Tar separation system and recovery method for carbonylation synthesis of acetic anhydride
By using equipment such as a tar tower in the acetic anhydride production process to react methanol with tar to produce methyl acetate, the problems of material waste and equipment blockage caused by tar are solved, and efficient recovery and stable production of acetic anhydride are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-03
AI Technical Summary
The generation of tar during the production of acetic anhydride increases the viscosity of the material, affecting production continuity and increasing costs, while also wasting effective components.
The separation system consists of a tar tower, condenser, gas-liquid separator, liquid seal tank, and defective product tank. Methanol is introduced to react with acetic anhydride in the tar to produce methyl acetate and acetic acid, which are then recovered as raw materials. Acetic acid is used as a solvent to dilute the tar, reduce the polymerization of high-boiling-point substances, and prevent equipment blockage.
Effective recovery of methyl acetate as a raw material reduces the waste of effective components, improves the recovery rate of acetic anhydride, reduces bottom emissions, ensures operational stability and safety, and saves production costs.
Smart Images
Figure CN121775768A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical production technology, and in particular to a carbonylation synthesis acetic anhydride tar separation system and recovery method. Background Technology
[0002] Acetic anhydride can be produced using the low-pressure carbonyl synthesis method of methyl acetate. This method uses methyl acetate as raw material, a rhodium-based catalyst, iodomethane as a co-catalyst, and lithium salt as a catalyst promoter. The temperature inside the reactor is 182-190℃, the pressure is 3.6-4.0 MPa, and CO gas is introduced to carry out a gas-liquid phase reaction to produce acetic anhydride. However, the acetic anhydride production process generates a large amount of tar, leading to increased material viscosity and restricting full-load, long-cycle production. The carbonyl synthesis of acetic anhydride can be divided into two main systems: a reaction system, which includes a reactor and a flash evaporator; and a separation system, also known as a purification system, which includes a light-light residue removal tower, an acetic acid tower, and an acetic anhydride tower. Tar is generated in both systems, containing acetic anhydride, EDA, impurities, etc. The tar produced by the reaction system is called reaction tar, and the tar produced by the separation system is called separation tar, such as... Figure 2 As shown.
[0003] The reasons for tar generation in the refining system include: First, acetaldehyde derivatives exist in the reactor system in the form of substances such as ethylidene diacetate, and a certain amount will inevitably be carried into the light tar removal tower, through the acetic acid tower, and finally into the acetic anhydride tower bottom, becoming a component in the tar separation process. Second, acetic acid and acetic anhydride have boiling points of 118℃ and 139℃, respectively. During the separation of acetic acid and the distillation of acetic anhydride, the tower bottom temperature will be higher than the boiling points of both. Under high temperature conditions, tar tends to continuously increase in the tower bottom, severely affecting mass and heat transfer, leading to reboiler blockage, and ultimately requiring shutdown and cleaning. During production, tar and other substances need to be continuously collected from the bottom of the acetic anhydride tower each shift for incineration, increasing production costs and causing environmental pollution. For a 100,000-ton / year acetic anhydride production system, the current discharge rate of tar collected from the bottom of the acetic anhydride tower is 20-40 kg / day. Based on 360 days of operation per year, the amount of waste acetic anhydride is 7,000-14,000 kg, resulting in a waste of the effective components in the material. Summary of the Invention
[0004] The purpose of this invention is to provide a carbonylation synthesis acetic anhydride tar separation system and recovery method to solve the problem of waste of effective components in the prior art.
[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: A carbonylation synthesis acetic anhydride tar separation system includes a tar tower, a condenser, a gas-liquid separator, a liquid seal tank, and a substandard product tank; The tar tower, the condenser, and the gas-liquid separator are connected in sequence. The gas flowing out of the gas-liquid separator enters the liquid seal tank, and the liquid flowing out of the gas-liquid separator enters the tar tower and the defective product tank. The liquid-sealed tank contains acetic anhydride, and the liquid-sealed tank is connected to the defective product tank; Tar and methanol are introduced into the tar tower to allow the methanol to react with the acetic anhydride in the tar.
