A molten salt steam generator

Abstract

The present application relates to a kind of fused salt steam generator, simplify existing fused salt steam generator volume, weight, reduce investment cost and manufacturing difficulty, improve heat exchange efficiency, reduce flow resistance;Fused salt steam generator includes: high-pressure side heat exchange plate, low-pressure side heat exchange plate, first steam drum, second steam drum, high-pressure side inlet pipe box, high-pressure side outlet pipe box, low-pressure side inlet pipe box and low-pressure side outlet pipe box, high-pressure side heat exchange plate and low-pressure side heat exchange plate surface are distributed with flow channel, high-pressure side heat exchange plate flow channel is divided into superheating zone, evaporation zone, preheating zone, in preheating zone close to high-pressure side inlet pipe box and with it communication for multiple Z-shaped flow channel, along flow direction, the end of Z-shaped flow channel is connected with multiple straight flow channel. Multiple high-pressure side and low-pressure side heat exchange plate orthogonally and alternately closely stacked, the front and back of stacked heat exchange plate are provided with metal cover plate, stacked heat exchange plate and metal cover plate are welded to form a complete cuboid, form the core body of fused salt steam generator.

Description

Technical Field

[0001] This invention relates to the technical field of solar thermal power generation, and in particular to a molten salt steam generator. Background Technology

[0002] In the field of solar thermal power generation, the molten salt steam generator system is the hub for energy conversion between the concentrating solar collector system and the power generation system. It is the core equipment that uses liquid binary molten salt as the heat transfer and heat storage medium to convert solar radiation energy into high-temperature, high-pressure steam to drive the steam turbine for power generation. It directly affects the stability and safety of the operation of the solar thermal power plant.

[0003] The existing molten salt steam generator system in a solar thermal power plant mainly consists of a preheater, a steam generator, a steam drum, and a superheater. It achieves the preheating, evaporation, and superheating of the water medium through staged heat exchange with high-temperature molten salt. The main heat exchangers are typically of the following types: a horizontal shell-and-tube heat exchanger for the preheater, a vertical shell-and-tube heat exchanger for the steam generator, and a horizontal U-tube shell-and-tube heat exchanger for the superheater.

[0004] Problems with existing molten salt steam generator systems: 1) The system has a complex structure, requiring various main heat exchange equipment and auxiliary equipment such as preheaters, steam generators, and superheaters. Often, the steam generator and steam drum are separated, connected by complex riser and downcomer pipes, resulting in high equipment costs and a large footprint. 2) The heat exchange equipment uses shell-and-tube heat exchangers, with molten salt flowing through the shell side and high-pressure steam / water flowing through the heat exchange tubes. High temperature and pressure conditions result in thick tube walls, low heat transfer coefficients, and long tube lengths, leading to significant steam / water flow resistance and high operating costs. 3) The tube sheet connection and the connection between the tube sheet and the shell in shell-and-tube heat exchangers are both welded, resulting in numerous welds and significant design and manufacturing difficulties. Welding defects and residual stress are prone to exist in the welds, leading to structural thermal stress and thermal fatigue under long-term high-temperature and frequent start-up and shutdown conditions, resulting in a high risk of heat exchanger leakage. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a molten salt steam generator that simplifies the complex system composition of existing molten salt steam generators, reduces the volume and weight of shell-and-tube heat exchangers, lowers investment costs, reduces design and welding manufacturing difficulties, improves the heat exchange efficiency of the main heat exchanger, and reduces flow resistance.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a molten salt steam generator, characterized in that the molten salt steam generator comprises: a high-pressure side heat exchange plate, a low-pressure side heat exchange plate, a first steam drum, a second steam drum, a high-pressure side inlet pipe box, a high-pressure side outlet pipe box, a low-pressure side inlet pipe box, and a low-pressure side outlet pipe box. Flow channels are distributed on the surfaces of both the high-pressure side heat exchange plate and the low-pressure side heat exchange plate. Multiple high-pressure side heat exchange plates and low-pressure side heat exchange plates are stacked alternately and tightly. After stacking, metal cover plates are provided on both the front and back sides of the heat exchange plates. The stacked heat exchange plates and metal cover plates are welded to form a complete cuboid, forming the core of the molten salt steam generator.

