Falling film element, high-viscosity fluid devolatilization device and application thereof

Abstract

The invention relates to the technical field of polymer devolatilization, and discloses a falling film element, a high-viscosity fluid devolatilization device and application thereof. The falling film element comprises a hollow vertical pipe and a convex spiral falling film runner arranged on the inner wall surface of the hollow vertical pipe, a falling film inlet and a falling film outlet are respectively formed in a top opening and a bottom opening of the hollow vertical pipe; the convex spiral falling film flow channel continuously extends to the falling film outlet from the falling film inlet along the inner wall surface of the hollow vertical pipe, and has at least two spiral periods. The convex spiral falling film runner is designed on the inner wall surface of the falling film element, so that high-viscosity fluid can uniformly flow in the falling film devolatilization process, the film forming area is increased, and the surface is updated at high frequency, thereby remarkably improving the devolatilization efficiency and the tackifying effect, and being beneficial to improving the polymer product quality and reducing the production energy consumption.

Description

Technical Field

[0001] This invention relates to the field of polymer devolatilization technology, and in particular to a falling film element, a high-viscosity fluid devolatilizer, and their applications. Background Technology

[0002] Polymer materials, including but not limited to synthetic fibers, engineering plastics, and specialty adhesives, have expanded their applications from everyday consumer goods to high-performance fields such as aerospace, electronics, and biomedicine. This broad applicability places extremely high demands on key quality indicators such as purity, molecular weight, and its distribution. In polymer production, devolatilization efficiency is a crucial parameter determining product quality and production economics. This is especially true when handling high-viscosity polymer systems, such as in the later stages of melt polymerization, solution concentration, or degassing of spinning solutions, where the system viscosity often reaches 10... 2 ~10 4 At Pa·s, the mass transfer resistance of volatile components increases significantly, leading to a sharp decline in the efficiency of traditional devolatilization methods. Melt polycondensation, due to its high efficiency and short process, has become the preferred process for the industrial production of engineering plastics such as polyesters and polyamides. This process drives the reaction forward by continuously removing small molecule byproducts. However, the resulting surge in system viscosity makes the removal of small molecules increasingly difficult, and mass transfer efficiency becomes the core challenge limiting the progress of the reaction and the improvement of product quality.

[0003] Horizontal stirred reactors commonly used in industry, such as disc or cage reactors, have significant limitations when processing such high-viscosity melts: severe material adhesion between stirring elements and insufficient effective surface renewal; dead zones in the equipment, resulting in a wide distribution of material residence time, with some materials over-reacting while others under-react, which can easily lead to problems such as a widening of the molecular weight distribution of products and an imbalance in the proportion of end groups.

[0004] Falling film devolatilization is another widely used devolatilization method that increases the mass transfer area by causing the material to flow in a film on a vertical surface. However, when processing high-viscosity fluids, traditional vertical falling film tubes are prone to self-accelerating flow due to gravity, leading to uneven film thickness, flow instability, and even rupture. This reduces the effective mass transfer area, makes it difficult to control the residence time, and results in low devolatilization efficiency, ultimately affecting both devolatilization efficiency and product uniformity.

[0005] In summary, to further improve polymer product quality, increase devolatilization efficiency, and reduce production energy consumption, it is necessary to continuously develop new devolatilization devices that can adapt to the characteristics of high-viscosity fluids and achieve stable film formation and efficient surface renewal. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a falling film element, a high-viscosity fluid devolatilizer, and their applications. The invention features an outwardly convex spiral falling film flow channel designed on the inner wall of the falling film element. This allows for uniform flow of the high-viscosity fluid during the falling film devolatilization process, increasing the film-forming area and enabling high-frequency surface renewal. This significantly improves devolatilization efficiency and viscosity enhancement, thereby improving polymer product quality and reducing production energy consumption.

[0007] The specific technical solution of the present invention includes:

[0008] In a first aspect, the present invention provides a falling film element, comprising a hollow vertical tube and an outwardly convex spiral falling film flow channel disposed on the inner wall of the hollow vertical tube. The hollow vertical tube has a falling film inlet at its top opening and a falling film outlet at its bottom opening; the outwardly convex spiral falling film flow channel extends continuously from the falling film inlet along the inner wall of the hollow vertical tube to the falling film outlet, and has at least two spiral cycles.

