High-low position integrated molten salt tank

Abstract

The invention relates to a molten salt tank and discloses a high-low position integrated molten salt tank which comprises a vertical molten salt storage tank and a low molten salt storage tank which are connected into a whole, the low molten salt storage tank is located on one side of the bottom of the vertical molten salt storage tank, and a molten salt inlet and a breathing opening are formed in the top of the vertical molten salt storage tank; a short shaft pump is mounted at the top of the low-position fused salt storage tank, and an outlet of the short shaft pump is connected with a fused salt conveying pipeline; and a communicating pipe is arranged between the top of the vertical molten salt storage tank and the top of the low-position molten salt storage tank. According to the molten salt tank, the short-shaft pump is used, the vibration problem caused by a long-shaft pump can be avoided, meanwhile, the lowest liquid level of molten salt can be lowered, the dead zone of the molten salt is reduced, the consumption of the molten salt is reduced, and the cost is saved; the molten salt is driven by gravity to flow, the complex and potential unreliable siphoning effect is replaced, system operation does not depend on precise control and external force any more, safety and reliability are achieved, and the situations that flow adjustment is difficult and siphoning fails due to the fact that a siphon pipeline changes along with the liquid level in a tank are avoided.

Description

Technical Field

[0001] This invention relates to a molten salt tank, and more particularly to a high-low integrated molten salt tank. Background Technology

[0002] Currently, large-scale tower solar thermal power plants typically employ a set of low-temperature (290℃) and high-temperature (565℃) vertical molten salt storage tanks for heat storage. The sidewall height of these vertical molten salt tanks generally does not exceed 15m, with the highest molten salt level at 12-13m and the lowest at 0.9m. The design of the lowest molten salt level needs to consider cavitation of the molten salt pump. The lowest level must ensure that cavitation does not occur in the molten salt pump within 10-15 minutes after a low-level alarm is triggered. This requires the liquid level to be sufficiently high, maintaining adequate static pressure head. Therefore, under current minimum molten salt level conditions, a molten salt dead zone is easily created, increasing the cost of molten salt usage.

[0003] Molten salt pumps are positioned above molten salt storage tanks. Large tower-type solar thermal power plants generally use long-shaft vertical molten salt pumps, with pump body lengths typically around 18 meters. However, long-shaft molten salt pumps present significant challenges in material selection, shaft stability, and sealing reliability. Furthermore, molten salt pumps operate at high temperatures for extended periods and are inherently prone to vibration, leading to bearing wear and impacting pump output. These inherent problems—high vibration, poor reliability, and difficult maintenance—significantly affect the operational reliability of solar thermal units and limit the widespread adoption of solar thermal technology.

[0004] To address this problem, existing technologies have proposed improved solutions. For example, patent CN202223272984.8 discloses a system that uses a siphon to connect a large-capacity storage tank and a small-capacity supply tank. While this avoids the need for a long-shaft pump, the siphon is a short-distance direct connection. The siphon effect relies on the natural height difference between the liquid levels in the two tanks, and the flow rate within the siphon is affected by this difference, requiring frequent adjustments to the electric regulating valve. This results in large flow fluctuations within the siphon and makes flow regulation difficult. Furthermore, this solution requires large holes or large-diameter valves to be installed at the bottom of the side wall of the large vertical storage tank, posing significant risks of molten salt leakage and freezing. Therefore, there is an urgent need for a new type of molten salt tank that can completely avoid the need for a long-shaft pump, further reduce the minimum liquid level, and possess extremely high operational reliability. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides an integrated high and low level molten salt tank, which can avoid the vibration problems caused by long-shaft pumps by using a short-shaft pump, and at the same time reduce the minimum liquid level of molten salt, reduce the dead zone of molten salt, reduce the amount of molten salt used, and save costs.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A high-low level integrated molten salt tank includes a vertical molten salt storage tank and a low-level molten salt storage tank connected as one unit. The low-level molten salt storage tank is located on one side of the bottom of the vertical molten salt storage tank. A molten salt inlet and a vent are provided at the top of the vertical molten salt storage tank. A short-shaft pump is installed at the top of the low-level molten salt storage tank, and the outlet of the short-shaft pump is connected to a molten salt delivery pipeline. A connecting pipe is provided between the top of the vertical molten salt storage tank and the top of the low-level molten salt storage tank.

