CN114181332A - Method and device for reducing fresh methanol consumption and process energy consumption in EVOH production process - Google Patents
Method and device for reducing fresh methanol consumption and process energy consumption in EVOH production process Download PDFInfo
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 418
- 229920000219 Ethylene vinyl alcohol Polymers 0.000 title claims abstract description 52
- 239000004715 ethylene vinyl alcohol Substances 0.000 title claims abstract description 51
- UFRKOOWSQGXVKV-UHFFFAOYSA-N ethene;ethenol Chemical compound C=C.OC=C UFRKOOWSQGXVKV-UHFFFAOYSA-N 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 40
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 36
- 230000008569 process Effects 0.000 title claims abstract description 30
- 238000005265 energy consumption Methods 0.000 title claims abstract description 16
- 238000006136 alcoholysis reaction Methods 0.000 claims abstract description 397
- 239000000463 material Substances 0.000 claims abstract description 115
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 claims abstract description 96
- 239000003054 catalyst Substances 0.000 claims abstract description 59
- 229920000642 polymer Polymers 0.000 claims abstract description 43
- 238000006243 chemical reaction Methods 0.000 claims abstract description 38
- 239000011344 liquid material Substances 0.000 claims abstract description 7
- 239000007788 liquid Substances 0.000 claims description 61
- 238000007599 discharging Methods 0.000 claims description 9
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 8
- 239000005977 Ethylene Substances 0.000 claims description 8
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 5
- 238000007664 blowing Methods 0.000 claims description 4
- 230000034659 glycolysis Effects 0.000 claims description 4
- 238000004064 recycling Methods 0.000 claims description 2
- 238000009776 industrial production Methods 0.000 abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 77
- 239000007789 gas Substances 0.000 description 77
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 41
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 40
- 238000006116 polymerization reaction Methods 0.000 description 25
- 239000000047 product Substances 0.000 description 22
- 229920005989 resin Polymers 0.000 description 13
- 239000011347 resin Substances 0.000 description 13
- 239000002994 raw material Substances 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 9
- 230000004888 barrier function Effects 0.000 description 9
- 238000007086 side reaction Methods 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000006227 byproduct Substances 0.000 description 6
- 239000004372 Polyvinyl alcohol Substances 0.000 description 5
- 150000002148 esters Chemical group 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- 229920002451 polyvinyl alcohol Polymers 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 238000011143 downstream manufacturing Methods 0.000 description 4
- 239000005038 ethylene vinyl acetate Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 description 4
- 238000005809 transesterification reaction Methods 0.000 description 4
- 239000004952 Polyamide Substances 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 238000009833 condensation Methods 0.000 description 3
- 230000005494 condensation Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229920002647 polyamide Polymers 0.000 description 3
- -1 polyethylene Polymers 0.000 description 3
- 238000010992 reflux Methods 0.000 description 3
- 238000007127 saponification reaction Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- IMROMDMJAWUWLK-UHFFFAOYSA-N Ethenol Chemical compound OC=C IMROMDMJAWUWLK-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 239000005033 polyvinylidene chloride Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920001328 Polyvinylidene chloride Polymers 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 238000012662 bulk polymerization Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000007720 emulsion polymerization reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- RZXDTJIXPSCHCI-UHFFFAOYSA-N hexa-1,5-diene-2,5-diol Chemical compound OC(=C)CCC(O)=C RZXDTJIXPSCHCI-UHFFFAOYSA-N 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 150000004702 methyl esters Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 235000021485 packed food Nutrition 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000002954 polymerization reaction product Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000010557 suspension polymerization reaction Methods 0.000 description 1
- 229940073455 tetraethylammonium hydroxide Drugs 0.000 description 1
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/02—Ethene
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- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention discloses a production method and a device for reducing the consumption of fresh methanol and process energy consumption in an EVOH production process. The method comprises the steps of enabling a material flow containing EVAC and a catalyst material flow to oppositely contact with methanol steam to carry out a first alcoholysis reaction, enabling a polymer liquid material flow and the catalyst material flow obtained by the reaction to oppositely contact with excessive fresh methanol steam to carry out a second alcoholysis reaction to obtain EVOH, wherein most of a gas phase material flow obtained after the second alcoholysis reaction reflows to be used as a main source of the methanol steam in the first alcoholysis reaction, and feeding the catalyst material flow in each alcoholysis reaction by adopting at least two different feeding positions. The method adopts double towers to increase the alcoholysis degree step by step, has the advantages of high alcoholysis degree, small using amount of fresh methanol, low process energy consumption, small equipment investment, good color of EOVH products and easy realization of industrial production.
Description
Technical Field
The invention relates to the field of ethylene-vinyl acetate copolymers, in particular to a production method and a device for reducing the consumption of fresh methanol and the process energy consumption in the production process of EVOH.
Background
Ethylene-vinyl acetate copolymer (EVOH) is a crystalline polymer with a chain molecular structure, is combined with polyvinylidene chloride (PVDC) and Polyamide (PA) to be called as world three-major high-barrier material, and has barrier property which is about ten thousand times that of polyethylene and polypropylene, is 100 times higher than that of PA, and is more than dozens of times higher than that of current common high-barrier material PVDC. EVOH resin has high barrier property to gas, water and chemical solvents, is an excellent barrier material at present, has great advantages in prolonging the storage period of packaged food and enabling plastic packages to further play the aspects of light weight, difficult breakage and the like, has special significance in improving the packaging quality, and has good application prospect and wide market.
