Molten salt heat storage and heat exchange efficiency optimization system and method in whole-plant technological process

Abstract

The invention discloses a molten salt heat storage and heat exchange efficiency optimization system and method in a whole-plant technological process. The system comprises a high-temperature molten salt storage tank, a low-temperature molten salt storage tank, a temperature sensor group, a variable-frequency pump group, a multi-stage heat exchanger, an intelligent control unit, a heat buffer module and the like, and the high-temperature molten salt storage tank and the low-temperature molten salt storage tank are connected through a conveying pipeline to form a circulation loop. The intelligent control unit regulates and controls the rotating speed of the pump set and the valve opening degree based on a fuzzy PID algorithm, the heat buffering module reduces heat loss, and the multi-stage heat exchanger enhances heat exchange. The method comprises the steps of temperature and flow data collection, efficiency deviation value calculation, fuzzy PID control, thermal buffer optimization, waste heat feedback and the like. Besides, the system also has the functions of digital twinborn prediction, multi-objective optimization, abnormal working condition self-healing and the like, can be connected with a DCS (Distributed Control System) to obtain energy consumption data and dispatch stored energy, and also can predict equipment faults. The fused salt heat energy storage and heat exchange efficiency is effectively improved, reasonable energy allocation and cost control are achieved, and the reliability and stability of the system are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt thermal storage and heat exchange, and specifically to a system and method for optimizing the efficiency of molten salt thermal storage and heat exchange in the whole plant process flow. Background Art

[0002] In modern industrial production, the efficient utilization and storage of energy are the keys to achieving sustainable development. The process flows of many factories involve a large amount of heat generation and consumption. However, due to the often mismatched heat energy supply and demand in terms of time and quantity, a large amount of waste heat is wasted and the energy utilization rate is low. Molten salt, as an excellent energy storage medium, has been widely used in the field of industrial thermal storage.

[0003] Patent document CN202411353198.1 discloses a single-tank molten salt heat storage system and method, which adopts a shell-and-tube heat exchanger and a molten salt circulation system with PID control. Although this system has certain advantages, such as adopting a single molten salt storage tank system, which greatly saves the floor area and cost of the molten salt storage tank, the floor area of the storage tank system is reduced by more than 50%; reducing the molten salt dead zone and improving the molten salt utilization rate, the molten salt storage volume is reduced by more than 20%, significantly reducing the molten salt consumption and the system cost. The heat exchanger adopts a traditional straight tube bundle design, resulting in low waste heat recovery efficiency, a large amount of waste heat cannot be effectively recovered and utilized, causing energy waste and increasing the energy cost of the factory. Summary of the Invention

[0004] The purpose of the present invention is to provide a system and method for optimizing the efficiency of molten salt thermal storage and heat exchange in the whole plant process flow to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A system for optimizing the efficiency of molten salt thermal storage and heat exchange in the whole plant process flow, comprising:

[0006] A high-temperature molten salt storage tank and a low-temperature molten salt storage tank are respectively connected to a heat exchanger through a conveying pipeline to form a closed-loop molten salt circulation loop, and an electric heater is installed on the pipeline of the circulation loop;

[0007] A temperature sensor group is arranged at the outlet of the high-temperature molten salt storage tank, the inlet of the low-temperature molten salt storage tank, and the inlet and outlet of the heat exchanger to monitor the molten salt temperature distribution in real time;

[0008] A variable-frequency pump group is configured on the conveying pipeline for dynamically adjusting the molten salt flow rate;

[0009] A multi-stage heat exchanger, the inside of which adopts a spiral baffle structure and is integrated with the waste heat recovery unit of the whole plant process to realize multi-stage countercurrent heat exchange between the molten salt and the waste heat medium;

[0010] The intelligent control unit receives the real-time data of the temperature sensor group and dynamically regulates the rotational speed of the variable-frequency pump group and the opening degree of the shunt valve of the heat exchanger based on a preset fuzzy PID algorithm to optimize the molten salt thermal energy storage efficiency and the heat exchange rate;

[0011] The thermal buffer module is arranged between the high-temperature molten salt storage tank and the heat exchanger, and reduces the heat loss during the molten salt transportation through the phase change material coating.

[0012] Furthermore, the intelligent control unit further includes:

[0013] The digital twin module constructs a three-dimensional thermodynamic simulation model synchronized with the physical system, receives sensor data in real time and predicts the change trend of the molten salt heat exchange efficiency within the next 10 minutes;

[0014] The multi-objective optimization engine performs weight allocation on the objective function based on the genetic algorithm and generates a Pareto optimal solution set among maximizing the heat exchange efficiency, minimizing the pump group energy consumption, and equalizing the equipment life;

[0015] The abnormal condition self-healing module automatically switches to a preset emergency control strategy when it detects that the molten salt temperature difference exceeds the threshold or the flow rate volatility is greater than 15%, including switching the molten salt reflux path, activating the heat exchanger bypass, and the alarm signal grading trigger mechanism.

