CN114522637A - Method and device for separating vinyl acetate by heat pump extractive distillation - Google Patents

Method and device for separating vinyl acetate by heat pump extractive distillation Download PDF

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CN114522637A
CN114522637A CN202210009954.3A CN202210009954A CN114522637A CN 114522637 A CN114522637 A CN 114522637A CN 202210009954 A CN202210009954 A CN 202210009954A CN 114522637 A CN114522637 A CN 114522637A
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tower
vinyl acetate
heat
gas
heat exchange
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范小强
王靖岱
任聪静
尤潇楠
杨遥
黄正梁
阳永荣
蒋斌波
陈言溪
吴傲
从文杰
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Zhejiang University ZJU
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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
    • B01J19/0006—Controlling or regulating processes
    • 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
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
    • B01D3/40—Extractive distillation
    • 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
    • B01D3/42—Regulation; Control
    • B01D3/4211—Regulation; Control of columns
    • B01D3/4216—Head stream
    • 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
    • B01J19/30—Loose or shaped packing elements, e.g. Raschig rings or Berl saddles, for pouring into the apparatus for mass or heat transfer
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/48—Separation; Purification; Stabilisation; Use of additives
    • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
    • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/48—Separation; Purification; Stabilisation; Use of additives
    • C07C67/58—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/02—Recovery or working-up of waste materials of solvents, plasticisers or unreacted monomers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency

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Abstract

The invention discloses a method and a device for separating vinyl acetate by heat pump extractive distillation, which are used for feeding materials rich in vinyl acetate into a refining system consisting of a light component removing tower and a heavy component removing tower for rectification separation. At least one part of the gas at the top of at least one of the light component removing tower and the heavy component removing tower is led out, the gas at the top of the tower exchanges heat with a heat exchange medium, the gas is condensed and refluxed by an auxiliary condenser at the top of the tower, and the heat exchange medium is compressed to supply heat to a tower kettle of the rectifying tower and then is recycled. The reboiling gas in the tower kettle flows through an auxiliary heat exchanger in the tower kettle before flowing back into the tower, and the liquid in the tower top flows through an auxiliary heat exchanger in the tower top before flowing back into the tower. The process is simple, can effectively reduce the consumption of thermal public works, and can not bring the pollution of other substances.

Description

Method and device for separating vinyl acetate by heat pump extractive distillation
Technical Field
The invention relates to the technical field of chemical product purification and energy conservation, in particular to a method for separating vinyl acetate by heat pump extractive distillation, which is used for the distillation separation of vinyl acetate, water, acetic acid, solvent oil, lubricating oil, acetaldehyde, ethyl acetate and methyl acetate.
Background
Vinyl acetate (VAc) is an important organic chemical raw material, is a colorless and transparent combustible liquid with strong odor at normal temperature and normal pressure, and is one of the fifty basic organic chemical raw materials with the largest world yield. Vinyl acetate is mainly used for producing derivatives such as polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl acetate copolymer emulsion or copolymer resin, vinyl chloride-vinyl acetate copolymer, acetal resin and the like through self polymerization or copolymerization with other monomers, and the derivatives have wide application and can be used for adhesives, sizing agents for paper or fabrics, coatings, inks, leather processing, fiber processing, emulsifiers, water-soluble films, soil conditioners and the like.
In the device for preparing the ethylene-vinyl acetate copolymer by the high pressure method, vinyl acetate is used as a comonomer and injected into a system, wherein only 15 to 35 percent of the vinyl acetate reacts and is converted into a product, and the rest part is recovered after system separation. The recovered vinyl acetate contains solvent oil and lubricating oil which enter the system, and also contains some byproducts such as acetic acid, acetaldehyde, ethyl acetate and methyl acetate. In order to recycle vinyl acetate monomer, the recovered vinyl acetate needs to be further refined, and the recovered vinyl acetate is injected into the system to participate in the reaction after reaching the corresponding index.
As can be known from thermal integration analysis, the separation and refinement rectifying tower has a large thermal platform at the top and the bottom, and the temperature difference is small, so that a heat pump technology is expected to be adopted. Because the separated substance vinyl acetate is easy to self-polymerize, the direct compression type heat pump rectification of the gas at the top of the tower is not used, and the closed type heat pump rectification is adopted.
Disclosure of Invention
The invention aims to solve the problem of high energy consumption in the prior art of recovering and separating vinyl acetate, and provides a method and a device for separating vinyl acetate by heat pump extractive distillation.
