Molten salt heat tracing system and control method thereof

Abstract

The invention discloses a fused salt heat tracing system and a control method thereof, the fused salt heat tracing system is used for preventing fused salt in a fused salt pipeline for conveying the fused salt from being solidified, and the fused salt heat tracing system comprises a heat tracing pipeline, a heat exchange pipeline and a heat exchange pipeline, and the heat tracing pipeline is suitable for circulating heated liquid or steam heat tracing fluid, so that when the heat tracing fluid flows through the heat tracing pipeline, heat is transferred to the molten salt pipeline through the heat tracing pipeline. According to the fused salt heat tracing system, efficient heat transfer is achieved through tight heat conduction connection between the heat tracing pipeline and the fused salt pipeline; the system can utilize the heat exchange temperature difference to the maximum extent by adopting a countercurrent heat exchange mode, and the thermodynamic efficiency is improved; the plurality of heat tracing pipelines are uniformly distributed in the circumferential direction, so that uniform temperature distribution is ensured; according to the system, through the heat conduction enhancing component and the optimized pipeline layout, the heat transfer efficiency is remarkably improved, and the heat energy loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of thermal energy engineering technology, specifically to a molten salt heat tracing system and its control method. Background Technology

[0002] In the chemical and energy sectors, molten salt is frequently used as a heat transfer and storage medium due to its excellent thermal stability and high specific heat capacity. However, molten salt is prone to solidification during transportation due to temperature drops, leading to pipeline blockages, system shutdowns, and even equipment damage. Current technologies typically employ external heating methods to maintain the temperature of molten salt pipelines, such as electric heating, steam heating, or thermal oil heating.

[0003] These existing heat tracing technologies have some inherent drawbacks. While electric heat tracing is easy to install, it relies on an external power supply, resulting in high energy consumption and posing safety hazards in flammable and explosive environments. Steam heat tracing requires additional steam generation equipment, making the system complex and less thermally efficient, especially when the steam temperature does not match the molten salt temperature, leading to wasted heat energy. Although thermal oil heat tracing offers more flexible temperature control, it requires a separate heating system and circulation device, increasing system complexity and maintenance costs.

[0004] More importantly, existing heat tracing technologies often employ static heating modes, lacking the dynamic response capability to changes in molten salt temperature. When the molten salt flow rate or ambient temperature changes, traditional heat tracing systems struggle to adjust heating power in a timely manner, potentially leading to localized overheating or insufficient heating. Furthermore, most existing systems fail to effectively utilize the molten salt system's own thermal energy, requiring additional energy input and reducing overall energy efficiency.

[0005] The root cause of these technical problems lies in the lack of organic thermal coupling and intelligent temperature coordination mechanisms between existing heat tracing systems and molten salt delivery systems, which makes it impossible to achieve precise temperature maintenance and efficient energy utilization. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a molten salt heat tracing system and its control method, which aims to solve the problems of high energy consumption, slow response and low thermal energy utilization efficiency in the prior art.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a molten salt tracing system for preventing molten salt from solidifying inside a molten salt pipeline for transporting molten salt, comprising: The heat tracing pipe is installed adjacent to and in close contact with the molten salt pipe in a thermally conductive manner; The heat tracing pipe is suitable for flowing with liquid or gaseous heat tracing fluid at a certain temperature, so that when the heat tracing fluid flows through the heat tracing pipe, it transfers heat to the molten salt pipe.

[0008] In some embodiments, the flow direction of the heat tracing fluid is opposite to the flow direction of the molten salt in the molten salt pipe, forming a countercurrent heat exchange coupling.

[0009] In some embodiments, the number of heat tracing pipes is at least two, the extension direction of the heat tracing pipes is consistent with the extension direction of the molten salt pipes, and they are evenly distributed around the circumference of the molten salt pipes.

[0010] In some embodiments, the heat source of the heat tracing pipe is derived from the high-temperature section of the molten salt pipe or from the working fluid system heated by the molten salt, so that the heat tracing pipe utilizes the thermal energy of the system in which the molten salt pipe is located.

[0011] In some embodiments, the heat tracing pipe is provided with at least one outlet, which is connected to a location in the working fluid system corresponding to the temperature level.

[0012] In some embodiments, the heat tracing fluid is high-temperature water or heat transfer oil directly or indirectly generated by the working fluid system.

[0013] In some embodiments, the heat tracing fluid is provided by an external heat source independent of the molten salt piping system.

[0014] In some embodiments, a thermally conductive enhancement member is further included, which is disposed between the molten salt pipe and the heat tracing pipe to enhance the heat transfer between the two.

