TWI574925B - Treatment of Polycarboxylic Acid Residues - Google Patents

Description

Method for treating polycarboxylic acid residue

The present invention relates to a method for treating a residue, and more particularly to a method for treating a polycarboxylic acid residue.

Many residues (such as terephthalic acid residues, phthalic acid residues, m-terephthalic acid residues, phthalic anhydride residues, maleic acid residues, adipic acid residues) are produced during the production of polycarboxylic acids. Waste water, for example, for the production of purified terephthalic acid (PTA), referring to Figure 1 and Figure 2, generally using p-xylene (PX) catalytic oxidation to form crude terephthalic acid (CTA), and then further hydrofining, The residue contains a variety of poorly soluble carboxylic acids and reaction catalysts (such as cobalt ions, manganese ions, etc.), which are generally considered to be factory waste and must be disposed of after disposal by relevant waste disposal procedures. Current methods for treating such residues mainly include high temperature incineration and biological decomposition.

In the high-temperature incineration method, the residue is mixed in a vapor state in a vapor state, directly mixed with heavy oil, and burned and incinerated at a high temperature of 900 °C. This method requires a lot of energy, and the generated exhaust gas contains heavy metal particles such as cobalt and manganese and organic acids that are incompletely burned, which may cause air pollution. In addition, the high-temperature incineration method can incinerate most of the organic matter in the residue, and can absorb and recover part of the metal waste catalyst by leaching, but it is easy to retain organic substances in the recovered metal waste catalyst, which will cause secondary in subsequent refining. Pollution.

Referring to Figure 3, the biodegradation method firstly forms a metal carbonate or hydrogen by a metal ion catalyst component such as cobalt ion or manganese ion through an alkali precipitation process (such as a carbonate precipitation process or a hydroxide precipitation process). Oxide (hydroxyoxide, The hydroxyl oxide is precipitated, and the precipitate is removed by filtration, adjusted to a suitable pH value, and then the obtained filtrate is subjected to an anaerobic biological reaction treatment and an aerobic biological reaction treatment such as an aerobic biological reaction treatment. To decompose the organic matter in the filtrate, comply with relevant waste discharge standards, and produce biogas (biogas) for use. However, the alkaline precipitation procedure must be carried out at high pH (eg, the carbonate precipitation procedure typically has a pH of up to 9.0, the hydroxide oxide precipitation procedure typically has a pH of up to 12.3), and the biodegradation procedure must be at 6.8- The pH of 7.2 is carried out. Therefore, in the biodegradation method, a large amount of alkali must be consumed to increase the pH of the residue for the alkali precipitation process, and then a large amount of acid must be consumed to lower the pH for the biodegradation process. Under this circumstance, the factory needs to purchase a large amount of acid and alkali for pH adjustment, and it takes a lot of manpower to carry out pH control, which leads to many operating costs.

Therefore, the object of the present invention is to provide a biological treatment method for wastewater containing a polycarboxylic acid residue, which can reduce the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of the residue, and reduce the acid-base chemistry required for treating the residue. The amount of products used, and increase the production of biogas, to reduce the operating costs of the plant and the purpose of resource reuse.

Thus, the wastewater biological treatment method of the polycarboxylic acid residue of the present invention comprises the following steps:

(a) mixing a polycarboxylic acid residue of 150 to 250 ° C with 5 to 40 times the solid weight of water in the residue to obtain a polyhydric carboxylic acid mixture; and (b) filtering the polycarboxylic acid mixture to A first filter cake and a first filtrate are obtained, the first filter cake having a pKa value ranging from 2.8 to 4.4.

The effect of the present invention is that the wastewater biological treatment method of the polycarboxylic acid residue of the present invention reduces the biochemical oxygen demand and chemical oxygen demand of the residue by reducing the water-insoluble polycarboxylic acid mixture from the residue. The residue treatment cost of a large number of acid-base chemicals can be used to recover a water-insoluble polycarboxylic acid mixture in the filter cake, thereby reducing the operation cost of the plant, reducing waste, and recycling resources, and generating Biogas used.

The contents of the present invention will be described in detail below:

In the biological treatment method for wastewater of the polycarboxylic acid residue of the present invention, the step (b) is carried out at 30 to 110 °C.

Preferably, the step (b) is carried out at 70-110 ° C, and after the step (b), further comprises cooling the first filtrate to 30-30 after the step of treating the wastewater of the polycarboxylic acid residue of the present invention. The step (c) of filtering is carried out to obtain a second filter cake and a second filtrate having a pKa value ranging from 2.8 to 4.4.

In the biological treatment method for wastewater of the polycarboxylic acid residue of the present invention, the moisture content of the first filter cake and the second filter cake is 40-70 wt%, respectively.