In order to achieve the purpose, the invention provides a method for separating vinyl acetate by heat pump extractive distillation, which comprises the following steps:
carrying out polymerization reaction on acetic acid and vinyl acetate in a high-pressure reactor, leading out an ethylene-vinyl acetate polymer, unreacted ethylene, vinyl acetate and a small amount of by-products from the reactor, and feeding the ethylene-vinyl acetate polymer, the unreacted ethylene, the vinyl acetate and a small amount of by-products into a high-pressure separator;
the gas phase discharged material led out by the high-pressure separator is cooled and dewaxed by a high-pressure circulation loop and then enters a secondary machine for recycling; leading out the liquid phase discharge to enter a low-pressure separator;
cooling and dewaxing the gas-phase material led out by the low-pressure separator through a low-pressure circulation loop, then feeding the gas-phase material into a first compressor, changing partial material into liquid phase after passing through the first compressor, recovering a material A rich in vinyl acetate through a vinyl acetate separator to a vinyl acetate recovery tank, then introducing the material A into a refining system consisting of a light component removal tower and a heavy component removal tower, and separating to obtain a high-purity vinyl acetate product (separating out one or more of water, acetic acid, ethyl acetate, methyl acetate, solvent oil and acetaldehyde);
at least one part of the overhead gas of at least one of the light component removal tower and the heavy component removal tower is led out, the overhead gas is cooled by an auxiliary heat exchanger at the top of the tower after exchanging heat with a heat exchange medium, one part is extracted as the waste liquid at the top of the tower, and the other part flows back to the tower; the heat exchange medium exchanges heat with the tower top gas and then is sent to a heat pump rectification compressor for compression, and then heat is supplied to a tower kettle of the refining system firstly and then is recycled as the heat exchange medium; one part of the tower bottom liquid is taken out as the tower bottom waste liquid, and the other part of the tower bottom liquid exchanges heat with the heat exchange medium and then flows back to the tower bottom through an auxiliary tower bottom heat exchanger. And the tower kettle auxiliary heat exchanger and the tower top auxiliary heat exchanger are used for controlling the reflux temperature.
When the material A rich in the vinyl acetate is introduced into a refining system, solvent oil can be added or not added; the solvent oil comprises one or more of n-hexane, cyclohexane, n-heptane, 6# solvent oil, 120# solvent oil, 200# solvent oil, petroleum ether, benzene, toluene, xylene, n-dodecane, isododecane, naphtha and a combination/mixture thereof. The heat exchange medium comprises R600, isobutane, R290, R601a, R345ca, R245fa, R134a and CF3I. One or more of hot water, air, oil, steam, and combinations/mixtures thereof.
The invention also provides a device for separating vinyl acetate by heat pump extractive distillation, which comprises:
a high-pressure separator: the device is used for carrying out gas-liquid separation on a polymer, an unreacted material and a byproduct led out from the high-pressure reactor, wherein the led-out liquid phase discharge enters a low-pressure separator, and the led-out gas phase discharge enters a secondary machine for recycling after being cooled and dewaxed by a high-pressure circulation loop;
the low-pressure separator is used for carrying out gas-liquid separation on the liquid-phase discharged material of the high-pressure separator, wherein the gas-phase discharged material is cooled by the low-pressure circulating loop to remove wax and is sent to the first compressor, and the liquid-phase discharged material is sent to extrusion granulation;
the first compressor comprises a supercharger and a primary machine which are connected in sequence and is used for compressing the gas-phase discharge material led out by the low-pressure separator;
the vinyl acetate separating tanks are used for carrying out gas-liquid phase separation on compressed materials at all stages in the first compressor; wherein, the gas phase enters a next-stage compression unit in a first compressor, and the liquid phase enters a vinyl acetate recovery tank;
a refining system, the inlet of which is connected with the liquid phase outlet of the vinyl acetate recovery tank; the refining system comprises a light component removing tower and a heavy component removing tower and is used for rectifying and separating vinyl acetate;
the tower top gas-heat supply network backwater heat exchanger is used for exchanging heat between the tower top gas of the rectifying tower and a heat exchange medium;
the inlet of the heat pump rectification compressor is connected with the tower top gas-heat network backwater heat exchanger, and the outlet of the heat pump rectification compressor is connected with the heat pump rectification heat exchanger and used for compressing a heat exchange medium;
the heat pump rectification heat exchanger is used for exchanging heat between a heat exchange medium and the tower bottom liquid of the rectification tower;
the inlet of the tower top auxiliary heat exchanger is connected with the tower top gas-heat network backwater heat exchanger and is used for controlling the temperature and the gas phase fraction of the rectifying tower top backwater liquid;
and the inlet of the tower kettle auxiliary heat exchanger is connected with the heat pump rectification heat exchanger and is used for controlling the temperature and the gas phase fraction of reboiled gas in the tower kettle of the rectification tower. The refining system can remove light components and heavy components at first, and can also remove heavy components and light components at first, preferably, the refining system removes light components and heavy components at first; the light component removing tower and the heavy component removing tower are plate towers or packed towers, and preferably, the light component removing tower and the heavy component removing tower are packed towers.
Through the technical scheme, the invention has the following advantages:
(1) at least one part of the overhead gas of at least one of the light component removing tower and the heavy component removing tower is led out, and the overhead gas exchanges heat with a heat exchange medium and is condensed and refluxed by an overhead auxiliary condenser. The heat exchange medium is compressed to supply heat to the tower kettle of the rectifying tower and then is recycled. The process is simple, can effectively reduce the consumption of thermal public works, and can not bring the pollution of other substances.