Since vinyl alcohol monomers cannot be stably present, EVOH resins can only be obtained by alcoholysis of ethylene-vinyl acetate copolymers (EVAC). EVAC can be generally formed by polymerization by a conventional method such as emulsion polymerization, solution polymerization, bulk polymerization and suspension polymerization, and EVAC polymerization liquid for producing EVOH resin having high barrier property is mainly obtained by solution polymerization because it is easy to control the composition, polymerization degree, branching degree and molecular weight distribution of EVAC. The properties of EVOH depend mainly on the mole fraction of two comonomers, and the gas barrier property, the moisture resistance and the processability of EVOH vary with the ethylene content, and when the ethylene content is increased, the gas barrier property is reduced, the moisture resistance is improved, and the resin is easier to process. When the ethylene content is more than 50%, the gas barrier property is seriously impaired, and thus the ethylene molar content in EVOH is usually 20 to 45%, and the vinyl alcohol molar content is usually 55 to 80%, which combines the gas barrier property of polyvinyl alcohol (PVA) and the processability of polyethylene. EVOH can be regarded as a modified PVA, and the production process of the EVOH is similar to that of PVA, and EVOH manufacturers are leading PVA manufacturers in the world at present.
At present, only a few countries in the world, such as the United states, the Japan and the daily, and the like, produce the EVOH resin, and the production technology is monopolized mainly by the Japan Colorado company (brand EVAL) and the Japan synthetic chemical industry company (brand Soarnol), the production of the EVOH resin is almost blank in China, the product mainly depends on import, and the cost is higher, so that the localization of the EVOH resin is realized, the application range of the EVOH resin in the field of barrier materials is expanded, and the EVOH resin has important social and economic significance for the development, research and application of the EVOH resin.
The alcoholysis process of the EVOH mainly occurs in an alcoholysis tower, and an EVAC polymerization solution from a polymerization unit and methanol steam undergo alcoholysis reaction under an alkaline catalyst, wherein the reaction is a reversible equilibrium reaction. Because reaction raw materials and product all contain polymer, consequently the alcoholysis tower can't set up the reboiler, and the heat that the reaction process required mainly relies on greatly excessive methanol steam to provide, if adopt fresh methanol as reaction raw materials, then can lead to the reaction process fresh methanol quantity big, and subsequent methanol recovery cost is high. In addition, alcoholysis processes typically undergo three types of reactions: transesterification, saponification and side reactions, wherein the transesterification is the main reaction, and the specific reaction equation is shown below. Methyl acetate as a side reaction product is generated in the ester exchange reaction process, the side reaction is gradually accelerated along with the increase of the amount of the methyl acetate, and the consumption of the basic catalyst is also increased, so that the addition amount and the feeding mode of the basic catalyst also have important influence on the alcoholysis process.
Ester exchange reaction:
saponification reaction:
side reaction:
CH3COOCH3+NaOH→CH3OH+CH3COONa。
CN204602161U discloses an alcoholysis reaction system used in an EVOH production process, which comprises an alcoholysis device, a metering pump, a heat exchanger, a pressure stabilizing valve, a condensate tank and an electric heater, wherein the alcoholysis device is simultaneously connected with an alcohol feeding pipeline, a resin feeding pipeline, a catalyst feeding pipeline, a gas inlet pipeline, an EVOH discharge pipeline and a steam discharge pipeline. When alcoholysis is carried out in production, liquid alcohol is continuously added into the lower part of an alcohol decomposer from an alcohol feeding pipeline through a first metering pump, meanwhile, inert gases such as air, nitrogen, methane or helium and the like are added through a gas inlet pipeline, and the pressure is controlled to be 0.2-1 Mpa; continuously adding a certain amount of catalysts such as NaOH or KOH alcohol solution and the like into the upper part of the alcoholysis device from a catalyst feeding pipeline through a second metering pump, and simultaneously continuously adding a polymerization solution obtained by copolymerizing ethylene and vinyl acetate into the upper part of the alcoholysis device through a third metering pump; and (3) carrying out alcoholysis reaction on the ascending pure steam and the resin under the action of a catalyst, allowing the generated EVOH resin to fall to the bottom of an alcoholysis device under the action of gravity, condensing the generated methyl ester from the top of the alcoholysis device to a heat exchanger to form liquid, storing the liquid in a condensate tank, and discharging non-condensable gas out of the system through a pressure stabilizing valve.
CN203269838U discloses an alcoholysis production system of ethylene-vinyl alcohol, which comprises a rectifying tower, a lateral line extraction tank connected with the side surface of the rectifying tower, and an electric heating sleeve connected with the extraction tank; the catalyst storage tank is connected with a catalyst feeding pump, and the feeding pump is connected with the top of the rectifying tower; the polymerization liquid storage tank is connected with a polymerization liquid feeding pump, and the feeding pump is connected with the top of the rectifying tower; the methanol storage tank is connected with a methanol feeding pump, and the feeding pump is connected with the bottom of the rectifying tower; the top of the rectifying tower is provided with a rectifying outlet.
CN106146720A discloses an alcoholysis method in the preparation process of an ethylene-vinyl alcohol copolymer, which comprises the following steps: (1) purifying and blending alcoholysis raw materials: the alcoholysis raw material is a polymerization reaction product prepared by polymerizing ethylene and vinyl acetate directly in the preparation process of EVOH; heating the alcoholysis raw material to 70-75 ℃, and adding methanol for solvent replacement to ensure that the content of VAC in the alcoholysis raw material is 0.1-3 wt% and the content of water is 0.05-0.3 wt%; then adding methanol for blending to obtain 5-50 wt% of ethylene-vinyl acetate copolymer solution; (2) preparing a catalyst solution: preparing a catalyst solution with the content of 3-10 wt% by mixing the catalyst and methanol, and stirring to fully dissolve the catalyst solution; wherein the catalyst is selected from sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide or tetraethylammonium hydroxide, or a mixed alkali composed of tetramethylammonium hydroxide and sodium hydroxide in a molar ratio of 4.5: 1-14: 1; (3) alcoholysis reaction: in the alcoholysis reaction, controlling the total amount of the catalyst solution and the amount of the ethylene-vinyl acetate copolymer solution in a weight ratio of 1-5: 10; in alcoholysis, under the stirring state that the stirring speed is 150-200 rpm, firstly, uniformly mixing 100 parts by weight of ethylene-vinyl acetate copolymer solution and 5-25 parts by weight of catalyst solution, pre-reacting for 10-30 min at the normal temperature to 40 ℃, then, heating to 65-85 ℃, then, adding the rest catalyst solution, mixing and continuing to react, continuously heating for azeotropy to take out a byproduct, reacting for 1-8 hours until alcoholysis is complete, and finally, squeezing and drying to obtain the EVOH.
