Nmp recovery and purification system and control method thereof

Abstract

The present invention relates to an NMP refining system and a control method thereof, and more particularly, to an NMP recovery refining system and a control method thereof. According to one embodiment of the present invention, an NMP recovery refining system can be provided, which includes a recovery device that operates to recover NMP contained in exhaust gas discharged from a secondary battery process, a recovered NMP storage tank for storing recovered NMP recovered in the recovery device and discharged from the recovery device, a refining device that operates to refine the recovered NMP supplied from the recovered NMP storage tank into high-purity NMP, a refined NMP storage tank for storing refined NMP refined in the refining device and discharged from the refining device, and a circulation line for circulating the refined NMP discharged from the refining device to the recovery device.

Description

Technical Field

[0001] This invention relates to an NMP purification system and its control method, and more specifically, to an NMP recovery purification system and its control method.

[0002] This application claims priority based on Korean Patent Application No. 10-2024-0036253, filed on March 15, 2024, and Korean Patent Application No. 10-2025-0033834, filed on March 17, 2025, the entire disclosure of which is incorporated herein by reference. Background Technology

[0003] High-quality NMP (N-methyl-2-pyridone) is used as a solvent when manufacturing electrodes for lithium-ion batteries.

[0004] In electrode manufacturing processes, a coating process is performed in which a slurry is applied to an electrode substrate and coated. Specifically, NMP is a component of the slurry and is contained in the gas discharged during the drying process of the coating process. NMP is particularly used in mixing processes where positive electrode materials are mixed.

[0005] Because NMP is very expensive and must be managed as a hazardous substance, used NMP is recovered in a condensed state through recycling devices or systems for reuse.

[0006] The recycled NMP is refined using a refining unit or system. The refined NMP can then be reused in coating processes.

[0007] The refining unit includes a refining column, and can be referred to as an apparatus for producing high-purity refined NMP by refining recycled NMP. The refining unit (especially the refining column) performs the refining process under very precise temperature and pressure control. Therefore, it can take a long time from start-up of the refining column to normal operation.

[0008] If there is an excess of purified NMP discharged from the purification column, the column needs to be temporarily shut down. However, when the purification column stops operating, the ratio of the dynamic gas to liquid phase inside the column changes drastically, and stabilization upon restarting takes a long time, resulting in a reduced purification yield. Furthermore, it may affect the yield of the entire electrode manufacturing process.

[0009] Meanwhile, in the existing NMP recycling and NMP refining systems, if the recycling tower stops operating, the refining tower will also stop operating from the local area, and vice versa.

[0010] As an example, if the recovery tower stops operating while both the recovery and purification towers are running normally, the amount of recovered NMP flowing into the purification tower will be insufficient, causing the purification tower to stop operating as well. Even if a temporary stoppage occurs in the recovery and purification towers, it takes a long time to return to normal operation after restarting.

[0011] Therefore, it is necessary to find a method that can effectively ensure the normal operation of the refining tower by effectively avoiding its shutdown or temporary cessation. Furthermore, for the normal operation of the refining tower, it is also necessary to find a method that can effectively ensure the normal operation of the recovery tower. Summary of the Invention

[0012] Technical issues

[0013] By way of an example of the present invention, the present invention aims to provide an NMP recycling and refining system and a control method thereof, which can maintain the normal operation of the refining tower even under the condition of temporary shutdown of the refining tower by recycling the NMP refined in the refining tower to the recycling tower.

[0014] Through one example of the present invention, the present invention aims to provide an NMP recycling and refining system and its control method. In this NMP recycling and refining system, the circulation area is further expanded so that: instead of re-introducing the NMP refined in the refining tower back into its own circulation, it is introduced into the recycling tower, and then introduced back into the refining tower via the recycling tower. This enables the organic linkage between the recycling tower and the refining tower, and ensures the safety and operational stability of the system.

[0015] By way of an example of the present invention, the present invention aims to provide an NMP recovery and purification system and a control method thereof, which can effectively reduce the impurity content in NMP reintroduced into the purification tower by additionally diluting the generated NMP peroxide in the recovery tower.

[0016] By way of an example of the present invention, the present invention aims to provide an NMP recovery and purification system and its control method, which can effectively prevent the purification tower from stopping due to the shutdown of the recovery tower by allowing the recovery tower to operate normally even under conditions where the recovery tower is shut down.

[0017] Technical solution

[0018] To achieve the above objectives, according to an example of the present invention, an NMP recovery and purification system can be provided, comprising: a recovery device that operates to recover NMP contained in waste gas discharged from a secondary battery process; a recovered NMP storage tank that stores the recovered NMP recovered by the recovery device and discharged from the recovery device; a purification device that operates to purify the recovered NMP supplied from the recovered NMP storage tank into high-purity NMP; a purified NMP storage tank that stores the purified NMP purified by the purification device and discharged from the purification device; and a circulation pipeline that circulates the purified NMP discharged from the purification device back to the recovery device.

[0019] The secondary battery process can be a coating process that coats a positive electrode material onto an electrode substrate, and NMP can be recovered from the exhaust gas discharged during the drying process of this coating process, purified, and reused. Since the recovered NMP has relatively low purity, it cannot be used directly, but the recovered NMP can be purified to high purity and reused.

