Fused salt heat storage and heat exchange method for optimizing whole-plant technological process

Abstract

The invention discloses a fused salt heat storage and heat exchange method for optimizing the whole-plant technological process. Firstly, appropriate fused salt is selected as a heat storage and heat exchange medium according to heat source and heat demand conditions in the whole plant technological process; and then a heat storage system comprising high-temperature and low-temperature fused salt storage tanks, a circulating pump and other equipment is built, and the storage tanks are subjected to good heat preservation treatment. In the heat absorption link, heat exchange equipment is arranged at a waste heat generation part, so that the fused salt absorbs heat and then is stored in a high-temperature fused salt storage tank; and in the heat release link, when heat is needed, the high-temperature fused salt releases heat through heat exchange equipment, and the high-temperature fused salt flows back to the low-temperature fused salt storage tank after being cooled. By monitoring the temperature and the liquid level of the fused salt storage tank and the heat requirement of the whole plant, parameters of the circulating pump and heat exchange equipment are automatically adjusted, and heat balance is achieved. In addition, safety guarantee measures such as a pressure monitoring device and a pressure relief device are further arranged. The method can effectively improve the energy utilization efficiency and ensure the stable operation of the system.

Description

Technical Field

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

[0002] The whole plant process flow covers many links, and there are generally problems of a large amount of waste heat loss and drastic fluctuations in heat demand. If the waste heat cannot be effectively recovered and utilized, it will not only cause a huge waste of energy, push up the production cost of enterprises, but also increase the environmental burden; and the frequent fluctuations in heat demand make it difficult to accurately match the energy supply, resulting in a long-term low energy utilization efficiency. The prior art application publication number: CN118031195A molten salt heat storage system. Although this technology solves the problem of over-temperature risk caused by excessive heat exchange in the heat exchanger in the molten salt heat storage system to a certain extent, and ensures the safe operation of the molten salt heat storage system through specific component settings and steam heat exchange process optimization. However, this technology also has obvious limitations. It mainly focuses on the heat exchange process between the main steam and hot re-steam of the coal-fired unit steam turbine and the molten salt. This technology is only designed around the heat exchange link between steam and molten salt, and cannot comprehensively consider the comprehensive utilization of various waste heat sources in the whole plant process flow and the complex and changeable heat demands in different links. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for optimizing the molten salt thermal storage and heat exchange in the whole plant process flow to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A method for optimizing the molten salt thermal storage and heat exchange in the whole plant process flow, including the following steps:

[0005] Step 1: Molten salt selection: According to the temperature range and heat load characteristics of the heat source and heat demand in the whole plant process flow, select a molten salt with appropriate melting point, boiling point, specific heat capacity and thermal stability as the heat storage and heat exchange medium. The melting point range of the molten salt is 150°C to 200°C, the boiling point is not lower than 600°C, and the specific heat capacity is between 1.2×10 3 J / (kg·°C) and 1.5×10 3 J / (kg·°C);

[0006] Step 2: Heat storage system: Build a molten salt heat storage system. The system includes at least one high-temperature molten salt storage tank and a low-temperature molten salt storage tank. The high-temperature molten salt storage tank and the low-temperature molten salt storage tank are connected by a pipeline, and a circulation pump is set on the pipeline. The circulation pump is used to drive the molten salt to circulate between the high-temperature molten salt storage tank and the low-temperature molten salt storage tank. Both the high-temperature molten salt storage tank and the low-temperature molten salt storage tank are provided with a heat insulation layer, and the thermal conductivity of the heat insulation layer is not higher than 0.05 W / (m·K);

[0007] Step 3: Heat absorption: In the processes of the whole plant's technological process that generate waste heat or excess heat, molten salt is introduced into the heat exchange equipment to conduct heat exchange between the molten salt and the heat source. The molten salt absorbs heat and its temperature rises. The heated molten salt flows into the high-temperature molten salt storage tank for storage. The heat exchange efficiency of the heat exchange equipment is not less than 85%;

