A molten salt thermal storage system with a front turbine and a method of operating the same

Abstract

The application discloses a molten salt heat storage system with a front turbine and an operation method thereof, and belongs to the technical field of coal-fired power generation. The application utilizes bypass reheat steam to heat the exhaust steam of the front turbine, so that the outlet steam temperature of the high-pressure cylinder of the turbine is within a reasonable range, the safe operation of the high-pressure cylinder is avoided from being threatened, and no energy outside the system needs to be consumed. Meanwhile, the bypass reheat steam after heating the exhaust steam of the front turbine is utilized to further heat the molten salt for heat storage. On the basis of maintaining the minimum heat load of the boiler of the coal-fired power generation system, the minimum electric load rate of the coal-fired power generation system is reduced, and the renewable energy power consumption of the power grid is promoted. Superheated steam generated by the molten salt heat storage system is injected into the front turbine to generate power, not only realizing the step-by-step utilization of energy, but also improving the rapid load change capability of the coal-fired power generation system, and effectively improving the safe and stable operation capability of the coal-fired power generation system.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, specifically to a molten salt thermal energy storage system with a front-mounted steam turbine and its operation method. Background Technology

[0002] Because renewable energy sources such as wind and solar power are intermittent and fluctuating, the output of wind and solar power plants has strong time-varying characteristics. The grid connection of large-scale renewable energy power poses a huge threat to the safe and stable operation of the power grid. Therefore, traditional coal-fired power generation systems need to make full use of their own adjustable characteristics to play a peak-shaving role and promote the grid's absorption of renewable power.

[0003] However, during deep peak shaving, the operating conditions of coal-fired power plants often deviate from their design conditions, leading to a decrease in the power generation efficiency of the coal-fired power generation system and reducing its economic viability. Furthermore, to ensure the safe and stable operation of boilers in coal-fired power generation systems, the minimum load factor is generally between 20% and 30%, which is still insufficient to meet the growing demand for renewable energy. While configuring a pre-turbine can solve the problem of reduced power generation efficiency at low loads, the main steam performs work in the pre-turbine before entering the high-pressure cylinder, resulting in a decrease in the outlet steam temperature of the high-pressure cylinder and threatening its safe operation.

[0004] Therefore, how to maintain the outlet steam temperature of the high-pressure cylinder while reducing the minimum electrical load rate of the coal-fired power generation system has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a molten salt thermal storage system with a front-mounted steam turbine and its operation method, so as to overcome the problem in the prior art that the outlet steam temperature of the high-pressure cylinder is reduced due to the front-mounted steam turbine.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] This invention provides a molten salt thermal storage system with a front-mounted steam turbine, comprising a molten salt thermal storage system and a coal-fired power generation system coupled thereto. The molten salt thermal storage system includes a front-mounted steam turbine, an auxiliary generator, a steam-steam heat exchanger, a reheat steam-molten salt heat exchanger, a low-temperature molten salt tank, a high-temperature molten salt tank, and a feedwater-molten salt heat exchanger.

[0008] The main steam outlet of the coal-fired power generation system is divided into two paths. The first main steam outlet merges with the steam outlet of the feedwater-molten salt heat exchanger and then connects to the steam inlet of the front turbine. The second main steam outlet connects to the steam inlet of the high-pressure cylinder of the turbine in the coal-fired power generation system. The front turbine is connected to the auxiliary generator for generating electricity. The steam outlet of the front turbine is divided into two paths. One path is connected to the low-temperature side steam inlet of the steam-steam heat exchanger, and the other path is connected to the steam inlet of the high-pressure cylinder of the turbine.

[0009] The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature steam inlet of the steam-steam heat exchanger. The low-temperature steam outlet of the steam-steam heat exchanger merges with the second main steam outlet and is then connected to the steam inlet of the high-pressure cylinder of the turbine. The high-temperature steam outlet of the steam-steam heat exchanger is connected to the water inlet of the coal-fired power generation system via the water inlet of the reheat steam-molten salt heat exchanger and the water outlet of the reheat steam-molten salt heat exchanger. The molten salt outlet of the reheat steam-molten salt heat exchanger is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger via the high-temperature molten salt tank, the feedwater-molten salt heat exchanger, and the low-temperature molten salt tank.

[0010] The boiler feedwater connection of the coal-fired power generation system is the water inlet of the feedwater-molten salt heat exchanger.