Disclosure of Invention
The invention provides a production method and a device for reducing the consumption of fresh methanol and process energy consumption in the EVOH production process, which aim to solve the problem in a targeted manner, can be used for guiding and easily realizing industrial production.
The invention relates to a production method and a device for reducing the consumption of fresh methanol and the process energy consumption in the production process of EVOH, which can be used in the alcoholysis process of EVOH production to realize continuous and efficient alcoholysis reaction, and has the advantages of simple flow, high alcoholysis degree, low consumption of fresh methanol, low process energy consumption, low equipment investment, good color of EOVH products and easy realization of industrial production.
One of the purposes of the invention is to provide a production method for reducing the fresh methanol consumption and the process energy consumption in the EVOH production process, which comprises the steps of enabling a material flow containing EVAC and a catalyst material flow to be in opposite contact with methanol steam for carrying out a first alcoholysis reaction, enabling a polymer liquid material flow and a catalyst material flow obtained by the reaction to be in opposite contact with excessive fresh methanol steam for carrying out a second alcoholysis reaction to obtain EVOH, wherein most of a gas phase material flow obtained after the second alcoholysis reaction reflows to be used as a main source of the methanol steam in the first alcoholysis reaction, and feeding the catalyst material flow in each alcoholysis reaction by adopting at least two different feeding positions.
In the technical scheme of the invention, the material flow containing EVAC and the catalyst material flow are in opposite contact with methanol steam to carry out a first alcoholysis reaction to obtain a polymer liquid with incomplete alcoholysis, and the polymer liquid material flow and the catalyst material flow are in opposite contact with fresh methanol steam to carry out a second alcoholysis reaction until the alcoholysis degree of the obtained EVOH reaches over 99 percent.
Preferably, the technical scheme adopted by the invention comprises the following steps:
1) feeding an EVAC-containing material flow from the upper part of an alcoholysis tower, feeding a catalyst material flow from at least the upper part of the alcoholysis tower and the middle part of the alcoholysis tower respectively, and blowing methanol steam into the bottom of the alcoholysis tower to generate a first alcoholysis reaction;
2) gas phase material flow obtained by the first alcoholysis reaction is taken as top gas of the alcoholysis first tower and discharged from the top of the tower, and polymer liquid material flow which is not subjected to complete alcoholysis is taken as bottom liquid of the alcoholysis first tower and discharged;
3) feeding the bottom liquid of the alcoholysis first tower to the upper part of the alcoholysis second tower, feeding the catalyst material flow at least from the upper part of the alcoholysis second tower and the middle part of the alcoholysis second tower respectively, and blowing excessive fresh methanol steam into the bottom of the alcoholysis second tower to generate a second alcoholysis reaction;
4) gas phase material flow obtained by the second glycolysis reaction is taken as top gas of an alcoholysis second tower and discharged from the top of the tower, wherein most of the gas phase material flow is introduced into the bottom of the alcoholysis first tower and is taken as a main source of methanol steam; and discharging the bottom liquid of the alcoholysis two-tower to obtain the EVOH.
In the technical scheme of the invention, the material flow containing EVAC is EVAC polymer liquid after ethylene and vinyl acetate are removed, and mainly contains EVAC and methanol.
In the technical scheme of the invention, the EVAC content in the EVAC-containing material flow is more than or equal to 20 wt%, and preferably more than or equal to 25 wt%.
In the technical scheme of the invention, the alkaline catalyst is methanol solution of alkali; the concentration of the alkali solution is preferably 2-20 wt%, and more preferably 5-10 wt%.
In the technical scheme of the invention, the alcoholysis degree of the EVOH obtained by the second glycolysis reaction is more than or equal to 99%.
In the technical scheme of the invention, in the step 1), the pressure of the EVAC-containing material flow fed into the alcoholysis tower is 0.3-0.9 MPaG, preferably 0.5-0.8 MPaG;
in the technical scheme of the invention, the pressure of the bottom of the alcoholysis tower is 0.3-0.8 MPaG, preferably 0.3-0.6 MPaG;
in the technical scheme of the invention, the top pressure of the alcoholysis tower is 0.2-0.7 MPaG, and preferably 0.3-0.6 MPaG.
In the technical scheme of the invention, in the step 3), the pressure of the bottom of the alcoholysis second tower is 0.3-0.8 MPaG, and preferably 0.3-0.6 MPaG.
In the technical scheme of the invention, the top pressure of the alcoholysis two-tower is 0.2-0.7 MPaG, and preferably 0.3-0.6 MPaG.
In the technical solution of the present invention, more preferably, the pressure of the alcoholysis second column is greater than the pressure of the alcoholysis first column.
In the technical scheme of the invention, in the step 1), the methanol vapor for the reaction in the alcoholysis one-tower is mainly from the top gas of the alcoholysis two-tower.
In the technical scheme of the invention, the amount of the fresh methanol supplemented by the alcoholysis tower accounts for 0-10 wt% of the total methanol amount of the alcoholysis tower, and preferably 0-5 wt%.