[0016] Furthermore, the thermal buffer module specifically includes:

[0017] From the inside to the outside, it is successively the molten salt flow channel layer, the phase change material layer, and the vacuum insulation layer, where the phase change material layer is supported by a honeycomb aluminum-based framework to enhance the heat conduction efficiency;

[0018] The phase change material layer is composed of 60-70wt% potassium nitrate, 20-30wt% graphene microflakes, and 10-15wt% ceramic fibers, with a phase change temperature of 380-420°C and a latent heat energy storage density ≥850kJ / kg;

[0019] The dynamic heat dissipation fin group is arranged on the outer wall of the buffer module, and the fin angle can be adjusted by a micro servo motor according to the ambient temperature, with an adjustment range of 30°-90°.

[0020] Furthermore, the spiral baffle structure of the heat exchanger is further optimized as:

[0021] A variable pitch spiral channel, with the pitch of the inlet section being 1.2 times the pipe diameter and the pitch of the outlet section gradually shrinking to 0.8 times the pipe diameter, so that the molten salt flow velocity is increased from 2.5m / s to 4.2m / s;

[0022] Spiral baffles, with a surface nano - coating forming an Al2O3 - TiO2 composite ceramic layer on the baffle surface by plasma spraying process. The coating thickness is 50 - 80μm, the surface roughness Ra ≤ 0.8μm, and the thermal conductivity is increased to 45W / (m·K);

[0023] Heat exchange tubes, which are evenly installed on the spiral baffles in multiple groups, and the heat exchange tubes supported in the middle are of variable diameter structure.

[0024] It also includes:

[0025] The whole - plant energy management interface, which is connected to the DCS system through the OPCUA protocol to obtain the energy consumption data and heat demand plan of each process section in real - time;

[0026] The dynamic scheduling module, which generates the charging / discharging strategy of the molten salt storage tank based on the heat demand plan. When the low - electricity - price period is predicted, it preferentially starts the electric heating compensation system for energy storage;

[0027] The predictive maintenance unit, which monitors the status of pump groups and valves through vibration sensors and acoustic emission probes, analyzes the equipment health index using convolutional neural networks, and warns of potential failure risks 14 days in advance.

[0028] A method for optimizing the molten salt heat storage and heat exchange efficiency in the whole - plant process flow, characterized by including the following steps:

[0029] Step 1: Real - time collect the temperature data of molten salt at the outlet of the high - temperature storage tank, the inlet and outlet of the heat exchanger, and the inlet of the low - temperature storage tank through a temperature sensor group, and synchronously monitor the molten salt flow rate;

[0030] Step 2: Based on the dynamic thermodynamic model, calculate the deviation value of the molten salt heat exchange efficiency under the current working conditions, and generate an optimization objective function in combination with the whole - plant process load demand;

[0031] Step 3: Adopt the fuzzy PID control algorithm to adjust the rotational speed of the variable - frequency pump group to match the target flow rate, and at the same time adjust the opening degree of the heat exchanger diversion valve to make the molten salt and the waste heat medium reach the optimal temperature difference during the counter - current heat exchange process;

[0032] Step 4: Introduce a heat buffer module into the molten salt circulation loop, and use its phase - change material coating to absorb the transient heat fluctuations during the transportation of high - temperature molten salt, reducing the influence of thermal inertia on the system response speed;

[0033] Step 5: Strengthen the turbulent effect through the spiral baffle structure of the multi - stage heat exchanger, improve the thermal conductivity between the molten salt and the waste heat medium, and feedback the optimized thermal energy to the whole - plant process flow through the waste heat recovery unit.

[0034] Further, the construction of the dynamic thermodynamic model further includes:

[0035] Establish the coupled equation of molten salt flow and heat transfer: where S V is the volume force source term applied by the pump set;

[0036] Define the multi-physical field boundary conditions, including the Nusselt number Nu = 0.023Re 0·8 Pr 0.4 on the heat exchanger wall surface, and adopt the heat flux continuity hypothesis at the molten salt-waste heat medium interface;

[0037] Discretize the solution domain by the finite volume method, encrypt the grid size to 0.1 mm in the near-wall region, and set the calculation residual convergence criterion to 10 -6 ;

[0038] The model parameters are updated in real time through the digital twin module, the sensor data is synchronized every 5 minutes, and the thermal conductivity and turbulent viscosity parameters are optimized by the particle swarm algorithm.