[0011] A further improvement of the present invention is that it also includes a main steam diversion valve and a first control valve. The first main steam outlet is connected to the steam inlet of the front turbine after merging with the steam outlet of the feedwater-molten salt heat exchanger via the main steam diversion valve. The low-temperature side steam outlet of the steam-steam heat exchanger is connected to the steam inlet of the high-pressure cylinder of the turbine after merging with the second main steam outlet via the first control valve.

[0012] A further improvement of the present invention is that it also includes a second control valve and a third control valve. The steam outlet of the front turbine is divided into two paths: one path is connected to the low-temperature steam inlet of the steam-steam heat exchanger via the second control valve, and the other path is connected to the steam inlet of the coal-fired power generation system via the third control valve.

[0013] A further improvement of the present invention is that it also includes a reheat steam diversion valve, wherein the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger via the reheat steam diversion valve.

[0014] A further improvement of the present invention is that the maximum steam diversion flow rate of the reheat steam diversion valve is 28% of the total mass flow rate of the reheat steam.

[0015] A further improvement of the present invention is that it also includes a low-temperature molten salt pump and a high-temperature molten salt pump. The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger via the low-temperature molten salt pump, and the molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the feedwater-molten salt heat exchanger via the high-temperature molten salt pump.

[0016] A further improvement of the present invention is that it also includes a feedwater diversion valve, through which the boiler feedwater of the coal-fired power generation system is connected to the water inlet of the feedwater-molten salt heat exchanger.

[0017] A further improvement of the present invention is that the steam-steam heat exchanger, the reheat steam-molten salt heat exchanger, and the feedwater-molten salt heat exchanger are all indirect heat exchangers.

[0018] A further improvement of the present invention is that the temperature of the steam outlet on the low-temperature side of the steam-steam heat exchanger is greater than 500°C, and the temperature range of the molten salt thermal storage system is 120°C to 280°C.

[0019] The present invention also provides an operation method for a molten salt thermal storage system with a front-mounted steam turbine, using the molten salt thermal storage system with a front-mounted steam turbine as described above;

[0020] When the coal-fired power generation system is in normal operation, it does not supply main steam and reheat steam to the molten salt thermal storage system, and the molten salt thermal storage system is not in operation.

[0021] When the coal-fired power generation system is operating at low load, the main steam outlet of the coal-fired power generation system delivers all the main steam to the front turbine through the first main steam outlet. The front turbine drives the auxiliary generator to generate electricity, reducing the throttling loss of the main steam. The reheat steam outlet of the coal-fired power generation system delivers reheat steam to the steam-steam heat exchanger. The reheat steam heats the exhaust steam of the front turbine. The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank for heat storage. The heat-exchanged reheat steam is delivered to the high-pressure cylinder of the turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder of the turbine.

[0022] When the coal-fired power generation system is operating at high load, it does not supply main steam to the molten salt thermal storage system. Instead, it sends reheat steam to the steam-steam heat exchanger through the reheat steam outlet to release the heat stored in the high-temperature molten salt tank. This heats the boiler feedwater of the coal-fired power generation system through the feedwater-molten salt heat exchanger, generating superheated steam. This superheated steam then drives the auxiliary generator to generate electricity, and the exhaust steam from the auxiliary generator is sent to the steam inlet of the coal-fired power generation system, thereby increasing the load change rate of the coal-fired power generation system.

[0023] Compared with the prior art, the positive and progressive effects of the present invention are as follows:

[0024] The molten salt thermal energy storage system with a front-mounted steam turbine provided by this invention utilizes bypass reheat steam to heat the exhaust steam of the front-mounted steam turbine, ensuring that the outlet steam temperature of the high-pressure cylinder of the turbine is within a reasonable range, thus avoiding threats to the safe operation of the high-pressure cylinder, and eliminating the need to consume external energy. Simultaneously, the bypass reheat steam after heating the exhaust steam of the front-mounted steam turbine further heats the molten salt for thermal storage, reducing the minimum electrical load rate of the coal-fired power generation system while maintaining the minimum thermal load of the boiler, thereby promoting the absorption of renewable energy power by the power grid. Furthermore, the superheated steam generated by the molten salt thermal energy storage system is injected into the front-mounted steam turbine to generate electricity, achieving not only cascaded energy utilization but also improving the rapid load change capability of the coal-fired power generation system, effectively enhancing its safe and stable operation. Attached Figure Description

