A liquid evaporation device and a falling film evaporator

Abstract

The present invention discloses a falling film evaporation liquid distribution device, comprising a cylindrical falling film evaporation tube and a liquid inlet tube, wherein the liquid outlet end of the liquid inlet tube is horizontal and perpendicular to the axis of the falling film evaporation tube; the liquid outlet end forms an opening for liquid outflow on the inner wall of the falling film evaporation tube; after the liquid flows out from the opening of the liquid outlet end, it has an initial velocity of circumferential flow around the inner wall of the falling film evaporation tube. The liquid of the present invention first enters a water storage tank, and after being accelerated by a counterclockwise rotating blade, enters from the liquid inlet of the spiral guide tube below the water storage tank, flows downward in the spiral guide tube after being accelerated by gravity and rotating blades, and then enters the falling film evaporation tube horizontally, and is evenly distributed on the inner wall of the falling film evaporation tube to form a liquid film; due to the large tangential velocity, the liquid rotates and flows down in the falling film evaporation tube, which increases the flow of the liquid in the falling film evaporation tube and can be fully heated.

Description

Technical Field

[0001] The invention relates to the technical field of evaporation heat exchange equipment, and in particular to an evaporation liquid distribution device for enhancing evaporation effect and a falling film evaporator. Background Art

[0002] Falling film evaporators are generally divided into horizontal falling film evaporators and vertical falling film evaporators. Vertical falling film evaporators are widely used in chemical, petroleum, seawater desalination, food and medicine due to their advantages such as high heat transfer coefficient, easy installation and small footprint. The principle is to rely on gravity and the action of the liquid distributor to distribute the liquid on the inner wall of the evaporation tube to form a liquid film flow, and the outside of the tube is heated by high-temperature steam to achieve the function of evaporation and concentration. Therefore, the flow condition of the liquid in the tube is very critical. Uneven distribution of the liquid film will cause the liquid film in the evaporation tube to be interrupted, resulting in local dry evaporation, and scaling problems are also prone to occur, further affecting the flow of the liquid. Therefore, whether the liquid distributor can evenly distribute the liquid on the inner wall of the vertical tube and the flow condition of the liquid on the inner wall of the evaporation tube will directly affect the evaporation performance and service life of the evaporator.

[0003] Patent CN106267867 discloses a liquid distributor for a falling film evaporator and a falling film evaporator, in which an annular gap is opened between the large end faces of the frustum-shaped tube connected to the guide tube to achieve smooth liquid flow and uniform and stable film distribution. The invention described requires the falling film evaporator to be installed vertically, which has high installation requirements. The vertical feeding method limits the residence time of the liquid in the tube, and cannot maximize the high heat transfer coefficient of the falling film evaporator.

[0004] Patent CN105771558A discloses a vertical tube type film dropper liquid distribution device without external drive, which uses the liquid flowing down from above and the gas generated in the tube as kinetic energy to drive a liquid distributor equipped with rolling bearings, wherein the liquid distributor is a hollow cone with a larger taper at the bottom and a smaller taper at the top, and fins are provided on the outer surface and the bottom. The liquid forms a liquid film on the tube wall through the rotating liquid distributor with fins for flow guidance. The bearings described in the invention will have problems such as shortened life or insensitivity due to factors such as high temperature, which will affect the film distribution, and will increase the resistance of gas phase flow, which is not conducive to evaporation. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a falling film evaporation liquid distribution device which has more uniform film distribution, more stable flow and can make the liquid flow longer, and a falling film evaporator using the liquid distribution device of the present invention.

[0006] A falling film evaporation liquid distribution device comprises a cylindrical falling film evaporation tube and a liquid inlet tube, wherein the liquid outlet end of the liquid inlet tube is horizontal and perpendicular to the axis of the falling film evaporation tube; the liquid outlet end forms an opening for liquid outflow on the inner wall of the falling film evaporation tube; after the liquid flows out from the opening of the liquid outlet end, it has an initial velocity of circumferential flow around the inner wall of the falling film evaporation tube.