[0008] Step 4: Heat release: When heat is required in the whole plant's technological process, the high-temperature molten salt in the high-temperature molten salt storage tank is transported through a pipeline to another heat exchange equipment. In this heat exchange equipment, the high-temperature molten salt conducts heat exchange with the medium to be heated. The molten salt releases heat and its temperature drops. The cooled molten salt flows into the low-temperature molten salt storage tank. During the heat exchange process of the heat exchange equipment, the temperature drop range of the molten salt is from 100°C to 200°C;

[0009] Step 5: Heat balance regulation: By monitoring the temperature and liquid level of the high-temperature molten salt storage tank and the low-temperature molten salt storage tank as well as the heat demand of the whole plant's technological process, automatically adjust the flow rate of the circulation pump and the operating parameters of the heat exchange equipment to achieve the heat balance of the molten salt heat storage and heat exchange system. When the temperature of the high-temperature molten salt storage tank is higher than 500°C and the heat demand is small, reduce the flow rate of the circulation pump; when the temperature of the low-temperature molten salt storage tank is lower than 250°C and the heat demand is large, increase the flow rate of the circulation pump and adjust the operating parameters of the heat exchange equipment.

[0010] Further, in Step 1, a thermal stability test is conducted on the candidate molten salt. The test method is to keep the candidate molten salt at 200°C to 500°C within its working temperature range for 1000 hours, and detect the composition change of the molten salt every 50 hours. If the composition change rate is less than 5%, the molten salt meets the thermal stability requirements. Finally, select the most suitable one from the molten salts that pass the thermal stability test as the heat storage and heat exchange medium.

[0011] Further, in Step 2, the materials of the high-temperature molten salt storage tank and the low-temperature molten salt storage tank are selected as high-temperature and corrosion-resistant alloy materials. The linear expansion coefficient of this alloy material within the molten salt working temperature range does not exceed 1.5×10 -5 / °C, and the corrosion resistance to the molten salt reaches the standard that the corrosion thickness does not exceed 0.5 mm within 10 years, so as to ensure the safety and stability of the storage tank during long-term use.

[0012] Further, in Step 3, the heat exchange equipment adopts a spiral tube heat exchanger structure. The molten salt flows inside the spiral tube, and the heat source flows around outside the spiral tube. The diameter of the spiral tube is 20 mm, the tube pitch is 30 mm, and the material of the spiral tube is 316L stainless steel. The thermal conductivity of this material is not less than 16 W / (m·K) to improve the heat exchange efficiency. At the same time, a flow guiding device is arranged outside the heat exchange equipment to make the heat source contact the spiral tube evenly, further optimizing the heat exchange effect.

[0013] Furthermore, in step 4, the heat exchange device is equipped with a temperature control system. This system uses temperature sensors to monitor the temperature of the medium to be heated in real time. When the medium temperature does not reach the set temperature value, the heat exchange rate is controlled by adjusting the flow rate and velocity of the high-temperature molten salt. The flow rate adjustment range of the high-temperature molten salt is 5m 3 / h to 20m 3 / h, and the velocity adjustment range is 0.2m / s to 1m / s, ensuring that the medium can be accurately heated to the required temperature.

[0014] Furthermore, in step 5, an energy management system is provided. This system collects the heat generation data, heat consumption data of each link in the whole plant process flow, and the operation parameters of the molten salt heat storage and heat exchange system, establishes a heat balance model, predicts the heat demand and heat supply conditions within the next 2 hours based on this model, and adjusts the flow rate of the circulation pump and the operation parameters of the heat exchange device in advance, making the heat balance regulation more intelligent and efficient.

[0015] Furthermore, in step 2, an impurity filtration device is also provided on the pipeline between the high-temperature molten salt storage tank and the low-temperature molten salt storage tank. This filtration device can filter out solid impurities in the molten salt, and the filtration accuracy reaches 50μm, preventing impurities from causing wear and blockage to the circulation pump and heat exchange device, and ensuring the normal operation of the molten salt heat storage and heat exchange system.

[0016] Furthermore, in steps 3 and 4, the heat exchange device is equipped with a pressure monitoring device to monitor the pressure change during the heat exchange process in real time. When the pressure exceeds the set safety pressure value of 2MPa, the pressure relief device is automatically started, and at the same time, the operation of the heat exchange device is stopped and an alarm is issued to ensure the safety of the heat exchange process.