[0039] Furthermore, the temperature data acquisition and correction in the first step further includes:

[0040] Deploy distributed fiber optic temperature sensors at intervals of 0.5 m along the axial direction of the conveying pipeline to obtain the axial temperature gradient distribution of the molten salt fluid in real time;

[0041] Scan the outer wall temperature field of the high-temperature molten salt storage tank through the infrared thermal imaging module, fuse it with the fiber optic sensor data, and establish a three-dimensional mapping model of the internal temperature of the molten salt;

[0042] Based on the ambient temperature, the thickness of the pipeline insulation layer, and the flow rate of the molten salt, dynamically compensate for the measurement error of the sensor. The compensation formula is:

[0043] ΔT = α·v·(T env -T pipe ) / (δ·ρ·C p ), where α is the correction coefficient, v is the flow rate of the molten salt, T env is the ambient temperature, T pipe is the pipeline surface temperature, δ is the thickness of the insulation layer, ρ is the density of the molten salt, and C p is the specific heat capacity.

[0044] Furthermore, the implementation of the fuzzy PID control algorithm in the third step includes:

[0045] Set the target temperature difference ΔT target of the molten salt to 1.2 - 1.5 times the temperature rise of the waste heat medium, and adjust the weight of the target function according to the real-time load;

[0046] Fuzzify the temperature deviation and flow rate volatility into three-level language variables of "high", "medium", and "low" through the membership function;

[0047] Generate the pump group speed adjustment amount Δn and the valve opening adjustment amount Δθ based on the rule base. An example of the rule is: If the temperature difference deviation is high and the flow rate fluctuation is low, then Δn increases by 15% and Δθ decreases by 10%.

[0048] Output the defuzzified control instruction to the variable frequency pump group and the flow splitting valve, with a response delay ≤ 200 ms.

[0049] Furthermore, the efficiency optimization of the thermal buffer module in step four includes:

[0050] Configure a composite phase change material layer, which is mixed in the proportion of 60 - 70 wt% potassium nitrate, 20 - 30 wt% graphene microflakes, and 10 - 15 wt% ceramic fibers, and the phase change temperature is set at 380 - 420 °C.

[0051] According to the molten salt flow rate and the ambient temperature, dynamically adjust the angle of the heat dissipation fins through a micro servo motor. The adjustment formula is: θ = 30° + 0.5·(v - 2 m / s) / (4 m / s)·60°, where v is the molten salt flow rate.

[0052] When it is detected that the molten salt temperature volatility ≥ 5 °C / min, activate the forced convection cooling mode of the phase change material layer.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] The multi-stage heat exchanger adopts a spiral baffle structure, which enhances the turbulent effect between the molten salt and the waste heat medium and improves the heat transfer coefficient. The optimized spiral baffle variable pitch design enables the molten salt flow rate to change reasonably during the heat exchange process, further strengthening the heat transfer effect, improving the waste heat recovery efficiency, and reducing energy waste.

[0055] The thermal buffer module absorbs the transient heat fluctuations during the transportation of high-temperature molten salt through the phase change material coating, reduces the influence of thermal inertia on the system response speed, and effectively reduces the heat loss during the transportation of molten salt. The reasonable selection of the phase change material and the design of the multi-layer buffer structure improve the stability and efficiency of the energy storage system.

[0056] The intelligent control unit is based on the fuzzy PID algorithm and can dynamically regulate the speed of the variable frequency pump group and the opening of the flow splitting valve of the heat exchanger according to the real-time monitored molten salt temperature and flow rate data. The application of the digital twin module and the multi-objective optimization engine realizes the accurate prediction and multi-objective optimization of the molten salt heat exchange efficiency. While improving the heat exchange efficiency, it reduces the energy consumption of the pump group and balances the equipment life.

[0057] Connect to the DCS system through the plant-wide energy management interface to obtain real-time energy consumption data and heat demand plans for each process section. The dynamic scheduling module generates the charging / discharging strategy for the molten salt storage tank based on this and combines it with the low electricity price period for energy storage, achieving reasonable energy allocation and cost control. The predictive maintenance unit warns of equipment failure risks in advance, ensuring the stable operation of the system, reducing downtime and maintenance costs.

[0058] When the abnormal condition self-healing module detects that the molten salt temperature difference exceeds the threshold or the flow rate volatility is greater than 15%, it automatically switches to the preset emergency control strategy to ensure the safe and stable operation of the system under abnormal conditions, improving the adaptability and reliability of the system. Brief Description of the Drawings

[0059] Figure 1 It is a schematic flow diagram of the method for optimizing the molten salt heat storage and heat exchange efficiency of the present invention;

[0060] Figure 2 It is a schematic diagram of the system for optimizing the molten salt heat storage and heat exchange efficiency of the present invention;

[0061] Figure 3 It is a schematic diagram of the heat buffer module of the present invention;

[0062] Figure 4 It is a schematic diagram of the spiral baffle plate assembly of the present invention.

