A heat exchange system applied to molten salt energy storage heating and a running method thereof

Abstract

The application discloses a heat exchange system applied to molten salt energy storage heating and an operation method thereof, and particularly relates to the field of molten salt energy storage heating, and comprises the following steps: S1, fault diagnosis is conducted on each device of the system; S2, high-temperature loop starting is completed through heat medium loop starting, circulating pump starting, flow regulation and buffer tank pressure correction; S3, the molten salt loop is started and temperature control is conducted, the valve opening degree is adjusted based on a formula to stabilize the flow of the high-temperature loop, the total flow of the circulating pump is controlled synchronously, and the stable conditions of flow, molten salt outlet temperature and pump pressure are met, so that it is determined that the loop starting is completed; the intermediate medium in the heat exchange system is liquid, and the heat exchange system is driven by a circulating pump, so that the operation reliability and economy are higher than those of gaseous medium; the heat exchange system can be applied to heat exchange with a temperature difference greater than 500 DEG C, and can guarantee the thermal stress safety of the heat exchanger and the medium safety; and the application reduces the investment cost of the pump by reducing the design temperature of the circulating pump.

Description

Technical Field

[0001] This invention relates to the field of molten salt energy storage and heating technology, and more specifically, to a heat exchange system and its operation method applied to molten salt energy storage and heating. Background Technology

[0002] With the gradual depletion of fossil fuels and the increasing severity of environmental problems, the energy supply system is shifting from being dominated by traditional thermal power generation to being dominated by clean energy sources such as wind and solar power. Wind and solar energy exhibit significant intraday fluctuations, and their peak power generation times are mismatched with peak electricity and heat loads. Molten salt-based energy storage and heating technology can store excess heat during clean energy power generation periods and release it during peak load periods, becoming one of the core technologies for mitigating this mismatch problem. It has already been initially applied in industrial heating and residential heating sectors.

[0003] The core advantage of existing molten salt energy storage heating technology lies in its ability to achieve long-term heat storage and on-demand release, effectively connecting new energy power generation with end-user heating demand. Molten salt also possesses characteristics such as high temperature resistance, high specific heat capacity, and strong chemical stability, making it suitable as a high-temperature heat storage medium. However, this technology has significant shortcomings when applied in the field of low-parameter heating: First, the storage temperature of molten salt is generally high, resulting in a large temperature difference between it and the low-parameter heat medium. This can easily lead to condensation and blockage of pipelines on the molten salt side due to localized low temperatures, while the heat medium on the cooling side may boil due to localized high temperatures, causing equipment overpressure. At the same time, the large temperature difference can generate severe thermal stress in the heat exchange equipment, leading to failures such as weld cracking and pipe wall deformation. Second, existing solutions often use air as an intermediate heat exchange medium to reduce localized temperature differences. However, air has extremely low thermal conductivity and volumetric specific heat, requiring a significant increase in the heat exchanger area to meet heat exchange requirements. This not only increases equipment investment costs but also necessitates the use of high-power fans to drive air circulation, resulting in high fan power consumption and high operating noise, making it difficult to balance economic efficiency and environmental protection.

[0004] Therefore, in response to the problems of equipment failure caused by large heat exchange temperature differences in low-parameter fields, poor economic efficiency of air heat exchange, and weak system adaptability to fluctuations in existing molten salt energy storage heating technology, there is an urgent need for a heat exchange system and its operation method for molten salt energy storage heating. By constructing a high-temperature-low-temperature dual heat exchange loop, designing a mixer with a free expansion structure, and establishing a full-parameter dynamic adjustment mechanism, safe heat exchange under large temperature differences can be achieved, while reducing equipment costs and operating energy consumption, and improving the system's adaptability to the fluctuations of new energy sources. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a heat exchange system and its operation method for molten salt energy storage and heating, and solves the problems mentioned in the background art through the following scheme.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a heat exchange operation method for molten salt energy storage and heating, comprising a high-temperature molten salt heat exchanger, a heating circulation heat exchanger, a mixer, a buffer tank, a circulation pump, a regulating valve, and a heat exchange circuit connecting the above devices, specifically further comprising:

[0007] S1. Perform fault diagnosis on each device in the system;

[0008] S2. The high-temperature circuit is started through the start-up of the heat medium circuit, the start-up and flow regulation of the circulating pump, and the pressure correction of the buffer tank.

[0009] S3. Start the molten salt circuit and control the temperature. Adjust the valve opening based on the formula to stabilize the flow rate of the high-temperature circuit. Synchronously control the total flow rate of the circulating pump. Once the flow rate, molten salt outlet temperature and pump pressure are stable, the circuit start-up is considered complete.

[0010] S4. Calculate the mixer outlet temperature by combining multiple parameters. If the temperature deviates from the set range, adjust the high and low temperature circuit flow ratio based on the formula to control the temperature within the set range.

[0011] S5. Ensure temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations;

[0012] S6. The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

[0013] Preferably, the fault diagnosis involves confirming that the heat exchange channels of the high-temperature molten salt heat exchanger and the heating circulation heat exchanger are not blocked, the thin-walled inner tube of the mixer is not deformed, the pressure sensor of the buffer tank, the speed sensor of the circulating pump, and the opening sensor of the regulating valve are all working normally, and the circulating pump and the regulating valve are in the closed state.

