A molten salt heat storage device for a thermal power plant

Abstract

The application relates to the technical field of molten salt heat storage, and discloses a molten salt heat storage device for a thermal power plant, which comprises a tank body, a heating area and a heat storage area arranged in the tank body, a heating box arranged in the heating area and internally provided with a heating device, a heat storage box arranged in the heat storage area and internally provided with a stirring device, and a circulating device arranged in the interlayer between the heating box and the heat storage box and in communication with the heating box and the heat storage box at two ends. The heating box comprises a primary heating box in communication with a molten salt feeding port at the top and internally provided with a plurality of heating devices, and a secondary heating box arranged below the primary heating box and internally provided with a heating device at the bottom. After the temperature of the molten salt in the heat storage area is reduced, the molten salt can also flow into the heating area for heating, heat loss is reduced, the molten salt is prevented from being frozen and blocked in a solid state, and the overall heat balance of the molten salt is ensured during use.

Description

Technical Field

[0001] This invention belongs to the field of molten salt thermal storage technology, and particularly relates to a molten salt thermal storage device for thermal power plants. Background Technology

[0002] With the rapid development of the global new energy industry, wind power and solar power, which are highly random and intermittent, pose significant challenges to the normal operation and management of the power grid. Correspondingly, various energy storage and thermal storage technologies have gradually come into focus. Molten salt thermal storage technology uses raw materials such as nitrates as heat transfer media to store or release energy by converting the heat energy generated by new energy sources with the internal energy of molten salt. It is generally combined with solar thermal power generation systems to enable solar thermal power generation systems to have energy storage and nighttime power generation capabilities, meet the peak shaving needs of the power grid, and has strong economic advantages.

[0003] Molten salt thermal energy storage technology is an emerging energy storage technology that uses molten salt to store thermal energy for later use when needed. Molten salt thermal energy storage technology has many advantages: it can achieve long-term storage, generate electricity at night or during periods of low electricity prices, and does not require the use of consumable energy or cause pollution. The principle is to use molten salt as a storage medium to store thermal energy. When thermal energy is needed, the molten salt is heated to evaporate, and the steam is used to generate electricity, thus achieving energy conservation. It features no consumable energy use, no pollution, small-scale and low-cost investment, and is safe, reliable, and reusable, thereby reducing dependence on fossil fuels and promoting the development of clean energy.

[0004] Existing molten salt thermal storage devices are mostly multi-tank designs, with molten salt inside the storage tanks. However, the external temperature is relatively low. When the external overflow pipe exchanges heat with the external environment, the overflow pipe temperature drops, causing the molten salt to solidify. At the same time, the temperature of the molten salt at the bottom of the high-temperature molten salt tank gradually decreases from bottom to top. When using molten salt-water exchange, there is a problem of uneven temperature. The heat preservation capacity of molten salt thermal storage also needs to be improved.

[0005] To address the aforementioned problems, Chinese Patent CN115523782A discloses an overflow molten salt thermal storage device and an overflow molten salt thermal storage system. The overflow of molten salt circulates through overflow pipes in each storage tank, effectively preventing the molten salt from solidifying due to a drop in temperature at the bottom. This improves the operating efficiency and stability of the overflow molten salt thermal storage device. However, during the flow process, when the temperature drops to a certain level, the overflow pipes are prone to blockage, resulting in poor insulation, severe heat loss, and an inability to achieve thermal equilibrium.

[0006] Therefore, how to provide a device with good heat preservation, low heat loss, and uniform molten salt heat storage is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a technical solution that achieves good heat preservation, low heat loss, and uniform heat storage in molten salt.

[0008] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0009] In some embodiments of this application, a molten salt thermal storage device for a thermal power plant is provided, characterized in that it includes a tank, wherein the tank is provided with a heating zone and a thermal storage zone.

