Device for recycling acetic acid and reducing wastewater discharge in vinyl acetate refining process

Abstract

The utility model discloses a device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process, and relates to the technical field of chemical industry production wastewater treatment. Comprising an acetic acid tower, a butenal finished product tank, a distillation separation system, a concentration system and an acetic acid recycling system, the acetic acid tower, the distillation separation system and the concentration system are sequentially connected through pipelines, the distillation separation system and the concentration system are respectively connected with the butenal finished product tank, and the concentration system is respectively connected with the middle part of the acetic acid tower and the kettle part of the acetic acid tower. The concentration system is connected with a dilute acetic acid spraying heat exchanger in the acetic acid recycling system, the dilute acetic acid spraying heat exchanger is connected with a dilute acetic acid spraying tank of a vinyl acetate degassing tower, the dilute acetic acid spraying tank of the vinyl acetate degassing tower is connected with a dilute acetic acid spraying pump, and the dilute acetic acid spraying pump is connected with the vinyl acetate degassing tower. The device is used for solving the problems of acetic acid resource waste and wastewater discharge pollution, and promoting the greenization and sustainable development of the vinyl acetate production process.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical production wastewater treatment, and in particular relates to a device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process. Background Art

[0002] Vinyl acetate is an important raw material widely used in the production of a series of chemical and chemical fiber products such as polyvinyl alcohol, coatings, slurries, adhesives, vinylon, films, vinyl copolymer resins, acetal resins, etc. There are currently two main synthesis methods: ethylene gas phase method and acetylene gas phase method. Among them, the acetylene method uses acetylene and acetic acid as raw materials to produce vinyl acetate. Due to its long production history and mature technology, and the abundance of limestone in northern my country, the use of calcium carbide acetylene to produce vinyl acetate still has certain economic and technical advantages.

[0003] The production of vinyl acetate by acetylene process is divided into fixed bed process and fluidized bed process. Fluidized bed has more side reaction products than fixed bed, and crotonaldehyde content is higher, which affects the activity of vinyl acetate and downstream applications. In the refining process of vinyl acetate, in order to separate the heavy component crotonaldehyde, a distillation method of water and crotonaldehyde azeotropy is usually adopted. However, in the overhead distillate aqueous phase component of the crotonaldehyde tower, a certain amount of acetic acid will be contained, and its concentration is about 30g / L. This part of acetic acid will enter the crotonaldehyde concentration tower together with crotonaldehyde, and will eventually be discharged from the tower bottom as wastewater. This wastewater discharge not only increases the environmental burden, but also wastes precious acetic acid resources.

[0004] Therefore, how to effectively reuse this part of acetic acid and reduce wastewater discharge has become an urgent problem to be solved in the current vinyl acetate production process. Utility Model Content

[0005] The utility model provides a device for recycling acetic acid and reducing wastewater discharge in the vinyl acetate refining process, which solves the problems of acetic acid resource waste and wastewater discharge pollution and promotes the green and sustainable development of the vinyl acetate production process.

[0006] The technical solutions used in this utility model are as follows:

[0007] A device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process comprises an acetic acid tower, a crotonaldehyde finished product tank, a distillation separation system, a concentration system, and an acetic acid recovery and reuse system. The acetic acid tower comprises an acetic acid tower middle part and an acetic acid tower bottom part.

[0008] The acetic acid tower is connected to the distillation separation system through a pipeline, the distillation separation system is connected to the concentration system through a pipeline, the distillation separation system and the concentration system are respectively connected to the crotonaldehyde finished product tank through pipelines, and the concentration system is respectively connected to the middle part of the acetic acid tower and the acetic acid tower kettle through pipelines.

