Heat exchange system applied to fused salt energy storage and heat supply and operation method of heat exchange system

Abstract

The invention discloses a heat exchange system applied to fused salt energy storage and heat supply and an operation method of the heat exchange system, and particularly relates to the field of fused salt energy storage and heat supply. S2, starting of a high-temperature loop is completed through starting of a thermal medium loop, starting of a circulating pump, flow adjustment and pressure correction of a buffer tank; s3, starting the molten salt loop and controlling the temperature, regulating the opening degree based on a formula to stabilize the flow of the high-temperature loop, synchronously controlling the total flow of the circulating pump, and judging that the loop is started when the flow, molten salt outlet temperature and pump pressure stable conditions are met; an intermediate medium of the heat exchange system is in a liquid state and is driven by the circulating pump, and operation reliability and economical efficiency are higher than those of a gaseous medium; the heat exchange system can be suitable for heat exchange with the temperature difference larger than 500 DEG C, and heat stress safety and medium safety of the heat exchanger can be guaranteed; the investment cost of the pump is reduced by reducing the design temperature of the circulating pump.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molten salt energy storage heating, and more particularly to a heat exchange system applied to molten salt energy storage heating and a method for operating the same. BACKGROUND

[0002] With the gradual depletion of fossil energy and the increasing seriousness of environmental problems, the energy supply system is transforming from traditional coal-fired power generation to clean energy dominated by wind and solar energy. Wind and solar energy have significant intra-day fluctuations, and their power generation peaks do not match the social electricity and heat load peaks in time. The molten salt-based energy storage heating technology can store excess heat during the clean energy generation period and release heat during the load peak period, becoming one of the core technologies to alleviate this mismatch problem and has been preliminarily applied in industrial heating and civil heating fields.

[0003] The core advantage of the existing molten salt energy storage heating technology is that it can achieve long-term storage and on-demand release of heat, effectively bridging new energy generation and terminal heat demand. Moreover, molten salt has the characteristics of high temperature resistance, large specific heat capacity, and strong chemical stability, making it suitable as a high-temperature heat storage medium. However, this technology has obvious shortcomings when applied in low-parameter heating fields. First, the storage temperature of molten salt is generally high, resulting in a large temperature difference between the molten salt and the low-parameter heat medium, which can easily cause condensation and blockage of the pipeline on the molten salt side due to local low temperature, and boiling on the cooling side due to local high temperature, leading to equipment overpressure. At the same time, the large temperature difference can cause severe thermal stress on the heat exchange equipment, resulting in equipment weld cracking, pipe wall deformation, and other failure problems. Second, existing solutions often use air as an intermediate heat exchange medium to reduce the local temperature difference, but air has a very low thermal conductivity and volumetric specific heat, requiring a large increase in heat exchanger area to meet the heat exchange demand, which not only increases equipment investment costs but also requires a large power fan to drive air circulation, resulting in high fan power consumption and high operating noise, making it difficult to balance economy and environmental protection.

[0004] Therefore, to address the problems of large heat exchange temperature difference leading to equipment failure, poor air heat exchange economy, and weak system adaptability to fluctuations in the existing molten salt energy storage heating technology in low-parameter fields, there is an urgent need for a heat exchange system applied to molten salt energy storage heating and a method for operating the same. By constructing a high-temperature and low-temperature double heat exchange circuit, designing a mixed temperature device with a free expansion structure, and establishing a full-parameter dynamic adjustment mechanism, safe heat exchange under large temperature difference is achieved, equipment costs and operating energy consumption are reduced, and the system's adaptability to new energy fluctuations is improved. SUMMARY

[0005] To overcome the above-mentioned defects of the prior art, the present application provides a heat exchange system applied to molten salt energy storage heating and a method for operating the same, which solves the problems raised in the background art by the following solutions.

