An online monitoring system for molten salt parameters

Abstract

This application discloses an online monitoring system for molten salt parameters, relating to the field of intelligent monitoring and diagnostic technology. The online monitoring system selects a first pipe with a curvature less than a preset threshold as the measurement segment in a concentrated solar power (CSP) plant, and installs pressure testing devices at both ends, constructing an online measurement structure based on the pressure difference principle. This system achieves real-time, in-situ monitoring of molten salt viscosity, overcoming the problems of poor timeliness and inability to reflect real-time operating status in traditional offline sampling and analysis. The limitation on pipe curvature ensures the stability of fluid flow, allowing the measured pressure difference to accurately reflect the viscous resistance of the molten salt. This solution has a compact structure, is easy to deploy in engineering, and provides stable and reliable technical support for real-time perception of the molten salt status, operational risk assessment, and early warning decision-making in CSP plants.

Description

Technical Field

[0001] This application relates to the field of intelligent monitoring and diagnostic technology, and in particular to an online monitoring system for molten salt parameters. Background Technology

[0002] Solar thermal power generation is an important technological approach to addressing energy and environmental challenges, characterized by its cleanliness and sustainability, and boasts broad development prospects. In this system, molten salt serves as a crucial heat storage and transfer medium, and its performance directly impacts system efficiency and operational safety.

[0003] Currently widely used molten salts (such as sodium nitrate-potassium nitrate mixtures) can corrode metal pipelines during long-term high-temperature operation, causing metallic impurities such as Fe, Cr, and Ni to dissolve into the molten salt. These impurities may alter the composition of the molten salt, leading to deterioration of its thermal properties, and react with the molten salt to form insoluble solid particles, causing pipeline blockage and threatening system safety. Meanwhile, the viscosity of the molten salt is a key indicator reflecting its flow state and "health." If the viscosity becomes excessive due to increased impurities, changes in composition, or abnormal temperatures during operation, it will increase pumping resistance and energy consumption, and may even cause equipment failure.

[0004] Therefore, in order to achieve long-term, efficient and stable operation of solar thermal power generation systems, it is necessary to monitor and evaluate molten salt parameters in real time. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method for online monitoring of molten salt parameters, used for real-time monitoring and evaluation of molten salt parameters in solar thermal power plants.

[0006] The embodiments of this application disclose the following technical solutions: The first aspect of this application provides an online monitoring system for molten salt parameters, which is applied to a concentrated solar power plant; the system includes a first pressure testing device and a second pressure testing device. The first pressure testing device and the second pressure testing device are respectively located at both ends of the first pipe in the solar thermal power plant; the curvature of the first pipe is less than a preset curvature threshold.

[0007] In one alternative implementation, the method of using the system includes: The viscosity of the molten salt flowing through the first pipe is determined based on the pressure difference between the first pressure and the second pressure; the first pressure is the pressure value measured by the first pressure testing device; the second pressure is the pressure value measured by the second pressure testing device.

[0008] In one alternative implementation, determining the viscosity of the molten salt flowing through the first pipe based on the pressure difference between the first pressure and the second pressure includes: Based on the pressure difference and Poiseuille's formula, the viscosity coefficient of the liquid corresponding to the molten salt flowing through the first pipe is determined. The viscosity of the molten salt flowing through the first pipe is determined by the liquid viscosity coefficient.

[0009] In one alternative implementation, the first pipe is a straight pipe.

[0010] In one optional implementation, both the first pressure testing device and the second pressure testing device are absolute pressure sensors or gauge pressure sensors.

[0011] In one alternative implementation, the system further includes a laser-induced breakdown spectroscopy system and a detection bypass; The detection bypass is connected in parallel with the second pipeline in the solar thermal power plant; an optical window is provided on the detection bypass. The laser-induced breakdown spectroscopy system is used to measure the composition of the molten salt flowing through the detection bypass.

[0012] In one alternative implementation, the system further includes a first valve and a second valve; The first valve is installed on the second pipeline and is used to control the connection or disconnection between the first end of the detection bypass and the second pipeline. The second valve is installed on the second pipeline and is used to control the connection and disconnection between the second end of the detection bypass and the second pipeline.

[0013] In one alternative implementation, the optical window is made of sapphire, fused silica, or magnesium fluoride.

[0014] In one alternative implementation, the material of the detection bypass is the same as the material of the pipes in the solar thermal power plant.

[0015] In one optional implementation, both the first valve and the second valve are electrically controlled valves, and both the first valve and the second valve are electrically connected to the target controller. The target controller is used to control the opening of the first valve and the second valve before starting the laser-induced breakdown spectroscopy system, so as to allow molten salt to flow into the detection bypass.

