A thermal power unit coupled with a low-temperature molten salt heat release system and method

Abstract

This invention belongs to the field of energy storage and peak shaving for thermal power generating units, and relates to a coupled low-temperature molten salt heat release system and method for thermal power generating units, to solve the problems of large high-grade steam loss, high heat exchange loss, and inflexible extraction steam replacement in molten salt heat release. The invention includes: a high-temperature molten salt tank outlet, molten salt sides of first and second molten salt heat exchangers, and a low-temperature molten salt tank inlet connected in series; a deaerator outlet feedwater pump connected to one end of a feedwater bypass, the other end of which branches into three valved branches, each branch connecting to the feedwater inlet of the second molten salt heat exchanger; the feedwater outlet of the second molten salt heat exchanger is connected between the first molten salt heat exchanger and the high-pressure heater group. By selecting branches to preferentially replace the higher-temperature heater, high-pressure steam extraction is reduced, allowing more high-quality steam to perform work in the turbine, increasing the boiler feedwater temperature and the average heat absorption temperature of the working fluid, reducing heat loss, achieving efficient energy utilization in a cascade manner, and enhancing peak shaving flexibility and overall thermal efficiency.

Description

Technical Field

[0001] This invention relates to the field of energy storage and peak shaving technology for thermal power generating units, specifically to a thermal power generating unit coupled with a low-temperature molten salt heat release system and method. Background Technology

[0002] With the continuous expansion of installed capacity of renewable energy sources such as wind power and photovoltaics, the peak-valley difference in power system load is widening, and energy supply and demand fluctuations are significantly increasing, posing severe challenges to the power system's regulation capacity, response speed, and power supply stability. Under these circumstances, new energy storage technologies, through flexible regulation via energy transfer in time and space, have become a key means to solve the peak-shaving problem of thermal power units and achieve thermal-electric decoupling.

[0003] Molten salt thermal energy storage technology has been widely used in thermal power energy storage and peak-shaving systems due to its advantages such as high specific heat capacity, wide operating temperature range, and high thermal stability. As the core functional module of molten salt energy storage systems, the scientific nature and efficiency of the heat release method of the molten salt storage process directly determine the overall performance of the system.

[0004] Existing thermal power units with coupled molten salt heat release systems mostly employ single-stage heat exchange or simple replacements for high-pressure heater extraction. However, these solutions suffer from significant high-grade steam heat loss and high heat exchange losses during the heat release process, resulting in insufficient energy utilization efficiency. Furthermore, existing systems lack flexibility in adapting to different high-pressure heater extraction conditions, making it difficult to achieve precise staged extraction replacement based on the actual operating requirements of the unit, thus limiting further improvements in the unit's peak-shaving capacity.

[0005] Therefore, there is an urgent need to provide a thermal power unit coupled with molten salt heat release scheme that can achieve cascaded heat release, reduce heat exchange losses, improve energy utilization efficiency, and have flexible steam extraction substitution capabilities, so as to improve the peak-shaving performance and operating economy of thermal power units under the new power system. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, namely the problems of large heat energy loss of high-grade steam, high heat exchange loss and insufficient flexibility of steam extraction substitution in the existing molten salt heat release system, the present invention provides a thermal power unit coupled with a low-temperature molten salt heat release system and method.

[0007] In a first aspect, the present invention proposes a thermal power unit coupled with a low-temperature molten salt heat release system, comprising a boiler, a steam turbine generator set, a regenerative heating unit, and a molten salt heat storage and release unit;

[0008] The steam turbine generator set includes a steam turbine, a generator, and a condenser; The molten salt heat storage and release unit includes a high-temperature molten salt tank, a low-temperature molten salt tank, a first molten salt heat exchanger, a second molten salt heat exchanger, and a high-temperature molten salt pump; Molten salt flows sequentially through the outlet of the high-temperature molten salt tank, the high-temperature molten salt pump, the molten salt side of the first molten salt heat exchanger, the molten salt side of the second molten salt heat exchanger, and the inlet of the low-temperature molten salt tank; wherein the flow direction of the molten salt is configured to release heat step by step through the first molten salt heat exchanger and the second molten salt heat exchanger to heat the feedwater; The regenerative heating unit includes a deaerator and a high-pressure heater group. The feed water pump inlet is connected to the deaerator outlet, and the feed water pump outlet is connected to the feed water bypass and the high-pressure heater group. The feed water bypass end is divided into a first branch, a second branch and a third branch. The first branch is connected to the inlet side of the high-pressure heater group, and the outlets of the first branch, the second branch and the third branch are connected to the inlet side of the second molten salt heat exchanger. The system is configured to: control the on / off state of the first branch, the second branch and the third branch so that the bypass portion of the feedwater received by the second molten salt heat exchanger is taken from different interstage positions of the high-pressure heater group, so as to selectively bypass at least one high-pressure heater in the high-pressure heater group according to the unit operating conditions, and preferentially bypass the high-pressure heater of the extraction steam high pressure.

