Vertical tube external falling film evaporator and evaporation method thereof

Abstract

The invention relates to the technical field of heat exchangers, and discloses a vertical tube outer falling film evaporator and an evaporation method thereof. A heating steam inlet penetrates through the top of the outer shell; a material inlet, a secondary steam outlet, a material outlet and an emptying opening are formed in the side wall of the outer shell; a non-condensed steam opening is formed in the bottom of the outer shell; a down-flow plate and a falling film evaporation unit are sequentially arranged in the outer shell along the downward direction of the heating steam inlet; the falling film evaporation unit comprises a first tube plate, a second tube plate and at least one heat exchange tube. Different numbers of down-flow discs can be arranged according to the length of the heat exchange pipe, liquid films outside the pipe can be collected on the down-flow discs in time through flow guiding on the down-flow discs, then the films are distributed again, and the uniformity of the liquid films is not affected by the length of the heat exchange pipe. In addition, due to the fact that the space of the shell pass is large, the influence of overflow of separated steam generated in the flowing process of the feed liquid on a liquid film outside the heat exchange pipe is smaller than that of film forming in the pipe.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and particularly to a vertical tube external falling film evaporator and an evaporation method thereof. Background Art

[0002] As an efficient evaporation device, the falling film evaporator is widely used in the fields of petrochemical industry, metallurgy, light industry, food processing, medicine, seawater desalination, sewage treatment, etc. due to its unique advantages. At present, the falling film evaporator is still mainly the in-tube falling film evaporator. Its working principle is usually to add the material from the upper tube box of the heating chamber of the falling film evaporator, and then through the liquid distribution and film-forming device, evenly distribute it into each heat exchange tube; and under the action of gravity, vacuum induction and air flow, a uniform film flows downward. Although the liquid in the upper part of the heat exchange tube section can form a film under the action of the film-forming device, the continuity and uniformity of the film formation in the lower part of the heat exchange tube section are poor. Especially for the long and thin heat exchange tubes, due to the small space inside the tube, as the steam overflows inside the tube, it further affects the uniformity of the liquid film, and it is very difficult to set a film-forming device inside the heat exchange tube. Therefore, it is very important to develop an evaporator in which the liquid can form a continuous and uniform liquid film during the flow. Summary of the Invention

[0003] Aiming at the above existing technical deficiencies, the technical problem to be solved by the present invention is to provide a vertical tube external falling film evaporator and an evaporation method thereof, aiming to solve the problem of poor liquid film uniformity of the existing falling film evaporator.

[0004] To solve the above technical problem, the present invention adopts the following technical solutions: The present invention provides a vertical tube external falling film evaporator, including: a housing; a heating steam inlet is provided through the top of the housing; A material inlet, a secondary steam outlet and a material outlet are provided on the side wall of the housing; A non-condensable gas port is provided at the bottom of the housing; A liquid dropping tray and a falling film evaporation unit are sequentially arranged inside the housing along the direction downward from the heating steam inlet; The falling film evaporation unit includes a first tube sheet, a second tube sheet and at least one heat exchange tube.

[0005] Further, the liquid dropping trays are uniformly arranged along the longitudinal direction of the heat exchange tubes.

[0006] Further, the liquid dropping tray includes a diversion tube, a steam rising tube and a tray body; The diversion tube is arranged outside the heat exchange tube, the steam rising tube penetrates through the tray body, and at the same time, the steam rising tube is arranged at intervals with the heat exchange tube along the longitudinal direction of the tray body.

[0007] Further, the diversion tube includes an upper liquid collecting conical tube, an overflow port and a lower diversion conical tube.

[0008] Furthermore, the upper liquid collecting cone tube and the lower flow guiding cone tube are vertically symmetrical, and the overflow port is arranged between the upper liquid collecting cone tube and the lower flow guiding cone tube.

[0009] Furthermore, the heat exchange tubes penetrate through the first tube sheet and the second tube sheet.

[0010] Furthermore, at least two distance pipes are arranged inside the outer shell; Wherein, the distance pipes are arranged longitudinally parallel to the heat exchange tubes; The distance pipes are arranged between the first tube sheet and the downcomer tray.

[0011] Furthermore, the distance pipes penetrate through the downcomer tray and are arranged on the first tube sheet.

[0012] Furthermore, the material inlet and the secondary steam outlet are arranged between the first tube sheet and the downcomer tray; The material outlet and the drain port are arranged between the second tube sheet and the downcomer tray.

