Multi-module fused salt phase change heat storage system capable of achieving stable heat output and regulation and control method

Abstract

The invention relates to the technical field of heat energy storage and conversion, and discloses a multi-module fused salt phase change heat storage system capable of achieving stable heat output and a regulation and control method. The system comprises a plurality of standardized fused salt heat storage / heat exchange modules, a water tank, a water supply pipeline, a steam main loop and a central control system with a sensor. During operation, fused salt solidification heat release is utilized to generate steam, the steam flow, the liquid level and the fused salt temperature gradient of each module are monitored in real time through the central controller, and heat exchange attenuation caused by solidification layer thickening is predicted. And the liquid level, start and stop of the modules are dynamically adjusted by adopting sequential alternate regulation, so that the outputs of the modules in different attenuation states are subjected to superposition compensation, and the stability of the total steam flow is maintained. According to the invention, the heat exchange area does not need to be overmatched, the 100-200 DEG C saturated steam can be output, and the device is suitable for the fields of chemical industry and the like, and has both stability and economical efficiency.

Description

Technical Field

[0001] The present invention relates to the field of thermal energy storage and conversion technology, and provides a multi-module molten salt phase change heat storage system and control method for achieving stable heat output. Specifically, it relates to the application of phase change heat storage technology, high-efficiency heat exchange technology, heat pipe technology (such as application) and automatic control systems in industrial heat energy supply. It is particularly suitable for industrial processes such as chemical, electric power, and food processing that require stable output of saturated steam (temperature range 100-200°C). Background Art

[0002] In many industrial fields such as chemical industry, electric power, textile, and food processing, systems that use the latent heat of phase change materials (PCM) to store and release thermal energy are gradually being applied. Among them, the technology of using molten salts (such as nitrate mixtures) with a melting point in the range of 100-200°C as PCMs and utilizing the latent heat released during their solidification process to stably produce saturated water vapor has significant application value. The basic operating mode of such systems is: during periods of surplus electricity or thermal energy (such as low electricity prices or periods of solar energy enrichment), the molten salt is heated by an external heat source (such as an electric heater, solar collector, or waste heat) to melt it and store the heat energy in the form of latent heat; when steam is needed, cold water is passed into the heat storage system, the molten salt solidifies and releases latent heat, which heats the water and converts it into steam for output.

[0003] However, this type of heat storage system based on molten salt solidification and heat release faces a fundamental physical limitation and the resulting engineering challenges in actual operation: when the molten salt solidifies on the heat exchanger wall (the outer wall of the water pipe), a solid molten salt layer will inevitably form. This solidified solid molten salt layer has a low thermal conductivity, which is equivalent to adding a continuously thickening thermal resistance layer between the heat exchange wall and the water. As the solidification process progresses, the thickness of this solid layer continues to increase, resulting in a continuous increase in the overall heat transfer resistance and a significant decrease in the heat flux density. The direct consequence is that the steam flow rate output by the system continues to irreversibly decay over time.

[0004] This steam flow rate decline has multiple adverse effects: 1. Steam supply fluctuations. Downstream steam-consuming equipment (such as reactors, dryers, and steam turbines) requires a continuous and stable steam flow and pressure input. This steam flow decline forces downstream equipment to frequently adjust the opening of its intake valves to maintain process parameters, increasing operational complexity and reducing equipment stability and reliability. 2. Water hammer can be induced. Frequent valve adjustments, especially when closing or opening rapidly to respond to flow rate fluctuations, can easily trigger destructive water hammer in steam piping, impacting piping, valves, and equipment, and even causing leaks or damage. 3. Equipment utilization is low. To mitigate the rapid decline in steam production, existing technologies generally adopt a passive approach: significantly oversizing heat exchange area during initial design (often by 300% or more of the design requirement). While this "trading space for time" strategy can somewhat delay the time it takes for steam flow to decline to unacceptable levels, it also carries serious negative consequences: a sharp increase in initial investment costs for equipment (primarily heat exchangers), a significant increase in system footprint, increased material consumption, and poor overall economic efficiency. Especially in space-constrained application scenarios (such as distributed energy stations, plant renovation projects, and compact container systems), this large-scale over-allocation solution is often difficult to implement or too costly.

[0005] Therefore, the industry urgently needs an innovative system-level solution and control strategy that can overcome the aforementioned physical heat transfer limitations. This solution should effectively overcome the heat transfer degradation caused by the molten salt solidification layer without significantly increasing (or even reducing) the initial equipment investment and floor space, achieving sustained and stable steam output and meeting the stringent requirements of downstream equipment for steam parameter stability (flow rate, pressure). Summary of the Invention

[0006] The purpose of this invention is to provide a multi-module molten salt phase-change heat storage system and control method that achieves stable heat output. Its core technical approach is to abandon the traditional design concept of a single large module or a small number of modules and instead adopt a large number of standardized small heat exchange modules operating in parallel, and introduce an intelligent time-series rotation control mechanism. A central controller precisely coordinates the operating status of each module (including liquid level and start-stop sequence), so that the inherent heat exchange attenuation characteristics of individual modules are offset at the system level, thereby achieving highly stable total steam flow throughout the system.

