System and method for improving water quality in the dehydration tower of a high purity terephthalic acid unit

Abstract

A system and method for improving the water quality of the dehydration tower of a high-purity terephthalic acid unit. In order to solve the problems of the prior art, the present invention provides a system for improving the water quality of the dehydration tower of a high-purity terephthalic acid unit, the system includes a dehydration and washing device, an exhaust gas condenser communicating with the top of the dehydration and washing device, and a water separator communicating with the exhaust gas condenser. The beneficial effects of the present invention are as follows: 1) energy consumption is reduced and economic benefits are increased; 2) the exhaust gas condenser uses the Nth heat exchanger as a heating medium; m The low-pressure steam of about 0.05 MPa generated by the condenser of the first stage is used as the heating medium; 3) the water separation tower is a tower-type multiple-effect evaporative water separation tower, the working medium is water and low-pressure steam, and no organic phase is involved in the process, making the reaction stable and essentially safe; 4) the water in the water separation tower is purified water and concentrated water, the purified water returns to the top of the dehydration tower, and the concentrated water enters the dehydration tower after being mixed with the mother liquor, thereby improving the efficiency of the dehydration tower and improving the water quality.

Description

[Technical field]

[0001] The present invention relates to a method for improving the water quality of the dehydration tower of a high purity terephthalic acid unit, and more particularly to a system and method for purifying and utilizing oxidation exhaust gas condensate in the PTA industrial production process. [Background technology]

[0002] In the preparation and production process of PTA (high purity terephthalic acid), exhaust gas condensate is purified. The purification of exhaust gas condensate currently generally uses the extraction method, that is, the purified mother liquor (condensate) of the PTA purification unit is heated with medium pressure steam, and then added to the extraction tower with the extractant paraxylylene (PX, hereinafter referred to as PX) for extraction. The extractant PX is used to extract the solutes (organic parts such as acetic acid, PT acid, etc.) in the original solvent into PX to form a PX extraction phase, among which the PX extraction phase returns to the oxidation reactor to continue reaction. For the raffinate phase (purified mother liquor after the separation of organic parts such as acetic acid, PT acid, etc. in the original solvent) the traditional dehydration tower is used to complete the rectification process and realize the exchange of water and acetic acid. The acetic acid vapor is condensed as acetic acid condensate, and the bottom of the dehydration tower is returned to the reactor to continue reaction, and the water is vaporized into water vapor. The oxidation exhaust gas is discharged from the top of the dehydration tower to the condenser for heat recovery, and the water vapor is condensed into condensate for other purposes. However, the above method has some problems: 1. The above technology uses PX extraction technology, the extraction flow is complicated, the system is huge, and the cost is high; 2. The purified mother liquor is the original solution. In the extraction process, in order to prevent the extraction tower from being blocked, the mother liquor needs to be heated. The heating requires medium pressure steam of 3.5-4.5 MPa (G), which results in very high steam consumption, and this medium pressure steam needs to be supplied from the outside world, which greatly increases the energy consumption and operation cost of the equipment; 3. The extraction process is a mass transfer process between PX organic phase and aqueous phase. Due to the existence of the organic phase, the safety requirements of the system are higher than those of the aqueous phase, and the construction cost increases. Summary of the Invention

[0003] The object of the present invention is to provide a system and method for improving the water quality of the dehydration tower of a high purity terephthalic acid unit, which achieves a purification or enrichment effect through the system and the corresponding method.

