Double-stage pipe liquid distribution system for horizontal tube falling film evaporator

Abstract

The application discloses a double-stage pipe type liquid distribution system for a horizontal tube falling film evaporator, and relates to the technical field of evaporation equipment.The double-stage pipe type liquid distribution system for the horizontal tube falling film evaporator comprises an evaporator body, heat exchange tubes and a tube plate flange, the evaporator body is internally provided with a double-stage liquid distribution system, and the double-stage liquid distribution system comprises a water inlet main pipe, a main liquid distributor and a secondary liquid distributor.The liquid distribution pipe adopts a single-layer arrangement mode, compared with the existing double-layer arrangement liquid distribution pipe structure, the single-layer liquid distribution pipe has consistent water inlet liquid levels, the same pressure in the pipe, uniform water discharge of each liquid distribution hole, and can form a uniform liquid film on the heat exchange tube; the liquid distribution system is designed as a double-stage structure with a main liquid distributor in the middle and secondary liquid distributors on both sides, the secondary liquid distributors can distribute liquid to the heat exchange tubes on both sides of the evaporator, widen the evaporator tube distribution space, compared with the existing evaporator heat exchange tubes which are only arranged at the central position, the heat exchange area is greatly improved, and thus the equipment capacity is improved.

Description

Technical Field

[0001] This invention relates to the field of evaporation equipment technology, and in particular to a two-stage tubular liquid distribution system for a horizontal falling film evaporator. Background Technology

[0002] Horizontal tube falling film evaporators are widely used in various industrial sectors such as chemical, light industry, chemical fiber, food processing, seawater desalination, pharmaceuticals, and wastewater treatment. They are currently the most widely used high-efficiency evaporation equipment. The main working principle of the evaporator is as follows: The raw material water solution is evenly sprayed onto the horizontal heat exchange tube bundle through a liquid distribution device, forming a liquid film on the outer surface of the tubes. Under gravity, the liquid film flows downwards along the outer wall of the heat exchange tubes. Saturated high-temperature steam is introduced into the inner side of the heat exchange tubes. The raw material water on the outer side of the tubes exchanges heat with the steam on the inner side of the tubes through the tube wall. The raw material water on the outer side absorbs heat and evaporates, entering the next stage of the evaporator, while the steam on the inner side of the heat exchange tubes releases heat and condenses into pure water, thus achieving the purpose of water purification. The heat exchange performance of the horizontal tube falling film evaporator is directly affected by the uniformity of liquid distribution and the flow pattern. Therefore, the spray structure of the liquid distribution device and the arrangement of the internal tube array are the main factors affecting the uniform distribution of liquid.

[0003] However, during the implementation of the above technical solutions, at least the following technical problems were found: Traditional liquid distribution devices can be divided into overflow type, plug type, and disc type from the perspective of design structure.

[0004] 1. Overflow type design is relatively simple and has low device resistance, but the distribution effect is not ideal and it is suitable for occasions with low requirements.

[0005] 2. The plug type has a better uniformity of the inner membrane, but the flow resistance is relatively large and it is prone to flow deviation.

