Fused salt electric heating device

Abstract

The invention discloses a fused salt electric heating device which comprises a fused salt pump box, a drain water converging assembly and a heat exchange assembly, a fused salt pump is arranged in the fused salt pump box, the input end of the drain water converging assembly communicates with a drain water outlet of a salt dissolving pipeline and is used for collecting salt dissolving drain water, and the heat exchange assembly is provided with a first flow channel and a second flow channel which are isolated from each other. The two ends of the first flow channel communicate with the output end of the drainage convergence assembly and the drainage mother pipe correspondingly, the two ends of the second flow channel communicate with a pipeline between the molten salt pump box and the molten salt pump and an inlet of the molten salt pump correspondingly, through the double-flow-channel isolation design, high-temperature drainage and molten salt are subjected to efficient heat exchange, drainage waste heat is recycled, the load of an electric heater is directly reduced, and the heat exchange efficiency is improved. Closed-loop regulation is formed through the first temperature detection component, the first control valve and the second control valve, and the drainage flow direction and flow are dynamically adjusted according to the temperature of preheated fused salt.

Description

Technical Field

[0001] This invention relates to the field of molten salt heating, and in particular to a molten salt electric heating device. Background Technology

[0002] In the fields of industrial energy storage, power plant peak shaving, and industrial steam supply, molten salt electric heating devices are widely used in the "off-peak electricity price heat storage - peak period steam supply" scenario due to the advantages of high molten salt energy storage density and wide operating temperature range (140-550℃). The core of the existing device includes a molten salt pump box (with built-in molten salt pump), a molten salt tank, an electric heater, a salt melting pipeline, a steam header, and a drain header. The operation revolves around "salt melting - molten salt circulation heating - demineralized water steam generation": the steam header delivers high-temperature steam (200-300℃) to the molten salt pump box salt melting pipeline and the molten salt tank salt melting pipeline to melt solid molten salt. The 120-140℃ salt condensate generated by steam condensation is directly discharged into the drain header through the first / second manual drain valve, without recovering waste heat.

[0003] Liquid molten salt is directly pumped from the molten salt pump box to the electric heater by a molten salt pump. After being heated to 380-420℃, it enters the molten salt tank for heat exchange and steam generation. After releasing heat (140-150℃), it returns to the pump box to form a cycle. However, the existing technology has obvious drawbacks: the waste heat from the condensate drainage is seriously wasted (approximately 2.1 × 10⁻⁶ tons of waste heat is wasted per day for every 50 tons of condensate discharged). 7 (kJ heat), molten salt is heated entirely by electric heating without preheating, resulting in high energy consumption. The dual-channel drainage makes it difficult to form a stable heat source. Furthermore, manual valve adjustment cannot dynamically control the amount of molten salt based on its temperature, which can easily lead to molten salt solidification or difficulty in controlling the temperature of the electric heater. Currently, the industry cannot achieve precise temperature control, and the equipment has long suffered from energy waste, high energy consumption, and poor stability. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that: in the prior art, the high-temperature condensate generated by the salt pipeline is directly discharged into the condensate header through the manual valve, resulting in waste of residual heat. Furthermore, the molten salt enters the electric heater directly without preheating, relying entirely on electric heating, which leads to high energy consumption. The independent discharge (on the molten salt pump box / molten salt tank side) cannot be concentrated to form a stable heat source and is difficult to recover and reuse.

[0005] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a molten salt electric heating device, which includes a molten salt pump box, a condensate collection component, and a heat exchange component. The molten salt pump box has a built-in molten salt pump. The input end of the condensate collection component is connected to the condensate outlet of the molten salt pipeline for collecting condensate from the molten salt. The heat exchange component has a first flow channel and a second flow channel that are isolated from each other. The two ends of the first flow channel are respectively connected to the output end of the condensate collection component and the condensate header. The two ends of the second flow channel are respectively connected to the pipeline between the molten salt pump box and the molten salt pump and the inlet of the molten salt pump. When the condensate from the molten salt flows through the first flow channel, it transfers heat to the molten salt flowing through the second flow channel through the wall of the heat exchange component.

[0006] In a preferred embodiment of the molten salt electric heating device of the present invention: the hydrophobic confluence assembly includes a hydrophobic confluence pipe, and the input end of the hydrophobic confluence pipe is provided with a first branch interface and a second branch interface.

[0007] In a preferred embodiment of the molten salt electric heating device of the present invention: the salt dissolving pipeline includes a molten salt pump box salt dissolving pipeline and a molten salt tank salt dissolving pipeline, the drain outlet of the molten salt pump box salt dissolving pipeline is the output end of a first drain manual valve, the drain outlet of the molten salt tank salt dissolving pipeline is the output end of a second drain manual valve, the first branch interface is connected to the first drain manual valve, and the second branch interface is connected to the second drain manual valve.