[0020] The recycling apparatus may include a recycling tower, and the refining apparatus may include a refining tower.

[0021] There are various methods for NMP recovery, and therefore, recovery equipment can be manufactured in various ways. A recovery tower, also known as an absorption tower, can be used to perform a process in which NMP is absorbed and recovered by condensate inside the tower. This recovery tower allows NMP in a liquid state to be recovered from waste gas. The recovery tower can be configured as a single tower or multiple towers, and through multiple recovery processes, the concentration of recovered NMP can be increased, while the content of impurities can be reduced.

[0022] Here, the impurities can be referred to as NMP peroxides. It cannot be overstated that impurities should be removed as much as possible to ultimately approach 100% purity.

[0023] There are various methods for refining NMP, and therefore, the recovery unit can also be manufactured in various ways. A refining column, also known as a distillation column, can be used to refine the recovered NMP, which is in a liquid state, into high-purity NMP in a vapor state by heating it inside the column.

[0024] Preferably, the purification column has a top column for separating high-concentration NMP from low-boiling-point impurities, a bottom column for separating high-purity NMP from high-boiling-point impurities, and an intermediate column for discharging high-purity purified NMP gas between the top and bottom columns. That is, the purification column can have multiple layers, and the functions performed at each location can be differentiated.

[0025] In the upper part of the purification column, low-boiling-point impurities such as water can be separated from high-concentration NMP. Therefore, high-purity NMP can be obtained from high-concentration NMP.

[0026] In the lower section of the purification column, high-boiling-point impurities such as NMP peroxide can be separated from high-purity NMP. Therefore, by removing impurities from high-purity NMP, NMP of even higher purity can be obtained.

[0027] In the middle section of the purification column, high-purity liquid NMP can be obtained in a gaseous state. Because the distillation process is continuous throughout the entire purification column and the purified NMP in the middle section is discharged outside the column, this can be called a side-stream distillation method.

[0028] The refining unit may include a condenser for condensing the high-purity refined NMP gas discharged from the intermediate tower for supplying it to a refined NMP storage tank. Specifically, the condenser is located in the refined NMP pipeline connecting the refining unit and the refined NMP storage tank, and the high-purity refined NMP liquid condensed from the gas is stored in the refined NMP storage tank.

[0029] Preferably, the circulation line is configured to connect the refining tower and the recovery tower. Here, the circulation line is a conduit that allows fluid flow from the refining tower to the recovery tower, and preferably, it blocks fluid flow in the opposite direction.

[0030] The circulation line may include a gas circulation line that circulates refined NMP gas from the upstream side of the condenser to the recovery tower.

[0031] The circulation line may include a liquid circulation line that circulates the condensed refined NMP from the downstream side of the condenser to the recovery tower.

[0032] The refined NMP can be introduced into the recovery tower via gas circulation lines and / or liquid circulation lines branching from the refined NMP pipeline.

[0033] A waste NMP storage tank and a flow control valve may be provided. The waste NMP storage tank stores waste NMP containing high-boiling-point impurities discharged from the bottom of the refining column, and the flow control valve is used to regulate the flow rate of waste NMP introduced into the waste NMP storage tank.

[0034] The flow control valve can be an automatic control valve that automatically adjusts its flow rate based on the liquid level in the waste NMP storage tank or the concentration of waste NMP.

[0035] Preferably, when the purification unit is operating normally, a circulation mode is executed when the liquid level of the purified NMP storage tank is equal to or higher than the preset liquid level or the liquid level of the recycled NMP storage tank is equal to or lower than the preset liquid level. In this circulation mode, the normal operation of the purification unit is maintained, and the high-purity NMP discharged from the purification unit is circulated to the recycling unit through the circulation pipeline.

[0036] Preferably, when the refining unit is operating normally, if the liquid level in the refined NMP storage tank is lower than the preset liquid level and the liquid level in the recycled NMP storage tank is higher than the preset liquid level, a basic mode is executed: in this basic mode, the recycled NMP is supplied from the recycled NMP storage tank to the refining unit, and the high-purity NMP refined in the refining unit is discharged to the refined NMP storage tank.

[0037] Normal operation of the refining unit can be defined as the operation of refining under optimal refining conditions within the refining unit. A series of continuous and organic operations—including the normal supply of recovered NMP to the refining unit, the normal refining of the recovered NMP, and the discharge of the refined high-purity NMP—can be termed normal operation.

[0038] For the purified high-purity NMP discharged from the normal operation of the purification unit, the basic mode is to supply it to the purified NMP storage tank and store it in the purified NMP storage tank.

[0039] Several situations may occur, such as the liquid level in the refined NMP storage tank reaching its upper limit, or the coating process being temporarily stopped, resulting in an excess of refined NMP. Furthermore, the amount of refined NMP may be increased beyond the amount required for the cathode mixing process.

[0040] This excess of refined NMP can be identified by the upper limit level inside the refined NMP storage tank.

[0041] In the positive electrode mixing process, the time required to manufacture the main mixer slurry (cycle time) can be approximately 1 hour, and the time required to manufacture the semi-finished products (binder solution, pre-dispersion solution) mixer can be approximately 4 hours and 8 hours, respectively. Therefore, it can be said that refined NMP, after being consumed, will be consumed again after a period of time. Thus, even if there is a current surplus of refined NMP, the surplus can be resolved after a certain period.

