A vacuum devolatilizer

Abstract

The present invention provides a vacuum devolatilizer comprising a vertical container, the container being provided with an exhaust port and a material inlet, a melt pressure chamber being provided at the upper portion of the container, the melt pressure chamber being connected to the material inlet; the devolatilizer being provided with at least one falling film tube, the inner wall of which serves as the contact surface for the falling film flow of the material; a vacuum chamber being provided above the melt pressure chamber within the container, the exhaust port being provided in the vacuum chamber; a gas phase passage being provided at the upper end of the falling film tube, which passes through the melt pressure chamber and communicates with the vacuum chamber. The present invention can improve the vacuuming effect and reduce the interference of volatile gases on the falling film flow of the material, while also having a compact internal structure and being easy to scale up industrially.

Description

Technical Field

[0001] The invention relates to a vacuum devolatilization device used in the fields of polymer devolatilization, polymer melt reaction preparation, spinning solution degassing and solution concentration, and belongs to the field of chemical production equipment. Background Art

[0002] During the melt polymerization process, polymers such as polyethylene terephthalate (PET), polyamide 6 (PA6), polybutylene succinate (PBS), polyamide 66 (PA66), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polycarbonate (PC), and polylactic acid (PLA) inevitably produce residual small-molecule monomers or byproducts, such as ethylene glycol and water in PET and caprolactam in PA6. The solution spinning process of polyacrylonitrile and polyimide requires the removal of air bubbles from the spinning solution to ensure smooth spinning. Devolatilization is essential during the preparation of these polymer materials to remove small molecules or bubbles. This process creates extremely high dynamic viscosity, sometimes varying by orders of magnitude during the process. This makes material flow and mixing difficult and reduces heat and mass transfer efficiency.

[0003] In the past, falling film devolatilization equipment used a vertical container with multiple falling film tubes installed in a large space. This system employed a vacuum port on one side of the container shell for vacuuming. For falling film outside the tubes, this vacuuming method can cause the following problems: the shear force exerted on the liquid film surface on different falling film tubes by the volatile gas flow varies, affecting the stability of the falling film flow; the vacuum level at different locations on the falling film tubes varies significantly, affecting the quality uniformity of the falling film devolatilization products. For falling film inside the tubes, as the material falls from top to bottom on the falling film tubes, the viscosity gradually increases and the volatile concentration gradually decreases, making the removal of residual volatiles more difficult. The downward movement of large amounts of volatiles further inhibits the removal efficiency of residual volatiles; the vacuum level at different locations on the falling film tubes also varies significantly, affecting the quality uniformity of the falling film devolatilization products. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the above-mentioned prior art and provide a vacuum devolatilizer that can improve the vacuuming effect and reduce the interference of volatile gases on the falling film flow of the material. At the same time, the internal components are compact and easy to scale up industrially. To this end, the present invention adopts the following technical solutions:

[0005] A vacuum devolatilizer comprises a vertical container, the vertical container is provided with an exhaust port and a material inlet, a melt pressure chamber is provided at the upper part of the container, and the melt pressure chamber and the material inlet are communicated; the characteristic is that the devolatilizer is provided with at least one falling film tube, the inner wall surface of the falling film tube is the material falling film contact surface, a vacuum chamber is provided above the melt pressure chamber in the container, and the exhaust port is provided in the vacuum chamber; a gas phase channel tube is provided at the upper end of the falling film tube, the gas phase channel tube passes through the melt pressure chamber and is communicated with the vacuum chamber.

[0006] On the basis of adopting the above technical solutions, the present invention may also adopt the following further technical solutions, or use these further technical solutions in combination:

[0007] The bottom plate of the melt pressure chamber is provided with a connecting hole for connecting to the upper end of the falling film tube. A circle of multiple film-making holes is arranged circumferentially on the inner side of the tube mouth at the upper end of the falling film tube. The film-making holes connect the melt pressure chamber and the falling film tube. The film-making ring forming the film-making holes is connected to the gas phase channel tube, and the falling film tube and the film-making ring are connected.

[0008] A material discharge chamber is provided at the bottom of the container, and a material outlet is provided in the material discharge chamber. The vertical container is provided with a heat exchange chamber between the melt pressure chamber and the material discharge chamber. The falling film tube passes through the heat exchange chamber, and the lower end is connected to the material discharge chamber.

[0009] The inscribed circle diameter of the falling film tube is 50-300 mm. When the falling film tube is a round tube, the inscribed circle diameter of the falling film tube is the inner diameter of the round tube. When the falling film tube is a special-shaped tube, the inscribed circle diameter of the falling film tube is the inscribed circle diameter of the inner wall of the special-shaped tube.

