Falling film evaporator

Abstract

The present invention relates to the technical field of falling film evaporators. Provided is a falling film evaporator, comprising a tower body having an evaporation cavity, the evaporation cavity sequentially having a liquid inlet, a gas inlet, a gas outlet and a liquid outlet from top to bottom, wherein a heat exchange tube is arranged inside the evaporation cavity and has an opening; a liquid intake cylinder is arranged inside the evaporation cavity and has a liquid intake cavity; and the liquid inlet is in communication with the liquid intake cavity, the liquid intake cavity has an outlet located above the opening, and the projection of the opening is located within the projection of the outlet. By means of the technical solution, the problems in the prior art of the poor film formation effect of heat exchange tubes and dimethyl carbonate liquid being prone to adhering to various parts inside a falling film evaporator that are caused by it not being possible to adapt the working principle and feeding mode of the falling film evaporator to an improved rectification process of dimethyl carbonate are solved.

Description

A falling film evaporator Technical Field

[0001] This invention relates to the field of falling film evaporator technology, specifically to a falling film evaporator. Background Technology

[0002] Falling film evaporators are a type of high-efficiency and energy-saving evaporation equipment, widely used in processes such as liquid concentration, solvent recovery, and crystallization in industries such as chemical, food, pharmaceutical, and environmental protection. Their design is based on the principle of falling film evaporation, where liquid raw materials flow along the heat exchange tube wall in the form of a thin film, thereby achieving efficient heat transfer and evaporation.

[0003] In the context of energy conservation and emission reduction, distillation is increasingly used to process dimethyl carbonate. In the traditional process, the air-cooled dimethyl carbonate liquid is pumped into the bottom of the column for evaporation and heat exchange again. This wastes the heat of the original dimethyl carbonate gas and incurs the operating cost of turning the gas into liquid. After entering the bottom of the column, it absorbs heat again. This process is repeated, resulting in a significant waste of thermal energy and fresh steam.

[0004] Therefore, the traditional process was improved by directly introducing the dimethyl carbonate-containing vapor from the top of the distillation column into a centrifugal compressor or screw compressor. The pressurized and heated vapor then enters the bottom of the column. The improved method greatly saves steam usage, and tests have shown that it saves 30% to 40% of energy consumption.

[0005] However, in the improved method, pressurized and heated steam enters the bottom of a tower such as a falling film evaporator. However, due to the working principle and feeding method of the falling film evaporator, the dimethyl carbonate liquid cannot be evenly distributed on the inner wall of the heat exchange tube, resulting in poor film formation inside the heat exchange tube. In severe cases, the liquid may even cause a "dry wall" phenomenon. At the same time, the dimethyl carbonate liquid tends to stick to various parts inside the falling film evaporator, which is not convenient for subsequent cleaning and wastes some of the dimethyl carbonate liquid. Summary of the Invention

[0006] This invention proposes a falling film evaporator, which solves the problems in related technologies where the working principle and feeding method of the falling film evaporator cannot adapt to the improved distillation process of dimethyl carbonate, resulting in poor film formation in the heat exchange tubes and easy adhesion of dimethyl carbonate liquid to various parts of the falling film evaporator.

[0007] The technical solution of the present invention is as follows:

[0008] A falling film evaporator, comprising:

[0009] The tower body has an evaporation chamber, which has a liquid inlet, an air inlet, an air outlet and a liquid outlet from top to bottom.

[0010] A heat exchange tube is disposed inside the evaporation chamber and has an opening;

[0011] A liquid inlet cylinder is disposed inside the evaporation chamber. The liquid inlet cylinder has a liquid inlet cavity, and the liquid inlet port is connected to the liquid inlet cavity. The liquid inlet cavity has an outlet, which is located above the opening, and the projection of the opening is located within the projection of the outlet.

[0012] As a further technical solution, the bottom of the liquid inlet chamber has a plurality of outlets, one end of the heat exchange tube has an opening, and there are a plurality of heat exchange tubes, with the outlets and the openings corresponding one-to-one.

