Multistage cross horizontal tube falling film devolatilizer

Abstract

The application discloses a multilayer cross horizontal tube falling film devolatilizer, which comprises a material chamber and multilayer horizontal tube bundles, and the upper and lower adjacent tube bundles are arranged in a cross mode; the bottom of the material chamber is provided with a film distribution plate, and the film distribution plate is provided with film distribution holes which are opposite to the cross positions of the vertical direction projection of the upper and lower tube bundles. The internal structure of the reactor is simple and compact, heat exchange is sufficient, there is no dead zone in flow, film forming efficiency is high, residence time is uniform and controllable, and the reactor is suitable for polymerization reaction, material concentration, spinning solution defoaming, stripping and other devolatilization processes.

Description

Technical Field

[0001] This invention relates to a devolatilizer used in polymerization reactions, material concentration, spinning solution degassing, stripping and other fields, and belongs to the field of materials and chemical production equipment. Background Technology

[0002] Deviation processes, which separate low molecular weight components from molten or solution materials, are widely used in polymer reactions, spinning solution degassing, vacuum evaporation, analysis, and material concentration. These processes often involve mass and heat transfer in viscous material flows, and the transfer properties of the system change along with the physical properties. In particular, for deviation processes of high-viscosity systems accompanied by polymerization reactions, the diffusion and mass transfer of small molecule compounds from high-viscosity systems is limited by the film thickness and uniformity of the material flow. However, the mismatch between the structural design of the equipment's internal components and the flow characteristics seriously affects the deviation effect, and complex internal components can easily introduce dead zones, causing a decrease in the quality of devolatilized products.

[0003] Existing industrial devolatilization devices include general static devolatilizers, rotary devolatilizers, strip devolatilizers, and falling film devolatilizers. Among them, general static devolatilizers are suitable for processing materials with low solution viscosity and low requirements for heat and mass transfer, and do not require a large area of ​​surface renewal. Rotary devolatilizers can handle high-viscosity materials, and the rotating components help improve surface renewal and promote heat and mass transfer during material flow, but their geometry is usually more complex and consumes more power. Strip devolatilizers have low power consumption and high material processing efficiency, and are suitable for flash evaporation operations with a large amount of volatiles and short residence time. The wall-mounted falling film devolatilizer, which has been developed in recent years, has improved the material film-forming flow area and heat and mass transfer performance to a certain extent. According to the structural design, the material residence time can be extended to produce high-viscosity materials through reactive devolatilization. However, the material flow behavior on the internal components of this type of devolatilizer is difficult to control and is easily affected by manufacturing and installation precision, resulting in local material inhomogeneity and coking, and uneven residence time, which affects the overall performance of the devolatilizer and its long-term temperature stability. There is an urgent need to develop a high-quality devolatilization device with a simple falling film flow support structure, uniform material film flow without dead zones, good heat and mass transfer performance, uniform residence time, and long-term operation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a horizontal tube falling film devolatilizer with a simple structure, high heat and mass transfer efficiency, and long operating cycle. To this end, this invention adopts the following technical solution:

[0005] A multi-layer cross-horizontal tube falling film devolatilizer includes a vertical tower body, a head connected to the upper end of the vertical tower body, an exhaust port, a material inlet, a material chamber, a bottom shell, and a material outlet. The devolatilizer has a devolatilization assembly below the material chamber. The devolatilization assembly is characterized by using a multi-layer horizontal tube bundle of no less than three layers, each layer of the tube bundle consisting of horizontal tubes arranged on the same plane, with adjacent upper and lower layers of horizontal tube bundles arranged in a cross pattern.

