JP6970280B2 - Organic solvent purification system and method - Google Patents

Description

The present invention relates to a system and a method for separating and purifying an organic solvent from a mixed solution of an organic solvent typified by N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP) and water, and particularly to a permeation vaporization method. Regarding the organic solvent purification system and method used.

Some organic solvents have high solubility in water. When such a water-soluble organic solvent is used and then recovered and reused, a mixed solution of the organic solvent and water is often recovered. Therefore, the organic solvent to be reused is separated from this mixed solution. Need to be purified. In addition to the organic solvent and water, the recovered mixed solution may contain refractory impurities such as ionic substances and fine particles, and organic substances different from the organic solvent to be reused. The mixed solution also contains a dissolved gas such as dissolved oxygen and dissolved carbon dioxide, depending on the form of use and recovery of the organic solvent.

NMP, which is one of the organic solvents having high solubility in water, is dried by applying, for example, a slurry in which particles such as an electrode active material are dispersed on an electrode current collector in the manufacturing process of a lithium ion secondary battery. It is widely used as a dispersion medium for slurry when forming an electrode. NMP can be recovered when the slurry is dried, and the recovered NMP can be reused after purification. In the recovery of NMP, a method of recovering the vaporized NMP by, for example, a water scrubber, or adsorbing the vaporized NMP to an adsorbent and then flowing water through the adsorbent to dissolve the NMP in water is used. Therefore, NMP is recovered as a mixed solution of NMP and water. At this time, the NMP concentration in the recovered mixed solution is about 70 to 99% by mass. Oxygen and carbon dioxide derived from the atmosphere are dissolved in the mixed liquid, and the above-mentioned refractory impurities and organic substances are mixed in the mixed liquid.

Conventionally, a distillation method is known as a method for separating and recovering an organic solvent from a mixed solution of an organic solvent and water, and in particular, a vacuum distillation method in which the mixed solution is distilled under reduced pressure is often used. However, the distillation method or the vacuum distillation method requires a large amount of energy and has a problem that a large-scale distillation facility is required when purifying the organic solvent to a desired purity. Therefore, the osmotic vaporization (PV) method is known as a separation method that does not require large-scale equipment and has excellent energy-saving performance.

In the permeation vaporization method, a separation membrane having an affinity for the component to be separated, for example, a separation membrane having an affinity for water is used, and a mixed solution containing this target component, for example, an organic solvent and water. The mixed solution with and is supplied to the concentrated side of the separation membrane, and the pressure is reduced or an inert gas is flowed on the permeation side of the separation membrane. As a result, the components are separated by the difference in the permeation rate of each component in the separation membrane. The separation membrane used in the osmotic vaporization method is called an osmotic vaporization membrane. As the separation membrane for allowing water to permeate, for example, a zeolite membrane is used. If only the water is moved to the permeation side by the separation membrane, the organic solvent remains on the concentration side of the separation membrane, and the organic solvent can be recovered. When separating water and an organic solvent by the osmotic vaporization method, heating is required for efficient separation. Further, as a method for removing ionic impurities contained in an organic solvent, for example, a method using an ion exchange resin is known. Patent Document 1 discloses a system in which an osmotic vaporizer is used as an NMP separation system for separating NMP from a mixed solution of NMP and water, and an ion exchange device is provided after the osmotic vaporizer. However, when an ion exchange device is provided after the permeation vaporizer, the ion exchange device removes ions from NMP, which is a non-aqueous solvent, so that the ion exchange efficiency is low and the ion exchange resin is used. There is a problem that it takes a lot of time and effort to replace. Further, if the ion exchange resin in the ion exchange device breaks through, impurities such as sodium and silicon derived from the separation membrane and the filtration membrane existing in the system may remain in the purified NMP.