The wastewater biological treatment method of the polycarboxylic acid residue of the present invention further comprises, after the step (b), washing the first filter cake and/or the second filter cake by water to reduce cobalt ions, manganese ions and sodium therein. Step (d) of ion and bromide ion content.

The wastewater biological treatment method of the polycarboxylic acid residue of the present invention, after the step (d), further comprises passing the washing water produced by the water washing through a strong acid type cation exchange resin to remove cobalt ions, manganese ions and sodium ions therein. Step (e).

The wastewater biological treatment method of the polycarboxylic acid residue of the present invention, after the step (c), further comprises the step (f) of adding an inorganic base to the second filtrate to precipitate and recover cobalt ions and manganese ions therein.

A biological treatment method for wastewater of a polycarboxylic acid residue of the present invention, which is selected from the group consisting of hydroxides, carbonates or combinations thereof. Preferably, the hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide or a combination thereof. Preferably, the carbonate is selected from the group consisting of magnesium carbonate, sodium carbonate, potassium carbonate, calcium carbonate or a combination thereof.

The wastewater biological treatment method of the polycarboxylic acid residue of the present invention further comprises, after the step (b), the anaerobic reaction in the reflux water produced by reacting the first filter cake and/or the second filter cake with an anaerobic biological reaction. The bicarbonate is contacted with step (g) and the carbon dioxide in the anaerobic reflux water is removed to provide a polycarboxylate feed.

The biological treatment method for wastewater of the polycarboxylic acid residue of the present invention, after the step (b), further comprises contacting the first filter cake and/or the second filter cake with aerobic reaction reflux water produced by aerobic biological reaction Step (h) to provide a polycarboxylate feed; the aerobic reaction reflux water has a pH in the range of 8-9.

The wastewater biological treatment method of the polycarboxylic acid residue of the present invention, the polycarboxylic acid residue is selected from the group consisting of terephthalic acid residue, phthalic acid residue, isophthalic acid residue, phthalic anhydride residue, maleic acid Residue, adipic acid residue or a combination thereof.

In the wastewater biological treatment method of the polycarboxylic acid residue of the present invention, the polycarboxylic acid residue is a terephthalic acid residue.

Preferably, the step (a) is a step of mixing a polycarboxylic acid residue of 150 to 250 ° C with 10 to 20 times the solid weight of water in the residue to obtain a polyvalent carboxylic acid mixture.

In the wastewater biological treatment method of the polycarboxylic acid residue of the present invention, the content of terephthalic acid in the first filter cake ranges from 10 to 60% by weight. The content of terephthalic acid in the second filter cake ranges from 0.1 to 1.0% by weight.

