Sludge separator, and NMP purification method and apparatus using same

Abstract

A sludge separator according to the present invention comprises a barrier layer having a plurality of barrier units spaced apart from each other, and thus the sludge separator has excellent performance and can prevent a gas flow path from being blocked. The NMP purification method and apparatus using the sludge separator can provide high-purity NMP by improving the recovery rate of NMP recovered from waste NMP.

Description

Sludge separator, method and device for purifying NMP using the same

[0001] The present invention relates to a sludge separator, a method for purifying NMP using the same, and a device therefor.

[0002]

[0003] 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.

[0004] 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.

[0005] 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.

[0006] For example, Korean Patent No. 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.

[0007] For NMP used in secondary batteries, the greater the amount of product recovered from commercial recycling facilities, the lower the manufacturing cost. However, in the case of NMP wastewater for secondary batteries, which generates a large amount of sludge, if this large amount of sludge is not properly handled, it can flow into the purification tower feed stage, potentially clogging the purification column. Furthermore, to treat this sludge, a feed solution primarily containing NMP solution must be used to discharge it externally, which reduces the NMP recovery rate.

[0008] To address these issues, a sludge separator equipped with a mesh filter, such as that shown in Fig. 2, is used to prevent sludge from entering. However, if viscous sludge adheres to the mesh, the flow path becomes blocked, preventing evaporation gas from passing through the filter.

[0009] [Prior Art Literature]

[0010] (Patent Document 1) Korean Patent No. 2050990

[0011]

[0012] Accordingly, as a result of research conducted by the inventors of the present invention, a sludge separator capable of solving the problems of conventional mesh filters was implemented by placing a specially designed barrier unit within the sludge separator.

[0013] Accordingly, the present invention provides a sludge separator that exhibits excellent sludge separation performance while preventing gas flow blockage. Furthermore, the present invention provides a method and apparatus for purifying NMP, capable of obtaining high-purity NMP from waste NMP with a high recovery rate, using the sludge separator.

[0014]

[0015] The present invention provides a sludge separator comprising a container (100); an inlet (200) through which waste liquid is supplied to the container; a gas discharge port (300) formed at the upper end of the container; a liquid discharge port (400) formed at the lower end of the container; and a sludge barrier (500) disposed on the upper side inside the container and having a plurality of barrier layers, wherein the barrier layer has a cross-section in the shape of a hat and has a plurality of barrier units (501) spaced apart from each other.

[0016] In addition, the present invention comprises: (1) a step of introducing waste NMP from a raw material tank into the sludge separator described above; (2) a step of discharging a first gas mixture including NMP separated in the sludge separator through the top of the sludge separator and discharging a mixture including sludge through the bottom of the sludge separator; (3) a step of introducing the first gas mixture including the discharged NMP into a first distillation column to perform a first purification; (4) a step of discharging an effluent including water separated through the first purification to the outside of the system through the top of the first distillation column and discharging a first drawout through the bottom of the first distillation column; (5) a step of introducing the discharged first drawout into a second distillation column to perform a second purification; (6) a step of discharging purified NMP separated through the second purification to the outside of the system through the top of the second distillation column and discharging a second drawout through the bottom of the second distillation column; (7) a step of introducing a mixture including sludge discharged in the step (2) into a filtrate recovery device and subjecting it to heat treatment; (8) a step of discharging the 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 second gas mixture including NMP through the upper end of the filtrate recovery device; (9) a step of introducing the second effluent discharged in the step (6) and the second gas mixture including NMP discharged in the step (8) into an impurity tank and mixing them; and (10) a step of circulating the mixture in the impurity tank to the raw material tank.

[0017] In addition, the present invention comprises: a raw material tank for supplying waste NMP; a sludge separator having the configuration described above, which discharges a first gas mixture including NMP separated from the supplied waste NMP through an upper portion and a mixture including sludge through a lower portion; a first distillation column which performs a first purification of the first gas mixture including NMP, discharges an effluent including water separated through the first purification to the outside of the system through an upper portion, and discharges the first draw-out through a lower portion; a second distillation column which distills the first draw-out to perform a second purification, discharges purified NMP separated through the second purification to the outside of the system through an upper portion, and discharges the second draw-out through a lower portion; a filtrate recovery device which heat-treats a mixture including sludge discharged from the sludge separator, discharges a third draw-out separated through the heat-treatment to the outside of the system through an lower portion, and discharges a second gas mixture including NMP through an upper portion; And an NMP purification device including an impurity tank for mixing a second gas mixture including a secondary effluent discharged from the secondary distillation tower and NMP discharged from the filtrate recovery device and injecting the mixture into the raw material tank is provided.

[0018]

[0019] The sludge separator according to the present invention can achieve excellent sludge separation performance while preventing gas flow blockage. Specifically, the present invention can overcome the problems associated with conventional mesh filters by arranging a specially designed barrier unit within the sludge separator.

[0020] Therefore, the method and device for purifying NMP using the sludge separator of the present invention can improve the recovery rate of NMP recovered from waste NMP and provide high-purity NMP.

[0021]

[0022] Figure 1 shows a cross-sectional view of a sludge separator according to one embodiment of the present invention.

[0023] Figure 2 shows the flow of gas in a mesh filter according to the prior art.

[0024] Figure 3 shows the flow of gas in a sludge barrier according to one embodiment of the present invention.

[0025] Figure 4 shows a cross-sectional view of a sludge barrier according to one embodiment of the present invention.

