A molten salt system and method with preheating and salt dissolving functions

Abstract

The application discloses a molten salt system and method with preheating and salt dissolving functions, which comprises a high-temperature device, a low-temperature device, a salt-dissolving device, an electric heater, a centrifugal fan and a molten salt hot air generator; the outlet of the high-temperature device is connected with the inlet of the low-temperature device; the outlet of the low-temperature device and the outlet of the salt-dissolving device are connected with the inlet of the electric heater; the outlet of the electric heater is connected with the inlet of the salt-dissolving device through a pipeline; the outlet of the centrifugal fan is connected with the air inlet of the molten salt hot air generator; the air outlet of the molten salt hot air generator is connected with the inlet of the high-temperature device and the inlet of the low-temperature device respectively; and the molten salt outlet of the molten salt hot air generator is connected with the salt-dissolving device. The electric heater in the conventional preheating and salt dissolving system is saved, the salt dissolving heat power is significantly improved, the construction of electric appliances, air ducts and salt dissolving pipelines is greatly reduced, the preheating and salt dissolving cost is effectively reduced, and the construction period is shortened.

Description

Technical Field

[0001] This invention belongs to the field of molten salt thermal storage, specifically relating to a molten salt system and method with preheating and salt melting functions. Background Technology

[0002] Energy storage technology is a crucial support for building a green and low-carbon new power system. Compared with lithium batteries, compressed air, and pumped hydro storage, molten salt thermal energy storage technology has advantages such as low cost, long lifespan, no pollution, and no geographical limitations, making it a highly promising energy storage technology. Currently, over 95% of molten salt thermal energy storage systems are built within solar thermal power plants. Molten salt thermal energy storage coupled with thermal power unit frequency regulation, peak shaving, and steam supply technologies can significantly improve the safe power supply and regulation role of thermal power units in the power grid. Some power plants in China have already begun related engineering demonstrations.

[0003] Molten salt is an excellent medium-to-high temperature thermal storage medium, characterized by low vapor pressure, good fluidity, and high storage temperature. Currently, the most widely used molten salt in engineering applications is solar salt (potassium nitrate + sodium nitrate). The biggest advantages of solar salt are its good thermal stability and low corrosiveness, while its disadvantage is its excessively high freezing point of approximately 220℃. Tank preheating and salt melting are essential components of molten salt thermal storage systems. The preheating process raises the tank temperature from ambient to the molten salt's operating temperature, avoiding thermal stress caused by large temperature differences. The salt melting process involves melting powdered or granular solid inorganic salts into a liquid through heating, which is then transported to the molten salt tank. Currently, solar thermal power plants use specialized equipment and natural gas for preheating and salt melting. However, thermal power plants are better suited to using electricity for preheating and salt melting. Therefore, developing a lower-cost and faster preheating and salt melting method based on the characteristics of molten salt thermal storage systems in thermal power plants has significant application value. Summary of the Invention

[0004] To address the drawbacks of current molten salt thermal storage systems, which require additional customized preheating and salt-melting equipment, resulting in high costs and long cycles, this invention proposes a molten salt system and method with preheating and salt-melting functions. This system can fully utilize existing equipment within the molten salt thermal storage system to complete the preheating and salt-melting processes, offering advantages such as minimal construction work, low salt-melting costs, and high salt-melting speed.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A molten salt system with preheating and salt dissolving functions includes a high-temperature device, a low-temperature device, a salt-removing device, an electric heater, a centrifugal fan, and a molten salt hot air blower. The outlet of the high-temperature device is connected to the inlet of the low-temperature device. The outlets of the low-temperature device and the salt-removing device are combined into one line and connected to the inlet of the electric heater. The outlet of the electric heater is connected to the inlet of the salt-removing device via a pipe. The outlet of the centrifugal fan is connected to the air inlet of the molten salt hot air blower, and the air outlet of the molten salt hot air blower is connected to both the inlet of the high-temperature device and the inlet of the low-temperature device. The molten salt outlet of the molten salt hot air blower is connected to the salt-removing device.

[0007] Furthermore, the high-temperature equipment includes a high-temperature tank, a high-temperature pump, a steam generator, and a high-temperature tank liquid distribution ring; the high-temperature pump is installed above the high-temperature tank, and the outlet of the high-temperature pump is connected in sequence to the steam generator and the inlet of the low-temperature equipment; the high-temperature tank liquid distribution ring is located at the bottom of the high-temperature tank, and the inlet of the high-temperature tank liquid distribution ring is connected to the air outlet of the molten salt hot air heater and the outlet of the electric heater, respectively.

