JP7136258B2 - Method and apparatus for producing organic carboxylic acid aqueous solution - Google Patents

Description

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

In the method for industrially producing methacrylic acid, as a first step, isobutylene or tert-butyl alcohol, or a mixture of both, is introduced as a raw material into a heat exchange multitubular reactor together with molecular oxygen, and gas is A phase catalytic oxidation reaction is used to produce methacrolein (methacrylaldehyde). In the second step, this methacrolein, or a mixture containing the methacrolein produced in the gas-phase catalytic oxidation reaction and the residual raw material isobutylene and tert-butyl alcohol is further subjected to gas-phase catalytic oxidation to produce methacrylic acid. .

In a plant that produces methacrylic acid using this method, a large amount of exhaust gas originating from the gas-phase catalytic oxidation reaction process and waste liquid associated with the extraction and purification processes of methacrylic acid after the reaction are generated. This exhaust gas contains nitrogen derived from the air used, water and carbon dioxide generated in the oxidation reaction, carbon monoxide, aldehyde, and other by-product organic compounds. On the other hand, in the waste liquid, in addition to a large amount of water used for the extraction and purification of methacrylic acid and the recovery of unreacted raw materials such as methacrolein, acetic acid and other organic by-products removed from the reaction gas in the above processes were collected. Contains compounds. Conventionally, carbon monoxide, aldehydes, acetic acid, and other by-product organic compounds contained in exhaust gas and waste liquid from these plants are removed and detoxified, and nitrogen, water, carbon dioxide, etc. Only those that do not contaminate the environment 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 the organic compounds contained in the waste liquid and discharging them as water and carbon dioxide. For example, when applied to the waste liquid of a methacrylic acid manufacturing plant, the waste liquid contains a large amount of water and therefore has a low concentration of organic compounds. Therefore, when the waste liquid is treated as it is, a large amount of the combustion improver is required compared to the amount of the waste liquid to be treated, which increases the treatment cost. Therefore, in general, in order to reduce the water concentration in the waste liquid and increase the organic compound concentration, a method of concentrating the waste liquid in advance as a pretreatment and then incinerating it is adopted.

Patent Document 1 discloses a method for treating exhaust gas generated in the synthesis of an organic compound by a gas phase reaction, as well as a waste liquid containing chemical oxygen-demanding substances (COD substances) derived from the reaction and a large amount of water, A step of directly contacting the exhaust gas with a waste liquid containing a large amount of water to concentrate the waste liquid is provided, and a step of burning chemical oxygen-requiring substances (COD substances) contained in the concentrated waste liquid is provided. Disclosed is a waste liquid and exhaust gas treatment method characterized by:

US Pat. No. 5,300,000 discloses a method for isolating pure acetic acid and pure formic acid, respectively, from an aqueous mixture of acetic acid, formic acid and high-boiling substances. In this method, a solvent is used to extract an aqueous mixture, the extract stream is directed to a distillation column, a mixture of mostly solvent is removed from the top of the column, and a mixture of formic acid, water and solvent is removed from a side draw. Take off and take off a mixture of acetic acid and high boilers 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 properties (c) to (e), which is purified by successively passing through the following steps (a) to (b), is used as at least a part of the extraction solvent. (a) A first step in which an extraction solvent and water are introduced into an extraction solvent recovery tower, and an azeotropic mixture composed of the extraction solvent and water is taken out as a distillate from the top of the recovery tower. (b) A second step of liquid-liquid separation of the azeotropic mixture, which is the distillate from the extraction solvent recovery tower, into a solvent phase and an aqueous phase. (c) forming an azeotrope with water; (d) not form an azeotrope with acetic acid; (e) have a boiling point higher than that of acetic acid;

Patent Document 4 discloses a method for efficiently recovering acetic acid from low-concentration wastewater containing 5% or less acetic acid. In this method, a noble metal catalyst is used to thermally decompose acetic acid-containing waste water in the presence or absence of an oxygen-containing gas under a pressure that keeps the waste water in a liquid phase, and then residual acetic acid is recovered. The wastewater after thermal decomposition treatment is extracted with an extractant in an extraction tower.

Patent Document 5 discloses a method for producing (meth)acrylic acid, which can extract (meth)acrylic acid from an aqueous solution of (meth)acrylic acid with high extraction efficiency when using an extraction solvent containing a water-insoluble solvent as a main component. disclosed. In this method, in the method for producing (meth)acrylic acid including an extraction step of contacting an aqueous solution of (meth)acrylic acid with an extraction solvent to extract (meth)acrylic acid, the extraction solvent is added to the total amount of the extraction solvent. 75.0 to 99.5% by mass of a water-insoluble solvent and 0.5 to 5.0% by mass of acetic acid relative to the total amount of the extraction solvent.

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

In the waste liquid and exhaust gas treatment method described in Patent Document 1, part of the moisture in the waste water is transferred to the exhaust gas by gas-liquid contact, but most of the carboxylic acid waste water is evaporated and burned. Residue that has not evaporated is also burned, and after both recover waste heat, it is released to the atmosphere.

In this method, although waste heat is recovered, most of the water contained in the wastewater is released to the atmosphere as steam. It can be said that the energy corresponding 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, which are azeotroped during evaporation, can be treated by a low-energy separation process.

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

According to one aspect of the invention,
A method for producing an organic carboxylic acid-containing aqueous solution enriched with organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material,
(a) contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution as a raw material to extract the organic carboxylic acid into the extraction phase;
(b) separating the extract phase obtained from step (a) into a fraction enriched in the extracting solvent and a fraction enriched in organic carboxylic acids; and (c) step (a). separating the raffinate phase discharged from the
A method for producing an organic carboxylic acid-containing aqueous solution is provided.

According to another aspect of the invention,
An apparatus for producing an organic carboxylic acid-containing aqueous solution enriched with organic carboxylic acid by concentrating an organic carboxylic acid-containing aqueous solution as a raw material,
an extractor for contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution as a raw material to extract the organic carboxylic acid into an extraction phase;
An extraction solvent collector for separating the extraction phase obtained from the extractor into a fraction enriched in the extraction solvent and a fraction enriched in organic carboxylic acid, and the raffinate phase discharged from the extractor a fraction enriched in extraction solvent and a fraction enriched in water;
an extraction solvent separator to separate into
An apparatus for producing an organic carboxylic acid-containing aqueous solution is provided.

