CN112694404B - Method and device for purifying vinyl acetate in EVOH production process - Google Patents
Method and device for purifying vinyl acetate in EVOH production process Download PDFInfo
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- CN112694404B CN112694404B CN201911009077.4A CN201911009077A CN112694404B CN 112694404 B CN112694404 B CN 112694404B CN 201911009077 A CN201911009077 A CN 201911009077A CN 112694404 B CN112694404 B CN 112694404B
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Abstract
The invention relates to a method and a device for purifying vinyl acetate in an EVOH production process, which mainly solve the problem of purifying the recovered vinyl acetate in the EVOH production preparation process, and adopts the following steps: the method is characterized in that crude vinyl acetate material flow containing impurities is sent into a product tower, heavy component material flow is obtained at the bottom of the tower, product material flow is collected at the side line, top gas material flow is obtained at the top of the tower, top liquid material flow is obtained after the top gas material flow is condensed by a heat exchanger, and the top liquid material flow is sent into a phase separator to be separated into light phase material flow mainly containing vinyl acetate and heavy phase material flow mainly containing water.
Description
Technical Field
The invention relates to a method and a device for purifying vinyl acetate in an EVOH production process.
Technical Field
Ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC) and Polyamide (PA) are called world three-high barrier resin, the barrier property of the resin is about ten thousand times of that of common polyethylene, and the resin is widely applied to the fields of packaging materials, automobile oil tanks, oxygen-resistant ground heating pipes, textile and medical materials and the like. In 2011, the worldwide annual capacity of the EVOH is about 12.6 ten thousand tons, the annual consumption total is about 11 ten thousand tons, the domestic annual consumption total is about 7300 tons, and the selling price is about 6 ten thousand yuan/ton. It is expected that by 2015 and 2020, world EVOH demand will reach 13 and 18 million tons, respectively, and asian regions will be the regions where EVOH is the fastest growing. The current EVOH production technology is mainly monopolized by Couloli Japan, synthetic chemistry and Taiwan Changchun in China.
EVOH is generally prepared by polymerizing ethylene and vinyl acetate by a conventional method such as emulsion polymerization, solution polymerization or suspension polymerization, and then saponifying the resulting product. In the copolymerization process of ethylene and vinyl acetate, the reaction efficiency is low, so that besides ethylene-vinyl acetate copolymer, a large amount of methanol as a solution, a large amount of unreacted ethylene and vinyl acetate exist in the outlet of the reactor, wherein a large amount of unreacted ethylene can be recovered after decompression flash evaporation, and the unreacted vinyl acetate needs to be recovered through a recovery process.
CN102942649A discloses a preparation method of ethylene vinyl alcohol copolymer, comprising the following steps: dissolving vinyl acetate and an oil-soluble initiator into monohydric alcohol with 1-5 carbon atoms, introducing ethylene gas to keep the reaction pressure at 5-50 atmospheric pressure, stirring and heating to 45-75 ℃, stirring at the speed of 25-500 rpm, and keeping the temperature to react for 0.5-10 hours to obtain an EVA solution; then adding 1-40% alkali liquor into EVA solution, stirring and heating to 50-85 deg.C, maintaining the temperature and making reaction for 0.5-12 hr, cooling to room temperature, adding water and cleaning, drying at 30-200 deg.C so as to obtain the invented EVOH.
CN 204607899U discloses an ethylene recovery system in EVOH production process, including the flash tank that is connected with feed line and ejection of compact pipeline simultaneously, the compressor, the condenser, vapour and liquid separator, the EVOH solution from polymerization system will be from the feed line lets in to the flash tank and carries out the flash distillation, liquid component flows into downstream device through ejection of compact pipeline after the flash distillation, ethylene gas gets into tubular condenser condensation to 10 ℃, the gas-liquid mixture after the condensation gets into vapour and liquid separator, mix in vapour and liquid separator and the fresh raw materials ethylene that lets in through the ethylene inlet line, the liquid that the separation produced returns to the flash tank, ethylene gas is then directly let in to the compressor, get back to polymerization system cyclic utilization after the compression. The utility model is only a device for recycling unreacted ethylene.