[0007] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0008] In a first aspect, the present invention provides a multi-module molten salt phase change thermal storage system for achieving stable heat output, comprising:

[0009] Multiple standardized molten salt heat storage / exchange modules arranged in parallel, each of which contains molten salt and a water tube bundle immersed in the molten salt;

[0010] Water supply system, used to supply saturated water to each standardized molten salt heat storage / heat exchange module;

[0011] The main steam loop is used to collect the steam generated by each standardized molten salt heat storage / heat exchange module and transport it to downstream steam-consuming equipment;

[0012] The central controller is configured to: monitor the operating status parameters of each standardized molten salt heat storage / heat exchange module in real time, wherein the parameters include at least the steam output flow rate, the water level height in the module, and the molten salt temperature gradient; predict the heat exchange performance attenuation of each module based on the operating status parameters; according to the target steam flow rate, dynamically adjust the water supply valve opening of each module to control the water level height in the module, and combine the timing rotation strategy of activating or deactivating the modules to make the steam output of the modules in different attenuation states compensate each other, so as to maintain the total steam flow of the system stable near the target value.

[0013] Preferably, in the above system, the water supply system includes a water tank, a water supply pipeline, a water supply pump and a plurality of module-level water supply regulating valves; the water tank is used to store saturated water with the same temperature as the phase change point of the molten salt, the water tank is connected to each standardized molten salt heat storage / heat exchange module through a water supply pipeline, the water supply pump is installed on the water supply pipeline, and the module-level water supply regulating valve is installed at the inlet of each module to regulate the water flow; it also includes a plurality of module-level steam outlet one-way valves, which are installed between the steam outlet of each module and the steam main circuit.

[0014] Preferably, the above system also includes multiple module-level steam flow meters, multiple module-level liquid level gauges and a temperature sensor network; the module-level steam flow meters are correspondingly installed at the steam outlet of each module to monitor the instantaneous steam output flow; the module-level liquid level gauges are correspondingly installed at each module to monitor the water level; the temperature sensor network is buried at a key position on the molten salt side of each module to monitor the molten salt temperature distribution and gradient; the central controller is electrically connected to the above-mentioned sensors and valves to collect parameters and output instructions.

[0015] Preferably, in the above system, the central controller is a PLC or an industrial control computer with a built-in solidification layer dynamic model and a time-series rotation control algorithm; the solidification layer dynamic model is used to predict the heat exchange performance attenuation and steam output trend of each module, and the time-series rotation control algorithm is used to calculate and output instructions to control the liquid level or instantaneous output of each module to achieve system logic control.

[0016] In a second aspect, the present invention provides a method for regulating and controlling heat output stability of the system as described above, comprising the following steps:

[0017] S1: Start the first standardized molten salt heat storage / exchange module and adjust its water supply valve so that the water level in the module reaches a first set height, which is determined by calculating the target flow rate, so that the module outputs steam at an initial output;

[0018] S2: Real-time monitoring of the steam output flow, water level and molten salt temperature gradient of the operating module, and prediction of the thickness of the molten salt solidification layer and the heat transfer performance attenuation trend in the module based on the accumulated operating time and temperature gradient;

[0019] S3: When it is monitored that the steam output flow rate of the operating module has decayed to a first predetermined proportion of its initial output, the second standardized molten salt heat storage / exchange module is started; the water supply valve of the second module is adjusted to make the second module output a supplementary output, and the supplementary output is equal to the flow rate decay of the operating module;

[0020] S4: Based on the real-time output and attenuation status of each operating module, dynamically adjust the opening of the water supply valve of each operating module to change its water level, so that the sum of the real-time output of all operating modules maintains the target steam flow rate;

[0021] S5: When the steam output flow rate of the first-run module decays to a second predetermined proportion of its initial output, the water supply valve of the module is closed to stop steam output, and a new module or a regenerated module is started; the water supply valve of the newly started module is adjusted to output an initial output; at the same time, the water levels of the other modules still in operation are dynamically adjusted so that the total system output maintains the target steam flow rate;

[0022] S6: If the target steam flow rate changes, the required total output is recalculated and the total system output is made to match the new target flow rate by adjusting the water level of the operating module or activating / deactivating the module.

[0023] Preferably, in the above control method, in step S2, the thickness of the molten salt solidification layer is predicted by obtaining the temperature difference between the heat exchange wall and the molten salt body through a temperature sensor network, and determining that the solidification layer is thickening and the thermal resistance is increasing when the temperature difference increases.

[0024] Preferably, in the above control method, in step S3, the first predetermined ratio is 90%; in step S5, the second predetermined ratio is 5-10%; the module that stops producing steam enters the molten salt melting regeneration stage, and serves as a backup module after the regeneration is completed.

[0025] Preferably, in the above-mentioned control method, in step S6, when the target steam flow fluctuates, if the target flow increases, the water level of the operating module is preferentially increased to increase the output, and if the operating module has reached the maximum output, a new module is activated; if the target flow decreases, the water level of some operating modules is lowered to reduce the output.

