CN110639461A - Falling film devolatilizer and falling film element thereof - Google Patents
Falling film devolatilizer and falling film element thereof Download PDFInfo
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- CN110639461A CN110639461A CN201810670679.3A CN201810670679A CN110639461A CN 110639461 A CN110639461 A CN 110639461A CN 201810670679 A CN201810670679 A CN 201810670679A CN 110639461 A CN110639461 A CN 110639461A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/1887—Stationary reactors having moving elements inside forming a thin film
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0053—Details of the reactor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/1893—Membrane reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/20—Stationary reactors having moving elements inside in the form of helices, e.g. screw reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/18—Details relating to the spatial orientation of the reactor
- B01J2219/185—Details relating to the spatial orientation of the reactor vertical
Abstract
The invention relates to a falling film devolatilization device and a falling film element thereof, comprising a vertical shell, a seal head connected with the upper end of the vertical shell, and a bottom shell connected with the lower end of the vertical shell, wherein a material box body and at least one falling film element are arranged in the devolatilization device, a plurality of falling film flow channels are arranged on the falling film element, a bottom plate of the material box body is a film distribution plate, and a film distribution structure is distributed on the film distribution plate for each falling film flow channel. The devolatilizer has the advantages of large film forming area, controllable film forming shape, wide flow regulating range and the like, and is suitable for devolatilization processes of high-viscosity polymer production, spinning solution deaeration, solution concentration and the like.
Description
Technical Field
The invention relates to falling film devolatilization equipment used in the fields of polymer production, spinning solution deaeration, solution concentration, vacuum evaporation and the like, in particular to a production device for polymer polycondensation reaction, and belongs to the field of chemical production equipment.
Background
In chemical operations such as polycondensation, deaeration of spinning solution, vacuum evaporation, desorption and the like, the mass transfer efficiency for gradually removing small molecular compounds is a key factor for controlling the devolatilization process. Since such processes usually occur in highly viscous systems, the diffusion of small molecular compounds in the system is very difficult, and the devolatilization effect is limited by the structure of the components in the equipment for material flow and the mixing characteristics of the material flow. There is a need to develop a devolatilizer with compact structure, fast surface update frequency and high heat and mass transfer efficiency to achieve the goal of high-capacity, high-efficiency and high-quality devolatilization.
In the process of preparing the polymer, the melt polycondensation reaction is a reversible polymerization reaction which continuously generates small molecular compounds, and the polymer including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyamide (PA66), Polycarbonate (PC) and the like can be prepared by the melt polycondensation reaction. When preparing the polymer, a devolatilization process for removing small molecular compounds generated must be continuously carried out to promote the reaction to be continuously carried out in a forward direction, the viscosity of the material is extremely high, particularly, the dynamic viscosity of the material can be changed in order of magnitude at the later stage of polycondensation, and the reaction is a viscosity changing process which relates to the coupling of chemical reaction and heat and mass transfer. Therefore, the melt polycondensation reaction effect depends on the flow characteristics and the heat and mass transfer interface characteristics of the devolatilization process material.
The existing equipment successfully applied to devolatilization of high-viscosity materials mainly comprises two types of horizontal stirring devices, namely a disc type horizontal stirring device and a cage frame type horizontal stirring device. The two types of equipment are both used for taking the melt in the molten pool into a film and devolatilizing the film when rotating by virtue of rotating equipment with the lower part immersed in the melt layer, the film forming efficiency of the melt is low, the surface updating is limited, and particularly when the viscosity of the material is high, the material is attached to a component in the device for a long time and side reaction occurs to cause the quality of a product to be reduced; in addition, the rotating shaft of such a stirring type reaction apparatus is usually connected to the outside of the housing, and a large amount of highly viscous material adheres to the stirrer to generate a considerable disturbance, and the sealing reliability of the apparatus is poor. Therefore, an efficient devolatilization device is urgently needed to be developed, materials in the device can have good film-forming performance, the surface is updated quickly, the retention time is uniform, the flowing has no dead zone, the device is easy to clean and has low energy consumption, the reaction process meets the requirements of flowing, mixing and heat and mass transfer, and the high-efficiency polycondensation is realized.