[0007] On the basis of the above scheme, the liquid outlet passes through the wall of the falling film evaporator tube and forms a guiding surface for liquid flow that is tangent to the inner wall of the falling film evaporator tube, the guiding surface is tangent to the inner wall of the falling film evaporator tube at the connection and the flow direction of the liquid at the connection is perpendicular to the axis of the falling film evaporator tube; or the liquid outlet is arranged inside the falling film evaporator tube and the liquid outlet is in contact with the inner wall of the falling film evaporator tube; the flow direction of the liquid when flowing out of the liquid outlet is perpendicular to the axis of the falling film evaporator tube.

[0008] Based on the above scheme, the initial velocity is obtained as follows:

[0009] The level of the liquid inlet end of the liquid inlet pipe is higher than that of the liquid outlet end, and the liquid is discharged at the outlet of the liquid outlet end by gravity during the flow of the liquid inlet pipe;

[0010] and / or

[0011] When the liquid enters the liquid inlet pipe or when the liquid flows in the liquid inlet pipe, it obtains a certain flow velocity, so that the liquid is obtained when it flows out from the liquid outlet end.

[0012] On the basis of the above solution, there are a plurality of liquid inlet pipes, and a plurality of liquid outlet ends of the plurality of liquid inlet pipes are evenly distributed on the circumference of the inner wall of the falling film evaporation tube.

[0013] On the basis of the above scheme, the liquid distribution device also includes a liquid storage tank, the interior of which is a cylindrical cavity and is coaxial with the falling film evaporation tube; the several liquid inlet ends of the several liquid inlet pipes form openings on the circular bottom surface of the liquid storage tank and the openings are evenly distributed along the circumference of the circular bottom surface of the liquid storage tank; preferably, the diameter of the circular bottom surface of the liquid storage tank is 1.4 to 1.6 times the diameter of the falling film evaporation tube.

[0014] Based on the above scheme, a rotating blade is arranged in the liquid storage tank, and a guide surface is formed at the opening of the liquid inlet end. When the rotating blade rotates, it first reaches the side where the guide surface contacts the circular bottom surface of the liquid storage tank.

[0015] On the basis of the above scheme, the liquid inlet end of the liquid inlet pipe is connected to a liquid inlet pump, and the liquid is supplied to the liquid inlet pipe by the liquid inlet pump; preferably, a plurality of liquid inlet pipes share one liquid inlet pump.

[0016] On the basis of the above scheme, it also includes an inner plug column, which is inserted into the top end of the falling film evaporator tube and is coaxial with the falling film evaporator tube, and the outlet of the liquid outlet end of the liquid inlet pipe is between the inner plug column and the falling film evaporator tube; optionally, the distance between the cylindrical outer wall of the inner plug column and the cylindrical inner wall of the falling film evaporator tube is 1-3mm.

[0017] A falling film evaporator uses the above-mentioned falling film evaporation liquid distribution device.

[0018] The liquid of the present invention first enters the water storage tank, and after being accelerated by the counterclockwise rotating blades, enters from the liquid inlet of the spiral guide tube below the water storage tank, flows downward in the spiral guide tube after being accelerated by gravity and the rotating blades, and then enters the falling film evaporation tube horizontally, and is evenly distributed on the circumference of the inner wall of the falling film evaporation tube to form a liquid film; due to the large tangential speed, the liquid rotates and flows down in the falling film evaporation tube, thereby increasing the flow rate of the liquid in the falling film evaporation tube and being fully heated. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the cross-sectional structure of an evaporation liquid distribution device;

[0020] Figure 2 It is a cross-sectional view of the connection between the falling film evaporation tube and the liquid inlet tube of the falling film evaporation liquid distribution device;

[0021] Figure 3 It is a cross-sectional view of the connection between the falling film evaporation tube and the liquid inlet tube of the evaporation liquid distribution device (four liquid inlet tubes);

