Energy-saving process and device for stripping PTA production reuse water
By introducing a flash tank and a steam generator coupled in the PTA production wastewater stripping unit to form a waste heat recovery network, the problems of waste heat waste and bottom liquid discharge were solved, achieving energy consumption reduction and improved operational stability, resulting in a comprehensive energy consumption reduction of 50%.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI UNIV OF TECH
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-19
AI Technical Summary
The existing PTA production wastewater stripping process suffers from problems such as waste heat, excessive reboiling energy consumption at the bottom of the tower, and increased discharge of bottom liquid, resulting in high energy consumption and unstable operation of the unit.
In a single-tower stripping unit, a tower bottom flash tank is introduced and coupled with a steam generator to form a complete waste heat recovery network. The flash tank reduces the pressure of the tower bottom liquid to generate steam, which is then used as makeup water for the steam generator, reducing external discharge. Combined with the deep coupling of the compressor and the stripping tower, internal energy circulation is achieved.
It significantly reduced the overall energy consumption of the device, improved operational stability and adaptability, achieved deep recovery of waste heat and efficient separation of organic matter, reduced comprehensive energy consumption by more than 50%, and avoided an increase in external drainage.
Smart Images
Figure CN122233477A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment in PTA (purified terephthalic acid) production, specifically to a stripping energy-saving process and apparatus for PTA production recycled water. Background Technology
[0002] PTA production units generate significant amounts of RO wastewater, alkaline wash water, and process wastewater. To achieve near-zero discharge, this wastewater typically undergoes multi-effect evaporation to remove heavy components before stripping the condensate to control the organic content in the recycled water. The condensate generally contains methanol, paraxylene, benzene compounds, esters, and other organic compounds, with a COD of 1000-5000 ppm. The COD needs to be reduced to below 100 ppm before reuse. The stripping principle for most of the organic matter in the condensate is similar to distillation, utilizing the differences in volatility of the components in the mixture to achieve mass and heat transfer in the packed bed or trays, separating the light and heavy components.
[0003] Li Xiuji (Steam Consumption Analysis and Optimization Strategy of Wastewater Stripping Unit [J]. Petroleum & Petrochemical Green and Low-Carbon) proposed an optimization method for wastewater stripping, transforming the double-tower stripping process into a single-tower pressurized side-stream ammonia stripping process. This involved finely controlling the operating pressure at the top of the stripping tower, increasing the production of low-grade steam as a byproduct of the heat pump system, and replacing the heat exchanger with a high-efficiency one, resulting in a 14.01% reduction in unit energy consumption. However, the addition of the heat pump system introduces additional makeup water, significantly increasing the discharge of the bottom liquid and making post-treatment of the bottom liquid more difficult. Furthermore, it results in insufficient utilization of the bottom waste heat.
[0004] Chinese patent CN117142678A proposes an energy-saving and environmentally friendly PTA wastewater treatment device, including a multi-effect evaporator and a furnace-front single-effect evaporator, which makes full use of the self-generated waste heat. However, the stripping tower does not consider the by-product stripping steam from its own waste heat during operation.
[0005] Therefore, further developing an energy-saving stripping process that is simple in process, has high waste heat recovery efficiency, and is highly adaptable has become an urgent technical problem to be solved in this field. Summary of the Invention
[0006] This invention aims to overcome the shortcomings of existing stripping distillation processes, such as wasteful waste of waste heat and excessive energy consumption for reboiling at the bottom of the column, and provides an energy-saving stripping process and apparatus for PTA production water recycling. This process introduces a flash evaporator into the existing single-tower stripping unit, coupling the flash evaporator with a steam generator to construct a complete waste heat recovery network covering both the top and bottom of the column. This invention can effectively reduce the overall energy consumption of the unit, shorten the investment payback period, and simultaneously improve the stability and adaptability of the unit's operation.