[0009] The acetic acid recovery and reuse system includes a spray dilute acetic acid heat exchanger, a vinyl acetate degassing tower dilute acetic acid spray tank, a spray dilute acetic acid pump and a vinyl acetate degassing tower. The concentration system is connected to the spray dilute acetic acid heat exchanger via a pipeline, the spray dilute acetic acid heat exchanger is connected to the vinyl acetate degassing tower dilute acetic acid spray tank via a pipeline, the vinyl acetate degassing tower dilute acetic acid spray tank is connected to the spray dilute acetic acid pump via a pipeline, and the spray dilute acetic acid pump and the vinyl acetate degassing tower are connected via a pipeline.

[0010] Further, the distillation separation system includes a crotonaldehyde tower kettle heat exchanger, a crotonaldehyde tower, a crotonaldehyde tower reboiler, a crotonaldehyde tower kettle liquid pump, a crotonaldehyde tower condenser, a crotonaldehyde tower separator, a crotonaldehyde tower water phase distillate pump and a crotonaldehyde tower oil phase extraction pump, the crotonaldehyde tower kettle heat exchanger is connected to the acetic acid tower and the crotonaldehyde tower respectively through pipelines, the crotonaldehyde tower is connected to the crotonaldehyde tower condenser and the crotonaldehyde tower kettle liquid pump respectively through pipelines, and the crotonaldehyde tower is connected to the crotonaldehyde tower condenser and the crotonaldehyde tower kettle liquid pump respectively through pipelines. The crotonaldehyde tower reboiler is connected, the crotonaldehyde tower bottom liquid pump is connected to the crotonaldehyde tower bottom heat exchanger through a pipeline, the crotonaldehyde tower separator is connected to the crotonaldehyde tower condenser through a pipeline, the crotonaldehyde tower separator is connected to the crotonaldehyde tower water phase distillate pump and the crotonaldehyde tower oil phase production pump through pipelines, respectively, the crotonaldehyde tower oil phase production pump is connected to the crotonaldehyde finished product tank through a pipeline, and the crotonaldehyde tower water phase distillate pump is connected to the concentration system through a pipeline.

[0011] Furthermore, the concentration system includes a crotonaldehyde concentration tower, a crotonaldehyde concentration tower reboiler, a crotonaldehyde concentration tower kettle pump and a crotonaldehyde concentration tower condenser. The crotonaldehyde concentration tower is connected to the distillation separation system through a pipeline, the crotonaldehyde concentration tower is connected to the crotonaldehyde concentration tower reboiler, the crotonaldehyde concentration tower is respectively connected to the crotonaldehyde concentration tower kettle pump and the crotonaldehyde concentration tower condenser through pipelines, the lower liquid of the crotonaldehyde concentration tower condenser is connected to the crotonaldehyde finished product tank through a pipeline, and the outlet of the crotonaldehyde concentration tower kettle pump is respectively connected to the middle part of the acetic acid tower and the acetic acid tower kettle through pipelines.

[0012] Furthermore, the cooling medium of the crotonaldehyde tower condenser and the spray dilute acetic acid heat exchanger is circulating water.

[0013] Furthermore, the crotonaldehyde tower reboiler and the crotonaldehyde concentration tower reboiler are also provided with steam regulating valves.

[0014] Furthermore, the cooling medium in the dilute acetic acid spray tank of the vinyl acetate degassing tower is low-temperature water.

[0015] Furthermore, a reflux regulating pump is also provided on the pipeline connecting the crotonaldehyde tower and the crotonaldehyde tower kettle liquid pump.

[0016] Furthermore, a first delivery regulating valve is provided on the pipeline connecting the water phase distillate pump of the crotonaldehyde tower and the concentration system, a second delivery regulating valve is provided on the pipeline connecting the oil phase extraction pump of the crotonaldehyde tower and the crotonaldehyde finished product tank, and a third delivery regulating valve is provided on the pipeline connecting the crotonaldehyde tower bottom liquid pump and the crotonaldehyde tower bottom heat exchanger.

[0017] The beneficial effects of the utility model are:

[0018] 1. The utility model is provided with a concentration system, which can concentrate the wastewater containing acetic acid and send the concentrated liquid into the middle part and the kettle part of the acetic acid tower respectively, thereby realizing the effective recovery of acetic acid, improving resource utilization, reducing wastewater discharge, and reducing environmental pollution.

