Falling film evaporator

Abstract

This invention discloses a falling film evaporator, relating to the field of evaporator technology. The falling film evaporator includes: a shell, and a first tube sheet and a second tube sheet located at the upper and lower ends of the shell's inner cavity, respectively. The first and second tube sheets sequentially divide the shell into a first tube box with a tube-side inlet at the top, a heat exchange chamber containing multiple heat exchange tubes, and a second tube box with a tube-side liquid outlet at the bottom. A double-layer distributor is disposed below the tube-side inlet within the first tube box. The double-layer distributor includes a first distribution plate and a second distribution plate, with the first distribution plate horizontally opposite to the second distribution plate via a locking mechanism. This invention solves the problem in traditional falling film evaporators where the falling film head is installed at the end of the heat exchange tubes on the upper tube sheet. Material is distributed into the tubes through the falling film head, but deformation after tube sheet welding leads to inconsistent material distribution in each tube after the falling film head is installed, resulting in inconsistent flow rates.

Description

TECHNICAL FIELD

[0001] The present application relates to the evaporator technical field, especially to a falling film evaporator. BACKGROUND

[0002] The falling film evaporator is a kind of equipment for evaporation separation, and is widely used in fine chemical industry, mainly used in petroleum chemical industry, fine chemical industry, polysilicon, organic silicon downstream product, silicone oil and other projects;

[0003] The falling film evaporation mainly uses hot water, steam, high-temperature heat-conducting oil and other materials as heat source to heat the material in the tube, and the material in the tube flows from top to bottom through the inner wall of the heat exchange tube to form a film on the inner wall, which is constantly evaporated under the heating of the high-temperature material in the shell side, and the material in the tube constantly absorbs heat during the heating process, and then starts to evaporate after absorbing latent heat of vaporization when the heat absorption reaches saturation temperature, which is used for purification process or separation of materials, and different boiling points of materials are used for separation;

[0004] The traditional falling film evaporator adopts falling film head installed at the end of the heat exchange tube of the upper tube plate, and the material is distributed to the inside of the tube through the falling film head and flows downward in the inside, but because the tube plate is deformed after welding, the material distribution of each tube is inconsistent after the installation of the falling film head, thereby causing the inconsistent flow of the distribution, and further causing the problem of poor effect of the evaporator or even evaporation failure, and currently there is no effective solution. SUMMARY

[0005] The present application provides a falling film evaporator to solve the above problems in the prior art.

[0006] Technical scheme: a falling film evaporator, comprising: a shell, and a first tube plate and a second tube plate respectively located at the upper and lower ends of the inner cavity of the shell, the first tube plate and the second tube plate sequentially separate the shell into a first tube box with a tube inlet at the top, a heat exchange cavity with a plurality of heat exchange tubes, and a second tube box with a tube outlet at the bottom; a double-layer distributor is arranged below the tube inlet in the first tube box, the double-layer distributor comprises: a first distribution disc and a second distribution disc, the first distribution disc is horizontally arranged opposite to the second distribution disc through a locking mechanism; a plurality of first distribution holes are uniformly arranged on the first distribution disc; a second distribution hole is arranged on the second distribution disc and opposite to the plurality of first distribution holes; the second distribution hole is provided with a through hole in the circumferential direction, and the diameter of the through hole is smaller than the diameter of the second distribution hole; when the liquid enters the double-layer distributor, it flows through the first distribution hole of the first distribution disc and the second distribution hole and the through hole of the second distribution disc in sequence, so that the flow rate of the liquid is stable and smooth.

[0007] As preferred, the shell side wall is provided with a first conical draft tube near the side of the first tube plate, and the first conical draft tube is provided with a first shell pass outlet.

[0008] As preferred, the shell is provided with a first jacket opposite to the first shell pass outlet, and the first jacket is used for uniformly diffusing steam.

[0009] As preferred, the shell side wall is provided with a second conical draft tube near the side of the second tube plate, and the second conical draft tube is provided with a shell pass inlet.

[0010] As preferred, the shell is provided with a second jacket opposite to the shell pass inlet, and the second jacket is used for uniformly diffusing steam.

[0011] As preferred, the shell side wall is provided with a second shell pass outlet away from the first shell pass outlet and near the first tube plate.

[0012] As preferred, the second tube box side wall is provided with a tube pass gas outlet away from the shell pass inlet and near the second tube plate.

