CN117986116A - Method and device for recovering vinyl acetate in ethylene-vinyl alcohol copolymer production process - Google Patents
Method and device for recovering vinyl acetate in ethylene-vinyl alcohol copolymer production process Download PDFInfo
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- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 title claims abstract description 119
- 238000000034 method Methods 0.000 title claims abstract description 29
- 229920000219 Ethylene vinyl alcohol Polymers 0.000 title claims abstract description 26
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 96
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000012535 impurity Substances 0.000 claims abstract description 38
- 238000010992 reflux Methods 0.000 claims abstract description 13
- 238000000926 separation method Methods 0.000 claims abstract description 10
- 239000007788 liquid Substances 0.000 claims abstract description 4
- 239000012071 phase Substances 0.000 claims description 124
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 45
- 239000000463 material Substances 0.000 claims description 24
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 claims description 15
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 claims description 15
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 claims description 15
- 238000007599 discharging Methods 0.000 claims description 7
- 238000005192 partition Methods 0.000 claims description 6
- 239000007791 liquid phase Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 239000012808 vapor phase Substances 0.000 claims description 3
- 238000011084 recovery Methods 0.000 abstract description 22
- 238000005265 energy consumption Methods 0.000 abstract description 18
- 239000004715 ethylene vinyl alcohol Substances 0.000 abstract description 11
- UFRKOOWSQGXVKV-UHFFFAOYSA-N ethene;ethenol Chemical compound C=C.OC=C UFRKOOWSQGXVKV-UHFFFAOYSA-N 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 19
- 238000000605 extraction Methods 0.000 description 10
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 7
- 239000005977 Ethylene Substances 0.000 description 7
- 230000004888 barrier function Effects 0.000 description 5
- 230000001112 coagulating effect Effects 0.000 description 5
- 238000005345 coagulation Methods 0.000 description 4
- 230000015271 coagulation Effects 0.000 description 4
- 238000005191 phase separation Methods 0.000 description 4
- 239000004952 Polyamide Substances 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000178 monomer Substances 0.000 description 3
- 229920002647 polyamide Polymers 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 2
- 238000007334 copolymerization reaction Methods 0.000 description 2
- 239000005038 ethylene vinyl acetate Substances 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000011344 liquid material Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 239000005033 polyvinylidene chloride Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- IMROMDMJAWUWLK-UHFFFAOYSA-N Ethenol Chemical compound OC=C IMROMDMJAWUWLK-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920001328 Polyvinylidene chloride Polymers 0.000 description 1
- JXLYSJRDGCGARV-WWYNWVTFSA-N Vinblastine Natural products O=C(O[C@H]1[C@](O)(C(=O)OC)[C@@H]2N(C)c3c(cc(c(OC)c3)[C@]3(C(=O)OC)c4[nH]c5c(c4CCN4C[C@](O)(CC)C[C@H](C3)C4)cccc5)[C@@]32[C@H]2[C@@]1(CC)C=CCN2CC3)C JXLYSJRDGCGARV-WWYNWVTFSA-N 0.000 description 1
- 238000006136 alcoholysis reaction Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007720 emulsion polymerization reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 235000021485 packed food Nutrition 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000010557 suspension polymerization reaction Methods 0.000 description 1
- 229960003048 vinblastine Drugs 0.000 description 1
- JXLYSJRDGCGARV-XQKSVPLYSA-N vincaleukoblastine Chemical compound C([C@@H](C[C@]1(C(=O)OC)C=2C(=CC3=C([C@]45[C@H]([C@@]([C@H](OC(C)=O)[C@]6(CC)C=CCN([C@H]56)CC4)(O)C(=O)OC)N3C)C=2)OC)C[C@@](C2)(O)CC)N2CCC2=C1NC1=CC=CC=C21 JXLYSJRDGCGARV-XQKSVPLYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Landscapes
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a method and a device for recovering vinyl acetate in the EVOH production process. The method comprises the following steps: rectifying the impurity-containing vinyl acetate and methanol mixed stream to obtain a first heavy component stream containing methanol and water and a gas-phase stream, condensing the gas-phase stream, and then separating the gas-phase stream into a first light-phase stream mainly containing vinyl acetate and a first heavy-phase stream mainly containing water, wherein the first heavy-phase stream is returned to the rectification step as reflux, the first light-phase stream is divided into two streams, and the first light-phase sub-stream I is returned to the rectification step as reflux; a first light phase sub-stream II in the first light phase stream is subjected to liquid-liquid separation to obtain a second light phase stream mainly containing vinyl acetate and a second heavy phase stream mainly containing water; and rectifying the second light phase stream, and separating to obtain an impurity-containing stream, a vinyl acetate stream and a third heavy component stream. The method has the advantages of simple recovery process flow, low energy consumption, high recovery rate and purity of the vinyl acetate and small equipment investment.
