Anti-crystallization purging system and method for fused salt heater

Abstract

The invention relates to the technical field of molten salt heaters, and discloses an anti-crystallization purging system and method for a molten salt heater, the anti-crystallization purging system comprises a purging unit and a salt discharging unit, the purging unit is provided with a nozzle capable of spraying high-temperature inert gas, and the nozzle is used for spraying the high-temperature inert gas into the heater; the high-temperature inert gas is used for disturbing and pushing the residual fused salt; the salt discharging unit is arranged at the low point of the heater, and the high-temperature inert gas purges the residual fused salt to the salt discharging unit and discharges the residual fused salt through the salt discharging unit; the blowing unit and the salt discharging unit are integrated on the fused salt heater, physical emptying of fused salt in the fused salt heater can be achieved, temperature maintaining is not needed, and the material basis of crystallization is fundamentally eliminated. High-temperature inert gas is introduced into the heater body, so that the residual fused salt is pushed and disturbed.

Description

Technical Field

[0001] This invention relates to the field of molten salt heater technology, and in particular to an anti-crystallization purging system and method for molten salt heaters. Background Technology

[0002] With the rapid development of the new energy industry, photovoltaic power generation, as an important form of clean and renewable energy utilization, has made technological breakthroughs in its energy storage segment crucial for improving energy efficiency. Molten salt energy storage, due to its advantages such as high energy density, strong stability, and long cycle life, has become one of the core technology solutions for large-scale energy storage in photovoltaic power generation systems. In molten salt energy storage systems, the initial temperature of the molten salt in the cold salt tank is typically maintained at 280℃. To meet the energy level requirements for energy storage and release, the molten salt temperature needs to be gradually increased to 565℃ through multi-stage molten salt heaters. This heating process generally requires 4-8 stages of molten salt heating units operating in tandem. However, after shutdown, due to factors such as the complex internal flow channel structure, dense arrangement of heating rods, and structural dead corners at the bottom of the equipment, some liquid molten salt is easily left inside the heater. This problem is particularly pronounced in the primary molten salt heater (stages 1-2). As the starting point of the entire heating chain, the operating status of the primary molten salt heater directly determines the operational stability of subsequent heating units and the energy efficiency level of the entire energy storage system. The remaining molten salt will gradually cool as the ambient temperature decreases. When the temperature drops below the molten salt's freezing point (approximately 240°C), it will rapidly solidify and crystallize. The volume change after solidification not only directly causes flow channel blockage but also leads to equipment malfunctions such as heating rod damage and heating tube rupture due to crystallization stress squeezing the heating tubes. In severe cases, it can even prevent the entire molten salt heating system from restarting normally, significantly impacting the continuous operation and reliability of the molten salt energy storage system. To address the aforementioned problem of residual molten salt solidification and blockage, the commonly used solution in existing technologies is to continuously operate some heaters after system shutdown to maintain the internal temperature of the equipment, waiting for the residual molten salt to flow back to the cold salt tank. However, practice has shown that this traditional solution has several significant drawbacks: First, the heat preservation effect of the heaters operating continuously at low power is limited, making it difficult to effectively return residual molten salt in dead corners of the flow channel and at the bottom of the equipment, resulting in minimal anti-blockage effect; Second, frequent start-ups and shutdowns and continuous low-load operation of the heaters when not in operation will accelerate the aging and wear of the heating elements, significantly reducing the overall service life of the heaters; Third, the large amount of electrical energy consumed to maintain the temperature cannot be converted into effective energy storage, resulting in serious energy waste and increasing the operating cost of the molten salt energy storage system, which contradicts the original intention of energy conservation and emission reduction in the utilization of new energy sources. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an anti-crystallization purging system and method for molten salt heaters. By integrating a purging unit and a salt discharge unit on the molten salt heater, the physical evacuation of molten salt inside the heater can be achieved, rather than temperature maintenance, thus fundamentally eliminating the material basis for crystallization.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, an anti-crystallization purging system for a molten salt heater includes: The purging unit is equipped with a nozzle that can spray high-temperature inert gas into the heater, thereby disturbing and pushing the residual molten salt. The salt removal unit is located at the lowest point of the heater. High-temperature inert gas is used to purge residual molten salt to the salt removal unit, where it is discharged.

