Recovery device for BDO in heavy-component hazardous waste in BDO production

Abstract

The utility model provides a device for recovering BDO in heavy-component hazardous waste in BDO production, which comprises a pretreatment tank, the pretreatment tank is connected with a film evaporator, the film evaporator is respectively connected with a light impurity recovery device and a short-range evaporator, the short-range evaporator is respectively connected with a hazardous waste intermediate tank and a light component storage tank, the light component storage tank is connected with a light component removal tower, and the light component removal tower is connected with the film evaporator. The light component removal tower is respectively connected with a light component collection device and a product tower, the top of the product tower is connected with a BDO collection device, and a tower kettle of the product tower is connected with a heavy component impurity extraction pipeline; the method is divided into three stages: a pretreatment stage for removing light component impurities in heavy components; the short-range evaporation stage is used for removing heavy component impurities in the heavy components; the BDO recovery stage is used for recovering different effective components in a classified manner; valuable products in the BDO heavy component hazardous waste can be recycled, the profit rate of an enterprise is increased, the hazardous waste treatment amount of external committee of the enterprise can be reduced, and the production cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of BDO recovery, and in particular to a BDO recovery device in heavy component hazardous waste of BDO production. Background Art

[0002] BDO (full name: Butane-1,4-diol, Chinese name: 1,4-butanediol) has the molecular formula of C4H10O2. It is a colorless or light yellow oily liquid and is an important chemical raw material.

[0003] The current domestic BDO production is about 2.6 million tons / year. The BDO refining tower kettle in the refining section of the BDO production unit will produce some BDO heavy component materials. Most domestic manufacturers now outsource this part of the material as hazardous waste (HW11216-131-11). This treatment method has caused an increase in the production cost of BDO. In addition, this part of the BDO heavy component hazardous waste also contains nearly 20% of BDO products that have not been recycled, resulting in a great waste of resources. There is currently no better recycling method.

[0004] After searching, the applicant retrieved prior art 1: a system for recovering BDO from BDO distillation condensate with application number: 201620605579.9, which discloses a technical solution, including a vacuum condenser, a sewage treatment tank, a storage tank, a delivery pump and a concentration tower. Through process optimization design, a pipeline is added at the bottom of the vacuum condenser to discharge the condensate into the storage tank, and finally pumped into the concentration tower through the delivery pump. The light component impurities are removed by the concentration tower to recover BDO, which not only recovers BDO from the waste liquid, but also relieves the sewage pressure of the sewage pipeline; the BDO recovery system from the BDO distillation condensate is reasonably designed, and the design of the vacuum condenser and the concentration tower is flexible, which can be added and improved according to the existing equipment or working conditions of the enterprise, so as to facilitate the advancement of the enterprise's technical transformation; the application mainly removes light component impurities by the concentration tower to recover BDO, but the BDO distillation condensate in the application does not contain heavy components, and there is no need to remove the heavy components.

[0005] However, the BDO heavy component material produced in the BDO refining tower kettle of the refining section of the BDO production device must be processed before it can be recycled. After searching by the applicant, no BDO recovery device or method was found in the hazardous waste.

[0006] Therefore, it is necessary to provide a new technical solution to solve the above technical problems. Utility Model Content

[0007] The present application provides a device for recovering BDO from heavy component hazardous waste produced by BDO, comprising: a pretreatment tank, the pretreatment tank is connected to a thin film evaporator, the top of the thin film evaporator is connected to a light impurity recovery device, the bottom of the thin film evaporator is connected to a short-path evaporator, the lower part of the short-path evaporator is respectively connected to a hazardous waste intermediate tank and a light component storage tank, the bottom of the light component storage tank is connected to a light component removal tower, the bottom of the light component removal tower is connected to a light component removal tower reboiler, the top of the light component removal tower is connected to a light component collecting device, the bottom of the light component removal tower is connected to a product tower, the bottom of the product tower is connected to a product tower reboiler, the top of the product tower is connected to a BDO collecting device, and the bottom of the product tower is connected to a heavy component impurity extraction pipeline.

[0008] As a preferred solution, the pretreatment tank adopts a heating treatment tank with a stirring function.

