CN111530114B - Rectification system, semi-continuous rectification method and application thereof - Google Patents

Rectification system, semi-continuous rectification method and application thereof Download PDF

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Publication number
CN111530114B
CN111530114B CN202010546911.XA CN202010546911A CN111530114B CN 111530114 B CN111530114 B CN 111530114B CN 202010546911 A CN202010546911 A CN 202010546911A CN 111530114 B CN111530114 B CN 111530114B
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rectification
tower
wire mesh
chlorotrifluoroethylene
structured packing
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CN111530114A (en
Inventor
李瑜哲
张智勇
艾波
吴高胜
许保云
杜丽君
吴君毅
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Shanghai Huayi Sanaifu New Material Co Ltd
Shanghai Research Institute of Chemical Industry SRICI
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Shanghai Huayi Sanaifu New Material Co Ltd
Shanghai Research Institute of Chemical Industry SRICI
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Priority to CN202010546911.XA priority patent/CN111530114B/en
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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
    • B01J19/32—Packing elements in the form of grids or built-up elements for forming a unit or module inside the apparatus for mass or heat transfer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14—Fractional distillation or use of a fractionation or rectification column
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14—Fractional distillation or use of a fractionation or rectification column
    • B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/322—Basic shape of the elements
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/322—Basic shape of the elements
    • B01J2219/32203—Sheets
    • B01J2219/3221—Corrugated sheets
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/322—Basic shape of the elements
    • B01J2219/32203—Sheets
    • B01J2219/32213—Plurality of essentially parallel sheets
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/322—Basic shape of the elements
    • B01J2219/32203—Sheets
    • B01J2219/32213—Plurality of essentially parallel sheets
    • B01J2219/3222—Plurality of essentially parallel sheets with sheets having corrugations which intersect at an angle different from 90 degrees
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/322—Basic shape of the elements
    • B01J2219/32203—Sheets
    • B01J2219/32224—Sheets characterised by the orientation of the sheet
    • B01J2219/32227—Vertical orientation
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/324—Composition or microstructure of the elements
    • 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
    • B01J2219/32—Details relating to packing elements in the form of grids or built-up elements for forming a unit of module inside the apparatus for mass or heat transfer
    • B01J2219/324—Composition or microstructure of the elements
    • B01J2219/32491—Woven or knitted materials

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Abstract

A rectification system, a semi-continuous rectification method and uses thereof are disclosed, the rectification system comprising a column bottom, a rectification column fluidly connected to the column bottom and a plurality of product storage tanks fluidly connected to the rectification column through control valves; the rectifying tower comprises a structured packing in the rectifying tower, the structured packing is formed by arranging a plurality of corrugated wire mesh sheets vertically arranged with a horizontal plane, adjacent corrugated wire mesh sheets are arranged in parallel, each wire mesh sheet is formed by weaving spiral winding type bifilar silk yarns, and the weaving density of the spiral winding type bifilar silk yarns is increased along the central direction to the peripheral direction of the wire mesh sheets.

Description

Rectification system, semi-continuous rectification method and application thereof
Technical Field
The invention relates to a structured packing, a rectification system and a rectification method adopting the structured packing, and a rectification system can effectively separate chlorotrifluoroethylene thermal cracking products. More specifically, the rectifying tower provided by the invention is used for semi-continuously rectifying the chlorotrifluoroethylene thermal cracking product, so that the rectifying efficiency can be favorably improved, the rectifying time can be shortened, the high-purity fractionated product can be obtained while the product cost is reduced, and good economic benefits can be obtained.
Background
Hexafluoro-1, 3-butadiene (C) in a wide variety of fluorine-containing etching gases4F6Hexafluorobutadiene for short) has the best C/F ratio, can obtain moderate etching rate, has better protection to 193nm photoresist, and can realize nearly vertical etching. Meanwhile, due to the above characteristics, hexafluorobutadiene can maintain a high selectivity and accuracy also in a process below 7 nm. More importantly, its GWP100The value is only 290, the atmospheric lifetime is less than 2 days, and C which is commonly used in the oxide film etching process is replaced by the value3F8And C-C4F8The volume fraction of perfluoroalkane hydrocarbons (PFCs) in the exhaust gas can be reduced by 80% and 82%, respectively, by the etching gas. Thus, hexafluorobutadiene is a new generation of etching gas that has been found to meet the development requirements of etching technology while minimizing the environmental impact, and is considered necessary for the production of next-generation semiconductor products.
The processes for preparing hexafluorobutadiene are currently extensive, such as the 1, 2-difluorodichloroethylene process, the chlorotrifluoroethylene process, and the 3, 4-dichlorohexafluoro-1-butene dechlorination process, among others. Wherein, the dechlorination method of the 3, 4-dichlorohexafluoro-1-butene has the characteristics of simple reaction, convenient control and easy industrialization, and has great application value.
The 3, 4-dichlorohexafluoro-1-butene is mainly prepared by the thermal cracking reaction of chlorotrifluoroethylene, and the cracked product comprises 1, 2-dichlorohexafluorocyclobutane besides the 3, 4-dichlorohexafluoro-1-butene. For example, the thermal cracking of chlorotrifluoroethylene to form a mixture comprising 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene at 450 ℃ to 710 ℃ and atmospheric pressure is reported by S.M.Ivanova, N.V. Zemlyanskaya et al, Zhu's Obshchey Khimii (volume 56), published in 1986.
The 1, 2-dichlorohexafluorocyclobutane can be used for medical anesthesia and related research of anesthesiology, or can be used as an intermediate of organic synthesis, can also be used as a raw material for producing hexafluorocyclobutane, and also has market application value. With the application of the two products gradually moving to the high-end level, the purity requirements of the market on the 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene products are higher and higher.
Zhang Chilean 'research on cracking reaction process of chlorotrifluoroethylene' ('organic fluorine industry', third 2016) reports that the yield of 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene in the thermal cracking product of chlorotrifluoroethylene can reach more than 36% at the reaction temperature of 420-450 ℃ and the retention time of 30 seconds.
1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene have low viscosity due to close boiling points, and are difficult to separate and obtain high-purity compound products efficiently. For example, US2668182 discloses thermal cracking of chlorotrifluoroethylene to 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene at 550 ℃, 34% conversion, 21% yield, and mentions that since both compounds are not easily fractionated, the mixture is directly reacted with chlorine gas to obtain 1,2,3, 4-tetrachlorohexafluorobutane and 1, 2-dichlorohexafluorocyclobutane, and after separating 1,2,3, 4-tetrachlorohexafluorobutane using rectification, it is reacted with zinc powder in a solvent to produce hexafluorobutadiene. In the method, 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene are difficult to separate, additional reaction is introduced, the complexity of the process is increased, the total conversion rate and yield are low, chlorine has high toxicity, and industrialization is difficult to realize.