[0017] Furthermore, in step 1, considering the economy of the molten salt, the cost of the candidate molten salt is evaluated. The cost evaluation includes the procurement cost, transportation cost, and later maintenance cost of the molten salt. On the premise of meeting the heat performance and stability requirements, the molten salt with a lower cost is preferentially selected as the heat storage and heat exchange medium.

[0018] Furthermore, in step 5, when there is a sudden change in heat demand in the whole plant process flow, the energy management system can respond quickly. On the one hand, by adjusting the maximum flow rate of the circulation pump not exceeding 30m 3 / h to increase or decrease the circulation volume of the molten salt, and on the other hand, by adjusting the heat exchange area of the heat exchange device to adapt to the change in heat demand, ensuring the stable operation of the whole plant process flow.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The method of the present invention can efficiently store and transfer heat within a wide temperature range. Compared with traditional heat storage media, molten salt has a higher heat capacity, can store more heat, and has good thermal stability at high temperatures, ensuring the stable storage and exchange of heat. The constructed molten salt heat storage system includes a high-temperature molten salt storage tank, a low-temperature molten salt storage tank, a circulation pump, and a storage tank with a low thermal conductivity insulation layer. This structural design reduces heat loss and improves heat storage efficiency. At the same time, the circulation pump can drive the molten salt to circulate between the storage tanks, ensuring the uniform distribution of the molten salt and the full progress of heat exchange. By monitoring the temperature, liquid level of the high-temperature molten salt storage tank and the low-temperature molten salt storage tank, as well as the heat demand of the whole plant process flow, automatically adjusting the flow rate of the circulation pump and the operating parameters of the heat exchange equipment, precise thermal balance control of the molten salt heat storage and heat exchange system can be achieved. When the temperature of the high-temperature molten salt storage tank is too high or the temperature of the low-temperature molten salt storage tank is too low, the system can respond in a timely manner, adjust the flow rate of the circulation pump and the parameters of the heat exchange equipment, ensure the stable operation of the whole plant process flow, and improve energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the method framework of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Please refer to Figure 1 , the present invention aims to provide the actual operation process and relevant details of a molten salt heat storage and heat exchange method for optimizing the whole plant process flow. Step 1: Molten salt selection

[0024] In the heat storage and heat exchange solution for optimizing the whole plant process flow, the selection of molten salt is a fundamental and crucial link. First, by installing high-precision temperature sensors, flow sensors, and heat load monitoring devices at each process link, accurately obtain the temperature range, heat load characteristic data of the heat source and heat demand. Through long-term data collection and statistical analysis, determine information such as the temperature fluctuation range of the heat source and the periodic and random change laws of the heat load in the whole plant process flow.

[0025] Based on these data, select candidate molten salts that meet the requirements from numerous molten salt types. The present invention has clear and strict requirements for the performance of molten salts. Its melting point range should be between 150°C and 200°C, the boiling point should not be lower than 600°C, and the specific heat capacity should be in the range of 1.2×10 3J / (kg·℃) to 1.5×10 3 J / (kg·℃) range. Such performance requirements are to ensure that the molten salt has a sufficient operating temperature range to store and exchange heat in the process flow, and has a high heat storage capacity, and can efficiently complete heat storage and heat exchange tasks under different working conditions.

[0026] The candidate molten salts are subjected to rigorous thermal stability tests. The specific operation is to place the candidate molten salt in a special high-temperature reactor, so that it is in an operating temperature range of 200°C to 500°C, and maintain it for 1000 hours. During this 1000-hour test, a small amount of molten salt samples are extracted every 50 hours using professional sampling equipment, and the composition of the molten salt is accurately detected using advanced spectral analysis, chromatographic analysis and other chemical analysis methods. If the composition change rate is less than 5%, it indicates that the molten salt has good thermal stability in a long-term high-temperature environment, which meets the requirements of the present invention for the thermal stability of molten salt. From the molten salts that pass this test, other performance indicators and cost factors are comprehensively considered, and the most suitable one is selected as a heat storage and heat exchange medium.