[0008] Furthermore, the cryogenic equipment includes a cryogenic tank, a cryogenic tank distribution ring, and a cryogenic pump; the cryogenic tank distribution ring is located at the bottom of the cryogenic tank; the cryogenic pump is installed above the cryogenic tank; the inlet of the cryogenic tank distribution ring is connected to a steam generator; and the outlet of the cryogenic pump is connected to the inlet of an electric heater.

[0009] Furthermore, the salt-removing device includes a salt-removing pump, a salt-removing tank, and an auxiliary electric heater; the salt-removing pump and the auxiliary electric heater are installed above the salt-removing tank; the outlet of the salt-removing pump is connected to the inlet of the electric heater and the low-temperature tank, respectively; the outlet of the electric heater is connected to the salt-removing tank.

[0010] Furthermore, a molten salt system with preheating and salt melting functions also includes multiple control valves installed on the connecting pipes.

[0011] A molten salt method includes a normal operating mode, a preheating mode, and a salt melting mode.

[0012] Furthermore, the normal operating mode specifically includes the following steps: during peak electricity consumption periods, high-temperature molten salt is transported to the steam generator via a high-temperature pump. The molten salt releases heat, lowers its temperature, and generates steam. The generated steam is used to increase the grid-connected power of the coal-fired power unit. Low-temperature molten salt flows through the low-temperature tank distribution ring and enters the low-temperature tank evenly.

[0013] During periods of low electricity demand, molten salt is transported to an electric heater via a cryogenic pump. The molten salt is heated by converting electrical energy into heat to reduce the grid connection power of coal-fired power units. After the temperature of the molten salt rises, it is evenly distributed into the high-temperature tank via a distribution ring. When equipment or pipelines need to discharge salt, the molten salt is released into a salt discharge tank, and then the salt discharge pump is used to transport the molten salt to the cryogenic tank.

[0014] Furthermore, the preheating mode specifically includes the following steps: adding solid salt to the salt-absorbing tank until it covers the heating element of the auxiliary electric heater; turning on the auxiliary electric heater to heat the solid salt until it is completely melted into a liquid state; turning off the auxiliary electric heater and turning on the electric heater and centrifugal fan; using the salt-absorbing pump to transport the liquid molten salt to the electric heater to increase the temperature; the high-temperature molten salt enters the molten salt hot air blower; the compressed air generated by the centrifugal fan absorbs the heat of the molten salt and its temperature rises; at this time, the high-temperature tank and the low-temperature tank are preheated; during the preheating process, the air temperature at the outlet of the molten salt hot air blower gradually increases from room temperature to the working temperature of the molten salt, and the air temperature increases with the increase of the power of the electric heater.

[0015] Furthermore, the salt-dissolving mode specifically includes the following steps: adding solid salt to the salt-dissolving tank until it covers the heating element of the auxiliary electric heater; turning on the auxiliary electric heater to heat the solid salt until it is completely melted into a liquid state; turning off the auxiliary electric heater and turning on the electric heater; using a salt-dissolving pump to transport the liquid molten salt to the electric heater to raise its temperature and then back to the salt-dissolving tank, until the overall temperature of the salt-dissolving tank reaches the salt-dissolving requirement; at this time, solid inorganic salt is continuously added to the salt-dissolving tank; part of the molten salt from the salt-dissolving pump outlet flows into the low-temperature tank, and another part of the molten salt enters the electric heater to raise its temperature and then flows back to the salt-dissolving tank; the amount of solid salt added to the salt-dissolving tank is basically equal to the amount of salt flowing into the low-temperature tank; part of the molten salt from the electric heater outlet flows back to the salt-dissolving tank, and another part of the molten salt flows into the high-temperature tank; the amount of solid salt added to the salt-dissolving tank is equal to the amount of salt flowing into the high-temperature tank, until the salt-dissolving process is completed.

[0016] The beneficial effects of this invention are:

[0017] This invention, by adding a few devices and control valves, enables the molten salt thermal storage system to have preheating and salt-melting functions while making full use of the existing equipment, eliminating the need for a custom-designed preheating and salt-melting system. This system saves on the electric heaters found in conventional preheating and salt-melting systems, significantly increases the salt-melting thermal power, and greatly reduces the construction work required for electrical systems, air ducts, and salt-melting pipelines. It effectively lowers preheating and salt-melting costs and shortens the construction period. Attached Figure Description

[0018] Figure 1 This is a system structure diagram of the present invention.