[0009] Furthermore, the regenerative heating unit also includes a low-pressure heater, with the condenser outlet connected to the low-pressure heater inlet via a condensate pump, and the low-pressure heater outlet connected to the deaerator inlet.

[0010] Furthermore, the high-pressure heater group includes a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater connected in series. The inlet of the high-pressure heater group is connected to the water supply pump. A first branch is provided between the outlet of the water supply pump and the inlet of the third high-pressure heater. A second branch is provided between the outlet of the third high-pressure heater and the inlet of the second high-pressure heater. A third branch is provided between the outlet of the second high-pressure heater and the inlet of the first high-pressure heater.

[0011] Furthermore, the system also includes a first valve, a second valve, and a third valve for controlling the water flow direction to selectively open the first branch, the second branch, or the third branch; The first valve is installed on the first branch, one end of the first branch is connected between the outlet of the feed water pump and the inlet of the third high-pressure heater, and the other end of the first branch is connected to the inlet of the second molten salt heat exchanger. The first valve is used to guide the feed water to bypass the first high-pressure heater, the second high-pressure heater, and the third high-pressure heater. The second valve is installed on the second branch, one end of which is connected between the outlet of the third high-pressure heater and the inlet of the second high-pressure heater, and the other end of which is connected to the inlet of the second molten salt heat exchanger. The second valve is used to guide the feedwater to bypass the first high-pressure heater and the second high-pressure heater. The third valve is installed on the third branch, one end of which is connected between the outlet of the second high-pressure heater and the inlet of the first high-pressure heater, and the other end of which is connected to the inlet of the second molten salt heat exchanger. The third valve is used to guide the feedwater to bypass the first high-pressure heater.

[0012] Furthermore, the feedwater outlet of the first high-pressure heater is connected to the cold-side inlet of the first molten salt heat exchanger, and the cold-side outlet of the first molten salt heat exchanger is connected to the boiler feedwater inlet.

[0013] Furthermore, the cold-side outlet of the second molten salt heat exchanger is connected to the feedwater outlet of the first high-pressure heater and the cold-side inlet pipe of the first molten salt heat exchanger.

[0014] Furthermore, the outlet of the high-temperature molten salt tank is connected to the inlet of the fourth valve, the outlet of the fourth valve is connected to the inlet of the high-temperature molten salt pump, the outlet of the high-temperature molten salt pump is connected to the molten salt side inlet of the first molten salt heat exchanger, the molten salt side outlet of the first molten salt heat exchanger is connected to the molten salt side inlet of the second molten salt heat exchanger, and the molten salt side outlet of the second molten salt heat exchanger is connected to the inlet of the low-temperature molten salt tank.

[0015] Furthermore, both the first molten salt heat exchanger and the second molten salt heat exchanger are molten salt-feedwater heat exchangers.

[0016] In a second aspect, the present invention provides a method for coupling low-temperature molten salt heat release in thermal power units, employing the system described in the first aspect, comprising the following steps: Start the high-temperature molten salt pump to transport the high-temperature molten salt in the high-temperature molten salt tank to the molten salt side of the first molten salt heat exchanger through the fourth valve; After the high-temperature molten salt exchanges heat with the first and second molten salt heat exchangers, it forms low-temperature molten salt, which then enters the low-temperature molten salt tank. Part of the feedwater flowing through the high-pressure heater group enters the feedwater side of the second molten salt heat exchanger via the first, second, or third branch of the feedwater bypass. After being heated, it flows into the feedwater outlet of the first high-pressure heater and the cold-side inlet pipe of the first molten salt heat exchanger. After merging with the feedwater from the high-pressure heater group, it enters the first molten salt heat exchanger for further heating and finally enters the boiler. The opening and closing states of the first valve, the second valve, and the third valve are controlled to selectively bypass at least one high-pressure heater in the high-pressure heater group, with priority given to bypassing the high-pressure heater of the extraction steam high pressure.