The invention provides a method and a device for purifying vinyl acetate, which aim to solve the problem in a targeted manner.
Disclosure of Invention
The invention relates to a method and a device for purifying vinyl acetate in an EVOH production process, which mainly solve the problem of purifying the recovered vinyl acetate in the EVOH production preparation process, can be used for a separation process in the EVOH production process, and have the advantages of simple purification process flow, low energy consumption, high vinyl acetate recovery rate and high vinyl acetate purity.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a) Sending a crude vinyl acetate material flow containing impurities into a product tower, obtaining a heavy component material flow at the tower bottom, collecting the product material flow at the side line, obtaining a tower top gas material flow at the tower top, condensing the tower top gas material flow through a heat exchanger to obtain a tower top liquid material flow, sending the tower top liquid material flow into a phase separator to be separated into a light phase material flow mainly containing vinyl acetate and a heavy phase material flow mainly containing water, wherein the light phase material flow is divided into two parts, 0-100% of the light phase material flow is returned to the upper part of the product tower to be used as a reflux material flow, 0-100% of the light phase material flow is used as a light phase collected material flow, and optionally, the heavy phase material flow is discharged out of a separation system;
b) Sending the light-phase extracted material flow into a light-component removal tower, separating to obtain an impurity material flow at the top of the tower, a return material flow at the bottom of the tower, and sending the return material flow into a product tower for recycling;
the method is characterized in that the ratio K of the reflux material flow to the light phase extracted material flow and the content w of impurities except water in the crude vinyl acetate material flow satisfy the following relation in percentage by weight:
K＝105.91×w-645.47×w 2 ，0.01％≤w≤3.5％。
in the technical scheme, technicians obtain rules among data through data induction and summarization through a large amount of experimental data, literature data and process simulation data, then regress to obtain a relational expression between the proportion K of a reflux material flow and a light-phase extracted material flow and the content w of impurities except water in a crude vinyl acetate material flow, and automatically adjust the reflux ratio according to the concentration of the impurities except water in a feed material flow, so that the product can be qualified. In actual operation, a corresponding relation graph between each reflux ratio and the concentration of the magazine can be drawn according to the relational expression, and a method for quickly and accurately determining the reflux ratio is provided for an operator of the device, so that the time for searching the reflux ratio is saved, the abnormal operation time of the device is greatly shortened, the benefit of the device is increased, and the energy is saved.
In the technical scheme of the invention, the content w of impurities except water in the crude vinyl acetate material flow is 0.01-3.5 percent by weight of the crude vinyl acetate material flow.
In the technical scheme of the invention, the water content in the crude vinyl acetate material flow is 0.01-3.0% by weight of the crude vinyl acetate material flow.
In the technical scheme of the invention, the impurities comprise one or more of acetaldehyde, acetone, methyl acetate and water.
In the technical scheme of the invention, the product material flow extraction position is positioned between the 1 st to 0.1N plates above the reboiler return opening of the tower kettle, and N is the number of tower plates of the product tower.
In the technical scheme of the invention, the operating pressure of the product tower is 0-250 KPaG, preferably 0-200 KPaG.
In the technical scheme of the invention, the temperature of the overhead gas of the product tower is 60-110 ℃, and preferably 60-100 ℃.
In the technical scheme of the invention, the temperature of the condensed tower top liquid of the heat exchanger is 10-60 ℃, preferably 15-50 ℃.
In the technical scheme of the invention, the operating pressure of the light component removal tower is 0-250 KPaG, preferably 0-200 KPaG.
In the technical scheme of the invention, the tower top temperature of the lightness-removing tower is 55-100 ℃, and preferably 55-90 ℃.
In the technical scheme of the invention, in the product tower, the boiling point of water in impurities is higher than that of vinyl acetate, the boiling points of other impurities are lower than that of vinyl acetate, and the impurity water and the vinyl acetate have an azeotropic phenomenon (by weight percentage, the normal-pressure azeotropic temperature is 66 ℃, the azeotropic composition is VAC 92.7% -water 7.3%), through a large amount of experimental data verification, the concentration of the vinyl acetate has a highest point in the tower, the highest point is positioned between 0-0.1N plates above a reboiler return opening of a tower kettle, and N is the number of tower plates of the product tower. Therefore, the vinyl acetate product material flow is taken out from the side line at the lower part of the tower, has higher purity and can be directly sent back to the reactor to take part in the reaction, thereby realizing the reutilization.
