Multi-stage centrifugal decoloring process for cyclic regeneration of DMT by chemical method

Abstract

The invention discloses a multistage centrifugal decoloring process for cyclic regeneration of DMT by a chemical method, which comprises the following steps: inputting DMT slurry into a system, separating by a first centrifugal separator, inputting the separated slurry into a DMT primary dilution tank for dilution, inputting diluted liquid into a second centrifugal separator for separation, inputting the separated slurry into a DMT secondary dilution tank for dilution, and inputting the diluted liquid into a DMT secondary dilution tank for dilution. According to the method, the DMT slurry is diluted through methanol according to the principle of similar dissolvability of organic matter, most of substances such as dye and inorganic salt are dissolved and brought out of the system, and the DMT slurry is separated through the third centrifugal separator, the separated slurry is input into the high-temperature DMT remelting tank to remove methanol, and finally the obtained DMT melt product is output to the DMT product storage tank. The multi-stage centrifugation and multi-stage dilution processes are designed, the DMT product can be effectively separated from the DMT slurry and decolorized, and the decolorization rate can reach 70% or above.

Description

Technical Field

[0001] The invention relates to the technical field of chemical recycling of waste textiles, and more specifically to a multi-stage centrifugal decolorization process for chemical recycling of DMT. Background Art

[0002] The chemical recycling technology for waste textiles uses waste textiles as raw materials, and undergoes processes such as alcoholysis and depolymerization, removal of foreign materials, concentration of alcoholysis solution, methanol ester exchange, DMT crystallization, centrifugal separation, and DMT distillation to synthesize regenerated DMT (dimethyl terephthalate), and uses the regenerated DMT as raw material to synthesize PET polyester chips, polyester yarns and other engineering plastics.

[0003] Chemical recycling technology can reduce the demand for the production of virgin textile fibers, reduce the pollution caused by the incineration of waste textiles, and reuse resources. It is worth vigorously promoting the use of recycled polyester materials to produce high value-added products such as polyester industrial yarn, differentiated and functional polyester filaments, and non-woven materials.

[0004] DMT (dimethyl terephthalate) is one of the important raw materials in the polyester industry and an important recycling product in the chemical recycling technology of waste textiles. However, in the actual production process, it is found that since waste textiles are used as raw materials, the composition of the recycled products is relatively complex, and since clothes contain a large amount of dyes, the recycled DMT produced has problems such as high Hasen color value and low yield. Summary of the invention

[0005] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a multi-stage centrifugal decolorization process for chemically recycling DMT. The present invention utilizes the "like dissolves like" principle of organic matter and uses methanol to dilute the DMT slurry to dissolve most of the dyes, inorganic salts and other substances and take them out of the system. The present invention designs multi-stage centrifugation and multi-stage dilution processes, which can effectively separate DMT from the DMT slurry (containing methanol, ethylene glycol, metal salts, dyes, etc.) and decolorize it.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A multi-stage centrifugal decolorization process for chemically recycling DMT comprises the following steps:

[0008] (a), collecting and transferring the DMT slurry precipitated by cooling the transesterification reaction to a crude DMT slurry storage tank;

[0009] (b) The DMT slurry in the crude DMT slurry storage tank is pumped to the first centrifugal separator for centrifugal separation, the separated liquid is transported to the mixed liquid tank through the liquid phase outlet of the first centrifugal separator, and the separated slurry is transported to the DMT primary dilution tank through the slurry outlet of the first centrifugal separator;

[0010] (c) The slurry in the DMT primary dilution tank is sprayed with methanol to form a mixed liquid. Methanol can remove dyes and impurities in the slurry;

[0011] (d) The mixed liquid formed in the DMT primary dilution tank is pumped to the second centrifugal separator for re-centrifugal separation, and the separated liquid is transported to the first separated methanol storage tank through the liquid phase outlet of the second centrifugal separator, and the separated slurry is transported to the DMT secondary dilution tank through the slurry outlet of the second centrifugal separator;

