CN116199576A - Method for refining acrylic acid - Google Patents
Method for refining acrylic acid Download PDFInfo
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- CN116199576A CN116199576A CN202310223557.0A CN202310223557A CN116199576A CN 116199576 A CN116199576 A CN 116199576A CN 202310223557 A CN202310223557 A CN 202310223557A CN 116199576 A CN116199576 A CN 116199576A
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- acrylic acid
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The present invention relates to a method for refining acrylic acid, comprising: the mixed gas containing acrylic acid is in countercurrent contact with a crude acrylic acid solution containing acetic acid from the top of a product tower in a light component removing tower, and the gas which is not liquefied rises to the bottom of a washing tower; part of acetic acid water liquid extracted from the upper part of the washing tower is cooled and then returned to the top of the washing tower, the other part of acetic acid water liquid is directly returned to the packing at the lower section of the washing tower, and water, acetic acid and other inert gases which are not condensed in the washing tower are sent to a waste gas treatment device or at least partially returned to a reaction unit for recycling; wherein the operation temperature of the top of the washing tower is 55-65 ℃, and a desalted water supplementing pipeline is arranged on the washing tower; and the solution at the bottom of the light component removal tower passes through a reboiler in the middle of the product tower, and enters the top of the product tower after being cooled to be used as reflux of the product tower. The invention saves steam consumption, does not use other solvents, does not need to discharge waste water, avoids environmental pollution, saves energy and reduces emission.
Description
The present application claims priority from chinese patent application No. 202310014183.1, the contents of which are incorporated herein by reference.
Technical Field
The invention relates to the technical field of acrylic acid refining, in particular to a method for refining acrylic acid.
Background
Acrylic acid contains active double bond and carboxyl functional group, is especially suitable for preparing high water absorption material, dispersing agent, flocculating agent and the like, and is widely used in a plurality of fields of chemical fiber, textile, coating and the like. In the existing acrylic acid production process, a propylene gas phase oxidation method is widely used, the reaction is divided into two steps, the propylene is oxidized into acrolein in the first step, the acrolein is oxidized into acrylic acid in the second step, an acrylic acid gas phase mixture is obtained at the outlet of a reactor, the main components of the acrylic acid gas phase mixture comprise acrylic acid gas, nitrogen, aldehyde compounds, carboxylic acid compounds, carbon dioxide, carbon monoxide, oxygen and the like, and the acrylic acid gas phase mixture is subjected to a refining separation system to obtain an acrylic acid product.
At present, three main methods for separating the acrylic acid gas phase are commonly used: organic solvent absorption rectification technology, azeotropic rectification technology and extractive rectification technology.
The solvent absorption and rectification technology has the advantages of short flow and low energy consumption; the method has the defects that the solvent is required to absorb the acrylic acid, the operation temperature is high, the acrylic acid is easy to polymerize, and the operation period is short. In patent CN1165808A, a mixture of diphenyl ether and biphenyl is used as an absorbent to absorb acrylic acid, and then rectification is performed to separate out purer acrylic acid, which requires the use of solvents harmful to the environment, and expensive polymerization inhibitors are added to prevent polymerization of acrylic acid in each step.
CN1865216a provides a "process for azeotropic refining of acrylic acid and recovery of acetic acid", in which ethylcyclohexane and toluene, ethyl propionate and toluene ligands are used as entrainers in azeotropic distillation of acrylic acid. The process method has higher dehydration rate and acetic acid removal rate, but has higher energy consumption, and the entrainer is a plurality of material ligands, so that more components to be separated are introduced into the system, the separation difficulty is also improved, and the separation energy consumption is increased; the organic film is a three-stage reverse osmosis film, so that the equipment cost is high, the service life is limited, periodic replacement is required, and the equipment cost and the operation cost are increased.
The energy consumption of extraction and rectification is low, but the flow is long, the investment cost is high, meanwhile, each tower is required to be added with a polymerization inhibitor to prevent the polymerization of acrylic acid, and the addition amount of the polymerization inhibitor is more. In patent CN1241892C it is proposed to separate acrylic acid from an aqueous solution by using an extractant. The residence time of the acrylic acid in the equipment is long, and the acrylic acid is easier to polymerize under the heated state to block the equipment.
