Purification method and purification apparatus for nmp

Abstract

The present invention relates to a purification method and purification apparatus for NMP. Specifically, according to one embodiment of the present invention, the purification method for NMP comprises the steps of: (1) distilling waste NMP in a primary distillation column so as to primarily purify same; (2) discharging an effluent containing water, separated out through the primary purification, to the outside of the system through the top of the primary distillation column, and discharging a primary bottom liquid through the bottom of the primary distillation column; (3) injecting the discharged primary bottom liquid into a secondary distillation column and secondarily purifying same; (4) discharging the purified NMP, separated out through the secondary purification, to the outside of the system through the top of the secondary distillation column, and discharging the secondary bottom liquid through the bottom of the secondary distillation column; (5) injecting the discharged secondary bottom liquid into a filtrate recovery device and heat treating same; (6) discharging a tertiary bottom liquid, separated out through the heat treatment, to the outside of the system through the bottom of the filtrate recovery device, and discharging a gas mixture containing NMP through the top of the filtrate recovery device; and (7) injecting the discharged gas mixture into the secondary distillation column, and thus the recovery rate of NMP recovered from waste NMP is improved such that high-purity NMP can be provided.

Description

Purification method and purification apparatus of NMP

[0001] The present invention relates to a method and apparatus for purifying waste NMP.

[0002] With the recent increase in technological development for portable devices such as mobile phones and cameras, interest in secondary batteries as energy sources has grown. Demand for lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rates, has rapidly increased. Research into their recycling is also ongoing.

[0003] N-Methyl-2-pyrrolidone (NMP), an organic solvent, is widely used as a solvent in industries such as petrochemicals, plastics, and pharmaceuticals due to its chemical stability, low volatility, and ability to dissolve various substances, and is also used in the process of manufacturing secondary batteries.

[0004] In particular, lithium ion secondary batteries are composed of a positive electrode manufactured by applying an electrode material including a lithium compound such as lithium cobaltate or lithium manganate, a binder such as polyvinylidene fluoride, and N-methyl-2-pyrrolidone (NMP) as a solvent to a substrate and firing the same, and a negative electrode manufactured by applying an electrode material including a lithium compound including carbon, titanium, etc., a binder such as polyvinylidene fluoride, and water as a solvent to a substrate and firing the same. As such, NMP is not only used as a main material for manufacturing the positive electrode in the electrode manufacturing process, but is also emitted in large quantities for use in cleaning and drying, and therefore research into technologies for effectively recovering it is ongoing.

[0005] For example, Korean Patent No. 10-2050990 discloses a system for separating and recovering NMP from NMP gas by bringing NMP-containing gas containing NMP into gas-liquid contact with water that has absorbed NMP, thereby allowing NMP in the NMP-containing gas to be absorbed into the water.

[0006] [Prior Art Literature]

[0007] [Patent Document]

[0008] (Patent Document 1) Korean Patent No. 2050990

[0009] Accordingly, the present invention aims to provide a method and a purification device for purifying NMP, which can improve the recovery rate of NMP recovered from waste NMP and provide high-purity NMP.

[0010] A method for purifying NMP according to one embodiment of the present invention comprises the steps of: (1) performing primary purification by distilling waste NMP in a primary distillation column; (2) discharging an effluent containing water separated through the primary purification to the outside of the system through the top of the primary distillation column and discharging a primary drawout through the bottom of the primary distillation column; (3) performing secondary purification by introducing the discharged primary drawout into a secondary distillation column; (4) discharging purified NMP separated through the secondary purification to the outside of the system through the top of the secondary distillation column and discharging a secondary drawout through the bottom of the secondary distillation column; (5) introducing the discharged secondary drawout into a filtrate recovery device and performing heat treatment; (6) discharging a third drawout separated through the heat treatment to the outside of the system through the bottom of the filtrate recovery device and discharging a gas mixture containing NMP through the top of the filtrate recovery device; and (7) a step of introducing the discharged gas mixture into the second distillation tower.