[0015] In some embodiments, the thermally conductive enhancement member is a welded layer, which is fixed to the outer surface of the molten salt pipe and / or the heat tracing pipe to fill the gap between the molten salt pipe and the heat tracing pipe.

[0016] In some embodiments, the weld layer is fixed to the outer surface of the heat tracing pipe, the weld layer is installed against the wall of the molten salt pipe, and a thermally conductive filler is applied to the outer contact surface of the weld layer.

[0017] In some embodiments, the thermally conductive enhancement member is a thermally conductive enhanced filler layer, which fills the contact interface between the molten salt pipe and / or the heat tracing pipe.

[0018] In some embodiments, the molten salt pipe and the heat tracing pipe are mechanically fixed together by clamping members.

[0019] In some embodiments, a power pump is also included for driving the heat tracing fluid to flow within the heat tracing pipe.

[0020] In some embodiments, the contact area between the thermally conductive enhancement member and the heat tracing pipe accounts for 1 / 50 to 2 / 3 of the corresponding surface area of ​​the heat tracing pipe.

[0021] In some embodiments, the contact surface between the thermally conductive enhancement member and the molten salt pipe is an arc surface, and the radius of curvature of the arc surface matches the outer diameter of the molten salt pipe.

[0022] Secondly, a control method applied to a molten salt heat tracing system as described above includes: The temperature at a predetermined location in the molten salt pipeline is detected to obtain a first temperature; The temperature at a set location on the heat tracing pipe is detected to obtain a second temperature; The first temperature is compared with the preset molten salt freezing point temperature, and the temperature deviation value is calculated, wherein the preset molten salt freezing point temperature is dynamically set based on the molten salt type and environmental conditions. Based on the temperature deviation value, the flow rate, temperature, or flow velocity of the heat tracing fluid in the heat tracing pipe are dynamically adjusted so that the temperature of the molten salt pipe is maintained at least higher than the preset molten salt freezing point temperature ∆T.

[0023] In some embodiments, ∆T is not lower than 10°C.

[0024] In some embodiments, when the heat source of the heat tracing pipe originates from the high-temperature section of the molten salt pipe or the working fluid system fluid heated by the molten salt, based on the real-time temperature distribution of the working fluid system, at least one outlet of the heat tracing pipe is connected to a location in the working fluid system corresponding to the temperature level, so that the outlet temperature of the heat tracing fluid matches the heat demand of the location.

[0025] In some embodiments, the detection of the first and second temperatures employs a temperature sensor array, which is arranged at intervals along the length of the molten salt pipe and the heat tracing pipe.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects: The molten salt heat tracing system of the present invention achieves efficient heat transfer through a tight thermally conductive connection between the heat tracing pipe and the molten salt pipe; the system can maximize the use of the heat exchange temperature difference by adopting a counter-current heat exchange method, thereby improving thermodynamic efficiency; the uniform distribution of multiple heat tracing pipes in a circumferential manner ensures uniform temperature distribution; the system significantly improves heat transfer efficiency and reduces heat loss through thermally enhanced components and optimized pipe layout. When utilizing the system's own thermal energy, intelligent temperature matching and flow control enable tiered energy utilization, significantly reducing external energy requirements. The dynamic temperature control mechanism can quickly respond to changes in molten salt temperature and adjust heat tracing parameters in a timely manner, ensuring that the molten salt is always maintained within a safe temperature range. The system structure design takes into account the adaptability to different application scenarios, and through adjustable pipe layout and heat conduction interface design, it can adapt to the heat tracing needs of molten salt pipes of various specifications.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0028] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a molten salt heat tracing system in one embodiment.

[0030] Figure 2 This is a schematic diagram of various structures of a heat tracing pipe in one embodiment.

[0031] Figure 3 This is a flowchart illustrating a control method for a molten salt heat tracing system in one embodiment. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may not be directly connected to the other devices but may have an intermediary device.

[0035] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0036] Reference Figure 1 and Figure 2 In a first aspect, this embodiment provides a molten salt tracing system for preventing molten salt from solidifying inside a molten salt pipeline 10 that transports molten salt, comprising: The heat tracing pipe 20 is installed adjacent to and in close contact with the molten salt pipe 10 in a heat-conducting manner; The heat tracing pipe 20 is suitable for flowing liquid or gaseous heat tracing fluid with a certain temperature, so that when the heat tracing fluid flows through the heat tracing pipe 20, it transfers heat to the molten salt pipe 10; the heat tracing fluid forms a liquid or gaseous state after being heated, and the heat tracing fluid flows in the heat tracing pipe 20 and transfers heat to the molten salt in the molten salt pipe 10. It should be noted that this embodiment creatively adopts the spatial relationship of the heat tracing pipe 20 and the molten salt pipe 10 being "adjacent and closely attached in a heat-conducting manner". In specific implementation, the heat tracing pipe 20 is attached to the outer wall of the molten salt pipe 10 in a close fit manner, and a large area of ​​heat conduction interface is formed between the two.

