Treatment device and treatment method for pbt waste liquid

Abstract

The application relates to a PBT waste liquid treatment device, which comprises a PBT waste liquid input system, a normal-pressure rectification system, a high-pressure rectification system and a waste water treatment system. The normal-pressure rectification system comprises a normal-pressure tower, the PBT waste liquid input system is communicated with the middle part of the normal-pressure tower; the high-pressure rectification system comprises a high-pressure tower, the top of the normal-pressure tower is communicated with the middle part of the high-pressure tower, and the top of the high-pressure tower is communicated with the middle part of the normal-pressure tower; the waste water treatment system comprises a waste water tower, and the tank bottom of the normal-pressure tower is communicated with the middle part of the waste water tower. The application solves the problem that the COD value of waste water generated in the THF purification process of PBT waste liquid is difficult to reduce.

Description

Technical Field

[0001] This application relates to the chemical industry, and in particular to the treatment of PBT waste liquid. Background Technology

[0002] Currently, almost all newly built polybutylene terephthalate (PBT) projects in China adopt the direct esterification process of purified terephthalic acid (PTA) and 1,4-butanediol (BDO). The direct esterification method for PBT production produces a waste liquid containing tetrahydrofuran (THF) (hereinafter referred to as "PBT waste liquid"). The main components of PBT waste liquid are THF and water, and it also contains small amounts of organic impurities such as BDO, PBT, and diacids. Recovering THF from PBT waste liquid can turn waste into treasure and increase the company's profits. Currently, the main methods for recovering THF from PBT waste liquid include pressure swing distillation and distillation-membrane coupling. During the THF recovery process, wastewater is generated. Because the boiling points of the impurities in PBT waste liquid are almost all higher than those of water, the impurities accumulate in the water, resulting in a high COD (approximately 25–40 g / L) in the wastewater.

[0003] Current technologies for recovering THF from PBT wastewater rarely report on the treatment of high-COD wastewater. Industrial wastewater treatment commonly employs two methods: one involves adding an equalization tank to mix low-COD wastewater (such as circulating water discharge, laboratory wastewater, flushing water, and initial rainwater) with high-COD wastewater from various areas, reducing the COD to meet the requirements of wastewater treatment plants before discharge; the other method involves designing a wastewater treatment system, typically including hydrolysis acidification, anaerobic, and aerobic processes, capable of treating wastewater with a COD of 5 g / L to below 0.3 g / L before discharge to a wastewater treatment plant. However, this method is limited by requiring the COD of the wastewater entering the treatment system to be approximately below 10 g / L.

[0004] However, the wastewater generated during the THF recovery process from PBT wastewater has a high COD (approximately 25-40 g / L), indicating that it cannot be directly treated in the wastewater treatment system. Furthermore, due to the high COD of this wastewater, if an equalization tank is used to adjust the COD to meet the wastewater treatment plant's acceptance requirements, preliminary calculations show that the required circulating water discharge flow rate would be approximately 7.0 times the wastewater flow rate, meaning the total wastewater discharge would increase by 7.0 times. This not only requires a larger equalization tank but also increases the load on the biological treatment process.

[0005] Therefore, how to effectively reduce the COD of wastewater has always been a difficult problem to solve in this field. Summary of the Invention

[0006] This application provides a PBT waste liquid treatment device and method to solve the technical problem that the COD value of wastewater generated during the THF recovery process from PBT waste liquid is difficult to reduce.

[0007] In a first aspect, embodiments of this application provide a PBT waste liquid treatment device, the PBT waste liquid treatment device comprising:

[0008] PBT waste liquid input system;

[0009] An atmospheric distillation system, comprising an atmospheric column, wherein the PBT waste liquid input system is connected to the middle section of the atmospheric column;

[0010] A high-pressure distillation system, comprising a high-pressure column, wherein the top of the atmospheric column is connected to the middle of the high-pressure column;

[0011] A wastewater treatment system, comprising a wastewater tower, wherein the bottom of the atmospheric pressure tower is connected to the middle section of the wastewater tower.

