Steam supply system and method for coupling fused salt energy storage and steam ejector of coal-fired unit

Abstract

The invention discloses a coal-fired unit coupling fused salt energy storage and steam ejector steam supply system and method, and belongs to the technical field of coal-fired power plant steam supply.The system comprises a coal-fired unit body, a fused salt energy storage system and a steam supply system.The coal-fired unit body comprises a boiler, a steam turbine high, medium and low pressure cylinder, a generator and a regenerative system which are sequentially connected; the fused salt energy storage system comprises an electric heater, a steam / fused salt heat exchanger, a high-low temperature fused salt tank, a fused salt / feed water heat exchanger, a plurality of groups of regulating valves and pressure reducing valves; and the steam supply system comprises a steam ejector, a plurality of groups of regulating valves and pressure reducing valves. Combined energy storage is carried out through reheat steam and abandoned electricity heating fused salt which cannot be connected to a network of a coal-fired unit, the lowest power load of the unit is reduced, meanwhile, the industrial steam using requirements of different parameters are met through double-path steam supply, and the problem that peak regulation and steam supply of a traditional unit are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention belongs to the field of steam supply technology for coal-fired power plants, and particularly relates to a steam supply system and method for coal-fired units coupled with molten salt energy storage and steam ejectors. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The large-scale grid connection of renewable energy sources such as wind power and photovoltaics will affect the safe and stable operation of the power grid, which places more stringent requirements on the deep peak-shaving capacity and operational flexibility of coal-fired power units. Expanding the load range of coal-fired power units to balance the peak-valley difference caused by large-scale wind and photovoltaic grid connection, and achieving precise matching of energy supply and grid demand in time and space, is an important way to improve the peak-shaving capacity of coal-fired power units. Introducing energy storage strategies such as electricity storage and thermal storage can improve the peak-shaving capacity of coal-fired power units. Compared with other energy storage technologies, molten salt materials are currently the preferred large-scale high-temperature thermal storage technology due to their advantages such as high operating temperature, high thermal stability, high specific heat capacity, high convective heat transfer coefficient, low viscosity, low saturated vapor pressure, and low price. Meanwhile, in the field of industrial steam supply for coal-fired power units, with the implementation of energy conservation and emission reduction in the energy industry, a large number of high-energy-consuming and high-polluting enterprises' self-owned industrial steam boilers have been restricted or shut down. The demand for high-parameter industrial steam of 3.5-4.8MPa and above has surged for chemical projects such as methanol, DCC to olefins, isooctane, polycarbonate, and urea. This steam can also be provided by large-scale cogeneration units.

[0004] However, existing coal-fired power unit thermal storage steam supply schemes have many problems in terms of the coordinated adaptation between unit peak shaving and industrial steam supply: On the one hand, there are obvious shortcomings in the selection of heat sources for molten salt energy storage: Currently, steam and electricity are widely used as heat sources. If main steam extraction is used to heat molten salt energy storage, it will disrupt the thermal balance of the boiler reheat heating surface, requiring complex modifications to the boiler heating surface, which is costly and affects the safe operation of the unit. If only pure electric heating of molten salt is used, although it can absorb the power that the unit cannot connect to the grid to expand the peak shaving range, there are problems with low efficiency and heat exchange efficiency, resulting in a large waste of high-grade energy and making it difficult to achieve large-scale energy storage. If only reheat steam extraction is used to heat molten salt energy storage, although it does not affect the heat transfer inside the boiler, the heat storage capacity of a single heat source is limited and cannot meet the energy storage capacity requirements for deep peak shaving, making it difficult for the unit's minimum power load to drop to the ideal range.

[0005] On the other hand, large coal-fired power units struggle to supply industrial steam of the appropriate level economically and safely: if high-parameter steam is supplied by direct throttling of main steam, it will result in huge loss of work capacity and high energy consumption; if medium-pressure reheat is used to supply steam, there are problems of unstable steam parameters and poor safety, and it cannot take into account the unit's power generation load; in addition, existing units can only supply industrial steam with a single parameter, which cannot meet the differentiated steam needs of different industrial users, resulting in a prominent supply-demand mismatch problem. Summary of the Invention

[0006] To address the existing problem of difficulty in simultaneously balancing peak shaving and steam supply in coal-fired power units, this invention provides a steam supply system and method for coal-fired power units coupled with molten salt energy storage and steam ejectors. This system utilizes reheat steam and surplus electricity from coal-fired power units that cannot be connected to the grid to jointly heat the molten salt, achieving combined energy storage. This reduces the minimum power load of the unit and simultaneously meets industrial steam demands with different parameters through dual-path steam supply, improving energy storage utilization, heating capacity, and heating quality. This achieves a simultaneous improvement in the unit's deep peak shaving capacity and industrial steam supply level.

[0007] In a first aspect, the present invention provides a steam supply system for a coal-fired power unit coupled with molten salt energy storage and a steam ejector.

