JP6943131B2 - Manufacturing method and equipment for organic carboxylic acid aqueous solution - Google Patents

Description

The present invention relates to a method and an apparatus for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating the organic carboxylic acid-containing aqueous solution. That is, the present invention relates to a method and an apparatus for producing an aqueous solution containing a higher concentration of an organic carboxylic acid from an aqueous solution containing an organic carboxylic acid as a raw material.

In the method for industrially producing methacrylic acid, as the first step, isobutylene, tert-butyl alcohol, or a mixture of both is used as a raw material and introduced into a heat exchange type multi-tube reactor together with molecular oxygen. Methacrolein (methacrylic aldehyde) is produced using a phase-contact oxidation reaction. In the second step, this methacrolein or a mixture containing methacrolein produced by the vapor phase catalytic oxidation reaction and the residual raw material isobutylene or tert-butyl alcohol is further subjected to vapor phase catalytic oxidation to produce methacrylic acid. ..

In a plant that produces methacrylic acid using this method, a large amount of exhaust gas derived from the vapor-phase catalytic oxidation reaction step and waste liquid associated with the steps of extracting and purifying methacrylic acid are generated after the reaction. This exhaust gas contains nitrogen derived from the air used, water generated by an oxidation reaction, carbon dioxide, carbon monoxide, aldehydes, and other by-produced organic compounds. On the other hand, the waste liquid includes a large amount of water used in the extraction and purification of methacrylic acid and the recovery process of unreacted raw material methacrolein, as well as acetic acid and other by-product organic substances removed from the reaction gas in the above process. Contains compounds. Conventionally, carbon monoxide, aldehydes, acetic acid, and other by-products organic compounds contained in the exhaust gas and waste liquid from these plants have been removed and detoxified, and the environment such as nitrogen, water, and carbon dioxide has been treated. Only those that are not a concern for contamination are finally discharged.

A direct combustion method is known as a method for treating such exhaust gas and waste liquid. This method is a method of incinerating an organic compound contained in a waste liquid and discharging it as water and carbon dioxide. For example, when applied to a effluent of a methacrylic acid production plant, the effluent contains a large amount of water and therefore has a low concentration of organic compounds. Therefore, when the treatment is performed as it is, a large amount of combustion improver is required as compared with the amount of the waste liquid to be treated, and the treatment cost is high. Therefore, in general, in order to reduce the water concentration in the waste liquid and increase the concentration of organic compounds, a method of pre-concentrating the waste liquid and then incinerating it is adopted as a pretreatment.

Patent Document 1 describes a method for treating exhaust gas generated by the synthesis of an organic compound by a gas phase reaction, and a waste liquid containing a chemical oxygen demand substance (COD substance) derived from the reaction and a large amount of water. A step of concentrating the waste liquid by directly contacting the exhaust gas with the waste liquid containing a large amount of water is provided, and a step of combusting the chemical oxygen demand substance (COD substance) contained in the concentrated waste liquid is provided. Disclosed is a waste liquid and exhaust gas treatment method characterized by the above.

Patent Document 2 discloses a method for isolating pure acetic acid and pure formic acid from an aqueous mixture consisting of acetic acid, formic acid and a high boiling point substance, respectively. In this method, a solvent is used to extract the aqueous mixture, direct the extraction stream to a distillation column, remove the mixture, which is mostly solvent, from the top of the column, and remove the mixture of formic acid, water and solvent from the side outlet. Remove and remove a mixture of acetic acid and high boiling material from the bottom.

Patent Document 3 discloses a method for recovering high-purity acetic acid from acetic acid-containing wastewater by an extraction method using an extraction solvent. In this method, a solvent having the following characteristics (c) to (e), which has been purified by sequentially passing through each of the following steps (a) to (b), is used as at least a part of the extraction solvent. (A) The first step in which the extraction solvent and water are introduced into the extraction solvent recovery tower, and the azeotropic mixture consisting of the extraction solvent and water is taken out as a distillate from the top of the recovery tower. (B) A second step of separating the azeotropic mixture, which is the distillate from the extraction solvent recovery tower, into the solvent phase and the aqueous phase. (C) To form an azeotropic mixture with water. (D) Do not form an azeotropic mixture with acetic acid. (E) Having a boiling point higher than the boiling point of acetic acid.

Patent Document 4 discloses a method for efficiently recovering acetic acid from low-concentration wastewater having an acetic acid content of 5% or less. In this method, a noble metal catalyst is used to heat-decompose the acetic acid-containing wastewater in the presence or absence of an oxygen-containing gas under a pressure at which the wastewater retains a liquid phase, and then the remaining acetic acid is recovered. The wastewater after the heat decomposition treatment is extracted by a drawing agent in the extraction tower.

Patent Document 5 describes a method for producing (meth) acrylic acid, which can extract (meth) acrylic acid from a (meth) acrylic acid aqueous solution with high extraction efficiency when an extraction solvent containing a water-insoluble solvent as a main component is used. Will be disclosed. In this method, in the method for producing (meth) acrylic acid, which comprises an extraction step of bringing the (meth) acrylic acid aqueous solution into contact with the extraction solvent to extract the (meth) acrylic acid, the extraction solvent is added to the total amount of the extraction solvent. On the other hand, it contains 75.0 to 99.5% by mass of a water-insoluble solvent and 0.5 to 5.0% by mass of acetic acid with respect to the total amount of the extraction solvent.

Japanese Unexamined Patent Publication No. 2001-179238 Japanese Patent Application Laid-Open No. 2003-505442 Japanese Unexamined Patent Publication No. 11-228486 Japanese Unexamined Patent Publication No. 9-122663 Japanese Unexamined Patent Publication No. 2009-263351

In the wastewater and exhaust gas treatment method described in Patent Document 1, although a part of the water in the wastewater is transferred to the exhaust gas by gas-liquid contact, most of the carboxylic acid wastewater is evaporated and burned. The residue that did not evaporate is also burned, and both are released to the atmosphere after recovering the exhaust heat.

Although this method recovers waste heat, most of the water contained in the waste water is released into the atmosphere as water vapor, so the amount of water released into the atmosphere and the latent heat of vaporization of the water It can be said that the energy equivalent to the product is lost.

Therefore, the present inventors have focused on the possibility of energy saving if only carboxylic acids such as acetic acid can be burned. Then, we investigated how water and carboxylic acids that azeotrope during evaporation can be treated by a process that separates them with low energy.

An object of the present invention is to provide a method and an apparatus capable of producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating the organic carboxylic acid aqueous solution with low energy consumption.

According to one aspect of the invention
A method for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
(A) A step of bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material to extract the organic carboxylic acid into the extraction phase.
(B) A step of separating the extraction phase obtained from the step (a) into a fraction enriched with an extraction solvent and a fraction enriched with an organic carboxylic acid, and a step (c). A step of separating the extracted residual phase discharged from the extract into a fraction enriched with an extraction solvent and a fraction enriched with water.
A method for producing an organic carboxylic acid-containing aqueous solution containing the above is provided.

According to another aspect of the invention
An apparatus for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
An extractor that extracts an organic carboxylic acid into an extraction phase by bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material.
The extraction solvent recovery device that separates the extraction phase obtained from the extractor into the fraction enriched with the extraction solvent and the fraction enriched with the organic carboxylic acid, and the extraction residual phase discharged from the extractor. Extraction solvent separator, which separates the extraction solvent-enriched fraction and the water-enriched fraction.
An apparatus for producing an organic carboxylic acid-containing aqueous solution containing the above is provided.

According to the present invention, there is provided a method and an apparatus capable of producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating the organic carboxylic acid aqueous solution with low energy consumption.

It is a process flow diagram which shows one form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows another form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus. It is a schematic diagram which shows the structural example of the extractor shown in FIG. It is a process flow diagram which shows one form of a wastewater treatment apparatus. It is a process flow diagram used in Example 1. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus. It is a process flow diagram which shows still another form of the organic carboxylic acid aqueous solution production apparatus.

As used herein, the term "enriching" means increasing the concentration. In the case of "obtaining a fraction enriched with a certain component from a certain fluid", the concentration of the component in the obtained fraction is higher than the concentration of the component in the fluid.