[0009] As a preferred solution, the light component impurity recovery device includes a light impurity condenser connected to the top of the thin film evaporator, the light impurity condenser is respectively connected to the non-condensable gas pipeline and the light impurity collection tank, and the bottom of the light impurity collection tank is used to extract the light component impurities.

[0010] As a preferred solution, the light component collection device includes a light component removal tower condenser, which is respectively connected to the non-condensable gas pipeline and the light component removal tower reflux tank. The bottom of the light component removal tower reflux tank is connected to the middle and upper part of the light component removal tower through a reflux pipeline, and the reflux pipeline is connected to the light component extraction pipeline.

[0011] As a preferred solution, the BDO collection device includes a product tower condenser, which is respectively connected to the non-condensable gas pipeline and the product tower reflux tank, the bottom of the product tower reflux tank is connected to the middle and upper part of the product tower through the product tower reflux pipeline, and the product tower reflux pipeline is connected to the BDO production pipeline.

[0012] As a preferred solution, the operating temperature of the pretreatment tank is 50°C-100°C, and the operating pressure is 0-50Kpa(A).

[0013] As a preferred solution, the operating temperature of the thin film evaporator is 80°C-130°C, and the operating pressure is 0-10Kpa(A).

[0014] As a preferred solution, the operating temperature of the short-path evaporator is 100°C-150°C, and the operating pressure is 0-10Kpa(A).

[0015] As a preferred solution, the operating temperature of the lightness removal tower is 80°C-180°C, and the operating pressure is 0-10Kpa(A).

[0016] As a preferred solution, the operating temperature of the product tower is 140°C-200°C, and the operating pressure is 0-10Kpa(A).

[0017] This application is mainly divided into three stages: a pretreatment stage for removing light component impurities from the heavy component; a short-path evaporation stage for removing heavy component impurities from the heavy component; and a BDO recovery stage for classifying and recovering different effective components. Through the above three stages, this application can realize the recovery of valuable products from BDO heavy component hazardous waste, increase corporate profit margins, and reduce the amount of hazardous waste treatment outsourced by the company, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of this application;

[0019] 1. Pretreatment device; 2. Short-path evaporation system; 3. BDO recovery system; 4. Pretreatment tank; 5. Material pipeline; 6. Feed pump; 7. Bottom pipeline of pretreatment tank; 8. Thin film evaporator; 9. Discharge pump of pretreatment tank; 10. Light impurity condenser; 11. Non-condensable gas pipeline; 12. Light impurity collection tank; 13. Vacuum pump; 14. Short-path evaporator; 15. Bottom pipeline of thin film evaporator; 16. Transfer pump; 17. Hazardous waste intermediate tank; 18. Light component storage tank; 19. Light component removal tower; 20. Light component storage tank pipeline; 21. Return 1. Feed pump of the collection system; 22. Reboiler of the light-removal tower; 23. Bottom pipeline of the light-removal tower; 24. Product tower; 25. Bottom liquid pump of the light-removal tower; 26. Reboiler of the product tower; 27. Heavy component impurity extraction pipeline; 28. Condenser of the light-removal tower; 29. ​​Reflux tank of the light-removal tower; 30. Reflux pipeline; 31. Reflux pump of the light-removal tower; 32. Light component extraction pipeline; 33. Condenser of the product tower; 34. Reflux tank of the product tower; 35. Reflux pipeline of the product tower; 36. Reflux pump of the product tower; 37. BDO extraction pipeline; 38. Bottom liquid pump of the product tower. DETAILED DESCRIPTION

[0020] The following is combined with Figure 1 The specific implementation of the utility model is described in detail. It should be noted that the specific implementation described here is only used to illustrate and explain the utility model, and is not used to limit the utility model.