[0008] A steam supply system for a coal-fired power unit coupled with molten salt energy storage and a steam ejector includes the coal-fired power unit body, the molten salt energy storage system and the steam supply system; The coal-fired unit body includes a boiler, a steam turbine with high, medium and low pressure cylinders, and a generator connected in sequence. The molten salt energy storage system includes an electric heater, a steam / molten salt heat exchanger, and high and low temperature molten salt tanks. The boiler's reheat steam pipeline is connected to the steam / molten salt heat exchanger, the generator is connected to the electric heater, and the low temperature molten salt tank is connected to the steam / molten salt heat exchanger and the electric heater through pipelines, and then connected to the high temperature molten salt tank, so that the low temperature molten salt is heated by reheat steam and the unit's waste power as dual heat sources and then stored in the high temperature molten salt tank. The steam supply system includes a steam ejector. The steam supply system uses reheated steam after heat exchange in a steam / molten salt heat exchanger to extract steam and provide low-parameter industrial steam. It also uses superheated steam generated by high-temperature molten salt to eject exhaust steam from the intermediate-pressure cylinder of the steam turbine via the steam ejector to provide high-parameter industrial steam.

[0009] In a further technical solution, the coal-fired unit body also includes a regenerative system, which includes a condenser, a condensate pump, a low-pressure regenerative heater, a deaerator, a first feedwater pump, and a high-pressure regenerative heater connected in sequence. This system is used to recover the waste heat from the exhaust steam of the coal-fired unit turbine to heat the boiler feedwater, and to cooperate with the molten salt energy storage system and the steam supply system for feedwater circulation.

[0010] A further technical solution is that a reheat steam regulating valve is provided on the reheat steam pipeline, and the outlet of the steam / molten salt heat exchanger is connected to the industrial user's steam connection port through a pipeline equipped with a second regulating valve. The boiler in the coal-fired unit generates reheat steam. After the reheat steam is extracted and its flow rate is regulated by the reheat steam regulating valve, it enters the steam / molten salt heat exchanger to release heat to heat the low-temperature molten salt. After the reheat steam is extracted and its flow rate is regulated by the second regulating valve, it provides low-parameter industrial steam to industrial users.

[0011] In a further technical solution, the high-temperature molten salt tank is connected to the molten salt / feed water heat exchanger through a pipeline equipped with a fifth molten salt regulating valve, the feed water outlet bypass of the deaerator in the regenerative system is connected to the molten salt / feed water heat exchanger through a pipeline equipped with a second feed water pump and a fifth regulating valve, and the outlet bypass of the molten salt / feed water heat exchanger is connected to the low-temperature molten salt tank through a pipeline equipped with a second circulation pump. The feedwater from the deaerator is fed into the molten salt / feedwater heat exchanger, and at the same time, high-temperature molten salt is fed into the molten salt / feedwater heat exchanger. The feedwater absorbs the heat released by the high-temperature molten salt to generate superheated steam, which is discharged from the outlet of the molten salt / feedwater heat exchanger. The low-temperature molten salt formed after the high-temperature molten salt releases heat is sent into the low-temperature molten salt tank.

[0012] In a further technical solution, the outlet of the high-temperature molten salt tank is connected to the molten salt / feedwater heat exchanger through a pipe equipped with a fifth molten salt regulating valve, the outlet of the molten salt / feedwater heat exchanger is connected to the high-pressure inlet of the steam ejector through a pipe equipped with a third regulating valve, the exhaust port of the intermediate-pressure cylinder of the steam turbine is connected to the low-pressure inlet of the steam ejector through a pipe equipped with a first regulating valve, and the outlet of the steam ejector is connected to the industrial user's steam connection port through a pipe equipped with a fourth regulating valve. The superheated steam discharged from the molten salt / feed water heat exchanger is fed into the high-pressure inlet of the steam ejector after the flow rate is regulated by the third regulating valve. The exhaust steam from the intermediate-pressure cylinder of the steam turbine is fed into the low-pressure inlet of the steam ejector after the flow rate is regulated by the first regulating valve. The superheated steam in the steam ejector injects the exhaust steam from the intermediate-pressure cylinder of the steam turbine to generate mixed steam. The mixed steam is fed into the industrial user's steam connection port after the flow rate is regulated by the fourth regulating valve, providing high-parameter industrial steam to the industrial user.

[0013] In a further technical solution, the industrial user steam connection port is connected to the condenser of the regenerative system through a pipe equipped with a pressure reducing valve. The industrial steam releases heat to supply heat to the industrial user, and after the heat is released, it is depressurized and regulated by the pressure reducing valve before being sent to the condenser.

[0014] In a further technical solution, the outlet bypass of the high-temperature molten salt tank is connected to the inlet bypass of the low-temperature molten salt tank through a pipeline equipped with a sixth molten salt regulating valve and a first circulation pump. The first circulation pump is driven to pump the molten salt in the high-temperature molten salt tank into the low-temperature molten salt tank, and the opening degree of the sixth molten salt regulating valve is controlled to regulate the molten salt temperature, so that the molten salt in the high-temperature molten salt tank and the low-temperature molten salt tank are always maintained within the set operating temperature range.

[0015] In a further technical solution, the molten salt used in the molten salt energy storage system is a binary molten salt consisting of 60% sodium nitrate and 40% potassium nitrate.