(2) Under extreme working conditions, solvent oil is optionally properly added into the recovered vinyl acetate solution to facilitate vinyl acetate refining, so that the content of heavy components in a final product can be effectively reduced. Heavy components include, but are not limited to, lubricating oil and acetic acid.
(3) The heat and material distribution of the whole system is adjusted by adding the tower top auxiliary heat exchanger and the tower kettle auxiliary heat exchanger, so that the system can still normally and stably operate when the feeding of the system fluctuates.
Drawings
The invention is described in detail below with reference to the accompanying drawings and specific embodiments:
FIG. 1 is a schematic diagram of the recycling of vinyl acetate in the process flow for preparing ethylene-vinyl acetate copolymer based on the high pressure tubular process of the present invention;
FIG. 2 is a schematic diagram of the recycling of vinyl acetate in the process flow of the invention for preparing ethylene-vinyl acetate copolymer based on the autoclave process;
FIG. 3 is a schematic diagram of the heat supply from the top gas of the heavy component removing column to the bottom of the heavy component removing column by coupling the rectification section of the present invention.
FIG. 4 is a schematic diagram of the heat supply from the top gas of the heavy component removing column to the bottom of the light component removing column in the coupling manner in the rectification section of the present invention.
FIG. 5 is a schematic diagram of the rectification section of the present invention coupling the use of all overhead gases of the light component removal column to supply heat to the heavy component removal column bottom.
FIG. 6 is a schematic diagram of the rectification section of the present invention coupling and utilizing all overhead gases of the light component removal column to supply heat to the bottom of the light component removal column.
Wherein, 1-a supercharger, 2-a primary machine, 3-a secondary machine, 4-a preheater, 5-a cooler A, 6-a cooler B, 7-a tubular reactor, 8-a pulse valve, 9-a cooler C, 10-a high pressure separator, 11-a low pressure separator, 12-a low circulation heat exchanger, 13-a high circulation heat exchanger, 14-a vinyl acetate recovery tank, 15-1 to 15-6-a vinyl acetate separation tank, 16-a kettle type reactor, 17-a light component removal tower, 18-a light component removal tower top part condenser, 19-a light component removal tower top part separation tank, 20-a light component removal tower top part reflux tank, 21-a light component removal tower top reflux pump, 22-a light component removal tower kettle reboiler, 23-a feeding pump, 24-heavy component removal tower, 25-overhead gas-heat network backwater heat exchanger, 26-overhead auxiliary heat exchanger, 27-heavy component removal tower overhead reflux tank, 28-vinyl acetate tank, 29-heavy component removal tower overhead reflux pump, 30-heat pump rectification compressor, 31-heat pump rectification heat exchanger, 32-tower kettle auxiliary heat exchanger, 33-heat pump rectification reflux tank, 34-throttle valve, 35-waste vinyl acetate tank A, 36-waste vinyl acetate tank B, 37-heavy component removal tower kettle reboiler and 38-heavy component removal tower overhead condenser.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a method for separating vinyl acetate by heat pump extractive distillation, wherein the preparation method comprises the following steps:
(1) as shown in fig. 1 and fig. 2, based on the high pressure method ethylene-vinyl acetate copolymer process, ethylene and vinyl acetate are subjected to radical polymerization in a high pressure reactor (a tubular reactor 7 or a tank reactor 16), polymer and unreacted materials are led out from the high pressure reactor (the tubular reactor 7 or the tank reactor 16) and enter a high pressure separator 10, and the gas phase discharge of the high pressure separator 10 is cooled by a high circulation heat exchanger 13 and then sent to a secondary machine 3; the liquid phase discharge, which carries a portion of the ethylene, vinyl acetate molten ethylene-vinyl acetate copolymer, enters a low pressure separator 11. And (3) cooling and dewaxing a gas-phase discharge material led out from the low-pressure separator 11 through a low-pressure circulation loop, then feeding the gas-phase discharge material into a first compressor (the first compressor comprises a supercharger 1 and a primary machine 2), converting part of the material into a liquid phase, recovering the liquid phase through vinyl acetate separation tanks 15-1-15-6 to obtain a material A rich in vinyl acetate, and feeding the material A to a recovered vinyl acetate recovery tank 14. Introducing the material A into a refining system (the refining system comprises a light component removing tower 17 and a heavy component removing tower 24, and can remove light components and then heavy components or remove heavy components and then light components), and separating one or more of water, acetic acid, ethyl acetate, methyl acetate, solvent oil and acetaldehyde, so as to obtain a high-purity vinyl acetate product. Alternatively, feed A may be mixed with solvent oil and introduced into the refining system.