Literature and calculation data show that the mutual solubility of vinyl acetate and water decreases with decreasing temperature. The product tower top gas flow is cooled to 10-60 ℃, preferably 15-50 ℃ for phase separation, mainly because when the phase separation temperature is too high, the mutual solubility of vinyl acetate and water is increased, and water distilled back along with light phase vinyl acetate is accumulated continuously, so that the liquid-liquid phase separation effect in a phase separator is influenced, and the energy consumption of a separation system is increased. The vinyl acetate contained in the heavy phase material flow water is increased, and the heavy phase is directly discharged from the separation system, so that the vinyl acetate loss is increased, the vinyl acetate recovery rate is reduced, and the material consumption of the device is increased. Therefore, the phase separation temperature is strictly controlled and cannot be too high. When the phase separation temperature is too low (lower than 15 ℃, especially lower than 0 ℃), although the phase separation is facilitated, the azeotropic material flow needs to be cooled by the low-temperature refrigerant, the use of the low-temperature refrigerant can greatly increase the operation cost, and simultaneously, the equipment material quality can be improved, the investment is increased, so that the azeotropic material flow is cooled to 15-50 ℃, the requirements can be met only by circulating cooling water or chilled water, and the operation cost is greatly reduced. In addition, only one phase separation groove (a vertical or horizontal container is provided with a partition plate) is needed for liquid-liquid phase separation, so that the equipment investment is extremely low, and the energy consumption is not consumed.
The invention also provides a device for recycling vinyl acetate in the EVOH production process, which comprises:
1) A product tower; the system is configured to receive a crude vinyl acetate material flow, receive a reflux material flow and a return material flow at the upper part, discharge a tower top gas material flow at the tower top, take a product material flow at a side line, and discharge a heavy component material flow at the tower bottom;
2) A light component removal tower; configured to receive a light phase withdrawn stream, discharge an impurity stream overhead, and a column bottoms return stream;
3) A heat exchanger; configured to receive said overhead gas stream and discharge an overhead liquid stream;
4) A phase splitter; configured to receive the overhead liquid stream and discharge a heavy phase stream and a light phase stream.
In the technical scheme of the invention, the phase separator is a common liquid-liquid phase separation container with a partition plate or a high-efficiency liquid-liquid phase separator.
All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, including definitions, will control.
When the specification concludes with claims with the heading "known to those skilled in the art", "prior art", or the like, to derive materials, substances, methods, procedures, devices, or components, etc., it is intended that the subject matter derived from the heading encompass those conventionally used in the art at the time of filing this application, but also include those that are not currently in use, but would become known in the art to be suitable for a similar purpose.
In the context of the present specification, anything or things which are not mentioned, except where explicitly stated, are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or concepts resulting therefrom are considered part of the original disclosure or original disclosure of the invention, and should not be considered as new matters not disclosed or contemplated herein, unless a person skilled in the art would consider such a combination to be clearly unreasonable.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Drawings
FIG. 1 shows a method for purifying vinyl acetate in the production of EVOH.
FIG. 1 depicts the following:
101. is a crude vinyl acetate stream
102. As a heavy component stream
103. For product logistics
104. As a stream of overhead gas
105. As an overhead liquid stream
106. As a heavy phase stream
107. As a reflux stream
108. For producing streams from light phases
109. As a stream of impurities
110. To return the material flow
11. Product tower
12. Heat exchanger
13. Phase splitter
14. Light component removing tower
In fig. 1, a crude vinyl acetate stream 101 containing impurities is sent to a product tower 11, a heavy component stream 102 is obtained at the bottom of the tower, a side-draw product stream 103 is obtained at the top of the tower, a top gas stream 104 is obtained at the top of the tower, the top gas stream 104 is condensed by a heat exchanger 12 to obtain a top liquid stream 105, the top liquid stream 105 is sent to a phase separator 13 to be separated into a light phase stream mainly containing vinyl acetate and a heavy phase stream 106 mainly containing water, the light phase stream is divided into two streams, one stream is returned to the upper part of the product tower to be used as a reflux stream 107, the other stream is used as a light phase draw stream 108, and the heavy phase stream 106 is discharged from a separation system; the light phase produced material flow 108 is sent to a lightness-removing column 14, the top of the column is an impurity material flow 109 obtained by separation, the bottom of the column is a return material flow 110, and the return material flow 110 is sent to the upper part of a product column 11 to be used as reflux.
