Method and system for recovering xylene in high-concentration xylene waste gas

Abstract

The invention relates to the technical field of waste gas treatment, and particularly discloses a method and system for recycling xylene in high-concentration xylene waste gas, the system comprises a precooler, an absorption system, a regeneration system and a receiving tank, the absorption system is composed of an absorption tower, a heat exchanger and a recooler, the precooler is connected with a lower inlet pipeline of the absorption tower, and the absorption tower is connected with a lower outlet pipeline of the heat exchanger; a booster fan is arranged in a pipeline connecting the precooler and the absorption tower, a bottom outlet of the absorption tower is connected with a first inlet pipeline of the heat exchanger, and a rich liquid pump is arranged on a pipeline connecting the absorption tower and the heat exchanger; the regeneration system comprises a regeneration tower, a condenser, a vacuum buffer tank, a vacuum pump tail cooler and a vacuum pump tail gas recooler. According to the invention, the high-concentration xylene waste gas can be stably and continuously treated, xylene in the xylene waste gas can be efficiently recovered, the quality of the recovered product is ensured, the absorbent can be recycled, the absorbent does not need to be replaced during treatment work, the production cost is saved, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of waste gas treatment, and in particular to a method and a system for recovering xylene from high-concentration xylene waste gas. Background Art

[0002] Xylene is a commonly used solvent, widely used in the pharmaceutical / fine chemical industry and other industries. The characteristics of waste gas emissions in this industry are intermittent emissions and extremely high concentrations (even up to saturation concentration). Direct catalytic oxidation or incineration treatment will cause a huge waste of resources. The industry is widely studying the recovery and utilization of xylene in this type of waste gas. The mainstream recovery processes are divided into two categories: one is activated carbon / activated carbon fiber / molecular sieve / resin adsorption + water vapor desorption concentration recovery. This type of technology has a low recovery efficiency. The product contains a small amount of water and cannot be used directly in production. It will also cause secondary pollution such as sewage; the other is activated carbon / activated carbon fiber / molecular sieve adsorption + hot nitrogen desorption concentration recovery. This type of technology also has a low recovery efficiency. Although there is no secondary pollution, the thermal regeneration desorption efficiency is low, which will affect the adsorption effect and make it difficult to meet the waste gas emission standards. Summary of the invention

[0003] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a method and system for recovering xylene in high-concentration xylene waste gas, which can realize stable and continuous treatment of high-concentration xylene waste gas, efficiently recover xylene in xylene waste gas and ensure the quality of recovered products. At the same time, the absorbent can be recycled and there is no need to replace the absorbent during processing work, thereby saving production costs and improving production efficiency.

[0004] The purpose of the present invention can be achieved through the following technical solutions: A xylene recovery system for high-concentration xylene waste gas, comprising a precooler, an absorption system, a regeneration system and a receiving tank, wherein the absorption system is composed of an absorption tower, a heat exchanger and a recooler, wherein the precooler is connected to the lower inlet pipeline of the absorption tower, a booster fan is arranged in the pipeline connecting the precooler and the absorption tower, the bottom outlet of the absorption tower is connected to the first inlet pipeline of the heat exchanger, and a rich liquid pump is arranged in the pipeline connecting the absorption tower and the heat exchanger; The regeneration system includes a regeneration tower, a condenser, a vacuum buffer tank, a vacuum pump tail cooler, and a vacuum pump tail gas recooler. The first outlet of the heat exchanger is connected to the middle inlet pipeline of the regeneration tower, the top outlet of the regeneration tower is connected to the inlet pipeline of the condenser, the outlet of the condenser is connected to the top inlet pipeline of the vacuum buffer tank, the bottom outlet of the vacuum buffer tank is connected to the first inlet pipeline of the receiving tank, and a product pump is provided on the pipeline connecting the vacuum buffer tank and the receiving tank; The top outlet of the vacuum buffer tank is connected to the inlet pipeline of the vacuum pump tail cooler, a vacuum pump is arranged on the pipeline connecting the vacuum buffer tank and the vacuum pump tail cooler, the outlet of the vacuum pump tail cooler is connected to the inlet pipeline of the vacuum pump tail gas recooler, and the outlet of the vacuum pump tail gas recooler is connected to the second inlet pipeline of the receiving tank.