Description
Technical Field
The invention relates to the field of ethylene-vinyl alcohol copolymer production, in particular to a method and a device for recycling vinyl acetate in the production process of ethylene-vinyl alcohol copolymer.
Background
Ethylene-vinyl alcohol copolymer (EVOH) is a crystalline polymer with chain molecular structure, and is also called as three high barrier materials in the world together with polyvinylidene chloride (PVDC) and Polyamide (PA), and the barrier property is about ten thousands times higher than that of polyethylene and polypropylene, 100 times higher than that of PA, and more than ten times higher than that of PVDC which is a high barrier material commonly used at present. The EVOH resin has high barrier property to gas, water and chemical solvents, is an excellent barrier material at present, has great advantages in the aspects of prolonging the storage period of packaged foods, further playing the roles of light weight, difficult breakage and the like of plastic packages, has special important roles in improving the packaging quality, and has good application prospect and wide market. The current EVOH production technology is mainly characterized by Japanese colali, synthetic chemistry and Taiwan vinblastine monopoli.
CN106146717a discloses a method for producing ethylene-vinyl alcohol copolymer, which comprises the following steps: 1) And (3) copolymerization reaction: the initial monomer ethylene and vinyl acetate are carried out at 40-100 ℃ and 2.5-6 MPa; 2) And (3) monomer removal: removing unreacted ethylene monomer by flash evaporation, and removing unreacted vinyl acetate by methanol; 3) Saponification: saponifying the methanol solution of ethylene-vinyl acetate copolymer with alkali as catalyst to produce ethylene-vinyl alcohol copolymer solution; 4) And (3) forming and granulating: the obtained ethylene-vinyl alcohol copolymer solution is pumped into an extruder, extruded into a coagulating bath to be coagulated into strips, wound by a winding roller arranged at the upper part or the side part of the coagulating bath, and then fed into a granulator for cutting into granules; wherein the coagulating bath is a vertical coagulating bath or a horizontal coagulating bath; the extruder is arranged at the lower part of the vertical coagulation bath or at the side part of the horizontal coagulation bath, and an extrusion head on the extruder is communicated into the vertical coagulation bath or the horizontal coagulation bath; 5) Post-treatment: and (5) centrifugally dehydrating the obtained ethylene-vinyl alcohol copolymer particles, and drying to obtain the finished product. The patent discloses only a method for preparing EVOH.
The ethylene-vinyl alcohol copolymer (EVAC) is prepared by the alcoholysis reaction of ethylene and vinyl acetate by the conventional methods such as emulsion polymerization, solution polymerization or suspension polymerization, and the proportion of the ethylene-vinyl acetate copolymer is generally 20-45% of ethylene mole content and 55-80% of vinyl alcohol mole content. In the copolymerization of ethylene and vinyl acetate, the reaction efficiency is low, so that a large amount of methanol as a solution and unreacted ethylene and vinyl acetate are contained in the outlet of the reactor, and the unreacted ethylene can be recovered after the flash evaporation under reduced pressure, while the unreacted vinyl acetate needs to be recovered by a recovery process.
The invention provides a method and a device for recovering vinyl acetate in the EVOH production process, which aims at solving the problem in a targeted way.
Disclosure of Invention
The invention relates to a method and a device for recovering vinyl acetate in the production process of EVOH, which mainly solve the problems of low recovery rate, high energy consumption, complex flow and high equipment investment of the vinyl acetate recovered in the production and preparation process of EVOH, can be used for the separation process in the production process of EVOH, and has the advantages of simple recovery process flow, low energy consumption, high recovery rate of vinyl acetate, high purity of vinyl acetate and low equipment investment.