[0006] 3. Currently, the most widely used liquid distribution device in actual production is the disc-type liquid distribution device. While its design is simple, it is less prone to scaling, and has good stability, it suffers from problems such as uneven liquid distribution, difficulty in adjusting level, and water accumulation at the distribution holes. Water accumulation at the distribution holes causes multiple water outlets in different rows to pool into a large water column, increasing the thickness of the liquid film below the collecting hole, reducing the heat transfer coefficient. Furthermore, the absence of raw water below the collecting hole leads to a dry pipe phenomenon, resulting in uneven liquid distribution, significantly reducing the effective heat transfer area of ​​the heat exchange tubes, and consequently decreasing equipment capacity. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a two-stage tubular liquid distribution system for horizontal tube falling film evaporators. This system solves the problem of the widely used disc-type liquid distribution devices in actual production, which are simple in design, less prone to scaling, and have good stability, but suffer from uneven liquid distribution, difficulty in adjusting level, and water accumulation at the distribution holes. Water accumulation at the distribution holes causes multiple distribution holes in different rows to pool into a large water column, increasing the liquid film thickness below the collecting hole, reducing the heat transfer coefficient, and resulting in a dry pipe phenomenon when there is no raw material water below the collecting hole. This uneven liquid distribution significantly reduces the effective heat transfer area of ​​the heat exchange tubes, leading to a decrease in equipment capacity.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A two-stage tubular liquid distribution system for a horizontal falling film evaporator includes an evaporator body, heat exchange tubes, and tube sheet flanges. The evaporator body is equipped with a two-stage liquid distribution system, which includes a main inlet pipe, a main liquid distributor, and a secondary liquid distributor. The main inlet pipe is located on the inner wall of the evaporator body, and a connecting pipe is fixedly installed at its upper end. The connecting pipe passes through and is fixedly installed at the circumferential end of the evaporator body. There are two tube sheet flanges, both of which are bolted to both ends of the evaporator body. There are at least two main liquid distributor distribution slots, each of which is equidistantly arranged on the evaporator body. The inner wall of the evaporator body has tube sheet flanges fixedly installed on both ends of the evaporator body. The main water inlet pipe is located above the main liquid distributor's distribution trough. At least two lower holes are opened through the lower end of the main water inlet pipe, directly opposite the circumferential end of each main liquid distributor trough. Upper holes are opened at both ends of the circumferential end of the main water inlet pipe. Main liquid distributor fixing plates are fixedly installed on the end faces of the main liquid distributor's distribution trough tube sheets near the evaporator tube sheet flanges on both sides. The lower ends of the remaining main liquid distributor's distribution trough tube sheets are all provided with first mounting holes. Each first mounting hole is equidistantly arranged, and a main liquid distribution pipe is fixedly installed through the inner wall of each first mounting hole. The main liquid distributor has a main liquid distribution groove at its upper end. Side plates are fixedly installed on both sides of the main liquid distribution groove of each main liquid distributor. A groove is formed through the end of each side plate. The auxiliary liquid distributor has at least two auxiliary liquid distribution grooves, each located on both sides of the main liquid distribution groove of the main liquid distributor. Each auxiliary liquid distribution groove is fixedly installed on the side end of a side plate. At least two second mounting holes are formed through the sides of the two middle auxiliary liquid distribution grooves. Each second mounting hole is equidistantly arranged. The auxiliary liquid distributor has an auxiliary liquid distribution groove at its upper end. Each side plate... Two limiting plates are also fixedly installed at the side ends. A secondary liquid distributor fixing plate is installed at the side ends of the secondary liquid distributors on both sides. At least two secondary liquid distribution pipes are fixedly installed between the second mounting holes at the lower ends of the tube sheets of two adjacent secondary liquid distribution tanks. Each heat exchange tube is located below the main liquid distribution pipe and the secondary liquid distribution pipe. Each secondary liquid distribution pipe is located on the inner side wall of the second mounting hole. At least two liquid distribution holes are opened through the lower ends of the main liquid distribution pipe and the secondary liquid distribution pipe. Each liquid distribution hole is staggered. A main welding groove is also opened through the side ends of the two tube sheet flanges. The two main liquid distributor fixing plates are fixedly installed on the inner side wall of the main welding groove.

[0012] Preferably, two auxiliary welding grooves are also provided through the side end of the tube sheet flange.

[0013] Preferably, each of the auxiliary liquid distributor fixing plates is fixedly installed on the inner side wall of the auxiliary welding tank, and at least two heat exchange tube holes are also opened through the side end of the tube sheet flange.

[0014] (III) Beneficial Effects

[0015] 1. This device consists of a two-stage liquid distribution system consisting of an inlet pipe, a main liquid distributor, and an auxiliary liquid distributor. The inlet pipe is located above the liquid distribution tank, and three water outlets are set above the four liquid distribution tanks. Water is mainly discharged through the openings on both sides, which can make the water injection in the liquid distribution tank more uniform. The openings at the bottom can help to drain excess raw material water in the inlet pipe after the equipment is stopped. At the same time, a small hole is opened above both sides of the main inlet pipe near the flange of the evaporator tube sheet, which can realize the air venting inside the pipe during the water intake process and maintain stable water pressure.