[0013] As a further technical solution, the outlet faces the opening, both the outlet and the opening are circular, coaxially arranged, and the cross-sectional area of ​​the outlet is larger than the cross-sectional area of ​​the opening.

[0014] As a further technical solution, the liquid inlet cylinder is pot-shaped, the cross-sectional area of ​​the liquid inlet cylinder remains constant from bottom to top and then gradually decreases, the inner wall of the liquid inlet cylinder has an arc-shaped flow surface, and the bottom center of the liquid inlet cavity has several outlets.

[0015] As a further technical solution, the top of the liquid inlet chamber has a liquid inlet channel, which extends through the liquid inlet.

[0016] As a further technical solution, the liquid inlet cylinder is movably disposed within the evaporation chamber, and further includes:

[0017] A blocking component is provided at the bottom of the inlet cylinder. After the inlet cylinder is moved, both the outlet and the blocking component move closer to or further away from the opening. The blocking component is used to adjust the flow rate at the opening.

[0018] As a further technical solution, it also includes:

[0019] A connecting plate is disposed within the liquid inlet chamber;

[0020] A support rod is provided at both ends of the connecting plate and the bottom of the liquid inlet cylinder, the support rod is located inside the liquid inlet chamber, and the blocking component is provided at the bottom of the liquid inlet cylinder through the connecting plate.

[0021] As a further technical solution, the blocking component has a through portion and a blocking portion in sequence from top to bottom. The through portion is disposed on the connecting plate and passes through the outlet, and the blocking component is located outside the liquid inlet cylinder.

[0022] As a further technical solution, it also includes:

[0023] A support plate is disposed inside the evaporation chamber, below the liquid inlet cylinder, and the openings of several heat exchange tubes are all disposed through the support plate;

[0024] A horn ring is disposed on the opening, the maximum cross-sectional area of ​​the horn ring is greater than the cross-sectional area of ​​the outlet, and the cross-sectional area of ​​the horn ring gradually increases from near to far from the opening.

[0025] As a further technical solution, the cross-sectional area of ​​the blocking part gradually increases from top to bottom and then gradually decreases. The blocking part is located inside the horn ring, and there are annular guide surfaces above and below the blocking part. A guide gap is formed between the annular guide surface below the blocking part and the inner wall of the horn ring.

[0026] The working principle and beneficial effects of this invention are as follows:

[0027] In this invention, to address the inability of traditional falling film evaporators to adapt to the improved dimethyl carbonate distillation process, and to avoid the uneven distribution of dimethyl carbonate liquid on the inner wall of the heat exchange tubes and adhesion to various parts of the evaporator due to the working principle and feeding method of the falling film evaporator, an inlet cylinder is added inside the traditional falling film evaporator. Unlike the traditional structure where the dimethyl carbonate liquid enters the evaporation chamber through the inlet at the top of the tower and gradually adheres to other components as it enters several sets of heat exchange tubes, the liquid flows directly from the inlet to the inlet cylinder. Finally, it distributes to the openings of each heat exchange tube through the outlet at the bottom of the inlet cylinder, forming a flow film. This facilitates the evaporation of the flow film within the heat exchange tubes by the high-temperature steam entering the tower from the gas inlet, thus fulfilling the function of the falling film evaporator. Finally, the concentrated product is discharged from the liquid outlet, and excess gas is discharged from the gas outlet.

[0028] The use of the inlet cylinder collects the dimethyl carbonate liquid that was originally scattered throughout the falling film evaporator, and then distributes it out. This avoids excessive adhesion of the dimethyl carbonate liquid to various parts of the falling film evaporator, which would make subsequent cleaning difficult. Instead, the inlet cylinder can be directly removed for cleaning, or an online cleaning mode can be used, where cleaning fluid is injected into the inlet during normal operation. This reduces downtime and improves equipment availability and maintenance efficiency. At the same time, the inlet cylinder is installed in the tower body with bolts and other fasteners, placing it above the heat exchange tubes, which facilitates the distribution of dimethyl carbonate liquid. The overall structure is also more compact, making it easier to install and maintain.

