NMP system and method for controlling same

Abstract

The present invention relates to a facility for manufacturing a secondary battery, and particularly, to an NMP system and a method for controlling same, whereby metal foreign substances that cause a low voltage of an electrode can be effectively removed. According to an embodiment of the present invention, it is possible to provide an NMP system comprising: a first storage tank for storing NMP recovered from an electrode process and purified; a main line which has two parallel lines in an initial section and transfers NMP from the first storage tank to a second storage tank for storing NMP used in a process for mixing a slurry used in the electrode process; and magnetic separators which are vertically installed on each of the two parallel lines and separate magnetic foreign substances from NMP discharged from the first storage tank.

Description

NMP system and its control method

[0001] The present invention relates to equipment for manufacturing secondary batteries, and more particularly, to an NMP system and a control method thereof, and more particularly, to an NMP system and a control method thereof capable of effectively removing metal foreign substances that cause low voltage of an electrode.

[0002] This application claims the benefit of priority to Republic of Korea Patent Application No. 10-2024-0096677, filed July 22, 2024, and Republic of Korea Patent Application No. 10-2025-0099146, filed July 22, 2025, the entire contents of which are incorporated herein by reference.

[0003] Secondary batteries are batteries that can be repeatedly charged and discharged, and are recently being widely used in automobiles and energy storage systems (ESS).

[0004] The electrodes, or positive and negative electrodes, of secondary batteries are manufactured by coating aluminum or copper foil with a slurry. The slurry contains not only the positive and negative electrode materials but also a solvent, which is then dried, recovered, and reused. NMP (N-methyl-2-pyrrolidone) is a commonly used solvent. Used NMP is recovered through condensation, and the recovered NMP is then purified and reused. This is because NMP is expensive and causes environmental pollution when discharged.

[0005] The mixing process for mixing the slurry and the electrode process for manufacturing the electrode are performed indoors, and therefore, at least part of the recovery system for recovering NMP from the electrode process is installed indoors. Typically, the NMP tank for recovering and refining NMP and storing the purified NMP is installed outdoors, and the NMP stored in the NMP tank is transported to an NMP tank installed indoors via a pipeline. The former can be referred to as an outdoor NMP tank, and the latter as an indoor NMP tank.

[0006] A recovery system including a recovery tower as an NMP recovery device performs the function of recovering NMP used in the coater. NMP in a gaseous state is recovered, and at this time, NMP liquid mixed with high-boiling-point impurities and low-boiling-point impurities (water) can be recovered in a recovery tank. The recovery tower can condense and recover NMP using deionized water, and various methods, such as condensation, adsorption, and absorption, can be used to recover NMP. Therefore, the recovery tower can be implemented as a form having a bottom, middle, and top, and deionized water can be supplied to the top. Furthermore, it is also possible to implement multiple recovery towers that are interconnected. As the high-temperature gaseous NMP rises, it condenses and collects at the bottom of the recovery tower, removing moisture to increase the NMP concentration. The recovered NMP is stored in a recovery NMP tank.

[0007] Since the recovered NMP cannot be used as is in the mixing process, it can be purified and reused. A purification system including a purification tower as a purification device that purifies the recovered NMP purifies the recovered NMP to convert it into high-purity NMP and reuses it in the mixing process. The purification tower heats the recovered NMP to discharge high-purity gaseous NMP, which is condensed and stored in a purified NMP tank. The purification tower can be implemented in a form having a bottom, middle, and top, and the high-purity gaseous NMP can be discharged to the outside from the middle.

[0008] Although the recovery and purification systems are connected via the recovery NMP tank, the recovery and purification processes are performed separately. During the recovery and purification processes, waste NMP containing high-boiling-point impurities is separated and stored separately. This waste NMP can then be transported to an external facility for a separate disposal process. By efficiently separating waste NMP during the recovery and purification processes, high-purity NMP can be smoothly purified and reused. The purified NMP from the purification tower is transported to an outdoor NMP storage tank for storage.

[0009] It is desirable to perform the electrode process, which involves coating the cathode material after mixing, continuously. This requires an adequate supply of NMP. Therefore, NMP stored in an outdoor NMP storage tank is transferred to an indoor NMP storage tank for the mixing process.

[0010] During this process, NMP stored in the "outdoor NMP storage tank" and metallic foreign substances (magnetic and non-magnetic) present in the "outdoor NMP storage tank & piping" are not sufficiently removed and may flow into the indoor cathode mixer raw material room, where they may be used as NMP raw materials for cathode slurry production. These metallic foreign substances may increase the risk of poor low-voltage quality of the electrode.

[0011] The inventors of the present invention were able to confirm that metallic foreign substances may be present within the towers, tanks, and piping of a solvent recovery plant (SRP) during the setup of the SRP or generated during operation. In particular, they were able to confirm that the source of metallic substances (magnetic and non-magnetic) that cause low-voltage quality in NCM and NCMA batteries also exists within the NMP raw material supplied from the SRP. In other words, the cause of the inflow of metallic substances that cause low-voltage quality was identified. Therefore, there is a need to develop effective removal methods for metallic foreign substances in NCM and NCMA secondary batteries and to develop configurations and operating methods for this purpose.

[0012] The present invention aims to solve the problems of conventional NMP systems and control methods.

[0013] An embodiment of the present invention provides an NMP system and control method capable of effectively blocking metal substances that cause low voltage quality of a secondary battery.

[0014] Through one embodiment of the present invention, an NMP system and control method are provided that can secure ease of cleaning and maintenance of the filter by arranging a magnetic filter and a mesh filter vertically and in parallel, respectively.

[0015] Through one embodiment of the present invention, it is intended to provide an NMP system and control method that can secure system freedom by enabling NMP to be supplied even during cleaning and maintenance of a filter.

[0016] Through one embodiment of the present invention, it is intended to provide an NMP system and control method capable of performing continuous and repetitive filtering by installing a circulation loop in which NMP discharged from an outdoor NMP tank is filtered and then circulated back to the outdoor NMP tank.

[0017] Through one embodiment of the present invention, it is intended to provide an NMP system and control method that can effectively select the circulation and supply of NMP by easily determining whether a magnetic filter and a mesh filter are contaminated.

[0018] Through one embodiment of the present invention, it is intended to provide an NMP system and control method capable of effectively removing metal substances from NMP discharged from an outdoor NMP tank, while additionally removing metal substances from NMP recovered and purified and flowing into the outdoor NMP tank.

[0019] Through one embodiment of the present invention, it is intended to provide an NMP system and control method capable of effectively removing foreign substances through circulation of NMP during a period in which the inflow of NMP into a first storage tank is restricted during a recovery and purification process and during a period in which the inflow of NMP from a first storage tank to a second storage tank is restricted for a mixing process.

[0020] In order to achieve the above-described object, according to one embodiment of the present invention, an NMP system can be provided, characterized by including: a first storage tank for storing NMP recovered and purified in an electrode process; a main line for transporting NMP from the first storage tank to a second storage tank for storing NMP used in a mixing process of a slurry used in the electrode process; a circulation line branched from the main line for circulating NMP discharged from the first storage tank to the first storage tank; an opening / closing valve provided after a branch point of the circulation line for selectively opening the main line and the circulation line; and a magnetic separator provided before a branch point of the circulation line for separating magnetic foreign substances from the NMP discharged from the first storage tank.