[0017] The beneficial effects of this invention are: This invention adopts a structure of dual heat exchangers in series and feedwater bypass for staged heat release. Molten salt flows sequentially through the first molten salt heat exchanger and the second molten salt heat exchanger for staged heat release, which makes the molten salt heat release temperature zone more matched with the boiler feedwater heating temperature zone, reduces the heat exchange end difference, and effectively reduces heat loss during the heat exchange process.

[0018] This invention, through a feedwater bypass combined with multiple valves, allows a portion of the feedwater from the deaerator outlet or the high-pressure heater group to be introduced into the second molten salt heat exchanger for heating. It also allows for selective bypass of different high-pressure heaters within the high-pressure heater group, replacing the corresponding turbine extraction steam. Based on the unit's operating conditions (such as temperature), it provides selectable branches to preferentially replace higher-temperature heaters. This structure reduces the consumption of high-grade extraction steam, allowing more high-grade steam to continue expanding and performing work in the turbine, thus improving unit output and energy conversion efficiency.

[0019] This invention connects the feedwater heated by the second molten salt heat exchanger to the feedwater pipeline between the first molten salt heat exchanger and the high-pressure heater group, thereby raising the feedwater temperature entering the first molten salt heat exchanger and the boiler, increasing the average heat absorption temperature of the working fluid in the boiler, reducing boiler heat loss, and increasing the work done by the turbine unit under the same boiler heat input, thus improving the thermal cycle efficiency.

[0020] This invention offers a wide range of technical solutions with low modification difficulty, applicable to thermal power units of different capacity levels and under varying deaerator water temperatures. The bypass range can be adjusted via valve switching, flexibly matching the unit's operational needs under different conditions. This reduces coal consumption during off-peak loads and rapidly releases stored heat to increase unit output during peak loads. Under different operating conditions, the feedwater temperature for heat exchange with molten salt can be flexibly adjusted via valve switching to better match the temperature of the low-temperature salt, thereby maintaining high energy conversion efficiency and reducing heat waste. Attached Figure Description

[0021] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a structural diagram of a thermal power unit coupled with a low-temperature molten salt heat release system according to the present invention; Figure 2 This invention provides a temperature-heat diagram of a thermal power unit coupled with a low-temperature molten salt heat release system under heat release conditions; wherein, the horizontal axis represents the cumulative heat exchange and the vertical axis represents the temperature; 1-Boiler; 2-Steam turbine; 3-Generator; 4-Deaerator; 5-Condenser; 7-Low-pressure heater unit; 8-Feed water pump; 9-Condensate pump; 10-High-temperature molten salt tank; 11-Low-temperature molten salt tank; 12-First molten salt heat exchanger; 13-Second molten salt heat exchanger; 14-First high-pressure heater; 15-Second high-pressure heater; 16-Third high-pressure heater; 17 - Third valve; 18 - Second valve; 19 - First valve; 20 - Fourth valve; 21-High-temperature molten salt pump. Detailed Implementation

[0022] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] The first embodiment of the present invention provides a thermal power unit coupled with a low-temperature molten salt heat release system. The system includes a boiler 1, a steam turbine generator set, a regenerative heating unit, and a molten salt heat storage and release unit; The steam turbine generator set includes a steam turbine 2, a generator 3, and a condenser 5; The molten salt heat storage and release unit includes a high-temperature molten salt tank 10, a low-temperature molten salt tank 11, a first molten salt heat exchanger 12, a second molten salt heat exchanger 13, and a high-temperature molten salt pump 21; Molten salt flows sequentially through the outlet of high-temperature molten salt tank 10, high-temperature molten salt pump 21, molten salt side of first molten salt heat exchanger 12, molten salt side of second molten salt heat exchanger 13, and inlet of low-temperature molten salt tank 11; wherein, the flow direction of molten salt is configured to release heat step by step through the first molten salt heat exchanger 12 and the second molten salt heat exchanger 13 to heat the feedwater. The regenerative heating unit includes a deaerator 4 and a high-pressure heater group; The inlet of the feedwater pump 8 is connected to the outlet of the deaerator 4. The outlet of the feedwater pump 8 is connected to the feedwater bypass and the inlet of the high-pressure heater group. The feedwater bypass is divided into a first branch, a second branch and a third branch. The first branch is connected to the inlet side of the high-pressure heater group. The outlets of the first branch, the second branch and the third branch are connected to the inlet side of the second molten salt heat exchanger 13. The system is configured such that by controlling the on / off states of the first branch, the second branch, and the third branch, the bypass portion of the feedwater received by the second molten salt heat exchanger 13 is taken from different interstage positions of the high-pressure heater group, so as to selectively bypass at least one high-pressure heater in the high-pressure heater group according to the unit operating conditions, and preferentially bypass the high-pressure heater of the extraction steam high pressure.