[0063] In the figure: 101, high-temperature molten salt storage tank; 102, low-temperature molten salt storage tank; 103, conveying pipeline; 104, heat exchanger; 105, temperature sensor group; 106, variable frequency pump group; 107, spiral baffle plate assembly; 107a, variable pitch spiral channel; 107b, spiral baffle plate; 107c, heat exchange tube; 108, waste heat recovery unit; 109, intelligent control unit; 110, heat buffer module; 110a, molten salt flow channel layer; 110b, phase change material layer; 110c, vacuum insulation layer; 110d, dynamic heat dissipation fin group; 111, electric heater. Detailed Embodiments

[0064] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0065] Please refer to Figure 1 —4, the present invention provides a technical solution: the implementation manner of the system and method for optimizing the molten salt heat storage and heat exchange efficiency in the whole plant process flow:

[0066] Install high-temperature molten salt storage tank 101 and low-temperature molten salt storage tank 102, and ensure that the tanks are stable and have good thermal insulation performance. Use the delivery pipeline 103 to connect the two tanks with the heat exchanger 104 to form a closed-loop molten salt circulation loop. The pipeline connection should be tight to prevent molten salt leakage. Install an electric heater 111 on the circulation loop pipeline and ensure that it is firmly connected to the pipeline and has a safe and reliable electrical connection.

[0067] Distributed optical fiber temperature sensors are deployed at intervals of 0.5 meters along the axial direction of the delivery pipeline 103 to obtain the axial temperature gradient distribution of the molten salt fluid in real time. Temperature sensor groups 105 are installed at the outlet of the high-temperature molten salt storage tank, the inlet of the low-temperature molten salt storage tank, and the inlet and outlet of the heat exchanger. At the same time, flow sensors are installed at appropriate locations of the pipeline to monitor the molten salt flow. The variable frequency pump group 106 is installed on the delivery pipeline 103 to ensure that its installation position is convenient for maintenance and operation, and is tightly connected to the pipeline to stably adjust the molten salt flow.

[0068] The heat exchanger is installed with a multi-stage heat exchanger 104 that uses a spiral baffle structure 107 inside, and it is integrated with the whole plant process waste heat recovery unit 108. The pipe connection between the heat exchanger and the waste heat recovery unit should follow the design specifications to ensure that the waste heat medium and the molten salt can smoothly perform multi-stage countercurrent heat exchange. The variable pitch spiral channel 107a, spiral baffle 107b and heat exchange tube 107c in the spiral baffle assembly 107 should be installed correctly to ensure the flow and heat exchange effect of the molten salt in the heat exchanger. Among them, the Al2O3-TiO2 composite ceramic layer on the surface of the spiral baffle 107b needs to check the coating quality before installation to ensure that the coating thickness is 50-80μm, the surface roughness Ra≤0.8μm, and the thermal conductivity coefficient meets the design requirements.

[0069] Install the intelligent control unit 109 and electrically connect it with the temperature sensor group 105, flow sensor, variable frequency pump group 106 and the diverter valve of the heat exchanger 104 to ensure stable data transmission and accurate control instructions. Configure functional components such as digital twin module, multi-objective optimization engine and abnormal condition self-healing module in the intelligent control unit to provide support for the intelligent control and optimized operation of the system.

[0070] A heat buffer module 110 is installed between the high-temperature molten salt storage tank 101 and the heat exchanger 104. The heat buffer module 110 is composed of a molten salt flow channel layer 110a, a phase change material layer 110b and a vacuum insulation layer 110c from the inside to the outside. When installing, pay attention to the close fit of each layer. The phase change material layer 110b is supported by a honeycomb aluminum-based skeleton to ensure its heat conduction efficiency. A dynamic heat dissipation fin group 110d is arranged on the outer wall of the buffer module, and a micro servo motor is connected to enable it to automatically adjust the fin angle according to the ambient temperature, and the adjustment range is 30°-90°.

[0071] Connect to the DCS system 902 via the OPC UA protocol to ensure real-time acquisition of energy consumption data and heat demand plans for each process section. Install vibration sensors and acoustic emission probes to monitor the status of pump sets and valves, and connect them to the predictive maintenance unit 904 to achieve monitoring of equipment health indices and early warning of failure risks.

[0072] After the system installation is completed, conduct a comprehensive inspection of all equipment to ensure correct installation and no damage. Calibrate the temperature sensors and flow sensors to ensure the accuracy of measurement data. Test the operation of the variable-frequency pump set, and check its flow regulation ability and stability. Conduct a pressure test on the heat exchanger to check for leakage problems. Test the data communication between the intelligent control unit and each device to ensure that control instructions can be correctly sent and received.

[0073] Set the initial parameters of the fuzzy PID algorithm in the intelligent control unit, including the proportional coefficient, integral coefficient, and differential coefficient. Set the target temperature difference ΔT of the molten salt target to be 1.2 - 1.5 times the temperature rise of the waste heat medium, and set the weight of the objective function according to the actual process load of the factory. Initialize the three-dimensional thermodynamic simulation model of the digital twin module and set the initial values of the model parameters. In the thermal buffer module, configure a composite phase change material layer, which is mixed in the ratio of 60 - 70 wt% potassium nitrate, 20 - 30 wt% graphene microflakes, and 10 - 15 wt% ceramic fibers, and set the phase change temperature to 380 - 420 °C.

