A power self-regulating molten salt electric heating device based on the flow of liquid film outside the tube

Abstract

The application discloses a molten salt electric heating device based on power automatic regulation and liquid film flow outside a tube; wherein three inlet molten salt pumps are connected with one upper zero potential molten salt tank respectively, each upper zero potential molten salt tank is connected with one electrode molten salt tank below through at least two groups of liquid film forming devices and single tube intervention gates, each electrode molten salt tank is connected with one lower zero potential molten salt tank below through at least one group of liquid film forming devices and single tube intervention gates, and each lower zero potential molten salt tank is connected with one outlet molten salt pump; the upper zero potential molten salt tank and the lower zero potential molten salt tank are electrically connected with a zero potential grounding device through respective stainless steel electrodes; each electrode molten salt tank is electrically connected with A phase, B phase and C phase of a three-phase alternating current power source through respective stainless steel electrodes, and the connection mode between the electrode molten salt tanks is parallel connection. The number of liquid film passage and the thickness of the liquid film participating in heating are adjusted by controlling the liquid level height, so that smooth control of heating power is realized.

Description

Technical Field

[0001] This invention belongs to the field of electric heating equipment and thermal energy engineering technology, specifically a molten salt electric heating device with automatic power adjustment based on the flow of liquid film outside the tube. Background Technology

[0002] With the rapid development of new energy, chemical, and thermal storage industries, there is an urgent need for a heat transfer and storage medium that can operate stably in high-temperature ranges for extended periods and is economically viable in fields such as concentrated solar power (CSP), large-scale energy storage, and grid peak shaving. Molten salt, with its advantages of high operating temperature, high heat capacity, low system pressure, and controllable cost, has become an ideal choice. However, its efficient, uniform, and reliable heating method remains one of the key technological challenges in the industry, directly affecting system energy efficiency, operational safety, and lifespan.

[0003] Traditional molten salt heating methods, such as external resistance wires or heating rods, suffer from low thermal efficiency, uneven temperature distribution, susceptibility to localized overheating leading to molten salt degradation, limited power density, and inconvenient maintenance. In contrast, electrode heating, as a direct and efficient internal heating method, offers advantages such as high thermal efficiency and fast response, and is increasingly being applied to system startup, insulation, and operation. However, achieving rapid, uniform, and efficient electrode heating in large-scale thermal storage systems, while avoiding uneven heating and thermal stress concentration caused by the "scale effect," remains a significant challenge that needs to be overcome.

[0004] Existing electrode heating technologies mostly rely on electronic control to regulate input power. Such methods are prone to inducing electric arcs on the electrode surface, accelerating electrochemical corrosion and ablation, shortening the electrode's lifespan, and also suffer from problems such as inconsistent and unstable power regulation and limited control precision. Therefore, there is an urgent need to explore a novel heating mechanism that does not solely rely on electronic control regulation, can fundamentally alleviate electrode arcing and corrosion, and achieve smooth power control. Summary of the Invention

[0005] To address the problems existing in the background art, this invention provides a molten salt electric heating device with automatic power regulation based on the flow of an external liquid film. The heating power is smoothly regulated by adjusting the liquid level changes of the heated molten salt. This method of automatically regulating power based on liquid level enables more natural, continuous, and stable power control. Simultaneously, the liquid film flow is combined with electrode heating. During heating, current passes through the entire molten salt film, causing the liquid film to heat up as a whole, which is conducive to forming a uniform temperature field and avoiding local overheating. The technical solution includes: three inlet molten salt pumps, three outlet molten salt pumps, stainless steel electrodes, zero potential grounding device, three-phase AC power supply, heat insulation shell, single-tube intervention gate, liquid film forming device, three upper zero potential molten salt tanks, three electrode molten salt tanks, and three lower zero potential molten salt tanks. Among them, the three inlet molten salt pumps are respectively connected to one upper zero potential molten salt tank. Each upper zero potential molten salt tank is connected to one lower electrode molten salt tank through at least two sets of liquid film forming devices and single-tube intervention gates. Each electrode molten salt tank is connected to one lower zero potential molten salt tank through at least one set of liquid film forming devices and single-tube intervention gates. Each lower zero potential molten salt tank is connected to one outlet molten salt pump.

[0006] The upper and lower zero-potential molten salt tanks are electrically connected to the zero-potential grounding device through their respective stainless steel electrodes; each electrode molten salt tank is electrically connected to phase A, phase B and phase C of the three-phase AC power supply through its own stainless steel electrodes, and the connection between the electrode molten salt tanks is in parallel.

[0007] The single-tube intervention gate is installed in the outlet pipeline between the liquid film forming device and the outlet below the molten salt tank. The single-tube intervention gate includes a gate body and a gate plate. The gate body is fixed to the outlet pipeline by flanges and bolts, and the gate plate is installed in the gate body. The opening and closing of the gate plate is controlled by the valve plate drive system.

