JP2004175797A - Method for producing terephthalic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aromatic dicarboxylic acid, capable of producing high-purity terephtalic acid with a good energy efficiency through simplified processes. <P>SOLUTION: In this method for producing the terephthalic acid comprising specified processes, a solid-liquid separation process and a washing process are conducted by using one apparatus, and a process for removing an adhered liquid remaining in a terephthalic acid cake by evaporation is so performed that at least a part of the evaporation of the adhered liquid is conducted by utilizing internal energy which the terephthalic acid cake and/or the adhered liquid has. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for producing an aromatic dicarboxylic acid, particularly terephthalic acid, and more specifically, in a method for producing a compound obtained by reacting under pressure and heat, separation and washing are performed in a single apparatus. The present invention relates to a method for producing terephthalic acid, which includes a step of utilizing internal energy for removing a reaction medium and / or a washing solution attached to a cake obtained.

  Terephthalic acid is generally obtained as a slurry which is a mixture with the reaction mother liquor. The slurry is obtained as a solid particle product by performing a unit operation of separation and drying.

  There have been many attempts to improve the above unit operation and process. For example, there are many options for a technique related to solid-liquid separation (for example, see Patent Document 1). In particular, devices such as a horizontal belt filter, a rotary vacuum filter, and a screen bowl decanter (screen bowl type centrifuge) have an advanced washing function in addition to separation. Using these devices, not only can separation and washing be performed simultaneously, but also a mother liquor containing a large amount of impurities, a washing filtrate with reduced impurities, and a washed cake can be separately collected. However, the cake contains a useful liquid, and further requires a drying operation and a solvent replacement operation in order to recover the adhering liquid. There is also an example in which a special separation device is used (for example, see Patent Document 2).

  On the other hand, as for the drying operation, an example of drying using a compressed air transfer type dryer and external heating using hot gas or hot air is disclosed (for example, see Patent Document 3). Further, there is disclosed an example in which a liquid of a slurry is evaporated in a heating tube to obtain a solid and a gas (for example, see Patent Documents 4 and 5). However, on the premise that these drying operations are performed independently, the cake is dried by newly applying heat, and therefore, a device for performing the drying operation and corresponding energy are required.

  In addition, it is common to carry out crystallization by lowering the temperature while maintaining a slurry state as a pretreatment for solid-liquid separation. For example, there is disclosed an example of evaporating a solvent to cause cooling to precipitate terephthalic acid (for example, see Patent Document 6). However, evaporation itself only slightly increases the slurry concentration, and has no effect on the process other than lowering the temperature.

  Also, there is disclosed an example in which terephthalic acid is reslurried with a cleaning liquid and flushed (for example, see Patent Document 7). Since it is difficult to extract the powder from the pressurized state, a method of extracting the powder by reslurrying is generally known, but attention has not been paid to a negative portion in which energy is lost by flashing. Therefore, the process of dissipating energy by lowering the temperature of the slurry and reheating by drying, as shown in the above two examples, cannot be said to use energy effectively.

  Further, although cake separation in a pressurized state is also disclosed, there is no mention that holding the thermal energy of the slurry before separation is effective for drying the cake (for example, see Patent Documents 8 and 9).

PCT93 / 24440 International Publication Japanese Unexamined Patent Publication No. 60-506461 JP-A-52-59177 JP-B-58-11418 JP-A-55-164650 British Patent No. 1152575 JP-A-11-33532 JP-A-1-299618 U.S. Pat. No. 5,698,734

  As described above, attempts to separately improve the separation operation and the drying operation have been made up to now, but they have been regarded as an integrated process, and no attempt has been made to simplify the apparatus and effectively use energy. Was.

  Therefore, an object of the present invention is to provide a method for producing a high-purity aromatic dicarboxylic acid such as terephthalic acid with high energy efficiency by a simplified process.

  The present inventors have conducted intensive studies in view of the above problems, and have performed separation and washing of the terephthalic acid cake under a pressure of at least atmospheric pressure using one apparatus, and subsequently adhered to the washed cake. By utilizing internal energy to remove the reaction medium and / or the washing liquid, the mother liquor with high impurity concentration, the washing filtrate with low impurities, and the crystals with low adhering liquid are collected through simple operations of separation and extraction. It has been found that high-purity terephthalic acid can be produced with good productivity, and the present invention has been achieved.

  That is, the gist of the present invention is that the following steps (A) to (D), (E) to (I), or (A) to (I) are steps of solid-liquid separation and washing, namely, step (B) ) And step (C) and / or step (G) and step (I) are performed using a single apparatus under a pressure higher than the atmospheric pressure, and the adhesion liquid remaining on the terephthalic acid cake is removed by evaporation. The above problem was solved by performing at least a part of the evaporation of the adhesion liquid in the step, that is, the step (D) and / or the step (I), by the internal energy of the terephthalic acid cake and / or the adhesion liquid. is there.

(A) a step of oxidizing para-xylene with molecular oxygen in a solvent mainly composed of acetic acid in the presence of a catalyst to obtain terephthalic acid.
(B) a step of solid-liquid separation of the slurry containing terephthalic acid crystals into a crude terephthalic acid cake and a mother liquor mainly composed of acetic acid;
(C) a step of washing the crude terephthalic acid cake using a washing solution;
(D) a step of removing an adhering liquid remaining on the washed crude terephthalic acid cake by evaporation.

(E) a step of contacting the crude terephthalic acid with hydrogen in a solvent mainly composed of water in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid.
(F) a step of reducing the pressure and temperature of the reaction solution to crystallize terephthalic acid in a medium mainly composed of water.
(G) a step of solid-liquid separating a slurry containing terephthalic acid crystals into a purified terephthalic acid cake and a mother liquor mainly composed of water;
(H) a step of washing the purified terephthalic acid cake using a washing solution;
(I) a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation.

  According to the present invention, a mother liquor having a high impurity concentration, a washing filtrate having a reduced impurity, and crystals having a reduced adhering liquid can be independently collected through simple operations of separation and extraction. Thereby, energy saving and simplification of the process can be greatly advanced. Therefore, the industrial value of the present invention is great.

Hereinafter, the present invention will be described in detail.
In the production method of the present invention, in the production of terephthalic acid, a step of solid-liquid separation for obtaining a terephthalic acid cake from a reaction mixture and a step of washing the terephthalic acid cake can be performed together, for example, a screen bowl Solid-liquid separation and washing are continuously performed under pressure using a centrifugal separator, rotary vacuum filter, horizontal belt filter, etc., and then the washed terephthalic acid cake is released under a lower pressure than the washing process ( (Flashing) and utilizing the internal energy of the terephthalic acid cake and / or its adhering liquid for the evaporation of the adhering liquid.