[0019] 2. In this utility model, the concentrated liquid is fed to the middle of the acetate column, where it forms an azeotrope with crotonaldehyde, aiding the refining process in the acetate column. A portion is added to the bottom of the acetate column as reaction water for acetic anhydride and ethylene diacetate, promoting the hydrolysis of these substances into acetic acid. The remainder is fed to the top of the vinyl acetate degassing column as spray water to scrub acetaldehyde and other impurities from the acetylene gas. Finally, the remaining liquid is fed to the vinyl acetate refining system to recover the acetic acid. The recovered acetic acid can be reused in the vinyl acetate production process, reducing raw material procurement costs, improving product quality, and ensuring the stability and reliability of downstream applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a system structure diagram of a device for recycling acetic acid and reducing wastewater discharge in the vinyl acetate refining process provided by the utility model.

[0021] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0022] 1. Crotonaldehyde tower; 2. Crotonaldehyde tower reboiler; 3. Crotonaldehyde tower bottom liquid pump; 4. Crotonaldehyde tower condenser; 5. Crotonaldehyde tower separator; 6. Crotonaldehyde tower water phase distillation pump; 7. Crotonaldehyde tower oil phase extraction pump; 8. Crotonaldehyde concentration tower; 9. Crotonaldehyde concentration tower reboiler; 10. Crotonaldehyde concentration tower bottom pump; 11. Crotonaldehyde concentration tower condenser; 12. Vinyl acetate degassing tower dilute vinegar Acid spray tank; 13. Crotonaldehyde tower kettle heat exchanger; 14. Spray dilute acetic acid heat exchanger; 15. Spray dilute acetic acid pump; 16. Acetic acid tower; 17. Crotonaldehyde finished product tank; 18. Vinyl acetate degassing tower; 19. Reflux regulating pump; 20. First delivery regulating valve; 21. Second delivery regulating valve; 22. Third delivery regulating valve; 161. Middle part of acetic acid tower; 162. Acetic acid tower kettle. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," and "connected" should be understood in a broad sense; for example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0025] like Figure 1 As shown, this embodiment provides a device for recycling acetic acid and reducing wastewater discharge in the vinyl acetate refining process, including an acetate tower 16, a crotonaldehyde finished product tank 17, a distillation separation system, a concentration system and an acetic acid recovery and reuse system, wherein the acetate tower 16 includes an acetate tower middle part 161 and an acetate tower bottom part 162, the acetate tower 16 is connected to the distillation separation system through a pipeline, the distillation separation system is connected to the concentration system through a pipeline, the distillation separation system and the concentration system are respectively connected to the crotonaldehyde finished product tank 17 through pipelines, and the concentration system is respectively connected to the acetate tower middle part 161 and the acetate tower bottom part 162 through pipelines.

[0026] Specifically, if Figure 1 As shown, the distillation separation system includes a crotonaldehyde tower kettle heat exchanger 13, a crotonaldehyde tower 1, a crotonaldehyde tower reboiler 2, a crotonaldehyde tower kettle liquid pump 3, a crotonaldehyde tower condenser 4, a crotonaldehyde tower separator 5, a crotonaldehyde tower water phase distillation pump 6 and a crotonaldehyde tower oil phase production pump 7.

[0027] The crotonaldehyde tower-tower heat exchanger 13 is connected to the acetic acid tower 16 and the crotonaldehyde tower 1 through pipelines, so that the waste liquid in the acetic acid tower 16 is sent into the crotonaldehyde tower 1 after heat exchange through the crotonaldehyde tower-tower heat exchanger 13. The crotonaldehyde tower 1 is connected to the crotonaldehyde tower reboiler 2, and the crotonaldehyde tower 1 is connected to the crotonaldehyde tower condenser 4 through a pipeline, wherein the cooling medium of the crotonaldehyde tower condenser 4 is circulating water, and the crotonaldehyde tower reboiler 2 is also provided with a steam regulating valve, which is used to adjust the steam flow rate, thereby controlling the temperature in the tower.