E-100‧‧‧film evaporation can

V-101‧‧‧ Residue temporary storage tank

P-102‧‧‧Filter Feed Pump

F-103‧‧‧Multi-section vacuum filter

V-104‧‧‧ first-order buffer tank

P-104‧‧‧First-stage buffer tank discharge pump

V-105‧‧‧ second-order buffer tank

P-105‧‧‧Second stage buffer tank discharge pump

V-106‧‧‧ third-order buffer tank

P-106‧‧‧ third-order buffer tank discharge pump

T-107‧‧‧ Closed Cooling Tower

B-107‧‧‧Scratch cooling tower bottom

P-107‧‧‧Second filtrate discharge pump

E-107‧‧‧Second filtrate preheater

J-108‧‧‧Air pump

V-108‧‧‧Water seal circulation tank

P-108‧‧‧Water seal circulating pump

E-109‧‧‧Water seal cycle heat exchanger

V-109‧‧‧Second filtrate temporary storage tank

P-109A/B‧‧‧Second filtrate carbon sink feed pump

P-110‧‧‧ filter press feed pump

F-110‧‧‧Closed plate and frame filter press

V-111‧‧‧Sodium carbonate mixing tank

P-111A/B‧‧‧Sodium carbonate pump

F-111‧‧‧Sodium carbonate filter

V-112‧‧‧ sodium carbonate storage tank

P-112A/B‧‧‧Sodium carbonate feed pump

V-113‧‧‧First carbon sink

M-114‧‧‧Header

V-114‧‧‧Second carbon sink

V-115‧‧‧carbon sink mud storage tank

P-116A/B‧‧‧plate frame filter press feed pump

F-116‧‧‧Shelf frame filter press

V-117‧‧‧filtrate sedimentation tank

FIC‧‧‧Flow Controller

FQC‧‧‧Flow Accumulation Controller

FQI‧‧‧Flow indicator accumulator

LIAC‧‧‧Level indicator alarm controller

LIC‧‧‧Level indicator controller

pHI‧‧‧pH indicator

pHIC‧‧‧pH indicator controller

PIC‧‧‧Pressure Indication Controller

SG‧‧ Sight mirror

WIC‧‧‧ Weight Indicator Controller

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a flow chart illustrating a CTA production step of a conventional PTA manufacturing process; [FIG. 2] is a The flow chart illustrates the PTA production step of the conventional PTA manufacturing process; [Fig. 3] is a flow chart illustrating the wastewater treatment step of the conventional PTA manufacturing process; [Fig. 4] is a flow chart illustrating the polycarboxylic acid residue of the present invention. a specific example of a biological treatment method for wastewater; [Fig. 5] is a flow chart illustrating a step of removing a metal waste catalyst in a specific example of a biological treatment method for wastewater of a polycarboxylic acid residue of the present invention; [Fig. 6] Is a flow chart illustrating a wastewater biological treatment step of a specific example of the biological treatment method for wastewater of the polycarboxylic acid residue of the present invention; [Fig. 7] is a flow chart of a plant equipment, illustrating a biological treatment method for wastewater of the polycarboxylic acid residue of the present invention. a specific example of the plant equipment configuration; and [Fig. 8] is a plant equipment flow diagram illustrating a specific example of the wastewater biological treatment method of the polycarboxylic acid residue of the present invention. Spent catalyst metal plant configuration.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to Figure 4, a method for biological treatment of wastewater of a polycarboxylic acid residue of the present invention comprises the following steps:

(a) mixing a polycarboxylic acid residue of 150 to 250 ° C with 5 to 40 times the solid weight of water in the residue to obtain a polycarboxylic acid mixture; and (b) the polycarboxylic acid The mixture was filtered to obtain a first cake and a first filtrate having a pKa in the range of 2.8 to 4.4.

In the process of separating the solid phase and the liquid phase to obtain the first filter cake and the first filtrate, washing water may be added for rinsing.

The polycarboxylic acid mixture in the polycarboxylic acid residue is precipitated in the step (a), and then filtered out of the first filter cake in the step (b), thereby separating the polycarboxylic acid mixture in the residue. . The water used in the step (a) may be deionized water, or may be a PTA discharge process water and a filtrate obtained in a subsequent step.

In the present invention, the polycarboxylic acid residue is a mixture of a plurality of components containing two or more kinds of polycarboxylic acids. Taking the residue of the terephthalic acid process as an example, the polycarboxylic acid may include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, benzoic acid, and Methylbenzoic acid, p-hydroxymethylbenzoic acid, p-carbonylbenzoic acid, 2,6-dicarboxy anthraquinone and 4,4'-diphenyl acid (4,4' -diphenic acid) and so on.

In a specific embodiment of the present invention, the filtration step of the step (b) is carried out at a temperature of 30 to 110 ° C to increase the content of the polycarboxylic acid in the first filter cake, and to reduce monobasic acid such as benzoic acid. The content.

The temperature of the step (b) can be carried out by any conventional heat exchanger, and the filtration of the step (b) can be carried out by any conventional method or equipment, for example, a plate and frame filter press, a multi-stage vacuum filter can be used. , rotary vacuum filter, or candle-top filter. The specific implementation manner of the filtering operation is the content of the general knowledge in the technology of the present invention based on the description of the present specification, and can be easily completed without the degree of experiment, and will not be described herein.

In this embodiment, the step (b) is carried out at 70-110 ° C, and after the step (b), further comprising the step (c) of cooling the first filtrate to 30-50 ° C and filtering, To obtain a second filter cake and a second filtrate, the second filter cake has a pKa value ranging from 2.8 to 4.4, to further separate the polycarboxylic acid mixture from the first filtrate, and recover the plurality of distillate in the second filter cake. a mixture of carboxylic acids.

The cooling of the step (c) can be carried out by any conventional method or equipment, for example, a cooling water tower or a literary rinsing tower or a crystallization tank (eg, a multi-stage crystallization tank, a drainage tube buffer crystallizer, an Oslo cooling crystallizer). , circulating liquid crystallizing tank) to carry out. The specific implementation of the chiller operation is based on the description of the present specification in the art of the present invention, and can be easily accomplished without undue experiment, and will not be described herein.

The first filter cake and the second filter cake both contain a mixture of polycarboxylic acids, but the composition is obviously different, and the use is also different, and contains heavy metal ions such as cobalt ions and manganese ions, which can only be sold separately as sub-low-grade products, possibly by A co-investment joint production plant further refines the first filter cake and the second filter cake.

Referring to Figure 5, the method of the present invention may further comprise a step of refining the first filter cake and the second filter cake to remove heavy metal ions therein, such as removal of heavy metal ions such as cobalt ions, manganese ions, bromide ions, etc. from the reaction catalyst. Therefore, in some embodiments of the present invention, the step (d) of reducing the cobalt ion, manganese ion, sodium ion and bromide ion content by washing the first filter cake and/or the second filter cake by water is included. . In this embodiment, the first filter cake and/or the second filter cake are repeatedly washed with 5-40 times of water based on the weight of the filter cake, so that the cobalt ion content in the filter cake is less than 20 ppm, and the manganese ion content is low. At 20 ppm, the sodium ion content is less than 100 ppm, and the bromide ion content is less than 1000 Ppm to increase its economic value. The cleaned filter cake can be directly dried as a low-grade industrial raw material and sold directly to the market.