[0007] The technical problem solved by this invention is achieved through the following technical solution: An energy-saving stripping process for PTA production recycled water includes the following steps: The PTA unit's four-effect evaporation condensate is preheated in the feed preheater (E01) and then enters the stripping tower (T01), where it is separated into overhead vapor and bottom liquid. The overhead vapor enters the steam generator (E02), and after cooling, it enters the reflux tank (V02) for gas-liquid separation. The liquid phase in the reflux tank (V02) is returned to the top of the tower, while all the vapor phase is collected. The bottom liquid enters the flash tank (V01), where flash vapor and low-temperature bottom liquid are generated. The low-temperature bottom liquid is pressurized by the bottom liquid pump (P01) and part of it is sent to the shell side of the steam generator (E02) as makeup water. The remaining bottom liquid is preheated in the feed preheater (E01) and then sent out after entering the bottom liquid water cooler (E04). The low-pressure steam produced by the steam generator (E02) is mixed with the flash vapor from the flash tank (V01) and then pressurized by the compressor (C01) before being sent to the bottom of the stripping tower (T01) as stripping steam. The stripping tower (T01) has an operating pressure of 190~205 kPa (A) at the top (absolute pressure), an operating pressure of 200-210 kPa (A) at the bottom, a vapor phase exit temperature of 115~121℃, a bottom temperature of 117~123℃, a reflux ratio of 14-16, and a theoretical plate number of 20-30. The raw material flows out of the feed preheater (E01) at a temperature of 90~105℃; The steam generator (E02) and flash tank (V01) operate at a pressure of 140~150 kPa (A). The steam produced is mixed and then enters the steam compressor (C01), with an outlet pressure of 200~230 kPa (A). The non-condensable discharge of hot stream from the steam generator is 0.5%–1.2% of the feed rate. The pressure of the by-product low-pressure steam is 50–60 kPa(A) lower than the operating pressure at the top of the stripping tower. The liquid in the bottom of the tower is subjected to vacuum flash evaporation, and the pressure after vacuum is 50–60 kPa(A) lower than the operating pressure at the bottom of the stripping tower. The temperature of the liquid flowing out of the water cooler (E04) from the bottom of the tower is ≤40℃, and the organic matter content is ≤100ppm; The reboiler (E03) uses live steam and operates at a pressure of 350-500 kPa (A). The operating pressure of the reflux tank (VO2) is 180~230 kPa; The PTA production wastewater multi-effect evaporation condensate composition by mass percentage includes 99.7%-99.8% water, 0.16%-0.26% methanol, and 0.01%-0.06% other organic impurities (benzene series compounds, esters); A stripping energy-saving device for PTA production recycled water includes a stripping tower (T01), a feed preheater (E01), a steam generator (E02), a reboiler (E03), a bottom liquid water cooler (E04), a flash tank (V01), a reflux tank (V02), a bottom liquid pump (P01), a reflux pump (P02), and a compressor (C01). In this PTA unit, the outlet of the condensate from the four-effect evaporation is connected to the feed preheater (E01), and the outlet of the preheater (E01) is connected to the feed inlet in the middle of the stripping tower (T01). The top of the stripping tower (T01) is sequentially connected to the tube side of the steam generator (E02) and the reflux tank (V02). The top of the reflux tank (V02) is connected to the non-condensable gas delivery pipeline, and the bottom is connected to the upper reflux feed inlet of the stripping tower (T01) via the reflux pump (P02). The bottom outlet of the stripping tower (T01) is connected to the bottom reboiler return feed inlet of the stripping tower (T01) via the tube side of the reboiler (E03). The steam pipe is connected to the reboiler. The shell side of (E03) is connected to the gas phase inlet, and the gas phase outlet is connected to the steam condensate pipeline; the bottom of the stripping tower (T01) is also connected to the inlet in the middle of the flash tank (V01); the bottom of the flash tank (V01) is connected to the bottom liquid pump (P01), and one outlet of the bottom liquid pump (P01) is connected to the bottom liquid delivery pipeline through the tube side of the feed preheater (E01), the bottom liquid water cooler (E04), and the bottom liquid external delivery pipeline; the other outlet of the bottom liquid pump (P01) passes through the shell side of the steam generator (E02), merges with the top pipeline of the flash tank (V01), and is connected to the bottom stripping gas inlet of the stripping tower (T01) through the compressor (C01); The stripping tower (T01) is a packed tower, which includes a gas-liquid separation chamber, a stripping section and a rectification section from bottom to top. It has 20-30 theoretical plates. The feed position is 8-10 theoretical plates from top to bottom. The reflux feed port is the first theoretical plate. The bottom reboiler return feed port and the bottom stripping gas feed port are located below the last theoretical plate. It is filled with 250Y or 350Y structured packing. A two-stage gas-liquid distributor is installed in the gas-liquid separation chamber.