[0014] Preferably, the heat medium circuit startup involves: opening the heat medium inlet and outlet valves of the heating circulation heat exchanger to allow the low-parameter heat medium to enter the low-temperature side at the designed flow rate; monitoring the heat medium inlet temperature in real time using a temperature sensor and controlling it to stabilize at the set value; the circulation pump startup and flow regulation involves: starting the circulation pump, initially setting the speed, and gradually increasing the speed to raise the heat medium flow rate in the low-temperature heat exchange circuit from 0 to the designed flow rate; during this process, flow data is collected in real time using a flow sensor; if the flow rate deviates from the design value, the speed is corrected by frequency conversion adjustment, with the following correction logic: when the flow rate is lower than 95% of the design value, the speed is increased by 50 r / min every 30 seconds; when the flow rate is higher than 105% of the design value, the speed is decreased by 50 r / min every 30 seconds until the flow rate stabilizes within a reasonable threshold range; and pressure data is collected in real time using a buffer tank pressure sensor. If the pressure deviates from the rated value, correction is made based on the correlation between the circulation pump speed and pressure, using the following correction formula. ,in This indicates the corrected circulating pump speed. This indicates the original circulating pump speed. Indicates the rated pressure of the buffer tank. Indicates the current pressure of the buffer tank. This indicates the rated outlet pressure of the circulating pump; the specific start-up criteria for the high-temperature circuit are: when the flow rate of the low-temperature heat exchange circuit stabilizes at 2.85-3.15 kg / s and the pressure of the buffer tank stabilizes at 1.14 × 10⁻⁶ kg / s. 5 -1.26×10 5 When the outlet temperature of the heat medium stabilizes within the threshold range, the low-temperature heat exchange circuit is considered to have completed startup and entered a stable operating state.

[0015] Preferably, the specific method for starting the molten salt circuit and controlling the temperature is as follows: Open the molten salt inlet valve and outlet valve of the high-temperature molten salt heat exchanger to allow the high-temperature molten salt to enter the high-temperature side at the designed flow rate; control the molten salt inlet temperature to stabilize at the set value using a temperature sensor; simultaneously monitor the molten salt outlet temperature, which must meet a dual threshold constraint condition, including threshold 1 and threshold 2, where threshold 1 is the molten salt outlet temperature. Molten salt initial crystallization temperature + safety redundancy; Threshold 2: molten salt outlet temperature The molten salt inlet temperature is reduced by twice the upper difference, where the safety redundancy is determined based on the molten salt flow rate. The upper difference represents the difference between the molten salt inlet temperature and the heat exchange medium outlet temperature in the high-temperature molten salt heat exchanger; the maximum value of the two thresholds is taken to avoid the risk of condensation.

[0016] Preferably, the specific method for adjusting the valve opening is as follows: the valve opening is initially set to 20%, the medium flow rate is collected by a flow sensor in the high-temperature heat exchange circuit, and the opening is gradually increased based on the correlation model of opening degree-flow rate-pressure, so that the flow rate approaches the design value. The correlation model formula is as follows: ,in This indicates the current flow rate of the high-temperature heat exchange circuit. This indicates the design flow rate of the high-temperature heat exchange circuit. Indicates the opening degree of the regulating valve. This indicates the current outlet pressure of the circulating pump. The specific method for controlling the total flow rate of the circulating pump is as follows: while adjusting the valve opening, simultaneously increase the circulating pump speed to stabilize the total output flow rate within ±5% of the designed total flow rate. During this process, it is necessary to ensure that the circulating pump outlet pressure gradually rises to the rated value to avoid sudden pressure increases that could cause pipeline impact. The circuit startup is complete when the high-temperature heat exchange circuit flow rate stabilizes at 2.375-2.625 kg / s, the molten salt outlet temperature stabilizes within the threshold range, and the circulating pump outlet pressure stabilizes at 2.375 × [value missing]. -2.625× When Pa is reached, it is determined that the high-temperature heat exchange circuit has been started and the system has entered the dual-circuit joint operation state.

[0017] Preferably, the calculation of the mixer outlet temperature is performed by using flow rate sensors connected to the low-temperature medium in the main pipe and the high-temperature medium in the branch pipe of the mixer to collect the flow rate of the medium in the main pipe. Flow velocity of medium in branch pipe Combined with the density of the heat exchange medium Calculate the mixer outlet temperature ,in Indicates the molten salt inlet temperature. This indicates a poor temperature difference at the top of the high-temperature molten salt heat exchanger. Indicates the flow rate of the low-temperature heat exchange circuit. Indicates the inlet temperature of the heat medium. This indicates the temperature difference at the lower end of the heat exchanger in the heating cycle. This represents the specific heat capacity of the heat exchange medium at constant pressure; the formula-based correction of the high and low temperature loop flow ratio: if If the value exceeds the threshold, it indicates that the proportion of high-temperature medium is too high, and the opening of the regulating valve needs to be reduced to lower the concentration. Make the flow rate higher than / Lower; if If the value is less than the threshold value of 2, increase the opening of the regulating valve to improve performance. The corrected flow ratio must meet the following requirements. ,in This represents the target value of the mixer outlet temperature. The target flow ratio is calculated using this formula, and then combined with... Stable value, reverse calculation Adjust the value, and it will eventually be Control within the set range to avoid molten salt condensation and boiling of the heating medium.