[0027] Step 2: Heat storage system construction

[0028] The system mainly consists of at least one high-temperature molten salt storage tank and one low-temperature molten salt storage tank, which are connected to each other through a special pipeline equipped with a circulation pump to drive the molten salt to circulate between the two tanks. The selection of the circulation pump is crucial and needs to be considered comprehensively based on factors such as the scale of the heat storage system, the flow rate and head requirements of the molten salt. Select a circulation pump with suitable flow and head parameters and efficient and stable operation to ensure that the molten salt can continuously and stably participate in the heat exchange process and achieve effective heat transfer and storage.

[0029] Both high-temperature molten salt storage tanks and low-temperature molten salt storage tanks are equipped with insulation layers. The material selection and construction process of the insulation layer directly affect its thermal conductivity. Select high-efficiency insulation materials with a thermal conductivity not higher than 0.05W / (m·K), such as nano aerogel felt, and use professional construction methods for installation to ensure that the insulation layer fits tightly to the surface of the storage tank without gaps and cracks, so as to effectively reduce heat loss and improve heat storage efficiency.

[0030] The material of the storage tank is a nickel-based alloy material that is resistant to high temperature and corrosion. In a laboratory environment, the operating temperature range of molten salt is simulated, and the alloy material samples are subjected to a long-term high-temperature test to measure their linear expansion coefficient. It is required that the linear expansion coefficient of the alloy material within the operating temperature range of molten salt does not exceed 1.5×10 -5 / °C to prevent the storage tank from deforming or cracking due to temperature changes. At the same time, the alloy material sample is immersed in molten salt for a 10-year simulated corrosion test. By regularly observing the surface, measuring the thickness, and analyzing the composition of the sample, it is ensured that its corrosion resistance to molten salt meets the standard that the corrosion thickness does not exceed 0.5 mm within 10 years. Such material selection can ensure the safety and stability of the storage tank during long-term use and extend the service life of the storage tank.

[0031] An impurity filtering device is also installed on the pipeline between the high-temperature molten salt storage tank and the low-temperature molten salt storage tank, and its filtering accuracy reaches 50 μm. The filtering device uses high-precision filter elements, such as metal sintered filter elements or ceramic filter elements, etc. During the installation process, it is ensured that the filtering device is tightly connected to the pipeline and has good sealing. This filtering device can effectively filter out solid impurities in the molten salt, such as metal particles, dust, etc., preventing these impurities from entering the circulation pump and heat exchange equipment, causing wear and blockage to the equipment, thus ensuring the normal operation of the molten salt heat storage and heat exchange system, and reducing equipment failures and maintenance costs.

[0032] Step Three: Heat Absorption

[0033] In the whole plant process flow, through the analysis and monitoring of the heat flow in each link, the links where waste heat or excess heat is generated are accurately identified, such as the smoke outlet of the industrial furnace and the discharge outlet of the chemical reaction kettle. Specific heat exchange equipment is installed in the waste heat generation link, and molten salt is introduced into the equipment to conduct heat exchange with the heat source.

[0034] The heat exchange equipment adopts a spiral tube heat exchanger structure, which has a high heat exchange efficiency and a compact space layout. The molten salt flows inside the spiral tube, while the heat source flows around the outside of the spiral tube, forming a countercurrent heat exchange method, which improves the driving force of heat exchange. The diameter of the spiral tube is 20 mm, the tube pitch is 30 mm, and the material is selected as 316L stainless steel, which has good thermal conductivity and corrosion resistance, and its thermal conductivity is not less than 16 W / (m·K).

[0035] A flow guiding device is set outside the heat exchange equipment to determine the shape, size, and installation position of the flow guiding device so that the heat source can evenly contact the spiral tube, further optimizing the heat exchange effect. It is required that the heat exchange efficiency of the heat exchange equipment is not less than 85%, so as to ensure that waste heat and excess heat can be fully recovered and the energy utilization efficiency can be improved.