The disclosed vertical devolatilization reactor (a tube-in-tube external falling film polycondensation reaction kettle, CN 102746499B; a multilayer falling film devolatilization reactor, CN 105903424B) has reduced energy consumption because it does not have a stirrer, and the film forming and surface updating can also meet certain production quality requirements, but the adjustable production material flow range is limited, when the material handling capacity is increased, the retention time is obviously reduced, and the product quality is reduced; and multilayer's umbrella skirt structure causes directly falling easily and can't get back to the hollow tube outer wall when falling liquid film in-process material breaks away from the umbrella skirt, forms so-called "short circuit" to make and take off the uneven of wave effect variation and material viscosity, simultaneously, multilayer structure also can cause easily to produce obvious dwell time difference when lower floor's column plate radial flow because of the gradual grow of material viscosity, and then influences and takes off and wave the effect. Therefore, it is urgently needed to provide devolatilization equipment with large film forming area, controllable film forming shape, no dead zone, fast surface updating, uniform and controllable residence time in the falling film process and large flow range adaptability.
Disclosure of Invention
It is a first object of the present invention to overcome the above deficiencies of the prior art by providing a falling film devolatilizer. Therefore, the invention adopts the following technical scheme:
falling film formula devolatilization ware, including vertical casing, connect in drain pan, material import, vacuum extraction opening, the material export of head and the lower extreme of vertical casing upper end, its characterized in that: be equipped with material box and at least one falling film component in the devolatilization ware, have a plurality of falling film runners on the falling film component, material import and material box are linked together, and the bottom plate of material box is the film distribution board, and the film distribution board is provided with the film distribution structure, each falling film runner is all distributed with the same film distribution structure.
Each falling film flow passage of the falling film element on the film distribution plate is provided with a film distribution hole as a film distribution structure. One preferred structure is: the number, the size and the relative position of the film distribution holes corresponding to each flow channel are completely the same. The material is distributed through the film distributing holes on the film distributing plate, enters the falling film flow channel to form falling film flow, and is devolatilized at the same time, the small molecules are pumped away from the vacuum suction port, and the material is discharged from the discharge port after slipping off from the falling film element.
Further, the membrane distribution hole corresponding to each flow channel is preferably one.
Specifically, the falling film element is used as a support for providing a material flowing falling film flow passage, and can be a straight pipe or a solid rod.
Further, the cross section of the falling film element can be circular, polygonal and the like.
Furthermore, a plurality of axial limiting walls are uniformly distributed on the periphery of the falling film element, and the falling film flow channel is an expanding flow channel formed by taking the outer wall of the falling film element as the bottom and taking two adjacent axial limiting walls of the same falling film element as side walls; the falling film element in the devolatilizer can also be uniformly distributed with a plurality of axial inward concave grooves at the periphery, and the falling film flow channel is a flaring flow channel formed by the surfaces of the axial inward concave grooves.
Furthermore, at least one up-to-the-air crosspiece is arranged between two adjacent axial limiting walls on the falling film element.
Further, the devolatilizer is provided with a heat transfer system and a heat preservation system, the heat transfer system comprises a falling film element, a heat medium inflow box and a heat medium outflow box, and an inner pipe and an outer pipe of the falling film element are respectively connected with the heat medium inflow box and the heat medium outflow box to form a circulation path of the heat transfer system; the heat preservation system comprises a shell jacket and a bottom shell jacket which are respectively arranged on a vertical shell and a bottom shell, the upper part and the lower part of the shell jacket are respectively provided with a shell jacket heat medium inlet and a shell jacket heat medium outlet, and the upper part and the lower part of the bottom shell jacket are respectively provided with a bottom shell jacket heat medium inlet and a bottom shell jacket heat medium outlet; the heat medium of the heat transfer system and the heat preservation system circulates to the outside and circulates after being heated or cooled.
Preferably, the falling film element has a double pipe structure, the inner pipe of the falling film element is open at both the upper end and the lower end, and the outer pipe of the falling film element is closed at both the upper end and the lower end, so that the heat medium passage is formed inside the inner pipe and in the gap between the inner pipe and the outer pipe.
It is another object of the present invention to overcome the above deficiencies of the prior art by providing a falling film element for a falling film devolatilizer. Therefore, the invention adopts the following technical scheme:
the falling film element is provided with a plurality of axial limiting walls which are uniformly distributed along the circumferential direction of the falling film element to divide the outer wall of the falling film element into a plurality of falling film flow channels.
Specifically, the falling film element is used as a support for providing a material flowing falling film flow passage, and can be a straight pipe or a solid rod.
Further, the cross section of the falling film element can be circular, polygonal and the like.
