Molten salt preheating and steam generation integrated heat storage tank and steam generation method thereof

Abstract

The invention provides a fused salt preheating and steam generating integrated heat storage tank which comprises a tank body, a high-temperature fused salt collecting and distributing area, a steam generating area, a packed bed heat storage area, a fused salt collecting and distributing area, an incoming water preheating area and a low-temperature fused salt collecting and distributing area are sequentially arranged in the tank body from top to bottom, and all the areas are sequentially communicated through perforated partition plates. A fused salt inlet and a fused salt outlet are formed in the tank body, the fused salt inlet is communicated with the high-temperature fused salt collecting and distributing area, and the fused salt outlet is communicated with the low-temperature fused salt collecting and distributing area; a coiled pipe surrounds the outer wall of the tank body, and the incoming water preheating area is communicated with the steam generation area through the coiled pipe; a steam pocket is arranged on the outer side of the tank body and communicated with the steam generation area. The invention further provides a steam generation method. The technical problems that an existing fused salt heat storage system is dispersed in equipment, large in heat loss, concentrated in heat stress, difficult to control, high in maintenance cost, complex in structure and large in occupied area are solved. Belongs to the technical field of fused salt heat storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt thermal energy storage, and particularly relates to a molten salt preheating and steam generation integrated heat storage tank and a steam generation method thereof. Background Art

[0002] As an efficient and reliable thermal energy storage method, molten salt thermal energy storage technology has been widely applied in the fields of solar thermal power generation CSP, industrial waste heat recovery, flexible peak shaving of thermal power units, and multi-energy complementarity.

[0003] A typical molten salt thermal energy storage system adopts a "double-tank" design, storing high-temperature molten salt and low-temperature molten salt respectively, and realizing the storage and release of energy with the help of heat exchangers and pumps. This structure is mature and stable, suitable for large-scale heat storage and 24-hour uninterrupted heating. However, its system composition is complex, including multiple large storage tanks, molten salt pumps and preheating units, not only with high initial investment, but also with large operation and maintenance costs. In addition, the traditional double-tank system has problems such as large floor area, long equipment installation cycle, and large system heat loss, which limit its popularization in distributed and space-limited application scenarios.

[0004] To reduce system complexity, single-tank molten salt thermal energy storage systems have become a research hotspot. A common form is a packed bed type single-tank system, which exchanges heat through the direct contact between the particle bed heat storage medium (such as ceramic balls, metal balls, phase change materials, etc.) and molten salt, and realizes temperature stratification and cascade release in the tank. However, under continuous operation conditions, the problem of internal thermal stress concentration in this system is relatively prominent, and the tank wall structure in the temperature gradient area is prone to deformation, with a potential risk of molten salt leakage. In addition, some single-tank systems need to be started and stopped frequently to complete the upper and lower layer heat exchange cycle, and it is difficult to achieve stable and continuous heating required by industrial processes.

[0005] In terms of system integration, the preheater and steam generator in traditional molten salt thermal energy storage systems are mostly designed in a split form and are thermally connected through long pipelines. This structure results in a long heat transfer path, large heat loss during the process, and low thermal efficiency. At the same time, the uneven arrangement of heat exchange elements and the asymmetric fluid flow are likely to form temperature difference concentration and flow dead zones in local areas, leading to problems such as material fatigue, deposition and scaling, and attenuation of heat exchange efficiency.

[0006] In terms of structural design, many current systems have deficiencies in stress distribution, thermal shock absorption, and maintenance convenience. Once phenomena such as lining cracks and scaling blockages in the diversion pipelines occur in the heat storage device, it often requires long-term shutdown for maintenance, seriously affecting the process continuity.

[0007] Therefore, how to further break through technical bottlenecks such as complex structure, large floor area, low heat exchange efficiency, thermal stress concentration, and difficult thermal management, and develop an integrated, modular, economical and efficient molten salt thermal energy storage device has become an important development direction and practical requirement in the current technical field. Summary of the Invention

[0008] The object of the present invention is to provide an integrated heat storage tank for molten salt preheating and steam generation and a steam generation method thereof, aiming to solve the technical problems existing in the existing molten salt heat storage system, such as scattered equipment, large heat loss, heat stress concentration, difficult control, high maintenance cost, complex structure and large floor area.

[0009] To achieve the above object, the technical solution adopted by the present invention is: to provide an integrated heat storage tank for molten salt preheating and steam generation, including a tank body. Inside the tank body, a high-temperature molten salt distribution area, a steam generation area, a packed bed heat storage area, a molten salt distribution area, a feed water preheating area and a low-temperature molten salt distribution area are sequentially arranged from top to bottom, and each area is sequentially connected through an opening partition; a molten salt inlet and a molten salt outlet are provided on the tank body, the molten salt inlet is communicated with the high-temperature molten salt distribution area, and the molten salt outlet is communicated with the low-temperature molten salt distribution area; a serpentine tube is wound around the outer wall of the tank body, and the feed water preheating area and the steam generation area are communicated through the serpentine tube; a steam drum is provided outside the tank body, and the steam drum is communicated with the steam generation area.

[0010] In one embodiment, a first opening partition, a second opening partition, a third opening partition, a fourth opening partition and a fifth opening partition are sequentially arranged in the tank body from top to bottom. The first opening partition is located between the high-temperature molten salt distribution area and the steam generation area, the second opening partition is located between the steam generation area and the packed bed heat storage area, the third opening partition is located between the packed bed heat storage area and the molten salt distribution area, the fourth opening partition is located between the molten salt distribution area and the feed water preheating area, and the fifth opening partition is located between the feed water preheating area and the low-temperature molten salt distribution area.

[0011] In one embodiment, a molten salt spreader is provided in the high-temperature molten salt distribution area. The top end of the molten salt spreader is communicated with the molten salt inlet, and the bottom end of the molten salt spreader is communicated with the steam generation area through the first opening partition.

[0012] In one embodiment, a plurality of heat exchange tubes are evenly distributed in a circumferential manner in the steam generation area. The heat exchange tubes are arranged between the first opening partition and the second opening partition, and the heat exchange tubes are respectively communicated with the high-temperature molten salt distribution area and the packed bed heat storage area through the first opening partition and the second opening partition.

