A molten salt storage tank bottom leakage guiding and safety monitoring device and method

Abstract

This invention relates to the field of safety monitoring technology for high-temperature molten salt storage tanks, and discloses a bottom leakage drainage and safety monitoring device and method for molten salt storage tanks. The device is integrally arranged within the bottom plate and foundation structure of the molten salt storage tank. By constructing a multi-layered structural system at the bottom of the tank that combines conductive leakage detection, anti-condensation heating, sand cushion layer drainage, and foundation settlement monitoring, comprehensive monitoring and graded alarms of leakage risk and structural safety status during the operation of the molten salt storage tank are achieved. The functional structures of this invention are mainly arranged within the foundation layer at the bottom of the tank, without altering the tank's structural form. Compared to invasive monitoring schemes or those requiring tank modifications, this invention has advantages such as lower engineering implementation difficulty, less impact on existing tank operation, and higher long-term operational stability, making it suitable for widespread application in existing solar thermal power plants.

Description

Technical Field

[0001] This invention relates to the field of safety monitoring technology for high-temperature molten salt storage tanks, and in particular to a device and method for bottom leakage drainage and safety monitoring of molten salt storage tanks. Background Technology

[0002] Concentrated solar power (CSP) converts solar energy into high-temperature heat energy through a concentrating solar collector system, which then generates steam via a heat exchanger to drive a turbine for power generation. Due to the diurnal cycle of solar irradiance and weather fluctuations, CSP plants typically employ a high-temperature molten salt thermal storage system as the core energy storage unit to improve unit output stability and grid integration capacity. A molten salt thermal storage system generally includes hot and cold molten salt tanks, molten salt pumps, heat exchangers, and associated piping. The hot and cold molten salt tanks are responsible for the large-capacity storage, distribution, and circulation of molten salt, and are crucial equipment for the safe and stable operation of the CSP plant.

[0003] High-temperature molten salt storage tanks operate under conditions of high temperature and large capacity for extended periods, with operating temperatures typically exceeding 500℃. During operation, these tanks not only bear the hydrostatic pressure of molten salt but are also subject to the combined effects of thermal expansion constraints, temperature shocks during start-up and shutdown, and long-term creep and fatigue. Simultaneously, the tank foundation and subgrade structure are affected by factors such as ambient temperature changes, groundwater conditions, differences in foundation bearing capacity, construction quality, and material aging, making them prone to uneven settlement or localized deformation. When abnormalities occur in the foundation or tank bottom structure, stress concentration can easily form in the tank bottom plate or circumferential weld area, inducing crack propagation and ultimately leading to molten salt leakage or spillage accidents.

[0004] If molten salt leaks, its high-temperature properties can wet and thermally damage the underlying insulation material, leading to decreased insulation performance, increased thermal conductivity of the foundation, and abnormal ground temperature.

[0005] Leakage can lead to a chain reaction of problems, such as cracking of the foundation structure and reduced load-bearing capacity, which in severe cases may cause the storage tank to shut down or even cause a safety accident. Therefore, during the operation of molten salt storage tanks, continuous monitoring, timely identification, and early warning of leakage risks and the safety status of the foundation structure are important technical requirements for the operation and maintenance management of concentrated solar power (CSP) plants.

[0006] Regarding the monitoring of bottom leaks in high-temperature molten salt storage tanks, existing technologies have yielded relevant research and application solutions. Invention patent CN 114554321 A discloses an array-based leak detection and prediction method for monitoring bottom leaks in high-temperature molten salt storage tanks. This method uses an array of temperature sensors arranged below the tank bottom plate to collect information on bottom temperature field changes, and combines this with a leak model to analyze temperature anomaly characteristics, thereby achieving the detection and location of bottom leaks in molten salt. This solution improves the automation level of leak detection to some extent and helps to achieve early identification of molten salt leaks. However, this technology mainly relies on temperature field changes as the judgment criterion, and the monitoring parameters are relatively singular, making it susceptible to changes in operating conditions and differences in the thermal conductivity of base materials, thus posing a risk of misjudgment or missed detection. Furthermore, this solution does not incorporate structural safety factors such as tank foundation settlement or structural deformation into a unified monitoring system, making it difficult to achieve a comprehensive assessment of structural risks before a leak occurs.