[0006] Furthermore, the multilayer horizontal tube bundle is composed of a first-direction horizontal tube bundle layer and a second-direction horizontal tube bundle layer, with the tube bundle layers of the first-direction horizontal tube bundle and the tube bundle layers of the second-direction horizontal tube bundle alternating. When the number of layers of the first-direction horizontal tube bundle layer is more than two, for the first-direction horizontal tube, the lower horizontal tube and the upper horizontal tube are arranged correspondingly, so that the falling film of the upper first-direction horizontal tube, after being re-filmed by the adjacent lower second-direction horizontal tube, still falls on the lower first-direction horizontal tube for re-filming. When the number of layers of the second-direction horizontal tube bundle layer is more than two, for the second-direction horizontal tube, the lower horizontal tube and the upper horizontal tube are arranged correspondingly, so that the falling film of the upper second-direction horizontal tube, after being re-filmed by the adjacent lower first-direction horizontal tube, still falls on the lower second-direction horizontal tube for re-filming.

[0007] Furthermore, the bottom plate of the material chamber is a membrane plate, with membrane holes directly opposite the intersection of the vertical projections of the tube bundles below. The material flows from the membrane holes into the first layer of tube bundles below, slides down the tube wall and into the next layer of intersecting tube bundles, completing the devolatilization process through alternating falling film flow and falling strip movement, and finally converges at the bottom of the reactor.

[0008] Furthermore, each layer of tube bundle consists of at least three horizontal tubes arranged in parallel at equal intervals, with the ratio of the tube spacing to the diameter of the circumscribed circle of the horizontal tube being 1 to 20.

[0009] Furthermore, adjacent upper and lower tube bundles are interconnected, and the horizontal tube bundle spacing from the shell to the bottom shell remains consistent or gradually increases, with the ratio of spacing to tube diameter ranging from 1 to 1000.

[0010] Furthermore, each layer of horizontal tube bundle is connected to a coiled tube on its periphery, and vertical tubes connect adjacent upper and lower layers of coiled tubes, which are connected to the vertical tower body.

[0011] Furthermore, the bottom of the vertical tower is provided with a groove-shaped dike, and there is a dike outlet on the dike that connects to the outside of the vessel, which can be used to discharge the residue on the inner wall of the devolatilizer.

[0012] Furthermore, the devolatilizer is equipped with a heat transfer system and a heat preservation system; the heat transfer system includes a fluid path consisting of a heat medium flowing into the tank, vertical pipes, coils and horizontal tube bundles, and a heat medium flowing out of the tank. In this embodiment, the aforementioned vertical pipes, coils and horizontal tube bundles are all simultaneously flow pipes for the heat exchange medium; the heat preservation system includes a vertical tower jacket and a bottom shell jacket respectively provided with heat medium inflow and outflow; the heat medium in the heat transfer system and the heat preservation system circulates to the outside and is then cooled or heated.

[0013] This invention utilizes a specially designed horizontal tube bundle arrangement, allowing materials to easily achieve a high devolatilization area during periodic flow around the tubes and falling strips. This results in rapid surface renewal, excellent transfer performance, and material flow properties that match the devolatilization process. More importantly, the intersecting arrangement of the horizontal tube bundles enhances material mixing and prevents uneven flow into the next layer caused by material deviation when the upper and lower horizontal tubes are arranged in parallel. Furthermore, the uniformity of material flow is unaffected by the falling film component structure, resulting in minimal differences in material residence time at different flow rates, no dead zones, long equipment operating cycles, easy cleaning, and high throughput, thus meeting the production requirements for high-quality devolatilization. Attached Figure Description

[0014] Figure 1 A schematic diagram of a multi-layer cross-horizontal tube falling film devolatilizer for implementing the present invention.

[0015] Figure 2 for Figure 1 The diagram shows a plan view of the two-layer horizontal tube bundle in the embodiment shown, where the solid line represents the upper horizontal tube bundle and the dashed line represents the lower horizontal tube bundle.

[0016] Figure 3 This is a schematic diagram of the material flow between the first-direction horizontal pipe and the second-direction horizontal pipe in an embodiment of the present invention.

[0017] Figure 4 for Figure 1 A schematic diagram showing the arrangement of the membrane holes on the membrane plate relative to the top horizontal tube bundle in the illustrated embodiment.