[0008] In a preferred embodiment of the molten salt electric heating device of the present invention: the heat exchange component is a shell-and-tube heat exchanger.

[0009] In a preferred embodiment of the molten salt electric heating device of the present invention: the first flow channel is the shell side of a shell-and-tube heat exchanger, and the second flow channel is the tube side of a shell-and-tube heat exchanger.

[0010] In a preferred embodiment of the molten salt electric heating device of the present invention: it further includes a molten salt tank and an electric heater, the output end of the molten salt pump is connected to the electric heater, the electric heater is connected to the molten salt tank, and the molten salt tank is connected to the molten salt pump tank to form a molten salt circulation loop.

[0011] In a preferred embodiment of the molten salt electric heating device of the present invention: the temperature of the molten salt increases after flowing through the second flow channel.

[0012] In a preferred embodiment of the molten salt electric heating device of the present invention: after the molten salt condensate flows through the first flow channel, it is discharged into the condensate header pipe.

[0013] In a preferred embodiment of the molten salt electric heating device of the present invention, a first temperature monitoring component is further included. The first temperature monitoring component is disposed between the output end of the second flow channel and the inlet of the molten salt pump and is used to monitor the temperature of the molten salt after preheating.

[0014] In a preferred embodiment of the molten salt electric heating device of the present invention, it further includes a first control valve, a second control valve, and a second temperature monitoring component. The first control valve is located at the first branch interface, the second control valve is located at the second branch interface, and the second temperature monitoring component is located between the first flow channel output end and the drainage header. The first control valve and the second control valve adjust the molten salt drainage inflow of the corresponding branch interface according to the monitoring result of the first temperature monitoring component.

[0015] The beneficial effects of this invention are as follows: by intercepting the condensate in the manifold and introducing it into the tubular heat exchanger, and through the dual-channel isolation design, the high-temperature condensate and molten salt can exchange heat efficiently, recover the waste heat of the condensate, directly reduce the load on the electric heater, and form a closed-loop control through the first temperature detection component, the first control valve and the second control valve, dynamically adjust the condensate flow direction and flow rate according to the molten salt temperature after preheating, avoid the molten salt from solidifying due to excessively low temperature or increasing the difficulty of temperature control due to excessively high temperature, and improve the stability of system operation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A schematic diagram of the overall system piping of the molten salt electric heating device is shown. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0019] Reference Figure 1This embodiment provides a molten salt electric heating device, including a molten salt pump box 1 and a condensate collection assembly 2. The whole is a pipeline integrated structure. The input end of the molten salt pump box 1 is connected to the condensate outlet of the salt pipeline through a tee joint to form a sealed connection. The connection method can be flange connection, welding or quick coupling (as long as the pressure resistance is ≥1.0MPa and there is no leakage). The diameter of its internal flow channel is designed according to the maximum flow rate of the salt condensate (DN50-DN150 can be selected) to ensure smooth and unobstructed condensate flow. The heat exchange assembly 3 adopts a dual-flow channel isolation design. The flow channel material can be stainless steel, Hastelloy, etc. (as long as the temperature resistance is ≥150℃ and the thermal conductivity is ≥15W / (m・K)). The first flow channel 31 and the second flow channel 32 are isolated by a thin-walled pipe wall. The pipe wall thickness can be selected from 1-5mm (adjusted according to the pressure requirements) to ensure efficient heat transfer and no medium mixing. No specific limitation is made here.

[0020] Specifically, salt melting is the core pretreatment process in the molten salt system. Since molten salt (such as nitric acid molten salt and fluoride molten salt) is easily solidified at room temperature or low temperature and cannot be transported by pump, high-temperature steam needs to be introduced into the tank (molten salt pump box, molten salt tank) to melt the solid molten salt into a liquid with good fluidity, ensuring smooth system circulation. This process is a routine and necessary step in the molten salt heating system in this field.

[0021] When the high-temperature steam (200-300℃) introduced into the molten salt pipeline comes into contact with the low-temperature molten salt (140-150℃) in the molten salt pump box / molten salt tank, the steam condenses into liquid water. This condensate is called "molten salt hydrophobic water" (temperature 120-140℃, still containing a large amount of residual heat). The molten salt applicable to this solution is commonly used industrial molten salt (such as KNO3-NaNO2-NaNO3 mixed molten salt, NaNO3-KNO3 mixed molten salt), whose melting point is usually 142-200℃. It is easy to solidify when the temperature is below the melting point, so a molten salt pipeline is needed to ensure its liquid state. At the same time, this type of molten salt has good thermal conductivity and stability, and the temperature resistance range can reach 150-550℃, which is compatible with the component materials (stainless steel, Hastelloy) in this solution.