[0025] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is a schematic diagram of the connection of a molten salt thermal storage system with a front-mounted steam turbine according to the present invention;

[0027] Among them, the components are: Boiler-1, High-pressure cylinder of steam turbine-2, Intermediate-pressure cylinder of steam turbine-3, Low-pressure cylinder of steam turbine-4, Generator-5, Condenser-6, Condensate pump-7, Low-pressure heater-8, Deaerator-9, Feedwater pump-10, High-pressure heater-11, Main steam diversion valve-12, First control valve-13, Front-mounted steam turbine-14, Auxiliary generator-15, Second control valve-16, Third control valve-17, Reheat steam diversion valve-18, Steam-steam heat exchanger-19, Reheat steam-molten salt heat exchanger-20, Low-temperature molten salt tank-21, Low-temperature molten salt pump-22, High-temperature molten salt tank-23, High-temperature molten salt pump-24, Feedwater-molten salt heat exchanger-25, and Feedwater diversion valve-26. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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 present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 according to the specific circumstances.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This is an explanation of the present invention and not a limitation thereof.

[0034] A molten salt thermal energy storage system with a front-mounted steam turbine includes a molten salt thermal energy storage system and a coal-fired power generation system coupled thereto. The molten salt thermal energy storage system includes a front-mounted steam turbine 14, an auxiliary generator 15, a steam-steam heat exchanger 19, a reheat steam-molten salt heat exchanger 20, a low-temperature molten salt tank 21, a high-temperature molten salt tank 23, and a feedwater-molten salt heat exchanger 25.

[0035] The main steam outlet of the coal-fired power generation system is divided into two paths. The first main steam outlet merges with the steam outlet of the feedwater-molten salt heat exchanger 25 and then connects to the steam inlet of the front turbine 14. The second main steam outlet connects to the steam inlet of the high-pressure cylinder 2 of the turbine in the coal-fired power generation system. The front turbine 14 is connected to the auxiliary generator 15 for external power generation. The steam outlet of the front turbine 14 is divided into two paths. One path is connected to the low-temperature side steam inlet of the steam-steam heat exchanger 19, and the other path is connected to the steam inlet of the high-pressure cylinder 2 of the turbine.

[0036] The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature steam inlet of the steam-steam heat exchanger 19. The low-temperature steam outlet of the steam-steam heat exchanger 19 merges with the second main steam outlet and is then connected to the steam inlet of the high-pressure cylinder 2 of the turbine. The high-temperature steam outlet of the steam-steam heat exchanger 19 is connected to the water inlet of the coal-fired power generation system via the water inlet and the water outlet of the reheat steam-molten salt heat exchanger 20. The molten salt outlet of the reheat steam-molten salt heat exchanger 20 is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger 20 via the high-temperature molten salt tank 23, the feedwater-molten salt heat exchanger 25, and the low-temperature molten salt tank 21.

[0037] The boiler feedwater connection of the coal-fired power generation system is the water inlet of the feedwater-molten salt heat exchanger 25.

[0038] Specifically, it also includes a main steam diversion valve 12 and a first control valve 13. The first main steam outlet is connected to the steam inlet of the front turbine 14 after merging with the steam outlet of the feedwater-molten salt heat exchanger 25 via the main steam diversion valve 12. The low-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the steam inlet of the high-pressure cylinder 2 of the turbine after merging with the second main steam outlet via the first control valve 13.

[0039] Specifically, it also includes a second control valve 16 and a third control valve 17. The steam outlet of the front turbine 14 is divided into two paths. One path is connected to the low-temperature steam inlet of the steam-steam heat exchanger 19 via the second control valve 16, and the other path is connected to the steam inlet of the coal-fired power generation system via the third control valve 17.

[0040] Specifically, it also includes a reheat steam diversion valve 18, through which the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature steam inlet of the steam-steam heat exchanger 19.

[0041] Specifically, the maximum steam diversion flow rate of the reheat steam diversion valve 18 is 28% of the total mass flow rate of the reheat steam.