[0026] Figure 5 shows an exploded perspective view of a sludge barrier according to one embodiment of the present invention.

[0027] Figure 6 shows a perspective view of a sludge barrier according to one embodiment of the present invention.

[0028] Fig. 7 shows a connection structure of a barrier unit and a connecting beam according to an embodiment.

[0029] Figure 8 shows a plan view of a sludge barrier according to one embodiment of the present invention.

[0030] Figure 9 shows the configuration of an NMP purification device according to one embodiment of the present invention.

[0031]

[0032] <Explanation of symbols>

[0033] W: sludge separator, 100: vessel, 200: inlet, 300: gas outlet, 400: liquid outlet, 500: sludge barrier, 501: barrier unit, 505: connecting beam, 509: fastening means, 510: first barrier layer, 520: second barrier layer, 530: third barrier layer, 600: separator plate, a: angle of the hat, L: length of one side of the hat, dL: vertical spacing between barrier layers, dU: horizontal spacing between barrier units, A: vacuum pump, B1: preheater, B2: sludge separator heater, B3: primary reboiler, B4: secondary reboiler, D1, D2: primary and secondary distillation columns, P1 to P6: primary to sixth pumps, R: Residue recovery device, RT: raw material tank, PT: impurity tank, ST: storage tank, T-1 to T-5, Y-1 to Y-4: discharge pipe, S-1 to S-5: circulation pipe, X-1 to X-5: input pipe.

[0034]

[0035] The present invention will be described in detail with reference to the drawings below.

[0036] If a detailed description of a related public notice or function in this specification is deemed to obscure the gist of the present invention, such detailed description will be omitted. Furthermore, the sizes of individual components in the drawings may be exaggerated or omitted for illustrative purposes, and may differ from the sizes actually applied.

[0037] 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.

[0038] 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.

[0039] In the following description, the description that one component is formed above / below another component or is connected or joined to each other includes all of the components being formed, connected or joined directly or indirectly through another component.

[0040] 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.

[0041] In this specification, when a numerical range with a limited upper limit and a numerical range with a limited lower limit are described to illustrate the size, physical properties, etc. of a component, it should be understood that a numerical range in which these upper and lower limits are combined is also included in the exemplary range of the present invention.

[0042] In this specification, singular expressions should be interpreted to include the singular or plural as interpreted in the context, unless otherwise stated.

[0043] The present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0044]

[0045] sludge separator

[0046] Figure 1 shows a cross-sectional view of a sludge separator according to one embodiment of the present invention.

[0047] Referring to FIG. 1, a sludge separator (W) according to one embodiment includes a container (100); an inlet (200) through which waste liquid is supplied to the container; a gas discharge port (300) formed at an upper end of the container; a liquid discharge port (400) formed at a lower end of the container; and a sludge barrier (500) disposed on an upper side inside the container and having a plurality of barrier layers, wherein the barrier layer has a plurality of barrier units (501) having a cross-section in the shape of a hat and spaced apart from each other.

[0048] In the sludge separator (W) according to the above embodiment, waste liquid is supplied into the container (100) through the inlet (200), and the sludge contained in the waste liquid is precipitated at the bottom of the container. The gas evaporated from the waste liquid moves to the upper part of the container and passes through the gap between the barrier units (501) of the sludge barrier (500), but the fine sludge contained in the gas is blocked by the barrier units (501) and falls down. Thereafter, the gas with the sludge blocked is discharged to the outside through the gas discharge port (300) at the top of the container (100), and the sludge precipitated at the bottom of the container (100) is discharged to the outside through the liquid discharge port (400).

[0049] Below, each component of the above sludge separator is described in detail.

[0050] The shape of the above container (100) may be cylindrical, for example, as shown in FIG. 1.

[0051] The diameter in the horizontal cross section of the container (100) may be, for example, 500 mm or more, 800 mm or more, or 1,000 mm or more, and may also be 3,000 mm or less, 2,500 mm or less, or 2,000 mm or less. Specifically, the diameter in the horizontal cross section of the container (100) may be 500 mm to 3,000 mm. More specifically, the diameter in the horizontal cross section of the container (100) may be 800 mm to 2,500 mm.

[0052] The height in the vertical cross-section of the container (100) may be, for example, 1,000 mm or more, 1,200 mm or more, or 1,600 mm or more, and may also be 4,000 mm or less, 3,000 mm or less, or 2,500 mm or less. Specifically, the height in the vertical cross-section of the container (100) may be 1,000 mm to 4,000 mm. More specifically, the height in the vertical cross-section of the container (100) may be 1,200 mm to 2,500 mm.

[0053] The wall thickness of the container (100) may be, for example, 5 mm to 10 mm. More specifically, the wall thickness of the container (100) may be, for example, 5 mm to 8 mm.

[0054] The material of the wall surface of the above container may be, for example, stainless steel (e.g., STS304, STS316(L)), Hastelloy alloy, etc.

[0055] Referring to Fig. 1, the container (100) is provided with an inlet (200) through which waste liquid is supplied. For example, the inlet may be formed on a side of the container. Through the inlet, waste liquid containing sludge is supplied to the sludge separator.

[0056] The diameter of the injection port (200) may be, for example, 15 mm or more, 30 mm or more, or 45 mm or more, and may also be 100 mm or less, 80 mm or less, or 60 mm or less. Specifically, the diameter of the injection port (200) may be 15 mm to 100 mm. More specifically, the diameter of the injection port may be 15 mm to 80 mm.