In the method of the present invention, steps (a) to (c) are performed.
(A) A step of bringing an organic carboxylic acid-containing aqueous solution as a raw material into contact with an extraction solvent to extract the organic carboxylic acid into the extraction phase.
(B) A step of separating the extraction phase obtained from the step (a) into a fraction enriched with an extraction solvent and a fraction enriched with an organic carboxylic acid.
(C) A step of separating the extracted residual phase discharged from the step (a) into a fraction enriched with an extraction solvent and a fraction enriched with water.
As the organic carboxylic acid-containing aqueous solution produced by the present invention, a fraction enriched with the organic carboxylic acid separated in the step (b) can be obtained.

An extractor, an extraction solvent recovery device and an extraction solvent separator can be used to perform the steps (a), (b) and (c), respectively.

The extractor is a device that brings an extraction solvent into contact with an aqueous solution containing an organic carboxylic acid to extract the organic carboxylic acid into the extraction phase. Typically, an extraction tower, particularly a liquid contact tower, is used as the extractor.

The extraction solvent recovery device is a device that separates the extraction phase obtained from the extractor into a fraction enriched with an extraction solvent and a fraction enriched with an organic carboxylic acid. Typically, a distillation column can be used as the extraction solvent recovery device. In particular, a fraction enriched with an extraction solvent can be obtained as a distillate component of the distillation column, and a fraction enriched with an organic carboxylic acid can be obtained as a canned liquid of the distillation column. ..

The extraction solvent separator is a device that separates the extraction residual phase discharged from the extractor into a fraction enriched with an extraction solvent and a fraction enriched with water. Typically, a distillation column can be used as the extraction solvent separator. In particular, a fraction enriched with an extraction solvent can be obtained as a distillate component of the distillation column, and a fraction enriched with water can be obtained as a canned liquid of the distillation column.

Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited thereto. Further, in the following, the present invention will be described mainly by using a case where an extraction column is used as an extractor and a distillation column is used as both an extraction solvent recovery device and an extraction solvent separator.

The extraction tower includes a Kuni-type liquid extractor, curl column (trade name, manufactured by Sumitomo Heavy Industries, Ltd.), MS column (trade name, manufactured by Kansai Kagaku Kikai Seisakusho Co., Ltd.), WINTRAY (trade name, manufactured by Nikki Co., Ltd.). (Manufactured by a company), etc., but WINTRAY is preferable from the viewpoint of energy saving.

Examples of the distillation column include a distillation column whose internal type is a sheave tray, a dual flow tray, a valve cap tray, a regular filling, or an irregular filling. In addition to the above-mentioned conventional distillation column, VC (Vapor compression), MVR (Mechanical Vapor Recompression), TVR (Thermal Vapor Recompression), AHP (Absorption Heat pump), CRHP (Compression Resorption Heat pump), TAHP (Thermo). -Energy-saving distillation columns such as Acoustic Heat Pump), HIDIC (Heat Integrated Distillation column), and DWC (Divided Wall Column) can also be used.

[First form of organic carboxylic acid aqueous solution production apparatus]
A mode of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

The organic carboxylic acid-containing aqueous solution as a raw material to be treated is supplied to the extraction tower A from the line 101, and the extraction solvent is supplied from the line 102. The mass-based ratio of the extraction solvent supplied to the extraction tower A to the organic carboxylic acid-containing aqueous solution supplied to the extraction tower A is preferably 1.0 to 1.5. The extraction operation temperature is preferably 25 ° C to 35 ° C. The supply position of the organic carboxylic acid-containing aqueous solution is set above the supply position of the extraction solvent, the organic carboxylic acid-containing aqueous solution and the extraction solvent come into countercurrent contact in the extraction tower, and the extraction phase is discharged from the top of the tower to the line 103. , The extraction residual phase is discharged to the line 104 from the bottom of the tower. Most of the organic carboxylic acids and most of the extraction solvent are contained in the extraction phase.

The number of theoretical plates of the extraction tower A is preferably one or more, more preferably two or more, and even more preferably three or more, from the combination of the organic carboxylic acid-containing aqueous solution and the extraction solvent used. Further, 12 steps or less is preferable, 11 steps or less is more preferable, and 10 steps or less is further preferable.

The extraction phase is supplied from the line 103 to the first distillation column (extraction solvent recovery device) B, and the fraction enriched with the extraction solvent is discharged from the column top to the line 105 to enrich the organic carboxylic acid. Minutes are discharged from the bottom of the tower to line 106. The organic carboxylic acid-enriched fraction obtained from the bottom of the first distillation column B is the organic carboxylic acid-containing aqueous solution produced by the present invention (the same applies to other forms). The operating pressure of the first distillation column is preferably 0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 103 ° C. to 108 ° C. as the column bottom temperature.

The number of theoretical plates of the first distillation column is preferably 3 or more, more preferably 5 or more, from the combination of the solvent used and the organic carboxylic acid-containing aqueous solution. Further, from the viewpoint of differential pressure and device scale, 30 steps or less is preferable, and 20 steps or less is more preferable.

The extraction residual phase is supplied from line 104 to the second distillation column (extraction solvent separator) C, the extraction solvent-enriched fraction is discharged to line 107, and the water-enriched fraction is discharged to line 108. Is discharged to. The operating pressure of the second distillation column is preferably 0.0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 98 ° C. to 103 ° C. as the column bottom temperature.

The number of theoretical plates of the second distillation column is preferably 3 or more, more preferably 5 or more, from the combination of the solvent used and the organic carboxylic acid-containing aqueous solution. Further, from the viewpoint of differential pressure and device scale, 30 steps or less is preferable, and 20 steps or less is more preferable.

An organic carboxylic acid-containing aqueous solution as a raw material is supplied from line 101 to the organic carboxylic acid aqueous solution producing apparatus shown in FIG. 1, and a concentrated organic carboxylic acid-containing aqueous solution is obtained from line 106. The high-concentration organic carboxylic acid-containing aqueous solution produced in this manner can be treated by a wastewater treatment method such as a combustion method.

The water-enriched fraction obtained from line 108 can be appropriately treated with activated sludge and discharged to the environment.

The extraction solvent-rich fraction obtained from line 105 or 107 is preferably recycled and used for extraction operations, as described in, for example, the second embodiment below, but this is not the case.

[Second form of organic carboxylic acid aqueous solution production apparatus]
Another embodiment of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

In this embodiment, the fraction enriched with the extraction solvent discharged from the top of the first distillation column (extraction solvent recovery device) B is supplied to the extraction column A via the line 205.
Further, a fraction enriched with the extraction solvent discharged from the top of the second distillation column (extraction solvent separator) C is supplied to the extraction column A via the line 207. As a result, the extraction solvent obtained from the tops of the first and second distillation columns can be recycled into the extraction column and effectively utilized. All or part of the extraction solvent-enriched fractions (fluids of lines 205 and 207) obtained from the first and second distillation columns can be recycled to the extraction column.

Except for this point, the process flow shown in FIG. 2 is the same as the process flow shown in FIG.

The mass-based ratio of the extraction solvent supplied to the extraction tower A (the total amount of the extraction solvents in the lines 202, 205 and 207) to the organic carboxylic acid-containing aqueous solution (line 201) supplied to the extraction tower A is 1.0 to 1. 1.5 is preferable. The extraction operation temperature is preferably 25 ° C to 35 ° C. The supply position of the organic carboxylic acid-containing aqueous solution is set above the supply position of the extraction solvent, the organic carboxylic acid-containing aqueous solution and the extraction solvent come into countercurrent contact in the extraction tower A, and the extraction phase is discharged from the top of the column to the line 203. Then, the extraction residual phase is discharged from the bottom of the tower to the line 204. Most of the organic carboxylic acids and most of the extraction solvent are contained in the extraction phase. The number of theoretical plates of the extraction tower A is preferably one or more, more preferably two or more, and even more preferably three or more, from the combination of the organic carboxylic acid-containing aqueous solution and the extraction solvent used. Further, 12 steps or less is preferable, 11 steps or less is more preferable, and 10 steps or less is further preferable. The operating pressure of the first distillation column (extraction solvent recovery device) B is preferably 0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 103 ° C. to 108 ° C. as the column bottom temperature. The operating pressure of the second distillation column (extraction solvent separator) C is preferably 0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 98 ° C. to 103 ° C. as the column bottom temperature. ..