[0007] Furthermore, regarding the foundation load-bearing and insulation issues of molten salt storage tanks, invention patent CN 113297412 A discloses a foundation structure for supporting high-temperature molten salt storage tanks. This structure, through a combination of multi-layered load-bearing and insulation materials, improves the load-bearing capacity of the tank foundation and effectively reduces the thermal impact of high-temperature molten salt on the foundation, thereby improving the structural stability of the tank under long-term operating conditions. This solution has certain engineering application value in terms of foundation structural safety and thermal performance; however, its technical means mainly focus on the passive protection design of the foundation structure, lacking online safety monitoring and alarm devices for the tank's operation, and therefore cannot detect problems during operation.

[0008] Real-time identification of molten salt leaks or structural anomalies during the process makes it difficult to detect and address potential safety hazards in a timely manner.

[0009] In summary, existing technical solutions either focus on molten salt leak detection based on a single temperature parameter or on passive safety and insulation design of the foundation structure. They generally suffer from problems such as limited monitoring information dimensions, insufficient ability to identify minute leaks, incomplete molten salt drainage paths, and a lack of coordinated monitoring of foundation settlement and leak risks. Existing solutions struggle to comprehensively identify and uniformly alarm for leak and structural safety risks during tank operation, failing to meet the needs of long-term safe operation and refined maintenance management of high-temperature molten salt storage tanks.

[0010] Based on this, the present invention aims to provide a device and method for bottom leakage drainage and safety monitoring of molten salt storage tanks. By integrating leakage detection, drainage and foundation settlement monitoring structures at the bottom of the storage tank, the invention achieves coordinated monitoring and alarm of molten salt leakage risk and structural safety status, thereby improving the reliability and engineering applicability of high-temperature molten salt storage tank operation safety monitoring. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a device and method for bottom leakage drainage and safety monitoring of molten salt storage tanks.

[0012] This invention is achieved through the following technical solution:

[0013] A device and method for bottom leakage drainage and safety monitoring of molten salt storage tanks are disclosed. The device is arranged as a whole within the bottom plate and foundation structure of the molten salt storage tank. By constructing a multi-layer structure system at the bottom of the tank that combines conductive leakage detection, anti-condensation heating, sand cushion layer drainage, and foundation settlement monitoring, the device achieves comprehensive monitoring and graded alarm of leakage risk and structural safety status during the operation of the molten salt storage tank.

[0014] Structurally, from top to bottom, the bottom of the storage tank includes, in sequence, a tank bottom plate, a sand cushion layer, a leak-proof bottom plate, a refractory brick layer, a ceramsite insulation layer, and a dense concrete load-bearing layer. The sand cushion layer is located between the tank bottom plate and the leak-proof bottom plate. The leak-proof bottom plate, as the bottom functional integrated layer, contains conductive detection structures and resistance heating structures to identify and prevent condensation during molten salt leakage.

[0015] The sand cushion layer is composed of high-temperature resistant quartz sand, ceramic sand, or similar heat-resistant granular materials, with a preferred thickness of 50–150 mm. The upper surface of the sand cushion layer forms a micro-slope structure, preferably 0.5%–2%, and employs a "four-quadrant flow guiding structure." This means the central region of the sand cushion layer forms a cross-shaped micro-ridge structure, dividing the sand cushion layer into four independent quadrants, each gradually decreasing in elevation from the center to the outer edge. A drainage outlet is located at the outer edge of each quadrant, connected to a downwardly extending drainage channel. Through this structural design, when molten salt leaks and remains liquid on the surface of the sand cushion layer, the leaking molten salt can quickly flow to the drainage outlet in the corresponding quadrant under the influence of gravity and the slope. This not only achieves unpowered drainage but also allows for rapid location of the approximate location of the leak based on the location of the drainage outlet into which the molten salt enters.

[0016] A leak-proof base plate is positioned below the sand cushion layer, preferably 6–12 mm thick, and is made of high-temperature resistant metal plate or metal composite plate. It prevents molten salt from seeping down from the sand cushion layer and provides a stable working interface for leak detection and heating. A conductive strip is installed on the upper surface of the leak-proof base plate or in the detection area near the upper surface. The conductive strip is made of a high-temperature resistant and molten salt corrosion-resistant conductive material, preferably 316L stainless steel flat strip or nickel-based alloy strip, with a width preferably 10–30 mm and a thickness of 1–3 mm. The arrangement of the conductive strip corresponds to the four-quadrant structure of the sand cushion layer, including a continuous annular conductive strip along the outer edge of the leak-proof base plate and at least two mutually perpendicular radial conductive strips inside the base plate.