[0004] A system for improving water quality in a dehydration tower of a high purity terephthalic acid unit includes a dehydration and scrubbing unit, an exhaust gas condenser in communication with the top of the dehydration and scrubbing unit, and a water separator in communication with the exhaust gas condenser;

[0005] The dehydration and washing apparatus includes a first-stage purified water washing unit located at the top of the apparatus, a second-stage concentrated water washing unit located in the middle of the apparatus, and / or a third-stage purified mother liquor washing unit located at the bottom of the apparatus;

[0006] The exhaust gas condensing device includes a first hot condensate drum for storing a first condensate obtained after the oxidation exhaust gas condenser in the system exchanges heat for the first time, a second condensate drum for storing a second condensate obtained after the oxidation exhaust gas condenser in the system exchanges heat for the second time, and a steam condenser for discharging steam. Derivation The road is connected,

[0007] Specifically, the exhaust gas condensation device includes a first oxidation exhaust gas condensation system composed of one or more stages of oxidation exhaust gas condensers connected in series, and a second oxidation exhaust gas condensation system located in the next step of the first oxidation exhaust gas condensation system and composed of one or more stages of oxidation exhaust gas condensers connected in series, each stage of the oxidation exhaust gas condensers in the first oxidation exhaust gas condensation system is connected to a first high-temperature condensate drum for storing a first condensate obtained after heat exchange in the oxidation exhaust gas condensers in the system, each stage of the oxidation exhaust gas condensers in the second oxidation exhaust gas condensation system is connected to a second condensate drum for storing a second condensate obtained after heat exchange in the oxidation exhaust gas condensers in the system, and a steam condenser for guiding steam. Derivation Connected to the road, Among them, an exhaust gas outlet is provided in the oxidation exhaust gas condenser provided in the tail,

[0008] The water separation device includes a multiple-effect evaporator unit for purifying and separating the second condensate, a purified water outlet after separation and purification, and a concentrated water outlet, the purified water outlet being connected to the first stage purified water washing unit through a purified water pipe, the second condensate drum being connected to a bottom of the first effect evaporator unit through a second condensate pipe to separate the condensate, and the steam Derivation the passage extends through a second steam line into the first effect evaporator unit to separate the condensate and provide a heat source for heat exchange; The concentrated water outlet is connected to the second-stage concentrated water washing unit through a concentrated water pipe, and a purified water heat exchanger is provided in the purified water pipe. The first high-temperature condensate drum exchanges heat with the purified water heat exchanger through the first high-temperature condensate pipe, and a concentrated water heat exchanger is provided in the concentrated water pipe. The first hot condensate drum exchanges heat with the condensed water heat exchanger via a second hot condensate line.

[0009] Furthermore, the dehydration and washing device is a dehydration and washing tower, the bottom of which is connected to the PTA oxidation reactor, and the strong reaction liquid after washing returns to the oxidation reactor to continue the reaction, in which a circulating pump can be used.

[0010] Furthermore, the first stage purified water washing unit, the second stage concentrated water washing unit and the third stage purified mother liquor washing unit are each provided with a nozzle, so that the exhaust gas is washed by means of a spray.

[0011] Furthermore, the first oxidation exhaust gas condensation system includes 1-4 stages of oxidation exhaust gas condensers, preferably 3 stages.

[0012] Furthermore, the second oxidation exhaust gas condensation system includes 1-4 stages of oxidation exhaust gas condensers, preferably 3 stages.

[0013] Furthermore, the water separation device is a water separation tower, an evaporation unit for purifying the condensate is provided in the tower body, a final effect condensation unit is provided below the evaporation unit, and a vacuum pump is connected to the bottom of the final effect condensation unit. The water separation tower may be a falling film evaporation water separation tower or a rising film evaporation water separation tower.

[0014] Preferably, the evaporation unit includes a first effect evaporation unit and a second effect evaporation unit, the first effect evaporation unit includes a second condensate inlet and a first heat exchange chamber, a first vapor passage for the vapor phase to enter the next effect evaporation unit and a first downcomer for the liquid phase to pass through and flow to the next effect evaporation unit are connected above the first heat exchange chamber, a first loop-shaped device is provided at the bottom of the first downcomer, the second effect evaporation unit includes a second heat exchange chamber, a second vapor passage for the vapor phase to pass through after the condensate has heat exchanged and a second downcomer for the liquid phase to pass through are provided above the second heat exchange chamber, a second loop-shaped device is provided at the bottom of the second downcomer, a first condensate passage for the condensate to flow to the next effect after heat exchange is provided below the second heat exchange chamber, a first U-shaped tube is provided at the bottom of the first condensate passage, and the first loop-shaped device is located between the second heat exchange chamber and the second mist eliminator.