[0006] To achieve the above object, the application provides the following technical scheme: a heat exchange operation method applied to molten salt energy storage heating, comprising a high-temperature molten salt heat exchanger, a heating cycle heat exchanger, a temperature mixer, a buffer tank, a circulating pump, a regulating valve and a heat exchange circuit connecting the above devices, and specifically comprising: S1, fault diagnosis is performed on each device of the system; S2, high-temperature circuit starting is completed through heat medium circuit starting, circulating pump starting, flow regulation and buffer tank pressure correction; S3, the molten salt circuit is started and temperature control is performed, the high-temperature circuit flow is regulated based on a formula, the total flow of the circulating pump is controlled synchronously, and the conditions of stable flow, molten salt outlet temperature and pump pressure are met, so that it is determined that the circuit starting is completed; S4, the temperature mixer outlet temperature is calculated in combination with multiple parameters, and if the temperature deviates from the set range, the high-temperature and low-temperature circuit flow ratio is corrected based on a formula to control the temperature in the set range; S5, real-time monitoring and correction of thermal stress and fluctuation adjustment are performed to ensure stable temperature and stress; S6, system shutdown is completed through high-temperature molten salt circuit shutdown, high-temperature circuit and regulating valve shutdown and system cooling and pressure relief.

[0007] Preferably, the fault diagnosis confirms that the heat exchange channels of the high-temperature molten salt heat exchanger and the heating cycle heat exchanger are not blocked, the thin-walled inner tube of the temperature mixer is not deformed, the buffer tank pressure sensor, the circulating pump speed sensor and the regulating valve opening degree sensor are all working normally, and the circulating pump and the regulating valve are in a closed state.

[0008] Preferably, the heat medium circuit starting opens the heat medium inlet valve and outlet valve of the heating cycle heat exchanger, so that the low-parameter heat medium enters the low-temperature side at a designed flow rate, the heat medium inlet temperature is monitored in real time through a temperature sensor, and the temperature is controlled to be stable at a set value; the circulating pump starting and flow regulation start the circulating pump, initially set the speed, gradually increase the speed to make the heat exchange medium flow of the low-temperature heat exchange circuit rise from 0 to the designed flow rate, collect flow data in real time through a flow sensor during the process, correct the speed through frequency regulation if the flow deviates from the designed value, the correction logic is as follows: when the flow is lower than 95% of the designed value, the speed is increased by 50 r / min every 30 s; when the flow is higher than 105% of the designed value, the speed is decreased by 50 r / min every 30 s, until the flow is stable within a reasonable threshold range; pressure data are collected in real time through a buffer tank pressure sensor, and correction is performed based on the correlation between the circulating pump speed and the pressure if the pressure deviates from the rated value, and the correction formula is as follows wherein represents the circulating pump speed after correction, represents the circulating pump speed before correction, represents the rated pressure of the buffer tank, represents the current pressure of the buffer tank, represents the rated outlet pressure of the circulating pump; the specific determination of the startup of the high-temperature circuit is that when the flow rate of the low-temperature heat exchange circuit is stabilized at 2.85-3.15 kg / s, the pressure of the buffer tank is stabilized at 1.14×10 5 -1.26×10 5 Pa, and the outlet temperature of the heat medium is stabilized at a threshold range, it is determined that the startup of the low-temperature heat exchange circuit is completed and enters a stable running state.

[0009] Preferably, the specific way of starting the molten salt circuit and controlling the temperature is that the molten salt inlet valve and outlet valve of the high-temperature molten salt heat exchanger are opened, so that the high-temperature molten salt enters the high-temperature side at a designed flow rate, and the molten salt inlet temperature is controlled to be stabilized at a set value through a temperature sensor; at the same time, the molten salt outlet temperature is monitored, and needs to meet a double threshold constraint condition, the double threshold constraint condition includes threshold 1 and threshold 2, the threshold 1 is that the molten salt outlet temperature is the primary crystal temperature of the molten salt plus a safety redundancy; the threshold 2 is that the molten salt outlet temperature is the molten salt inlet temperature minus twice the upper end difference, wherein the safety redundancy is determined according to the flow rate of the molten salt, and the upper end difference represents the difference between the molten salt inlet temperature and the outlet temperature of the heat exchange medium in the high-temperature molten salt heat exchanger; the maximum value of the two thresholds is taken to avoid condensation risk.