[0009] A high-pressure side outlet pipe box is welded to the upper side of the core, and a high-pressure outlet pipe is welded to the high-pressure side outlet pipe box. A high-pressure side inlet pipe box is welded to the lower side of the other side of the core, and a high-pressure inlet pipe is welded to the high-pressure side outlet pipe box. A low-pressure side inlet pipe box is welded to the top of the core, and a low-pressure inlet pipe is welded to the low-pressure side inlet pipe box.

[0010] The bottom end of the core is welded with a low-pressure side outlet pipe box, and a low-pressure side outlet pipe is welded onto the low-pressure side outlet pipe box. The first steam drum and the second steam drum are respectively welded to both sides of the core.

[0011] Furthermore, the flow channel distribution area of ​​the high-pressure side heat exchange plate is characterized as follows: from top to bottom, it is divided into three areas: superheated zone A, evaporation zone B, and preheating zone C. In the preheating zone C, there are multiple Z-shaped flow channels close to and connected to the high-pressure side inlet pipe box. Along the flow direction, the ends of the Z-shaped flow channels are connected to multiple direct flow channels.

[0012] In superheated zone A, near and connected to the high-pressure side outlet pipe box are multiple Z-shaped flow channels, and the starting end of the Z-shaped flow channel is connected to multiple direct flow channels.

[0013] In evaporation zone B, all channels are Z-shaped, and two channels are connected to the direct current channels of preheating zone C and superheating zone A respectively. The two Z-shaped channels are connected to the lower half of the first steam drum and the second steam drum on both sides of the core.

[0014] Furthermore, both the first steam drum and the second steam drum are semi-cylindrical or semi-elliptical cylindrical metal cavities;

[0015] The upper part of the first steam drum and the second steam drum are connected by two Z-shaped flow channels that extend upward. Several perforated plates are installed inside the first steam drum and the second steam drum. One end of the perforated plate is welded to the crossbeam and the other end is welded to the inner wall of the steam drum, dividing the steam drum into multiple fan-shaped areas.

[0016] The perforated plate is uniformly arranged with several through holes. Starting from the crossbeam and moving along the radial direction of the steam drum, the diameter of the through holes gradually increases. The through holes of adjacent perforated plates are staggered along the radial direction of the steam drum.

[0017] Furthermore, at the bottom of the steam drum, between several perforated plates, several fins are arranged.

[0018] Furthermore, the flow channel of the low-pressure side heat exchange plate is formed by the gaps between several airfoil-shaped fins, and the distribution of the airfoil-shaped fins corresponds to the division of the high-pressure side heat exchange plate into three regions, A', B', and C', from top to bottom.

[0019] Furthermore, in regions A' and C', several small airfoil-shaped fins are distributed in the areas near the low-pressure side inlet pipe box and the low-pressure side outlet pipe box. In region A', the small airfoil-shaped fins transform into large airfoil-shaped fins along the downward flow direction of the molten salt, while in region C', the opposite is true: along the downward flow direction, the large airfoil-shaped fins transform into small airfoil-shaped fins.

[0020] In region B', all the fins are small airfoil-shaped.

[0021] Furthermore, the cross-section of the flow channel is semi-circular or semi-elliptical.

[0022] Furthermore, after stacking, metal cover plates are installed on both the front and back sides of the heat exchange plates using a vacuum solid-state diffusion welding process.