[0010] The special-shaped tube is preferably a regular polygonal tube or a multi-petal plum blossom-shaped tube. Among the regular polygonal tubes, the preferred shapes are regular quadrilaterals, regular pentagons, regular hexagons, regular heptagons, regular octagons, regular nonagons, and regular decagons. Among the multi-petal plum blossom-shaped tubes, the preferred shapes are four-petal plum blossoms, five-petal plum blossoms, six-petal plum blossoms, seven-petal plum blossoms, eight-petal plum blossoms, nine-petal plum blossoms, and ten-petal plum blossoms.

[0011] When the dynamic viscosity of the material is 0.1~10Pa·s, the diameter of the inscribed circle of the falling film tube is 50~100mm; or, when the dynamic viscosity of the material is 10~100Pa·s, the diameter of the inscribed circle of the falling film tube is 60~180mm; or, when the dynamic viscosity of the material is 100~1000Pa·s, the diameter of the inscribed circle of the falling film tube is 80~250mm; or, when the dynamic viscosity of the material is 1000~10000Pa·s, the diameter of the inscribed circle of the falling film tube is 120~300mm.

[0012] The film distribution holes are evenly arranged around the circumference of the inner wall of the falling film tube. Each film distribution hole is not connected to each other. The interval M between adjacent film distribution holes is 1~20mm. The number of film distribution holes corresponding to each falling film tube is greater than or equal to 10.

[0013] The falling film tube has a length of 1 to 20 m. Further, the falling film tube has a length of preferably 3 to 12 m.

[0014] The inscribed circle diameter of the membrane hole is 2-15 mm, and the aspect ratio (L / D) of the membrane hole length L to the inscribed circle diameter D is 2-15. Furthermore, the membrane hole inscribed circle diameter is preferably 3-12 mm, and the aspect ratio is preferably 5-15; each membrane hole is uniform in size and shape.

[0015] The film-making hole is a circular hole or a non-circular hole or a hole formed by the groove and the inner wall of the falling film tube; when the film-making hole is a circular hole, the diameter of the inscribed circle of the film-making hole is the diameter of the circular hole; when the film-making hole is a non-circular hole, the diameter of the inscribed circle of the film-making hole is the diameter of the largest inscribed circle of the non-circular hole.

[0016] The melt pressure in the melt pressure chamber is 10-1000 kPa; further, the melt pressure in the melt pressure chamber is preferably 50-600 kPa.

[0017] When the film-making holes are circular or non-circular, the shortest distance X from the inner wall of the film-making holes to the inner wall of the falling film tube is less than or equal to 20 mm, which can be coordinated with the hole spacing and aspect ratio of the film-making holes so that the entire material flowing out of the film-making holes can be drawn to the inner wall of the falling film tube to form a continuous and uniform film.

[0018] The heat exchange chamber is the shell side between the melt pressure chamber and the material discharge chamber, and is provided with a heat medium inlet and a heat medium outlet.

[0019] A stirrer is provided in the bottom shell of the falling film devolatilizer, that is, in the discharge chamber, for homogenizing the material after falling film devolatilization.

[0020] Falling film in tubes offers unique advantages. By designing the film distribution hole structure parameters and the falling film tube parameters, it is possible to achieve continuous and stable film distribution of streams with different flow characteristics on the inner wall of the falling film tube through a non-connected perforated film distributor while maintaining high volume utilization (surface area per unit volume of the falling film tube). This minimizes fluctuations in the residence time of the streams during the falling film flow process, which is beneficial for improving the quality stability of the falling film product. This can reduce production costs and facilitate industrial scale-up.

[0021] The present invention provides a vacuuming solution for a falling-film devolatilizer employing an in-tube falling film. This solution improves vacuuming effectiveness and reduces interference of volatile gases with the falling film flow of the material. Furthermore, the internal components are compact and easily scaled up industrially. This solution ensures a sufficient gas phase channel volume during the falling film process, enabling efficient bottom-up removal of large amounts of hot volatile gases during the process. This ensures a high vacuum level during the falling film process, improves the falling film devolatilization efficiency, and is suitable for large-scale, continuous devolatilization of highly viscous materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the falling film devolatilizer provided by the present invention;

[0023] Figure 2 for Figure 1 Part of the falling film devolatilizer ( Figure 1 Center C) Enlarged image;

[0024] Figure 3 for Figure 1 NN cross-sectional view of the falling film devolatilizer using the first embodiment of the combination of film holes and falling film tubes;

[0025] Figure 4 for Figure 1 NN cross-sectional view of the falling film devolatilizer using the second embodiment of the combination of film holes and falling film tubes;