[0010] Preferably, the specific way of adjusting the valve opening degree is that the initial setting of the valve opening degree is 20%, the medium flow rate is collected through the flow rate sensor of the high-temperature heat exchange circuit, and the opening degree is gradually increased based on the correlation model of opening degree-flow rate-pressure, so that the flow rate approaches the designed value, and the correlation model formula is as follows: , wherein represents the current flow rate of the high-temperature heat exchange circuit, represents the designed flow rate of the high-temperature heat exchange circuit, represents the opening degree of the adjusting valve, represents the current outlet pressure of the circulating pump; the specific way of controlling the total flow rate of the circulating pump is that the opening degree of the adjusting valve is adjusted at the same time, and the rotating speed of the circulating pump is simultaneously improved, so that the total output flow rate of the circulating pump is stabilized within a range of ±5% of the designed total flow rate; during the process, it is necessary to ensure that the outlet pressure of the circulating pump gradually rises to the rated value, so as to avoid pipe impact caused by sudden pressure rise; the startup of the circuit is completed when the flow rate of the high-temperature heat exchange circuit is stabilized at 2.375-2.625 kg / s, the outlet temperature of the molten salt is stabilized at a threshold range, and the outlet pressure of the circulating pump is stabilized at 2.375× -2.625× Pa, it is determined that the startup of the high-temperature heat exchange circuit is completed, and the system enters a double-circuit combined running state.

[0011] Preferably, the outlet temperature of the mixing temperature device is calculated by connecting the flow rate sensors of the low-temperature medium in the main pipe and the high-temperature medium in the branch pipe of the mixing temperature device, respectively collecting the flow rates of the media in the main pipe and the branch 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.

[0012] 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 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. Avoiding too low outlet temperature of heat medium; whole adjustment process needs to ensure Stress within the set threshold, guaranteeing system stability.

[0013] Preferably, the high-temperature molten salt loop is closed: the high-temperature molten salt inlet valve is closed, the regulating valve opening is kept unchanged, the high-temperature heat exchange loop is continuously operated for 12 min, the molten salt outlet temperature is monitored by the temperature sensor, and the temperature is reduced to below 290℃, ensuring that the residual molten salt in the heat exchanger is completely discharged and no condensation occurs; the high-temperature loop and the regulating valve are closed: the regulating valve opening is gradually reduced, i.e. reduced by 10% every 30 s, until the opening is 0%, and the regulating valve is closed; at the same time, the high-temperature heat exchange loop is stopped, and the connection with the temperature mixer is cut off; the circulating pump and the low-temperature loop are closed: the circulating pump speed is reduced, i.e. reduced by 100 r / min every 30 s, until the speed is 0, and the circulating pump is closed; then the heat medium inlet valve and the outlet valve of the heat supply circulating heat exchanger are closed, and the heat medium loop is stopped; the system is cooled and depressurized: when the temperature of each device is reduced to 30-40℃ and the pipeline pressure is reduced to atmospheric pressure, the system vent valve is opened, and the shutdown operation is completed.

[0014] Preferably, a heat exchange system applied to molten salt energy storage heat supply includes a high-temperature molten salt heat exchanger, a heat supply circulating heat exchanger, a temperature mixer, a buffer tank, a circulating pump, a regulating valve, and a heat exchange loop connecting the above devices, and further includes: System initialization module: fault diagnosis is performed on each device of the system; Low-temperature heat exchange loop start-up and stability control module: high-temperature loop start-up is completed through heat medium loop start-up, circulating pump start-up and flow regulation, and buffer tank pressure correction; High-temperature heat exchange loop start-up and flow coordination regulation module: molten salt loop is started and temperature is controlled, the regulating valve opening is adjusted based on the formula to stabilize the high-temperature loop flow, and the total flow of the circulating pump is controlled synchronously to meet the flow, molten salt outlet temperature, and pump pressure stability conditions, i.e. the loop start-up is determined to be completed; Temperature mixer medium mixing and temperature precise control module: the temperature mixer outlet temperature is calculated based on multiple parameters, and if the temperature deviates from the set range, the high- and low-temperature loop flow ratio is corrected based on the formula to control the temperature within the set range; System operation state monitoring and dynamic adjustment module: temperature and stress stability are ensured through real-time monitoring and correction of thermal stress and fluctuation adaptive adjustment; System shutdown operation module: system shutdown is completed through high-temperature molten salt loop shutdown, high-temperature loop and regulating valve shutdown, and system cooling and depressurization.