[0022] The molten salt pump box 1 is a sealed box structure. Its volume is designed according to the system's molten salt circulation volume. The material can be carbon steel, Q345R, or stainless steel (as long as it meets the requirements of temperature resistance ≥200℃ and molten salt corrosion resistance; no specific limitation is made here). The molten salt pump 11 is fixed to the bottom of the molten salt pump box 1 through a flange. The pump shaft extends to the outside of the box and connects to the drive motor. The pump inlet faces the bottom of the molten salt pump box 1 to ensure that the liquid molten salt in the box can be fully extracted and to avoid dry running of the molten salt pump 11 inside the molten salt pump box 1.

[0023] The input end of the hydrophobic confluence component 2 is connected to the hydrophobic outlet of the salt dissolving pipeline for collecting salt hydrophobic water. The heat exchange component 3 has a first flow channel 31 and a second flow channel 32 that are isolated from each other. The two ends of the first flow channel 31 are connected to the output end of the hydrophobic confluence component 2 and the hydrophobic header, respectively. The two ends of the second flow channel 32 are connected to the pipeline between the molten salt pump box 1 and the molten salt pump 11 and the inlet of the molten salt pump 11, respectively. When the salt hydrophobic water flows through the first flow channel 31, it transfers heat to the molten salt flowing through the second flow channel 32 through the wall of the heat exchange component 3.

[0024] Specifically, the input end of the first flow channel 31 is fixed to the output end of the condensate drain assembly 2 via a flange, and the output end is connected to the power plant's existing condensate drain header via a pipeline. The input end of the second flow channel 32 is connected to the main pipeline between the molten salt pump box 1 and the molten salt pump 11 via a branch pipeline (the connection point is 50-500mm from the inlet of the molten salt pump 11). The output end is directly connected to the inlet flange of the molten salt pump 11 via a flange, forming a continuous flow path of "molten salt pump box → second flow channel → molten salt pump".

[0025] The high-temperature condensate (temperature 120-140℃) generated by the salt dissolving pipeline flows into the condensate collection component 2 and then enters the first flow channel 31. At the same time, the liquid molten salt (temperature 140-150℃) in the molten salt pump box 1 flows through the second flow channel 32 under the suction of the molten salt pump 11. The two media exchange heat through the isolation tube wall of the heat exchange component 3. The waste heat of the condensate is transferred to the molten salt, realizing the synergistic effect of condensate waste heat recovery and molten salt preheating.

[0026] Furthermore, the hydrophobic manifold assembly 2 includes a hydrophobic manifold pipe 21. The inlet end of the hydrophobic manifold pipe 21 is provided with a first branch interface 22 and a second branch interface 23. The main body of the hydrophobic manifold pipe 21 is an integrated tee or four-way pipeline structure (adjusted according to the number of salt pipelines). The length of the main pipe section can be selected from 300-1000mm, and the inner diameter is consistent with the flow channel diameter of the hydrophobic manifold assembly 2 (DN50-DN150). The material is consistent with the hydrophobic manifold assembly 2 (stainless steel 304, 316L or carbon steel lining can be selected, as long as it meets the requirements of temperature resistance and corrosion resistance). An insulation layer can be added to the outer wall of the pipeline (materials can be rock wool, aluminum silicate fiber, etc., with a thermal conductivity ≤0.04W / (m・K)) to reduce heat loss during the transportation of hydrophobic fluid.

[0027] Furthermore, the first branch interface 22 and the second branch interface 23 are symmetrically arranged on the main inlet section of the condensate manifold 21. The center-to-center distance between the interfaces can be selected from 100-300mm. The interface type is a flange interface or a threaded interface (matching the condensate outlet interface of the brine pipeline). The inner diameter of the interface can be selected from DN40 to DN125 (smaller than the inner diameter of the main section to ensure no turbulence during condensate flow). A sealing groove is reserved at each interface for installing a sealing ring (the material can be fluororubber, graphite gasket, etc., which can meet the requirements of temperature resistance ≥150℃ and no leakage).

[0028] Furthermore, the salt dissolving pipeline includes a molten salt pump box salt dissolving pipeline and a molten salt tank salt dissolving pipeline. The drain outlet of the molten salt pump box salt dissolving pipeline is the output end of the first drain manual valve 4, and the drain outlet of the molten salt tank salt dissolving pipeline is the output end of the second drain manual valve 5. The first branch interface 22 is connected to the first drain manual valve 4, and the second branch interface 23 is connected to the second drain manual valve 5.