[0011] According to another embodiment of the present invention, an NMP purification device includes: a supply unit for supplying waste NMP; a first distillation column for performing a first purification by distillation of the supplied waste NMP, discharging an effluent containing water separated through the first purification to the outside of the system through the upper portion, and discharging a first drawout through the lower portion; a second distillation column for performing a second purification by distillation of the first drawout, discharging purified NMP separated through the second purification to the outside of the system through the upper portion, and discharging a second drawout through the lower portion; and a filtrate recovery device for heat-treating the second drawout, discharging a third drawout separated through the heat-treatment to the outside of the system through the lower portion, and discharging a gas mixture containing NMP through the upper portion.

[0012] A method for purifying NMP according to one embodiment of the present invention comprises the steps of: (1) performing primary purification by distilling waste NMP in a primary distillation column; (2) discharging an effluent containing water separated through the primary purification to the outside of the system through the top of the primary distillation column and discharging a primary drawout through the bottom of the primary distillation column; (3) performing secondary purification by introducing the discharged primary drawout into a secondary distillation column; (4) discharging purified NMP separated through the secondary purification to the outside of the system through the top of the secondary distillation column and discharging a secondary drawout through the bottom of the secondary distillation column; (5) introducing the discharged secondary drawout into a filtrate recovery device and performing heat treatment; (6) discharging a third drawout separated through the heat treatment to the outside of the system through the bottom of the filtrate recovery device and discharging a gas mixture containing NMP through the top of the filtrate recovery device; And (7) a step of introducing the discharged gas mixture into the second distillation tower; thereby, the recovery rate of NMP recovered from waste NMP can be improved, and high-purity NMP can be provided.

[0013] In particular, moisture in the waste NMP can be effectively removed through the first purification, and substances with a boiling point higher than NMP that may be included in the third effluent discharged through the second purification can be effectively removed through heat treatment using a filtrate recovery device. In addition, the recovery rate and purity of NMP can be further improved by re-introducing the gas mixture containing NMP separated through heat treatment in the filtrate recovery device into the second distillation column.

[0014] Figure 1 schematically illustrates a flow chart of an NMP purification method according to one embodiment of the present invention.

[0015] Figure 2 illustrates an example of an NMP purification device according to another embodiment of the present invention.

[0016] Hereinafter, the present invention will be described in detail. The present invention is not limited to the contents disclosed below and may be modified in various forms without changing the gist of the invention.

[0017] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0018] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood to be modified by the term “about” in all cases unless otherwise specified.

[0019] When it is described in this specification that one component is formed on or under another component, it includes both cases where one component is formed directly on or under the other component, or indirectly through the interposition of another component.

[0020] In this specification, the terms "primary," "secondary," "first," and "secondary" are used to describe various components, and the components are not limited by the terms. The terms are used solely to distinguish one component from another.

[0021]

[0022] NMP purification method

[0023] A method for purifying NMP according to one embodiment of the present invention comprises the steps of: (1) performing primary purification by distilling waste NMP in a primary distillation column; (2) discharging an effluent containing water separated through the primary purification to the outside of the system through the top of the primary distillation column and discharging a primary drawout through the bottom of the primary distillation column; (3) performing secondary purification by introducing the discharged primary drawout into a secondary distillation column; (4) discharging purified NMP separated through the secondary purification to the outside of the system through the top of the secondary distillation column and discharging a secondary drawout through the bottom of the secondary distillation column; (5) introducing the discharged secondary drawout into a filtrate recovery device and performing heat treatment; (6) discharging a third drawout separated through the heat treatment to the outside of the system through the bottom of the filtrate recovery device and discharging a gas mixture containing NMP through the top of the filtrate recovery device; and (7) a step of introducing the discharged gas mixture into the second distillation tower.

[0024] FIG. 1 schematically illustrates a flow chart of an NMP purification method according to one embodiment of the present invention, and FIG. 2 illustrates an example of an NMP purification device according to another embodiment of the present invention. Specifically, FIG. 2 illustrates an NMP purification device comprising a supply section (SD), a primary distillation column (D1), a secondary distillation column (D2), and a filtrate recovery device (R).

[0025] Hereinafter, a method for purifying NMP according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

[0026]

[0027] Step (1) of performing primary purification by distilling waste NMP in a primary distillation tower

[0028] A method for purifying NMP according to one embodiment of the present invention includes a step of performing primary purification by distilling waste NMP in a primary distillation tower.