Furthermore, at least one up-to-the-air crosspiece is arranged between two adjacent axial limiting walls on the falling film element.
Furthermore, the number of the axial limiting walls distributed on each falling film element is 2-20, the diameter of an external circle of each falling film element is 10-200 mm, the length of each falling film element is 0.5-20 m, and the height of each axial limiting wall is 2-100 mm.
Furthermore, the falling film element is of a sleeve structure, the upper end and the lower end of the inner tube of the falling film element are all open, and the upper end and the lower end of the outer tube of the falling film element are closed, so that a heat medium channel is formed in the inner part of the inner tube of the falling film and a gap between the inner tube and the outer tube.
Furthermore, the falling film element is formed by connecting a plurality of sections of coaxial falling film parts from top to bottom, and the diameter of the circumscribed circle of each section of falling film part from top to bottom is gradually increased.
It is a further object of the present invention to overcome the above deficiencies of the prior art by providing an alternative falling film element for a falling film devolatilizer. Therefore, the invention adopts the following technical scheme:
the falling film element is provided with a plurality of axial inward concave grooves which are uniformly distributed along the circumferential direction of the falling film element to form a plurality of falling film flow channels.
In particular, the falling film element can be in a tubular shape or a solid rod shape as a support for providing a material flow falling film flow passage.
Furthermore, the number of the axially inward concave grooves distributed on each falling film element is 2-20, the diameter of an external circle of each falling film element is 20-300 mm, the length of each falling film element is 0.5-20 m, and the depth of each axially inward concave groove is 2-100 mm.
Furthermore, the falling film element is formed by connecting a plurality of sections of coaxial falling film elements from top to bottom, and the diameter of the circumscribed circle of each section of falling film element from top to bottom is gradually increased.
The invention divides the outer wall of the falling film element into a plurality of material falling film flowing areas through the structural design of the special falling film element and the combination of the special falling film element and the film distribution plate, has a film forming interface which can be restricted, and is easy to regulate and control the material residence time and the flowing form.
The other function of the invention is to make the material uniformly fall film on each flow channel and always maintain a larger devolatilization area, and the flared flow channel on the falling film element not only increases the devolatilization area but also has the function of extending the film surface, so that the film surface of the material film does not shrink in the falling process, the residence time of the melt film is uniform and the average residence time is prolonged, thereby being beneficial to the full reaction of the material, and further improving the devolatilization effect of the small molecular compound; meanwhile, the flaring flow channel has a flow guiding effect and is easier to cooperate with the vacuum air pumping condition to improve the devolatilization effect; the parameter-optimized falling film element provided by the structure supports the material flow, so that the material film forming is always uniformly limited in a controllable flow channel area; furthermore, a plurality of crosspieces are arranged between two adjacent axial limiting walls on the falling film element, so that the flowing speed of the materials can be reduced, the surface updating of the materials is enhanced, and the materials are mixed more uniformly.
Compared with the prior external falling film reactor, the devolatilization device has the advantages of simple and convenient operation, a constraint film forming interface, large film forming area, controllable film forming shape, no dead zone, quick surface updating, uniform and controllable residence time in the falling film process, and can meet the requirements of high-capacity and high-quality material devolatilization.
Drawings
FIG. 1 is a schematic view of the structure of a devolatilizer of example 1 provided in the present invention;
FIG. 2 is a schematic view of the structure of a devolatilizer of example 4 provided in the present invention;
figure 3 is a schematic diagram of a falling film element of example 1 provided by the present invention;
figure 4 is a schematic diagram of a falling film element of example 3 provided by the present invention;
figure 5 is a schematic view of a falling film element of example 5 provided by the present invention;
figure 6 is a schematic diagram of a falling film element of example 6 provided by the present invention;
FIG. 7 is a schematic view of the structure of a devolatilizer of example 8 provided in the present invention;
fig. 8 is a schematic view of a concave-shaped groove type profiled tubular falling film element according to the present invention;
figure 9 is a schematic view of a falling film element of example 8 provided by the present invention;
fig. 10 is a sectional view a-a in fig. 1.