[0036] The heat exchange equipment is equipped with a pressure monitoring device, which uses a high-precision pressure sensor to monitor the pressure changes during the heat exchange process in real time. The accuracy of the pressure sensor reaches ±0.01 MPa, which can timely and accurately reflect the minute changes in pressure. When the pressure exceeds the set safety pressure value of 2 MPa, the system will automatically trigger the pressure relief device. The pressure relief device uses a quick-response safety valve, which can open instantly to release the pressure. At the same time, the system will immediately stop the operation of the heat exchange equipment and send an alarm through the sound and light alarm device to remind the operator to handle it, so as to ensure the safety of the heat exchange process and prevent equipment damage and safety accidents caused by overpressure.

[0037] Step Four: Heat Release

[0038] When heat is required in a certain link of the whole plant process flow, the high-temperature molten salt in the high-temperature molten salt storage tank is transported through pipelines to another heat exchange equipment. In this heat exchange equipment, the high-temperature molten salt exchanges heat with the medium to be heated. The molten salt releases heat and its temperature decreases. The cooled molten salt flows into the low-temperature molten salt storage tank.

[0039] This heat exchange equipment is equipped with a temperature control system, which uses high-precision temperature sensors to monitor the temperature of the medium to be heated in real time. The accuracy of the temperature sensor reaches ±0.1 °C, which can accurately measure the temperature changes of the medium. If the medium temperature does not reach the set temperature value, the system will precisely adjust the flow rate and velocity of the high-temperature molten salt through advanced control algorithms and adjustment mechanisms to control the heat exchange rate. The flow rate adjustment range of the high-temperature molten salt is 5 m 3 / h to 20 m 3 / h, and the velocity adjustment range is 0.2 m / s to 1 m / s. Through this precise adjustment method, it is ensured that the medium can be precisely heated to the required temperature, meeting the requirements of the production process and improving product quality and production efficiency.

[0040] This heat exchange equipment is also equipped with a pressure monitoring device, which uses a pressure sensor with the same accuracy and performance as in Step Three to monitor the pressure in real time during the heat exchange process. When the pressure exceeds the safety pressure value of 2 MPa, the same safety measures as in Step Three will be taken, that is, automatically starting the pressure relief device, stopping the operation of the heat exchange equipment and sending an alarm, to ensure the safe progress of the heat exchange process and avoid harm to equipment and personnel caused by abnormal pressure.

[0041] Step Five: Heat Balance Regulation

[0042] By installing high-precision temperature sensors and liquid level sensors on the high-temperature molten salt storage tank and the low-temperature molten salt storage tank, the temperature and liquid level information of the molten salt can be obtained in real time. At the same time, heat flow meters, power sensors and other equipment are installed at each key link of the whole plant process flow to collect heat generation data, heat consumption data and the operation parameters of the molten salt heat storage and heat exchange system.

[0043] An energy management system is set up in the system. This system uses advanced data acquisition cards and industrial computers to quickly and accurately process various collected data. By establishing a heat balance model, comprehensively considering factors such as heat transfer, heat storage, and heat consumption in each link of the whole plant's process flow, and using complex mathematical algorithms and simulation technologies, it predicts the heat demand and heat supply situations within the next 2 hours. Based on this prediction result, the energy management system can adjust the flow rate of the circulation pump and the operating parameters of the heat exchange equipment in advance, making the heat balance regulation more intelligent and efficient.

[0044] When the temperature of the high-temperature molten salt storage tank is higher than 500 °C and the heat demand is small, the energy management system will automatically reduce the flow rate of the circulation pump, reduce the circulation speed of the molten salt, lower the heat absorption rate, and prevent the temperature of the high-temperature molten salt storage tank from rising further. When the temperature of the low-temperature molten salt storage tank is lower than 250 °C and the heat demand is large, the energy management system will increase the flow rate of the circulation pump and adjust the operating parameters of the heat exchange equipment, such as increasing the flow rate and velocity of the high-temperature molten salt, improving the heat exchange rate, and raising the temperature of the low-temperature molten salt storage tank as soon as possible to meet the heat demand.