The production process of terephthalic acid has two reaction steps of an oxidation step of the following step (A) and a reduction step of the step (E), and includes a solid-liquid separation step and a washing step, respectively. However, in the present invention, at least one of the solid-liquid separation step and the washing step is performed using one apparatus, and a combination with flash evaporation of the adhered liquid is used.
Preferably, in both of the post-steps of the oxidation reaction and the reduction reaction, the solid-liquid separation step and the washing step are performed using one apparatus, and a combination of evaporation of the adhered liquid by flashing is used. In the present specification, the following steps (A) to (D) are combined, the CAT step (crude terephthalic acid production step) is combined, and the steps (E) to (H) are combined to form a PTA step (purified terephthalic acid). Manufacturing process).

[Step (A)]
Step (A) is a step of oxidizing para-xylene with molecular oxygen in a solvent mainly composed of acetic acid in the presence of a catalyst to obtain terephthalic acid.
Terephthalic acid is one of the aromatic dicarboxylic acids. In the present invention, the reaction for producing terephthalic acid can be carried out according to a conventional method. Usually, terephthalic acid is obtained by reacting para-xylene with molecular oxygen in the presence of a catalyst containing a heavy metal such as, for example, cobalt, iron or manganese, preferably a salt of the heavy metal and bromine.

  A reaction medium mainly containing acetic acid is used. The amount of the acetic acid solvent to be used is usually 2 to 6 times the weight of para-xylene. The acetic acid solvent may contain other components such as water in an amount that does not affect the reaction, for example, 10% by weight or less.

  As the conditions of the oxidation reaction, the temperature is usually 130 to 250 ° C, preferably 150 to 230 ° C, and the pressure is usually 0.2 to 12 MPa, preferably 0.3 to 7 MPa, more preferably 1 to 3 MPa, and particularly preferably. Is 1 to 1.5 MPa.

  The reactor used for the oxidation reaction is not particularly limited, but usually a complete mixing tank type reactor equipped with a stirrer is used. The reaction is preferably carried out continuously, and the reaction time (average residence time) is usually 30 to 300 minutes. The oxidation reaction may be performed in a single step, but the oxidation reaction may be performed at a temperature slightly lower than the reaction temperature of the first step using a second-stage reactor in order to increase the conversion of para-xylene. When performing the second-stage oxidation reaction, the temperature is preferably 140 to 190 ° C. As the second stage reactor, a plug flow type reactor can be used in addition to a complete mixing tank type reactor.

  By the oxidation reaction, 95% by weight or more, preferably 99% by weight or more of para-xylene is converted to terephthalic acid, and a slurry in which crystals containing terephthalic acid are precipitated is obtained. Although some impurities are by-produced, the impurities are typically 4-carboxybenzaldehyde (hereinafter sometimes referred to as “4-CBA”), and the mixture after the oxidation reaction usually contains terephthalic acid. About 500 to 5000 ppm of 4-CBA.

[Step (B)]
The step (B) is a step of solid-liquid separation of the slurry containing the terephthalic acid crystals obtained in the step (A) into a crude terephthalic acid cake and a reaction mother liquor mainly composed of acetic acid under a pressure higher than the atmospheric pressure. is there.

As an apparatus used for the solid-liquid separation, an apparatus which performs the present step and the step (C) by one apparatus as described later can be used.
In the present invention, the crude terephthalic acid means a cake that has not undergone a 4-CBA reduction reaction. Usually, crude terephthalic acid contains 500 ppm or more of 4-CBA with respect to terephthalic acid.

The reaction mother liquor obtained by solid-liquid separation contains, in addition to acetic acid as a solvent, water, heavy metal catalysts, paratoluic acid, 4-CBA, and methyl acetate as reaction by-products.
The screen bowl decanter for performing solid-liquid separation is usually operated with a centrifugal force of 500 to 2000 G.

The lower limit of the pressure range of the solid-liquid separator is usually at least atmospheric pressure, preferably at least 0.2 MPa, more preferably at least 0.3 MPa. On the other hand, the upper limit of the pressure range is usually 22 MPa or less, preferably 12 MPa or less, more preferably 7 MPa or less, particularly preferably 1.5 MPa or less, and most preferably 1.2 MPa or less. From the viewpoint of energy efficiency, it is preferable to carry out the solid-liquid separation while maintaining at least a part of the pressure during the oxidation reaction in the step (A).
After the step (A), if it is desired that the pressure of the solid-liquid separator in the step (B) be higher than the pressure immediately before the step (B), the pressure is increased by a pump or the like when transferring the slurry.

[Step (C)]
Step (C) is a step of washing the crude terephthalic acid cake obtained in step (B) at a pressure equal to or higher than the atmospheric pressure using a cleaning liquid. As an apparatus used for this cleaning, an apparatus in which the step (B) and this step are performed by one apparatus as described later can be used.

  The washing liquid is not particularly limited, and is preferably a liquid containing acetic acid, which is the same as the main component of the oxidation reaction solvent. Further, the acetic acid content is preferably 90% or more. In addition, an acetate ester having a relatively small heat of vaporization, such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate, may be used.

  The lower limit of the pressure range in the washing step is usually at least atmospheric pressure, preferably at least 0.2 MPa, more preferably at least 0.3 MPa. On the other hand, the upper limit of the pressure range is usually 22 MPa or less, preferably 12 MPa or less, more preferably 7 MPa or less, particularly preferably 1.5 MPa or less, and most preferably 1.2 MPa or less.

[One device]
The above steps (B) and (C) can be performed using one apparatus. By performing these steps using one apparatus, the number of devices can be reduced, and the solid-liquid separation step (B) and the washing step (C) can be made to have the same pressure.

  One of the above-mentioned devices includes a horizontal belt filter, a rotary vacuum filter, a screen bowl decanter (screen bowl type centrifuge), and the like. Among these, a screen bowl decanter is most preferable. The screen bowl decanter is capable of performing solid-liquid separation and washing in an integrated apparatus. When the reacted crude terephthalic acid cake passes through the washing part provided with the filter material, the washing liquid is sprayed. Can wash the cake. Further, the washing liquid is separated from the cake through the filter material and can be collected.