[0029] Specifically, in industrial molten salt heating systems, the "molten salt pump box melting pipeline" is a standard and essential auxiliary pipeline used to introduce high-temperature steam into the molten salt pump box (the tank storing molten salt to be circulated), melting the solid molten salt inside the tank into a liquid state, preventing the molten salt pump from running dry or becoming clogged. This pipeline is usually connected at one end to the power plant's "melting steam main pipe" and at the other end to the inside of the molten salt pump box (near the bottom of the tank to ensure complete melting). The pipeline is usually equipped with a manual door or solenoid valve to control its on / off state. The "melting steam main pipe" is the common steam main pipeline in the power plant / molten salt system, used to centrally transport high-temperature saturated steam (normal temperature 200-300℃, pressure 0.8-1.6MPa) to provide a melting heat source for various equipment that requires melting (molten salt pump box, molten salt tank).

[0030] The "molten salt tank melting pipeline" is a conventional auxiliary pipeline of the molten salt energy storage system. Its function is the same as that of the molten salt pump box melting pipeline, but it serves the molten salt tank (the energy storage tank that stores high-temperature molten salt). Since the molten salt in the molten salt tank may solidify locally due to long-term static storage or temperature fluctuations, steam needs to be introduced through this pipeline to melt it and ensure that the molten salt flows back to the molten salt pump box smoothly.

[0031] The molten salt steam header is usually connected to the steam output end of the power plant boiler or the waste heat steam recovery system. It distributes steam to each molten salt pipeline through branch pipelines. The pipeline is equipped with a pressure regulating valve (to stabilize the steam pressure) and a flow meter (to monitor the total steam supply). It is the core power source for the molten salt system's molten salt function. This solution directly uses the existing header and only adds a condensate recovery branch to the molten salt pipeline.

[0032] Specifically, the molten salt pump box and molten salt tank molten salt pipelines are both existing steam molten salt pipelines in the power plant. Their inlet ends are connected to the molten salt steam header, and their outlet ends extend into the molten salt pump box 1 and molten salt tank 6, respectively, to allow steam to be introduced into the tanks to melt solid molten salt. The pipe diameters of both pipelines can be selected from DN40 to DN80, and the material is carbon steel or stainless steel (meeting a steam temperature resistance of ≥200℃). The first manual drain valve 4 and the second manual drain valve 5 are both gate valves or stop valves (selectable models include J41H-16C and Z41H-16C), with valve bodies made of carbon steel or stainless steel and sealing surfaces made of hard alloy to ensure high temperature resistance and wear resistance. The valves are installed at the end of the molten salt pipeline (near the drain outlet), with valve stems extending to the operating platform for easy manual opening or closing, used to control the timing and flow rate of molten salt drain discharge.

[0033] The first branch interface 22 is connected to the output flange of the first manual drain valve 4 via a short pipe, and the second branch interface 23 is connected to the output flange of the second manual drain valve 5 via a short pipe. The length of the short pipe can be selected from 100-500mm, and the material is the same as that of the branch interface. When connecting, bolts are used for fastening, and a sealing gasket is installed between the flange faces to ensure no water leakage.

[0034] Furthermore, the heat exchange component 3 is a shell-and-tube heat exchanger 33. The overall structure of the shell-and-tube heat exchanger 33 adopts a single-tube or multi-tube combination structure (selected according to the heat exchange area requirements). The overall length can be selected from 1 to 5m, and the installation method is horizontal or vertical (horizontal is preferred to facilitate sufficient contact of the medium). Tube boxes are provided at both ends of the heat exchanger to fix the inner and outer tubes and realize the inlet and outlet distribution of the medium. The material of the tube box is the same as that of the flow channel (stainless steel 316L, Hastelloy, etc. can be selected). The outer tube is the shell of the shell-and-tube heat exchanger 33, with an inner diameter of DN80-DN200 and a wall thickness of 3-8mm. The inner tube passes through the outer tube, with an inner diameter of DN40-DN100 and a wall thickness of 2-5mm. The inner and outer tubes are arranged coaxially, and the gap between them is 5-20mm (forming a flow channel space). The inner tube can be either a smooth tube or a threaded tube (threaded tubes have higher heat exchange efficiency, and serrated or spiral threads can be selected) to improve the heat exchange effect. The shell-and-tube heat exchanger 33 is fixed to the equipment foundation by a support, and a shock-absorbing pad (made of rubber or spring) is installed between the support and the heat exchanger to reduce vibration during operation. The tube boxes at both ends of the heat exchanger are respectively equipped with medium inlet and outlet flanges, which are connected to the pipelines of the first flow channel 31 and the second flow channel 32 through flanges to ensure a firm connection and reliable sealing.