[0016] In one alternative implementation, the system further includes an alarm device; The alarm device is used to issue an alarm signal when the viscosity of the molten salt flowing through the first pipe is greater than a preset viscosity threshold, and / or when the concentration of a specific impurity component in the molten salt flowing through the detection bypass exceeds a preset safety limit.

[0017] Compared with the prior art, this application has the following beneficial effects: The molten salt parameter online monitoring system provided in this application constructs an online measurement structure based on the principle of pressure difference by selecting a first pipe with a curvature less than a preset threshold as the measurement section in a concentrated solar power (CSP) plant and setting pressure testing devices at both ends of the pipe. This system achieves real-time, in-situ monitoring of molten salt viscosity, overcoming the problems of poor timeliness and inability to reflect real-time operating status in traditional offline sampling and analysis. The limitation on pipe curvature ensures the stability of fluid flow, allowing the measured pressure difference to accurately reflect the viscous resistance of the molten salt. This scheme is compact in structure and easy to deploy in engineering, providing stable and reliable technical support for real-time perception of molten salt status, operational risk assessment, and early warning decision-making in CSP plants. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an online monitoring system for molten salt parameters provided in an embodiment of this application; Figure 2 This is a schematic diagram of a laser-induced breakdown spectroscopy system and a detection bypass relative position relationship provided in an embodiment of this application. Detailed Implementation

[0020] Solar thermal power generation, as a green energy solution, has significant strategic value in alleviating environmental pressures and ensuring energy security. In this technological system, molten salt plays a crucial role in heat storage and transfer, and its physicochemical properties directly determine the overall efficiency and operational reliability of the power plant.

[0021] Currently, the commonly used molten salt system, after long-term operation under high-temperature conditions, will undergo a corrosion reaction with metal pipelines, causing metal ions such as iron, chromium, and nickel to dissolve into the molten salt system. The accumulation of these impurities may not only alter the basic composition of the molten salt, affecting its key thermophysical parameters such as phase transition temperature and specific heat capacity, but may also further form solid deposits, leading to a reduction in the pipeline's cross-sectional area and even the risk of blockage. In addition, the viscosity of molten salt is a core parameter characterizing its flow performance. If the viscosity becomes too high due to changes in composition, temperature fluctuations, or increased impurities, it will significantly increase the flow resistance and energy consumption of the conveying system, and in severe cases, may cause pump and valve equipment failure.

[0022] Therefore, establishing an effective real-time monitoring system for molten salt conditions is of paramount importance for ensuring the long-term stable operation of solar thermal power generation systems.

[0023] Based on this, this application provides an online monitoring system for molten salt parameters. This system selects a first pipe with a curvature less than a preset threshold as the measurement section in a concentrated solar power (CSP) plant, and installs pressure testing devices at both ends, constructing an online measurement structure based on the pressure difference principle. This system achieves real-time, in-situ monitoring of molten salt viscosity, overcoming the problems of poor timeliness and inability to reflect real-time operating status in traditional offline sampling and analysis. The limitation on pipe curvature ensures the stability of fluid flow, allowing the measured pressure difference to accurately reflect the viscous resistance of the molten salt. This scheme has a compact structure and is easy to deploy in engineering, providing stable and reliable technical support for real-time perception of the molten salt status, operational risk assessment, and early warning decision-making in CSP plants.

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0025] Figure 1 This is a schematic diagram of the structure of an online monitoring system for molten salt parameters provided in an embodiment of this application. Figure 1 On the one hand, it demonstrates the composition of the online monitoring system for molten salt parameters, and on the other hand, it demonstrates the specific connection method between the online monitoring system and the solar thermal power plant.

[0026] Combination Figure 1 As shown, the concentrated solar power plant system mainly includes a concentrating solar collector field (corresponding to...) Figure 1 The system consists of a mirror field loop, a hot salt tank, a heat exchanger, a cold salt tank, and supporting molten salt transport pipelines. Its basic workflow is as follows: low-temperature molten salt is pumped from the cold salt tank to the mirror field loop, where it absorbs solar energy in the concentrating solar collector area and is heated to high-temperature molten salt. It then returns to the hot salt tank for storage. During power generation, the high-temperature molten salt releases heat through the heat exchange system and returns to the cold salt tank, completing the thermal cycle.