In order to solve the above problems, it is an object of the present invention to provide a method for recovering vinyl acetate in an ethylene-vinyl alcohol copolymer production process, comprising the steps of:
a) Rectifying the impurity-containing vinyl acetate and methanol mixed stream to obtain a first heavy component stream containing methanol and water and a gas-phase stream, condensing the gas-phase stream, and then separating the gas-phase stream into a first light-phase stream mainly containing vinyl acetate and a first heavy-phase stream mainly containing water, wherein the first heavy-phase stream is returned to the rectification step as reflux, the first light-phase stream is divided into two streams, and the first light-phase sub-stream I is returned to the rectification step as reflux;
b) A second light phase sub-stream II in the first light phase stream is subjected to liquid-liquid separation to obtain a second light phase stream mainly containing vinyl acetate and a second heavy phase stream mainly containing water, and the second heavy phase stream is returned to the rectification step in the step a);
c) Rectifying the second light phase stream, and separating to obtain an impurity-containing stream, a vinyl acetate stream and a third heavy component stream, wherein the third heavy component stream is returned to the rectifying step in step a).
In the technical scheme of the invention, the content of the vinyl acetate in the impurity-containing vinyl acetate and methanol mixed flow is 15-40 wt%, the content of the impurity is less than 0.2wt% and the balance is methanol.
In the technical scheme of the invention, the impurities are one or more of acetaldehyde, acetone, methyl acetate and water.
In step a) of the technical scheme of the invention, the pressure of rectification is 0-250 KPaG, preferably 0-200 KPaG,
In step a) of the present invention, the first light phase sub-stream is 0 to 50wt%, preferably 5 to 30wt%, of the first light phase sub-stream.
In step a) of the technical scheme of the invention, the additional water stream is directly fed into the rectification step, and/or the additional water stream is returned to the rectification step after being combined with other streams returned to the rectification step.
In step a) of the process according to the invention, the gas phase stream is condensed to a temperature of from 10 to 60℃and preferably to a temperature of from 15 to 50 ℃.
In step b) of the present invention, the ratio of water in the second heavy phase stream to water in the second light phase sub-stream is > 0.9, preferably > 0.92.
In step b) of the present invention, the liquid-liquid separation is preferably performed by using a condensate collector.
In step c) of the present invention, the pressure of the rectification is 0 to 250KPaG, preferably 0 to 200KPaG.
In the technical scheme of the invention, in the step c), the rectification is carried out in a rectification tower, the number of tower plates of the rectification tower is N, a vertical partition plate is inserted between the tower plates of 0.1N-0.9N, the area between the tower plates of the rectification tower of 0.1N-0.9N is divided into two independent areas with equal or unequal areas, and the N is 30-60.
Preferably, the inlet of the second light phase stream into the rectifying tower and the outlet of the vinyl acetate stream extracted from the side line of the rectifying tower are respectively arranged at two sides of the partition plate.
In the technical scheme of the invention, in the raw material of the crude vinyl acetate, 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 azeotropic phenomenon (in terms of weight percentage, the normal pressure azeotropic temperature is 66 ℃, the azeotropic composition is formed, and VAC is 92.7% -7.3%) exists between the impurity water and the vinyl acetate. The literature and the calculation data show that the mutual solubility of vinyl acetate and water decreases with decreasing temperature. The invention cools the top gas stream after the first rectification to 10-60 ℃, preferably 15-50 ℃ for phase separation, mainly because the mutual solubility of vinyl acetate and water is increased when the phase separation temperature is too high, and the water in the first light phase produced stream is accumulated continuously to influence the liquid-liquid phase separation effect in the phase separator. The accumulated water forms a low-boiling azeotrope with impurities and/or vinyl acetate through the second rectifying tower and is directly discharged out of the separation system from the top of the tower, so that the loss of vinyl acetate is increased, the recovery rate of vinyl acetate is reduced, and the material consumption of the device is increased, and therefore, the phase separation temperature is not excessively high to be strictly controlled.
It is a second object of the present invention to provide an apparatus for recovering vinyl acetate in an ethylene-vinyl alcohol copolymer production process for carrying out the above-described process, comprising:
a first rectifying tower: which is configured to receive a mixed stream of vinyl acetate and methanol containing impurities, receive a reflux stream at an upper portion, discharge a vapor phase stream at the top of the column, and discharge a first heavy component stream at the bottom of the column. Optionally, the first rectification column upper section may also receive a make-up water stream.