[0010] A heating chamber is located in the heating area, and a heating device is installed inside the heating chamber;

[0011] A heat storage box is located in the heat storage area, and a stirring device is installed inside the heat storage box;

[0012] A circulation device is disposed in the interlayer between the heating box and the heat storage box; and its two ends are respectively connected to the heating box and the heat storage box through pipes.

[0013] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the tank is provided with molten salt feeding, level gauge, gas inlet, gas outlet and molten salt outlet interfaces, which are sequentially located at the top of the tank.

[0014] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the heating box includes a primary heating box, the top of which is connected to the molten salt feeding port, and multiple heating devices are provided inside the primary heating box;

[0015] A secondary heating box is located below the primary heating box, and a heating device is provided at the bottom of the secondary heating box;

[0016] The base is connected to the primary heating box and the secondary heating box. The base has a hollow structure and an overflow hole. The heating device is fixedly connected to the base.

[0017] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the stirring device includes,

[0018] An electric motor is located inside the tank; a limiting plate is fixed to the side walls of both sides of the heat storage tank to limit the molten salt level.

[0019] The flow guide block, fixed on the stirring plate shaft, is used to guide the molten salt.

[0020] A stirring shaft, the top of which is connected to a motor; a first rotating disk, which is fixedly connected to the stirring shaft; a baffle, the bottom of which is fixedly connected to the stirring shaft and located at the lower end of the first rotating disk, the bottom of which forms a semi-enclosed structure with respect to the first rotating disk from bottom to top, and the bottom of which is provided with mesh holes; and stirring blades, which are located at the lower end of the baffle and fixedly connected to the bottom end of the stirring shaft.

[0021] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the circulation device includes a circulation pump, a circulation pipe, and a floating valve. The circulation pump is configured as two sets, with one end of each set connected to a thermal storage tank and a heating tank via a pipe, and the other end of each set connected to the two inlet ends of a valve. The outlet end of the floating valve is connected to the heating tank and the thermal storage tank, respectively, and each of the two outlet ends of the valve is equipped with an electromagnetic valve.

[0022] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the floating valve includes two inlet ends and one outlet end, the floating valve is provided with a floating slider inside, the floating slider is provided with limiting shafts at both ends, and the floating slider is located in the limiting groove, the limiting shaft is a hollow structure, and the limiting shaft is a mesh structure.

[0023] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the amount of molten salt M in the tank is... x for:

[0024]

[0025] In the formula, Q c For the heating device's heat load, KW; C pc ΔT is the specific heat capacity of molten salt, in kJ / (kg·k); c The working temperature difference of the molten salt is K; the thermal efficiency of the heating box and the heat storage box is:

[0026]

[0027] In the formula, μ is the total thermal efficiency, t1 and t2 are the heating process, t3 and t4 are the start and end times of the thermal storage process, and Qb1 is the heat load of the thermal storage process at time t.

[0028] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the inner wall of the thermal storage box is provided with a baffle plate; the number of heating devices in the secondary heating box is greater than the number of heating devices in the primary heating box.

[0029] Preferably, in the preferred embodiment of the molten salt thermal storage device for thermal power plants described above, the inner wall of the thermal storage tank is provided with a heat insulation layer; the top of the tank is provided with a molten salt feeding port, a level gauge, a gas inlet, a gas outlet, and a molten salt outlet interface in sequence.

[0030] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] By simultaneously setting up a heating zone and a heat storage zone within a single tank, the molten salt inside can flow directly from the heating zone into the heat storage zone. The temperature of the molten salt is kept constant by a stirring device. At the same time, the molten salt in the heat storage zone will also flow into the heating zone for heating after its temperature drops, reducing heat loss and preventing it from becoming solid. This also ensures overall thermal balance of the molten salt during use. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 This is a schematic cross-sectional view of the tank body of the present invention;

[0034] Figure 2 This is a schematic cross-sectional view of the floating valve of the present invention;

[0035] Figure 3 This is a schematic diagram of the bottom structure of the baffle of the present invention.