[0026] Preferably, in the above control method, the instantaneous steam output rate of the standardized molten salt heat storage / heat exchange module is a function of the current water level and the accumulated operating time, and its instantaneous steam output rate is controlled by adjusting the water level.

[0027] The present invention provides a multi-module molten salt phase change heat storage system and a control method for achieving stable heat output:

[0028] Compared with traditional single-module or small-module over-provisioning solutions, it has the following significant technical advantages.

[0029] 1) Excellent time-averaged steam output stability: Through multi-module rotation and dynamic liquid level adjustment, fluctuations in total steam output at the system level are effectively suppressed. Measured data shows that under continuous operation, the system's total steam flow rate can be stably maintained near the set target value, with fluctuations within a range of ≤±4.8%. This high stability completely eliminates the problem of frequent inlet valve adjustments in downstream equipment due to steam flow attenuation, significantly improving downstream process stability and product quality, and fundamentally eliminating the risk of pipeline water hammer caused by frequent adjustments.

[0030] 2) Effectively maintain or improve system energy efficiency: This avoids the "big horse pulling a small cart" phenomenon (part of the heat exchange area is in an inefficient or ineffective working state for a long time) caused by severe over-allocation of heat exchange area in traditional solutions; by precisely controlling the liquid level and operating status of each module, the system always operates close to the design operating point, reducing unnecessary heat loss and pump power consumption; the modular design facilitates the isolation, maintenance or regeneration of individual modules with severely degraded performance without affecting the continued operation of the entire system, thereby improving the overall availability and energy efficiency of the system.

[0031] 3) Significant economic breakthrough: It greatly saves equipment investment and abandons the strategy of excessively over-allocating heat exchange area to delay attenuation in traditional solutions (usually over-allocating by 300%). The present invention achieves stable output through system-level intelligent control, and the total heat exchange area required is closer to actual demand, which significantly reduces the material cost and manufacturing cost of the core heat exchange equipment; the floor space is greatly reduced: the modular and compact design, combined with the improvement of area utilization, makes the floor space of the system of the present invention much smaller than that of traditional over-allocated large-scale heat exchange systems under the same steam production capacity. This has a decisive advantage for space-constrained application scenarios (such as urban distributed energy stations, factory renovation projects, and mobile steam supply units); reduces operation and maintenance costs: the stable operation of the system reduces the action frequency of actuators such as valves and extends their service life; the design of standardized modules also facilitates spare parts management and replacement, reducing maintenance complexity and cost; the system is highly flexible and scalable: the modular architecture makes it easy to adjust the system capacity by increasing or decreasing the number of modules to adapt to different steam demand scales. The intelligent control algorithm can also adapt to load fluctuations and provide flexible steam supply capabilities.

[0032] In summary, the present invention combines a multi-module parallel structure, molten salt solidification layer thickness monitoring / prediction technology, and an intelligent time-series rotation liquid level control strategy. It cleverly overcomes the inherent heat exchange attenuation problem of a single molten salt phase change heat storage module at the system level, achieves highly stable steam production output, and at the same time brings significant economic benefits and engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a multi-module molten salt phase change thermal storage system for achieving stable heat output provided by an embodiment of the present invention.

[0034] Figure 2 This is a flow chart of a method for regulating heat output stability provided by an embodiment of the present invention.

[0035] Reference numerals:

[0036] 101, first standardized molten salt heat storage / heat exchange module; 102, second standardized molten salt heat storage / heat exchange module; 10X, Xth standardized molten salt heat storage / heat exchange module;

[0037] 201, first module-level steam flow meter; 202, second module-level steam flow meter; 20X, Xth module-level steam flow meter;

[0038] 301, first module-level steam outlet one-way valve; 302, second module-level steam outlet one-way valve; 30X, Xth module-level steam outlet one-way valve;

[0039] 401, first module-level water supply regulating valve; 402, second module-level water supply regulating valve; 40X, Xth module-level water supply regulating valve;

[0040] 501, first module level gauge; 502, second module level gauge; 50X, Xth module level gauge;

[0041] 6. Water tank;

[0042] 7. Water supply pipeline;

[0043] 8. Water supply pump;

[0044] 9. Steam main circuit. DETAILED DESCRIPTION

[0045] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0046] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0047] Example 1:

[0048] like Figure 1 The figure shows a schematic diagram of the structure of a multi-module molten salt phase-change thermal storage system that achieves stable heat output according to an embodiment of the present invention. The embodiment of the present invention provides a multi-module molten salt phase-change thermal storage system that achieves stable heat output. The multi-module molten salt phase-change thermal storage system that achieves stable heat output includes multiple standardized molten salt heat storage / heat exchange modules (101-10X), a water supply system, a steam main circuit 9, a temperature sensor network, and a central controller.

