A pta sewage quality recovery treatment system and recovery treatment method

Abstract

The present application belongs to the field of wastewater treatment, and relates to a PTA wastewater separate-quality recovery treatment system and a recovery treatment method. The system comprises a PTA process wastewater treatment system, an accident water treatment system and an oxidation tail gas washing wastewater treatment system. The PTA process wastewater treatment system comprises a pretreatment unit, an anaerobic treatment unit, at least two-stage aerobic treatment units and a deep treatment unit connected in sequence. The accident water treatment system comprises an accident pool and an accident water heat exchanger, and the outlet of the accident pool is connected to the accident water heat exchanger. The oxidation tail gas washing wastewater treatment system comprises a filtration treatment unit, an ultrafiltration treatment unit, a nanofiltration treatment unit, a reverse osmosis treatment unit and a hydrogenation treatment unit connected in sequence. The accident water heat exchanger is connected to the pretreatment unit, the nanofiltration treatment unit is connected to the anaerobic treatment unit, and the hydrogenation treatment unit is connected to the aerobic treatment unit. The present application avoids the impact of accident water and oxidation tail gas washing wastewater on the treatment system, and efficiently treats the wastewater to reach the discharge standard.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a PTA wastewater separation and recycling system and method. Background Technology

[0002] Purified terephthalic acid (PTA) is a major raw material for the production of polyester (PET). In recent years, the rapid growth of global polyester production capacity has driven the rapid growth in PTA demand. According to statistics from 2000 to 2021, my country is the largest PTA producer and consumer in Asia. However, the large amount of high-concentration wastewater generated during PTA production is one of the typical and difficult-to-treat wastewaters in the petrochemical industry.

[0003] PTA wastewater generally includes continuous production wastewater, intermittent wastewater, and accidental wastewater. Continuous production wastewater includes acetic acid recovery wastewater, catalyst recovery wastewater, oxidation tail gas scrubbing wastewater, dryer exhaust scrubbing wastewater, and crystallizer wastewater. Intermittent wastewater is wastewater collected from the drainage system of the oxidation unit and refining unit. Accidental wastewater is wastewater generated during equipment and pipeline flushing during unit maintenance.

[0004] Traditional PTA wastewater treatment involves mixing the aforementioned wastewaters before treatment. However, due to differences in production processes, the quality of wastewater varies significantly between stages. Specifically, the organic pollutants in the oxidation tail gas scrubbing wastewater are of a single type and at low concentrations, but it contains large amounts of sodium bromide and sodium carbonate. Directly introducing this wastewater into the wastewater treatment system would severely impact the system and waste significant amounts of sodium bromide and sodium carbonate resources. Furthermore, the accidental wastewater generated during equipment and pipeline flushing during plant maintenance is not only massive in volume but also exhibits significant temperature and pH fluctuations, reaching up to 95°C and with a pH between 2 and 12. Direct mixing of this wastewater with the process wastewater would cause irreversible damage to the microorganisms in subsequent anaerobic and aerobic units.

[0005] Therefore, different treatment systems and methods should be adopted for different types of PTA wastewater, and the various treatment systems should be organically combined to ensure that the effluent meets the standards while realizing the resource utilization of wastewater. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing treatment technologies and provide a PTA wastewater separation and recycling system and method to reduce the impact of accidental wastewater on the treatment system, while maximizing the recycling and utilization of resources in the wastewater.

[0007] To achieve the above objectives, a first aspect of the present invention provides a PTA wastewater separation and recycling system, the recycling system comprising a PTA process wastewater treatment system, an emergency water treatment system, and an oxidation tail gas scrubbing wastewater treatment system.

[0008] The PTA process wastewater treatment system includes a pretreatment unit, an anaerobic treatment unit, at least two aerobic treatment units, and a deep treatment unit connected in sequence.

[0009] The emergency water treatment system includes: an emergency pool and an emergency water heat exchanger, wherein the outlet of the emergency pool is connected to the emergency water heat exchanger;

[0010] The oxidation tail gas scrubbing wastewater treatment system includes a filtration unit, an ultrafiltration unit, a nanofiltration unit, a reverse osmosis unit, and a hydrogen treatment unit connected in sequence.

[0011] The emergency water heat exchanger is connected to the pretreatment unit, the nanofiltration unit is connected to the anaerobic treatment unit, and the hydrogen treatment unit is connected to the aerobic treatment unit.

[0012] According to the present invention, preferably, in the PTA process wastewater treatment system, the pretreatment unit includes: a pretreatment heat exchanger and a homogenizing tank, wherein the homogenizing tank is equipped with a stirring device.