[0009] This invention, based on the hollow tubular falling film element of a conventional polymer devolver, incorporates an outwardly convex spiral falling film channel on its inner surface. Compared to conventional polymers falling vertically along the surface of the falling film element, when high-viscosity polymers containing volatiles are devolve in the falling film element of this invention, the polymer fluid, under the influence of gravity, can flow in a spiral ring along the inner wall of the outwardly convex spiral falling film channel. Because this outwardly convex spiral falling film channel structure significantly enhances the liquid film stability of high-viscosity polymers, increases the surface renewal frequency and mass transfer efficiency, it enables more efficient devolvement and is therefore applicable to polymers with a wider viscosity range.

[0010] Preferably, the angle A between the bottom surface of the outwardly convex spiral falling film channel and the axis of the hollow vertical tube is less than 90°.

[0011] Within the radial cross-section of the hollow vertical tube, the mass m of the fluid element subjected to gravity can be decomposed into a component force along the surface of the outwardly convex spiral falling film flow channel. Among these components, the radial constraint force F pointing towards the wall of the hollow vertical tube... in It can be represented as F in =mgcos(A). When A is less than 90°, cos(A) > 0, F in The direction is towards the pipe wall, which can create a "gravity-assisted wall-adhering effect", forcing the high-viscosity fluid to flow closely to the spiral surface and preventing the liquid film from detaching, breaking or becoming unstable.

[0012] Preferably, the width W of the outwardly convex spiral falling film channel, extending from the inner wall of the hollow vertical tube to its innermost side in a horizontal direction perpendicular to the axis of the hollow vertical tube, remains constant or gradually increases along the fluid flow direction. More preferably, the ratio between the width W and the inner diameter d of the hollow vertical tube is 0.05-0.5:1.

[0013] For high-viscosity fluids, their flow is jointly controlled by surface tension and viscous forces. When W / d < 0.05, the convex spiral falling film channel is too narrow to provide sufficient spreading area for the fluid, causing the fluid to cross the spiral and form "grooves" along the pipe wall, thus losing its spiral guiding and film-forming functions. This invention discovers that within the above range, the convex spiral falling film channel can effectively guide the fluid to form a film, avoiding flow failure.

[0014] Furthermore, to prevent high-viscosity fluids from failing to spread on the helical surface and degenerating into "channeling," based on the Young-Laplace equation and the wetting dynamics model of fluids on solid surfaces, the critical condition for effective film formation is that the lateral guiding force on the helical surface must overcome the surface tension contraction effect of the fluid. Let the fluid surface tension be... The density is The acceleration due to gravity is The characteristic length (capillary length) by which a fluid can spread under the influence of gravity, overcoming capillary forces. for: In order for the fluid to recognize the helical structure as an effective flow channel rather than a surface roughness, the helical width W must be significantly larger than the feature length.

[0015] Furthermore, based on the rheological characteristics of high-viscosity fluids exhibiting a dramatic increase in viscosity along the flow path during devolatilization: as the high-viscosity fluid flows from top to bottom, the system viscosity increases significantly with the continuous removal of volatiles, leading to an increase in liquid film thickness. If the width W of the outwardly convex spiral falling film channel remains constant, the high-viscosity fluid in the lower part is prone to overflowing the groove due to insufficient flow cross-section, disrupting the spiral flow path; while gradually increasing the width W can provide sufficient flow space for the high-viscosity section, ensuring that the fluid is always confined within the groove, maintaining a stable spiral falling film and efficient mass transfer. At the same time, the increased lower width also helps to suppress the "bridging" phenomenon of high-viscosity fluid in the narrow channel, increasing the gas-liquid and solid-liquid contact area, and enhancing the mass transfer efficiency in the diffusion control stage of the later devolatilization phase.

[0016] Preferably, the depth D of the outwardly convex spiral falling film channel remains constant or gradually increases along the fluid flow direction. More preferably, the ratio between the width W and the depth D is 1-60:1.

[0017] Setting the ratio of width W to depth D within the aforementioned range ensures that the convex spiral falling film channel has sufficient width, allowing the high-viscosity fluid to spread into a thin layer, thereby shortening the diffusion distance of volatiles from the bulk liquid phase to the gas-liquid interface and significantly reducing mass transfer resistance. If the ratio is too large, the depth of the convex spiral falling film channel will be too shallow, resulting in insufficient sidewall constraint and easily leading to fluid flooding and spiral flow failure. Conversely, if the ratio is too small, the convex spiral falling film channel will be too deep and narrow, easily forming flow dead zones and mass and heat transfer bottlenecks.

