Method for purifying and recovering NMP (N-Methyl Pyrrolidone) from NMP regenerated liquid

Abstract

The invention discloses a method for purifying and recovering NMP (N-Methyl Pyrrolidone) from NMP regenerated liquid, and relates to the technical field of waste treatment and recovery, the method comprises the following steps: inputting NMP solid-containing substances into a vacuum rake dryer, introducing steam into a heating interlayer for heating, and separating out NMP gas and a dried material; after NMP gas is condensed and liquefied, high-purity NMP regenerated liquid is collected through a buffer tank and a storage tank; the dried material is recycled by a special container; non-condensable gas in the recovery system is discharged to a tail gas header pipe through a vacuum pump; according to the method, traditional rectification is replaced by vacuum separation, so that the problem of packing blockage of a distillation tower is thoroughly avoided, and the recovery rate and purity of the NMP regenerated liquid and the recycling of rare earth metal are also improved; the whole recovery process is in closed operation, waste gas and residue pollution is greatly reduced, and the characteristics of high efficiency, low consumption and environmental protection are achieved; the technical problems of low NMP recovery rate, high cost and rare earth metal resource waste in the existing NMP regeneration liquid recovery technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste treatment and recycling, and particularly to a method for purifying and recycling N-methylpyrrolidone from NMP regenerant solution. Background Art

[0002] As a highly efficient polar aprotic solvent, N-methylpyrrolidone (NMP) is prone to mixing with electrode active materials such as conductive carbon black, lithium cobaltate, lithium manganate, and lithium nickelate during use, forming NMP waste liquid containing high-concentration solid particles (abbreviated as NMP solid content).

[0003] Currently, the industrial purification and regeneration of NMP solid content mainly adopts the distillation process; after preliminary filtration of the waste liquid, NMP and other components in the solid content are separated through a distillation column; however, this process has significant defects: the residual conductive carbon black and lithium salt particles (such as lithium cobaltate, lithium manganate, lithium nickelate, etc.) in the waste liquid, these particulate matters have small particle sizes (usually in the micron to submicron range), and form stable suspensions with NMP; during the distillation process, these particulate matters are extremely likely to adhere to the surface of the distillation column packing, causing blockage of the packing pores, a decrease in the tray efficiency, and even failures such as a sudden increase in the equipment pressure difference and local overheating.

[0004] To alleviate the blockage problem, the existing technology usually requires frequent shutdowns for cleaning or replacement of the packing, resulting in a shortened equipment operation cycle and a substantial increase in maintenance costs; in addition, the interference of particulate matters with the gas-liquid mass transfer efficiency will also reduce the recovery rate of NMP, and the purity of NMP in the regenerant solution is often difficult to meet the industrial standard (purity ≥ 99.5%) due to residual particulate matters, and secondary distillation is required in some scenarios, further increasing energy consumption and costs.

[0005] More seriously, the existing distillation process cannot effectively recover the conductive carbon black and lithium salt particles in the solid content. Such particulate matters usually enter the subsequent treatment link with the distillation residue; currently, the incineration method is generally used in the market to treat the residue, and the residual organic matter is decomposed by high-temperature oxidation, but this method has two major drawbacks: firstly, the un-recovered NMP during the incineration process generates harmful gases such as nitrogen oxides (NOx) due to pyrolysis, increasing the difficulty of tail gas treatment; secondly, the conductive carbon black and lithium salt particles are converted into ash residues with complex compositions after high-temperature incineration, and their original electrochemical activity and utilization value are completely destroyed, and finally can only be landfilled as general solid waste, resulting in the waste of rare earth resources such as cobalt, manganese, and nickel.

[0006] Therefore, there is an urgent need to develop a method for purifying and recycling NMP regenerant solution that combines high-efficiency separation, low energy consumption, high resource recovery rate, and environmental friendliness to break through the current recycling technology bottleneck and promote the sustainable development of the industry.