[0013] As preferred, the second tube box inner wall and opposite to the tube pass gas outlet is provided with a demisting structure, and the demisting structure comprises a bent baffle fixedly connected with the second tube box inner wall, and a demister is arranged between the inner wall of the bent baffle and the inner wall of the second tube box.

[0014] As preferred, the outer edge top of the first distribution disc is provided with a first surrounding plate, and the outer edge top of the second distribution disc is provided with a second surrounding plate.

[0015] As preferred, the upper surface and the inner surface of the first distribution disc and the second distribution disc and the inner surface of the first surrounding plate and the second surrounding plate are all polished, and the surface roughness is 0.1-0.3 μm.

[0016] As preferred, the heat exchange pipe is a corrugated pipe, and the internal surface roughness of the corrugated pipe is 0.2-0.4 μm.

[0017] In order to solve the problem that the traditional falling film head is suitable for material evaporation and separation, but there is a gap between the falling film head and the pipe, which leads to easy fouling inside and easy blockage of the flow channel, the application also provides the following technical scheme:

[0018] The falling film evaporator comprises a shell, a first tube plate and a second tube plate respectively arranged at upper and lower ends of an inner cavity of the shell, and the first tube plate and the second tube plate sequentially divide the shell into a first tube box with a tube-passing inlet at the top, a heat exchange cavity with a plurality of heat exchange tubes arranged therein, and a second tube box with a tube-passing liquid outlet at the bottom; an arc surface is arranged at a top of the heat exchange tube and a junction of the first tube plate, and an arc radius of the arc surface is in direct proportion to a film forming length.

[0019] As preferred, a double-layer distributor is arranged below the tube-passing inlet in the first tube box, and the double-layer distributor comprises a first distribution disc and a second distribution disc, the first distribution disc is arranged horizontally opposite to the second distribution disc through locking mechanisms, a plurality of first liquid distribution holes are uniformly arranged on the first distribution disc, a second liquid distribution hole is arranged opposite to the first liquid distribution holes on the second distribution disc, and a through hole is arranged in a circumferential direction of the second liquid distribution hole, and a diameter of the through hole is smaller than that of the second liquid distribution hole; when liquid enters the double-layer distributor, the liquid flows through the first liquid distribution holes of the first distribution disc and the second liquid distribution hole and the through hole of the second distribution disc in sequence, so that the flow rate of the liquid is stable and smooth.

[0020] Beneficial effects: in the embodiment of the present application, the double-layer distributor is additionally arranged, when liquid enters the double-layer distributor, the liquid flows through the first liquid distribution holes of the first distribution disc and the second liquid distribution hole and the through hole of the second distribution disc in sequence, so that the flow rate of the liquid is stable and smooth, the purpose of fluid stabilization is achieved, the technical effect of uniform flow of the heat exchange tubes is achieved, and the technical problem of the traditional falling film evaporator that the falling film head is arranged at the end of the upper tube plate heat exchange tube, the material is distributed to the inside of the tube through the falling film head, and then flows downward, but because the tube plate is deformed after welding, the material distribution of each tube is inconsistent after the falling film head is installed, the flow rate of the distribution is inconsistent, the effect of the evaporator is not good, and even the evaporator is invalid. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of the falling film evaporator of the present application;

[0022] Figure 2 is a double-layer distributor structural schematic diagram of the falling film evaporator of the present application;

[0023] Figure 3 is a first distribution disc structural schematic diagram of the falling film evaporator of the present application;

[0024] Figure 4 is a second distribution disc structural schematic diagram of the falling film evaporator of the present application;

[0025] Figure 5This is a schematic diagram of the heat exchange tube structure of the falling film evaporator of the present invention;

[0026] Figure 6 This is a schematic diagram of the tube laminar flow layer structure of the falling film evaporator of the present invention;

[0027] Figure 7 This is a schematic diagram of the corrugated tube laminar flow layer structure of the falling film evaporator of the present invention;

[0028] Figure 8 This is a schematic diagram of a conventional evaporator structure with a falling film head for the falling film evaporator of the present invention;

[0029] Figure 9 This is a schematic diagram of the structure of the falling film evaporator of the present invention without a falling film head;

[0030] Figure 10 This is a cross-sectional view (AA) of the falling film evaporator of the present invention.

