Rectification and purification method for recovering NMP (N-Methyl Pyrrolidone) from NMP regenerated liquid

Abstract

The invention relates to a rectification purification method for recovering NMP from NMP regeneration liquid, which is realized by depending on a purification device, the purification device comprises a dehydration tower, a dehydration condenser, a finished product tower and a finished product condenser, preheating type mixing assemblies are arranged in the dehydration tower and the finished product tower, each preheating type mixing assembly comprises a preheating collection cylinder, and the preheating collection cylinders are connected with the dehydration condenser and the finished product condenser. A side mining assembly is arranged on the preheating collecting barrel in the finished product tower; according to the invention, pressurized injection of NMP regeneration liquid and reflux liquid is utilized, and a preheating type mixing assembly is matched, so that the regeneration liquid in the tower body can be fully mixed in a multi-stage manner, the same flowing concentration of the regeneration liquid is ensured, the light component extraction effect is improved, the regeneration liquid can be preheated before entering the tower body, and the energy consumption of the reboiler is reduced; in addition, by combining a side mining assembly, partitioned side mining treatment of the NMP finished product is achieved, and the efficient side mining efficiency of the NMP finished product is ensured while the side mining qualification of the NMP finished product is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of distillation separation, and particularly to a distillation purification method for recovering NMP from NMP regeneration liquid. Background Art

[0002] With the booming development of the new energy vehicle industry, as the core component of new energy vehicles, the technology of power batteries has advanced by leaps and bounds. As an indispensable solvent in the manufacture of power batteries, the demand for N-methylpyrrolidone (NMP) has also increased sharply. Through research and market discovery, after distillation and purification, the NMP solvent used in power batteries can be reused. Therefore, the recovery of NMP regeneration liquid after the use of NMP in power batteries is an emerging market, which not only reduces the amount of hazardous waste disposal by power battery manufacturers, but also plays a positive role in energy conservation, emission reduction and environmental friendliness.

[0003] However, the traditional NMP regeneration liquid recovery process mainly uses a three-tower process. In comparison, it has problems such as complex operation, high energy consumption, and long qualified product replacement time, and cannot meet the urgent need for energy conservation and consumption reduction at present; and when the reboiler extracts the NMP regeneration liquid in the tower body for light component distillation separation, the discharge of the NMP regeneration mixed liquid before and after dehydration is often carried out synchronously, which is likely to cause incomplete removal of light components and lead to unqualified quality of the recovered NMP finished product.

[0004] In view of the above technical defects, a solution is proposed now. Summary of the Invention

[0005] The purpose of the present invention is to provide a distillation purification method for recovering NMP from NMP regeneration liquid. By using the pressurized injection of NMP regeneration liquid and reflux liquid, and cooperating with a preheating type mixing component, it can not only mix the regeneration liquid in the tower body multi-stage fully, ensure that the flowing concentration of the regeneration liquid is the same, improve the light component extraction effect, but also preheat the regeneration liquid before entering the tower body, reducing the energy consumption of the reboiler; in addition, combined with a side extraction component, it realizes the partitioned side extraction treatment of NMP finished product, improves the qualified rate of NMP finished product side extraction, and ensures the high-efficiency side extraction efficiency of NMP finished product, so as to solve the above-mentioned technical defects.

[0006] The purpose of the present invention can be realized through the following technical solutions: A distillation purification method for recovering NMP from NMP regeneration liquid, comprising the following steps: Step 1: Inject the NMP regeneration liquid into the dehydration tower in the purification device for dehydration distillation, and preheat the NMP regeneration liquid with the dehydrated NMP regeneration liquid. The light components in the dehydration tower are condensed by the dehydration condenser and enter the dehydration reflux tank, and the tail gas is sucked to the tail gas system under negative pressure. Part of the light components are pressurized and refluxed to the dehydration tower and fully mixed with the NMP regeneration liquid, and part of the light components are transported to the sewage treatment equipment for treatment; Step 2: The dehydrated NMP regenerant liquid is injected into the finished product tower for secondary dehydration rectification. A small amount of light components in the finished product tower are condensed by the finished product condenser and enter the finished product reflux tank. The tail gas is evacuated to the tail gas system under negative pressure. Part of the light components are pressurized and refluxed to the finished product tower and fully mixed with the dehydrated NMP regenerant liquid, and part is drawn out into the NMP crude product tank; Step 3: The secondary dehydrated NMP regenerant liquid is rectified in the finished product tower in combination with a heating rod, and the dehydrated NMP regenerant liquid is assisted in preheating synchronously. The NMP finished product is condensed by the side draw condenser and enters the side draw tank for temporary storage.

