JP2010163380A - Apparatus and method for producing aromatic carboxylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing an aromatic carboxylic acid, enabling long-term stable continuous operation, and providing a high-purity aromatic carboxylic acid having stabilized product quality, and to provide a method for producing the aromatic carboxylic acid. <P>SOLUTION: The apparatus for producing the aromatic carboxylic acid, having a liquid-preparing device, a heater and a hydrogenation reactor is equipped with a foreign matter-removing device for removing a massive material having the maximum major axis of >6 mm at least in one of a water-feeding pipe and a discharging pipe of the liquid-preparing device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for producing an aromatic carboxylic acid. More specifically, the present invention relates to a high-purity aromatic carboxylic acid production apparatus and production method capable of stabilizing the production process and product quality.

  Terephthalic acid, which is a typical example of aromatic carboxylic acid, uses a solvent containing an aliphatic carboxylic acid such as acetic acid, and in the presence of a heavy metal catalyst mainly composed of cobalt, manganese, etc. A method of producing by liquid phase oxidation under pressure with a gas containing molecular oxygen has been industrially performed. The terephthalic acid thus obtained contains impurities such as by-products and is generally called crude terephthalic acid.

  In order to reduce trace impurities as much as possible due to demands from commercial uses of terephthalic acid (such as the production of polyester resin), a further oxidation reaction process at higher temperatures and pressures is provided, and the terephthalic acid slurry after the oxidation reaction is separated. After drying, there is a method that involves dissolving in a solvent such as water at high temperature and high pressure and hydrogenating in the presence of the catalyst, then separating and purifying, etc., especially when high purity is required This purification method by hydrogenation is generally carried out. As the hydrogenation catalyst, a noble metal catalyst such as a palladium catalyst supported on activated carbon is mainly used. The main aim of the purification method is to reduce impurities such as 4-carboxybenzaldehyde to increase water solubility, to separate from terephthalic acid, which is a solid, to improve the purity, and to stabilize the crystal precipitation state of terephthalic acid. For this reason, the quality and powder characteristics of terephthalic acid crystals are maintained constant. The terephthalic acid thus obtained is generally called high-purity terephthalic acid.

  In order to obtain high-purity terephthalic acid, it is necessary to stably carry out raw material supply, reaction, crystal precipitation, solid-liquid separation, transfer within the process, and the like in the entire production process by hydrorefining. In particular, it is important to supply crude terephthalic acid as a raw material at a constant concentration. However, terephthalic acid repeatedly changes its state with solids, solutions, slurries, and solids within the hydrorefining process, and the temperature and pressure fluctuate over a wide range. It is difficult to maintain a continuous stable operation for a long period of time because products tend to be generated and the piping or the like is locally blocked or the slurry concentration or the solution concentration fluctuates.

  In addition, if the wash water, solid-liquid separation liquid, condensate, reflux liquid from the distillation tower, etc. discharged from the manufacturing process is reused as a solvent with the aim of effective use of resources, the solid content mixed in the solvent will cause local problems. The transfer piping may be blocked, and further adverse effects on stable operation may occur.

  Occurrence of such a clogging phenomenon impairs stable operation of the process, causing fluctuations in slurry concentration and solution concentration, and the quality of high-purity terephthalic acid as a product from which this can be obtained, in particular, variations in crystal properties. Bring. In addition to not being able to maintain the stabilization of quality, there is a situation in which the operation of the manufacturing process must be stopped to cope with the clogging phenomenon. It is a cause. Against this background, various proposals have been made as measures for stabilizing the quality in the production process of high-purity aromatic carboxylic acid and stabilizing the continuous operation of the process.

  For example, in Patent Document 1, in order to maintain the concentration of the aqueous terephthalic acid solution at a constant value close to the saturated dissolution concentration at the reaction temperature during the hydrogenation reaction, the aqueous terephthalic acid solution is provided in a circulation pipe provided outside the liquid preparation tank. A method has been proposed in which the concentration of water is measured and the concentration is adjusted by supplying water. However, the proposal mainly aims to obtain terephthalic acid crystals efficiently, and is insufficient to solve the problems related to the stabilization of continuous operation of the process.

  Patent Document 2 discloses that in a slurry agitation tank, a solid content collides with a baffle installed for improving agitation efficiency and adheres to and grows on a liquid surface to become a lump. In addition, it has been proposed to provide a slurry supply port and a discharge port below the liquid surface while holding the liquid surface at the upper end or above the baffle. However, this proposal only suppresses the generation of solid content generated in the middle of the process, and the effect is not sufficient, and the clogging phenomenon that occurs due to various factors cannot be completely eliminated.

  Moreover, in patent document 3, when mixing a crude aromatic carboxylic acid powder with a water solvent, in order to improve affinity with water, after mixing with water after forming a high concentration premixture with a kneading apparatus. A method of forming a slurry and performing a hydrogenation process has been proposed. However, this method increases the burden to the extent that it is not economically practical in terms of equipment costs.

  Furthermore, in Patent Document 4, as a measure for preventing the purification reaction of the crude aromatic carboxylic acid from being hindered by the lump produced in the storage tank of the crude aromatic carboxylic acid crystal, a slurry storage tank having a stirrer is provided and the temperature and In addition to controlling the slurry concentration, a filter is installed at the outlet of the storage tank to collect large particles with an average particle size of 24 mm or more. In this proposal, it is possible to prevent large particles with an average particle diameter of 24 mm or more from flowing into the slurry heating and melting process, but the collected large particles of 24 mm or more remain in the slurry storage tank, so the operation is stopped. The operation to extract is necessary.

As described above, the above-mentioned known techniques relating to the production process of high-purity aromatic carboxylic acid still have many problems, and in particular, a method capable of stably preparing the raw material to be supplied to the hydrogenation process is required.
JP-A-8-143504 JP 2004-168673 A JP 2000-1456 A US Pat. No. 6,245,939

  The present invention was devised in view of the above-mentioned problems, and is an aromatic carboxylic acid production apparatus and production capable of obtaining a high-purity aromatic carboxylic acid capable of long-term stable continuous operation and stable product quality. It aims to provide a method. In particular, when producing a high-purity aromatic carboxylic acid by purifying a crude aromatic carboxylic acid by hydrogenation, a long-term stable continuous operation is possible, and a high-purity aromatic carboxylic acid with stable product quality can be obtained. It aims at providing the manufacturing apparatus and manufacturing method of aromatic carboxylic acid.

  As a result of intensive studies to solve the above problems, the present inventors have found that by providing a specific device, the slurry concentration and the solution concentration can be stabilized, and consequently, long-term continuous operation and product quality can be stabilized. The present invention has been completed.

  That is, the first aspect of the present invention is a liquid material preparation apparatus for preparing a liquid material containing a crude aromatic carboxylic acid and water, and for preparing a crude aromatic carboxylic acid solution by heating the liquid material. An apparatus for producing an aromatic carboxylic acid having a heating device and a hydrogenation reaction device for hydrogenating a crude aromatic carboxylic acid solution, wherein the liquid material preparing device includes a crude aromatic compound in the liquid material preparing device. An aromatic carboxylic acid supply pipe for supplying carboxylic acid, a water supply pipe for supplying water to the liquid material preparation device, and a discharge pipe for discharging liquid material from the liquid material preparation device are connected to each other, and An object of the present invention is to provide an aromatic carboxylic acid producing apparatus comprising a foreign substance removing device for removing a lump exceeding a maximum major axis of 6 mm in at least one of a supply pipe and a discharge pipe. is there.

  In the first aspect, the foreign matter removing device preferably has a sieving function and a scraping function for removing clogging of the sieving function, and the scraping function is provided in the foreign matter removing device. It is preferable that the brush is used. Moreover, it is preferable that a foreign material removal apparatus has a foreign material discharge function.

  In the first aspect, the production apparatus further includes an oxidation reaction apparatus for obtaining an oxidation reaction treatment liquid containing a crude aromatic carboxylic acid by oxidizing an alkyl aromatic compound before the liquid material preparation apparatus. It is preferable to have a solid-liquid separation device for solid-liquid separation of the crude aromatic carboxylic acid from the oxidation reaction treatment liquid.