[0017] The intersections form a cross structure, thus dividing the detection area into four quadrants on the plane.

[0018] The working principle of conductive leakage detection is as follows: Under normal operating conditions, the area above the leak-proof base plate is dry or stably insulated, forming a stable electric field distribution between the conductive strips, and the equivalent resistance between adjacent conductive strips remains within a reference range. Let the detection voltage uij be applied between the i-th and j-th conductive strips, and the corresponding detection current be Iij, then its equivalent resistance is:

[0019]

[0020] When a small amount of molten salt leaks and seeps into the sand cushion layer, even if the leaked molten salt does not directly contact the conductive strips, it will still enter the electric field region between the conductive strips. The conductivity of the high-temperature molten salt and its alteration of the local dielectric electrical properties will cause a change in the electric field distribution between the conductive strips, resulting in a decrease in equivalent resistance or an increase in detection current. The system calculates the change in resistance as follows:

[0021]

[0022] in, The reference equivalent resistance. When Reaching 10% to 30%, or When the absolute change reaches 10² to 10⁴ Ω, the corresponding quadrant region is considered to have a risk of molten salt leakage. This detection method, based on the electric field coupling effect, can effectively identify leaks even if they occur in non-direct contact areas between conductive strips, thus avoiding detection blind spots.

[0023] A resistance heating wire, preferably made of high-temperature alloy, is installed inside the leak-proof base plate and laid in a serpentine or zoned pattern, with a spacing of 50–150 mm. A high-temperature insulating layer is placed between the resistance heating wire and the conductive strip to prevent the heating circuit from interfering with the conductive detection circuit. When the conductive strip detects a leakage risk signal, the control module activates the resistance heating wire in the corresponding area to maintain the temperature of the leak-proof base plate and the sand cushion layer above it above the molten salt solidification temperature, preferably 10–30°C above the solidification point.

[0024] Through heating, the leaked molten salt, which was originally easy to solidify and stagnate, is reheated to a flowable state and flows to the outer discharge outlet under the action of the sand cushion slope, thereby avoiding the local accumulation or solidification and blockage of molten salt at the bottom.

[0025] To verify the drainage process, temperature detection units are installed at the drainage outlet and within the drainage channel of the sand cushion layer. Thermocouples or platinum resistance temperature sensors are preferred for these units. The system detects temperature changes as follows:

[0026]

[0027] Where T is the real-time detected temperature, and T0 is the normal operating reference temperature. When ΔT reaches 30~80℃, it can be confirmed that high-temperature molten salt has entered the discharge channel, thereby upgrading the leakage status from suspected leakage to confirmed leakage, and triggering the corresponding level of alarm and linkage control.

[0028] Multiple settlement monitoring devices are arranged circumferentially around the perimeter of the tank foundation within the ceramsite insulation layer or the dense concrete bearing layer beneath it. Preferably, 3 to 6 monitoring points are used to acquire settlement information from different locations on the foundation. The settlement monitoring devices output the settlement amount at a single point.

[0029]

[0030] Where hi0 is the initial height of the i-th measuring point, and hi is the current height. Furthermore, the uneven settlement index of the foundation is calculated.

[0031]

[0032] When the settlement at a single point reaches 5–15 mm, or the settlement difference reaches 3–10 mm, or the settlement rate continues to increase, the system determines that there is an abnormal development trend in the foundation structure and raises the leakage risk warning level, thereby realizing the early identification of the evolution process of "foundation settlement—bottom stress concentration—leakage risk".

[0033] By organically integrating functions such as conductive electric field coupling leakage detection, anti-condensation heating, four-quadrant sand cushion layer diversion and discharge, and foundation settlement monitoring, this invention forms a multi-source collaborative safety monitoring technology solution for high-temperature molten salt storage tanks. Without relying on complex power systems, it achieves reliable identification, rapid location, and graded alarm of molten salt leakage risks and structural safety risks, and has good engineering feasibility and long-term operational reliability.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] (1) Due to the arrangement of cross-shaped conductive strips on the leak-proof base plate and the utilization of the spaces between the conductive strips

[0036] The electric field coupling effect formed during leak detection, compared to methods that rely solely on temperature anomalies or direct contact detection, enables early identification of minute leaks before molten salt shows obvious flow or temperature field anomalies, thus improving the sensitivity and foresight of leak detection.

