NMP (N-Methyl Pyrrolidone) recovery system for cleaning waste liquid of lithium battery positive electrode slurry mixing equipment

Abstract

The utility model relates to the technical field of lithium battery production, in particular to an NMP (N-Methyl Pyrrolidone) recovery system for cleaning waste liquid of lithium battery positive electrode slurry mixing equipment, which comprises a slurry recovery unit, a waste liquid recovery unit, a waste liquid recovery unit, a waste liquid recovery unit and a waste liquid recovery unit, and is characterized in that the slurry recovery unit is used for separating a positive electrode material and NMP-containing waste water from positive electrode slurry mixing cleaning waste water; the extraction unit is used for enabling an extraction agent to be in contact with the NMP-containing wastewater to obtain NMP-containing extraction liquid; and the rectification unit is used for rectifying and separating the NMP-containing extraction liquid into an extraction agent and NMP. The extraction unit provided by the utility model can effectively remove NMP content in wastewater, reduce COD and total nitrogen content in water, and create conditions for back-end wastewater biochemical treatment. The rectification unit can effectively separate the extraction agent and NMP, the purity of NMP is larger than 99.8%, economic benefits can be improved, and the extraction agent can return to the extraction unit to be reused.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium battery production, in particular to an NMP recovery system for cleaning waste liquid of lithium battery positive electrode slurry equipment. Background Art

[0002] With the rapid development of the lithium battery industry, the price of NMP (N-methylpyrrolidone) as a solvent for positive electrode materials has also increased year by year. NMP has stable chemical properties and is 100% miscible with water. When the positive electrode slurry equipment is cleaned, it enters the wastewater together with the positive electrode material. If the wastewater is directly discharged to the wastewater treatment station for treatment, it will not only waste the NMP dissolved in the water, but also greatly increase the COD and total nitrogen content in the water, making the existing wastewater treatment technology much more difficult.

[0003] Chinese patent CN107285495A discloses a lithium-ion battery production wastewater treatment device, including an organic separation tank, a distillation tower and a deep water purification tank; the top of the organic separation tank is sealed and connected to a tank cover, and a reagent addition port is provided at the top of the tank cover; the organic solvent is transported to the distillation tower through a pipeline, and the distillation tower includes a heating tank and a reflux separation tower; the deep water purification tank includes a deep water purification tank body, and an activated carbon filter plate, a first filter membrane, a second filter membrane and a third filter membrane are arranged in sequence inside the deep water purification tank along the wastewater conveying direction; the pore sizes of the first filter membrane, the second filter membrane and the third filter membrane decrease in sequence, and the spacings between the activated carbon filter plate, the first filter membrane, the second filter membrane and the third filter membrane decrease in sequence; the pipeline is equipped with a flow regulating valve, and the conveying power of the solution in the pipeline is provided by an electric pump.

[0004] For example, CN109912484B discloses a method for separating and reusing NMP from NMP brine, using high-boiling-point esters with stable physicochemical properties as extractants to separate NMP from brine, combining vacuum distillation technology to achieve good separation of NMP and the extractant, and directly collecting high-purity NMP from the top of the tower, including neutralization pretreatment, extraction, dehydration and vacuum distillation processes, using high-boiling-point esters as extractants to extract slag removal wastewater 3-5 times, with a solvent ratio of 1-3.5, combining the extract phases and dehydrating them, performing vacuum distillation on the dehydrated extract phases, and collecting NMP from the top of the tower.

[0005] In the prior art, NMP treatment systems add other reagents during the treatment process, that is, introduce new chemical substances. Although NMP can be recovered, it causes pollution to other products and is difficult to reuse other products. In addition, it is difficult for the existing NMP treatment system to recover the extractant and reuse it for extraction, and it is impossible to stably supply the recovered extractant to the extraction unit. At the same time, in the prior art, after the insoluble solids contained in the wastewater enter the extraction equipment and the distillation equipment, not only will the recovered NMP contain impurities, but it will also easily lead to more solid impurities remaining in the equipment. Utility Model Content

[0006] In order to solve the above problems, the purpose of the utility model is to provide an NMP recovery system for cleaning waste liquid of lithium battery positive electrode slurry mixing equipment.