  The screen bowl decanter is disclosed in, for example, WO98 / 18750, WO93 / 24440, and the like, in which a solid and a liquid are separated by centrifugal force, and the solid is provided with a filtering material using a spiral plate. Conveyed to the cleaning site

  There is no particular limitation on the material and shape of the filtering material, and examples thereof include a ceramic filter, a wire mesh, and a metal bar screen, and are selected in consideration of corrosion resistance and clogging. For example, when using a metal bar screen, clogging can be avoided by allowing a slight cake leak. The cake discharged from the screen bowl decanter is a liquid-containing cake whose impurity concentration has been reduced by removing the adhered mother liquor.

  In this screen bowl decanter, the mother liquor and the washing liquid can be separately collected, but a part of the washing liquid may be mixed into the mother liquor. The screen bowl decanter has high cake washability and can withstand use under commercial high pressure.

  When this screen bowl decanter is used, the pressure in the solid-liquid separation step in the step (B) and the pressure in the washing step in the step (C) are basically equal.

[Step (D)]
Step (D) refers to a step of removing the adhesion liquid remaining on the crude terephthalic acid cake obtained in step (C) by evaporation.
The type of the drying apparatus used in the present invention is not particularly limited as long as each operation of the drying step described below can be performed, but usually, a discharge valve (hereinafter sometimes simply referred to as a “valve”) is usually used. A pressure drying apparatus provided is used. The discharge valve is not particularly limited except that it has a function of cutting powder from under pressure to low pressure, and a valve as disclosed in WO 91/09661, US Pat. No. 5,589,079 or US Pat. No. 4,127,935 is used. . Continuous or intermittent extraction may be used. A singular or plural number is not particularly limited. For example, a plurality is exemplified by US Pat. No. 5,589,079, and a singular is exemplified by WO 91/09661. Furthermore, it is also possible to use the valve described in WO00 / 71226.

  Usually, a cake holding tank (cake chamber) is provided upstream of the discharge valve, and after washing in the step (C), the separated cake is held in a cake holding layer. The cake is withdrawn by opening the valve into the powder storage tank. The opening of the valve is preferably performed while controlling the amount of cake staying constant.

  The operating pressures of the cake holding tank and the step (C) are substantially the same. The pressure of the powder retention tank is lower than that of the cake holding tank. By releasing (flashing) the cake under pressure in the cake holding tank to a low pressure through a valve, the boiling point of the cake adhering liquid is lowered, and the sensible heat due to the boiling point difference, that is, the terephthalic acid cake and / or the adhering liquid The internal energy is used as heat of vaporization of the cake adhering liquid, and the cake adhering liquid evaporates. The temperature (TB) of the cake immediately before discharge in the cake holding tank is preferably higher than the boiling point (Bp) of the cake adhering liquid at atmospheric pressure.

  The lower limit of the pressure range of the drying device up to the upstream of the valve is usually at least atmospheric pressure, preferably at least 0.2 MPa, more preferably at least 0.3 MPa. On the other hand, the upper limit of the pressure range is usually 22 MPa or less, preferably 12 MPa or less, more preferably 7 MPa or less, particularly preferably 1.5 MPa or less, and most preferably 1.2 MPa or less.

  When the steps (B) and (C) are performed using a screen bowl decanter, the pressure in the steps (B) and (C) is maintained at or above the atmospheric pressure. Then, the pressure in the screen bowl decanter is almost maintained, and the terephthalic acid cake is supplied to the cake holding tank in the step (D). Therefore, as a preferred embodiment, the lower limit of the pressure range in the cake holding tank (that is, up to the upstream of the valve) in each of the steps (B), (C) and (D) is at least atmospheric pressure, preferably at least 0.2 MPa. And more preferably 0.3 MPa or more. On the other hand, the upper limit of the pressure range is usually 22 MPa or less, preferably 12 MPa or less, more preferably 7 MPa or less, particularly preferably 1.5 MPa or less, and most preferably 1.2 MPa or less. If the difference from the atmospheric pressure is too small, the internal energy released at the time of flashing becomes small, and the amount of evaporation of the cake adhering liquid tends to decrease. If the pressure is too high, a problem may occur in the cost of the pressure-resistant equipment.

  The range of the cake temperature immediately before discharge is from 50 ° C to 350 ° C, preferably from 100 ° C to 300 ° C, more preferably from 130 ° C to 250 ° C. The boiling point at the atmospheric pressure of the cake adhering liquid and the temperature difference (TB-Bp) of the cake immediately before discharge in the cake holding tank are preferably in the range of 5 ° C to 200 ° C, more preferably 10 ° C to 150 ° C. The range is particularly preferably in the range of 15 ° C to 100 ° C.

  The pressure in the powder stagnation tank is preferably atmospheric pressure, but the pressure in the powder stagnation tank is slightly higher than the atmospheric pressure due to gas evaporating during flashing. Further, the gas in the powder storage tank can be forcibly exhausted, and in this case, the pressure in the powder storage tank may be lower than the atmospheric pressure.

  Further, at least a part of the steam generated in the step (D) can be recovered and reused in the terephthalic acid production step. The vapor generated in the step (D) is mainly vapor of the cleaning liquid attached to the cake during the cleaning in the step (C). Therefore, when acetic acid is used as the washing liquid in the step (C), acetic acid vapor is generated, and it is particularly effective to use the solvent as the oxidation reaction solvent in the step (A). The steam may be supplied as it is to the reactor in step (A), or may be supplied after heat energy is recovered and condensed by a heat exchanger.

  Furthermore, at least a part of the crystals containing terephthalic acid accompanying the vapor generated in the step (D) can be recovered and re-supplied to the terephthalic acid production step. When the crude terephthalic acid cake is flashed in the step (D) and the cake adhering liquid is evaporated using the internal energy of the cake and / or the cake adhering liquid, the pressure in the system is reduced in a short time. May be accompanied by crystals containing terephthalic acid. In order to improve the yield of terephthalic acid, it is preferable to collect crystals accompanying the vapor. The recovered crystals can be re-donated to either the CTA step or the PTA step. However, since the crystals obtained here have completed the oxidation reaction, only the terephthalic acid crystals are recovered using a bag filter or the like. Is preferably provided to the step (E). In a more preferred embodiment, the terephthalic acid crystal accompanying the above is brought into contact with a liquid mainly composed of acetic acid to obtain a slurry, which is directly transferred to the CTA step, particularly to the step (A) and / or the step (B). Or indirectly.