[0007] In the above scheme, a molten salt inlet pipe is installed inside the molten salt inlet, extending into the bottom of the vertical molten salt storage tank. The bottom of the molten salt inlet pipe is connected to an annular distribution pipe, and nozzles are evenly distributed on the annular distribution pipe.

[0008] In the above scheme, a breathing bend is installed on the breathing port, and the opening of the breathing bend faces downward.

[0009] In the above scheme, the molten salt conveying pipeline is connected to the tower-type heat absorber, and a branch pipeline is provided on the molten salt conveying pipeline to connect to the molten salt inlet.

[0010] In the above scheme, the vertical molten salt storage tank and the low-level molten salt storage tank are integrally welded together, the connection is a rounded transition structure, and several anti-fatigue ribs are symmetrically arranged on the outside of the connection.

[0011] In the above scheme, the vertical molten salt storage tank and the low-level molten salt storage tank are completely connected, or a partition is provided. The upper part of the partition has several evenly distributed flow holes, and the lower part of the partition has a rectangular opening.

[0012] In the above scheme, the cross-section of the vertical molten salt storage tank and the low-level molten salt storage tank is circular, square, or rectangular.

[0013] In the above scheme, the vertical molten salt storage tank has a height of 15m, and the low-level molten salt storage tank has a height of 3m.

[0014] In a further technical solution, when the cross-section of the vertical molten salt storage tank and the low-level molten salt storage tank is circular, the diameter of the vertical molten salt storage tank is 20m~50m, and the diameter of the low-level molten salt storage tank is 3m.

[0015] In the above scheme, the vertical molten salt storage tank and the low-level molten salt storage tank are provided with a base at the bottom.

[0016] Through the above technical solution, the high and low level integrated molten salt tank provided by the present invention has the following beneficial effects: 1. This invention avoids the use of long-shaft pumps through an integrated design and adopts a short-shaft pump. The length of the entire pump body is generally 4-5 meters, which fundamentally eliminates the vibration, wear and maintenance problems caused by long-shaft pumps and significantly improves the reliability of the system. 2. The minimum operating liquid level that a short-shaft molten salt pump can achieve is much lower than that of a long-shaft molten salt pump of the same class. This invention, by using a short-shaft pump, can lower the minimum molten salt level, reduce the dead zone in the molten salt, reduce the amount of molten salt used, and save costs. 3. The integrated design of this invention avoids the need to open large holes or install large-diameter valves at the bottom of the side wall of large vertical storage tanks, fundamentally eliminating a major risk point of molten salt leakage. 4. This invention utilizes gravity to drive the flow of molten salt, replacing the complex and potentially unreliable siphon effect. This makes the system operation no longer dependent on precise control and external force, ensuring safety and reliability. It also avoids the difficulty of flow regulation caused by changes in the liquid level in the tank and the occurrence of siphon failure. 5. This invention achieves cost reduction and efficiency improvement through integrated design, realizing comprehensive cost reduction and energy efficiency improvement in terms of materials, installation, insulation, and land use; 6. The present invention reduces the heat dissipation area through integrated design, thereby reducing insulation costs and heat loss; at the same time, it eliminates the need for connecting pipes, supports and valves between tanks, simplifying the system and reducing construction and maintenance costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a schematic diagram of an integrated high and low level molten salt tank disclosed in an embodiment of the present invention; Figure 2 This is an enlarged schematic diagram of the connection between the vertical molten salt storage tank and the low-level molten salt storage tank. Figure 3 This is a schematic diagram of an anti-fatigue rib structure. Figure 4 This is a schematic diagram of the partition.