TW200540140A discloses a method for separating a thermal cracking product of chlorotrifluoroethylene using a batch distillation column. The method comprises the following steps: a stainless steel rectifying tube with the diameter of 50mm and the height of 5000mm is used for filling high-performance grid-shaped filler, and 99.9 percent of 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene can be obtained through separation of six different fractions, wherein the single-batch processing capacity of the rectifying tube is 15 kilograms. The method can separate the target product, but the product purity can not meet the requirements of the current semiconductor industry. In addition, the method uses a 50mm batch distillation tower for separation, the processing capacity is low, and the high-performance grid-shaped filler filled in the tower is only suitable for laboratory research, cannot be applied to industrial production and does not have the capacity of industrial amplification.
Rectification columns with structured packing are currently in wide use in industry. Wire mesh corrugated packing in structured packing is believed to have a higher separation efficiency. The use of the packing can not only obtain high-purity rectification products, but also greatly reduce the height of the rectification tower.
Wei FengThe performance of the wire mesh structured packing was studied in "mass transfer performance of the wire mesh structured packing" ("university of Tianjin" in 2007, 8 months), and the specific surface area of the packing used was 2500m2/m3。
However, there is still room for improvement in the fractionation efficiency of the conventional wire mesh structured packing. The existing means for improving the separation efficiency more adopt the technical means of improving the specific surface area of the wire mesh corrugated packing. But with the attendant increase in the effect of the phenomenon of the distillation column wall flow on the separation efficiency. Wall flow refers to the situation where the liquid phase in the column flows down directly along the column wall after contacting the column wall. The size of the wall flow directly determines the liquid amount flowing to the surface of the filler, the reduction of the liquid amount reduces the thickness of the liquid film, and the wetting of the filler is not uniform in severe cases, so that the original separation effect of the filler is greatly reduced. At present, the wall flow phenomenon is reduced by adding a wall flow prevention ring of a silk screen outside the regular packing in the industry.
For example, CN104275144A discloses a common design of wall flow preventing ring, in which each disk of packing is installed with a ring of wall flow preventing ring with an outward flanging structure, the outer side of the packing contacts with the column wall through the wall flow preventing ring, and when the liquid on the column wall flows downward and contacts the wall flow preventing ring, the wall flow preventing ring will guide the liquid to flow back to the surface of the packing again. But because of the structural characteristics of the wall flow preventing ring, the outer diameter of the packing is certainly slightly smaller than the inner diameter of the rectifying tower when in use.
Due to the simple structure of the anti-wall flow ring, the obvious action principle and the effect proved by practice, the anti-wall flow ring becomes generally accepted in the industry after the first appearance. CN1125673C suggests that the anti-wall flow ring can reduce the wall flow phenomenon, and that the separation efficiency of the packing can be improved.
There remains a need in the art to develop a structured packing having improved distillation efficiency as compared to existing structured packing.
There is also a need for developing a rectification column which can advantageously improve the rectification efficiency, shorten the rectification time, obtain a high-purity fractionated product while reducing the product cost, and achieve good economic benefits when a rectification system comprising the rectification column is used for, for example, separating a thermal cracked product of chlorotrifluoroethylene.
Disclosure of Invention
It is an object of the present invention to provide a structured packing having improved distillation efficiency as compared to existing structured packing.
It is a further object of the present invention to provide a rectification column which contains the structured packing of the present invention and has improved fractionation efficiency.
Another object of the present invention is to provide a rectification system comprising the rectification column of the present invention, which can advantageously improve the rectification efficiency, shorten the rectification time, obtain a high-purity fractionated product while reducing the product cost, and achieve good economic benefits when the rectification system comprising the rectification column is used for, for example, separating a thermal cracked product of chlorotrifluoroethylene.
It is still another object of the present invention to provide a semi-continuous rectification method for separating a thermal cracking product of chlorotrifluoroethylene, which can efficiently obtain a high-purity fractionated product in combination with the rectification column of the present invention.
Accordingly, one aspect of the present invention relates to a corrugated wire mesh sheet for forming structured packing, which is woven from spirally wound type bifilar wires having a higher weaving density in a central to peripheral direction of the wire mesh sheet.
The invention also relates to a structured packing, which is formed by arranging a plurality of corrugated silk screen sheets vertically arranged with a horizontal plane, wherein adjacent corrugated silk screen sheets are arranged in parallel, each silk screen strip sheet is formed by weaving spiral winding type bifilar silk yarns, the weaving density of the spiral winding type bifilar silk yarns is increased along the central direction to the peripheral direction of the silk screen strip sheet, and the structured packing can be provided with a wall flow prevention ring.
Another aspect of the present invention relates to a disc-shaped structured packing comprising a plurality of braids having different dense-sparse-dense distributions, the braids having the same length but different widths, the plurality of braids being vertically arranged in such a manner that they are arranged to form a disc having a height equal to the length of the braids, the disc cross-section being in a circumferential direction from the center of the circle, each vertical braid having substantially the same dense-woven structure in an outermost annular region, substantially the same sparse-woven structure in an intermediate annular region, and substantially the same dense-woven structure in a central annular region.
Another aspect of the present invention relates to a rectification column comprising a structured packing in the rectification column, the structured packing being formed by arranging a plurality of corrugated wire mesh sheets placed perpendicular to a horizontal plane, adjacent corrugated wire mesh sheets being arranged in parallel, each of the wire mesh sheets being formed by weaving spirally wound double-stranded wires, the weaving density of the spirally wound double-stranded wires being increased in a direction from a center to a periphery of the wire mesh sheets.
Another aspect of the invention relates to a rectification system comprising a column bottom, a rectification column of the invention fluidly connected to the column bottom, and a plurality of product storage tanks fluidly connected to the rectification column via control valves.
Still another aspect of the present invention relates to a semi-continuous rectification method for separating chlorotrifluoroethylene thermal cracking products, comprising:
inputting the chlorotrifluoroethylene thermal cracking product into a tower kettle, and heating;
continuously inputting the chlorotrifluoroethylene thermal cracking product, and continuously collecting light components and non-thermal cracking chlorotrifluoroethylene reactants from the top and the side of the tower;
stopping inputting the chlorotrifluoroethylene thermal cracking product, and sequentially collecting the rest rectification products from the tower top;
and (4) respectively conveying each rectification product to a corresponding product storage tank by adjusting a valve between the rectification tower and the product storage tank.