[Step (E)]
The step (E) is a step of dissolving the crude terephthalic acid in a solvent mainly composed of water and bringing it into contact with hydrogen in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid.

In carrying out the reduction reaction, the solubility of the crude terephthalic acid at room temperature is low, so it is necessary to raise the temperature in order to dissolve it in a solvent mainly composed of water. The temperature of the reduction reaction is usually from 230 to 330 ° C, preferably from 250 to 310 ° C. As for the pressure, a pressure higher than the vapor pressure is required to maintain the solvent as a liquid, and is usually 3 to 12 MPa, preferably 5 to 10 MPa.
In the step (E), 4-CBA contained in the crude terephthalic acid is reduced and converted to paratoluic acid.

[Step (F)]
Step (F) is a step in which the pressure and temperature of the reaction solution obtained in step (E) are reduced, and terephthalic acid crystals are crystallized in a medium mainly composed of water.

  The crystallization is carried out batchwise and continuously, and there is no particular limitation. Usually, the pressure is reduced stepwise continuously in two to six stages, preferably three to five stages. As a result, the solvent flash-evaporates, and the temperature in the system decreases. Since paratoluic acid in which 4-CBA is reduced has higher solubility in water than terephthalic acid, terephthalic acid is preferentially precipitated in crystallization. However, when the pressure drops to the atmospheric pressure, the temperature becomes about 100 ° C. and paratoluic acid co-crystallizes. Therefore, the final crystallization pressure is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, and particularly preferably 0.5 MPa or more. That is all. The upper limit of the pressure range is preferably 3 MPa or less, more preferably 1 MPa or less, and particularly preferably 0.7 Pa or less. The vapor generated during crystallization may be collected and reused in the terephthalic acid production process.

[Step (G)]
The step (G) is a step of subjecting the slurry containing the terephthalic acid crystals obtained in the step (F) to solid-liquid separation under a pressure of at least atmospheric pressure into a purified terephthalic acid cake and a reaction mother liquor mainly composed of water. .

In the present invention, the purified terephthalic acid means terephthalic acid that has undergone a 4-CBA reduction reaction. Usually, the purified terephthalic acid cake contains 30 ppm or less of 4-CBA based on terephthalic acid.
The method of solid-liquid separation and the preferable pressure range are substantially the same as those in the step (B). However, the upper limit of the pressure range is particularly preferably 1 MPa or less, most preferably 0.7 MPa or less.
The reaction mother liquor obtained by the solid-liquid separation contains, in addition to water as a solvent, a trace amount of acetic acid mixed in from the preceding oxidation reaction step, a heavy metal catalyst, 4-CBA as a reaction by-product, or a reducing substance thereof. Paratoluic acid and the like.

[Step (H)]
Step (H) is a step of washing the purified terephthalic acid cake using a washing solution. The cleaning is performed in the same manner as in the step (C) except that water is preferably used as a main component of the cleaning liquid.

[One device]
The steps (G) and (H) are preferably performed using one apparatus, and examples thereof include the apparatus used in the above step (C).

  In the above screen bowl decanter, solid-liquid separation and washing can be performed in an integrated apparatus, and when the reacted crude terephthalic acid cake passes through the washing part provided with the filter material, the washing liquid is removed. The cake can be washed by spraying. The washing liquid passes through a filter and is separated from the cake and can be collected. In the screen bowl decanter, the mother liquor and the cleaning liquid can be separately collected, but a part of the cleaning liquid may be mixed into the mother liquor.

  The washing liquid is not particularly limited, but is preferably an aqueous solvent or an oily solvent, for example, one containing water as the main component as the main component of the mother liquor. The cake discharged from the screen bowl decanter is a liquid-containing cake whose impurity concentration has been reduced by washing the adhered mother liquor.

[Step (I)]
Step (I) is a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation. It is the same as the step (D) except that the crude terephthalic acid was replaced with purified terephthalic acid.

[Practical aspects of the present invention]
A feature of the present invention is that the mother liquor, the washing filtrate, and the crystals with reduced adhering liquid can be respectively recovered through simple operations such as separation, washing and withdrawal. By recovering the crystals having a reduced amount of the adhering liquid, it becomes possible to omit a dryer or to realize a small and labor-saving process. Further, the mother liquor and the washing liquid can be collectively collected, but since the concentration of impurities is slightly higher in the mother liquor, it is preferable to collect them separately and reuse them in different systems.

  On the other hand, the fact that the mother liquor and the washing filtrate can be separately collected is also very effective for the process. Hereinafter, those practical aspects will be exemplified.

  At least a part of the washing solution (washing filtrate) after washing the crude terephthalic acid cake can be collected and reused as it is or after being processed in the terephthalic acid production process. Since impurities in the main washing filtrate are smaller than those of the separated mother liquor, the impurities can be reused as the oxidation reaction solvent in the step (A). Further, it can be used as an adsorbent for collecting terephthalic acid crystals accompanying the solvent vapor generated in the step (D).

  In addition, crystals containing terephthalic acid can be recovered from at least a part of the washing solution after washing the crude terephthalic acid cake, and the crystals can be re-supplied to the step of producing terephthalic acid. The crystals may be collected by subjecting the washing liquid to solid-liquid separation as it is, or may be further subjected to solid-liquid separation after lowering the temperature or pressure to promote crystallization. The solid-liquid separation is not particularly limited as long as it is a commonly employed technique, and centrifugation, filtration, sedimentation, and the like are used. The recovered crystals can be re-donated in either the oxidation step or the hydrogen reduction step, but the reaction is almost complete, and the donation to the oxidation step, particularly to the step (A) and / or step (B), is not possible. preferable.

  Further, at least a part of the separated mother liquor mainly composed of acetic acid obtained by subjecting the crude terephthalic acid slurry to solid-liquid separation can be recovered, reused as it is or treated, and used in the process of producing terephthalic acid. The mother liquor contains useful components including an oxidation reaction catalyst and a reaction intermediate, and can be reused as the oxidation reaction solvent in step (A).