[Third form of organic carboxylic acid aqueous solution production apparatus]
Another embodiment of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

In this form, in the step (a), the step (a1) and the step (a2) are performed.
(A1) The extraction solvent and an aqueous solution containing an organic carboxylic acid as a raw material are contact-mixed, and the obtained mixed solution is separated into a two-phase separation into an extraction solvent phase containing the extraction solvent as a main component and an aqueous phase containing water as the main component. Process to do. The mass-based ratio of the extraction solvent supplied to the step (a1) (device A1) to the organic carboxylic acid-containing aqueous solution supplied to the step (a1) (device A1) is preferably 0.01 to 0.3. The extraction operation temperature is preferably 25 ° C to 35 ° C.
(A2) A step of bringing an extraction solvent and an organic carboxylic acid-containing aqueous solution into contact with each other in an extraction tower to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase. The mass-based ratio of the extraction solvent supplied to the step (a2) (device A2) to the organic carboxylic acid-containing aqueous solution supplied to the step (a2) (device A2) is preferably 1.0 to 1.5. The extraction operation temperature is preferably 25 ° C to 35 ° C.

Here, the term "main component" refers to a component having a concentration of more than 50% by mass.

The extractor used in this form includes a first extraction device A1 and a second extraction device A2. The step (a1) is performed in the apparatus A1, and the details of this apparatus will be described later with reference to FIG.

An organic carboxylic acid-containing aqueous solution as a raw material is supplied from line 301, and an extraction solvent is supplied from line 302 to the apparatus A1 (hence, step (a1)).

The extraction solvent phase obtained from the apparatus A1 (thus step (a1)) is supplied to the apparatus A2 (thus step (a2)) from the line 312 as a surplus extraction solvent. Further, the aqueous phase obtained from the apparatus A1 (hence, the step (a1)) is supplied to the apparatus A2 (therefore, the step (a2)) from the line 311 as an organic carboxylic acid-containing aqueous solution.

Although the step (a2) is performed in the apparatus A2, the same extraction tower as the above-mentioned extraction tower (extraction tower A used for performing the step (a)) can be used as the apparatus A2. However, the extraction solvent is supplied to the apparatus A2 (hence, the step (a2)) from the line 313. Further, the line 312 is connected to the device A2 (in particular, it is connected to the tower top side of the line 311).

The extraction solvent phase obtained from the step (a2), in other words, the extractant phase obtained from the top of the extraction column (device A2) is the "extraction phase obtained from the step (a)" or "obtained from the extractor". The extraction phase is supplied to the extraction solvent recovery device (first distillation column) B via the line 303. The operating pressure of the extraction solvent recovery device (first distillation column) B is preferably 0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 103 ° C. to 108 ° C. as the column bottom temperature.

The extracted residual phase obtained from the step (a2), in other words, the extracted residual phase obtained from the bottom of the extraction tower (device A2) is the "extracted residual phase discharged from the step (a)" or "discharged from the extractor". The extracted residual phase is supplied to the extraction solvent separator (second distillation column) C via the line 304. The operating pressure of the extraction solvent separator (second distillation column) C is preferably 0 kPaG to 5.0 kPaG as the column top pressure, and the operating temperature is preferably 98 ° C. to 103 ° C. as the column bottom temperature.

Similar to the form shown in FIG. 1, from the extraction solvent recovery device (first distillation column) B, the fraction enriched with the extraction solvent is discharged from the column top to the line 305, and the organic carboxylic acid is enriched. The fraction is discharged from the bottom of the tower to the line 306. Further, from the extraction solvent separator (second distillation column) C, the fraction enriched with the extraction solvent is discharged from the top of the column to line 307, and the fraction enriched with water is discharged from the bottom of the column 308. Is discharged to.

Next, an apparatus that can be used as the apparatus A1 will be described with reference to FIG. This device includes a mixer A11 and a decanter A12.

The extraction solvent is supplied from the line 502 to the mixer A11, and the organic carboxylic acid-containing aqueous solution as a raw material is supplied from the line 501. The mass-based ratio of the extraction solvent supplied to the mixer A11 to the organic carboxylic acid-containing aqueous solution supplied to the mixer A11 is preferably 0.01 to 0.3. The extraction operation temperature is preferably 25 ° C to 35 ° C. In the mixer, the extraction solvent and the organic carboxylic acid-containing aqueous solution as a raw material are contact-mixed. The mixer is appropriately equipped with a stirrer (not shown). Inside the decanter, there are two tanks 52 and 53 separated from each other by a weir 51.

The mixture obtained from the mixer is supplied from the line 503 to the decanter A12, flows into the first tank 52, and is separated into an extraction solvent phase (upper layer) and an aqueous phase (lower layer) by settling. The extraction solvent phase flows into the second tank 53 over the weir 51 and is discharged from the second tank (particularly the bottom thereof) to the line 512. On the other hand, the aqueous phase is discharged from the first tank (particularly the bottom thereof) to line 511.

The polymer or solid matter can be discharged to the line 513 from the nozzle 54 of the first tank 52 that opens at the boundary between the extractor phase and the aqueous phase. This polymer or solid is a substance that is dissolved in an aqueous solution containing an organic carboxylic acid and appears at the liquid interface upon contact with a solvent. If a large amount of such a polymer or solid matter accumulates in the extraction tower, for example, the operation of the extraction tower may have to be stopped. Therefore, it is preferable to remove the polymer and solid matter as described above.

When the apparatus A1 shown in FIG. 5 is applied to the process shown in FIG. 3, lines 501, 502, 511 and 512 correspond to lines 301, 302, 311 and 312, respectively.

[Fourth Form of Organic Carboxylic Acid Aqueous Solution Production Equipment]
Another embodiment of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

This form differs from the third form shown in FIG. 3 in the following points.
i) The extraction solvent phase obtained from the apparatus A1 (thus step (a1)) is supplied to the extraction solvent recovery device B (thus step (b)) as an extraction phase via the line 412.
ii) The extraction phase obtained from apparatus A2 (thus step (a2)) is supplied to apparatus A1 (thus step (a1)) via line 403 as an extraction solvent, that is, recycled.
iii) The extraction solvent-enriched fraction obtained from the extraction solvent recovery device B (hence, step (b)) is supplied to the apparatus A2 (hence, step (a2)) as an extraction solvent via line 405. As a result, the extraction solvent can be recycled and effectively utilized.
iv) The extraction solvent enriched fraction obtained from the extraction solvent separator C (thus step (c)) is supplied to the extraction solvent recovery device B (thus step (b)) via line 407.
v) There is no line corresponding to line 313 (a line for supplying the extraction solvent to the apparatus A2 from outside the system).
vi) Line 402 is not used during steady operation. During steady operation, the extraction solvent is supplied to the apparatus A1 from the line 403 instead of from the line 402. Line 402 is used to supply the extraction solvent to device A1 at startup. Line 402 can also be used to replenish the extraction solvent if needed during operation.

For the iv, a diffuser (with a reboiler and no reflux mechanism) is used as the extraction solvent separator C. The operating pressure of the dissipating tower is preferably 0.0 kPaG to 5.0 kPaG as the top pressure, and the operating temperature is preferably 103 ° C to 108 ° C as the bottom temperature. The distillate gas (line 407) from the extraction solvent separator C is supplied to the extraction solvent recovery device B as it is without being condensed. Then, the liquid (mainly the extraction solvent) supplied from the line 412 is also supplied to the extraction solvent recovery tower B.

The form shown in FIG. 4 has the same process flow as the form shown in FIG. 3 except for the above points. Even in this form, the above-mentioned polymer and the like can be removed.

[Fifth Form of Organic Carboxylic Acid Aqueous Solution Production Equipment]
With reference to FIG. 8, when the first and second extraction solvents described in detail later are used, in particular, when a mixed extraction solvent in which the first extraction solvent and the second extraction solvent are mixed is used, the organic carboxyl is used. One form of the acid aqueous solution production apparatus will be described.

The differences between this form and the first form shown in FIG. 1 are as follows, and the present form can be the same as the first form in other respects.