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

1 is a process flow diagram showing one form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing another form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus. FIG. 5 is a schematic diagram showing a structural example of the extractor shown in FIG. 4; 1 is a process flow diagram showing one form of wastewater treatment system; 1 is a process flow diagram used in Example 1. FIG. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus. 4 is a process flow diagram showing still another form of an organic carboxylic acid aqueous solution production apparatus.

As used herein, the term "enrich" means to increase concentration. In the case of "obtaining a fraction enriched in 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 contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution as a raw material to extract the organic carboxylic acid into the extraction phase.
(b) separating the extract phase obtained from step (a) into a fraction enriched in the extraction solvent and a fraction enriched in organic carboxylic acids;
(c) separating the raffinate discharged from step (a) into a fraction enriched in extraction solvent and a fraction enriched in water.
The organic carboxylic acid-enriched fraction separated in step (b) can be obtained as an organic carboxylic acid-containing aqueous solution prepared according to the present invention.

An extractor, an extraction solvent collector and an extraction solvent separator can be used to carry out steps (a), (b) and (c), respectively.

The extractor is a device for contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution to extract the organic carboxylic acid into an extraction phase. Typically, extraction towers, especially liquid-liquid contact towers, are used as extractors.

The extraction solvent recovery device is a device that separates the extraction phase obtained from the extractor into a fraction enriched in the extraction solvent and a fraction enriched in the organic carboxylic acid. Typically, a distillation column can be used as the extraction solvent collector. In particular, a fraction enriched in the extraction solvent can be obtained as the distillate component of this distillation column, and a fraction enriched in organic carboxylic acid can be obtained as the bottom product of this distillation column. .

The extraction solvent separator is a device that separates the raffinate phase discharged from the extractor into an extraction solvent-enriched fraction and a water-enriched fraction. Typically, a distillation column can be used as the extraction solvent separator. In particular, a fraction enriched in the extraction solvent can be obtained as a distillate component of this distillation column, and a fraction enriched in water can be obtained as a bottom product of this distillation column.

The present invention will be described below with reference to the drawings, but the present invention is not limited thereto. In the following, the present invention will be described mainly taking as an example the case where an extraction tower is used as an extractor and a distillation tower is used as both an extraction solvent recovery device and an extraction solvent separator.

The extraction columns include a Kuni-type liquid-liquid extraction apparatus, Karl column (trade name, manufactured by Sumitomo Heavy Industries, Ltd.), MS column (trade name, manufactured by Kansai Chemical Machinery Co., Ltd.), WINTRAY (trade name, manufactured by JGC Corporation). company), but WINTRAY is preferable from the viewpoint of energy saving.

Distillation columns include distillation columns whose internal types are sieve trays, dual flow trays, valve cap trays, regular packings, or random packings. In addition to the above conventional distillation column, VC (Vapor compression), MVR (Mechanical Vapor)
Recompression), TVR (Thermal Vapor Recompression), AHP (Absorption Heat pump)
p), CRHP (Compression Resorption Heat pump), TAHP (Thermo-Acoustic Heat Pump)
ump), HIDIC (Heat Integrated Distillation column), DWC (Divided Wall Column)
It is also possible to use energy-saving distillation columns such as n).

[First Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
One embodiment of an organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

In the extraction tower A, an organic carboxylic acid-containing aqueous solution as a raw material, which is to be treated, is supplied to the line 101.
and the extraction solvent is supplied through 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 was 1.5.
0 to 1.5 are preferred. Further, the extraction operation temperature is preferably 25°C to 35°C. The supply position of the organic carboxylic acid-containing aqueous solution is above the supply position of the extraction solvent, and the organic carboxylic acid-containing aqueous solution and the extraction solvent are in countercurrent contact in the extraction tower, and the extraction phase flows from the top of the tower to the line 10.
3 and the raffinate phase is discharged in line 104 from the bottom of the column. Most of the organic carboxylic acids and most of the extraction solvent are contained in the extraction phase.

The number of theoretical plates in the extraction column A is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, depending on the combination of the organic carboxylic acid-containing aqueous solution and the extraction solvent used. 1 again
2 stages or less are preferable, 11 stages or less are more preferable, and 10 stages or less are even more preferable.

The extraction phase is supplied from line 103 to the first distillation column (extraction solvent recovery device) B, a fraction enriched in the extraction solvent is discharged from the top of the column to line 105, and a fraction enriched in organic carboxylic acid is discharged. The fraction is discharged in line 106 from the bottom of the column. 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 according to the present invention (the same applies to other forms). As the operating pressure of the first distillation column, the top pressure is 0 kPaG
~ 5.0 kPaG is preferable, and the operating temperature is 103 ° C. to 108 ° C. as the tower bottom temperature
is preferred.

The number of theoretical plates in the first distillation column is preferably 3 or more, more preferably 5 or more, depending on the combination of the solvent and the organic carboxylic acid-containing aqueous solution used. In terms of differential pressure and equipment scale, 3
0 stage or less is preferable, and 20 stages or less is more preferable.

The raffinate phase is fed via line 104 to a second distillation column (extraction solvent separator) C, the extraction solvent-enriched fraction is discharged in line 107 and the water-enriched fraction is discharged in line 108. discharged to The operating pressure of the second distillation column is 0.0 kPaG to 5.0 kP as the top pressure
aG is preferred, and the operating temperature is preferably 98° C. to 103° C. as the tower bottom temperature.

The number of theoretical plates in the second distillation column is preferably 3 or more, more preferably 5 or more, depending on the combination of the solvent and the organic carboxylic acid-containing aqueous solution used. In terms of differential pressure and equipment scale, 3
0 stage or less is preferable, and 20 stages 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 manufacturing apparatus shown in FIG. 1, and a concentrated organic carboxylic acid-containing aqueous solution is obtained from line 106 . The highly concentrated organic carboxylic acid-containing aqueous solution thus produced can be treated by a wastewater treatment method such as a combustion method.