A heat exchanger: configured to receive the vapor phase stream and discharge a first overhead condensate stream.
Phase splitter: which is configured to receive the first overhead condensate stream and discharge a first light phase stream comprising primarily vinyl acetate and a first heavy phase stream comprising primarily water.
Condensate collector: configured to receive a first light phase sub-stream two, with an upper portion discharging a second light phase stream and a lower portion discharging a second heavy phase stream.
And a second rectifying tower: which is configured to receive the second light phase stream, discharge the impurity stream overhead, discharge the third heavies stream from the bottom of the column, and produce a vinyl acetate stream from the middle side of the column.
In the technical scheme of the invention, the tray number of the first rectifying tower is preferably 30-60.
In the technical scheme of the invention, the phase separator is a common liquid-liquid phase separator with a baffle plate or a high-efficiency liquid-liquid phase separator.
In the technical scheme of the invention, the number of the tower plates of the second rectifying tower is N, and a vertical partition plate is inserted between the tower plates of 0.1N-0.9N (integer) to divide the area between the tower plates of the second rectifying tower into two independent areas with equal or unequal areas.
In the technical scheme of the invention, the number N of the tower plates of the second rectifying tower is 30-60.
Preferably, the inlet of the second light phase stream entering the second rectifying tower and the outlet of the vinyl acetate stream extracted from the side line of the second rectifying tower are respectively arranged at two sides of the partition plate.
The method can be used for efficiently recycling the vinyl acetate in the EVOH production process, and realizes the efficient recycling of the vinyl acetate by adopting the double-tower combination of the rectifying tower and the dividing wall tower, so that one set of rectifying device can be saved, the energy consumption is lower, and the cost is lower. The method has the advantages of simple recovery process flow, low energy consumption, high recovery rate of the vinyl acetate, high purity of the vinyl acetate and small equipment investment.
All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, definitions, will control.
When the specification derives materials, substances, methods, steps, devices, or elements and the like in the word "known to those skilled in the art", "prior art", or the like, such derived objects encompass those conventionally used in the art as the application suggests, but also include those which are not currently commonly used but which would become known in the art to be suitable for similar purposes.
In the context of this specification, any matters or matters not mentioned are directly applicable to those known in the art without modification except as explicitly stated. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or ideas thus formed are all deemed to be part of the original disclosure or original description of the present invention, and should not be deemed to be a new matter which has not been disclosed or contemplated herein, unless such combination is clearly unreasonable by those skilled in the art.
The present invention is further illustrated by, but not limited to, the following examples.
Drawings
Fig. 1 is a schematic flow chart of a method for recovering vinyl acetate in an EVOH production process.
Fig. 1 is a marked illustration:
101 is a first rectifying column feed stream;
102 is a first heavies stream;
103 is a first rectification overhead gas stream;
104 is a first rectifying column overhead condensate stream;
105 is a first heavy phase stream;
106 is a first light phase stream;
107 is a first light phase sub-stream one;
108 is a first light phase sub-stream two;
109 is a second light phase stream;
110 is a second heavy phase stream;
111 is a second rectification overhead gas stream;
112 is a vinyl acetate product stream;
113 is a third heavies stream;
114 is make-up water;
C1 is a first rectifying tower;
C2 is a second rectifying tower;
H1 is a heat exchanger;
V1 is a phase separator;
V2 is a condensate collector.
In fig. 1, a first rectifying tower feed stream 101 of a mixture of vinyl acetate and methanol containing impurities is sent to a first rectifying tower C1, a first heavy component stream 102 is obtained at the tower bottom, a first rectifying tower top gas stream 103 is obtained at the tower top, and a first rectifying tower top condensate stream 104 is obtained after the first rectifying tower top gas stream 103 is condensed by a heat exchanger H1; the first rectifying column overhead condensate stream 104 is fed to a phase separator V1 for separation into a first light phase stream 106 comprising mainly vinyl acetate and a first heavy phase stream 105 comprising mainly water; the first heavy phase stream 105 and make-up water 114 are combined and sent to the top of the first rectifying column C1 as a reflux stream; the first light phase stream 106 is divided into two streams, one stream returns to the upper part of the first rectifying tower C1 to serve as a first light phase sub-stream I107, and the other first light phase sub-stream II 108 serves as a light phase extraction stream to be sent to a condensate collector V2 to be separated into a second light phase stream 109 mainly containing vinyl acetate and a second heavy phase stream 110; the second light phase stream 109 is sent to a second rectifying tower C2, the top of the second rectifying tower is obtained by separation, a second rectifying tower top gas stream 111 is obtained by separation, a vinyl acetate product stream 112 is obtained by side line extraction, a third heavy component stream 113 is obtained by tower bottom, and the third heavy component stream 113 is returned to the first rectifying tower C1.