[0049] A number of standardized molten salt heat storage / heat exchange modules (101 to 10X) are the core units of the system. The number of modules X is determined according to the total capacity and stability requirements of the system, and is usually in the range of 10 to 100. The structure of each standardized molten salt heat storage / heat exchange module is the same, including built-in molten salt (as a phase change heat storage medium) and a water tube bundle immersed in the molten salt (as a steam generation heat exchange surface). The design of the standardized molten salt heat storage / heat exchange module must ensure that the molten salt is physically isolated from the water / steam in the water pipe, and heat exchange is only carried out through the pipe wall. Figure 1As shown, three standardized molten salt heat storage / heat exchange modules are shown, namely a first standardized molten salt heat storage / heat exchange module 101, a second standardized molten salt heat storage / heat exchange module 102 and an Xth standardized molten salt heat storage / heat exchange module 10X.

[0050] The water supply system is used to supply saturated water to each standardized molten salt heat storage / heat exchange module, including a water tank 6, a water supply pipeline 7, a water supply pump 8 and multiple module-level water supply regulating valves (401~40X). The water tank 6 is used to store supply water, and its water temperature needs to be maintained at a saturated water state at the same temperature as the phase change point (melting point / freezing point) of the molten salt used to minimize thermal shock and initial heat loss when the module is started. The water supply pump 8 pressurizes the saturated water from the water tank 6 and transports it to each module through the main water supply pipeline 7. An independent, precisely adjustable opening valve (such as an electric regulating valve) is installed at the inlet of each standardized molten salt heat storage / heat exchange module as a module-level water supply regulating valve to control the water flow entering the module, thereby precisely adjusting the water level in the module. The water level directly determines the effective immersed heat exchange area of ​​the water tube bundle in the standardized molten salt heat storage / heat exchange module. The number of module-level water supply regulating valves is consistent with the standardized molten salt heat storage / heat exchange module, such as Figure 1 As shown, three module-level water supply regulating valves are shown, namely the first module-level water supply regulating valve 401, the second module-level water supply regulating valve 402 and the Xth module-level water supply regulating valve 40X.

[0051] The steam main loop 9 collects the steam generated by all standardized molten salt heat storage / heat exchange modules (101~10X) and transmits it to the downstream steam-using equipment. A one-way valve is installed at the steam outlet of each standardized molten salt heat storage / heat exchange module (101~10X) as a module-level steam outlet one-way valve (301~30X). It has two functions: one is to prevent steam from flowing back to the module from the main loop; the other is to set a minimum opening pressure to ensure that the steam pressure in the module reaches a certain value (to ensure steam quality) before it can be output. Figure 1 As shown, three module-level steam outlet one-way valves are shown, namely the first module-level steam outlet one-way valve 301, the second module-level steam outlet one-way valve 302 and the Xth module-level steam outlet one-way valve 30X.

[0052] Multiple module-level steam flow meters (201-20X) are used to monitor the instantaneous steam output flow of each standardized molten salt heat storage / heat exchange module (101-10X) in real time, which is one of the most important feedback signals of the control system. Figure 1 As shown, three module-level steam flow meters are shown, namely a first module-level steam flow meter 201, a second module-level steam flow meter 202 and an Xth module-level steam flow meter 20X.

[0053] Multiple module-level liquid level gauges (501-50X) are used to monitor the water level in each standardized molten salt heat storage / heat exchange module (101-10X) in real time. Figure 1 As shown, three module-level liquid level gauges are shown, namely a first module-level liquid level gauge 501, a second module-level liquid level gauge 502 and an Xth module-level liquid level gauge 50X.

[0054] The temperature sensor network includes multiple thermocouples embedded in key locations on the molten salt side of each standardized molten salt heat storage / exchange module (101-10X), particularly near the heat exchange wall. These thermocouples monitor the temperature distribution and gradient of the molten salt in real time. By analyzing temperature differences between specific locations, the thickness of the solidified layer and its growth trend can be indirectly but effectively inferred. For example, a larger temperature difference between the pipe wall and the molten salt bulk away from the pipe wall generally indicates a thicker solidified layer and increased thermal resistance.

[0055] The central controller is the core processing unit of the system, typically implemented by a high-performance PLC (Programmable Logic Controller) or industrial control computer. Its core functions include: real-time acquisition of key operating parameters such as steam flow (201-20X), liquid level (501-50X), and molten salt temperature gradient (for solidification layer thickness prediction) for all modules; running a built-in temperature difference prediction algorithm or a more complex solidification layer dynamic model, combined with real-time data, to predict the current degree of heat transfer performance (thermal resistance) degradation and future steam production capacity trends for each module; executing the time-series rotation control algorithm designed in this invention based on the system's set total target steam flow (load demand) and the real-time status of each module, dynamically calculating and outputting instructions to each water supply regulating valve (401-40X) to accurately control the liquid level (i.e., its instantaneous output) of each module; and implementing logical control of the system's startup, operation, shutdown, and protection functions.