[0023] (III) Beneficial Effects

[0024] Compared with the prior art, the present invention provides a molten salt steam generator with the following advantages: it adopts a printed circuit board heat exchanger and forms micro heat exchange channels on the surface of the heat exchange plate by photochemical etching process, which has strong pressure resistance, can significantly reduce the wall thickness between heat exchange channels, reduce heat exchange thermal resistance, reduce the volume and weight of steam generator, and reduce welding defects in the core of steam generator by diffusion welding, resulting in high structural reliability.

[0025] By optimizing the flow channel distribution areas of the high-pressure and low-pressure heat exchange plates, heat exchange is enhanced and the overall flow resistance of the core is reduced, while also decreasing the volume and weight of the steam generator. The connection method between the flow channels of the high-pressure and low-pressure heat exchange plates and the steam drum integrates the steam generator with the originally separate steam drum, resulting in a more compact volume and saving space and metal material usage. The steam drum's design features, along with the internal perforated plates and fins, improve steam-water separation efficiency, enabling the evaporation zone to generate higher quality saturated steam. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the high-pressure side flow channel and the arrangement of the inlet and outlet pipe boxes;

[0028] Figure 3 This is a schematic diagram of the arrangement of the low-pressure side flow channel and the inlet and outlet pipe boxes;

[0029] Figure 4 These are cross-sectional views of the first and second steam drums;

[0030] Figure 5 This is a top view of the perforated plate structure.

[0031] The following labels are used in the attached diagram: 1. High-pressure side heat exchange plate; 2. Z-shaped flow channel; 3. Straight-through channel; 4. First steam drum; 4'. Second steam drum; 6. High-pressure side inlet pipe box; 7. High-pressure inlet pipe; 8. High-pressure side outlet pipe box; 9. High-pressure outlet pipe; 10. Low-pressure side heat exchange plate; 11. Small airfoil fin; 12. Large airfoil fin; 13. Low-pressure side outlet pipe; 14. Low-pressure side outlet pipe box; 15. Low-pressure side inlet pipe box; 16. Low-pressure inlet pipe; 17. Cover plate. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a molten salt steam generator, such as... Figures 1-3 As shown, the molten salt steam generator includes: a high-pressure side heat exchange plate 1, a low-pressure side heat exchange plate 10, a first steam drum 4, a second steam drum 4', a high-pressure side inlet pipe box 6, a high-pressure side outlet pipe box 8, a low-pressure side inlet pipe box 15, and a low-pressure side outlet pipe box 14.

[0034] like Figure 1 As shown, the core of the molten salt steam generator is a cuboid, vertically arranged, with its long side perpendicular to the horizontal plane. The high-pressure side heat exchange plate 1 and the low-pressure side heat exchange plate 10 are thin, flat metal plates. The surfaces of the heat exchange plates (front or both sides) are distributed with flow channels (the cross-section of the flow channels is semi-circular or semi-elliptical) processed by photochemical etching. Multiple rectangular high-pressure side heat exchange plates 1 and low-pressure side heat exchange plates 10 are stacked alternately and tightly. After stacking, metal cover plates 17 are provided on both the front and back sides of the heat exchange plates. The stacked heat exchange plates and metal cover plates 17 are welded together using a vacuum solid-phase diffusion welding process (advantages of this connection process: the interface of the materials to be welded does not melt, welding does not require solder, the welding strength is higher than fusion welding, and there are fewer welding defects) to form a complete cuboid, thus forming the core of the molten salt steam generator. A high-pressure side outlet pipe box 8 (see...) is welded (fusion welded) to the upper side of the core. Figure 2 A high-pressure outlet pipe 9 is welded to the high-pressure side outlet pipe box 8. A high-pressure side inlet pipe box 6 (see...) is welded to the lower part of the other side of the core. Figure 2A high-pressure inlet pipe 7 is welded to the high-pressure side outlet pipe box 6. A low-pressure side inlet pipe box 15 (see...) is welded to the top of the core. Figure 3 A low-pressure inlet pipe 16 is welded to the low-pressure side inlet pipe box 15; a low-pressure side outlet pipe box 14 is welded to the bottom end of the core (see...). Figure 3 The low-pressure side outlet pipe 13 is welded onto the low-pressure side outlet pipe box 14. The first steam drum 4 and the second steam drum 4' are welded onto both sides of the core body, respectively.