[0007] The technical solution provided by the utility model is:

[0008] In a first aspect, a NMP recovery system for washing waste liquid of a lithium battery positive electrode slurry mixing equipment comprises:

[0009] A slurry recovery unit, which is used to separate positive electrode materials and NMP-containing wastewater from positive electrode slurry washing wastewater;

[0010] An extraction unit, which is used to contact an extractant with NMP-containing wastewater to obtain an NMP-containing extract;

[0011] The distillation unit is used for distilling the NMP-containing extract into an extractant and NMP.

[0012] As an optional technical solution of the first aspect, the slurry recovery unit includes a centrifugal separation device and an ultrafiltration separation device connected in sequence; the slurry recovery unit is also used to remove insoluble solids in the NMP-containing wastewater.

[0013] Furthermore, the slurry recovery unit also includes a wastewater tank connected to the ultrafiltration separation device, and the wastewater tank is used to store NMP-containing wastewater.

[0014] Further, the wastewater tank includes a first box body mounted on a first base;

[0015] The first box body is provided with a first water inlet pipe connected to the water outlet of the ultrafiltration separation device, and a first solenoid valve and a first float valve are installed on the first water inlet pipe;

[0016] A first electromagnetic liquid level meter is installed at the side end of the first box;

[0017] A first breathing pipe and a first inspection manhole are installed at the top of the first box;

[0018] A first drain pipe is installed at the bottom end of the first box body, and a first gate valve is installed on the first drain pipe;

[0019] A first water outlet pipe is also installed at the bottom end of the first box body, and a first flow meter and a first vortex preventer are installed on the first water outlet pipe;

[0020] The first water outlet pipe is connected to the extraction unit through a first water pump.

[0021] Furthermore, the extraction unit comprises a plurality of centrifugal extractors connected in series.

[0022] Furthermore, the distillation unit includes a preheater, an ultra-gravity distillation tower, a condenser connected in sequence.

[0023] The preheater is used to heat the NMP-containing extract to the boiling point of the extractor;

[0024] The ultra-gravity distillation tower is used to separate the NMP-containing extract to obtain NMP and extractant vapor;

[0025] The condenser is used to condense the extractant vapor to obtain the liquid extractant.

[0026] Furthermore, the distillation unit further comprises an extractant tank connected to the condenser, and the extractant tank is used to store the liquid extractant;

[0027] The extractant box is connected to a second water pump, and the second water pump is used to transport the liquid extractant in the extractant box to the extraction unit.

[0028] Further, the extractant box includes a second box body mounted on a second base;

[0029] The second box body is provided with a second water inlet pipe connected to the outlet of the condenser, and a second solenoid valve and a second float valve are installed on the second water inlet pipe;

[0030] A second electromagnetic liquid level gauge is installed at the side end of the second box;

[0031] A second breathing pipe and a second inspection manhole are installed on the top of the second box;

[0032] A second drain pipe is installed at the bottom end of the second box body, and a second gate valve is installed on the second drain pipe;

[0033] A second water outlet pipe is also installed at the bottom end of the second box, and a second flow meter and a second vortex preventer are installed on the second water outlet pipe;

[0034] The second water outlet pipe is connected to the second water pump.

[0035] Furthermore, an extractant replenishing tube is installed at the top of the second box.

[0036] Furthermore, insect-proof nets are installed at the ends of the first breathing tube, the first air discharge tube, the second breathing tube and the second air discharge tube.

[0037] Compared with the prior art, the technical solution provided by the utility model has the following beneficial effects:

[0038] The extraction unit of the present application can effectively remove the NMP content in the wastewater, reduce the COD and total nitrogen content in the water, and create conditions for the back-end biochemical treatment of wastewater. The distillation unit can effectively separate the extractant and NMP. The purity of NMP is greater than 99.8%, which can improve economic benefits. The extractant can also be returned to the extraction unit for reuse. Moreover, before centrifugal extraction, the present application performs centrifugal separation and ultrafiltration separation on the wastewater in turn, which can not only recover the positive electrode material, but also remove insoluble solids. At the same time, the present application does not introduce new impurities during the treatment process, which reduces the difficulty of subsequent wastewater treatment and is also conducive to the reuse of various substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of an NMP recovery system in one embodiment of the present application;

[0040] Figure 2 This is a schematic diagram of multiple centrifugal extractors connected in series in one embodiment of the present application;

[0041] Figure 3 A top view of a waste water tank in one embodiment of the present application;

[0042] Figure 4 This is a side view of a waste water tank in one embodiment of the present application;

[0043] Figure 5 This is a top view of an extractant box in one embodiment of the present application;

[0044] Figure 6 This is a side view of an extractant box in one embodiment of the present application.