[0005] As a further implementation, the purging unit includes a high-temperature inert gas reservoir, which is installed at the end of the heater.

[0006] As a further implementation, the high-temperature inert gas reservoir is arranged in a ring shape and is coaxially arranged with each stage heater.

[0007] As a further implementation, the high-temperature inert gas reservoir is provided with multiple sets of nozzles along the circumferential direction, with the nozzle outlets extending into the heater.

[0008] As a further implementation, the nozzle is equipped with a jet solenoid valve.

[0009] As a further implementation, the high-temperature inert gas reservoir is equipped with an air inlet, and an air inlet valve and a pressure sensor are provided at the air inlet.

[0010] As a further implementation, a controller and a temperature sensor are also included, with the temperature sensor located on the high-temperature inert gas reservoir to monitor the temperature of the high-temperature inert gas.

[0011] As a further implementation, the salt discharge unit includes an arc-shaped molten salt discharge pipe, and the molten salt discharge pipe is equipped with a molten salt discharge valve.

[0012] As a further implementation, the molten salt heater is set up in four stages, and each stage heater is equipped with a high-temperature inert gas chamber.

[0013] Secondly, a method for preventing crystallization purging in a molten salt heater includes the following steps: After the molten salt heater is shut down, the controller receives a signal and starts the anti-crystallization program; high-temperature inert gas enters the high-temperature inert gas chamber, and the high-temperature inert gas chamber sprays the high-temperature inert gas into the heater through the nozzle, which disturbs and pushes the residual molten salt. The molten salt discharge valve on the molten salt discharge pipe of the salt discharge unit is opened. Under the action of high-temperature inert gas, the liquid molten salt flows back to the molten salt discharge pipe and then flows into the salt discharge pipeline back to the storage tank. At the same time, the high-temperature inert gas replaces the atmosphere inside the heater. By adjusting the temperature and pressure of the inert gas and determining a reasonable purging time, the heater is finally sealed in a dry and oxygen-free environment, waiting for the next start-up.

[0014] The beneficial effects of the present invention are as follows: 1. This invention integrates a purging unit and a salt removal unit into a molten salt heater, enabling the physical evacuation of molten salt from the heater rather than temperature maintenance, thus fundamentally eliminating the material basis for crystallization. By introducing high-temperature inert gas into the heater body, the residual molten salt is pushed and disturbed.

[0015] 2. This invention can replace the internal atmosphere of the heater with inert gas, avoiding various operational risks caused by crystallization. At the same time, the inert gas purging inhibits internal corrosion. Compared with the heat tracing system with continuous power supply, it is only used briefly when the heater is stopped, which significantly reduces energy consumption and extends the service life of the heater. It can be linked with the controller to realize one-button safe shutdown, reduce human operation errors, and has a high degree of automation. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a front view of the anti-crystallization purging system in an embodiment of the present invention; Figure 2 This is a side view of the anti-crystallization purging system in an embodiment of the present invention.

[0018] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0019] Among them: 10. Heater body, 101. Electric heating tube; 1. Primary heater, 2. Secondary heater, 3. Tertiary heater, 4. Quaternary heater; 5. High temperature inert gas tank, 51. Air inlet, 52. Nozzle, 53. Jet solenoid valve, 6. Molten salt discharge pipe, 7. Molten salt discharge valve, 8. Pipeline. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] Example 1 In a typical embodiment of the present invention, reference is made to Figure 1 As shown, an anti-crystallization purging system for a molten salt heater includes a purging unit and a salt discharge unit. The purging unit is used to purge the liquid molten salt in the molten salt heater after shutdown, purging the molten salt to the salt discharge unit, and then discharging it from the molten salt heater through the salt discharge unit.

[0022] The purging unit is equipped with a nozzle 52 that can spray high-temperature inert gas into the heater, thereby disturbing and pushing the residual molten salt. The salt discharge unit is located at the lowest point of the heater. The high-temperature inert gas purges the residual molten salt to the salt discharge unit and discharges it through the salt discharge unit.

[0023] like Figure 1 As shown, the purging unit includes a high-temperature inert gas reservoir, which is installed at the end of the heater (heater body 10). The heater body 10 is equipped with an electric heating tube 101 for heating.

