PTA mother liquor residue treatment system and process using a rotary pressure filter

Abstract

The application discloses a PTA mother liquor residue treatment system and process using a rotary pressure filter, which comprises a rotary pressure filter and a feeding unit and a discharging unit connected with the rotary pressure filter, the rotary pressure filter comprises a frame and a rotating drum, the rotating drum is divided into multiple filter unit chambers, the filter unit chambers comprise a filtering zone, a washing zone, a drying zone and a discharging zone, the feeding unit comprises a residual liquid extraction tank and a residual liquid neutralization tank feeding pump, the discharging unit comprises a beating tank and a mother liquor buffer tank in communication with the rotary pressure filter, the beating tank is in communication with a circulating solvent tank through a catalyst precipitation feeding pump, the mother liquor buffer tank is in communication with a neutralization tank through a mother liquor buffer tank pump, the washing zone of the rotary pressure filter is externally connected with a wastewater pipe network, and the drying zone and the discharging zone are both externally connected with a nitrogen pipe network. The application solves the technical problems of the existing PTA mother liquor residue treatment technology in resource recovery efficiency, energy consumption control, production continuity and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of PTA mother liquor residue treatment technology, specifically to a PTA mother liquor residue treatment system and process utilizing a rotary pressure filter. Background Technology

[0002] PTA (terephthalic acid) is a core raw material for the polyester industry, including polyester fibers and plastic bottle flakes. During its production, the oxidation unit generates a large amount of mother liquor residue. This residue has a complex composition, mainly containing precious metal catalysts (such as cobalt and manganese, which are key catalytic components in the oxidation reaction), unreacted raw material derivatives (terephthalic acid, benzoic acid, and other organic compounds), and small amounts of reaction byproducts. Direct discharge or simple treatment would not only result in a serious waste of resources such as cobalt and manganese catalysts and TA, but also create significant environmental protection pressure due to high organic content and excessive heavy metals, while increasing the material consumption costs of PTA production. Therefore, it has become a key process pain point that the PTA industry urgently needs to address.

[0003] Currently, the industry has established a preliminary process system for the treatment of the aforementioned mother liquor residue. However, existing mother liquor residue treatment processes and equipment still have many technical shortcomings, making it difficult to meet the development needs of the PTA industry for "high-efficiency recovery, energy saving and consumption reduction, and continuous production." Specific problems are as follows: Incomplete resource recovery leads to high raw material consumption. At the same time, unrecovered organic matter increases the ineffective consumption of paraxylene, reduces the overall conversion rate of paraxylene, and causes significant raw material waste.

[0004] The energy and material consumption is high, resulting in poor economic efficiency. The washing process in the existing process mostly uses fresh water as the washing liquid, which not only consumes a large amount of fresh water resources, but also increases the wastewater treatment load and energy consumption of the equipment because the wastewater after washing needs to be treated separately. On the other hand, since the filtrate still contains a lot of acidic organic matter such as TA and benzoic acid, a large amount of sodium carbonate needs to be added to adjust the pH value during the subsequent neutralization treatment, resulting in a large consumption of neutralizing agent, which further increases the total production cost.

[0005] Environmental protection is under great pressure and emission control is difficult. In the existing process, the filtrate temporarily stored in the mother liquor buffer tank is prone to volatile organic exhaust gas (such as benzoic acid vapor), and the treatment of washing wastewater and drying exhaust gas is not perfect. Some unrecovered organic matter and wastewater are directly discharged, which not only does not meet the increasingly strict environmental protection regulations, but also causes secondary pollution and waste of resources.

[0006] In summary, existing PTA mother liquor residue treatment technologies have significant shortcomings in resource recovery efficiency, energy consumption control, production continuity, and environmental protection. There is an urgent need to develop a new treatment device and process that can achieve comprehensive recovery of solids and organic matter in the residue, reduce energy and material consumption, ensure continuous production, and meet environmental protection requirements, so as to solve the existing pain points in the industry. Summary of the Invention

[0007] This invention provides a PTA mother liquor residue treatment system and process using a rotary pressure filter, which can solve the technical problems of existing PTA mother liquor residue treatment technologies in terms of resource recovery efficiency, energy consumption control, production continuity and environmental protection.