Detailed Description
The technical scheme of the invention is adopted by taking a crude vinyl acetate material flow with a flow rate of 3000kg/h as a reference, and the description is given by an embodiment.
[ example 1 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 200KPaG, the tower top temperature is 95 ℃, the tower bottom temperature is 112 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower bottom, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 200KPaG, the tower top temperature is 88 ℃, and the tower kettle temperature is 99 ℃.
The recovery rate of the vinyl acetate is 99.95 percent, the purity of the vinyl acetate is 99.92 percent, and 229kg standard oil/h is always consumed.
[ example 2 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 180KPaG, the temperature of the top of the tower is 92.9 ℃, the temperature of the bottom of the tower is 110 ℃, the number of the tower plates N is 40, the lateral line extraction position is the 1 st plate above the return port of the reboiler at the bottom of the tower, and the reflux ratio K is 2.24.
The operating pressure of the lightness-removing column is 180KPaG, the temperature at the top of the column is 86.2 ℃, and the temperature at the bottom of the column is 98 ℃.
The recovery rate of the vinyl acetate is 99.93 percent, the purity of the vinyl acetate is 99.92 percent, and the total energy consumption is 223kg standard oil/h.
[ example 3 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 160KPaG, the temperature of the top of the tower is 90.6 ℃, the temperature of the tower kettle is 110 ℃, the number of the tower plates N is 40, the lateral line extraction position is the 1 st plate above the return opening of the reboiler of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 160KPaG, the tower top temperature is 84.2 ℃, and the tower kettle temperature is 97 ℃.
The recovery rate of the vinyl acetate is 99.91 percent, the purity of the vinyl acetate is 99.92 percent, and the total energy consumption is 215kg standard oil/h.
[ example 4 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 120KPaG, the temperature of the tower top is 85.7 ℃, the temperature of the tower kettle is 101 ℃, the number of the tower plates N is 40, the lateral line extraction position is the 1 st plate above the return opening of the reboiler of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 120KPaG, the tower top temperature is 79.5 ℃, and the tower kettle temperature is 91 ℃.
The recovery rate of the vinyl acetate is 99.78 percent, the purity of the vinyl acetate is 99.92 percent, and the total energy consumption is 204kg standard oil/h.
[ example 5 ] A method for producing a polycarbonate
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 100KPaG, the temperature of the tower top is 83 ℃, the temperature of the tower bottom is 98 ℃, the number of tower plates N is 40, the lateral line extraction position is the 1 st plate above the reboiler return opening of the tower bottom, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 100KPaG, the tower top temperature is 78.3 ℃, and the tower kettle temperature is 89 ℃.
The recovery rate of the vinyl acetate is 99.74 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 192kg standard oil/h.
[ example 6 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 80KPaG, the temperature of the tower top is 80 ℃, the temperature of the tower bottom is 98 ℃, the number of tower plates N is 40, the lateral line extraction position is the 1 st plate above the reboiler return opening of the tower bottom, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 80KPaG, the tower top temperature is 74.1 ℃, and the tower kettle temperature is 86 ℃.
The recovery rate of the vinyl acetate is 99.69 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 183kg standard oil/h.
[ example 7 ] A method for producing a polycarbonate
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the tower top temperature is 76.7 ℃, the tower kettle temperature is 91 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 99.62 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 171kg standard oil/h.
[ example 8 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 40KPaG, the tower top temperature is 73.1 ℃, the tower kettle temperature is 88 ℃, the number of tower plates N is 40, the side draw position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 40KPaG, the tower top temperature is 67.0 ℃, and the tower kettle temperature is 80 ℃.