[0029] The above-mentioned waste NMP may be recovered after being used in a process for manufacturing a lithium secondary battery. For example, the above-mentioned waste NMP may be recovered after being used as a material for a lithium secondary battery, but is not limited thereto.

[0030] The above waste NMP may contain NMP in an amount of 70 wt% or more. For example, the content of NMP in the waste NMP may be 72 wt% or more, 75 wt% or more, 78 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more based on the total weight of the waste NMP.

[0031] Additionally, the waste NMP may contain moisture. For example, the moisture content in the waste NMP may be 30 wt% or less, 25 wt% or less, 20 wt% or less, or 15 wt% or less based on the total weight of the waste NMP.

[0032] In the above step (1), the waste NMP may be introduced into the upper portion of the primary distillation column. Specifically, it may be preferable for the waste NMP to be introduced into the middle portion of the primary distillation column or into a higher portion thereof to more efficiently perform primary purification, but the present invention is not limited thereto.

[0033] The primary purification of the above step (1) can be performed at a temperature of 50°C to 150°C and a pressure of 100 torr to 130 torr. For example, the primary purification can be performed at a temperature of 52°C to 145°C or 55°C to 143°C and a pressure of 105 torr to 130 torr or 110 torr to 125 torr. By satisfying the temperature and pressure conditions of the primary purification within the above ranges, moisture contained in the waste NMP can be effectively removed.

[0034]

[0035] Step (2) of discharging the effluent containing water separated through the first purification to the outside of the system through the top of the first distillation tower, and discharging the first draw-off liquid through the bottom of the first distillation tower

[0036] A method for purifying NMP according to one embodiment of the present invention includes a step of discharging an effluent containing water separated through the primary purification to the outside of the system through the top of the primary distillation column, and discharging the primary draw-off liquid through the bottom of the primary distillation column.

[0037] Specifically, the step (2) can improve the purity of NMP by lowering the content of moisture contained in the waste NMP by separating the effluent containing water from the waste NMP through the primary purification of the step (1) and discharging it to the outside of the system.

[0038] The moisture content in the primary effluent may be 0.01% or less. For example, the moisture content in the primary effluent may be 0.008% or less, 0.006% or less, or 0.005% or less.

[0039] In addition, the primary effluent may contain NMP in an amount of 99.9 wt% or more. For example, the content of NMP in the primary effluent may be 99.92 wt% or more, 99.94 wt% or more, or 99.95 wt% or more, based on the total weight of the primary effluent. By effectively removing most of the moisture in the waste NMP through the primary purification, the purity of NMP in the primary effluent can be further improved.

[0040]

[0041] Step (3) of performing secondary purification by putting the discharged primary effluent into a secondary distillation tower

[0042] The NMP purification method according to one embodiment of the present invention includes a step of performing secondary purification by introducing the discharged primary effluent into a secondary distillation tower.

[0043] The purity of NMP can be improved through the above secondary purification. Specifically, the waste NMP may contain components with a higher boiling point than the NMP along with the NMP. By performing a secondary purification in step (3) on the first effluent from which moisture has been removed through the first purification, components with a boiling point higher than the NMP can be effectively removed, thereby further improving the purity of the NMP.

[0044] In the above step (3), the first draw liquid may be introduced into the middle or lower portion of the second distillation column. Specifically, it may be preferable for the first draw liquid to be introduced into the middle or lower portion of the second distillation column to more efficiently perform the second distillation, but the present invention is not limited thereto.

[0045] The secondary purification may be performed at a temperature of 120°C to 150°C and a pressure of 50 torr to 90 torr. For example, the secondary purification may be performed at a temperature of 122°C to 148°C or 126°C to 145°C and a pressure of 55 torr to 85 torr or 65 torr to 80 torr. By satisfying the temperature and pressure conditions of the secondary purification within the above ranges, components having a boiling point higher than NMP contained in the primary extractant can be effectively removed.