[0021] NMP discharged from the first storage tank flows into a magnetic separator to filter out magnetic foreign substances, and can then be supplied to the second storage tank or flowed into the first storage tank through a circulation line. In other words, the supply and circulation of NMP can be selectively performed. Accordingly, the circulation of NMP can be performed continuously and repeatedly while the supply of NMP is stopped, thereby continuously and repeatedly filtering foreign substances from the NMP.

[0022] It is preferable that the above magnetic separator is a magnetic filter that filters magnetic foreign substances from NMP flowing by magnetism.

[0023] It is preferable that the above magnetic filter include a filter housing installed so that NMP flows in from the bottom and NMP flows out from the top, and a filter cover provided to be vertically connected and separated from the filter housing.

[0024] The structure and arrangement of these magnetic filters make it easy to clean and maintain the magnetic filters, and in particular, it is very easy to determine whether the magnetic filter is contaminated.

[0025] It is preferable that the above cover be provided with an air nozzle for relieving internal pressure of the magnetic filter. By easily relieving internal pressure of the magnetic filter through the air nozzle, it is easy to wash or observe the inside of the magnetic filter.

[0026] It is preferable that a shut-off valve be installed at the front and rear ends of the magnetic separator to separate the magnetic separator from the main line.

[0027] It is preferable that a drain valve be installed between the magnetic separator and the shut-off valve provided at the front end of the magnetic separator to discharge NMP to the outside.

[0028] By using these shut-off valves, drain valves and air nozzles, the magnetic separator can be separated from the main line and easily cleaned and maintained.

[0029] It is preferable to include a parallel line provided parallel to the main line up to the branch point of the above-mentioned circulation line.

[0030] The detailed configuration of the above parallel line may be identical to that of the main line running parallel to the above parallel line. That is, the configuration of the valves and their positions and connections, the magnetic separator, the drain valve, etc., as well as the configuration of the mesh filter described below may be identical.

[0031] A line extending from the first storage tank may be divided into two lines to form a parallel line with the main line, and at the branch point of the circulation line, the two lines may be combined again into one line to extend to the second storage tank.

[0032] That is, a pair of parallel lines can form a main line and then be combined again to extend to the second storage tank.

[0033] It may include a particle separator installed in series with the magnetic separator to separate non-magnetic foreign substances from the NMP discharged from the first storage tank using the size of the particles.

[0034] The above particle separator may include a mesh filter that separates non-magnetic metal foreign substances through the mesh.

[0035] It is preferable that the particle separator be installed at the rear end of the magnetic separator.

[0036] The above parallel line may be equipped with a magnetic separator and a particle separator, similar to the above main line.

[0037] It is desirable that the diameters of the main line and the parallel line be the same.

[0038] The magnetic separator and circulation line are preferably located near the first storage tank. The distance between the first and second storage tanks is very long, and therefore the entire main line is typically very long. Therefore, by shortening the circulation distance, the circulation volume can be effectively increased, while also minimizing contamination of the main line with foreign substances.

[0039] Additionally, by placing the first storage tank, the circulation line, and the components between them nearby, the work efficiency of the workers can be increased.

[0040] According to the present embodiment, an NMP system and a control method thereof can be provided, including a transfer pump driven for NMP transfer (transfer mode) through the main line and NMP circulation (circulation mode) through the circulation line, wherein the transfer pump is driven at different RPMs in the transfer mode and the circulation mode.

[0041] If non-contamination of the magnetic foreign matter is confirmed in the magnetic separator, the transfer mode can be performed automatically or manually.

[0042] The circulation mode opens both the main line and the parallel line, allowing both the main line magnetic separator and the parallel line magnetic separator to be utilized. In other words, by opening both pairs of parallel lines, the two magnetic separators can separate magnetic foreign substances from the discharged NMP. The NMP can then be returned to the first storage tank for circulation.

[0043] The circulation mode can be performed by opening only the main line or by opening only the parallel line. That is, magnetic foreign substances are separated through one magnetic separator and NMP is circulated, and contamination checks or cleaning can be performed on the remaining magnetic separator.

[0044] When the above transfer mode is stopped, the above circulation mode can be performed intermittently or periodically.

[0045] In order to achieve the above-described object, according to one embodiment of the present invention, an NMP system may be provided, including: a first storage tank for storing NMP recovered and purified in an electrode process; a main line for transporting NMP from the first storage tank to a second storage tank for storing NMP used in a mixing process of a slurry used in the electrode process, the main line having two parallel lines in an initial section; and a magnetic separator vertically installed in each of the two parallel lines for separating magnetic foreign substances from NMP discharged from the first storage tank.

[0046] When the magnetic separator is installed vertically, NMP flows from the bottom to the top of the magnetic separator, and after magnetic foreign substances are filtered out inside the magnetic separator, NMP can be discharged through the top of the magnetic separator.

[0047] The structure and layout of this magnetic separator makes it very easy to check for internal contamination and clean it. This means draining and relieving internal pressure are very easy, and access to the interior of the magnetic separator is very easy.

[0048] Of the two parallel lines, one can be designated as the main line and the other as the auxiliary line. The diameters of the main and auxiliary lines can be the same. Both the main and auxiliary lines can be open, or only one can be open. When a line is open, NMP can flow internally and pass through the magnetic separator.

[0049] Each of the two parallel lines may include a particle separator installed in series with the magnetic separator, which separates non-magnetic foreign substances from the NMP discharged from the first storage tank using the size of the particles.

[0050] The above two parallel lines can be branched off from one main line and then merged again.

[0051] The above two parallel lines may be branched off from the main line at the rear end of the junction, and a circulation line may be provided to circulate NMP discharged from the first storage tank to the first storage tank.

[0052] After the above-mentioned junction point, NMP can flow into the circulation line or through the main line to the second storage tank. That is, the circulation line and the main line can be selectively opened.

[0053] An on-off valve may be provided after the branch point of the above-mentioned circulation line to selectively open the main line and the circulation line. This on-off valve may be a three-way valve.

[0054] In order to achieve the above-mentioned object, according to one embodiment of the present invention, a control method for an NMP system may be provided, including a transfer step of operating a transfer pump from a first storage tank storing NMP recovered and purified in an electrode process to transfer NMP to a second storage tank storing NMP used in a mixing step of a slurry used in an electrode process through the entire main line; and a circulation step of operating the transfer pump to transfer and circulate the NMP transferred through a circulation line branched from an initial section of the main line to the first storage tank, wherein a magnetic separator for separating magnetic metal foreign substances and a mesh filter for separating non-magnetic metal foreign substances are provided in the NMP discharged from the first storage tank of the main line, and an operating load of the transfer pump in the transfer step is characterized in that it is greater than an operating load in the circulation step.

