CN110639461B - Falling film devolatilizer and falling film element thereof - Google Patents
Falling film devolatilizer and falling film element thereof Download PDFInfo
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- CN110639461B CN110639461B CN201810670679.3A CN201810670679A CN110639461B CN 110639461 B CN110639461 B CN 110639461B CN 201810670679 A CN201810670679 A CN 201810670679A CN 110639461 B CN110639461 B CN 110639461B
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- 239000011552 falling film Substances 0.000 title claims abstract description 217
- 239000000463 material Substances 0.000 claims abstract description 78
- 239000010408 film Substances 0.000 claims abstract description 69
- 238000009826 distribution Methods 0.000 claims abstract description 65
- 238000000605 extraction Methods 0.000 claims description 3
- 230000008676 import Effects 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 13
- 230000008569 process Effects 0.000 abstract description 13
- 229920000642 polymer Polymers 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000007789 sealing Methods 0.000 abstract description 6
- 238000009987 spinning Methods 0.000 abstract description 6
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 25
- 239000005020 polyethylene terephthalate Substances 0.000 description 25
- 238000006068 polycondensation reaction Methods 0.000 description 22
- 238000010438 heat treatment Methods 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
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- 239000002994 raw material Substances 0.000 description 8
- 150000001875 compounds Chemical class 0.000 description 6
- 238000005086 pumping Methods 0.000 description 6
- 239000004642 Polyimide Substances 0.000 description 5
- 229920001721 polyimide Polymers 0.000 description 5
- 238000004321 preservation Methods 0.000 description 5
- -1 polyethylene terephthalate Polymers 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 230000007812 deficiency Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229920001707 polybutylene terephthalate Polymers 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- 229920002215 polytrimethylene terephthalate Polymers 0.000 description 2
- 150000003384 small molecules Chemical class 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000007738 vacuum evaporation Methods 0.000 description 2
- 239000004952 Polyamide Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012824 chemical production Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
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- 238000005859 coupling reaction Methods 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
- 230000001151 other effect Effects 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 239000011112 polyethylene naphthalate Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
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Classifications
-
- 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 devolatilizer and a falling film element thereof, which comprises a vertical shell, a sealing 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 devolatilizer, the falling film element is provided with a plurality of falling film flow passages, the bottom plate of the material box body is a film distribution plate, and each falling film flow passage is distributed with a film distribution structure on the film distribution plate. The devolatilizer has the advantages of large film forming area, controllable film forming form, wide flow regulating range and the like, and is suitable for devolatilization processes such as high viscosity polymer production, spinning solution defoaming, 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 defoaming, 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, spinning solution defoaming, vacuum evaporation, desorption and the like, the mass transfer efficiency of gradually removing small molecular compounds is a key factor for controlling the devolatilization process. Since such processes typically occur in highly viscous systems, the diffusion of small molecular compounds in the system is difficult and the devolatilization effect is limited by the structure of the components within the equipment available for material flow and the mixing characteristics of the material flow. It is desirable to develop a devolatilizer having a compact structure, a fast surface renewal frequency, and a high heat and mass transfer efficiency to achieve the goal of high capacity, high efficiency, and high quality devolatilization.
In the process of preparing polymers, melt polycondensation is a reversible polymerization reaction that continuously produces small molecular compounds, and polymers including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyamide (PA 66), and Polycarbonate (PC) can be prepared by melt polycondensation. The polymer must be prepared by continuously performing a devolatilization process for eliminating small molecular compounds so as to promote the reaction to continuously proceed forward, the viscosity of the material is extremely high, and particularly in the later stage of polycondensation, the dynamic viscosity of the material can change by orders of magnitude, and the reaction is a viscosity-changing process involving coupling of chemical reaction and heat and mass transfer. Thus, the melt polycondensation reaction effect depends on the flow characteristics and the heat and mass transfer interface characteristics of the devolatilized process materials.