[0019] In the attached diagram: 1. High-temperature tank; 2. High-temperature pump; 3. Steam generator; 4. First valve; 5. Low-temperature tank; 6. Low-temperature tank distribution ring; 7. Low-temperature pump; 8. Second valve; 9. Electric heater; 10. Third valve; 11. High-temperature tank distribution ring; 12. Brine pump; 13. Brine tank; 14. Auxiliary electric heater; 15. Fourth valve; 16. Fifth valve; 17. Sixth valve; 18. Centrifugal fan; 19. Molten salt hot air heater; 20. Seventh valve; 21. Eighth valve; 22. Ninth valve. Implementation

[0020] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0022] like Figure 1 As shown, a molten salt system with preheating and salt melting functions includes:

[0023] High-temperature tank 1, high-temperature pump 2, steam generator 3, low-temperature tank 5, low-temperature tank liquid distribution ring 6, low-temperature pump 7, electric heater 9, high-temperature tank liquid distribution ring 11, brine pump 12, brine tank 13, auxiliary electric heater 14, centrifugal fan 18, molten salt hot air heater 19 and related control valves.

[0024] The high-temperature pump 2 is installed above the high-temperature tank 1, and its outlet is sequentially connected to the steam generator 3, the first valve 4, and the inlet of the low-temperature tank distribution ring 6, which is located at the bottom of the low-temperature tank 5. The low-temperature pump 7 is installed above the low-temperature tank 5, and its outlet is sequentially connected to the second valve 8 and the inlet of the electric heater 9. The brine pump 12 and the auxiliary electric heater 14 are installed above the brine tank 13, and the outlet of the brine pump 12 is connected to the inlet of the electric heater 9 through the fifth valve 16 and to the low-temperature tank 5 through the ninth valve 22. The electric heater 9... The outlet is connected to the brine tank 13 via the fourth valve 15, to the molten salt inlet of the molten salt hot air blower 19 via the sixth valve 17, and to the inlet of the high-temperature tank liquid distribution ring 11 via the third valve 10. The high-temperature tank liquid distribution ring 11 is located at the bottom of the high-temperature tank 1. The outlet of the centrifugal fan 18 is connected to the air inlet of the molten salt hot air blower 19. The air outlet of the molten salt hot air blower 19 is connected to the inlet of the high-temperature tank liquid distribution ring 11 via the seventh valve 20 and to the inlet of the low-temperature tank liquid distribution ring 6 via the eighth valve 21. The molten salt outlet of the molten salt hot air blower 19 is connected to the brine tank 13.

[0025] The centrifugal fan 18, molten salt hot air blower 19 and auxiliary electric heater 14 are new equipment compared to the original molten salt system, used to enable the molten salt system to have preheating and salt melting functions.

[0026] The molten salt hot air heater 19 is arranged downstream of the electric heater 9 according to the molten salt flow direction. After opening the sixth valve 17, the high-temperature molten salt is used to heat the air at the outlet of the centrifugal fan 18, and then the high-temperature air is used to preheat the high-temperature tank 1 and the low-temperature tank 5, and the preheating process begins.

[0027] The auxiliary electric heater 14 is arranged above the salt-absorbing tank 13. After the auxiliary electric heater 14 is turned on, it generates heat to heat the solid salt until it melts into a liquid state. The liquid salt is then sent to the electric heater 9 to raise its temperature and then returned to the salt-absorbing tank 13, thus starting the salt-melting process.

[0028] The molten salt system with preheating and salt dissolving functions operates in normal working mode, preheating mode and salt dissolving mode.

[0029] Normal operating mode: Close valves 15, 16, 17, 20, and 21, and open the remaining valves. During peak electricity consumption, high-temperature molten salt is transported to steam generator 3 via high-temperature pump 2. The molten salt releases heat, lowers its temperature, and generates steam. The generated steam is used to increase the grid power of the coal-fired power unit. Low-temperature molten salt flows through valve 4 and then enters low-temperature tank 5 evenly via low-temperature tank distribution ring 6. During off-peak electricity consumption, low-temperature molten salt is transported to electric heater 9 via low-temperature pump 7. The molten salt is heated by the conversion of electrical energy into heat to reduce the grid power of the coal-fired power unit. After the molten salt temperature rises, it enters high-temperature tank 1 evenly via high-temperature tank distribution ring 11. When equipment or pipelines need to discharge salt, the molten salt is released to salt discharge tank 13 and then transported to low-temperature tank 5 via salt discharge pump 12 and valve 22.