[0042] The problem is that until the excess of refined NMP is resolved, there is always a risk that the refining column will stop operating. In other words, there is a risk that it will become difficult to maintain normal operation.

[0043] Therefore, in this example, in order to address the excess of refined NMP and maintain the normal operation of the refining tower, a circulation mode can be provided: in this circulation mode, the refined NMP generated due to the normal operation of the refining tower is not supplied to the refined NMP storage tank, but is circulated and supplied to the recycling tower.

[0044] At the same time, several situations may occur, such as the liquid level in the NMP recovery storage tank reaching the lower limit, or the coating process being temporarily stopped, resulting in insufficient NMP recovery. That is, the amount of recovered NMP that should be supplied to the refining unit may be insufficient.

[0045] This insufficient NMP recovery can be identified by checking the lower limit level inside the NMP recovery storage tank.

[0046] The problem is that until the insufficient NMP level is resolved, there is always a risk that the purification column will stop operating. In other words, there is a risk that it will become difficult to maintain normal operation.

[0047] Therefore, in this example, in order to address the insufficient amount of recycled NMP and maintain the normal operation of the purification tower, a circulation mode can be provided: in this circulation mode, the purified NMP generated due to the normal operation of the purification tower is not supplied to the purified NMP storage tank, but is circulated and supplied to the recycling tower.

[0048] Ultimately, in this example, to avoid the intentional temporary shutdown of both the recycling unit and the refining unit, it is possible to maintain the normal operation of both the refining and recycling units by recycling the refined NMP that has been refined back to the recycling unit.

[0049] This allows for the prevention of losses due to the restart of the recycling and refining units after a shutdown, as well as losses from restart to normal operation. Furthermore, since the refined NMP that has undergone refining is partially used for NMP recovery, and the process is repeated thereafter, NMP peroxides can be separated more effectively during both the recycling and refining processes.

[0050] To achieve the above objectives, according to an example of the present invention, a control method for an NMP recovery and purification system can be provided, the control method comprising: an NMP recovery step, wherein NMP contained in waste gas discharged from a secondary battery manufacturing process is introduced into a recovery tower and the introduced gas is condensed in the recovery tower to recover NMP; a recovered NMP storage step, wherein the recovered NMP recovered and discharged in the recovery step is stored in a recovered NMP storage tank; an NMP purification step, wherein the stored recovered NMP is introduced into a purification tower and the recovered NMP introduced into the purification tower is heated to purify the recovered NMP into high-purity NMP; a purified NMP storage step, wherein the purified NMP purified and discharged in the purification step is stored in a purified NMP storage tank; and a circulation step, wherein the purified NMP purified and discharged in the purification step is bypassed and the purified NMP is introduced into the recovery tower.

[0051] The refined NMP storage and recycling steps can be performed selectively.

[0052] The mode used for storing purified NMP can be called the basic mode, and the mode used for recycling purified NMP to the recovery unit can be called the recycling mode. It is desirable to selectively execute both the basic mode and the recycling mode during normal operation. When the currently required amount of purified NMP is excessive or the required amount of recycled NMP is insufficient, from the perspective of the purification unit, it can be said that the output is excessive or the input is insufficient. In this case, it is preferable to execute the recycling mode, thereby avoiding temporary shutdowns of the purification unit and maintaining its normal operation.

[0053] Through the NMP purification step, purified NMP gas can be discharged from the purification tower, and the purified NMP gas can be condensed by a condenser.

[0054] The circulation steps may include a gas circulation step and a liquid circulation step. In the gas circulation step, purified NMP gas is introduced into the recovery tower, and in the liquid circulation step, condensed purified NMP is introduced into the recovery tower.

[0055] This cyclic step can be performed to maintain the normal operation of the NMP purification step when the amount of recovered NMP to be introduced into the purification tower is insufficient.

[0056] The state of insufficient NMP recovery can be determined based on the liquid level inside the NMP recovery storage tank. When the liquid level reaches the lower limit, this cycle mode can be executed.

[0057] This cyclic step can be performed to maintain the normal operation of the NMP purification step even when there is an excess of purified NMP discharged from the purification tower.

[0058] The excess amount of refined NMP can be determined based on the liquid level inside the refined NMP storage tank. When the liquid level reaches the upper limit, this cycle mode can be executed.

[0059] Beneficial effects

[0060] The purpose of this invention is to solve the problems of existing NMP recycling and NMP refining equipment.

[0061] An example of the present invention provides an NMP recycling and refining system and its control method, which maintains the normal operation of the refining tower even under conditions of temporary shutdown of the refining tower by recycling the NMP refined in the refining tower to the recycling tower.

[0062] An example of the present invention provides an NMP recycling and refining system and its control method. In this NMP recycling and refining system, the circulation area is further expanded so that: instead of re-introducing the refined NMP in the refining tower back into its own circulation, it is introduced into the recycling tower and then reintroduced into the refining tower via the recycling tower. This enables the organic linkage between the recycling tower and the refining tower and ensures the safety and operational stability of the system.

[0063] By way of an example of the present invention, an NMP purification system and control method thereof can be provided, which can effectively reduce the impurity content in NMP reintroduced into the purification tower by additionally diluting the generated NMP peroxide in the recovery tower.