[0015] A method for improving the water quality of a dehydration tower of a high purity terephthalic acid unit, comprising:

[0016] 1) after the reaction exhaust gas is discharged from the bottom of the oxidation reactor, it enters the lower part of the third-stage purified mother liquor washing unit, and in the process of rising, the reaction exhaust gas is first sprayed and washed with purified mother liquor through the third-stage purified mother liquor washing unit, then sprayed and washed with concentrated water through the second-stage concentrated water washing unit, and finally sprayed and washed with purified water through the first-stage purified water washing unit;

[0017] 2) After the reaction exhaust gas cleaned by the dehydration tower is discharged from the top of the exhaust gas condenser, it first enters the first-stage oxidation exhaust gas condenser, and then enters the other subsequent oxidation exhaust gas condensers in sequence for heat exchange and cooling, and some of the exhaust gas is condensed and turned into the first condensate, and the first condensate generated in each stage of oxidation exhaust gas condenser flows through a pipe into the first high-temperature condensate drum, and after condensation in the first oxidation exhaust gas condensation system, the reaction exhaust gas then enters the second oxidation exhaust gas condensation system to continue condensing, and forms the second condensate through the condensation process of the first oxidation exhaust gas condensation system, and then enters into the second condensate drum through a pipe, and the second steam that is not condensed is discharged upward;

[0018] 3) the second condensate enters the water separation tower for continuous separation and purification; the vacuum pump located at the bottom is opened, the second condensate enters the first heat exchange chamber through the second condensate inlet to prepare for evaporation; the second steam enters the pipe in the first heat exchange chamber through the second steam pipe; in the first heat exchange chamber, the second steam and the second condensate exchange heat; a part of the second condensate evaporates and flows upward into the first steam passage; the steam enters the pipe in the second effect evaporator through the first steam passage and exchanges heat with the condensate flowing out of the first downcomer as a heat source; the heat of the steam flows into the condensate; finally, the steam cools and flows out of the first condensate passage; a part of it is collected in the first U-shaped tube and flows into the purified water storage area at the bottom; and the unevaporated part enters the first downcomer and enters the next effect evaporator to continue evaporating, or remains in the first loop device;

[0019] 4) after separation, the purified water is discharged from the purified water outlet through a pipeline, and when passing through a purified water heat exchanger, it exchanges heat with the first high-temperature condensate, thereby increasing the temperature of the purified water, and then the reaction exhaust gas is sprayed as a cleaning liquid for the first-stage purified water washing unit, and the concentrated water is discharged from the concentrated water outlet through a pipeline, and when passing through a concentrated water heat exchanger, it is sprayed with the reaction exhaust gas as a cleaning liquid for the first-stage concentrated water washing unit for washing.

[0020] The beneficial effects of the present invention are as follows: 1) The present invention replaces the extraction technology with the water separation tower technology, saves the medium pressure steam required for extraction, reduces the external steam consumption by more than 0.2 tons per ton of product, greatly reduces energy consumption, and has a large economic benefit; 2) The exhaust gas condenser is the Nth m Condenser of stage N i+1 By simply using the low-pressure steam of about 0.05Mpa(G) generated in the condenser (one or more stages of the condenser from the first stage to the Nth stage) as the heating medium, the amount of low-quality steam entering the turbine of the air compressor system is greatly reduced, and the load on the air compressor (a plant with four roles in one machine) is reduced. The air compressor plant has reduced design and manufacturing difficulties, significantly reduced manufacturing costs, reduced cooling source losses in the plant with four roles in one machine, and reduced use of circulating cooling water; 3) the water separation tower is a tower-type multi-effect evaporative water separation tower, the working medium is water and low-pressure steam, and no organic phase is involved in the process, the reaction is stable, and it is essentially safe; 4) the water in the water separation tower is purified water and concentrated water, the purified water returns to the top of the dehydration tower, and the concentrated water enters the dehydration tower after being mixed with the mother liquor, greatly improving the efficiency of the dehydration tower and improving the water quality; 5) the system is simplified and the investment is low. [Brief description of the drawings]

