Molten salt heat storage energy-saving nitrogen sealing device

Abstract

The invention relates to a fused salt heat storage energy-saving type nitrogen sealing device, which is applied to a fused salt heat storage system comprising a cold fused salt tank, a hot fused salt tank and a salt dredging tank, and comprises a nitrogen balancing pipe, a nitrogen sealing device, a nitrogen sealing device, a nitrogen sealing device and a nitrogen sealing device, and is characterized in that the nitrogen balancing pipe is communicated with a top gas side space of the cold fused salt tank, the hot fused salt tank and the salt dredging tank; the breathing device is arranged on the nitrogen balance pipe, and the breathing device is configured to discharge gas in the nitrogen balance pipe when the internal pressure of the system exceeds a preset positive pressure threshold value and suck gas into the nitrogen balance pipe when the internal pressure of the system is lower than a preset negative pressure threshold value. According to the designed fused salt heat storage energy-saving nitrogen sealing device, the nitrogen balance pipe is used for communicating the gas side space of each storage tank, so that the pressure fluctuation in the system can be effectively buffered and balanced, the nitrogen loss caused by the volume change of fused salt is remarkably reduced, the supplement demand of external nitrogen is greatly reduced, and the nitrogen sealing efficiency is improved. Therefore, the nitrogen consumption of the fused salt heat storage system is greatly reduced, the operation cost is practically saved, and the economic benefit is improved.

Description

Technical Field

[0001] This invention relates to the field of molten salt energy storage technology, and in particular to a molten salt thermal energy storage energy-saving nitrogen sealing device. Background Technology

[0002] With the increasing demand for energy and growing environmental awareness, energy storage technology is being used more and more widely in power systems. Molten salt thermal energy storage technology, especially ternary salt-based molten salt thermal energy storage technology, has attracted much attention due to its high efficiency and economy. A typical molten salt thermal energy storage system usually includes multiple tanks such as cold molten salt tanks, hot molten salt tanks, and salt-repellent tanks, used to store and regulate the temperature of the molten salt during energy storage and release.

[0003] However, ternary molten salts often contain sodium nitrite, which readily reacts with oxygen in the air and oxidizes, altering the physical properties of the molten salt and consequently affecting its thermal storage efficiency and system lifespan. Therefore, inert gases (such as nitrogen) are needed to isolate and protect the molten salt to prevent oxidation.

[0004] In traditional designs, nitrogen replenishment systems typically supply nitrogen independently to hot salt tanks, cold molten salt tanks, and brine tanks to maintain internal pressure and isolate oxygen. Especially in large molten salt thermal power plants, the enormous tank volumes and the need for continuous nitrogen replenishment result in huge nitrogen consumption, leading to high operating costs and severely limiting the economic viability of molten salt thermal storage technology. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a molten salt thermal energy-saving nitrogen sealing device that significantly reduces nitrogen consumption and saves operating costs by constructing a nitrogen balance system and a breathing device.

[0006] To achieve the above objectives, the present invention designs an energy-saving nitrogen sealing device for molten salt thermal storage, applicable to a molten salt thermal storage system comprising a cold molten salt tank, a hot molten salt tank, and a salt-repellent tank, including: A nitrogen balance pipe connects the top gas-side space of the cold molten salt tank, the hot molten salt tank, and the salt-repellent tank; A breathing device is disposed on the nitrogen balance tube. The breathing device is configured to discharge gas from the nitrogen balance tube when the internal pressure of the system exceeds a preset positive pressure threshold, and to inhale gas into the nitrogen balance tube when the internal pressure of the system is lower than a preset negative pressure threshold. Wherein, the positive pressure threshold is less than the maximum design working pressure of the cold molten salt tank and the hot molten salt tank, and the negative pressure threshold is greater than the maximum design negative pressure of the cold molten salt tank and the hot molten salt tank.

[0007] Preferably, the system further includes a nitrogen replenishment pipe, which is connected to the nitrogen balance pipe for replenishing nitrogen to the molten salt thermal storage system, and the diameter of the nitrogen replenishment pipe is smaller than the diameter of the nitrogen balance pipe.

[0008] Preferably, the positive pressure threshold ranges from 2000 Pa to 4000 Pa; the negative pressure threshold ranges from -3000 Pa to -1000 Pa.

[0009] Preferably, the positive pressure threshold is 3000 Pa and the negative pressure threshold is -2000 Pa.

[0010] Preferably, the nitrogen balance pipe includes multiple branch pipes that are respectively connected to the top air-side space of the cold molten salt tank, the hot molten salt tank and the salt-repellent tank, and two breathing devices are provided in the nitrogen balance pipe, with the two breathing devices located between two adjacent branch pipes.

[0011] Preferably, the breathing device is a spring diaphragm breathing valve, and the top of the spring diaphragm breathing valve is provided with a rain cover.

[0012] Preferably, the molten salt is a ternary molten salt.