Parts, positions and numbers in the drawings: the device comprises a heat medium inlet 1, a feeding pipeline 2, a heat medium inflow box body 3, a heat medium outflow box body 4, a heat medium outflow box body upper cover plate 41, a heat medium outflow box body lower bottom plate 42, a material box body 5, a film distribution plate 51, a film distribution hole 511, a shell jacket heat medium inlet 6, a vertical shell 7, a shell jacket 8, a bottom shell flange 9, a bottom shell bolt 10, a bottom shell jacket heat medium inlet 11, a bottom shell 12, a bottom shell jacket 13, a material outlet 14, a bottom shell jacket heat medium outlet 15, a stirrer 16, a shell jacket heat medium outlet 17, a falling film element 18, an axial limiting wall 181, an inner pipe 182 of the falling film element, an outer pipe 183, a crosspiece 184 of the falling film element, a falling film runner 18a, a vacuum suction opening 19, a shell flange 20, a shell bolt 21, a heat medium outlet 22, an end enclosure 23 and a material.
Detailed Description
Example 1, with reference to figures 1, 3 and 10;
the falling film devolatilizer provided in this embodiment, as shown in fig. 1, includes a vertical shell 7, a bottom shell 12 connected to an end socket 23 at an upper end and a lower end of the vertical shell 7, a material inlet 24, a vacuum pumping port 21, and a material outlet 14, wherein a material box 5 and a plurality of falling film elements 18 are disposed in the devolatilizer, the falling film elements 18 are provided with a plurality of falling film runners 18a, the material inlet 24 is communicated with the material box 5, a bottom plate of the material box 5 is a film distribution plate 51, the film distribution plate 51 is provided with a film distribution structure, and each falling film runner 18a is provided with a film distribution structure.
The periphery of the falling film element 18 is distributed with a plurality of axial limiting walls 181, and the falling film runner 18a is a flaring runner formed by taking the outer wall of the falling film element 18 as the bottom and taking two adjacent axial limiting walls 181 of the same falling film element as the side walls.
As shown in fig. 3, the falling film element 18 in this embodiment is a straight tube with an inner sleeve and an outer sleeve, the axial limiting wall 181 is of a fin structure, the axial limiting wall 181 is vertically arranged in parallel with the central axis of the falling film element 18, the axial limiting wall 181 is uniformly distributed along the circumferential direction of the falling film element 18, the number of the axial limiting walls distributed on each falling film element 18 is 6, the length of the axial limiting wall is 0.5 to 20m, and the height of the axial limiting wall is 2 to 100 mm.
The falling film element 18 with the axial limiting wall 181 is a straight pipe with a constant diameter, and the outer diameter is 80 mm.
As shown in fig. 10, each falling film flow passage 18a of the falling film element 18 is assigned with one film distribution hole 511.
The axial limiting wall 181 is located below the film distribution plate 51 and close to the film distribution plate 51, so that the falling film formed by the film distribution holes 511 can enter the flow channel as soon as possible in time, and the film distribution and extension effects in the flared flow channel are improved.
The length of the falling film elements is 0.5 to 20m, and the ratio of the distance between the outer walls of two adjacent falling film elements 18 in the devolatilizer to the height of the axial limiting wall 181 is more than 2.
The inner tube 182 of the falling film element is open at the upper and lower ends, and the outer tube 183 of the falling film element is open at the upper and lower ends, so that the inner portion of the falling film inner tube 182 and the gap between the inner tube 182 and the outer tube 183 form a passage.
The devolatilizer is provided with a heat transfer system which comprises a heat medium inflow box body 3, a heat medium outflow box body 4, a falling film element 18 and a flow path formed by the falling film element 18, wherein a heat medium inlet 1 and a heat medium outlet 22 are respectively arranged on the heat medium inflow box body 3 and the heat medium outflow box body 4.
The devolatilizer is provided with a heat preservation system which comprises a vertical shell 7, a bottom shell 12 and a shell jacket 8 and a bottom shell jacket 13 which are respectively arranged on the periphery of the vertical shell and the bottom shell, the upper part and the lower part of the shell jacket 8 are respectively provided with a shell jacket heat medium inlet 6 and a shell jacket heat medium outlet 17, and the upper part and the lower part of the bottom shell jacket 13 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 system and the heat preservation system circulates to the outside and circulates after being heated or cooled.
The upper part of the devolatilizer consisting of the heat medium inflow box body 3, the heat medium outflow box body 4 and the material box body 5 is connected with the vertical shell 7 through a shell flange 20 and a shell bolt 21, the vertical shell 7 is connected with the bottom shell 12 through a bottom shell flange 9 and a bottom shell bolt 10, and the disassembly, the overhaul and the installation are convenient.