[0008] The essential features of this invention are: This invention incorporates a flash tank into the device, utilizing not only its pressure-reducing flash evaporation function but also, through deep coupling with the steam generator, compressor, and stripping tower within the system, forming a synergistic system that enhances internal material circulation. During flash evaporation, trace organic compounds (methanol, benzene series, etc.) remaining in the tower bottom liquid are further removed to ≤100ppm due to changes in partial pressure. This directly improves the purity of the final discharged bottom liquid, sharing some of the separation function of the main stripping tower, achieving dual functionality. A portion of the low-temperature bottom liquid treated by the flash tank is used as makeup water for the steam generator. The ingenuity of this design lies in the fact that the steam generator's makeup water originates entirely from the bottom liquid produced by the system itself, achieving "zero additional discharge." Traditional processes typically require the introduction of demineralized water to utilize waste heat from the tower top for steam production, which not only increases the total amount of discharged water but also disrupts the system's water balance. This invention, through the intervention of the flash tank, transforms the tower bottom liquid into a heat exchange medium and makeup water source, recovering waste heat without adding any additional discharge burden. This coupling approach goes beyond the conventional application of flash tanks as simple heat source devices. Furthermore, by connecting the flash tank in parallel with the steam generator, a steam source is provided, which collects and homogenizes the waste heat from the top and bottom of the column, thereby significantly reducing the compressor load.
[0009] The beneficial effects of this invention are as follows: The bottom liquid of the column contains a large amount of heat energy. Introducing it into the flash tank utilizes the principle of reduced pressure flash evaporation, where this residual heat immediately generates secondary steam. The steam generated in the flash tank requires no external heat source and simultaneously completes the secondary removal of light components from the bottom liquid, improving the purity of the effluent. The entire process is an internal energy and material cycle within the system, without introducing additional makeup water. Therefore, it does not increase the discharge volume of the bottom liquid and does not add difficulty to subsequent bottom liquid treatment.
[0010] This invention features a scientifically sound and rationally designed stripping energy-saving process for PTA production reclaimed water. It achieves deep recovery and utilization of waste heat from the stripping tower bottom. By adding a flash evaporator to the bottom and reducing pressure to produce low-grade steam as a byproduct, it not only facilitates waste heat recovery but also further enhances the separation capacity of organic matter in the bottom tower. The steam generator uses hot water from the bottom tower, avoiding the consumption of demineralized water and increasing the amount of wastewater discharged from the bottom tower. Employing steam compression heat pump technology, the compressor outlet pressure only needs to be higher than the pressure in the stripping tower bottom, reducing power consumption by more than 50% compared to the steam pressure required to reach the reboiler. The direct entry of stripping steam into the bottom tower also improves the removal efficiency of organic matter. This invention achieves full heat recovery, zero-emission recycling, and improved separation efficiency of the equipment's own waste heat, significantly reducing external steam consumption and operating energy consumption, with energy savings of 50% compared to traditional heat pumps. Attached Figure Description
[0011] Figure 1 A process flow diagram for energy-saving stripping of recycled water in PTA production; In the diagram, T01 is the stripping tower, E01 is the feed preheater, E02 is the steam generator, E03 is the reboiler, E04 is the bottom liquid water cooler, V01 is the flash tank, V02 is the reflux tank, P01 is the bottom liquid pump, P02 is the reflux pump, and C01 is the compressor. Detailed Implementation
[0012] The following is in conjunction with the appendix Figure 1 The invention is further illustrated by examples. However, the following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the invention.