(2) As shown in fig. 3 to 6, at least a part of the overhead gas of at least one of the light component removal column 17 and the heavy component removal column 24 is led out, the overhead gas exchanges heat with a heat exchange medium, and is cooled by the column top auxiliary heat exchanger 26, a part of the overhead gas is extracted as the column top waste liquid, and the other part of the overhead gas is refluxed into the column, and as shown in fig. 5 and 6, if the overhead gas is extracted from the light component removal column 17, a small amount of non-condensable gas is generated at the column top and needs to be extracted to a flare. The heat exchange medium is subjected to heat exchange, sent to the heat pump rectification compressor 30 to be compressed, and then firstly supplies heat to the tower kettle and then serves as the heat exchange medium for recycling.
(3) The reboiled gas in the tower kettle flows back to the tower kettle and passes through an auxiliary tower kettle heat exchanger 32, the liquid in the tower top flows back to the tower top and passes through an auxiliary tower top heat exchanger 26, and the two auxiliary tower top heat exchangers are all used for controlling the reflux temperature.
According to the invention, after the tower top gas exchanges heat with the heat exchange medium, the heat exchange medium is sent to the heat pump rectification compressor 30 to be compressed, and heat is supplied to the tower kettle after compression, wherein the tower top gas can come from the light component removing tower 17 or the heavy component removing tower 24, and the tower kettle can be a light component removing tower kettle or a heavy component removing tower kettle. Preferably, the overhead vapor from the heavies removal column 24 provides heat to the bottoms of the lights removal column.
According to the invention, at least a part of the at least one rectification column overhead gas, preferably the entire column overhead gas, is withdrawn for heat exchange with a heat exchange medium in order to utilize the latent heat of vaporization of the overhead vapor as much as possible.
According to the invention, the light component removing tower 17 and the heavy component removing tower 24 are plate towers or packed towers, and preferably the packed towers are used. On one hand, the packed tower has high efficiency and lower cost, and on the other hand, the packed tower is convenient to clean.
According to the present invention, the refining system includes, but is not limited to, double column rectification, preferably double column rectification. The rectifying towers are connected in a mode of connecting the double towers in series, and the refining system can remove light components firstly and then heavy components, can also remove heavy components firstly and then light components, and preferably removes light components firstly and then heavy components secondly.
According to the invention, the number of theoretical plates of the light component removing tower 17 is 4-35, preferably 8-20. The reflux ratio is 1 to 8, preferably 2 to 6. The operation pressure is 1-3 bar absolute pressure, preferably 1-2 bar absolute pressure, and more preferably 1-1.5 bar absolute pressure. The temperature of a condenser at the top part of the light component removal tower is 60-85 ℃, preferably 70-85 ℃, and more preferably 75-80 ℃. In the present invention, the pressure in the light ends removal column 17 should not be too high in order to suppress the self-polymerization of vinyl acetate.
According to the invention, the number of theoretical plates of the heavy component removing tower 24 is 3-50, preferably 10-30. The reflux ratio is 0.03-2. The operation pressure is 1-3 bar absolute pressure, preferably 1-2 bar absolute pressure, and more preferably 1-1.5 bar absolute pressure. The temperature of the tower kettle is 90-130 ℃, preferably 90-120 ℃, and more preferably 100-120 ℃. In the invention, the temperature of the tower kettle is not too low to ensure the recovery rate of the vinyl acetate, and is not too high to ensure the effect of removing heavy components.
According to the invention, the outlet temperatures of the condenser 18 (shown in figures 3 and 4) and the auxiliary heat exchanger 26 (shown in figures 5 and 6) at the top of the light component removing tower are not too low, so that the light component removing effect is up to the standard and the recovery rate of vinyl acetate is considered. The outlet temperature is 60-85 ℃, preferably 70-85 ℃, and more preferably 75-80 ℃.
According to the invention, the operation temperature of the inlet of the heat pump rectification compressor 30 is 50-85 ℃; the operation compression ratio of the heat pump rectification compressor 30 is 1-5; the operation temperature of the outlet of the heat pump rectifying compressor is 100-150 ℃. In the present invention, in order to ensure heat supply to the reboiler and to ensure economy in the production process, the outlet pressure of the heat pump distillation compressor 30 should not be too low.
According to the invention, the outlet temperature of the tower top auxiliary heat exchanger 26 is 60-85 ℃, preferably 70-85 ℃, and more preferably 75-80 ℃. The outlet temperature of the auxiliary heat exchanger 32 of the tower kettle is 90-130 ℃, preferably 90-120 ℃, and more preferably 100-120 ℃. The tower top auxiliary heat exchanger 26 and the tower bottom auxiliary heat exchanger 32 are mainly used for adjusting the heat and material distribution of the whole system and ensuring that the system can still normally and stably operate when the feeding of the system fluctuates.
According to the invention, the mass fraction of the vinyl acetate in the top of the heavy component removal tower 24 is more than or equal to 98 percent, preferably more than or equal to 99 percent, so as to ensure that the recycled vinyl acetate can be used for copolymerization with ethylene. The refined vinyl acetate should ensure that: the mass fraction of water is less than or equal to 500ppm, preferably less than or equal to 200 ppm; the mass fraction of acetic acid is less than or equal to 100 ppm.