[0015] Technical effects and advantages of the present application: ​1. The heat exchange system of the present application uses liquid as the intermediate medium, which is driven by a circulating pump, and the reliability and economy are higher than those of gaseous medium; the heat exchange system of the present application can be applied to heat exchange with a temperature difference of more than 500 DEG C, and can ensure the safety of the heat stress 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 application can be reduced by appropriately adjusting the flow ratio of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit, and the investment cost of the pump can be reduced by reducing the design temperature of the circulating pump; 2. The present application solves the problems of the background art, such as the large heat exchange temperature difference between the molten salt storage temperature and the low-parameter heat medium, the condensation blockage of the molten salt side, the boiling of the heat medium on the cooling side, the overpressure of the equipment, and the weld cracking and pipe wall deformation of the heat exchange equipment due to severe thermal stress, by using the high thermal conductivity and high volumetric specific heat characteristics of the liquid heat exchange medium, combining the high-temperature and low-temperature double heat exchange circuit cooperative operation mechanism, and matching the outlet temperature precise control formula of the temperature mixer and the heat stress dynamic correction formula of the heat exchange equipment; the device failure risk is reduced, the service life of the device is prolonged, and the continuous and safe operation of the system is ensured; 3. The present application uses heat-conducting oil instead of traditional air as the intermediate heat exchange medium, and combines the frequency conversion speed control of the circulating pump, to obtain the operation effect of reducing the heat exchange area of the heat exchanger and reducing the operating energy consumption of the circulating pump; the problems of the background art, such as the low thermal conductivity and volumetric specific heat of the air heat exchange medium, the need to greatly increase the heat exchanger area to cause high investment cost, and the high power fan drive to cause high power consumption and high operating noise, are solved; the heat exchange area of the heat exchanger is reduced, the initial investment cost of the equipment is reduced, the operating power consumption of the circulating pump is reduced, and the system operating noise is reduced, which takes into account the beneficial effects of economy and environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The device structure diagram of the present application is shown in the figure; Figure 2 The overall structure diagram of the present application is shown in the figure; Figure 3 The system structure diagram of the present application is shown in the figure; Figure 4 The internal structure diagram of the temperature mixer of the present application is shown in the figure.

[0017] In the figure: 1, high-temperature molten salt heat exchanger; 2, heat supply circulating heat exchanger; 3, temperature mixer; 3.1, main pipe; 3.2, branch pipe; 3.3, thin-walled inner pipe of main pipe; 3.4, thin-walled inner pipe of branch pipe; 4, buffer tank; 5, circulating pump; 6, regulating valve. DETAILED DESCRIPTION

[0018] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0019] A heat exchange operation method applied to molten salt energy storage heat supply, comprising a high-temperature molten salt heat exchanger 1, a heat supply circulating heat exchanger 2, a temperature mixer 3, a buffer tank 4, a circulating pump 5, an adjusting valve 6, and a heat exchange circuit connecting the above devices.

[0020] The heat exchange circuit uses liquid as the heat exchange medium.

[0021] The heat exchange system is composed of a high-temperature heat exchange circuit and a low-temperature heat exchange circuit, and the circuits share the pipeline from the temperature mixer 3 to the circulating pump 5 and have the same direction.

[0022] In the stable working condition, the heat loads of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit are the same.

[0023] In the stable working condition, the flow rate of the circulating pump 5 is the sum of the flow rates of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit.

[0024] The heat exchange circuit is provided with at least one flow rate adjusting valve on the non-shared pipeline of the heat exchange circuit.