[0008] The liquid film forming device includes: a liquid film outlet opening, a lower fixed conductive component, an upper fixed conductive component, and an insulating solid circular tube. The lowest end of the outlet pipe at the lower outlet of the molten salt tank is the liquid film outlet opening. A concentric insulating solid circular tube is provided at the liquid film outlet opening. The insulating solid circular tube is fixed to the corresponding outlet pipe through the upper fixed conductive component, thereby forming a continuous molten salt liquid film on the outside of the insulating solid circular tube. The insulating solid circular tube extends into the upper inlet of the molten salt tank at the top of the lower molten salt tank. The insulating solid circular tube is fixed to the lower molten salt tank through the lower fixed conductive component.

[0009] The upper fixed conductive component is a strip-shaped structure facing the axis of the insulating solid circular tube, thereby forming the smallest possible projection in the horizontal direction to facilitate a more continuous molten salt film; the cross-sectional area of ​​the space between the upper inlet of the molten salt tank and the insulating solid circular tube is not less than the cross-sectional area of ​​the lower outlet of the molten salt tank; the lower fixed conductive component and the upper fixed conductive component are used for electrical connection between the insulating solid circular tube and the upper molten salt tank and the lower molten salt tank, respectively;

[0010] The insulated solid round tube is made of ceramic, quartz or glass materials.

[0011] The molten salt electric heating device also includes: a measurement and control system;

[0012] The measurement and control system includes: an inlet valve frequency converter, an ultrasonic flow meter, a lower-level ultrasonic sensor, a lower-level demodulator, an upper-level ultrasonic sensor, an upper-level regulator, a DCS system, an engineering workstation, voltage transmitters, and current transmitters. Each inlet molten salt pump is connected to one inlet valve frequency converter, and each outlet molten salt pump and the pipeline near each inlet molten salt pump are equipped with an independent ultrasonic flow meter. The two stages of the three voltage transmitters are respectively connected by wires to the stainless steel electrode of an upper zero-potential molten salt tank and the corresponding electrode molten salt tank. The electrical connection between the stainless steel electrode behind each electrode molten salt tank and the three-phase AC power supply is... A current transmitter is installed on the road; a lower ultrasonic sensor is installed on the side of at least one set of liquid film forming devices between each upper zero-potential molten salt tank and the corresponding electrode molten salt tank; the lower ultrasonic sensor is connected to the DCS system through a lower demodulator; an upper ultrasonic sensor is installed on the side of at least one set of liquid film forming devices between each electrode molten salt tank and the corresponding lower zero-potential molten salt tank; the upper ultrasonic sensor is connected to the DCS system through an upper regulator; the valve plate drive system, voltage transmitter, current transmitter, inlet valve frequency converter, and ultrasonic flow meter in the single-tube intervention gate are all connected to the engineering station through the DCS system.

[0013] The lower and upper ultrasonic sensors are responsible for transmitting and receiving high-frequency sound waves and completing the sound-to-electric conversion. The upper regulator obtains the molten salt film thickness through the upper ultrasonic sensor, and the lower demodulator obtains the molten salt film thickness through the lower ultrasonic sensor. The lower demodulator and the upper regulator extract the effective signal from the high-frequency echo and input it into the heating power monitoring module to determine the thickness of the lower or upper molten salt film.

[0014] The DCS system includes a heating power monitoring module, which, when working, calculates and processes the real-time liquid film thickness data to obtain the heating resistance value at the corresponding liquid film thickness, and combines it with the voltage signal output by the voltage transmitter to realize real-time monitoring and feedback of the upper or lower heating power.

[0015] When it is necessary to adjust the heating power of the upper or lower layer, there are two methods: adjusting the molten salt level and adjusting the number of heating channels.

[0016] When adjusting the molten salt level, the thickness of the liquid film is controlled by controlling the molten salt level, thereby adjusting the heating power. When the molten salt temperature is too high, the molten salt level in the upper zero-potential molten salt tank or the middle electrode molten salt tank is increased, the liquid film thickness is reduced, and the heating power is decreased. When the molten salt temperature is too low, the molten salt level in the upper zero-potential molten salt tank or the middle electrode molten salt tank is decreased, the liquid film thickness is increased, and the heating power is increased.

[0017] When the number of heating channels needs to be adjusted, the number of parallel heating channels is controlled by controlling the opening and closing of the single-tube intervention gate, thereby achieving heating load control. While maintaining a constant liquid level, the number of molten salt liquid film channels in the liquid film forming device that participate in heating is changed by controlling the number of single-tube intervention gates connected to the upper zero-potential molten salt tank or the middle electrode molten salt tank, thereby controlling the flow rate of the heated molten salt. The more single-tube intervention gates are opened, the more molten salt liquid film channels participate in the liquid film forming device, and the greater the flow rate of the heated molten salt.

[0018] The adjustment logic for the molten salt level in the upper zero-potential molten salt tank is as follows: increase or decrease the opening and closing degree of the inlet molten salt pump until the liquid film thickness data output by the upper demodulator meets the requirements, and then the molten salt level is adjusted.