[0057] In addition, the angle of the inlet can be appropriately adjusted so that the waste liquid can be introduced into the container in an oblique direction to form a cyclone rotation.

[0058] A pipe for supplying waste liquid may be connected to the above inlet. In addition, a valve for controlling the supply amount of waste liquid may be installed in the inlet or the pipe connected thereto.

[0059] Referring to Fig. 1, a gas discharge port (300) is formed at the top of the container (100). Through the gas discharge port, gas generated through evaporation from waste liquid supplied inside the container is discharged to the outside.

[0060] The diameter of the gas outlet (300) may be, for example, 150 mm or more, 200 mm or more, or 250 mm or more, and may also be 500 mm or less, 400 mm or less, or 300 mm or less. Specifically, the diameter of the gas outlet (300) may be 150 mm to 500 mm. More specifically, the diameter of the gas outlet may be 200 mm to 400 mm.

[0061] A pipe for transporting gas to a subsequent process, such as additional purification, may be connected to the above gas outlet. In addition, a valve for controlling the amount of gas discharged may be installed on the above gas outlet or the pipe connected thereto.

[0062] Referring to Fig. 1, a liquid discharge port (400) is formed at the bottom of the container (100). Through the liquid discharge port, waste liquid containing sludge settled at the bottom of the container is discharged.

[0063] The diameter of the liquid discharge port (400) may be, for example, 40 mm or more, 80 mm or more, or 120 mm or more, and may also be 400 mm or less, 350 mm or less, or 300 mm or less. Specifically, the diameter of the liquid discharge port (400) may be 40 mm to 400 mm. More specifically, the diameter of the liquid discharge port may be 80 mm to 350 mm.

[0064] A pipe for transporting sludge solution to a subsequent process, such as filtrate recovery, may be connected to the above liquid discharge port. In addition, a valve for controlling the discharge amount of sludge solution may be installed in the above liquid discharge port or the pipe connected thereto.

[0065] Sludge within the wastewater falls vertically downwards within the sludge separator due to its weight and accumulates at the bottom of the container. The evaporated gas, due to its low density, moves vertically upwards. However, the vertically upward flow of gas impedes the downward flow of sludge, causing some of the lighter sludge to move vertically upwards along with the gas flow. To prevent the inflow of sludge moving vertically upward with the gas, a means is provided at the top of the sludge separator.

[0066] Figure 2 illustrates the flow of gas through a mesh filter according to prior art. While this mesh filter allows gas to pass through, preventing the inflow of sludge, there is a problem in that viscous sludge gradually adheres to the mesh and blocks the pores, thereby impeding the flow of gas through the mesh.

[0067] A sludge barrier according to one embodiment of the present invention can solve the problem of a conventional mesh filter by appropriately placing a specially designed barrier unit within a sludge separator.

[0068] Figure 3 shows the flow of gas in a sludge barrier according to one embodiment of the present invention.

[0069] Referring to FIG. 3, a sludge barrier (500) according to one embodiment has a plurality of barrier layers (510, 520, 530), and the barrier layers have a plurality of barrier units (501) spaced apart from each other and having a cross-section in the shape of a hat.

[0070] In particular, the above barrier unit (501) has a hat shape extending in one direction, and a plurality of barrier units (501) can be arranged in rows within each barrier layer.

[0071] Gas flowing vertically upwards refracts and moves along the empty spaces between the cap-shaped barrier units. During this process, sludge moving with the gas is blocked by the cap-shaped barrier units and falls back down. Furthermore, even if sludge is trapped and collected at the bottom of the cap, it does not block the space between the barrier units, so it does not affect the flow of gas passing through the sludge barrier.

[0072] The barrier layer and individual barrier units constituting the sludge barrier according to the above implementation example can exhibit better performance by adjusting the specifications such as the spacing and size between them within a specific range.

[0073] Figure 4 shows a cross-sectional view of a sludge barrier according to one embodiment of the present invention.

[0074] The above sludge barrier may have a structure in which three or more barrier layers are laminated. Specifically, the sludge barrier may have a structure in which a first barrier layer (610), a second barrier layer (620), a third barrier layer (630), etc. are laminated.

[0075] Within the above sludge barrier, individual barrier layers (510, 520, 530) may be spaced apart from each other by a constant vertical distance. The vertical distance between the barrier layers may be defined, for example, as the vertical distance between barrier units provided on adjacent barrier layers.

[0076] By adjusting the specifications of the above sludge barrier, such as the spacing between barrier layers (dL), the length of one side of the barrier unit (501) (L), and the spacing between barrier units (dU), the sludge blocking performance can be further improved.

[0077] Referring to FIG. 4, the vertical spacing (dL) between the barrier layers (510, 520, 530) may be, for example, 25 mm or more, 30 mm or more, or 35 mm or more, and may also be 50 mm or less, 45 mm or less, or 40 mm or less. Specifically, the vertical spacing (dL) between the barrier layers (510, 520, 530) may be 25 mm to 50 mm. More specifically, the vertical spacing (dL) between the barrier layers may be 30 mm to 40 mm.

[0078] In addition, the vertical spacing (dL) between the barrier layers can be adjusted within a certain ratio range based on the height of the barrier layer. For example, the vertical spacing (dL) between the barrier layers can be a spacing corresponding to 50% to 80%, more specifically, 50% to 70%, based on the height of the barrier layer.

