Falling film evaporator

Abstract

The invention belongs to the technical field of evaporation equipment, and particularly relates to a falling film evaporator which is characterized in that the lower end of a shell pass cylinder A is connected with a lower tube plate, the upper end of a shell pass cylinder B is connected with an upper tube plate, and the shell pass cylinder A is connected with the shell pass cylinder B through an expansion joint; the two ends of the heat exchange tube are connected with the upper tube plate and the lower tube plate respectively, the heat exchange tube penetrates through the baffle plate, and the baffle plate is fixed through a pull rod, a pipe spacer and a nut. The shell pass cylinder A is provided with a condensate water outlet, and the shell pass cylinder B is provided with a steam inlet; the lower tube box is connected with the lower tube plate through a lower tube box flange assembly; a liquid outlet is formed in the bottom of the lower tube box; the upper tube box A is connected with the upper tube plate, the upper tube box A is provided with a liquid inlet, the upper tube box B is provided with a gas outlet, the upper tube box A and the upper tube box B are connected through a flange assembly, an outer cover and an inner ring weir are arranged in the upper tube box, and a film distributor is arranged at the upper end of the heat exchange tube. The device is simple in structure, uniform in liquid distribution, high in evaporation efficiency, convenient to disassemble, clean and replace, and low in maintenance cost and technical difficulty.

Description

Technical Field

[0001] The invention belongs to the technical field of evaporation equipment, in particular to a falling film evaporator. Background Art

[0002] Falling film evaporation is to add the material from the upper tube box of the falling film evaporator heating chamber, and evenly distribute it to each heat exchange tube after passing through the film distributor. Under the action of gravity, vacuum induction and airflow, it flows from top to bottom in a uniform film. During the flow process, it is heated and vaporized by the shell side heating medium, and the generated steam and liquid phase enter the separation chamber of the evaporator together. After the vapor and liquid are fully separated, the steam enters the condenser for condensation or enters the next effect evaporator as a heating medium, thereby realizing multi-effect operation, and the liquid phase is discharged from the separation chamber.

[0003] In the existing falling film evaporator, the material usually enters the cavity directly from the top, and the material distribution is uneven before entering; due to the uneven distribution of the material in the heat exchange tube, the material causes scaling on the inner wall of the heat exchange tube, thereby affecting the performance of the heat exchange tube and reducing the evaporation efficiency and processing capacity of the evaporator. Or the film distributor of the conventional falling film evaporator is a non-detachable structure, which is not easy to disassemble, clean and replace, and the maintenance cost is high. Summary of the invention

[0004] In view of the above problems existing in the traditional falling film evaporator, the present invention provides a falling film evaporator. The falling film evaporator can effectively distribute the material evenly in each heat exchange tube, so that the material forms a uniform and stable film in each heat exchange tube, and the evaporation efficiency is high. It is easier to disassemble, clean and replace while ensuring the evaporation efficiency, thereby reducing maintenance costs and technical difficulties.