[0035] Furthermore, the first flow channel 31 is the shell side of the shell-and-tube heat exchanger 33, and the second flow channel 32 is the tube side of the shell-and-tube heat exchanger 33. The annular space between the outer tube and the inner tube of the shell-and-tube heat exchanger 33 is the shell side (i.e., the first flow channel 31), and the internal channel of the inner tube is the tube side (i.e., the second flow channel 32). The medium inlet on the shell side is located on the side of one end of the tube box of the heat exchanger, and the outlet is located on the side of the other end of the tube box, forming a "side-in, side-out" flow path. The medium inlet on the tube side is located on the end face of one end of the tube box, and the outlet is located on the end face of the other end of the tube box, forming an "end-in, end-out" flow path, ensuring that the two media flow in countercurrent or cocurrent (countercurrent is preferred to improve heat exchange efficiency). Baffles (made of the same material as the shell side) can be installed inside the shell side. The baffle spacing can be selected from 200-500mm, and the form is arc-shaped or disc-ring, used to change the flow direction of the condensate, increase the degree of turbulence, and avoid heat exchange dead zones. Turbulence elements (made of copper or stainless steel) can be installed inside the tube side to further enhance the heat transfer effect of molten salt.

[0036] Specifically, at both ends of the heat exchanger, the inner tubes are welded to the tube sheet, and the outer tubes are also welded to the tube sheet, ensuring complete isolation between the shell side and the tube side, eliminating the risk of media cross-flow. The tube sheet thickness can be selected from 10-30mm, designed according to the heat exchanger's operating pressure (selectable from 0.6-2.5MPa), ensuring structural strength.

[0037] Furthermore, it also includes a molten salt tank 6 and an electric heater 7. The molten salt tank 6 is a vertical or horizontal sealed box with a volume larger than that of the molten salt pump box 1 (5-50m³ is optional). The material is the same as that of the molten salt pump box 1 (it only needs to meet the requirements of temperature resistance ≥450℃ and resistance to molten salt corrosion).

[0038] The molten salt tank 6 is equipped with a heat exchange coil (used for subsequent heating of demineralized water, not detailed here), and a molten salt outlet pipeline at the bottom, which is connected to the inlet pipeline of the molten salt pump box 1 through a flange to form a molten salt return channel. The "molten salt return pipeline" is the core conventional pipeline of the molten salt circulation system, used to return the low-temperature molten salt (140-150℃) after heat release in the molten salt tank to the molten salt pump box to form a closed loop circulation. The electric heater 7 adopts a tubular electric heater or a plate electric heater (SRY type, HRY type, etc. can be selected). The heating power is designed according to the molten salt heating requirements (100kW-10MW can be selected). The material is high-temperature resistant stainless steel (such as 310S), and the surface load is ≤1.5W / cm² to avoid local overheating and decomposition of molten salt.

[0039] The input end of the electric heater 7 is connected to the output end of the molten salt pump 11 via a flange, and the output end is connected to the inlet end of the molten salt tank 6 via a flange. The pipeline material is high-temperature resistant stainless steel, and the pipe diameter matches the outlet diameter of the molten salt pump 11 (DN50-DN150). The output end of the molten salt pump 11 is connected to the electric heater 7, the electric heater 7 is connected to the molten salt tank 6, and the molten salt tank 6 is connected to the molten salt pump box 1 to form a molten salt circulation loop.

[0040] Furthermore, a check valve is installed on the output pipeline of the molten salt pump 11 (to prevent molten salt backflow), and thermometers and pressure gauges are respectively installed on the inlet and outlet pipelines of the electric heater 7 (to monitor the temperature and pressure of the molten salt). A regulating valve is installed on the return pipeline from the molten salt tank 6 to the molten salt pump box 1 (to control the return flow). All pipelines in the entire loop are wrapped with an insulation layer (the material is the same as that of the condensate manifold) to reduce heat loss.

[0041] Specifically, the molten salt, after being preheated by the heat exchange component 3, is drawn out by the molten salt pump 11 and sent to the electric heater 7 to be heated to the target temperature (e.g., 400℃). After the high-temperature molten salt enters the molten salt tank 6, it releases heat and the temperature drops to 140-150℃. Then it flows back to the molten salt pump tank 1 through the return pipeline, completing the complete cycle of "preheating-heating-heat release-return".

[0042] Furthermore, the temperature of the molten salt increases after flowing through the second flow channel 32. Before entering the second flow channel 32, the temperature of the molten salt is 140-150℃ (the temperature of the liquid molten salt in the molten salt pump box 1). When flowing through the second flow channel 32, it exchanges heat with the molten salt hydrophobic water (120-140℃) in the first flow channel 31. Since the temperature difference between the hydrophobic water and the molten salt is 10-30℃, and the heat transfer efficiency of the heat exchange component 3 is ≥80%, the temperature of the molten salt will increase by 5-20℃, eventually reaching 145-170℃. To ensure a stable increase in the temperature of the molten salt, the input flow rate of the hydrophobic water collection component 2 needs to be matched with the molten salt circulation flow rate (the ratio of hydrophobic water flow rate to molten salt flow rate can be selected as 1:5-1:10). The heat exchange area of ​​the heat exchange component 3 is designed according to the flow rate and temperature difference (selectable as 10-100m²). Meanwhile, by controlling the steam input of the salt dissolving pipeline, the condensate temperature is kept stable at 120-140℃, avoiding insufficient molten salt heating due to excessively low condensate temperature. After the molten salt temperature rises, the heating load of the subsequent electric heater 7 is reduced, which can save energy consumption. At the same time, the molten salt temperature is higher than the liquid critical temperature of 145℃, which reduces the risk of solidification in the molten salt pump 11 and pipeline, and improves the reliability of system operation.