[0012] (e) The slurry in the DMT secondary dilution tank is sprayed with methanol again to form a mixed liquid again;

[0013] (f) The mixed liquid formed in the DMT secondary dilution tank is pumped to the third centrifugal separator for a third centrifugal separation operation, the separated liquid is transported to the second separated methanol storage tank through the liquid phase outlet of the third centrifugal separator, and the separated slurry is transported to the DMT remelting tank through the slurry outlet of the third centrifugal separator;

[0014] (g) The temperature of the DMT remelting tank is maintained between 160 and 200°C. After the slurry enters the DMT remelting tank, the methanol is instantly volatilized and output to the methanol recovery tank. The DMT melt product separated in the DMT remelting tank is pumped to the DMT product storage tank.

[0015] Furthermore, the gas phase balance pipes on the liquid phase end outlet pipelines of the first centrifuge and the second centrifuge are connected to the condenser, and the gas phase outlets at the top of the DMT primary dilution tank and the DMT secondary dilution tank are also connected to the condenser through pipelines.

[0016] Furthermore, the DMT remelting tank is heated by coil heat transfer oil, and the DMT remelting tank is connected to a remelting tank heater, which can stabilize the required temperature of the DMT remelting tank.

[0017] Furthermore, the DMT remelting tank is connected to a remelting tank steam drum.

[0018] Furthermore, the DMT primary dilution tank pipeline is connected to a primary dilution methanol storage tank, and the primary dilution methanol storage tank provides methanol for spray dilution to the DMT primary dilution tank, and the DMT primary dilution tank provides methanol with a purity of 90% to 97.5%.

[0019] Furthermore, the methanol recovery tank pipeline is connected to the DMT secondary dilution tank, and the methanol recovery tank provides methanol for spray dilution to the DMT secondary dilution tank. The methanol recovery tank provides methanol with a purity of more than 97.5%. The methanol recovery tank pipeline is connected to a fresh methanol storage tank, and the fresh methanol storage tank replenishes methanol with a purity of more than 97.5% to the methanol recovery tank.

[0020] Furthermore, the third centrifuge pipeline is connected to an exhaust gas treatment system.

[0021] Furthermore, a safety valve is installed on the DMT remelting tank, and the safety valve is connected to a safety valve venting collection tank.

[0022] The beneficial effects of the present invention are:

[0023] The present invention utilizes the principle of "like dissolves like" of organic matter, adopts methanol to dilute DMT slurry, dissolves most of the dyes, inorganic salts and other substances and takes them out of the system. The present invention designs multi-stage centrifugation and multi-stage dilution processes, can effectively separate DMT from DMT slurry (containing methanol, ethylene glycol, metal salts, dyes, etc.), and decolorize it, the decolorization rate can reach more than 70%, reduces energy consumption for subsequent DMT distillation, and removes the influence of impurities, the present invention greatly improves the quality and yield of DMT. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the connection of all equipment used in the process of the present invention;

[0025] Figure 2 This is a schematic diagram of the internal structure of a DMT dilution tank in this embodiment;

[0026] Figure 3 This is a schematic structural diagram of a slurry dilution barrel of a DMT dilution tank in an empty state in this embodiment;

[0027] Figure 4 It is a schematic structural diagram of a slurry dilution barrel of a DMT dilution tank in this embodiment under load.