The method of the present invention may further comprise the step (e) of removing the cobalt ions, manganese ions and sodium ions from the washing water produced by the water washing through a strong acid type cation exchange resin (SAC) to meet emission standards or as a reusable The process water used is, for example, again used as the washing water for step (d).

The ion exchange resin technology used in the above steps is a conventional technique, and the specific embodiment thereof is based on the description of the present specification by those having ordinary knowledge in the technology of the present invention, and can be easily performed without going through the degree experiment, and will not be described herein.

The manufacturer may further process the refined first filter cake and/or the purified second filter cake into a low-grade polymer material. For example, a monohydric alcohol or a polyhydric alcohol and a catalyst may be added to the purified first filter cake and/or the purified second filter cake to carry out esterification polymerization to prepare a low-grade unsaturated resin material or alcohol. Acid resin material. In addition, since the composition of the first filter cake and the second filter cake may vary depending on the source of the residue and the operating conditions, it is possible to additionally add various organic acids in the foregoing reaction to adjust the need for progress. Material composition to meet specific purposes.

The method of the present invention may further comprise the step (f) of adding an inorganic base to the second filtrate to precipitate a cobalt ion and a manganese ion therein. For example, when treating a terephthalic acid process residue (the oxidation catalyst used contains cobalt ions and manganese ions), a carbonate (such as sodium carbonate) may be added to the second filtrate to a pH of 9.0 or above, or Sodium hydroxide is added to a pH of 12.3 or above to cause the cobalt ions in the second filtrate to form a carbonate or hydroxide oxide precipitate with the manganese ions, and the precipitate is removed by filtration. Alternatively, it can be extracted by means of a commercially available product such as P204 or Cyanex272. The agent extracts and removes cobalt ions and manganese ions from the second filtrate, and subsequently desorbs with a high concentration of HBr to recover the extracted cobalt ions and manganese ions. The second filtrate is sent to the wastewater treatment plant for biodegradation process through the above process fluid for removing cobalt ions and manganese from the sub-process, and the process can reduce the concentration of heavy metals in the wastewater in addition to the metal catalyst.

In this embodiment, the alkali precipitation procedure of the method of the present invention has the advantage that since the amount of the polycarboxylic acid remaining in the second filtrate is extremely small, the amount of alkali to be adjusted to adjust the pH required for the alkali precipitation process can be greatly reduced, and accordingly, It can also greatly reduce the amount of acid used to adjust the pH of the biodegradation process; and can greatly reduce the BOD value and chemical oxygen demand COD value of the wastewater. The present invention thus greatly reduces the cost of residue disposal.

Referring to FIG. 6, in some specific examples of the present invention, the first filter cake and/or the second filter cake may be dissolved by using the alkalinity of the wastewater to form an organic acid salt as an anaerobic bioreactor (the organic acid salt is converted). Re-feeding into bicarbonate), producing biogas, to digest factory waste. The method of the present invention may further comprise the step (g) of contacting the first filter cake and/or the second filter cake with bicarbonate in an anaerobic reaction reflux water produced by an anaerobic biological reaction, and removing the anaerobic reaction. The carbon dioxide in the reflux water is provided to provide a polycarboxylate feed. The organic acid in the first filter cake and/or the second filter cake (pKa value 2.8-4.4) can be neutralized with the hydrogencarbonate produced by the anaerobic biological reaction (the pKa value of carbonic acid is 6.35), when the process When the pH of the fluid drops to 2.8 (4.0) to 6.35, nearly 100% to 50% of the bicarbonate is converted into dissolved carbonic acid, and the dissolved carbonic acid and the carbon dioxide in the atmosphere are a balanced system, and the chemical process design is designed. A carbon dioxide removal tower can be used, which uses a large amount of air to blow out carbon dioxide in the process fluid, and in the process of removing carbon dioxide, promotes bicarbonate in the process fluid. Conversion into an organic acid salt, thereby greatly improving the dissolution of the organic acid, so that the process fluid forms a high BOD value, a high COD value and a low pH anaerobic reaction reflux water, and the anaerobic reaction reflux water can be reacted with an aerobic biological reaction. The aerobic reaction reflux water (pH 8.3-8.9, sodium ion concentration 150-1800ppm) is neutralized and refluxed for anaerobic biological reaction. The process can increase the methane concentration of the biogas, reduce the amount of alkali in the wastewater plant, and reduce the operating cost. Resource reuse.

The carbon dioxide removal column of step (g) can be carried out by any conventional method or apparatus, for example, using a storage tank, a column tank, and a packed column. The specific embodiment of the operation of the carbon dioxide removal tower is based on the contents described in the specification of the present invention, and can be easily performed without the degree of experiment, and will not be described herein.