[0013] According to the present invention, preferably, the anaerobic treatment unit comprises: at least one set of conditioning tank-anaerobic reactor and anaerobic effluent heat exchanger; the conditioning tank-anaerobic reactor is connected to the anaerobic effluent heat exchanger; the conditioning tank is provided with a pH adjustment device, a temperature adjustment device and a nutrient supplementation device; preferably, the number of conditioning tanks and anaerobic reactors in each set of conditioning tank-anaerobic reactors is 1:1 or 1:2, the outlet of the conditioning tank is connected to the inlet of the anaerobic reactor, and at least one outlet of the anaerobic reactor is connected to the inlet of the conditioning tank connected thereto.

[0014] In this invention, the outlet of the anaerobic reactor is connected to a conditioning tank, thereby forming a high-flow-rate circulation between the conditioning tank and the anaerobic reactor, which improves the anaerobic reactor's resistance to incoming water shock and its operational flexibility; the conditioning tank is equipped with pH adjustment, temperature adjustment, and nitrogen, phosphorus, and trace element replenishment devices.

[0015] In this invention, the outlet of the anaerobic reactor is connected to a corresponding conditioning tank, thereby forming a high-flow-rate circulation between the conditioning tank and the anaerobic reactor, which improves the anaerobic reactor's resistance to incoming water shock and its operational flexibility.

[0016] In this invention, the biogas produced by the anaerobic reactor enters the biogas collection and treatment device. Preferably, the biogas collection and treatment device includes a liquid separator, a desulfurization unit, a biogas pressure stabilizing cabinet, a biogas compressor, an emergency flare, etc. After purification, the biogas is pumped to the PTA unit by the compressor as fuel to achieve energy recovery and utilization. In case of an accident, the biogas enters the emergency flare for combustion and is then discharged into the atmosphere.

[0017] According to the present invention, preferably, the aerobic treatment unit includes: a first-stage aerobic treatment unit and a second-stage aerobic treatment unit; each aerobic treatment unit is provided with at least one set of aerobic reaction tank-sedimentation tank; preferably, the aerobic treatment unit includes a first-stage aerobic tank, a first-stage sedimentation tank, a second-stage aerobic tank and a second-stage sedimentation tank connected in sequence.

[0018] According to the present invention, preferably, the deep processing unit includes an air flotation tank, a high-density tank with sand and carbon addition, and a monitoring tank connected in sequence.

[0019] According to the present invention, preferably, the emergency water heat exchanger is connected to a homogenizing tank, and the homogenizing tank is sequentially connected to at least one set of conditioning tank-anaerobic reactor, anaerobic effluent heat exchanger, a first-stage aerobic tank, a first-stage sedimentation tank, a second-stage aerobic tank, a second-stage sedimentation tank, an air flotation tank, a sand-and-carbon high-density tank, and a monitoring tank.

[0020] According to the present invention, preferably, the nanofiltration treatment unit is connected to the anaerobic reactor; the hydrogen treatment unit is connected to a first-stage aerobic reaction tank and / or a second-stage aerobic reaction tank.

[0021] According to the present invention, preferably, the pretreatment unit is further provided with an acid precipitation tank; the acid precipitation tank is connected in sequence to the pretreatment heat exchanger and the homogenization tank.

[0022] According to the present invention, preferably, the sand-adding and carbon-adding high-density tank includes a contact tank, a coagulation tank, a maturation tank and an inclined plate clarification tank arranged in sequence.

[0023] A second aspect of the present invention provides a method for the separate recycling and treatment of PTA wastewater, wherein the recycling and treatment method is carried out in the recycling and treatment system, and PTA process wastewater, emergency wastewater and oxidation tail gas scrubbing wastewater are respectively entered into different systems and treated by different methods;

[0024] The PTA process wastewater enters the PTA process wastewater treatment system and is treated according to the following steps: pretreatment, anaerobic treatment, two-stage aerobic treatment, and advanced treatment;

[0025] The accident water enters the accident water treatment system and is treated in the following steps: homogenization treatment and cooling treatment;

[0026] The oxidation tail gas scrubbing wastewater enters the oxidation tail gas scrubbing wastewater treatment system and is treated in the following steps: filtration, ultrafiltration, nanofiltration, reverse osmosis and hydrogen treatment.

[0027] After cooling, the emergency water enters the pretreatment unit and is mixed with PTA process wastewater for pretreatment; the concentrate from the nanofiltration unit enters the anaerobic treatment unit as an alkalinity supplement; and the sodium dihydrogen phosphate solution generated by the hydrogen treatment unit is used as a nutrient solution for the aerobic treatment unit.

[0028] According to the present invention, preferably, the PTA process wastewater is treated according to the following steps:

[0029] Pretreatment: PTA process wastewater enters the pretreatment heat exchanger for cooling, and then enters the homogenization tank for stirring and mixing.