[0021] [Figure 1] 1 is a flowchart of the PTA short flow condensate purification process of the present invention. [Diagram 2] FIG. 2 is a flow block diagram of the PTA short flow condensate purification process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The invention will now be further elucidated and explained with reference to the drawings, in which:

[0023] As shown in FIG. 1, the dashed box contains an oxidation reactor (01) for producing PTA. PT and air are introduced into the oxidation reactor (01) containing acetic acid and the like, and reacted to obtain a reaction liquid. The reaction liquid is washed and other procedures are performed to obtain reactants and purified mother liquor. The purified mother liquor contains a large amount of organic moieties such as acetic acid and PT acid, so in the treatment system provided by the present invention, the purified mother liquor is used as the spray liquid for the third-stage purified mother liquor washing unit. In addition, since the reaction is an exothermic reaction, a large amount of heat energy is released during the reaction process, and part of the reaction solution (reaction exhaust gas) is discharged upward from the pipe. One of the objects of the present invention is to enrich the reaction exhaust gas, change it into a liquid form, and then return it to the oxidation reactor (01).

[0024] A system for improving the quality of water in a dehydration tower of a high purity terephthalic acid plant includes a dehydration and washing device 1, an exhaust gas condenser 2 communicating with the top of the dehydration and washing device 1, and a water separator 3 communicating with the exhaust gas condenser 2;

[0025] The dehydration and washing apparatus 1 includes a first-stage purified water washing unit 11 located at the top of the apparatus, a second-stage concentrated water washing unit 12 located in the middle of the apparatus, and / or a third-stage purified mother liquor washing unit 13 located at the bottom of the apparatus, each unit being washed by a spray means;

[0026] The reaction exhaust gas is discharged from the bottom of the oxidation reactor (01) and then introduced into the dehydration and washing device 1, with the inlet located below the third-stage purified mother liquor washing unit 13. During the upward flow of the reaction exhaust gas, it is first sprayed and washed with purified mother liquor through the third-stage purified mother liquor washing unit 13, then sprayed and washed with concentrated water through the second-stage concentrated water washing unit 12, and finally sprayed and washed with purified water through the first-stage purified water washing unit 11. After three sprays and washings, most of the organic parts in the reaction exhaust gas, such as acetic acid and PT acid, are collected at the bottom of the dehydration and washing device 1, and the enriched liquid of this part is returned to the oxidation reactor (01) by the action of the circulation pump 14 to continue to react. The reaction exhaust gas after washing, which contains a small amount of organic parts such as acetic acid and PT acid, is discharged from the top of the dehydration and washing device 1 and enters the next process for other treatment.

[0027] Preferably, the dehydration and washing device 1 is a dehydration and washing tower, the bottom of which is connected to a PTA oxidation reactor, and the concentrated reaction liquid after washing (containing a large amount of organic matter such as acetic acid, PT acid, etc.) returns to the oxidation reactor to continue the reaction, in which a circulating pump 14 can be used.

[0028] The exhaust gas condensation device 2 includes a first oxidation exhaust gas condensation system 21 composed of one or more stages of oxidation exhaust gas condensers connected in series, and a second oxidation exhaust gas condensation system 22 composed of one or more stages of oxidation exhaust gas condensers connected in series, which is located in the next step of the first oxidation exhaust gas condensation system 21. Each stage of oxidation exhaust gas condensers in the first oxidation exhaust gas condensation system 21 is connected to a first high-temperature condensate drum 4 for storing a first condensate obtained after heat exchange in the oxidation exhaust gas condenser in the system, and each stage of oxidation exhaust gas condensers in the second oxidation exhaust gas condensation system 22 is connected to a second condensate drum 5 for storing a second condensate obtained after heat exchange in the oxidation exhaust gas condenser in the system, and a steam condenser 6 for guiding steam. Derivation The exhaust gas condenser is connected to the exhaust passage, and the exhaust gas condenser is provided at the tail of the exhaust passage.

