Kettle type evaporator for fused salt steam generation system

Abstract

The utility model relates to a kettle type evaporator for a fused salt steam generation system. The kettle type evaporator comprises a first tube box, a second tube box, an evaporation kettle, a tube plate, a central cylinder and a heat exchange tube, the left end and the right end of the evaporation kettle are respectively connected with a first channel and a second channel through tube plates, the first channel is provided with a fused salt inlet, the second channel is provided with a fused salt outlet, the bottom of the evaporation kettle is provided with a water inlet, and the top of the evaporation kettle is provided with a steam outlet; a central cylinder is arranged in the evaporation kettle, the two ends of the central cylinder are connected with the two tube plates respectively, a plurality of heat exchange tubes are spirally wound on the periphery of the central cylinder, and the two ends of each heat exchange tube are fixedly arranged on the two tube plates respectively and are communicated with the first tube box and the second tube box respectively. According to the heat exchange tube of the kettle type evaporator, due to the fact that the spiral wound tube type structure is adopted, the heat exchange tube is more resistant to heat strain impact and more suitable for variable working condition operation, and meanwhile the heat exchange coefficient is improved. In addition, the molten salt evaporator is not limited by the length of a straight heat exchange tube any more, and possibility is provided for large scale of the molten salt evaporator.

Description

Technical Field

[0001] This utility model relates to the technical field of high-temperature thermal energy storage and conversion equipment, and in particular to a kettle evaporator for a molten salt steam generation system. Background Technology

[0002] Whether molten salt energy storage is used for solar thermal power generation or thermal power peak shaving, the heat stored in molten salt needs to be released to generate steam, which requires a molten salt steam generation system, and the molten salt evaporator is one of the key pieces of equipment in it.

[0003] Chinese patent document CN119289338A discloses a variable-diameter U-tube evaporator for molten salt thermal storage systems, comprising a shell, tube sheet, tube box baffle, U-shaped heat exchange tubes, baffles, and a drain port. The U-shaped heat exchange tubes are fixed to the tube sheet, which is connected to the tube box. The tube box is fixedly connected to the shell via flanges. All U-shaped heat exchange tubes employ a variable-diameter structure, with the diameter being larger at the inlet and smaller at the outlet. This evaporator uses a gradually changing U-shaped heat exchange tube bundle design. The variable-diameter structure optimizes the flow velocity and pressure distribution of the fluid inside the tubes, reducing the risk of local overheating and uneven evaporation, and effectively lowering flow resistance. The variable-diameter design also reduces thermal stress concentration, thereby improving the reliability and service life of the equipment. The defects and shortcomings of this variable diameter U-tube evaporator are: (1) When the U-shaped heat exchange tube generates thermal strain, it will exert a certain pull-out force on the tube sheet, and its impact resistance is weak; (2) Since the number of tube passes of the U-shaped heat exchange tube is even, the same tube sheet needs to withstand the large temperature difference between the inlet and outlet, resulting in large thermal strain of the tube sheet, which can easily lead to leakage or damage to the evaporator; (3) Molten salt mainly relies on straight tube sections for heat transfer in the U-shaped heat exchange tube, which is not conducive to the formation of turbulence, so the overall heat transfer coefficient is low; (4) This variable diameter U-tube evaporator is limited by the length of the straight tube section of the U-shaped tube, and the heat transfer area per cubic meter of volume is less than 100 square meters, which is not conducive to the large-scale development of the equipment. Utility Model Content

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, this utility model provides a kettle evaporator for a molten salt steam generation system, which solves the technical problem that the tube sheet of the existing U-tube evaporator has weak impact resistance and is easily damaged and leaks.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by this utility model include:

[0008] This utility model provides a kettle-type evaporator for a molten salt steam generation system, including a first tube box, a second tube box, an evaporation kettle, a tube sheet, a central cylinder, and heat exchange tubes;

[0009] The left and right ends of the evaporator are connected to the first tube box and the second tube box respectively through tube sheets. The first tube box is equipped with a molten salt inlet and the second tube box is equipped with a molten salt outlet. The bottom of the evaporator is equipped with a water inlet and the top of the evaporator is equipped with a steam outlet.

[0010] The evaporator has a central cylinder inside, with its two ends connected to two tube sheets. Multiple heat exchange tubes are spirally wound around the outer periphery of the central cylinder. The two ends of each heat exchange tube are fixedly mounted on two tube sheets and are connected to the first tube box and the second tube box, respectively.

[0011] Optionally, the multiple heat exchange tubes are divided into at least two groups, each group of heat exchange tubes constitutes a heat exchange tube bundle layer, and at least two heat exchange tube bundle layers are cylindrical structures and nested together.