  Further, in the first aspect, the water supplied from the water supply pipe to the liquid material preparation device is water discharged from the top of the reactor tower of the oxidation reaction device and separated by distillation, and solid-liquid separation is performed by the solid-liquid separation device. It is preferable to contain at least one selected from a cleaning liquid obtained by washing the crude aromatic carboxylic acid with water and water recovered after hydrogenating the crude aromatic carboxylic acid with a hydrogenation reactor.

  In the first aspect, it is also preferable that the aromatic carboxylic acid supply pipe includes a sieve for sieving the crude aromatic carboxylic acid having a maximum major axis exceeding 10 mm.

  The second aspect of the present invention is a liquid material preparation step for preparing a liquid material containing a crude aromatic carboxylic acid and water in a liquid material preparation device, and preparing a crude aromatic carboxylic acid solution by heating the liquid material And a hydrogenation reaction step of hydrogenating the crude aromatic carboxylic acid solution in an aqueous solvent, wherein the liquid material preparation apparatus includes the liquid material preparation apparatus. An aromatic carboxylic acid supply pipe for supplying crude aromatic carboxylic acid, a water supply pipe for supplying water to the liquid material preparation device, and a discharge pipe for discharging the liquid material from the liquid material preparation device are connected to each other. And providing a method for producing an aromatic carboxylic acid, characterized in that at least one of the water supply pipe and the discharge pipe is provided with a foreign substance removing device that removes a lump exceeding a maximum major axis of 6 mm. To solve .

  In the second aspect, the foreign matter removing device preferably has a sieving function and a scraping function for removing clogging of the sieving function, and the scraping function is provided in the foreign matter removing device. It is preferable that the brush is used. The foreign matter removing device preferably has a foreign matter discharging function.

  In addition, the production method of the second aspect includes an oxidation reaction step of oxidizing an alkyl aromatic compound to obtain an oxidation reaction treatment liquid containing a crude aromatic carboxylic acid, and an oxidation reaction before the liquid preparation step It is preferable to have a solid-liquid separation step for solid-liquid separation of the crude aromatic carboxylic acid from the treatment liquid.

  Further, in the second aspect, the water supplied from the water supply pipe to the liquid material preparation tank includes water discharged from the oxidation reaction step and distilled and separated, and a crude aromatic carboxylic acid that has been solid-liquid separated in the solid-liquid separation step It is preferable to contain at least one selected from a washing solution obtained by washing water with water and water recovered after hydrogenating the crude aromatic carboxylic acid in the hydrogenation reaction step.

  In the second aspect, it is also preferable that the aromatic carboxylic acid supply pipe is provided with a sieve for sieving the crude aromatic carboxylic acid having a maximum major axis exceeding 10 mm.

  In the second embodiment, the inner wall temperature of the aromatic carboxylic acid supply pipe is preferably higher by 10 to 50 ° C. than the liquid temperature in the liquid preparation apparatus.

Moreover, in a 2nd aspect, it is preferable that a liquid preparation apparatus is equipped with a stirring blade, and stirring power is 0.3 kW / m < ³ > or more.

  According to the present invention, the formation of lumps in a slurry composed of a crude aromatic carboxylic acid and water is suppressed, and there is no blockage of piping or cavitation of the pump. As a result, stable long-term continuous operation is possible. Further, since the concentration of the solution supplied to the hydrogenation reactor is stabilized, the product quality of the obtained high-purity aromatic carboxylic acid is stabilized, and the economic loss is reduced.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

FIG. 1 is a schematic view showing one embodiment of an apparatus for producing an aromatic carboxylic acid according to the present invention. A carboxylic acid production apparatus 500 shown in FIG. 1 includes an oxidation reaction apparatus 10, a solid-liquid separation washing and drying apparatus 20, a liquid material preparation apparatus 30, a heating apparatus 40, a hydrogenation reaction apparatus 50, a crystallization apparatus 60, and a solid-liquid separation. A cleaning / drying device 70 is provided. The method for producing the aromatic carboxylic acid of the present invention using this is as follows:
(1) Oxidation reaction step: In the oxidation reaction apparatus 10, the alkyl aromatic compound 1 is pressurized with a gas containing molecular oxygen 3 in the presence of a catalyst 4 using a solvent 2 containing an aliphatic carboxylic acid. Step of liquid-phase oxidation to obtain slurry-like oxidation reaction product 6 (2) Solid-liquid separation step: Slurry-like oxidation reaction product 6 is solid-liquid separated, washed and dried by solid-liquid separation washing and drying apparatus 20 Step of obtaining crude aromatic carboxylic acid crystal 7 (3) Liquid material preparation step: Crude aromatic carboxylic acid crystal 7 is mixed with solvent 5 mainly composed of water in liquid material preparation device 30, and crude aromatic carboxylic acid slurry is obtained. 8 is prepared by heating and dissolving in the heating device 40 to obtain a crude aromatic carboxylic acid solution 9 (4) Hydrogenation reaction step: The hydrogenation reaction device having the crude aromatic carboxylic acid solution 9 having a stationary phase catalyst 50 with hydrogen 13 Step (5) Crystallization Step of Obtaining Elementalization Reaction Solution 10: Crystallization of Hydrogenation Reaction Solution 10 with Crystallizer 60, and Obtaining High Purity Aromatic Carboxylic Acid Slurry 11 Subsequently, Solid-Liquid Separation Washing Drying The apparatus 70 has five steps of solid-liquid separation, washing and drying to obtain a high-purity aromatic carboxylic acid 12 as a product, and the present invention is particularly characterized by (3) a liquid preparation step. .

  Hereinafter, the present invention will be described in detail while sequentially explaining each step of (1) oxidation reaction step to (5) crystallization step according to FIG.

<(1) Oxidation reaction step>
(1) In the oxidation reaction step, in the oxidation reaction apparatus 10, the raw material alkyl aromatic compound 1 is liquidized in a gas containing molecular oxygen 3 in the presence of the catalyst 4 in the solvent 2 under a pressure exceeding normal pressure. Phase oxidation is performed to obtain a slurry-like oxidation reaction product 6 containing a crude aromatic carboxylic acid.

  The alkyl aromatic compound 1 that is a raw material for producing the aromatic carboxylic acid is not particularly limited, and the aromatic ring constituting the alkyl aromatic compound 1 may be monocyclic or polycyclic.

  Although there is no restriction | limiting in particular as an alkyl group which the alkyl aromatic compound 1 has, For example, a methyl group, an ethyl group, n-propyl group, an isopropyl group etc. can be mentioned. Moreover, each alkyl group which the alkyl aromatic compound 1 has may be partially oxidized. The partially oxidized alkyl group means that the alkyl group in the alkyl aromatic compound 1 is oxidized to an aldehyde group, an acyl group, a carboxyl group, a hydroxyalkyl group, etc., but is also oxidized to a carboxylic acid. It is not a group.

  Specific examples of the alkyl aromatic compound 1 used as a raw material in the present invention include m-diisopropylbenzene, p-diisopropylbenzene, m-cymene, p-cymene, m-xylene, p-xylene, trimethylbenzenes and the like. And alkylbenzenes having 2 to 4 alkyl groups having 1 to 4 carbon atoms, alkylnaphthalenes, and alkylbiphenyls. Specific examples of the alkyl aromatic compound 1 having a partially oxidized alkyl group include, for example, 3-methylbenzaldehyde, 4-methylbenzaldehyde, m-toluic acid, p-toluic acid, and 3-formylbenzoic acid. , 4-formylbenzoic acid, and 2-methyl 6-formylnaphthalene. These raw materials are used alone or in combination of two or more.