[0018] Preferably, the real-time monitoring and correction of thermal stress involves: collecting the thermal stress on the walls of the high-temperature molten salt heat exchanger and the heating cycle heat exchanger in real time using stress sensors. Based on the system operating parameters, the theoretical thermal stress was calculated using the following formula and then compared with the measured values ​​for verification: Where k represents the thermal conductivity of the heat transfer medium, if If the value exceeds the allowable value, it needs to be reduced synchronously. and Reduce total flow, adjustment range meets requirements This adjustment reduces thermal stress to within acceptable limits, preventing equipment failure due to excessive stress; the fluctuation adaptation adjustment: when the high-temperature molten salt inlet temperature fluctuates, it is adjusted... Adaptability: Increases with rising temperature To reduce the residence time of molten salt in the heat exchanger and avoid localized overheating; to reduce the temperature when decreasing. To extend the residence time and ensure sufficient heat exchange; when the inlet temperature of the heat medium fluctuates, adjustments are made to... Adaptability: Increases with rising temperature To improve heat exchange efficiency, reduce the temperature drop. Avoid using excessively low outlet temperatures for the heat transfer medium; the entire adjustment process must ensure... The thermal stress is always kept within the set threshold to ensure system stability.

[0019] Preferably, the high-temperature molten salt circuit is shut down as follows: close the high-temperature molten salt inlet valve, keep the regulating valve opening unchanged, continue running the high-temperature heat exchange circuit for 12 minutes, monitor the molten salt outlet temperature using a temperature sensor until the temperature drops below 290℃, ensuring that the residual molten salt in the heat exchanger is completely discharged and there is no condensation; the high-temperature circuit and regulating valve are shut down as follows: gradually reduce the regulating valve opening by 10% every 30 seconds until the opening is 0%, then close the regulating valve; simultaneously stop the operation of the high-temperature heat exchange circuit and disconnect it from the mixer; the circulating pump and low-temperature circuit are shut down as follows: reduce the circulating pump speed by 100 r / min every 30 seconds, so that... Gradually reduce the temperature to 0 and shut down the circulating pump; then close the inlet and outlet valves of the heating medium in the heating circulation heat exchanger to stop the operation of the heating medium circuit; system cooling and depressurization: when the temperature of each piece of equipment drops to 30-40℃ and the pipeline pressure drops to atmospheric pressure, open the system vent valve to complete the shutdown operation.

[0020] Preferably, a heat exchange system for molten salt energy storage and heating includes a high-temperature molten salt heat exchanger, a heating circulation heat exchanger, a mixer, a buffer tank, a circulation pump, a regulating valve, and a heat exchange circuit connecting the above devices, and further includes:

[0021] System initialization module: performs fault diagnosis on various devices in the system;

[0022] Low-temperature heat exchanger loop start-up and stability control module: High-temperature loop start-up is achieved through heat medium loop start-up, circulating pump start-up and flow regulation, and buffer tank pressure correction;

[0023] High-temperature heat exchanger loop start-up and flow coordinated regulation module: Starts the molten salt loop and controls the temperature, adjusts the valve opening based on the formula to stabilize the flow of the high-temperature loop, and controls the total flow of the circulating pump synchronously. When the flow rate, molten salt outlet temperature and pump pressure are stable, the loop start-up is determined to be complete.

[0024] Mixer medium mixing and precise temperature control module: Combines multiple parameters to calculate the mixer outlet temperature. If the temperature deviates from the set range, it corrects the high and low temperature loop flow ratio based on the formula to control the temperature within the set range.

[0025] System operation status monitoring and dynamic adjustment module: Ensures temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations;

[0026] System shutdown operation module: The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

[0027] The technical effects and advantages of this invention are as follows:

[0028] 1. The intermediate medium of the heat exchange system of the present invention is liquid, driven by a circulating pump, and has higher reliability and economy than gaseous medium. The heat exchange system of the present invention can be used for heat exchange with a temperature difference greater than 500℃, and can ensure the thermal stress safety of the heat exchanger and the safety of the medium. The operating temperature of the circulating pump in the heat exchange system of the present invention can be reduced by appropriately lowering the flow ratio of the high-temperature heat exchange circuit to the low-temperature heat exchange circuit, and the investment cost of the pump can be reduced by lowering the design temperature of the circulating pump.

[0029] 2. This invention utilizes the high thermal conductivity and high volumetric specific heat characteristics of the liquid heat exchange medium, combined with a high-temperature-low-temperature dual heat exchange loop synergistic operation mechanism, and employs a precise temperature control formula for the mixer outlet and a dynamic correction formula for thermal stress in the heat exchange equipment. This solves the problems in the prior art where a large temperature difference between the molten salt storage temperature and the low-parameter heat exchange medium leads to condensation and blockage of the pipeline on the molten salt side, boiling of the heat exchange medium on the cooling side causing equipment overpressure, and weld cracking / pipe wall deformation in the heat exchange equipment due to severe thermal stress. This reduces the risk of equipment failure, extends the service life of the equipment, and ensures the continuous and safe operation of the system.

[0030] 3. This invention achieves the operational benefits of reducing the heat exchanger area and lowering the energy consumption of the circulating pump by using heat transfer oil instead of traditional air as the intermediate heat exchange medium, combined with variable frequency speed control of the circulating pump. It solves the problems in the background technology where air heat exchange medium has extremely low thermal conductivity and volumetric specific heat, requiring a significant increase in heat exchanger area, resulting in high investment costs, and requiring a high-power fan drive, leading to high power consumption and high operating noise. It reduces the heat exchanger area, lowers the initial investment cost of the equipment, reduces the power consumption of the circulating pump and the operating noise of the system, and achieves the beneficial effects of both economy and environmental protection. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the overall structure of the present invention;

[0033] Figure 3 This is a schematic diagram of the system structure of the present invention;

[0034] Figure 4 This is a schematic diagram of the internal structure of the mixer of the present invention.