According to the present invention, optionally, solvent oil is added to the recovered vinyl acetate solution to facilitate vinyl acetate refining. The solvent oil includes, but is not limited to, one or more of n-hexane, cyclohexane, n-heptane, # 6 solvent oil, # 120 solvent oil, # 200 solvent oil, petroleum ether, benzene, toluene, xylene, n-dodecane, isododecane, naphtha, and combinations/mixtures thereof.
According to the invention, the heat exchange medium comprises but is not limited to R600, isobutane, R290, R601a, R345ca, R245fa, R134a, CF3I. Hot water, air, oil and combinations/mixtures thereof.
Example 1
This example is intended to illustrate the recovery of vinyl acetate by the process of the present invention.
This example is based on a process for preparing ethylene-vinyl acetate copolymers by the high-pressure tubular process. As shown in FIG. 3, the present example employs the removal of light components first followed by the removal of heavy components for the purpose of recycling vinyl acetate.
As shown in fig. 3, the vinyl acetate recovery tank 14 of this embodiment is connected to the light component removal column 17, the heavy component removal column 24, the vinyl acetate tank 28, and the secondary machine 3 in this order through pipes to form a circulating vinyl acetate system. In the circulating vinyl acetate system, the waste gas at the top of the light component removing tower 17 is discharged to a torch, and the waste liquid is discharged to a waste vinyl acetate tank A35; the bottoms are discharged to the heavies removal column 24. The tower top liquid of the heavy component removing tower 24 is a standard vinyl acetate monomer, is discharged to a vinyl acetate tank 28, and then is sent to a secondary machine 3 for recycling; the bottoms are discharged to waste vinyl acetate tank B36.
As shown in fig. 3, in this embodiment, after all the overhead gas in the heavy component removal column 24 exchanges heat with the heat exchange medium, it is cooled by the overhead auxiliary heat exchanger 26, and a part of the liquid phase is extracted as a product and the other part of the liquid phase is refluxed into the column. The heat exchange medium is subjected to heat exchange, sent to the heat pump rectification compressor 30 to be compressed, and then a part of steam is supplemented, and heat is supplied to the tower kettle of the heavy component removal tower firstly and then is recycled as the heat exchange medium.
Wherein, the liquid phase material of vinyl acetate recovered by the vinyl acetate recovery tank 14 is 2700 kg/h. The operating pressure of the high-pressure separator 10 is 25MPa, the operating pressure of the low-pressure separator 11 is 0.3MPa, and the outlet pressure of the primary machine 2 is 25 MPa. The light component removing tower 17 has the tray number of 15, the reflux ratio of 4.6, the tower top operation pressure of 1.22bar and the tower top operation temperature of 77 ℃. The tower number of the heavy component removing tower 24 is 22, the reflux ratio is 0.35, the operation pressure at the top of the tower is 1.22bar, and the operation temperature at the bottom of the tower is 110 ℃. The absolute pressure of the outlet of the heat pump rectification compressor 30 is 3.6bar, and the outlet temperature is 115 ℃.
After refining, the mass fraction of the vinyl acetate is 0.99, the mass fractions of water and acetic acid are both less than 100ppm, and the yield of the refined VA is 1830 kg/h. Energy consumption was reduced by 142kW compared to comparative example 1.
Example 2
This example is intended to illustrate the recovery of vinyl acetate by the process of the present invention.
This example is based on a process for preparing ethylene-vinyl acetate copolymers by the high-pressure tubular process. As shown in FIG. 4, this example employs the removal of light components first followed by the removal of heavy components for the purpose of recycling vinyl acetate.
As shown in fig. 4, the vinyl acetate recovery tank 14 of this example is connected to the light component removal column 17, the heavy component removal column 24, the vinyl acetate tank 28, and the secondary machine 3 in this order via pipes to form a circulating vinyl acetate system. In the circulating vinyl acetate system, the waste gas at the top of the light component removal tower 17 is discharged to a torch, and the waste liquid is discharged to a waste vinyl acetate tank A35; the bottoms are discharged to the heavies removal column 22. The tower top liquid of the heavy component removing tower 22 is a standard vinyl acetate monomer, is discharged to a vinyl acetate tank 28, and is sent to the secondary machine 3 for recycling; the bottoms are discharged to waste vinyl acetate tank B36.
As shown in fig. 4, in this embodiment, after all the overhead gas in the heavy component removal column 24 exchanges heat with the heat exchange medium, it is cooled by the overhead auxiliary heat exchanger 26, and a part of the liquid phase is extracted as a product and the other part of the liquid phase is refluxed into the column. The heat exchange medium is subjected to heat exchange, sent to the heat pump rectification compressor 30 to be compressed, and then a part of steam is supplemented, and heat is supplied to the tower kettle of the light component removal tower firstly and then is recycled as the heat exchange medium.