[0019] The adjustment logic for the molten salt level in the electrode molten salt tank is as follows: When it is necessary to lower the level, the number of single-tube intervention gates opened between the corresponding zero-potential molten salt tank and the electrode molten salt tank below is increased until the liquid film thickness data output by the lower demodulator meets the requirements, at which point the molten salt level adjustment is complete; when it is necessary to raise the level, the number of single-tube intervention gates closed between the corresponding zero-potential molten salt tank and the electrode molten salt tank below the single-tube intervention gate is increased until the liquid film thickness data output by the lower demodulator meets the requirements, at which point the molten salt level adjustment is complete.

[0020] If it is necessary to adjust the molten salt level in both the upper zero potential molten salt tank and the electrode molten salt tank simultaneously, adjust the molten salt level in the electrode molten salt tank first.

[0021] The DCS system also includes an early warning module. When the early warning module is working, the DCS system collects the power supply voltage signal of the heating device through a voltage transmitter and the total current signal of the heating circuit through a current transmitter. The two analog signals are sent to the DCS system for calculation and processing to monitor the total heating power of the entire heating device in real time. By monitoring abnormal fluctuations or over-limit states of the total current, the system can determine whether there are faults such as overall overload in the main heating circuit, providing a basis for the diagnosis of the overall operating status of the device and safety early warning.

[0022] The DCS system is connected to a K-type armored thermocouple, which is used to monitor the temperature of the molten salt. The K-type armored thermocouple is installed in the upper zero-potential molten salt tank, the electrode molten salt tank, and the lower zero-potential molten salt tank.

[0023] The single-tube intervention gate, liquid film forming device, all upper zero-potential molten salt tanks, all electrode molten salt tanks and all lower zero-potential molten salt tanks are all installed inside the heat-insulating shell;

[0024] The heat insulation shell includes: heat insulation bricks, heat insulation layer and metal shell arranged in sequence from the inside to the outside. The metal shell is used to bear pressure, the middle is the heat insulation layer, the heat insulation layer is used to maintain the temperature of molten salt, and the heat insulation bricks are refractory bricks used to construct the high-temperature cavity.

[0025] Vacuum jackets are provided in the gaps between the tank bodies and pipes of the upper zero-potential molten salt tank, the electrode molten salt tank, and the lower zero-potential molten salt tank to reduce heat loss.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. Excellent heating uniformity and stable temperature field: By controlling the liquid level height, the number and thickness of the liquid film participating in the heating process can be adjusted to achieve precise and smooth control of the heating power. This also ensures uniform heating of the molten salt, effectively avoiding localized overheating or underheating.

[0028] 2. High heating efficiency and fast thermal response: Direct heating is achieved by utilizing the resistance of the molten salt film itself, with heat generated within the film, avoiding heat loss common in traditional heating methods. Furthermore, due to the thinness and small heat capacity of the film, it can quickly respond to changes in heating power, allowing for more flexible and rapid temperature control.

[0029] 3. The heating power of the upper layer or the lower layer can be adjusted independently, which can make the wall temperature more gradual along the flow direction and avoid local overheating or underheating, especially suitable for liquid film flow conditions.

[0030] 4. By directly heating the molten salt with electrodes, the heating power of the electrodes on the molten salt is automatically adjusted by the changes in the liquid level in the molten salt tank, thereby controlling the power more smoothly, so that the molten salt is heated evenly and stably, avoiding the risk of local overheating and electric arc.

[0031] 5. Utilizing the self-heating of the molten salt film eliminates the need for additional heating elements, simplifying the structure and reducing costs and maintenance complexity. The molten salt tank physically isolates the electrodes of each phase, effectively preventing the risks of interphase short circuits and arc discharge, ensuring system safety. The electrode molten salt tank can be independently isolated for maintenance without interrupting the main system, improving operational reliability.

[0032] 6. High energy density and small equipment size: Liquid film heating is efficient and direct. Under the same heating power, the required heat exchange area is much smaller than that of traditional heating methods, making the equipment more compact. Attached Figure Description

[0033] Figure 1 This is an embodiment of a molten salt electric heating device with automatic power adjustment based on the flow of an external liquid film, according to the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of an embodiment of the present invention.

[0035] Figure 3 This is a top view schematic diagram of an embodiment of the present invention.

[0036] Figure 4 This is a longitudinal section diagram of an embodiment of the present invention near the gate valve.

[0037] Figure 5 This is a schematic diagram of the measurement and control system in an embodiment of the present invention.