[0055] The distance between the first and second storage tanks is relatively far, and the installation height of the second storage tank may be relatively higher than that of the first storage tank. Therefore, the operating load of the transfer pump during the transfer phase is very large. On the other hand, during the circulation phase, NMP is discharged from the first storage tank and only travels a short distance before returning to the first storage tank for circulation. Therefore, a relatively small operating load during the circulation phase is desirable.

[0056] In the initial section of the above main line, the main line is provided with two parallel lines, and the magnetic separator and the mesh filter are vertically mounted in series on each of the parallel lines, and it is preferable that the transport step and the circulation step are selectively performed.

[0057] According to one embodiment of the present invention, in an NMP system that recovers and purifies NMP and stores it in a first storage tank and transfers the NMP stored in the first storage tank to a second storage tank for a mixing process, an NMP system and a control method thereof are provided, characterized in that a first circulation mode is performed in which NMP, which has been purified and discharged from a purification tower, is circulated to a recovery tower while the first storage tank is in a high-level state and the mixing process is stopped, and a second circulation mode is performed in which NMP discharged from the first storage tank is filtered by a magnetic separator and circulated to the first storage tank.

[0058] Through one embodiment of the present invention, an NMP system and control method capable of effectively blocking a metal substance that causes low voltage quality of a secondary battery can be provided.

[0059] Through one embodiment of the present invention, an NMP system and control method can be provided that can secure ease of cleaning and maintenance of the filter by arranging a magnetic filter and a mesh filter vertically and in parallel, respectively.

[0060] Through one embodiment of the present invention, an NMP system and control method can be provided that can secure system freedom by enabling NMP to be supplied even during cleaning and maintenance of a filter.

[0061] Through one embodiment of the present invention, an NMP system and control method can be provided in which continuous and repetitive filtering can be performed by installing a circulation loop in which NMP discharged from an outdoor NMP tank is filtered and then circulated back to the outdoor NMP tank.

[0062] Through one embodiment of the present invention, it is possible to provide an NMP system and control method that can effectively select the circulation and supply of NMP by easily determining whether a magnetic filter and a mesh filter are contaminated.

[0063] Through one embodiment of the present invention, an NMP system and control method can be provided that can effectively remove metal substances from NMP discharged from an outdoor NMP tank, while additionally removing metal substances from NMP that is recovered and purified and then introduced into the outdoor NMP tank.

[0064] Figure 1 is a simplified configuration diagram of an NMP recovery and purification system among NMP systems according to one embodiment of the present invention.

[0065] Figure 2 is a control flow diagram of an NMP recovery and purification system among NMP systems according to one embodiment of the present invention.

[0066] Figure 3 illustrates the line configuration of a recovery purification system among NMP systems according to one embodiment of the present invention.

[0067] Figure 4 is a diagram of the piping between the first storage tank and the second storage tank, especially the piping near the first storage tank.

[0068] Figure 5 is a three-dimensional illustration of the piping structure of Figure 4,

[0069] Figure 6 is a perspective view of a magnetic separator.

[0070] Figure 7 illustrates the internal structure of a magnetic separator.

[0071] According to one embodiment of the present invention, a magnetic material can be repeatedly removed by a magnetic filter, and a non-magnetic material can be repeatedly removed by a mesh filter, and an NMP supply circulation loop can be configured to ensure the ease of cleaning of these filters and to confirm / secure the quality of NMP. The magnetic filter can be referred to as a magnetic separator as a configuration for separating a magnetic metal from NMP by magnetic force, and the mesh filter can be referred to as a particle separator for separating a non-magnetic metal from NMP by using the density or size of the non-magnetic metal particles.

[0072] The inventors of the present invention noted that the generation of metal impurities in the process of reusing NMP can occur repeatedly and continuously, rather than temporarily. These impurities can enter the electrode process and ultimately become a major cause of low-voltage failures in the electrode. Therefore, rather than simply removing these impurities temporarily, they studied a method for repeatedly removing them.

[0073] First, a magnetic separator was installed to remove magnetic metal contaminants including iron-based metal contaminants, and a method was developed to effectively manage contamination of the magnetic separator, such as by cleaning it. Specifically, by installing the magnetic separator vertically, the contamination level inside the magnetic separator can be easily identified with the naked eye, and the magnetic separator can be easily cleaned. In addition, a drain configuration including a drain valve was installed to effectively clean the magnetic separator after draining the NMP.

[0074] Additionally, by vertically arranging the magnetic separator, pressure builds up inside the magnetic separator. Therefore, by vertically arranging an air nozzle to relieve piping pressure, the pressure can be easily relieved and the magnetic separator can be cleaned.

[0075] Additionally, a particle separator for removing non-magnetic metal foreign matter is installed in series with the magnetic separator, and similarly, vertical installation allows for easy inspection and cleaning of the interior of the particle separator. The particle separator is preferably installed downstream of the magnetic separator. This is because it effectively removes magnetic metal foreign matter using magnetism, thereby reducing the load on the downstream particle separator.

[0076] Here, the magnetic separator and particle separator are preferably installed and maintained as a set. Shut-off valves are provided at the front end of the magnetic separator and the rear end of the particle separator, allowing the magnetic separator and particle separator to be cleaned by closing the shut-off valves. In this case, it is preferable to install only one drain valve and one air valve between the shut-off valves. That is, the drain valve can be installed at the lowest position between the magnetic separator and particle separator set, and the air valve can be installed at the highest position.

[0077] Meanwhile, if the magnetic separator and particle separator are contaminated with metal foreign substances, the metal foreign substances cannot be sufficiently separated thereafter. Therefore, in this case, it is not desirable to transfer NMP from the outdoor NMP tank (the first NMP tank) to the indoor NMP tank (the second NMP tank). In other words, NMP to be used in the electrode process may not be supplied sufficiently. For this reason, the magnetic separator and the particle separator may be provided in two sets, and one set and one set may be provided in parallel, respectively. That is, it is preferable that two branch lines are provided from the main line through which NMP is discharged from the outdoor NMP tank, and that a magnetic separator and a particle separator are provided in each branch line. Here, one branch line may be provided continuously with the main line, and the other branch line may be said to be a branch line branched from the main line. In other words, they may be provided as a pair of parallel lines. In addition, a connecting line connecting the middle of the branch line and the branch line may be provided, and the connecting line may connect the rear end of the magnetic separator and the rear end of the magnetic separator. Of course, the connecting line may also be equipped with an on-off valve. This allows NMP passing through the magnetic separator in a specific branch line to pass through the particle separator in another branch line.

[0078] In other words, one set of magnetic separators and mesh filters can be used or washed together, or one set of magnetic separators and mesh filters can be used or washed crosswise with another set of magnetic separators and mesh filters.

[0079] Since NMP can continuously flow into the outdoor NMP tank during the recovery and purification process of NMP, the NMP flowing into the outdoor NMP tank can continuously become contaminated with metallic foreign substances. Therefore, these foreign substances must be sufficiently removed before flowing into the indoor NMP tank. Therefore, it is preferable to install a magnetic separator and a particle separator on the outdoor NMP tank side. For example, the main line that transports NMP from the outdoor NMP tank to the indoor NMP tank can be very long, around 200 m. Therefore, by installing a magnetic separator and a particle separator near the outdoor NMP tank, metallic foreign substance contamination of the main line can be prevented. In other words, basically, the entire main line is manufactured from a material that prevents metallic foreign substances from being extracted or is specially coated. Afterwards, magnetic and non-magnetic foreign substances are sufficiently removed near the outdoor NMP tank, metallic foreign substance contamination of the main line can be prevented.