[0025] like Figure 1As shown, in the above system structure, molten salt flows sequentially through the outlet of the high-temperature molten salt tank 10, the high-temperature molten salt pump 21, the molten salt side of the first molten salt heat exchanger 12, the molten salt side of the second molten salt heat exchanger 13, and the inlet of the low-temperature molten salt tank 11, releasing the heat to heat the feedwater entering the unit to do work. Under the heat release condition, the heat stored in the molten salt heat storage unit is used to increase the boiler inlet feedwater temperature through the first molten salt heat exchanger 12, while the second molten salt heat exchanger 13 heats the feedwater bypass section, reducing the high-pressure steam extraction and reheating, so that more high-pressure steam continues to do work in the steam turbine 2. Depending on the unit conditions, one or more heaters in the high-pressure heater group can be bypassed.

[0026] This dual-heat-exchanger series structure enables the cascaded release of molten salt thermal energy, such as... Figure 2 As shown, the temperature-heat curve of the molten salt heat release process is highly matched with the temperature zones of the boiler feedwater heating, which effectively reduces the heat exchange end difference, reduces irreversible losses in the heat exchange process, and improves the effective utilization efficiency of heat.

[0027] In the regenerative heating unit, the feedwater pump 8 at the outlet of deaerator 4 pressurizes the deaerated feedwater and divides it into two paths: one path enters the inlet side of the high-pressure heater group along the conventional path for staged heating, and the other path is led out through the feedwater bypass. The feedwater bypass branches into a first branch, a second branch, and a third branch downstream of the outlet of feedwater pump 8. The first branch is equipped with a first valve 19 and is connected to the feedwater pipeline at the inlet side of the high-pressure heater group, used to supplement or regulate the feedwater flow to the high-pressure heater group under partial bypass conditions; the second branch is equipped with a second valve 18, and this second branch extends to the feedwater inlet of the second molten salt heat exchanger 13. By controlling the opening of the first valve 19, the flow rate of feedwater drawn from the outlet of feedwater pump 8 and sent to the second molten salt heat exchanger 13 can be adjusted. The second molten salt heat exchanger 13 heats the feedwater by using high-temperature molten salt flowing through its molten salt side. The heated feedwater flows out from the feedwater outlet of the second molten salt heat exchanger 13 and merges into the feedwater pipe located between the feedwater inlet of the first molten salt heat exchanger 12 and the feedwater outlet of the high-pressure heater group. The bypass-heated feedwater can mix with the feedwater from the high-pressure heater group and enter the first molten salt heat exchanger 12 together for further heating before entering the boiler 1, achieving smooth parallel flow of bypass feedwater and effective heat integration. Through the above structure, the boiler feedwater can receive additional heating from the molten salt heat release system before entering the boiler, thereby raising the boiler inlet feedwater temperature, increasing the average heat absorption temperature of the working fluid in the boiler, reducing boiler losses, and replacing the high-pressure heater, reducing high-pressure cylinder steam extraction, increasing the work done by the high-pressure cylinder under the same boiler heat input conditions, and thus improving the overall efficiency of the thermal cycle.

[0028] In a preferred embodiment, the high-pressure heater group includes a first high-pressure heater 14, a second high-pressure heater 15, and a third high-pressure heater 16 connected in series. The inlet of the high-pressure heater group is connected to the water supply pump 8. A first branch is provided between the outlet of the water supply pump 8 and the inlet of the third high-pressure heater 16. A second branch is provided between the outlet of the third high-pressure heater 16 and the inlet of the second high-pressure heater 15. A third branch is provided between the outlet of the second high-pressure heater 15 and the inlet of the first high-pressure heater 14. The feedwater outlet of the second molten salt heat exchanger 13 is connected between the feedwater inlet of the first molten salt heat exchanger 12 and the feedwater outlet of the third high-pressure heater 16.