[0007] Among them, the rectification and purification method for recovering NMP from the NMP regenerant liquid is realized by relying on a purification device. The purification device includes a dehydration tower, a dehydration condenser, a finished product tower and a finished product condenser. Preheating type mixing components are arranged in both the dehydration tower and the finished product tower. The preheating type mixing component includes a preheating collection cylinder and a hollow stirring rod located on one side of the preheating collection cylinder. A serpentine preheating pipe is installed inside the preheating collection cylinder; A side draw component is arranged on the preheating collection cylinder in the finished product tower. The side draw component includes a Z-shaped partition plate fixedly installed inside the corresponding preheating collection cylinder, and a side draw condenser and a side draw tank located outside the finished product tower.

[0008] Preferably, a reboiler is installed on one side of both the dehydration tower and the finished product tower. The dehydration tower, the finished product tower and the corresponding preheating collection cylinder are communicated through the reboiler pipelines on the reboiler. A NMP crude product tank is arranged on one side of the dehydration tower, and a crude product feed pipe is communicated between the NMP crude product tank and the serpentine preheating pipe in the dehydration tower. A crude product feed pump is arranged on the crude product feed pipe.

[0009] Preferably, a dehydration reflux tank and a finished product reflux tank are respectively arranged on one side of the dehydration tower and the finished product tower. The dehydration tower, the dehydration condenser and the dehydration reflux tank, and the finished product tower, the finished product condenser and the finished product reflux tank are communicated through light component pipelines.

[0010] Preferably, a liquid outlet pipe is communicated with the light component pipeline. Dehydration reflux pumps and finished product reflux pumps are respectively arranged on the two light component pipelines and are matched with the corresponding dehydration reflux tank and finished product reflux tank.

[0011] Preferably, a heavy component pipeline is communicated with the bottom of the preheating collection cylinder. A dehydration bottom pump and a finished product bottom pump are respectively arranged on the two heavy component pipelines. The heavy component pipeline on the dehydration tower bottom pump is communicated with the serpentine preheating pipe in the finished product tower.

[0012] Preferably, a mixing cylinder rotatably connected to the hollow stirring rod is fixedly connected between the end of the serpentine preheating pipe and the end of the light component pipeline. Arc-shaped liquid outlet pipes are respectively fixedly communicated with the ends of the serpentine preheating pipe and the light component pipeline, and a plurality of liquid outlet openings are obliquely arranged on the arc side of the arc-shaped liquid outlet pipe.

[0013] Preferably, an impeller is fixedly connected to the hollow stirring rod and located inside the mixing barrel, and a liquid inlet communicating with the mixing barrel is opened inside the hollow stirring rod, a plurality of hollow auxiliary rods are fixedly connected to the hollow stirring rod, and a plurality of liquid spray outlets are opened on the same side of the hollow auxiliary rod.

[0014] Preferably, a heating rod is installed in the preheating collection cylinder on the finished product tower, the side collection tank, the side collection condenser and the corresponding preheating collection cylinder are connected through the side collection finished product pipe, and a connecting port with an electromagnetic control valve installed inside is opened at the bottom of the Z-shaped partition.

[0015] The beneficial effects of the present invention are as follows: (1) The present invention uses pressurized injection of NMP regeneration liquid and reflux liquid to assist the impeller in carrying the hollow stirring rod to rotate, so that the regeneration liquid is initially mixed in the mixing cylinder, and the thrust of the regeneration liquid discharged from the hollow auxiliary rod is used to assist the rotation of the hollow stirring rod, thereby achieving secondary full mixing of the regeneration liquid in the tower body, so as to ensure that the concentration of the regeneration liquid entering the reboiler is the same, thereby achieving a high-efficiency light component distillation extraction effect; and by injecting the regeneration liquid after distillation into the preheating collection cylinder, the NMP regeneration liquid is injected into the tower body through the serpentine preheating pipe, thereby achieving a preheating effect before the regeneration liquid enters the tower body, achieving an energy-saving effect.