The existing equipment successfully applied to devolatilization of high-viscosity materials mainly comprises disc type and cage frame type horizontal stirring devices. The two types of equipment are that the melt in a molten pool is brought up to form a film and devolatilize when rotating by means of a rotating device with the lower part immersed in the melt layer, the film forming efficiency of the melt in the mode is low, the surface update is limited, and particularly when the viscosity of the material is high, the material is attached to an inner component of the device for a long time to cause side reaction, so that the quality of the product is reduced; in addition, the rotating shaft of such stirring type reaction device is usually communicated with the outside of the shell, a large amount of high-viscosity materials are attached to the stirrer to generate a considerable degree of disturbance, and the sealing reliability of the equipment is poor. Therefore, there is an urgent need to develop a high-efficiency devolatilizer, which can make the materials in the device have good film forming performance, fast surface renewal, uniform residence time, no dead zone in the flow, easy cleaning, low energy consumption, and the reaction process meets the requirements of flow, mixing and heat and mass transfer, so as to realize high-efficiency polycondensation.
The disclosed vertical devolatilization reactor (a shell and tube external falling film polycondensation reactor, CN 102746499B; a multilayer falling pipe type falling film devolatilization reactor, CN 105903424B) has the advantages that the energy consumption is reduced to some extent, the film forming and surface updating can meet certain production quality requirements, but the adjustable production material flow range is limited, the residence time is obviously reduced when the material throughput is increased, and the product quality is reduced; the multi-layer umbrella skirt structure is easy to cause that materials can not return to the outer wall of the hollow tube due to direct falling when the materials are separated from the umbrella skirt in the falling film process, so-called short circuit is formed, thereby the devolatilization effect is poor and the viscosity of the materials is uneven, meanwhile, the multi-layer structure is also easy to cause obvious residence time difference when the lower layer tower plates radially flow due to gradual increase of the viscosity of the materials, and the devolatilization effect is further influenced. Therefore, there is an urgent need to provide a devolatilizing device with large film forming area, controllable film forming form, no dead zone, fast surface update, uniform and controllable residence time in the falling film process, and large flow range adaptability.
Disclosure of Invention
A first object of the present invention is to overcome the above-mentioned deficiencies of the prior art by providing a falling film devolatilizer. For this purpose, the invention adopts the following technical scheme:
the falling film devolatilizer comprises a vertical shell, a bottom shell connected with an end socket at the upper end of the vertical shell and the lower end of the vertical shell, a material inlet, a vacuum extraction opening and a material outlet, and is characterized in that: the devolatilizer is internally provided with a material box body and at least one falling film element, the falling film element is provided with a plurality of falling film flow passages, the material inlet is communicated with the material box body, the bottom plate of the material box body is a film distribution plate, the film distribution plate is provided with a film distribution structure, and each falling film flow passage is distributed with the same film distribution structure.
Each falling film runner of the falling film element on the film distribution plate is provided with a film distribution hole as a film distribution structure. A preferred structure is: the number, the size and the relative positions of the film distribution holes corresponding to each flow channel are completely the same. After being distributed through the film distribution holes on the film distribution plate, the materials enter the falling film flow channel to form falling film flow, devolatilization is carried out simultaneously, small molecules are pumped out from the vacuum pumping hole, and after the materials slide down from the falling film element, the materials are finally discharged from the discharging hole.
Further, the film distribution holes corresponding to each flow channel are preferably one.
Specifically, the falling film element can be a straight pipe or a solid rod as a supporting piece for providing a material flow falling film flow channel.
Further, the cross section of the falling film element can be round, polygonal or the like.
Further, a plurality of axial limiting walls are uniformly distributed on the periphery of the falling film element, and the falling film flow passage is a flaring flow passage which is formed by taking the outer wall of the falling film element as a 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 be uniformly distributed with a plurality of axial concave grooves on the periphery, and the falling film flow passage is a flaring flow passage formed by the surfaces of the axial concave grooves.