[0079] Referring to FIG. 4, the spacing (dU) between the barrier units (501) may be, for example, 35 mm or more, 40 mm or more, or 45 mm or more, and may also be 55 mm or less, 50 mm or less, or 45 mm or less. Specifically, the spacing (dU) between the barrier units (501) may be 35 mm to 55 mm. More specifically, the spacing (dU) between the barrier units (501) may be 40 mm to 50 mm.

[0080] In addition, the spacing (dU) between the barrier units (501) can be adjusted within a certain ratio range based on the horizontal size of the barrier units. For example, the spacing (dU) between the barrier units (501) can be a spacing corresponding to 30% to 50%, more specifically, 35% to 45%, based on the horizontal size of the barrier units.

[0081] Referring to FIG. 4, the length (L) of one side of the hat shape in the cross-section of the barrier unit (501) may be, for example, 40 mm or more, 50 mm or more, or 60 mm or more, and may also be 100 mm or less, 85 mm or less, or 75 mm or less. Specifically, the length (L) of one side of the hat shape in the cross-section of the barrier unit (501) may be 40 mm to 100 mm. More specifically, the length (L) of one side of the hat shape in the cross-section of the barrier unit (501) may be 50 mm to 75 mm.

[0082] The angle (a) of the cross-section of the barrier unit (610) bent into a hat shape may be, for example, 60° to 120°. More specifically, the angle (a) of the cross-section of the barrier unit (610) bent into a hat shape may be 75° to 105°.

[0083] In particular, barrier units (501) provided on adjacent barrier layers may be arranged to be offset from each other.

[0084] Specifically, the center of a barrier unit provided in a barrier layer may be positioned on the same vertical line as the edge of a barrier unit provided in an adjacent barrier layer or the gap between barrier units. Accordingly, the effect of blocking sludge while allowing gas to pass smoothly can be enhanced.

[0085] Fig. 5 shows an exploded perspective view of a sludge barrier according to one embodiment of the present invention. Fig. 6 shows a perspective view of a sludge barrier according to one embodiment of the present invention.

[0086] Referring to FIGS. 5 and 6, the sludge barrier (500) may have a structure in which three or more barrier layers (510, 520, 530) are laminated.

[0087] The above barrier unit (501) has a hat shape extending in one direction, and a plurality of barrier units can be arranged in rows within individual barrier layers (510, 520, 530).

[0088] A plurality of barrier units (501) arranged in alignment with the above rows can be fastened to a connecting beam (505) arranged in a vertical direction with the rows.

[0089] Fig. 7 shows a connection structure of a barrier unit and connecting beams according to an embodiment.

[0090] Figure 8 shows a plan view of a sludge barrier according to one embodiment of the present invention.

[0091] Referring to FIG. 7, at least a portion of the barrier unit (501) may be fastened by contacting the connecting beam (505). For example, the cap-shaped top portion of the barrier unit may penetrate the connecting beam and be fastened. More specifically, grooves may be provided at regular intervals in the connecting beam, and the cap-shaped top portion of the barrier unit may be fastened to each of these grooves.

[0092] In addition, the above-mentioned connecting beam may be connected to another connecting beam located above or below it by a connecting means, so that the barrier units and connecting beams constituting the sludge barrier may be maintained in a combined state as a whole. As an example, a connecting beam connected to a barrier unit provided in a certain barrier layer may be connected to a connecting beam connected to a barrier unit provided in an adjacent barrier layer by a connecting means.

[0093] Specifically, the connecting beam connected to the barrier unit provided in the first barrier layer (510) can be connected to the connecting beam connected to the barrier unit provided in the second barrier layer (520) by a connecting means (509). In addition, the connecting beam connected to the barrier unit provided in the second barrier layer (520) can be connected to the connecting beam connected to the barrier unit provided in the third barrier layer (530) by a connecting means (509). Accordingly, all of the barrier units (501) and connecting beams (505) of all barrier layers (510, 520, 530) constituting the sludge barrier can be maintained in a connected state.

[0094] Additionally, both ends of the connecting beam (505) can be joined to the inner wall of the container (100).

[0095] The above sludge barrier may have a porosity within a certain range. If the porosity of the sludge barrier is too small, the flow of gas through it may not be smooth, and if the porosity is too large, the sludge filtering performance may not be sufficient.

[0096] For example, the porosity of the sludge barrier (500) may be 80% or more. Specifically, the porosity of the sludge barrier (500) may be 80% to 90%. More specifically, the porosity of the sludge barrier (500) may be 80% to 85%.

[0097] Such porosity can be calculated, for example, by calculating the ratio of the total pore area to the cross-sectional area of ​​the sludge barrier.

[0098] The type of sludge blocked by the above sludge barrier (500) may be, for example, floating matter in waste solution, substances precipitated by temperature change, etc., but is not limited thereto.

[0099] The above sludge separator may additionally include a separator plate (600) placed inside the container near the injection port (200).

[0100] In this way, the separator plate may be provided at a location where the waste liquid is fed into the sludge separator. At least a portion of the separator plate may be attached to the inner wall of the container, and the separator plate may be provided at a location lower than the sludge barrier.

[0101] The above separator plate can prevent the waste liquid injected into the container from directly contacting the sludge barrier (500). In addition, the above separator plate can guide the initial flow direction of the waste liquid injected into the container.

[0102] The above separator (600) may have, for example, a shape that is bent downward. Specifically, the separator may have a cross-section that is “ㄱ” shaped or diagonal, but is not limited thereto.