[0016] 2. The number of liquid distribution tanks in this device can be flexibly adjusted according to the length of the evaporator. Four liquid distribution tanks are used to divide the liquid distribution pipe into three distribution zones, so that the main liquid distribution pipe and the auxiliary liquid distribution pipe are divided into three sections. The middle section is connected to each liquid distribution tank through a tube sheet. This prevents the main liquid distribution pipe and the auxiliary liquid distribution pipe from being too long, which would cause an imbalance in the raw material water pressure in the middle and the two ends of the pipe and result in uneven longitudinal liquid distribution. On the one hand, it can avoid deformation caused by excessively long liquid distribution pipes. On the other hand, the four liquid distribution tanks can better ensure the uniformity of water intake in the liquid distribution pipe.

[0017] 3. The bottom plate of the liquid distribution tank has staggered openings for liquid distribution to the heat exchange tubes below the tank. This also facilitates the drainage of residual water after equipment shutdown. The side baffles of the liquid distribution tank are at the same height as the tube sheet, forming a water storage structure with the tube sheet and preventing structural deformation, while also facilitating welding and installation. The side plate of the main liquid distributor has a groove. When the water level in the main liquid distributor reaches the lower small opening, the raw water in the main liquid distribution tank flows through this opening to the auxiliary liquid distributor via the side plate. The higher square opening prevents overflow when the water level in the main liquid distributor is too high. Limiting plates on both sides constrain the flow of raw water from the main liquid distributor into the auxiliary liquid distributor.

[0018] 4. This device connects the tube sheet end faces of the main and auxiliary liquid distributors to a fixed plate, and connects the fixed plate to the tube sheet flanges on both sides of the evaporator. This enables the horizontal installation and positioning of the liquid distributor and the evaporator, ensuring high installation reliability and good levelness.

[0019] 5. This device is equipped with a main liquid distributor and a secondary liquid distributor. The main and secondary liquid distributors use liquid distribution pipes with the same orifice size and distribution spacing. The spacing between the liquid distribution holes on the liquid distribution pipes is the same, and the opening positions of adjacent liquid distribution pipes are staggered to further ensure the uniformity of liquid distribution. After the water inlet pipe is opened, the liquid distribution tank of the main liquid distributor fills with water first and distributes the liquid first, giving priority to ensuring the effective liquid distribution of the main heat exchange tubes. After the liquid distribution tank of the main liquid distributor is full of water, water is injected into the liquid distribution tank of the secondary liquid distributor through the opening of the side plate of the main liquid distributor. The liquid distribution pipe of the secondary liquid distributor gradually fills with water, and the heat exchange tubes on both sides of the evaporator also gradually achieve effective liquid distribution, ensuring the uniformity of liquid distribution and realizing the full utilization of the heat exchange area of ​​the evaporator heat exchange tubes and the high-efficiency improvement of heat exchange efficiency.

[0020] 6. This device employs a two-stage liquid distribution system with a single-layer arrangement of the distribution pipes. This solves the problems of inconsistent water output caused by pressure differences in the liquid levels of the two layers in existing two-layer distribution pipe structures. Specifically, the upper layer has lower pressure and lower water output, while the lower layer has higher pressure and higher water output. Furthermore, the liquid film thickness on the heat exchange tubes is uneven, resulting in inconsistent liquid distribution. The single-layer distribution pipe arrangement ensures a consistent inlet water level and pressure within the pipes, resulting in virtually no difference in the liquid output from each distribution hole. This leads to more uniform liquid distribution and the formation of a uniform liquid film on the heat exchange tubes. Moreover, the two-stage distribution system expands the space available for heat exchange tubes within the evaporator. The secondary distributor distributes liquid to the heat exchange tubes on both sides, improving the utilization rate of the heat exchange tube space, increasing the heat exchange area, and enhancing production capacity.

[0021] 7. Existing liquid distributors are mostly fixed to the evaporator by welding guide rails to the cylinder body. The welding of these guide rails has errors, making it difficult to align the liquid distribution pipe with the heat exchange tubes of the evaporator, resulting in liquid distribution deviation. This device uses main liquid distributor fixing plates and auxiliary liquid distributor fixing plates at both ends, which are welded to the main welding groove and auxiliary welding groove on the tube sheet flange. This ensures that the liquid distribution pipe of the liquid distributor is vertically aligned with the heat exchange tubes on the evaporator, thereby achieving a better liquid distribution effect. Attached Figure Description

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] Figure 1 This is an overall structural diagram of the evaporator of the present invention;

[0024] Figure 2 This is a diagram showing the internal structure of the evaporator of the present invention;