In the technical scheme of the invention, the catalyst material flow is added into the alcoholysis tower in different feeding positions.
According to a preferred embodiment of the present invention, the catalyst streams enter the alcoholysis one column at the upper and middle parts thereof, and the catalyst streams enter the alcoholysis two column at the upper and middle parts thereof, respectively.
In the technical scheme of the invention, the top of the alcoholysis tower discharges a material flow containing reaction by-products, namely methyl acetate and excessive methanol steam, the material flow is condensed to obtain a tower top noncondensable gas material flow and a tower top condensate material flow, and the condensate material flow is completely sent to a downstream process or partially refluxed and returned to the alcoholysis tower; and (2) discharging tower top gas containing a small amount of methyl acetate and a large amount of methanol steam from the top of the alcoholysis second tower, feeding most of the tower top gas into the bottom of the alcoholysis first tower to be used as gas-phase methanol feed, combining the rest part of the tower top gas with the non-condensable gas stream at the top of the alcoholysis first tower, and condensing to obtain a condensed liquid stream and a non-condensable gas stream, wherein the condensed liquid stream is completely fed into a downstream process or partially reflows to return to the alcoholysis second tower.
According to a preferred embodiment of the present invention, the process flow of the production method is as follows:
1) conveying the EVAC polymer liquid material flow from the polymerization unit to an alcoholysis first tower for alcoholysis under an alkaline condition, outputting polymer liquid which is not subjected to complete alcoholysis from the bottom of the alcoholysis first tower, conveying the polymer liquid to an alcoholysis second tower for continuous alcoholysis until the alcoholysis degree reaches more than 99%.
2) The methanol steam at the bottom of the alcoholysis one tower is mainly from the top gas of the alcoholysis two tower, and can be supplemented with no fresh methanol steam or only a small amount of fresh methanol steam.
3) Most of the top gas of the alcoholysis second tower is introduced into the bottom of the alcoholysis first tower to be used as a methanol raw material for alcoholysis and a heat source of the alcoholysis first tower.
4) The alkaline catalyst material is fed from the upper part and the middle part of the alcoholysis first tower respectively, and the alkaline catalyst material is fed from the upper part and the middle part of the alcoholysis second tower respectively.
The invention also aims to provide a device for reducing the consumption of fresh methanol and process energy in the EVOH production process, which is used for carrying out the method and comprises the following steps:
alcoholysis one column: configured to receive an EVAC-containing stream at an upper portion, a catalyst stream at an upper portion and a middle portion, a methanol vapor stream at a bottom portion, an alcoholysis-tower overhead gas stream at a top portion of the tower, and an alcoholysis-tower bottoms stream at a bottom portion of the tower;
alcoholysis two-column: configured to receive an alcoholysis one column bottoms stream at the upper portion, a catalyst stream at the upper and middle portions, a methanol vapor stream at the bottom, an alcoholysis two column overhead gas stream at the top of the column, and an alcoholysis two column bottoms stream at the bottom of the column;
alcoholysis-overhead condenser: configured to receive an alcoholysis-one column overhead gas stream and discharge a condensate and a non-condensable gas;
an alcoholysis second tower top condenser: configured to receive an alcoholysis second column overhead gas stream and a non-condensable gas from an alcoholysis first column condenser and to discharge a condensate and the non-condensable gas;
the apparatus is provided with a conduit for recycling the alcoholysis two column overhead gas stream to the bottom of the alcoholysis one column.
In the technical scheme of the invention, the alcoholysis degree of the bottom liquid discharged from the bottom of the alcoholysis second tower is more than 99%.
In the technical scheme of the invention, empty tower trays of 1-4 m, preferably 2-3 m, are reserved at the upper sections of the feeding positions of the alcoholysis one-tower and the alcoholysis two-tower.
In the present invention, EVAC and EVOH polymers are both relatively viscous, and in particular, increase exponentially with decreasing temperature. Alcoholysis processes typically undergo three types of reactions: transesterification, saponification and side reactions, of which transesterification is the main reaction. Methyl acetate which is a side reaction product is generated in the ester exchange reaction process, the side reaction is gradually accelerated along with the increase of the amount of the methyl acetate, and the consumption of the alkaline catalyst is also increased, so that the addition amount and the feeding mode of the alkaline catalyst also have important influence on the alcoholysis process. In addition, the alcoholysis process of the EVAC mainly occurs in an alcoholysis tower, an alcoholysis reaction is performed on an EVAC polymerization solution from a polymerization unit and counter-current methanol steam under an alkaline catalyst, the reaction is a reversible equilibrium reaction, and therefore in order to obtain an EVOH product with high alcoholysis degree, measures are required to fully remove a small molecular byproduct methyl acetate generated by an ester exchange reaction, and the reaction is promoted to move towards the right. The alcoholysis reaction is reported to be a rapid reaction and a slow reaction, the alcoholysis reaction is rapidly carried out after the alkaline catalyst is added, a large amount of micromolecular by-product methyl acetate is generated, and methyl acetate which cannot be removed at high temperature is easily oxidized into easily colored aldehyde substances, so that an EVOH final product has yellow color phase, poor appearance, odor and the like. Because reaction raw materials and products all contain polymers, the alcoholysis tower can not be provided with a reboiler, heat required in the reaction process is mainly provided by greatly excessive methanol steam, and if fresh methanol is adopted as the reaction raw materials, the fresh methanol consumption in the reaction process is large, and the subsequent methanol recovery cost is also high. Research shows that in the alcoholysis reaction process adopting double-tower cascade, the ester exchange reaction in the alcoholysis double-tower is very small, the content of a side reaction product methyl acetate in the top gas of the tower is very small, and the main component is methanol steam. Therefore, fresh methanol is used as a reaction raw material only in the alcoholysis second tower, the reaction raw material methanol steam of the alcoholysis first tower mainly comes from the top gas of the alcoholysis second tower, and only a small amount of fresh methanol is supplemented; secondly, the alkaline catalyst is divided into different positions and added into the alcoholysis tower, so that the distribution of the catalyst in the alcoholysis tower is improved, the alcoholysis reaction efficiency is increased, and the occurrence of side reactions is reduced. By adopting the design of the invention, on one hand, the consumption of fresh methanol can be obviously reduced, and the consumption can be reduced by about 50%; on the other hand, the steam quantity of the fresh methanol in the alcoholysis first tower is greatly reduced, most of the top gas of the alcoholysis second tower is directly sent to the alcoholysis first tower for supplementing heat sources and raw materials without condensation, so that the process energy consumption in the alcoholysis process is also obviously reduced.