As a method of further purifying the organic solvent after separating the organic solvent from water by the permeation vaporizer, a method of providing an evaporative can at the subsequent stage of the permeation vaporizer and distilling the organic solvent with the evaporative can is known. It is used for purification of alcohol and the like. The present inventors have already described in Patent Document 2 an organic solvent purification system that separates and purifies an organic solvent from a mixed solution containing water and an organic solvent having a boiling point of more than 100 ° C. at 1 atm. Therefore, a heating means for heating the mixed solution, a permeation vaporizer provided after the heating means provided with a permeation vaporization film to separate the organic solvent and water, and an organic recovered from the concentration side of the permeation vaporizer. Disclosed is a vacuum evaporating can to which a solvent is supplied, and a pipe for supplying the organic solvent vaporized by the decompressing evaporative can to the heating means as a heat source of the heating means. In the organic solvent purification system described in Patent Document 2, the heat of condensation of the organic solvent vaporized in the vacuum evaporative can is recovered and used as a heat source for the osmotic vaporizer. Therefore, a part or all of the amount of heat input to the vacuum evaporation can is recycled in the system, and the amount of energy required for the entire system can be reduced. Therefore, according to the method described in Patent Document 2, ionic impurities and fine particles can be reliably removed while achieving energy saving performance.

Japanese Unexamined Patent Publication No. 2013-18747 International Publication No. 2016/017491

An organic solvent purification system provided with a vacuum evaporating can at the subsequent stage of the osmotic vaporizer can obtain an organic solvent having a low impurity content from a mixed solution of an organic solvent and water. However, in this organic solvent purification system, the vacuum evaporative can is not a device with a large number of theoretical stages. Therefore, for example, when separating purified NMP from a mixed solution of water and NMP, impurities having a boiling point similar to that of NMP are removed from NMP. It has a problem that it is difficult to separate and there is a possibility that the purity may decrease. In particular, when the organic solvent is recovered in the form of a mixture with water from the equipment using the organic solvent, the organic solvent is separated and purified from this mixture, and the organic solvent is reused in the equipment using the organic solvent. However, there is a problem that the concentration of an impurity having a boiling point similar to that of the target organic solvent, particularly an impurity which is an organic substance, gradually increases during repeated circulation and reuse. In order to separate substances having the same boiling point from each other, it is common to use a multi-stage distillation column, but when a multi-stage distillation column is provided, energy consumption increases and energy consumption increases as described above. Although it is possible to obtain a high-purity substance, the recovery rate focusing on that substance decreases.

An object of the present invention is an organic solvent purification system using an osmotic vaporization method, which can reliably remove ionic impurities and fine particles, and can obtain a high-purity organic solvent with a high recovery rate. To provide systems and methods.

The organic solvent purification system of the present invention is an organic solvent purification system that separates and purifies an organic solvent from a mixed solution containing water and an organic solvent having a boiling point of more than 100 ° C. at 1 atm, and is mixed. A heating means for heating the liquid, a permeation vaporizer provided after the heating means and provided with a permeation vaporizing film to separate the organic solvent and water, and an organic solvent recovered from the concentration side of the permeation vaporizer are supplied. It has a vacuum evaporative can and a distillation apparatus provided independently of the decompression evaporative can, and (a) an organic solvent separated from the concentration side of the permeation vaporizer and the inlet of the decompression evaporative can, and (B) At least one of the part of the organic solvent discharged from the outlet on the gas phase side of the vacuum evaporative can was supplied to the distillation apparatus, and the organic solvent recovered from the reduced pressure evaporative can was distilled by the distillation apparatus. The organic solvent is mixed and supplied to the supply destination of the organic solvent.

The organic solvent purification method of the present invention is a method of separating an organic solvent from a mixed solution containing water and an organic solvent having a boiling point of more than 100 ° C. at 1 atm, and heating the mixed solution. A heating step for separating the heated mixed solution into an organic solvent and water using a permeation vaporization film, and a decompression evaporation step for evaporating the organic solvent recovered from the concentrated side of the permeation vaporization film under reduced pressure. A distillation step of distilling and purifying at least one of (a) a part of the organic solvent after the separation step and before the reduced pressure evaporation step, and (b) a part of the organic solvent recovered by the reduced pressure evaporation step. , And the organic solvent recovered by the vacuum evaporation step and not sent to the distillation step is mixed with the organic solvent purified by the distillation step and supplied to the supply destination of the organic solvent.

