Liquid distributor for falling film evaporation

Abstract

The application discloses a liquid distributor for falling film evaporation, which comprises a liquid inlet pipe and a first buffer chamber communicated with the liquid inlet pipe, a circular buffer chamber and a plurality of second buffer chambers matched with evaporation pipes arranged in sequence below the first buffer chamber, a plurality of evenly distributed spiral pipes communicated between the first buffer chamber and the circular buffer chamber, and a plurality of evenly distributed straight pipes communicated between the circular buffer chamber and the second buffer chambers; a plurality of membrane distribution pipes are evenly distributed at the bottom of the second buffer chambers and face the inner walls of the evaporation pipes; the liquid inlet pipe and the liquid outlet pipe are arranged in a staggered mode in the same buffer chamber; the liquid distributor can uniformly distribute the membrane whether the liquid distribution surface is flat or not, can adjust the liquid distribution flow, can effectively utilize the steam for preheating and can avoid the influence of the steam on the membrane distribution.

Description

Technical Field

[0001] This invention relates to evaporation equipment, and more particularly to a liquid distributor for falling film evaporation. Background Technology

[0002] A falling film evaporator is a device used for liquid concentration and evaporation, widely used in industries such as chemical, pharmaceutical, and food processing. Its main characteristic is that the liquid forms a thin film inside the evaporation tube, flowing downwards along the tube wall under gravity, while simultaneously being heated by steam outside the tube to achieve rapid evaporation and concentration.

[0003] In existing falling film evaporators, the evaporation tubes are often arranged in a hexagonal pattern. The liquid distributor above the heat exchanger is often a perforated plate at the bottom and an open top. The liquid flows out from the holes of the perforated plate under the action of gravity, falls vertically, lands on the top gap plane of the hexagonal evaporation tubes, and then flows back into the evaporation tubes.

[0004] Chinese invention patent CN106693420B discloses a falling film evaporator, including a shell, a feed inlet, a material distribution system, a liquid distribution plate, and a tube sheet. The material distribution system, liquid distribution plate, and tube sheet are arranged sequentially from top to bottom below the feed inlet. The material distribution system evenly distributes the liquid entering from the feed inlet onto the liquid distribution plate. A plurality of evaporation tubes are evenly inserted into the tube sheet. A plurality of distributors are provided on the lower surface of the liquid distribution plate, perpendicular to the plate, with their number and position corresponding to the evaporation tubes. A fixing part is fixed to the liquid distribution plate, and a film-forming part is inserted into the evaporation tubes. A plurality of through holes are also evenly arranged on the liquid distribution plate, staggered with the distributors. A regulator is provided on the liquid distribution plate, which can move the liquid distribution plate up and down. The falling film evaporator provided by this invention achieves online adjustable flow rate through the regulator on the liquid distribution plate, thereby improving the evaporation effect.

[0005] In the aforementioned prior art, the liquid flows into the evaporator tubes under gravity, requiring the liquid distribution plate and tube sheet to be perfectly horizontal. If the horizontality of these planes is insufficient, uniform liquid distribution and uniform film distribution cannot be achieved. Secondly, when the liquid flows into the evaporator tubes under gravity, if the inlet flow rate is too low, the liquid cannot cover the top gap plane of the tube sheet, resulting in uneven liquid flow into each evaporator tube and uneven film distribution. When the inlet flow rate is too high, for porous tanks, the liquid flowing out of the small holes is prone to turbulence and no longer flows vertically downwards, which also leads to uneven film distribution and limits the operational flexibility of the liquid distribution flow rate of the falling film evaporator. Furthermore, during the operation of the falling film evaporator, some of the vapor formed by liquid evaporation rises. This rising vapor may accumulate in a certain area below the liquid distribution plate, causing uneven pressure below the through holes, which in turn leads to uneven liquid distribution through the through holes. If too much vapor rises, some of it may even pass directly through the through holes of the distribution plate during its ascent, resulting in even more uneven liquid distribution. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a liquid distributor for falling film evaporation that can uniformly distribute the liquid regardless of whether the liquid surface is flat or not. Secondly, it has a large liquid flow rate adjustment range and can effectively utilize steam preheating while avoiding the influence of steam that causes uneven film distribution.