[0035] like Figure 2 As shown, the flow channel distribution characteristics of the high-pressure side heat exchange plate 1 are as follows: from top to bottom, it is divided into three regions: superheated zone A, evaporation zone B, and preheated zone C. In preheated zone C, multiple Z-shaped flow channels 2 are located near and connected to the high-pressure side inlet pipe box 6. Along the flow direction, the ends of the Z-shaped flow channels 2 are connected to multiple direct flow channels 3. In superheated zone A, multiple Z-shaped flow channels 2 are located near and connected to the high-pressure side outlet pipe box. The starting ends of the Z-shaped flow channels 2 are connected to multiple direct flow channels 3. The beneficial effects of the above are: the resistance coefficient of the Z-shaped flow channels 2 is larger than that of the direct flow channels 3, but the heat transfer coefficient is higher. The heat transfer temperature difference is smaller in the area near the high-pressure side inlet. The Z-shaped flow channels 2 are used to enhance heat transfer and improve heat transfer capacity. The resistance coefficient of the direct flow channels 3 is smaller. They are located in areas with larger heat transfer temperature differences to ensure that the flow resistance in preheated zone C is at a low level.

[0036] In evaporation zone B, all channels are Z-shaped 2, which are divided into two paths connecting to the direct current channels 3 of preheating zone C and superheating zone A. The two Z-shaped channels 2 are respectively connected to the lower halves of the first steam drum 4 and the second steam drum 4' on both sides of the core. The steam drums are semi-cylindrical or semi-elliptical cylindrical metal cavities. The upper halves of the first steam drum 4 and the second steam drum 4' are also connected to the two Z-shaped channels 2 extending upwards. Several perforated plates 5 are installed inside the first steam drum 4 and the second steam drum 4'. One end of the perforated plate 5 is welded to the crossbeam 502, and the other end is welded to the inner wall of the steam drum, dividing the steam drum into multiple fan-shaped areas (see...). Figure 4 A plurality of through holes 503 are evenly arranged on the perforated plate 5, extending radially from the crossbeam 502 along the steam drum (the crossbeam 502 is located inside the steam drum, welded to the side of the core, at the midpoint of the two Z-shaped flow channels 2, see...). Figure 1 The diameter of the through holes 503 gradually increases to balance the steam-water resistance of the Z-shaped flow channels 2 with different friction lengths, making the flow rate within the Z-shaped flow channels 2 more uniform. The through holes 503 of adjacent perforated plates 5 are arranged in a staggered manner along the radial direction of the steam drum, creating baffles during the steam-water inlet and outlet of the steam drum, facilitating steam-water separation. At the bottom of the steam drum, between the perforated plates 5, several fins 504 are provided to increase the heat conduction area at the bottom of the steam drum. Water droplets that are efficiently heated and intercepted by the perforated plates 5 and fall to the bottom of the steam drum are regenerated into saturated steam.

[0037] The beneficial effects of the above are as follows: In the B channel of the evaporation zone, water exchanges heat with the molten salt on the low-pressure side at a small temperature difference, resulting in phase change boiling and a large heat exchange. This area is entirely configured with Z-shaped channels 2 to enhance heat exchange and reduce the heat exchange area. The Z-shaped channels 2 are divided into two paths, which are connected to the steam drums on both sides of the core to increase the number of steam drums. The purpose is to increase the buffer volume of the steam drums and the steam-water separation space, thereby increasing the stability of steam production. The perforated plates 5 are used for steam-water separation. The through holes 503 of the perforated plates 5 are arranged in a staggered pattern along the radial direction of the steam drum, so that the steam and water flow into and out of the steam drum are deflected between several perforated plates 5 to intercept water droplets, facilitating the passage of steam and achieving efficient steam-water separation. The blocked water droplets fall to the bottom of the steam drum and are heated by the fins at the bottom to continue generating saturated steam, thus producing high-quality saturated steam.