[0030] Anaerobic treatment: Wastewater from the homogenization tank flows to the conditioning tank, where the pH, nutrient content, and temperature are adjusted. Then, it enters the anaerobic reactor to remove organic matter. The effluent from the anaerobic reactor enters the anaerobic effluent heat exchanger for cooling. Preferably, part of the effluent from the anaerobic reactor connected to the conditioning tank is returned to the conditioning tank.

[0031] Two-stage aerobic treatment: After cooling, the wastewater flows into the first-stage aerobic tank for aeration treatment, then passes through the first-stage sedimentation tank for mud-water separation, and the effluent flows to the second-stage aerobic tank for aeration treatment, and then enters the second-stage sedimentation tank for mud-water separation.

[0032] Advanced treatment: After the effluent from the two-stage sedimentation tank is further decomposed in the air flotation tank to remove suspended solids and residual COD, it enters the high-density tank to adsorb dissolved organic matter in the sewage. After flocculation and sedimentation, mud and water are separated, and the effluent from the high-density tank enters the monitoring tank.

[0033] In this invention, under extreme operating conditions, a portion of the effluent from the second-stage aerobic tank is returned to the inlet of the conditioning tank in the anaerobic treatment unit to dilute the concentration of the influent to the anaerobic reactor and avoid impacting the anaerobic microorganisms.

[0034] According to the present invention, preferably, in the pretreatment step, the PTA process wastewater first enters the acid precipitation tank to precipitate TA acid, and then enters the pretreatment heat exchanger for cooling. The temperature of the mixed wastewater is about 35~40℃, and the residence time is ≥36h.

[0035] According to the present invention, preferably, in the anaerobic treatment step, the anaerobic reactor is a high-efficiency mesophilic anaerobic reactor with a volumetric loading rate of 10~20 kg COD / m³·d; the anaerobic reactor is inoculated with acclimated anaerobic granular sludge with a particle size of 0.3~3 mm, an effective particle size ≥75%, a volatile suspended solids / total suspended solids ratio ≥0.7, a granular sludge settling velocity of 50~150 m / h, and a settling ratio ≥90%; the effluent from the anaerobic reactor is cooled to ≤35℃ by an anaerobic treatment heat exchanger.

[0036] According to the present invention, preferably, in the two-stage aerobic treatment steps, the first-stage aerobic tank is a jet aeration aerobic tank or a microporous aeration aerobic tank, with a COD removal rate ≥90% and a volumetric loading rate of 2~4 kgCOD / m³·d; preferably, part of the bottom sludge from the first-stage sedimentation tank is returned to the first-stage aerobic tank, and the other part is sent to the excess sludge treatment unit.

[0037] According to the present invention, preferably, the two-stage aerobic tank is an extended aeration aerobic tank or an MBBR aerobic tank, with a COD removal rate ≥80% and a volumetric loading rate of 0.3~0.35 kgCOD / m³·d; preferably, part of the bottom sludge of the two-stage sedimentation tank is returned to the two-stage aerobic tank, and the other part is sent to the excess sludge treatment unit.

[0038] According to the present invention, preferably, in the advanced treatment step, the pH value of the effluent from the flotation tank needs to be adjusted to ≤5, the high-density tank is a sand-added and carbon-added high-density tank, the effluent from the flotation tank first enters the contact tank to mix with activated carbon to adsorb dissolved organic matter in the sewage, then enters the coagulation tank to react with coagulant, then enters the maturation tank to mix with polymer and micro sand, and finally achieves high-speed sedimentation in the inclined plate clarification tank for mud-water separation; the retention time in the monitoring tank is ≥2h.

[0039] In this invention, the effluent from the flotation tank of the deep treatment unit needs to be pH adjusted to ≤5 in order to reduce the impact of alkalinity in PTA wastewater on the adsorption effect of activated carbon in the high-density sedimentation tank with added sand and carbon.

[0040] In this invention, the activated carbon dosage in the high-density sedimentation tank with added sand and carbon is adjusted according to the COD concentration of the effluent from the air flotation process to ensure that the effluent meets the standards. The mixture of micro-sand, sludge and activated carbon produced in the sedimentation tank is returned to the flocculation tank and activated carbon distribution tank for reuse after multi-stage separation. The remaining part overflows to the sludge tank and is pumped to the first-stage aerobic tank.

[0041] According to the present invention, preferably, the emergency water is treated according to the following steps: the emergency water enters the emergency pool, is thoroughly mixed and allowed to stand, and then is cooled by an emergency water heat exchanger.