[0008] To achieve the above objectives, in a first aspect, the present invention provides the following technical solution: a PTA mother liquor residue treatment system utilizing a rotary pressure filter, comprising a rotary pressure filter and a feeding unit and a discharging unit connected to the rotary pressure filter. The rotary pressure filter includes a frame and a rotating drum disposed within the frame. The rotating drum is divided into multiple filtration unit chambers, each filtration unit chamber including a filtration zone, a washing zone, a drying zone, and a discharging zone. The feeding unit includes a residual liquor extraction tank and a residual liquor neutralization tank feed pump. The discharging unit includes a pulping tank and a mother liquor buffer tank connected to the rotary pressure filter. The pulping tank is connected to a circulating solvent tank via a catalyst precipitation feed pump. The mother liquor buffer tank... The washing tank is connected to the neutralization tank via a mother liquor buffer tank pump. The washing section of the rotary pressure filter is connected to an external wastewater network, while the drying and unloading sections are connected to an external nitrogen network. The multi-zone design of the rotary pressure filter drum integrates the traditionally dispersed filtration, washing, and drying processes, avoiding residue transfer losses and efficiently separating solids, catalysts, and liquid impurities from the mother liquor. Useful components are recovered through the path of the slurry tank and the circulating solvent tank. The washing section is connected to an external wastewater network, using the equipment's wastewater to replace fresh water, reducing fresh water consumption and wastewater treatment volume. The drying and unloading sections use nitrogen to prevent the oxidation and deterioration of organic matter in the filter cake and to achieve efficient unloading through backflushing, preventing filter cake adhesion and blockage, and ensuring stable equipment operation.

[0009] Preferably, both the filtration zone and the washing zone are connected to the neutralization tank via pipelines. The initial filtrate produced by the filtration zone and the washing liquid produced by the washing zone can be directly transported to the neutralization tank without the need for transfer through the mother liquor buffer tank. This reduces losses during the transportation process, avoids impurity deposition caused by liquid stagnation, and ensures that most of the TA and benzoic acid in the directly transported filtrate and washing liquid have been retained by the filter cake. The organic matter content entering the neutralization tank is lower, which can reduce the amount of sodium carbonate required for neutralization.

[0010] Preferably, there are at least two washing zones and drying zones. Multiple washing zones can achieve washing multiple times, more fully replacing residual organic matter such as benzoic acid in the filter cake, and avoiding impurities from affecting the purity of recovered TA and catalyst. Multiple drying zones can achieve drying multiple times, further reducing the moisture content of the filter cake, reducing the interference of moisture in the slurry in the subsequent circulating solvent tank, and improving the reuse efficiency.

[0011] Preferably, the mother liquor buffer tank is also connected to the tail gas scrubbing tower via a pipeline. The filtrate temporarily stored in the mother liquor buffer tank may volatilize a small amount of organic tail gas. Connecting to the tail gas scrubbing tower can absorb and treat the tail gas, avoiding direct emission and causing air pollution, which meets industrial environmental protection requirements.

[0012] Preferably, a bypass pipeline is connected to the pipeline between the residual liquid extraction tank and the rotary pressure filter via a switching valve. The bypass pipeline is directly connected to the neutralization tank. When the rotary pressure filter needs maintenance, the bypass pipeline is opened via the switching valve, and the residual liquid can be directly transported to the neutralization tank via the bypass pipeline, bypassing the faulty equipment, avoiding the shutdown of the downstream catalyst recovery unit, and reducing downtime losses.

[0013] Preferably, the pipeline between the pulping tank and the rotary pressure filter is also connected to a mother liquor network. The mother liquor network can replenish the pulping tank with RPF mother liquor containing catalyst and circulating solvent, adjust the slurry concentration after the filter cake is pulped, and ensure that it is smoothly and without blockage when it is subsequently transported to the circulating solvent tank by the catalyst precipitation feed pump.