[0074] Dry potassium nitrate at 250 °C for 4 hours to remove crystal water, and treat graphene microflakes by plasma activation to improve dispersion.

[0075] According to the ratio of 65 wt% potassium nitrate, 25 wt% graphene, and 10 wt% ceramic fibers, achieve uniform compounding in an inert atmosphere using a high-shear mixer (rotation speed 3000 rpm, time 30 min).

[0076] Inject the mixture into a honeycomb aluminum-based framework (pore diameter 2 mm), cold press it at 10 MPa, and then heat-treat it at 400 °C for 2 hours to form a stable phase change structure.

[0077] Start the system for trial operation. First, operate at a lower molten salt flow rate and temperature, and observe the operation of each part of the system. Check whether the flow of molten salt in the circulation loop is smooth, whether the heat exchange effect of the heat exchanger is normal, and whether the thermal buffer module can effectively reduce heat loss. Adjust the rotation speed of the variable-frequency pump set and the opening of the diversion valve of the heat exchanger through the intelligent control unit, and observe the response speed and accuracy of the system to control instructions. During the trial operation, collect system operation data to preliminarily verify and optimize the dynamic thermodynamic model.

[0078] During the model initialization stage, the factory historical operation data is used for inverse parameter identification. The molten salt flow rate (2.5 - 4.2 m / s) and temperature gradient data (ΔT = 80 - 150 °C) under typical working conditions are selected, and the turbulent viscosity coefficient μ and thermal conductivity k are optimized through the Levenberg - Marquardt algorithm to make the simulation error ≤ 3%. Finally, μ = 0.015 Pa·s and k = 0.45 W / (m·K) are determined.

[0079] The sensor data is synchronized every 5 minutes. When a change in the molten salt composition is detected (such as the potassium nitrate content fluctuating by more than ±5%), the parameter recalibration process is triggered. The dynamic correction of the thermal conductivity is completed within 10 seconds through the particle swarm algorithm to ensure the model accuracy.

[0080] During the system operation, the temperature sensor group 105 collects the temperature data of the molten salt at the outlet of the high - temperature storage tank, the inlet and outlet of the heat exchanger, and the inlet of the low - temperature storage tank in real - time. The distributed optical fiber temperature sensor obtains the axial temperature gradient distribution of the molten salt fluid in real - time, and the flow sensor synchronously monitors the molten salt flow rate. The outer wall temperature field of the high - temperature molten salt storage tank is scanned through the infrared thermal imaging module and fused with the fiber optic sensor data to establish a three - dimensional mapping model of the internal temperature of the molten salt.

[0081] Based on the ambient temperature, the thickness of the pipeline insulation layer, and the molten salt flow rate, the compensation formula ΔT = α·v·(T env -T pipe ) / (δ·ρ·C p ) is used to dynamically compensate the sensor measurement error to ensure the accuracy of the collected data. Among them, α is the correction coefficient, v is the molten salt flow rate, T env is the ambient temperature, T pipe is the pipeline surface temperature, δ is the insulation layer thickness, ρ is the molten salt density, and C p is the specific heat capacity. The corrected data is transmitted to the intelligent control unit 109 in real - time.

[0082] After receiving the real - time data, the intelligent control unit 109 calculates the deviation value of the molten salt heat exchange efficiency under the current working conditions based on the dynamic thermodynamic model, and generates an optimization objective function in combination with the plant process load requirements. The digital twin module constructs a three - dimensional thermodynamic simulation model synchronized with the physical system, receives the sensor data in real - time, and predicts the change trend of the molten salt heat exchange efficiency within the next 10 minutes to provide a reference for optimization control.

[0083] The fuzzy PID control algorithm is adopted. The temperature deviation and flow rate volatility are fuzzified into three-level linguistic variables of "high", "medium", and "low" through the membership function. Based on the rule base, the pump group speed adjustment amount Δn and the valve opening adjustment amount Δθ are generated. For example, if the temperature difference deviation is high and the flow rate fluctuation is low, then Δn increases by 15% and Δθ decreases by 10%. The defuzzified control command is output to the variable frequency pump group and the shunt valve, with a response delay ≤ 200 ms, realizing the precise control of the molten salt flow rate and the heat exchange process, and enabling the molten salt and the waste heat medium to reach the optimal temperature difference during the countercurrent heat exchange process.

[0084] Rule base construction: A state matrix containing 49 control rules is established. Some of the core rules are as follows:

[0085]

[0086] Defuzzification method: The centroid method is used to calculate the accurate output value. The formula is:

[0087]

[0088] where μ i is the membership degree, u i is the control quantity reference value, ensuring the smooth transition of the command.