  Furthermore, a crystal containing terephthalic acid is recovered from at least a part of a separation mother liquor mainly composed of acetic acid obtained by solid-liquid separation of the crude terephthalic acid slurry, and the crystal is resupplied to a terephthalic acid production process. be able to. The crystal may be recovered by subjecting the separated mother liquor to solid-liquid separation as it is, or may be further subjected to solid-liquid separation after lowering the temperature or pressure to promote crystallization. Solid-liquid separation after further crystallization of the separated mother liquor is not particularly limited as long as it is a commonly employed technique, and centrifugation, filtration, sedimentation and the like are used. The recovered crystal can be re-donated in either the oxidation step or the hydrogen reduction step, but is preferably supplied to the step (A) because an acetic acid solvent accompanies.

  The separated mother liquor obtained by solid-liquid separation has the same temperature and pressure as the solid-liquid separation, and it is preferable that this separated mother liquor is recycled to the oxidation reaction step while maintaining high temperature and high pressure. By supplying the high-temperature mother liquor to the reactor, the amount of sensible heat equivalent energy for raising the oxidation reactant to a predetermined reaction temperature can be reduced. Thereby, energy recovery in the oxidation reaction is improved. However, recycling the entire separated mother liquor causes accumulation of impurities contained in the mother liquor in the system, which leads to deterioration of the quality of crude terephthalic acid obtained by solid-liquid separation. Therefore, part of the separated mother liquor, preferably 10 to 30%, is purged to prevent accumulation of impurities. The purge mother liquor contains organic impurities derived from impurities in the raw material para-xylene such as an acetic acid solvent, an oxidation reaction catalyst, and benzoic acid. Further, in the case of a high-temperature mother liquor, terephthalic acid dissolved in the mother liquor is also contained. This purge mother liquor is evaporated to evaporate the solvent component, leaving a high-boiling component as a residue. This residue contains a cobalt component, a manganese component, and organic impurities as catalyst components, and the catalyst components are recovered and regenerated in a catalyst regeneration system in a later step. Here, in order to recover the terephthalic acid component dissolved in the high-temperature mother liquor, first, a flash treatment is performed to evaporate and concentrate the solvent component. Here, terephthalic acid is precipitated by flash concentration and cooling, and this precipitate is recovered by a solid-liquid separation operation. The recovered solid is preferably provided to the oxidation reaction step. In addition, the separated liquid obtained by solid-liquid separation of the purge mother liquor can be used to separate and recover active components such as acetic acid, water and a catalyst, if necessary, and can be reused in the terephthalic acid production process.

  Further, at least a part of a separation mother liquor mainly composed of water obtained by subjecting a purified terephthalic acid slurry to solid-liquid separation can be recovered and reused as it is or after being processed in a terephthalic acid production step. This separated mother liquor may be subjected to solid-liquid separation, distillation or membrane purification treatment as necessary, and can be reused as the reduction reaction solvent in step (E).

  Further, a crystal containing terephthalic acid can be recovered from at least a part of the separation mother liquor mainly composed of water obtained from the purified terephthalic acid separation, and the crystal can be supplied again to the terephthalic acid production step. The crystals are preferably collected by subjecting the separated mother liquor to concentration and / or cooling to precipitate terephthalic acid crystals, followed by solid-liquid separation. The solid-liquid separation is not particularly limited as long as it is a commonly employed technique, and centrifugation, filtration, sedimentation, and the like are used. The recovered crystals (secondary crystals) can be re-donated in either the oxidation step or the hydrogen reduction step, but the concentration of the intermediate is high, and the donation to the oxidation step, particularly to the step (A), is preferred. Further, the mother liquor (secondary mother liquor) obtained here can also be directly or indirectly reused as the reduction reaction solvent in the step (E).

  Further, at least a part of the washing solution (washing filtrate) used for washing the purified terephthalic acid cake can be recovered and reused as it is or after being processed in the terephthalic acid production process. In particular, since the impurity concentration is low, it is effective to reuse the solvent as the reduction reaction solvent in the step (E). The washing filtrate may be subjected to a distillation or membrane purification treatment as necessary. Further, it can be used as an adsorbent for collecting terephthalic acid crystals accompanying the solvent vapor generated in the step (I).

  Furthermore, for example, in the case where the cleaning solution after washing the purified terephthalic acid cake contains terephthalic acid due to leakage during washing or the like, crystals containing terephthalic acid are recovered from at least a part of the washing solution by solid-liquid separation or the like. The crystals can then be re-donated to the terephthalic acid production process. The crystals may be collected by subjecting the washing liquid to solid-liquid separation as it is, or may be further subjected to solid-liquid separation after lowering the temperature or pressure to promote crystallization. The solid-liquid separation is not particularly limited as long as it is a commonly employed technique, and centrifugation, filtration, sedimentation, and the like are used. The recovered crystals can be re-donated in both the CTA step and the PTA step, but the reaction is almost completed, and the crystal is supplied to the PTA step, particularly to the separation step (F) and / or (G). Is preferred.

  Further, at least a part of the steam generated in the step (I) can be recovered and reused in the terephthalic acid production step. The vapor generated in the step (I) is mainly vapor of the cleaning liquid attached to the cake during the cleaning in the step (H). Accordingly, when water is used as the washing liquid in the step (H), water vapor is generated, so that it is particularly effective to use the solvent as the reduction reaction solvent in the step (E). The steam may be supplied as it is to the reactor of step (E), or may be supplied after heat energy is recovered and condensed by a heat exchanger.

  Further, at least a part of the crystals containing terephthalic acid accompanying the vapor generated in the step (I) can be collected and reused in the terephthalic acid production step. When the purified terephthalic acid cake is flashed in the step (I) and the cake adhering liquid is evaporated using the internal energy of the cake and / or the cake adhering liquid, the pressure in the system is reduced in a short time. Crystals containing terephthalic acid may accompany the vapor. In order to improve the yield of terephthalic acid, it is preferable to collect crystals accompanying the vapor. The recovered crystals can be re-donated to any of the CTA step and the PTA reaction step, but the crystals obtained here have been completed up to the reduction reaction and washing, and thus can be supplied as they are as products. The terephthalic acid crystals are preferably collected as a slurry by contacting with a liquid mainly composed of water, and the slurry can be provided to any of the steps (E) to (G).