[0025] In the stable working condition, the medium temperature in the shared pipeline of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit can be adjusted by adjusting the flow rate ratio of the high-temperature heat exchange circuit and the low-temperature heat exchange circuit. The adjusting formula is: Wherein, T is the medium temperature in the shared pipeline; Tin is the high-temperature medium inlet temperature; ΔT is the high-temperature molten salt heat exchanger temperature difference; m is the high-temperature heat exchange circuit medium mass flow rate; Tin is the low-temperature heat medium inlet temperature; ΔT is the heat supply circulating heat exchanger temperature difference; m is the low-temperature heat exchange circuit medium mass flow rate.

[0026] As shown in a heat exchange operation method applied to molten salt energy storage heat supply, Figure 2 The heat exchange operation method specifically further comprises: S1, fault diagnosis is performed on each device of the system; Specifically need to explain is: the fault diagnosis: confirm high temperature molten salt heat exchanger 1, heat supply circulating heat exchanger 2 heat exchange channel without jamming, mixed temperature ware thin wall inner tube without deformation, buffer tank pressure sensor, circulating pump speed sensor, regulating valve opening degree sensor are normal work, and circulating pump 5, regulating valve 6 are in closed state.

[0027] S2, through the heat medium loop start, circulating pump start and flow regulation and buffer tank 4 pressure correction complete high temperature loop start; Specifically need to explain is: the heat medium loop start: open heat supply circulating heat exchanger heat medium inlet valve and outlet valve, make low parameter heat medium with design flow into low temperature side, through temperature sensor real-time monitoring heat medium inlet temperature, control its stable at set value;The circulating pump start and flow regulation: start circulating pump, initial setting speed, gradually improve the speed and make the low temperature heat exchange loop heat exchange medium flow from 0 to design flow;In the process, through flow sensor real-time acquisition flow data, if the flow deviates from the design value, through frequency regulation speed correction, correction logic as follows: when the flow is lower than 95% of the design value, every 30s improve the speed 50r / min;When the flow is higher than 105% of the design value, every 30s reduce the speed 50r / min, until the flow is stable in reasonable threshold range;Through buffer tank pressure sensor real-time acquisition pressure data, if the pressure deviates from the rated value, based on the correlation between circulating pump speed and pressure correction, correction formula as follows , wherein N represents the corrected circulating pump speed, N represents the circulating pump speed before correction, P represents the rated pressure of buffer tank 4, P represents the current pressure of buffer tank 4, P represents the rated outlet pressure of circulating pump;The high temperature loop start is specifically determined as: when the low temperature heat exchange loop flow is stable at 2.85-3.15kg / s, the buffer tank 4 pressure is stable at 1.14×10 5 -1.26×10 5Pa, when the outlet temperature of the heat medium is stabilized in the threshold range, it is determined that the low-temperature heat exchange circuit is started and completed, and enters a stable running state. Among them, the order of "starting the low-temperature circuit (heat receiving end) first and then starting the high-temperature circuit (heat source end)" conforms to the control logic of the industrial heat exchange system "stabilizing the end first and then supplying the heat source": if the high-temperature circuit is started first, the high-temperature medium will cause the temperature of the temperature mixer to rise suddenly after entering the temperature mixer, which will directly cause the heat medium to boil; stabilizing the low-temperature circuit first can "absorb" the heat of the subsequent high-temperature medium through the continuous flow of the heat medium, thereby avoiding temperature fluctuations. The necessity of pressure correction of the buffer tank 4: when the circulating pump 5 is started or the flow is adjusted, the pressure of the pipeline will fluctuate instantaneously (such as the pressure rising sharply when the pump is started), and if it is not corrected, the pressure exceeding the threshold will cause the pipeline weld to crack, so the pressure fluctuation can be controlled within ±5% through the speed-pressure correlation formula, thereby ensuring the safety of the pipeline.