Further, at least one empty 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 heat transfer system circulation path; the heat preservation system comprises a vertical shell and a shell jacket and a bottom shell jacket, wherein the shell jacket and the bottom shell are respectively arranged, a shell jacket heating medium inlet and a shell jacket heating medium outlet are respectively arranged at the upper part and the lower part of the shell jacket, and a bottom shell jacket heating medium inlet and a bottom shell jacket heating medium outlet are respectively arranged at the upper part and the lower part of the bottom shell jacket; the heat medium of the heat transfer system and the heat preservation system circulates outside and is circularly operated after being heated or cooled.
Preferably, 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 tube and a gap between the inner tube and the outer tube.
Another object of the present invention is to overcome the above deficiencies of the prior art by providing a falling film element for a falling film devolatilizer. For this purpose, 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 and divide the outer wall of the falling film element into a plurality of falling film flow passages.
Specifically, the falling film element can be a straight pipe or a solid rod as a supporting piece for providing a material flow falling film flow channel.
Further, the cross section of the falling film element can be round, polygonal or the like.
Further, at least one empty crosspiece is arranged between two adjacent axial limiting walls on the falling film element.
Further, the number of the axial limiting walls distributed on each falling film element is 2-20, the diameter of the circumcircle of the falling film element is 10-200 mm, the length of the falling film element is 0.5-20 m, and the height of the axial limiting walls is 2-100 mm.
Further, 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.
Further, the falling film element is formed by connecting a plurality of sections of coaxial falling film components from top to bottom, and the diameter of the circumscribed circle of each section of falling film components from top to bottom becomes larger gradually.
It is yet another object of the present invention to provide another falling film element of a falling film devolatilizer that overcomes the above deficiencies of the prior art. For this purpose, the invention adopts the following technical scheme:
the falling film element is provided with a plurality of axial concave grooves which are uniformly distributed along the circumferential direction of the falling film element to form a plurality of falling film flow passages.
Specifically, the falling film element can be tubular or solid rod-shaped as a support for providing a material flow falling film runner.
Further, the number of the axial concave grooves distributed on each falling film element is 2-20, the diameter of the circumcircle of the falling film element is 20-300 mm, the length of the falling film element is 0.5-20 m, and the depth of the axial concave grooves is 2-100 mm.
Further, the falling film elements are 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 elements from top to bottom becomes larger gradually.
According to the invention, through the structural design of the special falling film element and the combination of the falling film element and the film distribution plate, the outer wall of the falling film element is divided into a plurality of material falling film flowing areas, and the falling film element has a constrained film forming interface, so that the material residence time and the flowing form are easy to regulate and control.
The invention has the other effects that the material can uniformly drop the film on each flow passage and can always maintain a larger devolatilization area, and the flaring flow passage on the falling film element not only increases the devolatilization area, but also has the effect of extending the film surface, so that the film surface of the material film is not contracted in the falling process, the retention time of the melt film is uniform and the average retention 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 runner has a diversion effect, and the devolatilization effect is improved more easily by cooperating with the vacuum pumping condition; the falling film element with optimized parameters provided by the structure supports the material to flow, so that the material film forming can be uniformly limited in a controllable flow channel area all the time; furthermore, a plurality of crosspieces are arranged between two adjacent axial limiting walls on the falling film element, so that the flow speed of materials can be reduced, the surface update of the materials is enhanced, and the materials are more uniformly mixed.
Compared with the traditional falling film reactor outside the pipe, the devolatilizer has the advantages of simple operation, restrained film forming interface, large film forming area, controllable film forming form, no dead zone, quick surface update, uniform and controllable stay time in the falling film process, and can meet the requirement of devolatilizing high-capacity and high-quality materials.