Referring to Figure 6, in some embodiments of the present invention, the method of the present invention may further comprise the step of contacting the first filter cake and/or the second filter cake with aerobic reaction reflux water produced by aerobic biological reaction (h) ) to provide a polycarboxylate feed; the aerobic reaction reflux water has a pH in the range of 8-9. The first filter cake and/or the second filter cake which cannot be digested by the production capacity are put into the outflow water generated by the aerobic biological reaction of the wastewater treatment plant (including: clarification tank, waste water from the waste water plant), and the polycarboxylic acid is dissolved into The polycarboxylate is provided to provide an anaerobic biological reaction feed, and after adjusting the pH to 6.8-7.2 in the neutralization tank, the polycarboxylic acid is converted into biogas by an anaerobic biological reaction tank. The process can produce biogas into plant energy, digest plant waste, reduce the amount of alkali used in wastewater plants, reduce operating costs and reuse resources. If the carbon dioxide is not removed from the column, most of the carbon dioxide will be present in the form of bicarbonate, thereby reducing the ability to neutralize the polycarboxylic acid and increasing the handling capacity of the wastewater treatment plant, but saving investment in the carbon dioxide removal column.

Taking the terresin in the first filter cake and the second filter cake as an example, the chemical reaction formula for producing methane and carbon dioxide is as follows:

The pH of the anaerobic bioreactor is controlled at 6.8 to 7.2, so about 82% of the carbon dioxide produced will form bicarbonate. The bicarbonate will consume the metal ions of the system, causing the pH to drop, and the bicarbonate will not be able to carbon dioxide. Remove.

While the first filter cake and the second filter cake have pKa values ranging from 2.8 to 4.4, the hydrogencarbonate can be neutralized therewith. Taking terephthalic acid in the first filter cake and the second filter cake as an example (pKa value is 3.51), the chemical reaction formula is as follows:

The terephthalic acid is dissolved into terephthalic acid, the carbon dioxide can be removed 100%, and the process fluid can again become the anaerobic bioreactor feed.

When the pH value is below 4.4, more than 99% of the bicarbonate is in the form of carbonic acid. The dissolved carbonic acid is in equilibrium with the carbon dioxide in the atmosphere. In the chemical process design, the carbon dioxide removal tower can be used to remove carbon dioxide. After the fluid dissolves the organic acid again to form the organic acid salt wastewater with high BOD value, high COD value and low pH value, it is neutralized with the outflow water produced by the aerobic biological reaction (including: clarification tank, wastewater plant outlet water) and then returned. Process.

There are many workarounds and operational flexibility in the process arrangement. Take the wastewater biological treatment step shown in Figure 6. For example, if the carbon dioxide is removed below pH 4.0, it means that nearly 100% carbonic acid is removed, and the polycarboxylate solubility is Extremely; if carbon dioxide is removed at pH 6.35, it means that only 50% of the carbonic acid will be removed, the polycarboxylic acid The salt solubility is only 50%, and the other 50% is bicarbonate; if carbon dioxide is removed at pH 7.0, it means that only about 18% of the carbonic acid will be removed, and the polycarboxylate solubility is only 18%. % is bicarbonate.

The process arrangement can also utilize the acidity of the pH range of 2.8 to 3.5 in the wastewater balance tank, and the first filter cake and/or the second filter cake which cannot be digested are put into the anaerobic biological reaction tank, and the effluent or reflux water is also pumped. It is sent to the wastewater balance tank. Naturally removes carbon dioxide by acid-base neutralization reaction and long-term retention, and increases the BOD value and COD value of the anaerobic bioreactor feed, and achieves the effect of dedigesting and increasing biogas production. .

When the plant has sufficient capacity, the process arrangement can also utilize the outflow water produced by the aerobic biological reaction (ie, aerobic reaction reflux water, pH 8.3-8.9) to neutralize the first filter cake and/or the second filter that cannot be digested. cake. Although carbonic acid is almost absent at a pH of 8.2 or higher, the pH after the neutralization reaction is lowered. For example, when the pH is lowered to 7.0, about 18% of the carbonic acid can be removed, and the process fluid dissolves a part of the mixture. The carboxylic acid forms a polycarboxylate.