[0103] Referring to Fig. 1, when the cross-section of the separator (600) is in the shape of the letter "ㄱ", the inner diameter of the separator may be 500 mm to 800 mm, and the vertical size may be 300 mm to 500 mm. More specifically, the inner diameter of the separator (600) may be 600 mm to 700 mm, and the vertical size may be 350 mm to 450 mm. Here, the inner diameter of the separator refers to the horizontal size up to the point where it is bent downward like the shape of the letter "ㄱ".

[0104] Such a sludge separator plate can primarily filter out sludge by obstructing the flow of waste liquid fed into the sludge separator, thereby not only removing sludge with high efficiency but also extending the life of the sludge barrier.

[0105] The above sludge separator can be used for purification of waste NMP.

[0106] Waste NMP recovered after use as a material for lithium secondary batteries may contain large amounts of sludge. This waste NMP, containing large amounts of sludge, is difficult to transport during the NMP recovery process, potentially blocking transport pipes and requiring a separate solution for transport.

[0107] However, by using the sludge separator described above for purification of waste NMP, a large amount of sludge contained in the waste NMP can be effectively separated, and as a result, the recovery rate of NMP recovered from the waste NMP can be improved, and high-purity NMP can be provided.

[0108]

[0109] NMP purification method

[0110] According to another aspect of the present invention, a method for purifying NMP comprises the steps of: (1) introducing waste NMP from a raw material tank into a sludge separator; (2) discharging a first gas mixture containing NMP separated from the sludge separator through the top of the sludge separator and discharging a mixture containing sludge through the bottom of the sludge separator; (3) introducing the first gas mixture containing the discharged NMP into a first distillation column to perform first purification; (4) discharging an effluent containing water separated through the first purification to the outside of the system through the top of the first distillation column and discharging a first drawout through the bottom of the first distillation column; (5) introducing the discharged first drawout into a second distillation column to perform second purification; (6) discharging purified NMP separated through the second purification to the outside of the system through the top of the second distillation column and discharging a second drawout through the bottom of the second distillation column; (7) a step of introducing a mixture containing the sludge discharged in the step (2) into a filtrate recovery device and subjecting it to heat treatment; (8) a step of discharging the 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 second gas mixture containing NMP through the upper end of the filtrate recovery device; (9) a step of introducing the second effluent discharged in the step (6) and the second gas mixture containing NMP discharged in the step (8) into an impurity tank and mixing them; and (10) a step of circulating the mixture in the impurity tank to the raw material tank.

[0111] Fig. 9 illustrates an example of an NMP purification device according to one embodiment of the present invention. Specifically, Fig. 9 illustrates an NMP purification device comprising a raw material tank (RT), a sludge separator (W), a primary distillation tower (D1), a secondary distillation tower (D2), a filtrate recovery device (R), and an impurity tank (PT).

[0112] Hereinafter, a method for purifying NMP according to one embodiment of the present invention will be described with reference to FIG. 9.

[0113] In step (1), waste NMP from the raw material tank is fed into a sludge separator.

[0114] A method for purifying NMP according to one embodiment of the present invention includes a step of introducing waste NMP from a raw material tank into a sludge separator.

[0115] The above-mentioned waste NMP may be recovered after being used in the process of manufacturing a lithium secondary battery, but is not limited thereto. For example, the above-mentioned waste NMP may be recovered after being used as a material for a lithium secondary battery and may contain a large amount of sludge.

[0116] 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.

[0117] 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.

[0118] The detailed configuration and characteristics of the above sludge separator are as described in the sludge separator according to the embodiment above. The NMP purification method according to one embodiment of the present invention can effectively separate a large amount of sludge contained in waste NMP by using the sludge separator having the above technical characteristics, thereby exhibiting excellent processability.

[0119] In addition, before introducing the waste NMP into the sludge separator in the step (1), a step (1-1) of preheating the waste NMP to a temperature of 60°C to 100°C may be additionally included. For example, the step (1-1) may be a step of preheating the waste NMP to a temperature of 65°C to 95°C, and the preheated waste NMP may be introduced into the sludge separator.

[0120] In step (2), a first gas mixture containing NMP separated in the sludge separator is discharged through the top of the sludge separator, and a mixture containing sludge is discharged through the bottom of the sludge separator.

[0121] A method for purifying NMP according to one embodiment of the present invention includes the steps of discharging a first gas mixture containing NMP separated in the sludge separator through the upper portion of the sludge separator and discharging a mixture containing sludge through the lower portion of the sludge separator.

[0122] Specifically, the step (2) can effectively separate the first gas mixture containing separated NMP and the mixture containing sludge using a sludge separator, thereby removing a large amount of sludge contained in waste NMP, thereby improving the process for recovering NMP and the recovery rate and purity of NMP.

[0123] In step (3), the first gas mixture containing the discharged NMP is introduced into a first distillation tower to perform first purification.

[0124] A method for purifying NMP according to one embodiment of the present invention includes a step of performing primary purification by introducing a first gas mixture containing the discharged NMP into a primary distillation column.

[0125] In the above step (3), the first gas mixture containing the discharged NMP may be injected into the upper portion of the first distillation column. Specifically, it may be preferable for the first gas mixture containing the NMP to be injected into the middle portion of the first distillation column or a higher portion thereof to more efficiently perform the first purification, but the present invention is not limited thereto.

[0126] The first purification of the above step (1) can be performed at a temperature of 50°C to 100°C and a pressure of 100 torr to 130 torr. For example, the first purification can be performed at a temperature of 52°C to 85°C or 55°C to 75°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 first purification within the above ranges, moisture contained in the first gas mixture containing NMP can be effectively removed.