[0019] In the diagram, 1. Vertical molten salt storage tank; 2. Low-level molten salt storage tank; 3. Base; 4. Molten salt inlet pipe; 5. Annular distribution pipe; 6. Nozzle; 7. Breathing bend; 8. Short-shaft pump; 9. Molten salt delivery pipeline; 10. Tower-type heat absorber; 11. Branch pipeline; 12. Connecting pipe; 13. Arc transition structure; 14. Fatigue-resistant rib; 15. Connecting plate one; 16. Connecting plate two; 17. Rib; 18. Arc-shaped surface; 19. Baffle; 20. Flow hole; 21. Rectangular opening. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] This invention provides an integrated high and low level molten salt tank, such as... Figure 1As shown, it includes a vertical molten salt storage tank 1 and a low-level molten salt storage tank 2 that are connected as one unit. The bottom of the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 are provided with a base 3 for load-bearing and heat preservation.

[0022] The low-level molten salt storage tank 2 is located at the bottom of the vertical molten salt storage tank 1. The cross-sections of both the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 are circular, square, or rectangular. The height of the vertical molten salt storage tank 1 is 15m, and the height of the low-level molten salt storage tank 2 is 3m. When the cross-sections of both the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 are circular, the diameter of the vertical molten salt storage tank 1 is 20m~50m, and the diameter of the low-level molten salt storage tank 2 is 3m.

[0023] The vertical molten salt storage tank 1 has a molten salt inlet and a breather at the top. A molten salt inlet pipe 4 is installed inside the molten salt inlet, extending into the bottom of the vertical molten salt storage tank 1. The bottom of the molten salt inlet pipe 4 is connected to an annular distribution pipe 5, and nozzles 6 are evenly distributed on the annular distribution pipe 5. A breather bend 7 is installed on the breather, with its opening facing downwards. This serves two purposes: maintaining pressure balance inside the tank and preventing rainwater and other debris from entering the tank.

[0024] A short-shaft pump 8 is installed at the top of the low-level molten salt storage tank 2. The outlet of the short-shaft pump 8 is connected to the molten salt conveying pipeline 9. The molten salt conveying pipeline 9 is connected to the tower-type heat absorber 10, and a branch pipeline 11 is set on the molten salt conveying pipeline 9 to connect to the molten salt inlet. When the molten salt in the vertical molten salt storage tank 1 remains stagnant for a long time, the high-temperature molten salt will generate a large temperature gradient, which will generate large thermal stress on the tank body and affect the safety of the tank body. Therefore, it is necessary to re-inject the molten salt into the vertical molten salt storage tank 1 to make the molten salt flow, establish self-circulation, and reduce the temperature gradient in the vertical molten salt storage tank 1.

[0025] A connecting pipe 12 is installed between the top of the vertical molten salt storage tank 1 and the top of the low-level molten salt storage tank 2 to maintain pressure balance between them. The connecting pipe 12 is made of the same material as the tank body and is heated by electric heat tracing. The outer layer is an insulation layer to prevent the internal molten salt from solidifying. When the molten salt is at a low level, as the liquid level rises, air is forced out through the connecting pipe 12, keeping the top of the low-level molten salt storage tank 2 air-free. As the liquid level continues to rise, the liquid level in the connecting pipe 12 remains the same as the liquid level in the vertical molten salt storage tank 1. When the liquid level drops from a high level, the liquid level in the connecting pipe 12 also remains the same as the liquid level in the vertical molten salt storage tank 1. When the liquid level continues to drop, there is no liquid in the connecting pipe, and the liquid levels in the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 remain the same.

[0026] The vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 are integrally welded together. Taking the vertical molten salt storage tank 1 with a circular cross-section and the low-level molten salt storage tank 2 with a rectangular cross-section as an example, ... Figure 2 As shown, the connection is a circular arc transition structure 13 to optimize stress distribution and prevent thermal stress concentration from causing cracking.