Drawings
FIG. 1 is a schematic view of the devolatilizer structure of example 1 according to the present invention;
FIG. 2 is a schematic view of the devolatilizer structure of example 4 according to the present invention;
FIG. 3 is a schematic view of a falling film element according to example 1 of the present invention;
FIG. 4 is a schematic view of a falling film element according to example 3 of the present invention;
FIG. 5 is a schematic view of a falling film element of example 5 provided by the present invention;
FIG. 6 is a schematic view of a falling film element of example 6 provided by the present invention;
FIG. 7 is a schematic view of the devolatilizer structure of example 8 according to the present invention;
FIG. 8 is a schematic view of a special-shaped tubular falling film element with a concave groove provided by the invention;
FIG. 9 is a schematic view of a falling film element of example 8 provided by the present invention;
fig. 10 is a cross-sectional view A-A of fig. 1.
Parts, parts and numbers in the figures: a heating medium inlet 1, a feeding pipeline 2, a heating medium inflow box 3, a heating medium outflow box 4, a heating medium outflow box upper cover plate 41, a heating medium outflow box lower bottom plate 42, a material box 5, a film distribution plate 51, a film distribution hole 511, a shell jacket heating medium inlet 6, a vertical shell 7, a shell jacket 8, a shell flange 9, a shell bolt 10, a shell jacket heating medium inlet 11, a shell 12, a shell jacket 13, a material outlet 14, a shell jacket heating medium outlet 15, a stirrer 16, a shell jacket heating 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 of the falling film element, a ledge 184, a falling film flow passage 18a, a vacuum pumping port 19, a shell flange 20, a shell bolt 21, a heating medium outlet 22, a sealing head 23 and a material inlet 24.
Detailed Description
Example 1, refer to fig. 1, 3 and 10;
the falling film devolatilizer provided in this embodiment, as shown in fig. 1, includes a vertical shell 7, a sealing head 23 connected to the upper end of the vertical shell 7, a bottom shell 12 connected to the lower end of the vertical shell, a material inlet 24, a vacuum pumping port 19, 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 channels 18a, the material inlet 24 is communicated with the material box 5, the 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 channel 18a is distributed with the 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 flow channel 18a is a flaring flow channel which takes the outer wall of the falling film element 18 as the bottom and takes two adjacent axial limiting walls 181 of the same falling film element as the side walls.
As shown in fig. 3, the falling film elements 18 in this embodiment are straight pipes with inner and outer sleeves, the axial limiting walls 181 are of fin structures, the axial limiting walls 181 are arranged in parallel with the central axis of the falling film elements 18 in the vertical direction, the axial limiting walls 181 are uniformly distributed along the circumferential direction of the falling film elements 18, the number of the axial limiting walls distributed on each falling film element 18 is 6, the length of the axial limiting walls is 0.5-20 m, and the height is 2-100 mm.
The falling film element 18 with the axial limiting wall 181 is a section of straight pipe with constant diameter, and the outer diameter is 80mm.
As shown in fig. 10, each falling film runner 18a on the falling film element 18 is assigned a film distribution hole 511.
The axial limiting wall 181 is positioned below the film distribution plate 51 and is close to the film distribution plate 51, so that a falling film formed by the film distribution holes 511 can enter the flow channel as soon as possible, and the film distribution and extension effects in the flaring flow channel are improved.
The length of the falling film elements is 0.5-20 m, and the ratio of the outer wall spacing of two adjacent falling film elements 18 in the devolatilizer to the height of the axial limiting wall 181 is greater than 2.
The inner tube 182 of the falling film element is entirely open at the upper and lower ends thereof, and the outer tube 183 of the falling film element is open at the upper end and closed at the lower end, so that the inside of the inner tube 182 of the falling film 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, wherein the heat medium inflow box body 3 and the heat medium outflow box body 4 are respectively provided with a heat medium inlet 1 and a heat medium outlet 22.
The devolatilizer is provided with a heat preservation system, and comprises a vertical shell 7, a bottom shell 12, a shell jacket 8 and a bottom shell jacket 13, wherein the peripheries of the vertical shell and the bottom shell are respectively provided with a shell jacket heating medium inlet 6 and a shell jacket heating medium outlet 17, the upper part and the lower part of the shell jacket 13 are respectively provided with a bottom shell jacket heating medium inlet 11 and a bottom shell jacket heating medium outlet 15.