[Preferred embodiment]
A preferred embodiment of the manufacturing method of the present invention will be described with reference to FIG.
In FIG. 1, 1 is an oxidation reactor used in the step (A), 2 is a crystallization tank, 3 is a separation and washing apparatus in which the steps (B) and (C) are integrated, and 4 is a powder retention tank. In addition, a cake holding tank and a discharge valve (not shown) are provided between the separation and washing device 3 and the powder stagnation tank 4. The crude terephthalic acid cake obtained by the separation and washing device 3 is flushed to the powder retention tank 4 via the cake holding tank, and the cake adhering liquid is evaporated. 5 is a reduction reactor used in the step (E), 6 is a crystallization tank used in the step (F), 7 is a separation and washing apparatus in which the steps (G) and (H) are integrated, and 8 is a dryer. A cake holding tank and a discharge valve (not shown) are provided between the separation washing device 7 and the dryer 8. The purified terephthalic acid cake obtained in the separation and washing device 7 is flushed to the dryer 8 to evaporate the cake adhering liquid. Note that the dryer 8 also serves as a powder retention tank. Since the cake adhering liquid is mainly composed of water, the adhering liquid does not completely evaporate only by flashing.

  Reference numeral 11 denotes a solvent recovery system (for example, a distillation column), which separates the mother liquor after the oxidation reaction together with a mixture containing acetic acid supplied from another place in the process into components. The mother liquor contains water produced by the oxidation reaction with acetic acid as a solvent, and high boiling components such as impurities and oxidation catalysts. Acetic acid can be supplied to oxidation reactor 1 via line 110. Water can be discarded via line 112 or used as is or as purified process water. Since the impurities are obtained as a residue, the active component such as a catalyst is recovered and the remainder is discarded.

  The cleaning liquid (liquid mainly composed of acetic acid) used in the separation and cleaning device 3 is sent to the oxidation reaction device via the line 131 after the cleaning. In the case where terephthalic acid, which has partially leaked, is separated from the cleaning liquid, the terephthalic acid is sent to the solid-liquid separation device 31 via the line 132. These terephthalic acid and acetic acid can each be reused in the process.

  When the terephthalic acid cake is flushed into the powder storage tank, the cake adhering liquid evaporates, but terephthalic acid accompanies the gas of the adhering liquid. The gas containing terephthalic acid crystals is condensed and returned to a liquid, which is sent to a solid-liquid separation device 41, where it is separated into terephthalic acid and an adhering liquid mainly composed of acetic acid. Alternatively, the terephthalic acid crystal entrained in the gas is brought into contact with acetic acid in the solid recovery device 42 to obtain a slurry, the gas is further condensed, and the slurry and the condensate are supplied to the oxidation reactor via the line 101.

  The mother liquor of the reduction reaction separated by the separation washing device 7 is sent to the solid-liquid separation device 21 via the line 121. In the solid-liquid separator 21, the separated mother liquor is concentrated and / or cooled to separate and recover a reaction intermediate such as terephthalic acid or paratoluic acid, and the remaining mother liquor mainly composed of water is discarded. Alternatively, it can be further purified by distillation or membrane and used as process water. Further, the active components such as the oxidation reaction catalyst and paratoluic acid contained in the water can be recovered by an ion exchange treatment or an adsorption treatment.

  The washing filtrate (liquid mainly composed of water) used in the separation washing device 7 is sent to the solid-liquid separation device 51 via the line 151 after washing. In the solid-liquid separation device 51, the solid containing terephthalic acid that has partially leaked is separated from the washing liquid. These terephthalic acid and water can each be reused in the process. In this case, it is preferable that the solid content is returned to the crystallization tank 6 and the washing liquid after separation is returned to the reduction reactor 5. The cleaning liquid itself containing terephthalic acid can be reused in the process without passing through the solid-liquid separation device 51.

  When the terephthalic acid cake is flushed to the dryer 8, the cake adhering liquid evaporates, but terephthalic acid accompanies the gas of the adhering liquid. The gas containing the terephthalic acid crystals is condensed and returned to a liquid, sent to a solid-liquid separator 61, and separated into terephthalic acid and an adhering liquid mainly composed of water. Alternatively, a terephthalic acid crystal entrained in the gas is brought into contact with water in the solid recovery device 62 to obtain a slurry, and in the case of a gas, the slurry is condensed. , The crystallization tank 6, or the separation and washing device 7.

  The solid-liquid separators 21, 31, 41, 51, 61 are provided with a washing device as required. The separated solids and liquids are re-supplied to the terephthalic acid production process through lines 101, 102, 103, 105, 106, 107, 171, 175, 176, and 177, respectively, as desired. Only solid or liquid may be used. The solid-liquid may be remixed, and further re-supplied directly to the terephthalic acid production process through lines 101, 102, 103, 105, 106, 107, 171, 175, 176, 177, bypassing the solid-liquid separation. Good. Further, some of them may be discarded. A product is obtained from the line 109.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist.

  In a facility where the production of terephthalic acid is 39 Ton / hr, paraxylene, acetic acid 5.5 times by weight of paraxylene, and cobalt acetate, manganese acetate, and hydrogen bromide as catalysts are continuously fed into the liquid phase oxidation reactor. The mixture was supplied, and an oxidation reaction was performed at a temperature of 197 ° C., a pressure of 1.45 Mpa, and a reaction time (average residence time) of 90 minutes. The amount of the catalyst used is such that the amount of the cobalt component is 280 ppm by weight, the amount of the manganese component is 280 ppm by weight, and the amount of the bromine component is 700 ppm relative to the solvent in terms of cobalt metal.

Air is used as a gas for performing an oxidation reaction by molecular oxygen. At this time, the oxygen content of the air is 21%. Then, compressed air was supplied into the reactor such that the oxygen concentration in the gas discharged from the reactor (hereinafter sometimes referred to as waste gas) became 5% by volume. Next, the oxidized slurry was continuously transferred to a low-temperature post-oxidation reactor, and air (oxygen content 21%) was used as a gas for performing an oxidation reaction at a temperature of 190 ° C., a pressure of 1.3 MPa, and a reaction time (average residence time) of 35 minutes.
%) Was supplied such that the oxygen concentration in the waste gas was 6% by volume, and low-temperature additional oxidation was performed.

The slurry after the low-temperature reoxidation reaction is continuously crystallized in a three-stage intermediate treatment tank, and solid-liquid separation is performed at atmospheric pressure, and then the crude terephthalic acid particles are dried by a dryer using steam as a heating source. Was.
The dried crude terephthalic acid particles were slurried in water and purified by hydrogenation at 280 ° C. under a reducing atmosphere of 8 MP. Thereafter, continuous crystallization was performed, and the pressure in the final crystallization tank was reduced to 0.62 MPa, and the temperature was reduced to 160 ° C.