[0014] Preferably, the rotary pressure filter is provided with a packing seal structure between the drum and the frame. The packing seal structure is made of acid and alkali resistant material. The acid and alkali resistant packing seal can adapt to the acidic environment of the mother liquor residue, avoid residual liquid leakage or nitrogen leakage under pressure, and improve the safety of equipment operation.

[0015] Preferably, both the pulping tank and the mother liquor buffer tank are equipped with stirring components. The stirring components can fully mix the filter cake discharged from the rotary pressure filter with the mother liquor replenished by the mother liquor pipeline, avoid slurry sedimentation and clumping, ensure that the catalyst is evenly dispersed in the slurry, and improve the catalyst recovery rate when the subsequent catalyst precipitation feed pump is transported.

[0016] In a second aspect, the present invention also provides a process for a PTA mother liquor residue treatment system utilizing a rotary pressure filter according to the first aspect, comprising the following steps: S1. Residual liquid feed: The mother liquor residue generated by the PTA oxidation unit is sent to the residual liquid extraction tank and then conveyed to the rotary pressure filter by the residual liquid neutralization tank feed pump. S2. Integrated Separation and Treatment: Start the rotary pressure filter. The drum rotates and, under pressure, the mother liquor residue enters the filtration zone to form a filter cake. The initial filtrate is directly transported to the neutralization tank. The filter cake then enters at least two washing zones with the drum. Wastewater passes through the filter cake for multi-stage washing, and the washing liquid is directly transported to the neutralization tank. Subsequently, the filter cake enters at least two drying zones, where nitrogen is introduced to purge and reduce the moisture content of the filter cake. Finally, the filter cake rotates to the unloading zone and is unloaded by nitrogen backflushing. S3. Filter cake recovery: After unloading, the filter cake enters the pulping tank. RPF mother liquor is added through the mother liquor pipeline to adjust the slurry concentration to 20-30wt%. It is then transported to the circulating solvent tank through the catalyst precipitation feed pump to complete the recovery of TA and catalyst. S4. Filtrate and exhaust gas treatment: A small amount of filtrate produced by the rotary pressure filter enters the mother liquor buffer tank, and is pumped to the neutralization tank by the mother liquor buffer tank pump. Sodium carbonate solution is added to the neutralization tank to adjust the pH to 6.5-7.0. The organic exhaust gas volatilized at the top of the mother liquor buffer tank is introduced into the exhaust gas scrubbing tower, and is purified by countercurrent contact with sodium hydroxide scrubbing liquid before being discharged. S5, Maintenance Bypass: When the rotary pressure filter needs maintenance, the switching valve of the bypass pipeline will directly transport the residual liquid to the neutralization tank to maintain a stable residual liquid treatment flow rate.

[0017] Preferably, in step S2, at least two washing zones are designated as a first washing zone and a second washing zone, wherein the feed flow rate of the PTA oxidation unit bottom wastewater in the first washing zone is 3-5 m³ / h. 3 / h, the feed flow rate in the second washing zone is 2-3m³ / h. 3 / h; and the operating pressure of the first washing zone is 0.35-0.45MPa, the operating pressure of the second washing zone is 0.3-0.4MPa, and the washing liquid of the first washing zone and the washing liquid of the second washing zone are combined and transported to the neutralization tank.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The multi-zone design of the rotary pressure filter drum integrates the traditionally dispersed filtration, washing, and drying processes, avoiding residue transfer losses and efficiently separating solids, catalysts, and liquid impurities from the mother liquor. Useful components are recovered through the path of the slurry tank and the circulating solvent tank. The washing zone is connected to an external wastewater network, using the plant's wastewater to replace fresh water, reducing fresh water consumption and wastewater treatment volume. The drying and unloading zones use nitrogen to prevent the oxidation and deterioration of organic matter in the filter cake, and achieve efficient unloading through backflushing, preventing filter cake adhesion and blockage, ensuring stable equipment operation. During maintenance, the rotary pressure filter can be bypassed, and the downstream catalyst recovery unit can continue uninterrupted. Attached Figure Description

[0019] Figure 1 This is a system structure diagram of the present invention.