  As the reaction solvent 2, aliphatic carboxylic acids such as acetic acid, propionic acid, formic acid and butyric acid are preferably used, but a solvent containing acetic acid as a main component is particularly preferable. As a solvent having acetic acid as a main component, a mixture of acetic acid and water is preferable, and usually a mixture in which 1 to 20 parts by mass of water and preferably 5 to 15 parts by mass of water are mixed with 100 parts by mass of acetic acid. Since water is by-produced by the reaction, the water in the reaction solvent 2 is adjusted by purging a part of the condensate obtained by condensing a reaction gas from the oxidation reaction apparatus 10 described later to the outside of the system. . For example, in the case of the production process of terephthalic acid, the amount of the solvent 2 used is preferably 2 to 6 times by mass, more preferably 2 to 4 times by mass with respect to paraxylene as a raw material. If the amount of the solvent 2 is too small, the reaction slurry temperature is too high, which may cause troubles such as clogging. This is economically undesirable.

  As the gas containing molecular oxygen 3, for example, a gas containing molecular oxygen such as air, oxygen diluted with an inert gas, or oxygen-enriched air is used. The supply amount is 3 to 100 times mol as molecular oxygen 3 with respect to the raw material, and air is preferably used practically. The oxygen content of the air at the entrance is 21% by volume. And it supplies so that the oxygen concentration in the waste gas discharged | emitted from the oxidation reaction apparatus 10 may be 1-8 volume%, Preferably it is 1.5-3 volume%.

  The catalyst 4 is not particularly limited as long as it has an ability to oxidize and convert the alkyl aromatic compound 1 to an aromatic carboxylic acid, but usually a heavy metal compound is used, and as a catalyst auxiliary as necessary. Bromine compounds may be used. Examples of the heavy metal in the heavy metal compound include cobalt, manganese, nickel, chromium, zirconium, copper, lead, hafnium, cerium and the like. These can be used alone or in combination. It is particularly preferable to use a combination of cobalt and manganese. Examples of such heavy metal compounds include acetate, nitrate, acetyl acetate, naphthenate, stearate, bromide, and the like, and acetate and bromide are particularly preferable.

  Examples of bromine compounds include inorganic bromine compounds such as molecular bromine, hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, manganese bromide, methyl bromide, methylene bromide, bromoform, and odor. And organic bromine compounds such as benzyl bromide, bromomethyltoluene, dibromoethane, tribromoethane, and tetrabromoethane. These bromine compounds are also used alone or as a mixture of two or more.

  When the aromatic carboxylic acid produced by the production method of the present invention is terephthalic acid, the catalyst 4 used for oxidizing the raw material paraxylene is specifically preferably a combination of cobalt, manganese and bromine, particularly A combination of cobalt acetate, manganese acetate and hydrogen bromide is preferred.

  In the present invention, when the catalyst 4 is composed of a combination of a heavy metal compound and a bromine compound, the bromine atom is desirably 0.05 to 10 moles, preferably 0.1 to 5 moles per mole of the heavy metal. Such a catalyst 4 is normally used in the range of 10 to 10000 mass ppm, preferably 10 to 3000 mass ppm as the heavy metal catalyst in the reaction solvent 2.

  The oxidation reaction temperature is usually 140 ° C to 250 ° C, preferably 150 ° C to 230 ° C. If the reaction temperature is too low, the reaction rate decreases, and if the temperature is too high, the amount of loss due to combustion of the reaction solvent 2 increases. The reaction pressure needs to be equal to or higher than the pressure at which the mixture can maintain a liquid phase at least at the reaction temperature, and needs to be a pressure higher than normal pressure. Specifically, 0.2 to 6 MPa (absolute pressure) is preferable, and 0.4 to 3 MPa (absolute pressure) is more preferable. In order to facilitate the transfer of the slurry-like oxidation reaction product 6 to be generated, it is better that the pressure is higher, which leads to suppression of side reactions. On the other hand, it is preferable that the pressure is low from the viewpoint of the pressure resistance strength of the oxidation reaction apparatus 10 and the equipment cost.

  The reaction is usually carried out continuously, and the reaction time (average residence time) is usually 30 to 300 minutes, preferably 40 to 150 minutes. If the reaction time is too short, the progress of the reaction is insufficient and the target product quality may not be obtained. On the other hand, if the reaction time is too long, the amount of loss due to combustion of the reaction solvent 2 increases and the capacity of the oxidation reaction device 10 increases. Not economical.

  The structure of the oxidation reaction apparatus 10 is often a stirring tank, but may be of a bubble column type. In the case of the bubble column, the molecular oxygen 3 supplied from the lower part of the bubble column is extracted from the bubble column as a reaction gas accompanied by a large amount of solvent vapor after being used for the oxidation reaction.

  The extracted reaction gas is preferably subjected to a treatment for recovering and reusing the solvent and energy. For example, the reaction gas is condensed by a condenser (not shown) installed in the upper part of the oxidation reaction apparatus 10, and the obtained condensate mainly containing the solvent is returned to the oxidation reaction apparatus 10 while being contained in the remaining exhaust gas. Water and aliphatic carboxylic acids are also separated and reused. After recovering the solvent and the like, the exhaust gas discharged from the upper part of the absorption tower is still maintained at a high pressure, so that it is made harmless after the energy is recovered and released. In the case of the reaction in the stirring tank, the reaction gas is similarly treated.

  As another preferred embodiment, instead of the condenser, a high-pressure distillation column is directly connected to the upper part of the oxidation reaction apparatus 10, and a separation mother liquor mainly composed of water solid-liquid separated in the crystallization step described later is It is introduced into the upper part of the high-pressure distillation column and brought into contact with the reaction gas of the oxidation reaction apparatus 10 to oxidize the intermediate intermediate in the separated mother liquor for reuse, and at the same time, aliphatic carboxylic acid, by-products, water, etc. It can also be separated and reused.

  (1) In the oxidation reaction step, additional oxidation treatment may be performed as necessary. The post-oxidation treatment means that the reaction mixture obtained by the above oxidation reaction is oxidized at least once in the presence of molecular oxygen without supplying the raw material alkyl aromatic compound 1 under low temperature conditions or high temperature conditions. To do. In that case, another oxidation reaction apparatus (not shown) is added. The slurry-like oxidation reaction product 6 obtained by the oxidation reaction is sent to the next (2) solid-liquid separation step.

<(2) Solid-liquid separation process>
The slurry-like oxidation reaction product 6 is solid-liquid separated by a solid-liquid separation washing / drying apparatus 20, washed, and dried to obtain a crude aromatic carboxylic acid crystal 7. Prior to the recovery of the crude aromatic carboxylic acid crystal 7, a plurality of crystallization tanks are provided, the pressure is lower than that during the oxidation reaction, the reaction is cooled by evaporation under reduced pressure, and a slurry-like oxidation reaction with an increased precipitation amount. Solid-liquid separation from the product 6 is also possible. In this case, it is preferable to install a plurality of crystallization tanks. The operation may be batch or continuous, but it is usually preferable to step down the pressure stepwise in two or more stages. The number of stages is preferably 6 or less, more preferably 5 or less. The pressure release pressure may finally be carried out at normal pressure.

  Solid-liquid separation can be carried out at normal pressure, reduced pressure, or increased pressure. In the case of pressure separation, the pressure is usually 0.01 MPa or more, preferably 0.03 MPa or more, more preferably 0.05 MPa or more. The upper limit is 20 MPa or less, preferably 10 MPa or less, more preferably 5 MPa or less, and particularly preferably 2 MPa or less.

  As the solid-liquid separator, a screen bowl decanter, a solid bowl separator, a rotary pressure filter, a rotary vacuum filter, a horizontal belt filter, and the like can be adopted. In this embodiment, the solid-liquid separation washing and drying apparatus 20 capable of performing solid-liquid separation, washing, and drying with one apparatus is illustrated for solid-liquid separation, washing, and drying operations. Cleaning and drying can also be performed in separate devices.

  The cleaning liquid is not particularly limited as long as it exists under the pressure and temperature conditions in the solid-liquid separation cleaning / drying apparatus 20 so as to hold the liquid. Although the thing compatible with the solvent used with the oxidation reaction apparatus 10 is preferable, generally water is used.

  The liquid content of the cake subjected to solid-liquid separation and washing is usually 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less.