[0029] Those skilled in the art will understand that the three high-pressure heaters mentioned above correspond to different stages of steam extraction ports of the turbine, used for heating boiler feedwater stage by stage. The connection point of the first branch is located between the outlet of feedwater pump 8 and the inlet of the third high-pressure heater 16. This means that when the first valve 19 is open and the second valve 18 and the third valve 17 are closed or adjusted according to the operating conditions, part of the feedwater from the outlet of feedwater pump 8 can enter the first branch without passing through or partially passing through the third high-pressure heater 16. The feedwater outlet connection point of the second molten salt heat exchanger 13 is located on the pipe section between the feedwater inlet of the first molten salt heat exchanger 12 and the feedwater outlet of the first high-pressure heater 14. With this configuration, the system can flexibly select the junction location and flow ratio of the bypass feedwater according to the actual operating load and peak-shaving requirements of the unit, achieving equivalent substitution of steam extraction of different grades, reducing the consumption of high-grade steam in the heaters, and allowing more high-quality steam to continue to expand and do work in the turbine, thereby increasing the unit output and power generation efficiency.

[0030] In a further optimized embodiment, the regenerative heating unit also includes a low-pressure heater group 7. The outlet of the condenser 5 is connected to the inlet of the low-pressure heater group 7 via a condensate pump 9, and the outlet of the low-pressure heater group 7 is connected to the inlet of the deaerator 4. The condenser 5 condenses the exhaust steam from the steam turbine 2 into water. The condensate is pressurized by the condensate pump 9 and flows sequentially through the low-pressure heater group 7 into the deaerator 4. The low-pressure heater group 7 uses the low-pressure extraction steam from the steam turbine 2 to preheat the condensate, while the deaerator 4 uses the extraction steam from the steam turbine 2 to deoxygenate the feedwater. Through the above connections, a complete regenerative cycle system for the thermal power unit is formed. Simultaneously, the steam-side inlet of the deaerator 4 is connected to the extraction steam port of the steam turbine 2, allowing the extraction steam that performs partial work in the steam turbine 2 to enter the deaerator 4 and heat the feedwater to the deoxygenation temperature, ensuring that the oxygen content of the boiler feedwater meets the standard requirements.

[0031] To further improve the system's adaptability to different steam extraction conditions, the first valve 19, the second valve 18, and the third valve 17 in this embodiment are used to control the feedwater flow direction to selectively open the first branch, the second branch, or the third branch. The first valve 19 is installed on the first branch. One end of the first branch is connected between the outlet of the water pump 8 and the inlet of the third high-pressure heater 16, and the other end of the first branch is connected to the inlet of the second molten salt heat exchanger 13. The first valve 19 is used to guide the water supply without passing through the first high-pressure heater 14, the second high-pressure heater 15, and the third high-pressure heater 16. The second valve 18 is installed on the second branch. One end of the second branch is connected between the outlet of the third high-pressure heater 16 and the inlet of the second high-pressure heater 15. The other end of the second branch is connected to the inlet of the second molten salt heat exchanger 13. The second valve 18 is used to guide the feed water to bypass the first high-pressure heater 14 and the second high-pressure heater 15. The third valve 17 is installed on the third branch. One end of the third branch is connected between the outlet of the second high-pressure heater 15 and the inlet of the first high-pressure heater 14, and the other end of the third branch is connected to the inlet of the second molten salt heat exchanger 13. The third valve 17 is used to guide the feed water to bypass the first high-pressure heater 14.

[0032] Specifically, when only the first valve 19 is opened and the second valve 18 and the third valve 17 are closed, the feedwater drawn from the outlet of the feedwater pump 8 enters the second molten salt heat exchanger 13 for heating. This part of the feedwater does not pass through the first high-pressure heater 14, the second high-pressure heater 15, and the third high-pressure heater 16, thus achieving maximum steam extraction substitution.

[0033] When the second valve 18 is opened and the first valve 19 and the third valve 17 are closed, part of the water supply in the second branch can be introduced into the second molten salt heat exchanger 13 for heating through the water supply pipe between the third high-pressure heater 16 and the second high-pressure heater 15 via the second valve 18. This part of the water supply does not pass through the first high-pressure heater 14 and the second high-pressure heater 15.

[0034] When the third valve 17 is opened and the first valve 19 and the second valve 18 are closed, part of the water supply in the third branch can be introduced into the second molten salt heat exchanger 13 for heating through the water supply pipe between the second high-pressure heater 15 and the first high-pressure heater 14 via the third valve 17. This part of the water supply does not pass through the first high-pressure heater 14.