[0007] In summary, it is found that the existing technology has at least the following technical problems: The existing NMP regeneration liquid recovery technology has technical problems such as low NMP recovery rate, high cost, and waste of rare earth metal resources. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid, so as to solve the technical problems of the existing NMP regeneration liquid recovery technology, such as low NMP recovery rate, high cost, and waste of rare earth metal resources.

[0009] The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects, which will be elaborated below.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions: The present invention provides a method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid, including a barrel material containing solid NMP; and a rake dryer connected to the discharge port of the barrel material. The rake dryer inputs solid NMP under a vacuum state, and then inputs steam with a pressure of at least 1.0 MPa from the steam inlet to heat the internal solid NMP, separating NMP gas and dried materials; and a condensation collector connected to the gas outlet of the rake dryer for condensing NMP gas into NMP droplets; and a buffer tank connected to the droplet outlet of the condensation collector for collecting NMP droplets to form NMP regeneration liquid; and a storage tank connected to the liquid outlet of the buffer tank. A raw material transfer pump is installed between the buffer tank and the storage tank for transporting the NMP regeneration liquid in the buffer tank to the storage tank; and a vacuum pump connected to the gas outlet of the buffer tank. The vacuum pump is used to discharge the non-condensable gas in the rake dryer, condensation collector, and buffer tank, and provide additional power for the NMP gas to move to the condensation collector, promoting the separation of NMP from the solid NMP.

[0011] In one embodiment, it further includes a residue collection container connected to the material outlet of the rake dryer for collecting dried materials.

[0012] In one embodiment, the gas outlet of the vacuum pump is used to discharge non-condensable gas, and the discharged non-condensable gas is input into the tail gas main pipe, or input into the gas purification device and then into the tail gas main pipe.

[0013] In one embodiment, the gas purification device is a liquid filter using ultrapure water as the purification solvent. The gas outlet of the vacuum pump is connected to the inlet of the liquid filter, and the outlet of the liquid filter is connected to the tail gas main pipe. The liquid filter is used to collect the NMP contained in the non-condensable gas discharged by the vacuum pump.

[0014] In one embodiment, it further includes a water container, a buffer collection tank, and a liquid sensor; the water inlet of the liquid filter is connected to the water container, and a water supply pump is installed between the liquid filter and the water container; the drain outlet of the liquid filter is connected to the buffer collection tank, and the buffer collection pipe is used to buffer the saturated purified liquid for secondary extraction of NMP regenerant liquid; the probe of the liquid sensor is arranged inside the liquid filter to detect the concentration of NMP in the purified solvent inside the liquid filter; when the concentration of NMP in the purified solvent inside the liquid filter reaches saturation, after controlling the liquid filter to input the saturated purified liquid into the buffer collection tank, then control the water supply pump to input ultrapure water into the liquid filter.

[0015] In one embodiment, a secondary drying box is further installed between the rake dryer and the residue collection container; the material inlet of the secondary drying box is connected to the material outlet of the rake dryer, and the material outlet of the secondary drying box is connected to the material inlet of the residue collection container; the gas outlet of the secondary drying box is connected to the gas inlet of the condensation collector; the drying working temperature inside the secondary drying box is higher than that of the rake dryer; the secondary drying box is used to evaporate the residual NMP in the dried material discharged from the rake dryer to form NMP gas.

[0016] In one embodiment, it further includes a heat pump; the heat absorption end of the heat pump is used to absorb the heat of any one or both of the condensation collector and the buffer tank; the heat release end of the heat pump is used to supply heat to the secondary drying box and the rake dryer.

[0017] In one embodiment, a first evaporator connected to the heat absorption end of the heat pump is installed inside the condensation collector.

[0018] In one embodiment, a second evaporator connected to the heat absorption end of the heat pump is installed inside the buffer tank.

[0019] In one embodiment, a first condenser connected to the heat release end of the heat pump is arranged inside the heating interlayer of the rake dryer; a second condenser connected to the heat release end of the heat pump is arranged inside the secondary drying box.