[0007] Technical solution: The liquid distributor for falling film evaporation of the present invention includes an inlet pipe and a first buffer chamber connected thereto, and further includes an annular buffer chamber and several annular second buffer chambers matched with the evaporation tubes arranged sequentially below the first buffer chamber. Several evenly distributed spiral tubes are connected between the first buffer chamber and the annular buffer chamber, and several evenly distributed straight tubes are connected between the annular buffer chamber and the second buffer chamber. Several film-forming tubes facing the inner wall of the evaporation tube are evenly distributed at the bottom of the second buffer chamber. The inlet pipe and the outlet pipe in the same buffer chamber are staggered.

[0008] Based on the above technical solution, after the liquid enters the first buffer chamber through the inlet pipe and is buffered, it flows evenly into the spiral tube. In the spiral tube, it is accelerated and then flows into the annular buffer chamber to form a circulation, thus ensuring that the liquid flows evenly into the straight pipe. This further ensures that the amount of liquid flowing into each of the second buffer chambers is balanced. The liquid undergoes another buffering process in the second buffer chamber, further ensuring that the amount of liquid finally sprayed from the film-distributing tube is uniform, achieving uniform film distribution. This device achieves uniform liquid distribution through multi-stage buffering, eliminating the need for the top surface of the tube sheet to be completely horizontal to achieve uniform film distribution. Moreover, based on the above process, each buffer chamber ensures that the liquid flow rate is... The liquid distribution is balanced and ensures uniform film formation. Instead of directly injecting liquid into the evaporator through the holes in the liquid distribution plate, the liquid flow direction on the liquid distribution plate becomes uncontrollable due to the flow rate, resulting in uneven liquid inflow through the holes. Therefore, this device has a wider range of liquid flow rate adjustment. Furthermore, because both the second buffer chamber and the annular buffer chamber are ring-shaped, the steam generated in the evaporation tube can flow upwards from the ring. This invention essentially provides a flow channel for the steam, preventing it from interfering with the liquid flow. Moreover, the upward flow of steam can preheat the liquid, providing less heat energy for the subsequent evaporation of the liquid film in the evaporation tube, thus saving energy.

[0009] Preferably, the first buffer chamber is spherical in shape.

[0010] The design employs a spherical shape, with the sidewall of the first buffer chamber being spherical, ensuring uniform liquid flow into the spiral tube.

[0011] Preferably, the distance from the spiral tube to the side wall of the first buffer chamber gradually increases and then decreases from top to bottom.

[0012] With the above-mentioned configuration, the spiral tube is thicker in the middle and thinner at both ends. This results in a longer overall length of the spiral tube at the same height, allowing the liquid to have a longer buffering and acceleration distance within the spiral tube.

[0013] Preferably, the inlet pipe is positioned directly opposite the center of the bottom of the first buffer chamber, and the top of the spiral tube is positioned on the upper side of the first buffer chamber.

[0014] The staggered arrangement of the inlet pipe and the spiral tube can prevent liquid from flowing directly into certain spiral tubes from the inlet pipe, thus avoiding uneven liquid distribution.

[0015] Preferably, the bottom of the spiral tube is located in the middle of the outer side of the annular buffer chamber.

[0016] The bottom of the spiral tube is positioned in the middle of the outer side of the annular buffer chamber, so it is not directly opposite the straight tube at the bottom of the annular buffer chamber. This prevents the liquid flowing out of the spiral tube from directly entering some straight tubes, which would result in uneven liquid distribution.

[0017] Preferably, the straight tube at the top of the second buffer chamber is staggered with the membrane tube at the bottom.

[0018] The staggered arrangement of straight pipes and membrane tubes can also prevent liquid flowing out of the straight pipes from flowing directly into some membrane tubes, thus avoiding uneven liquid distribution.

[0019] Preferably, the second buffer chamber is hexagonal and the adjacent sides of the second buffer chambers are connected to each other to form a planar grid.

[0020] The second buffer chamber adopts a hexagonal ring shape, which can accommodate the conventional hexagonal arrangement of evaporator tubes. The adjacent tubes are connected to form a planar grid, which can enhance the overall structural strength.

[0021] Preferably, the second buffer chamber is annular, and adjacent second buffer chambers are connected to each other to form a planar grid.

[0022] The second buffer chamber, being circular, has wider applicability and can be used for various arrangements of evaporator tubes. The interconnection of these tubes to form a planar grid also strengthens the overall structural strength.

[0023] Preferably, the membrane tube is a multi-segment tube.

[0024] The membrane tube is made of multi-segment tube, which allows for flexible adjustment of its connection position with the second buffer chamber and its orientation to the inner wall of the evaporator tube.

