Apparatus and method for purifying phenazine mixture byproduct of nitrobenzene rti process

Abstract

The present application relates to rubber antioxidant production technical field, especially disclose a kind of nitrobenzene method RT PEST production by-product phenazine mixture purification device and method.The main equipment used in the present application has aniline recovery column, tower kettle circulating pump, crystallization kettle, centrifuge, and the purification method is that crude aniline is continuously pumped into aniline recovery column and rectified, under certain vacuum pressure, by controlling tower top temperature and reflux ratio, the content of aniline in tower kettle is controlled within a certain range, then kettle liquid is continuously taken out to crystallization kettle cooling crystallization, and finally centrifugal separation;Centrifugal filtrate is returned to RT PEST production system as condensation liquid, and high-purity solid phenazine (filter cake) is used as hazardous waste disposal.The present application can obtain high-purity phenazine solid by adjusting RT PEST rectification process aniline recovery column operation, kettle liquid direct cooling crystallization separation, and the recovery rate of RT PEST is high, the operation process is short, automatic control, continuous operation.

Description

Technical Field

[0001] This invention relates to the field of rubber antioxidant production technology, and in particular to an apparatus and method for purifying a mixture of phenazine byproducts from the RT-process production of nitrobenzene. Background Technology

[0002] RT-Pyrate, chemically known as 4-aminodiphenylamine, is an important fine chemical intermediate. Currently, it is mainly used in the rubber additives industry in China as a raw material for producing rubber antioxidants, such as antioxidants 4010NA and 4020. In recent years, due to the high profit margin of antioxidant 4020, rubber additive companies have been expanding their operations, leading to a gradual increase in the demand for RT-Pyrate.

[0003] Currently, most RT (Retardant Tolerant) paste manufacturers both domestically and internationally employ the nitrobenzene process, a green technology route. Compared to processes like the diphenylamine and aniline methods, this process offers advantages such as less waste, higher yield, and better quality. However, it generates byproducts like phenazine, azobenzene, and 2-aminodiphenylamine during the reaction, ultimately resulting in waste liquid, primarily composed of phenazine residue, being discharged during the distillation process. The distillation process often suffers from poor distillation efficiency, packing blockage, and flow deviation, causing RT paste to be carried away during the separation of aniline, phenazine, and azobenzene. This results in a high concentration of RT paste in the phenazine residue waste liquid from the distillation vessel, impacting product yield and production costs.

[0004] Currently, the main methods for recycling phenazine waste liquid in China include melt separation, solvent separation, or a combination of these methods. Melt separation is a physical separation method that utilizes the different melting points of the components in the waste liquid, but it can only perform coarse separation, requires sophisticated separation equipment, and is difficult to apply in large-scale production. Solvent separation generally uses solvents such as ethanol and methanol to separate RT-perose, azobenzene, aniline, etc., from phenazine in the waste liquid. After the phenazine waste liquid is discharged, it will solidify upon cooling. When treated with solvents, it needs to be melted again, cooled again, and separated. The treated liquid phase also needs to be distilled and reused with solvent, making the process cumbersome, requiring large amounts of solvent, and posing significant safety risks. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides an apparatus and method for purifying phenazine mixtures, a byproduct of RT-process nitrobenzene production, which features automated control, continuous operation, a short operation process, and high product recovery rate.

[0006] This invention is achieved through the following technical solution: A device for purifying a mixture of phenazine byproducts from the RT-Pyrate production process using the nitrobenzene method includes an aniline recovery tower with its inlet connected to a crude aniline tank. The device is characterized in that: the aniline inlet of the aniline recovery tower is located in the middle of the tower; the top outlet of the aniline recovery tower is connected in sequence via pipelines to a condenser, a forced reflux tank, and an aniline reflux pump; the bottom outlet of the forced reflux tank is equipped with an aniline reflux pump; the aniline reflux pump is connected in parallel via pipelines to a reflux port on the top side of the aniline recovery tower and an aniline recovery storage tank; and the forced reflux tank is connected to a vacuum system via a top pipeline. The control unit (the vapor phase extraction pipeline from the top of the aniline recovery tower is connected to the forced reflux tank after passing through the condenser; the vacuum control unit regulates the vacuum level of the aniline recovery tower by controlling the vacuum of the forced reflux tank); the bottom outlet of the aniline recovery tower is connected in parallel to the reboiler and the intermediate discharge tank of the tower bottom via pipelines; the outlet of the intermediate discharge tank of the tower bottom is connected to two parallel crystallizers via pipelines; the pipeline connecting the crystallizers is equipped with a shut-off valve interlocked with the liquid level of the crystallizers; the bottom outlet of the crystallizers is connected to a centrifuge via pipelines; the centrifuge is connected to a washing tank and a filtrate tank via pipelines.