[0042] According to the present invention, preferably, the accident water includes at least one of the following: equipment drainage during equipment maintenance, hot alkaline solution, clean water flushing equipment wastewater, and pipeline wastewater; the temperature of the accident water is ≤95℃ and the pH value is 2~12.

[0043] According to the present invention, preferably, the cooled emergency water enters the pretreatment unit of PTA process wastewater in a small flow rate; preferably, the temperature of the cooled emergency water is 38~40℃.

[0044] According to the present invention, the cooled accident water preferably enters the homogenization tank.

[0045] According to the present invention, preferably, the oxidation tail gas scrubbing wastewater is treated according to the following steps:

[0046] Filtration: The wastewater from the oxidation tail gas washing process enters the filtration unit for filtration to remove large particles and macromolecular organic matter from the wastewater.

[0047] Ultrafiltration: Water effluent from the filtration unit enters the ultrafiltration unit for further removal of fine particulate matter;

[0048] Nanofiltration: The effluent from the ultrafiltration unit enters the nanofiltration unit, where sodium carbonate concentrate is separated and reused in the anaerobic treatment unit as an alkalinity supplement.

[0049] Reverse osmosis: The effluent from the nanofiltration unit enters the reverse osmosis unit, and the permeate is reused;

[0050] Hydrogenation: The concentrated water from the reverse osmosis treatment unit enters the hydrogenation treatment unit and reacts with concentrated phosphoric acid. The resulting sodium dihydrogen phosphate solution is used as the nutrient solution for the aerobic treatment unit, and the generated hydrogen bromide gas is sent to the PTA oxidation unit as a catalyst.

[0051] In this invention, the nanofiltration concentrate produced by the nanofiltration unit in the oxidative tail gas washing wastewater treatment system, i.e., sodium carbonate solution, can be used as an alkalinity supplement for the anaerobic treatment unit; the permeate from the reverse osmosis unit meets the reuse index, and the reverse osmosis concentrate, i.e., sodium bromide solution, reacts with concentrated phosphoric acid to produce sodium dihydrogen phosphate, which is used as a phosphorus nutrient solution for the aerobic treatment unit. The generated hydrogen bromide gas is collected and reused in the PTA oxidation unit as a catalyst.

[0052] According to the present invention, preferably, the PTA oxidation tail gas scrubbing wastewater is the wastewater generated after the tail gas of the PTA oxidation unit passes through the scrubbing tower.

[0053] According to the present invention, preferably, the filtration unit is a multi-media filtration or activated carbon filtration, the pore size of the ultrafiltration unit is 4~6nm, the nanofiltration unit has a retention efficiency of ≥75%, and the salt content of the reverse osmosis concentrate is ≥10%.

[0054] In this invention, the ultrafiltration, nanofiltration, and reverse osmosis treatment units can be equipped with multiple stages and series of membrane elements according to water quality and quantity.

[0055] According to the present invention, preferably, the wastewater from each treatment unit is transferred to the next treatment unit by gravity flow or by pump.

[0056] The present invention has the following beneficial effects:

[0057] It can avoid the impact of accidental water and oxidation tail gas washing wastewater on the PTA wastewater treatment system, efficiently treat PTA unit wastewater to meet discharge standards, and collect sodium carbonate and sodium bromide in the oxidation tail gas washing wastewater to reuse standards, while converting sodium bromide into hydrogen bromide, which is then used as a catalyst to be reused in the oxidation unit of the PTA unit, thus realizing the resource utilization of wastewater.

[0058] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0059] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0060] Figure 1 A process flow diagram of a system and method for the graded recycling and treatment of PTA wastewater provided by the present invention is shown.

[0061] Explanation of reference numerals in the attached figures

[0062] A is the process wastewater from the PTA unit, B is the emergency wastewater, and C is the wastewater from the oxidation tail gas scrubbing process.

[0063] A1. Pretreatment heat exchanger; A2. Homogenizing tank; A3. Conditioning tank; A4. Anaerobic reactor; A5. Anaerobic effluent heat exchanger; A6. Primary aerobic tank; A7. Primary sedimentation tank; A8. Secondary aerobic tank; A9. Secondary sedimentation tank; A10. Dissolved air flotation tank; A11. High-density tank; A12. Monitoring tank;

[0064] B1, Emergency Pool; B2, Emergency Water Heat Exchanger;

[0065] C1, Filtration unit; C2, Ultrafiltration unit; C3, Nanofiltration unit; C4, Reverse osmosis unit; C5, Hydrogen treatment unit. Detailed Implementation

[0066] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0067] Example 1

[0068] This embodiment illustrates a PTA wastewater separation and recycling system according to the present invention, and the process flow diagram is as follows: Figure 1 As shown.