In the present invention, when the organic solvent is dehydrated by permeation vaporization and then purified by vacuum evaporation, a part of the organic solvent after permeation vaporization or vacuum evaporation is further distilled. Therefore, even when the organic solvent is circulated and reused, it is possible to suppress an increase in the impurity concentration in the organic solvent. Since the amount of the organic solvent sent to the distillation treatment may be small, the amount of increase in energy consumption is small, and the deterioration of the recovery rate of the organic solvent is also small. Therefore, in the present invention, ionic impurities, fine particles, and the like can be reliably removed, and a high-purity organic solvent can be obtained with low energy consumption and high recovery rate.

It is a figure which shows the structure of the organic solvent purification system of one Embodiment of this invention. It is a figure which shows the structure of the organic solvent purification system of another embodiment of this invention. It is a figure which shows the structure of the system used in Example 1. FIG. It is a figure which shows the structure of the system used in the comparative example 1. FIG.

Next, a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a basic aspect of an organic solvent purification system based on the present invention as an organic solvent purification system according to an embodiment of the present invention. This organic solvent purification system 10 separates and purifies an organic solvent from a mixed solution of an organic solvent and water, and is recovered from, for example, a manufacturing process of a lithium ion secondary battery, NMP (that is, N-). It is used to separate and purify NMP by treating a mixed solution of methyl-2-pyrrolidone) and water. Hereinafter, the case where NMP is used as the organic solvent will be described, but the organic solvent to which the present invention can be applied is not limited to NMP. In the present invention, the boiling point at atmospheric pressure (0.1013Mpa) is generally higher than the boiling point of water, that is, 100 ° C., and the boiling point under atmospheric pressure is preferably the general operating temperature of the permeation vaporization film device. It can also be applied to organic solvents having a temperature of 120 ° C. or higher. Table 1 shows an example of such an organic solvent. In Table 1, the boiling point is a value at 0.1013 MPa.

As the organic solvent to which the present invention can be applied, an organic solvent that does not form an azeotropic mixture with water is more preferable. Among the organic solvents shown in Table 1, those excluding PGME, PGMEA and pyridine are organic solvents that do not form an azeotropic mixture with water.

For example, the NMP-using equipment 50 used in the manufacturing process of a lithium ion secondary battery or the like discharges NMP in the form of NMP gas. This NMP gas is recovered as an NMP aqueous solution by contacting it with water in a scrubber 51, or is recovered as an NMP aqueous solution by adsorbing it on an adsorbent 52 and then treating the adsorbent 52 with water. .. The NMP aqueous solution recovered in this manner is supplied to the organic solvent purification system 10 of the present embodiment.

The organic solvent purification system 10 has a stock solution tank 11 for storing a recovered NMP aqueous solution, that is, a mixed solution of NMP and water, and the mixed solution in the stock solution tank 11 is supplied to the permeation vaporizer 14 by a pump 12. Will be done. A heater 13 is provided between the pump 12 and the osmotic vaporizer 14 to heat the mixed liquid, and the heater 13 is supplied with steam and heats the mixed liquid by the steam. The mixed liquid supplied to the osmotic vaporizer 14 is heated to, for example, about 120 ° C. The osmotic vaporizer 13 is provided with an osmotic vaporizing membrane 15 made of, for example, zeolite, in which the mixed solution is separated into NMP and water. Since water permeates the osmotic vaporization membrane 15, it flows out in the form of water vapor from the permeation side outlet of the osmotic vaporizer 14. This water vapor is cooled by the condenser 16 to which cold water is supplied, condensed, and discharged. Zeolites are classified into A-type, Y-type, T-type, MOR-type, CHA-type, etc., depending on their skeletal structure and the ratio of silicon and aluminum contained in them. When composed of zeolite, it is preferable to use type A zeolite as described in Patent Document 2. When it is particularly necessary to prevent leakage, for example, it may be preferable to use a T-type, Y-type, or CHA-type zeolite membrane. Further, a zeolite containing A-type zeolite and a zeolite other than the above-mentioned A-type, for example, at least one type of zeolite selected from T-type, Y-type, MOR-type, and CHA-type can be used for the osmotic vaporization membrane 15. ..