-In this embodiment, as the extraction solvent (line 802), a mixed extraction solvent composed of the first and second extraction solvents is supplied to the extractor A. The first extraction solvent comprises one or a plurality of types selected from the group consisting of ethers of the structural formula 1 described later. The second extraction solvent comprises one or more selected from the group consisting of the aromatic hydrocarbon of structural formula 2, the ketone of structural formula 3, the cyclic ketone of structural formula 4, and the aromatic ketone of structural formula 5, which will be described later. .. The extractor A extracts the organic carboxylic acid contained in the raw material (line 801) into the extraction phase (line 803) containing the mixed extraction solvent.

-In the step (b), the step (b1) and the step (b2) are performed.
(B1) The extraction phase (line 803) obtained from the step (a) is mixed with the fraction (line 805) enriched with the first extraction solvent by using the first extraction solvent recovery device B1 and the second extraction solvent. The step of separating the extraction solvent and the organic carboxylic acid from the second fraction (line 806) enriched with the organic carboxylic acid.
(B2) The second fraction (line 806) obtained from the step (b1) is subjected to a third fraction (line 806) enriched with the second extraction solvent by using the second extraction solvent recovery device B2. A step of separating 813) and a fourth fraction (line 814) enriched with an organic carboxylic acid.

For this purpose, the second fraction obtained from the first extraction solvent recovery device B1 (thus step (b1)) is transferred to the second extraction solvent recovery device B2 (thus step (b2)) via the line 806. , Supply.

The extraction solvent recovery device used in this embodiment includes a first solvent recovery device (first extraction solvent recovery device B1) and a second solvent recovery device (second extraction solvent recovery device B2). including. The first extraction solvent recovery device B1 performs the step (b1), and the second extraction solvent recovery device B2 performs the step (b2).

[Sixth Form of Organic Carboxylic Acid Aqueous Solution Production Equipment]
A modified form of the form shown in FIG. 8 will be described with reference to FIG. The differences between this form and the form shown in FIG. 8 are as follows, and in other respects, this form can be the same as the form shown in FIG.

-In the step (a), the step (a1) and the step (a2) are performed. Therefore, the extractor includes a first extraction device A1 and a second extraction device A2. The steps (a1) and (a2) and the devices A1 and A2 are the same as those shown in FIG.

However, the extraction solvent phase obtained from the apparatus A1 (step (a1)) is sent to the first extraction solvent recovery device B1 (step (b1)) via the line 912, and the extraction phase obtained from the step a or the extractor. Supply as. Further, the extraction phase obtained from the apparatus A2 (hence the step (a2)) is extracted from the step a or the extractor into the first extraction solvent recovery device B1 (hence the step (b1)) via the line 903. Supplied as a phase.

Further, as in the form of FIG. 4, the extraction solvent enriched fraction (line 905) obtained from the extraction solvent recovery device B (step (b)) can be supplied to the apparatus A2 (step (a2)). In this embodiment, such an operation is not performed. Instead, the mixed extraction solvent is supplied to the apparatus A2 (step (a2)) from outside the system via the line 915. The first, third and fourth fractions can be discharged out of the system.

Therefore, the extraction solvent phase obtained from the apparatus A1 (thus step (a1)) is supplied to the first extraction solvent recovery device B1 (thus step (b1)) via the line 912, and the apparatus A2 (thus step (thus step (a1))). The extraction phase obtained from a2)) is supplied via line 903, and a fraction enriched with the extraction solvent obtained from apparatus C (thus step (c)) is supplied via line 907.

As the extraction solvent separator C, it is preferable to use a dissipation tower (with a reboiler and no reflux mechanism). The operating pressure of the dissipating tower is preferably 0.0 kPaG to 5.0 kPaG as the top pressure, and the operating temperature is preferably 103 ° C to 108 ° C as the bottom temperature. The distillate gas (line 907) from the extraction solvent separator C is supplied as it is to the first extraction solvent recovery device B1 without being condensed. Then, the liquid (mainly the extraction solvent) supplied from the line 912 is also supplied to the first extraction solvent recovery tower B1.

The number of theoretical plates of the distillation column of the first extraction solvent recovery device B1 is preferably 3 or more, and more preferably 5 or more, depending on the combination of the solvent used and the organic carboxylic acid aqueous solution. Further, from the viewpoint of differential pressure and device scale, 30 steps or less is preferable, and 25 steps or less is more preferable. The operating pressure of the first extraction solvent recovery device B1 is preferably 0 kPaG to 5 kPaG as the column top pressure and 60 ° C to 65 ° C as the column bottom temperature.

The number of theoretical plates of the distillation column of the second extraction solvent recovery device B2 is preferably 3 or more, and more preferably 5 or more, depending on the combination of the solvent used and the organic carboxylic acid aqueous solution. Further, from the viewpoint of differential pressure and device scale, 30 steps or less is preferable, and 20 steps or less is more preferable. The operating pressure of the second extraction solvent recovery device B2 is preferably 0 kPaG to 5 kPaG as the column top pressure and 100 ° C to 115 ° C as the column bottom temperature.

[7th Form of Organic Carboxylic Acid Aqueous Solution Production Equipment]
A modified form of the form shown in FIG. 9 will be described with reference to FIG. The differences between this form and the form shown in FIG. 9 are as follows, and the present form can be the same as the form shown in FIG. 9 in other respects.

The first fraction obtained from the first extraction solvent recovery device B1 (thus step (b1)) is supplied to the apparatus A1 (thus step (a1)) as an extraction solvent via line 1005. For efficient polymer removal, it is preferable to supply only ethers to apparatus A1 (and thus step (a1)).

The third fraction obtained from the second extraction solvent recovery device B2 (thus step (b2)) is supplied to the apparatus A2 (thus step (a2)) via line 1013 as an extraction solvent. As a result, the extraction solvent can be recycled and effectively utilized.

-Line 1002 is not used during steady operation. During steady operation, the extraction solvent (first fraction) is supplied to the apparatus A1 not from the line 1002 but from the line 1005. Line 1002 is used to supply the mixed extraction solvent or the first extraction solvent to the apparatus A1 at the time of start-up. The line 1002 can also be used to replenish the mixed extraction solvent or the first extraction solvent if necessary during operation. Further, the line 1015 is not used during steady operation. During steady operation, the extraction solvent (third fraction) is supplied to the apparatus A2 from the line 1013 instead of from the line 1015. Line 1015 is used to supply the mixed extraction solvent to device A2 at startup. Line 1015 can also be used to replenish the mixed extraction solvent if needed during operation.

Therefore, in the present embodiment, the first fraction (the fraction enriched with the ether component) obtained from the first extraction solvent recovery device B1 (hence, the step (b1)) is passed through the line 1005 to the apparatus A1 (therefore). Therefore, it is supplied to the step (a1)). Further, the second fraction obtained from the first extraction solvent recovery device B1 (thus step (b1)) is supplied from the line 1006 to the second extraction solvent recovery device B2 (thus step (b2)).

[Eighth Form of Organic Carboxylic Acid Aqueous Solution Production Equipment]
A modified form of the form shown in FIG. 10 will be described with reference to FIG. The differences between this form and the form shown in FIG. 10 are as follows, and in other respects, this form can be the same as the form shown in FIG.

As shown in FIG. 11, the first extraction solvent recovery device B1 has a structure capable of discharging the liquid to the middle stage thereof (for example, the middle stage of the distillation column, that is, the stage that is neither the top nor the bottom of the distillation column). By discharging the fifth fraction enriched with the extraction solvent (particularly the second extraction solvent) from the middle part of the tower of the first extraction solvent recovery device B1, the second extraction solvent recovery device B2 (especially the second extraction solvent) Therefore, the load of the step (b2)) can be reduced. In that case, the fifth fraction is preferably supplied to apparatus A2 (and thus step (a2)) via line 1120.