[0012] In some embodiments of this application, the atmospheric distillation system further includes an atmospheric column condenser, an atmospheric column reflux tank, and an atmospheric column reflux pump connected in sequence, wherein the atmospheric column condenser is connected to the top of the atmospheric column, and the atmospheric column reflux pump is connected to the upper part of the atmospheric column; and / or,

[0013] The atmospheric distillation system also includes an atmospheric column reboiler, one end of which is connected to the bottom of the atmospheric column and the other end of which is connected to the lower part of the atmospheric column.

[0014] The atmospheric distillation system also includes an atmospheric column bottom pump, one end of which is connected to the bottom of the atmospheric column and the other end of which is connected to the middle of the wastewater column.

[0015] In some embodiments of this application, the high-pressure distillation system further includes a high-pressure tower heat exchanger, a high-pressure tower reflux tank, and a high-pressure tower reflux pump connected in sequence, wherein the high-pressure tower heat exchanger is connected to the top of the high-pressure tower, and the high-pressure tower reflux pump is connected to the upper part of the high-pressure tower; and / or,

[0016] The high-pressure distillation system also includes a high-pressure tower reboiler, one end of which is connected to the bottom of the high-pressure tower, and the other end is connected to the lower part of the high-pressure tower.

[0017] In some embodiments of this application, the PBT waste liquid input system is connected to the middle of the atmospheric pressure tower via the high-pressure tower heat exchanger.

[0018] In some embodiments of this application, the wastewater treatment system further includes a wastewater tower condenser, a wastewater tower reflux tank, and a wastewater tower reflux pump connected in sequence, wherein the wastewater tower condenser is connected to the top of the wastewater tower, and the wastewater tower reflux pump is connected to the upper part of the wastewater tower; and / or,

[0019] The wastewater distillation system also includes a wastewater tower reboiler, one end of which is connected to the bottom of the wastewater tower, and the other end is connected to the lower part of the wastewater tower.

[0020] In some embodiments of this application, the wastewater treatment system further includes a wastewater tower heat exchanger, which is connected in parallel with both ends of the wastewater tower condenser, and the top of the atmospheric pressure tower is connected to the middle of the high pressure tower through the wastewater tower heat exchanger.

[0021] Secondly, embodiments of this application provide a method for treating PBT waste liquid, the method being implemented using the PBT waste liquid treatment apparatus described in any embodiment of the first aspect, the method comprising the following steps:

[0022] PBT waste liquid is fed into the middle of the atmospheric distillation column through the PBT waste liquid input system for atmospheric distillation;

[0023] The THF and low-boiling-point substances from the top of the atmospheric pressure column are fed into the middle of the high-pressure column for high-pressure distillation, and the primary wastewater from the bottom of the atmospheric pressure column is fed into the middle of the wastewater column.

[0024] The THF and high-boiling-point substances of water collected from the top of the high-pressure tower are recycled back to the middle of the atmospheric pressure tower, and the THF product in the bottom of the high-pressure tower is collected.

[0025] The secondary wastewater at the top of the wastewater tower is extracted, and the concentrate at the bottom of the wastewater tower is extracted.

[0026] In some embodiments of this application, the operating pressure of the atmospheric pressure tower is 60-180 kPaA, the reflux ratio is 0.5-3, the temperature at the top of the tower is 45-90°C, and the temperature at the bottom of the tower is 80-120°C.

[0027] In some embodiments of this application, the operating pressure of the high-pressure tower is 200-950 kPaA, the reflux ratio is 0.5-5, the temperature at the top of the tower is 90-150°C, and the temperature at the bottom of the tower is 120-160°C.

[0028] In some embodiments of this application, the operating pressure of the wastewater tower is 200-850 kPaA, the reflux ratio is 0.1-3, the temperature at the top of the tower is 100-170°C, and the temperature at the bottom of the tower is 110-190°C.