[0018] Parts and components numbered in the diagram: 1. Heat medium inlet; 2. Feed pipe; 3. Heat medium flowing into the tank; 4. Heat medium flowing out of the tank; 41. Heat medium tank outlet cover plate; 42. Heat medium tank outlet bottom plate (i.e., top plate of the material chamber); 5. Material chamber; 51. Membrane plate; 511. Membrane hole; 6. Shell jacket heat medium inlet; 7. Vertical tower body; 8. Shell jacket; 9. Bottom shell flange; 10. Bottom shell jacket heat medium inlet; 11. Bottom shell; 12. Bottom shell jacket; 13. Material outlet; 14. Bottom shell jacket heat medium outlet; 15. Agitator; 16. Weir; 17. Weir outlet; 18. Shell jacket heat medium outlet; 19. Vertical pipe connecting the horizontal tube bundle layer; 20. Coil connecting the horizontal pipes; 21. First direction horizontal pipe; 221. Second direction horizontal pipe; 222. Vacuum extraction port; 23. Shell flange; 24. Shell bolt; 25. Heat medium outlet; 26. End cap; 27. Material inlet; 28. Specific Implementation

[0019] Example 1

[0020] This embodiment provides a multi-layer cross-horizontal tube falling film devolatilizer, such as... Figure 1 As shown, the structure includes a vertical tower body 7, a head 27 connected to the upper end of the vertical tower body 7, and a bottom shell 12 at the lower end. The head 27 has a material inlet 28, the vertical tower body 7 has a vacuum extraction port 23, and the bottom shell 12 has a material outlet 14. The devolatilizer has a material chamber 5, the bottom plate of which is a membrane plate 51, and the bottom plate of the material chamber 5 is connected to the head 27. A devolatilization assembly is installed below the material chamber 5. The devolatilization assembly uses at least three layers of multi-layer horizontal tube bundles, each layer consisting of horizontal tubes arranged on the same plane, with adjacent upper and lower layers of horizontal tube bundles arranged in a crisscross pattern.

[0021] In this embodiment, three layers are used. The multi-layer horizontal tube bundle consists of two first-direction horizontal tube bundle layers and one second-direction horizontal tube bundle layer. The tube bundle layers of the first-direction horizontal tube bundle and the tube bundle layers of the second-direction horizontal tube bundle are arranged alternately. For the first-direction horizontal tube 221, the lower horizontal tube 221 and the upper horizontal tube 221 are arranged correspondingly, so that the falling film of the upper first-direction horizontal tube 221, after being re-filmed by the adjacent lower second-direction horizontal tube 222, still falls on the lower first-direction horizontal tube 221 for re-filming. The devolatilization assembly also includes vertical tubes 20 connecting the horizontal tube bundle layers and coils 21 connecting the horizontal tubes in series. The first horizontal tube bundle 221 and the second horizontal tube bundle 222 of each layer are mounted on the coils 21 of the corresponding layer to form a horizontal tube layer. The included angle between the projections of the upper and lower horizontal tube layers can be selected from acute and obtuse angles. The two ends of the coils 21 connecting the horizontal tubes in series are connected to the vertical tubes 20, with one end serving as the first connecting tube and the other end as the second connecting tube. The axes of the coils 21 connecting the horizontal tubes in series and the corresponding layer of horizontal tube bundles are on the same plane. Furthermore, the two horizontal tubes of the upper and lower horizontal tube bundles are adjacent and connected. The ratio of the interlayer spacing (distance between the bottom of the upper horizontal tube and the top of the lower horizontal tube) to the tube diameter (outer diameter) of the upper and lower horizontal tube bundles is 20:1. Preferably, the interlayer spacing of the horizontal tube bundles gradually increases from top to bottom. The material inlet 28 is connected to the feed pipe 2 extending into the material chamber 5. The film plate 51 is provided with rows of equally spaced film-forming holes 511, which are directly opposite the intersection of the vertical projection of the horizontal tube bundle below. (e.g.) Figure 4 (As shown).