[0018] Furthermore, based on the fluid characteristic of high-viscosity fluids where viscosity increases along the flow path during devolatilization: as volatiles are continuously removed, the fluid viscosity increases significantly, and the liquid film thickness increases. If the depth of the convex spiral falling film channel remains constant, it will be insufficient to accommodate the thickened liquid film at the bottom, easily causing liquid to overflow from the sidewall of the convex spiral falling film channel, resulting in fluid detaching from the channel and forming short-circuit flow, leading to a sharp decrease in devolatilization efficiency. Gradually increasing the depth D along the fluid flow direction can match the liquid film thickening trend, ensuring that the fluid is constrained by the convex spiral falling film channel throughout the entire process, maintaining a stable spiral flow path and a preset residence time. For operating conditions with a small viscosity variation range, a simplified design with a constant depth D can be adopted, meeting process requirements while reducing processing costs.

[0019] Preferably, the single spiral cycle length L of the convex spiral falling film flow channel is 50-2000 mm; the ratio of the single spiral cycle length L to the inner diameter d of the hollow vertical tube is 0.5-18:1.

[0020] The inclination of the spiral channel can be adjusted using the aforementioned ratios to match the flow and mass transfer requirements of materials with different viscosities. When the L / d ratio is small, i.e., the spiral is relatively gentle, the material residence time can be extended and the centrifugal effect around the flow can be enhanced, which is beneficial for deep devolatilization and surface renewal of low-viscosity materials. For example, when L / d = 0.5:1, the number of spiral turns per unit height is high. Although the axial guiding effect is weakened, it creates an extremely high gas-liquid interface renewal frequency, suitable for deep devolatilization where surface renewal is critical. When the L / d ratio is large, i.e., the spiral is relatively steep, it can provide a larger tangential component of gravity to overcome the huge flow resistance of high-viscosity materials and prevent material accumulation and blockage. For example, when L / d = 12, the axial component of gravity on the spiral surface dominates. This design is suitable for extremely high viscosity (>10). 4 For materials with a strength of Pa·s, it can provide a strong axial driving force, effectively preventing materials from sticking to the wall or becoming blocked due to excessive flow resistance.

[0021] Preferably, the spiral angle B formed by the outwardly convex spiral falling film channel and the central axis of the hollow vertical tube remains constant or gradually decreases along the fluid flow direction, and the spiral angle B is 10-80°.

[0022] In the critical flow condition, the driving force for the fluid to slide downward along the outwardly convex spiral falling film channel is the component of gravity in the spiral tangential direction. Where m is the mass of the fluid element and g is the acceleration due to gravity. If the helix angle B > 80°, the helix tends to be horizontal, which can easily lead to the accumulation of high-viscosity fluid polymers, flooding, and thermal degradation. If the helix angle B < 15°, the helix is ​​approximately vertical, which results in the loss of the advantages of helical flow guidance and surface renewal, and a significant reduction in devolatilization efficiency.

[0023] To achieve better devolatilization, the present invention can design the helix angle B of the convex spiral falling film channel to remain constant or gradually decrease along the fluid flow direction. Based on the rheological characteristics of high-viscosity fluids, the viscosity increases along the flow path during the devolatilization process: in the inlet section where the fluid viscosity is low, a larger helix angle can extend the flow path and enhance the centrifugal effect to strengthen surface renewal and mass transfer; in the outlet section where the fluid viscosity increases sharply, a gradually decreasing helix angle can provide a greater tangential driving force to overcome high viscosity resistance and prevent material retention and blockage.

[0024] More preferably, the outwardly convex spiral falling film flow channel includes, in sequence, an inlet section, a middle section, and an outlet section along the fluid flow direction; specifically:

[0025] The inlet section accounts for 10-30% of the length of the hollow vertical tube, and its helix angle B1 is 55°-80°;

[0026] The middle section accounts for 40-70% of the length of the hollow vertical tube, and its helix angle B1 is 30°-65°;

[0027] The outlet section accounts for 10-30% of the length of the hollow vertical tube, and its helix angle B1 is 10°-40°.

[0028] In the inlet section, the large tangential velocity and centrifugal effect are used to promote the rapid spread and film formation of low-viscosity fluid and extend the initial devolatilization residence time. The middle section can provide sufficient axial driving force while maintaining moderate surface renewal to adapt to the increase in viscosity and ensure sufficient mass transfer in the main devolatilization stage. The outlet section enhances gravity discharge capacity through steep flow channels to prevent the accumulation, blockage and thermal degradation of high-viscosity materials, and ensure smooth product discharge and uniform quality.