[0028] The butenal tower 1 is connected to the inlet of the butenal tower kettle liquid pump 3 through a pipeline, and the outlet of the butenal tower kettle liquid pump 3 is connected to the butenal tower kettle heat exchanger 13 through a pipeline, so that the butenal tower 1 kettle liquid is sent back to the acetic acid tower 16 after heat exchange. The butenal tower 1 kettle liquid is a dilute acetic acid with a content of about 94%, so it is refluxed to the acetic acid tower 16 for collection. In addition, a reflux regulating pump 19 is provided on the pipeline connecting the butenal tower 1 and the butenal tower kettle liquid pump 3, and a third discharge regulating valve 22 is provided on the pipeline connecting the butenal tower kettle liquid pump 3 and the butenal tower kettle heat exchanger 13. The reflux regulating pump 19 controls the reflux ratio of the kettle liquid of the crotonaldehyde tower 1 returning to the acetic acid tower 16 by adjusting its output flow rate, which can optimize energy consumption, reduce production costs and stabilize production operations while ensuring the separation effect; the third delivery regulating valve 22 is used to control the overall liquid level in the crotonaldehyde tower 1. By accurately controlling the overall liquid level, it can ensure that the chemical reaction in the tower is carried out at an appropriate pressure and temperature, thereby avoiding the occurrence of adverse situations such as flooding and dry tower. At the same time, the stable overall liquid level can also provide stable conditions for material circulation and heat transfer in the tower, further improving production efficiency and product quality.

[0029] The lower liquid of the crotonaldehyde tower condenser 4 is connected to the crotonaldehyde tower separator 5 through a pipeline, the water phase in the crotonaldehyde tower separator 5 is connected to the crotonaldehyde tower water phase distillate pump 6 through a pipeline, and the outlet of the crotonaldehyde tower water phase distillate pump 6 is connected to the concentration system through a pipeline to feed the crotonaldehyde concentration tower 8; the oil phase in the crotonaldehyde tower separator 5 is connected to the inlet of the crotonaldehyde tower oil phase extraction pump 7 through a pipeline, and the outlet of the crotonaldehyde tower oil phase extraction pump 7 is connected to the crotonaldehyde finished product tank 17 through a pipeline. In addition, a first delivery regulating valve 20 is provided on the pipeline connecting the crotonaldehyde tower water phase distillate pump 6 and the concentration system, and a second delivery regulating valve 21 is provided on the pipeline connecting the crotonaldehyde tower oil phase extraction pump 7 and the crotonaldehyde finished product tank 17. The first discharge regulating valve 20 is used to control the liquid level of the water phase distilled from the crotonaldehyde tower 1, which can ensure that impurities in the water phase will not accumulate too much in the tower, thereby affecting the product quality. At the same time, the stable water phase level can also provide a stable raw material flow for the subsequent separation and purification steps; the second discharge regulating valve 21 is used to control the liquid level of the oil phase distilled from the crotonaldehyde tower 1, ensuring that target products such as vinyl acetate can be efficiently separated from the tower, and reducing unnecessary energy consumption and material loss, providing reliable protection for the subsequent purification and refining steps.

