JP2694772B2 - Vertical falling film evaporator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a vertical falling liquid film evaporator. More specifically, it relates to the structure of the top of the heat transfer tube in the vertical falling liquid film evaporator.

(Prior Art) Vertical falling liquid film type evaporators are often used for evaporation and concentration of highly heat-sensitive fluids because the amount of retained liquid is small, a large overall heat transfer coefficient is obtained, and the boiling point rise of the liquid is small. Has been.

The most important item in the design of a vertical falling liquid film evaporator is that the liquid is evenly distributed in each heat transfer tube, a uniform and stable liquid film is formed on the inner wall of the tube, and a dry surface is formed on the inner surface of the tube. It is to prevent it from happening.

Now, as such a method for uniformly distributing the liquid in the evaporator, 1) a method of providing a spray nozzle in the heat transfer tube, 2) a method of providing a perforated plate at the upper part of the heat transfer tube, 3) a notch weir at the upper end of the heat transfer tube Method, 4) A method in which a notch weir and an upper porous plate are installed together at the upper end of the heat transfer tube is known.

The method of installing a spray nozzle inside the heat transfer tube of 1) is
This is a method in which a spray nozzle or a pipe having only holes formed therein is inserted into a heat transfer tube to disperse the liquid from the opening. This method has the problems that it is weak in the fluctuation range of the operating load and the structure is complicated.

The method of providing a perforated plate on the upper part of the heat transfer tube group in 2) is usually 2
A multi-perforated plate method of one or more sheets is adopted. The liquid is dispersed on each porous plate, flows down on the tube plate while maintaining an appropriate liquid depth, and is made to flow into each heat transfer tube from the upper tube end. In this case, the smoothness and levelness of the tube end surface are important for achieving uniform distribution, but since the heat transfer tube has not been processed, it is difficult to form a uniform and stable liquid film on the inner wall of the tube. There are drawbacks.

The method of providing a notch weir on the upper end of the heat transfer tube of 3) is most widely used as a method suitable for uniform distribution of liquid and formation of a uniform liquid film on the tube wall. In this method, a method of directly attaching a notch weir to the heat transfer tube, a method of inserting a socket with a notch weir, and a method of mounting by a screw method,
Etc.

In addition, various ideas such as a notch weir and a slit are made for the notch.

(Problems to be Solved by the Invention) In view of the problems of the prior art, in a vertical falling liquid film evaporator, the liquid is uniformly distributed in each heat transfer tube without special processing on the heat transfer tube or the tube plate. It is an object of the present invention to provide a heat transfer tube top structure in which a dry surface does not occur on the inner wall of the heat transfer tube.

(Means for Solving the Problems According to the Invention) In a falling liquid film evaporator in which a plurality of heat transfer tubes are erected vertically in a shell and a cutout weir is provided at the top of the heat transfer tubes, the cutout weir is rectangular. After forming a plurality of holes for the notch weir in the thin plate that was formed, make a cylinder with a diameter slightly larger than the diameter of the heat transfer tube, leaving a slit between both ends, and reduce the diameter a little and transfer it. It was inserted in the upper part of the heat tube.

In addition, a guide piece for directing a certain direction is provided in the hole of the cutout weir so that the liquid swirls and flows in.

Further, a drop-preventing projection was provided between the holes for the notch weir to prevent the drop from falling further into the heat transfer tube.

Furthermore, the cutout weir was attached so that the lower end edge of the cutout weir was located below the upper surface of the tube sheet, and the dimension management of the cutout weir was facilitated.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an evaporator embodying the present invention. The circulating liquid is extracted from the bottom of the evaporator (or distillation column) 1, and is passed through the pipe 3 by the circulation pump 2 to the insertion pipe 5 from the raw liquid supply port 4.
Thus, it is primarily dispersed on the porous dispersion plate 6 and uniformly dispersed on the tube plate 7. While maintaining an appropriate liquid depth on the tube plate 7, it flows down into the heat transfer tube 8 from the notched dam portion of the top cylinder 9 inserted into the upper end of the heat transfer tube 8 arranged in the shell 13,
Partial evaporation occurs while forming a stable liquid film. The vaporized vapor and the concentrated liquid enter the bottom of the tower or the can 1 through the vapor outlet 10 and are separated into the vapor and the concentrated liquid. The liquid is pumped up again as the bottom liquid of the tower 1, and most of the liquid is circulated to the raw liquid supply port 4.

A heating medium inlet 11 is provided at the upper part of the shell 13 and a heating medium outlet 12 is provided at the lower part thereof, and heat exchange is performed with the liquid film in the heat transfer tube 8.

FIG. 2 shows the details of the top cylinder 9. The top cylinder 9 is formed into a tubular shape after forming a plurality of holes for the notch weir 14 in a rectangular thin plate by, for example, press working. Therefore, the slit 15 is formed at the end-to-end joining portion. The diameter of this tubular body is slightly larger than the inner diameter of the heat transfer tube before insertion. When inserting into the top of the heat transfer tube 8 so that the slits 15 are made narrower and narrower, the top cylinder 9 tries to expand and a spring force acts. Due to this spring force, the top cylinder 9 adheres well to the top of the heat transfer tube 8 and is mounted without the need for any other fixing means. Reference numeral 16 is a protrusion for preventing slippage of the mounted top cylinder 9 and is provided between the holes for the notch weir. The projection 16 hits the top of the heat transfer tube 8 and is prevented from falling into the heat transfer tube 8. This protrusion
16 can be processed simultaneously when processing the notch weir 14 in a rectangular thin plate.