[0005] The objective of the present invention is achieved through the following technical solutions: The present invention comprises a shell side and a tube side, wherein the shell side comprises a shell side cylinder A, an expansion joint and a shell side cylinder B, wherein the upper end of the shell side cylinder A is connected to the lower end of the shell side cylinder B through an expansion joint, the lower end of the shell side cylinder A is connected to a lower tube sheet, the upper end of the shell side cylinder B is connected to an upper tube sheet, a condensate outlet is provided on the shell side cylinder A, and a steam inlet is provided on the shell side cylinder B; the tube side comprises a lower tube box located below the shell side and an upper tube box located above the shell side, the upper end of the lower tube box is connected to the lower tube sheet, a liquid outlet is provided at the bottom of the lower tube box, the upper tube box comprises an upper tube box A and an upper tube box B connected to each other, and the upper tube box A is connected to the upper tube sheet; a plurality of heat exchange tubes and a plurality of baffles are respectively provided in the shell side, each of the baffles is fixed between the upper tube sheet and the lower tube sheet from top to bottom through a spacing tube, a tie rod and a nut, and each of the heat exchange tubes is provided with a Each baffle passes through, and the upper and lower ends of each heat exchange tube are respectively connected to the upper tube plate and the lower tube plate; an outer cover with a notch is installed in the upper tube box, and an inner ring weir is provided in the outer cover and is located on the outer periphery of the upper end of each heat exchange tube, and a liquid inlet and a gas outlet are respectively opened on the upper tube box; a film distributor is installed on the upper end of each heat exchange tube, and the film distributor includes a fixed tube and an adjusting tube, the upper end of the heat exchange tube is inserted into the lower end of the fixed tube and remains relatively fixed, and the lower end of the adjusting tube is inserted into the upper end of the fixed tube and remains relatively fixed; the inner wall surface of the lower end of the fixed tube has a reduced diameter section, and the upper end surface of the heat exchange tube and the reduced diameter section of the inner wall surface of the lower end of the fixed tube are squeezed to form a line seal, and the inner wall surface of the upper end of the fixed tube is sealed with the outer surface of the lower end of the adjusting tube; the upper end of the adjusting tube is circumferentially opened with a tangential groove for overflowing materials, and the inner wall surface of the lower end of the adjusting tube is a conical surface A.

[0006] Wherein: the upper end surface of the fixed tube is an inclined surface, and the outer surface of the adjusting tube is provided with a positioning block, and the positioning block is always in contact with the upper end surface of the fixed tube; after the adjusting tube is inserted into the fixed tube, the positioning block falls on the upper end surface of the fixed tube, and the height of the film spreader is adjusted by rotating the adjusting tube, and the positioning block remains fixed with the fixed tube after being rotated into place, and the positioning block moves along the upper end surface of the fixed tube during the rotation of the adjusting tube.

[0007] The inner wall surface of the upper end of the fixed tube is provided with a stopper, and the stopper is located below the conical surface A. When the positioning block rotates with the adjusting tube to the lowest point of the inclined surface, the lower end surface of the adjusting tube abuts against the stopper, and the adjusting tube is positioned and supported by the stopper and the positioning block.

[0008] The reduced diameter section of the inner wall surface at the lower end of the fixed tube is a conical surface B, the lower end diameter of the conical surface B is larger than the upper end diameter, and the upper end surface of the heat exchange tube is squeezed with the conical surface B to form a line seal.

[0009] An annular groove is formed on the outer surface of the lower end of the adjusting tube, an O-ring is placed in the annular groove, and the outer surface of the lower end of the adjusting tube is sealed with the inner wall surface of the upper end of the fixing tube through the O-ring.

[0010] There are a plurality of tangential grooves which are evenly arranged along the circumferential direction. The tangential grooves are divided into two grooves with different depths, and the grooves with two different depths are arranged at intervals.

[0011] The fixed tube and the heat exchange tube as well as the fixed tube and the regulating tube are fixed by means of top screws.

[0012] The top screws that are kept fixed between the fixed tube and the heat exchange tube are evenly distributed along the circumferential direction.

[0013] The lower end of the outer cover is notched and the upper end is an open structure. The outer cover is connected to the upper tube box A through a rib plate B. A cone A is provided inside the upper end of the outer cover. The cone A is connected to the inner wall of the outer cover through the rib plate A. A baffle is provided inside the lower end of the outer cover. A positioning plate is provided on the outer side of the inner ring weir. The inner ring weir is fixed inside the outer cover through the positioning plate and the baffle, and is tightly fitted to the upper tube plate.

[0014] The liquid inlet is opened at a position near the lower end of the upper tube box A, the gas outlet is arranged on the upper tube box B, the inner extension pipe of the gas outlet is located above the outer cover, and a cone B is arranged at the upper end of the inner extension pipe of the gas outlet.

[0015] The advantages and positive effects of the present invention are: 1. The present invention sets an outer cover above the heat exchange tube, and sets a cone inside the outer cover, which can prevent the condensate generated during the outflow of the evaporated gas from the tube box from directly falling into the heat exchange tube to destroy the uniform film formation, thereby ensuring the stability of the film formation.