[0007] A more preferred technical solution of the present invention is as follows: The aniline recovery tower is equipped with a liquid separation component that works in conjunction with the aniline inlet pipeline, and the outlet of the reboiler is connected to the return port on the bottom side of the aniline recovery tower via a pipeline.

[0008] The reboiler is a steam tube heat exchanger, and a steam coil is installed at the bottom of the aniline recovery tower. The reboiler and the steam coil together form a dual heating device for the aniline recovery tower.

[0009] The crystallization vessel is equipped with dual cooling devices inside and outside, and is also equipped with a cooling interlock. A low-temperature water jacket is installed on the outer wall of the crystallization vessel, and a low-temperature water inner coil and a stirring device are installed inside the crystallization vessel. Temperature detection devices are installed on both the low-temperature water jacket and the low-temperature water inner coil. The temperature detection devices are all connected to the cooling interlock system. When the temperature inside the crystallization vessel reaches below 25°C, the cooling interlock stops the stirring and allows the material to stand still.

[0010] A further preferred technical solution is that the stirring device consists of two layers of blades located on the upper and lower sides of the low-temperature water inner coil, which fully stirs the material and improves the cooling efficiency.

[0011] The top feed inlet of the crystallizer is connected to a high-level tank via a pipeline, and the high-level tank is connected to the liquid phase outlet of the centrifuge.

[0012] A feed pump is installed at the outlet of the crude aniline tank. The feed pump is connected to the aniline inlet of the aniline recovery tower via a pipeline, and a feed rate regulating valve group is installed on the pipeline. A reboiler circulation pump is installed at the bottom outlet of the aniline recovery tower. The reboiler circulation pump is connected in parallel to the reboiler and the reboiler discharge intermediate tank via a pipeline. A reboiler material discharge regulating valve group is installed on the pipeline connecting the reboiler circulation pump and the reboiler discharge intermediate tank. A reflux regulating valve group is installed on the pipeline connecting the aniline reflux pump to the reflux port. An aniline discharge regulating valve group is installed on the pipeline connecting the aniline reflux pump to the aniline recovery storage tank. A vacuum regulating valve group is installed on the pipeline connecting the forced reflux tank to the vacuum control unit. An intermediate tank discharge pump is installed on the pipeline connecting the reboiler discharge intermediate tank to the crystallization vessel.

[0013] The feed rate regulating valve group consists of a flow meter and a regulating valve. The bottom material discharge regulating valve group, the reflux regulating valve group, and the aniline discharge regulating valve group all consist of a flow meter, a regulating valve, and a liquid level interlock controller.

[0014] The top cleaning inlet of the centrifuge is connected to the washing tank through a pipeline with a washing pump installed. The liquid phase outlet at the bottom of the centrifuge is connected to the filtrate tank through a pipeline. A filtrate pump is installed at the outlet of the filtrate tank. A large bag for holding solid phenazine is provided at the solid material outlet at the bottom of the centrifuge.

[0015] The centrifuge is a fully automatic feeding, unloading, and cleaning device. The entire automatic operation is a sealed process with nitrogen protection, and there is no waste gas throughout the process.

[0016] The method for purifying phenazine mixtures using the above-described apparatus includes the following steps: (1) Control the pressure at the top of the aniline recovery tower to -0.084 to -0.094 MPa, and control the feed flow rate from the crude aniline tank to the aniline recovery tower to be 2 m³ / s. 3 The temperature of the aniline recovery tower bottom is adjusted to 115–125℃ by controlling the feed rate of the reboiler and steam coil. The reflux ratio on the reflux pump outlet pipeline is controlled to be 1:15–1:5. The temperature of the aniline recovery tower top is adjusted to 80–100℃, so that while aniline is recovered at the top of the tower, the aniline content in the bottom material is maintained between 30% and 60% by mass concentration. The bottom material discharge regulating valve is adjusted to control the bottom discharge rate at 0.3–0.5 m³ / h. 3 / h, the material is collected and discharged into the intermediate discharge tank of the tower bottom; (2) The intermediate tank of the tower bottom feeds the material into the crystallizer. When the material reaches 2 / 3 of the full capacity of the crystallizer, the intermediate tank pump and the crystallizer feed shut-off valve are interlocked to stop the crystallizer feed. The cooling system of the crystallizer is started. When the material temperature drops below 25°C, the crystallizer standing interlock is started to let the material stand for 1 to 3 hours. (3) Turn on the centrifuge and fill the crystallization vessel with nitrogen to maintain a slightly positive pressure. Press the slurry in the crystallization vessel into the centrifuge for solid-liquid separation in batches. The solid after separation is a by-product with high phenazine content. Put it into a ton bag for incineration. The liquid is a high-content useful component. Put it into the filtrate tank for recycling in the product production system. After each batch is processed by the centrifuge, use the heated crude aniline in the washing tank to clean the filter cloth. The cleaning solution is recycled multiple times.