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

The extractant-enriched fraction obtained from line 105 or 107 is preferably, but not exclusively, recycled for use in extraction operations, for example as described in the second embodiment below.

[Second Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
Another form of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

In this embodiment, the extraction solvent-enriched fraction discharged from the top of the first distillation column (extraction solvent recovery device) B is supplied to extraction column A via line 205 .
A fraction enriched in the extraction solvent discharged from the top of the second distillation column (extraction solvent separator) C is supplied to the extraction column A through line 207 . As a result, the extraction solvent obtained from the tops of the first and second distillation towers can be recycled to the extraction tower for effective use. first
and the extraction solvent-enriched fraction obtained from the second distillation column (lines 205 and 207
fluid) can be recycled in whole or in part to the extraction column.

Except for this point, the process flow shown in FIG. 2 is similar to the process flow shown in FIG.

The ratio by mass of the extraction solvent supplied to extraction tower A (total amount of extraction solvent in lines 202, 205 and 207) to the organic carboxylic acid-containing aqueous solution (line 201) supplied to extraction tower A is from 1.0 to 1.5 is preferred. In addition, the extraction operation temperature is 25 ° C to 3
5°C is preferred. The supply position of the organic carboxylic acid-containing aqueous solution is above the supply position of the extraction solvent. and the raffinate phase is discharged to line 204 from the bottom of the column. Most of the organic carboxylic acids and most of the extraction solvent are contained in the extraction phase. The number of theoretical plates in the extraction column A is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, depending on the combination of the organic carboxylic acid-containing aqueous solution and the extraction solvent used. 12 steps or less is preferable,
11 stages or less are more preferable, and 10 stages or less are even more 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,
As for the operating temperature, the tower bottom temperature is preferably 103°C to 108°C. The operating pressure of the second distillation column (extraction solvent separator) C is 0 kPaG to 5.0 kP as the top pressure.
aG is preferred, and the operating temperature is preferably 98° C. to 103° C. as the tower bottom temperature.

[Third Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
Another form of the organic carboxylic acid aqueous solution production apparatus will be described with reference to FIG.

In this embodiment, step (a1) and step (a2) are performed in step (a).
(a1) An extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material are contacted and mixed, and the resulting mixture is separated into two phases, an extraction solvent phase containing the extraction solvent as the main component and an aqueous phase containing water as the main component. process to do. Step (a1) for the organic carboxylic acid-containing aqueous solution supplied to step (a1) (apparatus A1)
) The ratio by mass of the extraction solvent supplied to (apparatus A1) is preferably 0.01 to 0.3.
Further, the extraction operation temperature is preferably 25°C to 35°C.
(a2) A step of contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution in an extraction tower to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase. The ratio by mass of the extraction solvent supplied to step (a2) (apparatus A2) to the organic carboxylic acid-containing aqueous solution supplied to step (a2) (apparatus A2) is preferably 1.0 to 1.5. In addition, as the extraction operation temperature, 2
5°C to 35°C is preferred.

Here, the term "main component" refers to a component having a concentration greater than 50% by weight.

The extractors used in this configuration include a first extractor A1 and a second extractor A2.
Step (a1) is performed in apparatus A1, and the details of this apparatus will be described later with reference to FIG.

Apparatus A1 (thus step (a1)) is supplied with an organic carboxylic acid-containing aqueous solution as a raw material from line 301 and with an extraction solvent from line 302 .

The extraction solvent phase obtained from apparatus A1 (thus step (a1)) is fed as excess extraction solvent via line 312 to apparatus A2 (thus step (a2)). Also, device A1
The aqueous phase obtained from (thus step (a1)) is supplied as an organic carboxylic acid-containing aqueous solution from line 311 to apparatus A2 (thus step (a2)).

The step (a2) is performed in the apparatus A2, and the above-described extraction tower (step (a
) can be used in the same extraction column as the extraction column A). However, device A
2 (and thus step (a2)) is supplied with an extraction solvent via line 313 . A line 312 is also connected to the apparatus A2 (in particular, connected to the top side of the line 311).

The extraction solvent phase obtained from step (a2), in other words, the extractant phase obtained from the top of the extraction column (apparatus A2) is referred to as "the extraction phase obtained from step (a)" or "from the extractor." It is supplied to an extraction solvent recovery device (first distillation column) B via a line 303 as a "extracted phase". The operating pressure of the extraction solvent recovery device (first distillation column) B is 0 kPaG to 5 as the top pressure.
. 0 kPaG is preferable, and the operating temperature is preferably 103° C. to 108° C. as the tower bottom temperature.

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

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

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

Mixer A11 is supplied with an extraction solvent through line 502 and with an organic carboxylic acid-containing aqueous solution as a raw material through line 501 . The mass-based ratio of the extraction solvent supplied to mixer A11 to the organic carboxylic acid-containing aqueous solution supplied to mixer A11 is 0.0
1 to 0.3 is preferred. Further, the extraction operation temperature is preferably 25°C to 35°C. In a mixer, the extraction solvent and the organic carboxylic acid-containing aqueous solution as a raw material are contacted and mixed. The mixer is optionally equipped with an agitator (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 fed via line 503 to decanter A12, the first
and is separated into an extraction solvent phase (upper layer) and an aqueous phase (lower layer) by settling. The extraction solvent phase flows over the weir 51 into the second tank 53 and flows into the second tank (especially the bottom thereof).
to line 512. On the other hand, the aqueous phase is passed from the first tank (especially the bottom thereof) to line 5
11 is discharged.

From the nozzle 54 opening at the boundary between the extractant phase and the aqueous phase of the first tank 52, a line 513
polymer and solids can be discharged to These polymers and solids are dissolved in the organic carboxylic acid-containing aqueous solution and appear at the liquid-liquid interface upon contact with the solvent. When such polymers and solids accumulate in large amounts, for example, in an extraction tower, the operation of the extraction tower may be forced to stop. Therefore, it is preferable to remove the polymer and solid matter as described above.