[0056] The working principle of the multi-module molten salt phase change thermal storage system that achieves stable heat output is as follows:

[0057] The saturated water in the water tank 6 is pressurized by the water pump 8 and then transported through the main water supply pipeline 7. Taking the first standardized molten salt heat storage / heat exchange module 101 as an example, when the first module-level water supply regulating valve 401 at the inlet of a standardized molten salt heat storage / heat exchange module (e.g., 101) is opened, pressurized water enters the water tube bundle of that module. The latent heat stored in the molten salt (currently in liquid or partially liquid) within the first standardized molten salt heat storage / heat exchange module 101 is transferred to the water within the tubes through the tube walls. After absorbing the heat, the water undergoes a phase change, generating steam. As steam continues to be generated, the pressure within the first standardized molten salt heat storage / heat exchange module 101 increases. When the pressure exceeds the set opening pressure of the first module-level steam outlet check valve 301 of the first standardized molten salt heat storage / heat exchange module 101, the steam pushes open the check valve, enters the main steam loop 9, and is transported to downstream users. During this process, the molten salt gradually solidifies on the outer wall of the heat exchange tubes due to the release of latent heat.

[0058] From a heat transfer perspective, the steam production (flow) of a single standardized molten salt heat storage / heat exchange module at a certain moment is mainly affected by two key variables:

[0059] ① The water level within the module: The water level determines the effective heat exchange area within the water tube bundle that is submerged in the molten salt. The higher the water level, the larger the effective heat exchange area, theoretically increasing the amount of heat that can be transferred instantaneously and the potential for steam production.

[0060] ② The module's cumulative steam production time (i.e., the molten salt solidification and heat release time): As the heat release time increases, the solidified layer on the outer wall of the heat exchange tube continues to thicken, resulting in a continuous increase in thermal resistance. Even if the liquid level (heat exchange area) remains unchanged, the actual heat transfer rate (heat flux density) will significantly decrease, and steam production will also decline.

[0061] Therefore, for a single standardized molten salt heat storage / exchange module, its instantaneous steam output rate is a function of its current liquid level (which determines the heat exchange area) and its cumulative operating time (which determines the thermal resistance). From a regulatory perspective, the most direct and effective method is to adjust the water level within the module by adjusting the opening of the inlet water valve, thereby adjusting its instantaneous steam output. The higher the liquid level, the greater the proportion of the load currently borne by the standardized molten salt heat storage / exchange module.

[0062] Example 2:

[0063] The embodiment of the present invention provides a method for regulating heat output stability, which is implemented based on the multi-module molten salt phase change heat storage system for achieving heat output stability provided in Example 1. Figure 2 FIG. 1 is a flow chart of a method for regulating and controlling heat output stability provided by an embodiment of the present invention. The method for regulating and controlling heat output stability includes the following steps S1 to S6.

[0064] S1: Start the first standardized molten salt heat storage / exchange module and adjust its water supply valve so that the water level in the module reaches a first set height. The first set height is determined based on the target flow rate so that the module outputs steam at an initial output.

[0065] S2: Real-time monitoring of the steam output flow, water level and molten salt temperature gradient of the operating module, and prediction of the thickness of the molten salt solidification layer and the heat transfer performance attenuation trend in the module based on the accumulated operating time and temperature gradient.

[0066] S3: When the steam output flow rate of the operating module is monitored to have decayed to a first predetermined proportion of its initial output, the second standardized molten salt heat storage / exchange module is activated. The water supply valve of the second module is adjusted to cause the second module to output a supplemental output equal to the flow rate decay of the operating module. At the same time, the water level of the operating module is optionally adjusted to maintain or adjust its output.

[0067] S4: As the operation continues, based on the real-time output and attenuation status of each operating module, the water supply valve opening of each operating module is dynamically adjusted to change its water level height, so that the sum of the real-time output of all operating modules maintains the target steam flow.

[0068] S5: When the steam output flow of the earliest running module decays to the second predetermined proportion of its initial output, the water supply valve of the module is closed to stop it from outputting steam, and a new module or a regenerated module is started; the water supply valve of the newly started module is adjusted to output an initial output; at the same time, the water levels of other modules that are still in operation are dynamically adjusted so that the total output of the system maintains the target steam flow.

[0069] S6: If the target steam flow rate changes, the required total output is recalculated and the total system output is made to match the new target flow rate by adjusting the water level of the operating module or activating / deactivating the module.

[0070] In this embodiment, the above-mentioned heat output stable control method can be configured as a time-sequential rotation control algorithm or model, which is placed in the central controller of the system and executed and implemented by the central controller. Figure 1 The system structure diagram shown here illustrates an exemplary workflow for this method for stabilizing heat output. Specifically, the core of this method is to leverage the advantages of multiple modules in parallel, implementing dynamic, timed rotation control through a central controller. This allows each module to operate in different stages (e.g., full load, load ramping, load reduction, and standby), staggering their respective performance degradation curves, and implementing system-level compensation.

[0071] All standardized molten salt heat storage / heat exchange modules have the same designed maximum steam output (eg, the designed maximum output of each module is Q_max).

[0072] As described above, steps S1 to S3 correspond to the system startup and initial load maintenance phase, and in an exemplary embodiment, they are implemented through the following steps 1 to 7.

[0073] Step 1: System startup and initial stage.

[0074] When the system starts operating (or when demand begins), the central controller first activates only one standardized molten salt heat storage / exchange module. In this embodiment, taking the first standardized molten salt heat storage / exchange module 101 as an example, the central controller controls the opening of the first module-level feedwater regulating valve 401 of the first standardized molten salt heat storage / exchange module 101 so that its liquid level reaches a first set height determined by the target flow rate calculation. At this point, the first standardized molten salt heat storage / exchange module 101 outputs steam at its initial output (100% of the design steam flow rate, i.e., 100% × Q_max), and the total system output is 100% × Q_max.