[0016] 2. The inner ring weir of the present invention can distribute the liquid for the first time, so that the liquid flows evenly to each film distributor, ensuring that the liquid level at each film distributor is consistent, so that the film distributors can spread the film at the same time.

[0017] 3. The film distributor of the present invention can effectively prevent materials from entering the heat exchange tube from between the fixed tube and the heat exchange tube and between the regulating tube and the fixed tube through the line seal between the lower end of the fixed tube and the heat exchange tube and the O-ring seal between the upper end of the fixed tube and the regulating tube, ensuring that all materials enter the film distributor from the tangential grooves provided at the upper end of the regulating tube, flow along the inner wall of the film distributor into the inner wall of the heat exchange tube, and form a uniform and stable liquid film from top to bottom along the inner wall of the heat exchange tube.

[0018] 4. The positioning block on the regulating tube in the film spreader of the present invention cooperates with the upper inclined surface of the fixed tube, which can easily and accurately adjust the height of the film spreader, placing the film spreader connected to each heat exchange tube at the same plane height to ensure the consistency of the film forming timing in each heat exchange tube.

[0019] 5. The tangential groove on the upper end of the regulating tube and the conical surface on the inner wall of the lower end of the film distributor of the present invention can ensure that the material flows directly to the heat exchange tube wall, making the film formation more uniform and improving the heat exchange efficiency.

[0020] 6. The film distributor of the present invention adopts a non-welded structure, which makes it easier to disassemble, clean and replace while ensuring stable, uniform and efficient film formation, and reduces maintenance costs and installation technical difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional view of the internal structure of the present invention; Figure 2 It is a cross-sectional view of the internal structure of the membrane distributor of the present invention; Figure 3 for Figure 2 Middle A-direction view; Figure 4 for Figure 2 Middle B-B sectional view; Figure 5 for Figure 2 A partial enlarged view of the upper middle part; Figure 6 for Figure 5 A top view of the structure; Figure 7 This is one of the partial enlarged stereograms of the outer cover and cone A of the present invention; Figure 8 The second partial enlarged stereoscopic view of the outer cover and cone A of the present invention; Fig. 9 The third partial enlarged stereoscopic view of the outer cover and cone A of the present invention; Among them: 1 is the liquid outlet, 2 is the lower tube box, 3 is the lower tube sheet, 4 is the condensate outlet, 5 is the shell side cylinder A, 6 is the expansion joint, 7 is the shell side cylinder B, 8 is the support, 9 is the upper tube sheet, 10 is the liquid inlet, 11 is the upper tube box A, 12 is the flange assembly, 13 is the outer cover, 14 is the cone A, 15 is the upper tube box B, 16 is the cone B, 17 is the gas outlet, 18 is the rib plate A, 19 is the baffle, 20 is the rib plate B, 21 is the positioning plate, 22 is the inner ring weir, 23 is the film distributor, 24 is the steam inlet, 25 is the heat exchange tube, 26 is the baffle, 27 is the distance tube, 28 is the tie rod, 29 is the nut, and 30 is the lower tube box flange assembly; 2301 is a fixed tube, 2302 is an O-ring, 2303 is an adjusting tube, 2304 is a positioning stopper, 2305 is a top screw, 2306 is a stopper, 2307 is a tangential groove, 2308 is a cone surface A, 2309 is a cone surface B, and 2310 is an annular groove. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings.