[0035] In the diagram: 1. High-temperature molten salt heat exchanger, 2. Heating circulation heat exchanger, 3. Mixer, 3.1. Main pipe, 3.2. Branch pipe, 3.3. Main pipe thin-walled inner tube, 3.4. Branch pipe thin-walled inner tube, 4. Buffer tank, 5. Circulation pump, 6. Regulating valve. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] A heat exchange operation method for molten salt energy storage and heating includes a high-temperature molten salt heat exchanger 1, a heating circulation heat exchanger 2, a mixer 3, a buffer tank 4, a circulation pump 5, a regulating valve 6, and a heat exchange circuit connecting the above devices.

[0038] The heat exchange circuit uses liquid as the heat exchange medium.

[0039] The heat exchange system consists of a high-temperature heat exchange circuit and a low-temperature heat exchange circuit. The pipes from the mixer 3 to the circulating pump 5 share the same route.

[0040] Under stable operating conditions, the heat exchange circuit has the same heat load as the high-temperature heat exchange circuit and the low-temperature heat exchange circuit.

[0041] Under stable operating conditions, the flow rate of the circulating pump 5 in the heat exchange circuit is the sum of the flow rates of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit.

[0042] The heat exchange circuit shall have at least one flow regulating valve installed on a non-common pipeline.

[0043] Under stable operating conditions, the temperature of the medium in the shared piping of the high-temperature and low-temperature heat exchange circuits can be adjusted by regulating the flow rate ratio between the high-temperature and low-temperature heat exchange circuits. The adjustment formula is as follows: ,in: For the temperature of the medium in the shared pipeline; This refers to the inlet temperature of the high-temperature medium. The temperature difference at the top of the high-temperature molten salt heat exchanger; This refers to the mass flow rate of the medium in the high-temperature heat exchange circuit. This refers to the inlet temperature of the low-temperature heat medium. The lower end of the heat exchanger in the heating cycle is differentially oriented; This represents the mass flow rate of the medium in the low-temperature heat exchange circuit.

[0044] As attached Figure 2The heat exchange operation method shown, applied to molten salt energy storage and heating, further includes:

[0045] S1. Perform fault diagnosis on each device in the system;

[0046] Specifically, the fault diagnosis confirms that the heat exchange channels of the high-temperature molten salt heat exchanger 1 and the heating circulation heat exchanger 2 are not blocked, the thin-walled inner tube of the mixer is not deformed, the pressure sensor of the buffer tank, the speed sensor of the circulating pump, and the opening sensor of the regulating valve are all working normally, and the circulating pump 5 and the regulating valve 6 are in the closed state.

[0047] S2. The high-temperature circuit is started through the start-up of the heat medium circuit, the start-up and flow regulation of the circulating pump, and the pressure correction of the buffer tank 4.

[0048] Specifically, the following points need to be explained: The heat medium loop startup involves opening the inlet and outlet valves of the heating circulation heat exchanger to allow the low-parameter heat medium to enter the low-temperature side at the designed flow rate. The inlet temperature of the heat medium is monitored in real-time by a temperature sensor and controlled to remain stable at the set value. The circulation pump startup and flow regulation involve starting the circulation pump, initially setting the speed, and gradually increasing the speed to raise the flow rate of the heat exchange medium in the low-temperature heat exchange loop from 0 to the designed flow rate. During this process, flow data is collected in real-time by a flow sensor. If the flow rate deviates from the design value, the speed is corrected by frequency conversion adjustment. The correction logic is as follows: when the flow rate is lower than 95% of the design value, the speed is increased by 50 r / min every 30 seconds; when the flow rate is higher than 105% of the design value, the speed is decreased by 50 r / min every 30 seconds until the flow rate stabilizes within a reasonable threshold range. Pressure data is collected in real-time by a buffer tank pressure sensor. If the pressure deviates from the rated value, correction is made based on the correlation between the circulation pump speed and pressure. The correction formula is as follows. ,in This indicates the corrected circulating pump speed. This indicates the original circulating pump speed. This indicates the rated pressure of buffer tank 4. This indicates the current pressure of buffer tank 4. This indicates the rated outlet pressure of the circulating pump; the specific start-up criteria for the high-temperature circuit are: when the flow rate of the low-temperature heat exchange circuit stabilizes at 2.85-3.15 kg / s and the pressure of buffer tank 4 stabilizes at 1.14 × 10⁻⁶ kg / s. 5 -1.26×10 5When the outlet temperature of the heat transfer medium stabilizes within the threshold range, the low-temperature heat exchange circuit is considered to have completed its startup and entered a stable operating state. The sequence of "starting the low-temperature circuit (heat transfer end) first, then starting the high-temperature circuit (heat source end)" conforms to the control logic of industrial heat exchange systems: if the high-temperature circuit is started first, the high-temperature medium entering the mixer will not be buffered by the low-temperature medium, causing a sudden rise in the mixer temperature and directly triggering boiling of the heat transfer medium. Stabilizing the low-temperature circuit first allows the continuous flow of the heat transfer medium to "receive" the heat from the subsequent high-temperature medium, avoiding temperature fluctuations. The necessity of pressure correction in buffer tank 4: When the circulating pump 5 starts, stops, or its flow rate is adjusted, the pipeline pressure will experience instantaneous fluctuations (such as a sudden pressure rise when the pump starts). If not corrected, pressure exceeding the threshold will cause cracking of the pipeline welds. Therefore, by correcting using the speed-pressure correlation formula, pressure fluctuations can be controlled within ±5%, ensuring pipeline safety.