Drawings
The invention is further described below with reference to the accompanying drawings. In the drawings:
FIGS. 1a and 1b are schematic views of filaments used to form structured webs in one example of the invention;
FIGS. 2a and 2b are schematic illustrations of the arrangement of two adjacent strands of filaments of a structured screen in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a rectification system for rectifying a chlorotrifluoroethylene thermal cracking product in an embodiment of the present invention.
Detailed Description
The present inventors have found that conventional structured packing has room for improvement in various aspects such as structure, particularly wire mesh sheet structure, and the like, and can further improve fractionation efficiency.
The inventor of the present invention has also found that, for such substances with low viscosity as the thermal cracking product of chlorotrifluoroethylene, especially under the condition that the inner diameter of the tower is not more than 1000mm, the existing wall flow preventing ring can not only not reduce the wall flow phenomenon ideally, but also aggravate the imbalance of the gas-liquid phase distribution in the tower, which leads to better contact of less liquid phase and gas phase on the surface of the packing, and in addition, the reduction of the packing efficiency of the substances, which finally leads to the actual separation effect far from the nominal separation effect of the packing, sometimes the actual effect is even 30%.
In order to solve the problems, the inventor modifies the structure of the weaving silk threads and the weaving structure of the silk screen sheet of the regular packing, and adopts a brand-new silk screen sheet design with a dense-sparse-dense structure weaving density region distribution, so that the effect of efficient fractionation is achieved under the condition of no need of a wall flow prevention ring, and the obtained separation product has higher purity. In addition, even with the structure of the anti-wall flow ring, the regular packing prepared by the novel silk screen sheet has higher fractionation efficiency than the conventional regular packing with the structure of the anti-wall flow ring.
1.Rectifying tower
a) Structured packing
The rectifying tower comprises a structured packing, the structured packing is formed by arranging a plurality of corrugated wire mesh sheets vertically arranged with a horizontal plane, adjacent corrugated wire mesh sheets are arranged in parallel, and the wire mesh sheets are formed by weaving spiral winding type bifilar silk yarns.
The bifilar filaments used to weave the mesh sheet may be the same or different filaments, which are intertwined in a helical manner.
In one example of the present invention, the spirally wound type bifilar filament comprises a main filament and an auxiliary filament, which may be the same or different materials. In one example of the invention, materials used to form the wire include, for example, metals such as stainless steel, copper and copper alloys, nickel, monel, and non-metals such as fluoropolymers, e.g., polytetrafluoroethylene, may also be used.
In one embodiment of the invention, the secondary filaments are straight and the primary filaments are helically wound around the secondary filaments with the pitch of the primary filaments being 1 to 5 times, preferably 1.2 to 4 times, more preferably 1.4 to 3.5 times, preferably 1.5 to 3.2 times, and most preferably 1.8 to 3.0 times the diameter of the primary filaments.
In one embodiment of the invention, the main wire and the auxiliary wire are spirally wound with each other, and the pitch of the main wire is 2-4 times the diameter of the main wire.
In a preferred embodiment of the invention, the secondary filaments are straight and the primary filaments are helically wound around the secondary filaments, the pitch of the primary filaments being from 0.05 to 1mm, preferably from 0.06 to 0.8mm, more preferably from 0.07 to 0.7mm, preferably from 0.075 to 0.64mm, and preferably from 0.09 to 0.6 mm.
In one embodiment of the present invention, the main filaments have a filament diameter of 0.05 to 0.2mm, preferably 0.08 to 0.18mm, more preferably 0.1 to 0.15mm, preferably 0.12 to 0.13 mm; the auxiliary filaments have a diameter of 0.05-0.2mm, preferably 0.06-0.15mm, more preferably 0.08-0.12mm, most preferably 0.09-0.1 mm.
The silk screen sheet is formed by weaving spiral winding type double-strand silk yarns. The method of knitting is not particularly limited and may be a conventional method known in the art. In one example of the present invention, the mesh sheet is formed by plain weaving, twill weaving or microgroove weaving of a spirally wound type double-strand silk thread.
In one example of the present invention, when the spirally wound type double-stranded wire is braided, the spirally winding directions of two adjacent wires are the same, the spirally winding directions of two adjacent wires are different, or the spirally winding directions of two adjacent wires are randomly selected.
In one example of the present invention, when the spirally wound type bifilar filaments are braided, the braid is increased in the direction from the center to the edge.
In the present invention, the term "increased braid density" includes a uniform or non-uniform increase in braid density and/or a gradient increase in the direction from the center to the edge of the braid.
In one example of the invention, the braid has a rectangular configuration, with a density of the braid varying symmetrically in a gradient or gradient from one side edge to the other. In one embodiment of the invention, the braid has a rectangular configuration, and the density of the braid varies symmetrically in a density-density gradient from one side edge to the other side edge, and the braid density in the high density region is 10 to 50 mesh, preferably 15 to 45 mesh, more preferably 20 to 40 mesh, preferably 25 to 35 mesh, and preferably 28 to 32 mesh more than that in the low density region in terms of mesh number.
In one embodiment of the present invention, the region of the predetermined width from each side has a weaving density of 85 to 150 mesh, preferably 88 to 140 mesh, more preferably 95 to 135 mesh, preferably 98 to 130 mesh, and preferably 100 to 120 mesh in terms of mesh; the central region around the center of the braid has a braid density of 30 to 80 mesh, preferably 40 to 70 mesh, more preferably 45 to 65 mesh in terms of mesh number. In one embodiment of the invention, there is a transition zone between the two, having a weave density of 60 to 100 mesh, preferably 65 to 95 mesh, more preferably 70 to 90 mesh, and most preferably 75 to 85 mesh, on a mesh basis.
In an example of the present invention in which the column inside diameter is 200mm or less, the predetermined width is 10mm to 15% of the inside diameter of the rectifying column, preferably 12mm to 13% of the inside diameter of the rectifying column, more preferably 14mm to 11% of the inside diameter of the rectifying column, preferably 16mm to 9% of the inside diameter of the rectifying column, and preferably 18mm to 7% of the inside diameter of the rectifying column.
In an embodiment of the invention where the column internal diameter is greater than 200mm, the predetermined width is 5% to 15% of the rectification column internal diameter, preferably 6% to 14% of the rectification column internal diameter, more preferably 7% to 13% of the rectification column internal diameter, preferably 8% to 12% of the rectification column internal diameter, and preferably 9% to 11% of the rectification column internal diameter.
The braid constituting the structured packing of the present invention is corrugated, such as by stamping. The corrugated shape of the braid suitable for use in the structured packing of the present invention is not particularly limited and may be a corrugated shape known in the art. In one embodiment of the present invention, the corrugation has a peak height of 2 to 15mm, and the pitch of adjacent two corrugations in terms of the center of the peak is 3 to 20 mm.