[0042] Specifically, it also includes a cryogenic molten salt pump 22 and a high-temperature molten salt pump 24. The molten salt outlet of the cryogenic molten salt tank 21 is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger 20 via the cryogenic molten salt pump 22, and the molten salt outlet of the high-temperature molten salt tank 23 is connected to the molten salt inlet of the feedwater-molten salt heat exchanger 25 via the high-temperature molten salt pump 24.

[0043] Specifically, it also includes a feedwater diversion valve 26, through which the boiler feedwater of the coal-fired power generation system is connected to the water inlet of the feedwater-molten salt heat exchanger 25.

[0044] Specifically, the steam-steam heat exchanger 19, the reheat steam-molten salt heat exchanger 20, and the feedwater-molten salt heat exchanger 25 are all indirect heat exchangers.

[0045] Specifically, the temperature of the steam outlet on the low-temperature side of the steam-steam heat exchanger 19 is greater than 500℃, and the temperature range of the molten salt thermal storage system is 120℃~280℃.

[0046] Based on the same inventive concept, the present invention also provides an operation method for a molten salt thermal storage system with a front-mounted steam turbine, using the above-mentioned molten salt thermal storage system with a front-mounted steam turbine.

[0047] When the coal-fired power generation system is in normal operation, it does not supply main steam and reheat steam to the molten salt thermal storage system, and the molten salt thermal storage system is not in operation.

[0048] When the coal-fired power generation system is operating at low load, the main steam outlet of the coal-fired power generation system delivers all the main steam to the front turbine 14 through the first main steam outlet. The front turbine 14 drives the auxiliary generator 15 to generate electricity, reducing the throttling loss of the main steam. The reheat steam outlet of the coal-fired power generation system delivers reheat steam to the steam-steam heat exchanger 19. The reheat steam heats the exhaust steam of the front turbine 14. The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank 21 for heat storage. The heat-exchanged reheat steam is delivered to the high-pressure cylinder 2 of the turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder 2 of the turbine.

[0049] When the coal-fired power generation system is operating at high load, it does not supply main steam to the molten salt thermal storage system. Instead, it delivers reheat steam to the steam-steam heat exchanger 19 through the reheat steam outlet, releasing the heat stored in the high-temperature molten salt tank 23. The feedwater-molten salt heat exchanger 25 heats the boiler feedwater of the coal-fired power generation system, generating superheated steam. This superheated steam causes the front-mounted turbine 14 to drive the auxiliary generator 15 to generate electricity. The exhaust steam from the front-mounted turbine 14 is then delivered to the steam inlet of the coal-fired power generation system, thereby increasing the load change rate of the coal-fired power generation system.

[0050] Example 1

[0051] See Figure 1A molten salt thermal energy storage system with a pre-mounted steam turbine includes a molten salt thermal energy storage system and a coal-fired power generation system coupled thereto. The coal-fired power generation system includes a boiler 1, a high-pressure turbine cylinder 2, a medium-pressure turbine cylinder 3, a low-pressure turbine cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10, and a high-pressure heater 11. The main steam outlet of the boiler 1 is divided into two paths: one path leads to a main steam diversion valve 12, and the other path merges with the low-temperature side steam outlet of a first control valve 13 and a steam-steam heat exchanger 19 before connecting to the steam inlet of the high-pressure turbine cylinder 2. The extraction steam outlet of the high-pressure turbine cylinder 2 is connected to the steam inlet of the high-pressure heater 11, and the steam outlet of the high-pressure turbine cylinder 2 is connected to the reheat steam inlet of the boiler 1. The reheat steam outlet of the boiler 1 is divided into two paths: one path leads to a reheat steam diversion valve 18, and the other path connects to the steam inlet of the medium-pressure turbine cylinder 3. The medium-pressure turbine cylinder 3... The extraction steam outlet of the turbine is connected to the steam inlet of the deaerator 9; the steam outlet of the intermediate-pressure cylinder 3 of the turbine is connected to the steam inlet of the low-pressure cylinder 4 of the turbine; the extraction steam outlet of the low-pressure cylinder 4 of the turbine is connected to the steam inlet of the low-pressure heater 8; the steam outlet of the low-pressure cylinder 4 of the turbine is connected to the steam inlet of the condenser 6; the water outlet of the condenser 6 is connected to the water inlet of the low-pressure heater 8 via the condensate pump 7; the water outlet of the low-pressure heater 8 is connected to the water inlet of the deaerator 9; the water outlet of the deaerator 9 is connected to the water inlet of the feedwater pump 10; the water outlet of the feedwater pump 10 is connected to the water inlet of the high-pressure heater 11; the water outlet of the high-pressure heater 11 is divided into two paths, one leading to the feedwater diversion valve 26, and the other connecting to the feedwater inlet of the boiler 1; the high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4 of the turbine are connected by a rotating shaft and jointly drive the main generator 5 to output electrical power.