[0013] In one embodiment, a steam pipe is provided in the tank body. The inlet end of the steam pipe is communicated with the steam generation area, the outlet end of the steam pipe penetrates through the tank body and extends to the outside of the tank body, and the outlet end of the steam pipe is communicated with the steam drum.

[0014] In one embodiment, large-diameter heat storage balls, medium-diameter heat storage balls, and small-diameter heat storage balls are sequentially filled in the packed bed heat storage area from top to bottom. Phase change materials are filled in the large-diameter heat storage balls, the medium-diameter heat storage balls, and the small-diameter heat storage balls. Electric heating wires are wound around the inner wall of the tank body, and the electric heating wires are wound outside the large-diameter heat storage balls, the medium-diameter heat storage balls, and the small-diameter heat storage balls.

[0015] In one embodiment, a top uniform flow distributor is provided at the top of the packed bed heat storage area, and a bottom uniform flow distributor is provided at the bottom of the packed bed heat storage area. The packed bed heat storage area is communicated with the steam generation area and the molten salt collection and distribution area through the top uniform flow distributor and the bottom uniform flow distributor respectively.

[0016] In one embodiment, a plurality of columns evenly distributed in a circumferential direction are provided on the outer wall of the tank body. A baffle is provided between the columns and the incoming water preheating area. A plurality of groups of V-shaped heat exchange tubes are provided in the incoming water preheating area. Both ends of each group of V-shaped heat exchange tubes penetrate through the baffle and extend into adjacent two columns.

[0017] In one embodiment, a vertical partition is provided in any one of the columns. The vertical partition divides the column into a non-communicating first cavity and second cavity, and the V-shaped heat exchange tubes located in the first cavity and the second cavity are of different groups. A water inlet is communicated with the first cavity, a hot water outlet is communicated with the second cavity, a hot water inlet communicating with the steam generation area is provided on the side wall of the tank body, and the hot water outlet and the hot water inlet are communicated through the serpentine tube.

[0018] The present invention also provides a steam generation method, which uses the molten salt preheating and steam generation integrated heat storage tank described in any one of the above. The steam generation method includes the following steps: S1: Open the molten salt inlet, molten salt outlet, incoming water inlet, and steam drum. High-temperature molten salt enters the molten salt flow diffuser in the high-temperature molten salt collection and distribution area from the molten salt inlet, and then enters the heat exchange tubes in the steam generation area, and exchanges heat with the preheated incoming water in the steam generation area. The water absorbs heat and vaporizes into saturated steam, and enters the steam drum through the steam pipe. The high-temperature molten salt is cooled after absorbing heat. S2: The cooled molten salt enters the packed bed heat storage area, and exchanges heat with the large-diameter heat storage balls, medium-diameter heat storage balls, and small-diameter heat storage balls from top to bottom respectively. The molten salt is cooled again and enters the molten salt collection and distribution area. S3: The molten salt after re-cooling enters the incoming water preheating zone. Meanwhile, the incoming water is introduced into the V-shaped heat exchange tubes from the incoming water inlet. The molten salt after re-cooling exchanges heat with the incoming water, and the incoming water is heated and preheated. The preheated incoming water flows into the hot water inlet through the hot water outlet via the serpentine tube and enters the steam generation zone, where it exchanges heat with the high-temperature molten salt in the heat exchange tubes; the molten salt is cooled for the third time and enters the low-temperature molten salt collection and distribution zone, and finally flows out of the tank body through the molten salt outlet.

[0019] The present invention provides a molten salt preheating and steam generation integrated heat storage tank and its steam generation method. Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention integrates the incoming water preheating zone, the steam generation zone, the packed bed heat storage zone, the high-temperature molten salt collection and distribution zone, the molten salt collection and distribution zone, and the low-temperature molten salt collection and distribution zone in the same tank body structure to form a functionally integrated heat storage device, realizing efficient collaborative heat exchange and energy cascade utilization of multiple heat sources and multiple fluids in a single device, breaking the design inertia of the traditional heat storage system of "scattered functional modules and independent equipment units", achieving a highly integrated compact system configuration, and improving the thermal energy management efficiency and structural economy.

[0020] (2) The present invention constitutes a two-stage series countercurrent heat exchange system with the incoming water preheating zone and the steam generation zone, and with the heat storage buffer of the packed bed heat storage zone, the three work together to form a distributed gradient thermal management structure, which not only reduces the heat exchange area required for water-vapor conversion and the molten salt flow rate requirement, but also suppresses the concentration of thermal stress through sectional temperature difference control, improving the thermal stability of the system and the steam production efficiency.

[0021] (3) The present invention designs the top high-temperature molten salt collection and distribution zone, the middle molten salt collection and distribution zone, and the bottom low-temperature molten salt collection and distribution zone to form a complete three-stage molten salt flow organizational structure, ensuring that the molten salt flows evenly in different temperature zones, the temperature decreases layer by layer, avoiding scaling and heat exchange dead angles, effectively overcoming the problem of uneven flow distribution in the traditional packed bed or series tank system, and improving the dynamic stability and heat exchange efficiency of the system operation.

[0022] (4) The present invention uniquely constructs a three-layer axially arranged heat storage ball packed bed structure. Each layer of heat storage balls is filled with phase change materials with different phase change temperatures, which corresponds one by one to the temperature zones along the path of the incoming water from preheating to vaporization. Through the hierarchical configuration of the temperature gradient, a reasonably distributed heat exchange interface between the molten salt and the solid heat storage body is formed, realizing the hierarchical release of energy and the short-term buffer energy storage function, and effectively controlling the thermal inertia and thermal stress concentration of the system.