[0022] Figure 4 It is a cross-sectional view of the connection between the falling film evaporation tube and the liquid inlet tube of the evaporation liquid distribution device (two liquid inlet tubes);

[0023] Figure 5 It is a cross-sectional view of the connection between the falling film evaporation tube and the liquid inlet tube of the evaporation liquid distribution device (three liquid inlet tubes);

[0024] Figure 6 It is a schematic diagram of the three-dimensional structure of the evaporation liquid distribution device;

[0025] Figure 7 It is a schematic diagram of the structure of the evaporation liquid distribution device from a top view;

[0026] Figure 8 It is a schematic diagram of the structure of another evaporation liquid distribution device from a three-dimensional perspective;

[0027] Fig. 9 for Figure 6 The schematic diagram of the structure of the evaporation liquid distribution device shown retains a liquid inlet pipe;

[0028] Fig.10 for Figure 8The evaporation liquid distribution device shown retains a structural schematic diagram of a liquid inlet pipe (the liquid inlet pipe is a circular tube). DETAILED DESCRIPTION

[0029] The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art.

[0030] The present invention is further described in detail below in conjunction with specific examples and with reference to data. The following examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0031] like Figure 1-3 and Figure 8 As shown, a falling film evaporation liquid distribution device comprises a cylindrical falling film evaporation tube 5 and a liquid inlet tube 4, wherein the liquid outlet end 4-3 of the liquid inlet tube 4 is horizontal and perpendicular to the axis of the falling film evaporation tube 5; the liquid outlet end 4-3 forms an opening for liquid outflow on the inner wall of the falling film evaporation tube 5; after the liquid flows out from the opening of the liquid outlet end 4-3, it has an initial velocity of circumferential flow around the inner wall of the falling film evaporation tube 5.

[0032] The speed of the circumferential flow of the liquid around the inner wall of the falling film evaporation tube 5 after the liquid flows out can make the liquid flow down on the inner wall of the falling film evaporation tube 5 in a rotation manner, thereby increasing the flow of the liquid, prolonging the heating time, and making the liquid film more uniform and stable.

[0033] The initial velocity can be obtained by the gravity of the liquid, for example, the liquid inlet pipe 4 is designed to have a certain height difference, that is, the horizontal height of the liquid inlet end 4-1 is higher than the horizontal height of the liquid outlet end 4-3, so that the liquid can obtain a certain initial velocity at the outlet of the liquid outlet end 4-3 by the action of gravity during the flow in the liquid inlet pipe 4; Figure 1 As shown, the middle section 4-2 of the liquid inlet pipe 4 has a certain vertical height, and the specific structure can be a spiral ascending structure or a straight line or curve with an inclination. This structure can enable the liquid to obtain a certain speed due to gravity when flowing in the liquid inlet pipe 4.

[0034] In addition to the above method of obtaining the initial velocity, the liquid entering the liquid inlet pipe 4 can also obtain a certain flow velocity when entering or during the flow process, so that the liquid coming out of the liquid outlet end 4-3 can obtain the initial velocity; at the same time, this method can also be combined with gravity to make the liquid obtain the initial velocity.

[0035] The above two forms or the combination of the two forms can enable the liquid to obtain an initial velocity when it comes out from the liquid outlet end 4 - 3 and enters the falling film evaporation tube 5 .

[0036] In order to make the liquid flow along the circumferential direction of the inner wall of the falling film evaporation tube 5 after entering the falling film evaporation tube 5, it is required that the flow direction of the liquid when flowing out of the liquid outlet 4-3 is perpendicular to the axis of the falling film evaporation tube 5. As a specific implementation method, Figure 3-5 As shown, the liquid outlet 4-3 penetrates the wall of the falling film evaporation tube 5 and forms a guide surface 4-3a tangent to the inner wall of the falling film evaporation tube 5; the guide surface 4-3a is for liquid flow, and the guide surface 4-3a is tangent to the inner wall of the falling film evaporation tube 5 at the connection point, and the flow direction of the liquid at the connection point is perpendicular to the axis of the falling film evaporation tube 5. Figure 8 As shown, as another specific implementation, the liquid outlet 4-3 is arranged inside the falling film evaporation tube 5 and the liquid outlet 4-3 is in contact with the inner wall of the falling film evaporation tube 5; the tube wall on the side where the liquid outlet 4-3 is in contact with the inner wall of the falling film evaporation tube 5 becomes thinner toward the outlet; the flow direction of the liquid when flowing out of the liquid outlet 4-3 is perpendicular to the axis of the falling film evaporation tube 5.