[0069] The system includes: a PTA process wastewater treatment system, an emergency wastewater treatment system, and an oxidation tail gas scrubbing wastewater treatment system;

[0070] The PTA process wastewater treatment system comprises, in sequence: A1, pretreatment heat exchanger; A2, homogenizing tank; A3, conditioning tank; A4, anaerobic reactor; A5, anaerobic treatment heat exchanger; A6, primary aerobic tank; A7, primary sedimentation tank; A8, secondary aerobic tank; A9, secondary sedimentation tank; A10, dissolved air flotation tank; A11, high-density tank; A12, monitoring tank.

[0071] The emergency water treatment system includes: B1, the emergency pool, and B2, the emergency water heat exchanger.

[0072] The treatment system for the oxidized tail gas scrubbing wastewater includes, in sequence: C1, a filtration unit, C2, an ultrafiltration unit, C3, a nanofiltration unit, C4, a reverse osmosis unit, and C5, a hydrogen treatment unit.

[0073] Example 2

[0074] This embodiment illustrates the recycling and treatment method of the present invention using a PTA wastewater separation and recycling system, in which PTA process wastewater, emergency wastewater, and oxidation tail gas scrubbing wastewater are treated using different methods.

[0075] The PTA unit's process wastewater treatment system specifically includes the following processes:

[0076] A1) Homogenization: Depending on the water quality, the wastewater from the PTA unit is precipitated in the acid precipitation tank, cooled by the pretreatment heat exchanger, and then enters the homogenization tank. The homogenization tank is equipped with a stirring device to mix the wastewater evenly. Under normal circumstances, the temperature of the mixed wastewater is about 35~40℃, and the residence time is ≥36h.

[0077] (A2~3) Anaerobic Treatment: Wastewater from the homogenization tank is pumped to a conditioning tank. Acids / alkalis, nitrogen, phosphorus, and other nutrients are added to the conditioning tank to adjust the pH and nutrient content of the wastewater. The conditioning tank is also equipped with heating devices, such as steam nozzles, to maintain the temperature of the wastewater entering the anaerobic reactor. The effluent from the anaerobic reactor is connected to the conditioning tank to dilute the influent and reduce alkali consumption.

[0078] The anaerobic reactor is a high-efficiency mesophilic anaerobic reactor with a volumetric loading rate of 10~20 kgCOD / m³·d. The anaerobic reactor is inoculated with acclimatized anaerobic granular sludge with a particle size of 0.3~3 mm, an effective particle size ≥75%, a volatile suspended solids / total suspended solids ratio ≥0.7, a granular sludge settling velocity of 50~150 m / h, and a settling ratio ≥90%.

[0079] Organic matter in the wastewater is decomposed into biogas, primarily composed of methane and carbon dioxide, within the reactor. The biogas is collected by a three-phase separator and drawn from the top of the reactor. After passing through a separator and a desulfurization tower, it is sent to a biogas pressure regulator for pressure adjustment. The biogas purified by the desulfurization tower is then pressurized by a biogas compressor for reuse as fuel. When biogas cannot be supplied externally, it is switched to an emergency flare for combustion.

[0080] A4) Heat exchange: After the effluent from the anaerobic reactor is cooled to ≤35℃ by a heat exchanger, the activity of the aerobic activated sludge is improved.

[0081] A5) Primary aerobic stage: After heat exchange, the wastewater enters the primary aerobic tank. The primary aerobic tank can employ jet aeration or microporous aeration to achieve oxygenation and mixing. The COD removal rate of the primary aerobic tank is ≥90%, and the volumetric loading rate is 2~4 kg COD / m³·d.

[0082] A6) Secondary sedimentation: After the sludge-water mixture from the first aerobic tank is separated into sludge and water in the sedimentation tank, the effluent is pumped to the second aerobic tank. Part of the bottom sludge is returned to the first aerobic tank, and part is sent to the excess sludge treatment unit.

[0083] A7) Second-stage aerobic: The second-stage aerobic tank receives the effluent from the second sedimentation tank. It usually adopts extended aeration, MBBR and other types, with a COD removal rate of ≥80% and a volumetric loading rate of 0.3~0.35kgCOD / m³·d.

[0084] A8) Final sedimentation: After the sludge-water mixture from the second-stage aerobic tank is separated into sludge and water in the sedimentation tank, the effluent is lifted to the flotation tank, and part of the bottom sludge is returned to the second-stage aerobic tank and part is sent to the excess sludge treatment unit.

[0085] A9) Air flotation: The effluent from the final sedimentation tank is further treated in the air flotation tank to remove suspended solids and a small amount of COD.