[0020] The method for purifying and recovering N-methylpyrrolidone from the NMP regenerant liquid of the present invention overcomes the defects of the existing NMP regenerant liquid recovery technology by integrating steam heating, vacuum heating to strengthen NMP separation, and a multi-stage recovery structure. The specific beneficial effects are as follows: (1) Double improvement of NMP recovery rate and purity: Using a rake dryer as the core equipment, reducing the boiling point of NMP in a vacuum environment to avoid thermal decomposition loss of NMP at high temperature; at the same time, introducing high-pressure steam of at least 1.0 MPa into the heating interlayer of the rake dryer to heat the NMP solid content in the rake dryer through the interlayer, strengthening the mass transfer efficiency of NMP molecules from the solid phase to the gas phase, so that the NMP recovery rate is increased to more than 99%, and the purity of the NMP regenerant liquid stored in the storage tank is stably up to 100%, without secondary purification, greatly reducing the energy consumption of the recovery process.

[0021] (2)Completely avoid the risk of filler blockage: Abandon the traditional filler structure of the rectification column, dynamically turn the material through a rake stirrer, and combine with the air flow guiding effect of the vacuum negative pressure environment to efficiently separate NMP gas and particulate matters such as conductive carbon black and lithium salt particles from the NMP solid content, avoiding the deposition of particulate matters inside the recovery system, extending the continuous operation period of the equipment to more than 2000 hours, and greatly reducing the maintenance cost of equipment shutdown.

[0022] (3)Resource recovery of solid content: The dried residue, containing conductive carbon black, lithium cobaltate, lithium manganate, lithium nickelate, etc., is centrally collected in the form of dry powder, and can be directly used as raw materials for lithium batteries after packaging and returned to the lithium battery production line of the lithium power plant, or used in other industrial fields after simple screening, realizing the recycling of scarce metal resources and generating no hazardous waste.

[0023] (4)Significant environmental protection and emission reduction advantages: The recovery system operates the drying, condensation, and recovery steps in a vacuum environment and is fully enclosed. The exhaust gas only contains trace amounts of non-condensable gas (such as air and NMP gas) after condensation, which is centrally treated through the tail gas main pipe, avoiding the pollution caused by the volatilization of NMP particles; moreover, the generated residue does not need to be incinerated or landfilled, reducing the emission of toxic gases and the generation of ash residues, and promoting the reduction of environmental protection disposal costs.

[0024] (5)High equipment integration and stable operation: Through the linkage control of the buffer tank and the vacuum pump, dynamically adjust the pressure gradient of the recovery system to promote the rapid condensation and liquefaction of NMP gas; the design of the raw material transfer pump and the storage tank realizes the continuous discharge of the regenerated liquid, enhancing the anti-fluctuation ability of the recovery system, and is suitable for the treatment of solid content, high solid content, and multi-batch waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 is the process flow chart of the recovery process of the first embodiment of the present invention; Figure 2 is the process flow chart of the recovery process of the second embodiment of the present invention; Figure 3 is the process flow chart of the recovery process of the third embodiment of the present invention; Figure 4 is the process flow chart of the recovery process of the fourth embodiment of the present invention; Figure 5 is the process flow chart of the recovery process of the fifth embodiment of the present invention; Figure 6 It is the process flow chart of the recycling process of the sixth embodiment of the present invention; Figure 7 It is the process flow chart of the recycling process of the seventh embodiment of the present invention. Specific implementation manners

[0027] 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.

[0028] A method for purifying and recovering N-methylpyrrolidone from NMP regenerant liquid is provided in the specific implementation manners. The NMP solid-containing material is input into a vacuum rake dryer, and steam is introduced into the heating jacket for heating to separate NMP gas and dried materials; after the NMP gas is condensed and liquefied, high-purity NMP regenerant liquid is collected through a buffer tank and a storage tank; the dried materials are recycled and reused by a special container; the non-condensable gas in the recovery system is discharged to the tail gas main pipe through a vacuum pump; the present invention replaces traditional rectification with vacuum separation, completely avoiding the problem of blockage of the distillation tower packing, and also improving the recovery rate and purity of the NMP regenerant liquid and the recycling of rare earth metals; the entire recovery process operates in a closed manner, greatly reducing waste gas and residue pollution, and having the characteristics of high efficiency, low consumption and environmental protection; effectively solving the technical problems existing in the existing NMP regenerant liquid recovery technology, such as low NMP recovery rate, high cost and waste of rare earth metal resources.