[0023] (5) The present invention adopts a segmented structure layout and a flow field disturbance enhancement design of a self-designed V-shaped heat exchange tube flow channel structure, combined with a countercurrent operation mode and temperature difference gradient control, to achieve the slow release and dispersion of thermal stress in the vertical and radial directions. Combined with a three-layer temperature difference structure, the problem of transient temperature difference impact at the high-temperature heat exchange interface between the water side and the molten salt side is alleviated; in terms of structure, a buffer structure is adopted at the key interface to avoid local material fatigue and thermal stress concentration caused by the large temperature difference between the molten salt and the heat exchange wall surface in the traditional single-tank system, effectively ensuring the long-term stability and material safety of the system in a high-temperature operating environment.

[0024] The present invention provides an integrated molten salt preheating and steam generation storage tank with a compact structure, high heat exchange efficiency, and high degree of integration. Through the efficient heat exchange between high-temperature molten salt and the medium, it realizes the cascade storage and release of energy, solves the technical problems of the existing molten salt energy storage system, such as scattered equipment, large heat loss, thermal stress concentration, difficult control, high maintenance cost, complex structure, and large floor area, and has high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram of an integrated molten salt preheating and steam generation storage tank provided by an embodiment of the present application; Figure 2 For Figure 1 The main view sectional structural diagram of the integrated molten salt preheating and steam generation storage tank shown; Figure 3 For Figure 1 The top view structural diagram of the first opening partition in the integrated molten salt preheating and steam generation storage tank shown; Figure 4 For Figure 1 The top view sectional structural diagram of the incoming water preheating area in the integrated molten salt preheating and steam generation storage tank shown; Figure 5 For Figure 1 The main view sectional structural diagram of the packed bed heat storage area in the integrated molten salt preheating and steam generation storage tank shown.

[0027] Symbol description in the figure: 1. Tank body; 2. Molten salt inlet; 3. Steam drum; 4. Coiled tube; 5. Molten salt spreader; 6. High-temperature molten salt distribution area; 7. First perforated partition; 8. Steam generation area; 9. Second perforated partition; 10. Heat exchange tube; 11. Support column; 12. Third perforated partition; 13. Packed bed heat storage area; 14. Molten salt distribution area; 15. Fourth perforated partition; 16. Vertical partition; 17. V-shaped heat exchange tube; 18. Feed water preheating area; 19. Low-temperature molten salt distribution area; 20. Baffle; 21. Fifth perforated partition; 22. Molten salt outlet; 23. Feed water inlet; 24. Downcomer; 25. Downflow port; 26. Top uniform flow distributor; 27. Electric heating wire; 28. Large-diameter heat storage balls; 29. Medium-diameter heat storage balls; 30. Small-diameter heat storage balls; 31. Support frame; 32. Bottom uniform flow distributor; 33. Steam pipe; 34. Cylinder; 35. First cavity; 36. Second cavity; 37. Hot water outlet; 38. Hot water inlet; 39. Footing. Specific embodiments

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] It should be noted that when an element is referred to as being "fixed" or "disposed" with another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" with another element, it can be directly connected to the other element or indirectly connected to the other element.

[0030] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, and cannot be understood as indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0031] (1) Molten salt preheating and steam generation integrated heat storage tank The first aspect of the embodiments of the present application provides a molten salt preheating and steam generation integrated heat storage tank.

[0032] Please refer to Figure 1, which is a schematic structural diagram of an integrated heat storage tank for molten salt preheating and steam generation provided by an embodiment of the present application. For the convenience of description, only the parts related to this embodiment are shown and are described in detail as follows: In one embodiment, please refer to Figure 2 , an integrated heat storage tank for molten salt preheating and steam generation, comprising a tank body 1. Inside the tank body 1, a high-temperature molten salt distribution area 6, a steam generation area 8, a packed bed heat storage area 13, a molten salt distribution area 14, a feed water preheating area 18, and a low-temperature molten salt distribution area 19 are successively arranged from top to bottom. The areas are successively connected through perforated partitions; a molten salt inlet 2 and a molten salt outlet 22 are provided on the tank body 1. The molten salt inlet 2 is connected to the high-temperature molten salt distribution area 6, and the molten salt outlet 22 is connected to the low-temperature molten salt distribution area 19; a serpentine tube 4 is wound around the outer wall of the tank body 1. The feed water preheating area 18 and the steam generation area 8 are connected through the serpentine tube 4; a steam drum 3 is provided outside the tank body 1, and the steam drum 3 is connected to the steam generation area 8.

[0033] During use, high-temperature molten salt enters the tank body 1 from the molten salt inlet 2, successively passes through the high-temperature molten salt distribution area 6, the steam generation area 8, the packed bed heat storage area 13, the molten salt distribution area 14, the feed water preheating area 18, and the low-temperature molten salt distribution area 19 from top to bottom, and finally flows out of the tank body 1 through the molten salt outlet 22; since the feed water preheating area 18 and the steam generation area 8 are connected through the serpentine tube 4, preheated feed water from the feed water preheating area 18 is introduced into the steam generation area 8. In the steam generation area 8, heat exchange occurs between the high-temperature molten salt and the preheated feed water from the feed water preheating area 18 to generate high-temperature saturated steam, and the high-temperature saturated steam is stored in the steam drum 3 to realize the generation and storage of steam.

[0034] The present invention integrally arranges the feed water preheating area 18, the steam generation area 8, the packed bed heat storage area 13, the high-temperature molten salt distribution area 6, the molten salt distribution area 14, and the low-temperature molten salt distribution area 19 in the same tank body structure to form a functionally integrated heat storage device, realizing efficient collaborative heat exchange and energy cascade utilization of multiple heat sources and multiple fluids in a single device, breaking the design inertia of the traditional heat storage system of "dispersed functional modules and independent equipment units", realizing a highly integrated compact system configuration, and improving the heat energy management efficiency and structural economy; the present invention forms a secondary series countercurrent heat exchange system with the feed water preheating area 18 and the steam generation area 8, and with the heat storage buffer of the packed bed heat storage area 13, the three cooperate to form a distributed gradient heat management structure, which not only reduces the heat exchange area required for water-vapor conversion and the molten salt flow rate requirement, but also suppresses heat stress concentration through segmented temperature difference control, improving the thermal stability of the system and the steam production efficiency.