The heat medium of the heat transfer system and the heat preservation system circulates outside and is circularly operated 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, and the vertical shell 7 is connected with the bottom shell 12 through a bottom shell flange 9 and a bottom shell bolt 10, so that the disassembly, the overhaul and the installation are convenient.
Devolatilizer bottom shell 12 is provided with stirrer 16, the power of which is transmitted from the bottom.
The material flows in from a material inlet 24 arranged on the seal head 23, flows into the material box body 5 from the material inlet pipeline 2, is distributed through a film distribution hole 511 on a film distribution plate 51 at the bottom of the material box body 5, enters a falling film flow channel 18a to form falling film flow, is devolatilized at the same time, small molecules are pumped out from a vacuum pumping hole 19, and is further homogenized through a stirrer 16 after sliding down from the falling film element 18, and finally is discharged from a material outlet 14.
The devolatilizer is used for preparing a high-viscosity polymer through falling film melt polycondensation, and a 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; by adopting the preferable structural scheme to carry out PET melt polycondensation, the flow rate of each falling film element 18 is 5kg/h, and the intrinsic viscosity of the obtained product is 1.08dL/g, and the molecular weight distribution index is 1.55.
Example 2.
The devolatilization reaction was carried out using a PET melt having an intrinsic viscosity of 0.65dL/g and a molecular weight distribution index of 1.65 as a raw material to produce a high molecular weight PET, the flow rate of each falling film element was 20kg/h, and the other portions were the same as in example 1, whereby a product having an intrinsic viscosity of 1.01dL/g and a molecular weight distribution index of 1.53 was obtained.
Example 3.
As shown in fig. 4, the falling film element 18 with axial limiting walls is a straight pipe with a constant diameter, and crosspieces 184 are arranged between adjacent axial limiting walls 181 on the falling film element 18 at equal intervals, and the other parts are the same as those in embodiment 1; adopting a preferable structural scheme, taking PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, and carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, and the product has the intrinsic viscosity of 1.02dL/g and the molecular weight distribution index of 1.51.
Example 4.
In this embodiment, as shown in fig. 2, the outer tube 183 of the falling film element with the axial limiting wall 181 adopts a three-section diameter-variable coaxial straight tube, the outer tube 183 of the falling film element is diameter-variable within the same distance below the film-distributing plate 51, and the tube diameters are respectively 70mm, 80mm and 90mm from the lower side of the film-distributing plate 51 to the bottom end of the falling film element 18, and the other parts of this embodiment are the same as those of embodiment 1; taking PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, and carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, and the intrinsic viscosity of the obtained product is 1.05dL/g and the molecular weight distribution index is 1.52.
Example 5
In this embodiment, as shown in fig. 5, the falling film element of the devolatilizer adopts a regular hexagonal special tube with an axial limiting wall, the diameter of the circumscribed circle of the regular hexagon is 80mm, and other parts are the same as those of embodiment 1; taking PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, and carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, and the intrinsic viscosity of the obtained product is 1.01dL/g and the molecular weight distribution index is 1.54.
Example 6
In this embodiment, as shown in fig. 6, the falling film element of the devolatilizer adopts a quadrangular special tube with concave grooves, the diameter of the circumscribed circle of the quadrangle is 80mm, the depth of the grooves is 20mm, and other parts are the same as those of embodiment 1; taking PET melt with the intrinsic viscosity of 0.65dL/g and the molecular weight distribution index of 1.65 as a raw material, and carrying out devolatilization reaction to produce high molecular weight PET, wherein the flow rate of each falling film element is 20kg/h, and 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 fins distributed on each falling film element 18 is 12, and 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 to carry out devolatilization reaction to produce a PET material with higher molecular weight, wherein the flow rate of each falling film element is 10kg/h, and the other parts are the same as those in the embodiment 1; the intrinsic viscosity of the obtained product was 0.73dL/g, and the molecular weight distribution index was 1.62.