[0036] In the picture:

[0037] 1. Tank body; 2. Primary heating box; 3. Heat storage box; 4. Circulation device; 5. Secondary heating box; 21. Heating device; 23. Base; 22. Overflow hole; 3. Motor; 32. Stirring shaft; 33. First rotating disc; 34. Baffle; 341. Mesh; 35. Stirring blade; 36. Guide plate; 37. Limiting plate; 38. Guide block; 41. Circulation pump; 42. Circulation pipe; 43. Floating valve; 433. Floating slider; 434. Limiting shaft; 435. Limiting groove. Detailed Implementation

[0038] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] In the description of this application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0041] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0042] See Figure 1-3 As shown, according to some embodiments of this application, the feature is that it includes,

[0043] Tank 1, the tank body is provided with a heating area and a heat storage area.

[0044] A heating chamber is located in the heating area, and a heating device is installed inside the heating chamber;

[0045] A heat storage box 3 is located in the heat storage area, and a stirring device is provided inside the heat storage box;

[0046] The circulation device 4 is located in the interlayer between the heating box 2 and the heat storage box 3, and its two ends are respectively connected to the heating box 2 and the heat storage box 3 through pipes.

[0047] The technical effect achieved by this application through the above technical solution is that, since most multi-tank structures are designed, molten salt loses heat and solidifies during external transport. Therefore, the heating tank and the heat storage tank are combined into a single tank. The heating tank is equipped with a heating device. Solid molten salt enters the heating tank through the molten salt interface for heating. Then, a circulation device located in the interlayer between the heating tank and the heat storage tank transfers the molten salt in the heating tank to the heat storage tank for insulation. This eliminates the need for external transport, better insulates the molten salt, and greatly reduces heat loss.

[0048] See Figure 1-3 In a preferred embodiment of this application, the tank is provided with molten salt feeding, level gauge, gas inlet, gas outlet and molten salt outlet interfaces, which are sequentially located at the top of the tank.

[0049] The technical effect achieved by the above technical solution is as follows: the top of the tank is provided with molten salt feeding, level gauge, gas inlet, gas outlet and molten salt outlet interfaces in sequence. Molten salt heating is used to feed molten salt material into the tank from the outside. The level gauge is used to sense the volume of the added material. The gas inlet and gas outlet are used to discharge the gas generated during molten salt heating, maintain the internal pressure value and prevent damage to the tank.

[0050] See Figure 1 As shown, through the above technical solution, the heating box includes,

[0051] A primary heating chamber, the top of which is connected to the molten salt feeding port, and is equipped with multiple heating devices 21 inside;

[0052] A secondary heating box is located below the primary heating box, and a heating device is provided at the bottom of the secondary heating box;

[0053] The base 23 is connected to the primary heating box and the secondary heating box. The base is hollow and has an overflow hole 22. The heating device 21 is fixedly connected to the base.

[0054] The technical effect achieved by the above technical solution is that a primary heating box and a secondary heating box are provided in the heating box to heat the molten salt respectively. After the electric heating device inside the primary heating box preheats the bottom of the molten salt, the molten salt will flow into the secondary heating box through the overflow hole provided in the base. The secondary heating device continues to heat the molten salt. The heating device is a resistance wire heating method, and the outer layer of the resistance wire is provided with a protective cover.

[0055] In a preferred embodiment of this application, the stirring device includes,

[0056] Motor 31, the motor is disposed inside the tank;

[0057] Stirring shaft 32, one end of which is connected to a motor;

[0058] Limiting plates 37 are fixed to the side walls of both sides of the heat storage tank 3 and are used to limit the level of molten salt.

[0059] The flow guide block 38 is fixed on the stirring plate shaft 32 and is used to guide the molten salt.