[0075] Step 2: Attenuation monitoring and module relay start-up.

[0076] The central controller continuously monitors the steam flow rate (via a first-module-level steam flowmeter) and / or the molten salt temperature gradient (to predict the thickness of the solidified layer) of the first standardized molten salt thermal storage / exchange module 101. When the steam flow rate of the first standardized molten salt thermal storage / exchange module 101 decreases from its initial maximum to 90% of the initial output (i.e., 90% × Q_max) (this is a first predetermined ratio), the control action begins. The central controller opens the second-module-level feedwater regulating valve 402 of the second standardized molten salt thermal storage / exchange module 102. However, the central controller does not immediately raise the liquid level to its maximum. Instead, the central controller precisely controls the opening of the second-module-level feedwater regulating valve 402 to ensure that the initial liquid level of the second standardized molten salt thermal storage / exchange module 102 reaches a level that allows it to output approximately 10% × Q_max (i.e., the supplementary output is equal to the flow rate attenuation of the operating module by 10% × Q_max, and the second standardized molten salt thermal storage / exchange module 102 begins to assume 10% of the system load). At this time, the total output of the system is jointly maintained by the first standardized molten salt heat storage / heat exchange module 101 (about 90%×Q_max) and the second standardized molten salt heat storage / heat exchange module 102 (about 10%×Q_max), and the total is still 100%×Q_max.

[0077] Step 3: Progressive load transfer.

[0078] As the operation time of the first standardized molten salt heat storage / heat exchange module 101 continues to increase, its steam flow rate will further decrease.

[0079] Step 4. When the flow rate of the first standardized molten salt heat storage / heat exchange module 101 drops to 80% of the initial output (i.e., 80%×Q_max), the central controller increases the opening of the second module-level water supply regulating valve 402 of the second standardized molten salt heat storage / heat exchange module 102, raises its liquid level, and increases its output load to 20%×Q_max. At this time, the first standardized molten salt heat storage / heat exchange module 101 contributes 80%×Q_max, and the second standardized molten salt heat storage / heat exchange module 102 contributes 20%×Q_max, and the total is 100%×Q_max.

[0080] Step 5. When the flow rate of module 101 drops to 70% of the initial output (i.e., 70%×Q_max), the central controller continues to increase the liquid level of the second standardized molten salt heat storage / heat exchange module 102 to increase its load to 30%×Q_max (101: 70%×Q_max + 102: 30%×Q_max = 100%×Q_max).

[0081] Step 6. Similarly, when the flow rate of the first standardized molten salt heat storage / heat exchange module 101 drops to 60% (i.e., 60%×Q_max) and 50% (i.e., 50%×Q_max) of the initial output, the load of the second standardized molten salt heat storage / heat exchange module 102 is correspondingly increased to 40%×Q_max and 50%×Q_max.

[0082] Step 7: Introduce new modules.

[0083] When the liquid levels of the first standardized molten salt heat storage / heat exchange module 101 and the second standardized molten salt heat storage / heat exchange module 102 have reached the designed maximum value, that is, 101 and 102 are both at their respective maximum output states, but the sum of their steam outputs (for example, 101 at 50%×Q_max+102 at 50%×Q_max=100%×Q_max) cannot meet the system's current total load demand of 100%×Q_max or actual demand (that is, module 101 is too attenuated, and even if module 102 is at full output, it cannot be fully compensated), the controller opens the module-level feed water regulating valve of the next module. The next module can be, for example, the third standardized molten salt heat storage / heat exchange module (which is not in Figure 1 ), the initial liquid level of the third standardized molten salt heat storage / heat exchange module is controlled at a level that can output the required supplementary load. For example, if the total demand at this time is 100%×Q_max, 101+102 can only provide 90%×Q_max, then the third standardized molten salt heat storage / heat exchange module is initially set to output 10%×Q_max.

[0084] Figure 2Step S4 corresponds to the subsequent regulation and rotation phase, which continues based on the same regulation logic as steps S1-S3 (or steps 1-7 above). As the earliest operating module (e.g., 101) decays to a very low output, for example, below 5-10% of the initial output (i.e., the second predetermined ratio), or when the total liquid level of all modules reaches the upper limit and the total output is still insufficient, indicating that most modules have severely decayed, the central controller can selectively close the water inlet valve (e.g., 401) of the earliest operating module, stopping water intake and entering the molten salt melting regeneration or thermal recovery phase (if the system is designed with regeneration capabilities). At the same time, a new or previously recovered module is started to take its place, beginning a new round of load increase-decline cycle. In this way, multiple modules in the system are always in different performance states (from new and high output to old and low output). By dynamically adjusting their liquid levels or outputs, the total steam flow rate of the system can be accurately maintained stable near the set value.