[0005] Preferably, the first bottom outlet of the regeneration tower is connected to the second inlet pipeline of the heat exchanger, the second outlet of the heat exchanger is connected to the inlet pipeline of the subcooler, an absorbent circulation pump is provided on the pipeline connecting the heat exchanger and the subcooler, and the outlet of the subcooler is connected to the upper inlet pipeline of the absorption tower.

[0006] Preferably, a regeneration tower condenser is provided on the upper part of one side of the regeneration tower, a falling film evaporator is provided on the other side of the regeneration tower, a reflux pipeline is provided on the side wall of the falling film evaporator, one end of the reflux pipeline is connected to the upper inlet of the falling film evaporator, and the other end of the reflux pipeline is connected to the second bottom outlet of the regeneration tower, and an evaporation circulation pump is provided on the reflux pipeline.

[0007] Preferably, an external feed inlet is provided at the upper portion of the falling film evaporator, and a discharge port is provided at the lower portion of the falling film evaporator.

[0008] Preferably, the outlet of the receiving tank is connected to a product delivery pipeline, and a product delivery pump is provided on the product delivery pipeline.

[0009] Preferably, a sprayer is provided at the top of the absorption tower.

[0010] Preferably, the top outlet of the absorption tower is connected to a gas exhaust pipeline.

[0011] A method for recovering xylene from high-concentration xylene waste gas comprises the following steps: Xylene recovery from xylene waste gas: S1: Pass the xylene waste gas into the precooler for preliminary condensation treatment, and the condensation treatment temperature is 10~30℃; S2: The xylene waste gas after the preliminary condensation treatment is introduced into the absorption tower through the booster fan, and the sprayer at the top of the absorption tower sprays the absorbent down. The absorbent captures and absorbs the xylene waste gas after the preliminary condensation treatment and falls into the bottom of the absorption tower to obtain absorbent rich liquid and exhaust gas, which is discharged through the gas exhaust pipeline; S3: Use a rich liquid pump to pass the absorbent rich liquid from the bottom of the absorption tower into the heat exchanger for preheating, and then pass it into the regeneration tower; S4: The regeneration tower uses the steam generated by the falling film evaporator as a heat source to further heat the preheated absorbent rich liquid at a heating temperature of 80°C to 140°C. At the same time, a decompression treatment is performed at a negative pressure of -50 Kpa to -90 Kpa. Xylene is separated from the absorbent rich liquid through the regeneration tower condenser to obtain xylene and absorbent; S5: passing xylene into a condenser for condensation treatment at a condensation treatment temperature of -5°C to 40°C to obtain liquefied xylene, passing the liquefied xylene into a vacuum buffer tank, using a product pump to pass the liquefied xylene in the vacuum buffer tank into a receiving tank, and at the same time, using a vacuum pump to pass the xylene that is not completely liquefied in the vacuum buffer tank into a vacuum pump tail cooler and then into a vacuum pump tail gas recooler for re-condensation treatment at a condensation treatment temperature of -5°C to 40°C to obtain liquefied xylene, which is passed into a receiving tank; S6: Use a product delivery pump to deliver the liquefied xylene in the receiving tank to the outside through a product delivery pipeline for subsequent production; Recycling absorbent: S7: the absorbent obtained in S4 is reintroduced into the heat exchanger, and the absorbent exchanges heat with the absorbent rich liquid for cooling; S8: Use an absorbent circulation pump to pass the absorbent after heat exchange and cooling in the heat exchanger into a recooler for further cooling treatment. The cooling temperature is -10℃~30℃, and then pass it into the absorption tower for recycling.

[0012] Preferably, in S2, the absorbent comprises 10-60% by mass of alkyl benzoate, 1-20% by mass of fatty alcohol polyoxyethylene ether and 20-89% by mass of long carbon chain amide.