Referring to Fig. 1, Fig. 4 and Fig. 7, taking the biological treatment method of the terephthalic acid residue as an example, according to the plant equipment configuration of Fig. 7, the flow rate can be controlled by the feed pump plus the flow controller FIC, through the thin film evaporation tank. E-100 heats the feed liquid to above 200 °C under steam of 30-40 atm to evaporate the process water and acetic acid, and discharge the molten organic matter (ie, terephthalic acid residue), and quickly add 5-40 times process. After the water, a polycarboxylic acid mixture liquid is obtained, and the flow rate is controlled by the flow controller FIC, and the mixed precipitate crystal is temporarily deposited in the residue temporary storage tank V-101, and is sent to the multi-stage vacuum filter F through the filter feed pump P-102. -103 filter cleaning, system vacuum indication is not controlled, the obtained filter cake is the first filter cake with high polycarboxylic acid content. The process uses PTA wastewater as washing water, which can save deionized water, and passes through the first-order buffer tank V-104 and the first-stage buffer tank discharge pump. P-104, second-stage buffer tank V-105, second-stage buffer tank discharge pump P-105, third-stage buffer tank V-106, and third-stage buffer tank discharge pump P-106 counter-flow cleaning filter cake. The system is equipped with an lye cleaning system to handle blockage problems. The whole system is equipped with a separate water-sealed vacuum system, including: air extractor J-108, water seal circulation tank V-108, water seal circulation pump P-108, water seal circulation heat exchanger E-109 to provide multi-stage vacuum filtration The requirements of the machine F-103, the first-order buffer tank V-104, the second-stage buffer tank V-105, and the third-order buffer tank V-106. Excess condensate from the vacuum system can be returned to the process as process water. The obtained filtrate is the first filtrate, and the crystal precipitation is cooled by a closed cooling tower T-107 (cooling to 30-50 ° C), temporarily storing the bottom of the cooling water tank B-107, and then passing through the filter press P- 110 is transferred to a closed plate and frame filter press F-110, and filtered to obtain a second filter cake (washed with pure water) and a second filtrate. The second filtrate is heated by the second filtrate discharge pump P-107 and the second filtrate preheater E-107 to form process water again, and the excess second filtrate flows to the second filtrate temporary storage tank V-109 to Prepare for further processing.

Referring to FIG. 4 and FIG. 8 , the step of removing the metal waste catalyst in the biological treatment method of the wastewater of terephthalic acid residue is taken as an example. According to the factory equipment configuration of FIG. 8 , the process is divided into three parts: (1) sodium carbonate solution Preparation, (2) carbon precipitation reaction and (3) filtration system.

(1) Preparation of sodium carbonate solution: The sodium carbonate packaged in the space package is transported by the 2.5-ton stacker M-114, and the sodium carbonate mixing tank V-111 is put into the upper manhole cover, and the deionized water is distributed by the flow rate controller. The FQC was metered and formulated to obtain a 20-25% sodium carbonate solution. Through the sodium carbonate transfer pump P-111A/B, the sand is filtered by the sodium carbonate filter F-111, pumped to the sodium carbonate storage tank V-112, and the sodium carbonate storage tank V-112 is indicated by the liquid level indicating alarm controller LIAC To control the operation.

(2) Carbon precipitation reaction: the second filtrate remaining in the above process is temporarily stored in the second filtrate temporary storage tank V-109, and the liquid level indicating controller LIC controls the second filtrate temporary storage tank The liquid level of V-109 is pumped to the first carbon sink V-113 via the second filtrate carbon sink feed pump P-109A/B, by the flow indicating accumulator FQI, while passing through the sodium carbonate feed pump. P-112A/B is added to the sodium carbonate solution prepared above, and the pH of the first carbon sink tank V-113 is maintained at 8.8 with the pH indicating controller pHIC, and the reaction mud overflows to the second carbon sink tank V-114. At the same time, the sodium carbonate solution was added, and the pH of the second carbon sink tank V-114 was maintained at 9.0 with the pH indicating controller pHIC, and the reaction slurry was again overflowed to the carbon sink slurry storage tank V-115.

(3) Filtration system: The liquid level indicating controller LIC controls the level of the carbon sink mud storage tank V-115, and is fed by the automatic plate and frame filter press F-116. When the liquid level is high, start the plate filter press feed pump P-116A/B; when the liquid level is low, stop the plate filter press feed pump P-116A/B. Whether the filtrate is clarified can be viewed with the sight glass SG. The filtered wastewater can be monitored by the pH indicator pHI. The system is equipped with a return line, and there will be a small amount of solids leaking at the beginning of the plate frame filtration, first flowing back to the carbon sink slurry storage tank V-115. The feed end point is determined by the inlet pressure indicating controller PIC of the plate frame filter press F-116 (stop feeding when the pressure indication reaches the set value of 6.4 kg/cm ² G), the feeding step is completed, and the plate and frame filter press is performed. Follow-up steps of F-116: sludge removal → water washing → first section drying → second section drying → filter cake completion → manual cutting → restarting. The filter cake weight for blanking can be regulated by the weight indicating controller WIC. The system is equipped with a filtrate settling tank V-117, which can prevent the plate frame filter cloth from being damaged and carry out the final carbon sink, and can recover about 3% of the waste catalyst.

Since the storage, configuration, artificial panel blanking, raw materials, and finished product storage of sodium carbonate must be indoors, there must be an independent factory.