[0031] The attached figures are labeled as follows: 1. Shell; 2. First tube sheet; 3. Second tube sheet; 4. Tube-side inlet; 5. First tube box; 6. Heat exchange tube; 7. Heat exchange chamber; 8. Tube-side liquid outlet; 9. Second tube box; 10. Double-layer distributor; 11. First distribution plate; 12. Second distribution plate; 13. Locking mechanism; 14. First liquid distribution hole; 15. Second liquid distribution hole; 16. Through hole; 17. First conical guide tube; 18. First shell-side outlet; 19. First jacket; 20. Second conical guide tube; 21. Shell-side inlet; 22. Second jacket; 23. Second shell-side outlet; 24. Tube-side gas outlet; 25. Demisting structure; 26. Bending baffle; 27. Demister; 28. First enclosure plate; 29. ​​Second enclosure plate; 30. First channel; 31. Central channel; 32. Arc surface. Implementation

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

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 As shown, this application relates to a falling film evaporator. This falling film evaporator includes: a shell 1, and a first tube sheet 2 and a second tube sheet 3 located at the upper and lower ends of the inner cavity of the shell 1, respectively. The first tube sheet 2 and the second tube sheet 3 sequentially divide the shell 1 into a first tube box 5 with a tube-side inlet 4 at the top, a heat exchange chamber 7 with multiple heat exchange tubes 6 inside, and a second tube box 9 with a tube-side liquid outlet 8 at the bottom. By assembling multiple components, a preliminary structural prototype of the evaporator can be formed. The shell 1 refers to the outer shell 1 of the evaporator, which has the effect of accommodating and supporting other components, thereby forming a complete evaporator structure. By fixing the first tube sheet 2 and the second tube sheet 3 at the upper and lower ends of the shell 1, the shell 1 can be divided into cavities, thereby achieving its corresponding functions. The first tube sheet 2 refers to the upper tube sheet, used to separate the space between the first tube box 5 (upper tube box) and the heat exchange chamber 7, thereby preventing material from directly entering the heat exchange chamber 7. The second tube sheet 3 refers to the lower tube sheet, used to separate the space between the heat exchange chamber 7 and the lower tube box, thereby achieving a good physical separation effect.

[0037] like Figures 5-7As shown, the heat exchange tube 6 is a corrugated tube with an internal surface roughness of 0.2-0.4 μm. This addresses the problem that in traditional falling film heads, the liquid distribution in the tube side only flows along the inside of the tube after installation. While heat exchange tubes 6 are typically smooth tubes, facilitating material flow and evaporation, their surface area is too small, requiring a very long device. Excessive tube length leads to more ineffective sections at the bottom, negatively impacting heat transfer efficiency. In this application, corrugated pipes are used in falling film evaporators. The pipe materials can be selected from the following specifications: S30408, S30403, S31608, S31603, S32168, S22253, S32507, etc. Pipe specifications can be selected in diameters of 19X1, 19X0.8, 25X0.8-25X1.6, 25X2, 32X0.8, 32X1.0, 32X1.6, 32X2, 32X25, 38X1.5, 38X2, 38X2.5, 45X1.65, 45X2.77, 45X3, 48X1.65, 48X2, 48X2.77, 48X3, with outer diameters ranging from 19-90 mm. Tubes with wall thicknesses ranging from 0.8 to 5 mm are processed using rolling or pressing techniques to create corrugated tubes. The troughs and crests of these tubes are 5-15% of the tube's outer diameter, and the corrugation spacing is 1-5 times the outer diameter. The use of corrugated tubes significantly reduces the thickness of the laminar flow layer formed on the inner wall of the tubes, a key factor affecting heat transfer resistance. Furthermore, the tube ends of the tube sheet are flat-welded. Traditional tube ends extend 3-5 mm outwards, which hinders fluid flow into the heat exchange tubes 6 and downwards along the wall during operation. Flat-welded tube ends largely solve the problem of tube end blockage. Simultaneously, the tube sheet welding deformation is carefully controlled using a cross-welding method, reducing the deformation to within 1 mm. This ensures consistent flow of liquid into each heat exchange tube 6, guaranteeing that each tube operates at full load.