Wherein, the liquid phase material of vinyl acetate recovered by the vinyl acetate recovery tank 14 is 2700 kg/h. The operating pressure of the high-pressure separator 10 is 25MPa, the operating pressure of the low-pressure separator 11 is 0.3MPa, and the outlet pressure of the primary machine 2 is 25 MPa. The light component removing tower 17 has the tray number of 15, the reflux ratio of 4.6, the tower top operation pressure of 1.22bar and the tower top operation temperature of 77 ℃. The tower 24 of the heavy component removing tower has the tower plate number of 22, the reflux ratio of 0.35, the operation pressure at the top of the tower of 1.22bar and the operation temperature at the bottom of the tower of 110 ℃. The absolute pressure of the outlet of the heat pump rectification compressor 30 is 2.1bar, and the outlet temperature is 105 ℃.
The refined VA has the mass fraction of 0.99 of the vinyl acetate, the water content and the acetic acid content are the same as those of the example 2, and the refined VA yield is 1830 kg/h. The energy consumption was reduced by 165kW compared with comparative example 2.
Example 3
This example is intended to illustrate the recovery of vinyl acetate by the process of the present invention.
This example is based on a process for preparing ethylene-vinyl acetate copolymers by the high-pressure tubular process. As shown in FIG. 5, this example employs the removal of light components first followed by the removal of heavy components for the purpose of recycling vinyl acetate.
As shown in fig. 5, the vinyl acetate recovery tank 14 of this example is connected to the light component removal column 17, the heavy component removal column 24, the vinyl acetate tank 28, and the secondary machine 3 in this order via piping, to form a recycle vinyl acetate system. In the circulating vinyl acetate system, the waste gas at the top of the light component removal tower 17 is discharged to a torch, and the waste liquid is discharged to a waste vinyl acetate tank A35; the bottoms are discharged to the heavies removal column 24. The tower top liquid of the heavy component removing tower 24 is a standard vinyl acetate monomer, is discharged to a vinyl acetate tank 28, and then is sent to a secondary machine 3 for recycling; the bottoms are discharged to waste vinyl acetate tank B36.
As shown in fig. 5, in this example, after all the overhead gas in the light component removal column 17 exchanges heat with the heat exchange medium, it is cooled by the overhead auxiliary heat exchanger 26, and a part of the liquid phase is extracted as a product and the other part of the liquid phase is refluxed into the column. The heat exchange medium is subjected to heat exchange, sent to the heat pump rectification compressor 30 to be compressed, and then a part of steam is supplemented, and heat is supplied to the tower kettle of the light component removal tower firstly and then is recycled as the heat exchange medium.
Wherein the vinyl acetate liquid phase discharge recovered by the vinyl acetate recovery tank 14 was 2700 kg/h. The operating pressure of the high-pressure separator 10 is 25MPa, the operating pressure of the low-pressure separator 11 is 0.3MPa, and the outlet pressure of the primary machine 2 is 25 MPa. The light component removing tower 17 has the tray number of 15, the reflux ratio of 4.6, the tower top operation pressure of 1.22bar and the tower top operation temperature of 77 ℃. The tower number of the heavy component removing tower 24 is 22, the reflux ratio is 0.35, the operation pressure at the top of the tower is 1.22bar, and the operation temperature at the bottom of the tower is 110 ℃. The absolute pressure of the outlet of the heat pump rectification compressor 30 is 2.6bar, and the outlet temperature is 105 ℃.
The refined VA yield is 1830kg/h, wherein the mass fraction of the refined vinyl acetate is 0.99, and the mass fractions of the water and the acetic acid are the same as those in example 3. Compared with the comparative example 3, the energy consumption is reduced by 158 kW.
Example 4
This example is intended to illustrate the recycling of vinyl acetate by the process of the invention.
This example is based on a process for preparing ethylene-vinyl acetate copolymers by the high-pressure tubular process. As shown in FIG. 6, this example employs the removal of light components first followed by the removal of heavy components for the purpose of recycling vinyl acetate.
As shown in fig. 6, the vinyl acetate recovery tank 14 of this example is connected to the light ends removal column 17, the heavy ends removal column 24, the vinyl acetate tank 28, and the secondary machine 3 in this order via piping, to form a recycle vinyl acetate system. In the circulating vinyl acetate system, the waste gas at the top of the light component removal tower 17 is discharged to a torch, and the waste liquid is discharged to a waste vinyl acetate tank A35; the bottoms are discharged to the heavies removal column 24. The tower top liquid of the heavy component removing tower 24 is a standard vinyl acetate monomer, is discharged to a vinyl acetate tank 28, and then is sent to a secondary machine 3 for recycling; the bottoms are discharged to waste vinyl acetate tank B36.