The second fraction obtained from the first extraction solvent recovery device B1 (thus step (b1)) is supplied to the second extraction solvent recovery device B2 (thus step (b2)) via the line 1106. .. Further, the third fraction (the fraction enriched with the second extraction solvent) obtained from the second extraction solvent recovery device B2 (thus, the step (b2)) passes through the line 1113 and the apparatus A2 (therefore). Therefore, it is supplied to the step (a2)). Further, the fourth fraction (the fraction enriched with the organic carboxylic acid) is discharged to the line 1114 from the bottom of the second extraction solvent recovery device B2 (therefore, the step (b2)). The fluid obtained by combining the fifth fraction (line 1120) and the third fraction (line 1113) of the present embodiment shall be the same as the third fraction (line 1013) of the form shown in FIG. Can be done.

Step (b1) and step (b2) may be performed by one device. In that case, for example, a distillation column is used, and the first fraction (the fraction enriched with ethers) is obtained from the top of the column, and the third fraction (the remaining extraction solvent) is obtained from the middle stage of the column. A fourth fraction (a fraction enriched with an organic carboxylic acid) can be obtained from the bottom of the column.

[Aqueous solution containing organic carboxylic acid as a raw material to be concentrated]
In the present invention, the organic carboxylic acid-containing aqueous solution as a raw material is waste water discharged from the production process of acrylic acid, methacrylic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, maleic acid, phthalic acid, fumaric acid or propionic acid. It is preferably used when it is process wastewater).

The wastewater can contain one or more organic carboxylic acids represented by R-COOH. Here, R is selected from hydrogen and saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms.

In addition, when the waste water contains one or more organic carboxylic acids selected from the group consisting of formic acid, acetic acid, acrylic acid, methacrylic acid, propionic acid, maleic acid, maleic anhydride and α-methyl maleic anhydride. The invention is preferably used. The organic carboxylic acid may be anhydrous.

The total concentration of the organic carboxylic acid in the organic carboxylic acid-containing aqueous solution as a raw material to be concentrated, particularly in the waste water, is preferably 0.1% by mass or more and 50% by mass or less, and is preferably 10% by mass or less. Is more preferable.

Conventionally, a waste liquid combustion device is used by adjusting the concentration of carboxylic acids in the produced organic carboxylic acid-containing aqueous solution to 20% by mass to 50% by mass at least within a range not lower than the total concentration of organic carboxylic acids in waste water. It is preferable to treat with a waste liquid treatment process. Therefore, the concentration (total concentration) of carboxylic acids in the produced organic carboxylic acid-containing aqueous solution after concentration can be set in this range. The concentration after concentration is preferably 20% by mass or more from the viewpoint of energy saving effect, and preferably 25% by mass or less from the viewpoint of operational stability of the waste liquid combustion apparatus.

[Extraction solvent]
From the viewpoint of affinity with carboxylic acids (extraction efficiency from water), water insolubility, and low latent heat of vaporization, the extraction solvent is used.
Structural formula 1: R ^1- O-R ²
(In the formula, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms).
Ether represented by
Structural formula 2: Ph-R ³
(In the formula, Ph represents a phenyl group and R ³ represents an alkyl group having 3 or less carbon atoms).
Aromatic hydrocarbons represented by,
Structural formula 3: R ^4- C (= O) -R ⁵
(In the formula, R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms).
Ketone represented by,
Structural formula 4: CyR = O
(In the formula, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
Cyclic ketone represented by, and structural formula 5: Ph-C (= O) -R ⁶
(In the formula, Ph represents a phenyl group and R ⁶ represents an alkyl group having 3 or less carbon atoms).
It is preferable that it is one or more selected from the group consisting of aromatic ketones represented by.

More preferably, the extraction solvent consists of the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), diisopropyl ether (DIPE), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone. One or more species to be selected.

The extraction solvent is appropriately combined depending on the type of carboxylic acid contained in the aqueous organic carboxylic acid solution. For example, when a highly hydrophilic carboxylic acid such as maleic acid is contained, an extraction solvent containing ketones is preferable, but the organic carboxylic acid. It is preferable to use the first extraction solvent and the second extraction solvent from the viewpoint of achieving both the extraction efficiency of the above and the energy required for separating and removing the solvent. In this case, a mixed extraction solvent of the first extraction solvent and the second extraction solvent can be used.

Here, the first extraction solvent is composed of one or a plurality of types selected from the group consisting of ethers represented by the structural formula 1. The second extraction solvent is selected from the group consisting of aromatic hydrocarbons represented by structural formula 2, ketones represented by structural formula 3, cyclic ketones represented by structural formula 4, and aromatic ketones represented by structural formula 5. It is preferably composed of one or more kinds.

The ratio of the extraction solvents constituting the mixed extraction solvent at this time is the mass ratio of "first extraction solvent: second extraction solvent", and is preferably 6: 4 to 8: 2. This ratio is preferably 8: 2 or less from the viewpoint of extraction efficiency of a highly hydrophilic carboxylic acid such as maleic acid. On the other hand, 6: 4 or more is preferable from the viewpoint of suppressing an increase in the amount of the solvent dissolved on the aqueous phase side and suppressing an increase in energy when recovering and reusing the extraction solvent.

More preferably, the first extraction solvent comprises one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE). The second extraction solvent comprises one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone.

In step (b), the total concentration of carboxylic acid in the distillate component (fraction enriched with the extraction solvent) is 200 mass ppm from the viewpoint of extraction efficiency when this distillate component is reused as the extraction solvent. The following is preferable. As shown in FIGS. 8 to 10, when steps (b1) and (b2) are performed, the total carboxylic acid in the distillate fraction of step (b2), that is, the third fraction (lines 813, 913, 1013). The concentration is preferably 200 mass ppm or less. As shown in FIG. 11, the extraction solvent (particularly the second extraction solvent) is extracted from the middle part of the tower of the first extraction solvent recovery device B1 used in the step (b1) after performing the steps (b1) and (b2). When discharging the fifth fraction enriched with), the total concentration of carboxylic acids in the fluid including the third fraction and the fifth fraction is preferably 200% by mass or less.

In the step (c), from the viewpoint of suppressing solvent loss, the concentration of the extraction solvent in the canned liquid (water-enriched fraction) is preferably 100 mass ppm or less.

[Wastewater treatment]
In the above-mentioned industrial process for producing methacrylic acid, isobutylene and / or tert-butyl alcohol is used as a raw material, and methacrolein (methacrolein) is produced by using a vapor phase catalytic oxidation reaction, and the methacrolein or vapor phase contact is produced. A mixture containing methacrolein produced by an oxidation reaction and residual raw material isobutylene or tert-butyl alcohol is further vapor-phase catalytically oxidized to produce methacrylic acid.

FIG. 6 shows an example of a wastewater treatment process in which wastewater (an aqueous solution containing acetic acid and other by-product organic compounds) from this methacrylic acid production process is treated by combustion.

Wastewater is supplied to the wastewater evaporator 61 from the line 601. The evaporator is also supplied with exhaust gas from the methacrylic acid production process (including nitrogen, water, carbon dioxide, carbon monoxide, aldehydes and other by-product organic compounds) from line 611.

The wastewater evaporator 61 is provided with a reboiler (not shown) at the bottom thereof, and by supplying steam to the reboiler, heat is applied to the reboiler to evaporate the wastewater. Although steam is taken as an example of the heating medium here, a heating medium other than steam can also be used.

The gas obtained from the waste liquid evaporator is supplied to the exhaust gas combustion device 62 via the line 602 together with the air from the line 612 and a part of the combustion gas cooled by the first exhaust heat recovery device 63 from the line 604. NS.

In the exhaust gas combustion device 62, the combustibles contained in the mixed gas are burned.

The combustion gas is supplied from the line 603 to the first exhaust heat recovery device 63, the heat of the combustion gas is recovered as steam, the combustion gas is cooled, and the combustion gas is discharged to the line 605.

The wastewater that has not evaporated in the waste liquid evaporation device 61 is supplied to the concentrated waste liquid combustion device 64 together with the air from the line 613 via the line 606.

In the concentrated waste liquid combustion device 64, combustibles contained in the waste water that has not been evaporated by the waste liquid evaporation device 61 are burned.

The combustion gas is supplied from the line 607 to the second exhaust heat recovery device 65, the heat of the combustion gas is recovered as steam, the combustion gas is cooled, and the combustion gas is discharged to the line 608.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Example 1]
The thermal mass balance of the plant having the process flow shown in FIG. 7 was taken.