[0029] Furthermore, the projection of the opening at one end of the heat exchange tube is located within the projection of the outlet, which allows dimethyl carbonate liquid to flow smoothly into the heat exchange tube. Even if there is a certain gap between the inlet cylinder and the heat exchange tube, the dimethyl carbonate liquid flowing out of the outlet will not spread everywhere, increasing the need for subsequent cleaning steps. Instead, it will flow into the heat exchange tube from around the opening, ensuring the uniform distribution of dimethyl carbonate liquid in the heat exchange tube. This greatly increases the contact area between the liquid and the heat exchange tube wall, improving the heat transfer efficiency.

[0030] Furthermore, the gap between the liquid inlet cylinder and the heat exchange tube can be utilized to pre-treat the dimethyl carbonate liquid during the flow process within the gap, such as by filtering it with a filter screen, without affecting the operation of the falling film evaporator.

[0031] The improved down-flow evaporator is applied to the improved process, directly introducing the dimethyl carbonate-containing vapor from the top of the distillation column into a centrifugal compressor or screw compressor. The pressurized and heated vapor enters the column body. Tests have shown that this reduces energy consumption by 30% to 40%, lowers operating costs, and helps promote the technological upgrading of related industries and the achievement of energy conservation and emission reduction goals. Attached Figure Description

[0032] The preferred embodiments will now be described in a clear and easy-to-understand manner, in conjunction with the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of the present invention.

[0033] Figure 1 is a schematic diagram of a falling film evaporator according to the present invention;

[0034] Figure 2 is a partial structural schematic diagram of a falling film evaporator according to the present invention;

[0035] Figure 3 is a partial internal structure diagram of a falling film evaporator according to the present invention;

[0036] Figure 4 is a schematic diagram of the assembly of the blocking part in this invention;

[0037] Figure 5 is an enlarged view of part A in Figure 3 of the present invention;

[0038] Figure 6 is an enlarged view of part B in Figure 4 of the present invention;

[0039] Figure 7 is a cross-sectional view of the horn ring in this invention;

[0040] Figure 8 is a schematic diagram of the support rod structure in this invention.

[0041] In the diagram: 1. Tower body, 101. Evaporation chamber, 102. Liquid inlet, 103. Air inlet, 104. Air outlet, 105. Liquid outlet, 2. Heat exchange tube, 201. Opening, 3. Liquid inlet cylinder, 301. Liquid inlet chamber, 302. Outlet, 303. Liquid inlet channel, 4. Blocking component, 401. Through part, 402. Blocking part, 5. Connecting plate, 6. Support rod, 7. Support plate, 8. Horn ring, 9. Annular guide surface, 10. Guide gap. Detailed Implementation

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0043] To keep the drawings concise, each drawing only schematically shows the parts relevant to the invention; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0044] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0046] Referring to Figures 1 to 8, the first embodiment of the present invention proposes a falling film evaporator, comprising: a tower body 1, the tower body 1 having an evaporation chamber 101, the evaporation chamber 101 having, from top to bottom, a liquid inlet 102, an air inlet 103, an air outlet 104, and a liquid outlet 105; a heat exchange tube 2, the heat exchange tube 2 being disposed within the evaporation chamber 101, the heat exchange tube 2 having an opening 201; and a liquid inlet cylinder 3, the liquid inlet cylinder 3 being disposed within the evaporation chamber 101, the liquid inlet cylinder 3 having a liquid inlet cavity 301, the liquid inlet 102 being connected to the liquid inlet cavity 301, the liquid inlet cavity 301 having an outlet 302, the outlet 302 being located above the opening 201, and the projection of the opening 201 being located within the projection of the outlet 302.