[0029] Preferably, the bottom surface of the outwardly convex spiral falling film channel is a plane or has raised textures or microgrooves along the fluid flow direction.

[0030] The aforementioned raised textures or microgrooves help to guide the downward-flowing liquid film to generate local eddies, thereby further increasing interfacial disturbance and enhancing the surface renewal and mass transfer process.

[0031] More preferably, the angle between the direction of the texture or microgroove and the main spiral direction of the outwardly convex spiral falling film channel is 35°-75°.

[0032] Within the aforementioned angle range, the fluid can be better disturbed, increasing surface renewal.

[0033] In a second aspect, the present invention provides a high-viscosity fluid devolatilizer containing the above-mentioned falling film element, comprising:

[0034] A vertical cylindrical body; the top of the vertical cylindrical body is provided with a high-viscosity fluid inlet; the interior of the vertical cylindrical body is divided into a high-viscosity fluid receiving cavity at the top and a falling film element receiving cavity at the bottom of the high-viscosity fluid receiving cavity by a horizontally arranged film plate; the falling film element receiving cavity is provided with a number of vertically parallel falling film elements; each falling film element has a devolatilization pipe connected to its top opening; the devolatilization pipe passes through the high-viscosity fluid receiving cavity and extends to the outside of the vertical cylindrical body.

[0035] Bottom shell; the bottom shell is connected to the bottom of the vertical cylinder, and the falling film outlet of the falling film element extends downward into the bottom shell; the bottom of the bottom shell is provided with a high viscosity fluid outlet.

[0036] Preferably, on the film plate, a corresponding film hole is provided directly above the falling film inlet of each falling film element, thereby realizing the flow between the high viscosity fluid receiving cavity and the outwardly convex spiral falling film channel.

[0037] Preferably, all devolatilization pipes are connected and converged at the top of the vertical cylinder, and their ends are equipped with vacuum extraction ports for connection to matching vacuum equipment.

[0038] Thirdly, the present invention provides a falling film devolatilization method for high-viscosity fluids, comprising the following steps: a high-viscosity fluid containing volatiles enters a high-viscosity fluid receiving chamber through the high-viscosity fluid inlet of a high-viscosity fluid devolatilizer; guided by a film plate, it flows downward along the outwardly convex spiral falling film flow channel of the falling film element under the action of gravity and heating conditions; devolatilization occurs during the falling film flow; the high-viscosity fluid converges into the bottom shell of the high-viscosity fluid devolatilizer for further devolatilization and mixing homogenization; and the material is discharged after devolatilization is completed; simultaneously, the removed volatiles are discharged from the high-viscosity fluid devolatilizer through the devolatilization pipe under negative pressure from the hollow part of the falling film element.

[0039] Preferably, the high-viscosity fluid includes, but is not limited to, polyesters (such as PET, PBT, PTT), polyamides (such as PA6, PA66), polycarbonate (PC), polylactic acid (PLA), and their copolymers or blends.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] (1) The inner wall of the falling film element of the present invention is provided with an outwardly convex spiral falling film channel. When the high-viscosity fluid flows under the drive of gravity, the outwardly convex spiral falling film channel induces the high-viscosity fluid to spread along the spiral path through geometric constraints and channel guidance, forming a continuous and uniform spiral liquid film. This effectively improves the uniformity of liquid film distribution, prolongs the material process residence time, and increases the surface renewal frequency of the gas-liquid interface.

[0042] (2) In the high viscosity fluid devolatilization device of the present invention, each falling film element operates independently, ensuring that the devolatilization process of the high viscosity fluid inside each falling film element does not interfere with each other and maintains a highly efficient devolatilization state; in addition, by setting up an interconnected branch pipe network at the top of each falling film element to converge into a devolatilization main pipe, coordinated vacuum suction is achieved, creating a relatively independent negative pressure devolatilization environment for each falling film element.