[0013] The present invention uses an absorbent to absorb xylene in xylene waste gas, uses steam heating for analysis and recovers it through condensation, and arranges a vacuum pump tail cooler and a vacuum pump tail cooler recooler to re-condense the xylene that is not completely liquefied, thereby ensuring a high recovery efficiency of the xylene. The obtained xylene product has high purity and can be directly used in subsequent industrial production.

[0014] The device of the present invention uses a circulation system, and there is no need to replace the absorbent when the device is working, saving production costs. In the absorption tower, the absorbent captures and absorbs the xylene waste gas to obtain an absorbent rich liquid. The absorbent rich liquid is preliminarily heated by a heat exchanger and passed into a regeneration tower for heating and analysis, from which xylene and the absorbent are separated. The absorbent is recycled and passed into the heat exchanger again to exchange heat with the absorbent rich liquid. In this process, the absorbent not only helps to heat the absorbent rich liquid, but also cools down through its own heat exchange, thereby reducing the cooling time and energy consumption of the absorbent in the recooler. At the same time, by first heating the absorbent rich liquid in the heat exchanger and then passing it into the regeneration tower, the time and energy required for the heating process in the regeneration tower can be significantly reduced, thereby improving the processing efficiency of the entire device and reducing energy consumption. The steam in the falling film evaporator is also recycled to reduce the time required to reheat the steam and improve the processing efficiency.

[0015] The absorbent components used in the present invention include alkyl benzoate, fatty alcohol polyoxyethylene ether and long carbon chain amide, which have the characteristics of low viscosity, high boiling point, low freezing point and high miscibility with xylene. The components of the device of the present invention are reasonably arranged and closely matched, and can realize stable and continuous treatment of high-concentration xylene waste gas, ensuring that the exhaust gas obtained after the xylene waste gas is absorbed by the absorbent in the absorption tower can meet the emission standards. After simple treatment, xylene can be efficiently and high-quality recovered, with high economic benefits and basically no secondary pollution, and is suitable for industrial production.

[0016] The beneficial effects of the present invention are: The present invention uses an absorbent to absorb xylene in xylene waste gas, uses steam heating for analysis and recovers it through condensation, and arranges a vacuum pump tail cooler and a vacuum pump tail cooler recooler to re-condense the xylene that is not completely liquefied, thereby ensuring a high recovery efficiency of the xylene. The obtained xylene product has high purity and can be directly used in subsequent industrial production.

[0017] The device of the present invention uses a circulation system, and there is no need to replace the absorbent when the device is working, saving production costs. The absorbent not only helps to heat the absorbent rich liquid, but also cools down through its own heat exchange, thereby reducing the cooling time and energy consumption of the absorbent in the recooler. At the same time, by first heating the absorbent rich liquid in the heat exchanger and then passing it into the regeneration tower, the time and energy required for the heating process in the regeneration tower can be significantly reduced, thereby improving the processing efficiency of the entire device and reducing energy consumption. The steam in the falling film evaporator is also recycled to reduce the time required to reheat the steam and improve the processing efficiency.

[0018] The absorbent components used in the present invention include alkyl benzoate, fatty alcohol polyoxyethylene ether and long carbon chain amide, which have the characteristics of low viscosity, high boiling point, low freezing point and high miscibility with xylene. The components of the device of the present invention are reasonably arranged and closely matched, and can realize stable and continuous treatment of high-concentration xylene waste gas, ensuring that the exhaust gas obtained after the xylene waste gas is absorbed by the absorbent in the absorption tower can meet the emission standards. After simple treatment, xylene can be efficiently and high-quality recovered, with high economic benefits and basically no secondary pollution, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0020] Figure 1 It is a schematic diagram of the processing flow of the device of the present invention; Description of main component symbols: In the figure: 1. Precooler; 2. Absorption tower; 3. Heat exchanger; 4. Recooler; 5. Regeneration tower; 6. Condenser; 7. Vacuum buffer tank; 8. Vacuum pump tail cooler; 9. Vacuum pump tail gas recooler; 10. Receiving tank; 11. Falling film evaporator; P10101, rich liquid pump; P10102, absorbent circulation pump; P10103, evaporation circulation pump; P10104, product pump; P10105, product delivery pump; E10105, regeneration tower condenser; X10101, vacuum pump. DETAILED DESCRIPTION

[0021] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are clearly and completely described below in combination with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present application, it should be understood that the orientation or position relationship indicated by "inside" or "outside" is based on the orientation or position described in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, specific orientation structure and operation, and therefore cannot be understood as a limitation on the present application.