[0006] Furthermore, the carbonylation synthesis acetic anhydride tar separation system also includes a high-boiling-point tank, through which the tar enters the tar tower.
[0007] Furthermore, the carbonylation synthesis acetic anhydride tar separation system also includes an underground tank; The tar enters the underground tank from the bottom of the high-boiling-point tank and then enters the tar tower.
[0008] Furthermore, the carbonylation synthesis acetic anhydride tar separation system also includes an underground tank pump, which is located between the underground tank and the tar tower to deliver tar into the tar tower.
[0009] Furthermore, the carbonylation synthesis acetic anhydride tar separation system also includes a defective product pump, which is used to extract liquid from the defective product tank.
[0010] Furthermore, the carbonylation synthesis acetic anhydride tar separation system also includes a self-regulating valve, the inlet of which is connected to the liquid outlet of the gas-liquid separator; the two outlets of the self-regulating valve are respectively connected to the tar tower and the defective product tank. The self-regulating valve is used to control the flow rate of liquid entering the tar tower and the substandard product tank.
[0011] Furthermore, the tar tower is equipped with a heating pipe through which steam is passed to heat the methanol and acetic anhydride to react.
[0012] Furthermore, the liquid-sealed tank is provided with a gas outlet and a liquid outlet; The gas outlet is located at the top of the liquid-sealed tank, and the exhaust gas is discharged from the gas outlet and burned. After the gas flowing out of the gas-liquid separator is introduced into the liquid seal tank, the liquid level in the liquid seal tank rises. When the liquid level exceeds the height of the liquid outlet, the liquid flows into the defective product tank.
[0013] In another aspect, the present invention provides a recovery method using the above-described carbonylation synthesis acetic anhydride tar separation system, comprising the following steps: Methanol is introduced into the tar tower and heated to react with acetic anhydride to produce acetic acid and methyl acetate; Acetic anhydride, acetic acid, and methyl acetate rise to the top of the column, are condensed by the condenser, and then enter the gas-liquid separator. Part of the liquid flowing out of the gas-liquid separator flows into the tar tower, and the other part flows into the defective product tank; the gas flowing out of the gas-liquid separator enters the liquid seal tank, part of the gas dissolves in acetic anhydride, and the other part of the gas is discharged and enters the flare for combustion.
[0014] Furthermore, the temperature inside the tar tower is ≥130℃ and ≤140℃.
[0015] In summary, the technical effects achieved by this invention are as follows: The carbonylation synthesis acetic anhydride tar separation system provided by this invention includes a tar tower, a condenser, a gas-liquid separator, a liquid-sealed tank, and a defective product tank. The tar tower, condenser, and gas-liquid separator are connected in sequence. The gas flowing out of the gas-liquid separator enters the liquid-sealed tank, and the liquid flowing out of the gas-liquid separator enters the tar tower and the defective product tank. The liquid-sealed tank contains acetic anhydride and is connected to the defective product tank. Tar and methanol are introduced into the tar tower to react the methanol with the acetic anhydride in the tar.
[0016] The carbonylation synthesis acetic anhydride tar separation system provided by this invention continuously introduces methanol to react with tar. The resulting methyl acetate can be effectively recovered and reused as a raw material in the production of acetic anhydride, reducing the waste of effective components. Simultaneously, the acetic acid generated in the reaction acts as a solvent to dilute the tar, improving the recovery rate of acetic anhydride, slowing down the polymerization of high-boiling-point substances, and preventing equipment blockage. This ensures the operational stability and continuity of tar recovery and reuse while guaranteeing safety. After reaction separation, the bottom discharge from the tower is reduced from 20-40 kg per day to 2-4 kg per day; the tar content in the reduced discharge reaches approximately 99%. Based on a daily saving of 3000 yuan and assuming 360 days per year, this translates to annual cost savings of 1.08 million yuan.