As shown in fig. 6, in this example, after all the overhead gas in the light component removal column 17 exchanges heat with the heat exchange medium, it is cooled by the overhead auxiliary heat exchanger 26, and a part of the liquid phase is extracted as a product and the other part of the liquid phase is refluxed into the column. The heat exchange medium is subjected to heat exchange, sent to the heat pump rectification compressor 230 to be compressed, and then a part of steam is supplemented, and heat is supplied to the tower kettle of the heavy component removal tower firstly and then is recycled as the heat exchange medium.
The vinyl acetate liquid phase discharge recovered in the vinyl acetate recovery tank 14 was 2700 kg/h. The operating pressure of the high-pressure separator 10 is 25MPa, the operating pressure of the low-pressure separator 11 is 0.3MPa, and the outlet pressure of the primary machine 2 is 25 MPa. The light component removing tower 17 has the tray number of 15, the reflux ratio of 4.6, the tower top operation pressure of 1.22bar and the tower top operation temperature of 77 ℃. The tower number of the heavy component removing tower 24 is 22, the reflux ratio is 0.35, the operation pressure at the top of the tower is 1.22bar, and the operation temperature at the bottom of the tower is 110 ℃. The absolute pressure of the outlet of the heat pump rectification compressor 30 is 4.0bar, and the outlet temperature is 117 ℃.
The refined VA yield is 1830kg/h, wherein the mass fraction of the refined vinyl acetate is 0.99, and the mass fractions of the water and the acetic acid are the same as those in example 4. Energy consumption was reduced by 140kW compared to comparative example 4.
Comparative example 1
Vinyl acetate was recovered under the same process conditions as in example 1, except that: there is no process of recycling the latent heat of vaporization of the overhead vapor of the heavy component removal column 24, i.e., heat is directly supplied to the reboiler 37 of the heavy component removal column bottom by using a heat utility.
The refined VA yield is 1830kg/h, wherein the mass fraction of vinyl acetate, water and acetic acid after refining is 0.99, and the mass fractions of water and acetic acid are the same as in example 1. The energy consumption was increased by 142kW compared to example 1.
Comparative example 2
Vinyl acetate was recovered under the same process conditions as in example 2, except that: there is no process of recycling the latent heat of vaporization of the overhead vapor of the heavy component removing column 24, that is, the heat utility is directly used to supply heat to the reboiler 22 at the bottom of the light component removing column.
The refined VA yield is 1830kg/h, wherein the mass fraction of the refined vinyl acetate is 0.99, and the mass fractions of the water and the acetic acid are the same as those in example 2. The energy consumption was increased by 165kW compared to example 2.
Comparative example 3
Vinyl acetate was recovered under the same process conditions as in example 3, except that: the process of recycling the latent heat of vaporization of the overhead steam of the light component removing tower 17 is not adopted, namely, heat is directly supplied to the reboiler 37 at the bottom of the heavy component removing tower by using a heat public engineering.
The refined VA yield is 1830kg/h, wherein the mass fraction of the refined vinyl acetate is 0.99, and the mass fractions of the water and the acetic acid are the same as those in example 3. The energy consumption was increased by 158kW compared to example 3.
Comparative example 4
Vinyl acetate was recovered under the same process conditions as in example 4, except that: the process of recycling the latent heat of vaporization of the overhead steam of the light component removing tower 17 is not adopted, namely, heat is directly supplied to a reboiler 22 at the tower bottom of the light component removing tower by using a heat utility.
As a result, a mass fraction of vinyl acetate of 0.99 was obtained, and the purified VA was produced at a yield of 1830kg/h, in the same manner as in example 4 for both water and acetic acid. The energy consumption was increased by 140kW compared to example 4.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A method for separating vinyl acetate by heat pump extractive distillation is characterized by comprising the following steps:
carrying out polymerization reaction on acetic acid and vinyl acetate in a high-pressure reactor, leading out an ethylene-vinyl acetate polymer, unreacted materials and byproducts from the reactor, and feeding the ethylene-vinyl acetate polymer, the unreacted materials and the byproducts into a high-pressure separator; the gas phase discharged material led out by the high-pressure separator is cooled and dewaxed by a high-pressure circulation loop and then enters a secondary machine for recycling; the discharged liquid phase enters a low-pressure separator;
the gas phase discharged material led out by the low-pressure separator enters a first compressor after being cooled and dewaxed by a low-pressure circulation loop, part of the material is changed into a liquid phase after passing through the first compressor, a material A rich in vinyl acetate is recovered to a vinyl acetate recovery tank through a vinyl acetate separator, and then is led into a refining system consisting of a light component removal tower and a heavy component removal tower, and a high-purity vinyl acetate product is obtained through separation;
at least one part of the overhead gas of at least one of the light component removal tower and the heavy component removal tower is led out, the overhead gas is cooled by an auxiliary heat exchanger at the top of the tower after exchanging heat with a heat exchange medium, one part is extracted as the waste liquid at the top of the tower, and the other part flows back to the tower; the heat exchange medium exchanges heat with the tower top gas and then is sent to a heat pump rectification compressor for compression, and then heat is supplied to a tower kettle of the refining system firstly and then is recycled as the heat exchange medium; one part of the tower bottom liquid is taken out as the tower bottom waste liquid, and the other part of the tower bottom liquid exchanges heat with the heat exchange medium and then flows back to the tower bottom through an auxiliary tower bottom heat exchanger.