[0023] Example 1 Reference Figure 1The present invention discloses a system for recovering xylene from high-concentration xylene waste gas, comprising a precooler 1, an absorption system, a regeneration system and a receiving tank 10, wherein the absorption system is composed of an absorption tower 2, a heat exchanger 3 and a recooler 4, wherein the precooler 1 is connected to the lower inlet pipeline of the absorption tower 2, a booster fan is arranged in the pipeline connecting the precooler 1 and the absorption tower 2, the bottom outlet of the absorption tower 2 is connected to the first inlet pipeline of the heat exchanger 3, and a rich liquid pump P10101 is arranged on the pipeline connecting the absorption tower 2 and the heat exchanger 3; Reference Figure 1 The regeneration system includes a regeneration tower 5, a condenser 6, a vacuum buffer tank 7, a vacuum pump tail cooler 8, and a vacuum pump tail gas recooler 9. The first outlet of the heat exchanger 3 is connected to the middle inlet pipeline of the regeneration tower 5, the top outlet of the regeneration tower 5 is connected to the inlet pipeline of the condenser 6, the outlet of the condenser 6 is connected to the top inlet pipeline of the vacuum buffer tank 7, the bottom outlet of the vacuum buffer tank 7 is connected to the first inlet pipeline of the receiving tank 10, and a product pump P10104 is provided on the pipeline connecting the vacuum buffer tank 7 and the receiving tank 10; The top outlet of the vacuum buffer tank 7 is connected to the inlet pipeline of the vacuum pump tail cooler 8, and a vacuum pump X10101 is arranged on the pipeline connecting the vacuum buffer tank 7 and the vacuum pump tail cooler 8. The outlet of the vacuum pump tail cooler 8 is connected to the inlet pipeline of the vacuum pump tail gas recooler 9, and the outlet of the vacuum pump tail gas recooler 9 is connected to the second inlet pipeline of the receiving tank 10; the outlet of the receiving tank 10 is connected to the product delivery pipeline, and a product delivery pump P10105 is arranged on the product delivery pipeline; a sprayer is arranged at the top of the absorption tower 2; the top outlet of the absorption tower 2 is connected to the gas exhaust pipeline.

[0024] Reference Figure 1 The first bottom outlet of the regeneration tower 5 is connected to the second inlet pipeline of the heat exchanger 3, the second outlet of the heat exchanger 3 is connected to the inlet pipeline of the subcooler 4, the pipeline connecting the heat exchanger 3 and the subcooler 4 is provided with an absorbent circulation pump P10102, and the outlet of the subcooler 4 is connected to the upper inlet pipeline of the absorption tower 2.

[0025] Reference Figure 1 A regeneration tower condenser E10105 is arranged on the upper part of one side of the regeneration tower 5, and a falling film evaporator 11 is arranged on the other side of the regeneration tower 5. A reflux pipeline is arranged on the side wall of the falling film evaporator 11, one end of the reflux pipeline is connected to the upper inlet of the falling film evaporator 11, and the other end of the reflux pipeline is connected to the second bottom outlet of the regeneration tower 5. An evaporation circulation pump P10103 is arranged on the reflux pipeline; an external feed inlet is opened at the upper part of the falling film evaporator 11, and a discharge port is opened at the lower part of the falling film evaporator 11.

[0026] Example 2 The absorbent used in this embodiment is composed of 30% by mass of alkyl benzoate, 10% by mass of fatty alcohol polyoxyethylene alcohol and 60% by mass of long carbon chain amide.