[0038] like Figures 2-4As shown, a double-layer distributor 10 is installed below the tube inlet 4 inside the first tube box 5. The double-layer distributor 10 includes a first distribution plate 11 and a second distribution plate 12. The first distribution plate 11 is horizontally opposite to the second distribution plate 12 via a locking mechanism 13. This addresses the problem of excessive turbulence caused by the large diameter of the tube inlet 4 in traditional single-layer distribution plates, where the fluid flows too fast onto the plate and has not yet been properly organized. Therefore, this application uses a double-layer distribution plate, ensuring a stable and smooth flow after the fluid passes through both plates. Simultaneously, the flatness of the double-layer distributor 10 is maintained within ±1mm, ensuring uniform flow rate at each orifice after the fluid passes through the distribution plate, thus preparing the fluid for entry into the heat exchange tube 6. Furthermore, the locking mechanism 13 includes bolts fixedly connected to the upper surface of the first tube sheet 2. Two sets of nuts are positioned on the bolts at preset locations, with the first distribution plate 11 and the second distribution plate 12 positioned between each set of nuts. By employing a double-nut locking mechanism 13, the traditional distributor, due to its fixed and spaced tube structure and welded structure, faces challenges in controlling the flatness of the tube sheet and distributor during fixing, especially in falling film evaporators. These factors, often overlooked in traditional falling film evaporators, significantly impact efficiency. The flatness of the tube sheet after welding and the distributor, both neglected in traditional models, greatly affect the evaporator's performance. Welding deformation of the tube sheet is difficult to achieve due to welding stress, and adjusting the distributor's flatness is crucial. These factors directly influence material flow, affecting both the tube sheet and distributor's flatness, thus impacting the evaporator's separation efficiency.

[0039] The first distribution plate 11 has a plurality of first distributing holes 14 evenly distributed on it; by having a plurality of first distributing holes 14, the liquid can be initially divided. The second distribution plate 12 has a plurality of second distributing holes 15 disposed opposite to the plurality of first distributing holes 14; by having a plurality of second distributing holes 15, the liquid can be further divided, thereby achieving a uniform flow rate in the pipe. Preferably, the diameter of the first distributing holes 14 is the same as the diameter of the second distributing holes 15, ensuring a smooth flow of liquid from top to bottom. More preferably, the diameter of the first distributing holes 14 is 6-20 mm, achieving a good liquid flow effect.

[0040] The second distribution hole 15 has a through hole 16 arranged circumferentially, the diameter of which is smaller than that of the second distribution hole 15. By providing through holes 16 on the first tube sheet 2 along the circumference of the second distribution hole 15, the uniform flow of liquid can be further improved. Furthermore, there can be multiple through holes 16. This ensures a more uniform liquid flow while maintaining structural strength and economic efficiency. The number of through holes 16 can be adjusted according to actual usage; more through holes 16 can be added where the flow rate is high, and fewer can be added where the flow rate is low, allowing for flexible use. Simultaneously, the smaller diameter of the through holes 16 compared to the second distribution hole 15 ensures that most of the liquid flows through the distribution hole, thus meeting flow requirements. Preferably, the diameter of the through holes 16 is 3-6 mm, achieving a good auxiliary flow effect.

[0041] When the liquid enters the double-layer distributor 10, it flows sequentially through the first distribution hole 14 of the first distribution plate 11 and the second distribution hole 15 and through hole 16 of the second distribution plate 12, ensuring a stable and smooth flow rate. The liquid to be purified is diverted and stabilized by the first distribution plate 11 and the second distribution plate 12, ensuring that the flow rate and volume of the liquid entering the heat exchange tube 6 meet the actual usage requirements, thus providing a good foundation for subsequent film formation.

[0042] As can be seen from the above description, this application achieves the following technical effects:

[0043] In this embodiment, a double-layer distributor 10 is added. When the liquid enters the double-layer distributor 10, it flows sequentially through the first liquid distribution hole 14 of the first distribution plate 11 and the second liquid distribution hole 15 and through hole 16 of the second distribution plate 12, so that the liquid flow rate is stable and smooth, achieving the purpose of fluid flow stabilization. This achieves the technical effect of uniform flow of heat exchange tube 6, and solves the technical problem of traditional falling film evaporators where the falling film head is installed at the end of the heat exchange tube 6 on the upper tube sheet. The material is distributed into the tube through the falling film head and flows down into the tube. However, due to the deformation of the tube sheet after welding, the material distribution of each tube is inconsistent after the falling film head is installed, resulting in inconsistent flow rate and thus poor evaporator performance or even evaporation failure.

[0044] Furthermore, a first conical guide tube 17 is provided on the side wall of the shell 1 near the first tube sheet 2, and a first shell-side outlet 18 is provided on the first conical guide tube 17. By providing the first conical guide tube 17, the effect of directional steam movement can be achieved, thereby improving the steam utilization rate and thus improving the film formation effect of the heat exchange tube 6. At the same time, by providing the first shell-side outlet 18 on the side of the first conical guide tube 17 away from the shell 1, the effect of allowing steam to leave the inner cavity of the shell 1 can be achieved.