[0029] The first embodiment of the method for purifying and recovering N-methylpyrrolidone from NMP regenerant liquid is as Figure 1 shown, including a barreled material containing solid-containing NMP; and a rake dryer connected to the discharge port of the barreled material. The rake dryer inputs the solid-containing NMP under vacuum, and then introduces steam with a pressure of at least 1.0 MPa from the steam inlet to heat the internal solid-containing NMP to separate NMP gas and dried materials; and a condensation collector connected to the gas outlet of the rake dryer for condensing the NMP gas into NMP droplets; and a buffer tank connected to the droplet outlet of the condensation collector for collecting the NMP droplets to form NMP regenerant liquid; and a storage tank connected to the liquid outlet of the buffer tank. A raw material transfer pump is installed between the buffer tank and the storage tank for transporting the NMP regenerant liquid in the buffer tank to the storage tank; and a vacuum pump connected to the gas outlet of the buffer tank. The vacuum pump is used to discharge the non-condensable gas in the rake dryer, condensation collector and buffer tank, and provide additional power for the NMP gas to move to the condensation collector to promote the separation of NMP from the solid-containing NMP.

[0030] Among them, it also includes a residue collection container connected to the material outlet of the rake dryer for collecting the dried materials.

[0031] The gas outlet of the vacuum pump is used to discharge the non-condensable gas, and the discharged non-condensable gas is input into the tail gas main pipe.

[0032] After the recovery test, the recovery data table of the NMP solid content is as follows: From the recovery data table and Figure 1 it can be seen that S1 - S6 are the recovery paths in each link.

[0033] By using the method for purifying and recovering N - methylpyrrolidone with the NMP regeneration liquid of the present invention, inputting the NMP solid content from the barreled material to the rake dryer and inputting the recovered NMP regeneration liquid from the buffer tank to the storage tank, the recovery rate of the NMP regeneration liquid is as high as 99.947%. Compared with the traditional NMP recovery process, the recovery rate has been greatly improved, and the purity of the NMP regeneration liquid entering the storage tank reaches 100%, without particulate matters such as conductive carbon black, lithium cobaltate, lithium manganate, and lithium nickelate.

[0034] The method for purifying and recovering N - methylpyrrolidone with the NMP regeneration liquid of the present invention overcomes the technical problems of low NMP recovery rate, high cost, and waste of rare earth metal resources in the existing NMP regeneration liquid recovery technology by integrating steam heating, vacuum heating to strengthen NMP separation, and a multi - stage recovery structure. The specific beneficial effects are as follows: (1) Double improvement of NMP recovery rate and purity: Using the rake dryer as the core equipment, reducing the boiling point of NMP in a vacuum environment to avoid thermal decomposition loss of NMP at high temperatures; at the same time, introducing high - pressure steam of at least 1.0 MPa into the heating interlayer of the rake dryer to heat the NMP solid content in the rake dryer through the partition layer, strengthening the mass transfer efficiency of NMP molecules from the solid phase to the gas phase, increasing the NMP recovery rate to over 99%, and the purity of the NMP regeneration liquid entering the storage tank stably reaches 100%, without the need for secondary purification, greatly reducing the energy consumption of the recovery process.

[0035] (2) Completely avoiding the risk of packing blockage: Abandoning the traditional packing structure of the distillation column, dynamically turning the material through the rake stirrer, combined with the air flow guiding effect of the vacuum negative pressure environment, efficiently separating NMP gas and particulate matters such as conductive carbon black and lithium salt particles from the NMP solid content, avoiding the deposition of particulate matters inside the recovery system, extending the continuous operation period of the equipment to more than 2000 hours, and greatly reducing the maintenance cost of equipment shutdown.