[0028] Reference numerals: crude DMT slurry storage tank 1, first centrifugal separator 2, DMT primary dilution tank 3, mixed liquid tank 4, condenser 5, second centrifugal separator 6, DMT secondary dilution tank 7, first separated methanol storage tank 8, third centrifugal separator 9, DMT remelting tank 10, second separated methanol storage tank 11, remelting tank heater 12, remelting tank drum 13, DMT product storage tank 14, methanol recovery tank 15, primary dilution methanol storage tank 16, fresh methanol storage tank 17, tail gas treatment system 18, safety valve venting collection tank 19, tank body 31, slurry input port 311, partition 312, dilution liquid storage area 313, Liquid level meter 3131, slurry dilution barrel 32, liquid outlet 321, bottom cone 322, barrel base 323, tension column 324, methanol spray pipe 33, spray nozzle 331, dilution liquid recovery tank 34, auxiliary stirring mechanism 35, stirring shaft 351, stirring motor 352, blade 353, switch hanging plate 354, trigger switch 355, striker rack 356, striker 357, barrel jacket 36, elastic support mechanism 37, support column 371, tray 3711, weight sensor 3712, piston connecting rod 372, spring base 373, spring hole 3731, spring 374, guide piston 375, magnetic column 38. DETAILED DESCRIPTION

[0029] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0030] like Figure 1 A multi-stage centrifugal decolorization process for chemically recycling DMT shown includes the following steps:

[0031] (a) collecting and transferring the DMT slurry precipitated by cooling the transesterification reaction to a crude DMT slurry storage tank 1, wherein the DMT slurry at this time has a mixed composition and a dark color, and contains ethylene glycol, excess methanol, and a large amount of metal salts, dyes, and impurities produced by side reactions;

[0032] (b) The DMT slurry in the crude DMT slurry storage tank 1 is pumped to the first centrifugal separator 2 for centrifugal separation. The first centrifugal separator 2 is the first-stage centrifugal process, which is used to complete the preliminary impurity separation. The separated liquid is transported to the mixed liquid tank 4 through the liquid phase outlet of the first centrifugal separator 2. The main components of these liquids are ethylene glycol, metal salts, impurities produced by side reactions, etc. The liquid is stored in the mixed liquid tank 4 and waits for processing and recycling by other systems. The separated slurry is transported to the DMT primary dilution tank 3 through the slurry outlet of the first centrifugal separator 2. At this time, the color of the DMT slurry is relatively obvious. The first centrifugal separator 2 is protected by 0.1N (nitrogen);

[0033] (c) The slurry in the DMT primary dilution tank 3 is sprayed with methanol to form a mixed liquid. Organic matter has the characteristic of "like dissolves like". Using methanol to dilute the DMT slurry can dissolve and take out most of the dyes, inorganic salts and other substances. The DMT primary dilution tank 3 is the first spray dilution. For cost considerations, the DMT primary dilution tank 3 pipeline is connected to the primary dilution methanol storage tank 16. The primary dilution methanol storage tank 16 provides methanol for spray dilution for the DMT primary dilution tank 3. The DMT primary dilution tank 3 provides methanol with a purity of 90% to 97.5%, which is called fresher methanol in industry;

[0034] (d) The mixed liquid formed in the DMT primary dilution tank 3 is pumped to the second centrifugal separator 6 for re-centrifugal separation. The separated liquid is transported to the first separated methanol storage tank 8 through the liquid phase outlet of the second centrifugal separator 6. The separated slurry is transported to the DMT secondary dilution tank 7 through the slurry outlet of the second centrifugal separator 6. The liquid separated at the liquid phase outlet is mainly methanol, which brings out a large amount of dyes, inorganic salts and other substances. Therefore, the color of the DMT slurry output from the slurry outlet of the second centrifugal separator 6 is significantly improved;

[0035] (e) The DMT secondary dilution tank 7 slurry is sprayed with methanol again to form a mixed liquid again. The DMT secondary dilution tank 7 uses methanol with a purity of more than 97.5% for spraying, which is called fresh methanol in the industry. Methanol is used to remove dyes, inorganic salts and other substances in the slurry again. The secondary dilution is beneficial to improve the decolorization quality of DMT;