[0045] like Figure 10As shown, a first jacket 19 is provided inside the shell 1, opposite to the first shell-side outlet 18. The first jacket 19 is used to uniformly diffuse steam. By providing the first jacket 19, the effect of steam diffusion in the inner cavity of the shell 1 can be further improved, thereby achieving a uniform effect on the heat exchange tube 6. Preferably, the first jacket 19 has multiple first channels 30, which are symmetrically arranged about the horizontal center line. The aperture of the multiple first channels 30 increases from the shell-side inlet 21 to the inside of the shell 1, so as to disperse and circulate the steam, thereby achieving a uniform effect on the heat exchange tube. At the same time, the first channels 30 are not directly opposite the shell-side inlet 21, which can prevent steam from directly entering the first channel 30 from the shell-side inlet 21, resulting in excessive steam pressure at the initial position, which in turn leads to insufficient steam pressure in subsequent channels, thus affecting the uniform dispersion of steam. For example, the apertures or opening lengths of the multiple first channels 30 are L1, L2, L3, L4, and L5, respectively, where L1 < L2 < L3 < L4 < L5. By adopting the above-mentioned opening method, uneven steam dispersion due to pressure or temperature differences during steam flow in the shell can be avoided. Therefore, the diameter of the first channel 30, which is far from the shell inlet 21, is increased to ensure smooth steam entry. More preferably, multiple central channels 31 are also provided inside the shell 1. By providing multiple central channels 31, the effect of steam entering the center of the shell 1 can be achieved.

[0046] Furthermore, a second conical guide tube 20 is provided on the side wall of the shell 1 near the second tube sheet 3, and a shell-side inlet 21 is provided on the second conical guide tube 20. By providing the second conical guide tube 20, the steam can be directed, thereby improving the steam utilization rate and thus improving the film formation effect of the heat exchange tube 6. Simultaneously, by providing the shell-side inlet 21 on the side of the second conical guide tube 20 away from the shell 1, the steam can be directed into the inner cavity of the shell 1, thereby filling the inner cavity of the shell 1 with steam. Furthermore, a second jacket 22 is provided inside the shell 1 opposite to the shell-side inlet 21, and the second jacket 22 is used for uniformly dispersing the steam. The second jacket 22 further improves the diffusion effect of steam within the inner cavity of the shell 1, thereby achieving a uniform effect on the heat exchange tube 6. By using a shell-side inlet 21 and a first shell-side outlet 18, respectively, jacketed cylinders allow steam to enter the shell 1 and then the jacket. Holes are opened in the shell 1 within the jacket, allowing steam to continuously enter the shell 1 through the openings around the perimeter of the cylinder, evenly flowing into the tubes and tube bridge gaps, thus scouring the tube bundle. Combined with the circular and annular plates of the shell side, this uniform scouring achieves evaporation uniformity. Preferably, the shell-side inlet 21 is an annular inlet, allowing steam to enter the shell 1 more evenly and ensuring a more uniform outer wall of the tubes. Furthermore, vent holes are designed on the tube sheet to promptly remove non-condensable gases from the shell side. Timely removal of non-condensable gases greatly increases the contact opportunity between steam and the tubes, improving the condensation efficiency of the tube outer wall.

[0047] Furthermore, a second shell-side outlet 23 is provided on the side wall of the shell 1 away from the first shell-side outlet 18 and close to the first tube sheet 2. The second shell-side outlet 23 refers to the outlet where non-condensable gas is discharged in the shell side, which enables the non-condensable gas to be discharged from the inner cavity of the shell 1, thereby improving the displacement efficiency inside the shell 1 and thus improving the displacement effect.

[0048] Furthermore, a tube-side gas outlet 24 is provided on the side wall of the second tube box 9 away from the shell-side inlet 21 and close to the second tube sheet 3. This enables the tube-side gas to be discharged from the inner cavity of the shell 1, thereby achieving good separation and purification effects. Even further, a demisting structure 25 is provided on the inner wall of the second tube box 9, opposite to the tube-side gas outlet 24. The demisting structure 25 includes a bent baffle 26 fixedly connected to the inner wall of the second tube box 9, and a demister 27 is provided between the inner wall of the bent baffle 26 and the inner wall of the second tube box 9. By adding a demister structure 25 at the tube gas outlet 24, the problem of traditional falling film evaporators without a demister 27 is solved. The material after steaming exits directly from the side opening on the lower tank. Since steam often carries materials with similar boiling points, this application sets up a baffle and a demister structure 25. The baffle performs preliminary separation of steam and material. The liquid is sprayed onto the lower baffle and guided to one side. In addition, the steam passes through the rain-like curtain of the guide and enters the demister 27 for secondary separation. In this way, the quality of the steam after passing through the demister 27 is greatly improved.