[0045] Explanation of the symbols in the schematic diagram:

[0046] 1 a first centrifugal extractor, 2 a second centrifugal extractor, 3 a third centrifugal extractor, 4 a fourth centrifugal extractor, 5 a first water pump, 6 a wastewater tank, 7 an ultrafiltration separation device, 8 a centrifugal separation device, 9 an extractant tank, 10 a second water pump, 11 a condenser, 12 an ultra-gravity distillation tower, 13 a preheater;

[0047] 101 is the wastewater inlet of the first centrifugal extractor, 102 is the extractant inlet of the first centrifugal extractor, 103 is the heavy phase outlet of the first centrifugal extractor, and 104 is the light phase outlet of the first centrifugal extractor;

[0048] 201 is the wastewater inlet of the second centrifugal extractor, 202 is the extractant inlet of the second centrifugal extractor, 203 is the heavy phase outlet of the second centrifugal extractor, and 204 is the light phase outlet of the second centrifugal extractor;

[0049] 301 is the wastewater inlet of the third centrifugal extractor, 302 is the extractant inlet of the third centrifugal extractor, 303 is the heavy phase outlet of the third centrifugal extractor, and 304 is the light phase outlet of the third centrifugal extractor;

[0050] 401 is the wastewater inlet of the fourth centrifugal extractor, 402 is the extractant inlet of the fourth centrifugal extractor, 403 is the heavy phase outlet of the fourth centrifugal extractor, and 404 is the light phase outlet of the fourth centrifugal extractor;

[0051] 601 first box body, 602 first base, 603 first inspection manhole, 604 first inspection ladder, 605 first water inlet pipe, 606 first solenoid valve, 607 first float valve, 609 first electromagnetic level gauge, 610 first breathing tube, 611 first gate valve, 612 first drain pipe, 614 first flow meter, 615 first water outlet pipe, 616 first vortex preventer;

[0052] 901 second box body, 902 second base, 903 second inspection manhole, 904 second inspection ladder, 905 second water inlet pipe, 906 second solenoid valve, 907 second float valve, 908 extractant replenishing pipe, 909 second electromagnetic level gauge, 910 second breathing tube, 911 second gate valve, 912 second drain pipe, 914 second flow meter, 915 second water outlet pipe, 916 second vortex preventer. DETAILED DESCRIPTION

[0053] In order to further understand the content of the utility model, the utility model is described in detail in conjunction with the drawings and embodiments.

[0054] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present utility model. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on quoted in this specification are only for the convenience of description, and are not used to limit the scope of implementation. The change or adjustment of their relative relationship should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0055] In one embodiment, if Figure 1As shown, the present application proposes an NMP recovery system for the cleaning wastewater of the positive electrode slurry equipment of a lithium battery, comprising a slurry recovery unit, an extraction unit, and a distillation unit. Among them, the slurry recovery unit is used to separate the positive electrode material and the NMP-containing wastewater from the positive electrode slurry cleaning wastewater, and the ultrafiltration concentrated water is discharged to the wastewater station for treatment. The extraction unit is used to contact the extractant with the NMP-containing wastewater to obtain the NMP-containing extract, and the residue is discharged to the wastewater station for treatment. The distillation unit is used to distill and separate the NMP-containing extract into the extractant and NMP. High-purity NMP is recovered, and the extractant can be reused in the extraction unit for repeated use.

[0056] In this embodiment, the extraction unit may be a centrifugal extraction unit, and the distillation unit may be an ultra-gravity distillation unit. The extraction agent may be dichloromethane.

[0057] In this embodiment, the slurry recovery unit includes a centrifugal separation device 8 and an ultrafiltration separation device 7 connected in sequence. The positive electrode slurry cleaning wastewater is first centrifuged by the centrifugal separation device 8, and then filtered by the ultrafiltration membrane of the ultrafiltration separation device 7, so as to separate the positive electrode material, NMP-containing wastewater, and ultrafiltration concentrated water.

[0058] The slurry recovery unit is also used to remove insoluble solids from NMP-containing wastewater. The slurry recovery unit uses physical separation, does not introduce new chemicals into the water, and finally filters through an ultrafiltration membrane system to reduce the concentration of insoluble particles in the water.

[0059] The slurry recovery unit also includes a wastewater tank 6 connected to the ultrafiltration separation device 7, and the wastewater tank 6 is used to store NMP-containing wastewater. The wastewater tank 6 is made of a material that does not react or dissolve with the extract and NMP. In order to prevent negative pressure suction, the water inlet pipe adopts an indirect water inlet method.