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

[Fourth Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
Another form 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 apparatus A1 (thus step (a1)) is fed via line 412 to extraction solvent recovery vessel B (thus step (b)) as extraction phase.
ii) The extraction phase obtained from apparatus A2 (thus step (a2)) is fed, ie recycled, via line 403 to apparatus A1 (thus step (a1)) as extraction solvent.
iii) the extraction solvent enriched fraction obtained from extraction solvent recovery B (thus step (b)),
Via line 405, apparatus A2 (and thus step (a2)) is supplied as extraction solvent. As a result, the extraction solvent can be recycled and effectively used.
iv) the extraction solvent enriched fraction obtained from extraction solvent separator C (thus step (c)),
Via line 407 it is fed to extraction solvent recovery vessel B (thus step (b)).
v) There is no line corresponding to line 313 (a line for supplying extraction solvent from outside the system to apparatus A2).
vi) Line 402 is not used during steady state operation. During steady-state operation, extraction solvent is supplied to apparatus A1 through line 403 rather than through line 402 . Line 402 is used to supply extraction solvent to apparatus A1 at start-up. Line 402 can also be used to replenish the extraction solvent if needed during the run.

For the above iv, a stripping column (equipped with a reboiler and without a reflux mechanism) is used as the extraction solvent separator C. The operating pressure of the stripping tower is 0.0 kPaG ~
5.0 kPaG is preferable, and the operating temperature is preferably 103° C. to 108° C. as the tower bottom temperature. The distillate gas (line 407) from the extractant separator C is supplied to the extractant collector B as a gas 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 embodiment shown in FIG. 4 has the same process flow as the embodiment shown in FIG. 3 except as noted above.
Also in this form, it is possible to remove the above-mentioned polymer and the like.

[Fifth Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
Referring to FIG. 8, when using the first and second extraction solvents described in detail later, in particular, the first
An embodiment of an organic carboxylic acid aqueous solution production apparatus in the case of using a mixed extraction solvent obtained by mixing the extraction solvent and the second extraction solvent will be described.

The difference between this embodiment and the first embodiment shown in FIG. 1 is as follows, and the present embodiment can be the same as the first embodiment in other respects.

• In this embodiment, a mixed extraction solvent consisting of a first and a second extraction solvent is supplied to the extractor A as the extraction solvent (line 802). The first extraction solvent consists of one or more selected from the group consisting of ethers of structural formula 1 described below. The second extraction solvent is one or more selected from the group consisting of aromatic hydrocarbons of structural formula 2, ketones of structural formula 3, cyclic ketones of structural formula 4, and aromatic ketones of structural formula 5, which will be described later. . 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.
Extract to

- In a process (b), a process (b1) and a process (b2) are performed.
(b1) The extraction phase (line 803) obtained from step (a) is transferred to the first extraction solvent recovery vessel B1.
separating into a first fraction enriched in the extraction solvent (line 805) and a second fraction (line 806) enriched in the second extraction solvent and organic carboxylic acids using .
(b2) The second fraction (line 806) obtained from step (b1) is transferred to the second extraction solvent enriched third fraction (line 813) and a fourth fraction (line 814) enriched in organic carboxylic acids.

For this purpose, the second
is passed through line 806 to second extraction solvent recovery vessel B2 (thus step (b2))
supply to.

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

[Sixth Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
A modification of the form shown in FIG. 8 will be described with reference to FIG. The difference between this embodiment and the embodiment shown in FIG. 8 is as follows, and in other respects, this embodiment can be the same as the embodiment shown in FIG.

- In step (a), step (a1) and step (a2) are performed. The extractor thus comprises a first extraction device A1 and a second extraction device A2. Steps (a1), (a2) and apparatus A1, A2 are the same as those shown in FIG.

However, the extraction solvent phase obtained from apparatus A1 (step (a1)) is passed through line 912 to
It is supplied to the first extraction solvent recovery vessel B1 (step (b1)) as the extraction phase obtained from step a or the extractor. Also, the extract phase obtained from apparatus A2 (and thus step (a2))
Via line 903 to the first extraction solvent recovery vessel B1 (thus step (b1)), step a
Alternatively, it is supplied as an extract phase obtained from an extractor.

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

Therefore, the first extraction solvent recovery vessel B1 (and thus step (b1)) includes the apparatus A1 (
Thus, the extraction solvent phase obtained from step (a1)) is fed via line 912, the extraction phase obtained from apparatus A2 (hence step (a2)) is fed via line 903, and apparatus C (hence step (a2)) is fed via line 903. The extractant-enriched fraction obtained from c)) is fed to line 907
supplied via

As the extraction solvent separator C, it is preferable to use a stripping column (equipped with a reboiler and without a reflux mechanism). The operating pressure of the stripping tower is 0.0 kPaG to 5.0 kPaG as the tower top pressure.
0 kPaG is preferable, and the operating temperature is preferably 103° C. to 108° C. as the tower bottom temperature. The distillate gas (line 907) from the extraction solvent separator C is not condensed and is supplied as a gas to the first extraction solvent recovery device B1. The liquid (mainly the extraction solvent) supplied from the line 912 is also supplied to the first extraction solvent recovery column B1.

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

The theoretical number of stages of the distillation column of the second extraction solvent recovery device B2 is preferably 3 stages or more, more preferably 5 stages or more, depending on the combination of the solvent and the organic carboxylic acid aqueous solution used. In terms of pressure difference and apparatus size, 30 stages or less are preferable, and 20 stages or less are more preferable. As for the operating pressure of the second extraction solvent recovery device B2, the top pressure is preferably 0 kPaG to 5 kPaG, and the bottom temperature is preferably 100°C to 115°C.

[Seventh Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
A modification of the form shown in FIG. 9 will be described with reference to FIG. The difference between this embodiment and the embodiment shown in FIG. 9 is as follows, and the other points of this embodiment can be the same as those shown in FIG.

- the first fraction obtained from the first extraction solvent recovery vessel B1 (thus step (b1)),
Via line 1005, apparatus A1 (and thus step (a1)) is supplied as extraction solvent. For efficient polymer removal, only ethers are used in apparatus A1 (and thus step (a)
1)) is preferably supplied.