  In addition, as a solid-liquid separation device, using a device in which solid-liquid separation and washing are integrated, and replacing the solvent contained in the cake with water, a crude product containing water as it is without passing through a drying device. The aromatic carboxylic acid crystal 7 may be obtained. When not passing through the drying device, the crude aromatic carboxylic acid crystal 7 containing water is introduced into the liquid material preparing device 30 via the aromatic carboxylic acid supply pipe 31 in the next step.

  The separated mother liquor is preferably (1) recycled to the oxidation reaction, but is preferably partially purged from the viewpoint of quality maintenance. In that case, it is branched into the recycling mother liquor and the purge mother liquor while maintaining the pressure exceeding the normal pressure. “While maintaining a pressure exceeding normal pressure” is a pressure that substantially maintains the operation pressure of solid-liquid separation. As another embodiment, it is preferable to perform a solid-liquid separation and recycling while maintaining the temperature and pressure during the oxidation reaction, since this further saves energy. The branching ratio between the recycled mother liquor and the purge mother liquor can be arbitrarily adjusted according to the situation of the entire manufacturing process. Usually, the lower limit of the recycling rate {recycle mother liquor mass × 100 / (recycle mother liquor mass + purge mother liquor mass)} is , Preferably 50% by mass, more preferably 70% by mass. In such a range, there is an advantage that the amount of the purge mother liquor is reduced, and as a result, the loss of the mother liquor can be reduced. If the lower limit is further increased, there is an advantage that the methyl bromide concentration in the oxidation reaction apparatus exhaust gas can be lowered. The upper limit of the recycling rate is preferably 95% by mass, more preferably 90% by mass. By setting it in such a range, accumulation of impurities in the system can be suppressed, and product quality can be improved.

  The separated mother liquor / cleaning liquid to be purged contains many components such as aromatic carboxylic acid, unreacted raw material, by-product, catalyst, solvent, and water. Therefore, these valuable components are preferably recovered and reused. As a method for recovering / reusing reusable materials, a plurality of recovery methods are used in combination according to the physical properties and properties of the recovery target. Specifically, by using volatility, first a volatile substance is separated from a non-volatile substance with an evaporator, and then further separated from the volatile matter and the evaporator residue. Many methods such as a method of separating a soluble component and an insoluble component into an organic solvent side and a water side and further performing a separation treatment are known, and any method can be adopted.

  In the present embodiment, the (1) oxidation reaction step and (2) solid-liquid separation step for obtaining the crude aromatic carboxylic acid crystal 7 are continued with the steps after the (3) liquid preparation step described later. However, it may be divided. That is, a crude aromatic carboxylic acid crystal 7 is obtained in advance through (1) an oxidation reaction step and (2) a solid-liquid separation step, and transported, stored, etc., and then (3) a hopper 21 in a liquid preparation step. Or the like.

<(3) Liquid substance preparation process>
(3) In the liquid preparation step, the crude aromatic carboxylic acid crystal 7 obtained in the above (2) solid-liquid separation step is mixed with a solvent 5 mainly composed of water to obtain a crude aromatic carboxylic acid slurry 8 ( (Hereinafter also referred to simply as slurry 8), and (4) the slurry 8 is heated by the heating device 40 to supply the hydrogenation reaction device 50 in the hydrogenation reaction step in the form of a solution. In this step, the acid solution 9 is generated.

  The type of the solvent 5 is not particularly limited, but it is desirable to include water from the viewpoint of solubility of organic matter, boiling point, etc., more preferably 90% by mass or more is water, and even more preferably, almost 100% by mass is water. preferable.

  As the water used for the solvent 5, it is preferable to reuse the water generated in the production process of the high purity aromatic carboxylic acid of the present invention in order to suppress the consumption of water. For example, (1) water from the top of a distillation column or dehydration tower distilled and separated in the oxidation reaction apparatus in the oxidation reaction step, water extracted from reflux water to the top of the column, (2) solid-liquid separation step The washing liquid obtained by washing the crude aromatic carboxylic acid 7 solid-liquid separated in the solid-liquid separation drying washing apparatus 20 with water, the crude aromatic carboxylic acid solution 9 in an aqueous solvent in the hydrogenation reaction step (4) described later. Water recovered from the hydrogenation reaction apparatus 50 after hydrogenation can be preferably used. In addition, organic substances such as an oxidation intermediate dissolved in the mother liquor obtained after solid-liquid separation of the high-purity aromatic carboxylic acid 12 in the crystallization step (5) described later is again crystallized and separated as necessary. A part of the treatment liquid can also be used as a solvent after being recovered by extraction treatment or the like. Furthermore, a part of the mother liquor can be removed by adsorbing and concentrating trace impurities such as catalyst and dissolved organic matter contained using an ion exchange resin, reverse osmosis membrane system, etc., and the permeated water can be reused as a solvent. it can. In addition, about reuse of the water produced | generated within a manufacturing process, for example, EP4988591 gazette, WO94 / 19082 gazette, WO97 / 27168 gazette, WO96 / 11899 gazette, WO06 / 102459 gazette, WO01 / 12302 gazette JP-A-11-349529.

  (3) In the liquid preparation step, first, the crude aromatic carboxylic acid crystal 7 passes through the aromatic carboxylic acid supply pipe 31, and the solvent 5 mainly composed of water passes through the water supply pipe 32, respectively. The crude aromatic carboxylic acid slurry 8 is prepared by being charged into the liquid preparation device 30 and mixed. In order to ensure long-term stable operation of the entire aromatic carboxylic acid production process and to stably maintain the product quality of the aromatic carboxylic acid, it is most important to control the particle size of the lump in the slurry 8. is there.

  If there is a large lump when the slurry 8 is prepared, the discharge pipe 33 and the pressure pump 80 for discharging the slurry 8 from the liquid preparation device 30 may be blocked. In addition, if the particle size of the lump in the slurry 8 is too large, the dissolution rate of the slurry 8 becomes slow in the heating and melting step in the next heating device 40, and the slurry 8 cannot be completely dissolved. Due to the quality control of the high purity aromatic carboxylic acid 12 of the product, a part of the transfer pipe between the apparatus 30 and the hydrogenation reaction apparatus 50 is partially blocked and the solution concentration falls below the target value. Problems occur. Further, when the slurry 8 has a large lump and cannot be completely dissolved by the heating device 40, (4) the hydrogenation reaction does not proceed with respect to impurities remaining in the solid content in the hydrogenation reaction step. Not only does the purification effect not be exhibited, but there also occurs a situation in which the flow of the catalyst layer is blocked and the reaction does not proceed sufficiently.

  As a result of various investigations on the maximum particle size of the slurry 8 necessary to avoid these problems, the maximum long diameter of the aggregate contained in the slurry 8 is 6 mm or less upstream of the inlet of the pressurizing pump 80 in the discharge pipe 33. It was also found that the thickness is preferably 5 mm or less, particularly 4 mm or less. And in order to make the maximum long diameter of the lump contained in the slurry 8 within the above range, a foreign matter removing device 200 for removing the lump is installed in the discharge pipe 33 which is the outlet of the liquid preparation device 30. It has been found that it is effective to separate large particles that exceed the maximum major axis described above. In the present invention, the term “particles whose maximum major axis is a specific value or less” refers to particles that pass through a sieve having the specific value as the aperture diameter.

  The foreign matter removing device 200 may be any device that can remove the lump in the slurry 8, but the foreign matter removing device 200 has a sieve function and has a scraping function for removing clogging of the sieve function. It is preferable. Specifically, a switching type manual strainer, an automatic strainer, or the like is used. As the automatic type, an automatic cleaning strainer, an automatic rotary strainer, an automatic scraping type strainer, or the like is used, and among these, an automatic scraping type strainer is preferable.