[0043] Furthermore, after the brine condensate flows through the first channel 31, it is discharged into the condensate header. The condensate header is the main pipeline for centralized condensate recovery in the power plant / industrial system, used to collect low-temperature condensate (condensate) generated by various equipment (such as brine pipelines and heat exchangers), avoiding waste of water resources and waste heat. After the brine condensate flows through the first channel 31 and completes heat exchange with the molten salt, its temperature drops to 80-100℃. At this point, it is discharged into the power plant's existing condensate header through the output pipeline of the first channel 31. The discharge path is "first channel output end → short pipe → flange → condensate header branch interface". A filter (filter screen pore size ≤ 2mm) can be installed on the short pipe to prevent impurities carried by the condensate from entering the condensate header and causing blockage. To ensure smooth discharge of the condensate, a pressure reducing valve can be installed on the output pipeline of the first channel 31 (adjusting the pressure to 0.3-0.6MPa, matching the pressure of the condensate header) to avoid backflow of condensate due to excessive pressure or poor discharge due to excessive pressure. The pressure reducing valve is made of stainless steel and has an adjustment accuracy of ≤±0.05MPa.

[0044] Furthermore, the condensate drain header is an existing public pipeline in the power plant, used to collect low-temperature condensate from various systems and ultimately transport it to the deaerator or condenser for recycling. Therefore, the condensate discharge path of this scheme is compatible with the existing system of the power plant, requiring no new discharge facilities and reducing the cost of modification.

[0045] Furthermore, it also includes a first temperature monitoring component 8, which uses an industrial-grade platinum resistance thermometer (PT100 or PT1000 models optional), with a measurement range of 0-300℃, an accuracy class of ≤±0.5℃, and a protection class of ≥IP65, meeting the requirements of high-temperature and dusty environments on site. The thermometer is installed on the pipeline between the output end of the second flow channel 32 and the inlet of the molten salt pump 11 through a sleeve. The sleeve material is the same as the pipeline, and the insertion depth is 1 / 3-2 / 3 of the inner diameter of the pipeline to ensure that the temperature sensing element is in full contact with the molten salt and the measurement data is accurate. The first temperature monitoring component 8 is located between the output end of the second flow channel 32 and the inlet of the molten salt pump 11 to monitor the temperature of the molten salt after preheating.

[0046] Furthermore, the thermometer is connected to the power plant's DCS control system via wires to transmit the temperature data of the preheated molten salt in real time. When the temperature is below 145℃ (the critical temperature of liquid molten salt), the system issues an alarm signal, prompting operators to check the steam input of the salt melting pipeline or the working status of the heat exchange components; when the temperature is above 170℃, the steam input of the salt melting process can be appropriately reduced to avoid the molten salt temperature being too high and affecting the operation of the subsequent electric heater.

[0047] Specifically, the installation location is before the molten salt enters the molten salt pump 11, which can directly reflect the actual temperature of the molten salt after preheating, providing the most direct basis for subsequent system control. At the same time, it is far away from the high-temperature area of ​​the heat exchange components to avoid damage to the thermometer due to local overheating.

[0048] Furthermore, it also includes a first control valve 9, a second control valve 10, and a second temperature monitoring component 12. Both the first control valve 9 and the second control valve 10 are electric regulating valves (ZAZP type or QV type optional), the valve body material is stainless steel, the adjustment range is 0-100%, the action time is ≤5s, and the sealing level is ≥V. The valve is installed on the pipeline between the first branch interface 22 and the second branch interface 23 and the drain manual valve, and is fixed by a flange. The valve actuator is connected to the DCS control system and receives control signals. The second temperature monitoring component 12 is selected to be the same as the first temperature monitoring component 8 (PT100 platinum resistance thermometer), with a measurement range of 0-200℃ and an accuracy class of ≤±0.5℃. It is installed on the pipeline between the output end of the first flow channel 31 and the drain header through a sleeve to monitor the temperature of the drain after heat exchange and to assist in judging the heat exchange effect. The first control valve 9 is located at the first branch interface 22, and the second control valve 10 is located at the second branch interface 23. The second temperature monitoring component 12 is located between the output end of the first flow channel 31 and the drain header. The first control valve 9 and the second control valve 10 adjust the flow rate of the salt drain at the corresponding branch interface according to the monitoring results of the first temperature monitoring component 8.