[0086] (A10) High-density: The high-density sedimentation tank described in this invention is a sand- and carbon-added high-density sedimentation tank. The effluent from air flotation first enters the contact tank, where it mixes with the added and returned activated carbon, adsorbing dissolved organic matter in the wastewater. The mixture then enters the coagulation tank to react with the added coagulant. The coagulated wastewater and activated carbon mixture then enter a maturation tank containing micro-sand and polymer, where high-speed sedimentation is achieved in the inclined plate clarifier.

[0087] After passing through a separator, the mixture of activated carbon, sludge, and micro-sand is recycled to a maturation tank. Part of the mixture of activated carbon and sludge is returned to a contact tank for recycling, while part is discharged into an aerobic tank where activated carbon can further adsorb organic matter before being discharged with the remaining sludge.

[0088] The amount of micro-sand and activated carbon can be flexibly adjusted according to the water quality and quantity.

[0089] A11) Monitoring pool: The retention time in the monitoring pool is ≥2h, and the effluent from the monitoring pool is discharged after passing the test.

[0090] The PTA unit's emergency water treatment system specifically includes the following processes:

[0091] B1) Emergency Pool: PTA unit emergency water includes unit drainage during unit maintenance, hot alkaline solution or clean water flushing of equipment and pipelines, etc. The temperature can reach 95℃ and the pH fluctuates between 2 and 12. A large-capacity emergency pool is set up to allow emergency water of different temperatures and pH to be fully mixed in the pool, which can play a certain role in cooling and neutralization.

[0092] B2) Heat exchange: After the emergency water has been thoroughly mixed and allowed to settle, it is cooled to 38~40℃ through a heat exchanger. Depending on the water quality in the homogenization tank, a small flow rate is mixed into the process wastewater to avoid causing a large impact on the anaerobic system.

[0093] The oxidation tail gas scrubbing wastewater treatment system specifically includes the following processes:

[0094] C1) Filtration: Multi-media filters or activated carbon filters are used to filter the wastewater from the oxidation tail gas washing process, removing large particles and macromolecular organic matter from the wastewater.

[0095] C2) Ultrafiltration: After passing through a security filter, the effluent from the filter enters the ultrafiltration membrane element for further removal of fine particulate matter.

[0096] C3) Nanofiltration: The ultrafiltration effluent is separated into sodium carbonate concentrate in the nanofiltration separation unit, which can be reused in the A-series anaerobic treatment unit as an alkalinity supplement. The nanofiltration permeate enters the reverse osmosis unit.

[0097] C4) Reverse osmosis: The nanofiltration permeate is subjected to one or more stages of reverse osmosis to ensure that the permeate meets the reuse standard; the reverse osmosis concentrate is mainly sodium bromide solution, which can be directly collected and the sodium bromide salt can be recovered through evaporation and crystallization, or it can be sent to the hydrogen disposal unit.

[0098] C5) Hydrogen generation: The concentrated water from reverse osmosis reacts with concentrated phosphoric acid to produce sodium dihydrogen phosphate solution, which can be used as phosphorus nutrient solution for the aerobic unit of series A. The generated hydrogen bromide gas is collected and reused in the PTA oxidation unit as a catalyst.

[0099] The present invention provides a PTA wastewater separation and recycling treatment system and method, which can efficiently treat PTA plant wastewater to meet discharge standards. While ensuring the stable operation of the treatment system, it fully recovers and utilizes the resources in the wastewater, and achieves zero discharge of oxidation tail gas scrubbing wastewater.

[0100] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A PTA wastewater separation and recycling system, characterized in that, The recycling and treatment system includes a PTA process wastewater treatment system, an emergency water treatment system, and an oxidation tail gas scrubbing wastewater treatment system. The PTA process wastewater treatment system includes a pretreatment unit, an anaerobic treatment unit, an aerobic treatment unit, and an advanced treatment unit connected in sequence, and the aerobic treatment unit has at least two sections. The emergency water treatment system includes: an emergency pool and an emergency water heat exchanger, wherein the outlet of the emergency pool is connected to the emergency water heat exchanger; The oxidation tail gas scrubbing wastewater treatment system includes a filtration unit, an ultrafiltration unit, a nanofiltration unit, a reverse osmosis unit, and a hydrogen treatment unit connected in sequence. The hydrogen treatment unit is used to introduce the concentrated water from the reverse osmosis unit into the hydrogen treatment unit, where it reacts with concentrated phosphoric acid. The resulting sodium dihydrogen phosphate solution is used as the nutrient solution for the aerobic treatment unit, and the generated hydrogen bromide gas is sent to the PTA oxidation device as a catalyst. The emergency water heat exchanger is connected to the inlet of the pretreatment unit, the concentrate outlet of the nanofiltration treatment unit is connected to the inlet of the anaerobic treatment unit, and the hydrogen treatment unit is connected to the inlet of the aerobic treatment unit.