[0020] Figure label: 1. Residual liquid extraction tank; 11. Wastewater pipeline network; 12. Tail gas scrubbing tower; 13. Mother liquor pipeline network; 2. Residual liquid neutralization tank feed pump; 3. Rotary pressure filter; 4. Mother liquor buffer tank; 5. Mother liquor buffer tank pump; 6. Neutralization tank; 7. Pulping tank; 8. Catalyst precipitation feed pump; 9. Circulating solvent tank; 10. Nitrogen pipeline network. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] like Figure 1 As shown, this invention provides a technical solution to address the technical problems of existing PTA mother liquor residue treatment technologies in terms of resource recovery efficiency, energy consumption control, production continuity, and environmental protection. The invention provides the following technical solution: a PTA mother liquor residue treatment system utilizing a rotary pressure filter, comprising a rotary pressure filter 3 and a feeding unit and a discharging unit connected to the rotary pressure filter 3. The rotary pressure filter 3 includes a frame and a rotating drum disposed within the frame. The drum is divided into multiple filtration unit chambers, each including a filtration zone, a washing zone, a drying zone, and a discharging zone. The feeding unit includes a residual liquor extraction tank 1 and a residual liquor neutralization tank feed pump 2. The discharging unit includes a pulping tank 7 and a mother liquor buffer tank connected to the rotary pressure filter 3. The pulping tank 7 uses catalyst precipitation... The feed pump 8 is connected to the circulating solvent tank 9. The mother liquor buffer tank 4 is connected to the neutralization tank 6 through the mother liquor buffer tank pump 5. The washing section of the rotary pressure filter 3 is connected to the external wastewater network 11. The drying section and the unloading section are both connected to the external nitrogen network 10. The multi-section design of the rotary pressure filter 3 integrates the traditionally dispersed filtration, washing and drying processes, avoids residue transfer losses, and efficiently separates solid, catalyst and liquid impurities in the mother liquor. The useful components are recovered through the path of the pulping tank 7 and the circulating solvent tank 9. The washing section is connected to the external wastewater network, and the wastewater from the equipment is used to replace the fresh water, reducing the consumption of fresh water and the amount of wastewater treated. The drying section and the unloading section use nitrogen to avoid the oxidation and deterioration of organic matter in the filter cake, and achieve efficient unloading through backflushing, preventing the filter cake from sticking and clogging, and ensuring stable operation of the equipment.

[0023] Specifically, the rotary pressure filter 3 is model RPF-1000, with the drum speed set at 12 r / min, and the pressurization unit providing an operating pressure of 0.4 MPa; the residual liquid extraction tank 1 has a volume of 50 m³. 3 The material is 316L stainless steel, and it is equipped with a level gauge; the feed pump 2 for the residual liquid neutralization tank is a centrifugal pump; the wastewater pipeline 11 can transport wastewater from the bottom of the PTA oxidation unit tower, with a flow rate set at 6m³ / h. 3 / h; Nitrogen pipeline network 10 provides nitrogen with a purity of 99.9%, and the nitrogen inlet temperature in the drying zone is 90℃ with a flow rate of 8m³ / h. 3 / h, nitrogen backflushing pressure in the unloading zone is 0.25MPa.

[0024] The mother liquor residue from the PTA oxidation unit (solid content 10wt%, containing TA 5wt%, benzoic acid 0.8wt%, cobalt 500ppm, and manganese 400ppm) is fed into the residue extraction tank 1 and then pumped into the residue neutralization tank feed pump 2 at a rate of 10m³ / min. 3 The flow rate is delivered to the rotary pressure filter 3 at a rate of / h; under a pressure of 0.4MPa, the residual liquid enters the unit chamber of the filtration zone, and solid particles form a filter cake (5-8mm thick) on the wall of the unit chamber, resulting in initial separation of the filtrate; the filter cake rotates with the drum to the washing zone, 6m 3 The oxidizing wastewater per hour passes through the filter cake to displace residual benzoic acid; then the filter cake enters the drying zone and is purged with nitrogen at 90°C for 3 minutes, reducing the moisture content of the filter cake from 30% to 6%; finally, the filter cake rotates to the unloading zone and is unloaded by backflushing with nitrogen at 0.25MPa, entering the pulping tank 7; the filtrate produced by filtration enters the mother liquor buffer tank 4, and is then transported to the neutralization tank 6 by the mother liquor buffer tank pump 5.