[0022] The upper ends of the first and second connecting pipes pass through the material chamber 5 and are connected to the heat medium inflow box 3 and the heat medium outflow box 4 respectively located in the end cap 27; the ratio of the outer diameter of the connecting pipe to the outer diameter of the coil 21 connected to the horizontal pipe is 5:1, and the ratio of the outer diameter of the connecting pipe to the outer diameter of the horizontal pipes 221 and 222 is 10:1.

[0023] Material is injected from the inlet and diverted into the material chamber 5 via the feed pipe 2. It falls from the same row of membrane holes 511 to the top of the first direction horizontal tube bundle of the devolatilization element, making the probability of it flowing down to both sides along the circumference of a single horizontal tube approximately equal, and the flow rate approximately equal. The material flowing down to both sides along the circumference of the horizontal tube is kept approximately equal, forming an intermittent supported falling film flow along the outer wall of the horizontal tube. Membrane renewal is achieved during the falling process from one horizontal tube 221 in the first direction horizontal tube bundle to the lower second direction horizontal tube 222 that is intersected with the upper layer.

[0024] The reactor is equipped with a heat preservation and heating system. The heat transfer system includes a heat medium chamber, a vertical pipe 20 connecting the horizontal tube bundle layer, a coil 21 connected in series with the horizontal pipe, and horizontal pipes 221 and 222. These pipes form a fluid flow path. The upper ends of the connecting pipes at both ends of the coil 21 are connected to the upper heat medium chamber (heat medium flows into the box 3) and the lower heat medium chamber (heat medium flows out of the box 4, and the material chamber is below the lower heat medium chamber) respectively. The heat medium flows in from the heat medium inlet located at the top of the upper heat medium chamber, enters one end connecting pipe, splits into one end of the coil connected to the connecting pipe, flows through the horizontal tube bundle, enters the other end of the coil, and then flows from the other end connecting pipe to the lower heat medium chamber, and flows out from the heat medium outlet located on the side of the lower heat medium chamber. The insulation system consists of a vertical tower body and a bottom shell, as well as a shell jacket and a bottom shell jacket respectively installed on the outside. The upper end of one side of the shell jacket and the lower end of the opposite side are respectively provided with a shell jacket heat medium inlet 6 and a shell jacket heat medium outlet 19. The upper end of one side of the bottom shell jacket and the lower end of the opposite side are respectively provided with a bottom shell jacket heat medium inlet 11 and a bottom shell jacket heat medium outlet 15. The heat medium of the heat transfer and insulation system is shut off and flows to the outside for heating or cooling before circulating.

[0025] The aforementioned devolatilizer is used in the removal of monomers in falling film melt polycondensation reaction. Polyamide 6 melt with 10.2% extractable content is continuously injected into the reactor, which employs a preferred structure, through the feed inlet. After being distributed by the film distribution plate, the melt falls to the upper part of the horizontal tube under gravity, flowing circumferentially around the horizontal tube. It continues to flow to the next layer of horizontal tubes at the lower part of the horizontal tube. The projections of adjacent horizontal tubes are intersecting, providing support and mixing for the falling film flow. This results in rapid material surface renewal and high efficiency in removing small molecules of polyamide. The material undergoes polycondensation during flow, and the melt on the horizontal tube eventually slides down and converges to the bottom of the reactor. Further stirring and homogenization are achieved by the agitator. After the reaction is complete, the melt flows out from the outlet, yielding polyamide 6 with 0.6% extractable content.

[0026] Example 2

[0027] Using a raw material with an intrinsic viscosity of 0.67 dL / g and a molecular weight distribution index of 1.69, the material is continuously injected into the reactor with a preferred structure through the feed inlet; a melt polycondensation and thickening reaction is carried out to obtain a polyester product with an intrinsic viscosity of 1.03 dL / g and a molecular weight distribution index of 1.55. The intermittent falling film structure, consisting of a vertical tube 20 connecting the horizontal tube bundle coil 21, the coil 21 connected in series with the horizontal tubes, and the horizontal tube bundles 221 and 222, avoids uneven falling film flow caused by poor installation accuracy or disturbance of the falling film element in a single vertical falling film element. This is beneficial for obtaining a product with a narrow molecular weight distribution. After 700 hours of reactor operation, no coking residue was found on the horizontal tubes of the falling film structure.