[0036] (f) The mixed liquid formed in the DMT secondary dilution tank 7 is pumped to the third centrifugal separator 9 for the third centrifugal separation operation. The separated liquid is transported to the second separation methanol storage tank 11 through the liquid phase outlet of the third centrifugal separator 9, and the separated slurry is transported to the DMT remelting tank 10 through the slurry outlet of the third centrifugal separator 9. The liquid separated from the liquid phase outlet of the third centrifugal separator 9 is mainly methanol, which brings out a large amount of dyes, inorganic salts and other substances, but the purity of methanol is higher than that of the liquid separated from the liquid phase outlet of the second centrifugal separator 6. Therefore, the two centrifugal separators are respectively connected to different separation methanol storage tanks to obtain different subsequent treatments. The slurry output from the slurry outlet of the third centrifugal separator 9 is more obviously decolorized and meets the process requirements, but methanol exists in the slurry, so it needs to be subsequently processed in the DMT remelting tank 10;

[0037] (g) The DMT remelting tank 10 maintains a temperature between 160 and 200° C. After the slurry enters the DMT remelting tank 10, methanol is instantly volatilized and output to the methanol recovery tank 15 (the boiling point of methanol is 64.7 to 64.8° C.), leaving only the separated DMT melt product. The DMT melt product separated in the DMT remelting tank 10 is pumped to the DMT product storage tank 14. The impurities of the DMT melt product in the DMT product storage tank 14 are effectively removed, and the decolorization rate can reach more than 70%, which meets the recycling production requirements.

[0038] like Figure 1 As shown, the gas phase balance pipes on the liquid phase end outlet pipelines of the first centrifuge 2 and the second centrifuge 6 are connected to the condenser 5. Gas will be generated during the operation of the first centrifuge 2 and the second centrifuge 6. In order to balance the air pressure in the centrifuge, the generated gas (mainly methanol) will be released to the condenser 5 for treatment. The gas phase outlets at the top of the DMT primary dilution tank 3 and the DMT secondary dilution tank 7 are also connected to the condenser 5 by pipelines. During the spray dilution process of the dilution tank, part of the methanol will also volatilize. These methanol are guided to the condenser 5 by pipelines to restore to liquid state, and then wait for treatment and reuse.

[0039] like Figure 1 As shown, the DMT remelting tank 10 is heated by coil heat transfer oil. Since the DMT remelting tank 10 requires a temperature of 160-200°C, the DMT remelting tank 10 is connected and installed with a remelting tank heater 12. The remelting tank heater 12 can provide additional heat to the DMT remelting tank 10 to stabilize the DMT remelting tank 10 at the required temperature.

[0040] like Figure 1As shown, the DMT remelting tank 10 is connected to a remelting tank drum 13. DMT material sublimation may occur in the DMT remelting tank 10, which may cause loss of DMT. The remelting tank drum 13 can recover the sublimated DMT, convert it into gas-liquid, and return it to the DMT remelting tank 10 to be replenished after it becomes molten DMT.

[0041] like Figure 1 As shown, the methanol recovery tank 15 pipeline is connected to the DMT secondary dilution tank 7, and the methanol recovery tank 15 provides methanol for spray dilution to the DMT secondary dilution tank 7. The methanol recovery tank 15 receives the methanol instantly volatilized by the DMT remelting tank 10, and its methanol purity is above 97.5%, which can meet the demand of secondary spray dilution. Since the methanol recovery amount of the methanol recovery tank 15 cannot meet the demand of spraying amount, the methanol recovery tank 15 pipeline is connected to the fresh methanol storage tank 17, and the fresh methanol storage tank 17 replenishes the methanol recovery tank 15 with methanol with a purity of more than 97.5%. The bottom output pipes of the DMT primary dilution tank 3 and the DMT secondary dilution tank 7 are both installed with 6N (nitrogen) purge and methanol flushing devices. When the pipe is blocked, the methanol in the fresh methanol storage tank 17 can be introduced for flushing.

[0042] like Figure 1 As shown, the third centrifugal separator 9 is connected to the tail gas treatment system 18 through its pipeline. The third centrifugal separator 9 also generates gas during operation. To balance the internal air pressure of the third centrifugal separator 9, the released gas is guided to the tail gas treatment system 18 for treatment.