  A schematic diagram of a preferred foreign matter removing apparatus 200 applied to the present invention is shown in FIG. The foreign matter removing apparatus 200 of this embodiment is an automatic scraping type strainer, and the slurry 8 is introduced from the liquid material inlet 203 and passes from the inside to the outside of the cylindrical fixed element screen 201 fixed inside the cylindrical strainer. Then, the liquid material exits 204. Inside the element screen 201, a brush scraper 202 fixed to a rotating shaft is installed in close proximity, and sludge containing clogged masses inside the element screen 201 is always rotated at a low speed of about 10 rpm. The scraper 202 is automatically scraped, sent to the lower sludge pot, and automatically discharged from the sludge discharge port 205 to the outside by the discharge valve. The lump removal method in the foreign matter removing apparatus used in the present invention is not limited, but preferably has a foreign matter discharging function. The foreign matter discharging function is preferably a scraping and sucking method, for example, a method of providing a suction port in a rotating brush / scraper 202 for sucking a lump of lump and sending it to a lower sludge pot. . As described above, the scraping function is provided and the scraping suction method is used, so that the lump removed by the foreign matter removing device 200 is discharged without being stored on the upstream side of the sieve. Therefore, the continuous operation can be performed without temporarily stopping the apparatus for producing an aromatic carboxylic acid of the present invention and removing the lump.

  The strainer shape in the automatic scraping strainer 200 includes a straight shape that flows straight from the direction of the liquid flow, a T shape that bends at right angles, and a Y shape that bends in a Y shape. Moreover, a slit shape, a wedge wire shape, etc. are used for a screen, As a kind of screen, a slash screen, a slit grill, a wedge wire, a punching metal, a flat mesh, etc. are mentioned. The opening of the screen is indispensable to be 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less, in order to remove coarse lumps contained in the slurry 8. If the mesh opening is too large, the lump contained in the slurry 8 is too large, causing cavitation at the inlet of the pressurizing pump 80 or blocking it, thereby hindering operation. On the other hand, if the opening of the screen is too small, the screen is likely to be clogged, resulting in inefficiency. Therefore, the opening of the screen is preferably 100 μm or more, more preferably 500 μm or more. The shape of the brush scraper 202 includes a brush shape and a scraper plate shape, but a brush shape is appropriate. The sludge containing the collected lump may be recycled and reused in the (1) oxidation reaction step.

  In addition, although the installation location of the foreign material removal apparatus 200 is provided in the arbitrary positions between the liquid substance preparation apparatus 30 and the hydrogenation reaction apparatus 50, it is preferable that it is upstream from the heating apparatus 40, and a pressure pump More preferably, it is upstream of 80. If the foreign substance removing device 200 is provided on the upstream side of the heating device 40, the lump that has passed through the foreign substance removing device 200 can be further finely divided or dissolved by heating. In addition, if the foreign matter removing device 200 is provided upstream of the pressurizing pump 80, troubles due to blockage or overload of the pressurizing pump 80 can be prevented.

  Two or more foreign substance removing devices 200 may be provided at any position between the liquid material preparing device 30 and the hydrogenation reaction device 50. For example, one device is provided on the upstream side of the pressurizing pump 80, and one device is provided on the downstream side of the heating device 40, and finer foreign substances are removed by the latter, so that (4) the hydrogenation reaction step can be performed more stably. It can be performed.

  When the water generated in the manufacturing process as described above is reused as the solvent 5 for preparing the slurry 8, the foreign matter removing device 200 is also provided in the water supply pipe 32 to the liquid material preparing device 30. It is preferable to install an apparatus 300 similar to the above. When solid content is mixed in water generated in the manufacturing process, it is possible to prevent the piping from being blocked due to the solid content. The preferable shape and method, the opening diameter of the screen, and the installation effect are the same as those of the foreign matter removing apparatus 200 installed in the discharge pipe 33.

  By removing the lump with the foreign matter removing devices 200, 300, a long-term continuous stable operation of the manufacturing process is possible. In order to secure a stable operation over a longer period and maintain product quality more stably, It is preferable to take various measures for the following lump.

  (3) In the liquid preparation step, the crude aromatic carboxylic acid crystal 7 is supplied from the hopper 21 or the like to the liquid preparation device 30 via the aromatic carboxylic acid supply pipe 31 (hereinafter also simply referred to as the supply pipe 31). However, in some cases, the crude aromatic carboxylic acid crystals 7 aggregate in the supply pipe 31 and adhere to the wall of the supply pipe 31 to generate a lump. In this lump, the water vapor evaporated from the liquid material preparation device 30 is condensed on the inner wall surface of the supply pipe 31 to form water droplets, to which the crude aromatic carboxylic acid crystals 7 adhere, and further, moisture and crude aromatic carboxylic acid crystals. The deposits grow as 7 is embraced. If the lump on the wall of the supply pipe 31 becomes large, the supply pipe 31 is closed and the operation is stopped. As a workaround, the supply of the crude aromatic carboxylic acid crystal 7 is temporarily stopped and the deposits are intermittently deposited. Is removed and dropped into the tank. Meanwhile, the slurry concentration in the liquid material preparation device 30 is lowered, which is a problem in quality control.

  As a measure for preventing the supply pipe 31 from being blocked, it is preferable to maintain the inner surface temperature of the supply pipe 31 at a temperature equal to or higher than the liquid material preparation apparatus 30 temperature so that water droplets do not condense on the inner wall surface. Specifically, the inner surface temperature of the supply pipe 31 is preferably maintained in a range higher by 10 ° C. to 50 ° C. than the temperature of the slurry 8 in the liquid material preparation device 30. For this purpose, for example, there is a method in which the supply pipe 31 is a double pipe and the pipe is kept warm through a crude aromatic carboxylic acid crystal 7 on the inside and a heat medium on the outside. The heat medium is not particularly limited as long as it can heat the inner surface temperature of the supply pipe 31 within the above temperature range, such as steam or hot oil. A so-called trace pipe is installed around the supply pipe 31, and steam or hot oil or the like is passed as a heat medium for heat insulation, or an electric trace method for heat insulation while adjusting the temperature by energization. However, since the temperature distribution around the pipe tends to be unevenly distributed, a method using a double pipe is particularly preferable. The pipe is most preferably a straight pipe, and it is desirable to minimize bending as much as possible.

  Moreover, when the crude aromatic carboxylic acid crystal 7 is stored in the silo, the hopper 21 or the like, a lump may be partially formed. When this lump is supplied to the liquid preparation device 30, a phenomenon occurs in which it is not sufficiently dispersed in the liquid preparation device 30 and is blocked at the slurry discharge port or the discharge pipe 33 of the liquid preparation device 30. There are things to do. These lumps are those that adhere to the inner wall surface of the storage tank due to residual moisture in the solid content during storage in the hopper 21 and the like, and those that have been dried and solidified have peeled off. It is usually hardened so that it does not break easily. Therefore, as a measure for preventing such a lump from entering the liquid preparation device 30, a large particle separation device 400 is installed in the supply pipe 31 to the liquid preparation device 30 downstream of the hopper 21, It is preferable to separate and remove the lump. As the large particle separation device 400, a sieve capable of sieving large particles of the crude aromatic carboxylic acid crystal 7 is preferable, and examples thereof include a vibrating sieve, a rotating sieve, a shaking sieve, and a rotating sieve. A vibrating sieve is particularly preferable from the viewpoint of throughput. As the sieving surface used for sieving, a punched plate, a sieving net, or the like can be used. As the material, metal nets such as phosphor bronze, brass, steel, and stainless steel are mainly used, and resins such as nylon may be used. The shape of the sieve mesh is a square, a rectangle or a circle, but a square is preferably used. As for the weaving method of the sieve mesh, there are plain weaves and twill weaves as well as special weaves.

  As described above, the crude aromatic carboxylic acid crystal 7 preferably has large particles removed, and the maximum major axis is 10 mm or less, preferably 6 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less. For this reason, the opening of the sieve in the large particle separator 400 is 10 mm or less, preferably 6 mm or less, more preferably 5 mm or less, and further preferably 4 mm or less. Agglomerates having a particle size larger than the sieve mesh are collected by the sieve and can be prevented from entering the liquid preparation apparatus 30. If the opening is too large, the opening is blocked in the supply pipe 31 to the liquid material preparation device 30 or at the outlet of the liquid material preparation device 30. On the other hand, if the opening is too small, clogging increases and the efficiency is not high. Therefore, the opening is preferably 100 μm or more, preferably 500 μm or more. The sieved large particles may be recycled by returning to the above (1) oxidation reaction step.