- the third fraction obtained from the second extraction solvent recovery vessel B2 (thus step (b2)),
Via line 1013, apparatus A2 (and thus step (a2)) is supplied as extraction solvent. As a result, the extraction solvent can be recycled and effectively used.

- Line 1002 is not used during normal operation. During steady-state operation, the extraction solvent (first fraction) is supplied to apparatus A1 through line 1005 rather than through line 1002 . Line 1002 is used to supply mixed extraction solvent or first extraction solvent to apparatus A1 at start-up. Line 1002 can also be used to replenish the mixed extraction solvent or the first extraction solvent if needed during the run. Line 1015 is not used during steady operation. During steady-state operation, the extraction solvent (third fraction) is supplied to apparatus A2 through line 1013 rather than through line 1015 . Line 1015 is used to supply mixed extraction solvent to apparatus A2 at start-up. Line 1015 can also be used to replenish the mixed extraction solvent if needed during the run.

Therefore, in this embodiment, the first fraction (fraction enriched in ether components) obtained from the first extraction solvent recovery vessel B1 (thus the step (b1)) is passed through the line 1005 to the apparatus A
1 (thus step (a1)). Also, the second fraction obtained from the first extraction solvent recovery vessel B1 (hence step (b1)) is fed via line 1006 to the second extraction solvent recovery vessel B2 (hence step (b2)).

[Eighth Embodiment of Organic Carboxylic Acid Aqueous Solution Production Apparatus]
A modification of the form shown in FIG. 10 will be described with reference to FIG. Figure 1 of this form
0 are as follows, and in other respects, this embodiment can be the same as the embodiment shown in FIG.

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

In the second extraction solvent recovery device B2 (thus step (b2)), the first extraction solvent recovery device B
1 (thus step (b1)) is fed via line 1106. Also, the third fraction (second extraction solvent-enriched fraction) obtained from the second extraction solvent recovery vessel B2 (and thus step (b2)) is passed through line 1113 to apparatus A2 ( It is therefore supplied to step (a2)). In addition, the second extraction solvent recovery vessel B2 (thus the step (b2
)), a fourth fraction (a fraction enriched in organic carboxylic acids) is discharged in line 1114 . The combined fluid of the fifth fraction (line 1120) and the third fraction (line 1113) of this embodiment should be equivalent to the third fraction (line 1013) of the embodiment shown in FIG. can be done.

Step (b1) and step (b2) may be performed in one apparatus. In that case, for example, using a distillation column, the first fraction (fraction enriched with ethers) is obtained from the top of the column, and the third fraction (remaining extraction solvent A fraction enriched in ) was obtained and a fourth fraction (
A fraction enriched in organic carboxylic acids) can be obtained.

[Aqueous solution containing organic carboxylic acid as raw material to be subjected to concentration treatment]
The present invention uses an organic carboxylic acid-containing aqueous solution as a raw material to produce waste water ( process wastewater).

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, the waste water contains formic acid, acetic acid, acrylic acid, methacrylic acid, propionic acid, maleic acid,
The present invention is preferably utilized when one or more organic carboxylic acids selected from the group consisting of maleic anhydride and α-methylmaleic anhydride are included. In addition, an anhydride may be sufficient as an organic carboxylic acid.

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

The concentration of carboxylic acids in the produced organic carboxylic acid-containing aqueous solution is adjusted to 20% by mass to 50% by mass within a range not lower than the total concentration of organic carboxylic acids in the wastewater, and a waste liquid combustion apparatus is used. It is preferably treated with a liquid waste treatment process. Therefore, after concentration, the concentration (total concentration) of carboxylic acids in the produced organic carboxylic acid-containing aqueous solution can be within 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]
affinity with carboxylic acids (extraction efficiency from water), water insolubility, and low latent heat of vaporization;
From the point of view of
Structural Formula 1: R ¹ —OR ²
(Wherein, R ¹ and R ² each independently represent an alkyl group having 4 or less carbon atoms)
Ether represented by
Structural Formula ² : Ph-R3
(Wherein, 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
(wherein R ⁴ and R ⁵ each independently represent an alkyl group having 4 or less carbon atoms)
a ketone represented by
Structural Formula 4: CyR=O
(Wherein, CyR represents a cycloalkylidene group having 6 or less carbon atoms)
and structural formula 5: Ph--C(=O)--R ⁶
(Wherein, Ph represents a phenyl group and R6 represents an alkyl group having ³ or less carbon atoms)
It is preferably one or more selected from the group consisting of aromatic ketones represented by.

More preferably, the extraction solvent is methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), diisopropyl ether (D
IPE), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone.

The extraction solvent is appropriately combined depending on the type of carboxylic acid contained in the organic carboxylic acid aqueous solution. For example, when a highly hydrophilic carboxylic acid such as maleic acid is contained, an extraction solvent containing ketones is preferable. It is preferable to use the first extraction solvent and the second extraction solvent from the viewpoint of achieving both the extraction efficiency 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 consists of one or a plurality of types selected from the group consisting of ethers represented by 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 a plurality of species.

The ratio of the extracting solvents constituting the mixed extracting solvent at this time is preferably 6:4 to 8:2 in mass ratio of "first extracting solvent:second extracting solvent". This ratio is preferably 8:2 or less from the viewpoint of extraction efficiency of highly hydrophilic carboxylic acids 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 solvent dissolved in the aqueous phase and suppressing an increase in energy required for recovering and reusing the extraction solvent.

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

In step (b), the total concentration of carboxylic acids in the distillate (fraction enriched in extraction solvent) is
From the viewpoint of extraction efficiency when reusing this distillate component as an extraction solvent, 200 mass ppm
The following are preferred. As shown in FIGS. 8 to 10, when performing steps (b1) and (b2),
The total concentration of carboxylic acids in the distillate fraction of step (b2), ie, the third fraction (lines 813, 913, 1013) is preferably 200 mass ppm or less. As shown in FIG. 11, the steps (b1) and (b2) are performed, and the extraction solvent (especially the second extraction solvent ) enriched in ), the total carboxylic acid concentration in the combined fluid of the third and fifth fractions is 200
It is preferably mass ppm or less.