[0030] Specifically, the concentration system includes a crotonaldehyde concentration tower 8, a crotonaldehyde concentration tower reboiler 9, a crotonaldehyde concentration tower kettle pump 10 and a crotonaldehyde concentration tower condenser 11. The crotonaldehyde concentration tower 8 is connected to the outlet of the water phase extraction pump of the crotonaldehyde tower 1 through a pipeline. The crotonaldehyde concentration tower 8 is connected to the crotonaldehyde concentration tower reboiler 9, steam is introduced for heating, and is controlled by a steam regulating valve. The crotonaldehyde concentration tower 8 is connected to the crotonaldehyde concentration tower condenser 11 through a pipeline for distillation and condensation. The condensation medium of the crotonaldehyde concentration tower condenser 11 uses circulating water. The lower liquid of the crotonaldehyde concentration tower condenser 11 is connected to the crotonaldehyde concentration tower through a pipeline. The finished product tank 17 and the crotonaldehyde concentration tower 8 are connected to the inlet of the crotonaldehyde concentration tower kettle pump 10 through a pipeline, and the outlet of the crotonaldehyde concentration tower kettle pump 10 is connected to the middle part 161 of the acetic acid tower and the acetic acid tower kettle part 162 through pipelines respectively. In addition to acetic acid, the feed to the acetic acid tower 16 also contains crotonaldehyde, acetic anhydride, ethylene diacetate and other high-boiling substances, so that part of the kettle liquid of the crotonaldehyde concentration tower 8 is sent to the middle part 161 of the acetic acid tower to form an azeotrope with crotonaldehyde to ensure the purpose of refining acetic acid in the acetic acid tower 16, and part of it is sent to the acetic acid tower kettle part 162 to serve as reaction water of acetic anhydride and ethylene diacetate to hydrolyze them into acetic acid.

[0031] The acetic acid recovery and reuse system includes a spray dilute acetic acid heat exchanger 14, a vinyl acetate degassing tower dilute acetic acid spray tank 12, a spray dilute acetic acid pump 15 and a vinyl acetate degassing tower 18. The outlet of the crotonaldehyde concentration tower kettle pump 10 is also connected to the inlet of the spray dilute acetic acid heat exchanger 14 through a pipeline. The outlet of the spray dilute acetic acid heat exchanger 14 is connected to the inlet of the vinyl acetate degassing tower dilute acetic acid spray tank 12 through a pipeline and is cooled by low-temperature water. The outlet of the vinyl acetate degassing tower dilute acetic acid spray tank 12 is connected to the inlet of the spray dilute acetic acid pump 15 through a pipeline. The outlet of the spray dilute acetic acid pump 15 is connected to the top of the vinyl acetate degassing tower 18 through a pipeline. The dilute acetic acid is used as a washing liquid for the vinyl acetate degassing tower 18 to wash impurities such as acetaldehyde in the acetylene gas and finally sent to the vinyl acetate refining system to recover acetic acid.

[0032] The operating principle of this utility model is:

[0033] The crotonaldehyde waste liquid distilled from the acetic acid tower 16 is sent to the crotonaldehyde tower 1 through the crotonaldehyde tower kettle heat exchanger 13, steam is introduced into the crotonaldehyde tower reboiler 2, and the temperature is controlled to 104±1°C by the steam regulating valve, so as to control the acetic acid distilled from the crotonaldehyde tower 1 to be ≤45g / l, and the top distillate is condensed through the crotonaldehyde tower condenser 4, and the lower liquid temperature of the crotonaldehyde tower condenser 4 is controlled to be 60±1°C. After condensation, it enters the crotonaldehyde tower separator 5, and the lower water phase is sent to the crotonaldehyde concentration tower 8 through the crotonaldehyde tower water phase distillation pump 6, and the upper oil phase is sent to the crotonaldehyde finished product tank 17 through the crotonaldehyde tower oil phase extraction pump 7. In addition, the first discharge regulating valve 20 controls the liquid level of the water phase distilled from the crotonaldehyde tower 1 to be 45±5, the second discharge regulating valve 21 controls the liquid level of the oil phase distilled from the crotonaldehyde tower 1 to be 30±5, and the third discharge regulating valve 22 controls the liquid level of the crotonaldehyde tower 1 to be 40±5.

[0034] The effluent from the kettle of crotonaldehyde tower 1 is sent to the kettle heat exchanger through the crotonaldehyde tower kettle liquid pump 3, and then sent to the acetic acid tower 16, and the reflux ratio is controlled to 6-8 by the reflux regulating pump 19.