In one example of the invention, the corrugations may be the same or different.
b) Filling method
When the rectification tower is filled, a fabric surface which is formed by weaving spiral winding type double-strand silk threads and has corrugation is placed in a direction vertical to a horizontal plane. Therefore, in the present invention, the term "the structured packing is formed of a plurality of corrugated wire mesh strips arranged perpendicular to the horizontal plane, with adjacent corrugated wire mesh strips arranged in parallel" means that the woven faces of the corrugated wire mesh strips are arranged perpendicular to the horizontal plane, and the woven face of each of the corrugated wire mesh strips is parallel to the woven faces of the other corrugated wire mesh strips.
In the present invention, the term "vertical" is not limited to the arrangement at an angle of 90 °, and the weaving surface of the spirally wound type double-strand woven fabric is at an angle of 70 to 110 °, preferably 75 to 105 °, more preferably 80 to 100 °, preferably 85 to 95 °, preferably 88 to 92 ° to the horizontal plane, within the scope of "vertical" of the present invention.
In the present invention, the term "parallel" is not limited to the two woven faces forming an angle of 0 ° with each other, but the two woven faces forming an angle of 15 ° or less, preferably 12 ° or less, more preferably 10 ° or less, preferably 8 ° or less, more preferably 6 ° or less, and preferably 4 ° or less.
In one embodiment of the present invention, a plurality of braids having different dense-sparse-dense distribution structures are cut into pieces having the same length but different widths, the plurality of braids being vertically arranged in such a manner that they are arranged to form a cylinder (or disc) having a height equal to the length of the braids, the cross section of the cylinder being in a circumferential direction from the center of the circle, the vertical braids having substantially the same dense-woven structure in an outer annular region and substantially the same sparse-woven structure in a central circular region. In one example of the invention, the section of the cylinder is along the circle center to the circumferential direction, the vertical braided fabric has basically the same dense braiding structure in the outer ring area, the central circle part area has basically the same sparse braiding structure, and one or more transition areas are arranged between the two, so that the braiding density is increased along the circle center to the circumferential direction.
In one embodiment of the present invention, the radius of the central circular portion is 0.7 to 0.9, preferably 0.75 to 0.85, in terms of the radius of the cross section of the cylinder, based on the total radius of the cross section.
In one embodiment of the present invention, the diameter of the cylinder is substantially the same as the inner diameter of the rectification column, and the height of the cylinder is, for example, 40 to 300mm, preferably 60 to 280mm, more preferably 80 to 260mm, preferably 100 mm and 240mm, and preferably 120 mm and 220 mm.
In one embodiment of the invention, the cylinder is formed by arranging 5 to 500, preferably 10 to 450, more preferably 15 to 420, preferably 20 to 400, preferably 25 to 350 sheets of the corrugated wire mesh of the invention.
The method of packing in the rectification column is not particularly limited and may be a method known in the art. In one embodiment of the invention, a plurality of cylinders (disks) are stacked in a rectification column, the corrugated wire mesh sheets of the upper and lower cylinders being at an angle (or phase difference) of 0 to 90 °, preferably 5 to 85 °, more preferably 10 to 80 °, preferably 15 to 75 °, more preferably 20 to 70 °, preferably 25 to 65 °.
In the invention, each cylinder is formed by arranging the corrugated wire mesh sheets in parallel, so that the cylinders have an orientation parallel to the corrugated wire mesh sheets, and the included angle (phase difference) of the corrugated wire mesh sheets of the upper cylinder and the lower cylinder is the included angle between the orientations. According to the invention, the horizontal rotation arrangement of the regular packing cylinder is matched with the dense-sparse-dense structure to weave the density area distribution, so that the generation of wall flow is effectively prevented. Therefore, no matter an additional anti-wall flow device is added or not, the regular packing can obtain better rectification effect.
In one example of the present invention, a plurality of discs in a rectification column are stacked within the rectification column with one or more of the discs positioned proximate an inner wall of the rectification column. In one embodiment of the invention, a plurality of discs in the rectifying tower are stacked in the rectifying tower, and a wall flow preventing ring is arranged between one or more discs and the inner wall of the rectifying tower.
The anti-wall flow ring suitable for the rectifying column of the present invention is not particularly limited, and may be a conventional anti-wall flow ring known in the art, for example, the anti-wall flow ring disclosed in CN 104275144A.
FIGS. 1a and 1b are schematic views of filaments used to form a structured sheet in one example of the invention. As shown in fig. 1, the wire comprises a main wire 1 and an auxiliary wire 2 and a main wire pitch 3. Fig. 1a and 1b schematically show two types of wires with different main wire thread pitches and wire diameters.
FIGS. 2a and 2b are schematic illustrations of the arrangement of two adjacent strands of filament in a structured screen in accordance with an embodiment of the present invention. In fig. 2a, the direction of the spiral is the same for two adjacent threads, and in fig. 2b, the direction of the spiral is opposite for two adjacent threads.
In one embodiment of the invention, the main wire and the auxiliary wire of the winding silk thread are both made of 316L stainless steel, the diameters of the main wire and the auxiliary wire are respectively 0.09-0.11mm and 0.06-0.08mm, the winding mode that the main wire and the auxiliary wire are mutually wound is adopted, the pitch of the main wire is 0.14-0.18mm, and the silk screen weaving method adopts twill weaving and cis arrangement. The silk screen strip is made by cutting the silk screen, the weaving mesh number of the areas with the width of 8-12mm on the two sides of the horizontal direction is 90-120 meshes, and the weaving mesh number of the middle part of the strip is 70-85 meshes. The middle part of the silk screen strip is not provided with a hole. The corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 3-5mm, the wave distance is 6-8mm, the side length is 4-6mm, and the inclination angle between the corrugation direction and the vertical direction is 40-50 degrees. The structured packing is made by binding and fixing 10-14 sheets of the corrugated silk screen strips at the upper part and the lower part by 0.8mm metal wires, the height of each disc of packing is 35-45mm, and the outer diameter is 45-55 mm. When the packing device is installed, the upper and lower adjacent packing trays rotate by 85-95 degrees in the anticlockwise circumferential direction.