[0017] More preferably, in step (1), the weight ratio of the components of crude aniline in the crude aniline tank is: aniline 88% to 90%, azobenzene 0.1% to 0.7%, phenazine 4% to 5%, and peptone 0% to 6%.

[0018] More preferably, in step (3), the filter cloth is cleaned with aniline at 40-60°C after each batch of phenazine is processed by the centrifuge.

[0019] The crude aniline produced by the distillation process of RT pyridine production contains a large amount of aniline, a small amount of phenazine, RT pyridine, and azobenzene. The crude aniline is continuously pumped into the aniline recovery tower for distillation. Under a certain vacuum pressure, the content of aniline in the bottom of the tower is controlled within a certain range by controlling the temperature at the top of the tower and the reflux ratio. Then, the bottom liquid is continuously collected and sent to the crystallization tank for cooling and crystallization. Finally, it is separated by centrifugation. The centrifugal filtrate is returned to the RT pyridine production system as a condensation liquid, and the high-purity solid phenazine (filter cake) is treated as hazardous waste.

[0020] This invention effectively solves the technical problems of the phenazine mixture, a byproduct of the current RT-Pyrate production process, which contains a large amount of organic components such as RT-Pyrate, aniline, and azobenzene, making it difficult to dispose of, and the recovery process is cumbersome and costly. This invention obtains high-purity phenazine solid by adjusting the operation of the aniline recovery tower in the RT-Pyrate distillation process and directly cooling and crystallizing the bottom liquid. It has a high RT-Pyrate recovery rate, a short operation process, automated control, and continuous operation.

[0021] This invention fundamentally changes the operating effect of the aniline recovery tower in the conventional RT pyrolysis process. By adjusting and controlling the process, a certain amount of aniline is contained in the tower bottom and taken out to the crystallization kettle for cooling. After cooling, the impurity component phenazine will precipitate directly, and then be separated and the separation liquid is recycled.

[0022] This invention changes the conventional practice of completely separating aniline from other impurities in the raw material using a conventional aniline recovery tower. In the conventional method, the residue in the bottom of the aniline recovery tower is solid waste, containing a large amount of phenazine and p-xylene, and a small amount of aniline and azobenzene. Direct incineration is a waste of resources (the aniline, p-xylene, and azobenzene in the residue can be recycled back into the system, reducing production costs). In the prior art, solvent extraction and recrystallization of crude aniline mostly use ethanol, methanol, aniline, etc., which requires a large amount of solvent for extraction, making the operation complex and requiring redistillation of the extraction solvent, resulting in high energy consumption.

[0023] The process described in this application is simple and can achieve effective separation of aniline and phenazine without adding any solvent. This facilitates the recovery of reusable components (such as acetylene, aniline, and azobenzene) from the residue in the bottom of the tower, and greatly reduces production costs. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0026] In the diagram, 1 is the crude aniline tank, 2 is the feed pump, 3 is the feed rate regulating valve group, 4 is the aniline recovery tower, 5 is the tower bottom circulating pump, 6 is the reboiler, 7 is the steam coil, 8 is the condenser, 9 is the forced reflux tank, 10 is the reflux pump, 11 is the reflux regulating valve group, 12 is the aniline extraction regulating valve group, 13 is the tower bottom material extraction regulating valve, 14 is the tower bottom discharge intermediate tank, 15 is the crystallization vessel, 16 is the high-level tank, 17 is the centrifuge, 18 is the filtrate tank, 19 is the solid phenazine package, 20 is the filtrate pump, 21 is the washing tank, 22 is the washing pump, and 23 is the intermediate tank extraction pump. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention. Example 1:

[0028] As attached Figure 1 As shown, an apparatus for purifying a mixture of phenazine byproducts in the nitrobenzene RT peptone production process includes an aniline recovery tower 4, a tower bottom discharge intermediate tank 14, a crystallization kettle 15, and a centrifuge 17. The aniline recovery tower 4, the tower bottom discharge intermediate tank 14, the crystallization kettle 15, and the centrifuge 17 are connected in series via pipelines.