[0036] (3) Resource recovery of solid content: The dried residue, containing conductive carbon black, lithium cobaltate, lithium manganate, lithium nickelate, etc., is centrally collected in the form of dry powder, and can be directly used as raw materials for lithium batteries after packaging and returned to the lithium battery production line of the lithium power plant, or used in other industrial fields after simple screening, realizing the recycling of scarce metal resources without generating hazardous waste.

[0037] (4)Significant environmental protection and emission reduction advantages: The recycling system operates the drying, condensation, and recycling steps in a vacuum environment and is fully enclosed. After condensation, the exhaust gas contains only trace amounts of non-condensable gases, including air and NMP gas. The trace non-condensable gases after condensation are centrally treated through the tail gas main pipe to avoid the volatilization and pollution of NMP particles. Moreover, the generated residues do not need to be incinerated or landfilled, avoiding the generation of harmful gases such as nitrogen oxides, reducing the emission of toxic gases and the generation of ash residues, and promoting the reduction of environmental protection disposal costs.

[0038] (5)High equipment integration and stable operation: Through the linkage control of the buffer tank and the vacuum pump, the pressure gradient of the recycling system is dynamically adjusted to promote the rapid condensation and liquefaction of NMP gas. The design of the raw material transfer pump and the storage tank enables the continuous discharge of the regenerated liquid, enhancing the anti-fluctuation ability of the recycling system, and is suitable for the treatment of solid content, high solid content, and multi-batch waste liquid.

[0039] The second embodiment of the method for purifying and recycling N-methylpyrrolidone from NMP regenerated liquid is as Figure 2 shown. The difference between this embodiment and the first embodiment is that the outlet of the vacuum pump is used to discharge non-condensable gases, and the discharged non-condensable gases are input into the gas purification device and then into the tail gas main pipe.

[0040] The gas purification device is a liquid filter with ultrapure water as the purification solvent. The outlet of the vacuum pump is connected to the inlet of the liquid filter, and the outlet of the liquid filter is connected to the tail gas main pipe. The liquid filter is used to collect the NMP contained in the non-condensable gases discharged by the vacuum pump.

[0041] When in use, the liquid filter is a device that uses liquid as the filtering medium to purify and absorb the NMP in the non-condensable gases discharged by the vacuum pump and then discharges the clean gas.

[0042] Through the absorption and purification treatment of NMP gas or micro-droplets, and then the secondary extraction of the collected NMP aqueous solution; this step can recover the NMP flowing from the buffer tank to the vacuum pump in path S4, further improving the recovery rate of separating NMP from NMP solid content.

[0043] So that, it further improves the recovery rate of separating NMP from NMP solid content, and reduces the pressure on the tail gas main pipe to treat NMP-containing non-condensable gases, avoiding environmental pollution.

[0044] The third embodiment of the method for purifying and recycling N-methylpyrrolidone from NMP regenerated liquid is as Figure 3As shown, the difference between this embodiment and the second embodiment is that it further includes a water container, a buffer collection tank, and a liquid sensor; the water inlet of the liquid filter is connected to the water container, and a water supply pump is installed between the liquid filter and the water container; the drain outlet of the liquid filter is connected to the buffer collection tank, and the buffer collection pipe is used to buffer the saturated purification liquid saturated with NMP for secondary extraction of the NMP regeneration liquid; the probe of the liquid sensor is arranged inside the liquid filter and is used to detect the concentration of NMP in the purification solvent inside the liquid filter.

[0045] During application, due to the characteristic that NMP is soluble in water, ultrapure water is used to absorb the NMP gas in the non-condensable gas discharged from the purification vacuum pump, and by using the characteristic that ultrapure water contains no impurities, the difficulty of collecting the NMP aqueous solution collected by the buffer collection tank in the later stage is reduced, and impurities are reduced; through the absorption and purification treatment of the NMP gas, and then the NMP aqueous solution collected by the buffer collection tank is extracted twice; this step can recover the NMP flowing from the buffer tank to the vacuum pump in path S4, and further improve the recovery rate of NMP separated from the NMP solid content.