[0049] S3. Start the molten salt circuit and control the temperature. Adjust the valve opening based on the formula to stabilize the flow rate of the high-temperature circuit. Synchronously control the total flow rate of the circulating pump. Once the flow rate, molten salt outlet temperature and pump pressure are stable, the circuit start-up is considered complete.

[0050] Specifically, the method for starting the molten salt circuit and controlling the temperature is as follows: Open the molten salt inlet and outlet valves of the high-temperature molten salt heat exchanger, allowing the high-temperature molten salt to enter the high-temperature side at the designed flow rate. The molten salt inlet temperature is stabilized at a set value using a temperature sensor. Simultaneously, the molten salt outlet temperature is monitored and must meet a dual threshold constraint condition, which includes threshold 1 and threshold 2. Threshold 1 is the molten salt outlet temperature. Molten salt initial crystallization temperature + safety redundancy; Threshold 2: molten salt outlet temperature The molten salt inlet temperature is reduced by twice the upper difference, where the safety redundancy is determined based on the molten salt flow rate. The upper difference represents the difference between the molten salt inlet temperature and the heat exchange medium outlet temperature in the high-temperature molten salt heat exchanger. The maximum value of the two thresholds is used to avoid the risk of condensation. The specific method for adjusting the valve opening is as follows: the initial valve opening is set to 20%. The medium flow rate is collected by the flow sensor in the high-temperature heat exchange circuit. Based on the correlation model of opening degree-flow rate-pressure, the opening degree is gradually increased to make the flow rate approach the design value. The correlation model formula is as follows: ,in This indicates the current flow rate of the high-temperature heat exchange circuit. This indicates the design flow rate of the high-temperature heat exchange circuit. Indicates the opening degree of the regulating valve. This indicates the current outlet pressure of the circulating pump. The specific method for controlling the total flow rate of the circulating pump is as follows: while adjusting the valve opening, simultaneously increase the circulating pump speed to stabilize the total output flow rate within ±5% of the designed total flow rate. During this process, it is necessary to ensure that the circulating pump outlet pressure gradually rises to the rated value to avoid sudden pressure increases that could cause pipeline impact. The circuit startup is complete when the high-temperature heat exchange circuit flow rate stabilizes at 2.375-2.625 kg / s, the molten salt outlet temperature stabilizes within the threshold range, and the circulating pump outlet pressure stabilizes at 2.375 × [value missing]. -2.625× When the temperature reaches Pa, the high-temperature heat exchange loop is considered to have started successfully, and the system enters a dual-loop joint operation state. The core purpose of controlling the high-temperature molten salt outlet temperature is as follows: Molten salt solidifies when the temperature is below its freezing point, but in actual operation, if the molten salt stays in the heat exchanger for too long, the local temperature may fall below the freezing point. Therefore, setting "outlet temperature ≥ inlet temperature - 2 × upper end difference" ensures that the molten salt remains liquid in the heat exchanger, preventing blockage. The necessity of coordinated adjustment of the regulating valve opening and the total flow rate of the circulating pump is also crucial: The high-temperature loop flow rate is affected not only by the regulating valve opening but also by the circulating pump outlet pressure (the greater the pressure difference, the greater the flow rate). If only the opening is adjusted without adjusting the pump speed, the total flow rate will exceed the threshold, causing the circulating pump to overload. Therefore, synchronous adjustment ensures flow matching between the two loops, preventing system overload.

[0051] S4. Calculate the mixer outlet temperature by combining multiple parameters. If the temperature deviates from the set range, adjust the high and low temperature circuit flow ratio based on the formula to control the temperature within the set range.

[0052] Specifically, it should be noted that the calculation of the mixer outlet temperature is achieved by using flow rate sensors to collect the flow rate of the medium in the main pipe (for the low-temperature medium) and the branch pipe (for the high-temperature medium). Flow velocity of medium in branch pipe Combined with the density of the heat exchange medium Calculate the mixer outlet temperature ,in Indicates the molten salt inlet temperature. This indicates a poor temperature difference at the top of the high-temperature molten salt heat exchanger. Indicates the flow rate of the low-temperature heat exchange circuit. Indicates the inlet temperature of the heat medium. This indicates the temperature difference at the lower end of the heat exchanger in the heating cycle. This represents the specific heat capacity of the heat exchange medium at constant pressure; the formula-based correction of the high and low temperature loop flow ratio: if If the value exceeds the threshold, it indicates that the proportion of high-temperature medium is too high, and the opening of the regulating valve needs to be reduced to lower the concentration. Make the flow rate higher than / Lower; if If the value is less than the threshold value of 2, increase the opening of the regulating valve to improve performance. The corrected flow ratio must meet the following requirements. ,in This represents the target value of the mixer outlet temperature. The target flow ratio is calculated using this formula, and then combined with... Stable value, reverse calculation Adjust the value, and it will eventually be Control within the set range to avoid molten salt condensation and boiling of the heating medium.