[0080] It is desirable to configure a circulation line for continuous and repetitive removal of metallic foreign matter. That is, a circulation line can be configured to separate metallic foreign matter from NMP discharged from an outdoor NMP tank through a magnetic separator and a particle separator and then supply the separated NMP to the NMP tank. Therefore, by repeating the circulation of NMP through the circulation line, metallic foreign matter can be separated from NMP very effectively. In particular, the effect of removing metallic foreign matter can be enhanced by operating the circulation line during the off-season when NMP is not supplied from the outdoor NMP tank to the indoor NMP tank. In other words, it is desirable to continuously and repeatedly remove foreign matter from NMP even during the process of preparing for supply, rather than simply removing foreign matter from the supplied NMP. For circulation efficiency, it is desirable to install the magnetic separator and particle separator in the vicinity of the outdoor NMP tank.

[0081] Circulating NMP through the circulation line and transporting NMP through the main line can be performed selectively. In other words, from the perspective of the outdoor NMP tank, the modes of discharging NMP can be divided into two.

[0082] As mentioned above, the overall length of the main line is very long, while the length of the circulation line is relatively short. Furthermore, the indoor NMP tank can be located high indoors to ensure a height difference with the outdoor NMP tank. Therefore, it is desirable to set the load of the transfer pump in circulation mode, which circulates NMP, to be lower than the load in transfer mode. Furthermore, the circulation line and the main line may each be equipped with on-off valves. Of course, a three-way valve that selectively opens and closes the circulation line and the main line may also be equipped.

[0083] In this embodiment, a configuration and control logic can be provided to circulate at least a portion of the NMP discharged from the purification tower to a recovery device through a circulation line instead of discharging it to a purified NMP storage tank. In other words, by organically operating the recovery system and the purification system, an emergency situation of the purification system can be resolved, and at the same time, the recovery system that is the cause thereof can be normalized. In other words, it is possible to avoid the downtime of the recovery system and the purification system as much as possible, and at the same time, increase the efficiency of waste NMP separation. This is because the NMP peroxide already produced is diluted in the recovery system and discharged to the waste NMP tank of the recovery system, so that the impurity content of the NMP re-introduced into the purification system is reduced compared to the initial content.

[0084] The circulation line can be connected to the bottom or middle of the recovery tower, or even to the top. In this case, the NMP resupplied to the circulation line is preferably liquid NMP. Therefore, it is more preferable to connect it to the top of the recovery tower. Meanwhile, the recovery tower can be equipped as a single tower or multiple towers. As NMP flows from the upstream recovery tower to the downstream recovery tower, the concentration of the recovered NMP can increase. Therefore, it is preferable to connect the circulation line to the downstream recovery tower.

[0085] The low level of the recovery NMP storage tank and the high level of the purified NMP storage tank (outdoor NMP storage tank) can be controlled by being separated into at least two stages. For example, a first low level and a first high level can be sensed for performing the circulation mode. When performing the circulation mode, if a level higher than the first low level is sensed and a level lower than the first high level is sensed, the circulation mode is stopped, and a normal purification process can be performed. Of course, a normal recovery process can also be performed. When performing the circulation mode, if a second low level lower than the first low level is sensed and a second high level higher than the first high level is sensed, follow-up measures such as increasing the amount of NMP circulation can be performed. If necessary, the purification process can be stopped. However, if the purification process is stopped, stabilization time and yield loss are expected upon restart, so it is desirable to avoid stopping the purification process if possible.

[0086] Meanwhile, the division of the recovery tower and the purification tower into upper, middle, and lower levels is based on their positions in the overall tower, and each stage can be operated as a single recovery structure or purification structure, or as multiple recovery structures or purification structures.

[0087] In this embodiment, a waste NMP storage tank for storing waste NMP containing high boiling point impurities discharged from a lower tower of a purification tower and a flow control valve for controlling the flow rate of waste NMP flowing into the waste NMP storage tank may be included. The flow control valve may be provided to control the flow rate of the waste NMP discharged by automatically adjusting the opening degree. It is preferable that the flow rate control is performed based on the results of analyzing the components and contents of the impurities in the waste NMP. An analysis device capable of analyzing the components and contents of waste NMP impurities flowing into the waste NMP storage tank in real time inline may be provided, and the flow rate control may be performed based on the results of the analysis by the analysis device.

[0088] Hereinafter, an NMP system and control method according to an embodiment of the present invention will be described in more detail with reference to the attached drawings.

[0089] First, an embodiment for more effectively removing foreign substances from NMP stored in a purified NMP storage tank is described. This is done by circulating purified NMP to a recovery tower during the recovery and purification process of NMP, thereby additionally performing the recovery process and additionally performing the purification process, thereby more effectively removing foreign substances from the recovery tower and purification tower.

[0090] Figure 1 is a simplified schematic diagram of an NMP recovery and purification system based on NMP.

[0091] As illustrated, the coating system (1, coater) in which electrode coating is performed, the NMP recovery system (100), and the NMP purification system (200) are substantially separated. Of course, each system is connected through pipes or lines, and the core recovery tower (110) and purification tower (210) may be located at separate locations, separated from each other by a long distance.

[0092] The exhaust gas exhausted from the coating system (1) is introduced into the recovery tower (110) in a gaseous state through the booster fan (11). The recovery system (100) may include a recovery tower (110), a recovery 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 flows into the recovery NMP storage tank (14) and stored. In addition, the waste NMP accumulated through the operation of the recovery tower (110) flows into the waste NMP storage tank (15) and stored. The waste NMP is an impurity including NMP peroxide, and if included in the slurry, it may be a factor that deteriorates electrode performance.

[0093] The recovery tower (110) recovers NMP through various methods. For example, NMP can be recovered through condensation. To this end, a condensation system (13) may be provided to supply pure water (DI-water, De-Ionized water) corresponding to condensate within the recovery tower, particularly through the upper portion of the recovery tower.

[0094] Specifically, a recovery system (100) including a recovery tower as a recovery device performs the function of recovering NMP used in the cathode coater. Gaseous NMP is recovered, and at this time, NMP liquid mixed with high-boiling-point impurities and low-boiling-point impurities (water) can be recovered to a recovery tank. In the recovery tower, NMP can be condensed and recovered using DI water, and NMP can be recovered by various methods such as condensation, adsorption, and absorption. Therefore, the recovery tower can be implemented in a form having a bottom, a middle, and an upper part, and DI water can be supplied to the upper part. In addition, it is also possible to implement a plurality of recovery towers that are connected to each other. As high-temperature gaseous NMP rises, it is condensed and NMP gathers at the bottom of the recovery tower, and moisture can be removed to increase the NMP concentration. The recovered NMP is stored in a recovery NMP tank.