[0028] S3, starting the molten salt circuit and controlling the temperature, adjusting the valve opening to stabilize the flow of the high-temperature circuit based on the formula, synchronously controlling the total flow of the circulating pump, and meeting the conditions of stable flow, molten salt outlet temperature and pump pressure to determine that the circuit is started and completed; Specifically, the specific way of starting the molten salt circuit and controlling the temperature is: opening the molten salt inlet valve and outlet valve of the high-temperature molten salt heat exchanger, so that the high-temperature molten salt enters the high-temperature side at the designed flow rate, and the temperature of the molten salt inlet is controlled by the temperature sensor to be stable at the set value; at the same time, the outlet temperature of the molten salt is monitored, which needs to meet the double threshold constraint condition, the double threshold constraint condition includes threshold 1 and threshold 2, the threshold 1: the outlet temperature of the molten salt the initial melting temperature of the molten salt + safety redundancy; the threshold 2: the outlet temperature of the molten salt the inlet temperature of the molten salt minus twice the upper end difference, wherein the safety redundancy is determined according to the flow rate of the molten salt, and the upper end difference represents the difference between the inlet temperature of the molten salt and the outlet temperature of the heat exchange medium in the high-temperature molten salt heat exchanger; the maximum value of the two thresholds is taken to avoid condensation risk; the specific way of adjusting the valve opening is: initially setting the opening of the adjusting valve to 20%, collecting the medium flow through the flow sensor of the high-temperature heat exchange circuit, gradually increasing the opening based on the correlation model of opening-flow-pressure, so that the flow approaches the designed value, and the correlation model formula is as follows: wherein represents the current flow of the high-temperature heat exchange circuit, represents the designed flow of the high-temperature heat exchange circuit, represents the opening of the adjusting 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.

[0029] 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. 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. This makes 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 modified flow ratio needs to meet , wherein represents the mixed temperature outlet temperature target value, the target flow ratio is calculated by the formula, and the steady value is reversely calculated adjusted value, and finally controlled in the set range, so as to avoid molten salt condensation and hot medium boiling.

[0030] S5, real-time monitoring and correction of thermal stress and fluctuation adjustment to ensure temperature and stress stability; Specifically, the real-time monitoring and correction of thermal stress: through the stress sensor on the wall surface of the high-temperature molten salt heat exchanger and the heat supply circulating heat exchanger, the wall surface thermal stress of the equipment is collected in real time ; combined with the system operation parameters, the theoretical thermal stress is calculated by the following formula and compared with the measured value for verification: , wherein k represents the thermal conductivity of the heat transfer medium, if exceeds the allowable value, the total flow needs to be reduced by simultaneously reducing and , and the adjustment amplitude meets , through the adjustment, the thermal stress is reduced to the allowable range, so as to avoid equipment failure due to excessive stress; the fluctuation adjustment: when the high-temperature molten salt inlet temperature fluctuates, by adjusting adaptation: when the temperature rises, increase to reduce the residence time of molten salt in the heat exchanger and avoid local overheating; when the temperature decreases, decrease to prolong the residence time and ensure sufficient heat exchange; when the hot medium inlet temperature fluctuates, by adjusting adaptation: when the temperature rises, increase to improve the heat exchange efficiency, and when the temperature decreases, decrease to avoid too low outlet temperature of the hot medium; the whole adjustment process needs to ensure that and the thermal stress are always within the set threshold, so as to ensure the stability of the system.

[0031] S6, system shutdown is completed by stopping the high-temperature molten salt circuit, stopping the high-temperature circuit and adjusting valve, and cooling and depressurizing the system.

[0032] Specifically, the high-temperature molten salt loop shutdown: close the high-temperature molten salt inlet valve, keep the regulating valve opening unchanged, continue to run the high-temperature heat exchange loop for 12 minutes, monitor the molten salt outlet temperature through the temperature sensor, until the temperature drops to below 290℃, ensure that the residual molten salt in the heat exchanger is completely discharged and there is no condensation; the high-temperature loop and the regulating valve shutdown: gradually reduce the regulating valve opening, i.e. reduce by 10% every 30s, until the opening is 0%, close the regulating valve; at the same time, stop the high-temperature heat exchange loop operation, disconnect the connection with the temperature mixer; the circulating pump and the low-temperature loop shutdown: reduce the circulating pump speed, i.e. reduce by 100r / min every 30s, until the circulating pump is closed by gradually reducing to 0; then close the heat medium inlet valve and outlet valve of the heat supply circulating heat exchanger, stop the heat medium loop operation; the system cooling and pressure relief: when the temperature of each device drops to 30-40℃ and the pipeline pressure drops to atmospheric pressure, open the system vent valve to complete the shutdown operation.