[0053] S5. Ensure temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations;

[0054] Specifically, it should be noted that the real-time monitoring and correction of thermal stress involves collecting data on the thermal stress of the equipment walls in real time using stress sensors on the walls of the high-temperature molten salt heat exchanger and the heating circulation heat exchanger. Based on the system operating parameters, the theoretical thermal stress was calculated using the following formula and then compared with the measured values ​​for verification: Where k represents the thermal conductivity of the heat transfer medium, if If the value exceeds the allowable value, it needs to be reduced synchronously. and Reduce total flow, adjustment range meets requirements This adjustment reduces thermal stress to within acceptable limits, preventing equipment failure due to excessive stress; the fluctuation adaptation adjustment: when the high-temperature molten salt inlet temperature fluctuates, it is adjusted... Adaptability: Increases with rising temperature To reduce the residence time of molten salt in the heat exchanger and avoid localized overheating; to reduce the temperature when decreasing. To extend the residence time and ensure sufficient heat exchange; when the inlet temperature of the heat medium fluctuates, adjustments are made to... Adaptability: Increases with rising temperature To improve heat exchange efficiency, reduce the temperature drop. Avoid using excessively low outlet temperatures for the heat transfer medium; the entire adjustment process must ensure... The thermal stress is always kept within the set threshold to ensure system stability.

[0055] S6. The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

[0056] Specifically, the following should be noted: Shutting down the high-temperature molten salt circuit: Close the high-temperature molten salt inlet valve, keep the regulating valve opening unchanged, and continue running the high-temperature heat exchange circuit for 12 minutes. Monitor the molten salt outlet temperature using a temperature sensor until the temperature drops below 290℃, ensuring that any residual molten salt in the heat exchanger is completely discharged and there is no condensation. Shutting down the high-temperature circuit and regulating valve: Gradually reduce the regulating valve opening by 10% every 30 seconds until the opening is 0%, then close the regulating valve. Simultaneously, stop the operation of the high-temperature heat exchange circuit and disconnect it from the mixer. Shutting down the circulating pump and low-temperature circuit: Reduce the circulating pump speed by 100 r / min every 30 seconds. Gradually reduce the temperature to 0 and shut down the circulating pump; then close the inlet and outlet valves of the heating medium in the heating circulation heat exchanger to stop the operation of the heating medium circuit; system cooling and depressurization: when the temperature of each piece of equipment drops to 30-40℃ and the pipeline pressure drops to atmospheric pressure, open the system vent valve to complete the shutdown operation.

[0057] In another aspect, in some embodiments, this application provides a heat exchange system for molten salt energy storage and heating, as shown in the attached figure. Figure 1 and Figure 4 As shown, the system includes a high-temperature molten salt heat exchanger 1, a heating circulation heat exchanger 2, a mixer 3, a buffer tank 4, a circulating pump 5, a regulating valve 6, and a heat exchange loop connecting the above devices. The heat exchange system uses a liquid as the heat exchange medium, whose thermal conductivity and volumetric specific heat are significantly higher than those of a gaseous heat exchange medium. The heat exchange system is suitable for heat exchange scenarios with temperature differences of 150-500℃. The heat exchange loop consists of a high-temperature heat exchange loop and a low-temperature heat exchange loop, which are connected by a common pipeline. The high-temperature molten salt heat exchanger 1, mixer 3, buffer tank 4, circulating pump 5, and regulating valve 6 are sequentially connected by pipelines to form the high-temperature heat exchange loop. The heating circulation heat exchanger 2, mixer 3, buffer tank 4, and circulating pump 5 are sequentially connected by pipelines to form the low-temperature heat exchange loop. The heat exchange medium in the heat exchange loop includes molten salt, heat transfer oil, and liquid metal. The high-temperature molten salt heat exchanger in the heat exchange circuit can also be other types of heat exchangers. The heat source is not limited to molten salt, but includes, but is not limited to, solid heat storage medium and phase change heat storage medium. The mixer 3 consists of a main pipe 3.1 and a branch pipe 3.2. The branch pipe 3.2 is connected to the main pipe 3.1 upstream of the main pipe 3.1. Both the main pipe 3.1 and the branch pipe 3.2 consist of an outer pipe and a thin-walled inner pipe. The upstream end of the thin-walled inner pipe is fixed to the outer pipe, and the downstream end can expand freely. The upstream end of the thin-walled inner pipe 3.4 of the branch pipe is expanded and sealed and welded to the outer pipe of the branch pipe 3.2. The thin-walled inner pipe 3.4 of the branch pipe extends into the thin-walled inner pipe 3.3 of the main pipe.

[0058] As attached Figure 3 The heat exchange system shown, applied to molten salt energy storage and heating, further includes:

[0059] System initialization module: performs fault diagnosis on various devices in the system;

[0060] Low-temperature heat exchanger loop start-up and stability control module: High-temperature loop start-up is achieved through heat medium loop start-up, circulating pump start-up and flow regulation, and buffer tank pressure correction;

[0061] High-temperature heat exchanger loop start-up and flow coordinated regulation module: Starts the molten salt loop and controls the temperature, adjusts the valve opening based on the formula to stabilize the flow of the high-temperature loop, and controls the total flow of the circulating pump synchronously. When the flow rate, molten salt outlet temperature and pump pressure are stable, the loop start-up is determined to be complete.

[0062] Mixer medium mixing and precise temperature control module: Combines multiple parameters to calculate the mixer outlet temperature. If the temperature deviates from the set range, it corrects the high and low temperature loop flow ratio based on the formula to control the temperature within the set range.