[0016] (2) The present invention also provides a Z-shaped partition and a timed opening of an electromagnetic control valve in the preheating collection tube in the finished product tower, so as to divide the interior of the corresponding preheating collection tube into a temporary storage chamber and a side sampling chamber, thereby promoting secondary distillation of the light components in the regenerated liquid and synchronously carrying out distillation and side sampling of the NMP finished product in a zoned manner, thereby avoiding the problem of partial mixing of the two, thereby improving the qualification of the side sampling of the NMP finished product and ensuring the high efficiency of the side sampling of the NMP finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings; Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is a structural schematic diagram of a dehydration tower of the present invention; Figure 3 It is a structural schematic diagram of the finished product tower of the present invention; Figure 4 It is a structural schematic diagram of the preheating mixing assembly of the present invention; Figure 5 It is a schematic diagram of the coordination of the preheating mixing component and the side collection component of the present invention; Figure 6 It is a schematic diagram of the structure of the mixing barrel of the present invention; Figure 7 It is a schematic structural diagram of the hollow stirring rod of the present invention.

[0018] Legend: 1. Dehydration tower; 11. Dehydration condenser; 12. Product tower; 13. Product condenser; 14. Reboiler; 15. NMP crude product tank; 16. Crude product feed pump; 17. Dehydration reflux tank; 18. Product reflux tank; 19. Dehydration reflux pump; 110. Product reflux pump; 111. Dehydration bottom pump; 112. Product bottom pump; 2. Preheating type mixing assembly; 21. Preheating collection cylinder; 22. Hollow stirring rod; 23. Serpentine preheating pipe; 24. Mixing cylinder; 25. Arc-shaped liquid outlet pipe; 26. Impeller; 27. Hollow auxiliary rod; 3. Side drawing assembly; 31. Z-shaped partition board; 32. Side drawing condenser; 33. Side drawing tank; 34. Heating rod. Specific embodiments

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Embodiment 1: Please refer to Figures 1 - 7 As shown, in view of the problem that during the rectification and separation of light components in the prior art, the discharge of the NMP regeneration mixture before and after dehydration is carried out synchronously, which is likely to cause incomplete removal of light components, the following solutions can be adopted; In this embodiment, the rectification and purification method for recovering NMP from the NMP regeneration liquid is realized by relying on a purification device. The purification device includes a dehydration tower 1, a dehydration condenser 11, a product tower 12 and a product condenser 13. The dehydration tower 1 is used for the primary rectification and extraction of light components in the NMP regeneration liquid, and the product tower 12 is used for the secondary separation of a small amount of light components contained in the dehydrated NMP regeneration liquid, and realizes the rectification and extraction of NMP products. The dehydration tower 1 and the product tower 12 are both provided with a preheating type mixing assembly 2; To realize the secondary full mixing treatment of the regeneration liquid in the tower body, to ensure that the concentration of the regeneration liquid entering the reboiler 14 is the same, so as to achieve an efficient light component rectification and extraction effect, and to realize the preheating effect of the regeneration liquid before entering the tower body, playing an energy-saving effect. The preheating type mixing assembly 2 includes a preheating collection cylinder 21; The preheating collection cylinder 21 is provided for compartmentally receiving the dehydrated NMP regenerant liquid that has completed the separation of light components, preventing it from mixing with the NMP regenerant liquid entering the tower body, so as to avoid the problem that when the dehydrated NMP regenerant liquid is discharged, it takes away part of the NMP regenerant liquid, resulting in incomplete removal of light components, and the hollow stirring rod 22 located on one side of the preheating collection cylinder 21, and a serpentine preheating pipe 23 is installed inside the preheating collection cylinder 21; A side sampling assembly 3 is provided on the preheating collection cylinder 21 in the finished product tower 12 for side sampling of the NMP finished product separated by rectification in the finished product tower 12. The side sampling assembly 3 includes a Z-shaped partition 31 fixedly installed inside the corresponding preheating collection cylinder 21, and a side sampling condenser 32 and a side sampling tank 33 located outside the finished product tower 12.