[0046]

[0047] Step (4) of discharging purified NMP separated through the above secondary purification to the outside of the system through the top of the above secondary distillation tower, and discharging the secondary draw-off liquid through the bottom of the above secondary distillation tower.

[0048] A method for purifying NMP according to one embodiment of the present invention includes a step of discharging purified NMP separated through the secondary purification to the outside of the system through the top of the secondary distillation column, and discharging the secondary draw-off liquid through the bottom of the secondary distillation column.

[0049] Specifically, the step (4) can obtain purified NMP by discharging a secondary extract containing a component with a higher boiling point than NMP from the primary extract through the secondary purification of the step (3).

[0050] The secondary extract may contain a component having a boiling point higher than NMP in an amount of 1.0 wt% or less. For example, the content of the component having a boiling point higher than NMP in the secondary extract may be 0.8 wt% or less, 0.6 wt% or less, or 0.4 wt% or less, based on the total weight of the secondary extract.

[0051] The purity of the above purified NMP may be 99.9% or higher. For example, the purity of the above purified NMP may be 99.92% or higher, 99.94% or higher, or 99.95% or higher.

[0052]

[0053] Step (5) of heat-treating the secondary discharged liquid by putting it into a liquid recovery device

[0054] An NMP purification method according to one embodiment of the present invention includes a step of introducing the discharged secondary effluent into a filtrate recovery device and performing heat treatment.

[0055] Even if moisture and components with a boiling point higher than NMP contained in the waste NMP are removed through the above first and second purification, the secondary effluent discharged through the above second purification may contain NMP.

[0056] The above secondary extractant may contain NMP in an amount of 99 wt% or more. For example, the content of NMP in the secondary extractant may be 99.2 wt% or more, 99.4 wt% or more, or 99.6 wt% or more based on the total weight of the secondary extractant.

[0057] A method for purifying NMP according to one embodiment of the present invention includes a step of introducing the secondary effluent into a filtrate recovery device and performing heat treatment, thereby separating NMP contained in the secondary effluent in a gaseous form, and introducing this into the secondary distillation column to perform secondary purification, thereby improving the recovery rate of NMP.

[0058] In the above step (5), the heat treatment can be performed at a temperature of 110°C to 140°C and a pressure of 60 torr to 100 torr while stirring at 20 rpm to 80 rpm. For example, the heat treatment can be performed at a temperature of 115°C to 140°C, 125°C to 138°C, or 128°C to 135°C, and a pressure of 65 torr to 95 torr, or 75 torr to 85 torr while stirring at 25 rpm to 70 rpm, or 30 rpm to 60 rpm. When the process conditions of the heat treatment satisfy the above ranges, the recovery rate of NMP can be further improved.

[0059]

[0060] Step (6) of discharging the tertiary effluent separated through the above heat treatment to the outside of the system through the bottom of the filtrate recovery device, and discharging the gas mixture including NMP through the top of the filtrate recovery device.

[0061] A method for purifying NMP according to one embodiment of the present invention includes a step of discharging a third effluent separated through the heat treatment to the outside of the system through the lower end of the filtrate recovery device, and discharging a gas mixture including NMP through the upper end of the filtrate recovery device.

[0062] Specifically, the step (6) can separate components having a boiling point higher than NMP from the second extractant once again by discharging the third extractant through the heat treatment of the step (5), and can obtain a gas mixture containing NMP from the second extractant.

[0063] The above tertiary extract may contain a component having a boiling point higher than NMP in an amount of 1.5 wt% or less. For example, the content of the component having a boiling point higher than NMP in the above tertiary extract may be 1.0 wt% or less, 0.8 wt% or less, or 0.6 wt% or less, based on the total weight of the above tertiary extract.

[0064] Additionally, the gas mixture may contain NMP in an amount of 98.5 wt% or more. For example, the content of NMP in the gas mixture may be 99.0 wt% or more, 99.2 wt% or more, or 99.4 wt% or more, based on the total weight of the gas mixture.

[0065]

[0066] Step (7) of introducing the above discharged gas mixture into the second distillation tower

[0067] A method for purifying NMP according to one embodiment of the present invention includes a step of introducing the discharged gas mixture into the secondary distillation tower.