[0017] In contrast, existing technologies that recover large amounts of material from tar by adding a fixed amount of water and polymerization inhibitors during evaporation generate significant heat, causing the container to expand and posing a hazard. Therefore, water can only be added intermittently, resulting in poor operational continuity and safety. Attached Figure Description
[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0019] Figure 1This is a schematic diagram of the carbonylation synthesis acetic anhydride tar separation system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a carbonyl synthesis system for producing acetic anhydride.
[0020] Icons: 100, Tar tower; 200, Condenser; 300, Gas-liquid separator; 400, Liquid seal tank; 500, Substandard product tank; 600, High boiling point tank; 700, Underground tank; 800, Underground tank pump; 900, Substandard product pump; 10, Automatic control valve. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0023] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0024] For a 100,000-ton / year acetic anhydride production system, the current daily discharge of tar from the bottom of the acetic anhydride tower is 20-40 kg. Assuming 360 days of operation per year, the amount of waste acetic anhydride is 7,000-14,000 kg, resulting in a waste of the effective components in the material.
[0025] In view of this, the present invention provides a carbonylation synthesis acetic anhydride tar separation system, comprising a tar tower 100, a condenser 200, a gas-liquid separator 300, a liquid seal tank 400, and a defective product tank 500; the tar tower 100, condenser 200, and gas-liquid separator 300 are connected in sequence, the gas flowing out of the gas-liquid separator 300 enters the liquid seal tank 400, and the liquid flowing out of the gas-liquid separator 300 enters the tar tower 100 and the defective product tank 500; the liquid seal tank 400 contains acetic anhydride, and the liquid seal tank 400 is connected to the defective product tank 500; tar and methanol are introduced into the tar tower 100 to allow the methanol to react with the acetic anhydride in the tar.
[0026] The carbonylation synthesis acetic anhydride tar separation system provided by this invention continuously introduces methanol to react with tar. The resulting methyl acetate can be effectively recovered and reused as a raw material in the production of acetic anhydride, reducing the waste of effective components. Simultaneously, the acetic acid generated in the reaction acts as a solvent to dilute the tar, improving the recovery rate of acetic anhydride, slowing down the polymerization of high-boiling-point substances, and preventing equipment blockage. This ensures the operational stability and continuity of tar recovery and reuse while guaranteeing safety. After reaction separation, the bottom discharge from the tower is reduced from 20-40 kg per day to 2-4 kg per day; the tar content in the reduced discharge reaches approximately 99%.
[0027] In contrast, existing technologies that recover large amounts of material from tar by adding a fixed amount of water and polymerization inhibitors during evaporation generate significant heat, causing the container to expand and posing a hazard. Therefore, water can only be added intermittently, resulting in poor operational continuity and safety.
[0028] The following combination Figure 1 , Figure 2 The structure and shape of the carbonylation synthesis acetic anhydride tar separation system provided in this embodiment are described in detail below: In this optional embodiment, the high-boiling-point substance tank 600, the underground tank 700, and the underground tank pump 800 are used. Tar flows sequentially through the high-boiling-point substance tank 600, the underground tank 700, and the underground tank pump 800 before entering the tar tower 100 and reacting with methanol. Specifically, the tar enters the underground tank 700 from the bottom of the high-boiling-point substance tank 600 and is then pumped into the tar tower 100 by the underground tank pump 800. The high-boiling-point substance tank 600 is used to store and process high-boiling-point substances, and has good sealing and corrosion resistance to prevent leakage. The underground tank 700 is used to temporarily store high-boiling-point substances for subsequent processing and recovery.
[0029] In an optional embodiment, the carbonylation synthesis acetic anhydride tar separation system further includes a defective product pump 900, which is used to extract liquid from the defective product tank 500 to enter... Figure 2 The production system shown is used for the production of acetic anhydride.
[0030] In this embodiment, the tar tower 100 is equipped with a heating tube, through which steam is passed to heat the methanol and acetic anhydride, causing them to react. The steam pressure ranges from 0.8 MPa to 1.5 MPa; in this embodiment, a steam pressure of 1.3 MPa is selected. Specifically, the steam flows through the heating tube and exchanges heat with the substances inside the tar tower 100 to achieve heating.