[0024] The high-temperature inert gas reservoir 5 is arranged in a ring shape with an opening in the middle. The interior of the high-temperature inert gas reservoir 5 is sealed. It has an air inlet 51, and an air inlet valve and a pressure sensor are provided at the air inlet 51. The pressure sensor can detect the inert gas pressure and determine whether the gas supply system should continue to inject gas into the high-temperature inert gas reservoir 5 based on the pressure.

[0025] like Figure 1 As shown, each high-temperature inert gas reservoir 5 is coaxially arranged with each stage heater. Multiple sets of nozzles 52 are arranged circumferentially around the high-temperature inert gas reservoir 5. The nozzles 52 extend into the heater body and are equipped with jet solenoid valves 53. After the jet solenoid valves 53 are opened, the nozzles 52 can jet the high-temperature inert gas from the high-temperature inert gas reservoir into the heater body 10.

[0026] Preferably, the axis of the nozzle 52 is parallel to the axis of the heater body 10 to ensure the purging effect.

[0027] like Figure 1 and Figure 2 As shown, the molten salt heater in this embodiment is a four-stage molten salt heater, which includes a primary heater 1, a secondary heater 2, a tertiary heater 3 and a quaternary heater 4, and the heaters are connected to each other through a pipeline 8.

[0028] In an optional example, a high-temperature inert gas reservoir is provided on each of the primary heater 1, the secondary heater 2, the tertiary heater 3, and the quaternary heater 4. Figure 1 In this design, the high-temperature inert gas chamber on the secondary heater 2 is located at the right end of the secondary heater 2, and the high-temperature inert gas chamber on the primary heater 1 is located at the left end of the primary heater 1. The direction of the gas ejected from the high-temperature inert gas chamber on each stage of the heater is opposite to the direction of movement of the molten salt inside the heater. Similarly, the tertiary heater 3 and the quaternary heater 4 are also equipped with corresponding high-temperature inert gas chambers, so that the molten salt can flow back after the gas is ejected.

[0029] In other examples, high-temperature inert gas reservoirs are provided on the primary heater 1 and the secondary heater 2, but not on the tertiary heater 3 and the quaternary heater 4. This is because the temperature level of the molten salt in the tertiary heater 3 and the quaternary heater 4 is much higher than that in the primary heater 1 and the secondary heater 2. After shutdown, most of the molten salt remains in the primary heaters (primary heater 1 and secondary heater 2). Therefore, it is acceptable not to provide high-temperature inert gas reservoirs for the tertiary heater 3 and the quaternary heater 4.

[0030] The salt discharge unit includes an arc-shaped molten salt discharge pipe 6, which is equipped with a molten salt discharge valve 7. The molten salt discharge pipe 6 is connected to the heater. When the molten salt is pushed to this point by the inert gas, the molten salt discharge valve 7 opens, and the molten salt can flow out of the heater along the molten salt discharge pipe 6.

[0031] It also includes a controller and a temperature sensor. The temperature sensor is located at both ends of the outer wall of the heater to monitor the temperature of the hot gas. A temperature sensor is also installed on the high-temperature inert gas to monitor the temperature of the ejected high-temperature inert gas. The controller can control the purging unit and the salt removal unit.

[0032] In this embodiment, the salt discharge unit is provided on the primary heater 1 and the tertiary heater 3. The molten salt in the primary heater 1 and the secondary heater 2 is discharged from the salt discharge unit on the primary heater 1, and the molten salt in the tertiary heater 3 and the quaternary heater 4 is discharged from the salt discharge unit on the tertiary heater 3.

[0033] After the molten salt heater finishes heating, the controller opens the jet solenoid valve 53, activating the purging unit. Using a high-temperature inert gas (such as nitrogen) as power, a directional airflow is formed. This airflow provides pressure to push the liquid molten salt out of the flow channel and out of the salt discharge unit. Furthermore, after purging, it replaces the internal atmosphere, preventing air and moisture from entering and providing corrosion protection.

[0034] The molten salt drain pipe 6 is set in an arc shape to ensure that the molten salt can be completely collected and discharged by gravity. The molten salt drain pipe 6 is located at the lowest point of the heater, which ensures that there is no dead flow zone and achieves "self-draining".