[0029] The first oxidation exhaust gas condensation system 21 includes 1-N stages of oxidation exhaust gas condensers, preferably three stages, and FIG. 1 shows a two-stage oxidation exhaust gas condenser, with each stage of the oxidation exhaust gas condenser being provided with a cold water inlet 211 and a hot water outlet 212.

[0030] In FIG. 1, after the reaction exhaust gas cleaned by the dehydration tower is discharged from the top of the exhaust gas condenser 2, it first enters the first stage oxidation exhaust gas condenser, and then enters the other subsequent oxidation exhaust gas condensers in sequence. In the process of flowing through these oxidation exhaust gas condensers, it exchanges heat with the cold water flowing in from the cold water inlet 211, and then the temperature of the cold water rises, but the temperature of the reaction exhaust gas in the oxidation exhaust gas condenser decreases, and some of it turns into condensate, the first condensate. The first condensate generated in each stage of the oxidation exhaust gas condenser flows through a pipeline to the first high-temperature condensate drum 4, and after condensation in the first oxidation exhaust gas condensation system 21, the reaction exhaust gas then enters the second oxidation exhaust gas condensation system 22 to continue condensing. Due to the condensation process of the first oxidation exhaust gas condensation system 21, the temperature and pressure of the reaction exhaust gas decrease.

[0031] The second oxidation exhaust gas condensation system 22 includes 1 to 4 stages of oxidation exhaust gas condensers, preferably 3 stages. Figure 1 shows a 3-stage oxidation exhaust gas condenser. Each oxidation exhaust gas condenser in the second oxidation exhaust gas condensation system 22 does not use heat exchange with cold water. In the normal flow process, a part of the reaction exhaust gas is normally condensed into the second condensate, and then enters the second condensate drum 5 through a pipe, and the uncondensed reaction exhaust gas (second steam) is discharged upward.

[0032] The water separation device 3 includes a multiple-effect evaporation unit (31, 32, 33...) for purifying and separating the second condensate, a purified water outlet 35 after separation and purification, and a concentrated water outlet 34. The purified water outlet 35 is connected to the first-stage purified water washing unit 11 through a purified water pipe, and the second condensate drum 5 is connected to the bottom of the first-effect evaporation unit through a second condensate pipe to separate the condensate and the steam. DerivationThe line extends through a second steam line 221 into the first effect evaporation unit to separate condensate to provide a heat source for heat exchange, the concentrated water outlet 34 communicates with the second stage concentrated water washing unit 12 through a concentrated water line, a purified water heat exchanger 352 is provided in the purified water line, the first high temperature condensate drum 4 performs heat exchange through the purified water heat exchanger 352 through the first high temperature condensate line, a concentrated water heat exchanger 351 is provided in the concentrated water line, and the first high temperature condensate drum 4 performs heat exchange through the concentrated water heat exchanger 351 through a second high temperature condensate line.