[0060] In this embodiment, if Figure 3-4 As shown, the waste water tank 6 includes a first box body 601 installed on a first base 602. The height of the first base 602 is determined according to the installation height of the water pump, and the minimum is not less than 0.6m. The first box body 601 is made of a material that does not react with NMP and dichloromethane.

[0061] The first box 601 is provided with a first water inlet pipe 605 connected to the water outlet of the ultrafiltration separation device 7, and a first electromagnetic valve 606 and a first float valve 607 are installed on the first water inlet pipe 605. A first electromagnetic liquid level gauge 609 is installed at the side end of the first box 601. The first water inlet pipe 605 is controlled by the first electromagnetic valve 606 and the first float valve 607, and the first electromagnetic valve 606 is linked to the first electromagnetic liquid level gauge 609. When the water level in the first box 601 reaches the highest alarm water level, the water inlet valve is closed.

[0062] The top of the first box body 601 is provided with a first breathing tube 610 and a first inspection manhole 603. The side end of the first box body 601 is provided with a first inspection ladder 604.

[0063] An insect-proof net is installed at the end of the first breathing tube 610 to prevent insects from entering.

[0064] The first inspection manhole 603 should be locked and protected at ordinary times to prevent non-staff from entering. The first inspection ladder 604 is arranged near the first inspection manhole 603.

[0065] A first drain pipe 612 is installed at the bottom of the first box body 601, and a first gate valve 611 is installed on the first drain pipe 612. When draining the wastewater containing NMP, it is necessary to use a container to collect it and it must not be directly discharged into the sewage system. An 18-mesh insect-proof net should be set at the end of the first drain pipe 612 to prevent insects from entering the water tank.

[0066] A first water outlet pipe 615 is also installed at the bottom of the first box 601, and a first flow meter 614 and a first vortex preventer 616 are installed on the first water outlet pipe 615. The first water outlet pipe 615 is connected to the extraction unit through the first water pump 5. The first vortex preventer 616 can prevent the water pump from sucking in air and causing cavitation when the liquid level is too low. The first flow meter 614 is set on the first water outlet pipe 615, which can transmit data remotely.

[0067] The advantage of serial extraction is that the pipeline system is simple and the amount of extractant used is low; the disadvantage is that during the countercurrent extraction process, the NMP content in the extractant gradually increases and the unit extraction efficiency gradually decreases.

[0068] The advantage of parallel extraction is that the unit extraction efficiency is stable and the extraction efficiency of each stage is the same; the disadvantage is that the pipeline system is complex and the amount of extraction agent used is large.

[0069] In this embodiment, the extraction unit comprises a plurality of centrifugal extractors connected in series. Figure 2As shown, there are four centrifugal extractors, namely a first centrifugal extractor 1, a second centrifugal extractor 2, a third centrifugal extractor 3, and a fourth centrifugal extractor 4. Among them, 101 is the wastewater inlet of the first centrifugal extractor, 201 is the wastewater inlet of the second centrifugal extractor, 301 is the wastewater inlet of the third centrifugal extractor, and 401 is the wastewater inlet of the fourth centrifugal extractor; 102 is the extractant inlet of the first centrifugal extractor, 202 is the extractant inlet of the second centrifugal extractor, 302 is the extractant inlet of the third centrifugal extractor, and 402 is the extractant inlet of the fourth centrifugal extractor; 103 is the heavy phase outlet of the first centrifugal extractor, 203 is the heavy phase outlet of the second centrifugal extractor, 303 is the heavy phase outlet of the third centrifugal extractor, and 403 is the heavy phase outlet of the fourth centrifugal extractor; 104 is the light phase outlet of the first centrifugal extractor, 204 is the light phase outlet of the second centrifugal extractor, 304 is the light phase outlet of the third centrifugal extractor, and 404 is the light phase outlet of the fourth centrifugal extractor.

[0070] Wastewater enters from the lower part of the first-stage centrifugal extractor and flows out from the upper part. The intermediate centrifugal extractors are connected in series and finally flow out from the upper part of the fourth-stage centrifuge. The extractant flows from the lower part of the fourth-stage centrifuge and flows out from the upper part. The wastewater and the extract flow in the opposite direction to ensure that the two are fully mixed and improve the extraction efficiency. The raffinate is discharged to the wastewater treatment station for post-treatment, and the extract is discharged to the distillation unit for subsequent distillation and separation.

