cylinder, the medium-pressure cylinder or the low-pressure cylinder, and the other end is connected with the deaerator.

5. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, The steam turbine comprises a high-pressure cylinder and a medium-pressure cylinder, and the coal power unit further comprises a deaerator, The molten salt heat storage unit further comprises a steam-molten salt heat exchanger, the steam-molten salt heat exchanger is provided with a seventh flow path and an eighth flow path that exchange heat with each other, the seventh flow path, the second flow path and the third flow path are sequentially connected and form a loop, the eighth flow path is connected in series in the coal power unit, one end of the eighth flow path is connected with the outlet of the high-pressure cylinder or the medium-pressure cylinder, and the other end is connected with the deaerator.

6. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade thermal storage according to claim 5, characterized in that, The molten salt heat storage module further comprises: A first valve is connected between the eighth flow path and the steam turbine for controlling the on-off of the eighth flow path.

7. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, The molten salt heat storage module further comprises: A second valve is arranged on the side of the fourth flow path away from the steam turbine for controlling the on-off of the fourth flow path. A third valve is arranged between the first flow path and the boiler for controlling the on-off of the first flow path.

8. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, The solid heat storage module further comprises: A fourth valve is arranged between the fifth flow path and the boiler for controlling the on-off of the fifth flow path. A fifth valve is arranged on the side of the sixth flow path away from the steam turbine for controlling the on-off of the sixth flow path.

9. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, A flue gas shunt baffle is arranged in the boiler for controlling the flow direction and flow rate of flue gas.

10. The integrated energy storage system based on flue gas waste heat and steam thermal energy cascade storage according to claim 1, characterized in that, The heat storage medium is ceramic particles, high-temperature rock or concrete block.

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