[0029] The technical solutions provided in this application have the following advantages compared with the prior art:

[0030] The PBT wastewater treatment apparatus and method provided in this application embodiment involves inputting primary wastewater collected from the bottom of an atmospheric pressure distillation tower into the wastewater tower for distillation separation. After treating the primary wastewater with a COD of 25-40 g / L, secondary wastewater with a COD of 0.7-2 g / L is collected from the top of the wastewater tower, and a concentrated solution containing high concentrations of PBT and adipic acid is collected from the bottom of the wastewater tower. The secondary wastewater can be directly treated as sewage, and the concentrated solution can be further treated, thus solving the problem of difficulty in reducing the COD value of wastewater generated during the recovery of THF from PBT wastewater. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a PBT waste liquid treatment device provided in an embodiment of this application.

[0034] The reference numerals in the accompanying drawings of this application are as follows: 1-Atmospheric pressure tower, 2-Atmospheric pressure tower condenser, 3-Atmospheric pressure tower reflux tank, 4-Atmospheric pressure tower reflux pump, 5-Atmospheric pressure tower reboiler, 6-Atmospheric pressure tower bottom pump, 7-High pressure tower, 8-High pressure tower heat exchanger, 9-High pressure tower reflux tank, 10-High pressure tower reflux pump, 11-High pressure tower reboiler, 12-Wastewater tower, 13-Wastewater tower heat exchanger, 14-Wastewater tower condenser, 15-Wastewater tower reflux tank, 16-Wastewater tower reflux pump, 17-Wastewater tower reboiler. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] Unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any conflict, this specification shall prevail.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0038] There is a technical problem that the COD value of the wastewater generated during the recovery of THF from PBT waste liquid is difficult to reduce.

[0039] The technical solution provided in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0040] Firstly, embodiments of this application provide a PBT waste liquid treatment device, please refer to... Figure 1 The PBT waste liquid treatment device includes:

[0041] PBT waste liquid input system;

[0042] An atmospheric distillation system, comprising an atmospheric column 1, wherein the PBT waste liquid input system is connected to the middle section of the atmospheric column 1;

[0043] A high-pressure distillation system, comprising a high-pressure column 7, wherein the top of the atmospheric column 1 is connected to the middle of the high-pressure column 7, and the top of the high-pressure column 7 is connected to the middle of the atmospheric column 1;

[0044] A wastewater treatment system, comprising a wastewater tower 12, wherein the bottom of the atmospheric pressure tower 1 is connected to the middle of the wastewater tower 12.

[0045] Those skilled in the art will understand that the PBT waste liquid input system includes at least a pipeline for inputting PBT waste liquid; it may also include instruments such as pressure gauges and thermometers.

[0046] The function of the atmospheric distillation system is to distill off the low-boiling-point substances of THF and water, and the distilled low-boiling-point substances enter the high-pressure distillation system.

[0047] The function of the high-pressure distillation system is to distill off the high-boiling-point substances of THF and water. The high-boiling-point substances of THF and water collected from the top of the high-pressure column 7 are recycled back to the atmospheric column 1.

[0048] The wastewater treatment system's function is to perform distillation and separation of wastewater. Primary wastewater collected from the bottom of atmospheric distillation column 1 is fed into wastewater distillation column 12 for further distillation. Secondary wastewater is collected from the top of wastewater distillation column 12, and a concentrate is collected from the bottom. The COD of the primary wastewater is generally 25–40 g / L, while the COD of the secondary wastewater can be reduced to 0.7–2 g / L. The concentrate contains high concentrations of PBT, adipic acid, and other substances, and can be sent to a qualified facility for further incineration, thus reducing the burden on wastewater treatment.

[0049] In some embodiments of this application, in order to simplify the connection pipeline, an inlet connected to the PBT waste liquid input system is provided in the middle of the atmospheric pressure tower 1, and the top of the high pressure tower 7 is connected to the inlet together with the waste liquid input system.

[0050] This application separates the primary wastewater collected from the bottom of atmospheric pressure tower 1 into wastewater tower 12 through distillation. After treating the primary wastewater with a COD of 25-40 g / L, secondary wastewater with a COD of 0.7-2 g / L is collected from the top of wastewater tower 12, and a concentrated solution containing high concentrations of PBT and adipic acid is collected from the bottom of wastewater tower 12. The secondary wastewater can be directly treated as sewage, and the concentrated solution can be further treated, thus solving the problem of difficulty in reducing the COD value of wastewater generated during the recovery of THF from PBT waste liquid.