[0033] Preferably, the water separation device is a closed water separation tower 3, and an evaporation unit (31, 32, 33 ...) for purifying the condensate is provided in the tower body, and a final effect condensing unit 34 is provided below the evaporation unit, and a vacuum pump is connected to the bottom of the final effect condensing unit 34. As shown in FIG. 1, the evaporation unit includes a first effect evaporation unit 31 and a second effect evaporation unit 32, etc., and the first effect evaporation unit 31 includes a second condensate inlet 311 and a first heat exchange chamber 312, and the second condensate inlet 311 is located at the bottom of the first effect evaporation unit 31. The second steam is introduced into the first heat exchange chamber 312 through the second steam pipe 221 to provide a heat source for heat exchange. The second condensate exchanges heat with the second steam in the first heat exchange chamber 312, and a part of the second condensate is vaporized, thereby realizing separation of water and other organic matter. The first heat exchange chamber The second effect evaporator unit 32 includes a second heat exchange chamber 321, a second steam passage 323 for the gas phase to pass through after the condensate has been heat exchanged and a second downcomer 324 for the liquid phase to pass through, and a second loop device 325 is provided at the bottom of the second downcomer 324. The second effect evaporator unit 32 includes a second heat exchange chamber 321, a second steam passage 323 for the gas phase to pass through after the condensate has been heat exchanged and a second downcomer 324 for the liquid phase to pass through, and a second loop device 325 is provided at the bottom of the second downcomer 324. A first condensate passage 326 for the condensate to pass through to the next effect after heat exchange is provided below the second heat exchange chamber 32, and a first U-shaped tube 327 is provided at the bottom of the first condensate passage 326. The first loop device 325 is located between the second heat exchange chamber and the second mist eliminator. The steam entering the water separation tower is preferably steam of 0.05 MPa (G), and may be steam of 0.05 to 0.5 MPa (G) generated by an oxidation exhaust gas condenser at any stage, or may be steam introduced from the outside.

[0034] In the water separation tower, the second condensate is continuously separated and purified. The vacuum pump 36 located at the bottom is opened, the second condensate enters the first heat exchange chamber 312 through the second condensate inlet 311 to prepare for evaporation, the second steam enters the pipe in the first heat exchange chamber 312 through the second steam pipe 221, and in the first heat exchange chamber 312, the second steam and the second condensate exchange heat, a part of the second condensate evaporates and flows upward into the first steam passage 313, and the part that does not evaporate enters the first downcomer 314 and continues to evaporate in the next effect evaporation unit, or remains in the first loop device 315. The steam that enters the pipes of the second effect evaporator unit 32 through the first steam passage 313 exchanges heat with the condensate flowing out from the first downcomer 314 as a heat source, and the heat source of the steam flows into the condensate. Finally, the steam cools and flows out from the first condensate passage 326, part of which is collected in the first U-shaped tube 327, and finally flows into the purified water storage area at the bottom. The first loop device 315 and the first U-shaped tube 327 separate each effect unit. In this way, under the action of the vacuum pump 36, the pressure becomes lower and lower from top to bottom. Therefore, the first loop device 315 performs self-evaporation through the action of pressure difference and heat exchange, thereby realizing the separation of water from other substances. After separation, the purified water is discharged through a pipe from the purified water outlet 35, and when passing through the purified water heat exchanger 352, it exchanges heat with the first high-temperature condensate, and the temperature of the purified water is increased, and then sprays the reaction exhaust gas as the cleaning liquid of the first-stage purified water washing unit; the concentrated water is discharged through a pipe from the concentrated water outlet 34, and when passing through the concentrated water heat exchanger 351, it sprays and washes the reaction exhaust gas as the cleaning liquid of the first-stage concentrated water washing unit. The concentrated water generated in the novel water separation tower can enter the dehydration tower, and can further be used as a crude terephthalic acid (abbreviated as CTA in English, hereinafter referred to as CTA) solvent to replace the cleaning liquid of the plant.

[0035] In the whole system, as shown in the figure, various kinds of pumps or valves can be rationally installed according to actual needs to achieve the smoothness of the system.