[0037] As a specific implementation, there are several liquid inlet pipes 4, and there can be 2, 3, or 4 liquid inlet pipes 4. If the inner diameter of the falling film evaporation tube 5 is larger, the number of the liquid inlet pipes 4 can be more.

[0038] The plurality of liquid outlet ends 4 - 3 of the plurality of liquid inlet pipes 4 are evenly distributed in the circumferential direction of the falling film evaporation tube 5 . Preferably, the plurality of liquid outlet ends 4 - 3 are at the same level.

[0039] In order to provide a stable liquid source for the liquid inlet pipe 4, this embodiment provides a specific liquid supply method, such as Figure 1 , 2 and Figure 6 As shown, the liquid distribution device of this embodiment further includes a liquid storage tank 3, the interior of the liquid storage tank 3 is a cylindrical cavity, and is coaxial with the falling film evaporation tube 5; the plurality of liquid inlet ends 4-1 of the plurality of liquid inlet pipes 4 form openings on the circular bottom surface 3-1 of the liquid storage tank 3, and the openings are evenly distributed along the circumference of the circular bottom surface 3-1 of the liquid storage tank 3. The opening of the liquid inlet end 4-1 forms a guide surface 3-1a, and the liquid enters the guide pipe 4 from the liquid storage tank 3 along the guide surface 3-1a.

[0040] like Figure 1 , 6 As shown in Figures 7 and 8, in order to provide the liquid entering the liquid inlet pipe 4 with a faster speed and a larger flow rate when entering, the present embodiment provides a rotating blade 2 in the liquid storage tank 3. The rotating blade 2 rotates along the axis 1 to rotate the liquid in the liquid storage tank 3, thereby achieving the purpose of changing the speed and flow rate. The rotation direction of the rotating blade 2 is consistent with the direction in which the liquid enters the liquid inlet end 4-1; in this way, when the rotating blade 2 rotates, it first reaches the side where the guide surface 3-1a contacts the circular bottom surface 3-1 of the liquid storage tank 3, so that the liquid quickly enters the liquid inlet pipe 4 under the action of inertia.

[0041] As a preferred solution, the rotating blade 2 and the circular bottom surface 3 - 1 of the liquid storage tank 3 form an angle of 45-90 degrees.

[0042] The diameter of the circular bottom surface 3 - 1 of the liquid storage tank 3 is 1.4 to 1.6 times the diameter of the falling film evaporation tube 5 .

[0043] In addition to the liquid supply method provided in the above embodiment, this embodiment also provides another liquid supply method, specifically: the liquid inlet end 4-1 of the liquid inlet pipe 4 is connected to a liquid inlet pump, and the liquid is supplied into the liquid inlet pipe 4 by the liquid inlet pump. Several liquid inlet pipes 4 can share one liquid inlet pump. This solution directly provides an initial velocity for the liquid while supplying the liquid, and the magnitude of the liquid initial velocity can also be controlled by controlling the liquid inlet pump (not shown in the figure).