[0037] (2) Because the sand cushion layer is set as a four-quadrant flow guiding structure, and a cross-shaped micro-ridge is formed in the center, and a discharge outlet is set at the outer edge of each quadrant, compared with the traditional single discharge direction or no flow guiding design, it can not only realize the rapid passive discharge of leaked molten salt, but also quickly locate the leakage direction according to the location of the discharge outlet.

[0038] (3) Because a temperature confirmation structure is set in the sand pad layer outlet and the channel, and a temperature rise threshold is used to perform secondary verification of the conductivity detection results, compared with the existing technology that relies on a single electrical or temperature signal to directly alarm, the risk of false alarm caused by fluctuations in operating conditions is effectively reduced, and the accuracy and reliability of leakage judgment are improved.

[0039] (4) Because a settlement monitoring structure is arranged in the foundation bearing layer of the storage tank, and the settlement information is used as an important auxiliary basis for the judgment of leakage risk, compared with the passive handling only after the molten salt leakage occurs, it can output early warning in advance during the stage of uneven foundation settlement or structural abnormality, and realize the forward-looking monitoring of the evolution process of "structural abnormality - leakage risk".

[0040] (5) Since the functional structures of the present invention are mainly arranged in the foundation layer at the bottom of the storage tank and do not change the structure of the storage tank body, compared with the intrusive or tank modification monitoring scheme, it has the advantages of low engineering implementation difficulty, small impact on the operation of the original storage tank, and high long-term operation stability, and is suitable for promotion and application in existing solar thermal power plants. Attached Figure Description

[0041] Figure 1 is a schematic diagram of the structure of the present invention.

[0042] Figure 2 shows the planar layout of the micro-slope guiding structure and drainage outlet of the sand cushion layer of the present invention.

[0043] intention.

[0044] Figure 3 is a schematic diagram of the arrangement of the conductive strip and the built-in resistance heating wire on the anti-leakage base plate of the present invention.

[0045] Figure 4 is a schematic diagram of the arrangement of the settlement monitoring device in the ceramsite insulation layer of the present invention.

[0046] Labeling Explanation: 1. Tank wall insulation layer; 2. Tank wall; 3. Leakage confirmation temperature sensor; 4. Tank bottom plate; 5. Sand cushion layer; 6. Leak-proof bottom plate; 7. Drainage channel; 8. Alarm device; 9. Refractory brick layer; 10. Settlement monitoring device; 11. Ceramsite insulation layer; 12. Resistance heating wire; 13. Temperature sensor; 14. Temperature sensor; 15. Dense concrete bearing layer; 16. Ventilation duct; 17. Salt drain tank; 18. Heat-resistant concrete ring wall; 19. Lightweight heat-resistant concrete. Detailed Implementation

[0047] 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 some embodiments of the present invention, and not all embodiments. 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.

[0048] Figure 1 shows a schematic diagram of the overall structure of a preferred embodiment of the present invention. The device of this embodiment is arranged within the bottom plate and foundation structure of the molten salt storage tank, and from top to bottom includes: a tank wall insulation layer 1, a tank wall 2, a tank bottom plate 4, a sand cushion layer 5, a leak-proof bottom plate 6, a refractory brick layer 9, a ceramsite insulation layer 11, and a dense concrete bearing layer 15. The tank wall insulation layer 1 is provided on the outer side of the tank wall 2 to reduce radial heat dissipation during the operation of the molten salt storage tank and reduce the thermal stress between the tank wall and the bottom structure. The tank bottom plate 4 is welded to the tank wall 2 to form the molten salt storage tank body, and the sand cushion layer 5 and the leak-proof bottom plate are arranged sequentially below it.

[0049] 6. The sand cushion layer 5 is laid with high-temperature resistant quartz sand or ceramic sand, preferably 50-150 mm thick. While bearing the load of the storage tank, it serves as a guide and buffer layer for leaked molten salt. The leak-proof bottom plate 6 is a metal structural plate, preferably made of stainless steel or nickel-based alloy with a thickness of 6-12 mm. Its function is to receive, detect, and guide leaked molten salt when leakage occurs in the tank bottom plate 4, preventing the molten salt from directly intruding into the lower refractory brick layer 9 and the insulation structure. Below the leak-proof bottom plate 6, the refractory brick layer 9 and the ceramic clay insulation layer 11 are sequentially arranged. The refractory brick layer 9 is used to withstand high-temperature impact and form a stable support interface, while the ceramic clay insulation layer 11 is used to further reduce heat transfer downwards. A dense concrete load-bearing layer 15 is provided at the bottom.