[0035] When any one of the three valves is opened, feedwater can be distributed to the inlet of each stage of heaters, achieving partial load replacement. This combination of multi-valve configuration and branch connection provides flexible and versatile feedwater bypass paths, enabling selective bypass of different high-pressure heaters in the high-pressure heater group to replace the corresponding turbine extraction steam. Based on the unit's operating conditions (such as temperature conditions), it provides optional branches to prioritize the replacement of higher-pressure heaters, saving higher-grade high-pressure steam. This fully adapts to the actual needs of thermal power units of different capacity levels and under different peak-shaving conditions, maximizing the utilization of the work capacity of high-grade steam and improving heat-power conversion efficiency.

[0036] In terms of connection, the feedwater outlet of the first high-pressure heater 14 is connected to the feedwater inlet of the first molten salt heat exchanger 12, and the feedwater outlet of the first molten salt heat exchanger 12 is connected to the feedwater inlet of the boiler 1. Therefore, during normal operation, all the feedwater heated by the three-stage high-pressure heaters enters the first molten salt heat exchanger 12 to further absorb the heat released by the molten salt, and the temperature rises further before entering the boiler 1. When the feedwater bypass is activated, the feedwater heated by the second molten salt heat exchanger 13 flows through a branch into the pipeline between the inlet of the first molten salt heat exchanger 12 and the outlet of the first high-pressure heater 14, mixes with the feedwater at the outlet of the first high-pressure heater 14, and then enters the first molten salt heat exchanger 12 for further heating. This connection method ensures that regardless of how the bypass system is adjusted, the boiler inlet feedwater is always supplied after being heated by the first molten salt heat exchanger 12 and / or the high-pressure heater group, guaranteeing a stable supply of boiler feedwater and a high feedwater temperature.

[0037] In terms of molten salt transport, the outlet of the high-temperature molten salt tank 10 is connected to the inlet of the fourth valve 20, the outlet of the fourth valve 20 is connected to the inlet of the high-temperature molten salt pump 21, and the outlet of the high-temperature molten salt pump 21 is connected to the molten salt inlet of the first molten salt heat exchanger 12. The fourth valve 20 and the high-temperature molten salt pump 21 are connected in series. The fourth valve 20 is used to provide the initial transport pressure, drawing the high-temperature molten salt from the high-temperature molten salt tank 10 and sending it into the suction port of the high-temperature molten salt pump 21. The high-temperature molten salt pump 21 further pressurizes the molten salt, ensuring that the molten salt can enter the molten salt side of the first molten salt heat exchanger 12 with a stable flow rate and sufficient head. This series configuration effectively improves the reliability and adjustment flexibility of molten salt transport, and can adapt to the changes in the physical properties of molten salt at different temperatures and the flow rate adjustment requirements of the system under heat release conditions.

[0038] Furthermore, both the first molten salt heat exchanger 12 and the second molten salt heat exchanger 13 are molten salt-feed water heat exchangers. They are internally equipped with molten salt channels and feed water channels, allowing the two media to exchange heat indirectly through the heat exchange walls. The heat exchangers can adopt shell-and-tube, plate, or spiral plate structures suitable for high-temperature and high-pressure conditions, and are manufactured using high-temperature resistant, corrosion-resistant materials compatible with molten salt to ensure long-term safe and stable operation.

[0039] The above system embodiments fully disclose the specific connection relationships and cooperation principles of the various components of the present invention. Based on the above description, those skilled in the art can reproduce and implement the technical solution of the present invention without any creative effort. By adopting this system, through the synergistic effect of dual heat exchangers in series for cascaded heat release and multiple valves for selective steam extraction, under the same molten salt thermal storage conditions, the heat energy loss of high-grade steam can be significantly reduced, improving the unit's peak-shaving capacity and heat-to-work conversion efficiency, demonstrating good technical effects and promotional value.

[0040] After being heated by the first molten salt heat exchanger 12 and / or the high-pressure heater group, the feedwater temperature is relatively high. After entering the boiler 1, it can effectively improve the heat absorption capacity of the boiler water-cooled wall and the superheater heating surface, increase the boiler's evaporation rate and steam parameters, thereby increasing the steam turbine's steam intake and work capacity, and ultimately achieving an increase in the unit's electrical load or a reduction in coal consumption.