[0044] The falling film evaporation liquid distribution devices of the above-mentioned embodiments can form a uniform liquid film on the inner wall of the falling film evaporation tube 5. In order to enhance the film forming effect, this embodiment provides a more improved liquid distribution device, such as Figure 1 As shown, the liquid distribution device is provided with an inner plug column 6 on the basis of the above device, the inner plug column 6 is inserted into the top of the falling film evaporation tube 5, and is coaxial with the falling film evaporation tube 5, and the distance between the cylindrical outer wall of the inner plug column 6 and the cylindrical inner wall of the falling film evaporation tube 5 is 1-3mm. The liquid outlet end 4-3 of the liquid inlet pipe 4 is between the inner plug column 6 and the falling film evaporation tube 5 at the outlet of the falling film evaporation tube 5; this arrangement can make the liquid evenly distributed between the inner plug column 6 and the inner wall of the falling film evaporation tube 5 after flowing out, which is more conducive to the formation of the liquid film.

[0045] A falling film evaporator uses the above-mentioned falling film evaporation liquid distribution device and is applied to the fields of chemical industry, petroleum, seawater desalination, food and medicine.

[0046] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A falling film evaporation liquid distribution device, comprising a cylindrical falling film evaporation tube (5) and a liquid inlet tube (4), characterized in that: The liquid outlet end (4-3) of the liquid inlet pipe (4) is horizontal and perpendicular to the axis of the falling film evaporation tube (5); the liquid outlet end (4-3) forms an opening on the inner wall of the falling film evaporation tube (5) for liquid to flow out; after the liquid flows out from the opening of the liquid outlet end (4-3), it has an initial velocity of circumferential flow around the inner wall of the falling film evaporation tube (5); The liquid outlet (4-3) penetrates the wall of the falling film evaporation tube (5) and forms a guide surface (4-3a) tangent to the inner wall of the falling film evaporation tube (5) for liquid flow, the guide surface (4-3a) is tangent to the inner wall of the falling film evaporation tube (5) at the connection point, and the flow direction of the liquid at the connection point is perpendicular to the axis of the falling film evaporation tube 5; When the liquid enters the liquid inlet pipe (4) or when the liquid flows in the liquid inlet pipe (4), a certain flow velocity is obtained, so that when the liquid flows out from the liquid outlet end (4-3); The liquid distribution device further comprises a liquid storage tank (3), the interior of the liquid storage tank (3) being a cylindrical cavity and being coaxial with the falling film evaporation tube (5); a plurality of liquid inlet ends (4-1) of a plurality of liquid inlet tubes (4) forming openings on the circular bottom surface (3-1) of the liquid storage tank (3), and the openings being evenly distributed along the circumference of the circular bottom surface (3-1) of the liquid storage tank (3); A rotating blade (2) is arranged in the liquid storage tank (3), and a guide surface (3-1a) is formed at the opening of the liquid inlet end (4-1). When the rotating blade (2) rotates, it first reaches the side where the guide surface (3-1a) contacts the circular bottom surface (3-1) of the liquid storage tank (3).

2. The falling film evaporation liquid distribution device according to claim 1, characterized in that: There are a plurality of liquid inlet pipes (4), and a plurality of liquid outlet ends (4-3) of the plurality of liquid inlet pipes (4) are evenly distributed in the circumferential direction of the inner wall of the falling film evaporation tube (5).

3. The falling film evaporation liquid distribution device according to claim 1, characterized in that: The diameter of the circular bottom surface (3-1) of the liquid storage tank (3) is 1.4 to 1.6 times the diameter of the falling film evaporation tube (5).

4. The falling film evaporation liquid distribution device according to claim 1, characterized in that: It also comprises an inner plug-type column (6), which is inserted into the top end of the falling film evaporation tube (5) and is coaxial with the falling film evaporation tube (5), and the outlet of the liquid outlet end (4-3) of the liquid inlet tube (4) is between the inner plug-type column (6) and the falling film evaporation tube (5).

5. The falling film evaporation liquid distribution device according to claim 4, characterized in that: The distance between the cylindrical outer wall of the inner plug column (6) and the cylindrical inner wall of the falling film evaporation tube (5) is 1-3 mm.

6. A falling film evaporator, using the falling film evaporation liquid distribution device according to any one of claims 1 to 5.

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