The invention is further described in the following examples, but it should be understood that these examples are for illustrative purposes only and are not to be construed as limiting.

Example

[Analysis of refined terephthalic acid process residue samples]

The film evaporating tank feed of 100 g of terephthalic acid process was subjected to suction filtration, and the obtained filter cake was dried at 60 ° C for 12 h, and the weight of the original residue was measured, and the remaining solid weight accounted for 26.0 wt%, and analyzed. The residue was found to contain 12.0% by weight of water and 54% by weight of acetic acid.

[Example 1-1]

1000 g of terephthalic acid process film evaporation tank feed (volume 450 mL, solid content of about 260 g, containing cobalt ion 0.4 wt%, manganese ion 0.5 wt%, bromide ion 2.5 wt%, sodium ion 0.3 wt%) , and sent it to a 200 ° C oven to evaporate most of the water and acetic acid to a volume of 300 mL; then quickly pour it into 3000 g of ice pure water, stir well and let stand for 10 min; the resulting suspension is subjected to suction filtration. It was washed with 350 g of pure water to remove water on the crystal surface and cobalt ions and manganese ions to obtain a filter cake (weight: 375 g). After the filter cake was dried at 60 ° C for 12 hours, the weight was measured to be 175 g. It was calculated that the water content in the filter cake was 53% by weight, and the recovery of the solid content was 67%. That is, the method of the present invention can separate the solid matter of 60 wt% or more of the polycarboxylic acid in the residue, and can effectively reduce the biochemical oxygen demand and chemical oxygen demand of the residue.

[Example 1-2]

According to the same feed composition as in Example 1-1, 1000 g of the terephthalic acid process of the film evaporation tank was fed, and sent to a 200 ° C oven to evaporate most of the water and acetic acid to a volume of 300 mL; Then, it was quickly poured into 2700 g of pure water and stirred uniformly, placed in a 75 ° C thermostat overnight; the resulting suspension was subjected to suction filtration and washed with 100 g of pure water to remove water on the crystal surface and cobalt ions and manganese. The first filter cake (weight 200 g) and the first filtrate were obtained. After the first cake was dried at 60 ° C for 12 h, the weight was measured to be 92 g. The water content in the first filter cake was calculated to be 54% by weight, and the recovery of the solid content was 35%. The first filtrate was placed in a 35 ° C thermostat overnight; the resulting suspension was subjected to suction filtration and washed with 100 g of pure water to remove water on the crystal surface and cobalt ions and manganese ions to obtain a second filter cake (weight is 173 g) and the second filtrate. After the second cake was dried at 60 ° C for 12 hours, the weight was measured to be 83 g. The water content in the second filter cake was calculated to be 52% by weight, and the recovery of the solid content was 32%. That is, the method of the present invention can separate the solid matter of 60 wt% or more of the polycarboxylic acid in the residue, and can effectively reduce the biochemical oxygen demand and chemical oxygen demand of the residue.

The results of the component analysis are shown in Table 1 below.

The results of component analysis showed that in addition to moisture, the first filter cake mainly contained terephthalic acid (TA), benzoic acid (BA), isophthalic acid (IA), and trimellitic anhydride. (TM); the second filter cake mainly contains benzoic acid (BA), trimellitic anhydride (TM), and isophthalic acid (IA).

[Example 1-3]

According to the same feed composition as in Example 1-1, 1000 g of the terephthalic acid process of the film evaporation tank was fed, and sent to a 200 ° C oven to evaporate most of the water and acetic acid to a volume of 300 mL; Then, it was quickly poured into 2700 g of pure water and stirred uniformly, placed in a 95 ° C thermostat overnight; the resulting suspension was subjected to suction filtration and washed with 120 g of pure water to remove water and cobalt ions and manganese ions on the crystal surface. A first cake (weight 125 g) and a first filtrate were obtained. After the first cake was dried at 60 ° C for 12 h, the weight was measured to be 56 g. The water content in the first filter cake was calculated to be 55 wt%, and the recovery of the solid content was 22%. The first filtrate was placed in a thermostat at 30 ° C overnight; the resulting suspension was subjected to suction filtration and washed with 250 g of pure water to remove water on the crystal surface and cobalt ions and manganese ions to obtain a second filter cake (weight is 238 g) and the second filtrate. After the second cake was dried at 60 ° C for 12 h, the weight was measured to be 114 g. The water content in the second filter cake was calculated to be 52% by weight, and the recovery of the solid content was 44%. That is, the method of the present invention can separate the solid matter of 60 wt% or more of the polycarboxylic acid in the residue, and can effectively reduce the biochemical oxygen demand and chemical oxygen demand of the residue.

The results of the component analysis are shown in Table 2 below.

The results of the component analysis showed that the first filter cake mainly contained isophthalic acid (IA) and terephthalic acid (TA) in addition to moisture; the second filter cake mainly contained benzoic acid (BA).