[0045] When there is a sudden change in heat demand in the whole plant's process flow, such as a sudden increase or decrease in heat load in a certain production link, the energy management system can respond quickly. On the one hand, it adjusts the maximum flow rate of the circulation pump (not exceeding 30 m 3 / h) to increase or decrease the circulation volume of the molten salt, and quickly adjusts the heat supply capacity of the heat storage and heat exchange systems. On the other hand, the heat exchange equipment is designed with adjustable heat exchange elements, such as movable partitions or variable-angle fins, etc. The energy management system can control the position and angle of these heat exchange elements to adjust the heat exchange area of the heat exchange equipment to adapt to the change in heat demand, ensure the stable operation of the whole plant's process flow, and improve the reliability and adaptability of the system.

Claims

1. A molten salt thermal storage and heat exchange method for optimizing the whole-plant process flow, characterized in that, Including the following steps: Step 1: Molten salt selection: According to the temperature range and heat load characteristics of heat sources and heat demands in the whole plant's process flow, select a molten salt with appropriate melting point, boiling point, specific heat capacity, and thermal stability as the heat storage and heat exchange medium. The melting point range of the molten salt is from 150°C to 200°C, the boiling point is not lower than 600°C, and the specific heat capacity is between 1.2×10 3 J / (kg·°C) and 1.5×10 3 J / (kg·°C); Step 2: Thermal energy storage system: Build a molten salt thermal energy storage system, which includes at least one high-temperature molten salt storage tank and a low-temperature molten salt storage tank. The high-temperature molten salt storage tank and the low-temperature molten salt storage tank are connected by pipelines, and a circulation pump is set on the pipeline. The circulation pump is used to drive the molten salt to circulate between the high-temperature molten salt storage tank and the low-temperature molten salt storage tank. Both the high-temperature molten salt storage tank and the low-temperature molten salt storage tank are provided with thermal insulation layers, and the thermal conductivity of the thermal insulation layer is not higher than 0.05 W / (m·K). Step 3: Heat absorption: In the links of the whole plant process flow that generate waste heat or excess heat, introduce the molten salt into the heat exchange equipment to make the molten salt exchange heat with the heat source. The molten salt absorbs heat and its temperature rises. The molten salt after temperature rise flows into the high-temperature molten salt storage tank for storage. The heat exchange efficiency of the heat exchange equipment is not lower than 85%. Step 4: Heat release: When heat is needed in the whole plant process flow, transport the high-temperature molten salt in the high-temperature molten salt storage tank to another heat exchange equipment through pipelines. In this heat exchange equipment, the high-temperature molten salt exchanges heat with the medium to be heated. The molten salt releases heat and its temperature drops. The molten salt after temperature drop flows into the low-temperature molten salt storage tank. During the heat exchange process of the heat exchange equipment, the temperature drop range of the molten salt is 100°C to 200°C. Step 5: Thermal balance regulation: By monitoring the temperature, liquid level of the high-temperature molten salt storage tank and the low-temperature molten salt storage tank, as well as the heat demand of the whole plant process flow, automatically adjust the flow rate of the circulation pump and the operating parameters of the heat exchange equipment to achieve the thermal balance of the molten salt thermal energy storage and heat exchange system. When the temperature of the high-temperature molten salt storage tank is higher than 500°C and the heat demand is small, reduce the flow rate of the circulation pump; when the temperature of the low-temperature molten salt storage tank is lower than 250°C and the heat demand is large, increase the flow rate of the circulation pump and adjust the operating parameters of the heat exchange equipment.

2. The molten salt thermal storage and heat exchange method for optimizing the whole-plant process flow according to claim 1, characterized in that, In the said Step 1, conduct a thermal stability test on the candidate molten salt. The test method is to keep the candidate molten salt at 200°C to 500°C within its working temperature range for 1000 hours, and detect the composition change of the molten salt every 50 hours. If the composition change rate is less than 5%, then the molten salt meets the thermal stability requirements. Finally, select the most suitable one from the molten salts that pass the thermal stability test as the thermal energy storage and heat exchange medium.

