Falling film evaporator and distributor thereof

Abstract

The invention relates to the technical field of evaporators, in particular to a falling film evaporator and a distributor thereof, and the distributor of the falling film evaporator comprises an evaporation pipe arranged on the falling film evaporator. Comprising a sleeve, an air inlet pipe, a liquid spiral feeding head, an air guide pipe and a wind wheel, wherein the sleeve is arranged at the upper end of an evaporation pipe and is used for forming an overflow port; the air inlet pipe and the evaporation pipe are coaxially arranged; the liquid spiral feeding head is rotationally mounted in the evaporation pipe; the air guiding pipe is arranged outside the air guiding pipe, an air guiding opening is formed in the upper end of the air guiding pipe, and the air guiding structure is rotationally connected into the liquid spiral feeding head, driven by inlet steam to rotate and forms suction force at the air guiding opening. The falling film evaporator has the advantage of ensuring the falling film evaporation effect.

Description

Technical Field

[0001] This application relates to the technical field of evaporators, and particularly to a falling film evaporator and its distributor. Background Art

[0002] As an efficient heat transfer and concentration process, the core of the falling film evaporation technology lies in forming a continuous and uniform liquid film inside the heat exchange tubes for controllable evaporation of the liquid feed.

[0003] In the prior art, the liquid feed is usually distributed to the inner walls of each heat exchange tube through a liquid distributor (such as an overflow type, plug type, or spray type structure) at the top of the falling film evaporator, and forms a falling film flow relying on the action of gravity and vacuum induction. During this process, the heating medium in the shell side exchanges heat with the liquid film in the tube side, promoting partial vaporization of the liquid phase. Subsequently, the gas-liquid two-phase enters the separation chamber for phase separation, the steam enters condensation or the next effect cycle, and the concentrated liquid is discharged from the bottom of the separation chamber.

[0004] The existing liquid distributors have significant defects in practical applications. For example, the uniformity and continuity of the liquid film are insufficient. The overflow type structure is not easy to be blocked, has a large operation flexibility in liquid distribution, but it is difficult to ensure the distribution effect. The plug type structure has extremely high requirements for the processing accuracy of the pipe orifice and the matching degree between the plug and the pipe wall gap, and the liquid film is likely to break due to scaling or deformation during long-term operation. The spray type uses a feed spray head to sprinkle the liquid on the tube sheet of the evaporation tube, and the liquid flows into the tube along the tube, and it is difficult to ensure the liquid film forming effect and uniformity. Summary of the Invention

[0005] In order to ensure the effect of falling film evaporation, this application provides a falling film evaporator and its distributor.

[0006] On the one hand, a distributor of a falling film evaporator provided by this application adopts the following technical solution: A distributor of a falling film evaporator is arranged on the evaporation tube of the falling film evaporator, and includes a sleeve arranged at the upper end of the evaporation tube for forming an overflow port, an intake pipe coaxially arranged with the evaporation tube, a liquid spiral feeder rotatably installed inside the evaporation tube, a guide pipe connecting the liquid spiral feeder and the intake pipe, a wind wheel located inside the intake pipe and driving the liquid spiral feeder to rotate through the intake steam, an air guide pipe arranged outside the guide pipe and having an air intake at the upper end, and an air guide structure rotatably connected inside the liquid spiral feeder and driven by the intake steam to rotate and form a suction force at the air intake; A plurality of spiral grooves are arranged on the outer side wall of the liquid spiral feeder. The spiral grooves form a liquid inlet and a liquid outlet at the upper end and the lower end of the liquid spiral feeder respectively. The lower end of the liquid spiral feeder is provided with a first outlet communicating with the guide pipe and a second outlet communicating with the air guide pipe. Along the radial direction of the liquid spiral feeder, the second outlet is located between the liquid outlet and the first outlet; the position where the air intake is located is higher than the overflow port.

[0007] In one embodiment: The air guiding structure includes a pipe body communicated with the air duct, an air guiding wheel arranged in the pipe body and driven by the steam inlet to rotate the pipe body, and a wind blade arranged outside the pipe body. A gap communicated with the air guiding pipe is formed between the pipe body and the liquid spiral feeding head, and the lower end of the gap forms the second outlet.