[0043] like Figure 1 As shown, a safety valve is installed on the DMT remelting tank 10, and the safety valve is connected to a safety valve venting collection tank 19. The safety valve plays a safety protection role for the DMT remelting tank 10 to prevent the gas pressure in the tank from being too high. The safety valve venting collection tank 19 can collect and vent external emissions.

[0044] like Figure 2-Figure 4The DMT slurry dilution tank shown is used as a DMT primary dilution tank 3 and a DMT secondary dilution tank 7, and includes a tank body 31 and a dilution liquid recovery tank 34. A slurry input port 311 is provided on the top of the tank body 31. A horizontal partition 312 is installed in the tank body 31. A dilution liquid storage area 313 is set below the partition 312. A slurry dilution barrel 32 is installed on the partition 312. The DMT slurry input from the slurry input port 311 falls into the slurry dilution barrel 32. A circle of methanol spray pipes 33 are installed on the upper inner side of the tank body 31. A plurality of spray nozzles 331 are connected to the methanol spray pipes 33. The spray nozzles 331 are arranged facing the inside of the slurry dilution barrel 32. A plurality of liquid outlet holes are provided on the outer wall of the slurry dilution barrel 32. 321, the liquid outlet 321 outputs the diluted slurry, the dilution liquid recovery tank 34 is installed in the tank body 31, the dilution liquid recovery tank 34 is arranged below the slurry dilution barrel 32, the dilution liquid recovery tank 34 can collect the slurry output from the liquid outlet 321, the dilution liquid recovery tank 34 pipeline is connected to the dilution liquid storage area 313, the methanol spray pipe 33 of the spray nozzle 331 can spray methanol, methanol can form a dilution effect on the DMT slurry to form a diluted slurry, organic matter has the characteristic of "like dissolves like", the dyes, inorganic salts and other substances in the DMT slurry will dissolve in methanol, the diluted slurry output from the DMT slurry dilution tank is separated, and the dyes, inorganic salts and other substances in the DMT slurry can be effectively separated.

[0045] Since the DMT slurry input into the tank body 31 from the slurry input port 311 is very viscous, the present invention installs an auxiliary stirring mechanism 35 in the slurry dilution barrel 32. The auxiliary stirring mechanism 35 can break up the viscous slurry so that it is no longer stacked together (viscous slurry is easy to stack), and can be fully sprayed with methanol to promote the rapid molding of the diluent. The present invention bulges the bottom of the slurry dilution barrel 32 upward to form a bottom cone 322. The diluent will be concentrated along the bottom cone 322 to the corner of the barrel wall, so that it is just output from the liquid outlet 321 on the outer wall of the slurry dilution barrel 32. The auxiliary stirring mechanism 35 includes a stirring shaft 351 and a stirring motor 352. The stirring shaft 351 is connected to the output end of the stirring motor 352. A plurality of blades 353 are connected to the outer wall of the stirring shaft 351. The blades 353 match the bottom structure of the slurry dilution barrel 32, and can fully stir the input DMT slurry to make it evenly dispersed.