[0025] Figure 3 This is a structural diagram of the main water inlet pipe of the present invention;

[0026] Figure 4This is a structural diagram of the two-stage liquid distribution system of the present invention;

[0027] Figure 5 This is a structural diagram of the main and auxiliary liquid distributors of the present invention;

[0028] Figure 6 This is a structural diagram of the main and auxiliary liquid distribution tanks of the present invention;

[0029] Figure 7 This is a structural diagram of the tube sheet flange of the present invention;

[0030] Figure 8 This is a structural diagram of the auxiliary liquid distributor fixing plate of the present invention;

[0031] Figure 9 For the present invention Figure 8 An enlarged schematic diagram of the structure at point A.

[0032] Legend: 1. Evaporator body; 12. Heat exchange tube; 2. Main water inlet pipe; 21. Connecting pipe; 22. Upper row hole; 23. Lower row hole; 3. Main liquid distributor; 31. Main liquid distributor fixing plate; 32. First mounting hole; 33. Main liquid distribution tank; 34. Main liquid distribution pipe; 35. Groove; 36. Side plate; 37. Liquid distribution hole; 4. Secondary liquid distributor; 42. Secondary liquid distributor fixing plate; 43. Secondary liquid distribution pipe; 45. Secondary mounting hole; 46. Limiting plate; 47. Secondary liquid distribution tank; 5. Tube sheet flange; 52. Main welding groove; 53. Secondary welding groove; 54. Heat exchange tube hole. Detailed Implementation

[0033] This application provides a two-stage tubular liquid distribution system for a horizontal tube falling film evaporator, effectively solving the problems of disc-type liquid distribution devices widely used in actual production. While these devices are simple in design, less prone to scaling, and have good stability, they suffer from uneven liquid distribution, difficulty in adjusting level, and water accumulation at the distribution holes. Water accumulation at the distribution holes causes multiple holes in different rows to pool into a large water column, increasing the liquid film thickness below the collecting hole, reducing the heat transfer coefficient, and resulting in a dry pipe phenomenon due to the lack of raw water below the collecting hole. Uneven liquid distribution significantly reduces the effective heat exchange area of ​​the heat exchange tubes, leading to decreased equipment capacity. This device, through a two-stage liquid distribution system using a single-layer distribution tube arrangement, effectively solves the problems of pressure differences caused by the liquid level heights of the two layers in existing double-layer distribution tube structures, resulting in different water outputs. The upper layer has lower pressure and lower water output, while the lower layer has higher pressure and higher water output, leading to uneven liquid film thickness and uneven liquid distribution on the heat exchange tubes. A single-layer distribution pipe arrangement ensures consistent pressure on the pipes, minimal difference in liquid output, and more uniform liquid distribution.

[0034] Example

[0035] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 9 As shown, the technical solution in this application embodiment effectively solves the problem of disc-type liquid distribution devices widely used in actual production. While these devices are simple in design, not prone to scaling, and have good stability, they suffer from problems such as uneven liquid distribution, difficulty in adjusting level, and water accumulation at the distribution holes. Water accumulation at the distribution holes causes multiple distribution holes in different columns to converge into a large water column, increasing the thickness of the liquid film below the converging hole, reducing the heat transfer coefficient, and resulting in a dry pipe phenomenon due to the lack of raw material water below the converging hole. This uneven liquid distribution significantly reduces the effective heat transfer area of ​​the heat exchange tubes, leading to a decrease in equipment capacity. The overall approach is as follows: A two-stage tubular liquid distribution system for a horizontal falling film evaporator includes an evaporator body 1, heat exchange tubes 12, and tube sheet flanges 5. The evaporator body 1 is equipped with a two-stage liquid distribution system, which includes a main inlet pipe 2. After the main water inlet pipe 2 is opened, the main water distributor 3 stores water first and distributes the liquid preferentially. The raw water drips down through the main liquid distribution tank 33 and the liquid distribution hole 37 of the main liquid distribution pipe 34 and is evenly distributed on the surface of the heat exchange tube 12 below it. When the water storage of the main water distributor 3 meets the height limit of the groove 35, water is injected into the auxiliary water distributor 4. The auxiliary liquid distribution pipe 43 on the auxiliary water distributor 4 is gradually filled with water, and the heat exchange tubes 12 on both sides of the evaporator are also gradually and effectively distributed, ensuring the uniformity of liquid distribution and realizing the full utilization of the heat exchange area of ​​the heat exchange tubes 12 of the evaporator and the high efficiency of heat exchange.