[0027] A method for recovering xylene from high-concentration xylene waste gas, using the system in Example 1, comprises the following steps: Xylene recovery from xylene waste gas: xylene waste gas volume 600 m³ / h, xylene content 100000~150000ppm; S1: Pass the xylene waste gas into the precooler 1 for preliminary condensation treatment, and the condensation treatment temperature is 20°C; S2: The xylene waste gas after the preliminary condensation treatment is introduced into the absorption tower 2 through the booster fan, and the sprayer at the top of the absorption tower 2 sprays the absorbent down, and the absorbent captures and absorbs the xylene waste gas after the preliminary condensation treatment and falls into the bottom of the absorption tower 2 to obtain the absorbent rich liquid and exhaust gas, and the exhaust gas is discharged through the gas exhaust pipeline; S3: Use the rich liquid pump P10101 to pass the absorbent rich liquid from the bottom of the absorption tower 2 into the heat exchanger 3 for preheating, and then pass it into the regeneration tower 5; S4: The regeneration tower 5 uses the steam generated by the falling film evaporator 11 as a heat source to further heat the preheated absorbent rich liquid at a heating temperature of 120°C, and simultaneously performs a decompression treatment at a negative pressure of -70 Kpa, and decomposes xylene from the absorbent rich liquid through the regeneration tower partial condenser E10105 to obtain xylene and absorbent; S5: xylene is passed into condenser 6 for condensation treatment at a condensation treatment temperature of 10°C to obtain liquefied xylene, and the liquefied xylene is passed into vacuum buffer tank 7, and the liquefied xylene in vacuum buffer tank 7 is passed into receiving tank 10 using product pump P10104, and at the same time, the xylene that is not completely liquefied in vacuum buffer tank 7 is passed into vacuum pump tail cooler 8 and then into vacuum pump tail gas recooler 9 for re-condensation treatment at a condensation treatment temperature of 10°C to obtain liquefied xylene, which is passed into receiving tank 10; S6: Use the product delivery pump P10105 to deliver the liquefied xylene in the receiving tank 10 to the outside through the product delivery pipeline for subsequent production; Recycling absorbent: S7: the absorbent obtained in S4 is introduced back into the heat exchanger 3, and the absorbent exchanges heat with the absorbent rich liquid to reduce the temperature; S8: Use the absorbent circulation pump P10102 to pass the absorbent after heat exchange and cooling in the heat exchanger 3 into the recooler 4 for further cooling treatment. The cooling temperature is 20°C and then passed into the absorption tower 2 for recycling.

[0028] In this embodiment, the xylene in the exhaust gas is less than 40 mg / m³, the recovery efficiency of xylene is greater than 99%, and the purity is greater than 99%.

[0029] Example 3 The absorbent used in this embodiment is composed of 30% by mass of alkyl benzoate, 10% by mass of fatty alcohol polyoxyethylene alcohol and 60% by mass of long carbon chain amide.