[0033] Another aspect of the present application, in some embodiments, the present application provides a heat exchange system applied to molten salt energy storage heating, as shown in the accompanying Figure 1 and Figure 4 The heat exchange system includes a high-temperature molten salt heat exchanger 1, a heat supply circulating heat exchanger 2, a temperature mixer 3, a buffer tank 4, a circulating pump 5, a regulating valve 6, and a heat exchange loop connecting the above devices, wherein the heat exchange system uses liquid as the heat exchange medium, and its thermal conductivity and volumetric specific heat are significantly higher than those of gaseous heat exchange medium; the heat exchange system is suitable for heat exchange scenarios with a temperature difference of 150-500℃. The heat exchange loop is composed of a high-temperature heat exchange loop and a low-temperature heat exchange loop. The high-temperature heat exchange loop and the low-temperature heat exchange loop are connected by a common pipeline. The high-temperature molten salt heat exchanger 1, the temperature mixer 3, the buffer tank 4, the circulating pump 5, and the regulating valve 6 are connected by pipes in sequence to form the high-temperature heat exchange loop. The heat supply circulating heat exchanger 2, the temperature mixer 3, the buffer tank 4, and the circulating pump 5 are connected by pipes in sequence to form the low-temperature heat exchange loop. The heat exchange medium of the heat exchange loop includes molten salt, heat-conducting oil, and liquid metal. The high-temperature molten salt heat exchanger of the heat exchange loop can also be other forms of heat exchanger, and the heat source is not limited to molten salt, including but not limited to solid heat storage medium, phase change heat storage medium. The temperature mixer 3 is composed 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. The main pipe 3.1 and the branch pipe 3.2 are both composed 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 is free to expand. The upstream end of the branch pipe thin-walled inner pipe 3.4 is expanded and sealingly welded to the outer pipe of the branch pipe 3.2. The branch pipe thin-walled inner pipe 3.4 extends into the main pipe thin-walled inner pipe 3.3.

[0034] As shown in the accompanying Figure 3 A heat exchange system applied to molten salt energy storage heating also includes: System initialization module: fault diagnosis of each device in the system; ​Low-temperature heat exchange circuit start-up and stable control module: complete high-temperature circuit start-up through heat medium circuit start-up, circulating pump start-up and flow regulation, and buffer tank pressure correction; High-temperature heat exchange circuit start-up and flow coordination regulation module: start the molten salt circuit and control temperature, regulate the valve opening degree based on the formula to stabilize the high-temperature circuit flow, synchronously control the total flow of the circulating pump, and meet the stable conditions of flow, molten salt outlet temperature, and pump pressure to determine that the circuit start-up is completed; Mixing temperature device medium mixing and temperature accurate control module: combine multiple parameters to calculate the outlet temperature of the mixing temperature device, if the temperature deviates from the set range, correct the high and low temperature circuit flow ratio based on the formula to control the temperature within the set range; System running state monitoring and dynamic adjustment module: ensure temperature and stress stability through real-time monitoring and correction of thermal stress and fluctuation adaptive adjustment; System shutdown operation module: complete system shutdown through high-temperature molten salt circuit shutdown, high-temperature circuit and regulating valve shutdown, and system cooling and pressure relief.

[0035] Secondly: in the drawings of the disclosed embodiments, only the structures involved in the disclosed embodiments are involved, other structures can refer to the usual design, and in the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other; Finally: the above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

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. S5. Ensure temperature and stress stability through real-time monitoring and correction of thermal stress and adaptive adjustment to fluctuations; 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 system and its 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 design 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 design 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. 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 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 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.

7. A heat exchange operation method for molten salt energy storage and heating according to claim 1, characterized in 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 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 the set threshold to ensure system stability.

8. A 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.

9. 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 8, 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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