[0085] Figure 2 Step S5 corresponds to the demand fluctuation phase. That is, step S5 is executed when demand fluctuates. Specifically, if the system's real-time steam demand exceeds the maximum output of a single module (100% of the design value), for example, 120% × Q_max, the control method is similar but with a different starting point. For example, this can be implemented through the following steps S501-S504.

[0086] S501, initial state, the controller adjusts the first module-level water supply regulating valve 401 of the first standardized molten salt heat storage / heat exchange module 101 to reach a height determined by calculation according to the target flow rate, and outputs 100%×Q_max.

[0087] S502. The central controller opens the second module-level water supply regulating valve 402 of the second standardized molten salt heat storage / heat exchange module 102 and precisely controls its opening so that the initial liquid level of the second standardized molten salt heat storage / heat exchange module 102 reaches a level that can output an additional 20%×Q_max, that is, the second standardized molten salt heat storage / heat exchange module 102 initially outputs 20%×Q_max.

[0088] S503: Determine the total system output:

[0089] 120% × Q_max (101: 100% × Q_max + 102: 20% × Q_max).

[0090] S504, subsequent control operations.

[0091] During system operation, when the steam flow rate of the first standardized molten salt heat storage / heat exchange module 101 decays, for example, it drops to 90% of the initial design flow rate (i.e., 90%×Q_max), the central controller adjusts the liquid level of the second standardized molten salt heat storage / heat exchange module 102 to increase its steam output to 30%×Q_max. At this time, the total steam output of the system is 90%×Q_max+30%×Q_max=120%×Q_max, maintaining the initial target flow rate.

[0092] However, there are special circumstances in actual operation. If the output of the second standardized molten salt heat storage / exchange module 102 is increased to its maximum design output, that is, the output accounts for 100% × Q_max, while the steam flow of the first standardized molten salt heat storage / exchange module 101 continues to decline, for example, to 80% of the initial design flow (i.e., 80% × Q_max), if no regulation is performed at this time, the total system output will reach 180% × Q_max (80% × Q_max + 100% × Q_max), far exceeding the target requirement of 120% × Q_max.

[0093] Therefore, the control logic needs to be optimized. The optimized control logic is as follows: When the flow rate of the first standardized molten salt heat storage / heat exchange module 101 decreases and the output of the second standardized molten salt heat storage / heat exchange module 102 needs to be increased to maintain the total system output at 120% × Q_max, the second standardized molten salt heat storage / heat exchange module 102 is first determined to have reached its designed maximum output (100% × Q_max). If not, its output is directly increased. If it has reached its maximum output and the total output still does not meet the 120% × Q_max requirement, the third standardized molten salt heat storage / heat exchange module is activated, and its output supplement value is precisely set based on the total output shortfall (for example, the difference between the target 120% × Q_max and the current total output). Conversely, if the total output falls below the target due to module attenuation, the output of each module can be increased by raising the liquid level of the operating module or by activating a new module to supplement it. If the total output exceeds the target, the liquid level of some operating modules is lowered to reduce their steam output.

[0094] The core logic of step S6 is that the central controller always dynamically calculates and adjusts the liquid level setting value of each module (through the regulating valve) based on the total demand signal and the real-time output capacity of all modules (determined by their liquid level and attenuation status), so that the sum of the output of each module accurately matches the current total demand.

[0095] For example, when the target steam flow rate drops from 120%×Q_max to 100%×Q_max, the central controller can first lower the liquid level of the second standardized molten salt heat storage / heat exchange module 102 to reduce its output from 30%×Q_max to 10%×Q_max, while keeping the output of the first standardized molten salt heat storage / heat exchange module 101 stable at 90%×Q_max, and the total output is 90%×Q_max+10%×Q_max=100%×Q_max; if the output of the first standardized molten salt heat storage / heat exchange module 101 has decayed to 80%×Q_max at this time, the output of the second standardized molten salt heat storage / heat exchange module 102 can be adjusted to 20%×Q_max to ensure that the total maintains the target value.

[0096] When the steam flow rate of the first standardized molten salt heat storage / exchange module 101, which is running the earliest, decays to 5-10% of its initial output (i.e., a second predetermined ratio, such as 5% × Q_max), the central controller closes its first module-level feedwater regulating valve 401, causing it to stop producing steam and enter the molten salt melting and regeneration phase (using external heat source heating to melt the solidified layer and restore heat storage capacity). Simultaneously, the third standardized molten salt heat storage / exchange module (new or regenerated) is activated and its feedwater valve opening is adjusted to output steam at its initial output (100% × Q_max). At this time, if the current output of the second standardized molten salt heat storage / heat exchange module 102 is 40%×Q_max, in order to maintain the overall target of 100%×Q_max, the central controller will reduce the output of the second standardized molten salt heat storage / heat exchange module 102 to 0%×Q_max (or adjust it to the corresponding value according to the actual attenuation situation), and the third standardized molten salt heat storage / heat exchange module will solely bear the 100%×Q_max output, forming a cycle of old module deactivation and new module replacement.

[0097] Through the above-mentioned time-series rotation and dynamic load distribution strategy, the system can always maintain a stable total steam flow rate even when a single module continues to attenuate, avoiding the economic problems caused by over-allocation of heat exchange area in traditional solutions, while ensuring the stable operation of downstream steam-using equipment.