This apparatus includes an organic carboxylic acid aqueous solution production apparatus 71 and a wastewater treatment apparatus 72. The manufacturing apparatus 71 is an organic carboxylic acid aqueous solution producing apparatus having the process flow shown in FIG. Further, the wastewater treatment device 72 is a wastewater treatment device having the process flow shown in FIG.

An acetic acid aqueous solution 25 kg / h imitating wastewater from the methacrylic acid production process is supplied to line 701, and the flow is 17 kg / h (line 702) and 8 kg / h (line 703). Branched to.

The flow of line 702 was supplied as a raw material to the organic carboxylic acid aqueous solution production apparatus 71. The process flow of the manufacturing apparatus 71 is as shown in FIG. 4, and the flow of the line 702 of FIG. 7 is supplied to the line 401 of FIG.

-Organic Carboxylic Acid Aqueous Solution Concentration The thermal mass balance of the organic carboxylic acid aqueous solution production apparatus 71 was taken based on the process flow shown in FIG.

MTBE was used as the extraction solvent.
As the extraction tower A2, a countercurrent extraction tower (dispersing the aqueous phase) was used.
As the solvent recovery device B, a distillation column having an operating pressure of 0 kPaG was used.
As the solvent separator C, a dissipation tower having an operating pressure of 0 kPaG was used.

Further, the supply MTBE (line 402) was adjusted so that the MTBE sent from the line 405 to the extraction tower A2 in the steady state was 23.33 kg / h. Since the line 402 is not used in the steady state, the component flow rate is set to zero (0) in Table 4, and "S / U only" is described in the total flow rate column. S / U means startup.

The polymer discharged from the device A1 (particularly the decanter) is discharged in a small amount with long-term operation, and is therefore ignored here. However, the flow rate of the line 513 in Table 6 indicates the flow rate when the polymer is discharged intermittently irregularly according to the amount of the deposited polymer.

In this process, the total steam consumption of the reboiler provided in the solvent recovery device B and the reboiler provided in the solvent separator C was 2.5 kg / h.

In this way, acetic acid-containing wastewater (line 401) as a raw material is concentrated to produce a high-concentration acetic acid aqueous solution (line 406). This high-concentration acetic acid aqueous solution is discharged to line 704 in FIG. On the other hand, the water-enriched fraction obtained in line 408 of FIG. 4 is discharged to line 705 of FIG. The flow of line 705 can be appropriately treated by activated sludge treatment and then discharged to the environment.

The flow of line 704 merged with the flow of line 703 and was supplied from line 706 to the wastewater treatment apparatus 72. The process flow of the wastewater treatment apparatus 72 is as shown in FIG. 6, and the flow of the line 706 of FIG. 7 was supplied to the line 601 of FIG.

-Wastewater treatment For the wastewater treatment device 72, the thermal mass balance was taken based on the process flow shown in FIG.

A gas assuming exhaust gas from the methacrylic acid production process was supplied to line 611. The lines corresponding to the lines 611, 612, and 613 in FIG. 6 are not shown in FIG. 7.

The flow (combustion exhaust gas) obtained in line 605 of FIG. 6 is discharged to line 707 of FIG. The flow obtained in the line 608 of FIG. 6 is also discharged to the line 707 of FIG. 7 in the same manner as the line 605.

The details of the streams shown in FIG. 4 are shown in Table 1. Table 2 shows the main energy consumption of the organic carboxylic acid aqueous solution production apparatus and the wastewater treatment apparatus. Details of the streams shown in FIG. 6 are shown in Table 7.

In the table, the high boiling point substance means a substance that is solid at room temperature and a substance that has a higher boiling point than acetic acid. In addition, cooling, boosting, and depressurizing other than those described have been performed as appropriate, but they are omitted because they do not significantly affect the present invention.

[Comparative Example 1]
In FIG. 7, the entire amount of the acetic acid aqueous solution (line 701) assuming wastewater from the same methacrylic acid production process as in Example 1 was flowed through the line 703 and supplied to the wastewater treatment apparatus 72 via the line 706. Nothing was supplied to line 702. That is, the entire amount of the acetic acid aqueous solution was supplied to the wastewater treatment apparatus 72 without passing through the production apparatus 71.

Except for this, the heat substance balance was taken for the wastewater treatment apparatus 72 in the same manner as in Example 1.

Table 2 shows the main energy consumption of the wastewater treatment equipment. From Table 2, it can be seen that the total steam consumption of Example 1 was significantly smaller than that of Comparative Example 1, and therefore energy saving was achieved.

[Examples 2 to 4]
In Examples 2 to 4, the thermal mass balance was taken for the organic carboxylic acid aqueous solution production apparatus having the process flows shown in FIGS. 1, 2 and 3, respectively. For each example, the organic carboxylic acid-containing aqueous solution to be treated was the same as in Example 1. The thermal mass balance for each example is shown in Tables 3-5, respectively.

[Reference Example 1]
The thermomaterial balance was taken for the device shown in FIG. The organic carboxylic acid-containing aqueous solution supplied to this apparatus as a raw material was the same as in Example 1. The thermal mass balance is shown in Table 6.

[Example 5]
In the organic carboxylic acid aqueous solution production apparatus having the process flow shown in FIG. 4, a mixed extraction solvent in which MTBE and DEE were mixed at a mass ratio of 8: 2 as an extraction solvent was supplied from line 402 to apparatus A1 at the time of start-up. At this time, the supply mixed extraction solvent (line 402) has a mass flow rate of 25.22 kg / h of the fluid (fraction enriched with the mixed extraction solvent) sent from the line 405 to the extraction tower A2 in a steady state. Adjusted to. Since the line 402 is not used in the steady state, the component flow rate is set to zero (0) in Table 8, and "S / U only" is described in the total flow rate column.

The polymer discharged from the device A1 (particularly the decanter) is discharged in a small amount with long-term operation, and is therefore ignored here.

Other than this, it was the same as in Example 1. The thermal mass balance is shown in Table 8.

[Example 6]
In the organic carboxylic acid aqueous solution producing apparatus having the process flow shown in FIG. 4, an organic carboxylic acid aqueous solution containing maleic acid was used as a raw material, and MTBE was used as an extraction solvent. The components of the aqueous organic carboxylic acid solution other than maleic acid are the same as in Example 1.

Further, the supply MTBE (line 402) was adjusted so that the mass flow rate of the fluid (fraction enriched with the extraction solvent) sent from the line 405 to the extraction tower A2 in the steady state was 69.92 kg / h. Since the line 402 is not used in the steady state, the component flow rate is set to zero (0) in Table 9, and "S / U only" is described in the total flow rate column.

The polymer discharged from the device A1 (particularly the decanter) is discharged in a small amount with long-term operation, and is therefore ignored here.

Other than this, it was the same as in Example 1. The thermal mass balance is shown in Table 9.

In this process, the total steam consumption of the reboiler provided in the solvent recovery device B and the reboiler provided in the solvent separator C was 8.3 kg / h (see Table 2).

[Example 7]
A thermal mass balance was taken for the organic carboxylic acid aqueous solution production apparatus having the process flow shown in FIG.

At startup, a mixed extraction solvent in which MTBE and MEK are mixed at a mass ratio of 6: 4 as an extraction solvent is supplied from line 1015 to device A2, and only the first extraction solvent (MTBE) is supplied from line 1002 to device A1. Supplied.
As the extraction tower A2, a countercurrent extraction tower (dispersing the aqueous phase) was used.
As the first extraction solvent recovery device B1 and the second extraction solvent recovery device B2, a distillation column having an operating pressure of 0 kPaG was used.
As the solvent separator C, a dissipation tower having an operating pressure of 0 kPaG was used.

Further, the supply MTBE (line 1002) was adjusted so that the flow rate of the fluid (MTBE-enriched fraction) sent from the line 1005 to the extraction tower A1 in the steady state was 4.0 kg / h. Since the line 1002 is not used in the steady state, the component flow rate is set to zero (0) in Table 10, and "S / U only" is described in the total flow rate column.

The supply mixed extraction solvent (line 1015) was adjusted so that the fluid (mainly the mixed extraction solvent) sent from the line 1013 to the extraction tower A2 in the steady state was 19.57 kg / h. Since the line 1015 is not used in the steady state like the line 1002, the component flow rate is set to zero (0) in Table 10, and "S / U only" is described in the total flow rate column.