[0029] The aniline recovery tower 4 is equipped with a tubular reboiler 6 and a bottom steam coil 7 on its circulation pipeline, with double-interlocked temperature control. The bottom of the aniline recovery tower 4 is connected to the bottom circulation pump 5, the reboiler 6, and the side of the bottom of the aniline recovery tower via pipelines to form a bottom circulation system. A liquid separator is also installed in the feed inlet of the aniline recovery tower 4 to cooperate with the feed pipeline. The top of the aniline recovery tower 4 is connected to the condenser 8, the forced reflux tank 9, the reflux pump 10, and the reflux port on the side of the top of the aniline recovery tower 4 via pipelines to form a top reflux system.

[0030] The feed flow rate of the aniline recovery tower 4 is controlled at 2m³ using feed flow regulating valve group 3. 3 / h; The aniline recovery tower 4 controls the temperature of the tower bottom at 115-125℃ by regulating the flow rate of the hot medium in the reboiler 6 and the steam coil 7 in the tower bottom; the liquid level of the forced reflux tank 9 is kept stable by the interlocking control of the reflux regulating valve group 11 and the aniline collection regulating valve group 12, and the temperature of the top of the aniline recovery tower 4 is controlled between 80-100℃. The pressure of the top of the tower is regulated between -0.092 and -0.094MPa by the vacuum control unit; when the tower is running stably, the material collected from the bottom of the aniline recovery tower 4 is kept stable by the bottom material collection regulating valve group 13. At this time, a sample is taken from the bottom of the tower for gas chromatography detection. When the aniline content is about 30%, it is collected and sent to the intermediate discharge tank 14 of the bottom of the tower.

[0031] When the storage capacity of the intermediate tank 14 reaches 2 / 3 of its full capacity, the intermediate tank discharge pump 23 is interlocked and opened to release the material into the crystallizer 15. When the material reaches a certain level in the crystallizer 15, the intermediate tank discharge pump 23 and the crystallizer feed shut-off valve are interlocked to stop the feeding into the crystallizer 15. The aniline content in the material is adjusted to 30% by the aniline in the high-level tank 16. Then the cooling system of the crystallizer 15 is started. When the material temperature drops to 25°C, the crystallizer 15 is settling interlocked and the material is settling for 1 hour.

[0032] Turn on centrifuge 17 and purge the crystallization vessel 15 with nitrogen to maintain a slightly positive pressure. Press the slurry in the crystallization vessel 15 into centrifuge 17 for batch solid-liquid separation. The separated solid is a byproduct with high phenazine content, which is placed in a solid phenazine package 18 for incineration. The liquid is the useful components of high aniline and peptone, which is placed in filtrate tank 18 for recycling in the peptone production system. After each batch is processed by centrifuge 17, the filter cloth needs to be cleaned with crude aniline heated in washing tank 21 (40-60°C). The cleaning solution is recycled multiple times.

[0033] Gas chromatography analysis was performed on samples from the intermediate tank 14 at the bottom of the distillation column and the separated powdered solid phenazine. The mass content of each component in the material from the intermediate tank 14 at the bottom of the distillation column was as follows: aniline 31.2%, p-xylene and azobenzene 34.32%, phenazine 28.27%, and other organic components 7.7%. The weight of each batch of material transferred to the crystallization kettle was approximately 2.2 t. Three batches of each specification of material were tested for comparison. After processing, the powdered solid phenazine was compared with the original phenazine waste liquid from the distillation kettle. When the residual aniline content in the material collected from the bottom of the aniline recovery column 4 was 30%, the p-xylene recovery rate reached 94%–95.5%, and the phenazine yield was 83%–85%.