[0035] Specifically, please refer to Figure 2, inside the tank body 1, a first perforated partition 7, a second perforated partition 9, a third perforated partition 12, a fourth perforated partition 15, and a fifth perforated partition 21 are successively arranged from top to bottom. The first perforated partition 7 is located between the high-temperature molten salt gathering and distributing area 6 and the steam generation area 8. The second perforated partition 9 is located between the steam generation area 8 and the packed bed heat storage area 13. The third perforated partition 12 is located between the packed bed heat storage area 13 and the molten salt gathering and distributing area 14. The fourth perforated partition 15 is located between the molten salt gathering and distributing area 14 and the raw water preheating area 18. The fifth perforated partition 21 is located between the raw water preheating area 18 and the low-temperature molten salt gathering and distributing area 19. The high-temperature molten salt gathering and distributing area 6 is communicated with the steam generation area 8 through the first perforated partition 7. The steam generation area 8 is communicated with the packed bed heat storage area 13 through the second perforated partition 9. The packed bed heat storage area 13 is communicated with the molten salt gathering and distributing area 14 through the third perforated partition 12. The molten salt gathering and distributing area 14 is communicated with the raw water preheating area 18 through the fourth perforated partition 15. The raw water preheating area 18 is communicated with the low-temperature molten salt gathering and distributing area 19 through the fifth perforated partition 21.

[0036] Please refer to Figure 2 , in the high-temperature molten salt gathering and distributing area 6, a molten salt diffuser 5 is provided. The top end of the molten salt diffuser 5 is communicated with the molten salt inlet 2, and the bottom end of the molten salt diffuser 5 is communicated with the steam generation area 8 through the first perforated partition 7. The main function of the molten salt diffuser 5 is to enable the high-temperature molten salt to flow evenly into the steam generation area 8, playing a role of buffering and flow equalization. In this embodiment, the molten salt diffuser 5 is successively sleeved from the inside to the outside by a plurality of conical rings, facilitating the uniform transfer of the high-temperature molten salt to each heat exchange tube 10 in the steam generation area 8.

[0037] The high-temperature molten salt gathering and distributing area 6 has a heat storage function, which can suppress the fluctuations of the flow rate and temperature of the high-temperature molten salt entering the steam generation area 8, prevent the high-temperature molten salt from directly entering the steam generation area 8 and thus generating instability fluctuations, and smooth the output of the high-temperature molten salt.

[0038] Please refer to Figure 2 and Figure 3 , in the steam generation area 8, a number of heat exchange tubes 10 are circumferentially and evenly arranged. The heat exchange tubes 10 are arranged between the first perforated partition 7 and the second perforated partition 9, and the heat exchange tubes 10 are respectively communicated with the high-temperature molten salt gathering and distributing area 6 and the packed bed heat storage area 13 through the first perforated partition 7 and the second perforated partition 9. In this embodiment, the heat exchange tubes 10 are vertically arranged and welded between the first perforated partition 7 and the second perforated partition 9. The heat exchange tubes 10 adopt the concentric circle tube layout method and cooperate with the molten salt diffuser 5 to ensure that the high-temperature molten salt flowing out of the molten salt diffuser 5 can smoothly flow into the heat exchange tubes 10.

[0039] A steam pipe 33 is provided inside the tank body 1. The inlet end of the steam pipe 33 is communicated with the steam generation area 8, the outlet end of the steam pipe 33 penetrates through the tank body 1 and extends to the outside of the tank body 1, and the outlet end of the steam pipe 33 is communicated with the steam drum 3.

[0040] In the steam generation zone 8, the molten lava flows through the tube side, and the preheated incoming water flows through the shell side. The countercurrent heat exchange method is adopted to realize the gasification of water. High-temperature molten salt from the molten salt diffuser 5 is introduced into the heat exchange tube 10. After the high-temperature molten salt enters the heat exchange tube 10, it will exchange heat with the preheated incoming water from the incoming water preheating zone 18, generating high-temperature saturated steam. The high-temperature saturated steam enters the steam drum 3 through the steam pipe 33. The steam drum 3 is connected to the downstream steam system. When the steam in the steam drum 3 reaches a certain pressure, the steam drum 3 outputs steam externally.

[0041] Please refer to Figure 2 and Figure 5 , the internal of the packed bed heat storage zone 13 is filled with heat storage balls, and the heat storage balls are filled with phase change materials; the inner wall of the tank body 1 is surrounded by electric heating wires 27, and the electric heating wires 27 are surrounded outside the heat storage balls. The phase change material can be a paraffin-based phase change material or a metal-based phase change material. The phase change material undergoes solid-liquid phase change during the working process to achieve heat exchange. The electric heating wires 27 are used to start preheating and supplement heat to the molten salt at low temperature.

[0042] In this embodiment, three layers of heat storage balls with different diameters are filled in the packed bed heat storage zone 13 from top to bottom, namely large-diameter heat storage balls 28, medium-diameter heat storage balls 29, and small-diameter heat storage balls 30. The large-diameter heat storage balls 28, medium-diameter heat storage balls 29, and small-diameter heat storage balls 30 are all filled with phase change materials, and the electric heating wires 27 are surrounded outside the large-diameter heat storage balls 28, medium-diameter heat storage balls 29, and small-diameter heat storage balls 30. The molten salt flowing out from the steam generation zone 8 enters the packed bed heat storage zone 13 and exchanges heat with the three layers of heat storage balls with different diameters, thereby creating a temperature gradient with the low-temperature molten salt in the molten salt collection and distribution zone 14, and then realizing the gradient utilization of high-temperature molten salt. At the same time, the problem of excessive heat exchange temperature difference is solved.

[0043] Support columns 11 are provided in the packed bed heat storage zone 13 to ensure that the overall compressive strength of the tank body 1 meets the requirements. A support frame 31 is also provided at the bottom of the packed bed heat storage zone 13 to support the three layers of heat storage balls with different diameters.