[Example 1]
The obtained slurry containing the purified terephthalic acid is introduced into a screen bowl decanter (screen bowl type centrifuge), which is an integrated separation and washing machine, and then flashed to evaporate the adhering liquid using internal energy. The cake was passed through a valve (discharge valve). At this time, a flash valve equivalent to that disclosed in WO 91/09661 was used. The pressure in the cake holding tank upstream of the valve was 0.64 MPa, and the pressure in the powder holding tank downstream of the valve was open to the atmospheric pressure. The valve opening time per time was 1.0 second, and the cake discharge amount was 23 kg. The slurry supply amount to the screen bowl decanter was 4.5 T / hr, and the washing liquid (water) was 2.0 T / hr.
At this time, the impurities in the mother liquor separated and recovered by the centrifugal separator were 900 ppm, the impurities in the washing liquid after washing the separated cake were 240 ppm, the impurity concentration in the discharged cake was 115 ppm, and the liquid content (adhesion liquid weight / (Dry cake weight) was 4.3%.

[Reference Example 1]
The test was performed under the same conditions as in Example 1 except that the cleaning liquid was not supplied.
At this time, the impurity concentration of the discharged cake was 160 ppm.

[Reference Example 2]
Assuming that the mother liquor and the washing solution could not be separately recovered, the impurity concentration of the recovered solution was estimated to be 590 ppm.

[Reference Example 3]
Assuming that the flash valve was not used, when the internal energy could not be used for evaporating the adhesion liquid, the liquid content was estimated from the heat balance to be 8.8%.

[result]
As described above, the comparison between Example 1 and Reference Example 1 shows that the cleaning effect of the screen bowl decanter on the cake is very large. Next, comparison with Reference Example 2 shows that independent recovery of the cleaning solution is effective for use of the solution with reduced impurities. Also, comparison with Reference Example 3 shows that the use of internal energy is effective for energy saving. And it turns out that these effects are the special effects obtained by using a screen bowl decanter and internal energy together.

[Example 2]
The terephthalic acid slurry after low-temperature oxidation was directly introduced into a screen bowl decanter (screen bowl type centrifuge) without passing through a crystallization tank. The pressure in the screen bowl decanter was maintained at about 0.93 MPa. The slurry supply rate was 20 T / hr, and the washing liquid (acetic acid) was 18 T / hr.
In the screen bowl decanter, a cake and a mother liquor are separated by solid-liquid separation. The cake is washed with a washing solution (acetic acid). The washed cake is carried out to a cake holding tank. At this time, the pressure of the cake holding tank is maintained at about 0.93 MPa. A flash valve equivalent to that disclosed in WO 91/09661 is provided at the lower end of the cake holding tank, and the cake stored in the cake holding tank is opened by opening the flash valve. Then, it moves to the powder retention tank which is open to the atmospheric pressure. When the cake moves, the cake adhering liquid and the internal energy possessed by the cake are released, used as heat for vaporizing the adhering liquid, and the adhering liquid evaporates. The liquid content of the cake after flashing (weight of the attached liquid / weight of the dried cake) was 0.2%.
In other words, by separating and washing the terephthalic acid slurry under high pressure and subsequently using the CTA process to evaporate the adhering liquid by flashing, the crystallization tank and dryer required in the conventional CTA process become unnecessary, The plant equipment has been simplified.

[Example 3]
In Example 2, the reaction mother liquor separated and collected by the screen bowl decanter had a temperature of 185 ° C. and a pressure of 0.93 MPa. By purging 20% by weight of the reaction mother liquor, the other portions could be reused as they were in the oxidation reactor.
That is, by performing the separation and washing of the terephthalic acid slurry under high pressure, the energy of the reaction mother liquor could be effectively used as the energy required for the oxidation reaction without loss.

[Example 4]
In Example 2, when the cake was flushed, most of the cake adhering liquid mainly composed of acetic acid was evaporated. The amount of evaporation was 2 Ton / hr. Evaporated acetic acid gas was accompanied by some dried cake. Therefore, acetic acid vapor is introduced into the solid recovery device from below through a pipe, and liquid acetic acid is supplied from above by spraying, whereby terephthalic acid and acetic acid entrained in the acetic acid vapor are brought into contact to obtain a slurry. Was. This slurry could be directly supplied to the oxidation reaction step.
In addition, the acetic acid vapor that has passed through the solid recovery device also contains some by-produced methyl acetate, and the loss of the acetic acid solvent is reduced by recovering acetic acid and methyl acetate and supplying them to the oxidation reaction step. I was able to.

Flow chart showing a preferred embodiment of the production method of the present invention

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Oxidation reactor 2 Crystallization tank 3 Separation and washing apparatus 4 Powder retention tank 5 Reduction reactor 6 Crystallization tank 7 Separation and washing apparatus 8 Dryer 11 Distillation towers 21, 31, 41, 51, 61 Solid-liquid separation apparatus 42, 62 Solid recovery device 109 Product take-out line 101, 102, 103, 105, 106, 107, 111, 131, 141, 151, 161, 171, 175, 176, 177 Recycle line 112 Drain line 113 Impurity disposal line

Claims (16)