[0049] Furthermore, a first enclosure plate 28 is provided at the top of the outer edge of the first distribution plate 11, and a second enclosure plate 29 is provided at the top of the outer edge of the second distribution plate 12. By providing the first enclosure plate 28 and the second enclosure plate 29 respectively, the liquid can be gathered, thereby preventing the liquid from flowing directly from the outer edge of the distribution plate, thus ensuring a good diversion effect.

[0050] Furthermore, the upper and inner surfaces of the first distribution disk 11 and the second distribution disk 12, as well as the inner surfaces of the first enclosure plate 28 and the second enclosure plate 29, are all polished, with a surface roughness of 0.1-0.3 μm. By polishing the surfaces through which the liquid flows, the surface roughness meets the preset requirements, thereby improving the efficiency of the flow distribution and reducing resistance. Preferably, the surface roughness is 0.2 micrometers. This is easy to implement and also achieves a mirror effect, thereby reducing resistance and flow distribution in the distributor, and also solving the problem of evaporation of high-viscosity materials.

[0051] To address the problem that while traditional falling film heads are suitable for material evaporation and separation, the gap between the falling film head and the tube leads to easy scaling and blockage of the flow channel, this application also provides the following technical solution:

[0052] like Figures 8-9As shown, a falling film evaporator includes: a shell 1, and a first tube sheet 2 and a second tube sheet 3 located at the upper and lower ends of the inner cavity of the shell 1, respectively. The first tube sheet 2 and the second tube sheet 3 sequentially divide the shell 1 into a first tube box 5 with a tube-side inlet 4 at the top, a heat exchange chamber 7 with multiple heat exchange tubes 6 inside, and a second tube box 9 with a tube-side liquid outlet 8 at the bottom. By assembling multiple components, a preliminary structural prototype of the evaporator can be formed. The shell 1 refers to the outer shell 1 of the evaporator, which has the effect of accommodating and supporting other components, thereby forming a complete evaporator structure. By fixing the first tube sheet 2 and the second tube sheet 3 at the upper and lower ends of the shell 1, the shell 1 can be divided into cavities, thereby achieving its corresponding functions. Among them, the first tube sheet 2 refers to the upper tube sheet, which is used to separate the space of the first tube box 5 (i.e., the upper tube box) from the space of the heat exchange chamber 7, thereby preventing the material from directly entering the heat exchange chamber 7. Among them, the second tube sheet 3 refers to the lower tube sheet, which is used to separate the space of the heat exchange chamber 7 from the space of the lower tube box, thereby achieving a good physical separation effect.

[0053] An arc surface 32 is provided at the top junction of the first tube sheet 2 and the heat exchange tube 6. The radius of the arc surface 32 is proportional to the film formation length. By using a smooth transition at the junction of the upper surface of the first tube sheet 2 and the top of the heat exchange tube 6, i.e., by providing an arc surface 32, the liquid can flow smoothly and without obstruction. This solves the problem that although traditional falling film heads are suitable for material evaporation and separation, there is a gap between the falling film head and the tube, which easily leads to scaling and blockage of the flow channel over time. The arc surface 32 adopts an inward-shrinking welded structure. That is, by making the height of the top of the heat exchange tube 6 lower than the horizontal height of the first tube sheet 2, an inward-shrinking effect is formed, and then the arc surface 32 is formed by welding. The radius of the arc surface 32 is proportional to the film formation length. Simultaneously, the upper surface of the first tube sheet 2 and the inner surface of the heat exchange tube 6 are polished, meaning all surfaces in contact with the material are polished to a surface roughness of 0.38 micrometers. This prevents fluid from dripping and solves the problems of scaling and dripping. The tube ends of the heat exchange tube 6 are rounded, forming a radius (R-corner). The ordinary fillet weld is replaced with a 3.5mm inward reduction, and after welding, it is rounded while keeping the tube end flush with the tube sheet, facilitating more uniform fluid distribution. This also promotes film formation on the inner wall of the tube, making it suitable for large-scale falling film evaporation. The tube length can be increased, making it suitable for large-scale equipment designs. The tube end is scraped... Figure Eight Form, reduce resistance.