3. The molten salt heat storage and heat exchange method for optimizing the whole plant process flow according to claim 1, characterized in that, In the second step, the high-temperature molten salt storage tank and the low-temperature molten salt storage tank are made of alloy materials with high temperature resistance and corrosion resistance. The linear expansion coefficient of this alloy material within the working temperature range of the molten salt does not exceed 1.5×10 -5 / ℃, and the corrosion resistance to the molten salt reaches the standard that the corrosion thickness does not exceed 0.5 mm within 10 years, so as to ensure the safety and stability of the storage tank during long-term use.

4. The molten salt thermal storage and heat exchange method for optimizing the whole-plant process flow according to claim 1, characterized in that, In the said Step 3, the heat exchange equipment adopts a spiral tube heat exchanger structure. The molten salt flows inside the spiral tube, and the heat source flows around outside the spiral tube. The diameter of the spiral tube is 20 mm, the tube pitch is 30 mm, and the material of the spiral tube is 316L stainless steel. The thermal conductivity of this material is not lower than 16 W / (m·K) to improve the heat exchange efficiency. At the same time, a flow guiding device is set outside the heat exchange equipment to make the heat source evenly contact the spiral tube, further optimizing the heat exchange effect.

5. The molten salt thermal storage and heat exchange method for optimizing the whole-plant process flow according to claim 1, characterized in that, In the fourth step, the heat exchange device is equipped with a temperature control system. This system uses temperature sensors to continuously monitor the temperature of the medium to be heated. When the medium temperature does not reach the set temperature value, the heat exchange rate is controlled by adjusting the flow rate and velocity of the high-temperature molten salt. The flow rate adjustment range of the high-temperature molten salt is 5m 3 / h to 20m 3 / h, and the velocity adjustment range is 0.2m / s to 1m / s, ensuring that the medium can be accurately heated to the required temperature.

6. The molten salt heat storage and heat exchange method for optimizing the whole-plant process flow according to claim 1, characterized in that, In the said Step 5, an energy management system is set. This system collects the heat generation data, heat consumption data of each link in the whole plant process flow, as well as the operating parameters of the molten salt thermal energy storage and heat exchange system, establishes a thermal balance model, predicts the heat demand and heat supply situation within the next 2 hours based on this model, and adjusts the flow rate of the circulation pump and the operating parameters of the heat exchange equipment in advance to make the thermal balance regulation more intelligent and efficient.

7. The molten salt heat storage and heat exchange method for optimizing the whole plant process flow according to claim 1, characterized in that, In the second step, an impurity filtering device is further provided on the pipeline between the high-temperature molten salt storage tank and the low-temperature molten salt storage tank. This filtering device can filter out solid impurities in the molten salt, and the filtering accuracy reaches 50 μm, so as to prevent impurities from causing wear and blockage to the circulation pump and heat exchange equipment, and ensure the normal operation of the molten salt thermal storage and heat exchange system.

8. The molten salt heat storage and heat exchange method for optimizing the whole plant process flow according to claim 1, characterized in that, In the third and fourth steps, the heat exchange equipment is equipped with a pressure monitoring device to monitor the pressure change during the heat exchange process in real time. When the pressure exceeds the set safety pressure value of 2 MPa, the pressure relief device is automatically started, and at the same time, the operation of the heat exchange equipment is stopped and an alarm is issued to ensure the safety of the heat exchange process.

9. The molten salt heat storage and heat exchange method for optimizing the whole plant process flow according to claim 1, characterized in that, In the first step, considering the economy of the molten salt, the cost of the candidate molten salt is evaluated. The cost evaluation includes the procurement cost, transportation cost and later maintenance cost of the molten salt. On the premise of meeting the requirements of thermal performance and stability, the molten salt with a lower cost is preferentially selected as the thermal storage and heat exchange medium.

10. The molten salt thermal storage and heat exchange method for optimizing the whole-plant process flow according to claim 1, characterized in that, In the fifth step, when there is a sudden change in the heat demand in the whole plant's process flow, the energy management system can respond quickly. On the one hand, by adjusting the maximum flow rate of the circulation pump not to exceed 30 m 3 / h to increase or decrease the circulation volume of the molten salt, and on the other hand, by adjusting the heat exchange area of the heat exchange equipment to adapt to the change in heat demand, ensuring the stable operation of the whole plant's process flow.

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