[0063] System operation status monitoring and dynamic adjustment module: Ensures temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations;

[0064] System shutdown operation module: The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

[0065] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0066] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat exchange operation method applied to molten salt energy storage and heating, characterized in that, This includes a high-temperature molten salt heat exchanger, a heating circulation heat exchanger, a mixer, a buffer tank, a circulating pump, regulating valves, and a heat exchange circuit connecting the above devices. Specifically, it also includes: S1. Perform fault diagnosis on each device in the system; S2. The high-temperature circuit is started through the start-up of the heat medium circuit, the start-up and flow regulation of the circulating pump, and the pressure correction of the buffer tank. S3. Start the molten salt circuit and control the temperature. Adjust the valve opening based on the formula to stabilize the flow rate of the high-temperature circuit. Synchronously control the total flow rate of the circulating pump. Once the flow rate, molten salt outlet temperature and pump pressure are stable, the circuit start-up is considered complete. S4. Calculate the mixer outlet temperature by combining multiple parameters. If the temperature deviates from the set range, adjust the high and low temperature circuit flow ratio based on the formula to control the temperature within the set range. The mixing mixer outlet temperature is calculated by using flow rate sensors on the main pipe connected to the low-temperature medium and the branch pipe connected to the high-temperature medium to collect the flow rate of the medium in the main pipe. Flow velocity of medium in branch pipe Combined with the density of the heat exchange medium Calculate the mixer outlet temperature ,in Indicates the molten salt inlet temperature. This indicates a poor temperature difference at the top of the high-temperature molten salt heat exchanger. Indicates the flow rate of the low-temperature heat exchange circuit. Indicates the inlet temperature of the heat medium. This indicates the temperature difference at the lower end of the heat exchanger in the heating cycle. This represents the specific heat capacity of the heat exchange medium at constant pressure; the formula-based correction of the high and low temperature loop flow ratio: if If the value exceeds the threshold, it indicates that the proportion of high-temperature medium is too high, and the opening of the regulating valve needs to be reduced to lower the concentration. This makes the flow rate higher than / Lower; if If the value is less than the threshold, increase the opening of the regulating valve to improve performance. The corrected flow ratio must meet the following requirements. ,in This represents the target value of the mixer outlet temperature. The target flow ratio is calculated using this formula, and then combined with... Stable value, reverse calculation Adjust the value, and it will eventually be Keep it within the set range to avoid molten salt condensation and boiling of the heating medium; S5. Ensure temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations; The real-time monitoring and correction of thermal stress involves collecting data on the thermal stress of the equipment walls in real time using stress sensors on the walls of the high-temperature molten salt heat exchanger and the heating cycle heat exchanger. Based on the system operating parameters, the theoretical thermal stress was calculated using the following formula and then compared with the measured values ​​for verification: Where k represents the thermal conductivity of the heat transfer medium, if If the value exceeds the allowable value, it needs to be reduced synchronously. and Reduce total flow, adjustment range meets requirements This adjustment reduces thermal stress to within acceptable limits, preventing equipment failure due to excessive stress; the fluctuation adaptation adjustment: when the high-temperature molten salt inlet temperature fluctuates, it is adjusted... Adaptability: Increases with rising temperature To reduce the residence time of molten salt in the heat exchanger and avoid localized overheating; to reduce the temperature drop. To extend the residence time and ensure sufficient heat exchange; when the inlet temperature of the heat medium fluctuates, adjustments are made to... Adaptability: Increases with rising temperature To improve heat exchange efficiency, reduce the temperature drop. Avoid using excessively low outlet temperatures for the heat transfer medium; the entire adjustment process must ensure... The thermal stress is always kept within a set threshold to ensure system stability; S6. The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

2. The heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in that: The fault diagnosis confirmed that the heat exchange channels of the high-temperature molten salt heat exchanger and the heating circulation heat exchanger were not blocked, the thin-walled inner tube of the mixer was not deformed, the pressure sensor of the buffer tank, the speed sensor of the circulating pump, and the opening sensor of the regulating valve were all working normally, and the circulating pump and the regulating valve were in the closed state.

3. The heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in that: The heat medium circuit is started by opening the inlet and outlet valves of the heat medium in the heating circulation heat exchanger, allowing the low-parameter heat medium to enter the low-temperature side at the designed flow rate. The inlet temperature of the heat medium is monitored in real time by a temperature sensor and controlled to be stable at the set value. The circulation pump is started and the flow rate is adjusted by starting the circulation pump, setting the initial speed, and gradually increasing the speed to raise the flow rate of the heat exchange medium in the low-temperature heat exchange circuit from 0 to the designed flow rate. During the process, flow data is collected in real time via a flow sensor. If the flow rate deviates from the design value, the speed is corrected by frequency conversion adjustment. The correction logic is as follows: when the flow rate is lower than 95% of the design value, the speed is increased by 50 r / min every 30 seconds; when the flow rate is higher than 105% of the design value, the speed is decreased by 50 r / min every 30 seconds until the flow rate stabilizes within a reasonable threshold range. Pressure data is collected in real time via a buffer tank pressure sensor. If the pressure deviates from the rated value, correction is made based on the correlation between the circulation pump speed and pressure. The correction formula is as follows. ,in This indicates the corrected circulating pump speed. This indicates the original circulating pump speed. Indicates the rated pressure of the buffer tank. This indicates the current pressure of the buffer tank. This indicates the rated outlet pressure of the circulating pump; the specific start-up criteria for the high-temperature circuit are: when the flow rate of the low-temperature heat exchange circuit stabilizes at 2.85-3.15 kg / s and the pressure of the buffer tank stabilizes at 1.14 × 10⁻⁶ kg / s. 5 -1.26×10 5 When the outlet temperature of the heat medium stabilizes within the threshold range, the low-temperature heat exchange circuit is considered to have completed startup and entered a stable operating state.