[0025] In this embodiment, both the filtration zone and the washing zone are connected to the neutralization tank 6 via pipelines. The initial filtrate from the filtration zone and the washing liquid from the washing zone can be directly transported to the neutralization tank 6 without passing through the mother liquor buffer tank 4, reducing losses in the transportation process and avoiding impurity deposition caused by liquid stagnation. Most of the TA and benzoic acid in the directly transported filtrate and washing liquid have been retained by the filter cake, resulting in a lower organic content entering the neutralization tank, which can reduce the amount of sodium carbonate required for neutralization. Specifically, the initial filtrate from the filtration zone is directly transported to the neutralization tank 6 via pipelines; the washing liquid from the washing zone is directly transported to the neutralization tank 6 via pipelines; the two liquids are mixed in the main pipe and then enter the neutralization tank 6. A 30wt% sodium carbonate solution is slowly added to the neutralization tank 6 to adjust the pH to 6.5-7.0.

[0026] In this embodiment, there are at least two washing zones and drying zones. Multiple washing zones can achieve two or more washing cycles, more thoroughly replacing residual organic matter such as benzoic acid in the filter cake and preventing impurities from affecting the purity of the recovered TA and catalyst. Multiple drying zones can achieve two or more drying cycles, further reducing the moisture content of the filter cake and minimizing moisture interference from the slurry in the subsequent circulating solvent tank 9, thereby improving the reuse efficiency. Specifically, the outer surface of the rotary pressure filter 3 drum is divided into one filtration zone, two washing zones, two drying zones, and one unloading zone by a pressurization unit. Each zone is evenly distributed on the circumference of the drum, with each zone corresponding to a central angle of 60°. The wastewater flow rate of the first washing zone is set to 5 m³ / s. 3 / h, the wastewater flow rate of the second washing zone is set to 7m³ / h. 3 / h; Nitrogen temperature in the first drying zone is 80℃, and the flow rate is 7m³ / h. 3 / h, nitrogen temperature in the second drying zone is 100℃, flow rate is 9m³ / h 3 / h; The filter cake rotates with the drum to the first washing zone, 5m3 After being rinsed with wastewater at a rate of / h, the benzoic acid content in the filter cake decreased from 0.8wt% to 0.08wt%; it then entered the second washing zone, 7m 3 After being rinsed with wastewater, the benzoic acid content was further reduced to 0.02 wt%. Then it entered the first drying zone and was purged with nitrogen at 80°C for 3 minutes, reducing the moisture content of the filter cake from 30% to 10%. Then it entered the second drying zone and was purged with nitrogen at 100°C for 2 minutes, reducing the moisture content to 4.5%. Finally, it entered the unloading zone for unloading.

[0027] In this embodiment, the mother liquor buffer tank 4 is also connected to the tail gas scrubbing tower 12 via a pipeline. The filtrate temporarily stored in the mother liquor buffer tank 4 may volatilize a small amount of organic tail gas. Connecting to the tail gas scrubbing tower can absorb and treat the tail gas, avoiding direct emission and causing air pollution, which meets industrial environmental protection requirements. Specifically, the benzoic acid tail gas volatilized at the top of the mother liquor buffer tank 4 enters the bottom of the tail gas scrubbing tower 12 through a pipeline and comes into countercurrent contact with the sodium hydroxide scrubbing liquid sprayed from the top of the tower. The benzoic acid reacts with NaOH to produce sodium benzoate. The purified tail gas is discharged from the top of the tower after being demisted by a demister. After the scrubbing liquid is recycled for 8 hours, the concentration of sodium benzoate is detected to be 5wt%. It is then pumped to the by-product storage tank for recovery and fresh sodium hydroxide solution is added.