[0012] Optionally, it also includes a junction box and multiple electric heating elements;

[0013] One end of multiple electric heating tubes is fixedly mounted on a tube sheet near the first tube box, and the other end of the multiple electric heating tubes passes through the evaporator, another tube sheet, and the second tube box before connecting to a junction box.

[0014] Optionally, multiple electric heating tubes are located between adjacent heat exchange tube bundle layers and are spaced apart circumferentially along the central cylinder.

[0015] Optionally, it also includes an inlet distribution pipe, which includes a first pipe section and a second pipe section;

[0016] One end of the first pipe section is a water inlet, and the other end of the first pipe section enters the interior of the evaporator and is connected to the middle of the second pipe section. The length direction of the second pipe section is parallel to the length direction of the evaporator, and the pipe wall of the second pipe section has water outlet holes spaced along the length direction.

[0017] Optionally, it also includes steam manifolds;

[0018] Multiple steam outlets are spaced apart at the top of the evaporator along its length. All steam outlets are connected to a steam manifold via pipelines. One end of the steam manifold is sealed, and the other end of the steam manifold is the main steam outlet.

[0019] Optionally, a demister is provided on the inner wall of the evaporator corresponding to the steam outlet area.

[0020] Optionally, the bottom of the first and second tube boxes is provided with a salt-draining port.

[0021] Optionally, the top of the evaporator is provided with a manhole, and the manhole is equipped with a sealed door.

[0022] (III) Beneficial Effects

[0023] The beneficial effects of this invention are as follows: The kettle-type evaporator for a molten salt steam generation system includes a first tube box, a second tube box, an evaporation kettle, a tube sheet, a central cylinder, and heat exchange tubes. The first tube box is used to distribute the molten salt entering the evaporator; the tube sheet separates the tube box and the evaporation kettle into two fluid spaces and fixes the heat exchange tubes; the heat exchange tubes are channels for the flow of molten salt and facilitate heat exchange between the molten salt and water; the evaporation kettle is the space for vapor-liquid separation of steam; and the second tube box collects the molten salt flowing out of the heat exchange tubes. During operation, the molten salt in the heat exchange tubes releases heat, entering the first tube box through the molten salt inlet, then entering multiple spirally arranged heat exchange tubes, passing through the heat exchange tubes into the second tube box, and finally flowing out of the kettle-type evaporator through the molten salt outlet. The water in the evaporation kettle absorbs heat and evaporates, entering the evaporation kettle through the inlet, and under the heating action of the high-temperature molten salt, the water absorbs heat and undergoes a phase change, generating saturated steam that flows out of the kettle-type evaporator through the steam outlet. Compared with existing U-tube evaporators used in molten salt steam generation systems, firstly, the heat exchange tubes adopt a spiral wound structure, which can effectively absorb thermal strain in a timely manner. This makes the kettle-type evaporator of this invention more suitable for large temperature difference heat exchange conditions in molten salt. Furthermore, because the spiral heat exchange tubes can eliminate their own thermal stress, they have strong impact resistance and are more adaptable to variable load conditions, making them more suitable for peak shaving in power plants. Secondly, the two sides of the evaporation kettle use independent tube sheets, eliminating thermal strain caused by uneven temperature distribution on the tube sheets. Simultaneously, the pull-out force of the heat exchange tubes on the tube sheets is also eliminated, solving the problem of tube sheet leakage under large temperature difference heat exchange conditions. Thirdly, due to the spiral wound structure of the heat exchange tubes, the flow direction of molten salt within the heat exchange tubes is constantly changing, which easily forms turbulence and eliminates dead zones, thus greatly improving the heat transfer coefficient. Fourthly, the spiral wound structure of the heat exchange tubes removes the length limitation of the evaporator from the length of the straight tube section, which is beneficial for the large-scale development of the equipment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the kettle evaporator for a molten salt steam generation system of this utility model;

[0025] Figure 2 for Figure 1 An enlarged schematic diagram of the autoclave evaporator used in the molten salt steam generation system at point A;

[0026] Figure 3 for Figure 1 Cross-sectional view of the heat exchange tubes in the diagram

[0027] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the kettle evaporator for a molten salt steam generation system of this utility model;

[0028] Figure 5 for Figure 4 A cross-sectional view of the heat exchange tubes and electric heating tubes in the diagram.