[0052] The molten salt thermal energy storage system includes a main steam diversion valve 12, a first control valve 13, a front-mounted steam turbine 14, an auxiliary generator 15, a second control valve 16, a third control valve 17, a reheat steam diversion valve 18, a steam-to-steam heat exchanger 19, a reheat steam-molten salt heat exchanger 20, a cryogenic molten salt tank 21, a cryogenic molten salt pump 22, a high-temperature molten salt tank 23, a high-temperature molten salt pump 24, a feedwater-molten salt heat exchanger 25, and a feedwater diversion valve 26. A portion of the main steam diverted by the main steam diversion valve 12 merges with the working fluid from the steam outlet of the feedwater-molten salt heat exchanger 25 and enters the steam inlet of the front-mounted steam turbine 14. The front-mounted steam turbine 14 drives the auxiliary generator 15 to generate electricity. The steam outlet of the front-mounted steam turbine 14 is divided into two paths: one path passes through the second control valve 16 and the cryogenic side steam of the steam-to-steam heat exchanger 19. One path connects to the steam inlet of the condenser 6, while the other path merges into the steam inlet of the condenser 6 via the third control valve 17. A portion of the reheat steam diverted by the reheat steam diversion valve 18 enters the high-temperature side steam inlet of the steam-steam heat exchanger 19. The low-temperature side steam outlet of the steam-steam heat exchanger 19 merges with the main steam after the first control valve 13 and enters the steam inlet of the high-pressure cylinder 2 of the turbine. The high-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the water side working fluid inlet of the reheat steam-molten salt heat exchanger 20. The molten salt outlet of the low-temperature molten salt tank 21 is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger 20 via the low-temperature molten salt pump 22. The molten salt outlet of the reheat steam-molten salt heat exchanger 20 is connected to the molten salt inlet of the high-temperature molten salt tank 23. The water working fluid outlet of the reheat steam-molten salt heat exchanger 20 merges into the water working fluid inlet of the deaerator 9.

[0053] A portion of the boiler feedwater diverted by the feedwater diversion valve 26 is connected to the water inlet of the feedwater-molten salt heat exchanger 25; the water outlet of the feedwater-molten salt heat exchanger 25 merges with the main steam after the main steam diversion valve 12 and flows into the steam inlet of the front turbine 14; the molten salt outlet of the high-temperature molten salt tank 23 is connected to the molten salt inlet of the feedwater-molten salt heat exchanger 25 via the high-temperature molten salt pump 24; the molten salt outlet of the feedwater-molten salt heat exchanger 25 is connected to the molten salt inlet of the low-temperature molten salt tank 21.

[0054] Example 2

[0055] An operation method for a molten salt thermal energy storage system with a front-mounted steam turbine, using the molten salt thermal energy storage system with a front-mounted steam turbine as described in Example 1, is as follows:

[0056] When the coal-fired power generation system is in normal operation, the main steam diversion valve 12, the second control valve 16, the third control valve 17 and the reheat steam diversion valve 18 are all closed, the first control valve 13 is fully open, and the molten salt thermal storage system and the front turbine are not running.

[0057] When the coal-fired power generation system is operating at low load, the main steam diversion valve 12, the second control valve 16, and the reheat steam diversion valve 18 are opened, while the first control valve 13 and the third control valve 17 are closed. The cryogenic molten salt pump 22 is started. First, the work done by the front turbine 14 reduces the throttling loss of the main steam. Then, the reheat steam is diverted to heat the exhaust steam of the front turbine 14, increasing the inlet steam temperature of the high-pressure cylinder 2 of the turbine. This reduces the adverse effects of the low exhaust temperature of the high-pressure cylinder 2 of the turbine on the safe and stable operation of the coal-fired power generation system. Finally, the heating... After the exhaust steam from the front turbine 14 flows through the reheat steam diversion valve 18, the reheat steam (bypass steam) further heats the low-temperature molten salt in the low-temperature molten salt tank 21, thereby reducing the output load rate of the coal-fired power generation system. The operating objective of the system at this stage is: to reduce the main steam throttling loss by using the front turbine 14 while maintaining the minimum heat load of the coal-fired power generation system boiler, and at the same time to improve the operating safety of the coal-fired power generation system by using the diverted reheat steam to heat the exhaust steam from the front turbine 14, and finally to further reduce the minimum load rate of the coal-fired power generation system by using the molten salt thermal storage system.