[0030] Preheating mode: Open valve 16 and valve 17, and close other valves; add solid salt to salt-absorbing tank 13 until it covers the heating element of auxiliary electric heater 14, turn on auxiliary electric heater 14 to heat the solid salt until it is completely melted into liquid, turn off auxiliary electric heater 14, turn on electric heater 9 and centrifugal fan 18, use salt-absorbing pump 12 to transport liquid molten salt to electric heater 9 to increase the temperature, high temperature molten salt enters molten salt hot air heater 19 through valve 17, the compressed air generated by centrifugal fan 18 absorbs the heat of molten salt and the temperature rises, at this time, opening valve 20 can preheat high temperature tank 1, opening valve 21 can preheat low temperature tank 5; during the preheating process, the outlet air temperature of molten salt hot air heater 19 gradually rises from room temperature to above the working temperature of molten salt, the air temperature rises with the increase of power of electric heater 9.

[0031] Salt dissolving mode: Open the fourth valve 15 and the fifth valve 16, and close the other valves; add solid salt to the salt dissolving tank 13 until it covers the heating element of the auxiliary electric heater 14, turn on the auxiliary electric heater 14 to heat the solid salt until it is completely melted into a liquid state, turn off the auxiliary electric heater 14, turn on the electric heater 9, and use the salt dissolving pump 12 to transport the liquid molten salt to the electric heater 9 to increase the temperature, and then let it flow back to the salt dissolving tank 13 until the overall temperature of the salt dissolving tank 13 reaches the salt dissolving requirement; at this time, open the ninth valve 22 and adjust the opening degree, and continuously add salt to the salt dissolving tank 13. 3. Solid inorganic salt is added. A portion of the molten salt from the outlet of the salt-absorbing pump 12 flows into the low-temperature tank 5 through the ninth valve 22, while the other portion enters the electric heater 9 for heating and then flows back into the salt-absorbing tank 13. The amount of solid salt added to the salt-absorbing tank 13 is approximately equal to the amount flowing into the low-temperature tank 5. Alternatively, the third valve 10 can be opened and its opening adjusted. A portion of the molten salt from the outlet of the electric heater 9 flows back into the salt-absorbing tank 13 through the fourth valve 15, while the other portion flows into the high-temperature tank 1 through the third valve 10. The amount of solid salt added to the salt-absorbing tank 13 is approximately equal to the amount flowing into the high-temperature tank 1. This process continues until the salt-dissolving process is complete.

[0032] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Various other combinations, modifications, and environments are possible, and modifications can be made within the scope of the concept described herein through the above teachings or related field techniques or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A molten salt system with preheating and salt dissolving functions, characterized in that, It includes high-temperature equipment, low-temperature equipment, salt-removing equipment, electric heater (9), centrifugal fan (18) and molten salt hot air heater (19); the outlet of the high-temperature equipment is connected to the inlet of the low-temperature equipment; the outlet of the low-temperature equipment and the outlet of the salt-removing equipment are combined into one line and connected to the inlet of the electric heater (9); The outlet of the electric heater (9) is connected to the inlet of the desalination equipment via a pipe; the outlet of the centrifugal fan (18) is connected to the air inlet of the molten salt hot air blower (19); the air outlet of the molten salt hot air blower (19) is connected to the inlet of the high-temperature equipment and the inlet of the low-temperature equipment respectively; the molten salt outlet of the molten salt hot air blower (19) is connected to the desalination equipment. The high-temperature equipment includes a high-temperature tank (1), a high-temperature pump (2), a steam generator (3), and a high-temperature tank liquid distribution ring (11); the high-temperature pump (2) is installed above the high-temperature tank (1), and the outlet of the high-temperature pump (2) is connected to the steam generator (3) and the inlet of the low-temperature equipment in sequence; the high-temperature tank liquid distribution ring (11) is set at the bottom of the high-temperature tank (1), and the inlet of the high-temperature tank liquid distribution ring (11) is connected to the air outlet of the molten salt hot air heater (19) and the outlet of the electric heater (9) respectively; The cryogenic equipment includes a cryogenic tank (5), a cryogenic tank distribution ring (6), and a cryogenic pump (7); the cryogenic tank distribution ring (6) is located at the bottom of the cryogenic tank (5); the cryogenic pump (7) is installed above the cryogenic tank (5); the inlet of the cryogenic tank distribution ring (6) is connected to the steam generator (3); the outlet of the cryogenic pump (7) is connected to the inlet of the electric heater (9); The salt-removing device includes a salt-removing pump (12), a salt-removing tank (13), and an auxiliary electric heater (14); the salt-removing pump (12) and the auxiliary electric heater (14) are installed above the salt-removing tank (13); the outlet of the salt-removing pump (12) is connected to the inlet of the electric heater (9) and the low-temperature tank (5) respectively; the outlet of the electric heater (9) is connected to the salt-removing tank (13).