The stock solution supplied from the stock solution supply port 4 is kept at an appropriate depth on the tube plate 7 above the shell 13, and a large number of notch weirs are formed in the top cylinder 9 mounted on the top of each heat transfer tube 8. From 14 to the inner wall of the pipe 8.

In order to form a uniform and stable liquid film on the inner wall of the heat transfer tube 8, it is advisable to provide the notch weir 14 with guide pieces 14a (FIG. 3) which are all directed in the same direction, not just openings. The undiluted solution is guided in a tangential direction by this guide piece 14a and flows in, and while swirling, it becomes a stable liquid film and flows down in the heat transfer tube 8.

The notch weir 14 is formed with the projection 16 so that the lower edge 16b thereof is located below the upper surface of the tube sheet 7 when the top cylinder 9 is inserted into the heat transfer tube 8. With this configuration, it is not necessary to use the nerve to the left in aligning the lower edges of the plurality of cutout weirs 14, so that the press working becomes easy.

(Effect) After forming a plurality of holes for the notch weir in a rectangular thin plate, form the notch weir into a cylindrical shape leaving a slit between both ends and place it on the upper part of the heat transfer tube. Since it was inserted, 1) without any special processing on the tube sheet or heat transfer tube 8,
It is possible to evenly distribute the liquid in each heat transfer tube and form a liquid film so that a dry surface does not occur.

2) Compared to the case where a notch weir is processed directly on the heat transfer tube,
It is possible to provide a high-quality evaporator without problems of variation in processing accuracy and variation in assembly accuracy.

3) When the heat transfer tube is attached to the tube plate by welding, not only the welding method is difficult, but also distortion due to welding heat is generated and the notch weir at the end of the heat transfer tube is deformed. However, according to the present invention, it is possible to reduce the diameter of the shell and to provide an economical and high-quality evaporator. You can

4) Since the notch weir can be processed by pressing into a thin plate,
It is easy to position the notch weir below the upper surface of the tube sheet. Therefore, the start of liquid inflow is constant in each heat transfer tube. Therefore, it is not necessary to adjust the levelness of the pipe end surface and the notch weir, and an economical and high-performance evaporator can be provided.

5) Since the hole of the notch weir can be pressed, unified quality control is possible, and the size and shape can be easily set according to the flow rate fluctuation range and the heat transfer tube diameter.

6) Since the heat transfer tube is not processed, it is not necessary to stick to the plate thickness of the heat transfer tube, and since the top cylinder is equipped with a spring, it can be installed without sticking to the tolerance of the heat transfer tube.

7) Even in the case of multi-product switching operation of heavily contaminated liquid or process liquid, the notch weir is located below the top surface of the tube sheet, so after the operation is stopped, the tube sheet can be easily cleaned without any liquid accumulation, resulting in contamination. It is possible to provide a strong evaporator.

8) Also in the conventional thermosiphon type evaporator, the vertical falling liquid film type having a large overall heat transfer coefficient with a small amount of retained liquid only by modifying the upper and lower channel cover parts and attaching the top cylinder of the present invention to the heat transfer tube Since the evaporator can be easily modified, the existing device can be economically improved.

[Brief description of the drawings]

 Fig. 1 is a system diagram of the vertical falling film evaporator. FIG. 2 is an enlarged detailed view of the top cylinder. FIG. 3 is a plan view taken along the arrow III in FIG. In the figure; 1 ... Distillation tower or evaporator 2 ... Circulation pump, 3 ... Piping 4 ... Supply port, 5 ... Insertion pipe 6 ... Porous dispersion plate, 7 ... Tube plate 8 ... Heat transfer tube, 9 ... Top cylinder 10 ... Steam outlet, 11 ... Heating medium inlet 12 ... Heating medium outlet, 13 ... Shell 14 ... Many notched weirs, 14a ... Guide piece 14b. ) Lower edge 15 …… Slit 16 …… Slip-off prevention protrusion

Claims (4)

(57) [Claims] 1. A falling liquid film evaporator in which a plurality of heat transfer tubes are vertically provided in a shell, and a notch weir is provided at the top of the heat transfer tubes, wherein the notch weir has a rectangular thin plate. After forming a plurality of holes for the notch weir, it is formed into a cylindrical shape leaving a slit between both ends, and is inserted into the upper part of the heat transfer tube. Membrane evaporator. 2. The vertical falling liquid film evaporator according to claim 1, wherein the plurality of notch weir holes are provided with guide pieces oriented in a fixed direction. 3. The vertical falling liquid film evaporator according to claim 1, wherein a drop preventing projection is provided between the holes for the notch weir. 4. The notch weir is attached so that the lower end edge of the notch weir is positioned below the upper surface of the tube sheet.
The vertical falling liquid film evaporator according to (2) or (3).