[0068] In the above step (7), the gas mixture may be introduced into the middle or lower portion of the secondary distillation column. Specifically, it may be preferable for the gas mixture to be introduced into the middle or lower portion of the secondary distillation column to perform more effective purification, but the present invention is not limited thereto.

[0069] More specifically, the position at which the gas mixture is introduced into the secondary distillation column in step (7) may be the same as or lower than the position at which the first draw-off liquid is introduced into the secondary distillation column in step (3). Since the position at which the gas mixture is introduced in step (7) is the same as or lower than the position at which the first draw-off liquid is introduced into the secondary distillation column in step (3), NMP can be purified more effectively. In particular, since the final product, high-purity NMP, is discharged to the outside of the system through the top of the secondary distillation column, the first draw-off liquid and the gas mixture must be introduced into the middle and lower parts of the secondary distillation column to increase the efficiency of NMP purification, and by setting the introduction position of the gas mixture having a low NMP content relatively lower than the introduction position of the first draw-off liquid, more efficient purification can be performed.

[0070]

[0071] NMP purification unit

[0072] According to another embodiment of the present invention, an NMP purification device includes: a supply unit for supplying waste NMP; a first distillation column for performing a first purification by distillation of the supplied waste NMP, discharging an effluent containing water separated through the first purification to the outside of the system through the upper portion, and discharging a first drawout through the lower portion; a second distillation column for performing a second purification by distillation of the first drawout, discharging purified NMP separated through the second purification to the outside of the system through the upper portion, and discharging a second drawout through the lower portion; and a filtrate recovery device for heat-treating the second drawout, discharging a third drawout separated through the heat-treatment to the outside of the system through the lower portion, and discharging a gas mixture containing NMP through the upper portion.

[0073] Fig. 2 illustrates an example of an NMP purification device according to another embodiment of the present invention. Specifically, Fig. 2 illustrates an NMP purification device comprising a supply section (SD), a primary distillation column (D1), a secondary distillation column (D2), and a filtrate recovery device (R).

[0074] First, waste NMP is supplied to the primary distillation column (D1) through the supply section (SD). The supply can be performed through the primary pump (P1), and at this time, the waste NMP can be preheated through the preheater (B1).

[0075] The first distillation tower (D1) performs the first purification by distilling the supplied waste NMP, and the effluent containing water separated through the first purification is discharged to the outside of the system through the top of the first distillation tower (D1) (T-1), and the first draw-out liquid is discharged through the bottom of the first distillation tower (D1) (Y-1). The discharged first draw-out liquid can be transferred to the second distillation tower (D2) through the second pump (P2) (X-1), and can be circulated back to the first distillation tower (D1) (S-1). At this time, the first draw-out liquid can be preheated through the first reboiler (B2) before being fed back into the first distillation tower (D1).

[0076] The secondary distillation tower (D2) performs secondary purification by distilling the supplied primary drawdown, and the purified NMP separated through the secondary purification is discharged to the outside of the system through the top of the secondary distillation tower (D2) (T-2), and the secondary drawdown is discharged to the outside of the system through the bottom of the secondary distillation tower (D2) (Y-2). The purified NMP discharged to the outside of the system can be stored in a storage tank. In addition, the discharged secondary drawdown can be transferred to a filtrate recovery device (R) through a tertiary pump (P3) (X-2) and can be circulated back to the secondary distillation tower (D2) (S-2). At this time, the secondary drawdown can be preheated through a secondary reboiler (B3) before being fed back into the secondary distillation tower (D2).

[0077] The filtrate recovery device (R) heat-treats the introduced secondary effluent, and the tertiary effluent separated through the heat treatment is discharged to the outside of the system through the lower portion of the filtrate recovery device (R) (Y-3). In addition, the gas mixture including NMP separated through the heat treatment can be discharged through the upper portion of the filtrate recovery device (R) and circulated to the secondary distillation tower (D2) (S-3).