[0029] [Explanation of Labels in the Attached Image]

[0030] 1: First tube box; 2: Second tube box; 3: Evaporator; 4: Tube sheet; 5: End cap; 6: Molten salt inlet; 7: Molten salt outlet; 8: Salt drain port; 9: Support; 10: Steam outlet; 11: Steam manifold; 12: Plug; 13: Main steam outlet; 14: Demister; 15: Manhole; 16: Water inlet distribution pipe; 17: First tube section; 18: Second tube section; 19: Water inlet; 21: Central cylinder; 22: Heat exchange tube; 23: Gasket; 24: Junction box; 25: Electric heating tube. Detailed Implementation

[0031] To better explain and facilitate understanding of this utility model, a detailed description of its specific embodiments is provided below with reference to the accompanying drawings. In this document, directional terms such as "upper," "lower," "left," and "right" are used interchangeably. Figure 1 The orientation is used as a reference.

[0032] Example 1:

[0033] Reference Figure 1 and Figure 2 This embodiment provides a kettle-type evaporator for a molten salt steam generation system, including a first tube box 1, a second tube box 2, an evaporation kettle 3, two tube sheets 4, a central cylinder 21, and multiple heat exchange tubes 22.

[0034] The left and right ends of the evaporator 3 are connected to the first tube box 1 and the second tube box 2 respectively through the tube plate 4. The first tube box 1 is provided with a molten salt inlet 6, and the second tube box 2 is provided with a molten salt outlet 7. The bottom of the evaporator 3 is provided with a water inlet 19, and the top of the evaporator 3 is provided with a steam outlet 10.

[0035] The evaporator 3 has a central cylinder 21 inside. The two ends of the central cylinder 21 are connected to two tube sheets 4 respectively. Multiple heat exchange tubes 22 are spirally wound around the outer periphery of the central cylinder 21. The two ends of each heat exchange tube 22 are fixed on the two tube sheets 4 respectively and are connected to the first tube box 1 and the second tube box 2 respectively.

[0036] The kettle-type evaporator for a molten salt steam generation system in this embodiment includes a first tube box 1, a second tube box 2, an evaporation kettle 3, two tube sheets 4, a central cylinder 21, and multiple heat exchange tubes 22. The first tube box 1 distributes the molten salt into the evaporator. The tube sheets 4 separate the tube box and the evaporation kettle 3 into two fluid spaces and fix the ends of the heat exchange tubes 22. The middle part of the heat exchange tubes 22 is spirally wound around the periphery of the central cylinder 21. The central cylinder 21 is used to fix and support the heat exchange tubes 22. The heat exchange tubes 22 are channels for the flow of molten salt and for heat exchange between molten salt and water. The evaporation kettle 3 is a space for vapor-liquid separation of steam. The second tube box 2 is used to collect the molten salt flowing out of the heat exchange tubes 22. During operation, the molten salt in the heat exchange tubes 22 releases heat. That is, the molten salt enters the first tube box 1 through the molten salt inlet 6, then enters the multiple spirally arranged heat exchange tubes 22, enters the second tube box 2 through the heat exchange tubes 22, and flows out of the kettle-type evaporator through the molten salt outlet 7. Water in the evaporator 3 undergoes endothermic evaporation. Water enters the evaporator 3 through inlet 19 and, under the heating effect of high-temperature molten salt, absorbs heat and undergoes a phase change. The resulting saturated steam flows out of the evaporator through steam outlet 10. Compared to existing U-tube evaporators used in molten salt steam generation systems, firstly, the heat exchange tubes 22 adopt a spiral wound structure, which can effectively absorb thermal strain in a timely manner. This makes the evaporator in this embodiment more suitable for large temperature difference heat exchange conditions in molten salt. Furthermore, because the spiral heat exchange tubes 22 can eliminate their own thermal stress, they have strong impact resistance and are more adaptable to variable load conditions. This characteristic makes them more suitable for peak shaving in power plants. Secondly, the two sides of the evaporator 3 use independent tube sheets 4, eliminating thermal strain caused by uneven temperature distribution on the tube sheets 4. Simultaneously, the pull-out force of the heat exchange tubes 22 on the tube sheets 4 is also eliminated, solving the problem of tube sheet leakage under large temperature difference heat exchange conditions. Third, because the heat exchange tube 22 adopts a spiral wound tube structure, the flow direction of the molten salt inside the heat exchange tube 22 is constantly changing, which easily forms turbulence and eliminates dead zones, greatly improving the heat transfer coefficient. Fourth, the spiral wound tube structure of the heat exchange tube 22 eliminates the limitation on the length of the evaporator by the length of the straight tube section of the heat exchange tube 22, which is beneficial for the large-scale development of the equipment.