[0025] Preferably, the membrane tube comprises three sections connected in sequence, the first section is inclined, the second section is vertical, and the third section is inclined or horizontal. The first section is connected to the second buffer chamber, and the outlet of the third section faces the inner wall of the evaporation tube.

[0026] The membrane tube adopts the above three-section structure, which allows it to be connected to the inside of the second buffer chamber, better achieving misalignment with the straight tube, and also allows its bottom outlet to face the inner wall of the evaporator tube.

[0027] Beneficial effects: Compared with the prior art, the significant effects of this invention are as follows: through multi-stage buffering, the uniformly distributed liquid is directly sprayed onto the inner wall of the evaporator tube, so that the top surface of the tube sheet does not need to be completely horizontal; secondly, multi-stage buffering ensures uniform liquid distribution and also makes the liquid flow rate adjustment range larger; furthermore, a flow channel is set for the steam, which not only avoids its interference with the membrane, but also saves energy. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 for Figure 1 Enlarged view of a portion of point A in the middle;

[0030] Figure 3 This is a schematic diagram of the present invention mounted on the evaporator tube. Detailed Implementation

[0031] As shown in the figure, please note that... Figure 1 The six adjacent sides of the second buffer chamber appear to share a common edge, but in reality, the adjacent sides are independent of each other; this is only because the angle makes it impossible to visually demonstrate.

[0032] The present invention provides a liquid distributor for falling film evaporation, comprising an inlet pipe 1 and a first buffer chamber 2 connected thereto, and further comprising an annular buffer chamber 4 and a plurality of annular second buffer chambers 6 matched with evaporation tubes arranged sequentially below the first buffer chamber 2. A plurality of evenly distributed spiral tubes 3 are connected between the first buffer chamber 2 and the annular buffer chamber 4, and a plurality of evenly distributed straight tubes 5 are connected between the annular buffer chamber 4 and the second buffer chambers 6. A plurality of film-covering tubes 7 are evenly distributed at the bottom of the second buffer chambers 6 facing the inner wall of the evaporation tube.

[0033] The inlet and outlet pipes in the same buffer chamber are staggered. This is to avoid the inlet pipes being directly opposite some outlet pipes, which would cause more liquid to be discharged into those outlet pipes and result in uneven liquid distribution.

[0034] The inlet pipe 1 is located directly in the middle of the bottom of the first buffer chamber 2, and the inlet pipe 1 can be a vertical pipe of DN30.

[0035] The first buffer chamber 2 can be configured as a spherical cap, sphere, cylinder, frustum, prism, or frustum shape, etc., as long as its sides are evenly and symmetrically distributed to ensure that the liquid flows evenly into the spiral tube; the first buffer chamber 2 can be configured as a spherical cap, with the top using a horizontal circular surface with a diameter of 145mm and the bottom using a partially spherical surface with a diameter of 140mm or 150mm.

[0036] The top of the spiral tube 3 is positioned on the upper side of the first buffer chamber 2 to ensure misalignment with the inlet pipe 1. It is important to note that the tops of the spiral tubes 3 should be equidistantly distributed in a ring on the upper side of the first buffer chamber 2 to ensure uniform liquid flow into each spiral tube 3. Each spiral tube 3 is a circle of fixed diameter swept around two spiral paths with gradually changing diameters, forming a tubular shape. From bottom to top, the diameter of the lower spiral gradually increases, while the diameter of the upper spiral gradually decreases. The two spirals rotate in the same direction and transition smoothly at the connection point. The middle section of the spiral tube 3 is the thickest, allowing the liquid more buffering and acceleration distance at the same height. Under the combined action of gravity and injection pressure, the liquid gradually accelerates within the spiral tube 3 to form a circulation within the annular buffer chamber 4. All spiral tubes 3 have the same shape to ensure consistent buffering and acceleration for the liquid.

[0037] Six spiral tubes 3 can be set. The diameter of the spiral tubes 3 is 20mm. From bottom to top, the diameter of the lower spiral gradually changes from 180mm to 300mm with 0.1 turns, and the diameter of the upper spiral gradually changes from 300mm to 100mm with 0.4 turns.

[0038] The bottom of the spiral tube 3 is equidistantly arranged in a ring at the middle of the outer side of the annular buffer chamber 4. Several straight tubes 5 are evenly distributed at the bottom of the annular buffer chamber 4. After the liquid enters the annular buffer chamber 4 through the spiral tube 3, it forms a circulation that ensures that the liquid enters each straight tube 5 evenly.