The polymer discharged from the device A1 (particularly the decanter) is discharged in a small amount with long-term operation, and is therefore ignored here.

The organic carboxylic acid-containing aqueous solution (line 1001) to be treated was the same as in Example 6 (line 401). The thermal mass balance is shown in Table 10.

In this process, the total steam consumption in the reboiler provided in the first extraction solvent recovery device B1 and the second extraction solvent recovery device B2 and the reboiler provided in the solvent separator C was 6.0 kg / h (see Table 2). ..

Table 2 shows the main energy consumption of the wastewater treatment equipment. From Table 2, it can be seen that the total steam consumption of Examples 5 to 7 was smaller than that of Comparative Example 1, and therefore energy saving was achieved.

The total steam consumption in Example 7 is smaller than the total steam consumption in Example 6, and it is a mixed extraction solvent of the first extraction solvent (particularly ethers) and the second extraction solvent (particularly ketones). It can be seen that carboxylic acid can be efficiently concentrated even from an aqueous carboxylic acid solution containing a highly hydrophilic carboxylic acid such as maleic acid. Further, as can be seen from Tables 9 and 10, the amount of the extraction solvent used in Example 7 is smaller than the amount of the extraction solvent in Example 6, so that the equipment cost such as the pump and the tank and the running cost should be suppressed. Can be done.

A Extractor A1 First extraction device A2 Second extraction device A11 Mixer A12 Decanter B Extraction solvent recovery device B1 First extraction solvent recovery device B2 Second extraction solvent recovery device C Extraction solvent separator 51 Weir 52 First Tank 53 Second tank 54 Nozzle 61 Waste liquid evaporation device 62 Exhaust liquid combustion device 63 First waste heat recovery device 64 Concentrated waste liquid combustion device 65 Second waste heat recovery device 71 Organic carboxylic acid aqueous solution production device 72 Waste water treatment device

Claims (30)