[0037] Optionally, refer to Figure 2 The heat tracing pipe 20 has various structural forms, including circular pipes, trapezoidal pipes, and irregularly shaped pipes. It has a linear or arc-shaped surface as a heat conduction interface, which is tightly fitted to the molten salt pipe 10 to increase the heat exchange effect. Figure 2 The paper demonstrates several possible structural forms of the heat tracing pipe 20 when the heat conduction interface is a circular arc surface.

[0038] Preferably, the contact surface between the thermally conductive reinforcing member and the molten salt pipe 10 is an arc surface, and the radius of curvature of the arc surface matches the outer diameter of the molten salt pipe 10, ensuring the optimization of the heat transfer path and the tightness of the contact, and reducing gaps.

[0039] Furthermore, the independently heated liquid or gaseous heat-tracing fluid, at a certain temperature, flows within the heat-tracing pipe 20. The heat energy it carries is directly and efficiently transferred to the molten salt pipe 10 through the pipe wall, thereby continuously compensating for the heat loss of the molten salt during transportation. A significant advantage of this approach is that it establishes a closed-loop heat circulation system that is parallel to and physically independent of the molten salt pipe 10. This avoids the risk of localized overheating that may result from direct heating, while ensuring uniform and efficient heat transfer through large-area contact.

[0040] Preferably, the heat tracing pipe 20 is embedded in the insulation layer of the molten salt pipe 10, and the insulation layer simultaneously wraps the molten salt pipe 10 and the heat tracing pipe 20. The heat tracing pipe 20 is then thermally connected to the molten salt pipe wall by a high thermal conductivity material. This can further improve the efficiency of heat conduction and effectively block heat loss.

[0041] In one implementation, the flow direction of the heat tracing fluid is opposite to the flow direction of the molten salt in the molten salt pipe 10, forming a counter-current heat exchange coupling.

[0042] By making the flow direction of the heat-tracing fluid in the heat-tracing pipe 20 completely opposite to the flow direction of the molten salt in the molten salt pipe 10, from a thermodynamic perspective, this counter-current arrangement can maintain a more favorable average heat transfer temperature difference along the entire length of the heat exchanger. The high-temperature heat-tracing fluid first encounters the molten salt (at the end of the pipe), which has already cooled down. As it flows, the temperature of the heat-tracing fluid itself gradually decreases, while the temperature of the molten salt that exchanges heat with it gradually increases (towards the beginning of the pipe). This ensures that heat transfer always occurs under the drive of a large temperature difference, thereby significantly improving the overall heat exchange efficiency. Compared to co-current or other flow direction arrangements, the required heat transfer area or fluid flow rate can be reduced under the same heat load.

[0043] In some possible embodiments, in certain high-latitude regions or solar thermal power plant applications with significant seasonal variations, the heat tracing requirements of the molten salt pipeline 10 exhibit significant time-varying characteristics. While a fixed counter-current heat tracing mode can effectively increase the molten salt temperature at the pipeline end, under conditions of midday summer or strong radiation, it may lead to unnecessary heat loss due to overheating in localized areas of the pipeline, and even accelerate thermal fatigue of the pipeline material. Especially in solar thermal power plants employing dual-tank thermal storage systems, when the high-temperature molten salt tank is full and solar radiation remains intense, the fixed counter-current heat tracing mode will continuously consume system heat, resulting in energy waste.

[0044] To address this contradiction, this embodiment innovatively employs an adaptive flow direction switching mechanism based on multi-parameter collaborative judgment. The system dynamically adjusts the flow direction by real-time monitoring of four key parameters: the inlet temperature T of the molten salt pipe 10. in Outlet temperature T out Ambient temperature Tamb And real-time solar irradiance G. These parameters are collected through a distributed sensor network and sent to the central controller for mode decision-making.

[0045] The specific switching logic adopts a layered judgment strategy: First, the system will compare the temperature difference (ΔT=T) between the two ends of molten salt pipe 10. in -T out ) and a preset threshold θ1 (usually set to 15-25℃). When ΔT>θ1 and T out When the molten salt approaches the safe threshold for freezing, the system activates counter-current mode to ensure that the molten salt at the end is sufficiently heated; when ΔT < θ2 (θ2 < θ1) and G > 800 W / m is detected simultaneously. 2 When the system is in a state of sufficient irradiation, it will automatically switch to the co-current mode.