[0021] Embodiment 1:

[0022] The present embodiment provides a BDO recovery device in the heavy component hazardous waste of BDO production, comprising: a pretreatment device 1, the pretreatment device 1 is used to remove light component impurities in the heavy component; a short-path evaporation system 2, connected to the pretreatment device 1, and used to remove heavy component impurities in the heavy component; a BDO recovery system 3, connected to the short-path evaporation system 2, and used to classify and recover different effective components, wherein the pretreatment device 1 includes a pretreatment tank 4, the operating temperature of the pretreatment tank 4 is 50° C.-100° C., the operating pressure is 0-50Kpa (A), the pretreatment tank 4 introduces raw materials through a material pipeline 5, the material pipeline 5 is provided with a feed pump 6, and the pretreatment tank 4 adopts a heating device with a stirring function. The pretreatment tank increases the fluidity of the material so that the material has better film-forming performance in the next device. The bottom of the pretreatment tank 4 is connected to the middle and upper part of the thin film evaporator 8 through the pretreatment tank bottom pipeline 7. The operating temperature of the thin film evaporator 8 is 80°C-130°C, and the operating pressure is 0-10Kpa (A); a pretreatment tank discharge pump 9 is arranged on the pretreatment tank bottom pipeline 7, and the top of the thin film evaporator 8 is connected to the light impurity recovery device. Specifically, the light component impurity recovery device includes a light impurity condenser 10 connected to the top of the thin film evaporator 8, and the light impurity condenser 10 is respectively connected to the non-condensable gas pipeline 11 and the light impurity collection tank 12, and the non-condensable gas pipeline 11 is provided with a vacuum pump 13; the light impurity collection tank 1 2 is used to extract light component impurities; the bottom of the thin film evaporator 8 is connected to the short-path evaporation system, the short-path evaporation system includes a short-path evaporator 14 connected to the bottom of the thin film evaporator 8, the bottom of the thin film evaporator 14 is connected to the upper part of the short-path evaporator 14 through the thin film evaporator bottom pipeline 15, the operating temperature of the short-path evaporator 14 is 100°C-150°C, and the operating pressure is 0-10Kpa(A); a delivery pump 16 is provided on the thin film evaporator bottom pipeline 15, the lower part of the short-path evaporator 14 is respectively connected to the hazardous waste intermediate tank 17 and the light component storage tank 18, the bottom of the hazardous waste intermediate tank 17 is used to extract hazardous waste liquid, and the bottom of the light component storage tank 18 is connected to the BDO recovery system. The BDO recovery system includes a light-removing tower 19 connected to the bottom of a light component storage tank 18, the operating temperature of the light-removing tower 19 is 80°C-180°C, and the operating pressure is 0-10Kpa(A); the bottom of the light component storage tank 18 is connected to the middle and upper part of the light-removing tower 19 through a light component storage tank pipeline 20, and a recovery system feed pump 21 is provided on the light component storage tank pipeline 20, the bottom of the light-removing tower 19 is connected to a light-removing tower reboiler 22, and the top of the light-removing tower 19 is connected to a light component collecting device, and the bottom of the light-removing tower 19 is connected to the middle and upper part of a product tower 24 through a light-removing tower bottom pipeline 23, and the operating temperature of the product tower 24 is 140°C-200°C, and the operating pressure is 0-10Kpa(A);A de-light tower bottom liquid pump 25 is provided on the bottom pipeline 23 of the de-light tower, a product tower reboiler 26 is connected to the bottom of the product tower 24, a BDO collecting device is connected to the top of the product tower 24, a heavy component impurity extraction pipeline 27 is connected to the bottom of the product tower 24, a product tower bottom liquid pump 38 is provided on the heavy component impurity extraction pipeline 27, and the heavy component impurity extraction pipeline 27 is used to extract the heavy fusel oil in the product tower 24; the de-light tower reboiler 22 and the product tower reboiler 26 are heated by 250°C heat transfer oil or high-pressure steam. ;

[0023] The main function of the pretreatment device 1 is to remove light impurities from the heavy components. The system is operated under negative pressure. The process of the pretreatment device 1 is as follows: the BDO heavy component material is sent to the pretreatment tank 4 through the feed pump 6, and is preheated by the pretreatment tank 4 with stirring to increase fluidity, so that the material has better film-forming performance in the next device. The preheated material is sent to the thin film evaporator 8 through the pretreatment tank discharge pump 9. In the thin film evaporator 8, the material is evenly filmed, and the light component impurities are evaporated by steam heating and recovered by the light component impurity recovery device. BDO and the heavy component are sent to the short-path evaporation system through the bottom delivery pump 16 of the thin film evaporator 8;

[0024] The main function of the short-path evaporation system is to remove heavy component impurities such as tar. The system adopts negative pressure operation. The process of the short-path evaporation system is as follows: BDO and heavy components are sent to the short-path evaporator 14 for evaporation through the flow rate controlled by the delivery pump 16 at the bottom of the thin film evaporator 8. In the short-path evaporator 14, the light components and BDO are heated by the short-path evaporator 14 and move to the condenser surface. After being condensed, they flow into the light component storage tank 18 by gravity and are extracted through the BDO recovery system 3. The heavy components flow into the hazardous waste intermediate tank 17 by gravity.