  In order to prevent the lump from entering the liquid material preparation device 30, a pulverizer (not shown) may be installed in place of the large particle separation device 400 to take measures for pulverizing the large particles. Examples of the pulverizer include a compression pulverizer, an impact compression pulverizer, a shear pulverizer, and a friction pulverizer.

Further, in the liquid material preparation device 30, the concentration distribution of the slurry in the device is unevenly distributed, so that the solid content is distributed more in the lower part of the liquid material preparation device 30, and the crude aromatic carboxylic acid crystal 7 is aggregated and grows. In some cases, a lump may be generated. Further, starting from the adhesion of the slurry 8 to the inner wall surface of the liquid material preparation apparatus 30, a lump may be formed by drying and growth, and this may fall into the tank. These aggregates cause clogging at the outlet of the liquid material preparation device 30, clogging of the discharge pipe 33, cavitation of the pressure pump 80, and the like. As a measure for preventing adhesion and blocking to the inner wall surface of the liquid material preparation device 30, the method described in Patent Document 2, that is, considering the positional relationship between the baffle and the liquid level, the liquid level is set at the upper end of the baffle or above. The supply pipe 31 and the discharge pipe 33 of the liquid material preparation device 30 can be partly prevented by providing the liquid material preparation device 30 below the liquid surface, but the solids must be further increased if the dispersion force in the liquid material preparation device 30 is not increased. The particles settle, the distribution of the slurry concentration in the liquid preparation device 30 is non-uniform, and the large particle size solids tend to accumulate at the bottom of the liquid preparation device 30. The inventors of the present invention have found that strengthening the dispersion power by strengthening the stirring ability is particularly effective for solving the above situation. Strategies for strengthening the stirring force include a plurality of stages of stirring blades, appropriate selection of stirring blades, and appropriate setting of stirring power. It is desirable to install two or more stirrer blades. However, it is sufficient that even if one stirrer blade is combined with the stirrer blade and stirring power, an appropriate dispersion force can be maintained. As the shape of the stirring blade, a propeller, a turbine, a flat blade, an anchor, a helical ribbon, etc. can be adopted. The stirring power may be 0.3 kw / m ³ or more per unit volume. Preferably 0.4 kw / ^{m 3} or more, more preferably 0.5 kw / ^{m 3} or more, and usually 2.0 kW / ^{m 3} or less, preferably 1.5 kw / ^{m 3} or less. If the stirring power is too small, uniform stirring cannot be performed, and sufficient stirring effect of the particles cannot be obtained, and the particles partially settle. On the other hand, if the agitation power is too large, the power consumption becomes excessive. Therefore, it is appropriately set in consideration of the uniformity of the flow state of the slurry in the tank.

  A propeller is preferably used as the stirring blade. When a propeller is used, the number of rotations is not limited because it depends on the shape and size of the liquid material preparation device 30, but is preferably 30 to 500 rpm, more preferably 50 to 300 rpm, and still more preferably 70 to 100 rpm.

  (3) In the liquid preparation process, to ensure long-term stable operation more reliably and maintain product quality in a stable manner, the slurry concentration and slurry concentration fluctuations are combined with various measures for the lump as described above. It is preferable that the width is also adjusted.

  The slurry concentration is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and usually 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less. If the concentration is low, the apparatus becomes large and not economical. On the other hand, if the concentration is high, the fluidity of the slurry 8 increases, and special equipment is required, resulting in an increase in equipment costs.

  The preferable control range of the slurry concentration is within ± 1.5 mass% of the target slurry concentration, preferably within the target value ± 1.0 mass%, particularly preferably within the target value ± 0.5 mass%. If the fluctuation range of the slurry concentration is large, (4) the reaction in the hydrogenation reaction step becomes a heterogeneous reaction, or (5) the crystallographic property changes greatly in the crystallization step, and the particle size and particle shape are not stabilized. Sometimes. As a result, the quality of the high-purity aromatic carboxylic acid 12 that is the product becomes unstable, which is not desirable.

  The slurry residence time in the liquid preparation apparatus 30 is preferably 10 to 60 minutes, particularly preferably 15 to 30 minutes. If the residence time is too short, the preparation of the slurry concentration is insufficient. On the other hand, if the residence time is too long, a large facility is required and it is not economical.

  The crude aromatic carboxylic acid slurry 8 obtained by the liquid material preparation device 30 is sent to the heating device 40 and heated and dissolved to 230 ° C. or higher to become the crude aromatic carboxylic acid supply liquid 9, and the pressure pump 80 ( 4) It is sent to the hydrogenation reaction step. The heating device 40 includes a plurality of stages of heat exchange devices. The steam recovered from the manufacturing process is used, and the deficiency is heated with hot oil or the like.

<(4) Hydrogenation reaction step>
(4) In the hydrogenation reaction step, the crude aromatic carboxylic acid supply liquid 9 obtained in the above (3) liquid material preparation step is supplied to the hydrogenation reaction apparatus 50 for the hydrogenation reaction, and the hydrogenation reaction liquid 10 It is the process of obtaining. The crude aromatic carboxylic acid supply liquid 9 supplied to the hydrogenation reactor 50 is preferably in a completely dissolved state, but it can be dissolved before contacting the stationary phase carrying the catalyst inside the hydrogenation reactor 50. For example, trace amounts of residues may be included.

  The reaction temperature with hydrogen 13 is 230 to 320 ° C., preferably 240 to 300 ° C., the partial pressure of hydrogen 13 is usually 0.05 to 2 MPa, and ruthenium, rhodium, palladium, platinum, osmium, iridium or the like alone or Contact with a Group 8 metal catalyst such as a mixture, usually for 1 to 100 minutes. These Group 8 metals are usually used by being supported on a carrier insoluble in a hot aromatic carboxylic acid aqueous solution, such as activated carbon. Among these, from the viewpoint of the purification effect, it is particularly preferable to use palladium supported on activated carbon as a fixed bed. The pressure during the reaction is usually 3 MPa or more, preferably 5 MPa or more. Moreover, it is 20 MPa or less normally, Preferably it is 15 MPa or less, More preferably, it is 12 MPa or less.

  (4) Oxidation intermediates that are impurities in the crude aromatic carboxylic acid solution 9, such as 4-carboxybenzaldehyde and 3-carboxybenzaldehyde, are reduced to paratoluic acid, metatoluic acid, and the like by the hydrogenation reaction step. The reduced product such as toluic acid is generally more water-soluble than aromatic carboxylic acids such as terephthalic acid and isophthalic acid. Therefore, from the hydrogenation reaction liquid 10 by the solid-liquid separation operation in (5) crystallization step described later. Can be separated.

<(5) Crystallization process>
(5) The crystallization step is a step of crystallizing the hydrogenation reaction liquid 10 to obtain a high-purity aromatic carboxylic acid slurry 11, and then solid-liquid separation, washing and drying to obtain a high-purity aromatic carboxylic acid 12. is there.

  Examples of the crystallization method include a method by evaporating and removing water as a solvent and cooling, a method of cooling by releasing pressure, and the like. The crystallizer 60 is composed of a plurality of crystallizers connected in series, and cools in stages to crystallize. The number of stages is usually 2 or more, preferably 3 or more. Moreover, it is usually 6 steps or less, preferably 5 steps or less. The crystallization pressure in the final stage is usually 0.1 MPa or more, preferably 0.3 MPa or more, more preferably 0.5 MPa or more, and the upper limit is preferably 3 MPa or less, more preferably 1 MPa or less, particularly preferably 0.7 MPa. It is as follows. The high-pressure steam discharged during crystallization can be recovered and reused as thermal energy.