Since the NMP does not permeate the osmotic vaporization membrane 15, it is discharged from the outlet provided on the concentration side (that is, the supply side of the mixed liquid across the osmotic vaporization membrane 15) in the osmotic vaporizer 14 and supplied to the reduced pressure evaporation can 20. Will be done. Although not shown in FIG. 1, a vacuum pump is connected to the reduced pressure evaporator 20 via a pipe, and the pressure inside the reduced pressure evaporator 20 is set so that the boiling point of NMP is, for example, 130 ° C. The pressure is controlled. The reduced pressure evaporation can 20 is supplied with an amount of steam required for vaporizing NMP. The reduced pressure evaporation can 20 is provided to remove volatile impurities such as ionic impurities and fine particles.

A pipe 21 for discharging the NMP vaporized in the reduced pressure evaporation can 20 is attached to the outlet on the vapor phase side of the reduced pressure evaporation can 20, that is, the outlet on the distillation component side, and a pipe 21 for condensing the NMP is attached in the middle of the pipe 21. A cooler 22 is provided. The pipe 24 and the pipe 25 are connected to the outlet of the pipe 21, and a part of the NMP flowing out from the outlet of the pipe 21 splits and flows into the pipe 24, and the rest flows into the pipe 25. The piping 24 is provided with a distillation apparatus 31 for further purifying NMP. The supply pipe through which the NMP collected from the reduced pressure evaporation can 20 and supplied to the NMP supply destination flows is composed of the pipe 21 and the pipe 25. The pipe 24 is a branch pipe that branches from the supply pipe and is connected to the inlet of the distillation apparatus 31 to supply a part of the NMP obtained by the reduced pressure evaporation can 20 to the distillation apparatus 31. As the outlet of the reduced pressure evaporation can 20, not only the outlet on the vapor phase side, that is, the outlet on the distillation component side, but also the outlet on the liquid phase side, that is, the outlet for discharging the concentrated liquid (also referred to as the residual liquid in the can) is provided. In the system shown in the figure, in order to send the residual liquid of the reduced pressure evaporator 20 to the distillation apparatus 31, a pipe 35 connecting the outlet on the liquid phase side of the reduced pressure evaporator 20 and the distillation apparatus 31 is provided. Further, as shown by the broken line in FIG. 1, the NMP diverted from the pipe between the concentration side of the osmotic vaporizer 14 and the inlet of the reduced pressure evaporation can 20 may be directly supplied to the distillation apparatus 31.

Various types of distillation apparatus 31 used for distilling NMP are known. Here, for example, a precision distillation apparatus that separates NMP and a substance having a boiling point higher than that of NMP, that is, a substance having a boiling point higher than that of NMP, and NMP. A separation tower for separating substances having a boiling point lower than that of NMP, a two-tower type precision distillation apparatus for separating NMP and a substance having a high boiling point, and the like can be used. The distillation apparatus 31 may be a continuous type or a batch type. A pipe 33 is connected to the outlet of the NMP distillate of the distillation apparatus 31, and the pipe 33 joins the pipe 25. As a result, in this organic solvent purification system 10, the NMP flowing through the pipe 25, that is, the NMP recovered from the reduced pressure evaporation can 20 but not sent to the distillation apparatus 31, is distilled in the distillation apparatus 31. The NMP obtained in the above will be mixed. The mixed NMP is supplied to the NMP supply destination, for example, the above-mentioned NMP use facility 50 as the NMP supplied from the organic solvent purification system 10.