[0031] In an optional embodiment, the tar tower 100 is provided with two heating tubes to ensure uniform heating, avoid local overheating, improve heating efficiency, and prevent uneven flow caused by uneven heating.
[0032] In this embodiment, the tar tower 100 is equipped with a packing layer to increase the gas-liquid contact area, reduce the pressure drop inside the tower, improve separation efficiency, enhance adaptability, and reduce scaling and clogging. Specifically, the packing layer can be made of ceramic Raschig rings.
[0033] In an optional embodiment, at least two packing layers are included, with a heating tube disposed below the packing layers, methanol introduced from below the heating tube, and tar introduced between the two packing layers.
[0034] In this embodiment, the gas-liquid separator 300 is used to separate gas and liquid, improving processing efficiency. Specifically, the gas-liquid separator 300 is higher than the tar tower 100 so that the liquid flowing out of the gas-liquid separator 300 can flow back to the top of the tar tower 100 under gravity. The reflux liquid flowing from top to bottom comes into contact with useful materials such as methyl acetate rising in the tar tower 100 to improve the separation effect. At the same time, it can flush the tar at the top of the tar tower, control the temperature at the top of the tower, and prevent heavy tar components from moving upward.
[0035] In this embodiment, the gas flowing out of the gas-liquid separator 300 is introduced into the bottom of the liquid seal tank 400, thereby allowing the gaseous methyl acetate and acetic anhydride to fully dissolve in the liquid acetic anhydride in the tank, and causing the liquid level to rise.
[0036] Specifically, the liquid-sealed tank 400 is equipped with a gas outlet and a liquid outlet. The gas outlet is located at the top of the liquid-sealed tank 400, from which waste gas is discharged and enters the flare for combustion. After the gas flowing from the gas-liquid separator 300 enters the liquid-sealed tank 400, the liquid level inside the tank rises. When the liquid level exceeds the height of the liquid outlet, the liquid flows into the defective product tank 500. The liquid acetic anhydride stored in the liquid-sealed tank 400 facilitates the separation of useful materials in the gas phase, such as methyl acetate and acetic anhydride, from impurities, enabling further absorption and purification. Figure 1 As shown, the liquid seal tank 400 is equipped with three switch valves from top to bottom. The switch valve at the highest position is connected to the liquid outlet and is kept in the open state, while the other two switch valves are kept in the closed state.
[0037] In an optional embodiment, the carbonylation synthesis acetic anhydride tar separation system further includes a self-regulating valve 10, used to control the liquid flow rate entering the tar tower 100 and the defective product tank 500, ensuring sufficient flow back to the tar tower 100. The self-regulating valve 10 reduces the use of equipment such as centrifugal pumps, achieving high efficiency and energy saving. Specifically, the inlet of the self-regulating valve 10 is connected to the liquid outlet of the gas-liquid separator 300; the two outlets of the self-regulating valve 10 are respectively connected to the tar tower 100 and the defective product tank 500. The self-regulating valve 10 is an existing structure and will not be described in detail here.
[0038] The working process of the carbonylation synthesis acetic anhydride tar separation system provided in this embodiment is as follows: The tar from the production system is introduced into a high-boiling-point tank 600. The tar is then drained from the lowest point of the high-boiling-point tank 600 into an underground tank 700, where it enters the tar tower 100 under the action of an underground tank pump 800. Steam is introduced through two heating pipes inside the tar tower 100 to heat the temperature to 130℃~140℃, causing the methanol introduced into the tar tower 100 to react with the acetic anhydride in the tar to produce methyl acetate and acetic acid. The methanol flow rate is selected as 0.16~0.17 m³ / h. 3 / h. Methyl acetate has a boiling point of 57℃, acetic acid has a boiling point of 118℃, and acetic anhydride has a boiling point of 139℃. Therefore, under the temperature conditions inside tar tower 100, useful materials such as acetic acid and methyl acetate will rise to the top of the tower, and at the same time, some acetic anhydride will also rise to the top of the tower. The packing layer inside tar tower 100 allows methanol and acetic anhydride to react fully.