[0016] Secondly, the present invention provides a steam supply method for a coal-fired power unit coupled with molten salt energy storage and a steam ejector.

[0017] A steam supply method for a coal-fired power unit coupled with molten salt energy storage and a steam ejector, based on the industrial steam supply system proposed in the first aspect, includes a low-parameter industrial steam supply process, as follows: When industrial users require low-parameter industrial steam, the reheat steam regulating valve, the second regulating valve, and related regulating and pressure reducing valves are opened. After the reheat steam extraction flow rate is regulated by the reheat steam regulating valve, it enters the steam / molten salt heat exchanger to release heat. At the same time, low-temperature molten salt is pumped into the steam / molten salt heat exchanger to absorb the heat released by the reheat steam and form high-temperature molten salt. The high-temperature molten salt is then pumped into a high-temperature molten salt tank for storage. After the heat is released, the reheat steam extraction flow rate is regulated by the second regulating valve to provide low-parameter industrial steam to industrial users. After the industrial steam is used, it is depressurized by the pressure reducing valve and recovered to the condenser of the regenerative system.

[0018] Further technical solutions also include high-parameter industrial steam supply processes, namely: When industrial users require high-parameter industrial steam, the first regulating valve and related regulating and pressure reducing valves are opened. After the high-temperature molten salt releases heat in the molten salt / feed water heat exchanger, it is sent to the low-temperature molten salt tank. The bypass feedwater of the deaerator is pumped into the molten salt / feed water heat exchanger to absorb the heat released by the high-temperature molten salt and generate superheated steam. The superheated steam enters the high-pressure inlet of the steam ejector and ejects the exhaust steam from the intermediate-pressure cylinder of the steam turbine. The mixed, heated and pressurized steam is provided to industrial users as high-parameter industrial steam. After the industrial steam is used, it is depressurized by the pressure reducing valve and recovered to the condenser of the regenerative system.

[0019] Further technical solutions also include the pure condensing steam operation process of the unit, as follows: When the unit is running in pure condensing steam mode, the sixth molten salt regulating valve is opened, and the high-temperature molten salt in the high-temperature molten salt tank is pumped into the low-temperature molten salt tank by the first circulation pump to regulate the molten salt temperature, so that the molten salt in the high-temperature molten salt tank and the low-temperature molten salt tank are always maintained within the set operating temperature range.

[0020] The above one or more technical solutions have the following beneficial effects: This invention proposes a steam supply system and method for coal-fired power units coupled with molten salt energy storage and steam ejectors. It utilizes reheat steam and surplus electricity from the coal-fired unit that cannot be connected to the grid to jointly heat the molten salt for combined energy storage, reducing the unit's minimum power load. Simultaneously, it meets industrial steam demands with different parameters through a dual-path steam supply. Specifically, to meet industrial steam demand, on the one hand, it uses reheated steam after heat release to extract low-parameter industrial steam; on the other hand, it generates superheated steam by heating the deaerator bypass feedwater with high-temperature molten salt. This superheated steam is then used to eject exhaust steam from the intermediate-pressure cylinder of the steam turbine to generate high-parameter industrial steam required by industrial users. This effectively improves energy storage utilization, heating capacity, and heating quality, achieving a simultaneous improvement in the unit's deep peak-shaving capacity and industrial steam supply level. This invention can significantly improve the operational flexibility and industrial steam supply capacity of coal-fired power units, allowing for flexible adjustment of steam supply parameters according to user needs, improving the unit's energy utilization efficiency and steam supply level, and solving current problems in peak-shaving and steam supply for coal-fired power units.

[0021] Advantages of additional aspects 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

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the 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.

[0023] Figure 1 This is a schematic diagram of the steam supply system of the coal-fired unit coupled with molten salt energy storage and steam ejector in Embodiment 1 of the present invention.

[0024] The components include: 1. Boiler; 2. High-pressure cylinder; 3. Medium-pressure cylinder; 4. Low-pressure cylinder; 5. Generator; 6. Deaerator; 7. High-pressure regenerative heater; 8. Low-pressure regenerative heater; 9. Condenser; 10. Electric heater; 11. High-temperature molten salt tank; 12. Low-temperature molten salt tank; 13. Steam / molten salt heat exchanger; 14. Molten salt / feedwater heat exchanger; 15. Steam ejector; 16. Industrial user steam connection port; 17. First feedwater pump; 18. Condensate pump; 19. First low-temperature molten salt pump; 20. Second low-temperature molten salt pump. 21. High-temperature molten salt pump; 22. First circulation pump; 23. Second circulation pump; 24. Second feed water pump; 25. First regulating valve; 26. Reheat steam regulating valve; 27. Second regulating valve; 28. First molten salt regulating valve; 29. ​​Second molten salt regulating valve; 30. Third molten salt regulating valve; 31. Fourth molten salt regulating valve; 32. Fifth molten salt regulating valve; 33. Sixth molten salt regulating valve; 34. Third regulating valve; 35. Fourth regulating valve; 36. Fifth regulating valve; 37. Pressure reducing valve. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and are intended only to describe specific embodiments and to provide further explanation of the invention, and are not intended to limit the scope of exemplary embodiments of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Example 1 To address the challenge of simultaneously balancing peak shaving and steam supply in existing coal-fired power units, this embodiment provides a steam supply system for coal-fired power units coupled with molten salt energy storage and steam ejectors, such as... Figure 1 As shown, it includes the coal-fired unit body, molten salt energy storage system and steam supply system.