[0030] Xylene recovery from xylene waste gas: xylene waste gas volume 1500 m³ / h, xylene content 1000~6000ppm; S1: Pass the xylene waste gas into the precooler 1 for preliminary condensation treatment, and the condensation treatment temperature is 10°C; S2: The xylene waste gas after the preliminary condensation treatment is introduced into the absorption tower 2 through the booster fan, and the sprayer at the top of the absorption tower 2 sprays the absorbent down, and the absorbent captures and absorbs the xylene waste gas after the preliminary condensation treatment and falls into the bottom of the absorption tower 2 to obtain the absorbent rich liquid and exhaust gas, and the exhaust gas is discharged through the gas exhaust pipeline; S3: Use the rich liquid pump P10101 to pass the absorbent rich liquid from the bottom of the absorption tower 2 into the heat exchanger 3 for preheating, and then pass it into the regeneration tower 5; S4: The regeneration tower 5 uses the steam generated by the falling film evaporator 11 as a heat source to further heat the preheated absorbent rich liquid at a heating temperature of 100°C, and at the same time performs a decompression treatment with a negative pressure of -70 Kpa, and decomposes xylene from the absorbent rich liquid through the regeneration tower partial condenser E10105 to obtain xylene and absorbent; S5: xylene is passed into condenser 6 for condensation treatment at a condensation treatment temperature of 5°C to obtain liquefied xylene, and the liquefied xylene is passed into vacuum buffer tank 7, and the liquefied xylene in vacuum buffer tank 7 is passed into receiving tank 10 using product pump P10104, and at the same time, the xylene that is not completely liquefied in vacuum buffer tank 7 is passed into vacuum pump tail cooler 8 and then into vacuum pump tail gas recooler 9 for re-condensation treatment at a condensation treatment temperature of 5°C to obtain liquefied xylene, which is passed into receiving tank 10; S6: Use the product delivery pump P10105 to deliver the liquefied xylene in the receiving tank 10 to the outside through the product delivery pipeline for subsequent production; Recycling absorbent: S7: the absorbent obtained in S4 is introduced back into the heat exchanger 3, and the absorbent exchanges heat with the absorbent rich liquid to reduce the temperature; S8: Use the absorbent circulation pump P10102 to pass the absorbent after heat exchange and cooling in the heat exchanger 3 into the recooler 4 for further cooling treatment. The cooling temperature is 10°C and then passed into the absorption tower 2 for recycling.

[0031] In this embodiment, the xylene in the exhaust gas is less than 30 mg / m³, the recovery efficiency of xylene is greater than 99%, and the purity is greater than 99%.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A system for recovering xylene from high-concentration xylene waste gas, characterized in that: The invention comprises a precooler (1), an absorption system, a regeneration system and a receiving tank (10), wherein the absorption system is composed of an absorption tower (2), a heat exchanger (3) and a recooler (4), wherein the precooler (1) is connected to the lower inlet pipeline of the absorption tower (2), a booster fan is arranged in the pipeline connecting the precooler (1) and the absorption tower (2), the bottom outlet of the absorption tower (2) is connected to the first inlet pipeline of the heat exchanger (3), and a rich liquid pump (P10101) is arranged in the pipeline connecting the absorption tower (2) and the heat exchanger (3); The regeneration system comprises a regeneration tower (5), a condenser (6), a vacuum buffer tank (7), a vacuum pump tail cooler (8), and a vacuum pump tail gas recooler (9); the first outlet of the heat exchanger (3) is connected to the middle inlet pipeline of the regeneration tower (5); the top outlet of the regeneration tower (5) is connected to the inlet pipeline of the condenser (6); the outlet of the condenser (6) is connected to the top inlet pipeline of the vacuum buffer tank (7); the bottom outlet of the vacuum buffer tank (7) is connected to the first inlet pipeline of the receiving tank (10); and a product pump (P10104) is provided on the pipeline connecting the vacuum buffer tank (7) and the receiving tank (10); The top outlet of the vacuum buffer tank (7) is connected to the inlet pipeline of the vacuum pump tail cooler (8); a vacuum pump (X10101) is provided on the pipeline connecting the vacuum buffer tank (7) and the vacuum pump tail cooler (8); the outlet of the vacuum pump tail cooler (8) is connected to the inlet pipeline of the vacuum pump tail gas recooler (9); and the outlet of the vacuum pump tail gas recooler (9) is connected to the second inlet pipeline of the receiving tank (10).

2. A system for recovering xylene from high-concentration xylene waste gas according to claim 1, characterized in that: The first bottom outlet of the regeneration tower (5) is connected to the second inlet pipeline of the heat exchanger (3), the second outlet of the heat exchanger (3) is connected to the inlet pipeline of the subcooler (4), an absorbent circulation pump (P10102) is provided on the pipeline connecting the heat exchanger (3) and the subcooler (4), and the outlet of the subcooler (4) is connected to the upper inlet pipeline of the absorption tower (2).