A method for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
(A) A step of bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material to extract the organic carboxylic acid into the extraction phase.
(B) A step of separating the extraction phase obtained from the step (a) into a fraction enriched with an extraction solvent and a fraction enriched with an organic carboxylic acid, and a step (c). A step of separating the extracted residual phase discharged from the extract into a fraction enriched with an extraction solvent and a fraction enriched with water.
Including
Step (a)
(A1) The extraction solvent and an aqueous solution containing an organic carboxylic acid as a raw material are contact-mixed, and the obtained mixed solution is separated into a two-phase separation into an extraction solvent phase containing the extraction solvent as a main component and an aqueous phase containing water as the main component. Process and
(A2) Including a step of bringing the extraction solvent and the organic carboxylic acid-containing aqueous solution into contact with each other in the extraction tower and extracting the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into the extraction phase.
The extraction solvent phase obtained from the step (a1) is supplied to the step (a2) as an extraction solvent.
The aqueous phase obtained from the step (a1) is supplied to the step (a2) as an organic carboxylic acid-containing aqueous solution.
A method for producing an aqueous solution containing an organic carboxylic acid. A method for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
(A) A step of bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material to extract the organic carboxylic acid into the extraction phase.
(B) A step of separating the extraction phase obtained from the step (a) into a fraction enriched with an extraction solvent and a fraction enriched with an organic carboxylic acid, and a step (c). A step of separating the extracted residual phase discharged from the extract into a fraction enriched with an extraction solvent and a fraction enriched with water.
Including
Step (a)
(A1) The extraction solvent and the organic carboxylic acid-containing aqueous solution as a raw material are contact-mixed, and the obtained mixed solution is separated into a two-phase separation into an extraction solvent phase in which the extraction solvent is the main component and an aqueous phase in which water is the main component. And the step of removing the polymer formed between the aqueous phase and the extraction solvent phase, and
(A2) Including a step of bringing the extraction solvent and the organic carboxylic acid-containing aqueous solution into contact with each other in the extraction tower and extracting the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into the extraction phase.
The aqueous phase obtained from the step (a1) is supplied to the step (a2) as an organic carboxylic acid-containing aqueous solution.
The extraction solvent phase obtained from the step (a1) is supplied to the step (b) as an extraction phase.
A method for producing an organic carboxylic acid-containing aqueous solution, in which the extraction phase obtained from the step (a2) is supplied to the step (a1) as an extraction solvent. The method according to claim 1 or 2, wherein in step (b), separation is performed using a distillation column to obtain a fraction enriched with the extraction solvent as a distillate component of the distillation column. The method according to any one of claims 1 to 3, wherein in the step (c), separation is performed using a distillation column to obtain a fraction enriched with the extraction solvent as a distillate component of the distillation column. Method. The method according to any one of claims 1 to 4, wherein a part or all of the extraction solvent obtained from the step (b) and the extraction solvent obtained from the step (c) is supplied to the step (a). The extraction solvent is
Structural formula 1: R ^1- O-R ²
(In the formula, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms).
Ether represented by
Structural formula 2: Ph-R ³
(In the formula, Ph represents a phenyl group and R ³ represents an alkyl group having 3 or less carbon atoms).
Aromatic hydrocarbons represented by,
Structural formula 3: R ^4- C (= O) -R ⁵
(In the formula, R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms).
Ketone represented by,
Structural formula 4: CyR = O
(In the formula, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
Cyclic ketone represented by, and structural formula 5: Ph-C (= O) -R ⁶
(In the formula, Ph represents a phenyl group and R ⁶ represents an alkyl group having 3 or less carbon atoms).
Consists of one or more species selected from the group consisting of aromatic ketones represented by
The method according to any one of claims 1 to 5. The extraction solvent is selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), diisopropyl ether (DIPE), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone. The method according to claim 6, which comprises one or a plurality of types. As the extraction solvent
A first extraction solvent consisting of one or more kinds selected from the group consisting of ethers of the structural formula 1 and
It comprises a second extraction solvent composed of one or more kinds selected from the group consisting of the aromatic hydrocarbon of the structural formula 2, the ketone of the structural formula 3, the cyclic ketone of the structural formula 4, and the aromatic ketone of the structural formula 5. The method according to claim 6, wherein a mixed extraction solvent is used. The first extraction solvent comprises one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE).
The second extraction solvent comprises one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone.
The method according to claim 8. As the extraction solvent, a mixed extraction solvent composed of a first extraction solvent and a second extraction solvent is used.
The first extraction solvent is
Structural formula 1: R ^1- O-R ²
(In the formula, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms).
Consists of one or more species selected from the group consisting of ethers represented by
The second extraction solvent is
Structural formula 2: Ph-R ³
(In the formula, Ph represents a phenyl group and R3 represents an alkyl group having 3 or less carbon atoms).
Aromatic hydrocarbons represented by,
Structural formula 3: R ^4- C (= O) -R ⁵
(In the formula, R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms).
Ketone represented by,
Structural formula 4: CyR = O
(In the formula, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
Cyclic ketone represented by, and structural formula 5: Ph-C (= O) -R ⁶
(In the formula, Ph represents a phenyl group and R ⁶ represents an alkyl group having 3 or less carbon atoms).
Consists of one or more species selected from the group consisting of aromatic ketones represented by
The step (a) includes a step of extracting the organic carboxylic acid into an extraction phase containing the mixed extraction solvent.
Step (b) is
(B1) The extraction phase obtained from the step (a) is a second fraction enriched with the first extraction solvent and a second fraction enriched with the second extraction solvent and the organic carboxylic acid. The process of separating into fractions and
(B2) The second fraction obtained from the step (b1) is divided into a third fraction enriched with the second extraction solvent and a fourth fraction enriched with an organic carboxylic acid. The method according to any one of claims 1 to 4, which comprises a step of separating. The first fraction is supplied to the step (a1) as an extraction solvent, and the first fraction is supplied to the step (a1).
The third fraction is supplied to step (a2) as an extraction solvent.
The method according to claim 10. The first extraction solvent comprises one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE).
The second extraction solvent comprises one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone.
The method according to claim 10 or 11. Claim that the organic carboxylic acid-containing aqueous solution as a raw material is waste water discharged from the production process of acrylic acid, methacrylic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, maleic acid, phthalic acid, fumaric acid or propionic acid. The method according to any one of 1 to 12. The wastewater contains one or more organic carboxylic acids represented by R-COOH.
Here, R is selected from hydrogen and saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms, and the total concentration of organic carboxylic acids in the waste water is 0.1 to 50% by weight.
The method according to claim 13 , wherein the amount of the extraction solvent used in the step (a) is 0.1 to 10.0% by mass with respect to the wastewater. The waste water contains one or more organic carboxylic acids selected from the group consisting of formic acid, acetic acid, acrylic acid, methacrylic acid, propionic acid, maleic acid, maleic anhydride and α-methylmaleic anhydride.
The total concentration of organic carboxylic acids in wastewater is 0.1 to 50% by weight.
The method according to claim 13 , wherein the amount of the extraction solvent used in the step (a) is 0.1 to 10.0% by mass with respect to the wastewater. An apparatus for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
An extractor that extracts an organic carboxylic acid into an extraction phase by bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material.
The extraction solvent recovery device that separates the extraction phase obtained from the extractor into the fraction enriched with the extraction solvent and the fraction enriched with the organic carboxylic acid, and the extraction residual phase discharged from the extractor. Extraction solvent separator, which separates the extraction solvent-enriched fraction and the water-enriched fraction.
Including
The extractor
A mixer that catalytically mixes an extraction solvent and an aqueous solution containing an organic carboxylic acid as a raw material.
A decanter that separates the mixed solution obtained from the mixer into an extraction solvent phase whose main component is an extraction solvent and an aqueous phase whose main component is water. An opening is provided between the extraction solvent phase and the aqueous phase. Includes a decanter with a nozzle for
A line that supplies the extraction solvent phase obtained from the decanter to the extraction tower as an extraction solvent,
It has a line for supplying the aqueous phase obtained from the decanter to the extraction tower as an organic carboxylic acid-containing aqueous solution.
Equipment for producing an aqueous solution containing an organic carboxylic acid. An apparatus for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material.
An extractor that extracts an organic carboxylic acid into an extraction phase by bringing the extraction solvent into contact with an aqueous solution containing an organic carboxylic acid as a raw material.
The extraction solvent recovery device that separates the extraction phase obtained from the extractor into the fraction enriched with the extraction solvent and the fraction enriched with the organic carboxylic acid, and the extraction residual phase discharged from the extractor. Extraction solvent separator, which separates the extraction solvent-enriched fraction and the water-enriched fraction.
Including
The extractor
A mixer that catalytically mixes an extraction solvent and an aqueous solution containing an organic carboxylic acid as a raw material.
A decanter that separates the mixed solution obtained from the mixer into an extraction solvent phase whose main component is an extraction solvent and an aqueous phase whose main component is water. An opening is provided between the extraction solvent phase and the aqueous phase. It includes a decanter provided with a nozzle to be used, and an extraction tower in which an extraction solvent is brought into contact with an organic carboxylic acid-containing aqueous solution to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase.
A line for supplying the aqueous phase obtained from the decanter to the extraction tower as an organic carboxylic acid-containing aqueous solution,
A line that supplies the extraction solvent phase obtained from the decanter to the extraction solvent recovery device as an extraction solvent,
It has a line for supplying the extraction phase obtained from the extraction tower to the mixer as an extraction solvent.
Equipment for producing an aqueous solution containing an organic carboxylic acid. The apparatus according to claim 16 or 17 , wherein the extraction solvent recovery device is a distillation column configured to obtain a fraction enriched with the extraction solvent as a distillate component. The apparatus according to any one of claims 16 to 18 , wherein the extraction solvent separator is a distillation column configured to obtain a fraction enriched with the extraction solvent as a distillate component. The apparatus according to any one of claims 16 to 19 , further comprising a line for supplying a part or all of the extraction solvent obtained from the extraction solvent recovery device and the extraction solvent obtained from the extraction solvent separator to the extractor. The extraction solvent is
Structural formula 1: R ^1- O-R ²
(In the formula, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms).
Ether represented by
Structural formula 2: Ph-R ³
(In the formula, Ph represents a phenyl group and R ³ represents an alkyl group having 3 or less carbon atoms).
Aromatic hydrocarbons represented by,
Structural formula 3: R ^4- C (= O) -R ⁵
(In the formula, R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms).
Ketone represented by,
Structural formula 4: CyR = O
(In the formula, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
Cyclic ketone represented by, and structural formula 5: Ph-C (= O) -R ⁶
(In the formula, Ph represents a phenyl group and R ⁶ represents an alkyl group having 3 or less carbon atoms).
Consists of one or more species selected from the group consisting of aromatic ketones represented by
The device according to any one of claims 16 to 19. The extraction solvent is selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), diisopropyl ether (DIPE), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone. 21. The apparatus of claim 21, comprising one or more of these. The extraction solvent
A first extraction solvent consisting of one or more kinds selected from the group consisting of ethers of the structural formula 1 and
It comprises a second extraction solvent composed of one or more kinds selected from the group consisting of the aromatic hydrocarbon of the structural formula 2, the ketone of the structural formula 3, the cyclic ketone of the structural formula 4, and the aromatic ketone of the structural formula 5. The device according to claim 21 , which is a mixed extraction solvent. The first extraction solvent comprises one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE).
The second extraction solvent comprises one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone.
The device according to claim 23. As the extraction solvent, a mixed extraction solvent composed of a first extraction solvent and a second extraction solvent is used.
The first extraction solvent is
Structural formula 1: R ^1- O-R ²
(In the formula, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms).
Consists of one or more species selected from the group consisting of ethers represented by
The second extraction solvent is
Structural formula 2: Ph-R ³
(In the formula, Ph represents a phenyl group and R3 represents an alkyl group having 3 or less carbon atoms).
Aromatic hydrocarbons represented by,
Structural formula 3: R ^4- C (= O) -R ⁵
(In the formula, R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms).
Ketone represented by,
Structural formula 4: CyR = O
(In the formula, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
Cyclic ketone represented by, and structural formula 5: Ph-C (= O) -R ⁶
(In the formula, Ph represents a phenyl group and R ⁶ represents an alkyl group having 3 or less carbon atoms).
Consists of one or more species selected from the group consisting of aromatic ketones represented by
The extractor is configured to extract the organic carboxylic acid into the extraction phase containing the mixed extraction solvent.
The extraction solvent recovery device
The extraction phase obtained from the extractor is separated into a first fraction enriched with the first extraction solvent and a second fraction enriched with the second extraction solvent and organic carboxylic acid. The first extraction solvent recovery device and
The second fraction obtained from the first extraction solvent recovery device is divided into a third fraction enriched with the second extraction solvent and a fourth fraction enriched with an organic carboxylic acid. The apparatus according to any one of claims 16 to 19 , which includes a second extraction solvent recovery device for separation. A line for supplying the first fraction to the mixer as an extraction solvent, and
25. The apparatus according to claim 25 , which has a line for supplying the third fraction to an extraction tower as an extraction solvent. The first extraction solvent comprises one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE).
The second extraction solvent comprises one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone.
The device according to claim 25 or 26. Claim that the organic carboxylic acid-containing aqueous solution as a raw material is waste water discharged from the production process of acrylic acid, methacrylic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, maleic acid, phthalic acid, fumaric acid or propionic acid. The apparatus according to any one of 16 to 27. The wastewater contains one or more organic carboxylic acids represented by R-COOH.
Here, R is selected from hydrogen and saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms.
The total concentration of organic carboxylic acids in wastewater is 0.1 to 50% by weight.
The amount of the extraction solvent used in the extractor is 0.1 to 10.0% by mass with respect to the wastewater.
28. The apparatus of claim 28. The waste water contains one or more organic carboxylic acids selected from the group consisting of formic acid, acetic acid, acrylic acid, methacrylic acid, propionic acid, maleic acid, maleic anhydride and α-methylmaleic anhydride.
The total concentration of organic carboxylic acids in wastewater is 0.1 to 50% by weight.
The amount of the extraction solvent used in the extractor is 0.1 to 10.0% by mass with respect to the wastewater.
28. The apparatus of claim 28.

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