FIG. 2 is a schematic flow chart of a process for recovering vinyl acetate of comparative example 2.
Fig. 2 label description:
201 is a first rectifying column feed stream;
202 is a first heavies stream;
203 is the first rectification overhead gas stream;
204 is a first rectifying column overhead condensate stream;
205 is a first heavy phase stream;
206 is a first light phase stream;
207 is the first light phase sub-stream one;
208 is a first light phase sub-stream two;
209 is a second rectification overhead gas stream;
210 is a second rectification column overhead condensate stream;
211 is a third rectification overhead gas stream;
212 is a vinyl acetate product stream;
213 is the second rectifying column bottom effluent stream;
214 is makeup water;
215 is the second light phase substream one;
216 is a second heavy phase stream;
217 is the second light phase substream two;
218 is the third rectification column bottom effluent stream;
c21 is a first rectifying tower;
c22 is a second rectifying tower;
c23 is a third rectifying tower;
H21 is a first heat exchanger;
H22 is a second heat exchanger;
v21 is a first phase separator;
v22 is the second phase separator.
In fig. 2, a first rectifying tower feed stream 201 of a mixture of vinyl acetate and methanol containing impurities is sent to a first rectifying tower C21, a first heavy component stream 202 is obtained at the tower bottom, a first rectifying tower top gas stream 203 is obtained at the tower top, and a first rectifying tower top condensate stream 204 is obtained after the first rectifying tower top gas stream 203 is condensed by a heat exchanger H21; the first rectifying overhead condensate stream 204 is fed to a first phase separator V21 for separation into a first light phase stream 206 comprising mainly vinyl acetate and a first heavy phase stream 205 comprising mainly water; the first heavy phase stream 205 and make-up water 214 are combined and sent to the top of the first rectifying column C21 as a reflux stream; the first light phase stream 206 is split into two streams, one stream is returned to the upper part of the first rectifying tower C21 as a first light phase sub-stream 207, and the other first light phase sub-stream two 208 is sent to the second rectifying tower C22 as a light phase extraction stream; the second rectifying tower top obtains a second rectifying tower top gas stream 209, a second rectifying tower top condensate stream 210 is obtained after the second rectifying tower top is condensed by a heat exchanger H22, a tower bottom is a second rectifying tower bottom discharge stream 213, and a vinyl acetate product stream 212 is obtained by measuring. The second rectifying overhead condensate stream 210 is fed to a second phase separator V22 and separated into a second light phase sub-stream one 215 comprising predominantly vinyl acetate and a second light phase sub-stream two 217 and a second heavy phase stream 216 comprising predominantly water. The first light phase sub-stream 215 is sent to the upper part of a second rectifying tower C22 to be used as reflux, the second light phase sub-stream 217 is sent to a third rectifying tower C23, a third rectifying tower top gas stream 211 and a third rectifying tower bottom discharging stream 218 are obtained at the top of the tower, and the third rectifying tower bottom discharging stream 218 is sent to a second phase splitter V22.
Detailed Description
The present invention is described in detail below with reference to specific embodiments, and it should be noted that the following embodiments are only for further description of the present invention and should not be construed as limiting the scope of the present invention, and some insubstantial modifications and adjustments of the present invention by those skilled in the art from the present disclosure are still within the scope of the present invention.