Claims

1. Reaction exhaust gas discharged from the PTA oxidation reactor of a purified terephthalic acid (PTA) plant A system for improving water quality in a dewatering wash, comprising: a scrubbing device; an exhaust gas condensing device communicating with the top of the dehydration and scrubbing device; a water separator in communication with the apparatus; The dehydration and cleaning device includes a purified water cleaning unit located at the top of the dehydration and cleaning device, and A concentrated water washing unit located below the water preparation washing unit; a purified mother liquor washing unit located on the side of the purified mother liquor washing unit; an inlet through which the reaction exhaust gas discharged from the PTA oxidation reactor is introduced; The bottom of the dewatering and washing device, in which the enriched liquid resulting from the above-mentioned process is collected, is in fluid communication with the PTA oxidation reactor. are transmissively connected, The exhaust gas condenser is configured to condense gas discharged from the top of the dehydration and cleaning device into the exhaust gas condenser. This is to store the first condensate obtained after the first heat exchange in the oxidation exhaust gas condenser of the condensation device. The first high temperature condensate drum and the exhaust gas condensing device further include another oxidation exhaust gas condenser. a second condensate drum for receiving the second condensate obtained after the second heat exchange; a steam outlet passage for outletting steam from the exhaust gas condenser; The water separation device is a water separation tower, into which the second condensate drum is introduced; a multi-effect evaporation unit for purifying the above-mentioned mixture, and a a final effect condensing unit; a vacuum pump connected to the bottom of the last effect condensing unit; The multiple-effect evaporation unit includes a first-effect evaporation unit and a second-effect evaporation unit. a plurality of effect evaporating units in fluid communication with the last effect condensing unit; The first effect evaporative unit includes a second condensate inlet and a first heat exchange chamber. Above the first heat exchange chamber, a first evaporator for the vapor phase to enter the second effect evaporator unit. A first downcomer is connected to the second effect evaporator unit for passing the gas passage and the liquid phase therethrough. A first loop-shaped device is provided at the bottom of the first downcomer, and the second effect evaporation unit is a second heat exchange chamber, and above the second heat exchange chamber, the condensate is heat exchanged therewith, A second vapor passage for passing the vapor phase and a second downcomer for passing the liquid phase are provided, A second loop-shaped device is provided at the bottom of the second downcomer, below the second heat exchange chamber, A first condensate passage is provided for the condensate to flow to the next effect evaporator unit after heat exchange, a first U-shaped tube is provided at a bottom portion of the first condensate passage; the first loop device and the first U-tube partition the plurality of effect evaporation units; When the vacuum pump is operating, the pressure in the water separation tower decreases from top to bottom. A pressure difference is created, and the water is separated from other substances by the action of heat exchange and the pressure difference. A purified water outlet provided at the bottom of the water separation tower for discharging purified water after separation and purification. and a concentrated water outlet for discharging concentrated water produced in the multiple effect evaporation unit, The purified water outlet is connected to the purified water washing unit through a purified water pipe, and the second return The water drum is connected to the bottom of the first effect evaporator unit via a second condensate line to separate the condensate. The vapor outlet passage extends into the first effect evaporating unit via a second vapor pipe. providing a heat source for the heat exchange in the multiple effect evaporation unit; moreover, the concentrate outlet communicates with the concentrate wash unit via a concentrate line; and The purified water pipe is provided with a purified water heat exchanger, and the first hot condensate drum is Heat exchange is performed through the purified water heat exchanger via a condensate pipe, and the concentrated water outlet and the concentrated water outlet are A concentrated water heat exchanger is provided in the concentrated water pipe communicating with the water washing unit, and the first high-temperature recovery The water drum exchanges heat with the concentrated water heat exchanger via a second high-temperature condensate pipe. A system characterized by:

2. The exhaust gas condensation device is a first stage that is composed of one or more oxidation exhaust gas condensers connected in series. A first oxidation exhaust gas condensation system and a second oxidation exhaust gas condensation system located in the next step of the first oxidation exhaust gas condensation system. A second oxidation exhaust gas condensation system is provided, which is composed of one or more stages of oxidation exhaust gas condensers connected in series. and each stage of the oxidation exhaust gas condenser in the first oxidation exhaust gas condensation system comprises: The first condensate obtained after the heat exchange in the oxidation exhaust gas condenser is stored in the 1. A high-temperature condensate drum is connected to the second oxidation exhaust gas condenser of each stage of the second oxidation exhaust gas condenser system. The condenser is used to store the second condensate obtained after the heat exchange in the oxidation exhaust gas condenser. and a steam outlet passage for outletting the steam.

2. The system of claim 1 .

3. The dehydration and washing device is a dehydration and washing tower, and the bottom of the dehydration and washing tower is the PTA oxidation reactor. The concentrated reaction liquid after washing returns to the PTA oxidation reactor and continues to react.