[0054] The experimental results are as follows: First, the condition for film formation inside heat exchanger tube 6 is that the Reynolds number of the material flowing on the inner wall of heat exchanger tube 6 should be above 2000-4500 for the best film formation effect.

[0055] II. Therefore, when the radius of curvature of arc surface 32 is R2, the film length is relatively uniform within 3.5 meters and no cracking or dry burning will occur; when the radius of curvature of arc surface 32 is R3, the film length can reach about 4.5 meters; when the radius of curvature of arc surface 32 is R5, the film length can reach about 7 meters, and cracking will basically occur beyond 7 meters; when the radius of curvature of arc surface 32 is R6 or R7, the film length is basically about 9 meters.

[0056] III. The viscosity of the materials used in the experiment was based on 35% alcohol as the experimental simulation basis;

[0057] IV. The film thickness at the inlet of heat exchange tube 6 can reach about 4 mm. The film thickness at the cracked flow is 1.0-1.5 mm. Further down the length of heat exchange tube 6, about 500-800 mm, is the cracked flow zone, which is basically negligible in the calculation. The higher the viscosity of the liquid, the greater the film thickness at the end of the cracked flow.

[0058] 5. The smaller the kinematic viscosity coefficient of the liquid, the smaller the film thickness generated at the end of the heat exchange tube 6, which is more conducive to film formation.

[0059] The working principle of this invention is as follows:

[0060] The purified liquid enters the evaporator cavity through the top inlet of tube-side inlet 4, impacting the double-layer distribution plates. It first passes through the first distribution plate 11 for separation, with the holes on the distribution plate aligned with the center of the tube holes. The liquid flows from the first distribution plate through the second distribution plate 12, which has through-holes 16 distributed around the center of the heat exchange tubes 6. The heat exchange tubes 6 are corrugated pipes with perforations on the tube bridge. Each layer of the distributor is surrounded by a baffle plate, 150-200mm high. Both the baffle plate and the inner surface of the distributor are polished to a smoothness of 0.2 micrometers to ensure unimpeded liquid flow. The flatness of the distributor is within 1mm. After passing through the second distributor, the liquid falls onto the first tube sheet 2.

[0061] The liquid then accumulates and flows into the corrugated tube, continuously gathering on the heat exchange tube 6 and the tube sheet bridge before flowing evenly into the heat exchange tube 6. Because the first tube sheet 2 has excellent flatness, the liquid flows almost uniformly through the inside of the corrugated tube. The tubes and tube sheet are welded using an internal shrinkage weld, and the tube head weld is scraped to form an R-arc surface, which facilitates the uniform distribution of the liquid. After flowing through the corrugated tube, the liquid forms a liquid film on the inner wall of the tube, with the thickness of the liquid film controlled at 1-3 mm.

[0062] When high-temperature steam enters the shell side from the first shell side outlet 18, it first enters the shell side through the jacket, which is located inside the shell 1. The jacket has evenly spaced holes around its perimeter, allowing steam to flow into the shell 1. The steam then flows upwards, continuously contacting the heat exchange tubes 6 as it enters the shell side. After entering the shell side, the steam heats the material inside the bellows. The material inside the bellows begins to evaporate under the heating of the steam. As the steam continues to move upwards, it continuously adds liquid to the bellows. After the liquid evaporates, it exits through the gas outlet on the lower tank, thus achieving liquid purification.

[0063] When the liquid flows into the inner wall of heat exchange tube 6, due to the use of a corrugated pipe, the expansion and contraction of the corrugated pipe repeatedly changes the flow state of the fluid on the inner wall of the tube after the liquid flows into the heat exchange tube 6 from the top. The laminar layer of the liquid is continuously thinned. From the perspective of heat transfer mechanism, the heat transfer resistance comes from three places: first, the convective condensation heat transfer between the outer wall of the tube and the outer wall of the heat exchange tube 6, where the heat transfer coefficient of this convective and condensation heat transfer is very large; second, the thermal resistance of the heat pipe wall thickness, which is basically fixed. The wall thickness of heat exchange tube 6 is basically 2-3 mm thick, and the corrugated pipe thickness can be 0.8-1.2 mm, which can maximize the thermal resistance of the tube wall thickness. The third part of the thermal resistance comes from the evaporative convection heat transfer inside the tube. The liquid flows through the inner wall of the tube, which is 2-3 mm thick. The resistance in this part is mainly determined by the thickness of the laminar flow layer of the liquid on the corrugated tube. Ordinary straight tubes have flat inner walls and a relatively thick laminar flow layer. However, the corrugated inner wall allows the fluid to flow up and down continuously, greatly reducing the thickness of the laminar flow layer. This significantly reduces the thermal resistance of the inner wall of the tube, thus enabling the corrugated tube to achieve a higher heat transfer coefficient, which is about 2-3 times that of ordinary straight tubes of the same area. This can greatly reduce the volume and cost of falling film evaporators.