[0023] like Figure 1 and Figures 7 to 9 As shown, the present invention includes a shell side and a tube side, the shell side includes a shell side cylinder A5, an expansion joint 6 and a shell side cylinder B7, the upper end of the shell side cylinder A5 is connected to the lower end of the shell side cylinder B7 through the expansion joint 6, the lower end of the shell side cylinder A5 is connected to the lower tube plate 3, the upper end of the shell side cylinder B7 is connected to the upper tube plate 9, a condensate outlet 4 is provided on the shell side cylinder A5, and a steam inlet 24 is provided on the shell side cylinder B7; the condensate outlet 4 of this embodiment is provided at a position near the lower end of the shell side cylinder A5 and above the lower tube plate 3, the steam inlet 24 is provided at a position near the upper end of the shell side cylinder B7 and below the upper tube plate 9, a support 8 is fixedly connected to the shell side cylinder B7, and the support 8 is located below the steam inlet 24. The tube side includes a lower tube box 2 located below the shell side and an upper tube box located above the shell side. The upper end of the lower tube box 2 is connected to the lower tube sheet 3 through the lower tube box flange assembly 30. The bottom of the lower tube box 2 is provided with a liquid outlet 1. The upper tube box includes an upper tube box A11 and an upper tube box B15. The lower end of the upper tube box A11 is connected to the upper tube sheet 9. The upper end of the upper tube box A11 is connected to the upper tube box B15 through the flange assembly 12. The lower tube box flange assembly 30 and the flange assembly 12 of this embodiment are both prior art and are not described in detail here.

[0024] A plurality of heat exchange tubes 25 and a plurality of baffles 26 are respectively arranged in the shell side. Each baffle 26 is fixed from top to bottom between the upper tube sheet 9 and the lower tube sheet 3 by means of a distance tube 27, a tie rod 28 and a nut 29. Adjacent baffles 26 are respectively fixed on the left and right sides of the axial section of the shell side. The structure in which the baffles 26 of this embodiment are fixed from top to bottom between the upper tube sheet 9 and the lower tube sheet 3 by means of a distance tube 27, a tie rod 28 and a nut 29 is prior art and will not be described in detail here. Each heat exchange tube 25 passes through each baffle 26, and the upper and lower ends of each heat exchange tube 25 are respectively connected to the upper tube sheet 9 and the lower tube sheet 3. An outer cover 13 with a notch is installed in the upper tube box, and an inner ring weir 22 is arranged in the outer cover 13 and is located on the outer periphery of the upper end of each heat exchange tube 25. The outer cover 13 has a notch at the lower end and an open structure at the upper end. The outer cover 13 is connected to the upper tube box A11 through a rib plate B20. A cone A14 is provided inside the upper end of the outer cover 13. The cone A14 is connected to the inner wall of the outer cover 13 through a rib plate A18. A baffle 19 is provided inside the lower end of the outer cover 13. A positioning plate 21 is provided outside the inner ring weir 22. The inner ring weir 22 is fixed inside the outer cover 13 through the positioning plate 21 and the baffle 19, and is tightly fitted with the upper tube plate 9. The upper tube box is provided with a liquid inlet 10 and a gas outlet 17. The liquid inlet 10 of this embodiment is provided at a position close to the lower end of the upper tube box A11. The gas outlet 17 is provided on the upper tube box B15. The inner extension pipe of the gas outlet 17 is located above the outer cover 13, and a cone B16 is provided at the upper end of the inner extension pipe of the gas outlet 17.

[0025] In this embodiment, a film distributor 23 is installed at the upper end of each heat exchange tube 25. Figures 1 to 4 As shown, the film distributor 23 includes a fixed tube 2301 and an adjusting tube 2303. The upper end of the heat exchange tube 25 is inserted into the lower end of the fixed tube 2301 and kept relatively fixed. The lower end of the adjusting tube 2303 is inserted into the upper end of the fixed tube 2301 and kept relatively fixed. The inner wall surface of the lower end of the fixed tube 2301 has a reduced diameter section. The upper end surface of the heat exchange tube 25 and the reduced diameter section of the inner wall surface of the lower end of the fixed tube 2301 are squeezed to form a line seal. The inner wall surface of the upper end of the fixed tube 2301 is sealed with the outer surface of the lower end of the adjusting tube 2303. The upper end of the adjusting tube 2303 is provided with a tangential groove 2307 for overflowing materials along the circumferential direction. The inner wall surface of the lower end of the adjusting tube 2303 is a conical surface A2308, and the lower end diameter of the conical surface A2308 is larger than the upper end diameter.