2. The system of claim 1 .

4. The purified water washing unit, the concentrated water washing unit, and the purified mother liquor washing unit Each is provided with a nozzle, which cleans the exhaust gas by means of a spray.

2. The system of claim 1 .

5. the first oxidation exhaust gas condensation system includes 1 to 4 stages of oxidation exhaust gas condensers; and / or or the second oxidation exhaust gas condensation system includes 1 to 4 stages of oxidation exhaust gas condensers.

3. The system of claim 2.

6. For dehydrating and cleaning the reaction exhaust gas discharged from the PTA oxidation reactor of the high-purity terephthalic acid plant 10. A method of using the system of claim 2 to improve water quality in a water supply system, comprising the steps of: 1) The reaction exhaust gas is discharged from the top of the PTA oxidation reactor and then dehydrated and washed. The reaction exhaust gas enters the purification equipment below the purified mother liquor washing unit, and the reaction exhaust gas enters the dehydration washing equipment below the purified mother liquor washing unit. During the ascending process in the plant, first, the purified PTA is purified through the purified mother liquor washing unit. Spray and wash with mother liquor, then spray with the concentrate through the concentrate wash unit. and finally, the purified water is sprayed through the purified water washing unit to wash the and 2) The reaction exhaust gas cleaned by the dehydration and cleaning device is exhausted from the top of the dehydration and cleaning device. After that, in the first oxidation exhaust gas condensation system, first, a first stage oxidation exhaust gas condensation The reaction mixture is then cooled by heat exchange in the oxidation exhaust gas condenser. A part of the reaction exhaust gas is converted into a first condensate in the oxidation exhaust gas condenser of each stage, and the first The condensate flows through a line to the first hot condensate drum, and the first oxidation exhaust gas condensation system After condensation at the second oxidation exhaust gas condensation system, the remainder of the reaction exhaust gas is then and continues to condense in the second oxidation exhaust gas condensation system. The second condensate is formed, and the second condensate enters the second condensate drum via a line, and a second non-condensed condensate is Discharging the steam upwardly; 3) The second condensate enters the water separation tower, and the second condensate is separated into the water separation tower. To continuously separate and purify the water, the vacuum pump located at the bottom of the water separation tower is opened. The second condensate is introduced from the second condensate inlet into the first heat exchange chamber of the first effect evaporator unit. Enter the chamber to prepare for evaporation. The second vapor enters the second vapor line into a line in the first heat exchange chamber, the second steam and the second condensate exchange heat in the first heat exchange chamber; A portion of the second condensate is vaporized and flows upward into the first vapor passage, The steam entering the pipes in the second effect evaporator unit through the air passage is used as a heat source to cool the first downflow condensate. The steam exchanges heat with the condensate that flows out of the tube, and the heat of the steam flows into the condensate, and finally, the steam is cooled. Then, the liquid flows out of the first condensate passage, and a part of the liquid that flows out is collected in the first U-shaped tube, Flows into the purified water storage area at the bottom of the first U-tube, The portion of the second condensate that is not evaporated enters the first downcomer and is passed through the second effect evaporator. entering the unit and continuing to evaporate or remain in the first loop device; 4) After separating other substances, the purified water is discharged from the purified water outlet through a pipe. The purified water heat exchanger is provided in the purified water pipe, and the purified water is passed through the purified water heat exchanger. When the purified water is passed through the first high-temperature condensate drum, the purified water is heat exchanged with the first high-temperature condensate discharged from the first high-temperature condensate drum. The temperature of the purified water is then increased, and the reaction exhaust gas is then scrubbed as a cleaning liquid for the purified water cleaning unit. The concentrated water is supplied to the concentrated water heat exchanger. When the concentrated water is discharged from the concentrated water outlet through a pipe and passed through the concentrated water heat exchanger, spraying the reaction exhaust gas as a cleaning liquid for the unit to clean it; Includes A method comprising:

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