[0043] (3) The structural design of this invention, which combines an "outwardly convex spiral flow channel" with "independent parallel connection of falling film elements," provides smooth and controllable flow without dead angles or stagnation in both the axial and circumferential directions. Furthermore, thanks to the continuous liquid film surface renewal mechanism and efficient phase interface mass transfer capability, it greatly enhances the removal effect of small molecule volatiles. On the other hand, it significantly improves the consistency of the product's molecular weight and its distribution. This devolatilizer is particularly well-suited to the polycondensation and devolatilization processes of high-viscosity polymer melts and can directly contribute to the preparation of high-quality, high-molecular-weight polymer products. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a falling film element in Embodiment 1 of the present invention;

[0045] Figure 2 This is a schematic diagram of the falling film element in Embodiment 1 of the present invention from a top view (top) and an AA cross-sectional view (bottom);

[0046] Figure 3 This is a schematic diagram of a falling film element in Embodiment 2 of the present invention;

[0047] Figure 4 This is a schematic diagram of a falling film element in Embodiment 3 of the present invention.

[0048] Figure 5 This is a schematic diagram of a high-viscosity fluid devolatilizer in Embodiment 1 of the present invention;

[0049] Figure 6 This is a schematic diagram of a connection between the falling film element and the devolatilization pipe in Embodiment 1 of the present invention;

[0050] Figure 7 This is a three-dimensional connection diagram of the falling film element and the film plate in Embodiment 1 of the present invention;

[0051] The attached figures are labeled as follows: 1. High viscosity fluid inlet; 2. High viscosity fluid accommodating cavity; 3. Film plate; 4. Melt cavity jacket; 5. Heat medium inlet; 6. Vertical cylinder; 7. Hollow vertical pipe; 8. Bottom shell flange; 9. Bottom shell bolt; 10. Bottom shell jacket heat medium inlet; 11. Bottom shell; 12. Bottom shell jacket; 13. High viscosity fluid outlet; 14. Bottom shell jacket heat medium outlet; 15. Agitator; 16. Heat medium outlet; 17. Deviation pipe; 18. Vacuum extraction port; 31. Film distribution hole; 71. Outwardly convex spiral falling film channel; 71. Microgroove; 711. Detailed Implementation

[0052] To enhance understanding of the present invention, the following detailed description of the present invention will be provided using combined embodiments. These embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0053] In a first aspect, a falling film element includes a hollow vertical tube and an outwardly convex spiral falling film flow channel disposed on the inner wall of the hollow vertical tube. The hollow vertical tube has a falling film inlet and a falling film outlet at its top opening; the outwardly convex spiral falling film flow channel extends continuously from the falling film inlet along the inner wall of the hollow vertical tube to the falling film outlet, and has at least two spiral cycles.

[0054] In some preferred embodiments, the angle A between the bottom surface of the outwardly convex spiral falling film channel and the axis of the hollow vertical tube is less than 90°.

[0055] In some preferred embodiments, the width W of the outwardly convex spiral falling film channel, extending from the inner wall of the hollow vertical tube to the innermost side of the outwardly convex spiral falling film channel in a horizontal direction perpendicular to the axis of the hollow vertical tube, remains constant or gradually increases along the fluid flow direction.

[0056] In some further preferred embodiments, the ratio between the width W and the inner diameter d of the hollow vertical tube is 0.05-0.5:1.

[0057] In some preferred embodiments, the depth D of the outwardly convex spiral falling film channel remains constant or gradually increases along the fluid flow direction.

[0058] In some further preferred embodiments, the ratio between the width W and the depth D is 1-60:1.

[0059] In some preferred embodiments, the single spiral period length L of the convex spiral falling film channel is 50-2000 mm; the ratio of the single spiral period length L to the inner diameter d of the hollow vertical tube is 0.5-18:1.

[0060] In some preferred embodiments, the spiral angle B formed by the outwardly convex spiral falling film channel and the central axis of the hollow vertical tube remains constant or gradually decreases along the fluid flow direction, with the spiral angle B being 10-80°.

[0061] In some further preferred embodiments, the outwardly convex spiral falling film channel sequentially includes an inlet section, a middle section, and an outlet section along the fluid flow direction; specifically: the inlet section occupies 10-30% of the length of the hollow vertical tube, and its spiral angle B1 is 55°-80°; the middle section occupies 40-70% of the length of the hollow vertical tube, and its spiral angle B2 is 30°-65°; the outlet section occupies 10-30% of the length of the hollow vertical tube, and its spiral angle B3 is 10°-40°.

[0062] In some preferred embodiments, the bottom surface of the outwardly convex spiral falling film channel is flat or has raised textures or microgrooves along the fluid flow direction.