[0047] In this embodiment, as shown in Figures 1-3, to address the issue that traditional falling film evaporators cannot adapt to the improved dimethyl carbonate distillation process, and to avoid the situation where dimethyl carbonate liquid cannot be evenly distributed on the inner wall of the heat exchange tube 2 and adheres to various parts of the falling film evaporator due to the working principle and feeding method of the falling film evaporator, a liquid inlet cylinder 3 is added inside the traditional falling film evaporator. This prevents the dimethyl carbonate liquid entering the evaporation chamber 101 from the liquid inlet 102 at the top of the tower 1 from becoming unevenly distributed, unlike in the traditional structure. As the dimethyl carbonate liquid gradually enters several sets of heat exchange tubes 2, it does not adhere excessively to other components. Instead, it flows directly through the inlet 102 to the inlet chamber 301 of the inlet cylinder 3. Finally, it is distributed through the outlet 302 at the bottom of the inlet cylinder 3 to the openings 201 of each heat exchange tube 2, forming a film. This facilitates the entry of high-temperature steam from the inlet 103 into the tower body 1, evaporating the film inside the heat exchange tubes 2 and functioning as a falling film evaporator. Finally, the concentrated product is discharged from the outlet 105, and excess gas is discharged from the outlet 104.

[0048] The use of the inlet cylinder 3 collects the dimethyl carbonate liquid that was originally scattered throughout the falling film evaporator in the inlet cylinder 3 before distributing it out. This avoids excessive adhesion of the dimethyl carbonate liquid to various parts of the falling film evaporator, which would make subsequent cleaning difficult. Instead, the inlet cylinder 3 can be directly removed for cleaning, or an online cleaning mode can be used, where cleaning fluid is injected into the inlet 102 during normal operation. This reduces downtime and improves equipment availability and maintenance efficiency. At the same time, the inlet cylinder 3 is installed inside the tower body 1 with bolts and other fasteners, placing it above the heat exchange tube 2, which facilitates the distribution of dimethyl carbonate liquid. The overall structure is also more compact, making it easier to install and maintain.

[0049] Furthermore, the projection of the opening 201 at one end of the heat exchange tube 2 is located within the projection of the outlet 302, which allows the dimethyl carbonate liquid to flow smoothly into the heat exchange tube 2. Even if there is a certain gap between the liquid inlet cylinder 3 and the heat exchange tube 2, the dimethyl carbonate liquid flowing out of the outlet 302 will not spread everywhere, increasing the need for subsequent cleaning steps. Instead, it will flow into the heat exchange tube 2 from all around the opening 201, ensuring the uniform distribution of the dimethyl carbonate liquid in the heat exchange tube 2. This greatly increases the contact area between the liquid and the wall of the heat exchange tube 2, improving the heat transfer efficiency.

[0050] Furthermore, the gap between the liquid inlet cylinder 3 and the heat exchange tube 2 can be utilized to pre-treat the dimethyl carbonate liquid during the flow process within the gap, such as by filtering it with a filter screen, without affecting the operation of the falling film evaporator.

[0051] The improved down-flow evaporator is applied to the improved process, directly introducing the dimethyl carbonate-containing vapor from the top of the distillation column into a centrifugal compressor or screw compressor. The pressurized and heated vapor enters column 1. Tests have shown that this reduces energy consumption by 30% to 40%, lowers operating costs, and helps promote the technological upgrading of related industries and the achievement of energy conservation and emission reduction goals.

[0052] Furthermore, the bottom of the liquid inlet chamber 301 has several outlets 302, one end of the heat exchange tube 2 has an opening 201, and there are several heat exchange tubes 2, with the outlets 302 and openings 201 corresponding one-to-one.

[0053] Furthermore, the outlet 302 faces the opening 201. Both the outlet 302 and the opening 201 are circular and are coaxially arranged. The cross-sectional area of ​​the outlet 302 is larger than that of the opening 201.

[0054] In this embodiment, as shown in Figures 1-3, the outlet 302 is arranged at the bottom of the liquid inlet cylinder 3 and corresponds one-to-one with several openings 201, so that the dimethyl carbonate liquid can flow completely from the liquid inlet cylinder 3 to the heat exchange tube 2 and be evenly distributed on the inner wall of each heat exchange tube 2 to form a uniform liquid film, thereby improving the heat transfer efficiency.