[0038] in,

[0039] 1. Inlet molten salt pump; 2. Upper zero-potential molten salt tank; 3. Electrode molten salt tank; 4. Single-pipe intervention gate; 5. Lower outlet of molten salt tank; 6. Insulated solid round tube; 7. Stainless steel electrode; 8. Zero-potential grounding device; 9. Three-phase AC power supply; 10. Flow control valve; 11. Insulating brick; 12. Insulation layer; 13. Metal shell; 14. Vacuum jacket; 15. Voltage transmitter; 16. Current transmitter; 17. Lower ultrasonic sensor; 18. Lower demodulator; 19. K-type armored thermocouple; 20. Ultrasonic flow meter; 21. DCS system; 22. Engineering workstation; 23. Upper ultrasonic sensor; 24. Outlet molten salt pump; 25. Upper demodulator; 26. Inlet valve frequency converter; 27. Lower zero-potential molten salt tank; 28. Upper inlet of molten salt tank;

[0040] 100. Insulated outer casing;

[0041] 300. Liquid film forming apparatus; 301. Lower fixed conductive component; 302. Upper fixed conductive component;

[0042] 400. Gate body; 401. Gate plate; Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings.

[0044] like Figures 1-4 The embodiment of the present invention shown includes: three inlet molten salt pumps 1, three outlet molten salt pumps 24, stainless steel electrodes 7, a zero-potential grounding device 8, a three-phase AC power supply 9, a heat-insulating shell 100, a single-tube intervention gate 4, a liquid film forming device 300, three upper zero-potential molten salt tanks 2, three electrode molten salt tanks 3, and three lower zero-potential molten salt tanks 27.

[0045] Among them, three inlet molten salt pumps 1 are respectively connected to an upper zero potential molten salt tank 2. Each upper zero potential molten salt tank 2 is connected to a lower electrode molten salt tank 3 through at least two sets of liquid film forming devices 300 and a single tube intervention gate 4. Each electrode molten salt tank 3 is connected to a lower lower zero potential molten salt tank 27 through at least one set of liquid film forming devices 300 and a single tube intervention gate 4. Each lower zero potential molten salt tank 27 is connected to an outlet molten salt pump 24.

[0046] Stainless steel electrodes 7 are installed on both the upper zero-potential molten salt tank 2 and the lower zero-potential molten salt tank 27 via electrical connections, and are electrically connected to the zero-potential grounding device 8 via their respective stainless steel electrodes 7.

[0047] Each molten salt electrode 3 is electrically connected to a stainless steel electrode 7, which is electrically connected to phases A, B, and C of the three-phase AC power supply 9. The molten salt electrode 3 is connected in parallel, with each electrode molten salt electrode corresponding to two zero-potential molten salt electrodes forming an independent conductive circuit. When a group of electrode heating units malfunctions or requires maintenance, the power to that phase circuit can be cut off and isolated without shutting down the other two heating units or the entire device, thus improving the continuity of device operation and preventing molten salt freezing and blockage accidents.

[0048] like Figure 2 As shown, the single-tube intervention gate 4, the liquid film forming device 300, all the upper zero-potential molten salt tanks 2, all the electrode molten salt tanks 3, and all the lower zero-potential molten salt tanks 27 are all installed inside the heat insulation shell 100; the heat insulation shell 100 includes: heat insulation bricks 11, heat insulation layer 12, and metal shell 13 arranged sequentially from the inside to the outside, wherein the metal shell 13 is used to bear pressure, the middle is the heat insulation layer 12, the heat insulation layer is used to maintain the temperature of the molten salt, and the heat insulation bricks 11 are refractory bricks used to construct the high-temperature cavity;

[0049] In this embodiment, a vacuum interlayer 14 is provided in the gap between the tank body and the pipe of each molten salt tank (upper zero potential molten salt tank 2, electrode molten salt tank 3 and lower zero potential molten salt tank 27) to reduce heat loss.

[0050] like Figure 1 and Figure 4 The single-tube intervention gate 4 shown is installed in the outlet pipeline between the liquid film forming device 300 and the outlet 5 below the molten salt tank. The single-tube intervention gate 4 includes a gate body 400 and a gate plate 401. The gate body 400 is fixed to the outlet pipeline by a flange and bolts. The gate plate 401 is installed in the gate body 400. The opening and closing of the gate plate 401 is controlled by a valve plate drive system.

[0051] like Figure 1 and Figure 4 The liquid film forming apparatus 300 shown includes: a liquid film outlet opening 310, a lower fixed conductive component 301, an upper fixed conductive component 302, and an insulating solid circular tube 6. The lowest end of the outlet pipe of the outlet 5 below the molten salt tank is the liquid film outlet opening 310. A concentric insulating solid circular tube 6 is provided at the liquid film outlet opening 310. The insulating solid circular tube 6 is fixed to the corresponding outlet pipe through the upper fixed conductive component 302, thereby forming a continuous molten salt liquid film on the outside of the insulating solid circular tube 6. The insulating solid circular tube 6 extends into the upper inlet 28 of the molten salt tank at the top of the lower molten salt tank. The insulating solid circular tube 6 is fixed to the lower molten salt tank through the lower fixed conductive component 301.