[0013] An evaporation method for a vertical falling film evaporator outside the tube includes: Adding the material liquid to be processed from the upper part of the shell side; Under the action of gravity, the material liquid flows downward and passes through multiple downcomer trays arranged inside the shell side; Each downcomer tray is provided with a diversion tube, and the material liquid is evenly distributed on the outer wall of each heat exchange tube through the diversion tube to form a continuous liquid film; The distance between the downcomer trays is fixed by distance pipes to ensure that the material liquid can descend stably and evenly; Heating steam is introduced into the heat exchange tubes to heat the liquid film formed on the outer wall of the heat exchange tubes to generate secondary steam; As the heating process progresses, the material liquid evaporates and concentrates during the process of flowing downward along the outer wall of the heat exchange tube, and the concentrated material liquid is obtained at the bottom of the shell side. The beneficial effects of the present invention are as follows: 1. The present invention can set different numbers of downcomer trays according to the length of the heat exchange tubes. The diversion on the downcomer trays can timely collect the liquid film outside the tubes in the downcomer trays and then re-distribute the film, so that the uniformity of the liquid film is not affected by the length of the heat exchange tubes.

[0014] 2. Since the space of the shell side of the present invention is large, the influence of the separated steam generated during the flow of the material liquid on the liquid film outside the heat exchange tubes is smaller than that on the liquid film formed inside the tubes. Description of the Drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 Schematic structural diagram of a vertical tube external falling film evaporator provided by an embodiment of the present invention.

[0017] Figure 2 Schematic structural diagram of a downcomer tray.

[0018] Figure 3 For Figure 2 Cross-sectional view A-A in

[0019] Figure 4 Schematic structural diagram of a guide pipe; Explanation of reference numerals: 1, outer shell; 2, heating steam inlet; 3, tube box; 4, first tube sheet; 5, second tube sheet; 6, material inlet; 7, secondary steam outlet; 8, heat exchange tube; 9, downcomer tray; 10, spacer tube; 91, guide pipe; 92, steam riser; 93, tray body; 912, upper liquid collection cone tube; 913, overflow port; 914, lower guide cone tube; 11, material outlet; 12, drain port; 13, non-condensable gas port; 14, condensate outlet. Detailed implementation manners

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0021] Embodiment 1

[0022] As Figures 1 to 4 shown, this embodiment provides a vertical tube external falling film evaporator, including an outer shell 1; as Figure 1 shown, a heating steam inlet 2 penetrates through the top of the outer shell 1; there is a tube box 3 below the heating steam inlet 2; a material inlet 6, a secondary steam outlet 7, a material outlet 11 and a drain port 12 are arranged on the side wall of the outer shell 1; a non-condensable gas port 13 and a condensate outlet 14 are arranged at the bottom of the outer shell 1; a downcomer tray 9 and a falling film evaporation unit are sequentially arranged inside the outer shell 1 along the direction downward from the heating steam inlet 2; the falling film evaporation unit includes a first tube sheet 4, a second tube sheet 5 and at least one heat exchange tube 8; the downcomer trays 9 are uniformly arranged along the longitudinal direction of the heat exchange tubes 8.

[0023] Specifically, as Figure 2 shown, the downcomer 9 includes a diversion pipe 91, a steam riser 92 and a tray body 93; as Figure 3 shown, the diversion pipe 91 is arranged outside the heat exchange tubes 8, the steam riser 92 penetrates through the tray body 93, and at the same time, the steam riser 92 is arranged at intervals with the heat exchange tubes 8 in the longitudinal direction of the tray body 93; as Figure 4 shown, the diversion pipe 91 includes an upper liquid collecting cone pipe 912, an overflow port 913 and a lower diversion cone pipe 914; the upper liquid collecting cone pipe 912 and the lower diversion cone pipe 914 are symmetrically arranged up and down, and the overflow port 913 is arranged between the upper liquid collecting cone pipe 912 and the lower diversion cone pipe 914; the heat exchange tubes 8 penetrate through the first tube sheet 4 and the second tube sheet 5; at least two spacing pipes 10 are further arranged inside the outer shell 1; wherein, the spacing pipes 10 are arranged longitudinally and parallel to the heat exchange tubes 8; the spacing pipes 10 are arranged between the first tube sheet 4 and the downcomer 9; the spacing pipes 10 penetrate through the downcomer 9 and are arranged on the first tube sheet 4; the material inlet 6 and the secondary steam outlet 7 are arranged between the first tube sheet 4 and the downcomer 9; the material outlet 11 and the drain port 12 are arranged between the second tube sheet 5 and the downcomer 9.