[0046] In co-current mode, the heat tracing fluid flows in the same direction as the molten salt. The waste heat of the molten salt in the high-temperature section is absorbed by the heat tracing fluid and transferred to the heat storage system through an integrated heat exchanger. This process not only avoids energy waste but also achieves a functional transformation in heat transfer—the heat tracing system transforms from a simple energy consumer into an energy management system. To achieve smooth switching, the system also dynamically adjusts the pump frequency and valve opening during mode transitions to ensure continuous stability of flow and pressure parameters.

[0047] The greatest advantage of this adaptive flow control lies in its intelligent ability to cope with complex operating conditions. For example, in regions with large diurnal temperature differences in spring, the system can use co-current energy storage during the day and automatically switch to counter-current heat tracing at night to achieve 24-hour autonomous energy balance.

[0048] This embodiment embodies the design concept shift of modern energy systems from "one-way heating" to "two-way energy interaction," providing an innovative solution for thermal management in the field of renewable energy. Through adaptive control of the flow direction, it not only solves the limitations of fixed flow direction but also opens up a new way for heat tracing systems to participate in global energy optimization.

[0049] As one implementation method, since unilateral heating can easily lead to uneven thermal stress or local solidification of the molten salt pipe 10, this embodiment employs at least two heat tracing pipes 20, evenly distributed around the circumference of the molten salt pipe 10. For example, for a single molten salt pipe 10, two heat tracing pipes 20 can be symmetrically arranged on both sides of its bottom, or three pipes can be arranged around it at a 120-degree angle. This symmetrical layout ensures that heat is simultaneously input into the molten salt pipe 10 from multiple circumferential directions, resulting in a more uniform temperature field distribution across the cross-section of the molten salt pipe 10 and effectively eliminating heating dead zones. This not only improves the reliability of anti-solidification but also reduces the internal stress of the pipe material caused by temperature gradients, which is beneficial for the long-term safe operation of the equipment.

[0050] In one implementation, the heat source of the heat tracing pipe 20 comes from the high-temperature section of the molten salt pipe 10 or the working fluid system fluid heated by molten salt, so that the heat tracing pipe 20 utilizes the heat energy of the system in which the molten salt pipe 10 is located.

[0051] It should be noted that, in order to solve the technical and economic problems of high system energy consumption and the need for an external heat source, and to achieve the self-circulation of energy within the system, this embodiment traces the heat source of the heat tracing pipe 20 back to the molten salt pipe 10 system itself during implementation. Optionally, one approach is to extract some heat energy from the high-temperature section of the molten salt pipe 10, such as near the outlet of the molten salt heater, through a branch pipe. When the heat from the high-temperature section is guided to the low-temperature section, if there is a large temperature gradient or insufficient insulation in the heat transfer path, the heat will be lost to the environment during the transfer process, thereby increasing the overall heat loss of the system. In order to avoid the loss during the heat recovery process being greater than the energy saved, in addition to using an insulation layer to wrap both the molten salt pipe 10 and the heat tracing pipe 20, this approach also adjusts the flow rate and temperature of the heat tracing fluid based on real-time temperature detection. The system monitors the temperature gradient between the high-temperature section and the low-temperature section, and only activates the mode when the net benefit of heat transfer is positive (i.e., the recovered heat is greater than the transfer loss). This avoids the energy waste caused by blind heating. Alternatively, another approach is to utilize the working fluid system fluid heated by molten salt, such as superheated steam or high-temperature heat transfer oil in a power generation system.

[0052] Preferably, the heat tracing pipe 20 has at least one outlet, which is connected to a location in the working fluid system corresponding to the temperature level. By providing at least one outlet and connecting it to a location in the working fluid system (such as a high-pressure heater, deaerator, etc.) that matches the temperature level, this means that after the heat tracing fluid completes its heat tracing task on the molten salt pipe 10, the residual heat it carries is not wasted, but is instead transported to equipment or nodes in the working fluid system that require the required temperature level of heat energy. This achieves "cascade utilization" of heat energy and greatly improves the energy utilization efficiency of the entire system.

[0053] In one implementation, the heat tracing fluid is high-temperature water or heat transfer oil directly or indirectly generated by the working fluid system.

[0054] Since the molten salt pipeline 10 supplies energy to the working fluid system, thereby generating high-temperature products, the working fluid system will directly or indirectly produce high-temperature water or heat transfer oil. Using this high-temperature water or heat transfer oil as the heat tracing fluid has the following advantages: First, these fluids are from the same source as the main working fluid system, eliminating the risk of chemical incompatibility; second, there is no need to prepare or purchase a special heat tracing medium, reducing operating costs; third, their thermal properties are known and stable, which is beneficial for system design and control. This is conducive to system integration and resource optimization.