The recovery rate of the vinyl acetate is 99.56 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 175kg standard oil/h.
[ example 9 ] A method for producing a polycarbonate
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 20KPaG, the tower top temperature is 69 ℃, the tower kettle temperature is 83 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 20KPaG, the tower top temperature is 63.4 ℃, and the tower kettle temperature is 76 ℃.
The recovery rate of the vinyl acetate is 99.49 percent, the purity of the vinyl acetate is 99.94 percent, and the total energy consumption is 181kg standard oil/h.
[ example 10 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 10KPaG, the tower top temperature is 66.7 ℃, the tower bottom temperature is 83 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower bottom, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 10KPaG, the tower top temperature is 63.4 ℃, and the tower kettle temperature is 76 ℃.
The recovery rate of the vinyl acetate is 99.48 percent, the purity of the vinyl acetate is 99.94 percent, and the total energy consumption is 190kg standard oil/h.
[ example 11 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 5KPaG, the tower top temperature is 65.5 ℃, the tower kettle temperature is 80 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the lightness-removing column is 5KPaG, the temperature at the top of the column is 60.1 ℃, and the temperature at the bottom of the column is 73 ℃.
The recovery rate of the vinyl acetate is 99.42 percent, the purity of the vinyl acetate is 99.94 percent, and the total energy consumption is 198kg standard oil/h.
[ example 12 ] A method for producing a polycarbonate
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 0.5 percent of water, and 3.0 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the tower top temperature is 76.7 ℃, the tower kettle temperature is 91 ℃, the number of tower plates N is 40, the side line extraction position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.60.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 99.62 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 181kg standard oil/h.
[ example 13 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.5 percent of water, 2.0 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the tower top temperature is 76.7 ℃, the tower kettle temperature is 91 ℃, the number of tower plates N is 40, the side line extraction position is the 2 nd plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 1.86.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 99.62 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 166kg standard oil/h.
[ example 14 ]
The product stream comprises, in weight percent: 97.5 percent of vinyl acetate, 1.5 percent of water, and 1.0 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the tower top temperature is 76.7 ℃, the tower kettle temperature is 91 ℃, the number of tower plates N is 40, the side line extraction position is the 3 rd plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 0.99.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 99.62 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 164kg standard oil/h.
[ example 15 ]
The product stream comprises, in weight percent: 98.5 percent of vinyl acetate, 1.0 percent of water, 0.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the temperature of the tower top is 76.7 ℃, the temperature of the tower kettle is 91 ℃, the number of the tower plates N is 40, the lateral line extraction position is the 4 th plate above the return opening of the reboiler of the tower kettle, and the reflux ratio K is 0.51.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 99.62 percent, the purity of the vinyl acetate is 99.93 percent, and the total energy consumption is 160kg standard oil/h.
[ COMPARATIVE EXAMPLE 1 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 60KPaG, the tower top temperature is 76.7 ℃, the tower kettle temperature is 91 ℃, the number of tower plates N is 40, the side line extraction position is the 10 th plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 60KPaG, the tower top temperature is 71.2 ℃, and the tower kettle temperature is 83 ℃.
The recovery rate of the vinyl acetate is 89.62 percent, the purity of the vinyl acetate is 80.93 percent, and the total energy consumption is 371kg standard oil/h.
[ COMPARATIVE EXAMPLE 2 ]
The product stream comprises, in weight percent: 96.5 percent of vinyl acetate, 1.0 percent of water, and 2.5 percent of impurities of acetaldehyde and acetone.
The operating pressure of the product tower is 300KPaG, the tower top temperature is 106.5 ℃, the tower kettle temperature is 126 ℃, the number of the tower plates N is 40, the side draw position is the 1 st plate above the reboiler return opening of the tower kettle, and the reflux ratio K is 2.24.
The operating pressure of the light component removal tower is 300KPaG, the tower top temperature is 98 ℃, and the tower kettle temperature is 109 ℃.
The recovery rate of the vinyl acetate is 98.62 percent, the purity of the vinyl acetate is 98.93 percent, and the total energy consumption is 426kg standard oil/h.