The devolatilizer bottom shell 12 is provided with an agitator 16, the power of which is transmitted from the bottom.
The material flows in from the material inlet 24 on the end socket 23, flows into the material box body 5 from the feeding pipeline 2, is distributed through the film distribution holes 511 on the film distribution plate 51 at the bottom of the material box body 5, enters the falling film flow channel 18a to form falling film flow, and is devolatilized at the same time, so that the small molecules are pumped out from the vacuum suction port 19, and after the material slides out from the falling film element 18, the material is further homogenized through the stirrer 16, and finally is discharged from the material outlet 14.
The devolatilizer is used for falling film melt polycondensation to prepare a high-viscosity polymer, and polyethylene terephthalate (PET) melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 is used as a raw material to produce high-molecular-weight PET; the PET melt polycondensation reaction is carried out by adopting a preferable structural scheme, the flow rate of each falling film element 18 is 5kg/h, the intrinsic viscosity of the product is 1.08dL/g, and the molecular weight distribution index is 1.55.
Example 2 was carried out.
The PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 is used as a raw material to carry out devolatilization reaction to produce the high molecular weight PET, the flow rate of each falling film element is 20kg/h, other parts are the same as those in the example 1, and the product with the intrinsic viscosity of 1.01dL/g and the molecular weight distribution index of 1.53 can be obtained.
Example 3 was carried out.
As shown in fig. 4, the falling film element 18 with the axial limiting wall is a straight pipe with a constant diameter, the crosspieces 184 are arranged between the adjacent axial limiting walls 181 on the falling film element 18 and are distributed at equal intervals, and the rest is the same as that in embodiment 1; by adopting an optimized structural scheme, a PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 is used as a raw material, devolatilization reaction is carried out to produce the high molecular weight PET, the flow rate of each falling film element is 20kg/h, the intrinsic viscosity of the obtained product is 1.02dL/g, and the molecular weight distribution index is 1.51.
Example 4 was carried out.
In the present embodiment, as shown in fig. 2, the falling film element outer tube 183 with the axial limiting wall 181 is a communicated three-section reducing coaxial straight tube, the falling film element outer tube 183 is reduced in diameter at the same distance below the film distribution plate 51, the tube diameters from the bottom of the film distribution plate 51 to the bottom of the falling film element 18 are respectively 70mm, 80mm and 90mm, and the rest of the present embodiment is the same as that of embodiment 1; taking a PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, the intrinsic viscosity of the obtained product is 1.05dL/g, and the molecular weight distribution index is 1.52.
Example 5
In this example, as shown in fig. 5, a regular hexagonal shaped tube with an axial limiting wall was used as the falling film element of the devolatilizer, the diameter of the circumscribed circle of the regular hexagon was 80mm, and the rest was the same as in example 1; taking a PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, the intrinsic viscosity of the obtained product is 1.01dL/g, and the molecular weight distribution index is 1.54.
Example 6
In this example, as shown in fig. 6, a quadrangular special pipe with an inward concave groove is used as the falling film element of the devolatilizer, the diameter of the circumscribed circle of the quadrangle is 80mm, the depth of the groove is 20mm, and the rest is the same as that of example 1; taking a PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, the intrinsic viscosity of the obtained product is 1.06dL/g, and the molecular weight distribution index is 1.52.
Example 7
In the embodiment, the number of the fins distributed on each falling film element 18 is 12, a PET melt with the intrinsic viscosity of 0.35dL/g and the molecular weight distribution index of 1.81 is used as a raw material, devolatilization reaction is carried out to produce a PET material with higher molecular weight, the flow rate of each falling film element is 10kg/h, and other parts are the same as those in the embodiment 1; the product obtained had an intrinsic viscosity of 0.73dL/g and a molecular weight distribution index of 1.62.
Example 8
The falling film devolatilizer provided in this embodiment, as shown in fig. 7, includes a vertical shell 7, a head 23 connected to an upper end of the vertical shell 7, and a bottom shell 12 connected to a lower end of the vertical shell 7, wherein a material inlet 24 is disposed at a top of the head 23, a vacuum pumping port 19 and a material box 5 are disposed at an upper portion of the vertical shell 7, a bottom plate of the material box 5 is a film distribution plate 51, and a film distribution hole 511 is distributed on the film distribution plate 51 for each flow channel.
A plurality of falling film elements 18 are arranged in the devolatilizer, the falling film elements are vertically arranged, the lower end of the falling film elements is suspended, and a material outlet 14 is arranged at the bottom of the bottom shell 12.