[0127] In step (4), 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, and the first draw-off liquid is discharged through the bottom of the first distillation tower.

[0128] 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.

[0129] Specifically, the step (4) can improve the purity of NMP by lowering the moisture content by separating the effluent containing water from the first gas mixture containing NMP through the primary purification of the step (3) and discharging it to the outside of the system.

[0130] 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.

[0131] 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 99.9 wt% or more, 99.92 wt% or more, or 99.94 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.

[0132] In step (5), the discharged primary effluent is introduced into a secondary distillation tower to perform secondary purification.

[0133] 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.

[0134] 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 (5) 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.

[0135] In the above step (5), the first distillate may be injected into the middle or lower portion of the second distillation column. Specifically, it may be preferable for the first distillate to be injected 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.

[0136] The secondary purification can 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 can 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.

[0137] In step (6), the purified NMP separated through the secondary purification is discharged to the outside of the system through the top of the secondary distillation tower, and the secondary draw-off liquid is discharged through the bottom of the secondary distillation tower.

[0138] 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.

[0139] Specifically, the step (6) can obtain purified NMP by discharging the second extract containing a component having a boiling point higher than NMP from the first extract through the second purification of the step (5).

[0140] 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.

[0141] 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.

[0142] The purity of the purified NMP may be 99.9% or greater. For example, the purity of the purified NMP may be 99.92% or greater, 99.94% or greater, or 99.95% or greater.

[0143] In step (7), the mixture containing the sludge discharged in step (2) is introduced into a sludge recovery device and heat-treated.

[0144] A method for purifying NMP according to one embodiment of the present invention includes a step of introducing a mixture containing sludge discharged in step (2) into a filtrate recovery device and subjecting it to heat treatment.

[0145] Specifically, since the mixture containing the sludge separated through the sludge separator may also contain NMP, the mixture containing the sludge may be fed into a filtrate recovery device and subjected to heat treatment, thereby separating the NMP contained in the mixture containing the sludge in a gaseous form and recycling it.

[0146] In the above step (7), the heat treatment can be performed at a temperature of 110°C to 140°C and a pressure of 60 torr to 100 torr. 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. By satisfying the process conditions of the heat treatment within the above range, the recovery rate of NMP can be further improved.

[0147] Additionally, the pressure of the filtrate recovery device can be controlled via a vacuum pump connected to the filtrate recovery device. Since controlling the pressure of the filtrate recovery device is important for achieving the intended effects of the present invention, the pressure of the filtrate recovery device can be controlled via a vacuum pump.

[0148] In step (8), the tertiary effluent separated through the heat treatment is discharged to the outside of the system through the lower part of the filtrate recovery device, and the second gas mixture containing NMP is discharged through the upper part of the filtrate recovery device.

[0149] 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 second gas mixture containing NMP through the upper end of the filtrate recovery device.

[0150] Specifically, the step (8) can separate the third effluent and the second gas mixture containing NMP through heat treatment in the step (7), and the second gas mixture containing NMP can be circulated and utilized, thereby improving the processability and the recovery rate of NMP.

[0151] The second gas mixture containing the NMP may contain a component having a boiling point higher than that of NMP in an amount of 30 wt% or less. For example, the content of the component having a boiling point higher than that of NMP in the second gas mixture containing the NMP may be 1.5 wt% or less, 1.0 wt% or less, 0.8 wt% or less, or 0.6 wt% or less, based on the total weight of the second gas mixture containing the NMP.

[0152] In step (9), the second gas mixture containing the secondary discharged liquid from step (6) and the NMP discharged from step (8) is introduced into an impurity tank and mixed.

[0153] A method for purifying NMP according to one embodiment of the present invention includes a step of introducing a second gas mixture containing the secondary effluent discharged in step (6) and the NMP discharged in step (8) into an impurity tank and mixing them.

[0154] The mixture in the impurity tank 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 mixture in the impurity tank may be 1.0 wt% or less, 0.8 wt% or less, 0.6 wt% or less, or 0.4 wt% or less, based on the total weight of the mixture in the impurity tank.

[0155] According to another embodiment of the present invention, a step (9-1) of cooling the second gas mixture containing NMP discharged in the step (9) to 45°C or lower before introducing it into the impurity tank may be additionally included.

[0156] The second gas mixture containing NMP discharged in the above step (9) may be circulated by being injected into an impurity tank without separate treatment, but in order to facilitate mixing with the secondary effluent discharged in the above step (6), a step (9-1) of cooling it to 40°C or lower or 35°C or lower using a cooler may be additionally performed before being injected into the impurity tank.

[0157] In step (10), the mixture in the impurity tank is circulated to the raw material tank.

[0158] A method for purifying NMP according to one embodiment of the present invention includes a step of circulating a mixture in the impurity tank to the raw material tank.

[0159] Specifically, by introducing the mixture from the impurity tank into the raw material tank and circulating it, the recovery rate of NMP can be improved. In particular, through this circulation, components with a boiling point higher than NMP can serve as transport materials for waste NMP, thereby facilitating their use in the NMP purification process and thus improving processability.

[0160] According to another embodiment of the present invention, a step (11) of heat-treating the mixture in the impurity tank and then introducing it into the secondary distillation tower may be additionally included. Specifically, the mixture in the impurity tank may be introduced into the raw material tank and circulated, and after heat treatment, introduced into the secondary distillation tower and circulated, thereby further improving the recovery rate of NMP.