[0027] Due to the difference in molten salt level and temperature between the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2, the integrated structure will generate complex structural thermal stress. Therefore, a local reinforcement design was implemented in the connection area, and several anti-fatigue ribs 14 were symmetrically arranged on the outer side of the connection to effectively suppress thermal stress fatigue caused by the difference in liquid level / temperature between the two tanks. Figure 3 As shown, the fatigue-resistant rib 14 includes a first connecting plate 15 and a second connecting plate 16, which are respectively connected to the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2. The first connecting plate 15 and the second connecting plate 16 are arc-shaped or flat to fit the shapes of the vertical molten salt storage tank 1 and the low-level molten salt storage tank 2. Several ribs 17 are connected between the first connecting plate 15 and the second connecting plate 16 to strengthen the structure and reduce local deformation. The inner side of the middle of the rib 17 is an arc-shaped surface 18, which is adapted to the arc transition structure 13.

[0028] The vertical molten salt storage tank 1 and the low-level molten salt storage tank 2 are completely connected, or a partition 19 is installed, such as... Figure 4 As shown, the upper part of the partition 19 has several evenly distributed large-diameter flow holes 20, and the lower part of the partition has a rectangular opening 21 for the balance and flow of molten salt.

[0029] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-low level integrated molten salt tank, characterized in that, The system includes a vertical molten salt storage tank and a low-level molten salt storage tank that are connected as one unit. The low-level molten salt storage tank is located on one side of the bottom of the vertical molten salt storage tank. The top of the vertical molten salt storage tank has a molten salt inlet and a vent. A short-shaft pump is installed on the top of the low-level molten salt storage tank, and the outlet of the short-shaft pump is connected to a molten salt delivery pipeline. A connecting pipe is provided between the top of the vertical molten salt storage tank and the top of the low-level molten salt storage tank.

2. The high-low level integrated molten salt tank according to claim 1, characterized in that, The molten salt inlet is equipped with a molten salt inlet pipe that extends into the bottom of the vertical molten salt storage tank. The bottom of the molten salt inlet pipe is connected to an annular distribution pipe, and nozzles are evenly distributed on the annular distribution pipe.

3. The high-low level integrated molten salt tank according to claim 1, characterized in that, A breathing bend is installed on the breathing port, with the opening of the breathing bend facing downwards.

4. The high-low level integrated molten salt tank according to claim 1, characterized in that, The molten salt delivery pipeline is connected to the tower-type heat absorber, and a branch pipeline is provided on the molten salt delivery pipeline to connect to the molten salt inlet.

5. The high-low level integrated molten salt tank according to claim 1, characterized in that, The vertical molten salt storage tank and the low-level molten salt storage tank are integrally welded together, with the connection being a rounded transition structure, and several anti-fatigue ribs are symmetrically arranged on the outside of the connection.

6. The high-low level integrated molten salt tank according to claim 1, characterized in that, The vertical molten salt storage tank and the low-level molten salt storage tank are completely connected, or a partition is provided. The upper part of the partition has several evenly distributed flow holes, and the lower part of the partition has a rectangular opening.

7. The high-low level integrated molten salt tank according to claim 1, characterized in that, The cross-section of the vertical molten salt storage tank and the low-level molten salt storage tank is circular, square, or rectangular.

8. The high-low level integrated molten salt tank according to claim 1, characterized in that, The vertical molten salt storage tank has a height of 15m, and the low-level molten salt storage tank has a height of 3m.

9. A high-low level integrated molten salt tank according to claim 7, characterized in that, When the cross-section of the vertical molten salt storage tank and the low-level molten salt storage tank is circular, the diameter of the vertical molten salt storage tank is 20m~50m, and the diameter of the low-level molten salt storage tank is 3m.

10. A high-low level integrated molten salt tank according to claim 1, characterized in that, The vertical molten salt storage tank and the low-level molten salt storage tank are equipped with bases at their bottoms.

Images