[0046] When the concentration of NMP in the purification solvent (ultrapure water) inside the liquid filter reaches saturation, after controlling the liquid filter to input the saturated purification liquid into the buffer collection tank, then control the water supply pump to input ultrapure water into the liquid filter; to achieve the continuous filtration function of the liquid filter and continuously absorb the NMP in the non-condensable gas; this step can recover the NMP flowing from the buffer tank to the vacuum pump in path S4, and realize the secondary extraction and recovery of NMP from the purification solvent.

[0047] The fourth embodiment of the method for purifying and recovering N-methylpyrrolidone from the NMP regeneration liquid is as Figure 4 shown. The difference between this embodiment and the first embodiment or the third embodiment is that a secondary drying oven is further installed between the rake dryer and the residue collection container; the material inlet of the secondary drying oven is connected to the material outlet of the rake dryer, and the material outlet of the secondary drying oven is connected to the material inlet of the residue collection container; the gas outlet of the secondary drying oven is connected to the gas inlet of the condensation collector; the secondary drying oven is used to evaporate the residual NMP in the dried material discharged from the rake dryer to form NMP gas.

[0048] Specifically, the drying working temperature inside the secondary drying oven can be higher than the drying working temperature of the rake dryer, but must be lower than the thermal decomposition temperature of NMP to avoid releasing impurity gases or substances by decomposition.

[0049] During application, the residual NMP in the dried materials discharged by the rake dryer evaporates to form NMP gas, which is collected in the condensation collector and then condensed into the buffer tank. The residual NMP in path S6 is extracted and collected for the second time, further improving the recovery rate of NMP separated from the NMP solid content. At the same time, the secondary drying box discharges the dried materials after secondary drying into the residue collection container for the second time, reducing the NMP content in the rare earth metals collected by the residue collection container and reducing the extraction cost for the subsequent extraction steps of recycling rare earth metals.

[0050] The fifth embodiment of the method for purifying and recycling N-methylpyrrolidone from NMP regeneration liquid is as Figure 5 shown. The difference between this embodiment and the fourth embodiment is that it further includes a heat pump; the heat absorption end of the heat pump is used to absorb the heat of any one or both of the condensation collector and the buffer tank; the heat release end of the heat pump is used to supply heat to the secondary drying box and the rake dryer.

[0051] A first condenser connected to the heat release end of the heat pump is provided in the heating interlayer of the rake dryer; a second condenser connected to the heat release end of the heat pump is provided in the secondary drying box.

[0052] During application, due to the characteristics of the heat pump of small power consumption for transporting a large capacity, the heat released by the condensation collector is absorbed, the heat of the buffer tank is continuously absorbed to maintain the low temperature state of the buffer tank, and the heat is transported to the secondary drying box and the rake dryer, reducing the steam consumption when the rake dryer dries the NMP solid content and reducing the energy for the secondary drying box to further dry the dried materials discharged by the rake dryer at a high temperature. Thus, the energy consumption of the entire recovery system is reduced, and the recovery costs of NMP and rare earth metals are reduced, playing a role in environmental protection, cost reduction and efficiency improvement.

[0053] The sixth embodiment of the method for purifying and recycling N-methylpyrrolidone from NMP regeneration liquid is as Figure 6 shown. The difference between this embodiment and the fifth embodiment is that a first evaporator connected to the heat absorption end of the heat pump is installed in the condensation collector.

[0054] During application, by setting the first evaporator of the heat pump in the condensation collector, the continuous condensation temperature of the condensation collector can be reduced, further improving the continuous condensation speed of the condensation collector, enabling sufficient condensation effect even when the NMP gas flow rate is high, improving the collection of NMP in path S3, reducing the damage of NMP in path S4, and improving the recovery rate of NMP recovered by the buffer tank for the first time.

[0055] The seventh embodiment of the method for purifying and recycling N-methylpyrrolidone from NMP regeneration liquid is as Figure 7 shown. The difference between this embodiment and the sixth embodiment is that a second evaporator connected to the heat absorption end of the heat pump is installed in the buffer tank.