[Example 2] Removal of metal waste catalyst

1000 g of the first filter cake obtained in the above Example 1-2 was taken, and the impurities were washed with 7000 g of deionized water, followed by suction filtration, and then the metal ions contained in the first cake were washed with 1500 g of deionized water. The main component of the first filter cake after washing is a mixture of polycarboxylic acids, wherein the dry composition analysis results: cobalt ion <20 ppm, manganese ion <20 ppm, sodium ion <100 ppm, and bromide ion <1000 ppm.

The second filtrate obtained by filtration is treated with a strong acid type cation exchange resin (SAC), and the cobalt ion and the manganese ion in the filtrate are recovered, and the treated aqueous solution can be recycled as a process water, and the analysis result is: cobalt ion <3.0 ppm , manganese ion <5.0ppm, iron ion <3ppm, nickel ion <3ppm, chromium ion <3ppm.

[Example 3] Biological treatment of wastewater

Take 10000g of anaerobic biological reaction tank discharge, add 100g of the first filter cake obtained in the above Example 1-2, pass air to react for 30min, filter to remove residual solid 31 g of the body, 2500 g of clarifier drain water was added to the filtrate to obtain 12563 g of an anaerobic bioreactor feed.

The weight and composition analysis results are shown in Table 3 below.

In summary, the present invention can reduce the biochemical oxygen demand and chemical oxygen demand of the residue by adding water to the polycarboxylic acid in the residue, and can recycle and reuse the polycarboxylic acid to reduce the operating cost and regeneration of the plant. The effect of using economically valuable resources. The recovered polycarboxylic acid can be further purified to approach market demand. The organic carboxylic acid filter cake which cannot be digested by the market can also be converted into biogas and recovered calorific value by using an existing anaerobic biological reaction tank, so that the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

Claims (12)

A method for treating a polycarboxylic acid residue, comprising the steps of: (a) mixing a polycarboxylic acid residue of 150 to 250 ° C with 5-40 times of solid weight of water in the residue to obtain a polycarboxylic acid mixture; b) filtering the polycarboxylic acid mixture to obtain a first filter cake and a first filtrate, the first filter cake having a pKa value ranging from 2.8 to 4.4. The method for treating a polycarboxylic acid residue according to claim 1, wherein the step (b) is carried out at 30 to 110 °C. The method for treating a polycarboxylic acid residue according to claim 2, wherein the step (b) is carried out at 70-110 ° C, and after the step (b), further comprising cooling the first filtrate to 30- The step (c) of filtration is carried out at 30 ° C to obtain a second filter cake and a second filtrate having a pKa value ranging from 2.8 to 4.4. The method for treating a polycarboxylic acid residue according to claim 3, wherein the first filter cake and the second filter cake have a water content of 40 to 70% by weight, respectively. The method for treating a polycarboxylic acid residue according to any one of claims 1 to 3, further comprising, after the step (b), washing the first filter cake and/or the second filter cake by water Step (d) of reducing the content of cobalt ions, manganese ions, sodium ions and bromide ions therein. The method for treating a polycarboxylic acid residue according to claim 5, further comprising, after the step (d), passing the washing water produced by the water washing through a strong acid type cation exchange resin to remove cobalt ions and manganese therein. Step (e) of ions and sodium ions. The method for treating a polycarboxylic acid residue according to claim 3, further comprising, after the step (c), the step of adding an inorganic base to the second filtrate to precipitate a cobalt ion and a manganese ion therein (f) ). The method for treating a polycarboxylic acid residue according to claim 7, wherein the inorganic base is selected from the group consisting of hydroxides, carbonates, or a combination thereof. The method for treating a polycarboxylic acid residue according to any one of claims 1 to 3, further comprising, after the step (b), the first filter cake and/or the second filter cake and anaerobic The anaerobic reaction produced by the biological reaction is carried out in the step (g) of contacting the bicarbonate in the reflux water, and the carbon dioxide in the reflux water of the anaerobic reaction is removed to provide a polycarboxylate feed. The method for treating a polycarboxylic acid residue according to any one of claims 1 to 3, further comprising, after the step (b), the first filter cake and/or the second filter cake and aerobic The aerobic reaction produced by the biological reaction is subjected to step (h) of contacting with reflux water to provide a polycarboxylate feed; the aerobic reaction reflux water has a pH in the range of 8-9. The method for treating a polycarboxylic acid residue according to any one of claims 1 to 3, wherein the polycarboxylic acid residue is selected from the group consisting of terephthalic acid residues, phthalic acid residues, and isophthalic acid residues. Phthalic anhydride residue, maleic acid residue, adipic acid residue or a combination thereof. The method for treating a polycarboxylic acid residue according to claim 11, wherein the polycarboxylic acid residue is a terephthalic acid residue.