[0013] like Figure 1 As shown, the present invention provides a stripping energy-saving device for PTA production recycled water, which includes a stripping tower (T01), a feed preheater (E01), a steam generator (E02), a reboiler (E03), a bottom liquid water cooler (E04), a flash tank (V01), a reflux tank (V02), a bottom liquid pump (P01), a reflux pump (P02), and a compressor (C01). In this PTA unit, the outlet of the condensate from the four-effect evaporation is connected to the feed preheater (E01), and the outlet of the preheater (E01) is connected to the feed inlet in the middle of the stripping tower (T01). The top of the stripping tower (T01) is sequentially connected to the tube side of the steam generator (E02) and the reflux tank (V02). The top of the reflux tank (V02) is connected to the non-condensable gas delivery pipeline, and the bottom is connected to the upper reflux feed inlet of the stripping tower (T01) via the reflux pump (P02). The bottom outlet of the stripping tower (T01) is connected to the bottom reboiler return feed inlet of the stripping tower (T01) via the tube side of the reboiler (E03). The steam pipe is connected to the reboiler. The shell side of (E03) is connected to the gas phase inlet, and the gas phase outlet is connected to the steam condensate pipeline; the bottom of the stripping tower (T01) is also connected to the inlet in the middle of the flash tank (V01); the bottom of the flash tank (V01) is connected to the bottom liquid pump (P01), and one outlet of the bottom liquid pump (P01) is connected to the bottom liquid delivery pipeline through the tube side of the feed preheater (E01), the bottom liquid water cooler (E04), and the bottom liquid external delivery pipeline; the other outlet of the bottom liquid pump (P01) passes through the shell side of the steam generator (E02), merges with the top pipeline of the flash tank (V01), and is connected to the bottom stripping gas inlet of the stripping tower (T01) through the compressor (C01); The stripping tower (T01) includes a gas-liquid separation chamber and a rectification section from bottom to top. The rectification section is equipped with structured packing with a theoretical number of 30 plates. From top to bottom, there are 10 plates for the raw material feed position; 1 plate for the reflux feed port; and the bottom reboiler return feed port and the bottom stripping gas feed port are located below the 30th plate.
[0014] The raw material enters the raw material preheater (E01) which is equipped with a flow meter; Both the boiler liquid entering the steam generator (E02) and the tower bottom water cooler (E04) are equipped with flow meters; The stripping tower (T01), flash tank (V01), and reflux tank (V02) are all equipped with level gauges; The stripping tower (T01) has 10 theoretical plates in the upper section (DN2400×4500mm), 10 theoretical plates in the middle section (DN3200×4500mm), and 10 theoretical plates in the lower section (DN3200×4500mm), and is filled with 350Y structured packing. In the process: The PTA unit's fourth-effect evaporation condensate is preheated by the feed preheater (E01) and then enters the stripping tower (T01), where it is separated into overhead vapor and bottom liquid. The overhead vapor enters the steam generator (E02) to provide heat for the by-product low-pressure steam. Tower top gas After condensation, the liquid enters the reflux tank (VO2) for gas-liquid separation. The liquid phase obtained from the reflux tank (VO2) is returned to the top of the column, while all the gas phase is collected and sent out. The bottom liquid enters the flash tank (VO1), where flash evaporation produces flash vapor. low temperature The low-temperature reactor liquid is pressurized by the reactor liquid pump (P01) and part of it is sent to the shell side of the steam generator (E02) as makeup water to produce low-pressure steam. The remaining reactor liquid is preheated by the feed preheater (E01) and then sent to the reactor liquid water cooler (E04) for external distribution. The low-pressure steam produced by the steam generator (E02) is mixed with the flash steam in the flash tank (V01) and then pressurized by the compressor (C01) and sent to the bottom of the stripping tower (T01) as a direct heat source.