According to a preferred embodiment of the present invention, the method for recovering vinyl acetate comprises the steps of:
a) The mixed material flow of the vinyl acetate and the methanol containing impurities is sent to a first rectifying tower, a first heavy component material flow containing the methanol and the water is obtained at the tower bottom, a first tower top gas material flow is obtained at the tower top, the first tower top gas material flow is condensed by a first heat exchanger to obtain a first tower top liquid material flow, the first tower top liquid material flow is sent to a phase separator to be separated into a first light phase material flow mainly containing the vinyl acetate and a first heavy phase material flow mainly containing the water, the first heavy phase material flow is returned to the top of the first rectifying tower to be used as reflux, the first light phase material flow is divided into two parts, 0-50wt% of the first light phase material flow is returned to the top of the first rectifying tower to be used as reflux, and the rest of the first light phase material flow II is sent to a condensate collector.
B) The first light phase sub-stream II is sent to a condensate collector and separated into a second light phase stream mainly containing vinyl acetate and a second heavy phase stream mainly containing water, the second light phase stream is sent to a second rectifying tower, and the second heavy phase stream returns to the upper part of the first rectifying tower.
C) And separating the second light phase material flow in a second rectifying tower, obtaining a second tower top material flow containing impurities at the tower top, obtaining a vinyl acetate product material flow at the middle side line of the tower, obtaining a third heavy component material flow at the tower bottom, and returning the third heavy component material flow to the upper part of the first rectifying tower.
In the technical scheme of the invention, the operating pressure of the first rectifying tower is 0-250 KPaG, preferably 0-200 KPaG.
In the technical scheme of the invention, the operating pressure of the second rectifying tower is 0-250 KPaG, preferably 0-200 KPaG.
In the technical scheme of the invention, the ratio of the water in the second heavy phase flow to the water in the second light phase sub-flow is more than 0.9, preferably more than 0.92 in percentage by weight.
The technical scheme of the invention is adopted by taking a crude vinyl acetate stream with a flow of 11000kg/h as a reference, and is illustrated by examples.
[ Example 1]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate, and the process flow is shown in figure 1.
The operation pressure of the first rectifying tower is 200KPaG, the temperature of the top of the tower is 88.8 ℃, the temperature of the tower bottom is 114.7 ℃, and the number of tower plates N is 41.
The second rectifying tower has operation pressure of 190KPaG, tower top temperature of 95.5 deg.c, tower bottom temperature of 109.3 deg.c, tower plate number of N40 and side line of 35.
The cooling temperature of the first rectifying tower top gas stream is 20 ℃, the cooling temperature of the second rectifying tower top gas stream is 40 ℃, the discharging temperature of the vinyl acetate product is 40 ℃, the ratio of water in the second heavy phase stream to water in the first light phase sub-stream II is 0.95, the first light phase sub-stream I is 15wt% of the first light phase stream, and the partition board is between 15 th and 36 th plates.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.88%, and the total energy consumption is 956.49kg standard oil/h.
[ Example 2]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 180KPaG, the tower top temperature is 86.4 ℃, the tower bottom temperature is 112.6 ℃, and the tower plate number N is 41.
The second rectifying tower has operation pressure of 170KPaG, tower top temperature of 93.3 deg.c, tower bottom temperature of 106.7 deg.c, tower plate number of N40 and side line of 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.89%, and the total energy consumption is 940.24kg standard oil/h.
[ Example 3]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
the operating pressure of the first rectifying tower is 120KPaG, the temperature of the top of the tower is 78 ℃, the temperature of the bottom of the tower is 105.6 ℃, and the number of tower plates N is 41.
The second rectifying tower has operation pressure of 110KPaG, tower top temperature of 89.25 deg.c, tower bottom temperature of 97.9 deg.c, tower plate number of N40 and side line of 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.89%, and the total energy consumption is 886.43kg standard oil/h.
[ Example 4]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 100KPaG, the temperature of the top of the tower is 74.7 ℃, the temperature of the tower bottom is 103 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 90KPaG, the temperature of the top of the tower is 82.5 ℃, the temperature of the tower bottom is 94.5 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.90%, and the total energy consumption is 866.80kg standard oil/h.
[ Example 5]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 80KPaG, the temperature of the top of the tower is 71.1 ℃, the temperature of the tower bottom is 100.1 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 70KPaG, the temperature of the top of the tower is 79.2 ℃, the temperature of the tower bottom is 90.9 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.91%, and the total energy consumption is 846.64kg standard oil/h.