[0098] The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention. The scope of patent protection of the present invention should be defined by the claims.

Claims

1. A multi-module molten salt phase change heat storage system that achieves stable heat output, characterized in that: include: Multiple standardized molten salt heat storage / exchange modules arranged in parallel, each of which contains molten salt and a water tube bundle immersed in the molten salt; Water supply system, used to supply saturated water to each standardized molten salt heat storage / heat exchange module; The main steam loop is used to collect the steam generated by each standardized molten salt heat storage / heat exchange module and transport it to downstream steam-consuming equipment; The central controller is configured to: monitor the operating status parameters of each standardized molten salt heat storage / heat exchange module in real time, wherein the parameters include at least the steam output flow rate, the water level height in the module, and the molten salt temperature gradient; predict the heat exchange performance attenuation of each module based on the operating status parameters; according to the target steam flow rate, dynamically adjust the water supply valve opening of each module to control the water level height in the module, and combine the timing rotation strategy of activating or deactivating the modules to make the steam output of the modules in different attenuation states compensate each other, so as to maintain the total steam flow of the system stable near the target value.

2. The system according to claim 1, wherein: The water supply system includes a water tank, a water supply pipeline, a water supply pump and multiple module-level water supply regulating valves; the water tank is used to store saturated water with the same temperature as the phase change point of the molten salt. The water tank is connected to each standardized molten salt heat storage / heat exchange module through a water supply pipeline. The water supply pump is installed on the water supply pipeline. The module-level water supply regulating valve is installed at the inlet of each module to regulate the water flow; it also includes multiple module-level steam outlet one-way valves, which are installed between the steam outlet of each module and the steam main circuit.

3. The system according to claim 1, wherein: It also includes multiple module-level steam flow meters, multiple module-level liquid level gauges and a temperature sensor network; the module-level steam flow meters are installed at the steam outlet of each module to monitor the instantaneous steam output flow; the module-level liquid level gauges are installed at each module to monitor the water level; the temperature sensor network is buried at key positions on the molten salt side of each module to monitor the molten salt temperature distribution and gradient; the central controller is electrically connected to the above-mentioned sensors and valves to collect parameters and output instructions.

4. The system according to claim 1, wherein: The central controller is a PLC or industrial control computer with a built-in solidification layer dynamic model and a time-series rotation control algorithm; the solidification layer dynamic model is used to predict the heat exchange performance attenuation and steam output trend of each module, and the time-series rotation control algorithm is used to calculate and output instructions to control the liquid level or instantaneous output of each module to achieve system logic control.

5. A method for controlling heat output stability based on the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Start the first standardized molten salt heat storage / exchange module and adjust its water supply valve so that the water level in the module reaches a first set height, which is determined by calculating the target flow rate, so that the module outputs steam at an initial output; S2: Real-time monitoring of the steam output flow, water level and molten salt temperature gradient of the operating module, and prediction of the thickness of the molten salt solidification layer and the heat transfer performance attenuation trend in the module based on the accumulated operating time and temperature gradient; S3: When it is monitored that the steam output flow rate of the operating module has decayed to a first predetermined proportion of its initial output, the second standardized molten salt heat storage / exchange module is started; the water supply valve of the second module is adjusted to make the second module output a supplementary output, and the supplementary output is equal to the flow rate decay of the operating module; S4: Based on the real-time output and attenuation status of each operating module, dynamically adjust the opening of the water supply valve of each operating module to change its water level, so that the sum of the real-time output of all operating modules maintains the target steam flow rate; S5: When the steam output flow rate of the first-run module decays to a second predetermined proportion of its initial output, the water supply valve of the module is closed to stop steam output, and a new module or a regenerated module is started; the water supply valve of the newly started module is adjusted to output an initial output; at the same time, the water levels of the other modules still in operation are dynamically adjusted so that the total system output maintains the target steam flow rate; S6: If the target steam flow rate changes, the required total output is recalculated and the total system output is made to match the new target flow rate by adjusting the water level of the operating module or activating / deactivating the module.

6. The control method according to claim 5, characterized in that: In step S2, the thickness of the molten salt solidification layer is predicted by obtaining the temperature difference between the heat exchange wall and the molten salt body through a temperature sensor network, and determining that the solidification layer is thickening and the thermal resistance is increasing when the temperature difference increases.

7. The control method according to claim 5, characterized in that: In step S3, the first predetermined ratio is 90%; in step S5, the second predetermined ratio is 5-10%; the module that stops producing steam enters the molten salt melting regeneration stage and serves as a backup module after the regeneration is completed.

8. The control method according to claim 5, characterized in that: In step S6, when the target steam flow fluctuates, if the target flow increases, the water level of the operating module is prioritized to increase the output. If the operating module has reached the maximum output, a new module is activated. If the target flow decreases, the water level of some operating modules is lowered to reduce the output.

9. The control method according to claim 5, characterized in that: The instantaneous steam output rate of the standardized molten salt heat storage / heat exchange module is a function of the current water level and the accumulated operating time, and its instantaneous steam output rate is controlled by adjusting the water level.

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