[0021] Reboilers 14 are installed on one side of both the dehydration tower 1 and the finished product tower 12. The dehydration tower 1, the finished product tower 12 and the corresponding preheating collection cylinder 21 are all connected through the reboil pipelines on the reboilers 14, for rectifying and extracting light components from the NMP regenerant liquid in the dehydration tower 1 and the dehydrated NMP regenerant liquid in the finished product tower 12. A crude NMP tank 15 is provided on one side of the dehydration tower 1. The NMP regenerant liquid is stored in the crude NMP tank 15 by a transport vehicle, and a crude product feed pipe is connected between the crude NMP tank 15 and the serpentine preheating pipe 23 in the dehydration tower 1, and a crude product feed pump 16 is provided on the crude product feed pipe; The crude product feed pump 16 combines with the crude product feed pipe to inject the NMP regenerant liquid in the crude NMP tank 15 into the serpentine preheating pipe 23 in the dehydration tower 1, and then enters the bottom of the dehydration tower 1, and is dehydrated and rectified by the reboiler 14. The dehydrated NMP regenerant liquid is injected into the preheating collection cylinder 21 in the dehydration tower 1, and the heat energy contained therein is transferred to the NMP regenerant liquid through the serpentine preheating pipe 23, thereby preheating the NMP regenerant liquid.

[0022] A dehydration reflux tank 17 and a finished product reflux tank 18 are respectively provided on one side of the dehydration tower 1 and the finished product tower 12. The dehydration tower 1, the dehydration condenser 11 and the dehydration reflux tank 17, and the finished product tower 12, the finished product condenser 13 and the finished product reflux tank 18 are all connected through light component pipelines. The light component pipelines include an upper pipeline and a lower pipeline. The upper pipeline connects the dehydration tower 1, the dehydration condenser 11 and the dehydration reflux tank 17, and the lower pipeline connects the bottom of the dehydration reflux tank 17 to the middle of the dehydration tower 1. The finished product tower 12, the finished product condenser 13 and the finished product reflux tank 18 are connected in the same way; The tops of the dehydration reflux tank 17 and the finished product reflux tank 18 are both fixedly connected with air pipes, and a vacuum pump (not shown in the figure) is provided on the air pipes, which is used to drain and extract the light components in the dehydration tower 1 and the finished product tower 12, and to draw the non-condensable tail gas under negative pressure to the tail gas system for treatment. The light components coming out from the top of the dehydration tower 1 combine with the upper pipeline of the light component pipeline, enter the dehydration reflux tank 17 after being condensed by the dehydration condenser 11, and then combine with the lower pipeline of the light component pipeline, and part of them flow back to the dehydration tower 1. The treatment process of the light components coming out from the top of the finished product tower 12 is the same as that of the light components in the dehydration tower 1.

[0023] A liquid outlet pipe is connected to the light component pipeline. The dehydration reflux pump 19 and the finished product reflux pump 110 that cooperate with the corresponding dehydration reflux tank 17 and the finished product reflux tank 18 are respectively provided on the two light component pipelines. The dehydration reflux pump 19 and the finished product reflux pump 110 are provided for the pressurized discharge of the light components in the dehydration reflux tank 17 and the finished product reflux tank 18. Flow control valves are provided on both the lower pipeline of the light component pipeline and the liquid outlet pipe to control the amount of solution flowing back to the dehydration tower 1 and the finished product tower 12. The end of the liquid outlet pipe on the dehydration tower 1 is connected to the wastewater treatment equipment to treat part of the light components in the dehydration reflux tank 17. The end of the liquid outlet pipe on the finished product tower 12 is connected to the NMP crude product tank 15.

[0024] The bottom of the preheating collection cylinder 21 is connected with a heavy component pipeline. The dehydration bottom pump 111 and the finished product bottom pump 112 are respectively provided on the two heavy component pipelines. The dehydration bottom pump 111 and the finished product bottom pump 112 are provided for the pressurized discharge of the dehydrated NMP regeneration liquid or the heavy components in the dehydration tower 1 and the finished product tower 12. The heavy component pipeline on the bottom pump of the dehydration tower 1 communicates with the serpentine preheating pipe 23 in the finished product tower 12, which is used to inject the dehydrated NMP regeneration liquid into the interior of the finished product tower 12 under pressure.