[0028] Example 3

[0029] The aforementioned devolatilizer is used for degassing spinning solution. The spinning solution is continuously injected into the reactor with a preferred structure from the inlet. After being distributed by the film plate, it falls to the upper part of the horizontal tube under gravity and flows around the circumference of the horizontal tube. It continues to flow to the next layer of horizontal tubes at the lower part of the horizontal tube. The projections of adjacent layers of horizontal tubes are intersecting. The horizontal tubes provide support and mixing for the falling film flow of the material, resulting in rapid surface renewal of the liquid film and high efficiency in removing small molecules. The material undergoes degassing during the flow. The spinning solution on the horizontal tubes eventually slides down and converges to the bottom of the reactor, where it is further stirred and mixed by the agitator before flowing out from the outlet. The obtained degassed spinning solution has a solvent loss of 4% and the number of bubbles is reduced to 2.

Claims

1. A multi-layer cross-horizontal tube falling film devolatilizer, comprising a vertical tower body, a head connected to the upper end of the vertical tower body, an exhaust port, a material inlet, a material chamber, a bottom shell, and a material outlet, wherein a devolatilization assembly is provided below the material chamber, characterized in that: The devolatilization assembly employs a multi-layered horizontal tube bundle with no less than three layers. Each layer of the tube bundle consists of horizontal tubes arranged on the same plane, and adjacent upper and lower layers of horizontal tube bundles are arranged in a cross pattern. The multi-layer horizontal tube bundle is composed of a first-direction horizontal tube bundle layer and a second-direction horizontal tube bundle layer, with the tube bundle layers of the first-direction horizontal tube bundle and the tube bundle layers of the second-direction horizontal tube bundle alternating. When the number of layers of the first-direction horizontal tube bundle layer is more than two, for the first-direction horizontal tube, the lower horizontal tube and the upper horizontal tube are arranged correspondingly, so that the falling film of the upper first-direction horizontal tube, after being re-filmed by the adjacent lower second-direction horizontal tube, still falls on the lower first-direction horizontal tube for re-filming. When the number of layers of the second direction horizontal tube bundle layer is more than two, for the second direction horizontal tube, the lower horizontal tube and the upper horizontal tube are set accordingly, so that the falling film of the upper second direction horizontal tube, after being re-laid by the lower adjacent first direction horizontal tube, still falls on the lower second direction horizontal tube for re-laying. The bottom plate of the material chamber is a membrane plate, and the membrane plate has membrane holes that are directly opposite the intersection of the vertical projection of the horizontal tube bundle below.

2. The multi-layer cross-horizontal tube falling film devolatilizer as described in claim 1, characterized in that: The multi-layer horizontal tube bundles are arranged in a cross shape between adjacent upper and lower layers, so that the membrane surfaces formed by the upper and lower layers of horizontal tube bundles are similar.

3. The multi-layer cross-horizontal tube falling film devolatilizer as described in claim 1, characterized in that: Each layer of tube bundle consists of at least three horizontal tubes arranged in parallel at equal intervals, with the ratio of the tube spacing to the diameter of the circumscribed circle of the horizontal tube being 1 to 20.

4. The multi-layer cross-horizontal tube falling film devolatilizer as described in claim 1, characterized in that: From top to bottom, the spacing between horizontal tube bundle layers remains consistent or gradually increases, and the ratio of the spacing between layers to the tube diameter is 1 to 1000.

5. A multi-layer cross-horizontal tube falling film devolatilizer as described in claim 1, characterized in that: Each layer of horizontal tube bundle is connected to a coiled tube on its periphery, and the coiled tubes of adjacent upper and lower layers are connected by vertical tubes, with the upper end of the vertical tubes connected to the vertical tower body.

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