[0063] In some further preferred embodiments, the angle between the direction of the texture or microgroove and the main spiral direction of the outwardly convex spiral falling film channel is 35°-75°.

[0064] In a second aspect, a high-viscosity fluid devolatilizer containing the aforementioned falling film element comprises:

[0065] A vertical cylindrical body; the top of the vertical cylindrical body is provided with a high-viscosity fluid inlet; the interior of the vertical cylindrical body is divided into a high-viscosity fluid receiving cavity at the top and a falling film element receiving cavity at the bottom of the high-viscosity fluid receiving cavity by a horizontally arranged film plate; the falling film element receiving cavity is provided with a number of vertically parallel falling film elements; each falling film element has a devolatilization pipe connected to its top opening; the devolatilization pipe passes through the high-viscosity fluid receiving cavity and extends to the outside of the vertical cylindrical body.

[0066] Bottom shell; the bottom shell is connected to the bottom of the vertical cylinder, and the falling film outlet of the falling film element extends downward into the bottom shell; the bottom of the bottom shell is provided with a high viscosity fluid outlet; a stirrer is provided inside the bottom shell below the falling film element.

[0067] In some preferred embodiments, a corresponding film-laying hole is provided on the film-laying plate directly above the falling film inlet of each falling film element, thereby enabling the flow between the high-viscosity fluid accommodating cavity and the outwardly convex spiral falling film channel.

[0068] In some preferred embodiments, all devolatilization pipes are connected and converged at the top of the vertical cylinder, and their ends are provided with vacuum extraction ports for connection to a matching vacuum pumping device.

[0069] Thirdly, a falling film devolatilization method for high-viscosity fluid includes the following steps: the high-viscosity fluid containing volatiles enters the high-viscosity fluid receiving chamber through the high-viscosity fluid inlet of the high-viscosity fluid devolatilizer, and flows downward along the outwardly convex spiral falling film flow channel of the falling film element under the guidance of the film plate and under the action of gravity and heating conditions, and devolatilization is carried out during the falling film flow. The high-viscosity fluid converges into the bottom shell of the high-viscosity fluid devolatilizer for further devolatilization and mixing and homogenization. After the devolatilization is completed, the fluid is discharged. At the same time, the removed volatiles are discharged from the high-viscosity fluid devolatilizer through the devolatilization pipe under the action of negative pressure through the hollow part of the falling film element.

[0070] In some preferred embodiments, the high-viscosity fluid includes, but is not limited to, polyesters (such as PET, PBT, PTT), polyamides (such as PA6, PA66), polycarbonate (PC), polylactic acid (PLA), and their copolymers or blends.

[0071] Example 1

[0072] A high-viscosity fluid devourer, such as Figure 5 As shown, it includes a vertical cylindrical body 6 and a bottom shell 11 that are detachably connected (achieved via a bottom shell flange 8 and bottom shell bolts 9); the top of the vertical cylindrical body is provided with a high-viscosity fluid inlet 1, and the bottom of the bottom shell is provided with a high-viscosity fluid outlet 13. Wherein:

[0073] The vertical cylinder is divided into a high-viscosity fluid receiving chamber 2 at the top and a falling film element receiving chamber at the bottom by a horizontally arranged film plate 3. For example... Figure 6 As shown, the falling film element accommodating cavity of the film plate has 10 falling film elements arranged in parallel (the falling film elements are arranged vertically and parallel within the vertical cylinder); as Figure 7 As shown, on the film plate, a corresponding film-laying hole 31 is provided directly above the falling film inlet at the top of each falling film element. The top opening of a single falling film element is connected to a devolatilization pipe 17 that penetrates the high-viscosity fluid containment cavity and extends to the outside of the vertical cylinder. All devolatilization pipes are connected and converged at the top outside of the vertical cylinder, and their ends are provided with vacuum extraction ports 18.

[0074] The falling film outlet of a single falling film element extends into the bottom shell; a high-viscosity fluid outlet 13 is provided at the bottom of the bottom shell; a stirrer 15 is provided between the bottom of the falling film element and the high-viscosity fluid outlet.

[0075] In addition, the vertical cylindrical shell has a heat medium inlet 5 and a heat medium outlet 16 on its wall, with the heat medium inlet positioned higher than the heat medium outlet. A melt chamber jacket 4 is provided outside the high-viscosity fluid accommodating cavity of the vertical cylindrical shell. A bottom shell jacket 12 is provided on the side wall of the bottom shell, with a bottom shell jacket heat medium inlet 10 and a bottom shell jacket heat medium outlet 14, the bottom shell jacket heat medium inlet positioned higher than the bottom shell jacket heat medium outlet.