[0025] A mixing cylinder 24 rotatably connected with the hollow stirring rod 22 is fixedly connected between the serpentine preheating pipe 23 and the end of the light component pipeline. The serpentine preheating pipe 23 and the end of the light component pipeline are respectively fixedly connected with an arc-shaped liquid outlet pipe 25. A plurality of liquid outlet openings are obliquely arranged on the arc-shaped side of the arc-shaped liquid outlet pipe 25. The inner diameter size of the arc-shaped liquid outlet pipe 25 gradually decreases towards its free end direction to maintain the same impact effect when the regeneration liquid inside the arc-shaped liquid outlet pipe 25 is discharged through the plurality of liquid outlet openings. By using the pressurized injection of the NMP regeneration liquid and the reflux liquid, the preliminary mixing treatment effect of the regeneration liquid in the mixing cylinder 24 is achieved.

[0026] An impeller 26 is fixedly connected to the hollow stirring rod 22 and is located inside the mixing cylinder 24. A liquid inlet communicating with the mixing cylinder 24 is provided inside the hollow stirring rod 22. A plurality of hollow auxiliary rods 27 are fixedly communicated with the hollow stirring rod 22, and a plurality of liquid spraying ports are provided on the same side of the hollow auxiliary rods 27. By means of the pressurized injection of the NMP regeneration liquid and the reflux liquid, the impeller 26 is jointly assisted to drive the hollow stirring rod 22 to rotate, so that the regeneration liquid is preliminarily mixed in the mixing cylinder 24 first; Then, it enters the hollow stirring rod 22 through the liquid inlet on the hollow stirring rod 22, and then is discharged through the liquid spraying ports on the plurality of hollow auxiliary rods 27. By means of the thrust generated by the discharge of the regeneration liquid from the hollow auxiliary rods 27, the rotation effect of the hollow stirring rod 22 is secondarily assisted, so as to realize the secondary sufficient mixing treatment of the regeneration liquid in the tower body, ensure that the concentration of the regeneration liquid entering the reboiler 14 is the same, and further achieve the efficient light component rectification and extraction effect.

[0027] Embodiment Two: Please refer to Figure 3 and Figure 5 As shown, for the problem that there is partial mixing between the NMP finished product and the light component extraction, resulting in the inability to efficiently collect the NMP finished product, the following solution can be adopted; In this embodiment, a side extraction assembly 3 is arranged on the preheating and collecting cylinder 21 in the finished product tower 12. The side extraction assembly 3 includes a Z-shaped partition plate 31 fixedly installed inside the corresponding preheating and collecting cylinder 21, and the bottom of the Z-shaped partition plate 31 is located below the end of the reboiling pipeline, which is used to divide the inside of the corresponding preheating and collecting cylinder 21 into a temporary storage chamber and a side extraction chamber, so as to promote the secondary rectification of the light components in the regeneration liquid and simultaneously carry out the rectification side extraction of the NMP finished product in a partitioned manner, avoiding the problem of partial mixing between the two, and a side extraction condenser 32 and a side extraction tank 33 located outside the finished product tower 12.

[0028] A heating rod 34 is installed in the preheating and collecting cylinder 21 on the finished product tower 12. The side extraction tank 33, the side extraction condenser 32 and the corresponding preheating and collecting cylinder 21 are communicated through a side extraction finished product pipe. A communication port with an electromagnetic control valve I installed inside is opened at the bottom of the Z-shaped partition plate 31, and an electromagnetic control valve II is installed on the heavy component branch pipeline connected to the finished product tower 12. By opening the electromagnetic control valve I and closing the electromagnetic control valve II, the secondary dehydrated NMP regeneration liquid located above the Z-shaped partition plate 31 is discharged into the preheating and collecting cylinder 21 below it; It is heated and rectified by the heating rod 34, so that the NMP finished product evaporates and then enters the side extraction tank 33 through the side extraction finished product pipe in combination with the side extraction condenser 32 for temporary storage. Then, by closing the electromagnetic control valve I and opening the electromagnetic control valve II, the heavy components are discharged. A gas pipe is fixedly communicated with the top of the side extraction tank 33, and a vacuum pump (not shown in the figure) is provided on the gas pipe, which is used to drain and extract the NMP finished product in the side extraction tank 33, and draw the non-condensable tail gas to the tail gas system for treatment under negative pressure.