[0035] It is understandable that the temperature of the inert gas is 305-315℃, which can reduce the viscosity of the molten salt solution, preferably 310℃.

[0036] Example 2 like Figure 1 and Figure 2 As shown, an anti-crystallization purging method for a molten salt heater, employing any of the aforementioned anti-crystallization purging systems, includes the following steps: After the molten salt heater stops, the controller receives a signal and initiates the anti-crystallization program, controlling the opening of the air inlet valve and the jet solenoid valve 53. High-temperature inert gas enters the high-temperature inert gas reservoir 5 through the air inlet 51. The high-temperature inert gas reservoir 5 sprays the high-temperature inert gas into the heater through the nozzle 52, disturbing and pushing the residual molten salt. The residual molten salt in the secondary heater 2 flows into the primary heater 1, and the residual molten salt in the quaternary heater 4 flows into the tertiary heater 3. The molten salt discharge valve on the molten salt discharge pipe of the salt discharge unit opens, and under the action of the high-temperature inert gas, the liquid molten salt flows back to the molten salt discharge pipe 6, and then flows into the salt discharge pipeline back to the storage tank. At the same time, the high-temperature inert gas replaces the internal atmosphere of the heater. By adjusting the inert gas temperature and pressure and determining a reasonable purging time, the heater is finally sealed in a dry and oxygen-free environment, waiting for the next start-up.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A purging system for preventing crystallization in a molten salt heater, characterized in that, include: The purging unit is equipped with a nozzle that can spray high-temperature inert gas into the heater, thereby disturbing and pushing the residual molten salt. The salt removal unit is located at the lowest point of the heater. High-temperature inert gas is used to purge residual molten salt to the salt removal unit, where it is discharged.

2. The anti-crystallization purging system for a molten salt heater according to claim 1, characterized in that, The purging unit includes a high-temperature inert gas reservoir, which is installed at the end of the heater.

3. The anti-crystallization purging system for a molten salt heater according to claim 2, characterized in that, The high-temperature inert gas reservoir is arranged in a ring shape and is coaxial with each stage heater.

4. The anti-crystallization purging system for a molten salt heater according to claim 3, characterized in that, The high-temperature inert gas chamber is provided with multiple sets of nozzles along the circumference, and the nozzle outlets extend into the heater.

5. The anti-crystallization purging system for a molten salt heater according to claim 4, characterized in that, The nozzle is equipped with a jet solenoid valve.

6. The anti-crystallization purging system for a molten salt heater according to claim 2, characterized in that, The high-temperature inert gas reservoir is equipped with an air inlet, and an air inlet valve and a pressure sensor are provided at the air inlet.

7. A purging system for preventing crystallization in a molten salt heater according to any one of claims 2-6, characterized in that, It also includes a controller and a temperature sensor, with the temperature sensor located on the high-temperature inert gas reservoir to monitor the temperature of the high-temperature inert gas.

8. The anti-crystallization purging system for a molten salt heater according to claim 1, characterized in that, The salt discharge unit includes an arc-shaped molten salt discharge pipe, which is equipped with a molten salt discharge valve.

9. A purging system for preventing crystallization in a molten salt heater according to claim 1, characterized in that, The molten salt heater has four stages, and each stage is equipped with a high-temperature inert gas chamber.

10. A method for preventing crystallization by purging in a molten salt heater, characterized in that, The anti-crystallization purging system as described in any one of claims 2-9 includes the following steps: After the molten salt heater is shut down, the controller receives a signal and starts the anti-crystallization program; high-temperature inert gas enters the high-temperature inert gas chamber, and the high-temperature inert gas chamber sprays the high-temperature inert gas into the heater through the nozzle, which disturbs and pushes the residual molten salt. The molten salt discharge valve on the molten salt discharge pipe of the salt discharge unit is opened. Under the action of high-temperature inert gas, the liquid molten salt flows back to the molten salt discharge pipe and then flows into the salt discharge pipeline back to the storage tank. At the same time, the high-temperature inert gas replaces the atmosphere inside the heater. By adjusting the temperature and pressure of the inert gas and determining a reasonable purging time, the heater is finally sealed in a dry and oxygen-free environment, waiting for the next start-up.

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