Here, the ratio of NMP sent to the distillation apparatus 31 in the organic solvent purification system 10 of the present embodiment will be described. In the following, it is assumed that the ratio of NMP is expressed with respect to the mass. Higher purity NMP can be obtained through the distillation apparatus 31, but the energy consumption is increased by the amount of distillation. Further, as the purity of the obtained NMP is increased, the recovery rate of NMP in the distillation step tends to decrease. Therefore, in the present embodiment, it is preferable to use a distillation apparatus 31 having a configuration in which the loss of the organic solvent during distillation can be ignored, and only a part of the organic solvent purified and supplied to the supply destination is distilled. It shall be through the process. In order to suppress the increase of impurities due to the circulation and reuse of the organic solvent, the amount of the organic solvent supplied to the distillation apparatus 31 is, for example, 0.1% based on the amount of the organic solvent supplied to the supply destination. The above is preferable, 0.5% or more is more preferable, and 1.5% or more is further preferable. However, if the amount of the organic solvent supplied to the distillation apparatus 31 increases, a large distillation apparatus 31 is required and the energy required for distillation increases, so that an excessively large amount of the organic solvent is distilled. It is preferable not to supply to the device 31. From the viewpoint of preventing an increase in energy consumption and an increase in equipment scale, the amount of organic solvent supplied to the distillation apparatus 31 should be, for example, 50% or less based on the amount of organic solvent supplied to the supply destination. It is preferably 20% or less, more preferably 10% or less, and even more preferably 10% or less. Regarding the organic solvent supplied to the supply destination, the purity does not exceed the purity of the organic solvent obtained by the distillation apparatus 31, and the increase in the purity reaches a plateau as the proportion of the organic solvent obtained by the distillation apparatus 31 increases. Although there is a tendency, the energy consumed by the distillation apparatus 31 increases linearly. The amount of the organic solvent supplied to the distillation apparatus 31 may be determined in relation to the purity required at the supply destination and the allowable energy consumption.

Therefore, in the configuration of FIG. 1, if the loss of NMP in the distillation apparatus 31 is negligible and the amount of NMP sent to the distillation apparatus 31 via the pipe 35 is negligible, the NMP flowing out from the outlet of the pipe 21 is negligible. It is preferable that, for example, 0.1% or more and 50% or less of the above is supplied to the distillation apparatus 31 via the pipe 24, and the rest flows into the pipe 25. Actually, NMP is also contained in the residual liquid of the vacuum evaporation can 20, so the ratio of NMP flowing from the pipe 21 to the pipe 24 and the pipe 25 is determined while considering the amount of NMP contained in the residual liquid of the can. You just have to decide.

When NMP is recycled and reused, the recovered NMP contains organic impurities having a boiling point similar to that of NMP. In the organic solvent purification system 10 of the present embodiment, by further purifying a part of NMP recovered from the vacuum evaporating can 20 by the distillation apparatus 31, impurities having a boiling point similar to that of NMP are removed by distillation. Even when the NMP is recycled and reused, the increase in the impurity concentration in the NMP can be suppressed. Further, since distillation is performed, the NMP supplied to the distillation apparatus 31 does not have to be separated from the outlet side of the reduced pressure evaporator 20, and flows out from the concentrated side of the permeation vaporizer 14 to the inlet of the reduced pressure evaporator 20. A part of the NMP before reaching it may be supplied to the distillation apparatus 31.