[0089] In the molten salt circulation loop, the phase change material layer 110b of the thermal buffer module 110 absorbs the transient thermal fluctuations during the transportation of high-temperature molten salt, reducing the influence of thermal inertia on the system response speed. According to the molten salt flow rate and the ambient temperature, the angle of the heat dissipation fin group 110d is dynamically adjusted by the micro servo motor according to the adjustment formula θ = 30° + 0.5·(v - 2 m / s) / (4 m / s)·60°. When it is detected that the molten salt temperature volatility ≥ 5 °C / min, the forced convection cooling mode of the phase change material layer is activated to further optimize the performance of the thermal buffer module.

[0090] The spiral baffle structure 107 of the multi-stage heat exchanger 104 strengthens the turbulence effect. The variable pitch spiral channel 107a increases the molten salt flow rate from 2.5 m / s to 4.2 m / s, and the surface nano-coating increases the heat transfer coefficient to 45 W / m·K, enhancing the heat transfer effect between the molten salt and the waste heat medium. The optimized thermal energy is fed back to the whole plant process flow through the waste heat recovery unit 108 to improve the energy utilization rate.

[0091] The whole plant energy management interface is connected to the DCS system 902 through the OPCUA protocol to obtain the energy consumption data and heat demand plan of each process section in real time. The dynamic scheduling module generates the charging / discharging strategy of the molten salt storage tank based on the heat demand plan. When the low electricity price period is predicted, the electric heating compensation system 702 is preferentially started for energy storage, realizing the reasonable allocation and cost control of energy.

[0092] The predictive maintenance unit 904 monitors the status of pump sets and valves through vibration sensors and acoustic emission probes, analyzes the equipment health index using a convolutional neural network (CNN), and warns of potential faults 14 days in advance. Based on the warning information, equipment maintenance and repair work are promptly arranged to ensure the stable operation of the system, reduce downtime, and cut maintenance costs. The abnormal condition self-healing module continuously monitors the molten salt temperature difference and flow rate volatility. When the detected molten salt temperature difference exceeds the threshold or the flow rate volatility is greater than 15%, it automatically switches to a preset emergency control strategy, including switching the molten salt reflux path, activating the heat exchanger bypass, and triggering a graded alarm signal mechanism, ensuring the safe and stable operation of the system under abnormal conditions.

[0093] Molten salt leakage emergency: When the pressure sensor detects that the pipeline pressure drops suddenly by >20 kPa / s:

[0094] Immediately close the upstream and downstream valves and activate the molten salt reflux path (switch to the emergency storage tank).

[0095] Activate the nitrogen purging system to replace the oxygen around the leakage point within 5 seconds.

[0096] Trigger an audible and visual alarm and push a maintenance work order to the MES system.

[0097] Treatment for heat exchanger blockage:

[0098] Short-term blockage (pressure difference ΔP < 50 kPa): Start the backwashing mode and switch the molten salt flow direction for 30 seconds.

[0099] Severe blockage (ΔP ≥ 50 kPa): Fully open the bypass valve, isolate the faulty unit, and start the standby heat exchanger.

[0100] Waste heat recovery in the steel rolling process of a steel plant

[0101] Operating conditions: Periodic waste heat fluctuations (800 - 1200°C flue gas, fluctuation period 15 min)

[0102] System response:

[0103] The heat exchanger automatically switches to the variable pitch mode (inlet pitch 1.5 times the pipe diameter), and the flow velocity is increased to 4.5 m / s.

[0104] The phase change material layer starts latent heat absorption at 380°C, suppressing temperature fluctuations by >40%.

[0105] The dynamic scheduling module increases the energy storage ratio to 85% during the off-peak electricity period (23:00 - 7:00).

[0106] Effect: The waste heat recovery rate is increased from 62% to 78%, and the energy consumption per ton of steel is reduced by 12.7%.

[0107] Continuous production mode in a chemical plant

[0108] Operating condition: Steady-state heat load (molten salt flow rate 8 m 3 / h ± 5%)

[0109] System optimization:

[0110] The digital twin model predicts the heat demand in the next 10 minutes and adjusts the pump speed to 82 Hz in advance.

[0111] The angle of the heat dissipation fins is locked at 60°, and the surface temperature of the thermal buffer module is maintained ≤ 65°C.

[0112] After optimization by the genetic algorithm, the energy consumption of the pump group is reduced by 18%, and the equipment life balance is increased by 23%.

[0113] System effectiveness verification

[0114] Comparative test: Compare with the traditional system under the same operating conditions:

[0115] Index The system of the present invention Traditional system Improvement range Waste heat recovery rate 82％ 58％ +41％ Heat storage loss (24h) 4.2％ 9.8％ -57％ Response delay (step disturbance) 180ms 650ms -72％ Energy consumption of pump group (annual average) 1.2MW·h 1.8MW·h -33％

[0116] Long-term stability test: After continuous operation for 3000 hours, the thermal decay rate of the phase change material < 3%, the wear of the spiral baffle coating ≤ 5 μm, and the system comprehensive efficiency remains above 95% of the initial value.