[0036] The main water inlet pipe 2 is located on the inner wall of the evaporator body 1. A connecting pipe 21 is fixedly installed at the upper end of the main water inlet pipe 2. The connecting pipe 21 passes through and is fixedly installed at the circumferential end of the evaporator body 1. There are two tube sheet flanges 5, both of which are fixedly installed at both ends of the evaporator body 1 by bolts. There are at least two main liquid distribution tanks 33, each of which is equidistantly arranged on the inner side wall of the evaporator body 1. Tube sheet flanges 5 are fixedly installed at both ends of the evaporator body 1. The main water inlet pipe 2 is located above each main liquid distribution tank 33. The lower end of the main water inlet pipe 2 is circumferentially... At least two lower drain holes 23 are provided at the end of the main inlet pipe 2, and upper drain holes 22 are provided at the circumferential ends of both ends of the main inlet pipe 2. The raw water enters the main inlet pipe 2 from the raw water connection pipe 21. A two-stage liquid distribution system is set below the main inlet pipe 2. Multiple lower drain holes 23 are provided below the main inlet pipe 2, with water mainly exiting through the holes on both sides, which can make the water injection in the liquid distribution tank more uniform. The lower drain holes 23 can help to drain excess raw water in the inlet pipe after the equipment is stopped. At the same time, the upper drain holes 22 are also provided on the main inlet pipe 2, which can realize the air venting inside the pipe during the water intake process and maintain stable water intake pressure.

[0037] Main liquid distributor fixing plates 31 are fixedly installed on the end face of the main liquid distributor 3 ...

[0038] The auxiliary liquid distributor 4 has at least two auxiliary liquid distribution grooves 47. Each auxiliary liquid distribution groove 47 is located at both ends of the main liquid distributor 3. Each auxiliary liquid distribution groove 47 is fixedly installed at the side end of the side plate 36. The lower end of the tube plate of the remaining auxiliary liquid distribution grooves 47 of the auxiliary liquid distributor 4 is provided with at least two second mounting holes 45. The upper end of the auxiliary liquid distributor 4 is provided with auxiliary liquid distribution grooves 47. Each side plate 36 is also fixedly installed with two limiting plates 46. The limiting plates 46 on both sides can realize the flow constraint when the raw material water is injected into the auxiliary liquid distributor 4 from the main liquid distributor 3.

[0039] Each secondary liquid distributor 4 has a secondary liquid distributor fixing plate 42 fixedly installed on both sides. At least two secondary liquid distribution pipes 43 are fixedly installed between the second mounting holes 45 at the lower end of the tube plates of two adjacent secondary liquid distribution tanks 47. Each secondary liquid distribution pipe 43 is located on the inner side wall of the second mounting hole 45. At least two liquid distribution holes 37 are opened through the lower ends of the main liquid distribution pipe 34 and the secondary liquid distribution pipe 43.

[0040] The two tube sheet flanges 5 are also provided with main welding grooves 52 through their side ends. The two main liquid distributor fixing plates 31 are fixedly installed on the inner side wall of the main welding grooves 52. The tube sheet flanges 5 are also provided with two auxiliary welding grooves 53 through their side ends. Each auxiliary liquid distributor fixing plate 42 is fixedly installed on the inner side wall of the auxiliary welding groove 53. The tube sheet flanges 5 are also provided with at least two heat exchange tube holes 54 through their side ends. The ends of the main liquid distributor 3 and the auxiliary liquid distributor 4 are fixedly welded through the main liquid distributor fixing plate 31, the auxiliary liquid distributor fixing plate 42 and the main welding grooves 52 and auxiliary welding grooves 53 on the tube sheet flanges 5. The tube sheet flanges 5 are connected to the evaporator body 1 by bolts, which can realize the horizontal installation and positioning requirements of the two-stage liquid distribution system and the evaporator body 1. The installation reliability is high and the levelness is good.