[0055] Furthermore, the circular outlet 302 is positioned facing the circular opening 201, with the two coaxial. The cross-sectional area of ​​the outlet 302 is larger than that of the opening 201 to prevent them from being eccentric. This would prevent uneven flow of liquid from the outlet 302 to the periphery of the opening 201, which could lead to uneven distribution of dimethyl carbonate liquid within the heat exchange tube 2, especially for high-viscosity and easily crystallizing materials.

[0056] Furthermore, the inlet cylinder 3 is pot-shaped, and the cross-sectional area of ​​the inlet cylinder 3 remains constant from bottom to top and then gradually decreases. The inner wall of the inlet cylinder 3 has an arc-shaped flow surface, and the bottom center of the inlet cavity 301 has several outlets 302.

[0057] Furthermore, the top of the liquid inlet chamber 301 has a liquid inlet channel 303, which extends through the liquid inlet 102.

[0058] In this embodiment, as shown in Figure 3, the inlet cylinder 3 is further configured as a pot-shaped vessel with an arc-shaped flow surface on its inner wall. This is to prevent the dimethyl carbonate liquid from directly impacting the inner wall when it enters from the inlet channel 303 at the top, which would cause unstable flow and uneven flow velocity. Therefore, after entering from the inlet channel 303, the liquid slowly flows along the arc-shaped flow surface to several outlets 302 spaced apart at the bottom center of the inlet cylinder 3. This requires the cross-sectional area of ​​the inlet cylinder 3 to remain constant from bottom to top and then gradually decrease to meet the physical requirements of the above situation. Instead of directly injecting the dimethyl carbonate liquid into the inlet port 102, the liquid is injected into the inlet channel 303 that penetrates the inlet port 102, so that it can smoothly enter the inlet cylinder 3 and facilitate the function of the falling film evaporator.

[0059] Furthermore, the liquid inlet cylinder 3 is movable within the evaporation chamber 101 and also includes a plug 4. The plug 4 is located at the bottom of the liquid inlet cylinder 3. After the liquid inlet cylinder 3 is moved, both the outlet 302 and the plug 4 are close to or away from the opening 201. The plug 4 is used to adjust the flow rate at the opening 201.

[0060] In this embodiment, as shown in Figures 4 and 6-8, to further improve the practicality of the device, the dimethyl carbonate liquid flow rate is adjusted to adjust the thickness of the liquid film on the inner wall of the heat exchange tube 2, thereby improving the film-forming effect of the liquid film in the falling film evaporator tube and avoiding the phenomenon of "dry wall". This achieves the purpose of improving the evaporation efficiency of the falling film evaporator without compromising the overall structural compactness or adding too many power sources and structures. Therefore, the blocking component 4 is only installed at the bottom of the liquid inlet cylinder 3, i.e., in the gap between the outlet 302 and the opening 201, using fasteners such as bolts. After the liquid inlet cylinder 3 moves, it can drive the blocking component 4 to move closer to or further away from the opening 201 to reduce or increase the flow rate at the opening 201. No other power source is required. Instead, the liquid inlet channel 303, which passes through the liquid inlet port 102, is marked with graduations, and the liquid inlet cylinder 3 is marked with several height installation positions. The height of the entire liquid inlet cylinder 3 can be adjusted in advance by manually adjusting the liquid inlet channel 303, thereby driving the liquid inlet cylinder 3 to move, so as to adjust the gap between the blocking component 4 and the opening 201.

[0061] Furthermore, it also includes: a connecting plate 5, which is disposed in the liquid inlet chamber 301; a support rod 6, with both ends of the support rod 6 disposed at the bottom of the connecting plate 5 and the liquid inlet cylinder 3 respectively, the support rod 6 being located in the liquid inlet chamber 301, and the blocking component 4 being disposed at the bottom of the liquid inlet cylinder 3 through the connecting plate 5.