Claims

1. An optimization system for molten salt thermal storage and heat exchange efficiency in the whole plant process flow, characterized in that, Including: A high-temperature molten salt storage tank (101) and a low-temperature molten salt storage tank (102), which are respectively connected to a heat exchanger (104) through a conveying pipeline (103) to form a closed-loop molten salt circulation loop, and an electric heater (111) is installed on the pipeline of the circulation loop; A temperature sensor group (105), which is arranged at the outlet of the high-temperature molten salt storage tank, the inlet of the low-temperature molten salt storage tank and the inlet and outlet of the heat exchanger to monitor the molten salt temperature distribution in real time; A variable-frequency pump group (106), which is configured on the conveying pipeline (103) to dynamically adjust the molten salt flow rate; A multi-stage heat exchanger (104), the inside of which adopts a spiral baffle structure (107) and is integrated with the whole-plant process waste heat recovery unit (108) to realize multi-stage countercurrent heat exchange between the molten salt and the waste heat medium; An intelligent control unit (109), which receives the real-time data of the temperature sensor group (105) and dynamically regulates the rotation speed of the variable-frequency pump group (106) and the opening degree of the shunt valve of the heat exchanger (104) based on a preset fuzzy PID algorithm to optimize the molten salt thermal energy storage efficiency and heat exchange rate; A heat buffer module (110), which is arranged between the high-temperature molten salt storage tank (101) and the heat exchanger (104) to reduce the heat loss during the molten salt transportation through a phase change material coating.

2. A method for optimizing the molten salt thermal storage and heat exchange efficiency in the whole plant process flow, using the system described in claim 1, characterized in that Including the following steps: Step 1: Collect the temperature data of the molten salt at the outlet of the high-temperature storage tank, the inlet and outlet of the heat exchanger and the inlet of the low-temperature storage tank in real time through the temperature sensor group, and synchronously monitor the molten salt flow rate; Step 2: Based on the dynamic thermodynamics model, calculate the deviation value of the molten salt heat exchange efficiency under the current working condition, and generate an optimization objective function in combination with the whole-plant process load demand; Step 3: Adopt the fuzzy PID control algorithm to adjust the rotation speed of the variable-frequency pump group to match the target flow rate, and at the same time adjust the opening degree of the shunt valve of the heat exchanger to make the molten salt and the waste heat medium reach the optimal temperature difference during the countercurrent heat exchange process; Step 4: Introduce a heat buffer module into the molten salt circulation loop, and use its phase change material coating to absorb the transient heat fluctuation during the transportation of the high-temperature molten salt, and reduce the influence of the thermal inertia on the system response speed; Step 5: Strengthen the turbulence effect through the spiral baffle structure of the multi-stage heat exchanger, improve the heat transfer coefficient between the molten salt and the waste heat medium, and feedback the optimized thermal energy to the whole-plant process flow through the waste heat recovery unit.

3. The molten salt thermal storage and heat exchange efficiency optimization system in the whole plant process flow according to claim 1, wherein The intelligent control unit (109) further includes: A digital twin module, which constructs a three-dimensional thermodynamics simulation model synchronized with the physical system, receives the sensor data in real time and predicts the change trend of the molten salt heat exchange efficiency within the next 10 minutes; A multi-objective optimization engine, which assigns weights to the objective function based on the genetic algorithm and generates a Pareto optimal solution set among maximizing the heat exchange efficiency, minimizing the pump group energy consumption and equalizing the equipment life; An abnormal condition self-healing module, when it detects that the molten salt temperature difference exceeds the threshold or the flow rate volatility is greater than 15%, automatically switches to a preset emergency control strategy, including switching the molten salt reflux path, activating the heat exchanger bypass and a graded alarm signal triggering mechanism.

4. The molten salt thermal storage and heat exchange efficiency optimization system in the whole plant process flow according to claim 1, characterized in that, The heat buffer module (110) specifically includes: From the inside to the outside, there are a molten salt flow channel layer (110a), a phase change material layer (110b), and a vacuum insulation layer (110c) in sequence. Among them, the phase change material layer (110b) is supported by a honeycomb aluminum-based framework to enhance the heat conduction efficiency; The phase change material layer (110b) is composed of 60 - 70wt% potassium nitrate, 20 - 30wt% graphene microflakes, and 10 - 15wt% ceramic fibers. The phase change temperature is 380 - 420 °C, and the latent heat energy storage density ≥ 850 kJ / kg; The dynamic heat dissipation fin group (110d) is arranged on the outer wall of the buffer module. The fin angle can be adjusted by a micro servo motor according to the ambient temperature, and the adjustment range is 30° - 90°.