[ Example 6]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 60KPaG, the temperature of the top of the tower is 67.7 ℃, the temperature of the tower bottom is 97 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 50KPaG, the temperature of the top of the tower is 75.6 ℃, the temperature of the tower bottom is 87 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.92%, and the total energy consumption is 827.59kg standard oil/h.
[ Example 7]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
the operating pressure of the first rectifying tower is 40KPaG, the temperature of the top of the tower is 65.2 ℃, the temperature of the tower bottom is 93.7 ℃, and the number of tower plates N is 41.
The second rectifying tower has operation pressure of 30KPaG, tower top temperature of 71.5 deg.c, tower bottom temperature of 82.7 deg.c, tower plate number of N40 and side line of 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.95%, and the total energy consumption is 810.80kg standard oil/h.
[ Example 8]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
the operating pressure of the first rectifying tower is 20KPaG, the temperature of the top of the tower is 63.7 ℃, the temperature of the tower bottom is 89.9 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 10KPaG, the temperature of the top of the tower is 66.8 ℃, the temperature of the tower bottom is 77.8 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.97%, and the total energy consumption is 797.03kg standard oil/h.
[ Example 9]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operation pressure of the first rectifying tower is 200KPaG, the temperature of the top of the tower is 88.8 ℃, the temperature of the tower bottom is 114.7 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 10KPaG, the temperature of the top of the tower is 66.8 ℃, the temperature of the tower bottom is 77.8 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.97%, and the total energy consumption is 946.11kg standard oil/h.
[ Example 10]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 100KPaG, the temperature of the top of the tower is 74.7 ℃, the temperature of the tower bottom is 103 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 10KPaG, the temperature of the top of the tower is 66.8 ℃, the temperature of the tower bottom is 77.8 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.97%, and the total energy consumption is 860.69kg standard oil/h.
[ Example 11]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operating pressure of the first rectifying tower is 10KPaG, the temperature of the top of the tower is 63.4 ℃, the temperature of the tower bottom is 87.9 ℃, and the number of tower plates N is 41.
The second rectifying tower has operation pressure of 5KPaG, tower top temperature of 65.5 deg.c, tower bottom temperature of 76.5 deg.c, tower plate number of N40 and side line of 20.
The recovery rate of the vinyl acetate is more than 96.5%, the purity of the vinyl acetate is 99.97%, and the total energy consumption is 788.03kg standard oil/h.
[ Comparative example 1]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The embodiment is the same as in example 1, except that:
The operation pressure of the first rectifying tower is 200KPaG, the temperature of the top of the tower is 88.8 ℃, the temperature of the tower bottom is 114.7 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 10KPaG, the temperature of the top of the tower is 66.8 ℃, the temperature of the tower bottom is 77.8 ℃, the number of tower plates N is 40, and the side line extraction position is 35.
The ratio of water in the second heavy phase stream to water in the second light phase sub-stream was 0.89.
The recovery rate of the vinyl acetate is 95.19%, the purity of the vinyl acetate is 99.95%, and the total energy consumption is 1127.11kg standard oil/h.
[ Comparative example 2]
The product stream comprises, in weight percent: 75% of methanol, 24.8% of vinyl acetate, 0.2% of impurity water, acetaldehyde, acetone and methyl acetate. The process flow is shown in fig. 2.
The operating pressure of the first rectifying tower is 100KPaG, the temperature of the top of the tower is 74.7 ℃, the temperature of the tower bottom is 103 ℃, and the number of tower plates N is 41.
The operating pressure of the second rectifying tower is 10KPaG, the temperature of the top of the tower is 68 ℃, the temperature of the bottom of the tower is 77.8 ℃, and the number of tower plates N is 38.
The operating pressure of the third rectifying tower is 10KPaG, the temperature of the top of the tower is 67.1 ℃, the temperature of the bottom of the tower is 70.2 ℃, and the number of tower plates N is 51.
The recovery rate of the vinyl acetate is 96.5%, the purity of the vinyl acetate is 99.96%, and the total energy consumption is 1139.60kg standard oil/h.