[0015] Example 1: The following is an example of processing 200 tons of evaporative condensate per hour to reduce the organic matter content to below 100 ppm.
[0016] The PTA production wastewater multi-effect evaporation condensate composition by mass percentage includes 99.77% water, 0.17% methanol, and 0.06% other organic impurities (benzene compounds, esters). The raw materials from the pipeline are preheated to 105°C in the raw material preheater (E01) and then enter the stripping tower (T01). The stripping tower (T01) has 30 theoretical plates and 10 feed theoretical plates. The operating pressure is 200 kPa, the vapor phase exit temperature is 120°C, and the exit rate is 34.5 t / h (reflux ratio is 15.4). The reboiler operates at a pressure of 350 kPa.
[0017] The gas phase at the top of the tower is cooled to 117°C by the steam generator (E02) (operating pressure 150 kPa) and enters the reflux tank (V02) for gas-liquid separation. The reflux tank operates at 203 kPa. 2.1 t / h of the separated gas phase (non-condensable hot stream from the steam generator, accounting for 1.05% of the feed) is completely collected, and 32.4 t / h of the separated liquid phase is completely refluxed. The bottom liquid at 122℃, 233.7t / h (including 35.8t / h of by-product steam), enters the flash tank (V01) for flash evaporation at 150kPa pressure. The flash steam of 4.7t / h (pressure 150kPa) is mixed with the by-product steam of 31.1t / h (pressure 150kPa) from the steam generator (E02). The flash liquid is then pressurized by the bottom liquid pump (P01) and divided into two streams. One stream of 31.1t / h enters the steam generator (E02) as makeup water, and the rest enters the raw material preheater (E01), and then enters the bottom liquid water cooler (E04) for cooling before being sent out at a flow rate of 197.9t / h. The bottom liquid water cooler (E04) consumes 415t / h of circulating water (inlet temperature 32℃, outlet temperature 40℃). After the two steam streams are mixed, they enter the compressor (C01) and are pressurized to 220 kPa before directly entering the stripping tower as a heat source. The compressor (C01) has a power of 860 kW. The reboiler (E03) uses 350 kPa, 3.7 t / h saturated steam as a heat source.
[0018] The reboiler (E3) is a thermosiphon reboiler.
[0019] The non-condensable gas discharged from the reflux tank (VO2) consists of 78.4% water, 15.8% methanol, and 5.8% other organic impurities (benzene series compounds and esters). The externally sent liquid contains 99.994% water, 0.006% methanol, and less than 100 ppm organic matter. The COD index is controlled by controlling the liquid phase temperature in the control tower bottom.
[0020] Comparative Example 1: The other parts of the apparatus in this comparative example are the same as those in Example 1, except that: (1) the steam generator in this comparative example uses 95°C demineralized water; (2) there is no flash tank in this comparative example 1 apparatus, and there is no connection between the flash tank and the steam generator and the feed preheater. The liquid in the reactor directly enters the raw material preheater, and then enters the reactor liquid water cooler for cooling before being sent out; (3) the compressor outlet pressure in this comparative example 1 is 350 kPa higher.
[0021] The comparative example uses the same condensate as in Example 1, with the steam generator E2 employing 95°C demineralized water, and the by-product steam being pressurized by a steam compressor before entering the reboiler.