In one embodiment of the invention, the main wire and the auxiliary wire of the winding silk thread are made of 316L stainless steel, the diameters of the main wire and the auxiliary wire are 0.09-0.11mm and 0.06-0.08mm respectively, the main wire and the auxiliary wire are wound with each other, the pitch of the main wire is 0.18-0.22mm, and the silk screen weaving method adopts twill weaving and reverse arrangement. The silk screen strip is made by cutting the silk screen, the weaving mesh number of the areas with the width of 8-12mm on both sides of the horizontal direction is 90-120 meshes, and the weaving mesh number of the middle part of the strip is 60-80 meshes. The middle part of the silk screen strip is not provided with a hole. The corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 3-5mm, the wave distance is 5-8mm, the side length is 8-10mm, and the inclination angle between the corrugation direction and the vertical direction is 40-50 degrees. The structured packing is made by binding and fixing 118 sheets of the corrugated wire mesh strips at the upper, middle and lower parts by 1mm of metal wires, wherein the height of each disc of packing is 130-160mm, and the outer diameter is 350-450 mm. When the packing device is installed, the upper and lower adjacent packing discs rotate 12-18 degrees in the anticlockwise circumferential direction.
2.Rectification system
Another aspect of the invention relates to a rectification system comprising a column bottom, a rectification column of the invention in fluid communication with a heating reservoir and a plurality of product reservoirs in fluid communication with the rectification column through control valves.
Fig. 3 is a rectification system for separating chlorotrifluoroethylene thermal cracking products in one embodiment of the present invention, the rectification system comprising a column bottom 2, a rectification column 4 filled with the above-mentioned structured packing and fluidly connected to the column bottom, a condenser 3 fluidly connected to the top of the rectification column 4, a first storage tank 6 fluidly connected to a side draw outlet of the rectification column 4 via a second regulating valve 11 and a cut-off valve 18, a second storage tank 9 and a third storage tank 10 fluidly connected to a top outlet of the rectification column 4 via a first regulating valve 15, a reboiler 12 fluidly connected to the column bottom 2, and a first filter 24 fluidly connecting the column bottom 2 to a feed reservoir (not shown).
In one example of the present invention, the rectification system further comprises a tower tank liquid level meter 1 for measuring the liquid level of the tower tank, a fourth storage tank 5, a fifth storage tank 7 and a sixth storage tank 8 which are in fluid connection with the top outlet of the rectification tower 4 through a first regulating valve 15, a circulating pump 13 and a second filter 23 for circularly heating the materials in the tower tank, a regulating valve 14-a regulating valve 16, a cut-off valve 17-a cut-off valve 22, a tower top thermometer 25 and a tower top pressure gauge 26.
In one example of the invention, the first filter 24 is fluidly connected to the second regulating valve 14 via a pipe and finally fluidly connected to the column tank 2; the reboiler 12 is installed in a manner of being directly fluidly connected with the tower kettle 2 or being fluidly connected with the tower kettle 2 through a pipeline; the condenser 3 is directly arranged on the rectifying tower 4 or is in fluid connection with the rectifying tower through a pipeline; the fourth storage tank 5, the fifth storage tank 7, the 6 th storage tank 8, the second storage tank 9 and the third storage tank 10 are in fluid connection with a tower top extraction pipe of the rectifying tower 4 through a first regulating valve 15 and first to fifth cut-off valves; the first storage tank 6 is in fluid connection with a side draw-off pipe of the rectifying tower 4.
In one embodiment of the present invention, the particle-trapping capacities of the first filter 24 and the second filter 23 are sequentially increased, and the mesh number of the filter medium of the first filter 24 is 150 to 250 meshes, preferably 180 to 220 meshes; the second filter 23 has a filter medium mesh number of 250 to 350 mesh, preferably 280 to 320 mesh.
In one embodiment of the present invention, the diameter of the distillation column 4 is 50-1000mm, preferably 80-950mm, more preferably 100-900mm, preferably 150-850mm, and preferably 200-800 mm.
In one embodiment of the present invention, the material of each device of the rectification system is selected from stainless steel, nickel, monel or a combination thereof.
3.Semi-continuous rectification method of chlorotrifluoroethylene thermal cracking product
Still another aspect of the present invention relates to a semi-continuous rectification method for separating chlorotrifluoroethylene thermal cracking products, comprising: inputting the chlorotrifluoroethylene thermal cracking product into a tower kettle, and heating; continuously inputting the chlorotrifluoroethylene thermal cracking product, and continuously collecting light components and non-thermal cracking chlorotrifluoroethylene reactants from the top and the side of the tower; stopping inputting the chlorotrifluoroethylene thermal cracking product, and sequentially collecting the rest rectification products from the tower top; and (4) respectively conveying each rectification product to a corresponding product storage tank by adjusting a valve between the rectification tower and the product storage tank.
In one embodiment of the invention, the semi-continuous rectification method comprises the following steps:
i) opening a second regulating valve 14 and a third regulating valve 16 to enable the product of the thermal cracking of the chlorotrifluoroethylene to enter a tower kettle 2 through a first filter 24 and the second regulating valve 14, and closing the second regulating valve 14 after a liquid level meter 1 of the tower kettle reaches a preset value; in one embodiment of the present invention, the predetermined liquid level of the tower tank liquid level meter 1 is 20% to 100%, preferably 30% to 99%, more preferably 40% to 97%, preferably 50% to 95%, and preferably 60% to 90% of the maximum liquid level of the tower tank;
ii) the circulation pump 13 is opened to enable the materials to pass through the second filter 23 and enter the reboiler 12 for heating, and after the reading of the overhead thermometer 25 begins to rise, the opening degree of the third regulating valve 16 is adjusted to control the overhead pressure to be stable. In one embodiment of the invention, the overhead pressure is from 0.1 to 0.35MPaG, preferably from 0.12 to 0.33MPaG, more preferably from 0.15 to 0.30MPaG, preferably from 0.18 to 0.28MPaG, preferably from 0.20 to 0.25 MPaG;
iii) complete the total reflux operation with stable reading at the overhead pressure gauge 26;
iv) opening the first regulating valve 15 and the first cut-off valve 17, collecting light components from the tower top to the fourth storage tank 5, opening the fourth regulating valve 11 and the sixth cut-off valve 18, collecting the non-thermally cracked chlorotrifluoroethylene reactant from the side to the first storage tank 6, and opening the second regulating valve 14 to continuously supplement the thermally cracked chlorotrifluoroethylene product to the tower kettle 2 after the liquid level meter 1 of the tower kettle is lowered;
v) when the liquid level meter 1 of the tower bottom reaches the highest liquid level, closing the second regulating valve 14, and when the extraction of the non-thermally cracked chlorotrifluoroethylene reactant is finished, closing the fourth regulating valve 11, the first regulating valve 15, the first cut-off valve 17 and the sixth cut-off valve 18;
vi) adjusting the opening of the third adjusting valve 16, reducing the pressure at the top of the tower, controlling the pressure to be stable, and finishing the total reflux operation under the condition that the reading of the pressure gauge 26 at the top of the tower is stable; in one embodiment of the invention, the overhead pressure is from 0 to 0.2MPaG, preferably from 0.02 to 0.18MPaG, more preferably from 0.04 to 0.16MPaG, preferably from 0.06 to 0.14MPaG, preferably from 0.08 to 0.12 MPaG;
vii) opening the first adjusting valve 15 and the second cut-off valve 19, extracting the transition component 1 to the fifth storage tank 7, and closing the second cut-off valve 19 after the extraction of the transition component 1 is finished;
viii) opening the third cut-off valve 20, extracting the transition component 2 into the sixth storage tank 8, and closing the third cut-off valve 20 after the extraction of the transition component 2 is finished;
ix) opening the fourth cut-off valve 21, extracting the 1, 2-dichlorohexafluorocyclobutane product into the second storage tank 9, and closing the fourth cut-off valve 21 after the 1, 2-dichlorohexafluorocyclobutane product is extracted;
x) opening the third cut-off valve 20, extracting the transition component 3 into the sixth storage tank 8, and closing the third cut-off valve 20 after the extraction of the transition component 3 is finished;
xi) opening the fifth cut-off valve 22, extracting the 3, 4-dichlorohexafluoro-1-butene product into the third storage tank 10, and closing the fifth cut-off valve 22 after the 3, 4-dichlorohexafluoro-1-butene product is extracted;
xii) opening the third stop valve 20, extracting the transition component 4 to the sixth storage tank 8, and after the extraction of the transition component 4 is finished, closing the third stop valve 20, the first regulating valve 15 and the circulating pump 13, and draining the tower kettle waste liquid.