The method of the invention adopts double towers to increase the alcoholysis degree step by step, and has the advantages of high alcoholysis degree, small using amount of fresh methanol, low process energy consumption, small equipment investment, good color of EOVH products and easy realization of industrial production.
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 thus formed are considered part of the original disclosure or original disclosure of the present 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 is a schematic flow chart of a production method for reducing the amount of fresh methanol and the energy consumption of the process in the production process of EVOH according to an embodiment of the present invention.
FIG. 1 depicts the following:
a-alcoholysis one column;
b-alcoholysis two-column;
a C-alcoholysis-one tower top condenser;
d-alcoholysis two-tower top condenser;
1-basic catalyst solution I;
2-an EVAC-containing stream;
3-fresh methanol vapor I;
4-alcoholysis of the bottom liquid of the first column;
5-basic catalyst solution II;
6-alcoholysis of the top gas of the first column;
refluxing the top gas of the 7-alcoholysis second tower;
8-alcoholysis two-tower top gas;
combining the overhead gas in the 9-alcoholysis tower;
the top gas of the 10-alcoholysis tower is non-condensable gas;
11-alcoholysis of the overhead gas condensate of the first column;
12, carrying out alcoholysis on the top gas of the second tower to obtain non-condensable gas;
13-alcoholysis second tower top gas condensate;
14-fresh methanol vapor II;
15-alcoholysis two-tower bottom liquid.
In FIG. 1, a stream 2 containing EVAC enters an alcoholysis tower A from the upper part, meanwhile, a stream 1 containing a basic catalyst solution I is added from the alcoholysis tower A, the stream 1 is divided into two streams and respectively enters the alcoholysis tower A from the upper part and the middle part of the alcoholysis tower A, and no or a small amount of fresh methanol steam I stream 3 is introduced into the bottom of the alcoholysis tower A; carrying out alcoholysis reaction on a material flow containing EVAC and methanol in an alcoholysis tower A under the action of an alkaline catalyst, discharging an alcoholysis tower top gas material flow 6 containing reaction by-products, namely methyl acetate and excessive methanol steam from the top of the tower, condensing the material flow 6 by a alcoholysis tower top condenser C to obtain an alcoholysis tower top gas condensate material flow 11 and an alcoholysis tower top gas noncondensable gas material flow 10, and feeding the material flow 11 to a downstream process or partially refluxing and returning the material flow to the alcoholysis tower A; the bottom of the alcoholysis first tower A is alcoholysis first tower bottom material 4 mainly containing EVOH and EVAC which is not completely alcoholyzed, the material flow 4 is sent to the upper part of the alcoholysis second tower B to be used as feed, meanwhile, material flow 5 of alkaline catalyst solution II is added from the alcoholysis second tower B, the material flow 5 is divided into two parts and enters the alcoholysis second tower B from the upper part and the middle part of the alcoholysis second tower B, and material flow 14 of excessive fresh methanol steam II is added to the bottom of the alcoholysis second tower B; obtaining top gas containing a small amount of methyl acetate and a large amount of methanol steam from the top of an alcoholysis second tower, wherein the top gas is divided into two streams, a small stream of top gas material 8 of the alcoholysis second tower and a noncondensable gas material stream 10 of the top gas of an alcoholysis first tower are combined into a combined top gas material stream 9 of the alcoholysis second tower, the material stream 9 is condensed by a condenser D at the top of the alcoholysis second tower to obtain noncondensable gas 12 of the top gas of the alcoholysis second tower and a condensate material stream 13 of the top gas of the alcoholysis second tower, the material stream 13 is sent to a downstream process or is partially refluxed and returned to the alcoholysis second tower B, and the other reflux material stream 7 of the top gas of the alcoholysis second tower is sent to the bottom of the alcoholysis first tower A to be used as gas-phase methanol feed; discharging the ethanol hydrolysis second tower bottom material flow 15 of the ethanol hydrolysis second tower B for post-treatment, washing and drying to obtain an EVOH product.
FIG. 2 is a schematic flow chart showing a production process of EVOH through alcoholysis of a polymerization solution of EVAC in a comparative example.
FIG. 2 depicts the following:
s1-alcoholysis tower;
s2-alcoholysis two-column;
s3-alcoholysis-tower top condenser;
s4-alcoholysis two-tower top condenser;
101-basic catalyst solution I;
102-an EVAC-containing stream;
103-alcoholysis of the top gas of the first column;
104-alcoholysis tower bottom liquid;
105-fresh methanol vapor I;
106-basic catalyst solution II;
107-fresh methanol vapor II;
108-alcoholysis second tower top gas;
109-alcoholysis tower bottom liquid;
the top gas of the 110-alcoholysis second tower is non-condensable gas;
condensate of the top gas of the 111-alcoholysis second tower;
112-alcoholysis tower top gas is non-condensable gas;
113-alcoholysis of overhead gas condensate from a column.