The above description assumes that the distillation apparatus 31 is provided on-site, but in the present embodiment, the distillation apparatus 31 provided on-site is used. You can also do it. When the distillation apparatus 31 provided in the off-site is used, NMP outlets are provided at the tips of the pipes 24, 31, and 35, and the NMP obtained from these outlets is transported to the off-site distillation apparatus 31. Instead of providing the pipe 33, the pipe 25 may be provided with an NMP receiving port, and the NMP distilled and transported by the off-site distillation apparatus 31 may be received by this receiving port and introduced into the pipe 25.

Next, another embodiment of the present invention will be described. The organic solvent refining system shown in FIG. 2 transfers the latent heat of condensation of the NMP gas recovered from the vacuum evaporating can 20 to the NMP and water supplied to the permeation vaporizer 14 in the same manner as described in Patent Document 2. It is used for heating the mixed solution of. In the organic solvent refining system shown in FIG. 2, in the organic solvent refining system 10 shown in FIG. 1, a heater 40 for heating the mixed liquid is further provided in the pipe between the pump 12 and the heater 13, and the pipe 21 is provided. Is to go through this heater 40. The position of the heater 40 is between the decompression evaporation can 20 and the cooler 22 in the pipe 21, and the heat energy of the NMP gas flowing through the pipe 21 is used to heat the mixed liquid in the heater 40. Further, a microfiltration membrane 26 is arranged at the outlet of the cooler 22, and NMP that has passed through the microfiltration membrane 26 is supplied to the pipes 24 and 25. At the outlet of the condenser 16, a permeated water tank 17 for storing the water condensed by the condenser 16 is provided.

In the organic solvent refining system shown in FIG. 2, NMP at, for example, 130 ° C. vaporized from the reduced pressure evaporation 20 is supplied to the heater 40 as a heat source of the heater 40 via the pipe 21. The NMP vapor supplied to the heater 40 condenses when the mixed liquid flowing through the heater 40 is heated. Therefore, the heater 40 heats the mixed liquid and also functions as a condenser of NMP steam. Since it is possible to directly exchange heat between NMP steam and a mixed solution of NMP and water without using an external heat source such as steam as a heat medium for heating in the heater 40, the NMP steam temperature becomes excessive. It does not need to be high and is energy efficient for NMP purification. Since the cooler 22 and the microfiltration membrane 26 are connected in this order to the outlet on the NMP steam side of the heater 40, the NMP is cooled by the cooler 22 and becomes a completely liquid state, and the microfiltration membrane 26 makes it completely liquid. The fine particles are finally removed. As a result, purified NMP can be obtained from the outlet of the microfiltration membrane 26, that is, the outlet of the pipe 21. A part of the purified NMP is sent to the distillation apparatus 21 via the pipe 24 for further purification.

In the organic solvent purification system shown in FIG. 2, as shown in Patent Document 2, an ion exchange device for removing ionic impurities from the mixed liquid may be provided in the pipe between the pump 12 and the heater 40. A degassing device for degassing the mixed liquid before being supplied to the ion exchange device may be provided. Further, two osmotic vaporizers may be connected in series to improve the removal rate of water from NMP.

Next, the present invention will be described in more detail based on Examples and Comparative Examples of the present invention.