[0044] A top uniform flow distributor 26 is provided at the top of the packed bed heat storage zone 13, and a bottom uniform flow distributor 32 is provided at the bottom of the packed bed heat storage zone 13. The packed bed heat storage zone 13 is connected to the steam generation zone 8 and the molten salt collection and distribution zone 14 through the top uniform flow distributor 26 and the bottom uniform flow distributor 32 respectively. In this embodiment, the top uniform flow distributor 26 and the bottom uniform flow distributor 32 are arranged on the inner wall of the tank body 1. The functions of the top uniform flow distributor 26 and the bottom uniform flow distributor 32 are to divide the molten salt flow, so that it can flow evenly, ensure that its through-flow heat exchange is more uniform, and eliminate heat exchange dead zones.

[0045] The heat storage balls can be made by oneself or purchased as finished products from the market. If made by oneself, the preparation process mainly includes the following steps: (1)Wire cut the stainless steel metal ball into two parts: the ball cover and the hemispherical body.

[0046] (2)After filling an appropriate amount of phase change material into the metal ball, place it in a furnace for heating to melt the phase change material. The heating temperature is 20°C higher than the melting point temperature of the phase change material. After the furnace temperature reaches the maximum heating temperature of the heat storage ball, keep it at a constant temperature for 20 minutes to ensure that the phase change material in the heat storage ball is fully melted, and then cool it naturally to form a dense structure of the phase change material.

[0047] (3)Repeat step (2) for three fillings. The first filling is 35% of the internal hollow volume of the heat storage ball, the second filling is 30% of the internal hollow volume of the heat storage ball, and the third filling is 15% of the internal hollow volume of the heat storage ball. After the three fillings are completed, the filling volume of the phase change material in the heat storage ball is about 80%.

[0048] (4)Adopt the welding and encapsulation process to weld the ball cover on the hemispherical body to seal the phase change material.

[0049] Please refer to Figure 2 , the molten salt flowing out from the heat storage area 13 of the packed bed flows into the molten salt distribution area 14. The function of the molten salt distribution area 14 is similar to that of the high-temperature molten salt distribution area 6. It has a heat storage function and can suppress the fluctuations of the flow rate and temperature of the molten salt entering the raw water preheating area 18, avoid the direct entry of the molten salt into the raw water preheating area 18, thereby generating unstable fluctuations, and smooth the output of the molten salt.

[0050] Please refer to Figure 2 and Figure 4 , several columns 34 are evenly distributed in a circle on the outer wall of the tank body 1. A baffle 20 is provided between the column 34 and the raw water preheating area 18; several groups of V-shaped heat exchange tubes 17 are provided in the raw water preheating area 18. Both ends of each group of V-shaped heat exchange tubes 17 penetrate through the baffle 20 and extend into the adjacent two columns 34. In this embodiment, the number of columns 34 is set to 4, the number of V-shaped heat exchange tubes 17 is set to 4 groups. The V-shaped heat exchange tubes 17 are fixed on the baffle 20 by the expanding tube method. The V-shaped heat exchange tubes 17 are arranged in a central symmetry to strengthen the fluid disturbance and improve the heat transfer coefficient. The "V" shape of the V-shaped heat exchange tubes 17 can increase the turbulence degree of the molten salt, improve the convective heat transfer amount, is conducive to uniform preheating, and avoid the formation of flow dead zones.

[0051] Any one of the cylinders 34 is provided with a vertical partition 16. The vertical partition 16 divides the cylinder 34 into a non-communicating first cavity 35 and a second cavity 36, and the V-shaped heat exchange tubes 17 located in the first cavity 35 and the second cavity 36 are of different groups; a water inlet 23 is communicated with the first cavity 35, a hot water outlet 37 is communicated with the second cavity 36, and a hot water inlet 38 communicating with the steam generation area 8 is provided on the side wall of the tank body 1. The hot water outlet 37 and the hot water inlet 38 are connected through a serpentine tube 4.

[0052] In the raw water preheating area 18, the raw water flows through the tube side, and the molten salt flows through the shell side, adopting a countercurrent heat exchange method. The raw water enters the first cavity 35 from the raw water inlet 23, then enters the V-shaped heat exchange tube 17. After passing through 4 tube passes, the raw water enters the second cavity 36, and flows through the serpentine tube 4 through the hot water outlet 37 into the hot water inlet 38 and enters the steam generation area 8. The molten salt flowing out from the molten salt gathering and distributing area 14 flows into the raw water preheating area 18. At the same time, the raw water is introduced into the V-shaped heat exchange tube 17 from the raw water inlet 23. The molten salt exchanges heat with the raw water, and the raw water is heated and preheated. The preheated raw water flows through the serpentine tube 4 through the hot water outlet 37 into the hot water inlet 38 and enters the steam generation area 8 to exchange heat with the high-temperature molten salt in the heat exchange tube 10; the molten salt is cooled and enters the low-temperature molten salt gathering and distributing area 19. The raw water flows through the tube side, and the tube side is 4 passes. Utilizing the elbow effect, the water flow turbulence is promoted, the heat exchange effect is improved, and at the same time, the space utilization efficiency of the raw water preheating area 18 is improved.

[0053] In this embodiment, the raw water preheating area 18 is further provided with a downpour port 24 and a downflow port 25. Both the downpour port 24 and the downflow port 25 are communicated with the raw water preheating area 18. The downpour port 24 is also communicated with the molten salt gathering and distributing area 14, and the downflow port 25 is also communicated with the low-temperature molten salt gathering and distributing area 19. The downpour port 24 and the downflow port 25 play a role in diverting. Part of the molten salt in the molten salt gathering and distributing area 14 flows into the raw water preheating area 18 through the downpour port 24, and then flows into the low-temperature molten salt gathering and distributing area 19 through the downflow port 25, avoiding the occurrence of molten salt flow dead zones, and being beneficial to the flow and uniform heat exchange of the molten salt.

[0054] Please refer to Figure 2 , the molten salt flowing out from the raw water preheating area 18 flows into the low-temperature molten salt gathering and distributing area 19. The function of the low-temperature molten salt gathering and distributing area 19 is similar to that of the molten salt gathering and distributing area 14, which will not be elaborated here.