[0050] As the main load-bearing structure of the entire tank foundation, ventilation ducts 16 can be pre-embedded inside or at the bottom for ventilation, dehumidification and temperature equalization of the foundation interlayer.

[0051] Figure 2 shows a schematic diagram of the planar arrangement of the sand cushion layer micro-slope guiding structure 21 and the discharge outlet 20. In this embodiment, the upper surface of the sand cushion layer 5 is integrally processed to form the micro-slope guiding structure 21, the slope of which is preferably 0.5% to 2%, and can be approximately 1%. The guiding structure of the sand cushion layer 5 adopts an arrangement of "slightly higher in the middle and inclined towards the outer edge". By setting a cross-shaped boundary on the plane, the entire bottom area of ​​the storage tank is divided into four guiding quadrants. A relatively high ridge structure is formed at the cross boundary, so that the leaked molten salt in each quadrant flows naturally towards the corresponding discharge outlet 20 along the micro-slope direction of its respective quadrant under the action of gravity. A discharge outlet 20 is set at the outer edge of each quadrant. The discharge outlet 20 is connected to the outwardly extending discharge channel 7. The discharge channel 7 is further connected to the salt discharge trough 17 around the storage tank foundation, thereby forming four independent molten salt guiding and discharge paths. With this arrangement, when a bottom leak occurs, not only can the molten salt be passively and without power to drain, but the quadrant area where the leak occurred can also be quickly determined based on which drain outlet 20 first shows molten salt flowing out, thus improving the location efficiency.

[0052] Figure 3 shows a schematic diagram of the arrangement of the conductive detection structure 22 and the built-in resistance heating structure 23 on the leak-proof base plate 6. The detection is performed on the upper surface or near the upper surface of the leak-proof base plate 6.

[0053] Within the area, a conductive detection structure 22 is installed. The conductive detection structure 22 includes: an annular conductive strip continuously arranged along the outer edge of the leak-proof base plate, and at least two mutually perpendicular radial conductive strips arranged inside the base plate. The radial conductive strips intersect to form a cross structure, thereby dividing the leak-proof base plate detection area into four electrical detection zones. The conductive strips are preferably made of 316L stainless steel flat strips or nickel-based alloy strips, with a width preferably of 10–30 mm and a thickness of 1–3 mm, capable of withstanding high-temperature molten salt environments for extended periods. Each conductive strip is electrically isolated from the others and electrically connected to the data acquisition and alarm device 8. Under normal operating conditions, the medium below the leak-proof base plate 6 is in a dry or stable state, and the equivalent resistance between adjacent conductive strips remains within a reference range. When a small amount of molten salt leaks, the high-temperature molten salt enters the area below the leak-proof base plate, changing the conductivity of the medium between the conductive strips, causing a significant decrease in resistance or an increase in leakage current between adjacent conductive strips. By real-time monitoring of the changes in the equivalent resistance between the conductive strips, the system can achieve early identification of small leaks before the molten salt forms a significant flow. A resistance heating structure 23 is also provided inside the leak-proof base plate 6. The resistance heating structure 23 is the same as the high-temperature alloy resistance heating wire 12, and is preferably laid in a serpentine or partitioned manner, with a preferred spacing of 50-150 mm. A high-temperature resistant insulating layer is provided between the conductive strip 22 and the resistance heating wire 23 to avoid mutual electrical interference. When the conductive detection structure 22 determines that there is a leakage risk, the control system activates the resistance heating wire 23 of the corresponding partition to maintain the temperature of the leak-proof base plate 6 and its adjacent area above the solidification temperature of molten salt, thereby preventing the small amount of leaked molten salt from solidifying in situ at the bottom and ensuring that it has the thermal conditions to continue to flow and discharge along the sand cushion layer 5.

[0054] As shown in Figure 1, temperature sensors 3, 13, and 14 are respectively installed at the outlet 20 of the sand pad layer and within the guide channel 7. Thermocouples or platinum resistance temperature sensors are preferred. When molten salt is guided into the guide channel 7 under the action of conductivity detection and heating, its high-temperature characteristics will cause a significant temperature rise in the guide channel and outlet area. Temperature sensors 3, 13, and 14 collect temperature signals in the guide area in real time. When an abnormal increase in temperature relative to the baseline state is detected, the system upgrades the "suspected leak" status in the conductivity detection stage to "confirmed leak."