[0051] This application can also be supplied via a skid-mount model, which has the advantages of high integration and minimal on-site modifications.

[0052] In some embodiments of this application, the atmospheric distillation system further includes an atmospheric column condenser 2, an atmospheric column reflux tank 3, and an atmospheric column reflux pump 4 connected in sequence, wherein the atmospheric column condenser 2 is connected to the top of the atmospheric column 1, and the atmospheric column reflux pump 4 is connected to the upper part of the atmospheric column 1; and / or,

[0053] The atmospheric distillation system also includes an atmospheric column reboiler 5, one end of which is connected to the bottom of the atmospheric column and the other end of which is connected to the lower part of the atmospheric column.

[0054] The atmospheric distillation system also includes an atmospheric distillation tower bottom pump 6, one end of which is connected to the bottom of the atmospheric distillation tower, and the other end is connected to the middle of the wastewater tower.

[0055] Those skilled in the art will understand that the atmospheric pressure tower condenser 2, atmospheric pressure tower reflux tank 3, and atmospheric pressure tower reflux pump 4 function to reflux a portion of the low-boiling-point substances from the top of atmospheric pressure tower 1. The atmospheric pressure tower reboiler 5 functions to reboil a portion of the primary wastewater from the bottom of atmospheric pressure tower 1. The atmospheric pressure tower bottom pump 6 functions to input the primary wastewater collected from the bottom of atmospheric pressure tower 1 into wastewater tower 12.

[0056] In some embodiments of this application, the high-pressure distillation system further includes a high-pressure tower heat exchanger 8, a high-pressure tower reflux tank 9, and a high-pressure tower reflux pump 10 connected in sequence, wherein the high-pressure tower heat exchanger 8 is connected to the top of the high-pressure tower 7, and the high-pressure tower reflux pump 10 is connected to the upper part of the high-pressure tower 7; and / or,

[0057] The high-pressure distillation system also includes a high-pressure tower reboiler 11, one end of which is connected to the bottom of the high-pressure tower, and the other end is connected to the lower part of the high-pressure tower.

[0058] Those skilled in the art will understand that the high-pressure tower heat exchanger 8, the high-pressure tower reflux tank 9, and the high-pressure tower reflux pump 10 serve to reflux a portion of the high-boiling-point substances from the top of the high-pressure tower 7. The high-pressure tower reboiler 11 serves to reboil a portion of the THF product from the bottom of the high-pressure tower 7. The high-pressure tower heat exchanger 8 achieves condensation through heat exchange.

[0059] In some embodiments of this application, the PBT waste liquid input system is connected to the middle of the atmospheric pressure tower 1 through the high-pressure tower heat exchanger 8.

[0060] Those skilled in the art will understand that the PBT waste liquid and the high-boiling-point substances at the top of the high-pressure tower 7 exchange heat in the high-pressure tower heat exchanger 8, which can achieve the preheating of the PBT waste liquid and the condensation of the high-boiling-point substances, thereby reducing the energy consumption of the device.

[0061] In some embodiments of this application, after the high-boiling-point material at the top of the high-pressure tower 7 passes through the high-pressure tower heat exchanger 8, the high-pressure tower reflux tank 9, and the high-pressure tower reflux pump 10, a portion of the high-boiling-point material is refluxed back to the high-pressure tower 7, while the other portion of the high-boiling-point material, together with the PBT waste liquid, is input into the atmospheric distillation tower system, thereby achieving connection with the middle part of the atmospheric tower 1.

[0062] In some embodiments of this application, the wastewater treatment system further includes a wastewater tower condenser 14, a wastewater tower reflux tank 15, and a wastewater tower reflux pump 16 connected in sequence, wherein the wastewater tower condenser 14 is connected to the top of the wastewater tower 12, and the wastewater tower reflux pump 16 is connected to the upper part of the wastewater tower 12; and / or,

[0063] The wastewater distillation system also includes a wastewater tower reboiler 17, one end of which is connected to the bottom of the wastewater tower, and the other end is connected to the lower part of the wastewater tower.