[0055] Please refer to Figure 1 , the bottom of the tank body 1 is provided with a foot 39, and the foot 39 plays a role in supporting the tank body 1.

[0056] In the present invention, high-temperature molten salt enters the tank body 1 from the molten salt inlet 2, and successively passes through the high-temperature molten salt distribution area 6, the steam generation area 8, the packed bed heat storage area 13, the molten salt distribution area 14, the incoming water preheating area 18 and the low-temperature molten salt distribution area 19 from top to bottom, and finally flows out of the tank body 1 through the molten salt outlet 22. In the steam generation area 8, the molten salt flows through the tube side, and the preheated incoming water flows through the shell side; in the incoming water preheating area 18, the incoming water flows through the tube side, and the molten salt flows through the shell side; during the entire heat exchange process, the flow directions of the incoming water and the molten salt are opposite, that is, countercurrent heat exchange.

[0057] (II) Steam generation method The second aspect of the embodiments of the present application provides a steam generation method.

[0058] In one of the embodiments, please refer to Figures 1 - 5 , a steam generation method, using the above-mentioned molten salt preheating and steam generation integrated heat storage tank, the steam generation method includes the following steps: S1: Open the molten salt inlet 2, the molten salt outlet 22, the incoming water inlet 23, and the steam drum 3. The high-temperature molten salt enters the molten salt diffuser 5 in the high-temperature molten salt distribution area 6 from the molten salt inlet 2, and then enters the heat exchange tube 10 in the steam generation area 8, and exchanges heat with the preheated incoming water in the steam generation area 8. The water absorbs heat and vaporizes into saturated steam, and enters the steam drum 3 through the steam pipe 33. The high-temperature molten salt is cooled after absorbing heat.

[0059] Specifically, open the molten salt inlet 2, the molten salt outlet 22, the incoming water inlet 23, and the steam drum 3. The high-temperature molten salt enters the molten salt diffuser 5 in the high-temperature molten salt distribution area 6 from the molten salt inlet 2. After being split by the molten salt diffuser 5, the high-temperature molten salt uniformly enters the heat exchange tube 10 in the steam generation area 8 through the first perforated partition 7; Since the incoming water preheating area 18 and the steam generation area 8 are connected by the serpentine tube 4, the preheated incoming water from the incoming water preheating area 18 is introduced into the steam generation area 8. After the high-temperature molten salt enters the heat exchange tube 10 in the steam generation area 8, it will exchange heat with the preheated incoming water in the steam generation area 8. The water absorbs heat and vaporizes into saturated steam. The high-temperature saturated steam enters the steam drum 3 through the steam pipe 33 for storage, and the high-temperature molten salt is cooled after absorbing heat.

[0060] S2: The cooled molten salt enters the packed bed heat storage area 13, and exchanges heat with the large-diameter heat storage balls 28, the medium-diameter heat storage balls 29, and the small-diameter heat storage balls 30 respectively from top to bottom. The molten salt is cooled again and enters the molten salt distribution area 14.

[0061] Specifically, the cooled molten salt flowing out from the steam generation area 8 enters the packed bed heat storage area 13 through the second perforated partition 9, and exchanges heat with the heat storage balls of three different diameters, namely the large-diameter heat storage balls 28, the medium-diameter heat storage balls 29, and the small-diameter heat storage balls 30, from top to bottom; the molten salt is cooled again and enters the molten salt collection and distribution area 14 through the third perforated partition 12.

[0062] S3: The molten salt after being cooled again enters the raw water preheating area 18. At the same time, the raw water is introduced into the V-shaped heat exchange tubes 17 through the raw water inlet 23. The molten salt after being cooled again exchanges heat with the raw water, and the raw water is heated and preheated. The preheated raw water flows through the hot water outlet 37 through the serpentine tube 4 into the hot water inlet 38 and enters the steam generation area 8, where it exchanges heat with the high-temperature molten salt in the heat exchange tubes 10; the molten salt is cooled for the third time and enters the low-temperature molten salt collection and distribution area 19, and finally flows out of the tank body 1 through the molten salt outlet 22.

[0063] Specifically, the molten salt after being cooled again flowing out from the molten salt collection and distribution area 14 enters the raw water preheating area 18 through the fourth perforated partition 15. At the same time, the raw water is introduced into the V-shaped heat exchange tubes 17 through the raw water inlet 23. The molten salt after being cooled again exchanges heat with the raw water, and the raw water is heated and preheated. The preheated raw water flows through the hot water outlet 37 through the serpentine tube 4 into the hot water inlet 38 and enters the steam generation area 8, where it exchanges heat with the high-temperature molten salt in the heat exchange tubes 10; The molten salt is cooled for the third time, enters the low-temperature molten salt collection and distribution area 19 through the fifth perforated partition 21, and finally flows out of the tank body 1 through the molten salt outlet 22.

[0064] In the present invention, the molten salt can be a mixed nitrate or other types of molten salts.

[0065] In the present invention, the tank body 1 also has the function of storing molten salt. When the tank body 1 is in a non-operating state, the molten salt inlet 2 is opened and the molten salt outlet 22 is closed. The molten salt enters the tank body 1 from the molten salt inlet 2. After all the molten salt has flowed into the tank body 1, the molten salt inlet 2 is closed. At this time, the tank body 1 can be used as a molten salt storage tank.

[0066] Taking a certain project as an example: The diameter of the steam generation area 8 is 1000 mm, the heat exchange tubes 10 with Φ25×50 are adopted, the temperature of the high-temperature molten salt is 575 °C, the temperature of the preheated raw water is 260 °C, the saturation steam temperature is 311 °C, and the molten salt outlet temperature is 400 °C; the diameter of the packed bed heat storage area 13 is 1000 mm, the molten salt inlet temperature is 400 °C, and the molten salt outlet temperature is 320 °C; the diameter of the raw water preheating area 18 is 1000 mm, the V-shaped heat exchange tubes 17 with Φ25×20 are adopted, the raw water temperature is 200 °C, the temperature of the preheated raw water is 260 °C, the molten salt inlet temperature is 320 °C, and the molten salt outlet temperature is 290 °C.