[0060] The first rotating disk 33 is fixedly connected to the stirring shaft;

[0061] Baffle 34, the bottom of which is fixedly connected to the stirring shaft and located at the lower end of the first rotating disk, the baffle has a semi-enclosed structure from bottom to top of the first rotating disk, and the bottom of the baffle is provided with mesh holes; stirring blade 35, the stirring blade is located at the lower end of the baffle and is fixedly connected to the other end of the stirring shaft, and a guide plate 36 is provided between the stirring blade and the bottom of the baffle.

[0062] See appendix Figure 1As shown, due to the tendency for thermal stratification to occur within the molten salt storage device, the molten salt temperature exhibits a pattern of higher temperatures at the top and lower temperatures at the bottom. Therefore, it is necessary to activate the stirring device to disrupt this thermal stratification and maintain a balanced internal temperature. When the molten salt in the storage tank reaches or exceeds the height of the baffle, the motor drives the stirring shaft to rotate, which in turn drives the first rotating disk to rotate. Since the baffle is located at the lower end of the first rotating disk, and the bottom of the first rotating disk is fixedly connected to the stirring shaft, the baffle has a semi-enclosed structure from bottom to top, with only an opening at the top. Furthermore, the bottom of the baffle has mesh holes. When the stirring shaft rotates, it drives the first rotating disk to rotate, simultaneously melting the molten salt. The molten salt flows in a circular motion within the space above the first rotating disk. Some of the molten salt flows into the space below the first rotating disk through the gap between the first rotating disk and the baffle. Under the action of the first rotating disk, it flows in a circular motion. Some of the molten salt flows into the bottom through the mesh at the bottom of the baffle and moves to both sides through the guide plate 36. The guide plate distributes the molten salt to both sides. At the same time, the rotation of the stirring blades generates an outward force, which drives the molten salt outward and causes it to reciprocate, stirring the molten salt and preventing it from standing still. This effectively achieves uniform temperature of the molten salt from top to bottom, thus effectively preventing the molten salt in a static state from having a low temperature at the bottom and solidifying. Specifically, an arc-shaped baffle is installed at the top of the heat storage device to limit the liquid level and provide a certain passage for the solution. When a certain height is reached, the level gauge will sense it, the circulation pump will stop operating, and heat storage will begin. When the first rotating disk rotates, the internal circular motion generates an outward force, and some of the solution will flow into the area below the first rotating disk. The outward force of the circular motion will then drive some of the liquid through the mesh of the baffle to the area below the baffle. At the same time, the rotation of the stirring blades forces the solution to diffuse to both sides. At this time, the pressure outside the baffle is greater than the pressure inside, so the liquid outside the baffle will flow into the baffle, thus realizing a reciprocating circulation process. This internal circulation breaks the phenomenon of thermal stratification. Furthermore, through the circulation device, when the overall temperature decreases, self-heating can be achieved, thereby ensuring the utilization rate of electrical energy.

[0063] The achieved technical effect is that, because the flow field is constantly changing over time during the heat release process, at the beginning of the heat release process, the molten salt flows into the tank from the inlet with a relatively low overall velocity, and the flow field tends to be stable, with no vortices generated at the heating rod. As the heat release process continues, the velocity of the molten salt inside the tank gradually increases, and under the influence of the heating device and the side walls of the tank, vortices are formed, causing the flow field to become turbulent. The molten salt field at the bottom of the tank remains unchanged and flows smoothly, spreading outwards along the bottom of the tank, with the velocity continuously decreasing, generating vortices when it encounters the side walls of the tank. Under the influence of the stirring device, it circulates, maintaining the internal heat at a uniform temperature.