[0055] The alarm device 8 outputs audible and visual alarms or remote alarm signals. At the same time, a heat-resistant concrete ring wall 18 and a lightweight heat-resistant concrete 19 are installed below and around the discharge channel 7 to provide structural constraint and thermal insulation protection for the discharge area, ensuring that the molten salt does not cause secondary thermal damage to the surrounding foundation and structure during the discharge process.

[0056] likeFigure 4 The diagram shows the arrangement of the settlement monitoring device 10 within the ceramsite insulation layer. In this embodiment, multiple settlement monitoring devices 10 are arranged along the foundation of the storage tank within the ceramsite insulation layer 11, preferably five measuring points: one measuring point at the center of the bottom of the storage tank and one measuring point in each of the four quadrants. The settlement monitoring device 10 can employ displacement sensors, settlement gauges, or other structural deformation monitoring elements to acquire the settlement amount and trend of the foundation in real time at different locations. When uneven settlement occurs in the foundation, the settlement amount output by each measuring point will show significant differences. The system evaluates the foundation structural condition by calculating the settlement difference and settlement rate, and outputs a signal through the alarm device 8. Since uneven settlement of the foundation introduces additional stress into the bottom plate 4 of the storage tank and its welded areas, thereby significantly increasing the risk of molten salt leakage, this invention uses the settlement monitoring results as important auxiliary information for determining leakage risk. When the settlement index continues to deteriorate, even if no obvious leakage signal has appeared, the system can output early warning information in advance, realizing proactive monitoring of leakage risks caused by structural anomalies.

[0057] In this embodiment, the sedimentation monitoring device 10, the leakage confirmation temperature sensor 3, and the conductive detection structure and resistance heating wire 12 in the anti-leakage base plate 6 are all electrically connected to the alarm device 8 through signal lines. The alarm device 8 serves as a unified data acquisition, logic judgment, and control output unit to realize integrated processing and linkage control of multi-source monitoring signals.

[0058] As can be seen from the above implementation process, this invention constructs a multi-layered structural system at the bottom of the storage tank, integrating gravity-guided discharge, temperature monitoring, conductive leak detection, anti-condensation heating, and foundation settlement monitoring. This achieves automatic identification, coordinated response, and tiered alarm for molten salt leaks and structural anomalies. This implementation method primarily uses gravity-guided discharge and employs electrical and thermal signal coupling as the detection method, eliminating the need for a complex power system to complete leak detection, anti-condensation control, and discharge.

[0059] Confirmed. All detection units and alarm devices are connected and centrally processed, enabling the device to automatically complete detection, heating, anti-condensation, and alarm output in the event of molten salt leakage or foundation abnormalities, forming an integrated safety monitoring solution with simple structure, rapid response, and strong engineering applicability.

[0060] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A molten salt storage tank bottom leakage guiding and safety monitoring device and method, characterized in that, The device is arranged within the bottom plate (4) and foundation structure of the molten salt storage tank, and from top to bottom includes the tank bottom plate (4), sand cushion layer (5), leak-proof bottom plate (6), refractory brick layer (9), ceramsite insulation layer (11), and dense concrete bearing layer (15). The sand cushion layer (5) is laid between the tank bottom plate (4) and the leak-proof bottom plate (6), and is filled with high-temperature resistant granular material. The upper surface of the sand cushion layer (5) has a slope and is provided with a cross-shaped dividing structure to divide the planar area of ​​the sand cushion layer (5) into four flow guidance quadrants. Each flow guidance quadrant has a drainage outlet (20) at its outer edge. The drainage outlet (20) is connected to a drainage channel (7) extending to the periphery of the tank foundation. The leak-proof bottom plate (6) is a metal plate, which is set on the sand cushion layer. Below (5), a conductive detection structure (22) is provided to receive and guide the leaked molten salt; a conductive detection structure (22) is provided on the upper surface or near the upper surface of the leak-proof base plate (6). The conductive detection structure (22) includes an annular conductive strip along the outer edge of the leak-proof base plate (6) and at least two mutually perpendicular radial conductive strips in the plane of the leak-proof base plate (6). The radial conductive strips intersect to form a cross structure, dividing the detection area into four electrical detection zones corresponding to the current-guiding quadrant. Each conductive strip is electrically isolated from the others and electrically connected to the data acquisition and alarm device (8); a resistance heating structure (23) is also provided inside the leak-proof base plate (6). A high-temperature resistant insulating isolation layer is provided between the resistance heating structure (23) and the conductive detection structure (22). Electrically connected to the data acquisition and alarm device (8); a leakage confirmation temperature sensor (3, 13, 14) is installed in the discharge outlet (20) and / or the discharge channel (7) to detect the temperature rise caused by molten salt flowing into the discharge channel (7); in the ceramsite insulation layer (11) or the dense concrete bearing layer (15) below it, a plurality of settlement monitoring devices (10) are arranged along the tank foundation for monitoring foundation settlement, and the settlement monitoring devices (10) are connected to the data acquisition and alarm device (8) for signal connection.