Example 8
The falling film devolatilizer provided in this embodiment, as shown in fig. 7, includes a vertical housing 7, a sealing head 23 connected to the upper end of the vertical housing 7, and a bottom shell 12 connected to the lower end of the vertical housing 7, wherein a material inlet 24 is provided at the top of the sealing head 23, a vacuum extraction opening 19 and a material box 5 are provided at the upper part of the vertical housing 7, a bottom plate of the material box 5 is a film distribution plate 51, and film distribution holes 511 are allocated on the film distribution plate 51 for each flow passage.
A plurality of falling film elements 18 are arranged in the devolatilizer, are vertically arranged, are suspended at the lower end, and are provided with a material outlet 14 at the bottom of the bottom shell 12.
The falling film devolatilizer is applied to defoaming of polyimide spinning dope. 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 runners 18a.
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 10m.
The 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 material feeding pipeline 2, is distributed through a film distribution hole 511 on a film distribution plate 51 at the bottom of the material box body 5, enters a film falling flow passage 18a to form a film falling flow, and is devolatilized at the same time, the flow rate on each film falling element 18 is 30kg/h, small molecular compound bubbles escaping from the polyimide solution are pumped out from a vacuum pumping hole 19, and the polyimide solution is discharged from a material outlet 14 after sliding down from the film falling elements 18, so that the spinnable polyimide spinning solution without bubbles is obtained.
In this embodiment, the same reference numerals as those in embodiment 1 denote 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 melt polycondensation reaction, and melt flows out from a slit-shaped film distribution hole to the outer wall surface of the tube for the falling film melt polycondensation reaction, and the rest is the same as in example 1; the melt polycondensation reaction of PET is carried out by adopting the falling film melt polycondensation reactor, the flow rate on each falling film element is 5kg/h, and 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 melt polycondensation reaction, and melt flows out from a slit-shaped film distribution hole to the outer wall surface of the tube for the falling film melt polycondensation reaction, and the rest is the same as in example 1; the melt polycondensation reaction of PET is carried out by adopting the falling film melt polycondensation reactor, the flow rate on each falling film element is 20kg/h, and 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 melt polycondensation reaction of PET was carried out by using the falling film melt polycondensation reactor described in the comparative example 1, and the melt polycondensation reaction was carried out by using a PET melt having an intrinsic viscosity of 0.35dL/g and a molecular weight distribution index of 1.81 as a raw material to produce a PET material having a higher molecular weight, the flow rate on each falling film element was 10kg/h, and 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 the out-of-tube falling film melt polycondensation reactor with annular gap film distribution (comparative example), the out-of-tube melt coating is incomplete, the film thickness of the falling film flowing melt is uneven, the residence time of the falling film of the melt is shorter, the PET intrinsic viscosity after reaction increases at a slower rate, the molecular weight distribution of the product is significantly wider, and the intrinsic viscosity of the product is significantly reduced when the material flow is increased; when the reactor is adopted, the falling film element fin structure design is unique, the falling film process has a constrained film forming interface, the film forming area is large, the film forming form is controllable, no dead zone exists, the surface updating is fast, the residence time in the falling film process is uniform and controllable, and the high-molecular weight and narrow-distribution high-performance polyester industrial yarn material can be efficiently prepared; more importantly, when the flow is obviously increased, the device can still obtain products with high intrinsic viscosity and narrow molecular weight distribution, which indicates that the adjustable flow range of the processed materials is wide, and the device is beneficial to large-volume 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, the devolatilization reaction of PET using the falling film devolatilizer and falling film element provided by the present invention shows that when the intrinsic viscosity of the feed is low, a very good devolatilization effect can be obtained, whereas when an off-tube falling film reactor is used, the intrinsic viscosity of the obtained product is limited in growth, and the molecular weight distribution of the product is also 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 with comparative example 3
The above embodiments are merely examples of the present invention, but the present invention is not limited thereto, and any changes or modifications made by those skilled in the art are included in the scope of the present invention.