[0041] To address the problems existing in the prior art, this invention provides a two-stage tubular liquid distribution system for a horizontal tube falling film evaporator. This device employs a single-layer liquid distribution tube arrangement in a two-stage liquid distribution system. In existing two-layer liquid distribution tube structures, the difference in liquid level between the two layers leads to pressure variations, resulting in different water output rates. The upper layer has lower pressure and a smaller water output, while the lower layer has higher pressure and a larger water output, causing uneven liquid film thickness on the heat exchange tube 12 and inconsistent liquid distribution. In contrast, a single-layer liquid distribution tube arrangement ensures consistent pressure across the tubes, resulting in virtually no difference in water output and more uniform liquid distribution.

[0042] Working principle:

[0043] After the main water inlet pipe 2 is opened, the main liquid distributor 3 first stores water and distributes it preferentially. The raw water drips down through the main liquid distribution tank 33 and the distribution holes 37 of the main liquid distribution pipe 34, and is evenly distributed on the surface of the heat exchange tube 12 below it. When the water storage in the main liquid distribution tank 33 of the main liquid distributor 3 meets the height limit of the groove 35, water is injected into the secondary liquid distribution tank 47 of the secondary liquid distributor 4. The secondary liquid distribution pipe 43 on the secondary liquid distributor 4 is gradually filled with water, and the heat exchange tubes 12 on both sides of the evaporator also gradually achieve effective liquid distribution, ensuring the uniformity of liquid distribution. This system fully utilizes the heat exchange area of ​​the evaporator heat exchange tube 12 and significantly improves its heat exchange efficiency. Raw water enters the main inlet pipe 2 from the raw water connection pipe 21. A two-stage liquid distribution system is installed below the main inlet pipe 2, with multiple lower drain holes 23. Water is primarily discharged through holes on both sides, ensuring more even water distribution in the liquid distribution tank. The lower drain holes 23 also facilitate the emptying of excess raw water from the inlet pipe after equipment shutdown. Additionally, an upper drain hole 22 is also provided on the main inlet pipe 2. This system allows for air venting inside the pipes during water intake, maintaining stable water pressure. The raw water drips evenly onto the outer wall of the heat exchange tube 12. Limiting plates 46 are fixedly installed on both sides of each main distribution groove 33 of the main distributor 3 to prevent raw water overflow. The ends of the main distributor 3 and the auxiliary distributor 4 are fixedly welded through the main distributor fixing plate 31, the auxiliary distributor fixing plate 42, and the main welding groove 52 and auxiliary welding groove 53 on the tube sheet flange 5. The tube sheet flange 5 is connected to the evaporator body 1 by bolts, which can meet the horizontal installation and positioning requirements of the two-stage liquid distribution system and the evaporator body 1. The installation reliability is high and the levelness is good. A three-zone liquid distribution structure is adopted, that is, the two-stage liquid distribution system uses four distribution grooves to divide the liquid distribution pipe into three distribution zones. This zoned liquid distribution method can avoid deformation caused by excessive length of heat exchange tube 12. On the other hand, the four distribution grooves can better ensure the uniformity of water intake in the liquid distribution pipe and avoid the problem of uneven water volume in the liquid distribution pipe, with more at both ends and less in the middle. The bottom plate of the liquid distribution tank has staggered openings for distributing liquid to the heat exchange tubes 12 below the liquid distribution tank. This also facilitates the drainage of residual water inside the liquid distribution tank after the equipment is shut down. The side baffles of the liquid distribution tank are at the same height as the tube sheet, forming a water storage structure with the tube sheet and preventing structural deformation, while also facilitating welding and installation. The upper end of the main liquid distributor 3 has a main liquid distribution tank 33. When the water level in the main liquid distribution tank 33 reaches the lower small opening, the raw water in the main liquid distributor 3 flows through this main liquid distribution tank 33 into the auxiliary liquid distributor 4. The higher square opening prevents overflow when the water level in the main liquid distributor 3 is too high. The limiting plates 46 on both sides constrain the flow of raw water from the main liquid distributor 3 into the auxiliary liquid distributor 4.