2. The molten salt storage tank bottom leakage guiding and safety monitoring device according to claim 1, characterized in that, The slope of the sand cushion layer (5) is 0.5%~2%, and the high-temperature resistant granular material filled in it is high-temperature resistant quartz sand or ceramic sand, with a thickness of 50~150mm.

3. The molten salt storage tank bottom leakage guiding and safety monitoring device according to claim 1, characterized in that, The thickness of the anti-leakage base plate (6) is 6~12mm, and it is made of stainless steel or nickel-based alloy plate; the conductive strip of the conductive detection structure (22) is made of conductive material that is resistant to high temperature and molten salt corrosion, and its width is 10~30mm and its thickness is 1~3mm.

4. The molten salt storage tank bottom leakage guiding and safety monitoring device according to claim 1, characterized in that, The resistance heating structure (23) is formed by laying high-temperature alloy resistance heating wires (12) in a serpentine or partitioned manner with a laying spacing of 50 to 150 mm. It is used to heat the corresponding area when a leakage risk is detected, so that the temperature is maintained above the solidification point of molten salt.

5. The molten salt storage tank bottom leakage guiding and safety monitoring device according to claim 1, characterized in that, The leakage confirmation temperature sensors (3, 13, 14) are thermocouples or platinum resistance temperature sensors. When the temperature inside the drain outlet (20) or drain channel (7) rises by 30~80°C relative to the reference temperature, it is determined to be a molten salt confirmed leak.

6. The molten salt storage tank bottom leakage guiding and safety monitoring device according to claim 1, characterized in that, The number of settlement monitoring devices (10) is 3 to 6, arranged circumferentially around the perimeter of the tank foundation. The settlement monitoring devices (10) are displacement sensors or settlement sensors. It is determined that there is an anomaly in the foundation structure when the monitored settlement reaches 5-15 mm at a single point, or the maximum settlement difference between monitoring points reaches 3-10 mm, or the settlement rate continues to increase.

7. The molten salt storage tank bottom leakage drainage and safety monitoring device according to claim 1, characterized in that, It also includes a salt drain tank (17), which is located around the base of the storage tank and connected to the end of each of the drainage channels (7) for collecting and draining leaked molten salt.

8. A method for bottom leakage drainage and safety monitoring of a molten salt storage tank, characterized in that, The method, applicable to any one of claims 1 to 7, comprises: real-time monitoring of the equivalent resistance between adjacent conductive bands within each electrical detection zone using the conductive detection structure (22); when the equivalent resistance of a certain zone decreases by 10% to 30% relative to the reference equivalent resistance, or the absolute change reaches 10² to 10... 4 When the value is Ω, it is determined that there is a risk of molten salt leakage in the zone, and the resistance heating structure (23) of the corresponding area is activated for heating and anti-condensation. After determining that there is a risk of leakage, the temperature in the drain outlet (20) and / or drain channel (7) is continuously monitored. When the temperature rises by 30~80℃ relative to the reference temperature, it is determined that the molten salt leakage is confirmed and a leakage alarm is triggered. The settlement monitoring device (10) monitors the settlement at different locations of the tank foundation in real time. When the settlement amount, settlement difference or settlement rate of a single point is detected to exceed the preset threshold, a structural abnormality warning is triggered and the risk warning level of the leakage monitoring system is increased.

9. The method according to claim 8, characterized in that, After the resistance heating structure (23) is activated, the temperature of the corresponding area is controlled to be maintained at 10~30℃ above the solidification point of molten salt.

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