[0013] The molten salt thermal energy-saving nitrogen sealing device designed in this invention utilizes a nitrogen balance pipe to connect the gas-side space of each storage tank, effectively buffering and balancing internal pressure fluctuations. This significantly reduces nitrogen loss caused by changes in molten salt volume, greatly reducing the need for external nitrogen replenishment, thereby drastically reducing nitrogen consumption in the molten salt thermal storage system, effectively saving operating costs and improving economic efficiency. Simultaneously, the regulating function of the breathing device effectively controls internal pressure fluctuations within a preset safe range, avoiding potential risks to the tank structure caused by excessively high or low pressure, and significantly improving the operational safety and reliability of the molten salt thermal storage system. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the molten salt thermal energy-saving nitrogen sealing device provided in the embodiments of this application.

[0015] Figure 2 This is a schematic diagram of the structure of the breathing device provided in the embodiments of this application.

[0016] The system includes: 10 cold molten salt tanks, 20 hot molten salt tanks, 30 salt-removing tanks, 40 nitrogen balance tubes, 50 breathing devices, 51 rain covers, and 60 nitrogen replenishment tubes. Detailed Implementation

[0017] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0018] The molten salt thermal energy-saving nitrogen sealing device described in this embodiment is applied to a molten salt thermal storage system comprising a cold molten salt tank 10, a hot molten salt tank 20, and a salt-repellent tank 30, to provide energy storage support. The molten salt used in this embodiment is a ternary molten salt, with sodium nitrite, sodium nitrate, and potassium nitrate as its main components. Figure 1 , Figure 2 As shown, the device mainly includes a nitrogen balance tube 40 and a breathing device 50, which aims to reduce the oxidation caused by prolonged contact between sodium nitrite in the ternary molten salt and oxygen in the air, thus preventing changes in the physical properties of the ternary molten salt.

[0019] The nitrogen balance pipe 40 connects the top gas-side spaces of the cold molten salt tank 10, the hot molten salt tank 20, and the salt-repellent tank 30, forming a gas-side connected system. Thus, when molten salt is transferred between the cold molten salt tank 10 and the hot molten salt tank 20, for example, when molten salt is pumped from the cold molten salt tank 10 to the hot molten salt tank 20, the volume of the gas-side space in the cold molten salt tank 10 increases, while the volume of the gas-side space in the hot molten salt tank 20 decreases. Due to the connection effect of the nitrogen balance pipe 40, the decrease in pressure in the gas-side space of the cold molten salt tank 10 and the increase in pressure in the gas-side space of the hot molten salt tank 20 can cancel each other out and balance each other, making the gas-side pressure of the entire molten salt thermal storage system tend to stabilize and reducing pressure fluctuations within the system.

[0020] A breathing device 50 is mounted on the nitrogen balance pipe 40, as shown in Figure 2. In this embodiment, the breathing device 50 preferably adopts a spring diaphragm type breathing valve. The breathing device 50 is configured to discharge gas, such as excess nitrogen, from the nitrogen balance pipe 40 when the internal pressure of the system exceeds a preset positive pressure threshold, in order to release excessive pressure and prevent the system from operating under overpressure; and to draw in gas into the nitrogen balance pipe 40 when the internal pressure of the system is lower than a preset negative pressure threshold, in order to compensate for the pressure drop caused by factors such as temperature decrease or molten salt volume contraction, and prevent the system from experiencing negative pressure. In other words, the breathing device 50 can reduce the emission of nitrogen into the external environment while ensuring the safety of the storage tank, ultimately achieving the effect of energy saving and consumption reduction.

[0021] To ensure the safe and reliable operation of the molten salt thermal storage system, the positive pressure threshold is lower than the maximum design working pressure of the cold molten salt tank 10 and the hot molten salt tank 20, ensuring that the system pressure will not exceed the safe pressure range of the tanks under any circumstances. Similarly, the negative pressure threshold is higher than the maximum design negative pressure of the cold molten salt tank 10 and the hot molten salt tank 20, to avoid excessively low negative pressure in the system, which could damage the tanks.

[0022] In some embodiments, to adapt to molten salt thermal storage systems of different scales and operating conditions, the positive pressure threshold can be adjusted according to actual needs, with a preferred range of 2000 Pa to 4000 Pa; the negative pressure threshold can also be adjusted similarly, with a preferred range of -3000 Pa to -1000 Pa. In one specific embodiment, the positive pressure threshold is set to 3000 Pa, and the negative pressure threshold is set to -2000 Pa. However, it should be emphasized that the above threshold ranges and specific values ​​are only examples. In practical applications, comprehensive consideration and adjustments should be made based on specific system design parameters, such as the volume of the cold molten salt tank 10, the hot molten salt tank 20, and the nitrogen balance pipe 40, the design pressure of the tanks, and the operating conditions, to ensure the safe and stable operation of the system and minimize nitrogen loss.