[0046] like Figure 2As shown, the slurry dilution barrel 32 is movably installed on the partition 312, and an elastic support mechanism 37 is installed on the partition 312. The elastic support mechanism 37 supports the slurry dilution barrel 32. The bottom of the slurry dilution barrel 32 is connected to a barrel base 323. The elastic support mechanism 37 includes a support column 371 and a spring base 373. The top of the support column 371 is connected to a tray 3711, and the barrel base 323 is connected to the tray 3711. The bottom of the support column 371 is connected to a piston connecting rod 372. The spring base 373 is fixedly installed on the partition 312. A spring hole 3731 is opened in the spring base 373. A spring 374 and a guide piston 375 are installed in the spring hole 3731. The piston connecting rod 372 extends into the spring hole 3731 and is connected to the guide piston 375. The guide piston 375 is pressed against the spring 374. Figure 3 As shown, the empty slurry dilution barrel 32 is light in weight and is lifted up under the force of the spring 374. The spring 374 plays the role of elastic support for the empty slurry dilution barrel 32. As the DMT slurry is input into the slurry dilution barrel 32, the load of the slurry dilution barrel 32 will increase, and the slurry dilution barrel 32 will have a tendency to compress the spring 374 and move downward. The present invention installs a weight sensor 3712 on the tray 3711. The weight sensor 3712 can sense the load weight data of the slurry dilution barrel 32. Two tension columns 324 are connected to the bottom of the slurry dilution barrel 32. Two magnetic columns 38 are installed on the partition 312. The magnetic columns 38 are arranged one by one corresponding to the tension columns 324. After the load data sensed by the weight sensor 3712 exceeds the set amount, the magnetic column 38 is energized to generate a magnetic force, and the tension column 324 will be attracted to the magnetic column 38 under the magnetic effect. This is like Figure 4 In the state shown, the slurry dilution barrel 32 is completely lowered and the spring 374 is compressed.

[0047] Since the slurry dilution barrel 32 does not need methanol spraying and slurry stirring when it is unloaded or under low load, the present invention fixes the stirring motor 352 of the auxiliary stirring mechanism 35 in the support column 371. The support column 371 is a hollow column. The stirring shaft 351 extends into the support column 371 and is connected to the output end of the stirring motor 352. A switch hanging plate 354 is connected to the outer wall of the support column 371, and a trigger switch 355 is installed on the switch hanging plate 354. A striker rack 356 is installed on the partition 312, and a striker 357 is upright on the striker rack 356. The striker 357 is arranged on the downward movement trajectory of the trigger switch 355. Figure 3 As shown, the empty slurry dilution barrel 32 is lifted upward, at which time the trigger switch 355 is disengaged from the striker 357, and the stirring motor 352 will not start, that is, the auxiliary stirring mechanism 35 will not start. Figure 4As shown, the loaded slurry dilution barrel 32 is magnetically attracted downward, the trigger switch 355 contacts the striker 357, and the auxiliary stirring mechanism 35 starts stirring. Since there is a large amount of DMT slurry in the loaded slurry dilution barrel 32, the stirring is started at the right time. After the DMT slurry in the slurry dilution barrel 32 is diluted, the slurry dilution barrel 32 will resume to be empty. At this time, the sensing data of the weight sensor 3712 returns to the initial state, and the magnetic suction column 38 is de-energized and demagnetized. At this time, the slurry dilution barrel 32 loses its magnetic attraction and is only supported by the spring 3712. 74 lifting force, the unloaded slurry dilution barrel 32 will rise back to its original position again. In the present invention, the methanol spray pipe 33 is linked with the stirring motor 352 of the auxiliary stirring mechanism 35. After the stirring motor 352 is turned on, the methanol spray pipe 33 also starts spraying. The advantage of the above design is that the start of methanol spraying and stirring operations are controlled according to the load change of the slurry dilution barrel 32. Compared with the traditional direct spraying dilution tank, the DMT slurry dilution tank of the present invention has the advantages of saving energy and materials.

[0048] The present invention is provided with a barrel jacket 36 on the tank body 31, and the barrel jacket 36 is matched and mounted on the outside of the slurry dilution barrel 32. Figure 3 As shown, the empty slurry dilution barrel 32 is completely retracted into the barrel jacket 36, as shown in FIG. Figure 4 As shown, the loaded slurry dilution barrel 32 will move downward and partially extend out of the barrel jacket 36. The outer wall of the extended part is provided with a liquid outlet 321, which is convenient for the output of the dilution liquid. After the dilution operation is completed, the unloaded slurry dilution barrel 32 continues to retract upward into the barrel jacket 36. The barrel jacket 36 can form a cleaning effect on the outer wall of the slurry dilution barrel 32.