[0039] The annular buffer chamber 4 is formed by rotating a circle with a diameter of 50 mm around an axis that is coplanar with the circle, with a rotation radius of 90 mm.

[0040] The top of the second buffer chamber 6 is evenly distributed with several straight pipes 5. The straight pipes 5 at the top of the second buffer chamber 6 are staggered with the membrane pipes 7 at the bottom. The diameter of the straight pipes 5 is 8mm.

[0041] The second buffer chamber 6 can be a hexagonal ring, a circular ring, or other rings that match the arrangement of the evaporator tubes, such as an octagonal ring. Adjacent second buffer chambers 6 are connected to each other to form a planar grid. The second buffer chamber 6 can be a hexagonal ring with a circular tube on each side, and the diameter of each circular tube is 10mm.

[0042] The membrane distribution tube 7 is a multi-segment tube, such as three segments connected in sequence. The first segment connects to the inside of the second buffer chamber 6 and is inclined downwards. The second segment is vertical. The outlet of the third segment is inclined or horizontally facing the inside of the evaporation tube. Each segment of the membrane distribution tube 7 can be a circular tube with a diameter of 2mm. The first segment is inclined downwards at 45°, and the third segment is horizontal or inclined downwards at 45°. By setting it into three segments, the liquid is sprayed from the inside of the second buffer chamber 6 towards the inside of the second buffer chamber 6, and then diverted by the latter two segments to spray towards the inner wall of the evaporation tube. This solves the problem that the membrane distribution tube 7 is difficult to set on the outside of the second buffer chamber 6. The membrane distribution tube 7 can also be set as an arc-shaped tube to divert the liquid from the inside of the second buffer chamber 6 to the outside and spray it towards the inner wall of the evaporation tube. Since the membrane distribution tube 7 is also evenly distributed, uniform membrane distribution can be achieved.

[0043] In one embodiment of the present invention, the membrane distribution tube 7 has 444 tubes. To demonstrate the ability of the liquid distributor to distribute the membrane evenly, a CFD simulation was performed. The fluid was set to water, and the inlet flow rate of the liquid distributor was 1 kg / s. The flow rates at the outlets of the 444 membrane distribution tubes are shown in the table below. The uniformity (calculated as 1 - standard deviation / average) is 95.78%, which is within the allowable deviation range, indicating that the device of the present invention can achieve uniform membrane distribution.

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

Claims

1. A liquid distributor for falling film evaporation, comprising an inlet pipe (1) and a first buffer chamber (2) connected thereto, characterized in that: It also includes an annular buffer chamber (4) and several annular second buffer chambers (6) that match the evaporation tubes arranged sequentially below the first buffer chamber (2). Several evenly distributed spiral tubes (3) are connected between the first buffer chamber (2) and the annular buffer chamber (4). Several evenly distributed straight tubes (5) are connected between the annular buffer chamber (4) and the second buffer chamber (6). Several film-covering tubes (7) facing the inner wall of the evaporation tube are evenly distributed at the bottom of the second buffer chamber (6). In the first buffer chamber (2), the annular buffer chamber (4) and the second buffer chamber (6), the liquid inlet pipe and the liquid outlet pipe are staggered.

2. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The first buffer chamber (2) is spherical.

3. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The diameter of the spiral tube (3) gradually increases from top to bottom and then decreases.

4. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The inlet pipe (1) is directly opposite the bottom center of the first buffer chamber (2), and the top of the spiral pipe (3) is located on the upper side of the first buffer chamber (2).

5. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The bottom of the spiral tube (3) is located in the middle of the outer side of the annular buffer chamber (4).

6. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The straight tube (5) at the top of the second buffer chamber (6) and the membrane tube (7) at the bottom are misaligned.

7. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The second buffer chamber (6) is hexagonal and the adjacent sides of the second buffer chambers (6) are connected to each other, forming a planar grid.

8. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The second buffer chamber (6) is in the shape of a ring, and adjacent second buffer chambers (6) are connected to each other to form a planar grid.

9. A liquid distributor for falling film evaporation according to claim 1, characterized in that: The membrane tube (7) is a multi-segment tube.

10. A liquid distributor for falling film evaporation according to claim 9, characterized in that: The membrane tube (7) includes three sections connected in sequence. The first section is inclined, the second section is vertical, and the third section is inclined or horizontal. The first section is connected to the second buffer chamber (6), and the outlet of the third section faces the inner wall of the evaporation tube.

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