[0052] In this embodiment, the upper fixed conductive component 302 is a strip structure oriented towards the axis of the insulating solid circular tube 6, thereby forming a projection as small as possible in the horizontal direction to facilitate a more continuous molten salt film. The cross-sectional area of ​​the space between the upper inlet 28 of the molten salt tank and the insulating solid circular tube 6 is not less than the cross-sectional area of ​​the lower outlet 5 of the molten salt tank to ensure that the molten salt film will not overflow due to excessive flow. The lower fixed conductive component 301 and the upper fixed conductive component 302 are used for electrical connection between the insulating solid circular tube 6 and the upper molten salt tank and the lower molten salt tank, respectively. The upper fixed conductive component 302, the lower fixed conductive component 301, the upper zero-potential molten salt tank 2, the electrode molten salt tank 3, and the lower zero-potential molten salt tank 27 are all made of TP304H stainless steel, and all positions in contact with the molten salt are provided with an anti-corrosion coating.

[0053] In this embodiment, the insulating solid circular tube 6 is made of ceramic, quartz or glass material, and its surface is precision polished and hydrophilic modified to facilitate the formation and flow of liquid film.

[0054] like Figure 5As shown, the embodiment also includes a measurement and control system, which includes: an inlet valve frequency converter 26, an ultrasonic flow meter 20, a lower ultrasonic sensor 17, a lower demodulator 18, an upper ultrasonic sensor 23, an upper regulator 25, a DCS system 21, an engineering station 22, a K-type armored thermocouple 19, a voltage transmitter 15, and a current transmitter 16; each inlet molten salt pump 1 is connected to one inlet valve frequency converter 26, and each outlet molten salt pump 24 and each inlet molten salt pump 1 are equipped with an independent ultrasonic flow meter 20 on the pipelines near them; The two stages of the three voltage transmitters 15 are respectively connected to the stainless steel electrode 7 of an upper zero-potential molten salt tank 2 and the corresponding stainless steel electrode 7 of an electrode molten salt tank 3 via wires; a current transmitter 16 is installed on the circuit between the stainless steel electrode 7 behind each electrode molten salt tank 3 and the three-phase AC power supply 9; each upper zero-potential molten salt tank 2, each electrode molten salt tank 3 and each lower zero-potential molten salt tank 27 is equipped with an independent K-type armored thermocouple 19 for monitoring the molten salt temperature (the installation position is located below the molten salt base operating liquid level of the corresponding molten salt tank);

[0055] At least one set of liquid film forming devices 300 between each upper zero potential molten salt tank 2 and the corresponding electrode molten salt tank 3 is equipped with a lower ultrasonic sensor 17 on its side; the lower ultrasonic sensor 17 is connected to the DCS system 21 through a lower demodulator 18.

[0056] At least one set of liquid film forming devices 300 between each electrode molten salt tank 3 and the corresponding lower zero potential molten salt tank 27 is equipped with an upper ultrasonic sensor 23 on its side; the upper ultrasonic sensor 23 is connected to the DCS system 21 through an upper demodulator 25.

[0057] The valve plate drive system, voltage transmitter 15, current transmitter 16, K-type armored thermocouple 19, inlet valve frequency converter 26 and ultrasonic flow meter 20 in the single-tube intervention gate 4 are all connected to the engineer station 22 through the DCS system 21.

[0058] The monitoring and control system uses the DCS system 21 as its control center. It collects operating parameters from various field sensors, including a current transmitter 16, a lower-level demodulator 18, an upper-level regulator 25, a K-type armored thermocouple 19, and an ultrasonic flow meter 20. After processing by the DCS, it outputs key monitoring parameters such as voltage, current, liquid film thickness, and heating power, and uploads them to the engineering station 22 for real-time monitoring and maintenance management by operations and maintenance personnel. Simultaneously, the DCS system 21 outputs control commands to the inlet valve frequency converter 26 and the single-tube intervention gate 4 based on the control signals, completing power regulation and process control.

[0059] The inlet valve frequency converter 26 and the molten salt pump 2 are the core control devices of the molten salt pump system. The inlet valve frequency converter 26 receives control signals and adjusts the output in real time, thereby changing the motor speed of the molten salt pump 2, realizing continuous flow regulation and maintaining system stability. It can also be used for anti-condensation and pressure stabilization, and is suitable for special working conditions such as high temperature, high viscosity and easy solidification of molten salt.

[0060] The lower ultrasonic sensor 17 and the upper ultrasonic sensor 23 are responsible for transmitting and receiving high-frequency sound waves and completing the sound-to-electric conversion. The upper regulator 25 obtains the molten salt film thickness through the upper ultrasonic sensor 23, and the lower demodulator 18 obtains the molten salt film thickness through the lower ultrasonic sensor 17. The lower demodulator 18 and the upper regulator 25 extract effective signals from the high-frequency echoes and input them into the heating power monitoring module to determine the thickness of the lower or upper molten salt film, thereby calculating the heating power of a single layer respectively. The DCS system 21 includes a heating power monitoring module and an early warning module.

[0061] When the heating power monitoring module is working: it calculates and processes the real-time liquid film thickness data to obtain the heating resistance value at the corresponding liquid film thickness, and combines it with the voltage signal output by the voltage transmitter 15 to realize real-time monitoring and feedback of the upper or lower heating power; the upper or lower heating power can be adjusted independently, which can make the wall temperature more gradual along the flow direction and avoid local overheating or underheating, which is especially suitable for liquid film flow conditions.