[0055] In another implementation, the heat tracing fluid is supplied by an external heat source independent of the molten salt pipe 10 system.

[0056] To provide system redundancy and flexibility, and to address the issue of heat tracing assurance when the system's own heat energy is insufficient or unavailable, this implementation configures the heat tracing system with an independent external heat source, such as a small electric heating boiler, a gas-fired boiler, or a heat source drawn from other process systems. When the main system's heat source is available, priority is given to utilizing the main system's heat energy. During main system startup, shutdown, or maintenance, this external heat source can be activated, ensuring that the molten salt pipeline 10 receives the necessary heat tracing under any operating condition, thus enhancing the reliability and adaptability of the entire system.

[0057] As one implementation method, the heat tracing fluid combines the two approaches described above. In practical applications of molten salt heat tracing systems, organically coupling the internal heat source with an independent external heat source is a crucial technical measure to improve system reliability and adaptability. This hybrid heat source design can cope with complex and variable operating conditions, prioritizing the use of internal waste heat resources to achieve optimal energy efficiency while providing robust operational support through an external heat source, thus achieving a delicate balance between energy saving and reliability.

[0058] More specifically, the system continuously monitors key state parameters characterizing the availability of internal heat sources, primarily including the temperature of the high-temperature section of the molten salt pipeline 10, the temperature and pressure of the working fluid system available for heat tracing, and the available flow rates of these fluids. These parameters collectively determine the "quality" and "quantity" of the internal heat sources. When monitoring data indicates that the temperature and flow rate of the internal heat sources can meet the current heat tracing requirements, the control system should prioritize the activation of the internal heat sources. This prioritization strategy maximizes the utilization of waste heat from the process, achieving cascaded energy utilization and conforming to the basic principles of energy conservation and consumption reduction.

[0059] When insufficient quality or quantity of the internal heat source is detected, the control logic needs to intervene promptly. Specific judgment conditions can be set as follows: when the temperature of the molten salt high-temperature section falls below its safe operating threshold, or the temperature of the working fluid system falls below the minimum heating temperature required to maintain the molten salt fluid's flowability, or its flow rate cannot maintain the minimum flow velocity required within the heating pipe 20, the system determines that the internal heat source is in an "unavailable" or "weakly available" state. At this time, the control system should smoothly start the external heat source. The external heat source (such as an electric heater, gas boiler, etc.) acts as an independent heat input, and its startup and power regulation should be able to quickly respond to the attenuation of the internal heat source, ensuring the continuity of the heating effect and preventing the molten salt from solidifying due to interruption of heat replenishment.

[0060] As one implementation, a thermally conductive enhancement component is also included. The thermally conductive enhancement component is disposed between the molten salt pipe 10 and the heat tracing pipe 20 to enhance the heat transfer between the two and solve the key physical problem of contact thermal resistance between the heat tracing pipe 20 and the molten salt pipe 10.

[0061] Optionally, the thermally conductive reinforcing member is a welded layer, which is fixed to the outer surface of the molten salt pipe 10 and / or the heat tracing pipe 20 to fill the gap between the molten salt pipe 10 and the heat tracing pipe 20. The thermally conductive reinforcing member is used to fill the mating gap between the molten salt pipe 10 and the heat tracing pipe 20, so that the two are tightly connected, and the heat tracing pipe 20 is fixed to the molten salt pipe 10 by welding process (such as continuous welding or intermittent welding). Optionally, the welded layer is fixed to the outer surface of the heat tracing pipe 20, and the welded layer is installed against the wall of the molten salt pipe 10. A thermally conductive filler is applied to the outer contact surface of the welded layer. In other words, a welded metal layer is first prepared on the outer surface of the heat tracing pipe 20, and this welded layer is then attached to the outer wall of the molten salt pipe 10, with microscopic gaps further eliminated using thermally conductive adhesives or other fillers. This metal-to-metal welded connection significantly reduces contact thermal resistance, and its thermal conductivity is far superior to that of mechanical contact.

[0062] In one implementation, the thermally reinforced component is a thermally reinforced filler layer, which is filled at the contact interface between the molten salt pipe 10 and / or the heat tracing pipe 20. Instead of welding, a flexible filler with high thermal conductivity (such as thermally conductive silicone grease, metal thermal paste, or phase change thermally conductive material) is filled at the contact interface of the two pipes to form a thermally reinforced filler layer, which simplifies construction and allows it to withstand certain vibrations and deformations.