[0095] Since the recovered NMP cannot be used as is in the cathode material mixing process, it can be purified and reused. A purification system (200) including a purification tower (210) as a purification device for purifying the recovered NMP purifies the recovered NMP and converts it into high-purity NMP, which is then reused in the cathode material mixing process.

[0096] In the purification tower (210), the recovered NMP is heated to discharge high-purity gaseous NMP, and the discharged high-purity gaseous NMP is condensed and stored in the purified NMP tank (23). The purification tower (210) can be implemented in a form having a bottom, a middle, and an upper part, and the high-purity gaseous NMP can be discharged to the outside from the middle part. Since the purified high-purity gaseous NMP is discharged from the middle part of the purification tower, this can be called a side-cut distillation method.

[0097] Although the recovery system (100) and the purification system (200) are connected via the recovery NMP tank (14), the recovery process and the purification process are performed separately. That is, the operation of the recovery tower (110) and the operation of the purification tower (210) can be individually controlled and performed.

[0098] In the recovery and purification processes, waste NMP containing high-boiling-point impurities is separated and stored in waste NMP storage tanks (15, 24), and then transported to the outside for a separate disposal process. By efficiently separating waste NMP in the recovery and purification processes, high-purity NMP purification and reuse can be smoothly performed.

[0099] After being stored in the purified NMP storage tank (23) in the purification system (200), it is supplied to the raw material room (25). The purified NMP supplied to the raw material room (25) can be used in the cathode material mixing process.

[0100] The electrode process, which coats the cathode material after mixing it, should preferably be performed continuously. This requires an adequate supply of NMP. This implies that the NMP purification process must be performed continuously and efficiently. Furthermore, for the purification process to be performed continuously and efficiently, the recovery process, which supplies recovered NMP to the purification process, must also be performed continuously and efficiently. In other words, the recovery process and the purification process must be performed organically.

[0101] In order to continuously perform the purification process, the raw material, recovered NMP, must be supplied adequately, and the purified NMP must be appropriately reused.

[0102] From the perspective of normal operation of the purification tower (210), if the amount of purified NMP is excessive, normal operation of the purification tower is not easy, and if the amount of recovered NMP, which is the raw material, is insufficient, normal operation of the purification tower is not easy.

[0103] For example, if the amount of recovered NMP in the recovery NMP tank is insufficient (low level or lower limit level) or if the amount of purified NMP in the purification NMP tank is excessive (high level or upper limit level), the purification process cannot be performed smoothly. When such a problem, i.e., an emergency in the purification tower, occurs, the problem was temporarily resolved by resupplying the discharged NMP after purification in the purification tower to the recovery NMP tank or by controlling the amount of discharged NMP. In other words, the problem was attempted to be solved in the purification tower itself.

[0104] However, since the refining process in the secondary battery manufacturing process must be performed organically with the electrode and recovery processes, the cause of the refining tower failure may not simply be the refining tower itself. Therefore, a fundamental and effective solution is necessary.

[0105] In this embodiment, a configuration and control logic can be provided to circulate at least a portion of the high-purity NMP discharged after purification in the purification tower (210) to the recovery device (100), particularly the recovery tower (110), through the circulation line (300) instead of discharging it 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 at the same time enabling the normalization of the recovery system (100) that is the cause thereof. In other words, not only can the normal operation of the purification system be guaranteed or maintained, but also the normal operation of the recovery system can be guaranteed or maintained.

[0106] In addition, in this embodiment, it is possible to increase the separation efficiency of waste NMP while avoiding the shutdown of the recovery system (100) and the purification system (200) as much as possible. This is because the NMP peroxide already produced is diluted in the recovery system (100) and discharged to the waste NMP tank (15) of the recovery system (100), so that the impurity content in the NMP re-introduced into the purification system (200) can be further reduced compared to the initial level.

[0107] The circulation line (300) may be connected to the bottom or middle of the recovery tower (110), or may be connected to the top. In this case, it is preferable that the NMP resupplied to the circulation line be liquid NMP. Therefore, it is more preferable to be connected to the top of the recovery tower. Of course, the NMP resupplied to the circulation line may be gaseous NMP. For example, liquid NMP and gaseous NMP may be selectively or simultaneously supplied to the recovery tower. In this case, the circulation line (300) may include multiple branch lines, and each branch line may be connected to the recovery tower (110) at a different location.

[0108] Meanwhile, the recovery tower may be a single tower or multiple towers. As NMP flows from the upstream recovery tower to the downstream recovery tower, the concentration of recovered NMP may increase. Therefore, it is desirable for the circulation line to be connected to the downstream recovery tower.

[0109] When multiple recovery towers are installed, NMP discharged from the first recovery tower can be re-introduced into the first recovery tower via the second recovery tower. Finally, the recovered NMP can be discharged from the first recovery tower. In this case, the second recovery tower can recover NMP in a liquid state from the gaseous NMP and supply it to the specific recovery tower.

[0110] Multiple recovery towers of the same type may be installed. That is, the NMP recovery capacity can be distributed across multiple recovery towers. In this case, the circulation line extending from a single purification tower can be connected to each recovery tower.

[0111] When the above purification tower (210) is operating normally, the purification process is continuously performed and purified high-purity NMP is discharged. The mode in which high-purity NMP is stored in a purified NMP storage tank can be referred to as the basic mode.

[0112] When the above purification tower (210) is operating normally in the basic mode, normal operation may be interrupted for various reasons. For example, this may be due to an excessive amount of high-purity purified NMP or an insufficient amount of recovered NMP, which is a purification raw material.

[0113] According to the present embodiment, when the level of the purified NMP storage tank is lower than a preset level and the level of the recovery NMP storage tank is higher than a preset level during normal operation of the purification device, it is preferable that a basic mode is performed in which the recovered NMP is supplied from the recovery NMP storage tank to the purification device and the high-purity NMP purified in the purification device is discharged to the purified NMP storage tank.

[0114] According to the present embodiment, when the level of the purified NMP storage tank is higher than a preset level or the level of the recovery NMP storage tank is lower than a preset level during normal operation of the purification device, it is preferable that a circulation mode is performed to maintain normal operation of the purification device and circulate high-purity NMP discharged from the purification device to the recovery device through the circulation line.

[0115] Normal operation of the above purification unit can be defined as operation in which purification is performed under optimal purification conditions. Normal operation can be defined as a continuous and organic series of operations in which the recovered NMP to be purified is normally supplied to the purification unit, the recovered NMP is normally purified, and the purified, high-purity NMP is discharged.

[0116] The basic mode is performed in which the purified high-purity NMP discharged from the above purification device during normal operation is supplied to and stored in the purified NMP storage tank.

[0117] Circumstances may arise where the liquid level in the purified NMP storage tank reaches the upper limit, or the coating process is temporarily stopped, resulting in an excessive amount of purified NMP. Furthermore, the amount of purified NMP may increase beyond the amount of NMP required in the anode mixing process.

[0118] The excessive amount of purified NMP can be identified through the upper limit level inside the purified NMP storage tank.