[0041] Taking a 600MW pure condensing unit as an example, under the condition that the boiler input remains at 100% rated load, using the system and method of this embodiment, when the molten salt heat release is 139MW, the unit's additional output power is approximately 58MW, and the heat-to-power conversion efficiency of molten salt heat release reaches 41.4%. Combined with a suitable extraction steam heating molten salt thermal storage scheme, the cycle efficiency (round-trip efficiency) of the molten salt energy storage system for one charge-discharge cycle can reach 75-80%. Compared with other molten salt heat release schemes that do not increase the boiler inlet feedwater temperature and do not replace the high-pressure heater, under the premise of keeping the above operating conditions unchanged, this embodiment can increase the unit's additional output power by 6-12MW under heat release conditions, and reduce the unit's coal consumption rate by 3-6g / kWh. These data fully verify the significant advantages of this invention in improving energy utilization efficiency, reducing unit coal consumption, and enhancing peak-shaving capacity.

[0042] The second embodiment of the present invention proposes a method for coupling low-temperature molten salt heat release in thermal power units, using the system described in the first embodiment, and includes the following steps: Start the high-temperature molten salt pump 21 to transport the high-temperature molten salt in the high-temperature molten salt tank 10 to the molten salt side of the first molten salt heat exchanger 12 through the fourth valve 20; After the high-temperature molten salt exchanges heat with the first molten salt heat exchanger 12 and the second molten salt heat exchanger 13, it forms low-temperature molten salt and enters the low-temperature molten salt tank 11. Part of the feedwater flowing through the high-pressure heater group enters the feedwater side of the second molten salt heat exchanger 13 via the first, second, or third feedwater bypass branch. After being heated, it flows into the feedwater outlet of the first high-pressure heater 14 and the cold-side inlet pipe of the first molten salt heat exchanger 12. After merging with the feedwater from the high-pressure heater group, it enters the first molten salt heat exchanger 12 for further heating and finally enters the boiler 1. The opening and closing states of the first valve 19, the second valve 18, and the third valve 17 are controlled to selectively bypass at least one high-pressure heater in the high-pressure heater group.

[0043] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process and related explanations of the methods described above can be found in the corresponding processes of the foregoing system embodiments, and will not be repeated here. The above embodiments detail the system structure and method steps of the present invention, covering all the technical content of the present invention, and each part of the description has been adapted to be feasible for those skilled in the art without creative effort. It should be understood that the above embodiments are only used to explain the technical solutions of the present invention and are not intended to limit its scope of protection; equivalent substitutions or conventional modifications made based on the ideas of the present invention are all within the scope of protection of the present invention.

[0044] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0045] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0046] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A thermal power unit coupled with a low-temperature molten salt heat release system, comprising a boiler (1), a steam turbine generator set, a regenerative heating unit, and a molten salt heat storage and release unit, characterized in that, The steam turbine generator set includes a steam turbine (2), a generator (3), and a condenser (5); The molten salt heat storage and release unit includes a high-temperature molten salt tank (10), a low-temperature molten salt tank (11), a first molten salt heat exchanger (12), a second molten salt heat exchanger (13), and a high-temperature molten salt pump (21). Molten salt flows sequentially through the outlet of the high-temperature molten salt tank (10), the high-temperature molten salt pump (21), the molten salt side of the first molten salt heat exchanger (12), the molten salt side of the second molten salt heat exchanger (13), and the inlet of the low-temperature molten salt tank (11); wherein, the flow direction of the molten salt is configured to release heat step by step through the first molten salt heat exchanger (12) and the second molten salt heat exchanger (13) to heat the feed water; The regenerative heating unit includes a deaerator (4) and a high-pressure heater assembly; The inlet of the water pump (8) is connected to the outlet of the deaerator (4). The outlet of the water pump (8) is connected to the water supply bypass and the inlet of the high-pressure heater group. The water supply bypass is divided into the first branch, the second branch and the third branch. The first branch is connected to the inlet side of the high-pressure heater group. The outlets of the first branch, the second branch and the third branch are connected to the inlet side of the second molten salt heat exchanger (13). The system is configured such that by controlling the on / off of the first branch, the second branch and the third branch, the bypass portion of the feedwater received by the second molten salt heat exchanger (13) is taken from different interstage positions of the high-pressure heater group, so as to selectively bypass at least one high-pressure heater in the high-pressure heater group according to the unit operating conditions, and preferentially bypass the high-pressure heater of the extraction steam high pressure.