  The crystallized high-purity aromatic carboxylic acid slurry 11 is separated into a crystal, a mother liquor, and a cleaning liquid by a solid-liquid separation cleaning / drying apparatus 70, and the crystal is dried to be a high-purity aromatic carboxylic acid 12. . From the mother liquor / cleaning liquid, valuable substances that are oxidation intermediates (for example, when terephthalic acid is the target product, paratoluic acid, metatoluic acid, etc.) are recovered by crystallization separation, and returned to the above (1) oxidation reaction step for fragrance. It is preferable to be recycled as a group carboxylic acid raw material. Further, a part of the mother liquor can be reused as a solvent, or trace impurities remaining in the separated mother liquor can be concentrated by reverse osmosis membrane treatment, ion exchange treatment, etc., and a part of the permeate can be crude aromatic carboxylic acid. If it is reused as a solvent, it is preferable because the amount of water used and the amount of drainage can be reduced.

  Further, as described in (1) Oxidation reaction step, the upper part of the oxidation reaction apparatus 10 in the (1) oxidation reaction step without separating the oxidation intermediates such as paratoluic acid and metatoluic acid contained in the mother liquor / cleaning liquid. It is also possible to reduce the amount of water used by reducing the amount of water used by recycling to the high-pressure distillation tower installed in the plant.

  Solid-liquid separation can be performed at normal pressure, reduced pressure, or increased pressure. In the case of pressure separation, the pressure is usually 0.01 MPa or more, preferably 0.03 MPa or more, more preferably 0.05 MPa or more. The upper limit is 20 MPa or less, preferably 10 MPa or less, more preferably 5 MPa or less, and particularly preferably 2 MPa or less.

  In this embodiment, the solid-liquid separation, washing, and drying operations are illustrated in the solid-liquid separation washing and drying apparatus 70 that can perform solid-liquid separation, washing, and drying with one apparatus. Can also be implemented in a separate device. As the solid-liquid separation device, screen bowl decanter, solid bowl separator, rotary pressure filter, rotary vacuum filter, horizontal belt filter, etc. can be adopted. As drying device, pressure dryer by pressure release evaporation, normal fluid dryer For example, a known method can be used. When the dried cake is insufficiently dried, it is preferably further dried using a fluidized bed dryer, a rotary dryer or the like.

  By carrying out the production process as described above, a long-term stable operation of the aromatic carboxylic acid production process can be secured, and the loss due to the operation stop can be greatly reduced. As a result, the high-purity aromatic carboxylic acid 12 having stable quality such as particle size and transmittance can be produced efficiently in terms of time and economy.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to an Example unless it is contrary to the meaning.

Example 1
In a production facility for high-purity terephthalic acid (production amount 75 ton / hr), para-xylene and acetic acid approximately 3 mass times that of para-xylene are continuously added to the liquid-phase oxidation reactor, and cobalt acetate, manganese acetate, and hydrogen bromide as catalysts And the oxidation reaction was carried out at a temperature of 185 to 195 ° C., a pressure of 1.0 to 1.7 MPa, and a reaction time (average residence time) of 90 minutes. With respect to the amount of catalyst used, the cobalt component and the manganese component were each 300 ppm by mass in terms of metal with respect to the solvent, and the bromine component was 700 ppm. Air was used as a gas for performing an oxidation reaction with molecular oxygen. At this time, the oxygen content of the air was 21% by volume, and compressed air was supplied into the oxidation reaction device so that the oxygen concentration in the gas discharged from the oxidation reaction device was 3-7% by volume.

  Next, the slurry obtained by the oxidation reaction was continuously transferred to a low-temperature oxidation reaction apparatus, and a further oxidation reaction was performed at a temperature of 180 to 195 ° C., a pressure of 0.9 to 1.7 MPa, and a reaction time of 40 to 60 minutes. Compressed air (oxygen content 21 volume%) was supplied as a gas for performing the oxidation reaction so that the oxygen concentration in the exhaust gas was 3 to 7 volume%. While maintaining the temperature and pressure of the slurry-like oxidation reaction product after the reaction, solid-liquid separation and washing were performed with a screen bowl decanter to obtain a crude terephthalic acid cake. For the cleaning, a part of water obtained by condensation from the oxidation reactor exhaust gas was used. Further, the crude terephthalic acid cake was dried with a steam dryer to obtain crude terephthalic acid, which was once stored in a silo located above the liquid material preparation device before being transferred to the next liquid material preparation step. The moisture content (water content) at this point was 0.1% by mass.

  In order to prevent clogging, the aromatic carboxylic acid supply pipe from the silo to the liquid material preparation equipment is equipped with a cleaning device that mechanically drops the attached crude terephthalic acid cake, temporarily stopping the supply of crude terephthalic acid. The cleaning device was operated intermittently.

  On the other hand, as water supplied to the liquid preparation apparatus as the solvent, water containing the separated mother liquor discharged from the solid-liquid separation step in the crystallization step described later and the mother liquor after recovering the dissolved organic matter was reused. Since solids are mixed in these waters, a foreign substance removing device (automatic strainer) was installed in the water supply pipe to remove solids exceeding the maximum major axis of 5 mm. The foreign matter removing apparatus used here was a scraping and suction type sieving type apparatus having a screen of 5 mm opening having a structure shown in FIG. 2 and removing clogging with a brush.

The liquid preparation apparatus used was a stirring tank, and the shape of the stirring blade was an inclined paddle blade, which was equipped with five baffles. The upper end of the baffle was positioned slightly below the liquid level. The crude terephthalic acid cake is introduced from the upper part of the liquid preparation device, and water is introduced from the lower side of the liquid surface on the side of the liquid preparation device. Extracted from the opposite side. The stirring power of the stirring shaft was operated at 0.5 kw / m ³ .

  The pressure of the liquid preparation apparatus was normal pressure and the temperature was 90 ° C. The residence time was 15 minutes. An automatic strainer having a screen with an opening of 5 mm and having a structure shown in FIG. 2 was installed at the outlet of the liquid preparation apparatus to automatically remove lumps exceeding 5 mm in the slurry. A pressure pump was provided between the liquid preparation device and the hydrogenation reaction device. The concentration of the slurry at the inlet of the pressure pump was 30 ± 0.5% by mass, and the maximum major axis was 5 mm or less.

  The obtained slurry was passed through a plurality of serially connected multi-pipe heat exchangers using a pressure pump, and heated and pressurized to 290 ° C. and 8.5 MPa with steam and heat transfer oil (hot oil) to form terephthalate. The acid was completely dissolved. Thereafter, an aqueous terephthalic acid solution was introduced together with hydrogen into a hydrogenation reaction apparatus using palladium-activated carbon as a fixed bed, and the impurity 4-carboxybenzaldehyde was changed to p-toluic acid. The aqueous solution of terephthalic acid after the hydrogenation reaction was continuously sent to a crystallizer, and was subjected to pressure-release cooling and crystallization sequentially in a four-stage crystallization process, followed by solid-liquid separation at 100 ° C. The pure terephthalic acid cake was washed with water and dried. A screen bowl decanter was used as the solid-liquid separator. As the dryer, a pressure dryer by pressure-release evaporation and a fluidized bed dryer were used, and a high purity terephthalic acid cake was obtained in a yield of 75 Ton / hr. Since the mother liquor separated into solid and liquid contains an oxidation intermediate such as p-toluic acid, it was further cooled to precipitate crystals, separated into solid and liquid, recovered as a solid, and recycled to the liquid phase oxidation reaction step. Part of the mother liquor after solid-liquid separation of the oxidized intermediate was reused as an aqueous solvent in the crystallization step.

  As a result of continuous operation with this method, it was possible to continue production stably for 6 months or longer without stopping operation, and it was confirmed that operation was stabilized and product quality was stabilized.

(Example 2)
The crude terephthalic acid cake obtained in the same manner as in Example 1 was once stored in a silo. In place of the cleaning device used in Example 1, a vibrating sieve (4 mm aperture) was installed downstream of the silo, and the mass produced by the silo wall or steam dryer was screened and passed through the crude terephthalic acid The cake was transferred by a conveyor and supplied to the liquid preparation device by adjusting the supply amount using a rotary valve. The crude terephthalic acid supply pipe to the liquid preparation apparatus was made into a double pipe to prevent clogging, and steam was flowed to the outside to keep the inner wall temperature of the supply pipe at 100 ° C. In addition, an automatic strainer was installed in the water supply pipe used as a solvent in the same manner as in Example 1 to remove solids having a maximum major axis of 4 mm or more.