[0064] An example of the present invention provides an NMP recycling and refining system and its control method, which effectively prevents the refining tower from stopping due to the shutdown of the recycling tower by allowing the recycling tower to operate normally even when the recycling tower is shut down. Attached Figure Description

[0065] Figure 1 This is a simplified structural diagram of an NMP recycling and refining system according to an example of the present invention; Figure 2 This is a control flow diagram of an NMP recycling and refining system according to an example of the present invention; and Figure 3 The piping configuration of an NMP recycling and refining system according to an example of the present invention is shown. Detailed Implementation

[0066] In the following, with reference to the accompanying drawings, an example of an NMP recycling and refining system and its control method according to the present invention will be described in detail.

[0067] Figure 1 This is a simplified structural diagram of an NMP-based NMP recycling and refining system.

[0068] As shown in the figure, the coating system (1, coating machine) for performing electrode coating, the NMP recovery system (100), and the NMP refining system (200) are basically separate. Of course, each system can be connected by pipes or pipelines, and the core recovery tower (110) and refining tower (210) can be located in different places, with a long distance between them.

[0069] Exhaust gas discharged from the coating system (1) is introduced into the recovery tower (110) in gaseous state by a booster fan (11). The recovery system (100) may include the recovery tower (110), a recovered NMP storage tank (14), and a waste NMP storage tank (15). The recovered NMP recovered through the operation of the recovery tower (110) is discharged from the recovery tower (110) and introduced into the recovered NMP storage tank (14) for storage. Then, the waste NMP accumulated through the operation of the recovery tower (110) is introduced into the waste NMP storage tank (15) for storage. Waste NMP is an impurity containing NMP peroxide, which can be a factor that degrades electrode performance when NMP peroxide is contained in the slurry.

[0070] The recovery tower (110) recovers NMP by various methods, among which, as an example, NMP can be recovered by condensation. For this purpose, a condensate system (13) can be provided for supplying pure water (DI-water, deionized water) equivalent to condensate through the interior of the recovery tower, and especially through the upper part of the recovery tower.

[0071] Specifically, the recovery system (100), including a recovery tower as a recovery device, performs the function of recovering NMP used in the cathode material coating machine. Gaseous NMP is recovered, wherein liquid NMP mixed with high-boiling-point impurities and low-boiling-point impurities (water) can be recovered to a recovery tank. In the recovery tower, deionized water can be used to condense and recover NMP, and NMP can be recovered by various methods such as condensation, adsorption, and absorption. Therefore, the recovery tower can be implemented in the form of a bottom, middle, and top section, and deionized water can be supplied to the top section. Furthermore, multiple recovery towers connected to each other can also be implemented. As the high-temperature gaseous NMP rises, it is condensed and NMP accumulates at the bottom of the recovery tower, where moisture can be removed to increase the NMP concentration. The recovered NMP is stored in a NMP recovery tank.

[0072] Since the recovered NMP cannot be directly used in the cathode material mixing process, it can be refined and reused. A refining system (200), including a refining tower (210) as a refining device for refining the recovered NMP, refines the recovered NMP and converts it into high-purity NMP, which is then reused in the cathode material mixing process.

[0073] The refining column (210) heats the recovered NPM to discharge high-purity gaseous NMP, wherein the discharged high-purity gaseous NMP is condensed and stored in a refined NMP tank (23). The refining column (210) can be implemented in the form of a bottom, a middle section, and a top section, and the high-purity gaseous NMP can be discharged to the outside from the middle section. Since the refined high-purity gaseous NMP is discharged from the middle section of the refining column, this can be referred to as side-cut distillation.

[0074] The recycling system (100) and the refining system (200) are connected via a recycling NMP tank (14), but the recycling process and the refining process are performed separately. That is, the operation of the recycling tower (110) and the operation of the refining tower (210) can be controlled and performed separately.

[0075] In the recycling and refining processes, waste NMP containing high-boiling-point impurities is separated and stored in each waste NMP storage tank (15, 24) before being transported externally for separate waste treatment. By efficiently separating waste NMP in the recycling and refining processes, the refining and reuse of high-purity NMP can be successfully performed.

[0076] The refined NMP, after being refined in the refining system (200), is stored in a refined NMP storage tank (23) and then supplied to the raw material chamber (25). The refined NMP supplied to the raw material chamber (25) can be used in the cathode material mixing process.

[0077] Preferably, the electrode process of coating the cathode material after mixing is performed continuously. For this, NMP must be supplied appropriately. This means that the NMP refining process must be performed continuously and efficiently. Furthermore, in order to perform the refining process continuously and efficiently, the recovery process that supplies the recovered NMP to the refining process must also be performed continuously and efficiently. That is, the recovery process and the refining process must be performed organically.

[0078] In order to continuously carry out the refining process, the recycled NPM must be supplied appropriately as raw material, and the refined NPM must be properly reused.

[0079] From the perspective of normal operation of the purification tower (210), it is not easy to operate the purification tower normally when the amount of purified NMP is excessive, and it is also not easy to operate the purification tower normally when the amount of recovered NMP as raw material is insufficient.