3. A system for recovering xylene from high-concentration xylene waste gas according to claim 2, characterized in that: A regeneration tower condenser (E10105) is arranged on the upper part of one side of the regeneration tower (5), and a falling film evaporator (11) is arranged on the other side of the regeneration tower (5). A reflux pipeline is arranged on the side wall of the falling film evaporator (11), one end of the reflux pipeline is connected to the upper inlet of the falling film evaporator (11), and the other end of the reflux pipeline is connected to the second bottom outlet of the regeneration tower (5), and an evaporation circulation pump (P10103) is arranged on the reflux pipeline.

4. A system for recovering xylene from high-concentration xylene waste gas according to claim 3, characterized in that: An external feed inlet is provided at the upper portion of the falling film evaporator (11), and a discharge port is provided at the lower portion of the falling film evaporator (11).

5. The system for recovering xylene from high-concentration xylene waste gas according to claim 1, characterized in that: The outlet of the receiving tank (10) is connected to a product delivery pipeline, and a product delivery pump (P10105) is provided on the product delivery pipeline.

6. A system for recovering xylene from high-concentration xylene waste gas according to claim 1, characterized in that: A sprayer is provided at the top of the absorption tower (2).

7. The system for recovering xylene from high-concentration xylene waste gas according to claim 1, characterized in that: The top outlet of the absorption tower (2) is connected to a gas exhaust pipeline.

8. A method for recovering xylene from high-concentration xylene waste gas, based on a system for recovering xylene from high-concentration xylene waste gas according to any one of claims 1 to 7, characterized in that: The steps include: Xylene recovery from xylene waste gas: S1: Passing the xylene waste gas into the precooler (1) for preliminary condensation treatment, the condensation treatment temperature is 10~30℃; S2: The xylene waste gas after the preliminary condensation treatment is introduced into the absorption tower (2) through a booster fan, and the sprayer at the top of the absorption tower (2) sprays the absorbent down, and the absorbent captures and absorbs the xylene waste gas after the preliminary condensation treatment and falls into the bottom of the absorption tower (2), thereby obtaining an absorbent-rich liquid and exhaust gas, and the exhaust gas is discharged through a gas exhaust pipeline; S3: Use a rich liquid pump (P10101) to pass the absorbent rich liquid from the bottom of the absorption tower (2) into the heat exchanger (3) for preheating, and then pass it into the regeneration tower (5); S4: The regeneration tower (5) uses the steam generated by the falling film evaporator (11) as a heat source to further heat the preheated absorbent rich liquid at a heating temperature of 80°C to 140°C. At the same time, a pressure reduction treatment is performed at a negative pressure of -50 Kpa to -90 Kpa. Xylene is separated from the absorbent rich liquid through the regeneration tower condenser (E10105) to obtain xylene and absorbent; S5: xylene is passed into a condenser (6) for condensation treatment at a condensation treatment temperature of -5°C to 40°C to obtain liquefied xylene, and the liquefied xylene is passed into a vacuum buffer tank (7). The liquefied xylene in the vacuum buffer tank (7) is passed into a receiving tank (10) using a product pump (P10104). At the same time, the xylene that has not been completely liquefied in the vacuum buffer tank (7) is passed into a vacuum pump tail cooler (8) and then into a vacuum pump tail gas recooler (9) for re-condensation treatment at a condensation treatment temperature of -5°C to 40°C to obtain liquefied xylene, which is passed into a receiving tank (10); S6: using a product delivery pump (P10105) to deliver the liquefied xylene in the receiving tank (10) to the outside through a product delivery pipeline for subsequent production; Recycling absorbent: S7: the absorbent obtained in S4 is reintroduced into the heat exchanger (3), where the absorbent exchanges heat with the absorbent rich liquid for cooling; S8: Use the absorbent circulation pump (P10102) to pass the absorbent after heat exchange and cooling in the heat exchanger (3) into the recooler (4) for further cooling treatment. The cooling temperature is -10°C~30°C, and then pass it into the absorption tower (2) for recycling.

9. A method for recovering xylene from high-concentration xylene waste gas according to claim 8, characterized in that: In the S2, the absorbent includes 10-60% by mass of alkyl benzoate, 1-20% by mass of fatty alcohol polyoxyethylene ether and 20-89% by mass of long carbon chain amide.

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