[0064] Those skilled in the art will understand that the wastewater tower condenser 14, wastewater tower reflux tank 15, and wastewater tower reflux pump 16 are used to reflux a portion of the secondary wastewater from the top of wastewater tower 12. The wastewater tower reboiler 17 is used to reboil a portion of the concentrated liquid from the bottom of wastewater tower 12.

[0065] In some embodiments of this application, the wastewater treatment system further includes a wastewater tower heat exchanger 13, which is connected in parallel with both ends of the wastewater tower condenser 14, and the top of the atmospheric pressure tower 1 is connected to the middle of the high pressure tower 7 through the wastewater tower heat exchanger 13.

[0066] Those skilled in the art will understand that the THF and low-boiling-point substances extracted from the top of the atmospheric pressure tower 1 exchange heat with the secondary wastewater in the wastewater tower heat exchanger 13, thereby achieving preheating of the low-boiling-point substances and condensation of the secondary wastewater. The secondary wastewater condensed in the wastewater tower heat exchanger 13 and the secondary wastewater condensed in the wastewater tower condenser 14 are combined and then enter the wastewater tower reflux tank 15.

[0067] In some embodiments of this application, the bottom of the atmospheric pressure tower 1 is connected to the middle of the wastewater tower 12 via the atmospheric pressure tower bottom pump 6.

[0068] Secondly, embodiments of this application provide a method for treating PBT waste liquid, the method being implemented using the PBT waste liquid treatment apparatus described in any embodiment of the first aspect, the method comprising the following steps:

[0069] S1: PBT waste liquid is fed into the middle of the atmospheric distillation tower 1 through the PBT waste liquid input system for atmospheric distillation;

[0070] S2: The low-boiling-point THF and water collected from the top of the atmospheric pressure tower 1 are fed into the middle of the high-pressure tower 7 for high-pressure distillation, and the primary wastewater collected from the bottom of the atmospheric pressure tower 1 is fed into the middle of the wastewater tower 12.

[0071] S3: The high-boiling-point THF and water extracted from the top of the high-pressure tower 7 are recycled back to the middle of the atmospheric tower 1, and the THF product in the bottom of the high-pressure tower 7 is collected.

[0072] S4: Extract the secondary wastewater from the top of the wastewater tower 12 and extract the concentrate from the bottom of the wastewater tower 12.

[0073] Those skilled in the art will understand that steps S3 and S4 are not sequential and are generally performed simultaneously.

[0074] In some embodiments of this application, the operating pressure of the atmospheric pressure column 1 is 60-180 kPaA, the reflux ratio is 0.5-3, the temperature at the top of the column is 45-90°C, and the temperature at the bottom of the column is 80-120°C.

[0075] In some embodiments of this application, the operating pressure of the high-pressure tower 7 is 200-950 kPaA, the reflux ratio is 0.5-5, the temperature at the top of the tower is 90-150°C, and the temperature at the bottom of the tower is 120-160°C.

[0076] In some embodiments of this application, the operating pressure of the wastewater tower 12 is 200-850 kPaA, the reflux ratio is 0.1-3, the temperature at the top of the tower is 100-170°C, and the temperature at the bottom of the tower is 110-190°C.

[0077] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0078] Example

[0079] PBT waste liquid is provided from the PBT production unit. The parameters of the PBT waste liquid are as follows: temperature 30°C, pressure 200 kPaA, flow rate 300 kg / h, THF content 34.4 wt%, water content 64.4 wt%, PBT content 0.6 wt%, and adipic acid content 0.6 wt%.

[0080] The PBT waste liquid is first heated by the high-pressure tower heat exchanger 8, and then enters the atmospheric tower 1 for distillation. The atmospheric tower 1 has an operating pressure of 108 kPaA, 20 theoretical plates, a mass reflux ratio of 2.0, a top temperature of 65.2℃, and a bottom temperature of 99.2℃.