In the step (c), from the viewpoint of suppressing solvent loss, it is preferable that the extraction solvent concentration in the bottoms (water-enriched fraction) is 100 ppm by mass or less.

[Wastewater treatment]
In the aforementioned process for industrial methacrylic acid production, isobutylene and/or t
Using ert-butyl alcohol as a raw material, methacrolein (methacrylaldehyde) is produced using a gas phase catalytic oxidation reaction, and this methacrolein or methacrolein produced by the gas phase catalytic oxidation reaction and the remaining raw material isobutylene and tert-butyl alcohol is further subjected to gas-phase catalytic oxidation to produce methacrylic acid.

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

Wastewater is supplied from line 601 to wastewater evaporator 61 . In addition, this evaporator has
Line 611 also feeds off-gas from the methacrylic acid manufacturing process (including nitrogen, water, carbon dioxide, carbon monoxide, aldehydes, and other by-product organic compounds).

The waste liquid evaporator 61 has a reboiler (not shown) at its bottom, and by supplying steam to the reboiler, heat is given to the evaporator to evaporate the waste water. Although steam is used 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 through line 602 together with air from line 612 and part of the combustion gas cooled by the first exhaust heat recovery device 63 from line 604. be.

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 to cool the combustion gas, and the combustion gas is discharged to the line 605 .

Waste water that has not been evaporated in the waste liquid evaporator 61 is supplied to the concentrated waste liquid combustion device 64 through line 606 together with air from line 613 .

In the concentrated waste liquid combustion device 64, combustible substances contained in the waste water that has not been evaporated in the waste liquid evaporator 61 are burned.

The combustion gas is supplied from 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 discharged to line 608 .

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited by these.

[Example 1]
A heat and mass balance was taken for a plant having the process flow shown in FIG.

This apparatus has an organic carboxylic acid aqueous solution manufacturing apparatus 71 and a wastewater treatment apparatus 72 . This production apparatus 71 is an organic carboxylic acid aqueous solution production apparatus having the process flow shown in FIG. Also, this wastewater treatment apparatus 72 is a wastewater treatment apparatus having the process flow shown in FIG.

25 kg/h of acetic acid aqueous solution simulating the waste water from the methacrylic acid production process is passed through line 701.
to the 17 kg/h flow (line 702) and the 8 kg/h flow (line 7
03) branched into two streams.

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

Concentration of Organic Carboxylic Acid Aqueous Solution For the organic carboxylic acid aqueous solution manufacturing apparatus 71, the heat and mass balance was obtained based on the process flow shown in FIG.

MTBE was used as an extraction solvent.
As the extraction tower A2, a countercurrent extraction tower (water phase dispersed) was used.
As the solvent collector B, a distillation column with an operating pressure of 0 kPaG was used.
As the solvent separator C, a diffusion tower with an operating pressure of 0 kPaG was used.

Feed MTBE (line 402) is also supplied from line 405 to extraction tower A at steady state conditions.
The MTBE sent to 2 was adjusted to 23.33 kg/h. Line 402 is not used at steady state, so in Table 4 the component flow rate is set to zero (0) and the total flow column is labeled "S/U only". S/U means startup.

A small amount of polymer discharged from the apparatus A1 (especially the decanter) was disregarded here because it was discharged in a small amount during long-term operation. However, the flow rate of line 513 in Table 6 indicates the flow rate when discharged intermittently at irregular intervals depending on the amount of deposited polymer.

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

In this manner, acetic acid-containing waste water (line 401) as a raw material is concentrated to produce a highly concentrated acetic acid aqueous solution (line 406). This high-concentration acetic acid aqueous solution is discharged to line 704 in FIG. Meanwhile, the water-enriched fraction obtained in line 408 of FIG. 4 is discharged in line 705 of FIG. The stream in line 705 can optionally be treated by activated sludge treatment and discharged to the environment.

The stream in line 704 was combined with the stream in line 703 and fed via line 706 to wastewater treatment unit 72 . The process flow of wastewater treatment unit 72 is as shown in FIG. 6, with the stream in line 706 of FIG. 7 feeding into line 601 of FIG.

- Waste water treatment A heat and mass balance was obtained for the waste water treatment device 72 based on the process flow shown in FIG.

A gas assumed to be an exhaust gas from a methacrylic acid production process was supplied to line 611 . Note that lines corresponding to lines 611, 612, and 613 in FIG. 6 are not shown in FIG.

The resulting stream (flue gas) in line 605 in FIG. 6 is discharged in line 707 in FIG. The resulting stream in line 608 of FIG. 6 is also discharged in line 707 of FIG.

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 device and the wastewater treatment device. Details of the streams shown in FIG. 6 are shown in Table 7.

In the table, a high boiling point substance means a substance that is solid at room temperature and a substance that has a boiling point higher than that of acetic acid. In addition, cooling, pressurization, and depressurization other than those described above are 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) assumed to be the waste water from the methacrylic acid production process similar to that of Example 1 was flowed through the line 703 and supplied to the waste water treatment device 72 through the line 706. Nothing was fed into line 702 . That is, the entire amount of the acetic acid aqueous solution was supplied to the wastewater treatment device 72 without passing through the production device 71 .

The heat and mass balance of the wastewater treatment device 72 was obtained in the same manner as in Example 1 except for this.

Table 2 shows the main energy consumption of the wastewater treatment plant. From Table 2, it can be seen that the total steam consumption was significantly lower in Example 1 than in Comparative Example 1, thus achieving energy savings.

[Examples 2 to 4]
In Examples 2 to 4, heat and mass balances were taken for the organic carboxylic acid aqueous solution production apparatuses 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 heat-mass balance for each example is shown in Tables 3-5, respectively.

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

[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 was supplied from line 402 to apparatus A1 as an extraction solvent at startup. At this time, the feed mixed extraction solvent (line 402
) was adjusted so that in steady state the mass flow rate of the fluid (fraction enriched in mixed extraction solvent) sent from line 405 to extraction column A2 was 25.22 kg/h. Line 402 is not used at steady state, so in Table 8 the component flow rate is set to zero (0) and the total flow column is labeled "S/U only".