[0080] As an example, the refining process cannot proceed smoothly when the amount of recovered NMP in the recovered NMP tank is insufficient (low level or lower limit) or when the amount of refined NMP in the refined NMP tank is excessive (high level or upper limit). When such a problem (i.e., an emergency in the refining column) has occurred, the problem is traditionally temporarily addressed by resupplying the NMP discharged from the refining column after refining to the recovered NMP tank or adjusting the amount of discharged NMP. In other words, an attempt is made to solve the problem within the refining column itself.

[0081] However, since the refining process in secondary battery manufacturing must be organically integrated with electrode or recycling processes, the cause of an emergency in the refining tower may not lie solely in the refining tower itself. Therefore, a fundamental and effective solution to the underlying cause is needed.

[0082] In this example, a configuration and its control logic can be provided in which at least a portion of the high-purity NMP discharged after purification in the purification tower (210) is circulated through a circulation line (300) to the recovery unit (100), particularly the recovery tower (110), instead of being discharged to the purified NMP storage tank (23). That is, by organically operating the recovery system (100) and the purification system (200), an emergency situation in the purification system (200) can be resolved, while the recovery system (100) that caused the emergency situation can be restored to normal. In other words, the normal operation of the recovery system can be ensured or maintained, and the normal operation of the purification system can also be ensured or maintained.

[0083] Furthermore, in this example, the separation efficiency of waste NMP can be improved while minimizing downtime of the recovery system (100) and the purification system (200). This is because, by diluting the generated NMP peroxide in the recovery system (100) and discharging it into the waste NMP tank (15) of the recovery system (100), the impurity content in the NMP reintroduced into the purification system (200) can be further reduced compared to the initial level.

[0084] The circulation line (300) can be connected to the bottom or middle of the recovery tower (110), and can also be connected to the top. Preferably, the NMP resupplying through this circulation line is liquid NMP. Therefore, it is more preferable that the circulation line is connected to the top of the recovery tower. Of course, the NMP resupplying through this circulation line can also be gaseous NMP. As an example, liquid NMP and gaseous NMP can also be supplied to the recovery tower selectively or simultaneously. In this case, the circulation line (300) can include multiple branch lines, and each branch line can be connected to the recovery tower (110) at different locations.

[0085] Meanwhile, the recovery tower can be configured as a single tower or multiple towers. As NMP flows from the upstream recovery tower to the downstream recovery tower, the concentration of recovered NMP can be increased. Therefore, it is preferable that the circulation line is connected to the downstream recovery tower.

[0086] When multiple recovery towers are configured, NMP discharged from the first recovery tower can be reintroduced into the first recovery tower via a second recovery tower. The recovered NMP can then eventually be discharged from the first recovery tower. In this case, the second recovery tower can recover liquid NMP from gaseous NMP and supply it to a specific recovery tower.

[0087] Multiple recycling towers of the same type can also be provided. That is, NMP recycling capacity can be allocated to multiple recycling towers. In this case, the circulation pipeline extending from a single refining tower can be connected to each recycling tower.

[0088] When the purification tower (210) is operating normally, the purification process is continuously performed, and purified high-purity NMP is discharged. The mode of storing high-purity NMP in a purified NMP storage tank can be called the basic mode.

[0089] When the purification tower (210) is operating normally in its basic mode, normal operation may be interrupted for various reasons. As an example, the reason may be an excess of high-purity purified NMP or an insufficient amount of recovered NMP used as feedstock for purification.

[0090] According to this example, when the purification unit is operating normally, when the liquid level in the purified NMP storage tank is lower than the preset liquid level and the liquid level in the recycled NMP storage tank is higher than the preset liquid level, a basic mode is preferably executed: in this basic mode, recycled NMP is supplied from the recycled NMP storage tank to the purification unit, and the purified high-purity NMP in the purification unit is discharged to the purified NMP storage tank.

[0091] According to this example, when the purification unit is operating normally, a circulation mode is preferably executed when the liquid level of the purified NMP storage tank is equal to or higher than a preset liquid level, or when the liquid level of the recycled NMP storage tank is equal to or lower than a preset liquid level. In this circulation mode, the normal operation of the purification unit is maintained, and the high-purity NMP discharged from the purification unit is circulated to the recycling unit through the circulation pipeline.

[0092] Normal operation of the refining unit can be defined as the operation of refining under optimal refining conditions within the refining unit. A series of continuous and organic operations—including the normal supply of recovered NMP to the refining unit, the normal refining of the recovered NMP, and the discharge of the refined high-purity NMP—can be termed normal operation.

[0093] Execution of basic mode: In this basic mode, the purified high-purity NMP discharged during the normal operation of the purification unit is supplied to the purified NMP storage tank and stored.

[0094] Several situations may occur, such as the liquid level in the refined NMP storage tank reaching its upper limit, or the coating process being temporarily stopped, resulting in an excess of refined NMP. In addition, the amount of refined NMP may increase beyond the amount of NMP required for the cathode mixing process.

[0095] This excess of refined NMP can be identified by the upper limit level inside the refined NMP storage tank.