[0071] The distillation unit includes a preheater 13, an ultra-gravity distillation tower 12, and a condenser 11 connected in sequence, wherein the preheater 13 is used to heat the NMP-containing extract to the boiling point of the extractant. The ultra-gravity distillation tower 12 is used to separate the NMP-containing extract to obtain NMP and extractant vapor. The condenser 11 is used to condense the extractant vapor to obtain a liquid extractant.

[0072] The ultra-gravity factor β of the ultra-gravity distillation tower is 350-450, the temperature of the preheater 13 is determined according to the lower boiling point between the extractant and the extracted component, and the temperature of the condenser 11 needs to be able to meet the temperature for the conversion of the vapor phase to the liquid phase.

[0073] The distillation unit further includes an extractant tank 9 connected to the condenser 11, and the extractant tank 9 is used to store the liquid extractant. The extractant tank 9 is made of a material that does not react or dissolve with the extract or NMP. To prevent negative pressure suction, the water inlet pipe adopts an indirect water inlet method.

[0074] After preheating, the extract is separated and treated in an ultra-gravity distillation tower 12 to separate the vaporized extractant and the high-purity NMP stock solution. The separated vaporized extractant enters the extractant box 9 after condensation and then returns to the extraction unit for recycling. The high-purity NMP stock solution is returned to the positive electrode slurry workshop to participate in production.

[0075] In this embodiment, if Figure 5-6 As shown, the extractant tank 9 is connected to a second water pump 10, and the second water pump 10 is used to transport the liquid extractant in the extractant tank 9 to the extraction unit.

[0076] The extractant box 9 includes a second box body 901 installed on a second base 902. The height of the second base 902 is determined according to the installation height of the water pump, and the minimum is not less than 0.6m. The second box body 901 is made of a material that does not react with NMP and dichloromethane.

[0077] The second box 901 is provided with a second water inlet pipe 905 connected to the outlet of the condenser 11, and a second electromagnetic valve 906 and a second float valve 907 are installed on the second water inlet pipe 905. A second electromagnetic liquid level gauge 909 is installed at the side end of the second box 901. The second water inlet pipe 905 is controlled by the second electromagnetic valve 906 and the second float valve 907, and the second electromagnetic valve 906 is linked to the second electromagnetic liquid level gauge 909. When the water level in the second box 901 reaches the highest alarm water level, the water inlet valve is closed.

[0078] The second breathing tube 910 and the second inspection manhole 903 are installed at the top of the second box body 901. The second inspection ladder 904 is installed at the side end of the second box body 901.

[0079] An insect-proof net is installed at the end of the second breathing tube 910 to prevent insects from entering.

[0080] The second inspection manhole 903 should be locked and protected at ordinary times to prevent non-staff from entering. The second inspection ladder 904 is arranged near the second inspection manhole 903.

[0081] The bottom of the second box 901 is provided with a second drain pipe 912, and a second gate valve 911 is provided on the second drain pipe 912. When the extract is drained, it needs to be collected in a container and must not be directly discharged into the sewage system. An 18-mesh insect-proof net should be provided at the end of the second drain pipe 912 to prevent insects from entering the water tank.

[0082] A second water outlet pipe 915 is also installed at the bottom of the second box 901, and a second flow meter 914 and a second vortex preventer 916 are installed on the second water outlet pipe 915. The second water outlet pipe 915 is connected to the second water pump 10. The second vortex preventer 916 can prevent the water pump from sucking in air and causing cavitation when the liquid level is too low. A second flow meter 914 is installed on the second water outlet pipe 915, which can transmit data remotely.

[0083] The top of the second tank 901 is also equipped with an extractant replenishing pipe 908. The extractant is replenished according to the liquid level of the extractant. The replenishing pipe and the liquid inlet pipe are set separately. One pipe shall not be used. The replenishing pipe shall meet the requirements of indirect water replenishment. The distance between the replenishing pipe port and the highest liquid level in the tank shall not be less than 100mm. The switch of the extractant replenishing pipe shall be linked with the liquid level. It shall be turned on when the liquid level drops to the replenishing water level and turned off when the liquid level returns to the normal water level.

[0084] The liquid inlet of each processing unit is pumped. The low alarm water level should be able to activate the water pump. When the water level is lower than the low alarm water level, the water pump will be shut down and an alarm will be sent to the on-duty personnel to prevent the water pump from idling and overheating. The installation height of the water pump should be able to meet the requirements of self-priming water suction of the water pump.