[0058] When the coal-fired power generation system is operating at high load, the feedwater diversion valve 26, the first control valve 13, and the third control valve 17 are opened, while the main steam diversion valve 12, the reheat steam diversion valve 18, and the second control valve 16 are closed. The high-temperature molten salt pump 24 is started, and the heat stored in the molten salt thermal storage system is used to heat the bypass boiler feedwater in the feedwater-molten salt heat exchanger 25. The superheated steam generated is then injected into the front turbine 14 to generate electricity, thereby improving the rapid load change capability of the coal-fired power generation system. The operating objective of the system at this stage is to rapidly change the output power of the coal-fired power generation system and improve the load change rate of the coal-fired power generation system by releasing the heat stored in the molten salt thermal storage system without increasing the boiler heat load of the coal-fired power generation system.

[0059] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of this invention. Their purpose is to clearly illustrate the concept, principle, and application of this invention through specific examples, and is by no means intended to limit the scope of protection of this invention to these specific embodiments. In fact, the true value of this invention lies in its proposed technical ideas and innovations, rather than its manifestations or implementation methods.

[0060] For those skilled in the art, after thoroughly reading and understanding the technical solution of this invention, they are fully capable of making various changes, modifications, or equivalent substitutions to the specific implementation of the invention based on their own professional knowledge and skills. These changes may include, but are not limited to: adjusting the range of technical parameters, optimizing the algorithm flow to improve efficiency, and replacing some technical components to achieve better compatibility or reduce costs. As long as these modified technical solutions substantially retain the technical features claimed by the original invention, that is, they can still achieve the core functions and effects of this invention, then these changes should be considered to fall within the scope of protection of the pending claims of this invention.

[0061] Furthermore, with the continuous progress and development of technology, new technical means and methods are constantly emerging, which provides ample space for further improvement and perfection of this invention. Therefore, the scope of protection of this invention should also include reasonable and foresightful improvements and extensions based on existing technology. As long as these improvements and extensions do not depart from the basic principles and core concepts of this invention, they should be considered equivalents of this invention and are equally protected by patent rights.

Claims

1. A molten salt thermal energy storage system with a front-mounted steam turbine, characterized in that, It includes a molten salt thermal storage system and a coal-fired power generation system coupled thereto. The molten salt thermal storage system includes a front-mounted steam turbine (14), an auxiliary generator (15), a steam-steam heat exchanger (19), a reheat steam-molten salt heat exchanger (20), a low-temperature molten salt tank (21), a high-temperature molten salt tank (23), and a feedwater-molten salt heat exchanger (25). The main steam outlet of the coal-fired power generation system is divided into two paths. The first main steam outlet merges with the steam outlet of the feedwater-molten salt heat exchanger (25) and is connected to the steam inlet of the front turbine (14). The second main steam outlet is connected to the steam inlet of the high-pressure cylinder (2) of the turbine of the coal-fired power generation system. The front turbine (14) is connected to the auxiliary generator (15) for external power generation. The steam outlet of the front turbine (14) is divided into two paths. One path is connected to the low-temperature side steam inlet of the steam-steam heat exchanger (19), and the other path is connected to the steam inlet of the high-pressure cylinder (2) of the turbine. The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature steam inlet of the steam-steam heat exchanger (19). The low-temperature steam outlet of the steam-steam heat exchanger (19) merges with the second main steam outlet and is then connected to the steam inlet of the high-pressure cylinder (2) of the turbine. The high-temperature steam outlet of the steam-steam heat exchanger (19) is connected to the water inlet of the reheat steam-molten salt heat exchanger (20) and the water outlet of the reheat steam-molten salt heat exchanger (20) in sequence. The molten salt outlet of the reheat steam-molten salt heat exchanger (20) is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger (20) in sequence via the high-temperature molten salt tank (23), the feedwater-molten salt heat exchanger (25), and the low-temperature molten salt tank (21). The water inlet of the boiler feedwater connection to the molten salt heat exchanger (25) of the coal-fired power generation system.