[0027] In this embodiment, the coal-fired unit body includes a boiler 1, a high-pressure cylinder 2 of a steam turbine, a medium-pressure cylinder 3 of a steam turbine, a low-pressure cylinder 4 of a steam turbine, a generator 5, and a regenerative system connected in sequence. The regenerative system includes a condenser 9, a condensate pump 18, a low-pressure regenerative heater 8, a deaerator 6, a first feedwater pump 17, and a high-pressure regenerative heater 7 connected in sequence. It is used to recover the waste heat from the exhaust steam of the steam turbine of the coal-fired unit to heat the boiler feedwater, and to cooperate with the molten salt energy storage system and the steam supply system for feedwater circulation.

[0028] like Figure 1 As shown, the new steam pipe of boiler 1 is connected (in this embodiment, the connection is a pipe connection, which will not be described again later) to the steam inlet of the high-pressure cylinder 2 of the steam turbine. The exhaust port of the high-pressure cylinder 2 of the steam turbine is connected to the reheater inlet of boiler 1. The reheat steam pipe of boiler 1 (which is equipped with a reheat steam regulating valve 26) is connected to the steam inlet of the intermediate-pressure cylinder 3 of the steam turbine and the steam side inlet of the steam / molten salt heat exchanger 13. The exhaust port of the intermediate-pressure cylinder 3 of the steam turbine is connected to the steam inlet of the low-pressure cylinder 4 of the steam turbine and the low-pressure inlet of the steam ejector 15. The exhaust port of the low-pressure cylinder 4 of the steam turbine is connected to the inlet of the condenser 9. The inlet of the condenser 9 is connected to the low-pressure cylinder of the steam turbine. The exhaust pipe of 4, the drain pipe of the low-pressure regenerative heater 8, and the outlet of the industrial steam supply pipe are connected. The outlet of the condenser 9 is connected to the inlet of the deaerator 6 via the condensate pump 18 and the low-pressure regenerative heater 8. The inlet of the deaerator 6 is connected to the extraction pipe of the intermediate-pressure cylinder 3 of the turbine, the drain pipe of the high-pressure regenerative heater 7, and the outlet feedwater pipe of the low-pressure regenerative heater 8. The outlet feedwater pipe of the deaerator 6 is connected to the feedwater inlet pipe of the boiler 1 via the first feedwater pump 17 and the high-pressure regenerative heater 7. The extraction steam of the high-pressure regenerative heater 7 comes from the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 of the turbine, and the extraction steam of the low-pressure regenerative heater 8 comes from the low-pressure cylinder 4 of the turbine.

[0029] In this embodiment, the molten salt energy storage system includes an electric heater 10, a high-temperature molten salt tank 11, a low-temperature molten salt tank 12, a steam / molten salt heat exchanger 13, a molten salt / feed water heat exchanger 14, a first low-temperature molten salt pump 19, a second low-temperature molten salt pump 20, a high-temperature molten salt pump 21, a first circulation pump 22, a second circulation pump 23, a second feed water pump 24, and first to sixth molten salt regulating valves 28 to 33.

[0030] like Figure 1 As shown, the electric heater 10 is connected to the generator 5. The outlet of the low-temperature molten salt tank 12 is connected to the steam / molten salt heat exchanger 13 and the electric heater 10 via pipelines, and then to the high-temperature molten salt tank 11. This allows the low-temperature molten salt to be heated by both reheat steam and the unit's surplus power before being stored in the high-temperature molten salt tank. Specifically, the cold molten salt at the outlet of the low-temperature molten salt tank 12 is divided into two paths. One path enters the steam / molten salt heat exchanger 13 through the first low-temperature molten salt pump 19 and the third molten salt regulating valve 30 to absorb heat from the reheat steam. The other path enters the electric heater 10 through the second low-temperature molten salt pump 20 and the fourth molten salt regulating valve 31 to absorb heat. The two paths of high-temperature molten salt are then combined through the first molten salt regulating valve 28 and the second molten salt regulating valve 29 to enter the high-temperature molten salt pump 21, and finally enter the high-temperature molten salt tank 11.

[0031] In addition, the outlet of the high-temperature molten salt tank 11 is connected to the molten salt / feed water heat exchanger 14 through a pipe equipped with a fifth molten salt regulating valve 32. The outlet bypass of the molten salt / feed water heat exchanger 14 is connected to the low-temperature molten salt tank 12 through a pipe equipped with a second circulating pump 23. The high-temperature molten salt tank 11 outputs high-temperature molten salt to the molten salt / feed water heat exchanger 14 for heat release, and the low-temperature molten salt formed after heat release is sent into the low-temperature molten salt tank 12. At the same time, the feed water outlet bypass of the deaerator in the regenerative system is connected to the molten salt / feed water heat exchanger 14 through a pipe equipped with a second feed water pump and a fifth regulating valve. The feed water of the deaerator is sent into the molten salt / feed water heat exchanger 14, and at the same time, the high-temperature molten salt is sent into the molten salt / feed water heat exchanger 14. The fed water absorbs the heat released by the high-temperature molten salt to generate superheated steam, which is discharged from the outlet of the molten salt / feed water heat exchanger. The low-temperature molten salt formed after the high-temperature molten salt releases heat is sent into the low-temperature molten salt tank.