In one example of the present invention, the products of the thermal cracking of chlorotrifluoroethylene include, but are not limited to: chlorotrifluoroethylene, 1, 2-dichlorohexafluorocyclobutane, 3, 4-dichlorohexafluoro-1-butene, halogenated hydrocarbons having an atmospheric boiling point lower than chlorotrifluoroethylene, halogenated hydrocarbons having an atmospheric boiling point between chlorotrifluoroethylene and 1, 2-dichlorohexafluorocyclobutane, halogenated hydrocarbons having an atmospheric boiling point higher than 3, 4-dichlorohexafluoro-1-butene;
in one embodiment of the invention, the duration of the total reflux operation is from 1 hour to 24 hours;
in view of the above-mentioned deficiencies of the prior art, the present invention is primarily improved in two ways: firstly, the rectifying tower is filled with the structured packing of the invention, and secondly, a semi-continuous rectifying method is adopted.
The structured packing has strong wetting capacity, good wall flow prevention effect and high separation efficiency on substances with low viscosity, can greatly reduce the required height of the packing, but reduces the flux, so that the treatment time is increased. In order to make up for the problem of time increase brought by improving the separation efficiency, the method in the industry is to increase the diameter of a rectifying tower, but the investment cost is undoubtedly improved. Through the mutual matching of the packing and the semi-continuous rectification method, the effects of improving the separation efficiency, reducing the height of the packing and not increasing the processing time of unit raw materials are achieved.
The two improved methods can be used for separating and obtaining two products of 1, 2-dichlorohexafluorocyclobutane and 3, 4-dichlorohexafluoro-1-butene, recovering the non-thermal cracked chlorotrifluoroethylene reactant, and have the advantages of high separation efficiency, high product purity, low investment cost, flexible operation mode and industrialization.
In one embodiment of the present invention, the indexes of the extraction completion of each stage in the semi-continuous rectification method of the present invention are: the extraction of the non-thermal cracked trifluorochloroethylene reactant is specifically completed by reducing the purity of the trifluorochloroethylene in the extraction to 96%, the extraction of the transition component 1 is specifically completed by reducing the purity of 1, 2-dichlorohexafluorocyclobutane in the extraction of the tower top to 85%, the extraction of the transition component 2 is completed by reducing the purity of 1, 2-dichlorohexafluorocyclobutane in the extraction of the tower top to 99.99%, the extraction of the 1, 2-dichlorohexafluorocyclobutane product in the extraction of the tower top is specifically completed by reducing the purity of 1, 2-dichlorohexafluorocyclobutane in the extraction of the tower top to 99.99%, the extraction of the transition component 3 is completed by specifically reducing the purity of 3, 4-dichlorohexafluoro-1-butene in the extraction of the tower top to 99.95%, the extraction of the 3, 4-dichlorohexafluoro-1-butene product in the extraction of the tower top is specifically completed by reducing the purity of 3, 4-dichlorohexafluoro-1-butene in the extraction of the tower top to 99.95%, the extraction of the transition component 4 is completed, in particular, the purity of 3, 4-dichlorohexafluoro-1-butene extracted from the tower top is reduced to 85 percent.
According to the common rectification method, rectification packing commonly used in the industry is matched, and the packing height of at least 40 meters is required in the industry to meet the separation requirement. The rectifying device and the method are adopted to separate the products of the thermal cracking of the chlorotrifluoroethylene, the height of the filler can be reduced to be less than 20 meters, the purity of the obtained 1, 2-dichlorohexafluorocyclobutane product can reach 99.99 percent and above, the purity of the 3, 4-dichlorohexafluoro-1-butene product can reach 99.95 percent and above, and the purity of the reactants of the chlorotrifluoroethylene without thermal cracking can reach 96 percent and above.
When the content of the chlorotrifluoroethylene in the chlorotrifluoroethylene thermal cracking product is less than 10%, the distillation device and the batch distillation operation method can be used for separation. Instead of batch rectification, the second regulating valve 14 should be kept closed in step iv) of the process according to the invention.
The invention has the advantages that:
i) the packing height is greatly reduced by adopting a regular packing;
ii) a semi-continuous rectification method is adopted, so that the single batch processing capacity of a batch device is exerted to the maximum extent;
iii) the regular packing and the semi-continuous rectification method are combined with each other, and the processing time of unit raw material can be maintained or even reduced under the condition of reducing the height of the packing and achieving the purity of the product;
iv) the composition of the thermal cracking products of the chlorotrifluoroethylene is not limited, and a semi-continuous rectification method or a batch rectification method can be flexibly selected according to actual conditions;
v) the invention can be directly applied to industrialized production
Examples
The present invention is further described in the following description of the specific embodiments, which is not intended to limit the invention, but various modifications and improvements can be made by those skilled in the art according to the basic idea of the invention, within the scope of the invention, as long as they do not depart from the basic idea of the invention.
Structured packing
Structured packing A
The main wire and the auxiliary wire of the winding wire are made of 316L stainless steel, the diameters of the main wire and the auxiliary wire are respectively 0.1mm and 0.08mm, the winding mode that the main wire and the auxiliary wire are mutually wound is adopted, the thread pitch of the main wire is 0.2mm, and the silk screen weaving method adopts twill weaving and cis arrangement. The screen strips are made by cutting the screen, the weaving mesh number of the areas with the width of 10mm on both sides in the horizontal direction is 100 meshes, and the weaving mesh number of the middle part of the strip is 80 meshes. The middle part of the silk screen strip is not provided with a hole.
The corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 4.2mm, the wave distance is 7.3mm, the side length is 5.6mm, and the inclination angle between the corrugated direction and the vertical direction is 45 degrees.
The structured packing is made by binding and fixing 12 sheets of the corrugated silk screen strips by 0.8mm metal wires at the upper part and the lower part, the height of each disc of packing is 40mm, and the outer diameter is 50.4 mm. When the packing device is installed, the upper and lower adjacent packing trays rotate 90 degrees in the anticlockwise circumferential direction.
Structured packing B
The main wire and the auxiliary wire of the winding wire are made of 316L stainless steel, the diameters of the main wire and the auxiliary wire are respectively 0.1mm and 0.08mm, the winding mode that the main wire and the auxiliary wire are mutually wound is adopted, the thread pitch of the main wire is 0.2mm, and the silk screen weaving method adopts twill weaving and reverse arrangement. The screen strips are made by cutting the screen, the weaving mesh number of the areas with the width of 10mm on both sides in the horizontal direction is 100 meshes, and the weaving mesh number of the middle part of the strip is 80 meshes. The middle part of the silk screen strip is not provided with a hole.
The corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 3.4mm, the wave distance is 6.8mm, the side length is 9.4mm, and the inclination angle between the corrugated direction and the vertical direction is 45 degrees.
The structured packing is made by binding and fixing 118 sheets of the corrugated wire mesh strips at three positions of the upper part, the middle part and the lower part of a 1mm metal wire, the height of each disc of packing is 150mm, and the outer diameter is 401.2 mm. When the packing device is installed, the upper and lower adjacent packing discs rotate 15 degrees in the anticlockwise circumferential direction.
Structured packing C (comparative example)
The 80-mesh silk screen is woven by adopting a monofilament twill made of 316L stainless steel with the silk diameter of 0.1mm without holes. The silk screen strip is made by cutting the silk screen, the corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 3.4mm, the wave distance is 6.8mm, the side length is 9.4mm, and the inclination angle between the corrugated direction and the vertical direction is 45 degrees. The regular packing is made by 114 sheets of the corrugated silk screen strip sheets fixed at the upper and lower parts by 20mm wide hoops, and the outer side of the upper hoops is provided with wall flow preventing rings. The height of each disk of packing is 150mm, and the outer diameter of the packing excluding the wall flow prevention ring is 387.6 mm. When the packing device is installed, the upper and lower adjacent packing discs rotate 15 degrees in the anticlockwise circumferential direction.
Structured packing D
The main wire and the auxiliary wire of the winding wire are made of 316L stainless steel, the diameters of the main wire and the auxiliary wire are respectively 0.1mm and 0.08mm, the winding mode that the main wire and the auxiliary wire are mutually wound is adopted, the thread pitch of the main wire is 0.2mm, and the silk screen weaving method adopts twill weaving and reverse arrangement. The screen strips are made by cutting the screen, the weaving mesh number of the areas with the width of 10mm on both sides in the horizontal direction is 100 meshes, and the weaving mesh number of the middle part of the strip is 80 meshes. The middle part of the silk screen strip is not provided with a hole.
The corrugated silk screen strip is made by punching corrugations from the silk screen strip, the peak height of the corrugations is 3.4mm, the wave distance is 6.8mm, the side length is 9.4mm, and the inclination angle between the corrugated direction and the vertical direction is 45 degrees.
The structured packing is made by 115 sheets of the corrugated silk screen strip sheets fixed at the upper and lower parts by 20mm wide hoops, and the outer side of the upper hoops is provided with wall flow preventing rings. The height of each disk of packing is 150mm, and the outer diameter of the packing excluding the wall flow prevention ring is 391 mm. When the packing device is installed, the upper and lower adjacent packing discs rotate 15 degrees in the anticlockwise circumferential direction.
Example 1
The semi-continuous rectification method is carried out by adopting the system shown in FIG. 3, the processed raw material is R-1, and the highest liquid level of the tower bottom 2 corresponds to 10 kg of feeding amount. The diameter of the rectifying tower 4 is 50mm, the height of the packing is 12m, and the regular packing A is filled.
The thermal cracking product of chlorotrifluoroethylene is added to the column bottom 2, and when the liquid level meter 1 of the column bottom reaches 80% of the maximum liquid level, the feeding is stopped, and 8 kg of the material is fed in total. The pressure at the top of the column was controlled to 0.3MPaG after the start of heating, light components were withdrawn from the top of the column after the total reflux for 4 hours, and the thermally uncracked chlorotrifluoroethylene reactant was withdrawn from the side at 0.04 kg/hr. When the liquid level meter 1 in the column bottom was lowered to 78% of the maximum liquid level, the thermal cracking product of chlorotrifluoroethylene was continuously fed to the column bottom at a rate of 0.2 kg/hr over a period of 5 hours. 12 hours after the feeding is finished, the pressure at the top of the tower is reduced to 0.15MPaG and the full reflux is carried out for 4 hours, and fractions at different stages are sequentially extracted from the top of the tower to corresponding storage tanks. The reflux ratios corresponding to steps 4, 7, 8, 9, 10, 11, and 12 are 50:1, 20:1, 25:1, 15:1, and 8:1, respectively.
The total treatment time was 146 hours, the throughput was 11 kg/batch, the unit raw material treatment time was about 13.3 hours/kg, and the product number was P-1.
Example 2
By adopting the semi-continuous rectification method shown in FIG. 3, the processed raw material is R-2, and the corresponding feeding amount of the highest liquid level of the tower bottom 2 is 3.9 tons. The diameter of the rectifying tower 4 is 400mm, the height of the packing is 18m, and the regular packing B is filled.
Adding the chlorotrifluoroethylene thermal cracking product into the tower kettle 2, and stopping feeding when the liquid level meter 1 of the tower kettle reaches 90% of the maximum liquid level, wherein the total amount of the feeding is 3.5 tons. The pressure at the top of the column was controlled to 0.35MPaG after the start of heating, and light components were withdrawn from the top of the column after 8 hours of total reflux, and 50 kg/hr of the thermally uncracked chlorotrifluoroethylene reactant was withdrawn from the side. When the liquid level meter 1 in the column bottom was lowered to 81% of the maximum liquid level, the thermal cracking product of chlorotrifluoroethylene was continuously fed to the column bottom at a rate of 90 kg/hr over 10 hours. And 0.6 hour after the feeding is finished, reducing the pressure at the top of the tower to 0.01MPaG, carrying out total reflux for 12 hours, and sequentially extracting fractions at different stages from the top of the tower to corresponding storage tanks. The reflux ratios corresponding to steps 4, 7, 8, 9, 10, 11 and 12 are 30:1, 15:1, 20:1, 30:1, 40:1, 20:1 and 10:1, respectively.