[0049] A liquid level meter 3131 is installed in the diluent storage area 313, and the pump is turned on when the storage volume of the diluent storage area 313 is large.

[0050] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A multi-stage centrifugal decolorization process for chemically recycling DMT, characterized in that: The steps include: (a), collecting the DMT slurry precipitated by cooling and crystallizing the transesterification reaction and transferring it to a crude DMT slurry storage tank (1); (b), the DMT slurry in the crude DMT slurry storage tank (1) is transported to the first centrifugal separator (2) by a pump for centrifugal separation, the separated liquid is transported to the mixed liquid tank (4) through the liquid phase outlet of the first centrifugal separator (2), and the separated slurry is transported to the DMT primary dilution tank (3) through the slurry outlet of the first centrifugal separator (2); (c) The slurry in the DMT primary dilution tank (3) is sprayed with methanol to form a mixed liquid. The methanol can remove the dye and impurities in the slurry; (d) The mixed liquid formed in the DMT primary dilution tank (3) is pumped to the second centrifugal separator (6) for re-centrifugal separation, the separated liquid is transported to the first separated methanol storage tank (8) through the liquid phase outlet of the second centrifugal separator (6), and the separated slurry is transported to the DMT secondary dilution tank (7) through the slurry outlet of the second centrifugal separator (6); (e) The slurry in the DMT secondary dilution tank (7) is sprayed with methanol again to form a mixed liquid again; (f) The mixed liquid formed in the DMT secondary dilution tank (7) is pumped to the third centrifugal separator (9) for a third centrifugal separation operation, the separated liquid is transported to the second separated methanol storage tank (11) through the liquid phase outlet of the third centrifugal separator (9), and the separated slurry is transported to the DMT remelting tank (10) through the slurry outlet of the third centrifugal separator (9); (g) The DMT remelting tank (10) maintains a temperature between 160 and 200° C. After the slurry enters the DMT remelting tank (10), the methanol is instantly volatilized and output to the methanol recovery tank (15). The DMT melt product separated in the DMT remelting tank (10) is pumped to the DMT product storage tank (14).

2. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The gas phase balance pipes on the liquid phase end outlet pipelines of the first centrifugal separator (2) and the second centrifugal separator (6) are connected to the condenser (5), and the gas phase outlets at the top of the DMT primary dilution tank (3) and the DMT secondary dilution tank (7) are also connected to the condenser (5) through pipelines.

3. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The DMT remelting tank (10) is heated by coil heat transfer oil. The DMT remelting tank (10) is connected to a remelting tank heater (12). The remelting tank heater (12) can stabilize the required temperature of the DMT remelting tank (10).

4. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The DMT remelting tank (10) is connected to a remelting tank drum (13).

5. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The DMT primary dilution tank (3) is connected to a primary dilution methanol storage tank (16) through a pipeline. The primary dilution methanol storage tank (16) provides methanol for spray dilution to the DMT primary dilution tank (3). The DMT primary dilution tank (3) provides methanol with a purity of 90% to 97.5%.

6. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The methanol recovery tank (15) is connected to the DMT secondary dilution tank (7) through a pipeline. The methanol recovery tank (15) provides methanol for spray dilution to the DMT secondary dilution tank (7). The methanol recovery tank (15) provides methanol with a purity of more than 97.5%. The methanol recovery tank (15) is connected to a fresh methanol storage tank (17) through a pipeline. The fresh methanol storage tank (17) replenishes the methanol recovery tank (15) with methanol with a purity of more than 97.5%.

7. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The pipeline of the third centrifugal separator (9) is connected to an exhaust gas treatment system (18).

8. According to claim 1, a multi-stage centrifugal decolorization process for chemically recycling DMT is characterized in that: The DMT remelting tank (10) is provided with a safety valve, which is connected to a safety valve venting collection tank (19).

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