[0008] In one embodiment: The rotating direction of the air guiding wheel is opposite to that of the wind wheel when driven by the steam inlet.

[0009] In one embodiment: The liquid spiral feeding head rotates along the opening direction of the liquid inlet.

[0010] In one embodiment: A frustum-shaped distribution plate is formed by extending the lower end of the liquid spiral feeding head, and the lower end of the distribution plate is larger than the upper end.

[0011] In one embodiment: The distance between the lower end of the distribution plate and the inner wall of the evaporation pipe is greater than or equal to the width of the spiral groove in the radial direction.

[0012] In one embodiment: The second outlet is formed between the air guiding structure and the distribution plate, and the second outlet is inclined along the direction towards the inner wall of the evaporation pipe.

[0013] In one embodiment: Turbulence vanes for forming a swirl are arranged at the lower end of the liquid spiral feeding head at the position where the second outlet is located.

[0014] On the other hand, a falling film evaporator provided by the present application adopts the following technical solutions: A falling film evaporator sequentially includes a feeding section, a heating section, and a separation section from top to bottom in the vertical direction. The feeding section is provided with a liquid inlet and a steam inlet, the heating section is provided with a plurality of evaporation pipes, and the distributor is arranged between the steam inlet and the evaporation pipes; the separation section is provided with a liquid outlet and a steam outlet.

[0015] In one embodiment: A steam equalizing chamber is arranged in the feeding section, the liquid inlet is arranged above the steam equalizing chamber, and a liquid leakage port is formed between the steam equalizing chamber and the outer wall of the feeding section; an upper chamber communicated with the steam inlet and a lower chamber communicated with the air inlet pipe are arranged in the steam equalizing chamber, and a plurality of communicating through holes are arranged on the partition plate between the upper chamber and the lower chamber.

[0016] In summary, the present application has the following beneficial effects: On the one hand, high-temperature steam is introduced into the evaporation tube through the intake pipe. The high-temperature steam flows in the same direction as the liquid film, which can assist in pushing the liquid film to flow downward, reduce the fluctuations of the liquid film caused by gravity or surface tension, and enhance stability. On the second hand, after the high-temperature steam is introduced into the intake pipe, it drives the wind wheel to rotate. The wind wheel drives the liquid spiral feeder head to rotate. After the solution passes through the spiral grooves on the liquid spiral feeder head, a relatively uniform liquid film can be formed on the inner wall of the evaporation tube. The rotation of the liquid spiral feeder head can not only increase the flow rate, but also form a centrifugal force, further ensuring the uniformity and continuity of the liquid film after forming, and can also clean the inside of the evaporation tube, effectively avoiding the problem of scale formation.

[0017] In addition, when the high-temperature steam flow enters the evaporation tube from the first outlet, the flow rate decreases and the static pressure increases due to the enlarged diameter. The increased static pressure exerts a pressure perpendicular to the tube wall on the liquid film, thereby forming an impact on the liquid film and triggering the oscillation of the liquid film, which affects the uniformity. Therefore, through the design of the air guiding structure, a negative pressure is formed from the air guiding opening of the air guiding pipe to form an air flow, so that an air flow is also formed at the second outlet. The air flow here is relatively small and is located between the liquid outlet and the first outlet, thereby forming a certain blockage to the air flow at the first outlet and reducing the impact on the liquid film. In addition, since the liquid film is formed by a spiral and centrifugal structure in the area near the first outlet, the spiral flow and the relatively fast flow rate can also reduce the impact on the high-temperature steam flowing out from the first outlet. Brief Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the falling film evaporator of this embodiment; Figure 2 is a schematic structural diagram of the feeding section in the falling film evaporator of this embodiment; Figure 3 is a schematic structural diagram of the distributor in this embodiment.

[0019] In the figure, 10, feeding section; 11, liquid inlet; 12, steam inlet; 13, liquid leakage port; 20, heating section; 21, evaporation tube; 22, distributor; 30, separation section; 31, liquid outlet; 32, steam outlet; 40, steam equalizing chamber; 41, partition plate; 42, upper chamber; 43, lower chamber; 100, sleeve; 200, intake pipe; 300, liquid spiral feeder head; 310, spiral groove; 320, distribution plate; 321, turbulence blade; 330, first outlet; 340, second outlet; 400, air guide pipe; 500, wind wheel; 600, air guiding pipe; 700, air guiding structure; 710, pipe body; 720, air guiding wheel; 730, air blade. Detailed Embodiment

[0020] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, elaborate in detail on the specific implementation manners, structures, features, and their effects of the present invention as follows.