2. The molten salt system with preheating and salt dissolving functions according to claim 1, characterized in that, It also includes multiple control valves installed on the connecting pipes.

3. A molten salt method, employing a molten salt system with preheating and salt-dissolving functions as described in any one of claims 1 to 2, characterized in that, It includes normal working mode, preheating mode and salt dissolving mode.

4. The molten salt method according to claim 3, characterized in that, The normal working mode specifically includes the following steps: During the peak electricity consumption period, high-temperature molten salt is transported to the steam generator (3) through the high-temperature pump (2). The molten salt releases heat, the temperature decreases, and steam is generated. The generated steam is used to increase the grid power of the coal-fired power unit. Low-temperature molten salt flows through the low-temperature tank distribution ring (6) and enters the low-temperature tank (5) evenly. During periods of low electricity demand, the low-temperature molten salt is transported to the electric heater (9) via the low-temperature pump (7). The molten salt is heated by the conversion of electrical energy into heat to reduce the grid power of the coal-fired power unit. After the temperature of the molten salt rises, it is evenly fed into the high-temperature tank (1) via the liquid distribution ring (11). When the equipment or pipeline needs to discharge salt, the molten salt is discharged to the salt discharge tank (13), and then the salt discharge pump (12) is used to transport the molten salt to the low-temperature tank (5).

5. The molten salt method according to claim 3, characterized in that, The preheating mode specifically includes the following steps: Add solid salt to the salt-absorbing tank (13) until it covers the heating tube of the auxiliary electric heater (14). Turn on the auxiliary electric heater (14) to heat the solid salt until it is completely melted into liquid. Turn off the auxiliary electric heater (14), turn on the electric heater (9) and the centrifugal fan (18), and use the salt-absorbing pump (12) to transport the liquid molten salt to the electric heater (9) to increase the temperature. The high-temperature molten salt enters the molten salt hot air blower (19). The compressed air generated by the centrifugal fan (18) absorbs the heat of the molten salt and its temperature rises. At this time, the high-temperature tank (1) and the low-temperature tank (5) are preheated. During the preheating process, the outlet air temperature of the molten salt hot air blower (19) gradually rises from room temperature to the working temperature of the molten salt. The air temperature rises with the increase of the power of the electric heater (9).

6. The molten salt method according to claim 3, characterized in that, The salt-dissolving mode specifically includes the following steps: adding solid salt to the salt-dissolving tank (13) until it covers the heating element of the auxiliary electric heater (14), turning on the auxiliary electric heater (14) to heat the solid salt until it is completely melted into a liquid state, turning off the auxiliary electric heater (14) and turning on the electric heater (9), using the salt-dissolving pump (12) to transport the liquid molten salt to the electric heater (9) to raise the temperature and then flow back to the salt-dissolving tank (13) until the overall temperature of the salt-dissolving tank (13) reaches the salt-dissolving requirement; at this time, continuously adding solid salt to the salt-dissolving tank (13) 13) Solid inorganic salt is added. A portion of the molten salt from the outlet of the salt-absorbing pump (12) flows into the low-temperature tank (5), and another portion of the molten salt enters the electric heater (9) to heat up and then flows back to the salt-absorbing tank (13). The amount of solid salt added to the salt-absorbing tank (13) is basically equal to the amount of salt flowing into the low-temperature tank (5). A portion of the molten salt from the outlet of the electric heater (9) flows back to the salt-absorbing tank (13), and another portion of the molten salt flows into the high-temperature tank (1). The amount of solid salt added to the salt-absorbing tank (13) is equal to the amount of salt flowing into the high-temperature tank (1) until the salt-absorbing process is completed.

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