[0119] In the cathode material mixing process, the time required for the main mixer slurry production (tact time) may be approximately 1 hour, and the times required for the semi-finished product (binder solution, pre-dispersed solution) mixer production may be approximately 4 hours and 8 hours, respectively. Therefore, it can be said that the purified NMP is consumed again after a certain period of time. Therefore, if the current amount of purified NMP is excessive, the transient state may be resolved after a certain period of time.

[0120] The problem is that there is a constant risk of the purification tower shutting down until the excessive amount of purified NMP is resolved. In other words, normal operation becomes difficult to maintain.

[0121] Accordingly, in this embodiment, in order to resolve the excessive state of the purified NMP amount and maintain normal operation of the purification tower, a circulation mode can be provided in which purified NMP is circulated to the recovery tower instead of being supplied to the purified NMP storage tank due to normal operation of the purification tower.

[0122] Meanwhile, situations may arise where the liquid level in the recovery NMP storage tank reaches the lower limit or the coating process is temporarily stopped, resulting in an insufficient amount of recovered NMP. In other words, the amount of recovered NMP that should be supplied to the purification device may be insufficient.

[0123] This state of insufficient recovered NMP can be identified through the lower limit level inside the recovered NMP storage tank.

[0124] The problem is that until the NMP shortage is resolved, there is a constant risk of the purification tower shutting down. This means that normal operation will become difficult to maintain.

[0125] Accordingly, in this embodiment, in order to resolve the state of insufficient amount of recovered NMP and maintain normal operation of the purification tower, a circulation mode can be provided in which purified NMP due to normal operation of the purification tower is not supplied to the purified NMP storage tank but is circulated and supplied to the recovery tower.

[0126] Finally, in this embodiment, in order to avoid intentional temporary stoppage of the purification device and intentional temporary stoppage of the recovery device, purified NMP that has been purified can be circulated to the recovery device, thereby maintaining normal operation of the purification device and the recovery device.

[0127] This approach prevents losses associated with restarting the recovery and purification equipment after a shutdown, as well as losses until normal operation resumes. Furthermore, by using a portion of the purified NMP to recover NMP and then reprocessing it, the recovery and purification processes, in particular, enable more effective separation of NMP peroxide.

[0128] The low level of the recovery NMP storage tank and the high level of the purified NMP storage tank can be controlled by being separated into at least two stages. For example, a first low level and a first high level can be sensed for performing the circulation mode. When performing the circulation mode, if a level higher than the first low level is sensed and a level lower than the first high level is sensed, the circulation mode is stopped, and a normal purification process can be performed. Of course, a normal recovery process can also be performed. When performing the circulation mode, if a second low level lower than the first low level is sensed and a second high level higher than the first high level is sensed, follow-up measures such as increasing the amount of NMP circulation can be performed. If necessary, the purification process can be stopped. However, if the purification process is stopped, stabilization time and yield loss are expected upon restart, so it is desirable to avoid stopping the purification process if possible.

[0129] Meanwhile, the division of the recovery tower and the purification tower into upper, middle, and lower levels is based on their positions in the overall tower, and each stage can be operated as a single recovery structure or purification structure, or as multiple recovery structures or purification structures.

[0130] Hereinafter, the control logic and main configuration of the NMP recovery purification system will be described in detail with reference to FIGS. 2 and 3.

[0131] Exhaust gas discharged during the coating process is fed into a recovery tower (110) through a blower or the like (S10). The recovery tower (110) may be composed of an upper layer (111), a middle layer (112), and a lower layer (113).

[0132] Exhaust gas fed into the recovery tower at a high temperature rises and is condensed by condensate and collected in the lower layer (113). DI water for condensation can be supplied into the upper layer of the recovery tower (110), and NMP condensate collected in the lower layer can be circulated into the upper layer to separate NMP in the exhaust gas.

[0133] NMP can be recovered by removing water from the NMP condensate collected in the lower layer. Approximately 50 to 85 wt% of NMP can be recovered through the recovery process.

[0134] NMP recovered from the recovery tower (110) is fed into the recovery NMP storage tank (14) and stored.

[0135] The stored recovered NMP becomes the raw material for NMP purification and is purified into high-purity NMP through the purification process and reused in the subsequent coating process.

[0136] The purification device includes a purification tower (210), and the purification tower (210) may also be formed in multiple layers. For example, it may be formed in an upper layer (211), a middle layer (212), and a lower layer (213), and the middle layer may be formed in multiple layers.

[0137] The recovered NMP introduced into the purification tower (210) can be purified by being heated inside the purification tower and going through a distillation process, and the purified NMP can be discharged from the middle layer (212) and a side cut distillation method can be applied.

[0138] High-purity purified NMP discharged from the purification tower (210) is stored in the purified NMP storage tank (23) through the purified NMP line (26). That is, during normal operation, the purification tower (210) continuously produces high-purity purified NMP, and high-purity purified NMP can be stored in the basic mode.

[0139] In this embodiment, a waste NMP storage tank (24) for storing waste NMP containing high boiling point impurities discharged from the lower tower of the purification tower and a flow control valve (29a) for controlling the flow rate of waste NMP flowing into the waste NMP storage tank may be included. A flow control valve may be provided in the waste NMP line (29).

[0140] The flow control valve (29a) may be provided to automatically control the flow rate of the discharged waste NMP by adjusting the opening degree. It is preferable that the flow rate control be performed based on the results of analyzing the components and contents of impurities in the waste NMP. An analysis device (29b) capable of analyzing the components and contents of impurities in real time in-line in the waste NMP flowing into the waste NMP storage tank is provided, and the flow rate control may be performed based on the results of the analysis by the analysis device.

[0141] The above-mentioned analysis device (29b) may be equipped to automatically adjust the opening degree of the flow control valve (29a) by monitoring the waste NMP concentration. In other words, by monitoring the waste NMP concentration, the opening degree can be quantitatively adjusted, thereby securing the freedom to implement the advancement of the NMP recovery and purification system from the viewpoints of control, yield improvement, etc.

[0142] Monitoring of the concentration of waste NMP can be performed online or offline, and when the concentration of waste NMP is low, the recovery rate of NMP can be increased by reducing the opening rate, and when the concentration of waste NMP is high, the recovery efficiency can be increased by increasing the opening rate. The above-mentioned analysis device (29b) may be a gas chromatography mass spectrometer such as a GC-MS analyzer.

[0143] As described above, waste NMP can be separated in both the recovery tower (110) and the purification tower (210). That is, it is desirable to separate NMP peroxide as much as possible so that it is not ultimately included in the high-purity purified NMP.

[0144] According to this embodiment, high-purity purified NMP can be fed back into the recovery tower (110) under certain conditions. That is, during normal operation of the purification tower (210), it can be fed back into the recovery tower (110) under certain conditions and used again in the recovery process.

[0145] Therefore, waste NMP can be filtered again in the recovery tower, which means that the amount of NMP peroxide flowing into the purification tower (210) is further reduced. As a result, the purity of high-purity purified NMP can be further increased.

[0146] The purified NMP circulation line (300) can be connected to the purification tower (210) in the same form as the purified NMP line (26). That is, the purified NMP circulation line (300) and the purified NMP line (26) can be selectively opened.