[0063] In one implementation, the molten salt pipe 10 and the heat tracing pipe 20 are mechanically fixed together by clamping components. Using clamping components (such as pipe clamps or clamps) to press the two pipes together is suitable for situations where connection is not allowed or disassembly is required.

[0064] Optionally, the clamping component and the thermally conductive reinforced filler layer can be coupled in two ways to satisfy the reliability of the detachable fixed connection and improve the thermal conductivity.

[0065] As one implementation, a power pump is also included to drive the flow of the heat tracing fluid within the heat tracing pipe 20. The power pump provides the necessary head for the heat tracing fluid to circulate in the closed or open heat tracing pipe 20 loop, overcoming the pipe friction resistance and ensuring that the heat tracing fluid can flow through the entire pipe section requiring heat tracing at the designed flow rate and velocity. This is the basis for achieving active and controllable heat tracing.

[0066] Optionally, the contact area between the thermally conductive reinforcing member and the heat tracing pipe 20 accounts for 1 / 50 to 2 / 3 of the corresponding surface area of ​​the heat tracing pipe 20.

[0067] From the perspective of heat transfer efficiency, the contact area ratio directly determines the effectiveness of the heat flow path. When the contact area is too small (less than 1 / 50), a significant "bottleneck effect" will occur in the heat flow path. Even with high thermal conductivity materials, the overall thermal resistance will still be high, making effective heat transfer impossible. Conversely, when the contact area ratio is too large (more than 2 / 3), although it theoretically maximizes the heat transfer path, it significantly increases material costs and structural complexity, while the improvement in heat transfer efficiency exhibits a diminishing marginal return effect.

[0068] At the structural mechanics level, this ratio range cleverly balances the requirements of thermal stress distribution and mechanical constraints. When the contact area is small, there is sufficient deformation gap between the heat tracing pipe 20 and the molten salt pipe 10, which can effectively absorb the stress caused by the difference in thermal expansion coefficients. When the contact area ratio is controlled below 2 / 3, the system retains the necessary flexibility, avoiding stress concentration problems caused by a completely rigid connection. At the same time, the lower limit of 1 / 50 ensures the most basic structural stability and thermal conductivity continuity, preventing connection failure due to local overheating or mechanical vibration.

[0069] Secondly, referring to Figure 3 This embodiment provides a control method for a molten salt heat tracing system as described in the above embodiments, comprising: The temperature at a set position in the molten salt pipeline 10 is detected to obtain the first temperature; The temperature at a set location on the heat tracing pipe 20 is detected to obtain a second temperature. The first temperature is compared with the preset molten salt freezing point temperature, and the temperature deviation value is calculated. The preset molten salt freezing point temperature is dynamically set based on the molten salt type and environmental conditions. Based on the temperature deviation value, the flow rate, temperature or flow velocity of the heat tracing fluid in the heat tracing pipe 20 are dynamically adjusted so that the temperature of the molten salt pipe 10 is maintained at least higher than the preset molten salt freezing point temperature ∆T.

[0070] By detecting the temperature at key points in the molten salt pipe 10 and the heat tracing pipe 20, namely the first temperature and the second temperature, and comparing them with the freezing point temperature dynamically set based on the characteristics of the molten salt, the flow rate, temperature, or velocity of the heat tracing fluid can be dynamically adjusted. The ultimate goal is to maintain the molten salt temperature within a safe range above its freezing point, which realizes the transformation from "continuous heating" to "precise heat tracing on demand".

[0071] The freezing point temperature of molten salts is closely related to the type of molten salt and environmental conditions. Molten salts with different compositions exhibit consistent phase transition characteristics, with the freezing point primarily depending on their chemical composition and ratio. For example, the freezing point of a common binary salt is approximately 220℃, while that of a ternary molten salt can drop to 142℃. Furthermore, environmental conditions have a dynamic impact on the freezing point in several ways: changes in ambient temperature alter the heat loss rate of the molten salt system, thus affecting its supercooling; ambient pressure indirectly affects the freezing point by altering the vapor-liquid equilibrium of the molten salt; and atmospheric humidity and other conditions can cause the molten salt to absorb moisture, changing its composition and thus affecting its phase transition characteristics. Therefore, in practical engineering applications, it is essential to establish a dynamic relationship model between the freezing point and these parameters.

[0072] Optionally, ∆T is not lower than 10℃.

[0073] In one implementation, when the heat source of the heat tracing pipe 20 originates from the high-temperature section of the molten salt pipe 10 or from the working fluid system heated by molten salt, based on the real-time temperature distribution of the working fluid system, at least one outlet of the heat tracing pipe 20 is connected to a location in the working fluid system corresponding to the temperature level, so that the outlet temperature of the heat tracing fluid matches the heat demand at that location. For the scenario of system self-circulation, an additional step is added to control the connection position of the outlet of the heat tracing pipe 20 based on the real-time temperature distribution of the working fluid system, achieving dynamic matching of heat supply and demand, and improving the efficiency and versatility of the self-circulation mode.