[0022] The raw materials from the pipeline network are preheated to 105°C in the raw material preheater (E01) and then enter the stripping tower (T01). The stripping tower (T01) has 30 theoretical plates, 10 feed plates, an operating pressure of 200 kPa, a vapor phase exit temperature of 120°C, and an exit rate of 34.5 t / h. The vapor phase at the top of the tower is cooled to 117°C by the steam generator (E02) and then enters the reflux tank (V02) for gas-liquid separation. 2.1 t / h of the separated vapor phase is completely collected, and 32.4 t / h of the separated liquid phase is completely refluxed. The bottom liquid at 122°C, at a rate of 197.9 t / h, enters the raw material preheater (E01), and then enters the bottom liquid water cooler (E04) for cooling before being sent out. The bottom liquid water cooler (E04) consumes 640 t / h of circulating water. 31.1 t / h of demineralized water enters the steam generator (E02). The by-product steam enters the compressor (C01) for pressurization and then enters the reboiler as a heat source. The compressor (C01) has a power of 2000 kW. The reboiler (E03) additionally uses 8.6 t / h of saturated steam at 350 kPa as a heat source.
[0023] Compared to Example 1, this comparative example uses a 95°C demineralized water steam generator, which increases costs compared to the flash-evaporated bottom liquid used in Example 1. Furthermore, due to the absence of a flash tank, there is less by-product steam, higher circulating water consumption, and no secondary separation of organic matter in the bottom liquid, resulting in a relatively higher COD. In addition, the compressor outlet pressure of Comparative Example 1 is 350 kPa, which is higher than the compressor outlet pressure of 220 kPa in Example 1, increasing power consumption.
[0024] Compared with Comparative Example 1, the kettle liquid water cooler (E04) in Example 1 saved 225 t / h of circulating water; no additional boiler water was introduced into the steam generator (E02), saving 31.1 t / h of boiler water; the flash steam and by-product steam were mixed and introduced into the reboiler (E03) as a heat source, saving 4.9 t / h of saturated steam, while reducing the power of the compressor (C01) by about 1100 kW, thus reducing the energy consumption of the equipment.
[0025] Through the above embodiments and comparative examples, the process of the present invention does not change the main body of the system (stripping tower). By adding a flash tank, the liquid in the bottom of the stripping tower is flashed. Flashing can provide a sufficient heat exchange temperature difference between the liquid in the bottom and the steam at the top of the tower. After flashing, part of the liquid in the bottom (without the need to introduce additional demineralized water) is used by the steam generator to exchange heat with the steam at the top of the tower to produce low-grade steam. After mixing with the flash steam in the bottom of the tower and pressurizing it (reducing the compressor outlet pressure and reducing power consumption), it directly enters the stripping tower as a heat source, replacing most of the primary steam. The direct entry of the stripping steam into the bottom of the tower also improves the removal effect of organic matter. Compared with the traditional heat pump process, the overall energy consumption reduction rate is more than 50%. Long-term operation can significantly reduce the operating cost of the unit, achieve deep recovery of the waste heat in the bottom of the tower, and ensure the continuous and stable operation of the distillation unit.
[0026] Matters not covered in this invention are common knowledge.
Claims
1. A stripping energy-saving process for PTA production water recycling, characterized in that, The process includes the following steps: The PTA unit's four-effect evaporation condensate is preheated in the feed preheater (E01) and then enters the stripping tower (T01), where it is separated into overhead vapor and bottom liquid. The overhead vapor enters the steam generator (E02), and after cooling, it enters the reflux tank (V02) for gas-liquid separation. The liquid phase in the reflux tank (V02) is returned to the top of the tower, while all the vapor phase is collected. The bottom liquid enters the flash tank (V01), where flash vapor and low-temperature bottom liquid are generated. The low-temperature bottom liquid is pressurized by the bottom liquid pump (P01) and part of it is sent to the shell side of the steam generator (E02) as makeup water. The remaining bottom liquid is preheated in the feed preheater (E01) and then sent out after entering the bottom liquid water cooler (E04). The low-pressure steam produced by the steam generator (E02) is mixed with the flash vapor from the flash tank (V01) and then pressurized by the compressor (C01) before being sent to the bottom of the stripping tower (T01) as stripping steam. The stripping tower (T01) has an operating pressure of 190-205 kPa (A) at the top, an operating pressure of 200-210 kPa (A) at the bottom, a vapor phase exit temperature of 115-121℃, a bottom temperature of 117-123℃, a reflux ratio of 14-16, and a theoretical plate count of 20-30.