In FIG. 2, EVAC-containing stream 102 enters alcoholysis one column S1 from above while stream 101 of basic catalyst solution I is added from the top of alcoholysis one column S1, and stream 105 of fresh methanol vapor I is introduced at the bottom of alcoholysis one column S1 in large quantities; carrying out alcoholysis reaction on polymer solution EVAC and methanol in an alcoholysis tower S1 under the action of an alkaline catalyst, discharging an alcoholysis tower top gas stream 103 containing a reaction by-product methyl acetate and excessive fresh methanol steam from the top of the tower, condensing the stream 103 by an alcoholysis tower top condenser S3 to obtain alcoholysis tower top gas condensate 113 and alcoholysis tower top gas noncondensable gas 112, and discharging the alcoholysis tower top gas condensate stream 113 and feeding the same to a downstream system or returning a part of the condensate to the alcoholysis tower S1; the bottom of the first alcoholysis tower S1 is an alcoholysis tower bottom material flow 104 mainly containing EVOH and EVAC which is not completely alcoholyzed, the material flow 104 is sent to the upper part of a second alcoholysis tower S2 to be used as a feed, meanwhile, a material flow 106 of alkaline catalyst solution II is added from the upper part of the second alcoholysis tower S2, and a material flow 107 of excessive fresh methanol steam II is added from the bottom of the second alcoholysis tower S2; obtaining a top gas stream 108 containing a small amount of methyl acetate and a large amount of methanol vapor at the top of the alcoholysis second tower, condensing the stream 108 by a top condenser S4 of the alcoholysis second tower to obtain a top gas condensate stream 111 of the alcoholysis second tower and a top gas noncondensable gas stream 110 of the alcoholysis second tower, wherein the top gas condensate stream 111 of the alcoholysis second tower can be discharged and sent to a downstream system or a part of the top gas condensate stream is refluxed and returned to the alcoholysis second tower S2; and discharging the alcoholysis second tower bottom material flow 109 for post-treatment, washing and drying to obtain an EVOH product.
Detailed Description
While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.
The technical scheme of the invention is adopted by taking a product material flow with a flow of 10000kg/h as a reference, and the description is carried out by embodiments.
[ example 1 ]
The process scheme of this example is shown in FIG. 1, wherein 2.5m empty trays are left at the upper section of the feeding positions of the alcoholysis one-column and alcoholysis two-column.
The EVAC polymerization liquid stream comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 20t/h, and the flow rate of the material flow 7 is 9.5t/h, so that the alcoholysis degree of the EVAC polymer solution in the first alcoholysis tower can reach 98.45%, the content of methyl acetate in the material flow 4 in the tower bottom is 1960ppm, the alcoholysis degree of the EVAC polymer solution in the second alcoholysis tower can reach 99.13%, the content of methyl acetate in the material flow 15 in the tower bottom is 95ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 7128.38 Kw.
[ example 2 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 22t/h, and the flow rate of the material flow 7 is 11.5t/h, so that the alcoholysis degree of the EVAC polymer liquid in the first alcoholysis tower can reach 98.47%, the content of methyl acetate in the material flow 4 in the tower bottom is 1980ppm, the alcoholysis degree of the EVAC polymer liquid in the second alcoholysis tower can reach 99.22%, the content of methyl acetate in the material flow 15 in the tower bottom is 88ppm, and the color of a post-processed product is white. The total fresh methanol consumption was 7841.22 Kw.
[ example 3 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 25t/h, the flow rate of the material flow 7 is 14.5t/h, the alcoholysis degree of EVAC polymer liquid in the first alcoholysis tower can reach 98.48%, the content of methyl acetate in material flow 4 in the tower bottom is 2032ppm, the alcoholysis degree of EVAC polymer liquid in the second alcoholysis tower can reach 99.34%, the content of methyl acetate in material flow 15 in the tower bottom is 76ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 8910.48 Kw.
[ example 4 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 28t/h, the flow rate of the material flow 7 is 17.5t/h, the alcoholysis degree of EVAC polymer liquid in the first alcoholysis tower can reach 98.50%, the content of methyl acetate in material flow 4 in the tower bottom is 2056ppm, the alcoholysis degree of EVAC polymer liquid in the second alcoholysis tower can reach 99.43%, the content of methyl acetate in material flow 15 in the tower bottom is 62ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 9979.74 Kw.
[ example 5 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 30t/h, the flow rate of the material flow 7 is 19.5t/h, the alcoholysis degree of EVAC polymer liquid in the first alcoholysis tower can reach 98.52%, the content of methyl acetate in the material flow 4 in the tower bottom is 2050ppm, the alcoholysis degree of EVAC polymer liquid in the second alcoholysis tower can reach 99.54%, the content of methyl acetate in the material flow 15 in the tower bottom is 56ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 10692.6 Kw.
[ example 6 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 0t/h, fresh methanol steam consumed by the second alcoholysis tower is 32t/h, and the flow rate of the material flow 7 is 21.5t/h, so that the alcoholysis degree of the EVAC polymer liquid in the first alcoholysis tower can reach 98.55%, the content of methyl acetate in the material flow 4 in the tower bottom is 2090ppm, the alcoholysis degree of the EVAC polymer liquid in the second alcoholysis tower can reach 99.64%, the content of methyl acetate in the material flow 15 in the tower bottom is 40ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 11405.4 Kw.
[ example 7 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis tower is 0.37MPaG, and the pressure in the top of the alcoholysis tower is 0.35 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.55MPaG, and the pressure of the top of the alcoholysis second tower is 0.50 MPaG.
The condensation liquid at the top of the alcoholysis first tower and the alcoholysis second tower does not flow back.