2. The method of claim 1, wherein the vinyl acetate-rich material a is introduced into the refining system with or without the addition of mineral spirits; the solvent oil comprises one or more of n-hexane, cyclohexane, n-heptane, 6# solvent oil, 120# solvent oil, 200# solvent oil, petroleum ether, benzene, toluene, xylene, n-dodecane, isododecane, naphtha and a combination/mixture thereof.
3. The method according to claim 1, wherein the number of theoretical plates of the light component removal tower is 4-35, the reflux ratio is 1-8, and the operation pressure is 1-3 bar absolute; the number of theoretical plates of the heavy component removing tower is 3-50, the reflux ratio is 0.03-2, and the operating pressure is 1-3 bar absolute.
4. The method of claim 1, wherein the overhead gas that exchanges heat with the heat exchange medium comes from a light component removal column or a heavy component removal column, and the heat exchange medium supplies heat to a bottom of the light component removal column or the heavy component removal column after being compressed.
5. The process according to claim 1 or 4, wherein preferably all overhead gases of the heavy ends removal column are withdrawn for heat exchange with a heat exchange medium, more preferably all overhead gases of the heavy ends removal column and the light ends removal column are withdrawn for heat exchange with a heat exchange medium.
6. The method according to claim 1, wherein the operating temperature at the inlet of the heat pump rectification compressor is 50-85 ℃, the compression ratio is 1-5, and the operating temperature at the outlet is 100-150 ℃.
7. The method according to claim 1, wherein the outlet temperature of the overhead auxiliary heat exchanger is 60-85 ℃, preferably 70-85 ℃, and more preferably 75-80 ℃; the outlet temperature of the auxiliary heat exchanger of the tower kettle is 90-130 ℃, preferably 90-120 ℃, and more preferably 100-120 ℃.
8. The method of claim 1, wherein the high purity vinyl acetate product has a vinyl acetate mass fraction of greater than or equal to 98%; the mass fraction of water is less than or equal to 500 ppm; the mass fraction of acetic acid is less than or equal to 100 ppm.
9. An apparatus for using the method of claim 1, comprising:
a high-pressure separator: the device is used for carrying out gas-liquid separation on a polymer, an unreacted material and a byproduct led out from the high-pressure reactor, wherein the led-out liquid phase discharge enters a low-pressure separator, and the led-out gas phase discharge enters a secondary machine for recycling after being cooled and dewaxed by a high-pressure circulation loop;
the low-pressure separator is used for carrying out gas-liquid separation on the liquid-phase discharged material of the high-pressure separator, wherein the gas-phase discharged material is cooled by the low-pressure circulating loop to remove wax and is sent to the first compressor, and the liquid-phase discharged material is sent to extrusion granulation;
the first compressor comprises a supercharger and a primary machine which are connected in sequence and is used for compressing the gas-phase discharge material led out by the low-pressure separator;
the vinyl acetate separating tanks are used for carrying out gas-liquid phase separation on compressed materials at all stages in the first compressor; wherein, the gas phase enters a next-stage compression unit in a first compressor, and the liquid phase enters a vinyl acetate recovery tank;
a refining system, the inlet of which is connected with the liquid phase outlet of the vinyl acetate recovery tank; the refining system comprises a light component removing tower and a heavy component removing tower and is used for rectifying and separating vinyl acetate;
the tower top gas-heat supply network backwater heat exchanger is used for exchanging heat between the tower top gas of the rectifying tower and a heat exchange medium;
the inlet of the heat pump rectification compressor is connected with the tower top gas-heat network backwater heat exchanger, and the outlet of the heat pump rectification compressor is connected with the heat pump rectification heat exchanger and used for compressing a heat exchange medium;
the heat pump rectification heat exchanger is used for exchanging heat between a heat exchange medium and the tower bottom liquid of the rectification tower;
the inlet of the tower top auxiliary heat exchanger is connected with the tower top gas-heat network backwater heat exchanger and is used for controlling the temperature and the gas phase fraction of the rectifying tower top backwater liquid;
and the inlet of the tower kettle auxiliary heat exchanger is connected with the heat pump rectification heat exchanger and is used for controlling the temperature and the gas phase fraction of reboiled gas in the tower kettle of the rectification tower.
10. The method of claim 1, wherein the refining system removes light components first and then heavy components, and also removes heavy components first and then light components; the light component removing tower and the heavy component removing tower are plate towers or packed towers.
CN202210009954.3A 2022-01-06 2022-01-06 Method and device for separating vinyl acetate by heat pump extractive distillation Pending CN114522637A (en)

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Application publication date: 20220524