CN102775295a discloses a method for purifying acrylic acid, which comprises two technological processes of an absorption tower and a purification tower. The method has relatively simple flow and reduces equipment investment cost and operation cost. However, the acrylic acid content in the tail gas at the top of the absorption tower is higher (about 0.3 wt%) and the propylene unit consumption is increased, so that the production cost is increased more.
Disclosure of Invention
The invention provides a method for refining acrylic acid, which has the characteristics of low energy consumption and no waste liquid.
The present invention provides a method for refining acrylic acid, comprising:
the mixed gas containing acrylic acid obtained from the acrylic acid reactor is in countercurrent contact with a crude acrylic acid solution containing acetic acid from the top of a product tower in a light component removal tower, most of high boiling point substances such as acrylic acid in a gaseous reaction mixture are cooled into a liquid state, and the gas which is not liquefied and the gas on a tower plate of the light component removal tower rise to the bottom of a washing tower together;
a washing tower circulating cooler is arranged at the upper part of the washing tower, a part of acetic acid water liquid extracted from the upper part of the washing tower is cooled and then returned to the top of the washing tower for absorbing acrylic acid contained in ascending gas, the other part of acetic acid water liquid extracted from the upper part of the washing tower is directly returned to the packing at the lower section of the washing tower, and water, acetic acid and other inert gases which are not condensed in the washing tower are sent to a waste gas treatment device or at least partially returned to a reaction unit for recycling; wherein the operation temperature of the top of the washing tower is 55-65 ℃, and a desalted water supplementing pipeline is arranged on the washing tower; and the solution at the bottom of the light component removal tower passes through a reboiler in the middle of the product tower, and enters the top of the product tower after being cooled to be used as reflux of the product tower.
According to one aspect of the invention, the overhead gas phase of the product column is condensed in two stages and returned to the light ends column as the gas coolant.
According to one aspect of the invention, the side line of the product tower is used for obtaining the high-concentration acrylic acid product, the purity is more than 99.5wt%, and the acrylic acid heavy component is obtained in the tower kettle.
According to one aspect of the invention, the operating temperature of the top of the light component removing tower is 45-50 ℃, the operating temperature of the tower kettle is 80-90 ℃, and the operating pressure of the top of the tower is 20-40 Kpa.
According to one aspect of the invention, the operating temperature of the top of the washing tower is 55-65 ℃, the operating temperature of the tower kettle is 75-85 ℃, and the operating pressure of the top of the washing tower is normal pressure.
The beneficial technical effects of the invention are as follows:
controlling the acrylic acid content at the top of the tower to be less than 500ppm by adjusting the temperature at the top of the washing tower to be 55-65 ℃ and adding desalted water;
and the acrylic acid solution at the bottom of the light component removing tower passes through a reboiler in the middle of the product tower, and enters the top of the product tower after being cooled, so that the energy consumption is reduced. The steam consumption of the existing four-tower process is 2.4t/t acrylic acid, the steam consumption of the CN105435805A two-tower process is preferably 1.1t/t acrylic acid, and the steam consumption of the invention can be reduced to 0.87t/t acrylic acid;
acrylic acid solution containing acetic acid is used as quenching medium, acetic acid aqueous solution is used as absorbent to absorb acrylic acid, thereby reducing cost and increasing benefit.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of an energy-saving and emission-reducing process method for refining acrylic acid.
The correspondence between the reference numerals and the component names in fig. 1 is:
e-101-light ends removing tower reboiler, E-102 washing tower circulating cooler, E-103 product tower intermediate reboiler, E-201 product tower condenser, E-202 product tower aftercooler, E-203 product tower reboiler, C-110 light ends removing tower, C-120 washing tower, C-210 product tower, P-101 light ends removing tower bottom circulating pump, P-102 washing tower bottom circulating pump, P-103 washing tower top circulating pump, P-201 product tower reflux pump and P-202 product tower bottom pump.
Detailed Description
The description of the embodiments of this specification should be taken in conjunction with the accompanying drawings, which are a complete description of the embodiments. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated simply or conveniently. Furthermore, portions of the structures in the drawings will be described in terms of separate descriptions, and it should be noted that elements not shown or described in the drawings are in a form known to those of ordinary skill in the art.
Any references to directions and orientations in the description of the embodiments herein are for convenience only and should not be construed as limiting the scope of the invention in any way. The following description of the preferred embodiments will refer to combinations of features, which may be present alone or in combination, and the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.