[0028] In this embodiment, a bypass pipeline is connected to the pipeline between the residual liquid extraction tank 1 and the rotary pressure filter 3 via a switching valve. This bypass pipeline is directly connected to the neutralization tank 6. When the rotary pressure filter 3 needs maintenance, the bypass pipeline is opened by switching the three-way valve, allowing the residual liquid to be directly transported to the neutralization tank 6, preventing downtime of the downstream catalyst recovery unit. During maintenance, the residual liquid throughput remains at 10m³. 3 / h (consistent with normal operating conditions), production downtime was reduced from 8 hours to 0, resulting in an annual reduction of approximately 480,000 yuan in downtime losses. When the rotary pressure filter 3 experiences a "unit chamber blockage" fault, the maintenance procedure is initiated as follows: ① Shut down the residual liquid neutralization tank feed pump 2; ② Switch the three-way valve via the PLC control system; ③ Restart the feed pump 2 and adjust the bypass pipeline flow regulating valve to stabilize the residual liquid flow at 10m³ / h. 3 / h, directly conveyed to neutralization tank 6; ④ Overhaul the rotary pressure filter 3; ⑤ After overhaul, reverse the three-way valve to restore the delivery of residual liquid to filter 3.

[0029] In this embodiment, the pipeline between the pulping tank 7 and the rotary pressure filter 3 is also externally connected to a mother liquor network 13. The mother liquor network 13 can replenish the pulping tank 7 with RPF mother liquor containing catalyst and circulating solvent, adjust the slurry concentration after filter cake pulping, and ensure smooth and unobstructed transport to the circulating solvent tank 9 via the catalyst precipitation feed pump 8. Specifically, the filter cake discharged from the rotary pressure filter 3 enters the pulping tank 7 at a rate of 1.2 tons / hour. The initial slurry concentration is 94 wt%. After detection by the densitometer, the solenoid valve is triggered to open, and the mother liquor network 13 is pumped at a rate of 2 m... 3 The RPF mother liquor is replenished at a flow rate of / h; after the stirring component stirs for 5 minutes, the slurry concentration is detected to drop to 25wt%, and the solenoid valve is closed; when the slurry concentration rises to 28wt% due to the continuous addition of filter cake, the solenoid valve is reopened to replenish the RPF mother liquor to 25wt%; after stabilization, the slurry is transported to the circulating solvent tank 9 through the catalyst precipitation feed pump 8.

[0030] Preferably, the rotary pressure filter 3 has a packing seal structure between the drum and the frame. The packing seal structure is made of acid and alkali resistant material, which can adapt to the acidic environment of the mother liquor residue, avoid residual liquid leakage or nitrogen leakage under pressure, and improve the safety of equipment operation. Specifically, the packing seal structure includes a packing cavity, wherein the annular cavity between the drum bushing and the frame is 10mm wide, the packing is made of PTFE and graphite mixed in a 7:3 ratio to form a 5mm×5mm rectangular cross-section rope packing, wound in 3 layers, with a total thickness of 15mm; the packing gland is made of 316L stainless steel and is tightened by 4 M16 bolts with a preload of 50N·m; and a nitrogen sealing interface.

[0031] In this embodiment, both the pulping tank 7 and the mother liquor buffer tank 4 are equipped with stirring components. The stirring components can fully mix the filter cake discharged from the rotary pressure filter 3 with the mother liquor replenished by the mother liquor pipeline 13, avoid slurry sedimentation and agglomeration, ensure that the catalyst is evenly dispersed in the slurry, and improve the catalyst recovery rate when the subsequent catalyst precipitation feed pump 8 is transported.