2. The stripping energy-saving process for PTA production recycled water as described in claim 1, characterized in that, The raw material flows out of the feed preheater (E01) at a temperature of 90~105℃; The steam generator (E02) and flash tank (V01) operate at a pressure of 140~150 kPa (A). The generated steam is mixed and then enters the steam compressor (C01). The compressor outlet pressure is 200~230 kPa (A). The non-condensable discharge of hot stream from the steam generator is 0.5%~1.2% of the feed rate. The pressure of the by-product low-pressure steam is 50-60 kPa (A) lower than the operating pressure at the top of the stripping tower. The bottom liquid is flashed under reduced pressure, and the pressure after reduced pressure is 50-60 kPa (A) lower than the operating pressure at the bottom of the stripping tower. The temperature of the liquid flowing out of the water cooler (E04) from the bottom of the tower is ≤40℃, and the organic matter content is ≤100ppm; The reboiler (E03) uses live steam and operates at a pressure of 350-500 kPa (A). The operating pressure of the reflux tank (V02) is 180~230 kPa.
3. The stripping energy-saving process for PTA production recycled water as described in claim 1, characterized in that, The PTA production wastewater multi-effect evaporation condensate composition by mass percentage includes 99.7%-99.8% water, 0.16%-0.26% methanol, and 0.01%-0.06% other organic impurities (benzene series compounds, esters).
4. A stripping energy-saving device for PTA production water recycling, characterized in that, The unit includes a stripping tower (T01), a feed preheater (E01), a steam generator (E02), a reboiler (E03), a bottom liquid water cooler (E04), a flash tank (V01), a reflux tank (V02), a bottom liquid pump (P01), a reflux pump (P02), and a compressor (C01). In this PTA unit, the outlet of the condensate from the four-effect evaporation is connected to the feed preheater (E01), and the outlet of the preheater (E01) is connected to the feed inlet in the middle of the stripping tower (T01). The top of the stripping tower (T01) is sequentially connected to the tube side of the steam generator (E02) and the reflux tank (V02). The top of the reflux tank (V02) is connected to the non-condensable gas delivery pipeline, and the bottom is connected to the upper reflux feed inlet of the stripping tower (T01) via the reflux pump (P02). The bottom outlet of the stripping tower (T01) is connected to the bottom reboiler return feed inlet of the stripping tower (T01) via the tube side of the reboiler (E03). The steam pipe is connected to the reboiler. The shell side of (E03) is connected to the gas phase inlet, and the gas phase outlet is connected to the steam condensate pipeline; the bottom of the stripping tower (T01) is also connected to the inlet in the middle of the flash tank (V01); the bottom of the flash tank (V01) is connected to the bottom liquid pump (P01), and one outlet of the bottom liquid pump (P01) is connected to the bottom liquid delivery pipeline through the tube side of the feed preheater (E01), the bottom liquid water cooler (E04), and the bottom liquid external delivery pipeline; the other outlet of the bottom liquid pump (P01) passes through the shell side of the steam generator (E02), merges with the top pipeline of the flash tank (V01), and is connected to the bottom stripping gas inlet of the stripping tower (T01) through the compressor (C01).
5. The stripping energy-saving device for PTA production recycled water as described in claim 4, characterized in that, The stripping tower (T01) is a packed tower, which includes a gas-liquid separation chamber, a stripping section and a rectification section from bottom to top. It has 20-30 theoretical plates. The feed position is 8-10 theoretical plates from top to bottom. The reflux feed port is the first theoretical plate. The bottom reboiler return feed port and the bottom stripping gas feed port are located below the last theoretical plate. It is filled with 250Y or 350Y structured packing. A two-stage gas-liquid distributor is installed in the gas-liquid separation chamber.