2. The PTA wastewater separation and recycling treatment system according to claim 1, wherein, In the PTA process wastewater treatment system, the pretreatment unit includes a pretreatment heat exchanger and a homogenizing tank, and the homogenizing tank is equipped with a stirring device. The anaerobic treatment unit includes: at least one set of conditioning tank-anaerobic reactor and anaerobic effluent heat exchanger; the conditioning tank-anaerobic reactor is connected to the anaerobic effluent heat exchanger; the conditioning tank is equipped with a pH adjustment device, a temperature adjustment device and a nutrient supplementation device. The aerobic treatment unit includes: a primary aerobic treatment unit and a secondary aerobic treatment unit; each aerobic treatment unit is equipped with at least one set of aerobic tank-sedimentation tank. The deep processing unit includes an air flotation tank, a high-density tank with added sand and carbon, and a monitoring tank connected in sequence. The emergency water heat exchanger is connected to the inlet of the homogenizing tank, and the homogenizing tank is sequentially connected to at least one set of conditioning tank-anaerobic reactor, anaerobic effluent heat exchanger, first-stage aerobic tank, first-stage sedimentation tank, second-stage aerobic tank, second-stage sedimentation tank, air flotation tank, sand and carbon high-density tank and monitoring tank. The concentrate outlet of the nanofiltration treatment unit is connected to the inlet of the anaerobic reactor; the hydrogen treatment unit is connected to the inlet of the first aerobic tank and / or the inlet of the second aerobic tank.

3. The PTA wastewater separation and recycling treatment system according to claim 2, wherein, In each conditioning tank-anaerobic reactor group, the number of conditioning tanks and anaerobic reactors is 1:1 or 1:

2. The outlet of the conditioning tank is connected to the inlet of the anaerobic reactor, and at least one outlet of the anaerobic reactor is connected to the inlet of the conditioning tank to which it is connected.

4. The PTA wastewater separation and recycling treatment system according to claim 2, wherein, The aerobic treatment unit includes an aerobic tank, a sedimentation tank, a second aerobic tank, and a second sedimentation tank connected in sequence.

5. The PTA wastewater separation and recycling treatment system according to claim 2, wherein, The pretreatment unit is also equipped with an acid precipitation tank; the acid precipitation tank is connected in sequence to the pretreatment heat exchanger and the homogenization tank. The high-density sand and carbon addition tank includes a contact tank, a coagulation tank, a maturation tank, and an inclined plate clarification tank arranged in sequence.

6. A method for the graded recycling and treatment of PTA wastewater, characterized in that, The recycling and treatment method is carried out in the recycling and treatment system described in any one of claims 1-5, wherein PTA process wastewater, emergency water and oxidation tail gas scrubbing wastewater are respectively entered into different systems and treated by different methods; The PTA process wastewater enters the PTA process wastewater treatment system and is treated according to the following steps: pretreatment, anaerobic treatment, two-stage aerobic treatment, and advanced treatment; The accident water enters the accident water treatment system and is treated in the following steps: homogenization treatment and cooling treatment; The oxidation tail gas scrubbing wastewater enters the oxidation tail gas scrubbing wastewater treatment system and is treated in the following steps: filtration, ultrafiltration, nanofiltration, reverse osmosis and hydrogen treatment. After cooling, the emergency water enters the pretreatment unit and is mixed with PTA process wastewater for pretreatment; the concentrate from the nanofiltration unit enters the anaerobic treatment unit as an alkalinity supplement; and the sodium dihydrogen phosphate solution generated by the hydrogen treatment unit is used as a nutrient solution for the aerobic treatment unit.

7. The recycling method according to claim 6, wherein, The PTA process wastewater is treated according to the following steps: Pretreatment: PTA process wastewater enters the pretreatment heat exchanger for cooling, and then enters the homogenization tank for stirring and mixing. Anaerobic treatment: Wastewater from the homogenization tank flows to the conditioning tank, where the pH, nutrient content and temperature are adjusted. Then it enters the anaerobic reactor to remove organic matter. The effluent from the anaerobic reactor enters the anaerobic effluent heat exchanger for cooling. Two-stage aerobic treatment: After cooling, the wastewater flows into the first-stage aerobic tank for aeration treatment, then passes through the first-stage sedimentation tank for mud-water separation, and the effluent flows to the second-stage aerobic tank for aeration treatment, and then enters the second-stage sedimentation tank for mud-water separation. Advanced treatment: After the effluent from the two-stage sedimentation tank is further decomposed in the air flotation tank to remove suspended solids and residual COD, it enters the high-density tank with sand and carbon addition to adsorb dissolved organic matter in the sewage. After flocculation and sedimentation, mud and water separation is carried out. The effluent from the high-density tank with sand and carbon addition enters the monitoring tank.