[0039] The useful materials rising in the tar tower 100, including light components such as acetic anhydride, acetic acid, and methyl acetate, are condensed in the condenser 200 after reaching the top of the tower and then enter the gas-liquid separator 300. Part of the liquid phase flowing out of the gas-liquid separator 300 enters the top of the tar tower 100 and flows downwards, thus contacting the rising useful materials inside the tower to improve the separation effect; the other part enters the defective product tank 500.
[0040] The gaseous material flowing out of the gas-liquid separator 300 enters the liquid seal tank 400 from the top of the gas-liquid separator 300 and is introduced into the bottom of the liquid seal tank 400 to ensure that the gaseous material fully contacts the liquid acetic anhydride inside the liquid seal tank 400. Acetic anhydride, methyl acetate, and other substances in the gaseous material dissolve in the liquid acetic anhydride, causing the liquid level in the liquid seal tank 400 to rise. When the liquid level rises to the liquid outlet of the liquid seal tank 400, it overflows into the defective product tank 500. Impurities in the gaseous material that are insoluble in the liquid acetic anhydride rise and enter the flare for combustion through the gas outlet.
[0041] The material in the defective product tank 500 is then pumped into the production system by the defective product pump 900 for use, thereby reducing the waste of useful materials.
[0042] In addition, the material at the bottom of the tar tower 100 is extracted and incinerated.
[0043] Based on the carbonylation synthesis acetic anhydride tar separation system provided in this embodiment, a recovery method is proposed, which uses the above-mentioned carbonylation synthesis acetic anhydride tar separation system and includes the following steps: Methanol is introduced into tar tower 100 and heated to react with acetic anhydride to produce acetic acid and methyl acetate. The temperature inside tar tower 100 is ≥130℃ and ≤140℃ to ensure the reaction proceeds.
[0044] Acetic anhydride, acetic acid, and methyl acetate rise to the top of the column, are condensed by condenser 200, and then enter gas-liquid separator 300.
[0045] Part of the liquid flowing out of the gas-liquid separator 300 flows into the tar tower 100, and the other part flows into the defective product tank 500; the gas flowing out of the gas-liquid separator 300 enters the liquid seal tank 400, part of the gas dissolves in acetic anhydride, and the other part of the gas is discharged and enters the flare for combustion.
[0046] The carbonylation synthesis acetic anhydride tar separation system provided in this embodiment has the following advantages: The tar extracted from the production system is recycled by reacting methanol with acetic anhydride to produce easily recoverable methyl acetate, minimizing the waste of acetic anhydride in the tar and achieving full utilization of the materials. Furthermore, the acetic acid in the product acts as a good solvent to dilute the tar, slowing down the continued polymerization of high-boiling-point substances, which helps improve reaction efficiency and reduce tower sticking.
[0047] Methanol is added to the lower part of the tar tower 100 to ensure a complete reaction and generate useful light components. This effectively prevents further polymerization of high-boiling-point substances, avoids equipment blockage, and ensures the operational stability and continuity of tar recovery and reuse while guaranteeing safety. After reaction and separation, the daily discharge from the bottom of the tower is reduced from 20-40 kg to 2-4 kg, with the tar content in the reduced discharge reaching approximately 99%. Based on a daily saving of 3,000 yuan and assuming 360 days a year, this translates to annual cost savings of 1.08 million yuan.
[0048] Two heating tubes are installed inside the tar tower 100 to prevent material from flowing out of the pipeline, while also making better use of energy and saving energy and reducing consumption.
[0049] The tar enters the middle section between the two packing layers, ensuring a uniform distribution of the material entering the tar tower 100 within the packing layer. This improves heat transfer efficiency, promotes uniform material flow, and prevents uneven accumulation and localized blockages in the packing layer. It also facilitates temperature control, maintaining optimal heat transfer performance.