[0076] In the aforementioned high-viscosity fluid devourer, such as Figure 1 and Figure 2 As shown, a single falling film element includes a hollow vertical tube 7 (a hollow circle in radial cross-section) and an outwardly convex spiral falling film channel 71 disposed on its inner wall. The hollow vertical tube has a falling film inlet at the top opening and a falling film outlet at the bottom opening, respectively; the outwardly convex spiral falling film channel extends continuously from the falling film inlet along the inner wall of the hollow vertical tube to the falling film outlet, and has 4 spiral cycles.

[0077] More specifically, the bottom surface of the convex spiral falling film flow channel is a plane, with an angle A of 72° between it and the axis of the hollow vertical tube. The width W of the convex spiral falling film flow channel remains constant from top to bottom, and is 28 mm, with a ratio of 0.28:1 to the inner diameter d of the hollow vertical tube. The tube wall thickness t is 4 mm. The depth D of the convex spiral falling film flow channel remains constant from top to bottom, and is 7 mm, with a width W to depth D ratio of 4:1. The length L of a single spiral cycle of the convex spiral falling film flow channel is 314 mm (total height of the hollow vertical tube is 1256 mm), and the ratio of the spiral cycle length L to the inner diameter d of the hollow vertical tube is 4:1. The spiral angle B of the convex spiral falling film flow channel remains constant from top to bottom, with a value of 45°.

[0078] The working principle of the high viscosity fluid devolatilizer in this embodiment is as follows: The high viscosity fluid containing volatiles enters the high viscosity fluid receiving chamber through the high viscosity fluid inlet of the high viscosity fluid devolatilizer. Guided by the film plate, it flows from top to bottom along the outward spiral falling film flow channel of the falling film element under the action of gravity and heating. Devolatilization occurs during the falling film flow. The high viscosity fluid converges into the bottom shell of the high viscosity fluid devolatilizer for further devolatilization and mixing and homogenization. After the devolatilization is completed, the fluid is discharged. At the same time, the removed volatiles are discharged from the high viscosity fluid devolatilizer through the devolatilization pipe under negative pressure through the hollow part of the falling film element.

[0079] Example 2

[0080] The difference between the falling film element in this embodiment and the falling film element in Embodiment 1 is that the helix angle is not a fixed value, such as... Figure 3 As shown, compared with Example 1, in this example, the helix angle B of the outwardly convex spiral falling film flow channel decreases in a stepwise manner along the fluid flow direction of the material (from top to bottom) (sequentially including the inlet section, the middle section, and the outlet section), thereby achieving progressive control of the fluid flow state. Specifically:

[0081] The width W of the outwardly convex spiral falling film flow channel is 12 mm, the inner diameter d of the hollow vertical tube is 60 mm, the depth D is 4 mm, and the tube wall thickness t is 5 mm.

[0082] The effective height of the hollow vertical tube is 480mm.

[0083] The height of the inlet section is 120mm, its helix angle B1 is 75°, and the corresponding helix period length L is 50.5mm;

[0084] The height of the middle section is 240mm, its helix angle B2 is 45°, and the corresponding helix period length L is 132mm;

[0085] The height of the exit section is 120mm, its helix angle B3 is 35°, and the corresponding helix period length L is 326mm.

[0086] In the process of devolatilization using the falling film element of this embodiment, in order to adapt to the drastic change in fluid viscosity from low to high, a design is adopted in which the helix angle decreases in stages from top to bottom: a large angle at the inlet section to stabilize the flow and prevent splashing, an angle adjustment in the middle section to balance the flow rate, and a small angle at the outlet section to strongly push and prevent blockage, thereby maintaining a stable thin liquid film throughout the process and achieving efficient and controllable devolatilization.

[0087] Example 3

[0088] The difference between the falling film element in this embodiment and the falling film element in Embodiment 1 lies in the different bottom surface structure of the outwardly convex spiral falling film channel, such as... Figure 4 As shown, compared with Example 1, in this example, the falling film element has a microgroove 711 on the bottom surface of the outwardly convex spiral falling film channel, and the angle between the direction of the microgroove and the main spiral direction of the outwardly convex spiral falling film channel is 55°.