A small amount of polymer discharged from the apparatus A1 (especially the decanter) was disregarded here because it was discharged in a small amount during long-term operation.

Other than this, the procedure 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 production 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 organic carboxylic acid aqueous solution other than maleic acid are the same as in Example 1.

Feed MTBE (line 402) is also supplied from line 405 to extraction tower A at steady state conditions.
The mass flow rate of the fluid (fraction enriched in extraction solvent) sent to 2 was adjusted to 69.92 kg/h. Line 402 is not used at steady state, so in Table 9 the component flow rate is set to zero (0) and the total flow column is labeled "S/U only".

A small amount of polymer discharged from the apparatus A1 (especially the decanter) was disregarded here because it was discharged in a small amount during long-term operation.

Other than this, the procedure was the same as in Example 1. The heat and mass balance is shown in Table 9.

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

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

At startup, a mixed extraction solvent obtained by mixing MTBE and MEK at a mass ratio of 6:4 is supplied from line 1015 to apparatus A2, and the first extraction solvent (M
TBE) was supplied from line 1002 to apparatus A1.
As the extraction tower A2, a countercurrent extraction tower (water phase dispersed) was used.
As the first extraction solvent recovery device B1 and the second extraction solvent recovery device B2, the operating pressure is 0 kPa
A distillation column of G was used.
As the solvent separator C, a diffusion tower with an operating pressure of 0 kPaG was used.

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

Also, the feed mixed extraction solvent (line 1015) was adjusted so that the fluid (mainly the mixed extraction solvent) sent from line 1013 to extraction column A2 was 19.57 kg/h in steady state. Like line 1002, line 1015 is not used during steady state, so Table 1
At 0, the component flow rate was set to zero (0), and "S/U only" was written in the total flow column.

A small amount of polymer discharged from the apparatus A1 (especially the decanter) was disregarded here because it was discharged in a small amount during long-term operation.

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, a total of 6
. It was 0 kg/h (see Table 2).

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

The total steam consumption in Example 7 is less than the total steam consumption in Example 6, and the mixed extraction solvent of the first extraction solvent (especially ethers) and the second extraction solvent (especially ketones) By using, it can be seen that carboxylic acid can be efficiently concentrated even from a carboxylic acid aqueous solution containing a highly hydrophilic carboxylic acid such as maleic acid. In addition, as can be seen from Tables 9 and 10, the amount of extraction solvent used in Example 7 is smaller than the amount of extraction solvent used in Example 6, so equipment costs such as pumps and tanks and running costs can be suppressed. can be done.

A extractor A1 first extractor A2 second extractor A11 mixer A12 decanter B extraction solvent collector B1 first extraction solvent collector B2 second extraction solvent collector C extraction solvent separator 51 weir 52 first Tank 53 Second tank 54 Nozzle 61 Waste liquid evaporator 62 Exhaust gas combustion device 63 First exhaust 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 (21)