[0021] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0022] A falling film evaporator, as Figure 1 shown, sequentially includes a feeding section 10, a heating section 20, and a separation section 30 from top to bottom in the vertical direction. The feeding section 10 is provided with a liquid inlet 11 and a steam inlet 12. The liquid inlet 11 is arranged at the top of the feeding section 10, and the steam inlet 12 is arranged on the side of the feeding section 10.

[0023] The heating section 20 is provided with a plurality of evaporation tubes 21, and a distributor 22 is arranged between the steam inlet 12 and the evaporation tubes 21. The separation section 30 is provided with a liquid outlet 31 and a steam outlet 32.

[0024] Referring to Figure 2 , a steam equalizing chamber 40 is arranged in the feeding section 10. The liquid inlet 11 is arranged above the steam equalizing chamber 40, and a liquid leakage port 13 is formed between the steam equalizing chamber 40 and the outer wall of the feeding section 10. The liquid leakage ports 13 are evenly distributed on the outside of the steam equalizing chamber 40. The solution is fed into the feeding section 10 from the liquid inlet 11 and directly contacts the steam equalizing chamber 40. On the one hand, the solution can be heated and insulated through the steam equalizing chamber 40. On the other hand, it can enter through the liquid leakage ports 13 on the side, avoiding directly entering the evaporation tubes 21.

[0025] The steam equalizing chamber 40 is provided with an upper chamber 42 communicated with the steam inlet 12 and a lower chamber 43 communicated with the evaporation tubes 21. A plurality of communicating through holes are arranged on the partition plate 41 between the upper chamber 42 and the lower chamber 43.

[0026] As Figure 3 shown, the distributor 22 includes a sleeve 100 arranged at the upper end of the evaporation tube 21 for forming an overflow port, an air inlet pipe 200 coaxially arranged with the evaporation tube 21, a liquid spiral feeder 300 rotatably installed in the evaporation tube 21, a guide air pipe 400 connecting the liquid spiral feeder 300 and the air inlet pipe 200, a wind wheel 500 located in the air inlet pipe 200 to drive the liquid spiral feeder 300 to rotate through the steam, an air guide pipe 600 arranged outside the guide air pipe 400 and having an air inlet at the upper end, and an air guiding structure 700 rotatably connected in the liquid spiral feeder 300 to be driven to rotate by the steam and form a suction force at the air inlet.

[0027] In this embodiment, in order to simplify the structure, the sleeve 100 is integrally provided with the evaporation tube 21. The height of the overflow port is increased through the structure of the sleeve 100, so that when the solution is higher than the overflow port, it enters the overflow port through the overflow method. In this way, it is more conducive to the formation of the liquid film.

[0028] The intake pipe 200 is directly installed at the lower end of the steam equalizing chamber 40 and communicates with the lower chamber 43. The steam equalizing chamber 40 and the lower chamber 43 are communicated through the intake pipe 200.

[0029] In order to drive the liquid spiral feeding head 300 to rotate, the upper end of the air guide pipe 400 is rotatably connected to the intake pipe 200, and the lower end is fixedly connected to the liquid spiral feeding head 300.

[0030] The lower end of the air induction pipe 600 is fixedly connected to the liquid spiral feeding head 300, and it is located between the sleeve 100 and the air guide pipe 400. A gap is formed between the air induction pipe 600 and the sleeve 100 for the solution to enter, and a gap is formed between the air induction pipe 600 and the air guide pipe 400 for air to enter, and the position of the air induction port is higher than the overflow port.

[0031] A plurality of spiral grooves 310 are provided on the outer side wall of the liquid spiral feeding head 300. The spiral grooves 310 form a liquid inlet 11 and a liquid outlet 31 at the upper end and the lower end of the liquid spiral feeding head 300 respectively.