[0085] The above schematically describes the present invention and its implementation methods, which are not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A NMP recovery system for cleaning waste liquid of lithium battery positive electrode slurry equipment, characterized in that: include: A slurry recovery unit, which is used to separate NMP-containing wastewater from cathode slurry washing wastewater; An extraction unit, which is used to contact an extractant with NMP-containing wastewater to obtain an NMP-containing extract; A distillation unit is used to separate the NMP-containing extract into an extractant and NMP.

2. The NMP recovery system according to claim 1, wherein: The slurry recovery unit is also used to separate positive electrode materials from positive electrode slurry washing wastewater.

3. The NMP recovery system according to claim 1 or 2, characterized in that: The slurry recovery unit comprises a centrifugal separation device (8) and an ultrafiltration separation device (7) which are connected in sequence.

4. The NMP recovery system according to claim 3, wherein: The slurry recovery unit is also used to remove insoluble solids from the NMP-containing wastewater.

5. The NMP recovery system according to claim 3, characterized in that: The slurry recovery unit also includes a wastewater tank (6) connected to the ultrafiltration separation device (7), and the wastewater tank (6) is used to store wastewater containing NMP.

6. The NMP recovery system according to claim 5, characterized in that: The waste water tank (6) comprises a first tank body (601) mounted on a first base (602); The first housing (601) is provided with a first water inlet pipe (605) connected to the water outlet of the ultrafiltration separation device (7), and a first solenoid valve (606) and a first float valve (607) are installed on the first water inlet pipe (605); A first electromagnetic liquid level meter (609) is installed at the side end of the first box body (601); A first water outlet pipe (615) is also installed at the bottom end of the first box body (601), and a first flow meter (614) and a first vortex preventer (616) are installed on the first water outlet pipe (615); The first water outlet pipe (615) is connected to the extraction unit via a first water pump (5).

7. The NMP recovery system according to claim 6, characterized in that: A first breathing tube (610) and a first inspection manhole (603) are installed at the top of the first box body (601); A first drain pipe (612) is installed at the bottom end of the first box body (601), and a first gate valve (611) is installed on the first drain pipe (612); Anti-insect nets are installed at the ends of the first breathing tube (610) and the first air discharge tube (612).

8. The NMP recovery system according to claim 1, characterized in that: The extraction unit comprises a plurality of centrifugal extractors connected in series.

9. The NMP recovery system according to claim 1, characterized in that: The distillation unit comprises a preheater (13), an ultra-gravity distillation tower (12), and a condenser (11) which are connected in sequence; The preheater (13) is used to heat the NMP-containing extract to the boiling point of the extractor; The ultra-gravity distillation tower (12) is used to separate the NMP-containing extract liquid into NMP and extractant vapor; The condenser (11) is used to condense the extractant vapor to obtain the liquid extractant.

10. The NMP recovery system according to claim 9, characterized in that: The distillation unit further comprises an extractant tank (9) connected to the condenser (11), and the extractant tank (9) is used to store a liquid extractant; The extractant tank (9) is connected to a second water pump (10), and the second water pump (10) is used to transport the liquid extractant in the extractant tank (9) to the extraction unit.

11. The NMP recovery system according to claim 10, characterized in that: The extractant box (9) comprises a second box body (901) mounted on a second base (902); The second housing (901) is provided with a second water inlet pipe (905) connected to the outlet of the condenser (11), and a second solenoid valve (906) and a second float valve (907) are installed on the second water inlet pipe (905); A second electromagnetic liquid level meter (909) is installed at the side end of the second box body (901); A second water outlet pipe (915) is also installed at the bottom end of the second box body (901), and a second flow meter (914) and a second vortex preventer (916) are installed on the second water outlet pipe (915); The second water outlet pipe (915) is connected to the second water pump (10).

12. The NMP recovery system according to claim 11, characterized in that: A second breathing tube (910) and a second inspection manhole (903) are installed at the top of the second box body (901); A second drain pipe (912) is installed at the bottom end of the second box body (901), and a second gate valve (911) is installed on the second drain pipe (912); Anti-insect nets are installed at the ends of the second breathing tube (910) and the second air discharge tube (912).

13. The NMP recovery system according to claim 11, characterized in that: An extractant replenishing tube (908) is also installed at the top of the second box (901).

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