Claims (10)
1. A method for recovering vinyl acetate in the production process of ethylene-vinyl alcohol copolymer, comprising the following steps:
a) Rectifying the impurity-containing vinyl acetate and methanol mixed stream to obtain a first heavy component stream containing methanol and water and a gas-phase stream, condensing the gas-phase stream, and then separating the gas-phase stream into a first light-phase stream mainly containing vinyl acetate and a first heavy-phase stream mainly containing water, wherein the first heavy-phase stream is returned to the rectification step as reflux, the first light-phase stream is divided into two streams, and the first light-phase sub-stream I is returned to the rectification step as reflux;
b) A second light phase sub-stream II in the first light phase stream is subjected to liquid-liquid separation to obtain a second light phase stream mainly containing vinyl acetate and a second heavy phase stream mainly containing water, and the second heavy phase stream is returned to the rectification step in the step a);
c) Rectifying the second light phase stream, and separating to obtain an impurity-containing stream, a vinyl acetate stream and a third heavy component stream, wherein the third heavy component stream is returned to the rectifying step in step a).
2. The method according to claim 1, characterized in that in step a):
the content of the vinyl acetate in the mixture flow of the vinyl acetate and the methanol containing the impurities is 15 to 40 weight percent;
The impurity content of the mixture stream of vinyl acetate and methanol containing impurities is less than 0.2wt percent;
The impurity is one or more of acetaldehyde, acetone, methyl acetate and water.
3. The method according to claim 1, characterized in that in step a):
The pressure of rectification is 0-250 KPaG, preferably 0-200 KpaG;
Condensing the gas phase stream to a temperature of 10 to 60 ℃, preferably 15 to 50 ℃;
the first light phase sub-stream is 0 to 50wt%, preferably 5 to 30wt%, of the first light phase stream in weight percent.
4. The method according to claim 1, characterized in that in step a):
The rectification step is returned to the rectification step directly after feeding the make-up water stream, and/or after combining the make-up water stream with other streams returned to the rectification step.
5. The method according to claim 1, characterized in that in step b):
the ratio of water in the second heavy phase stream to water in the second light phase sub-stream is > 0.9, preferably > 0.92.
6. The method according to claim 1, characterized in that in step c):
The pressure of the rectification is 0 to 250KPaG, preferably 0 to 200KPaG.
7. The method according to claim 1, characterized in that in step c):
The rectification is carried out in a rectifying tower, the number of tower plates of the rectifying tower is N, a vertical baffle plate is inserted between the tower plates of 0.1N-0.9N, the area between the tower plates of 0.1N-0.9N of the rectifying tower is divided into two independent areas with equal or unequal areas, and the N is 30-60.
8. The method according to claim 7, wherein:
the inlet of the second light phase material flow entering the rectifying tower and the outlet of the vinyl acetate material flow extracted from the side line of the rectifying tower are respectively arranged at two sides of the partition board.
9. An apparatus for recovering vinyl acetate in an ethylene-vinyl alcohol copolymer production process for carrying out the method as claimed in any one of claims 1 to 8, comprising:
A first rectifying tower: configured to receive a mixed stream of vinyl acetate and methanol containing impurities, an upper portion receiving a reflux stream, a top discharge gas phase stream, and a bottom discharge first heavy component stream;
A heat exchanger: configured to receive the vapor phase stream and discharge a first overhead condensate stream;
Phase splitter: configured to receive the first overhead condensate stream and discharge a first light phase stream comprising primarily vinyl acetate and a first heavy phase stream comprising primarily water;
Condensate collector: configured to receive a first light phase sub-stream two, with an upper portion discharging a second light phase stream and a lower portion discharging a second heavy phase stream;
and a second rectifying tower: which is configured to receive the second light phase stream, discharge the impurity stream overhead, discharge the third heavies stream from the bottom of the column, and produce a vinyl acetate stream from the middle side of the column.
10. The apparatus according to claim 9, wherein:
the number of the tower plates of the first rectifying tower is 30-60;
the phase separator is a common liquid-liquid phase separator with a baffle or a high-efficiency liquid-liquid phase separator;
the number of the tower plates of the second rectifying tower is between 30 and 60, a vertical baffle plate is inserted between the tower plates of between 0.1 and 0.9, and preferably, the inlet of the second light phase material flow entering the second rectifying tower and the outlet of the vinyl acetate material flow extracted from the side line of the second rectifying tower are respectively arranged at two sides of the baffle plate.
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