[0074] In one implementation, the first and second temperatures are detected using a temperature sensor array, which is spaced apart along the length of the molten salt pipe 10 and the heat tracing pipe 20. By using a temperature sensor array spaced apart along the length of the pipes to perform temperature detection, more comprehensive and representative temperature field information is obtained, providing a reliable data foundation for precise control.

[0075] As one implementation method, for complex molten salt heat tracing systems that integrate internal heat sources, external heat sources, and countercurrent switching functions, a decision-making mechanism based on multi-objective optimization is established, which can dynamically select the optimal combination of heat sources and flow patterns according to real-time system status, external environmental parameters, and energy demand.

[0076] In terms of control architecture design, a multi-parameter fusion state awareness layer needs to be introduced. The system requires real-time acquisition of diverse data, including the inlet / outlet temperature of molten salt pipeline 10, ambient temperature, solar irradiance, state of charge (SOC) of the thermal storage tank, and external energy price signals. A dynamic weighting evaluation model is established to prioritize optimization objectives under different operating scenarios. For example, during peak energy cost periods, the weight of energy-saving objectives increases; under extreme weather conditions, the weight of reliability objectives becomes dominant. This dynamic weighting mechanism ensures that the control system can adapt to the conflicting needs of different scenarios.

[0077] Specifically, regarding scenario-based strategy selection, when the system detects that the temperature at the end of molten salt pipeline 10 is close to its freezing point and the ambient temperature drops sharply (such as on a winter night), the control system should prioritize the counter-current + external heat source mode. In this mode, the counter-current arrangement maximizes the heating efficiency at the end, while the external heat source provides a stable and reliable heat input, ensuring anti-condensation safety. Conversely, during sunny days when the high-temperature molten salt tank is nearing full capacity and the temperature at the front end of molten salt pipeline 10 is high, the system should switch to the co-current + self-heating source mode. In this mode, the co-current arrangement allows for effective recovery of the waste heat from the high-temperature molten salt, and the recovered heat can be used for energy storage or other process needs, achieving cascaded energy utilization.

[0078] The criteria for determining the timing of energy storage should be based on multi-timescale forecasting and control. In the short term, when a peak in heat tracing demand (e.g., low nighttime temperatures) or a rise in external energy prices is predicted within the next few hours, the system can utilize the current flow mode for energy storage during the current period. In the medium to long term, the system can adjust its energy storage strategy in advance by combining weather forecasts and production plans. Energy storage triggering conditions can be set as follows: when the SOC of the heat storage tank is below a threshold (e.g., 30%) and an increase in heat tracing demand is predicted, the current flow mode should be prioritized for energy storage; when the SOC is high (e.g., exceeding 80%) and heat tracing demand is stable, energy storage activities should be reduced.

[0079] To achieve the aforementioned complex decision-making, the control method needs to incorporate an algorithm combining fuzzy logic and model predictive control. Fuzzy logic handles qualitative descriptions such as "low temperature" and "sufficient sunshine," while model predictive control, based on the system's thermodynamic model, predicts and optimizes the system's state over a future period. Simultaneously, the control method should possess a smooth mode-switching mechanism. When switching from co-current energy storage mode to counter-current heat tracing mode, the flow rate and pressure should be smoothly transitioned by adjusting the pump frequency and valve opening to avoid fluid shock.

[0080] In summary, compared with the prior art, the above embodiments have at least the following technical advantages: The molten salt heat tracing system of the present invention achieves efficient heat transfer through a tight thermally conductive connection between the heat tracing pipe 20 and the molten salt pipe 10; the system can maximize the use of the heat exchange temperature difference by adopting a counter-current heat exchange method, thereby improving thermodynamic efficiency; the uniform distribution of multiple heat tracing pipes 20 in a circumferential manner ensures uniform temperature distribution; the system significantly improves heat transfer efficiency and reduces heat loss through thermally enhanced components and optimized pipe layout. When utilizing the system's own thermal energy, intelligent temperature matching and flow control enable tiered energy utilization, significantly reducing external energy requirements. The dynamic temperature control mechanism can quickly respond to changes in molten salt temperature and adjust heat tracing parameters in a timely manner, ensuring that the molten salt is always maintained within a safe temperature range. The system structure design takes into account the adaptability to different application scenarios. Through adjustable pipe layout and heat conduction interface design, it can adapt to the heat tracing needs of molten salt pipes of various specifications.