[0067] The method for steam generation is as follows: S1: Open the molten salt inlet 2, the molten salt outlet 22, the incoming water inlet 23, and the steam drum 3. The high-temperature molten salt at 575 °C enters the molten salt spreader 5 in the high-temperature molten salt distribution area 6 from the molten salt inlet 2, and then enters the heat exchange tubes 10 in the steam generation area 8, where it exchanges heat with the preheated incoming water (10 MPa, 260 °C) in the steam generation area 8. The water absorbs heat and vaporizes into saturated steam (10 MPa, 311 °C), which enters the steam drum 3 through the steam pipe 33. The high-temperature molten salt is cooled to 400 °C after releasing heat.

[0068] S2: The molten salt cooled to 400 °C enters the packed bed heat storage area 13, where it exchanges heat with the large-diameter heat storage balls 28, medium-diameter heat storage balls 29, and small-diameter heat storage balls 30 from top to bottom. The molten salt is cooled to 320 °C again and enters the molten salt distribution area 14.

[0069] S3: The molten salt cooled to 320 °C enters the incoming water preheating area 18. At the same time, the incoming water (10 MPa, 200 °C) is introduced into the V-shaped heat exchange tubes 17 from the incoming water inlet 23. The 320 °C molten salt exchanges heat with the incoming water, and the incoming water is heated and preheated to 260 °C. The preheated incoming water at 260 °C flows through the hot water outlet 37, through the serpentine tube 4, and enters the hot water inlet 38, then enters the steam generation area 8, where it exchanges heat with the 575 °C high-temperature molten salt in the heat exchange tubes 10. The molten salt is cooled to 290 °C and enters the low-temperature molten salt distribution area 19, and finally flows out of the tank body 1 through the molten salt outlet 22.

[0070] In summary, the present invention provides a molten salt preheating and steam generation integrated heat storage tank and its steam generation method. Compared with the prior art: (1) The present invention integrates the incoming water preheating area, the steam generation area, the packed bed heat storage area with the high-temperature molten salt distribution area, the molten salt distribution area, and the low-temperature molten salt distribution area in the same tank body structure, forming a functionally integrated heat storage device, realizing efficient collaborative heat exchange and energy cascade utilization of multiple heat sources and multiple fluids in a single device, breaking the design inertia of the traditional heat storage system of "scattered functional modules and independent equipment units", achieving a highly integrated compact system configuration, and improving the heat energy management efficiency and structural economy.

[0071] (2) The present invention forms a secondary series countercurrent heat exchange system by combining the incoming water preheating area and the steam generation area, and with the heat storage buffer of the packed bed heat storage area, the three work together to form a distributed gradient heat management structure, which not only reduces the heat exchange area required for water-vapor conversion and the molten salt flow rate requirements, but also suppresses heat stress concentration through segmented temperature difference control, improving the thermal stability of the system and the steam production efficiency.

[0072] (3) By designing a high-temperature molten salt collection and distribution area at the top, a molten salt collection and distribution area in the middle, and a low-temperature molten salt collection and distribution area at the bottom, the present invention forms a complete three-stage molten salt flow organizational structure, ensuring that the molten salt flows uniformly in different temperature zones, the temperature decreases layer by layer, avoiding fouling and heat transfer dead angles, effectively overcoming the problem of uneven flow distribution in traditional packed beds or series tank systems, and improving the dynamic stability and heat transfer efficiency of the system operation.

[0073] (4) The present invention uniquely constructs a heat storage ball packed bed structure arranged axially in three layers. Each layer of heat storage balls is filled with phase change materials with different phase change temperatures, corresponding to the temperature zones one by one along the path of the incoming water from preheating to vaporization. Through the hierarchical configuration of the temperature gradient, a reasonably distributed heat transfer interface between the molten salt and the solid heat storage body is formed, realizing the hierarchical release of energy and the short-term buffer energy storage function, and effectively controlling the system thermal inertia and thermal stress concentration.

[0074] (5) The present invention adopts a segmented structure layout and a flow field disturbance strengthening design of a self-designed V-shaped heat exchange tube flow channel structure, combined with a countercurrent operation mode and temperature difference gradient control, to realize the slow release and dispersion of thermal stress in the vertical and radial directions. Combined with a three-layer temperature difference structure, it alleviates the problem of transient temperature difference impact at the high-temperature heat transfer interface between the water side and the molten salt side; structurally, a buffer structure is adopted at the key interface to avoid local material fatigue and thermal stress concentration caused by the large temperature difference between the molten salt and the heat transfer wall surface in the traditional single-tank system, effectively ensuring the long-term stability and material safety of the system in a high-temperature operating environment.

[0075] The present invention provides a molten salt preheating and steam generation integrated heat storage tank with a compact structure, high heat transfer efficiency, and high degree of integration. Through the efficient heat transfer between the high-temperature molten salt and the medium, it realizes the cascade storage and release of energy, solves the technical problems of the existing molten salt heat storage system such as scattered equipment, large heat loss, thermal stress concentration, difficult control, high maintenance cost, complex structure, and large floor area, and has high practicability. The present invention can be widely applied to the technical field of molten salt heat storage.

[0076] The above-described embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An integrated heat storage tank for molten salt preheating and steam generation, characterized in that, It includes a tank body (1), inside which there are successively arranged from top to bottom a high-temperature molten salt gathering and distributing area (6), a steam generation area (8), a packed bed heat storage area (13), a molten salt gathering and distributing area (14), a feed water preheating area (18) and a low-temperature molten salt gathering and distributing area (19). Each area is successively connected through an opening partition board; there are a molten salt inlet (2) and a molten salt outlet (22) on the tank body (1). The molten salt inlet (2) is connected to the high-temperature molten salt gathering and distributing area (6), and the molten salt outlet (22) is connected to the low-temperature molten salt gathering and distributing area (19); a serpentine tube (4) is wound around the outer wall of the tank body (1). The feed water preheating area (18) and the steam generation area (8) are connected through the serpentine tube (4); a steam drum (3) is arranged outside the tank body (1), and the steam drum (3) is connected to the steam generation area (8).