[0034] Example 2:

[0035] The crude aniline was processed according to the method of Example 1, using the same material from the intermediate tank 14 at the bottom of the tower as in Example 1. The crystallization time of phenazine was controlled to be about 3 hours. Solid powdered phenazine samples were taken for gas chromatography analysis. The peptone recovery rate reached 95-96%, and the phenazine yield was 86-90%. Specific data are as follows: Example 3:

[0036] Crude aniline was processed according to the method in Example 1. The pressure at the top of the column was controlled between -0.088 and -0.090 MPa. Gas chromatography analysis of the bottom product showed that the aniline content was approximately 40%, at which point the bottom product was collected. Under the same conditions and methods, the phenazine crystallization time was controlled to approximately 3 hours. Gas chromatography analysis of the bottom product from the intermediate tank and solid phenazine samples revealed the following composition: aniline 40.2%, peptone and azobenzene 32.06%, phenazine 23.44%, and other organic components 4.29%. Each batch transferred to the crystallization reactor weighed approximately 2.2 tons. After processing, the powdered solid phenazine was compared with the previously discharged phenazine waste liquid from the distillation vessel. When the residual aniline content in the bottom product of the aniline recovery column was 40%, the peptone recovery rate reached 96-97%, and the phenazine yield was 80-83%. Specific data are as follows: Example 4:

[0037] Crude aniline was processed according to the method in Example 1. The pressure at the top of the column was controlled between -0.084 and -0.086 MPa. Gas chromatography analysis of the bottom product showed that the aniline content was approximately 50%, at which point the bottom product was collected. Under the same conditions and methods, the phenazine crystallization time was controlled to approximately 3 hours. Gas chromatography analysis of the phenazine sample showed that, compared to the previously discharged phenazine waste liquid from the distillation vessel, when the residual aniline content in the bottom product of the aniline recovery column was 50%, the peptone recovery rate reached 98-99%, and the phenazine yield was 75-79%. Specific data are as follows: Example 5:

[0038] The crude aniline was processed using the method described in Example 1. The pressure at the top of the column was controlled between -0.080 and -0.082 MPa. Gas chromatography analysis of the bottom product showed that the aniline content was approximately 60%, at which point the bottom product was collected. Under the same conditions and methods, the phenazine crystallization time was controlled to approximately 3 hours. Gas chromatography analysis of the phenazine sample showed that, compared to the previously discharged phenazine waste liquid from the distillation vessel, when the residual aniline content in the bottom product of the aniline recovery column was 60%, the peptone recovery rate reached 98.5%–99.7%, and the phenazine yield was 70%–74%. Specific data are as follows:

[0039] Comparative example: 100g of phenazine waste from the aniline recovery tower was taken and mixed with 100g of aniline. The mixture was heated to 80℃ until completely melted, then cooled to 30℃ and allowed to stand for 12 hours. After filtration and solid-liquid separation, 166.4g of filtrate and 32.4g of filter cake were obtained. The components of the phenazine waste, filtrate, and filter cake were analyzed by gas chromatography, and the results are shown in the table below.

[0040] Calculations showed that the peptone yield obtained through solid-liquid separation was 68.85%, and the phenazine yield was 68.22%. Both the peptone yield and phenazine yield were lower than those in Examples 1-5 of this invention.

[0041] Obviously, the embodiments described above are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for purifying a mixture of phenazine byproducts from the RT-Pyrate production process using the nitrobenzene method, characterized in that, Includes the following steps: (1) Control the pressure at the top of the aniline recovery tower to -0.084 to -0.094 MPa, and control the feed flow rate from the crude aniline tank to the aniline recovery tower to be 2 m³ / s. 3 The temperature of the aniline recovery tower bottom is adjusted to 115–125℃ by controlling the feed rate of the reboiler and steam coil. The reflux ratio on the reflux pump outlet pipeline is controlled to be 1:15–1:

5. The temperature of the aniline recovery tower top is adjusted to 80–100℃, so that while aniline is recovered at the top of the tower, the aniline content in the bottom material is 30–60% by mass concentration. The bottom material discharge regulating valve is adjusted to control the bottom discharge rate at 0.3–0.5 m³ / h. 3 / h, the material is collected and discharged into the intermediate discharge tank of the tower bottom; (2) The intermediate tank of the tower bottom feeds the material into the crystallizer. When the material reaches 2 / 3 of the full capacity of the crystallizer, the intermediate tank pump and the crystallizer feed shut-off valve are interlocked to stop the crystallizer feed. The cooling system of the crystallizer is started. When the material temperature drops below 25°C, the crystallizer standing interlock is started to let the material stand for 1 to 3 hours. (3) Turn on the centrifuge and fill the crystallization vessel with nitrogen to maintain a slightly positive pressure. Press the slurry in the crystallization vessel into the centrifuge for solid-liquid separation in batches. The solid after separation is a by-product with high content of phenazine. The liquid is placed in the filtrate tank and recycled to the pecs production system. After each batch is processed by the centrifuge, the filter cloth is cleaned with heated crude aniline in the washing tank. The cleaning solution is recycled multiple times. The apparatus for implementing the above method includes an aniline recovery tower with its inlet connected to a crude aniline tank. The aniline inlet of the aniline recovery tower is located in the middle of the tower. The top outlet of the aniline recovery tower is connected in sequence to a condenser, a forced reflux tank, and an aniline reflux pump via pipelines. An aniline reflux pump is installed at the bottom outlet of the forced reflux tank. The aniline reflux pump is connected in parallel to the reflux port on the top side of the aniline recovery tower and the aniline recovery storage tank via pipelines. The forced reflux tank is connected to a vacuum control unit via a top pipeline. The bottom outlet of the aniline recovery tower is connected in parallel to a reboiler and a bottom outlet intermediate tank via pipelines. The outlet of the bottom outlet intermediate tank is connected to two parallel crystallizers via pipelines. A shut-off valve interlocked with the liquid level of the crystallizer is installed on the pipeline connecting to the crystallizer. The bottom outlet of the crystallizer is connected to a centrifuge via pipelines. The centrifuge is connected to a washing tank and a filtrate tank via pipelines.

2. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: In step (1), the weight ratio of the components of crude aniline in the crude aniline tank is: aniline 88%–90%, azobenzene 0.1%–0.7%, phenazine 4%–5%, and peptone 0%–6%.

3. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: In step (3), the filter cloth is cleaned with aniline at 40-60°C after each batch of phenazine is processed by the centrifuge.

4. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: The aniline recovery tower is equipped with a liquid separation component that works in conjunction with the aniline inlet pipeline, and the outlet of the reboiler is connected to the return port on the bottom side of the aniline recovery tower via a pipeline.

5. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: The reboiler is a steam tube heat exchanger, and a steam coil is installed at the bottom of the aniline recovery tower.

6. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: The crystallization vessel is equipped with a low-temperature water jacket on its outer wall, and a low-temperature water inner coil and a stirring device are installed inside the crystallization vessel. Temperature detection devices are installed on both the low-temperature water jacket and the low-temperature water inner coil, and the temperature detection devices are connected to the cooling interlock system. The stirring device consists of two layers of blades located on the upper and lower sides of the low-temperature water inner coil. The top feed inlet of the crystallization vessel is connected to a high-level tank through a pipeline, and the high-level tank is connected to the liquid phase outlet of the centrifuge.

7. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: A feed pump is installed at the outlet of the crude aniline tank. The feed pump is connected to the aniline inlet of the aniline recovery tower via a pipeline, and a feed rate regulating valve group is installed on the pipeline. A reboiler circulation pump is installed at the bottom outlet of the aniline recovery tower. The reboiler circulation pump is connected in parallel to the reboiler and the reboiler discharge intermediate tank via a pipeline. A reboiler material discharge regulating valve group is installed on the pipeline connecting the reboiler circulation pump and the reboiler discharge intermediate tank. A reflux regulating valve group is installed on the pipeline connecting the aniline reflux pump to the reflux port. An aniline discharge regulating valve group is installed on the pipeline connecting the aniline reflux pump to the aniline recovery storage tank. A vacuum regulating valve group is installed on the pipeline connecting the forced reflux tank to the vacuum control unit. An intermediate tank discharge pump is installed on the pipeline connecting the reboiler discharge intermediate tank to the crystallization vessel.

8. The purification method for the phenazine mixture byproduct of the RT-Plast production process according to claim 7, characterized in that: The feed rate regulating valve group consists of a flow meter and a regulating valve. The bottom material discharge regulating valve group, the reflux regulating valve group, and the aniline discharge regulating valve group all consist of a flow meter, a regulating valve, and a liquid level interlock controller.

9. The purification method for the phenazine mixture, a byproduct of the RT-Plast production process using the nitrobenzene method, as described in claim 1, is characterized in that: The top cleaning inlet of the centrifuge is connected to the washing tank through a pipeline with a washing pump installed. The liquid phase outlet at the bottom of the centrifuge is connected to the filtrate tank through a pipeline. A filtrate pump is installed at the outlet of the filtrate tank. A large bag for holding solid phenazine is provided at the solid material outlet at the bottom of the centrifuge.

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