[0032] In practice, to meet the demand for high-parameter and low-parameter industrial steam, the heat release process must employ molten salt steam generation. This places higher demands on the molten salt temperature: the hot molten salt temperature should reach approximately 500°C at the end of the heat storage process. This requirement further limits the choice of heat storage configuration. Specifically, in traditional methods, due to phase change heat transfer involved in reheat steam, the final temperature of the hot molten salt can only reach around 350°C. While electric heating allows for flexible selection of the final molten salt temperature, its efficiency is too low, only around 40%, resulting in significant energy waste. Therefore, this embodiment adopts the aforementioned method of using reheat steam and electric heating as dual heat sources for heat storage. This method combines the advantages of high molten salt temperature and high heat exchange efficiency, and can meet the demand for high-parameter steam generation during the heat release stage.

[0033] By combining reheat steam and the abandoned electricity from coal-fired units to heat molten salt, the system can improve the utilization level of heat source energy by utilizing the high heat transfer efficiency of reheat steam storage. Compared with pure electric heating storage, it can also significantly improve heat exchange efficiency and heat transfer efficiency. At the same time, since the extraction of reheat steam has no impact on the boiler side, there is no need to modify the boiler heating surface. On the other hand, the system can reduce the minimum power load of the unit to near zero output, which greatly expands the deep peak shaving range of large coal-fired units and is conducive to improving the operational flexibility of the unit.

[0034] As one implementation method, in this embodiment, the molten salt used in the molten salt energy storage system is a binary molten salt of 60% sodium nitrate and 40% potassium nitrate, with an operating temperature range of 220~600℃. Its melting point is relatively high; if the temperature deviates from this range during operation, "pipe freezing" is highly likely, causing pipe blockage, which significantly increases the system's operational safety risks and leads to energy waste. To address this, this embodiment also designs a targeted temperature control bypass to adjust the molten salt temperature in real time and precisely, ensuring stable system operation. Specifically, the outlet bypass of the high-temperature molten salt tank 11 is connected to the inlet bypass of the low-temperature molten salt tank 12 via a pipeline equipped with a sixth molten salt regulating valve and a first circulation pump. The first circulation pump drives the molten salt in the high-temperature molten salt tank to enter the low-temperature molten salt tank, and controls the opening of the sixth molten salt regulating valve to adjust the molten salt temperature, ensuring that the molten salt in both the high-temperature and low-temperature molten salt tanks remains within the set operating temperature range.

[0035] Furthermore, the opening and closing of the regulating valve and circulating pump can be automatically controlled by setting temperature sensors and corresponding processors and controllers. For example, the temperature of the molten salt in the cold tank can be detected in real time by the temperature sensor. When the temperature of the molten salt in the cold tank drops to the set danger value, the processor analyzes and generates a control signal to the controller, which automatically opens the regulating valve, adjusts the opening to a reasonable degree, and starts the circulating pump to allow the high-temperature molten salt in the hot tank to enter the cold tank to regulate the temperature of the molten salt. Similarly, when the temperature of the molten salt in the cold tank is detected to reach the operating temperature, the regulating valve is automatically locked or closed, and the circulating pump is turned off.

[0036] Preferably, the temperature drop in the cold molten salt tank is usually only related to heat dissipation from the tank body, pipes and environment. Therefore, the regulating valve can be fixed at a certain opening, the circulating pump is kept on, and a stream of molten salt is always drawn from the hot molten salt tank to regulate the temperature of the cold molten salt tank, thus preventing the pipes from freezing.

[0037] As a further technical solution, considering heat loss, the design temperature of the cold molten salt can be slightly increased in actual implementation. This is because the molten salt thermal storage system will not experience pipe freezing when it is working, and the coupling of molten salt thermal storage often participates in grid peak shaving and frequency regulation, which is an hourly thermal storage measure. Therefore, when the molten salt thermal storage system is not working, it is only necessary to minimize heat loss. From a design perspective, the temperature of the cold molten salt can be increased to 280℃, which is much higher than its melting point. At this time, the connecting pipe between the hot tank and the cold tank only plays the role of accident regulation and emergency regulation.

[0038] In this embodiment, the steam supply system includes a steam ejector 15, an industrial user steam connection port 16, a second feedwater pump 24, a first regulating valve 25, a reheat steam regulating valve 26, a second regulating valve 27, third to fifth regulating valves 34-36, and a pressure reducing valve 37. Considering that industrial steam supply is divided into low-parameter industrial steam and high-parameter industrial steam, this embodiment designs a dual-path steam supply to meet the industrial steam demand of different parameters. The steam supply system uses reheat steam extracted after heat exchange in a steam / molten salt heat exchanger to provide low-parameter industrial steam, and uses superheated steam generated by high-temperature molten salt to inject exhaust steam from the intermediate-pressure cylinder of the steam turbine through the steam ejector to provide high-parameter industrial steam. After use, the industrial steam is recycled to the condenser of the regenerative system.