2. The integrated heat storage tank for molten salt preheating and steam generation according to claim 1, wherein Inside the tank body (1), there are successively arranged from top to bottom a first opening partition board (7), a second opening partition board (9), a third opening partition board (12), a fourth opening partition board (15) and a fifth opening partition board (21). The first opening partition board (7) is located between the high-temperature molten salt gathering and distributing area (6) and the steam generation area (8), the second opening partition board (9) is located between the steam generation area (8) and the packed bed heat storage area (13), the third opening partition board (12) is located between the packed bed heat storage area (13) and the molten salt gathering and distributing area (14), the fourth opening partition board (15) is located between the molten salt gathering and distributing area (14) and the feed water preheating area (18), and the fifth opening partition board (21) is located between the feed water preheating area (18) and the low-temperature molten salt gathering and distributing area (19).

3. The integrated heat storage tank for molten salt preheating and steam generation according to claim 2, wherein, A molten salt flow diffuser (5) is arranged in the high-temperature molten salt gathering and distributing area (6). The top end of the molten salt flow diffuser (5) is connected to the molten salt inlet (2), and the bottom end of the molten salt flow diffuser (5) is connected to the steam generation area (8) through the first opening partition board (7).

4. The integrated heat storage tank for molten salt preheating and steam generation according to claim 2, wherein, A number of heat exchange tubes (10) evenly distributed in a circumferential direction are arranged in the steam generation area (8). The heat exchange tubes (10) are arranged between the first opening partition board (7) and the second opening partition board (9), and the heat exchange tubes (10) are respectively connected to the high-temperature molten salt gathering and distributing area (6) and the packed bed heat storage area (13) through the first opening partition board (7) and the second opening partition board (9).

5. The integrated heat storage tank for molten salt preheating and steam generation according to claim 1, characterized in that, A steam pipe (33) is arranged inside the tank body (1). The inlet end of the steam pipe (33) is connected to the steam generation area (8), the outlet end of the steam pipe (33) penetrates through the tank body (1) and extends to the outside of the tank body (1), and the outlet end of the steam pipe (33) is connected to the steam drum (3).

6. The integrated heat storage tank for molten salt preheating and steam generation according to claim 1, wherein Inside the packed bed heat storage area (13), large-diameter heat storage balls (28), medium-diameter heat storage balls (29), and small-diameter heat storage balls (30) are filled in sequence from top to bottom. Phase change materials are filled in the large-diameter heat storage balls (28), the medium-diameter heat storage balls (29), and the small-diameter heat storage balls (30). Electric heating wires (27) are wound around the inner wall of the tank body (1), and the electric heating wires (27) are wound outside the large-diameter heat storage balls (28), the medium-diameter heat storage balls (29), and the small-diameter heat storage balls (30).

7. The integrated heat storage tank for molten salt preheating and steam generation according to claim 1, wherein, A top uniform flow distributor (26) is provided at the top of the packed bed heat storage area (13), and a bottom uniform flow distributor (32) is provided at the bottom of the packed bed heat storage area (13). The packed bed heat storage area (13) is communicated with the steam generation area (8) and the molten salt collection and distribution area (14) respectively through the top uniform flow distributor (26) and the bottom uniform flow distributor (32).

8. The integrated heat storage tank for molten salt preheating and steam generation according to claim 1, characterized in that Several cylinders (34) evenly distributed in a circle are provided on the outer wall of the tank body (1). A baffle (20) is provided between the cylinders (34) and the incoming water preheating area (18). Several groups of V-shaped heat exchange tubes (17) are provided in the incoming water preheating area (18). Both ends of each group of V-shaped heat exchange tubes (17) penetrate through the baffle (20) and extend into adjacent two cylinders (34).

9. The integrated heat storage tank for molten salt preheating and steam generation according to claim 8, wherein A vertical partition plate (16) is provided in any one of the cylinders (34). The vertical partition plate (16) divides the cylinder (34) into a non-communicating first cavity (35) and a second cavity (36). And the V-shaped heat exchange tubes (17) located in the first cavity (35) and the second cavity (36) are of different groups. A water inlet (23) is communicated with the first cavity (35), a hot water outlet (37) is communicated with the second cavity (36). A hot water inlet (38) communicating with the steam generation area (8) is provided on the side wall of the tank body (1). The hot water outlet (37) and the hot water inlet (38) are communicated through the serpentine tube (4).

10. A method for generating steam, characterized in that, Using the molten salt preheating and steam generation integrated heat storage tank according to any one of claims 1-9, the steam generation method comprises the following steps: S1: Open the molten salt inlet (2), the molten salt outlet (22), the incoming water inlet (23), and the steam drum (3). High-temperature molten salt enters the molten salt diffuser (5) in the high-temperature molten salt collection and distribution area (6) from the molten salt inlet (2), and then enters the heat exchange tubes (10) in the steam generation area (8), and exchanges heat with the preheated incoming water in the steam generation area (8). The water absorbs heat and vaporizes into saturated steam, and enters the steam drum (3) through the steam pipe (33). The high-temperature molten salt is cooled after absorbing heat; S2: The cooled molten salt enters the packed bed heat storage area (13), and exchanges heat with the large-diameter heat storage balls (28), the medium-diameter heat storage balls (29), and the small-diameter heat storage balls (30) from top to bottom respectively. The molten salt is cooled again and enters the molten salt collection and distribution area (14); S3: The molten salt after re-cooling enters the incoming water preheating zone (18). Meanwhile, the incoming water is introduced into the V-shaped heat exchange tubes (17) from the incoming water inlet (23). The molten salt after re-cooling exchanges heat with the incoming water, and the incoming water is heated and preheated. The preheated incoming water flows through the hot water outlet (37), through the serpentine tube (4) into the hot water inlet (38), and enters the steam generation zone (8) to exchange heat with the high-temperature molten salt in the heat exchange tubes (10); the molten salt is cooled for the third time, enters the low-temperature molten salt collection and distribution zone (19), and finally flows out of the tank body (1) through the molten salt outlet (22).

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