[Example 1]
The device shown in FIG. 3 was assembled. This device includes a stock solution tank 11 that stores a mixed solution of NMP and water, that is, an NMP aqueous solution, a permeation vaporization device 14 having a permeation vaporization film 15, and a pump that feeds the NMP aqueous solution in the stock solution tank 11 to the permeation vaporization device 14. 12, the decompression vaporization can 20 connected to the outlet on the concentration side of the permeation vaporizer 14, and the NMP recovered from the outlet on the gas phase side of the decompression vaporization can 20 are supplied via the pipe 21 to store the NMP. It is provided with a purification liquid tank 60. A heater 13 is provided between the pump 12 and the osmotic vaporizer 14 to heat the NMP aqueous solution to 120 ° C., and steam is supplied to the heater 13. A condenser 16 that cools and condenses the water that has passed through the osmotic vaporization membrane 15 is connected to the outlet on the osmotic side of the osmotic vaporizer 14. The pipes between the outlet on the concentration side of the permeation vaporizer 14 and the decompression evaporator 20 and the pipes 21 are provided with coolers 19 and 22 for cooling the NMP flowing through those pipes to room temperature, respectively. Cooling water is supplied to the coolers 19 and 22. Steam was supplied to the reduced pressure evaporation can 20 so that the reduced pressure evaporation of NMP was performed at a temperature of 120 ° C. Further, in the apparatus shown in FIG. 3, in order to imitate the circulation reuse of NMP, a pipe 61 for circulating NMP from the refined liquid tank 60 to the undiluted liquid tank 11 is provided. In order to imitate the distillation of a part of the NMP recovered from the vacuum evaporation can 20, a pipe 62 for discharging a part of the NMP flowing there is connected from the pipe 61, and from the connection point with the pipe 62. At a position on the downstream side, a pipe 63 for injecting NMP (purity: 99.9%, hereinafter referred to as distilled NMP) purified in advance by distillation into the system was connected to the pipe 61. The pipe 62 is also connected to a pipe 35 connected to an outlet for discharging the residual liquid of the decompression evaporation can 20, that is, an outlet on the liquid phase side. Therefore, the amount of NMP extracted by the pipe 62 is the sum of the amount of NMP extracted from the pipe 61 and the amount of NMP in the residual liquid of the can extracted from the pipe 35. The amount of NMP extracted by the pipe 62 and the amount of distilled NMP injected by the pipe 63 were made equal to each other.

After preparing an NMP aqueous solution having a water content of 20% on a mass basis in the stock solution tank 11, the purity of the NMP aqueous solution in the stock solution tank 11 as NMP was confirmed by a GC (gas chromatograph) device. Then, the pump 12 is driven to supply the NMP aqueous solution in the stock solution tank 11 to the permeation vaporizer 14 to perform permeation vaporization and dehydration at 120 ° C., and then the dehydrated NMP is continuously supplied to the decompression evaporation can 20. Then, evaporation under reduced pressure was performed at 120 ° C. The NMP that had undergone vacuum evaporation was stored in the purification liquid tank 60.

The water content of the NMP aqueous solution in the stock solution tank 11 was measured while circulating NMP from the purification liquid tank 60 via the pipe 61, and pure water was added to the stock solution tank 11 so that the water content was maintained at 20%. .. Further, as described above, the amount of NMP extracted through the pipe 62 is extracted through the pipe 62, and the amount of NMP extracted via the pipe 62 changes in the range of 0.5% to 10% with respect to the amount of NMP discharged from the undiluted solution tank 11. Then, the same amount of distilled NMP as the extracted NMP was injected into the pipe 61 via the pipe 63. While continuously circulating MMP through the pipe 61, adding pure water to the stock solution tank 11, extracting NMP from the pipe 62, and injecting distilled NMP from the pipe 63, the NMP in the refined liquid tank 61 Purity was observed over time with a GC device. The results are shown in Table 2.

[Comparative Example 1]
As Comparative Example 1, the apparatus shown in FIG. 4 was assembled. The device shown in FIG. 4 is the device shown in FIG. 3 with the pipes 35, 62, and 63 removed. Therefore, the apparatus shown in FIG. 4 corresponds to an organic solvent purification system used for purifying NMP to be recycled but not equipped with a distillation apparatus. In the apparatus of FIG. 4, as in the case of the first embodiment shown in FIG. 3, the purified liquid tank is continuously circulated through the pipe 61 and the pure water is continuously added to the undiluted liquid tank 11. The purity of NMP in 61 was observed over time by GC. The results are shown in Table 2.