[0081] The low-boiling-point vapor at the top of atmospheric column 1 is condensed and enters atmospheric column reflux tank 3. The condensate in atmospheric column reflux tank 3 is pressurized by atmospheric column reflux pump 4. One stream is used as reflux for atmospheric column 1, and the other stream is heated by wastewater heat exchanger 13 and enters high-pressure column 7. The high-pressure column 7 has an operating pressure of 800 kPaA, a theoretical plate number of 20, a mass reflux ratio of 2.5, a top temperature of 134.2℃, and a bottom temperature of 146.7℃.

[0082] The primary wastewater from the bottom of atmospheric pressure tower 1 was tested and found to have a COD of approximately 31.6 g / L. After being pressurized by the bottom pump 6 of the atmospheric pressure tower, the primary wastewater enters wastewater tower 12. Wastewater tower 12 has an operating pressure of 600 kPaA, a theoretical plate number of 20, a mass reflux ratio of 0.3, a top temperature of 150.4℃, and a bottom temperature of 175.5℃.

[0083] The high-boiling-point vapor at the top of high-pressure tower 7 is condensed by high-pressure tower heat exchanger 8 and enters high-pressure tower reflux tank 9. The condensate in high-pressure tower reflux tank 9 is pressurized by high-pressure tower reflux pump 10; one stream becomes reflux from high-pressure tower 7, and the other stream mixes with PBT waste liquid from the PBT production unit and enters high-pressure tower heat exchanger 8. At the bottom of high-pressure tower 7, a qualified THF product with a flow rate of 102.3 kg / h, a mass fraction of 99.89 wt%, and a yield of 99.0% is obtained.

[0084] The gas phase at the top of wastewater tower 12 is divided into two parts: one part of the gas phase preheats the feed from high-pressure tower 7 through wastewater tower heat exchanger 13, and then condenses and enters wastewater tower reflux tank 15. The other part of the gas phase is condensed in wastewater tower condenser 14 and then enters wastewater tower reflux tank 15. The condensate in wastewater tower reflux tank 15, i.e., secondary wastewater, is pressurized by wastewater tower reflux pump 16. One stream is used as wastewater tower 12 reflux, and the other stream, after meeting the discharge requirements, is sent to the sewage treatment plant for treatment. The COD of this wastewater stream is approximately 0.9 g / L. A small amount of concentrated liquid collected from the bottom of wastewater tower 12 is sent to a qualified unit for incineration. The concentrated liquid contains approximately 37.8 wt% PBT, approximately 37.8 wt% adipic acid, and approximately 24.4 wt% water.

[0085] Calculations show that if the wastewater is not separated by distillation through a wastewater treatment system, the flow rate of the circulating water to reduce the COD of the primary wastewater to meet the requirements of the sewage treatment plant would need to be about 7.0 times the flow rate of the wastewater discharged from the bottom of the atmospheric pressure tower 1. This means that the total wastewater discharge increases by 7.0 times, which not only requires a larger equalization tank but also increases the load on the biological treatment.

[0086] This embodiment ensures a THF yield of 99.0% while controlling the COD of secondary wastewater to 0.9 g / L, significantly reducing the difficulty and workload of biochemical treatment. Furthermore, the design of the high-pressure tower heat exchanger 8 and the wastewater tower heat exchanger 13 together saves approximately 25% of steam consumption.

[0087] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0088] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. For associations involving three or more related objects described using "and / or", it indicates that any one of the three related objects can exist alone, or at least two of them can exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "more" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0089] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A device for treating PBT waste liquid, characterized in that, The PBT waste liquid treatment device includes: The PBT waste liquid input system refers to the tetrahydrofuran-containing waste liquid that is a byproduct of the PBT production process based on the direct esterification method. An atmospheric distillation system, comprising an atmospheric column, wherein the PBT waste liquid input system is connected to the middle section of the atmospheric column; A high-pressure distillation system, comprising a high-pressure column, wherein the top of the atmospheric column is connected to the middle of the high-pressure column; A wastewater treatment system, the wastewater treatment system including a wastewater tower, wherein the bottom of the atmospheric pressure tower is connected to the middle of the wastewater tower; The bottom of the atmospheric pressure tower is used to collect primary wastewater, and the wastewater tower is used to distill and separate the primary wastewater to collect secondary wastewater at the top of the wastewater tower and to collect a concentrated solution containing high concentrations of PBT and adipic acid at the bottom of the wastewater tower. The COD of the primary wastewater is 25-40 g / L, and the COD of the secondary wastewater is 0.7-2 g / L.