5. The molten salt thermal energy storage and heat exchange efficiency optimization system in the whole plant process flow according to claim 1, characterized in that, The spiral baffle structure (107) of the heat exchanger (104) is further optimized as follows: A variable pitch spiral channel (107a), the pitch of the inlet section is 1.2 times the pipe diameter, and the pitch of the outlet section gradually shrinks to 0.8 times the pipe diameter, so that the molten salt flow rate is increased from 2.5 m / s to 4.2 m / s; A spiral baffle (107b), the surface nano - coating forms an Al2O3 - TiO2 composite ceramic layer on the baffle surface by plasma spraying process. The coating thickness is 50 - 80 μm, the surface roughness Ra ≤ 0.8 μm, and the heat conduction coefficient is increased to 45 W / (m·K); The heat exchange tubes (107c) are uniformly installed on the spiral baffle (107b) in multiple groups, and the heat exchange tubes (107c) supported in the middle are of variable diameter structure.

6. The molten salt thermal energy storage and heat exchange efficiency optimization system in the whole plant process flow according to claim 1, wherein It also includes: The whole - plant energy management interface is connected to the DCS system (902) through the OPCUA protocol to obtain the energy consumption data and heat demand plan of each process section in real - time; The dynamic scheduling module generates the charging / discharging strategy of the molten salt storage tank based on the heat demand plan. When the low - electricity - price period is predicted, the electric heating compensation system (702) is preferentially started for energy storage; The predictive maintenance unit monitors the status of the pump group and valves through vibration sensors and acoustic emission probes, analyzes the equipment health index using a convolutional neural network (CNN), and warns of potential failure risks 14 days in advance.

7. The method for optimizing the molten salt thermal storage and heat exchange efficiency in the whole plant process flow according to claim 2, characterized in that, The construction of the dynamic thermodynamic model further includes: Establish the coupled equations of molten salt flow and heat transfer: where S V is the volume force source term applied by the pump set; Define multi-physics boundary conditions, including the Nusselt number Nu = 0.023Re of the heat exchanger wall 0.8 Pr 0.4 , and the heat flux continuity assumption is adopted at the molten salt-waste heat medium interface; The solution domain is discretized by the finite volume method, and the grid size is refined to 0.1 mm in the near-wall region. The convergence criterion for the calculation residual is set to 10 -6 ; The model parameters are updated in real - time through the digital twin module. The sensor data is synchronized every 5 minutes, and the particle swarm algorithm is used to optimize the thermal conductivity and turbulent viscosity parameters.

8. The method for optimizing the molten salt thermal storage and heat exchange efficiency in the whole-plant process flow according to claim 2, characterized in that, The temperature data acquisition and correction in the first step further includes: Distributed optical fiber temperature sensors are deployed at intervals of 0.5 meters along the axial direction of the conveying pipeline to obtain the axial temperature gradient distribution of the molten salt fluid in real - time; The outer wall temperature field of the high - temperature molten salt storage tank is scanned by the infrared thermal imaging module and fused with the fiber optic sensor data to establish a three - dimensional mapping model of the internal temperature of the molten salt; Based on the ambient temperature, the thickness of the pipeline insulation layer, and the molten salt flow rate, the measurement error of the sensor is dynamically compensated. The compensation formula is: ΔT = α·v·(T env - T pipe ) / (δ·ρ·C p ), where α is the correction coefficient, v is the molten salt flow rate, T env is the ambient temperature, T pipe is the pipe surface temperature, δ is the insulation layer thickness, ρ is the molten salt density, C p is the specific heat capacity.

9. The method for optimizing the molten salt thermal storage and heat exchange efficiency in the whole plant process flow according to claim 2, characterized in that, The implementation of the fuzzy PID control algorithm in the third step includes: Set the target temperature difference ΔT of molten salt target It is 1.2 - 1.5 times the temperature rise of the waste heat medium, and adjust the weight of the objective function according to the real-time load; The temperature deviation and flow rate volatility are fuzzified into three - level linguistic variables of "high", "medium", and "low" through the membership function; Based on the rule base, the pump group speed adjustment amount Δn and the valve opening adjustment amount Δθ are generated. A rule example is: if the temperature difference deviation is high and the flow rate fluctuation is low, then Δn increases by 15% and Δθ decreases by 10%; Output the defuzzified control instructions to the variable-frequency pump group and the shunt valve, with a response delay ≤ 200 ms.

10. The method for optimizing the molten salt thermal storage and heat exchange efficiency in the whole plant process flow according to claim 2, wherein, The efficiency optimization of the thermal buffer module in step 4 includes: Configure a composite phase change material layer, mixed in the proportion of 60 - 70 wt% potassium nitrate, 20 - 30 wt% graphene microflakes, and 10 - 15 wt% ceramic fibers, and set the phase change temperature to 380 - 420 °C; According to the molten salt flow rate and the ambient temperature, dynamically adjust the angle of the heat dissipation fins through a micro servo motor, and the adjustment formula is: θ = 30° + 0.5·(v - 2 m / s) / (4 m / s)·60°, where v is the molten salt flow rate; When it is detected that the molten salt temperature volatility ≥ 5 °C / min, activate the forced convection cooling mode of the phase change material layer.

Images