Claims (10)
1. Falling film devolatilizer, including vertical casing (7), head (23) and drain pan (12) of lower extreme, material import (24), vacuum extraction opening (19), material export (14) of being connected in vertical casing (7) upper end, its characterized in that: a material box body (5) and at least one falling film element (18) are arranged in the devolatilizer, a plurality of falling film flow passages (18 a) are formed in the falling film element (18), a material inlet (24) is communicated with the material box body (5), a bottom plate of the material box body (5) is a film distribution plate (51), the film distribution plate (51) is provided with a film distribution structure, and each falling film flow passage (18 a) is distributed with the film distribution structure;
a plurality of axial limiting walls (181) are distributed on the periphery of the falling film element (18), and the falling film flow channel (18 a) is a flaring flow channel which takes the outer wall of the falling film element (18) as the bottom and takes two adjacent axial limiting walls (181) of the same falling film element as the side walls; or, a plurality of axial concave grooves are distributed on the periphery of the falling film element (18), and the falling film flow passage (18 a) is a flaring flow passage formed by the surfaces of the axial concave grooves;
each falling film runner (18 a) of the falling film element (18) is provided with at least one film distribution hole (511) serving as a film distribution structure on the film distribution plate (51).
2. The falling film devolatilizer as defined in claim 1, wherein: at least one hollow crosspiece (184) is arranged between two adjacent axial limiting walls (181) on the falling film element (18).
3. The falling film devolatilizer as defined in claim 1, wherein: the falling film element (18) is of a sleeve structure, the upper end and the lower end of the inner tube (182) of the falling film element are all open, and the upper end and the lower end of the outer tube (183) of the falling film element are open and the lower end is closed, so that a channel is formed in the inner tube (182) and a gap between the inner tube (182) and the outer tube (183).
4. Falling film element of falling film devolatilizer, its 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 passages (18 a);
the number of the axial limiting walls (181) distributed on each falling film element (18) is 2-20.
5. The falling film devolatilizer falling film element of claim 4, wherein: at least one hollow crosspiece (184) is arranged between two adjacent axial limiting walls (181) on the falling film element (18).
6. The falling film devolatilizer falling film element of claim 4, wherein: the diameter of the circumscribed circle of the falling film element (18) is 10-200 mm, and the length of the falling film element (18) is 0.5-20 m.
7. Falling film element of falling film devolatilizer, its characterized in that: the falling film element (18) is provided with a plurality of axial concave grooves which are distributed along the circumferential direction of the falling film element (18) to form a plurality of falling film flow passages (18 a);
the number of the axially inward concave grooves distributed on each falling film element (18) is 2-20.
8. The falling film devolatilizer falling film element of claim 7, wherein: the diameter of the circumscribed circle of the falling film element (18) is 20-300 mm, and the length of the falling film element (18) is 0.5-20 m.
9. The falling film element of a falling film devolatilizer as defined in claim 4 or 7, wherein: the falling film element (18) is of a sleeve structure, the upper end and the lower end of the inner tube (182) of the falling film element are all open, and the upper end and the lower end of the outer tube (183) of the falling film element are open and the lower end is closed, so that a channel is formed in the falling film inner tube (182) and a gap between the inner tube (182) and the outer tube (183).
10. The falling film element of a falling film devolatilizer as defined in claim 4 or 7, 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 circumcircle of each section of falling film element from top to bottom is gradually increased.
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| CN113999332A (en) * | 2021-11-17 | 2022-02-01 | 华东理工大学 | Supercritical carbon dioxide assisted periodic devolatilization process and device |
| CN114672010A (en) * | 2022-04-01 | 2022-06-28 | 温州邦鹿化工有限公司 | Continuous polymerization devolatilization method and device for polylactic acid |
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