[0027] Combination Figure 1 As shown, the online monitoring system for molten salt parameters in this application mainly includes: a first pressure testing device, a second pressure testing device, a detection bypass, a host computer, and a laser-induced breakdown spectroscopy (LIBS) system.

[0028] The integration method of the online monitoring system with the solar thermal power plant is as follows: On the main delivery pipeline at the output end of the mirror field loop, a straight pipe section that meets the preset curvature threshold requirement is selected as the first pipeline, and a first pressure testing device is installed at both ends of the first pipeline. Figure 1 P1) and the second pressure testing device ( Figure 1 (P2) and the other two are used to simultaneously measure the molten salt pressure at both ends of the pipe section and calculate the real-time viscosity of the molten salt based on the measured pressure difference.

[0029] Simultaneously, a detection bypass is connected in parallel within the molten salt circulation loop. This bypass is connected to the main loop at both ends via a first valve and a second valve, and an optical window for spectral detection is provided on the bypass. In this application, the pipe between valve 1 and valve 2 is the second pipe; a laser-induced breakdown spectroscopy system is arranged near the optical window corresponding to the detection bypass.

[0030] It should be noted that, in this application, the first valve is installed on the second pipeline to control the connection and disconnection between the first end of the detection bypass and the second pipeline; the second valve is installed on the second pipeline to control the connection and disconnection between the second end of the detection bypass and the second pipeline.

[0031] This application specifies that the first and second pressure testing devices are installed at both ends of the first pipe in the solar thermal power plant, and requires that the curvature of the first pipe be less than a preset curvature threshold. The purpose of this limitation is to ensure that the molten salt flow within the measurement pipe section is stable and fully developed by constraining the pipe curvature, thereby minimizing flow distortion and additional pressure loss caused by local structures such as bends. Under these conditions, the pressure difference between the two ends of the pipe can accurately and directly reflect the frictional resistance generated by the viscous internal friction of the molten salt, thus satisfying the application prerequisites of laminar flow models such as Poiseuille's law, and providing the necessary hydrodynamic conditions for accurate calculation of the molten salt viscosity using pressure difference data.

[0032] For example, the first pipe is a straight pipe.

[0033] In one optional implementation, both the first valve and the second valve are electrically controlled valves, and both are electrically connected to the target controller; the target controller (Figure...) Figure 1 The microcomputer in the system is used to control the opening of the first valve and the second valve before starting the laser-induced breakdown spectroscopy system, so that molten salt flows into the detection bypass.

[0034] The advantages of this automatic control scheme are as follows: it achieves automation and precise timing control of the detection process, ensuring that the bypass is filled with flowing molten salt before laser-induced breakdown spectroscopy analysis, thereby avoiding the analysis of air or unrepresentative residual molten salt and ensuring the representativeness and accuracy of the component detection results; it allows for the opening and closing of valves via remote or automatic commands without shutting down the system or affecting the normal operation of the main circuit, thereby completing periodic molten salt status sampling and detection, which greatly improves the system's operability, monitoring flexibility and integration with the power plant's centralized control system, and reduces the risk of manual intervention and operation and maintenance costs.

[0035] In one optional implementation, the material of the detection bypass is the same as that of the main transmission pipeline in the solar thermal power plant. For example, if the main transmission pipeline in the solar thermal power plant is made of 347H austenitic stainless steel, then the detection bypass is also made of 347H austenitic stainless steel; if the main transmission pipeline is made of Inconel 625 nickel-based high-temperature alloy, then the detection bypass is also made of Inconel 625.

[0036] Using a bypass with the same material as the main circuit piping offers the following technical advantages: it ensures that the bypass has the same coefficient of thermal expansion, corrosion resistance, and long-term structural stability as the main circuit in a high-temperature molten salt environment, avoiding localized thermal stress or electrochemical corrosion caused by differences in material properties, thus guaranteeing the overall operational safety and lifespan of the system; the consistent material can simulate the actual flow and heat transfer state of molten salt in the main circuit to the greatest extent and avoid introducing additional impurities, so that the molten salt composition and physical property data measured in the bypass can more realistically and representatively reflect the actual service state of the molten salt in the main circuit, thereby improving the accuracy and reliability of the monitoring results.

[0037] The optical window in this application must meet the following conditions: it must operate stably for a long time in a high-temperature, highly corrosive molten salt environment and maintain excellent optical performance. Its material should possess high transmittance (especially at the laser wavelength and characteristic spectral band used), high heat resistance, excellent thermal stability, good resistance to molten salt chemical corrosion, and sufficient mechanical strength and sealing reliability. To ensure effective laser incidentness and efficient collection of plasma characteristic spectra, and to guarantee the accuracy and reliability of long-term monitoring, the optical window material can be sapphire, fused silica, or magnesium fluoride.