[0026] In this embodiment, the heat exchange tube 25, the fixed tube 2301 and the regulating tube 2303 are all hollow circular tubes, and their axial center lines are collinear.

[0027] In this embodiment, the upper end face of the fixed tube 2301 is an inclined surface, and a positioning block 2304 is welded on the outer surface of the adjusting tube 2303, and the positioning block 2304 is always in contact with the upper end face of the fixed tube 2301; after the adjusting tube 2303 is inserted into the fixed tube 2301, the positioning block 2304 falls on the upper end face of the fixed tube 2301, and the height of the film spreader 23 is adjusted by rotating the adjusting tube 2303, and it remains fixed with the fixed tube 2301 after being rotated into place, and the positioning block 2304 moves along the upper end face of the fixed tube 2301 during the process of rotating the adjusting tube 2303. In this embodiment, a stop 2306 is provided on the inner wall surface of the upper end of the fixed tube 2301, and the stop 2306 is located below the conical surface A2308. When the positioning block 2304 rotates to the lowest point of the inclined surface along with the adjusting tube 2303, the lower end surface of the adjusting tube 2303 abuts against the stop 2306, and the adjusting tube 2303 is jointly positioned and supported by the stop 2306 and the positioning block 2304.

[0028] In this embodiment, the reduced diameter section of the inner wall surface of the lower end of the fixed tube 2301 is a conical surface B2309, the lower end diameter of the conical surface B2309 is larger than the upper end diameter, and the upper end surface of the heat exchange tube 25 is squeezed with the conical surface B2309 to form a line seal.

[0029] In this embodiment, an annular groove 2310 is formed on the outer surface of the lower end of the adjusting tube 2303 , and an O-ring 2302 is placed in the annular groove 2310 . The outer surface of the lower end of the adjusting tube 2303 is sealed with the inner wall surface of the upper end of the fixing tube 2301 through the O-ring 2302 .

[0030] In this embodiment, there are multiple tangential grooves 2307, which are evenly arranged along the circumference. The tangential grooves 2307 are divided into two grooves with different depths, and the two grooves with different depths are arranged at intervals. Figure 5 , Figure 6 As shown, four tangential grooves 2307 with a depth of L1 and four tangential grooves 2307 with a depth of L2 are respectively opened at the upper end of the regulating tube 2303, and the tangential grooves 2307 with a depth of L1 and the tangential grooves 2307 with a depth of L2 are arranged at intervals.

[0031] In this embodiment, the fixed tube 2301 and the heat exchange tube 25 and the fixed tube 2301 and the regulating tube 2303 are fixed by means of the top screws 2305. The top screws 2305 that are fixed between the fixed tube 2301 and the heat exchange tube 25 are evenly distributed along the circumferential direction, and the top screws 2305 that are fixed between the fixed tube 2301 and the regulating tube 2303 are only used to restrict the regulating tube 2303 from coming out of the fixed tube 2301, so the number and the setting position are not required.

[0032] The upper tube box A11 of this embodiment is in direct contact with the material and is made of titanium material with good corrosion resistance; the upper tube box B15 is not in direct contact with the material and is made of low-priced stainless steel material, which can greatly reduce the manufacturing cost.