[0044] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A two-stage tubular liquid distribution system for a horizontal tube falling film evaporator, comprising an evaporator body (1), heat exchange tubes (12), and tube sheet flanges (5), characterized in that: The evaporator body (1) is equipped with a two-stage liquid distribution system; The dual-stage liquid distribution system includes a main water inlet pipe (2), a main liquid distributor (3), and a secondary liquid distributor (4). The main water inlet pipe (2) is located on the inner wall of the evaporator body (1). The upper end of the main water inlet pipe (2) is fixedly installed with a connecting pipe (21). The connecting pipe (21) is fixedly installed through the circumferential end of the evaporator body (1); The tube sheet flange (5) is two in number, and both tube sheet flanges (5) are fixedly installed at both ends of the evaporator body (1) by bolts; The main liquid distributor (3) includes at least two main liquid distribution tanks (33), each of which is equidistantly arranged on the inner wall of the evaporator body (1). The main water inlet pipe (2) is located above each main liquid distribution tank (33) of the main liquid distributor (3). At least two lower holes (23) are provided at the circumferential end of the lower end of the main water inlet pipe (2) above each main liquid distribution tank (33). The main liquid distributor (3) is located near the tube sheet flange (5) on both sides. 3) The main liquid distribution tank (33) is fixedly installed with a main liquid distributor fixing plate (31) on the tube sheet end face. The lower end of the tube sheet of the other main liquid distribution tanks (33) of the main liquid distributor (3) is provided with a first mounting hole (32). The main liquid distributor fixing plate (31) is fixedly installed with a main liquid distributor fixing plate (31) on the tube sheet end face of the main liquid distribution tank (33) of the main liquid distributor (3) near the tube sheet flange (5). The lower end of the tube sheet of the other main liquid distribution tanks (33) of the main liquid distributor (3) is provided with a first mounting hole (32). A mounting hole (32) is provided, and a main liquid distribution pipe (34) is fixedly installed through the inner wall of each first mounting hole (32). The number of secondary liquid distribution grooves (47) of the secondary liquid distributor (4) is at least two. The secondary liquid distribution grooves (47) of each secondary liquid distributor (4) are located at both ends of the main liquid distributor (3). At least two second mounting holes (45) are provided through the two ends of the two secondary liquid distribution grooves (47) located in the middle. Among them, two adjacent secondary liquid distribution grooves (34) are fixedly installed through the main liquid distributor (34). At least two auxiliary liquid distribution pipes (43) are fixedly installed between the second mounting holes (45) at the lower end of the tube sheet (47). Each heat exchange tube (12) is located below the main liquid distribution pipe (34) and the auxiliary liquid distribution pipe (43). Each auxiliary liquid distribution pipe (43) is located on the inner side wall of the second mounting hole (45). At least two liquid distribution holes (37) are opened through the lower ends of the main liquid distribution pipe (34) and the auxiliary liquid distribution pipe (43). Each liquid distribution hole (37) is staggered.

2. The two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 1, characterized in that: The circumferential ends of both ends of the main water inlet pipe (2) are provided with upper row holes (22).

3. The two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 2, characterized in that: Each of the first mounting holes (32) is arranged at equal intervals.

4. The two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 3, characterized in that: The upper end of the main liquid distributor (3) is provided with a main liquid distribution groove (33), and side plates (36) are fixedly installed on both sides of the main liquid distributor (3). Each of the side plates (36) has a groove (35) extending through its end.

5. The two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 4, characterized in that: Each of the secondary liquid distributors (4) has a secondary liquid distribution tank (47) fixedly installed at the side end of the side plate (36).

6. The two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 5, characterized in that: Each of the second mounting holes (45) is equidistant; The upper end of the auxiliary liquid distributor (4) is provided with an auxiliary liquid distribution groove (47), and two limiting plates (46) are fixedly installed on the side end of each side plate (36).

7. A two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 6, characterized in that: A secondary liquid distributor fixing plate (42) is installed on the side ends of the secondary liquid distributors (4) located on both sides.

8. A two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 7, characterized in that: The two tube sheet flanges (5) are also provided with main welding grooves (52) through their side ends; The two main liquid distributor fixing plates (31) are fixedly installed on the inner side wall of the main welding groove (52).

9. A two-stage tubular liquid distribution system for a horizontal tube falling film evaporator as described in claim 8, characterized in that: Two auxiliary welding grooves (53) are also provided through the side end of the tube sheet flange (5); Each of the auxiliary liquid distributor fixing plates (42) is fixedly installed on the inner side wall of the auxiliary welding groove (53); The tube sheet flange (5) also has at least two heat exchange tube holes (54) through it at its side end.

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