[0032] The lower end of the liquid spiral feeding head 300 is provided with a first outlet 330 communicating with the air guide pipe 400 and a second outlet 340 communicating with the air induction pipe 600. Along the radial direction of the liquid spiral feeding head 300, the second outlet 340 is located between the liquid outlet 31 and the first outlet 330. Among them, in order to make the solution form better centrifugal force and downward power in the liquid spiral feeding head 300, the liquid spiral feeding head 300 rotates along the opening direction of the liquid inlet 11.

[0033] Among them, the air induction structure 700 includes a pipe body 710 communicating with the air guide pipe 400, an air induction wheel 720 arranged in the pipe body 710 and driving the pipe body 710 to rotate through the intake steam, and a wind blade 730 arranged outside the pipe body 710. Among them, the rotation direction of the air induction wheel 720 is opposite to that of the wind wheel 500 when driven by the intake steam.

[0034] The lower end of the liquid spiral feeding head 300 extends to form a frustum-shaped distribution plate 320, and the lower end of the distribution plate 320 is larger than the upper end. The liquid flowing out from the liquid outlet 31 of the spiral groove 310 is further guided through the gap formed between the lower end of the distribution plate 320 and the inner wall of the evaporation tube 21, so that the formed liquid film is more uniform.

[0035] To avoid the distribution plate 320 from blocking the solution and affecting the uniformity of the liquid film, the distance between the lower end of the distribution plate 320 and the inner wall of the evaporation tube 21 is greater than or equal to the width of the spiral groove 310 in the radial direction.

[0036] A gap communicating with the air guiding pipe 600 is formed between the pipe body 710 and the liquid spiral feeding head 300. The second outlet 340 is formed between the lower end of the gap and the distribution plate 320, so that the second outlet 340 is inclined in the direction towards the inner wall of the evaporation tube 21.

[0037] In addition, at the position where the lower end of the liquid spiral feeding head 300 is located at the second outlet 340, there are spoiler vanes 321 for forming a swirl. The spoiler vanes 321 are arranged on the inner wall of the distribution plate 320. The length direction of the spoiler vanes 321 is distributed along the axial direction. There are multiple of them, and the multiple spoiler vanes 321 are evenly distributed around the axis of the distribution plate 320. The thickness of the spoiler vanes 321 is equal to or less than the thickness of the gap between the distribution plate 320 and the pipe body 710. In this embodiment, the thickness of the spoiler vanes 321 is preferably slightly less than the thickness of the gap between the distribution plate 320 and the pipe body 710, so as to reduce the frictional force between the two.

[0038] On the one hand, this application passes high-temperature steam into the evaporation tube 21 through the air inlet pipe 200. The high-temperature steam flows in the same direction as the liquid film, which can assist in pushing the liquid film to flow downward, reduce the fluctuations of the liquid film caused by gravity or surface tension, and enhance stability. On the second hand, after the high-temperature steam is introduced into the air inlet pipe 200, it drives the wind wheel 500 to rotate. The wind wheel 500 drives the liquid spiral feeding head 300 to rotate. After the solution passes through the spiral groove 310 on the spiral feeding head, a relatively uniform liquid film can be formed on the inner wall of the evaporation tube 21. The rotation of the liquid spiral feeding head 300 can not only increase the flow rate, but also form a centrifugal force, further ensuring the uniformity and continuity of the liquid film after forming, and can also clean the inside of the evaporation tube 21, effectively avoiding the problem of scale formation.

[0039] In addition, when the high-temperature steam flow enters the evaporation tube 21 from the first outlet 330, the flow rate will decrease due to the increase in the diameter, and the static pressure will increase. The increase in the static pressure will exert a pressure perpendicular to the pipe wall on the liquid film, thereby forming an impact on the liquid film and triggering the oscillation of the liquid film, which affects the uniformity. Therefore, through the design of the air guiding structure 700, a negative pressure is formed from the air inlet of the air guiding pipe 600 to form an air flow, so that an air flow is also formed at the second outlet 340. The air flow here will be relatively small and is located between the liquid outlet 31 and the first outlet 330, thereby forming a certain blockage to the air flow at the first outlet 330 and reducing the impact on the liquid film. In addition, since the liquid film is formed by a spiral and centrifugal structure in the area near the first outlet 330, the spiral flow and the relatively fast flow rate can also reduce the impact on the high-temperature steam flowing out from the first outlet 330.