[0035] The aqueous phase distilled from the top of crotonaldehyde tower 1 is fed into crotonaldehyde concentration tower 8. Steam is introduced into the reboiler 9 of the crotonaldehyde concentration tower to control the temperature in crotonaldehyde concentration tower 8 at 95±2°C. The vapor phase distilled from crotonaldehyde concentration tower 8 is directed to the crotonaldehyde tower condenser 4, and the lower liquid enters the crotonaldehyde finished product tank 17. Part of the stagnation liquid from crotonaldehyde concentration tower 8 is sent to the middle section 161 of the acetic acid tower, and part is sent to the acetic acid tower stagnation section 162. The remainder is cooled to 18°C ​​in the crotonaldehyde tower stagnation heat exchanger 13 before being sent to the dilute acetic acid spray tank 12 of the vinyl acetate degassing tower. Finally, it is sent to the top of the vinyl acetate degassing tower 18 via the dilute acetic acid spray pump 15, where it serves as the scrubbing liquid for the vinyl acetate degassing tower 18, scrubbing acetaldehyde and other impurities from the acetylene gas. The dilute acetic acid is then sent to the vinyl acetate refining system to recover the acetic acid. Specifically, in this embodiment, the output of the kettle of the crotonaldehyde concentration tower 8 is about 800 L / h, the output of the kettle of the crotonaldehyde concentration tower 8 to the kettle part 162 of the acetic acid tower is controlled to be 100 L / h, and the output of the kettle of the crotonaldehyde concentration tower 8 to the middle part 161 of the acetic acid tower is controlled to be 80 L / h.

[0036] The waste liquid in the acetic acid tower 16 is separated by the crotonaldehyde tower 1. After the aqueous phase is concentrated, part of it is refluxed to the middle part 161 of the acetic acid tower to form an azeotrope with crotonaldehyde, promoting the refining of acetic acid; part of it is sent to the bottom part 162 of the acetic acid tower as reaction water to promote the hydrolysis of acetic anhydride and ethylene diacetate to produce acetic acid. In addition, the remaining part after concentration is also passed through the acetic acid recovery and reuse system as the washing liquid of the vinyl acetate degassing tower 18 to wash the impurities in the acetylene gas, and finally sent to the vinyl acetate refining system, achieving deep recovery of acetic acid. This series of processes recovers the bottom liquid of the crotonaldehyde concentration tower 8 as the feed component of the acetic acid tower 16, and the final feed amount of the crotonaldehyde concentration tower 8 is 1m 3 / h, the acetic acid content is 30g / L, and the annual acetic acid recovery is about 30*1*24(h)*330(days) / 1000=237.6 tons. This not only significantly improves the acetic acid recovery rate, reduces wastewater discharge, and reduces environmental pollution, but also optimizes the production process, improves the product quality of vinyl acetate, and saves raw material costs, thereby improving the economic benefits of the enterprise.

[0037] The above describes an embodiment of the present invention in detail. However, the above content is only a preferred embodiment of the present invention and should not be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent application of the present invention.

Claims

1. A device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process, characterized in that: The method comprises an acetic acid tower (16), a crotonaldehyde finished product tank (17), a distillation separation system, a concentration system and an acetic acid recovery and reuse system. The acetic acid tower (16) comprises an acetic acid tower middle part (161) and an acetic acid tower bottom part (162). The acetic acid tower (16) is connected to the distillation separation system via a pipeline, the distillation separation system is connected to the concentration system via a pipeline, the distillation separation system and the concentration system are respectively connected to the crotonaldehyde finished product tank (17) via pipelines, and the concentration system is respectively connected to the acetic acid tower middle part (161) and the acetic acid tower bottom part (162) via pipelines. The acetic acid recovery and reuse system comprises a spray dilute acetic acid heat exchanger (14), a vinyl acetate degassing tower dilute acetic acid spray tank (12), a spray dilute acetic acid pump (15) and a vinyl acetate degassing tower (18); the concentration system is connected to the spray dilute acetic acid heat exchanger (14) via a pipeline; the spray dilute acetic acid heat exchanger (14) is connected to the vinyl acetate degassing tower dilute acetic acid spray tank (12) via a pipeline; the vinyl acetate degassing tower dilute acetic acid spray tank (12) is connected to the spray dilute acetic acid pump (15) via a pipeline; and the spray dilute acetic acid pump (15) and the vinyl acetate degassing tower (18) are connected via a pipeline.

2. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 1, characterized in that: The distillation separation system comprises a crotonaldehyde tower-tower heat exchanger (13), a crotonaldehyde tower (1), a crotonaldehyde tower reboiler (2), a crotonaldehyde tower bottom liquid pump (3), a crotonaldehyde tower condenser (4), a crotonaldehyde tower separator (5), a crotonaldehyde tower water phase distillation pump (6) and a crotonaldehyde tower oil phase extraction pump (7), wherein the crotonaldehyde tower-tower heat exchanger (13) is connected to the acetic acid tower (16) and the crotonaldehyde tower (1) through pipelines, respectively, the crotonaldehyde tower (1) is connected to the crotonaldehyde tower condenser (4) and the crotonaldehyde tower bottom liquid pump (3) through pipelines, and the crotonaldehyde tower ( 1) is connected to the crotonaldehyde tower reboiler (2), the crotonaldehyde tower bottom liquid pump (3) is connected to the crotonaldehyde tower bottom heat exchanger (13) through a pipeline, the crotonaldehyde tower separator (5) is connected to the crotonaldehyde tower condenser (4) through a pipeline, the crotonaldehyde tower separator (5) is connected to the crotonaldehyde tower water phase distillate pump (6) and the crotonaldehyde tower oil phase extraction pump (7) through pipelines, respectively, the crotonaldehyde tower oil phase extraction pump (7) is connected to the crotonaldehyde finished product tank (17) through a pipeline, and the crotonaldehyde tower water phase distillate pump (6) is connected to the concentration system through a pipeline.

3. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 2, characterized in that: The concentration system comprises a crotonaldehyde concentration tower (8), a crotonaldehyde concentration tower reboiler (9), a crotonaldehyde concentration tower kettle pump (10) and a crotonaldehyde concentration tower condenser (11); the crotonaldehyde concentration tower (8) is connected to the distillation separation system via a pipeline; the crotonaldehyde concentration tower (8) is connected to the crotonaldehyde concentration tower reboiler (9); the crotonaldehyde concentration tower (8) is connected to the crotonaldehyde concentration tower kettle pump (10) and the crotonaldehyde concentration tower condenser (11) via pipelines, respectively; the lower liquid of the crotonaldehyde concentration tower condenser (11) is connected to the crotonaldehyde finished product tank (17) via a pipeline; and the outlet of the crotonaldehyde concentration tower kettle pump (10) is connected to the middle part (161) and the acetic acid tower kettle part (162) via pipelines.

4. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 3, characterized in that: The cooling medium of the crotonaldehyde tower condenser (4) and the dilute acetic acid spraying heat exchanger (14) is circulating water.

5. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 3, characterized in that: The crotonaldehyde column reboiler (2) and the crotonaldehyde concentration column reboiler (9) are also provided with steam regulating valves.

6. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 1, characterized in that: The cooling medium in the dilute acetic acid spray tank (12) of the vinyl acetate degassing tower is low-temperature water.

7. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 2, characterized in that: A reflux regulating pump (19) is further provided on the pipeline connecting the crotonaldehyde tower (1) and the crotonaldehyde tower bottom liquid pump (3).

8. The device for recycling acetic acid and reducing wastewater discharge in a vinyl acetate refining process according to claim 2, characterized in that: A first delivery regulating valve (20) is provided on the pipeline connecting the crotonaldehyde tower water phase distillation pump (6) and the concentration system, a second delivery regulating valve (21) is provided on the pipeline connecting the crotonaldehyde tower oil phase extraction pump (7) and the crotonaldehyde finished product tank (17), and a third delivery regulating valve (22) is provided on the pipeline connecting the crotonaldehyde tower bottom liquid pump (3) and the crotonaldehyde tower bottom heat exchanger (13).

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