[0050] Existing technologies for processing tar involve adding a fixed amount of water and polymerization inhibitors during evaporation to recover a large amount of material from the tar. This method generates a significant amount of heat, causing the container to expand and posing a hazard. Therefore, water can only be added intermittently, resulting in poor operational continuity and safety. In contrast, this embodiment operates within the tar tower 100, increasing operational stability and continuity, allowing for continuous methanol flow, and offering high operational safety.
[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A carbonylation synthesis acetic anhydride tar separation system, characterized in that, It includes a tar tower (100), a condenser (200), a gas-liquid separator (300), a liquid seal tank (400), and a defective product tank (500); The tar tower (100), the condenser (200), and the gas-liquid separator (300) are connected in sequence. The gas flowing out of the gas-liquid separator (300) enters the liquid seal tank (400), and the liquid flowing out of the gas-liquid separator (300) enters the tar tower (100) and the defective product tank (500). The liquid seal tank (400) contains acetic anhydride, and the liquid seal tank (400) is connected to the defective product tank (500); Tar and methanol are introduced into the tar tower (100) to allow the methanol to react with the acetic anhydride in the tar.
2. The carbonylation synthesis acetic anhydride tar separation system according to claim 1, characterized in that, It also includes a high-boiling-point tank (600), through which tar enters the tar tower (100).
3. The carbonylation synthesis acetic anhydride tar separation system according to claim 2, characterized in that, It also includes an underground trench (700); The tar enters the underground tank (700) from the bottom of the high-boiling-point tank (600) and then enters the tar tower (100).
4. The carbonylation synthesis acetic anhydride tar separation system according to claim 3, characterized in that, It also includes an underground tank pump (800), which is located between the underground tank (700) and the tar tower (100) for feeding tar into the tar tower (100).
5. The carbonylation synthesis acetic anhydride tar separation system according to claim 4, characterized in that, It also includes a defective product pump (900) for extracting liquid from the defective product tank (500).
6. The carbonylation synthesis acetic anhydride tar separation system according to claim 1, characterized in that, It also includes a self-regulating valve (10), the inlet of which is connected to the liquid outlet of the gas-liquid separator (300); the two outlets of the self-regulating valve (10) are respectively connected to the tar tower (100) and the defective product tank (500); The self-regulating valve (10) is used to control the flow rate of liquid entering the tar tower (100) and the defective product tank (500).
7. The carbonylation synthesis acetic anhydride tar separation system according to claim 1, characterized in that, The tar tower (100) is equipped with a heating tube through which steam is passed to heat the methanol and acetic anhydride to react.
8. The carbonylation synthesis acetic anhydride tar separation system according to claim 7, characterized in that, The liquid-sealed tank (400) is provided with a gas outlet and a liquid outlet; The gas outlet is located at the top of the liquid-sealed tank (400), and the exhaust gas is discharged from the gas outlet and burned. After the gas flowing out of the gas-liquid separator (300) is introduced into the liquid seal tank (400), the liquid level in the liquid seal tank (400) rises. When the liquid level exceeds the height of the liquid outlet, the liquid flows into the defective product tank (500).
9. A recycling method, characterized in that, The carbonylation synthesis acetic anhydride tar separation system according to any one of claims 1-8 includes the following steps: Methanol is introduced into the tar tower (100) and heated to react with acetic anhydride to produce acetic acid and methyl acetate; Acetic anhydride, acetic acid, and methyl acetate rise to the top of the column, are condensed by the condenser (200), and then enter the gas-liquid separator (300). Part of the liquid flowing out of the gas-liquid separator (300) flows into the tar tower (100), and the other part flows into the defective product tank (500); the gas flowing out of the gas-liquid separator (300) enters the liquid seal tank (400), part of the gas dissolves in acetic anhydride, and the other part of the gas is discharged and enters the flare for combustion.
10. The recycling method according to claim 9, characterized in that, The temperature inside the tar tower (100) is ≥130℃ and ≤140℃.