As shown in FIG. 1, a process for refining acrylic acid comprises an improved process flow of three columns, namely a light ends removal column C-110, a washing column C-120 and a product column C-210, wherein the mixed gas containing acrylic acid obtained from an acrylic acid reactor is in countercurrent contact with a crude acrylic acid solution from the top of the product column C-210 in the light ends removal column C-110, thereby cooling most of the high boiling substances such as acrylic acid in the gaseous reaction mixture into a liquid state. The gas which is not cooled and liquefied rises to the bottom of the scrubber together with the gas on the tray. The operating temperature of the top of the light component removing tower C-110 is 45-50 ℃, the operating temperature of the tower kettle is 80-90 ℃, and the operating pressure of the top of the tower is 20-40 KPa. The top of the washing tower C-120 is provided with a circulating cooler E-102. After separation, acetic acid generated by the reaction is discharged from the top of the washing tower C-120, and the concentration of the acrylic acid aqueous solution in the tower bottom reaches 90wt%; the acrylic acid solution in the bottom of the light component removal tower C-110 passes through a reboiler E-103 in the middle of the product tower, and enters the top of the product tower C-210 after being cooled to be used as reflux of the product tower C-210. The product tower C-210 has no rectification, and the gas phase at the top of the tower returns to the light component removing tower after two-stage condensation to be used as a gas cooling agent. High-concentration acrylic acid product with purity of 99.75wt% can be obtained from the side line of the product tower C-210, and the acrylic acid heavy component is obtained from the tower kettle.
The acrylic acid heavy component is obtained from the tower kettle of the product tower C-210, and the specific composition is shown in the following table 1:
TABLE 1
The mixed gas containing acrylic acid obtained from the acrylic acid reactor is in countercurrent contact with the crude acrylic acid solution containing acetic acid from the top of the product column in the light component removing column, thereby cooling most of the high boiling point substances such as acrylic acid in the gaseous reaction mixture into a liquid state. The gas which is not cooled and liquefied rises to the bottom of the scrubber together with the gas on the tray. The operating temperature of the top of the light component removing tower is 45-50 ℃, the operating temperature of the tower kettle is 80-90 ℃, and the operating pressure of the top of the tower is 20-40 KPa.
The upper part of the washing tower is provided with a circulating cooler E102, a part of acetic acid water liquid pumped out from the upper part is cooled and returned to the top of the tower, acrylic acid contained in rising gas is absorbed, and a part of acrylic acid is directly returned to the lower-stage packing. The uncondensed water, acetic acid and other inert gases can be directly sent to an exhaust gas treatment device, and also can be partially returned to a reaction unit for recycling; after separation, acetic acid and water generated by the reaction are discharged from the top of a washing tower, and an acrylic acid aqueous solution is obtained at the tower bottom; the operation temperature of the top of the washing tower is 55-65 ℃, the operation temperature of the tower kettle is 75-85 ℃, and the operation pressure of the top of the washing tower is normal pressure. There are three degrees of freedom on the top of the scrubber, namely pressure, temperature and composition, respectively, and there is a specific relationship between temperature and composition with the pressure fixed. When the temperature at the top of the washing column exceeds 65 ℃, water and acetic acid which come out from the top of the washing column are increased accordingly, so that the acrylic acid content is increased. And when the temperature at the top of the washing column is lower than 55 ℃, the amount of water and acetic acid which run out is small, but even if the acrylic acid content is small, the quality of the product is not acceptable.
And (3) enabling the acrylic acid solution at the bottom of the light component removal tower to pass through a reboiler in the middle of the product tower, cooling, and then entering the top of the product tower to be used as reflux of the product tower. The product tower has no rectifying section. The gas phase at the top of the tower is returned to the light component removing tower after two-stage condensation and is used as a gas cooling agent. High-concentration acrylic acid products can be obtained from the side line of the product tower, and acrylic acid heavy components can be obtained from the tower bottom. The operating temperature of the top of the light component removing tower is 50-60 ℃, the operating temperature of the tower kettle is 85-95 ℃, and the operating pressure of the top of the tower is 2-8 Kpa. The material at the bottom of the light component removal tower is used as reflux of the top of the product tower, the low temperature is beneficial to the separation of the product tower, and the separation of the product tower is also needed to add heat, and a part of the heat is born by the material at the bottom of the light component removal tower, so that the energy consumption is correspondingly reduced. The steam consumption of the existing four-tower process is 2.4t/t acrylic acid, the steam consumption of the CN105435805A two-tower process is preferably 1.1t/t acrylic acid, and the steam consumption of the invention can be reduced to 0.87t/t acrylic acid.