[0033] The working principle of the present invention is: High-temperature steam enters from the steam inlet 24, flows evenly inside the shell-side cylinder B7 and the shell-side cylinder A5 along the path formed by the baffle 26 in the shell side, heats each heat exchange tube 25, and the steam condensate generated during the flow flows out from the condensate outlet 4; the material enters the upper tube box through the liquid inlet 10, and flows into the outer side of the inner ring weir 22 through the notch set on the outer cover 13. As the material liquid level rises, the material flows evenly from the inner wall of the inner ring weir 22 to the upper tube plate 9, and the material liquid level rises twice. When it reaches the tangential opening at the upper end of the regulating tube 2303, the material flows into the upper tube plate 9. When the material reaches the groove 2307 with a deeper depth, less material will flow downward. When more and more material reaches the tangential groove 2307 with a shallower depth, more material will flow downward. This design facilitates the distribution of materials and can make the material distribution in the heat exchange tube 25 more uniform. The conical surface A2308 on the inner side of the lower end of the regulating tube 2303 can ensure that the material flows downward closely against the wall of the regulating tube 2303, and finally flows evenly to the heat exchange tube 25 through the fixed tube 2301, so that the material flows downward along the inner wall of the heat exchange tube 25 in a film-like manner. The material flowing downward evenly is heated by the heat exchange tube 25 and evaporates on the inner wall of the heat exchange tube 25. The liquid that is not evaporated flows out from the liquid outlet 1 due to gravity, and the gas formed by evaporation flows upward from the center of the heat exchange tube 25 and finally flows out from the gas outlet 17. The condensate generated during the outflow of the rising gas will flow back to the outside of the inner ring weir 22 along the outer cover 13 and the outer sides of the cones A14 and B16 due to the obstruction of the outer cover 13 and the cones A14 and B16, and then repeat the above cycle to evaporate again.

[0034] The positioning block 2304 on the regulating tube 2303 cooperates with the inclined surface at the upper end of the fixed tube 2301 to adjust the height of the film spreader 23 and place the film spreader 23 connected to each heat exchange tube 25 at the same plane height to ensure the consistency of the film forming timing in each heat exchange tube 25.

[0035] The technical solutions disclosed in the present invention are not limited to the technical solutions disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A falling film evaporator, comprising a shell side and a tube side, wherein the shell side comprises a shell side cylinder A (5), an expansion joint (6) and a shell side cylinder B (7), wherein the upper end of the shell side cylinder A (5) is connected to the lower end of the shell side cylinder B (7) via the expansion joint (6), the lower end of the shell side cylinder A (5) is connected to a lower tube sheet (3), the upper end of the shell side cylinder B (7) is connected to an upper tube sheet (9), the shell side cylinder A (5) is provided with a condensate outlet (4), and the shell side cylinder B (7) is provided with a steam inlet (24); the tube side comprises a lower tube box (2) located below the shell side and an upper tube box located above the shell side, the upper end of the lower tube box (2) is connected to the lower tube sheet (3) ), the bottom of the lower tube box (2) is provided with a liquid outlet (1), the upper tube box comprises an upper tube box A (11) and an upper tube box B (15) connected to each other, the upper tube box A (11) is connected to the upper tube plate (9); a plurality of heat exchange tubes (25) and a plurality of baffles (26) are respectively provided in the shell side, each of the baffles (26) is fixed from top to bottom between the upper tube plate (9) and the lower tube plate (3) by means of a spacing tube (27), a tie rod (28) and a nut (29), each of the heat exchange tubes (25) passes through each baffle (26), and the upper and lower ends of each of the heat exchange tubes (25) are respectively connected to the upper tube plate (9) and the lower tube plate (3); the characteristics are as follows: An outer cover (13) with a notch is installed in the upper tube box, and an inner ring weir (22) is provided in the outer cover (13) and is located on the outer periphery of the upper end of each heat exchange tube (25). The upper tube box is provided with a liquid inlet (10) and a gas outlet (17). A film distributor (23) is installed on the upper end of each heat exchange tube (25), and the film distributor (23) includes a fixed tube (2301) and a regulating tube (2303). The upper end of the heat exchange tube (25) is inserted into the lower end of the fixed tube (2301) and kept relatively fixed. The regulating tube (2303) is provided with a liquid inlet (10) and a gas outlet (17). The lower end is inserted into the upper end of the fixed tube (2301) and maintained relatively fixed; the inner wall surface of the lower end of the fixed tube (2301) has a reduced diameter section, the upper end surface of the heat exchange tube (25) and the reduced diameter section of the inner wall surface of the lower end of the fixed tube (2301) are squeezed to form a line seal, and the inner wall surface of the upper end of the fixed tube (2301) is sealed with the outer surface of the lower end of the regulating tube (2303); the upper end of the regulating tube (2303) is provided with a tangential groove (2307) for overflowing materials along the circumferential direction, and the inner wall surface of the lower end of the regulating tube (2303) is a conical surface A (2308).