[0040] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A distributor of a falling film evaporator, which is arranged on the evaporation tube (21) of the falling film evaporator, and is characterized in that: It includes a casing (100) provided at the upper end of the evaporation tube (21) for forming an overflow port, an air inlet pipe (200) coaxially arranged with the evaporation tube (21), a liquid spiral feeding head (300) rotatably installed in the evaporation tube (21), a gas guide pipe (400) connecting the liquid spiral feeding head (300) and the air inlet pipe (200), a wind wheel (500) located in the air inlet pipe (200) that drives the liquid spiral feeding head (300) to rotate through the incoming steam, an air guiding pipe (600) provided outside the gas guide pipe (400) and having an air inlet at the upper end, and an air guiding structure (700) rotatably connected inside the liquid spiral feeding head (300) that is driven to rotate by the incoming steam and forms a suction force at the air inlet; A plurality of spiral grooves (310) are provided on the outer sidewall of the liquid spiral feeding head (300). The spiral grooves (310) form a liquid inlet (11) and a liquid outlet (31) at the upper and lower ends of the liquid spiral feeding head (300) respectively. A first outlet (330) communicating with the gas guide pipe (400) and a second outlet (340) communicating with the air guiding pipe (600) are provided at the lower end of the liquid spiral feeding head (300). Along the radial direction of the liquid spiral feeding head (300), the second outlet (340) is located between the liquid outlet (31) and the first outlet (330); The position of the air inlet is higher than the overflow port.

2. The distributor (22) of the falling film evaporator according to claim 1, characterized in that: The air guiding structure (700) includes a pipe body (710) communicating with the gas guide pipe (400), an air guiding wheel (720) provided inside the pipe body (710) that drives the pipe body (710) to rotate through the incoming steam, and air blades (730) provided outside the pipe body (710). A gap communicating with the air guiding pipe (600) is formed between the pipe body (710) and the liquid spiral feeding head (300), and the lower end of the gap forms the second outlet (340).

3. The distributor (22) of the falling film evaporator according to claim 1 or 2, characterized in that: The rotating directions of the air guiding wheel (720) and the wind wheel (500) are opposite when driven by the incoming steam.

4. The distributor (22) of the falling film evaporator according to claim 1, characterized in that: The liquid spiral feeding head (300) rotates along the opening direction of the liquid inlet (11).

5. The distributor (22) of the falling film evaporator according to claim 1, characterized in that: A frustum-shaped distribution plate (320) is formed by extending the lower end of the liquid spiral feeding head (300), and the lower end of the distribution plate (320) is larger than the upper end.

6. The distributor (22) of the falling film evaporator according to claim 5, characterized in that: The distance between the lower end of the distribution plate (320) and the inner wall of the evaporation tube (21) is greater than or equal to the width of the spiral groove (310) in the radial direction.

7. The distributor (22) of the falling film evaporator according to claim 6, characterized in that: The second outlet (340) is formed between the air guiding structure (700) and the distribution plate (320), and the second outlet (340) is inclined in the direction towards the inner wall of the evaporation tube (21).

8. The distributor (22) of the falling film evaporator according to claim 7, characterized in that: Turbulence blades (321) for forming a swirl are provided at the lower end of the liquid spiral feeding head (300) at the position where the second outlet (340) is located.

9. A falling film evaporator, which sequentially includes a feeding section (10), a heating section (20), and a separation section (30) from top to bottom in the vertical direction, is characterized in that: A liquid inlet (11) and a steam inlet (12) are provided on the feeding section (10). A plurality of evaporation tubes (21) are provided on the heating section (20). A distributor (22) according to any one of claims 1-8 is provided between the steam inlet (12) and the evaporation tube (21); A liquid outlet (31) and a steam outlet (32) are provided on the separation section (30).

10. The falling film evaporator according to claim 9, characterized in that: A steam equalizing chamber (40) is provided in the feeding section (10). The liquid inlet (11) is arranged above the steam equalizing chamber (40), and a liquid leakage port (13) is formed between the outer wall of the steam equalizing chamber (40) and the feeding section (10). An upper chamber (42) communicated with the steam inlet (12) and a lower chamber (43) communicated with the intake pipe (200) are provided in the steam equalizing chamber (40). A plurality of communicating through holes are provided on a partition plate (41) between the upper chamber (42) and the lower chamber (43).

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