[0049] Specifically, the target temperature range for molten salt preheating is set (e.g., 150-160℃). When the temperature measured by the first temperature monitoring component 8 is below 150℃, the DCS system sends an opening signal to the first control valve 9 and the second control valve 10 to increase the flow of molten salt condensate and improve the heat exchange capacity. In particular, the DCS system (distributed control system) is a conventional automated control platform in industrial production, used to centrally monitor and regulate the operating parameters (temperature, pressure, flow rate) of various equipment.

[0050] When the measured temperature exceeds 160℃, the system sends a shut-off signal to reduce the amount of hydrophobic water flowing in and prevent the molten salt temperature from becoming too high.

[0051] Furthermore, when the second temperature monitoring component 12 measures a condensate temperature below 80°C, it indicates that the heat exchange is sufficient. If the molten salt temperature still does not meet the standard, the first control valve 9 corresponding to the molten salt pump box and the salt dissolving pipeline can be opened first to ensure that the molten salt temperature in the molten salt pump box is stable. The two control valves can be adjusted independently or synchronously, and can be flexibly controlled according to the condensate temperature and flow rate of the two salt dissolving pipelines.

[0052] In summary, the existing steam header is first activated, and high-temperature steam is introduced into the molten salt pump box melting pipeline and the molten salt tank melting pipeline. The steam enters the molten salt pump box 1 via the melting pipeline, melting any solidified molten salt inside. Simultaneously, it enters the molten salt tank 6 via the melting pipeline, melting the solidified molten salt inside. During this process, the steam condenses into high-temperature molten salt condensate (120-140℃) upon contact with the low-temperature molten salt. This condensate is discharged through the first manual condensate valve 4 and the second manual condensate valve 5. Then, the first control valve 9 and the second control valve 10 are opened. The molten salt pump box 1 side condensate is precisely connected to the first branch interface 22 of the newly added condensate collection component 2 via the first manual condensate valve 4 and the first control valve 9. The molten salt tank 6 side condensate is precisely connected to the second branch interface 23 of the condensate collection component 2 via the second manual condensate valve 5 and the second control valve 10. The two condensate streams ultimately converge at the condensate collection component 2. The condensate flows within pipe 21, forming a stable waste heat source. Unlike existing technologies where dual condensate channels discharge directly without confluence, this solution uses a combination of branch interfaces and a confluence pipe to achieve centralized condensate recovery, providing a stable medium flow for subsequent heat exchange. The high-temperature condensate after confluence enters the newly added heat exchange component 3, namely the first flow channel 31 (shell side) of the shell-and-tube heat exchanger 33. In the diagram, the upper part of the shell-and-tube heat exchanger 33 is the first flow channel 31, and the lower part is the inlet (shell-side inlet). The other part is the outlet (shell-side outlet) of the first flow channel 31. Simultaneously, the liquid molten salt (140-150℃) in the molten salt pump box 1 is pumped by the molten salt pump 11. Under the suction effect, the condensate enters the second flow channel 32 (tube side) of the shell-and-tube heat exchanger 33. Since the first flow channel 31 and the second flow channel 32 are isolated from each other by the thin-walled tube wall of the shell-and-tube heat exchanger 33, the residual heat of the high-temperature condensate is efficiently transferred to the low-temperature molten salt through the tube wall, realizing the preheating of the molten salt. During this process, the newly added first temperature monitoring component 8 monitors the molten salt temperature at the output end of the second flow channel 32 in real time (i.e., the molten salt temperature after preheating). If the temperature is lower than 150℃ (the lower limit of the target preheating temperature), the DCS system controls the first control valve 9 and the second control valve 10 to open wider, increasing the condensate inflow to improve the heat exchange. If the temperature is higher than 150℃, the DCS system controls the first control valve 9 and the second control valve 10 to open wider, increasing the condensate inflow to improve the heat exchange. At 160℃ (the upper limit of the target preheating temperature), the control valve is closed slightly to ensure the molten salt temperature is stable. Through the coordination of "monitoring and control", the preheating effect is guaranteed. The molten salt, which is preheated by the shell-and-tube heat exchanger 33 (temperature rises by 5-20℃, reaching 145-170℃), enters the existing molten salt pump 11 after passing through the first temperature monitoring component 8, and is then transported to the existing electric heater 7 to be heated to the target temperature (such as 400℃). Subsequently, it enters the existing molten salt tank 6 to release heat (the demineralized water in the heating tank generates steam). The molten salt after releasing heat (temperature drops to 140-150℃) flows back to the molten salt pump box 1 through the existing return pipeline, completing the molten salt cycle.Meanwhile, the condensate that has completed heat exchange (temperature reduced to 80-100℃) is output from the first flow channel 31 of the shell-and-tube heat exchanger 33. After passing through the newly added second temperature monitoring component 12 (to verify the adequacy of waste heat recovery and ensure that the condensate temperature meets the standard), it is discharged into the existing condensate header and finally enters the power plant's condensate recovery system. During the continuous operation of the entire device, the first temperature monitoring component 8 and the second temperature monitoring component 12 transmit temperature data in real time. The first control valve 9 and the second control valve 10 are dynamically adjusted according to the signal from the first temperature monitoring component 8. If the condensate temperature in the molten salt tank's salt melting pipeline is low, the second control valve 10 can be closed slightly and the first control valve opened wider. Door 9 prioritizes the use of the higher-temperature condensate on the molten salt pump box side to ensure preheating efficiency. The system adaptability is improved through independent control of dual valves. By adding a condensate collection component 2, a shell-and-tube heat exchanger 33, a first control valve 9 and a second control valve 10, as well as a first temperature detection component 8 and a second temperature monitoring component 12, the innovative function of "recovery of waste heat from condensate drainage - preheating of molten salt - precise temperature control" is achieved without modifying the existing steam salting, molten salt circulation, and condensate recovery system. This solves the problems of waste heat from condensate drainage and high energy consumption for molten salt heating in the existing technology. Moreover, the usage process of all innovative components is clear and they are seamlessly integrated with the existing system.