[0023] In some embodiments, such as Figure 1 As shown, the device also includes a nitrogen replenishment pipe 60, which is connected to the nitrogen balance pipe 40. This pipe is used to replenish nitrogen to the molten salt thermal storage system when necessary, compensating for nitrogen losses caused by minor leaks at interfaces, flanges, and other connection points during system operation. Since this nitrogen leakage is slow and continuous, frequent or high-flow-rate nitrogen replenishment is unnecessary. To achieve a smoother and more controllable nitrogen replenishment process and avoid severe local pressure shocks to the system's internal gas pressure caused by nitrogen replenishment, the diameter of the nitrogen replenishment pipe 60 is designed to be smaller than that of the nitrogen balance pipe 40 in this embodiment. This structure limits the nitrogen replenishment flow rate, allowing the replenished nitrogen to enter the system more gently. It also helps maintain the pressure balance of the entire system, preventing damage to the storage tank or other equipment caused by sudden pressure changes or direct contact of room-temperature nitrogen with the tank, thereby ensuring the safe and stable operation of the molten salt thermal storage system.

[0024] In some implementations, such as Figure 1 As shown, the nitrogen balance pipe 40 includes multiple branch pipes respectively connected to the top gas-side space of the cold molten salt tank 10, the hot molten salt tank 20, and the brine tank 30. Two breathing devices 50 are provided on the nitrogen balance pipe 40, each located between two adjacent branch pipes. This arrangement of two breathing devices 50 between adjacent branch pipes of the nitrogen balance pipe 40 allows the breathing devices to more sensitively sense pressure changes in different areas within the system and react promptly. For example, when the pressure in a storage tank abnormally rises, the nearby breathing device can open more quickly to release the pressure and prevent further pressure buildup.

[0025] In some embodiments, such as Figure 2As shown, a rain cover 51 is provided on the top of the spring diaphragm breather valve. The breather valve usually contains metal components such as springs, which are prone to corrosion if exposed to rainwater for a long time, affecting its sensitivity and service life. In this embodiment, the main function of the rain cover 51 is to prevent rainwater from entering the breather valve and to ensure the valve's sensitivity and reliability.

[0026] The molten salt thermal energy-saving nitrogen sealing device provided in this embodiment utilizes a nitrogen balance pipe to connect the gas-side space of each storage tank, which effectively buffers and balances the internal pressure fluctuations of the system. This significantly reduces nitrogen loss caused by changes in molten salt volume and greatly reduces the need for external nitrogen replenishment, thereby drastically reducing the nitrogen consumption of the molten salt thermal energy storage system, effectively saving operating costs and improving economic efficiency. At the same time, the regulating function of the breathing device can effectively control the internal pressure of the system within a preset safe range, avoiding potential risks to the tank structure caused by excessively high or low pressure, and significantly improving the operational safety and reliability of the molten salt thermal energy storage system.

[0027] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A molten salt thermal energy-saving nitrogen sealing device, applied to a molten salt thermal storage system comprising a cold molten salt tank, a hot molten salt tank, and a salt-removing tank, characterized in that, include: A nitrogen balance pipe connects the top gas-side space of the cold molten salt tank, the hot molten salt tank, and the salt-repellent tank; A breathing device is disposed on the nitrogen balance tube. The breathing device is configured to discharge gas from the nitrogen balance tube when the internal pressure of the system exceeds a preset positive pressure threshold, and to inhale gas into the nitrogen balance tube when the internal pressure of the system is lower than a preset negative pressure threshold. Wherein, the positive pressure threshold is less than the maximum design working pressure of the cold molten salt tank and the hot molten salt tank, and the negative pressure threshold is greater than the maximum design negative pressure of the cold molten salt tank and the hot molten salt tank.

2. The molten salt thermal energy-saving nitrogen sealing device according to claim 1, characterized in that, It also includes a nitrogen replenishment pipe, which is connected to the nitrogen balance pipe and is used to replenish nitrogen to the molten salt thermal storage system. The diameter of the nitrogen replenishment pipe is smaller than the diameter of the nitrogen balance pipe.

3. The molten salt thermal energy-saving nitrogen sealing device according to claim 1, characterized in that, The positive pressure threshold ranges from 2000 Pa to 4000 Pa; the negative pressure threshold ranges from -3000 Pa to -1000 Pa.

4. The molten salt thermal energy-saving nitrogen sealing device according to claim 3, characterized in that, The positive pressure threshold is 3000 Pa, and the negative pressure threshold is -2000 Pa.

5. The molten salt thermal energy-saving nitrogen sealing device according to claim 1, characterized in that, The nitrogen balance pipe includes multiple branch pipes that are respectively connected to the top air-side space of the cold molten salt tank, the hot molten salt tank and the salt-repellent tank. Two breathing devices are provided in the nitrogen balance pipe, and the two breathing devices are respectively located between two adjacent branch pipes.

6. The molten salt thermal energy-saving nitrogen sealing device according to claim 1, characterized in that, The breathing device is a spring diaphragm breathing valve, and the top of the spring diaphragm breathing valve is equipped with a rain cover.

7. The molten salt thermal energy-saving nitrogen sealing device according to claim 1, characterized in that, The molten salt is a ternary molten salt.

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