[0029] Example 3: Please refer to Figures 1 - 7 As shown, the present invention also proposes a rectification and purification method for recovering NMP from the NMP regeneration liquid, including the following steps: Step 1: The NMP regeneration liquid is stored in the NMP crude product tank 15 in the purification device through a transport vehicle, and then the NMP regeneration liquid in the NMP crude product tank 15 is injected into the serpentine preheating pipe 23 in the dehydration tower 1 through the crude product feed pump 16 and the corresponding arc-shaped liquid outlet pipe 25, hollow stirring rod 22 and hollow auxiliary rod 27, and enters the bottom of the dehydration tower 1. Dehydration rectification is carried out through the reboiler 14, and the dehydrated NMP regeneration liquid is injected into the preheating collection cylinder 21 in the dehydration tower 1 for partitioned storage, and at the same time, the NMP regeneration liquid injected into the dehydration tower 1 is preheated. The vacuum pump on the dehydration reflux tank 17 combines with the gas pipe to drain and extract the light components in the dehydration tower 1, and the non-condensable tail gas is sucked to the tail gas system under negative pressure for treatment. The light components coming out from the top of the dehydration tower 1 enter the dehydration reflux tank 17 after being condensed by the dehydration condenser 11. The light component liquid in the dehydration reflux tank 17 is pressurized by the dehydration reflux pump 19, and part of it is transported to the sewage treatment equipment for treatment, and part of it is refluxed to the dehydration tower 1 and combined with the injection of the NMP regeneration liquid to jointly drive the impeller 26 to drive the hollow stirring rod 22 to rotate, and the hollow stirring rod 22 combines with the hollow auxiliary rod 27 to fully mix the liquid in the dehydration tower 1. Step 2: The dehydrated NMP regeneration liquid in the preheating collection cylinder 21 in the dehydration tower 1 is injected into the finished product tower 12 through the dehydration bottom pump 111 and combined with the reboiler 14 for secondary dehydration rectification, and the secondary dehydrated NMP regeneration liquid is injected into the preheating collection cylinder 21 in the finished product tower 12. A small amount of light components coming out from the top of the finished product tower 12 enter the finished product reflux tank 18 after being condensed by the finished product condenser 13. The non-condensable tail gas in the finished product reflux tank 18 is sucked to the tail gas system under negative pressure. The light component liquid in the finished product reflux tank 18 is pressurized by the finished product reflux pump 110, and part of it is taken out to the NMP crude product tank 15, and part of it is refluxed to the finished product tower 12 and combined with the injection of the dehydrated NMP regeneration liquid to jointly drive the hollow stirring rod 22 to rotate to fully mix the liquid in the finished product tower 12. Step 3: When the dehydrated NMP regeneration liquid enters the preheating collection cylinder 21 in the finished product tower 12, it is first stored in the preheating collection cylinder 21 above the Z-shaped partition 31, and then through the timed opening of the electromagnetic control valve 1, it is introduced into the preheating collection cylinder 21 below the Z-shaped partition 31. The secondary dehydrated NMP regeneration liquid is rectified through the heating rod 34, and the introduced dehydrated NMP regeneration liquid is assisted in preheating. The NMP finished product enters the side collection tank 33 for temporary storage after being condensed by the side collection condenser 32. The heavy components in the preheating collection cylinder 21 in the finished product tower 12 are discharged through the opening of the electromagnetic control valve 2.

[0030] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A distillation and purification method for recovering NMP from NMP regeneration liquid, characterized in that: The following steps are involved: Step 1: The NMP regeneration liquid is injected into the dehydration tower (1) in the purification device for dehydration and rectification, and the NMP regeneration liquid is preheated by the dehydrated NMP regeneration liquid. The light components in the dehydration tower (1) are condensed by the dehydration condenser (11) and enter the dehydration reflux tank (17). The tail gas is negatively pressured and pumped to the tail gas system. Part of the light components are pressurized and refluxed to the dehydration tower (1) and are fully mixed with the NMP regeneration liquid. Part of the light components are transported to the sewage treatment equipment for treatment. Step 2: The dehydrated NMP regeneration liquid is injected into the finished product tower (12) for secondary dehydration and distillation. A small amount of light components in the finished product tower (12) are condensed into the finished product reflux tank (18) through the finished product condenser (13). The tail gas is negatively pressured and pumped to the tail gas system. Some of the light components are pressurized and refluxed to the finished product tower (12) and are fully mixed with the dehydrated NMP regeneration liquid. Some of them are extracted to the NMP crude product tank (15). Step 3: The secondary dehydrated NMP regeneration liquid is distilled in the finished product tower (12) in combination with the heating rod (34), and the dehydrated NMP regeneration liquid is simultaneously preheated. The NMP finished product is condensed by the side sampling condenser (32) and enters the side sampling tank (33) for temporary storage.