The structure, operating pressure, temperature, and residence time of the liquid material preparation apparatus are the same as in Example 1. However, by increasing the number of revolutions of the stirring shaft, the stirring power is increased from that in Example 1 to 0.6 kw / m. I drove at ³ . An automatic strainer was installed at the outlet of the liquid preparation tank in the same manner as in Example 1 to automatically remove lumps exceeding 4 mm in the slurry. The concentration of the slurry at the inlet of the pressure pump was 30 ± 0.5% by mass, and the maximum major axis was 4 mm or less. In the case of Example 1, the slurry concentration may fluctuate intermittently, but not in Example 2 and is stable. The obtained slurry was heated and pressurized in the same manner as in Example 1 to completely dissolve terephthalic acid, and in the same manner as in Example 1, hydrogenation reaction, crystallization, solid-liquid separation, washing with water and drying were carried out to obtain high purity terephthalic acid. An acid cake was obtained with a yield of 75 Ton / hr.

  As a result of continuous operation by this method, it was possible to continue production stably for 10 months or longer without stopping the operation, and it was confirmed that operation was stabilized and product quality was stabilized.

(Comparative Example 1)
Production similar to Example 1 except that the automatic strainer was not installed downstream of the water supply pipe and the discharge pipe at the outlet of the liquid preparation apparatus, and that the stirring power in the liquid preparation apparatus was set to 0.3 kw / m ^3. The method produced high-purity terephthalic acid.

  As a result, the slurry concentration upstream of the pressure pump inlet was 30 ± 2% by mass. In addition, as a result of continuous operation by this method, blockage occurred at intervals of about two weeks on the supply side or the outlet side of the liquid material preparation device, and it was necessary to temporarily stop the operation to eliminate the blockage. As a result of confirming the blockage, there was a lump of crude terephthalic acid having a maximum particle size of about 10 to 30 mm.

It is the schematic which shows one Embodiment of the aromatic carboxylic acid manufacturing apparatus which concerns on this invention. It is the schematic of the preferable foreign material removal apparatus 200 applied to this invention.

DESCRIPTION OF SYMBOLS 10: Oxidation reaction apparatus 20: Solid-liquid separation washing | cleaning drying apparatus 30: Liquid substance preparation apparatus 31: Aromatic carboxylic acid supply pipe 32: Water supply pipe 33: Discharge pipe 40: Heating apparatus 50: Hydrogenation reaction apparatus 60: Crystallization Apparatus 70: Solid-liquid separation washing and drying apparatus 80: Pressure pump 200, 300: Foreign substance removal apparatus 201: Element screen 202: Brush scraper 400: Large particle separation apparatus 500: Aromatic carboxylic acid production apparatus

Claims (16)

A liquid preparation device for preparing a liquid containing a crude aromatic carboxylic acid and water,
A heating device for heating the liquid to prepare a crude aromatic carboxylic acid solution;
And a hydrogenation reactor for hydrogenating the crude aromatic carboxylic acid solution,
An apparatus for producing an aromatic carboxylic acid having
The liquid preparation apparatus includes an aromatic carboxylic acid supply pipe that supplies the crude aromatic carboxylic acid to the liquid preparation apparatus, a water supply pipe that supplies water to the liquid preparation apparatus, and the liquid preparation apparatus And a discharge pipe that discharges the liquid material from each other, and at least one of the water supply pipe and the discharge pipe is provided with a foreign substance removing device that removes a lump exceeding a maximum major axis of 6 mm. An apparatus for producing an aromatic carboxylic acid. The apparatus for producing an aromatic carboxylic acid according to claim 1, wherein the foreign matter removing device has a sieving function and a scraping function for removing clogging of the sieving function. The apparatus for producing aromatic carboxylic acid according to claim 2, wherein the scraping function is performed by a brush provided in the foreign matter removing apparatus. The apparatus for producing an aromatic carboxylic acid according to any one of claims 1 to 3, wherein the foreign matter removing device has a foreign matter discharging function. Prior to the liquid material preparation device, an oxidation reaction device for obtaining an oxidation reaction treatment liquid containing a crude aromatic carboxylic acid by oxidizing an alkyl aromatic compound, and the crude aromatic from the oxidation reaction treatment solution The apparatus for producing aromatic carboxylic acid according to any one of claims 1 to 4, further comprising a solid-liquid separation device for solid-liquid separation of carboxylic acid. The water supplied from the water supply pipe to the liquid material preparing device is discharged from the top of the reactor tower of the oxidation reaction device and distilled and separated, and the crude fragrance subjected to solid-liquid separation by the solid-liquid separation device It contains at least 1 or more types chosen from the washing | cleaning liquid at the time of wash | cleaning an aromatic carboxylic acid with water, and the water collect | recovered after hydrogenating the said crude aromatic carboxylic acid with the said hydrogenation reaction apparatus. Aromatic carboxylic acid production equipment. The apparatus for producing aromatic carboxylic acid according to any one of claims 1 to 6, wherein the aromatic carboxylic acid supply pipe is provided with a sieve for sieving the crude aromatic carboxylic acid having a maximum major axis of 10 mm or more. . A liquid preparation step of preparing a liquid containing a crude aromatic carboxylic acid and water in a liquid preparation apparatus;
Heating the liquid to prepare a crude aromatic carboxylic acid solution,
And a hydrogenation reaction step of hydrogenating the crude aromatic carboxylic acid solution in an aqueous solvent,
A process for producing an aromatic carboxylic acid having
The liquid preparation apparatus includes an aromatic carboxylic acid supply pipe that supplies the crude aromatic carboxylic acid to the liquid preparation apparatus, a water supply pipe that supplies water to the liquid preparation apparatus, and the liquid preparation apparatus And a discharge pipe that discharges the liquid material from each other, and at least one of the water supply pipe and the discharge pipe is provided with a foreign substance removing device that removes a lump exceeding a maximum major axis of 6 mm. A method for producing an aromatic carboxylic acid. The method for producing an aromatic carboxylic acid according to claim 8, wherein the foreign substance removing device has a sieving function and a scraping function for removing clogging of the sieving function. The method for producing an aromatic carboxylic acid according to claim 9, wherein the scraping function is performed by a brush provided in the foreign matter removing apparatus. The method for producing an aromatic carboxylic acid according to any one of claims 8 to 10, wherein the foreign matter removing device has a foreign matter discharging function. Prior to the liquid preparation step, an oxidation reaction step of further oxidizing the alkyl aromatic compound to obtain an oxidation reaction treatment liquid containing a crude aromatic carboxylic acid;
The method for producing an aromatic carboxylic acid according to any one of claims 8 to 11, further comprising a solid-liquid separation step of solid-liquid separation of the crude aromatic carboxylic acid from the oxidation reaction treatment liquid. The water supplied from the water supply pipe to the liquid material preparation device is water that is discharged from the oxidation reaction step and distilled and separated, and the crude aromatic carboxylic acid that has been solid-liquid separated in the solid-liquid separation step is water. The aromatic carboxylic acid according to claim 12, comprising at least one selected from a washing liquid when washed with water and water recovered after hydrogenating the crude aromatic carboxylic acid in the hydrogenation reaction step. Production method. The method for producing an aromatic carboxylic acid according to any one of claims 8 to 13, wherein the aromatic carboxylic acid supply pipe includes a sieve for sieving the crude aromatic carboxylic acid having a maximum major axis of 10 mm or more. . The aromatic carboxylic acid according to any one of claims 8 to 14, wherein an inner wall temperature of the aromatic carboxylic acid supply pipe is set to be 10 to 50 ° C higher than a liquid temperature in the liquid preparation apparatus. Acid production method. The method for producing an aromatic carboxylic acid according to any one of claims 8 to 15, wherein the liquid material preparation apparatus includes a stirring blade and the stirring power is 0.3 kW / m ³ or more. .

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