Claims (14)
1. A method for purifying vinyl acetate in an EVOH production process comprises the following steps:
a) Sending a crude vinyl acetate material flow containing impurities into a product tower, obtaining a heavy component material flow at the tower bottom, collecting the product material flow at the side line, obtaining a tower top gas material flow at the tower top, condensing the tower top gas material flow through a heat exchanger to obtain a tower top liquid material flow, sending the tower top liquid material flow into a phase separator to be separated into a light phase material flow mainly containing vinyl acetate and a heavy phase material flow mainly containing water, wherein the light phase material flow is divided into two parts, 0-100% of the light phase material flow is returned to the upper part of the product tower to be used as a reflux material flow, 0-100% of the light phase material flow is used as a light phase collected material flow, and optionally, the heavy phase material flow is discharged out of a separation system;
b) Sending the light-phase extracted material flow into a light-component removal tower, separating to obtain an impurity material flow at the top of the tower, a return material flow at the bottom of the tower, and sending the return material flow into a product tower for recycling;
the method is characterized in that the ratio K of the reflux material flow to the light phase extracted material flow and the content w of impurities except water in the crude vinyl acetate material flow satisfy the following relation in percentage by weight:
K＝105.91×w-645.47×w 2 ，0.01％≤w≤3.5％；
the product material flow extraction position is positioned between the 1 st to 0.1N plates above the reboiler return opening of the tower kettle, and N is the number of tower plates of the product tower.
2. The method of claim 1, wherein the crude vinyl acetate stream has a water content of 0.01% to 3.0% by weight of the crude vinyl acetate stream.
3. The method of claim 1, wherein the impurities in the crude vinyl acetate stream comprise one or more of acetaldehyde, acetone, methyl acetate, and water.
4. The method of claim 1, wherein the crude vinyl acetate stream has a level w of impurities other than water of from 0.01% to 3.5% by weight of the crude vinyl acetate stream.
5. The method of purifying vinyl acetate in EVOH production process of claim 1, wherein the product column operating pressure is 0-250 KPaG.
6. Method for the purification of vinyl acetate in the production of EVOH according to any of the claims 1-4, characterized in that the product column operating pressure is 0-200 KPaG.
7. The method of purifying vinyl acetate in EVOH production process of claim 1, wherein the overhead gas temperature of the product column is 60-110 ℃.
8. Process for the purification of vinyl acetate in the production of EVOH according to any of claims 1 to 5, characterized by a product column overhead temperature of 60-100 ℃.
9. The method for purifying vinyl acetate in the production of EVOH according to claim 1, wherein the temperature of the top liquid of the heat exchanger after condensation is 10-60 ℃.
10. Method for the purification of vinyl acetate in the production of EVOH according to any of claims 1-5, 7, characterised in that the temperature of the top liquid after condensation in the heat exchanger is 15-50 ℃.
11. The method for purifying vinyl acetate in EVOH production process according to claim 1, characterized in that the operating pressure of the light component removal column is 0-250 KPaG.
12. Process for the purification of vinyl acetate in the manufacture of EVOH according to any of claims 1 to 5, 7, 9, characterized in that the lightness-removing column is operated at a pressure of 0 to 200KPaG.
13. The method for purifying vinyl acetate in the production of EVOH according to claim 1, wherein the temperature of the top of the lightness-removing column is 55-100 ℃.
14. Process for the purification of vinyl acetate in the manufacture of EVOH according to any of claims 1 to 5, 7, 9, 11, characterised in that the lightness-removing column top temperature is 55-90 ℃.
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| CN104030921A (en) * | 2013-07-05 | 2014-09-10 | 中石化上海工程有限公司 | Method for separating vinyl acetate |
| CN107011172A (en) * | 2017-04-25 | 2017-08-04 | 天津大学 | A kind of utilization partition tower refines the method and device of vinyl acetate |
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| CN104030921A (en) * | 2013-07-05 | 2014-09-10 | 中石化上海工程有限公司 | Method for separating vinyl acetate |
| CN107011172A (en) * | 2017-04-25 | 2017-08-04 | 天津大学 | A kind of utilization partition tower refines the method and device of vinyl acetate |
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