[0039] Specifically, for low-parameter industrial steam, a reheat steam regulating valve 26 is installed on the reheat steam pipeline. The outlet of the steam / molten salt heat exchanger 13 is connected to the industrial user steam connection port 16 through a pipeline equipped with a second regulating valve 27. Based on this, the boiler in the coal-fired unit generates reheat steam. The reheat steam extraction, after its flow rate is regulated by the reheat steam regulating valve 26, enters the steam / molten salt heat exchanger 13 to release heat and heat the low-temperature molten salt. After heat release, the reheat steam extraction, after its flow rate is regulated by the second regulating valve 27, is sent to the industrial user steam connection port 16 to provide low-parameter industrial steam to the industrial user. Preferably, the reheat steam extraction rate is limited by the minimum cooling flow rate of the turbine's low-pressure cylinder to ensure the safe operation of the turbine.

[0040] For high-parameter industrial steam, the feedwater outlet of deaerator 6 is bypassed and connected to molten salt / feedwater heat exchanger 14 via a pipeline equipped with a second feedwater pump 24 and a fifth regulating valve 36. This feedwater absorbs heat to become superheated steam. The outlet of molten salt / feedwater heat exchanger 14 is connected to the high-pressure inlet of steam ejector 15 via a pipeline equipped with a third regulating valve 34. The exhaust port of intermediate-pressure cylinder 3 of the steam turbine is connected to the low-pressure inlet of steam ejector 15 via a pipeline equipped with a first regulating valve 25. The outlet of steam ejector 15 is connected to... Industrial user steam connection port 16. Based on this, the superheated steam discharged from the molten salt / feed water heat exchanger is regulated by the third regulating valve 34 and then sent to the high-pressure inlet of the steam ejector 15. The exhaust steam from the intermediate-pressure cylinder 3 of the steam turbine is regulated by the first regulating valve 25 and then sent to the low-pressure inlet of the steam ejector 15. The steam ejector uses superheated steam to eject the exhaust steam from the intermediate-pressure cylinder 3 of the steam turbine to generate mixed steam. This mixed steam is regulated by the fourth regulating valve 35 and then sent to the industrial user steam connection port 16 to supply high-parameter industrial steam to industrial users.

[0041] Considering that the existing steam supply system only provides steam through a single path, directly using reheat steam to inject exhaust steam from the intermediate-pressure cylinder, it sacrifices the work capacity of the reheat steam entering the turbine. Furthermore, molten salt-generated steam supply is limited by the use of only reheat steam for heat storage, resulting in low molten salt temperatures and poor steam quality. To address this, this embodiment introduces the aforementioned design. On one hand, using reheat steam after heat release can simultaneously meet the needs of deep peak shaving and supplying low-parameter steam. On the other hand, molten salt-generated steam is not directly supplied; instead, a high-temperature, high-pressure steam with temperatures and pressures exceeding the standards for high-parameter industrial steam is generated through the molten salt steam generation system. This steam is introduced into the steam ejector to efficiently inject exhaust steam from the intermediate-pressure cylinder, forming high-parameter industrial steam with a larger flow rate that meets the standards after the steam ejector. This maximizes the utilization of molten salt heat storage and increases the steam supply, resulting in higher energy efficiency and stronger heating capacity.

[0042] As a further technical solution, considering that in the existing industrial steam supply system of coal-fired units, the steam used by industrial users is mostly directly discharged or simply treated, which not only wastes water resources and waste heat, but also increases the cost of environmental protection treatment and makes it impossible to realize the cascade utilization of energy, this embodiment also sets up a closed-loop recovery channel. The industrial steam supply comes from the coal-fired unit, and the industrial steam supplied to industrial users is depressurized by the pressure reducing valve 37 after use and then sent to the condenser 9.

[0043] The aforementioned steam ejector 15 is a fixed-structure single-phase ejector. The flow rate of the working steam at the high-pressure inlet of the steam ejector is regulated by a third regulating valve, and the flow rate of the ejector steam at the low-pressure inlet is regulated by a first regulating valve. Based on this, the structural parameters of the steam ejector can be designed and the flow rates of the working steam and ejector steam configured according to the industrial steam demand. This allows the steam ejector to maintain a high ejection ratio while achieving high parameters for industrial steam, thereby improving the coal-fired unit's ability to supply industrial steam.

[0044] Preferably, the steam ejector can be an adjustable ejector with a high-pressure nozzle and an adjustable mixing chamber throat area.

[0045] Example 2 This embodiment provides a steam supply method for coal-fired power units coupled with molten salt energy storage and steam ejectors, based on the industrial steam supply system proposed in Embodiment 1, including a low-parameter industrial steam supply process and a high-parameter industrial steam supply process.