[0038] The flow channels of the low-pressure side heat exchange plate 10 are formed by the gaps between several airfoil-shaped fins, which are also processed on the surface of the heat exchange plate by photochemical etching. The distribution of the airfoil-shaped fins corresponds to the division of the high-pressure side heat exchange plate 1 into three regions, A', B', and C', from top to bottom.

[0039] In regions A' and C', several small airfoil-shaped fins 11 are distributed near the low-pressure side inlet pipe box 15 and the low-pressure side outlet pipe box 14. In region A', along the downward flow direction of the molten salt, the small airfoil-shaped fins 11 transform into large airfoil-shaped fins 12 (both the width in the horizontal direction and the length in the vertical direction increase). In region C', the opposite occurs: along the downward flow direction, the large airfoil-shaped fins 12 transform into small airfoil-shaped fins 11. In region B', all fins are small airfoil-shaped fins 11. The beneficial effect is similar to the arrangement of regions A, B, and C of the high-pressure side heat exchange plate 1, increasing the fin density near the pressure-side inlet in region A' and near the outlet in region C', increasing the heat exchange area, and enhancing heat exchange in areas with small temperature differences on the low-pressure side. Region B', corresponding to the high-pressure side heat exchange plate B, undergoes a vaporization phase change, requiring a large heat flux density; therefore, region B' is entirely composed of small fins, increasing the heat exchange area per unit volume. Enhanced heat transfer reduces the size of the heat exchange plates, thereby reducing the volume of the core. The large airfoil fins 12 are used in areas with low heat flux density and form larger flow channels with lower flow resistance, which can reduce the overall flow resistance of the low-pressure side heat exchange plates.

[0040] Workflow:

[0041] High-temperature molten salt (~565℃, ~0.5MPa) enters the low-pressure side inlet pipe box 15 through the low-pressure inlet pipe 16. It flows from top to bottom through the flow channels (2-5mm in diameter) formed between the airfoil-shaped fins in zones A', B', and C'. After heat exchange with the high-pressure side steam-water working fluid, it becomes low-temperature molten salt and enters the low-pressure side outlet pipe box 14, exiting through the low-pressure side outlet pipe 13. The high-pressure side steam-water and the low-pressure side molten salt form a counter-current heat exchange, which is the optimal heat exchange method and yields the highest heat exchange efficiency.