[0026] Figure 5 for Figure 1 NN cross-sectional view of the falling film devolatilizer using the third combination of film holes and falling film tubes;

[0027] Figure 6 for Figure 1 NN cross-sectional view of the falling film devolatilizer using the fourth embodiment of the combination of film distribution holes and falling film tubes. DETAILED DESCRIPTION

[0028] In order to deepen the understanding of the present invention, the present invention will be further described in detail with reference to the following examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] Example 1, with reference to Figure 1 、 2 , 3

[0030] This embodiment provides a vacuum devolatilizer, such as Figure 1 、 2As shown, it uses a vertical container, including a heat exchange chamber 5, a melt pressure chamber 4 above the heat exchange chamber 5, a material discharge chamber 10 below the heat exchange chamber 5, and a vacuum chamber 2 above the melt pressure chamber 4. A falling film tube 6 is vertically installed in the heat exchange chamber 5. A gas phase channel 18 is provided at the upper end of the falling film tube 6. The gas phase channel 18 vertically passes through the melt pressure chamber 4 and communicates with the vacuum chamber 2. The vacuum chamber 2 is provided with a gas extraction port 19. Film spreading holes 15 are provided at the intersection of the falling film tube 6 and the gas phase channel 18. The film spreading holes 15 connect the melt pressure chamber 4 and the falling film tube 6. The film spreading holes 15 are evenly arranged along the circumference of the falling film tube inner wall. A film spreading ring 16 forming the film spreading holes 15 is connected to the gas phase channel 18, and the falling film tube 6 and the film spreading ring 16 are connected.

[0031] The top plate 17 of the melt pressure chamber 4 serves as a partition plate between the vacuum chamber 2 and the melt pressure chamber 4. The bottom plate 14 of the melt pressure chamber 4 is provided with a connecting hole for connecting the upper end of the falling film tube. The lower part of the falling film tube is fixed on the falling film tube fixed bed 9. A discharge chamber 10 is provided at the bottom of the container. The falling film tube fixed bed 9 serves as its top plate. The discharge chamber 10 is provided with a material outlet 11. The vertical container is provided with a heat exchange chamber 5 between the melt pressure chamber 4 and the discharge chamber 10. The falling film tube 6 passes through the heat exchange chamber 5, and the lower end is connected to the discharge chamber 10.

[0032] The shell of the vertical container is composed of a cylindrical main tank body, a tank top and a substantially conical tank bottom, wherein the tank top and the tank bottom are connected to the main tank body through flanges 3 and 8.

[0033] Multiple falling film tubes are vertically installed in the devolatilizer. The falling film tubes are round tubes with an inner tangential circle diameter of 250 mm.

[0034] The film holes 15 are formed by the semicircular groove on the film ring and the inner wall of the falling film tube. The maximum inscribed circle P has a diameter of 6 mm. The aspect ratio of the film hole length L to the inscribed circle diameter D is 9. The shortest distance X from the inner wall of the film hole to the inner wall of the falling film tube is 0 mm. The film holes are evenly arranged along the circumferential direction of the inner wall of the falling film tube. Figure 3 shown.

[0035] The devolatilizer is provided with a heat transfer system, including the heat exchange chamber 5, the heat medium inlet 7, and the heat medium outlet 13, so as to ensure the required heat for the devolatilization process of the material.

[0036] The bottom shell of the devolatilizer is provided with a stirrer 12 for homogenizing the material, and the stirring power is introduced from the bottom.

[0037] Example 2, reference Figure 1 、 2 , 4

[0038] In this embodiment, the film-laying holes are circular holes, the falling film tubes are circular tubes, and the diameter of the inscribed circle of the falling film tubes is 150 mm.

[0039] The film holes 15 are circular holes on the film ring, with a diameter of 5 mm. The aspect ratio of the film hole length L to the inscribed circle diameter D is 12. The shortest distance X from the inner wall of the film hole to the inner wall of the falling film tube is 5 mm. The film holes are evenly arranged along the circumferential direction of the inner wall of the falling film tube, as shown in FIG. Figure 4 As shown, the rest is the same as Example 1.

[0040] Example 3, reference Figure 1 、 2 , 4

[0041] In this embodiment, the film-laying holes are circular holes, the falling film tubes are circular tubes, and the diameter of the inscribed circle of the falling film tubes is 110 mm.

[0042] The film holes 15 are circular holes on the film ring, with a diameter of 5 mm. The aspect ratio of the film hole length L to the inscribed circle diameter D is 10. The shortest distance X from the inner wall of the film hole to the inner wall of the falling film tube is 4 mm. The film holes are evenly arranged along the circumferential direction of the inner wall of the falling film tube, as shown in FIG. Figure 4 As shown, the rest is the same as Example 1.