[0161] In the above step (11), the heat treatment can be performed at a temperature of 100°C to 130°C. For example, in the above step (11), the heat treatment can be performed at a temperature of 105°C to 130°C or 115°C to 130°C.

[0162] Additionally, the mixture of the impurity tank heat-treated in the above step (11) 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.

[0163] More specifically, the position at which the mixture of the heat-treated impurity tank in the step (11) is introduced into the secondary distillation column may be the same as or lower than the position at which the first draw-out liquid is introduced into the secondary distillation column in the step (5). Since the position at which the mixture of the heat-treated impurity tank in the step (11) is introduced is the same as or lower than the position at which the first draw-out liquid is introduced in the step (5), 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 mixture of the first draw-out liquid and the heat-treated impurity tank 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 mixture of the heat-treated impurity tank having a low NMP content relatively lower than the introduction position of the first draw-out liquid, more efficient purification can be performed.

[0164]

[0165] NMP purification unit

[0166] According to another aspect of the present invention, an NMP purification device comprises: a raw material tank for supplying waste NMP; a sludge separator having the configuration described above, which discharges a first gas mixture containing NMP separated from the supplied waste NMP through an upper portion and discharges a mixture containing sludge through a lower portion; a first distillation column which primarily purifies the first gas mixture containing NMP, discharges an effluent containing water separated through the first purification to the outside of the system through an upper portion, and discharges the first drawout through a lower portion; a second distillation column which distills the first drawout to second purify it, discharges purified NMP separated through the second purification to the outside of the system through an upper portion, and discharges the second drawout through a lower portion; a filtrate recovery device which heat-treats a mixture containing sludge discharged from the sludge separator, discharges a third drawout separated through the heat treatment to the outside of the system through an lower portion, and discharges a second gas mixture containing NMP through an upper portion; And it includes an impurity tank for mixing a second gas mixture including the secondary effluent discharged from the secondary distillation tower and NMP discharged from the filtrate recovery device and injecting the mixture into the raw material tank.

[0167] Fig. 9 illustrates an example of an NMP purification device according to another embodiment of the present invention. Specifically, Fig. 9 illustrates an NMP purification device comprising a raw material tank (RT), a sludge separator (W), a primary distillation tower (D1), a secondary distillation tower (D2), a filtrate recovery device (R), and an impurity tank (PT).

[0168] First, waste NMP is supplied to the sludge separator (W) through the raw material tank (RT) (X-1).

[0169] The above supply can be performed through a primary pump (P1), and at this time, the waste NMP can be preheated through a preheater (B1).

[0170] The sludge separator (W) may include a sludge filter (W1) provided on the upper part of the interior and a sludge separator plate (W2) provided on the upper side of the interior at a lower position than the sludge filter.

[0171] The above sludge separator (W) separates waste NMP or preheated waste NMP through the sludge filter (W1) and the sludge separator (W2). The first gas mixture containing NMP is discharged through the top of the sludge separator (T-1) and is fed into the first distillation column (D1) through the tertiary pump (P3) (X-2), and the mixture containing sludge is discharged through the bottom of the sludge separator (Y-1).

[0172] The mixture containing the discharged sludge can be transferred to a filtrate recovery device (R) via a secondary pump (P2) (X-3) and then circulated to a sludge separator (W) again (S-1).

[0173] At this time, the mixture containing the sludge can be heated through the sludge separator heater (B2) before being fed back into the sludge separator (W).

[0174] The first distillation tower (D1) performs the first purification by distilling the first gas mixture containing the introduced 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-2), and the first draw-out liquid is discharged through the bottom of the first distillation tower (D1) (Y-2). The discharged first draw-out liquid can be transferred to the second distillation tower (D2) through the fourth pump (P4) (X-3), and can be circulated back to the first distillation tower (D1) (S-2). At this time, the first draw-out liquid can be heated through the first reboiler (B3) before being re-introduced to the first distillation tower (D1).

[0175] The secondary distillation tower (D2) distills the supplied primary drawdown to perform secondary purification, 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-3), and the secondary drawdown is discharged to the outside of the system through the bottom of the secondary distillation tower (D2) (Y-3). The purified NMP discharged to the outside of the system can be stored in a storage tank (ST). In addition, the discharged secondary drawdown can be transferred to an impurity tank (PT) through a fifth pump (P5) (X-4) and can be circulated back to the secondary distillation tower (D2) (S-3). At this time, the secondary drawdown can be heated through a secondary reboiler (B4) before being fed back into the secondary distillation tower (D2).

[0176] The sludge recovery device (R) heat-treats a mixture containing the introduced sludge, and at this time, the pressure can be controlled through a vacuum pump (A).

[0177] The tertiary effluent separated through the above heat treatment is discharged outside the system through the lower end of the filtrate recovery device (Y-4), and the second gas mixture containing NMP is discharged through the upper end of the filtrate recovery device (T-5) and fed into the impurity tank (PT) through the 6th pump (P6) (X-5). At this time, the discharged second gas mixture containing NMP can be cooled through the cooler (C1) and then fed into the impurity tank (PT).

[0178] The impurity tank (PT) mixes and mixes a second gas mixture containing the secondary effluent discharged from the secondary distillation tower (D2) and the NMP discharged from the filtrate recovery device (R), and then circulates the mixture to the raw material tank (RT) (S-5). At this time, a heat treatment device may be additionally provided so that the mixture in the impurity tank can be heat-treated and fed into the secondary distillation tower (D2) (S-4).