[0037] Please refer to Figure 3 Preferably, the multiple heat exchange tubes 22 are divided into at least two groups, each group of heat exchange tubes 22 forming a heat exchange tube bundle layer. At least two heat exchange tube bundle layers are cylindrical structures and are nested together. Spacers 23 are provided between adjacent heat exchange tube bundle layers to position and fix the heat exchange tubes 22. In addition, tube clamps are provided on the heat exchange tubes 22, and wrapping cylinders are provided around the heat exchange tube bundle layers. The tube clamps are used to fix the position of the heat exchange tubes 22, and the wrapping cylinders are thin-walled cylinders wrapped around the outermost layer of the heat exchange tube bundle layers.

[0038] In this embodiment, the heat exchange tube 22 is spirally wound and layered, resulting in a compact structure. Compared with the existing U-tube heat exchanger, its heat exchange area per unit volume is significantly increased.

[0039] Preferably, the bottom of the first tube box 1 and the second tube box 2 is provided with a salt drain port 8. The purpose of providing the salt drain port 8 is to drain the molten salt in the first tube box 1, the second tube box 2 and the heat exchange tube 22 in a timely manner when the autoclave evaporator stops running, so as to prevent the molten salt from solidifying and clogging the heat exchange tube 22 due to heat loss.

[0040] Preferably, the kettle evaporator further includes a water inlet distribution pipe 16, which includes a first pipe section 17 and a second pipe section 18. One end of the first pipe section 17 is a water inlet 19, and the other end of the first pipe section 17 enters the interior of the evaporator 3 and communicates with the middle part of the second pipe section 18. The length direction of the second pipe section 18 is parallel to the length direction of the evaporator 3, and the pipe wall of the second pipe section 18 has water outlet holes spaced apart along the length direction.

[0041] It should be noted that the water flows from the inlet 19 into the first section 17 of the water distribution pipe 16, and then through multiple outlet holes on the second section 18 to various positions outside the heat exchange tube 22, thereby maintaining a certain water level in the evaporator 3.

[0042] Preferably, the kettle evaporator further includes a steam manifold 11. Multiple steam outlets 10 are spaced apart along the length of the top of the evaporator 3. All steam outlets 10 are connected to the steam manifold 11 via pipes. One end of the steam manifold 11 is sealed with a plug 12, and the other end is a total steam outlet 13. It should be noted that the multiple steam outlets 10 spaced apart on the top of the evaporator 3 allow steam to enter the steam manifold 11 from the steam outlets 10 and then exit the kettle evaporator through the total steam outlet 13. This design allows steam to exit from different locations within the evaporator 3, ensuring uniform steam output and facilitating steam-water separation.

[0043] Furthermore, a demister 14 is provided on the inner wall of the evaporator 3 corresponding to the area of ​​the steam outlet 10. The purpose of providing the demister 14 is to further separate steam and water, thereby increasing the dryness of the steam and improving the steam quality.

[0044] Furthermore, a support 9 is provided on the lower surface of the evaporator 3, which is used to support the body of the evaporator 3.

[0045] Preferably, the first tube box 1 and the second tube box 2 are provided with end caps 5 on the side away from the tube sheet 4.

[0046] Furthermore, a manhole 15 is provided on the top of the evaporator 3, and a sealed door is provided at the manhole 15. It should be noted that the purpose of providing the manhole 15 is to facilitate workers to enter the evaporator 3 to maintain and repair the pipelines.

[0047] Example 2:

[0048] Reference Figure 4 and Figure 5 This embodiment provides another type of kettle evaporator for a molten salt steam generation system. Unlike embodiment 1, the kettle evaporator in this embodiment also includes a junction box 24 and multiple electric heating tubes 25.

[0049] One end of multiple electric heating tubes 25 is fixedly mounted on a tube sheet 4 near the first tube box 1. The other ends of the multiple electric heating tubes 25 pass through the evaporator 3, another tube sheet 4, and the second tube box 2 in sequence, and are connected to the junction box 24. The function of the electric heating tubes 25 is to heat the heat exchange tubes 22 inside the evaporator 3.

[0050] It should be noted that molten salt solidifies when the temperature is below its freezing point, thus clogging the heat exchange tubes. While the spiral-wound tube structure of the heat exchange tube 22 has the advantages mentioned above, the long flow path of the molten salt increases the risk of blockage. To address this issue, this embodiment arranges multiple electric heating tubes 25 inside the evaporator 3. These tubes heat the heat exchange tubes 22, maintaining the water temperature inside the evaporator and melting the molten salt in case of solidification, thus clearing the blockage in the heat exchange tubes 22.