[0043] Example 4, with reference to Figure 1 、 2 , 5

[0044] In this embodiment, the film-laying holes are circular holes, the falling film tubes are regular hexagonal tubes, and the diameter of the inscribed circle of the falling film tubes is 140 mm.

[0045] The film holes 15 are circular holes on the film ring, with a diameter of 6 mm. The aspect ratio of the film hole length L to the inscribed circle diameter D is 10. The shortest distance X from the inner wall of the film hole to the inner wall of the falling film tube is 5 mm. The film holes are evenly arranged along the circumferential direction of the inner wall of the falling film tube, as shown in FIG. Figure 5 As shown, the rest is the same as Example 1.

[0046] Example 5, with reference to Figure 1 、 2 , 6

[0047] In this embodiment, the film-laying holes are circular holes, the falling film tubes are six-petal plum blossom tubes, and the diameter of the inscribed circle of the falling film tubes is 230 mm.

[0048] The film holes 15 are circular holes on the film ring, the inscribed circle diameter of the circular hole is 6 mm, the aspect ratio of the film hole length L to the inscribed circle diameter D is 9, the shortest distance X from the inner wall of the film hole to the inner wall of the falling film tube is 3 mm, and the film holes are evenly arranged along the circumferential direction of the inner wall of the falling film tube, such as Figure 6 As shown, the rest is the same as Example 1.

[0049] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. It should be noted that a person skilled in the art can make various modifications and variations without departing from the principles of the present invention, and such modifications and variations should also be considered within the scope of protection of the present invention.

Claims

1. A vacuum devolatilizer, comprising a vertical container, wherein the container is provided with an air extraction port (19) and a material inlet (1), a melt pressure chamber (4) is provided on the upper portion of the container, and the melt pressure chamber (4) is communicated with the material inlet (1); characterized in that: The devolatilizer is provided with at least one falling film tube (6), the inner wall surface of the falling film tube (6) being the contact surface for the falling film flow of the material; a vacuum chamber (2) is provided above the melt pressure chamber (4) in the container, and the air extraction port (19) is provided in the vacuum chamber (2); a gas phase passage tube (18) is provided at the upper end of the falling film tube (6), and the gas phase passage tube (18) passes through the melt pressure chamber (4) and communicates with the vacuum chamber (2); The bottom plate (14) of the melt pressure chamber (4) is provided with a connection hole for connecting to the upper end of the falling film tube (6). A plurality of film-making holes (15) are arranged circumferentially on the inner side of the upper end of the falling film tube (6). The film-making holes (15) connect the melt pressure chamber (4) and the falling film tube (6). The film-making ring (16) of the film-making holes (15) is connected to the gas phase channel tube (18), and the falling film tube (6) and the film-making ring (16) are connected; A discharge chamber (10) is provided at the bottom of the vertical container, and a material outlet (11) is provided in the discharge chamber (10); a heat exchange chamber (5) is provided between the melt pressure chamber (4) and the discharge chamber (10) in the vertical container, the falling film tube (6) passes through the heat exchange chamber (5), and the lower end of the falling film tube (6) is connected to the discharge chamber (10); The diameter of the inscribed circle of the membrane hole is 2-15 mm, and the aspect ratio L / D of the length L of the membrane hole to the inscribed circle diameter D is 2-15; When the dynamic viscosity of the material is 0.1~10Pa·s, the diameter of the inscribed circle of the falling film tube is 50~100mm; or, when the dynamic viscosity of the material is 10~100Pa·s, the diameter of the inscribed circle of the falling film tube is 60~180mm; or, when the dynamic viscosity of the material is 100~1000Pa·s, the diameter of the inscribed circle of the falling film tube is 80~250mm; or, when the dynamic viscosity of the material is 1000~10000Pa·s, the diameter of the inscribed circle of the falling film tube is 120~300mm.

2. The vacuum devolatilizer according to claim 1, wherein The film-laying hole (15) is a circular hole or a non-circular hole or a hole formed by a groove and the inner wall of the falling film tube; the shortest distance X from the inner wall of the film-laying hole (15) to the inner wall of the falling film tube is less than or equal to 20 mm.

3. The vacuum devolatilizer according to claim 1, wherein The heat exchange chamber (5) is a shell side between the melt pressure chamber (4) and the material discharge chamber (10), and is provided with a heat medium inlet (7) and a heat medium outlet (13).

4. The vacuum devolatilizer according to claim 1, wherein The melt pressure in the melt pressure chamber (4) is 10-1000 kPa.

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