[0179] The NMP purification method and device according to the present invention can improve the recovery rate of NMP recovered from waste NMP and provide high-purity NMP. Specifically, the NMP purification method according to one embodiment of the present invention can improve the processability as well as the recovery rate and purity of NMP by purifying a first gas mixture including NMP separated through a sludge separator before performing NMP purification. In particular, the sludge separator includes a sludge barrier, so that a large amount of sludge contained in waste NMP can be effectively separated simply without specially controlling process conditions.

[0180] In addition, by introducing a mixture containing sludge separated through the sludge separator into a filtrate recovery device and subjecting it to heat treatment, components having a boiling point higher than NMP contained in the mixture containing the sludge can be effectively removed.

[0181] In addition, by introducing a second gas mixture containing the secondary effluent discharged through secondary purification and the NMP discharged from the filtrate recovery device into an impurity tank and mixing them, and then introducing them back into the raw material tank and circulating them, the recovery rate and purity of NMP can be improved, and since a component having a higher boiling point than the circulated NMP acts as a transport material for waste NMP, it can be easily utilized in the NMP purification process, thereby improving the processability.

[0182] In addition, when the mixture in the above impurity tank is heat-treated and then introduced into a secondary distillation tower, the recovery rate of NMP can be further improved.

Claims

1. Courage (100); An inlet (200) through which waste liquid is supplied to the above container; A gas outlet (300) formed at the top of the container; A liquid discharge port (400) formed at the bottom of the above container; and A sludge barrier (500) is disposed on the upper side of the inside of the container and has a plurality of barrier layers; A sludge separator having a plurality of barrier units (501) spaced apart from each other and having a cross-section in the shape of a hat.

2. In paragraph 1, The above barrier unit (501) has a hat shape extending in one direction, A sludge separator in which a plurality of barrier units are arranged in rows within individual barrier layers.

3. In paragraph 1, A sludge separator, wherein the spacing between the above barrier units (501) is 35 mm to 55 mm.

4. In paragraph 1, A sludge separator, wherein the length of one side of the hat-shaped cross section of the above barrier unit (501) is 40 mm to 100 mm.

5. In paragraph 1, A sludge separator in which barrier units provided on adjacent barrier layers are arranged at an offset from each other.

6. In paragraph 5, The above sludge barrier (500) It has a structure in which three or more barrier layers are laminated, A sludge separator in which individual barrier layers are spaced apart from each other at a constant vertical interval.

7. In paragraph 6, A sludge separator wherein the upper and lower spacing between the above barrier layers is 25 mm to 50 mm.

8. In paragraph 1, A sludge separator, wherein the porosity of the above sludge barrier (500) is 80% to 90%.

9. In paragraph 2, A plurality of barrier units (501) arranged in the above rows are These columns are connected to a connecting beam (505) arranged in a vertical direction, A sludge separator in which both ends of the above connecting beam (505) are connected to the inner wall of the above container (100).

10. In paragraph 1, The above sludge separator It additionally includes a separator (600) placed inside the container near the injection port, The above separator (600) is a sludge separator that prevents the waste liquid injected into the container from directly contacting the sludge barrier (500).

11. In paragraph 10, The above separator (600) has a shape that is bent downward, A sludge separator, wherein the inner diameter of the above separator is 500 mm to 800 mm and the vertical size is 300 mm to 500 mm.

12. In paragraph 1, The above sludge separator is a sludge separator used for purification of waste NMP. 　 13.(1) Step of charging waste NMP from the raw material tank into the sludge separator of paragraph 1; (2) A step of discharging a first gas mixture containing NMP separated in the sludge separator through the top of the sludge separator, and discharging a mixture containing sludge through the bottom of the sludge separator; (3) A step of performing primary purification by introducing the first gas mixture containing the discharged NMP into a primary distillation tower; (4) 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; (5) A step of performing secondary purification by putting the discharged primary effluent into a secondary distillation tower; (6) 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; (7) A step of heat-treating a mixture containing the sludge discharged in the above step (2) by putting it into a sludge recovery device; (8) A step of discharging the tertiary effluent separated through the heat treatment to the outside of the system through the lower part of the filtrate recovery device, and discharging the second gas mixture containing NMP through the upper part of the filtrate recovery device; (9) A step of mixing the second gas mixture containing the secondary discharged liquid from the step (6) and the NMP discharged from the step (8) by introducing them into an impurity tank; and (10) A method for purifying NMP, comprising a step of circulating a mixture of the impurity tank to the raw material tank.

14. Raw material tank supplying waste NMP; A sludge separator having the configuration of the first clause, discharging a first gas mixture containing NMP separated from the supplied waste NMP through the top, and discharging a mixture containing sludge through the bottom; A first distillation column that purifies a first gas mixture containing the above NMP, discharges an effluent containing water separated through the first purification to the outside of the system through the top, and discharges the first effluent through the bottom; A secondary distillation tower that distills the primary effluent to perform secondary purification, discharges purified NMP separated through the secondary purification to the outside of the system through the top, and discharges the secondary effluent through the bottom; A filtrate recovery device that heat-treats a mixture containing sludge discharged from the sludge separator, discharges the third effluent separated through the heat treatment to the outside of the system through the bottom, and discharges a second gas mixture containing NMP through the top; and An NMP purification device including an impurity tank for mixing a second gas mixture containing the secondary effluent discharged from the secondary distillation tower and NMP discharged from the filtrate recovery device and introducing the mixture into the raw material tank.

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