[0064] In a preferred embodiment of this application, the circulation device 4 includes a circulation pump 41, a circulation pipe 42, and a floating valve 43. Two sets of circulation pumps are configured, with one end of each set connected to a heat storage tank and a heating tank via a pipe, and the other end connected to the two inlet ends of a valve. The outlet end of the floating valve is connected to both the heating tank and the heat storage tank. Each outlet end of the valve is equipped with an electromagnetic valve. A sensing device is installed within the circulation pipe. When molten salt needs to be transported from the heating tank to the heat storage tank, the circulation pump is activated. Simultaneously, the molten salt in the heating tank flows through the pipe and the floating valve. At the same time, an electric valve above the heat storage tank senses the molten salt coming from the pipe within the heat storage tank and opens, completing the transport from the heating area to the heat storage area. Similarly, when molten salt needs to be transported from the heat storage tank to the heating tank, the circulation pump is activated, and the electric valve above the heating tank opens, completing the transport of molten salt from the heat storage tank to the heating tank. The electric valve, circulation pump, and sensing device are electrically connected.

[0065] In a preferred embodiment of this application, the floating valve 43 includes two inlet ends 431 and one outlet end 432. The floating valve is provided with a floating slider 433 inside. The floating slider is provided with limiting shafts 434 at both ends, and the floating slider is located in a limiting groove 435. The limiting shaft 434 is a hollow structure and is designed with a mesh structure.

[0066] The achieved technical effect is as follows: The inlet end of the floating valve is connected to two pipes. When molten salt circulates from the heating zone to the heat storage zone in one of the pipes, the floating slider inside the floating valve is forced to float to one side. Simultaneously, the engagement of the limiting groove and the limiting shaft blocks the passage on one side, forcing the molten salt to flow along the pipe to the upper end of the heat storage zone. The outlet pipes of the heating zone and the heat storage zone are located at the top to better agitate the molten salt and prevent it from becoming stagnant, thus preventing cooling blockage. The molten salt in the heat storage zone flows from top to bottom, which agitates it. When the molten salt reaches the height of the baffle, the injection stops. At the same time, the stirring device agitates the molten salt periodically, creating a flow vortex inside. When needed, steam is generated through the heat-water exchanger, effectively achieving a thermal equilibrium effect.

[0067] In a preferred embodiment of this application, the inner wall of the heat storage tank is provided with a heat insulation layer; the number of heating devices in the secondary heating tank is greater than the number of heating devices in the primary heating tank; and the top of the tank is provided with molten salt feeding, a level gauge, a gas inlet, a gas outlet, and a molten salt outlet interface in sequence.

[0068] With the future exponential increase in wind and solar power generation, storing this electricity is crucial for a successful transition. The heating device heats molten salt into a liquid, which then flows through a floating valve 43 via an inlet on one side of the circulation device, into the thermal storage unit. Simultaneously, electric valves are installed at both outlets of the circulation pipe. When the internal floating valve moves, the electric valves sense this movement and simultaneously open or close one of the outlet pipe's electric valves, ensuring that the flow is directed into only one pipe. Once the heating device heats the molten salt to a certain temperature, the circulation pump propels the molten salt through the pipes into the thermal storage unit. Conversely, when the temperature inside the thermal storage unit drops to a certain level, the circulation device also allows the molten salt to flow into the heating zone through the floating valve; this reciprocating motion continuously maintains the molten salt temperature. The top of the tank is equipped with a molten salt feeding port, a level gauge, a gas inlet, a gas outlet, and a molten salt outlet. After heat exchange with the outside environment, the molten salt circulates back to the heating zone of the tank from the molten salt feeding port. The gas outlet and gas inlet ensure that the pressure inside the tank remains balanced. The inner wall of the heat storage tank is equipped with an insulation layer, and the outer side of the tank is equipped with a vacuum layer. The vacuum layer on the outer side of the tank better preserves the internal heat storage. Molten salt thermal storage technology mainly utilizes the melting point of ordinary salts. When the temperature rises, the salt changes from a solid to a liquid state, generating a large amount of heat, which is stored in the liquid molten salt. When the temperature drops, the molten salt changes from a liquid to a solid state, releasing a large amount of heat. This heat can be used for thermal power generation in power plants or for hot water supply. Because the length of the electric heater is limited by the diameter of the molten salt storage tank, and to prevent molten salt leakage when replacing the electric heater, a sleeve structure is used. The electric heating rod does not directly contact the molten salt, preventing the wall temperature of the electric heating rod from becoming too high. The heating device is evenly distributed on the base to ensure uniform heating and complete melting of the molten salt inside the tank. Since commonly used thermal storage materials for molten salt include binary mixed nitrates and ternary mixed nitrates, which are corrosive, and the commonly used materials for molten salt storage tanks are Q345R and 346L, according to GB... According to 150.2-2011, the allowable working stresses at a working temperature of 450℃ are 66MPa and 84MPa, respectively. 316L material has a high Mo content, which gives it good corrosion resistance, high temperature resistance and weldability. In order to reduce the effects of σ phase embrittlement and creep on the storage tank under long-term high temperature environment, low carbon austenitic stainless steel 316L (022Cr17Ni12Mo2) was selected as the material.