2. The system according to claim 1, characterized in that, The regenerative heating unit also includes a low-pressure heater (7). The outlet of the condenser (5) is connected to the inlet of the low-pressure heater (7) via a condensate pump (9), and the outlet of the low-pressure heater (7) is connected to the inlet of the deaerator (4).

3. The system according to claim 1, characterized in that, The high-pressure heater group includes a first high-pressure heater (14), a second high-pressure heater (15), and a third high-pressure heater (16) connected in series. The inlet of the high-pressure heater group is connected to the water supply pump (8). A first branch is provided between the outlet of the water supply pump (8) and the inlet of the third high-pressure heater (16). A second branch is provided between the outlet of the third high-pressure heater (16) and the inlet of the second high-pressure heater (15). A third branch is provided between the outlet of the second high-pressure heater (15) and the inlet of the first high-pressure heater (14).

4. The system according to claim 3, characterized in that, It also includes a first valve (19), a second valve (18), and a third valve (17) for controlling the water supply direction to selectively open the first branch, the second branch, or the third branch; The first valve (19) is installed on the first branch. One end of the first branch is connected between the outlet of the water pump (8) and the inlet of the third high-pressure heater (16). The other end of the first branch is connected to the inlet of the second molten salt heat exchanger (13). The first valve (19) is used to guide the water supply without passing through the first high-pressure heater (14), the second high-pressure heater (15), and the third high-pressure heater (16). The second valve (18) is installed on the second branch. One end of the second branch is connected between the outlet of the third high-pressure heater (16) and the inlet of the second high-pressure heater (15). The other end of the second branch is connected to the inlet of the second molten salt heat exchanger (13). The second valve (18) is used to guide the feed water to bypass the first high-pressure heater (14) and the second high-pressure heater (15). The third valve (17) is installed on the third branch. One end of the third branch is connected between the outlet of the second high-pressure heater (15) and the inlet of the first high-pressure heater (14). The other end of the third branch is connected to the inlet of the second molten salt heat exchanger (13). The third valve (17) is used to guide the feed water to bypass the first high-pressure heater (14).

5. The system according to claim 3, characterized in that, The feedwater outlet of the first high-pressure heater (14) is connected to the cold side inlet of the first molten salt heat exchanger (12), and the cold side outlet of the first molten salt heat exchanger (12) is connected to the feedwater inlet of the boiler (1).

6. The system according to claim 1, characterized in that, The cold side outlet of the second molten salt heat exchanger (13) is connected to the water supply outlet of the first high-pressure heater (14) and the cold side inlet of the first molten salt heat exchanger (12).

7. The system according to claim 1, characterized in that, The outlet of the high-temperature molten salt tank (10) is connected to the inlet of the fourth valve (20), the outlet of the fourth valve (20) is connected to the inlet of the high-temperature molten salt pump (21), the outlet of the high-temperature molten salt pump (21) is connected to the molten salt side inlet of the first molten salt heat exchanger (12), the molten salt side outlet of the first molten salt heat exchanger (12) is connected to the molten salt side inlet of the second molten salt heat exchanger (13), and the molten salt side outlet of the second molten salt heat exchanger (13) is connected to the inlet of the low-temperature molten salt tank (11).

8. The system according to claim 1, characterized in that, Both the first molten salt heat exchanger (12) and the second molten salt heat exchanger (13) are molten salt-feed water heat exchangers.

9. A method for coupling cryogenic molten salt heat release in a thermal power unit, employing the system as described in claim 4, characterized in that, Includes the following steps: Start the high-temperature molten salt pump (21) to transport the high-temperature molten salt in the high-temperature molten salt tank (10) to the molten salt side of the first molten salt heat exchanger (12) through the fourth valve (20); After the high-temperature molten salt is heated by the first molten salt heat exchanger (12) and the second molten salt heat exchanger (13), it forms low-temperature molten salt and enters the low-temperature molten salt tank (11). Part of the feedwater flowing through the high-pressure heater group enters the feedwater side of the second molten salt heat exchanger (13) via the first, second, or third feedwater bypass branch. After being heated, it flows into the feedwater outlet of the first high-pressure heater (14) and the cold-side inlet pipe of the first molten salt heat exchanger (12). After merging with the feedwater from the high-pressure heater group, it enters the first molten salt heat exchanger (12) for further heating and finally enters the boiler (1). Control the opening and closing states of the first valve (19), the second valve (18) and the third valve (17) to selectively bypass at least one high-pressure heater in the high-pressure heater group, and preferentially bypass the high-pressure heater of the extraction steam high pressure.

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