[0096] In the positive electrode mixing process, the time required to manufacture the main mixer slurry (cycle time) can be approximately 1 hour, and the time required to manufacture the semi-finished products (binder solution, pre-dispersion solution) mixer can be approximately 4 hours and 8 hours, respectively. Therefore, it can be said that refined NMP, after being consumed, will be consumed again after a period of time. Thus, even if there is a current surplus of refined NMP, the surplus can be resolved after a certain period.

[0097] The problem is that until the excess of refined NMP is resolved, there is always a risk that the refining column will stop operating. In other words, there is a risk that it will become difficult to maintain normal operation.

[0098] Therefore, in this example, in order to address the excess of refined NMP and maintain the normal operation of the refining tower, a circulation mode can be provided: in this circulation mode, the refined NMP generated due to the normal operation of the refining tower is not supplied to the refined NMP storage tank, but is circulated and supplied to the recycling tower.

[0099] At the same time, several situations may occur, such as the liquid level in the NMP recovery storage tank reaching the lower limit, or the coating process being temporarily stopped, resulting in insufficient NMP recovery. That is, the amount of recovered NMP that should be supplied to the refining unit may be insufficient.

[0100] This insufficient NMP recovery can be identified by checking the lower limit level inside the NMP recovery storage tank.

[0101] The problem is that until the insufficient NMP level is resolved, there is always a risk that the purification column will stop operating. In other words, there is a risk that it will become difficult to maintain normal operation.

[0102] Therefore, in this example, in order to address the insufficient amount of recycled NMP and maintain the normal operation of the purification tower, a circulation mode can be provided: in this circulation mode, the purified NMP generated due to the normal operation of the purification tower is not supplied to the purified NMP storage tank, but is circulated and supplied to the recycling tower.

[0103] Ultimately, in this example, to avoid the intentional temporary shutdown of both the recycling unit and the refining unit, it is possible to maintain the normal operation of both the refining and recycling units by recycling the refined NMP that has been refined back to the recycling unit.

[0104] This allows for the prevention of losses due to the restart of the recycling and refining units after a shutdown, as well as losses from restart to normal operation. Furthermore, since the refined NMP that has undergone refining is partially used for NMP recovery, and the process is repeated thereafter, NMP peroxides can be separated more effectively during both the recycling and refining processes.

[0105] The low level in the NMP recycling tank and the high level in the NMP refining tank can be controlled by dividing the system into at least two levels. As an example, a first low level and a first high level can be sensed for executing the circulation mode. While executing the circulation mode, if a level equal to or higher than the first low level and a level equal to or lower than the first high level are sensed, the circulation mode can be stopped, and the normal refining process can be executed. Alternatively, the normal recycling process can also be executed. While executing the circulation mode, if a second low level lower than the first low level and a second high level higher than the first high level are sensed, subsequent measures, such as increasing the NMP circulation volume, can be taken. If necessary, the refining process can also be stopped. However, stopping the refining process is expected to result in stabilization time upon restart and yield loss, therefore, stopping the refining process is preferable to avoid it as much as possible.

[0106] Meanwhile, the recycling tower and the refining tower are divided into top, middle and bottom sections based on their location within the entire tower. It is also possible that each stage can operate as a single recycling or refining structure, or as multiple recycling or refining structures.

[0107] In the following text, reference will be made to Figure 2 and Figure 3 This section describes in detail the control logic and main components of the NMP recycling and refining system.

[0108] The exhaust gas from the coating process is introduced into the recovery tower (110) by a blower or the like (S10). The recovery tower (110) may consist of a top layer (111), an intermediate layer (112) and a bottom layer (113).

[0109] The waste gas introduced into the recovery tower at high temperature is condensed by condensate water as it rises, thus accumulating in the bottom layer (113). Deionized water for condensation can be supplied to the interior of the top layer of the recovery tower (110), and the NMP condensate accumulated in the bottom layer can be circulated and introduced into the interior of the top layer, thereby separating the NMP from the waste gas.

[0110] NMP can be recovered by removing water from the NMP condensate that accumulates in the bottom layer. Approximately 50 to 85% by weight of NMP can be recovered through this recovery process.

[0111] The NMP recovered in the recovery tower (110) is introduced into the recovered NMP storage tank (14) and stored.

[0112] The stored recycled NMP becomes a raw material for NMP refining, which is refined into high-purity NMP through a refining process and then reused in subsequent coating processes.

[0113] The refining apparatus may include a refining tower (210), and the refining tower (210) may also be formed as multiple layers. For example, it may be formed as a top layer (211), an intermediate layer (212) and a bottom layer (213), wherein the intermediate layer may be formed of multiple layers.

[0114] The recovered NMP introduced into the purification column (210) can be heated inside the purification column and purified by a distillation process, and since the purified NMP is discharged from the intermediate layer (212), a side-stream distillation method can be applied.

[0115] The high-purity refined NMP discharged from the refining tower (210) is stored in the refined NMP storage tank (23) via the refined NMP pipeline (26). That is, during normal operation, the refining tower (210) can continuously produce high-purity refined NMP, and the high-purity refined NMP can be stored in the basic mode.

[0116] In this example, a waste NMP storage tank (24) containing high-boiling-point impurities discharged from the bottom of the refining tower may be included, as well as a flow control valve (29a) for regulating the flow rate of waste NMP into the waste NMP storage tank. The flow control valve may be installed on the waste NMP line (29).