2. The PBT waste liquid treatment device according to claim 1, characterized in that, The atmospheric distillation system further includes an atmospheric column condenser, an atmospheric column reflux tank, and an atmospheric column reflux pump connected in sequence, wherein the atmospheric column condenser is connected to the top of the atmospheric column, and the atmospheric column reflux pump is connected to the upper part of the atmospheric column; and / or, The atmospheric distillation system also includes an atmospheric column reboiler, one end of which is connected to the bottom of the atmospheric column and the other end of which is connected to the lower part of the atmospheric column; The atmospheric distillation system also includes an atmospheric column bottom pump, one end of which is connected to the bottom of the atmospheric column and the other end of which is connected to the middle of the wastewater column.

3. The PBT waste liquid treatment device according to claim 1, characterized in that, The high-pressure distillation system further includes a high-pressure tower heat exchanger, a high-pressure tower reflux tank, and a high-pressure tower reflux pump connected in sequence, wherein the high-pressure tower heat exchanger is connected to the top of the high-pressure tower, and the high-pressure tower reflux pump is connected to the upper part of the high-pressure tower; and / or, The high-pressure distillation system also includes a high-pressure tower reboiler, one end of which is connected to the bottom of the high-pressure tower, and the other end is connected to the lower part of the high-pressure tower.

4. The PBT waste liquid treatment device according to claim 3, characterized in that, The PBT waste liquid input system is connected to the middle of the atmospheric pressure tower through the high-pressure tower heat exchanger.

5. The PBT waste liquid treatment device according to claim 1, characterized in that, The wastewater treatment system further includes a wastewater tower condenser, a wastewater tower reflux tank, and a wastewater tower reflux pump connected in sequence, wherein the wastewater tower condenser is connected to the top of the wastewater tower, and the wastewater tower reflux pump is connected to the upper part of the wastewater tower; and / or, The wastewater distillation system also includes a wastewater tower reboiler, one end of which is connected to the bottom of the wastewater tower, and the other end is connected to the lower part of the wastewater tower.

6. The PBT waste liquid treatment device according to claim 5, characterized in that, The wastewater treatment system also includes a wastewater tower heat exchanger, which is connected in parallel with both ends of the wastewater tower condenser. The top of the atmospheric pressure tower is connected to the middle of the high pressure tower through the wastewater tower heat exchanger.

7. A method for treating PBT waste liquid, characterized in that, The method is implemented using the PBT waste liquid treatment device according to any one of claims 1-6, and the method includes the following steps: PBT waste liquid is fed into the middle of the atmospheric distillation column through the PBT waste liquid input system for atmospheric distillation; The THF and low-boiling-point substances from the top of the atmospheric pressure column are fed into the middle of the high-pressure column for high-pressure distillation, and the primary wastewater from the bottom of the atmospheric pressure column is fed into the middle of the wastewater column. The THF and high-boiling-point substances of water collected from the top of the high-pressure tower are recycled back to the middle of the atmospheric tower, and the THF product collected from the bottom of the high-pressure tower is collected. The secondary wastewater at the top of the wastewater tower is extracted, and the concentrate at the bottom of the wastewater tower is extracted.

8. The method for treating PBT waste liquid according to claim 7, characterized in that, The atmospheric pressure tower operates at a pressure of 60–180 kPaA, has a reflux ratio of 0.5–3, a top temperature of 45–90°C, and a bottom temperature of 80–120°C.

9. The method for treating PBT waste liquid according to claim 7, characterized in that, The high-pressure tower operates at a pressure of 200–950 kPaA, a reflux ratio of 0.5–5, a top temperature of 90–150°C, and a bottom temperature of 120–160°C.

10. The method for treating PBT waste liquid according to claim 7, characterized in that, The operating pressure of the wastewater tower is 200–850 kPaA, the reflux ratio is 0.1–3, the temperature at the top of the tower is 100–170°C, and the temperature at the bottom of the tower is 110–190°C.

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