[0042] High-pressure softened water (~255℃, ~14.7MPa) enters the high-pressure side inlet pipe box 6 through the high-pressure inlet pipe 7, and then enters the high-pressure side flow channel (flow channel diameter 2mm) to exchange heat with the molten salt on the low-pressure side. Preheating is completed in area C, and the high-pressure softened water temperature rises to ~335℃. Then it enters area B to continue exchanging heat with the molten salt at a small temperature difference. The high-pressure softened water begins to boil, forming a steam-water mixture that flows upwards in two streams into the two steam drums on both sides of the core. The two steam drums act as steam-water separators and steam buffer tanks. Two streams of saturated steam flow out from the upper part of the two steam drums, and then merge upwards into one stream, which enters area A to exchange heat with the high-temperature molten salt. The saturated steam is heated into superheated steam (540℃) and then enters the high-pressure side outlet pipe box 8. Finally, it flows out from the high-pressure side outlet pipe, thus producing high-quality superheated steam.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A molten salt steam generator, characterized in that, The molten salt steam generator includes: a high-pressure side heat exchange plate, a low-pressure side heat exchange plate, a first steam drum, a second steam drum, a high-pressure side inlet pipe box, a high-pressure side outlet pipe box, a low-pressure side inlet pipe box, and a low-pressure side outlet pipe box. The surfaces of the high-pressure side heat exchange plate and the low-pressure side heat exchange plate are distributed with flow channels. Multiple high-pressure side heat exchange plates and low-pressure side heat exchange plates are stacked tightly and alternately. After stacking, metal cover plates are provided on the front and back sides of the heat exchange plates. The stacked heat exchange plates and metal cover plates are welded to form a complete cuboid, which forms the core of the molten salt steam generator. A high-pressure side outlet pipe box is welded to the upper side of the core, and a high-pressure outlet pipe is welded to the high-pressure side outlet pipe box. A high-pressure side inlet pipe box is welded to the lower side of the other side of the core, and a high-pressure inlet pipe is welded to the high-pressure side outlet pipe box. A low-pressure side inlet pipe box is welded to the top of the core, and a low-pressure inlet pipe is welded to the low-pressure side inlet pipe box. The bottom end of the core is welded with a low-pressure side outlet pipe box, and a low-pressure side outlet pipe is welded on the low-pressure side outlet pipe box. The first steam drum and the second steam drum are respectively welded to both sides of the core. The flow channel distribution area of ​​the high-pressure side heat exchange plate is divided into three areas from top to bottom: superheated zone A, evaporation zone B, and preheating zone C. In preheating zone C, there are multiple Z-shaped flow channels close to and connected to the high-pressure side inlet pipe box. Along the flow direction, the ends of the Z-shaped flow channels are connected to multiple direct flow channels. In superheated zone A, near and connected to the high-pressure side outlet pipe box are multiple Z-shaped flow channels, and the starting end of the Z-shaped flow channel is connected to multiple direct flow channels. In evaporation zone B, all channels are Z-shaped, and two channels are connected to the direct current channels of preheating zone C and superheating zone A respectively. The two Z-shaped channels are connected to the lower half of the first steam drum and the second steam drum on both sides of the core.

2. The molten salt steam generator according to claim 1, characterized in that, Both the first and second steam drums are semi-cylindrical or semi-elliptical cylindrical metal cavities. The upper part of the first steam drum and the second steam drum are connected by two Z-shaped flow channels that extend upward. Several perforated plates are installed inside the first steam drum and the second steam drum. One end of the perforated plate is welded to the crossbeam and the other end is welded to the inner wall of the steam drum, dividing the steam drum into multiple fan-shaped areas. The perforated plate is uniformly arranged with several through holes. Starting from the crossbeam and moving along the radial direction of the steam drum, the diameter of the through holes gradually increases. The through holes of adjacent perforated plates are staggered along the radial direction of the steam drum.

3. A molten salt steam generator according to claim 2, characterized in that, At the bottom of the steam drum, between several perforated plates, there are several fins.

4. A molten salt steam generator according to claim 3, characterized in that, The flow channel of the low-pressure side heat exchange plate is formed by the gaps between several airfoil-shaped fins. The distribution of the airfoil-shaped fins corresponds to the division of the high-pressure side heat exchange plate into three regions, A', B', and C', from top to bottom.

5. A molten salt steam generator according to claim 4, characterized in that, In regions A' and C', several small airfoil-shaped fins are distributed near the low-pressure side inlet pipe box and the low-pressure side outlet pipe box. In region A', the small airfoil-shaped fins transform into large airfoil-shaped fins along the downward flow direction of the molten salt, while in region C', the opposite is true: along the downward flow direction, the large airfoil-shaped fins transform into small airfoil-shaped fins. In region B', all the fins are small airfoil-shaped.

6. A molten salt steam generator according to claim 5, characterized in that, The cross-section of the flow channel is semi-circular or semi-elliptical.

7. A molten salt steam generator according to claim 6, characterized in that, After stacking, metal cover plates are installed on both the front and back sides of the heat exchange plates using a vacuum solid-state diffusion welding process.

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