[0147] Additionally, the purified NMP circulation line (300) may be provided by branching off from the purified NMP line (26). That is, purified NMP discharged through the purified NMP line may continuously flow into the storage tank (23) or flow into the recovery tower (110) along the circulation line (300).

[0148] The purified NMP line and the circulation line may each be equipped with valves to control the opening and closing of the flow path and, if necessary, a flow control valve.

[0149] Meanwhile, the NMP discharged through the purified NMP line (26) may be in a gaseous state and may be converted to a liquid state through a condenser (27). This means that the NMP in a gaseous state may be branched and circulated from the purified NMP line (26), or the NMP in a liquid state may be branched and circulated.

[0150] Accordingly, in the circulation mode, high-purity purified NMP in a liquid or gaseous state can be circulated to the recovery tower (110) as needed. At this time, it may also be possible to selectively circulate NMP to the upper, middle, or lower layers of the recovery tower (110). For example, liquid NMP can be introduced into the lower layer of the recovery tower, and gaseous NMP can be introduced into the upper layer of the recovery tower. Of course, the opposite can also be done.

[0151] In other words, in order to maintain normal operation of the recovery tower in circulation mode, the purified NMP flowing into the recovery tower can be selected as either gas or liquid, taking into account the current conditions within the recovery tower, such as the concentration, temperature, and pressure of the recovered NMP. Of course, the location for the purified NMP flow can also be selected.

[0152] Therefore, according to this embodiment, the normal operation of the purification device can be continuously maintained, and the normal operation of the recovery tower can also be continuously maintained. In addition, since the separation of waste NMP can be performed in a circulation mode, the purity of the purified NMP can be further increased.

[0153] As illustrated in Fig. 2, during normal operation from the perspective of the recovery tower, exhaust gas injection (S10), NMP recovery (S20), and recovered NMP storage (S30) are organically, continuously, and continuously performed. From the perspective of the purification tower, during normal operation, recovered NMP is injected into the purification tower (S40), NMP purification (S50), and purified NMP storage (S60) are organically, continuously, and continuously performed. In other words, the basic mode is performed.

[0154] However, if a temporary shutdown condition occurs in the purification tower, the circulation mode (S70) can be performed without the purification tower being shut down. One of the temporary shutdown conditions for the purification tower may also be a temporary shutdown condition for the recovery tower. That is, by performing the circulation mode, the temporary shutdown condition for the purification tower and the temporary shutdown condition for the recovery tower are resolved, allowing normal operation of both to continue.

[0155] Suspension conditions can vary, and various shifts or sensing values ​​can be preset to determine them. For example, excessive purified NMP storage can be determined based on the liquid level in the purified NMP storage tank, while insufficient recovered NMP storage can be determined based on the liquid level in the recovered NMP storage tank.

[0156] This circulation mode extends NMP circulation beyond the purification tower or purification system itself, extending to the recovery tower area. Therefore, the control logic that links NMP use, recovery, and purification can be reliably configured and operated.

[0157] In the above, the first circulation line and circulation mode for effectively removing foreign substances contained in NMP during the process of NMP recovery and purification before being introduced into the first storage tank (23) were described.

[0158] Below, the second circulation line and circulation mode for effectively removing foreign substances contained in NMP before the NMP stored in the first storage tank (23) flows into the second storage tank (23a) for the mixing process are described in detail.

[0159] Figure 4 is a piping diagram between the first storage tank (23) and the second storage tank (23a), and Figure 5 is a three-dimensional diagram of the piping structure (400) near the first storage tank (23).

[0160] The first storage tank (23) is part of the outdoor facility, where NMP is recovered, purified, and stored. The NMP stored in the first storage tank (23a) is supplied to the second storage tank (23a), which is part of the indoor facility, for the mixing process.

[0161] The NMP stored in the first storage tank (23) may contain traces of foreign matter, which may cause electrode undervoltage. It is desirable to remove even very small amounts of such foreign matter, such as magnetic and non-magnetic foreign matter, before supplying it to the second storage tank (23a).

[0162] NMP is discharged from the first storage tank (23) by the operation of the pump (411). Basically, NMP is transported through the main line (410).

[0163] In this embodiment, the main line (41) may be branched near the first storage tank (23) to form a first parallel line (412) and a second parallel line (413). These parallel lines may then be combined into one and connected to the second storage tank.

[0164] That is, a magnetic separator (430) and a particle separator (417) that can effectively filter out magnetic and non-magnetic foreign substances in a pipe before it is branched and combined can be provided.

[0165] That is, a magnetic separator and a particle separator may be provided in each parallel line with the same shape, structure, and arrangement. In addition, the shut-off valves (414), drain valves (414), and air nozzles may also be provided in each parallel line with the same shape, structure, and arrangement.

[0166] After the parallel lines merge, the main line (410) can be connected to a circulation line (420). The circulation line (420) can be referred to as a second circulation line to distinguish it from the circulation line (first circulation line) in the NMP recovery and purification system.

[0167] Also, the main line (410) and the circulation line (420) may each be equipped with an on-off valve (419, 418). The two on-off valves may be a three-way valve. That is, either the circulation line (420) or the main line (410) may be opened.

[0168] A connecting line (430) may be provided between two parallel lines to connect them to each other.

[0169] Through this structure, foreign substances can be filtered out from both parallel lines or from one of the parallel lines. With the main line closed, NMP can be continuously circulated and filtered through the circulation line (420).

[0170] Afterwards, one of the parallel lines can be closed to perform contamination inspection and cleaning, and then the other parallel line can be closed to perform contamination inspection and cleaning. Through this process, if no further contamination is detected, i.e., if it is determined that foreign substances have been completely removed from the NMP, the circulation line can be closed to supply the NMP to the second storage tank (23a). In other words, the circulation mode can be switched to a supply mode or a transfer mode.

[0171] As shown in Fig. 5, the parallel lines (412, 413) are positioned low so that workers can easily access them.

[0172] In particular, the position of the drain valve (415), the position and shape of the magnetic separator (430), and the position and shape of the particle separator (417) are designed to facilitate worker access for separation and cleaning. In addition, an on-off valve (414) is provided at the front end of the drain valve (415), the rear end of the magnetic separator (430), and the front and rear ends of the particle separator (417), so that the flow of NMP can be caused to cross between the parallel lines through the connecting line. In addition, observation and cleaning become very easy.

[0173] Figures 6 and 7 illustrate examples of magnetic separators that can be used in one embodiment of the present invention.

[0174] The magnetic separator (43) may include a housing (431). The housing may be arranged vertically and may be formed so that NMP flows into the housing from the bottom vertically upward and NMP is discharged from the top side. The housing may be formed so that a certain length of pipe diameter increases from the bottom to the top, thereby increasing the contact area between the magnetic filter and the NMP.

[0175] An opening (435) is formed at the top of the housing (431), and NMP flows into the housing through the lower inlet (433) of the housing, then passes through the body (432) and is discharged through the outlet (434) formed at the upper side of the housing.

[0176] The upper opening (435) of the above housing and a detachable cap (436) may be provided. The cap may be detachably attached to the housing through a coupling, thereby ensuring ease of maintenance.