The falling film devolatilizer is applied to defoaming of polyimide spinning solution. The falling film element 18 of the devolatilizer adopts a solid rod structure, and as shown in fig. 9, concave grooves uniformly distributed on the periphery of the falling film element 18 are falling film flow channels 18 a.
The diameter of the circumscribed circle of the falling film element 18 is 120mm, the depth of the groove is 20mm, and the length of the tube is 10 m.
Polyimide spinning solution containing bubbles flows in from a material inlet 24 arranged on a seal head 23, flows into a material box body 5 from a feeding pipeline 2, is distributed through film distribution holes 511 on a film distribution plate 51 at the bottom of the material box body 5, then enters a falling film flow channel 18a to form falling film flow, and is devolatilized at the same time, the flow rate on each falling film element 18 is 30kg/h, small molecular compound bubbles escaping from the polyimide solution are pumped out from a vacuum suction port 19, and the polyimide solution is discharged from a material outlet 14 after slipping from the falling film elements 18, so that the bubble-free spinnable polyimide spinning solution is obtained.
The same component numbers in this example as in example 1 represent the same meanings.
Comparative example 1.
In the comparative example, a vertical circular tube with a constant diameter is used as a falling film element for the melt polycondensation reaction, and the melt flows out of the slit-shaped film distribution holes to the outer wall surface of the tube to carry out the falling film melt polycondensation reaction, which is otherwise the same as that in example 1; the falling film melt polycondensation reactor is adopted to carry out the melt polycondensation reaction of PET, the flow rate on each falling film element is 5kg/h, the intrinsic viscosity of the obtained product is 0.94dL/g, and the molecular weight distribution index is 1.60.
Comparative example 2.
In the comparative example, a vertical circular tube with a constant diameter is used as a falling film element for the melt polycondensation reaction, and the melt flows out of the slit-shaped film distribution holes to the outer wall surface of the tube to carry out the falling film melt polycondensation reaction, which is otherwise the same as that in example 1; the falling film melt polycondensation reactor is adopted to carry out the melt polycondensation reaction of PET, the flow rate on each falling film element is 20kg/h, the intrinsic viscosity of the obtained product is 0.81dL/g, and the molecular weight distribution index is 1.59.
Comparative example 3
In the comparative example, the falling film melt polycondensation reactor described in the same comparative example 1 was used to perform the melt polycondensation of PET, and a PET melt with an intrinsic viscosity of 0.35dL/g and a molecular weight distribution index of 1.81 was used as a raw material to perform the melt polycondensation to produce a PET material with a higher molecular weight, the flow rate per falling film element was 10kg/h, the intrinsic viscosity of the obtained product was 0.52dL/g, and the molecular weight distribution index was 1.69.
Comparing examples 1 to 6 with comparative examples 1 to 2, as shown in table 1, for an outside-tube falling-film melt polycondensation reactor with annular gap film distribution (comparative example), the outside-tube melt is not completely coated, the thickness of the melt film flowing in the falling film is uneven, the residence time of the melt falling film is short, the increase speed of the intrinsic viscosity of the PET after reaction is slow, the molecular weight distribution of the product is remarkably wide, and the intrinsic viscosity of the product is remarkably reduced when the material flow is increased; when the reactor is adopted, because the fin structure design of the falling film element is unique, the falling film process has a constraint film forming interface, the film forming area is large, the film forming shape is controllable, no dead zone exists, the surface is updated quickly, the residence time in the falling film process is uniform and controllable, and the high-performance polyester industrial yarn material with high molecular weight and narrow distribution can be efficiently prepared; more importantly, when the flow rate is obviously increased, the device can still obtain products with high intrinsic viscosity and narrow molecular weight distribution, which shows that the adjustable flow rate range of the processing materials is wide, and the device is favorable for large-capacity production.
Table 1 comparison of experimental results of examples 1 to 6 with comparative examples 1 and 2
Comparing example 7 with comparative example 3, as shown in table 2, when the falling film devolatilizer and the falling film element provided by the present invention are used for the devolatilization of PET, it can be seen that when the intrinsic viscosity of the feed is low, a very good devolatilization effect can be obtained, while when the falling film reactor outside the tube is used, the intrinsic viscosity of the obtained product is increased to a limited extent, and the molecular weight distribution of the product is wide, which indicates that the present invention is suitable for producing polyester materials with different viscosity grades.