[0069] Preferably, the amount of molten salt M in the tank 1 x for:

[0070]

[0071] In the formula, Q c For the heating device's heat load, KW; C pcΔT is the specific heat capacity of molten salt, in kJ / (kg·k); c The working temperature difference of the molten salt is K; the thermal efficiency of the heating box and the heat storage box is:

[0072]

[0073] In the formula, μ is the overall thermal efficiency, t1 and t2 are the heating processes, t3 and t4 are the start and end times of the thermal storage process, and Qb1 is the heat load of the thermal storage process at time t.

[0074] When the thermal power unit has peak load demand, it is preheated through the primary heating zone of the molten salt thermal storage device by an electric heater, and at the same time, part of it flows into the secondary heating device for complete heating. When the internal temperature reaches a certain level and after a period of time, the molten salt flows into the thermal storage device for storage through a circulation pump. When in use, the molten salt in the storage tank enters the steam-water heat exchanger through a high-temperature molten salt pump, and heats the water in the steam-water heat exchanger to a steam state, thereby realizing industrial steam supply. At the same time, the cooled molten salt is circulated through the external circulation device to be heated in the heating zone of the molten salt thermal storage device.

[0075] When exchanging steam with the outside environment, the molten salt thermal storage cycle involves electrically heating the molten salt in a molten salt thermal storage device and then transferring the heated molten salt to a storage area via a circulating pump, completing the thermal storage cycle. The molten salt exothermic cycle involves the high-temperature molten salt in the hot salt tank entering the heat exchange system via a molten salt pump to exchange heat with the feedwater. The feedwater is heated into steam, and the exothermic molten salt enters the heating zone within the thermal storage device for further heating, completing the molten salt exothermic cycle. Finally, the steam-water heat exchange cycle involves the steam generated after the feedwater is heated exothermically and then exchanged with the circulating water in the power plant area. Water is used for heat exchange, and the condensate after steam heat exchange is treated and returned to the molten salt exothermic cycle for continued use. The circulating water after heat exchange is used in the power plant pipeline to complete the steam-water heat exchange cycle, which can alleviate the phenomenon of power wastage to a certain extent. Since the melting point of molten salt is 142℃, molten salt will inevitably solidify at room temperature. In order to prevent the molten salt from freezing and blocking, when the temperature of molten salt is lower than 286℃ of the wall surface, it is returned from the heat storage device to the heating zone through the circulation device for continued heating, which effectively ensures that the molten salt will not freeze and block.

[0076] Furthermore, due to the reflux of molten salt in the single-tube tank, the temperature inside the molten salt vessel gradually decreases, which increases the power of the electric heating. Because of the temperature gradient layer inside the molten salt tank, a stirring device ensures temperature uniformity. Since single-tank thermal storage offers advantages such as flexible layout, small footprint, and low cost, the electric heater can be concentrated on a single tank, or a combination of top-mounted and side-wall mounted arrangements can be used. The temperature sensor, electric valve, and level gauge are all electrically connected to an external control terminal.