[0025] The main function of the BDO recovery system 3 is to classify and recover different effective components. The system adopts negative pressure operation, and the main process is: BDO and light components from the light component storage tank 18 of the short-path evaporation system 2 are sent to the light component removal tower 19 through the recovery system feed pump 21. In the light component removal tower 19, the light component is evaporated, and then a part of it is returned to the light component removal tower 19 as reflux through the light component collection device, and a part of it is extracted as a light component product, such as being sent to the light component product storage tank, etc. The bottom liquid of the light component removal tower 19 is extracted to the product tower 24 through the light component removal tower bottom pump 25, and BDO with a content of ≥97% is extracted at the top of the product tower 24, and the remaining heavy component impurities are extracted at the bottom of the product tower 24 through the heavy component impurity extraction pipeline 27; the three-stage process in this embodiment can effectively recover BDO and other effective components from BDO heavy component hazardous waste.

[0026] Embodiment 2:

[0027] This embodiment describes the light component collecting device and the BDO collecting device, specifically:

[0028] The light component collecting device comprises a light component removal tower condenser 28 connected to the top of the light component removal tower 19, the light component removal tower condenser 28 is connected to the non-condensable gas pipeline 11 and the light component removal tower reflux tank 29 respectively, the non-condensable gas pipeline 11 extracts the non-condensable gas in the light component removal tower condenser 28, and the liquid phase flows into the light component removal tower reflux tank 29, the bottom of the light component removal tower reflux tank 29 is connected to the middle and upper part of the light component removal tower 19 through the reflux pipeline 30, and the reflux pipeline 30 is provided with a light component removal tower reflux pump 31, and the reflux pipeline 30 is connected to the light component extraction pipeline 32; the light component gas phase rises to the light component removal tower condenser 28 and is condensed, and then flows into the light component removal tower reflux tank 29 by gravity, and then is pressurized by the light component removal tower reflux pump 31 to control the flow rate, a part of which is returned to the light component removal tower 19 as reflux, and a part of which is discharged from the system as a light fusel oil product.

[0029] The BDO collecting device includes a product tower condenser 33 connected to the top of the product tower 24, the product tower condenser 33 is connected to the non-condensable gas pipeline 11 and the product tower reflux tank 34 respectively, the bottom of the product tower reflux tank 34 is connected to the middle and upper part of the product tower 24 through the product tower reflux pipeline 35, the product tower reflux pipeline 35 is provided with a product tower reflux pump 36, and the product tower reflux pipeline 35 is connected to the BDO production pipeline 37; light components such as BDO rise to the product tower condenser 33, the product tower condenser 33 produces non-condensable gas through the non-condensable gas pipeline 11, and the liquid phase after condensation flows into the product tower reflux tank 34 by itself, and then is pressurized by the product tower reflux pump 36, and the flow rate is controlled, a part of it is returned to the product tower 24 as reflux, and a part of it is produced as BDO product through the BDO production pipeline production system.

[0030] Embodiment three:

[0031] This embodiment provides a specific application scenario:

[0032] The raw material from the previous section is pressurized to 200Kpa(A) by the feed pump 6 and then sent to the pretreatment tank 4. The pretreatment tank 4 is heated by 500Kpa(A) saturated steam. When the material in the pretreatment tank 4 is heated to about 80°C, it is pressurized to 300Kpa(A) by the pretreatment tank discharge pump 9 and then sent to the thin film evaporator 8. The thin film evaporator 8 is heated by 500Kpa(A) saturated steam. In the thin film evaporator 8, the material is evenly filmed, and then the light component impurities (trace water, light alcohol, etc.) are evaporated out of the system by heat, condensed by the light impurity condenser 10, and then go to the light impurity collection tank 12, and then discharged from the system. The material at the bottom of the thin film evaporator 8 is transported into the short-path evaporation system 2 by the delivery pump 16. The operating temperature of the thin film evaporator 8 is 120°C and the operating pressure is 5Kpa(A);The light impurity-free material delivered by the delivery pump 16 enters the short-path evaporator 14. In the short-path evaporator 14, the mean free paths of the molecules of different substances are different, so the components are separated. When the liquid mixture flows along the heating plate and is heated, the light and heavy molecules will escape from the liquid surface and enter the gas phase. Since the free paths of light and heavy molecules are different, the molecules of different substances move different distances after escaping from the liquid surface. The light molecules reach the condensation plate and are condensed and flow into the light component storage tank 18 by gravity, while the heavy molecules cannot reach the condensation plate and are discharged along the mixed liquid to the hazardous waste intermediate tank 17. The material in the light component storage tank 18 is fed by the recovery system feed pump 2. 1 is pressurized to 400Kpa(A) and sent to BDO recovery system 3. The operating pressure of short-path evaporator 14 is 3Kpa(A) and the operating temperature is 100℃. The light components sent by recovery system feed pump 21 first enter light component removal tower 19 for light component removal treatment (mainly removing light components such as 4-methyl-1-hexanol, heptyl acetate, 3-tetrahydrofuran methanol, etc.). The light component removal tower reboiler 22 of the tower kettle of light component removal tower 19 is heated by 250℃ heat transfer oil or high-pressure steam. Under the action of tower internals, light components rise and heavy components fall. The light component gas phase rises to light component removal tower condenser 28, is condensed, and then flows into the degassing tower by itself. The light tower reflux tank 29 is then pressurized to 400Kpa (A) by the light tower reflux pump 31, and the flow rate is controlled. A part of it is returned to the light tower 19 as reflux, and a part of it is taken out of the system as a light fusel oil product through the light component production pipeline 32. The bottom material of the light tower 19 is sent to the product tower 24 through the light tower bottom liquid pump 25. The operating pressure of the light tower 19 is 10Kpa (A), the top temperature of the light tower 19 is 110°C, the bottom temperature of the light tower 19 is 170°C, the reflux ratio of the light tower 19 is 4, and the bottom liquid pump 25 pressurizes the bottom material of the light tower to 400Kpa and sends it to the middle and lower part of the product tower 24. The product tower reboiler 26 is heated by 250℃ heat transfer oil or high-pressure steam. Under the action of the tower internals, light components such as BDO rise to the product tower condenser 33, and flow into the product tower reflux tank 34 after being condensed. Then, after being pressurized to 400Kpa(A) by the product tower reflux pump 36, the flow rate is controlled, and a part of it is returned to the product tower 24 as reflux, and a part of it is taken out of the system as BDO product through the BDO production pipeline 37. The operating pressure of the product tower 24 is 10Kpa(A), the top temperature of the product tower 24 is 150℃, the bottom temperature of the product tower 24 is 200℃, and the reflux ratio of the product tower 24 is 2. ;

[0033] In this embodiment, more than 99.5% of BDO products can be produced. The operating temperature may vary slightly depending on the composition of the raw materials.

[0034] Embodiment 4:

[0035] This embodiment provides another specific application scenario:

[0036] The difference from the third embodiment is that in this embodiment, only the pretreatment stage and the short-path evaporation stage are involved in the work, and the BDO recovery stage is not involved. This embodiment can produce a low-concentration BDO product, that is, not only can the concentration be adjusted by adjusting the parameters of each device, but also the purity of the BDO product can be adjusted by controlling whether the BDO recovery stage is involved in the work.