2. The molten salt thermal storage system with a front-mounted steam turbine according to claim 1, characterized in that, It also includes a main steam diversion valve (12) and a first control valve (13). The first main steam outlet is connected to the steam inlet of the front turbine (14) after merging with the steam outlet of the feedwater-molten salt heat exchanger (25) via the main steam diversion valve (12). The low-temperature side steam outlet of the steam-steam heat exchanger (19) is connected to the steam inlet of the high-pressure cylinder (2) of the turbine after merging with the second main steam outlet via the first control valve (13).

3. The molten salt thermal storage system with a front-mounted steam turbine according to claim 1, characterized in that, It also includes a second control valve (16) and a third control valve (17). The steam outlet of the front turbine (14) is divided into two paths. One path is connected to the low-temperature steam inlet of the steam-steam heat exchanger (19) via the second control valve (16), and the other path is connected to the steam inlet of the coal-fired power generation system via the third control valve (17).

4. A molten salt thermal energy storage system with a front-mounted steam turbine according to claim 1, characterized in that, It also includes a reheat steam diversion valve (18), through which the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger (19).

5. A molten salt thermal energy storage system with a front-mounted steam turbine according to claim 4, characterized in that, The maximum steam diversion flow rate of the reheat steam diversion valve (18) is 28% of the total mass flow rate of the reheat steam.

6. A molten salt thermal energy storage system with a front-mounted steam turbine according to claim 1, characterized in that, It also includes a low-temperature molten salt pump (22) and a high-temperature molten salt pump (24). The molten salt outlet of the low-temperature molten salt tank (21) is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger (20) via the low-temperature molten salt pump (22), and the molten salt outlet of the high-temperature molten salt tank (23) is connected to the molten salt inlet of the feedwater-molten salt heat exchanger (25) via the high-temperature molten salt pump (24).

7. A molten salt thermal storage system with a front-mounted steam turbine according to claim 1, characterized in that, It also includes a feedwater diversion valve (26), through which the boiler feedwater of the coal-fired power generation system is connected to the water inlet of the feedwater-molten salt heat exchanger (25).

8. A molten salt thermal energy storage system with a front-mounted steam turbine according to claim 1, characterized in that, The steam-steam heat exchanger (19), the reheat steam-molten salt heat exchanger (20), and the feedwater-molten salt heat exchanger (25) are all indirect heat exchangers.

9. A molten salt thermal storage system with a front-mounted steam turbine according to claim 1, characterized in that, The temperature of the steam outlet on the low-temperature side of the steam-steam heat exchanger (19) is greater than 500℃, and the temperature range of the molten salt heat storage system is 120℃~280℃.

10. A method for operating a molten salt thermal energy storage system with a front-mounted steam turbine, characterized in that, The molten salt thermal storage system with a front-mounted steam turbine as described in any one of claims 1 to 9 is adopted; When the coal-fired power generation system is in normal operation, it does not supply main steam and reheat steam to the molten salt thermal storage system, and the molten salt thermal storage system is not in operation. When the coal-fired power generation system is in a low-load operation state, the main steam outlet of the coal-fired power generation system delivers all the main steam to the front turbine (14) through the first main steam outlet. The front turbine (14) drives the auxiliary generator (15) to perform external power generation, reducing the throttling loss of the main steam. The reheat steam outlet of the coal-fired power generation system delivers reheat steam to the steam-steam heat exchanger (19). The reheat steam heats the exhaust steam of the front turbine (14). The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank (21) for heat storage. The reheat steam after heat exchange is delivered to the high-pressure cylinder (2) of the turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder (2). When the coal-fired power generation system is operating at high load, it does not supply main steam to the molten salt thermal storage system. Instead, it delivers reheat steam to the steam-steam heat exchanger (19) through the reheat steam outlet, releasing the heat stored in the high-temperature molten salt tank (23). The feedwater-molten salt heat exchanger (25) heats the boiler feedwater of the coal-fired power generation system, generating superheated steam. This causes the front turbine (14) to drive the auxiliary generator (15) to generate electricity. The exhaust steam from the front turbine (14) is then delivered to the steam inlet of the coal-fired power generation system, thereby increasing the load change rate of the coal-fired power generation system.

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