[0056] When applying, setting the second evaporator of the heat pump in the buffer tank can reduce the storage temperature in the buffer tank, improve the stability of NMP remaining in the buffer tank in liquid form, reduce the damage of NMP in path S4, and improve the recovery rate of the first NMP recovery in the buffer tank.

[0057] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid, characterized in that: Including barreled materials containing NMP solids; and a rake dryer connected to the discharge port of the barreled material, wherein the rake dryer inputs NMP solids under vacuum, and then introduces steam with a pressure of at least 1.0 MPa from the steam inlet to heat the internal NMP solids, and separates NMP gas and dried materials; and a condensation collector connected to the gas outlet of the rake dryer, for condensing the NMP gas into NMP droplets; and a buffer tank connected to the droplet outlet of the condensation collector, for collecting NMP droplets to form NMP regeneration liquid; and a storage tank connected to the liquid outlet of the buffer tank, wherein a raw material transfer pump is installed between the buffer tank and the storage tank for transporting the NMP regeneration liquid in the buffer tank to the storage tank; and a vacuum pump connected to the gas outlet of the buffer tank, the vacuum pump is used to discharge the non-condensable gas of the rake dryer, the condensate collector and the buffer tank, and provide additional power for the NMP gas to move to the condensate collector, thereby promoting the separation of NMP from the NMP solids.

2. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 1, characterized in that: It also includes a residue collection container, which is connected to the material outlet of the rake dryer and is used to collect the dried material.

3. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 2, characterized in that: The gas outlet of the vacuum pump is used to discharge non-condensable gas, and the discharged non-condensable gas is input into the tail gas main pipe, or input into the gas purification device and then into the tail gas main pipe.

4. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 3, characterized in that: The gas purification device is a liquid filter using ultrapure water as a purification solvent, the gas outlet of the vacuum pump is connected to the gas inlet of the liquid filter, the gas outlet of the liquid filter is connected to the tail gas main pipe, and the liquid filter is used to collect NMP contained in the non-condensable gas discharged by the vacuum pump.

5. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 4, characterized in that: Also included are water containers, cache collection tanks, and liquid sensors; The water inlet of the liquid filter is connected to the water container, and a water supply pump is installed between the liquid filter and the water container; The drain outlet of the liquid filter is connected to the buffer collection tank, and the buffer collection pipe is used to buffer the saturated purified liquid for secondary extraction of NMP regeneration liquid; The probe of the liquid sensor is arranged in the liquid filter, and is used to detect the concentration of NMP in the purification solvent in the liquid filter; when the concentration of NMP in the purification solvent in the liquid filter reaches saturation, the liquid filter is controlled to input the saturated purified liquid into the cache collection tank, and then the water supply pump is controlled to input ultrapure water into the liquid filter.

6. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 4, characterized in that: A secondary drying box is also installed between the rake dryer and the residue collection container; The material inlet of the secondary drying box is connected to the material outlet of the rake dryer, and the material outlet of the secondary drying box is connected to the material inlet of the residue collection container; the gas outlet of the secondary drying box is connected to the gas inlet of the condensation collector; The drying operating temperature inside the secondary drying box is higher than the drying operating temperature of the rake dryer; The secondary drying box is used to evaporate the residual NMP in the dried material discharged from the rake dryer to form NMP gas.

7. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 4, characterized in that: Also included are heat pumps; The heat absorbing end of the heat pump is used to absorb heat from either or both of the condensation collector and the buffer tank; The heat release end of the heat pump is used to supply heat to the secondary drying box and the rake dryer.

8. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 7, characterized in that: A first evaporator connected to the heat absorption end of the heat pump is installed in the condensation collector.

9. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to claim 8, characterized in that: A second evaporator connected to the heat absorption end of the heat pump is installed in the buffer tank.

10. The method for purifying and recovering N-methylpyrrolidone from NMP regeneration liquid according to any one of claims 8 or 9, characterized in that: A first condenser connected to the heat release end of the heat pump is provided in the heating interlayer of the rake dryer; A second condenser connected to the heat release end of the heat pump is arranged in the secondary drying box.

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