[0177] A plurality of magnetic rods (438) and dummy rods (439) can be formed integrally at the bottom of the cap. The dummy rods can be positioned between the magnetic rods to increase the contact area between the magnetic rods and the NMP.

[0178] The cap (436) may be equipped with a handle (437), and an air valve and an air pipe for relieving internal pressure may be formed integrally and provided on the cap.

[0179] The worker can check the level of contamination and clean it by holding the handle of the cap, separating the cap, and inspecting the magnetic rod.

[0180] While circulating NMP through the second circulation line (420), it is possible to self-inspect whether magnetic foreign matter continues to be captured in the magnetic separator. If magnetic foreign matter continues to be captured, the magnetic foreign matter can be removed from the magnetic separator while continuing the circulation mode. This can be accomplished through a pair of parallel lines.

[0181] If magnetic foreign matter is not captured in the magnetic separator while circulating NMP through the second circulation line (420), a supply mode or transfer mode can be performed to supply NMP to the second storage tank (23a) without circulating NMP any further.

[0182] According to this embodiment, a facility system for recovering and purifying NMP and using the purified NMP for mixing can be provided.

[0183] During the recovery and refining process, the first storage tank may become full, and the NMP in the mixing process (i.e., the raw material room) may not be depleted. Furthermore, the purified NMP may contain magnetic impurities.

[0184] By continuously performing the recovery and purification of NMP in an excessively purified state, the system can be stabilized, and additional foreign substances can be removed from the NMP during this process. In this case, foreign substances can be removed more effectively from the NMP by circulating the NMP from the first storage tank to the second storage tank instead of transferring it.

[0185] As described in the detailed description of the invention.

Claims

1. A first storage tank for storing NMP recovered and purified in the electrode process; A main line for transporting NMP from the first storage tank to the second storage tank for storing NMP used in the mixing process of the slurry used in the electrode process; A circulation line branching from the main line and circulating NMP discharged from the first storage tank to the first storage tank; An opening / closing valve provided after a branch point of the above circulation line to selectively open the main line and the circulation line; and An NMP system characterized by including a magnetic separator provided before a branch point of the above circulation line to separate magnetic foreign substances from NMP discharged from the first storage tank.

2. In paragraph 1, An NMP system characterized in that the above magnetic separator is a magnetic filter that filters magnetic foreign substances from NMP flowing by magnetism.

3. In paragraph 2, An NMP system characterized in that the magnetic filter includes a filter housing installed so that NMP flows in from the bottom and NMP flows out from the top, and a filter cover provided to be vertically connected and separated from the filter housing.

4. In paragraph 3, An NMP system characterized in that the cover is provided with an air nozzle for relieving the internal pressure of the magnetic filter.

5. In paragraph 1, An NMP system characterized in that a shut-off valve is installed at the front and rear ends of the magnetic separator to separate the magnetic separator from the main line.

6. In paragraph 5, An NMP system characterized in that a drain valve for discharging NMP to the outside is installed between a blocking valve provided at the front end of the magnetic separator and the magnetic separator.

7. In paragraph 1, An NMP system characterized by including a parallel line provided parallel to the main line up to the branch point of the above-mentioned circulation line.

8. In paragraph 7, An NMP system characterized in that the detailed configuration of the above parallel line is identical to the configuration of the main line parallel to the above parallel line.

9. In paragraph 7, An NMP system characterized in that one line extending from the first storage tank is divided into two lines to form a parallel line with the main line, and the two lines are combined again into one line at the branch point of the circulation line and extended to the second storage tank.

10. In paragraph 9, An NMP system characterized by including a particle separator installed in series with the magnetic separator and separating non-magnetic foreign substances from NMP discharged from the first storage tank using the size of the particles.

11. In paragraph 10, An NMP system characterized in that the particle separator includes a mesh filter that separates non-magnetic metal foreign substances through a mesh.

12. In paragraph 11, An NMP system characterized in that the particle separator is installed at the rear end of the magnetic separator.

13. In paragraph 12, An NMP system characterized in that the above parallel line is equipped with a magnetic separator and a particle separator identical to the above main line.

14. In paragraph 13, An NMP system characterized in that the diameters of the main line and the parallel line are the same.

15. In any one of paragraphs 1 to 14, An NMP system characterized in that the magnetic separator and circulation line are provided near the first storage tank.

16. In paragraph 15, An NMP system comprising a transfer pump driven for NMP transfer (transfer mode) through the main line and NMP circulation (circulation mode) through the circulation line, wherein the transfer pump is driven at different RPMs in the transfer mode and the circulation mode.

17. In paragraph 16, An NMP system characterized in that, when non-contamination of the magnetic foreign substance is confirmed in the magnetic separator, the transfer mode is performed automatically or manually.

18. In paragraph 16, An NMP system characterized in that the circulation mode is performed intermittently or periodically when the above transport mode is stopped.

19. A first storage tank for storing NMP recovered and purified in the electrode process; A main line having two parallel lines in the initial section, which transfers NMP from the first storage tank to a second storage tank for storing NMP used in the mixing process of the slurry used in the electrode process; and An NMP system including a magnetic separator installed vertically in each of the two parallel lines to separate magnetic foreign substances from NMP discharged from the first storage tank.

20. In paragraph 19, An NMP system characterized by including a particle separator installed in series with the magnetic separator in each of the two parallel lines and separating non-magnetic foreign substances from the NMP discharged from the first storage tank using the size of the particles.

21. In paragraph 19, An NMP system characterized in that the above two parallel lines are branched from one main line and then merged again.

22. In paragraph 21, An NMP system including a circulation line that branches off from the main line at the rear end of the junction of the two parallel lines and circulates NMP discharged from the first storage tank to the first storage tank.

23. In paragraph 22, An NMP system characterized by including an opening / closing valve provided after a branch point of the above circulation line and selectively opening the main line and the circulation line.

24. A transfer step of operating a transfer pump from a first storage tank storing NMP recovered and purified in the electrode process to transfer NMP to a second storage tank storing NMP used in the mixing process of the slurry used in the electrode process through the entire main line; and It includes a circulation step of operating the transfer pump through a circulation line branched from the initial section of the main line to transfer and circulate the NMP to the first storage tank. A magnetic separator for separating magnetic metal foreign substances from NMP discharged from the first storage tank of the main line and a mesh filter for separating non-magnetic metal foreign substances are provided. A control method for an NMP system, characterized in that the operating load of the transfer pump in the transfer step is greater than the operating load in the circulation step.

25. In paragraph 24, A control method for an NMP system, characterized in that the initial section of the main line is provided with two parallel lines, the magnetic separator and the mesh filter are vertically mounted in series on each of the parallel lines, and the transport step and the circulation step are selectively performed.

26. An NMP system for recovering and refining NMP, storing it in a first storage tank, and transferring the NMP stored in the first storage tank to a second storage tank for a mixing process, characterized in that a first circulation mode is performed in which the NMP purified and discharged from the purification tower is circulated to a recovery tower while the first storage tank is in a high-level state and the mixing process is stopped, and a second circulation mode is performed in which the NMP discharged from the first storage tank is filtered by a magnetic separator and circulated to the first storage tank.

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