[0032] As a specific implementation method in this embodiment: Normal operation phase: Residual liquor feed: The mother liquor residue from the PTA oxidation unit, with a solid content of 10 wt%, TA 5 wt%, benzoic acid 0.8 wt%, cobalt 500 ppm, and manganese 400 ppm, is pumped into residual liquor extraction tank 1 via a transfer pump; the residual liquor neutralization tank feed pump 2 is started, and the residual liquor is pumped at a rate of 10 m³ / min via a three-way switching valve. 3 A flow rate of / h is delivered to the rotary pressure filter 3.

[0033] Integrated separation: The rotary pressure filter 3 is started, with the drum speed at 12 r / min and the pressurization unit pressure at 0.4 MPa. The residual liquid enters the filtration zone, forming a 5-8 mm thick filter cake. The initial filtrate is directly transported to the neutralization tank 6 through a DN80 pipeline. The filter cake rotates to the first washing zone, then to the second washing zone, where the washing liquid is directly transported to the neutralization tank 6 through a pipeline. Subsequently, the filter cake enters the first drying zone, then the second drying zone, where the moisture content is reduced to 4.5%. Finally, the filter cake rotates to the unloading zone, where it is backflushed with nitrogen at 0.25 MPa and enters the pulping tank 7. The feed flow rate of the PTA oxidation unit bottom wastewater in the first washing zone is 3-5 m³ / min. 3 / h, the feed flow rate in the second washing zone is 2-3m³ / h. 3 The first washing zone operates at a pressure of 0.35-0.45 MPa, and the second washing zone operates at a pressure of 0.3-0.4 MPa. The washing liquids from the first and second washing zones are combined and transported to the neutralization tank 6. In this technical solution, the first washing zone uses a higher flow rate and pressure to quickly flush away most of the free impurities in the filter cake, such as unreacted raw materials and soluble byproducts. The second washing zone uses a lower flow rate and pressure to finely wash away the trace impurities remaining in the filter cake pores, forming a stepped washing mode of coarse and fine washing. Compared with a single washing zone, this method removes impurities more efficiently and improves the purity of TA (terephthalic acid) and catalyst in the filter cake. At the same time, the lower pressure in the second washing zone avoids excessive compaction of the filter cake structure by high pressure, maintains the permeability of the filter cake pores, ensures that the washing liquid fully contacts the residual impurities, and reduces the loss of TA and catalyst with the washing liquid, thereby improving the recovery efficiency.

[0034] Filter cake recovery: The paddle agitator in pulping tank 7 is started, and RPF mother liquor is simultaneously replenished through mother liquor pipeline 13 to control the slurry concentration at 25wt%; after stirring for 8 minutes, the catalyst precipitation feed pump 8 is started to pump the slurry at a rate of 5m³ / min. 3 A flow rate of / h is delivered to the circulating solvent tank 9 to complete the recovery of TA and catalyst.

[0035] Filtrate Treatment and Tail Gas Purification: The anchor-type stirring assembly of the mother liquor buffer tank 4 is activated to receive a small amount of filtrate from the rotary pressure filter 3; the benzoic acid tail gas volatilized at the top of the buffer tank enters the tail gas scrubbing tower 12 and is mixed with 5m³ of filtrate. 3 A 10wt% NaOH washing solution is applied countercurrently per hour, and the purified exhaust gas is discharged. Pump 5 in the mother liquor buffer tank pumps the filtrate at a rate of 7.5 m³ / h. 3 A flow rate of / h is delivered to neutralization tank 6, and 30wt% sodium carbonate solution is added to neutralization tank 6 to adjust the pH to 6.8±0.16.

[0036] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0037] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly and specifically defined.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

Claims

1. A PTA mother liquor residue treatment system utilizing a rotary pressure filter, characterized in that, The rotary pressure filter (3) includes a rotary pressure filter (3) and a feeding unit and a discharging unit connected to the rotary pressure filter (3). The rotary pressure filter (3) includes a frame and a rotating drum set inside the frame. The rotating drum is divided into multiple filtration unit chambers. The filtration unit chambers include a filtration zone, a washing zone, a drying zone and a discharge zone. The feeding unit includes a residual liquid extraction tank (1) and a residual liquid neutralization tank feed pump (2). The discharging unit includes a pulping tank (7) and a mother liquor buffer tank (4) connected to the rotary pressure filter (3). The pulping tank (7) is connected to a circulating solvent tank (9) through a catalyst precipitation feed pump (8). The mother liquor buffer tank (4) is connected to a neutralization tank (6) through a mother liquor buffer tank pump (5). The washing zone of the rotary pressure filter (3) is connected to a wastewater pipeline (11). The drying zone and the discharging zone are both connected to a nitrogen pipeline (10).

2. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: Both the filtration zone and the washing zone are connected to the neutralization tank (6) via pipelines.

3. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: There are at least two washing and drying zones.

4. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: The mother liquor buffer tank (4) is also connected to the tail gas scrubbing tower (12) via a pipeline.

5. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: The pipeline between the residual liquid extraction tank (1) and the rotary pressure filter (3) is also connected to a bypass pipeline via a switching valve, and the bypass pipeline is directly connected to the neutralization tank (6).

6. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: The pipeline between the pulping tank (7) and the rotary pressure filter (3) is also connected to a mother liquor pipeline (13).

7. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: The rotary pressure filter (3) has a packing seal structure between the drum and the frame, and the packing seal structure is made of acid and alkali resistant material.

8. The PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that: Both the pulping tank (7) and the mother liquor buffer tank (4) are equipped with stirring components.

9. A process for a PTA mother liquor residue treatment system using a rotary pressure filter according to claim 1, characterized in that, Includes the following steps: S1. Residual liquid feed: The mother liquor residue generated by the PTA oxidation unit is sent to the residual liquid extraction tank (1) and then transported to the rotary pressure filter (3) through the residual liquid neutralization tank feed pump (2). S2, Integrated Separation and Treatment: Start the rotary pressure filter (3), the drum rotates, and under pressure, the mother liquor residue enters the filtration zone to form a filter cake. The initial filtrate is directly transported to the neutralization tank (6). The filter cake enters at least two washing zones in sequence with the drum. Wastewater passes through the filter cake for multi-stage washing, and the washing liquid is directly transported to the neutralization tank (6). Subsequently, the filter cake enters at least two drying zones and is purged with nitrogen to reduce the moisture content of the filter cake. Finally, the filter cake rotates to the unloading zone and is unloaded by nitrogen backflushing. S3, Filter cake recovery: The filter cake after unloading enters the pulping tank (7), and the RPF mother liquor is added through the mother liquor pipeline (13) to adjust the slurry concentration to 20-30wt%. It is then transported to the circulating solvent tank (9) through the catalyst precipitation feed pump (8) to complete the recovery of TA and catalyst. S4. Filtrate and tail gas treatment: A small amount of filtrate generated by the rotary pressure filter (3) enters the mother liquor buffer tank (5), and is transported to the neutralization tank (6) by the mother liquor buffer tank pump (5). Sodium carbonate solution is added to the neutralization tank (6) to adjust the pH to 6.5-7.

0. The organic tail gas volatilized at the top of the mother liquor buffer tank (4) is introduced into the tail gas scrubbing tower (12), and is purified by countercurrent contact with sodium hydroxide scrubbing liquid before being discharged. S5, Maintenance Bypass: When the rotary pressure filter (3) needs maintenance, the switching valve of the bypass pipeline is switched to directly transport the residual liquid to the neutralization tank (6) to maintain a stable residual liquid treatment flow rate.

10. The process of the PTA mother liquor residue treatment system using a rotary pressure filter according to claim 9, characterized in that, In step S2, at least two washing zones are designated as the first washing zone and the second washing zone, wherein the feed flow rate of the PTA oxidation unit bottom wastewater in the first washing zone is 3-5 m³ / h. 3 / h, the feed flow rate in the second washing zone is 2-3m³ / h. 3 / h; and the operating pressure of the first washing zone is 0.35-0.45MPa, the operating pressure of the second washing zone is 0.3-0.4MPa, and the washing liquid of the first washing zone and the washing liquid of the second washing zone are combined and transported to the neutralization tank (6).

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