Fresh methanol steam consumed by the first alcoholysis tower 3 is 0.5t/h, fresh methanol steam consumed by the second alcoholysis tower 14 is 30t/h, and the flow rate of the material flow 7 is 19.5t/h, so that the alcoholysis degree of the EVAC polymer liquid in the first alcoholysis tower can reach 98.56%, the content of methyl acetate in the material flow 4 in the tower bottom is 2068ppm, the alcoholysis degree of the EVAC polymer liquid in the second alcoholysis tower can reach 99.60%, the content of methyl acetate in the material flow 15 in the tower bottom is 42ppm, and the chroma of a post-processed product is white. The total energy consumption of fresh methanol is 10860.60 Kw.
[ example 8 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis tower is 0.37MPaG, and the pressure in the top of the alcoholysis tower is 0.35 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 1t/h, fresh methanol steam consumed by the second alcoholysis tower is 30t/h, and the flow rate of the material flow 7 is 19.5t/h, so that the alcoholysis degree of the EVAC polymer liquid in the first alcoholysis tower can reach 98.63%, the content of methyl acetate in the material flow 4 in the tower bottom is 2085ppm, the alcoholysis degree of the EVAC polymer liquid in the second alcoholysis tower can reach 99.65%, the content of methyl acetate in the material flow 15 in the tower bottom is 36ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 11049.00 Kw.
[ example 9 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis tower is 0.42MPaG, and the pressure in the top of the alcoholysis tower is 0.40 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.55MPaG, and the pressure of the top of the alcoholysis second tower is 0.50 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 1t/h, fresh methanol steam consumed by the second alcoholysis tower is 30t/h, and the flow rate of the material flow 7 is 19.5t/h, so that the alcoholysis degree of the EVAC polymer solution in the first alcoholysis tower can reach 98.68%, the content of methyl acetate in the material flow 4 in the tower bottom is 2110ppm, the alcoholysis degree of the EVAC polymer solution in the second alcoholysis tower can reach 99.68%, the content of methyl acetate in the material flow 15 in the tower bottom is 32ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 11038.6 Kw.
[ example 10 ]
The implementation is the same as example 1, except that the polymerization liquid stream of EVAC comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 4wt percent by weight.
The pressure in the bottom of the alcoholysis tower is 0.37MPaG, and the pressure in the top of the alcoholysis tower is 0.35 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower is 1t/h, fresh methanol steam consumed by the second alcoholysis tower is 30t/h, the flow rate of the material flow 7 is 19.5t/h, the alcoholysis degree of EVAC polymer liquid in the first alcoholysis tower can reach 98.03%, the content of methyl acetate in material flow 4 in the tower bottom is 2032ppm, the alcoholysis degree of EVAC polymer liquid in the second alcoholysis tower can reach 99.18%, the content of methyl acetate in material flow 15 in the tower bottom is 40ppm, and the chroma of a post-processed product is white. The total fresh methanol consumption was 11049.00 Kw.
[ COMPARATIVE EXAMPLE 1 ]
The process flow of this comparative example is shown in FIG. 1.
The EVAC polymerization liquid stream comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 0.5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.26MPaG, and the pressure in the top of the alcoholysis one tower is 0.24 MPaG.
The pressure in the bottom of the alcoholysis second tower is 0.28MPaG, and the pressure in the top of the alcoholysis second tower is 0.26 MPaG.
Fresh methanol steam consumed by the first alcoholysis tower 105 is 0t/h, fresh methanol steam consumed by the second alcoholysis tower 107 is 30t/h, the alcoholysis degree of EVAC polymer liquid in the first alcoholysis tower can reach 76.51%, the content of methyl acetate in tower bottom material flow 104 is 1750ppm, the alcoholysis degree of EVAC polymer liquid in the second alcoholysis tower can reach 80.20%, and the content of methyl acetate in tower bottom material flow 109 is 500 ppm. The alcoholysis degree of the product is too low, the phenomenon of tower blockage is easy to occur, and the total energy consumption of the fresh methanol is 10500.50 Kw.
[ COMPARATIVE EXAMPLE 2 ]
The process flow of this comparative example is shown in FIG. 2, where a portion of the top condensate of the alcoholysis one and two columns is refluxed.
The EVAC polymerization liquid stream comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
The alcoholysis first tower consumes 14.5t/h of fresh methanol steam material flow 105, the alcoholysis second tower consumes 20t/h of fresh methanol steam material flow 107, the alcoholysis degree of EVAC polymer liquid in the alcoholysis first tower can reach 98.51%, the content of methyl acetate in tower bottom material flow 104 can reach 2050ppm, the alcoholysis degree of EVAC polymer liquid in the alcoholysis second tower can reach 99.37%, the content of methyl acetate in tower bottom material flow 109 can reach 62ppm, and the color of the post-processed product is white. The total fresh methanol consumption was 12296.5 Kw.
[ COMPARATIVE EXAMPLE 3 ]
The process flow of this comparative example is shown in FIG. 2, wherein the top condensates of the alcoholysis one and two columns are not refluxed.
The EVAC polymerization liquid stream comprises, in weight percent: 70 wt% methanol, 30 wt% EVAC copolymer, pressure 0.6 MPaG.
The concentration of the sodium hydroxide lye is 5 weight percent.
The pressure in the bottom of the alcoholysis one tower is 0.32MPaG, and the pressure in the top of the alcoholysis one tower is 0.30 MPaG.
The pressure of the bottom of the alcoholysis second tower is 0.57MPaG, and the pressure of the top of the alcoholysis second tower is 0.55 MPaG.
The condensation liquid at the top of the alcoholysis first tower and the alcoholysis second tower does not flow back.
The alcoholysis degree of the EVAC polymer liquid in the first alcoholysis tower can reach 98.56%, the content of methyl acetate in the tower bottom material flow 104 can reach 2067ppm, the alcoholysis degree of the EVAC polymer liquid in the second alcoholysis tower can reach 99.57%, the content of methyl acetate in the tower bottom material flow 109 can reach 60ppm, and the chroma of the post-processed product is white when the fresh methanol steam material flow 105 consumed by the first alcoholysis tower and the fresh methanol steam material flow 107 consumed by the second alcoholysis tower are 20 t/h. The total fresh methanol consumption was 14078.60 Kw.