The total treatment time was 228 hours, the throughput was 4.4 tons/batch, the unit raw material treatment time was about 51.8 hours/ton, and the product number was P-2.
Comparative example 1
The batch rectification method is adopted, the treated raw material is R-2, and the corresponding feeding amount of the highest liquid level of the tower kettle 2 is 3.9 tons. The diameter of the rectifying tower 4 is 400mm, the height of the packing is 45m, and the regular packing C is filled.
3.9 tons of chlorotrifluoroethylene thermal cracking product are added into the tower kettle 2. The pressure at the top of the column was controlled to 0.35MPaG after the start of heating, and light components were withdrawn from the top of the column after 8 hours of total reflux, and 50 kg/hr of the thermally uncracked chlorotrifluoroethylene reactant was withdrawn from the side. After completion of the withdrawal, the overhead pressure was reduced to 0.01MPaG and total reflux was carried out for 12 hours, as in example 2.
The total treatment time was 202.8 hours, the throughput was 3.9 tons/batch, the unit raw material treatment time was about 52.0 hours/ton, and the product number was P-3.
Comparative example 2
The batch rectification method is adopted, the treated raw material is R-2, and the corresponding feeding amount of the highest liquid level of the tower kettle 2 is 3.9 tons. The diameter of the rectifying tower 4 is 400mm, the height of the packing is 18m, and the regular packing B is filled.
3.9 tons of chlorotrifluoroethylene thermal cracking product are added into the tower kettle 2. The pressure at the top of the column was controlled to 0.35MPaG after the start of heating, and light components were withdrawn from the top of the column after 8 hours of total reflux, and 50 kg/hr of the thermally uncracked chlorotrifluoroethylene reactant was withdrawn from the side. After completion of the withdrawal, the overhead pressure was reduced to 0.01MPaG and total reflux was carried out for 12 hours, as in example 2.
The total treatment time was 239.5 hours, the throughput was 3.5 tons/batch, the unit treatment time per raw material was about 61.4 hours/ton, and the product number was P-4.
Comparative example 3
The semi-continuous rectification method is adopted, the processed raw material is R-2, and the corresponding feeding amount of the highest liquid level of the tower bottom 2 is 3.9 tons. The diameter of the rectifying tower 4 is 400mm, the height of the packing is 18m, and the regular packing C is filled. Otherwise, the product number is P-5 as in example 2.
Example 3
The procedure of example 2 was repeated, but with structured packing D being loaded with product number P-6.
Table 1 raw material table
Figure BDA0002541022220000161
TABLE 2 product table
Figure BDA0002541022220000162
As can be seen from the experimental results of Table 2, the rectification efficiencies of example 2 (product P-2, using a combination of the structured packing of the invention and the semi-continuous process) and comparative example 1 (product P-3, using structured packing formed from monofilaments and the batch process) were substantially the same (51.8 hours per kg of the invention and 52 hours for the comparative example) while treating the same raw material R-2, but the packing height was greatly reduced (18 meters for the invention and 45 meters for the comparative example) and the product purity was improved. The product purity of example 2 (product P-2, using a combination of structured packing according to the invention and a semi-continuous process) was essentially the same as that of comparative example 2 (product P-4, using a combination of structured packing according to the invention and a batch process), but the rectification efficiency was improved (the treatment time per kg of starting material according to the invention was 51.8 hours, while the comparative example required 61.4 hours). In addition, the packing box is also provided with the anti-wall flow ring, and when the regular packing is formed by matching the winding wire with the wire mesh with the density of dense-sparse-dense weaving instead of the conventional regular packing, the rectification efficiency is higher.

Claims (7)

1. A rectification system comprises a tower kettle, a rectification tower and a plurality of product storage tanks, wherein the rectification tower is in fluid connection with the tower kettle, and the product storage tanks are in fluid connection with the rectification tower through control valves; the rectification column comprises structured packing within the rectification column;
the structured packing is formed by arranging a plurality of corrugated wire mesh sheets vertically arranged with a horizontal plane, the adjacent corrugated wire mesh sheets are arranged in parallel, each wire mesh sheet is formed by weaving spiral winding type bifilar wires, and the weaving density of the spiral winding type bifilar wires is increased along the direction from the center to the periphery of the wire mesh sheet;
the structured packing is disc-shaped structured packing, the corrugated wire mesh sheets have sheets with the same length but different widths, and a plurality of the corrugated wire mesh sheets are vertically placed in such a way that the corrugated wire mesh sheets are arranged to form a disc, and the height of the disc is equal to the length of the corrugated wire mesh sheets;
the disc section of the disc-shaped structured packing is in the circumferential direction along the circle center, the vertical corrugated wire mesh sheets have the same dense weaving structure in the outer layer circular ring area, and the central circle part area has the same sparse weaving structure; the mesh number of the dense weaving structure is 10-50 meshes larger than that of the sparse weaving structure in terms of mesh number.
2. Rectification system according to claim 1, characterized in that the radius of the central circle in the radial direction amounts to 0.7-0.9 of the radius of the circular disc.
3. The rectification system of claim 1, wherein the disk-shaped structured packing is stacked such that the corrugated wire mesh sheets of the upper and lower structured packing disks are in a phase difference of 0 to 90 °.
4. The rectification system of claim 1 wherein at least one tray of the disc-shaped structured packing is free of wall flow prevention devices.
5. The rectifying system according to claim 1, wherein when the spirally wound type bifilar filaments are braided, the spirally winding directions of two adjacent filaments are the same, the spirally winding directions of two adjacent filaments are different or the spirally winding directions of two adjacent filaments are randomly selected.
6. A semi-continuous rectification method for separating a chlorotrifluoroethylene thermal cracking product using the rectification system of any one of claims 1-5, comprising:
inputting the chlorotrifluoroethylene thermal cracking product into a tower kettle, and heating;
continuously inputting the chlorotrifluoroethylene thermal cracking product, and continuously collecting light components and non-thermal cracking chlorotrifluoroethylene reactants from the top and the side of the tower;
stopping inputting the chlorotrifluoroethylene thermal cracking product, and sequentially collecting the rest rectification products from the tower top;
and (4) respectively conveying each rectification product to a corresponding product storage tank by adjusting a valve between the rectification tower and the product storage tank.
7. Use of a rectification system according to any one of claims 1 to 5 for separating chlorotrifluoroethylene thermal cracking products.
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