[0077] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A molten salt thermal storage device for a thermal power plant, characterized in that, include, Tank (1), wherein the tank (1) is provided with a heating area and a heat storage area; A heating chamber is located in the heating area, and a heating device is installed inside the heating chamber; A heat storage box (3) is located in the heat storage area, and a stirring device is provided inside the heat storage box; The circulation device (4) is located in the interlayer between the heating box and the heat storage box; and its two ends are respectively connected to the heating box and the heat storage box through pipes. The heating box includes, A primary heating box (2) is provided with a molten salt feeding port at the top and the heating device (21) is provided inside; A secondary heating box (5) is located below the primary heating box (2), and the heating device (21) is provided at the bottom of the secondary heating box (5). The base (23) is hollow and has an overflow hole (22). The two ends of the base are connected to the primary heating box (2) and the secondary heating box (5). The heating device (21) is fixedly connected to the base (23). The stirring device includes, Motor (31), the motor is located inside the tank (1); A stirring shaft (32), the top of which is connected to the motor; Limiting plates (37) are fixed to the side walls of both sides of the heat storage tank (3) to limit the level of molten salt. The flow guide block (38) is fixed on the stirring plate shaft (32) and is used to guide the molten salt. The first rotating disk (33) is fixedly connected to the stirring shaft (32); Baffle (34), the bottom of the baffle (34) is fixedly connected to the stirring shaft (33) and located at the lower end of the first rotating disk (33). The bottom of the baffle (34) forms a semi-enclosed structure with respect to the first rotating disk (33) from bottom to top. The bottom of the baffle (34) is provided with mesh (341). A stirring blade (35) is provided at the lower end of the baffle (34) and is fixedly connected to the bottom end of the stirring shaft (33). A guide plate (36) is provided between the stirring blade (35) and the bottom of the baffle (34). The circulation device (4) includes a circulation pump (41), a circulation pipe (42), and a floating valve (43). The circulation pump (41) is configured as two sets. One end of each set of circulation pumps (41) is connected to the heat storage tank (3) and the heating tank (2) through a pipe. The other end of each set of circulation pumps (42) is connected to the two inlet ends of the floating valve (43). The outlet end of the floating valve (43) is connected to the heating tank (2) and the heat storage tank (3) respectively. The two outlet ends of the circulation pipe (42) are respectively equipped with electromagnetic valves. The floating valve (43) includes two inlet ends and one outlet end. The floating valve (43) is provided with a floating slider (433) inside. The floating slider (433) is provided with limiting shafts (434) at both ends. The floating slider (433) is located in the limiting groove. The limiting shaft (434) is a hollow structure and is designed with a mesh structure.

2. The molten salt thermal storage device for a thermal power plant according to claim 1, characterized in that, The number of heating devices in the secondary heating box (5) is greater than the number of heating devices in the primary heating box (2).

3. The molten salt thermal storage device for a thermal power plant according to claim 1, characterized in that, The inner wall of the heat storage box (3) is provided with a heat insulation layer, and the outer side of the tank (1) is provided with a vacuum layer.

4. A molten salt thermal storage device for a thermal power plant according to claim 1, characterized in that, The top of the tank (1) is provided with interface pipes for molten salt feeding, level gauge, gas inlet, gas outlet and molten salt outlet in sequence.

5. A molten salt thermal storage device for a thermal power plant according to claim 1, characterized in that, The amount of molten salt M in the tank (1) x for: In the formula, Q c For the heating device's heat load, KW; C pc ΔT is the specific heat capacity of molten salt, in kJ / (kg·k); c The working temperature difference of the molten salt is K; The thermal efficiency of the heating box and the heat storage box is: In the formula, μ is the overall thermal efficiency, t1 and t2 are the heating processes, t3 and t4 are the start and end times of the thermal storage process, and Qb1 is the heat load of the thermal storage process at time t.

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