[0089] The aforementioned microgrooves help to guide the downward-flowing liquid film to generate local eddies, thereby further increasing interfacial disturbance and enhancing the surface renewal and mass transfer process.

[0090] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention, and the patent protection scope of the invention should be defined by the claims.

Claims

1. A falling film element, characterized in that: It includes a hollow vertical tube and an outwardly convex spiral falling film flow channel disposed on the inner wall of the hollow vertical tube; The hollow vertical tube is provided with a falling film inlet and a falling film outlet at the top opening and bottom opening, respectively; The convex spiral falling film channel extends continuously from the falling film inlet along the inner wall of the hollow vertical tube to the falling film outlet, and has at least two spiral cycles.

2. The falling film element according to claim 1, characterized in that: The angle between the bottom surface of the outwardly convex spiral falling film channel and the axis of the hollow vertical tube is less than 90°.

3. The falling film element according to claim 1, characterized in that: The width of the outwardly convex spiral falling film channel, from the inner wall of the hollow vertical tube to the innermost side of the outwardly convex spiral falling film channel, remains constant or gradually increases along the fluid flow direction in a horizontal direction perpendicular to the axis of the hollow vertical tube. The ratio between the width W and the inner diameter of the hollow vertical tube is 0.05-0.5:

1.

4. The falling film element according to claim 1, characterized in that: The depth of the outwardly convex spiral falling film channel remains constant or gradually increases along the fluid flow direction; The ratio between the width and the depth is 1-60:

1.

5. The falling film element according to claim 1, characterized in that: The length of a single spiral cycle in the convex spiral falling film channel is 50-2000 mm; The ratio of the length of a single spiral period to the inner diameter of the hollow vertical tube is 0.5-18:

1.

6. The falling film element according to claim 1, characterized in that: The spiral angle formed by the outwardly convex spiral falling film channel and the central axis of the hollow vertical tube remains constant or gradually decreases along the fluid flow direction, with a spiral angle of 10-80°.

7. The falling film element according to claim 6, characterized in that: The outwardly convex spiral falling film channel includes, in sequence, an inlet section, a middle section, and an outlet section along the fluid flow direction; The inlet section accounts for 10-30% of the length of the hollow vertical tube, and its helix angle is 55°-80°; The middle section accounts for 40-70% of the length of the hollow vertical tube, and its helix angle is 30°-65°; The outlet section accounts for 10-30% of the length of the hollow vertical tube, and its helix angle is 10°-40°.

8. The falling film element according to claim 1, characterized in that: The bottom surface of the outwardly convex spiral falling film channel is either flat or has raised textures or microgrooves along the fluid flow direction; The angle between the direction of the texture or microgroove and the main spiral direction of the outwardly convex spiral falling film channel is 35°-75°.

9. A high-viscosity fluid devolatilizer comprising a falling film element according to any one of claims 1-8, characterized in that: include: A vertical cylindrical body; the top of the vertical cylindrical body is provided with a high-viscosity fluid inlet; The vertical cylinder is divided into a high-viscosity fluid receiving cavity at the top and a falling film element receiving cavity at the bottom of the high-viscosity fluid receiving cavity by a horizontally arranged film plate. The falling film element receiving cavity is provided with several vertically parallel falling film elements. Each falling film element has a devolatilization pipe connected to its top opening. The devolatilization pipe passes through the high-viscosity fluid receiving cavity and extends to the outside of the vertical cylinder. Bottom shell; the bottom shell is connected to the bottom of the vertical cylinder, and the falling film outlet of the falling film element extends downward into the bottom shell; the bottom of the bottom shell is provided with a high viscosity fluid outlet.

10. The application of the high-viscosity fluid devolatilizer of claim 9 in the devolatilization of high-viscosity fluids, characterized in that: include: High-viscosity fluid containing volatiles enters the high-viscosity fluid receiving chamber through the high-viscosity fluid inlet of the high-viscosity fluid devolatilizer. Guided by the film plate, it flows downward along the convex spiral falling film channel of the falling film element under the action of gravity and heating. Deviation occurs during the falling film flow. The high-viscosity fluid converges into the bottom shell of the high-viscosity fluid devolatilizer for further devolatilization and mixing and homogenization. After the devolatilization is completed, the fluid is discharged. At the same time, the removed volatiles are discharged from the high-viscosity fluid devolatilizer through the devolatilization pipe under negative pressure through the hollow part of the falling film element.

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