[0117] The flow control valve (29a) can be configured to control the flow rate of discharged waste NMP by automatically adjusting its opening. Preferably, flow control is performed based on the results of analysis of the composition and content of impurities in the waste NMP. An analytical device (29b) is provided that can perform real-time online analysis of the composition and content of impurities in waste NMP flowing into the waste NMP storage tank, and flow control can be performed based on the results of the analysis by this analytical device.

[0118] The analytical device (29b) can be configured to automatically adjust the opening of the flow control valve (29a) by monitoring the concentration of waste NMP. That is, by quantitatively adjusting the opening rate by monitoring the concentration of waste NMP, the system can be made more advanced in terms of control and yield improvement.

[0119] This monitoring of waste NMP concentration can be performed online or offline, and when the waste NMP concentration is low, the aperture ratio can be reduced to improve NMP recovery, while when the concentration is high, the aperture ratio can be increased to improve recovery efficiency. The analytical device (29b) can be a gas chromatograph-mass spectrometer such as a GC-MS analyzer.

[0120] As described above, waste NMP can be separated in both the recovery tower (110) and the purification tower (210). That is, it is preferable to separate NMP peroxide as much as possible and ultimately not include it in the high-purity purified NMP.

[0121] According to this example, under certain conditions, high-purity purified NMP can be reintroduced into the recovery tower (110). That is, during normal operation of the purification tower (210), high-purity purified NMP can be introduced into the recovery tower (110) under certain conditions and reused in the recovery process.

[0122] Therefore, waste NMP can be filtered out again in the recovery tower, which means that the amount of NMP peroxide introduced into the purification tower (210) is further reduced. As a result, the purity of high-purity purified NMP can be further improved.

[0123] The refined NMP circulation line (300) can be connected to the refining tower (210) in the same manner as the refined NMP line (26). That is, the refined NMP circulation line (300) and the refined NMP line (26) can be selectively turned on.

[0124] Furthermore, the refined NMP circulation line (300) can be configured to branch off from the refined NMP line (26). That is, the refined NMP discharged through the refined NMP line can be introduced into the storage tank (23) or introduced into the recovery tower (110) along the circulation line (300).

[0125] The refined NMP pipeline and circulation pipeline can be equipped with valves for controlling the opening and closing of the flow path, and flow control valves can also be installed if necessary.

[0126] Meanwhile, the NMP discharged through the refined NMP line (26) can be in a gaseous state and can be converted into a liquid state through the condenser (27). This means that gaseous NMP can branch off from the refined NMP line (26) and circulate, or liquid NMP can branch off from the refined NMP line (26) and circulate.

[0127] Therefore, in circulation mode, high-purity purified NMP in liquid or gaseous state can be recycled to the recovery tower (110) as needed. Alternatively, NMP can be selectively recycled to the top, middle, or bottom layer of the recovery tower (110). As an example, liquid NMP can be introduced to the bottom layer of the recovery tower, and gaseous NMP can be introduced to the top layer. Of course, the reverse approach is also possible.

[0128] In other words, in the circulation mode, the recovery tower can be maintained in normal operation continuously, and the purified NMP introduced into the recovery tower can be selected as gaseous or liquid by considering the current conditions inside the recovery tower (such as the concentration, temperature, and pressure of the recovered NMP). Of course, the location where the purified NMP is introduced can also be selected.

[0129] Therefore, according to this example, the purification unit and the recovery tower can be maintained in normal operation continuously. Furthermore, since waste NMP can be separated additionally in the circulation mode, the purity of the purified NMP can be further improved.

[0130] like Figure 2 As shown, from the perspective of the recovery tower, during normal operation, the introduction of waste gas (S10), NMP recovery (S20), and storage of recovered NMP (S30) are performed organically and continuously. From the perspective of the purification tower, during normal operation, the introduction of recovered NMP into the purification tower (S40), NMP purification (S50), and storage of purified NMP (S60) are performed organically and continuously. That is, the basic mode is executed.

[0131] However, when a temporary stop condition occurs in the refining column, a cyclic mode (S70) can be executed without temporarily stopping the refining column. One of the temporary stop conditions for the refining column can also be a temporary stop condition for the recovery column. That is, by executing this cyclic mode, the temporary stop conditions for both the refining column and the recovery column can be eliminated, thereby enabling the continuous normal operation of both.

[0132] The conditions for temporary stoppage can be varied, and various speed changes or sensing values ​​can be preset to determine these conditions. As an example, it is possible to determine whether the amount of refined NMP stored is excessive based on the level in the refined NMP storage tank, and it is also possible to determine whether the amount of recycled NMP stored is insufficient based on the level in the recycled NMP storage tank.

[0133] This cyclical model does not circulate NMP within the refining tower or refining system itself, but rather extends it to the recycling tower area. Therefore, control logic linked to the use, recycling, and refining of NMP can be stably built and operated.

[0134] Industrial applicability

[0135] As described in the detailed description of this invention.

Claims

1. An NMP recycling and refining system, comprising: A recovery device, which operates to recover NMP contained in the exhaust gas from the secondary battery process; A recycled NMP storage tank stores recycled NMP recovered by and discharged from the recycling unit; A refining apparatus, which operates to refine the recycled NMP supplied from the recycled NMP storage tank into high-purity NMP; A refined NMP storage tank, wherein the refined NMP storage tank stores refined NMP refined by and discharged from the refined unit; as well as A circulation pipeline that recycles the refined NMP discharged from the refining unit to the recovery unit.