[0038] In one optional implementation, both the first and second pressure testing devices are absolute pressure sensors or gauge pressure sensors. This consistent design fundamentally eliminates systematic errors introduced by different measurement benchmarks, ensuring that the pressure difference obtained through simple differential calculations accurately corresponds to the actual frictional resistance loss caused by internal friction (viscosity effect) when molten salt flows in the pipeline; thus guaranteeing the physical validity and computational accuracy of the online monitoring results. Using sensors with different benchmarks in combination will distort the pressure difference information, thereby rendering the entire viscosity monitoring function ineffective.

[0039] Figure 2 This is a schematic diagram of a laser-induced breakdown spectroscopy system and a detection bypass system, provided as embodiments of this application, illustrating their relative positional relationships. (Combined with...) Figure 2 As shown, the laser-induced breakdown spectroscopy system includes a high-energy laser source, a collecting lens, and a spectrometer. The laser beam emitted by the high-energy laser source is focused and passes through an optical window in the detection bypass, then incident on and focused onto the molten salt sample flowing inside the detection bypass pipe. The laser interacts with the molten salt, instantaneously generating high-temperature plasma. The characteristic spectrum emitted during the plasma de-excitation process passes back through the same optical window, is received by the collecting lens, and coupled to the spectrometer. The spectrometer analyzes the acquired spectral signals, thereby achieving qualitative or quantitative detection of impurity elements (such as Fe, Cr, Ni ions) in the molten salt.

[0040] In one alternative implementation, the pressure is measured using a first pressure testing device and a second pressure testing device. Figure 1 The viscosity of the molten salt in the solution is determined as follows: First, calculate the difference between the first pressure measured by the first pressure testing device and the second pressure measured by the second pressure testing device; Then, the difference is substituted into Poiseuille's formula to calculate the viscosity coefficient of the liquid flowing through the first pipe. The Poisson formula is: Q = (π × r⁴ × ΔP) / (8ηL).

[0041] Where Q is the liquid flow rate (volume flowing per unit time, such as milliliters / minute); r is the radius of the first pipe; ΔP is the pressure difference between the two ends of the first pipe; η is the liquid viscosity coefficient; and L is the length of the first pipe.

[0042] Finally, the viscosity of the molten salt flowing through the first pipe is determined using the liquid viscosity coefficient.

[0043] Since the viscosity coefficient of a liquid in a Newtonian fluid is the dynamic viscosity of the fluid and is an intrinsic physical property parameter characterizing the viscosity of the fluid, the calculated viscosity coefficient value can be directly used as the dynamic viscosity of the molten salt under the current temperature, pressure and flow conditions, thereby enabling the determination and monitoring of the viscosity of the molten salt flowing through the first pipe.

[0044] As described above, the online monitoring system in this application can simultaneously monitor the viscosity and composition of molten salt. In practical applications, changes in the composition of molten salt usually cause corresponding changes in its viscosity. Therefore, to optimize the monitoring strategy, improve system efficiency, and achieve intelligent early warning, the following process can be adopted: First, the viscosity of the molten salt is measured in real time, and based on continuous analysis and trend judgment of the viscosity data, a preliminary assessment of whether the molten salt state is abnormal is made. If the viscosity value changes significantly or deviates from the normal range, the laser-induced breakdown spectroscopy (LIBS) system is further triggered to perform targeted analysis of the molten salt composition to trace the root cause of the viscosity abnormality (e.g., to determine whether it is caused by an increase in the concentration of specific metal impurity ions, an increase in insoluble matter, or a component imbalance). This selective component monitoring mechanism based on viscosity change-driven analysis can achieve a comprehensive and in-depth diagnosis of the molten salt state, effectively reduce unnecessary frequent starts of the LIBS system, help reduce system energy consumption, extend the life of key components, and improve the intelligence and economy of the overall monitoring process.

[0045] In one alternative implementation, it is also possible to... Figure 1 The system's host computer presets alarm thresholds for viscosity and composition. When the real-time monitored molten salt viscosity value or the concentration of specific impurity ions (such as Fe, Cr, Ni) continuously exceeds or is about to reach the preset safety limit, the system can automatically trigger audible and visual alarms, interface warnings, and send early warning signals to the power plant's centralized control system. This enables early warning of abnormal molten salt conditions, guiding maintenance personnel to take timely intervention measures such as molten salt purification, filtration, replacement, or system operating parameter adjustments. This effectively prevents operational risks such as pipeline blockage, pump and valve failure, or decreased heat transfer efficiency caused by molten salt deterioration, ensuring the safe, stable, and economical operation of the solar thermal power plant.