[0081] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A molten salt heat tracing system for preventing solidification of molten salt within a molten salt pipe conveying the molten salt, characterized by, The system comprises: a heat tracing pipe, which is in thermal contact with the molten salt pipe; wherein the heat tracing pipe is adapted to circulate a liquid or gaseous heat tracing fluid with a certain temperature, so that when the heat tracing fluid flows through the heat tracing pipe, heat is transferred from the heat tracing pipe to the molten salt pipe.

2. The system according to claim 1, wherein: the flow direction of the heat tracing fluid is opposite to the flow direction of the molten salt in the molten salt pipe, forming a counterflow heat exchange coupling.

3. The system according to claim 1, wherein: the number of the heat tracing pipes is at least two, the extension direction of the heat tracing pipes is consistent with the extension direction of the molten salt pipe, and the heat tracing pipes are uniformly distributed around the circumference of the molten salt pipe.

4. The system according to claim 1, wherein: the heat source of the heat tracing pipe is derived from the high-temperature section of the molten salt pipe or the working fluid system heated by the molten salt, so that the heat tracing pipe utilizes the heat energy of the system in which the molten salt pipe is located.

5. The system according to claim 4, wherein: the heat tracing pipe is provided with at least one outlet, and the outlet is in communication with a position corresponding to a temperature level in the working fluid system.

6. The system according to claim 4, wherein: the heat tracing fluid is high-temperature water or heat conducting oil directly or indirectly generated by the working fluid system.

7. The system according to claim 1, wherein: the heat tracing fluid is heated and provided by an external heat source independent of the molten salt pipe system.

8. The system according to any one of claims 1 to 7, further comprising: a heat conduction enhancement member, which is arranged between the molten salt pipe and the heat tracing pipe, and is used to enhance the heat transfer between the two.

9. The system according to claim 8, wherein: the heat conduction enhancement member is a welding layer, which is fixed to the outer surface of the molten salt pipe and / or the heat tracing pipe, and is used to fill the gap between the molten salt pipe and the heat tracing pipe.

10. The system according to claim 9, wherein: the welding layer is fixed to the outer surface of the heat tracing pipe, the welding layer is installed in close contact with the molten salt pipe, and a heat conduction enhancement filler is applied to the outer contact surface of the welding layer.

11. The system according to claim 8, wherein: the heat conduction enhancement member is a heat conduction enhancement filler layer, which is filled in the contact interface of the molten salt pipe and / or the heat tracing pipe.

12. The system according to claim 8, wherein: the molten salt pipe and the heat tracing pipe are mechanically fixed and connected by a clamping member.

13. The system according to any one of claims 1 to 7, further comprising: a power pump for driving the heat tracing fluid to flow in the heat tracing pipe.

14. The system according to claim 8, wherein: the contact area of the heat conduction enhancement member with the heat tracing pipe accounts for 1 / 50 to 2 / 3 of the corresponding surface area of the heat tracing pipe.

15. The system according to claim 8, wherein: The contact surface of the heat conduction enhancement member and the molten salt pipeline is a circular arc surface, and the curvature radius of the circular arc surface matches the outer diameter of the molten salt pipeline.

16. A control method for applying a molten salt heat tracing system according to any one of claims 1 to 15, characterized in that, Comprise: Detecting the temperature of the molten salt pipeline at a set position to obtain a first temperature; Detecting the temperature of the heat tracing pipeline at a set position to obtain a second temperature; Comparing the first temperature with a preset molten salt freezing point temperature to calculate a temperature deviation value, wherein the preset molten salt freezing point temperature is dynamically set based on the type of molten salt and environmental conditions; Based on the temperature deviation value, dynamically adjusting the flow rate, temperature or flow speed of the heat tracing fluid in the heat tracing pipeline to maintain the temperature of the molten salt pipeline at least higher than the preset molten salt freezing point temperature by ΔT.

17. The control method of claim 16, wherein ΔT is not less than 10°C.

18. The control method of claim 16, wherein When the heat source of the heat tracing pipeline comes from the high-temperature section of the molten salt pipeline or the working fluid system heated by the molten salt, according to the real-time temperature distribution of the working fluid system, at least one outlet of the heat tracing pipeline is controlled to communicate with a position corresponding to a temperature level in the working fluid system, so that the outlet temperature of the heat tracing fluid matches the heat demand of the position.

19. The control method of claim 16, wherein The detection of the first temperature and the second temperature uses a temperature sensor array, and the temperature sensor array is arranged at intervals along the length direction of the molten salt pipeline and the heat tracing pipeline.

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