An aqueous solution containing 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 ( containing organic carboxylic acid as raw material) A method for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an aqueous solution ) ,
(a) contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution as a raw material to extract the organic carboxylic acid into the extraction phase;
(b) separating the extract phase obtained from step (a) into a fraction enriched in the extracting solvent and a fraction enriched in organic carboxylic acids; and (c) step (a). separating the raffinate phase discharged from the
including
As the extraction solvent,
a first extraction solvent consisting of one or more selected from the group consisting of methyl tert-butyl ether (MTBE), diethyl ether (DEE), diisobutyl ether (DIBE), and diisopropyl ether (DIPE) ;
Using a mixed extraction solvent consisting of a second extraction solvent consisting of one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone ,
A method for producing an organic carboxylic acid-containing aqueous solution. 2. The process according to claim 1, wherein in step (b) the separation is carried out using a distillation column and a fraction enriched in said extraction solvent is obtained as the distillate component of this distillation column. 3. The process according to claim 1 or 2, wherein in step (c) the separation is carried out using a distillation column and a fraction enriched in said extraction solvent is obtained as the distillate component of this distillation column. A process according to any one of claims 1 to 3, wherein part or all of the extraction solvent obtained from step (b) and the extraction solvent obtained from step (c) are fed to step (a). step (a) is
(a1) An extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material are contacted and mixed, and the resulting mixture is separated into two phases, an extraction solvent phase containing the extraction solvent as the main component and an aqueous phase containing water as the main component. and
(a2) contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution in an extraction tower to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase;
supplying the extraction solvent phase obtained from step (a1) as extraction solvent to step (a2);
supplying the aqueous phase obtained from step (a1) to step (a2) as an organic carboxylic acid-containing aqueous solution;
The method according to any one of claims 1-3. step (a) is
(a1) An extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material are contacted and mixed, and the resulting mixture is separated into two phases, an extraction solvent phase containing the extraction solvent as the main component and an aqueous phase containing water as the main component. and removing the polymer formed between the aqueous phase and the extraction solvent phase, and
(a2) contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution in an extraction tower to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase;
supplying the aqueous phase obtained from step (a1) to step (a2) as an organic carboxylic acid-containing aqueous solution;
feeding the extraction solvent phase obtained from step (a1) as the extraction phase to step (b);
Process according to any one of claims 1 to 3, wherein the extraction phase obtained from step (a2) is supplied as extraction solvent to step (a1). step (a) comprises extracting an organic carboxylic acid into an extraction phase comprising said mixed extraction solvent;
step (b)
(b1) dividing the extract phase resulting from step (a) into a first fraction enriched in said first extraction solvent and a second fraction enriched in said second extraction solvent and organic carboxylic acid; separating into fractions, and
(b2) dividing the second fraction obtained from step (b1) into a third fraction enriched in said second extraction solvent and a fourth fraction enriched in organic carboxylic acids; A method according to any one of claims 1 to 3, comprising a step of separating. step (a) is
(a1) An extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material are contacted and mixed, and the resulting mixture is separated into two phases, an extraction solvent phase containing the extraction solvent as the main component and an aqueous phase containing water as the main component. and removing the polymer formed between the aqueous phase and the extraction solvent phase, and
(a2) contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution in an extraction tower to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into an extraction phase;
supplying the aqueous phase obtained from step (a1) to step (a2) as an organic carboxylic acid-containing aqueous solution;
feeding the extraction solvent phase obtained from step (a1) to step (b1) as the extraction phase obtained from step (a);
8. A process according to claim 7 , wherein the extracted phase obtained from step (a2) is also fed to step (b1) as the extracted phase obtained from step (a). supplying the first fraction as an extraction solvent to step (a1);
supplying said third fraction to step (a2) as an extraction solvent;
9. The method of claim 8 . The organic carboxylic acid-containing aqueous solution as a raw material is wastewater discharged from a production process of acrylic acid, methacrylic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, maleic acid, phthalic acid, fumaric acid or propionic acid. 10. The method according to any one of 1 to 9 . 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 wastewater is 0.5. 1 to 50% by weight,
The amount of extraction solvent used in step (a) is 0.00 to the waste water. 11. The method according to claim 10 , which is 1 to 10.0 times by mass. An aqueous solution containing 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 ( containing organic carboxylic acid as raw material) A device for producing an organic carboxylic acid-containing aqueous solution enriched with an organic carboxylic acid by concentrating an aqueous solution ) ,
an extractor for contacting an extraction solvent with an organic carboxylic acid-containing aqueous solution as a raw material to extract the organic carboxylic acid into an extraction phase;
an extraction solvent collector for separating the extraction phase obtained from the extractor into a fraction enriched in the extraction solvent and a fraction enriched in the organic carboxylic acid, and the raffinate phase discharged from the extractor. into an extraction solvent-enriched fraction and a water-enriched fraction;
including
A mixed extraction solvent consisting of a first extraction solvent and a second extraction solvent is used as the extraction solvent,
The first extraction solvent is
consisting of 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 is
consisting of one or more selected from the group consisting of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone ,
an extractor configured to extract an organic carboxylic acid into an extraction phase comprising said mixed extraction solvent;
The extraction solvent collector is
separating the extract phase obtained from the extractor into a first fraction enriched in said first extraction solvent and a second fraction enriched in said second extraction solvent and organic carboxylic acid; a first extraction solvent collector for
a second fraction obtained from the first extraction solvent recovery vessel into a third fraction enriched in said second extraction solvent and a fourth fraction enriched in organic carboxylic acids; and a separating second extraction solvent collector. 13. The apparatus of claim 12 , wherein the extraction solvent recovery device is a distillation column configured to obtain a fraction enriched in said extraction solvent as a distillate component. 14. Apparatus according to claim 12 or 13 , wherein the extraction solvent separator is a distillation column configured to obtain a fraction enriched in said extraction solvent as a distillate component. 15. Apparatus according to any one of claims 12 to 14 , comprising a line for feeding 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 extractor
A mixer for contact-mixing an extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material,
A decanter for separating a mixed liquid obtained from a mixer into two phases, an extraction solvent phase containing an extraction solvent as a main component and an aqueous phase containing water as a main component, wherein an opening is provided between the extraction solvent phase and the water phase. and an extraction tower for contacting an extraction solvent with an aqueous solution containing an organic carboxylic acid to extract the organic carboxylic acid into an extraction phase,
a line for supplying the extraction solvent phase obtained from the decanter to the extraction tower as an extraction solvent;
15. The apparatus according to any one of claims 12 to 14 , further comprising a line for supplying the aqueous phase obtained from the decanter to the extraction column as an organic carboxylic acid-containing aqueous solution. the extractor
A mixer for contact-mixing an extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material,
A decanter for separating a mixed liquid obtained from a mixer into two phases, an extraction solvent phase containing an extraction solvent as a main component and an aqueous phase containing water as a main component, wherein an opening is provided between the extraction solvent phase and the water phase. and an extraction tower for contacting the extraction solvent with the organic carboxylic acid-containing aqueous solution to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into the extraction phase,
a line for supplying the aqueous phase obtained from the decanter to the extraction column as an organic carboxylic acid-containing aqueous solution;
a line for supplying the extraction solvent phase obtained from the decanter to an extraction solvent collector as an extraction solvent;
a line for supplying the extraction phase obtained from the extraction column to the mixer as an extraction solvent;
A device according to any one of claims 12-14 . the extractor
A mixer for contact-mixing an extraction solvent and an organic carboxylic acid-containing aqueous solution as a raw material,
A decanter for separating a mixed liquid obtained from a mixer into two phases, an extraction solvent phase containing an extraction solvent as a main component and an aqueous phase containing water as a main component, wherein an opening is provided between the extraction solvent phase and the water phase. and an extraction tower for contacting the extraction solvent with the organic carboxylic acid-containing aqueous solution to extract the organic carboxylic acid from the organic carboxylic acid-containing aqueous solution into the extraction phase,
a line for supplying the aqueous phase obtained from the decanter to the extraction column as an organic carboxylic acid-containing aqueous solution;
a line for supplying the extraction solvent phase obtained from the decanter to the first extraction solvent collector as the extraction phase obtained from the extractor;
18. The apparatus according to claim 17 , comprising a line for supplying the extracted phase obtained from the extraction column to the first extraction solvent recovery vessel as the extracted phase obtained from the extractor. a line supplying the first fraction to the mixer as an extraction solvent;
19. Apparatus according to claim 18 , comprising a line for feeding said third fraction to an extraction tower as extraction solvent. The organic carboxylic acid-containing aqueous solution as a raw material is wastewater discharged from a production process of acrylic acid, methacrylic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, maleic acid, phthalic acid, fumaric acid or propionic acid. 20. Apparatus according to any one of claims 12-19 . The wastewater contains one or more organic carboxylic acids represented by R-COOH,
wherein 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 the waste water is 0.1 to 50% by weight,
The amount of the extraction solvent used in the extractor is 0.1 to 10.0 times the weight of the wastewater.
21. Apparatus according to claim 20 .

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