[0062] Furthermore, the blocking component 4 has a through portion 401 and a blocking portion 402 from top to bottom. The through portion 401 is disposed on the connecting plate 5 and passes through the outlet 302. The blocking component 4 is located outside the liquid inlet cylinder 3.

[0063] In this embodiment, as shown in Figures 4, 6-8, due to the position and shape of the outlet 302 and the opening 201, the plugging part 4 between them needs to be stably supported while not affecting the flow of dimethyl carbonate liquid. Therefore, a support rod 6 is first welded inside the inlet cylinder 3, and a circular connecting plate 5 is welded on the support rod 6 so that several plugging parts 4 can be welded or threaded to the circular connecting plate 5. Furthermore, the cross-sectional area of ​​the through part 401 of the plugging part 4 is smaller than the cross-sectional area of ​​the outlet 302, and it penetrates through the outlet 302, ensuring that the plugging part 402 welded to the through part 401 can be stably supported. This allows the plugging part 402 to be stably supported between the outlet 302 and the opening 201, making it easy for the moving cylinder to move and change its position to adjust the flow rate at the opening 201.

[0064] Furthermore, it also includes: a support plate 7, which is disposed inside the evaporation chamber 101 and located below the liquid inlet cylinder 3, with the openings 201 of several heat exchange tubes 2 all passing through the support plate 7; and a horn ring 8, which is disposed on the opening 201, with the maximum cross-sectional area of ​​the horn ring 8 being greater than the cross-sectional area of ​​the outlet 302, and the cross-sectional area of ​​the horn ring 8 gradually increasing from near to far from the opening 201.

[0065] In this embodiment, as shown in Figures 4, 6-8, each of the heat exchange tubes 2 installed inside the tower body 1 requires a detachable circular support plate 7 at both ends. The opening 201 at the end of the heat exchange tube 2 penetrates the support plate 7, providing stable support. Furthermore, during the flow of dimethyl carbonate liquid from the outlet 302 to the opening 201, it may adhere to the support plate 7. To avoid this situation, reduce subsequent cleaning operations, and ensure easy disassembly of the entire heat exchange tube 2 group through the support plate 7, several horn rings 8 are welded at the opening 201 of the support plate 7. The maximum cross-sectional area of ​​the horn ring 8 is larger than the cross-sectional area of ​​the outlet 302, and the cross-sectional area of ​​the horn ring 8 gradually increases from near to far from the opening 201, ensuring that all flowing dimethyl carbonate liquid is covered and smoothly guided to the inner wall of the heat exchange tube 2.

[0066] Furthermore, the cross-sectional area of ​​the blocking part 402 gradually increases from top to bottom and then gradually decreases. The blocking part 402 is located inside the horn ring 8, and there are annular guide surfaces 9 above and below the blocking part 402. A guide gap 10 is formed between the annular guide surface 9 below the blocking part 402 and the inner wall of the horn ring 8.