Claims (12)
1. A production method for reducing fresh methanol consumption and process energy consumption in an EVOH production process comprises the steps of enabling material flow containing EVAC and catalyst material flow to be in opposite contact with methanol steam to carry out a first alcoholysis reaction, enabling polymer liquid material flow and catalyst material flow obtained through the reaction to be in opposite contact with excessive fresh methanol steam to carry out a second alcoholysis reaction to obtain EVOH, enabling most of gas phase material flow obtained after the second alcoholysis reaction to return to be used as a main source of the methanol steam in the first alcoholysis reaction, and feeding the catalyst material flow in each alcoholysis reaction in a mode of at least two different feeding positions.
2. The production method according to claim 1, characterized by comprising the steps of:
1) feeding an EVAC-containing material flow from the upper part of an alcoholysis tower, feeding a catalyst material flow from at least the upper part of the alcoholysis tower and the middle part of the alcoholysis tower respectively, and blowing methanol steam into the bottom of the alcoholysis tower to generate a first alcoholysis reaction;
2) gas phase material flow obtained by the first alcoholysis reaction is taken as top gas of the alcoholysis first tower and discharged from the top of the tower, and polymer liquid material flow which is not subjected to complete alcoholysis is taken as bottom liquid of the alcoholysis first tower and discharged;
3) feeding the bottom liquid of the alcoholysis first tower to the upper part of the alcoholysis second tower, feeding the catalyst material flow at least from the upper part of the alcoholysis second tower and the middle part of the alcoholysis second tower respectively, and blowing excessive fresh methanol steam into the bottom of the alcoholysis second tower to generate a second alcoholysis reaction;
4) gas phase material flow obtained by the second glycolysis reaction is taken as top gas of an alcoholysis second tower and discharged from the top of the tower, wherein most of the gas phase material flow is introduced into the bottom of the alcoholysis first tower and is taken as a main source of methanol steam; and discharging the bottom liquid of the alcoholysis two-tower to obtain the EVOH.
3. The production method according to claim 2, characterized in that:
in the step 1), the amount of the fresh methanol supplemented to the alcoholysis tower accounts for 0 to 10 wt% of the total methanol amount in the alcoholysis tower, and preferably 0 to 5 wt%.
4. The production method according to claim 2, characterized in that:
in the step 1), the pressure of the EVAC-containing material flow sent into the alcoholysis tower is 0.3-0.9 MPaG, and preferably 0.5-0.8 MPaG; and/or the presence of a gas in the gas,
the pressure of the bottom of the alcoholysis tower is 0.3-0.8 MPaG, preferably 0.3-0.6 MPaG; and/or the presence of a gas in the gas,
the top pressure of the alcoholysis tower is 0.2-0.7 MPaG, preferably 0.3-0.6 MPaG.
5. The production method according to claim 2, characterized in that:
in the step 3), the pressure of the bottom of the alcoholysis second tower is 0.3-0.8 MPaG, preferably 0.3-0.6 MPaG; and/or the presence of a gas in the gas,
the top pressure of the alcoholysis second tower is 0.2-0.7 MPaG, preferably 0.3-0.6 MPaG.
6. The production method according to claim 5, characterized in that:
the pressure of the alcoholysis second tower is greater than the pressure of the alcoholysis first tower.
7. The production method according to any one of claims 1 to 6, characterized in that:
the EVAC-containing material flow is EVAC polymer liquid after ethylene and vinyl acetate are removed, and the material flow comprises EVAC and methanol.
8. The production method according to claim 7, characterized in that:
the EVAC content of the EVAC-containing stream is greater than or equal to 20 wt%, preferably greater than or equal to 25 wt%.
9. The production method according to any one of claims 1 to 6, characterized in that:
the catalyst is methanol solution of alkali;
the concentration of the alkali solution is 2-20 wt%, preferably 5-10 wt%.
10. The production method according to any one of claims 1 to 6, characterized in that:
the alcoholysis degree of the EVOH obtained by the second glycolysis reaction is more than or equal to 99 percent.
11. An apparatus for reducing the amount of fresh methanol and the energy consumption of the process in the production of EVOH, for carrying out the method of any one of claims 1-10, comprising:
alcoholysis one column: configured to receive an EVAC-containing stream at an upper portion, a catalyst stream at an upper portion and a middle portion, a methanol vapor stream at a bottom portion, an alcoholysis-first column overhead gas stream at a top portion of the column, and an alcoholysis-first column bottoms stream at a bottom portion of the column;
alcoholysis two-column: configured to receive an alcoholysis one column bottoms stream at the upper portion, a catalyst stream at the upper and middle portions, a methanol vapor stream at the bottom, an alcoholysis two column overhead gas stream at the top of the column, and an alcoholysis two column bottoms stream at the bottom of the column;
alcoholysis-overhead condenser: configured to receive an alcoholysis-one column overhead gas stream and discharge a condensate and a non-condensable gas;
an alcoholysis second tower top condenser: configured to receive an alcoholysis second column overhead gas stream and an alcoholysis first column non-condensable gas, and to discharge a condensate and the non-condensable gas;
the apparatus is configured with a conduit for recycling the alcoholysis two column overhead gas stream to the bottom of the alcoholysis one column.
12. The apparatus of claim 11, wherein:
an empty tray with the length of 1-4 m is reserved at the upper section of the feeding positions of the alcoholysis one-tower and the alcoholysis two-tower, and the empty tray with the length of 2-3 m is preferred.
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