[0062] When the early warning module is working: the DCS system 21 collects the power supply voltage signal of the heating device through the voltage transmitter 15 and the total current signal of the heating circuit through the current transmitter 16. The two analog signals are sent to the DCS system 21 for calculation and processing, and the total heating power of the entire heating device is monitored in real time, thereby providing comprehensive monitoring of the operating status of the heating system. By monitoring abnormal fluctuations or over-limit states of the total current, it can determine whether there are faults such as overall overload in the main heating circuit, providing a basis for the diagnosis of the overall operating status of the device and safety early warning.

[0063] Current loop and heating process: For any solid insulating tube 6 covered by a molten salt film, the molten salt film on its outside forms a resistor; the current starts from the three-phase AC power supply 9, passes through the electrode molten salt tank 3, flows through the entire molten salt film on the outside of the corresponding solid insulating tube 6, reaches the corresponding upper zero-potential molten salt tank 2 and lower zero-potential molten salt tank 27, and finally flows into the zero-potential grounding device 8, forming a complete loop; the current generates Joule heat when flowing through the molten salt, directly heating the molten salt film on the outside of the solid insulating tube 6.

[0064] When this invention is put into use, the equipment is first preheated with hot air, and then the molten salt pumps 1 at each inlet are started to inject cold molten salt. The cold molten salt flows sequentially through the upper zero-potential molten salt tank 2, the middle electrode molten salt tank 3, and the lower zero-potential molten salt tank 27. When the flow rates of the pumped-in and pumped-out molten salt are consistent, the liquid level in the molten salt tank is stable, and the liquid film thickness is uniform, the molten salt flow is considered stable. At this time, the power is turned on, and the heating power and molten salt temperature of the equipment are monitored in real time through the DCS control system 21. The heating output is adjusted according to the target operating conditions to ensure that the molten salt temperature and flow rate are stable within the target range, so as to achieve continuous and safe operation.

[0065] When it is necessary to adjust the heating power (upper layer heating power or lower layer heating power), there are two methods: adjusting the molten salt level and adjusting the number of heating channels.

[0066] When adjusting the molten salt level, the thickness of the liquid film is indirectly controlled by controlling the molten salt level, thereby adjusting the heating power. When the molten salt temperature is too high, the molten salt level in the upper zero-potential molten salt tank 2 or the middle electrode molten salt tank 3 is increased, and the liquid film thickness is reduced, thereby reducing the heating power. Conversely, when the molten salt temperature is too low, the molten salt level in the upper zero-potential molten salt tank 2 or the middle electrode molten salt tank 3 is decreased, and the liquid film thickness is increased, thereby increasing the heating power.

[0067] When the number of heating channels needs to be adjusted, the number of parallel heating channels is controlled by controlling the opening and closing of the single-tube intervention gate 4 to achieve heating load control. While maintaining a constant liquid level, the number of openings of the single-tube intervention gate 4 connected to the upper zero-potential molten salt tank 2 or the middle electrode molten salt tank 3 changes the number of molten salt liquid film channels in the liquid film forming device 300 (insulated solid round tube 6) participating in heating, thereby controlling the flow rate of the heated molten salt. The more single-tube intervention gate 4s are opened, the more molten salt liquid film channels in the liquid film forming device 300 participating in heating, and the greater the flow rate of the heated molten salt.

[0068] The adjustment logic for the molten salt level in the upper zero-potential molten salt tank 2 is as follows: increase or decrease the opening and closing degree of the inlet molten salt pump 1 until the liquid film thickness data output by the upper demodulator 25 reaches the requirement, and then the molten salt level is adjusted.

[0069] The adjustment logic for the molten salt level in electrode molten salt tank 3 is as follows: When the level needs to be lowered, the number of single-tube intervention gates 4 opened between the corresponding zero-potential molten salt tank below (upper zero-potential molten salt tank 2 or lower zero-potential molten salt tank 27) and electrode molten salt tank 3 is increased until the liquid film thickness data output by the lower demodulator 18 meets the requirements, at which point the molten salt level adjustment is complete; when the level needs to be raised, the number of single-tube intervention gates 4 closed between the corresponding zero-potential molten salt tank below (upper zero-potential molten salt tank 2 or lower zero-potential molten salt tank 27) and electrode molten salt tank 3 is increased until the liquid film thickness data output by the lower demodulator 18 meets the requirements, at which point the molten salt level adjustment is complete.

[0070] If it is necessary to adjust the molten salt level in both the upper zero potential molten salt tank 2 and the electrode molten salt tank 3 at the same time, adjust the molten salt level in the electrode molten salt tank 3 first.