2. The distillation purification method for recovering NMP from NMP regeneration liquid according to claim 1 is implemented by a purification device, and the purification device comprises a dehydration tower (1), a dehydration condenser (11), a finished product tower (12) and a finished product condenser (13), characterized in that: The dehydration tower (1) and the finished product tower (12) are both provided with a preheating mixing assembly (2), the preheating mixing assembly (2) comprising a preheating collecting cylinder (21) and a hollow stirring rod (22) located on one side of the preheating collecting cylinder (21), and a serpentine preheating tube (23) is installed inside the preheating collecting cylinder (21); A side collection assembly (3) is provided on the preheating collection cylinder (21) in the finished product tower (12), and the side collection assembly (3) comprises a Z-shaped partition (31) fixedly installed inside the corresponding preheating collection cylinder (21), and a side collection condenser (32) and a side collection tank (33) located outside the finished product tower (12).

3. The method for rectifying and purifying NMP from NMP regeneration liquid according to claim 2, characterized in that: A reboiler (14) is installed on one side of the dehydration tower (1) and the finished product tower (12). The dehydration tower (1) is connected to the finished product tower (12) and the corresponding preheating collection cylinder (21) through a reboiler pipeline on the reboiler (14). A crude NMP product tank (15) is provided on one side of the dehydration tower (1). A crude product feed pipe is connected between the crude NMP product tank (15) and the serpentine preheating pipe (23) in the dehydration tower (1). A crude product feed pump (16) is provided on the crude product feed pipe.

4. The method for reclaiming NMP from NMP regeneration liquid according to claim 2, characterized in that: A dehydration reflux tank (17) and a finished product reflux tank (18) are respectively provided on one side of the dehydration tower (1) and the finished product tower (12); the dehydration tower (1), the dehydration condenser (11) and the dehydration reflux tank (17), and the finished product tower (12), the finished product condenser (13) and the finished product reflux tank (18) are all connected via a light component pipeline.

5. The method for reclaiming NMP from NMP regeneration liquid according to claim 4, characterized in that: The light component pipeline is connected to a liquid outlet pipe, and the two groups of light component pipelines are respectively provided with a dehydration reflux pump (19) and a finished product reflux pump (110) that cooperate with the corresponding dehydration reflux tank (17) and finished product reflux tank (18).

6. The method for reclaiming NMP from NMP regeneration liquid according to claim 2, characterized in that: The bottom of the preheating collection cylinder (21) is connected to a heavy component pipeline, and two groups of heavy component pipelines are respectively provided with a dehydration bottom pump (111) and a finished product bottom pump (112). The heavy component pipeline on the bottom pump of the dehydration tower (1) is connected to the serpentine preheating pipe (23) in the finished product tower (12).

7. The method for reclaiming NMP from NMP regeneration liquid according to claim 5, characterized in that: A mixing cylinder (24) rotatably connected to the hollow stirring rod (22) is fixedly connected between the serpentine preheating pipe (23) and the end of the light component pipeline, and an arc-shaped liquid outlet pipe (25) is fixedly connected to the end of the serpentine preheating pipe (23) and the light component pipeline, respectively, and a plurality of liquid outlets are obliquely provided on the arc-shaped side of the arc-shaped liquid outlet pipe (25).

8. The method for reclaiming NMP from NMP regeneration liquid according to claim 7, characterized in that: An impeller (26) is fixedly connected to the hollow stirring rod (22) and is located inside the mixing barrel (24), and a liquid inlet communicating with the mixing barrel (24) is provided inside the hollow stirring rod (22). A plurality of hollow auxiliary rods (27) are fixedly connected to the hollow stirring rod (22), and a plurality of liquid spraying ports are provided on the same side of the hollow auxiliary rods (27).

9. The method for reclaiming NMP from NMP regeneration liquid according to claim 2, characterized in that: A heating rod (34) is installed in the preheating collection cylinder (21) on the finished product tower (12); the side collection tank (33), the side collection condenser (32) and the corresponding preheating collection cylinder (21) are connected through the side collection finished product pipe; and a communication port in which an electromagnetic control valve is installed is provided at the bottom of the Z-shaped partition (31).

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