Table 2 comparison of experimental results of example 7 and comparative example 3
The above description is only an embodiment of the present invention, but the structural features of the present invention are not limited thereto, and any changes or modifications within the scope of the present invention by those skilled in the art are covered by the present invention.
Claims (13)
1. Falling film formula devolatilizer, including vertical casing (7), connect in bottom shell (12), material import (24), vacuum extraction opening (21), material export (14) of head (23) and the lower extreme of vertical casing (7) upper end, its characterized in that: be equipped with material box (5) and at least one falling film component (18) in the devolatilizer, there are a plurality of falling film runners (18a) on falling film component (18), material import (24) are put through with material box (5) mutually, and the bottom plate of material box (5) is film distribution plate (51), and film distribution plate (51) are provided with the film distribution structure, each falling film runner (18a) all is furnished with the film distribution structure.
2. The falling film devolatilizer as set forth in claim 1 wherein: the periphery of the falling film element (18) is distributed with a plurality of axial limiting walls (181), and the falling film flow channel (18a) is a flaring flow channel formed by taking the outer wall of the falling film element (18) as the bottom and taking two adjacent axial limiting walls (181) of the same falling film element as the side walls.
3. The falling film devolatilizer as set forth in claim 1 wherein: a plurality of axial inward concave grooves are distributed on the periphery of the falling film element (18), and the falling film flow channel (18a) is a flaring flow channel formed by the surfaces of the axial inward concave grooves.
4. The falling film devolatilizer as set forth in claim 1 wherein: the film distribution plate (51) is provided with at least one film distribution hole (511) as a film distribution structure for each falling film flow channel (18a) of the falling film element (18).
5. The falling film devolatilizer as set forth in claim 2 wherein: at least one up-to-the-air crosspiece (184) is arranged between two adjacent axial limiting walls (181) on the falling film element (18).
6. The falling film devolatilizer as set forth in claim 2 or claim 3 wherein: the falling film element (18) is of a double-pipe structure, the upper end and the lower end of an inner pipe (182) of the falling film element are all open, the upper end and the lower end of an outer pipe (183) of the falling film element are closed, and therefore the inner part of the inner pipe (182) and a gap between the inner pipe (182) and the outer pipe (183) form a channel.
7. A falling film element of a falling film devolatilizer, characterized in that: the falling film element (18) is provided with a plurality of axial limiting walls (181), and the axial limiting walls (181) are distributed along the circumferential direction of the falling film element (18) to divide the outer wall of the falling film element (18) into a plurality of falling film flow channels (18 a).
8. A falling film element of a falling film devolatilizer, characterized in that: the falling film element (18) is provided with a plurality of axial inwards concave grooves which are distributed along the circumferential direction of the falling film element (18) to form a plurality of falling film flow channels (18 a).
9. The falling film element of a falling film devolatilizer as set forth in claim 7 wherein: at least one up-to-the-air crosspiece (184) is arranged between two adjacent axial limiting walls (181) on the falling film element (18).
10. The falling film element of a falling film devolatilizer as set forth in claim 7 wherein: the number of the axial limiting walls (181) distributed on each falling film element (18) is 2-20, the diameter of an external circle of each falling film element (18) is 10-200 mm, the length of each falling film element (18) is 0.5-20 m, and the height of each axial limiting wall (181) is 2-100 mm.
11. The falling film element of a falling film devolatilizer as set forth in claim 8 wherein: the number of the axial inward concave grooves (18b) distributed on each falling film element (18) is 2-20, the diameter of an external circle of each falling film element (18) is 20-300 mm, the length of each falling film element (18) is 0.5-20 m, and the depth of each axial inward concave groove (18b) is 2-100 mm.
12. The falling film element of a falling film devolatilizer as set forth in claim 7 or 8 wherein: the falling film element (18) is of a double-pipe structure, the upper end and the lower end of an inner pipe (182) of the falling film element are all open, the upper end and the lower end of an outer pipe (183) of the falling film element are closed, and therefore the inner part of the falling film inner pipe (182) and a gap between the inner pipe (182) and the outer pipe (183) form a channel.
13. The falling film element of a falling film devolatilizer as set forth in claims 7 and 8 wherein: the falling film element (18) is formed by connecting a plurality of sections of coaxial falling film elements from top to bottom, and the diameter of the circumscribed circle of each section of falling film element from top to bottom is gradually increased.
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