Claims

1. A molten salt electric heating device with automatic power regulation based on external liquid film flow, characterized in that, include: Three inlet molten salt pumps (1), three outlet molten salt pumps (24), stainless steel electrodes (7), zero potential grounding device (8), three-phase AC power supply (9), heat insulation shell (100), single-tube intervention gate (4), liquid film forming device (300), three upper zero potential molten salt tanks (2), three electrode molten salt tanks (3) and three lower zero potential molten salt tanks (27), wherein the three inlet molten salt pumps (1) are respectively connected to one upper zero potential molten salt tank (2), each upper zero potential molten salt tank (2) is connected to one lower electrode molten salt tank (3) through at least two sets of liquid film forming devices (300) and single-tube intervention gate (4), each electrode molten salt tank (3) is connected to one lower lower zero potential molten salt tank (27) through at least one set of liquid film forming devices (300) and single-tube intervention gate (4), and each lower zero potential molten salt tank (27) is connected to one outlet molten salt pump (24); The upper zero-potential molten salt tank (2) and the lower zero-potential molten salt tank (27) are electrically connected to the zero-potential grounding device (8) through their respective stainless steel electrodes (7); each electrode molten salt tank (3) is electrically connected to the A phase, B phase and C phase of the three-phase AC power supply (9) through its respective stainless steel electrodes (7), and the connection between each electrode molten salt tank (3) is in parallel.

2. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 1, characterized in that, The single-tube intervention gate (4) is installed in the outlet pipeline between the liquid film forming device (300) and the outlet (5) below the molten salt tank. The single-tube intervention gate (4) includes: a gate body (400) and a gate plate (401). The gate body (400) is fixed to the outlet pipeline by flanges and bolts. The gate plate (401) is installed in the gate body (400). The opening and closing of the gate plate (401) is controlled by the valve plate drive system.

3. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 1, characterized in that, The liquid film forming device (300) includes: a liquid film outlet opening (310), a lower fixed conductive component (301), an upper fixed conductive component (302), and an insulating solid circular tube (6). The lowest end of the outlet pipe of the lower outlet (5) of the molten salt tank is the liquid film outlet opening (310). A concentric insulating solid circular tube (6) is provided at the liquid film outlet opening (310). The insulating solid circular tube (6) is fixed to the corresponding outlet pipe through the upper fixed conductive component (302), thereby forming a continuous molten salt liquid film on the outside of the insulating solid circular tube (6). The insulating solid circular tube (6) extends into the upper inlet (28) of the molten salt tank at the top of the lower molten salt tank. The insulating solid circular tube (6) is fixed to the lower molten salt tank through the lower fixed conductive component (301).

4. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 1, characterized in that, The upper fixed conductive component (302) is a strip structure arranged towards the axis of the insulating solid round tube (6), thereby forming the smallest possible projection in the horizontal direction so that the formed molten salt film is more continuous; the cross-sectional area of ​​the space between the upper inlet (28) of the molten salt tank and the insulating solid round tube (6) is not less than the cross-sectional area of ​​the lower outlet (5) of the molten salt tank; the lower fixed conductive component (301) and the upper fixed conductive component (302) are used for electrical connection between the insulating solid round tube (6) and the upper molten salt tank and the lower molten salt tank, respectively; The insulated solid round tube (6) is made of ceramic, quartz or glass.

5. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 1, characterized in that, Also includes: Measurement and control system; The measurement and control system includes: an inlet valve frequency converter (26), an ultrasonic flow meter (20), a lower ultrasonic sensor (17), a lower demodulator (18), an upper ultrasonic sensor (23), an upper regulator (25), a DCS system (21), an engineering station (22), a voltage transmitter (15), and a current transmitter (16); each inlet molten salt pump (1) is connected to an inlet valve frequency converter (26), and each outlet molten salt pump (24) and each inlet molten salt pump (1) are equipped with an independent ultrasonic flow meter (20) on the pipelines near them; the two stages of the three voltage transmitters (15) are respectively connected to the stainless steel electrode (7) of an upper zero potential molten salt tank (2) and the stainless steel electrode (7) of the corresponding electrode molten salt tank (3) through wires; the circuit between the stainless steel electrode (7) behind each electrode molten salt tank (3) and the three-phase AC power supply (9) is also included. A current transmitter (16) is installed on the top; a lower ultrasonic sensor (17) is installed on the side of at least one set of liquid film forming devices (300) between each upper zero potential molten salt tank (2) and the corresponding electrode molten salt tank (3); the lower ultrasonic sensor (17) is connected to the DCS system (21) through the lower demodulator (18); an upper ultrasonic sensor (23) is installed on the side of at least one set of liquid film forming devices (300) between each electrode molten salt tank (3) and the corresponding lower zero potential molten salt tank (27); the upper ultrasonic sensor (23) is connected to the DCS system (21) through the upper regulator (25); the valve plate drive system, voltage transmitter (15), current transmitter (16), inlet valve frequency converter (26) and ultrasonic flow meter (20) in the single-tube intervention gate (4) are all connected to the engineer station (22) through the DCS system (21).

6. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 5, characterized in that, The lower ultrasonic sensor (17) and the upper ultrasonic sensor (23) are responsible for transmitting and receiving high-frequency sound waves and completing the sound-to-electric conversion; the upper regulator (25) obtains the thickness of the molten salt film through the upper ultrasonic sensor (23), and the lower demodulator (18) obtains the thickness of the molten salt film through the lower ultrasonic sensor (17). The lower demodulator (18) and the upper regulator (25) extract effective signals from the high-frequency echo and input them into the heating power monitoring module to determine the thickness of the lower or upper molten salt film. The DCS system (21) includes: a heating power monitoring module, wherein when the heating power monitoring module is working: it calculates and processes the heating resistance value under the corresponding liquid film thickness based on the real-time liquid film thickness data, and combines the voltage signal output by the voltage transmitter (15) to realize real-time monitoring and feedback of the upper heating power or the lower heating power. When it is necessary to adjust the heating power of the upper or lower layer, there are two methods: adjusting the molten salt level and adjusting the number of heating channels. When adjusting the molten salt level, the thickness of the liquid film is controlled by controlling the molten salt level, thereby adjusting the heating power. When the molten salt temperature is too high, the molten salt level in the upper zero potential molten salt tank (2) or the middle electrode molten salt tank (3) is increased, the liquid film thickness is reduced, and the heating power is decreased. When the molten salt temperature is too low, the molten salt level in the upper zero potential molten salt tank (2) or the middle electrode molten salt tank (3) is decreased, the liquid film thickness is increased, and the heating power is increased. When the number of heating channels needs to be adjusted, the number of parallel heating channels is controlled by controlling the opening and closing of the single-tube intervention gate (4) to achieve heating load control; while maintaining the liquid level height, the number of openings of the single-tube intervention gate (4) connected to the upper zero potential molten salt tank (2) or the middle electrode molten salt tank (3) is controlled to change the number of molten salt liquid film channels of the liquid film forming device (300) participating in heating, thereby controlling the flow rate of the heated molten salt. The more single-tube intervention gates (4) are opened, the more molten salt liquid film channels of the liquid film forming device (300) participating in heating, and the greater the flow rate of the heated molten salt.

7. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 6, characterized in that, The adjustment logic for the molten salt level in the upper zero potential molten salt tank (2) is as follows: increase or decrease the opening and closing degree of the inlet molten salt pump (1) until the liquid film thickness data output by the upper demodulator (25) meets the requirements, and the molten salt level is adjusted. The adjustment logic for the molten salt level in the electrode molten salt tank (3) is as follows: When it is necessary to lower the level, the number of single-tube intervention gates (4) between the corresponding zero-potential molten salt tank and the electrode molten salt tank (3) is increased until the liquid film thickness data output by the lower demodulator (18) meets the requirements, and the molten salt level is adjusted; When it is necessary to raise the level, the number of single-tube intervention gates (4) between the corresponding zero-potential molten salt tank and the electrode molten salt tank (3) is increased until the liquid film thickness data output by the lower demodulator (18) meets the requirements, and the molten salt level is adjusted. If it is necessary to adjust the molten salt level in the upper zero potential molten salt tank and the electrode molten salt tank (3) at the same time, first adjust the molten salt level in the electrode molten salt tank (3).

8. The molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 5, characterized in that, The DCS system (21) also includes an early warning module. When the early warning module is working, the DCS system (21) collects the power supply voltage signal of the heating device through the voltage transmitter (15) and collects the total current signal of the heating circuit through the current transmitter (16). The two analog signals are sent to the DCS system (21) for calculation and processing, and the total heating power of the entire heating device is monitored in real time. By monitoring the abnormal fluctuation or over-limit status of the total current, it is determined whether there is an overall overload or other fault in the main heating circuit, and provides a basis for the diagnosis of the overall operating status of the device and safety early warning.

9. A molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 5, characterized in that, The DCS system (21) is connected to a K-type armored thermocouple (19). The K-type armored thermocouple (19) used to monitor the temperature of the molten salt is installed in the upper zero-potential molten salt tank (2), the electrode molten salt tank (3), and the lower zero-potential molten salt tank (27).

10. A molten salt electric heating device with automatic power adjustment based on external liquid film flow according to claim 1, characterized in that, The single-tube intervention gate (4), liquid film forming device (300), all upper zero potential molten salt tanks (2), all electrode molten salt tanks (3) and all lower zero potential molten salt tanks (27) are installed inside the heat-insulating shell (100); The heat insulation shell (100) includes: heat insulation bricks (11), heat insulation layer (12) and metal shell (13) arranged sequentially from the inside to the outside. The metal shell (13) is used to bear pressure, and the middle is the heat insulation layer (12). The heat insulation layer is used to maintain the temperature of the molten salt. The heat insulation bricks (11) are refractory bricks used to construct the high-temperature cavity. Vacuum jackets (14) are provided in the gaps between the tank bodies and pipes of the upper zero potential molten salt tank (2), the electrode molten salt tank (3), and the lower zero potential molten salt tank (27) to reduce heat loss.

Images