(A) a step of oxidizing para-xylene with molecular oxygen in a solvent mainly containing acetic acid in the presence of a catalyst to obtain terephthalic acid;
(B) a step of solid-liquid separating the slurry containing terephthalic acid crystals into a crude terephthalic acid cake and a mother liquor mainly composed of acetic acid under a pressure of at least atmospheric pressure;
(C) a step of washing the crude terephthalic acid cake with a washing liquid under a pressure of at least atmospheric pressure;
(D) a step of removing the adhesion liquid remaining on the washed crude terephthalic acid cake by evaporation,
In the method for producing crude terephthalic acid having
Performing step (B) and step (C) using one apparatus,
At least a part of the evaporation of the adhesion liquid in the step (D) is performed by the internal energy of the terephthalic acid cake and / or the adhesion liquid,
A method for producing terephthalic acid, comprising: (E) contacting the crude terephthalic acid with hydrogen in a solvent mainly composed of water in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid;
(F) a step of reducing the pressure and temperature of the reaction solution and causing terephthalic acid to crystallize in a medium mainly composed of water;
(G) a step of solid-liquid separating a slurry containing terephthalic acid crystals into a purified terephthalic acid cake and a reaction mother liquor mainly composed of water under a pressure of at least atmospheric pressure;
(H) a step of washing the purified terephthalic acid cake with a washing solution under a pressure of at least atmospheric pressure;
(I) a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation;
In the method for producing terephthalic acid having
Performing step (G) and step (H) using one apparatus,
At least a part of the evaporation of the deposit in the step (I) is performed by the internal energy of the terephthalic acid cake and / or the deposit.
A method for producing terephthalic acid, comprising: (A) a step of oxidizing para-xylene with molecular oxygen in a solvent mainly containing acetic acid in the presence of a catalyst to obtain terephthalic acid;
(B) a step of solid-liquid separating the slurry containing terephthalic acid crystals into a crude terephthalic acid cake and a mother liquor mainly composed of acetic acid under a pressure of at least atmospheric pressure;
(C) a step of washing the crude terephthalic acid cake with a washing liquid under a pressure of at least atmospheric pressure;
(D) a step of removing the adhesion liquid remaining on the washed crude terephthalic acid cake by evaporation,
(E) contacting the crude terephthalic acid with hydrogen in a solvent mainly composed of water in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid;
(F) a step of reducing the pressure and temperature of the reaction solution and causing terephthalic acid to crystallize in a medium mainly composed of water;
(G) a step of solid-liquid separating a slurry containing terephthalic acid crystals into a purified terephthalic acid cake and a mother liquor mainly composed of water;
(H) a step of washing the purified terephthalic acid cake using a washing solution;
(I) a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation;
In the method for producing terephthalic acid having
Performing step (B) and step (C) using one apparatus,
At least a part of the evaporation of the adhesion liquid in the step (D) is performed by the internal energy of the terephthalic acid cake and / or the adhesion liquid,
A method for producing terephthalic acid, comprising: (A) a step of oxidizing para-xylene with molecular oxygen in a solvent mainly containing acetic acid in the presence of a catalyst to obtain terephthalic acid;
(B) a step of solid-liquid separating the slurry containing terephthalic acid crystals into a crude terephthalic acid cake and a reaction mother liquor mainly composed of acetic acid;
(C) washing the crude terephthalic acid cake using a washing solution;
(D) a step of removing the adhesion liquid remaining on the washed crude terephthalic acid cake by evaporation,
(E) contacting the crude terephthalic acid with hydrogen in a solvent mainly composed of water in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid;
(F) a step of reducing the pressure and temperature of the reaction solution and causing terephthalic acid to crystallize in a medium mainly composed of water;
(G) a step of solid-liquid separating the slurry containing terephthalic acid crystals into a purified mother terephthalic acid cake and a reaction mother liquor mainly composed of water under a pressure higher than atmospheric pressure;
(H) a step of washing the purified terephthalic acid cake with a washing solution under a pressure of at least atmospheric pressure;
(I) a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation;
In the method for producing terephthalic acid having
Performing step (G) and step (H) using one apparatus,
At least a part of the evaporation of the deposit in the step (I) is performed by the internal energy of the terephthalic acid cake and / or the deposit.
A method for producing terephthalic acid, comprising: (A) a step of oxidizing para-xylene with molecular oxygen in a solvent mainly containing acetic acid in the presence of a catalyst to obtain terephthalic acid;
(B) a step of solid-liquid separating the slurry containing terephthalic acid crystals into a crude terephthalic acid cake and a mother liquor mainly composed of acetic acid under a pressure of at least atmospheric pressure;
(C) a step of washing the crude terephthalic acid cake with a washing liquid under a pressure of at least atmospheric pressure;
(D) a step of removing the adhesion liquid remaining on the washed crude terephthalic acid cake by evaporation,
(E) contacting the crude terephthalic acid with hydrogen in a solvent mainly composed of water in the presence of a catalyst to reduce at least a part of impurities in the crude terephthalic acid;
(F) a step of reducing the pressure and temperature of the reaction solution and causing terephthalic acid to crystallize in a medium mainly composed of water;
(G) a step of solid-liquid separating a slurry containing terephthalic acid crystals into a purified terephthalic acid cake and a mother liquor mainly composed of water under a pressure of at least atmospheric pressure;
(H) a step of washing the purified terephthalic acid cake with a washing solution under a pressure of at least atmospheric pressure;
(I) a step of removing the adhesion liquid remaining on the purified terephthalic acid cake by evaporation;
In the method for producing terephthalic acid having
Steps (B) and (C) are performed using one apparatus, and steps (G) and (I) are performed using one apparatus.
At least a part of the evaporation of the deposit in the step (D) and the step (I) is performed by the internal energy of the terephthalic acid cake and / or the deposit.
A method for producing terephthalic acid, comprising:   The method for producing terephthalic acid according to any one of claims 1, 3, 4, and 5, wherein the washing solution used in step (C) contains acetic acid.   The terephthalic acid according to any one of claims 1, 3, 4, 5, and 6, wherein at least a part of the vapor generated in the step (D) is recovered, and used as it is or treated and reused in the terephthalic acid production step. Manufacturing method.   The method for producing terephthalic acid according to claim 7, wherein at least a part of the steam generated in the step (D) is recovered, and is recovered as it is or is reused in the step (A).   9. The method according to claim 1, wherein at least a part of a crystal containing terephthalic acid accompanying the vapor generated in the step (D) is recovered, and the crystal is re-supplied to a terephthalic acid production step. The method for producing terephthalic acid according to the above.   The method for producing terephthalic acid according to claim 9, wherein at least a part of crystals containing terephthalic acid accompanying the vapor generated in the step (D) is recovered and re-supplied to the step (A).   The method for producing terephthalic acid according to any one of claims 2 to 10, wherein the cleaning liquid used in the step (H) is mainly composed of water.   The method for producing terephthalic acid according to any one of claims 2 to 11, wherein at least a part of the vapor generated in the step (I) is recovered and used as it is or treated and reused in the step of producing terephthalic acid.   The method for producing terephthalic acid according to claim 12, wherein at least a part of the vapor generated in the step (I) is recovered, and is recovered as it is or is used in the step (E).   The terephthalic acid according to any one of claims 2 to 13, wherein at least a part of crystals containing terephthalic acid accompanying the vapor generated in the step (I) is recovered, and the crystals are re-supplied to the step of producing terephthalic acid. Production method.   15. The terephthalic acid according to claim 14, wherein at least a part of crystals containing terephthalic acid accompanying the vapor generated in the step (I) is recovered, and the crystals are supplied to the step (E) and / or the step (F). Manufacturing method.   The method for producing terephthalic acid according to any one of claims 1 to 15, wherein the one device is a screen bowl decanter.

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