2. The NMP recovery and purification system according to claim 1, characterized in that, The recycling apparatus includes a recycling tower, and the refining apparatus includes a refining tower.

3. The NMP recovery and purification system according to claim 2, characterized in that, The refining column has a top column for separating high-concentration NMP from low-boiling-point impurities, a bottom column for separating high-purity NMP from high-boiling-point impurities, and an intermediate column for discharging high-purity refined NMP gas between the top column and the bottom column.

4. The NMP recovery and purification system according to claim 3, characterized in that, The refining apparatus includes a condenser for condensing the high-purity refined NMP gas discharged from the intermediate tower to supply it to the refined NMP storage tank.

5. The NMP recovery and purification system according to claim 4, characterized in that, The circulation pipeline is configured to connect the refining tower and the recovery tower.

6. The NMP recovery and purification system according to claim 5, characterized in that, The circulation pipeline includes a gas circulation pipeline that circulates the refined NMP gas from the upstream side of the condenser to the recovery tower.

7. The NMP recovery and purification system according to claim 5, characterized in that, The circulation pipeline includes a liquid circulation pipeline that circulates the condensed refined NMP from the downstream side of the condenser to the recovery tower.

8. The NMP recovery and purification system according to claim 4, characterized in that, This includes a refined NMP pipeline, through which the refined NMP discharged from the refining tower is transported to the refined NMP storage tank, and The circulation line branches off from the refined NMP line and connects to the recovery tower.

9. The NMP recovery and purification system according to claim 3, characterized in that... include: A waste NMP storage tank and a flow control valve are provided, wherein the waste NMP storage tank stores waste NMP containing high-boiling-point impurities discharged from the bottom column of the refining column, and the flow control valve is used to regulate the flow rate of waste NMP introduced into the waste NMP storage tank.

10. The NMP recovery and purification system according to claim 9, characterized in that, The flow control valve is an automatic control valve that automatically adjusts its flow rate based on the liquid level in the waste NMP storage tank or the concentration of the waste NMP.

11. The NMP recovery and purification system according to any one of claims 1 to 10, characterized in that, When the refining device is operating normally, when the liquid level of the refined NMP storage tank is equal to or higher than the preset liquid level, or when the liquid level of the recycled NMP storage tank is equal to or lower than the preset liquid level, a circulation mode is executed: in the circulation mode, the normal operation of the refining device is maintained, and the high-purity NMP discharged from the refining device is circulated to the recycling device through the circulation pipeline.

12. The NMP recovery and purification system according to claim 11, characterized in that, When the refining device is operating normally, if the liquid level of the refined NMP storage tank is lower than the preset liquid level and the liquid level of the recycled NMP storage tank is higher than the preset liquid level, the basic mode is executed: In the basic mode, the recycled NMP is supplied from the recycled NMP storage tank to the refining device, and the high-purity NMP refined in the refining device is discharged to the refined NMP storage tank.

13. A control method for an NMP recovery and purification system, comprising: The NMP recovery step involves introducing NMP contained in the exhaust gas from the secondary battery manufacturing process into a recovery tower, and condensing the introduced gas in the recovery tower to recover NMP. The NMP recycling and storage step involves storing the recycled NMP recovered and discharged in the recycling step in a recycled NMP storage tank. The NMP purification step involves introducing the stored recycled NMP into a purification column and heating the recycled NMP introduced into the purification column to purify the recycled NMP into high-purity NMP. The refined NMP storage step involves storing the refined NMP that has been refined and discharged in the refining step in a refined NMP storage tank. as well as The recycling step bypasses the refined NMP that has been refined and discharged in the refining step and introduces the refined NMP into the recovery tower.

14. The control method for an NMP recovery and purification system according to claim 13, characterized in that, The refined NMP storage step and the cyclic step are performed selectively.

15. The control method for an NMP recovery and purification system according to claim 13, characterized in that, In the NMP purification step, purified NMP gas is discharged from the purification tower and condensed by a condenser.

16. The control method for an NMP recovery and purification system according to claim 15, characterized in that, The circulation steps include a gas circulation step and a liquid circulation step. In the gas circulation step, the purified NMP gas is introduced into the recovery tower. In the liquid circulation step, the condensed purified NMP is introduced into the recovery tower.

17. The control method for an NMP recovery and purification system according to any one of claims 13 to 16, characterized in that, In order to maintain the normal execution of the NMP purification step when the amount of recovered NMP to be introduced into the purification tower is insufficient, the cyclic step is performed.

18. The control method for an NMP recovery and purification system according to claim 17, characterized in that, The state of insufficient NMP recovery is determined based on the liquid level inside the NMP recovery storage tank.

19. The control method for an NMP recovery and purification system according to any one of claims 13 to 16, characterized in that, In order to maintain the normal execution of the NMP purification step when there is an excess of purified NMP discharged from the purification tower, the cyclic step is performed.

20. The control method for an NMP recovery and purification system according to claim 19, characterized in that, The excess amount of refined NMP is determined based on the liquid level inside the refined NMP storage tank.

Images