The beneficial technical effects of the invention are as follows:
1. the acrylic acid content of the tower top can be controlled to be less than 500ppm by adjusting the temperature of the tower top of the washing tower to 55-65 ℃ and supplementing desalted water, so that the product quality meets the requirements.
2. And the acrylic acid solution at the bottom of the light component removing tower passes through a reboiler in the middle of the product tower, and enters the top of the product tower after being cooled, so that the energy consumption is reduced.
3. Acrylic acid solution containing acetic acid is used as quenching medium, acetic acid aqueous solution is used as absorbent to absorb acrylic acid, thereby reducing cost and increasing benefit.
The above description is only one embodiment of the present invention and is not intended to limit the present invention, and various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A method for purifying acrylic acid, comprising:
the mixed gas containing acrylic acid obtained from the acrylic acid reactor is in countercurrent contact with a crude acrylic acid solution containing acetic acid from the top of a product tower (C-210) in a light component removing tower (C-110), most of high boiling point substances such as acrylic acid in the gaseous reaction mixture are cooled into liquid state, and the gas which is not liquefied and the gas on a tower plate of the light component removing tower (C-110) rise to the bottom of a washing tower (C-120);
a washing tower circulating cooler (E-102) is arranged at the upper part of the washing tower (C-120), part of acetic acid water liquid extracted from the upper part of the washing tower (C-120) is cooled and then returned to the top of the washing tower (C-120) for absorbing acrylic acid contained in ascending gas, the other part of acetic acid water liquid extracted from the upper part of the washing tower (C-120) is directly returned to the packing at the lower section of the washing tower (C-120), and water, acetic acid and other inert gases which are not condensed in the washing tower (C-120) are sent to an exhaust gas treatment device or at least partially returned to a reaction unit for recycling;
wherein the operation temperature of the top of the washing tower (C-120) is 55-65 ℃, and a desalted water supplementing pipeline is arranged on the washing tower (C-120);
and the tower bottom solution of the light component removal tower (C-110) passes through a product tower intermediate reboiler (E-103), and enters the top of the product tower (C-210) after being cooled to be used as the reflux of the product tower (C-210).
2. The method for purifying acrylic acid according to claim 1, wherein the overhead gas phase of the product column (C-210) is returned to the light component removal column (C-110) after two-stage condensation as a gas coolant.
3. The method for purifying acrylic acid according to claim 2, wherein the side line of the product column (C-210) gives a high-concentration acrylic acid product having a purity of more than 99.5% by weight, and the bottom of the product column (C-210) gives an acrylic acid heavy component.
4. The method for purifying acrylic acid according to claim 1, wherein the overhead operating temperature of the light component removal column (C-110) is 45 to 50 ℃, the bottom operating temperature of the light component removal column (C-110) is 80 to 90 ℃, and the overhead operating pressure of the light component removal column (C-110) is 20 to 40Kpa.
5. The method for purifying acrylic acid according to claim 1, wherein the operation temperature of the column bottom of the washing column (C-120) is 75 to 85 ℃, and the operation pressure of the column top of the washing column (C-120) is normal pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310014183 | 2023-01-05 | ||
| CN2023100141831 | 2023-01-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116199576A true CN116199576A (en) | 2023-06-02 |
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Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310223557.0A Withdrawn CN116199576A (en) | 2023-01-05 | 2023-03-09 | Method for refining acrylic acid |
| CN202311835884.8A Pending CN118290255A (en) | 2023-01-05 | 2023-12-28 | Method and system for refining acrylic acid |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311835884.8A Pending CN118290255A (en) | 2023-01-05 | 2023-12-28 | Method and system for refining acrylic acid |
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| Country | Link |
|---|---|
| CN (2) | CN116199576A (en) |
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2023
- 2023-03-09 CN CN202310223557.0A patent/CN116199576A/en not_active Withdrawn
- 2023-12-28 CN CN202311835884.8A patent/CN118290255A/en active Pending
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| Publication number | Publication date |
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| CN118290255A (en) | 2024-07-05 |
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Application publication date: 20230602 |