[0067] In this embodiment, as shown in Figures 4 and 6-8, the cross-sectional area of ​​the blocking part 402 is limited to gradually increasing and then gradually decreasing from top to bottom, and is located inside the horn ring 8 to ensure that the blocking part 402 functions normally. Furthermore, annular guide surfaces 9 are opened above and below it, so that a guide gap 10 is formed between the annular guide surface 9 below the blocking part 402 and the inner wall of the horn ring 8. The maximum cross-sectional area of ​​the blocking part 402 is smaller than the cross-sectional area of ​​the outlet 302. On the one hand, this ensures that some dimethyl carbonate liquid can flow closer to the inner wall of the horn ring 8 under the action of the annular guide surface 9 above, avoiding it from flowing into the heat exchange tube 2 from the periphery of the opening 201 to form a film, but instead flowing directly into the center of the heat exchange tube 2, resulting in the inability to form a film. On the other hand, the position of the blocking part 402 is adjusted to adjust the gap thickness, thereby better restricting all the dimethyl carbonate liquid from flowing from the periphery of the opening 201 to the inner wall of the heat exchange tube 2 through the gap to form a film, thus completing the function of the falling film evaporator.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A falling film evaporator, characterized in that The application relates to a tower body (1) with an evaporation cavity (101) which has, from top to bottom, a liquid inlet (102), an air inlet (103), an air outlet (104) and a liquid outlet (105); a heat exchange pipe (2) arranged in the evaporation cavity (101), the heat exchange pipe (2) having an opening (201); a liquid inlet cylinder (3) arranged in the evaporation cavity (101), the liquid inlet cylinder (3) having a liquid inlet cavity (301), the liquid inlet (102) being communicated with the liquid inlet cavity (301), the liquid inlet cavity (301) having an outlet (302), the outlet (302) being located above the opening (201), and the opening (201) being projected in the projection of the outlet (302). The bottom of the liquid inlet cavity (301) is provided with a plurality of outlets (302), one end of the heat exchange pipe (2) is provided with the opening (201), and the heat exchange pipe (2) is a plurality of heat exchange pipes, and the outlet (302) and the opening (201) are in one-to-one correspondence. The outlet (302) faces the opening (201), the outlet (302) and the opening (201) are both circular, coaxially arranged, and the cross-sectional area of the outlet (302) is larger than that of the opening (201). The liquid inlet cylinder (3) is in the shape of a kettle, the cross-sectional area of the liquid inlet cylinder (3) gradually decreases from bottom to top, the inner wall of the liquid inlet cylinder (3) is provided with an arc wall flow surface, and the bottom center of the liquid inlet cavity (301) is provided with a plurality of outlets (302).

2. A falling film evaporator according to claim 1, characterized in that The top of the liquid inlet cavity (301) is provided with a liquid inlet channel (303) penetrating through the liquid inlet (102).

3. A falling film evaporator according to claim 2, characterized in that The liquid inlet cylinder (3) is movably arranged in the evaporation cavity (101), and further comprises a blocking piece (4) arranged at the bottom of the liquid inlet cylinder (3), after the liquid inlet cylinder (3) is moved, the outlet (302) and the blocking piece (4) are close to or away from the opening (201), and the blocking piece (4) is used for adjusting the flow rate at the opening (201).

4. A falling film evaporator according to claim 2, characterized in that Further comprising a connecting plate (5) arranged in the liquid inlet cavity (301); and a supporting rod (6) with two ends arranged at the connecting plate (5) and the bottom of the liquid inlet cylinder (3) respectively, the supporting rod (6) being located in the liquid inlet cavity (301), and the blocking piece (4) being arranged at the bottom of the liquid inlet cylinder (3) through the connecting plate (5).

5. A falling film evaporator according to claim 1, characterized in that The blocking piece (4) has, from top to bottom, a penetrating portion (401) and a blocking portion (402) in sequence, the penetrating portion (401) is arranged on the connecting plate (5) and penetrates through the outlet (302), and the blocking piece (4) is located outside the liquid inlet cylinder (3).

6. A falling film evaporator according to claim 3, characterized in that Further comprising ​ 7. A falling film evaporator according to claim 6, characterized in that ​ ​ ​ 8. A falling film evaporator according to claim 7, characterized in that ​ 9. A falling film evaporator according to claim 8, characterized in that ​ Support plate (7) is arranged in the evaporation cavity (101) below the liquid inlet cylinder (3), and the openings (201) of the plurality of heat exchange pipes (2) are arranged on the support plate (7); The horn ring (8) is arranged on the opening (201), the maximum cross-sectional area of the horn ring (8) is greater than the cross-sectional area of the outlet (302), and the cross-sectional area of the horn ring (8) gradually increases from close to far from the opening (201).

10. A falling film evaporator according to claim 9, characterized in that The cross-sectional area of the blocking part (402) gradually increases first and then gradually decreases from top to bottom, the blocking part (402) is located in the horn ring (8), and the upper and lower parts of the blocking part (402) are provided with annular flow guide surfaces (9), and the annular flow guide surface (9) below the blocking part (402) and the inner wall of the horn ring (8) form a flow guide gap (10).

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