4. The heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in that: The specific method for starting the molten salt circuit and controlling the temperature is as follows: Open the molten salt inlet valve and outlet valve of the high-temperature molten salt heat exchanger to allow high-temperature molten salt to enter the high-temperature side at the designed flow rate. Use a temperature sensor to control the molten salt inlet temperature to stabilize it at a set value. Simultaneously monitor the molten salt outlet temperature, which must meet a dual threshold constraint condition. This dual threshold constraint condition includes threshold 1 and threshold 2. Threshold 1 is the molten salt outlet temperature. Molten salt initial crystallization temperature + safety redundancy; Threshold 2: molten salt outlet temperature The molten salt inlet temperature is reduced by twice the upper difference, where the safety redundancy is determined based on the molten salt flow rate. The upper difference represents the difference between the molten salt inlet temperature and the heat exchange medium outlet temperature in the high-temperature molten salt heat exchanger; the maximum value of the two thresholds is taken to avoid the risk of condensation.

5. A heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in that: The specific method for adjusting the valve opening is as follows: the initial valve opening is set to 20%. The flow rate of the medium is collected by the flow sensor in the high-temperature heat exchange circuit. Based on the correlation model of opening degree, flow rate, and pressure, the opening degree is gradually increased to make the flow rate approach the design value. The correlation model formula is as follows: ,in This indicates the current flow rate of the high-temperature heat exchange circuit. This indicates the design flow rate of the high-temperature heat exchange circuit. Indicates the opening degree of the regulating valve. This indicates the current outlet pressure of the circulating pump. The specific method for controlling the total flow rate of the circulating pump is as follows: while adjusting the valve opening, simultaneously increase the circulating pump speed to stabilize the total output flow rate within ±5% of the designed total flow rate. During this process, it is necessary to ensure that the circulating pump outlet pressure gradually rises to the rated value to avoid sudden pressure increases that could cause pipeline impact. The circuit startup is complete when the high-temperature heat exchange circuit flow rate stabilizes at 2.375-2.625 kg / s, the molten salt outlet temperature stabilizes within the threshold range, and the circulating pump outlet pressure stabilizes at 2.375 × [value missing]. -2.625× When Pa is reached, it is determined that the high-temperature heat exchange circuit has been started and the system has entered the dual-circuit joint operation state.

6. The heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in that: The high-temperature molten salt circuit shutdown: Close the high-temperature molten salt inlet valve, keep the regulating valve opening unchanged, and continue running the high-temperature heat exchange circuit for 12 minutes. Monitor the molten salt outlet temperature using a temperature sensor until the temperature drops below 290℃, ensuring that the residual molten salt in the heat exchanger is completely discharged and there is no condensation. The high-temperature circuit and regulating valve shutdown: Gradually reduce the regulating valve opening by 10% every 30 seconds until the opening is 0%, then close the regulating valve. Simultaneously, stop the operation of the high-temperature heat exchange circuit and disconnect it from the mixer. The circulating pump and low-temperature circuit shutdown: Reduce the circulating pump speed by 100 r / min every 30 seconds. Gradually reduce the temperature to 0 and shut down the circulating pump; then close the inlet and outlet valves of the heating medium in the heating circulation heat exchanger to stop the operation of the heating medium circuit; system cooling and depressurization: when the temperature of each piece of equipment drops to 30-40℃ and the pipeline pressure drops to atmospheric pressure, open the system vent valve to complete the shutdown operation.

7. A heat exchange system for molten salt energy storage and heating, used to implement the heat exchange operation method for molten salt energy storage and heating as described in any one of claims 1 to 6, characterized in that, It includes a high-temperature molten salt heat exchanger, a heating circulation heat exchanger, a mixer, a buffer tank, a circulating pump, a regulating valve, and a heat exchange circuit connecting the above devices, and also includes: System initialization module: performs fault diagnosis on various devices in the system; Low-temperature heat exchanger loop start-up and stability control module: High-temperature loop start-up is achieved through heat medium loop start-up, circulating pump start-up and flow regulation, and buffer tank pressure correction; High-temperature heat exchanger loop start-up and flow coordinated regulation module: Starts the molten salt loop and controls the temperature, adjusts the valve opening based on the formula to stabilize the flow of the high-temperature loop, and controls the total flow of the circulating pump synchronously. When the flow rate, molten salt outlet temperature and pump pressure are stable, the loop start-up is determined to be complete. Mixer medium mixing and precise temperature control module: Combines multiple parameters to calculate the mixer outlet temperature. If the temperature deviates from the set range, it corrects the high and low temperature loop flow ratio based on the formula to control the temperature within the set range. System operation status monitoring and dynamic adjustment module: Ensures temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations; System shutdown operation module: The system shutdown is completed by shutting down the high-temperature molten salt circuit, shutting down the high-temperature circuit and regulating valve, and cooling and depressurizing the system.

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