[0078] [Explanation of symbols]

[0079] D1: 1st distillation column

[0080] D2: Secondary distillation column

[0081] P1: Primary pump

[0082] P2: Secondary pump

[0083] P3: tertiary pump

[0084] R: Liquid recovery device

[0085] SD: Supply Department

[0086] B1: Preheater

[0087] B2: Primary reboiler

[0088] B3: Secondary reboiler

[0089] T-1, T-2, Y-1, Y-2, Y-3: Emission stage

[0090] S-1, S-2, S-3: Cycle phases

[0091] X-1, X-2: Deployment phase

Claims

1. (1) A step of performing primary purification by distilling waste NMP in a primary distillation tower; (2) A step of discharging the effluent containing water separated through the first purification to the outside of the system through the top of the first distillation tower, and discharging the first draw-off liquid through the bottom of the first distillation tower; (3) A step of performing secondary purification by putting the discharged primary effluent into a secondary distillation tower; (4) A step of discharging purified NMP separated through the secondary purification to the outside of the system through the top of the secondary distillation tower, and discharging the secondary draw-off liquid through the bottom of the secondary distillation tower; (5) A step of heat-treating the discharged secondary effluent by putting it into a filtrate recovery device; (6) A step of discharging the tertiary effluent separated through the heat treatment to the outside through the bottom of the filtrate recovery device, and discharging the gas mixture including NMP through the top of the filtrate recovery device; and (7) A method for purifying NMP, comprising the step of introducing the discharged gas mixture into the second distillation tower.

2. In paragraph 1, A method for purifying NMP, wherein the above-mentioned NMP contains NMP in an amount of 70 wt% or more.

3. In paragraph 1, A method for purifying NMP, wherein in the above step (1), waste NMP is introduced into the upper part of the first distillation tower.

4. In paragraph 1, A method for purifying NMP, wherein the first extraction solution contains NMP in an amount of 99.9 wt% or more.

5. In paragraph 1, A method for purifying NMP, wherein the moisture content in the first extraction solution is 0.01% or less.

6. In paragraph 1, A method for purifying NMP, wherein in the above step (3), the first distillate is injected into the middle and lower portion of the second distillation tower.

7. In paragraph 1, A method for purifying NMP, wherein the secondary extract contains NMP in an amount of 99 wt% or more.

8. In paragraph 1, A method for purifying NMP, wherein in the above step (7), the gas mixture is injected into the middle and lower portion of the second distillation tower.

9. In paragraph 1, A method for purifying NMP, wherein the position at which the gas mixture is fed into the second distillation tower in the step (7) is the same as or lower than the position at which the first distillate is fed into the second distillation tower in the step (3).

10. In paragraph 1, The first purification of the above step (1) is performed at a temperature of 50°C to 150°C and a pressure of 100 torr to 130 torr, An NMP purification method, wherein the secondary purification of the above step (3) is performed at a temperature of 120°C to 150°C and a pressure of 50 torr to 90 torr.

11. In paragraph 1, A method for purifying NMP, wherein the heat treatment in the above step (5) is performed at a temperature of 110°C to 140°C and a pressure of 60 torr to 100 torr while stirring at 20 rpm to 80 rpm.

12. In paragraph 1, A method for purifying NMP, wherein the secondary extraction solution contains 1.0 wt% or less of a component having a boiling point higher than that of NMP.

13. In paragraph 1, A method for purifying NMP, wherein the above-mentioned third extraction solution contains 1.5 wt% or less of a component having a boiling point higher than that of NMP.

14. In paragraph 1, A method for purifying NMP, wherein the gas mixture contains NMP in an amount of 98.5 wt% or more.

15. In paragraph 1, A method for purifying NMP, wherein the purity of the NMP purified in the above step (4) is 99.99% or higher.

16. Supply unit for supplying waste NMP; A first distillation tower for performing a first purification by distillation of the supplied waste NMP, discharging the effluent containing water separated through the first purification to the outside of the system through the top, and discharging the first draw-out liquid through the bottom; A second distillation tower that distills the first extract to perform a second purification, discharges the purified NMP separated through the second purification to the outside of the system through the top, and discharges the second extract through the bottom; and An NMP purification device comprising a filtrate recovery device that heat-treats the above-mentioned secondary effluent, discharges the tertiary effluent separated through the heat treatment to the outside of the system through the bottom, and discharges a gas mixture including NMP through the top.

Images