[0051] Preferably, the electric heating tubes 25 are located between adjacent heat exchange tube bundle layers and are spaced apart circumferentially along the central cylinder 21. The purpose of this arrangement is to ensure that the electric heating tubes 25 are in uniform contact with the heat exchange tube bundle layers, so that when the electric heating tubes 25 are activated, they can quickly melt the solidified molten salt.

[0052] Preferably, the kettle evaporator in this embodiment further includes a controller and a temperature sensor. The controller is connected to the junction box 24 and the temperature sensor, which is installed inside the evaporation kettle 3 to monitor the water temperature inside the kettle 3. When the kettle evaporator is working, the temperature sensor monitors the water temperature inside the evaporation kettle 3 and sends the water temperature data to the controller. The controller determines whether the water temperature data is lower than a preset value. If so, the controller activates multiple electric heating tubes 25 through the junction box 24. At the same time, if molten salt solidifies and blocks the heat exchange tube 22, the electric heating tubes 25 can quickly melt the molten salt because they are in direct contact with the heat exchange tube 22, thereby clearing the blockage in the heat exchange tube 22.

[0053] The remaining parts that are the same as in Example 1 will not be repeated here.

[0054] In the description of this utility model, it should be understood that 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0055] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0056] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0057] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A kettle-type evaporator for a molten salt steam generation system, characterized in that, It includes a first tube box (1), a second tube box (2), an evaporator (3), a tube sheet (4), a central cylinder (21), and heat exchange tubes (22); The left and right ends of the evaporator (3) are connected to the first tube box (1) and the second tube box (2) respectively through the tube plate (4). The first tube box (1) is provided with a molten salt inlet (6), and the second tube box (2) is provided with a molten salt outlet (7). The bottom of the evaporator (3) is provided with a water inlet (19), and the top of the evaporator (3) is provided with a steam outlet (10). The evaporator (3) is equipped with a central cylinder (21) inside. The two ends of the central cylinder (21) are connected to two tube sheets (4) respectively. Multiple heat exchange tubes (22) are spirally wound around the outer periphery of the central cylinder (21). The two ends of the heat exchange tubes (22) are fixed on the two tube sheets (4) respectively and are connected to the first tube box (1) and the second tube box (2) respectively.

2. The kettle evaporator for a molten salt steam generation system as described in claim 1, characterized in that: Multiple heat exchange tubes (22) are divided into at least two groups, each group of heat exchange tubes (22) constitutes a heat exchange tube bundle layer, and at least two heat exchange tube bundle layers are cylindrical structures and are nested together.

3. The kettle evaporator for a molten salt steam generation system as described in claim 2, characterized in that: It also includes a junction box (24) and multiple electric heating elements (25); One end of multiple electric heating tubes (25) is fixed on a tube plate (4) near the first tube box (1), and the other end of multiple electric heating tubes (25) passes through the evaporator (3), another tube plate (4) and the second tube box (2) and is connected to the junction box (24).

4. The kettle evaporator for a molten salt steam generation system as described in claim 3, characterized in that: Multiple electric heating tubes (25) are located between adjacent heat exchange tube bundle layers and are spaced apart circumferentially along the central cylinder (21).

5. The kettle evaporator for a molten salt steam generation system as described in claim 1, characterized in that: It also includes an inlet distribution pipe (16), which includes a first pipe section (17) and a second pipe section (18); One end of the first pipe section (17) is a water inlet (19), and the other end of the first pipe section (17) enters the interior of the evaporator (3) and is connected to the middle of the second pipe section (18). The length direction of the second pipe section (18) is parallel to the length direction of the evaporator (3), and the pipe wall of the second pipe section (18) has water outlet holes spaced apart along the length direction.

6. The kettle evaporator for a molten salt steam generation system as described in claim 1, characterized in that: It also includes steam manifold (11); Multiple steam outlets (10) are spaced apart along the length of the top of the evaporator (3). All steam outlets (10) are connected to the steam manifold (11) through pipelines. One end of the steam manifold (11) is provided with a plug (12), and the other end of the steam manifold (11) is the main steam outlet (13).

7. The kettle evaporator for a molten salt steam generation system as described in claim 6, characterized in that: A demister (14) is provided on the inner wall of the evaporator (3) in the area corresponding to the steam outlet (10).

8. The kettle evaporator for a molten salt steam generation system as described in claim 1, characterized in that: The bottom of the first tube box (1) and the second tube box (2) are provided with a salt-draining port (8).

9. The kettle evaporator for a molten salt steam generation system as described in claim 1, characterized in that: The top of the evaporator (3) is provided with a manhole (15), and a sealed door is provided at the manhole (15).

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