8. The recycling method according to claim 7, wherein, The effluent from the anaerobic reactor connected to the conditioning tank is partially returned to the conditioning tank.

9. The recycling method according to claim 7, wherein, In the pretreatment step, the PTA process wastewater first enters the acid precipitation tank to precipitate TA acid, and then enters the pretreatment heat exchanger to cool down. The temperature of the mixed wastewater is 35~40℃, and the residence time is ≥36h. In the anaerobic treatment step, the anaerobic reactor is a high-efficiency mesophilic anaerobic reactor with a volumetric loading rate of 10~20 kgCOD / m³·d; the anaerobic reactor is inoculated with acclimated anaerobic granular sludge with a particle size of 0.3~3 mm, an effective particle size ≥75%, a volatile suspended solids / total suspended solids ratio ≥0.7, a granular sludge settling velocity of 50~150 m / h, and a settling ratio ≥90%; the effluent from the anaerobic reactor is cooled to ≤35℃ by an anaerobic treatment heat exchanger. In the two-stage aerobic treatment steps, the first-stage aerobic tank is a jet aeration aerobic tank or a microporous aeration aerobic tank, with a COD removal rate ≥90% and a volumetric loading rate of 2~4 kgCOD / m³·d; The two-stage aerobic tank is an extended aeration aerobic tank or an MBBR aerobic tank, with a COD removal rate ≥80% and a volumetric loading rate of 0.3~0.35 kgCOD / m³·d; In the advanced treatment step, the pH value of the effluent from the flotation tank is ≤5. The effluent from the flotation tank first enters the contact tank and mixes with activated carbon to adsorb dissolved organic matter in the wastewater. Then it enters the coagulation tank to react with coagulant, then enters the maturation tank to mix with polymer and micro sand. Finally, it undergoes high-speed sedimentation in the inclined plate clarification tank for sludge-water separation. The retention time in the monitoring tank is ≥2h.

10. The recycling method according to claim 9, wherein, Part of the sludge from the sedimentation tank is returned to the aerobic tank, while the other part is sent to the excess sludge treatment unit.

11. The recycling method according to claim 9, wherein, Part of the sludge from the two-stage sedimentation tank is returned to the two-stage aerobic tank, while the other part is sent to the excess sludge treatment unit.

12. The recycling method according to claim 6, wherein, The emergency water is treated according to the following steps: the emergency water enters the emergency pool, is thoroughly mixed and allowed to stand, and then is cooled through an emergency water heat exchanger. The accident water includes at least one of the following: equipment drainage during equipment maintenance, hot alkaline solution, wastewater from equipment flushing, and pipeline wastewater; the temperature of the accident water is ≤95℃, and the pH value is 2~12. The cooled-down accident water enters the pretreatment unit for PTA process wastewater.

13. The recycling method according to claim 12, wherein, The temperature of the accident water after cooling was 38~40℃.

14. The recycling method according to claim 12, wherein, The cooled-down accident water enters the homogenization tank.

15. The recycling method according to claim 6, wherein, The oxidation tail gas scrubbing wastewater is treated according to the following steps: Filtration: The wastewater from the oxidation tail gas washing process enters the filtration unit for filtration to remove large particles and macromolecular organic matter from the wastewater. Ultrafiltration: Water effluent from the filtration unit enters the ultrafiltration unit for further removal of fine particulate matter; Nanofiltration: The effluent from the ultrafiltration unit enters the nanofiltration unit, where sodium carbonate concentrate is separated and reused in the anaerobic treatment unit as an alkalinity supplement. Reverse osmosis: The effluent from the nanofiltration unit enters the reverse osmosis unit, and the permeate is reused; Hydrogenation: The concentrated water from the reverse osmosis treatment unit enters the hydrogenation treatment unit and reacts with concentrated phosphoric acid. The resulting sodium dihydrogen phosphate solution is used as the nutrient solution for the aerobic treatment unit, and the generated hydrogen bromide gas is sent to the PTA oxidation unit as a catalyst.

16. The recycling method according to claim 15, wherein, The PTA oxidation tail gas scrubbing wastewater is the wastewater generated after the tail gas of the PTA oxidation unit passes through the scrubbing tower.

17. The recycling method according to claim 16, wherein, The filtration unit is a multi-media filtration or activated carbon filtration unit, the pore size of the ultrafiltration unit is 4~6nm, the nanofiltration unit has a retention efficiency of ≥75%, and the salt content of the reverse osmosis concentrate is ≥10%.

18. The recycling method according to any one of claims 6-17, wherein, Wastewater from each treatment unit is either gravity-fed or pumped to the next treatment unit.

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