In the comparative example corresponding to the case where the distillation apparatus was not provided as shown in Table 2, the NMP purity was reduced from 99.860% to 99.844% by the circulation and purification of NMP for 60 days. On the other hand, in the example corresponding to distilling a part of the NMP recovered from the vacuum evaporation can 20, the decrease in NMP purity is small even if the NMP is circulated and purified for 60 days, and the extraction amount is 1. When it exceeds about 5.5%, the purity of NMP is rather improved. Further, it can be seen from this that if the extraction amount is as much as 10 to 20%, the NMP purity can be 99.9% or more.

10 Organic solvent refining system 11 Undiluted solution tank 13 Heater 14 Penetration vaporizer 20 Decompression evaporation can 21,24,25,33,35 Piping 22,32 Cooler 31 Distiller

Claims (10)

An organic solvent purification system that separates and purifies the organic solvent from a mixed solution containing water and an organic solvent having a boiling point of more than 100 ° C. at 1 atm.
A heating means for heating the mixed liquid and
An osmotic vaporizer provided after the heating means and provided with an osmotic vaporizing membrane to separate the organic solvent and the water.
A vacuum evaporator to which the organic solvent recovered from the concentration side of the permeation vaporizer is supplied, and
A distillation apparatus provided independently of the vacuum evaporation can,
Have,
(A) The organic solvent diverged from between the concentrated side of the permeation vaporizer and the inlet of the reduced pressure evaporator, and (b) the organic solvent discharged from the outlet on the gas phase side of the reduced pressure evaporator. At least one of the parts of the above is supplied to the distillation apparatus.
An organic solvent refining system that mixes the organic solvent recovered from the vacuum evaporation can with the organic solvent distilled by the distillation apparatus and supplies the organic solvent to the supply destination of the organic solvent. The organic solvent purification system according to claim 1, wherein the liquid discharged from the outlet on the liquid phase side of the reduced pressure evaporator is also supplied to the distillation apparatus. A supply pipe connected to the outlet on the gas phase side of the reduced pressure evaporator and through which an organic solvent collected from the reduced pressure evaporator and supplied to the supply destination flows.
A branch pipe that branches from the supply pipe and connects to the inlet of the distillation apparatus,
A pipe connecting the outlet of the organic solvent distillate of the distillation apparatus and the supply pipe, and
The organic solvent purification system according to claim 1 or 2, further comprising. The organic solvent refining system according to claim 3, wherein the organic solvent that vaporizes in the vacuum evaporating can and flows through the supply pipe is used as a heat source for the heating means. The amount of the organic solvent supplied to the distillation apparatus is 0.1% by mass or more based on the amount of the organic solvent supplied to the supply destination, according to any one of claims 1 to 4. The organic solvent purification system described. The organic solvent purification system according to any one of claims 1 to 5, wherein the supply destination is equipment using the organic solvent, and the mixed liquid is a recovery liquid recovered from the equipment. A method of separating and purifying the organic solvent from a mixed solution containing water and an organic solvent having a boiling point of more than 100 ° C. at 1 atm.
The heating step of heating the mixed solution and
A separation step of separating the heated mixed solution into the organic solvent and the water using an osmotic vaporizing membrane.
A vacuum evaporation step of vacuum evaporation of the organic solvent recovered from the concentrated side of the osmotic vaporization membrane, and
(A) A part of the organic solvent after the separation step and before the reduced pressure evaporation step, and (b) a part of the organic solvent recovered by the reduced pressure evaporation step are distilled and purified. Distillation process and
A method of mixing the organic solvent purified in the distillation step with the organic solvent recovered by the vacuum evaporation step and not sent to the distillation step and supplying the organic solvent to the supply destination of the organic solvent. The method according to claim 7, wherein the heat energy of the organic solvent vaporized by the reduced pressure evaporation step is used as a heat source in the heating step. The method according to claim 7 or 8, wherein the amount of the organic solvent sent to the distillation step is 0.1% by mass or more based on the amount of the organic solvent supplied to the supply destination. The method according to any one of claims 7 to 9, wherein the supply destination is equipment using the organic solvent, and the mixed liquid is a recovery liquid recovered from the equipment.

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