[0046] When industrial users require low-parameter industrial steam, the reheat steam regulating valve, the second regulating valve, and related regulating and pressure-reducing valves are opened. Specifically, reheat steam regulating valve 26, the second regulating valve 27, the first molten salt regulating valve 28, the third molten salt regulating valve 30, and the pressure-reducing valve 37 are opened. The reheat steam extraction, after its flow rate is regulated by reheat steam regulating valve 26, enters the steam / molten salt heat exchanger 13 to release heat. Simultaneously, low-temperature molten salt is pumped into the steam / molten salt heat exchanger 13 by the first low-temperature molten salt pump 19 to absorb the heat from the reheat steam. The resulting high-temperature molten salt is pumped into the high-temperature molten salt tank by high-temperature molten salt pump 21 for storage. The reheat steam extraction after heat release is regulated by the second regulating valve 27 and sent to the industrial user's steam connection port 16, supplying low-parameter industrial steam to the industrial user, thus completing the low-parameter industrial steam supply process. Finally, after use, the industrial steam is depressurized by the pressure-reducing valve and recovered to the condenser of the regenerative system.

[0047] When industrial users require high-parameter industrial steam, the first regulating valve and related regulating and pressure-reducing valves are opened, namely the first regulating valve 25, the third to fifth regulating valves 34-36, and the pressure-reducing valve 37. After the high-temperature molten salt releases heat in the molten salt / feed water heat exchanger 14, it is fed into the low-temperature molten salt tank by the second circulating pump 23. The bypass feedwater of the deaerator 6 is pumped into the molten salt / feed water heat exchanger 14 by the second feed water pump 24 to absorb the heat of the high-temperature molten salt and generate superheated steam. The superheated steam enters the high-pressure inlet of the steam ejector 15 and ejects the exhaust steam of the intermediate-pressure cylinder 3 of the steam turbine. The mixed, heated and pressurized steam is provided to industrial users as high-parameter industrial steam. After the industrial steam is used, it is depressurized by the pressure-reducing valve and recovered to the condenser of the regenerative system, completing the high-parameter industrial steam supply process.

[0048] As a further technical solution, the pure condensing steam operation process of the unit is also included: when the unit is running in pure condensing steam mode, the sixth molten salt regulating valve 33 is opened, and the high-temperature molten salt in the high-temperature molten salt tank 11 is sent to the low-temperature molten salt tank by the first circulation pump 22 to regulate the temperature of the molten salt, so that the molten salt in the high-temperature molten salt tank and the low-temperature molten salt tank are always maintained within the operating temperature range, so as to prevent the molten salt from deviating from its operating temperature range, which would lead to increased operating risks and energy waste.

[0049] The steps involved in the above embodiment two correspond to those in embodiment one. For specific implementation details, please refer to the relevant description section of embodiment one.

[0050] The above description is only a preferred embodiment of the present invention. Although the specific implementation of the present invention has been described in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A steam supply system for a coal-fired power unit coupled with molten salt energy storage and a steam ejector, characterized in that, This includes the coal-fired power unit itself, the molten salt energy storage system, and the steam supply system; The coal-fired unit body includes a boiler, a steam turbine with high, medium and low pressure cylinders, and a generator connected in sequence. The molten salt energy storage system includes an electric heater, a steam / molten salt heat exchanger, and high and low temperature molten salt tanks. The boiler's reheat steam pipeline is connected to the steam / molten salt heat exchanger, the generator is connected to the electric heater, and the low temperature molten salt tank is connected to the steam / molten salt heat exchanger and the electric heater through pipelines, and then connected to the high temperature molten salt tank, so that the low temperature molten salt is heated by reheat steam and the unit's waste power as dual heat sources and then stored in the high temperature molten salt tank. The steam supply system includes a steam ejector. The steam supply system uses reheated steam after heat exchange in a steam / molten salt heat exchanger to extract steam and provide low-parameter industrial steam. It also uses superheated steam generated by high-temperature molten salt to eject exhaust steam from the intermediate-pressure cylinder of the steam turbine via the steam ejector to provide high-parameter industrial steam.

2. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 1, characterized in that, The coal-fired unit also includes a regenerative system, which comprises a condenser, a condensate pump, a low-pressure regenerative heater, a deaerator, a first feedwater pump, and a high-pressure regenerative heater connected in sequence. The regenerative system is used to recover the waste heat from the exhaust steam of the coal-fired unit turbine to heat the boiler feedwater, and works in conjunction with the molten salt energy storage system and the steam supply system to circulate the feedwater.

3. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 1, characterized in that, The reheat steam pipeline is equipped with a reheat steam regulating valve, and the outlet of the steam / molten salt heat exchanger is connected to the industrial user's steam connection port through a pipeline equipped with a second regulating valve. The boiler in the coal-fired unit generates reheat steam. After the reheat steam is extracted and its flow rate is regulated by the reheat steam regulating valve, it enters the steam / molten salt heat exchanger to release heat to heat the low-temperature molten salt. After the reheat steam is extracted and its flow rate is regulated by the second regulating valve, it provides low-parameter industrial steam to industrial users.

4. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 2, characterized in that, The high-temperature molten salt tank is connected to the molten salt / feed water heat exchanger through a pipeline equipped with a fifth molten salt regulating valve. The feed water outlet bypass of the deaerator in the regenerative system is connected to the molten salt / feed water heat exchanger through a pipeline equipped with a second feed water pump and a fifth regulating valve. The outlet bypass of the molten salt / feed water heat exchanger is connected to the low-temperature molten salt tank through a pipeline equipped with a second circulation pump. The feedwater from the deaerator is fed into the molten salt / feedwater heat exchanger, and at the same time, high-temperature molten salt is fed into the molten salt / feedwater heat exchanger. The feedwater absorbs the heat released by the high-temperature molten salt to generate superheated steam, which is discharged from the outlet of the molten salt / feedwater heat exchanger. The low-temperature molten salt formed after the high-temperature molten salt releases heat is sent into the low-temperature molten salt tank.

5. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 4, characterized in that, The outlet of the high-temperature molten salt tank is connected to the molten salt / feed water heat exchanger through a pipe equipped with a fifth molten salt regulating valve. The outlet of the molten salt / feed water heat exchanger is connected to the high-pressure inlet of the steam ejector through a pipe equipped with a third regulating valve. The exhaust port of the intermediate-pressure cylinder of the steam turbine is connected to the low-pressure inlet of the steam ejector through a pipe equipped with a first regulating valve. The outlet of the steam ejector is connected to the industrial user's steam connection port through a pipe equipped with a fourth regulating valve. The superheated steam discharged from the molten salt / feed water heat exchanger is fed into the high-pressure inlet of the steam ejector after the flow rate is regulated by the third regulating valve. The exhaust steam from the intermediate-pressure cylinder of the steam turbine is fed into the low-pressure inlet of the steam ejector after the flow rate is regulated by the first regulating valve. The superheated steam in the steam ejector injects the exhaust steam from the intermediate-pressure cylinder of the steam turbine to generate mixed steam. The mixed steam is fed into the industrial user's steam connection port after the flow rate is regulated by the fourth regulating valve, providing high-parameter industrial steam to the industrial user.

6. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 5, characterized in that, The industrial user's steam connection port is connected to the condenser of the regenerative system through a pipe equipped with a pressure reducing valve. The industrial steam releases heat to supply heat to the industrial user, and after the heat is released, it is depressurized and regulated by the pressure reducing valve before being sent to the condenser.

7. The steam supply system for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 1, characterized in that, The outlet bypass of the high-temperature molten salt tank is connected to the inlet bypass of the low-temperature molten salt tank through a pipeline equipped with a sixth molten salt regulating valve and a first circulation pump; the first circulation pump is driven to pump the molten salt in the high-temperature molten salt tank into the low-temperature molten salt tank, and the opening of the sixth molten salt regulating valve is controlled to regulate the molten salt temperature, so that the molten salt in the high-temperature molten salt tank and the low-temperature molten salt tank are always maintained within the set operating temperature range; the molten salt used in the molten salt energy storage system is a binary molten salt of 60% sodium nitrate and 40% potassium nitrate.

8. A steam supply method for a coal-fired power unit coupled with molten salt energy storage and a steam ejector, characterized in that, Based on the steam supply system according to any one of claims 1-7, the process includes a low-parameter industrial steam supply process, which is as follows: When industrial users require low-parameter industrial steam, the reheat steam regulating valve, the second regulating valve, and related regulating and pressure reducing valves are opened. After the reheat steam extraction flow rate is regulated by the reheat steam regulating valve, it enters the steam / molten salt heat exchanger to release heat. At the same time, low-temperature molten salt is pumped into the steam / molten salt heat exchanger to absorb the heat released by the reheat steam and form high-temperature molten salt. The high-temperature molten salt is then pumped into a high-temperature molten salt tank for storage. After the heat is released, the reheat steam extraction flow rate is regulated by the second regulating valve to provide low-parameter industrial steam to industrial users. After the industrial steam is used, it is depressurized by the pressure reducing valve and recovered to the condenser of the regenerative system.

9. The steam supply method for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 8, characterized in that, It also includes high-parameter industrial steam supply processes, namely: When industrial users require high-parameter industrial steam, the first regulating valve and related regulating and pressure reducing valves are opened. After the high-temperature molten salt releases heat in the molten salt / feed water heat exchanger, it is sent to the low-temperature molten salt tank. The bypass feedwater of the deaerator is pumped into the molten salt / feed water heat exchanger to absorb the heat released by the high-temperature molten salt and generate superheated steam. The superheated steam enters the high-pressure inlet of the steam ejector and ejects the exhaust steam from the intermediate-pressure cylinder of the steam turbine. The mixed, heated and pressurized steam is provided to industrial users as high-parameter industrial steam. After the industrial steam is used, it is depressurized by the pressure reducing valve and recovered to the condenser of the regenerative system.

10. The steam supply method for a coal-fired unit coupled with molten salt energy storage and a steam ejector as described in claim 8, characterized in that, It also includes the pure condensing steam operation process of the unit, which is: When the unit is running in pure condensing steam mode, the sixth molten salt regulating valve is opened, and the high-temperature molten salt in the high-temperature molten salt tank is pumped into the low-temperature molten salt tank by the first circulation pump to regulate the molten salt temperature, so that the molten salt in the high-temperature molten salt tank and the low-temperature molten salt tank are always maintained within the set operating temperature range.

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