[0037] Specifically, the raw material from the previous section is pressurized to 200Kpa (A) by the feed pump 6 and then sent to the pretreatment tank 4, which is heated by 500Kpa (A) saturated steam. When the material in the pretreatment tank 4 is heated to about 80°C, it is pressurized to 300Kpa (A) by the pretreatment tank discharge pump 9 and then sent to the thin film evaporator 8, which is heated by 500Kpa (A) saturated steam. In the thin film evaporator 8, the material is evenly filmed, and then the light component impurities (trace water, light alcohol, etc.) are evaporated out of the system by heat, condensed by the light impurity condenser 10, and then sent to the light impurity collection tank 12, and then discharged from the system. The material at the bottom of the thin film evaporator 8 is transported into the short-path evaporation system 2 by the delivery pump 16. The operating temperature of the thin film evaporator 8 is 120°C, and the operating pressure is 2Kpa (A). The light impurity-free material delivered by the delivery pump 16 enters the short-path evaporator 14. In the short-path evaporator 14, the mean free paths of the molecules of different substances are different, thereby achieving the separation of the components. When the liquid mixture flows along the heating plate and is heated, the light and heavy molecules will escape from the liquid surface and enter the gas phase. Since the free paths of the light and heavy molecules are different, the molecules of different substances move different distances after escaping from the liquid surface. The light molecules reach the condensation plate and are condensed and flow into the light component storage tank 18 by gravity, while the heavy molecules cannot reach the condensation plate and are discharged along the mixed liquid to the hazardous waste intermediate tank 17. The operating pressure of the short-path evaporator 14 is 3Kpa (A), and the operating temperature is 120°C.

[0038] According to this embodiment, more than 90% of BDO products can be produced. The operating temperature may vary slightly depending on the composition of the raw materials.

[0039] This application is mainly divided into three stages: a pretreatment stage for removing light component impurities from the heavy component; a short-path evaporation stage for removing heavy component impurities from the heavy component; and a BDO recovery stage for classifying and recovering different effective components. Through the above three stages, this application can realize the recovery of valuable products from BDO heavy component hazardous waste, increase corporate profit margins, and reduce the amount of hazardous waste treatment outsourced by the company, thereby reducing production costs.

[0040] The preferred embodiments of the present application are described in detail above in conjunction with the accompanying drawings; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0041] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of this application will not be described separately.

[0042] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A device for recovering BDO from heavy waste of BDO production, characterized in that: The invention comprises a pretreatment tank (4), wherein the pretreatment tank (4) is connected to a thin film evaporator (8), the top of the thin film evaporator (8) is connected to a light impurity recovery device, the bottom of the thin film evaporator (8) is connected to a short-path evaporator (14), the lower part of the short-path evaporator (14) is respectively connected to a hazardous waste intermediate tank (17) and a light component storage tank (18), the bottom of the light component storage tank (18) is connected to a light component removal tower (19), the bottom of the light component removal tower (19) is connected to a light component removal tower reboiler (22), the top of the light component removal tower (19) is connected to a light component collection device, the light component removal tower (19) is connected to a product tower (24), the bottom of the product tower (24) is connected to a product tower reboiler (26), the top of the product tower (24) is connected to a BDO collection device, and the tower kettle of the product tower (24) is connected to a heavy component impurity extraction pipeline (27).

2. The device for recovering BDO from heavy waste of BDO production according to claim 1, characterized in that: The pretreatment tank (4) is a heating treatment tank with a stirring function.

3. The device for recovering BDO from heavy waste of BDO production according to claim 1, characterized in that: The light impurity recovery device comprises a light impurity condenser (10) connected to the top of the thin film evaporator (8), the light impurity condenser (10) is respectively connected to the non-condensable gas pipeline (11) and the light impurity collection tank (12), and the bottom of the light impurity collection tank (12) is used to extract the light impurities.

4. The device for recovering BDO from heavy waste of BDO production according to claim 1, characterized in that: The light component collecting device comprises a light component removal tower condenser (28), the light component removal tower condenser (28) is respectively connected to the non-condensable gas pipeline (11) and the light component removal tower reflux tank (29), the bottom of the light component removal tower reflux tank (29) is connected to the middle and upper part of the light component removal tower (19) through a reflux pipeline (30), and the reflux pipeline (30) is connected to the light component extraction pipeline (32).

5. The device for recovering BDO from heavy waste of BDO production according to claim 1, characterized in that: The BDO collecting device comprises a product tower condenser (33), the product tower condenser (33) is connected to the non-condensable gas pipeline (11) and the product tower reflux tank (34) respectively, the bottom of the product tower reflux tank (34) is connected to the middle and upper part of the product tower (24) through the product tower reflux pipeline (35), and the product tower reflux pipeline (35) is connected to the BDO extraction pipeline (37).

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