2. The falling film evaporator according to claim 1, characterized in that: The upper end surface of the fixed tube (2301) is an inclined surface, and a positioning block (2304) is provided on the outer surface of the adjusting tube (2303), and the positioning block (2304) is always in contact with the upper end surface of the fixed tube (2301); after the adjusting tube (2303) is inserted into the fixed tube (2301), the positioning block (2304) falls on the upper end surface of the fixed tube (2301), and the height of the film distributor (23) is adjusted by rotating the adjusting tube (2303), and after being rotated into place, the adjusting tube (2303) remains fixed to the fixed tube (2301), and the positioning block (2304) moves along the upper end surface of the fixed tube (2301) during the process of rotating the adjusting tube (2303).

3. The falling film evaporator according to claim 2, characterized in that: The inner wall surface of the upper end of the fixed tube (2301) is provided with a stopper (2306), and the stopper (2306) is located below the conical surface A (2308). When the positioning stopper (2304) rotates with the adjusting tube (2303) to the lowest point of the inclined surface, the lower end surface of the adjusting tube (2303) abuts against the stopper (2306), and the adjusting tube (2303) is positioned and supported by the stopper (2306) and the positioning stopper (2304).

4. The falling film evaporator according to claim 1, characterized in that: The reduced diameter section of the inner wall surface at the lower end of the fixed tube (2301) is a conical surface B (2309), the lower end diameter of the conical surface B (2309) is larger than the upper end diameter, and the upper end surface of the heat exchange tube (25) and the conical surface B (2309) are squeezed to form a linear seal.

5. The falling film evaporator according to claim 1, characterized in that: An annular groove (2310) is provided on the outer surface of the lower end of the regulating tube (2303), an O-ring (2302) is placed in the annular groove (2310), and the outer surface of the lower end of the regulating tube (2303) is sealed with the inner wall surface of the upper end of the fixed tube (2301) via the O-ring (2302).

6. The falling film evaporator according to claim 1, characterized in that: The tangential grooves (2307) are multiple and are evenly arranged along the circumferential direction. The tangential grooves (2307) are divided into two grooves with different depths, and the grooves with two different depths are arranged at intervals.

7. The falling film evaporator according to claim 1, characterized in that: The fixed tube (2301) and the heat exchange tube (25) as well as the fixed tube (2301) and the regulating tube (2303) are both fixed by means of a top screw (2305).

8. The falling film evaporator according to claim 7, characterized in that: The top screws (2305) that are kept fixed between the fixed tube (2301) and the heat exchange tube (25) are evenly distributed in the circumferential direction.

9. The falling film evaporator according to claim 1, characterized in that: The outer cover (13) has a notch at the lower end and an open structure at the upper end. The outer cover (13) is connected to an upper tube box A (11) via a rib plate B (20). A cone A (14) is provided inside the upper end of the outer cover (13). The cone A (14) is connected to an inner wall of the outer cover (13) via a rib plate A (18). A baffle plate (19) is provided inside the lower end of the outer cover (13). A positioning plate (21) is provided on the outer side of the inner ring weir (22). The inner ring weir (22) is fixed inside the outer cover (13) via the positioning plate (21) and the baffle plate (19), and is tightly fitted to the upper tube plate (9).

10. The falling film evaporator according to claim 1, characterized in that: The liquid inlet (10) is opened at a position close to the lower end of the upper tube box A (11), the gas outlet (17) is arranged on the upper tube box B (15), the inner extension pipe of the gas outlet (17) is located above the outer cover (13), and a cone B (16) is provided at the upper end of the inner extension pipe of the gas outlet (17).

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