[0046] In summary, this application provides an online monitoring system for molten salt parameters in concentrated solar power plants. This system combines two technologies—pressure differential viscosity measurement and laser spectroscopy composition measurement—to achieve comprehensive online monitoring of molten salt performance. This system has at least the following advantages: First, this system integrates a pressure difference viscosity measurement module based on Poiseuille's law and a laser-induced breakdown spectral composition analysis module into the same monitoring platform. Under normal operating conditions of a solar thermal power plant, it can simultaneously acquire viscosity data and impurity element content of molten salt, and comprehensively evaluate changes in the physical state and chemical composition of molten salt.

[0047] Secondly, the viscosity measurement is based on classical fluid mechanics theory. By selecting pipe sections that meet the curvature requirements and installing pressure sensors of the same type, it is ensured that the measured pressure difference accurately reflects the viscous resistance, providing a reliable data basis for accurate viscosity calculation. This structure can be directly modified from existing pipelines in the power plant, making the project simple to implement and cost-effective.

[0048] Third, the optical window is made of special optical materials that are resistant to high temperatures, corrosion, and have high transmittance; the material of the detection bypass is consistent with that of the main circuit to avoid introducing material compatibility issues; and the pressure sensors use the same type of configuration to ensure consistent measurement standards. These designs ensure the long-term operational stability and data accuracy of the system in high-temperature and corrosive environments.

[0049] Fourth, by monitoring and analyzing the viscosity and impurity composition of molten salt in real time, potential risks such as molten salt deterioration and impurity deposition can be warned in advance, guiding operation and maintenance personnel to take timely and targeted measures to effectively prevent unplanned shutdowns such as pipeline blockage and equipment failure, providing important technical support for the safe, stable and efficient operation of solar thermal power plants.

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the method embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments. The method embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate. The components indicated as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0051] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An online monitoring system for molten salt parameters, characterized in that, The system is applied to a solar thermal power plant; the system includes a first pressure testing device and a second pressure testing device. The first pressure testing device and the second pressure testing device are respectively located at both ends of the first pipe in the solar thermal power plant; the curvature of the first pipe is less than a preset curvature threshold.

2. The system according to claim 1, characterized in that, The method of using the system includes: The viscosity of the molten salt flowing through the first pipe is determined based on the pressure difference between the first pressure and the second pressure; the first pressure is the pressure value measured by the first pressure testing device; the second pressure is the pressure value measured by the second pressure testing device.

3. The system according to claim 2, characterized in that, Determining the viscosity of the molten salt flowing through the first pipe based on the pressure difference between the first pressure and the second pressure includes: Based on the pressure difference and Poiseuille's formula, the viscosity coefficient of the liquid corresponding to the molten salt flowing through the first pipe is determined. The viscosity of the molten salt flowing through the first pipe is determined by the liquid viscosity coefficient.

4. The system according to claim 1, characterized in that, The first pipe is a straight pipe.

5. The system according to claim 1, characterized in that, Both the first pressure testing device and the second pressure testing device are absolute pressure sensors or gauge pressure sensors.

6. The system according to any one of claims 1-5, characterized in that, The system also includes a laser-induced breakdown spectroscopy system and a detection bypass; The detection bypass is connected in parallel with the second pipeline in the solar thermal power plant; an optical window is provided on the detection bypass. The laser-induced breakdown spectroscopy system is used to measure the composition of the molten salt flowing through the detection bypass.

7. The system according to claim 6, characterized in that, The system also includes a first valve and a second valve; The first valve is installed on the second pipeline and is used to control the connection or disconnection between the first end of the detection bypass and the second pipeline. The second valve is installed on the second pipeline and is used to control the connection and disconnection between the second end of the detection bypass and the second pipeline.

8. The system according to claim 6, characterized in that, The optical window is made of materials including sapphire, fused silica, or magnesium fluoride.

9. The system according to claim 6, characterized in that, The material of the detection bypass is the same as the material of the pipes in the solar thermal power plant.

10. The system according to claim 7, characterized in that, The system also includes an alarm device; The alarm device is used to issue an alarm signal when the viscosity of the molten salt flowing through the first pipe is greater than a preset viscosity threshold, and / or when the concentration of a specific impurity component in the molten salt flowing through the detection bypass exceeds a preset safety limit.

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