[0024] Embodiment 2

[0025] Based on Embodiment 1, this embodiment further provides an evaporation method for a vertical tube external falling film evaporator, including: Adding the material liquid to be processed from the material inlet 6; Under the action of gravity, the material liquid flows downward and passes through multiple downcomers 9 arranged inside the shell side; Each downcomer 9 is provided with a diversion pipe 91, and the material liquid is evenly distributed on the outer walls of each heat exchange tube 8 through the diversion pipe 91 to form a continuous liquid film; The distance between the downcomers 9 is fixed by the spacing pipes 10 to ensure that the material liquid can descend stably and evenly; Heating steam is introduced into the heat exchange tubes 8 to heat the liquid film formed on the outer walls of the heat exchange tubes 8 to generate secondary steam and discharge it through the secondary steam outlet 7; As the heating process progresses, the material liquid evaporates and concentrates during the process of flowing downward along the outer walls of the heat exchange tubes 8, and the concentrated material liquid is obtained at the bottom of the shell side and discharged through the material outlet 11.

[0026] Wherein, during equipment cleaning or maintenance, the residual material or cleaning liquid in the shell side is discharged through the drain port 12 arranged on the side wall of the outer shell; the non-condensable gas in the system is discharged through the non-condensable steam port 13 arranged at the bottom of the outer shell; the water formed by the condensation of the heating steam is discharged through the condensate outlet 14 arranged at the bottom of the outer shell.

[0027] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A vertical tube falling film evaporator, characterized in that: include: outer shell; A heating steam inlet is provided on the top of the outer shell; The side wall of the outer shell is provided with a material inlet, a secondary steam outlet and a material outlet; The bottom of the outer shell is provided with a non-condensable steam port; The interior of the outer shell is provided with a liquid dropper and a falling film evaporation unit in sequence along the downward direction of the heating steam inlet; The falling film evaporation unit comprises a first tube sheet, a second tube sheet and at least one heat exchange tube.

2. A vertical tube falling film evaporator as claimed in claim 1, characterized in that: The downcomers are evenly arranged along the longitudinal direction of the heat exchange tube.

3. A vertical tube falling film evaporator according to any one of claims 1 or 2, characterized in that: The downcomer includes a draft tube, a steam riser and a downcomer body; The flow guide pipe is arranged outside the heat exchange pipe, and the steam riser is passed through the disc body. Meanwhile, the steam riser is arranged at intervals from the heat exchange pipe along the longitudinal direction of the disc body.

4. A vertical tube falling film evaporator as claimed in claim 3, characterized in that: The guide pipe comprises an upper liquid collecting cone pipe, an overflow port and a lower guide cone pipe.

5. A vertical tube falling film evaporator as claimed in claim 4, characterized in that: The upper liquid collecting cone tube and the lower flow guiding cone tube are symmetrical in vertical direction, and the overflow port is arranged between the upper liquid collecting cone tube and the lower flow guiding cone tube.

6. A vertical tube falling film evaporator as claimed in claim 1, characterized in that: The heat exchange tube passes through the first tube sheet and the second tube sheet.

7. A vertical tube falling film evaporator as claimed in claim 1, characterized in that: At least two distance tubes are also arranged inside the outer shell; Wherein, the distance tube is arranged longitudinally parallel to the heat exchange tube; The distance pipe is arranged between the first tube sheet and the downcomer.

8. A vertical tube falling film evaporator as claimed in claim 7, characterized in that: The distance pipe passes through the downcomer tray and is arranged on the first tube sheet.

9. A vertical tube falling film evaporator as claimed in claim 1, characterized in that: The material inlet and the secondary steam outlet are arranged between the first tube sheet and the downcomer; The material outlet and the drain outlet are arranged between the second tube sheet and the downcomer.

10. An evaporation method based on a vertical tube falling film evaporator according to claim 1, characterized in that: include: Add the material liquid to be treated from the material inlet; Under the action of gravity, the material liquid flows downward and flows through the multi-layer downcomer trays arranged inside the shell side; A guide pipe is provided on each layer of the downcomer plate, and the material liquid is evenly distributed on the outer wall of each heat exchange tube through the guide pipe to form a continuous liquid film; The distance between the dropper plates is fixed by distance pipes to ensure that the material liquid can drop stably and evenly; Heating steam is introduced into the heat exchange tube through the heating steam inlet, heating the liquid film formed on the outer wall of the heat exchange tube to generate secondary steam and then discharged through the secondary steam outlet arranged on the side wall of the outer shell; As the heating process proceeds, the material liquid evaporates and concentrates while flowing downward along the outer wall of the heat exchange tube, and the concentrated material liquid is obtained at the bottom of the shell and discharged through the material outlet.

Images