[0053] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A molten salt electric heating device, characterized in that: Molten salt pump box (1), hydrophobic manifold assembly (2), heat exchange assembly (3); The molten salt pump box (1) has a built-in molten salt pump (11). The input end of the hydrophobic confluence component (2) is connected to the hydrophobic outlet of the salt dissolving pipeline for collecting salt dissolving hydrophobic water. The heat exchange component (3) has a first flow channel (31) and a second flow channel (32) that are isolated from each other. The two ends of the first flow channel (31) are respectively connected to the output end of the hydrophobic confluence component (2) and the hydrophobic header. The two ends of the second flow channel (32) are respectively connected to the pipeline between the molten salt pump box (1) and the molten salt pump (11) and the inlet of the molten salt pump (11). When the molten salt flows through the first channel (31), it transfers heat to the molten salt flowing through the second channel (32) through the wall of the heat exchange component (3).

2. The molten salt electric heating device according to claim 1, characterized in that: The hydrophobic manifold assembly (2) includes a hydrophobic manifold pipe (21), and the input end of the hydrophobic manifold pipe (21) is provided with a first branch interface (22) and a second branch interface (23).

3. The molten salt electric heating device according to claim 2, characterized in that: The salt dissolving pipeline includes a molten salt pump box salt dissolving pipeline and a molten salt box salt dissolving pipeline. The drain outlet of the molten salt pump box salt dissolving pipeline is the output end of the first drain manual valve (4), and the drain outlet of the molten salt box salt dissolving pipeline is the output end of the second drain manual valve (5). The first branch interface (22) is connected to the first drain manual valve (4), and the second branch interface (23) is connected to the second drain manual valve (5).

4. The molten salt electric heating device according to claim 3, characterized in that: The heat exchange component (3) is a shell-and-tube heat exchanger (33).

5. The molten salt electric heating device according to claim 4, characterized in that: The first flow channel (31) is the shell side of the shell-and-tube heat exchanger (33), and the second flow channel (32) is the tube side of the shell-and-tube heat exchanger (33).

6. The molten salt electric heating device according to claim 5, characterized in that: It also includes a molten salt tank (6) and an electric heater (7). The output end of the molten salt pump (11) is connected to the electric heater (7), the electric heater (7) is connected to the molten salt tank (6), and the molten salt tank (6) is connected to the molten salt pump box (1) to form a molten salt circulation loop.

7. The molten salt electric heating device according to any one of claims 1 to 6, characterized in that: The temperature of the molten salt increases after it flows through the second channel (32).

8. The molten salt electric heating device according to claim 7, characterized in that: After the salt-water-drained water flows through the first flow channel (31), it is discharged into the drainage header.

9. The molten salt electric heating device according to claim 8, characterized in that: It also includes a first temperature monitoring component (8), which is located between the output end of the second flow channel (32) and the inlet of the molten salt pump (11) to monitor the temperature of the molten salt after preheating.

10. The molten salt electric heating device according to claim 9, characterized in that: It also includes a first control valve (9), a second control valve (10), and a second temperature monitoring component (12); The first control valve (9) is located at the first branch interface (22), the second control valve (10) is located at the second branch interface (23), and the second temperature monitoring component (12) is located between the output end of the first flow channel (31) and the drain header. The first control valve (9) and the second control valve (10) adjust the flow rate of the salt-hydrophobic water into the corresponding branch interface according to the monitoring results of the first temperature monitoring component (8).

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