[0064] The present invention has the following beneficial effects:

[0065] 1. Increases the efficiency of falling film steam turbines by 2-3 times;

[0066] 2. Increase the effective tube area of ​​the falling film evaporator by approximately 25%;

[0067] 3. Reduce the cost of falling film evaporators by 50%.

[0068] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and all such equivalent transformations fall within the protection scope of the present invention.

Claims

1. A falling film evaporator, characterized in that, include: The shell (1) and the first tube sheet (2) and the second tube sheet (3) located at the upper and lower ends of the inner cavity of the shell (1) respectively. The first tube sheet (2) and the second tube sheet (3) sequentially divide the shell (1) into a first tube box (5) with a tube inlet (4) at the top, a heat exchange chamber (7) with multiple heat exchange tubes (6) inside, and a second tube box (9) with a tube liquid outlet (8) at the bottom. A double-layer distributor (10) is provided in the first tube box (5) below the tube inlet (4). The double-layer distributor (10) includes a first distribution plate (11) and a second distribution plate (12). The first distribution plate (11) is horizontally opposite to the second distribution plate (12) through a locking mechanism (13). The first distribution plate (11) is provided with a plurality of first liquid dispensing holes (14) evenly distributed on it; The second distribution plate (12) is provided with a second distribution hole (15) that is directly opposite to a plurality of the first distribution holes (14); The second liquid distribution hole (15) is provided with a through hole (16) in the circumferential direction, and the diameter of the through hole (16) is smaller than the diameter of the second liquid distribution hole (15); When the liquid enters the double-layer distributor (10), it flows sequentially through the first liquid distribution hole (14) of the first distribution plate (11) and the second liquid distribution hole (15) and the through hole (16) of the second distribution plate (12) to make the liquid flow rate stable and smooth. The heat exchange tube (6) is a corrugated tube, and the internal surface roughness of the corrugated tube is 0.2-0.4μm; A second conical guide tube (20) is provided on the side wall of the shell (1) near the second tube sheet (3), and a shell-side inlet (21) is provided on the second conical guide tube (20); The second tube box (9) has a tube gas outlet (24) on the side wall away from the shell inlet (21) and close to the second tube sheet (3); A demisting structure (25) is provided on the inner wall of the second tube box (9) and opposite to the gas outlet (24) of the tube. The demisting structure (25) includes a bent baffle (26) fixedly connected to the inner wall of the second tube box (9). A demister (27) is provided between the inner wall of the bent baffle (26) and the inner wall of the second tube box (9). An arc surface (32) is provided at the top junction of the first tube sheet (2) and the heat exchange tube (6), and the radius of the arc surface (32) is proportional to the film length.

2. The falling film evaporator according to claim 1, characterized in that, A first conical guide tube (17) is provided on the side wall of the shell (1) near the first tube sheet (2), and a first shell-side outlet (18) is provided on the first conical guide tube (17).

3. The falling film evaporator according to claim 2, characterized in that, The shell (1) is provided with a first jacket (19) opposite to the first shell outlet (18), and the first jacket (19) is used to uniformly diffuse steam.

4. The falling film evaporator according to claim 1, characterized in that, The shell (1) is provided with a second jacket (22) opposite to the shell side inlet (21), and the second jacket (22) is used to uniformly diffuse steam.

5. The falling film evaporator according to claim 2, characterized in that, The shell (1) has a second shell outlet (23) on the side wall away from the first shell outlet (18) and close to the first tube sheet (2).

6. The falling film evaporator according to claim 1, characterized in that, The first distribution plate (11) has a first enclosure plate (28) at the top of its outer edge, and the second distribution plate (12) has a second enclosure plate (29) at the top of its outer edge.

7. The falling film evaporator according to claim 6, characterized in that, The upper and inner surfaces of the first distribution disk (11) and the second distribution disk (12), as well as the inner surfaces of the first enclosure plate (28) and the second enclosure plate (29), are all polished, and their surface roughness is 0.1-0.3μm.

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